ON WHICH SAID SHEET MATERIAL IS WOUND

Field of the invention

[0001] The present invention relates to a method for removing a sheet material from a tubular core on which the sheet material is wound, primarily for the purpose of recovering the tubular core, but also in order to recycle the sheet material more easily. The invention also relates to an apparatus to carry out such a method.

[0002] For instance, the tubular core can be made of cardboard or plastic, but also of a metal, while the sheet material can be a polymeric material, paper, aluminium, or any other flexible sheet material of various thicknesses.

Description of the prior art

[0003] As well known, it is sometimes necessary to remove a material wound on a tubular core from the latter, in particular, in the case of coils that contains a defected sheet material or a sheet material that cannot be used as such for any reason, in order to reuse at least the tubular core for making a new coil, while the removed material is normally recycled or treated as a waste.

[0004] To this purpose, equipment is described, for instance, in KR I Q- 2101508, US 2020/262674 A1 , US 5,759,350. In some prior art equipment, a cutting technique using a pressurised fluid is exploited to improve cutting precision, when required, and to produce less dust and swarf, which is an issue when using common motor toothed saws. However, these prior art systems do not save the tubular core, which is intended to be recovered to make new coils and which is normally made of cardboard or plastic and, therefore, cannot resist to the action of toothed saws or pressurised fluid jets, and is finally engraved.

[0005] US 2005/211040 A1 describes a cut machine in which a circular blade is arranged to longitudinally cut a material wound on a tubular core of a coil. The blade is mounted to a support which is in turn mounted to a carriage configured to move longitudinally along the axis of the coil. Moreover, the support allows the blade to approach to the coil. The coil core is held in place by a force-fit connection to mandrels which grip the core only at the end portions thereof and which have a conical shape, in order to fit tubular cores of any internal diameter. The distance between the mandrels can be adjusted depending on the length of the core.

Summary of the invention

[0006] It is an object of the present invention to provide a method and an apparatus for removing a sheet material wound on a tubular core that allow the tubular core to be maintained substantially intact, so that it is available for reuse. [0007] It is also an object of the invention to provide such a method and apparatus that further allow a considerable cut depth and that, at the same time, allow removing all the wound sheet material without engraving the core.

[0008] It is also an object of the invention to provide such a method and apparatus that enable coils with tubular cores of different inner diameters to be processed and that make it possible to switch from one diameter to another with little or no adjustment of the machine structure.

[0009] These and other objects are achieved by an apparatus and method for removing a sheet material from a tubular core as defined in claims 1 and 6. Modifications and advantageous embodiments of the method and apparatus are defined in the dependent claims.

[0010] According to one aspect of the invention, an apparatus is provided for removing a sheet material from a tubular core on which the sheet material is wound, the apparatus comprising: a support shaft having a predetermined diameter and a longitudinal axis; a circular blade having a cutting edge and an initial position in which the cutting edge is at an initial distance from the longitudinal axis, the circular blade arranged to perform an idle rotation movement about an own rotation axis, a control unit, in which values of the diameter of the support shaft and of the initial distance of the blade cutting edge from the longitudinal axis are stored; wherein the control unit is further configured to: receive a value of a measured thickness of the tubular core; compute a computed distance to be covered by the cutting edge in order to reach a surface of the tubular core, starting from: the initial distance of the cutting edge from the axis of the support shaft; the diameter of the support shaft; the measured thickness of the tubular core; perform a cutting step of cutting the sheet material by a plurality of forward and return longitudinal translatory movements of the circular blade, in such a way that the cutting edge of the blade rolls on the sheet material and progressively cuts the sheet material until a current distance of the cutting edge becomes equal to the computed distance, wherein the apparatus further comprises: a transverse abutment located at an axial reference position of the support shaft at a predetermined distance from a first end of the support shaft, the transverse abutment arranged to receive a first end of the coil in abutment against itself; a push-and-lock device of the coil on the support shaft for longitudinally locking the coil at a second end of the coil opposite to the first end.

[0011] According to another aspect of the invention, a method is provided for removing a sheet material from a tubular core on which the sheet material is wound, wherein the steps are provided of: prearranging a support shaft having a predetermined diameter and a longitudinal axis; prearranging a circular blade having a cutting edge in an initial position at an initial distance from the longitudinal axis, the circular blade arranged to perform an idle rotation about its own rotation axis, storing the diameter of the support shaft and the initial distance of the blade cutting edge from the longitudinal axis into a control unit; the method comprising a work cycle in which steps are provided of: measuring the thickness of the tubular core; setting the thickness of the tubular core in the control unit; arranging the tubular core on the support shaft; arranging a transverse abutment in an axial reference position of the support shaft, at a predetermined distance from a first end of the support shaft, so as to receive a first end of the coil in abutment against itself; longitudinally locking the coil on the support shaft at a second end of the coil opposite to the first end; computing, by the control unit, a computed distance to be covered by the cutting edge in order to reach a surface of the tubular core, starting from: the initial distance of the cutting edge from the axis of the support shaft; the diameter of the support shaft; the measured thickness of the tubular core; cutting the sheet material by a plurality of forward and return longitudinal translatory movements of the circular blade, in such a way that the cutting edge of the blade rolls on the sheet material and progressively cuts the sheet material until a current distance of the cutting edge becomes equal to the computed distance; removing the sheet material from the tubular core.

[0012] This way, the core rests on the support shaft at its own uppermost generatrix, under the action of its own weight. This makes it possible to use one support shaft for a wide range of coil core diameters, and it Is not necessary to replace the support shaft when changing core sizes. The blade, rolling on the coil, applies a cutting force lying in a vertical plane passing through the generatrices of the support shaft and of the core that are in contact with each other, and can the cut action is assisted by the reaction force arising from the interposition of the wound material to be cut between the blade and the support shaft. During the cutting step, the longitudinal locking of the coil between the transverse abutment and the push-and-lock device stabilises the coil on the support shaft, thus preventing unwanted displacements in the longitudinal direction and oscillation movements in the transverse direction, which can unfavourably affect the cutting operation.

[0013] This computed distance is obtained as the difference between the initial distance of the cutting edge from the tubular core and the sum of the radius of the support shaft and the measured thickness of the tubular core. In particular, the initial distance of the cutting edge from the tubular core and the diameter (and therefore the radius) of the support shaft are quantities known to the control unit as factory settings, and the value of the diameter of the support shaft can be changed in the control unit when replacing the support shaft. On the other hand, the thickness of the tubular core is a quantity measured and set for each cutting cycle, or for each group of consecutive cutting cycles, in which tubular cores having a same thickness are processed.

[0014] This way, the last longitudinal stroke of the circular blade, in which the last cutting operation is performed, takes place with the blade arranged at the surface of the tubular core, or at a very short distance therefrom, therefore substantially all the sheet material is removed from the tubular core without damaging the tubular core.

[0015] In particular, the idle arrangement of the circular blade about its own axis causes the cutting edge of the circular blade to penetrate the sheet material without forming dust or any particulate matter, and the sheet material is cut with precision at each stroke, so that all the sheet material is easily removed from the tubular core, without damaging the tubular core and without requiring any expensive dust and particulate matter removal means. Moreover, the cutting edge of the circular blade encounters a stable resistance to cutting, since the rigid support shaft, on which the tubular core rests, applies a significant reaction force to the sheet material and to the core.

[0016] Generally, the tubular core has an internal diameter larger than the diameter of the support shaft, therefore the tubular core rests on the support shaft with an uppermost internal generatrix of the tubular core lying on an uppermost generatrix of the support shaft. It is therefore possible to treat tubular cores of different diameters with a limited number of support shafts of different diameters, or even with one support shaft only, without reducing the cutting accuracy, since the contact of the tubular core on the support shaft occurs just along said generatrices, which? concentrates the cutting force along a well- defined line.

[0017] In an advantageous modification of the method, the cutting step comprises, in addition to the plurality of longitudinal translatory movements, a plurality of approach translatory movements by which the circular blade approaches the support shaft, and in which the cutting edge lies on a cutting plane passing through the longitudinal axis; wherein: at least one longitudinal translatory movement is performed between any two consecutive approach translatory movements; a last longitudinal translatory movement is carried out after a last approach translatory movement, in which a current distance of the cutting edge becomes equal to the computed distance.

To this purpose, the control unit of an apparatus according to a corresponding embodiment is configured to perform the translatory movements described above.

[0018] In particular, the transverse abutment comprises at least one protrusion or projection of the support shaft. Preferably, the transverse abutment comprises a pair of removable elongated radial protrusions extending from opposite sides of the support shaft and perpendicularly to the support shaft. The transverse abutment can be arranged on the support shaft itself, for example it can be a pin inserted and locked in a transverse through hole of the support shaft. Several such holes can also be provided at different longitudinal positions along the support shaft.

[0019] Advantageously, the apparatus includes a prop member for bearing the support shaft at the first end thereof, comprising: an upper bearing portion for the support shaft; an upright rotatably arranged about a horizontal rotation axis between a coil-insertion position and a support shaft-bearing position, the rotation axis located proximate to a lower portion of the frame, so as to allow the coil to be inserted on the support shaft.

[0020] The prop member, arranged proximate to the front end of the support shaft, can provide a mounting location for the transverse abutment, which can be mounted to an upper end portion of the prop member. For instance, the transverse abutment can comprise a pair of rods or pins extending from opposite sides of the upper bearing portion of the prop member and perpendicularly thereto, wherein, when the prop member is in the support shaft-bearing position, these rods or pins can receive in abutment the coil previously arranged on the support shaft, provided the coil has been moved forward.

[0021] Advantageously, the prop member is provided with an actuator unit arranged to cause the upright to rotate about its own horizontal rotation axis. In this case, preferably, the prop member further comprises a locking pin to be locked with the support shaft, configured to move from a release rearward position, in which the support shaft is disengaged from the prop member, to a lock position, in which the locking pin is engaged in a bore of the support shaft making the locking pin and the support shaft integral with each other. This makes it possible to stabilise the support shaft with respect to the prop member, in particular, when the coil is brought in abutment to the transverse abutment, when the latter is mounted to the prop member.

[0022] Advantageously, the locking pin is provided with an actuator arranged to move the locking pin between the release position and the lock position. In one embodiment, the locking pin, arranged on the opposite side of the first end of the support shaft with respect to the prop member, when the latter is in the support shaft-bearing position, can act itself as a transverse abutment, arranged to receive in abutment the first end of the coil, which considerably simplifies the apparatus.

[0023] Preferably, the push-and-lock device comprises a locking bar slidably mounted along the direction of the axis of the support shaft and transversally oriented with respect to the support shaft, the locking bar arranged to engage in abutment the second end of the coil with an own central portion. Advantageously, a threaded through hole is provided at the centre of the central portion of the locking bar and is configured to screwably receive a threaded straight member including an adjustment means for adjusting the length of its own end portion protruding upwards from the upper face of the central portion, so that said end portion bears the support shaft at a lowermost generatrix thereof. This makes it possible to limit or even to suppress a deflection of the support shaft under the action of the circular blade during the cutting operation, and under the weight of the coil.

[0024] The push-and-lock device can be operated manually, or it can be motorised so as to shorten the operation time and to reduce the operator’s effort In the latter case, in an advantageous embodiment, the push-and-lock device comprises a pair of lateral belts parallel to each other and to the support shaft, each belt stretched between respective pulleys, wherein a driving pulley thereof is mounted to an output shaft of a driving unit, and the locking bar has opposite ends fixed to the two lateral belts, such that a rotation of the driving unit causes the locking bar to slide along the direction of the axis of the support shaft on which a coil can be pushed until it abuts the transverse abutment.

[0025] In an advantageous modification of this embodiment, an encoder is associated to the output shaft of the motor driving the push-and-lock device, and is configured to generate an angular position signal related to an angular position of the output shaft and of the driving pulley. In this case, the control unit of the apparatus is configured to receive this angular position signal and to calculate from it a longitudinal position of the locking bar.

[0026] The method can also include steps of measuring the width of the sheet material, and of setting this width in the control unit. In a corresponding embodiment of the apparatus, the control unit is configured, in addition to receive the width value, to cause the forward and return longitudinal translatory movements of the blade to have an extension at least equal to the width of the sheet material, between two stroke-end positions, in which the cutting edge of the circular blade is located at the first end the tubular core and at a second end thereof, opposite to the first end, respectively.

[0027] This way, longitudinal translatory movements, i.e. cutting strokes, are possible, of such an extension to cut along the whole width of the sheet material, i.e. longitudinal translatory movements with no portions beyond the ends of the coil, thus saving time with respect to the case of longitudinal strokes of fixed extension, i.e. independent of the width of the sheet material to be cut.

[0028] particular, the control unit of the embodiment described above, equipped with an encoder, is further configured to: receive a locking bar stop signal to stop the locking bar or the motor; store the longitudinal position of the locking bar when the stop signal is received; calculate the length of the coil, i.e. the width of the sheet material, from the longitudinal position of the locking bar as stored. This way, the operator does no longer need to measure the coil manually and to input the measured value into the control unit, in order to calculate the extension of the longitudinal stroke of the circular blade.

[0029] In some embodiments, the support shaft has an inner longitudinally elongated cavity that is in communication with the outside of the support shaft through a pair of diametrically opposed longitudinally elongated lateral openings, provided in the wall of the longitudinally elongated cavity at a determined distance from the first end of the support shaft, wherein a connection element is slidingly arranged within the longitudinally elongated cavity, and two portions of the transverse abutment are connected to the connection element by respective torsional elastic elements, said torsional elastic elements arranged to apply respective elastic torques to both portions of the transverse abutment, said elastic torques configured to open said two portions, i.e., configured to move the two portions away from the operating screw, so as to elastically bring the transverse abutment from a closed configuration, in which the two portions are substantially parallel to each other and to the support shaft, to an open configuration, in which the two portions are arranged at 180° from each other. Briefly, these embodiments provide a mechanism for opening and positioning the transverse abutment along the support shaft.

[0030] In one of these embodiments, an operating screw is arranged within the longitudinally elongated cavity, the operating screw engaging by its own first end with an internally screwed plug element arranged to close the first end of the support shaft, and the operating screw further engages with a threaded through hole, not shown, of the connection element. This way, a displacement of the connection element and of the stop cross member along the support shaft can be actuated by a rotation of the operating screw.

[0031] In a motorised modification of this embodiment, the longitudinally elongated cavity extends along the full length of the support shaft, and a second end of the operating screw, opposite to the first end thereof, is connected with an output shaft of a driving unit arranged at the second end of the support shaft. [0032] In a manually actuated modification of this embodiment, the operating screw is connected by its first end with a handwheel to manually actuate the rotation of the operating screw and, consequently, the displacement of the connection element and of the transverse abutment along the support shaft.

[0033] In one of these embodiments, an opening and positioning mechanism of the transverse abutment is provided, and a piston or cylinder of a preferably pneumatic, or even hydraulic actuator comprising a piston-cylinder assembly is integrally connected to the connection element.

[0034] Preferably, there is provided a photoelectric safety sensor configured to emit a light radiation transversally to the support shaft and arranged opposite to the coil with respect to the position of the transverse abutment, at a position intermediate between the axial reference position and the first end of the support shaft, at a predetermined distance from the axial reference position, so as to detect an abnormal presence/movement of the coil beyond the axial reference position towards the first end of the support shaft. This allows the control unit, which is configured to receive a signal from the photoelectric safety sensor, to notify the operator of such an abnormal condition, which can occur if the transverse abutment is incorrectly positioned or absent of in the reference position.

[0035] In particular, the work cycle comprises, prior to the cutting step, a preliminary approach movement step of the circular blade to the surface of the sheet material, wherein the cutting edge of the blade moves from the initial position to a contact position with the sheet material. The preliminary approach movement step of the circular blade towards the support shaft can be actuated manually by an operator. As an alternative, the preliminary approach movement step can be actuated automatically at the beginning of a work cycle. To this purpose, in one embodiment of the apparatus, the control unit is further configured to cause the circular blade to carry out such a preliminary approach movement.

[0036] In this case, in order to stop the movement of the circular blade when the cutting edge reaches the sheet material, the method can include steps to determine a force acting on the circular blade in opposition to the movement, and to stop the preliminary approach movement when this force exceeds a predetermined limit value. [0037] In this case, the apparatus can comprise a force sensor associated to the circular blade and arranged to measure a force acting on the circular blade in opposition to the preliminary approach movement, so as to stop the preliminary approach movement when this force exceeds a predetermined limit value, typically, when the cutting edge of the blade reaches the surface of the material. To this purpose, the control unit is configured to receive a force signal emitted by the force sensor, to compare the force signal with the force limit value, and to issue a command to stop the preliminary approach movement when the measured force exceeds the limit value.

[0038] As an alternative, the preliminary movement of the circular blade to the sheet material can be interrupted by providing steps of: determining an initial distance between the initial position of the cutting edge and the sheet material; comparing a distance travelled by the cutting edge during the preliminary approach movement with the initial distance; stopping the preliminary approach movement when the distance travelled becomes substantially equal to the initial distance.

[0039] In a first alternative, the step of determining the initial distance of the cutting edge from the wound material can be based on a thickness measurement, for example a manual thickness measurement, of the sheet material wound on the tubular core. Assuming that the initial position with respect to the longitudinal axis of the support shaft is known by the control unit, the initial distance between the cutting edge and the surface of the sheet material can be obtained as the difference between the initial distance of the cutting edge from the axis of the support shaft and the sum of the radius of the support shaft, the thickness of the tubular core and the thickness of the sheet material wound on it, since all the terms of this sum are known to the control unit.

[0040] Preferably, the circular blade with a cutting edge has a diameter between 150 mm and 350 mm, even more preferably between 200 mm and 300 mm. In particular, the larger the diameter, and therefore the heavier the blade, the higher is the cut efficiency of blades having a smooth cutting edge, as in the case of a bevel cut. [0041] Advantageously, a step is provided of setting a single-stroke cut depth in the control unit, and the approach translatory movements of the circular blade to the support shaft generally have a pitch equal to this single-stroke cut depth. In a corresponding apparatus, the control unit is configured to receive the value of this single-stroke cut depth, and to cause the blade to perform approach translatory movements whose pitch is equal to the single-stroke cut depth. This makes it possible to select a suitable single-stroke cut depth for each kind of sheet material to be cut, based on its hardness, elasticity, and other features. In particular, for softer materials, a shorter number of cutting strokes having a deeper single-stroke cut depth can be allowed, which accelerates the work cycles, with respect to the case of an apparatus performing approach movements with a fixed single-stroke cut depth for all the materials for which the apparatus is designed.

[0042] Advantageously, the work cycle further includes steps of: calculating a thickness of the sheet material to be cut between the contact position and the surface of the tubular core as a difference of respective distances from the longitudinal axis; calculating the number of approach translatory movements at least required to reach the surface of the tubular core by the cutting edge, the approach translatory movements having pitches equal to the set singlestroke cut depth; calculating a difference between the sum of the calculated pitches and the thickness of the sheet material to be cut; wherein at least one of the approach movements has a pitch equal to the singlestroke cut depth minus this difference, or wherein, upon reaching the contact position by the cutting edge, a step is performed of moving the cutting edge away from the longitudinal axis by an amount equal to the difference, and all the approach translatory movements are performed with a pitch equal to the set single-stroke cut depth.

[0043] In an advantageous modification, the method further includes, after the step of cutting the sheet material: a step of causing the tubular core to rotate by a predetermined rotation angle, e.g. 180°, and subsequently, a step of automatically repeating the step of cutting the sheet material.

The rotation of the tubular core can even be performed manually by an operator, or the control unit is configured to automatically perform this step, or to perform it upon receiving a command to do so.

[0044] In one embodiment, the control unit is configured to cause the tubular core to automatically rotate by a predetermined angle, in particular by a 180° rotation angle, after the cutting step, and for automatically repeating the step of cutting the sheet material.

[0045] In yet another advantageous embodiment, the control unit of the apparatus is configured to cause the circular blade to perform, simultaneously with at least one portion of the forward and return longitudinal translatory movements, a gradual approach translatory movement towards the support shaft while the circular blade moves from a lateral portion towards a central position of the sheet material, and a gradual retreat translatory movement away from the support shaft while the circular blade moves from the central position towards another lateral portion of the web. This way, the cutting edge "follows" the profile of the uppermost generatrices subsequently exposed by the sheet material as the cut operation proceeds, and a substantially uniform cut depth is possible for all the forward and/or return stroke, even if the support shaft and the coil itself are bent due to the weight of the coil, which is the case for coils having a width considerably shorter than the overall length of the support shaft, simply supported or fixed at its end portions, and/or for large diameter coils or in any case for heavy coils.

[0046] In particular, the gradual approach and retreat translatory movements have a same predetermined length, so that, at the beginning and at the end of a same longitudinal forward or return longitudinal translatory movement, the cutting edge is at a same nominal distance from the support shaft.

Brief description of the drawings

[0047] The invention will be illustrated below with the following description of its embodiments, made by way of example and not limitation, with reference to the accompanying drawings, in which Fig. 1 is a diagrammatical longitudinal cross-sectional view of an apparatus according to an embodiment of the invention, with the circular blade in an initial position of a work cycle and a coil arranged on the support shaft;

Fig. 2 is an enlarged longitudinal sectional view showing a detail of the end portion of the coil of Fig. 1 ;

Fig. 3 is a diagrammatical cross-sectional view of the coil and of the support shaft of the apparatus of Fig. 1 ;

Fig. 3A is a side view of an alternative circular blade in Fig. 3;

Figs. 4 and 5 are diagrammatical perspective views of an apparatus according to an embodiment of the invention, in which some covering elements and other details have been removed;

Figs. 6 and 7 show the apparatus of Fig. 1 at an intermediate time and at the end of a preliminary movement of the blade towards the sheet material to be cut, respectively;

Figs. 8 and 9 illustrate two different procedures for determining the initial distance of the surface of the sheet material to be cut from the cutting edge of the blade, when the blade is in an initial position of a work cycle;

Fig. 10 is a partial diagrammatical cross-sectional view similar to the view of Fig. 7, in which a different criterion for stopping the preliminary blade approach movement is illustrated;

Fig. 1 1 is a diagrammatical cross-sectional view of the coil and of the shaft during a longitudinal translatory movement of the blade towards a startcutting position;

Fig. 12 is a diagrammatical cross-sectional view of the coil and of the shaft with the blade in the above-mentioned start-cutting position;

Fig. 13 is a diagrammatical cross-sectional view of the coil and shaft, showing an initial movement of a plurality of approach translatory movements to bring the blade closer to the support shaft and increase the cut depth;

Fig. 14 is a diagrammatical cross-sectional view of the coil and of the shaft during a first stroke or longitudinal translatory movement of the blade;

Fig. 15 is a diagrammatical cross-sectional view of the coil and of the shaft with the blade in the end position of the return stroke in Fig. 14; Fig. 16 is a diagrammatical cross-sectional view of the coil and of the shaft, showing a second approach translatory movement of the blade towards the support shaft;

Fig. 17 is a diagrammatical cross-sectional view of the coil and of the shaft during a generic subsequent blade stroke;

Fig. 18 is a rear perspective view of the coil and of the shaft during a generic blade return stroke;

Fig. 19 is a diagrammatical cross-sectional view of the coil and of the shaft with the blade in an end-stroke position;

Fig. 20 is a diagrammatical cross-sectional view of the coil and of the shaft with the blade in an end-stroke position, in which the cutting of the coil sheet material is completed;

Fig. 21 is a partial perspective view of the apparatus of Fig. 5;

Fig. 22 is a perspective view of the locking bar;

Fig. 23 is a perspective view of the lateral belt drive components of the push-and-lock device;

Figs. 24 and 25 are perspective views of the support shaft prop member in a coil-insertion position and in a support shaft-bearing position, respectively; Fig. 26 is a diagrammatical front view of a prop member fitted with an automatic locking pin to lock the support shaft;

Fig. 27 is a diagrammatical side view of the prop member in Fig. 26.

Fig. 28 is a diagrammatical frontal view of the support shaft element in a modification of the prop member of Fig. 26, in which the locking pin also serves as a transverse abutment for the coil;

Fig. 29 is a diagrammatical side view of the prop member in Fig. 28;

Figs. 30 and 31 are perspective views of a cutting head according to an embodiment of the invention in a resting configuration and a cutting configuration, respectively;

Fig. 32 is a front view of the coil and of the shaft of the apparatus, under the conditions of Fig. 20;

Figs. 33 and 34 are front views of the coil and of the shaft respectively during and at the end of a step of rotation of the core and sheet material around the axis of the tubular core; Figs. 35 and 36 are partial longitudinal and cross-sectional views of the coil and support shaft respectively, showing devices for the automatic determination of the thickness of the coil sheet material, according to two different embodiments;

Fig. 37 is a diagrammatical cross-sectional view in which the coil and shaft are deflected by the weight of the coil, and in which the longitudinal movement of the circular blade is performed in such a way to maintain a single cut depth, compensating for this deflection ;

Fig. 38 shows an example of a qualitative trend of a gradual approach movement performed during the longitudinal movement of the circular blade, in a portion of a return stroke;

Fig. 39 is a diagrammatical cross-sectional view of the coil and of the shaft of an apparatus according to an embodiment in which the locking element is configured to bear the support shaft of Fig. 36 in an intermediate portion to limit its deflection, in particular, during a cutting operation;

Figs. 40 and 41 diagrammatically show the locking element of Fig. 39 in a cross-section view, together with the support shaft and a coil, and in a perspective view, respectively;

Figs. 42-47 are longitudinal cross-section top views of a support shaft and a transverse pin according to an embodiment of the invention, in various steps of a positioning sequence of the transverse pin, coil and locking bar; Figs. 48 and 49 are longitudinal cross-section top views of a support shaft and of a transverse pin according to two further embodiments.

Detailed description of some embodiments

[0048] With reference to Figs. 1 to 3, an apparatus 100 is described for removing a sheet material 2 from a coil 3 consisting of a tubular core 1 and layers of sheet material 2 wound onto it, primarily for the purpose of recovering tubular core 1 so that it can be reused to form other coils.

[0049] Sheet material 2 is typically off-spec material, or in any case a material to be disposed, or possibly recovered and/or reused. Sheet material 2 can be a polymeric material, aluminium, paper or even a fabric.

[0050] Apparatus 100, in one embodiment as shown in Figs. 4 and 5, comprises a frame 10, in this case of a parallelepiped shape, formed by a plurality of uprights 1 1 , in particular four uprights 1 1 at respective vertical edges of the parallelepiped shape, and by a plurality of transverse members 13 and longitudinal members 14, and further comprises a plurality of closure panels, of which a ceiling panel 15 and a front panel 16 are shown in Figs. 4 and 5. Support feet 27 can be attached to the bottom frame 10.

[0051] Apparatus 100 comprises a support shaft 21 arranged horizontally, extending along an axis 22 and having a diameter s (Fig. 2). Support shaft 21 is configured to receive coil 3 (Fig. 1 ) by inserting support shaft 21 into the cavity of the tubular core and by leaning the uppermost inner generatrix of the tubular core on a generatrix of the support shaft.

[0052] Support shaft 21 is preferably cantilevered to a rear side of frame 10, at its own mounting end 21 b, hereinafter referred to as the second end, opposite to a first end 21 a of support shaft 21 , hereinafter referred to as the first end.

[0053] Apparatus 1 further includes a circular blade 32, shown more in detail in Figs. 1 and 3. Circular blade 32 is typically of the bevel type, i.e. it is provided with at least one circumferential bevel, preferably two circumferentially symmetrical bevels that terminate(s) in a cutting edge 35. In Fig. 1 , circular blade 32 is shown in a predetermined initial position 37 of a work cycle, wherein cutting edge 35 is at an initial distance Da from axis 22 of support shaft 21 .

[0054] Circular blade 32 preferably has a diameter of the cutting edge between 150 mm and 350 mm, in particular the diameter is set between 200 mm and 300 mm.

[0055] Circular blade 32 is mounted to a cutting head 30a or 30b, described more in detail below, which is configured to cause circular blade 32 to perform approach translatory movements 60,61 ,62...6N towards support shaft 21 , and longitudinal movements 7f,7b parallel to support shaft 21. Circular blade 32 is also arranged to perform an idle rotation movement 8 about its own horizontal rotation axis 36, as shown in Figs. 6-20.

[0056] As shown in Fig. 3, the approach translatory movements of circular blade 32 towards support shaft 21 take place with cutting edge 35 of the blade lying in a cutting plane IT passing through axis 22 of support shaft 21 .

[0057] Longitudinal translatory movements 7 of circular blade 32 include return strokes 7b (Figs. 14 and 18) and forward strokes 7f (Figs. 1 1 and 17) both parallel to support shaft 21. The terms "forward" and "return" identify, respectively, directions of movement of circular blade 32 and of cutting edge 35 thereof away from free end 21 a of support shaft 21 , through which coil 3 is inserted.

[0058] As shown in Fig. 21 , in an axial reference position of support shaft 21 for coil 3, at which a first end 3a of coil 3 or tubular core 1 is arranged, there is provided a transverse abutment 23, also visible in the overall view of Fig. 4 only, arranged to receive coil 3 in abutment, in particular, at end 3a of coil 3. Transverse abutment 23 can be a projection such that coil 3 can abut against it. For example, as shown in Figs. 4, 5, 21 , the transverse abutment can be a transverse pin 23 comprising two radial protrusions 23a preferably perpendicular to support shaft 21 and preferably aligned with each other.

[0059] According to the invention, apparatus 100 further comprises a pushand-lock device 55 for pushing and locking coil 3 on support shaft 21 , shown in an overall view only in Fig. 4 and, more in detail, in Figs. 21 -23, for locking longitudinally, but also transversally, coil 3 before cutting it by circular blade 32, once coil 3 has been brought to abutment to transverse abutment 23 of support shaft 21 .

[0060] Push-and-lock device 55 can comprise a locking bar 56 (Fig. 22) mounted longitudinally along axis 22 of support shaft 21 and oriented transversally with respect to support shaft 21 , preferably below it. Locking bar

56 is arranged to engage coil 3 by its own central portion 56a on the opposite side of transverse abutment 23 with respect to coil 3 itself.

[0061] In one embodiment, in order to cause locking bar 56 to slide along axis 22 of support shaft 21 , there is provided a pair of lateral belts 57 parallel to each other and to support shaft 21 (Fig. 23). Each of lateral belts 57 is stretched between an idle pulley 57a and a driving pulley 57b, in this case arranged on the side of first end 21 a and on the side of second end 21 b of support shaft 21 , respectively.

[0062] In particular, locking bar 56 has end portions 56b fixed to lateral belts

57 by means of respective housings 56d formed in respective sliders 57c configured to slidably engage two tracks parallel to support shaft 21. Driving pulley 57b of each belt 57 is mounted to an output shaft 58c of a driving unit 58, preferably a gearmotor unit 58 comprising a motor 58a and a speed reducer 58b, to rotatably drive driving pulleys 57b and thereby cause lateral belts 57 and locking bar 56 to move.

[0063] In an advantageous modification, gearmotor unit 58 and output shaft 58c are associated to an encoder 58d configured to generate a rotation signal that expresses angular position values of output shaft 58c and of pulleys 57b, which are easily correlated to corresponding longitudinal position values of locking bar 56, which encoder 58d allows to be notified to a control unit 90, described below.

[0064] In addition, apparatus 100 can comprise a photoelectric safety sensor or photocell 80 having a light axis 80a transverse to support shaft 21 , arranged on the opposite side of coil 3 with respect to the position of transverse abutment 23, at a predetermined distance from transverse abutment 23. Therefore, if coil 3 unwantedly moves towards first end 21 a of support shaft 21 , photoelectric safety sensor 80 emits a presence signal indicating the presence of coil 3 at its position, along support shaft 21 , corresponding to light axis 80a. The presence signal can therefore be interpreted as an abnormal advancement of coil 3 towards free end 21 a of support shaft 21. This can occur, for instance, if the operator has forgotten to place transverse pin 23 at the axial reference position after arranging coil 3 on support shaft 21 .

[0065] A prop member 24 for bearing support shaft 21 (Figs. 4 and 5) is preferably provided at the bottom of the front side of frame 10, comprising a bearing portion 24b, preferably provided with rollers rotatably arranged around an axis 24e orthogonal to the median plane of frame 10, and further comprising a rotatable post 24a having a first end connected to prop member 24b and a second end radially connected to a shaft 24c rotatably arranged about a horizontal rotation axis 26 proximate to lower transverse member 13. In the embodiments shown in Figs. 4 and 5, prop member 24 can be rotated and moved away from the support position shown in Figs. 4 and 5 by means of a dumbbell 25a. This allows coil 3 to be positioned on support shaft 21 and clean tubular core 1 to be removed from support shaft 21 .

[0066] Figs. 24 and 25 show a modification of prop member 24 in a coilinsertion position (B) and in a support shaft-bearing position (A) of shaft support 21 during normal operation of apparatus 100, respectively. In this modification, prop member 24 is provided with an actuator unit 25 comprising a motor 25b for rotating post 24a about axis 26. In this case, motor 25b can be connected to shaft 24c by a belt transmission 25c. In particular, a proximity sensor 26a can be provided, preferably an induction-type one, collaborating in this case with a metal target 26b integral with post 24a.

[0067] With reference to Figs. 26 and 27, prop member 24, in its motorised modification, can comprise a locking pin 24d to lock the prop member to support shaft 21 , said locking pin configured to move from a rearward release position, in which support shaft 21 is disengaged from prop member 24, to a lock position, in which locking pin 24d is engaged in a bore, not shown, of support shaft 21. Locking pin 24d is preferably provided with an actuator 24e, for example, of a pneumatic type.

[0068] Moreover, irrespective of the above, transverse abutment 23 can be mounted to an end portion of prop member 24.

[0069] With reference to Figs. 28 and 29, in a further modification, locking pin 24d itself can play the role of transverse abutment 23, if arranged on the opposite side of first end 21 a with respect to prop member 24, provided actuator 24e is arranged in such a position that does not create interference with coil 3 when the latter approaches transverse abutment 24d.

[0070] Cutting head 30a, 30b comprises a first slide 31 slidably arranged longitudinally in the direction of axis 22 of support shaft 21 . In the embodiments shown in Figs. 4 and 5, apparatus 100 comprises a belt-driven linear axis 44 in turn comprising a linear guide 44a parallel to support shaft 21 and one or more lateral drive belts 42, each stretched between a driving pulley, not shown, and a driven pulley 43b. First slide 31 is slidably arranged along linear guide 44a and is connected to lateral drive belt(s) 42. In order to actuate longitudinal translatory movements 7 of cutting head 30a, 30b and, therefore, of circular blade 32, cutting head 30a, 30b comprises a motor 40, in particular an asynchronous motor, associated to a speed reducer 41 , the output shaft of which, not shown, is connected to the driving pulley of belt-driven linear axis 44, so as to transform the rotary motion of the output shaft of speed reducer 41 into an alternating translatory motion of first slide 31 . [0071] An encoder 49 is preferably associated to gearmotor assembly 40-41 to follow the rotary motion of the output shaft of gearmotor assembly 40-41 and, thus, to follow the longitudinal translational motion of first slide 31 along linear axis 44. Encoder 49 is configured to output a position signal of first slide 31 intended for control unit 90, as described further below.

[0072] In order to actuate the approach translatory movements of circular blade 32 towards support shaft 21 , the circular blade is mounted to a second slide 34, which is in turn arranged to slide in a direction perpendicular to the sliding direction of first slide 31 , defined by linear axis 44. In other words, second slide 34 acts as a blade-holding element and is mounted to first slide 31 so as to slide vertically with respect thereto. Cutting head 30a, 30b further comprises a box element 45a or 45b for protecting blade 32.

[0073] In cutting head 30a of Fig. 4, more detail, in a resting configuration R and in a cutting configuration T of Figs. 30 and 31 , respectively, protection element 45a is integral with first slide 31. In resting configuration R, in which second slide 34 is in a rearward position with respect to first slide 31 , blade 32 is completely enclosed in protection box element 45a. Blade 32 has a portion protruding from protection box element 45a only when it is close to cutting configuration T, due to a downwards advancement of second slide 34 with respect to first slide 31.

[0074] On the other hand, in cutting head 30b of Fig. 5, protection element 45b is integral with second slide 34 and is mounted so as to allow blade 32 to protrude by a suitable circular segment so as to be able to perform the operation of cutting sheet material 2 when second slide 34 is in a lowered cutting position, as shown in Fig. 4. In this case, apparatus 100 further includes fixed side protection elements 38 to prevent any accidental contact of an operator with circular blade 32, downwardly protruding from blade-holding element 45a.

[0075] A screw 46, for example a trapezoidal screw associated to a bronze nut screw, is mounted to a horizontal portion of second slide 34. Fig. 4 only shows a coupling flange thereof for coupling with second slide 34, while this screw is better visible in Fig. 31. Screw 46 is arranged to be rotatably actuated by a drive assembly that preferably consists of a motor 47 (Figs. 5,30,31 ) and of a transmission/reduction device 48, preferably a belt transmission/reduction device, the output shaft of which is arranged to cause screw 46 to rotate. Such a driving unit 47-48 is supported by a support plate 43 connected to first slide 31 . Screw 46 is selected as a short-pitch screw so as not to change its position under any force coming from the blade. Motor 47 can be a DC motor, preferably a brushless-type motor, including a built-in encoder, so as to precisely follow the rotary motion of the output shaft of gearmotor assembly 47-48 and, therefore, to precisely follow approach translatory movements 60,61 ,62...6N of second slide 34 and, therefore, of circular blade 32 and of cutting edge 35 towards support shaft 21 .

[0076] Moreover, emergency end-of-stroke sensors 33 (Figs. 5,30,31 ) can also be integrally mounted to first slide 31 to control the movement thereof with respect to axis 22.

[0077] Electric motors 40,47 are electrically connected to a switchboard 50 of apparatus 100, from which they receive their drive power.

[0078] Moreover, circular blade 32 is mounted to a horizontal shaft 39 that has an axis 36 and is rotatably arranged in seats provided in the walls of second slide 34, and a rolling bearing is advantageously arranged between horizontal shaft 39 and each of said seats.

[0079] Apparatus 100 is further provided with a control unit 90 for managing the work cycle, which includes approach translatory movements 60,61 ,62...6N and longitudinal translatory movements 7f,7b of circular blade 32, described above. In the embodiments shown in Figs. 4 and 5, control unit 90 is preferably arranged within frame 10 of apparatus 100, in particular it is mounted to front panel 16 arranged between two uprights 1 1 of frame 10, with an interface portion 91 facing outside frame 10 on front panel 16.

[0080] In particular, control unit 90 is configured to receive, at the beginning of each work cycle, a measured value of a thickness Tc of tubular core 1 (Fig. 2). In particular embodiments, described below, control unit 90 is further configured to receive values of a width W of sheet material 2 (Fig. 1 ), also referred to hereafter as the length of coil 3, minus the length of end portions 3a, 3b of tubular core 1 protruding from sheet material 2 wound on it, and/or values of the desired single-stroke cut depth P by circular blade 32 (Fig. 14). [0081] In the embodiments shown in Figs. 4 and 5, interface portion 91 of control unit 90 comprises a touch-sensitive screen in which fields are provided for entering each of said values, and a numeric keypad is provided for entering said values, also including an acknowledgement key. Control unit 90 is further configured to receive the value of diameter s of support shaft 21 (Fig. 2), preferably as a factory setting.

[0082] The control unit further includes manoeuvre buttons 81 to start and stop the work cycle, an emergency reset button 82 and an emergency lockout mushroom button 83.

[0083] According to the invention, control unit 90 is configured to actuate an automatic cutting step of cutting sheet material 2 by means of circular blade 32. [0084] This cutting step comprises a sequence of a number N of approach translatory movements 61 ,62...6j, j=1 ...N of circular blade 32 towards support shaft 21 (Figs. 13, 16 and 19).

[0085] As sequentially shown in Figs. 1 1 to 16, between any two consecutive approach translatory movements 6j-1 ,6j, in order to cut sheet material 2 down to tubular core 1 , the cutting step includes at least one longitudinal translatory movement 7f,7b in a direction parallel to support shaft 21 , along the entire width W of the sheet material. Longitudinal translatory movements 7 comprise forward strokes 7f (Figs. 11 , 17, 20) and return strokes 7b (Fig. 14), as described above, between respective stroke-end positions.

[0086] Moreover, as Figs. 19 and 20 show, a last longitudinal translatory movement 7f and/or 7b (Fig. 20) is performed after a last approach translatory movement 6N (Fig. 19) during which a distance D travelled by cutting edge 35 from its initial position becomes equal to a calculated initial distance De, i.e. during which cutting edge 35 reaches the surface of tubular core 1 .

[0087] As shown in Figs. 1 and 2, initial distance De of cutting edge 35 from tubular core 1 , i.e. the whole distance that cutting edge 35 must travel towards support shaft 21 to reach the surface of tubular core 1 , is obtained by the formula:

De = Da - S = Da - ( ¹ /2 s + Tc) where Da is the initial distance of cutting edge 35 from axis 22 of support shaft 21 , and is known to control unit 90 preferably as a factory setting; ct>s is the diameter of support shaft 21 , and is also known to control unit 90 preferably as a factory setting, with the possibility of modifying this setting if different diameter shafts are used in the equipment;

Tc is the thickness of the tubular core, and is set in control unit 90, for each cutting cycle, or for consecutive cutting cycles in which tubular cores having a same thickness are processed.

[0088] In the same embodiment, control unit 90 comprises a calculation means configured to calculate an extension L of forward and return strokes 7f,7b, from the width W of sheet material 2. Extension L of forward and return strokes 7f,7b is preferably determined to be slightly longer than or at least equal to width W of sheet material 2. At the same time, control unit 90 is configured to define two end-stroke or start-stroke positions at first end 3a of coil 3, and at a second end 3b opposite to first end 3a, respectively.

[0089] In apparatus 100 according to the modification of the embodiment shown in Fig. 21 , wherein push-and-lock device 55 for locking coil 3 between locking bar 56 and transverse abutment 23 comprises encoder 58d, the measurement of width W of sheet material 2, i.e. the length of coil 3, can be obtained by processing a longitudinal position signal indicating the position of locking bar 56 along support shaft 21 , provided by encoder 58d. More in detail, control unit 90 acquires the longitudinal position signal of locking bar 56 and stores its value in order to calculate length W of coil 3 upon receiving a stop signal from locking bar 56 or from motor 58a actuating belts 57 of the push-and- lock device 55.

[0090] In a modification, not shown, control unit 90 is configured to generate the stop signal for stopping motor 58a based on a torque control on the motor in which the stop signal is triggered if the torque exceeds a predetermined torque value. In another modification, not shown, control unit 90 is configured to generate the stop signal for stopping 58a if the control unit for has not been receiving any new signal from encoder 58d for at least a predetermined waiting time. [0091] Control unit 90 is further configured to receive a setting of the number M of outward and/or return strokes 7f,7b to be performed between two consecutive approach translating movements 6j, 6j+ 1 . In particular, said number M can be 1 , in which case only one forward or return stroke is performed between two consecutive approach translatory movements, or it can be 2, in which case one forward stroke and one return stroke are performed between two consecutive approach translatory movements.

[0092] Therefore, as shown in Figs. 13 and 16, each approach translatory movement 6j covers a distance corresponding to a single-stroke cut depth P and cutting edge 35 increases its penetration Pj into sheet material 2 by an amount equal to P. Figs. 13 and 16 show the first and the second approach translatory movements 61 and 62, j=1 .2.

[0093] Therefore, the cutting action takes place by causing circular blade 32 to roll on sheet material 2, more precisely along a generatrix of the cylinder formed by sheet material 2.

[0094] As shown in Figs. 6 and 7, in a particular embodiment, control unit 90 is advantageously configured to cause circular blade 32 to perform a preliminary approach movement 60 to sheet material 2, in order to bring cutting edge 35 into contact with sheet material 2. Stopping the automatic approach 60 of circular blade 32 to sheet material 2 can be controlled by control unit 90 in various ways, as described below.

[0095] However, in a modification of the method, preliminary approach movement 60 can be performed manually by an operator. In this case, the above-mentioned configuration of control unit 90 can be omitted.

[0096] In another embodiment, control unit 90 is configured to receive a value of the desired single-stroke cut depth P by circular blade 32.

[0097] In this case, the work cycle further comprises an overall cut depth calculation step performed by control unit 90, in which the overall depth that is necessary to cut all sheet material 2 up to tubular core 1 , i.e. the thickness Tm of sheet material 2 is calculated to be cut between the contact position and the surface of tubular core 1 . This calculation is performed as the difference Dc-D1 of respective distances from axis 22. It is also provided a step of calculating a number N of approach translatory movements 6j required that is to reach the surface of tubular core 1 by cutting edge 35, as well as a step of calculating a difference between the sum of the calculated pitches NxP and calculated thickness Tm=Dc-D1 of sheet material 2 to be cut.

[0098] In order to ensure that cutting edge 35 does not cut into tubular core 1 , at least one approach movement, for example the last approach movement 6N, can have a pitch equal to the single-stroke cut depth P decreased by the difference NxP-Tm calculated as above. In other words, as shown in Fig. 19, the last approach translatory movement 6N is performed in such a way that the increasing penetration Pj of cutting edge 35 becomes equal to sheet material thickness Tm of sheet material 2 wrapped on tubular core 1. Under such conditions, cutting edge 35 reaches exactly the surface of tubular core 1 . Finally, as shown in Fig. 20, the cutting step includes a last forward or return stroke 7f or 7b to remove the last layer of sheet material 2 without cutting tubular core 1 . [0099] As an alternative, still in order to prevent tubular core 1 from being engraved of after the last approach translatory movement 6N, a step of retracting, i.e. of moving cutting edge 35 away from axis 22 can be performed upon reaching the contact position with a surface 2' of sheet material 2, by a pitch equal to the difference NxP-Tm calculated as above, and all the N approach translatory movements 6j can be performed with a same pitch equal to the set single-stroke cut depth P.

[0100] Finally, a step is provided of removing sheet material 2 from tubular core 1 , described more in detail below.

[0101] In one embodiment of apparatus 100, and in a corresponding modification of the method as shown in Figs. 32-34, control unit 90 can be configured to automatically cause tubular core 1 to perform a rotation 9 by a predetermined rotation angle a after the cutting step described above, and to automatically repeat the step of cutting sheet material 2 as described above. Subsequently, sheet material 2 can be easily removed from tubular core 1 and collected in a special area of apparatus 100, to be unloaded later, and sent to storage and/or to recycling or disposal.

[0102] To this purpose, as shown in Fig. 5, the lower part of frame 10 is configured as a collection container 51 provided with at least one lateral discharge door 52 rotatably arranged about a horizontal axis at the base of frame 10, in such a way to be able to rotate by an angle between 90° and 180°, preferably by 180°, thus allowing the recovered cores to be discharged horizontally and then possibly to fall down, once collection container 51 has been removed from apparatus 100 and lifted, for instance, by a forklift or the like. A knob 54 is provided for opening/closing the door. In particular, collection container 51 is removable from frame 10 and, preferably, is provided with wheels 28 to facilitate its removal from frame 10 (Figs. 4 and 5).

[0103] Figs. 32-34 show a single rotation 9 of the tubular core and of the sheet material, in which the rotation angle a is 180°, however, several rotations of an angle narrower than 180° are possible, in particular, in the case of large- diameter coils 3 .

[0104] Referring to Figs. 2 and 3 again, tubular core 1 can have an inner diameter <3>i longer than diameter s of support shaft 21. In this case, tubular core 1 rests on support shaft 21 with an uppermost inner generatrix 17 of tubular core 1 lying on an uppermost generatrix 21 ' of support shaft 21 , and the cutting plane IT contains these generatrices, besides axis 22 of support shaft 21. Therefore, a gap 19 is formed between lowermost generatrix of support shaft 21 and lowermost inner generatrix of tubular core 1 .

[0105] In this case, the above-mentioned rotation or rotations 9 are preferably performed manually by an operator. As an alternative, the apparatus can provide a rotation means, not shown, for causing support shaft 21 to rotate about its axis 22, and the control unit 21 can be configured to operate such rotational means by rotating support shaft 21 , whereby the rotation 9 of tubular core 1 occurs due to the rolling friction forces exerted between tubular core 1 and support shaft 21 .

[0106] Figs. 7-10 relate to diverse ways to carry out preliminary approach movement 60 of circular blade 32 to sheet material 2, in particular, the criteria are shown that control unit 90 is configured to use in order to stop the approach movement of circular blade 32 in a close proximity to or at a first contact with surface 2’ of sheet material 2.

[0107] In particular, Fig. 10 relates to an embodiment of apparatus 100, and to a corresponding modification of the method, in which apparatus 100 comprises a sensor, not shown, that is incorporated in the translation means of circular blade 32 and is arranged to measure a force F acting on circular blade 32 in opposition to preliminary approach movement 60, typically when cutting edge 35 comes into contact with sheet material 2. To this purpose, control unit 90 is configured to receive a force signal, not shown, from this force sensor and to stop preliminary approach movement 60 when said signal indicates a force F exceeding a predetermined threshold value.

[0108] Figs. 7-9 refer to alternative embodiments of apparatus 100 and to an alternative criterion, wherein control unit 90 includes a calculation means for determining the initial distance D1 between initial position 37 of cutting edge 35 and surface 2’ of sheet material 2 to be cut, and for comparing distance D travelled by cutting edge 35 during preliminary approach movement 60 with said initial distance D1. Control unit 90 is further configured to stop preliminary approach movement 60 when travelled distance D becomes equal to initial distance D1 .

[0109] In particular, as shown in Fig. 8, control unit 90 is configured to receive the value of thickness Tm of sheet material 2 wound on tubular core 1 , i.e. thickness Tm to be cut, and the calculation means are configured to calculate initial distance D1 as the difference between initial distance Da of cutting edge 35 from axis 22 of support shaft 21 , previously set in control unit 90, and the sum of the radius Rs= s/2 of support shaft 21 , thickness Tc of tubular core 1 and thickness Tm of sheet material 2, i.e. by the formula

D1 = Da-(Rs+Tc+Tm).

[0110] On the other hand, in an alternative embodiment of apparatus 100 as shown in Fig. 9, and in a corresponding modification of the method, apparatus 100 comprises a sensor 70 configured to detect the presence of surface 2’ of sheet material 2 and to calculate the distance Ds between itself and surface 2’, and the calculation means are configured to calculate initial distance D1 between cutting edge 35 and surface 2’ of sheet material 2 by a difference between distance Ds of sensor 70 from surface 2’ of sheet material 2 and the distance, measured in the radial direction of coil 3, between sensor 70 and initial position 37 of cutting edge 35, previously set in control unit 90, i.e. by the formula

D1 = Ds-Df. [0111] As shown in Fig. 35, in an alternative configuration, the position sensor is a photoelectric sensor, i.e. a measuring photocell 70 comprising an emitter 76 of a light radiation in the form of a beam 72, in particular a laser emitter. Photoelectric sensor 70 is integrally mounted to cutting head 30 of apparatus 100, in particular to first slide 31 , so that beam 72 of the emitted light radiation is projected vertically towards axis 22 of support shaft 21 , and orthogonally to support shaft 21 . This way, measuring sensor 70 is configured to detect an overall thickness Tb=Tm+Tc of coil 3, including thickness Tc of tubular core 1 and thickness Tm of sheet material 2 wound on tubular core 1 . If tubular core 1 protrudes longitudinally from sheet material 2 wound on it, in the configuration of Fig. 9 measuring sensor 70 is also able to read only thickness Tc of tubular core 1 .

[0112] Accordingly, the calculation means of control unit 90 is configured to assume as corresponding to a zero-thickness the position signal emitted by measuring sensor 70 corresponding to the detection of support shaft 21 . In order to read the thickness, a scanning step can be provided by longitudinal translation 7 of the cutting head and of measuring sensor 70 integral therewith. Therefore, when beam 72 of the light radiation encounters surface 2’ of sheet material 2 or the outer surface of the portion of tubular core 1 longitudinally protruding from sheet material 2, the signal relates to the overall thickness Tm+Tc of coil 3 and to thickness Tc of tubular core 1 alone, respectively.

[0113] Fig. 36 diagrammatically shows a different device for measuring or automatically determining thickness Tb of coil 3. In such a device, a photoelectric sensor, i.e. a measuring photocell 75 comprises an emitter 77 of a light radiation, preferably a laser radiation, configured to emit a light curtain 78 of width Hf, and a receiver 79 of said light radiation 78, wherein emitter 77 and receiver 78 face each other and are arranged at opposite sides of support shaft 21 . Emitter 77 is further arranged in such a way that light curtain 78 is projected horizontally, above support shaft 21 and perpendicularly thereto. Measuring photoelectric sensor 75 is configured to emit a position signal 79a, 79b of an obstacle interposed between emitter 77 and receiver 79, responsive to a fraction of light curtain 78 that the obstacle hides to receiver 79. [0114] In this case, control unit 90 is configured to retain the position signal 79a which is emitted by photoelectric sensor 75 at the uppermost generatrix of support shaft 21 , when coil 3 is not present, as a zero-thickness signal of coil 3 and to calculate overall thickness Tb=Tm+Tc of coil 3 from position signal 79b that photoelectric sensor 75 emits at the uppermost generatrix of coil 3, once coil 3 is present on support shaft 21 .

[0115] As an alternative to light curtain emitter 77, a plurality of emitters can be provided, not shown, in which the emitters are configured to emit respective light beams, and the thickness calculation is based on the fraction of beams that are hidden to light radiation receiver 79.

[0116] In a modification, not shown, photoelectric sensor 75 is slidably arranged along the direction of support shaft 21 , so that light radiation curtain 78 can be projected to "cut" any portion of tubular core 1 protruding from the sheet material wound on it, and thus to read only thickness Tc of tubular core 1 . [0117] Fig. 37 shows a condition in which the horizontally arranged support shaft 21 is bent primarily due the force applied by blade 32 onto coil 3, possibly in addition to the weight of the coil, and in which coil 3 is also bent accordingly. For the sake of clarity, the bending of support shaft 21 and of coil 3 has been exaggerated in proportion to the respective dimensions thereof. As a result of the bending, surface 2’ of sheet material 2 to be cut by circular blade 32 has two raised end portions 2a and a lowered central portion 2b.

[0118] In these conditions, if longitudinal translatory movements 7f,7b of circular blade 32 were carried out maintaining the height of circular blade 32 throughout the forward stroke 7f or return stroke 7b, the cut depth of each stroke would change along the stroke.

[0119] Advantageously, in a modification of the method, it is provided that circular blade 32 further performs a gradual approach 6x towards support shaft 21 while circular blade 32 moves from an end portion 2a towards central position 2b of coil 3, simultaneously with at least one portion of its own longitudinal movements 7f,7b, and performs a gradual retreat translatory movement from support shaft 21 while circular blade 32 moves from central position 2b towards one of the end portions 2a of coil 3, said gradual retreat and then gradual approach movement 6x preferably having a same predetermined length. This way, as diagrammatically shown in Fig. 38, the lower portion of cutting edge 35 follows a downwardly-curved line 78 that separates from and then approaches a horizontal line 79, and at the beginning and at the end of a same forward or return stroke 7f,7b, cutting edge 35 of circular blade 32 is at a same nominal distance from support shaft 21 .

[0120] Gradual approach translatory movement 6x can be, for instance, a substantially continuous movement, as diagrammatically shown in Fig. 38, or, in a modification not shown, it can change stepwise.

[0121] In order to actuate the above, in a corresponding embodiment of the apparatus, control unit 90 is configured to cause circular blade 32 to perform said gradual approach/retreat translatory movements 6x to/from support shaft 21 during at least one part of forward strokes 7f and of return strokes 7b, so that at the beginning and at the end of a same forward or return stroke 7f,7b, cutting edge 35 of circular blade 32 is at a same nominal distance from support shaft 21. This way, cutting edge 35 "follows" the profile 78 of the subsequent uppermost generatrices exposed by sheet material 2, along which the cut is to be performed.

[0122] As shown in Figs. 39-41 , in another embodiment, a threaded through hole 56e is provided at the centre of central portion 56a of locking bar 56 of Figs. 21 and 22, the through hole configured to screwably receive a threaded straight member 59 such as a threaded bar. Threaded straight member 59 preferably includes an adjustment means 59a for adjusting the length of an end portion 59b of threaded straight member 59 protruding upwards from the upper face of central portion 56a of locking bar 56, so that end portion 59b bears support shaft 21 at the lowermost generatrix thereof, thereby limiting or preventing deflection of support shaft 21 , shown in Fig. 37. In this case, locking bar 56, besides locking the coil on support shaft 21 , also plays the role of bearing support shaft 21 itself against an excessive deflection thereof during the cutting operation of sheet material 2.

[0123] Figs. 42-49 relate to some embodiments of the invention in which a mechanism for positioning the transverse abutment is provided, in the form of a transverse pin 23, as shown in Figs. 4 and 21 . [0124] In the embodiment shown in Figs. 42-47, support shaft 21 is a shaft provided with a longitudinally elongated cavity 21 d which is in communication with the outside of support shaft 21 through a pair of longitudinally elongated lateral openings 21 c diametrically opposed to each other, provided in the wall of longitudinally elongated cavity 21 d at a given distance from first end 21 a of support shaft 21. A connection element 23b is slidably arranged within longitudinally elongated cavity 21 d to which two portions 23a of transverse pin 23 are connected, by means of respective torsional elastic elements, not shown. Torsional elastic elements are arranged so as to apply respective elastic torques to portions 23a of the pin, which recall portions 23a back to an open configuration, i.e. away from the operating screw. In other words, the torsional elastic elements are configured to elastically move two portions 23a from a closed configuration, shown in Fig. 42, in which two portions 23a are parallel to each other, to an open configuration, shown in Figs. 44-47, in which two portions 23a are arranged at 180° from each other.

[0125] In the embodiments of Figs. 42-47 and Fig. 48, in order to actuate the displacement 4 of connection element 23b, an operating screw 23c is arranged within longitudinally elongated cavity 21 d which engages with an internally screwed plug element 23d arranged to close first end 21 a of support shaft 21 . Operating screw 23c also engages with a threaded through hole, not shown, of connection element 23b.

[0126] In particular, in the embodiment of Figs. 42-47, the opposite end of the operating screw is connected to the output shaft, not shown, of a driving unit 23f arranged at second end 21 b of support shaft 21 , whereby longitudinally elongated cavity 21 d extends along the full length of support shaft 21 .

[0127] On the contrary, in the embodiment shown in Fig. 48, the operating screw is connected with a handwheel at its first end for manually actuating the rotation of operating screw 23c and, accordingly, the displacement 4 of connection element 23b and transverse abutment 23, so as to open/close the latter.

[0128] In the embodiment of Fig. 49, to actuate displacement 4, connection element 23b is integrally connected to an element selected between the piston 23j and the cylinder 23i of a piston-cylinder assembly 23g that, in a preferred modification, is actuated pneumatically, or even hydraulically.

[0129] In the embodiments of Figs. 48 and 49, longitudinally elongated cavity 21 d of support shaft 21 can extend along a single front portion, i.e., adjacent to to first end 21 a, of limited extension with respect to the overall length of support shaft 21 .

[0130] With reference to the first of the embodiments described just now, Figs. 42-47 show different steps of a positioning sequence of transverse pin 23, coil 3 and locking bar 56. Initially (Fig. 42), the two portions 23a of transverse pin 23 are enclosed in a forward portion of longitudinally elongated cavity 21 d and are maintained in the closed configuration by the wall of tubular support shaft 21. The coil is arranged on the support shaft in a position generically beyond the working position. By actuating operating screw 23c, connection element 23b and two portions 23a of transverse pin 23 perform a translation movement 4 towards longitudinally elongated lateral openings 21 c (Fig. 43) whereby, when the reaction of the wall of tubular support shaft 21 is no longer present, two portions 23a perform opposite rotations 5 until they reach the open configuration (Fig. 44). As the translation movement 4 proceeds, transverse pin 23 is brought to the reference position (Fig. 45) at which the front end of coil 3 is to be positioned. Subsequently (Fig. 46), locking bar 56 is actuated to perform a translation 8 towards the front end 21 a of support shaft 21 , and pushes coil 3 until first end 3a of coil 3 attains the reference position (Fig. 47), after which the cutting cycle of the material wound on coil 3 can be started, as previously described.

[0131] The aforementioned description of specific embodiments is capable of showing the invention from a conceptual point of view in such a way that others, using the known technique, will be able to modify and/or adapt in various applications such specific embodiments without further research and without departing from the inventive concept and, therefore, it is understood that such adaptations and modifications will be considered as equivalents of the specific embodiments. The means and materials for realising the various functions described can be of various kinds without departing from the scope of the invention. It is understood that the expressions or terminology used are purely descriptive and, therefore, not limiting.