FIELD OF THE INVENTION

The present invention relates to the technical sector concerning numerically controlled automatic cutting machines for cutting sheet materials, such as skins, leather sheets, hides, synthetic leathers, etc.

In particular, the present invention relates to an improved pneumatic cutting device having an oscillating blade destined to be mounted on the cutting machines.

DESCRIPTION OF THE PRIOR ART

As is known, cutting machines comprise: a work plane, where the materials to be cut are laid out, such as for example leather sheets, synthetic skins and the like; a frame, mounted movably above the work plane; and a cutting device mounted on the frame and inferiorly provided with a cutting blade.

Movement means are also comprised, which are borne by the frame so as to move the cutting device according to the three Cartesian axes above the work plane.

In this way, the cutting device can be positioned above the leather sheets, and the cutting blade can be lowered to score the leather and be moved according to a given cutting pathway so as to cut the skins on the basis of prefixed and/or desired profiles.

The cutting devices used for this purpose are predisposed so that the cutting blade can be made to oscillate vertically during the cutting of the leather sheets, from a lower cutting position to an upper cutting position, while always remaining within the thickness of the material to be scored/cut.

For this purpose, at present pneumatically-powered cutting devices are particularly used in which the cutting blade is made to oscillate vertically by means of a pneumatic supply (for example compressed air). A known pneumatic cutting device with an oscillating blade is for example described in International Patent Application WO2018/203199, filed in the name of the same Applicant.

This pneumatic cutting device (90) comprises a body (C) and a cutting blade (L) for cutting a leather sheet stretched on a work plane.

This pneumatic cutting device (90) is realised and configured in such a way as to pneumatically activate the cutting blade (L) in order that it can oscillate vertically so as to score and cut the leather sheet.

Figures 1A and 1B illustrate, in respective frontal views, the improved pneumatic cutting device (90) described in this document, with the cutting blade (L) represented in two different operating configurations attainable during oscillation thereof, respectively a lower cutting position (L1) (see figure 1A) and an upper cutting position (L2) (see figure 1 B).

The cutting device (90) is realised in such a way as to comprise, internally of the body (C), an oscillating chamber (1), which is conformed in such a way as to have an upper end-run wall (11) and a lower end-run wall (12), and an oscillating piston (10), having a head (13) and a rod (14) (see figures 2A and 2B).

The oscillating piston (10) is arranged with the head (13) thereof inserted in the oscillating chamber (1), between the upper end-run wall (11) and the lower end-run wall (12), the rod (14) being connected to the cutting blade (L).

When the head (13) of the oscillating piston (10) is in abutment against the lower end-run wall (12) of the oscillating chamber (1) (figure 2A), the cutting blade (L) is in the lower cutting position (L1), while when the head (13) of the oscillating piston (10) is in abutment against the upper end-run wall (11) of the oscillating chamber (1) (figure 2B), the cutting blade (L) is in the upper cutting position (L2).

The upper end-run wall (11) is arranged in the body (C) at a distance with respect to the lower end-run wall (12) so that, when the head (13) of the oscillating piston (10) reaches contact with the upper end-run wall (11), the cutting blade (L) reaches an upper cutting position (L2) such that it remains substantially in contact with the leather sheet to be cut, or slightly extracted, with the aim of guaranteeing continuity to the cutting operation.

The distance between the upper wall (11) and the lower wall (12) thus determines the entity of the oscillation stroke that the cutting blade (L) can make.

For the pneumatic activation of the oscillation of the head (13) of the oscillating piston (10) in the relative oscillating chamber (1), and thus for the vertical oscillation of the cutting blade (L), the pneumatic cutting device (90) is provided with a relative pneumatic activating system (P) communicating with the oscillating chamber (1).

The pneumatic cutting device (90) realised according to what is described in this patent application belonging to the Applicant is able to carry out the switching of the oscillating piston (10) stroke entirely automatically, i.e. without the presence of external valve organs and/or switching organs, due to the following characteristics: the particular conformation of the rod (14) of the piston (10), the special conformation of the head (13) of the piston (10) and the special conformation of the pneumatic supply system (P).

These particular characteristics are illustrated in detail in figures 2A and 2B which illustrate the views along section lines l-l, and ll-ll respectively of figures 1A and 1B.

The pneumatic activating system (P) comprises a pneumatic supply source (for example compressed air), denoted schematically by arrow (P1), an upper discharge (S1) and a lower discharge (S2).

The body (C) is made in such a way as to comprise a cylindrical cavity (16) and the rod (14) of the oscillating piston (10) is predisposed so as to be slidable alternatingly in the cylindrical cavity (16).

Further, the rod (14) of the oscillating piston (10) is conformed in such a way as to have, in a relative sliding part in the cylindrical cavity (16) below the oscillating chamber (1), and thus in a lower position than the head (13): an upper annular portion (141) and a lower annular portion (142), which are in sliding contact with the walls of the cylindrical cavity (16); an annular recess (140), comprised between the two annular portions (141, 142); and an internal conduit (17).

The rod (14) is further provided with through-holes (18) which are predisposed along the rod (14) in a position below the lower annular portion (142) and such as to place the internal conduit (17) in communication with the outside of the rod (14).

The head (13) of the oscillating piston (10) is provided with at least a through- hole (130) which is arranged so as to place the internal conduit (17) of the rod (14) in communication with a part (1B) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11) of the oscillating chamber (1).

The pneumatic activating system (P) is arranged and configured in the following way.

It comprises: a switching chamber (8) of the oscillation of the oscillating piston (10) which is conformed in such a way as to comprise an upper annular chamber (8A) and a lower annular chamber (8B) realised in a portion of the walls of the cylindrical cavity (16) in a position below the oscillating chamber (1) at the oscillation zone of the two annular portions (141, 142) of the rod (14); a main conduit (81) which is realised and predisposed in the body (C) so as to be in communication, on one side, with the pneumatic supply source (P1) and, on the other side, with a part of the lower annular chamber (8B) of the switching chamber (8); a secondary conduit (82) realised and predisposed in the body (C) so as to place the upper annular chamber (8A) of the switching chamber (8) in communication with the oscillating chamber (1) via a passage hole (83) realised in the lower end-run wall (12) of the oscillating chamber (1).

The upper discharge (S1) is made in a portion of the walls of the cylindrical cavity (16) below the oscillating chamber (1) and above the upper annular chamber (8A) of the switching chamber (8), and communicating with the outside via a first discharge conduit (92) also realised and predisposed in the body (C).

In turn, the lower discharge (S2) is made in a portion of the walls of the cylindrical cavity (16) below the oscillating chamber (1) and below the lower annular chamber (8B) of the switching chamber (8), and communicates with the outside via a second discharge conduit (94) realised and predisposed in the body (C).

Further, the annular recess (140) of the rod (14) has dimensions so that the holes (18) of the rod (14) are positioned below the lower annular portion (142) and with respect to the annular recess (140) in such a way that, with the alternating sliding of the rod (14) in the cylindrical cavity (16) the following conditions occur: when the annular recess (140) of the rod (14) is positioned at the switching chamber (8) so as to place the lower annular chamber (8B) and the upper annular chamber (8A) in communication, the holes (18) of the rod (14) are positioned at the lower discharge (S2) (see figure 2A), so that the main conduit (81) is in communication, via the lower annular chamber (8B), the annular recess (140) and the upper annular chamber (8A), with the secondary conduit (82) and therefore the pneumatic supply source (P1) is in communication with the part (1A) of the oscillating chamber (1) comprised between the head (13) of the oscillating piston (10) and the lower end-run wall (12) (see the arrows with the continuous line, again in figure 2A), while the part (1 B) of the oscillating chamber (1), comprised between the head (13) of the oscillating piston (10) and the upper end-run wall (11), is in communication with the lower discharge (S2), and then via the second discharge conduit (94) with the outside, through the hole (130) of the head (13) of the piston (10), the internal conduit (17) of the rod (14) and the holes (18) of the rod (14) (see the arrows with the broken line in figure 2A), so that the oscillating piston (10) can be pneumatically pushed upwards; and when the annular recess (140) of the second upper rod part (14) is positioned at both the upper discharge (S1) and in the upper annular chamber (8A) of the switching chamber (8) communicating with the secondary conduit (82), the holes (18) of the rod (14) are at the lower annular chamber (8B) of the switching chamber (8) and are therefore in communication with the main conduit (81) (see figure 2B), so that the source of pneumatic power supply (P1), via the main conduit (81), the holes (18) of the rod (14), the internal conduit (17) of the rod (14) and the hole (130) present in the head (13) of the oscillating piston (10), is in communication with the second part (1 B) of the oscillating chamber (1) between the upper end-run wall (11) and the head (13) of the oscillating piston (10) (see the arrows with the continuous line, again in figure 2B), while the first part (1A) of the oscillating chamber (1) between the head (13) of the oscillating piston (10) and the lower end-run wall (12) is in communication with the upper discharge (S1) via the secondary conduit (82), the upper annular chamber (8A) of the switching chamber (8) and the annular recess (140), and then via the first discharge conduit (92) with the outside environment (see the arrows with the broken line in figure 2B), so that the oscillating piston (10) can be pneumatically pushed downwards.

Owing to the special characteristics as set out in the foregoing, in the pneumatic cutting device (90) described in the above-mentioned patent application belonging to the Applicant, the switching of the oscillation of the piston is activated and determined by the piston, according to the position of the relative rod with respect to the cylindrical cavity of the body, and in particular of the relative annular recess with respect to the switching chamber (upper annular chamber and lower annular chamber) and the two discharges (upper discharge and lower discharge). This pneumatic cutting device has been found to be very effective for carrying out the cutting of materials in sheet form, such as leather sheets and/or hides.

Over time, the Applicant has however encountered the need to be able to more accurately control the step of inverting the oscillating motion of the oscillating piston, which occurs together with the impact of the oscillating piston head against the upper and lower end run walls, as well as to be able to obtain a greater oscillation velocity with a smaller use of compressed air on the part of the pneumatic supply source.

SUMMARY OF THE INVENTION

An aim of the present invention is therefore to disclose a new improved pneumatic cutting device having an oscillating blade for leather cutting machines able to attain the aims as indicated in the foregoing.

Further, another aim of the present invention is to provide a novel improved pneumatic cutting device having a more functional and less complex overall structure, and which thus enables a simplification at production level.

The above-cited aims are attained with an improved pneumatic cutting device having an oscillating blade for leather cutting machines according to the contents of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics of a preferred embodiment of the improved pneumatic cutting device with an oscillating blade for leather cutting machines of the invention are described in the following with reference to the accompanying tables of drawings, in which:

- figures from 1A to 1 B illustrate, mentioned in the foregoing, in respective frontal views, the pneumatic cutting device described in the above-mentioned patent application cited and filed by the same Applicant, with the cutting blade represented in two different operating positions, respectively a lower cutting position (L1) in figure 1A, and an upper cutting position (L2) in figure 1B; - figure 2A is a larger-scale view along section plane l-l of figure 1A;

- figure 2B is a larger-scale view along section plane ll-ll of figure 1B;

- figures from 3A to 3C illustrate, in respective frontal views, the improved pneumatic cutting device of the present invention, illustrated with the cutting blade represented in three different operating positions, respectively a lower cutting position (L1) in figure 3A, an intermediate cutting position (LM) in figure 3B, and an upper cutting position (L2) in figure 3C;

- figure 4A is a larger-scale view along the transversal and vertical section plane Ill-Ill of figure 3A;

- figure 4B is a larger-scale view along the transversal and vertical section plane IV-V of figure 3B;

- figure 4C is a larger-scale view along the transversal and vertical section plane V-V of figure 3C;

- figure 5A is a larger-scale view along the transversal and vertical section plane of the improved pneumatic cutting device of the invention in a cutting position between the intermediate cutting position (LM) and the upper cutting position (L2);

- figure 5B is a larger-scale view along the transversal and vertical section plane of the improved pneumatic cutting device of the invention in a cutting position between the intermediate cutting position (LM) and the lower cutting position (L1).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the appended tables of drawings, reference numeral (100) denotes the improved pneumatic cutting device with an oscillating blade for leather cutting machines of the present invention, in its entirety.

The improved pneumatic cutting device (100) comprises some of the same characteristics as the pneumatic cutting device of the above-mentioned and described patent application belonging to the same Applicant, in particular concerning the usual general characteristics present in pneumatic cutting devices.

Therefore, in the following description, the parts of the improved pneumatic cutting device (100) of the present invention that correspond to those described in the foregoing for the pneumatic cutting device of the mentioned patent application will be indicated using the same numerals and letters.

The improved pneumatic cutting device (100) therefore comprises a body (C), a cutting blade (L) for cutting a leather sheet stretched on a work plane (the leather sheet and work plane are not illustrated in the figures, as they are not pertinent to the invention).

The improved pneumatic cutting device (100) in this regard is predisposed and configured so as to be mountable on cutting machines, for example numerically controlled.

The device is configured and predisposed in such a way as to pneumatically activate the cutting blade (L) in order that it can oscillate vertically so as to score and cut the leather sheet.

Figures from 3A to 3C illustrate, in frontal views, the improved pneumatic cutting device (100) of the invention, with the cutting blade (L) represented in different operating configurations attainable during oscillation thereof, respectively a lower cutting position (L1) (see figure 3A), in which the cutting blade (L) crosses the whole thickness of the leather, an intermediate cutting position (LM) (figure 3B) in which the cutting blade (L) is internal of the thickness of the leather sheet, and an upper cutting position (L2) (figure 3C), in which the cutting blade (L) is substantially at the top of the leather sheet.

The improved pneumatic cutting device (100) is provided, internally of the body (C), with an oscillating chamber (1), which is conformed in such a way as to define an upper end-run wall (11), a lower end-run wall (12) and a lateral surface (10A) between the upper end-run wall (11) and the lower end-run wall (12), and an oscillating piston (10). The oscillating piston (10) comprises a head (13) and a rod (14), the oscillating piston (10) is predisposed with respect to the body (C) so that the head (13) thereof is inserted in the oscillating chamber (1), between the upper end-run wall (11) and the lower end-run wall (12), and with the rod (14) slidably arranged in a sliding seat (14A), realised longitudinally in the body (C), and communicating with the oscillating chamber (1), to enable the rod to be connected, by the opposite end to the end to which it is connected to the oscillating piston (10), to the cutting blade (L) (see for example figures 4A to 5C).

The rod (14) comprises a proximal portion (148), connected to the head (13) of the oscillating piston (10), and a distal portion (149) which is connected to the cutting blade (L).

For example, the sliding seat (14A) can have a cylindrical shape with the upper part communicating with the oscillating chamber (1) via a through- window made in the lower end-run wall (12), and the rod (14) can also have a cylindrical shape.

The head (13) of the oscillating piston (10) is conformed in such a way as to comprise an upper abutment surface (131), a lower abutment surface (132) and a lateral surface (130), between the upper abutment surface (131) and the lower abutment surface (132).

For the oscillation of the head (13) in the oscillating chamber (1), the cutting device (100) comprises a pneumatic activating system (P) comprising a pneumatic supply source (P1) (schematically illustrated by a continuous arrow line).

The pneumatic activating system (P) is configured so that a first part (1A) of the oscillating chamber (1) comprised between the lower abutment surface (132) of the head (13) of the oscillating piston (10) and the lower end-run wall (12), and a second part (1 B) of the oscillating chamber (1) comprised between the upper abutment surface (131) of the head (13) of the oscillating piston (10) and the upper end-run wall (11), are placed in communication alternatively with the pneumatic supply source (P1).

In this way, pneumatically, by the injection of compressed air, the head (13) of the oscillating piston (10) is made to oscillate inside the oscillating chamber (1) between a lower end-run position (PL) (see figure 4A), in which the lower abutment surface (132) of the head (13) is in abutment against the lower endrun wall (12), and an upper end-run position (PS) (see figure 4C), in which the upper abutment surface (131) of the head (13) is in abutment against the upper end-run wall (11), and then make the rod (14), and consequently the cutting blade (L), oscillate vertically between a lower cutting position (L1) (figure 3A) of the leather sheet, and an upper cutting position (L2) (figure 3C) of the leather sheet.

The oscillating chamber (1) is conformed in such a way that the upper end-run wall (11) is arranged at a distance with respect to the lower end-run wall (12) so that, when the upper abutment surface (131) of the head (13) of the oscillating piston (10) reaches into contact against the upper end-run wall (11), the cutting blade (L) reaches an upper cutting position (L2) such that it remains substantially in contact with the leather sheet to be cut, or (possibly) slightly extracted, with the aim of guaranteeing continuity to the cutting operation.

The special characteristics of the improved pneumatic cutting device (100) of the present invention relate to the special conformation of the rod, in the relative proximal portion (148) in proximity of the head (13) of the oscillating piston (10), and the particular conformation and configuration of the pneumatic activating system (P) responsible for the oscillation of the head (13) of the piston (10) in the oscillating chamber (1), and therefore responsible also for the vertical oscillation of the cutting blade (L), as described in detail in the following.

The proximal portion (148) of the rod (14) is realised and configured in such a way as to have a respective transversal section lower than the transversal section of the sliding seat (14A), in such a way that, during the oscillation of the rod (14), between the proximal portion (148) of the rod (14) and the sliding seat (14A) a passage channel (150) is defined that communicates with the first part (1A) of the oscillating chamber (1) comprised between the lower abutment surface (132) of the head (13) and the lower end-run wall (12), and the distal portion (149) of the rod (14) has a respective transversal section such as to be able to sealingly slide with the sliding seat (14A).

The pneumatic activating system (P) is made and configured in such a way as to comprise: a switching chamber (30) realised in the body (C) in a lower position than the oscillating chamber (1) and which is communicating with the sliding seat (14A) of the rod (14); a main supply conduit (61), which is realised in the body (C) and which is arranged and configured in such a way that a first end (61A) of the main supply conduit (61) is in communication with the pneumatic supply source (P1) and a second end (61 B) of the main supply conduit (61) is in communication with the switching chamber (30); a secondary supply conduit (62) which is realised in the head (13) of the oscillating piston (10) and internally of the rod (14), and which has an extension such that it comprises a first end (62A), at a first passage hole (F1) realised in the upper abutment surface (131) of the head (13), in such a way that the secondary supply conduit (62) is in communication with the second part (1B) of the oscillating chamber (1) comprised between the upper abutment surface (131) of the head (13) and the upper end-run wall (11), and a second end (62B) at a second passage hole (F2) realised on a portion of the lateral surface of the distal portion (149) of the rod (14) in such a way that the secondary supply conduit (62) is in communication with the outside of the rod (14); a first discharge hole (51), in communication with the outside, which is made in the lateral surface (10A) of the oscillating chamber (1) at an upper part (30A) of the oscillating chamber (1); a second discharge hole (52), in communication with the outside, which is made in the lateral surface (10A) of the oscillating chamber (1) below the first discharge hole (51) and at a lower part (30B) of the oscillating chamber (1).

In greater detail, the head (13) of the oscillating piston (1) is dimensioned, the rod (14) is dimensioned and the switching chamber (30) is realised in the body (C) in a lower position than the oscillating chamber (1) so that: when the head (13) of the oscillating piston (1) is in the lower end-run position (PL), with the lower abutment surface (132) of the head (13) in abutment against the lower end-run wall (12) (see for example figure 4A), the rod (14) is in a position with respect to the sliding seat (14A) such that the passage channel (150) defined between the proximal portion (148) of the rod (14) and the sliding seat (14A) is in communication with the switching chamber (30), the second passage hole (F2) present in the distal portion (149) of the rod (14) is closed by the lateral surface of the sliding seat (14A), the first discharge hole (51) is in communication with the upper part (30A) of the oscillating chamber (1) and the second discharge hole (52) is closed by the lateral surface (130) of the head (13), therefore the main supply conduit (61) (see the arrows with the continuous line in figure 4A), via the switching chamber (30) and the passage channel (150) is in communication with the first part (1A) of the oscillating chamber (1) comprised between the lower abutment surface (132) of the head (13) and the lower end-run wall (12) while the second part (1B) of the oscillating chamber (1) comprised between the upper abutment surface (131) of the head (13) and the upper end-run wall (11) (see the arrows with the continuous line in figure 4A) is in communication, via the first discharge hole (51), with the outside, so that the pneumatic supply source (P1) is in communication with the first part (1A) of the oscillating chamber (1) while the second part (1B) of the oscillating chamber (1) is in communication with the outside, so that the oscillating piston (10) can be pneumatically pushed upwards; when the head (13) of the oscillating piston (1) is in the upper end-run position (PS), and the upper abutment surface (131) of the head (13) is in abutment against the upper end-run wall (11) (see figure 4C), the rod (14) is in a position, with respect to the sliding seat (14A) such that the passage channel (150) defined between the proximal portion (148) of the rod (14) and the sliding seat (14A) is no longer in communication with the switching chamber (30), the second passage hole (F2) present in the distal portion (149) of the rod (14) is in communication with the switching chamber (30), the first discharge hole (51) is closed by the lateral surface (130) of the head (13) and the second discharge hole (52) is in communication with the lower part (30B) of the oscillating chamber (1), and therefore the main supply conduit (61) (see the arrows with the continuous line in figure 4C), via the switching chamber (30), the second passage hole (F2), the secondary supply conduit (62) and the first passage hole (F1) is in communication with the second part (1 B) of the oscillating chamber (1) comprised between the upper abutment surface (131) of the head (13) and the upper end-run wall (11) while the first part (1A) of the oscillating chamber (1) (see the arrows with the continuous line in figure 4C) between the lower abutment surface (132) of the head (13) and the lower endrun wall (12) is in communication, via the second discharge hole (52), with the outside, so that the pneumatic supply source (P1) is in communication with the second part (1 B) of the oscillating chamber (1) while the first part (1A) of the oscillating chamber (1) is in communication with the outside so that the oscillating piston (10) can be pneumatically pushed downwards.

Therefore, in the improved pneumatic cutting device (100) of the present invention, the switching of the oscillation of the oscillating piston (10) in the oscillating chamber (1) takes place automatically and owing to the presence of the switching chamber (30) which via the passage channel (150), present between the proximal portion (148) of the rod (14) and the sliding seat (14A), and the secondary supply conduit (62), present internally of the rod (14) and the head (13) of the oscillating piston (10), is placed in communication alternatively with the first part (1A) and the second part (1B) of the oscillating chamber (1).

Further, the discharge holes are realised in such a way as to be directly communicating with the oscillating chamber (1) (the first discharge hole (51) communicating with the upper part (30A) of the oscillating chamber (1) and the second discharge hole (52) communicating with the lower part (30B) of the oscillating chamber (1)), which enables a reduction in the extension and overall length of the piston rod.

Consequently, the improved pneumatic cutting device of the present invention has a smaller and less complex structure, in particular in the structure of the oscillating piston, as in the relative rod, in the part situated below the oscillating chamber, the two annular projections and the annular recess are no longer present.

Further, the presence of the passage channel, between the proximal portion of the rod and the sliding seat, renders superfluous the realising of secondary conduits in the device body which were necessary for placing the switching chamber in communication with the first part of the oscillating chamber comprised between the oscillating piston head and the lower end-run wall.

Definitively, therefore, the structure of the oscillating piston (head plus rod) is simpler and slimmer, and can also be realised with a smaller dimension (length of the lower rod) with respect to the cutting device of the document cited in the foregoing.

Consequently, the improved pneumatic cutting device proposed by the present invention is lighter and therefore able to reach an activation velocity, i.e. switching the oscillation stroke of the oscillating piston, and therefore of the velocity of the cutting blade, significantly greater with respect to the prior art case.

Further, the flow path for supply of compressed air supply is shorter, enabling the obtaining of a greater fluid-dynamic efficiency, reducing the time required for filling and emptying, and with a consequent improvement both in terms of increase of velocity and of lower consumption of compressed air.

Further particularly advantageous aspects of the improved pneumatic cutting device (100) of the present invention are as follows.

The head (13) of the oscillating piston (10) and the rod (14) are further conformed and dimensioned in such a way that when the head (13) is located, in the oscillating chamber (1), in an intermediate position (PM) between the lower end-run position (PL) and the upper end-run position (PS) (see figure 4B), the lower abutment surface (132) is at a first distance from the lower endrun wall (12) and the upper abutment surface (131) is at a second distance from the upper end-run wall (11) equal to the first distance, the first discharge hole (51) and the second discharge hole (52) are closed by the lateral surface (130) of the head (13) and the switching chamber (30) is closed by a portion of the lateral surface of the distal portion (149) of the rod (14), in such a way that the first part (1A) and the second part (1B) of the oscillating chamber (1) are isolated with respect to the pneumatic supply source (P1) and with respect to the outside.

This enables obtaining a sort of control on the deceleration of the piston before the head reaches the end run position, lower or upper, for the inversion of the oscillation stroke.

In practice, as will be described in detail in the following, a sort of air cushion is created that performs a braking action and thus a slowing action of the piston stroke.

Further, before the piston head reaches contact against the upper end-run wall (see figure 5A) or against the lower end-run wall (see figure 5B), a flow of compressed air will act thereon, contrary to the displacement direction thereof (the one responsible for the inversion of the oscillation thereof) which will further contribute to slowing the stroke and thus significantly reducing the entity of the contact against the upper and lower end run walls.

For example, take, for reference, the lower end-run position (PL) of the head (13) of the oscillating piston (10) internally of the oscillating chamber (1) in which the lower abutment surface (132) of the head (13) is in contact with the lower end-run wall (12) (see the situation illustrated in figure 4A).

In this situation, as illustrated in the foregoing: the rod (14) is in a position, with respect to the sliding seat (14A) such that the passage channel (150) defined between the proximal portion (148) of the rod (14) and the sliding seat (14A) is in communication with the switching chamber (30), the second passage hole (F2) present in the distal portion (149) of the rod (14) is closed by the lateral surface of the sliding seat (14A); the first discharge hole (51) is in communication with the upper part (30A) of the oscillating chamber (1) while the second discharge hole (52) is closed by the lateral surface (130) of the head (13).

Therefore the main supply conduit (61), via the switching chamber (30) and the passage channel (150) is in communication with the first part (1A) of the oscillating chamber (1) comprised between the lower abutment surface (132) of the head (13) and the lower end-run wall (12) while the second part (1B) of the oscillating chamber (1), comprised between the upper abutment surface (131) of the head (13) and the upper end-run wall (11), is in communication, via the first discharge hole (51), with the outside.

In this way, the compressed air coming from the pneumatic supply source (P1) (see the arrows in constant lines, again in figure 4A), via the main supply conduit (61), the switching chamber (30), the passage channel (150), reaches the first part (1A) of the oscillating chamber (1).

As the second part (1B) of the oscillating chamber (1) is in communication, via the first discharge hole (51), with the outside, the head (13) is thrust by the compressed air entering the first part (1A) of the oscillating chamber (1) in an upwards direction, i.e. towards the upper end-run wall (11), and the air present in the second part (1B) of the oscillating chamber (1) is discharged to the outside environment (see the arrows in broken lines, again in figure 4A).

As it rises, the head (13) of the oscillating piston (10) reaches the intermediate position (PM), see figure 4B, at which, for a very short time, the first discharge hole (51) and the second discharge hole (52) are both closed by the lateral surface (130) of the head (13), and the switching chamber (30) is closed by a part of the lateral surface of the distal portion (149) of the rod (14) so that both the first part (1A) of the oscillating chamber (1) comprised between the lower abutment surface (132) of the head (13) and the lower end-run wall (12), and the second part (1 B) of the oscillating chamber (1), comprised between the upper abutment surface (131) and the upper end-run wall (11), are isolated with respect to the pneumatic supply source (P1) and with respect to the outside.

In this configuration, the head (13) of the oscillating piston (10) is no longer subjected to an upwards thrust (as the passage channel (150) is no longer in communication with the switching chamber (30), and therefore with the main supply conduit (61) and the upwards displacement thereof, which thus occurs by inertia, is opposed by an air cushion which is created in the second part (1B) of the oscillating chamber (1) as it is no longer in communication with the outside (the first discharge hole (51) is closed by the lateral surface (130) of the head (13)).

Therefore, in substance, the upwards run of the piston head experiences a first slowing down.

As it proceeds in its inertia run upwards (i.e. towards the upper end-run wall (11), the head (13) of the oscillating piston (10) will pass through the intermediate position (PM) (see figure 4B) reaching an interposed position between the intermediate position (PM) and the upper end-run position (PS), which is illustrated in figure 5A.

In the position of the head (13) illustrated in figure 5A, in which the head (13) has passed beyond the intermediate position (PM) thereof but is still to reach the upper end-run position (PS), the second passage hole (F2) present in the lateral surface distal portion (149) of the rod (14) will begin to face the switching chamber (30), placing the secondary supply conduit (62) in communication with the main supply conduit (61), and thus with the pneumatic supply source (P1), while the second discharge hole (52), no longer completely closed by the lateral surface (130) of the head (13), will begin to be in communication with the first part (1A) of the oscillating chamber (1).

Therefore, before the head (13) of the oscillating piston (10), proceeding by inertia in its upwards stroke, i.e. towards the upper end-run wall (11), reaches into abutment with the upper abutment surface (131) against the upper endrun wall (11), there will be a moment in which the second part (1B) of the oscillating chamber (1), comprised between the upper abutment surface (131) and the upper end-run wall (11), is already in communication with the pneumatic supply source (P1), and therefore the compressed air (see the arrows with the continuous line in figure 5A) already begins entering the second part (1B) of the oscillating chamber (1), performing a further braking action, and a slowing down, on the head (13) of the oscillating piston (1), therefore significantly reducing the entity of the contact between the upper abutment surface (131) of the head (13) and the upper end-run wall (11).

In correspondence with the inversion of the direction of oscillation of the oscillating piston (from above downwards) there will be fewer stresses, fewer vibrations and less noise.

The same situation will occur once the oscillation stroke of the oscillating piston head is inverted, and therefore when the oscillating piston head passes from the upper end-run position (PS) (figure 4C) to the lower end-run position (PL) (figure 4A), newly passing through the intermediate position (PM) (figure 4B).

Once the intermediate position (MP) has been passed (figure 4B, in which both the first part (1A) and the second part (1 B) of the oscillating chamber (1) are isolated with respect to both the pneumatic supply source (P1) and to the outside environment, as described in the foregoing) and proceeding in its run by inertia in a downwards direction (i.e. towards the lower end-run wall (12)), the head (13) of the oscillating piston (10) reaches an interposed position between the intermediate position (PM) and the lower end-run position (PS), illustrated in figure 5B.

In the position of the head (13) illustrated in figure 5B, in which the head (13) has passed beyond the intermediate position (PM) thereof but is still to reach the lower end-run position (PS), the second passage hole (F2) present in the lateral surface of the distal portion (149) of the rod (14) will be closed by the lateral surface of the sliding seat (14A), the passage channel (150) will begin to face, and to be in communication with, the switching chamber (30) and thus the main supply conduit (61), and thus with the pneumatic supply source (P1), while the first discharge hole (51), no longer closed by the lateral surface (130) of the head (13), will begin to be in communication with the second part (1 B) of the oscillating chamber (1).

Therefore, before the head (13) of the oscillating piston (10), proceeding by inertia in its downwards stroke, i.e. towards the lower end-run wall (12), reaches into abutment with the lower abutment surface (132) against the lower end-run wall (12), there will be a moment in which the first part (1A) of the oscillating chamber (1) comprised between the lower abutment surface (132) and the lower end-run wall (11), is already in communication with the pneumatic supply source (P1), and therefore the compressed air (see the arrows with the continuous line in figure 5B) begins entering the first part (1A) of the oscillating chamber (1), performing a further braking action, and a slowing down, on the head (13) of the oscillating piston (1), therefore significantly reducing the entity of the contact between the lower end-run surface (132) of the head (13) and the lower end-run wall (12).

In this case, therefore, in correspondence with the inversion of the direction of oscillation of the oscillating piston (from below upwards) there will be fewer stresses, fewer vibrations and less noise.

In a preferred aspect, the pneumatic supply system (P) is made in such a way as to comprise a discharge conduit (41) realised in the body (C) and which is arranged in such a way as to have a first end (41A) in communication with the outside and comprising a first branch conduit (411) and a second branch conduit (412).

The first branch conduit (411) is in communication with the first discharge hole (51) while the second branch conduit (412) is in communication with the second discharge hole (52).