The present invention refers to a system comprising a track and a steering carriage.

In the state of the art, systems comprising a circuit, or a track and carriages constrained to move along the track are known. The track comprises rectilinear guide portions, i.e. , with null curvature, and constant curvature curved guide portions with different radii connected to each other.

Curvature means a reciprocal of an osculating radius at a point of an inner or outer side or along a middle line of the guide portion of the track where the curvature is measured.

Constant curvature curved guide portions means that the osculating radius is constant along all the points of the curved guide portion.

A junction between a rectilinear guide portion and a curved guide portion or between two curved guide portions with different radius of curvature, causes a punctual discontinuity of the curvature of the track causing a sudden modification in the acceleration profile of the carriage. Thus, the carriage, when passing on the junction between rectilinear guide portion and curved guide portion, is subjected to vibrations and forces which compromise the useful life of the carriage over time. The same occurs between two curved guide portions with different curvature.

Another problem is that related to the play between carriage caster and track.

Disadvantageously , these two factors of play and discontinuity of the curvature can lead to instability and uncertainty about the control of the position of the carriage along the track.

Object of the present invention is to make a system comprising a track and a carriage which eliminate the clearance between carriage wheels and track and reduce or suppress the vibrations and the forces due to discontinuity in the curvature of the track.

In accordance with the invention, such object is achieved by a system according to claim 1.

Other features are provided in the dependent claims .

The features and the advantages of the present invention will be more apparent from the following, exemplary and not limiting, description, referred to the attached schematic drawings in which: figure 1 is a perspective view of a system comprising a track and a steering carriage according to the present invention; figure 2 is a bottom plan view of the system comprising the track and the steering carriage of figure 1; figure 3 is a sectional view according to the line III-III of figure 2 showing a possible profile of the track according to a cross-section; figure 4 is a perspective view of the steering carriage ; figure 5 is a top plan view of a possible embodiment of the invention formed by three guide portions of the track which are a single piece and form an angle of 90 sexagesimal degrees between the two extreme transverse faces on a geometric plane on which the track rests; figure 6 shows a top plan view of a possible embodiment of the invention formed by five guide portions of the track which are a single piece and form an angle of 180 sexagesimal degrees between the extreme transverse faces thereof on the geometric plane on which the track rests; figure 7 shows a top plan view of a possible embodiment of the invention formed by three guide portions of the track which are a single piece and form an angle of less than 90° between the extreme transverse faces thereof on the geometric plane on which the track rests .

More generally, the guide segment according to the invention can be selected based on the requirements to form any angle between the transverse faces thereof, as long as the continuity of the curvature on the junctions of the track is ensured.

More generally said guide segment according to the invention can be formed by the only variable curvature portion or any combination providing constant, variable, and/or rectilinear curvature.

As particularly shown in figures 1 and 2 a system 100 comprises a track 10 and at least one steering carriage 20 comprising two pairs of load-bearing wheels 31-34 engaged with said track 10.

A plurality of steering carriages 20 can engage the track 10.

The track 10 comprises a plurality of guide portions 11-13 as shown in figures 1, 2, 5, 6, and 7.

The guide portions 11-13 can be divided in more pieces as shown in figures 1 and 2 or be comprised in a single piece block as shown in figures 5-7 embedding the portions 11-13 together. The plurality of guide portions 11-13 of said track

10 comprising at least one variable curvature guide portion 13 wherein a curvature of said at least one variable curvature guide portion 13 varies along a length of said at least one variable curvature guide portion 13.

Preferably said curvature of said at least one variable curvature guide portion 13 varies linearly along the length of said at least one variable curvature guide portion 13 following a clothoid-shaped profile.

The curvature is measured on a point of the guide portion 11-13 which can be an inner side 14 or an outer side 15 or a middle line 16 of the track 10.

Linear variation of the curvature means that the curvature varies linearly along the curvilinear abscissa defined on the inner 14 or outer 15 side or on the midline 16 of the track 10.

Said at least one variable curvature guide portion 13 connects a first end of a first guide portion 11 and a second end of a second guide portion 12 of said plurality of guide portions 11-13 of said track 10.

Advantageously a curvature of a first end of said at least one variable curvature guide portion 13 is equal to a curvature of said first end of said first guide portion 11 and a curvature of a second end of said at least one variable curvature guide portion 13 is equal to a curvature of said second end of said second guide portion 12.

Advantageously the variable curvature guide portion 13 allows to reduce and/or suppress vibrations and forces generated by a direct junction between the first portion

11 and the second portion 12 of the track 10, in particular when one of the two portions 11, 12 is a null curvature rectilinear segment and the other of the two portions 11, 12 is a constant curvature segment, or when one of the two portions 11, 12 is a constant curvature segment and the other of the two portions 11, 12 is a constant curvature segment with different curvature with respect to the first portion.

The track 10 can comprise a plurality of portions 11-13 and connecting portions.

The connecting portions are always variable curvature guide portions 13.

The other guide portions 11-13 of the track 10 can be null curvature rectilinear guide portions, constant curvature guide portions, and variable curvature guide portions .

For example, said at least one variable curvature guide portion 13 combines said first guide portion 11 and said second guide portion 12, wherein at least one of said first guide portion 11 and said second guide portion 12 is a constant curvature guide portion.

For example, said at least one variable curvature guide portion 13 combines said first guide portion 11 and said second guide portion 12, wherein at least one of said first guide portion 11 and said second guide portion 12 is a variable curvature guide portion.

For example, said at least one variable curvature guide portion 13 combines said first guide portion 11 and said second guide portion 12, wherein at least one of said first guide portion 11 and said second guide portion 12 is a null curvature rectilinear guide portion.

For example, said at least one variable curvature guide portion 13 combines said first guide portion 11 and said second guide portion 12 which can be null curvature rectilinear guide portions, constant curvature guide portions, and variable curvature guide portions.

In figures 5-7 for example a track segment comprising a first constant curvature portion 11 and a second rectilinear portion 12, being connected by single piece to each other by means of variable curvature guide portions 13 is reported.

In particular, as shown in figure 5, three single piece guide portions 11-13 of the track 10 form an angle of 90 sexagesimal degrees between extreme transverse faces thereof on a geometric plane on which the track 10 rests .

In particular, as shown in figure 6, five single piece guide portions 11-13 of the track 10 form an angle of 180 sexagesimal degrees between the extreme transverse faces thereof on the geometric plane on which the track 10 rests.

In particular, as shown in figure 7, three single piece guide portions 11-13 of the track 10 form an angle of less than 90° between the extreme transverse faces thereof on the geometric plane on which the track 10 rests .

It is possible to provide that the only variable curvature guide portion 13 can form any sexagesimal angle on the geometric plane on which the track 10 rests and not only those shown in figures 5-7.

Furthermore, it is possible to provide that the variable curvature guide portion 13 by single piece with at least one of the first portion 11 and the second portion 12 can form any sexagesimal angle on the geometric plane on which the track 10 rests and not only those shown in figures 5-7.

Extreme transverse faces mean extreme transverse sections of the respective guide portions 11-13.

As particularly shown in figures 1, 2 and 4 said at least one steering carriage 20 comprises a plate 21 comprising a front axle 22 rotatably mounted with said plate 21, a rear axle 23 rotatably mounted with said plate 21, a first pair of load-bearing wheels 31, 32 is mounted with said front axle 22, a second pair of loadbearing wheels 33, 34 is mounted with said rear axle 23.

Each pair of load-bearing wheels 31, 32 or 33, 34 comprises a wheel 31, 33 engaged with the outer side 15 of the track 10 and a wheel 32, 34 engaged with the inner side 14 of the track 10.

Advantageously the steering wheel carriage 20 allows to suppress the play between track 10 and carriage 20.

Even more preferably said front axle 22 is rotatably mounted with said plate 21 independently of said rear axle 23.

The front axle 22 is rotatably mounted with said plate 21 by means of a pin 24 and at least one pad.

The rear axle 23 is rotatably mounted with said plate 21 by means of a pin 25 and at least one pad.

Even more advantageously as shown in figure 3 it is provided that said track 10 comprises a cross-section of constant width H, wherein said width H of the crosssection of said track 10 corresponds to a distance between an inner side 14 and an outer side 15 of said track 10.

More preferably the cross-section of said track 10 comprises a constant height profile (Z) tapering to the sides 14, 15 as shown in figure 3.

Tapering means that the height Z is reduced towards both the inner side 14 and the outer side 15 of the track 10.

More preferably the height Z of the cross-section of said track 10 is linearly reduced.

The shape of the profile of the cross-section of said track 10 is complementary to the shape of the wheels 31-34 of the carriage 20 so that the carriage 20 is constrained in its movement to the track 10.

More preferably it is provided that at least one load-bearing wheel 31-34 of each pair of wheels 31-34 of said two pairs of load-bearing wheels 31-34 is of the concentric type.

More preferably it is provided that at least one load-bearing wheel 31-34 of each pair of wheels 31-34 of said two pairs of load-bearing wheels 31-34 is of the eccentric type.

Two wheels 31-34 of a same pair of wheels 31-34 mounted on the same axle 22, 23 can be both concentric, both eccentric, or one concentric and the other eccentric .

Advantageously each axle 22, 23 is independent and the track 10 according to the present invention has a cross-section of constant width H, the play is totally suppressed and the preload on the wheels 31-34 of the carriage is ideally the same on each point of the track 10.

Advantageously the track 10 according to the present invention simultaneously allows the wheels 31- 34 and thus the carriage 20 itself to switch from a straight segment to a curved segment and vice versa, without running into sudden variations of speed during motion, due to the presence of discontinuity on the profile of curvature of the guided path.

Advantageously the system 100 according to the present invention allows to suppress the play along all the track 10 and allows to ideally reduce and/or suppress impacts and vibrations, thus allowing a much lower maintenance, further allows a strong reduction in operating noise.

Alternatively, and more generally, it is possible to provide that said curvature of said at least one variable curvature guide portion 13 varies according to the Cesaro equation representing the curvature "k" : along the length of said at least one variable curvature guide portion 13 following a clothoid-shaped profile, wherein "s" is a coordinate which follows the length of said at least one variable curvature guide portion 13 measured on the inner side 14 or on the outer side 15 or on the midline 16, "n" represents a parameter, if n=l, then the variation of the curvature is linear, "a" represents another numerical parameter.

In said more general alternative, if the parameter "n" is different from 1, then the variation of the curvature along the length of the at least one variable curvature portion 13 should ensure the continuity between the other two portions 11, 12 it is connected to .

Alternatively, it is possible to provide that said at least one variable guide portion 13 varies according to a quadratic equation conic along the length of said at least one variable curvature guide portion 13. Quadratic equation conic means for example a parabola, an ellipse, a hyperbole. According to this alternative, the variable guide portion 13 varies according to the square of at least one spatial coordinate. The track rests on a geometric plane defined by two spatial coordinates x and y, thus the variable guide portion 13 varies according to the square of at least one of the two spatial coordinates x and y. Alternatively, it can vary according to the square of both the spatial coordinates x and y. More generally, the curvature varies with a quadratic equation in the form ax ² + 2bxy + cy ² + 2dx + 2ey + f = 0 where a, b, c, d, e, f represent constants.

If b ² -ac is equal to zero, then the equation represents a parabola, if less than 0, then it is an ellipse, otherwise if more than zero, then it is a hyperbole .

Alternatively, the variable curvature guide portion 13 is defined according to a spline function along the length of said at least one variable curvature guide portion 13. In said alternative the spline function is a polynomial function of selected degree and coefficients such that the polynomial function has both a first derivative and a second derivative continuous at each point of said at least one portion of variable curvature guide 13, where each point of the at least one variable curvature guide portion 13 means each point at least of the middle line 16 or at least of the inner side 14 or at least of the outer side 15 of the at least one variable curvature guide portion 13.

Alternatively, and more generally, the variable curvature guide portion 13 varies according to a function of at least class C ² along the length of said at least one variable curvature guide portion 13.

It is specified that said at least one variable curvature guide portion 13 varies continuously along a length of said at least one variable curvature guide portion 13, these words meaning that it varies continuously according to a function of class C ² which suppresses curvature discontinuity in the connecting points representing the variable curvature guide portion 13 between guide portions of different curvature 11-13. The functions of class C ² have first and second derivatives continuous at each point at least of the middle line 16 or at least of the inner side 14 or at least of the outer side 15 of the at least one variable curvature guide portion 13.

It is specified that the conic sections, the quadratic equations, the spline functions and the clothoid reported in the previous exemplary embodiments are functions of class C ² .

Alternatively, it is possible to provide that the profile of the cross-section of the track 10 has different shapes from those represented in figure 3 but keeps the width H between the inner side 14 and the outer side 15 of the track 10 constant. The different shapes of the profile of the cross-section of the track 10 depend on the complementary shape of the wheels 31-34 of the carriage 20. The invention thus conceived is susceptible to a number of modifications and variations, all falling within the scope of the inventive concept. Practically, the used materials, as well as the size, can be whatever depending on the technical requirements.