Guide structure for chains for an article conveyer

Abstract

A guide structure for a chain for an article conveyor is disclosed. The guide structure includes a guide for guiding the chain along a direction of movement of the chain and having at least two rails each delimiting a respective guide channel for at least partly accommodating the chain. An accompanying means for supporting the chain and accompanying it into the guide channel, wherein the accompanying means comprises a contact surface adapted to be in contact with the chain while the chain is accompanied into the guide channel. A fixing means for keeping the accompanying means in fixed position with respect to the guide. And, an adjusting means for adjusting a position of the accompanying means generally orthogonal to the direction of movement of the chain to adjust the angular position of the accompanying means with respect to the guide in at least a first and a second angular positions.

Claims

1. Guide structure for a chain for an article conveyor, said guide structure comprising: a guide for, in use, guiding a chain along a first direction being a direction of movement of the chain, wherein the guide comprises a first surface and at least two rails, each one extending along a second direction orthogonal to the first direction, each pair of rails delimiting, along a third direction orthogonal to the first and second directions, a respective guide channel for, in use, at least partly accommodating the chain, an accompanying means for supporting the chain and accompanying it into the guide channel, wherein the accompanying means comprises a contact surface adapted to be in contact with the chain while the chain is accompanied into the guide channel, a fixing means for keeping the accompanying means in fixed position with respect to the guide, and an adjusting means for adjusting an angular position of the accompanying means along the second direction, wherein the adjusting means is adapted to adjust the angular position of the accompanying means with respect to the guide in at least a first and a second angular positions, wherein in the first angular position the minimum distance of the contact surface from the first surface along the second direction has a first distance value, and in the second angular position the minimum distance of the contact surface from the first surface along the second direction has a second distance value, the second distance value being different from the first distance value, and the fixing means keeping the accompanying means in the adjusted angular position.

2. The guide structure according to claim 1, wherein the first surface, in use, faces the chain, and wherein the guide has a second surface opposite the first surface, and wherein the at least two rails each extend from the first surface to a third surface between the first and second surfaces.

3. The guide structure according to claim 1, wherein the contact surface has a rounded profile.

4. The guide structure according to claim 1, wherein the accompanying means comprises a further contact surface opposite to said contact surface, and wherein the accompanying means can be arranged in a first mounting configuration in which the contact surface faces, in operation, the chain, or in a second mounting configuration in which the further contact surface faces, in operation, the chain.

5. The guide structure according to claim 4, wherein the further contact surface has a rounded profile.

6. The guide structure according to claim 5, wherein the contact surface and the further contact surface define a substantially pear shaped cam profile of the accompanying means.

7. The guide structure according to claim 4, wherein the accompanying means is rotatable about a rotation axis parallel to the third direction, and wherein the rotation axis has, along the second direction, a first distance from the contact surface and a second distance from the further contact surface, the first distance being different from the second distance whereby, when the accompanying means is arranged in the second mounting configuration, the rotation of the accompanying means between said first and second angular positions determines, respectively, first and second further distances values of the minimum distance between the further contact surface and the first surface along the second direction, the first and second further distance values being different from the first and second distance values, respectively.

8. The guide structure according to claim 1, wherein the accompanying means comprises a cylinder, the accompanying means being rotatable between the first and second angular positions by rotation of the cylinder about an eccentric rotation axis being eccentric compared to the cylinder axis.

9. The guide structure according to claim 1, further comprising a protective casing having two opposite side walls within which the guide is provided, the adjusting means comprising a pair of circular through holes each one formed at a respective wall of the protective casing.

10. The guide structure according to claim 1, wherein the adjusting means is configured to adjust the angular position of the accompanying means to accommodate a chain having a thickness between 3 millimeters and 13 millimeters.

11. Guide structure for a chain for an article conveyor, said guide structure comprising: a guide for, in use, guiding a chain along a first direction, the first direction being a direction of movement of the chain, wherein the guide comprises a guide channel having a first surface extending in the first direction for accommodating the chain, an accompanying means for supporting the chain and accompanying it into the guide channel, wherein the accompanying means comprises a contact surface adapted to be in contact with the chain while the chain is accompanied into the guide channel, a fixing means for keeping the accompanying means in fixed position with respect to the guide, and an adjusting means having an axis of rotation, the adjusting means configured to adjust an angular position of the accompanying means along a second direction orthogonal to the first direction when the accompanying means is rotated about the axis of rotation, wherein the adjusting means is adapted to adjust the angular position of the accompanying means with respect to the guide in at least a first and a second angular positions, wherein in the first angular position the minimum distance of the contact surface from the first surface along the second direction has a first distance value, and in the second angular position the minimum distance of the contact surface from the first surface along the second direction has a second distance value, the second distance value being different from the first distance value, and the fixing means keeping the accompanying means in the adjusted angular position.

12. The guide structure according to claim 11, wherein the guide comprises at least two rails, each one extending along the second direction, where the guide has a first surface that, in use, faces the chain, and a second surface opposite the first surface, and wherein the at least two rails each extend from the first surface to a third surface between the first and second surfaces.

13. The guide structure according to claim 11, wherein the contact surface has a rounded profile.

14. The guide structure according to claim 11, wherein the accompanying means comprises a further contact surface opposite to said contact surface, and wherein the accompanying means can be arranged in a first mounting configuration in which the contact surface faces, in operation, the chain, or in a second mounting configuration in which the further contact surface faces, in operation, the chain.

15. The guide structure according to claim 14, wherein the further contact surface has a rounded profile.

16. The guide structure according to claim 15, wherein the contact surface and the further contact surface define a substantially pear shaped cam profile of the accompanying means.

17. The guide structure according to claim 14, wherein the axis of rotation is parallel to a third direction, orthogonal to the first and second directions, and wherein the axis of rotation has, along the second direction, a first distance from the contact surface and a second distance from the further contact surface, the first distance being different from the second distance whereby, when the accompanying means is arranged in the second mounting configuration, the rotation of the accompanying means between said first and second angular positions determines, respectively, first and second further distances values of the minimum distance between the further contact surface and the first surface along the second direction, the first and second further distance values being different from the first and second distance values, respectively.

18. The guide structure according to claim 11, wherein the accompanying means comprises a cylinder, the accompanying means being rotatable between the first and second angular positions by rotation of the cylinder about an eccentric rotation axis being eccentric compared to the cylinder axis.

19. The guide structure according to claim 11, further comprising a protective casing having two opposite side walls within which the guide is provided, the adjusting means comprising a pair of circular through holes each one formed at a respective wall of the protective casing.

20. The guide structure according to claim 11, wherein the adjusting means is configured to adjust the angular position of the accompanying means to accommodate a chain having a thickness between 3 millimeters and 13 millimeters.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) One or more embodiments of the present invention, as well as further features and the related advantages, will be better understood with reference to the following detailed description, given purely by way of non-limitative example only, to be read in conjunction with the accompanying figures (wherein corresponding elements are indicated with the same or similar references and their explanation is not repeated for the sake of brevity). In particular:

(2) FIGS. 1A, 1B and 1C show perspective views of a known guide structure for an article conveyor, with chains having different thicknesses;

(3) FIGS. 2A, 2B and 2C show side views of a guide structure according to an embodiment of the present invention, in respective angular positions of accompanying means thereof;

(4) FIG. 2D shows a side view of the guide structure of FIGS. 2A, 2B and 2C, with the accompanying means illustrated in the angular positions of the FIGS. 2A, 2B and 2C overlapped to each other;

(5) FIGS. 2E and 2F show perspective and partially exploded views with removed parts of the guide structure of FIGS. 2A-2D, wherein both adjusting and fixing means are visible;

(6) FIGS. 3A and 3B show side views of a guide structure according to another embodiment of the present invention, with accompanying means in respective angular positions and in a first mounting configuration;

(7) FIGS. 3C and 3D show, respectively with chain and without chain, a side view of the guide structure of FIGS. 3A and 3B, with the accompanying means illustrated in the angular positions of the FIGS. 3A and 3B overlapped to each other;

(8) FIGS. 3E and 3F show perspective and partially exploded views with removed parts of the guide structure of FIGS. 3A-3D, wherein both adjusting and fixing means are visible;

(9) FIG. 3G shows a side view of the guide structure of FIGS. 3A-3D, with the accompanying means illustrated, for the same angular position, in the first mounting configuration of FIGS. 3A-3D and in a second mounting configuration overlapped to each other;

(10) FIGS. 3H and 3I show side views of the guide structure of FIGS. 3A-3D, with the accompanying means in the second mounting configuration of FIG. 3G and in respective angular positions;

(11) FIGS. 4A, 4B and 4C show side views of a guide structure according to another embodiment of the present invention, in respective angular positions of accompanying means thereof, and

(12) FIGS. 4D and 4E show perspective and partially exploded views with removed parts of the guide structure of FIGS. 4A, 4B and 4C, wherein both adjusting and fixing means are visible.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(13) With references to the drawings, guides structures for an article conveyor are shown.

(14) In the following, directional terminology (for example, top, bottom, upper, lower, side, central, longitudinal, transverse, vertical) associated with the guide structures and components thereof will be used in relation to the intended orientation of use (i.e., the orientation upon installation and operation of an article conveyor comprising such guide structures).

(15) The article conveyor, not shown in its entirety, typically comprises one or more movable chains, briefly discussed later on by referring only to functional elements deemed relevant for the understanding of the present invention, drive elements (for example, electric motors, pinions and cogwheels, not shown) for moving/driving the chain(s) along a predefined conveyor path (i.e. along a respective forwardfor example, uppersection that allows the articles to be conveyed, and/or along a respective return for example, lowersection), and a guide structure for guiding the chain(s) along said conveyor path.

(16) With reference to the drawings, FIGS. 1A, 1B and 1C show perspective views of a known guide structure 100 for an article conveyor, with chains having different thicknesses (in the example at issue, the chain illustrated in FIGS. 1A and 1B, denoted by C.sub.1A, has a higher thickness than the chain illustrated in FIG. 1C, denoted by C.sub.1C). The chains C.sub.1A, C.sub.1C are not part of the guide structure 100, however their representation, and particularly the representation of chains having different thicknesses, in these figures is functional to the understanding of the technical problem affecting the known guide structure 100.

(17) For the purposes of the present description, each chain C.sub.1A, C.sub.1C comprises a plurality of links each one identifying a rest/support surface (an upper surface, taking as reference the forward section) for the articles to be conveyed, with the rest surfaces of the links that, in the forward section, define as a whole a rest plane of the chain C.sub.1A,C.sub.1C. As exemplary illustrated, each link of the chain C.sub.1A,C.sub.1C may for example comprise a first link part or element (in the illustrated example, a plate) C.sub.1A,P,C.sub.1C,P for supporting the articles to be conveyed and a second link part or element (in the illustrated example, a link body) C.sub.1A,LB,C.sub.1C,LB for supporting the plate C.sub.1A,P,C.sub.1C,P.

(18) In the illustrated example, the guide structure 100 comprises a protective casing (carter) 100.sub.C, inside which a forward guide 100.sub.F for guiding the chain C.sub.1A,C.sub.1C, in a longitudinal direction X (i.e. a direction of movement of the chain C.sub.1A,C.sub.1C), along at least a portion of the forward section of the conveyor path, and a return guide 100.sub.R for guiding the chain C.sub.1A,C.sub.1C, in the longitudinal direction X, along at least a portion of the return section of the conveyor path, are provided. In the illustrated example, the forward guide 100.sub.F and the return guide 100.sub.R are fastened to each another (e.g., in a reversible manner), with the forward 100.sub.F and return 100.sub.R guides that preferably identify, in operation, top and bottom guides, respectively, of the guide structure 100.

(19) However, as will be appreciated in the following while discussing embodiments of the present invention, the present invention equivalently applies to guide structures having no forward guide, in that the issues which the present invention is intended to address mainly affect the return guides. For this reason, only the return guide 100.sub.R will be deeply discussed in the following (with some elements of the forward guide 100.sub.F that will be introduced and discussed only when relevant).

(20) The return guide 100.sub.R comprises a surface 105.sub.RL that, in use, faces (and preferably contacts) the chain C.sub.1A,C.sub.1C and is oriented downwards, thus referred to as lower surface hereinafter, and a surface 105.sub.RU, opposite the lower surface 105.sub.RL, that, in use, is oriented upwards, thus referred to as upper surface hereinafter, and faces the forward guide 100.sub.R (e.g., as illustrated, a lower surface thereof), when a forward guide is provided.

(21) The return guide 100.sub.R preferably comprises a number I of rails (i=1, . . . , with I2), each one extending, along n vertical direction Y orthogonal to the longitudinal direction X, from the lower surface 105.sub.RL of the return guide 100.sub.R downwards, and, along a transversal direction Z orthogonal to the longitudinal X and vertical Y directions, parallel to each other. Each pair of rails delimits, along the transversal direction Z, a number J of guide channels (j=1, . . . , J, with J=I1) each one for receiving or accommodating a respective chain C.sub.1A,C.sub.1C or a portion (preferably a lower portion) thereof, thereby allowing each chain C.sub.1A,C.sub.1C to be guided along the return section of the conveyor path.

(22) In the example at issue, two rails 110.sub.R1,110.sub.R2 are provided (the rail 110.sub.R2 being not visible), which delimit one guide channel 115R (i.e. a return guide channel, as opposed to a forward guide channel provided in the forward guide 100.sub.F), the return guide 100.sub.R thus identifying a single-channel return guide. In any case, as will be understood from the following discussion, the present invention is not limited to a specific number of guide channelsfor example, the present invention equivalently applies to a return guide formed as a multi-channel return guide for moving multiple parallel chains.

(23) In the considered example, each rail 110.sub.R1,110.sub.R2 comprises a respective lower wall 110.sub.R1W,110.sub.R2W parallel to the upper 105.sub.RU and lower 105.sub.RF surfaces of the return guide 110.sub.R, and respective vertical side walls 110.sub.R1S1,110.sub.R1S2 and 110.sub.R2S1,110.sub.R2S2 (the vertical side walls 110.sub.R2S1,110.sub.R2S2 being not visible) extending, along the vertical direction Y, from opposite side ends of the respective lower wall 110.sub.R1W,110.sub.R2W, to the lower surface 105.sub.RL. The lower walls 110.sub.R1W,110.sub.R2W of the rails 110.sub.R1,110.sub.R2 thus identify, as a whole, a lowermost surface of the return guide 100.sub.R. The vertical side walls (of the rails 110.sub.R1,110.sub.R2) facing each other delimit the guide channel 115.sub.R (in the example at issue of single channel, the vertical side wall 110.sub.R1S2 of rail 110.sub.R1 and the vertical side wall 110.sub.R2S1 of rail 110.sub.R2 delimit the guide channel 115.sub.R).

(24) As illustrated, the guide channel 115.sub.R is adapted to slidably receive within it a portion of the chain C.sub.1A,C.sub.1C (e.g., the link body C.sub.1A,LB,C.sub.1C,LB thereof), with the lower walls 110.sub.R1W,110.sub.R2W of the rails 110.sub.R1,110.sub.R2 that face the chain C.sub.1A,C.sub.1C and preferably form a slide abutment for another portion of the chain C.sub.1A,C.sub.1C (e.g., the plate C.sub.1A,P,C.sub.1C,P thereof). In order to achieve that, in the considered example, the guide structure 100 comprises magnetic interaction means adapted in use to magnetically interact with magnetic interaction means of the chain C.sub.1A,C.sub.1C to cause a magnetic attraction of the chain C.sub.1A,C.sub.1C within the guide channel 115.sub.R (i.e., substantially along the vertical direction Y). The magnetic interaction means of the guide structure 100 may comprise one or more magnetic field generation elements (for example, electromagnets or permanent magnetsin the following, magnets), not shown, whereas the magnetic interaction means of the chain C.sub.1A,C.sub.1C may comprise one or more elements of the chain C.sub.1A,C.sub.1C (such as, just as an example, coupling pins C.sub.1A,Pin, C.sub.1C,Pin intended to couple links of each chain C.sub.1A,C.sub.1C to each other) made in ferritic steel or other ferromagnetic material so as to be responsive to the magnetic fields. The magnet may be arranged in the return guide 110.sub.R and/or in the forward guide 110.sub.F (when provided). For example, the magnets may be arranged in appropriate seats (not shown) of the return guide 110.sub.R, and may be disposed above the guide channel 115.sub.R (so as to determine the magnetic attraction of the chain C.sub.1A,C.sub.1C to the return guide channel 115.sub.R, and, to a certain extent, to the forward guide channel).

(25) However, as will be appreciated in the following while discussing embodiments of the present invention, the present invention may equivalently be applied to guide structures having no magnets, in that the issues which the present invention is intended to address generally affect any guide structure requiring accompanying means for accompanying the movement of the chain with respect to the guide channel. Therefore any guide structure in which accompanying means to promote an input of the chain into the guide channel (and/or accompanying means to promote an output of the chain from the guide channel) are required, may benefit from the present invention. By way of example only, known guide structures (not shown) provided with grooves (along the vertical side walls delimiting the guide channel) for accommodating the chain within the guide channel and supporting it from below (hence, without any magnet) may also benefit from the present invention.

(26) As visible in FIG. 1A, the guide structure 100 further comprises accompanying means for supporting the chain C.sub.1A,C.sub.1C and accompanying it into the guide channel 115.sub.R. The accompanying means is in the form of an idle roller 120 positioned in proximity of the inlet of the guide channel 115R at such a distance (along the vertical direction Y) from the lowermost surface of the guide channel 115R (hereinafter referred to as vertical distance, or vertical distance from the guide channel 115.sub.R) that the chain C.sub.1A,C.sub.1C, by sliding on the roller 120, is substantially aligned with the inlet of the guide channel 115R, and sufficiently close to the magnets to be effectively intercepted by the field lines of the magnetic field generated by them. Once entered the guide channel 115.sub.R, the magnetic interaction between the chain C.sub.1A,C.sub.1C and the magnets causes the attraction of the chain C.sub.1A,C.sub.1C toward, and retention of the chain C.sub.1A,C.sub.1C at the lower surface 105.sub.RL of the guide channel 115.sub.R (which is actually the guide channel top) thereby allowing the guided sliding of the chain C.sub.1A,C.sub.1C within the guide channel 115.sub.R (i.e., at the inlet thereof).

(27) As visible in FIG. 1A, adjusting means is also provided for adjusting the position of the roller 120 (i.e., of a contact surface thereof intended in use to be in contact with the chain C.sub.1A,C.sub.1C while the chain C.sub.1A,C.sub.1C is accompanied into the guide channel 115.sub.R) with respect to the guide channel 115.sub.R. Particularly, the vertical distance of the roller 120 is adjustable (along the vertical direction Y) according to the size of the chain C.sub.1A,C.sub.1C (e.g., the thickness of the plates C.sub.1A,P,C.sub.1C,P). In this regard, the adjusting means comprises two elongated vertical openings or slots 125 at respective opposite side walls of the carter 100.sub.C, so that the roller 120 can vertically slide along the openings 125, and be fixed (and kept) in the desired positionfor example, by bolts 130 or other fixing means.

(28) The adjustment of the vertical distance of the rollers 120 from the guide channel 115.sub.R allows the guide structure 100 to be adapted to chains (with plates) having different thicknesses. In the illustrated example, the vertical distance of the roller 120 from the guide channel 115.sub.R can be adjusted from a maximum value (corresponding to the positioning of the roller 120 at the lower end of the opening 125, as visible in FIG. 1A) allowing the roller 120 to support and accompany a chain having a relatively high thickness, such as the chain C.sub.1A, to a minimum value (corresponding to the positioning of the roller 120 at the upper end of the openings 125, positioning not shown) allowing the roller 120 to support and accompany a chain with a lower thickness, such as the chain C.sub.1C.

(29) The Applicant has understood that the vertical elongated openings 125 involve complex and costly machining. In fact, in order to manufacture the vertical elongated openings 125 multiple positioning and complex machining at both side walls of the carter 100.sub.C are required. Moreover, adjusting the position of the roller 120 along the vertical direction Y determines long times and requires too many operators (in fact, at least two operators are required for adjusting the vertical position of the roller 120, i.e. each operator at a respective side, and a third operator is recommended in order to check whether the adjustment of the roller 120 is correct and to instruct the other operators in respect of actions to be taken in order to compensate tor possible misalignments). Last but not least, the chain thicknesses that are admitted by the guide structure 100 strongly depend on the length of the vertical elongated openings 125. Since machining complexity and costs increase as the length of the vertical elongated openings 125 increases, then the guide structure 100 is recommended to be provided with vertical elongated openings 125 with reduced lengths, whereby the guide structure 100 is not adapted to accompany into the guide channel 115.sub.R chains having wide thickness ranges.

(30) According to the principles of the present invention, the adjusting means is adapted to adjust the angular position of the accompanying means with respect to the guide channel in at least a first and a second angular positions, such that in the first angular position the minimum vertical distance of the contact surface from the guide channel has a first distance value, and in the second angular position the minimum vertical distance of the contact surface from the guide channel has a second distance value different from the first distance value, with the accompanying means that are kept in the adjusted angular position by the fixing means.

(31) As will be understood from the following discussion, the specific shape or profile of the accompanying means is not limitative for the present invention. Therefore, although in the following discussion explicit reference will be made to exemplary and advantageous shapes or profiles of the accompanying means, the principles of the present invention equivalently apply when the accompanying means is embodied as a shoe (e.g., a wedge-shaped a cam-shaped shoe), a ramp, a cylinder, or the like.

(32) With reference to FIGS. 2A, 2B and 2C, they show side views of a guide structure 200 according to an embodiment of the present invention, in respective angular positions of the accompanying means.

(33) In this exemplary embodiment of the present invention, the accompanying means of the guide structure 200 comprises a shoe 220 whose contact surface has a rounded profile. In the exemplary considered embodiment, the shoe 220 comprises a base 220.sub.B (e.g., as illustrated, a rectilinear base), a rectilinear side 220.sub.S having length L and extending orthogonally (or substantially orthogonally) from an end of the base 220.sub.B (i.e., the end that, in operation, is proximal to the inlet of the guide channel 115.sub.R), an arc-shaped side 220.sub.A extending from the opposite end of the base 220.sub.B to a point that, along a direction orthogonal to the base 220.sub.B, is at a distance H from the base 220.sub.B higher than the length L, and an elbow side 220.sub.E connecting the rectilinear side 220.sub.S to the arc-shaped side 220.sub.A. In the following, for ease of description, the elbow side 220.sub.E will be referred to as lobe of the shoe 220, whereas the end of the base 220.sub.B connected to the arc-shaped side 220, will be referred to as tip of the shoe 220. In this exemplary shape, the contact surface of the shoe 220 is defined by the arc-shaped side 220.sub.A and by the lobe 220.sub.E (or at least a portion thereof).

(34) For ease of representation, FIGS. 2A, 2B and 2C comprise each one a top drawing illustrating the guide structure 200 with the shoe 220 in a respective angular position and with an exemplary chain C.sub.2A, C.sub.2B, C.sub.2C resting and sliding on the shoe 220 (i.e., on its contact surface) when the shoe 220 is fixed in that angular position, and a bottom drawing illustrating the same guide structure 200 with the shoe 220 in the same angular position, but with the same chain C.sub.2A, C.sub.2B, C.sub.2C shown with a simplified representation, for better intelligibility. The chains C.sub.2A, C.sub.2B, C.sub.2C are not part of the guide structure 200, however their representation, and particularly the representation of chains having different thicknesses, is, in these and in the following figures, functional to the understanding of the contribution made by the guide structures according to embodiments of the present invention.

(35) In an exemplary angular position, illustrated in FIG. 2A, the shoe 220 (i.e., the rectilinear base 220.sub.B) is substantially parallel with respect to a horizontal plane parallel to the guide channel 115.sub.R (i.e., parallel to the lower surface of the guide channel, or, equivalently, parallel to the lowermost surface of the guide channel)rotation angle .sub.A0). In this angular position (in this case, horizontal position), the minimum distance between the contact surface and the guide channel 115.sub.R (i.e., between the contact surface and a plane on which the lower walls 110.sub.R1W, 110.sub.R2W of the rails 110.sub.R1, 110.sub.R2 lay) is substantially in correspondence of the contact point between the arch-shaped side 220.sub.A and the lobe 220.sub.E, and has a distance value d.sub.A. As should be readily understood, in this first exemplary angular position, the shoe 220 according to this embodiment is able to support and accompany into the guide channel 115.sub.R a chain C.sub.2A with a thickness that depends on an actual positioning of the shoe 220 along the vertical direction Y (i.e., its vertical position), and, once the vertical position has been chosen, on the curvatures of the arch-shaped side 220.sub.A and/or of the lobe 220E (the curvatures of the arch-shaped side 220A and/or of the lobe 220.sub.E in turn depending, for example, on parameters such as height H and length L). By way of example only, and for only purposes of comparison with respect to the chains C.sub.2B and C.sub.2C respectively illustrated in FIGS. 2B and 2C, the chain C.sub.2A may have a thickness of about 8.7 mm.

(36) In another exemplary angular position, illustrated in FIG. 2B, the shoe 220 is anticlockwise rotated, with respect to the horizontal plane, by a rotation angle .sub.B that determines, with respect to the vertical direction Y and with respect to the horizontal position, a lowering of the lobe 220.sub.E and a rising of the tip. This determines that the minimum distance between the contact surface and the guide channel 115.sub.R is substantially in correspondence of the centre of the arc-shaped side 220.sub.A. Therefore, in this exemplary angular position, the minimum distance of the contact surface from the guide channel 115.sub.R has a distance value d.sub.B that is higher than the distance value d.sub.A, which allows the shoe 220 to support and accompany into the guide channel 115.sub.R a chain C.sub.2B with thickness higher than the thickness of the chain C.sub.2A. By way of example only, the chain C.sub.2B may have a thickness of about 12.7 mmin any case, the percentage increase in thickness with respect to the exemplary angular position having rotation angle .sub.A0 may depend on different design options, such as curvature of the arc-shaped side 220.sub.A and/or of the lobe 220.sub.E. This exemplary angular position may substantially represent a maximum rotation in the anticlockwise direction compatible with a correct operation of the shoe 220 in its accompanying function (in fact, a further anticlockwise rotation of the shoe 220 would result, by construction, in an excessive rising of the tip which would hinder the sliding of the chain C.sub.2B).

(37) In another exemplary angular position, illustrated in FIG. 2C, the shoe 220 is clockwise rotated, with respect to the horizontal plane, by a rotation angle .sub.C that determines, with respect to the vertical direction Y and with respect to the horizontal position, a raising of the lobe 220.sub.E and a lowering of the tip. This determine that the minimum distance between the contact surface and the guide channel 115.sub.R is substantially in correspondence of the lobe 220.sub.E (in the example at issue, between a lobe centre and the contact point between the arc-shaped side 220.sub.A and the lobe 220.sub.E). Therefore, in this exemplary angular position, the minimum distance of the contact surface from the guide channel 115.sub.R has a distance value d.sub.C that is lower than the distance value d.sub.A, which allows the shoe 220 to support and accompany into the guide channel 115.sub.R a chain C.sub.2C with thickness lower than the thickness of the chain C.sub.2A. By way of example only, the chain C.sub.2C may have a thickness of about 5 mmin any case, the percentage reduction in thickness with respect to the exemplary angular position having rotation angle .sub.A0 may depend on different design options, such as curvature of the arc-shaped side 220.sub.A and/or of the lobe 220.sub.E. This exemplary angular position may substantially represent a maximum rotation in the clockwise direction compatible with a correct operation of the shoe 220 in its accompanying function (moreover, a further clockwise rotation of the shoe 220 would not result, by construction, in a further or significant reduction of the minimum distance).

(38) The exemplary angular positions illustrated in FIGS. 2A, 2B and 2C are also visible, overlapped to each other, in FIG. 2D. In this figure, the differences between the distance values d.sub.A, d.sub.B and d.sub.C and the respective rotation angles .sub.A, .sub.B and .sub.C can be better appreciated with a single viewit is worth noting that, although three exemplary angular positions of the shoe 220 are illustrated in the figures, a number of angular positions (e.g., with rotation angles between the rotation angle .sub.B and the rotation angle .sub.C) are possible. FIG. 2D also shows that the angular positions at the rotation angles .sub.A, .sub.B and .sub.C (and at any other rotation angle between the rotation angle .sub.B and the rotation angle .sub.C) are obtained by rotation of the shoe 220 about a rotation axis O (as better discussed in the following, the rotation axis O identifying or being defined by the position of the adjusting and fixing means of the guide structure 200 with respect to the shoe 220).

(39) As mentioned above, the guide structure 200 also comprises adjusting means for adjusting the angular position of the shoe 220 with respect to the guide channel 115.sub.R and fixing means for keeping the shoe 220 in the adjusted angular position. With reference now to FIGS. 2E and 2F, they show perspective and partially exploded views with removed parts of the guide structure 200, wherein both adjusting and fixing means according to an embodiment of the present invention are visible (for ease of representation, only in FIG. 2F a chain is also illustratedjust as an example the chain C.sub.2B is illustrated).

(40) The adjusting means preferably comprises two circular holes (through holes) 225 at respective opposite side walls of the carter 200.sub.C, and the fixing means comprises screws 230 adapted to be screwed into two threaded holes 235 (advantageously, circular in shape as well) formed in the shoe 220 (only one threaded hole 235 being visible in FIG. 2F)as will be understood from the following discussion, the threaded holes 235 acting both as fixing means (in that, the fixing of the shoe 220 is carried out by screwing the screws 230 thereinto), and as adjusting means (as the threaded holes 235 also define or are identified by the rotation axis O of the shoe 220). The threaded holes 235 are preferably formed from respective side walls of the shoe 220 that, in operation, face the side walls of the carter 200.sub.D, and extend inside the shoe 220, along the transversal direction Z (when considering the shoe 220 in position between the carter side walls), for an extent corresponding to the screw lengthas an alternative, not shown, a single through hole may be formed inside the shoe 220, along the transversal direction Z, such that the shoe 220 may be kept in the desired angular position by a bolt and nut pair as a fixing means. Therefore, in operation, when positioning the shoe 220 between the side walls of the carter 200.sub.C (with the threaded holes 235 of the shoe 220 matching respective through holes 225 of the carter 200.sub.C) and inserting and partially screwing the screws 230 into the through holes 225 of the carter 200C and into the threaded hole 235 of the shoe 220, the shoe 220 can be adjusted or oriented or rotated by an operator in the desired angular position depending on the chain to be used. Upon rotating the shoe 220 in the desired angular position, further screwing of the screws 230 allows the shoe 220 to be firmly kept in the desired angular position.

(41) Therefore, the vertical position of the shoe 220 can be adjusted by rotation of the shoe 220 about a rotation axis O identified by the threaded holes 235. Compared to the guide structure 100, in which the vertical position of the accompanying means is adjusted by means of its vertical sliding along the (vertical) elongated openings 125, the present invention allows achieving a same, or even better, adjusting of the vertical position by means of circular holes formed in the carter 200.sub.C. Circular holes instead of vertically elongated openings are advantageous in that they allow simple and cheap machining. Moreover, adjusting the vertical position of the shoe 220 requires reduced times and only one operator. Last but not least, the chain thicknesses that are admitted by the guide structure 200 depend on the shape or profile of the shoe 220, rather than on the shape and the precision (i.e., tolerances) of the holes 225, whereby the guide structure 200 is adapted to accompany into the guide channel 115.sub.R chains having wide thickness ranges.

(42) FIGS. 3A and 3B show side views of a guide structure 300 according to another embodiment of the present invention, with accompanying means in respective angular positions, and FIGS. 3C and 3D show, respectively with chains and without chains, a side view of the guide structure 300 (with the accompanying means illustrated in the angular positions of FIGS. 3A and 3B overlapped to each other).

(43) In this exemplary embodiment of the present invention, the accompanying means of the guide structure 300 comprises a shoe 320 having a contact surface with a rounded profile (in the example at issue, the contact surface is the same as the contact surface of the shoe 220, i.e. it is defined by the arc-shaped side 220.sub.A and byat least a portion ofthe lobe 220.sub.E), and a further contact surface opposite to the contact surface, such that the shoe 320 can be arranged in a first mounting configuration (illustrated in FIGS. 3A-3D) in which the contact surface faces, in operation, the chain, or a in second mounting configuration (illustrated in FIGS. 3F and 3G) in which the further contact surface faces, in operation, the chain (the first mounting configuration and the second mounting configuration overlapped to each other being illustrated, for a same angular position of the shoe 320, in FIG. 3G).

(44) In the illustrated example, the second contact surface has a rounded profile.

(45) According to an embodiment of the present invention, the rounded profile of the further contact surface may be the same as the rounded profile of the contact surface. According to an alternative embodiment of the present invention, as herein assumed and illustrated, the rounded profile of the further contact surface differs (or, as illustrated, slightly differs) from the rounded profile of the contact surface.

(46) In both embodiments, however, the shoe 320 comprises, in addition to the arc-shaped side 220.sub.A, and to the lobe 220.sub.B, a rectilinear side 320.sub.S, a further arc-shaped side 320.sub.A from the tip of the shoe 320, and a further lobe 320.sub.E connecting the further arc-shaped side 320.sub.A to the rectilinear side 320.sub.S (the rectilinear side 320.sub.S being similar to the rectilinear side 220.sub.S but preferably having a different length L due to the presence of the further arc-shaped side 320.sub.A and of the further lobe 320.sub.E). In the example at issue, the further contact surface of the shoe 320 is defined by the further arc-shaped side 320.sub.A and by (at least a portion of) the further lobe 320.sub.E. Therefore, the shoe 320 results in a substantially pear shaped cam profile.

(47) With reference first to FIGS. 3A and 3B, the guide structure 300 is illustrated with the shoe 320 in respective angular positions and with exemplary chains C.sub.3A,C.sub.3B resting and sliding on the shoe 320 (wherein, for ease of illustration, the chains C.sub.3A,C.sub.3B are shown with a simplified representation). The exemplary angular positions illustrated in FIGS. 3A and 2B are also visible, overlapped to each other, in FIG. 3C.

(48) The exemplary angular position of the shoe 320 illustrated in FIG. 3A is the same angular position of the shoe 220 illustrated in FIG. 2A (i.e., taking the rectilinear side 320.sub.S as a reference, with the shoe 320 that has its rectilinear side 320.sub.S substantially orthogonal with respect to the horizontal plane parallel to the guide channel 115.sub.R). Therefore, in the example at issue in which the shoe 220 and the shoe 320 have same contact surface (and assuming that the shoe 320 has the same vertical position as the shoe 220), the minimum distance between the contact surface and the guide channel 115.sub.R has a distance value d.sub.A=d.sub.A that allows the shoe 320 to support and accompany into the guide channel 115 a chain C.sub.3A with thickness of about 8.7 mm (similarly to the chain C.sub.2A illustrated in FIG. 2A). Having taken the rectilinear side 320.sub.S as a reference, the angular position of the shoe 320 illustrated in FIG. 3A identifies a rotation angle .sub.A90 between the rectilinear side 320.sub.S and the horizontal plane (as should be readily understood, the rotation angles .sub.A and .sub.A are phase-shifted by 90 due to the fact that in FIG. 2A the angular position of the shoe 220 has been identified by taking the base 220.sub.B of the shoe 220 and the horizontal plane as reference, whereas in FIG. 3A the angular position of the shoe 320 has been identified by taking the rectilinear side 320.sub.B of the shoe 320 and the horizontal plane as reference, the rectilinear side 320.sub.B and the base 220.sub.B being orthogonal to each other).

(49) The exemplary angular position of the shoe 320 illustrated in FIG. 3B is the same angular position of the shoe 220 illustrated in FIG. 2B (i.e., with the shoe 320 that is anticlockwise rotated, with respect to the horizontal plane, by a rotation angle .sub.B). Therefore, in the example at issue in which the shoe 220 and the shoe 320 have same contact surface (and assuming that the shoe 320 has the same vertical position as the shoe 220), the minimum distance between the contact surface and the guide channel 115.sub.R has a distance value d.sub.B=d.sub.B that allows the shoe 320 to support and accompany into the guide channel 115.sub.R a chain C.sub.3B with thickness of about 12.7 mm (similarly to the chain C.sub.2B illustrated in FIG. 2B).

(50) Although not shown, the shoe 320 may also take the same angular position of the shoe 220 illustrated in FIG. 2C (i.e., with the shoe 320 that is anticlockwise rotated, with respect to the horizontal plane, by a rotation angle .sub.C), in which case the minimum distance between the contact surface and the guide channel 115.sub.R has a distance value d.sub.C=d.sub.C that allows the shoe 320 to support and accompany into the guide channel 115.sub.R a chain C.sub.3C with thickness of about 5 mm (similarly to the chain C.sub.2C illustrated in FIG. 2C).

(51) Naturally, same considerations about the thickness of the chains C.sub.2A,C.sub.2B,C.sub.2C and its dependence on design options such as curvature of the arc-shaped side 220.sub.A and/or of the lobe 220.sub.E, and/or vertical position of the shoe 220, equivalently apply to the thickness of the chains C.sub.3A,C.sub.3B,C.sub.2C, at least in this first mounting configuration (in which the shoe 220 and the shoe 320 have same contact surface).

(52) Similarly to the guide structure 200, the guide structure 300 also comprises adjusting means for adjusting the angular position of the shoe 320 with respect to the guide channel 115.sub.R and fixing means for keeping the shoe 320 in the adjusted angular position. With reference now to FIGS. 3E and 3F, they show perspective and partially exploded views with removed parts of the guide structure 300, wherein both adjusting and fixing means according to an embodiment of the present invention are visible.

(53) Similarly to the guide structure 200, the adjusting means of the guide structure 300 preferably comprises two holes (through holes) 325 at respective opposite side walls of the carter 300.sub.C, and the fixing means comprises screws 330 adapted to be screwed into two threaded holes 335 formed in the shoe 320 (only one threaded hole 335 being visible in FIG. 3F). The threaded holes 335 are preferably formed from respective side walls of the shoe 320 that, in operation, face the side walls of the carter 300.sub.C, and extend inside the shoe 320, along the transversal direction Z (when considering the shoe 320 in position between the carter side walls), for an extent corresponding to the screw lengthas an alternative, not shown, a single through hole may be formed inside the shoe 320, along the transversal direction Z, such that the shoe 320 may be kept in the desired angular position by a bolt and nut pair as a fixing means. Therefore, in operation, when positioning the shoe 320 between the side walls of the carter 300.sub.C (with the threaded holes 335 of the shoe 320 matching respective through holes 325 of the carter 300.sub.C) and inserting and partially screwing the screws 330 into the through holes 325 of the carter 300.sub.C and into the threaded hole 335 of the shoe 320, the shoe 320 can be adjusted or oriented or rotated (about a rotation axis O) by an operator in the desired angular position depending on the chain to be used. Upon rotating the shoe 320 in the desired angular position, further screwing of the screws 330 allows the shoe 320 to be firmly kept in the desired angular position.

(54) Similarly to the previous embodiment, the rotation axis O identifies or is defined by the position of the threaded hole 335 with respect to the shoe 320. In addition, in the guide structure 300, the position of the rotation axis O also determines different uses of the shoe 320 in the first and second mounting configurations, as explained here below.

(55) According to an embodiment of the present invention, not shown, the rotation axis O has, along the vertical direction Y, a distance p from the contact surface and a same distance p from the further contact surface, whereby when the shoe 320 is arranged in the second mounting configuration (with the further contact surface facing the chain), the angular positions of the shoe 320 determine substantially same distance values of the minimum distances between the further contact surface and the guide channel 115.sub.R (especially when considering essentially same rounded profiles of the contact surface and of the further contact surface). This embodiment could be useful when high wear of the contact surface is expected (e.g., due to the friction of the chain sliding thereon), such that the further contact surface may act as a backup contact surface that avoids replacement of the whole shoe 320.

(56) According to the exemplary considered embodiment, the rotation axis O has, along the vertical direction Y, a distance p from the contact surface and a further distance p from the further contact surface (for ease of illustration, the distance p and the further distance p are illustrated only in FIGS. 3A, 3G and 3H). The distance p and the further distance p are different from each other, whereby when the shoe 320 is arranged in the second mounting configuration (with the further contact surface facing the chain), the angular positions of the shoe 320 determines distance values of the minimum distances between the further contact surface and the guide channel 115.sub.R that are different from the corresponding distance values (i.e., the distance values at the same angular positions) of the shoe 320 in the first mounting configuration. This embodiment could be useful when chain thicknesses out of the range of chain thicknesses allowed by the contact surface are required, as better discussed here below.

(57) The mounting of the shoe 320 in the second mounting configuration (i.e., upside down with respect to the first mounting configuration) has the effect that, for the same angular positions of the shoe 320, the further contact surface is closer or farther to the guide channel 115.sub.R according to a ratio between the distance p and the further distance p. In the example at issue in which the further distance p is higher than the distance p, in the second mounting configuration of the shoe 320 (i.e., further contact surface-facing the chain) the further contact surface is closer to the guide channel 115.sub.R than the contact surface is, for the same angular position, in the first mounting configuration (i.e., contact surface facing the chain), as visible in FIG. 3G (wherein the shoe 320 in the first mounting configuration is illustrated, in dashed line, overlapped to the shoe 320 in the second mounting configuration, in solid line).

(58) With reference now to FIGS. 3H and 3I, they show side views of the guide structure 320, with the shoe 320 in the second mounting configuration and in respective angular positions.

(59) The exemplary angular position of the shoe 320 illustrated in FIG. 3H is the same angular position of the shoe 220 illustrated in FIG. 2C, i.e. with the shoe 320 that is clockwise rotated, with respect to the horizontal plane, by a rotation angle that determines, with respect to the vertical direction Y and with respect to the horizontal position, a raising of the further lobe 320.sub.E and a lowering of the tip. This determines that the minimum distance between the further contact surface and the guide channel 115.sub.R is substantially in correspondence of the further lobe 320.sub.E (in the example at issue, between a centre of the further lobe and the contact point between the further arc-shaped side 320.sub.A and the further lobe 320.sub.E). Therefore, in this exemplary angular position, the minimum distance of the further contact surface from the guide channel 115.sub.R has a distance value d.sub.C that is lower than the distance value d.sub.C that, for the same angular position of the shoe 320, the contact surface has from the guide channel 115.sub.R when the shoe 320 is in the first mounting configuration. This allows the shoe 320 to support and accompany into the guide channel 115.sub.R a chain C.sub.3H with thickness lower than the thickness of the chain C.sub.2C (or C.sub.3C). By way of example only, the chain C.sub.3H may have a thickness of about 3 mmin any case, the percentage reduction in thickness with respect to the same angular position with the shoe 320 in the first configuration depends on different design options, such as curvature of the further arc-shaped side 320.sub.A and/or of the further lobe 320.sub.E, and/or vertical position of the rotation axis O (i.e., ratio between the distance p and the further distance p). This exemplary angular position may substantially represent a maximum rotation in the clockwise direction compatible with a correct operation of the shoe 320 (in the second mounting configuration) in its accompanying function (moreover, a further clockwise rotation of the shoe 320 would not result, by construction, in a further or significant reduction of the minimum distance).

(60) The exemplary angular position of the shoe 320 illustrated in FIG. 3I is the same angular position of the shoe 220 illustrated in FIG. 2B and of the shoe 320 illustrated in FIG. 3B, i.e. with the shoe 320 that is anticlockwise rotated, with respect to the horizontal plane, by a rotation angle that determines, with respect to the vertical direction Y and with respect to the horizontal position, a lowering of the further lobe 320.sub.E and a rising of the tip. This determines that the minimum distance between the further contact surface and the guide channel 115.sub.R is substantially in correspondence of the centre of the further arc-shaped side 320.sub.A. Therefore, in this exemplary angular position, the minimum distance of the further contact surface from the guide channel 115.sub.R has a distance value d.sub.B that is lower than the distance value d.sub.B that, for the same angular position of the shoe 320, the contact surface has from the guide channel 115.sub.R when the shoe 320 is in the first mounting configuration. This allows the shoe 320 to support and accompany into the guide channel 115.sub.R a chain C.sub.3I with thickness lower than the thickness of the chains C.sub.2B and C.sub.3B. By way of example only, the chain C.sub.3I may have a thickness of about 6 mmin any case, the percentage reduction in thickness with respect to the same angular position with the shoe 320 in the first configuration may depend on different design options, such as curvature of the further arc-shaped side 320.sub.A and/or of the further lobe 320.sub.E, and/or vertical position of the rotation axis O. This exemplary angular position may substantially represent a maximum rotation in the anticlockwise direction compatible with a correct operation of the shoe 320 in its accompanying function (in fact, a further anticlockwise rotation of the shoe 320 would result, by construction, in an excessive rising of the tip which would hinder the sliding of the chain C.sub.3I).

(61) Therefore, in the example at issue wherein the contact surface allows supporting and accompanying chains whose thicknesses range from 5 mm to 12.7 mm (see FIGS. 2A-2C and 3A-3B), the shoe 320 in the second mounting configuration (and, hence, the further contact surface) advantageously allows supporting and accompanying chains having thicknesses ranging from 3 mm to 5 mm.

(62) With reference now to FIGS. 4A, 4B and 4C, they show side views of a guide structure 400 according to another embodiment of the present invention, in respective angular positions of accompanying means thereof.

(63) In this exemplary embodiment of the present invention, the accompanying means of the guide structure 400 comprises a cylinder 420, the contact surface being thus a side surface 420.sub.A of the cylinder 420. The cylinder 420 is rotatable about an eccentric rotation axis O being eccentric compared to the cylinder axis O.sub.C (i.e., the axis of symmetry of the cylinder).

(64) In FIGS. 4A, 4B and 4C, the guide structure 400 is illustrated with the cylinder 420 in respective angular positions and with exemplary chains C.sub.4A,C.sub.4B,C.sub.4C resting and sliding on the shoe 420 (wherein, for ease of illustration, the chains C.sub.4A,C.sub.4B,C.sub.4C are shown with a simplified representation).

(65) In an exemplary angular position, illustrated in FIG. 4A, the cylinder axis O.sub.C and the eccentric rotation axis O are substantially aligned along the vertical direction Y, i.e. the eccentric rotation axis O is, on a plane parallel to the bases of the cylinder 420, at a rotation angle .sub.A0 with respect to a plane f parallel to the vertical direction Y and passing for the cylinder axis O.sub.C. In this angular position, the minimum distance between the contact surface and the guide channel 115.sub.R (i.e., between the contact surface and a plane on which the lower walls 110.sub.R1W,110.sub.R2W of the rails 110.sub.R1,110.sub.R2 lay) has a distance value d.sub.A. As should be readily understood, in this first exemplary angular position, the cylinder 420 according to this embodiment is able to support and accompany into the guide channel 115.sub.R a chain C.sub.4A with a thickness that depends on an actual positioning of the cylinder 420 along the vertical direction Y (i.e., its vertical position), and, once the vertical position has been chosen, on the size of the cylinder 420 (i.e., its diameter). By way of example only, and for only purposes of comparison with respect to the chains C.sub.4B and C.sub.4C respectively illustrated in FIGS. 4B and 4C, the chain C.sub.4A may have a thickness of about 5 mm.

(66) In another exemplary angular position, illustrated in FIG. 4B, the eccentric rotation axis O is, on the plane parallel to the bases of the cylinder 420, at a rotation angle .sub.B with respect to the plane f (in the example at issue, .sub.B95 in the clockwise direction from the angular position of the eccentric rotation axis O illustrated in FIG. 4A) that determines, with respect to the vertical direction Y, a lowering of the cylinder 420. This determines that the minimum distance between the contact surface and the guide channel 115.sub.R has a distance value d.sub.B that is higher than the distance value d.sub.A, which allows the cylinder 420 to support and accompany into the guide channel 115.sub.R a chain C.sub.4B with thickness higher than the thickness of the chain C.sub.4A. By way of example only, the chain C.sub.4B may have a thickness of about 8.7 mmin any case, the percentage increase in thickness with respect to the exemplary angular position having rotation angle .sub.A0 may depend on different design options, such as vertical position and diameter of the cylinder 420.

(67) In another exemplary angular position, illustrated in FIG. 4C, the eccentric rotation axis O is, on the plane parallel to the bases of the cylinder 420, at a rotation angle .sub.C with respect to the plane f (in the example at issue, .sub.B180 in the clockwise direction from the position of the eccentric rotation axis O illustrated in FIG. 4A) that determines, with respect to the vertical direction Y, a further lowering of the cylinder 420. This determines that the minimum distance between the contact surface and the guide channel 115.sub.R has a distance value d.sub.C that is lower than the distance value d.sub.B, which allows the cylinder 420 to support and accompany into the guide channel 115.sub.R a chain C.sub.4C with thickness higher than the thickness of the chain C.sub.4B. By way of example only, the chain C.sub.4C may have a thickness of about 12.7 mmin any case, the percentage increase in thickness with respect to the exemplary angular position having rotation angle .sub.B95 may depend on different design options, such as vertical position and diameter of the cylinder 420.

(68) As should be readily understood, due to the symmetry of the cylinder 420, a further rotation of the cylinder (about the eccentric rotation axis O) in the clockwise direction from the position of the eccentric rotation axis O illustrated in FIG. 4C determines a progressive raising of the cylinder 420 until reaching the angular position of FIG. 4A (i.e., rotation angle of 360).

(69) The angular positions at the rotation angles .sub.A, .sub.B and .sub.C (and at any other rotation angle between the rotation angle .sub.A and the rotation angle .sub.C) are obtained by rotation of the cylinder 420 about the eccentric rotation axis O, which also identifies or is defined by the position of the adjusting and fixing means of the guide structure 400 with respect to the cylinder 420.

(70) With reference now to FIGS. 4D and 4E, they show perspective and partially exploded views with removed parts of the guide structure 400, wherein both adjusting and fixing means according to an embodiment of the present invention are visible.

(71) The adjusting means preferably comprises two holes (through holes) 425 at respective opposite side walls of the carter 400.sub.C, and the fixing means comprises screws 430 adapted to be screwed into two threaded holes 435 formed in the cylinder 420 (only one threaded hole 435 being visible in FIG. 4D). The threaded holes 435 are preferably formed from respective side walls of the cylinder 420 that, in operation, face the side walls of the carter 400.sub.C, and extend inside the shoe 220, along the transversal direction Z (when considering the cylinder 420 in position between the carter side walls), for an extent corresponding to the screw lengthas an alternative, not shown, a single through hole may be formed inside the cylinder 420, along the transversal direction Z, such that the cylinder 420 may be kept in the desired angular position by a bolt and nut pair as a fixing means. Therefore, in operation, when positioning the cylinder 420 between the side walls of the carter 400.sub.C (with the threaded holes 435 of the cylinder 420 matching respective through holes 425 of the carter 400.sub.C) and inserting and partially screwing the screws 430 into the through holes 425 of the carter 400.sub.C and into the threaded hole 435 of the cylinder 420, the cylinder 420 can be adjusted or oriented or rotated by an operator in the desired angular position depending on the chain to be used. Upon rotating the cylinder 420 in the desired angular position, further screwing of the screws 430 allows the cylinder 420 to be firmly kept in the desired angular position.

(72) Therefore, the vertical position of the cylinder 420 (i.e., its position along the vertical direction Y) can be adjusted by rotation of the cylinder 420 about an eccentric rotation axis O identified by the threaded holes 435. With respect to the known solutions of guide structures, such as the guide structure 100 discussed in the foregoing, in which the vertical position of the accompanying means is adjusted by means of its vertical sliding along the (vertical) elongated openings 125, the present invention allows achieving a same, or even better, adjusting of the vertical position by means of circular holes formed in the carter 400.sub.C (with the advantages of having circular holes instead of vertically elongated openings that have been also discussed in the foregoing).

(73) Although the embodiments of the present invention discussed above have been presented as particularly advantageous in terms of machinery complexity (due to the absence of vertically elongated openings formed in the carter side walls), the present invention can be also used in, and hence adapted to, conventional and existing guide structures having such vertically elongated openings.

(74) Naturally, in order to satisfy contingent and specific requirements, a person skilled in the art may introduce the present invention many modifications and logical and/or physical changes. More specifically, although the present invention has been described with a certain level of detail with reference to one or more embodiments thereof, it should be understood that various omissions, substitutions and changes in the form and details as well as other embodiments are possible. In particular, various embodiments of the present invention may be put into practice even without the specific details (such as the numerical examples) set forth in the description to provide a more complete understanding thereof; on the contrary, well-known features may be omitted or simplified in order not to obscure the description with unnecessary details. Moreover, it is expressly intended that specific elements described in relation to each embodiment of the present invention may be incorporated in any other embodiment as a normal design choice.

(75) Similar considerations apply if the guide structure comprises equivalent components. In any case, any component may be separated into more elements, or two or more components may be combined into a single element; furthermore, each component may be replicated to support the execution of the corresponding operations in parallel. It is also pointed out that (unless otherwise specified) any interaction between different components generally does not need to be continuous, and may be direct or indirect through one or more intermediaries.