Pulley device

Abstract

The invention relates to a pulley device (1) for a transmission element, comprising a pulley (2, 46, 70), a bearing (3) and at least one bushing (31, 32, 63, 64, 78, 79) freely mounted in a hole (13) of an inner ring (6) of the bearing (3). The pulley device (1) also includes at least one annular protective shield (4, 5, 47, 48, 61, 62, 80, 81, 82, 83) which is axially retained in a first element (2, 46, 63, 64, 78, 79, 84, 85, 86) originating from the pulley (2, 46, 70, 86) and adjacent to another element (31, 32, 70, 84, 85, 86), the other element (31, 32, 70, 84, 85, 86) having at least one shoulder (44, 45, 71, 77, 87, 91, 89, 93) which protrudes radially to ensure that it retains the second end in the axial direction.

Description

Technical Field

[0001] The invention relates to a pulley arrangement. The field of the invention is that of tensioning rollers, rollers, belt tensioners, loose pulleys and any other rotating transmission support component for tensioning chains or belts for motion transmission. Background Art

[0002] As is known, such a pulley arrangement may include a bearing, a pulley and a fastening screw. The bearing generally includes a fixed inner ring having a hole through which the screw passes, a rotating outer ring on which the pulley is mounted (surmounted) and at least one row of rolling elements between the inner ring and the outer ring. The screw includes a head and a threaded shaft. The screw passes through the inner ring of the bearing so that the threaded shaft of the screw enters a threaded hole provided in a support member (e.g., an engine block).

[0003] It is advisable to avoid mechanical contact between the rotating elements of the bearing and the support, in particular, the support may be placed in the engine compartment of a motor vehicle and subjected to frequent vibrations. For this purpose, it is known to use a spacer to space the bearing from the support in the axial direction. For example, it is known from DE-A-19850157 to provide a bushing which is overmolded or fitted into the inner ring of the bearing and is provided with ends forming a spacer between the support. In an earlier disclosure FR-A1-3029586, the pulley arrangement comprises two bushings mounted head to tail in the bore of the inner ring in a rigidly connected manner. However, the manufacturing tolerances of the bushings and the bore of the inner ring must be extremely precise to ensure an effective rigid connection, thereby preventing any relative movement both during the transport of the pulley to the installation position of the pulley and during the operation of the pulley.

[0004] Such pulley arrangements are often also equipped with seals or additional protective shields to help protect the arrangement from contaminants or splashes from the external environment. However, particles or other contaminants may penetrate into the vicinity of the sealing components for the bearings and may accumulate in the vicinity of the sealing components for the bearings over time. Since the sealing components may wear, the risk of contaminants penetrating into the bearing chamber increases with the age of the pulley arrangement. This internal contamination may lead to accelerated degradation of the components inside the bearing, in particular to accelerated degradation of the contact surfaces between the rolling elements and the inner and outer rings. As a result, this may lead to a reduction in the quality of the rotating mechanical linkage provided by the pulley arrangement and to a shortened life of its internal components. In particular, the risk of rupture is also greater in operating mode. Summary of the invention

[0005] The present invention aims to overcome these above-mentioned disadvantages.

[0006] More specifically, the present invention aims at providing such a pulley arrangement which is resistant to highly contaminating conditions, is particularly economical, is easy and reliable to install, forms a non-detachable subassembly and has reduced axial and radial space requirements.

[0007] The invention relates to a pulley arrangement for a transmission element, comprising a pulley, a bearing and at least one bushing, the pulley having an outer surface for engaging the transmission element.

[0008] The bearing is provided with a rotating outer ring, a fixed inner ring and at least one row of rolling elements, the pulley is mounted on the outer surface of the outer ring, the bushing is accommodated in the hole of the inner ring, the inner ring and the outer ring are coaxial and form a radial space between the inner ring and the outer ring, and the at least one row of rolling elements is arranged in the radial space.

[0009] According to the invention, the bushing is freely mounted in the bore of the inner ring. The pulley arrangement further comprises at least one annular protective shield. The shield has a substantially radial body extending between a first end, which is axially retained in a first element originating from the pulley and the bushing, and a second end, which is adjacent to another element originating from the pulley and the bushing, the other element having at least one shoulder, the at least one shoulder protruding radially to ensure that the at least one shoulder retains the second end axially.

[0010] Thanks to the invention, the annular protective shield is mounted, for example, rigidly connected to the pulley arrangement with satisfactory concentricity, avoiding the design of complex parts.

[0011] The intrusion of contaminants into the pulley arrangement, more particularly into the radial space between the coaxial rings of the bearing, is prevented, thereby improving the life and quality of the mechanical linkage provided by the bearing.

[0012] Furthermore, the shield forms an axial stop for the bushing to ensure that it remains in the bore of the inner ring. The bushing is freely mounted in the bore of the inner ring, i.e. there is radial play between the outer surface of the bushing and the inner surface of the bore, but the bushing remains rigidly connected axially to the inner ring and thereby to the pulley arrangement. The necessary tolerances therefore require less precision, saving time and reducing manufacturing costs.

[0013] According to other advantageous but not essential advantages of the present invention, the pulley device may also include the following features, which may be implemented individually or in any technically permissible combination:

[0014] - The first element is a pulley and the other element is a bushing.

[0015] - The first element is a bushing and the other element is a pulley.

[0016] The pulley arrangement comprises two bushings arranged on both axial sides in the bore of the inner ring.

[0017] - A first end of the shield is rigidly connected to the first element.

[0018] - The shield is formed in a single piece with the first element.

[0019] - the pulley is provided with at least one pulley element, the at least one pulley element having a C-shaped axial cross-section and having an inner part, an outer part and an intermediate part, the inner part being mounted on the outer surface of the outer ring of the bearing, the outer part having an outer surface for engaging the transmission element, the intermediate part extending substantially radially between axial ends of the inner part and the outer part along a first axial side, the shield extending laterally and substantially radially from an axial end of the inner part axially away from the intermediate part, and the pulley element being formed as a single piece.

[0020] The first end of the shield is axially secured by a radially projecting shoulder, the first element being provided with a radially projecting shoulder.

[0021] The first end of the shield is held rigidly connected to the first element originating from the pulley and the bushing by means of compression bulging at a plurality of circumferential locations.

[0022] - said further element comprises a hollow area in which the free end of said shield is housed.

[0023] - The shoulder is annular.

[0024] - the shoulder extends over a portion of the circumference of the further element.

[0025] - The shoulder is formed by a collar, the further element being provided with a collar.

[0026] - The cage maintains the circumferential spacing of the rolling elements.

[0027] - The rolling elements are balls.

[0028] The pulley device further comprises a rear sealing member and a front sealing member closing the radial space on each axial side.

[0029] - The pulley is made of metal, for example, the pulley is made of steel.

[0030] The belt pulley is made of plastic, for example, the belt pulley is made of polyamide.

[0031] - The pulley is formed by overmoulding plastic on the outer ring of the bearing.

[0032] - The shield is made of metal, for example, the shield is made of steel.

[0033] The shield is made of plastic or synthetic material, for example, the shield is made of polyamide.

[0034] - The bushing is made of metal, for example, the bushing is made of steel.

[0035] - The bushing is made of plastic or synthetic material, for example, the bushing is made of polyamide. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention will be better understood by reading the following description given purely as a non-limiting example.

[0037] The description is made with reference to the accompanying drawings, in which:

[0038] Figure 1 is an axial cross-sectional view of a pulley device according to a first embodiment of the present invention;

[0039] Figure 2 is an axial cross-sectional view of a pulley device according to a second embodiment of the present invention;

[0040] Figure 3 is an axial cross-sectional view of a pulley device according to a third embodiment of the present invention;

[0041] Figure 4 is an axial cross-sectional view of a pulley device according to a fourth embodiment of the present invention; and

[0042] Figure 5 1 is an axial cross-sectional view of a pulley device according to a fifth embodiment of the present invention. DETAILED DESCRIPTION

[0043] like Figure 1 As can be seen in the drawing, a pulley arrangement is indicated in its entirety by reference numeral 1, for example for a tensioning roller, a belt tensioner, a pinion or a gear. The pulley arrangement 1 has a geometric axis X1 and comprises a pulley 2, a bearing 3 and two protection shields 4, 5, the pulley 2 being suitable for engaging a transmission element (not shown) such as a belt or a chain.

[0044] The bearing 3 comprises a stationary inner ring 6 and a rotating outer ring 7, said rings 6, 7 being coaxial about the axis X1 and forming between them a radial space 8. The bearing 3 also comprises two rows of rolling elements 9 and 10 placed between the two rings, and cages 11 and 12 respectively maintaining the circumferential spacing of the rolling elements 9 and 10, in this case made as balls.

[0045] The inner ring 6 and the outer ring 7 are coaxial. In the exemplary embodiment shown, the rings are solid, i.e. they are obtained by machining or grinding to remove material from a metal tube, bar, forging or rolled blank. In an alternative not shown, the rings may be non-coaxial and have an eccentric axis.

[0046] The inner ring 6 comprises a bore 13 , an outer surface 14 , the cylindrical portion of which is provided with raceways 15 , 16 , the axial section of which has a concave annular inner profile adapted to the balls 9 , 10 , and rear and front lateral surfaces 17 , 18 .

[0047] The hole 13 of the inner ring 6 is suitable for receiving a screw 33, the body 34 of which extends axially beyond the rear lateral surface 17 of the fixed inner ring 6, and includes a threaded portion for screwing into a corresponding threaded opening ( / corresponding tapped opening) of a support (not shown) for the pulley device 1.

[0048] The outer ring 7 comprises a cylindrical hole 19 , an outer cylindrical surface 22 , and rear and front lateral surfaces 23 , 24 . The cylindrical hole 19 is provided with raceways 20 , 21 , the axial cross-section of which has a concave annular inner profile suitable for the balls 9 , 10 , and the pulley 2 is mounted on the outer cylindrical surface 22 .

[0049] Advantageously, the bearing 3 comprises an annular rear seal 25 and an annular front seal 26 to close, on each axial side, the radial space 8 present between the rings 6 , 7 and housing the rolling elements 9 , 10 inside it.

[0050] Advantageously, each seal 25, 26 comprises a first end fixed in a circumferential groove provided at a portion of the bore 19 of the outer ring 7 and a second end formed by a lip in sliding contact against a portion of the outer surface 14 of the inner ring 6. In this way, the radial space 8 is closed between the two seals 25, 26 in an axially sealed manner.

[0051] As an alternative, the bearing may comprise a different number of rows of rolling elements arranged between the outer ring and the inner ring, for example a single row of rolling elements.

[0052] As an option, the bearing may include other types of rolling elements, such as tapered rollers or needle rollers.

[0053] The pulley 2 comprises an outer cylindrical surface 27 for engaging a transmission element such as a belt or chain and an inner surface 28 mounted rigidly connected to the outer surface 22 of the outer ring 7. The pulley has a mainly tubular shape and is centered on a central axis X1. The friction between the outer surface 27 and the transmission element allows the transmission of torque.

[0054] According to another embodiment not shown, the transmission element can be a toothed belt, in particular a poly-V type or any other type of toothed belt, but this does not limit the invention. Thus, the outer surface 27 is provided with elements such as ribs or notches to match the shape of the belt.

[0055] The pulley 2 further comprises a rear portion 29 and a front portion 30 protruding in the axial direction with respect to the rear lateral surface 23 and the front lateral surface 24, respectively, of the outer ring 7. The rear portion 29 and the front portion 30 protruding in the axial direction are stepped.

[0056] Advantageously, the pulley 2 can be made of plastic, preferably, the pulley 2 can be made of polyamide, for example, the pulley 2 can be made of PA6 or PA66. Advantageously, the pulley 2 can be formed by overmolding plastic on the outer ring 7 of the bearing 3. The result is excellent cohesion between these parts (outer ring 7 and pulley 2). As an option, the pulley 2 can be made of a metal material and tightly mounted on the outer cylindrical surface 22 of the outer ring 7, for example, the pulley 2 can be made of steel. The pulley 2 can also have other shapes optimized according to the requirements of use.

[0057] The pulley device 1 also includes a rear sleeve 31 and a front sleeve 32 mounted in the hole 13 of the fixed inner ring 6. The sleeves 31, 32 are made of plastic or synthetic material, for example, the sleeves 31, 32 are made of glass fiber reinforced polyamide. As an option, the sleeves can be made of metal, for example, the sleeves can be made of steel.

[0058] The front bushing 32 is arranged radially between the inner ring 6 and the screw 33, on the side of the head 35 of the screw 33. The front bushing 32 is used to supportively receive the head 35 of the screw 33 when the screw 33 is tightened in the corresponding internal thread of the engine support. The front bushing 32 is centered on the axis X32, which, in the configuration of the pulley device 1, converges with the central axis X1. The front bushing 32 includes an axial cylindrical body 36 placed radially between the inner ring 6 and the body 34 of the screw 33. The cylindrical body 36 is freely mounted in the hole 13 of the inner ring 6, so that after installation there is a radial gap between the two elements. The front bushing 32 also includes a radial skirt 37 placed radially between the front lateral surface 18 of the inner ring 6 and the head 35 of the screw 33. The skirt 37 extends axially beyond the front lateral surface 18 of the inner ring 6.

[0059] The rear bushing 31 is intended to be arranged radially between the inner ring 6 and the support of the device 1. The rear bushing 31 is intended to receive the inner ring 6 in a supporting manner when the inner ring 6 is fastened against the engine support by means of the screws 33. The rear bushing 31 is intended to form a seat (rest) for the device 1 on its support. The rear bushing 31 is centered on the axis X31, which, in the installed configuration of the pulley device 1, converges with the central axis X1. The rear bushing 31 includes an axial cylindrical body 38 radially placed between the inner ring 6 and the body 34 of the screw 33. The cylindrical body 38 is freely mounted in the hole 13 of the inner ring 6, so that after installation there is a radial gap between the two elements. The rear bushing 31 also includes a radial skirt 39 radially placed between the rear lateral surface 17 of the inner ring 6 and the support. The skirt 39 extends axially beyond the rear lateral surface 17 of the inner ring 6 , thereby creating a space for a support of the pulley device 1 , preventing any mechanical contact between the rotating elements of the device 1 and the support.

[0060] exist Figure 1 In the embodiment shown in the figure, the rear bushing 31 and the front bushing 32 are identical and are mounted in an axially symmetrical manner. As an option, the rear bushing and the front bushing can be different, for example, the size of the rear skirt is different from the size of the front skirt according to the requirements of the axial spacing between the device 1 and its support.

[0061] The pulley device 1 also comprises a rear protective shield 4 and a front protective shield 5 mounted on both sides of the sealed radial space 8. More precisely, the rear protective shield 4 covers the rear seal 25 and the front protective shield 5 covers the front seal 26 to provide primary protection against external contamination, in particular dust and particles.

[0062] The front shield 5 has a generally radial body extending between a first outer end ( / outer first end) and a second inner end ( / inner second end), wherein the first outer end is mounted in an axially protruding front portion 30 of the pulley 2, and the second inner end is adjacent to the outer surface of the skirt 37 of the front bushing 32.

[0063] The rear shield 4 has a substantially radial body extending between a first outer end mounted in the axially protruding rear portion 29 of the pulley 2 and a second inner end adjacent to the outer surface of the skirt 39 of the rear bushing 31 .

[0064] Advantageously, the shield is formed by cutting a strip made of metal, for example, the shield is formed by cutting a strip made of steel. As an alternative, the shield may be made of plastic or a synthetic material, for example, the shield may be made of polyamide.

[0065] according to Figure 1 In the first embodiment of the invention shown in FIG. 1 , the first outer ends of the rear shield 4 and the front shield 5 are rigidly connected to the pulley 2 . Figure 1 In the example shown in , the first outer end of the front shield 5 rests against the collar 40 of the stepped and protruding front portion 30 of the pulley 2 in the axial direction, and is retained in the other axial direction by a crimping portion 41 obtained by plastic deformation of the lateral edge of the front portion 30. Similarly, the first outer end of the rear shield 4 rests against the collar 42 of the stepped and protruding rear portion 29 of the pulley 2 in the axial direction, and is retained in the other axial direction by a crimping portion 43 obtained by plastic deformation of the lateral edge of the front portion 29. Advantageously, the crimping portions are regularly distributed throughout the axially protruding rear portion 29 and the front portion 30 of the pulley 2 in the circumferential direction. As an alternative, the shield can be rigidly connected to the axially protruding portion of the pulley by any suitable fixing means (for example, by bonding or overmolding).

[0066] according to Figure 1In the first embodiment of the present invention shown in , the second inner ends of the rear shield 4 and the front shield 5 respectively hold the rear bushing 31 and the front bushing 32 in the axial direction. The rear bushing 31 includes a shoulder 44, which protrudes in the radial direction and is axially accommodated between the second inner end of the rear shield 4 and the rear lateral surface 17 of the inner ring 6. In this way, the shoulder 44 is blocked in the axial direction by the rear shield 4, which is itself rigidly connected to the pulley 2. Therefore, the rear bushing 31 cannot be removed from the pulley device 1. Similarly, the front bushing 32 includes a shoulder 45, which protrudes in the radial direction and is axially accommodated between the second inner end of the front shield 5 and the front lateral surface 18 of the inner ring 6. In this way, the shoulder 45 is blocked in the axial direction by the front shield 5, which is itself rigidly connected to the pulley 2. Therefore, the front bushing 32 cannot be removed from the pulley device 1.

[0067] Figure 2 A second embodiment is shown in FIG. 1 . According to this alternative embodiment, the pulley device 1 and Figure 1 The previous embodiment shown in FIG. 4 differs in that the pulley 46 forms a one-piece assembly with the rear shield 47 and the front shield 48 .

[0068] More specifically, the pulley 46 includes a rear pulley element 49 and a front pulley element 50 .

[0069] The rear pulley element 49 comprises an outer annular portion 51 having a cylindrical hole (not indicated) and an outer cylindrical surface 52 that can engage a transmission member. The element 49 also comprises an inner annular portion 53 having an outer cylindrical surface (not indicated) and a cylindrical hole 54 that fits tightly on the outer cylindrical surface 22 of the rotating outer ring 7 of the bearing 3. The outer annular portion 51 is tubular and has a larger diameter than the diameter of the inner annular portion 53, which is also tubular, and radially surrounds the inner annular portion 53. The outer annular portion 51 also has an axial dimension that is larger than the axial dimension of the inner annular portion 53, and the outer annular portion 51 protrudes axially relative to the inner annular portion 53 on the rear axial side of the device 1.

[0070] Finally, the rear pulley element 49 comprises an intermediate portion 55 for connecting the inner annular portion 53 and the outer annular portion 51. The intermediate portion 55 extends radially between the inner portion 53 and the front axial ends of the outer portion 51 of the rear pulley element 49.

[0071] The rear pulley element 49 has a substantially C-shaped axial section defining an annular opening open at the rear axial side of the device 1 in the direction of the support on which the device 1 is intended to be mounted.

[0072] The front pulley element 50 comprises an outer annular portion 56 having a cylindrical hole (not indicated) and an outer cylindrical surface 57 that can engage a transmission member. The element 50 also comprises an inner annular portion 58 having an outer cylindrical surface (not indicated) and a cylindrical hole 59 that fits tightly on the outer cylindrical surface 22 of the rotating outer ring 7 of the bearing 3. The outer annular portion 56 is tubular and has a larger diameter than the diameter of the inner annular portion 58, which is also tubular, and radially surrounds the inner annular portion 58. The outer annular portion 56 also has an axial dimension that is larger than the axial dimension of the inner annular portion 58, and the outer annular portion 56 protrudes axially relative to the inner annular portion 58 at the front axial side of the device 1.

[0073] Finally, the front pulley element 50 comprises an intermediate portion 60 for connecting the inner annular portion 58 and the outer annular portion 56. The intermediate portion 60 extends radially between the rear axial ends of the inner portion 58 and the outer portion 56 of the front pulley element 50.

[0074] The front pulley element 50 has a substantially C-shaped axial section defining an annular opening open at the front axial side of the device 1 , in a direction opposite to the support on which the device 1 is intended to be mounted.

[0075] The front pulley element 50 and the rear pulley element 49 are mounted on the rotating outer ring 7 of the bearing 3 so that their middle parts 60 and 55 bear against each other in the radial direction. The pulley elements 50, 49 are mounted in a symmetrical manner in the axial direction. The outer cylindrical surface 57 of the outer annular part 56 of the front pulley element 50 and the outer cylindrical surface 52 of the outer annular part 51 of the rear pulley element 49 together form a surface for engaging with the transmission element.

[0076] according to Figure 2 In the embodiment of the invention shown in FIG. 4 , the rear pulley element 49 is provided with a rear shield 47 .

[0077] The rear shield 47 extends substantially radially from an axial end of the middle portion 55 of the inner portion 53 axially away from the rear pulley element 49. The rear shield 47 bears axially against the rear lateral surface 23 of the outer ring 7 of the bearing 3. The rear shield 47 is provided with a free end which abuts against the outer surface of the axially protruding rear skirt 39 of the rear bushing 31 to form a radial narrow passage.

[0078] Similarly, in the axially opposite direction of the rear shield 47, the front pulley element 50 is provided with a front shield 48. The front shield 48 extends substantially radially from an axial end of the inner portion 58 axially away from the middle portion 60 of the front pulley element 50. The front shield 48 axially bears against the front lateral surface 24 of the outer ring 7 of the bearing 3. The front shield 48 is provided with a free end which is adjacent to the outer surface of the axially protruding front skirt 37 of the front bushing 32 to form a radial narrow passage.

[0079] Advantageously, each of the rear pulley element 49 and the front pulley element 50 is formed as a single piece, and advantageously, each of the rear pulley element 49 and the front pulley element 50 is formed by cutting and stamping a metal plate, for example, by cutting and stamping a metal plate made of steel.

[0080] The inner ends of the rear shield 47 and the front shield 48 hold the rear bushing 31 and the front bushing 32 in the axial direction, respectively. The rear bushing 31 includes a shoulder 44 that projects radially and is axially accommodated between the second inner end of the rear shield 47 and the rear lateral surface 17 of the inner ring 6. In this way, the shoulder 44 is blocked in the axial direction by the rear shield 47 formed integrally with the rear pulley element 49. Therefore, the rear bushing 31 cannot be removed from the pulley device 1. Similarly, the front bushing 32 includes a shoulder 45 that projects radially and is axially accommodated between the second inner end of the front shield 48 and the front lateral surface 18 of the inner ring 6. In this way, the shoulder 45 is blocked in the axial direction by the front shield 48 itself formed integrally with the front pulley element 50. Therefore, the front bushing 32 cannot be removed from the pulley device 1.

[0081] In an alternative not shown, only one of the front pulley element 50 and the rear pulley element 49 may be provided with a lateral portion.

[0082] Figure 3 A third embodiment is shown in . It differs from the two previous embodiments in that the rear shield 61 and the front shield 62 are rigidly connected to the rear bushing 63 and the front bushing 64 respectively.

[0083] More precisely, the rear bushing 63 comprises a cylindrical body 65 housed in the inner ring 6 and an outer radial skirt 66 protruding axially rearwardly relative to the rear lateral surface 17 of the inner ring 6 of the bearing 3. The skirt 66 comprises a radially protruding convex ring 67. The inner end of the rear shield 61 is held axially against the convex ring 67 by a pressed ridge 68 obtained by plastic deformation of the lateral edges of the skirt 66. In this way, the rear shield 61 is rigidly connected to the rear bushing 63. The rigid connection may be achieved by any other suitable means, for example by bonding.

[0084] The rear shield 61 extends generally radially from the inner end rigidly connected to the bushing 63 toward the outer end of the inner surface of the portion 69 protruding axially rearwardly adjacent to the pulley 70 to form a narrow channel. The portion 69 includes at least one shoulder 71 extending radially inwardly to block the outer end of the rear shield 61 in the axial direction.

[0085] The front bushing 64 comprises a cylindrical body 72 housed in the inner ring 6 and an outer radial skirt 73 protruding axially forward relative to the front lateral surface 18 of the inner ring 6. The skirt 73 comprises a radially protruding convex ring 74. The second inner end of the front shield 62 is held axially against the convex ring 74 by a pressed bulge 75 obtained by plastic deformation of the lateral edge of the skirt 73. In this way, the front shield 62 is rigidly connected to the front bushing 64. The rigid connection can be achieved by any other suitable means, for example, by bonding.

[0086] The front shield 62 extends generally radially from the inner end rigidly connected to the front bushing 64 toward the outer end of the inner surface of the portion 76 protruding axially forward adjacent to the pulley 70 to form a narrow channel. The portion 76 includes at least one shoulder 77 extending radially inward to block the outer end of the front shield 61 in the axial direction.

[0087] Advantageously, the shoulders 71 , 77 of the pulley 70 holding the rear 61 and front 62 screens are formed by pressed ridges, but each shoulder leaves axial play for free movement of the outer ends of said screens.

[0088] Thanks to the invention, the rear shield 61 and the front shield 62 are axially blocked in hollow areas formed at the axially protruding rear portion 69 and front portion 70 of the pulley 70. Since the shields 61, 62 each have an inner end rigidly connected to the bushings 63, 64, respectively, both the rear bushing 63 and the front bushing 64 are thus axially held by the pulley 70 in the device 1.

[0089] Figure 4 A fourth embodiment is shown in . It differs from the previous embodiments in that the rear bushing 78 and the rear shield 80 form a one-piece component, and the front bushing 79 and the front shield 81 also form a one-piece component.

[0090] Figure 5 A fifth embodiment is shown in . It differs from the preceding embodiments in that the rear shield 82 and the front shield 83 are mounted in such a way that they are not rigidly connected to the pulley 86 and the rear bushing 84 and the front bushing 85 but at the same time are held axially by these elements.

[0091] More precisely, the rear shield 82 extends between a first outer end and a second inner end. The outer end is accommodated in a hollow area 87 formed at the inner surface of a portion 88 of the pulley 86 that protrudes axially backward. Advantageously, the hollow area 87 is formed between the convex ring of the portion 88 and the pressed bulge formed by the plastic deformation of the rear lateral edge of the portion 88. The second inner end is accommodated in a hollow area 89 formed at the outer surface of the skirt 90 that protrudes axially backward of the rear bushing 84. The inner and outer ends of the rear shield 82 are blocked in the hollow areas 87, 89 in the axial direction, but have an axial gap that provides a certain degree of freedom. In this way, the rear bushing 84, which is freely mounted in the inner ring 6, is retained in the axial direction. The retaining device does not require high precision in terms of mounting adjustment and tolerance.

[0092] Similarly, the front shield 83 extends between a first outer end and a second inner end. The outer end is accommodated in a hollow area 91 formed at the inner surface of a portion 92 of the pulley 86 that protrudes forward in the axial direction. Advantageously, the hollow area 91 is formed between the convex ring of the portion 92 and the pressed bulge formed by the plastic deformation of the front lateral edge of the portion 92. The second inner end is accommodated in a hollow area 93 formed at the outer surface of a skirt 94 of the front bushing 85 that protrudes forward in the axial direction. The inner and outer ends of the front shield 83 are blocked in the hollow areas 91, 93 in the axial direction, but have an axial gap that provides a certain degree of freedom. In this way, the front bushing 84 freely mounted in the inner ring 6 is retained in the axial direction.

[0093] In addition, the technical features of each embodiment can be complete, and only for some of its technical features, can be combined with other features. Therefore, the pulley device can be adjusted in terms of cost, performance and simplicity of implementation.

Claims

1. A pulley device (1) for a transmission element, the pulley device (1) comprising: - a pulley (2, 46, 70) having an outer surface (27, 52, 57) for engaging the transmission element, - a bearing (3) provided with a rotating outer ring (7), a fixed inner ring (6) and at least one row of rolling elements (9, 10), the pulley being mounted on the outer surface (22) of the outer ring (7), the inner ring (6) and the outer ring (7) being coaxial and forming a radial space (8) between the inner ring (6) and the outer ring (7), the at least one row of rolling elements (9, 10) being arranged in the radial space (8), and - at least one bushing (31, 32, 63, 64, 78, 79) housed in the bore (13) of said inner ring (6), Characterized in that the bushing (31, 32, 63, 64, 78, 79, 84, 85) is freely mounted in the hole (13) of the inner ring (6), and the pulley device (1) also includes at least one annular protective shield (4, 5, 47, 48, 61, 62, 80, 81, 82, 83), the shield (4, 5, 47, 48, 61, 62, 80, 81, 82, 83) having a substantially radial body extending between a first end and a second end, the first end being axially retained in the pulley (2, 46, In one of the pulley and the bushing, the second end is adjacent to the other of the pulley and the bushing, and the other has at least one shoulder (44, 45, 71, 77, 87, 91, 89, 93), and the at least one shoulder (44, 45, 71, 77, 87, 91, 89, 93) protrudes radially to ensure that the at least one shoulder (44, 45, 71, 77, 87, 91, 89, 93) holds the second end in the axial direction.

2. The pulley device according to claim 1, characterized in that: A first end of the shield (4, 5, 47, 48, 61, 62, 80, 81) is rigidly connected to said one of the pulley and the bushing.

3. The pulley device according to claim 1, characterized in that: The shield is formed as a single piece with the one of the pulley and the bushing (47, 48, 80, 81).

4. The pulley device according to claim 3, characterized in that: The pulley (46) is provided with at least one pulley element (49, 50), the at least one pulley element (49, 50) having a C-shaped axial cross section and having an inner portion (53, 58), an outer portion (51, 56) and an intermediate portion (55, 60), the inner portion (53, 58) being mounted on the outer surface (22) of the outer ring (7) of the bearing (3), the outer portion (51, 56) having an outer surface (52, 57) for engaging the transmission element, the intermediate portion (55, 60) extending substantially radially between axial ends of the inner portion (53, 58) and the outer portion (51, 56) along a first axial side, the shield (47, 48) extending laterally and substantially radially from an axial end of the inner portion (53, 58) axially remote from the intermediate portion (55, 60), and the pulley element (49, 50) being formed as a single piece.

5. The pulley device according to claim 1, characterized in that: The first end of the shield (4, 5, 61, 62) is held by being pressed and bulged at a plurality of circumferential locations so as to be rigidly connected to the one of the pulley and the bushing.

6. The pulley device according to any one of claims 1 to 5, characterized in that The shoulder (44, 45, 71, 77) is formed by a raised ring, and the other of the pulley and the bushing is provided with the raised ring.

7. The pulley device according to any one of claims 1 to 5, characterized in that The pulley device (1) comprises two bushings (31, 32, 63, 64, 78, 79, 84, 85) arranged on both axial sides in the hole (13) of the inner ring (6).

8. The pulley device according to any one of claims 1 to 5, characterized in that The shoulder is arranged such that the bushing can be retained axially by interaction between the shoulder and the shield.

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