Protection device for bearings of pulleys in belt drives

Abstract: A device for protecting bearings of idle pulleys in belt drives comprises a cover (22) having a countershaped circumferential connecting portion (23) operatively engageable with a terminal edge (13a) of a fastening collar (13) positioned on said pulley and housing the bearing (18) inside. Elastic tongues (26) projecting from the cover (22) are provided at their ends with corresponding hooking teeth (24) able to clicked get into corresponding through engaging openings (25) obtained in a disc-shaped flange (14), which interconnects the fastening collar (13) with a cylindrical rolling portion (13) of the pulley. The tongues (26) are elastically deformable by virtue of the centrifugal force so that the interference between the hooking teeth (24) and the interconnecting flange (14) is increased by increasing the rotation speed of the pulley (2).

Description: The present invention concerns a pulley assembly for belt drives according to the preamble of claim 1. In particular, the object of the present invention is intended to be used on belt drives of the type mounted on motorvehicle engines and the like. As known, in the motorvehicle engines and the like, the actuating of the common members, as for instance, the a.c. generator and the cooling pump, the pump of the power steering, the compressor of the air conditioner and other ones, is given to a driving belt extending according to a closed line around a driving pulley, moved by the engine itself, as well as around different driven pulleys arranged for setting in action the above said members. Moreover, in a lot of cases there are provided one or more idle pulleys, used as simple slide guide pulleys and/or associated to known belt tensioners apt to give a constant tensioning to the belt itself, to assure a uniform transmission of motion in absence of slipping actions. The above said idle pulleys usually are mounted on respective supporting pivots upon previous interposition of rolling ball bearings or rollers. More particularly, each bearing has its own fixed inner ring, rigidly fitted around a supporting core borne by the stationary structure of the engine or by a movable arm making part of the belt tensioner as well as a rotating outer ring, anchored in an engagement housing obtained within a fastening collar making part of the pulley. A disc-shaped flange radially projects from the fastening collar of substantially cylindrical shape, said disc-shaped flange supporting, in a radially outer position, a cylindrical rolling portion which circumscribes coaxially the fastening collar and has an outer working area arranged to act in contact relation with the driving belt. In consideration of the aforesaid, it is pointed out that the bearings mounted on the above said pulleys are subjected to working situations that expose them to risks of premature wearing and/or seizing owing to the great quantity of dust, deposits, water and other outer agents to which they are exposed. It is clear that such a situation represents a great problem, since in consequence of the bearing seizing, the driving belt breaks owing to the strong sliding of the same on the locking pulley. The attempts made up to now to overcome said type of problem are potentially directed to use protecting elements secured to the supporting central core of the bearing in order to protect this latter from the contact with the above mentioned outer agents. By way of example, see what shown in the figures of the U.S. Patents No. 4,551,120 and No. 4,698,049 and of U.K. patent No. 2,258,287. However, these solutions cannot guarantee an absolute protection of the bearing since, in order to avoid mechanical interferences between the fixed protection and the pulley or the movable part of the bearing, it is necessary to provide mechanical clearances that, as far as reduced, constitute in any case a way through which the outer agents can reach the bearing. FR-A-2274461 discloses a pulley assembly as claimed in the preamble of claim 1, including a pulley mounted on a shaft through the interposition of a bearing assembly and a protecting device to protect the bearing assembly. The protecting device presents a relatively complex and expensive structure, since it is formed by two different elements, a sealing ring forced inside the pulley and against the outer ring of a rolling bearing of the bearing assembly, and a cover coupled to the sealing ring. In agreement with the present invention, it has been found that the bearing is perfectly protected utilizing a cover engageable in a tight manner on any one of the two terminal edges of the fastening collar and anchorable in a removable manner to the pulley by hooking means operating across through openings obtained in the disc-shaped-flange; it is solved the technical problems deriving from the anchoring of the cover itself on the pulley rotatable part in presence of the considerable centrifugal stresses, the whole maintaining the possibility of easily removing the cover itself and considerably containing the costs for its realization. More particularly, the invention concerns a pulley assembly for belt drives according to the preamble of claim 1, including a device for protecting said bearing characterized by the features according to the characterizing portion of claim 1. Moreover it is provided that the said elastic means are also elastically deformable in consequence of the centrifugal force, so that the interference between the hooking means and the radially outer edges of said openings tends to increase by increasing the rotation speed of the pulley. Advantageously, said hooking means comprise a plurality of hooking teeth circumferentially arranged around the axis of the cover and each showing a substantially wedge-shaped profile defined by an inclined guide surface directed to the opposite part with respect to the cover and arranged to interfere with the radially outer edge of the corresponding engaging opening to which a stop surface follows; said stop surface being turned towards the cover and oriented in a substantially radial direction with respect to the axis of this latter to act in abutment relationship against the disc-shaped flange, on the opposite part with respect to the cover, said guide and stop surfaces meeting at an apex spaced from the axis of the cover according to a measure greater than the radial distance of the outer edge of said engaging opening with respect to the axis of the pulley. Preferably, the elastic means comprise on their turn a plurality of elastic tongues extending in a projecting manner from said cover and each supporting at their ends one of said hooking teeth. Preferably there are also provided centering means associated to said cover to guide it coaxially to the fastening collar during the engagement of the cover itself with the pulley. Advantageously, said centering means comprise circumferentially distributed pins, extending in a projecting manner from the cover and arranged to slidly act in opposition relation, on the outer cylindrical surface of the fastening collar. According to the requirements, it is possible to provide at least two hooking teeth and at least two elastic tongues placed in diametrically opposite positions with respect to the axis of the cover and able to operatively fit into corresponding through engaging openings, or at least three hooking teeth and at least three corresponding closing tongues, distributed angularly at 120 degrees with respect to the axis of said cover. More in detail, in a preferred embodiment the device forming the object of the present invention comprises four hooking teeth and four corresponding closing tongues, distributed according to an angular pitch of 90 degrees with respect to the axis of the cover and arranged to fit into corresponding through engaging openings. Further features and advantages will better appear from the detailed description of some preferred, but not exclusive, embodiments, of a device for protecting bearings of pulleys in belt drives according to the present invention. Said description will be made hereinafter with reference to the attached sheets of drawing, supplied by way of non-limiting example, wherein: Figure 1 shows schematically a discontinued perspective view of a belt drive associated to a motorvehicle engine and provided with a tensioner to assure a correct tensioning action of the belt; figure 2 is an exploded perspective view of a pulley provided with the device for protecting the bearing according to the present invention; figure 3 is a lateral view of a pulley provided with the protecting device forming the object of the present invention; figure 4 is a sectional view of the pulley of figure 3. With reference to the cited figures, and in particular to figures 2 and 4, reference numeral 1 indicates a device for protecting bearings of pulleys in belt drives, taken as a whole, according to the present invention. In the example referred to in figure 1, the device 1 is associated to an idle pulley 2, operatively connected to a movable arm 3 making part of a conventional belt tensioner 4, associated on their turn to a belt drive of a motorvehicle engine indicated as a whole with reference numeral 5 in figure 1, in order to assure a correct tensioning action to a driving belt 6. As information, in the example of figure 1 the driving belt 6, moved by a driving pulley 7, put into rotation by the engine, provides to set in action a first, second, third, fourth and fifth driven pulley 8, 9, 10, 11 and 12, respectively associated to a cooling pump (not shown), a pneumatic feed pump 9a for a ventilating circuit of the vehicle, an alternator 10a, a compressor 11a for the cooling circuit of an air conditioner, as well as to a hydraulic pump of a power steering (not shown). The pulley 2 is of the type made of plastic material molded by injection and has conventionally a fastening collar 13 of a substantially cylindrical configuration, a connecting disc-shaped flange 14 extending coaxially around the fastening collar 13 substantially according to a plane perpendicular to the axis of this latter, as well as a cylindrical rolling portion 15 circumscribing coaxially the fastening collar 13 and the connecting flange 14. An outer working area 15a is obtained on said cylindrical rolling portion 15, said outer working area 15a being arranged to act in contact relationship on the driving belt 6, in a length comprised between the third and the fourth driven pulleys 10 and 11. Radial ribs 14a equally angularly spaced are moreover arranged between the fastening collar 13 and the cylindrical rolling portion 15. Inside the fastening collar 13 there is an engagement housing 16 in which an outer ring 17 is fixed, said outer ring 17 making part of a common ball bearing 18 whose inner ring 19 is coaxially fitted around a supporting core 20 projecting from the above said arm 3. More particularly, the fixing of the outer ring 17 in the engagement housing 16 can be obtained, for example, by forcing the bearing 18 into the fastening collar 13, or by forming the pulley 2 directly around the outer ring itself after having placed the bearing 18 inside the injection mould utilized for realizing the pulley 2. The inner ring 19, on its turn, is fixed on the supporting core 20 through a forcing action and/or with the aid of an axial blocking threaded device 21. The device according to the present invention aims to protect the bearing 18 from the contact with dust, sand, particles, water and any other substance that can cause a premature wearing and/or impair its functionality. To this end, the device 1 comprises at least a cover 22 placed coaxially against one side of the pulley 2, as clearly visible in figures 2 and 3. The cover 22 has a circumferential connecting portion 23 countershaped to and operatively engageable with one of the terminal edges 13a of the fastening collar 13. As it can be easily noticed from figure 3, the engagement between the circumferential connecting portion 23 of the cover 22 and the corresponding terminal edge 13a of the fastening collar 13 takes place substantially in a hermetic seal relationship, so that, on the side of the pulley 2 supporting the cover itself, the bearing 18 is completely protected from the contact with the outer agents. In the represented example, on the side of the pulley 2 opposite to the cover 22, the protection of the bearing 18 from the contact with particles and impurities is given, in a way known per se, to a flat screening surface 3a defined on the movable arm 3, or on another fixed structure bearing the supporting core 20, extending close by the terminal edge 13a opposite to that mounting the cover 22. Alternatively, it is possible to arrange two covers 22, one per side of the pulley 2. Of course, the outer shape of the cover 22 can be any one depending on the requirements. By way of example, in the embodiment shown in figures 3 and 4, where the threaded device 21 has a flattened head 21a, the shape of the cover is substantially flat. Instead, in the example of figures 1 and 2, the cover 22 has a cupola-like shape and is fitted to house threaded elements having larger axial overall dimensions. Always in agreement with the present invention, the engagement of the cover 22 with the pulley 2 is obtained through hooking means 24 operatively connected to the cover itself and able to be inserted into corresponding through engaging openings 25 obtained in the disc-shaped flange 14, as it will better appear hereinafter. Interconnecting elastic means 26 operate between the hooking means 24 and the cover 22. Preferably, said elastic means 26 are constituted by elastic tongues extending in a projecting manner from the cover itself and enabling the hooking means to be inserted with snapping action into the through openings 25 on the radially outer edges 25a. More particularly, the above said hooking means comprise a plurality of hooking teeth 24 circumferentially distributed around the axis of the cover 22, each borne by one of the elastic tongue 26, at the end. As clearly visible in figure 2, each hooking tooth 24 has a substantially wedge-shaped profile, defined by an inclined guide surface 24a, directed to the opposite part with respect to the cover 22, to which a stop surface 24b follows; said stop surface 24b being turned towards the cover itself and oriented in a substantially radial direction with respect to the axis of this latter. The guide surface 24a and the stop surface 24b meet at an apex 24c spaced from the axis of the cover 22 according to a slightly larger size than the radial distance of the outer edge 25a of the corresponding engaging opening 25 with respect to the axis of the pulley 2. In this way, the application of the cover 22 requires only that this latter be coaxially pushed against the pulley 2 on the side of this latter where the cover itself will be engaged. In fact, in said a situation the hooking teeth 24 at the beginning will go to interfere with the radially outer edges 25a of the engaging openings 25 through the respective inclined guide surfaces 24a. In consequence of said interference, the hooking teeth 24 will be pushed radially toward the axis of the cover 22, upon the elastic deformation of the tongues 26, as long as the apices 24c will have passed over completely the radially outer edges 25a of the corresponding engaging openings 25. At this point, the elastic action of the tongues 26 will make the hooking teeth 24 click radially towards the outside, so that the stop surfaces 24b offer to act in abutment relationship against the disc-shaped flange 14, on the part opposite to the cover 22, to hold this latter axially against the corresponding side of the pulley 2. In this situation, the cover 22 will be with its circumferential connecting portion 23 in engagement relationship with the corresponding terminal edge 13a of the fastening collar 13, assuring the optimal protection of the bearing 18 from the contact with the impurities coming from outside. Advantageously, when the pulley 2 rotates at high speed in consequence of the pulling by the belt 6, the effect of the centrifugal force on the hooking teeth 24 is such that, thanks to the elastic deformability of the tongues 26, the interference between the teeth and the outer edges 25a of the openings 25 tends to be increased of a measure as greater as the rotation speed is higher. In other words, the effect of the centrifugal force is a bar to the movement of the teeth 24 towards the axis of the pulley 2 and the cover 22, of a measure as greater as the rotation speed is higher. This situation represents an optimal security, since it eliminates any risk of an accidental release of the cover 22 in consequence of the rotation. When the pulley is not working, it will be sufficient to act on one or more of the elastic tongues 22 with the point of a screwdriver or other suitable tool to obtain the release of the hooking teeth 24 from the disc-shaped flange 14 and the consequent removal of the cover 22 in case of necessity, for instance to allow the access to the bearing 18 for maintenance operations and/or to remove the pulley 2. In a preferred embodiment, the cover 22 is moreover associated to centering means, constituted for instance by circumferentially distributed centering pins 27, extending in a projecting manner from the protection cover itself and arranged to act in opposition relation on the outer cylindrical surface of the fastening collar 13 so that, during the assemblage, the cover itself is suitably guided coaxially to the fastening collar. Therefore, it is achieved a further simplification of the operations of application of the cover 22 on the pulley 2, as well as the elimination of any possibility to insert the teeth 24 in a not correct position, with the consequent risk of damaging the teeth themselves and/or the elastic tongues 26. In the shown example, it is provided that two of said centering pins 27 be placed alongside each elastic tongue 26, symmetrically on opposite parts. Of course, also the number of hooking teeth 24 and elastic tongues 26, as well as the corresponding openings 25, can be any one depending on the requirements. In the shown example, there are arranged four hooking teeth 24 and as many elastic tongues 26 distributed according to an angular pitch of 90 degrees, arranged to go into the four corresponding engaging openings 25. Alternatively, it could be possible to use only two hooking teeth 24 and corresponding elastic tongues 26, arranged in positions diametrally opposite with respect to the axis of the cover 22 or, preferably, at least three hooking teeth 24 and corresponding elastic tongues 26, arranged angularly at 120 degrees with respect to the axis of the cover. Thus the invention achieves important advantages. As clearly results from what previously described, the protetion device forming the object of the present invention is an optimal protection for the bearing without leaving, on the side of the pulley 2 supporting the cover 22, any space that can constitute an access way for the impurities towards the bearing. Also it is noted that the perfect closing made by the cover 22 on the terminal edge 13a of the fastening collar 13 enables the cover itself to be an efficacious means to contain the noise transmitted by the bearing 18 towards outside, in consequence of the rolling action at high speed. Thanks to the arrangement of the through openings 25 across the disc-shaped flange 14, the device forming the object of the present invention permits moreover to apply the cover on both sides of the pulley, without requiring to this end any additional elements and/or structural modifications of the same. Moreover the protection cover can be easily removed from the pulley in case of need, without that said removal easiness produces risks of accidental disengagement by the cover itself during the rotation at high speed. In fact, as it has been seen, the effects of the centrifugal force assure a greater stability of the connection. Moreover, it is pointed out that the device forming the object of the present invention achieves all the above mentioned advantages also maintaining a very simple and essential structure, realizable at greatly contained costs. Of course, the invention as herein drawn-up can include numerous amendments and alternative embodiments, all deriving from the inventive principle that characterizes the same, which is defined by the claims.

Claims: Pulley assembly for belt drives comprising: a pulley (2) having a fastening collar (13) in which there is an engagement housing (16) for an outer ring (17) of a rolling bearing (18), a connecting disc-shaped flange (14) extending coaxially around said fastening collar (13) substantially according to the plane perpendicular to the axis of this latter, and a rolling cylindrical portion (15) coaxially circumscribing the fastening collar (13) and the disc shaped flange (14) and showing an outer working area (15a) arranged to act in contact relationship on a driving belt (6), and a device (1) protecting said rolling bearing (18); characterized by the fact that said device (1) comprises: at least a cover (22) having a circumferential connecting portion (23) operatively engaging with a terminal edge (13a) of said fastening collar (13); a plurality of hooking means (24) operatively connected with the cover (22), each engaging a corresponding through engaging openings (25) in said disc-shaped flange (14) and acting in abutment relationship on the disc-shaped flange itself, on the opposite part with respect to the cover (22), fixing this latter in a removable manner to said pulley (2); and a plurality of interconnecting elastic means (26) operating between the hooking means (24) and the cover (22) and snapping the hooking means themselves on the radially outer edges (25a) of said engaging openings (25). Pulley assembly according to claim 1, characterized by the fact that said hooking means comprise a plurality of hooking teeth (24) circumferentially distributed around the axis of the cover (22) and each having a substantially wedge-shaped profile defined by an inclined guide surface (24a) directed to the opposite part with respect to the cover (22) and arranged to interfere with the radially outer edge (25a) of the corresponding engaging opening (25), to which a stop surface (24b) follows up, said stop surface (24b) being turned towards the cover (22) and oriented in a substantially radial direction with respect to the axis of this latter to act in abutment against the connecting disc-shaped flange (14), on the opposite part with respect to the cover itself, said guide surface (24a) and stop surface (24b) joining at an apex (24c) spaced from the axis of the cover (22) according to a measure greater than the radial distance of the outer edge (25a) of said engaging opening (25) with respect to the axis of the pulley (2). Pulley assembly according to claim 2, characterized by the fact that said elastic means comprise a plurality of elastic tongues (26) extending in a projecting manner from said cover (22) and each bearing at their ends one of said hooking teeth (24). Pulley assembly according to claim 1, characterized by the fact of comprising moreover centering means (27) associated to said cover (22) to pilot it coaxially to the fastening collar (13) during the engagement of the cover with the pulley (2). Pulley assembly according to claim 4, characterized by the fact that said centering means comprise centering pins (27), circumferentially distributed, extending in a projecting manner from the protection cover (22) and arranged to act in a sliding manner on the outer cylindrical surface of the fastening collar (13), in opposition relation. Pulley assembly according to claim 3, characterized by the fact of comprising at least two hooking teeth (24) and at least two elastic tongues (26) placed in diametrically opposite positions with respect to the axis of the cover (22) and able to operatively engage with corresponding through engaging openings (25). Pulley assembly according to claim 3, characterized by the fact of comprising at least three hooking teeth (24) and at least three corresponding elastic tongues (26), distributed angularly at 120 degrees with respect to the axis of said cover (22) and able to operatively engage with corresponding through engaging openings (25). Pulley assembly according to claim 3, characterized by the fact of comprising four hooking teeth (24) and four corresponding elastic tongues (26), distributed according to an angular pitch of 90 degrees with respect to the axis of the cover (22) and arranged to engage with corresponding through engaging openings (25). Pulley assembly according to anyone of the foregoing claims, wherein said elastic means (26) are moreover elastically deformable in consequence of the centrifugal force, so that the interference between the hooking means (24) and the radially outer edges (25a) of said openings (25) tends to increase by increasing the rotation speed of the pulley (2).

Inventors: FOLEY MARK PATRIK, ROCCA CARLO EMILIO, FOLEY, MARK PATRIK, ROCCA, CARLO EMILIO
Applicants: DAYCO EUROP SRL, DAYCO EUROPE S.R.L.
Application year: 1995
Main classification: F16C33
IPC codes: F16C33, F16C13, F16H55