Title of Invention

"A TENSIONING ROLLER FOR A FLEXIBLE DRIVE"

Abstract

A tensioning roller or a return pulley for a flexible drive, comprising a roller bearing (3), the inner ring (8) of which is positioned by means of a spacer (4a, 4b) and a bolt (5), and a flexible drive element is carried on an idler sheave (2) of the tensioning roller (1) enclosing an outer ring (10) of the roller bearing (3), the roller bearing (3) enclosing, at least on one side, an axially spaced sealing cap (13a, 13b). which engages over an annular gap (14) between the inner ring (8) and the outer ring (10), characterized in that the sealing cap (13a, 13b), which is detachably fixed indirectly or directly to the outer ring (10) of the roller bearing (3) by a positively interlocking and/or non-positive connection together with the spacer (4a, 4b) forms a labyrinth seal (23a, 23b), and the sealing cap (13a, 13b) is connected to the spacer (4a, 4b) so that these components with the tensioning roller (1) are captively combined into one basic unit (34). Figure 1

Full Text

The present invention relates to a tensioning roller for a flexible drive. The present invention relates to a seal for a roller bearing of a tensioning roller or a return pulley, which is positioned by a spacer. The seal comprises a sealing cap, which covers an annular gap between an inner bearing ring and an outer bearing ring of the roller bearing. The sealing cap rotating with the bearing ring and spaced at an axial distance from the rolling elements of the roller bearing is guided maintaining a seal gap up to the spacer. Background of the invention The published patent application DE 41 33 777 Al shows the construction of a tensioning roller for a flexible drive. The tensioning roller supported on roller bearings comprises an inner bearing ring, which arranged on an adjusting bush connected to a spacer, is fixed to the casing, in particular to the crankcase of an internal combustion engine, by means of a separate fixing bolt. The known tensioning roller does not demonstrate any measure by means of which the spacer, with the tensioning mechanism in the pre-assembled state, can be held captive to the tensioning mechanism. The known seal is unsuitable for vehicles used in off-road operation that involves running through water and/or a massive ingress of dirt into the space provided for installation of the internal combustion engine. Providing tensioning rollers with a spacer, on which the inner ring of the roller bearing is preferably positioned, in order to obtain a defined installation position, is also known. A fastener, in particular a bolt, is in this case led through the longitudinal hole in the spacer and the bearing inner ring, in order to fix the basic unit, the tensioning roller and the spacer, for example, to an internal combustion engine. Spacers used in this way have a centering step to accommodate the inner bearing ring, and a flange which extends radially over the entire end face contour of the roller bearing. On the outside the flange with a cylindrical collar covers a hub area of an idler sheave, which is rotationally locked to the outer bearing ring of the roller bearing. This known construction means that the spacer has to be locked to the tensioning roller during assembly, for example by means of a separate locking device, which after assembly of the tensioning roller is in each case redundant - The object of the invention is to provide a simple tensioning roller which is inexpensive to assemble and the associated spacer of which is held captive to the tensioning roller. The aforesaid object is achieved by the features of claim 1. According to this the tensioning roller or return pulley- comprises a sealing cap which is dstachably fixed indirectly or directly to th* outar bearing ring of the tensioning roller by a positively interlocking and/or non-positive connection. The sealing cap is furthermore connected to the spacer with a certain amount of play, forming a labyrinth seal. According to the invention the sealing cap makes possible a basic unit in which the components, the tensioning roller, the spacer and the sealing cap, are held captive to one another. The entire basic unit can thereby be delivered already complete to an assembly device, which, for example, automatically fixes the basic unit according to the invention to the internal combustion engine. The invention reduces the cycle times for assembly and permits an optimum cost-effective assembly process. The construction of the tensioning roller or return pulley according to the invention comprises an idler sheave which externally encloses the roller bearing and on which the flexible drive element of the flexible drive is carried. The roller bearing is preferably centered by positive interlocking on a spacer, the basic unit comprising the tensioning roller and spacer components being detachably connected to a casing of an internal combustion engine, for example, by means of a bolt. In contrast to the known state of the art, a sealing cap is according to the invention assigned to the basic tensioning roller unit previously described. Together with the spacer, the positioned sealing lip fixed indirectly or directly to the outer bearing ring of the roller bearing by a positively interlocking and/or non-positive connection furthermore forms a labyrinth seal. For this purpose the labyrinth seal is designed so as to ensure a captive attachment of the spacer to the sealing cap having a certain play. The invention consequently provides a basic unit in which all components, the tensioning roller, the spacer and the sealing cap, are held captive together. Advantageous developments of the invention form the subject matter of the dependent claims 2 to 18. The tensioning roller advantageously comprises a plastic idler sheave, which may also be referred to as a plastic pulley, which encloses the outer bearing ring of the roller bearing. This measure ensures cost-effective manufacturing of the idler sheave by means of a plastic injection molding process, this process permitting direct molding around the outer bearing ring. The plastic idler sheave, which is advantageously provided with strengthening ribs, possesses sufficient rigidity and has a weight advantage compared to a steel idler sheave. The plastic idler sheave is advantageously provided with an axially projecting, closed cylindrical step. When fitted, a cylindrical flank of the sealing cap engages over the step of the idler sheave. Lugs on the flank, integrally connected to the cylindrical flank and advantageously in part directed radially inwards, grip in a snap-groove geometry of the axially projecting step on the idler sheave in order to achieve a positively interlocking fit. The sealing cap according to the invention is advantageously provided with at least one, and advantageously with a plurality of holes or gaps aligned symmetrically with one another in the cylindrical flank of the scaling cap. The configuration or arrangement of these holes is such that they allow dirt particles or liquids to escape from an annular gap axially defined by the roller bearing and the sealing cap. This allows the escape of contaminants occurring under centrifugal force in the operating state, that is to say when the tensioning roller is rotating, to be optimized in that the contour of the axial step on the idler pulley is beveled in order thereby to optimize the escape of contaminants from the intermediate space formed as an annular gap. The sealing cap is preferably rotationally locked to the idler sheave of the tensioning roller. One possibility according to the invention is to provide the sealing cap with an axially aligned projection, which when installed engages with a positive interlock in an end-face recess of the axial step. The invention further encompasses alternative solutions for achieving an effective rotational locking between the idler pulley and the sealing cap. According to the invention in one development of the labyrinth seal between the sealing cap and the spacer the radial flank of the sealing cap engages with a certain play in an annular groove in the spacer. The engagement of the flank in the annular groove is designed so as to achieve an optimum in terms of assembly on the one hand and sealing effect on the other, A radial overlap of > 0.5 mm between the inner contour of the sealing cap and the wall height on the spacer in the area of the annular groove is particularly suitable for this purpose. The choice of material for the sealing cap and the design may have an influence on the radial overlap by giving it a certain alasticity. Thie means that a certain radial deflection of the radial flank o£ the sealing cap occurs during assembly, said flank automatically springing back on reaching the annular groove in the spacer and engaging in the annular groove with a certain amount of play. In order to facilitate assembly and to avoid any damage, particularly of the sealing cap, the latter in the area of the radial flank advantageously has zones of reduced wall thickness distributed around the circumference. This measure, advantageously combined with a circumferential chamfer, on the end face of the relevant circumferential surface of the spacer and internally on th* radial flank of the sealing cap, result in easier, non-destructive fitting of the sealing cap. To improve the action of the labyrinth seal, the annular groove in the spacer is defined by groove walls which differ from one another in their height. The annular groove remote from the roller bearing in this case exceeds the height of the opposing annular groove. so that overall an extended seal gap is created in the area of the labyrinth seal. This design principle decisively improves the sealing (juality and when the internal combustion engine is running thereby reduces tb« ingress of contaminants or liquids via the seal gap of the labyrinth seal into the internal space between the roller bearing and the sealing cap. According to the invention, the invention furthermore encompasses the design of a spacer, the radial flank of which is in the fitted position assigned with a certain amount of play to a shoulder, which is formed between the roller bearing and the sealing cap. This design is suitable for fitting the sealing cap once the roller bearing, in conjunction with the idler pulley, has been positioned on a centering spigot of the spacer, before then fixing the sealing cap, fed axial ly over the spacer, to the idler pulley. A defined co-ordination of the roller bearing and spacer components is advantageously achieved in that tho spacer has a centering flange or a centering spigot, on which the inner bearing ring of the roller bearing is pressed. This design configuration ensures a correct angular alignment of the roller bearing in conjunction with the idler pulley on the spacer which is necessary for functioning of the flexible drive. As a measure designed to facilitate assembly, the cylindrical rim of the sealing cap is according to the invention also provided with indentations which are distributed around the circumference and which extend to a limited degree into the radial flank. During fitting, this allows the rim to be radially deflected without sustaining damage. According to a further advantageous development of the invention the sealing cap is provided with an offset in the area of the radial flank. This feature firstly permits a defined axial distance between the labyrinth seal and the roller bearing. The offset furthermore improves the elasticity of the sealing cap, which in particular makes it easier to fit the sealing cap into an annular groove in the spacer. As an alternative to an arrangement of the sealing cap on the spacer affording a certain amount of play in the area of the labyrinth seal, one possibility according to the invention is to provide a seal, in particular a felt sealing ring. This felt sealing ring, which reduces the seal gap, improves the sealing effect without any detrimental permanent contact with the spacer. This improves the seal quality without at the same time affecting the mechanical load stress on the roller bearing due to higher component temperatures. As an alternative to a felt seal or a felt sealing ring in the araa of the labyrinth seal, according to the invention a grease collar may be provided internally on the radial flank of the sealing cap. A highly viscous grease, which adheres permanently to the sealing cap and therefore also enhances the sealing effect, is suited to this purpose. The sealing cap according to the invention can be manufactured cost-effectively from a metallic material by a chipless, deep-drawing process. A suitable alternative to this is a plastic sealing cap, an injection molding process being particularly well-suited to production in large quantities. Brief description of die drawings Tensioning rollers in conjunction with sealing caps of different designs according to the invention are represented in two drawings, of which: Fig. 1 shows a half-sectional view of a tensioning roller, the sealing cap of which together with a step of the spacer forms a labyrinth seal; Pig. 2 shows a tonsioning roller in which the associated sealing cap engages in an annular groove in the spacer to form a labyrinth seal; Fig. 3 shows a longitudinal section through the tensioning roller in Fig. 2. Detailed description of the drawings Pig. 1 shows a tensioning roller 1, the construction of which comprises a plastic idler sheave 2, which is designed, by way of a roller bearing 3, to rotate in relation to a spacer 4a. When fitted, the tensioning roller 1 is fixed by means of a bolt 5 fed through a longitudinal hole 6 in the spacer 4a and supported on the roller bearing 3. The spacer 4a is provided with a centering flange 7, on which an inner ring 8 of the roller bearing 3 is positioned, preferably by means of a press-fit, and at the end face is supported on a shoulder 9 of the spacer 4a. An outer ring 10 of the roller bearing 3 is externally enclosed by and thereby positively connected to the idler sheave 2. Rolling elements 12 carried in a cage 11 are arranged between the inner ring 8 and the outer ring 19 of the roller bearing 3 spaced at a radial distance from one another. The tensioning roller 1 furthermore has a sealing cap 13a, which on the one hand seals off an annular gap 14 occurring between the spacer 4a and the idler sheave 2, and which furthermore ensures a captive attachment of the spacer 4a to the tensioning roller 1. For this purpose the sealing cap 13a is positioned by way of a cylindrical rim 15 on a step 16 of the idler sheave 2. The cylindrical rim 15 engages over the axial ly projecting step 16 and by means of lugs 17 in part arranged radially inwards is at the same time connected by positively interlocking in an annular groove 18 of the step 16, said groove representing a snap-roller geometry. By means of a flank 19a directed radially inwards, the sealing cap 13a is guided up to a circumferential surface 21 of the spacer 4a whilst maintaining a seal gap 20. The free end of the radial flank 19a is furthermore spaced at an axial distance from a radial step 22 of the spacer 4, so that a labyrinth seal 23a is created between the radial flank 19 and the spacer 4a. A rotational lock 24 is furthermore provided between the sealing cap 13a and the idler sheave 2. For this purpose an axially aligned projection 25 of the sealing cap 13a interlocks in a correspondingly designed recess 26 in the axially aligned step 16 of the idler sheave 2. The radial flank 19a of the sealing cap 13a further comprises an offset 27, which serves to determine a defined distance between the roller bearing 3 and the sealing cap 13a. The offset 27 furthermore permits a certain elasticity, in order to facilitate fitting of the sealing cap 13a. One possible means of reducing the seal gap 21 is to provide an annular groove 28 on the inside of the radial flank 29, in order to accommodate a sealing ring. A felt sealing ring 39 which, taken up to the circumferential surface 21 of the sealing cap 13a, after a running-in phase forms a tightly defined seal gap, is advantageously suited to this purpose, in the area of the cylindrical rim 15 the sealing cap I3a is also provided with at least one hole 40. The function of the hole 40 is to allow contaminants which have got into the annular gap 14 during operation, that is to say when the idler sheave 2 is rotating, to escape under centrifugal force. Fig. 2 shows the tensioning roller 1 having a construction largely corresponding to that in Fig. 1. All differences from the tensioning roller 1 shown in Fig. 1 will be explained below. The spacer 4b forms an annular groove 29, into which the free end of the radial flank 19b of the sealing cap 13b interlocks with a certain amount of play. For this purpose the free end of the radial flank 19b is, when fitted, spaced at an axial distance from each of the groove walls 30, 31 and a groove base 32 of the annular groove 29. This arrangement forms the labyrinth seal 23b. Pig. 2 shows the sealing cap 13b in the fitted position, in which a radial overlap "Y" occurs between an inner contour of the radial flank 19b of the sealing cap 13b and the groove wall 31, or the circumferential surface 35 of the spacer 4b adjoining the former. The radial overlap *Y* in conjunction with the positively interlocking attachment of the sealing cap 13b to the idler sheave 2, as mentioned in the description of Pig. 1, creates a captive arrangement of all components of the tensioning roller 1, in order to form one basic unit 34. The spacer 4b and the sealing cap 13b are provided with design measures in order to facilitate assembly of these components. For this purpose the spacer 4b at the end face has a circumferential outer chamfer 36 in a transitional zone between the shoulder 33 and a circumferential surface 35. Matching this, the radial flank 19b of the spacer 4a is provided with an inner chamfer 37, these chamfers together facilitating assembly of the sealing cap 13b and spacer 4b components. As a further measure facilitating assembly, tha sealing cap 13b is in part provided in the area of the radial flank 19b with zones 38 of reduced wall thickness running radially from the inner contour, so that when fitting the sealing cap 13b onto the spacer 4b the radial flank I9b can be more easily deflected radially, resulting in a non-destructive assembly process. The zone 38 of reduced wall thickness, especially in conjunction with the offset 27 in the area of the radial flank 19b, has a. positive effect in obtaining a desired elasticity of the sealing cap 13b, which is necessary for non-destructive assembly. A suitable alternative to different wall thicknesses are radial indentations of limited length in the area of the zone 38. As a further aid to assembly, the sealing cap 13b is provided with indentations 41, which extend over the entire length of the cylindrical rim 15 and reach into the flank 19b. Fig. 3 shows a longitudinal section through the tensioning roller 1, which together with the sealing cap 13b and the spacer 4b forms the basic unit 34. This representation also contains a bolt 5, by means of which the unit can be detachably fixed, for example, to a casing of an internal combustion engine not shown in Fig. 3. For this purpose the bolt 5 is inserted into the longitudinal hole 6 in the spacer 4b. A bolt head 42 rests flat against the inner ring 8 of the roller bearing 3. In the fitted position the bolt 5 produces a non-positive* braced support for the inner ring 8 on the shoulder 33 of the spacer 4b, which is supported on the internal combustion engine by way of an end face 43. Reference minerals 1 Tensioning roller 2 Idler sheave 3 Roller bearing 4a Spacer 4b Spacer 5 Bolt 6 Longitudinal hole 7 Centering flange 8 inner ring 9 Shoulder 10 Outer ring 11 Cage 12 Rolling element 13a Scaling cap 13b sealing cap 14 Annular gap 15 Rim 16 Step 17 Lug 18 Annular groove 19a Flank 19b Flank 20 Seal gap 21 Circumferential surface 22 Step 23a Labyrinth seal 23b Labyrinth seal 24 Rotational lock 25 Projection 26 Recess 27 Offset 28 Annular groove 29 Annular groove 30 Groove wall 31 Groove wall 32 Groove base 33 Shoulder 34 Basic unit 35 Circumferential surface 36 Outer chamfer 37 inner chamfer 38 Zone 39 sealing ring 40 Hole 41 indentation 42 Bolt head 43 End face We claim: 1. A tensioning roller or a return pulley for a flexible drive, comprising a roller bearing (3), the inner ring (8) of which is positioned by means of a spacer (4a, 4b) and a bolt (5), and a flexible drive element is carried on an idler sheave (2) of the tensioning roller (1) enclosing an outer ring (10) of the roller bearing (3), the roller bearing (3) enclosing, at least on one side, an axially spaced sealing cap (13a, 13b) which engages over an annular gap (14) between the inner ring (8) and the outer ring (10), characterized in that the sealing cap (13a, 13b), which is detachably fixed indirectly or directly to the outer ring (10) of the roller bearing (3) by a positively interlocking and/or non-positive connection together with the spacer (4a, 4b) forms a labyrinth seal (23a, 23b), and the sealing cap (13a, 13b) is connected to the spacer (4a, 4b) so that these components with the tensioning roller (1) are captively combined into one basic unit (34). 2. The tensioning roller as claimed in claim 1, wherein the outer ring (10) of the roller bearing (3) is enclosed by the idler sheave (2) made from plastics, a plastic pulley. 3. The tensioning roller as claimed in claim 1, wherein the idler sheave (2) comprises an axially projecting step (16), which forms a snap roller geometry in the form of an annular groove (18) for the sealing cap (13a, 13b). 4. The tensioning roller as claimed in claim 3, wherein when fitted the sealing cap (13a, 13b) with a cylindrical rim (15) engages over the axially projecting step (16) of the idler sheave (2) and with lugs (17) at least in part directed radially inwards latches in the annular groove (18) in the step (16). 5. The tensioning roller as claimed in claim 4, wherein the sealing cap (13a) in the area of the cylindrical rim (15) has at least one radially aligned hole (40) or gap. 6. The tensioning roller as claimed in claim 4, wherein an axially aligned projection (25) of the sealing cap (13a) engages in an end recess (26) of the step (16), integrally connected to the idler sheave (2), in order to provide a rotational lock (24). 7. The tensioning roller as claimed in claim 1, wherein the sealing cap (13b) engages with a positive interlock and a certain amount of play in an annular groove (29) in the spacer (4b), the groove being inserted axially offset in relation to a shoulder (33) of the spacer (4b) on which the inner ring (8) of the roller bearing (3) is supported. 8. The tensioning roller as claimed in claim 7, wherein a radial overlap "Y" of > 0.5 mm is provided between an inner contour of the radial flank (19b) of the sealing cap (13b) and a groove wall (31) or circumferential surface (35) of the spacer (4b). 9. The tensioning roller as claimed in claim 7, wherein the radial flank (19b) of the sealing cap (13b) assigned to the labyrinth seal (23b) is provided with zones (38) of reduced wall thickness distributed over parts of the circumference. 10. The tensioning roller as claimed in claim 7, wherein the annular groove (29) in the spacer (4b) is defined by groove walls (30, 31) which differ in their height. 11. The tensioning roller as claimed in claim 1, wherein the sealing cap (13a) with the radial flank (19a) is assigned with a certain amount of play to a radial step (22) of the spacer (4a). 12. The tensioning roller as claimed in claim 1, wherein the roller bearing (3) positioned on a centering flange (7) of the spacer (4a) is supported on a shoulder (9). 13. The tensioning roller as claimed in claim 4, wherein the cylindrical rim (15) of the sealing cap (13b) has indentations (41) distributed over the circumference, which are of limited length and extend into the radial flank (19b). 14. The tensioning roller as claimed in claim 1, wherein the radial Hank (19a, 19b) of the sealing cap (13a, 13b) has an offset (27) in order to obtain a defined axial distance between the labyrinth seal (23a, 23b) and the roller bearing (3). 15. The tensioning roller as claimed in claim 1, wherein the radial flank (19a) of the sealing cap (13a) comprises a sealing ring (39), in particular a felt sealing ring, in the area of the labyrinth seal (23a). 16. The tensioning roller as claimed in claim 1, wherein the sealing cap (13a, 13b) encloses a circumferential grease collar in the area of the labyrinth seal (23a, 23b). 17. The tensioning roller as claimed in claim 1, wherein the sealing cap (13a, 13b) is manufactured from a metallic material by a chipless process, in particular by means of a deep-drawing process. 18. The tensioning roller as claimed in claim 1, wherein the sealing cap (13a, 13b) is made front an elastic material, in particular a plastic material.

Documents:

536-DELNP-2006-Abstract (5-1-2010).pdf

536-delnp-2006-abstract.pdf

536-DELNP-2006-Claims (5-1-2010).pdf

536-delnp-2006-claims.pdf

536-DELNP-2006-Correspondence-Others (5-1-2010).pdf

536-delnp-2006-correspondence-others-1.pdf

536-delnp-2006-correspondence-others.pdf

536-DELNP-2006-Description (Complete) (5-1-2010).pdf

536-delnp-2006-description (complete).pdf

536-DELNP-2006-Drawings (5-1-2010).pdf

536-delnp-2006-drawings.pdf

536-DELNP-2006-Form-1 (5-1-2010).pdf

536-delnp-2006-form-1.pdf

536-delnp-2006-form-18.pdf

536-DELNP-2006-Form-2 (5-1-2010).pdf

536-delnp-2006-form-2.pdf

536-DELNP-2006-Form-3 (5-1-2010).pdf

536-delnp-2006-form-3.pdf

536-delnp-2006-form-5.pdf

536-DELNP-2006-GPA (5-1-2010).pdf

536-delnp-2006-pct-210.pdf

536-delnp-2006-pct-304.pdf

536-delnp-2006-pct-308.pdf

536-DELNP-2006-Petition-137 (5-1-2010).pdf

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