WO2006096407A1

WO2006096407A1 - Self adjusting pivot type tensioner

Info

Publication number: WO2006096407A1
Application number: PCT/US2006/007263
Authority: WO
Inventors: Thomas R. Bober; Daniel R. Mclarty; John S. Hayward
Original assignee: Timken Us Corporation
Priority date: 2005-03-03
Filing date: 2006-03-01
Publication date: 2006-09-14

Abstract

An automatic pivot tensioner for maintaining a desired tension on a drive member includes a one-way clutch configured to be supported adjacent the drive member and including a first clutch member and a second clutch member. The clutch is configured to allow rotation of the first clutch member with respect to the second clutch member in a first direction and to inhibit rotation of the first clutch member with respect to the second clutch member in a second opposite direction. A clutch lever is supported on one of the first clutch member and the second clutch member for rotation therewith. An idler member is supported on a first portion of the clutch lever and is configured for contact with the drive member. A biasing member is attached to the clutch lever for biasing the clutch lever for rotation in the first direction.

Description

SELF ADJUSTING PIVOT TYPE TENSIONER

CROSS REFERENCE TO OTHER APPLICATIONS

[0001] This application claims priority under 35 U.S. C. sec. 119 to provisional patent application no. 60/658,072, filed on March 3, 2005, the entire contents of which is hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a device that automatically adjusts the slack in a drive member such as a belt or a chain as the drive member wears over its design life.

BACKGROUND

[0003] In a drive system where power is transferred from one shaft to another via a drive member such as a belt or chain, it is desirable to maintain a specific range of tension in the belt, or slack in the chain, which is sufficient to keep the belt engaged with the sheaves so that power loss due to slippage is avoided, or excessive noise or slippage is avoided in the chain system. Additionally, it is desirable to limit the maximum deflection of the drive member so that backlash is controlled within a minimum range.

[0004] As a drive system is operated over its life, wear takes place that has the effect of lengthening the drive member, which causes slack in the drive system to increase. If the amount of slack in the drive system is not periodically checked and adjusted via a routine manual maintenance procedure, the drive system will become sufficiently slack to impair the power transfer function, i.e., the belt or chain will slip due to excess slack. If the drive member is adjusted improperly during the maintenance procedure, it can be set incorrectly, either too tightly or too loosely. If the drive member is adjusted too tightly, excessive loading of the drive system can occur.

SUMMARY

[0005] The tensioner of the present invention controls the amount of tension and slack in the drive system automatically so that periodic maintenance is eliminated. The tensioner continuously senses the amount of slack in a drive system and automatically compensates for excessive slack via a one-way pivot clutch.

[0006] In one embodiment, an automatic pivot tensioner for maintaining a desired tension on a drive member includes a one-way clutch, a clutch lever, an idler member, and a biasing member. The one-way clutch is configured to be supported adjacent the drive member and includes a first clutch member and a second clutch member. The clutch is configured to allow rotation of the first clutch member with respect to the second clutch member in a first direction and to inhibit rotation of the first clutch member with respect to the second clutch member in a second opposite direction. A clutch lever is supported on one of the first clutch member and the second clutch member for rotation therewith. An idler member is supported on a first portion of the clutch lever and is configured for contact with the drive member. A biasing member is attached to the clutch lever for biasing the clutch lever for rotation in the first direction.

[00071 In another embodiment, an automatic pivot tensioner for maintaining a desired tension on a drive member includes a one-way clutch, a clutch lever, an idler member, and a biasing member. The one-way clutch is configured to be supported adjacent the drive member and includes a fixed post, a sprag, and a clutch housing. The sprag is located in a sprang slot of the clutch housing and allows rotation of the clutch housing with respect to the fixed post in a first direction and inhibits rotation of the clutch housing with respect to the fixed post in a second opposite direction. The clutch lever is supported on the clutch housing for rotation therewith. The idler member is supported on a first portion of the clutch lever and configured for contact with the drive member. The biasing member is attached to the clutch lever for biasing the clutch lever for rotation in the first direction. Rotation of the clutch lever in the first direction causes the idler member to remove slack from the drive member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig. 1 is a front isometric view of a pivot tensioner of the present invention;

[0009] Fig. 2 is a front exploded isometric view of the pivot tensioner of Fig. 1; [0010] Fig. 3 is a rear isometric view of the one-way clutch of the pivot tensioner of Fig. 1;

[0011] Fig. 4 is a rear exploded isometric view of the one-way clutch of Fig. 3;

[0012] Fig. 5 is a front plan view of the clutch of Fig. 3 with the clutch cap removed and illustrating a force in the released, tensioning direction; and

[0013] Fig. 6 is a front plan view similar to Fig. 5 illustrating a force in the engaged, non- tensioning direction.

DETAILED DESCRIPTION

[0014] The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, "top", "bottom", "right", "left", "front", "frontward", "forward", "back", "rear" and "rearward", is used in the following description for relative descriptive clarity only and is not intended to be limiting.

[0015] Referring to Figs. 1 and 2, a pivot tensioner 10 generally includes a mounting bracket 12, a biasing member such as spring 16, a one-way clutch 20, a clutch lever 40 and an idler member such as idler wheel 50. As a general overview, the pivot tensioner 10 continuously senses the amount of slack of a drive member 51 such as a drive belt or chain and automatically compensates to maintain a desired tension on the drive member 51.

[0016] The mounting bracket 12 can be mounted in a drive assembly adjacent the drive member 51. The mounting bracket 12 is configured to support the one-way clutch 20. The biasing member is chosen to provide a desired tension on the drive member 51. The illustrated one-way clutch 20 includes a first clutch member such as clutch housing 24 and a second clutch member such as post 22. As more fully explained below, the one-way clutch is configured to allow rotation of the first clutch member with respect to the second clutch member in a first direction and to inhibit rotation of the first clutch member with respect to the second clutch member in a second opposite direction. The clutch lever 40 can be supported on either the first clutch member or the second clutch member for rotation therewith. In the illustrated embodiment, the clutch lever 40 has an opening 46 configured to receive the clutch housing 24 at a pivot point of the clutch lever 40 such that the clutch lever 40 pivots in conjunction with the clutch housing 24. At one end, the clutch lever 40 supports the idler wheel 50 configured to contact the drive member 51. The idler member could also take the form of a sprocket configured to contact and engage the drive member 51. At the other end, the clutch lever 40 is engaged by the spring 16 such that the spring biases the clutch lever 40 in a first tensioning or slack removing direction.

[0017] Referring to Figs. 2-4, the one-way clutch 20 will be further described. The post 22 can be fixedly attached to the mounting bracket 12, for example, via a bore 14 configured to receive the post 22. The post 22 is configured to be received in a through bore 25 of the clutch housing 24. In the illustrated embodiment, the clutch housing 24 is supported for rotation about the fixed post 22. A seal 23 or the like can be provided between the clutch housing 24 and the mounting bracket 12 to prevent debris from entering the clutch housing 24.

[0018] The clutch housing 24 has an outer projection 27 configured to be received in a radial notch 48 extending from the clutch lever opening 46 such that rotation of the clutch lever 40 will be transmitted to the clutch housing 24 via the interaction of the projection 27 with the radial notch 48. The clutch housing 24 includes a sprag slot 26 extending radially from the through bore 25. The sprag slot 26 is configured to receive a sprag 28 having a complementary configuration. Operation of the sprag 28 will be described below.

[0019] Once the sprag 28 is positioned in the sprag slot 26, a clutch cap 30 is positioned over the through bore 25 of the clutch housing 24 and is secured to the post 22 via a screw 34 or the like. A biasing member in the form of a spring plunger 29 biases the sprag 28 into engagement with the post 22. hi the illustrated embodiment, the spring plunger 29 is received in an aperture in the clutch housing 24. However, in other embodiments, other biasing members and biasing member arrangements can be used to bias the sprag 28 into engagement with the second clutch member. Referring to Fig. 4, the clutch cap 30 has a rear cavity 31 configured to receive an end of the sprag 28, the function of which is described below. The front surface of the clutch cap 30 has a block 32 with a configured opening 33. The block 32 can be used for manual disengagement of the pivot tensioner 10 to remove the drive belt or the like, as described in more detail below. [0020] Referring to Fig. 2, the illustrated clutch lever 40 has opposed legs 42, 44 extending at a generally right angle relative to one another. However, in other applications, the clutch lever can have other configurations in which the opposed legs may extend at other suitable angles relative to one another. One leg 42 has a hole 43 configured to receive and retain an end of the spring 16. The other leg 44 includes a bore 45 for mounting of an idler post 52. An idler bearing 54 is configured to be supported on the idler post 52. The idler wheel 50 is configured to be supported for rotation with the outer race of the idler bearing 54. While the idler wheel 50 is shown as having a smooth surface, for example for engagement with a belt, the wheel 50 may also be configured with teeth to engage a drive chain.

[0021] Having described the components of an embodiment of the present invention, operation thereof will be described with reference to Figs. 1 and 5-6. The pivot tensioner 10 is mounted in a drive assembly via the mounting bracket 12. The spring 16 extends between the clutch lever 40 and a fixed point, for example in a drive assembly housing (not shown) or on the mounting bracket 12. The spring 16 biases the clutch lever 40 for rotation in the direction of arrow X in Fig. 1. Rotation of the clutch lever 40 in the direction X causes the idler wheel 50 to contact the drive belt or chain (not shown) to remove slack therefrom. The spring 16 is chosen to provide a desired tension on the drive belt or chain.

[0022] As shown in Figs. 5 and 6, the sprag 28 has a smaller cross sectional width A in one circumferential direction and a larger cross sectional width B in the opposite circumferential direction. When the spring force is applied to the clutch lever 40, and thereby the clutch housing 24 via the projection 27 and notch 48 interaction, the clutch housing 24 is caused to rotate in the direction X. i)ue to the small width A, the sprag 28 does not bind between the clutch housing 24 and the post 22, thereby allowing the spring force to rotate the clutch lever 40 and thereby the idler wheel 50 against the drive belt or chain. Once the slack is removed from the drive belt or chain, the drive belt or chain applies a resisting force against the idler wheel 50 and thereby the clutch lever 40. The clutch lever 40 attempts to rotate the clutch housing 24 in the opposite direction Y as indicated in Fig. 6. The larger width B of the sprag 28 binds between the clutch housing 24 and the post 22 when a force in the direction Y is applied to the clutch housing 24. Since the post 22 is fixed, binding of the sprag 28 between the clutch housing 24 and the post 22 will inhibit rotation of the clutch housing 24 in the direction Y, and thereby inhibit rotation of the clutch lever 40. hi such a manner, the pivot tensioner 10 automatically maintains the drive belt or chain at a desired tension. The self-adjusting feature is continuously active. Excessive slack is eliminated as soon as it becomes present.

[0023] The drive belt tension can be released to change the belt by placing a wrench or other suitable tool on the clutch cap block 32 or in the block configured opening 33 and turning the clutch cap 30 towards the release direction X. The action of turning the clutch cap 30 in this manner causes the clutch cap cavity 31 to contact the sprag 28 and move it out of the engaged position and into a released position, thereby unlocking the one-way pivot clutch 20. This allows the pivot tensioner 10 to be retracted from the belt.

[0024] Those skilled in the art will understand that the illustrated sprag-type one-way clutch is only one type of one-way clutch, and that other known configurations of one-way clutches can be substituted if desired.

[0025] Various features and advantages of the invention are set forth in the following claims.

Claims

What is claimed is:

1. An automatic pivot tensioner for maintaining a desired tension on a drive member, the pivot tensioner comprising: a one-way clutch supported adjacent the drive member, including a first clutch member and a second clutch member, and configured to allow rotation of the first clutch member with respect to the second clutch member in a first direction and to inhibit rotation of the first clutch member with respect to the second clutch member in a second opposite direction; a clutch lever supported on one of the first clutch member and the second clutch member for rotation therewith; an idler member supported on a first portion of the clutch lever and configured for contact with the drive member; and a biasing member attached to the clutch lever for biasing the clutch lever for rotation in the first direction.

2. The automatic pivot tensioner of claim 1, wherein the first and second clutch members include a clutch housing and a post.

3. The automatic pivot tensioner of claim 2, further including an outer proj ection on the clutch housing which engages a notch formed in the clutch lever.

4. The automatic pivot tensioner of claim 2, wherein the clutch housing is allowed to rotate with respect to the post in the first direction and the clutch housing is inhibited from rotation with respect to the post in the second direction.

5. The automatic pivot tensioner of claim 2, further including a mounting bracket for fixing the location of the post.

6. The automatic pivot tensioner of claim 2, wherein the clutch further includes a sprag, and the sprag allows rotation of the clutch housing with respect to the post in the first direction and inhibits rotation of the clutch housing with respect to the post in the second direction.

7. The automatic pivot tensioner of claim 6, wherein the sprag is located within a sprag slot in the clutch housing.

8. The automatic pivot tensioner of claim 6, further including a clutch cap having a cavity configured such that when the clutch cap is turned towards the first direction, the sprag is moved into a released position such that the one-way clutch is unlocked.

9. The automatic pivot tensioner of claim 1, wherein the clutch lever includes opposed first and second legs, the first leg coupled to the biasing member and the second leg coupled to idler member.

10. The automatic pivot tensioner of claim 9, wherein the opposed first and second legs extend at a generally right angle relative to one another.

11. The automatic pivot tensioner of claim 9, wherein the clutch is located at a pivot point of the clutch lever.

12. The automatic pivot tensioner of claim 1, wherein the idler member is coupled for rotation with a bearing.

13. The automatic pivot tensioner of claim 1, wherein slack in the drive member allows rotation of the clutch lever in the first direction causing the idler member to move in a direction so as to remove the slack.

14. An automatic pivot tensioner for maintaining a desired tension on a drive member, the pivot tensioner comprising: a one-way clutch configured to be supported adjacent the drive member and including a fixed post, a sprag, and a clutch housing, wherein the sprag is located in a sprag slot of the clutch housing and allows rotation of the clutch housing with respect to the fixed post in a first direction and inhibits rotation of the clutch housing with respect to the fixed post in a second opposite direction; a clutch lever supported on the clutch housing for rotation therewith; an idler member supported on a first portion of the clutch lever and configured for contact with the drive member; and a biasing member attached to the clutch lever for biasing the clutch lever for rotation in the first direction; wherein rotation of the clutch lever in the first direction causes the idler member to remove slack from the drive member.

15. The automatic pivot tensioner of claim 14, further including a mounting bracket for fixing the location of the post.

16. The automatic pivot tensioner of claim 14, further including a clutch cap having a cavity configured such that when the clutch cap is turned towards the first direction, the sprag is moved into a released position such that the one-way clutch is unlocked.

17. The automatic pivot tensioner of claim 14, wherein the clutch lever includes opposed first and second legs, the first leg coupled to the biasing member and the second leg coupled to the idler member.

18. The automatic pivot tensioner of claim 17, wherein the opposed first and second legs extend at a generally right angle relative to one another.

19. The automatic pivot tensioner of claim 14, wherein the idler member is coupled for rotation with a bearing.

20. The automatic pivot tensioner of claim 14, further including an outer projection on the clutch housing which engages a notch formed in the clutch lever.