WO2008089000A2

WO2008089000A2 - Torque transfer assembly

Info

Publication number: WO2008089000A2
Application number: PCT/US2008/050625
Authority: WO
Inventors: Mark A. Joki
Original assignee: The Timken Company
Priority date: 2007-01-12
Filing date: 2008-01-09
Publication date: 2008-07-24
Also published as: WO2008089000A3

Abstract

A torque transfer assembly includes first and second torque transfer devices (110,210) positioned between a first member (26) and a second member (36).Each of the devices includes a first race (114,214) selectively engageable with the first member, and a second race (122,222) coaxial with the first race. The second race of the first device is coupled to the first race of the second device, and the second race of the second device is coupled to the second member. Each of the devices also includes axially-extending pockets, defined between the first and second races, rollers (118,218) positioned in the respective pockets, and an axial gap formed in one of the first and second races. A force applied to the first race of the first device indexes the first race of the first device relative to the second race of the first device to radially expand the first device to frictionally engage the first member.

Description

TORQUE TRANSISTOR

RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial

No. 60/884,657 filed on January 12, 2007, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to clutches and other devices operable to transfer torque from a first member to a second member.

BACKGROUND OF THE INVENTION

[0003] Geared drives are often used to provide high torque from a low torque control source. However, the output power of the gear drive is equal to the input control power less the inefficiency of the gearbox. This requires high actuation power.

SUMMARY OF THE INVENTION

[0004] The present invention allows a low power control gate to control a large output power. The remaining power is drawn from an uncontrolled source. The present invention eliminates the need for high speed motion from the control device to provide fast response for the output torque. The present invention could be utilized with a gate valve closer or other mechanical device.

[0005] The present invention provides, in one aspect, a torque transfer assembly operable to selectively transmit torque from a first member to a second member coaxial with the first member. The torque transfer assembly includes a first torque transfer device and a second torque transfer device coaxial with the first torque transfer device and positioned between the first member and the second member. Each of the first and second torque transfer devices includes a first race selectively engageable with the first member, and a second race coaxial with the first race. The second race of the first torque transfer device is coupled to the first race of the second torque transfer device, and the second race of the second torque transfer device is coupled to the second member. Each of the first and second torque transfer devices also includes a plurality of axially-extending pockets defined between the first and second races, a plurality of rollers positioned in the respective pockets, and an axial gap formed in one of the first and second races. A force applied to the first race of the first torque transfer device indexes the first race of the first torque transfer device relative to the second race of the first torque transfer device to radially expand the first torque transfer device to frictionally engage the first member.

[0006] The present invention provides, in another aspect, a torque transfer assembly operable to selectively transmit torque from a first member to a second member coaxial with the first member. The torque transfer assembly includes a first torque transfer device, and a second torque transfer device coaxial with the first torque transfer device and positioned between the first member and the second member. Each of the first and second torque transfer devices includes a slipper race selectively engageable with the outer periphery of the first member, and an outer race disposed radially outwardly of the slipper race. The outer race of the first torque transfer device is coupled to the slipper race of the second torque transfer device, and the outer race of the second torque transfer device is coupled to the second member. Each of the first and second torque transfer devices also includes a plurality of axially-extending pockets defined between the first and second races, a plurality of rollers positioned in the respective pockets, an axial gap formed in the slipper race, and a control force member operable to selectively apply a control force to the slipper race of the first torque transfer device to index the slipper race of the first torque transfer device relative to the outer race of the first torque transfer device to radially expand the first torque transfer device to frictionally engage the first member.

[0007] The present invention provides, in yet another aspect, a method of selectively transmitting torque from a first member to a second member coaxial with the first member. The method includes providing a first torque transfer device, and positioning a second torque transfer device coaxial with the first torque transfer device and between the first and second members. Each of the first and second torque transfer devices includes a first race selectively engageable with the first member, a second race coaxial with the first race, a plurality of axially-extending pockets defined between the first and second races, a plurality of rollers positioned in the respective pockets, and an axial gap formed in one of the first and second races. The method also includes applying a first force to the first race of the first torque transfer device to index the first race of the first torque transfer device relative to the second race of the first torque transfer device to radially expand the first torque transfer device to frictionally engage the first member, coupling the second race of the first torque transfer device to the first race of the second torque transfer device, coupling the second race of the second torque transfer device to the second member, and applying a second force to the first race of the second torque transfer device with the second race of the first torque transfer device to index the first race of the second torque transfer device relative to the second race of the second torque transfer device to radially expand the second torque transfer device to frictionally engage the first member. The second force is greater than the first force.

[0008] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a cross-sectional view of a single torque transfer device selectively engaging a shaft and an outer housing.

[0010] FIG. 2 is a cross-sectional view of a torque transfer assembly of the present invention, including a plurality of torque transfer devices of FIG. 1, selectively engaging a shaft and an outer housing.

[0011] FIG. 3 is a cross-sectional view of a second construction of the torque transfer assembly of FIG. 2.

[0012] FIG. 4 is a cross-sectional view of a third construction of the torque transfer assembly of FIG. 2.

[0013] FIG. 5 is a cross-sectional view of a fourth construction of the torque transfer assembly of FIG. 2.

[0014] FIG. 6 is a cross-sectional view of a fifth construction of the torque transfer assembly of FIG. 2.

[0015] FIG. 7 is a top view of a portion of the torque transfer assembly of FIG. 6.

[0016] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

DETAILED DESCRIPTION

[0017] FIG. 1 illustrates a single torque transfer device or slipper clutch 10 that includes an inner race or slipper 14, rollers 18 (only one of which is shown in FIG. 1), and an outer race 22. The slipper 14 defines a plurality of recesses 32 (only one of which is shown in FIG. 1) having opposed arcuate or curved ramps 33a, 33b and an axial gap or slot 34 located in one of the recesses 32. The outer race 22 also defines a plurality of recesses 42 (only one of which is shown in FIG. 1) having opposed arcuate or curved ramps 43a, 43b. The recesses 32, 42 of the respective slipper 14 and outer race 22, when angularly aligned, define a plurality of pockets that receive the respective rollers 18.

[0018] The slipper clutch 10 is positioned between a first member (e.g., a shaft 26 having a central axis 31) and a second member (e.g., an output member or outer housing 36 coaxial with the shaft 36) to selectively transfer torque between the shaft 26 and the outer housing 36. As shown in FIG. 1, the outer race 22 is press-fit or otherwise fixed to the outer housing 36. Alternatively, the outer race 22 may be integrally formed with the outer housing 36. As will be explained in greater detail below, the slipper clutch 10 may be utilized in either a "brake" application, in which the outer housing 36 is fixed or grounded and the slipper clutch 10 applies a braking torque to the shaft 26 to slow the rotation of the shaft 26, or a "clutch" application, in which both the outer housing 36 and shaft 26 are rotatable about the central axis 31, and the slipper clutch 10 applies a torque to one of the outer housing 36 and the shaft 26 to accelerate the housing 36 or shaft 26. [0019] With continued reference to FIG. 1, the inner diameter of the slipper 14 is sized to selectively allow the shaft 26 to slip relative to the slipper 14. The axial gap 34 facilitates variation in the inner diameter of the slipper 14, and subsequently variation in the clamping force applied to the shaft 26 by the slipper 14.

[0020] As the shaft 26 rotates about the axis 31 in the direction of arrow 30, the drag on the slipper 14 tends to rotate or index the slipper 14 relative to the outer race 22 in the direction of arrow 30. By slightly indexing the slipper 14 relative to the outer race 22, the recesses 32 in the slipper 14 and the recesses 42 in the outer race 22 become slightly misaligned, causing the rollers 18 to ride up or jam between the respective ramps 33b, 43 a of the slipper 14 and the outer race 22 and slightly collapse the slipper 14 onto the shaft 26. In other words, jamming the rollers 18 between the respective ramps 33b, 43a of the slipper 14 and the outer race 22 generates contact forces Fc between the slipper 14, the outer race 22, and the rollers 18. As illustrated in FIG. 1, the contact forces F_c act along a line (only one of which is shown) that extends through the center of each roller 18 and the locations where the roller 18 contacts the respective ramps 33b, 43 a.

[0021] As shown in FIG. 1, the contact force F_c exerted by the outer race 22 on the slipper 14 has orthogonal components: a radial or normal force F_N and a tangential force F_τ. One of ordinary skill in the art would understand that the slipper 14 exerts a contact force (not shown) on the outer race 22 along the same line as the illustrated contact force Fc, but in the opposite direction. As such, the slipper 14 applies a tangential force (not shown) on the outer race 22 equal in magnitude and opposite in direction to the illustrated tangential force F_T. It should be understood that all of the forces illustrated in FIG. 1, including F_f, discussed below, are illustrated in a direction as acting on the slipper 14.

[0022] The normal forces F_N acting on the slipper 14 as a result of the contact forces

Fc discussed above reduce the size of the axial gap 34 and the clearance between the slipper 14 and the shaft 26. As a result, the normal force F_N is transferred to the shaft 26, generating a friction force Ff between the slipper 14 and the shaft 26 that tends to rotate the slipper 14 in the direction of the arrow Ff (in the direction of rotation of the shaft 26, indicated by arrow 30), as illustrated in FIG. 1. As would be understood by one of ordinary skill in the art, the friction force Ff equals the radial or normal force F_N X μ, where μ is the coefficient of friction between the slipper 14 and the shaft 26. Any desirable coefficient of friction or range of coefficients of friction can be achieved by selecting materials used to form the clutch 10, lubricants utilized by the clutch 10, etc.

[0023] As illustrated in FIG. 1, a ramp angle θ is defined as the angle between the contact force F_c and the normal force F_N- AS would be understood by one of ordinary skill in the art, the ramp angle θ is a function of the geometry or curvature of the curved ramps 33 a, 33b, 43a, 43b. Accordingly, the curvature of the ramps 33a, 33b, 43a, 43b can be designed to achieve any desired ramp angle θ.

[0024] Typically, a slipper clutch is designed such that the tangent of the ramp angle θ is substantially less than the coefficient of friction μ. If the tangent of the ramp angle θ is substantially less than the coefficient of friction μ, the drag between the slipper 14 and the shaft 26 (i.e., the friction force Ff) far exceeds the opposing tangential force F_T, thereby allowing the drag between the slipper 14 and the shaft 26 to index the slipper 14 relative to the outer race 22 and lock the slipper 14 to the shaft 26 to transfer a relatively large amount of torque or force from the shaft 26 to the outer race 22.

[0025] However, in the illustrated slipper clutch 10, the tangent of the ramp angle θ is kept higher than the coefficient of friction μ, thereby providing a non-locking force gain. In other words, if the tangent of the ramp angle θ is greater than the coefficient of friction μ, the drag between the slipper 14 and the shaft 26 (i.e., the friction force F_f) is insufficient by itself to cause the slipper 14 to index relative to the outer race 22 and lock to the shaft 26. In other words, the drag between the slipper 14 and the shaft 26 when the recesses 32, 42 of the slipper 14 and the outer race 22 are substantially aligned is insufficient to overcome the tangential force F_T, applied to the slipper 14 by the outer race 22. Therefore, as the shaft 26 rotates, the clutch 10 will not lock the shaft 26 and the outer race 22, and the torque or force transmitted from the shaft 26 to the outer race 22 is relatively small.

[0026] However, when an externally applied control force Fj is applied to the slipper

14 in the direction of rotation of the shaft 26 or in the direction of the friction force F_f , as illustrated in FIG. 1, the balance between the drag or friction force F_f and the tangential force F_T is upset, and the forces applied to the slipper 14 in the direction of shaft rotation sufficiently exceed the opposing tangential force F_τ. As a result, the slipper 14 incrementally rotates with the shaft 26 and indexes relative to the outer race 22, causing the slipper 14 to frictionally engage the shaft 26 to allow the clutch 10 to transmit torque or force from the shaft 26 to the outer race 22.

[0027] When a control force Fj is applied to the slipper 14 in the direction of rotation of the shaft 26 in the manner described above, the gap 34 shrinks to allow the slipper 14 to frictionally engage the shaft 26 (see FIG. 1). As a result, the inner diameter of the slipper 14 decreases, effectively increasing the radial thickness of the clutch 10 or "radially expanding" the clutch 10. In an alternative construction of the clutch in which the outer race 22, rather than the inner race 14, is configured as the slipper and includes the radial slot or gap, indexing the outer race 22 relative to the inner race 14 would cause the rollers 18 to ride up or jam between the respective ramps 33b, 43a of the inner race 14 and the outer race 22 and outwardly deflect or expand the outer race 22 to frictionally engage the outer housing 36. As a result, the gap in the outer race 22 increases and the outer diameter of the outer race 22 increases, effectively increasing the radial thickness of the clutch or "radially expanding" the clutch.

[0028] With reference to FIG. 1, a control force member 38 is utilized to apply the control force Fi to the slipper 14. When the slipper clutch 10 is utilized in a brake application, the control force member 38 maybe grounded or fixed to the stationary outer housing 36. However, when the slipper clutch 10 is utilized in a clutch application, the control force member 38 may be mounted to the clutch 10 to co-rotate with the clutch 10. The control force member 38 can be any suitable device, such as mechanical or electromechanical devices, including a motor and gear reducer, pneumatic cylinder, lever and spring, and the like. Also, in some constructions, the control force member can vary the magnitude of the control force F₁- that is applied to the slipper 14 as desired. FIGS. 4-7, described in more detail below, illustrate different constructions of a control force member 38 utilized in a clutch application of the slipper clutch 10.

[0029] With the control force Fj , the tangential force balance on the slipper 14 is such that: F_t + F_f - F_τ = 0

F_n

Note :F_f = F_Nμ =

Tanθ ^'

Thus . - F₁ + - μ - F_τ = 0

Tanθ

Solving this for Fτ/Fj, which is the force gain of the clutch 10 is:

^F> I — ^- Tanθ

[0030] Therefore, in one construction, for a ramp angle θ of 10 degrees and a coefficient of friction μ of 0.15, the force gain Fτ/Fj is 6.7 or approximately 7. Thus, a IN control force Fj applied to the slipper race 14 would provide approximately 7N of tangential or output force F_T at the outer race 22.

[0031] FIG. 2 illustrates a torque transfer assembly including a plurality of slipper clutches 110, 210, 310, 410, 510, 610, 710 cascaded or axially arranged along the shaft 26. The slipper clutches 110, 210, 310, 410, 510, 610, 710 are similar to the slipper clutch 10 illustrated in FIG. 1. Like components are labeled with like reference numbers plus 100, 200, 300, and so forth.

[0032] The clutches 110, 210, 310, 410, 510, 610, 710 are cascaded on the shaft 26 such that each slipper 214, 314, 414, 514, 614, 714 of a following stage is connected to the outer race 122, 222, 322, 422, 522, 622 of a preceding stage. Thus, the outer race 122 of the clutch 110 is connected to the slipper 214 of the following clutch 210, the outer race 222 of the clutch 210 is connected to the slipper 314 of the following clutch 310, the outer race 322 of the clutch 310 is connected to the slipper 414 of the following clutch 410, and so forth. With continued reference to FIG. 2, each of the outer races 110, 210, 310, 410, 510, 610 is L- shaped and includes a tab 126, and each of the slippers 214, 314, 414, 514, 614, 714 includes a slot 130 configured to receive the tab on the outer race 110, 210, 310, 410, 510, 610 of the preceding clutch 110, 210, 310, 410, 510, 610. The engagement of the tab 126 and slot 130 of the outer race 122 and the slipper 214, for example, rotationally interconnects the outer race 122 and the slipper 214 such that the slipper 214 co-rotates with the outer race 122. Because they are identical, each of the outer races 110, 210, 310, 410, 510, 610 can be made using the same manufacturing process. The slipper 114 of the first clutch 110 is also L- shaped and includes a tab 123 to which the control force Fj is applied.

[0033] The outer race 722 of the last clutch 710 is connected to an output device (e.g., outer housing 36) such that the output torque or force of the clutches 110, 210, 310, 410, 510, 610, 710 is extracted from the outer race 722 of the last clutch 710. As shown in FIG. 2, the outer races 122, 222, 322, 422, 522, 622 of the respective clutches 110, 210, 310, 410, 510, 610 are radially spaced from the inner periphery of the outer housing 36, while the outer race 722 of the clutch 710 is fixed to the inner periphery of the outer housing 36 (e.g., by a press- fit) such that the outer race 722 co-rotates with the outer housing 36. Alternatively, the outer race 722 may be integrally formed with the outer housing 36. Also, as shown in FIG. 2, the length of the rollers 618, 718 in the clutches 610, 710 increases to allow the clutches 610, 710 to handle an increasing amount of torque transferred from the shaft 26 to the outer housing 36. Alternatively, the clutches 210, 310, 410, 510 may incorporate progressively increasing roller lengths.

[0034] hi an alternative construction of the torque transfer assembly illustrated in

FIG. 2, a second plurality of slipper clutches (not shown) may be cascaded or axially arranged along the shaft 26 at a location on the shaft 26 disposed from the first plurality of slipper clutches 110, 210, 310, 410, 510, 610, 710. Respective control force members 38 associated with the first and second plurality of slipper clutches 110, 210, 310, 410, 510, 610, 710 may act in opposite directions, such that the first plurality of slipper clutches 110, 210, 310, 410, 510, 610, 710 may be actuated when the shaft 26 is rotating in the direction indicated by arrow 30 in FIG. 1, and the second plurality of slipper clutches may be actuated when the shaft 26 is rotating in a direction opposite the direction indicated by arrow 30 in FIG. 1. Such a configuration substantially eliminates backlash in the assembly.

[0035] FIG. 3 illustrates a second construction of a torque transfer assembly including a plurality of slipper clutches HOa, 210a, 310a, 410a, 510a, 610a, 710a cascaded or axially arranged along the shaft 26. Like components are labeled with like reference numerals plus the letter "a." The clutches HOa, 210a, 310a, 410a, 510a, 610a include respective outer races 122a, 222a, 322a, 422a, 522a, 610a, each having a slot 131 formed therein. The clutches HOa, 210a, 310a, 410a, 510a, 610a, 710a also include respective slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a each having a slot 132 formed therein. A plurality of plates 134, each including a radially outwardly-extending tabl38 and a radially inwardly-extending tab 142, rotationally interconnect adjacent clutches (e.g., clutches 110a and 210a, clutches 210a and 310a, and so forth). Specifically, the radially outwardly-extending tabs 138 of the plates 134 are configured to be received within the slots 131 of the respective outer races 122a, 222a, 322a, 422a, 522a, 622a, and the radially inwardly-extending tabs 142 of the plates 134 are configured to be received within the slots 132 of the respective slippers 214a, 314a, 414a, 514a, 614a, 714a. As such, the plates 134 rotationally interconnect the outer race (e.g., outer race 122a) with the slipper (e.g., slipper 214a) of an adjacent clutch.

[0036] With continued reference to FIG. 3, each of the outer races 122a, 222a, 322a,

422a, 522a, 622a, 722a includes the same race profile (i.e., including ramps 43a, 43b) such that all of the outer races 122a, 222a, 322a, 422a, 522a, 622a, 722a may be cut from a single piece of material. Likewise, each of the slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a includes the same race profile (i.e., including ramps 33a, 33b) such that all of the slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a may be cut from a single piece of material. Because they are identical, all of the plates 134 can also be made using the same manufacturing process.

[0037] With reference to FIG. 3, the control force Fj is applied to the slipper 114a of the first clutch 100a via an end plate 146 to initiate actuation of the torque transfer assembly. Like the plates 134, the end plate 146 includes a radially inward-extending tab 147 received in the slot 132 of the slipper 114a. As discussed above, applying the control force F₁ to the slipper 114a causes the slipper 114a to index relative to the outer race 122a and collapse upon the rotating shaft 26 to frictionally engage (but not lock to) the shaft 26. The friction force between the slipper 114a and the shaft 26 and the control force F₁ on the slipper 114a are transferred to the slipper 214a of the clutch 210a via the outer race 122a and the plate 134 positioned between the clutches 110a, 210a, subsequently causing the slipper 214a to index relative to the outer race 222a and collapse upon the rotating shaft 26 to frictionally engage (but not lock to) the shaft 26. The slippers 314a, 414a, 514a, 614a, 714a collapse upon the rotating shaft 26 to frictionally engage the shaft 26 in a similar manner, allowing the friction forces between the respective slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a and the rotating shaft 26 (resulting in a net torque about the rotational axis 31 of the shaft 26) to be transferred to the outer housing 36 via the outer race 722a. [0038] Using the example above, if the ramp angle θ of the clutches 110a, 210a, 310a,

410a, 510a, 610a, 710a is 10 degrees, the frictional coefficient μ of the clutches HOa, 210a, 310a, 410a, 510a, 610a, 71 Oa is 0.15 , and the control force Fj at clutch 11 Oa is 1 N, the output force F_T at the first clutch 110a is approximately 7 N. Because the outer race 122a of the first clutch 110a is connected to the slipper 214a of the second clutch 210a via the tab and slot arrangement discussed above, the output force F_T of the first clutch 110a (7 N) becomes the control force Fj of the second clutch 210a. Therefore, at the second clutch 210a with a control force Fj of 7 N, the output force F_T is approximately 49 N. The output forces F_T continues to multiply through the sixth and seventh clutches 610a and 710a until the output torque is extracted from the outer race 722a of the clutch 710a. In the illustrated construction, with seven clutches cascaded along the shaft 26 with the ramp angle θ of 10 degrees, and the frictional coefficient μ of 0.15, the torque gain is 7 to the 7^th power or approximately 823,540. Thus, the 1 N control force Fj applied at the first clutch HOa can generate approximately 823,540 N of output force at the outer race 722a of the clutch 710a.

[0039] The greater the control force Fj applied to the respective slippers 114a, 214a,

314a, 414a, 514a, 614a, 714a, the greater the clamping load that can be applied to the rotating shaft 26 by the slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a, and subsequently the greater amount of torque that can be transferred from the rotating shaft 26 to the outer housing 36. It should also be understood that upon removal of the control force F; from the slipper 114a, the clamping load applied by the rotating shaft 26 by the slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a is also substantially removed, allowing the slip between the shaft 26 and the outer housing 36 to resume such that torque is not substantially transferred from the shaft 26 to the outer housing 36. Each of the clutches 110a, 210a, 310a, 410a, 510a, 610a, 710a may also include a biasing member (e.g., a spring) biasing the slippers 114a, 214a, 314a, 414a, 514a, 614a, 714a relative to the respective outer races 122a, 222a, 322a, 422a, 522a, 622a, 722a to maintain the alignment of the pockets defined by the recesses 32, 42. The operation of the torque transfer assembly of FIG. 2 is substantially similar to the above-described operation of the torque transfer assembly of FIG. 3. As discussed above, the control force member 38 can be utilized to vary the magnitude of the control force F;. Accordingly, the user can vary the control force F; to provide the desired tangential or output force F_τ. [0040] FIG. 4 illustrates a third construction of a torque transfer assembly including a plurality of slipper clutches HOb, 210b, 310b, 410b, 510b, 610b, 710b cascaded or axially arranged along the shaft 26. Like components are labeled with like reference numerals plus the letter "b." In this arrangement, the clutches 110b, 210b, 310b, 410b, 510b, 610b, 710b are utilized in a "clutch" application, such that the outer housing 36 rotates continuously, and actuation of the torque transfer assembly transfers torque from the rotating outer housing 36 to the shaft 26 to control the rotation of the shaft 26. Also, in this arrangement, the clutches 110b, 210b, 310b, 410b, 510b, 610b, 710b are rotatable with the outer housing 36 about the central axis 31 of the shaft 26, and a nominal clearance exists between the respective slippers 114b, 214b, 314b, 414b, 514b, 614b, 714b and the shaft 26 to allow the shaft 26 to slip relative to the slippers 114b, 214b, 314b, 414b, 514b, 614b, 714b.

[0041] With continued reference to FIG. 4, the torque transfer assembly includes a control force member 38b having a rotatable member 150 coupled for rotation with the slipper 114b and a braking member 152 selectively engageable with the rotatable member 150. Specifically, the rotatable member 150 includes a radially inwardly-extending tab 154 that engages the slot 132 in the slipper 114b, such that the rotatable member 150 co-rotates with the slipper 114b about the central axis 31, and a braking surface 156 on the outer periphery of the rotatable member 150. The braking member 152 includes a brake pad 158 having a braking surface 160 corresponding to the shape (e.g., an arcuate shape) of the braking surface 156 on the rotatable member 150. Alternatively, the brake pad 158 may be substantially flat. The braking member 152 also includes an arm 162 coupled to the brake pad 158. The arm 162 may be configured as the extensible rod of a pneumatic or hydraulic cylinder. Alternatively, the arm 162 may be one component of a linkage configured to move the brake pad 158 between a non-braking position in which the brake pad 158 is spaced from the braking surface 156 of the rotatable member 150 (shown in FIG. 4), and a braking position, in which the respective braking surfaces 156, 160 of the rotatable member 150 and the brake pad 158 are fhctionally engaged.

[0042] To initiate actuation of the torque transfer assembly, the brake pad 158 is moved from the non-braking position illustrated in FIG. 4 to the braking position. The frictional engagement of the respective braking surfaces 156, 160 of the rotatable member 150 and the brake pad 158 slows the rotation of the rotatable member 150 relative to the outer housing 36, causing the rotatable member 150 and the slipper 114b to index relative to the outer race 122b and the slipper 114b to collapse upon the shaft 26 in the manner discussed above. To cease transferring torque from the outer housing 36 to the shaft 26, the control force Fi is removed by moving the brake pad 158 from the braking position back to the non- braking position shown in FIG. 4. Removing the control force Fj, as discussed above, also substantially removes the clamping load exerted by the slippers 114b, 214b, 314b, 414b, 514b, 614b, 714b on the shaft 26 to allow the outer housing 36 and clutches 110b, 210b, 310b, 410b, 510b, 610b, 710b to slip relative to the shaft 26.

[0043] FIG. 5 illustrates a fourth construction of a torque transfer assembly including a plurality of slipper clutches HOc, 210c, 310c, 410c, 510c, 610c, 710c cascaded or axially arranged along the shaft 26. Like components are labeled with like reference numerals plus the letter "c." In this arrangement, the clutches HOc, 210c, 310c, 410c, 510c, 610c, 710c are utilized in a "clutch" application, such that either the outer housing 36 or the shaft 26 rotates continuously, and actuation of the torque transfer assembly transfers torque from the rotating outer housing 36 or shaft 26 to the other of the outer housing 36 and shaft 26 to control its rotation. When the outer housing 36 is continuously rotatable, the clutches 110c, 210c, 310c, 410c, 510c, 610c, 710c are rotatable with the outer housing 36 about the central axis 31 of the shaft 26, and a nominal clearance exists between the respective slippers 114c, 214c, 314c, 414c, 514c, 614c, 714c and the shaft 26 to allow the shaft 26 to slip relative to the slippers 114c, 214c, 314c, 414c, 514c, 614c, 714c. However, when the shaft 26 is continuously rotatable, the clutches 110c, 210c, 310c, 410c, 510c, 610c, 710c are stationary with the outer housing 36.

[0044] With continued reference to FIG. 5, the torque transfer assembly includes a control force member 38c having a first rotatable member 164 coupled for rotation with the slipper 114c, a second rotatable member 166 coupled for rotation with the shaft 26, and an electromagnet 168 operable to generate a magnetic field to attract the second rotatable member 166 toward the first rotatable member 164. Specifically, the second rotatable member 166 includes a radially inwardly-extending tab 170 that engages a keyway or slot 172 in the shaft 26, such that the second rotatable member 166 co-rotates with the shaft 26. The control force member 38c also includes a biasing member 174 (e.g., a compression spring) positioned between the first and second rotatable members 164, 166 to axially bias the second rotatable member 166 from the first rotatable member 164. The first and second rotatable members 164, 166 include respective opposed braking surfaces 176, 178 that are spaced from each other when the second rotatable member 166 is in a non-braking position (shown in FIG. 5), and that are frictionally engaged to each other when the second rotatable member 166 is moved to a braking position.

[0045] To initiate actuation of the torque transfer assembly when the outer housing 36 is continuously rotatable and the rotation of the shaft 26 is controlled by actuation of the torque transfer assembly, the second rotatable member 166 is moved from the non-braking position illustrated in FIG. 5 to the braking position by activating the electromagnet 168 to attract the second rotatable member 166 toward the first rotatable member 164. The frictional engagement of the respective braking surfaces 176, 178 of the rotatable members 164, 166 slows the rotation of the first rotatable member 164 relative to the outer housing 36, causing the first rotatable member 164 and the slipper 114c to index relative to the outer race 122c and the slipper 114c to collapse upon the shaft 26 in the manner discussed above. To cease transferring torque from the outer housing 36 to the shaft 26, the control force F; is removed by deactivating the electromagnet 168, allowing the biasing member 174 to axially displace the second rotatable member 166 from the first rotatable member 164 back to the non-braking position shown in FIG. 5. Removing the control force Fj, as discussed above, also substantially removes the clamping load exerted by the slippers 114c, 214c, 314c, 414c, 514c, 614c, 714c on the shaft 26 to allow the outer housing 36 and clutches 110c, 210c, 310c, 410c, 510c, 610c, 710c to slip relative to the shaft 26.

[0046] To initiate actuation of the torque transfer assembly when the shaft 26 is continuously rotatable and the rotation of the outer housing 36 is controlled by actuation of the torque transfer assembly, the second rotatable member 166 is moved from the non- braking position illustrated in FIG. 5 to the braking position by activating the electromagnet 168 to attract the second rotatable member 166 toward the first rotatable member 164. The frictional engagement of the respective braking surfaces 176, 178 of the rotatable members 164, 166 increases the rotation of the first rotatable member 164 relative to the outer housing 36, causing the first rotatable member 164 and the slipper 114c to index relative to the outer race 122c and the slipper 114c to collapse upon the shaft 26 in the manner discussed above. To cease transferring torque from the shaft 26 to the outer housing 36, the control force Fj is removed by deactivating the electromagnet 168, allowing the biasing member 174 to axially displace the second rotatable member 174 from the first rotatable member 164 back to the non-braking position shown in FIG. 5. Removing the control force Fj, as discussed above, also substantially removes the clamping load exerted by the slippers 114c, 214c, 314c, 414c, 514c, 614c, 714c on the shaft 26 to allow the shaft 26 to slip relative to the outer housing 36 and clutches HOc, 210c, 310c, 410c, 510c, 610c, 710c.

[0047] FIG. 6 illustrates a fifth construction of a torque transfer assembly including a plurality of slipper clutches HOd, 21Od, 31Od, 41Od, 510d, 61Od, 71Od cascaded or axially arranged along the shaft 26. Like components are labeled with like reference numerals plus the letter "d." In this arrangement, the clutches 11Od, 21Od, 310d, 41Od, 51Od, 61Od, 71Od are utilized in a "clutch" application, such that either the outer housing 36 or the shaft 26 rotates continuously, and actuation of the torque transfer assembly transfers torque from the rotating outer housing 36 or shaft 26 to the other of the outer housing 36 and shaft 26 to control its rotation. When the outer housing 36 is continuously rotatable, the clutches 11Od, 21Od, 310d, 41Od, 510d, 61Od, 71Od are rotatable with the outer housing 36 about the central axis 31 of the shaft 26, and a nominal clearance exists between the respective slippers 114d, 214d, 314d, 414d, 514d, 614d, 714d and the shaft 26 to allow the shaft 26 to slip relative to the slippers 114d, 214d, 314d, 414d, 514d, 614d, 714d. However, when the shaft 26 is continuously rotatable, the clutches 11Od, 21Od, 31Od, 41Od, 510d, 61Od, 71Od are stationary with the outer housing 36.

[0048] With continued reference to FIG. 6, the torque transfer assembly includes a control force member 38d having a rotatable member 180 coupled for rotation with the slipper 114d, a first electromagnet 182 positioned on one side of the rotatable member 180 to selectively attract the rotatable member 180, a second electromagnet 184 positioned on an opposite side of the rotatable member 180 to selectively attract the rotatable member 180, and a pin 186 coupled to the rotatable member 180 and at least partially received within a slot 188 in the outer housing 36. Specifically, the rotatable member 180 includes a radially inwardly- extending tab 190 that engages the slot 132 in the slipper 114d, such that the rotatable member 180 co-rotates with the slipper 114d. As shown in FIG. 7, the slot 132 in the outer housing 36 is oriented substantially diagonally relative to the central axis 31, such that axial movement of the rotatable member 180 toward either of the electromagnets 182, 184 is translated by the pin 186 and slot 188 to a rotational movement, about the axis 31, of the rotatable member 180 relative to the outer housing 36. [0049] To initiate actuation of the torque transfer assembly when the outer housing 36 is continuously rotatable and the rotation of the shaft 26 is controlled by actuation of the torque transfer assembly, the rotatable member 180 is axially moved in a first direction (indicated by arrow 192 in FIG. 6) toward the electromagnet 184 by activating the electromagnet 184. As discussed above, the axial movement of the rotatable member 180 is translated to rotational movement of the rotatable member 180 relative to the outer housing 36 by the pin 186 and slot 188, causing the slipper 114d to index relative to the outer race 122d and the slipper 114d to collapse upon the shaft 26 in the manner discussed above. To cease transferring torque from the outer housing 36 to the shaft 26, the direction of the control force Fj is reversed by deactivating the electromagnet 184, and activating the other electromagnet 182 to axially move the rotatable member 180 in a second direction (indicated by arrow 194) opposite the first direction. Reversing the direction of the control force Fj substantially re-aligns the pockets in the clutches HOd, 21Od, 310d, 41Od, 510d, 61Od, 71Od, and substantially removes the clamping load exerted by the slippers 114d, 214d, 314d, 414d, 514d, 614d, 714d on the shaft 26 to allow the outer housing 36 and clutches HOd, 21Od, 310d, 410d, 510d, 61Od, 71Od to slip relative to the shaft 26.

[0050] To initiate actuation of the torque transfer assembly when the shaft 26 is continuously rotatable and the rotation of the outer housing 36 is controlled by actuation of the torque transfer assembly, the same process as discussed above is employed. To cease transferring torque from the shaft 26 to the outer housing 36, the direction of the control force Fj is reversed as discussed above to substantially re-align the pockets in the clutches 11Od, 21Od, 310d, 41Od, 510d, 61Od, 71Od to substantially remove the clamping load exerted by the slippers 114d, 214d, 314d, 414d, 514d, 614d, 714d on the shaft 26 to allow the shaft 26 to slip relative to the outer housing 36 and clutches HOd, 21Od, 310d, 41Od, 510d, 61Od, 71Od.

[0051] Of course, while each of the respective torque transfer assemblies of FIGS. 2-6 includes seven cascaded clutches 110, 210, 310, 410, 510, 610, 710, or 110a, 210a, 310a, 410a, 510a, 610a, 710a, in other constructions, any suitable number of clutches can be utilized having any suitable ramp angle θ and coefficient of friction μ to facilitate achieving the desired force gain.

[0052] Various features of the invention are set forth in the following claims.

Claims

CLAIMS What is claimed is:

1. A torque transfer assembly operable to selectively transmit torque from a first member to a second member coaxial with the first member, the torque transfer assembly comprising: a first torque transfer device; a second torque transfer device coaxial with the first torque transfer device and positioned between the first member and the second member, each of the first and second torque transfer devices including a first race selectively engageable with the first member; a second race coaxial with the first race, the second race of the first torque transfer device coupled to the first race of the second torque transfer device, and the second race of the second torque transfer device coupled to the second member; a plurality of axially-extending pockets defined between the first and second races; a plurality of rollers positioned in the respective pockets; and an axial gap formed in one of the first and second races; wherein a force applied to the first race of the first torque transfer device indexes the first race of the first torque transfer device relative to the second race of the first torque transfer device to radially expand the first torque transfer device to frictionally engage the first member.

2. The torque transfer assembly of claim 1, wherein the frictional engagement of the first race of the first torque transfer device and the first member indexes the first race of the second torque transfer device relative to the second race of the second torque transfer device to radially expand the second torque transfer device to frictionally engage the first member and to transfer torque from the first member to the second member.

3. The torque transfer assembly of claim 2, wherein the force applied to the first race of the first torque transfer device is a first force, and wherein the frictional engagement of the first race of the first torque transfer device and the first member applies a second force on the first race of the second torque transfer device through the second race of the first torque transfer device that is a multiple of the first force.

4. The torque transfer assembly of claim 3, wherein the second force is greater than the first force.

5. The torque transfer assembly of claim 1, further comprising a third torque transfer device coaxial with the first and second torque transfer devices, wherein the third torque transfer device is substantially similar to the first and second torque transfer devices, and wherein the second race of the third torque transfer device is coupled to the first race of the first torque transfer device.

6. The torque transfer assembly of claim 1 , wherein the first race of each of the first and second torque transfer devices is a slipper race, wherein the second race of each of the first and second torque transfer devices is an outer race disposed radially outwardly of the respective slipper races of the first and second torque transfer devices, and wherein the axial gap is formed in the slipper race.

7. The torque transfer assembly of claim 1, further comprising a control force member operable to apply the force to the first race of the first torque transfer device to index the first race of the first torque transfer device relative to the second race of the first torque transfer device.

8. The torque transfer assembly of claim 7, wherein the control force member includes a rotatable member coupled for rotation with the first race of the first torque transfer device; and a braking member selectively engageable with the rotatable member.

9. The torque transfer assembly of claim 7, wherein the control force member includes a first rotatable member coupled for rotation with the first race of the first torque transfer device; a second rotatable member coupled for rotation with the first member; and an electromagnet operable to generate a magnetic field to attract the second rotatable member toward the first rotatable member to selectively engage the second rotatable member and the first rotatable member.

10. The torque transfer assembly of claim 7, wherein the control force member includes a rotatable member coupled for rotation with the first race of the first torque transfer device; an electromagnet positioned on one side of the rotatable member to selectively attract the rotatable member; and a pin coupled to the rotatable member and at least partially received within a slot in the second member, wherein axial movement of the rotatable member toward the electromagnet is translated by the pin and slot to a rotational movement of the rotatable member relative to the second member.

11. A torque transfer assembly operable to selectively transmit torque from a first member to a second member coaxial with the first member, the torque transfer assembly comprising: a first torque transfer device; a second torque transfer device coaxial with the first torque transfer device and positioned between the first member and the second member, each of the first and second torque transfer devices including a slipper race selectively engageable with the outer periphery of the first member; an outer race disposed radially outwardly of the slipper race, the outer race of the first torque transfer device coupled to the slipper race of the second torque transfer device, and the outer race of the second torque transfer device coupled to the second member; a plurality of axially-extending pockets defined between the first and second races; a plurality of rollers positioned in the respective pockets; an axial gap formed in the slipper race; and a control force member operable to selectively apply a control force to the slipper race of the first torque transfer device to index the slipper race of the first torque transfer device relative to the outer race of the first torque transfer device to radially expand the first torque transfer device to frictionally engage the first member.

12. The torque transfer assembly of claim 11 , wherein the control force member applies the control force to the slipper race of the first torque transfer device in a direction of rotation of the first member relative to the second member.

13. The torque transfer assembly of claim 11 , wherein the frictional engagement of the slipper race of the first torque transfer device and the first member indexes the slipper race of the second torque transfer device relative to the outer race of the second torque transfer device to radially expand the second torque transfer device to frictionally engage the first member to transmit torque from the first member to the second member.

14. The torque transfer assembly of claim 11, wherein the control force applied to the slipper race of the first torque transfer device is a first control force, and wherein the frictional engagement of the slipper race of the first torque transfer device and the first member applies a second control force on the slipper race of the second torque transfer device through the outer race of the first torque transfer device that is a multiple of the first control force.

15. The torque transfer assembly of claim 14, wherein the second control force is greater than the first control force.

16. The torque transfer assembly of claim 11 , wherein the control force member includes a rotatable member coupled for rotation with the first race of the first torque transfer device; and a braking member selectively engageable with the rotatable member.

17. The torque transfer assembly of claim 11 , wherein the control force member includes a first rotatable member coupled for rotation with the first race of the first torque transfer device; a second rotatable member coupled for rotation with the first member; and an electromagnet operable to generate a magnetic field to attract the second rotatable member toward the first rotatable member to selectively engage the second rotatable member and the first rotatable member.

18. The torque transfer assembly of claim 11 , wherein the control force member includes a rotatable member coupled for rotation with the first race of the first torque transfer device; an electromagnet positioned on one side of the rotatable member to selectively attract the rotatable member; and a pin coupled to the rotatable member and at least partially received within a slot in the second member, wherein axial movement of the rotatable member toward the electromagnet is translated by the pin and slot to a rotational movement of the rotatable member relative to the second member.

19. A method of selectively transmitting torque from a first member to a second member coaxial with the first member, the method comprising: providing a first torque transfer device; positioning a second torque transfer device coaxial with the first torque transfer device and between the first and second members, each of the first and second torque transfer devices including a first race selectively engageable with the first member; a second race coaxial with the first race; a plurality of axially-extending pockets defined between the first and second races; a plurality of rollers positioned in the respective pockets; an axial gap formed in one of the first and second races; applying a first force to the first race of the first torque transfer device to index the first race of the first torque transfer device relative to the second race of the first torque transfer device to radially expand the first torque transfer device to frictionally engage the first member; coupling the second race of the first torque transfer device to the first race of the second torque transfer device; coupling the second race of the second torque transfer device to the second member; and applying a second force to the first race of the second torque transfer device with the second race of the first torque transfer device to index the first race of the second torque transfer device relative to the second race of the second torque transfer device to radially expand the second torque transfer device to frictionally engage the first member, wherein the second force is greater than the first force.

20. The method of claim 19, further comprising: providing a third torque transfer device substantially similar to the first and second torque transfer devices; positioning the third torque transfer device coaxial with the first and second torque transfer devices; and coupling the second race of the third torque transfer device to the first race of the first torque transfer device; wherein applying the first force to the first race of the first torque transfer device includes applying the first force with the second race of the third torque transfer device.