Abstract:
An overrunning roller/ramp clutch assembly is disclosed which has a cylindrical drive and driven member. Between the surfaces of these members, a plurality of segmented retainers, each containing a bearing, is located. Each of the retainers defines a ramped surface for engagement with the bearings. A connector interconnects all of the retainers together and causes the retainers to circumferentially move in unison with one another.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a clutch bearing assembly which engages upon torque being applied by an input member when rotating in one direction, and acting as a rolling element anti-friction bearing when the input member rotates in the opposite direction. More specifically, the present invention relates to a one-way clutch assembly of a roller/ramp variety and the mechanism by which rollers are retained and biased in the assembly. 
     2. Description of the Prior Art 
     One-way clutch bearing assemblies are used in a wide variety of applications. One possible application is use in a paper copier or other low torque applications. During operation of a copier, it is often desirable to disconnect the drive shafts or rollers of the copier from the drive train. When disconnected, the paper feeding shafts can rotate freely with respect to the drive train and, accordingly, they are free to rotate with regard to the speed of the drive train. At other times, it is preferred that the paper feeding elements of the copiers automatically lock to the drive train whenever there is a relative disproportional rotation between the paper drive rollers and the input member from the drive train. The above mentioned clutch assemblies have also been provided where a clutch assembly transfers torque in two directions and where the torque can be transferred in two directions. 
     In one type of clutch assembly, concentric driving and driven members are provided with a driving member having axial surfaces which face toward another member. Upon each surface, a roller is loosely held. The assemblies are referred to as roller/ramp clutch assemblies. The rollers are initially responsive to acceleration of the driving member and when the rotational acceleration of the driving member occurs, the inertia of the rollers causes them to move along the surfaces toward a side edge of the surfaces. At the side edge, the distance between the surfaces and the driven member is less than the diameter of the roller and the roller contacts the driven member, becoming engaged or locking in the wedge fault between the axial surfaces of the drive member and the circumference of the driven member. In some varieties, the rollers can move along the axial surface to either side. In other types, the engagement of the driven member is only possible by movement of the roller to one side of the surface. 
     In the later systems, however, complex mechanisms are used to retain the rollers into the grooves. The mechanisms have also generally failed to ensure that the rollers will engage between the driving and driven members at the same time. Failure to provide simultaneous engagement results in disproportionate stresses being applied to the rollers, the driven members, and the driving member. Additionally, non-simultaneous engagement of the rollers has the effect of making the engagement and disengagement more noticeable during the operation of the copier or other device. 
     Prior designs of roller/ramp clutch assemblies have also used a common biasing member to bias all of the rollers to their non-engaged positions. As a result, greater biasing forces are required and the failure of the biasing member results in the assembly functioning improperly. It is the later type of assembly that the present invention particularly relates. 
     In view of the foregoing limitations and shortcomings of the prior art devices, as well as other disadvantages not specifically mentioned above, there exists a need in the art for an improved roller/ramp clutch assembly. The primary object of the current invention is to provide a one-way clutch which is relatively simple in construction and yet has both the function of a one-way clutch and the function of a roller bearing. Therefore, as compared to the conventional arrangement using a separate radial bearing, the inventive arrangement achieves decreases in axial dimension, weight and cost, and is suitable particularly for applications having limitations of size, weight and cost. Further, standard bearing rings can be used as the inner and outer members either intact or by applying more or less processing thereto; which is very advantageous from the standpoint of cost. 
     SUMMARY OF THE INVENTION 
     Briefly described, these and other objects are accomplished according to the present invention by providing a one-way clutch assembly having a roller/ramp design. The assembly includes independently rotatable inner and outer bearing race members, either of which can function as a driving or driven members. The races are opposing cylindrical surfaces, are concentric about a central axis, and define a gap therebetween. 
     Formed in at least one of the cylindrical surfaces is a raceway for receiving the rolling elements, in this case ball elements. 
     Located between the inner and outer races are a plurality of ball elements, each ball element being located within the bearing raceway. A series of segmented retainers are circumferentially disposed between the ball elements so that they can all rotate about a central axis independently of the other ball elements. A connector circumferentially interconnects all of the retainers so that they can rotate about a central axis independently of the inner and outer races. By utilizing the connector, the retainers can all substantially move circumferentially in unison and, therefore, the ball elements can engage and disengage between the members in unison. 
     The segmented retainers feature a “U” shaped open groove, which forms a pair of ramps for engaging an adjacent ball element when the relative rotation between race members is in one direction. As the rollers or bearings move up the ramps, the segmented retainer and the engaging ball elements wedged between the races. This action results in torque being transferred between the inner and outer race members. This can be used as a brake when one race member is coupled to a ground structure, or to transfer rotational torque to another machine element. The ball elements are also independently biased by the connector element which is coupled to the rotating segmented retainers. In one embodiment, the biasing is provided by resilient tabs that engage the surface of the ball elements. In another embodiment, the ball elements are biased by engagement with the supported segmented retainer. 
     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and dependent claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view illustrating the embodiment of the one-way clutch bearing assembly of the present invention in it&#39;s disengaged position; 
     FIG. 2 is a partial section view of the embodiment of the present invention showing the bearing in both the engaged and unengaged condition; 
     FIGS. 3 a,    3   b  are a partial view of the ball element associated segmented retainer in the disengaged position and engaged position respectfully; 
     FIG. 4 is a cross-sectional view of the ball element and associated segmented retainer in the engaged position; 
     FIG. 5 is a cross-sectional view of the retainer as shown through Section  5 — 5  of FIG. 1; 
     FIG. 6 is a cross-sectional view of the clutch assembly of the current invention through Section  6 — 6  of FIG. 4; and 
     FIG. 7 depicts the connecting element showing its interconnection with the segmented retainer. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now in detail to the drawings, there is shown in FIG. 1 an assembly  10  embodying a outer race  14  supported by bearing elements  16  for rotation about an inner race  20  of the assembly  10 . 
     Respectively formed in the outer and inner races  14  and  20  are a pair of opposed cylindrical surfaces  22  and  24  which are herein referred to as outer cylindrical surface  22  and inner cylindrical surface  24 . Since the outer race  14  and the inner race  20  are mounted for independent rotation about a common axis  26 , the opposed cylindrical surfaces  22  and  24  are likewise independently rotatable about that axis  26  and are concentric with respect to one another. 
     A series of axially oriented segmented retainers  32  are disposed between the cylindrical surfaces  22  and  24 . Disposed within the segmented retainers  32 , are bearing elements  16 . As seen in FIG. 2, the bearing elements  16  are moveable within the segmented retainer  32  between a first unlocked position  35  and a second locked position  36 . As shown, when the bearing elements  16  translate from unlocked position  35  to locking position  36 , the segmented retainer  32  is translated radially inwardly toward cylindrical surface  24 . 
     As further seen in FIG. 2, segmented retainer  32  has a datum as defined by A—A. When the bearing element  16  is in the unlocked position  35 , datum A—A is a first distance from a center datum C—C of bearing element  16 . As bearing element  16  translates to the locked position  36  the segmented retainer  32  translates toward one of the cylindrical surfaces  22  and  24 . Datum A—A translates to position A 1 —A 1  which is a different distance from center datum C—C of bearing element  16 . It must be noted that the translation of the position of datum A—A to A 1 —A 1  must be gradual so bearing element  16  does not jump out of the segmented retainer  32 . This also aids in the disengagement of the bearing elements  16 . 
     As best seen in FIGS. 3 a  and  3   b,  the bearing element  16  is disposed between a pair of generally parallel arm members  36  and  38  of the segmented retainer  32 . Each of the arm members  36  and  38  have spaced side surfaces  44  and  46 . The surfaces  46  and  44  of the segmented retainer  32  define a radius which conforms to portions of the surface of bearing element  16 . As seen in FIG. 3 a,  when the bearing element  16  is in its unlocked position  35 , the surfaces  46  and  44  force the bearing element  16  to “ride up” the surfaces  44  and  46 , causing the bearing element  16  to move radially outward relative to axis. As best seen in FIG. 3 b,  when the bearing element  16  is in its locked position  36 , the inner radial surfaces  44  and  46  of the segmented retainer  32  has a surface radius which conforms to the medial portion  49  of the bearing element  16 . When the bearing element  16  translates from its unlocked position  35  to its locked position  36 , the segmented retainer  32  is forced radially into one cylindrical surface  24 . The change in curvature over the equidistantly spaced surfaces  46  and  44  is gradual, allowing for easy translation of bearing element  16  between arm members  36  and  38 . 
     As best seen in FIG. 4, when bearing element  16  is in its engaged position within the segmented retainer  32 , the retainer&#39;s lower surface  52  is engaged onto the cylindrical surface  24  of inner race  20 , thus providing a torque transferring mechanism. Further shown in FIG. 4, connector element  34  ensures that all of the bearing elements  16  are translated from the unlocked position  35  to locked position  36  of their respective segmented retainers  32  at the same time. Connector element  34  also ensures that the bearing elements  16  are transferred from the locked position  36  to the unlocked position  35  simultaneously. 
     FIG. 5 shows a cross-sectional view of the one-way clutch of the current invention shown in FIG.  1  through line  5 — 5 . As can be seen, surfaces  46  and  44  of segmented retainer  32  have radii which conform to the lower portion  48  (see FIG. 3 a ) of the bearing element  16  and the bearing element  16  is always in contact with the races  14  and  20  disposed on the opposing cylindrical surfaces  22  and  24 . Although shown as curved surfaces, these races can take any form as known in the art. 
     FIG. 6 shows a cross-sectional view of the one-way clutch as depicted in FIG.  4  through cross-section  6 — 6 . The clutch is shown in its engaged position. Internal surfaces  44  and  46  of segmented retainer  32  are shown having a radius, which conforms to the medial portion  49  of bearing element  16 . Retainer lower surface  52  of the segmented retainer  32  is shown engaging the cylindrical surface  24  of the inner race  20 . As can be seen, the bearing element  16  is always in contact with the upper and lower races  14  and  20 . 
     Depicted in FIG. 7 is a top view of the connector  34 . The connector  34  defines a plurality of holes  53  which allow the bearing elements  16  to engage the inner and outer races  14  and  20 . The connector  34  also defines a plurality of key-ways  50  which allow the installation of the connector  34  after the bearings and retainers have been placed between the inner and outer races  20  and  14 . Also shown is the relation of connector  34  with the segmented retainer  32 . 
     Which of the cylindrical surfaces  22  and  24  will be engaged depends on the particular geometry of the segmented retainer  32  and, therefore, it depends on the particular application of the present invention. It is shown and preferred that the segmented retainer  32  engages the inner cylindrical surface  24  through contact with the retainer lower surface  52 . 
     While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope and fair meaning of the accompanying claims.