Abstract:
Example aspects of the present invention broadly comprise at least two concentric rings with complementary ramped surfaces, at least one of the rings being rotatable relative to another one of the rings so that contact is made at the ramped surfaces. The complementary ramped surfaces form respective circumferences of the rings. At least one of the ramped surfaces may have a sinusoidal profile, or a profile forming at least one of a straight line, concave, or convex. In some example embodiments of the invention, a first one of the rings is a coupling member and a second one of the rings is a tubular slipper with a friction surface radially opposite of the ramped surface. The tubular slipper is arranged to radially expand or contract upon contacting the coupling member.

Description:
FIELD OF THE INVENTION 
     This application claims the benefit of provisional U.S. Application No. 61/116,932, filed Nov. 21, 2008, which is hereby incorporated by reference, as if set forth fully herein. 
    
    
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 6,409,001 (Kerr), hereby incorporated by reference in its entirety as if set forth fully herein, discloses a multi-directional coupling including a tubular slipper, a tubular member, a race, and roller members disposed in a channel defined by the tubular slipper and the tubular member. Torque applied to the member forces the rollers to roll up the side walls of the channels, forcing the slipper to radially expand, thereby increasing the radial force exerted on the slipper against the race. As more torque is applied to the member, the slipper and the race will become rotationally locked to the member. 
     Kerr is limited in that it includes rollers. Rollers occupy valuable radial space in the coupling. Furthermore, rollers add expense. Thus, there is a long-felt need for a multi-directional coupling without roller elements. 
     BRIEF SUMMARY OF THE INVENTION 
     Example aspects of the present invention broadly comprise at least two concentric rings with complementary ramped surfaces, at least one of the rings being rotatable relative to another one of the rings so that contact is made at the ramped surfaces. The complementary ramped surfaces extend from respective circumferences of the rings. At least one of the complementary ramped surfaces may have a sinusoidal profile, or a straight line, concave, or convex profile. 
     In some example embodiments of the invention, a first one of the rings is a coupling member and a second one of the rings is a tubular slipper with a friction surface radially opposite of the ramped surface. The tubular slipper is arranged to radially expand or contract upon contacting the coupling member. In an example embodiment of the invention, the profile provides an optimum strut angle to lock the coupling. In some example embodiments of the invention, the tubular slipper includes at least one axial slit, the slit permitting varying slipper diameters. 
     Other example aspects of the present invention broadly comprise at least one first slipper ring with a first ramp profile and at least one second slipper ring with a second ramp profile. The at least one second ramp profile is complementary to and arranged to become in mating engagement with the first ramp profile. A circumference of the first slipper ring is discontinuous. In some example embodiments of the invention, at least one of the first ramp profile and the second ramp profile forms at least one of an involute, an arc, and an angled slope. In some example embodiments of the invention, relative rotation between the first slipper ring and the second slipper ring adjusts the circumference of the first slipper ring. 
     Some example embodiments of the invention include a friction ring. In an example embodiment of the invention, adjustment of the circumference engages the first slipper ring with the friction ring by increasing the circumference to expand the first slipper ring against an inner diameter of the friction ring. In another example embodiment of the invention, adjustment of the circumference decreases the circumference to contract the first slipper ring against an outer diameter of the friction ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures. 
         FIG. 1  is a perspective view of a coupling design according to an example aspect of the invention. 
         FIG. 2  is a section view of a coupling design according to an example aspect of the invention. 
         FIG. 3A  is a detail view of encircled region  3  in  FIG. 2  with a radial gap shown between the rings for clarity. 
         FIG. 3B  is a detail view of encircled region  3  in  FIG. 2  with the coupling shown in a freewheel state. 
         FIG. 3C  is a detail view of encircled region  3  in  FIG. 2  with the coupling shown in a locked state. 
         FIG. 3D  is a detailed view of a section of an embodiment of a coupling. 
         FIG. 3E  is a detailed view of the section of  FIG. 3D  with the coupling shown in a locked state. 
         FIG. 4  is a section view of a coupling design according to an example aspect of the invention disposed within further a outer ring. 
         FIG. 5  is a detailed view of an embodiment of a coupling disposed around a further inner ring according to an example aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     At the outset, it should be appreciated that like drawing numbers appearing in different drawing views identify identical, or functionally similar, structural elements. Furthermore, it is understood that this invention is not limited only to the particular embodiments, methodology, materials and modifications described herein, and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the following example methods, devices, and materials are now described. 
     The following description is made with reference to  FIG. 1 .  FIG. 1  is a perspective view of a coupling design according to an example aspect of the invention. Coupling (also referred to as a “slipper clutch”)  10  includes rings  12  and  14 . Coupling  10  may also include optional retaining ring  16 , although it is not required in other embodiments After ring  12  is axially aligned with ring  14 , retaining ring  16  may be installed onto ring  12  to prevent axial displacement of ring  12  relative to ring  14  along axis  18 . After installation, rings  12  and  14  are concentric. That is, rings  12  and  14  share common axis  18 . 
     The following description is made with reference to  FIGS. 1 and 2 .  FIG. 2  is a section view of a coupling design according to an example aspect of the invention. Rings  12  and  14  include ramped surfaces  20  and  22 , respectively, wherein surface  20  forms an outer surface of ring  12  and surface  22  forms an inner surface of ring  14  that faces an inner bore formed by the ring  14 . Surfaces  20  and  22  are complementary. That is, ramped surface  20  on ring  12  mates with ramped surface  22  on ring  14 . Ramped surface  20  contacts ramped surface  22  when ring  14  is rotated relative to ring  12  about axis  18  (or vice versa). That is, ramped surfaces  20  and  22  make contact when ring  14  is rotated relative to ring  12  (or vice versa). In an example embodiment of the invention, ramped surfaces  20  and  22  extend around the circumferential surface of rings  12  and  14 , respectively. 
     The following description is made with reference to  FIG. 3A .  FIG. 3A  is a detail view of encircled region  3  in  FIG. 2  with radial gap  23  shown between the rings for clarity. In one example embodiment of the invention, ramped surfaces  20  and  22  each have a sinusoidal profile. Although sinusoidal profiles are shown, profiles  20  and  22  may be straight lines forming a peak, fines with an angled slope, concave and convex arcs, involute or any other arcuate form, another suitable shape with a varying radius, or any combination thereof. In an example embodiment of the invention, ring  12  is a coupling member and ring  14  is a tubular slipper having outer friction surface  24  radially opposite of ramped surface  22 . 
     The following description is made with reference to  FIGS. 3A-3C .  FIG. 3B  is a detail view of encircled region  3  in  FIG. 2  with coupling  10  shown in a freewheel state.  FIG. 3C  is a detail view of encircled region  3  in  FIG. 2  with coupling  10  shown in a locked state. Tubular slipper  14  is arranged to radially expand upon contacting coupling member  12 . For example,  FIG. 3B  depicts coupling  10  in a freewheel state. The profiles of surfaces  22  and  24  as shown in  FIG. 3B  are circumferentially aligned so that peak  25  of profile  22  rests in valley  27  of profile  20 . Alternatively stated, in the freewheel state the concave and convex portions of the profile of surface  20  and the convex and concave portions of the profile of surface  22 , respectively, arc aligned so that the outer diameter of slipper  14  (formed by the surface  24 ) is in a non-engaged or contracted (minimized) state. In some embodiments of the invention (not shown), a pin or other feature prevents relative rotation of slipper  14  relative to member  12 , preventing engagement of coupling  10 . 
       FIG. 3C  depicts coupling  10  in a locked state. Ring  14  is rotated in direction of arrow  26 . Peak  25  of ramped surface  22  is approaching peak  29  of ramped surface  20 , causing radial expansion of slipper  14 , thereby increasing (expanding) the diameter of friction surface  24 . In an example embodiment of the invention shown in  FIG. 3D , tubular slipper  14  is disposed within coupling member  12  and arranged to radially contract upon contacting coupling member  12 . For example, as shown in  FIG. 3E , when ring  14  rotates in direction of arrow  26 , peak of ramped surface  22  approaches peak  29  of ramped surface  20 , forcing slipper  14  radially inward, thereby decreasing (contracting) the diameter of an inner friction surface of ring  14 . 
     The following description is made with reference to  FIG. 4 .  FIG. 4  is a section view of a coupling design according to an example aspect of the invention disposed within further outer ring  28 . Coupling  10  is disposed within further outer ring  28  and relative rotation of ring  14  relative to ring  12 , and resulting diameter increase of surface  24 , frictionally locks coupling  10  with further outer ring  28 . 
     Also according to an example embodiment of the invention, the profiles of surfaces  20  and  22  are configured to provide an optimum strut angle to lock the coupling. For example, a sinusoidal and/or ramp profile can be selected to maximize radially outwardly directed force exerted by friction surface  24  to friction ring  28 , while minimizing a tendency for rings  12  and  14  to become frictionally locked preventing release of coupling  10 . The contact angle (or strut angle) between surfaces  20  and  22  of rings  12  and  14 , respectively, controls the amount of rotational force that is redirected as radial force when the rings are rotated relative to one another. Friction between mating surfaces  20  and  22  can oppose release of coupling  10  if the friction force between the mating surfaces is higher than the friction force between friction surface  24  and a mating circumferential surface, surface  32  of ring  28 , for example. Therefore, the contact angle must be selected to be shallow enough so that friction from a slight interference fit between friction ring  28  and surface  24  of ring  14  is sufficient to begin engagement of coupling  10 , but steep enough to prevent surfaces  20  and  22  from becoming frictionally locked, preventing disengagement of coupling  10 . 
     In an example embodiment of the invention, tubular slipper  14  includes axial slit  30  permitting varying slipper diameters. Slipper clutch  10  includes slipper ring  14  with ramped surface  22 . Clutch  10  further includes ring  12  with ramped surface  20 . The profile of surface  20  is complementary to and in mating engagement with ramped surface  22 . The circumference of ring  14  is discontinuous at slit  30  ( FIG. 2 ), for example. One or both of those profiles may he an involute, an arc, or an angled slope. 
     In operation, rotation of slipper ring  14  relative to ring  12  (or vice versa) adjusts circumference of the surface  24  of slipper ring  14 . Slipper clutch  10  may also include optional friction ring  28 , with inner circumferential surface  32  disposed adjacent surface  24 . When friction ring  28  is present, adjustment of surface  24  in the above manner engages slipper ring  14  with friction ring  28 . That is the adjustment increases the circumference of surface  24  to expand slipper ring  14  against inner circumferential surface  32  of friction ring  28 . In another example embodiment shown in  FIG. 5 , friction ring  28  is disposed within slipper ring  14  and the adjustment decreases an inner circumference of surface  54  of the slipper ring  14  to contract slipper ring  14  against an outer circumferential surface  52  of friction ring  28 . 
     Although the foregoing description described slipper ring  14  disposed radially around the ring  12 , the scope of the present invention is not limited to that configuration only, and broadly construed, alternatively can also include ring  14  disposed radially inside of ring  12 . 
     In that case, ring  14  can radially contract to lock an inner circumferential surface of ring  14  to friction ring  28 . 
     The disclosed coupling is described without roller elements. Rollers add expense and occupy radial space. Elimination of the rollers reduces manufacturing and assembly costs and improves durability of the components. Furthermore, a contact radius between ring  12  and slipper ring  14  is moved radially out when compared to a contact radius between a roller and an inner ring. That is, for the same diameter of surface  24  of slipper ring  14 , a design with rollers must move a contact radius between ring  14  and the rollers radially in to accommodate for the added radial space occupied by the roller body. As torque is a function of radius, the inventive design allows the same torque transmission with lower forces. 
     Of course, changes and modifications to the above examples of the invention should be readily apparent to those having ordinary skill in the art, without departing from the spirit or scope of the invention as claimed. Although the invention is described by reference to specific preferred and/or example embodiments, it is clear that variations can be made without departing from the scope or spirit of the invention as claimed.