Abstract:
A locking clutch of the present invention comprises a toothed member which is connectable to a drive part and a slide assembly which is connectable to a driven part. The toothed member comprises a cylindrical surface and a plurality of teeth spaced about and extending from said cylindrical surface. The slide assembly comprises a base and a wall extending from an end surface of the base. The wall is narrower than the base, and the base and wall define a shoulder where they intersect. A plurality of pockets are formed in the shoulder and extend axially into the base from the shoulder. A plurality of grooves are formed in the wall above the pockets, there being one groove for each pocket. A slide member (such as a roller) and a resilient member (such as a coiled spring) are received in each pocket. The slide member is slidable axially in the pocket, and the spring member urges said slide member toward the mouth of the pocket. A stop, preferably in the form of a snap ring, extends around the slide assembly wall above the slide members. The snap ring is positioned to prevent the slide members from fully exiting the pockets to maintain the slide members in the slide assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not Applicable  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    This invention relates to clutches, and, in particular, to a locking clutch that connects two or more mechanical components together for torque and/or power transmission.  
           [0004]    Various clutching devices are used to selectively connect mechanical components together so that they can rotate at the same angular speed about a common axis, allowing torque and power to be transmitted from one component to the other. There are two common types of clutches: (1) progressive engagement clutches, such as friction clutches; and (2) positive engagement clutches, such as dog clutches. A friction clutch assembly usually contains two sets of friction plates mounted respectively to driving and driven parts. It relies on friction force to transmit torque and power. The friction clutch provides high performance at differential speed engagement. Frictional clutches are widely used in automotive transmissions. The construction of a friction clutch, however, is very complex, involving frictional materials and usually requiring hydraulic systems to provide and maintain adequate normal forces. Consequently, the costs associated with design and manufacture of friction clutches are high. In addition, the power losses of running the hydraulic system associated with friction clutches are high.  
           [0005]    Dog clutches are much simpler in construction. A dog clutch typically includes a pair of jaws directed towards each other for engaging or disengaging the driving and driven parts. Dog clutches are used in hydro-mechanical transmissions and other continuously variable transmissions. They are also used in four-wheel drive vehicles for engaging the secondary driving wheels. However, the engagement is not always trouble free. There are times when the jaws of one member are not aligned up well with the grooves on the mating member. In this instance, the jaws will not engage into the grooves no matter what force is used to push the two members together.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    Briefly stated, a locking clutch of the present invention comprises a toothed member which is connectable to a drive part and a slide assembly which is connectable to a driven part. The tooth member and the slide assembly can be brought into and out of engagement to transfer (or stop the transfer) of power and/or torque from the drive part to the driven part.  
           [0007]    The toothed member comprises a cylindrical surface and a plurality of teeth spaced about and extending from the cylindrical surface.  
           [0008]    The slide assembly comprises a base and a wall extending from an end surface of said base. The wall is narrower than the base, and the base and wall define a shoulder where they intersect. A plurality of pockets are formed in the shoulder and extend axially into the base from the shoulder. A plurality of grooves are formed in the wall above the pockets, there being one groove for each pocket. Thus, the groove is, in effect, a continuation of the pocket. A slide member (such as a roller) and a resilient member (such as a coiled spring) is received in each pocket. The slide member is slidable axially in the pocket, and the spring member urges the slide member toward the mouth of the pocket. A stop, preferably in the form of a snap ring, extends around the slide assembly wall above the slide members. The snap ring is positioned to prevent the slide members from fully exiting the pockets to maintain the slide members in the slide assembly pockets.  
           [0009]    The teeth of the toothed member are spaced apart to define a gap between the teeth. The gap has a width, at the radial ends of the teeth, at least as large as the width of the slide members. When the toothed member and the slide assembly are urged into engagement, at least one of the slide members is received in a tooth gap of the toothed member, thereby positionally fixing the toothed member and the slide assembly relative to each other, to enable the transfer of power and/or torque from the drive part to the driven part. The remaining slide members are urged at least partially into their respective pockets by the axial ends of the teeth.  
           [0010]    The number of teeth in the toothed member is not equal to (and is preferably smaller than) the number of slide members in the slide assembly. Preferably, the number of teeth is evenly divisible by the difference between the number of slide members and the number of teeth. The gap or space between adjacent teeth has a width, at the ends of the teeth, greater than the width of the slide members. Additionally, the side surfaces of the teeth have a shape which corresponds generally to the shape of the slide members.  
           [0011]    In one preferred embodiment, the teeth are formed on an exterior surface of the toothed member. In this instance, the slide assembly base and wall share a common outer surface. The slide assembly base and wall define a ring, and the shoulder extends radially inwardly from the inner surface of the ring. Hence, the pockets, grooves, and slide members are all positioned along an inner surface of the slide assembly ring.  
           [0012]    In a second embodiment, the toothed member is annular in shape and has an inner surface from which the teeth extend. In this embodiment, the toothed surface is the inner surface of the toothed member. The slide assembly base and wall, in this instance, share a common inner surface (or are cylindrical in shape); the grooves are formed on an exterior surface of the slide assembly wall; and the shoulder extends radially outwardly from the wall. Hence, the pockets, grooves, and slide members are all positioned along an outer surface of the slide assembly.  
           [0013]    In a third embodiment, the toothed member is in the shape of a ring and has both an inner surface and an outer surface, with teeth extending from both the inner and outer surfaces. The clutch includes an outer slide assembly which is engageable with the outer teeth and an inner slide assembly which is engageable with the inner teeth. The outer slide assembly is identical to the slide assembly described above in the first embodiment, and the inner slide assembly is identical to the slide assembly described above in the second embodiment. In this third embodiment, a single drive part can drive two driven parts, either individually or simultaneously. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is an exploded view of a first illustrative embodiment of a locking clutch of the present invention showing a toothed member and slide assembly of the locking clutch;  
         [0015]    [0015]FIG. 2 is an exploded view of the slide assembly;  
         [0016]    [0016]FIG. 3 is a cross-sectional view of the slide assembly taken along line  3 - 3  of FIG. 1  
         [0017]    [0017]FIG. 4 show the fit between adjacent slide members of the slide assembly with teeth of the toothed member;  
         [0018]    FIGS.  5 - 7  depict different angular alignments about a common axis between the toothed member and the slide assembly; and  
         [0019]    [0019]FIG. 8 is an exploded view of a second illustrative embodiment of the locking clutch; and  
         [0020]    [0020]FIG. 9 is an exploded view of an alternative embodiment of the locking clutch of FIG. 1. 
     
    
       [0021]    Corresponding reference numerals will be used throughout the several figures of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what I presently believe is the best mode of carrying out the invention.  
         [0023]    A locking clutch  10  of the present invention is shown generally in FIGS. 1 and 2. The locking clutch includes a toothed member  12  and a slide assembly  14  to which a drive and driven parts are operatively connected. As will be discussed below, the toothed member  12  and slide assembly  14  can be engaged to transmit torque and power from a drive part to a driven part, and disengaged to stop the transmission of power and torque from the drive part to the driven part. When assembled to the drive and driven parts, the toothed member  12  is preferably connected to the drive part and the slide assembly is preferably connected to the driven part. However, the toothed member  12  can be connected to the driven part and the slide assembly can be connected to the drive part.  
         [0024]    The toothed member  12  includes a plate  16  which is preferably circular in plan. The plate  16  has a circumferential surface  18  with a plurality of teeth  20  having side surfaces  22  (FIG. 4). As seen, the tooth surfaces  22  define an arc. The teeth  20  are evenly and regularly spaced about the circumferential surface  18 . A shaft  24  extends from the plate  16 . The shaft  24  allows for the toothed member  12  to be connected to the drive or driven part. The shaft  24  can be connected to the drive or driven part in any conventional manner. Although the toothed member is shown as a plate with a shaft, the toothed member could also simply be a shaft having the teeth  20  formed around its circumferential surface at the end of the shaft.  
         [0025]    The slide assembly  14  includes a ring  30  having a base  32  and a wall  34  extending up from the base. The ring  30  has a single continuous outer surface  36  which forms an outer surface for both the base  32  and the wall  34 . The base  32  and wall  34  also have inner surfaces  38  and  40 , respectively. As seen in FIG. 2, the wall  34  is narrower than the base  32 , and hence, a shoulder  42  is formed at the juncture of the wall  34  and base  32 . A series of pockets  44  are formed in the base  32 , and extend axially from the top surface of the shoulder  42 . A groove  46  is formed in the inner surface  40  of the wall  34  above each pocket  44 . The groove  46  has a surface which is effectively a continuation of the surface of pocket. Hence, there is a smooth transition between the pockets  44  and their corresponding grooves  46 . Additionally, the grooves  46  have a radial depth of about one-half the diameter of the pockets  44 . Although, the radial depth of the grooves  46  depends on the positioning of the pocket relative to the wall  34 . The pockets  44  and corresponding grooves  46  are spaced evenly about the ring. The pockets  44  are shown to be circular in plan, and the grooves  46  are shown to be semi-circular. A circumferential slit or groove  48  is formed in the inner surface  40  of the wall  34 , near the top of the ring  30 .  
         [0026]    The slide assembly  14  also includes a slide member  50  and a spring  52  which is received in each pocket  44 . A snap ring  54  is received in the circumferential groove  48 . The spring (which is preferably a coil spring) is received in the bottom of the pocket  44 , and the slide member  50  is positioned in the pocket  44  and groove  46  above the spring. Hence, the spring  52  biases the slide member  50  axially, away from the base, and against the snap ring  54 . The pocket  44  has a depth, such that when the spring  52  is compressed, the slide member  50  is substantially fully received in the pocket. Additionally, the snap ring  54  is positioned on the wall  34  such that the effective length of the groove  46  is less than the length of the slide member  50 . Hence, the spring  52  cannot push the slide member  50  out of the pocket  44 , and at least a portion of the slide member  50  will be received in the pocket when the slide member  50  is pushed against the snap ring  54 . The slide member  50  is illustratively shown to be a roller. However, the slide member  50  could be any desired polygonal shape.  
         [0027]    As can be appreciated, the pockets  44  and grooves  46  are shaped complementarily to the slide members  50 . Hence, if a differently shaped slide member is used, the shape of the pockets and grooves would most likely also change.  
         [0028]    The slide assembly  14  is preferably operatively connected to the driven part; however, as noted above; it can alternatively operatively be connected to the drive part. As seen, the slide assembly  14  is annular or ring-shaped and includes a central opening. The drive or driven part can be force fit within this opening to be frictionally received within the ring base  32 , or otherwise positionally fixed within the opening to operatively connect the drive or driven part to the slide assembly. Alternatively, the bottom of the slide assembly can be closed (i.e., so that there is no opening), and a shaft can extend from the bottom of the slide assembly to operatively connect the slide assembly  14  to the drive or driven part. The exterior surface  36  of the ring can be grooved or toothed to operatively connect the inner ring to the drive or driven part by gears, a chain, or a pulley. Of course, other mechanical means known to those skilled in the art can be employed to connect the slide assembly  14  to the drive or driven part.  
         [0029]    The shape and width of the teeth  20  are designed such that the teeth can fit between any of two adjacent slide members, as seen in FIG. 4. Additionally, the distance between adjacent teeth  20  is greater than the diameter of the slide member  50 . The number of teeth  20  on the plate  16  is chosen to be different from the number of slide members  50  in the slide assembly  14 . When the two members (i.e., the toothed member  12  and the slide assembly  14 ) are pushed together for engagement, at least, but not all, of the slide members  50  will be received between the teeth  20  of the toothed member. The slide members  50  in the slide assembly  14  that do not fall between two adjacent teeth will be pushed into the slide member pockets  44  or seats. The interaction of the slide members  50  that are received in the gap between the teeth  20 , and the teeth  20 , will rotationally fix the toothed member and slide assembly together. Hence, rotational movement of the toothed member will be transferred to the slide assembly.  
         [0030]    For any angular alignment of the two members  12  and  14 , there will always be N number of slide members  50  that align between two adjacent teeth  20 . These slide members will not be pushed into the slide assembly pockets, and instead, they will engage with the teeth  20  to transmit torque and/or power from the drive part to the driven part. FIGS.  5 - 7  depict different angular alignments about a common axis between the toothed member  12  and the slide assembly  14 . In each Figure, there are always six (6) slide members S 1 -S 6  that fall between adjacent teeth.  
         [0031]    The number N of slide members that engage with the teeth is equal to the difference between the number of slide members (S) and the number of teeth (T). Hence, the number N of slide members that engage the teeth is given by the following equation: 
         N=S−T  (1) 
         [0032]    To ensure the engaging slide members evenly share the torque load, the umber of teeth (T) is chosen to be evenly divisible by N. Stated differently, the modulus of T/N=0. Hence, T=qN, where q is a positive integer (i.e., q≧1).  
         [0033]    The maximum angular clearance D (in radians) (FIG. 5) between a slide member and a tooth is shown by the following equation:  
             D   =         2        π        (     S   -   T     )           T   2                     radians             (   2   )                               
 
         [0034]    The maximum angular clearance D represents the worst case scenario that an initial relative angular movement could occur before torque and/or power is transferred between the drive and driven parts. For most cases, the initial angular movement between two engaging members will be smaller than the value D given by the equation. As can be seen, from the equation (2), increasing the number of teeth (T) can effectively reduce the maximum possible clearance between a slide member and tooth, and thus increase the smoothness for torque and/or power transmission.  
         [0035]    In the figures, the toothed member  12  has 36 teeth, and the slide member assembly has  42  slide members. Hence, per equation (1), there are 42-36 or 6 slide members S 1 -S 6  that engage the teeth when the two members are engaged; and the maximum angular clearance D is:  
       D   =         2        π        (     42   -   36     )           36   2       =     0.029                 radian                             
 
         [0036]    In operation, the toothed member  12  and the slide assembly  14  are operatively connected to drive and driven parts, respectively. When the two members are not engaged, no power or torque is transmitted from the drive to the driven part. As the two members are brought together, N number of tooth gaps will align with N number of slide members. The remaining slide members will be pushed into their respective pockets  44  by the teeth  20 , as the axial surface of the teeth engage the end surface of the slide members. When the two members  12  and  14  are engaged, the slide members  50  will be held in the gap between the teeth, rotationally fixing the two members together. Hence, the drive part and driven part will be operatively connected via the clutch  10 , and the drive part can transfer torque and/or power to the driven part.  
         [0037]    As noted above, the surfaces  22  of the teeth  20  are curved, or define an arc. As seen in the figures, the arc or curvature of the tooth surfaces  22  is slightly greater than the curvature of the slide member  50 . However, the slide members need not be circular in cross-section. Rather, the slide members  50  can have generally any desired polygonal shape. The pockets  44  and grooves  46  of the slide assembly are preferably shaped to correspond to the shape of the slide members so that the slide members can smoothly slide axially in the pockets  44  and grooves  46 . Additionally, the tooth surfaces  22  should correspond generally to the shape of the slide member (i.e., the tooth surfaces  22  should have the same basic shape as the slide members  50 ) to allow for a efficient engagement between the slide members  50  and the teeth  20 .  
         [0038]    Another embodiment of the locking clutch is shown in FIG. 8. The locking clutch  100  is similar to the locking clutch  10 , however, rather than having one toothed member and one slide assembly, the clutch  100  includes one toothed member  120  and two slide assemblies—an inner slide assembly  113  and an outer slide assembly  114 .  
         [0039]    The toothed member  112  has a ring  120  at its end having an inner surface  122  and an outer surface  124 . A plate  126  covers one end of the ring  120 , and a shaft  128  extends from the plate  126  to connect the member  112  to a drive part. A plurality of inner teeth  128  are formed on the inner surface; and a plurality of outer teeth  130  are formed on the outer surface  124 . The teeth  128  and  130  are generally similar in shape to each other, and to the teeth  20  of the clutch  10 , inasmuch as the teeth have side surfaces which, as shown, are arcuate. The teeth  128  and  130  are evenly and regularly spaced about their respective surfaces. The toothed member  112  could also be formed from a shaft having a cup formed at its end. This cup would then have a toothed outer surface and a toothed inner surface.  
         [0040]    The outer slide assembly  114  is identical to the slide assembly  14  of the clutch  10 , and is not described herein. When the outer slide assembly  114  is engaged with the toothed member  112 , at least one of the slide members  150  of the outer slide assembly are received in at least one of the gaps between the outer teeth  130  of the toothed member. The engagement of the outer slide assembly with the outer teeth  130  of the toothed member is identical to the engagement of the slide members  50  of the slide assembly  14  with the teeth  20  of the toothed member  12 , as described above.  
         [0041]    The inner slide assembly  113  is generally similar in construction to the outer slide assembly  114 . However, rather than having slide members in pockets on the interior of the slide assembly, the slide assembly  113  has slide members  160  received in pockets on the exterior surface of the slide assembly  113 . The manner in which the exterior surface of the inner slide assembly is formed is substantially similar to the manner in which the interior surface of the outer slide assembly  114  (or the slide assembly  14 ) is formed. That is, the slide assembly  113  has a base  162  from which a wall  164  extends to define an outer shoulder. Pockets (not shown) are formed in the outer shoulder, which open into grooves  166  in the wall. Springs (not shown) and the slide members  160  are received in the pockets and held in place in the slide assembly  113  by a snap ring  168  which surrounds the wall  164 .  
         [0042]    When the inner slide assembly  113  is engaged with the toothed member  112 , some of the slide members  160  of the inner slide assembly are received in the gaps between inner teeth  128  of the toothed member  112 . The engagement of the inner slide assembly  113  with the inner teeth  128  of the toothed member is identical to the engagement of the slide members  50  of the slide assembly  14  with the teeth  20  of the toothed member  12 , as described above.  
         [0043]    The clutch  100  allows for one or both of the ring assemblies  113  and  114  to be engaged with the toothed member  112  at any one time. Hence, two driven parts can be driven by a single drive part. Thus, the clutch has four modes or operating positions: (1) neither slide assembly is engaged with the toothed member  112 , preventing any transmission of torque and/or power from the drive part to either driven part; (2) only the inner slide assembly  113  is engaged with the toothed member  112  so that torque and/or power is transmitted only to a first of the driven parts; (3) only the outer slide assembly  114  is engaged with the toothed member  112  so that torque and/or power is transmitted only to a second of the driven parts; or (4) both ring assemblies are engaged with the toothed member  112 , so that torque and/or power is transmitted to both of the driven parts.  
         [0044]    As can be appreciated, the inner slide assembly  113  can be connected to a first driven member; and the outer slide assembly  114  can be connected to a second driven member. For example, the inner slide assembly  113  is shown to be annular and has a central opening. The first driven part can be force fit within this opening, or otherwise permanently fixed within the opening. Alternatively, the bottom of the inner slide assembly can be closed (i.e., so that there is no opening), and a shaft can extend from the bottom of the inner slide assembly to operatively connect the inner slide assembly  114  to the first driven part. Further, the exterior surface of the inner ring base  162  can be grooved or toothed to operatively connect the inner ring to the drive part by gears or by a pulley.  
         [0045]    The outer slide assembly can similarly have a toothed or grooved outer surface to connect the outer slide assembly  114  to the second driven part by means of gearing, a chain, or a pulley. Other mechanical expedients known to those skilled in the art can also be used to connect the outer slide assembly  114  to the second drive part.  
         [0046]    Another embodiment of the clutch is shown in FIG. 9. The clutch  200  of FIG. 9 includes the inner slide member  113  of FIG. 8. The toothed member  220  is substantially similar to the toothed member  120  of FIG. 8. However, the toothed member  220  has a smooth, rather than a toothed, outer surface. As can be appreciated, the clutch  200  is substantially the clutch  100 , but without the outer slide member  114 .  
         [0047]    As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Although a coiled spring is preferred to urge the slide members outwardly of their pockets, the coiled spring could be replaced with any compressible, resilient member. The snap rings  54  and  166  act as stops to prevent the slide members (or other tooth engaging members) from exiting their respective pockets. Other types of stops could be used as well. For example, a pin could extend radially through the slide members which is received in a closed groove in the pocket (i.e., the groove does not open into the slide assembly shoulder), or the slide member could be provided with a foot, and the pocket could have a shoulder near the top surface of the base which would engage the slide member foot. Both these modifications would require that the ring be formed as a two piece part—a main body with the pockets which are opened at the bottom to receive the slide member (or tooth engaging member) and a bottom cover to close the bottom of the body. The toothed member and the slide assemblies can be operatively connected to their respective drive and driven parts in any conventional manner. These examples are merely illustrative.