Abstract:
A rotary suspension system includes a housing and a first suspended component affixed to the housing. A shaft is rotatably mounted in the housing, and a second suspended component is affixed to the shaft. The first cam member may be affixed for rotational movement with the shaft and axial movement along the shaft. A mating cam is associated with the housing to cause axial movement of the first cam along the shaft as the shaft is rotated. A biasing element is mounted in the housing and coacts with the first cam to resiliently resist axial movement of the cam mounted on the shaft upon rotation of the shaft in one direction.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to suspension mechanisms, more particularly to suspension mechanisms for a wheel, and most particularly to suspension mechanisms for the rear wheel of a bicycle.  
       BACKGROUND OF THE INVENTION  
       [0002]     A variety of suspension mechanisms for bicycles are available. All have their meritable aspects; however, many are complex, hard to service, not durable, or otherwise not satisfactory for bicycle use. A suspension mechanism that is easily installed and serviced is desirable.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention provides a simple, serviceable mechanism that can be easily assembled, serviced, and used. The suspension system is a rotary system comprising a housing and a first suspended component affixed to the housing. In a preferred embodiment, this first suspended component would be the forward portion of the frame of a bicycle. A shaft is rotatably mounted in the housing, and a second suspended component is affixed to the shaft. In a preferred embodiment, the second suspended component would be the rear arm supporting the rear wheel of a bicycle. A first cam is mounted on the shaft. A mating cam is associated with the housing for causing axial movement of one of the cams relative to the shaft within the housing. One of the mating cam and the first cam is mounted for axial movement when the first cam rotates with the shaft. A biasing element is mounted in the housing and coacts with the axially movable cam to resiliently resist axial movement of the mating cam upon rotation of the first cam. In a preferred embodiment, the biasing element is a plurality of Belleville washers or springs. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0005]      FIG. 1  is an isometric view of a bicycle incorporating the suspension mechanism of the present invention;  
         [0006]      FIG. 2  is a simplified schematic model of the suspension mechanism of the present invention;  
         [0007]      FIG. 3  and  FIG. 4  are isometric views of a preferred form of the housing incorporating the suspension mechanism of the present invention;  
         [0008]      FIG. 5  and  FIG. 6  are exploded isometric views of the components of the suspension mechanism of the present invention looking from the right and from the left, respectively; and  
         [0009]      FIG. 7  is a longitudinal, cross-sectional view of an assembled suspension mechanism of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]     Referring first to  FIG. 1 , the schematic of the bicycle includes a main frame  10  that supports a fork and front wheel, a rear suspension arm  12  that supports a rear wheel  14 , and a suspension hub  16 . The suspension hub is affixed in a conventional manner to the main frame  10 . The suspension arm is mounted on a shaft  30  for rotation about a transverse axis  18  through the hub  16 . An internal suspension mechanism biases the suspension arm  12  toward a home position. When weight is placed on the bicycle frame or when an obstacle is encountered by the wheel  14 , the suspension arm angulates upwardly in the direction of arrow  20  relative to hub  16  and the mainframe  10 . When the weight or obstacle is removed, the suspension mechanism resiliently returns the arm  12  to its home position.  
         [0011]     Referring to  FIG. 2 , a schematic of the hub and biasing structure is shown in simplified form. A shaft  30  is mounted for rotation in the hub  16  for rotation about the axis  18 . A cam  32  is attached to the inner end of the shaft  30  and mates with a corresponding cam  34 . Cam  34  is mounted to the frame so that it cannot rotate, but so that it can move axially along the axis  18  on the internal portion of the shaft  30 . Frustoconically-shaped spring washers  36  (also known as Belleville washers or springs) are stacked between the axially movable cam  34  and the left-hand interior end wall of the hub  16 . As the shaft  30  is rotated clockwise in the direction of arrow  38 , cam  32  rotates in a clockwise direction with the shaft  30 . Cams  32  and  34  interact so that cam  34  is moved axially away from cam  32  in the direction of arrow  39  along the axis  18  against the biasing force of the Belleville washers  36 . Once the torque that caused rotation of the shaft  30  in a clockwise direction is relieved, the cam  34  will be moved axially in a direction opposite to arrow  39  along the axis  18  by the biasing force of the Belleville washers  36 . The coaction of the cams  32  and  34  then will cause the rotation of the cam  32  and thus the shaft  30  in a counterclockwise direction opposite to arrow  38 , thus causing a suspension arm connected to shaft  30  to swing to a home position.  
         [0012]      FIGS. 3 and 4  are isometric views of the external portion of the hub  20 . Referring collectively to  FIGS. 3-6 , the hub  20  comprises four components: right-end wall  20   a,  right-half housing  20   b,  a spacer  20   c,  left-half housing  20   d,  and left-end wall  20   e.  The right-half housing  20   b  of the hub is a hollow shell having an enlarged diameter end portion  70  that forms an annular shoulder  72  on the interior. The right-end wall  20   a  fits in the enlarged region  70  and abuts against the shoulder  72 . Similarly, the left-end wall  20   e  of the housing  20  has an increased diameter portion  76  terminating in a shoulder  78  against which the left-end wall  20   e  abuts. Retaining rings  40  abut against the outer surfaces of end walls  20   a  and  20   e  and fit in annular grooves (not shown) to hold the end walls  20   a  and  20   e  in place. The left-half housing  20   d  and the right-half housing  20   b  are joined so that they are oriented coaxially with each other. Fasteners (not shown) are inserted through apertures  80  in the left-half housing  20   d  into threaded openings  82  in the right-half housing  20   b  to securely fasten the two sections of the housing together.  
         [0013]     Right-half housing  20   b  carries internal threads  84 . The threads are right-handed when viewed from the right side of the housing  20   b.  In this embodiment, the shaft  30  is coaxially mounted in the housing portions  20   b  and  20   d.  Each of the end walls  20   e  and  20   a  carry a concentric axial bore that receives respectively the left end  30   c  of the shaft and the right end  30   b  of the shaft. The central portion  30   a  of the shaft  30  is square in cross section. A gear  32   a  with a square hole in the middle is slidably fitted onto the central, square portion  30   a  of the shaft  30 . The external portion of the gear  32   a  has external threads that mate with the internal threads  84  on the right-half housing portion  20   b.  As the shaft rotates in a clockwise direction, the gear  32   a  will move axially from right to left within the right-half housing portion  20   b  as the gear  32   a  threads along internal threads  84 . Shaft bearings  42  and  46  are provided and fit into shoulders  44  provided on the internal walls of the housing ends  20   e  and  20   a  of the housing  20 . The shaft ends  30   c  and  30   b  are rotatably mounted in the bearings  42  and  46 .  
         [0014]     A spacer  20   c  is interposed in the left-half housing portions  20   d.  The left-side of the spacer  20   c  bears against the inner side of left-end wall and is shaped to clear the left bearing  46 . The stack of Belleville washers bears against the internal right-hand wall of the spacer  20   c  and are compressed as the shaft  30   b  is rotated in a clockwise direction looking from the right side of the suspension mechanism. Thus, as the shaft  30  is rotated in a clockwise direction looking from the right, the internal threads  84  and the threads on the gear  32   a  intermesh so that the gear  32   a  will travel axially along the central, square portion  30   a  of the shaft  30  toward the spacer  20   c,  thus resiliently compressing the Belleville washers  36  against the wall of spacer  20   c.  The Belleville washers thus exert a reverse biasing force on the gear  32   a  so that when the torque on the shaft  30  causing the clockwise rotational motion is relieved, the Belleville washers will force the gear  32   a  in the opposite direction on the shaft  30 , causing it to rotate in a counterclockwise direction (looking from the right) as it meshes with internal threads  84 .  
         [0015]     Thus, in this embodiment, the threads on the gear  32   a  and the internal threads  84  are a coacting cam mechanism that will exert a compression force on the Belleville washers  36  when the shaft  30  is rotated in one direction. The Belleville washers  36  will exert a biasing force on the gear  32   a,  which will cause the shaft  30  to rotate in a counter direction when the torque on shaft  30  is released. The Belleville washers function as an excellent spring and shock absorbing device. The Belleville washers can be provided so that each has a different spring rate, which will, for example, allow easy rotation through the first few degrees of motion and will gradually increase the resistive force because of an increased spring rate as the rotational travel is increased.  
         [0016]     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.