Abstract:
A Progressive Compression Suspension is disclosed. The suspension operates to provide floating opposed mounting points for each end of the suspension&#39;s shock absorber. The bottom end of the shock absorber pivotally attaches to the lower suspension arm, and the upper end of the shock absorber pivotally attaches to a compression linkage. The compression linkage is pivotally attached to the vehicle frame or chassis, such that it rocks back forth when the suspension engages rough terrain and the top of the shock absorber works in opposition to the bottom of the shock absorber. The rocking of the compression linkage is created by an actuating linkage interconnecting the compression linkage and an eccentric arm extending inwardly towards the frame from the pivot point of the lower suspension arm. As a result of this geometry, if the lower suspension arm is driven upwardly by the terrain, it will (through operation of the eccentric arm, actuating linkage and compression linkage) cause the top mounting point of the shock absorber to be driven downwardly. By correctly calculating the dimensional relationships, the resultant effect progressive dampening that is responsive to suspension travel, rather than simple linear dampening.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to vehicle suspension systems and, more specifically, to a Progressive Compression Suspension.  
         [0003]     2. Description of Related Art  
         [0004]     The deserts of southwestern United States have become an adult playground for many people. In these regions, many people spend a great deal of their recreational time and money engaging driving a variety of different types of vehicles around the desert sand dunes. The most widely prevalent vehicle type is the dune or sand buggy. Sand buggies come in a variety of sizes and shapes depending upon their intended use pattern and purpose. There are sand buggies that are essentially cars or trucks with increased suspension travel, large sand-compatible tires, and engines modified to be durable in the hot sandy desert environment.  
         [0005]     Other sand buggies go far beyond the basic version described above. These high-end sand buggies have specialized frames, seats, engines, tires and suspension systems so that they can not only be used to drive around the sand dunes, but can actually be raced at high speed in these environments. The suspensions in these high-end sand buggies tend to be an area of particular operational (and therefore design) concern. In sand buggies, having a powerful engine will be worthless if it is being supported by a weak suspension. Particularly because the more powerful the engine, the faster the buggy will go, and therefore the more punishment that the buggy&#39;s suspension will sustain. Sand buggy manufacturers and aficionados are constantly in search of new improvements in sand buggy suspensions.  
         [0006]      FIG. 1  is a partial cutaway rear view of a conventional sand buggy front suspension  10 . As discussed above, there are many shapes and sizes for buggy suspensions, with this version being provided only to give the reader an introduction to the prior art approaches and general layout of buggy suspensions.  
         [0007]     The front suspension  10  of a prior sand buggy (half of which is shown here) has a large, ballooning tire  16  attached to a oversized wheel  12 . The wheel  12  spins on a short axle  14 . A front brake rotor  20  is usually associated with the wheel  12  to provide additional stopping power to the vehicle.  
         [0008]     The wheel  12  extends from a spindle  18 . The spindle  18  provides the support for the wheel  12  and allows it to be operatively turned by the steering linkage  28  (which is driven by the non-depicted steering system). In its classic form, an off-road front suspension has an upper A arm  22  pivotally connected to the buggy frame  26  and terminating in a swiveling “knuckle” joint at the spindle  18 .  
         [0009]     Similarly, a lower A arm  24  is also pivotally attached to the frame  26  and also terminates in a knuckle joint at the spindle  18 . As should be casually obvious, the pivotal connections at the ends of the upper and lower A arms  22  and  24  will permit the wheel  12  to travel up and down while keeping the tire tread substantially parallel to the ground.  
         [0010]     The off road shock assembly  30  is the device that creates the horizontal support necessary to allow the suspension  10  to bear the load of the buggy, as well as permitting the large suspension travel needed for sand activities. The shock assembly  30  of course also provides shock absorption to stabilize the buggy&#39;s ride. The shock assembly  30  attaches to the frame  26  at its upper end, and to a midpoint of the lower A arm  24  at its lower end. In this position, the shock assembly  30  will work on the relative motion between the top of the frame  26  and the pivot point where it attaches to the lower A arm  24 . The upper A arm  22  simply keeps the spindle  18  upright as the shock assembly  30  permits the lower A arm  22  to travel up and down due to external force from bumps and the like.  
         [0011]     The shock assembly  30  used with the prior art off road suspension systems is the focal point of these systems. Most owners of vehicles employing the depicted design will spend substantial time and money improving the performance of the shock assembly  30  in order to improve the overall performance of the suspension  10 . The assembly  30  typically has a spring-assisted shock absorber  32 , which is a heavy duty shock absorber that has a spring mechanism to provide the suspension with support as well as dampening. Many times, there is also an oil reservoir  34  attached to the assembly  30  to allow for the expanded travel of the shock without enlarging the shock cylinder.  
         [0012]     Another approach to improving the shock assembly  30  for off road use is to use a 2-stage spring assembly  36  (versus a single stage). The 2-stages of such a spring assembly provide a spring assisted shock that has different spring tensions for different compression conditions (i.e. lower spring tension when the shock is under low compression, but high spring tension once the low spring tension spring is fully compressed by excessive shock travel). Adding the second spring stage adds cost, of course, and really doesn&#39;t improve the mechanics of the suspension  10 .  
         [0013]     Still another approach for improving performance of the suspension is to add an additional shock absorber that works somewhat in tandem with the two-stage spring shock  30 . These “override” shock assemblies are designed to improve suspension dampening when the suspension is at the end of what would be a standard suspension&#39;s compressed travel. Adding an override shock also adds substantial cost to the suspension  10 , as well as another item that will require periodic replacement.  
         [0014]     What is really needed is a new suspension geometry that allows the suspension to use a fairly low-cost single-stage spring-assisted shock absorber, while providing the necessary suspension travel and vibration dampening for high-speed sand travel.  
       SUMMARY OF THE INVENTION  
       [0015]     In light of the aforementioned problems associated with the prior devices and systems, it is an object of the present invention to provide a Progressive Compression Suspension. The suspension should operate to provide floating opposed mounting points for each end of the suspension&#39;s shock absorber. The bottom end of the shock absorber should pivotally attach to the lower suspension arm, and the upper end of the shock absorber should pivotally attach to a compression linkage. The compression linkage should be pivotally attached to the vehicle frame or chassis, and should rock back forth when the suspension engages rough terrain so that the top of the shock absorber works in opposition to the bottom of the shock absorber. The rocking of the compression linkage should be created by an actuating linkage interconnecting the compression linkage and an eccentric arm extending inwardly towards the frame from the pivot point of the lower suspension arm. As a result of this geometry, if the lower suspension arm is driven upwardly by the terrain, it should (through operation of the eccentric arm, actuating linkage and compression linkage) cause the top mounting point of the shock absorber to be driven downwardly. If the dimensional relationships are calculated correctly, the resultant effect should be to obtain progressive dampening that is responsive to suspension travel, rather than simple linear dampening.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, of which:  
         [0017]      FIG. 1  is a partial cutaway rear view of a conventional sand buggy front suspension;  
         [0018]      FIG. 2  is a partial cutaway rear view of a sand buggy having a preferred embodiment of the progressive compression front suspension of the present invention;  
         [0019]      FIG. 3  is a partial cutaway rear view of the suspension of  FIG. 2  when the wheel has traveled upward;  
         [0020]      FIG. 4  is a partial cutaway rear view of the suspension of  FIGS. 2 and 3  when the wheel has traveled downward;  
         [0021]      FIGS. 5A and 5B  are rear and top views, respectively, of the compression linkage of the suspension of  FIGS. 2-4 ;  
         [0022]      FIG. 6  is a top view of the lower A arm having eccentric actuator of the suspension of  FIGS. 2-4 ;  
         [0023]      FIG. 7  is a top view of the upper A arm of the suspension of  FIGS. 2-4 ; and  
         [0024]      FIG. 8  is a side view of the suspension of the present invention adapted to be a motorcycle rear suspension.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor of carrying out his invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide a Progressive Compression Suspension.  
         [0026]     The present invention can best be understood by initial consideration of  FIG. 2 .  FIG. 2  is a partial cutaway rear view of a sand buggy having a preferred embodiment of the progressive compression front suspension  40  of the present invention. The suspension  40  has a conventional spindle  18 , and a generally conventional upper A arm  22  (although it may be modified to allow for the modified geometry of the other components in the suspension). The upper A arm  22  interconnects the spindle  18  with the upper portion of the frame  26 A, and as with the prior suspension, causes the spindle  18  to remain upright while the lower A arm having eccentric actuator  42  travels up and down.  
         [0027]     It is the lower A arm having eccentric actuator  42 , as well as other new elements that cause the unique performance attributes of this suspension  40 . The lower A arm having eccentric actuator  42  has an A arm portion  44  (much like a conventional lower A arm), but also has an eccentric arm portion  46  extending from the frame-side end of the A arm portion  44 .  
         [0028]     The simplified off road shock assembly  52  has a (typically single-stage) spring-assisted shock assembly that attaches to the A arm portion  44  of the lower A arm having eccentric actuator  42  (similar to the prior art lower A arm). At its top end, however, the shock assembly  52  attaches to a new suspension element—the compression linkage  48 . The compression linkage  48  is pivotally attached to the frame  26 A such that it can exercise a rocking motion. This rocking motion will allow the top end of the shock assembly  52  to travel up and down, rather than being fixed in a single position as with the prior art suspension design.  
         [0029]     The compression linkage  48  is driven through this rocking motion by an actuating linkage  50 . The actuating linkage  50  is pivotally attached at one end to the end of the eccentric arm portion  46 , and at its other end to the compression linkage  48 . As shown, there is an angle between the longitudinal axis of the A arm portion  44  and the eccentric arm portion  46  and the A arm portion  44  (i.e. the eccentric arm portion angles upwardly from a longitudinal axis defined by the A arm portion) at an angle between zero and ninety degrees.  
         [0030]     As should be apparent, movement of the eccentric arm portion  46  will cause the actuating linkage  50  to also move, which in turn will cause the compression linkage  48  to rock either upwardly or downwardly. Rocking of the compression linkage  48  will either increase or decrease the compression or extension of the shock assembly  54 .  FIG. 3  is provided to assist in the understanding of the effect created by this novel design.  
         [0031]      FIG. 3  is a partial cutaway rear view of the suspension  40  of  FIG. 2  when the wheel has traveled upward. Here, the dashed lines are provided to show the suspension  40  when it is in its rest position “R” (which was shown in  FIG. 2 ). The solid lines depict the suspension  40  when the external forces on the suspension  40  have driven it into an upwardly-deflected condition “U.” 
         [0032]     As the wheel travels upwardly, the spindle  18  forces the A arm portion  44  to pivot around the lower A arm pivot axis  54  (where the lower A arm pivotally attaches to the frame  26 A). The A arm portion will move in direction X AU  (“AU” denotes A-arm Up), which will cause the shock lower mount  56  to travel upwardly (similar to the conventional suspension of  FIG. 1 ).  
         [0033]     The eccentric arm portion  46 , however, will be caused to rotate in the opposite direction relative to the A arm portion  44 , since it is on the opposite side of the pivot axis  54 . The eccentric arm portion  46  will therefore move in direction X EU . By moving in direction X EU , the eccentric arm portion  46  pulls the actuating linkage  50  downwardly. Moving the actuating linkage  50  down will cause the compression linkage  48  to rock downwardly in direction X CU . The downward rocking motion of the compression linkage  48  will cause some additional compressive force on the shock assembly  52  where it attaches at the shock upper mount  58 .  FIG. 4  provides clarity as to the suspension function when deflected in the opposite direction.  
         [0034]      FIG. 4  is a partial cutaway rear view of the suspension  40  of  FIGS. 2 and 3  when the wheel has traveled downward. In this figure, the solid lines depict the suspension  40  in a downwardly-deflected condition “D.” Here, the A arm portion has moved in direction XAD, causing the eccentric arm portion  46  to move in direction XED. Moving in direction XED pushes the actuating linkage  50  upwardly, which in turn causes the compression linkage  48  to rock in a counter-clockwise direction XCD. As can be seen here, the upper mount  58  has moved upwardly, further adding to the extending velocity and force that the shock assembly  52  experiences (as compared to the prior art suspension having a fixed upper shock mount).  
         [0035]     Because of the ratio between the lengths of the eccentric arm portion  46  and the A arm portion  44 , the relative rate of motion of the eccentric arm portion  46  and therefore the shock upper mount  58  will vary (relative to the A arm portion and lower mount  56 ) depending upon where the A arm portion  44  is in its travel. This changing relative compressive (or extending) speed causes the shock assembly  52  to have compound and variable spring and dampening characteristics. When the suspension  40  is near the rest condition R, the suspension  40  tends to react similar to a conventional non-progressively compressive suspension. As the suspension  40  moves away from the rest condition R, the relative motion (either compressing or extending) between the upper and lower shock mounts  58  and  56  will progressively increase. This increase tends to resist bottoming out of the suspension  40  in both the hyper-compressive and hyper-extensive situations. The elegance of this present invention is that it would be counter-intuitive that intentionally over-compressing or hyper-extending the shock absorber by accelerating the shock top mount either up or down would actually create a very controlled and effective dampening force to the vehicle&#39;s suspension performance, even in the most aggressive terrain. Now turning to  FIGS. 5A and 5B , we can examine the next element of this new suspension.  
         [0036]      FIGS. 5A and 5B  are rear and top views, respectively, of the compression linkage  48  of the suspension of  FIGS. 2-4 . The linkage  48  has an upper shock mount  58  at one end, and a pair of frame mounting pegs  62  at its opposite end. The actuating linkage pivotally attaches to the compression linkage  48  at the actuating linkage attachment point  60 . The frame mounting pegs  62  enable a pivotal connection between the compression linkage  48  and the frame. First and second rails  64 A and  64 B provide the major structural strength of the linkage  48 . The actuating linkage point  60  is preferably an aperture formed in the pair of walls extending downwardly from each rail  64 . We shall now turn to  FIG. 6  to examine the design of the lower A arm used in this suspension.  
         [0037]      FIG. 6  is a top view of the lower A arm having eccentric actuator  42  of the suspension of  FIGS. 2-4 . The A arm  42  has first and second struts  68 A and  68 B extending between the pivot axis  54  and the spindle knuckle  70 . Located in between these two ends is the shock lower mount  56  which serves as the pivot/attachment point of the shock assembly as well as a strengthening brace for the A arm  42 . A brace  72  interconnects the distal ends of the struts  68 A and  68 B. The struts  68 , spindle knuckle  70 , shock lower mount  56  and brace  72  together form the A arm portion of the lower A arm having eccentric actuator  42 .  
         [0038]     The eccentric arm portion  46  comprises a pair of elongate lobes extending from the opposing side of the brace  72  at a relative angle to the struts  68 . The eccentric arm portion  46  has defines an actuating linkage lower mount axis  74 , which is where the actuating linkage pivots when actuated. As discussed above, the relationships between the various pivot axes located along the lower A arm  42  provide the variable ratio between the movement of the actuating linkage and the shock lower mount  56 . Specifically, distance L 1 , the distance between the actuating linkage lower mount axis  74  and the pivot axis  54  is much smaller than either the distance L 2  between the pivot axis  54  and the central axis of the lower shock mount  56 , or the distance L 3  between the central axis of the lower shock mount  56  and the spindle knuckle  70 .  
         [0039]      FIG. 7  is a top view of the upper A arm  22  of the suspension of  FIGS. 2-4 . Unless adjusted to account for the addition of the compression linkage and actuating linkage, the upper A arm  22  is essentially unchanged from the prior art. There is a pivot axis  80  opposite from the upper spindle knuckle joint  70 . First strut  76 A and second strut  76 B interconnect the two, with first and second braces  78 A and  78 B providing structural integrity of the arm  22 .  
         [0040]     While the application for the suspension of the present invention is depicted here for a front suspension, it is also very suitable for the rear suspension. In fact, the front suspension of a sand buggy tends to suffer more failures than the rear suspension due to the additional punishment being at the leading edge of the vehicle, as well as due to the additional vulnerabilities added by the steering system. Yet another application for this novel suspension arrangement is shown in  FIG. 8 .  
         [0041]      FIG. 8  is a side view of the suspension of the present invention adapted to be a motorcycle rear suspension  40 A. Here, the lower A arm of the buggy suspension is converted to a swing arm having eccentric actuator  42 A. The swing arm  42 A has a swing arm portion  90  extending from the pivot point  54 A to the axle  14 A. Here, the axle  14 A has an axis that is transverse to the swing arm  90 . The drive wheel  12 A rotates around the axle  14 A and is driven by a drive pulley  82  and drive belt  84 .  
         [0042]     The eccentric arm portion  46 A of the swing arm having eccentric actuator  42 A extends in an angled upward direction away from the swing arm portion  90 . As with the buggy suspension, there is an actuating linkage  50 A, a compression linkage  48 A and a shock assembly  52 A. The progressively compressive action of this novel invention will provide the same substantial benefit to a motorcycle as it does to a sand buggy.  
         [0043]     By way of summary, the following is a list of critical benefits resulting from the advancement provided by the present invention: 
    1. The system does not require the weight of the vehicle to absorb the kinetic energy created by the spring and shock attempting to compress after hitting a bump. The suspension of the present invention is a true rising rate system, and the result imparts less kinetic energy to the frame or body of the vehicle (and its passengers).     2. The system of the present invention substantially reduces the stress on the frame and body components of the vehicle. No compound springs or complex progressive (valved) shock systems are necessary, thereby eliminating a major cost and maintenance component.     3. Vehicle handling is radically improved, in part due to a drastic reduction of body roll.    
 
         [0047]     When turning the vehicle&#39;s outside wheel suspension action becomes progressively stiffer in relation to its position, while the inside wheel suspension becomes progressively softer, causing less push towards the outside of the turn (i.e. roll). 
    4. Adjustability and adaptability are provided by this system by virtue of the simplicity of tuning the various linkage lengths and relationships to provide a suspension that can be fine-tuned not only to the vehicle, but also the driver and the terrain being transited.    
 
         [0049]     Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.