Abstract:
A vehicle damper comprises a fluid filled cylinder, a piston for movement within the cylinder, at least two fluid ports formed in the piston and at least one shim at least partially blocking the ports. In one embodiment, a fluid collection area is formed between the ports and the shim, the collection area permitting communication between fluid in the ports. In another embodiment, the piston includes at least one aperture constructed and arranged to receive a threaded bleed valve.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the invention generally relate to a damper assembly for a vehicle. More specifically, certain embodiments relate to valves used in conjunction with a vehicle damper. 
         [0003]    2. Description of the Related Art 
         [0004]    Vehicle suspension systems typically include a spring component or components and a dampening component or components. Typically, mechanical springs, like helical springs, are used with some type of viscous fluid-based dampening mechanism and the two are mounted functionally in parallel. In some instances, features of the damper or spring are user-adjustable. What is needed is an improved method and apparatus for varying dampening characteristics in a shock absorber. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention generally relates to a vehicle damper comprising a fluid filled cylinder, a piston for movement within the cylinder, at least two fluid ports formed in the piston and at least one shim at least partially blocking the ports. In one embodiment, a fluid collection area is formed between the ports and the shim, the collection area permitting communication between fluid in the ports. In another embodiment, the piston includes at least one aperture constructed and arranged to receive a threaded bleed valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0007]      FIG. 1  is a perspective view of a fluid damper for a vehicle. 
           [0008]      FIG. 2  is an exploded view of a piston for a fluid damper according to one embodiment. 
           [0009]      FIG. 3  is a top view of the piston of  FIG. 2 , shown installed in a damper body. 
           [0010]      FIG. 4  is a section view of the piston of  FIG. 3 , taken at a line  4 - 4  and shown in a damper body. 
           [0011]      FIG. 5  is a section view of the piston of  FIG. 3 , taken at a line  5 - 5  and shown in a damper body. 
           [0012]      FIG. 6  is an exploded view of a piston for a fluid damper according to another embodiment. 
           [0013]      FIG. 7  is a top view of the piston of  FIG. 6 , shown installed in a damper body. 
           [0014]      FIG. 8  is a section view of the piston of  FIG. 7 , taken along a line  8 - 8 . 
           [0015]      FIG. 9  is a section view of the piston of  FIG. 7 , taken along a line  9 - 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    As used herein, the terms “down,” “up,” “downward,” “upward,” “lower,” “upper” and other directional references are relative and are used for reference only. Certain features of dampers, including damping pistons, are shown and described in U.S. Pat. No. 7,374,028, which is incorporated herein, in its entirety, by reference. The operation of a fluid damper is further described in detail in US Patent Publication No. 2009/0277734 A1 and that publication is incorporated by reference herein in its entirety. 
         [0017]      FIG. 1  is a perspective view of a shock absorber  100  for a vehicle. The shock absorber includes a fluid damper having a body  110  with a rod  115  extending therefrom and a reservoir  120  in fluid (e.g. damping fluid such as hydraulic oil) communication with the damper body. The shock absorber  100  further includes a helical spring  125  annularly disposed about the damper body and captured axially between an upper and lower end of the damper body. Typically, shock absorbers like the one shown in  FIG. 1  are installed on a vehicle with an upper end  130  connected to the vehicle frame and a lower end  135  connected to the vehicle suspension. In operation, a piston (not shown) mounted on the rod meters fluid between a compression and rebound side of the damper body. In a compression stroke, as the rod  115  moves into the body  110 , displaced fluid travels from the body to the reservoir  120 . In a rebound stroke, the operation takes place in reverse. The spring is constructed and arranged to provide position sensitive resistance as the shock absorber compresses. 
         [0018]      FIG. 2  is an exploded view of a piston  200  for a fluid damper according to one embodiment. The piston includes compression ports  210  that are radially disposed around the piston and serve to permit fluid to travel through the piston in a compression stroke of the damper. A compression shim or shims  215  serve to meter the fluid as it passes from the piston to a rebound side of the damper body. A similar arrangement exists on an opposite side of the piston and in a rebound stroke, fluid is metered by a separate shim or shims  220  as exits rebound ports  212  (the underside of which are visible in  FIG. 2 ). The piston  200  and each shim  215 ,  220  have a central bore for receiving a piston shaft (not shown). The piston of  FIG. 2  is a “dual bleed” valve piston having an independent bleed valve for each of the compression and rebound damping fluid flow. In  FIG. 2 , the compression bleed valve  225  is shown. 
         [0019]      FIG. 3  is a top view of the piston of  FIG. 2 , shown installed in a damper body. 
         [0020]      FIG. 4  is a section view of the piston of  FIG. 3 , taken at a line  4 - 4  and shown in a damper body  110 . As is typical, the piston  200  is sealed in the damper body with a sealing member  201  and reciprocates between a compression  260  and rebound  270  side of the body  110 , metering fluid as it travels. The piston  200  includes a pair of threaded apertures whereby each of the compression  225  and rebound  230  bleed valves are threaded into the piston body to form a threaded connection  231  therebetween. The purpose of the bleed valves  225 ,  230  is to pass a predetermined volume of fluid in the compression and rebound strokes without interference from the shims that meter fluid passing through compression and rebound ports. For example, in the compression stroke shown in  FIG. 3  (and notated by directional arrow  241 ), compression shim flow  250  as well as compression bleed flow  255  are each shown passing through the piston  200 . The diameter of each valve orifice  232 ,  234  may vary between the compression  225  and the rebound  230  valves, thereby allowing for the damper to be tuned with different bleed rates in rebound versus compression. 
         [0021]    Considering the bleed valves in greater detail, a compression check plate  236  checks fluid flow (e.g. substantially blocks) from the rebound side  270  to the compression side  260  of the piston body  110  while a rebound check plate  238  checks fluid flow (e.g. substantially blocks) from the compression side to the rebound side of the piston body. Each check plate is biased toward engagement with a plate sealing surface  239  of the piston body by an energizing spring  240 . In the embodiment shown, the piston is constructed and arranged whereby the bleed vales may be chosen and inserted to meet the needs of a particular user with no need to enlarge a fixed aperture in the piston  200  through drilling. In one example, sizes range between 0.0025″ and 0.150″ with each 0.005″ increase resulting in a 15% incremental increase in flow area through the valve. 
         [0022]    As illustrated by the directional arrow  241 , the piston in  FIG. 4  is moving in a compression stroke. Consequently, fluid pressure on compression check plate  236  has depressed energizing spring  240  and opened the bleed valve  225  to the flow of fluid therethrough. Importantly, the flow of fluid through the bleed valves  225 ,  230  is unencumbered by the shims  215 ,  220  as the shims are arranged to act only on fluid flowing through the compression  210  and rebound  212  ports (see  FIG. 5 ). As illustrated, the flow path from the bleed valves  225 ,  230  takes place at a lower elevation than the separate, shimmed flow path through the compression  210  and rebound  212  ports.  FIG. 2  also illustrates the difference in relative height between the fluid exiting from the bleed valve  225  and the exiting fluid from compression port  210 . 
         [0023]      FIG. 5  is a section view of the piston of  FIG. 3 , taken at a line  5 - 5  and shown in a damper body  110 .  FIG. 5  shows the operation of the compression ports  210  and the fluid path  250  through them which is blocked by compression shims  215  until enough pressure is developed to deflect and open the shims. While the shims are shown as a single plate-like unit, they may optionally comprise multiple shims (as shown, for instance, in  FIG. 8 ). In a rebound stroke of the piston, the rebound sealing shim  220  checks damping fluid flow from the rebound side  260  to the compression side  270 . Either or both of the compression and rebound shims may be completely circumferential or partially circumferential to cover only certain flow ports (e.g. “clover leafed”). 
         [0024]      FIG. 6  is an exploded view of a piston for a fluid damper according to another embodiment. The piston  200  of  FIG. 6  includes plates  300 ,  305  installed at an upper and lower side of the piston, between the compression ports  210  and the shim  215  on a compression side and between rebound ports  212  and shim  220  on a rebound side. The purpose of the plates  300 ,  305  is to create a digressive damping characteristic when using the so-equipped piston  200 . As shown, each plate  300 ,  305  includes four radially spaced apertures  310  that are constructed and arranged to be aligned with the ports of the piston. In operation, fluid entering the plate through any port is permitted to collect in a fluid collection area  315  formed in each plate. Because the shims sit on a sealing edge of the plates, the fluid forms a pool-like mass and acts upon the shim uniformly over its entire exposed area, rather than only at specific points where the ports are located. Such more even distribution results in a more distributed opening force along the circumference of the shim providing a more complete opening at opening pressure. Because the valve opens more completely, more damping fluid tends to be allowed through and the corresponding damping rate drops off markedly. For example, operation of a damper with the embodiment of  FIG. 6  can result in an initially steep dampening curve which flattens considerably as the shimmed piston valve opens and the collected pool of fluid is released. The embodiment of  FIG. 6  includes the previously explained bleed valves but it will be understood that the bleed valves and digressive plates can be used together or separately. 
         [0025]      FIG. 7  is a top view of the piston of  FIG. 6 , shown installed in a damper body and will be discussed in connection with  FIG. 8 , a section view of the piston of  FIG. 7 , taken along a line  8 - 8  and  FIG. 9 , a section view of the piston of  FIG. 7 , taken along a line  9 - 9 . In  FIG. 8 , the compression plate  300  with its fluid collection area  315  is visible along with shim  215  that is shown in an “open” position to permit shimmed flow  250  to exit the piston into the rebound side  270  of the damper body  110 . In the embodiment shown, the shim  215  is “preloaded” due to the fact that the single plate responsible for sealing the compression port  210  is mounted in a fashion that results in its inner edge adjacent rod  115  being lower than its outer edge that seals against sealing edge  320 . In one embodiment shown in  FIG. 8 , additional “large diameter” rebound and/or compression dish shims (circumferential in one embodiment) are added to restrict fluid flow upon opening of the relevant main valve stack, thereby reducing the amount of fluid “dump” or digressive damping that may occur upon valve stack opening. In  FIG. 8 , the compression ports  210  of the piston  200  are aligned with the compression apertures  310  of the compression plate  300 , resulting in a direct flow path  250  between the compression and rebound sides of the damper body. 
         [0026]    In  FIG. 9 , like  FIG. 8 , the piston  200  is shown in a compressive stroke ( 241 ) and shimmed flow is escaping to a rebound side of the damper body  110 . However, the ports visible in the piston are the rebound ports  212 , not the compression ports  210  and therefore, no fluid path is available therethrough. The fact that compressive flow is escaping in the section view of  FIG. 9  illustrates the operation of the compression plate which, with its fluid collection area  315 , permits distribution of fluid around an entire perimeter of the shim. 
         [0027]    It is noteworthy that while examples herein are discussed in the context or rebound and or compression sides of damping pistons, any of the features disclosed herein may be used solely with compression damping, solely with rebound damping or with both and further any suitable combination of the features discussed herein may be used. For example, one of the bleed valves could be plugged, preventing operation in one direction. 
         [0028]    While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.