Abstract:
A shock absorber includes a two stage valve assembly that has two valve discs. The second valve disc defines the first stage at lower valve pressures and the first valve disc defines the second stage at higher valve pressures. The two valve discs can be defined by a single piece component or they can be separate components. The second valve disc can permit fluid flow by deflection of the second valve disc or by movement of the entire second valve disc. The two stage valve assembly can be incorporated into the piston assembly of the shock absorber and/or the two stage valve assembly can be incorporated into a base valve assembly.

Description:
FIELD 
       [0001]    The present disclosure relates to automotive shock absorbers. More particularly, the present disclosure relates to valve assemblies incorporated into the shock absorber which use two stage valving and/or hydraulically damped valving. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Shock absorbers are used in conjunction with automotive suspension systems and other suspension systems to absorb unwanted vibrations which occur during movement of the suspension system. In order to absorb these unwanted vibrations, automotive shock absorbers are generally connected between the sprung (body) and the unsprung (suspension/chassis) masses of the vehicle. 
         [0004]    The most common type of shock absorbers for automobiles is the dashpot type which can be either a mono-tube design or a dual-tube design. In the mono-tube design, a piston is located within a pressure tube and is connected to the sprung mass of the vehicle through a piston rod. The pressure tube is connected to the unsprung mass of the vehicle. The piston divides the pressure tube into an upper working chamber and a lower working chamber. The piston includes compression valving which limits the flow of damping fluid from the lower working chamber to the upper working chamber during a compression stroke and rebound valving which limits the flow of damping fluid from the upper working chamber to the lower working chamber during a rebound or extension stroke. Because the compression valving and the rebound valving have the ability to limit the flow of damping fluid, the shock absorber is able to produce a damping force which counteracts the vibrations which would otherwise be transmitted from the unsprung mass to the sprung mass. 
         [0005]    In a dual-tube shock absorber, a fluid reservoir is defined between the pressure tube and a reservoir tube which is positioned around the pressure tube. A base valve assembly is located between the lower working chamber and the fluid reservoir to control the flow of dampening fluid. The compression valving of the piston is moved to the base valve assembly and is replaced in the piston by a compression check valve assembly. In addition to the compression valving, the base valve assembly includes a rebound check valve assembly. The compression valving of the base valve assembly produces the damping force during a compression stroke, and the rebound valving of the piston produces the damping force during a rebound or extension stroke. Both the compression and rebound check valve assemblies permit fluid flow in one direction, but prohibit fluid flow in an opposite direction and these valves can be designed such that they generate a damping force also. 
         [0006]    The valve assemblies for the shock absorber have the function of controlling oil flow between two chambers during the stroking of the shock absorber. By controlling the oil flow between the two chambers, a pressure drop is build up between the two chambers and this contributes to the damping forces of the shock absorber. The valve assemblies can be used to tune the damping forces to control ride and handling as well as noise, vibration and harshness. 
       SUMMARY 
       [0007]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0008]    The present disclosure is directed to a shock absorber which includes one or more two stage valve assemblies for the shock absorber. The two stage valve assemblies are designed to combine the performance properties of a sliding valve assembly with the Noise, Vibration and Harshness (NVH) properties of a clamped valve assembly. In addition, the two stage valve of the present disclosure can incorporate hydraulic damping which controls the opening of the valve assembly. 
         [0009]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0010]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0011]      FIG. 1  is a schematic representation of a typical automobile which incorporates the two-stage valving in accordance with the present disclosure; 
           [0012]      FIG. 2  is a side sectional view of the shock absorber in accordance with the present disclosure; 
           [0013]      FIG. 3  is an enlarged cross-sectional view of the piston assembly in accordance with the present disclosure; 
           [0014]      FIG. 4  is an enlarged cross-sectional view of the base valve assembly in accordance with the present disclosure; 
           [0015]      FIG. 5  is an enlarged cross-sectional view of a piston assembly in accordance with another embodiment of the present disclosure; 
           [0016]      FIG. 6  is an enlarged cross-sectional view of a base valve assembly in accordance with the present disclosure; 
           [0017]      FIG. 7  is an enlarged cross-sectional view of a piston assembly in accordance with another embodiment of the present disclosure; 
           [0018]      FIG. 8  is an enlarged cross-sectional view of a base valve assembly in accordance with the present disclosure; 
           [0019]      FIG. 9  is an enlarged cross-sectional view of a piston assembly in accordance with another embodiment of the present disclosure; 
           [0020]      FIG. 10  is an enlarged cross-sectional view of a base valve assembly in accordance with the present disclosure; 
           [0021]      FIG. 11  is an enlarged cross-sectional view of a piston assembly in accordance with another embodiment of the present disclosure; 
           [0022]      FIG. 12  is an enlarged cross-sectional view of a base valve assembly in accordance with the present disclosure. 
       
    
    
     DESCRIPTION 
       [0023]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0024]    Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in  FIG. 1  a vehicle which includes a suspension system incorporating the unique shock absorbers in accordance with the present disclosure and which is designated generally by the reference numeral  10 . Vehicle  10  includes a rear suspension  12 , a front suspension  14  and a body  16 . Rear suspension  12  has a transversely extending rear axle assembly (not shown) adapted to operatively support a pair of rear wheels  18  of vehicle  10 . The rear axle assembly is operatively connected to body  16  by means of a pair of shock absorbers  20  and a pair of helical coil springs  22 . Similarly, front suspension  14  includes a transversely extending front axle assembly (not shown) to operatively support a pair of front wheels  24  of vehicle  10 . The front axle assembly is operatively connected to body  16  by means of a second pair of shock absorbers  26  and by a pair of helical coil springs  28 . Shock absorbers  20  and  26  serve to dampen the relative motion of the unsprung mass (i.e., front and rear suspensions  12  and  14 , respectively) and the sprung mass (i.e., body  16 ) of vehicle  10 . While vehicle  10  has been depicted as a passenger car having front and rear axle assemblies, shock absorbers  20  and  26  may be used with other types of vehicles or in other types of applications such as vehicles incorporating independent front and/or independent rear suspension systems. Further, the term “shock absorber” as used herein is meant to refer to dampers in general and thus will include MacPherson struts. 
         [0025]    Referring now to  FIG. 2 , shock absorber  20  is shown in greater detail. While  FIG. 2  illustrates only shock absorber  20 , it is to be understood that shock absorber  26  also includes the unique valve assembly described below for shock absorber  20 . Shock absorber  26  only differs from shock absorber  20  in the manner in which it is adapted to be connected to the sprung and unsprung masses of vehicle  10 . Shock absorber  20  comprises a pressure tube  30 , a piston assembly  32 , a piston rod assembly  34 , a reservoir tube  36  and a base valve assembly  38 . 
         [0026]    Pressure tube  30  defines a working chamber  42 . Piston assembly  32  is slidably disposed within pressure tube  30  and divides working chamber  42  into an upper working chamber  44  and a lower working chamber  46 . A seal  48  is disposed between piston assembly  32  and pressure tube  30  to permit sliding movement of piston assembly  32  with respect to pressure tube  30  without generating undue frictional forces as well as sealing upper working chamber  44  from lower working chamber  46 . Piston rod assembly  34  is attached to piston assembly  32  and extends through upper working chamber  44  and through an upper end cap  50  which closes the upper end of pressure tube  30 . A sealing system seals the interface between upper end cap  50 , reservoir tube  36  and piston rod assembly  34 . The end of piston rod assembly  34  opposite to piston assembly  32  is adapted to be secured to the sprung portion of vehicle  10 . Valving within piston assembly  32  controls the movement of fluid between upper working chamber  44  and lower working chamber  46  during movement of piston assembly  32  within pressure tube  30 . Because piston rod assembly  34  extends only through upper working chamber  44  and not lower working chamber  46 , movement of piston assembly  32  with respect to pressure tube  30  causes a difference in the amount of fluid displaced in upper working chamber  44  and the amount of fluid displaced in lower working chamber  46 . The difference in the amount of fluid displaced is known as the “rod volume” and it flows through base valve assembly  38 . 
         [0027]    Reservoir tube  36  surrounds pressure tube  30  to define a fluid reservoir chamber  52  located between tubes  30  and  36 . The bottom end of reservoir tube  36  is closed by an end cap  54  which is adapted to be connected to the unsprung portion of vehicle  10 . The upper end of reservoir tube  36  is attached to upper end cap  50 . Base valve assembly  38  is disposed between lower working chamber  46  and reservoir chamber  52  to control the flow of fluid between chambers  46  and  52 . When shock absorber  20  extends in length, an additional volume of fluid is needed in lower working chamber  46  due to the “rod volume” concept. Thus, fluid will flow from reservoir chamber  52  to lower working chamber  46  through base valve assembly  38  as detailed below. When shock absorber  20  compresses in length, an excess of fluid must be removed from lower working chamber  46  due to the “rod volume” concept. Thus, fluid will flow from lower working chamber  46  to reservoir chamber  52  through base valve assembly  38  as detailed below. 
         [0028]    Referring now to  FIG. 3 , piston assembly  32  comprises a piston body  60 , a rebound valve assembly  62  and a compression valve assembly  64 . Compression valve assembly  64  is assembled against a shoulder  66  on piston rod assembly  34 . Piston body  60  is assembled against compression valve assembly  64  and rebound valve assembly  62  is assembled against piston body  60 . A retainer  68  secures these components to piston rod assembly  34 . 
         [0029]    Piston body  60  defines a plurality of rebound passages  70  and a plurality of compression passages  72 . Seal  48  extends around piston body  60  to provide the seal between piston assembly  32  and pressure tube  30 . 
         [0030]    Rebound valve assembly  62  comprises a retainer  78 , a valve disc  80  and a spring  82 . Retainer  78  abuts retainer  68  on one end and piston body  60  on the opposite end. Valve disc  80  abuts piston body  60  and closes rebound passages  70  while leaving compression passages  72  open. Spring  82  is disposed between retainer  78  and valve disc  80  to bias valve disc  80  into engagement with piston body  60 . During a rebound stroke of shock absorber  20  (extension in length), fluid in upper working chamber  44  is pressurized causing fluid pressure in upper working chamber  44  to react against valve disc  80 . When the fluid pressure against valve disc  80  overcomes the biasing load of spring  82 , valve disc  80  separates or disengages from piston body  60  by moving axially on retainer  78  to open rebound passages  70  and allow fluid flow from upper working chamber  44  to lower working chamber  46 . The damping characteristics for shock absorber  20  during a rebound stroke are controlled by the strength of spring  82  and the size of rebound passages  70 . During a compression stroke of shock absorber  20  (reduction in length), rebound passages  70  are closed by valve disc  80 . 
         [0031]    Compression valve assembly  64  comprises a backup washer  84 , a spring  86 , a clamped valve disc  88  and a sliding valve disc  90 . Backup washer  84  abuts or engages piston body  60  and is slidably disposed on piston rod assembly  34 . Backup washer  84  abuts shoulder  66  on piston rod assembly  34 . Retainer  68  secures rebound valve assembly  62 , piston body  60  and compression valve assembly  64  to piston rod assembly  34 . A solid metal connection exists between shoulder  66  on piston rod assembly  34 , backup washer  84 , piston body  60 , retainer  78  and retainer  68 . 
         [0032]    Sliding valve disc  90  is slidingly received on backup washer  84  and abuts or engages piston body  60  to close compression passages  72 . A first plurality of through holes  92  extend completely through sliding valve disc  90  to open rebound passages  70 . A second plurality of through holes  94  extend completely through sliding valve disc  90  to enable fluid communication between compression passages  72  and clamped valve disc  88  as discussed below. Clamped valve disc  88  is slidingly received on backup washer  84  and abuts or engages sliding valve disc  90  to close through holes  94 . Clamped valve disc  88  includes a plurality of through holes  96  which extend completely through clamped valve disc  88  to allow fluid communication from upper working chamber  44 , through through holes  96 , through through holes  92  and into rebound passages  70 . Spring  86  is disposed between backup washer  84  and clamped valve disc  88  to bias clamped valve disc  88  against sliding valve disc  90  and sliding valve disc  90  against piston body  60 . Spring  86  engages the inside diameter of clamped valve disc  88  adjacent backup washer  84  and inside of through holes  92  to clamp clamped valve disc  88  against the inside diameter portion of sliding valve disc  90  to form a fulcrum point for the deflection of clamped valve disc  88 . 
         [0033]    During a compression stroke (reduction in length) of shock absorber  20 , fluid in lower working chamber  46  is pressurized causing fluid pressure to react against clamped valve disc  88  and against sliding valve disc  90 . The increase in fluid pressure will react against clamped valve disc  88  and when this fluid pressure reacting against clamped valve disc  88  overcomes the bending load for clamped valve disc  88 , clamped valve disc  88  elastically deflects at the fulcrum point defined by spring  86  opening through holes  94  allowing fluid flow from lower working chamber  46  to upper working chamber  44  through compression passages  72  and through through holes  94 . Spring  86  clamps the inside diameter of clamped valve disc  88  against sliding valve disc  90  during the deflection of clamped valve disc  88 . The use of clamped valve disc  88  for the initial opening of compression passages  72  provides for a generally better NVH performance because of the gradual opening of compression valve assembly  64 . As fluid pressure in lower working chamber  46  increases, the fluid pressure will react against sliding valve disc  90 . When the fluid pressure reacting against sliding valve disc  90  overcomes the biasing load of spring  86 , sliding valve disc  90  and clamped valve disc  88  will slide axially along backup washer  84  to completely open compression passages  72 . Thus, the present disclosure utilizes the NVH performance characteristics of a clamped valve designs at the initial opening of the valve and also utilizes the performance characteristics of the sliding valve design at higher velocities and increasing pressure drops while eliminating the performance limitations at increasing pressure drops at higher velocities of the clamped valve design and eliminating the NVH issues with the sliding valves which are caused by the sudden opening of the sliding valve design. 
         [0034]    Referring now to  FIG. 4 , base valve assembly  38  comprises a valve body  100 , a compression valve assembly  102  and a rebound valve assembly  104 . Rebound valve assembly  104  and compression valve assembly  102  are attached to valve body  100  using a bolt  106  and a retainer  108 . Valve body  100  defines a plurality of compression passages  110  and a plurality of rebound passages  112 . Compression valve assembly  102  is similar to rebound valve assembly  62  and rebound valve assembly  104  is similar to compression valve assembly  64 . 
         [0035]    Compression valve assembly  102  comprises retainer  108 , a valve disc  114  and a spring  116 . Retainer  108  abuts valve body  100 . Valve disc  114  abuts valve body  100  and closes compression passages  110  while leaving rebound passages  112  open. Spring  116  is disposed between retainer  108  and valve disc  114  to bias valve disc  114  into engagement with valve body  100 . During a compression stroke of shock absorber  20 , fluid in lower working chamber  46  is increased in pressure causing fluid pressure in lower working chamber  46  to react against valve disc  114 . When the fluid pressure against valve disc  114  overcomes the biasing load of spring  116 , valve disc  114  separates or disengages from valve body  100  by moving axially on retainer  108  to open compression passages  110  and allow fluid flow from lower working chamber  46  to reservoir chamber  52 . The damping characteristics for shock absorber  20  during a compression stroke are controlled by the strength of spring  116  and the size of compression passages  110 . During a rebound stroke of shock absorber  20  (extension in length), compression passages  110  are closed by valve disc  114 . 
         [0036]    Rebound valve assembly  104  comprises a backup washer  124 , a spring  126 , a clamped valve disc  128  and a sliding valve disc  130 . Backup washer  124  abuts or engages valve body  100  and is slidably disposed on bolt  106 . Retainer  108  is illustrated as a nut which threadingly engages bolt  106  and retainer  108  abuts or engages valve body  100 . Retainer  108  secures compression valve assembly  102 , valve body  100  and rebound valve assembly  104 . A solid metal connection exists between, retainer  108 , valve body  100 , backup washer  124  and bolt  106 . 
         [0037]    Sliding valve disc  130  is slidingly received on backup washer  124  and abuts or engages valve body  100  to close rebound passages  112 . A first plurality of through holes  132  extend completely through sliding valve disc  130  to open compression passages  110 . A second plurality of through holes  134  extend completely through sliding valve disc  130  to enable fluid communication between rebound passages  112  and clamped valve disc  128  as discussed below. Clamped valve disc  128  is slidingly received on backup washer  124  and abuts or engages sliding valve disc  130  to close through holes  134 . Clamped valve disc  128  includes a plurality of through holes  136  which extend completely through clamped valve disc  128  to allow fluid communication from lower working chamber  46 , through through holes  136 , through through holes  132  and into compression passages  110 . Spring  126  is disposed between backup washer  124  and clamped valve disc  128  to bias clamped valve disc  128  against sliding valve disc  130  and sliding valve disc  130  against valve body  100 . Spring  126  engages the inside diameter of clamped valve disc  128  adjacent backup washer  124  and inside of through holes  132  to clamp clamped valve disc  128  against the inside diameter portion of sliding valve disc  130  to form a fulcrum point for the deflection of clamped valve disc  128 . 
         [0038]    During a rebound stroke (extension in length) of shock absorber  20 , fluid in lower working chamber  46  is reduced in pressure causing fluid pressure from the fluid in reservoir chamber  52  to react against clamped valve disc  128  and against sliding valve disc  130 . The increase in fluid pressure will react against clamped valve disc  128  and when this fluid pressure reacting against clamped valve disc  128  overcomes the bending load for clamped valve disc  128 , clamped valve disc  128  elastically deflects at the fulcrum point defined by spring  126  opening through holes  134  allowing fluid flow from reservoir chamber  52  to lower working chamber  46  through rebound passages  112  and through through holes  134 . Spring  126  clamps the inside diameter of clamped valve disc  128  against sliding valve disc  130  during the deflection of clamped valve disc  128 . The use of clamped valve disc  128  for the initial opening of rebound passages  112  provides for a generally better NVH performance because of the gradual opening of rebound valve assembly  104 . As fluid pressure in lower working chamber  46  continues to decrease, the fluid pressure from the fluid in reservoir chamber  52  will react against sliding valve disc  130 . When the fluid pressure reacting against sliding valve disc  130  overcomes the biasing load of spring  126 , sliding valve disc  130  and clamped valve disc  128  will slide axially along backup washer  124  to completely open rebound passages  112 . Thus, the present disclosure utilizes the NVH performance characteristics of a clamped valve designs at the initial opening of the valve and also utilizes the performance characteristics of the sliding valve design at higher velocities and increasing pressure drops while eliminating the performance limitations at increasing pressure drops at higher velocities of the clamped valve design and eliminating the NVH issues with the sliding valves which are caused by the sudden opening of the sliding valve design. 
         [0039]    Referring now to  FIGS. 5-6 , a portion of a shock absorber  420  in accordance with another embodiment of the present disclosure is illustrated. Shock absorber  420  can be a replacement for shock absorber  20  and/or shock absorber  26 . Shock absorber  420  is the same as shock absorber  20  except that compression valve assembly  64  of piston assembly  32  has been replaced by compression valve assembly  424  and rebound valve assembly  104  of base valve assembly  38  has been replaced with rebound valve assembly  426 . 
         [0040]    A piston assembly  432  comprises piston body  60 , rebound valve assembly  62  and compression valve assembly  424 . Rebound valve assembly  62  is assembled against retainer  68  on piston rod assembly  34 . Piston body  60  is assembled against rebound valve assembly  62  and compression valve assembly  424  is assembled against piston body  60  and shoulder  66 . Retainer  68  secures these components to piston rod assembly  34 . 
         [0041]    Rebound valve assembly  62  is detailed above and therefore will not be repeated here. Compression valve assembly  424  comprises backup washer  84 , a sliding valve disc  434 , a plurality of transfer discs  436  and one or more preload discs  438 . Backup washer  84  abuts or engages piston body  60  and shoulder  66  and is slidably disposed on piston rod assembly  34 . Retainer  68  is illustrated as a nut which threadingly engages piston rod assembly  34 . Retainer  68  secures rebound valve assembly  62 , piston body  60  and compression valve assembly  424  to piston rod assembly  34 . A solid metal connection exists between shoulder  66  on piston rod assembly  34 , backup washer  84 , piston body  60 , retainer  78  and retainer  68 . 
         [0042]    Sliding valve disc  434  is slidingly received on backup washer  84  and abuts or engages piston body  60  to close compression passages  72 . A plurality of through holes  440  extend completely through sliding valve disc  434  to open rebound passages  70 . The plurality of transfer discs  436  abut or engage sliding valve disc  434  and the one or more preload discs  438  abut and engage both the plurality of transfer discs  436  at their inside diameter and a projection  442  formed on backup washer  84 . The one or more preload discs  438  are flexed toward sliding valve disc  434  at their outside diameter to provide a preload for sliding valve disc  434  at the inside diameter of sliding valve disc  434 . This preload extends through the plurality of transfer discs  436  to sliding valve disc  434 . Backup washer  84  and the one or more preload discs  438  define a damping chamber  444  which operates to dampen the opening of sliding valve disc  434  as discussed below. The preload disc  438  which directly abuts projection  442  defines a controlled always open orifice  446  which allows fluid flow between damping chamber  444  and upper working chamber  44 . 
         [0043]    During a compression (reduction in length) of shock absorber  420 , fluid in lower working chamber  46  is pressurized causing fluid pressure to react against sliding valve disc  434 . The increase in fluid pressure will react against sliding valve disc  434  and when this fluid pressure reacting against sliding valve disc  434  overcomes the biasing load provided by the plurality of preload discs  438 , sliding valve disc  434  and the plurality of transfer discs  436  will slide axially along backup washer  84  to completely open compression passages  72 . The axial movement of sliding valve disc  434  and the plurality of transfer discs  436  will be damped by damping chamber  444  because the volume of damping chamber  444  will be reduced by the axial movement of sliding valve disc  434 , the plurality of transfer discs  436  and the subsequent movement of the inner diameter of the plurality of preload discs  438 . This volume reduction forces the fluid in damping chamber  444  to flow through controlled orifice  446 . This flow creates a pressure drop over controlled orifice  446  and this pressure drop creates a controlled, counteracting force on the movement of sliding valve disc  434  to dampen the axial movement. The amount of damping can be controlled by the area of the controlled orifice  446  and the area that covers damping chamber  444 . The stiffness of compression valve assembly  424  can be controlled by the thickness and number of the plurality of preload discs  438 . The preload on sliding valve disc  434  can be controlled by the thickness of the plurality of transfer discs  436  and the design for the plurality of preload discs  438 . 
         [0044]    Referring to  FIG. 6 , the lower portion of shock absorber  420  is illustrated and it includes a base valve assembly  450  which comprises valve body  100 , compression valve assembly  102  and rebound valve assembly  426 . Rebound valve assembly  426  is similar to compression valve assembly  424 . Rebound valve assembly  426  and compression valve assembly  102  are attached to valve body  100  using bolt  106  and retainer  108 . Valve body  100  defines the plurality of compression passages  110  and the plurality of rebound passages  112 . 
         [0045]    Compression valve assembly  102  is described above and the description will not be repeated here. Rebound valve assembly  426  comprises backup washer  124 , a sliding valve disc  454 , a plurality of transfer discs  456  and one or more preload discs  458 . Backup washer  124  abuts or engages valve body  100  and is slidably disposed on bolt  106 . Retainer  108  is illustrated as a nut which threadingly engages bolt  106 . Retainer  108  secures compression valve assembly  102 , valve body  100  and rebound valve assembly  426  to bolt  106 . A solid metal connection exists between retainer  108 , valve body  100 , backup washer  124  and bolt  106 . 
         [0046]    Sliding valve disc  454  is slidingly received on backup washer  124  and abuts or engages valve body  100  to close rebound passages  112 . A plurality of through holes  460  extend completely through sliding valve disc  454  to open compression passages  110 . The plurality of transfer discs  456  abut or engage sliding valve disc  454  and the one or more preload discs  458  abut and engage both the plurality of transfer discs  456  at their inside diameter and a projection  462  formed on backup washer  124 . The one or more preload discs  458  are flexed toward sliding valve disc  454  at their outside diameter to provide a preload for sliding valve disc  454  at the inside diameter of sliding valve disc  454 . This preload extends through the plurality of transfer discs  456  to sliding valve disc  454 . Backup washer  124  and the one or more preload discs  458  define a damping chamber  464  which operates to dampen the opening of sliding valve disc  454  as discussed below. The preload disc  458  which directly abuts projection  462  defines a controlled always open orifice  466  which allows fluid flow between damping chamber  464  and lower working chamber  46 . 
         [0047]    During a rebound stroke (extension in length) of shock absorber  420 , fluid in lower working chamber  46  is reduced in pressure causing fluid pressure from reservoir chamber  52  to react against sliding valve disc  454 . The increase in fluid pressure will react against sliding valve disc  454  and when this fluid pressure reacting against sliding valve disc  454  overcomes the biasing load provided by the plurality of preload discs  458 , sliding valve disc  454  and the plurality of transfer discs  456  will slide axially along backup washer  124  to completely open rebound passages  112 . The axial movement of sliding valve disc  454  and the plurality of transfer discs  456  will be damped by damping chamber  464  because the volume of damping chamber  464  will be reduced by the axial movement of sliding valve disc  454 , the plurality of transfer discs  456  and the subsequent movement of the inner diameter of the plurality of preload discs  458 . This volume reduction forces the fluid in damping chamber  464  to flow through controlled orifice  466 . This flow creates a pressure drop over controlled orifice  466  and this pressure drop creates a controlled, counteracting force on the movement of sliding valve disc  454  to dampen the axial movement. The amount of damping can be controlled by the area of the controlled orifice  466  and the area that covers damping chamber  464 . The stiffness of rebound valve assembly  426  can be controlled by the thickness and number of the plurality of preload discs  458 . The preload on sliding valve disc  454  can be controlled by the thickness of the plurality of transfer discs  456  and the design for the plurality of preload discs  458 . 
         [0048]    Referring now to  FIGS. 7-8 , a portion of a shock absorber  520  in accordance with another embodiment of the present disclosure is illustrated. Shock absorber  520  can be a replacement for shock absorber  20  and/or shock absorber  26 . Shock absorber  520  is the same as shock absorber  20  except that compression valve assembly  64  of piston assembly  32  has been replaced by compression valve assembly  524  and rebound valve assembly  104  of base valve assembly  38  has been replaced with rebound valve assembly  526 . 
         [0049]    A piston assembly  532  comprises piston body  60 , rebound valve assembly  62  and compression valve assembly  524 . Rebound valve assembly  62  is assembled against retainer  68  on piston rod assembly  34 . Piston body  60  is assembled against rebound valve assembly  62  and compression valve assembly  524  is assembled against piston body  60  and shoulder  66 . Retainer  68  secures these components to piston rod assembly  34 . 
         [0050]    Rebound valve assembly  62  is detailed above and therefore will not be repeated here. Compression valve assembly  524  comprises backup washer  84 , a clamped valve disc  534 , a sliding valve disc  536 , the plurality of transfer discs  436  and the one or more preload discs  438 . Backup washer  84  abuts or engages piston body  60  and shoulder  66  and is slidably disposed on piston rod assembly  34 . Retainer  68  is illustrated as a nut which threadingly engages piston rod assembly  34 . Retainer  68  secures rebound valve assembly  62 , piston body  60  and compression valve assembly  524  to piston rod assembly  34 . A solid metal connection exists between shoulder  66  on piston rod assembly  34 , backup washer  84 , piston body  60 , retainer  78  and retainer  68 . 
         [0051]    Sliding valve disc  536  is slidingly received on backup washer  84  and abuts or engages piston body  60  to close compression passages  72 . A first plurality of through holes  542  extend completely through sliding valve disc  536  to open rebound passages  70 . A second plurality of through holes  544  extend completely through sliding valve disc  536  to enable fluid communication between compression passages  72  and clamped valve disc  534 . Clamped valve disc  534  is slidingly received on backup washer  84  and abuts or engages sliding valve disc  536  to close through holes  544 . Clamped valve disc  534  includes a plurality of through holes  546  which extend completely through clamped valve disc  534  to allow fluid communication from upper working chamber  44 , through through holes  546 , through through holes  542  and into rebound passages  70 . The plurality of transfer discs  436  abut or engage clamped valve disc  534  and the one or more preload discs  438  abut and engage both the plurality of transfer discs  436  at their inside diameter and projection  442  formed on backup washer  84 . The one or more preload discs  438  are flexed toward clamped valve disc  534  at their outside diameter to provide a preload for clamped valve disc  534  at the inside diameter of clamped valve disc  534  to form a fulcrum point for the deflection of clamped valve disc  534 . This preload extends through the plurality of transfer discs  436  and through clamped valve disc  534  to urge sliding valve disc  536  against piston body  60 . Backup washer  84  and the one or more preload discs  438  define damping chamber  444  which operates to dampen the opening of sliding valve disc  536  as discussed below. The preload disc  438  which directly abuts projection  442  defines the controlled always open orifice  446  which allows fluid flow between damping chamber  444  and upper working chamber  44 . 
         [0052]    During a compression (reduction in length) of shock absorber  520 , fluid in lower working chamber  46  is pressurized causing fluid pressure to react against clamped valve disc  534  and sliding valve disc  536 . The increase in fluid pressure will react against clamped valve disc  534  and when this fluid pressure reacting against clamped valve disc  534  overcomes the bending load for clamped valve disc  534 , clamped valve disc  534  elastically deflects at the fulcrum point defined by transfer discs  436  opening compression passages  72  allowing fluid flow from lower working chamber  46  to upper working chamber  44  through compression passages  72 . The plurality of preload discs  438  operating through transfer discs  436  clamp the inside diameter of clamped valve disc  534  against sliding valve disc  536  and sliding valve disc  536  against piston body  60 . The initial use of clamped valve disc  534  for the initial opening of compression passages  72  provides for a generally better NVH performance because of the gradual opening of compression valve assembly  524 . As fluid pressure in lower working chamber  46  increases, the fluid pressure reacting against sliding valve disc  536  increases. When the fluid pressure reacting against sliding valve disc  536  overcomes the biasing load provided by the plurality of preload discs  438 , sliding valve disc  536 , clamped valve disc  534  and the plurality of transfer discs  436  will slide axially along backup washer  84  to completely open compression passages  72 . The axial movement of sliding valve disc  536 , clamped valve disc  534  and the plurality of transfer discs  436  will be damped by damping chamber  444  because the volume of damping chamber  444  will be reduced by the axial movement of sliding valve disc  536 , clamped valve disc  534 , the plurality of transfer discs  436  and the subsequent movement of the inner diameter of the plurality of preload discs  438 . This volume reduction forces the fluid in damping chamber  444  to flow through controlled orifice  446 . This flow creates a pressure drop over controlled orifice  446  and this pressure drop creates a controlled, counteracting force on the movement of sliding valve disc  536  to dampen the axial movement. The amount of damping can be controlled by the area of the controlled orifice  446  and the area that covers damping chamber  444 . The stiffness of compression valve assembly  524  can be controlled by the thickness and number of the plurality of preload discs  438 . The preload on clamped valve disc  534  can be controlled by the thickness of the plurality of transfer discs  436  and the design for the plurality of preload discs  438 . 
         [0053]    Thus, the present disclosure utilizes the NVH performance characteristics of a clamped valve designs at the initial opening of the valve and also utilizes the performance characteristics of the sliding valve design at higher velocities and increasing pressure drops while eliminating the performance limitations at increasing pressure drops at higher velocities of the clamped valve design and eliminating the NVH issues with the sliding valves which are caused by the sudden opening of the sliding valve design. 
         [0054]    Referring to  FIG. 8 , the lower portion of shock absorber  520  is illustrated and it includes a base valve assembly  550  which comprises valve body  100 , compression valve assembly  102  and rebound valve assembly  526 . Rebound valve assembly  526  and compression valve assembly  102  are attached to valve body  100  using bolt  106  and retainer  108 . Valve body  100  defines the plurality of compression passages  110  and the plurality of rebound passages  112 . 
         [0055]    Compression valve assembly  102  is described above and the description will not be repeated here. Rebound valve assembly  526  comprises backup washer  124 , a clamped valve disc  554 , a sliding valve disc  556 , the plurality of transfer discs  456  and one or more preload discs  458 . Backup washer  124  abuts or engages valve body  100  and is slidably disposed on bolt  106 . Retainer  108  is illustrated as a nut which threadingly engages bolt  106 . Retainer  108  secures compression valve assembly  102 , valve body  100  and rebound valve assembly  526  to bolt  106 . A solid metal connection exists between retainer  108 , valve body  100 , backup washer  124  and bolt  106 . 
         [0056]    Sliding valve disc  556  is slidingly received on backup washer  124  and abuts or engages valve body  100  to close rebound passages  112 . A first plurality of through holes  562  extend completely through sliding valve disc  556  to open compression passages  110 . A second plurality of through holes  564  extend completely through sliding valve disc  556  to enable fluid communication between rebound passages  112  and clamped valve disc  554 . Clamped valve disc  554  is slidingly received on backup washer  84  and abuts or engages sliding valve disc  556  to close through holes  564 . Clamped valve disc  554  includes a plurality of through holes  566  which extend completely through clamped valve disc  554  to allow fluid communication from lower working chamber  46 , through through holes  566 , through through holes  562  and into compression passages  110 . The plurality of transfer discs  456  abut or engage clamped valve disc  554  and the one or more preload discs  458  abut and engage both the plurality of transfer discs  456  at their inside diameter and a projection  568  formed on backup washer  124 . The one or more preload discs  458  are flexed toward clamped valve disc  554  at their outside diameter to provide a preload for clamped valve disc  554  at the inside diameter of clamped valve disc  554  to form a fulcrum point for the deflection of clamped valve disc  554 . This preload extends through the plurality of transfer discs  456  and clamped valve disc  554  to bias sliding valve disc  556  against valve body  100 . Backup washer  124  and the one or more preload discs  458  define damping chamber  464  which operates to dampen the opening of sliding valve disc  556  as discussed below. The preload disc  458  which directly abuts projection  462  defines controlled always open orifice  466  which allows fluid flow between damping chamber  464  and lower working chamber  46 . 
         [0057]    During a rebound (extension in length) of shock absorber  20 , fluid in lower working chamber  46  reduces in pressure causing fluid pressure from reservoir chamber  52  to react against clamped valve disc  554  and sliding valve disc  556 . The increase in fluid pressure will react against clamped valve disc  554  and when this fluid pressure reacting against clamped valve disc  554  overcomes the bending load for clamped valve disc  554 , clamped valve disc  554  elastically deflects at the fulcrum point defined by transfer discs  456  opening rebound passages  112  allowing fluid flow from reservoir chamber  52  to lower working chamber  46  through rebound passages  112 . The plurality of preload discs  458  operating through transfer discs  456  clamp the inside diameter of clamped valve disc  554  against sliding valve disc  556  and sliding valve disc  556  against valve body  100 . The initial use of clamped valve disc  554  for the initial opening of rebound passages  112  provides for a generally better NVH performance because of the gradual opening of rebound valve assembly  526 . As fluid pressure in lower working chamber  46  continues to decrease the fluid pressure from the fluid in reservoir chamber  52  reacting against sliding valve disc  556  increases. When the fluid pressure reacting against sliding valve disc  556  overcome the biasing load provided by the plurality of preload discs  458 , sliding valve disc  556 , clamped valve disc  554  and the plurality of transfer discs  456  will slide axially along backup washer  124  to completely open rebound passages  112 . The axial movement of sliding valve disc  556 , clamped valve disc  554  and the plurality of transfer discs  456  will be damped by damping chamber  464  because the volume of damping chamber  464  will be reduced by the axial movement of sliding valve disc  556 , clamped valve disc  554 , the plurality of transfer discs  456  and the subsequent movement of the inner diameter of the plurality of preload discs  458 . This volume reduction forces the fluid in damping chamber  464  to flow through controlled orifice  466 . This flow creates a pressure drop over controlled orifice  466  and this pressure drop creates a controlled, counteracting force on the movement of sliding valve disc  556  to dampen the axial movement. The amount of damping can be controlled by the area of the controlled orifice  466  and the area that covers damping chamber  464 . The stiffness of rebound valve assembly  526  can be controlled by the thickness and number of the plurality of preload discs  458 . The preload on sliding valve disc  556  can be controlled by the thickness of the plurality of transfer discs  456  and the design for the plurality of preload discs  458 . 
         [0058]    Thus, the present disclosure utilizes the NVH performance characteristics of a clamped valve designs at the initial opening of the valve and also utilizes the performance characteristics of the sliding valve design at higher velocities and increasing pressure drops while eliminating the performance limitations at increasing pressure drops at higher velocities of the clamped valve design and eliminating the NVH issues with the sliding valves which are caused by the sudden opening of the sliding valve design. 
         [0059]    Referring now to  FIGS. 9-10 , a portion of a shock absorber  620  in accordance with another embodiment of the present disclosure is illustrated. Shock absorber  620  can be a replacement for shock absorber  20  and/or shock absorber  26 . Shock absorber  620  is the same as shock absorber  20  except that compression valve assembly  64  of piston assembly  32  has been replaced by compression valve assembly  624  and rebound valve assembly  104  of base valve assembly  38  has been replaced with rebound valve assembly  626 . 
         [0060]    Referring now to  FIG. 9 , a piston assembly  632  comprises piston body  60 , rebound valve assembly  62  and compression valve assembly  624 . Rebound valve assembly  62  is assembled against retainer  68  on piston rod assembly  34 . Piston body  60  is assembled against rebound valve assembly  62  and compression valve assembly  624  is assembled against piston body  60  and shoulder  66 . Retainer  68  secures these components to piston rod assembly  34 . 
         [0061]    Piston body  60  defines the plurality of rebound passages  70  and the plurality of compression passages  72 . Seal  48  extends around piston body  60  to provide the seal between piston assembly  632  and pressure tube  30 . 
         [0062]    Rebound valve assembly  62  is described above and the description will not be repeated here. Compression valve assembly  624  comprises a backup washer  634 , a spring  636 , a first sliding valve disc  638  and a second sliding valve disc  640 . Backup washer  634  abuts or engages piston body  60  and shoulder  66  and is slidably disposed on piston rod assembly  34 . Retainer  68  is illustrated as a nut which threadingly engages piston rod assembly  34 . Retainer  68  secures rebound valve assembly  62 , piston body  60  and compression valve assembly  624  to piston rod assembly  34 . A solid metal connection exists between shoulder  66  on piston rod assembly  34 , backup washer  634 , piston body  60 , retainer  78  and retainer  68 . 
         [0063]    First sliding valve disc  638  is slidingly received on backup washer  634  and abuts or engages piston body  60  to close compression passages  72 . A first plurality of through holes  642  extend completely through first sliding valve disc  638  to open rebound passages  70 . A second plurality of through holes  644  extend completely through first sliding valve disc  638  to enable fluid communication between compression passages  72  and second sliding valve disc  640  as discussed below. Second sliding valve disc  640  is slidingly received on first sliding valve disc  638  and abuts or engages first sliding valve disc  638  to close through holes  644 . Spring  636  is disposed between backup washer  634  and first sliding valve disc  638  to bias first sliding valve disc  638  against piston body  60 . 
         [0064]    During a compression stroke (reduction in length) of shock absorber  620 , fluid in lower working chamber  46  is pressurized causing fluid pressure to react against second sliding valve disc  640  and against first sliding valve disc  638 . The increase in fluid pressure will react against second sliding valve disc  640  and when this fluid pressure reacting against second sliding valve disc  640  overcomes the weight or load for second sliding valve disc  640 , second sliding valve disc  640  moves axially opening through holes  644  allowing fluid flow from lower working chamber  46  to upper working chamber  44  through compression passages  72 . In order to adjust the opening of second sliding valve disc  640 , a biasing member  646  can be disposed between second sliding valve disc  640  and first sliding valve disc  638  as illustrated in dashed lines in  FIG. 11 . The use of low pressure second sliding valve disc  640  for the initial opening of compression passages  72  provides for a generally better NVH performance because of the gradual opening of compression valve assembly  624 . As fluid pressure in lower working chamber  46  increases, the fluid pressure will react against first sliding valve disc  638 . When the fluid pressure reacting against first sliding valve disc  638  overcomes the biasing load of spring  636 , first sliding valve disc  638  and second sliding valve disc  640  will slide axially along backup washer  84  to completely open compression passages  72 . Thus, the present disclosure utilizes the NVH performance characteristics of the second sliding valve design at the initial opening of the valve and also utilizes the performance characteristics of the first sliding valve design at higher velocities and increasing pressure drops while eliminating the performance limitations at increasing pressure drops at higher velocities of the clamped valve design and eliminating the NVH issues with the single sliding valves which are caused by the sudden opening of the single sliding valve design. 
         [0065]    Referring now to  FIG. 10 , the lower portion of shock absorber  620  is illustrated and it includes base valve assembly  648  which comprises valve body  100 , compression valve assembly  102  and rebound valve assembly  626 . Rebound valve assembly  626  and compression valve assembly  102  are attached to valve body  100  using bolt  106  and retainer  108 . Valve body  100  defines the plurality of compression passages  110  and the plurality of rebound passages  112 . 
         [0066]    Compression valve assembly  102  is described above and the description will not be repeated here. Rebound valve assembly  626  comprises a backup washer  654 , a spring  656 , a first sliding valve disc  658  and a second sliding valve disc  660 . Backup washer  654  abuts or engages valve body  100  and is slidably disposed on bolt  106 . Retainer  108  is illustrated as a nut which threadingly engages bolt  106 . Retainer  108  secures compression valve assembly  102 , valve body  100  and rebound valve assembly  626 . A solid metal connection exists between, retainer  108 , valve body  100 , backup washer  654  and bolt  106 . 
         [0067]    First sliding valve disc  658  is slidingly received on backup washer  654  and abuts or engages valve body  100  to close rebound passages  112 . A first plurality of through holes  662  extend completely through first sliding valve disc  658  to open compression passages  110 . A second plurality of through holes  664  extend completely through first sliding valve disc  658  to enable fluid communication between rebound passages  112  and second sliding valve disc  660  as discussed below. Second sliding valve disc  660  is slidingly received on first sliding valve disc  658  and abuts or engages first sliding valve disc  658  to close through holes  664 . Spring  656  is disposed between backup washer  654  and first sliding valve disc  658  to bias first sliding valve disc  658  against valve body  100 . 
         [0068]    During a rebound stroke (increase in length) of shock absorber  620 , fluid in lower working chamber  46  is reduced in pressure causing fluid pressure from the fluid in reservoir chamber  52  to react against first sliding valve disc  658  and against second sliding valve disc  660 . The increase in fluid pressure will react against second sliding valve disc  660  and when this fluid pressure from the fluid in reservoir chamber  52  reacting against second sliding valve disc  660  overcomes the weight or load for second sliding valve disc  660 , second sliding valve disc  660  moves axially opening through holes  664  allowing fluid flow from reservoir chamber  52  to lower working chamber  46  through rebound passages  112 . In order to adjust the opening of second sliding valve disc  660 , a biasing member  666  can be disposed between first sliding valve disc  658  and second sliding valve disc  660  as illustrated in dashed lines in  FIG. 12 . The use of low pressure second sliding valve disc  660  for the initial opening of rebound passages  112  provides for a generally better NVH performance because of the gradual opening of rebound valve assembly  104 . As fluid pressure in lower working chamber  46  continues to decrease, the fluid pressure from the fluid in reservoir chamber  52  will react against first sliding valve disc  658 . When the fluid pressure reacting against first sliding valve disc  658  overcomes the biasing load of spring  656 , first sliding valve disc  658  and second sliding valve disc  660  will slide axially along backup washer  654  to completely open rebound passages  112 . Thus, the present disclosure utilizes the NVH performance characteristics of the second sliding valve design at the initial opening of the valve and also utilizes the performance characteristics of the first sliding valve design at higher velocities and increasing pressure drops while eliminating the performance limitations at increasing pressure drops at higher velocities of the clamped valve design and eliminating the NVH issues with the single sliding valves which are caused by the sudden opening of the single sliding valve design. 
         [0069]    Referring now to  FIGS. 11-12 , a portion of a shock absorber  720  in accordance with another embodiment of the present disclosure is illustrated. Shock absorber  720  can be a replacement for shock absorber  20  and/or shock absorber  26 . Shock absorber  720  is the same as shock absorber  20  except that compression valve assembly  64  of piston assembly  32  has been replaced by compression valve assembly  724  and rebound valve assembly  104  of base valve assembly  38  has been replaced with rebound valve assembly  726 . 
         [0070]    A piston assembly  732  comprises piston body  60 , rebound valve assembly  62  and compression valve assembly  724 . Rebound valve assembly  62  is assembled against retainer  68  on piston rod assembly  34 . Piston body  60  is assembled against rebound valve assembly  62  and compression valve assembly  724  is assembled against piston body  60  and shoulder  66 . Retainer  68  secures these components to piston rod assembly  34 . 
         [0071]    Rebound valve assembly  62  is detailed above and therefore will not be repeated here. Compression valve assembly  724  comprises a backup washer  734 , a sliding valve disc  736  and a spring  738 . Backup washer  734  abuts or engages piston body  60  and shoulder  66  and is slidably disposed on piston rod assembly  34 . Retainer  68  is illustrated as a nut which threadingly engages piston rod assembly  34 . Retainer  68  secures rebound valve assembly  62 , piston body  60  and compression valve assembly  724  to piston rod assembly  34 . A solid metal connection exists between shoulder  66  on piston rod assembly  34 , backup washer  734 , piston body  60 , retainer  78  and retainer  68 . 
         [0072]    Sliding valve disc  736  is slidingly received on backup washer  734  and abuts or engages piston body  60  to close compression passages  72 . A plurality of through holes  740  extend completely through sliding valve disc  736  to open rebound passages  70 . Spring  738  provides a preload for sliding valve disc  736  at the inside diameter of sliding valve disc  736 . Backup washer  734  and sliding valve disc  736  define a damping chamber  744  which operates to dampen the opening of sliding valve disc  736  as discussed below. A controlled always open orifice  746  which allows fluid flow between damping chamber  744  and upper working chamber  44  extends through sliding valve disc  736 . 
         [0073]    During a compression (reduction in length) of shock absorber  720 , fluid in lower working chamber  46  is pressurized causing fluid pressure to react against sliding valve disc  736 . The increase in fluid pressure will react against sliding valve disc  736  and when this fluid pressure reacting against sliding valve disc  736  overcomes the biasing load provided by spring  738 , sliding valve disc  736  will slide axially along backup washer  734  to completely open compression passages  72 . The axial movement of sliding valve disc  736  will be damped by damping chamber  744  because the volume of damping chamber  744  will be reduced by the axial movement of sliding valve disc  736 . This volume reduction forces the fluid in damping chamber  744  to flow through controlled orifice  746 . This flow creates a pressure drop over controlled orifice  746  and this pressure drop creates a controlled, counteracting force on the movement of sliding valve disc  736  to dampen the axial movement. The amount of damping can be controlled by the area and/or number of the controlled orifice  746  and the area that covers damping chamber  744 . The stiffness of compression valve assembly  724  can be controlled by the design of spring  738 . The preload on sliding valve disc  736  can also be controlled by the design of spring  738 . 
         [0074]    Referring to  FIG. 12 , the lower portion of shock absorber  720  is illustrated and it includes a base valve assembly  750  which comprises valve body  100 , compression valve assembly  102  and rebound valve assembly  726 . Rebound valve assembly  726  and compression valve assembly  102  are attached to valve body  100  using bolt  106  and retainer  108 . Valve body  100  defines the plurality of compression passages  110  and the plurality of rebound passages  112 . 
         [0075]    Compression valve assembly  102  is described above and the description will not be repeated here. Rebound valve assembly  726  comprises a backup washer  754 , a sliding valve disc  756  and a spring  758 . Backup washer  754  abuts or engages valve body  100  and is slidably disposed on bolt  106 . Retainer  108  is illustrated as a nut which threadingly engages bolt  106 . Retainer  108  secures compression valve assembly  102 , valve body  100  and rebound valve assembly  726  to bolt  106 . A solid metal connection exists between retainer  108 , valve body  100 , backup washer  754  and bolt  106 . 
         [0076]    Sliding valve disc  756  is slidingly received on backup washer  754  and abuts or engages valve body  100  to close rebound passages  112 . A plurality of through holes  760  extend completely through sliding valve disc  756  to open compression passages  110 . Spring  758  provides a preload for sliding valve disc  756  at the inside diameter of sliding valve disc  756 . Backup washer  754  and sliding valve disc  756  define a damping chamber  764  which operates to dampen the opening of sliding valve disc  756  as discussed below. Sliding valve disc  756  defines a controlled always open orifice  766  which allows fluid flow between damping chamber  764  and reservoir chamber  52 . 
         [0077]    During a rebound (increase in length) of shock absorber  720 , fluid in lower working chamber  46  is reduced in pressure causing fluid pressure from the fluid in reservoir chamber  52  to react against sliding valve disc  756 . The increase in fluid pressure will react against sliding valve disc  756  and when this fluid pressure reacting against sliding valve disc  756  overcomes biasing load provided by spring  758 , sliding valve disc  756  will slide axially along backup washer  754  to completely open rebound passages  112 . The axial movement of sliding valve disc  756  will be damped by damping chamber  764  because the volume of damping chamber  764  will be reduced by the axial movement of sliding valve disc  756 . This volume reduction forces the fluid in damping chamber  764  to flow through controlled orifice  766 . This flow creates a pressure drop over controlled orifice  766  and this pressure drop creates a controlled, counteracting force on the movement of sliding valve disc  756  to dampen the axial movement. The amount of damping can be controlled by the area and/or number of controlled orifice  766  and the area that covers damping chamber  764 . The stiffness of rebound valve assembly  426  can be controlled by the design of spring  758 . The preload on sliding valve disc  756  can be controlled by the design for spring  758 . 
         [0078]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.