CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and claims priority to the U.S. Provisional Patent Application No. 62/185,157 filed on Jun. 26, 2015, entitled “DUAL PISTON SYSTEM” by Bryan Wesley Anderson, assigned to the assignee of the present application, having Attorney Docket No. FOX-P3-24-15-US.PRO, and is hereby incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    The invention relates generally to vehicle suspensions and, more specifically, to a vehicle suspension having multiple flow pathways that are independently adjustable with regard to high speed compression and rebound and low speed compression and rebound. 
       BACKGROUND 
       [0003]    Vehicle suspension systems typically include some form of a shock absorber. Many integrated damper/spring shock absorbers include a damper body surrounded by a mechanical spring. The damper body often consists of a vented piston and a shaft telescopically mounted in a fluid cylinder. Some shock absorbers utilize gas as a spring medium in place of, or in addition to, a mechanical spring. The spring rate of such shock absorbers may be adjustable such as by adjusting the preload of a mechanical spring or adjusting the pressure of the gas in the shock absorber. In that way, the shock absorber can be adjusted to accommodate heavier or lighter carried weight, or greater or lesser anticipated impact loads. 
         [0004]    Some shock absorbers also utilize flow paths there through as a way to control the compression and rebound rate of the shock absorber. For example, a shock absorber may have a lever that has three possible compression settings at three different positions: 1) a soft setting; 2) a medium setting; and 3) a firm setting. In the soft setting, the valve(s) through which a flow path is situated is in the open position. As such, fluid flows freely and communicates across the valves, creating for the vehicle rider a feeling of a comfortable plush ride. In the medium setting, the valve(s) is partially open, partially blocking the flow of fluid there through, creating for the vehicle rider a feeling of firmness and support in the damper for pedaling. In the firm setting, the valve(s) is closed and locks out the flow of fluid there through, up to a maximum threshold, creating a very firm setting, which is good for pedaling on the open road, etc. 
         [0005]    One disadvantage with conventional shock absorbers that have a lever with various settings, such as soft, medium and firm settings, is that in order to compensate for component positioning of one element, another is compromised. For example, when a rider goes over a jump and lands, the shock absorber (that is in an open soft setting) experiences compression at a high speed. This event may require a lower force threshold at a higher velocity, while a firm setting for maximum pedaling efficiency will require a high force threshold at a low velocity. If the two settings share the same threshold force, one setting will be compromised. The same is true for compression and rebound circuits. There are instances during a ride in which it is desired that the vehicle shock absorber rebound at a much lower speed than that speed at which the vehicle shock absorber compressed, and visa versa. 
         [0006]    As the foregoing illustrates, what is needed in the art are improved systems and techniques for isolating and independently adjusting the soft, medium and firm settings of a shock absorber while providing the most comfortable ride possible to the vehicle rider. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present technology for a dual piston system, and, together with the description, serve to explain the principles discussed below: 
           [0008]      FIG. 1  is a side elevation view of a bicycle having a front wheel suspension fork and a rear shock, in accordance with an embodiment. 
           [0009]      FIG. 2  is a side elevation view of the suspension fork of  FIG. 1 , which is illustrated as removed from the bicycle. 
           [0010]      FIG. 3A  is a side elevation view of a gas spring shock absorber, in accordance with an embodiment. 
           [0011]      FIG. 3B  is a sectional side elevation view of the gas spring shock absorber of  FIG. 3A , in accordance with an embodiment, thus illustrating the internal components of the gas spring shock absorber. 
           [0012]      FIG. 4A  is an exploded elevation view of the dual piston system  300  of  FIG. 3B , in accordance with an embodiment. 
           [0013]      FIG. 4B  is an exploded elevation view of the dual piston system  300  of  FIG. 3B , in accordance with an embodiment. 
           [0014]      FIG. 4C  is a sectional side elevation view of section B of  FIG. 3B , in accordance with an embodiment. 
           [0015]      FIG. 5  is a sectional side elevation view of section B of  FIG. 3B , in accordance with an embodiment. 
           [0016]      FIG. 6A  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway AA, during low speed rebound flow, in accordance with an embodiment. 
           [0017]      FIG. 6B  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway BB, during high speed rebound flow, in accordance with an embodiment. 
           [0018]      FIG. 7A  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway CC in regard to low speed compression flow, in accordance with an embodiment. 
           [0019]      FIG. 7B  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway DD, in regard to high speed compression fluid flow, in accordance with an embodiment. 
           [0020]      FIG. 8  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway EE, in regard to lockout, in accordance with an embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]      FIG. 1  illustrates an off-road bicycle, or mountain bike  100 , including a frame  112  which is comprised of a main frame portion  108  and a swing arm portion  116 . The swing arm portion  116  is pivotally attached to the main frame portion  108 . The bicycle  100  includes front and rear wheels,  102  and  118 , respectively, connected to the main frame  108 . A seat  110  is connected to the main frame  108  in order to support a rider of the bicycle  100 . 
         [0022]    The front wheel  102  is supported by an embodiment of a suspension fork  104  which, in turn, is secured to the main frame  108  by a handlebar assembly  106 . The rear wheel  118  is connected to the swing arm portion  116  of the frame  112 . A rear shock  114  is positioned between the swing arm  116  and the frame  112  to provide resistance to the pivoting motion of the swing arm  116 . Thus, the illustrated bicycle  100  includes suspension members between the front wheel  102  and the main frame  108  and the rear wheel  118  and the frame  112 , which operate to substantially reduce wheel impact forces from being transmitted to the rider of the bicycle  100 . 
         [0023]      FIG. 2  illustrates the suspension fork  104  detached from the bicycle  100  of  FIG. 1 . The suspension fork  104  includes right and left legs  206  and  216 , respectively, as reference by a person in a riding position on the bicycle  100 . The right leg  206  includes a right upper tube  208  telescopically received in a right lower tube  204 . Similarly, the left leg  216  includes a left upper tube  214  telescopically received in a left lower tube  218 . A crown  210  connects the right upper tube  208  to the left upper tube  214 , thereby connecting the right leg  206  to the left leg  216  of the suspension fork  104 . In addition, the crown  210  supports a steerer tube  212 , which passes through, and is rotatably supported by, the frame  112  of the bicycle  100 . The steerer tube  212  provides a means for connection of the handlebar assembly  106  to the suspension fork  104 , as illustrated in  FIG. 1 . 
         [0024]    Each of the right lower tube  204  and the left lower tube  218  includes a drop out  202  for connecting the front wheel  102  to the fork  104 . An arch  224  connects the right lower tube  204  and the left lower tube  218  to provide strength and minimize the twisting thereof. Preferably, the right lower tube  204 , the left lower tube  218  and the arch  224  are formed as a unitary piece. However, the tubes  204  and  218  and arch  224  may be separate pieces and connected by a suitable fastening method. 
         [0025]    The suspension fork  104  also includes a pair of rim brake bosses  220  to which a standard rim brake may be mounted. In addition, the fork  104  may include a pair of disc brake bosses  222  to which a disc brake may be mounted. Of course, the suspension fork  104  may include only one or the other of the rim brake bosses  220  and disc brake bosses  222 , depending on the type of brake system desired. 
         [0026]    Of note, while embodiments of the present technology described herein are discussed in reference to a rear shock  114  (and more particularly, an integrated damper/spring vehicle shock absorber, such as the gas spring shock absorber shown in  FIGS. 3A and 3B ), it should be appreciated that the suspension fork, such as the suspension fork  104  of  FIG. 1 , may also include the embodiments described herein. Of further note, embodiments may also be included within vehicles other than bicycles, such as, but not limited to, cars, motorcycles, trucks, side-by-sides, etc. 
         [0027]    Further, as used herein and as would be recognized by those skilled in the art, shaft “speed” refers to, for example, the speed of the shock absorber&#39;s shaft when the bicycle and therefore the shaft are subjected to the impact of a compressive force, such as but not limited to a terrain feature. The shock absorber&#39;s shaft may sometimes be referred to as the piston rod by those skilled in the art. For a bicycle shock absorber, the normal operating range for main shaft speeds may be, for example, from 0 inches/second to 100 inches/second or more. Additionally, for clarity, as used herein, “compression forces” are the forces created by the impact of the bicycle with, for example, a terrain feature. “Compression damping forces” are the forces created by the shock absorber to slow the speed at which the shock absorber actually compresses when subjected to the compression force. Compression damping forces are created by the compression damping circuits restricting fluid flow through the fluid passageways. 
         [0028]    In one embodiment, the rear shock, such as the rear shock  114  of  FIG. 1  is an integrated damper/spring vehicle shock absorber. Integrated damper/spring vehicle shock absorbers often include a damper body surrounded by a mechanical spring or constructed in conjunction with an air spring. The damper body often consists of a piston and shaft telescopically mounted in a fluid filled cylinder. The mechanical spring may be a helically wound spring that surrounds the damper body. Various integrated shock absorber configurations are described in U.S. Pat. Nos. 5,044,614, 5,803,443, 5,553,836, and 7,293,764, each of which is herein incorporated, in its entirety, by reference. 
         [0029]    Conventional technology provides that the compression of a shock absorber at a large displacement is followed by the rebound of the shock absorber at a high speed. Similarly, the compression of a shock absorber at a small displacement is conventionally followed by the rebound of the shock absorber at a low speed. Further, conventional technology provides that the high speed fluid flow within the shock absorber is directed through fluid pathways that are positioned toward the inner diameter of the shock absorber, while the low speed fluid flow is directed through fluid pathways that are positioned toward the outer diameter of the shock absorber. 
         [0030]    In contrast to conventional technology, embodiments of the present technology provide for the ability to independently adjust the fluid pathways within the shock absorber such that the high speed compression rate and the high speed rebound rate may be adjusted independent of each other, and the low speed compression rate and the low speed rebound rate may be adjusted independent of each other. 
         [0031]    In one embodiment of the present technology, the threshold fluid flow rate is at least one guiding factor in component placement. While the force threshold needed to activate the lock-out position (firm setting) is higher than the force threshold needed to activate the high-speed compression blow off (soft setting), the fluid flow rate is much lower. For optimal performance, it follows that components requiring a lower flow rate occupy regions of smaller flow area and components of a higher flow rate occupy regions of larger flow area. For example, low speed flow is routed toward the center of the damper tube and high speed flow is routed toward the outside of the damper tube. 
         [0032]    Further, embodiments of the present technology guide the fluid that is experiencing a high fluid flow rate during high speed compression and/or high speed rebound to and along the outer most flow channels disposed within the dual piston valve of the shock absorber, while guiding the fluid that is experiencing a low fluid flow rate during low speed compression and/or low speed rebound to and along the inner most flow channels disposed within the dual piston valve of the shock absorber. This is advantageous at least because the outer diameter of the dual piston valve provides a greater region (and thus the potential for a greater area of fluid flow pathways) for larger amounts of fluid to flow there through, while the inner diameter has less available area for the fluid to flow there through. Additionally, the fluid pathway that accommodates the high speed compression flow is different from that fluid pathway that accommodates the high speed rebound flow. Similarly, the fluid pathway that accommodates the low speed compression flow is different from that fluid pathway that accommodates the low speed rebound flow. Further, the fluid pathway that accommodates the lockout position, according to embodiments, is different from the fluid pathways associated with high speed compression and rebound flows and low speed compression and rebound flows. 
         [0033]    In accordance with embodiments, while the fluid flow paths occupy a combination of different passageways (or channels) throughout the dual piston system, sets of annular shims are strategically disposed within the dual piston system to completely block, partially block, and selectively block (e.g., bending open in response to a force applied thereto by fluid resulting from fluid pressure ultimately caused by compression and/or rebound of the shock absorber) fluid flow through these passageways. Such a design, in combination with two adjustable orifices that also selectively allow a particular amount of fluid there through, provide a system that enables the independent adjustment of low speed compression as compared to low speed rebound and high speed compression as compared to high speed rebound, as well as a fluid flow lockout position. 
         [0034]    The ability to independently adjust and thus customize the fluid flow rates of the compression flow as compared to the rebound flow for the vehicle rider (as well as the lockout fluid flow rate) ultimately provides more efficient compression and rebound damping and a more comfortable, and/or at least a more desirable, ride for the vehicle rider. 
         [0035]    The following discussion focuses upon a general description of the individual components and the order of assembly for these components. The discussion moves forward with a description of the fluid flow paths for low speed rebound flow, high speed rebound flow, low speed compression flow, high speed compression flow and lockout. The particularized structure and design of the individual components involved in these various fluid flow paths will be described in further detail at such time of discussion. 
         [0036]      FIG. 3A  is a side elevation view of a gas spring shock absorber, in accordance with an embodiment. As shown in  FIG. 3A , the gas spring shock absorber  350  includes the gas cylinder  354  and the damping fluid cylinder  356 .  FIG. 3B  is a sectional side elevation view of the gas spring shock absorber  350  of  FIG. 3A , in accordance with an embodiment. The shock absorber  350  in  FIG. 3B  is shown in an extended position and may be mounted to the rear linkage of a vehicle via the eyelet  362 , which may include a bearing (not shown). The shock absorber  350  is an integrated damper/gas spring type shock absorber that includes a damping fluid cylinder  356  telescopically housed within a gas cylinder  354 . A shaft  306  connects a sealed, upper end of the gas cylinder  354  with a dual piston valve  360  movably mounted within the damping fluid cylinder  356 . The upper end of the gas cylinder  354  is sealed via the mounting element  352 . The damping fluid cylinder  356  is coupled to the dual piston valve  360  on a sealed, upper end of the damping fluid cylinder  356  and movably mounted within the gas cylinder  354 . 
         [0037]      FIG. 4A  is an exploded elevation view of the dual piston system  300  of  FIG. 3B , in accordance with an embodiment.  FIG. 4B  is an exploded view of the dual piston system  300  of  FIG. 3B , in accordance with an embodiment.  FIG. 4C  is a sectional side elevation view of section B of  FIG. 3B , in accordance with an embodiment.  FIG. 5  is an enlarged sectional side elevation view of section B of  FIG. 3B , in accordance with an embodiment. 
         [0038]    The following is a list of the components of the dual piston system  300 , as shown in  FIGS. 4A, 4B, and 5 , followed by a description of each&#39;s respective function. While  FIGS. 4A and 4B  show the dual piston system  300  in an exploded view,  FIG. 5  shows the dual piston valve  360  with the components shown in  FIGS. 4A and 4B  as assembled. 
         [0039]    With reference now to  FIGS. 4A and 5 , it is shown that the rebound adjust rod  302  includes taper “C” at one end  404  and the adjuster element  402  at the other end. The rebound adjust rod  302  is hollow and is designed to fit, end  404  first, into the hollow shaft  306 , up until the adjuster element  402 , since the adjuster element  402  is wider than the inner diameter of the shaft  306 . Thus, the adjuster element  402  does not fit within the hollow shaft  306 . A set of holes  444  (one or more holes, hidden) is located at the end  406  of the shaft  306 . The set of holes  444  traverse the wall of the shaft  306  such that fluid may flow between the area external to the surface of the outer wall of the shaft  306  and area internal to the surface of the inner wall of the shaft  306 . 
         [0040]    The rebound check plate  324  is rotatably secured to one end of the shaft  306  via the hollow piston bolt  322 . The hollow piston bolt  322  includes threads on its outer surface, that match the threads disposed on the inner surface of the end  406  of the shaft  306 . The rebound check plate  324  is attached to the piston bolt  322 . In one embodiment, the piston bolt  322  and the rebound check plate  324  are manufactured to be one piece. In another embodiment, the piston bolt  322  and the rebound check plate  324  are manufactured as separate pieces that attach to each other via various methods of attachment known in the art. 
         [0041]    Of note, the end  404  of the rebound adjust rod  302  includes the taper C, which tapers such that the thickest (widest) section of taper C is located closest to the adjuster element  402  and the thinnest (narrowest) section is that part of the rebound adjust rod  302  which is first inserted into the piston bolt  322 . Thus, when the taper C at the end  404  is inserted into the central hole of the piston bolt  322 , depending upon the extent of insertion, either the entirety of the width of the taper C will fill the entirety of the opening of the hole central to the piston bolt  322  or a portion of taper C will fill a portion less than the entirety of the opening of the hole of the piston bolt  322 . Thus, if a portion less than the whole of the entirety of the opening of the hole in the piston bolt  322  is occupied by a portion less than the widest part of the taper C, then a gap  602  (see  FIGS. 6A and 6B ) remains between the inner diameter of the opening of the hole central to the piston bolt  322  and the outer diameter of the taper C. According to embodiments, in some instances and as will be explained herein, fluid may flow through this gap  602 . 
         [0042]    As shown in  FIG. 4A , between (and inclusive) the rebound check plate  324  and the end  406  of the shaft  306 , the following components are shown, and are listed as ready for assembly in the order beginning with those components closest to the adjuster element  402  of the rebound adjust rod  302 : compression check plate  308 ; low speed compression check shims  408 ; pivot shims  410 ; high speed compression shims  412 ; main damping piston  316  (also referred to as first damping piston  316 ); shims  414 ; and small diameter shims  416 . Of note, a certain number of low speed compression check shims  408 , pivot shims  410 , high speed compression shims  412 , shims  414 , and small diameter shims  416  are shown. However, in various embodiments, it should be appreciated that there may be more or less shims than those shown in the figures herein, such as, but not limited to,  FIGS. 4A and 4B . 
         [0043]    The inner surface of the side wall of the main damping piston  316  has threads that match the threads of the outer surface of the side wall of the secondary (lockout) damping piston  332  (also referred to as second damping piston  332 ). Thus, the secondary (lockout) damping piston  332  screws into the main damping piston  316 , having disposed there between the rebound check plate  324 . In between the secondary (lockout) damping piston  332  and the bottom of the rebound check plate  324 , the following components are shown ready for assembly and are listed in the order closest to the end  406  of the shaft  306 : larger diameter shim  418 , pivot shims  420 ; and shims  422 . Of note, a certain number of larger diameter shims  418 , pivot shims  420  and shims  422  are shown. However, in various embodiments, it should be appreciated that there may be more or less shims than those shown in the figures herein, such as, but not limited to,  FIGS. 4A and 4B . 
         [0044]    The compression adjust rod  340  is designed to be inserted into the holes shown central to the following components and inserted in the following order: secondary (lockout) damping piston  332 ; shims  422 ; pivot shims  420 ; larger diameter shim  418 ; rebound check plate  324 ; piston bolt  322 ; small diameter shims  416 ; shims  414 ; main damping piston  316 ; high speed compression shims  412 ; pivot shims  410 ; low speed compression check shims  408 ; compression check plate  308 ; shaft  306 ; and rebound adjust rod  302 . The end  424  of the compression adjust rod  340  includes the taper D, which tapers such that the thickest (widest) section of taper D is located next to the lockout plate/rebound check valve  338  and the thinnest (narrowest) section is closest to the secondary (lockout) damping piston  332 . Thus, when the taper D at the end  424  is inserted into the central hole of the secondary (lockout) damping piston  332 , depending upon the extent of the insertion, either the entirety of the width of the taper D will fill the hole central to the secondary (lockout) damping piston  332  or fill a portion less than the whole of the hole central to the secondary (lockout) damping piston  332 . Thus, if a portion less than the whole of the hole in the secondary (lockout) damping piston  332  is occupied with a portion less than the widest section of the taper D, then a gap  502  (see  FIG. 5  for an indication of location of the gap  502 , should it exist) remains between the inner diameter of the hole central to the secondary (lockout) damping piston  132  and the outer diameter of the taper D. According to embodiments, in some instances and as will be explained herein, fluid may flow through the gap  502 . 
         [0045]      FIG. 4C  shows at least the following components described herein: the lockout plate/rebound check valve  338 ; the secondary (lockout) damping piston  332 ; the rebound check plate  324 ; the piston bolt  322 ; the main damping piston  316 ; the compression check plate  308 ; the compression adjust rod  340 ; the rebound adjust rod  302 ; and the shaft  306 . 
         [0046]    Next will be described the following fluid flow modes and various adjustable fluid flow pathways associated therewith: the low speed rebound flow using fluid flow pathway AA ( FIG. 6A ); the high speed rebound flow using fluid flow pathway BB ( FIG. 6B ); the low speed compression flow using fluid flow pathway CC ( FIG. 7A ); the high speed compression flow using fluid flow pathway DD ( FIG. 7B ); and the lockout using fluid flow pathway EE ( FIG. 8 ). 
         [0047]    When the vehicle traverses small bumps, experiences braking and a rider&#39;s weight redistribution, etc., the shock absorber compresses at a low compression speed, compared to when the vehicle lands from a large jump. Thus, when the vehicle initially reacts to large bumps, landings, etc., the shock absorber compresses at a high compression speed. Generally and conventionally, after the shock absorber compresses at a slow compression speed, it rebounds at a slow rebound speed. Likewise, after the shock absorber compresses at a high compression speed, it rebounds at a high rebound speed. When the shock absorber does not compress or rebound at all, it is in a lockout mode. Embodiments enable the independent adjustment of the shock absorber&#39;s low compression speed and its low rebound speed, as well as the independent adjustment of the shock absorber&#39;s high compression speed and its high rebound speed. Further, the fluid flow rate threshold associated with the lockout mode (that fluid flow rate threshold that is necessary to be met for the lockout mode to become triggered) is capable of being adjusted independent of the adjustments made to accommodate other fluid flow modes. 
         [0048]    Referring briefly to  FIG. 3B , during an event causing the shock absorber  350  to compress, a portion of a vehicle attached to the mounting element  352  moves downward, thereby forcing the mounting element  352  (to which the vehicle is attached) downward. The mounting element  352  is attached to the gas cylinder  354 . The dual piston valve  360  is pushed into the damping fluid cylinder  356  as the damping fluid cylinder  356  moves into the gas cylinder  354 . Fluid of the fluid volume  358  flows from a first side  366  of the dual piston valve  360  to a second side  368  of the dual piston valve  360 . 
         [0049]    During an event causing the shock absorber  350  to rebound, a portion of the vehicle attached to the mounting element  352  moves upward, thereby releasing the downward pressure that is forcing the mounting element  352  downward and/or pulling the mounting element  352  upwards. The damping fluid cylinder  356  moves out of the gas cylinder  354  as the dual piston valve  360  moves closer to the top of the damping fluid cylinder  356 . Further, as the dual piston valve  360  moves further to the top of the damping fluid cylinder  356 , the fluid that had previously flowed to the second side  368 , during the event causing the shock absorber  350  to compress, now flows from the second side  368  to the first side  366 . 
         [0050]    Embodiments enable the low speed rebound fluid flow to be adjusted independently of the high speed compression fluid flow and the high speed rebound fluid flow to be adjusted independently of the high speed compression fluid flow. 
         [0051]      FIG. 6A  is an enlarged sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway AA in regard to low speed rebound fluid flow, in accordance with an embodiment. With reference to  FIGS. 4A and 6A , the low speed and the high speed rebound fluid flow rate may be adjusted by adjusting the rebound adjust rod  302  such that the taper C (and the end  404 ) lies further into the shaft  306  and thus further into the piston bolt  322 . Of note, and referring to  FIGS. 4A and 6A , the piston bolt  322  is hollow and also includes and connects to the rebound check plate  324 . The rebound check plate  324  includes one or more channels  604  through which fluid may flow. As can be seen in  FIGS. 4A and 4B , the secondary (lockout) damping piston  332  has a concave shape with a base  442  and a side surface  450  that includes a portion of the base  442  and a lip  616  (see  FIG. 6A ). The base  442  has disposed there through two sets of passageways (a set [one or more] of outer diameter passageways  610  and a set [one or more] of inner diameter passageways  614 ). The side surface  450  has disposed thereon the threads  440 . 
         [0052]    As will be described later in regards to the lockout mode, on the outer bottom surface of the base  442  of the secondary (lockout) damping piston  332  is disposed a set (one or more) of channels  612  that are indentations carved into the outer bottom surface of the base  442 , extending from the inner most part (closest to the core of the secondary [lockout] damping piston  332 ) of the set of inner diameter passageways  614  opening[s]) to the outermost edge of the outer bottom surface of the base  442  of the secondary (lockout) damping piston  332 . 
         [0053]    In various embodiments, depending upon an adjustment made by the user or the adjustment set by the manufacturer, the upper surface  618  of the lockout plate/rebound check valve  338  is spaced a distance  650  away from the outer bottom surface of the base  442  of the secondary (lockout) damping piston  332 . Thus, in one embodiment, the outer bottom surface of the base  442  of the secondary (lockout) damping piston  332  and the upper surface  618  of the lockout plate/rebound check valve  338  do not touch, leaving a gap  620 . The fluid then flows out of the set of outer diameter passageways  610 , wherein the gap  620  is the distance  650  equal to a measurement that is greater than zero. In this instance, fluid may flow through the gap  620 . 
         [0054]    In another embodiment, if the distance  650  is zero, then the outer bottom surface of the base  442  of the secondary (lockout) damping piston  332  and the upper surface  618  of the lockout plate/rebound check valve  338  touch and do not leave a gap  620 . The lockout plate/rebound check valve  338  includes a set (one or more) of channels  622  that traverse the entirety of the lockout plate/rebound check valve  338 , from the upper surface  618  to the lower surface  624 . As discussed, the shim  426  is disposed underneath the lockout plate/rebound check valve  338 . Underneath the shim  426  is a smaller diameter shim  428 . When the lockout plate/rebound check valve  338  is positioned such that it is against the secondary (lockout) damping piston  332 , then the fluid that flows through the set of outer diameter passageway  610  flows through the set of channels  622  while pushing against the shim  426  to displace an edge  628  of the shim  426  away from the lower surface  624  of the lockout plate/rebound check valve  338 . Directly below and pressing up against the rebound check plate  324  is the larger diameter shim  418  which is flexible, and bends in reaction to a particular force of fluid pressing against it to let fluid flow there through. It should be appreciated that such flexibility is due to the disposition of the larger diameter shim  418 , and the extent to which the larger diameter shim  418  bends is due to, at least, the amount of force applied thereto by the fluid under pressure. 
         [0055]    Thus, with reference to  FIGS. 4A, 4B, 5 and 6A , in describing the low speed rebound flow of path AA, and as discussed herein, it is first seen that in response to an event that causes rebound to occur in the shock absorber  350 , the damping fluid cylinder  356  moves out of the gas cylinder  354  such that the dual piston valve  360  moves from a position lower in the damping fluid cylinder  356  to a position that is higher in the damping fluid cylinder  356 . In accomplishing this movement, since the dual piston valve  360  is moving upwards in the damping fluid cylinder  356 , the portion of the fluid volume  358  that is at the second side  368  of the damping fluid cylinder  356  is pushed through the dual piston valve  360  to the first side  366  of the damping fluid cylinder  356 . 
         [0056]    In moving through the dual piston valve  360  in response to an event causing low speed rebound to occur in the shock absorber  350 , it can be seen that a portion of the fluid that is located at the second side  368  moves into the set of holes  444  that are disposed at the end  406  of the shaft  306 . The fluid then flows through the gap  602  (see  FIG. 6A ) between the outer surface of the taper C at the end  404  of the rebound adjust rod  302  and the inner surface of the piston bolt  322 . Of note, since the fluid flow rate is low during a low speed rebound, the gap  602  that allows fluid to flow there through is sufficiently large to allow all or, at least, most of the fluid to flow there through at the low fluid flow rate caused by the event. This gap  602  is thus an adjustable orifice. 
         [0057]    Of note, and as will be discussed with reference to  FIG. 6B , in addition to the fluid flowing through the gap  602  (or in the alternative if the gap  602  is closed, such that there is no gap  602 ), if the fluid flow rate is too great for the fluid to successfully flow through the gap  602  at a fluid flow rate caused by the shock absorber  350  experiencing a rebound event, then the fluid will also flow through the channel  436  (see  FIG. 6B ). 
         [0058]    Still with reference to  FIG. 6A , during the response to the event causing the low speed rebound flow, after moving through the gap  602 , the fluid then moves through the channel  626  in the piston bolt  322  towards the damping fluid cylinder  356 . This channel  626  is disposed between the outer surface of the rebound adjust rod  302  and the inner surface of the wall of the hollow piston bolt  322 . The fluid then flows into the channel  604  of the rebound check plate  124 . Next, the fluid flows out of the channel  604  (that is disposed in the rebound check plate  324 ) and through the larger diameter shim  418  that is flexible and will bend when a certain amount of force is applied to it by the pressure created from the flow of the fluid initiated by the movement of the dual piston valve  360  upwards in the damping fluid cylinder  356  (during an event causing a rebound in the shock absorber  350  to occur). Once through the larger diameter shim  418 , the fluid will flow into the set of outer diameter passageways  610 . It should be appreciated that there may be one or more outer diameter passageways in the set of outer diameter passageways  610 . Once through the larger diameter shim  418 , if a gap  620  exists between the lockout plate/rebound check valve  338  and the bottom surface of the base  442  of the secondary (lockout) damping piston  332 , then the fluid will flow out of the set of outer diameter passageways  610 , through the gap  620 , along the section  606  of the pathway AA. If a gap  620  does not exist between the lockout plate/rebound check valve  338  and the bottom surface of the base  442  of the secondary (lockout) damping piston  332 , then the fluid will flow out of the channel  622  disposed in the lockout plate/rebound check valve  338 , thereby pushing open the shim  426  to flow there through and into the first side  366  of the damping fluid cylinder  356 . 
         [0059]    Thus, it can be seen that the rate of flow regarding the low speed rebound fluid flow may be adjusted by adjusting the rebound adjust rod  302  via a mechanism connected to the adjuster element  402 . In such a manner, the rebound adjust rod  302  may be moved upwards or downwards, thereby moving the taper C at the end  404  of the rebound adjust rod  302  further into or out of the interior of the piston bolt  322 . By pulling the rebound adjust rod  302  further out of the shaft  306 , the gap  602  widens, thereby enabling the flow of the fluid through the gap  602  during low speed rebound to increase, and thereby lessening the damping effect experienced by the shock absorber  350 . However, by pushing the rebound adjust rod  302  further into the shaft  306 , the gap  602  narrows, thereby further limiting the ability of the flow of fluid to flow through the gap  602 , and thereby increasing the damping effect experienced by the shock absorber  350 . Of additional note, the low speed rebound flow path AA initially flows through channels close to the inner diameter of the dual piston valve  360 , and then moves further away from the core of the dual piston valve  360  and to channels located close to the outer diameter of the dual piston valve  360 . This is in contrast to the location of the channels through which fluid flows for the high speed rebound flow, as will be discussed next with reference to  FIG. 6B . 
         [0060]      FIG. 6B  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway BB, in regard to high speed rebound fluid flow, in accordance with an embodiment. The fluid pathway BB is disposed within the dual piston valve  360  and lies in parallel with the low speed rebound fluid pathway AA (shown in  FIG. 6A ). That is, during the low speed rebound flow, the fluid flow through the fluid pathway AA travels from the second side  368  to the first side  366  of the dual piston valve  360  within the damping fluid cylinder  356 . Likewise, during the high speed rebound flow, the fluid flow through the fluid pathway BB travels from the second side  368  to the first side  366  of the dual piston valve  360  within the damping fluid cylinder  356 . Both fluid pathways AA and BB eventually flow out of the set of outer diameter passageways  610 . Both fluid pathways AA and BB enable fluid to flow from the second side  368  to the first side  366  of the dual piston valve  360  within the damping fluid cylinder  356 . However, a substantial portion of the fluid pathway AA is disposed at a different location within the dual piston valve  360  than the fluid pathway BB. The low speed rebound flow of the fluid travels through the fluid pathway AA, in which a substantial portion of the fluid pathway AA is located closer to the core of the dual piston valve  360  than a substantial portion of the fluid pathway BB that is designed for the high speed rebound flow of fluid. This design is advantageous to enable more efficiently functioning rebound damping since the area for which fluid may flow is smaller when closer to the core of the dual piston valve  360  than the area for which fluid may flow when closer to the outer diameter of the dual piston valve  360 . Thus, when the fluid needs to flow faster to accommodate a greater flow rate, such as during high speed rebound flow events, the fluid is enabled to flow in the larger fluid passageways that are disposed toward the outer diameter of the dual piston valve  360  (e.g., channel  436 , set [one or more] of inner diameter passageways  614  of the main damping piston  316 , the gap  632  between the rebound check plate  324  and the surface of the inner wall of the secondary [lockout] damping piston  332 , and the set of outer diameter passageways  610 ). However, when the fluid does not need to flow as fast, such as during low speed rebound flow events, the fluid flows in the smaller fluid passageways that are disposed closer to the core of the dual piston valve  360  (e.g., the channel  626  in the piston bolt  322  and the channel  604 ). 
         [0061]    Of note, as can be seen in  FIGS. 4A and 6B , the main damping piston  316  has a concave shape with a base  636  and a side surface  634  that includes a portion of the base  636  and a lip  638  (see  FIG. 6B ). The base  636  has disposed there through two sets of passageways (a set [one or more] of inner diameter passageways  630  disposed closer to the core of the main damping piston  316  and a set [one or more] of outer diameter passageways  640  disposed closer to the outer diameter of the main damping piston  316 ). In one embodiment, the set of inner diameter passageways  630  has a smaller diameter than that diameter(s) of the set of outer diameter passageways  640 . The inner surface of the lip  638  includes threads  642  which match the threads  440  disposed on the side surface  450  of the secondary (lockout) damping piston  332 , such that the secondary (lockout) damping piston  332  and the main damping piston  316  may be screwed together. On the outer bottom surface of the base  636  of the main damping piston  316  is disposed a set (one or more) of channels  436  that are indentations carved into the outer part of the bottom surface of the base  636 , extending from the inner most part (closest to the core of the main damping piston  316 ) of the set of inner diameter passageways  630  openings(s) to the outermost edge of the outer bottom surface of the base  636  of the main damping piston  316 . 
         [0062]    Thus, with reference to  FIGS. 4A, 4B, 5 and 6B , in describing the high speed rebound flow of path BB, it is noted and as described herein, that in response to an event that causes rebound to occur in the shock absorber  350 , the damping fluid cylinder  356  moves out of the gas cylinder  354  such that the dual piston valve  360  moves from a position lower in the damping fluid cylinder  356  to a position that is higher in the damping fluid cylinder  356 . In accomplishing this movement, since the dual piston valve  360  is moving upwards in the damping fluid cylinder  356 , the portion of the fluid volume  358  that is at the second side  368  of the damping fluid cylinder  356  is pushed through the dual piston valve  360  to the first side  366  of the damping fluid cylinder  356 . 
         [0063]    During the movement through the dual piston valve  360  in response to an event causing high speed rebound flow to occur in the shock absorber  350 , it can be seen that a portion of the fluid that is located at the second side  368  moves into the set of holes  444  that are disposed at the end  406  of the shaft  306 . If the area of the gap  602  is not large enough for the fluid that is flowing at a certain rate to move there through, then the fluid that is not able to move through the gap  602  is pushed through the fluid pathway BB (which is the high speed rebound fluid pathway). 
         [0064]    The fluid pathway BB begins with the flow of fluid through the set of channels  436  of the main damping piston  316 . From the set of channels  436 , the fluid moves into the set of inner diameter passageways  630  (which, of note, is still closer to the outer diameter of the dual piston valve  360  than the channel  626  [of the fluid flow pathway AA] through the piston bolt  322 ). From the set of inner diameter passageways  630 , the fluid pushes open the shims  414 . Of note, it should be appreciated that the shims  414  are manufactured to have a particular flexibility such that a particular predetermined amount of pressure causing fluid to press against the shims  414  will cause the shims  414  to bend a particular amount. As the shims  414  are pinched at the inner edge to or near the piston bolt  322 , the outer edge of the shims  414  may move and bend in the direction of the lockout plate/rebound check valve  338  when enough force is applied to the shims  414  via a particular pressure causing the fluid to flow at a particular rate. 
         [0065]    Of further note, the rebound check plate  324  lies within the concave portion of the main damping piston  316 . The inner bottom surface of the concave portion of the main damping piston  316  is separated from the top surface  646  of the rebound check plate  324  by the shims  414  and the small diameter shims  414 . After pushing the outer edge of the shims  414  open, the fluid enters the gap  632  between the rebound check plate  324  and the inner surface of the lip  616  of the secondary [lockout] damping piston  332 ) and/or the inner surface of the lip  638  of the main damping piston  316 . 
         [0066]    However, in this situation, the shims  422  block the fluid from flowing into the set of inner diameter passageways  614  of the secondary (lockout) damping piston  332 . The gap  632  is positioned above the opening to the set of outer diameter passageways  610  of the secondary (lockout) damping piston  332 . 
         [0067]    As with the fluid pathway AA, if the gap  620  exists between the lockout plate/rebound check valve  338  and the bottom surface of the base  442  of the secondary (lockout) damping piston  332 , then the fluid will flow out of the set of outer diameter passageways  610 , through the gap  620 , and along the section  606  of the path AA. If a gap  620  does not exist between the lockout plate/rebound check valve  338  and the bottom surface of the base  442  of the secondary (lockout) damping piston  332 , then the fluid will flow out of the channel  622  disposed in the lockout plate/rebound check valve  338 , thereby pushing open the shim  426  to flow there through and into the first side  366  of the damping fluid cylinder  356 . 
         [0068]    As can be seen, the high speed rebound flow path BB initially flows through and remains flowing through channels positioned closer to the outer diameter of the dual piston valve  360  than those channels involved in the low speed rebound flow path AA. 
         [0069]      FIG. 7A  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway CC in regard to low speed compression flow, in accordance with an embodiment. The low speed fluid flow rate may be adjusted by adjusting the compression adjust rod  340  such that the taper D (and the end  424 ) lies further into the secondary (lockout) damping piston  332  and the rebound check plate  324 . Of note, the piston bolt  322  includes a set (one or more) of pivot bolt holes  702  disposed at the base of the piston bolt  322  close to the rebound check plate  324  and below the threads  712  on the outer surface of the piston bolt  322 . Additionally, the rebound check plate  325  includes a top surface  708  and a bottom surface  710 . The bottom surface has an annular lip  704  extending therefrom. The annular lip  704  surrounds a hole disposed central thereto. The compression check plate  308  includes a first surface  714  and a second surface  730 . Indentations  718  in the second surface  730  provide a channel for fluid to flow there through. At least a portion of the indentations  718  connect to the inner most edge  716  of the compression check plate  308 , such that the pivot bolt holes  702  and the indentations  718  provide a continuous channel for which the fluid to flow. However, the indentations  718  do not extend to the outer diameter edge  728  of the compression check plate  308 . 
         [0070]    Directly underneath the indentations  718  are disposed low speed compression check shims  408 . Underneath the low speed compression check shims  408  are pivot shims  410 . The low speed compression check shims  408  and the pivot shims  410  are pinched (herein, the term, “pinched” refers to a component being clamped to another component such that the pinched component remains at a particular location) at the edge closest to the central core of the dual piston valve  360  such that the inner edges do not move, while allowing for the outer edges of the low speed compression check shims  408  to move away from the indentations  718  of the compression check plate  308  when fluid flow pushes against the low speed compression check shims  408  with enough force to cause the outer edge of the low speed compression check shims  408  to flex downwards and away from the indentations  718 . 
         [0071]    With reference to  FIGS. 4A, 4B and 7A , in describing the low speed compression flow of path CC, it should first be noted that in response to an event that causes compression to occur in the shock absorber  350 , the damping fluid cylinder  356  moves into the gas cylinder  354  such that the dual piston valve  360  moves from a position higher in the damping fluid cylinder  356  to a position that is lower in the damping fluid cylinder  356 . In accomplishing this movement, since the dual piston valve  360  is moving downwards in the damping fluid cylinder  356 , the portion of the fluid volume  358  that is at the first side  366  of the damping fluid cylinder  356  is pushed through the dual piston valve  360  to the second side  368  of the damping fluid cylinder  356 . 
         [0072]    In moving through the dual piston valve  360  in response to an event causing low speed compression to occur in the shock absorber  350 , it can be seen that a portion of the fluid that is located at the first side  366  moves into the gap  620  and then through the gap  502  at the taper D at the end  424  of the compression adjust rod  340 . The gap  502  is an adjustable orifice. The fluid then flows through the channel  706  disposed between the lip  704  and the taper D. Subsequently, the fluid continues to flow from the channel  706  to and through the channel  626  in the piston bolt  322 . From the channel  626 , the fluid flows through the pivot bolt holes  702  and into the indentations  718  disposed in the compression check plate  308 . The fluid flow pushes against the low speed compression check shims  408 , and upon the flexing (bending) of the outer edge of the low speed compression check shims  408  downwards and away from the indentations  718 , the fluid flows out of the indentations  718  (that provide a channel through the compression check plate  308 ) and into the second side  368  of the damping fluid cylinder  356 . 
         [0073]    Of note, a substantial portion of the low speed compression fluid flow along flow path CC occurs in fluid flow paths disposed closer to the core of the dual piston valve  360 . 
         [0074]      FIG. 7B  is a sectional side elevation view of section B of  FIG. 7B  illustrating fluid pathway DD, in regard to high speed compression fluid flow, in accordance with an embodiment. The fluid pathway DD is disposed with the dual piston valve  360  and lies in parallel with the low speed compression fluid pathway CC (shown in  FIG. 7A ). That is, during the low speed compression flow, the fluid flow through the fluid pathway CC travels from the first side  366  to the second side  368  of the dual piston valve  360  within the damping fluid cylinder  356 . Likewise, during the high speed compression flow, the fluid flow through the fluid pathway DD travels from the first side  366  to the second side  368  of the dual piston valve  360  within the damping fluid cylinder  356 . Both of the fluid pathways CC and DD enable fluid to flow from the first side  366  to the second side  368  of the dual piston valve  360  within the damping fluid cylinder  356 . However, a substantial portion of the fluid pathway CC is disposed at a different location within the dual piston valve  360  than the fluid pathway DD. The low speed compression flow of the fluid travels through the fluid pathway CC, in which a substantial portion of the fluid pathway CC is located closer to the core of the dual piston valve  360  than a substantial portion of the fluid pathway DD that is designed for the high speed compression flow of fluid. As discussed herein, this design is advantageous to enable more efficiently functioning compression damping since the area for which fluid may flow is smaller when closer to the core of the dual piston valve  360  than the area for which fluid may flow when closer to the outer diameter of the dual piston valve  360 . 
         [0075]    Thus, with reference to  FIGS. 4A, 4B and 7B , in describing the high speed compression flow of path DD, it is noted and as described herein, that in response to an event that causes compression to occur in the shock absorber  350 , the damping fluid cylinder  356  moves into the gas cylinder  354  such that the dual piston valve  360  moves from a position higher in the damping fluid cylinder  356  to a position that is lower in the damping fluid cylinder  356 . In accomplishing this movement, since the dual piston valve  360  is moving downwards in the damping fluid cylinder  356 , the portion of the fluid volume  358  that is at the first side  366  of the damping fluid cylinder  356  is pushed through the dual piston valve  360  to the second side  368  of the damping fluid cylinder  356 . 
         [0076]    During this movement through the dual piston valve  360  and in response to an event causing high speed compression flow to occur in the shock absorber  350 , it can be seen in  FIG. 7B  that a portion of the fluid that is located at the first side  366  moves into the gap  502  and through the channel  706 . If the area of the gap  502  is not large enough for the fluid that is flowing at a certain rate to move there through, then the fluid that is not able to move through the gap  502  is pushed through the fluid pathway DD, the high speed compression fluid pathway. 
         [0077]    The fluid pathway DD begins with the flow of fluid, that is located at the first side  366 , into the gap  620 , and then through the set of outer diameter passageways  610 . The fluid flow then pushes against the high speed compression shims  412  with enough force to cause the high speed compression shims  412  to bend and thus open up, thereby letting the fluid flow there through and into the second side  368 . 
         [0078]    As can be seen, the high speed compression flow path DD initially flows through and remains flowing through channels positioned closer to the outer diameter of the dual piston valve  360  than the position of the channels involved in the low speed compression flow path CC. 
         [0079]    Thus, it can be seen that the rate of fluid flow regarding the low speed compression fluid flow may be adjusted by adjusting the compression adjust rod  340  via a mechanism connected to the compression adjust rod  340 . As the compression adjust rod  340  is raised and lowered, the amount of fluid that enters the flow paths CC and DD is varied. For example, in one embodiment, the compression adjust rod  340  is connected to an adjuster. The adjuster can be twisted, which in turn causes the compression adjust rod  340  to slide up or down. For example, adjusting the compression adjust rod  340  such that more fluid flows into the fluid pathway CC (by opening the gap  502  between the taper D and the secondary [lockout] damping piston  332 ) will create a higher compression flow rate, as is discussed above with respect to  FIG. 7B . The higher compression flow rate will not only cause a portion of the fluid to flow through the fluid pathway CC designed for low speed compression flow, but cause a portion of the fluid to flow through the checked fluid pathway DD (see  FIG. 7B ), which can accommodate a greater level of fluid flow there through. 
         [0080]      FIG. 8  is a sectional side elevation view of section B of  FIG. 3B  illustrating fluid pathway EE, in regard to lockout, in accordance with an embodiment. Lockout occurs when the shock absorber experiences a great enough force such that the shock absorber does not move to provide a damping effect. However, embodiments enable a lockout circuit to be adjusted independently of the compression and rebound modes. 
         [0081]    The flow of fluid along pathway EE begins, when the lockout plate/rebound check valve  338  is positioned such that it is lying against the secondary (lockout) damping piston  332  and the shims  426  and  428  are lodged against the lockout plate/rebound check valve  338  such that the fluid on the first side  366  of the damping fluid cylinder  356  is not able to flow between the taper D at the end  336  and the secondary (lockout) damping piston  332  or flow through the set of outer diameter passageways  610 . 
         [0082]    However, even though the entrance from the first side  366  to the set of outer diameter passageways  610  and the gap  502  are closed, fluid is still able to flow through the set of channels  612 , push open the shims  422  that are blocking the exits of the set of channels  612 , flow into the set of outer diameter passageways  614 , and push open the high speed compression shims  412 . The lockout circuit fluid pathway EE keeps the shock absorber  350  from experiencing a high enough force that the shock absorber  350  does not want to move (such as during the event when a rider comes off a jump and slams the frame down onto the ground). Thus, if the shock absorber  350  experiences an excess of a certain amount of fluid pressure due to a certain force, it allows for a blow off of this pressure to occur. 
         [0083]    Of note, in one embodiment, the dual piston system  300  includes two concentric knobs with concentric cams that translate the movement into an up and down sliding movement of the rods that are connected to tapers. The two concentric knobs control the low speed compression and rebound fluid flow. The compression and rebound forces on the shims that are required to be present to cause the shims to flex is set at the manufacturer. 
         [0084]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be implemented without departing from the scope of the invention, and the scope thereof is determined by the claims that follow.
A dual piston system for independently controlling compression and rebound flowpaths therein, the dual piston system comprising: a first adjustable orifice configured for controlling rebound fluid flow, wherein the first adjustable orifice controls the rebound fluid flow through a first pathway associated with a low speed rebound flow and a second pathway associated with a high speed rebound flow; and a second adjustable orifice configured for controlling compression fluid flow, wherein the second adjustable orifice controls the compression fluid flow through a third pathway associated with a low speed compression flow and a fourth pathway associated with a high speed compression flow.