Patent Description:
Vehicle suspension systems typically include a spring component or components and a damping component or components. Typically, mechanical springs, like helical springs are used with some type of viscous fluid-based damping mechanism and the two are mounted functionally in parallel. In some instances, a spring may comprise pressurized gas and features of the damper or spring are user-adjustable, such as by adjusting the air pressure in a gas spring. A damper may be constructed by placing a damping piston in a fluid-filled cylinder (e.g., liquid such as oil). As the damping piston is moved in the cylinder, fluid is compressed and passes from one side of the piston to the other side. Often, the piston includes vents therethrough which may be covered by shim stacks to provide for different operational characteristics in compression or extension.

Conventional damping assemblies include multiple fluid passageways (also called fluid circuits), disposed within a piston, to account for varying speeds during compression, ranging from low speed compression to high speed to lockout compression mode. The piston is disposed within a cylinder with a limited sized diameter. A damping assembly's design takes into account the weight of the shock absorber (including the oil disposed therein) balanced against the size (diameter) of the shock absorber. Generally, a lighter shock absorber means a lighter vehicle for the rider to use. Additionally, the larger the diameter of the shock absorber (and the cylinders therein), the greater is the capability of the shock absorber to provide a damping function, and hence, enable an enhanced performance.

Typically, there are at least two separate fluid circuits to accommodate both high speed compression and low speed compression of the shock absorber. Thus, when an adjustment knob is turned, a high speed compression circuit may be closed, and upon such closing, a separate circuit for low speed compression may be opened. These multiple fluid circuits are disposed within the piston (the piston being within the shock absorber's cylinder) and are limited in size due to the need for multiple fluid circuits for varying compression speeds.

As the foregoing illustrates, what is needed in the art are improved techniques for adjusting compression speeds within a shock absorber, while increasing the performance of the shock absorber and maintaining or reducing its weight.

<CIT> discloses a vehicle suspension damper for providing a variable damping rate. The vehicle suspension damper comprises a first damping mechanism having a variable first threshold pressure, a second damping mechanism having a second threshold pressure, and a compressible chamber in communication with a damping fluid chamber, wherein the second damping mechanism is responsive to a compression of said compressible chamber. <CIT> discloses a damper comprising a positionally adjustable floating shim stack.

According to some embodiments of the present invention there is provided a damper comprising a recirculation system configured for using only one type of oil, said recirculation system comprising:
a cartridge comprising a compression damper of a shock absorber, said compression damper comprising:.

In some aspects said multiple compression speeds comprise a low speed compression. In other aspects said multiple compression speeds comprise a high speed compression. In yet other aspects said multiple compression speeds comprise a lockout speed.

In some embodiments said positionally adjustable floating shim stack comprises:.

In certain aspects said position adjustment is accomplished via a manual rotation of a knob coupled with said positionally adjustable floating shim stack.

In some embodiments said first component comprises a pre-load hat.

In some aspects the compression damper further comprises a second component providing a second pre-load against said top surface at said second end during an upward flexing of said second end.

In certain embodiments said second component comprises a wave spring.

In yet other aspects said first component comprises:
a pre-load hat, wherein a first portion of said pre-load hat presses against said positionally adjustable floating shim stack, and a second portion of said pre-load hat presses against said second component, thereby supporting said second pre-load being applied against said top surface at said second end of said positionally adjustable floating shim stack during an upward flexing of said second end.

In some embodiments said positionally adjustable floating shim stack comprises a first position corresponding to a low speed compression adjustment wherein said positionally adjustable floating shim stack lies flat across said opening to said fluid passageway.

In certain aspects said positionally adjustable floating shim stack comprises:
a second position corresponding to a compression speed greater than a minimum compression adjustment speed, wherein said second position comprises:.

In other embodiments the damper further comprises:
a rod telescopically positioned within said cartridge, wherein a first end of said rod is mounted within said cartridge and, upon compression and rebound, is enabled to move into and out of said cartridge, respectively, through a U-shaped component that seals a cartridge end of said cartridge through which said rod interacts, and a second end of said rod is positioned in an oil bath, wherein said U-shaped component comprises:
a sealing element that is configured for allowing oil from said oil bath that is sticking to a shaft of said rod to remain on said shaft as said shaft enters said fluid filled chamber of said cartridge during compression, and for scraping off said oil from said shaft as said shaft leaves said fluid filled chamber during rebound, thereby leaving said oil that was scraped off in said fluid filled chamber.

According to other embodiments of the invention there is provided a vehicle comprising a damper as aforesaid.

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:.

Reference will now be made in detail to embodiments of the present technology, examples of which are illustrated in the accompanying drawings. While the technology will be described in conjunction with various embodiment(s), it will be understood that they are not intended to limit the present technology to these embodiments.

Furthermore, in the following description of embodiments, numerous specific details are set forth in order to provide a thorough understanding of the present technology. However, the present technology may be practiced without these specific details. In other instances, well known methods, procedures, and components have not been described in detail as not to unnecessarily obscure aspects of the present disclosure.

Embodiments describe a compression piston disposed within a shock absorber, wherein the compression piston has a single adjustable circuit there through that, via a single control knob and a floating shim stack that may be variably pre-loaded, controls damping for low speed compression to high speed compression to lockout compression of the damper within the shock absorber. Further, embodiments provide a secondary pre-loaded component to be applied against the floating shim stack. Additionally, embodiments provide an oil recirculation system within the shock absorber, in which the same oil is used throughout the fork comprising the shock absorber; upon rebound, a portion of the recirculation system ingests the oil into the fluid filled chamber and from an area exterior to the compression damper and the fluid filled chamber, and upon compression, another portion of the recirculation system exhausts the oil out of the fluid filled chamber and into the exterior of the compression damper.

The following discussion will first briefly describe various embodiments. The discussion then turns to a description of the <FIG> and embodiments shown therein.

<FIG> depicts a cross-sectional view of a monotube damper <NUM>, in accordance with an embodiment. The monotube damper <NUM> shown is configured for being disposed within a suspension fork. The monotube damper <NUM> shows a rod <NUM> telescopically disposed within the cartridge <NUM>. The cartridge <NUM> is shown to include a fluid filled chamber <NUM>, the compression damper <NUM> that is coupled with the knob <NUM> and the main piston <NUM> that is coupled with the rod <NUM>. The compression damper <NUM> includes the independent floating piston (IFP) <NUM> and the compression piston <NUM> (also called a base valve). The portion of the rod <NUM> that is exposed to an oil bath within the shock absorber is indicated as element <NUM>.

<FIG> depict cross-sectional views of the monotube damper <NUM>, with the needle in the low-speed compression position, a high-speed compression position, a higher speed compression position, and a lockout position, respectively, in accordance with an embodiment.

<FIG> depicts an enlarged cross-sectional view of the compression damper <NUM> of <FIG>, in accordance with an embodiment. The compression damper <NUM> is coupled with the knob <NUM> having a hex shaft <NUM> with shaft threads <NUM> disposed thereon. The compression damper <NUM> also includes a shaft <NUM> surrounding a needle <NUM> and a coil spring <NUM> positioned around the shaft <NUM>. As will be explained in more detail below, the compression damper <NUM> also includes at least the IFP <NUM>, a dowel pin <NUM>, a pre-load hat <NUM>, a shim stack <NUM> (also commonly called a valve stack in the industry) of predetermined stiffness, and the compression piston <NUM>. The compression piston <NUM> is disposed within and in between a first side <NUM> and a second side <NUM> of the fluid filled chamber <NUM>, wherein the fluid is oil <NUM>. The IFP <NUM> separates the air chamber <NUM> (filled with air) from the fluid filled chamber <NUM>. Also shown in <FIG> is a leak path <NUM>. The leak path <NUM> includes the curved recess <NUM> disposed in the shaft <NUM> and the passageway <NUM> disposed in the wall of the air chamber <NUM>.

<FIG> depict, in one embodiment, enlarged cross-sectional views of a portion of the compression damper <NUM>, and more specifically, the IFP <NUM>, the compression piston <NUM>, and surrounding areas, in accordance with embodiments. Further, <FIG> depict positions of the shim stack <NUM> at varying compression speeds ranging from low-speed compression to high-speed compression to lockout. <FIG> show the IFP <NUM> with an outside seal <NUM> and inside seal <NUM>, and a dowel pin <NUM> lodged within the pre-load hat <NUM> and separating the needle <NUM> and shaft <NUM> of the compression piston <NUM> from the pre-load hat <NUM>. <FIG> also show the wave spring <NUM>, the gap <NUM> between the inner edge <NUM> of the shim stack <NUM> and a component of the base valve positioned closest to the inner edge <NUM> such that the shim stack <NUM> effectively "floats" and is not clamped (pinched) into a particular position. This gap <NUM> is maintained during operation, regardless of whether the shim stack <NUM> is positioned in the low-speed compression mode, high-speed compression mode or lockout mode. The shim stack <NUM> has an outer edge <NUM> and the inner edge <NUM> (as previously noted). Also shown is the piston face <NUM> of the compression piston <NUM>, the fluid passageway <NUM> disposed through the compression piston <NUM>, a shim <NUM> and a spring <NUM>. Of note, also shown is the check valve <NUM> that enables fluid to flow from the second side <NUM> (see <FIG>) of the compression piston <NUM> to the first side <NUM> of the compression piston <NUM>, but blocks the flow of fluid through the passageway <NUM> from the first side <NUM> to the second side <NUM>.

In one embodiment, the knob <NUM> may be turned upwards of approximately <NUM> degrees from its original position. It should be appreciated that in other embodiments, the knob <NUM> may be rotated more or less than <NUM> degrees. It should be noted that in one embodiment, the knob <NUM> is continuously adjustable. Further, in one embodiment, the knob <NUM> has one or more detents that correspond with different compression force(s). In one embodiment, the knob <NUM> is affixed to a hex shaft <NUM> of a screw (or other type of small bolt), wherein the hex shaft <NUM> is configured for rotatably coupling with the needle <NUM> (having a first end <NUM> and a second end <NUM>), such that by turning the knob <NUM>, the needle <NUM> is also turned, and is caused to move up or down within the air chamber <NUM>. In one embodiment, the hex shaft <NUM> has threads <NUM> thereon and the needle <NUM> has matching threads <NUM> thereon at the first end <NUM> of the needle <NUM>, such that when the knob <NUM> is turned, the hex shaft <NUM> turns, and then the needle <NUM> turns and moves up and down along the threads <NUM> of the hex shaft <NUM>. The movement of the needle <NUM> downwards will ultimately cause the second end <NUM> of the needle <NUM> to push against the dowel pin <NUM>. The dowel pin <NUM> then pushes downward against the pre-load hat <NUM>. The pre-load hat <NUM> then pushes downward against the shim stack <NUM>. In general, the greater the rotation of the knob <NUM>, the further downwards into the fluid filled chamber <NUM> the second end <NUM> of the needle <NUM> travels such that the dowel pin's <NUM> downward movement causes the pre-load hat <NUM> to push the first end <NUM> of the shim stack <NUM> further into the passageway <NUM>. In one embodiment, the first end <NUM> of the shim stack <NUM> may be pushed, and thus moved, into the passageway <NUM> by as much as <NUM> (.

During operation, and with reference to <FIG>, when an event that causes compression within the monotube damper <NUM> occurs, the rod <NUM> moves into the fluid filled chamber <NUM>, pushing the oil <NUM> within the fluid filled chamber <NUM> in the direction of the knob <NUM> and through the compression piston <NUM> from the first side <NUM> of the compression piston <NUM> to the second side <NUM> of the compression piston <NUM>. The oil <NUM> then pushes against the IFP <NUM>, causing the IFP <NUM> to travel upward (toward the direction of the knob <NUM>). When an event that causes rebound within the monotube damper <NUM> occurs, the rod <NUM> moves out of the fluid filled chamber <NUM>, and the oil <NUM> flows from the second side <NUM> of the compression piston <NUM>, through the compression piston <NUM>, to the first side <NUM> of the compression piston <NUM>. Further, during rebound, the IFP <NUM> travels downward (toward the direction of the main piston <NUM>).

According to embodiments, during compression, oil <NUM> flows from the first side <NUM> of the compression piston <NUM> to the second side <NUM> of the compression piston <NUM>, at varying compression speeds, via a single circuit disposed within the compression piston <NUM>. The quantity and speed of the oil <NUM> flowing through the single circuit is controlled via a manual rotation of the knob <NUM>, such manual rotation ultimately adjusting the force with which the pre-load hat <NUM> pushes against the shim stack <NUM>. The more force that the pre-load hat <NUM> uses to push on the shim stack <NUM>, the more fluid pressure is required to push the shim stack <NUM> open in order that the oil <NUM> may flow from the first side <NUM> of the compression piston <NUM> to the second side <NUM> of the compression piston <NUM> through the gap <NUM>. Thus, the more resistance (provided by the shim stack <NUM>) to the oil <NUM> flow through the gap <NUM>, the greater the compression damping that occurs in the compression damper <NUM> (and hence the shock absorber having the monotube damper <NUM> therein). Additionally, in some embodiments and in response to the oil <NUM> flowing through the gap <NUM>, the fluid flow causes the shim stack <NUM> to flex upwards enough to touch the wave spring <NUM>, such that the wave spring <NUM> provides an additional, but light pre-load to the shim stack <NUM>.

<FIG> depicts the shim stack <NUM> in a low-speed compression position ("first position"). The knob <NUM> is set at a position such that the pre-load hat <NUM> is caused to be in contact with the shim stack <NUM>, but the pre-load hat <NUM> is not pushing against the shim stack <NUM> so that the shim stack <NUM> moves toward and/or into the passageway <NUM>. In this position, in response to and during a compression event, fluid (oil) pressure is applied to the shim stack <NUM>, and the second end <NUM> of the shim stack <NUM> (that has a predetermined stiffness) flexes upwards (shown as element <NUM>) (in the direction of the knob <NUM>). The oil <NUM> will then flow through the passageway <NUM> and then through the gap <NUM>, traveling from the first side <NUM> of the compression piston <NUM> to the second side <NUM> of the compression piston <NUM>. If enough fluid pressure is applied (such as through a compression event causing a greater fluid flow rate), the shim stack <NUM> will flex upwards such that it meets and touches the wave spring <NUM>. The wave spring <NUM> has a predetermined stiffness, and while it may flex upwards to a certain extent, the wave spring <NUM> presses against the upward flexing <NUM> shim stack <NUM> and therefore applies a light pre-load onto the shim stack <NUM>. This light pre-load provides a resistance to any further flexing upward by the shim stack <NUM>. The light pre-load applied to the shim stack <NUM> by the wave spring <NUM> also functions to maintain the relative positioning of the floating shim stack <NUM> that is being held in place by the pre-load hat <NUM>.

<FIG> depicts the shim stack <NUM> flexing <NUM> in a second position, that is set for a speed of compression that is higher than the low-speed compression setting of the first position, shown in <FIG>, in accordance with an embodiment. The knob <NUM> is set at a position such that the pre-load hat <NUM> is caused to be in contact with the shim stack <NUM> and the pre-load hat <NUM> is pushing against the shim stack <NUM> so that the shim stack <NUM> moves a certain distance ("distance one") that is greater than zero toward and/or into the passageway <NUM>. In this position, in response to and during the compression event, fluid pressure is applied to the shim stack <NUM>, and the shim stack <NUM> (that has a predetermined stiffness) flexes upwards (shown as element <NUM>) (in the direction of the knob <NUM>). Of note, the shim stack <NUM>, while flexed, appears to have a slightly concave shape ("concavity shape one"). The oil <NUM> will then flow through the passageway <NUM> and then through the gap <NUM>, traveling from the first side <NUM> of the compression piston <NUM> to the second side <NUM> of the compression piston <NUM>. If enough fluid pressure is applied (such as through a compression event causing enough of a fluid flow rate that overcomes the stiffness of the shim stack <NUM>), the shim stack <NUM> will flex upwards <NUM> such that it meets the wave spring <NUM>. As described herein with respect to the low-speed compression positioning of the shim stack <NUM>, the wave spring <NUM> functions to provide resistance to any further flexing upward by the shim stack <NUM> and helps hold the shim stack <NUM> relatively in place during such a compression event.

<FIG> depicts the shim stack <NUM> in a third position, that is set for a higher speed compression than the compression speed setting of the second position, shown in <FIG>, in accordance with an embodiment. The knob <NUM> is set at a position such that the pre-load hat <NUM> is caused to be in contact with the shim stack <NUM> and the pre-load hat <NUM> is pushing against the shim stack <NUM> so that the shim stack <NUM> moves a certain distance ("distance two") greater than "distance one" toward and/or into the passageway <NUM>. In this position, in response to and during the compression event, fluid pressure is applied to the shim stack <NUM>, and the shim stack <NUM> (that has a predetermined stiffness) flexes upwards (shown as element <NUM>) (in the direction of the knob <NUM>). Of note, the shim stack <NUM>, while flexed, appears to have a concave shape ("concavity shape two") that is more concave shaped than "concavity shape one". The oil <NUM> will then flow through the passageway <NUM> and then through the gap <NUM>, traveling from the first side <NUM> of the compression piston <NUM> to the second side <NUM> of the compression piston <NUM>. If enough fluid pressure is applied (such as through a compression event causing a fluid flow rate that overcomes the stiffness of the shim stack <NUM>), the shim stack <NUM> will flex upwards such that it meets the wave spring <NUM>. As described herein with respect to the low-speed compression positioning of the shim stack <NUM>, the wave spring <NUM> functions to provide resistance to any further flexing upward by the shim stack <NUM> and helps hold the shim stack <NUM> relatively in place during such a compression event.

Of note, it should be appreciated that the shim stack <NUM> may move greater or less distances than that of "distance one" and "distance two" and may be caused to have a greater or lesser concave shape than "concavity shape one" and "concavity shape two".

<FIG> depicts, in accordance with an embodiment, the shim stack <NUM> in a fourth position, that is set for a lockout compression position, which is for a higher speed compression setting than the compression speed setting of the third position, shown in <FIG>. In one embodiment, to achieve the "lockout compression position" of the shim stack <NUM>, the knob <NUM> is rotated to be positioned at its greatest possible rotation. Thus, if the knob <NUM> is rotatable to <NUM> degrees, then the knob <NUM> is turned to the rotation position of <NUM> degrees to achieve the lockout compression position for the shim stack <NUM>. In one embodiment, the knob <NUM> is set at a position such that the pre-load hat <NUM> is caused to be in contact with the shim stack <NUM> and the pre-load hat <NUM> is pushing against the shim stack <NUM> so that the shim stack <NUM> moves a certain distance ("distance three") greater than "distance two" toward and/or into the passageway <NUM>. In one embodiment, the "distance three" is the maximum distance that the shim stack <NUM> is able to be moved into the passageway <NUM>. In this position, in response to and during the compression event, fluid pressure is applied to the shim stack <NUM>, and the shim stack <NUM> (that has a predetermined stiffness) does not respond to this fluid pressure with any movement such that the shim stack <NUM> does not flex upwards anymore than it has already flexed upwards (shown as element <NUM>) (in the direction of the knob <NUM>) due to second end <NUM> of the shim stack <NUM> being held against the piston face <NUM>. Of note, the shim stack <NUM>, while flexed, appears to have a concave shape ("concavity shape three") that has a greater concave shape than "concavity shape two". The oil <NUM> will not be able to flow through the passageway <NUM> because the force of the oil in the direction of the knob <NUM> and against the lower surface <NUM> of the shim stack <NUM> is not enough to overcome the force of the pre-load hat <NUM> against the upper surface <NUM> of the shim stack <NUM> in the direction of the main piston <NUM> and the rod <NUM>.

<FIG> depicts an enlarged cross-sectional view a portion of the compression damper, and more particularly, the knob <NUM> and the first end <NUM> of the needle <NUM>, in accordance with an embodiment. Shown is the knob <NUM>, the hex shaft <NUM> (of a screw, small bolt, etc.) having the shaft threads <NUM>, and the needle <NUM> having the needle threads <NUM> at the first end <NUM>. Also depicted are "needle distance one" <NUM>, "needle distance two" <NUM> and "needle distance three" <NUM>, according to one embodiment. In one embodiment, as shown in <FIG>, the knob <NUM> and consequently the needle <NUM> are positioned at the low-speed compression setting such that the pre-load hat <NUM> is not applying any pre-load onto the shim stack <NUM> other than that pre-load that is incidental to the pre-load hat <NUM> being in contact with the shim stack <NUM>. In one embodiment, a position of the pre-load hat <NUM> is a default position that occurs when the knob <NUM> is at zero degrees rotation (i.e., the knob <NUM> has not been manually rotated from a possible rotation position of, for example, <NUM> to <NUM> degrees, and remains at <NUM> degrees, wherein the <NUM> degrees represents a lockout compression speed position). The "needle distance one" <NUM> represents the amount of travel of the needle <NUM> caused by the rotation of the knob <NUM> to a position between the minimum and the maximum knob rotation possibilities (e.g., <NUM> to <NUM> degrees, etc.).

In relation to <FIG>, the "needle distance one" <NUM> corresponds to the compression speed setting shown in <FIG>, when the shim stack <NUM> moves "distance one" toward and/or into the passageway <NUM>, creating the shim stack "concavity shape one". The "needle distance two" <NUM> corresponds to the compression speed setting shown in <FIG>, when the shim stack <NUM> moves "distance two" toward and/or into the passageway <NUM>, creating the shim stack "concavity shape two". The "needle distance three" corresponds to the compression speed setting shown in <FIG>, when the shim stack <NUM> moves "distance three" <NUM> toward and/or into the passageway <NUM>, creating the shim stack "concavity shape three".

Thus, as is depicted in <FIG>, the compression piston <NUM> has one circuit (fluid pathway) there through. The opening of this circuit is selectively blocked with a flexible and positionally adjustable shim stack <NUM>. The position (and hence the selective blocking of the circuit) of the shim stack <NUM> is manipulated with the knob <NUM>. As described herein, depending on the position of the shim stack <NUM>, a desired damping rate for a particular compression speed of the shock absorber (e.g., a range between the lowest speed compression to lockout compression [including high speed compression]) is accomplished.

The benefits of embodiments of the present technology are numerous. For example, embodiments have an adjustable single fluid circuit that enables multiple damping rates for a range of compression speeds. This is in contrast to conventional technology which requires multiple circuits to enable multiple damping rates for the same range of compression speeds. Thus, to accomplish the same damping functions, conventional technology requires a manufacture of more components for a multiple fluid circuit design and thus such manufacturing process is more expensive than the manufacturing of components associated with embodiments of the present technology. Further, in one embodiment, the diameter of the fluid filled chamber <NUM> and the air chamber <NUM>, and hence the compression piston <NUM> and the fluid passageway <NUM> therein are larger than the diameter of the fluid passageways of conventional technology. For example, a current piston diameter may be roughly <NUM>. mm, whereas the diameter of an embodiment of the compression piston <NUM> is <NUM>. The larger the diameter of the fluid passageway <NUM>, the more oil is able to pass there through at a greater rate, if need be, and thus such larger diameter increases the performance of the compression damper <NUM> during compression as compared to the narrower fluid passageways within conventional technology. Thus, embodiments of the present technology are designed to be of a lower manufacturing cost and to have higher performance characteristics than those of conventional technology.

Additionally and as noted herein, the wave spring <NUM> helps to maintain the relative positioning of the floating shim stack <NUM> within the compression damper <NUM>. In so doing, the wave spring <NUM> also reduces potential noise problems by keeping the shim stacks <NUM>, which are moving components, from flopping around within the compression damper <NUM> during operation.

Conventional fork and damper technology provides for a damper placed inside of a fork leg of a fork. The damper includes a rod telescopically positioned with a cartridge. During compression and rebound, the rod moves into and out of the cartridge, respectively. One end of the rod is located in an oil bath of the fork leg (oil that serves to lubricate other moving components existing outside of the compression damper components), while the other end of the rod is located in a fluid filled damper. Conventionally, the oil within the oil bath is of a different type than that oil found within the fluid filled damper. Typically, the rod must pass through a seal before any further portion of it enters the cartridge. This seal is designed to keep any oil from the oil bath that is sticking to the shaft from entering the fluid filled chamber as the shaft passes into the fluid filled chamber. The seal scrapes off the oil from the rod's shaft as the rod's shaft enters the fluid filled chamber. Consequently, this scraping causes a certain amount of friction between the rod's shaft and the seal as the rod's shaft moves into the fluid filled chamber.

<FIG> is an enlarged cross-sectional view of a portion of the rod <NUM>, and more particularly the main piston <NUM> and the seal head <NUM> shown in <FIG>, in accordance with an embodiment. Embodiments of the present technology provide a system for reducing friction between the shaft <NUM> and a sealing head <NUM> as the shaft <NUM> of the rod <NUM> moves into the fluid filled chamber <NUM> during compression and rebound. According to embodiments, the monotube damper <NUM> shown in <FIG> is placed within a fork leg of a fork. A portion of the rod <NUM> is located within an oil bath within the fork leg (fork leg not shown).

<FIG> shows the main piston <NUM>, the shaft <NUM> and the needle <NUM> of the rod <NUM>, a U-Cup <NUM> that includes: the seal head <NUM> (that functions to keep the fluid within the fluid filled chamber <NUM> from exiting the fluid filled chamber <NUM>); a lip <NUM>; and a seal <NUM>. A bushing <NUM> is shown disposed between the shaft <NUM> of the rod <NUM> and the seal head <NUM> and functions at least to guide the shaft <NUM> into the fluid filled chamber <NUM>. The main piston <NUM> is shown positioned between a first side <NUM> of the compression piston <NUM> and the chamber <NUM>. The needle <NUM> is shown to include a hole <NUM> through which the oil <NUM> (see <FIG>) may flow along pathway <NUM> from the chamber <NUM> to the first side <NUM> of the compression piston <NUM>. The main piston <NUM> is shown to include a check valve <NUM> (also called the "mid-valve") and rebound shims <NUM> through which fluid flows along pathway <NUM>.

With reference now to <FIG>, <FIG> and <FIG> and according to an embodiment, the following fluid flow and fluid recirculation, from the oil bath, through the main piston <NUM> and compression piston <NUM>, out of the wall of the air chamber <NUM> and back to the oil bath, is described in conjunction with the functioning of embodiments of components described herein.

As the fork leg, including the monotube damper <NUM>, vibrates and shakes during a vehicle's operation, the oil <NUM> in the oil bath moves around and ultimately temporarily adheres to the shaft <NUM> of the rod <NUM>. In response to an event causing compression of the shock absorber, the shaft <NUM> of the rod <NUM> moves into a portion <NUM> of the fluid filled chamber <NUM>. The oil <NUM> on the shaft <NUM> also moves into the fluid filled chamber <NUM>. In response to an event causing a rebound of the shock absorber, the shaft <NUM> of the rod <NUM> moves out of the fluid filled chamber <NUM>, and the oil <NUM> that was temporarily adhering to the shaft <NUM> is scraped off and remains within the portion <NUM> of the fluid filled chamber <NUM>. As the main piston <NUM> moves downward and in a direction away from the knob <NUM>, a first portion of the oil within the portion <NUM> of the fluid filled chamber <NUM> moves through the hole <NUM> within the needle <NUM> and along the pathway <NUM> into the first side <NUM> of the compression piston <NUM>. Another portion of the oil <NUM> within the fluid filled chamber <NUM> moves along pathway <NUM>, pushes open the rebound shims <NUM> and moves through the resulting gap <NUM> into the first side <NUM> of the compression piston <NUM>. Thus, a portion of the oil <NUM> that was in the oil bath is now inside of the fluid filled chamber <NUM>.

As the shock absorber continues to compress and rebound, more oil transfers over into the fluid filled chamber <NUM>. The fluid filled chamber <NUM> then starts to become overfilled with the oil <NUM>. Depending on the amount of overfilling having occurred in the fluid filled chamber <NUM>, the vehicle may hit a bump that causes the shock absorber to compress to the extent that the IFP <NUM> moves upwards along the shaft <NUM> such that it becomes positioned within the recess <NUM>. Since the IFP <NUM> has an outside seal <NUM> and an inside seal <NUM>, the IFP <NUM> moves into the recess <NUM> enough that it loses its seal between the shaft <NUM> and the inner surface of the wall of the air chamber <NUM>. A gap between the shaft <NUM> and the IFP <NUM> is created such that the oil <NUM> then moves out of the fluid filled chamber <NUM> and through the passageway <NUM> along the leak path <NUM>. The oil <NUM> then leaks back along the exterior of the fluid filled chamber <NUM> and falls once again into the oil bath.

Thus, the combination of the compression and rebound movements of the monotube damper <NUM>, along with the design of the seal head <NUM> within a U-Cup <NUM> as well as the leak path <NUM> that includes the recess <NUM> etched into the shaft <NUM> and the passageway <NUM> enables an oil to be recirculated throughout the shock absorber. Such a recirculation system eliminates the friction occurring in conventional systems that function to keep two oils within a shock absorber separated.

Claim 1:
A damper (<NUM>) comprising a recirculation system configured for using only one type of oil, said recirculation system comprising:
a cartridge (<NUM>) comprising a compression damper (<NUM>) of a shock absorber, said compression damper comprising
a fluid filled chamber (<NUM>),
a single adjustable fluid circuit configured for controlling a damping rate associated with multiple compression speeds of said shock absorber, wherein said single adjustable fluid circuit comprises:
a fluid passageway (<NUM>) through a base valve (<NUM>);
characterised by
a positionally adjustable floating shim stack (<NUM>) positioned at one end of said fluid passageway (<NUM>), said positionally adjustable floating shim stack (<NUM>) configured for selectively blocking a flow of fluid through said fluid passageway;
a leak path (<NUM>) configured for, upon compression, enabling oil to leak from said fluid filled chamber (<NUM>) of said compression damper (<NUM>) to a position exterior to said fluid filled chamber, wherein said leak path is part of said recirculation system of said shock absorber, said leak path comprising
a recess (<NUM>) in a shaft (<NUM>) of said compression damper (<NUM>), wherein during said compression an independent floating piston (<NUM>) is pushed upwards along said shaft by said flow of said oil until reaching said recess (<NUM>), at which point said oil leaks through a gap between a surface of said recess (<NUM>) and said independent floating piston (<NUM>), wherein said recess comprises
a curvature at one side configured for guiding said oil toward a wall of an air chamber (<NUM>) of said compression damper (<NUM>) and
a passageway (<NUM>) in said wall of said air chamber through which said oil flows.