Abstract:
A bicycle shock absorber for differentiating between rider-induced forces and terrain-induced forces includes a first fluid chamber having fluid contained therein, a piston for compressing the fluid within the fluid chamber, a second fluid chamber coupled to the first fluid chamber by a fluid communication hose, and an inertial valve disposed within the second fluid chamber. The inertial valve opens in response to terrain-induced forces and provides communication of fluid compressed by the piston from the first fluid chamber to the second fluid chamber. The inertial valve does not open in response to rider-induced forces and prevents communication of the fluid compressed by the piston from the first fluid chamber to the second fluid chamber.

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/811,784, filed Mar. 29, 2004, now U.S. Pat. No. 6,991,076, which is a continuation of U.S. patent application Ser. No. 09/919,582, filed Jul. 31, 2001, now U.S. Pat. No. 6,722,678, which is a continuation of U.S. patent application Ser. No. 09/288,003, filed April 6, 1999, now U.S. Pat. No. 6,267,400. 

   INCORPORATION BY REFERENCE 
   The entireties of U.S. patent application Ser. No. 10/811,784, filed Mar. 29, 2004, U.S. patent application Ser. No. 09/919,582, filed Jul. 31, 2001, and U.S. patent application Ser. No. 09/288,003, filed Apr. 6, 1999, are hereby expressly incorporated by reference herein and made a part of this specification. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to the field of bicycle suspensions. More particularly, the invention relates to a damping enhancement system for a bicycle. 
   2. Description of the Related Art 
   For many years bicycles were constructed using exclusively rigid frame designs. These conventional bicycles relied on air-pressurized tires and a small amount of natural flexibility in the frame and front forks to absorb the bumps of the road and trail. This level of shock absorption was generally considered acceptable for bicycles which were ridden primarily on flat, well maintained roads. However, as “off-road” biking became more popular with the advent of All Terrain Bicycles (“ATBs”), improved shock absorption systems were needed to improve the smoothness of the ride over harsh terrain. As a result, new shock absorbing bicycle suspensions were developed. 
   Two such suspension systems are illustrated in  FIGS. 1 and 2 . These two rear suspension designs are described in detail in Leitner, U.S. Pat. No. 5,678,837, and Leitner, U.S. Pat. No. 5,509,679, which are assigned to the assignee of the present application. Briefly,  FIG. 1  illustrates a telescoping shock absorber  110  rigidly attached to the upper arm members  103  of the bicycle on one end and pivotally attached to the bicycle seat tube  120  at the other end (point  106 ).  FIG. 2  employs another embodiment wherein a lever  205  is pivotally attached to the upper arm members  203  and the shock absorber  210  is pivotally attached to the lever  205  at an intermediate position  204  between the ends of the lever  205 . 
   There are several problems associated with the conventional shock absorbers employed in the foregoing rear suspension systems. One problem is that conventional shock absorbers are configured with a fixed damping rate. As such, the shock absorber can either be set “soft” for better wheel compliance to the terrain or “stiff” to minimize movement during aggressive pedaling of the rider. However, there is no mechanism in the prior art which provides for automatic adjustment of the shock absorber setting based on different terrain and/or pedaling conditions. 
   A second, related problem with the prior art is that conventional shock absorbers are only capable of reacting to the relative movement between the bicycle chassis and the wheel. In other words, the shock absorber itself has no way of differentiating between forces caused by the upward movement of the wheel (i.e., due to contact with the terrain) and forces caused by the downward movement of the chassis (i.e., due to movement of the rider&#39;s mass). 
   Thus, most shock absorbers are configured somewhere in between the “soft” and “stiff” settings (i.e., at an intermediate setting). Using a static, intermediate setting in this manner means that the “ideal” damper setting—i.e., the perfect level of stiffness for a given set of conditions—will never be fully realized. For example, a rider, when pedaling hard for maximum power and efficiency, prefers a rigid suspension whereby human energy output is vectored directly to the rotation of the rear wheel. By contrast, a rider prefers a softer suspension when riding over harsh terrain. A softer suspension setting improves the compliance of the wheel to the terrain which, in turn, improves the control by the rider. 
   Accordingly, what is needed is a damping system which will dynamically adjust to changes in terrain and/or pedaling conditions. What is also needed is a damping system which will provide to a “stiff” damping rate to control rider-induced suspension movement and a “soft” damping rate to absorb forces from the terrain. Finally, what is needed is a damping system which will differentiate between upward forces produced by the contact of the wheel with the terrain and downward forces produced by the movement of the rider&#39;s mass. 
   SUMMARY OF THE INVENTION 
   A bicycle shock absorber for differentiating between rider-induced forces and terrain-induced forces including a first fluid chamber having fluid contained therein. A piston is configured to compress the fluid within the fluid chamber. A second fluid chamber is coupled to the first fluid chamber by a fluid communication hose and an inertial valve is disposed within the second fluid chamber. The inertial valve is configured to open in response to terrain-induced forces and provides communication of fluid compressed by the piston from the first fluid chamber to the second fluid chamber. The inertial valve does not open in response to rider-induced forces and prevents communication of the fluid compressed by the piston from the first fluid chamber to the second fluid chamber. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention can be obtained from the following detailed description in conjunction with the following drawings, in which: 
       FIG. 1  illustrates a prior art rear suspension configuration for a bicycle. 
       FIG. 2  illustrates a prior art rear suspension configuration for a bicycle. 
       FIG. 3  illustrates one embodiment of the present invention. 
       FIG. 4  illustrates an embodiment of the present invention reacting to a rider-induced force. 
       FIG. 5  illustrates an embodiment of the present invention reacting to a terrain-induced force. 
       FIG. 6  illustrates the fluid refill mechanism of an embodiment of the present invention. 
       FIG. 7  illustrates another embodiment of the present invention. 
       FIG. 8  is an enlarged schematic view of an embodiment of the present invention wherein the primary tube is mounted directly to an upper arm member and the remote tube is connected to an upper arm member of a bicycle. An angled position of the remote tube is shown in phantom. 
       FIG. 9  is an enlarged schematic view of an embodiment of the present invention wherein the primary tube is mounted directly to an upper arm member and the remote tube and the primary tube are a single unit. An angled position of the remote tube is shown in phantom. 
       FIG. 10  is an enlarged schematic view of embodiment of the present invention wherein the primary tube is mounted to a lever and the remote tube is connected to an upper arm member of a bicycle. An angled position of the remote tube is shown in phantom. 
       FIG. 11  is an enlarged schematic view of an embodiment of the present invention wherein the primary tube is mounted to a lever and the remote tube and the primary tube are a single unit. An angled position of the remote tube is shown in phantom. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A damping enhancement system is described which differentiates between upward forces produced by the contact of the bicycle wheel with the terrain and downward forces produced by the movement of the rider&#39;s mass. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one of ordinary skill in the art that the present invention may be practiced without some of these specific details. In other instances, certain well-known structures are illustrated and described in limited detail to avoid obscuring the underlying principles of the present invention. 
   An Embodiment of the Damper Enhancement System 
   One embodiment of the present damper enhancement system is illustrated in  FIG. 3 . The apparatus is comprised generally of a primary tube  302  and a remote tube  304  coupled via a connector hose  306 . 
   The damper enhancement system described hereinafter may be coupled to a bicycle in the same manner as contemporary shock absorbers (i.e., such as those illustrated in  FIGS. 1 and 2 ). For example, the damper enhancement system may be coupled to a bicycle as illustrated in  FIG. 1  wherein the upper mount  318  is pivotally coupled to the seat tube at point  106  and the lower mount  342  is fixedly coupled to the upper arm member  103 . Moreover, the damper enhancement system may be coupled to a bicycle as illustrated in FIG.  2  wherein the upper mount  318  is pivotally coupled to the seat tube at a point  206  and the lower mount  342  is fixedly coupled to a point  204  on lever  211 . These two constructions are illustrated in  FIGS. 8-9  and  FIGS. 10-11 , respectively. 
   In addition, depending on the particular embodiment of the damper enhancement system, the connector hose may be of varying lengths and made from varying types of material. For example, the connector hose  306  may be short and comprised of metal. In this case, the primary tube  302  and the remote tube  304  will be closely coupled together—possibly in a single unit. Such a construction is illustrated in  FIG. 9  and  FIG. 11 . By contrast, the connector hose may be long and comprised of a flexible material. In this case, the remote tube  304  may be separated from the primary tube  302  and may be independently connected to the bicycle (e.g., the remote tube may be connected to one of the wheel members such as upper arm member  103  in  FIG. 1 ).  FIG. 8  and  FIG. 10  illustrate such a construction, wherein the primary tube  302  is coupled to upper arm member  103  and the remote tube  304  is connected to the upper arm member  103  by a connector. Regardless of how the remote tube  304  is situated in relation to the primary tube  302 , however, the underlying principles of the present invention will remain the same. 
   A piston  308  on the lower end of a piston rod  310  divides the inside of the primary tube  302  into and upper fluid chamber  312  and a lower fluid chamber  314  which are both filled with a viscous fluid such as oil. The piston rod  310  is sealed through the cap with oil seals  316  and an upper mount  318  connects the piston to the chassis or sprung weight of the bicycle (e.g., to the seat tube). A lower mount  342  connects the primary tube  302  to the rear wheel of the bicycle via one or more wheel members (e.g., upper arm members  103  in  FIG. 1  or lever  205  of  FIG. 2 ). Longitudinally extending passages  320  in the piston  308  provide for limited fluid communication between the upper fluid chamber  312  and lower fluid chamber  314 . 
   An inertial valve  322  which is slightly biased by a lightweight spring  324  moves within a chamber  326  of the remote tube  304 . The lightweight spring  324  is illustrated in a fully extended state and, as such, the inertial valve  322  is illustrated at one endmost position within its full range of motion. In this position, fluid flow from the primary tube  302  to the remote tube  304  via the connector hose  306  is blocked or reduced. By contrast, when the lightweight spring  324  is in a fully compressed state, the inertial valve resides beneath the interface between the remote tube  304  and the connector hose  306 . Accordingly, in this position, fluid flow from the primary tube  302  to the remote tube  304  through the connector hose  306  is enabled. In one embodiment, the inertial valve  322  is composed of a dense, heavy metal such as brass. 
   Disposed within the body of the inertial valve  322  is a fluid return chamber  336 , a first fluid return port  337  which couples the return chamber  336  to the connector hose  306 , and a second fluid return port  339  which couples the return chamber  336  to remote fluid chamber  332 . A fluid return element  338  located within the fluid return chamber  336  is biased by another lightweight spring  340  (hereinafter referred to as a “fluid return spring”). In  FIG. 3  the fluid return spring  340  is illustrated in its fully extended position. In this position, the fluid return element  338  separates (i.e., decouples) the fluid return chamber  336  from the fluid return port  337 . By contrast, when the fluid return spring  340  is in its fully compressed position, the fluid return element  338  no longer separates the fluid return chamber  336  from the fluid return port  337 . Thus, in this position, fluid flow from the fluid return chamber  336  to the connector hose  306  is enabled. The operation of the inertial valve  322  and the fluid return mechanism will be described in detail below. 
   The remaining portion of the remote tube  304  includes a floating piston  328  which separates a gas chamber  330  and a fluid chamber  332 . In one embodiment of the present invention, the gas chamber  330  is pressurized with Nitrogen (e.g., at 150 p.s.i.) and the fluid chamber  332  is filled with oil. An air valve  334  at one end of the remote tube  322  allows for the gas chamber  330  pressure to be increased or decreased as required. 
   The operation of the damping enhancement system will be described first with respect to downward forces produced by the movement of the rider (and the mass of the bicycle frame) and then with respect to forces produced by the impact between the wheel and the terrain. 
   1. Forces Produced by the Rider 
   A rider-induced force is illustrated in  FIG. 4 , forcing the piston arm  310  in the direction of the lower fluid chamber  314 . In order for the piston  308  to move into fluid chamber  314  in response to this force, fluid (e.g., oil) contained within the fluid chamber  314  must be displaced. This is due to the fact that fluids such as oil are not compressible. If lightweight spring  324  is in a fully extended state as shown in  FIG. 4 , the inertial valve  322  will be “closed” (i.e., will block or reduce the flow of fluid from lower fluid chamber  314  through the connector hose  306  into the remote fluid chamber  332 ). Although the entire apparatus will tend to move in a downward direction in response to the rider-induced force, the inertial valve  322  will remain in the nested position shown in  FIG. 4  (i.e., it is situated as far towards the top of chamber  326  as possible). Accordingly, because the fluid in fluid chamber  314  has no where to flow in response to the force, the piston  308  will not move down into fluid chamber  314  to any significant extent. As a result, a “stiff” damping rate will be produced in response to rider-induced forces (i.e., forces originating through piston rod  310 ). 
   2. Forces Produced by the Terrain 
   As illustrated in  FIG. 5 , the damping enhancement system will respond in a different manner to forces originating from the terrain and transmitted through the bicycle wheel (hereinafter “terrain-induced forces”). In response to this type of force, the inertial valve  322  will move downward into chamber  326  as illustrated and will thereby allow fluid to flow from lower chamber  314  into remote chamber  332  via connector hose  306 . The reason for this is that the entire apparatus will initially move in the direction of the terrain-induced force while the inertial valve  322  will tend to remain stationary because it is comprised of a dense, heavy material (e.g., such as brass). Thus, the primary tube  302  and the remote tube  304  will both move in a generally upward direction and, relative to this motion, the inertial valve  322  will move downward into chamber  326  and compress the lightweight spring  324 . As illustrated in  FIG. 5  this is the inertial valve&#39;s “open” position because it couples lower fluid chamber  314  to remote fluid chamber  332  (via connector hose  306 ). 
   Once the interface between connector hose  306  and remote fluid chamber  332  is unobstructed, fluid from lower fluid chamber  314  will flow across connector hose  306  into remote fluid chamber  332  in response to the downward force of piston  308  (i.e., the fluid can now be displaced). As remote fluid chamber  314  accepts additional fluid as described, floating piston  328  will move towards gas chamber  330  (in an upward direction in  FIG. 5 ), thereby compressing the gas in gas chamber  330 . The end result, will be a “softer” damping rate in response to terrain-induced forces (i.e., forces originating from the wheels of the bicycle). 
   Once the inertial valve moves into an “open” position as described above, it will eventually need to move back into a “closed” position so that a stiff damping rate can once again be available for rider-induced forces. Thus, lightweight spring  324  will tend to move the inertial valve  322  back into its closed position. In addition, the return spring surrounding primary tube  302  (not shown) will pull piston rod  310  and piston  308  in an upward direction out of lower fluid chamber  314 . In response to the motion of piston  308  and to the compressed gas in gas chamber  330 , fluid will tend to flow from remote fluid chamber  332  back to lower fluid chamber  314  (across connector hose  306 ). 
   To allow fluid to flow in this direction even when inertial valve  322  is in a closed position, inertial valve  322  (as described above) includes the fluid return elements described above. Thus, as illustrated in  FIG. 6 , in response to pressurized gas in gas chamber  330 , fluid in remote fluid chamber  332  will force fluid return element  338  downward into fluid return chamber  336  (against the force of the fluid return spring  340 ). Once fluid return element  338  has been forced down below fluid return port  337 , fluid will flow from remote fluid chamber  332  through fluid return port  339 , fluid return chamber  336 , fluid return port  337 , connector hose  306 , and finally back into lower fluid chamber  314 . This will occur until the pressure in remote fluid chamber  336  is low enough so that fluid return element  338  can be moved back into a “closed” position (i.e., when the force of fluid return spring  340  is greater than the force created by the fluid pressure). 
   The sensitivity of inertial valve  322  may be adjusted by changing the angle with which it is positioned in relation to the terrain-induced force. For example, in  FIG. 5 , the inertial valve  322  is positioned such that it&#39;s movement in chamber  326  is parallel (and in the opposite direction from) to the terrain-induced force. This positioning produces the greatest sensitivity from the inertial valve  322  because the entire terrain-induced force vector is applied to the damper enhancement system in the exact opposite direction of the inertial valve&#39;s  322  line of movement. 
   By contrast, if the remote tube containing the inertial valve  322  were positioned at, for example, a 45 degree angle from the position shown in  FIG. 5  the inertial valve&#39;s  322  sensitivity would be decreased by approximately one half because only one half of the terrain-induced force vector would be acting to move the damper enhancement system in the opposite direction of the valve&#39;s line of motion. Thus, twice the terrain-induced force would be required to trigger the same response from the inertial valve  322  in this angled configuration.  FIGS. 8-11  illustrate the remote tube  304  positioned at an angle from the primary tube  302  (shown in phantom), With such a construction, the sensitivity of the inertial value  322  may be adjusted as described immediately above. 
   Thus, in one embodiment of the damper enhancement system the angle of the remote tube  304  in which the inertial valve  322  resides is manually adjustable to change the inertial valve  322  sensitivity. This embodiment may further include a sensitivity knob or dial for adjusting the angle of the remote tube  304 . The sensitivity knob may have a range of different sensitivity levels disposed thereon for indicating the particular level of sensitivity to which the damper apparatus is set. In one embodiment the sensitivity knob may be rotatably coupled to the bicycle frame separately from the remote tube, and may be cooperatively mated with the remote tube (e.g., with a set of gears). Numerous different configurations of the sensitivity knob and the remote tube  304  are possible within the scope of the underlying invention. The connector hose  306  of this embodiment is made from a flexible material such that the remote tube  304  can be adjusted while the primary tube remains in a static position. 
   Another embodiment of the damper enhancement system is illustrated in  FIG. 7 . Like the previous embodiment, this embodiment includes a primary fluid chamber  702  and a remote fluid chamber  704 . A piston  706  coupled to a piston shaft  708  moves within the primary fluid chamber  702 . The primary fluid chamber  702  is coupled to the remote fluid chamber via an inlet port  714  (which transmits fluid from the primary fluid chamber  702  to the remote fluid chamber  704 ) and a separate refill port  716  (which transmits fluid from the remote fluid chamber  704  to the primary fluid chamber  702 ). 
   An inertial valve  710  biased by a lightweight spring  712  resides in the remote fluid chamber  704 . A floating piston  720  separates the remote fluid chamber from a gas chamber  718 . In response to terrain-induced forces (represented by force vector  735 ), the inertial valve, due to its mass, will compress the lightweight spring  712  and allow fluid to flow from primary fluid chamber  702  to remote fluid chamber  704  over inlet port  714 . This will cause floating piston  720  to compress gas within gas chamber  718 . 
   After inertial valve  710  has been repositioned to it&#39;s “closed” position by lightweight spring  712 , fluid in remote fluid chamber  704  will force fluid refill element  722  open (i.e., will cause fluid refill spring  724  to compress). Thus, fluid will be transmitted from remote fluid chamber  704  to primary fluid chamber  702  across refill port  716  until the pressure of the fluid in remote fluid chamber is no longer enough to keep fluid refill element  722  open. Thus, the primary difference between this embodiment and the previous embodiment is that this embodiment employs a separate refill port  716  rather than configuring a refill port within the inertial valve itself.