Abstract:
A bicycle fork leg including a pressurized gas chamber functioning as a shock absorber and a piston adjacent to the bicycle fork leg. A movable compression rod which moves toward the piston when a force is imparted to the bicycle leg. A rubber or compliant member within the piston. The movable compression rod coming in contact with the compliant member to reduce low amplitude high frequency shocks.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the field of bicycle forks and in particular, to the spring system incorporated into bicycle forks. 
         [0003]    2. Description of the Prior Art 
         [0004]    A bicycle fork is the portion of a bicycle that holds the front wheel and allows the rider to steer and balance the bicycle. A fork consists of two fork ends which hold the front wheel axle, two blades which join at the fork crown, and a steering tube which is attached to the handle bars. 
         [0005]    On most mountain bicycles, the fork contains a set of shock absorbers so that the blades typically consist of upper and lower telescoping tubes which are called legs. 
         [0006]    A portion of the legs is the shock absorber which usually consists of two parts: a spring and a damper. The spring can be a metal coil but more commonly is now compressed air. Air springs utilize the thermodynamic property of gasses that their pressures increase as they are compressed adiabatically. The spring constant can be adjusted by adjusting the air pressure. This allows a fork to be tuned to a rider&#39;s weight. 
         [0007]    The damper usually forces oil to pass through one or more small openings in the suspension fork. 
         [0008]    In a traditional system, the compression rod which is usually a hard material such as aluminum or plastic pushes directly on the piston. The piston also usually is made out of aluminum, plastic or similar material. Until the load in the compression rod exceeds the static friction of the piston assembly seal, the suspension does not compress. The result is an undesirable harshness. 
         [0009]    U.S. Pat. No. 6,592,136 discloses a standard connection between a piston assembly and a compression rod assembly. U.S. Pat. No. 2,212,759 discloses rubber isolators  28  and  47 . 
         [0010]    There is a significant need for an improved suspension system in a bicycle fork that addresses the problems set forth above. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is an isolator within a piston to reduce the transmission of high frequency/low amplitude vibration to the rider and eliminate piston seal breakaway harshness. The suspension consists of a telescoping leg within a lower casting. The leg contains a top cap assembly fixed to the leg, a piston assembly movable within the leg, and a lower cap assembly fixed to the leg. The piston assembly contains a seal which contacts the inside of the leg. The leg, top cap assembly and piston assembly define a pressurized gas chamber. A valve in the top cap assembly is fixed to allow adjustment of the gas pressure within the chamber. A compression rod assembly is fixed to the lower casting and contains a head that contacts an isolator within the piston assembly. 
         [0012]    The compression rod assembly applies a load to the piston assembly when a bump is encountered. If the load is below the static friction between the piston assembly seal and fork leg, then the isolator deforms, allowing compression of the suspension without translation of the piston. Once the load exceeds the static friction of the piston assembly seal, the piston translates which reduces the volume of the gas chamber, resulting in a higher pressure. 
         [0013]    The fork consists of a telescoping assembly with a spring system using a compressed air chamber. The compression rod moves upward with the wheel when a bump is encountered. This translates the piston, compressing the air chamber, resulting in a higher pressure. This creates a position dependent force, or spring. In a traditional system, the rod, which is usually a hard material like aluminum or plastic, pushes directly on the piston. The piston is also usually made of aluminum, plastic or similar material. In the present invention system, a rubber or other compliant member creates a buffer between the compression rod and piston. 
         [0014]    The present invention has the following advantages: 
         [0015]    The invention provides a soft connection between the compression rod and the piston, thereby isolating high frequency/low amplitude vibration; 
         [0016]    The invention eliminates harshness transmitted to the rider due to static friction of the piston seal; and 
         [0017]    The present invention reduces friction effects transmitted to the rider due to seal drag on the moving piston. 
         [0018]    It is an object of the present invention to put a rubber piece between the end of the compression rod and the piston itself so that the rubber can compress and allow the wheel to move slightly before it has to break the seal friction and start the piston moving upwards. This has the biggest effect on low amplitude high frequency types of bumps. 
         [0019]    It is a further object of the present invention to add a rubber seal around the OD of the piston that keeps the air captured in the chamber and there is a rubber cylinder pressed into the bottom of the piston and a compression rod contacts that rubber. That is the innovation. It is an isolator between the rod and the piston. 
         [0020]    It is additionally an object of the present invention to lessen the transmission of harshness through to the rider. For example, if the piston seal creates five pounds of friction then that friction creates a step force that would transmit through to the rider before the tire can move upwards. By putting a compliant member between the compression rod and the piston it can allow the wheel to begin its movement before it has to break that friction and transfer the force to the piston. 
         [0021]    Further novel features and other objects of the present invention will become apparent from the following detailed description, discussion and the appended claims, taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    Referring particularly to the drawings for the purpose of illustration only and not limitation, there is illustrated: 
           [0023]      FIG. 1  is a side elevational view in partial cross-section of a bicycle fork including the present invention seal; and 
           [0024]      FIG. 2  is a detailed cross-sectional view illustrating the present invention seal in place between the piston and the gas chamber compression spring. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Although specific embodiments of the present invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims. 
         [0026]    Referring to  FIGS. 1 and 2 , there is illustrated one-half of a bicycle fork leg  10  which includes conventional parts and the present invention incorporated into the fork leg  10 . A conventional bicycle fork has two such fork legs  10  which are parallel to each other and supported by a crown  100 . The crown is affixed to a steerer tube which in turn is affixed to handlebars. 
         [0027]    The fork leg  10  includes a top cap assembly  20  which is fixed to the fork leg  10 . The top cap assembly includes a pressurized gas chamber  30  which is filled with gas such as air and which acts as a shock absorbing spring. The pressurized gas chamber  30  includes a valve  22  by which the amount of gas within the pressurized gas chamber can be adjusted and a seal  24  to seal the top end of the pressurized gas chamber  30 . The valve  22  in the top cap assembly  20  is fixed to allow adjustment of the gas pressure within the chamber of the pressurized gas chamber  30 . The valve  22  and seal  24  are incorporated into the top cap body  26  located at the top end  32  of the pressurized gas chamber  30 . 
         [0028]    The fork leg  10  also comprises a piston assembly  60  which is movable within the fork leg  10 . The piston assembly  60  includes a seal  62  which contacts the inside  8  of the fork leg  10 . 
         [0029]    The piston assembly  60  also includes a piston body  64 , a glide ring  70  and a rubber piece  90 . Partially inserted into the fork leg  10  is a compression rod assembly  40  which includes a compression rod  42  which is movable up and down within the fork leg  10  and towards the pressurized gas chamber  30  when the wheel to which the fork leg  10  is attached hits a bump. To facilitate the up and down movement of the compression rod  42 , the compression rod assembly  40  further comprises a top out spring  46  adjacent the lower end  48  of the compression rod assembly  40 , which in turn is connected to a top out spacer  50 . The compression rod assembly  40  further includes a head  66 . 
         [0030]    A lower casting  80  includes an upper bushing  52 , a lower bushing  54 , a foam ring  63 , and a wiper  68  to facilitate movement of the leg  10 . The glide ring  70  further facilitates movement of the piston  64  which is pushed by the compression rod assembly  40 . The piston assembly  60  lies adjacent to the lower end  31  of the gas compression chamber  30 . The lower end  41  of the fork leg  10  includes an end cap body  43 . 
         [0031]    The present invention is the rubber piece  90  more generally defined as a compliant member, which functions as an isolation member between the head  66  of top end  45  of the compression rod  40  and the piston  64  so that upon an upward movement of the compression rod  40 , the rubber piece  90  can be compressed by a few millimeters. That is the innovation of the present invention. The rubber piece or cylinder  90  is an isolator between the compression rod  40  and the piston  64 . 
         [0032]    Discussed further, the present invention is to place a rubber piece  90  between the top end  45  of the compression rod  42  and the piston  64  so that the rubber  90  can compress a few millimeters which allows the wheel to move slightly before it has to break the seal friction required for piston movement. This invention is expected to have the highest effect on low magnitude high frequency types of bumps. 
         [0033]    The insertion of the rubber piece  90  provides a soft connection between the compression rod assembly  40  and the piston assembly  60 , thereby isolating high frequency. low amplitude vibrations. 
         [0034]    In summary, the fork consists of a telescoping assembly with the spring system using a compressed air chamber  30 . A compression rod  42  moves with a wheel to which the fork is attached when a bump is encountered by the wheel. This upward movement of the compression rod  40  translates to a piston  64 , compressing the air chamber  30 , resulting in a higher pressure. 
         [0035]    The suspension consists of a fork leg  10  telescoping within the lower casting  80 . The fork leg  10  contains a top cap assembly  20  fixed to the fork leg  10 , a piston assembly  60  movable within the fork leg  10  and a lower cap assembly  41  affixed to the fork leg  10 . The piston assembly  60  contains a seal  62  which contacts the inside of the fork leg  10 . The fork leg  10 , top cap assembly  20  and piston assembly  60  define a pressurized gas chamber  30 . A valve  22  in the top cap assembly  20  allows adjustment of the gas pressure within the chamber. A compression rod assembly  40  is fixed to the lower casting and contains a head  66  that contacts the rubber piece  90  within the piston assembly  60 . The lower casting is illustrated with the inner surface of the lower casting numbered  80  and the outer surface of the lower casting numbered  80 A. 
         [0036]    The compression rod assembly  40  applies a load to the piston assembly  60  when a bump is encountered. If the load is below the static friction of the piston seal  62 , the rubber piece  90  deforms, allowing compression of the suspension without translation of the piston body  64 . Once the load exceeds the static friction of the piston seal  62 , the piston body  64  translates which reduces the volume of the pressurized gas chamber  30  resulting in a higher pressure. 
         [0037]    The key to the present invention is an isolator within a piston to reduce the transmission of high frequency amplitude vibration to the rider and eliminate piston seal breakaway harshness. 
         [0038]    In a traditional system, the compression rod  42  which is usually a hard material like aluminum or plastic pushes directly on the piston body  64 , also usually made of aluminum, plastic or similar material. The innovation of the present invention is the insertion of a rubber or other compliant member to create a buffer between the compression rod  42  and the piston body  64 . 
         [0039]    Of course the present invention is not intended to be restricted to any particular form or arrangement, or any specific embodiment, or any specific use, disclosed herein, since the same may be modified in various particulars or relations without departing from the spirit or scope of the claimed invention hereinabove shown and described of which the apparatus or method shown is intended only for illustration and disclosure of an operative embodiment and not to show all of the various forms or modifications in which this invention might be embodied or operated.