Abstract:
An improvement to damping cylinders in which the damping fluid needs to be separated from a gas is disclosed. In particular, an annular bladder is used. An annular bladder allows for a control shaft to extend at least a portion of the length of the damping cylinder. This configuration effectively and simply reduces most issues that result from when an IFP is used for the same purpose.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. patent application Ser. No. 11/291,058 filed Nov. 29, 2005, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is generally related to the field of damping cylinders. More particularly, the present invention is an improvement to damping cylinders previously having both internal floating pistons and shafts. 
     2. Description of the Related Art 
     The use of internal floating pistons, also known as and will be referred to herein as IFPs, in damping cylinders to compensate for volume changes due to the displacement of damping fluid within the damping cylinder and thermal expansion of the damping fluid, is well known. For example, the following Fox Racing Shox (Fox Factory, Inc.) patents depict the use of an IFP: U.S. Pat. No. 6,135,434; U.S. Pat. No. 6,296,092; U.S. Pat. No. 6,311,962; U.S. Pat. No. 6,360,857; U.S. Pat. No. 6,415,895; and U.S. Pat. No. 6,604,751 and are incorporated by reference herein as are all the patents and published patent applications referred to within this patent application. 
     Furthermore, it is often common to have shafts extending the longitudinal length of the damping cylinder. The shaft may comprise a piston rod, a valve control rod, or a combination of both. For example, in FOX U.S. Pat. No. 6,360,857, we depict the use of a shaft extending the length of the damping cylinder wherein the shaft comprises a piston shaft and a control shaft. In another FOX patent, the shaft passes through the IFP. See U.S. Pat. No. 6,415,895 ( FIG. 7 ). 
     SUMMARY OF THE INVENTION 
     The present invention is an extremely simple to implement improvement and innovation in damping cylinders, and especially those damping cylinders that may have originally been designed to have both IFPs and shafts or in any other damping cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a simplified schematic depicting a prior art damping cylinder having an IFP and a shaft. 
         FIG. 2  is a cross section along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a simplified schematic of a damping cylinder according to a first exemplary embodiment of the invention. 
         FIG. 4  is a cross section along line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a detailed cross-section of a lower portion a damping cylinder according to an exemplary embodiment of the invention. 
         FIG. 6  is a simplified schematic of a damping cylinder according to a second exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a simplified schematic depicting a prior art damping cylinder having an IFP and a shaft.  FIG. 2  is a cross section along line  2 - 2  of  FIG. 1 . Damping cylinders such as these have widespread application in many diverse devices, including but not limited to, shock absorbers and forks for two-wheeled vehicles. Damping cylinder  100  generally comprises a cylinder body  110  having an inner wall  110   a  and that is divided into fluid chamber  103  and fluid chamber  115  by a partition  117 . Partition  117  may comprise a wall (as shown) or a piston (not shown) sealed against inner wall  110   a . Fluid will be able to flow into (arrow A) and out of (arrow B) fluid chamber  115  via conventional fluid flow control valves V 1 , V 2 , such as check valves, spring-biased valves or deflectable disc valves (shown schematically and collectively in black-box form by valves V 1 , V 2 ). In other situations, such as will be described with respect to  FIG. 6 , fluid chamber  115  will contain an axially movable shaft  120  supporting a piston  195  having a seal  160   a  and are used to impart a force onto and displace the damping fluid within fluid chamber  115 . Fluid chamber  115  generally comprises a single open volume defined by inner walls  110   a  of cylinder body  110 . Furthermore, extending a substantial length of cylinder body  110  is a shaft  120  having a shaft surface  120   a . As previously mentioned, the shaft  120  may comprise a piston rod, a valve control rod, or a combination of both. For example, as shown in  FIG. 1 , by turning knob K on the end of shaft  120 , through a mechanism passing through shaft  120 , it is possible to control one or more flow characteristics of valves V 1 , V 2 . While in no way critical to this invention, valves V 1 , V 2  may control, for example, rebound damping, low and/or high speed compression damping, lockout, bleed, or blowoff threshold. 
     Cylinder body  110  will also contain an IFP  150  that divides fluid chamber  115  into first and second fluid chambers  115   a ,  115   b , respectively. While in  FIG. 1 , IFP  150  is backed by a pressurized and compressible fluid, typically in the form of a gas G contained within second fluid chamber  115   b , in other situations the IFP may be backed by a coil spring (not shown). The pressure of gas G within second fluid chamber  115   b  can either be at ambient (atmospheric) pressure when the damping cylinder is at full extension or may optionally be varied using optional pressurization valve  170 , which can be a Schrader Valve (shown schematically). To prevent pressurized gas G within second fluid chamber  115   b  or damping fluid within first fluid chamber  115   a  from intermingling, seals, typically in the form of o-rings  160   a ,  160   b , will be used to seal the IFP  150  against the inner wall  110   a  of cylinder body  110  and the outer surface  120   a  of shaft  120  (see also e.g. Fox U.S. Pat. No. 6,415,897 ( FIG. 7 )). 
     As is known, IFP  150  will be able to move longitudinally within cylinder body  110 , as shown by arrows C dependent upon the flow direction of the damping fluid within first fluid chamber  115   a . However, due to the seals running against the inner walls of cylinder body  110   a  and the outer surface of shaft  120   a , friction is created. In many damper applications, the effects of friction are undesirable. Finally, for there to be a good seal between the seals and the inner walls  110   a  of cylinder body  110  and the outer surface  120   a  of shaft  120 , typically the inner walls  110   a  of cylinder  110  and the outer surface  120   a  of shaft  120  must be properly prepared with a smooth high-quality surface finish and toleranced/dimensioned, adding cost to the overall damping cylinder. 
     Having described the prior art, a damping cylinder according to multiple exemplary embodiments of the invention will now be described. 
       FIG. 3  is a simplified schematic of a damping cylinder according to a first exemplary embodiment of the invention.  FIG. 4  is a cross section along line  4 - 4  of  FIG. 3 . When referring to  FIGS. 3 and 4 , where similar elements are found in  FIGS. 1 and 2 , the same reference numerals are used. 
     According to an exemplary embodiment of the invention, IFP  150  is simply replaced with a properly and securely mounted annular bladder  200  (see  FIG. 5 ). Annular bladder  200  will typically comprise a unitary body having outer and inner annular walls  200   a ,  200   c , respectively that are substantially parallel to shaft  120  and connected to each other by a third wall  200   b  that closes off an end of annular bladder  200  so as to define a bladder fluid chamber  210  within bladder  200 . Bladder  200  has no structural connection with the bulk of the damping cylinder  100 , except in the area of base  175 . Cf. U.S. Pat. No. 4,700,815 (edge of bag  44  is fixed around the inner end of the tubular extension  30  of the cap  22  by means of a spring ring  48 ). The gas G is contained within the bladder fluid chamber  210  defined by annular bladder  200 . As shown in  FIG. 4 , annular bladder  200  will surround shaft  120  without there being any intermediate structures and with there being a space  205  between shaft  120  and bladder  200  for fluid to be able to fill. The annular bladder  200  may completely surround shaft  120  as shown in the present FIGs, or may at least partially surround the shaft  120  and have, for example, a “c”-shape (not shown). Shaft  120  will extend through space  205  defined by inner annular wall  200   c . Furthermore, bladder  200  will also not necessarily come into contact with (and therefore have a clearance from) the inner walls  110   a  of cylinder body  110 . Bladder  200  will typically be constructed from an elastomeric material, capable of withstanding typical damping fluids and elevated temperatures, for example, a high-grade rubber. 
       FIG. 5  depicts an exemplary method for attaching bladder  200  to cylinder base  175 . The open end of bladder  200  will have mounting beads  201  and inner  207  and outer sealing beads  203  formed thereon. Mounting beads  201  will be securely press-fit into grooves  176  of cylinder base  175 . Inner sealing beads  207  will be pressed against shoulder  128  of shaft  120  to create a fluid seal for space  205  as well as provide additional structural support for inner bladder wall  200   c . Outer sealing beads  203  will be pressed against inner walls  110   a  of cylinder body  110  to create another fluid seal as well as provide additional structural support for outer bladder wall  200   a.    
     It should be noted that there is a clearance  204  between the outer walls  200   a  of bladder  200  and the inner walls  110   a  of cylinder body  110 . This clearance, as well as space  205  allow for the purging of excess air and oil from cylinder body  110  during the manufacture of damping cylinder  100 . In particular, damping cylinder  110  is manufactured generally as follows:
         1) Damping cylinder  100  is inverted from the orientation shown in  FIGS. 3-6 ;   2) Oil is filled into fluid chamber  115  in the same way as if one were filling a cup;   3) Bladder  200  is inserted into the oil-filled chamber  115 ;   4) Excess oil flows out clearance  204  and space  205 ;   5) Cylinder base  175  is used to seal off damping cylinder  100 .       

     Finally, as can be seen in  FIG. 5 , shaft  120  actually may comprise a stationary outer shaft  125  and an inner control rod  127 . Inner control rod  127  may be connected to knob K and used to control valves V 1 , V 2 , as mentioned above. In some instances, it is possible for there to be multiple control rods associated with multiple valves and/or knobs. 
     The use of bladders, in general, is known in the art of damping cylinders. Furthermore, annular bladders have also been used. For example, annular bladders were described in U.S. Pat. No. 2,571,279 and U.S. Pat. No. 4,700,815. However, in these patents, the bladder and the shaft are not designed to be immediately adjacent each other without any intermediate structures, as they are in the current exemplary embodiments of the invention. 
     Therefore, bladders separating a single fluid chamber into two fluid chambers and having a shaft passing there through have not been implemented. It is assumed that they were not used in such situations because it was not readily evident how to effectively maintain the fluid seal between the shaft  120  and the hole that would be needed in the bladder for the shaft to pass through (cf. Fox U.S. Pat. No. 6,415,895 (o-rings between piston and rod)). Note that in U.S. Pat. No. 2,708,112, a metallic member is used to define a reservoir and surrounds a shaft, but it is intended in that patent that fluid can pass from inside the reservoir to outside the reservoir. However, in the present invention, damping fluid is completely retained on one side of the bladder in the bladder fluid chamber and we have found a way to implement a bladder around a shaft without having to worry about any sealing losses due to, for example, degradation of o-rings. 
     Thus, according to this exemplary embodiment of the invention, as fluid either enters cylinder body  110  via valve V 1  or is moved due to shaft  120  and piston  195  ( FIG. 6 ), the increasing volume of fluid within chamber  115  will result in the partial compression of bladder  200  against the internal pressure of gas G in the direction of arrows F. Then, as fluid either leaves the cylinder body  110  via valve V 2  or has more volume to fill due to the retraction of shaft  120  and piston  195 , the internal pressure of gas G will result in the expansion of the bladder  200  against the fluid to prevent, for example, the creation of a vacuum within cylinder body  110  or the cavitation of the fluid within cylinder body  110 . While as the bladder  200  expands and contracts it may come into contact with the inner wall  110   a  of the cylinder body  110  and/or the outer surface  120   a  of shaft  120 , friction is negligible and much lower than would result from an IFP application. Furthermore, as opposed to applications in which the “bladder” may be fixed at both its ends (e.g. U.S. Pat. No. 4,700,815), the presently described bladder is much more easily and flexibly compressed. 
     While the invention has been disclosed with reference to certain exemplary features, the scope of the invention shall only be defined by the appended claims.