Abstract:
In a preferred embodiment, a light weight telescope assembly for bicycles that is readily adjustable by riders in the field and that provides smooth action of the suspension system. This telescope assembly contains roller bearings to reduce stiction and prevent torsional losses. The adjustment mechanism includes an adjustable outer race shim composed of two oppositely tapered races moving longitudinally in relation to each other, thereby causing their combined thickness to expand or contract thus allowing the bearing pre-load to be adjustable. Integral with this adjustable pre-load mechanism is a bayonet-style collar whose design enables bearing pre-load adjustment from a position that is readily accessible by consumers. In addition, this collar enables greater geometric latitude on the shape of the inner tube, thereby enabling significant strengthening of the telescoping assembly using light weight materials and lower cost manufacturing processes that hitherto have been unachievable.

Description:
[0001]    Related Applications:  
                                                           5,320,374   June 1994   Farris et al.           5,494,302   February 1996   Farris et al.           5,702,092   December 1997   Farris et al.           5,924,714   July 1999   Farris et al.           6,007,056   December 1999   Farris et al.           6,155,541   December 2000   Farris et al.           5,509,675   April 1996   Barnett           5,195,766   March 1993   Dohrmann et al.           4,971,344   November 1990   Turner           4,609,202   September 1986   Miyakushi et al.                      
 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to bicycle suspension systems and more particularly to a suspension fork assembly. This invention is an improvement on the system first described by Farris et al. U.S. Pat. No. 5,320,374 and subsequent patents (U.S. Pat. Nos. 5,494302, 5,702,092, 5,924,714, 6,007,056, and 6,155,541). The related patents address the geometric configuration of two tubes, one inside the other, both containing several fiats permitting the insertion of hardened races and roller needle bearings between the two tubes. The resulting telescoping action provides longitudinal motion, but prohibits torsional movement. A key objective is to achieve a smooth, plush feel of the telescoping action.  
           [0004]    2. Description of the Prior Art  
           [0005]    Various suspension systems have been proposed and developed for bicycles. Many of these systems utilize a pair of telescoping assemblies between which the front wheel is mounted. Each assembly comprises an outer tube and an inner tube which is free to move in and out of the outer tube and is cushioned by a damper of one sort or another. The outer tubes are connected at the lower ends to the bicycle axle of the front wheel and the upper ends of the inner tube are connected together in a fashion similar to the usual upper end of a bicycle fork.  
           [0006]    As is known to those skilled in the art, these types of suspension systems use anti-friction bushings to allow free movement of the inner tube within the outer tube. These bushings have undesirable static friction called “stiction.” Because of this, the suspension systems using such bushings tend to stick and release. In addition, the two telescoping assemblies also have to be fixed together in some manner as through a “U” shaped yoke at the upper ends of the tubes to eliminate twisting. Even with this “U” shaped yoke the torsional stiffness of these types of assemblies is still limited.  
           [0007]    A prior art example of a system which overcomes this issue is shown in Farris et al. U.S. Pat. No. 5,320,374 and subsequent applications. In this example an improved form of suspension system is described using an outer tube which is adapted to be mounted in and extend through the head tube of the bicycle frame and an inner tube connected to the fork of the bicycle which telescopes within the outer tube. The inner surface of the outer tube and the outer surface of the inner tube each have a plurality of axially arranged opposing longitudinal flat sections such as four on each tube. A plurality of hardened steel inner race shims are positioned longitudinally on the flats of the inner tube. A plurality of hardened steel outer race shims are positioned longitudinally on the flats of the outer tube. A plurality of needle bearings are disposed between the tubes in between the respective inner and outer race shims. This arrangement allows the two tubes to freely telescope in and out with respect to one another without any significant static friction and also serves to transmit the torsional steering force from the outer tube to the inner tube. This particular system is used extensively today because it can bear a combination of loads comprising very high radial loads and at the same time provide stable and tight rotational motion in steering of the front wheel through the suspension system from the handlebars.  
           [0008]    Several problems exist, however, with the practicality of the needle bearing system. First, the preferred embodiment and alternate embodiment described in the prior art for the purpose of adjusting bearing pre-load are impractical, difficult to adjust and expensive. Tolerance stack-up during the manufacturing process makes it difficult and costly to attain the desired bearing pre-load. Assembly time renders the adjustment of multiple shims in the described embodiments impractical and expensive. Excessive bearing pre-load develops objectionable noise, excessive heat and wear, and a non-smooth feeling ride. Insufficient bearing pre-load encourages migration of the bearings and races, resulting in a poorly or non-functioning unit. Consumer preference would be to have the ability to adjust the bearing pre-load depending on the ride and to be able to do it quickly and simply. The prior art designs are impractical as the adjustment mechanisms are located on the outer tube which is fixed inside the head tube of the bicycle and inaccessible without disassembly of the front fork.  
           [0009]    Secondly, the highly stressed inner tube must be formed of a material and in a manner such that it bends rather than breaks. High strength steel is commonly used for the inner tube for this purpose, but it is heavy and counter to the consumer&#39;s preference. Lighter materials such as Aluminum in combination with strengthening processes such as shot-peening to strengthen the outer skin have been used as a material for the inner tube. Here-to-for, unfortunately, telescope assemblies whose inner tube connects to the fork crown with greater than 70 mm length of travel have been unable to pass stress testing using the present art as described in the aforementioned patents despite the additional costly process of shot-peening and use of expensive high-strength aluminum alloys. Attempting to increase the diameter of the tubes to add strength is also impractical as larger tube diameters increase cost, obsolete existing factory tooling and is generally counter to the consumer&#39;s aesthetic preference.  
           [0010]    A collar on the telescope assembly plays a vital role in the functioning of the telescoping system. The collar has a very fine thread that grips the outer tube. This fine thread makes the mating parts expensive to make, and prone to scrap because of the propensity to cross thread during assembly. Another key function of the lower collar is to prevent the bearing needles from exiting the telescope at the bottom of its excursion. If the bearing needles escape, the entire front fork will come apart. This is prevented by closing down the internal diameter of the collar. However, it cannot be closed down enough to encounter the full length of the bearing cage because the bending of the inner tube when under load may cause it to rub against the collar. A compromise must be made that places severe restrictions on the design, including the outside diameter of the inner tube.  
         SUMMARY OF THE INVENTION  
         [0011]    This present invention is an improvement on the telescoping system described in U.S. Pat. No. 5,320,374 and subsequent related patents (U.S. Pat. Nos. 5,494,302, 5,702,092, 5,924,714, 6,007,056, and 6,155,541). It is a principal object of the present invention to provide an improved mechanism that allows for adjustment of the pre- load applied to the bearing train. In particular, this invention uses a unique method for achieving adjustable race thickness within an extremely tight space without negatively impacting either the outer or inner tube&#39;s strength and with convenient user access for adjustment in the field.  
           [0012]    It is yet another object of the invention to provide a low cost collar design which enables consistent and accurate orientation of the collar in relation to the needle bearings preventing the needle bearings from exiting the space in between the inner tube and outer tube. It is yet another object of the invention to provide a collar with access to one of the outer races to allow user adjustment of the compressive load in the field.  
           [0013]    It is yet another object of the invention to provide a telescoping assembly with at least 80mm of travel made of light weight aluminum to qualify or pass life testing while maintaining the present outside geometric configuration of the telescoping system and the connection of the inner tube to the fork crown. This is accomplished through the use of a shaped inner tube and conical relief of the outer tube. The shaped inner tube has additional strength characteristics at critical locations to help reduce breaking under stress. In addition, the shaped inner tube eliminates the need for shot-peening or expensive light weight alloys to increase strength, yet does not increase the size of the entire telescoping assembly. The inner tube remains small in less critical areas so as to minimize weight, and allows sufficient clearance with the collar so as to eliminate interfering with the collar during stress loading. The conical relief allows the flexing of the shaped inner tube under load so as not to interfere or scrape the outer tube. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 shows a simplified view illustrating the preferred form of suspension fork according to the present invention.  
         [0015]    [0015]FIG. 2A is an exploded view of the telescoping assembly in its preferred embodiment illustrating inner and outer tubes, a needle bearing assembly, an inner race, outer adjustable race, collar and cam.  
         [0016]    [0016]FIG. 2B is a partial view of a needle bearing assembly showing the relationship of the cage and needle.  
         [0017]    [0017]FIG. 2C is a cross-sectional view illustrating the relationship of outer races, bearing assemblies, inner races, inner tube and outer tube in assembly form.  
         [0018]    [0018]FIG. 3A shows the cross-sectional view of the relationship of the collar, cam, outer tube and the adjustable race.  
         [0019]    [0019]FIG. 3B shows the exploded view of the adjustable race and cam operation.  
         [0020]    [0020]FIG. 3C shows a detailed view of the adjustable race profile.  
         [0021]    [0021]FIG. 3D shows the cam positions.  
         [0022]    [0022]FIG. 4A shows the detailed configuration of the preferred embodiment of the outer tube.  
         [0023]    [0023]FIG. 4B shows the detailed configuration of the preferred embodiment of the outer tube.  
         [0024]    [0024]FIG. 4C shows the relationship of the collar chords and inner tube.  
         [0025]    [0025]FIG. 4D shows a cross-sectional of the outer tube at the mating end with the collar.  
         [0026]    [0026]FIG. 5A shows a detailed view of the inner tube designed for minimum weight and high strength.  
         [0027]    [0027]FIG. 5B shows the relationship of the flats on the inner tube and their relationship to the outer tube.  
         [0028]    [0028]FIG. 6A illustrates a cross-sectional view of the inner tube in relationship to the fork crown.  
         [0029]    [0029]FIG. 6B shows a detailed cross-sectional view of the inner tube shape in relationship to the fork crown.  
         [0030]    [0030]FIG. 7 shows an alternate embodiment for a collar configuration with a collar shim. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    [0031]FIG. 1 shows a bicycle frame (partial)  101  along with a head tube  102 . A fork crown (partial)  103  has an inner tube  104  of a telescoping assembly affixed into it. The outer tube  105  of the telescoping assembly is pressed into the head tube  102  using upper and lower journal bearings (not shown) to allow for steering rotation. The upper end of the outer steer tube  102  is connected to the handlebar stem (not shown).  
         [0032]    [0032]FIG. 2A is an exploded view of the telescoping assembly showing parts germane to this invention. The outer wall of the inner tube  104  depicts a plurality of axially extending longitudinal flat surfaces or flats of which one is shown  801 . In the preferred embodiment there are three such flats, however there can be more or less flats used. In the inner wall of the outer tube  105 , there are axially extending flats of which one is shown  805  that are opposing the corresponding flats on the inner tube. Contained between the inner and outer tube sets of flats are sets of outer races of which one is adjustable and shown  810 , bearing needle assemblies of which one is shown  811  and inner races of which one is shown  814 . The inner and outer races are commonly made of hardened carbon steel or stainless steel. There are a corresponding number of sets of bearing needle assemblies with the number of flats on the outer tube and inner tube. In the preferred embodiment there are 3 sets of bearing assemblies, however, there could be more or less.  
         [0033]    [0033]FIG. 2B shows a detailed view of the bearing needle assemblies. These assemblies are a plurality of hardened chrome steel needle bearings  817  typically 22 needle bearings housed in a plastic cage  818  and ride in between corresponding inner and outer races.  
         [0034]    [0034]FIG. 2C shows a cross-sectional view of the preferred embodiment of the telescope highlighting the relationship of the inner tube  104 , the outer tube  105 , the inner races  814 - 816 , the outer races  808 - 810  and the needle bearing assemblies  811 - 813 . The needle bearing assemblies  811 - 813  allow the inner tube  104  to travel freely in an axial direction with respect to the outer tube  105 . Additionally, the needle bearing assemblies in conjunction with the associated flats on the inner tube, inner races  814 - 816 , outer races  808 - 810  and outer tube  105  enable the steering torsional or rotary action to be imparted from handlebars connected to the handlebar stem via the telescoping tubes to the fork and to the front wheel (not shown). The needle bearings bear high radial loads from the fork during movement over rough terrain. The length of the flats on the inner tube determine the amount of telescoping action. Typically the amount of telescoping action is desired to be 70 mm to 130 mm. It is important to note that the maximum diameter desired of the inner tube  104  at the connection with the fork is 1.250″. This provides sufficient strength while minimizing weight. Increasing the diameter at this connection would strengthen the assembly, but also increase the dimensions of the fork crown  103 , head tube  102  and outer tube  105  as well as the upper and lower journal bearings (not shown). These components are already considered aesthetically oversized and therefore enlarging the outside dimensions of these components is undesirable.  
         [0035]    In FIG. 2A, lower collar  819  houses an adjustable cam  820  for adjusting the thickness of outer race  810  as well as serve to contain the needle bearing assemblies from exiting the telescoping assembly when the inner tube  104  is fully extended relative to the outer tube  105 .  
         [0036]    [0036]FIG. 3A shows a cross-sectional view of the telescoping assembly illustrating how the adjustable race components are configured. Adjustable outer race shim-set  810  is comprised of two races  901  and  902  that are sandwiched together. Cam  820  fits through a hole in the collar  819 , outer tube  105 , and race  901  to enable longitudinal adjustment of race  902 , thereby increasing the thickness of the adjustable race shim-set  810  and adjustment of the pre-load on the needle bearing assembly  811 .  
         [0037]    [0037]FIG. 3B illustrates the ability to adjust the outer race thickness through the use of cam element  820 . The cam element  820  resides in a hole  904  located in the collar  819 . The hole in the collar is aligned with a corresponding hole through the wall of the outer tube (not shown) so that the cam element can mate with the two saw tooth races  901  and  902 . The cam element has an eccentric anvil  903  which passes through the semi-circular cutout  905  in the saw tooth race  901  and mates with the oval cutout  906  in the saw-tooth race  902 . The cam element  820  can be turned using a standard screwdriver (not shown) by means of a slot  907 . As the cam element is turned, the saw-tooth race  902  is moved up or down relative to race  901  causing thickness expansion or contraction. The saw-tooth race  901  is stationary. The saw-tooth race  902  moves up or down with the cam eccentric anvil position.  
         [0038]    [0038]FIG. 3C illustrates a detailed cross-sectional view of the saw-tooth pattern on each side of races  901  and  902 . Linear movement of race  902  relative to  901  causes the saw-tooth profiles on each race to ride up or down on each other causing thickness expansion or contraction. In the preferred embodiment, the saw tooth angle would be such that a race linear motion of 0.125″ would generate a thickness expansion of 0.0014.″ It should be noted that the angle can vary depending on the degree of adjustable and that the linear motion relative to the thickness expansion can be more or less than the preferred embodiment. The number of saw teeth on each shim will be dependent on the angle and the length of travel desired.  
         [0039]    [0039]FIG. 3D shows a detailed view of the anvil position in the fully compressed position  908 , the half expanded position  909  and the fully expanded  910 . The oval  906  moves up or down with the anvil  903 , shown in FIG. 3D in the half expanded position.  
         [0040]    [0040]FIG. 4A shows the outer tube  105  that contains three bayonet type grooves  401 - 403  on its outer periphery in relationship to the internal flats.  
         [0041]    [0041]FIG. 4B shows the collar  819  that contains three pins  404 - 406  that line up with the vertical portion of the bayonet grooves on the outer tube. The collar is pushed on and twisted allowing the pins  404 - 406  to slide into the horizontal portion of the groove on the outer tube, locking the collar in place. Collar chords  407 - 409  are designed to move into position across the corresponding flats on the inner tube to prevent bearing assemblies from exiting outside the outer tube in the space created between the inner tube and outer tube.  
         [0042]    [0042]FIG. 4C shows the relationship of the inner tube  104 , outer tube  105  and bayonet collar  819 . The bayonet style collar  819  allows for a shaped inner tube which has a diameter greater than the chord diameter of the collar  819 . The inner tube  104  can be pushed fully into the outer tube  105  allowing the collar to be put in place. Only then can the inner tube  104  be extended to its normal position allowing the larger diameter inner tube to pass through the collar in the space between the chords. Collar chords of which one is shown  408  are aligned with the corresponding flats on the inner tube of which one is shown  801  allowing these smaller chords to contain the needle bearings from exiting the telescoping assembly  
         [0043]    [0043]FIG. 4D shows a cross-section view of the outer tube  105  at the collar end showing a conical internal shape  410 . This conical shape permits the larger diameter inner tube to flex during fork loading so as not to contact the inner diameter of the outer tube  105 .  
         [0044]    [0044]FIG. 5A illustrates the inner tube  104 . The inner tube has a plurality of axially extending longitudinal flat surfaces or flats  801 - 803 . Either three or four flats are commonly used, more or less could be used as well. In the preferred embodiment three flats are used. In this embodiment, it is desired to have the inner tube be of light weight material such as aluminum. It is also desired to eliminate costly strengthening processes such as shot peening of the inner tube. The inner tube therefore has been strengthened by enlarging the inner tube diameter except in area  501 , which is buried in the fork crown and not subject to lateral forces. At area  501  the diameter is typically 1.250″ extending upwards in this embodiment to 1.300″ for the rest of the tube.  
         [0045]    [0045]FIG. 5B shows the relationship of the inner tube and the outer tube when assembled. It is important for the proper function of the lightweight telescope to have the race flats continue to the transition point where the inner tube diameter decreases back to 1.250″ indicated by line  503 . The extension of these flats allows for assembly of the collar  819  to the outer tube  105  without interference from the larger diameter of the inner tube  104 . The collar  819  is twisted and locked into place allowing the collar chords on the collar to be positioned over the flats to prevent needle bearings from exiting the telescope assembly.  
         [0046]    [0046]FIG. 6A illustrates a cross-sectional view of the inner tube configuration and its relationship to the fork crown. The inner tube  104  is normally pressed into the fork crown  103 . FIG. 6B shows a detailed cross-sectional view of the fork crown  103  and the inner tube  104 , whereby the diameter of the inner tube  104  remains enlarged into the press area of the fork crown  103 . The line  503  indicates the point where the inner tube diameter decreases back to 1.250″. By pressing the inner tube into the fork crown  103  past the point where the diameter is smallest, allows for increased strength at the position on the inner tube where the maximum lateral forces are concentrated.  
         [0047]    [0047]FIG. 7 illustrates an alternate embodiment of the collar configuration. The collar  819  has no chords of smaller diameter, but relies on a steel shim  950  and orientation pin  951  as a means of preventing bearing needle assemblies of travelling past the end of the outer tube (not shown). Steel shim  950  has the chords built in and relies on orientation pin  951  to align the chords with the flats on the inner tube so that the collar/shim combination can be assembled over the inner tube and onto the outer tube in the same manner as described previously.