Abstract:
A suspension fork for cycles includes an operating device mounted externally on a telescopic fork leg that permits the rider to selectively shorten or lengthen the extent of relative travel between the inner and outer tubular sections of the fork. Preferably, an operating knob or lever is coupled with a rotary cylinder contained within the hollow compression rod by a torsion overload spring, thereby to displace a stop dog between extended and retracted positions relative to the compression rod via a slot contained in the compression rod wall.

Description:
FIELD OF THE INVENTION 
     A suspension fork for cycles includes adjustment means operable by the rider externally of the fork for selectively controlling the extent of relative axial travel of the telescopic leg sections of the fork. 
     BACKGROUND OF THE INVENTION 
     BRIEF DESCRIPTION OF THE PRIOR ART 
     The adaptation of suspension elements to the front forks of bicycles has increased the functionality of the bicycle and the enjoyment thereof by the user by insulating the rider from the bumps or obstacles in the road or trail. Early suspension forks had only 50 mm of travel, which at the time seemed to be a great improvement. As riders adapted to the increased off-road abilities of bicycle due to the suspension fitted to the bicycle, they soon sought even more suspension travel to be able to attack more difficult terrain and at higher speeds. 
     As suspension travel increased, it became apparent that improved comfort and control riding rough or downhill terrain could be achieved with ever longer travel forks. However, it also became apparent that with this increased travel, there was a compromise in the ideal bicycle geometry or riding position for riding on level or uphill terrain. This left the rider with a need to choose between a suspension optimized with longer travel for rugged downhill terrain or somewhat shorter travel for efficiency on smoother and uphill terrain. 
     The first attempt to build a suspension fork that addressed this multi-travel need was taught by the Stewart, et al., U.S. Pat. No. 5,470,090. This invention allowed the user to assemble the same fork in two different configurations, one being a short travel version and one being a longer travel configuration. This allowed the rider to better optimize his fork to riding different terrain without having to buy two different forks or switch forks on the frame. However, this design did require considerable disassembly and re-assembly of the suspension fork to effect the change from long travel to short travel, which was not convenient or often utilized by the end user. 
     The next improvement in forks with multi-travel capabilities was the Rock Shox PSYLO fork. This improvement allowed the user to adjust the fork travel by turning a screw located inside the stanchion (inner leg). This used a screw type ramp mechanism to shorten or lengthen the fork travel within a range to better suit the particular terrain to be ridden. Although this method did not require considerable disassembly of the fork, which was a significant improvement, it did require the user to stop riding the bicycle, obtain tools and remove some elements of the fork to gain access to the adjusting mechanism and then replace them before continuing on. 
     The present invention was developed to provide a new improved suspension fork for cycles, such as bicycles and motorcycles, wherein the rider could utilize the clear advantages of a fork, the travel of which could be adjusted to best suit the particular terrain the rider encountered during the course of the ride. During many typical rides, many types of terrain and riding conditions are encountered and the potential existed for the need to change the travel characteristics of the fork several times even during the same ride. The key to product success was to allow the end user to adjust travel “on the fly” with on-off switch convenience. This needed to be accomplished by the rider out on the trail with no tools and no fork disassembly; as simple as a flip of a lever. 
     SUMMARY OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide a suspension fork for cycles including adjustment means operable by the cyclist externally of the fork for adjusting the relative length of travel between the telescopic sections of at least one leg of the suspension fork. Preferably an adjustment knob or lever is arranged at either the bottom or the top of the fork leg at a location readily accessible to the cyclist, whereby the travel adjustment is easily and positively accomplished without the need of any tools and/or any disassembly of the fork. 
     According to a more specific object of the invention, the compression rod that is contained within the telescopic sections of the leg and which cooperates with the compression spring to bias the sections apart toward an expanded condition is hollow and includes alternately retractable and extensible stop means that are operable externally of the fork leg. These stop means are arranged intermediate the first and second travel limiting means of the fork, whereby when the stop means are in the extended condition, the relative length of travel of the telescopic leg sections is shortened. 
     According to another object of the invention, the stop means includes at least one stop dog that is displaceable from a retracted position within the hollow compression rod to an extended position in which the stop dog extends partially outwardly of the compression rod via a slot contained in the wall thereof. Various types of operating means may be used for displacing the stop dog to its extended position, including wedge means, cam means, and rotary operating means. 
     According to the preferred embodiment of the invention, a pair of stop dogs extend outwardly via opposed slots contained in the compression rod. The stop dogs include longitudinally extending pivot shafts that extend within eccentrically arranged bores contained in one end of an inner cylindrical operating member that is rotatably mounted coaxially within the compression rod. According to an important feature of the invention, the operating lever or knob that is externally arranged on the upper or lower end of the fork is coupled to the cylindrical operating member via a torsion overload spring, thereby to achieve positive extension or retraction of the stop dogs. Preferably, the stop dogs are provided with angularly arranged surfaces that prevent the stop dogs from being caught on the end of the rebound spring or on the rebound spring capture means. 
     According to a further object of the invention, a set of sliding stop dogs is used to control the position of the stanchions relative to the outer assembly. The true advantage of this feature is to allow the user to have the benefit of a short travel fork for climbing and a long travel fork for descent all in one fork, accessed by at the mere flip of a lever. The addition of a torsion spring, between the lever and sliding dogs, allows for the travel to be set at any point in the stroke of the fork. Once set, the travel will be limited during the stroke or at the next stroke (depending upon the position selected). The particular execution of the travel adjustment means utilizes a switching adjustment lever at the bottom or the top of the leg of the suspension fork. By placing the adjustment knob at the top of the fork, and ever greater level of rider convenience is provided for switching travel length to meet varied terrain and riding conditions without the need for stopping or dismounting the bicycle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawings, in which: 
     FIG. 1 is a sectional view taken of a bicycle front fork assembly including the present invention, and FIG. 2 is a sectional view taken along  2 — 2  of FIG. 1; 
     FIG. 3 is an elevational view of the compression rod assembly of the present invention, FIG. 4 is a sectional view taken along line  4 — 4  of FIG. 3, and FIG. 5 is a sectional view taken along line  5 — 5  of FIG. 4; 
     FIG. 6 is a sectional view illustrating the cooperation between the U-shaped detent spring and the adjustment knob of FIGS. 3-5; 
     FIG. 7 is a longitudinal sectional view taken through the lower operating member, and FIGS. 8 and 9 are bottom and top views of the lower inner operating member of FIG. 7; 
     FIGS. 10 and 11 are longitudinal sectional and bottom views, respectively, of the support housing for the lower inner operating member of FIG. 7; 
     FIGS. 12 and 13 are front and side elevation views, respectively, of the torsion spring member; 
     FIG. 14 is a detailed elevational view of the upper end of the compression rod, 
     FIG. 15 is a longitudinal sectional view of the upper end of the compression rod, and 
     FIG. 16 is a top plan view of the compression rod; 
     FIGS. 17 and 18 are side elevation and top plan views, respectively, of the helical rebound spring; 
     FIG. 19 is a transverse sectional view of the upper inner operating member, and FIGS. 20 and 21 are side elevation and top plan views, respectively; 
     FIGS. 22,  23 , and  24  are side elevation, end elevation, and bottom views, respectively, of one of the stop dog members; 
     FIGS. 25-28 are top diagrammatic illustrations of the manner of extension and withdrawal of the opposed stop dog members; 
     FIG. 29 is a longitudinal sectional view of the bottom portion of a telescopic fork leg according to the present invention, with the stop dog means being in the retracted condition, and FIG. 30 is a sectional view taken along line  30 — 30  of FIG. 29; 
     FIG. 31 is a longitudinal sectional view of the bottom portion of a fork leg with the stop dog in its radially outwardly extending position relative to the compression rod, and FIG. 32 is a sectional view taken along line  32 — 32  of FIG. 31; 
     FIG. 33 is a sectional view of a modification of the telescopic fork leg of FIG.  2 ;and 
     FIG. 34 is a somewhat diagrammatic sectional view of a second embodiment of the stop dog means. 
    
    
     DETAILED DESCRIPTION 
     Referring first more particularly to FIGS. 1 and 2, the front suspension fork  2  of the present invention includes a crown  4  that is connected with the steerer shaft  6  of the cycle, and a pair of telescopic legs  8  and  10  that extend downwardly from the ends of the crown fork, respectively. The left hand leg  8  includes inner and outer telescopic sections  12  and  14  that are connected at the remote ends with the crown  4  and with the axle of the wheel W of the cycle, shown in phantom. Needle valve means  16  and  18  control the damping characteristics of the fork leg  8  and form no part of the present invention. 
     The other leg  10  of the fork includes inner and outer telescopic sections  20  and  22  that are respectively connected at their remote ends with the crown member  4 , and with the wheel axle via the axle catch portion  23 . Arranged concentrically within the inner section  20  is a helical compression spring  24  that reacts with a tubular compression rod  26  that is connected at its lower end with the lower end of the outer leg section  22 , thereby biasing the telescopic sections axially apart toward their normal expanded condition shown in FIG.  1 . The upper ends of the outer sections  14  and  22  are connected by a conventional brake arch  30 , as is known in the art. 
     As shown in greater detail in FIGS. 3-5, the compression rod assembly  26  includes a tubular compression rod  40  that is provided at its upper end with a pair of longitudinally spaced annular flanges  40   a  and  40   b  that react with the adjacent ends of the compression spring  24  and a helical rebound spring  44 , respectively. The rebound spring  44  is captured at its lower end with an end closure assembly  46  that is connected with the lower end of the inner leg section  20 , as shown in FIGS. 1 and 2. At the lower end of the compression rod assembly  26  is concentrically mounted an annular resilient bottom out bumper  48 . At its lower end, the compression rod  40  is threadably connected with a tubular support shaft  50  in which is rotatably mounted the lower cylindrical operating member  52 . Rotatably mounted within the counter bore contained in the compression rod  40 , is an upper cylindrical operating member  54 . The lower and upper cylindrical operating members are connected by a torsion spring  60  as will be described in greater detail below, a pair of stop dogs  62  are pivotally connected with the upper end of the upper inner operating member  54 . An adjustment knob or lever  64  is connected with the lower end of the lower operating member  52  by the screw  66 . As will be described below, rotation of the adjustment lever  64  in one direction produces rotation of the lower operating member  52  which is transmitted to the upper inner member  54  by the torsion spring  60 . Thus, the upper cylindrical member  54  is rotated relative to the depression rod to cause displacement of the stop dogs  62  from their retracted positions within the compression rod to radially outwardly extend position via corresponding slots contained in the wall of the compression rod  40 . 
     As shown in FIG. 6, the adjustment knob  64  includes a cylindrical inner surface that contains detent grooves that receive the bent end portions  65   a  of the generally U-shaped detent spring  65 , thereby to define two positions of the adjusting knob  64  relative to the lower end of the outer leg section  22 , as will be described in greater detail below. 
     Referring now to FIGS. 7-9, the lower inner operating member  52  comprises a cylinder container a threaded bore  70  at its lower end for receiving the screw  66  of the adjustment knob  64 . At its upper end, the lower operating member contains an annular groove  72  for receiving the O-ring  74  shown in FIGS. 4 and 5. At its upper end, the lower inner operating member contains a diametrically extending slot  74  that receives the bent circular portion  60   a  at the lower end of the torsion spring  60 , as shown in FIGS. 12 and 13. As shown in FIGS. 10 and 11, the lower inner member  52  rotates freely within the tubular support shaft  50 , the upper portion  50   a  of which is threadably connected with the lower end of the compression rod  40 . 
     Referring now to FIGS. 14-16, the tubular compression rod  40  contains a counter bore  41  for receiving the lower and upper inner operating members  52  and  54 , respectively. At its upper end, the counter bore  41  contains a pair of radially extending slots  43  that receive the stop dogs  62 , respectively. 
     As shown in FIGS. 17 and 18, the rebound spring  44  comprises a helical compression spring the remote end  44   a  of which is secured to the adjacent turn of the coil. At its lower end, the helical compression spring is captured by the end closure assembly  46  that is connected with the lower end of the inner leg section  20 . Thus, the lower assembly  46  slides vertically upwardly and downwardly on the compression rod  40  in accordance with the displacement of the inner and outer leg sections  20  and  22  relative to each other. 
     As shown in FIGS. 19-21, the upper inner operating member  54  comprises a cylinder that is provided at its lower end with a diametrically extending slot  55  that receives the bent circular upper portion  60   b  of the torsion rod  60 . At its upper end, the upper inner operating member  54  contains a pair of eccentrically arranged bores  57  that rotatably receive the downwardly extending projecting portions  62   a  of the stop dogs  62  best shown in FIGS. 22-24. The lower edge portions of the stop dog  62  are provided with reversely inclined surfaces  62   b  (FIG. 22) that serve to prevent the stop dogs from being pivoted toward the retracted position at an inopportune time. Furthermore, the longitudinal edge of the stop dog includes inclines second surface  62   c  that serves to displace the stop dog to its retracted position within the compression rod during transition of the apparatus from the high travel to the low travel condition. As shown in FIGS. 26 and 27, when then upper inner cylinder  54  is rotated in the clockwise direction in FIG. 25, the stop dogs  62  are pivotally displaced to extend outwardly from the periphery of the compression rod  44 . Rotation of the inner cylinder  54  in the counterclockwise direction relative to the compression rod  40  causes the stop dogs  62  to be retracted into the compression rod, as shown in FIG.  27 . 
     Referring now to FIGS. 29 and 30, when the stop dogs  62  are in their retracted positions within the tubular compression rod  40 , the upper end of the helical rebound spring  44  is in engagement with the lower stop flange  40   b  of the tubular compression rod  40 . The inner leg section  20  is thus biased by compression spring  24  upwardly relative to the outer leg section  22 . Thus, the lower end of the inner leg section  20  is spaced a given distance D 1  from the bottom out member  48  and its support washer  49 . 
     As indicated in FIGS. 31 and 32, in order to reduce the length of travel of the inner leg section  20  relative to the outer leg section  22 , the adjustment knob  64  is rotated through 90° as determined by the cooperation between the detent spring  65  and the dimpled recesses  64   a.  As the rotation of the lower inner operating member  52  is transmitted to the upper inner operating member  54  by the torsion spring  60 , the stop dogs  62  are displaced outwardly owing to the rotation of the upper inner member  54  relative to the slots  57  contained in the stationary compression rod  40 , whereupon the stop dogs are pivoted outwardly toward their extended positions. As shown in FIGS. 31 and 32, the upper end of the rebound spring  44  now cooperates with the lower surface  62   b  of the stop dog  62 , whereby the length of travel D 2  between the lower end of the inner leg section  20  and the outer leg section  22 , as determined by the bottom out bumper  48  and a support washer  49 , is reduced. 
     The torsion overload spring serves two purposes. It prevents any damage to the mechanism if it is inadvertently turned in the wrong direction, and it provides preload for the dogs so that when the detent knob is turned to change the travel the dogs are preloaded to either retract or extend when the fork is pushed down. When changing from the higher travel to the lower travel, the dogs will try to come out in the middle of the spring or the inner leg end cap. The torsion spring allows the dogs to be pushed back into the compression rod by the cap and spring but still extend after the top-out spring has gone past. When changing from the lower travel to the higher travel, the dog is designed so that it will not disengage from the top-out spring until the rider pushes on the fork, again the torsion spring allows the dogs to be preloaded without disengaging prematurely. 
     The dog was designed with the angled surface  62   c  on the top side so that the spring and cap would slide down past the top-out spring and leg end cap when the fork is pushed down. The lower angled surface  62   b  prevents the dog from retracting until the fork is pushed down by the rider. This is a safety feature. If the fork was allowed to spring back into the higher travel position as soon as the detent knob was turned, it is possible that the rider while bending over to reach the knob at bottom of the fork would have their face close to some part of the bicycle would be hit and injured. 
     As indicated previously, the present invention is particularly suitable for use in the suspension fork of a bicycle, but it could also be used in connection with the suspension fork of a motorcycle. Furthermore, the invention could be included in a suspension fork having a single leg comprising a pair of telescopically displaceable sections. 
     Furthermore, instead of providing the adjustment knob  64  at the bottom of the leg  10 , in the embodiment of FIG. 33, the outer section  22  is reversed and arranged at the upper end of the leg relative to the inner section  20 ′, whereby the adjustment knob  64 ′ is arranged at the top of the leg. 
     Also, various other methods and means may be provided for displacing the stop dogs between their extended and retracted positions. To this end, as shown in FIG. 34, the stop dogs  162  could be pivotally connected by pivot means  164  for pivotal movement between retracted and expanded positions relative to the compression rod  140 . In this case, the dogs are biased inwardly by spring means  166 , and an axially displaceable wedge member  168  is operable by the adjusting knob  164  to displace the stop dogs  162  outwardly toward their radially extended positions. Alternately, the stop dogs could be mounted for sliding radial displacement relative to the slots in the compression rod within which the dogs are mounted. 
     While in accordance with the provisions of the Patent Statutes the preferred form and embodiment of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes may be made without deviating from the inventive concepts set forth above.