Abstract:
A suspension system for a handlebar-steered vehicle includes an upper tube, a lower tube reciprocally slidable relative to the upper tube. A positive spring assembly biases the upper and lower tubes away from each other. A piston assembly is attached to the lower tube. The suspension includes a travel adjustment mechanism including a locking mechanism and an actuator. The locking mechanism is connected to the positive spring assembly and selectively maintains a first portion of the positive spring assembly in a compressed state with the upper and lower tubes drawn toward each other. The actuator is operatively connected to the locking mechanism to releasably engage the locking mechanism to maintain the first portion of the positive spring assembly in the compressed state.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to suspension systems and more particularly to a suspension system including a travel adjustment mechanism for adjusting the travel and/or length of the suspension system by selectively maintaining a portion of a positive spring assembly in a compressed state. 
       SUMMARY OF THE INVENTION 
       [0002]    The present invention provides a suspension system for a handlebar-steered vehicle that includes a travel adjustment mechanism. The suspension system generally includes an upper tube and a lower tube reciprocally slidable relative to each other. A positive spring assembly biases the upper and lower tubes away from each other. A piston assembly is attached to the lower tube and deflects the positive spring assembly under loading. The travel adjustment mechanism includes a locking mechanism and an actuator. The locking mechanism is connected to the positive spring assembly and selectively maintains a first portion of the positive spring assembly in a compressed state with the upper and lower tubes drawn toward each other. The actuator is operatively connected to the locking mechanism to releasably engage the locking mechanism to maintain the first portion of the positive spring assembly in the compressed state. 
         [0003]    In one embodiment of the present invention, the positive spring assembly includes first and second positive springs in series. The locking mechanism selectively maintains the first positive spring in the compressed state. The second positive spring is attached to the piston assembly. The locking mechanism includes a displaceable sleeve engaged with and displacing the first and second positive springs to position the displaceable sleeve into a locked position. The locking mechanism further includes a connector attached to the upper tube and a locking element. The displaceable sleeve is displaceable relative to the connector. The locking element releasably locks the displaceable sleeve and the connector to each other to maintain the first positive spring in the compressed state. The locking element is radially biased by the actuator to engage a groove in either the connector or the displaceable sleeve to lock the connector and the displaceable sleeve to each other with the upper and lower tubes drawn toward each other. The actuator includes a magnet radially biasing the locking element to disengage the groove in either the connector or the displaceable sleeve to unlock the connector and the displaceable sleeve from each other with the upper and lower tubes drawn away from each other. 
         [0004]    The suspension system may further include a negative spring biasing the upper and lower tubes toward each other. In alternative embodiments of the present invention, the first and second positive springs may be any combination of coil and gas springs or the like. Further, the positive spring assembly may include only a single positive coil spring wherein a portion of the single coil spring is selectively maintained in a compressed state with the upper and lower tubes drawn toward each other. 
         [0005]    The travel adjustment mechanism may selectively adjust the suspension system between at least a first travel setting and a second travel setting. In the first travel setting, the positive spring assembly has a first preload. In the second travel setting, the first portion of the positive spring assembly maintained in the compressed state has a second preload without increasing the preload in a second portion of the positive spring assembly. 
         [0006]    These and other features and advantages of the present invention will be more fully understood from the following description of one or more embodiments of the invention, taken together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a front cross-sectional view of a suspension system in a long travel setting according to one embodiment of the present invention; 
           [0008]      FIG. 2  is a front cross-sectional view of the suspension system of  FIG. 1  in a short travel setting; 
           [0009]      FIG. 3  is an enlarged front cross-sectional view of detail A of  FIG. 1  showing a travel adjustment mechanism in the long travel setting; 
           [0010]      FIG. 4  is a front cross-sectional view of the travel adjustment mechanism of  FIG. 3  during an adjustment of the travel setting from the long travel setting to the short travel setting; 
           [0011]      FIG. 5  is an enlarged front cross-sectional view of detail B of  FIG. 2  showing the travel adjustment mechanism in the short travel setting; 
           [0012]      FIG. 6  is a front cross-sectional view of the travel adjustment mechanism of  FIG. 5  during an adjustment of the travel setting from the short travel setting to the long travel setting; 
           [0013]      FIG. 7  is a partial front cross-sectional view of the travel adjustment mechanism including a displaceable sleeve according to another embodiment of the present invention in the long travel setting; 
           [0014]      FIG. 8  is a front cross-sectional view of  FIG. 7  showing the travel adjustment mechanism in a short travel setting; 
           [0015]      FIG. 9  is a front cross-sectional view of  FIG. 7  showing the travel adjustment mechanism in a mid travel setting; 
           [0016]      FIG. 10  is a front cross-sectional view of  FIG. 7  showing the travel adjustment mechanism in a mid travel setting partially compressed under load; 
           [0017]      FIG. 11  is a front cross-sectional view of a suspension system in a long travel setting accordingly to another embodiment of the present invention; 
           [0018]      FIG. 12  is a front cross-sectional view of the suspension system of  FIG. 11  in a short travel setting; 
           [0019]      FIG. 13  is an enlarged front cross-sectional view of detail C of  FIG. 11  showing a travel adjustment mechanism in the long travel setting; 
           [0020]      FIG. 14  is an enlarged front cross-sectional view of detail D of  FIG. 11 ; 
           [0021]      FIG. 15  is an enlarged front cross-sectional view of detail E of  FIG. 12  showing the travel adjustment mechanism in the short travel setting; 
           [0022]      FIG. 16  is an enlarged front cross-sectional view of detail F of  FIG. 12 ; and 
           [0023]      FIG. 17  is a side cross-sectional view of a leg of a suspension system according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIGS. 1-6  illustrate a suspension system  10  including a travel adjustment mechanism  12  according to one embodiment of the present invention. The suspension system  10  depicted is a bicycle front suspension fork having a crown  14  that is connected to a steerer tube  16 , a first leg  18  that contains a biasing mechanism or a positive spring assembly  20  and a second leg  22  that contains a damping mechanism  24 . The damping mechanism  24  includes an oil compression damping system  26  and an oil rebound damping system  28 . Each of the legs  18 ,  22  includes an upper tube  30  and a lower tube  32 . Although the upper tubes  30  are shown as inner tubes slidable within the lower outer tubes  32 , it will be appreciated that the lower tubes  32  may alternatively be reconfigured as inner tubes slidable within reconfigured outer tubes. Additionally, although the tubes  30 ,  32  are shown to have substantially circular cross sections, it is understood that they may assume any cross-sectional shape. The inner and outer tubes  30 ,  32  are connected at their remote ends  34 ,  36  to the crown and a wheel axle (not shown) through dropouts  38 ,  40 , respectively. It is to be understood that although the present invention is described with respect to a front suspension fork, the suspension system  10  may also be embodied as other suspension components disposed at other locations on a bicycle frame. Further, the suspension system  10  of the present invention may be used on motorcycles as well as other handlebar-steered vehicles. 
         [0025]    The suspension system  10  includes a piston assembly  42  having a piston  44  and a rod  46 . One end  48  of the rod  46  is attached to the end  36  of the lower tube  32  by a screw  50 . The other end  52  of the rod  46  extends into the upper tube  30  and is attached to the piston  44 . The positive spring assembly  20  includes first and second positive springs  54 ,  56  in series, in this embodiment, coil springs functioning as one spring. The spring rate K t  for the combined positive springs  54 ,  56  is determined by 1/K t =1/K 1 +1/K 2 , where K 1  is the rate of the first positive spring  54  and K 2  is the rate of the second positive spring  56 . The first and second positive springs  54 ,  56  bias the upper and lower tubes  30 ,  32  apart or away from each other. One end  58  of the first positive spring  54  is attached is a top cap  60  disposed at the end  34  of the upper tube  30 . The other end  62  of the first positive spring  54  is engaged with the travel adjustment mechanism  12 . The second positive spring  56  is attached to the travel adjustment mechanism  12  at one end  64  and is attached to the piston  44  at the other end  66 . The suspension system  10  also includes a negative or top-out spring  68  biasing the upper and lower tubes  30 ,  32  toward each other. One end  70  of the top-out spring  68  is attached to an end  72  of the upper tube  30  and the other end  74  of the top-out spring  68  is attached to a top-out stop element  76  limiting the expansion of the upper and lower tubes  30 ,  32  when a long travel setting is selected. When a short travel setting is selected, the top-out stop element  76  no longer contacts the piston  44 . The piston rod  52  extends through the top-out spring  68 . 
         [0026]    The travel adjustment mechanism  12  adjusts the travel and/or length of the suspension system  10 . Travel of the suspension system  10  refers to a maximum amount the upper and lower tubes may slidably displace relative to each other. The length of the suspension system  10  is measured between an end of the upper tube and an end of the lower tube. The suspension system  10  has at least two travel settings, long and short travel settings.  FIG. 1  shows the suspension system  10  in a long travel setting having a length L 1  and a travel T 1  and  FIG. 2  shows the suspension system  10  in a short travel setting having a shorter length L 2  and a shorter travel T 2 . Looking to  FIGS. 3-6 , the travel adjustment mechanism  12  includes an actuator  78  and a locking mechanism  80 . The actuator  78  includes an external knob  82  connected to a shaft  84  extending through a connector, in this embodiment a tube  86 , and the top cap  60  attached to the end  34  of the upper tube  30 . One end  88  of the tube  86  is attached to the top cap  60  and the other end  90  of the tube  86  extends through the first and second positive springs  54 ,  56 . The tube  86  includes a helical slot  85  for receiving a pin  87  fixed to the shaft  84 . The shaft  84  is connected to a spring  92  which is attached to a poker  94 . The poker  94  is stacked on a magnet  96  which is stacked on a return spring  98  stacked on a set screw  100  that preloads the return spring  98 . The actuator  78  also includes detent balls  102  received in slots  104 ,  105  in the shaft  84  and tube  86 , respectively, to signal the rider when the next travel setting has been selected and allows the shaft  84  to axially displace within the tube  86 . The locking mechanism  80  includes a displaceable sleeve  106  and a locking element, in this embodiment, metal balls  108 . The metal balls  108  are received in holes  110  in the tube  86 . The sleeve  106  is engaged with the end  62  of the first positive spring  54  and is connected to the end  64  of the second positive spring  56 . The tube  86  extends through the sleeve  106 . The sleeve  106  includes a groove  112  to receive the metal balls  108  to lock the tube  86  and sleeve  106  together. 
         [0027]    Looking to  FIGS. 3-6 , to adjust the travel from a long travel setting to a short travel setting, the rider rotates the knob  82  to the short travel setting. As the shaft  84  is rotated, the pin  87  displaces in the helical slot  85  which drives the shaft  84  to preload or compress the spring  92  which in turn applies a force against the poker  94  (see  FIG. 4 ). The force against the poker  94  causes the poker  94  to press against the metal balls  108 . The shaft  84  is prevented from returning to the long travel setting because the slot  85  is configured such that the last few degrees of rotation are flat with no pitch which causes the force generated by the spring  92  to be perpendicular to the slot  85 , thus preventing the spring  92  from being able to return the shaft  84  to the long travel setting. Next, the rider pushes down, compressing the entire fork, causing the sleeve  106  to displace toward the top cap  60  and compress the first positive spring  54  until the metal balls  108  align with the groove  112  in the sleeve  106 . Once the metal balls  108  are aligned with the groove  112 , the spring  92  downwardly displaces the poker, which in turn, displaces the metal balls  108  radially outward into the groove  112 , locking the sleeve  106  and tube  86  together. A chamfer  114  on the poker  94  biases the metal balls  108  radially outwardly. The first positive spring  54  is now locked in a compressed state and has a higher preload than when in the long travel setting (see  FIG. 5 ). The length of the entire suspension fork is generally shortened by the length that the first positive spring  54  has been compressed when the sleeve  106  and the tube  86  are locked together. The preload of the second positive spring  56  does not increase from the long travel setting to the short travel setting. In this embodiment, the second positive spring  56  has zero preload in the short travel setting. Since the first positive spring  54  has been essentially negated or removed from the spring assembly  20  in the short travel setting, the spring rate K t  for the spring assembly  20  in the short travel setting equals the second positive spring, K 2 . 
         [0028]    To adjust the travel from a short travel setting to a long travel setting, the rider rotates the knob  82  to the long travel setting causing the shaft  84  to displace toward the knob  82  which in turn unloads the preloaded spring  92 . The poker  94  does not return on its own to the long travel setting due to the transverse forces on the metal balls  108  created by the compressed first positive spring  54 . The rider must compress the entire fork until the forces between the first and second positive springs  54 ,  56  are substantially equal to zero. When the net force between the first and second positive springs  54 ,  56  across the sleeve  106  is substantially zero, the radially outward force on the metal balls  108  is near zero which allows the poker  94  to slide up and out of the way. The return spring  98  returns the poker  94  to its long travel setting (see  FIG. 6 ). The metal balls  108  are free to move radially inwardly towards the center of the tube  86  without obstruction, but with a net zero force on the sleeve  106 , the metal balls  108  do not return to the long travel setting by themselves. There are several ways to return the metal balls  108  to the long travel setting. In this embodiment, the force of the magnet  96  biases the metal balls  108  radially inwardly toward the tube  86 . Once the metal balls  108  are back in the tube  86 , the sleeve  106  displaces back to the long travel setting. Alternatively, a sloped poker may be used to return the metal balls  108  radially inwardly toward the tube  86 . 
         [0029]      FIGS. 7-10  shows another embodiment of the present invention similar to  FIGS. 1-6  except that the sleeve  106  has been replaced with a sleeve  116  that includes an axially-extending counterbore  118  adjacent to a groove  120  and an additional chamfer  115  to provide three travel settings, long, mid and short travel settings. Alternatively, the travel adjustment mechanism  12  may have more than three travel settings.  FIGS. 7 and 8  show the travel adjustment mechanism  12  in the long and short travel settings, respectively. In the mid travel setting, the metal balls  108  are located at an end  122  of the counterbore  118  opposite the groove  120  and are adjacent the chamfer  115  (see  FIG. 9 ). The sleeve  116  is locked to the tube  86  in the extension (outward) direction so that the first positive spring  54  is held in a partially compressed state rather than near a maximum compressed state as in the short travel setting. Although, the sleeve  116  may not move in the extension direction, the sleeve  116  may still move in the compression direction between the end  122  of the counterbore  118  and the groove  120  when the force of the second positive spring  56  is equal to the compressed force of the first positive spring  54  (see  FIG. 10 ). This allows the system to still use the remainder of the available spring travel held in the first positive spring  54 . In the mid travel setting, the spring rate at the beginning and end of the fork stroke is that of the second positive spring  56  only and the spring rate of the middle portion of the stroke is that of the first and second positive spring  54 ,  56  combined in series. 
         [0030]    Alternatively, the second positive spring  56  may be held in compression to shorten the travel and/or length of the fork rather than the first positive spring  54 . Also, the first and second positive springs  54 ,  56  may be replaced with a single spring wherein a portion of the single spring may be held in a compressed state to shorten the travel of the fork. 
         [0031]    Looking to  FIGS. 11-16 , a suspension system  130  is shown according to another embodiment of the present invention similar to the previous embodiments except that the first and second positive coil springs  54 ,  56  have been replaced with first and second gas springs  132 ,  134 .  FIG. 11  shows the suspension system  130  in a long travel setting having a length L 3  and a travel T 3  and  FIG. 12  shows the suspension system  130  in a short travel setting having a shorter length L 4  and a shorter travel T 4 . The suspension system  130  includes a piston assembly  131  having a piston  133  and a rod  135 . One end  137  of the rod  135  is attached to the end  36  of the lower tube  32  by a screw  139 . The other end  141  of the rod  135  extends into the upper tube  30  and is attached to the piston  133  by a screw  147 . One end of a negative spring or top-out spring  143  is engaged with the underside of the piston  133 . The other end of the spring  143  is attached to a spring retainer  145 . The spring  143  biases the upper and lower tubes  30 ,  32  toward each other. 
         [0032]    A travel adjustment mechanism  136  includes an actuator  138  and a locking mechanism  140 . The actuator  138  includes an external knob  142  connected to a coupler  151  connected to shaft  144 , both extending through a connector, in this embodiment a tube  146 , and a top cap  148  threaded to the upper tube  30 . One end  150  of the tube  146  is threadably connected to the top cap  148  and the other end  152  of the tube  146  extends through the first and second positive gas springs  132 ,  134 . The tube  146  includes a helical slot  153  for receiving a set screw  155  fixed to the shaft  144 . The shaft  144  is connected to a spring  154  which is attached to a poker  156 . The poker  156  is stacked on a magnet  158  which is stacked on a return spring  160  stacked on a screw  162  which preloads the return spring  160 . The locking mechanism  140  includes a displaceable sleeve  164  and a locking element, in this embodiment, metal balls  166 . The metal balls  166  are received in holes  168  in the tube  146 . The displaceable sleeve  164  includes a piston  170  sealingly separating the first positive gas spring  132  from the second positive gas spring  134 . The sleeve  164  includes a groove  173  to receive the metal balls  166  to lock the tube  146  and the sleeve  164  together. An end  172  of the displaceable sleeve  164  is attached to the spring retainer  145  which is attached to the negative spring  143 . The piston  133  slides within the displace sleeve  164 . 
         [0033]    The first positive gas spring  132  extends between the top cap  148  and the piston  170  and the second positive gas spring  134  extends between the piston  170  and the piston  133  of the piston assembly  131 . The piston  133  includes O-rings  175 ,  178  to sealingly separate the first positive gas spring  132  and second positive gas spring  134 . The piston  170  includes O-rings  176 ,  179  to sealingly separate the second positive gas spring  134  from the lower tube. The top cap  148  includes O-rings  180 ,  182  to seal the first positive gas spring  132 . The first and second positive gas springs  132 ,  134  are filled by a Schrader valve  184  extending the coupler  151 . The gas enters the first gas spring  132  through fill ports  186  in the coupler  151  and the second positive gas spring  134  is filled through a bypass dimple  188  in the tube  146 . Although, the first and second positive gas springs  132 ,  134  are connected at top out through the bypass dimple  188 , during compression, a kick spring  174  displaces the displaceable sleeve  164  to close the bypass dimple  188  with the O-ring  175  on the piston  170 . Looking to  FIG. 17 , alternatively, the second gas spring  134  may be replaced with a coil spring  190  having one end  191  attached to a displaceable sleeve  192  similar to the displaceable sleeve  106  in  FIGS. 1-6 . The other end  194  of the coil spring  190  attached to a piston  196 . The piston  196  is attached to one end  197  of a rod  198 . The other end  199  of the rod  198  is attached to the lower tube  32 . 
         [0034]    Looking to  FIGS. 13-16 , to adjust the travel from a long travel setting to a short travel setting, the rider rotates the knob  142  to the short travel setting which rotates the coupler  151  and shaft  144 . As the shaft  144  is rotated, the set screw  155  displaces in the helical slot  153  which drives the shaft  144  to preload or compress the spring  154  which in turn applies a force against the poker  94 . The force against the poker  156  causes the poker  156  to press against the metal balls  166 . The shaft  144  is prevented from returning to the long travel setting because the slot  153  is configured such that the last few degrees of rotation are flat with no pitch which causes the force generated by the spring  154  to be perpendicular to the slot  153 , thus preventing the spring  154  from being able to return the shaft  144  to the long travel setting. Next, the rider pushes down, compressing the entire fork  130 , causing the piston assembly  131  to slidably displace within the sleeve  164  which increases pressure in the second positive gas spring  134 . This increase in pressure displaces the sleeve  164  which compresses the first gas spring  132  until the metal balls  166  align with the groove  173 . Once the metal balls  166  are aligned with the groove  173 , the spring  154  downwardly displaces the poker, which in turn, displaces the metal balls  166  radially outward into the groove  173 , locking the sleeve  164  and the tube  146  together. A chamfer  194  on the poker  156  biases the metal balls  166  radially outwardly. The first positive gas spring  132  is now locked in a compress state. The length of the entire suspension fork  130  is shortened by the length that the first positive gas spring  132  has been compressed when the sleeve  164  and the tube  146  are locked together. The preload of the second positive spring  134  does not increase from the long travel setting to the short travel setting. 
         [0035]    To adjust the fork travel from a short travel setting to a long travel setting, the rider rotates the knob  142  to the long travel setting causing the shaft  144  to displace toward the knob  142  which in turn unloads the preloaded spring  154 . The poker  156  does not return on its own to the long travel setting do to the transverse forces on the metal balls  166  created by the compressed first positive spring  132 . The rider must compress the entire fork until the forces between the first and second positive springs  132 ,  134  are substantially equal to zero. When the net force between the first and second positive springs  132 ,  134  across the sleeve  164  is substantially zero, the radially outwardly force on the metal balls  166  is near zero which allows the poker  156  to slide up and out of the way. The return spring  160  returns the poker  156  to its long travel setting. The metal balls  166  are free to move radially inwardly towards the center of the tube  146  without obstruction, but with a net zero force on the sleeve  164 , the metal balls  166  do not return to the long travel setting by themselves. There are several ways to make the metal balls  166  return to the long travel setting. In this embodiment, the force of the magnet  158  pulls or biases the metal balls  166  radially inwardly toward the tube  146 . Once the metal balls  166  are back in the tube  146 , the sleeve  164  displaces back to the long travel setting. Alternatively, a sloped poker may be used to return the metal balls  166  to the tube  146 . 
         [0036]    While this invention has been described by reference to several embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.