Abstract:
A hydraulic type shock-absorbing front fork used in a bicycle includes a locking mechanism fixedly mounted in the upper fork tube of the front fork, a main adjustment unit mounted in the top end of the upper fork tube of the front fork and adjustable to allow or not allow the hydraulic fluid to pass through the locking mechanism, and a fine adjustment unit mounted in the top end of the upper fork of the front for regulating the range of transient release of pressure during the lockout mode of the front fork to provide a comfortable riding to the user.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates a bicycle front fork shock-absorbing structure and more particularly, to a hydraulic type shock-absorbing front fork.  
         [0003]     2. Description of the Related Art  
         [0004]      FIG. 1  shows a front fork  1  for bicycle that achieves the designed shock absorbing effect by means of controlling the flowing speed of the internal hydraulic fluid  2 .  
         [0005]     As illustrated, the upper fork tube  3  has filled therein the hydraulic fluid  2  and mounted therein a flow speed control mechanism, which comprises an adjustment device  4  and a flow interceptor  5 . The flow interceptor  5  is affixed to the inside wall of the upper fork tube  3 , having an overflow vent  5   a  and a tapered inner surface  5   b . The adjustment device  4  comprises a plug  4   a  fastened to the top end of the upper fork tube  3 , a rotary knob  4  disposed outside the plug  4   a , a control rod  4   c , which has one end connected to the rotary knob  4  through a screw joint and the other end extending through the plug  4   a  and the overflow vent  5   a  of the flow interceptor  5  and fixedly mounted with a stopper  4   d . The stopper  4   d  has a tapered outer surface  4   c  facing the tapered inner surface  5   b.    
         [0006]     When rotating the rotary knob  4   b  clockwise or counter-clockwise the control rod  4   c  is moved vertically upwards or downwards. When lifting the control rod  4   c , the tapered outer surface  4   c  is approaching the tapered inner surface  5   b . On the contrary, when lowering the control rod  4   c , the tapered outer surface  4   c  is moving apart from the tapered inner surface  5   b . By means of adjusting the gap between the tapered inner surface  5   b  and the tapered outer surface  4   c , the flow rate and speed of the hydraulic fluid  2  that passes through the flow interceptor  5  are controlled, thereby obtaining the desired buffer effect.  
         [0007]     The aforesaid flow speed control mechanism achieves the expected buffer effect, however simply using the rotary knob  4   b  to move the control rod  4   c  and to further control the gap between then the tapered inner surface  5   b  and the tapered outer surface  4   c  is less precise on flow rate and flow speed control. Further, when the bicycle is moving over a sharply curved uneven road surface area after the tapered inner surface  5   b  and the tapered outer surface  4   c  have been closely attached together to lock out the hydraulic fluid  2 , a heavy impact may be produced transiently against the parts of the flow speed control mechanism, causing loosening of the parts or damage to the parts.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a hydraulic type shock absorbing front fork, which precisely controls the flow rate and speed of the hydraulic fluid. It is another object of the present invention to provide a hydraulic type shock absorbing front fork, which releases the pressure upon a sudden impact during the lockout mode, preventing damage to the parts.  
         [0009]     To achieve these and other objects of the present invention, the hydraulic type shock absorbing front fork comprises an upper fork tube, the upper fork tube having a top end and a bottom end; a bottom fork tube axially slidably coupled to the bottom end of the upper fork tube; a hydraulic fluid movable in between the upper fork tube and the bottom fork tube; a locking mechanism immovably mounted inside the upper fork tube below the fluid level of the hydraulic fluid and dividing the upper fork tube into an upper fluid chamber and a lower fluid chamber, the locking mechanism comprising a valve body, the valve body having an inlet for allowing the hydraulic fluid to pass from the lower fluid chamber to the upper fluid chamber and at least one return hole for allowing the hydraulic fluid to pass from the upper fluid chamber to the lower fluid chamber; a main adjustment unit, the main adjustment unit comprising a rotary knob and a control shaft, the rotary knob being disposed above the top end of the upper fork tube for rotation by the user to move the control shaft of the main adjustment unit to close/open the inlet, the control shaft of the main adjustment unit having an axial center through hole in communication with the inlet of the locking mechanism, a shoulder disposed in the axial center through hole, and at least one side hole in communication between the axial center through hole and the upper fluid chamber; and a fine adjustment unit, the fine adjustment unit comprising an adjustment knob disposed above the top end of the upper fork tube, a control shaft mounted in the axial center through hole of the control shaft of the main adjustment unit and coupled to the adjustment knob and movable axially in the axial center through hole upon a rotary motion of the adjustment knob, a stopper, and a spring that imparts a pressure to the stopper to force the stopper against the shoulder in the control shaft of the main adjustment unit and to further block the inlet from the at least one side hole of the control shaft of the main adjustment unit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a sectional view of a front fork according to the prior art.  
         [0011]      FIG. 2  is a sectional view of a hydraulic type shock absorbing front fork according to the present invention.  
         [0012]      FIG. 3  is an exploded view of a part of the present invention.  
         [0013]      FIG. 4  is an exploded view of the main adjustment unit and the fine adjustment unit according to the present invention.  
         [0014]      FIG. 5  is an enlarged view of the upper part of  FIG. 2 , showing the front fork under the lockout mode.  
         [0015]      FIG. 6  is a similar to  FIG. 5 , showing the lockout status of the lockout valve and upward displacement of the piston and the stopper upon an impact.  
         [0016]      FIG. 7  is similar to  FIG. 5 , showing the stopper opened, the piston and the lockout valve moved upwards.  
         [0017]      FIG. 8  is similar to  FIG. 5 , showing the control shaft of the fine adjustment unit moved inwards relative to the lockout valve. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     Referring to  FIGS. 2-5 , a hydraulic type shock absorbing front fork  100  in accordance with the present invention is adapted for use in a bicycle, and can control the flow rate and speed of the hydraulic fluid  101  therein and release the pressure during the lockout mode to prevent damage.  
         [0019]     The hydraulic type shock absorbing front fork  100  comprises an upper fork tube  10  and a bottom fork tube  12  axially coupled together to hold the hydraulic fluid  101 , a damper  14 , a locking mechanism  20 , a main adjustment unit  40 , and a fine adjustment unit  50 . The damper  14  comprises an end plug  141 , an axle  142 , and a piston  143 . The end plug  141  is fastened to the bottom end of the upper fork tube  10 . The axle  142  has a bottom end connected to the bottom fork tube  12  and a top end inserted through the end plug  141 . The piston  143  is fastened to the to the top end of the axle  142  and suspending inside the upper fork tube  10 . When the bicycle is running over an uneven road surface to cause a relative movement between the upper fork tube  10  and the bottom fork tube  12 , the hydraulic fluid  101  is forced to move by the piston  143 .  
         [0020]     The locking mechanism  20  comprises an inner tube  22 , a valve body  24 , a socket  26 , a retaining ring  28 , a valve flap  30 , a first spring  36 , a second spring  32 , and a piston  34 .  
         [0021]     The inner tube  22  has one end fastened to the end plug  141  of the damper  14  through a screw joint and the other end fastened to the valve body  24  through a screw joint, supporting the valve body  24  immovably inside the upper fork tube  10 .  
         [0022]     The valve body  24  divides the inside space of the upper fork tube  10  into an upper fluid chamber  10   a  and a lower fluid chamber  10   b , having an inlet  241  (see  FIG. 6 ) for allowing the hydraulic fluid  101  to pass from the lower fluid chamber  10   b  to the upper fluid chamber  10   a , a plurality of return holes  242  for allowing the hydraulic fluid  101  to flow backwards from the upper fluid chamber  10   a  to the lower fluid chamber  10   b , two side holes  243  and two radial through holes  244  symmetrically disposed at two sides at different elevations in communication between the inlet  241  and the upper fluid chamber  10   a  (only one side hole and one radial through hole are shown), which side holes  243  having an opening gradually increasing in direction from the side close to the bottom hydraulic fluid chamber  10   b  toward the upper hydraulic fluid chamber  10   a , two peripheral grooves  245  respectively extending across the radial through holes  244 , an inner thread  246  formed in the top end of the inlet  241 , and a shoulder  247  formed in the inlet  241  below the inner thread  246 .  
         [0023]     The socket  26  is press-fitted into the inlet  241  of the valve body  24 , having two holes  261  and a locating groove  262  extending around the periphery near the bottom side. The retaining ring  28  is fastened to the locating groove  262 .  
         [0024]     The valve flap  30  and the second spring  32  are mounted around the periphery of the socket  26 . The second spring  32  is stopped between the retaining ring  28  and the valve flap  30 , supporting the valve flap  30  in the operative position where the valve flap  30  blocks the return holes  242  of the valve body  24 .  
         [0025]     The piston  34  is mounted in the inlet  241  of the valve body  24  and forced downwards by the first spring  36  to touch the socket  26  and to simultaneously block the two side holes  243 .  
         [0026]     The main adjustment unit  40  comprises a rotary knob  42 , a bottom block  44 , a control shaft  46 , and a spring clamp  49 .  
         [0027]     The rotary knob  42  is disposed above the top end of the upper fork tube  10 . The bottom block  44  is rotatable by the rotary knob  42 , having a through hole  441  and two bottom drive rods  442 .  
         [0028]     The control shaft  46  comprises a cylindrical transmission member  47 , and a lockout valve  48 . The transmission member  47  has two recessed top receiving portions  471  coupled to the bottom drive rods  442  of the bottom block  44 , two symmetrical bottom extension strips  472 , and a locating groove  473  respectively formed on the periphery of the bottom extension strips  472 .  
         [0029]     The lockout valve  48  has two coupling grooves  484  respectively coupled to the bottom extension strips  472  of the transmission member  47 , two locating grooves  485  extending around the periphery and connected between the two coupling grooves  484  at two opposite sides, an outer thread  483  extending around the periphery below the elevation of the coupling grooves  484 , a bottom cone head  481  for contacting the shoulder  247  of the valve body  24  (see  FIG. 5 ), a neck  482  connected between the outer thread  483  and the bottom cone head  482 , an axial center through hole  486 , which extends axially through the top and bottom ends thereof, a screw hole  487  in one end of the axial center through hole  486 , two side holes  488  symmetrically formed in the neck  481  at two sides in communication between the axial center through hole  486  and the upper fluid chamber  10   a , an elongated slot  489  longitudinally formed in one coupling groove  484  in communication between the screw hole  487  and the upper fluid chamber  10   a , and a shoulder  486   a  formed in the axial center through hole  486  near the bottom. Further, a fluid chamber  10   c  is defined between the bottom side of the lockout valve  48  and the piston  34 . Further, a C-shaped retainer  45  is fastened to the locating groove  473  and the locating groove  485  to secure the transmission member  47  and the lockout valve  48  together.  
         [0030]     The spring clamp  49  is fastened to the peripheral grooves  245  of the valve body  24  and the neck  481  of the lockout valve  48  to secure the lockout valve  48  to the valve body  24 . The width of the neck  481  is slightly greater than the width of the spring clamp  49  so that the lockout valve  48  is movable relative to the valve body  24  within a limited range subject to the vertical length of the neck  481 .  
         [0031]     The fine adjustment unit  50  comprises an adjustment knob  52 , a control shaft  54 , a steel ball  60 , a spring  62 , and a stopper  64 .  
         [0032]     The adjustment knob  52  is supported on the top side of the rotary knob  42 .  
         [0033]     The control shaft  54  comprises an adjustment rod  55 , a bolt  56 , a pin  57 , and a driven rod  58 .  
         [0034]     The adjustment rod  55  is inserted through the through hole  441  of the bottom block  44  and fastened to the rotary knob  42  with the bolt  56 , having two longitudinal slots  551 . The pin  57  is transversely inserted through the top end of the driven rod  58  with the two ends respectively coupled to the longitudinal slots  551 . The driven rod  58  has a bottom outer thread  581  threaded into the screw hole  487  of the lockout valve  48  and a locating groove  582  extending around the periphery near the bottom end.  
         [0035]     The steel ball  60  is put in the elongated slot  489  of the lockout valve  48  after connection of the driven rod  58  to the lockout valve  48  and before connection of the bottom extension strips  472  of the transmission member  47  to the coupling grooves  484  of the lockout valve  48 . After mounting of the C-shaped retainer  45  in the locating groove  473  and the locating groove  485  to secure the transmission member  47  and the lockout valve  48  together, the steel ball  60  is stopped in the elongated slot  489  by the bottom extension strips  472  and partially engaging into the locating groove  582  of the driven rod  58  to stop the driven rod  58  from axial movement.  
         [0036]     The spring  62  and the stopper  64  are set in the axial center through hole  486  of the lockout valve  48  before connection of the driven rod  58  to the lockout valve  48 . The spring  62  has one end stopped against the driven rod  58  and the other end stopped against the stopper  64  to force the stopper  64  into contact with the shoulder  486   a  and to block the side holes  488 .  
         [0037]     The above statement describes the component parts of the hydraulic type shock absorbing front fork  100  and their relative positioning. The buffering action and the control of the flow speed rate and flow speed of the hydraulic fluid are outlined hereinafter.  
         [0038]      FIG. 5  shows the lockout status of the front fork  100 . Under this mode, the bicycle is suitable for running on a slope or a smooth road area for a long distance at a high efficiency. At this time, the piston  34  touches the socket  26 , the cone head  482  of the lockout valve  48  of the main adjustment unit  40  touches the shoulder  247  of the valve body  24 , and the front end of the stopper  64  touches the shoulder  486   a  of the lockout valve  48 .  
         [0039]     Referring to  FIG. 6 , when a sudden impact is produced as the bicycle is moving over an obstacle (a stone or cave) on the road under the lockout mode, the hydraulic fluid pressure in the fluid chamber  10   c  above the piston  34  surpasses the predetermined spring force of the spring  62 . Therefore, the stopper  64  is moved upwards at this time, and the hydraulic fluid  101  moves the piston  34  rapidly and at the same time flows through the through hole  243  of the valve body  24  and the side holes  488  of the lockout valve  48  into the upper fluid chamber  10   a  to release the pressure transiently. When passed over the obstacle, the springs  36  and  62  respectively push the piston  34  and the stopper  64  back to the lockout status. During the aforesaid process, the front fork  100  can still release the pressure transiently during the lockout mode when encountered an impact due to an obstacle on the road, preventing damage or loosening of the internal parts of the front fork  100 .  
         [0040]      FIG. 7  shows the front fork  100  set in the mode of being capable of producing a buffering effect for enabling the bicycle rider to ride the bicycle on an uneven rod surface for a long distance comfortably. In order to achieve this object, the bicycle rider rotates the rotary knob  42  to move the lockout valve  48 , leaving a gap between the cone head  482  and the shoulder  247  of the valve body  24 . At this time, the hydraulic fluid  101  is in an open status and allowed to pass through the locking mechanism  20 . When the bicycle is moving on an uneven road surface, the piston  34  is forced upwards by the hydraulic fluid  101 , allowing a part of the hydraulic fluid  101  to pass through the aforesaid gap to the upper fluid chamber  10   a . Because side holes  243  have an opening gradually increasing in direction from the side close to the bottom hydraulic fluid chamber  10   b  toward the upper hydraulic fluid chamber  10   a , the flow rate and speed of the hydraulic fluid passing through the side holes  243  are gradually increasing during upward displacement of the piston  34  to fork with the viscous characteristic of the hydraulic fluid  101 , thereby achieving the desired buffering effect.  
         [0041]     Further, the K value of the coefficient of elasticity of the spring  62  surpasses the K value of the coefficient of elasticity of the spring  36 . Therefore, unless encounters a sharp geographic change on the road, for example, a cave on the road, the stopper  64  is normally kept in the lockout status.  
         [0042]     Further, the bicycle rider can also operate the adjustment knob  52  to move the control shaft  54  inwards or outwards relative to the lockout valve  48  to further change the spring force of the spring  62 .  FIG. 8  shows the control shaft  54  moved inwards relative to the locknut  48 . At this time, the spring forced of the spring  62  is relatively increased, and the hydraulic fluid  101  must impart a relatively greater upward push force to move the piston  64 , i.e., the piston  64  will be moved upwards under this mode only when the bicycle is moving over an obstacle on the road.  FIG. 5  shows the control shaft  54  moved outwards relative to the lockout valve  48  and the spring force of the spring  62  is relatively reduced, and therefore the piston  64  can relatively easily be moved upwards by the hydraulic fluid  101 . As stated above, the find adjustment unit  50  allows the user to adjust the range of the transient relief of the pressure when the front fork  100  is under the lockout mode. Therefore, the invention allows accurate adjustment of the damping resistance to fit different road conditions.  
         [0043]     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.