Abstract:
A hydraulic front fork includes a fixed locking mechanism mounted in the upper fork tube, and a first adjustment mechanism mounted in the top end of the upper fork tube adjustable to control the flowing path of the hydraulic fluid through the locking mechanism such that the bicycle is suitable for running on slopes and smooth road surfaces efficiently when the hydraulic fluid is locked out and prohibited from passing through the locking mechanism, and the hydraulic front fork can absorb shocks when the hydraulic fluid is allowed to pass through the locking mechanism.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates a bicycle front fork shock-absorbing structure and more particularly, to a hydraulic front fork that provides a locking function. 
   2. Description of the Related Art 
   A hydraulic type shock-absorbing front form for bicycle comprises an upper fork tube and a bottom fork tube axially coupled together, and a locking mechanism mounted on the inside. When the bicycle is moving over an uneven road surface to cause a relative movement between the upper fork tube and the lower fork tube, the internal hydraulic fluid is forced through the locking mechanism to change the flow path, thereby absorbing the shocks to provide a comfortable riding effect. 
     FIG. 1  shows a hydraulic front fork according to the prior art. According to this design, the front fork  1  has the inside space filled with a hydraulic fluid. Further, the front fork  1  comprises an upper fork tube  2 , a bottom fork tube  3 , a valve bush  4 , which is fixedly mounted in the bottom side of the upper fork tube  2  and has one inlet  4   a  and two return-flow holes  4   b , a flap  5  fastened to the bottom side of the valve bush  4  and adapted to cover the return-flow holes  4   b , a needle valve  6 , which is axially mounted in the upper fork tube  2  and has a conical front end  6   a  facing the top end of the inlet  4   a  and a rear end  6   b  extending out of the top end of the upper fork tube  2  for driving by an external force to adjust the pitch between the front end  6   a  and the top end of the inlet  4   a  and to further achieve changing of the flow rate and speed of the hydraulic fluid passing through the valve bush  4 . 
   When the front end  6   a  is stopped against the inlet  4   a  to block the passage and when the upper fork tube  2  and the bottom fork tube  3  are moved relative to each other (i.e., the bicycle is moving over an uneven road surface), the needle valve  6  receives an impact force from the hydraulic fluid that flows upwards through the inlet  4   a . Under the repeated impact effect of the hydraulic fluid, the connection area between the needle valve  6  and the upper fork tube  2  becomes loosened quickly. 
   SUMMARY OF THE INVENTION 
   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 front fork, which prevents loosening of the structure due to rushing of the hydraulic fluid when the locking mechanism is set in the lockout status, thereby providing a comfortable riding effect. 
   To achieve this and other objects of the present invention, the hydraulic 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; and 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 a first hydraulic fluid chamber and a second hydraulic fluid chamber, the locking mechanism comprising a valve body, the valve body having an axial center through hole disposed in communication with the first hydraulic fluid chamber, at least one return-flow holes disposed in communication between the axial center through hole and the second hydraulic fluid chamber, at least one side hole disposed in communication with the axial center through hole and the first hydraulic fluid chamber, an inner thread formed in a top end of the axial center through hole, and a shoulder formed in the axial center through hole below the outer thread, a piston axially movably mounted in the axial center through hole of the valve body, and spring means adapted to force the piston toward the second hydraulic fluid chamber; a first adjustment mechanism coupled to the top end of the upper fork tube remote from the bottom fork tube, the first adjustment mechanism comprising a rotary knob rotatably mounted on the top end of the upper fork tube, the rotary knob having a drive unit extending to the first hydraulic fluid chamber inside the upper fork tube, a control shaft, the control shaft having an outer thread threaded into the inner thread of the valve body, a front end terminating in a cone head, a rear end terminating in a driven unit and coupled to the drive unit of the rotary knob, a through hole, and at least one radial hole disposed in communication between the axial center through hole and the first hydraulic fluid chamber, and a discharge control device set mounted in the through hole of the control shaft, the discharge control device set comprising a stopper movable in the through hole of the control shaft and a spring member, which forces the stopper to block the passage between the through hole of the control shaft and the first hydraulic fluid chamber; wherein rotating the rotary knob clockwise/counter-clockwise causes the control shaft to be moved axially forwards/backwards between a lockout position where the front cone head of the control shaft is stopped at the shoulder in the axial center through hole of the valve body to block the passage through the axial center through hole of the valve body, and an open position where the front cone head of the control shaft is opened from the shoulder for allowing the hydraulic fluid to pass through the axial center through hole of the valve body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of a front fork according to the prior art. 
       FIG. 2  is a sectional view of a hydraulic front fork according to the present invention. 
       FIG. 3  is an enlarged view of the upper part of  FIG. 2 . 
       FIG. 4  is an exploded view of a part of the present invention. 
       FIG. 5  is an exploded view of the first adjustment mechanism of the hydraulic front fork according to the present invention. 
       FIG. 6  is an elevational view of the first adjustment mechanism and the locking mechanism of the hydraulic front fork according to the present invention. 
       FIG. 7  is an enlarged view of the lower part of  FIG. 2 . 
       FIG. 8  is an exploded view of a part of the second adjustment mechanism of the hydraulic front fork according to the present invention. 
       FIG. 9  is similar to  FIG. 3  but showing the locking valve in the lockout status, the stopper and the piston slightly moved upwards. 
       FIGS. 10 and 11  show the locking valve in the open status, the stopper in the lockout status, the piston moved upwards. 
       FIG. 12  is similar to  FIG. 3 , showing downward movement of the hydraulic fluid. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 2 and 3 , a hydraulic front fork  100  is shown comprising an upper fork tube  101 , a bottom fork tube  102  partially sleeved onto the upper fork tube  101 , a hydraulic fluid  103  filled in and movable between the upper fork tube  101  and the bottom fork tube  102 , a first adjustment mechanism  10  mounted in the top end of the upper fork tube. 101 , a locking mechanism  30 , a second adjustment mechanism  50 , and an inner tube  60 . The inner tube  60  is mounted inside the upper fork tube  101 , having a first screw hole  60   a  and a second screw hole  60   b  respectively formed in the two distal ends. The first screw hole  60   a  is threaded onto the outer thread  321  of the valve body  32  of the locking mechanism  30 . The second screw hole  60   b  is threaded onto the first outer thread  521  of the stepped end screw cap  52  of the second adjustment mechanism  50 . 
   Referring to  FIGS. 4 and 5  and  FIG. 3  again, the first adjustment mechanism  10  comprises: 
   a top screw cap  12 , which has a threaded shank  121  threaded into the top screw hole  101   a  of the upper fork tube  101 , a center through hole  122 , and two bottom countersunk holes  123 ; 
   a rotary knob  14 , which comprises a handle  141 , a base  142 , which is upwardly inserted through the center through hole  122  of the top screw cap  12  and has a plurality of recessed locating holes  142   a  equiangularly spaced around the center axis thereof and disposed at the bottom side of the top screw cap  12  and two bottom drive rods  142   b  that form a driving unit, and a tie pin  143  fastened to the handle  141  and the base  142  to secure the handle  141  and the base  142  together; 
   two spring members  16  respectively mounted in the bottom countersunk holes  123  of the top screw cap  12 ; 
   two steel balls  18  respectively supported on the spring members  16  at the bottom side and selectively engaged into the recessed locating holes  142   a  subject to the control of the rotary knob  14 ; 
   a control shaft  20 , which comprises a cylindrical transmission member  22 , which has two recessed top receiving portions  221  that form a driven unit and are respectively coupled to the bottom drive rods  142   b  of the base  142  of the rotary knob  14 , two symmetrical bottom extension strips  222 , and two retaining groove  223  respectively formed on the periphery of the bottom extension strips  222 , and a locking valve  24 , which has two coupling grooves  241  respectively coupled to the bottom extension strips  222  of the cylindrical transmission member  22 , two retaining grooves  242  extending around the periphery and connected between the two coupling grooves  241  at two opposite sides, an outer thread  243  extending around the periphery below the elevation of the coupling grooves  241 , a bottom cone head  245 , a neck  244  connected between the outer thread  243  and the bottom cone head  245 , an axial center through hole  246 , which extends axially through the top and bottom ends thereof, the locking valve  24  and has a narrow diameter portion  246   a , and two radial holes  247  disposed at two opposite sides in communication between the axial center through hole  246  and a first hydraulic fluid chamber  104  defined in the upper fork tube  101 ; 
   a C-shaped retainer  26  fastened to the retaining grooves  223  of the cylindrical transmission member  22  and the retaining grooves  242  of the locking valve  24  to secure the cylindrical transmission member  22  and the locking valve  24  together; and 
   a discharge control device set  28 , which is mounted in the axial center through hole  246  of the locking valve  24 , comprising a locating block  283  fixedly fastened to the axial center through hole  246  near the top, a stopper  281  adapted to stop the narrow diameter portion  246   a  of the axial center through hole  246  to further block the passage between the axial center through hole  246  and the first hydraulic fluid chamber  104 , and a spring member  282  set in the axial center through hole  246  between the locating block  283  and the stopper  281  to force the stopper  281  against the narrow diameter portion  246   a.    
   When rotating the rotary knob  14  of the first adjustment mechanism  10 , the control shaft  20  is rotated with the rotary knob  14  in the same direction. 
   The locking mechanism  30  is mounted in the top end of the inner tube  60  below the fluid level of the hydraulic fluid  103 , dividing the inside space of the upper fork tube  101  into a first hydraulic fluid chamber  104  and a second hydraulic fluid chamber  105 . As shown in  FIG. 2 , the second hydraulic fluid chamber  105  is defined inside the inner tube  60  between the valve body  32  of the locking mechanism  30  and the stepped end screw cap  52  of the second adjustment mechanism  50 . 
   Referring to  FIG. 6  and  FIG. 3  again, the locking mechanism  30  comprises: 
   a valve body  32 , which has an axial center through hole  322  disposed in communication with the first hydraulic fluid chamber  104 , a plurality of return-flow holes  323  spaced around and disposed in communication with the first and the second hydraulic fluid chamber  104 ,  105 , two side holes  324 , which are symmetrical disposed in communication with the axial center through hole  322  at two opposite sides above the return-flow holes  323  (only one side hole  324  is shown) and made having a diameter gradually increasing in direction from the side close to the second hydraulic fluid chamber  105  toward the first hydraulic fluid chamber  104 , two radial through holes  325  in communication with the axial center through hole  322 , two peripheral grooves  326  respectively extending across the radial through holes  325 , an inner thread  327  formed in the top end of the axial center through hole  322  and threaded onto the outer thread  243  of the locking valve  24  (see  FIG. 3 ), and a shoulder  328  formed in the axial center through hole  322  below the outer thread  327 ; 
   a substantially U-shaped spring clamp  34  fastened to the peripheral grooves  326  of the valve body  32  and the neck  244  of the locking valve  24  to secure the locking valve  24  to the axial center through hole  322  of the valve body  32  for allowing axial movement of the locking valve  24  relative to the valve body  32  within a limited range subject to the vertical length of the neck  244 ; 
   a socket  36 , which is press-fitted into the axial center through hole  322  of the valve body  32  from the bottom side, having two holes  361  respectively disposed below the return-flow holes  323  (only one hole  361  is shown in  FIG. 3 ) and a retaining groove  362  extending around the periphery near the bottom side; 
   a valve flap  38  mounted on the periphery of the socket  36  before connection of the socket  36  to the valve body  32 ; 
   a retaining ring  42  fastened to the retaining groove  362  of the socket  36 ; 
   a spring member  40  sleeved onto the socket  36  and stopped between the valve flap  38  and the retaining ring  42  to support the valve flap  38  in the close position to close the return-flow holes  323 ; 
   a spring member  46  mounted in the axial center through hole  322  of the valve body  32  before connection of the locking valve  24  of the control shaft  20 ; and 
   a piston  44 , which is mounted in the axial center through hole  322  of the valve body  32  before connection of the locking valve  24  of the control shaft  20  to the valve body  32  and adapted to block the side holes  324  and to further stop the passage between the first hydraulic fluid chamber  104  and the second hydraulic fluid chamber  105  during the stage shown in  FIG. 3 , having a front end  44   a , which is forced by the spring force of the spring member  46  against the socket  36  and a through hole  44   b  in the front end  44   a.    
   Referring to  FIG. 11 , when the hydraulic fluid  103  is forced through the return-flow holes  323  to push the valve flap  38  downwards, the hydraulic fluid  103  will pass through the holes  361  of the socket  36  toward the second hydraulic fluid chamber  105 . 
   Referring to  FIGS. 7 and 8 , the second adjustment mechanism  50  comprises: 
   a stepped end screw cap  52 , which has a first outer thread  521  and a second outer thread  522  respectively threaded into the second screw hole  60   b  of the inner tube  60  and the bottom screw hole  101   b  of the upper fork tube  101  to secure the inner tube  60  and the locking mechanism  30  to the inside of the upper fork tube  101  and a axial center through hole  523 ; 
   a sleeve  54 , which is inserted through the axial center through hole  523  of the stepped end screw cap  52 , having a side hole  541  near the top end; 
   a damper  56 , which is fixedly mounted in the top end of the sleeve  54  above the side hole  541  to divide the second hydraulic fluid chamber  105  into an upper space  105   a  and a lower space  105   b , having a plurality of through holes  561  disposed in communication between the upper space  105   a  and the lower space  105   b;    
   a spring member  59 ; 
   a valve flap  58  forced by the spring member  59  to block the through holes  561 ; 
   an axle  62 , which is inserted into the sleeve  54 , having a top notch  621  facing the side hole  541  of the sleeve  54  to let the upper space  105   a  be in communication with the lower space  105   b , and a plughole  622  disposed adjacent to the top notch  621 ; and 
   a locating pin  64  inserted through the side hole  541  of the sleeve  54  and fastened to the plughole  622  of the axle  62 . 
   The bottom end of the axle  62  extends downwardly to the outside of the bottom fork tube  102  for enabling the axle  62  to be rotated by an external force to change the opening status of the notch  521  relative to the side hole  541  and to further control the flow rate of the hydraulic fluid  103 . 
   The aforesaid locating pin  64  is movable with the axle  62  between the top and bottom ends of the side hole  541  to limit the damping force adjustment range. 
   The above statement describes the component parts of the hydraulic front fork  100  and their relative positioning. When rotating the rotary knob  14  clockwise or counter-clockwise, the locking valve  24  of the control shaft  20  is moved forwards or backwards relative to the valve body  32 . As shown in  FIG. 3 , when the bottom cone head  245  of the locking valve  24  is stopped at the shoulder  328  in the axial center through hole  322  of the valve body  32 , the hydraulic front fork  100  is held in a lockout status without buffer, suitable for running on a slope or smooth road surface to enhance the bicycle pedaling efficiency. 
   When the bicycle encountered an unexpected uneven road surface under the aforesaid lockout status during running, the hydraulic fluid  103  in the second hydraulic fluid chamber  105  of the hydraulic front fork  100  is forced to push the piston  44  and the stopper  281  upwards, as shown in  FIG. 9 . At this time, the hydraulic fluid  103  passes through the side holes  324  and the radial holes  247  into the first hydraulic fluid chamber  104  to discharge the pressure instantly, preventing the production of an impact force against the component parts of the hydraulic front fork  100 . After passed over the uneven road surface, the piston  44  and the stopper  281  are respectively returned to their former lockout position (see  FIG. 3 ) by the respective spring members  46  and  282 , keeping the hydraulic front fork  100  in the lockout status. Therefore, the invention provides a comfortable riding environment to the bicycle rider. 
   If the bicycle rider is going to ride the bicycle on an uneven road or ground area for a long distance, the bicycle rider can operate the first adjustment mechanism  10  to keep the bottom cone head  245  of the locking valve  24  spaced from the shoulder  328  of the valve body  32  at a distance. When the bicycle is moving over a small and moderately curved uneven road surface area at this time, the piston  44  will be forced to move slightly upwards (see  FIG. 10 ). When the bicycle is moving over a sharply curved uneven road surface area, the piston  44  will be forced upwards at a rush to increase the opening status of the side holes  324  (see  FIG. 11 ), enabling the hydraulic fluid  103  to pass through the side holes  324  at a gradually increasing flow rate to buffer and absorb shocks. Further, the K value of the coefficient of elasticity of the spring member  282  surpasses the K value of the coefficient of elasticity of the spring member  46 . Therefore, unless encountering a sharp geographic change in the way, the stopper  281  is normally kept in the lockout status when the bicycle is moving on an uneven road surface or ground area for a long distance. 
     FIG. 12  shows the bottom fork tube  102  moved relative to the upper fork tube  101  and returned to the former position. At this time, the hydraulic fluid  103  flows from the first hydraulic fluid chamber  104  back to the second hydraulic fluid chamber  105  through the return-flow holes  323  and the holes  361  of the socket  36 , keeping the upper fork tube  101  and the bottom fork tube  102  in balance. 
   Further, the second adjustment mechanism  50  that is adapted to push the hydraulic fluid  103  in the second hydraulic fluid chamber  104  acts in accordance with the first adjustment mechanism  10 , for enabling the hydraulic front fork  100  to be accurately adjusted to the desired damping resistance. Further, the design of the present invention can reduce the use of the amount of the hydraulic fluid, thereby lowering the total weight of the hydraulic front fork. 
   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.