Abstract:
A brake system includes two springs which are connected to a frame and when the initial force applied to the brake system when braking is larger than the force of the spring, the frame is shifted so as to reduce the initial force to the rider and the disk can be released for very short period of time. After the initial force is reduced, the spring force moves the frame back and the disk is clamped again.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a brake system for bicycles, and more particularly, to an anti-brake system for bicycles. 
     BACKGROUND OF THE INVENTION 
     A conventional disk brake system for bicycles is shown in FIG.  1  and generally includes an arm  1 , a clamp assembly  2  and a brake cable  3 . Although the disk brake system is welcomed by the users for its stable and sharp braking, it could brake too sharp so that the rider cannot control the bicycle especially when the bicycle is ridden at a high speed. The initial force makes the rider to fall if the brake system is activated too sharp. 
     The present invention intends to provide a disk brake system wherein the disk is not clamped during braking so as to reduce the initial force applied to the riders. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, there is provided a brake system connected to a front fork or seat stays and activated by a brake cable so as to clamp a disk. The brake system comprises a frame located on a side of the disk and a rack is arranged on a side of the frame. A positioning member is fixed to the front fork or the seat stays. A clamping assembly is movably connected onto the disk and operatively connected to the frame and the positioning member. The clamping assembly includes a clamp member which has a slot in which the disk is received therein. A passage is defined in the clamp member and two blocks are located below the passage. An activation member is slidably received in the passage of the clamp member and is connected to the frame. A groove is defined in each of two sides of the activation member and two springs are received in the two grooves. One of tow ends of each of the springs is engaged with a protrusions extending from an insides of each of the grooves, and the other end of each of the springs contacts the blocks. A pawl is located in the clamp member and includes teeth engaged with the rack. A plurality of beads are installed at a side of the pawl. A main shaft is located in the clamp member and between a side of the disk and the pawl. A plurality of tear-shaped recesses are defined in a side of the disk portion and each recess includes a shallow portion and a deep portion. The beads are movably received in the recesses. An adjusting cover is located in the clamp member and on the other side of the disk. Two linings are located on the two sides of the disk and between the main shaft and the adjusting cover. The linings may clamp the disk when the brake cable is pulled. 
     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a conventional brake system; 
     FIG. 2 is a perspective view to show the brake system of the present invention; 
     FIG. 3 is a plane view to show the brake system of the present invention; 
     FIG. 4 shows the cross sectional view taken from the plane  4 — 4  as illustrated in FIG. 3; 
     FIG. 5 shows that the brake system of the present invention is not yet activated; 
     FIG. 6 shows that the brake system of the present invention is activated; 
     FIGS. 7 and 8 show the actions that the brake system of the present invention is activated and the disk is discontinuously clamped, and 
     FIG. 9 is an exploded view to show another embodiment of the brake system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 2, the brake system of the present invention can be installed on the front fork  6  or the seat stays and is activated by a brake cable  8  connected to an arm  9 , so that disk  7  is clamped. The brake assembly  5  comprises a frame  10 , a positioning member  20  and a clamping assembly  30 . The frame  10  is located on a side of the disk  7  and has holes  11 ,  12 ,  13  on an upper portion and a lower portion thereof. A rack  15  is arranged on a side of the frame  10 . 
     The positioning member  20  includes a main part  21  which has two threaded holes  26  so as to be fixed to the front fork  6  or the seat stays. A first part  22  and a second part  23  are connected to the main part  21 . The first part  22  has a hole  221  through which a first adjusting rod  24  is connected, the other end of the first adjusting rod  24  is engaged with the hole  11  in the frame  10 . The second part  23  has a hole  231  through which a second adjusting rod  25  is connected, the other end of the second adjusting rod  25  is engaged with the other hole  12  in the frame  10 . The first part  22  and the second part  23  are parallel with each other. A bush  241  is mounted to the first adjusting rod  24 . Another bush  251  and a C-shaped clamp  252  are respectively mounted to the second adjusting rod  25 . An off-set portion  28  is formed on the main part  21  and reinforcement ribs  281  and  282  are defined in the off-set portion  28 . 
     The clamping assembly  30  is movably connected onto the disk  7  and operatively connected to the frame  10  and the positioning member  20 . The clamping assembly  30  includes a clamp member  31  which has a slot  311  in which the disk  7  is installed, and a passage  312  is defined in the clamp member  31 . An extension  313  extends from the clamp member  31  so as to be connected to the brake cable  8 . Two blocks  314  are located at a bottom of the passage  312  and two durable plates  315  are inserted in the passage  31 . Each durable plate  315  includes a flange  316  so as to be fixed to the blocks  314  by bolts  318 . 
     An activation member  32  is slidably received in the passage  312  of the clamp member  31  and has two threaded holes  321  so as to be connected to the frame  10  by extending bolts  322  through the threaded holes  321  and engaged with the frame  10 . A groove  323  is defined in each of two sides of the activation member  32  and two springs  33  are received in the two grooves  323 . One of tow ends of each of the springs  33  is engaged with a protrusions  324  extending from an insides of each of the grooves  323 , the other end of each of the springs  33  is compressed by the blocks  314 . 
     A pawl  34  is located in the clamp member  31  and includes a central hole  341 . The teeth  342  on the pawl  34  are engaged with the rack  15  and a plurality of beads  345  are installed at a side of the pawl  34  facing the disk  7 . 
     A main shaft  35  is located in the clamp member  31  and between a side of the disk  7  and the pawl  34 . The main shaft  35  has a disk portion  351  with a O-ring  35 B and a shank  352  extends from a side of the disk portion  351 . The shank  352  with a bush  353  mounted thereon extends through the central hole  341  of the pawl  34  and the clamp member  31 . A plurality of tear-shaped recesses  354  are defined in a side of the disk portion  351  and each recess  354  includes a shallow portion  355  and a deep portion  356 . The beads  345  are movably engaged with the recesses  354 . A nipple  357  extends from the other side of the disk portion  351  and toward the disk  7 . A head  358  is formed on the nipple  357  and an engaging groove  359  is defined in the nipple  357  so that a flexible clamp  35 A is engaged with the engaging groove  359 . 
     An adjusting cover  36  is located in the clamp member  31  and on the other side of the disk  7 . The adjusting cover  36  includes teeth  361  on a periphery thereof and a holding portion  366 . A stopper assembly  362  is engaged with the teeth  361 . A nipple  363  extends from the adjusting cover  36  and toward the disk  7 . A head  364  is formed on the nipple  363  and an engaging groove  365  is defined in the nipple  363  so that a flexible clamp  36 A is engaged with the engaging groove  365 . A durable ring  36 B is mounted to the adjusting cover  36  so that the adjusting cover  36  can be moved toward the disk  7  by rotating the holding portion  366 . 
     Two linings  37  are located on the two sides of the disk  7  and between the main shaft  35  and the adjusting cover  36 . Each lining  37  has a concavity  371  defined in a side which faces the nipple  357 / 363  so that the two flexible clamps  35 A and  36 A are received in the concavities  371 . The two linings  37  are connected to the main shaft  35  and the adjusting cover  36  by the expansion of the two flexible clamps  35 A,  36 A. When the brake cable  8  is pulled, the linings  37  clamp the disk  7 . 
     Referring to FIGS. 5 to  8 , when the brake system is activated at a high speed, the brake cable  8  pivots the arm  9  to let the main shaft  35  rotated counter clockwise. The tear-shaped recesses  354  are rotated with the main shaft  35  and the beads  345  are moved from the deep portion  356  to the shallow portion  355 . The beads  345  are then protruded from the recesses  354  and push the main shaft  35  toward the disk  7  and the two linings  37  clamp the disk  7  as shown in FIGS. 5 and 6. 
     When the initial force is larger than the force of the springs  33 , the disk  7  drives the clamping assembly  30  along the direction of the groove  323  of the activation member  32 , so that the blocks  314  of the clamp member  31  compress the springs  33 . The pawl  34  is rotated counter clockwise by the rack  15  so that the beads  345  move from the shallow portions  355  to the deep portion  356  of the recesses  354 . This makes the linings  37  disengage the disk  7  as shown in FIG.  7 . 
     After a small gap of time two or three thousandth second, the initial force is less than the force of the springs  33 , the clamping assembly  30  is pushed back to its original position and the pawl  34  is rotated clockwise and the beads  345  again protrude and push the main shaft  35  to let linings  37  clamp the disk  7  again as shown in FIG.  8 . The disk  7  is clamped and released within a very short period of time so as to prevent the rider from falling by the initial force. 
     FIG. 9 shows another embodiment of the present invention wherein the brake system includes a frame  50 , a positioning member  60 , and a clamping assembly  70  which includes a clamp member  71 , a activation member  72 , a pawl  73 , a main shaft  74 , an adjusting cover  75  and two linings  76 , wherein the frame  50  and the rack  51  are made into a one-piece member. 
     While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.