Abstract:
A hydraulic brake master cylinder includes a cylinder unit having first and second spaces, a channel communicating the spaces and an adjuster exposed outside; a piston slidably disposed in the first space; a first spring applying an elastic force to the piston; a rod moving relative to the piston; a second spring applying an elastic force to the rod; a seal attached to the rod and moving controllably to seal the channel; and a nut threaded onto the rod. The adjuster is rotatable to make the nut and the rod rotate with respect to each other so as to change the distance between the seal and the end of the channel to adjust the free stroke.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to hydraulic brake master cylinders and more particularly, to a hydraulic brake master cylinder capable of pad contact point adjustment. 
     2. Description of Related Art 
     A hydraulic brake master cylinder of a bicycle is adapted to be mounted to a handle bar of the bicycle and connected with a brake to lever. During the process of user&#39;s pulling the brake lever toward the handle bar, brake fluid in the hydraulic brake master cylinder is vented into a hose and delivered to calipers so that the brake pads are forced to move to contact a brake disc so as to slow the bicycle. 
     Generally speaking, during the user&#39;s brake lever pressing process, the hydraulic brake master cylinder may be configured, to have a free stroke during which no brake fluid is vented out. The length of the free stroke influences how the brake lever feels to the user, how far the brake pads move and how far the brake lever must be pulled to slow the bicycle. The shorter the free stroke is, the faster the brake reacts and the firmer the brake feels. 
     The hydraulic brake master cylinder capable of pad contact point adjustment is well developed and commercially available. It allows the user to adjust the distance that the brake pads move and the brake effect by adjusting the free stroke thereof. However, conventional hydraulic brake master cylinders capable of pad contact point adjustment cannot be easily manufactured and assembled due to complicated constructions thereof. In addition, these hydraulic brake master cylinders are inconvenient in use because they can be adjusted only when the users utilize some tools. Therefore, hydraulic brake master cylinders capable of pad contact point adjustment still need further improvement. 
     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in view of the above-noted circumstances. It is an objective of the present invention to provide a hydraulic brake master cylinder capable of pad contact point adjustment, which can be adjusted without any tool and has a simple construction so as to be manufactured and assembled easily. 
     To attain the above objective, the present invention provides a hydraulic brake master cylinder which comprises a cylinder unit, a piston, a first spring, a rod, a second spring, a seal, and a nut threaded onto the rod. The cylinder unit includes a first space, a second space, a channel communicating the first space and the second space, an outlet communicating the first space with outside of the cylinder unit, and an adjuster exposed outside. The piston is provided with a guide hole and axially slidably disposed in the first space. The first spring applies an elastic force to the piston. The rod has a first end portion disposed in the guide hole of the piston in a way that the first end portion is slidable in the guide hole of the piston when the piston is forced to slide in the first space relative to the rod, and a second end portion disposed opposite to the first end portion. The second spring applies an elastic force to the second end portion of the rod. The seal is attached to the rod and movable with the rod to seal the channel so as to block the first space from communicating with the second space. The adjuster is rotatable to make the nut and the rod rotate with respect to each other so as to change a distance between the seal and the end of the channel. 
     The hydraulic brake master cylinder is applied to a bicycle handle bar in such a way that the cylinder unit is mounted to the handle bar of the bicycle; the piston is connected with a brake lever; the first space and second space are filled with brake fluid. During the process of user&#39;s pressing the brake lever to make the piston slide from an initial position toward the second space, the hydraulic brake master cylinder will have at first a free stroke during which no brake fluid is vented out until the seal seals the end of the channel. Thereafter, brake fluid will be vented out through the outlet. The user can rotate the adjuster to change the distance from the seal to the channel so as to adjust the free stroke of the hydraulic brake master cylinder. As a result, the hydraulic brake master cylinder is capable of pad contact point adjustment and can be adjusted without any tool. Another advantage is, the hydraulic brake master cylinder is simple in construction so as to be manufactured and assembled easily. 
     Further scope of applicability of the present invention become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is an assembled perspective view of a hydraulic brake master cylinder according to a first preferred embodiment of the present invention, which is mounted to a handle bar and connected with a brake lever; 
         FIG. 2  is an exploded perspective view of the hydraulic brake master cylinder and the brake lever in  FIG. 1 ; 
         FIG. 3  is a sectional view of a main cylinder body, a connector and an adjuster of the hydraulic brake master cylinder according to the first preferred embodiment of the present invention; 
         FIGS. 4-6  are sectional views illustrating the process of how the hydraulic brake master cylinder acts; 
         FIG. 7  is an assembled perspective view of a hydraulic brake master cylinder according to a second preferred embodiment of the present invention, which is mounted to a handle bar and connected with a brake lever; 
         FIG. 8  is an exploded perspective view of the hydraulic brake master cylinder and the brake lever in  FIG. 7 ; 
         FIG. 9  is a sectional view of a main cylinder body of the hydraulic brake master cylinder according to the second preferred embodiment of the present invention; and 
         FIG. 10  is a sectional view of the hydraulic brake master cylinder, the handle bar and the brake lever in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First of all, it is to be mentioned that same reference numerals used in the following preferred embodiments and the appendix drawings designate same or similar elements throughout the specification for the purpose of concise illustration of the present invention. 
     As shown in  FIGS. 1-4 , a hydraulic brake master cylinder  10 , which is provided by a first preferred embodiment of the present invention, comprises a cylinder unit  20  and an action mechanism  30  disposed in the cylinder unit  20 . 
     The cylinder unit  20  primarily comprises a main cylinder body  21 , a connector  22 , an adjuster  23 , a cap  24  and a membrane  25 , wherein the main cylinder body  21 , the connector  22  and the adjuster  23  are tubular. One end of the adjuster  23  is rotatably attached to the connector  22  which is threaded into one end of the main cylinder body  21 . The membrane  25  is attached to one end of the cap  24  which is attached to another end of the adjuster  23 , and the membrane  25  is located inside the adjuster  23 . As a result, inside the cylinder unit  20  there are a first space  212  inside the main cylinder body  21 , a second space  232  inside the adjuster  23 , a channel  222  inside the connector  22  communicating the first space  212  and the second space  232 , and a reserved space  242  developed between the membrane  25  and the cap  24 . The main cylinder body  21  also has an outlet  214  communicating the first space  212  with the outside of the cylinder unit  20 , and the adjuster  23  has a drive portion  234  defined by a hexagonal inner wall. 
     The action mechanism  30  primarily comprises a piston  31 , a rod  32 , a first spring  33 , a second spring  34 , a nut  35  and a seal  36 . 
     The piston  31 , which has a guide hole  312  at its center at an end face thereof, is disposed in the first space  212  and slidable from an initial position P 1  as shown in  FIG. 4  toward the second space  232  when receiving an external force. 
     The rod  32  has a first end portion  321  limited in the guide hole  312  of the piston  31  by a first washer  324 , and a second end portion  322  opposite to the first end portion  321  and disposed in the second space  232 . The second end portion  322  is hexagonal and complementarily received in the drive portion  234  of the adjuster  23  so that the second end portion  322  is slidable along the drive portion  234 , and the rod  32  is rotatable by the rotation motion of the adjuster  23  directly. In addition, the piston  31  is movable relative to the rod  32  to make the first end portion  321  of the rod  32  slide deep inside the guide hole  312 . 
     The first spring  33  is a compression spring disposed in the first space  212  and stopped between the piston  31  and the main cylinder body  21  through the first washer  324  and a second washer  326  so as to provide an elastic force for driving the piston  31  to move back to the initial position P 1 . 
     The second spring  34  is a compression spring disposed in the second space  232  and stopped between the connector  22  and the second end portion  322  of the rod  32  so as to provide an elastic three to push the rod  32  toward the cap  24 . Therefore, the second spring  34  can prohibit the first end portion  321  of the rod  32  from sliding along the guide hole  312  of the piston  31  to make the rod.  32  move with the piston  31 . 
     The nut  35  is axially movably disposed in the first space  212  and threaded on to the rod  32 . Because of the design of shape, the nut  35  can&#39;t rotate relative to the main cylinder body  21 . When the rod  32  is rotated by the adjuster  23 , the rod  32  rotates relative to the nut  35 ; meanwhile, the nut  35  slides along the rod  32  so that the position of the nut  35  relative to the rod  32  changes. 
     The seal  36 , which is located between the nut  35  and the connector  22 , is sleeved onto the rod  32  and fastened to the nut  35 . The seal  36  is movable with the axial movement of the rod  32  seal one end of the channel  222  so as to block the first space  212  from communicating with the second space  232 . 
     When the hydraulic brake master cylinder  10  is in use, the main cylinder body  21  is mounted to a handle bar  40  of a bicycle in such a way that a connecting linkage  52  is connected between the piston  31  and a brake lever  54 , and the first space  212  and the second space  232  are filled with brake fluid. As shown in  FIGS. 4-6 , in a process of user&#39;s pressing the brake lever  54  toward the handle bar  40 , the piston  31  is pushed by the connecting linkage  52  to slide from the initial position P 1  toward the second space  232 . At an initial stage, the rod  32  synchronously moves along with the piston  31  whose axially sliding motion forces the brake fluid in the first space  212  to vent to the second space  232  until the seal  36  abuts against and seals said end of the channel  222 , as shown in  FIG. 5 . Thereafter, because the nut  35  is stopped at the shoulder provided between the first space  212  and the channel  222  the rod  32  can&#39;t continuously move toward the second space  232  with the piston  31 . Therefore, at this stage the piston  31 , which is forced to continuously move toward the second space  232 , moves relative to the rod  32  to cause the first end portion  321  of the rod  32  to slide into deep inside of the guide hole  312 , as shown in  FIG. 6 . At the same time, the brake fluid in the first space  212  is vented through the outlet  214  into a hose  60  to initiate the bicycle brake action. In other words, the initial stage, i.e. the period the rod  32  slides along with the piston  31  until the seal  36  seals the channel  222 , is a free stroke of the hydraulic brake master cylinder  10 , during which no brake fluid is vented out. 
     If the user feels that the brake reacts too slowly or the brake force is insufficient, the user can rotate the adjuster  23  to make the nut  35  axially move toward the second space  232  relative to the rod  32  to shorten the free stroke of the hydraulic brake master cylinder  10 . This feature means the hydraulic brake master cylinder  10  is capable of pad contact point adjustment and can be adjusted by rotating the adjuster  23  without any tool. Another advantage is, the hydraulic brake master cylinder  10  is simple in construction so as to be manufactured and assembled easily. 
     As shown in  FIGS. 7-10 , a hydraulic brake master cylinder  70 , which is provided by a second preferred embodiment of the present invention, comprises a cylinder unit  80  and an action mechanism  90  disposed in the cylinder unit  80 . 
     The cylinder unit  80  primarily comprises a main cylinder body  81 , a cap  82  and a piston rod  83  disposed in two ends of the main cylinder body  81  respectively, a membrane  84  disposed between the cap  82  and the main cylinder body  81 , and an adjuster  85  sleeved onto the piston rod  83  in such a way that the adjuster  85  is able to rotate the piston rod  83 . The cylinder unit  80  is the same as in aforesaid first preferred embodiment, inside the cylinder unit  80  there are a first space  811 , a second space  812 , a channel  814  communicating the first space  811  and the second space  812 , an outlet  816  communicating the first space  811  with the outside of the cylinder unit  80 , and a reserved space  822  developed between the membrane  84  and the cap  82 . However, the cylinder unit  80  differs from the cylinder unit  20  in that the first space  811 , the second space  812  and the channel  814  are all located inside the main cylinder body  81 . 
     The action mechanism  90  is the same as in aforesaid first preferred embodiment. The action mechanism  90  comprises a piston  91 , a rod  92 , a first spring  93 , a second spring  94 , a nut  95  and a seal  96 . However, the action mechanism  90  differs from the action mechanism  30  in that the piston  91  is attached to the piston rod  83  which is connected with the brake lever  54  by the connecting linkage  52 , and the nut  95  is disposed in the guide hole  912  of the piston  91  and complementary in shape with the guide hole  912 . As a result, when the adjuster  85  is rotated by the user, the nut  95  is driven by the adjuster  85  through the piston rod  83  and the piston  91  to synchronously rotate, resulting in that the rod  92  axially moves relative to the nut  95 , and the position of the nut  95  relative to the rod  92  changes. Another difference between mechanism  30  and  90  is, the sea  96  is fastened to the rod  92  instead of the nut. Therefore, the user can rotate the adjuster  85  to make the seal  96  move with the rod  92  to change the distance from the seal  96  to the channel  814  so as to change the length of the free stroke of the hydraulic brake master cylinder  70 . This feature means the hydraulic brake master cylinder  70  is capable of pad contact point adjustment and can be adjusted by rotating the adjuster  85  without any tool. This hydraulic brake master cylinder  70  is also simple in construction allowing it to be manufactured and assembled easily. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.