Abstract:
A bicycle cable disc brake is provided with a cam assembly that has improved efficiency during movement under high pressure. Basically, the cable disc brake has a cable housing, a pair of friction members and an actuated mechanism. The first friction member is movably coupled to the caliper housing between a release position and a braking position. The second caliper is also coupled to the caliper housing and arranged substantially parallel to the first friction member to form a rotor receiving slot therebetween. The actuated mechanism is movably coupled to the caliper housing to move the first friction member from the release position towards the second friction member to the braking position. The actuated mechanism has a pair of cam members movably arranged between an axially retracted position and an axially extended position with a guide member interconnecting the cam members during movement between the axial retracted position and the axially extended position. In the preferred embodiment, the guide member is a guide pin that extends from one of the cam members and is received in a bore of the other cam member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a cable operated disc brake for a bicycle. More specifically, the present invention relates to a cable operated disc brake with cam members for moving a friction member. 
     2. Background Information 
     Bicycling is becoming an increasingly popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving their components. One particular component of the bicycle, which has been extensively redesigned over the past years, is the braking systems of bicycles. In particular, the braking power of the braking systems is constantly being increased. 
     There are several types of bicycle brake devices, which are currently available on the market. Examples of some types of common bicycle brake devices include rim brakes, caliper brakes and disc brakes. If a rider wants a very high performance brake system, then the rider typically wants a disc brake system. Disc brake systems provide a substantial braking power in relationship to the amount of braking force applied to the brake lever. Moreover, disc brake systems typically provide a high level of consistency in all types of weather and riding conditions. Of course, riders constantly desire better performance from disc braking systems, i.e., disc brake systems that have more braking power. 
     Conventionally, a disc brake is composed of a pair of brake pads that are movably mounted to a caliper housing. The brake pads are pressed against a disc or rotor that is fixed to the wheel to halt the rotation of the disc and thus the wheel. The brake pads are moved toward the disc hydraulically or mechanically such as by a cam mechanism. The hydraulic disc brake systems are typically complicated in construction and expensive to manufacture. Moreover, hydraulic disc brake systems are often quite heavy in construction. 
     The mechanical disc brake system includes a caliper housing with one brake pad that is fixed to the caliper housing and one brake pad that is movably mounted to the caliper housing by a cam mechanism. A swinging arm is coupled to the cam mechanism to move the movable pad by a cam action. Typically, a conventional brake cable is coupled to a brake lever to move the swinging arm, and thus, operate the cam mechanism. While mechanical disc brake systems are typically less expensive and lighter than hydraulic disc brake systems, mechanical disc brake systems can still be complicated in construction and require many parts resulting in expensive manufacturing costs, as with a hydraulic disc brake system. Another drawback of many mechanical disc brake systems is that the cam mechanism often has a loss of efficiency during a movement of the cam mechanism under high pressure. 
     In view of the above, there exists a need for a disc brake, which overcomes the problems of prior art disc brakes. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a cable disc brake that prevents loss of efficiency during a movement of the cam mechanism under high pressure. 
     Another object of the present invention is to provide a cable disc brake that is relatively compact and lightweight in relation to the amount of braking power. 
     Another object of the present invention is to provide a cable disc brake that is relatively inexpensive to manufacture. 
     The foregoing objects can be basically attained by providing a cable disc brake comprising a caliper housing, a first friction member, a second friction member and an actuated mechanism. The first friction member is movably coupled to the caliper housing between a release position and a braking position. The second friction member is coupled to the caliper housing and arranged substantially parallel to the first friction member to form a rotor receiving slot therebetween. The actuated mechanism is movably coupled to the caliper housing to move the first friction member from the release position towards the second friction member to the braking position. The actuated mechanism has first and second cam members movably arranged between an axially retracted position and an axially extended position with a guide member interconnecting the first and second cam members during movement between the axially retracted position and the axially extended position. 
     These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the attached drawings which form a part of this original disclosure: 
     FIG. 1 is a side elevational view of a bicycle with a pair of cable disc brakes coupled thereto in accordance with one embodiment of the present invention; 
     FIG. 2 is a side elevational view of a front portion of a bicycle with a front cable disc brake coupled thereto in accordance with one embodiment of the present invention; 
     FIG. 3 is a side elevational view of a rear portion of a bicycle with a rear cable disc brake coupled thereto in accordance with one embodiment of the present invention; 
     FIG. 4 is an enlarged, partial side elevational view of the front cable disc brake in accordance with the embodiment of the present invention illustrated in FIG. 2; 
     FIG. 5 is a longitudinal cross-sectional view of the front cable disc brake, as viewed along section lines  5 — 5  of FIG. 4; 
     FIG. 6 is an exploded elevational view of the front cable disc brake illustrated in FIGS. 2,  4  and  5 ; 
     FIG. 7 is a front elevational view of a left caliper portion of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 8 is a bottom plan view of the left caliper portion of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 9 is a rear elevational view of the left caliper portion illustrated in FIGS. 7 and 8 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 10 is a left side elevational view of the left caliper portion illustrated in FIGS. 7-9 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 11 is a right side elevational view of the left caliper portion illustrated in FIGS. 7-10 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 12 is a cross-sectional view of the front left caliper portion illustrated in FIGS. 7-11, as viewed along section lines  12 — 12  of FIG. 7; 
     FIG. 13 is a side elevational view of the cable adjusting bolt for the adjusting unit of the front cable disc brake illustrated in FIGS.  2  and  4 - 5 ; 
     FIG. 14 is an end elevational view of the cable adjusting bolt illustrated in FIG. 13 for the cable adjusting unit of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 15 is a partial, longitudinal cross-sectional view of the cable adjusting bolt illustrated in FIGS. 13 and 14 for the cable adjusting unit of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 16 is a side elevational view of the cable adjusting nut for the cable adjusting unit of the front cable disc brake illustrated in FIGS.  2  and  4 - 5 ; 
     FIG. 17 is an end elevational view of the cable adjusting nut for the cable adjusting unit of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 18 is an inside elevational view of the right caliper portion of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 19 is a side elevational view of the right caliper portion of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 20 is a bottom plan view of the right caliper portion illustrated in FIGS. 18 and 19 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 21 is a side elevational view of one of the brake pads for the front cable disc brake illustrated FIGS.  2  and  4 - 6 ; 
     FIG. 22 is an edge elevational view of the brake pad illustrated in FIG. 21 for the front cable disc break illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 23 is a side elevational view of the pad axle for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 24 is an end elevational view of the pad axle illustrated in FIG. 23 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 25 is an elevational view of the pad spring prior to bending for the front cable disc brake illustrated FIGS.  2  and  4 - 6 ; 
     FIG. 26 is a side elevational view of the pad spring illustrated in FIG. 25 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 27 is a top plan view of the pad spring illustrated in FIGS. 25 and 26 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 28 is an end elevational view of the pad spring illustrated in FIGS. 25-27 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 29 is a side elevational view of the input cam for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 30 is an end elevational view of the input cam illustrated in FIG. 29 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 31 is an end elevational view of the input cam illustrated in FIGS. 29 and 30 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 32 is a partial, cross-sectional view of the input cam illustrated in FIGS. 29-31 as viewed along section lines  32 — 32  of FIG. 31; 
     FIG. 33 is a partial, longitudinal cross-sectional view of the input cam illustrated in FIGS. 29-32 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 34 is a side elevational view of the output cam for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 35 is an end elevational view of the output cam illustrated in FIG. 34 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 36 is an end elevational view of the output cam illustrated in FIGS. 34 and 35 for the front disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 37 is a partial cross-sectional view of the output cam illustrated in FIGS. 34-36 as viewed along section lines  37 — 37  of FIG. 35; 
     FIG. 38 is a partial, longitudinal cross-sectional view of the output cam illustrated in FIGS. 34-37 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 39 is an end elevational view of the output cain rotation stopper for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 40 is a side edge elevational view of the output cam rotation stopper illustrated in FIG. 39 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 41 is a transverse cross-sectional view of the output cam rotation stopper illustrated in FIGS. 39 and 40 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 , as viewed along section lines  41 — 41  of FIG. 39; 
     FIG. 42 is an output cam return spring for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 43 is an end elevational view of the output cam return spring illustrated in FIG. 42 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 44 is an end elevational view of the actuating arm for the front cable disc brake illustrate FIGS.  2  and  4 - 6 ; 
     FIG. 45 is a side edge elevational view of the actuating arm illustrated in FIG. 44 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 46 is a bottom plan view of the actuating arm for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 47 is a cross-sectional view of the actuating arm illustrated in FIGS. 44-46 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 , as viewed along section line  47 — 47  of FIG. 44; 
     FIG. 48 is an inside end elevational view of the actuating arm illustrated in FIGS. 44-47 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 49 is an end elevational view of the return spring for the actuating assembly of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 50 is a side elevational view of the return spring illustrated in FIG. 49 for the actuating assembly of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 51 is an end elevational view of the return spring illustrated in FIGS. 49 and 50 for the actuating assembly of the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; 
     FIG. 52 is an end elevational view of the cover of the actuating assembly for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 ; and 
     FIG. 53 is a side elevational view of the front cover illustrated in FIG. 52 for the front cable disc brake illustrated in FIGS.  2  and  4 - 6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to FIGS. 1-3, front and rear portions of a bicycle  10  are illustrated with a pair of cable disc brakes  12   a  and  12   b  coupled thereto in accordance with one embodiment of the present invention. Bicycles such as bicycle  10  are well known in the art, and thus, bicycle  10  and its various components will not be discussed or illustrated in detail herein. It will be apparent to those skilled in the art that bicycle  10  can be any type of bicycle, e.g., mountain bike, a hybrid bike or a road bike. Bicycle  10  is a conventional bicycle, which basically includes a bicycle frame  13  with a handlebar  14  front and rear forks  15   a  and  15   b , front and rear wheels  16   a  and  16   b  and a drive train  17 . 
     As seen in FIGS. 2 and 3, the front and rear cable disc brakes  12   a  and  12   b  are identical to each other, except for their connections to the bicycle  10  and their respective brake operating mechanisms  18   a  and  18   b . Specifically, the front cable disc brake  12   a  is mounted to the front fork  15   a  and operatively coupled to the front brake operating mechanism  18   a  via a front brake cable  19   a . The rear cable disc brake  12   b , on the other hand, is coupled to the rear fork  15   b  and the rear brake operating mechanism  18   b  via a rear brake cable  19   b . The front and rear brake operating mechanisms  18   a  and  18   b  are well known in the art, and thus, they will not be discussed or illustrated in detail herein. 
     Basically, the front brake operating mechanism  18   a  is designed to actuate the front disc brake  12   a  to stop rotation of front wheel  16   a . More specifically, the front brake operating mechanism  18   a  is operatively coupled to the front disc brake  12   a  by front brake cable  19   a  to apply a forcible gripping action on a front disc brake rotor  20   a  that is fixedly coupled to the front wheel  16   a . Likewise, the rear brake operating mechanism  18   b  is designed to actuate the rear disc brake  12   b  to stop rotation of rear wheel  16   b . More specifically, the rear brake operating mechanism  18   b  operatively coupled to the rear disc brake  12   b  by rear brake cable  19   b  to apply a forcible gripping action on a rear disc brake rotor  20   b  that is fixedly coupled to the rear wheel  16   b.    
     Preferably, the brake operating mechanisms  18   a  and  18   b  are mounted on handlebar  14 . In particular, as seen in FIG. 2, the brake operating mechanism  18   a  has a brake lever  21   a  that includes a mounting portion  22   a  and a lever portion  23   a . Mounting portion  22   a  is designed to be clamped onto handlebar  14  in a conventional manner. Lever portion  23   a  is pivotally coupled to mounting portion  22   a  for movement between a release position and a braking position. Normally, the lever portion  23   a  is maintained in a release position in a conventional manner, e.g. by a return spring (not shown). Likewise, as seen in FIG. 3, the rear brake operating mechanism  18   b  has a brake lever  21   b  that includes a mounting portion  22   b  and a lever portion  23   b . Mounting portion  22   b  is designed to be clamped onto handlebar  14  in a conventional manner. Lever portion  23   b  is pivotally coupled to mounting portion  22   b  for movement between a release position and a braking position. Normally, the lever portion  23   b  is maintained in a release position in a conventional manner, e.g. by a return spring (not shown). 
     The front and rear brake cables  19   a  and  19   b  are well known in the art, and thus, they will not be discussed or illustrated in detail herein. Basically, the front brake cable  19   a  has an outer casing  24   a  and an inner wire  25   a . The outer casing  24   a  extends between the mounting portion  22   a  of the brake lever  21   a  and an adjusting unit  26   a  that is mounted on the front cable disc brake  12   a . The inner wire  25   a  is fixedly coupled to the lever portion  23   a  of the brake lever  21   a  and a portion of the front cable disc brake  12   a  as discussed below. Similarly, the rear brake cable  19   b  has an outer casing  24   b  and an inner wire  25   b . The outer casing  24   b  extends between the mounting portion  22   b  of the brake lever  21   b  and an adjusting unit  26   b  that is mounted on the rear cable disc brake  12   b . The inner wire  25   b  is fixedly coupled to the lever portion  23   b  of the brake lever  21   b  and a portion of the rear cable disc brake  12   b  in the same manner as in the front cable disc brake  12   a  discussed below. 
     Still referring to FIGS. 2 and 3, the front cable disc brake  12   a  is coupled to the front fork  15   a  via a mounting bracket  28   a  and four bolts  29   a . Similarly, the rear cable disc brake  12   b  is coupled to the rear fork  15   b  via a mounting bracket  28   b  and four bolts  29   b . Of course, it will be apparent to those skilled in the art from this disclosure that various other types of mounting mechanisms or assemblies can be utilized as needed and/or desired. Since cable brake discs  12   a  and  12   b  are identical to each other, only cable disc brake  12   a  will be discussed and illustrated in detail herein. 
     Basically, as seen in FIGS. 5 and 6, the cable disc brake  12   a  includes a caliper housing  30 , a pair of brake pads or friction members  32 , a cam assembly  34  and an actuating assembly  36 . The cam assembly  34  and the actuating assembly  36  together form a cable actuated mechanism that moves the brake pads between a release position and a braking position. The caliper housing  30  is mounted to the frame  13  of the bicycle  10  via the bracket  28   a  and bolts  29   a . The brake pads  32  are movably coupled to the caliper housing  30  to move between the release position and the braking position via the cam assembly  34  and the actuating assembly  36  (cable actuated mechanism). In the release position, the pads  32  are spaced from the disc brake rotor  20   a  to allow free rotation thereof. In the braking position, the brake pads  32  are pressed against the sides of the disc brake rotor  20   a  to stop rotation of the bicycle wheel  16   a  and the disc brake rotor  20   a.    
     Turning to FIGS. 4-6, the caliper housing  30  basically includes a left caliper portion  38  and a right caliper portion  40  that are fixedly coupled together by a pair of bolts  41 . When the left and right caliper housings  38  and  40  are coupled together, an internal cavity is formed for movably supporting the brake pads  32  and the cam assembly  34 , as discussed below. The left and right caliper housings  38  and  40  are preferably constructed of a hard, rigid material, such as a metallic material. Of course, other suitable materials can be utilized for the left and right caliper housings  38  and  40 . 
     As seen in FIGS. 7-12, the left caliper portion  38  basically has a body portion  42  a pair of mounting flanges  43  and a cable support flange  44 . The body portion  42  has a pad support bore  45  extending in a longitudinal direction and an axially extending internal bore  46  that extends longitudinally between a first open end  48  and a second open end  50  of the left caliper portion  38 . The pad support bore  45  is utilized to support the brake pads  32  on the caliper housing  30  as discussed below. 
     Basically, the internal bore  46  can be divided into three sections  51 ,  52  and  53  for supporting a part of the cam assembly  34 , as discussed below. The first section  51  of the internal bore  46  is a cylindrical bore with the smallest diameter. The first section  51  of the internal bore  46  is located at a first end  48  of the left caliper portion  38 . The first end  48  of the left caliper portion  38  has the actuating assembly  36  coupled thereto, as discussed below. Preferably, end surface of the first end  48  of the left caliper portion  38  has an annular step to form a pair of annular end surfaces  54  and  55  that lie in different planes. The inner end surface  55  adjacent the first section  51  of the internal bore  46  is preferably provided with three through bores  56  that are adapted to receive a part of the actuating assembly  36 , as discussed below. Preferably, the centers of these bores  56  are spaced approximately twenty degrees apart in a circumferential direction. These bores  56  allow for adjustment of the actuating assembly  36 , as discussed below. The middle one of the bores  56  is preferably spaced approximately four degrees in a circumferential direction from the center plane P 1  of the disc brake device  12   a.    
     The second section  52  of the internal bore  46  is also a cylindrical bore that is located between the first section  51  and the third section  53 . The second section  52  of the internal bore  46  has a larger diameter than the first section  51  of the internal bore  46 . Thus, an internal abutment surface or end wall  64  is formed radially between the first and second sections  51  and  52  of the internal bore  46 . 
     The third section  53  of the internal bore  46  is also cylindrical, but is a discontinuous cylinder. Specifically, the third section  53  of the internal bore  46  has a pair of longitudinal slots  65  and an annular groove  66  formed therein. The slots  65  that are spaced 180° apart and divide the annular groove  66  into two sections. 
     The second end  50  of the left caliper portion  38  is provided with a pair of threaded bores  69  for receiving the bolts  41  to secure the left and right caliper housings  38  and  40  together. The second end  50  of the left caliper portion  38  has a brake pad mounting recess  67  that is substantially identical to the outer periphery of the brake pads  32 . The bottom of the brake pad mounting recess  67  is open and the sides of the second end  50  of the caliper housing  38  has a pair of cutouts  68  for accommodating a portion of the disc brake rotor  20   a  therein. 
     The mounting flanges  43  of the left caliper portion  38  preferably have slots  70  to allow axial adjustment to and from the disc brake rotor  20   a . The slots  70  receive the mounting bolts  29   a  therethrough to fasten the left caliper portion  38  to the front bracket  28   a.    
     As seen in FIGS. 2,  4 ,  7  and  8 , the cable support member or flange  44  extends outwardly from the body portion  42  in a direction that is substantially tangent to an imaginary circle with its center located at the center axis of the internal bore  46 . The free end of the cable support flange  44  has a threaded hole  72  therein for receiving a cable adjusting bolt  73  of the cable adjusting unit  26   a  as seen in FIGS. 2 and 4. The cable adjusting unit  26   a  adjusts the relative tension between the outer casing  24   a  and the inner wire  25   a . Specifically, as seen in FIGS. 13-15, the cable adjusting bolt  73  has a head portion  73   a  and a threaded shaft portion  73   b  with an axially extending bore  73   c  extending through both the head portion  73   a  and the threaded shaft portion  73   b .The bore  73   c  is step-shaped for accommodating outer casing  24   a  and inner wire  25   a  in a conventional manner. The head portion  73   a  is a tubular member with a textured outer surface. 
     The threaded shaft portion  73   b  has threads on its outer surface that threadedly engaged the internal threads of the threaded hole  72 . Accordingly, rotation of the cable adjusting bolt  73  causes the cable adjusting bolt  73  to move axially relative to the cable support flange  44 . As seen in FIGS. 2 and 4, the cable adjusting bolt  73  has a cable adjusting nut  74  located on the threaded shaft portion  73   b . The cable adjusting bolt  73  (FIGS. 13-15) and the cable adjusting nut  74  (FIGS. 16 and 17) form the cable adjusting unit  26   a  for controlling the tension within the brake cable  19   a.    
     Turning now to FIGS.  6  and  18 - 20 , the right caliper portion  40  is fixedly coupled to the second end  50  of the left caliper portion  38  by the bolts  41 . The right caliper portion  40  substantially closes off the open end of the second end  50  of the left caliper portion  38 , except for a slot for accommodating the disc brake rotor  20   a . Accordingly, the right caliper portion  40  has a pair of through bores  75  for receiving the bolts  41  therein. Preferably, these through bores  75  are step-shaped so that the heads of the bolts  75  are recessed from the outer surface of the right caliper portion  40 . 
     Also, the right caliper portion  40  has a threaded bore  76  for receiving the pad axle  77  therein. Preferably, as seen in FIGS. 23 and 24, the pad axle  77  is a threaded bolt having a head portion  77   a  and a shaft portion  77   b  extending outwardly from the head portion  77   a . The section of the shaft portion  77   b  adjacent the head portion  77   a  is provided with threads  77   c  that threadedly engage the threaded bore  76  of the right caliper portion  40 . The free end of the shaft portion  77   b  is preferably provided with an annular recess  77 d for receiving a retaining clip  78 . 
     The inner surface of the right caliper portion  40  has a brake pad mounting recess  80  that has the shape of the periphery of the brake pad  32 , such that the right brake pad  32  is securely retained against the inner surface of the right caliper portion  40 . This brake pad mounting recess  80  should be sized and shaped such that the right brake pad  32  does not rotate or move. The side edges of the right caliper portion  40  has a pair of cutout portions  82  for forming a half of the disc brake rotor slot. 
     As seen in FIGS. 5 and 6, the left and right brake pads  32  are substantially identical to each other and can preferably be interchanged with each other. As seen in FIGS. 21 and 22, the right and left brake pads  32  each include a rigid support plate  83  and an arcuate portion of friction material  84  attached to the support plate  83  for engaging the brake rotor  20   a . The rigid support plate  83  having a mounting tab  85  with a bore  86  therein for receiving the pad axle  77  (FIGS. 6,  23  and  24 ) therethrough. When the brake pads  32  are mounted on the pad axle  77 , the brake pads  32  can move axially on the pad axle  77 , but cannot rotate due to the structure of the brake pad mounting recesses  67  and  80  of the left and right caliper housings  38  and  40 . 
     As seen in FIGS.  6  and  25 - 28 , a pad spring  87  is provided between the left and right brake pads  32  to bias them apart. The pad spring  87  is preferably constructed of a thin resilient material, such as a spring steel. The pad spring  87  has a central connecting portion  87   a  and a pair of biasing portions  87   b  extending outwardly from opposite ends of the connecting portion  87   a . The connecting portion  87   a  is preferably an inverted U-shaped member with a pair of axially aligned holes  87   c  that receive the pad axle  77 . The biasing portions  87   b  are also inverted U-shaped members that diverge outwardly to their free ends relative to a center line bisecting the connecting portion  87   a.    
     Turning again to FIGS. 5 and 6, the cam assembly  34  basically includes an input cam  90 , an output cam  91 , a set of rolling members  92 , a return spring  93 , an output cam rotation stopper  94 , a retainer  95  and a bushing  96 . Basically, the cam assembly  34  is located in the internal bore  46  of the left caliper portion  38  and is adapted to expand in an axial direction by movement of the actuating assembly  36  via the brake operating mechanism  18   a . In particular, rotation of the input cam  90  by the actuating assembly  36  causes the output cam  91  to move in an axial direction against the force of the return spring  93  and the pad spring  87  to compress the left and right brake pads  32  together against the disc brake rotor  20   a.    
     As seen in FIGS. 29-33, the input cam  90  has a cam member  90   a  with an operating shaft  90   b  extending from one end and a guide pin  90   c  extending outwardly from the other end. The cam member  90   a  has an axially facing camming surface  90   d  with three camming slots  90   e  that receive the three roller members  92  (balls). These camming slots  90   e  are preferably arcuate slots that curve about the center rotational axis of the input cam  90 . These camming slots  90   e  are ramp-shaped and have an angled bottom surface that is preferably sloped approximately 17° relative to a plane passing perpendicularly through the axis of rotation of the input cam  90 . Accordingly, when the input cam  90  is rotated, the rolling members  92  will move in a circumferential direction within the camming slots  90   e , such that all of the rolling members  92  are located at the same position within the camming slots  90   e  to axially move the output cam  91 . 
     The operating shaft  90   b  is preferably a step-shaped shaft having a first cylindrical section  90   f , a second non-cylindrical section  90   g  and a third cylindrical section  90   h . The first cylindrical section  90   f  is sized to be received in the first section  51  of the internal bore  46  of the left caliper portion  38 . Preferably, the bushing  96  is located around the first cylindrical section  90   f  as seen in FIG.  5 . The second non-cylindrical section  90   g  of the operating shaft  90   b  is adapted to non-rotatably support a portion of the actuating assembly  36 , as discussed below. The third cylindrical section  90   h  of the operating shaft  90   b  is preferably threaded for receiving a nut  97  to secure the actuating assembly  36  thereto. 
     The guide pin  90   c  is preferably a short pin that is located on the longitudinal axis of the input cam  90  and engages the output cam  91  to ensure smooth movement of the output cam  91  relative to the input cam  90 . 
     Referring now to FIGS. 34-38, the output cam  91  basically includes a camming member  91   a  and a thrust shaft  91   b . The camming member  91   a  is preferably a cylindrical member having a camming surface  91   c  facing the camming surface  90   d  of the input cam  90 . The camming surface  91   c  is preferably provided with three camming slots  91   d  that are substantially identical to the camming slots  90   e  of the input cam  90  and are adapted to engage the rolling members  92  to move the output cam  91  axially in response to rotational movement of the input cam  90 . 
     As seen in FIGS. 5,  34  and  38 , the camming surface  91   c  of the output cam  91  is also provided with a centrally located blind bore  91   e  that is adapted to receive the guide pin  90   c  therein. Preferably, the lengths of the guide pin  90   c  and the blind bore  91   e  are such that they do not disengage at any time during the axial movement of the output cam  91  relative to the input cam  90 . The thrust shaft  91   b  of the output cam  91  is preferably a non-circular member that engages the output cam rotation stopper  94 , which in turn engages the left caliper portion  38  so that the output cam  91  cannot rotate relative to the left caliper portion  38 . 
     In particular, the rotation stopper  94 , as seen in FIGS. 39-41, has an annular center section  94   a  with a non-circular hole  94   b  that is adapted to receive the thrust shaft  91   b  of the output cam  91  therein such that there is no relative rotation therebetween. A pair of tabs  94   c  are located 180° apart and extend radially outwardly from the center section  94   a  of the rotation stopper  94 . These tabs  94   c  are received in the slots  65  of the left caliper portion  38  such that the rotation stopper  94  cannot rotate relative to the left caliper portion  38 . Thus, since the rotation stopper  94  cannot rotate, the output cam  91  cannot rotate. The rotation stopper  94  is secured on the thrust shaft  91   b  of the output cam  91  by the retainer  95 . The retainer  95  is preferably a C-shaped snap ring. This C-shaped snap ring or retainer  95  is received in the annular groove  66  formed in the internal bore  46  of the left caliper portion  38 . 
     As seen in FIG. 5, the return spring  93  for the output cam  91  is located between the output cam  91  and the output cam rotation stopper  94 . Preferably, the return spring  93  is a conically-shaped compression spring (as seen in FIGS. 42 and 43) that has an inner diameter at its small end  93   a  that is substantially equal to the outer width of the thrust shaft  91   b  of the output cam  91 , and an outer diameter at its large end  93   b  that is substantially equal to or slightly smaller than the inner diameter of the second section  52  of the left caliper portion  38 . When the cable disc brake  12   a  is assembled, the return spring  93  should not be compressed, or only under a slight amount of compression. However, this compression should not be such that it has a biasing force of the return spring  93  that is greater than the biasing force of the pad spring  87 . In other words, the biasing force of the output cam return spring  93 , relative to the biasing force of the pad spring  87  in its normal rest position, should not compress the pad spring  87 . 
     The actuating assembly  36  basically includes an actuating arm  98 , a return spring  99  and a cover  100  that are secured on the first end  48  of the left caliper portion  38  via the nut  97 . The actuating assembly  36  basically includes an actuating arm  98  that is fixedly secured to the third section  90   h  of the operating shaft  90   b  of the input cam  90 . 
     As seen in FIGS. 44-48, the actuating arm  98  has a cylindrical main portion  98   a  with an outwardly extending cable mounting portion  98   b . The central mounting portion  98   a  has a step-shaped bore  98   c  extending therethrough with a first cylindrical section  98   d  and a second non-cylindrical section  98   e . An abutment surface  98   f  is formed between the first cylindrical section  98   d  and the second non-cylindrical section  98   e . This abutment surface  98   f  has three bores  102  for mounting the return spring  99  thereto. Preferably, the centers of the bores  56  are spaced approximately twenty-five degrees apart in a circumferential direction. 
     As seen in FIGS. 2 and 4, the cable mounting portion  98   b  has a threaded bore  98   g  at its free end for receiving a clamping bolt  103  with a clamping plate  104  to secure the end of the inner wire  25   a  of the cable  19   a  thereto. Preferably, the cable mounting portion  98   b  also has a recess  98 h around the threaded bore  98   g  for receiving the clamping plate  104 , and to prevent relative rotation of the clamping plate  104 . A projection  98   i  is formed at the free end in the direction of the inner wire  25   a  of the cable  19   a . This projection  98   i  has a curved surface for supporting the inner wire  25   a  of the cable  19   a  during rotation of the actuating arm  98 . 
     As seen in FIGS. 5,  6  and  49 - 51 , the return spring  99  is preferably a torsion spring having a coil portion  99   a  with first and second ends  99   b  and  99   c  extending in opposite axial directions from the coil portion  99   b . The first end  99   c  is received in one of the bores  56  of the left caliper portion  38 , while the second end  99   c  of the return spring  99  is received in one of the bores  102  of the actuating arm  98 . The first and second ends  99   b  and  99   c  are preferably longitudinally aligned with each other in the rest position. 
     The bores  56  and  102  form an adjustment mechanism for controlling the biasing force of the return spring  99  on the actuating arm  98 . The biasing force between the caliper housing  30  and the actuating arm  98  can be adjusted by selecting various combinations of the bores  56  and  102 . If both the first and second ends  99   b  and  99   c  of the return spring  99  are moved one hole in the same direction, then a 5° adjustment can be attained. For example, if the first and second ends  99   b  and  99   c  are located in the center bores  56  and  102 , then either direction will result in a ±5° change in the biasing or urging force of the return spring  99 . Of course, the first and second ends  99   b  and  99   c  can be adjusted independently for greater adjustment. 
     Moreover, it will be apparent to those skilled in the art from this disclosure that additional hole bores  56  and  102  can be provided for additional adjustment. Moreover, the angular spacing of the bores  56  and  102  can be changed as needed and/or desired. In any event, the angular spacing between the bores  56  and the angular spacing between bores  102  are preferably different from each other to provide for a small incremental adjustment of the return spring  99 . As seen in FIG. 4, only five of the bores  56  and  102  are illustrated since one of the bores  56  is axially aligned with one of the bores  102 . 
     When the cable disc brake  12   a  is in the assembled position, the return spring  99  normally biases the input cam  90  and the actuating arm  98  to a brake releasing position. When the rider squeezes the brake lever  21   a , the inner wire  25   a  of the cable  19   a  moves relative to the outer casing  24   a  of the cable  19   a  to cause the actuating arm  98  and the input cam  90  to rotate together. This rotation causes the rolling members  92  to move from the deep ends of the camming slots  90   e  and  91   d  to the shallow ends of the camming slots  90   e  and  91   d . As the rolling members  92  move within the camming slots  90   e  and  91   d , the output cam  91  is moved in an axial direction against the biasing force of the output cam return spring  93 . This axial movement of the output cam  91  causes the left brake pad  32  to move against the urging force of the pad spring  87  to engage the rotor  20   a , which is then pressed against the right brake pad  32 . This engagement of the brake pads  32  with the disc brake rotor  20   a  causes the braking action of the cable disc brake  12   a.    
     Referring now to FIGS. 5,  52  and  53 , a cover  100  is located between the actuating arm  98  and the first end  48  of the left caliper portion  38 . Preferably, this cover  100  fits on the outer annular end surface  54  of the first end  48  of the left caliper portion  38  so as to seal the space between the actuating arm  98  and the left caliper portion  38 . 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.