CALLIPER BRAKE

Abstract: The brake incorporates brake shoes (2) and a double apparatus (8) in which two cams (8a,8b) come succes­ sively into operation to provide for constant speed of opera­ tion of a brake applying control (W,8,6), a first rapid move­ ment of the brake shoes followed by a slower movement of the brake shoes.

Description: "CALIPER BRAZE" This invention relates to calliper brakes as used mainly on bicycles, and more particularly to a calliper brake which is actuated by pulling a control wire so that an arm actuator connected thereto operates to cause a pair of braking arms carrying brake shoes to swing and urge the brake shoes against a wheel rim for exerting the braking action. Generally, a calliper brake of a centre-pull type or side-pull type is well-known. The centre-pull type calliper brake comprises a gate-like supporting member, a pair of brake arms which are pivoted thereto, carry at the lower ends brake shoes respectively, and are spaced from one another at their upper ends, and an arm actuator interposed between said spaced upper ends, the arm actuator being connected to a control wire, the fixing member carrying an outer sheath guiding the control wire so that while no braking action is being performed a constant clearance gap is maintained between the wheel rim and each brake shoe. For initiating a braking action, the control wire is pulled to move the arm actuator upwardly to swing the brake arms, thereby urging the brake shoes towards the wheel rim. This fixed clearance gap keeps the brake shoesfrom contacting the wheel rim in conditions of vibration. However, in the conventional calliper brake, the angle of swing of each brake arm, that is, the amount of movement of each brake shoe towards the wheel rim, is unchanged with respect to the stroke of upward movement of the arm actuator from the beginning of its movement to the end so that the brake shoes move at a speed which is in a fixed relation to the speed of upward movement of the arm actuator. In other words, the feeding speed of each brake shoe prior to its contact with the wheel rim is substantially the same as that obtaining during the action of braking. Thus, when the control wire is pulled to exert a braking action the distance traversed by each brake shoe before it contacts the wheel rim despite the absence of braking effect is the same with respect to a particular movement of the arm actuator as the distance traversed after coming into contact with the rim. As a result the movement of the control wire necessary to bring the brake shoes into contact with the wheel rim is- considerably greater than that required for achieving the braking effect so that the movement of a brake lever for pulling the control wire is also greater thus leading to a delay in the application of the braking effect. This invention is designed to overcome the disadvantage described. An object of the invention is to provide a calliper brake which can have an optimum gap between the wheel rim and each brake shoe and yet achieve a quick braking effect even with a small movement of the wire. According to the invention there is provided a calliper brake for exerting a braking action on the rim of a wheel by a pull of a control wire comprising a supporting member, a pair of brake arms pivoted to the supporting member, one end (normally the lower end) of each of said brake arms carrying a brake shoe and the ot-her (normally upper) ends of the brake arms being spaced apart, a return spring interposed between said supporting member and each of said brake arms and an arm actuator movable with respect to the supporting member interposed between said other ends of the brake arms, said arm actuator having a wire connector for securing one end of a control wire and presenting cam faces engageable with the upper ends of said brake arms so that said control wire when pulled moves 'the arm actuator thereby causing the brake arms to swing and move said brake shoes toward the rim of the wheel, said cam faces comprising first cam faces arranged to move said brake shoes toward the rim of the wheel at a given rate with respect to a given amount oi movement of said arm actuator and second cam faces arranged to move the brake shoes toward the rim of the wheel at a smaller rate with respect to said given amount of movement of the arm actuator, so that said first cam faces are operative to swing the brake arms to bring said brake shoes into contact with the rim of the wheel and said second cam faces are operative to swing the brake arms to urge the brake shoes against the rim of the wheel for achieving the braking effect. The arm actuator may be formed of a plate member having two lateral surfaces disposed adjacent the upper ends of the brake arms, said lateral surfaces being formed at the upper portions thereof with first cam faces and at the lower portions with second cam faces as continuations of the respective first cam faces. Alternatively, the arm actuator may be composed of a base member, a pair of first and second cam bodies, a third cam body, and an elastic member connecting the third cam body with the base member. In this instance, cam faces including the first and second cam faces are formed on the first and second cam bodies and a wire connector for securing one end of a control wire is mounted on the third cam body. Alternatively, the arm actuator may be composed of a base member and a pair of fourth and fifth cam bodies which are formed with cam faces and are pivoted to the base member, the base member supporting the connector for the control wire. In these embodiments the wire is pulled to allow the first and second cam bodies or the fourth and fifth cam bodies to swing so that these cam bodies function to provide a transition from the first cam faces to the second cam faces. The aforesaid first cam faces function to move the brake shoes quickly towards the wheel rim with respect to a given amount of movement of the arm actuator, that is, to a particular movement of the control wire, and are each inclined at Åa smaller angle to a line perpendicular to a line disposed in the direction of pull of the control wire. The second cam faces are for slow feed of the brake shoes and are each inclined at a larger angle to a line perpendicular to said vertical line. The first and second cam faces need not be formed only on tte arm actuator, but may be simulated by appropriate swinging motions of the first and second, or fourth and fifth cam bodies as above described. In any case, the arm actuator is formed with two first cam faces and two second cam faces, the respective first and second cam faces having different angles of inclination so that when the brake arms swing under the control of the first and second cam faces the brake shoes are moved quickly until they are brought into contact with the wheel rim and then are moved slowly after contacting the rim. Hence, a reliable braking effect is achieved even with a movement of the control wire smaller than the conventional movement and the brake shoes, after contacting the rim, are urged thereto with greater force with respect to the effort exerted in pulling the control wire, thereby achieving an intensive braking effect. These and other objects and features of the invention will be apparent from the following detailed description which is taken in conjunction with the accompanying drawings. Fig. 1 is a front view of an embodiment of a calliper brake of the invention Fig.-2 is a side view of the embodiment in Fig. 1, Fig. 3 is a sectional view of a principal portion of the Fig. 1 embodiment, Fig. 4 is a sectional view taken on the line IV-IV in'Fig. 1, Fig. 5 is a partial front view of a modified embodiment of the invention, Fig. 6 is a view explanatory of operation of the Fig. 5 embodiment, Fig. 7 is a partial front view of another modified embodiment of the invention, and Fig. 8 is a view explanatory of operation of the Fig. 7 embodiment. Referring to Figs. 1 to 4, reference numeral 1 designates a supporting member of an inverted Y-like shape arranged to be fixed to a frame of a bicycle. The supporting member 1 has at its central upward projection a vertically elongate slot la and pivotally supports at the ends of both side downward projections a pair of brake arms 3 and 4 each carrying at the lower end thereof a brake shoe 2. The brake arms 3 and 4 are approximately C-shaped and are pivoted at intermediate points to the supporting member 1 through pivot pins 5 respectively, return springs 14 being interposed between the supporting member 1 and the brake arms 3 and 4. The upper end portions of brake arms 3 and 4 are spaced from one another and are formed with recesses 3a and 4a for receiving therein an arm actuator to be hereinafter described. With the recesses 3a and 4a, roller cam followers 6 are supported rotatably by pins 7. The arm actuator 8 is interposed between the spaced upper end portions of brake arms 3 and 4 in such a way as to be vertically movable with respect to the supporting member 1. The actuator 8 has a wire connector 9 for securing one end of a control wire W and cam faces engageable with the roller cam followers 6 of the brake arms 3 and 4, so that the roller contacts 6 elastically contact the cam faces by means of return springs 14 respectively, whereby the arm actuator 8 is located betwen tan oppoite upper end portions of brake arms 5 ar, . The car faces each comprise a first cam face ba for quick teed of the corresponding brake shoe 2 towards te wheel rim R-with respect to a given amount of movement of the arm actuator 8 and a second cam face 8b for slow feed of the brake shoe 2. The brake arms 3 and 4 swing by movement of the roller cam followers 6 first alone the first cam faces 8a to bring the brake shoes 2 into contact with the wheel rim R, and then along the second car faces Bu to urge the brake shoes 2 against the wheel rir R for achieving the braking effect. The first and second cam faces 8a and 8b are inclined at angles #1 and #2 respectively with respect to a straight line Y-Y perpendicular to a vertical line X-X disposed in the direction of lifting of the arm actuator 8 as show in Fig. 3, where the angle 4 of inclination is made smaller and #2 is made larger. Hence, the respective brake arms 3 and 4 can swing as the rollers 6 move along the first cam face 8a through a large angle of swing with respect to an upward stroke of the arm actuator 8, that is, a stroke of pulling the control wire W, thereby quickly moving the brake shoes 2 toward the wheel rim R. On the other hand, the brake arms 3 and 4 each swing as the rollers 6 move along the second cam face 8b through a smaller angle of swing, whereby the brake shoes 2 move slowly with respect to the stroke of the arm actuator 8 and are urged against the wheel rim R for the braking effect. In other words, when the brake arms 3 and 4 swinging as the rollers 6 move along the first cam faces 8a reach the ends of this swinging movement the brake shoes 2 are brought into contact with the wheel rim R. Thereupon the brake arms 3 and 4 continue their swinging movement as the rollers 6 move along the second cam faces 8b to urge the brake shoes 2 against the rim R. gence, even when the wire W is pulled slowly the brake shoes 2 make rapid contact with the wheel rim H and even when the wire W is pulled with a low effort the brake shoes 2 each provide an intensive braking effect thus ensuring a rapid braking action. The arm actuator 8, as shown in Figs. 1 to 4, is formed of a plate member of approximately trapezoidal shape with both widthwise outside surfaces adjacent the upper ends of the brake arms 3 and 4, said widthwise opposite outside surfaces being formed at the upper portions thereof with the first cam faces 8a and at the lower portions with the second cam faces 8z in continuation of the cam faces 8a respectively. The calliper brake as shown in Figs. 1 to 3 is in brake-off condition in which the roller cam followers 6 of the arms 3 and 4 are in engagement with the first cam faces 8a. When the wire W is pulled for exerting the braking action, the arm actuator 8 moves upward to cause the brake arms 3 and 4 to swing on movement of the rollers 6 first along the first cam faces 8a, thereby moving the brake shoes 2 toward the wheel rim R. Next, the brake arms 3 and 4, after swinging, reach the ends of first cam faces 8a, and then the brake shoes 2 are brought into contact with the wheel rim R. The brake shoes 2 are moved quickly in this first action because the brake arms 3 and 4 each swing under the action of the rollers 6 moving along the first cam faces 8a through a large angle of swing with respect to the amount of movement of the arm actuators 8, thereby being brought into contact with the wheel rim R even with a small movement of the wire W. Then, the brake arms 3 and 4 further swing as the rollers 6 move along the second cam faces Bb and the brake shoes 2 are moved slowly against the wheel rim R because the brake arms 3 and 4 each swing at a smaller angle of swing with respect to the amount of movement of arm actuator 8. Hence, the brake shoes 2 intensify the force braking effect even it low pullin vapplied to the wire W, thus achieving a quick and powerful braking effect. In the calliper brake shown in Figs. 1 and 2, the support member 1 carries a support 11 having a holder 10 for an outer sheath 0 guiding the control wire W. The support 11 is fitted to be vertically movable in the slot la and carries a rotatable quick-releasing lever 12. The quick-releasing lever 12 is used to vary the distance between the brake shoes 2 and thus the clearance between the -fully withdrawn shoes and the wheel and has a projection 13 attached to the supporting member 1 and a cam face having at its one side a rotation-stop 12a. The rotation stop 12a engages with the projection 13 to fix the holder 10 to the supporting member 1, thereby keeping constant the length of control wire W relative to the outer sheath 0. The lever 12 is turned counterclockwise in Fig. 1 to release the holder 10 so that it is downwardly movable whereupon the return springs 14 act to swing the brake arms 3 and 4, thereby enlarging the interval between the brake shoes 2. In addition, in Fig. 2, reference numeral 15 designates a mounting bolt for fixing the supporting member 1 to the bicycle frame. Alternatively, the arm actuator 8 may be constructed as shown in Figs. 5 and 6, or 7 and 8. Referring to Figs. 5 and 6, a modified embodiment of the invention is shown, in which the arm actuator 8 comprises a bar-like base member 83, a pair of first and second cam bodies 81, a third cam body 82, and an elastic member 84 formed mainly of a coiled spring for connecting the third cam body 82 to the base member 83. The first and second cam bodies 81 are formed of link-like plate members pivoted to opposite lengthwise ends of the base member 83 and provided at the widthwise outer surfaces with cam faces 81a and at the widthwise inner surfaces with engaging faces 81b. The third cam body 82 is formed of an elongate plate member which has control faces 82a at both widthwise outer surfaces, carries the wire connector 9 for the control wire W, and is interposed between the first and second cam bodies 81 so that the control faces 82a engage the engaging faces 81b at the first and second cam bodies 81 respectively. In addition, the elastic member 84 is arranged to exert a spring force greater than the sum of the forces exerted by the return springs 14. In this construction, when the control wire W is pulled to initiate the braking action, the first and second cam bodies 81 and the third cam body 82 are moved simultaneously upwardly without relative movement therebetween and elastic deformation of elastic member 84 takes place while the brake arms 3 and 4 swing freely by movement of the rollers 6 along the cam faces 81a until they contact with the wheel rim R, at which time, the cam faces 81a function as the first cam faces to move the brake shoes 2 quickly against the wheel rim R. After the brake shoes 2 contact the wheel rim R, contact resistance between the rim R and each brake shoe 2 increases to overcome the spring force of the elastic member 84 and the swinging motion of the brake arms 3 and 4 meets considerable opposition so that the third cam body 82 only is moved upwardly, whereby the first and second cam bodies 81 swing as a result of the engaging faces 81b moving along the control faces 82a of the third cam body 82. Hence, the angle of inclination of the cam faces is changed so that they function as the second cam faces, thereby moving the brake shoes 2 slowly against the wheel rim R. Accordingly, in Fig. 5, when the control wire W is pulled, the brake arms 3 and 4, as foregoing, swing as the rollers 6 move along the cam faces 81a which initially act as the first cam faces, so that the brake shoes 2 are moved quickly. Next, the third cam body 82 only, as described above, moves upwards and the cam bodies 81 move along the control faces 82a at a larger angle of swing whereby the brake shoes 2 are moved slowly toward the wheel rim R. Another modified embodiment of the invention is shown in Figs. 7 and 8 in which the arm actuator 8 comprises a substantially triangular base member 86 and a pair of fourth and fifth cam bodies 85 having cam faces 85a and pivoted to opposite ends of the base of base member 86, the wire connector 9 for the wire W being mounted on the top of the base member 8. In this construction, the wire W is pulled to move the base member 86 upwardly whereby to lift, towards the positions 2 in Fig. 8, the pivot points Ol at which the fourth and fifth cam bodies 85 are pivoted to the base member 86. When the pivot points Ol move upward -to allow the roller cam followers 6 in engagement with the cam faces 85a to move beyond the foot of a perpendicular dropped from each pivot point Ol to each cam face the fourth and fifth cam bodies 85 swing by weans of the forces of return springs 14 in the direction of the arrow Z in Fig. 8, so that the inclination of each cam face 85a becomes greater so that the cam faces 85a now function as the aforesaid second cam faces. It is to be noted that the cam faces 85a have a smaller angle of inclination and function as the aforesaid first cam faces prior to the swinging motion of the fourth and fifth cam bodies 85. It is preferable in the construction illustrated in Figs. 7 and 8 to provide projections 87 at either the fourth and fifth cam bodies 85 or the base member 86 and to provide guide portions 88 engageable with the projections 87 in either the cam bodies 85 or the base member 86, whereby the projections 87 and guide portions 88 set a maximum angle of swing of each cam body 85. In Fig. 7, the control wire W is pulled to move upwardly the base member 86 and the fourth and fifth cam bodies 85. In the situation where the amount of the upward movement of the cam bodies 85 is less than the prescribed value, the cam bodies 85 and the base member 86 move simultaneously without relative movement so that the brake arms 3 and 4 swing quickly as the rollers 6 move along the cam faces 85a which function as the aforesaid first cam faces. Next, when the base member 86 moves further upwardly to bring the pivot points 01 to the positions 02 in Fig. 8, the return springs 14 act to swing the cam bodies 85 in the direction of the arrow Z in Fig. 8. The swinging motion of the cam bodies 85 changes the function of the cam faces 85a from that of the aforesaid first cam faces for quick arm movement to that of the second cam faces for achieving the braking effect, thereby urging the brake shoes 2 against the wheel rim R with low speed and higher effort. In this embodiment, each cam body 85 has only one cam face 85a so that the cam faces set for quick feed change accurately into cam faces set for high braking effort. According to this invention as described hereinabove, the arm actuator movable by pulling the control wire is provided with the first cam faces capable of moving the brake shoes quickly towards the wheel rim and with the second cam faces arranged to provide slow movement of the brake shoes for achieving the braking effect. Hence, the optimum gap can be kept between each brake shoe and the wheel rim and the angle of inclination of each brake arm can be made larger with respect to a given wire movement of the control wire whereby even with a small wire movement the brake arms can achieve full braking effect. As a result, a smaller leverstroke for the braking action enables a quick braking action and eliminates a delayed braking effect. Furthermore an intensive braking effect can be readily achieved without a great force of pull on the control wire.

Claims: CLAIMS 1. A calliper brake for exerting a braking action on the rim of a wheel by a pull of a control wire comprises, a supporting member, a pair of brake arms pivoted t6 the supporting member, one end (normally the lower end) of each of said brake arms carrying a brake shoe and the other (normally upper) ends of the brake arms being spaced apart, a return spring interposed between said supporting member and each of said brake arms and an arm actuator movable with respect to the supporting member interposed between said other ends of the brake arms, said arm actuator having a wire connector for securing one end of a control wire and presenting cam faces engageable with the upper ends of said brake arms so that said control wire when pulled moves the arm actuator thereby causing the brake arms to swing and move said brake shoes toward the rim of the wheel, said cam faces comprising first cam faces arranged to move said brake shoes toward the rim of the wheel at a given rate with respect to a given amount of movement of said arm actuator and second cam faces arranged to move the brake shoes toward the rim of the wheel at a smaller rate with respect to said given amount of movement of the arm actuator, so that-said first cam faces are operative to swing the brake arms to bring said brake shoes into contact with the rim of the wheel and said second cam faces are operative to swing the brake arms to urge the brake shoes against the rim of the wheel for achieving the braking effect. 2. A calliper brake according to claim 1 in which the arm actuator comprises a plate member presenting to said normally upper ends of the brake arms edge faces each formed as a first cam face merging into a second cam face. 3. A calliper brake according to claim 1 in which therm actuator comprises a base member; first and second cam bodies pivoted to said base member and having outer edge faces facing away from one another and each formed to present a first and second cam face and inner edge faces facing towards one another and formed as engaging faces, a third cam body formed with two c trol faces engageable with respective engaging faces of z.e first and second cam bodies and an elastic member connecting said third cam body with said base member, said third cam body carrying said wire connector for said control wire and being movable with respect to the first and second cam bodies so as to be capable of swinging the first and second cam bodies, so that the first and second cam faces of the first and second cam bodies are operable successively first to move the brake shoes quickly toward the rim of the wheel and then to urge the brake shoes more slowly against the rim of the wheel. 4. A calliper brake according to claim 3 in which the elastic member is arranged to exert a force greater than the sum of the forces exerted by the return springs. 5. A calliper brake according to claim 1 in which the arm actuator comprises a base member and a pair of cam bodies pivoted to said base member, each cam body having outer edge faces facing away from one another and each constituting a first and second cam face said base member carrying said wire connector for said control wire, the points where the cam bodies are pivoted to the base member being located so that when said control wire is pulled to move said base member taking with it the pivot points where said cam bodies are pivoted to said base member the cam engaging position of said normally upper end of each of said brake arms with the respective cam face is initially nearer the line of the control wire than said pivotal point and as said base member continues to move said cam engaging position moves along the inclined cam face until said cam engaging position is farther from the line of the control wire whereupon the thrust of the brake arm on the cam body causes the cam body to swing about lt pivotal connection to the base member and change the inclination of the cam face with respect to the control wire so that said cam face now constitutes the second cam face. 6. A calliper brake according to claim 5, in which interengaging projections and guide portions are provided on the base member and cam bodies for controlling movement of the cam bodies about their pivotal points to the base member.

Inventors: SHIMANO, KEIZO
Applicants: SHIMANO INDUSTRIAL COMPANY LIMITED
Application year: 1980
Main classification: B62L1
IPC codes: F16D49, B62L1