CALIPER BRAKE

Abstract: A caliper brake having caliper arms (2, 3) and a return spring (6), provided with spacer members (9) to be fitted onto spring legs of the return spring and invertible around the spring legs respectively, the spacer members each provided with first and second contact portions (92, 93) different in distance from a fitting bore for the spring leg, so that the spacer member is inverted to adjust the spring reaction force of the return spring.

Description: The present invention relates to a caliper brake for a bicycle. Generally, a caliper brake, as disclosed in United States Patent No 4,263,990, has a set of caliper arms (carrying brake shoes) pivotally supported on a pivot shaft fixed to the bicycle frame. A caliper return spring arranged on the pivot shaft and acting on the caliper arms serves to bias the arms so that the brake shoes tend to move away from each other. When a brake operating lever is released, the caliper return spring returns each caliper arm, and the brake lever is returned simultaneously by a control wire connecting the caliper arms with the brake lever. Hitherto, a cycle brake has been proposed which is provided with a brake lever return spring arranged to act directly on the brake lever. In the case where both caliper return and lever return springs are installed, the restoring forces of these return springs may be reduced so that even when the transmission efficiency of the control wire is impaired after long use, the brake lever action has a good return feeling while the entire braking action is exerted always in a light touch,thereby enabling a rider to steer the bicycle without anxiety. Thus, a caliper brake intended for operation by a spring-returned lever should have a relatively weak caliper return spring. However, such a relatively weak spring is not reliable in a caliper brake for use with a brake lever having no return spring since the relatively weak caliper return spring may eventually fail to return the brake lever through an impaired control wire transmission. An object of the invention is to provide a caliper brake having a caliper return spring which is simply adjustable for use either with a brake lever provided with a lever return spring or a brake lever having no lever return spring. According to the present invention, there is provided a caliper brake for a bicycle, comprising a pivot shaft adapted for fixing to a bicycle frame, a caliper having a set of caliper arms mounted on the pivot shaft, and a caliper return spring having spring legs acting on respective caliper arms and urging same to open the caliper; each spring leg acting on its associated caliper arms by way of a spacer member rotatably mounted on its spring leg by means of a bore in the spacer and offset With respect to a centre line of the spacer. The spacer members by virtue of the offset bore each have first and second contact portions contactable with the caliper arms. The distance between the first contact portion and the centre of the bore is smaller than that between the second contact portion and the bore. Each spacer member can be inverted through 180° around the bore, so that the spacer member can be changed between a first position where the first contact portion contacts with the caliper arm and a second position where the second contact portion contacts with the same. Accordingly, the first and second contact portions are selected by the inversion of spacer member to change the position of each spring leg of the return spring with respect to the caliper arm, thereby enabling the spring reaction force of the return spring for the caliper arm to be adjusted. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:- Fig. 1 is a rear view of an embodiment of a caliper brake of the invention; Fig. 2 is a perspective sectional view to a larger scale of part of Fig. 1; Fig. 3 is a sectional view to a larger scale on the line III-III in Fig. 1; Fig. 4 corresponds with Fig. 1, but shows a spacer member inverted; Fig. 5 corresponds with Fig. 2, but shows a spacer member inverted; Fig. 6 is a perspective view of a spacer number only; Fig. 7 is an enlarged plan view of a modified embodiment of a spacer member ; Fig. 8 is a right-side view of the modified embodiment in Fig. 7; Fig. 9 is a sectional view taken on the line IX-IX in Fig. 7; and Fig. 10 is a sectional view taken on the line X-X in Fig. 8. Referring to Fig. 1, a caliper brake is shown which pivotally supports a pair of caliper arms 2,3 having brake shoes 4 and 5. A pivot shaft 1 fixed to, for example, a front fork of a bicycle (not shown) is provided between the caliper arms 2 and 3 and carries a caliper return spring 6 for biasing the caliper arms 2 and 3 in the direction of moving the brake shoes 4 and 5 away from each other, that is to open the caliper. A fixture 7 for clamping one end of a control wire W is mounted on the free end of one caliper arm 2. A holder 8 for an outer sheath O for guiding the control wire W is mounted on an arm 3a provided at an intermediate portion of the other caliper arm 3. The fixture 7 and holder 8 are arranged opposite each other so that the wire W may be pulled to swing the caliper arms 2 and 3 against the restoring force of the caliper return spring 6 to thereby apply the brake. In the embodiment shown in Figs. 1 through 6, a pair of spacer members 9 having bores 91 engageable with spring legs 61 of the caliper return spring 6 adjacent the caliper arms 2 and 3 are rotatably mounted on the spring legs 61 to be invertible around the respective spring legs 61. The caliper arms 2 and 3 are provided with respective abutments 21 and 31 for engagement by the spacer numbers 9. The spacer members 9, as seen from Fig. 6, each have a rectangular parallelepiped form with side surfaces 92 and 93. The bore 91 is offset with respect to the centre-line of the spacer towards the side surface 92 so that the distance between the side surface 92 and the bore 91 is smaller than that between the opposite side surface 93 and the bore 91. Thus, the spacer members 9 can be inverted by turning around the bores 91 so as to change from a first position in which the side surfaces 92 contact the abutments 21 and 31 of the caliper arms 2 and 3 to a second position in which the side surfaces 93 contact the abutments 21 and 31; or vice versa, thereby enabling the spring reaction force of the caliper return spring 6 to be adjusted, being relatively weak at the first position and relatively strong at the second position. The return spring 6 shown in the drawing uses a single elastic wire whose centre portion is retained on the pivot shaft 1, and a pair of spring legs 61 extend from the centre and are coiled on the way respectively. When the spacer numbers 9 are in the first positions as shown in Figs. 1 through 3, the spring reaction force of the return spring 6 is, for example, about 800g of the minimum requirement value of a spring force when the caliper brake is used with a brake lever having a lever return spring. When the spacer numbers 9 are in the second positions as shown in Fig 4 and 5, the spring reaction force is greater, equal to a spring force required for a caliper brake to be used with a brake lever having no lever return spring. The abutments 21 and 31 are formed on the brake-shoe-holding sides of the caliper arms 2 and 3 respectively and provided with lugs 22 and 32 opposite to the surfaces of the caliper arms 2 and 3 to define recesses for receiving the spacer members 9. Also, each spacer member 9, as shown in Fig. 6, is provided at each end with projecting portions or rims 94 engageable with the sides of the lugs 22 and 32 to locate the spacer members 9from shifting with respect to each caliper arm 2 or 3. The surfaces 2b and 3b of the caliper arms 2 and 3 opposite to the lugs 22 and 32 are inclined to a reference horizontal plane X as shown in Fig. 3, whereby the spacer members 9 ar e better secured between the lugs 22 and 32 and the surfaces 2b and 3b . Each spacer member 9 is provided at one end face with an elastically deformable tongue 95 adjacent the bore 91, so that when the spring leg 61 is fitted in the bore, the tongue 95 is elastically deflected to contact with the surface of the spring leg 61, thereby frictionally resisting movement of the spacer member 9 on the spring leg, so to reduce inadvertent loss of the spacer member. In the case where a caliper brake of the present invention constructed as above described is used with, for example, a brake lever provided with a lever return spring, the side surfaces 92 of the spacer members 9 are chosen for contact with the abutments 21 and 31 so that the spacer members 9 are disposed in the first positions where the restoring force of the return spring 6 is relatively weak. In this case, an operating force for the braking action can be less because of the relatively weak restoring force of the return spring 6, so that, even when the transmission efficiency of the control wire W lowers, a light or sensitive braking action is maintained with a good return feeling of the brake lever. The spacer members 9 are held between the lugs 22 and 32 and the surfaces 2b and 3b opposite thereto and inclined with respect to the horizontal plane X parallel to the direction of restoration of the return spring 6, whereby although the restoring force of the return spring 6 is relatively weak, the spacer members 9 are reliably prevented from escaping from the abutments 21 and 31. In the case where the caliper brake of the invention is used in combination with the more usual brake lever having no lever return spring, the spacer members 9 are released from contact with the abutments 21 and 31 and are inverted by rotation around the spring legs 61 without being removed therefrom, so that the side surfaces 93 are brought into contact with the abutments 21 and 31, thus the return spring 6 is adjusted or re-set so that the restoring force of the return spring 6 is greater with respect to the caliper arms 2 and 3. In this case, since the restoring force of the return spring 6 is greater, even when the transmission efficiency of the control wire W is deteriorated, the brake lever can reliably be returned to its brake-release position. The spacer members 9 are simply inverted without being removed from the spring legs 61, thereby enabling the spring setting of the spring legs 61 to be adjusted easily. Since the tongues 95 provided on the spacer members 9 contact with the surfaces of the spring legs 61 to give resistance against movement of the spacer members 9 with respect to the spring legs 61, when the setting of the spring legs 61 is changed the spacer members 9 can be prevented from escaping inadvertently from the spring legs 61. The tongues 95 may, as shown in Figs. 7 through 10, be provided at intermediate portions of the spacer members 9. Thus, each inversion member 9A shown in Figs. 7 through 10 has a curved bore 91A as shown in Fig. 10 and at a lengthwise intermediate portion of the bore 91A is provided a tongue 95A for frictional contact with the spring leg 61 to be fitted into the bore 91A . In addition, each spacer member 9A of course has a side surface 92A and 93A projecting portions 94A corresponding with the parts having the same numeral references as previously described. The return spring 6 may be replaced by separate return springs, one for each caliper arms 2, 3. In the case where the caliper brake of the invention is used in combination with the usual brake lever having no lever return spring, the restoring force of the return spring 6 may be set relatively weak for a good transmission efficiency of the control wire W and the setting may be intensified when the transmission efficiency becomes impaired. The present invention is applicable to a centre-pull type caliper brake and to a cantilever type caliper brake as well as the above-described side-pull type caliper brake.

Claims: 1. A caliper brake for a bicycle, comprising a pivot shaft (1) adapted for fixing to a bicycle frame, a caliper having a set of caliper arms (2,3) mounted on the pivot shaft (1), and a caliper return spring (6) having spring legs (61) acting on respective caliper arms (2,3) and urging same to open the caliper; characterisedinthat each spring leg (61) acts on its associated caliper arms (2,3) by way of a spacer member (9) rotatably mounted on its spring leg (2,3) by means of a bore (91) in the spacer (9) and offset with respect to a centre line of the spacer (9). 2. A caliper brake according to claim 1; characterisedinthat each caliper arm (2,3) has a recess (2b, 21, 22) in which is located the associated spacer member (9), said recess being defined on one side by a surface part (2b) of the caliper arm (2) and on a side adjacent the one side by an abutment (21) and on a side opposite the one side by a lug (22). 3. A caliper brake according to claim 2, characterisedinthat each spacer member (9) is provided with mutually spaced projecting portions (94) disposed to lie on opposite sides of said lug (22) for location of the spacer member (9) in said recess (2b, 21,22). 4. A caliper brake according to any one of the preceding claims; characterisedinthat each spacer member (9) includes a yieldably resilient tongue (95) (95A) which bears on the associated spring leg (16). and provides frictional resistence to shifting of the spacer member (9) with respect to its spring leg (16).

Inventors: NAGANO, MASASHI
Applicants: SHIMANO INDUSTRIAL COMPANY LIMITED
Application year: 1987
Main classification: B62L1
IPC codes: B62L1