GB1580404A

GB1580404A - Brake for a bicycle

Info

Publication number: GB1580404A
Application number: GB1617977A
Authority: GB
Original assignee: Shimano Industrial Co Ltd
Current assignee: Shimano Inc
Priority date: 1976-04-19
Filing date: 1977-04-19
Publication date: 1980-12-03

Description

(54) BRAKE FOR A BICYCLE (71) We, SHIMANO INDUSTRIAL COM PANY LIMITED, a Company organised and existing under the laws of Japan, of 77, 3-cho, Oimatsu-cho, Sakai-shi, Osaka, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be performed, to be particularly described in and by the following statement:- This invention relates to a brake for a bicycle.

Several types of brakes for bicycles are in current use. Caliper brakes, in which brake blocks grip a wheel rim, are satisfactory in dry conditions but in wet weather water on the rims may lower their braking effect so much as to be unsafe. Conventional hub brakes, in which a flexible brake band encircles a drum rotating with a bicycle wheel and has its opposed ends connected to a fixed member and a pivotable bell crank respec tively, the brake being operated by moving a control cable connected to the bell crank so that the bell crank contacts the drum, suffer from problems associated with the flexibility of the brake band and from the fact that the distance through which the bell crank must be moved to operate the brake is large com pared with the distance through which a conventional handlebar-mounted operating lever moves the wire of a control cable, so that the distance from the pivot of the bell crank to its point of attachment to the brake band cannot be larger than the distance from this pivot to the point of attachment to the wire of the control cable. Thus, the ball crank cannot provide any mechanical advantage for operating the brake and thus the braking force which can be applied is limited. In addition, little or no braking is obtainable when the bicycle is moving backwards, which can be dangerous if, for example, the bicycle begins rolling back down a hill. Moreover, after long use the brake tends to generate dis turbing noises and the brake linings tend to wear rapidly.

Other known bicycle brakes, for example disc brakes and coaster brakes, tend to be expensive to manufacture because of the complicated structure.

The present invention seeks to provide a brake for a bicycle which will at least partially overcome the disadvantages of known bicycle brakes, which will provide adequate braking regardless of the direction the bicycle is running and which can be made simple in construction, light-weight and compact.

Accordingly, the invention provides a brake for a bicycle, the brake comprising: a brake disc for mounting upon a bicycle wheel; base plate for fixed mounting upon the frame of a bicycle; a pair of brake arms pivotally mountable upon the base plate so that the brake arms lie adjacent the periphery of the disc on opposed sides thereof and for movement to and from a braking position in use of the brake, said brake arms having braking surfaces for contacting the periphery of said disc in said braking position; a first retaining means mounted upon one brake arm for fixedly retaining the sheath of a Bowden cable and a second retaining means mounted upon the other brake arm for fixedly retaining the wire of the Bowden cable; and a biasing means for biasing the two brake arms apart, a solid lubricant being provided on the periphery of the disc or one or both braking surfaces at least at those portions where the pressure during braking, in use of the brake, is greatest.

The invention also provides a bicycle incorporating a brake, which brake comprises: a disc mounted so as to rotate with one of the wheels of the bicycle; a base plate fixedly mounted upon the frame of the bicycle; a pair of brake arms pivotally mounted upon the base plate so as to lie adjacent the periphery of the disc on opposed sides thereof and for movement to and from a braking position, said brake arms having braking surfaces for contacting the periphery of the disc in said braking position; a first retaining means mounted upon one brake arm for fixedly retaining the sheath of a Bowden cable and a second retaining means mounted upon the other brake arm for fixedly retaining the wire of the Bowden cable; and a biasing means biasing the two brake arms apart, a solid lubricant being provided on the periphery of the disc or one or both brake arms at least at those portions where the pressure during braking is greatest.

Preferably in the brake of the invention, each braking surface has the form of part of the surface of a cylinder of substantially the same radius as the disc. Conveniently, either the outer periphery of the disc is provided with a groove extending therearound and the brake arms are formed so as to be capable of entering the groove, or the braking surfaces of the brake arms are provided with grooves and the periphery of the disc is formed so as to be capable of entering the grooves.

According to the invention, either the periphery of the disc or one or both braking surfaces has mounted thereon a solid lubricant at least at those portions where the pressure during braking is greatest, the solid lubricant preferably comprising one or more bodies each of which is partially embedded in the surface on which it is mounted, such that when the outer periphery of the disc and the braking surfaces on the brake arms come into contact, pressure will be exerted on each of the bodies.

The most preferred solid lubricant is brass.

In the bicycle of the invention desirably at least that brake arm which is the leading arm when the bicycle is moving forwardly is mounted upon the base plate by means of a link plate, said brake arm being freely pivotally mounted on the link plate and the link plate being pivotally-mounted upon the base plate and provided with a link plate biasing means which biases it radially outwardly from the disc. Preferably also, the said leading arm is longer than the other brake arm.

Very desirably, the brake arms are pivoted on the base plate at a point or points which lie radially outwardly of the periphery of the disc.

Preferred embodiments of the invention will now be described, though by way of illustration only, with reference to the accompanying drawings, in which Figure 1 is a rear elevation of a first brake of the invention assembled on a bicycle, and shows associated parts of the bicycle; Figure 2 is a side elevation of the brake shown in Figure 1; Figure 3 is a radial section through the periphery of the disc and the adjacent part of a brake arm of the brake shown in Figures 1 and 2; Figure 4 is a view, similar to Figure 3, of a modified disc and brake arm which can be used in the brake shown in Figures 1 and 2; Figures 5 is a part side elevation, partly in section, of the brake shown in Figures 1 and 2 and shows the solid lubricant bodies provided therein; Figure 6 is a side elevation of a second brake of the invention and associated parts of a bicycle; Figure 7 is a rear elevation of the brake shown in Figure 6; and Figure 8 is a side elevation of a third brake of the invention and associated parts of a bicyle.

In Figures 1 and 2, a rear wheel hub (generally designated 1) of a bicycle comprises a hub shaft 4 fixed to a bicycle frame 2 by nuts 3 and a hub shell 5 rotatably mounted on the shaft 4 by bearings (not shown). A driving member 7 bearing a sprocket 6 is fixedly mounted at the right-hand end (in Figure 1) of the hub shell 5 by means of engaging screw threads on the two parts. The hub shell 5 also bears integral flanges 8 and 9 on which are mounted the wheel spokes (not shown).

A disc 10 of a brake of the invention is fixedly mounted on one end of the hub 1 for rotation therewith the disc 10 lying axially outwardly of the flange 8, and having a central bore which engages the hub shell 5.

The disc is forced over the hub shell 5 under pressure so that the friction between the shell 5 and the walls of the bore in the disc prevent relative rotation therebetween. Alternatively the disc may engage the hub by means of screw threads or be integral with part of the hub shell.

An "L"-shaped plate 11 is fixed at one end to the bicycle frame 2 by means of a ring clamp 12 and the central part of the plate has a bore which slips over the end of the shaft 4, the plate 11 being held on the shaft by one of the nuts 3A. The opposed end of the plate extends radially outwardly beyond the periphery of the disc 10 and bears a pivot 13 on which a pair of brake arms 14 and 15 is pivotally mounted. These brake arms 14 and 15 are substantially C-shaped and each has on its radially-inward face a braking surface having the form of the part of the surface of a cylinder having the same radius as the disc 10. As shown in Figure 3, the outer periphery of the disc 10 bears a groove 10a and the radially-inward parts of the brake arms (only the arm 14 is shown but the arm 15 has a similar form) are formed with a trapezoidal section 14a which can enter the groove 10a.

Alternatively, as shown in Figure 4, the brake arms may bear a groove 14b and the periphery of the disc 10 be formed with a flange 10b which can enter the groove 14b.

The ends of the arms 14 and 15 remote from the pivot 13 are biased apart by a return spring 19 so that the braking surfaces of the arms lie concentric with the periphery of the disc but spaced therefrom. The axial position of the arms is fixed by a combination of a collar 16 surrounding the pivot 13 and interposed between the plate 11 and the arms 14 and 15 and a retaining spring 18 which is fixed to a bolt 17 mounted on the plate 11 and which biases the lower end of the arm 14 away from the plate 11.

The lower end of the arm 14 carries a first retaining means 23 to which is secured the sheath 22 of a conventional Bowden cable.

The wire 20 of this cable is secured to a second retaining means 21 on the lower end of arm 15. The end of the cable remote from the brake is secured to a handlebar-mounted brake control lever in the conventional manner. When the brake control lever is operated, the end of the wire 20 attached to the arm 15 is pulled into the sheath 22, thus drawing the lower ends of the arms 14 and 15 together against the bias of the return spring 19, and contacting the braking surfaces on these arms with the periphery of the disc 10, and braking the bicycle. It will be seen that the braking action is equally effective whichever way the bicycle wheel and the disc 10 are rotating; during forward rotation (in the direction of arrow X in Figure 2), the arm 14 is the leading arm, whilst during backward rotation (arrow Y in Figure 2), the arm 15 is the leading arm.

The increased area of contact between the arms and the disc provided by the groove 10a and trapezoidal section 14a (or by the flange 10b and groove 14b) assists in providing a reliable braking action in both directions.

The brake arms 14 and 15 are made of steel and the friction at a steel surface tends to vary depending upon the exact manufacturing conditions under which the steel was produced. The variations encountered in commercial steel are not nearly enough to affect the safety of a bicycle incorporating one or two brakes of the invention, but in order to ensure that the brakes of the invention are of consistent quality, a solid lubricant is provided between the braking surfaces on the brake arms and the periphery of the disc. As shown in Figure 5, a block 24 is partially embedded in a recess in the braking surface of each brake arm 14 or 15, such that when the braking surfaces contact the periphery of the disc, pressure is applied to the blocks and fine particles thereof become embedded in the contacting surfaces of the arms 14 and 15 and the periphery of the disc 10, thus ensuring a consistent braking action. The blocks 24 are of brass; silver may alternatively be used but is normally uneconomic. The blocks 24 are embedded under pressure in their recesses at least at those positions where the pressure during braking is greatest, and it will be apreciated that the blocks may alternatively be mounted on the disc 10 instead of on the brake arms 14 and 15.

In the embodiment of the invention shown in Figure 1 to 3 and 5, the large area of contact between the disc and the arms during braking tends to promote "binding" of the contacting surfaces as a result of which the brake arms tend not to leave the periphery of the disc after the brake control lever is released. To overcome this problem, the bias exerted by the return spring 19 can be made stronger, but this makes the action of the brake control lever heavier than is desirable.

The second embodiment of the invention, shown in Figures 6 and 7, overcomes this problem by interposing a link plate 25 between the arm 14, which is the leading arm during forward running of the bicycle, and the pivot 13. The link plate 25 is actually formed of two identical plates 25a and 25b (see Figure 7) which lie on opposed sides of the arm 14. The plates 25a and 25b are spaced apart by a collar 26 which encircles the pivot 13. The arm 14 is freely pivotally mounted on the plates 25a and 25b by means of a pivot 29, whilst the plates 25a and 25b can pivot about the pivot 13 but are biased in one direction (clockwise in Figure 6) by a link plate biasing means in the form of a spring 28 whose one end contacts a stop on the plates 25a and 25b, whose central portion encircles the pivot 13 and whose opposed end contacts a stop pin 27 fixed on the fixed plate 11.

When the brake control lever is operated so as to move the arms 14 and 15 towards the periphery of the disc 10, the arm 15 pivots about the pivot 13 and the arm 14 about the pivot 29. If the bicycle is moving forwards, the friction between the leading arm 14 and the disc 10 causes the link plate 25 to pivot anticlockwise (in Figure 6) about the pivot 13 so compressing the spring 28. When the brake control lever is released, the spring 28 serves.

to disengage the arm 14 from the disc 10.

Obviously, during forward running of the bicycle, disengagement of the trailing arm 15 presents no problems.

The third embodiment of the invention shown in Figure 8, has both brake arms 14 and 15 connected to the pivot 13 by a single "U"-shaped link plate 25, the arm 15 being connected to this link plate 25 by a pivot 30.

In the operation of this embodiment because of the greater frictional forces operating on the leading brake arm the end of the plate 25 attached to the leading arm approaches the disc 10 when the brake is applied, e.g. during forward running of the bicycle (rotation of the disc in direction of arrow X in Figure 8), braking causes the pivot 29 to approach the disc 10 and the link plate 25 swings anticlockwise in Figure 8 about the pivot 13.

Once braking ceases, the spring 28 returns to the central position shown in Figure 8, thus disengaging the leading arm from the disc; as before, the trailing arm will disengage auto matically. Obviously the link plate 25 secures proper disengagement of the leading arm whichever way the bicycle is running.

The use of a link plate 25 enables the contact areas between the disc and the arms to be greater than they are in conventional bicycle brakes, thus enhancing the braking performance.

Although the embodiments of the invention described above are for use on the rear wheel of a bicycle, the brake of the invention is equally suitable for use on the front wheel thereof. Furthermore, although in the embodi ments described above the arms 14 and 15 are equal in length, the arm 14 (which, as stated above, is the leading arm during forward running of the bicycle) may be made longer than the arm 15 to provide enhanced braking during forward running.

Considerable heat is of course generated in the brake of the invention during braking and to assist the loss of such heat from the brake, the disc and/or one or both brake arms may be fitted with a radiator plate.

As will be seen from the description of the preferred embodiments of the invention above, the brake of the invention can be made simpler in construction, and smaller than a conventional hub brake, and light in weight.

In addition, the contact pressure between the braking surfaces of the brake arms and the disc can be made such that the brake will function properly even under wet conditions.

WHAT WE CLAIM IS 1. A brake for a bicycle, the brake comprising: a brake disc for mounting upon a bicycle wheel; a base plate for fixed mounting upon the frame of a bicycle; a pair of brake arms pivotally mountable upon the base plate so that the brake arms lie adjacent the periphery of the disc on opposed sides thereof and for movement to and from a braking position, in use of the brake, said brake arms having braking surfaces for contacting the periphery of said disc in said braking position; a first retaining means mounted upon one brake arm for fixedly retaining the sheath of a Bowden cable and a second retaining means mounted upon the other brake arm for fixedly retaining the wire of a Bowden cable; and a biasing means for biasing the two brake arms apart, a solid lubricant being provided on the periphery of the disc or one or both braking surfaces at least at those portions where the pressure during braking, in use of the brake, is greatest.

2. A brake as claimed in Claim 1, in which each braking surface has the form of part of the surface of a cylinder of substantially the same radius as the disc.

3. A brake as claimed in Claim 1 or 2, in which the outer periphery of the disc is provided with a groove extending therearound and the brake arms are formed so as to be capable of entering the groove.

4. A brake as claimed in Claim 1 or 2, in which the braking surfaces of the brake arms are provided with grooves and the periphery of the disc is formed so as to be capable of entering the groove.

5. A brake as claimed in any of the preceding claims in which the brake arms are made of steel.

6. A brake as claimed in any one of Claims 1 to 5, in which the solid lubricant comprises one or more bodies each of which is partially embedded in the surface on which it is mounted, such that when the outer periphery of the disc and the braking surfaces on the brake arms come into contact, pressure will be exerted on each of the bodies.

7. A brake as claimed in any one of Claims 1 to 6, in which the solid lubricant is brass.

8. A brake as claimed in any of the preceding claims, further comprising at least one link plate by means of which one of the brake arms can be mounted upon the base plate, the said brake arm being capable of being freely pivotally mounted on the link plate and the link plate being capable of being pivotally mounted upon the base plate so as to be biased radially outwardly from the disc by a link plate biasing means.

9. A brake as claimed in any of the preceding claims, in which at least one brake arm is provided with a radiator plate to assist heat loss therefrom.

10. A brake for a bicycle, the brake being substantially as herein described with reference to and as illustrated in Figures 1 to 3 and 5, Figures 1 to 3 and 5 as modified by Figure 4, Figures 6 and 7, or Figure 8 of the accompanying drawings.

11. A bicycle incorporating a brake, which brake comprises: a disc mounted so as to rotate with one of the wheels of the bicycle; a base plate fixedly mounted upon the frame of the bicycle; a pair of brake arms pivotally mounted upon the base plate so as to lie adjacent the periphery of the disc on opposed sides thereof and for movement to and from a braking position, said brake arms having braking surfaces for contacting the periphery of the disc in said braking position; a first retaining means mounted upon one brake arm for fixedly retaining the sheath of a Bowden cable and a second retaining means mounted upon the other brake arm for fixedly retaining the wire of the Bowden cable; and a biasing means biasing the two brake arms apart, a solid lubricant being provided on the periphery of the disc or one or both brake arms at least at those portions where the pressure during braking is greatest.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. contact areas between the disc and the arms to be greater than they are in conventional bicycle brakes, thus enhancing the braking performance. Although the embodiments of the invention described above are for use on the rear wheel of a bicycle, the brake of the invention is equally suitable for use on the front wheel thereof. Furthermore, although in the embodi ments described above the arms 14 and 15 are equal in length, the arm 14 (which, as stated above, is the leading arm during forward running of the bicycle) may be made longer than the arm 15 to provide enhanced braking during forward running. Considerable heat is of course generated in the brake of the invention during braking and to assist the loss of such heat from the brake, the disc and/or one or both brake arms may be fitted with a radiator plate. As will be seen from the description of the preferred embodiments of the invention above, the brake of the invention can be made simpler in construction, and smaller than a conventional hub brake, and light in weight. In addition, the contact pressure between the braking surfaces of the brake arms and the disc can be made such that the brake will function properly even under wet conditions. WHAT WE CLAIM IS

1. A brake for a bicycle, the brake comprising: a brake disc for mounting upon a bicycle wheel; a base plate for fixed mounting upon the frame of a bicycle; a pair of brake arms pivotally mountable upon the base plate so that the brake arms lie adjacent the periphery of the disc on opposed sides thereof and for movement to and from a braking position, in use of the brake, said brake arms having braking surfaces for contacting the periphery of said disc in said braking position; a first retaining means mounted upon one brake arm for fixedly retaining the sheath of a Bowden cable and a second retaining means mounted upon the other brake arm for fixedly retaining the wire of a Bowden cable; and a biasing means for biasing the two brake arms apart, a solid lubricant being provided on the periphery of the disc or one or both braking surfaces at least at those portions where the pressure during braking, in use of the brake, is greatest.

12. A bicycle as claimed in Claim 11, in

which each braking surface has the form of part of the surface of the cylinder of substantially the same radius as the disc.

13. A bicycle as claimed in Claim 11 or 12, in which the outer periphery of the disc is provided with a groove extending therearound and the brake arms are formed so as to be capable of entering the groove.

14. A bicycle as claimed in Claim 11 or 12, in which the braking surfaces of the brake arms are provided with a groove and the periphery of the disc is formed so as to be capable of entering the groove.

15. A bicycle as claimed in any of Claims 11 to 14, in which the brake arms are made of steel.

16. A bicycle as claimed in any one of Claims 11 to 15, in which the solid lubricant comprises one or more bodies each of which is partially embedded in the surface on which it is mounted, such that when the outer periphery of the disc and the braking surfaces on the brake arms come into contact, pressure will be exerted on each of the bodies.

17. A bicycle as claimed in any one of Claims 11 to 16 in which the solid lubricant is brass.

18. A bicycle as claimed in any of Claims 11 to 17, in which at least that brake arm which is the leading arm when the bicycle is moving forwards is mounted upon the base plate by means of a link plate, said brake arm being freely pivotally mounted on the link plate and the link plate being pivotally mounted upon the base plate and provided with a link biasing means which biases it radially outwardly from the disc.

19. A bicycle as claimed in any of Claims 11 to 18, in which that brake arm which is the leading arm when the bicycle is moving forwards is longer than the other brake arm.

20. A bicycle as claimed in any of Claims 11 to 19, in which at least one brake arm is provided with a radiator plate to assist heat loss therefrom.

21. A bicycle as claimed in any of Claims 11 to 17, in which the two brake arms are mounted on the base plate by means of a common pivot.

22. A bicycle as claimed in any of Claims 11 to 17 or in Claim 21, in which the brake arms are pivoted on the base plate at a point or points which lie radially outwardly of the periphery of the disc.

23. A bicycle as claimed in Claim 11 and substantially as herein described, with reference to and as illustrated in Figures 1 to 3 and 5, Figures 1 to 3 and 5 as modified by Figure 4, Figures 6 and 7, or Figure 8 of the accompanying drawings.