GB1587778A

GB1587778A - Disc parking brakes

Info

Publication number: GB1587778A
Application number: GB6953/78A
Authority: GB
Original assignee: Automobiles Citroen SA
Current assignee: Automobiles Citroen SA
Priority date: 1977-02-28
Filing date: 1978-02-22
Publication date: 1981-04-08
Also published as: IT7867387A0; DE2806821A1; ES467239A1; RO79814A; IT1107098B

Description

(54) IMPROVEMENTS IN OR RELATIN G TO DISC PARKING BRAKES (71) We, SOCIETE ANONYME AUTO MOBILES CITIZOEN, a French body corporate of Quai Andre Citroen 75747 Paris Cedex 15, France, 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 particularly described in and by the following statement: The present invention relates to disc parking brakes for motor vehicles.

According to a first aspect of the invention, there is provided a disc parking brake for motor vehicles comprising a disc, friction linings disposed on both sides of the disc, at least one control lever pivotably mounted on a stationary axle and connected by a system of rods to a lever or to a pedal for actuation by a driver, and a cam connected with the lever for so acting on one of the friction linings that the disc is clamped between the linings, the cam and the control lever being independently movable, while being pivotably mounted on the same axle, a rod being screwed into the control lever and engaging the cam to transmit movement of the lever to the cam, means being provided which, when the brake is inoperative, maintain the cam in a position in which the cam is inactive.

According to a second aspect of the invention, there is provided a parking brake for a motor vehicle, the brake comprising a disc for connnection to a part of the vehicle to be braked, brake linings disposed on opposite sides of the disc, a cam mounted for pivotal movement between an operative position, in which the cam acts on the brake linings to clamp the disc therebetween, and an inoperative position, a lever mounted independently of the cam for pivotal movement between operative and inoperative positions by an actuating device controlled, in use, by a driver of the motor vehicle, a rod mounted on the lever and in engagement with the cam to pivot the cam to the operative position thereof on pivotal movement of the lever to the operative position thereof by the actuating device, means being provided for returning the cam to the inoperative position when the lever is moved to the inoperative position thereof by the actuating device.

The following is a description, by way of example, of several forms of construction of a disc brake according to the invention with reference to the attached drawings in which: Figure 1 shows a first form of construction of the brake, the right-hand half of the Figure being in elevation and the left-hand half being a cross-section along the line I-I of Fig. 2; Figure 2 is a side view of the brake of Figure 1, partly sectioned along the line 11-11 of Fig. 1; Figure 3 is a cross-sectional view of a cam of the brake of Figure 1, along line IIIIlI of Fig. 1; Figure 4 is a detailed view of a second form of construction of the brake; Figure 5 is a detailed view of a modified form of the brake of Figure 4; Figure 6 is a detailed view of a further modification of the brake of Figure 4; Figure 7 shows a third form of construction of the brake, the right-hand half of the Figure being in elevation, and the lefthand half being a cross-section along the line VII--VIIII of Figure 8; Figure 8 is a side view of the brake of Figure 7 and shows a detail of the brake; Figure 9 shows a fourth form of construction of the brake, the right-hand half of the Figure being in elevation, and the left-hand half being a cross-section along the line IX-IX of Fig. 10; Figure 10 is a side view of the brake of Figure 9, partially in cross-section along the line X-X of Fig. 9.

Referring first to Figures 1 to 3, the first form of construction of the parking brake comprises a stirrup-piece 1 astride a disc 2 which is rigidly fixed on a wheel shaft (not shown) and on both sides of which friction linings 3 are disposed. The linings 3 are fixed on rigid plates 4 which are held in place by a spring 5 and they are able to be pushed towards the disc 1 by a control device described hereinunder.

To press each of the linings 3 against the disc 2, there are provided two cams 6 each of which is in contact with a corresponding one of the plates 4 and is pivotably mounted on a bearing 7 which is held by a screw 8.

A lever 9 is also pivotably mounted on each bearing 7 (see Figure 2) with the scerw 8 fixing the axial position of the associated cam and lever on the stirrup-piece 1. In the example shown in Figures 1 to 3, the cam and the lever are both fork-shaped and a branch of one is engaged between the branches of the other, as may be seen in Figs. 2 and 3. The two levers 9 are connected to a further lever or to a brake control pedal (not shown) by a system of a usual type comprising a cable 10 which is fixed to one of the levers and is mounted in a sheath 11 supported on the other lever; a return spring 12 being disposed between the two levers 9.

The connnection between each lever 9 and the corresponding cam 6 is effected by a rod 13 whose upper part has a polygonal crosssection, for example a hexagonal crosssection and whose lower section is threaded and screwed into a boss 14 provided on a bottom part of the lever 9; the end of this threaded portion engages on the associated cam 6. A return spring 15 is wound in a cup 16 situated between the cam 6 and the head of the screw 8. One of the ends 15a of this spring engages a side of the cam 6 which is opposite, relatively to the axis of the screw 8, the point of engagement between the rod 13 and the cam. The other end 15b of the spring 15 is held in a slit 14a formed in the boss 14. This spring thus tends to press the cam onto the end of rod 13.

A spring 17 is also provided which engages one of the longitudinal faces of the part of rod 13 which is of polygonal section.

This spring 17 is disposed in a bore 18 of a boss 19 provided at the upper part of the lever 9.

The brake described above with reference to Figures 1 to 3 operates in the following way: when a driver actuates the parking brake pedal or lever, the levers 9 are moved by the cable 10 and the sheath 11 in a direction which brings them closer together, against the action of the spring 12. The levers 9 swivel about the axes of the screws 8 and the movement is transmitted by the rods 13 to the cams 6 which move to operative positions to shift the friction linings 3 to clamp the disc 2 between them.

When the driver releases the parking brake, the two levers 9 pivot about the axes of the screws 8 and are returned to their initial inoperative positions by the spring 12.

The cams 6 also resume their initial inoperative rest positions under the action of the springs 15, while remaining in contact with the rods 13.

When the wear of the friction linings 3 is sufficiently great to prevent correct operation of the brake, the threaded rods 13 are screwed further into the bosses 14, for example by means of a hexagonal spanner, in such a way as to increase the angle between the levers 9 and the cams 6 and to bring these cams closer to the plates 4.

The springs 17 cushion return pivotal movement of the rods 13 and prevent an alteration of the adjustment of the brake as a result of vibration.

In the embodiment of Fig. 4, the - springs 17 provided in the embodiment of Figures 1 to 3 are omitted and the lower end of each of the rods 13 is cylindrical and guided in a bore 20 provided in the associated boss 14. The upper end of each rod 13 is threaded and screwed into a threaded hole in a boss 21 provided at an upper end of the associated lever 9. The rods 13 are held in required axial positions by lock-nuts 22. The upper face of each rod has a slit 13a which allows rotation of the rod by, for example, a blade of a screwdriver.

In the alternative arrangement shown in Fig. 5, the axial position of each rod 13 is maintained by a brace 23 which is interposed between the rod and the threaded hole of the boss 21 and bears inserted self-locking inner threads.

In the alternative arrangement of Fig. 6, the assembly of rods 13 is the same as iii Fig. 4, but the springs 15 and the cups 16 are omitted. Each cam 6 is maintained in engagement with the corresponding rod 13 by a pawl 24 which is disposed in a bore 25 provided in the associated boss 14 and which is forced into contact with the associated cam by means of a spring 26 interposed between said pawl and the bottom of the bore.

In the embodiment of Figures 7 and 8, levers 9 are fork-shaped, but each cam 6 is in one piece, and is disposed between branches 9a and 9b of the associated lever.

Each of the return springs 15 is wound on a cup 16 interposed between the cam 6 and the head of the corresponding screw.

One end 15a of each of these springs rests on a pawl 27 rigidly connected to the cam 6 while the other end 15b rests against a flat face 13a of the hexagonal rod 13. Thus the spring 15, in this embodiment, tends to press the cam on the end of rod 13 and to resist the pivoting of said rod 13 under the action of vibrations.

In the embodiment of Figs. 9 and 10, an elastic washer 28 is interposed between each of the cams 6 and one of the branches 9a and 9b of the associated control lever 9.

Moreover, the return spring 12 has, at each end, a branch 12a supported on one of the faces associated rod 13 which is situated on the same side as the said end.

When the parking brake is actuated, the levers 9 swivel about the axles 8 and drive the cams 6 through the medium of the rods 13. The swivelling of the cams 6 causes the axial displacement of the friction linings 3 which clamp the disc 2 between them.

When the parking brake is released, the levers 9 resume their initial position under the action of the return springs 12; during this movement the cams 6 are moved by the levers 9 as a result of the friction exerted by the resilient washers 28 and the cams also resume also initial positions, remaining in engagement with the rods 13.

The adjusting rods 14 are held by tile branches 12a of the spring 12 and cannot therefore rotate as a consequence of vibrations.

WHAT WE CLAIM IS:- 1. A disc parking brake for motor vehicles comprising a disc, friction linings disposed on both sides of the disc, at least one control lever pivotably mounted on a stationary axle and connected by a system of rods to a lever or to a pedal for actuation by a driver, and a cam connected with the lever for so acting on one of the friction linings that the disc is clamped between the linings, the cam and the control lever being independently movable, while being pivotably mounted on the same axle, a rod being screwed into the control lever and engaging to transmit movement of the lever to the cam, means being provided which, when the brake is inoperative, maintain the cam in a position in which the cam is inactive.

2. A disc brake according to Claim 1, wherein the said maintaining means are resilient return means for maintaining the cam in engagement with the rod.

3. A disc brake according to Claim 2, wherein the resilient means comprise a coil spring which is disposed coaxially with said axle, one end of the spring bearing against the lever, while the other end bears against the cam, on a side of the cam which is opposite, relatively to the said axle, to the point of engagement of the rod with the cam.

4. A brake according to Claim 3, wherein the spring is disposed in a cup fixed at one end of the axle.

5. A disc brake according to Claim 2, wherein the resilient means comprise a pawl movable in a bore provided in the lever on a side thereof opposite the rod, relative to the axle, and urged into engagement with the cam by a compression spring.

6. A disc brake according to Claim 1, wherein the maintaining means comprise means for exerting a frictionally applied couple between the lever and the cam.

7. A brake according to Claim 6, wherein the portion of control lever connected to the pivoting axle has the form of a fork between the arms of which the cam is disposed, and wherein the means for exerting a couple between the lever and the cam comprise a resilient washer disposed between the cam and one of the arms of the form of the control lever.

8. A disc brake according to any one of the preceding claims wherein the rod has a part of polygonal section, and wherein there are provided resilient means pressing against said polygonal part.

9. A disc brake according to Claim 8 wherein the said resilient means comprise a spring disposed in a bore of the lever and pressing on one of the longitudinal faces of the polygonal portion of the rod.

10. A dic brake according to Claim 8 wherein the said resilient means comprise portions of a spring for returning the lever to an inoperative position, the spring having at one end thereof a branch engaging one of the faces of the polygonal portion of the rod.

11. A disc brake according to any of Claims to 7, wherein the rod is screwed into a first boss provided on a portion of the control lever remote from the cam and is guided in a bore of a second boss provided on a portion of said lever adjacent the cam, means being provided for preventing rotation of the rod in the first boss.

12. A disc brake according to Claim 11 wherein the rotation prevention means comprise a lock-nut.

13. A disc brake according to Claim 11 wherein the resilient return means comprise a tubular brace having self-locking threads and disposed between the thread of the first boss and the thread of the rod.

14. A disc brake according to Claim 2 wherein the resilient return means comprise means for preventing vibration of the rod.

15. A disc brake according to Claim 1 wherein the resilient return means comprise a spring disposed coaxially with the axle, the spring including a first branch engaging the cam and a second branch engaging a flat face of a part of the rod whose section is polygonal.

16. A parking brake for a motor vehicle, the brake comprising a disc for connection to a part of the vehicle to be braked, brake linings disposed on opposite sides of the disc, a cam mounted for pivotal movement between an operative position, in which the cam acts on the brake linings to clamp the disc therebetween, and an inoperative position, a lever mounted inde- pendently of the cam for pivotal movement

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of the faces associated rod 13 which is situated on the same side as the said end. When the parking brake is actuated, the levers 9 swivel about the axles 8 and drive the cams 6 through the medium of the rods 13. The swivelling of the cams 6 causes the axial displacement of the friction linings 3 which clamp the disc 2 between them. When the parking brake is released, the levers 9 resume their initial position under the action of the return springs 12; during this movement the cams 6 are moved by the levers 9 as a result of the friction exerted by the resilient washers 28 and the cams also resume also initial positions, remaining in engagement with the rods 13. The adjusting rods 14 are held by tile branches 12a of the spring 12 and cannot therefore rotate as a consequence of vibrations. WHAT WE CLAIM IS:-

1. A disc parking brake for motor vehicles comprising a disc, friction linings disposed on both sides of the disc, at least one control lever pivotably mounted on a stationary axle and connected by a system of rods to a lever or to a pedal for actuation by a driver, and a cam connected with the lever for so acting on one of the friction linings that the disc is clamped between the linings, the cam and the control lever being independently movable, while being pivotably mounted on the same axle, a rod being screwed into the control lever and engaging to transmit movement of the lever to the cam, means being provided which, when the brake is inoperative, maintain the cam in a position in which the cam is inactive.

between operative and inoperative positions by an actuating device controlled, in use, by a driver of the motor vehicle, a rod mounted on the lever and in engagement with the cam to pivot the cam to the operative position thereof on pivotal movement of the lever to the operative position thereof by the actuating device, means being provided for returning the cam to the inoperative position when the lever is moved to the inoperative position thereof by the actuating device.

17. A disc parking brake, substantially as hereinbefore described with reference to the accompanying drawings.