GB1602846A

GB1602846A - Sliding caliper disc brake

Info

Publication number: GB1602846A
Application number: GB12905/77A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1977-03-28
Filing date: 1977-03-28
Publication date: 1981-11-18
Also published as: FR2385950A1; FR2385950B1; JPS53127973A; IT1102150B; AU524745B2; AU3440578A; ES468266A1; DE2813244C2; ZA781742B; ES476454A1; DE2813244A1; IT7848630A0

Description

(54) SLIDING CALIPER DISC BRAKE (71) We, GIRLING LIMITED, a British company of Kings Road, Tyseley, Birming- ham, B26 L11, West Midlands, 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: This invention relates to sliding caliper disc brakes and more particularly to friction pad assemblies for such brakes.

Vehicle brakes of the type comprising a torque taking member for fixing to a vehicle frame or like portion, a caliper member adapted to straddle a minor portion of the periphery of a rotatable disc and an actuator for urging a first friction pad onto one side of the disc to cause the caliper member to slide relative to the torque member to apply by reaction an opposite friction pad to the other side of the disc are known.

These brakes are generally provided with pad wear warning indicators, one known arrangement including a trigger in the form of a contact partially embedded in a respective friction pad so as to co-operate with the disc when the pad is worn to actuate an electrical warning device. The contact which lies in parallel to a backing plate for the pad, extends beyond both the peripery of the disc and that of said plate towards a crown portion of the caliper member for bridging the disc's periphery and so may utilise an undesirable amount of space.

A more compact arrangement, but which is possibly less effective in some respects, may be provided by another known contact which is mounted in the backing plate adjacent the edge of the friction pad and within the sweep of the disc. Initially the contact is spaced from the respective face of the disc during braking but wear of the pad eventually brings the contact to bear against the disc to actuate the indicator. However, connection between the contact and the disc after a given amount of pad wear may initially be uncertain since the contact, being spaced from the friction pad, lies outside the region where braking occurs and may, possibly be affected by distortion of the brake parts through use.

Thus there is the problem of providing a friction pad assembly with a warning device trigger whose connections may be arranged in a limited space, which trigger at the same time may be arranged to give an accurate indication of when the pad has worn to a predetermined thickness.

One aim of the invention is to provide a trigger arrangement which permits a compact construction of brake with the trigger being embedded in a friction pad of the brake.

The invention resides in a friction pad assembly having a backing plate, to which a pad of friction material is secured, fastening means serving to guide, support and retain both an electrical conductor and an anti-rattle spring on said backing plate, the conductor providing a trigger which in use can actuate a warning device when the pad is worn to a predetermined thickness.

Additionally the invention provides a sliding caliper disc brake comprising a torque taking member, a caliper member for straddling a minor portion of a rotatable disc, said caliper member being slidably mounted relative to the torque member and an actuator for urging a first friction pad assembly onto one side of the disc to cause the caliper member to slide relative to the torque member to apply by reaction ttn opposite friction pad assembly to the other side of the disc, one assembly having a backing plate to which a pad - of friction material is secured, fastening means serving to guide, support and retain both an electrical conductor and an anti-rattle spring on said backing plate, the conductor providing a trigger adapted to actuate a warning device when the pad is worn to a predetermined thickness.

In a preferred embodiment of the invention, the conductor is guided through a hollow rivet serving to secure the anti-rattle spring to the backing plate, the spring, in the assembled brake, urging the friction pad assembly against the torque plate, and the caliper member against its sliding guides to reduce rattling between these parts. The advantage of employing the rivet for guiding the conductor through the backing plate lies in the fact that the dimensions of the backing plate need not be increased as compared with those of a plate already known for carrying an anit-rattle spring by means of a rivet.

The rivet may conveniently be fitted with an insulating plug carrying the conductor and having an extension reaching into the pad, the trigger comprising a wire contact encased within the extension and leading to the conductor in the plug.

The invention is described further, by way of example, with reference to the drawings accompanying the Provisional Specification wherein: Fig. 1 is a plan view of a sliding caliper dis brake according to the invention: Fig. 2 is a sectional view along the line II-II in Fig. 1 Fig. 3 is a rear view of the disc brake of Fig. 1 cut away along the line III in Fig. 1; and Fig. 4 is a fragmentary section through a friction pad assembly of the brake of Fig.

1; and with reference to the accompanying Fig. 5 which is a view similar to Fig. 4 but including diagrammatic details of a pad wear warning indicator circuit.

The disc brake shown in Figs. 1 to 4 comprises ta torque member 10, and a caliper member 12 having pins 14 (only one of which is shown in Fig. 3) slidably received in bores 16 in the torque member 10 for guiding the caliper member 12 for sliding relative to the torque member 10. The caliper member 12 also has a centrally apertured crown portion 18 interconnecting a front limb 20 and a rear limb 22 disposed on opposite sides of a rotatable disc 24.

The rear limb 22 of the caliper member is formed with an hydraulic cylinder containing a piston 26 which abuts against a directly actuated friction pad assembly 28.

A second, indirectly actuated, friction pad assembly 30 is engaged by the front limb 20 of the caliper member.

The two friction pad assemblies are arranged adjacent to the periphery of the disc 24, on opposite sides thereof, in recesses 32 in the torque member 10. Each assembly includes a pad of friction material 34 and a backing plate 36 which has two lateral shoulders 38 engaged with sliding surfaces 40 on the torque member 10. The pads 34 are thus slidably mounted on the torque member 10 for actuation by the caliper member 12.

Extending from the radially outer edge of each backing plate 36, beyond the periphery of the disc 24 and into the recess in the crown portion 18 of the caliper member 12, is a tongue 42 carrying a respective rivet 44. The rivets 44 serve to secure to the backing plates 36 anti-rattle springs 46.

Each spring 46 engages the caliper member 12 (see Fig. 3) to press the associated backing plate 36 against the sliding surfaces 40.

At the same time the springs urge the caliper member 12 radially of the disc 24 away from the torque member 10 so taking up any tolerance between the pins 14 and bores 16.

Turning now to Fig. 4, one of the friction pad assemblies is shown in greater detail. The illustrated rivet 44 is hollow and carries an insulating plug 48, the plug 48 having on its body resilient teeth 50 which are compressed to retain the plug within the rivet. An elongate extension 52 of the plug 48 leads to and has its end embedded in the pad 34. This extension encases a sensor or trigger which in the present instance comprises a wire contact 54 guided along almost the whole length of the extension and connected to a conductive pin 56 held by the plug 48. This pin 56 is engageable within a conductive socket 58 in a second insulating plug 60 (shown in dotted lines) which is coupled via a led 62 to a warning indicator in the form of a lamp 64.

As described below, the wire 54 forms one contact of a switch in a circuit containing the warning indicator, the other contact being provided by the disc 24.

Braking is effected by introducing hydraulic fluid under pressure into the cylinder in the rear limb 22 of the caliper member 12 to cause the directly actuated friction pad assembly 28 to be urged against one side of the disc 24. This results in the caliper member 12 sliding relative to the torque member 10 to apply by reaction the indirectly actuated friction pad assembly 30 to the other side of the disc 24.

Over a period, the pads 34 wear under the braking demands and when a predetermined denth of pad has been worn away, braking causes the disc 24 to bear against the extension 52. This also wears until the wire 54 is exposed to the disc 24, the two co-operating together as the electrical switch controlling the warning indicator.

Now, when braking occurs, the wire contacts the disc to make the electric circuit containing the warning indicator. Of course, the circuit may be designed so that the wire contacts the disc to break a circuit arranged to actuate the warning indicator on being broken.

Utilising the sensor arrangement shown in Fig. 4, the crown portion of the caliper member may occupy almost the whole of the space between the periphery of the disc and the inside of the road wheel without obstructing the connection wire to the sensor.

Claims

WHAT WE CLAIM IS:-

1. A sliding caliper disc brake comprising a torque taking member, a caliper member for straddling a minor portion of a rotatable disc, said caliper member being slidably mounted relative to the torque member and an actuator for urging a first friction pad assembly onto one side of the disc to cause the caliper member to slide relative to the torque member to apply by reaction an opposite friction pad assembly to the other side of the disc, one assembly having a backing plate to which a pad of friction material is secured, fastening means serving to guide, support and retain both an electrical conductor and an anti-rattle spring on said backing plate, the conductor providing a trigger adapted to actuate a warning device when the pad is worn to a predetermined thickness.

2. A disc brake as claimed in claim 1, wherein said trigger is adapted to co-operate with the disc during braking when the pad is worn to the predetermined thickness to actuate said warning device.

3. A disc brake as claimed in claim 2 wherein said trigger is adapted to co-operate with the disc as a switch to complete a warning device circuit during braking when the pad is worn to said predetermined thickness.

4. A disc brake as claimed in claim 1, 2 or 3, in which the fastening means is in the form of a hollow rivet.

5. A disc brake as claimed in claim 4, in which the conductor extends through the hollow rivet.

6. A disc brake as claimed in any one of the preceding claims wherein the spring acts between the caliper member and said one assembly in such a manner as to inhibit vibrational movement of the torque member, the caliper member and said one assembly relative to one another.

7. A disc brake as claimed in any one of the preceding claims in which the fastening means is fitted with an insulating plug carrying the conductor.

8. A disc brake as claimed in claim 7, wherein an extension of the plug reaches into the pad and wherein the trigger comprises a wire contact encased within the extension.

9. A disc brake as claimed in claim 7 or 8, wherein the insulating plug is provided with resilient projections arranged to engage the internal wall of the rivet and directed so as to resist withdrawal of the plug from the rivet.

10. A disc brake as claimed in claim 1 in combination with the warning device, the trigger being connected to the warning device so as to actuate said device when the pad is worn to the predetermined thickness.

11. A disc brake as claimed in claim 10 mounted so that the caliper member straddles the rotatable disc, the trigger being arranged so as to co-operate with the disc during braking when the pad is worn to the predetermined thickness, to actuate the warning device.

12. A disc brake as claimed in claim 11 wherein the trigger and the disc form the two contacts of a switch and are arranged to abut one another to complete a circuit through the warning device during braking when the pad is worn to the predetermined thickness.

13. A friction pad assembly for use in the disc brake as claimed in claim 1, said assembly having a backing plate to which a pad of friction material is secured, fastening means serving to guide, support and retain both an electrical conductor and an anti-rattle spring on said backing plate, the conductor providing a trigger which in use can actuate a warning device when the pad is worn to a predetermined thickness.

14. An assembly as claimed in claim 13, wherein a hollow rivet forms said fastening means and is fitted with an insulating plug carrying the conductor.

15. An assembly as claimed in claim 14, wherein an extension of the plug reaches into the pad and wherein the trigger comprises a wire contact encased within the extension.

16. An assembly as claimed in claim 14 or 15, wherein the insulating plug is provided with resilient projections arranged to engage the internal wall of the rivet and directed so as to resist withdrawal of the plug from the rivet.

17. A friction pad assembly constructed substantially as herein particularly described with reference to and as illustrated in Figs.

1 to 4 of the drawings accompanying the Provisional Specification.

18. A disc brake constructed substantially as herein particularly described with reference to and as illustrated in Figs. 1 to 4 of the drawings accompanying the Provisional Specification.