GB2205362A - Brake drum seal - Google Patents

Abstract

A protective brake drum seal is formed of an annular movable seal (5) between the rotating brake drum (1) and the back plate (3). The seal may also be formed by a barrier of fluid e.g. air, in excess of atmospheric pressure, an outlet of which is located within the drum (1), and thus escapes between the seal face (5) and the rotating drum (1). <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO VEHICLE BRAKES The present invention relates to vehicle brakes and in particular to drum brakes for use on vehicles which are likely to be used in cross-country and other off-road applications where they rtght be exposed to mud and water.

Conventional drum brakes are well knoz7n for their lack of efficiency after immersion in water, mud or slurry. For this reason drivers are often advised by roadside signs to test their brakes after negotiating fords or flooded roads. In such circumstances it is often necessary to drive for some distance with the brakes lightly applied in order to dry tham out more rapidly and restore their efficiency.

It is an object of the present invention to provide reans for eliminating or substantially reducing the ingress of undesirable efficiency reducing materials such as mud and water.

According to the present invention in one aspect thereof a seal for a vehicle drum brake includes means for controllably interposing an annular seal between a drum and a backplate of said drum brake.

The seal may be formed by a barrier of by fluid from a fluid supply at a pressure in excess of atmospheric pressure, an outlet of said fluid supply being located within the drum brake. The fluid may then be air supplied through an orifice in the drum brake backplate.

Conveniently the air supply is fed from a conventional air brake system air reservoir. The air supply may be controlled by means of any know-n fluid control valve located between the air reservoir and the backplate. The arranges nt may further include control means for automatically or manually opening the fluid control valve whenever the vehicle is or is about to traverse a hostile environint.

The seal may be an annular friction surface slidably mounted on mounting means attached to the periphery of the backplate and controllably slidable axially with respect to the drum and backplate assembly from a first position, in which it defines one edge of an annular radially extending passage connecting the outside atmosphere to the interior of the absently to allow cooling air to flow therethrough, and a second position, in which it sealably contacts an external annular surface of the drum, sealing the interior of the drum thereby.

The mounting means may be formed as an outer annular channel rigidly secured to the backplate and the annular friction surface may be formed at one end of a sliding nwsILer slidably mounted within the channel. In this case the friction surface may be controllably driven into engagement with the outer surface of the drum by means of a piston acting between the mounting means and the slidable rnert'ber. The piston may be pneumatically, hydraulically or electronically operated.

Resilient means may be provided between the slidable m Eber and the mounting means in order to release the friction surface whenever the pneumatic or hydraulic or electronic power to the piston is removed.

The seal may alternatively be formed of a combination of said movable friction surface and a fluid barrier as previously described.

ibodizents of the invention will now be described by way of example only and with reference to the accompanying drawings of which: Figures la, Ib and lc are front, side and rear views respectfully of a drum brake assembly including a controllable seal according to the invention, Figures 2a, 2b and 2c are cross-sectional views of different forrls of similar parts of the assembly shown in Figure 1, Figure 3 is an exploded perspective part--çiew of a brake sealing device according to the present invention, and Figures 4a and 4b illustrate the operation of the part shown in Figure 2a.

In the following description elents which are cowc,lon to various enbodiments shown in the drawings have been given common reference numbers.

In Figures la, Ib and lc a vehicle brake drum shown generally at 1 has wheel studs 2 for attaching a wheel (not shown) and a backplate 3. These parts of the drum brake asseMbly are conventional.

I4orrally there will be a small air gap between the drum cover 1 and the backplate 3 to allow cooling air to pass into the brake assembly when the vehicle is in motion. This gap also would usually allow ingress of mud and water when the vehicle is required to traverse a hostile environirtent. However, in this case a controllable seal is provided comprising annular outer and inner channel sections 4a and 4b, an annular moving friction surface 5 and a circular flexible seal 6 disposed between outer and inner channel sections. The outer channel section 4a is rigidly secured to the backing plate 3 by an attachment ring 7 and attachment ring bolts 8.The inner channel 4b is slidably mounted within the outer channel 4a so that it is able to move frizz a position in which there is an annular air gap between the friction surface 5 and the opposing surface of the drum cover 1 and a second position in which the friction surface 5 is brought into sealable contact with that opposing surface. These two extreme positions are shown in Figures 4a and 4b respectively.

various mechanisms can be used to effect the relative Eovnment between he outer and inner channel sections 4a and 4b. Three such mechanisms are shown in Figures 2a, 2b and 2c. Figure 2a is a pneumatic device in which an annular flexible air cylinder 9 is disposed within the cavity defined by inner surfaces of the outer and inner channels 4a and 4b respectively. The flexible air cylinder 9 may be connected by suitable means (not shos.n) to an air supply, for example an additional air reservoir of an air brake system.An automatically or manually operated control valve (not shown) in the air supply line to the flexible air cylinder 9 may control the supply of air to the cylinder which will expand when air is supplied to it to move the inner channel 4b and its attached friction surface 5 axially with respect to the brake drum assembly to bring friction surface 5 into contact with he opposing surface of the drum cover 1.

Figure 2b shows a hydraulic mechanism comprising a slave cylinder 10 and ram 11 assembly mounted within the cavity defined by inner surfaces of the outer and inner channels a and 4b. The ram bears against the inner surface of the moveable inner channel 4b so cleat when hydraulic fluid is supplied to the slave cylinder 10 by its of a supply indicated at 12 the friction surface 5 is brought into sealable contact with the opposing surface of the drurn cover 1.

Figure 2c illustrates an arrangement similar to that of Figure 2b except that an electrically operated solonoid 13 is used to effect movements of the ram il and of course the supply 12 is a suitable supply of DC voltage. In the devices of Figures 2b and 2c the hydraulic slave cylinder 10 or electronic solonoid 13 may be mounted on the outside of the backplate 3 to aid sizing requirements and cooling requirements.

In all three devices shown in Figures 2a, 2b and 2c a circular flexible seal 6 is disposed between outer surfaces of the outer and inner channel sections 4a and 4b to prevent dirt and water from spoiling the sliding surfaces of those sections. In all three devices a return spring 14 housed within a suitable spring cover 15 is connected between the attachment rir.g 7 and a suitable ron.ber 15 attached to the inner sliding channel section 4b free to move within a slot located on the outer most surface of the outer channel section 4a. alle spring 14 bias' the friction surface 5 in a direction away from contact with the drum cover 1 and returns the inner channel section 4b to its housed noncontact position whenever the air/hydraulic electric supply, used for effecting sealing of the drum brake assembly, is removed.

CXle friction surface 5 may be made of a P7rE type material and it may be provided with a groove or slot on its bearing surface indicated at 16 in Figure 3 angled so as not to avoid comprising the sealing action and designed to aid cutting and cleaning by the friction surface.

A low pressure air supply may be fed into the back of the drum to provide pos tive pressure to blow out any water, mud or slurry that attempts to enter the drum before sealing is effected by the friction surface 5.

The outer and inner channel sections 4a and 4b, the attachment ring 7 and attachment ring bolts 8, the pneumatic, hydraulic or electronic operating device, the friction surface 5, the sealing ring 6 and the springs 14 and covers 15 may altogether provide a bolt-on adaptation to an existing drum brake. Such adaptations may be made and supplied independently of supplies of the vehicles per se to vehicle users for self-fitment. Such users would then have to provide a suitable air, hydraulic or DC supply to power the sealing device.

rLny modifications and improvements of the embodiments described above will now suggest '-hemselves to those skilled in the art.

Claims (1)

1 A seal for a vehicle drum brake including means for controllably interposing an annular seal between a drum and back piate of said drum brake.