Lucas Industries Public Limited Company

Lucas Industries Limited

Graham J Gornall

Anthony G Price

Roy Campbell

David Parry

A self-energizing disc brake of the spreading type is disclosed. In the disc brake rotatable friction discs provided on opposite sides with linings are adapted to be brought into engagement with radial braking surfaces in a housing by an actuator assembly. The actuator assembly comprises pressure plates located between the discs and centered by pilot lugs, and balls located in oppositely inclined recesses in the adjacent faces of the pressure plates. At least the linings which engage with the pressure plates are separated into annular rings by an annular groove, and the groove is substantially coincident with a pitch circle of constant diameter upon which the recesses lie in an angularly spaced relationship. The groove increases the degree of cooling in the regions of the base of the recesses, thereby reducing the likelihood of hot spotting occurring in such regions.

Self energizing disc brakes

An hydraulic actuator comprising a pair of oppositely acting hydraulic pistons working in a bore incorporates an automatic slack adjuster assembly which is housed in aligned bores in the pistons and acts as a strut to determine the relative retracted positions of the pistons. The adjuster assembly comprises a clamp member movable with the piston, and an adjuster member, the members including interengaging parts which co-operate with each other to form a releasable detent, in combination with a spring ring for biassing the interengaging parts into engagement, and the piston and the clamp member are provided with interengaging inclined faces to provide a wedge action and enhance the engagement of the interengaging parts when the bore is pressurized, and a stop loaded by a spring is provided in the bore with which the adjuster member is adapted to co-operate when movement of that member in a brake-applying direction exceeds a distance sufficient to take up the braking clearances. Additional movement of the clamp member in the same direction is operative to increase the effective length of the strut with the detent released until the force of the engagement of the interengaging parts at a predetermined point exceeds the force of the spring. The detent is re-engaged to prevent further relative axial movement between the two members whereafter, further movement of the strut with the piston is accommodated by movement of the stop against the loading in the spring.

Hydraulic actuator assemblies for vehicle brakes

In a master cylinder assembly comprising two pedal-operated master cylinders, each master cylinder comprises a pedal-operated piston of stepped outline working in a complementary stepped bore in a housing and having an inner end of smaller area carrying a first seal and an outer end of greater area carrying a second seal, a pressure space in the bore in advance of the inner end of the piston, a quick-fill chamber defined in the bore between the inner and outer ends of the piston, a normally-open recuperation valve providing communication between a reservoir for fluid and the pressure space at least when the piston is in a retracted position, and a normally-closed pressure-limiting valve assembly between the quick-fill chamber and the same or a second reservoir. The pressure-limiting valve assembly is adapted to open at a threshold value when the piston is moved in a brake-applying direction and following closure of the recuperation valve and the transfer of fluid to the pressure-space to take up the braking clearances, further movement of the piston in the same direction pressurizes fluid in the pressure space to apply the brake. The two quick-fill chambers are connected through a transfer passage so that fluid can be transferred between the two quick-fill chambers when both master cylinders are operated simultaneously at least until the said threshold value is attained.

Master cylinder assembly for a vehicle hydraulic braking system

In a disc brake the application of the brake is initiated by angular movement of at least one pressure plate with respect to a reaction member to cause the pressure plate to move axially into engagement with a friction disc which, in turn, is urged into engagement with a surface in a stationary housing. The angular movement is effected hydraulically by an actuator comprising a piston working in a bore of a cylinder, the axis of which is substantially at right angles to that of the brake. The piston acts through a part-spherical rocking thrust coupling associated with a pull-rod passing through the actuator with a substantial clearance, the inner end of the pull-rod being pivotally coupled to a lug on the pressure plate, and the outer end being adapted for connection to a hand lever by which the pull-rod can be moved in a brake-applying direction. A thrust member is disposed between the piston and the spherical rocking coupling and is engagable with a thrust transmitting face on the piston for sliding movement in a transverse direction with respect to the axis of the cylinder to accommodate angular movement of the pull-rod when the brake is applied. The thrust member and the coupling are biassed towards each other by a compression spring so that the thrust member is restrained from moving radially with respect to the coupling when the brake application is effected by the hand lever. In another construction the spring is omitted and the biassing is achieved by the inherent resilience of a boot for sealing the outer end of the cylinder.

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West Midlands, United Kingdom

Graham J Gornall