Disc brakes for vehicles including a screw-threaded draw bar assembly

#This invention relates to improvements in disc brakes for vehicles of the kind in which a first friction pad assembly is adapted to be urged directly into engagement with one face of a rotatable disc by actuating means, and a second friction pad assembly is adapted to be applied indirectly to the opposite face of the disc by the reaction of the actuating means which is applied to the second friction pad assembly through a clamping member straddling a portion of the periphery of the disc and movable axially with respect to a relatively stationary carrier member, the clamping member comprising a yoke assembly consisting of a pair of pressure plates which are chordal to the disc and are located on opposite sides thereof, and circumferentially spaced draw-bars which interconnect the pressure plates at their outermost ends and determine the axial spacing between the pressure plates.

#In one known disc brake of the kind set forth at least one end of each draw-bar is threaded and is screwed into a threaded blind bore of a nut until the threaded end engages with the base of the bore which defines a stop and means, for example split pins, are provided to lock the nut against rotation. The stops determine the effective lengths of bars between the pressure plates and hence set the spacing therebetween. The opposite ends of the draw-bars may be formed with integral heads which bear on one of the pressure plates or, alternatively, the said opposite ends may also be screw-threaded and screwed into blind bores in one of the pressure plates.

#The provision of blind threaded bores is an expensive operation and requires considerable skill particularly when the depth of a bore is to be controlled within close tolerances. A heading operation is also very expensive, particularly because of the material which has to be used is of high strength.

#Two embodiments of our invention are illustrated in the accompanying drawings in which:

#FIG. 1 is a section through one circumferential half of a disc brake;

#FIG. 2 is an elevation of a portion of a pressure-plate into which a draw-bar is screwed;

#The disc brake for vehicles illustrated in the accompanying drawings comprises a carrier member 1 of generally U-shaped outline which straddles the peripheral edge of a disc 50 and is mounted on a stationary part adjacent to one face of the disc.

#Friction pad assemblies 2, 3 for engagement with opposite faces of the disc are guided for movement towards and away from the disc 50 in the staionary member 1. Each friction pad assembly 2, 3 comprises a pad 4 of friction material for engagement with the disc, and a rigid backing plate 5 carrying the pad 4 and having end edges slidably engaged with drag-taking abutment surfaces 6, 7 in the carrier member 1.

#A clamping member 8 comprising a yoke assembly fitting over the disc comprises a pair of pressure plates in the form of an actuating beam 9 and a reaction beam 10 which are chordal with respect to the disc, and a pair of circumferentially spaced circular draw-bars 11 which extend through clearance openings 12 in carrier member 1. The draw-bars 11 interconnect the pressure plates 9 and 10 at their outermost ends.