Patent GB-1139061-A (GB)
Title: Improvements in or relating to brakes for vehicles
Inventor: FARR GLYN PHILLIP REGINALD
IPC: F16D65/14
Filed: 1965-10-08
Abstract: 1,139,061. Brakes. GIRLING Ltd. 4 Oct., 1966 [8 Oct., 1965; 13 April, 1966], Nos. 42858/65 and 16204/66. Heading F2E. A brake actuator and automatic adjuster, particularly for a disc brake of the swinging caliper type, comprises a housing 10 which may be suitably pivoted for swinging towards and away from a brake disc (not shown), a brake pad applying piston 12 in an axial bore of the housing, a threaded shaft 14 engaged in a threaded bore in the piston, a fluid-pressure responsive plunger 24 which, as shown, operates in a bore 52 of the housing forming together with space 54 within the plunger an air space, but which may operate in a transverse bore in the shaft 14 (Figs. 7 and 8, not shown), a pawl-and-ratchet mechanism 26, 28 causing movement of the plunger to rotate the ratchet ring 28 about the axis of the shaft 14, and a clutch between the ratchet ring and the shaft which is engageable in response to movement of piston 12, the arrangement being such that the pawl-and-ratchet mechanism is effective to rotate rod 14 only if the piston 12 has moved sufficiently to engage the clutch before pressure in the working space which is effective also on the plunger 24 has moved the plunger, against the resistance of a spring 27, to the limit of its stroke which limit is reached at a predetermined pressure which is less than the full braking pressure, whereby the effects of distortion of the brake parts is minimized. In the embodiment shown, the ratchet ring 28 is rotatable on a ring 32 secured to a flanged ring 34, the latter being splined to the shaft 14 and engaging a shoulder of the shaft under the influence of a trapped compression spring 36. When piston 12 moves to the left, as shown in Fig. 1, to apply the brake, a flange 30 of ring 32 engages a conical face of the ratchet ring 28 to clutch the latter to the rod 14, a ring 42 preventing axial movement of the ring 28, whereby spring 36 determines the clutch engagement pressure. The assembly is positioned axially by the end of a manual brake-applying rod 16 which is formed as a cam for applying the brake mechanically upon rotation of the rod 16, the spring 36 then acting as a release spring. In the modification of Figs. 3 and 4 (not shown) the spring 36 is replaced by a star-shaped spring disc (46) and the whole arrangement thereby made more compact. In a further embodiment (Figs. 5 and 6, not shown), the ratchet wheel (82) is actually formed on the shaft 14 which, instead of engaging directly in the piston, engages in a nut member (62) rotatable in a cavity of the piston, there being a cone clutch arrangement (64, 66) between the nut member and the piston to take the place of the clutch 28, 30 in Fig. 1. By this arrangement, a seal placed on the shaft 14 allows the pawl-and-ratchet mechanism to operate in air so that it is accessible without interfering with the fluid circuits. In the embodiment of Figs. 7 and 8 (not shown), referred to above, the pawl (72) is mounted in one transverse bore (86) in an enlargement of the shaft (14) and the fluid-responsive plunger (92) in another bore at right angles to the first. Operation of the plunger causes the pawl to react with internal ratchet teeth (88) fixed with respect to the housing so that the shaft (14) is rotated, return movement of the plunger causing the pawl to abut a stop (102) which withdraws the pawl. Rotation of the shaft (14) is transmitted via a cone clutch to the piston as referred to above in connection with Figs. 5 and 6. Fig. 9 (not shown) is a modification of the arrangement of Figs. 5 and 6 wherein the shaft (14) is formed as the nut to receive a threaded shaft portion associated with the cone clutch.