GB1446419A - Brake mechanisms - Google Patents

Abstract

1446419 One-way detent brakes; electromagnetic control R E KNIGHTS 8 Nov 1973 [9 Nov 1972 28 June 1973] 51832/72 Heading F2E A brake mechanism for use with a rotatable shaft 1 or 2 comprises a rotary member 2 or 49 adapted to be connected to the shaft for rotation therewith, a pawl 21 or 52 and a rotatable reaction member 3 or 43, the pawl being mounted in the reaction member and being engageable with one or more abutment faces 7 or 51 of the rotary member upon rotation thereof in a given direction (as shown, counterclockwise), to rotate the reaction member as one unit with the rotary member, the reaction member forming a rigid housing which houses both the rotary member and the pawl, and at least one limited-displacement damping unit 16 or 46 adapted to damp and to limit the rotation of the reaction member. In Fig. 1, shaft 1 is the propeller shaft of a heavy road vehicle and has secured to it a rotary member 2 formed of two generally semicircular halves joined at 4; the member inincludes two flanges 6, Fig. 3, which carry between them a pair of ratchet cams 7 and a pair of lifting cams 8, Fig. 1. The reaction member 3, rotationally mounted on shaft 1, is axially retained by a location of a part 31 of the reaction member between the flanges 6; the reaction member is pivoted to the damping unit 16, pivoted in turn to a bracket 17 on the vehicle body. The pawl 21 pivoted to the reaction member or housing 3 is urged into engagement with ratchet cams 7 by a spring-loaded plunger 22. In operation, normal rotation of shaft 1 is clockwise and at normal speeds cams 7 and 8 ensure only light contact between pawl 21 and the rotating assembly. When the vehicle tends to roll back from rest, it is stopped by engagement of a cam 7 with surface 23 of pawl 21. The shock of engagement is absorbed in unit 16 in consequence of slight counter-clockwise rotation of the housing 3. For reversing the vehicle, a cam lever 26, normally held out of engagement with pawl 21 by a spring-loaded plunger 27, is moved clockwise by a solenoid-operated plunger 28 to tilt pawl 21 out of engagement with cams 7; solenoid 29 is automatically energised when the vehicle is put into reverse gear. If the solenoid is de-energised during reversing at high speed, lifting cams 8, together with the inertia of pawl 21, ensure that cams 7 and pawl 21 do not engage. Solenoid 29 may be energised by a speed-governor mechanism in forward and/or reverse direction. In Fig. 5, shaft 42 is that of an electric motor. The housing 43 of the braking device includes support plates 47, 47a, each mounted by means of a rubber block 46 or 46a on a pillar 45 or 45a secured to a foundation 44. Cam member 49 has two lifting faces 50 and two abutment faces 51 which co-operate with pawl 52 to allow clockwise rotation but normally to block counter-clockwise rotation. Preferably a solenoid 55 is automatically de-energised immediately the power supply to the motor is cut off to permit a spring-loaded plunger 54 to depress the pawl. Solenoid 55 may be energised via a centrifugal switch at speed or via a manually-operated switch if reverse rotation is required.