Patent GB-1416799-A (GB)
Title: Braking systems
IPC: B60T7/12
Filed: 1973-02-20
Abstract: 1416799 One-way acting brakes; fluid pressure control of brakes MASSEY-FERGUSON Inc 20 Feb 1973 [22 Feb 1972] 8175/73 Headings F2E and F2F In a braking system for preventing rearward movement of a vehicle there is provided a driven member such as a driveshaft 38 connected to a wheel, a housing 62 rotatable about the driven member and carrying a brake which acts upon the driven member to oppose rotation thereof when actuated, clutch means activating the actuator upon rotation of the wheel in one direction and means for selectively preventing actuation of the brake. As shown in Figs. 2 to 5 a lined brake band 74 surrounding a wheel 54 splined to the drive shaft 38 of a forestry vehicle (not shown) has its upper end 84 engaged by a pivotable L-shaped arm 82. A clutch 148 surrounding shaft 38 has parts 186, 188 rotating with the shaft and parts 168, 170 held stationary when the shaft rotates in the clockwise direction (arrow Fig. 3) corresponding to forward motion of the vehicle. If shaft 38 tends to rotate counter-clockwise, clutch parts 168, 170 are urged counter-clockwise and by means of lugs 174 force leftwards (Figs. 4 and 5) the spool of a control valve 136 so that fluid from a pump 138 is fed to a cylinder 100 behind the piston while fluid in front of the piston is discharged at 140 to a reservoir 142. The piston in cylinder 100 is moved so that the piston-rod 110 pivots arm 82 about a pin 124 fixed in housing 62 to apply the brake and prevent the vehicle running backwards. To enable the vehicle to be reversed when necessary a transmission shift lever 46, Fig. 5, is moved to the dotted line position, such movement transposing an inhibitor valve 42 to effect fluid-operated retraction of the piston in cylinder 100. In Figs. 8 and 9 a modified clutch whose relatively movable parts are centrifugally separated at a certain forward speed, includes a plate 240. The direction of rotation corresponding to backward running of the vehicle is in this case clockwise, the plate 240 operating through linkage a switch 200 to move downwards electromagnetically a valve 210 to permit fluid-pressure operation of brake-actuating cylinder 206. In Figs. 10, 11 two ratchet wheels 270, 272 are splined to shaft 38 and clockwise rotation corresponds to forward vehicle movement. A housing 282, 284 is pivoted about shaft 38 and linked at 300 to a piston 304. Spring-urged pawls 276, 334 co-operate with ratchet wheels 270, 272 respectively but are movable alternately out of engagement by arms 298, 330 respectively which are pivoted at 320 to the gear-box 32 and linked by a spring 326. The components are shown in the position for preventing backward motion of the vehicle (pawl 276 engaging ratchet wheel 270). When inhibitor valve 314 is lowered by lever 46 chamber 308 is drained, piston 304 descends, pawl 276 rides up on to arm 298 and pawl 334, moving right, engages ratchet wheel 272. The vehicle may now be reversed. To re-set, valve 314 is raised and the shaft 38 turned clockwise slightly to cause wheel 272 to move pawl 334 and hence housing 282, 284 so that piston 304 is raised and the components are restored to the positions of Fig. 10.