GB1195328A - Hydraulic Motor Stroke Limiting Means - Google Patents

Abstract

1,195,328. Shovelling machines. MITSUBISHI JUKOGYO K.K. 17 Oct., 1968 [17 Oct., 1967], No. 49264/68. Heading E1F. '[Also in Division F1] Limitation of the stroke of a hydraulic piston and cylinder motor 22 Fig. 2 subject to inertia loads and for oscillating a vertical pillar 15 .linked to the back hoe or shovel of an excavator is effected by a value assembly 29 interposed in lines 24 to 27 connecting a conventional four-way spool value 5 with opposite ends of motor 22 and comprising a out-off valve member 32 Fig. 3 urged by a spring 33 against a cam 23 adjustably secured to the pillar -15 so that when the motor is in its mid-stroke position member 32 is in its open central .position and lines 24, 25 are connected to lines 26, 27 respectively, whereas at a predetermined end of stroke position of actuator 22, cam 23 displaces valve member 32 so as to cut off lines 24, 25 from lines 26, 27, and the assembly 29 also comprises relief valves 39, 41 between value 32 and the actuator 22 wheretey .fluid from the exhaust end of the motor 22 is returned through valve 41 Fig. 4 to the supply end thereby cushioning the motor piston at the end of its stroke. To initiate the return stroke of motor 22 from the position shown in Fig. 4 valve 5 is switched to its other extreme position and with value 32 ':still blocking lines 24 to 27 pressure in line 24 opens a check valve 35 within valve 32 to allow pressure fluid to enter line 26 whilst exhaust fluid in line 27 opens a check valve 37 in valve 32 and gains access to line 25. Check valves 35, 37 remain open until the cam 23 displaces valve 32 to its open central position after which valves 35, 37 close and remain closed, until after completion of the motor stroke they are re-opened to initiate a further stroke. The casing of valve 5 contains three other distributing valves for controlling actuators 9, 10, 11.