GB717358A - Improvements in or relating to industrial trucks - Google Patents

Abstract

717,358. Grab arm attachments for fork lift trucks. RANSOMES SIMS & JEFFERIES, Ltd. May 5, 1953, [May 5, 1952.] No. 11318/52. Class 78 (3). In a fork truck 1 the tines (not shown) or side grab arms 8, 9 are movable laterally either simultaneously or independently by hydraulic thrustors. As shown in Fig. 1, grab arms 8, 9 are slidably mounted on the lifting carriage 5 and are actuated by hydraulic rams A, B which, as shown in Fig. 4 are connected in circuit with a manually operated control valve 12 and a pedal operated selector valve 15. The valve 12 is provided with a rotary plug 30 which, in the position shown, admits fluid from the inlet pipe 38, via valve 15, to the inner ends of ram cylinders 6, 7 and allows the outer ends of the cylinders to exhaust to the reservoir through pipe 40, whilst when the plug is rotated through go degrees, the pipe 38 is put into direct communication with the outer ends of the cylinders and the inner-ends of the cylinders exhaust to the reservoir through the valve 15 and pipe 40. When the valve 15 is unoperated it is spring urged into the neutral position shown in which movement of plug 30 extends and retracts the rams simultaneously, but when pedal 18 is depressed port 48 is closed and the effective aperture of port 47 is increased so that, with plug 30 in the position shown no fluid is admitted to cylinder 6 whilst an increased flow is admitted to the inner end of cylinder 7 which thereby produces an amplified movement of arm 9 only. With pedal 18 depressed and the plug 30 rotated through go degrees pressure is applied to the outer ends of both cylinders, but as the return flow from the inner end of cylinder 6 is blocked at port 48 ram A and, thus arm g, is retracted at an increased speed. With pedal ig depressed similar independent movement of ram B and arm 8 is obtained. In a modification valve 15 may be operated manually, electromagnetically or hydraulically.