Patent GB-150791-A (GB)
Title: Improvements in connection with lifting appliances worked by rotary pumps of variable capacity
IPC: B66B1/04
Filed: 1919-06-04
Abstract: 150,791. Variable Pumps & Motors, Ltd., Wood, E. J., and Meacock, T. June 4, 1919. Fluid-pressure, ram, and like apparatus.-Lifting appliances worked by rotary pumps of variable capacitv are controlled by means of a handwheel or a drum 5, Fig. 1, around which passes a control rope 70, Fig. 5, carrying tappets 75, 76, the shaft of the drum being provided with a loosely-mounted bevel-wheel 7 for controlling the pump, a cam 20 for operating the switch 21 of an electric driving motor, a cam 24 for operating the exhaust valve of the lifting cylinder, and a cam 31 for controlling the rheostat cf the driving motor. When the prime mover is other than electric, the cam 20 serves to operate a clutch. When the drum 5 is operated, the first part of its movement puts in the starting-switch 21, and the pump 1 is operated to deliver liquid past a valve 49 and through a port 58 to the lifting cylinder. Further movement causes a lug 14 on a spring- supported cap carried by a collar 8 fixed to the drum shaft to move out of engagement with a cam surface 15, and a tooth 11 then engages a notch 13 in a member fixed to the bevel wheel 7. The latter is then operated and drives the spindle 17 acting on the control ring 18 to increase the pump output. When the cam 31 depresses a spindle 32 to open a valve 33, liquid flows through a pipe 61 and passages 62, 63 into a cylinder 34 and operates a piston 35 controlling the rheostat 36, 37, the rate of movement of the piston being controlled by a cock in the pipe 61. In the form above-mentioned operated by a clutch, the piston 35 acts on the clutch levers to increase the grip. Simultaneously with the depression of the spindle 32, a spring 44 raises a spindle 43 and a valve 46 closes a passage 64. When the drum is reversed, as by the tappet 75, the pump output is progressively diminished, and the cam 31 allows the valve 33 to be closed, and the valve 46 to be opened, the cylinder 34 exhausting through the passages 63, 62, 64, 65, and 68. The time for closing the valve 33 is made longer than that for opening it by employing a cam 39, Fig. 3<a>, with a movable part 38 attached to it by a spiral spring and operative only on the return stroke. The part 38 is allowed to spring back in the direction of the arrow before the roller leaves the part 39 by making the distance 1, 2 less than the distance 3, 4. When the lift is to be lowered, the drum 5 is operated to cause the cam 24 to open the exhaust valve 26 of the lifting-cylinder. The valve 26 also acts as a relief valve at any time when a predetermined pressure is exceeded. The spindle of the valve 46 is provided with a piston 47 in a chamber 48, the upper part of which communicates by a pipe 67 with the space above the valve 49, and the lower part by a passage 80 with the passage 62, so that should the lift cease to ascend owing to failure of the current supply, the piston 47 has pressure only on the top, which causes it to descend and open the rheostat exhaust valve 46. Tn a modification, the drum 5 is mounted horizontally and loosely on the rod 17 and carries the various cams together with the collar 8, while the member 6 is fixed on the rod 17.