Controller for pneumatically-operated balancing hoists

摘要

1,147,303. Load balancing hoists. BIRFIELD ENG. Ltd. 4 July, 1967 [11 July, 1966], No. 30641/67. Heading B8B. [Also in Division G3] A pneumatically operated balancing hoist in which compressed air is supplied to a chamber at one side of a piston controlling axial movement of the hoist drum mounted on a ball nut and screw arrangement, is provided with an air supply controller including main and pilot air regulators 74, 78 and a piston or flexible diaphragm 148 therebetween, the diaphragm controlling main air supply to and from the hoist. Compressed air is supplied to the controller at 68 through a filter 72 and passes into a pilot passage 92 and a main passage 118. Pilot air then passes through the regulator 78, a trim valve 80, a diaphragm chamber 114, an auxiliary trim valve 82 and a vent line 22 to a manually operated control valve 24. Main air from the passage 118 passes through the main air regulator 74, a diaphragm chamber 124, past an air operated check valve 76 and through an inlet passage 77 leading to the hoist drum chamber. The control valve 24 can be manually set to a first position in which no pilot air is bled therefrom, whereupon full pilot air pressure and hence full main air pressure is applied to the hoist causing it to raise a heavy load, a second position in which a little air is bled off whereupon medium loads are lifted by the hoist, and a third position in which the air bleed is such that the hoist load is just balanced. In the latter case, a manual raising of the load reduces the main air pressure in the hoist drum chamber and below the diaphragm 148, whereupon the latter is depressed by the pilot air pressure causing a valve body 128 to be resiliently depressed to permit inflow of compressed air to the hoist drum chamber to balance the load in its elevated position. A manual lowering of the load causes an increased pressure in the hoist drum chamber and under the diaphragm 148, causing the latter to be lifted to raise a ball or cone headed link 154 from a vent passage 158 in the valve body 128, whereupon excess pressure is vented to atmosphere and the load is balanced in its lowered position. The pilot air regulator 78 comprises a screw adjuster 110 which through spring 108, flexible diaphragm 104 and stem 96 adjusts valve 98 controlling the pilot air flow. The stem 96 registers with a passage 106 in the diaphragm 104, through which excess air pressure is released to atmosphere if the adjuster is screwed down excessively. The check valve 76 comprises a spring biased plunger 162 which shuts off the passage 77 unless compressed air is supplied to the connector whereupon the main air is in communication with a chamber 170 in which a piston 168 coupled to the plunger 162 is adapted to move to open the passage 77.