GB611525A - Improvements in or relating to electric or diesel-electric jib cranes - Google Patents

Abstract

611,525. Tilting cranes. NAAMLOOZE VENNOOTSCHAP ELECTROTECHNISCHE INDUSTRIE VOORHEEN W. SMIT & CO. Jan. 9, 1946, No. 800. Convention date, Sept. 14, 1943. [Class 78 (iv)] An electric or diesel-electric derricking jib crane 2 comprises a differential gear control mechanism 8 adapted to operate an electric motor starter or controller (not shown) for controlling the operation of the hoisting mechanism of the crane so that one driving component thereof receives a movement from the jib or luffing mechanism of the crane proportional to the vertical component of the luffing movement of the jib 2 and so that the second driving component thereof receives a compensating movement from the hoisting mechanism so as to cause it to control the hoisting mechanism automatically and to cause the load to move in a substantially horizontal path during the luffing action of the crane. As shown, the tilting movement of crane 2 causes, through the medium of pin-and-slot 3, 4, toothed rack 5 to reciprocate and so, through pinion 6, rotates shaft 7 of differential 8. The casing 12 of the latter carries gear ring 13 which drives shaft 15 which controls the actuating resistance of the hoisting motor. Shaft 9 may be coupled at 10 to the hoisting drum. Operation.-Firstly, uncouple coupling 10 and hoist the load, without luffing, to the desired height, the differential gear not being employed. Secondly, luff the jib 2 and throw in the coupling 10. The upward movement of jib 2 is transmitted through shafts 7 and 15 to operate the starting resistance of the hoisting motor (which at this moment is in neutral) and so to pay out the hoisting cable. Also the hoisting motor rotates shaft 9 in a direction which (through the differential gear) tends to move the starting resistor back to neutral and so to stop the hoisting motor itself. In consequence, the hoisting rope is paid out proportionately to the luffing displacement of the jib and the gears are so chosen that the " feedback " of shaft 9 restores the hoisting motor resistance to the neutral position when the luffing movement is completed. The coupling 10 may be controlled by an electric push-button or by an auxiliary handle on the control handle of the luffing motor. The motors are reversible.