GB1272803A - Cable control system - Google Patents

Abstract

1,272,803. Constant tension winches. CANADA, MINISTER OF NATIONAL DEFENCE. 12 Aug., 1969, No. 40222/69. Heading B8B. [Also in Division F2] Apparatus for maintaining a desired tension in a length of cable 5A by which a helicopter is hauled down on to a ship's deck 3 comprises a cable tensioning winch 19 driven by a reversible hydraulic motor 15, and an accumulator 23 arranged to store a variable length loop of cable 5 between the winch and the said length of cable, the direction and speed of the winch driving motor being controlled by signals representative of the actual and desired cable tension, the actual winch speed and the actual speed of the length of cable 5A. The cable 5 extends from the drum 19, around biased apart sets of pulleys 23A, 23C, 23E and 23B, 23D of the accumulator 23 and over guide sheaves 31,33, 35 prior to passing up through the deck 3 to the helicopter. The sheave 35 is supported via a load cell 37 which produces a signal representative of the actual tension in the cable portion 5A and this is compared with a resistor setting variable by a handle 53, which is representative of the desired cable tension, any difference between the signals causing energization of an operating coil 67 of an hydraulic amplifier 47 which actuates a servo valve controlling a variable displacement pump 13 for the winch motor 15. A second operating coil 46 of the amplifier 47 is energizable by a signal representative of a difference in cable velocity at opposite sides of the accumulator, i.e. at the winch drum 19 and at the guide sheave 31, as registered by tachogenerators 41, 43, this controlling the winch motor pump as a result of sudden changes in cable tension which are absorbed by the accumulator 23. The motor 15 may alternatively drive a winch drum 21 for traversing the helicopter once on the deck, a switch 63 being provided for selecting connection between the coil 67 and the haul down circuit including the handle 53, or the traverse circuit including a handle 51. A piston rod of the servo valve is connected to a potentiometer 103 in the transverse circuit to provide a signal indicative of the winch motor pump setting and thus of the actual traverse speed.