Patent GB-910441-A (GB)
Title: Improvements in or relating to load-engaging and releasing devices
IPC: B66C1/34
Filed: 1961-03-24
Abstract: 910,441. Hooks. EASTERN ROTORCRAFT CORPORATION. March 24, 1961 [March 28, 1960], No. 10835/61. Class 89 (2). [Also in Group XXX] A device for holding suspended loads, e.g. at the end of a cable depending from a helicopter used as a flying crane, consists of a suspensible frame in which is formed a generally vertical downwardly open slot 30 (see Figs. 4 and 5) beside which slot extends a pivoted arm of which the portion 35 lying below the pivot 38 carries a lever 31 which normally extends across the slot (as in Fig. 5), whilst the portion 41 lying above the pivot is connected to a toggle linkage 42 which, when in its dead centre position, holds the lever 31 in position across the slot but is displaceable to release the load by retraction of the lever 31 into the position of Fig. 4. In the form shown, two such arms are provided, each carrying its lever 31 so that the two levers 31 substantially close the slot, and there are two toggle levers 42, 42a having a common pivot 43 and connected to the upper portions 41, 41b of the respective pivoted arms. In the normal position of the mechanism, a ring or the like 18, Fig. 5, attached to the load is supported by the levers 31 as shown, engagement of the load by the levers having been effected by upward displacement of their free ends about pivots 34 by which they are carried on the arm portions 35, stops 37 on the levers engaging the arm portions 35 to prevent tilting of the levers' free ends below the load holding position shown. Displacement of the toggle links for load release may be effected either mechanically or electrically. The mechanical means comprises a knob 33, Figs. 2 and 6 (not shown), whose spindle 46, Figs. 4 and 5, carries a cam 48 which, when the knob is turned against a spring, engages an extension 45 on the toggle link 42a to effect change-over of the mechanism from the Fig. 5 to the Fig. 4 condition. Electrical release is by means of an actuating motor 56, Fig. 7, energized by leads 101 extending through the suspension cable 13, Fig. 5, and through slip ring connections 97 in the swivel head 20 by which the device is suspended. The motor shaft 57, Fig. 9, rotates an arm 58 engaged with a slotted coupling member 61 to raise a shaft 54 which, as shown in Fig. 4, is mounted in a block 52 which carries the toggle linkage pivot 43, the block being vertically guided by rollers 50, 53 engaged in a guideway (not shown) in the frame of the apparatus. The actuating motor normally makes a single revolution, initiated by the momentary closure of a starting switch which is in series with a switch 66, Fig. 9, controlled by the arm 58 and bellcrank 63 and which switches off the power when the single revolution has been made. The starting switch may be (a) a switch, not shown, in the cab of a helicopter from which the device is suspended and connected to the motor via one of the leads 101; (b) a switch, operable at the site of loading, the manually operable lever of which is shown at 78 in Fig. 5; (c) a switch 76, Fig. 5, in series with an arming switch in the helicopter cab, and operable to effect automatic retraction of the levers 31 when the load is deposited on a supporting surface; or (d) an explosive-cartridge-actuated emergency release device. The automatic disengagement control switch 76 is closed by a lever 73 acted on by a spring 71 which is compressed when the device is loaded but releases to close the switch when the load is supported. The emergency release cartridge 116, Fig. 7, is electrically fired via the leads 101 and the explosion gases pass through a vent 121 to act on a piston 105 in cylinder 104, Fig. 8. The piston has steps 111 which raise a platform 113 leaving depending legs 112 engageable by the steps, the platform being downwardly biased by a spring 114. The platform 113, when raised, acts directly on block 52 to raise the toggle pivot 43, Fig. 4.