Patent GB-1308740-A (GB)
Title: Rope-gripping device
IPC: B66D5/16
Filed: 1971-09-03
Abstract: 1308740 Rope grips C H ARNOLD 3 Sept 1971 [4 Sept 1970] 41112/71 Heading F2X A rope-gripping device, for use in combination with a length of rope 1 as in a hoisting or pulling device, comprises a pair of jaws 11, 12 carried by a housing 2 on opposite sides of the rope 1, the jaws being formed with inner opposed parallel rope-engaging surfaces, and a swingablysupported cam member 48, 49 mounted outwardly of an outer camming surface of each jaw 11, 12 and adapted to co-operate at its periphery with the camming surface in rolling engagement, the camming surfaces and members 48, 49 urging the jaws towards each other and into gripping relation with the rope when the jaws are moved longitudinally of the rope in the vertical direction. Where the device is used with a hoist, the rope 1 is fixed at its upper end and the hoist travels along the length of the stationary rope, gripping the rope when the relative speed between the hoist and the rope exceeds a predetermined safe amount. Alternatively, the device is used in combination with a rope-pulling device, e.g. as used in erecting telephone wires. The jaws 11, 12 slide against the front cover-plate 3 of the housing 2 on one side while on their opposite side they have upper and lower pins 13, 14 received within horizontally-elongate slots 15, 16 in a retainer plate 17. At its lower end, the retainer plate 17 has a horizontally-extending flange 20 through an aperture in which passes a plunger 23, the latter being housed along its centre portion in a fixed guide 28. A compression spring 30 between the fixed guide 28 and the flange 20, the latter being engaged by a radial enlargement at the upper end of the plunger 23, urges the retainer plate 17 and the plunger 23 upwardly at all times. However, the jaws 11, 12 and their associated retainer plate 17 and plunger 23 are retained in the lower inoperative position (as shown) by a sear 32 fixed at its lower end on a shaft 33 and provided at its upper end with a tooth 34 adapted to engage a shoulder 35 on the sidewall of the plunger 23. A torsion spring 38 surrounding the shaft 33 normally urges the sear 32 into holding relation with the plunger 23. Spaced downwardly from the plunger 23 are a pair of wheels 70, 71 between which the rope 1 passes, the wheel 71 being rotatably mounted on a shaft 73 carried by a spring-loaded carriage 75. A centrifugal speed sensor (not shown) on the end of shaft 73 is arranged, when the speed of the rope 1 relative to the device exceeds a predetermined amount, to engage a trip lever 88, thus allowing a sear actuating lever 96 to cause the sear 32 to disengage from the shoulder 35 of the plunger 23, thereby releasing the latter for upward movement under the action of the spring 30. This up ward movement forces the jaws 11, 12 upwardly along the length of the rope 1 and the outer camming surfaces of the jaws engage the circular peripheries of the cam members 48, 49, resulting in considerable inward movement of the jaws 11, 12 to achieve the desired gripping effect. The inner surfaces of the jaws 11, 12 are held parallel at all times, which prevents pinching of the rope 1. The inner surfaces are of arcuate form (Fig. 2, not shown) preferably with a central recess to enhance the gripping effect. This recess may house an insert of polyurethane plastics. To provide smooth engagement between the rope and the jaws, the latter are formed with conical portions at their upper ends (Fig. 3, not shown). The device may be returned to its normal inoperative position by means of a reset lever 103 swingably mounted on a shaft 104 so that when turned by a handle (not shown) it engages a flange 105 on the retainer plate 17 to urge the latter, together with the jaws 11, 12, downwardly to the normal position.