Patent GB-1182603-A (GB)
Title: Self-Releasing Load Sensing Hook
Inventor: POULTON THOMAS ALFRED
IPC: F16B45/02
Filed: 1966-03-09
Abstract: 1,182,603. Hooks. PARSONS CHAIN CO. Ltd. 2 June, 1967 [9 March, 1966], No. 10299/ 66. Heading E2A. A load sensing, self releasing hook unit comprises a main support 1 on which a hook 5 is pivotally carried for movement from an inoperative to an operative position and viceversa, a retaining device 6 adapted to move relative to the support for movement into and out of engagement with the hook to retain it in its operative position, a suspension plate 20 for connection when the hook unit is in use to a hoisting rope, rod or chain, the plate which is mounted on the support, being capable of limited displacement when the hook unit is placed under load and a spring biassed actuating means 13 for cooperation with the retaining device and so arranged that when the hook unit is placed under load, the suspension plate in performing the said limited displacement moves it against its spring to a position to hold the retaining device in its operative position but when the load has been lowered until it becomes supported the actuating means automatically moves the retaining device to release the hook. In the construction shown the retaining device comprises a member having a depending portion provided with a heel 7 for engagement with a corresponding heel 8 at the end of the hook 5, the member having a projection 36 which is engaged by a projection 14' of the actuating means to retain the retaining device in engagement with the hook. In addition the retaining device includes a catch 10 which is biassed by a compression spring 16 the catch having a plunger 11 with a head 12, the head being projected by the spring 16 into the path of a projection 14 of the actuating means 13 so that when the load on the hook is supported by the ground so, that the suspension plate 20 no longer holds the actuating means in the position in which the projection 14' engages the projection 36 of the retaining device, the spring 21 moves the actuating means so that the projection 14 engages the head 12 and pivots the retaining device so that its heel 7 releases the heel 8 of the hook. The plunger can be moved against the bias of the spring 16 by an eye bolt 17 so that the retaining device can be pivoted to engage the heel 7 with the heel 8 of the hook while the actuating means is still in its lowermost position; when the hook unit is then lifted the projection 14 of the actuating means which has a bevelled face engages a bevelled face of the head 12 and causes withdrawal of the plunger against the bias of the spring 16 until the projection 14 has passed the head 12. The eye bolt when it has been pulled outwardly can be rotated through 90 and located in grooves 18 in plates of the support 1 to hold it in its withdrawn position and in this position it prevents automatic release of the hook. The actuating means is slidably supported between the plates and includes a part-spherical pressure member 32 which is engaged by a fork of the suspension plate. An indicator device is provided to show the position of the hook as the load is raised. For this purpose the side plates are provided with slots in which ride opposite end portions of a pin secured to a plate 24 of the actuating means so that as the load is taken by the hoisting rope, rod or chain and the actuating means is moved against the bias of its spring 21, the pin rides up the slots until it finally comes to rest against fall load markings provided by indentations in the plates.