Patent GB-187011-A (GB)
Title: An improved automatic lifting grab
IPC: B66C1/42
Filed: 1921-07-11
Abstract: 187,011. Knight, S. C. July 11, 1921. Lifting-dogs.-A grab for lifting plates, girders, bars, shells, barrels, cases, &c. comprises gripping jaws 10 mounted on levers 12 pivoted at 13 in a frame 14. The grab is suspended from lifting tackle by a collar 29 which engages a head 27 on a spindle 26 passing through a block 21 which slides in the frame. Pins 20 on the block pass through slots in levers 17 which are pivoted to the frame at 18 and are slotted at. 16 to engage pins on the levers 12. Relative movement between the block and frame therefore causes the jaws 10 to grip or to release the plates. Catch mechanism whereby the grab automatically grips the load, and releases it on lowering to the ground is shown in Fig. 2. In the position shown, the collar 29 suspended from the lifting tackle supports the frame 14 on pivoted catches 30, and the block 21 is in its lowest position in the frame so that the gripping jaws 10 are open. The grab is lowered and the top edge of the plate to be lifted engages and raises the spindle 26 relatively to the block so that side-bars 32 are moved outwardly from the spindle 26 and withdraw the catches 30 from the frame, the left-hand bar withdrawing the right-hand catch. The block 21 now rests on the plates and the frame 14 drops, closing the jaws. On lifting, the collar 29 engages the head 27 to take the weight of the load and fingers 31<a> pass above the ends of the bars 32 so that the catches 30 are returned by springs. On lowering, when the plates rest on the ground, the collar 29 falls, the catches 30 which are pivoted pass below the top of the frame. the fingers 31<a> being provided so that the catches are not withdrawn although the bars 32 are still extended. On raising the collar 29, the frame is now lifted to release the jaws and the parts resume the position shown. A rack 38, Fig. 1, may be provided on the frame, co-operating with a pawl on the block so that the jaws are held closed, when the loaded grab is lowered to the ground, until the pawl is released by a hand chain 41. In a modification suitable for lifting barrels, the block 21, Figs. 5 and 7, free to slide in the frame 14, is connected to extensions 42 of the jaws 10 by links 44. The lifting shackle 28 is attached to the collar 29 on which are pivoted spring-pressed pawls 52. The central spindle 26 carries a catch member 47 pivoted at 45, and a loose collar 49 co-operating with the pawls. Fig. 7 shows the position of the parts with the grab suspended by the collar 29 with the frame 14 supported on the pawls 52 and the jaws open. When the open grab is lowered on to a barrel 55 as shown in Fig. 9, the spindle 26 is raised and the catch 47 is moved clear of the block 21 and swings outwards engaging and lifting the collar 49 which engages the pawls 52 and withdraws them from shoulders 54 on the frame 14. The collar 29 can now be raised, the pawls 52 passing above the shoulders 54 on the frame, and when the collar 29 engages the head of the spindle 26, the block 21 rises in the frame and the jaws grip and lift the barrel, the parts now being in the position shown in Fig. 10. On lowering to the ground, the parts take the position shown in Fig. 11, the jaws are open, and the frame can be lifted by the collar 29 and pawls 52, the parts resuming the position shown in Fig. 7.