Patent GB-187060-A (GB)
Title: Improvements in and relating to grabs
IPC: B66C3/06
Filed: 1921-08-02
Abstract: 187,060. Barnard, D. J. Aug. 2, 1921. Grab-buckets.-Relates to single-chain grabs particularly of the type described in Specifications 10153/15 and 141,484, in which spreader arms 8 are pivoted to independent cross-bars 6, 7 and guiding means such as the telescopic rods and sockets 9, 10, 12 are provided on the grab-head, the lower cross-bar 5 and the lower block 13 for ensuring correct alignment between the parts of the locking mechanism on the block 13 and the lower cross-beam 5. The invention comprises (1) means for locking the buckets in the closed position and releasing them by dumping or in midair: (2) means for preventing opening when the lead is removed from the hoisting chain in transporting; (3) means for obtaining a six to one or in a modification a four to one purchase; and (4) a modification of the lazy-tongs guiding mechanism described in Specification 10153/15. (1) A pair of gravity catches 25, 26, Figs. 4 and 5, are pivoted on the lower cross-bar 5 and connected one to the other by a pin and slot 27, 28 so that they move together to engage or disengage lugs 29, 30 on the lower block 13. A lever 32 pivoted on the lower block at 33 engages a projection on the catch 25 to lock the catch with the buckets closed. In the position shown in Figs. 4 and 5, with the block 13 raised to the grab-head and the buckets closed, a sliding rod 34 on the block 13 is depressed by a stop 38 on the grab-head, and the lever 32 is free to be turned out of engagement with the catch 25 either by gravity on dumping, or by a hand rope. In the position of the buckets shown in Fig. 3, the rod 34 is raised by the spring 39 so that a plate 36, Fig. 4, on the rod engages a pin on the lever 32 and keeps the lever in the locking position whilst the buckets are closing. In a modification, the lever 32 is replaced by a weight which slides in guides on the block 13 to engage the catch 25 and is raised for opening the buckets by a lever controlled by a spring and rod such as 39, 34. (2) For use with a transporter, the grab-head is provided with a part 49, Fig. 4, adapted to be engaged by the trolley and to take the weight of the grab during transporting. A gravity catch 50 pivoted on the grab-head engages a toothed member 51 on the lower block 13 so as to take the weight off the hoisting chain. The lower end of the catch 50 is engaged by the lever 32 or by the sliding weight so that the movement of the lever 32 to discharge the grab also releases the catch 50. The parts 32, 50, 51 may be provided on both sides of the grab, the two levers 32 being connected to one another. (3) As shown in Fig. 3, the hoisting chain is secured to the grab-head at 23 and is rove around pulleys 20, 16, 19, 18, 15, 17 so as to give a six to one purchase. In Figs. 4 and 5, the chain is secured at 58 and passes round pulleys 57, 54, 56 giving a four to one purchase, the pulley 54 being set at a suitable angle. (4) The lazy-tongs device, Fig. 8, is arranged at the side 14 of the lower block opposite to the side on which the locking mechanism is carried. It comprises short links 64 pivoted together at 65 in a slot in the lower block, and long links 62, 59, the latter being pivoted on a member 60 sliding on the lower cross-beam 5.