GB226651A - Improvements in and relating to grabs - Google Patents

Abstract

226,651. Barnard, D. J. Nov. 10, 1923. Grab-buckets.-Relates to single-chain grabs of the type having spreader arms 8 pivoted to independent top cross bars 6, 7, and means such as telescopic rods and guides on the grab-head, the lower sheave-block 12 and the lower cross beam for guiding the moving parts into the correct position for locking the lower cross beam to the lower sheave block by means of a gravity catch such as a hook 15 pivoted on the lower sheave block at 14 and engaging a pin 16 on the lower cross beam. Improved means for securing the gravity catch 15, 16 whilst the load is supported from a transporter carriage comprises a hook 20 which is pivoted on a member 21 sliding in the grab-head and is adapted to engage a pin 19 on an upward extension of the hook 15 when the member 21 is suspended from the transporter carriage and the hoisting rope is slackened. As shown in end view in Fig. 3, the lower part of the member 21 is forked, straddles the upper sheave-block 22 and moves in guides 23 on the grab-head. When the pin 19 is engaged by the hook 20 as described above, the lower ends of the guides 23 rest on projections 30 at the lower end of the member 21 so that the whole of the weight is taken by the transporter carriage through the member 21. The operation of the gravity catch 15 is as follows. With the brackets closed and the lower sheave-block in the position shown, a weighted arm 17 on the hook 15 is free to turn the catch aside and release the pin 16 on the lower cross beam when the brackets are lowered and rest on the ground with the hoisting rope slack. The buckets are then opened by hauling in the rope. When the rope is again payed out, the lower sheave-block 12 is lowered away from the upper block 22, and the rod 26 is free to be moved upwards by the spring 29 so that a plate 25 on the rod lifts the arm 17 and holds the hook 15 yieldingly in the locking position. Specification 187,060 is referred to.