Patent GB-398564-A (GB)
Title: Improvements relating to grab buckets
IPC: B66C3/08
Filed: 1932-03-24
Abstract: 398,564. Grab-buckets. HEWETSON, A. H. F., 67, Lee Street, Holderness Road, Hull. March 24, 1932, No. 8765. [Class 78 (iv).] Relates to single-rope grabs in which the lower sheave-block 26 supporting the crossbeam 24 is looked by struts connected with the grab-head when the buckets are fully opened, in order to permit lifting the grab from the discharging ring by hooks 4, and the struts are automatically released when the open buckets rest upon the ground. The struts comprise rods 16, carried by the grab-head, sliding in guides 22 on the cross-beam 24, and the struts are locked by gravity pawls 28 which engage beneath the rods 16 and are held by locking members which engage beneath them when tension is applied to the rope. As shown in Fig. 3, the rods 16 are connected by links 18 with a cross-bar 20 secured to a casting 6 which slides in the grab-head 8. When the grab is suspended on the discharging ring with the buckets fully opened, the pawls 28 pivoted on the guides 22 swing inwards beneath the ends of the rods 16. The sheave-block 26 is connected with the cross-beam 24 by a pin-and-slot joint at 32, and when the block is raised relatively to the cross-beam as shown, arms 34 rigid with the block engage beneath the pawls and lock them so that further movement of the block lifts the grab. A weight 10 which is free to slide on the casting 6 and is provided with sloping surfaces 12 to bear upon the hooks 4 spreads the hooks so that when the casting 6 is lowered it will engage the inner ends of the hooks and force them apart. When the open grab rests upon the ground the sheave-block 26 falls relatively to the cross-beam 24 and releases the pawls 28 so that on lifting, the rods 16 can turn the pawls aside and the buckets close, the cross-bar 20 and casting 6 now taking their lowest position in the grab-head 8, with the upper end of weight 10 housed within the head of the casting 6. When the closed grab is raised up to the discharging ring, the casting 6 forces the hooks 4 apart. and the hooks then swing beneath the rim of the casting in readiness to support it, the weight 10 being inoperative until the grab is opened and the cross-beam 20 is raised in the grab-head to the position shown. In another form, Figs. 8 and 12, the rods 16 co-operate with a hook or hooks 36 engaging the discharging ring 2. The hook is pivoted on a pin 42 in the grab-head by a slot 40, and other slots 44 in the hook engage a pin 46 on a tumbler 48 which also is pivoted on the pin 42. When the closed grab is suspended by the rope the hook is in its lowest position on the pin 42 and is turned inwards, as shown in Fig. 12, by the weight of the tumbler 48 in readiness to ride over and engage the ring 2. When the grab is suspended on the ring, the pin 42 moves to the bottom of the slot 40, turning the tumbler 48 clockwise. The tumbler is connected by links 56 and levers 54, 50 to the rods 16 so that this movement of the tumbler raises the rods 16 in the grab-head. When the grab is opened and when the rope is again lifted, the rods are locked in their guides by pawls as described above. The upper ends of the rods abut against the pin 42 so that the open grab is lifted. The rods now hold the tumbler 48 in the position shown in Fig. 8 and the hook 36 falls outwards, turning about the pin 46 so that the open grab can be lowered free of the ring 2. When the open grab rests upon the ground and the pawls release the rods 16, the tumbler 48 falls to the position shown in Fig. 12, bringing the hook into position to re-engage the ring on lifting. Movement of the hook over the outer edge of the ring is facilitated by a pin-and-slot connection between the links 56 and the lever 54. Specification 200,410, [Class 78 (iv), Loading &c.], is referred to.