GB549274A - Improvements relating to bucket grabs - Google Patents

Abstract

549,274. Bucket grabs. CAULFIELD, W. J., and WESTWOOD & CO., Ltd., J. Sept. 22, 1941, No. 12264. [Class 78 (iv)] Relates to bucket grabs of the type in which the buckets are pivotally connected to a beam 5 which in the closing and opening movements respectively of the buckets is raised and lowered toward and away from a head 4 from which a system of chain, rope &c. purchase blocks 2 depends for connection of the lower blocks 3 to the beam 5 during the operation of closing the buckets, the purchase gear being employed during that operation to raise the beam 5 and thereby close the buckets, and there being between the lower blocks 3 of the gear and the beam 5 a coupling which is engageable automatically upon the nearing of the blocks 3 to the beam 5 and is disengageable (a) by hand when the grab is in mid-air, or (b) automatically upon the grab being lowered on to the dump. The coupling comprises a link 14 on the beam 5 which, when the coupling is engaged and under load, interlocks by a projection 17 on the link with a dog 18 pivoted to the lower block 3, and which is pushed aside by the dog as the latter, during the approach of the block 3 to the beam 5 moves past the projection 17 to lock therewith. The dog 18 is prevented from swinging under the action of the load by a pin 25 on a pivoted detent 27, which pin engages an upright 20 on the dog 18. The projection 17 bears on the supporting surface 21 of the dog 18 at a point slightly out of line with the vertical through the pivots of the link 14 and dog 18, thus permitting the projection 17 to slip off as soon as the detent 27 is pulled down by a cord 28 from the cabin or ground, this being assisted, if necessary, by a kick from the detent 27 on the arm 20 as soon as the pin 25 has risen clear thereof. Automatic release when the grab rests on the dump is effected by a sliding weight 34 which bears on the detent 27 and frees the pin 25 from the dog 18. Pull on the lifting cable 1 then raises the block 3 and the buckets open as the grab is raised. A small amount of lost motion is allowed between the connected block 3 and the beam 5 to permit of this. Balance weights 30, 33, 35, or springs, restore the various parts to re-engaging position.