GB636585A - Improvements in grabs - Google Patents

Abstract

636,585. Grab-buckets. ETABLISSEMENTS CAILLARD & CIE, and CAILLARD, J. G. March 12, 1948, Nos. 7637 and 7638. Convention dates, March 24, 1947 and Aug. 27, 1947. [Class 78 (iv)] In a grab comprising two jaws which are closed by moving two members comprising respectively a cross member on which the jaws are pivoted and the head of the grab secured to a supporting cable together, a lever is pivoted on either of the two members and has one arm connected by a tie rod to the other of the two members and a second arm 'secured to a cable for closing the jaws. The lever is disposed so that the one arm forms a small angle or a large angle with the tie rod according as the jaws are closed or open while the second arm makes a small or a large angle with the closing cable according as the jaws are open or closed, so that the closing force increases as the jaws close. As shown in Fig. 4, the jaws 1, 1<SP>1</SP> of a grab are pivoted at 21, 21<SP>1</SP> to a cross-member 20 and connected to move together by teeth 22, 22<SP>1</SP>. The jaw 1 is connected by a link 24 to a lever 25 pivoted at 231 to the jaw 1<SP>1</SP> and suspended by a cable 27. A lever 6 is pivoted at 2 to the cross member 20 and is connected at 7 to a tie rod 8 pivoted to the lever 25 and is connected at 9 to a hoisting cable 10 passing over a pulley 28 and serving to close the jaws. In the position shown the lever 6 causes a slight reduction of the mechanical advantage of the cable 10 compared with a direct connection to the cross-member 20, but in the closed position of the jaws, the lever causes considerable increase in the mechanical advantage. In an alternative construction, the pivots 21, 211 are co-incident, the teeth 22, 22<SP>1</SP> are omitted, and the lever 25 is replaced by a head to which both jaws 1, 11 are connected by links such as 24. In the construction of Fig. 6, the lever 6 is pivoted on the head and has an arm connected by a tie rod 8 to a cross-shaft 2 on which the jaws 1, 1<SP>1</SP> are pivoted, and an arm connected to the closing cable 10 which passes around a pulley 32 loose on the shaft 2 and a pulley 31, the arm being disposed as in Fig. 4 to increase the mechanical advantage in the closed position of the jaws while decreasing it slightly in the open position.