GB747526A - A lifting device - Google Patents

Abstract

747,526. Lifting devices for lifting stacks of sheets. JAEGER MACHINE CO. April 2, 1954 [May 27, 1963], No. 9719/54. Class 78 (4). A pivoted tong structure which tends to contract into gripping position upon the application of a lifting force thereto has fluid-pressure means for freely permitting expansion of the tongs, but normally preventing contraction thereof. As shown, the tongs structure comprises a support bar 10 provided with a loop 15 for engagement by a crane hook a pair of end tong frames 18, a central tong frame 18a with which the fluid-pressure means is associated, and a pair of jaws 31 having ledges 34 for engaging under the load, e.g. a pile of metal sheets. Each tong frame 18 comprises a bar 19 secured to support 10, two pairs of arms 20 and 22 pivoted respectively on a shaft 21 interconnecting the frames and carried by the support 10, and on a pivot 23 on bar 19, two vertical links 24 pivoted to the outer ends of arms 20 and 22 to form two parallelograms, links 24 being secured to the jaws 31, and a pair of links 27 pivotally connected between shafts 29 interconnecting arms 20 of the frames and a shaft 28 interconnecting the frames and slidable in slots 30 in the bars 19. The tong frame 18a has a pair of corresponding arms 20a, vertical links 24a, and links 27a similarly associated with shafts 21, 28 and 29. The fluid-pressure means comprises a cylinder 71 pivoted on shaft 28, a piston whose pistonrod 72 is pivoted on shaft 21, and a conduit 74, 75 for transferring fluid between the ends of the cylinder in which is inserted a ball check valve whose ball 77 is spring urged into closed position so that fluid can force its way past in transferring from bottom to top of the cylinder, allowing opening of the tongs in contact with the ground when loop 15 is lowered, opening being aided by torsion springs 57, while fluid is prevented from passing the ball in the reverse direction, thus holding the tongs open when loop 15 is lifted. For closing the tongs to engage the load, a rod 79 slidable in the valve housing is adapted to be depressed through a lever (not shown) when a cable 48 is pulled so as to push the ball out of its seating and thereby allow reverse movement of the fluid. Specification 707,409 is referred to.