The Mechanical Handling and Storing of Material

4o6 THE MECHANICAL HANDLING OF MATERIAL tne plate tor passing the crane sliding block, and also free to rist in a veitical position, the line was then drawn taut, when the spring released the bail, and, changing its position, locked the apparatus, then by a circular motion the load was filled and raised. The patent for the Hone grab as now manufactured was granted in 1894. It is illustrated in Fig. 574, and apart from being the first single-chain grab, it was the first which pivoted the jaws from the haunches. The working parts of the grab consist of a rising and falling sheave block a (called the sliding block), having two vertical loose sheaves mounted in it, and arranged to rise and fall within a guide of four vertical angle steels of the framework. A single vertical loose sheave b, mounted on a circular horizontal plate, this plate forming a cap to the four vertical angle steel guides mentioned above, and having suitable holes in chain through. A crosshead c, situated below the : and fall in the same four angle steel guides, has a fixed vertical central pin with a semicircular notch across it. 1 he top end of the pin is so arranged as to enter the vertical hole in the lower end of the sliding block, and the bottom extension of this pin is formed into lugs, to which the closing rods d d connecting the jaws are attached, so that when the crosshead is lifted in the guides the jaws are closed. This horizontal locking pin fits into a horizontal hole through, and at the bottom of, the sliding block, in such a position that half its diameter passes through the notch in the vertical pin on the crosshead. The locking pin has also a notch in it, in such a position that when the notches come opposite each other the crosshead pin is free to disengage from the sliding blocks. The releasing lever e is “swung free” on one end of the locking pin, and having a balance weight f at its back short end, the long end at the other side of its centre is free to rise. A vertical stop and balance weight is fixed to the locking pin, and is of sufficient weight to keep the pin always locked. To this plate two stop pins are fixed, and the long end of the releasing lever e is always . bearing against the top one in consequence of its balance weight. The second stop pin fitted on the same plate lower down is only pro- vided for safety. A ring g is hung from the jib-head, of sufficient diameter to allow the vertical framework to enter it easily, but not large enough to allow the long end of the releasing lever to pass without being either depressed or raised. A vertical oil-checking cylinder h is fixed at its upper end to the top horizontal plate of framework, and its piston rod passes through a gland at the bottom end of its cylinder, a suitable vertical clearing hole in the sliding block being provided, and is then attached to the crosshead c. The grab is worked as follows :— The ring g is hung from the jib-head at any required height which suits the point of discharge. To rig the chain, the free end of the crane chain is passed down through the central hole of the top plate, then under one of the sheaves in the sliding block below, up through second hole in top plate, under the second sheave in sliding block, and up again to the under side of top plate, to which it is attached by a bolt and lug, no special link