The Mechanical Handling and Storing of Material

404 THE MECHANICAL HANDLING OF MATERIAL substance. 1 he jaws are manipulated by means of a chain which is divided into four strands, each of which is attached to one of the four corners of the grab. This con- struction of grab is limited in its use on account of the division of the chain, which will not admit of its being raised as close to the top of the jib as would be the case with grabs of other design. Two-Rope Grab of the Brown Hoisting Machinery Co.—The grab, which is illustrated in Fig. 572, has a capacity of 2 tons, and is used for unloading coal as well as for handling ore; it is also made for a capacity of 1 ton. The larger size, when used on coal, will handle 84 cub. ft., and when used on iron ore about 35 cub. ft., which would mean approximately 2 tons of either material. When handling coal, the pile taken by the grab is indicated by the line a b c. When handling ore the attachments G G Fig. 573. Cross Section through Brown Grab. are removed, leaving the ends of the jaws open ; the grab can thus only take a pile of ore as indicated by the line d e f. This form of grab works sat- isfactorily with coal of all sizes, and it is specially claimed for it that it will handle very large pieces. It also works successfully with nearly all kinds of iron ore, with perhaps the exception of some of the lumpiest Swedish ores. It has, however, been proved capable of handling all kinds of Spanish ores satisfactorily. The illustration gives over-all dimensions of the grab when open. The accompanying drawing, Fig. 573, shows a cross section through the grab when closed, with dotted lines indicating the path of its jaws from an open to a closed position. To the housing of the grab is fastened (to obtain the com- pound movement) a rail or track t, upon which are hung sliding blocks or pieces bb, pivotally connected with the forward portion of the jaws jj, which are composed of two parallel sides pp, joined at their outer ends by cutting blades dd which are set at a sharp outward angle. The parallel sides pp, however, are cut away and recede upwardly from the lower or scraping edges toward their upper ends, so that when the jaws jj are brought together and the grab thereby closed, a small portion of the sides will remain open. In the form shown in the drawings, the front and rear of the jaws are preferably unenclosed, and extend out beyond the housing when opened to their outward limit. The sidespp are stiffened by diagonal ties ee. Centrally within the housing of the grab is the block c, carrying a series of sheaves M, mounted upon a common journal or shaft j. The block is provided with trunnions which fit into vertical guide grooves on the inside of the casing. The lower ends of these grooves are closed so that the descent of the trunnions is limited.