The Mechanical Handling and Storing of Material

556 THE MECHANICAL HANDLING OF MATERIAL 2,000 lb. per square inch, and thé working pressure is 750 lb. per square inch. Each tip was constructed to fulfil the following requirements :— A loaded wagon having been placed upon the cradle, to lift it 45 ft. above the quay, tip the contents of the wagon into the shoot, return the wagon to the quay level, and run it off the cradle within thirty seconds—and this can be accomplished. The cradle is lifted from the ground level to any height up to 45 ft. by means of four direct acting hydraulic rams, two on either side of the cradle. These are as follows :— Two small rams, one on each side, are in constant communication with the high- pressure mains, and act as counterbalances for the weight of the cradle itself. The large ram and cylinder on each side of the cradle are intended to deal with the weight of the wagon with load, and of that portion of the cradle not balanced by the small rams. They are capable of lifting the cradle with a fully loaded 10-ton wagon upon it at the rate of 180 ft. per minute. The platform or cradle upon which the trucks are raised is shown in the front view in the illustration at its lowest position, whilst in the side view it is shown raised and tipped. The A-shaped sides of the cradle a are connected at the top by a girder b, this is again connected by the rods cc to a second girder which slides in the guides dd, which extend above the actual framework of the structure. The second girder is manipulated by the four hydraulic rams already mentioned. The appliances for working the cradle are fitted with automatic stops l\, so that, the height at which the tip shoot is required to work having once been fixed, the cradle when started ascends to the tipping point, where it is automatically stopped, so that the attendant has only to start the cradle for lifting, when he is free to handle the lever for tipping without further attention to the lifting of the cradle. Again, in lowering, as soon as the wagon has been tipped, the top man has only to open the release valve and the cradle descends, and is automatically stopped as it reaches the bottom. Each tip is fitted with two anti-breakage cranes and Thomas’s patent anti-breakage boxes (see Figs. 782 and 783), and is capable of “boxing” (as it is termed) as rapidly as the coal can be delivered into the shoot. The small anti-breakage crane is also fitted with slewing gear for conveying coal screenings ashore. The tip shoots h are 24 ft. long, but can be lengthened up to 30 ft., and in order that the coal may slide gently out of the shoots to avoid breakage, they can be rapidly adjusted by means of ropes g g and f. The tips are quite large enough to hold a 10-ton wagon of coal, the largest size used in the district. The shoots are fitted with double wings for assisting in the trimming of the coal and also in the boxing, and they are further made to radiate 5 ft. in either direction from the centre line of the tip, so as to assist in minimising the trimming. In connection with each tip is a traversing turntable platform, and two turntables, one for the empty and the other for the full load. These platforms are also fitted with hydraulic capstans of a capacity of 2 tons’ pull, which can be moved to suit the position of the tips. The whole of the hydraulic power required is brought to these tips by two mains, each 8 in. in diameter, so arranged that in the case of the failure of either one or the other, it is possible, by an arrangement of stop valves and branches connecting them together at intervals, to cut out any section of these pipes and so turn the water past the defective section. The return water is carried back by a 12-in. main to the hydraulic engines. Two large accumulators are fed from these mains; one at the extern end of the tips, the other at the engine-house. The water is pumped by three pairs of compound “tandem” engines, collectively capable of delivering 1,440 gals, of water at a pressure of 750 lb. per square inch per minute.