The Mechanical Handling and Storing of Material

DISCHARGING BY MEANS OF SKIPS AND GRABS 413 It will be noted that the form e is provided with an outer flange ev and an inner flange e2, in addition to the central upwardly-extending flange e3, which centrally supports the winding. The inner and outer flanges are carefully finished, and engage with finished surfaces on the inner and outer pole faces of the magnet case, thus completely sealing the lower face of the winding chamber, a water-tight joint being ensured by clamping the flanges in place with screws ev e±, spaced 4 in. apart entirely around the flanges <?x and e2. Since the winding is clamped to the form e by the radial clamp f, and the form e is clamped in the magnet case as already mentioned, it will be readily seen that the winding is rigidly held against displacement. With the winding thus assembled in the magnet case, the lower face of the coil form e is covered by a heavy annular plate G of (non-magnetic) manganese steel, which in turn is held in place by pole shoes H and 1, bolted respectively to the inner and outer poles of the magnet case. Both the pole shoes are provided with shoulders, which protect the clamping bolts from sheering strains. At the heads of the outer pole clamping bolts j are located between adjacent ribs on the outer surface of the magnet case, where they are protected from abrasion. In the sectional view it will be noticed that the practically non-magnetic manganese steel plate G carries raised shoulders around its inner and outer peripheries by means of which the plate is made to seat against the magnet poles, and an air space or cushion is left under the winding at g. This results in the shocks taken by the outer plate G being transmitted directly to the magnet frame, instead of being taken by the windings as would necessarily be the case if a plain bottom plate were used. The pole shoes are so disposed with respect to the outer plate G that none of the clamping surfaces can become battered over, and therefore the plate G as well as the whole wearing surface may always be readily renewed. The terminal cavity is surrounded by a ridge kk cast integral with the magnet case, and of a thickness to make it as strong as the magnet case itself. The- terminal cavity is closed with a heavy steel cover L, which seats against a gasket to form a water-tight joint, and is firmly bolted in place, the heads of the bolts being protected from abrasion by the ridge of the terminal cavity. All the terminal parts are thus enclosed in a waterproof box of steel, the terminals themselves being of the plug type, which permits of quick attachment and detachment of the service wires. The female members m of the terminal are enclosed in an insulated-tube, so that a ground or short circuit cannot result even if the service wires are left hanging from the crane with the current on. The insulating tubes are each encased in a steel tube to prevent abrasion of the insulation, and these steel tubes fit closely into babbited openings N in a side of the terminal chamber. The male member p of the plug connectors is mounted upon a heavy plate r of fireproof insulating material, which closes the entrance to the winding chamber and is seated upon a gasket to effect a water-tight joint. The plugs proper are separable from the terminals by removing the nuts which hold them in place. The plugs, and also the plate r, may therefore be removed without throwing any strain on the connections to the winding ; the connections consist of loops of very flexible copper ribbon, these loops being stowed away in the box-like ends of the terminal studs. This construction permits of great flexibility, and at the same time makes it impossible for the flexible leads which connect the two ends of the magnet windings to come accidentally into contact. These features show how carefully the design of type S. A. magnets has been considered and worked out from the mechanical and electrical standpoint. Fig. 586 shows a lifting magnet of the Cutler-Hammer Co., Milwaukee, U.S.A., from which it will be seen that here the terminal box is separate, and not cast together with the body of the magnet, and that the whole apparatus is held together by through bolts.