GB123983A - Improvements in and relating to Magnetic Chucks. - Google Patents

Abstract

123,983. Blackall, F. S., (Assignee of Simmons. F. L.). Feb. 26, 1918, [Convention date]. Electro-magnetic chucks and work-holders.-A magnetic chuck is built up of a number of magnetic units each comprising (a) a mild-steel core part, Fig. 4, consisting of a base-plate 2 carrying preferably eight vertical webs 5 around which the energizing-coils 20, Fig. 3, are fitted, and (b) corresponding pole-pieces, shown in perspective in Fig. 6, and in end view in Fig. 9. A non-magnetic housing 8, Fig. 3, preferably of aluminium, is cast around the core-part and solid with the base-plate 2, so as to form a box-like base for the chuck. Similarly, eight of the pole-pieces shown in Fig. 6 are placed side by side so that the lateral projections 14 and recesses interfit, but with clearance, and the whole is cast solid with aluminium 15, Fig. 3, so as to form a species of lid for the box-like base. The two castings are then machined and the pole-pieces fitted over the core part, so that the webs 17 make good contact to the webs 5. The whole is then bolted together with bolts 10, a thin gasket of paper &c. being inserted around the side walls so as to make a wax-tight joint. The energizing-coils on adjacent cores are wound in opposite directions, so that the pole-pieces are alternately north and south. This arrangement of casting with non- magnetic metal increases the efficient flux density of the chuck face-plate bv reducing leakage through the work-holder and tool, and at the same time gives a rigid support for the chuck, which is clamped to the machine frame by the flange 7, Fig. 3. A distance-piece for positioning the work is fastened to the edge of the face-plate, and a back-rest 26 is also provided. By means of a switch, the windings may all be placed in series or half of them may be in parallel., according to the voltage available. Alternate forms of interlocking pole-pieces are shown, bv the use of which the whole face-plate can be built up with polepieces drop-forged from only two dies.