GB510280A - Improvements in or relating to magnetic clamping appliances - Google Patents

Abstract

510,280. Magnetic work-holders. BING, J., and BLOCK, O. April 22, 1938, Nos. 12141 and 12142. Convention dates, May 22, 1937 and April 14, 1938. [A Specification was laid open to inspection under Sect. 91 of the Acts, Oct. 24, 1938] [Class 60] [Also in Group XXXV] A magnetic work-holder, comprising a substantially cylindrical permanent magnet 5 and a pair of soft iron pole pieces 2a, 2b which form the work holding surface and by which the magnetic flux may be short circuited as the magnet is rotated, has the pole pieces separated from the magnet by a cylindrical air gap coaxial with the axis of rotation of the magnet. The pole pieces 2b are mounted on a base 1 of magnetic material whilst the pole pieces 2a are separated by non-magnetic bars 8. The permanent magnet may be supported by the pole faces or by plates attached to the ends of the pole pieces. The movement of the magnets may be synchronised by toothed gearing 13 and is not limited to 90 degrees, but is so arranged that it is possible to reverse the polarity of the pole pieces by exceeding this angle. A clamping plate 17 formed of a number of parallel bars 15, 16 made of alternate strips of magnetic and non-magnetic material, e.g., iron and brass, may be used. The magnetic bars 15 are formed with projections 15b which contact the pole pieces so that one bar joins up the poles of N-polarity whilst the next bar joints up those of S-polarity. The width of the strips may be varied to.suit the workpieces. In a modification, the pole pieces 2a, 2b are vertically arranged on a base of non-magnetic material. The permanent magnets may be formed as thin walled sheaths filled with granulated material, and they may be synchronised by other means than toothed gearing. The invention is not limited to the use of bi-polar magnets. The construction of the holder is such that it may be made of any length by the use of any number of separate units. The air gap between the magnet and the pole pieces may be filled with oil or grease to prevent the ingress of moisture and dust. The use of a single unit pivotally mounted on a holder suitable for clamping in a vice is also described. Specification 472,426 is referred to. The Specification as open to inspection under Sect. 91 comprises also a work-holder in which the permanent magnets are short-circuited by rectilinear displacement of the magnets relative to the pole pieces. This subject-matter does not appear in the Specification as accepted.