GB272990A - Improvements in or relating to electro-magnetic apparatus for use with gramophones in conjunction with loud speaking telephonic apparatus - Google Patents

Abstract

272,990. Rickets, W. J., and Paddle, L. K. March 19, 1926. Magnetic instruments.-Relates to apparatus for use in gramophones associated with telephonic loud-speaker apparatus. At the end of the tone-arm is mounted a non-magnetic holder 1, Fig. 1. in which is supported by screws 6a a U-shaped permanent magnet 5, shown diagrammatically in Figs. 5 and 6. Secured to the pole-piece 5a is a plate 6 of magnetic material on which are disposed the soft-iron cores 7, 8 of a polarized electromagnet. Between the lower ends of the cores 7, 8 and the lower forked pole-piece 5b of the permanent magnet, a soft iron armature 14 is disposed, the ends of which extend under the polar faces of the cores 7, 8. The armature is pivoted at 12<a> in a stirrup 11 of non-magnetic material connected in a detachable manner, as at 11<c>, Fig. 1, to a, non- magnetic closing member 4 fixed in the lower part of the holder 1. The pivot axis may be below the plane of the armature, as shown, or in that plane. Extending at right-angles to the armature is the stylus-lever 12, which may also form the pivot member. The armature movements are damped by pads 15 and the bearings 12a may be rubber-lined journal bearings. The electromagnet windings 9, 10 are connected in series to terminals 3 on the holder 1 and the central point 3a of the windings may be earthed through a terminal 3<a>, if desired. The felt or like damping pads 15 may be adjusted by setscrews 18.