GB396875A - Improvements in electromagnetic pick-ups for gramophones - Google Patents

Abstract

396,875. Gramophone pick-ups. LOWE, A. E. BOWYER-, Diamond Works, Coombe Road, Brighton. April 20, 1932, No. 11292. [Class 40 (iv).] The armature of a gramophone pick-up is damped by passing its inner end through a puncture in a sheet rubber diaphragm clamped on the polepieces by a bridge or equivalent having an aperture to leave free the punctured centre of the diaphragm, the damping effect of the diaphragm being made variable by providing for the adjustment of the pressure of the bridge thereon. Fig. 1 shows one form of construction in which the flattened end 4 of the armature 2 is passed through a puncture in a sheet 3 of indiarubber which is clamped to the polepieces 1 by a channel-shaped bridge member 5 and screws 6. The bridge may be clamped more or less to pinch the sheet and so vary the amount of damping on the armature. Fig. 4 shows a modification in which the damping is varied.by altering the pressure of the springy fingers 7, whilst in Fig. 5, the lip of the hole in the bridge 5 is made smaller and brought up at an angle as at 8. According to a further modification, Figs. 7 and 8, the bridge 5 is formed with one or more presser bars 9 which are slightly above the general level of the base of the bridge. The diaphragm 3 is permanently gripped by the edges 10 and its effective area between these edges is damped by the bars 9, the pressure of which is varied by distorting the bridge 5 by adjusting the screws 11 which bear on the polepieces 1. The armature is gripped in a rubber sleeve 12 between the lower polepieces.