Patent GB-239573-A (GB)
Title: Improvements in and relating to self stopping and self repeating mechanism for gramophones talking machines and the like
IPC: G11B3/095
Filed: 1924-05-14
Abstract: 239,573. Mitchell, F. B. May 14, 1924. Stopping; brakes, arrangement and disposition of; returning sound-box to starting point.-Brake mechanism, and, if desired, repeating mechanism, in gramophones is automatically actuated by a device tracking the record adjacent the stylus and adapted on escaping from the last or inner groove to slip on the smooth part of the records and thereby bring the mechanism into operation. As applied to a braking device, a fine wire or wires B, Figs. 1 and 8, clamped in a support B<1> pivoted to the sound-box S tracks the record groove adjacent the stylus A, and a projection B<12> from the support holds a pivoted lever D with brake-shoe D' clear of the record. When the wire B passes out of the innermost record groove, or is forced therefrom by the traverse of the soundbox, on to the smooth record surface, it slips, the support B<1> rocking and the projection B<12> releasing the lever D so that the brake pad D<1> comes on to the record and also lifts the sound-box slightly. The tone-arm T is traversed outwards by the drag on the pad D<1>, assisted if desired by a constantly-acting spring, and is arrested by a pivoted lever T<2> adapted to engage a pivoted arm L adjustable for records of different diameter. In modifications, the lever T<2> may be pivoted to hang vertically, and may engage a notch in the flanged bearing of the tone-arm to hold the tone-arm at the completion of playing, or it may be linked to an eccentric pin on the end disc of the swan-neck joint of the tone-arm so that lifting of the soundbox withdraws the lever to permit the tone-arm to be turned clear of the record. Further, adjustable screws may be provided in each stop face L<1>, L<2> of the arm L for fine adjustment. In a further modification, the rocking movement of the support B<1> when permitted by the tracking wire B may release a trip holding a spring-controlled Bowden wire which then acts to apply a brake in any desired position. In Fig. 17, which shows a gramophone with a Large diaphragm K, a spring- pressed brake lever H is held out of action by a Bowden wire G<1> bearing against the pivoted support B<1> carrying the tracking wire B, the escape of which from the record groove with consequent rocking of the support B<1> releases the wire. Resetting is effected by finger pressure at the part H<1> of the brake lever H. For repeating, an unbalanced cam C, Figs. 10 and 11, preferably rubber covered, mounted on a pin projecting from the sound-box and carrying a pivoted pawl C<3> is normally held by a pin D<7> projecting from the brake lever D before this is released. When, however, the brake lever is released by the tracker wire B and moves to the vertical position, the pin D<7> moves clear of the pawl C<3> and the unbalanced cam C turns clockwise until arrested by an arm C<1> contacting the record. The reproducer is traversed outwardly to starting position by the contact of the record with the brake pad on the lever D, and when the arm C<1> passes over the edge of the record the cam C turns further and is engaged by the record, whereby it is reset or turned to its initial position, Fig. 11, during which movement it lifts the sound-box and brake and another cam C<2> on the spindle C<6> acts on the pin D<7> to reset the brake lever D, the pawl C<3> being flung over by the centrifugal action to engage the pin D<7>. A crank pin C<6> on the spindle C<6> resets the pivot tracer block B<1>.