Patent GB-429363-A (GB)
Title: Improvements in automatic cut-off or stopping devices for use with electric gramophones
IPC: G11B17/02
Filed: 1933-12-13
Abstract: 429,363. Gramophones. MANN, G. S., 101, Rosehill Road, Ipswich. Dec. 13, 1933, No. 35022. [Class 40 (ii)] An automatic stopping-device for electricallydriven gramophones comprises a switch in the motor circuit, operated when the pick-up arm or tone-arm comes to rest by the overrunning of the arm by a part driven at the same angular speed as that of the arm during the playing of a record, the switch being mounted upon the said part. The switch-carrying part is driven from the turntable spindle through a friction clutch, and the switch is reset and automatically closed when the pick-up arm is raised from a played record and swung back to the starting position. The pick-up arm 1 is pivoted at 2 on a boss 4, mounted on ball bearings on a tubular post 5 into which a sleeve 8 on the boss extends. A disc 12, which carries a switch in the motor circuit, is rotatably mounted on the post 5, and has a friction-clutch connection with a toothed wheel 15. This is driven by the turntable spindle 17 through worm gearing which is such that during the playing of a record the switch-carrying disc 12 and the pick-up arm 1 have the same angular speed. The switch comprises a lever 24, pivoted on an insulating block 13, and carrying a contact 26 coacting with a contact 27 on a cover-plate 28, a spring 29 being adapted to cause the contacts to meet, to close the circuit of the motor. The bevelled end 32 of a lever 31 is, however, adapted to be raised by a spring 33 behind the lever 24 so as to hold it in the position shown in Fig. 11, when the motor circuit is to be opened. During the playing of a record, the lever 31 is held inoperative by engagement with a notch 36 in a trip lever 34, Fig. 7. The upper end of the lever 34 is adjacent to one end of an horizontal lever 39, Fig. 1, pivoted at 40 upon a bracket on the block 13. The forward arm of this lever lies, whilst a record is being played, close to a cam 42 fixed to the boss 4 supporting the pick-up arm. At the end of the playing of a record, when the needle passes into the run-off groove, the cam 42 first moves away from the lever 39 and then comes to rest. The switch plate 12 continues to revolve, carrying the lever 39 with it, so that the latter is turned by the cam 42 and shifts the trip lever 34. The lever 31 is thereby freed, and its spring 33 causes it to separate the switch contacts. A resetting lever 43, acted upon by a spring 45, is pivoted at 44 to the boss 4, Fig. 1, and its tail end 48 engages the switch block 13 at the commencement of the playing of a record. The tail 48 separates from the block 13 during playing, but when the pick-up arm is swung back for playing a fresh record, the tail resets the switch block 13 to its initial position relatively to the pick-up arm. A spring-pressed plunger 50, Fig. 4, is mounted in a gap in the boss 4, and is depressed by a lug 49 on the arm 1 when the pick-up is raised. The part 50 carries a screw 54, adapted to act upon a second plunger 55, Fig. 7, which is mounted in the switch block 13 and is shaped so as to operate the levers 24, 31 when it is depressed. By these means, the switch 26, 27 is closed, to restart the motor, when the pickup arm has been raised and swung outwards to the starting-point of a fresh record. A handoperated cut-off switch 61, Fig. 1, is also provided. When the invention is applied to a magazine gramophone such as is described in Specification 402,779, the lever 24 may carry a second contact adapted to start an auxiliary motor for the purpose of record changing.