Patent GB-307768-A (GB)
Title: Automatic talking machines
IPC: G11B17/16
Filed: 1927-12-09
Abstract: 307,768. Marks, E. C. R., (Deca-Disc Phonograph Co.). Dec. 9, 1927. Magazine gramophones; returning tone-arm to starting position; driving; stopping.-Relates to magazine gramophones of the kind in which the turntable is adapted to be moved vertically up and down in axial alignment with a stack of records to receive the records one at a time so that they may be played successively. The invention consists mainly in the provision of two electromotors, one, preferably an induction motor, serving to drive the turntable, and the other, for operating the record-changing mechanism, being switched on by the final movement of the tonearm after the playing of a record, and being automatically switched off when a record-changing operation has been completed. A pile of records is held, before use, on three pivoted supports 94, protruding from posts 90 arranged concentrically round the turntable 26. Each support 94 is associated with a lever 96, Fig. 11, and with another lever 91, carrying a finger 92 for the purpose stated below. The turntable rests upon, and is frictionally driven by, a support 32, itself driven by the induction motor 23, the disc armature 25 of the motor being fixed on a sleeve 27, which drives through a pin-and-slot connection a tubular shaft 31, the latter being attached to the member 32, and held up by a spring. A rod 33, to which the turntable 26 is fixed, passes through the tube 31, its lower end being surrounded by a sleeve 40 which contains a pawl 35 normally engaging with ratchet teeth 34 on the rod 33. A spring 41 within the tube 40 tends to force the rod upwardly. A pin 33a on the sleeve 40 engages in a groove in a cylindrical cam 38 which, when it is rotated, acts, through the mechanism described, to raise and lower the turntable. The cam 38 is fixed on a shaft 42, which is rotatable by a motor 43<1>, this motor being geared to the shaft through gearing which includes a frictionallymounted wheel 48, whereby slipping can occur if the driven shaft becomes jammed. The shaft 42 also carries a cam 55, which, when it rotates, serves to return the tone-arm from the innermost to the outer or starting position. The tone-arm is provided with an arm 61, Fig. 2, coupled with a pivoted arm 67 which carries a finger 70 engaging with the cam 55, the arm 67 being pressed by a spring-actuated bell-crank lever 74 so as to hold the finger 70 against the cam. The latter is formed with two surfaces 59, 60, at different heights and at different radial distances from the shaft 42, whereby the extent of outward movement of the tone-arm may be varied according to the size of the record about to be played. Mechanism, operated by a hand lever 81, Fig. 1, is provided for shifting the arm 67 up or down, as required, so that the finger 70 can engage with the appropriate cam surface. The circuits of the motors 23, 43<1> are arranged as shown in Fig. 12, and include, in addition to a main hand-operated switch 134, a switch 116 controlled jointly by the tone-arm and by the record-releasing mechanism, switches 126, 127 both actuated by the cam 38, and a switch 141 operated by the recordreleasing mechanism after a predetermined number of records has been played. The switch 116 comprises a spring-pressed actuating arm 120, Fig. 2, which is normally held inoperative by a detent 113, but when the detent is tripped by a screw 64 on the arm 61, presses together two contacts. The arm 120 is reset, to open the switch, by a member rssociated with one of the record-supports 94. The switches 126, 127 each comprise a fixed contact and a spring contact, the latter being provided with an insulating block 130 or 133 adapted to be moved so as to operate the switch when a projection 52 or 53 on the cam 38 coacts therewith. The switch 126 controls the operation of the motor 43<1>. The function of the switch 127 is to short-circuit momentarily one of the coils of the induction motor 23 as the reproducing needle is applied to the surface of a record, thereby producing initially an extra torque. The switch 141, Fig. 2, comprises two spring fingers, normally in contact, and arranged near to an escapement wheel 138 carrying a pin 143. The wheel 138 can be turned by hand, against the action of a spring, so that the pin 143 is at a predetermined distance from the contact-fingers. During the operation of the machine, an anchor 140 is rocked by the movement of a part 146 extending from one of the levers 91, Fig. 11, and allows the wheel 138 to move step by step, one tooth escaping each time a record is changed. Thus, after a given number of records has been played, according to the setting of the wheel 138, the pin 143 breaks the circuit of the motor 23 at 141. To prevent the switch 141 from operating, it may be short-circuited by a switch 164, Fig. 12. The whole machine operates as follows. Starting with one record on the turntable, and the others piled on the supports 94, the switch 141 is set as required, and the main switch 134 is closed, starting the turntable motor. At the end of the playing of the first record, a " rapid advance " groove thereon carries the tone-arm inwards sufficiently to enable it to operate the switch 116. The motor 43<1> then starts, and the cam 55 first swings the tone-arm out, after which the cam 38 raises the turntable. As the record thereon reaches the level of the lower surface of the bottom record in the pile, a pin 37 on the cam 38 enters a slot 39 in a tubular guide surrounding the sleeve 40, and pushes the pawl 35 out of engagement with the ratchet teeth 34 on the rod 33. Meanwhile, the parts 94, 96 have been pushed in by the turntable as it rises, and the fingers 92 have been protruded between the lowest record of the pile and those above it. Thus the upward movement of the turntable is limited, but a slight further rise of the sleeve 40 occurs, and the pawl 35 is enabled to engage in a tooth higher up the ratchet 34. By this means, when the cam 38 allows the turntable to descend, the parts 94, 96, 91, 92 resume their original position and the next record of the series, having been released, lies upon the previously played record, and is carried down by the turntable to the playing level. The unplayed records are, as before, supported by the fingers 92. The movements of one of the levers 91 cause the pin 143 of the switch 141 to advance, as previously described. Another of the levers 91 opens the switch 116, but before this happens the switch 126 is allowed by the projection 52 on the cam 38 to close, so keeping the motor 43<1> running until the record-changing is completed. When the fresh record is in the playing position, the cam 55 allows the tone-arm to swing in to the proper position, and a subsequent slight rise of the turntable brings the record against the needle. The sequence of operations is then repeated. The mechanism associated with the supports 94 is so constructed that after all the records have been deposited on the turntable and the last record of the series has been played, when the turntable finally rises and falls, all the records are left upon the supports 94. Manual means are provided for operating the switch 116 at will, so that the record-changing mechanism may be set in operation at any time.