Patent GB-333571-A (GB)
Title: Improvements in automatic gramophones
IPC: G11B17/02
Filed: 1929-04-15
Abstract: 333,571. Small, T. W., and Guest, S. A. April 15, 1929. Magazine gramophones. - Records are fed singly from one end of a stack, in which they are supported one on another, to a turntable, and after playing are removed and returned in reversed position to the other end of the stack, provision being made for lifting, returning, and lowering the reproducing device after playing each record. All the changing movements are controlled by cams on a common shaft which makes one complete revolution to effect a change of a record, and friction clutches in the transmission slip in case of an obstruction. The turntable is preferably driven by a spring motor and the recordchanging mechanism by an electric motor which, during changing of a record, also winds up the spring motor. The change movements are controlled by a multiple switch actuated from the controlling cam shaft to make and break the circuits to the motor and to the amplifier circuit of the pick-up, and a tilting mercury switch actuated by the passage of the stylus into the terminal groove, and also a manual or coin-controlled switch, are provided in the motor circuit. The stack of records R, Fig. 5, is normally supported on a platform 100 and on side ledges 92 carried on rocking arms 91, and the top record is fed off and over a guide roll to the turntable 4 by a sliding frame 50 carrying an arm 58 with an adjustable tongue to engage the central hole in the record, the frame being moved by a slotted bracket 55 thereon engaging a pin 49 on a chain 47 which is driven by a chain 40 and gearing provided with a friction clutch from a wheel 35 on a shaft 36 carrying cams for controlling the various operations required in changing a record. The cam shaft 36 is driven by a chain 31 and worm gear 18, 19 from a shaft 12 connected by a belt 13 with a pulley 14 on the electric motor shaft, and the worm wheel 19 is freely mounted on the winding spindle 20, Fig. 4, of the spring motor 21 driving the turntable 4, but can drive it through a friction clutch 25 which slips when the spring is fully wound. Fig. 13 shows the circuit and switches for starting and stopping the motor 2 to effect a change of record, an arm 146 on the controlling cam shaft 36 carrying triple contact fingers 147a movable over circular contacts 149, 150, 151, connected as shown to circuits containing respectively a manual or coincontrolled switch 142, a mercury tipping switch 141, and the pick-up amplifier. Assuming switch 142 closed and a record being played, the circuit to the electric motor 2 is broken at the main switch 147<a> and also at the mercury switch 141 which is then horizontal. When the record is played, the passage of the stylus to the known concentric inner groove, or into a known eccentric groove, effects a movement of the tone-arm 115 which causes, as described later, the switch 141 to tilt and complete a circuit to the electric motor 2 whereby the cam shaft 36 is driven through the gear 18, 19, chain 31, and gearing 34, 35. A cam 135 on this cam shaft now acts through a lever 132 and link 130 to lift a pivoted arm 121 normally centering the record on the turntable, and thereby lifts the pick-up 117, Fig. 4; another cam on the shaft then permits a pivoted spring-pressed lever 7 to actuate a link 6 to apply a brake to the turntable; and the shaft acts through gearing 35, 38, chains 40 and 47, and the pin 49 to slide the frame 50 so that pivoted fingers 57 thereon push the played record off the turntable on to a spring-supported plate 66 at the same time that a fresh record from the top of the stack is fed over the turntable by the arm 58 on the frame. As the frame moves forwards, a projection 126 thereon swings the tone-arm 115 so that the pick-up 117 rides along the support 121 to starting position, and another projection 71 engages a lug 70 on the pivoted plate 66 and rocks this together with the played record thereon into a vertical position in which the record is engaged by fingers 84 on a shaft rocked from the cam shaft. These fingers support the record whilst lowering it gently in reversed position on to rails 72 along which it is moved to a position below the turntable by a chain 73, a lug on which also advances the preceding reversed and played record resting on the rails 72 over the support 100 for the stack, which support has been lowered from the stack now supported on the side ledges 92 by means controlled from the cam shaft. As the cam shaft continues its rotation, the brake is removed from the turntable, the pin 49 operates trip gear to lower the pick-up on to the record, the stack support 100 is raised by a cam 111 acting through an arm 110 and chain 105 to lift the played record up to the bottom of the stack, and the frame 50 is returned to initial position, the cam shaft coming to rest after completion of a revolution owing to opening of the motor circuit at the contacts 147a, the circuit at switch 141 having already been opened by the levelling of the mercury container on lowering the pick-up. Pick-ups, raising, positioning, and lowering. The tone-arm 115, Fig. 11, carries a pivoted finger 177, 178 arranged to move over an inclined plane 179 and a ribbed plate 180 secured to a pivoted lever 166 normally held by a pivoted trigger 167 carrying a switch 141 in a control motor circuit. When the stylus passes into an eccentric groove at the end of the record, the finger 178 rides on and depresses the ribbed plate 180 by the oscillation of the tone-arm. When, however, the stylus passes by a steep curve into a concentric groove, the bar carrying the finger rides on and depresses the inclined plane 179. In either case, the lever 166 is depressed and releases the trigger 167 which is rocked by a spring into an inclined position, whereby a container 141, with mercury and circuit terminals, is tilted and completes a circuit to a motor to drive a cam shaft for controlling the changing of records in a magazine gramophone. A cam on the shaft acts to apply a brake to the turntable, another cam operates a lever to lift and support the pick-up, which is returned along the support to starting position by the record-changing slide, the operating mechanism of which resets the trigger mechanism prior to the lowering of the pick-up.