Patent GB-814974-A (GB)
Title: Improvements in or relating to sound reproducing machines
Inventor: MALLARD RICHARD HENRY
IPC: G11B17/16
Filed: 1956-03-19
Abstract: 814,974. Gramophones. FOSTER-MALLARD Ltd. March 28, 1957 [March 19, 1956], No. 8537/56. Class 40 (2). In a record changer wherein movement of the pick-up to the inner end of a record groove triggers mechanism to bring the pick-up to a starting position on another record and to drop a record from a stack supported coaxially above the turntable on a spindle or the like rotating with the turntable, the mechanism may be selectively set so that at each triggering it reverses the electric motor driving the spindle and turntable and, depending on the direction of rotation of the turntable at the time, either drops a record and brings the pick-up into starting position on the upper surface thereof, or brings the pick-up into starting position on the under surface of the lowest record of the stack; the mechanism may be such that if not so set, it repeats the first of these functions at the end of each record and does not reverse the electric motor. General operation.-A gear wheel 33, normally at rest with a gap in its teeth facing its driving pinion 24 on the turntable shaft, is engaged with the pinion by sliding a bar 39 to the left, Fig. 3, to project a rocker 38 on the wheel 33 into the path of a pin 37 on the pinion, the drive being taken up smoothly by spring-loaded toothcarrying arms pivoted to the wheel 33 at the gap ends. A finger 117 on the wheel 33 misses or engages a movable reversing switch 73 for the turntable motor 27, according as the switch is held clear (as shown) by a spring-loaded slide bar 121, or, after turning about its pivot 118 by a knob 123, is held in the finger path by a latch 126. The slide bar 39 is initially actuated by a knob 63 through the ramp 58 of a spring- loaded slide 59 which also carries an insulated ramp 74 to close a main switch 71 previously opened by the weight of the pick-up arm 44 resting on a cradle 66; in subsequent recordchanging cycles, the slide bar 39 is actuated as the pick-up reaches the inner end of a record, by an arm 56 secured to the pick-up arm shaft. During the first quarter-turn of the wheel 33 in either direction a cam 75 and follower 76 move a slide bar 77 to the right, which rotates a plate 78 about its pivot 79; an arcuate ramp 54 acts on a push-rod 53 to raise the pick-up from the record (or from the cradle 66), and a stud 89 engages a further arm 57 secured to the pick-up arm shaft to swing the pick-up to its outermost position beyond the record rims (the position of the pick-up arm for engagement with the cradle 66 is defined by a hook 131 which drops away from a fixed lug 132 when the stud 89 takes over the load of a spring 109 pressing a lug 108 against the arm 57). During the next half-turn of the wheel 33 (or two quarter-turns in opposite directions if the switch 73 is in the path of the finger 117) a cam 172 or 173 rocks a spring- loaded rod 171 to cause an arm 169 to rise towards a push-rod 164, Fig. 10, of the record releasing mechanism (see below); if a pivoted striker arm 166 is interposed, a record is released from the upper stack 155 on to the turntable 22, but the arm 166 is withdrawn if both (a) the bar 121 is held by the latch 126 so that a ramp thereon depresses a fork 94 into the path of trip members 98, 99 (pivoted to the wheel 33 and sprung against back-stops 103, 104); and (b) the wheel 33 is rotating clockwise (Fig. 3) whereby the fork 94, a snap lever 92 on which it is mounted, and the pivoted bracket 167 of the arm 166 linked thereto, are all swung anticlockwise by the trip 98 to the other of their two extremities defined by stops 95, 96. The cam 173 yields during clockwise rotation of the wheel 33 to avoid a double record-release in any one record-changing cycle. According to the Provisional Specification, the arm 166 is replaced by a pad slidable on the arm 169, or may be omitted entirely so that the arm 169 acts directly on the push-rod 164, the cam 172 then being arranged to yield during clockwise rotation of the wheel 33. During the final quarter-turn of the wheel 33, the cam 75 allows the spring 109 to rotate the plate 78 anti-clockwise until a link 112 brings a lever 113 against a cam 114 manually set to stop the lug 108 in a position corresponding to the record size; thereafter the lever 57 is free to move further with the pick-up arm after the pick-up has engaged the record groove. The pick-up has two styli, the upper being engaged with the underside of the lowest record on the stack 155 by an arcuate wedge cam 84, Fig. 3, pivoted at 83 to the plate 78 and serving (as the plate 78 completes its anti-clockwise movement) to increase the distance between the bottom of the pick-up arm push-rod 53 and a back-stop 85 brought into operative position by a link 91 when the snap lever 92 is at its anticlockwise extremity; a spring-loaded knee-joint in the pick-up arm regulates the upward pressure of the stylus. When the back-stop 85 is inoperative, the arcuate ramp 54 allows the push-rod 53 to drop so that the lower pick-up stylus engages the upper surface of the top record on the turntable 22. Record-releasing and automatic stop mechanism.-A stem 148, Fig. 10, projecting from the turntable centre has a coaxial upper part which carries the stack 155, and an inclined central part 149 definining a step 151 off which the lowest record of the stack is pushed by interengaged pivoted levers 157, 161 housed in a slot 156 in the part 149 and actuated by the push-rod 164 through a pin and cam-slot connection 163, 162. For easy removal of the records, the upper part of the stem is tapered at 154 opposite the step 151, a sliding key 153 being housed in a groove 152 to keep all but the lowest record coaxial with the turntable during use. A pillar 177 with a disc base 176 fits on to the stem 148 to keep the stack 155 horizontal, and its lower end is counterbored to allow a substantial drop over the step 151 when the last record is released, this movement being transmitted by an arm 17 .to a vertically slidable rod 138 (Fig. 3) which depresses a lever 137 linked to a rocker 134 pivoted at 135; an arm 139 normally clear of the wheel 33 is thus brought into the path of a stud 141, but the wheel 33 stops just before the stud reaches the arm. Immediately the wheel is started again after the last record has been played, stud 141 moves the rocker 134 anticlockwise until a stop arm 142 drops over an edge 144 and prevents return: the rocker depresses a slide bar 128 to withdraw the latch 126 (whereby if the reversing switch 73 is in operative position, it is swung clear of the finger 117 by the spring of the slide bar 121), and a ramp 133 thereon lifts the hook 131 into line with the lug 132. When the pick-up arm is allowed by the cam 75 to move inwards during the final quarterturn of the wheel 33, it is arrested over the cradle 66 by the hook 131, and as it is lowered by the ramp 54 a cam stud 147 (Fig. 12, not shown) on the wheel 33 trips the stop arm 142 to release the rocker 134; pressure on the cradle 66 then opens the main switch 71. Turntable drive.-The motor 27 is spring- loaded at 185 about its pivot 28 whereby a friction wheel 31 is pressed between the turntable rim and a 3-step driving wheel 29 on the motor shaft; a manually operated double cam 187 engages a lever 191 to shift the wheel 31 axially to that part of the wheel 29 giving the required turntable speed, the motor 27 being retracted for this purpose by a link 192 and lever 193 actuated by lobes 189 on the radial part of the cam 187; the pivot of the wheel 31 is slidable circumferentially of the turntable sufficiently to provide a smooth take-up to the drive.