Patent GB-676426-A (GB)
Title: Improvements in and relating to phonographs
IPC: G11B17/16
Filed: 1948-12-06
Abstract: 676,426. Automatic gramophones. MARSDEN, V. P., and McGAIN, R. P. Dec. 30, 1949. [Dec, 6, 1948] No. 31496/48. Class 40 (ii). A phonograph mechanism of the type having a motoroperateu turntable adapted to carry a stack of records and a tone arm is provided with two record changing arms 46, 47 having claws 66 adapted to engage the edge portions of a record on the turntable at opposite positions, the arms and associated claws being adapted when one side of a record on the turntable has been played to grip and to raise the record and to reverse it by the claws being turned in relation to the arms, and to lower it again to the turntable, the arms and claws being further adapted, when the second side of the record has been played, to grip and raise the record and deposit it out of the way such as on a suitable magazine. The object is to play both sides of each record in turn stacked on the table and then to remove the record. A cam shaft 88 is driven from the shaft 42, which carries the turntable, through a pawl and ratchet. The cam shaft carries a cam 87 which controls the rotation of a lateral shaft 45, cams 121, 122 which control the movement of a record gauge and cams 112, 113 which control the movement of the tone arm (Fig. 26). Record changing arms. The connection between the cam 87 and the lateral shaft 45 is through a lever arm 84 which carries a roller 86, co-acting with the cam groove, and which is linked at one end to a crank on the shaft 45. The arms 46, 47 are mounted at opposite ends of the shaft 45 and are raised and lowered by rotation of the shaft. Their mounting is pivotal ; so they can also swing inwards and outwards, and this swinging movement is governed by a sleeve 49, slidable on the shaft 45, and connected to the arm 46 at a point behind its mounting on the shaft 45 by a member 51 and connected to the arm 47 at a point in front of its mounting on the shaft 45 by a member 52. The sleeve 49 is slid on the shaft 45 against a spring 55 by a forked lever arm 100 which is moved, through a spring 104 to compensate for wear, by a cam 101 on a shaft 105 which revolves once for every two revolutions of the shaft 88. The arm 47 is tubular and houses a rod normally pressed forwards by. a spring and fitted at its front end with a rack which engages a pinion fixed to the axle of its claw 66. The rear end of the rod is fitted with a finger piece which projects through a slot in the rear of the tubular arm and engages a cam mounted on a bracket 77 in which the shaft 45 is journalled. The other claw 66 is simply pivoted on the arm 46. Both claws are spring-pressed slightly inwards from the arms ; when. they are pressed outwards by a record between them a detent on each cam enters a notch and prevents them from turning back after rotating 180 degrees. Each claw has two gripping members for two sizes of records, consisting of a length of spring steel bent downwards and inwards to engage the edges of the records. The pawl and ratchet drive (Fig. 16) between the shaft 42. and the cam shaft 88 comprises a worm 89 on the shaft 42 driving a worm wheel 90 free on the shaft 88 and having ratchet teeth 91. A pawl 92 is mounted on a curved spring 95 secured to a boss which is fixed to the shaft 88. The spring is held back by a finger 96 on a spring-loaded, pivoted plate 97 (Fig. 1) and the withdrawal of this finger allows the spring 95 to spring the pawl 92 into engagement with the ratchet 91, so setting the record changing apparatus in motion. Tone arm. The tone arm 109 is mounted on a vertical shaft 110 (Fig. 26, inverted plan). Movement of the cam 112 causes a lever 115 to press on a plate 116 fastened to the shaft 110 so as to cause the outer end of the tone arm to lift. The cam 113 acts through a bar 117 on an arm plate 118 on a sleeve 119 through which the shaft 110 passes, being slidable but not rotatable therein. A plate 143 which has a finger 142 at one end and a stop 145 at the other end is pivoted on the sleeve 119 and urged by a torsion spring for the stop 145 to engage the arm plate 118. A spring 120 which is connected to the arm 118 and acts to operate the tone arm 109 is also connected to the plate 143. Recordgauge. A tubular upright 129 (Fig. 24) is rotatably and slidably movable in a bush 130, mounted on, the deck plate 40 near the turntable, and is mounted on a plate 125. The plate 125 is turned by the cam 121 through a bar 124 (Fig. 26) and is raised by the cam 122 through a lever 127 whose opposite end presses under the plate 125. At the top of the upright 129 is an arm 131 carrying a roller 132 and a right-angled arm 133a (Fig. 25) which is pivoted at 134 and carries a roller 135. If there are a large and small record on top of one another on the turntable and the large record is uppermost the roller 135. will rest on the edge of the large record, but if the small record is uppermost the roller 132 will rest on the edge of the small record. The arm 133a has a trigger 136 passing down through the upright 129 and urged by a leaf spring 137 to keep the roller 135 at a slightly lower lever than the roller 132, as is possible when a small record.is uppermost. In this condition the lower end of the trigger, extending below the bottom of the upright 129, operates a lever 138 pivoted at 139 below the deck plate (Fig. 26) in such a way that a flange 141 extending downwards from the lever 138 holds back the finger 142 on the plate 143 and so causes the spring 120 to be slightly tensioned. That spring therefore pulls upon the arm 118 and causes the tone arm 109 to swing further inwards than it would if the finger 142 were not held back. If a large record is uppermost on the turntable the trigger 136 is held to the other side by the roller 135 and the lever 138 is then positioned so that the finger 142 moves in front of the flange 141 and the spring 120 is less tensioned, and then the tone arm 109 moves inwards by a less distance. Shut off. To cause automatic shut off when the second side of the last record has been played a cam 147 (Fig. 32) is fastened to the inner end of the shaft 105 and presses upwards on the free end of a fulcrummed plate 148 (Fig. 1) which has a catch 149. Since the shaft 105 rotates only once for every two revolutions of the cam shaft 88 the cam 147 will not be brought into engagement with the plate until after the playing of the second side of the record, and if it is the last record its removal will allow a pivoted latch 150 to swing and engage the catch 149. At this, the plate 148 pivots about the fulcrum 152 (Fig. 1) and causes a lever 151 to press a bearing member 153 against the rim of the turntable and also to operate a switch to shut off the motor. To shut off the machines before the last record is played a slidable member 99 is pushed inwards and slides under the plate 148. The inward movement of the member 99 also turns the plate 97 and so withdraws the finger 96 from the spring 95, so setting in motion the record-changing mechanism including the cam 147. When the cam 147 rises the thickness of the member 99 causes the catch 149 to engage the latch 150 although the latter has not swung down and so the mechanism is stopped. Brake release (Fig. 18.). To enable the motor to overcome the inertia of a record newly deposited on the turntable the influence of the speed governor is temporarily removed. A cam 157 fitted on the shaft 88 and acting on a brake lever 158 to hold it against the governor plate 159 has a depression at the appropriate position whereby a spring 161 is allowed to withdraw the lever 158 from the governor plate. Operation. The cams on the shaft 88, acting through their connecting mechanism, first lift the record gauge, by the plate 125, and traverse it over the edges of the records on the turntable and then lower it. If the top record is of smaller size its edge is engaged by the roller 132, but if it is of larger size its edge is engaged by the roller 135 which, when the gauge is depressed, causes the trigger 136 to operate the lever 138 and so to modify the connecting mechanism between the tone arm traversing cam 113 and the tone arm. At the same time the cam 112 lifts the tone arm. The cam 113 then traverses the tone arm, doing so to a less extent if a large record is on top, suitable to engaging the needle therewith. The record commences to be played in the usual manner and the record gauge is then lifted, traversed away from the turntable and lowered. When the first side of the record has been played the tone arm is located at the inner part of the record and an arm 162 mounted on the sleeve 119 is also swung inwards so that a pivoted member 163 at its outer end will be engaged by an arm 164 on the shaft 42 from the motor. When the member 163 is so engaged it acts upon the pivot plate 97 to cause the clutch devices 90 to 95 to operate, thereby operating the shaft 88. The tone arm is lifted and is traversed away from the played record. The cam 87 then operates the shaft 45 to cause the arms 46, 47 to lift somewhat from the deck plate 40, and the cam 101 operates to slide the sleeve 49 so that the arms move inwards. Since the members 51, 52 are connected to the arms 46, 47 on opposite sides of their pivots on the shaft 45, the arms move in opposite directions. When the claws 66 have gripped the record the cam 87 causes the arms to rise, and as they do so the finger piece on the end of the rod in the arm 47 rides over the cam on the bracket 77 resulting in the rod being retracted so as to cause its rack to turn the pinion on the axle of the claw 66 and there to turn the claw. The other claw, freely pivoted, engaging the other side of the record, is of course turned at the same time. Thus the record is turned through 180 degrees as it is lifted, and the detents on the claws, entering the notches, retain the axles of the claws 66 in retracted position. The cam 87 thus operates to lower the arms, carrying the reversed record down to the turntable. The ca