Patent GB-1227745-A (GB)
IPC: G11B3/08
Filed: 1967-07-14
Abstract: 1,227,745. Record-changer pickup-arm control. GARRARD ENG. Ltd. 5 July, 1968 [14 July, 1967], No. 32574/67. Heading G5R. The invention relates to automatic recordchanger mechanisms of the kind in which a cam member, arranged to perform a single revolution for each record-changing operation, is employed to produce for each revolution of the cam member a single reciprocatory movement of a drive plate, to which a member participating in the inward and outward movement of the pick-up arm (this member being called the pickup plate) is arranged to be coupled during movement of the drive plate in one direction after the termination of the playing of a record; the coupling of the drive plate and the pick-up plate is maintained or effected for other phases of the record-changing operation. The invention provides an improved mechanism for coupling the pick-up plate to the drive plate; a link for this purpose is connected to the drive plate by a friction-loaded pivot connection and has a plurality of cam-edge portions facing opposite sides of its radial length; two of these cam-edge portions co-operate with one or more pins projecting from the pick-up plate, while the remainder co-operate with relatively stationary, or stationary abutments. Parts relevant to the invention are shown in Fig. 1. The order in which they are here described is the order in which they occur, from the top downwards. The pick-up arm 8 is pivoted for vertical movement on a verticallyextending portion of a pick-up plate 10 which is pivoted at 9 for horizontal movement. A horizontally-extending portion of plate 10 has an aperture 10a through which extends a pin 13 which is operated to raise and lower the pick-up arm 8. The pick-up plate 10 also includes a downwardly-extending coupling pin 15 and a number of saw-shaped teeth 11 intended to co-operate with a record-size-selecting stop 12. Below pick-up plate 10 is disposed a coupling link 18 (see also Fig. 2) having a slot 17 and periphery both characteristically shaped. Below coupling link 18 is disposed a drive plate 4 to which the link is connected by a pivot 19, 19a, subjected to controlled friction. In a recess in a base-plate 1 is accommodated a turntable 2, rotatable about an axis 2a and associated with a cycling cam 3 which, in known manner, at the end of playing of a record, is coupled to the turntable to perform one revolution. The drive plate 4 is pivoted at 5 to the underside of the part of plate 1 forming the recess and is oscillated, when the cycling cam 3 is rotated, by engagement of a roller 6 on the drive plate in a cam track 3a provided in the cycling cam. The drive plate 4 is urged in the direction A by a tension spring 22. The parts, (except for turntable 2), are shown in their rest position, i.e., when a record is being played. The drive plate 4 is flat except for a face cam portion 14, separated from the remaining part of the plate by a slot (unreferenced), and provided near its centre with a depressed portion to furnish a ramp 14a for raising and lowering the arm-lifting pin 13. Two fixed guide stems 20, 21, co-operate with the outside periphery of the coupling link 18, while the coupling pin 15 co-operates with the slot 17. Operation.-As shown, the parts are so shaped and arranged that in that position there is no mechanical connection between the pick-up plate 10 and the coupling link 18: the pick-up arm 8 is thus completely free to follow the record groove with a minimum of resistance. At the end of playing of a record, the drive plate 4 is forced by the cam 3 to make one excursion in the direction A and back again. During this excursion the following sequence takes place:- (a) The pin 13 is raised by ramp 14a to clear the pick-up stylus from the record grooves; (b) The pick-up arm 8 is swung away from the centre of the turntable by interaction of link 18 with pin 15 (on pick-up plate 10); (c) This outward swing is terminated (at a point clear of the largest records to be used) by transient inter-action of link 18 with pin 13 (acting as a stop) and consequent freeing of pin 15; (d) Movement of plate 4 and link 18 continues without affecting the pick-up arm position; (e) Drive plate 4 begins to reverse when the innermost point of cam track 3a is reached; (f) The pick-up arm 8 is swung towards the centre of the turntable until the appropriate put-down position selected by stop 12 is reached; (g) The stylus is lowered into the record groove by release of pin 13 by ramp 14a. Thus the movements of the pick-up arm 8 are governed partly by the shapes of the outer and inner peripheries of the link 18 and partly by the relative movement of link 18 and plate 4: such relative movement occurs only when the friction of pivot 19, 19a is overcome; and the overcoming, or not, of this friction depends on the inter-actions of link 18 with stops 20, 21 and pins 13, 15.