Patent GB-332004-A (GB)
Title: Improvements in and relating to automatic control mechanism for gramophones and the like
IPC: G11B3/095
Filed: 1929-05-27
Abstract: 332,004. Columbia Graphophone Go., Ltd., and Mitchell, F. A. May 27, 1929. Brakes, arrangement and disposition of; multiple machines; returning sound-box to starting point; sound grooves and traces. - An automatic control device, for gramophones and the like comprises a member intermittently moved towards its operative position by the tonearm or like travelling element and adapted to actuate the control device when the rate of said movement is increased beyond a prearranged value. As shown applied to a gramophone braking device, the tone-arm T, Fig. 1, has a lug L engaging a lever A pivoted at P on a base-plate. One end of a lever B frictionally engages the lever A, so that when the latter is moved it will also move the lever B, provided no resistance is offered to the lever B. The other end B' of the lever B operates in conjunction with a cam C rotated by the turntable shaft W. During reproduction, the end B' is moved towards the cam C by the members A, B, L, and on each revolution of the cam a projection C<1> thereon moves the end B<1> outwardly. When the stylus S' enters the finishing groove R<4> of coarse pitch, the end B' moves a distance greater than the normal and engages a radial face on the projection C<1>, as in Fig. 7. As the cam C is held frictionally on the turntable spindle W, the latter is thus braked. In a modification, an intermediate spring-controlled member is arranged between the cam C and the end B<1> of the lever B. In another modification, the lever A, Fig. 18, is reset by hand and the lever B is pivoted to a base-plate at P<1> instead of at the friction joint between the levers A and B. The cam C operates a rocker U which co-operates with a step B<2> on the lever B during inward movement of the tone-arm T, the operation being such that when the inward movement of the tone-arm exceeds the pre-arranged value, the cam C is prevented from rotating. A lever J movable over a dial J<1> permits the automatic control to be put out of action, or permits of hand control. In another modification, the lever B is frictionally mounted directly on the tone-arm support. In another modification, in which the control is operated by excessive movement of the tone-arm in either direction, a pawl B<3>, Fig. 21, pivoted to a lever A is held in the position shown by a spring V. The edge B<4> engages the arm Q<2> of a lever Q pivoted at Q<3> and having an arm Q<1> engageable with the cam C. The normal movement given to the lever A by the tone-arm T causes the pawl B<3> to drag on the arm Q<2> and to be slightly tilted, and each time. the cam engages the arm Q<1> the pawl B<3> returns to its normal position again. When the stylus S<1> reaches the finishing groove, the extra tilting of the pawl B<3> permits the lever Q to move sufficiently to enable the edge Q<4> thereof to engage the radial part of the cam C and so stop the apparatus. In another construction, the levers A, B, D, Fig. 8, are frictionally pivoted together at P<2> and the lever D is pivoted to the base-plate at D<1>. During normal operation, the end of the lever D holds a switch E<2> closed so that current is supplied to the turntable motor E. When the stylus S' engages the finishing groove R', the flat face of the cam C engages the end of the lever B and thus turns the lever D about its pivot D' to open the motor switch E<2>. In this construction, the lever D could apply a mechanical brake, or the switch E<2> may switch off the amplifier associated with the pick-up S<2>. The control mechanism may be put out of action by raising a spring-controlled pin N which normally engages the fingers A<1>, A<2>, on the lever A. As applied to a record repeating device, the end of the lever B, Fig. 11, normally holds the contacts 0, O<2> apart so that the circuit of an electromagnet M is broken, enabling the stylus S<1> to engage a record. At the end of recording, the extra movement given to the arm B enables the contacts 0, O<2> to close the magnet circuit whereupon the stylus S<1> is raised from the record and the pick-up arm T<1>, under the action of a spring Y, swings outwardly to the beginning of the record. When this position is reached, a pin N on the lever L<1> strikes the finger A<2> of the lever A and the lever B is moved to separate the contacts 0, O<2> and the stylus again drops to the record. Reproduction is thus repeated. A disc. X, Fig. 12, pivoted eccentrically to the pick-up S<3>, allows the stylus S<1> to be gently lowered into the record groove. The pin N<2> is adjustable about a pivot N<3> so that the apparatus may be adjusted for records of various sizes. The lever B or other moving part may actuate mechanical record-repeating or record-changing apparatus, or the control device may actuate to start repeating, changing or like apparatus which has been pre-set or is operated bv mechanism other than the turntable motor, such as is shown, e.g. in Specification 191,413. The cam C may be driven by some part of the mechanism other than the turntable shaft or by a separate motor. The control mechanism may function, to actuate mechanism without stopping the record by providing a groove of coarse pitch between adjacent, sound grooves on the record, and it may be arranged to operate with records working from the centre outwards. The contacting faces between co-operating metal parts may be insulated by sound-absorbing material, such as leather, rubber, or paper, or the cam C, levers, or other parts, may be made of fibre, vulcanite,. or other material, instead of metal.