US2930623A

US2930623A - Gramophone tone-arm positioning mechanism

Info

Publication number: US2930623A
Application number: US708726A
Authority: US
Inventors: Lee James Alexander
Original assignee: Plessey Co Ltd
Current assignee: Plessey Co Ltd
Priority date: 1958-01-13
Filing date: 1958-01-13
Publication date: 1960-03-29
Anticipated expiration: 1977-03-29

Description

J. A. LEE

March 29, 1960 GRAMOPHONE TONE-ARM POSITIONING MECHANISM Filed Jan. 15, 1958 United States Patent GRAMOPHONE TONE-ARM POSITIONING MECHANISM James Alexander Lee, Walthamstow, London, England,

assignor to The Plessey Company Limited, Ilford, England, a British company Application January 13, 1958, Serial No. 708,726

2 Claims. (Cl. 274-15) This invention relates to gramophone tone-arm positioning mechanism and is an improvement in or modification of the invention described in co-pending patent application Serial No. 655,920 by H. Da Costa assigned to the same company as the present specification.

When the device according to said co-pending applications is used for operation with records of three different sizes, care must be taken to make the inertia of the feeler member and of the parts actuated thereby small, to reduce the risk that these elements when actuated by a record of the intermediate size may, due to inertia action, move beyond their appropriate position so as to place the tone-arm mistakenly in the starting position corresponding to a large-size record.

According to the present invention a single feeler member, engaged by both large-diameter and intermediate-diameter records is employed, but overshooting the intermediate position is prevented by a step which requires displacement in a direction substantially perpendicular to that causing the transition from the smalldiameter position to the intermediate-diameter position in order to permit the further transition of the largediameter position.

Thus in the case of a control element rotatable about a vertical axis, an axial displacement is required on reaching the intermediate-diameter position, to permit the further movement to the large-diameter position.

This axial displacement is preferably arranged to be effected by the weight of the record depressing the feeler arm with its shaft against spring action. The amount of the displacement required is very small, thus reducing any inertia delays to a minimum.

An embodiment of the invention is illustrated in the accompanying perspective drawing, in which Figs. 1 and 2 respectively show the mechanism in the intermediatediameter position and in the large-diameter position.

A stop member 1 having a flange 13 co-operates with a teasing lever similarly as shown in the said-co-pending application to control, in a known manner, the end of the tone-arm positioning movement. The stop member 1 is mounted on a vertical shaft 2 which is rotatable in the gramophone base 4 and carries a flag-type feeler arm 5. In its normal position prior to the release of a record this arm projects into the path of 10 and 12" diameter records as they move individually down from a stack to the turntable 10 of the record changer, while the arm is clear of the path of the periphery of 7" diameter records. This arm is provided with an inclined ramp surface a, whereby a record of 10" or 12" diameter moving to the turntable will swing the arm 5 about the axis of shaft 2 in the direction of arrow x as long as the arm is free so to move, and until it is clear of the edge of the record in question. This rotation of shaft 2 will turn the stop member 1, against a light return spring 33, to its 10" or 12" position according to the diameter of the record. A latch lever 8, formed with

abutment shoulders

11 and 12, serves to retain the stop member 1 in this position until it is released in due course for the resetting of the mechice anism before the next record of the stack is allowed to drop onto the turntable. This release is efiected in any convenient or conventional manner by an element 12 of the change-cycle mechanism of the record changer.

In order to prevent the feeler arm 5 and the stop 1 from overshooting the 10" position and from thus setting the tone arm mistakenly for a 12" record when a 10 record drops onto the turntable, a stop pin 34 projects down from the gramophone base 4 into the path of an abutment edge 35 of the stop member 1 so as to normally prevent the latter from moving beyond the 10" position shown in Fig. l, to the 12" position. In order, however, to allow such further movement when a 12" record is released from the stack, the shaft 2 with the stop member 1 is enabled to move downwardly under the weight of the record against the action of a light supporting spring 36, sufliciently for the stop member 1 to clear the end of pin 34. Thus when a 12" record has been released from the stack, the stop member 1 is free to move, under the action of the feeler arm 5, to the 12" position illustrated in Fig. 2, since the weight of the record still rests on the arm 5 to hold the shaft and stop member depressed when the latter passes the 10" position. When on the other hand, a 10" record has been released, the weight of the record, even if it has been sufi'lcient to depress the shaft and stop member, ceases to act when the 10" position is reached, whereupon the spring 36 will at once lift the shaft to return the stop member 1 to its position for cooperation with stop pin 34. It will be appreciated that the pin 34 may be arranged to arrest the rotation of the stop member 1 at a point some distance beyond the 10" position but short of the 12" position. This provides ample time for the spring 36 to render the stop pin effective, whereupon the spring 33 will immediately return the stop member as far as the 10" position stop 11 of the latch member 8 will permit. If desired, however, a fixed auxiliary abutment 37 (Fig. 2) or the like may be provided which prevents the shaft and stop member from downward movement up to a point at which the arm 5 is out of the reach of a 10" record.

What I claim is:

1. In a tone arm positioning mechanism for turntable gramophones the combination of a feeler arm mounted on and rotatable with a vertical spindle, spring means biasing said feeler arm and spindle for rotation to a normal position in which the feeler arm extends near to the centre of the gramophone turntable, said feeler arm having a cam surface for co-operation with the edge of a record disc moving from a magazine to said turntable to move the arm, when engaged by such edge, about the axis of said spindle from said normal position to one or both of two predetermined further positions, according to the diameter of such record, a stop member mounted for rotation with said spindle and selectively controlling the positioning of the gramophone tone arm to three positions according to whether said feeler arm is in said normal position or in one or in the other of said predetermined further positions, and releasable retaining means terminating, until released, the return movement of said feeler arm and stop member under the action of said spring means at that one of said two predetermined further positions which is first reached in such return movement, mounting means for said spindle permitting the spindle to move axially as well as rotatably, resilient means normally retaining said spindle in a relatively high position when no record rests on the feeler member, abutment means fixed on said spindle, and a stationary limit stop member so arranged and dimensioned as to co-operate when said spindle is in said relatively high position, with said abutment means, for terminating rotation of said spindle against the action of said spring means at a position intermediate between said two pre- 3 determined further positions,z but to be cletrofthe path of said abutment means and thus permit rotation of said spindle against the action of said spring means beyond said intermediate position when, due to the weight of a record: resting onsaid feeler arm, said spindle is,=against the action of said resilient means, depressed from said relatively high position; v

2. A combinationas claimed in claim 1, including an auxiliary stop preventing downward movement of said spindle to clear said limitstopmember when said am is 10 between its normal position and the position correspondin'gto that of said predetermined" furtherpositions which is first reached by rotary movement against the action of said spring means.

References Cited in the file of this patent UNITED STATES PATENTS 2,752,159 Bacher e June 26, 1956 FQREIGN PATENTS 382,276 Great Britain i Oct. 17, 1932 770,094 Great Britain Mar. 13, 1957