US2585396A - Gramophone tone arm moving device - Google Patents

Description

Feb. 12, 1952 J 5, 2,585,396

GRAMOPHONE TONE ARM MOVING DEVICE Filed Feb. 7, 1947 INVENTOR \rose S. Mm bc'm.

ATTORNEY Patented Feb. 12, 1952 Application February 7, 1947, Serial No. 727,100

InSpain January 22, 1947 2' Claims.

The present invention refers to an improvement in devices for moving gramophone tonearms In present-day gramophones, the device supporting the pickup which, by means of a needle, receives the vibrations engraved in the grooves of therecords, consists of an arm turning on a shaft and the needle, fixed to same, is guided in its. displacement by thespiral movement of the grooves. In other words, the needle traverses the arc ofa circle. centered at said shaft.

In the recording process, the recording device is maintained parallel to itself throughout its travel,v and its vibratory plane occupies always the tangent of one of the grooves. During soundreproduction, however, the needle. traverses an arc of av circle in which the different radii corresponding to the several points of contact'of the needle, in the grooves, do not correspond to their respective tangents.

During recording, furthermore, the needle, in its advance towards the center of'the record, cuts the groove and fixesthe recording with greater clearness on the inside edge of same. During reproduction, however, the groove guides the needle, which makes its way to the centre more strongly supported on the outside of. said groove.

It isthe. object. of. the device according, to this invention, to correct these errors, having the vibratory plane of the sound receiver or pickup, at each point of eachv groove, occupy a position corresponding. to its tangent, and causing the needle to be more strongly supported by the in sideedge of the same groove.

The first, objectis attained by means by asliding motion of the arm on its own turning point, in agreement with the angular displacement of same, an arrangement which makes it possible to modify the effective length of the arm, and which placestheneedle at a point corresponding to the geometrical tangent of each groove. Thesecond object is attained by placing asuitable spring ontheturning shaft so as tohave the arm moved towardsthe center through spring action the groove. serving. as. a brake to same.

In, order that the invention may be more clearly understood, the following diagrammatic draw.- ings, approximatescale 1 2, will nowbe explained in detail. In the drawings:

FigureI illustratesaplan projectionof'a tonearm equipped. with a gramcphone. receiver or pickup, in accordance with, the. invention Figure. II is a vertical section of the same, as well asv of. its. moving, arrangement, 7, through. line AB= of Figure III.

Figure III is a diagrammaticrepresentation of the movement of the devicewith relationto a record. 7

n Figure I the sound-receiving or pickup devicev is shown as an arm,3 supporting the receiver or pickup 4. carrying needle In the figure, the structure is assumed to be transparent inorder to show the mounting arrangements. v

Arm; 3' i's mounted on horizontal shaft 6', on which it is freely rockable,

This rocker arm shaft 6 is in turn fixedto a plate or elongated piece 1,, of suitable cross-section and conveniently bent, one end of which is provided. with asocket 8.- for a vertical rotating shaft, the other end-being: equipped with aguide or slot 9* extending,in-alengthwise direction.-

This lengthwise slot 9 is engaged by a pivot-l6, fi-xedi to the supportinggbaseof theentiredevice, said pivot serving as fulcrum point and atthe same: time permitting, lengthwise sliding motion.

A crank-shaped part H includes arms orshafts l2:and l3, vertically placed and parallelv to one another at aproper distance, arranged inopposite directions; 7 I

Shaft 13, is housed: within fixed bushing l4, within which itmay freely turn, said bushing serving as support and turning: centerto part I I.

In. turn, shaft I2; is housed in biishing 8,-servingtosupport piece I and arm 3. I

A spiralspring t5, acting on shaft [3 urges the arm in thedirection indicated by the arrow, thatis to-say, towards the center offthe record.

FigureII shows a vertical section of the device (when same isin position A --B QiIFigureIIl') the essential parts. of' the invention having. been shown: in brokenlines.

Piece Llwith its. shaft 6 serving as a rocking support to arm 3, its/bushing BZ'serViiig'ia's'independent. supporting, base and swivel" 9' serving as a guidtditsslidihi motion.

This swivefis engaged on fixedpivotlfi', winch serves asa turning spindle for the angular movement of the arm; v H

Crankrsliapedipice llfwi'tlisl'iaft' I 2 servinfs rotating support. to'rpi'cei T, aridlshaft l 3 serving as its own support" andturningciiter; Y

And. fixed bushing, 14 housing shaft 13'" and serving assupportingbase for thewhfol'e" assemblyispring,linemen-shawls: V

The, diagram of Frg'ureIIrshowsa gramophone recording licentuedl on: shaft. 2. concent1-'iccir cles, suitably spaced, represent the recording groove spiral.z

I, the arm being at rest with regard to the record. l5, |0--5" and lll' indicate the figure axes of the same arm in its several positions over the record.

The repetition, in broken lines, of the receiving device or pickup over line A-B shows the position same occupies when the needle reaches the more or less central groove of the recorded zone. Its axis A-B forms with the center line l02 an angle a (in this case approximately which is the angle arbitrarily chosen to serve as a basis for the calculations of the drawing in order to establish the position of the third turning center [3. This angle is the one corresponding to the angle of the vibratory shaft of receiver or pickup 4 with the axis of arm 3. i

This 20 angle having been taken for a, its complementary angle 1) is fixed at It follows that the geometrical place of the vertices of all the '70-angles whose sides may pass through points l0 and 2, corresponds to the arc of circle l052, the center of which is at 16.

Once the correct situation of three points such as 5' 5" 5" (for example) has been established,

the position corresponding to [2, l2", I2 is obtained by transferring fixed distance 5-l2 over their respective radii centered at 19.

And once the positions I2, 12 and I2 have been fixed, the position of shaft l3 corresponding to the center of the circle passing through those three points, is also fixed.

Operation The operation of the device is simple, being automatically brought about through the displacement of the needle through the groove, as is usual.

In fact, spring [5 tends to cause the rotation of the arm towards'the center of the disc or record, but the receiving needle engaged in the groove acts as a brake on same, permitting only the angular movement of the arm as the spiral groove progresses. In this manner, although the needle may be more strongly supported on the inside edge of the groove, the automatic movement of the arm takes place as controlled by the spiral of the groove.

Arm 3 is pivoted on shaft 6 (for vertical movement) but in a horizontal sense its lengthwise axis always coincides with that of'swivel 9.

Crank-shaped part i I, although serving to support the entire assembly, does so fioatingly, without hindering its free angular movement.

The'angular position of the arm axis is thus determined only by points it] and 5: and as Ill is a fixed point, the angular movement of the arm is exclusively subordinated to the position of 5, i. e., that of the needle-point.

The needle on being placed in the first groove same will occupy position 5' and the arm will be placed at 5'lll.

As the record turns, the needle will be laterally displaced, first coming nearer to, and then going farther from axis A-B, i. e., angle 5l05" will at first diminish and then increase up to 5"- llI--5".

In agreement with these changes of the angle with regard to vertex II], the variation of the angle with vertex l3 will also be brought about, obliging shaft l2 in its successive displacements to travel through an: |2'|2f-l2'.

The arm will consequently be slidingly displaced in one or the other-direction (its values being a function of the variations of the cosine of the angle at l3) obliging the needle to keep it self practically over are 5'5-5"'.

In view of the fact that from any point of this are 5-55 the inscribed angle, its sides passing through points it and 2, is always 70, and as angle a is also constant H fixed at 20, the value of the angle formed by the vibratory shaft with the radius of the record, corresponding to the point of contact, is constantly In other words, the vibratory axis of the receiver or pickup occupies with regard to all of the grooves the position of a geometrical tangent, thus being a true repetition of the recording operation.

The position of shaft I3 is not critical; it is a function of the position of point l0 and its distance from 2 and the angle may b changed to suit. Those employed have been chosen arbitrarily.

Consequently the structure, shape and coupling arrangement of the essential parts of the invention are the sliding support and the crank support, as well as the actuating spring. These parts may be changed indefinitely, mechanically, structurally and artistically without thereby modifying the essential nature of the invention.

A structural modification would be, for example, to revert the position of pivot, I0 and fix it to the sliding part i. The guide slot would then be fixed outwardly.

The operation as resulting therefrom would be the same, for instead of the mobile slot sliding over th fixed pivot, a mobile pivot would slide over a fixed slot. In that case, a curved slot would have to be calculated for each solution.

In the same manner, the shape of the guideslot may be changed in order to free the arm of adjustment, which is rigorously precise according to the position of the needle, when same is no longer resting in the record groove.

It is considered unnecessary to enter into details regarding such changes of shape, owing to the fact that same do not alter the essential nature of the invention as defined in the following claims.

I claim:

1. In a gramophone, the combination, comprising a support, a turntable rotatable on the support, a bushing on the support, a crank member including a horizontal portion and upwardly and downwardly extendin arms, said downwardly extending arm being rotatable in said bushing, a second member of longitudinally stepped crosssection having means at one end for receiving the upwardly directed arm of said crank member and provided at its opposite end with guide means adapted to engage a pivot pin on said support, a pick-up arm adapted to carry a needle for record engagement, a horizontally disposed transverse shaft for pivoting said pick-up arm to the upper portion of said second member to permit the tone arm to respond to vibrations in a vertical plane, and a coil spring having one end anchored to the support and its other end anchored to the downwardly extending arm of said crank member and tending to rotate said crank toward the axis of th turntable.

2. In a gramophone, the combination, comprising, a support, a turntable rotatable on the support, a crank member including upwardly and downwardly extending arms and having said latter arm pivotally mounted in the support, spring means for biasing th crank member to urge its upwardly extending arm toward the axis of the turntable, a second member having a socket at 6 one end for pivotally receiving the said upwardly Number Name Date extending arm, cooperating guide means respec- 2,006,605 Putnoky July 2, 1935 tively on the end of said second member opposite 2,025,300 Mueller Dec. 24, 1935 the socket and said support, and a pick-up arm 2,192,464 Yasuda et a1 Mar. 5, 1940 connected to said second member by a. horizontal 2,303,619 Davis Dec. 1, 1942 pivot. ENT

JOSE SOLER MARTiN. FOREIGN PAT S Number Country Date REFERENCES CITED 676,429 France Nov. 28, 1929 10 328,222 Great Britain Apr. 22, 1930 g f fiyg f i fg are the 386,851 Great Britain Jan. 26, 1933 UNITED STATES PATENTS Number Name Date 1,866,403 Elmer July 5, 1932 15

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