US1817094A - Production of phonograph styli - Google Patents

Description

Aug. 4, 1931. MOORE 1,817,094

PEDDUCTION OF PHONOGRAPH STYLI Filed Jan. 22, 1929 2 Sheets-Sheet l INVENTOR 'MTW &2 a 4 TORNEY Aug. 4, 1931. s, MOORE 1,817,094

PRODUCTION OF PHONOGRAPH STYLI Filed Jan. 22, 1929 2 Sheets-Sheet 2 INVENTOR TTORNEY Patented Aug. 4, 1931 Ullffil? STATES Parser DFFECE SHERWOOD T. MOORE, OF ORANGE, NEW JERSEY, ASSIGNOR T THOMAS A. EDISON, IN- COR-EORATED, OF \VEST ORANGE, NEvV JERSEY, A CQRPOBATION OF NEW JERSEY PRODUCTION OF PROMOS-RAPE STYLI Application filed January 22, 1929.

My invention relates to the production of phonograph styli and particularly to the production of such styli as are designed to track and reproduce so-called hill and dale records wherein the undulations corresponding to the sound waves are formed on the bottom of the record grooves, and where the grooves of such records are very minute, that is, of extremely small depth and width. In a well-known make of disc phonograph record of the hill and dale type, the record grove has a pitch of 1/150, that is, the record disc has 150 threads per radial inch, the bottom of the groove in transverse cross-section has the form of a circular arc and the groove has a maximum depth of about .0017 and a maximum width ofahout .006'6, the grooves in the master of such a record being cut by a style with a circular cutting edge which has a diameter of .008. The stylus employed for tracking and reproducing such a record is made from a suitable piece of very hard longovearing material, preferably diamond, and comprises a cone-shaped portion having a rounded end designed properly to fit freely in and track the record groove, such tracking end usually being formed as part of a sphere having a diameter a of .0075. The spherical tracking end portion of such a stylus is formed by a grinding operation, usually carried on in an automatic grinding machine, wherein the pointed end of the conical portion ofthe stylus is maintained in engagement with a fiat surface of a rotating lap charged with diamond dust, while the stylus is at the same time rotated about its axis and also oscillated about the point where is engages the lap.

. In the case of a hill and dale record of the character described but in which the record groove has a pitch materially less than 1/150 the m aximum depth and width of the groove are necessarily considerably less than 5 in the case of a 150 thread record and it is also necessary in order to obtain a groove of suflicient depth topermit proper tracking thereof by a reproducing stylus, that the bottom of the groove in t. vrse cross-section be formed rcular J example, in t or a hill and dale Serial No. 334,152.

record of this character having 450 threads to the radial inch, the maximum depth of the record groove is about .0005, the maximum width thereof is about .002 and the groove in the masters of such records is cut with a style having a circular cutting edge which is about .003 in diameter. It is impracticable, however, to employ for tracking and repro ducing recor ls having such extremely minute grooves, the usual form of stylus having a rounded or spherical tracking end portion of such size as properly to fit the grooves, for such aspherical tracking portion would of necessity be formed on such a small radius as to be the equivalent of a point and would in fact be so sharp that in tracking the record groove it would cut into and gouge the record to such an extent as to soon render the record useless. Moreover, such spherical tracking end portions of conical-shaped styli of diamond or the like designed for use with a minute record groove of the form just referred to, are of such small dimensions that attempts to form the same by the usual grinding operations above described invariably result in the breakage of such end portions.

The principal objects oi my invention are to provide a new, improved and practicable method for producing phonograph styli with tracking end portions adapted to fit very minute record grooves of the character referred to, and which are of such term that they will not cut into the material of the records in tracking the grooves thereof; and to provide improved apparatus for effectively carrying out such method.

Generally described, my improved method consists in grinding the tracking end portion of a stylus to form by effecting tracking movement of the stylus in the groove of a grooved lap formed of or charged with abrasive material and simultaneously effecting relative rocking movement of the lap and stylus preferably in the direction of said groove. The groove of the lap is preferably spiral and such trackir movement of the stylus in said groove is -rably effected by rotating the h o while he stylus is maintained in engagement with the groove and the relative rocking move- 7 ing of the groove of the lap by the stylus is preferably substantially uniform in extent and rate and is preferably effected by rocking the stylus.

Other objects and features of my invention will be hereinafter more specifically described and claimed.

In order that my invention may be more lea ly unde stood a tent on i d rected to ,,tl e

Fig. 2 is a view in side elevation looking.

from the right in Fig. 1; anenlargedl detailed view in side elevation ofthe. stylus supporting means of the machine shown in Figs. 1 and Q and of parts associated therewith;

4 is a diagrammatic plan view illustrating the feeding movement partaken of a; stylus being formed by the use of the machine shown in Figs. 1 to 3 in tracking a grooved lap actuated by such machine, the stylus being shown in the position it occupies in an outer and an inner convolution of such groove (the other convolutions of the groove being omitted) and with its tracking portion shown in horizontal cross-section in sub stantially the ultimate desired form thereof, the stylus and also the inner and outer con- Yolutions of the groove of the lap being great ly exaggerated inv size; h

"Fig.5is a view similar to Fig. 4 but with that portion of the inner convolution of the groove of the lap shown in Fig. d as engaged by the stylus, superimposed on the ,cor responding portion of the outer convolution of such groove; Y r

Fig. 6 is'a greatly enlarged view inside elevation, partly broken away, of stylus provided with tracking portion produced in accordance with my invention, looking toward one side such tracking portion;

Fig@ 7 isaview sim to Fig. 6 but look ing toward an end oi the tracking portion of'the' stylus; i V

. Fig. 8 is an enlarged fragmcntal sect al view of the grinding lap taken transvesely of the groove therein, showing a stylus 6T ga-glngv suchgroove; 7

i F 9.is a view similarto 8 of a record with-whicha stylus hav n the chin g portion formed in accordance with my inven tion isdesigned to be used and showing the tracking portion of such a stylus in engagement with the groove of therecort, the dimensions of the record groove, however, being shown on a larger scale than the groove of the lap shown in Fig. 8 and Fig. 10 is a viewsimilar to Fig. 9, th tion, however, being taken lengthwise record groove.

The apparatus illustrated in Figs. 1 to 3 for carrying out my improved method comprises a substantially rectangular casing 1 on which is rotatably mounted a turntable 2 for carrying a lap A, said turntable being applied to the upper end of a vertical shaft 3 which is journaled in a suitable bearing 4; with which the top of the casing is provided. An arm 5 comprising a supporting means for styli the tracking end portions of which are to be formed by the machine, is. mounted for swinging movement about a fixed axis and also for movement in the direction of such axis by being secured to a rod 6 which is rotatably and slidably mounted in spaced vertically aligned bearings 7 and 8 with which the top and front wall of the casing l are provided. The arm 5. comprises a lower horizontal portion extending rearwardly from the rod 6 within'the casing 1, a vertical portion 5 eX- tending upwardly within the casing from said horizontal portion and through an opening 9 in the top of the casing, and a horizontal'upper end portion 5 extending forwardly from the vertical portion 5. An attachment 10 is removably secured to the upper end of arm 5, by the 'turnable collar 10, the construction and arrangement being such that when said arm is swung about its pivotal axis the attachment 10 will be moved over and across the turntable 2. The attachment 10 is similar to a well-known form of phonograph reproducer for playing hill and dale records except that the usual flexible diaphragm of the reproducer cup is replaced by a stiff metal disc 11. This attachment comprises a member in the form of a floating weight 13 which carries a stylus lever and which is connectedto the cup wherein disc 11 is mounted for lateral and vertical movements relatively to the cup, by means of the pivotal and spring mounting 14, such movements of said weight being limited by the coaction of'a pin 15 secured to the weight with a loopor stirrup 16 secured to the cup and into which said pin extends. The stylus lever 17 is removably mounted at 18-011 the weight 13 for pivotal movement about a horizontal axis, said lever having a stylus B to be formed secured in one end thereof and having its other end flexibly connected with the disc 11 by a link prefcrably in the form of a cord 19, which extends through a suitable opening provided in said weight.

. A horizontal shaft 21 is mountedin suitable fixed bearings provided onthe. rear wall of the casing 1 adjacent the top of the latter, and is adapted to be driven by an electric motor or other suitable source of power asby means of a pulley 22 secured to the shaft and a belt 23 passing over said pulley. The shaft 21 also has three additional pulleys 24, 25 and 26 secured thereto. Apulley 27 is secured to the turntable shaft 3 and the latter and thereby the turntable 2 are adapted to be driven from the shaft 21 by a belt 28 passing over the pulleys 24 and 27 and two intermediate idler pulleys 29.

Suitable automatic feeding means is provided for swinging the arm 5 about its pivotal axis to thereby move the attachment 10 across the turntable 2 and the disc-shaped lap A removably mounted on the turntable. As shown, this automatic feeding means comprises a segmental rack 30 formed on one end of an arm 31 which is pivotally mounted at .32 adjacent its other end on a bracket 33 secured to the rod 6, and a worm 34 with which the rack 30 normally engages. The worm 34 is secured to a horizontal shaft 35 which is journaled in fixed bearings 36 and has one end extending outwardly through a side wall of the casing 1. A spring 37 fixed at one end to the arm 5 and at its other end to the arm 31 at a pointintermediate the rack 30 and the pivot 32, tends to hold the rack 30 always 1n engagement with the worm 34. The shaft 35 and the worm 34 carried thereby are driven from the shaft 21 by a belt 38 which passes over the pulley 25 on the shaft 21 and a second pulley 39 secured to the outer end of said shaft.

The vertical position of the support or arm 5 and of the stylus carrying attachment 10 is controllable by suitable manually operable means, such as the cam 40 which is pivotally mounted at 41 on the upper end. portion of the rod 6 above the bearing 7 and is provided with an operating handle 42. lVhen the said handle is moved to the dotted line position shown in Fig. 3, the cam 40 coacts with the upper surface of bearing 7 to move the rod 6 and thereby the arm 5 and attachment 10 upwardly to a. raised inoperative position, in which movement the floating weight 13 will be raised by engagement of the bottom of loop 16 with pin 15 and thereby lift the stylus'B from engagement with the lap A. \Vhen the arm 5 and rod 6 are thus raised, the spring 37 will of course act to hold the rack 30 in engagement with worm 34. I provide suitable means, however, whereby the rack 30 may readily be raised from engagement with worm 34 against the action of spring 3'? so as to permitthe arm 5, when in said raised inoperative position, to be swung about its pivotal axis and the stylus B brought to any desired position over the lap A. This means as shown consists of a. stirrup 44 pivotally mounted on a collar 45 fixed to the rod 6, such stirrup having an arm 46 extendin outwardly and upwardly through an opening in the front wall of casing 1 and also having rearwardly extending curved leg portions 47 in the ends of which is fixed a pin 48 arranged to coact with the en d portion 31 of the rack arm 31. The handle or arm 46 is located adjacent the handle 42 of cam 40 so that it may readily be engaged and moved by a finger of the hand of the operator used in moving said cam. When thus moved to the dotted line position shown in Fig. 3, the stirrup 44 will of course be moved about its pivot and the pin 48 will coact with the end portion 31 of the rack arm 31 to move the latter to the dotted line position shown with the rack 30 disengaged from the worm 34.

Vhen the handle 42 is raised to vertical position, rod 6 and arm 5 and of course the parts carried by the same, move under the action of gravity to their lowered operative position, as shown in full lines in Fig. 3, and are supported in such position by an eccentric or cylindrical cam 49 which is disposed a suitable distance below the pivoted end of the arm 5; the said cam being fixed to a horizontal shaft 50 which is ournaled in spaced bearings 51 provided on the casing 1 and which extends outwardly through one side wall of the casing. A pulley 52 is applied to the outer end of shaft 51, and the latter and cam 49 are adapted to be driven from the shaft 21 by a belt 53 which passes over the pulleys 26 and 52. I preferably provide suitable means whereby rod 6 and arm 5 and the parts carried thereby, when in lowered operative position, are adjustably supported by the cam 49. As shown this means comprises an arm or member 55 pivotally con nected at one end to a bracket 56 on the arm 5 and disposed between the latter and the cam, a spring 57 which is connected at its ends to the arm 5 and member 55 and which constantly tends to move the latter towards said arm, and a screw 58 which is threaded through a lug 59 provided on arm 5 and which when turned coacts with member 55 at its free end to adjust the position thereof with respect to arm 5.

The construction and arrangement are such that when the arm 5 and rod 6 are lowered to operative position in which they are supported by the cam or eccentric 49 (through the engagement of the latter by member 55) cam 40 will be spaced somewhat above bearing 7 whatever the angular position of the eccentric, and weight 13, by reason of the engagement of stylus B with lap A, will be moved upwardly to a position in which pin 15 is raised from engagement with the bottom of loop 16, all as shown in full lines in Fig. 3. If the eccentric 49 is now rotated this will obviously effect vertical reciprocatory movement of arm 5 and thereby similar movement of the relatively fixed parts of attachment 10 towards and away from lap A. During such rectilinear reeiprocatory movement of arm 5 and the relatively fixed parts of attachment 10, the said parts will, because of the connection 14, move vertically with respect to the floating weight 13, which will then act to maintain the stylus B in engagement with lap A; and at the same time, because of the flexible connection 19 between stylus lever 17 and plate 11, a slight ver ic l r cking mo eme ill b impar ed t said e nd ty us. ab u th Pi t 1.8, The limits of theroclrin-g movement so imeart 9 th stylus and ylu le e a i a e in u a d dotted lin in F she arrangement is alsorpreferably such that the rocking movement imparted to the stylus B will be substantially in the direction of any portion of the groove of lap A with which the stylus may he engaged. In the reciproca- Y v me ts o rm a th l ti e y linen parts of attachment 1.0 effected lay rota: ti-on of canrll) when said arm and parts are in their operative positions, the vbottom of loop 16 should never engage pin 15 as this woulidresultin disengaging stylus B from lap Aand also interrupt the desired rocking movement of the stylus; and this result may be n r d'in any by p ep y dj t n the memberfit with respect toarm 5 by means of screw 58. This adjustable feature is important as different laps. which may be used with the machine, as well .as the styli to be formed and the levers for such styli, will vary somewhat in their dimensions. For a given speed of rotation of the driving shaft 21, it. is apparent that the reciprocatory movement of arm 5. and the rocking movement of stylus lever 1? resulting from the rotation of cam 49v as above described, will each at a uniform rate. The extent of th e movem ll the b un form-a d while of course dependent, in part at least, on the eccentricity of cam 49, is preferably small; the extent of the reciprocatory movement of arm 5 being represented by the dis.- tance between. the horizontal lower portion thereof and the, dotted line and the limits of the rocking movementof stylus lever 17. being indicated bythe full and-dotted line positions thereof (Fig. K

The lap A is preferably in the form of a metal" disc or plate having a spiral groove G therein and charged with a suitable finely divided abrasive material, preferably diamond dust. To facilitate the application of th diamond dust to the lap,'the same is mixed with a suitable carrier, prefe ably either olive oil or machine oil. The pitch of groove G is of little importance except that it should be such that a stylus tracking the groove will be fed thereby'across-the lap at the same rate M which the arm 5 and attachment 10 are moved transversely of the turin tab 2, in he pe a on i he ma ine hv thefeeding means comprising rack 30 and worm 3a. For forming the tracking portions of stylidesigned for reproducing hill and dale" records such as hereinbefiore described and having 450 threads per radial inch, 1 pres fer to usea lap A. in which the groove Grhas a pitch of a unifo m dth of ap- P X iI e -dy a a uni Qrm ep h ,app oxlm tely 1 a d i bs iellv sem -sma l an v e sw e s-sea, it

will be noted that the g-rooveG is about three times as deep and about one-half again as wide as the groove of such a 450 thread record at the points in the-latter of maximum depth and width, although the bottoms of both such grooves in transverse section, are formed on c rcular arcs of the same rad us. The groove-E of lap A, as shown in the drawings, is supposed to represent a spiral groove depth and width of the grooves of the records with which the sty li to be formed are designed to be used.

, Informing the tracking portion of a stylus B having a conical-shaped portion C, in QC? cordance with my invention and with the apparatus described, the procedure is preferahly as follows: Thestylus B is preferably permanently mounted in one end of a stylus lever 17, which is to eventually constitute a part of the reproducer of a phonograph, with its conical portion C projecting from the lever. T he lever 17 is then pivotally mounted at 18 on the floating weight 13 of attachment 10 and connected to the disc 11 of the latter by the flexible cord or link 19, and said attachment is secured in proper position on the free end of arm 5, by the collar 10. The arm .5 is brought to a position corresponding to that shown in full lines in Fig. 1, in which the stylus B will be directly above the outer convolution G of the groove in lap A and is then lOWBIQd/liQ operative position, by moving the cam {l0 to the full line position shown in F 1g. 3, to engage the pointed end of stylus BWith such outer coI Volution, while the rack 30 is at the same time permitted to engage worm 34-. Assuming that the shaft 21 is being rotated at constant speed, which is the case in the normal operation of'the machine,

the arm 5 will'now be slowly moved about the axis of rod 6 to the dotted line position thereof shown in Fig. 1 and cause the end of the stylus to track the groove G of the rotating: lap A to the inner convolution G thereof, while at, the same time vertical rocking movement uniform in extent andrate and substantially'in the direction of the groove, will be imparted to the stylus, The arm and attachment 10 are then raised to inoperative position, corresoonding to the uppermost 12L dotted line positions thereof showniin Fig. 3, by moving the handle 42 to horizontal position, to thereby disengage the stylus from the lap and re ch 30 is i l 3% by actuating the yo'lreor through handle, 46, thereof. The oper just described are repeated to cause the stylus to retrackthe groove G or any e ec-teg portion or portions thereof as in i nec ssary to grind the sir n portion of the stylus to the desired form. Usually it is found that the tracking portion of the stylus will be ground to the desired form after being fed across the lap or portions thereof from four to twelve times.

The tracking portion of the stylus produced in the manner described above, designated by reference character T in Figs. 4 to 10, is in the form of a narrow elongated shouldered shoe or runner the long dimension of which is in the direction of the groove of the lap. Referring to Figs. 4 and 5, in which D represents the axis of rod 6 about which the stylus B moves in tracking the groove G of lap A, and'EE represents the are on which said stylus moves in tracking said groove from the outer convolution G to the inner convolution G thereof, it will be seen that the angular position of the stylus with respect to said groove constantly changes as the stylus moves towards the inner convolution. Because of this the end portions of the tracking shoe or runner T will be ground narrower than the central portion thereof, and such central portion itself will be ground somewhat narrower than the width of groove G. Accordingly the shoe or tracking portion T as. finally formed, will fit freely without bindinggin both the inner and outer convolutions G and G, as Well as all intermediate convolutions. This is well illustrated in Fig. 5, wherein the inner convolution G of the groove in the lap is represented, by dotted lines, in the position it would occupy if moved about the axis D in fixed relation to a radius from axis D to arc EE, until the portion thereof shown in Fig. 4 as engaged by shoe T is superimposed on the corresponding por tion of the outer convolution G. The ends of the shoe consist of portions of the surface of the cone G into which the surfaces of the sides of the shoe smoothly merge. The bottom of the runner or shoe T, in the direction of its length, is formed on a fairly fiat arc, due to the slight rocking movement imparted to the stylus as it tracks the groove of the lap A; but the radius of said arc is such that the toe and heel at the ends of the said bottom of the shoe T will, when the latter is tracking a 450 thread record, clear all portions of the bottom of the record groove. To illustrate this, a stylus B having such a shoe or runner T is shown in Fig. 10 as tracking a portion of the groove K of a 450 thread record R which represents sound waves of substantially the highest frequency which are ever phonographically recorded, or in other words a portion of such a groove in which the hills and dales are the steepest which occur.

While the contour of the sides and bottom of the shoe T, at any transverse cross-section of the latter, is substantially a smooth curve, it is not circular, for the upper portions of the shoe during the forming thereof in the manner described, are ground to a thickness somewhat less than the width of the upper portions of the groove Gr of lap A. Accordingly, when tracking the groove of a 450 thread record of the character described, said shoe will generally ride on the bottom of such groove and clear the top side edges thereof. This is illustrated in Fig. 9 which shows the shoe T engaging the groove K of a 450 thread record R, said figure being a sectional view of a fragment of the record taken transversely of such a groove where it is of substantially maximum depth.

The shoe or tracking portion T of a stylus formed as described will wear away the side walls of the curved record grooves but very slowly, for in tracking such grooves it will have an extended bearing pared with the usual forms of styli heretofore employed.

hen the operations necessary for farming the tracking portion of a stylus have been completed in the apparatus described, the

stylus lever 17 in which the stylus is fixed may be removed from the apparatus for assembly in a reproducer, and replaced by a like lever having mounted therein another stylus to be formed with such a tracking portion.

It is to be understood that the apparatus and method herein shown and specifically described are subjected to many changes and modifications without departing from the spirit of my invention or the scope of the appended claims.

Having now described my invention what I claim and desire to protect byLetters Patent, is as follows:

1. Apparatus of the character described comprising a rotatably mounted spirally grooved lap, means for rotating said lap, a stylus support, said lap and support being arranged for relative feeding movement to cause a stylus carried by the support to track the groove of the lap when the latter is rotated, and means for effecting relative rocking movement of said lap and stylus as the latter tracks said groove, substantially as described.

2. Apparatus of the character described comprising a rotatably mounted spirally grooved lap, means for rotating said lap, a stylus support, said lap and support being arranged for relative feeding movement to cause a stylus carried by the support to track the groove of the lap when the latter is rotated, and means for effecting rocking movement of said stylus substantially in the direction of said groove while tracking the latter, substantially as described.

3. Apparatus of the character described comprising a rotatably mounted spirally grooved lap, a stylus support adapted and arranged to be fed transversely of said lap when the latter is rotated to thereby cause a stylus carried by the support totrack the d-i cation towed-s swing ng gi'db'il; (if-"the lap, hie-ins fe eflecting tiziliy the dii'e'ct'ien of said grcsove while tracking the Iatt eQ-SUB tdntiaII-Y as described.

4-; ii piifzims' cf the cl macterdesefibed; a fotafiszbly mounted "spirally gfdc'ii ed la means for mating the same, a siiifij-ieit mounted for feeding moveme .t

sfii'd with 'i'epe'c't to and whereby said membf is: adapted to be suppefte'd by said cam-,- sub stziiitialiy as described.-

8i Inapparatus (if the character described, aturnt-abie rotatzib'le about 2; 'v'eitic'zil axis, a ineiil'be'r' mOL'int-ed for swinging movement ab'tiut-Ei veitic'fil axi cross said tiirntable 21nd also fOrhioveinent in she direction of its said axis, means for imparting such s'\ vinging movement to six-1d member when said turntable is rotated; iifloating Weight connectedeinem; in ii -11ec oii' 1d t effeet'ii such swinging ind'i e 6f o erator, siibsmnti-ei deseribea;

r vertical axis a-efos's saidm iimbieaiid.

mei nbei' when the tiii 'i'itzible is f at we (mafia saidig'seiid 7 member when therlattef is n ndrml 0pmac'iiiii f'ofitiible about iis;

Tire

11. In apparatus of the character described, a lap support rotatable about a fixed axis, a member mounted for swinging movement about a vertical axis and also for vertical movement towards and away from said support, a floating weight connected to said member for limited relative movement, a stylus lever pivoted on said weight and having a flexible connection at one end with said member, a rotatable cam adapted to support said member in the lowered position thereof in which said stylus lever will be in operative relation to said support, means for rotating said cam when said support is rotated to thereby ei'i ect limited movement of said member towards and away from said support, feeding means for imparting swinging movement to said member when said support is rotated, and means for moving said member and thereby said stylus lever to raised inoperative positions with respect to said cam and lap support respectively, substantially as described.

12-. In apparatus of the character described, a. spirally grooved disc lap mounted for rotation about a given axis, driving means for rotating said lap, a support carrying a stylus and mounted for swinging movement across said lap about an axis substantially parallel to the axis of said lap to cause the stylus to traverse said lap in tracking engagement with the groove therein, means for imparting such swinging movement to said support when said lap is rotated, and means actuatable by said driving means and coacting with said support for effecting rocking movement of said stylus back and forth substantially in the direction of said groove while tracking the latter, substantially as described.

13. In apparatus of the character described, a spirally grooved disc lap mounted for rotation about a vertical axis, driving means for rotating said lap, a stylus support adapted and arranged to be fed across said lap when the latter is rotated to thereby cause a stylus carried by the support to track the groove of the lap, and means actuatable by said driving'means and coacting with said support for effecting a substantially vertical rocking movement of said stylus substantially in the direction of said groove while tracking the latter, substantially as described.

This specification signed this 8th day of I January, 1929.

SHERWOOD T. MOORE.

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