US2418212A - Phonographic stylus - Google Patents

Description

Patented Apr. 1, 1947 UNITED STATES PATENT OFFICE PHONOGRAPHIC STYLUS Fred E. Williamson, Chicago, Ill.

Application July 3, 1943, Serial No. 493,387

2 Claims. l

This invention relates to phonographic styli and particularly to such styli for use with laterally cut phonographic records. v It is generally recognized that the attainment of the desired reproduction of recorded sound is in a large measure dependent upon the proper functioning of the phonographic stylus and proper cooperation thereof with the modulated record groove, and although many other factors exert a vital influence on such quality and fidelity of the reproduced sound, the `functioning of thev stylus clearly represents the most troublesome and frequently encountered source of objection in this regard; and to improve the functioning of phonographic styli and the cooperation thereof with laterally modulated record grooves so as to attain improved quality and fidelity of reproduction is the primary object of this invention.

The difliculties encountered in attaining the desired quality and delity of phonographic reproduction have centered in a large measure about the closely inter-related problems of surface noise, distortion of the reproduced sound, and wear of the record gro-ove and the stylus, which wear, of course, aggravates such surface noise and produces additional distortion. Attempts have, of course, been made to obviate or reduce such surface noise, distortion, and Wear of the record groove and stylus, as for example through the use of what have been termed "so1t styli made from nbre or made from steel so as to be vertically or universally flexible. Most of such prior expedients have, however, resulted in excessive reduction of the output oi the reproducer, due to losses of mechanical energy in the stylilbetween the record-engaging tip and the shank of the styli which is rigidly mounted in the mounting socket of the phonographic pickup mechanism. The use of such conventional soft styli has also been considered to be objectionable by reason of the direct acoustic radiation which is inherent in the operation of such styli, and for the further reason that such soit styli often tend to resonate to the predominating frequency of the surface noise, thereby to aggravate rather than to correct this undesirable condition.

Surface noise may be due in some'instances to imperfections in the record groove as originally produced, or to other causes, but it is generally conceded that the primary cause is the presence of small particles, such as dust, grit and the like, disposed in the record groove. As a practical matter, such particles usually consist of small pieces of the record material Which are cut orworn away as an incident to the use of the record, and because of this it is clear that by avoiding such wear and cutting of the record, it is possible to reduce surface noise to an unobjectionable level, while at the same time the distortion normally occasioned by such wearI will 'oe correspondingly reduced. One of the primary causes of such wear and cutting of laterally cut record groove has been recognized as being due to the varying effective width of such grooves, which results in narrow or pinch sections where the modulations of the groove extend at an angle to the direction of the unmodulated groove. Thus there are two such pinch sections in the groove for each cycle of the primary recorded frequency, and as these pinch sections engage the tip of the stylus, the sides of the groove exert upward forces on the tip so as` to tend to raise the stylus and the pickup mechanism in which it is mounted. Ordinarily, however, the inertia of the stylus and its pickup is relatively great, and as a result, the upward forces exerted on the tip by the sides of the record groove are resisted to such an extent that the tip of the stylus gouges into one or both lsides 'of' the groove, thereby to wear away the desired modulated surfaces of the groove and produce fine particles of record material which thereafter function to produce additional undesired surface noise. The wearing of the modulated Sides of` the groove is highly objectionable since it results in distortion of the sound at such worn portions of the groove; and in addition, the tip of theV stylus is worn away quite rapidly in the course of such gouging of the record groove, thus necessitating frequent changes of the styli. The pinch eiect or pinch sections also have caused distor` tionlby reason of the fact that the upward forces exerted on the tip by such pinch sections have in the past thrown the tip upwardly with such frequency and to such an 4extent that the tip was often out of contact with one or both of the Walls of the groove. When this occurs the tipY isv free and uncontrolled as to its lateral movements'` with the result that distortion is introduced in the reproduced sound.

As hereinbefore pointed out, the action of such Pinch sections in the record groove incausing the stylus to'gouge and Wear the groove has here.-V tofore been recognized, and phonographic Styli have been proposed which in theory, at least, might tend to obviate this objectionable result, for such proposed styli have incorporated provision for resiliency or compliance oi the tip of the Styli in a, generally vertical direction so as to enable thetip to move up and down in conform:

' ord groove.

3 ity with the effective width of the modulated rec- Such prior expedients have, however, neglected other vital considerations which have a bearing upon the attainment of proper operation and reproduction, as for example` the resonating characteristics of the styli, and the tracking ability or characteristics of the styl'i. Thus, with regard to the tracking ability of such styli it is known that a sudden increase in the recorded'amplitude of the sound and particularly'in the case of a loud bass note or sound following a sequence of high frequency sounds, is represented by a sudden change and increase in the steepness of the wave front recorded in the modulations of the record groove, and where a stylus is relatively stiff in a lateral sense, it often happens that such a sudden increase in the steepness of the wave fronts of the record groove will impart suchupward and lateral forces to the stylus that the stylus will be thrown out of the portion'ofthe sound groove with which it is then engaged and will come to rest in another portion of the sound groove.

duction and causes damage to the record as well asto the stylus. jump from one groove portion to another, it is said to -lazk tracking ability or to have low tracking ability. This problem has long been encountered inthe art,and to increase the tracking ability of many prior styli it has been customary to soA form such styli as to incorporate lateral compliance or flexibility therein. The extent orV amount `of such lateral compliance necessary to avoid lateral jumping of the stylus from one portion of the groove to another has been heretofore determined, and is well understood in the art, but in the past such lateral compliance in phonographic styli has been treated as an independent `function or action, with the result that simultaneous elimination of obiectionable resonance, the gouging action and lateral jumping o f lthe stylus has heretofore been unobtainable. Accordingly, it is a further object of this invention to enable elimination of such objectionable resonance, distortion. the gouging action, and lateral jumping of phonographic styli to be attained, and objects related to the foregoing are` to attain this result through the use of a novel form in the styli,V to enable this result to be attained with phonographic styli which are adapted for use in and cooperation with most conventional phonographic pickup apparatus, and to enable this result to be attained in such a manner that vwear on the tip of the Styli and upon the record groove are minimized, to thereby reduce surface noise to an unobjectionable level andl prolong the useful life of the record and the stylus.

In phonographic styli as heretofore constructed the manner in which vert" cal and lateral compliance has been attained has resulted in i deformation of the same portions of the styli in dire :tion to be attained by a bending action whileV the compliance in the other direction is attained by torsion of a,predet.erminedpart of the styli,

This is. of course, undesirable, for it destroys the continuity of repro- Where a stylus thus tends tov Other and further obects/of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment and the principle thereof and what I now consider to be the best mode in which I have contemplated applying that principle. Other embodiments of the invention embodying the same or equivalent principle may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims. Y

In the drawings;

Fig, l is an enlarged side elevational view of a phonographic -stylus embodying the features of the invention, the stylus being disposed in the position which it occupies when mounted in a phonographic pickup;

Fig. 2 is a front elevational view of the stylus;

Fig. 3 is a view taken from the line 3-3 of Fig. l; f I

Fig. 4 is a plan View of the stylus;

Fig. 5 is a sectional View taken along the line 5-5 of Fig. 1;

Fig. 6 is a bottom plan view taken partially in section along the line 3 6 of Fig. l; and

Fig. 'l is a sectional view taken substantially along the line 'I--1 of Fig. 1.

The stylus of this invention is formed of metal which has resilient characteristics, such as ordinary cold rolled steel, bronze, and other metal alloys familiar to those in the industry.

In the form chosen for disclosure herein the invention is embodied in a phonographic stylus iD having a relatively large and rigid mounting shank Il which is adapted to be inserted into a mounting socket of a phonographic pickup, and a longitudinally extending flattened surface `I2 is formed on the upper side surface of the shank II so as to provide shoulders I3 and I4 at the ends of the surface I2, and these shoulders and the surface I2 serve as means for insuring location of the stylus in a predetermined position in the phonographic pickup or mounting. It will be understood that the usual set screw of the mounting socket is engaged with the flat surface I2 to hold the stylus in this predetermined operative position. When the shank II .is thus mounted it is ordinarily positioned at an angle of substantially 60 degrees, as shown in Fig..1,

with respect to the record surface which is indicated at I5 in Figs. 1 and 2. At its lower end the shank I I has a resilient connecting web I6 formed integrally therewith, as by swaging of the metal from which the shank I I is made, and the web IB is relatively wide as indicated at Il, adjacent to the lower end of the shank I I. This wide portion I1 of the web is joined to the lower end of the shank by means including a tapered lower end portion I8 of the shank, and just below the lower end of the tapered portion I8, the web I6 is bent upon a relatively largeradius curve as indicatedV at I9 in Fig. 1 so that the end portion of the web is bent toward a position substantially parallel to the record surface I5.V The bend I9 is formed about an axis which is located in a transverse relation to the axis of the shank I I and the curve I9 terminates in such a way that a portion of the web, which may be termed the free end por- Y tion, is relatively flat and extendsV substantially parallel to the record surface I 5. VAs herein shown the web I6 tapers outwardly for a short distance from its point of joinder with the .shank II to thereby vafford the wide portionl'l of the` web, and thereafter the side, edges of the web taper gradually toward each other as shown in Fig. 4 so that the web is relatively narrow adjacent to its forward end. In the form herein shown the width of the web i6 at its forward or free end is substantially equal to the thickness of the web.

At the forward end of the web i6, an integral extension rod or torsion section 2B is extended in substantially the plane of the flat forward portion of the web, and as shown in Fig. '7, the torsion section 20 is in the present case of round cross section of a diameter substantially equal to the thickness of the web l. The forward end of the torsion section 2li is bent downwardly at si on a relatively short radius to aiford a downwardly projecting arm 22 which is disposed in the plane of the shank Il. The lower end of the arm 22 has a tip 23 mounted on its lower end, and this tip may be made from a semiprecious stone or from a suitable alloy such as an osmium alloy, and the shape of the tip 23 is such that it may cooperate with the conventional form of a laterally cut or laterally modulated sound groove. It will be observed that the angle of the arm 22 with respect to the record surface i5 is substantially greater than the angle of the shank Il, and this angular disposition of the arrn22 is preferably such that :the arm is nearly perpendicular to the record surface. In practice it is preferred that the angle between the record surface and the arm 22 be between 75 and 87 degrees,

for such an arrangment materially iniiuences and increases the output of the stylus.

The phonographic stylus which has thus been described has the elements thereof so formed and related to each other that the stylus has an unusually high degree of tracking ability, and addition, the stylus of this invention is so formed and arranged that gouging of the record is avoided, and because of this the surface noise is maintained at an unobjectionable level and wear of the tip of the stylus and record groove are reduced. In attaining this novel result the present invention provides a stylus wherein the lateral vcompliance and the vertical compliance are acn curately controlled and accurately interrelated. Thus, as will be evident by comparison of Figs. 1 and 2, the desired amount cf lateral compliance is governed by the torsional strength of the torsion section 20 and the relation of this torsional strength to the length of the arm 22. When a lateral force is applied in one direction or the other to the tip 23, the arm 22 acts, in accordance with the length of the arm and the magnitude of the lateral force, to impart torsional Stresses to the torsion section 2i), and the cross sectional area of the torsion section 2E! and the length of the arm 22 are proportioned under the usual test conditions so as to enable twisting of i;

the torsion section 20 to give just enough lateral compliance to the tip 23 to avoid jumping of the tip from the groove of the record. Thus these portions of the stylus are preferably tested upon a record wherein the sound groove is modulated I established by shortening the arm 22 when the lateral compliance is too greator by lengthening the arm 22 when the lateral compliance is too small. Similar correction of the lateral compliance may be attainedby varying the cross sectional area of the torsionsection 2t. Thus, if the tip 23 is thrown out of the test groove, the compliance in a lateral sense may be increased by lling or otherwise reducing or varying the cross section or area of the torsion section 20 until such jumping is avoided.

Having established the desired degree lof lateral compliance in the manner just described, or by other means if desired, the vertical compliance of the stylus is then'interrelated to the lateral compliance, and in this connection it will be observed that the web I6 is of such a cross section at all points and is so merged with the torsion section 2i! that the torsional deformation which takes place during lateral compliance of the tip 23 is confined to the torsion section 2i), thereby to be accurately` controlled and afford an accurately determined lateral compliance.

The desired Vertical compliance of the present stylus is attained through bending of the web I6, and it will be observed that the width `of the web I6 is so related to the point of application of the vertical forces to the tip 23 that such bendling takes place in the curved portion I9 of the web.

The vertical compliance may, of course, be controlled by variations in the width of the web I6 in the curved portion i9, by variations in the thickness or cross sectional form of the web, or by variations in the effective lever arm through which the vertical forces aretransmitted from the tip 23 to the curved portion I9 of the web, but liV prefer to accomplish such control of thevertical compliance primarily through control or variation in the thickness of the web. Thus the thicknessof the web l 5 may be determined after the lateral compliance has been fixed and determined as herein above described.

In accordance with the present invention the relationship between the vertical compliance and the lateral compliance is determined in such aV manner that gouging of the record is avoided.`

In arriving at this desirable result the characteristics of the record groove have been taken into account and the Vertical compliance is such that the tip may move up and down as it passes through the pinch sections of the record groove. It has been determined that such pinch sections are inter-related with the frequency of the recorded sound in such a manner that the vertical movements of the tip 23 induced by the pinch sections must occur at twice` the frequency of the lateral movements of the tip, and I have discovered that by making the vertical compliance of the stylus equal to substantially twice the lateral compliance, the required vertical movements of the tip 23 may take place at the frequency 4determined by the pinch sections while assuring firm Contact of the tip with the sides of the groove. Thus, when such a 2 to 1 ratio is established, a predetermined upward force applied to the tip will displace the tip through a vertical distance substantially equal to twice the lateral displacement of the tip which is produced whe the same force is applied laterally with respect to the tip. Furthermore, I have discovered that by maintaining the ratio between vertical compliance and lateral compliance at substantially 2 to 1, the vertical movements of the tip may take place without introducing resonant vibrations in the stylus. Thus, the desired delity and intensity of transmission of the lateral vibrations of the tipr23 to the shank Il is attained and is unaffected by the vertical vibrations of the tip.

When the stylus l of the present invention is mounted in the holder of a conventional pickup mechanism and the tip 23 is rested in a record groove, the weight of the pickup mechanism is such that the web I6 is placed under tension,

thereby to slightly1 bend the web I6 in the curved portion I9 thereof. By reason of this tension, the tip 23 is caused to follow the record groove with a rm engagement despite the vertical movements which are imparted to the tip by reason of the pinch sections which are present in the groove. Hence the tip 23 is accurately responsive to the lateral modulations of the groove, and the signal frequencies are thereby faithfully imparted to the tip 23. Such signal frequencies appear as Vlateral movements of the tip 23 and by reason of the relatively wide character of the web I6, such Vlateral movements of the tip are faithfully transmitted at a relatively high output level to the shank l I so that when the stylus of the present invention is used, the output of the phono- -graphic apparatus may be maintained at a relatively high level. It has been pointed out hereinbefore that one of the primary causes of surface noise in phonographic reproduction is the presence of relatively small particles of material,

such as the record material, in the record grooves, and when these small particles are engaged by the tip 23, the tip must move upwardly so as to pass over such particles. When the vertical compliance of the stylus is maintained at substantially twice the lateral compliance, the tip 23 may move over such small particles in such a manner that relatively little surface noise is created, and so long as the aforesaid 2 to l ratio is maintained between the vertical compliance and the lateral compliance of the stylus, the requisite vertical movement of the tip 23 in response to such record particles may take place without creating resonance in the stylus. In prior styli, such resonance ordinarily has been found to take place at the predominating frequency of the surface noise which is in the neighborhood of three thousand cycles per second, but with the stylus of the present invention it has been found that there is no resonant peak of surface noise such as is ordinarily found at the predominating frequency of such surface noise.

When the tip of a stylus is located in a particular relationship to the record groove, as by locating the arm 22 at a particular angle to the surface i5 of the record, the engagement of the tip with the sides of the record groove tends to produce angularly related flat side surfaces on the opposite sides of the tip, and in order that the maximum output may be maintained, it is desirable that the maximum area of these flat surfaces be maintained in engagement with the sides ofr the record groove. Such maximum engagement is disturbed in the event that the angle of the arm 22 with respect to the record surface is varied, and in the stylus of the present invention it'has been found that this angle of the tipcarrying arm with respect to therecord surface undergoes 'substantially less variation than in prior phonographic styli. It appears that this result iiows from the fact that the vertical compliance in the present stylus is attained by bending the web I6 about a curve I9 of a relatively large radius which disposes the fiat end portion Vof the shankat an angle of substantially 120 with respect to the shank, for it has been found that when such .a large radius and such an. an-

gular relationship are notemployed,V the varia-l tion in the angle of the arm 22 is objectionably increased. Since the angle of the arm 22 with respect to the record surface i5 is maintained with-- 5 in relatively small limits of variation, the variations in the output level which would ordinarily result are obviated, and hence the fidelity of reproduction is enhanced by the use of the present stylus.

Since the stylus of the present invention permits vertical compliance in such a manner as to avoid resonance within the stylus, the outputA or transmission efficiency of the present stylus is relatively high, and since this stylus avoids gouging of the record grooves, the wear upon the record and upon the stylus are reduced, with a correproduction lof sound from laterally modulated record grooves cut in a flat record, an elongated body affording a substantially rigid upper shank, a torsion section and a lower arm connected in an angular relation and disposed in a plane with the axis of said shank, an integral resilient web Connecting said torson section to the lower end of the shank and said web curving from the plane of said shank to a plane substantially parallel to the surface of the record and diminishing in Width from a width substantially greater than the diameter of the shank to a width substantially equal to the diameter ofthe torsion section, and a record-engaging tip mounted on thefree end of said arm.

2. In a phonograph stylus for use with lateral cut record grooves, a rigid mounting shank of relatively large cross sectional area adapted 'for mounting in an operative position in a stylus holder with the shank in a predetermined angular relation to a record, a relatively thin and at 50 connecting web merging into the lower end of said shank and extending longitudinally therefrom to a forward end and being formed ina gradual curve about an 'axis disposed parallel to said web and transversely with respect to said 55 Shank to thereby dispose the relatively at p01'- tion of the web at an angle to the axis of the shank and the forward end thereof generally parallel to the adjacent record surface when the stylus is mounted in said operative position, an 6o extension rod of relatively small cross sectional area merging with the forward end of the web and extending longitudinally therefrom in thev plane ofthe forward end portion of theweb, a relatively short arm extending downwardly from theextension rod and disposed in a plane which includes the axis of the shank, and a record en` gaging` tip on the lower end of said arm, said web being flared laterally to a substantial width adjacent the shank with the cross sectional area 7o thereat substantially the same as that of the shank and tapering gradually to the forward'end adjacent the extension rod with the cross sectional area gradually decreasing toward that of the extension rod to provide for vertical bending displacement along the thin :fiat connecting web 9 and for torsional displacement along the extension rod.

FRED E. WILLIAMSON.

REFERENCES CITED The following references are of record in the le of this patent:

Number 10 UNITED STATES PATENTS Name Date Andres Aug. 10, 1943 Ahlstrom Dec. 10, 1929 Muller Jan. '7, 1919 Hasbrouck, Jr Apr. 21, 1942 Grilley et al Sept. 22, 1925 Dally June 1,1943 Fitzpatrick Apr. 28, 1908 Capps Sept. '7, 1943 Tourtel et a1 June '7, 1904

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