[1]Patented Feb. 5, 1952 2@584@922 UNITED STATES PATGNT OFFIC'E 2,584,922 'UNIVERSAL REPRODUCING STYLUS John Drysdale Reid, Cincinnati, Ohio, assignor to Avco Manufactur2.ng Corporation, Cincinnati, Ohio, a corporation of Delaware AppHcation JuIy 20, 1949, Serial No. 105,696 I Claim. (Cl. @274--38) 2 : The present invention relates to a vibration transl ating device, including a tilted stylus, for. use. with phonographs, such device having th .,e capaci ty of properly tracking, the distinct types of grooves in standard sound disc records and 5 in "long playing" or fine groove records. At the present time the availability of, and the strong business competition between, the manufactur ers of, three distinct types of record discs, has imposed a severe hardship on the consuming 1) public in that no needle heretofore offered for sale has the capacity successfully to follow the distinc t types.of grooves used in these discs. A furthe r burden has been imposed on the public by the absence of a turntable which can support 13 all three types. It is believed that the devices shown and claimed in my copending TJ. S. Patent Applic ations, Serial Nos. 78,949, now Patent No. 2,577, 035, issued December 4, 1951, and 90,716, filed in the U. S. Patent Office on March 1, 1949, and April 30, 1949, entitled "Universal Phono. graph Turntable" and "Universal Sound Reproducing Stylus," respectively, and assigned to the same assignee as the present application and in. ventio n, successfully, solve the turntable and stylus problem. The primary object of the present inven.tion is to Provide another type of vibration translating device , including 4 stylus, which can be successfully employed in playing any one or all of the 30 three major types of record discs. The worthiness of this object is indicated by the discussion imme diately following. A bitter competitive struggle is now in existenc.e, involving the standard large-diameter 78 35 R@@ P. M. record disc, the long playing 331/3 R P M. Columbia discs, and the seven-inch .45 R. RCA disc. The present invention provides a stylus construction which may be used with any of these types of record discs. 4o The term "standard record discs" is hereinafter used to designate tlle large-groove 78 R. P. M. types. In accordance with present day practice, the so-called standard discs conform to the following speciflee@tions: 40- United States 881 groove angle .006 inch width of groove .0023 inch bottom radius of groove 50 England 881 groove angle .0065 inch width .0017 inch bottom radius The following standards have been proposed: I United States' 90' groove angle -50 .006inchgroovewidthminimum @0025 inch groove radius -.0005 inch England 87.51 groove Angle -2.5 10067 inch groove width .00165 inch groove radius -.00015 inch B. E. C. Mittell, in his inforihai leciure erititied "Commercial Disc Recording and Processing," delivered to the Radio Section of the Institution of Electrical Engineers, Great Britain, on December 9, 1947, printed by permission of the Institution of Electrical Engineers, Savoy Place, London, W. C. 2, states'that present day English grooves vary from 95, with a .0023 inch bottom radius and a .0024 inch de t@ to a minimum of 86.51 with p a .0015 inch bottom radius and a de-pth of .0029 inch. I-Ie also ciies a 1936 English record put out by I-1. M. V. (DB2605, side 1) wbich had a 96, groove with a bottom radius of .0025 1 inch and a depth of .0021 inch resulting in a width of .0067 inch. This was stated to be representative of the practice in 1936. H . C o u r t n e y B r y s o n , i n h i s b o o k " T h e G r a m o - phone Record," publish I ed in 1935 by Ernest tenn Ltd., London, states that the average groove was .006 inch wide and .0025 inch deep. He states that the depth of grooves varies I from OOi8 inch to .0035 inch, the average being .0025 inch. His figure 35 shows a, groove which is .006 inch wide and .0025 inch deep and has a 75o angle. At p age gl e h b ' 79 he states that the groove an as een v aried from 601 to 901 with the groove depth kept approximately .0025 inch by changing the bottom radius; that the practice h@s been to use a small bottom radius of about .0015 inch for 90' grooves and a wide bottom radius of .003 inch for 60' grooves. At page 80 are pho aphs of the crogssections of four makes of records. Scaling these drawings would indicate as follows: The Columbia records had groove anklei Of
[2]3 95', were .007 inch wide, and had a .0023 inch bottom radius. The Decca grooves had an angle of 971, were .007 inch wide, and had a bottom radius of .0025 inch. The Regal paper records had a groove angle of 851, a groove width of .0075 inch, and a bottom radius of .0035 inch. 'Ehe Polydor records had a groove angle of 901, a groove width of .0075 inch, and a bottom radius of .0023 inch. It is understood that some 78 R. P. M. records have been s6ld iii the United States with a groove angle of @pproxiinately 1000. The maximum record groove dimensions for standard record discs which would be encountered in practice at the present time are approximately as follows, 100' angle .006 inch width .0023 inch bottom radius The dimensions of 331/3 and 45 R. P. M. flne groove records used in present day practice are next considered. According to RCA record drawing No. P327117, dated December 13, 1948, the P.CA record groove is held to a maximum width of .003 inch but may go down to a minimum of .0025 inch. Other dimensions of ihi@ groov6 are: Included angle-85'-51 Bottom radius@.00025 inch maximum l,ead out and eccentric grooves-same dimensions According to Colunibia drawing No. TD203 dated December 2, 1948, the groove width is held to a minimum of .0027 inch and is allowed to vary to a maximum of .0030 inch. other diinensions are: Groove angle-871-3' Bottom radius-.0002 inch iiiaximum Lead out gro6ve and eccentric spiral@increased in depth to .003 inch +.0005inch -.000 making width .006 inch approximateiy. In July 1948, I measiiied a group bf six Columbia records and found that the groove width av@raged .00277 indh but varied from .00211 inch (#2008, side 2) to .00383 inch (#4028, side 1). it appears that the minitnum width of fine groove records to be encountered in practice approxiinates .0021 inch. It will be understood, of cours6, that @ame fiiie groove record di@es are designed for a speed of 78 R. P. M. T'he above considerations have comp6lled the public to purchase at least tWo distinct types of needles and to go to the trouble of adjusting record players to place one or the other type of needle into operation, depending on the type of disc to be played. Some crystal cartridges are ibquipped with two needles, one of which becomes an undesired mechanically resonant system when the other is used. At best, such cartridges must be adjusted to select one needle or the other. Alternatively, consumers are forced to use one type of disc exclusively and are deprived of the use of the other types. These hardships haive created a great amount of confusion, caution, and sales resistance on the part of the public and have contracted the market for record changers, :tecord players, and combination radiophonograph sets. Therefore the need for a univers;@ltype phonograph needle is v6ry urgent. The 2,584,922 4 patent application Serial No. 90,716 are directed to the satisfaction of that need. Accordingly, the primary object of the present invention is to provide a vibration translating apparatus, including a stylus, which accurately and faithfully follows the modulations of both standard and fine groove record discs. The principal advantages flowing from the use of the invention are as follows: (1) Operation is siinplified in that turntable speed is the only variable which must be selected in accordance with the type of disc to be played; (2) Th6re i@ no nec6ssit@ to teplace a needle br vary the tilt or turn 6f 6 dartridge when select1 5 ing a different type of record disc; (3) No tone-arm weight change is required; (4) The vibration translating device tracks aU commercially-employed records, the 78 R. P. M. standard a-ild fine groove types, the 45 R. P. M. 20 fine groove type, and the 332/3 R. P. M. standard and fine grbove types; (5) The vibration translating device reduces manufacturing costs of the phonograph as a whole, in that it eliminates one or more of a ,!r, plurality of needles, tone-arm weight-changing levers, tone-arm cartridge bearings, certain amplifier stages atid compensation networks; (6Y The stylus in the iiibration translating d6vice is positively driven by both side walls of ,,,i the grogve. Another iriiljortant object of the present invention is to provide a vibration translating apparatiis, including it stylus, which is so akranged a8 to niiniihize record disc and stylus wear. Since the width of the fine grooveg is less than the Width oi th6 8tandt@td grooves, the areas of the stylus which contact the fine grooves are not coextensive Wiih the artat Which eontact the standard gro6ves. The dotistruction in accord40 ance With the in,@eiitioil 6nhandes the life of the stylus and capitalizes on the divergence of stylus wear ar6as. These advantages are further enhanc@d by a feature of the inv6ntion in accordance with which the stylus may be tilted in either 45 direction. A@ stated iii rh3f U. S. Pdtent No. 2,251,204, issu6d iiily 29, 1941, entitl6d "Sound Reproduction" and blssigned to the same assigriee as the present application and invention, it has been found that 50 the bbttom portioli of A recbrd disd groove does not cut so cleanly as the upper part of the groove, greater pressiite being iequired to dut the fuU depth atid to push @,way th6 to@ilings. This factor causes the 16i#er patt of the gtoove to becorne lr55 tegular and iinp6kfect. A reproducing stylus Which follows the bottom part bf the groove is aff beted by these irj:egularities, resulting in a loss of electrical response to tl!6 di@sired modulation, in inereased distortion and rd@ponse to undesired 60 modulation. It might also be mentioned that records are often formed by the iise of a stamper which pres@es a mass of moldable material into final form. The raised portions of the stamper arL@, those v@hich cokrespond t6 the bottbm of the 61 groove, anct it is these taised portions which r6ceive the greater wear during the manufacturing process and which ar6 most stibiect to beiiig m@Lrred or sctatched dilting processing. Consequently every impetfection present upon the 6x70 posed surface of the stamp6r Pppears in exact rerlica at the bottom of the groove and thus aggrava es the inheren eg ari es o e bo tom of the groove. The s iiieluded in the vibration translating apliAratii8 of th6 preseiit inpresent invention and that of riay copending 75 vention does hot iide iiboh these irr6gula@ and
[3]2,584,9 22 lmporfect portions, and the undesirable effects thereof are not present in the 6utout of a repro" ducing device with which the invention is employ6d. For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to, the accompany-ing description of the drawings, in which there are illustrated several embodiments of the invention. 10 In the drawings, Fig. I is emplo@6d a4s an I iiid 'm developing the mathematical relationship Which must be satisfied by a tilted stylus for operation with standard groove record discs; Mg. 2 is similarly used to develop the mathematical relation- 1.5 ship which must be satisfied by a tilted stylus for operation with fine groove record. discs,-, -Fig.. @3 is a set of-curves showing the required relationship between slope angle and tip radius for standard grooves and fine grooves; Mg. 4 is a perspective 9,0 view of a stylus and cartridge assembly suitable for use with the invention., Figs. 5-7, 8-10i and 11-13 are three groups of - figures. showing, in greatly enlarged form, tbree suitable stylus sizes, progressing fr<)m top to bottom, a 1001.@conical 2@1 stylus tilted at 10,', an 80' stylus tilted at, 20', and a 50' stylus tilted at 35', together with stylus grooves into which each stylus fits, progressing from left to right, an RCA type of fine groove, a Colu@,nbia type of fine groove, and a standard 30 groove; Mgs@ 14, 15, 16, and 17 show, respectively, an embodiment of the invention in which the stylus is tilted by bending of the stylus spring, an embodiment in which the stylus is tilted by tilting the crystal cartridge, an embodiment in which the 35 connector between cartridge and spring is. tilted, and a fourth embodiment in which.the tone arm itself is tilted. In accordance with the invention, ther'e is prowhich includes a tone arm and means secured to the tone arm for generating electrical signals representative of.-sound as modulated on any one of a plurality of distinct types of record discs hav. ing laterally modulated grooves, a novel vibration translation device. This device controls the signal generator, generally a piezo7electric crystal, in accordance with the modulations. The device comprises a. stylus having a tip and an upper groove contacting portion. The device also com- 56 prises mounting means secured to the generator or crystal for supporting the stylus at an angle with respect to the plane of the record disc. This angle is transverse to any of the grooves and is so determined that the tip of the stylus contact@ 15 the side of the largest one of the grooves at a point not 1,Dwer than, and preferably above, the line of tangency between the arcuate bottom of the largest groove and the side of the largest groove. The angle is also so determined. that 60 the stylus contacts the smallest one of the grooves at a point below the shouldered top of the smallest groove. While the tip of the stylus always contacts, a side of a groove, the other groovecontacting portion of the stylus always contacts 65 the shouldered top of the groove on the side opposite to the side contacted by the tip. The present irivention contemplates the combination of a styl.us and means for positioning the stylus at a transverse angle so that it fits into and! is posi- 70 tively driven at two points by a groove, whether it be. a fine groove @or a standard groove. The stylus makes contact on the top side wall or shoulder of one side of the groove and @ also with the 6ther side wall of the groove, thus affording posir 75 6 tive drivi3 ftom@.I,the laterai moauiations of the groove. @ It'has been. determined' that a stylus having an included angle of 80'. and a tip radius of 0.0014 inch performs satisfactorily in both. standard and micro-groove records when set at an angle of 20',from,the vertical; for example.-@ I have also-found that@ a stylus designed for fine groove records can be rnade to operate satisfactorily with b flne groove record discs an standard-groove record discs when included in combination with means which tilts the stylus at a transverse angle on the order of 351 from the vertical. I have found that a conical stylus having an Ineluded angle, slightly smaller than, that of the smallest-angle record groove, and a curved tip, can be used on all of the three types of records when the stylus is tilted io the side and fixed. Additionally, the factors determinative of the angle of tilt have been ascertained. The limit7 irig factors are as follows: (1) 7 A portion of the stylus must rest I one edge or shoulder 6f the largest groove to be encountered in practice, and at the same time the StYlUs tip must touch the opposite wall at or above the point of tangency of the bottom radius and the straight portion of.the groove side waU; A portion of the st@lus must rest on one edge or '@houlder 6f tlie@ smallest groove to@ be'@encountered in practice'arid mulst be tang@l@t to, the o@posite wall at or below the top edge of @the@sid6 wall. These 6onditions are illustrated in Figs. I I and 2, the pertinent dimensions being indicated by symbols as follows: W designates the groove width of an assiimed large groove; G is the included angle of such large groove; Rg is the bottom radiu@ of the large groove; P is the included angli) of the stylus tip; T is the angle of sideward tilt of the stylus away from tho vertical; S -is the angle between the si(ie of the S'tylus and the plane of the record disc surface. Prime marks are employed to designate the correspondingdimensions of an assumed flne groove, the fine groove being synibolically illustrated in Fig. 2, while the large groove is.i@ltistrated in Fig. 1. @] Other dimensions stich as L,. d, and 4@are used in deriving the relations involved. L is the horizontal projection of the distance between, the point of contact of groove shoulder. and, stylus and the locus from which the radial tip is gener7 ated; d is the vertical projection of the distance between the plane surface of the record disc, and said locus; h is the vertical projection of the distance between the top @lane of the record disc and the point of contact between stylus tip and groove side wall. It wiR be observed that in the combination in accordance with the invention there is included a stylus having a virtua-Ily truncated portion which terminates in a circular tip, having a radius Rp. The included angle of this truncated portion is designated by the symbol P. I have found that when P is decreased, the angle T must be increased in order to satisfy the required conditions of operation outlined above. In other words, a sharper conical stylus requires a greater angle of tilt. Referring now to Fig. 1, there is shown a larlki@ groove h6,ving. top shoulders 20 and 2 i, side walls vided in a sound-translating device of the type 4" Rp is the tip radius of the stylus;
[4]t2 atkd 23 ' and an areuste bottom 2.4, the rrols@ sectioriofwhichicgenerated,by,:a,ra,cliusRg. The stylus,ho@s a portion 2i, which contaetsshoulder 20, ilnd a -tip 28 which contacts _side waH 23, -opposite to shoulder 20, at a point 2-,7 below shoul- .1 der 21, just at:the point or@ line @at which bottom 241s.tangent-towall.23. Undertheseconditiom: G) h..('W - R, 00. --i.2 2. -G 2 10 d--h-B, siii 2 G 'coo - 15 2 air) S= RI d @p S and 20 w +R, Cos G sin S-(E@-R, Cos g) Coss (T 1 2 2 tan G RV= 2 G 25 1 -.sin (-i-s) ,Curve,A in F*. 3 show-,s the relation between S and-R when the conditiqas of Fig. I are satisfled. Values iDf 6, &lope angle in degrees. be30 tween the side of the 5tylus Axid the recora casc plane surface, are plotted as ordinates against values of Rp, the stylus tip yadiqs. as abscissae. C.urve A is bwd on the followi,ng given data, Rg=0.0025 inch 3 5 W=0.006 inqh G=93' which makes I?, 4.7 $in S - I..3 G ta n - 40 2 Siii -in (46.5@0- -- 8) It wjll be observed that, if. it be. assumed that the stylus tip is tangexit to wall 23 just at,tlie point where the groove bottom is tangei)Lt @tO Wall 4,r) 23, ari increase in tip radius must be accornpanied by an increase in the slope angle. When the tip is to be made tangent to wall 23 at a point above tb6 point at which the groove bottom is -tangent -to waU 23 then S niust be less than the critical value -,-, i) plottew in curve A, Fig. 3. Referring to Fig. 2, there is shown im fine groove haviiig top shoulders 31 and 32, side walls 33 and 34, and an arcuate bottom 35. The stylus has it portion which contacts shoulder 3 1, and a tip 2 6. r)5 which contacts groove side wall 34, o,pposite to shoulder 3 1, at shoulder 32. Under these conditions: ,4'-= 0 d' R , sin 2 @Gi RV .sin 81 @di 65 Lt and WI sgzlwt @values @of Rp as abscissee. It lwill be noted that S' agairl ineremeo witti Rp but at greater @rate than the increases of S wit@i BP.. When the tip is to be made tangent to wall 34 at a pc)int below shoulder 32, then S' must be greater than the critical value plotted in curve B, Fig. 3. -the following given idatil. Curve B is based on Rlg=0.0005 inch W'.=0.0025 Inch G'=80' 2.5 which makes R,= 6428 1 .7660-'-@- + tan.81 gin Since the slope angle must be less than the eritical value plotted in curve A @and greaterthiln the critical value plotted in curve B, the values of slope angle employed.in practice are those included in the area between the two curves to the left of their intersection, which occurs at a point where the -slope angle is equal fo 25' and Rp-- 0.00142 inch. Now, then, if the@slope angle is taken equal to 25', the largest value of the stylus @cone included angle (P) for the smah groove is determined as follows: P=900-Sl+ GI 900-250+4,00=1050 T)ie largest value of the stylus cone included a@igle for the large gr-pove is determined a,s follows: P;==90'-25'+40.5'=111.5' Accoridingly, a stylus cone arigle not exceedingly 105' may be employed, when S is taken equal to 25'. I-lowever, in order to minimize the tilt angle (T), the included angle (P) of the stylus cone must be as large as possible, for p T = 90'- S-.@@=90'-25'- 52.5'= 12.5' in the particular example. Generalizing, the angle @of tilt must be increased asthe sharpness of the conical stylus is inereased. It will be understood that stylus cone angles considerably smaller than 105' may be used, and such cone angle can be even sma;ller than the groove angle of the smallest groove to be encountered in practice. When the stylus cone angle is decreased, the tilt angle is increased by an amount equal to one-half the decrease -in cone angle. -Ilaving discussed in detail the factors which determine the dimensions of a stylus suitable for employment in the combination in accordance with the invention, the description now proceeds to a detailed discussion of the means utilized to impart to the stylus an initial tilt. I7a the claim-t appended hereto, such expressions as the following are employed: "mounting means for so supporting said stylus" and "means for supporting said stylus." Such -expressions are employed 94 proper cohective terms to designate the various specific mounting arrangement that may be.,employ-ed in order to impart a transverse -tilt to the stylus. Refer.r@ng,now to Fig. 4, there@ is r>hown, asuitable @stylus asseinbly for use with t)ie invention. The needle 40 is sec-ured as by press Att@ng to a GI . G'- 7( spring. 42 whieh terminateis at its -otlier exid in @4 CQS y@sin 3,+ lug 43 including an aperture -44 through @which a 2 WI-n-s mechanical ronnector m@ember 45 project,5,. The Curve B in Fig. 3 shows the relations betwo,- en member 45 is secured to the tartridge 4,6 in a conS' and Rp. wlien the conditions of Fig. .2 @are ventional f"Won Etnd its lower end -is screwsatisfied. Values of S' arie plotted@'M ordinates 75 tbxeaded to @intextt with.& -knurled binding nut
[5]9 48. The parts are shown in, diassembly for purposes of clar@ity, and the assembly in which the partg are :fttted together is so obvious to those skilled in this art as not to require further discussion. The cartridge 46 Is secured to a tone arm 49. Referring now to Fig. 14, the electric signal generator or piezoelectric crystal cartridge 46 is ,secured to the tone arm in conventional fashion and tilt is imparted to the needle by twisting of the spring 42. The mounting means in this embodiment comprises the twisted spring 42 and the conventional elements 43, 44, 45, and 48. It will be observed that the spring can be twisted in either direction as suggested by the full line and the dashed line positions of the needle in Fig. 14. In the Flg. 15 embodiment, tilt is imparted to the needle 40 by diagorially mounting the cartridge 46 in the tone arm 49. In this embodiment the means for mounting the stylus with respect to the plane of the record disc constitutes the cartridge 46 and the elements depending therefrom, and associated with the stylus 40. As indicated by the dashed line alternative position of the needle 40 in Fig. 15, the cartridge can be inclined in either direction in order to impart the necessary tilt to the needle, one position being shown in full lines in Fig. 15 and the other position being show-n in dashed lines. It will, of course, be obvious in the light of this disclosure that provision can be made, as by lugs and lock screws, for adjustably tilting the cartridge in either direction. In the Mg. 16 embodiment, the cartridge 46 is again secured to the tone arm 49 in conventional manner, but the coupler member 45 is secured to the cartridge with an initial angular tilt. Again, as indicated by the full and dashed lines, the needle may be angularly disposed in either direction relative to the record disc grooves. In this embodiment the coupler or connector 45 and the elements depending therefrom and associated with the needle 40 constitute the mounting means for imparting angular tilt tO the needle. In the fourth embodiment sbown in Fig. 17, the tone arm 49 may be tilted to either of the positions indicated by the full or dashed lines to tilt the needle 40 in the corresponding direction. Various other equivalent arrangements will now be obvious to those who have this disclosure before them, such as tilting of the turntable or bending the shank of needle 40. Ilu- is thought that the disclosure should be fairly confined within reasonable limitations by describing the illustrative embodiments shown and designating all embodiments, with their equivalentsi in the claim by the use of "means" expressions. Referring now to Figs. 5 through 13, the grooves in Figs. 5, 8, and 11 are of the RCA type, drawn to an extremely large scale. The grooves in Figs. 6, 9, and 12 are of the Columbia type and the Figs. 7, 10, and 13 are of the standard type. In Figs. 5, 6, and 7 there is shown a stylus suitable for use in the combination of the invention. This stylus has an included angle of 100, and is tilted away from the vertical by 101. Figs. 8, 9, and 10 show another suitable stylus, in this case having an included angle of 80- and tilted from the vertical by 201. A third stylus is shown in Figs. 11, 12, and 13. The last illustrative stylus has an included angle of 50' and is tilted 35' from the vertical. It will be seen in oach instance by an inspection of Is tan S' Sin S' 2 584,922 10 these flgures that each stylus has a portion which contacts the shoulder of each groove aiid a tiP portion which contacts the opposite side wall, at a point located above the point of tangency of the grooved bottom and -the side wall. In this manner the stylus @is positively driven at two points on opposite sides of a grobve and it follows the modulations with great fidelity. Additionally, the stylus does not contact the rougher io areas on the grooved bottom. It will be seen that by imparting additional tilt to the sylus a wide range of stylus designs, having different cone angles, may be employed. It will also be apparent that the life of both needle and record 15 disc are increased by tilting the needle in one dirention and at a later time tilting it in another direction, thereby to achievd maximum utilization of stylus contact areas. Whle there have been shown and described 20 what are at present corzidered to be the preferred erribodiments of the present invention, it will be apparent to those skilled in the art that various changes, modifications, and substitutions of equivalents may be made without departing from 25 the true scope of the invention as deflned by the appended ciaim. I
