US2473374A

US2473374A - Phonograph needle

Info

Publication number: US2473374A
Application number: US590329A
Authority: US
Inventors: William H Hutter
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-04-26
Filing date: 1945-04-26
Publication date: 1949-06-14
Anticipated expiration: 1966-06-14

Description

June 14, 1949. w. H. HUTTER PHONOGRAPH NEEDLE Filed April 26, 1945 I Ziz/ezzioz" Made? Patented June 14, 1949 M73314 PHONOGRAPWNEEDEE This invention relates..-to1;phonographsneedlesi and in; particular to. thosel'manufaicturedr. from: 'aplastic material:

The present application is a continuatiqniin; part. ofv my copendin rapplicationazfierialliNo. 529,-269, filed. April.:.3 19514,.1101W abandoned,- which. relates to plastic phonoemnh needlesr The advantages 'ofs a; plastic needle-woven a needle fabricated. fnomcmetalaon oth irsuhstances havin zr'a; comparativelyrhigh stiffn and. density; areset .-:-or tlirin:v detail; inxthat an: plication.1 stated.zgenerallyi1- the advantages-ate better'trackinslless needle; resonemeiwithinthe audible r nseilower needle-nqintzimhedameiand greater latitudeoi design; 1

Where a, cartrid e haabeen desisnedzsnecifie alliy foliuse:withiaiplflfit mnfl dljfil the .imenei n of both he ne dle..-.and thanca ltriide zoa trolled to ivethe. desired-.sti fness i v hi h. utput-1 An. xample. if-5 ec carte shown in my copending applica 56 6 howl-Patent NQ. 2; .5' tZ2 ,,i v 1 19.48. A high volta oute td t ea idenhm r e l tevv pon, .theapes c ..-eo m iee tween-..:the needle. ands he hratimaa mcem ts t n m mber,. and as. shown ini heteahl? 01.1; the proper. up in m wuir a.: s;pec1a1.;-ti%ne ofchuck anda speciallywshaped needle.

But, when a. cartridge; been v desighfldwto accommodate the usual. metal: needle. additional a ns re impo ed; oh h design-to ab es: ticneed le.

It is. an i obj ectof, this; invention; :to proyidea plastic needle, which is adahted ionuse in con,-

junction with the usual;pickeup ehuclnwhifihieme I sired distributed com'pliance'and damping of a.

plastic needle togetherwith the -high 'ioutputwhich results: from: a comparativelytightclrcou; pling.

It is a further; object not: my inventionrtdproe vide a plastic needle .adaptedioncooneratiomwith .Suchhee l 2.. thtdlSllfiPPiCk-lll) chuck; which has-an interiordiameter no greater than that necessary toreceive the usual metal needle.

Another objectis to provide a phonograph:-

needle having a longwearing, hard record engaging-point at one end; a metallic portion at theotherendwhich is adapted to be gripped by the clamping means of a chuck, and anintermediate-portion separating the two end portions; said'intermediate: portion being fabricated from a plasticmaterialhavingimpr0ved -vibration transmitting characteristics:

A; further object is to provide in a phonographneedle of the so-calledplastic type, an improved construction .formounting the record engaging point in the plastic needler A- still further object-is to provide an improved needle construction which will absorb the vertical vibrations of the record-engaging point, but which will transmit faithfully the lateral vibra tions thereof to its associated parts; also to provideameans for increasing the vertical compliance and reducing: the :mass of: the needle be-; yond'that-indicated by: the shape and dimensions ofitheineedl'ew-ithout substantially increasing :the lateralicompliancal Qtheezobjects; features and advantages will. become. apparent." as. the. description proceeds.-

Withmeferencenew to l the: drawings, .in which likesreference. numerals designate like parts.

Figs iais aside elevation .015- aneedle embody-q ing a preferred form of this invention Fig: 2.;is1a frontiviewmf-Eig. 1;;

Fig is an .enlargedxysection of the lowerend Qf*'th&=.=TIE3dIE-ShOWiH4 a. means of securingythe record; engagingepointl with resp ct to. h plass tic. =need1e;:and.-.

With reference now to Figs. 1 and 2 the: ref: re ce numeral. 0.d s enates-ee ere y the-ma bodwp trt onsaof a-phono anh e dm wh chd noh io i st-iorme of: a suitable organic plas ic, 511911335 h se en ra y e e r o as. synthet resins, orlcellulgsebase plastics. As. any example o ma rialsfrom. h chit is body port qn abe formedelave .u dithat. cellulose cetate; c ulose nitm eace lulosea c atetbutyrate. ethyl celluloseand methillz m thacry a e,,-u a,z d amina polystyrene and. vinylidenework satisfactorilx.

, The b dr o i l l pris s a hank H, and a. forwardly. bent end; portion. 2,.o f reduced dij-. me tions- Ai cor n gi po nt. 3: s olmtnact: hae remitr o t e r a dly t. end. port on; Ii; as wi labe hereinafter es r b d;

\ 'rheiueeeranorticn or the Shank. H s, stiffened by a metallic insert M, which is preferably molded into the shank. The upper portion of the metallic insert I4 preferably projects beyond the end of the shank, as indicated by the reference numeral I5, and this projecting portion is adapted to be inserted within the chuck of th usual pick-up. The projecting portion may be of slightly greater diameter, and may be provided with a flat or slabbed portion i8 which is engaged by the set screw of the usual chuck.

Although with certain types of plastic material the stiffening member or metal insert could v insertion of a plastic shank which is extended to the same length as the insert. Furthermore, the set screw might inadvertently be screwed up too tightly, thereby deforming or fracturing certain types of plastic material.

The manner of mounting the point is shown in Fig. 3. The point 53 comprises a cylindrical member 98 which is provided with a conical tip 19. The end portion 12 of the needle is provided with a bore which is of a diameter slightly smaller than the diameter of the cylindrical member H3. The pointed cylindrical member is then inserted into the bore from the upper surface of the needle, and it can be forced through the bore, due to its conical tip l9, into the position shown in Fig.- 3. As the flat end 2! of the cylindrical member I8 is pushed beneath the surface of the plastic the resilience of the plastic causes the bore to contract to a certain extent, as indicated by the reference numeral 22. This small amount of contraction I have found is suificient to prevent the point from creeping upwardly within the bore 253. Thus a secure mounting for the point is provided.

1 As an example, I have found that the point, including the cylindrical member l8 and the integral conical tip l9, may be formed from a sapphire, and the plastic body portion of the needle formed from a diamine plastic such as that known as nylon. The diameter of the cylindrical member may be .018 inch and the diameter of the bore .015 inch. Diamine plastic is quite tough and resists satisfactorily the shear that is created by the needle pressure which acts on the contracted portion 22 of the bore.

The construction shown in Fig. 3 is particularly well adapted for use in connection with sapphire points, because of the small dimensions of the sapphires that are available at reasonable costs. It will be understood, however, that is construction is equally well adapted for use with metal points.

The plastic body portion Ill, or shank of the needle, may be made from any organic plastic material which has desirable vibration transmitting properties. Such materials, in general, can be defined as those having a density of less than 2.0 grams per cubic centimeter and a Youngs modulus of less than 10 x10 dynes per square centimeter. I have found that a needle constructed in accordance with my invention is substantially free from needle resonance at frequencies within the audible range, and furthermore, it contributes materially to low impedance of the pick-up as a whole. The length of the metal member is somewhat less than threeeighths of an inch, and the diameter of the projecting portion thereof is approximately one- 4 eighth of an inch. Thus to whatever extent the mass of the whole needle is increased by the use of the metal member, the actual increase in the moment of inertia of the needle about the longitudinal axis of the chuck and its associated parts is comparatively small. Thus the acoustical properties such as the impedance and the resonance frequency are of the same order as that of a needle which is fabricated entirely from a plastic. More specifically, the low generalized stifiness resulting from the use of a plastic needle is combined with a comparatively high localized stiffness to produce the desired tight coupling.

As an example of the latitude of design which is afforded by the use of a plastic needle having stiffening means associated therewith, I have shown a needle with a forwardly bent end portion iii of gradually tapering dimensions, this construction affording increased compliance with reape-ct to vertical vibrations of the point. The width, or lateral dimension, is greater than the thickness'of the needle. These proportions also serve to increase the vertical compliance of the needle.

The generalized stiffness and the generalized mass of the needle are determined by the Young's modulus and the density of the materials used, and also by the dimensions and shape of the r dle'. After the needle has been designed to give the proper compliance in one direction, in this instance in the horizontal direction, I have found that the vertical compliance may be increased and the mass still further reduced by providing

apertures

23 and 24 in the body portion iii oi the needle. These apertures which are symmetrical with respect to the longitudinal axis of the needle, do not materially increase the lateral compliance, due to the fact that the amount of stiffness contributed by the material which is close to the neutral plane of the needle, is comparatively small.

Furthermore, there being a lesser amount of material at the lower end of the needle, the moment of inertia or generalized mass is reduced to a greater extent than the reduction in the actual mass would indicate. Thus, the expedient of providing apertures in the lower part of the needle, permits a still further latitude of design. For instance, the reduction of mass at this-point permits a greater increase of mass at other points, without lowering the resonance frequency. In this particular instance the added mass is in the form of a stiffening member, or insert, and also in the increased lateral dimensions, which prorides increased lateral stiffness.

Furthermore, the point l3, instead of being a sapphire point, may be fabricated from tungsten, or from steel, the steel being tipped with a suitablehard alloy, such as osmium-platinum alloy. If a sapphire point is used it is preferred to have a rough ground sapphire, inasmuch as the roughened surface provides a bond which is a little more secure. Similarly a metallic point can be provided with a slightly roughened surface. In certain instances, the point is coated with a suitable lubricant such as a solvent, or a plasticizer, Or a cement before it is forced into the bore of the plastic needle.

The stiffening member, or insert l4, may be of any substance having a stiffness substantially greater than that of the plastic needles, although a metal is preferred. More specifically, I have found that light weight metals or alloys work 7 5 satisfactorily, such as aluminum or magnesium.

The foregoing description and the accompanying drawings are deemed to be illustrative only, and my invention is to be limited only by the appended claim.

I claim:

A phonograph needle formed from an organic plastic material having comparatively low stiffness and mass comprising a shank portion and a lower portion, said lower portion being curved forwardly, the width of said shank portion being greater than the thickness thereof in order to provide greater stiffness in a lateral direction than in a vertical direction, a stiffenin member received in only the upper part of said shank portion to provide a localized stiffness, and a record engaging point mounted in the end of said curved lower portion, said curved lower portion being provided with an aperture passing through the needle in the direction of its thickness to offset the increase in generalized mass effected by the greater width of the needle, and by the stiff en- 6 ing member, the major part of that portion of the needle which is formed from organic plastic material being free from the stiflening effect provided by said stiffening member.

WILLIAM H. HUTTER.

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

UNITED STATES PATENTS