US2356810A - Electromagnetic translating device - Google Patents

Description

BEST AVAILABIE COPY A 29 1944. B. B. BAUER ELECTROMAGNETIC TRANSLATING DEVICE Filed Feb. 7, 1941 2 Sheets-Sheet 1 fmszm Aug. 29, 1944. B BAUER 2,356,810

ELECTROMAGNETIC TRANSLATINC- DEVICE Filed Feb. 7, 1941 2 Sheets-Sheet 2 'mmax Patented Aug. 29, 1944 UNITED STATES v PATENT OFFICE y \f 2,356,810 ELECTRQMAGNETIC TRANSISATING DEVICE Benjamin B. Bauer, Chicago, 111., assignor to S. N. Shure and Frances Shure, trustee, doing business as Shure Brothers, a partnership 7 Application Febuary 7, 1941, Serial No. 377,855 I 17 Claims.

This invention relates to an electromagnetic translating device and more particularly to a phonograph recorder or reproducer.

(Cl. PIS-100.41)

entire vibratory system may be supported bev tween the pole pieces.

The recorders of the prior art have been generally characterized by heavy magnetic structures and relatively complicated vibratory systems. As a rule, the magnet has pole pieces of complex shape whose fabrication is inexpensive. The assembling of the entire deviceis inherently expensive also.

The vibratory portions of the recorders of the art are either mechanically complex and expensive or have undesirable vibratory characteristics.

The present invention provides a construction which is mechanically simple, ,yvhich has desir-' able and closely controllable characteristics in quantity production and which is sturdy. One important feature of the invention resides in the magnetic circuit construction whereby lightness, accuracy, economy and magnetic eificiency are attained. Another important feature of the in vention resides in the vibratory system. By vir.

\ tue of the construction of the vibratory system,

extreme mechanical simplicity and highly desirable vibratory characteristics result.

Mechanical simplicity in a vibratory device is highly desirable from a theoretical angle. Each discrete physical element in a system has its own mass and elasticity. The more elements there are in a vibratory system, the greater the problem of resonance and transfer of energy from one element to another. Y

The present invention in general contemplates a compact permanent magnet having a ge eral block shape and provided with pole faces. fer to use cobalt bearing alloys as Alnico or similar alloys having high coercive force and relatively low remanence.

prefer to have the length of the magnet; i. e., the dimension along the interior flux path, of the pre- In using such alloys, I

same order as the transverse dimension or (11- mensions and preferably equal or even less than the transverse dimension. In such 'amagnet,

the projected pole area becomes substantial and comparable to the projected area 'oithe remainder of the magnet. Thus full advantage of theproperties of modern magnet materials is taken. The magnet materials are generally hard so that they may be punched or stamped as desired; The

I a finished pole face is easily, accurately and eco 7 with its length as its The vibratory system consists of a combined armature and torsion spring piece and a rigid drive rod upon which aneedle may be mounted.

The construction is exceedingly simpleand concentrates substantially all of the elasticity'of the system within the one. armature and sprin piece.

This is important since elasticity is one of the determinants oi the vibratory characteristics of the system. The elasticity and mass of the armature and spring piece may be closely, controlled in production. This results, in accuratecontrol of the overall characteristics as will be apparent later. .The physical coupling between the drive rod and armature-spring piece isiaccomplished I in a simple but highly effective manner 'sothat for practical purposes the two may be considered as one. 1 I. i

The entire device is noteworthy for the ease and lack of delicacy necessary for assembling. All parts to be assembled are firmly and "accurately retained in position and the final product isdependent upon a few manufacturing tolerances rather than any assembly technique. In

one species of the invention, however, there is" I positioning the form of Fig. '6 is a sectional elevation alongline 6-8 of Fig. 5; I

Fig. '7 is an elevation from the rear; Fig. 8 isa perspective detail of the magnet and pole pieces of the modification;

Fig. 9 is a sectional plan view of a different modification; v I

Fig. 10 is a side elevation of the recorder of Fig.9;and v 1 Fig. 11 is'a section on |lll of Fig." 10.

Referring to Figs. -1 to 4 inclusive, a magnet [0, preferably of some cobalt bearing alloy such as Alnico has two pole faces II and 12 ground smooth. As shown, the magnet is rather squatshortest dimension and has its pole faces at each end. Any desired shape or magnet may be provided. In general, the projected pole areas, here the areas or the faces,

- othe -to form 'an air gap limits.

are comparable to'the projected areas of the re- 'maining magnet sides. Disposed on the magnet I pole faces are soft iron orsoft steel frame members l3 and 14 maintained in position by non,-

magnetic rivets IQ of brass, aluminum or the like.

The frame members are thin enough to be stamped or punched out of sheet metal. By using hi hly permeable metalfor the pole pieces the flux density therein may safely be higher than the normally lowdensity in the magnet proper.

Frame members l3.an d l4 extend beyond magnet It! to enclose the various parts of the recorder;

While the frame members are hown as generally fiat pieces lying in generally parallel planes it is -to be understood that they may have any de,-

sired shape and lie in any desired position relative to each other depending upon the mechanical details of construction. As shown here, frame members 13 and 14 extend away from magnet Ill for a distance andare provided with blocks I 8 I and [9 of non-magnetic material. Non-magnetic rivets maintain blocks l8 and IS in position.

Blocks l8 and I3 may be of metal or not and preferably are rigid enough so that a strong structure will result. Y

By having frame-members l3 and I4 extend beyond magnet 10, a region 2 is provided between them in which the vibratory portion of the recorder may be disposed. Adjacent region .2l, frame members l3 and. I have lateral extensions 22 and 23 bent out of the plane of the.

of extensions may be omitted and leave only one air'gap." 4

Operating within the twoair gaps are two portions 21 and 28 of a unitary armature whose center section 30 is extended to form a torsion tall piece 3|. This combined; armature and spring is of elastic magnetic material and may be of soft iron or soft steel. -As shown in tl'ie drawings, the armature-spring member has a generally T-shape. While the armature portions 21 and 28 are shown as equal and rectangular {it is clear that they may have any shape and length. Thus by tapering the armature portions,

the stiffness and mass may be varied, In fact by controlling the shape and dimensions of the armature and tail portions, any desired vibratory characteristic may be obtained. In any event,

this unitary piece is preferably a stamping and may be duplicated in production to within close slot 33 is preferably so dimensioned that armat e section 30 fits tightly therein. Thus the gr p between the two parts extends over the entire opposing surfaces. Rivets 31 and 33 extending transversely through the bifurcated rod end 75 providedin the pole pieces at the air gaps and 2,356,810 I r V andarmature section 30 hold the two tightly is ;suitably apertured at an end together. Other means as welding or soldering may be provided. It is evident therefore that rod 35 is supported for oscillation about its "1011- gitudinal axis.

Drive rod 35 is preferably cylindrical and may be of. aluminum or any other'metal, magnetic or non-magnetic. Irrespective of the length of lo dinar'ily the only factor, from a-vibratory angle, present in rod 35 is inertia and thisis susceptible to close control in fabrication. The rod is simple and maybe made accurately in quantity. In

fact, by using aluminum or other light weight is material for the drive rod and rivets 31 and 33,

the tolerances may be increased without ad-.

versely aifeoting the vibratory characteristics.

Rigid drive rod 35 is here shown as having substantial length and provided with some support for its free end. This consists of a sleeve 40 of rubber or other resilient material disposed around the free end of rod 35 and supported in registering semi-circular channels ll in blocks I8 and I9. A v

This resilient support for the drive rod 35 permits the rod to oscillate about its longitudinal axis. The sleeves 32 and 33 furnish a rigid support for the other end of the assembly comprise ing the drive M35 and the elastic spring 30. 30 There is. no intermediate support. The spring providestorsional compliance for the drive rod and, inaddition, since the spring is in the form of a flat leaf spring with its thin dimension extending vertically and its wide dimension exvice shown in Fig. 1), it possesses elastic compliance in a vertical direction and substantially no compliance in a horizontaldirection.

o v The free end of drive rod 35 is provided with 4 ah axial bore 42 extending inwardly for a substantial distance and threaded to accommodate *9 a lockingscrew 43. Transverse to bore 42 at an P intermediate portion of rod 35 is a needle channel 45 into which a needle 48 may be clamped by 45, screw 43. Needle 48 as a rule is of hardsteel so that screw 43 does not bite intoit, Needle ll may pass through anaperture 41 in bottom frame member M.

'The, cutter or recorder in use is normally dis- I 50 posed in the position shown in Fig. 1 where frame in case of accidental dropping, the needle point ordinarily strikes. first and drives the needle up to cause slippage. 'Io cushion the shock, a rub- 4 her or similar flexible pad 50 is disposed below top frame piece l3 and above the needle bearing portion'of.the drive rod. i-Ience the cutter is protected against damage. Pad so also functions normally as a stop when i rting a needle.

Disposed between top and ottorn ,frame members l3 and H are spools 51 and 58 carrying the voice current'coils 53. Where only one air gap and armature section are provided,only one spool would be present. The spools have narrow chanj nels 6|! through which armature sections 21 and 28 are threaded and are disposed as close as 7 possible to the air gaps. I

Rubber sleeves El and 32 around drive rod;35 are thick enough to reach thesides-ogthe spools and may provide spool spacing; means as well as v *some non-resonant damping. Slots 83 may be rod 35, the torsional elasticity is negligible. Or-

tending horizontally (in the position of the demember I3 is on top. As a rule, the deviceielfim properties to magnet I0, has finished pole faces II and I2.

Soft steel pole pieces I3 and 74 are disposed against the opposite pole faces II and I2. Said pole pieces have extensions I5 and I5 and U-shaped end portions I6 and 76 terminating in pole tips TI, TI and I8, I8 and forming air gaps l9 and 80.

The pole pieces and magnet may be maintained intact in any manner and as shown are pressed together by a spring iJ-shaped frame member 82 of sheet brass, aluminum or other non-magnetic metal. The arms 83 and 83' of the frame member may have retaining screws 84 passing through and engaging the pole pieces.

Frame member 82 has its bight portion 85 provided with a centrally disposed generally semi-circular longitudinal channel 86'. This channel may be formed by shaping the frame metal. Resting within said channel is the drive rod portion of the vibratory system and consists of rod 90 having spaced resilient sleeves BI and 92 with curved metal grips 93 and 94 almost surrounding the rubber sleeves. The drive rod assembly is maintained in position by spaced metal straps 95 and 96 extending transversely thereof and having the ends thereof rigidly fastened to'frame member 82 by screws 91.. The object of the drive rod mounting is to provide a generally resilient mounting similar in properties to the mounting between blocks 58 and I9 in Fig. 1.

One end 99 of drive rod 90 is bifurcated and grips a flat spring armature I extending upwardly .at right angles to said rod. The general rod and armature construction is the same as in Figs. 1 to 'inclusive, except that armature I00 has a tongue I01 at the extreme end. As shown in Fig. 7, armature I00 extends through both air g ps l9 and 80. Drive rod 90 has a transverse needle channel I03 in which a needle I04 may be clamped by screw I operating in axial threaded bore I06. Needle I04 may extend through a suitable aperture I01 in frame channel 86;

While the drive rod mounting .may be relied upon to furnish a restoring force to the armature. to position the same in the center of the air gaps, nevertheless additional means is preferred. This means may consist of a resilient strip 0 into which armature tongue Inf may 'be disposed. The ends of strip I I0 may be anextensions I32 and 833. Thus the armature and spring member has a generally H-shape. The supports consist of screens I34 to E3! inclusive in spaced opposed pairs threaded in top and bottom frame members I3 and I4. The points of support for the spring lateral extensions I32 and I33 may be'separated as widely as desired or may Y In this'modification, asin that of Figs. 1 to 4,

the spring member provides torsional and vertical compliance and substantially no horizontal compliance.

In the various modifications, the drive rod has 3 been disclosed as a rod of uniform cross-section throughout its effective length. This construction is the simplest to make and may sufi'ice fOr many purposes. However, in the event that torsional elasticity in the drive rod is to be provided to a substantial degree or increased above that due to uniform cross section then a departure from cross sectional uniformity may be provided. Obviously the circular cross-section may be reduced to a small circular section or changed to a narrow rectangular section. In other words, between the armature mounting part of the rod and needle carrying part thereof a short length of the rod may be flattened, re- ,duced to a smaller rod section or treated in some manner to introduce. a local torsional What is claimed is:

1. In an electromagnetic translating device, the combination of a magnetic circuit havingat least one air gap, a drive rod oscillatable about its longitudinal axis, means consisting of a metallic torsion spring joined to said drive rod and extending from an end thereof in a direction longitudinally or said drive rod for supporting said end of said drive rod and biasing said rod to a prechored by screws I H and H2 engaging the pole pieces. Strip H0 may be and is preferably -adjustably mounted to permit accurate centering of'armature I00. Because strip IIO extends on both sidesof ton ue IOI, it is clear that the damping force ofthe strip is exerted both in compressipn and tension; I

Surrounding armature I00 is a. voice current coll H5 carried on a spool and firmly wedged in between the Us of thepole pieces.

Figs. 9 .to 11 inclusive show amodification of rubber or the like havin certain of the features of both preceding constructions. the magnet arid-pole piece construction follow lines of Figs. 1 to 4 inclusive. The vibratory system differs both in the mounting and damping. Armature portions I21 and I28 havea center section I30 extended to form a torsion piece l3! and has lateral 75 determined at rest position fromwhich it may be oscillated, said torsion spring possessing elastic compliance in a direction transversely thereof and 50 being substantially rigid in a direction normal to said direction of compliance, a substantiallyrigid support for said torsion spring at a portion thereof spaced from said end of saiddrive rod, a support for said drive rod ata portion thereof spaced from said end of said drive rod, an armature carried by said rod and consisting of a fiat member extending transversely from said rod into said air gap, at leastone voice current coil around said armature, and means on said rod between said support for said'rod and said end of said rod joined to said torsion spring for supporting a stylus member in a pesition with its axis extending generally in the direction of said torsion spring transverse compliance.

2. in an electromagnetic phonograph translating device, the combination of a magnetic circuit having at least one air gap, a drive rod oscillatable about its longitudinal axis, a unitary flat metallic member having a resilient spring portion for sup porting and torsionally biasing said rod and an armature portion extending into said air gap, said spring portionhaving elastic compliance i a direction normal to the plane of said flat member .and being substantially rigid in a direction 'parallel to saidmlane, a voice current coil around compliance. 4

tensions being disposed toward said magnet, and an armature supported in said air gap.

17. In an electromagnetic translating device, a permanent magnet having pole faces on opposite sides thereof, pole piece fixed to said pole iaces respectively and extending beyond said magnet in spaced opposing relation to each other,

each of said pole pieces having a pair of extensions bent toward the opposing pole piece at points spaced from each other and from said magnet to form a pair of air gaps between said extensions, and armature means supported in said air gaps.

BENJAMIN B. BAUER.

. CERTIFICATE- 0F 'CLORRECTION. Patent No. 2, 56,810. s 9, 19M- BMJAMIN B. BAUER.

I15 15 hereby e rtified' tht error appears in the ebeve numbered patent requirin correqiion as fellows In the grant, li e 2, for the word "TRUSTEES" read -"-TRJSTEE--;111 1e 15 f or"es Trutees" read "Trustee"; page L'fira-t olunin, line 8, for "ineipensive" read. --e x pens1ve=-;fl in6 37, and second. column, line 50, ineert qiiotation marks before and after the werd "A1n1e o" .page 5, second column, line-'5, for screens re'ada-acrewsarid that I said Lettere Patent should be read with table eorrection therein that the same may co'niorm to the reeord of the case in the Patten t Offi B.

- sign'ed-a'hil sealec} fimsjaothfg'a 01 January, 4. DZ 1915.

Leslie Frazer (Send) I Acting Commissioner of Patents.

7 CERTIFICATE OF cpnREcnon. Patent No. 2, 56,810. ,Aug'ust 29, 191m.

' BENJAMIN B. BAUER.

It is hereby e rtified that error appears in the above nmnbered. patent requiring correc ion as follows In the grant, line 2, for the word "TRUSTEES" read -'IHISI'EE--; line l'yjfor "es Trustees" read --Trustee page l,'fire-t column, line 8, for "inexpensive" read --expens1ve-'-;fline 57, and second column, line 50, insert q xiotation marks before and after the word "Alniovo";

.page5, second column, line 5, for "screens" read --sorews- -;.a1id that the said Letters Patent should be read with this correction therein that the same may conform to the reeord of the case in the Patent Office.

- Signed me sealer; this 30th ea of January, 4;. D: 1915.

Leslie Frazer (Seal) Acting Commissioner of Patents.

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