US2492186A - Reproducer for hill and dale and lateral cut phonograph records - Google Patents

Description

Dec, 27, 1949 M. F. RoYsToN REPRODUCER FOR HILL AND DALE AND LATERAL CUT PHONOGRAPH RECORDS 2 Sheets-Sheet 1 Filed July 23, 1946 ATTORNEYS Dec. 27, 1949 M. F. RoYsToN 2,492,186

REPRODUCER FOR HILL AND DALE AND LATERAL CUT PHONOGRAPH RECORDS lFiled July 23, 1946 2 Sheets-Sheet 2 jrg. 5

ATTORNEYS Patented Dec. 27, 1949 REPRODUCER FOR HILL AND DAL AND LATERAL CUT PHONOGRAPH RECORDS YMarvin F. Royston, Poughkeepsie, N. Y., assignerl to American Type Founders, Incorporated, Elizabeth, N. J., a corporation of New Jersey Application July 23, 1946, Serial No. 685,593

Claims. 1

Thisvinvention relates to electromagnetic relproducers for phonograph and like records comand the low moment of inertia thereof about the eiective axis of torsional vibration.

Another object is to provide a reproducer which is convertible for use with either vertical or lateral recordings by an adjustment of the magnetic circuit thereof.

Another object is to provide a convertible reproducer for playing both lateral and vertical recordings which has a moving system of no greater mass or moment vof inertia than is required in a similar moving system of a reproducer for playing either Vtype of recording alone.

A further object is to provide a method of converting an electromagnetic reproducer, excited by permanent magnet means, from an arrangement suitable for playing vertically cut records to one suitable for playing laterally cut records, and vice versa, which involves a rearrangement of said permanent magnet means only, without switching of the electrical circuits of the reproducer.

Two general types of convertible reproducers have been proposed and used heretofore, one of which employs a pair of laterally spaced coils respectively moving in spaced magnetic elds, and the other of which employs a pair of coaxial coils moving in the same magnetic eld. In both types r,conversion from one use to the other is effected by switching the connections to the two coils to cause the respective voltages induced therein to be in aiding relationship for the particular condition under which the reproducer is used. LA

ing vthe magnetic circuit of the reproducer for vconversion purposes, whereby the voltages developed in dierent portionsvof a single coil may be to linear vibration along the axis of the coil, when vertically cut records are played, or to oscillation about an axis normal to the coil axis, when laterally cut records are played.

Lowered moving mass and moment of inertia resulting from the single coil moving system of the invention in comparison with the dual coil systems of prior art permit higher compliances, both linear and torsional, to be employed and an improved high frequency response to be attained thereby. Wear of the sound groove and stylus are also reduced.

The moving system, and resilient support therefor, employed in the reproducer of the present invention, as illustrated herein, may be similar to that disclosed in my copendingwapplication Serial No. 674,456, led June 5, 1946.

The invention will be better understood from consideration of the following detailed description, with reference to the appended drawings in which:

Fig. 1 is an enlarged side elevational view of one embodiment of the convertible reproducer of the invention, showing the arrangement thereof for playing lateral recordings;

Fig. 2 is a similar elevational view showing the arrangement of the reproducer of Fig. 1 for playing vertical recordings;

Fig. 3 is a section along the line 3-3 of Fig. 1;

Fig. 4 is a bottom plan view and Fig. 5 is a partial top plan view of the reproducer of Fig. 1;

Fig. 6 is an enlarged side elevational view of a modification of the reproducer of Fig. 1, assembled in a housing shown in section;

Fig. '7 is a section along the line 1 1 of Fig. 6, showing the reproducer permanent magnets arranged for playing lateral recordings;

Fig. 8 is a fractional view generallysimilar to Fig. '7, showing the arrangement of the permanent magnets for playing vertical recordings and showing an index adjacent the reproducer housing; and

Fig. 9 is an elevational view of the coil support of the reproducer, shown approximately full size.

In Figs. 1 to 5, representing one embodiment of the convertible reproducer of the invention, all of which figures are greatly enlarged for clearness of illustration, a moving system and suspension therefor are shown similar to that disclosed in copending application Serial No. 674,456, referred to above. The single pick-up coil Il comprising, for example, 30 or 40 turns of No. 44

' B. & S. gauge enameled copper wire is supported caused to be in aiding relation responsive either on a cup-shaped portion of a light coil support I2, preferably of aluminum, having a cylindrical extension I2 along the coil axis which carries the reproducing stylus I3. Fig. 9 shows coil support I2 approximately full size, from which an idea of the size of the other parts and of the assembly of thereproducer may be gained.

Coil II is disposed principally within annular air gaps I4, I4 formed between a central cylindrical core I5 and the tips of pole pieces I5, I6', respectively. Both core and pole pieces are of material having good magnetic permeability, such as soft iron.

The suspension for coilV support I2 isA constituted by a pair of substantially parallel cantilever springs I'I and I8 spaced apart in the direction of the axis of support I2 and coil II thereon. Upper spring I'I is a. leaf spring, for example, of .003 inch steel, clamped at one end between clamping plate and spacer 2I fixed to supporting member 22 of non-magnetic rnaterial, such as grass, which is pressed over core I5 and extends laterally beyond pole pieces I5, I6' in both directions. Spring I'I is preferably of triangular formy in the free portion thereof and has holes 25 formedy therein to decrease the mass and adjust the compliances thereof. At its free end, spring II is attached to extension i2 of coil support I2 by being pressed over a shoulder '25 on -the* coil support, the spring having a hole suitable for this purpose. The edge of shoulder 26 isV then spun or peened over to eifect a rm attachment.

Spring I 8 may be constituted by a piece of "steel music wire, for example, .004 inch in diameter, which is fixed to stationary means, as by soldering to the end of a screw 2l projecting beyond clamping plate 20, with clearance between the wire and plate. -At its free end spring I8 is attached to coil support extension I2 by being I closely coiled thereabout.

The principal axes of springs I1 and I8, respectively, are substantially parallel to the axis of symmetry of air gaps I4, It'V and intersect the axis of coil II- substantially normally thereto. The compliance of spring I8 for linear displacements in all directions except along the principal axis thereof is relatively high, as is also the torsional compliance. The compliance of spring I1 is relatively high for linear displacements along the coil axis but relatively low for i' other linear displacements. Due to the low lateral compliance of spring I1, when stylus I3 is oscillated transversely of the principal axis of this spring, as in following the sound track of a laterally cut record, coil II is oscillated substantially about the principal axis of spring I1, which thus becomes the effective axis of torsional vibration of the moving system. Spring I8 serves chiefly to hold the coil axis vertical by resisting the drag of the sound groove on the stylus.

For exciting magnetic ux in air gaps I4, I4 there is provided a pair of permanent magnets 30, 30" of high coercive force material, such as Alnico V. Magnet 30 extends between core -I5 and pole piece I6 and may be cemented to adjacent ends of magnets 30, 30 are of unlike polarity and the flux path is as'indicated by the arrows.

In this arrangement little or no iiux passes through core I5 and the flux supplied to gaps I4, I4 is in the same direction in both gaps. When, therefore, coil II is oscillated about the principal axis olf spring I'I by the lateral vibration of stylus I3 in the playing of a record, the axial components of the Vdisplacements of the two portions of the coil in gaps I4, I4", respectively, have opposite directions. The voltages respectively generated in these coil portions are therefore additive around the coil. Any voltages due toY axial displacement of the stylus are in opposition in the two coil portions referred to and so cancel one another.

By reversi-ng the position or polarity of magnet 30 so that adjacent ends of the two permanent magnets are of like polarity, as shown in Fig. 2, the flux follows parallel paths, indicated by the arrows. The ux in this case is in opposite directions in gaps I4, I4. This is the arrangement for playing vertically cut records. Up and down or axial vibration of' stylus I3 by contact with the sound groove of a record of this type causes the portions of coil II Vdisposed in gaps I4, I4', respectively, to move in the same axial direction and therefore the voltages respectively generated therein are again in aiding relation around the coil. Voltages due to lateral variation ori the sound groove which cause twisting of coil II about the axes of spring Il are in opposition in the coil portions respectively disposed in the two gaps, and so cancel out.

The modification of the invention shown in Figs. 6-8 provides means for readily eecting the reversal of one of the exciting permanent magnets of thev reproducer. In this modification magnet 40', corresponding to magnet 3U" of the previously described arrangement, isV centrally pivoted by attachment to a Shaft 4I journaled on the reproducer housing 42, which may be a part of the tone or reproducer arm of a phonograph. Magnet 40. may then be reversed in position and thereby reversedin polarity relaof dissimilary material, preferably non-magnetic,

may be introduced between core I5, pole pieces I5, I6 and the magnets, or one or both of the rubbing surfaces maybe plated, as with chromium. Tapped holes 46 may be provided in support 22 in order to secure the reproducer in a housing or to attach it` to other supporting means.

The magnetic circuit and the variations thereof are the same in the modification of Figs. 6-8

as in the modification of Figs. 1-5 and may readily be traced by the arrows in Figs. 1 and 2.

There has been disclosed herein a convertible electromagnetic reproducer adaptable to play either vertically cut or laterally cut records. The conversion from one use tothe other is effected by a change of path of the exciting magnetic flux, the single moving coil being unchanged in either its mechanical or electrical aspects.

It will be understood that various modifications i of the invention not shown or described herein may be made within the spirit of the invention and that, therefore, the scope of the invention is limited only by the appended claims.

I claim:

1. In an electromagnetic reproducer for phonograph and like records, a pick-up coil, a suspension for said coil permitting both linear vibration thereof along the coil axis and torsional vibration thereof about an axis perpendicular to the coil axis, a stylus operatively connected to said coil, said stylus being adapted to actuate the coil according to said linear and torsional modes of vibration while following vertically cut and laterally cut sound tracks, respectively, and a pair of permanent magnets and associated magnetic circuit means for producing substantially constant magnetic flux intersecting portions of said coil oppositely disposed relative to said axis of torsional vibration, the relative polarity of said two magnets being adjustable to control the relative directions of the flux intersecting said two coil portions.

2. In a convertible electromagnetic phonograph reproducer, a pick-up coil, suspension means for said coil having a linear mode of vibration along the coil axis and a torsional mode of vibration about an axis adjacent the coil and intersecting the coil axis normally thereto, and a pair of permanent magnets and associated magnetic circuit for creating a substantially constant magnetic field intersecting portions of said coil respectively oppositely disposed relative to said axis of torsional vibration in a direction normal to both said longitudinal and pivotal coil axes, the relative polarity of said two magnets being reversible to reverse the sense of said eld at the intersection thereof with one, only, of said opposite coil portions.

3. In a convertible electromagnetic phonograph reproducer, a pick-up coil, a resilient suspension adapting said coil for axial and torsional vibration, the effective axis of torsional vibration being adjacent the coil and intersecting the longitudinal axis of the coil normally thereto, and magnetic circuit means for producing flux cutting said coil comprising a central core, a pair of pole pieces having end portions thereof respectively spaced from said core t form therewith a pair of annular air gaps in which said coil is located, said two gaps being symmetrical about an axis parallel said torsional axis of vibration, a pair of permanent magnets for creating a magnetic field in said air gaps, said magnets respectively connecting said core and said pole pieces at the ends thereof remote from said gaps, and means for reversing the position of one of said magnets relative to said core and pole pieces to reverse the direction of the magnetic eld in one of said gaps.

4. In a convertible electromagnetic phonograph reproducer, a pick-up coil, a stylus, support means connecting said coil and stylus, a resilient suspension for said coil and stylus adapted and arranged to cause axial and torsional vibration of said coil upon vibration of said stylus along and transverse the coil axis, respectively, said torsional vibration occurring about an axis perpendicular to the coil axis, a magnetic structure supplying iux for coaction with said coil comprising a central core, pole pieces oppositely laterally spaced therefrom, corresponding terminal portions of said core and pole pieces forming a pair of gaps in which said coil is disposed, and a pair of permanent magnets respectively joining terminal portions of said core and pole pieces opposite said gaps each having poles of opposite polarity respectively adjacent said members joined thereby, and means for rotating one of said magnets about an axis intermediate said opposite poles thereof to reverse the polarity of said one magnet relative to said other magnet and thereby reverse the flux in one of said gaps.

5. In a convertible electromagnetic phonograph reproducer, a supporting block of non-magnetic material, a pair of pole piecesfextending from the top of said block downwardly along the vertical lateral sides thereof and having pole tips extending inwardly along the bottom surface thereof, a central cylindrical magnetically permeable core secured vertically in said block and extending from the top thereof downwardly between said pole tips to provide a ,pair of annular air gaps, a pickup coil, a stylus, a support connecting said coil and stylus, a resilient suspension for said support attached to said block and disposing said coil around said core in said annular air gaps, said resilient supension comprising an upper leaf spring and a lower wire spring adapted and arranged to allow axial and torsional vibration of said coil upon vibration of said stylus along and transverse the coil axis, respectively, said torsional vibration occurring about an axis perpendicular to the coil axis, and a pair of permanent magnets on top of said supporting block joining respective pole pieces and said central core, one of said magnets being affixed to said block, and means for reversing the position of the other magnet to reverse the direction of the magnetic field in one of said gaps.

Y MARVIN F. ROYSTON.

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

UNITED STATES PATENTS Number Name Date 2,027,169 Harrison Jan. '7, 1936 2,347,347 Yenzer Apr. 25, 1944

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