US2141584A - Sound reproducing and recording apparatus - Google Patents

Description

De'c.27, 1938. swlTTANDER 2,141,584 v SOUND REPRODUCING AND RECORDING APPARATUS Filed Deo. 2, 1956 2 Sheets-Sheet 1 f ho/ef Dec. 27, 1938. s. WITTANDER SOUND REPRODUCING AND RECORDING APPARATUS Filed Deo. 2, 1956 v 2 Sheets-Sheet 2 Patented Dec. 27, 1938 maar PATENT oFFicE soUND REPRonUoING AND RECORDING APrARATUs Samuel Wittander, Traneberg, Sweden o o Application December 2, 1936, serial No. 113,917

In Sweden February 22, 1936 2 Claims.

Electric devices hitherto used in the reproduction of sound from gramophone records operate in such manner that an alternating current is induced in a stationary electric conductor arranged 5 in a magnetic eld, said conductor having usually the form of a coil mounted between magnetic poles. In such devices the induction of the alternating current in the coil takes place by an armature'swingably mounted between the pole pieces l and adapted, by means of an auxiliary member such as a needle or the like, mechanically to transfer vibrations from thersoundtrack of the gramophone record.

This manner of reproducing sound recorded on i l' a gramophone record has the disadvantage of the sound being distorted to a great degree which in turn depends on physical as well as material difficulties which could not hitherto be eliminatedk constructively. Some of said difficulties depend on the natural vibrations of the armature, the

residual magnetism, the mounting of the armature in soft material such as rubber or the like and the damping of the armature to eliminate its natural-vibration, which damping often consists v in said armature being,wholly or in part, em-

bedded in rubber or the'like.

The above said physical and material diiculties in the reproduction are also present, although in reversed order` when using similar devices for VY recording sound by tracking gramophone records,

causing the sound recorded to be distorted already in the tracking operation. In thereproduction of sound recorded in such manner the distortion is, consequently, very apparent, by the reproduction often lacking the greatest part of the fundamental frequencies which give deep and harmonic resonance to the intermediate frequencies carried by same and by the higher frequencies which give character to the sound being lost, wholly or in part.

The principal object of my invention is to provide a new method for recording as well as for reproducing sound whereby the above said diffiv culties are eliminated. Y 15v In reproducing vibrations from the soundtrack of a gramophone record I transfer such vibrations inknown manner by means of an auxiliary member such as steel needle or the like which is brought-to follow the variations of amplitude of said track. The motion derived therefrom I transmit to a stably mounted movable member, which carries the needle. If an electric conductor is secured to said movable member and insulatedY therefrom and the member is arranged to move in 5 5; a magnetic eld, Vthe needle will impart to said conductor a vibratory motion in the stationary magnetic field causing an alternating current to be induced in the conductor, the magnitude and frequency of said current being determined by said motion. An alternating current induced in 5; such manner is wholly identical with the motion imparted to the conductor as it does not suffer from the above mentioned distorting facto-rs.

Based on the above knowledge my new method for recording and reproducing sound, e. g. from l0'. gramophone records, comprises bringing movable electric conductor to vibrate about an approximately diametral or diagonal imaginary axis in two magnetic fields separated from each other and having opposed polarities thereby causing 16: an alternating current to be induced in said conductor, utilizing said current to modulate an amplification tube, and transferring, by means of a member connected to said tube, the alternating current into audible vibrations. 2 0- A further object of my invention is to provide a device to transfer sound from a gramophone record, sound band or the like provided with soundtrack, said device comprising an electric conductor movably mounted between two sepa- 2:5l rated magnetic fields and adapted to be brought into vibrations about an approximately diametral or diagonal imaginary axis, said magnetic fields having opposed polarities. Said conductor is arranged about a central cross, two diametrically 30 opposed arms of which are provided with edges forming centres for the vibratory motion, an intermediate member being provided between the magnets to separate said elds magnetically, said member being at its one side formed with grooves 3,5'l or the like of such a shape as to provide a sufficient space for the vibrating edges which latter bear on the bottom of said grooves.

A still further object of my invention is to provide means on a gramophone or talking machine 40e enabling alternative use of the common sound box or a pick-up or only the latter, said means being preferably formed as a detachable coupling.

To this end I form the one end of the movable portion of the sound channel of the gramophone 45;

and the pick-up arm, respectively, in such a manner as to be easily inserted into and removed from a common atachment, fitting or the like. This fitting I may x to the stationary portion of the sound channel, e. g. at the place thereof at 5 07 which said channel protrudes throughthe plate carrying the driving means of the gramophone,

or at any other suitable place of said plate outside the stationary sound channel. The fitting may be provided with means to engage themovable pori` tion of the sound channel and the pick-up arm, respectively, so as to maintain same in position.

At the place of said attachment means or fitting I may provide contacts for the electric wires of the pick-up to connect same with contact bushes or the like arranged at any place of the plate carrying the driving means of the gramophone or the side frame thereof.

In gramophones having a permanently fixed sound arm a universal fittingY according to my invention may render possible to attach a pickup also in such cases when said device is not enclosed in the gramophone. When the pick-up is removed the universal fitting may serve as hold-er for a receptacle or receptacles for needles. A cover serves to maintain the needles on transport. These and further objects of my invention will be apparent according as the following description proceeds reference being had to the accompanying drawings shown by way of example some embodiments of the invention.

In the drawingsz- Y Fig. 1 is a diagrammatic front view of an apparatus according to the invention.

Fig. 2 is a corresponding Vplan vi-ew seen from below of Fig. 1.

Figs. 3 to 6, inclusive, are different views of an embodiment of a supporting means for the electric conductor, Fig. 3 being a cross sectional viewQFig. 4 a plan view, Fig. 5 across sectional View along a plane perpendicularly to that of Fig. 3, and Fig. 6 a perspective view of said means.

Fig. '7 is a top plan View of a gramophone of conventional type.

Fig. 8 is a vertical cross sectional view on an enlarged scale of a universal tting and a sound arm for acoustic reproduction attached thereto.

Fig. )V is a view similar to Fig. 8 with a pickup fixed to said universal fitting.

Fig. l isa top plan view of the fitting.

Fig. 1l is a vertical cross sectional view or" another embodiment of a fitting formed as a holder for a receptacle for needles.

FigflZ is a top plan view of Fig. 11, the cover being removed.

Referring especially to Figs. l and 2 of the drawings I and 2 designate two independent magnets magnetically insulated from each other and rigidly secured to a non-magnetic centre piece 3 as for instance by screws 4. Preferably, this piece 3 is formed out of aluminium, and in order further to reduce its weight it may be provided with Vbores and 6 which may be threaded to serve as fastening means for the magnets i and 2 or for a holder (not shown). At its lower surface the centre piece 3 is formed to provide two supporting studs 'I which at their lower free end are formed with a wedge-shaped groove 8. Y

At their lower endthemagnets I and 2 are provided' with arc-shaped air-gaps iii and Il formed by inner pole-pieces'li and l5 and outer pole-pieces I3, i3, the'latter being divided by a slotI'I. Principally, the polarity of the'magnets are such that the pole-pieces Ifl and i5 have op'- Y According to Figs. 3 to 6, inclusive, the support 'Y of the coil I 2 has substantially the shape of a cross comprising a needle holder 20 having a needle hole 2I and two pairs of opposed arms I8 and I9 extending from said-holder. The arms I9 are shaped similar to a scale-beam, each arm comprising ltwo bearing parts 29 and 30 arranged in alignment with each other on different levels and connected by an intermediate part SI. The edge-shaped bearing parts 39 nearest to the needle holder arerformed to fit into the Wedgeshaped groove 8 ci the bearing studs l1 and I2 (see Fig. 2) and are preferably made with a smaller edge angle than said grooves 8. The bearing parts 2Q are adapted centrally to equalize the pressure from suspending means for the swingable system. Preferably, such suspending members are made by soit'material such as rubber in the form of a strip or th-e like as shown at 33 and 3ft of Fig. 6 or in the form of pieces of any suitable shape capable of being arranged as intermediate layers for carrying members of more solid material (not shown) 1 The needle holder comprises an attaching member Z having a threaded hole 2l in which the needle may b-e rigidly secured by a screw 28 (see Fig. 5), or the needle hole 2l may be conical as shown at Z2 and formed with a groove-shaped enlargement in the one or both of its side walls 23. In the latter case the needle is mounted loosely within the holder but is maintained in position on the one hand by the pressure of the needle against the conical portion of the hole and on the other hand by the lateral pressure created when the needle is forced against the grooved portion of the hole by a rotating gramophone record.

The arms I8 are adapted to transmit the motion t0 the swinging coil I2 and is shaped so as to have smallest possible weight and greatest possible firmness in the direction of movement. For this reason the arms I8 may be provided with a plurality of holes 24.

The supporting means I8, I9, 20 is connected to the inner side 32 of the swinging coil I2 preferably by means of a cement which becomes invariably rm after drying inan atmosphere or normal moisture and temperature. In order to ensure a firm joint, especially in the direction of motion of the coil, the arms YI8 may at their free ends be bevelrled to a smaller width as shown at in Figs. 3 and 6.

By means oi" a transmitting member such as a gramophone needle or the like the swinging sys- Ytem I2, IB, I9, 26 is caused to swing about an axis forming 90 degrees with thergeometrical axis of the swinging coil I2 and coinciding with the Ycentral limiting lines 2Q and 36 of the support l, l, 'Eil (see Figs. 4 and 5). Consequently, the two portions of the coil move in opposite directions, by the action of the respective magnetic field the Vcoil portion in the magnetic field il? moving downwardly and simultaneously the coil portion in the magnetic eld I I moving upwardly and vice versa. `On account of the polarities of the respective pcie-pieces being opposed as set forth above, a current willgbe induced in the conductor i2 of a direction depending on the direction of motion of the coil I2, said current direction being reversed, when the direction oi motion or the coil is reversed. VThe alternating voltage thereby induced is withdrawn between the Vend pieces Sland 38 of the conductor, said end pieces being preferably formed by an easily ilexible, insulated metal wirewhich is coupled to a" coupling plug (not shown) in any suitable manner. Y y

In engraving soundtracks in wax or the like the operations of the parts above described are reversed. An alternating current is impressed on the conductor through the end pieces 3l and 38 thereof so as to cause the conductor to be moved by dynamical force. This motion is transmitted to the supporting means of the conductor thereby causing a transmitting member such as an engraving needle or the like secured to said member to be moved identically with the-impressed alternating current. The motion is recorded in a surface of soft material by engraving.

My invention may also be applied to other purposes of use as for instance in photographic recording. In this case a suitable connection is provided between the swingable system I2, i8, i9, 25 and a light valve whereby a light ray is controlled by the movements of the swingable system.

Amongst other purposes of use my invention may be applied at advantage to acoustic reproduction. In such case the swinging system is connected with a membrane by means of a vibration transmitting member, preferably consisting of an extension of the arm i8 and, if required, a connecting link arranged perpendicularly thereto.

The pick-up or engraving apparatus according to my invention is preferably provided with a protecting casing of a light firm material, such as sheet of aluminium or other suitable metal and/or Bakelite. A controlling member may be arranged within the same casing as the other means of the apparatus.

Referring now to Figs. 7 to 12, inclusive, and

especially to Fig. 7, reference numeral 5i designates the side frame of a gramophone, 52 a plate carrying a driving means, e. g. an electric motor, spring motor or the like designated by 51, 53 the mouth of the xed sound channel, 54 th-e inner surface thereof in alignment with the movable sound arm, 55 a universal fitting and 56 the periphery of the turn-table.

The movable sound arm (see Fig. 8) is at its lower end formed with threads and a sleeve 5| is threaded thereon. An outer bearing cap 53 carries a bawl 64 threaded thereinto. Balls 52 are provided between the bearing cap 63 and the sleeve 6l as well as between the latter and the bawl 64. The bearing cap is provided with lugs 65 to facilitate its turning and with inwardly extending projections 66 for engagement with the universal fitting 55.

According to Fig. 9 the sound arm 60 shown in Fig. 8 is replaced by a pick-up arm the lower portion 67 of which is shown in said figure having a channel 58 serving as protection for the electric wires 59, 7i! of the pick-up. 'H and 12 are contacts provided on the pick-up arm and i3, 'lli corresponding contacts onthe universalrfitting i5, 'i6 are electric wires leading to Contact bushes or the like (not shown).

According to Fig. 11 'l1 designates a cover for the fitting 55 which in this case is formed to carry one or more cups 18, 'i9 for gramophone needles.A 59 designates the hole in the plate 52 which as shown is somewhat greater than the hole 55a of the previous embodiments.

The fitting 55 may be xed to the plate 52 by means of screws 55a and has a border forming grooves Si which together with the projections 56 form a bayonet clutch 82 (see Figs. 10 and 12).

The universal fitting 55 may be fixed at the place of the plate 52 at which the fixed sound channel 53.0pens, or it may be arranged at any other place on said plate 52, e. g. at 58 (see Fig. '7) on the free portion outside the periphery 55 of the turn-table.

What I claim is:-

1. In an apparatus for engraving sound records and for reproducing such records, the combination of two magnetic ields, a cross having a plurality of arms, edges on at least two arms of said cross, an electric conductor movable between said magnetic fields, said electric conductor being arranged about said cross and bearing on said edges so as to cause same to vibrate about an approximately diametral or diagonal axis.

2. In an apparatus according for engraving sound records and for reproducing such records, the combination of two magnetic fields, an intermediate member adapted to separate said magnetic iields and having grooves, a cross-like member having a plurality of arms andedges thereon bearing on the bottom of said grooves, and an electric conductor arranged about said cross-like member, said cross-like member being adapted to vibrate about an approximately diametral or diagonal axis and said grooves having such a shape as to provide space for the vibration of said cross-like member.

SAMUEL WITTANDER.

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