US2483398A

US2483398A - Recording process utilizing the magnetic field of a current conducted by the record member

Info

Publication number: US2483398A
Application number: US580820A
Authority: US
Inventors: William A Brastad; Lester F Borchardt
Original assignee: General Mills Inc
Current assignee: General Mills Inc
Priority date: 1945-03-03
Filing date: 1945-03-03
Publication date: 1949-10-04
Anticipated expiration: 1966-10-04

Description

1949- w. A. BRASTAD ET AL 2,483,398

RECORDING PROCESS UTILIZING THE MAGNETIC FIELD OF A CURRENT CONDUCTED BY THE RECORD MEMBER Filed March 3. 1945 2 Sheets-Sheet l BY ATTY.

Dot. 4, 1949. B STAD ET AL 2,483,398

THE MAGNETI W RECORD PRO SS U IZING C FIELD OF A U REN ONDUCTED BY THE RECORD MEMBER Filed March 3, 1945 2 Sheets-Sheet 2 0 65 76 78 e4 9o 9' t 8) -r -Fm\ |Mfl um 4 so J IN VE N TORS. WILLIAM A. BRASTAD LESTER F. BORCHARDT forms of recording heads for Patented Oct. 4, 1949 UNITED sures 2,433,398 I RECORDING PROCESS UTILIZING THE MAG- NETIC FIELD OF A CURRENT BY THE REGORD MEMBER William A. Brastad and Lester Minneapolis, Minn, assignorszto ooNnporen F. Borchardt, General Mills,

This invention relates to recording sound on wire, tape, disks, and like paramagnetic mediums.

Heretofore recordings of sound on wire have been made by transmuting the energy of sound by means of a suitable microphone into an alternating or pulsating current which then acts through a suitable electromagnet to produce a corresponding pulsating magnetic field through which the paramagnetic material, as wire, ribbon, disk, etc., passes to receive a magnetic recording.

By means of this invention the recording can be done Without the use of electromagnets or of any paramagnetic material other than that in the wire or other medium on which the record is made. Instead, the recording is done by passing the recording current into and out of said medium.

An object of this invention is to provide a simple and efiicient method of and apparatus for recording sound on wire.

This and other objects as will hereinafter appear, are accomplished by this invention, which is fully described in the present application, and shown in the accompanying drawings in which Figure 1 is a diagrammatic view of the apparatus for recording sound on wire and for reproducing the same;

Fig. 2 is an enlarged perspective view of one form of recording head for use in this invention;

Fig. 3 is an enlarged section on the line 3 of Fig. 2;

Fig. 4 is a similar view of another form of recordin head;

Fig. 5 is an enlarged section on the line 5 of Fig. 4;

Figs. 6 and 7 are perspectives of still other use in this invention;

Fig. 8 is an enlarged section on'the line 8 of Fig. 7; and

Fig. 9 is a perspective of of recording head.

The embodiment diagrammatically illustrated in Fig. 1 consists of reels A and B with a wire W still another form wound thereon which is unreeled from the reel A, passes around sheaves C, D, is wound up on the reel B. Apparatus for operating the reels A and B, to reel the wire from reel A to reel 3, and then from reel B to reel A, is well known in this art, and is not illustrated as it forms no part of the present invention.

Sound to be recorded on the wire W, enters the microphoneE, from which it emerges as an electric current which when suitably amplified in the amplifier F, may pass through a transformer G, receive a biasing current from a suitable source such as battery H, the current then flowing in the leads J, which acts through a recording head K to energize the wire W, as will now be described in detail. a

The recording head K may take any of the forms shown in Figs. 2, 4, 6, 7, 9 and'others operating along similar lines. The recording head K in Fig. 2 consists of a block lil of suitable electrical insulating material like fiber. Around this are secured two metal wire loops l2, It, which are connected to the leads J of Fig. 1. These loops serve to retain themselves on the block it and are separated at the bottom, as shown, but at the top are quite close together, preferably separated by a space N5 of approximately the diameter of the wires 52, I4 and W, namely .004". e In the present setup a stepdown transformer is used to lower the voltage and increase the magnitude of current put out by the amplifier F. The use of this transformer, however, is a matter of choice, depending largely on the current and voltage output of the amplifier.

For our purposes we have found that a speed of 5 it. per second on wire W is suitable both for recording and, reproducing. This, however, may be varied considerably.

In the setup as shown in Figs. 1, 2 and 3, with the Wire W moving approximately normal to the conductors I2, it, current enters the wire W through one of the conductors 52, i l and leaves through the other. Alternations of this current in the output of the amplifier are recorded on the wire W and can be picked up, either at once or later, by a suitable electromagnetic reproducer 20, which in turn generates an alternating current in the leads 22. This current then being amplified in the amplifier L is converted into sound in the loud speaker M.

Applicants theory of how the recording occurs, but by which they do not wish to be bound, is as follows: A biasing current preferably of the order of one ampere is supplied to the leads J by the battery H and on this current is superimposed a pulsating or alternating audio current by the secondary coil of the transformer G. Referring now to Fig. 3, these combined currents flow through the spaced Wires l2, M and thence through the steel wire W on which a recording is to be made. Because of the relatively large elec tric currents and the small cross-sectional area of the current path through the steel wire W, the magnetic fields generated by these electric currents are sufiiciently strong to leave a magnetic sound record on the moving wire. It is to be understood applicants are not limited to D. C. biasing but may use any other well known form such as supersonic.

In Fig. 4 is shown a modified form of the recording head Kl in which two thin sheets of

metal

30, 32 are separated by a suitable insulator 34, and connected through leads J1 to the recording amplifier circuit of Fig. 1. The

plates

30, 32 and insulator 34 are pressed between suitable insulatin blocks 38 38 which firmly hold them in place.

The wire W1 of the circuit shown in Fig. 4, passes through a notch 39 which, as shown in Fig. 5, is approximately one-half the depth of the wire. The recording by means of the apparatus shown in Fig. 4 is quite similar to that shown in Figs. 1 and 2. The same reproducer serves in. both cases.

In Fig. 6 is shown a pair of spaced metal electrodes 4t, 42 connected through wires J2 to a suitable source of energizing current as that supplied by the leads J of Fig. 1, with a thin strip of permalloy or the like 44 of the order of .002 to .020" in thickness, between them but spaced therefrom by a suitable insulator as two Scotch tape strips 55, the whole being held clamped between

insulating blocks

46, 48. A wire W2 similar to W of Fig. 1 slides through notches 49 in the tops of the

electrodes

40, 52 and strip 44. Thus, with current flowing from electrode 40 to the wire on its underside where they are in contact, the electromagnetic field generated will largely be confined to the space surrounding this area particularl the area of last contact. This latter is close to the permalloy strip 44, and this strip further increases the leakage of magnetic lines of force which stray from the wire to surrounding space thereby increasing ease with which the record is picked up and the sound reproduced. The foregoing is the theory of what takes place as understood by us but we do not wish to be bound by this theory.

The recording head K3 illustrated in Fig. 7 is much like that shown in Fig. 4, except that the metal electrodes 5, 52 which are also insulated from each other, are relatively longer and are preferably provided with grooves 59, for the passage of the wire W3, whose depth may be considerably greater than the diameter of the wire. Wire leads J: are connected to the battery H and transformer G of Fig. 1. These electrodes are suitably secured to an insulating block 54.

In Fig. 9 is shown still another modification of the recording head K4. In this arrangement the wire Wi passes between metal rollers 60, 62 which are suitably journalled on studs =64, 66, respectively, and retained by set collars E5, and set screws 61. The stud 56, is attached to a base 63, which is secured by screws to a block of insulation 10, which in turn is secured by screws 12, to a part of the recorder frame Hi. The stud 64 is carried by a member 16 which is hingedly mounted on a pin 18, secured in the block of insulation '30. A spring 85, yieldably forces the roller 60 toward the roller 52, thereby gripping the wire W4 between them. The rollers can be powered so as to drive the wire W4 or the wire can be drawn by other means thus causing the rollers to rotate about their axes as idlers. An adjusting screw 8! is an electric insulator to prevent current short circuiting the rollers fill, 62.

Electric current fluctuations to be recorded are made to flow to the rollers 60 and 62 by means of

suitable brushes

82 and 89, of carbon or the like, held in

tubular lugs

83 and 84, and yieldably, pressed against the peripheries of the roller by means of a

spring

86, 90, adjustably held by screws 88 and 9|.

As the recording is made, the wire W, in Fig. 1, feeds from the reel A over sheaves C, D and past the recording head K to the reel B. The wire can be played by means of the reproducing head immediately after recording or at any later time by running the wire in the same direction. While we have discussed only a recording medium in the form of a wire, it will be realized that this method may be satisfactorily employed with other forms of recording media such as tapes, disks, and cylinder.

Recordings made on this apparatus have proved to be quite satisfactory. Thus, it will be seen that we have provided very simple and eflicient forms of sound recorder and such as yield excellent records of sound on wire.

While we have shown and described but a few forms of our apparatus, it will be apparent that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as defined by the appended claims.

We claim as our invention:

1. The method of recording sound on paramagnetic wire comprising moving the wire at a uniform rate across electrodes closely spaced longitudinally of the wire and in contact therewith, and impressing on the electrodes a suitable direct current voltage and a pulsating voltage to :be recorded whereby a conduction current through the recording wire causes the sound .to be recorded magnetically on the wire.

2. Apparatus for recording sound on paramagnetic wire comprising spaced insulated electrodes, means for moving a wire across said electrodes and in contact therewith, means for impressing on said electrodes simultaneously a biasing voltage and a pulsating voltage to be recorded.

3. Apparatus for recording sound on paramagnetic wire comprising spaced electrodes consisting of two thin metal plates separated by a sheet of insulation of the order of .003 in thickness, means for moving a wire across said electrodes and in contact therewith, and means for impressing on said electrodes a pulsating voltage to be recorded, the wire passing through a groove whose depth is less than the diameter of the wire. 7

4. The method of recording sound on paramagnetic wire comprising developing an electrical voltage corresponding to a sound to be recorded, applying the electrical voltage to closely spaced electrodes, and moving the wire longitudinally across the electrodes and in contact therewith, whereby a varying current through the recording wire between the electrodes causes the sound to be recorded magnetically on the wire.

5. Apparatus for recording sound on paramagnetic wire comprising spaced electrodes, means for developing an electrical voltage corresponding to a sound to be recorded, means for applying said electrical voltage to the electrodes, and means for moving a wire across the electrodes and in contact therewith, thereby causing a varying current to flow in the wire between the electrodes to record the sound magnetically on the wire.

6. Apparatus for recording sound on paramagnetic wire comprising spaced electrodes consisting of two metal wires separated by a space of the order of .003" supported by electrical insulating material, means for developing a biasing voltage and a pulsating voltage corresponding to a sound to be recorded, means to apply said voltages to the electrodes, and means for moving a wire across the electrodes and in contact therewith, thereby causing a varying current to flow in the wire between the electrodes to record the sound magnetically on the wire.

7. Apparatus for recording sound on paramag netic wire comprising spaced electrodes consisting of two thin metal plates separated by a sheet of insulation of the order of .003" in thickness, means for developing an electrical voltage corresponding to a sound to be recorded, means to apply said electrical voltage to the electrodes, and means for moving a wire across said electrodes and in contact therewith, thereby causing a varying current to flow through the portion of the wire between the electrodes to record the sound magnetically on the wire.

8. Apparatus for recording sound on a paramagnetic wire comprising spaced electrodes, a strip of material highly permeable to magnetic flux between said electrodes and insulated therefrom, means for developing an audio frequency voltage corresponding to a sound to be recorded, means for applying said audio voltage to the electrodes, and means for moving a wire across the electrodes and strip, thereby causing a varying audio frequency current to pass through the wire between the electrodes to record the sound magnetically on the wire.

9. Apparatus for recording sound on a paramagnetic wire comprising spaced electrodes, a

strip of material highly permeable to magnetic flux between the electrodes and from, means for developing an electrical voltage corresponding to a sound to be recorded, means for applying said electrical voltage to the electrodes, and means for moving a wire across the electrodes and strip through a groove whose depth is less than the diameter of the wire, thereby causing a correspondingly varying electrical current to pass through the wire between the electrodes to record the sound magnetically on 45 the wire.

10. Apparatus for recording sound on a paramagnetic wire comprising spaced electrodes the thickness of which is several times the diameter insulated theregrooves across the electrodes and strip, means for 7 developing an electrical voltage corresponding to a sound to be recorded, and means for applying said electrical voltage to the electrodes, thereby causing a correspondingly varying current in the wire between the electrodes to record the sound magnetically'on the wire.

11. Apparatus for recording sound on a paramagnetic wire comprising spaced insulated electrodes, means for moving a wire past said electrodes with one electrode in contact with one point on the wire and the other electrode in contact with a different point on the wire, means for developing an electrical voltage corresponding to a sound to be recorded, and means for applying said electrical Voltage to the electrodes, thereby causing a varying current to flow through the portion of the wire between said points to record the sound magnetically on the wire.

12. Apparatus for recording sound on paramagnetic wire comprising spaced insulated electrodes, means for moving a wire past said electrodes with one electrode in contact with one on the wire and the other electrode in contact with a point on the wire spaced longitudinally from the first named point, means for de- Veloping an electrical voltage corresponding to a sound to be recorded, and means for applying said electrical voltage to the electrodes, thereby causing a correspondingly varying current to flow through the portion of wire between said points to record the sound magnetically on the wire.

WILLIAM BRASTAD. LESTER F. BORCHARDT.

Country Date France Oct. 24, 1930 Number