US1891780A - Method of and apparatus for recording and reproducing electrical impulses - Google Patents

Description

Dec. 20, 1932.

R. E. RUTHERFORD METHOD. OF AND APPARATUS FOR RECORDING AND REPRODUCING ELECTRICAL IMPULSES Original Filed Dec. 20, 1928 Patented Dec. 20, 1932 UNITED STATES,

PATENT OFFICE ROBERT E. RUTHERFORD, OF IPHILADIEH'JPHIA, PENNS Y LVANIA METHOD OF AND APPARATUS FOR RECORDING AND REPRODUCING ELECTRICAL IMPULSES Application filed December 20, 1928, Serial No. 327,333. Renewed July 29, 1932.

My invention relates to the recording of electrical impulses, and particularly to the electrical recording of sound.

An objectof my invention is to provide a new and simple method of sound recordation.

Another object of my invention is to provide a means of recording any succession of electrical impulses, as for example telegraph or television signals.

Still another object of my invention is to provide a method of recordin sounds, which is substantially free from e ects producing subsidiary or interferent noises.

A further object of my invention is to provide an inexpensive and practically permanent sound record.

My invention possesses other objects and valuable features, some of which will be set forth in the following description of my invention which is illustrated in the drawing forming part of the specification. It is to be understood that I do not limit myself to the showing made by the said description and drawing, as I may adopt varying forms of my invention within the scope of the claims.

Referring to the drawing:

Figure 1 is a plan View of an electrical recorder and reproducer embodying my invention.

Figure 2 is a longitudinal sectional View of the apparatus shown in Figure 1, the

- plane of section being on the line 2-2 of Fig. 1. The electrical circuits used in recording and reproducing sound are diagrammatically shown in this figure.

Considered broadly, my invention comprises the recording of electrical impulses by electrizing a dielectric,and their reproduction by afl'ecting an electrostatically sensitive relay by the electrized dielectric.

Electrostatic charges are usually of a temporary character and dissipate themselves or are discharged within a short time. It has been known for some years, however, that it is. possible to produce permanent electrical charges upon certain dielectrics, and for this processthe term electrization has been proposed and has come to be generally accepted as meaning a permanent electrification.

While electrization of some dielectrics may be produced by bombardment with cathode rays, the more convenient method is to allow a liquid or molten dielectric. to solidify'in an electrostatic field. Most dielectrics are better conductors in a liquid than in a solid state, and it appears probable that ions are formed in the liquid dielectric which cannot recombine and neutralize their charges when the material solidifies. This phenomenon has been observed in such dielectrics as beeswax, resins, carnauba wax, shellac, parafiin, and various mixtures6 of these and other ingredients. Whatever the mechanics of the effect-may be, it is known that the electrization remains sensibly constant for periods of several years, or as long as the effects have been under observation. These elfects are utilized in my method of electrical recording.

In the form of my invention which I have chosen for detailed description, the impulses to be recorded are sound waves translated into electrical impulses by the microphone 1 which'feeds into a speech amplifier 2. The entire recording apparatus is mountedon a grounded metal base 6. The record is formed on a paper strip or tape 7, which is impreg nated with a dielectric such as parafiin having a suitable melting point, i. e., one higher than the ambient temperatures to which it may be subjected but not so high as to injure the paper. In making the record the tape is transferred from a feed reel 8 to a receiving reel 9, the reels being journaled respectively on the standards 11 and 12 mounted on opp0 site ends of the base 6.

The tape is drawn thru the apparatus by a pair of rubber covered rollers 13 and 14, which are fixed to the shafts 16 and 17, journaled in the bracket 18. A pulley 19 on the shaft 16 is geared to the motor 21 by the belt 22 and drive pulley 23. A smaller pulley 24, fixed to the shaft 17, drives-the recelving reel 9 by means of the slip-belt 26 and pulley 27 on the reel shaft 28. The speed of the tape is thus determined by the roller 14, but the tape is constantly kept taut by the reel9, whose tendency to over-run is compensated for by the slipping of the belt 26.

Adjacent the feed reel 8 the tape runs under a guide wheel 31 and thence over an electrical heating element 32 mounted on a bracket 33 secured to the base. Closely adjacent the heating element is a hollow platen 34 supplied with inlet and outlet pipes 36 and 37 thru which water or cold brine may be circulated. It will thus be seen that as the tape is run thru the machine, the dielectric is melted by the heater and then quickly chilled by the cooling platen.

Mounted above the platen on the insulating pillars 38 is a conducting plate 39, spaced above the platen just sufiiciently to allow the easy passage of the tape therebetween. This plate is connected to the plate circuit of the output tube of the speech amplifier 2, which is actuated by the electrical impulses to be recorded. A strong variable electrostatic field is therefore established between the plate and the platen, which is grounded to the base and hence connected to the grounded side of the amplifier output circuit.

It will be seen that as the tape is rapidly and uniformly drawn thru the apparatus, there is a fixed position or narrow line determined by the critical temperature of the dielectric within the field at which solidification and electrization of the dielectric occurs. The field atthis position changes with the incoming electrical impulses, and the successive elementary areas of the dielectric are differentially electrized in correspondence with the successive impulses. The use of a fairly wide conductor plate and platen maintains the, line of solidification in the electrostatic field during minor temperature variations.

The fixed charges due to the electrization have a maximum value of the same order of magnitude as the maximum temporary charges which can be produced by friction. P

The formation of such temporary charges can be largely suppressed and anomalous results prevented by metallizing the grounded surface 41 of the paper strip or otherwise rendering it conducting. This appears to have an additional advantage in rendering the electrization more permanent, but altho it is a desirable expedient, it is not an essential one.

The reproducing e uipment is shown as mounted on the same ase 6 as the recorder. This comprises a pair of insulating brackets 46 which carry a pair of conductors 47 and 48, connected to the filament 49 and grid 51, respectively, of anamplifier 52 which feeds a loudspeaker 53. The form of the conductors is not important as long as their opposed area is small, so that they form a ca acity presenting a substantially line sur ace to the record tape. They may be merely a pair of parallel wires between which the tape is drawn, but I prefer to use rollers of small diameter as shown, with the upper or grid roller 48 pressed downward against the tape by springs 54.

It is not contemplated'that the recordin and reproducing systems will usually be use simultaneously, altho this is sometimes done for the purpose of monitoring the record. It is of course apparent that recorder and reproducer can be mounted entir ly separately, if desired.

In reproduction the electrized dielectric is drawn between the reproducing electrodes at substantially the same speed as for recording. The electrostatically sensitive vacuum tube relay is affected by the differentially electrized tape within the field of the conductors, and the original impulses are reproduced in its output circuit, to be translated into sound by the loudspeaker.

Practically all incidental orinterferent noise can be eliminated in this device. By making the only parts which touch the record before it passes thru the reproducing capacitor of metal, substantially all tem orary electrical charges are removed, and t ese are the chief possible source of interference. When the tape is reeled up, such temporary charges as may have been accumulated are dissipated by the conducting surface of the dielectric.

I claim:

L-The step in the method of recording sound impulses which comprises electrizing a dielectric.

2. The method of recording sound which comprises the translation of the sound into electrical impulses, and electrizing a dielectric therewith.

3. The method of recording sound impulses which comprises electrizing elementary areas of a dielectric in correspondence with the potentials to be recorded.

4. The method of recording sound imulses which comprises establishing an electrostatic field correspondin to said impulses. and causing a molten diefectric to solidify within said field.

5. The method of recording electrical impulses which comprises establishing an electrostatic field corresponding to'said impulses bringing a molten dielectric within said field by a relative motion therebetween, and cansing the dielectric to solidify within said field.

6. The method of recording sound impulses which comprises electrizing successive elementary areas of a dielectric in correspondence with the successive impulses to be recorded.

7. A'recorder for electrical impulses comprising means for establishing an electrostatic field corresponding to said impulses, means for causing a relative movement between said field and a dielectric, means for melting a portion of the dielectric, and means for causing the solidification of the melted dielectric within the field.

8. A recorder for electrical impulses com-- prising means for establishing an electrostatic field corresponding to said impulses, means for moving a dielectric-thru said field,

means for melting a rtion ofthe dielectric,

and means for causing the solidification of the melted dielectric within the field.

9. A recorder for electrical impulses comprising'a heater, a cooler adjacent thereto,

means for moving a dielectric past said heaterand cooler, and means for establishing an electrostatic field thru the dielectric within the field of action of the cooler.

10. A record of sound impulses comprising an electrized dielectric.

11. A record of sound impulses comprising a differentially electrized dielectric.

12. A record of sound impulses comprising a paper impregnated with an electrized dielectric.

13. A record of sound impulses comprising a paper having a conducting surface and impregnated with an electrized dielectric.

14. The method of reproducing electrical impulses which comprises causing electrized areas of a dielectric successively to actuate an electrically sensitive detector.

15. The method of reproducing sound which comprises causing successive elementary electrized areas of a dielectric, to actuate an electrically sensitive detector to produce electrical impulses, and translating said impulses into sound.'-

and means for util ,a dielectric in intensities 16. A phonographic method comprising means for translating the sound into electrical impulses, means for successively electrizing elementary areas of a dielectric with said impulses, and means for reproducing the sound from the record thus formed. i 17. A sound reproducing system comprising an electrized dielectric, a pair'of opposed conductors bringing successive elementary areas of the dielectric Within the field of the condenser, an electrostatically sensitive detector havingan actuatingcircuit connected to said condenser,

said heating means for cooling said strip, and a plate Insulated from said heating and cool- 111g means positioned to establish an electrotion.

19. The method of recording sound which comprises electrizing distributed areas along proportional to the sound impulses.

. In testimony whereof, I have hereunto set my hand. ROBERT E. RUTHERFORD.

forming a condenser, means for p ing the output of said detector to produce sound. 18. A recorder for'electrical impulses comprising means for moving a dielectric strip, means for heating said strip, means adjacent static field thru said strip in the cooling por- Y

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