US1575701A - Electric gas-discharge tube for photographic sound recording - Google Patents

Description

March 9 1926. 1,575,701

H. G. MATTHEWS ELECTRIC GAS DISCHARGE TUBE FOR PHOTCGRAPHIC SOUND RECORDING- Fied July 10, 1923 Patented Mar. 9, 1926.

UNITED STATES v 1,575,101 PATENT OFFICE.

HARRY GRINDELL MATTHEWS, OE'LONDON, ENGLAND.

ELECTRIC GAS-DISCHARGE TUBE FOR PHOTOGRAPHIG SOUND RECORDING.

Application filed iuly 10, 1923. Serial No. 650,690.

charge tubes, to be employed more especiallyv as a source of sound-varied light for use in effecting a record on a sensitive film or other light-sensitive surface, but capable of other applications.

discharge tube is employed as a source of actinic light, varied by the circuit of a microphone or other electrical soundrecep tor.

An advantage accruing from the use of a gas discharge tube as compared with other electrical sources of light, is the smallness of the sound-varied current suflicing to vary the light, thus avoiding any. tendency for the microphone or the like to burn out.

.The ob ect, of the present invention is to provide the light emitting electrode of a gas discharge tube employed as avaried source of light, with an elongated light-emitting surface of an area considerably greater. than the sectional area of the beam of light emitted thereby, such that the superposed effect of points of light emission are concentrated in the beam.

For this purpose, according to the invention, the surface of the light emitting electrode (cathode) of the gas discharge tube is formed with a deep longitudinal groove.

By a deep groove is meant one of which the depthis'several times the width of the mouth of the groove I lVith-a suitably located anode and with a suitable pressure of gas in the tube,,the glow of light will be located within the groove ofthe cathode.

The efi'ectof-the groove in the cathode is not only to concentrate the light emitting surface but results in an increasedyvariation of the light when influenced by soundvaried currents. Such increased variation moreover being localized, is therefore-constantly positioned for'acting on a light sensitive surface through a small slot.

.An example of a gas discharge tube ac:

cording to the invention and a representat1ve diagram of the connections suitable for employing such a tube for photo-graphically recording sound on a travelling sensitivefilm, are illustrated on the accompanying -drawing, in which Fig. 1 is a sectional plan of one form of gas discharge tube, and

Fig. 2 is a transverse section thereof.

Fig. 3 is a diagram of-the electrical connections of the tube with a microphone.

Referring to Figs. 1 and 2, an electrode a of a gas discharge tube a is formed with a deep longitudinal groove 6, by the electrode a consisting of a sheet of metal folded For recording purposes, an electric gas about its middle and with outwardly turned borders, see Fig. 2.

The other electrode consists of a. 0 with a hole d opposite the groove the first electrode a and adjacent to the outwardly turned borders thereof.

The electrode a is'the cathode and electrode 0 is the anode.

As shown in Fig. 1, the groove '6 of the electrode a is arranged opposite and parallel to a gate 0 behind which passes a travelling. light-sensitive film f, 50 that variations in the light emitted from the electrode a, with in the groove 6, effect a varying: photo graphic record on the film f.

the i In the illustrated example, the film f istowards the film f, light from a surface of greater area thanrthe area of the beam of In the representativediagram of electrical connections shown in ,Fig. 3, the tube a -is connected to an energizing battery of-250- 300- volts 9 through" a --graphite segment potentiometer h, with'the secondary i of a low frequency transformer a in parallel with the tube a j is a voltameter in shunt across the terminals of the tubea and his a microammeter in series with the tube. Z is a telephone in series with the secondary Z of an. air core. transformer, the primary Z of which is in serieswith-the'tube m for en abling audible observation 'of the .battery' and tube circuit. The telephone Z may, howlight acts upon the film and thereforeintem 'SlfiGS the photographic efiect and exaggerates the variations thereof.

ever, be directly connected in the battery and tube circuit. is the battery switch, 9 is a fixed condenser for preventing dlscharge of the battery 9 through the primary winding i and g is a choking coll for preventing the pulsations from the transformer '11 assmg through the battery circuit.

he primary i of the transformer i is connected in series with the plate circuit of a pair of thermionic valves m in parallel, the grid circuit of which is connected in series with the secondary n of a low frequency transformer 71.. 0 is the hlgh tension battery and p the low tension filament battery of the valves m.

The primary n of the transformer 11. is connected in series with the plate circuit of a thermionic valve g, the grid circuit of which is connected to the secondary r of a low frequency transformer r. s is the high tension battery and t the low tension battery of the valve 9.

The primary 7' of the transformer 1' is in series with a battery u of about 4% volts, in the circuit of which is a microphone 'v, or a plurality of microphones variously connected, i. e. in series, parallel or seriesparallel.

I claim:

In an electric gas discharge tube, a light emitting cathode consisting of a sheet of metal folded about its middle with outwardly turned borders, and an anode consisting of a plate with a hole opposite said folded portion of said sheet and adjacent said outwardly turned borders thereof.

In testimony whereof I have signed my name to this specification.

HARRY GRINDELL MATTHEWS.

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