US2300809A - Glow tube - Google Patents

Description

Nov. 3, 1942. 4 A. E. REEVES 2,300,809

GLOW TUBE Filed Jan. 16, 1959 2 Sheets-Sheet 1 26 z 24 22 f i .4 @I

i z, M/cro one:

INVENTOR.

Arfiiur Feerea BY ATTORNEY 0 3, 1942- A. E. REEVES 2,300,809

GLOW TUBE Filed Jan. 16, 1939 2 Sheets-Sheet 2 INVENTOR Ar/fiur 5 Few e5 ATTORNEY Patented Nov. 3, 1942 UNITED STATES PATENT OFFICE Arthur E. Reeves, us Angeles, Calif.

Application January 16, 1939, Serial No. 251,155

3Claims.

This invention relates to sound recording; and particularly by photographic means.

Such systems are in general use. The recording is accomplished by varying the intensity of a beam of actinic radiations, which is directed toward a moving medium carrying a photosensitive surface. Motion picture film is usually employed for thi medium, especially where the "sound track" or record is to be utilized for talking motion pictures.

The source of variable illumination may be any of several types; but this invention deals with glow tubes that have been commonly employed for this purpose. Such glow tubes employ a pair.

described in detail; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims. 0

Referring to the drawings:

Figure 1 is a side elevation, partly in a glow tube embodying the invention; 1

r Fig. 21s an enlarged sectional view, taken along plane 2-4 of F18. 1;

Fig. 3 is a view, partly in section, taken from the left of Fig.2;

Fig. 4 is a diagrammatic plan view of a recording system utilizing the invention; 1 i

Fig. 5 is a diagrammatic elevation of the sys tem shown in Fig. 4;

Fig. 6 is a view similar to Fig. 1, but of a modified form of the invention:

Fig. 7 is an enlarged fragmentary end view, partly in section, of the glow tube elements of F18. 6; i

Fig. 8 is a schematic wiring diagram illustrating the manner in which the glow tube of Fig. 8 may section, of

be utilized: and

variations do not accurately follow the impulses.

This lack of fidelity is often due to overloading of the tube, in an eflort to secure adequate illumina- Y tion.

It is one of the objects of this invention to make it possible to overcome these difliculties.

In using glow tubes, the current glowing be tween the electrodes produces heating. It is another object of this invention to make it possible in a simple manner to dissipate the heat.

It is still another object of this invention to arrange the electrodes in such manner as tosecure a more intense illumination. In this connection, there is provided a lens system to produce an image of the glow focused upon the recording surface; this image is of the desired size to obviate the necessity of a mechanical slit, and the reduction in size also produces a greater intensity of illumination.

It is still another object of this invention to make it possible in a simple manner to record a double sound track simultaneously.

This invention possesses many other advantages,and has other objects which may be made more easily apparent from a consideration oi? sev eral embodiments of the invention. For this purpose there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms, which illustrate the Fig. 9 is a fragmentary view of a sound record made by the aid of the system illustrated in The glowtube illustrated inFigs. 1, 2 and 3 in- 1 eludes a sealed transparent envelope I. This enyelope'may be made from such material as glass or Pyrex, capable of passing substantially all wave lengths in the visible spectrum. The glow is intended to be produced over an extensive surface 'of one of a pair of electrodes 2 and 3, which. are

shown as closely spaced in this instance. These electrodes are made from suitable sheet metal, having similar opposed surfaces. In the present instance these surfaces are parallel planes. The spacing between the surfaces is such that the usual potential differences of several hundred volts across the electrodes may cause the creation of a glow between the electrodes or over one of the electrode surfaces. A suitable combination of ionizable rare gases at the usual pressures, may

be employed in the envelope.

These electrodes are supported within the tube or envelope i in any suitable manner. For example, a glass press I may be provided extending longitudinally of the tube i. In this press are sealed the lead-in conductors and i for the electrodes 2 and 3 respectively. A base 1 of insnla tion material, with suitable prongs l and I, is affixed to the right hand end of the envelope I. The lead-in wires 5 and i are attached to the respec- 'tive electrodes in a manner to be hereinafter degeneral principles'of the invention, will now be 55 scribed.

The electrodes are so arranged that a beam of actinic rays emerges from the left hand end "of the envelope I, in a thin, flat form, and edgewise from between the active electrode surfaces. Thus the glow from the whole space between these electrodes is rendered eil'ective to add to the beam intensity. Provisions are made to limit the glow to the space between the electrodes, as by covering the reverse sides of the electrodes by a layer of insulation.

Preferably in the present instance, these electrode surfaces are covered by the comparatively massive blocks II and II, made of a refractory insulation material. such as lavite. The opposed faces of these blocks are recessed as indicated at l3, I3, for the reception of the electrodes. The connections II, I, forming extensions of the lead-in wires 3 and 8, are accommodated in appropriate grooves in these blocks. Beads I8, I! may respectively be placed over the connections ll, II, and between the edge of the corresponding block II, II and the end of the press 4. In order to lend further rigidity to the electrode structure, as well as to maintain the active electrode surfaces at the desired separation, spacers l8 and I! may be provided adjacent the lateral edges of the blocks II, II. Bolts 28, II may be used to fasten the assembly together.

The areas of the spaced active electrode surfaces are made quite substantial. The current density of the electrode surface is therefore low during glow periods, even when a relatively heavy modulating current passes between the surfaces. Accordingly, the variations in glow intensity follow very faithfully the impulses to be recorded, irrespective of the intensity of the impulses.

The passage of the glow current between the electrodes 2 and 3 produces a considerable amount of heat. The massive blocks I8 and Ii, being in good heat receiving relation with respect to the electrodes, serve to receive the generated heat and to dissipate it effectively.

As stated hereinbefore, the glow between the electrodes I and 3 is in the form of a thin flat sheet. As shown most clearly in Figs. 4 and 5, the glow produces a narrow beam of illumination 23: it is caused to affect a photosensitive surface on a moving illm 23 to produce a variable density record. An optical system is provided through which the beam 23 is so refracted as to produce a reduced brilliant image of the glow upon the him 33 at the place 38. This system is so arranged that the thickness of the image in the direction of travel of film 33 is suiliciently small, considering the speed of film travel as to make it possible to record the highest desired frequencies. In the usual systems, this thickness is of the order of one or two thousandths of an inch. The width of the beam is restricted to agree with the desired width of the sound track.

To eifect these results, the optical system includes a cylindrical lens 28 having opposite cylindrlcsl surfaces. This lens acts to reduce the width of the beam 22. If desired aslot forming plate 38 may be interposed in the path of the beam to ensure against transmission of light beyond the edges of the lens 38. The thickness of the glow image is reduced to the desired value by the aid of another cylindrical lens 21, the axis of which is parallel to the width of the beam 22. This lens acts to focus the reduced image onto the film 33. If desired, a slot forming plate 28 maybe interposed between lenses 25 and 21 to ensure against any undesired light transmission.

A very brilliant effect is obtained, with attend- 7 variable density tracks 38 ant well-defined record lines even for low intensity signals. This eilect is due to the cooperation of several features incorporated in the appa ratus. One is that the glow between the electrodes 2 and 3, forming a glow discharge which may be a positive column or a negative glow, is distributed over a considerable area, and this glow is presented edgewise toward the recording medium 23. Accordingly the full depth of the glow is effective. Another element entering into the creation of a satisfactorily luminous recording beam is the provision of the cylindrical lenses that reduce the glow image to the prescribed dimensions needed. Furthermore, such a lens system obviates any mechanical slits or their equivalents.

In Fig. 5, there are indicated simplified electrical connections for a recording system utilizing the glow tube. For example, the electrodes 3 and 8 can be connected to opposite sides of a source 28 of direct current of the order of several hundred volts. In series with this source is the secondary coil 38 of a transformer 3|. The primary coil 32 is shown as fed from an amplifier 33, the input side of which may be connected to an appropriate source of impulses to be recorded, such as the microphone circuit 34. With the microphone circuit 33 inactive, the potential of source I! is sufllcient to produce a glow of intermediate intensity between the electrodes 2, 3. As the transformer 3| however transmits impulses to the electrode circuit, these impulses modulate the electromotive force across the electrodes, and consequently the intensity of the glow.

In the form of the glow tube illustrated in Figs. 6, '7 and 8, one of the electrodes is made in two parts so as to form a double sound track record. Such a record is illustrated in Fig. 9. Here the film record carrier 35 is shown as carrying the and 31, offset in phase. There are inherent and distinct advantages that are now well recognized, of such double track records. It is relatively simple to obtain such a double track by the aid of this invention. Thus the double track record can be obtained by providing a split cathode with the electrically separated parts 38, 39. The anode 48 has a surface cooperating with both parts 38, 39. The structure of the glow tube is quite similar to that already described. However, since one electrode is split, the supporting press ll serves as a seal for three lead-in wires l2, I3, 44, which connect respectively to the electrode elements 38, 38, 48. Likewise the tube base 45 is provided with three connecting prongs it, 41, 88. The lavite blocks 48, it serve the same purpose as the blocks l8 and i I of the first form described.

The wiring diagram, Fig. 8, illustrates how the double record may be secured. The parts 38, 38 of the cathode are connected to opposite terminals of the secondary coil ii of the transthat the impulse is in such direction as to make the upper terminal of coil 5i positive, then the force is induced in coil ii; if we assume potential or member it is augmented, and the potential of the other member II is reduced. The glow between member SI and the anode II is accordingly reduced, because the potential diilerence between these electrodes is reduced. At the same time. the slow between member 3! and anode ll is increased. Upon a change in sign or the impulse, the glow increases between member GI and the anode 40: and the glow is reduced between member I! and mode ll. Since the impulses to be recorded are passed to the glow tube circuit through a transformer such as it, the potentials across the coil ll change in sign as the impulses vary in the microphone circuit. The action of the glow tube is analogous to that of a push-pull audion circuit.

The resultant double track record Ii, 31 (Fig. 9) accordingly is such that the light and heavy lines in one track are displaced along the film II .with respect to the corresponding light and heavy lines in the other track. By appropriate well-known sound reproducing systems, this type 01 double track can be readily reproduced.

What is claimed is: i

1. An apparatus for the production or a phonofilm having a glow discharge tube as the source of light and electrical means for modulating the glow in correspondence with sound variations; characterized in that the slow tubecomprises a pair oi electrodes having opposed closely spaced surfaces .between which the sound modulated glow is produced, the film being disposed in a plane substantially pe p ndicular to said electrode surfaces and receiving the edgewise glow of the tube, and a pair of cylindrical lenses interposed between the tube and the film, said lenses subtending the entire sectional area 01' the glow and serving to focus substantially the total glow oi the said edge upon the film and to condense the same to suitable for sound records thereby eliminating the use of slits and the like.

2. An apparatus for the production of a phonofilm having a glow discharge tube as the source of light and electrical means for modulating the substantially perpendicular to the said electrode surfaces and receiving the edgewise glow of the said sheet, and a pair of cylindrical lenses interposed between the tube and the film, said lenses subtending the entire sectional area oi the glow and serving to focus substantially the total glow of the said edge upon the film and to condense the same to suitable dimensions for sound records thereby eliminating the use or slits and the like.

3. An apparatus for the production of a phonofilm having a glow discharge tube as the source of light and electrical means for modulating the glow in correspondence with sound variations: characterized in that the glow tube comprises a pair 0! electrodes having opposed closely spaced surfaces between which the sound modulated glow is produced, the film being disposed in a plane substantially perpendicular to said electrode surfaces and receiving the edgewise glow of the tube, and a lens system interposed between the tube and the film subtendlng the entire sectional area of the glow and serving to teens substantially the total glow oi the saidedge upon the film and to condense the same to suitable dimensions for sound records thereby eliminating the use of slits and the like.

ARTHUR E. REEVES.

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