US2438579A

US2438579A - Electric gas discharge tube

Info

Publication number: US2438579A
Application number: US658408A
Authority: US
Inventors: Schouwstra Pieter
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-06-16
Filing date: 1946-03-30
Publication date: 1948-03-30
Anticipated expiration: 1965-03-30
Also published as: FR895531A; GB617112A; CH240681A; NL59720C

Description

March 30, 1948. P. SCHOUWSTRA (I ELECTRIC GAS DISCHARGE TUBE Filed March 50, 1946 INVENTOR: PIETER SCHOUWSTRA BY I .515 ATTORNEY Patented Mar. 30, 1948 ELECTRIC GAS DISCHARGE TUBE Pieter Schouwstra, Eindhoven, Netherlands, assignor to General Electric Company, Schenectady, N. Y.

Application March 30, 1946, Serial No. 658,408 In the Netherlands June 16, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires June 16, 1962 The invention relates-to electric gas discharge tubes comprising an incandescent electrode and a thermal switch which reacts to the temperature of this electrode. By electric gas discharge tubes" are meant hereinafter not only discharge tubes filled with one or more gases-but also tubes filled with vapour or with a mixture of gas and vapour.

The invention relates to an improvement in these discharge tubes.

According to the invention, the switch is constructed and arranged in such manner that the incandescent electrode is invisible from the discharge path. Owing to this arrangement there is achieved an arrangement wherein the particles disintegrating from the electrode are intercepted in the direction of the discharge path and wherein an associated switch has two functions. There is therefore no need for providing a separate screen for intercepting the disintegrated cathode particles. The switch may be constructed in such manner that the incandescent electrode is also invisible from the direction perpendicular to the discharge path and is accessible from the direction away from the discharge path. It is thus achieved that the discharge also appears hehind the electrode so that the presence of dark ends of the tube may be avoided.

In one advantageous form of construction of the gas discharge tube according to the invention the element responsive to heat semi-cylindrically surrounds the incandescent electrode which extends perpendicularly to the discharge path and this element may be provided with sidefiaps or positionable appendages integral with the shield structure which cover the ends of this semi-cylinder.

The switch responsive to the temperature of the electrode may be utilized for different purposes. It may serve, for example, to put the discharge path under tension, to alter the heating of the electrode or of a supply which gives 01! metal vapour or of a substance evolving gas, to act upon an ignition mechanism, to switch into c rcuit a cooling device of the tube, to connect the two ends of the electrode to one another after the discharge has occurred, etc. In some of these cases there may occur the risk of the production of a discharge between the incandescent electrode and one of the contact pieces of the switch. This may be avoided by housing that contact piece of the switch which is secured to the ther mally responsive element arranged in the discharge chamber and serving to screen the incandescent electrode, and also the counter contact 6 Claims. (C1.17c 122) 2 piece in a chamber of insulating material which communicates with the discharge chamber via a narrow aperture which is partly closed by the said Contact piece.

According to one particular embodiment of the invention, the contact chamber may have a cylindrical shape and the contact piece may be movable in the axis of the chamber. It is thus possible to reduce the aperture by means of which the Contact chamber communicates with the discharge chamber, to a minimum without retardmg or hindering the movement of the contact member. Accordingly, a very simple construction of a contact chamber may be obtained by using a glass tube one end of which is sealed to the pinchor disc-shaped end of the tube which carries the incandescent electrode, as disclosed and claimed in U. S. Patent 2,313,683, filed by R. N. Thayer and assigned to the assignee oi'this application. In some cases it is still simpler to utilize a cylindrical cavity or this pinchas the contact chamber.

If one of the contacts or the thermal switch has to be connected to the non-adlacent electrode, this may advantageously be effected by means of a conductor which is secured to or in the discharge tube itself. By this means radio interferences caused by the tube are reduced. In addition, this procedure facilitates the ignition and the re-ignition oi the tube. The circuit arrangement of the tube may also be simplified by this procedure because this conductor may connect the two electrodes of the tube via the switch without any need of utilizing for this purpose a,

particular conductor outside the tube. Under certain circumstances the presence of the conductor on the outside 01' the wall may be more advantageous than on the inside of the discharge vessel. In the latter case it is more difficult to insulate the conductor from the discharge and, in addition, there arise other disadvantages, for example, those associated with providing and maintaining a luminescent layer of powder on the inside of the wall of the discharge vessel. The conductor may be provided on the outside of the wall by sealing it thereto by means of a kind of glass of low melting-point or by securing it thereto with the aid 0! an insulating and ference. According to one advantageous embodiment of the invention. a condenser of, say. from 5000 to 50,000 mo. which shunts the switch and, as the case may be, also the incandescent electrode, is incorporated in a stem tube or a cap of the discharge tube, It is thus achieved that all the elements necessary for the operation or the tube, with the exception of the steadying series-impedance, are united with the tubeso that it suffices to utilize two supply conductors, two connecting members of the tube and two connecting members in the holder orholders of the tube, which simplifies the component parts and facilitates the mounting of the tube. By incorporating also the steadying series-impedance of the tube in the holder or holders, it is achieved that the mounting is as simple as that of an incandescent lamp.

The invention will be explained more fully with reference to the accompanying drawin which represents, by way of example, one embodiment thereof.

Figure 1 represents a low-pressure mercury-vapour discharge tube serving for the radiation of light, which tube substantially consists of a glass tube I having, for example, an external diameter of 35 mms. and a length of 100 cms. This tube is hermetically closed at either end and comprises incandescent or thermionic electrodes 2 and 3 of the usual type. The tube contains a small or low melting-point. Figure 2 shows in section a portion 01 the wall or the tube with the conductor I4. Those portions of the wires and I3 which are remote from the discharge chamber are conquantity of mercury whichyields the required v mercury vapour with an operating pressure of about 0.01 mm. of mercury and, in order to facilitate the ignition, it may be filled, in addition, with a gas mixture consisting for example of neon and argon and having a pressure of a few mms. On the inside of the wall the tube may be coated with a luminescent layer or it may consist of luminescent glass.

The electrode 2 ismounted on supporting wires 4 and 5 which hermetically pass through the pinch 6 of a stem tube I. A bi-metallic element 9 which semi-cylindrically surrounds substantially the full length of the electrode 2, which extends perpendicularly to the axis of the discharge path, in the direction of the electrode 3, is secured to the supporting wire 5 through the intermediary of a wire 8 which is bent at a right angle. Thebi-metallic element 9, for example, may be a shield concave toward the press or pinch 6 and, may be provided with two side-flaps In which shut the side-apertures of the semi-cylinder; for the sake of clearness the'right-hand side-flap is shown in a plane parallel to the supporting wire. To the front-side of the bi-metallic element 9 is secured the upper end of a wire II which has been bent twic at a right angle and the lower end of which acts as a contact piece and is movable like a piston in 8. cylindrical cavity I2 of the pinch 6. Into the lower part of this cavity I2 protrudes a supply wire I3 whose upper end constitutes the counter contact piece of the switch. The supply wire I3 may, for example, be hermetically provided. by means ofa glass bead, in an originally throughgoing bore I2. Instead of the cavity I2 of the pinch 6 use might also be made of a tube of insulating material, for example glass, which is secured to the upper-side or under-side of the pinch or to another hermetically obturating member of the tube end. That end of the supply wire I3 which is remote from the discharge chamber is connected to the electrode 3 by means of a conductor I4 which is secured to the outside of the tube I with the aid of an insulating and preferably transparent strip I5 which may consist, for example, of a kind of glass nected to another by means of a condenser I6 of the order of magnitude of 0.01 at. This condenser shunts the contact pieces II and I3 via the wire element 9 and can easily be housed in-the hollow space between the stem tube 1 and a cap I'I. It

would also be possible to connect this condenser,

which acts as a capacity for eliminating radio interferences, between the wires 4 and I3, in which case the contacts are shunted by the capacity I6 plus the resistance of the electrode 2.

To the supporting wire 4 of the electrode 2 may be secured a wire-shaped auxiliary contact I8 and this in such manner, that it makes contact with the central piece of the wire II which has been bent twice at a right angle, after the'bi-metallic element 9 has attained the position of ordinary source of current is connected, through the intermediary of a choke coil 24, to that end of the electrode 3 which is remote from the conductor I4. The

choke coils

20 and 24 or a single choke coil substituted for them may be housed in the holders I9 and/or 25, in which case the mounting -of the tube I is as simple-as that of a tubular incandescent lamp. 4

The device operates as follows: I n-the cold condition of the bimetallic element the ends of the wires II and I3 are in contact with one another so that, after the main switch 2I has been closed, the incandescent electrodes 2 and'3 are traversed by a series-current which is substan tially determined by the impedance of the electrodes and the choke coils. This current rapidly raises the electrodes; to the emission temperature whereby the bimetallic element 9 undergoes'a deformation such that the contact piece. II- is drawn away from the counter contact piece I3 with the result that the mutual connection between the two electrodes is broken so that the discharge path is no longer short-circuited and the tube can be ignited, which is facilitated by a voltage impulse which is furnished by the choke coils upon the interruption of the said series cir cuit. During the normal operation the electrode 2 is heated exclusively by the discharge. The bimetallic switch is kept open in this case by the heat given out by'the electrode 2 and by the heat pair of cooperating'electrodes at least one of which is a thermionic electrode supported by a stem press, a bimetallic shield concave toward said press and extending about substantially the full length. or said thermionic electrode. the other one of said cooperating electrodes being positioned so that it faces the convex side of said shield, and contact means actuated by said shield.

2. An electric discharge device comprising a pair of cooperating electrodes at least one of which is a thermionic electrode supported by a stem press, a closed-end semi-cylindrical bimetallic shield concave toward said press and extending about substantially the full length of said thermionic electrode, the other one of said cooperating electrodes being positioned so that it faces the convex side of said shield, and contact means actuated by said shield.

3. electric discharge device comprising a pair of cooperating electrodes at least one of which is a thermionic electrode supported by a stem press, a closed-end semi-cylindrical bimetallic shield concave toward said press and extending about substantially the full length of said thermionic electrode with the axis of the electrode perpendicular to the arc discharge path, the other one of said cooperating electrodes being positioned so that it faces the convex side oi. said shield, and contact means actuated by said shield.

4. An-electric discharge device comprising a pair of cooperating electrodes at least one of which is a thermionic electrode supported by a stem press, a bimetallic shield concave toward said press and extending about substantially the full length of said thermionic electrode, the other one of said cooperating electrodes being positioned so that it faces the convex side of said shield, a stationary contact mounted in a cavity in said press,

- and a movable contact means actuated by said shield for engagement with said stationary contact,

5. A gaseous electric discharge device comprising a sealed envelope containing cooperating electrodes at least one ofwhich is a thermionic electrode, a switch comprising a bimetallic member mounted within said envelope and in heat-receiving relation to said thermionic electrode, saidbione end or said thermionic electrode, contact means carried by and actuated to open-circuit position by said bimetallic member upon heating thereof, and means electrically connecting said bimetallic member with the other end ofsaid thermionic electrode upon expansion of said himetallic member to short-circuit said electrode during operation of the device.

6. An electrode structure for an electric discharge device comprising in combination a vitreous stem, a pair of lead-in wires fused to said stem, a support wire fused to said stem, a thermionic electrode connected to and between one of said lead-in wires and said support wire, a bimetallic member concave toward said stem and enclosing said thermionic electrode, said bimetallic meme ber being supported at one end from said support wire and electrically connected to the adjacent end of said thermionic electrode, movable contact means carried by the other end or said bimetallic member and normally engaging one end of said other lead-in wire, and a second contact member on said one lead-in wire located in the path of movement of said movable contact means to electrically connect said bimetallic member with the other end oi. said thermionic electrode upon expansion of said bimetallic member to short-circuit said electrode during operation of the device.

PIETER SCHOUWS'I'RA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number