US2182643A - Anode heater for high voltage rectifiers - Google Patents

Description

Dec. 5, 1939. H. A. ROSE ANODE HEATER FOR HIGH VOLTAGE RECTIFIERS Filed Sept. 23, 1937 w am 2 2 I WITNESSES:

v INVENTOR Herbs/#14. Hose ATTORNEY Patented Dec. 5, 1939 UNITED stares AT E FFlCE ANODE HEATER FOR HIGH VOLTAGE RECTIFIERS sylvania Application September 23, 1937, Serial No. 165,344

3 Claims.

My invention relates to electric discharge devices and more particularly to heating means for controlling the condensation of the working vapor in certain portions of vapor-arc devices.

It is. well known in the art of metallic vapor devices that considerable difficulty is experienced in keeping the condensable medium for providing the operating vapor to such devices from condensing in the cooler portions of the container. This is especially true in spaces surrounding the electrode structures. It is equally well known that such condensation also occurs within the electrode chambers. The condensation of the condensable vapor on the anode surface is considered the principal cause of backfire.

Normally, the temperatures of regions near the electrode surface are lower than the temperatures of the electrodes themselves. It is desirable to maintain the temperature above the condensation temperature of the condensable vapor at all times. Numerous means have been utilized for raising the temperatures of the space surrounding the anode and the anode itself during light load operation. It is well known to those acquainted with the art that when anode voltages are at a high difference of potential with respect to the cathode or other parts of the rectifying circuit that it becomes a diificult problem to properly insulate the heater circuit especially if an auxiliary source of heat supply is used.

According to my invention, I eliminate the aforesaid mentioned difficulties by providing a heating means for parts of the anode structure. Moreover, I provide a suitable control means for rendering such heating means inoperative when the conditions are such as to eliminate the necessity of such heating means. Briefly, I utilize the anode current to supply energy to my heating means as ordinarily the current, particularly in high voltage rectifiers is of the order of only a few amperes. The voltage drop across the heater is comparatively small as the quantity of heat desired is low., Moreover the regulation of the output current is not affected to any appreciable extent because the energy required to heat the electrode is negligible.

It is, therefore, an object of my invention to eliminate condensation of metallic vapor in certain portions of electric discharge devices during operation.

Another object of my invention is to provide a. suitable heater which derives its supply of energy from the working or anode current.

Still further, it is an object of my invention to provide a suitable means for rendering the heater inoperative when the proper temperatures have been reached.

It is still further an object of my invention to provide a simple and efficient means for maintaining the electrodes at a non-condensing temperature.

Other objects and advantages of my invention will be apparent from the following detailed description, taken in conjunction with the accomm panying drawing, in which:

The figure is a longitudinal cross sectional View of an electric discharge device embodying the invention.

The illustrative embodiment of my invention 13 comprises a container 3 which is normally vacuum tight. Within the container 3 is a suitable vaporizable material, preferably mercury, for providing the operating vapor for the device,

said vaporizable material preferably comprising 20 at least a portion of the cathode 5, and an anode I.

The anode 1 consists in general of an anode head It and a shaft 9. The shaft 9 of the anode l has'a hollow center and encloses a connection IE to the anode head It from an outside source 11. The upper portion of the anode shaft 9 is firmly held in place by a suitable insulator l8 which is mounted on the connection l5 extending through the anode shaft 9. The connection I5 extends to the upper portion of the anode l terminating in the cap I! of the anode l. Ordinarily, the anode heat I3 is made of steel or graphite with the lower surface convex in order to distribute the arm more uniformly on the the strip 23 are contacts 25 which open or close 5 according to operating conditions. The other end of the bimetallic strip 23 is in metallic contact with the wall of the supporting stem 9. The

moving element of the bimetallic strip 23 associated with the outside heater [9 is insulated from the device by a suitable insulating material 21. Likewise, a suitable heat insulating material (not shown) shields the outside heater l9 to prevent loss of heat.

Although I have shown only two electrodes 5 u and in my illustration, it is apparent that the invention is just as applicable to similar electric discharge devices using more than these two electrodes.

The principle of my invention may be more easily understood by considering different temperatures of the region surrounding the anode structure on the supporting side or within the hollow shaft 9 itself. If the temperatures are below that necessary to keep the vaporizable medium in its evaporated state, the anode current will flow through the connection |5 and the heaters I9 and 2| which are in series with it keep the anode parts warm so as to prevent condensation of mercury on the electrode surfaces.

perature of the anode region has been reached or that temperature necessary to maintain the vaporizable material in its evaporated state, the heat developed by the heaters I9 and 2| cause the thermostatic control or more specifically the bimetallic strip to function so that the contacts 25 become closed and shunt out the heaters l9 or 2|. Current continues to flow through the thermostatic switch 23 to the anode head l3.

It is to be understood that the thermostatic switches 23 operate independently of each other. When a predetermined temperature of a certain region has been reached, the heater l9 or 2| serving that region is shunted out. During a particular instance, current may be flowing through one heater H! or 2| and by-passing the other.

While for purposes of illustration, I have shown and described a specific embodiment of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made therein without departing from the true spirit thereof or from the scope of the appended claims.

I claim as my invention:

1. A vapor discharge device comprising a container, an anode and a vaporizable cathode for providing operating vapor, said anode having a hollow stem portion, a plurality of heaters in series with said anode at least one of which is inside said hollow stem, separate shunting means associated with said heaters, any one of said heaters capable of being disconnected from its Working circuit by said shunting means.

2. A vapor electric discharge device comprising an evacuated container, a vaporizable cathode therein, an anode cooperating with said cathode, an anode connection extending within said container, a hollow anode stem enclosing a portion of said anode connection, insulating means interposed between said stem and said connection, a heating element connected to said stem and said anode connection and a heat responsive switch controlled by the temperature of said stem connected in shunt with said heating element.

3. A vapor-electric device comprising an evacuated container, a cathode of vaporizable condensing material in said container, an anode c0- operating with said cathode, a connection for supplying current to said anode, said connection extending within said container, a heating element connected in series between said connection and said anode, said heating element being traversed by the anode current to raise the anode structure to a temperature above the condensing temperature of the vaporizable cathode and a heat responsive switch for lay-passing the anode current around said heating element when the anode temperature is above the condensing temperature of the vaporizable cathode material.

HERBERT A. ROSE.

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