US2459828A - Electric valve with grid mounted on divided anode insulator - Google Patents

Description

Jan. 25, 1949.

O. K. MARTI ETAL ELECTRIC VALVE WITH GRID MOUNTED Filed Sept. 15, 1945 ON DIVIDED ANODE INSULATOR fuor/www., W,

ATTORNEY Patented Jan. 25, 1949 ELECTRIC VALVE WITH GRID MOUNTED o'N DIVIDED ANoDE msULATon Othmar K. Marti, Wauwatos'a, and Ervin 'B.

Steinberg, Milwaukee, Wis., assignors to Allis- Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application September 15, 1945, Serial No. 616,558

This invention relates in general to improvements in electric discharge devices and more particularly to improvements in such devices utilizing a metallic casing and wherein parts ofthe device are sealed in uid tight relation in such manner as to obviate the necessity of exhausting the device during operation thereof.

It is an object of the present invention to provide an improved metal enclosed electric discharge device comprising fluid tight seals which are shielded against heat radiation originating within the device.

Another object of the present invention is to provide an improved electric discharge device of the metal enclosed type in which a common seal structure remote from the discharge serves to insulate the leads of an anode and of the Vassociated control electrode.

' set forth will be apparent from the following when air cooling is resorted to. Jacket Il may also be provided with suitable means for guiding the ilow of cooling water therethrough as is wel] known.

The steel used for section 9 may have any known composition suitable for the. application thereto of anyl of the vitreous compositions known under the general designation of vitreous enamels. Both section 9 and jacket Il however are preferably made of steelcontaining substantially 18% chrome and 8% nickel to prevent corrosion of the surfaces thereof in contact with cooling water. Section 9 is provided with a top'fiange portion I2 serving for the support of a cover I3 and extended by a frusto-conical edge portion I4 for centering the cover and for providing a convenient location for a vacuum tight'bead of weld metal I5. Cover I3 mayalso ybe welded to edge portion I4 by a series of overlapping spot weldS. Flange I2fur- 20 ther serves to rest'the device on anyfsuitable support (not shown) through a clamp ring I6 'provided with a plurality of vearsv I'I welded thereon. The lower partof casing section 9 is provided with a converging"frusto-conical edge'portion I8 formed integrally therewith by spinning or pressdescription when read in connection with the accompanying drawing, in which:

Fig. l is a view in vertical cross section through one embodiment of the present invention show- ,I

8 consisting of a pool of suitable vaporizing metal such as mercury. Casing 6 is made up from a plurality of sections joined together in permanently uid tight relation. More specifically casing 6 comprises an anode-containing section 9 made from a length of welded or seamless steel tubing. Section 9 is preferably associated with suitable means for removing the heat radiated thereto from the electrodes and from the discharge taking place within the casing. For this purpose section 9 may be provided with a jacket Il to dene a passage for the flow of cooling water or may be provided with ns (not shown) ing. Casing 6 further comprises a cup-shaped cathode-containing section I9 forming'a wellfor receiving the liquid cathode in 'electrically conductive connection therewith. Section I9 is preferably made of metal'having the same ycomposition as the metalv of section 9 and is provided with Condensed cathode material is prevented from forming a'conductive connectionbetween casing sections 9, I9 by 'the provision o f a coating of vitreous insulating material 23 'applied vto the inner surface of section` I9 and extending A froml edge portion 2Iv to :at least thesurfaceof cathode 8. The joint between sections 9, I9 and coating 23 are protected from the'heat radiated from the discharge extending between anode I `and cathode 8 by means 'of a ring '24 of suitable refractory insulating material, such as quartz. The space vabout ring 24 is sealed against the discharge by a ring 25 welded'to casing section 9 cooperatingwith a split vfunnel 26 engaging the top edge of ring 24. A steel washer'21 disposed on the bottom of the cathode well is first .dishe'd' by spinning or outer surface of pipe 'Il to give an indication of the degree of fluidity of lining 12 when pipe 1l is heated by application thereto of electric current through a pair of clamped terminals 14.

The vitreous material referred to herein may be any suitable known material of the class generally designated as vitreous enamels and may comprise any number of coats that may be required to obtain the desired thickness, including a so-called ground coat When the nature of the supporting metal requires it. Before the elements of the device are assembled al1 the portions thereof requiring coating with vitreous material for sealing or insulating purposes are separately coated with the necessary number of.

coats of material and are subjected to the corresponding .number of irings at the required temperatures. Washers 35 and the members welded thereto are then assembled and suitably supported while being additionally fired to cause the coatings of adjacent washers to coalesce and form a single layer uniting the washers in fluid tight insulated relation. Casing sections 9, I9 and seal members 55, 56 are likewise united in fluid tight insulated relation. In each instance the component parts are provided with a coating of vitreous material preferably between fifteen and twenty-five thousandths of an inch in thickness and when adjacent parts are united by fusion of their vitreous coatings the vitreous material confined between the parts is partly squeezed out to leave an intervening layer of total thickness between twenty and thirty-five thousandths of an inch, depending on the thickness of the original coating on the parts.

The dierent elements of the device with the exception of cathode 8 are then assembled as shown on the drawing and cover I3 is welded to casing section 9. The device is connected' to suitable evacuating means through pipe 1| and is subjected to a suitable heating and evacuating process to cause removal of the gases occluded within the walls of the casing and within the members contained within the casing. 'The cathode material is thereafter distilled into the casing through pipe 'H and the device may be permanently sealed. For this purpose current is passed through pipe 1I by means of clamps 14 to heat the lined portion of the pipe. Heating is continued until the vitreous lining has reached its fusion temperature, which may be ascertained by observing spot 13, while the evacuating means are maintained in operation.

It will be noted that during such heating lining 'l2 substantially reduces the emission of occluded gases from the wall of pipe 1I toward the inside thereof while the absence of any vitreous lining on the outside surface of pipe 'll permits the free emission of such occluded gases into the atmosphere. The thickness of the vitreous coating should preferably be above the lower limit, of ten thousandths of an inch, hereinabove specified to avoid the coating being disintegrated by the passage of gas bubbles therethrough, and the thicknessshould preferably be below the upper limit, of iifteen thousandths of an inch, to permit obtaining a mechanically resistant seal.

During heating of pipe 1l the gas pressure within the pipe is momentarily increased bythe emission of occluded gases, and is thereafter returned to a value within the permissible range by the action of the evacuating means. As soon as the gas pressure is again normal a short length of pipe 1| is attened by any suitable means, for example by pinching-in a hydraulic vise, until the pipe thickness is reduced to preferably slightly less than twice the original wall thickness. In the course of this operation, the opposite portions of the vitreous material lining the flattened pipe section are first caused to coalesce, and the pipe is further flattened to reduce the thickness of the coalesced portion of vitreous material to a substantial extent, and preferably appreciablyless than one-half of its original thickness. 'Satisfactory results have been obtained by reducing the thickness of vitreous material to two thousandths of an inch or slightly less. It is preferable to bring the thickness of vitreous material within the latter limit because the resistance of the joint to mechanical efforts and to thermal stresses is adversely affected by the presence of a large volume of vitreous material within the flattened pipe section. When pipe 'il has cooled to the extent that the vitreous lining has returned to the solid condition, the attened pipe section is therebypermanently sealed and the pipe portion extending beyond the flattened section may be sawed oi to reduce the space taken by the device.

To place the device in operation, anode 5l and cathode 8 are connected to a source of direct current through solenoid 64, thereby energizing the solenoid which causes immersion of plunger 62. The `solenoid circuit is thereby interrupted between anode 5l' and cup 63 and an arc discharge is established therebetween. Attachment of the arc at plunger 62, which would cause vaporization of metal from the plunger,

cannot take place as only c up 53 emerges fromcathode 8 at the time of establishment of an arc between anode 5I and the cathode material contained in cup 63. Upon immersion of cup 63 the cathode spot of the arc is transferred to the surface of cathode 8. If la source of alternating current is connected with a load device through anode 'l and cathode 3, and grid 4l is at the proper potential, anode 'l carries current during its periods of positive energization with respect to the cathode potential. 'During the idle periods of anode 1, grid 4I and shell 45 deionize the space surrounding anode 'l to prevent accidental reversal of the flow of current between anode l and cathode 8.

If grid 4| operates rwithout energization the potential thereof during the anode idle periods is determined to a large extent by the action of washers 35 dividing the potential between anode l and casing 6 by capacitive action, whereby the grid is caused to assume a definite potential varying with the anode potential. If the grid is connected to a source of alternating current through a resistor of relatively high value as is common practice, the Icapacitive couplingV of grid 4I with anode 1 and casing 6 through washers 35 prevents the control operation of the grid from being disturbed by transient potentials appearing in adjacent elements of the device.

During operation of the device veporized cathode material condenses on the walls of casing 6 including the coatings of vitreous material provided adjacent the dilferent insulating seals thereof. The coatings however are all made sufficiently wide to insure that condensed cathode material cannot bridge the adjacent conductive members to provide a, conductive connection therebetween.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that tember 15, 1945.

It is claimed and desired to secure by Letters Patent:

1. An electric discharge device comprising a fluid tight metallic casing, an anode, a cathode and a control electrode, means for supporting said anode in said casing comprising a rigid conductor and a metallic cap, means for supporting said cap on said casing in fluid tight insulated relation thereto comprising a stack of metal washers disposed about said rigid conductor and a plurality of layers of vitreous material severally uniting each said washer with the adjacent said washers in fluid tight insulated relation, and means for supporting said control electrode on said casing comprising a second conductor `connected between said control electrode and an intermediate washer of said stack of washers.

2. An electric discharge device comprising `a fluid tight metallic casing, an anode, a cathode and' a control electrode, means for supporting said anode in said casing comprising a rigid conductor and a metallic cap, means for supporting said cap on said casing in fluid tight insulated re lation thereto comprising a stack of meta-l washers disposed about said rigid conductor and a plurality of layers of vitreous material severally uniting each said washer with the adjacent said washers in fluid tight insulated relation, and means for supporting said control electrode on said casing comprising a tubular conductor surrounding said rigid conductor and connected between said control electrode and an intermediate washer of said'stack of washers.

3. An electric discharge device comprising a iluid tight metallic casing, an anode, a. cathode and a control electrode, means for supporting said anode in said casing comprising a rigid conductor and a metallic cap, means for supporting said cap on said casing in fluid tight insulated relation thereto comprising a stack of metal washers disposed about said rigid conductor and a plurality of layers `of vitreous material severally uniting each said washer with the adjacent said washers in fluid tight insulated relation, means for supporting said control electrode on said casing comprising a second conductor connected between sai-d control electrode `and an intermediate washer of said stack of washers, and means for controlling the temperature distribution of said washers comprising a tubular heat insulator disterialseverally uniting each said washer with the adjacent saidwashers in fluid tight insulated relation, means for. supporting said control electrode on said casing comprising a second conductor connected between said control electrode and an intermediate washer of said stack of washers, and. means for preventing conductive connection of said casing with said second conductor through condensed cathode material comprising -a coating of vitreous insulating material on the portion of the inner surface of said casing adjacent said stack of washers.

5. An electric discharge device comprising a iiuid tight metallic casing, a cathode, an anode having an-arcing surface facing said cathode and a `heat radiating surface facing said casing, means for supporting said anode in said casing comprising a rigid conductor and a metallic cap, means for supporting said cap on said casing in fluid tight insulated relation thereto comprising a stack of metal washers surrounding said rigid conductor and. a plurality of layers of vitreous trol electrode on said casing comprising a tubular conductor surrounding said rigid conductor and attached to an intermediate washer of said stack of washers, a conductive flange attached to said tubular conductor, and :a perforated conductive shell pervious A-to heat radiation attached between said ilange yand said control electrode for controlling the ionization of the space between said heat radiating surface and said casing. n

6. An` electric discharge device comprising a y fluid tight metallic casing, an anode and a cathposed about said rigid conductor and within said and said conductor.

ous material severally uniting each said washer with the adjacent said washers in iluid tightin- `sulated relation to form a plurality of serially connected capacitors dividing the potential difference between said anode 4and said casing, and

.meansfor controlling the ionization in the space adjacent said anode comprising a control electrode assembly connected with an intermediate washer of said s-tack of washers to receive potential therefrom and disposed about said anode OTHMAR K. MARTI. ERVIN B. STEINBERG.

REFERENCES CITED The following references are of record in the ille of thisfpatent:

UNITED STATES' PATENTS Number Name Date 1,456,110 Mackay May 22, 1923 2,175,019 Edwards v Oct. 3, 1939 2,262,189 Marti Nov. 11, 1941

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