US2459827A - Electric valve with vitreous enamel seals - Google Patents

Description

O. K. MARTI ELECTRIC VALVE WITH VITREOUS ENAMEL SEALS 'Filed Sept. l5, 1945 ATTORNEY Patented Jan. 25, 1949 UNITED STATES PATENT OFFICE ELECTRIC VALVE WITH VITREOUS ENAMEL SEALS Application September 15, 1945, Serial No. 616,557

4 Claims. 1

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 of the device are sealed in fluid 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 condensed operating vapor is prevented from eiecting conductive connections between elements of the device insulated from each other.

Another object of the present invention is to provide an improved electric discharge device of the meal enclosed type in which the casing may be sealed after its evacuation by a seal which is resistant to mechanical efforts and to attack by the operating vapor, and which is permanently impervious to air leakage.

Objects and advantages other than those above set forth will be -apparent from the following description 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 showing a portion of the exhaust pipe on an enlarged scale;

Fig. 2 is a View in cross section taken along line II-II in Fig, 1 but drawn on an enlarged scale; and

Fig. 3 is a view in cross section taken along line III-III in Fig. 1.

Referring more particularly to the drawing by characters of reference, the device illustrated in Fig. 1 comprises a fluid tight metallic casing generally designated by 6, an anode 1, and a cathode 8 consisting of a pool of suitable vaporizable metal such as mercury. Casing 6 is made up from a plurality of sections joined together in permanently fluid 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 I I to dene a passage for the flow of cooling water or may be provided with ns (not shown) when air cooling is resorted to. Jacket Il may also be provided with suitable means for guiding the flow of cooling water therethrough as is well known.

The steel used for section 9 may have any known composition suitable for the application thereto of any of the vitreous compositions known under the general designation of vitreous enamels.' Both section 9 and jacket H however are preferably made of steel containing substantially 18% crome and 8% nickel to prevent corrosion of the surfaces thereof in Contact with cooling water. Section 9 is provided with a top flange portion l2 serving for the support of a cover i3 and extended by a truste-conical edge portion I4 for centering the cover and for providing a convenient location for a vacuum tight bead of weld metal l5. Cover I3 may also be welded to edge portion I4 by a series of overlapping spot welds. Flange l2 further serves to rest the device on any suitable support (not shown) through a clamp ring i6 provided with a plurality of ears l1 welded thereon.

The lower part of casing section 9 is provided with a converging frusto-conical edge portion i8 formed integrally therewith by spinning or pressing. Casing 6 further comprises a cup-shaped cathode-containing section I9 forming a Well for receiving the liquid cathode in electrically conductive connection therewith. Section I9 is preferably made of metal having the same composition as the metal of section 9 and is provided with a diverging frusto-conical edge portion 2i complementary of edge portion I8 and likewise formed by spinning or pressing. Edge portions I8, 2| are united in fluid tight insulated relation by means of a layer of vitreous material 22. Section i9 may be provided with an expandable wall portion 20 to mitigate the effects on layer '22 of mechanical efforts exerted on section iS.

Condensed cathode material is prevented from forming a conductive connection between casing sections 9, i9 by the provision of a coating of vitreous insulating material 23 applied to the inner surface of section i9 and extending from edge portion 2i to at least the surface oi cathode 8. The joint between sections 5, i9 and coating 23 are protected from the heat radiated from the discharge extending between anode 'l and cathode 8 by means of a ring 24 of suitable refractory insulating material, such as quartz. The space about ring 24 is sealed against the discharge by a ring 25 Welded to casing section 9 cooperating with a split funnel 26 engaging the top edge of ring 24. A steel Washer 21 disposed on the bottom of the cathode well is rst dished by spinning or pressing and thereafter attened to the extent required for accurately supporting ring 24 and funnel 26 in arc impervious engagement with ring 25.

Anode l consists of a block of suitable refractory conductive material such as graphite machined to dei-lne a plane surface 28 facing cathode 8 and a cylindrical surface 29 facing casing section 9. Surface 28 serves principally as arcing surface for the establishment of an arc discharge between the anode and the cathode. Surface 2t erves principally as heat radiating surface to transmit the heat developed at the anode to casing section 9. Anode l is supported on cover i3 by means of a metal cap 3| and of a rigid conductor 32 screwed into anode 'l and cap 3l. A suitable radiator 33 is provided on cap 3l for controlling the temperature thereof. Radiator 33 also serves as anode terminal and is adapted for bolting a suitable conductor 3Q thereto.

Cap 3l is supported on cover i3 in fluid tight insulated relation through a stack of flat or frustoconical Washers 35 surrounding conductor 32, the top Washer being Welded to cap 3i and the bottom washer being Welded to cover i3 by means of weld metal suitable for the application of vitreous material thereto. A plurality oi layers 35 of vitreous material serve to unite each washer with the adjacent washer in iiuid tight insulated relation thereto.

Cathode material is prevented from forming a conductive connection between the dilerent washers and cover i3 by means of a coating of vitreous insulating material 37 extending over the inner surfaces of the washers and the inner Y surface oiV casing i3 `adjacent the stack of washers. A similar coating 38 is provided on the inner surface of cap 3i adjacent the stack of washers. The temperature distribution oi washers S is controlled by means of a tubular member Se disposed about conductor 32 and made of any suitable refractory heat insulating material such as sillimanite and shielding washers 35 against heat radiation from conductor 32.

A control electrode il of the grid type is disposed adjacent arcing surface 28 for controlling the flow of current between anode i and cathode d. Grid El may be made of any suitable refractory conductive material such as graphite and its mesh size may be so selected that either the grid does not require energization or the grid must be connected to a source of potential to enable anode 'i to carry current. Grid 4l is sup ported in casing -S by means of a tubular conductor i2 welded to an intermediate Washer 43 of stack 35, a frusto-ccnical conductive ilange M screwed on conductor 42, and a perforated conductive shell 415 pervious to heat radiation suitably attached between fiange fle and grid 4l for controlling the ionization of the space coni-ined between anode surface 2Q and casing sectiony 9. Grid lil and shell t5 may also be made in one piece machined out of a block of graphite.

The vapor density within the space surrounding anode l and grid il is controlled by means of an annular baiile it suspended from cover I3 through conductive straps el and lenticular baiiie it is supported from baille lit through conductive straps 49.

Cathode 3 is to be continuously maintained in electron -emissive condition by an auxiliary arc discharge established between the cathode and an ignition-excitation anode 5l suspended from halie i8 in insulated rela-tion thereto through an insulated stud '52. Anode 5l may be connected with a source of potential through stud a metallic cable 53 enclosed in a refractory insulating tube 5t and a conductor 55 shaped as a cone preferably having an angle of divergence of between zl0 and 60 degrees. The latter conductor is supported on cover i3 through acomp.ernentary funnel-shaped member 56 welded to vthe cover. Members 55, 5t are united in iluid tight insulated relation by means of a layer of vitreous material 5i, and the tubular portion S6 oi member 5t is made sufliciently thin and of suicient length as to prevent overheating of l while member 5S is being welded to cover by any suitable known method. Conductive connection between members 55, n through condensed cathode material is prevented by a layer of vitreous material 58 on memer E- and a coating of vitreous material 59 on the opposite surface of member 56. The insulatmembers enclosing stud 52 and cable 53 are so joined as to prevent any conductive connection between anode 5l and baille 48 through graphite dust or metal vaporized from cathode 3 or from other metallic members of the device.

anode 5S is associated with an arc igniting system comprising a cylinder 6l having a wall of nonmagnetic metal and depending from the cathode -well in vertical alignment with anode El. A plunger t2 of magnetic material is disposed in cylinder El for reciprocatory movement.

i cup $3 of refractory conductive material such graphite is mounted on plunger 62 to raise material from cathode 3 into engagement with anode 5i in response to buoyant emergence of plunger Ii from the cathode. A solenoid oli disposed about cylinder El may be energized for urging plunger 62 downward to cause total immersion of the plunger and of cup 63. Cup G3 is made of greater diameter than plunger 62 to add buoyancy to the'plunger and thereby accelerate its emergence upon deenergization of solenoid il@ without however materially hindering the action of the solenoid on the plunger.

Plonger 62 has a diameter which is slightly smaller than the inside diameter of cylinder 5l to prevent sticking of the plunger to the cylinder by capillary action. The periphery of plunger 62 is provided with a plurality of ribs 65 for guiding the plunger in the cylinder and is further provided with a plurality of grooves 65 for the flow of cathode material displaced by movement of the plunger.

Cylinder Si if; joined to the bottom portion of the casing section I9 by a ange Si formed on the cathode well by pressing or spinning and defining a diverging nozzle. Momente-ry short circuiting of anode 5i and cathode 8 by surging of the cathode material in response to immersion of plunger 62 and cup `653 into the cathode is thereby prevented. The cathode well is cooled by means of a water jacket B8 serving as cathode 'terminal for the attachment thereto of a suitable cathode conductor 69. Jacket 53 may also be replaced by fins when the device is air cooled.

Casing S is provided with a metallic pipe 'Il welded to cover I3 for connecting the casing with suitable evacuating meansV (not shown). Pipe Tl comprises a section providedA with an inner f lining l2 of vitreous material of appropriate side diameter of one-half inch particularly desirable results are obtained with a lining having a thickness between ten and fteen thousandths of an inch. A spot 'I3 of vitreous material may be provided on the outer surface of pipe 'H to give an indication to the degree of fluidity of lining 'i2 when pipe 'll 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 all 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 rings at the required temperatures. Washers and the members welded thereto are then assembled and suitably supported while being additionally tired to cause the coatings of adjacent washers to coalesce and form a single layer uniting the washers in fluid tight insulated relation. Casing sections Q, i9 and seal members 55, 5d are likewise united. in fluid tight insulated relation. In each instance the component parts are provided with a coating of vitreous material preferably between iifteen and twenty-five thousandths of an inch in thickness and when adjacent parts are united by fusion ci 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 different elements of the device with the exception of cathode 8 are then assembled as shown no the drawing and cover I3 is welded to casing section 9. rihe device is connected to suitable evacuating means through pipe 'll 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 'ii and the device may be permanently sealed. For this purpose current is passed through pipe 'H by means of clamps 'i4 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 ll toward the inside thereof while the absence of any vitreous lining on the outside surface of pipe 'il 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 specied to avoid the coating being disintegrated by the passage of gas bubbles therethrough, and the thickness should preferably be below the upper limit, of fifteen thousands of an inch, to permit obtaining a mechanically resistant seal.

During heating of pipe 'H the gas pressure within the pipe is momentarily increased by the 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 1l is flattened 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 fiattened to reduce the thickness of the coalesced portion of vitreous material to a substantial extent, and preferably appreciably less 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 thicknkess 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 attened pipe section. When pipe H has cooled to the extent that the vitreous lining has returned to the solid condition, the flattened pipe section is thereby permanent-ly sealed andthe pipe portion extending beyond the iiattened section may be sawed off 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 Si, thereby energizing the solenoid which causes immersion of plunger 62. The solenoid circuit is thereby interrupted between anode 5S and cup S3 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 piace as only cup 63 emerges from cathode 8 at the time of establishment of an arc between anode 5l and the cathode material contained in cup 63. Upon immersion of cup E3 the cathode spot of the arc is transferred to the surface of cathode 8. If a source oi alternating current is connected with a load device through anode 'i and cathode 8, and grid di is at the proper potential, anode 'l carries current during its periods of positive energization with repect to the cathode p0- tential. During the idle periods of anode grid 4l and shell 45 deionize the space surrounding anode l to prevent accidental reversal of the flow of current between anode 'i and cathode 8.

If grid fr! operates without 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 S by capacitive action, whereby the grid is caused tc 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 capacitive coupling of grid 4l with anode 'I and casing l 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 vaporized cathode material condenses on the walls of casing 6 including the coatings of vitreous material provided adjacent the different insulating seals thereof. The coatings however are all made suiciently 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 various changes and modifications may be made therein i Without departing from the spirit of the invention or from the scope of the appended claims. Features disclosed but not claimed herein are claimed in a copending application of Othmar K. Marti and Ervin lsteinberg, Serial No. 616,558,

. filed September 15, 1945.

It is claimed and desired to secure by Letters Patent:

1. An electric discharge device comprising a uid tight metallic casing, an anode and a cathode, said casing comprising an anode-containing section provided with a converging frusto-conical edge portion and a cathode-containing section provided with a diverging irusto-conical edge portion complementary of said converging edge portion, and a layer of vitreous material uniting said edge portions in fluid tight insulated relation.

2. An electric discharge device comprising a uid tight metallic casing, said casing comprising an anode-containing section. provided with a converging frusto-conical edge portion and a cathode-containing section provided with a diverging rusto-conical edge portion complementary of said converging portion, an anode disposed Within said anode-containing section in insulated relation therewith, a liquid cathode disposed in said cathode-containing section in conductive relation therewith, a layer of vitreous material uniting said edge portions in uid tight insulating relation, and means for preventing conductive interconnection of `said casing sections through condensed cathode material comprising a coating of vitreous insulating material on the inner surface of said cathode-containing section and extending from said diverging edge portion to at least the surface of said liquid cathode.

3. An electric discharge device comprising a fluid tight metallic casing, a metallic evacuating4 pipe connected to said casing in iiuid tight rela` tion thereto, a lining of vitreous material fused on the inside surface of said pipe, said pipe comprising a attened section having its opposite walls joined in fluid tight relation by coalesced portions of said lining.

4. An electrical device comprising a uid tight casing, a conductor extending through said casing comprising a member having a conical outer surface, a funnel shaped member comprising a tubular portion and a portion having a conical inner surface complementary of said outer surface, a layer of vitreous material confined between said surfaces and uniting said members in fluid tight insulated relation, and a Welded joint uniting an element of said casing in uid tight relation With a point of said tubular portion remote from said vitreous material.

OTHMAR K. MARTE.

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

UNITED STATES PATENTS Number Name Date 1,011,160 Coin v Dec. 12, 1911 2,223,031 Edwards Nov, 26, r9-i0

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