US3130344A

US3130344A - Gas-filled electric discharge devices

Info

Publication number: US3130344A
Application number: US166283A
Authority: US
Inventors: Baker Basil Offor; Wheldon Robert Joseph
Original assignee: MO Valve Co Ltd
Current assignee: MO Valve Co Ltd
Priority date: 1961-01-20
Filing date: 1962-01-15
Publication date: 1964-04-21
Anticipated expiration: 1981-04-21
Also published as: FR1312277A; NL273635A; GB931760A

Description

April 21, 1964 B. o. BAKER ETAL GAS-FILLED ELECTRIC DISCHARGE DEVICES Filed Jan. 15, 1962 q-rToRNe'Ys 3,130,344 GAS-FILLED ELECTRIC DISCHARGE DEVICES .Basil Olior Baker, Croxley Green, and Robert Joseph Wheldon, Chaliont St. Peter, England, assignors to The M-O Valve Company Limited, London, England Filed Jan. 15, 1962, Ser. No. 166,283 Claims priority, application Great Britain Jan. 20, 1961 Claims. (Cl. 313-220) This invention relates to gas-filled electric discharge devices.

It is an object of the present invention to provide a convenient form of gas-filled electric discharge device of the kind having an envelope comprising at least two metal parts arranged to be maintained at different potentials in operation and insulated from one another by means of a ceramic portion which also forms part of the envelope of the device.

According tothe invention, a gas-filled electric discharge device has a sealed gas-filled envelope including a hollow generally metallic structure, an annular ceramic member sealed to said hollow structure and a metallic closure member sealed to the ceramic member so as to close the aperture in the ceramic member, and the device has an electrode system including at least a cathode and an anode and disposed within said hollow structure so that the main discharge path between the electrodes of said system lies on the side of the anode remote from the ceramic member, the anode being electrically connected to the closure member and electrically insulated from said -with the length of the shortest path within the envelope between the closure member and said hollow structure via the gas-filling.

One arrangement in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing which is a diagrammatic sectional view of a thyratron having a peak inverse and forward hold-otf voltage rating of 40 kilovolts.

Referring to the drawing, the valve has a sealed, deuterium-filled envelope which includes a copper portion including a relatively wide tubular section 1 and relatively narrow tubular section 2 which is coaxial with and extends beyond one end of the section 1. The sections 1 and 2 are joined together by means of a copper flange 3 which is sealed to the inside of the section 1 and to the outsideof the section 2, one face of the flange 3 being coplanar with the relevant end surface of the section 2. The section 1 has a length of about 5.5 inches, an outside diameter of 2.0 inches and an internal diameter of 1.875 inches. The section 2 has a length of 1.125 inches and an internal diameter of 0.787 inch; over most of its length the outside diameter of the section 2 is 1.0 inch, but over a length of 0.25 inch extending from the end remote from the section 1 this is reduced to 0.95 inch. The length of the section 2 extending beyond the end of the section 1 is 0.875 inch, and the section 2 has formed on it an external planar flange 4 whose main face remote from the section 1 is disposed at a distance of 0.328 inch from the end of the section 2 remote from the section '1.

The envelope also includes an annular ceramic mem her 5 having a length of 0.5 inch, an outside diameter of 3.0 inches and an inside diameter of 1.0 inch. The ceramic member 5' and the copper sections 1 and 2 of the envelope are arranged coaxially lengthwise, one end face of the ceramic member 5 being sealed to the face of the United States Patent 0 copper-ceramic seal.

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flange 4 that is remote from the section 1, so that the end of the section 2 projects into the ceramic member 5 to a depth of 0.328 inch. A ceramic backing ring 6 is sealed to the other face of the flange 4 to relieve stresses in the After the envelope has been assembled the external surface of the ceramic member 5 is glazed.

The section 1 is divided into two compartments 7 and 8 by means of a copper partition 9 extending transversely across the section 1 about two thirds of the way along its length from the section 2. The electrode system of the valve is housed within the larger compartment 7 and includes a thermionic cathode 10, a heater 11 for the cathode 10 and a heat shield 12 partially surrounding the cathode 10, all disposed about a third of the way along the compartment '7 from the partition 9. The electrode system further includes an anode 13 disposed at the other end of the compartment 7, and between the cathode 10 and the anode 13, in the order stated, a first baflle 14, a control electrode 15 and a second baflle 16. The cathode 10 and one end of the heater 11 are electrically connected to the copper portion of the envelope, and the other end of the heater 11 is connected to a lead 17 which passes through the partition 9 and the smaller compartment 8, and is sealed through a circular copper plate 18 which is sealed into the end of the section 1, the lead 17 being insulated from the copper portion of the envelope.

The compartment 8 houses a replenisher 19 for the gas filling of the valve, the replenisher 19 including a heater 20 which is arranged to be supplied with electric current from the same source as the cathode heater 11.

The control electrode 15 is provided with a lead 21 in the form of a nickel rod which is sealed in an'insulated manner through the curved portion of the wall of the compartment 7 in the region of the control electrode 15.

The baflle 16 is secured to the inside of the section 1 r and the baflle 14 is supported on the end of a short copper rod 22 which extends between the

baflles

14 and 16 via an aperture in the control electrode 15. The purpose of the baflfle 14 is to prevent the evaporation of electron emissive material from the cathode 10 onto the control electrode 15 and to direct the triggering discharge to the edges of the control electrode 15 in operation; the bafiie 16 serves to screen the anode 13 from the cathode 10 while not preventing the passage of a discharge between these two electrodes.

The anode 13 is in the form of a copper disc, of diameter 1.457 inches, disposed perpendicular to the axis of the envelope and spaced a distance of 0.195 inch from the end surface of the section 2 that is coplanar with the flange 3. The anode 13 is supported by means of a copper rod '23 of diameter 0.472 inch which also serves as a lead to the anode 13, the rod 23 extending perpendicularly away from the centre of the anode 13 coaxially through the section 2 and the ceramic member 5. A further copper flange 24, of diameter 2.0 inches, is sealed around the rod 23 and is sealed adjacent its periphery to the second end face of the ceramic member 5 thus serving to close the aperture in the ceramic member 5. At the centre of the face of the flange 24 adjacent the ceramic member 5 there is formed a circular recess 25 of diameter 1.625 inches and depth 0.025 inch; the flange 24 is, therefore, in contact with the ceramic member 5 only over an annular surface of internal diameter 1.625 inches and external diameter 2.0 inches. A ceramic backing ring 26 whose purpose is to relieve the stresses in the seal between the flange 24 and the ceramic member 5 is sealed to the surface of the flange 24 remote from the ceramic member 5.

It will be apparent from the dimensions given above that the shortest path Within the envelope between the flange 24 and the section 2 via the gas-filling is 0.197 inch long. Since the flange 24 and the section 2 are respectively at the anode and cathode potentials in operation, the length of this path cannot be appreciably increased without incurring a risk of the occurrence of a breakdown between these two members via a path through the gasfilling. Breakdown between the flange 24 and the section 2 may also occur in operation along a path over the surface of the ceramic between these two members unless the shortest such path is arranged to be considerably longer than 0.197 inch. This is achieved in the valve described above by the provision of the recess 25 and by the reduction in outside diameter at the end of the section 2 adjacent the ceramic member 5; this results in the flange 24 and the section 2 overlapping the ceramic member 5 without touching it by 0.308 inch and 0.250 inch respectively so that the shortest path within the envelope between the flange 24 and the section 2 along the surface of the ceramic is approximately 0.730 inch long.

Prevention of breakdown between the flange 24 and the section 2 along a path over the external surface of the ceramic member 5 is assisted by the glazing on the external surface of the ceramic member 5.

A further feature of the valve described, by way of example, is that the ceramic member 5 is well removed from the path of the discharge which occurs between the anode 13 and the cathode in operation; this materially reduces the possibility of sputtering causing a reduction of the surface resistance of the inner surface of the ceramic member 5.

We claim: 1

1. A gas-filled electric discharge device comprising an electrode system, a sealed gas-filled envelope within which the electrode system is mounted, said envelope including an elongated hollow generally metallic structure, a closure member sealing one end of said structure, an annular ceramic member sealed to the other end of said structure, and a metallic closure member sealed to the ceramic member so as to close the aperture in the ceramic mem ber, the electrode system including at least an anode and a cathode and being disposed within said hollow structure so that the main discharge path between the electrodes of said system lies on the side of the anode remote from the ceramic member, the anode being electrically connected to said metallic closure member and electrically insulated from said hollow structure, and part of at least one of said metallic closure member and said hollow structure overlapping the ceramic member without touching it so that the length of the shortest path within the envelope between said metallic closure member and said hollow structure along the surface of the ceramic member is relatively long compared with the shortest path within the envelope between said metallic closure member and said structure via the gas filling, at least part of the overlap being between the internal surface of the ceramic member and the surface of a portion of one of said metallic closure member and said hollow structure which portion projects part way through the aperture in the ceramic member.

2. A device according to claim 1 wherein the end of the ceramic member adjacent said hollow structure is sealed to one face of an external planar flange formed on said hollow structure at a position such that one end of said hollow structure projects into the aperture in said ceramic member, at least a part of the portion of said hollow structure disposed within the aperture in said ceramic member overlapping the ceramic member without touching it.

3. A device according to claim 1 wherein said hollow structure comprises a first relatively wide tubular metal section and a second relatively narrow tubular metal section which is disposed coaxial with and extends beyond one end of the first section, the ceramic member being sealed to the second section so as to be disposed coaxially lengthwise with respect to said first and second sections, the electrode system being disposed within said first section, said metallic closure member being constituted by a metal flange sealed to the ceramic member and the electrical connection between the anode and said metallic closure member being in the form of a metal rod which extends coaxially through the second section and the ceramic member and is joined to said flange.

4. A gas-filled electric discharge device comprising an electrode system, a sealed gas-filled envelope within which the electrode system is mounted, said envelope including an elongated hollow generally metallic structure, a closure member sealing one end of said structure, an annular ceramic member sealed to the other end of said structure, and a metallic closure member sealed to the ceramic member so as to close the aperture in the ceramic member, the electrode system including at least an anode and a cathode and being disposed within said hollow structure so that the main discharge path between the electrodes of said system lies on the side of the anode remote from the ceramic member, the anode being electrically connected to said metallic closure member and electrically insulated from said hollow structure, and part of at least one of said metallic closure member and said hollow structure overlapping the ceramic member without touching it so that the length of the shortest path within the envelope between said metallic closure member and said hollow structure along the surface of the ceramic member is relatively long compared with the shortest path within the envelope between said metallic closure member and said structure via the gas filling, at least part of the overlap being between the internal surface of the ceramic member and the surface of a portion of said hollow structure which portion projects part way through the .sealed to the end of the ceramic member remote from the hollow structure, said planar face having formed in it a recess so that a part of said face overlaps the ceramic member without touching it.

References Cited in the file of this patent UNITED STATES PATENTS Hull Nov. 28, 1944 Clark Oct. 31, 1950

Claims

1. A GAS-FILLED ELECTRIC DISCHARGE DEVICE COMPRISING AN ELECTRODE SYSTEM, A SEALED GAS-FILLED ENVELOPE WITHIN WHICH THE ELECTRODE SYSTEM IS MOUNTED, SAID ENVELOPE INCLUDING AN ELONGATED HOLLOW GENERALLY METALLIC STRUCTURE, A CLOSURE MEMBER SEALING ONE END OF SAID STRUCTURE, AN ANNULAR CERAMIC MEMBER SEALED TO THE OTHER END OF SAID STRUCTURE, AND A METALLIC CLOSURE MEMBER SEALED TO THE CERAMIC MEMBER SO AS TO CLOSE THE APERTURE IN THE CERAMIC MEMBER, THE ELECTRODE SYSTEM INCLUDING AT LEAST AN ANODE AND A CATHODE AND BEING DISPOSED WITHIN SAID HOLLOW STRUCTURE SO THAT THE MAIN DISCHARGE PATH BETWEEN THE ELECTRODES OF SAID SYSTEM LIES ON THE SIDE OF THE ANODE REMOTE FROM THE CERAMIC MEMBER, THE ANODE BEING ELECTRICALLY CONNECTED TO SAID METALLIC CLOSURE MEMBER AND ELECTRICALLY INSULATED FROM SAID HOLLOW STRUCTURE, AND PART OF AT LEAST ONE OF SAID METALLIC CLOSURE MEMBER AND SAID HOLLOW STRUCTURE OVERLAPPING THE CERAMIC MEMBER WITHOUT TOUCHING IT SO THAT THE LENGTH OF THE SHORTEST PATH WITHIN THE ENVELOPE BETWEEN SAID METALLIC CLOSURE MEMBER AND SAID HOLLOW STRUCTURE ALONG THE SURFACE OF THE CERAMIC MEMBER IS RELATIVELY LONG COMPARED WITH THE SHORTEST PATH WITHIN THE ENVELOPE BETWEEN SAID METALLIC CLOSURE MEMBER AND SAID STRUCTURE VIA THE GAS FILLING, AT LEAST PART OF THE OVERLAP BEING BETWEEN THE INTERNAL SURFACE OF THE CERAMIC MEMBER AND THE SURFACE OF A PORTION OF ONE OF SAID METALLIC CLOSURE MEMBER AND SAID HOLLOW STRUCTURE WHICH PORTION PROJECTS PART WAY THROUGH THE APERTURE IN THE CERAMIC MEMBER.