Title of Invention

"A METAL DEVICE FOR INTEGRATING A GLASS PART AND A METAL PART A METHOD THEREOF"

Abstract

Metal ferrule device 4 of the type used for fastening a glass piece 1 to a metal piece having different expansion coefficients. The ferrule 4 is circular and comprises a first portion 5 intended to be in contact with the metal piece, a second portion 7 intended to be in contact with.the glass piece 1 and a connecting portion 6 lying between the said first and second portions. The second portion 7 has a thickness of less than the thickness of the first portion 5 and of the connecting portion 6 so as to match the expansion of the glass piece 1 while exerting, on the latter, stresses which are less than the strength limit of the said glass piece 1.

Full Text

The invention relates to a metal device for integrading a glass part and a metal part and method thereof. The present invention relates to the field of metal-to-glass connection, inparticular when these two materials possess "difference expansion coefficients. In electromagnetic-radiation components, in particular X-ray tubes, such connections are used so as to allow electrical conductors to pass through the glass wall of an X-ray tube so as to connect the cathode and anode of the X-ray tube to an electrical power supply. This is because the cathode and anode are placed inside a glass wall and are maintained under vacuum. The junction between the electrical conductors and the glass wall must therefore be sealed. In a known manner, a glass tube may be used, for example one made of glass manufactured by the company SCHOTT under the Nos. 8245 and 8250, this being sealed with a ferrule made of Kovar (an iron-nickel-cobalt alloy) whose thermal expansion coefficients are similar. These materials are therefore suitable for use in an X-ray tube whose temperature varies over a wide range, from ambient temperature to approximately 450°C. However, the cost of such a glass tube is very high. It is also possible to use a Pyrex(R) tube and a Kovar ferrule. Since Pyrex and Kovar possess different expansion coefficients, a graded junction is produced by means of a succession of glasses having expansion coefficients which vary from that of Kovar to that of Pyrex, for example glasses of the 8447, 8448, 8449 and 7740 type from the company SCHOTT. The Pyrex tube is therefore provided at its end connected to the Kovar ferrule with a plurality of rings of these various types of glass. It may be readily understood that the manufacture of such a Pyrex tube is very expensive. The object of the present invention is to remedy the drawbacks of the above devices by providing a ferrule device capable of being connected to a glass piece having a different expansion coefficient. The object of the invention is also to provide a ferrule intended to be fitted to a -Pyrex piece, The metal ferrule device, according to the invention, is of the type used for fastening a glass piece to a metal piece having different expansion coefficients. The ferrule is cylindrical and comprises a first portion intended to be in contact with the metal piece, a second portion intended to be in contact with the glass piece and a connecting portion lying between the said first and second portions. The second portion has a thickness of less than the thickness of the first portion and of the connecting portion so as to match the expansion of the glass piece while exerting, on the latter, stresses which are less than the strength limit of the said glass piece. An inexpensive glass piece may thus be used without the risk of breaking it during variations in the temperature. In one embodiment of the invention, the thickness of the second portion is less than a tenth of the thickness of the first portion and of the connecting portion. The second portion is thus considerably more flexible than the first portion and the connecting portion. Advantageously, the second portion is bevelled, the free end of the second portion having a thickness of approximately 10 microns. In one embodiment of the invention, the second portion has .a thickness of less than 200 microns. Advantageously, the second portion has an angle with respect to the axis of the ferrule of approxim¬ately 1°. The ferrule may be made of stainless steel, for example of the ,304L type. The subject of the invention is also an electromagnetic-radiation component, for example an X-ray tube, comprising a glass tube, a cathode and an anode, the anode comprising an electrical conductor provided with a connection to the outside of the tube. The electromagnetic-radiation component comprises a ferrule, as described above, lying between the glass tube and the connection. Preferably, the tube is made of Pyrex. It is thus possible to reduce the cost of the tube equipped with its ferrule by a factor of about 50% to 70%. The subject of the invention is also a process for manufacturing a circular ferrule comprising a first portion intended to be in contact with a metal piece, a second portion intended to be in contact with a glass piece and a connecting portion lying between the said first and second portions. The process comprises the following steps: - forming the first and second portions and the connecting portion of the ferrule by drawing; - machining the second portion, in order to give it a bevel with an angle of 1°; and - electropolishing the second portion. A subsequent step of oxidizing the surface of the second portion of the ferrule is provided, this step making it possible to improve the fastening of the ferrule to the glass piece. This fastening may be carried out by steps of continuing to heat the glass piece and then of axially inserting the ferrule into one end of the glass piece having the same diameter as the said ferrule. The second portion is thus inserted into the thickness of the glass, thereby ensuring vacuum-tightness between the ferrule and the glass piece. Electropolishing the second portion makes it possible to reduce its thickness, thereby corres¬pondingly reducing the stresses exerted on the glass piece by the second portion during temperature variations. By virtue of the invention, the manufacturing costs of a glass piece in vacuum-tight contact with a metal piece are considerably reduced, while guaranteeing vacuum-tightness and solidity which are satisfactory over a wide temperature range. The present invention will be more clearly understood and other advantages will appear from the detailed description of an embodiment given by way of purely non-limiting example and illustrated by the appended drawings in which; To meet the aforementioned objectives the invention provides for a metal device for integrating a glass part and a metal part of different coefficients of expansion, the device comprising a first portion intended to be in contact with the metal part, a second portion intended to be in contact with the glass part and a bonding portion placed between said first and second portions, wherein the second portion is not as thick as the first portion and is not as thick as the bonding portion, so that it can adjust to the expansion of the glass part by exerting stresses on the latter below the limit of resistance of the glass part and wherein the thickness of the second portion is less than one-tenth the thickness of the first portion and less than one-tenth the thickness of the bonding portion. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS Figure 1 is an axial sectional view of an X-ray tube equipped with a ferrule according to the invention; and Figure 2 is a detail of Figure 1. As may be seen in the figures, the piece 1 has a circular shape comprising a first open end 2 and a second open end 3. The first open end 2 is intended to accommodate a rotating anode, not depicted, which is in the form of a rotating circular plate rotated by an electric motor, the rotor of which is placed in a cylindrical portion la of the piece 1 and the stator of which is placed around the said cylindrical portion la. The second open end 3 is designed to accommodate a cathode, not depicted. The open end 2 of the piece 1 is fastened to a ferrule 4 by a process which will be described later. The ferrule 4 is made of stainless steel, for example stainless steel of the 304L type. The ferrule 4 comprises a first cylindrical portion 5, a second portion 7 designed to be in contact with the piece 1 and a connecting portion 6 lying between the first portion 5 and the second portion 7. The first portion 5 is designed to be fastened in a vacuum-tight manner, for example by soldering, to a metal element, not depicted, ensuring electrical connection between the anode and means for supplying electrical power to the anode, these means lying outside the glass piece 1. The diameter of the first portion 5 of the ferrule 4 matches that of the connecting element. Fastening by soldering ensures a perfectly vacuum-tight seal between the ferrule 4 and the connecting element, this constituting a major advantage over a ferrule made of the alloy Kovar, which is difficult to solder to. The ferrule 4 is manufactured from a stainless steel tube which is formed by drawing, thereby giving it its general shape. The second portion 7 of the ferrule 4 is then machined so as to reduce its thickness and give it a bevel with an angle of approxi¬mately 1°. Finally, the second portion 7 is electro-polished in a sulphophosphoric solution which has the effect of further reducing the thickness of the said second portion 7 and of obtaining a free end 7a of the said second portion 7 which is extremely thin, about 10 microns. Thus, a second portion 7 is obtained whose maximum thickness is less than a tenth of the thickness of the first portion and of the connecting portion, in other words a thickness of less than 200 microns. The free end of the second portion 7 is extremely thin, thereby facilitating its subsequent sealing to the piece 1. The ferrule is then subjected to heat and chemical treatment operations, in particular to a treatment of oxidizing the surface of the second portion 7 which improves the subsequent sealing of the metal to the glass by the binding of oxygen atoms in vacancies in the glass. The ferrule 4 thus obtained is ready for being sealed to the open end 2 of the piece 1. The piece 1 is heated to a high temperature so as to make the glass pasty. The ferrule 4 is presented coaxially with the piece I with its second portion 7 directed towards the open end 2. Then, by moving the ferrule 4 axially, the second portion 7 is inserted into the glass of the open end 2 of the piece 1, the second portion 7 and the open end 2 having the same diameter. As may be more particularly seen in Figure 2, the second portion 7 is inserted into the glass so that there is an equal thickness of glass on each side of the said second portion 7 in order to ensure maximum solidity of the glass piece 1. Next, the glass piece 1 equipped with the ferrule 4 is cooled without the risk of breaking the glass because of the different expansion between the stainless steel of which the ferrule 4 is composed and the Pyrex of which the piece 1 is composed, by virtue of the ability of the second portion 7 to deform because of its small thickness, without exerting excessive stress on the piece 1. The cathode is sealed to the glass piece 1 which is then evacuated in order to propagate electro¬magnetic radiation, in particular X-rays, satisfactor¬ily. The sealing of the anode and cathode must therefore be vacuum-tight and must moreover withstand large temperature variations. When not in operation the glass piece 1 is at ambient temperature, and, in operation, it may reach a temperature of approximately 450°C. The sealing of the anode and the cathode must therefore remain vacuum-tight over this temperature range. By virtue of the invention, it is possible to seal together an inexpensive Pyrex tube and a stainless steel ferrule 4 which can be easily soldered to a connecting element made of an alloy, for example cuproaluminium, which ensures excellent cooling of the anode but is very difficult to solder to Kovar. The invention applies, of course, to all types of metal ferrules intended to be sealed to a glass piece having a different expansion coefficient. We Claim: 1. A metal device for integrating a glass part and a metal part of different coefficients of expansion, the device comprising a first portion intended to be in contact with the metal part, a second portion intended to be in contact with the glass part. and a bonding portion placed between said first and second portions, wherein the second portion is not as thick as the first portion and is not as thick as the bonding portion, so that it can adjust to the expansionof the glass part by exerting stresses on the latter below the limit of resistance of the glass part and wherein the thickness of the second portion is less than one-tenth the thickness of the first portion and less than one-tenth the thickness of the bonding portion. 2. A device as claimed in claim 1, wherein the second portion is beveled, the free end of the second portion being 10 microns thick. 3. A device as claimed in claim 1 or 2, wherein the second portion has a bevel with a 1° angle. 4. A method of integrating a glass part and a metal part having different coefficients of expansion comprising the steps: (1) forming a device for integrating the metal part and glass part by: (a) forming, a first portion of said device for contacting said metal part; (b) forming, a second portion of said device for contacting said glass part; (c) forming, a bonding portion of said device for bonding said first and second portions; (cl) machining said second portion to give it a bevel with a 1° angle; (e) electrolytically polishing said second portion; and, (2) constant heating the glass part and axially insetting said second portion of the device into one end of the glass part of the same diameter as the device. 5. The method as claimed in claim 5, comprising a step of oxidizing the surface of the second portion of the device. 7. A metal device substantially as herein described with reference to the accompanying drawings.

Documents:

3498-del-1998-abstract.pdf

3498-del-1998-claims.pdf

3498-del-1998-correspondence-others.pdf

3498-del-1998-correspondence-po.pdf

3498-del-1998-description (complete).pdf

3498-del-1998-drawings.pdf

3498-del-1998-form-1.pdf

3498-del-1998-form-19.pdf

3498-del-1998-form-2.pdf

3498-del-1998-form-3.pdf

3498-del-1998-form-4.pdf

3498-del-1998-form-6.pdf

3498-del-1998-gpa.pdf

3498-del-1998-pa.pdf

3498-del-1998-petition-124.pdf

3498-del-1998-petition-138.pdf

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