EP1658657A1

EP1658657A1 - Electrical feedthroughs for ultravacuum application

Info

Publication number: EP1658657A1
Application number: EP03818409A
Authority: EP
Inventors: Emanuele Madonna
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-27
Filing date: 2003-08-27
Publication date: 2006-05-24
Also published as: WO2005022694A1; AU2003265145A1

Abstract

A device that provides for the passage of an electrical current through a wall of separation of rooms operating under even very different thermal, atmospheric conditions. The invention uses metal leads fitted with interference into one or more adjacent coaxial discs of plastic materials with high electrical, mechanical, thermal, chemical resistance to provide the electrical feedthroughs. An embodiment of the invention (Fig. 1) consists of electrical feedthroughs formed of one or more cylindrical metal leads (6) that have a short length with larger diameter which interferes with the corresponding hole of the discs of plastic material (5, 5'), thus ensuring the vacuum tightness. The discs (5, 5') are located between and pressed by two adjacent, coaxial metal rings (2, 3) rigidly connected to each other by sealing. Metal ring (2) is sealed to the wall and provides for the separation of the rooms and the passage of the electrical current- Components (4, 1) can be threaded at their outer surfaces to allow electrical connectors to be used.

Description

ELECTRICAL FEEDTHROUGHS FOR ULTRAVACUUM APPLICATION

The present invention relates to electrical feedthroughs operating under critical conditions as well as providing electrical feedthroughs and vacuum- tight conditions by metal leads fitted with interference into one or more adjacent, coaxial discs of plastic material with high electrical, mechanical, thermal, chemical resistance in order to guarantee the quality of the required performance, to improve the mean life with respect to the current devices and above all to reduce the production cost. The invention also relates to the methods of providing such electrical feedthroughs. Multiple electrical feedthroughs for ultravacuum application at operating temperatures of 70 to 530°K are known in the art. These devices provide the electrical feedthroughs by metal leads and ensure the vacuum tightness, the electrical, thermal insulation by using and sealing ' glass, quartz or ceramic materials according to the operating conditions. The sealing of metal leads, insulating materials, and outer supporting metal ring is carried out by using a number of technologies, all of them being specialized. In applications where the operating conditions require temperatures near 77 or 530°K with a vacuum degree of 10^"7 Pa, the manufacturers of electrical feedthroughs guarantee the required performance by using ceramics as insulation materials of the device and the refined, expensive metal-ceramics-metal brazing technique as sealing means . Such solutions require the use of sophisticated technologies, expensive materials, complex setting b steps, high-technology equipment and highly specialized labour. In particular, the insulating materials such as glass, quartz and ceramics perfectly meet the requirements both of manufacturers and users of electrical

10 feedthroughs generally because of their peculiar physical-chemical features: their use together with the metal-ceramics-metal brazing technique allows high-quality devices to be provided. Unfortunately, in addition to the cited features, glass, quartz and

15 ceramics are also hard and above all brittle, which is the weak point of the current electrical feedthroughs along with the high production cost because of the unavoidable thermal, mechanical stresses inherent to the specific use.

20 According to the present invention, such drawbacks are minimized by electrical feedthroughs having the same performance but avoiding the brittleness of the device as well as the metal-ceramics-metal brazing and then reducing greatly the production cost, increasing the

25 lifetime, and answering for a better operation capability for the user. Essentially, there is provided electrical feedthroughs including one or more solid metal leads with a cylindrical section fitted into holes formed in one or jC more plastic discs adjacent and coaxial to one another allowing the electrical current to pass and the vacuum degree required by the specification to be provided because of their mechanical, thermal, chemical, electrical characteristics as well as their special coupling to the leads and outer supporting rings.

The tightness between solid metal lead and plastic disc is provided by a suitable interference between both such parts so as to provide the requested vacuum degree even under varying operating temperatures. In particular, the above-mentioned coupling has a certain amount of interference between both parts such as to ensure always the vacuum tightness without causing a permanent deformation of the plastic disc. In fact, a permanent deformation of the hole of the plastic disc would not allow the thermal dilatations of the materials involved to be taken up in the whole operating range.

•In the disclosed invention, the interference mentioned above is provided by different methods and building solutions which are used in relation to the thermal fields or the extreme operating temperatures required. Of course, the cost of the electrical feedthroughs increases according to the heaviness of the operation. In the following specification there are described three different mechanical solutions allowing the interference tightness between metal lead and plastic disc and/or discs to be provided: • The first solution provides that the electrical feedthroughs consist of a plastic insulator made by two adjacent, coaxial discs, in which one or more cylindrical metal leads having a very short length with larger diameter are fitted. The two segments of the metal leads with lower diameter are fitted into holes arranged geometrically in the two discs forming the insulating support, while the length of the metal leads with larger diameter is placed between the two discs of the insulator accordingly. The choice of suitable tolerances between the meal leads and the plastic support allows a forced coupling to be provided able to guarantee the vacuum degree required by the specifications.

• In the second solution that can be used according to the requirements, the electrical feedthroughs consist of one or more cylindrical metal leads having a short length with larger diameter which is fitted into a hole of the disc of plastic material and guarantees the vacuum tightness.

• The third solution provides electrical feedthroughs consisting of one or more cylindrical metal leads with uniform diameter which are fitted into holes with larger diameter arranged geometrically and formed in plastic discs adjacent and coaxial to one another. The vacuum tightness is provided by a little perforated cylinder or sleeve which is coaxial to the metal leads and arranged between the two plastic discs. The choice of suitable coupling tolerances between metal leads, perforated little cylinders, and plastic discs, and the pressing of the two discs to each other until their two opposite surfaces are brought into contact provides a forced coupling between the two discs and the metal lead. Finally, the perforated little cylinder consists of a type of plastics that makes coupling and keeping the vacuum degree easier. The assembly of insulator and electrical leads described above in three different embodiments is pressed between two adjacent, coaxial metal rings rigidly sealed to each other. The metal ring with larger opening has a circular saw tooth projection at its inner flat wall, that enters the plastic material by the pressure exerted on the insulator before sealing both such metal rings, thus ensuring the vacuum tightness. The metal ring with its projection is sealed to the wall so that the rooms are separated. The two metal rings containing the insulator are connected to two bushes by sealing. Both bushes can be threaded at their cylindrical outer and/or inner surface to allow electrical connectors to be used. At last, the insulator is made by using special plastic or thermoplastic materials able to guarantee high electrical, mechanical, thermal, chemical resistance under all operating conditions, as mentioned in the specifications. According to another embodiment of the invention, the assembly of insulator and electrical leads can be incorporated by moulding and casting such metal leads into a suitable thickness of an insulator of plastic or thermoplastic material. Alternatively, the vacuum and pressure tightness between metal leads and insulator can be obtained according to the invention by putting the opposite ends of the metal leads suitably provided with diametrical pads into corresponding holes of two insulating discs which are then pressed to one another. Advantageously, the tightness is also ensured by that a coaxial seat shaped like the pads of such metal leads is formed around each hole of the discs.

The invention will be more readily apparent from the following detailed description with reference to the accompanying drawings that show only by way of a not limiting example some preferred embodiments thereof. In the drawings :

Fig. 1 shows a section of the electrical feedthroughs where all components according to a first embodiment of the insulator are illustrated;

Fig . 2 shows a section of the electrical feedthroughs where all components according to a second embodiment of the insulator ' are illustrated;

Fig. 3 shows a section of the electrical feedthroughs where all components according to a third embodiment of the insulator are illustrated;

Fig. 4 is a section of the particular indicated at 2 in Figs. 1, 2 and 3;

Fig. 5 is a section of the particular indicated at 3 in Figs. 1, 2 and 3;

Figs . 6 and βa show a section and a view of the particular 5, 5' in Figs. 1, 2 and 3, respectively;

Figs. 7 and 7a show a section and a view of the particular 5a in Figs. 1, 2 and 3, respectively;

Fig. 8 shows a section of particular 7 of Fig. 3;

Figs. 9 and 10 show the two steps of the forced insertion with interference according to a preferred method of the invention;

Figs. 11 and 12 show the two steps of providing the assembly of insulator and metal leads by casting or pressure die-casting;

Figs . 13 and 13a show a top plan view and a section of the assembling step of the two insulating discs pressed to the metal leads provided with diametrical pads, respectively, and

Fig. 14 shows the assembly of insulator and leads as made.

With reference to Figure 1, according to a first embodiment, the invention consists of a plastic insulator made by two adjacent, coaxial discs 5, 5' in which one or more cylindrical metal leads 6 are fitted, such leads having a very short length with larger diamete . The two segments of the metal leads with lower diameter are fitted into holes geometrically arranged in both discs 5, 5' forming the insulating support, while the length of the metal leads with larger diameter is located between the two discs of the insulator accordingly. The choice of suitable tolerances between metal leads 6 and plastic supports 5, 5' allows a forced coupling to be provided able to guarantee the vacuum degree required by the specifications. The assembly of insulator and electrical leads 5, 6, 5' is pressed between two adjacent, coaxial metal rings 2, 3 connected by sealing to each other. The metal ring with larger opening 2 has a circular saw tooth projection at its inner flat wall, that forms a circular seat in the plastic material by the pressure exerted on the insulator before sealing both metal rings 2, 3, thus ensuring the vacuum tightness. Metal ring 2 with its projection is sealed to the wall so that the rooms are separated. The side flat surfaces of the two metal rings 2, 3 of the insulator 5, 5' are connected to two bushes 1, 4 by sealing. The two bushes 1, 4 can be threaded at their cylindrical outer and/or inner surface to allow electrical connectors to be used.

In the second embodiment shown in Fig. 2 there is provided a plastic insulator shaped as a cylindrical disc 5a in which one or more cylindrical metal leads 6b are fitted and characterized by a short length with larger diameter suitably provided for a forced coupling to the holes geometrically arranged in disc 5a. The choice of suitable tolerances between metal leads 6b and plastic support 5a allows the vacuum degree required by the specifications to be ensured. The assembly of insulator 5a and electrical leads 6b is pressed between two adjacent, coaxial metal rings 2, 3 rigidly sealed to each other. The metal ring 2 with larger opening has a circular saw tooth projection at its inner flat wall, that forms a circular seat in the plastic material of disc 5a by the pressure exerted on the insulator before sealing both such metal rings 2, 3, thus ensuring the vacuum tightness. The metal ring 2 with its projection is sealed to the wall so that the rooms are separated. The side flat surfaces of the two metal rings 2, 3 of insulator 5a are connected to two bushes 1, 4 by sealing. The two bushes 1, 4 can be threaded at their cylindrical outer and/or inner surface to allow electrical connectors to be used. In the third embodiment shown in Fig. 3, the invention consists of one or more cylindrical metal leads with constant diameter 6a which are fitted into holes with larger diameter arranged geometrically and formed in plastic discs 5, 5' adjacent and coaxial to each another. The vacuum tightness is provided by a little perforated cylinder or sleeve which is coaxial to the metal leads and arranged between the two plastic discs 5, 5¹. The choice of suitable coupling tolerances between metal leads 6a, perforated little cylinders 7, and plastic discs 5, 5', and the pressing of the two discs 5, 5' to each other until they are brought into contact provides a forced coupling between the two discs 5, 5' and metal lead 6a.

The assembly of insulator 5, 5' and electrical leads 6a is pressed between two adjacent, coaxial metal rings 2, 3 rigidly sealed to each other. The metal ring 2 with larger opening has a circular saw tooth projection at its inner flat wall, that forms a circular seat in the plastic material of disc 5 by the pressure exerted on the insulator before sealing both such metal rings 2, 3, thus ensuring the vacuum tightness. The metal ring 2 with its projection is sealed to the wall so that the rooms are separated. The side flat surfaces of the two metal rings 2, 3 of insulator 5, 5' are connected to two bushes 1, 4 by sealing during the assembling step of the electrical feedthroughs. The two bushes 1, 4 can be threaded at their cylindrical outer and/or inner surface to allow electrical connectors to be used. Figure 4 shows a section and a view of the particular 2 of Figures 1, 2 and 3: such component is made of metal and has a hollow cylindrical shape with circular steps sloping down to the axis. In particular, such component is provided with a circular saw tooth projection at one flat inner wall.

Figure 5 shows a section and a view of particular 3 of Figures 1, 2 and 3: such component is made of metal and has a hollow cylindrical shape with circular steps sloping down to the axis both at the outside and the inside of the cylinder. This particular geometrical shape is needed to receive and press uniformly the plastic insulator together with particular 2. Figures 6 and 6a show a section and a front view of particular 5, 5' of Figures 1 and 3, respectively: 5 such component is of plastic or thermoplastic material with any fibre reinforcement and has a cylindrical shape with a diameter-to-height ratio varying from 8 to 10. The disc is provided with one or more through holes parallel to the axis. The diameter of the holes

10 of the disc is such as to provide a free displacement coupling with the leads 6, 6a along all of their length except for the short length with larger diameter of lead 6 where a forced coupling is provided.

15 Figure 7 and 7a show a section and a view of particular 5a of Figure 2: such component is of plastic or thermoplastic material provided with any fibre reinforcement and having a cylindrical shape with a diameter-to-height ratio of the cylinder

20 varying from 4 to 5. The disc is provided with one or more through holes parallel to the axis. The diameter of the holes of the disc is such as to provide a free displacement coupling with the leads 6b along all of their length except for the short length with larger

25 diameter of lead 6b where a forced coupling is provided. Figure 8 shows a section of particular 7 of Fig. 3: such component is of plastic material and has a complex shape formed of a cylinder on which a

:;.". truncated cone is placed. The solid described above has a through cavity, the inner diameter of which is such as to provide a transition push fit with metal leads 6a.

Figures 9 and 10 show the steps of pressure fitting with interference according to the first method of the invention.

As can be seen in Fig. 9, after having made one or more through holes with a certain diameter in the insulating member of plastic material 5, a plurality of metal leads 6 the diameter of which is such as to provide an interference able to guarantee the vacuum and pressure tightness are fitted into such holes. The result is shown in Fig. 10. Advantageously, during the pressure fitting an auxiliary receiving equipment 9 can be used so that metal leads 6 can be kept in the desired arrangement.

Fig. 11 shows schematically the embodying of metal leads 6 inside the thickness of an insulator 5 by moulding or casting of plastic or thermoplastic material by the aid of a mould 10. The result is shown in Fig. 12.

At last, in the embodiment shown in Fig. 13, once a plurality of metal leads 6 provided with diametrical pads 11 are arranged, two insulating flat members 5 and 5' parallel to each other and provided with a grid of corresponding holes and seats 12 coaxial to each such holes and shaped such as to mate the shape of pads 11 of such metal leads are first fitted from opposite sides on such metal leads 6. The two insulating members 5 are then pressed to each other, as shown in Fig. 14, so that a vacuum and pressure tightness at such pads is obtained. The present invention has been illustrated and described according to some preferred embodiments thereof, however, it should be understood that those skilled in the art can make modifications without departing from the scope of the present industrial invention.

Claims

1. A device that provides for the passage of an electrical current through a wall of separation of rooms operating under even very different thermal and atmospheric conditions, otherwise referred to as electrical feedthroughs, characterized in that it includes : an insulator of plastic material or thermoplastic technopolymer with a high electrical, mechanical, thermal, chemical resistance consisting of one or more adjacent, coaxial discs in which one or more metal leads are fitted with interference, said interference being such as to guarantee always the vacuum tightness even if the operating temperature is varying without causing the plastics of the insulator to be permanently deformed.

2. The device or electrical feedthroughs according to claim 1, characterized in that the insulator consists of two adjacent, coaxial discs (5, 5') in which one or more cylindrical rigid metal leads (6) are fitted, the diameter of which is larger at the length interfering with the corresponding hole of the discs of plastic material, thus ensuring the vacuum tightness.

3. The device or electrical feedthroughs according to the preceding claim, characterized in that the extension of the length with larger diameter is at least the same as the thickness of the insulating discs . . The device or electrical feedthroughs according to the preceding claims, characterized in that the assembly of insulator and electrical leads is included in a suitable seat formed in a metal ring (2) that allows the electrical feedthroughs to be connected to the wall that should be crossed by welding to the outer surface thereof.

10 5. The device or electrical feedthroughs according to claim 4, characterized in that the inner flat wall of the seat of metal ring (2) has a circular saw tooth projection able to provide a circular impression or

15 groove by pressure in the plastic material of the insulating disc (5) to guarantee the vacuum tightness.

6. The device or electrical feedthroughs according to claim 2,' characterized in that the assembly of

20 insulator and electrical leads (5, 6, 5' ) is pressed between two adjacent, coaxial metal rings (2, 3) rigidly sealed or welded to each other.

7. The device or electrical feedthroughs according to 25 claim 6, characterized in that the two side flat surfaces of the two metal rings (2, 3) of the insulator are structurally connected to two bushes (1, 4) -

7.1 The device or electrical feedthroughs according to claim 7, characterized in that the two bushes (1, 4) are threaded at their cylindrical outer and/or inner surface to allow electrical connectors to be used.

;;

9. The device or electrical feedthroughs according to claim 7, characterized in that metal ring (2) is formed in one piece with bush (1) .

10. The device or electrical feedthroughs according to 10 claim 7, characterized in that metal ring (3) is made in one piece with bush (4) .

11. The device or electrical feedthroughs according to claim 1, characterized in that the assembly of

15 insulator and electrical leads consists of a member shaped as a cylindrical disc (5a) and one or more rigid metal leads (6a), the diameter of which is enlarged along a length which is at least double as long as the thickness of the insulating disc (5a) . on 12. The device or electrical feedthroughs according to the preceding claim, characterized in that the metal leads (6a) have a larger diameter along their whole length.

23 13. The device or electrical feedthroughs according to claim 1, characterized in that an insulator is provided consisting of two adjacent, coaxial discs (5, 5'), in which one or more rigid wires or leads (6a) .< with an uniform diameter along their whole length are fitted into holes with a larger diameter, the vacuum tightness being obtained by inserting one or more plastic sleeves (7) coaxially to the wires into the same holes between the two plastic discs and by pressing said discs to each other.

14. The device or electrical feedthroughs according to the preceding claim, characterized in that said sleeve (7) has the shape of a cylinder with an end shaped as a truncated cone.

15. The device or electrical feedthroughs according to claims 11 and 12, characterized in that the wires (6, 6a) are forcedly coupled to the through holes of the plastic discs (5, 5a, 5') at their length with larger diameter.

16. The device or electrical feedthroughs according to ^{•' ''} claim 14, characterized in that member (7) provides a transition push fit with the metal leads (6a) .

17. The device or electrical feedthroughs according to claim 14, characterized in that the lesser base of the truncated cone of member (7) is directed to the side flat surface of component (5) .

18. The device or electrical feedthroughs according to the preceding claims, characterized in that components (5, 5", 5a, 7) are made of plastics or thermoplastic high-performance technopolymers .

19. The device or electrical feedthroughs according to the preceding claims, characterized in that technopolymers such as Rayton PPS, Vitrex Pek, Vitrex Peek, Noryl GTX, Vespel, Teflon, Rulon are used as material for the insulator.

20 A device that provides for the passage of an electrical current through a wall of separation of rooms operating under even very different thermal and atmospheric conditions, otherwise referred to as electrical feedthroughs, characterized in that it includes : an assembly of insulator and electrical leads formed of two perfectly equal, adjacent, coaxial discs of plastics or thermoplastic technopolymers (5, 5') and one or more rigid wires (6) with a larger diameter along a length which is the same as the thickness of the single insulating discs (5, 5'); • a metal ring (2) able to receive said assembly of insulator and electrical leads into its opening, said metal ring allowing the electrical feedthrough to be connected to the wall which has to be crossed by sealing; • a metal ring (3) supporting, containing and pressing the assembly of insulator and wires (5, 6, 5') by sealing to metal ring (2); and • two bushes (1, 4) structurally connected to the side flat free surfaces of the two metal rings (2, 3) , respectively.

21. The device or electrical feedthroughs according to any preceding claim, characterized in that it can be used for ultravacuum applications at operating temperatures between 70 and 530°K.

22. A method of providing vacuum and pressure tightness between metal leads and insulators in electrical feedthroughs, characterized in that said metal leads are passed into an insulator of plastic material or thermoplastic high-performance technopolymer with an interference degree able to ensure always the vacuum tightness even as the operating temperature varies without causing any permanent deformation in the plastics of the insulator.

23. The method of providing vacuum and pressure tightness between metal leads and insulators in electrical feedthroughs according to the preceding claim, characterized by the following steps: a) providing an insulator of plastics or thermoplastic technopolymer with suitable thickness; b) drilling one or more through holes with a predetermined diameter into said insulator; c) pressure fitting into said holes metal leads with such a diameter as to provide an interference able to guarantee the vacuum and pressure tightness.

24. The method of providing vacuum and pressure tightness between metal leads and insulators in electrical feedthroughs according to claim 22, characterized by the following steps: a) providing one or more metal leads in the desired arrangement, and b) moulding or casting an insulator with such a thickness as to incorporate said leads to provide the tightness and to ensure at the same time the electrical insulation between the leads.

25. The method of providing vacuum and pressure tightness between metal leads • and insulators in electrical feedthroughs according to claim 22, characterized by the following steps: ^"a) providing a plurality of metal leads provided with diametrical pads; b) fitting from opposite sides on said metal leads two insulating flat members parallel to each other and provided with a grid of corresponding holes as well as seats coaxial to each said holes and shaped such as to mate the shape of the pads of said metal leads; c) pressing the two insulating members to each other in order that a vacuum and pressure tightness at said pads is obtained.