GB1566733A

GB1566733A - Cryogenic connectzor

Info

Publication number: GB1566733A
Application number: GB4391376A
Authority: GB
Original assignee: Kernforschungszentrum Karlsruhe GmbH
Current assignee: Forschungszentrum Karlsruhe GmbH
Priority date: 1975-11-03
Filing date: 1976-10-22
Publication date: 1980-05-08
Also published as: FR2337837A1; DE2549061A1

Description

(54) CRYOGENIC CONNECTOR (71) We, KERNPORSCHUNGSZENTRUM KARLSRUHE GESELLSCHAI7r MIT BESCH RAENKTER HAFTUNG, formerly Gessellschaft filr Kernforschung m.b.H. of 5 Weberstrasse, 75 Karlsruhe, Federal Republic of Germany, a German body corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a releasable, vacuum tight single or multiple conduit connector including a sealing and/or insulating body, a receptacle body to which the connector is secured and a press mount.

The use of electrically insulated conduits, for example, at cryotemperatures raises considerable difficulties. For example, if a plastics material is used for the sealing and insulating material, the seal will become less tight when the conduit is cooled, due to the thermal shrinkage of the sealing or insulating material. The reason for this is that plastics materials, compared to metals, generally have a coefficient of thermal expansion which is greater by about one order of magnitude than that of metals. Thus, during cooling the sealing material always loosens from the metallic carrier. However, the use of plastics material is necessary if electrical insulation or high voltage insulà- tion is required.

It has been proposed to resolve such difficulties by placing the connector into the warm region of a cryostat and thus avoid the problems involved with low temperatures (W. G. Fastowski, Kryotechnik [cryo technologyj, published by Akademie-Verlag, Berlin, 1970). But, this is not always possible for example, with cryostats which are accessible only from the bottom or under very cramped conditions where the appropriate heat resistor cannot be installed.

It has also been attempted to use cast resins with appropriate fillers to reduce the coefficient of thermal expansion (w. R.

Roach and J. C. Wheatley, Rev. Sci. Instr.

35, 634 (1964). Due to the occurrence of thermal stresses and resulting cracks, the use of such resins did not produce sufficient success. Furthermore, their manufacture is relatively expensive. Sometimes the required fillers have additional, disturbing magnetic properties which influence the electrical connector.

The use of sealing and insulation materials of glass or ceramic also does not provide a satisfactory solution. When such materials are used there exists the danger that the thermal stresses of the cooling process cause these materials to break.

It is therefore the object of the present invention to provide a single or multiple conduit connector, which is continuously vacuum tight, easily releasable and capable of being disassembled, can be used at crylo- temperatures, is heat resistant and electrically insulated so that it can be used for high voltages where large dimensions of the insulation material become necessary.

According to the present invention there is provided a releasable, vacuum tight single or multiple conduit connector comprising a sealing and insulating element, a receptacle having a protruding receiving ring with a cutting edge, and a casing around the sealing and insulating element, the sealing and insulating element having at least two mutually independent sealing surfaces with respect to the receptacle and to a conduit passing through the connector and having a cylindrical portion with an annular groove, the receiving ring engaging in the annular groove and the inner surface of the receptacle corresponding with one of the inner surfaces of the annular groove of the sealing and insulating element, and the outer surface of the receptacle corresponding with the other inner surface of the annular groove.

A further modification of the invention provides that the one inner sealing and insulating element surface of the annular groove and the inner surface of the outer ring are designed as conical surfaces. It may also be possible that the outer surface of the ring of the receptacle is shaped into a cutting edge and that the portion of the sealing and insulating element disposed between the annular groove and the outer surface of the sealing and insulating element is shaped into a sealing lip and an additional conical ring presses the sealing lip of the sealing and insulating element against the cutting edge of the peripheral ring of the receptacle.

In one embodiment of the invention, through-bores may be provided in the sealing and insulating element in order to accommodate the conduit to be insulated.

The particular advantages of the invention are that the difference in coefficient of thermal expansion of metals and plastics materials can be utilized to produce a seal which has a high contact pressure even at the lowest temperatures. The resulting sealing pressures lie in the order of magnitude of about 200 bar.

The present invention will be further illustrated, by way of example with reference to the accompanying drawing, in which: Figure 1 is a sectional view of a schematically represented conduit, and Figure 2 is a sectional view of a multiple conduit.

Figure 1 shows an electrical connector 1 and concentrically therearound a casing 2, a sealing and insulating element 3 located between the two, a receptacle 4 on which the connector assembly is seated and a conical ring 5. The casing 2 can be screwed to the receptacle 4 by means of a thread 6 and thus presses the sealing lip 16 of the sealing and insulating element 3 against a peripheral receiving ring 7 which is provided with a cutting edge 8. The outwardly oriented cutting edge 8 is embedded in an annular groove 9 which itself is formed in the sealing and insulating element 3.

The contact pressure is exerted by means of the casing 2 and the sealing effect between electrical connector 1 and sealing and insulating element 3 as well as between receptacle 4 and sealing and/or insulating element 3 is present at room temperature as well as at cryotemperature at the contact surfaces of bore 10 or at 16 and 17, respectively. At cryotemperature the sealing effect is increased by shrinkage of the sealing and insulating element 3.

The receptacle 4 may here be a fixed component of a cryovessel which is not shown in detail, into which it is welded or screwed with an indium seal.

Figure 2 shows a multiple connector with conductors 18 which may be arranged around axis 12. This embodiment is a modification of the connector shown in Figure 1 so that the corresponding parts have the same reference numerals. Only those parts which are required for understanding of the figure are provided with numerals. The sealing effect between the insulating element 3 or the sealing process during thermal contraction and expansion corresponds to that described in connection with the arrangement of Figure 1. Additionally the casing 2 here presses a sliding cylinder 19 onto the sealing and insulating element 3. This cylinder also encloses the conical ring 5.

This facilitates installation of the connector.

Suitable materials for the sealing and insulating element 3 are, for example, polyethylene or polytetraftuoroethylene or polytrifluoro monochloroethylene.

The sealing and insulating element 3 must have such dimensions that the parts 1 or 18, respectively, of the connector as well as the receptacle 4 with its receiving ring 7 can be pressed in a press fit. The required excess in dimensioning at the inner conical part including surface 11 and at the sealing lip 16 takes care of the final seal at room temperature by compressive deformation.

Too much compressive deformation is prevented by application of slide cylinder 19.

for example in the embodiment of Figure 2.

The embodiment of Figure 2 has a helium leakage rate of 10-9 Torr 1/sec.

WHAT WE CLAIM IS:- 1. A releasable, vacuum tight single or multiple conduit connector comprising a sealing and insulating element, a receptacle having a protruding receiving ring with a cutting edge, and a casing around the sealing and insulating element, the sealing and insulating element having at least two mutually independent sealing surfaces with respect to the receptacle and to a conduit passing through the connector and having a cylindrical portion with an annular groove, the receiving ring engaging in the annular groove and the inner surface of the receptacle corresponding with one of the inner surfaces of the annular groove of the sealing and insulating element, and the outer surface of the receptacle corresponding with the other inner surface of the annular groove.

2. A connector as claimed in claim 1, wherein the one inner surface of the annular groove and the inner surface of the receptacle have a conical shape.

3. A connector as claimed in claim 1 or 2, wherein the outer surface of the receptacle is shaped to form a cutting edge and the portion of the sealing and insulating element which is disposed between the annular groove and the outer surface of the sealing and insulating element is shaped to form a sealing lip.

4. A connector as claimed in claim 1, 2 or 3 wherein through-bores are provided in the sealing and insulating element to accommodate conduits.

5. A connector as claimed in claim 3,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. a cutting edge and that the portion of the sealing and insulating element disposed between the annular groove and the outer surface of the sealing and insulating element is shaped into a sealing lip and an additional conical ring presses the sealing lip of the sealing and insulating element against the cutting edge of the peripheral ring of the receptacle. In one embodiment of the invention, through-bores may be provided in the sealing and insulating element in order to accommodate the conduit to be insulated. The particular advantages of the invention are that the difference in coefficient of thermal expansion of metals and plastics materials can be utilized to produce a seal which has a high contact pressure even at the lowest temperatures. The resulting sealing pressures lie in the order of magnitude of about 200 bar. The present invention will be further illustrated, by way of example with reference to the accompanying drawing, in which: Figure 1 is a sectional view of a schematically represented conduit, and Figure 2 is a sectional view of a multiple conduit. Figure 1 shows an electrical connector 1 and concentrically therearound a casing 2, a sealing and insulating element 3 located between the two, a receptacle 4 on which the connector assembly is seated and a conical ring 5. The casing 2 can be screwed to the receptacle 4 by means of a thread 6 and thus presses the sealing lip 16 of the sealing and insulating element 3 against a peripheral receiving ring 7 which is provided with a cutting edge 8. The outwardly oriented cutting edge 8 is embedded in an annular groove 9 which itself is formed in the sealing and insulating element 3. The contact pressure is exerted by means of the casing 2 and the sealing effect between electrical connector 1 and sealing and insulating element 3 as well as between receptacle 4 and sealing and/or insulating element 3 is present at room temperature as well as at cryotemperature at the contact surfaces of bore 10 or at 16 and 17, respectively. At cryotemperature the sealing effect is increased by shrinkage of the sealing and insulating element 3. The receptacle 4 may here be a fixed component of a cryovessel which is not shown in detail, into which it is welded or screwed with an indium seal. Figure 2 shows a multiple connector with conductors 18 which may be arranged around axis 12. This embodiment is a modification of the connector shown in Figure 1 so that the corresponding parts have the same reference numerals. Only those parts which are required for understanding of the figure are provided with numerals. The sealing effect between the insulating element 3 or the sealing process during thermal contraction and expansion corresponds to that described in connection with the arrangement of Figure 1. Additionally the casing 2 here presses a sliding cylinder 19 onto the sealing and insulating element 3. This cylinder also encloses the conical ring 5. This facilitates installation of the connector. Suitable materials for the sealing and insulating element 3 are, for example, polyethylene or polytetraftuoroethylene or polytrifluoro monochloroethylene. The sealing and insulating element 3 must have such dimensions that the parts 1 or 18, respectively, of the connector as well as the receptacle 4 with its receiving ring 7 can be pressed in a press fit. The required excess in dimensioning at the inner conical part including surface 11 and at the sealing lip 16 takes care of the final seal at room temperature by compressive deformation. Too much compressive deformation is prevented by application of slide cylinder 19. for example in the embodiment of Figure 2. The embodiment of Figure 2 has a helium leakage rate of 10-9 Torr 1/sec. WHAT WE CLAIM IS:-

1. A releasable, vacuum tight single or multiple conduit connector comprising a sealing and insulating element, a receptacle having a protruding receiving ring with a cutting edge, and a casing around the sealing and insulating element, the sealing and insulating element having at least two mutually independent sealing surfaces with respect to the receptacle and to a conduit passing through the connector and having a cylindrical portion with an annular groove, the receiving ring engaging in the annular groove and the inner surface of the receptacle corresponding with one of the inner surfaces of the annular groove of the sealing and insulating element, and the outer surface of the receptacle corresponding with the other inner surface of the annular groove.

5. A connector as claimed in claim 3,

wherein a peripheral conical ring presses the sealing lip of the sealing and insulating element against the cutting edge or against the receptacle.

6. A releasable, vacuum tight single or multiple conduit connector, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.