GB2117852A - Seals and connectors incorporating such seals - Google Patents

Abstract

A tapered connector (2) is provided for insertion into a tapered bore in a recipient (1). The connector carries a raised knife edge (4) which cold works recipient material (6) into a recess (5) to form a fluid tight seal upon insertion of the connector into the bore. <IMAGE>

Description

SPECIFICATION Seals and connectors incorporating such seals This invention relates to seals and to connectors incorporating such seals.

In installations wherein electrical or gas conduits have to be fed from an exterior to within a recipient of one form or another, it is often necessary to ensure that fluid leakage does not take place between the outside and inside of the recipient via the access point of the conduit. One particular type of installation wherein such a situation obtains is a gas centrifuge installation used for example in separation of uranium isotopes. In this type of installation, pressure within a centrifuge cascade is much lower than atmosphere, whereas outside the cascade atmospheric pressure exists. Gas conduits feed into the cascade and electrical supplies are also required.

An object of the present invention is to tend to provide a seal and a connector incorporating such a seal which enables conduits to be fed from outside a recipient to within the recipient with high fluid integrity.

According to one aspect of the present invention, a seal for sealing a conduit to a recipient, comprises at least one protuberance disposed on the conduit or recipient and a recess disposed on the conduit or recipient, the protuberance being cold worked into the recess or cold working material of the recipient or conduit into the recess on insertion of the conduit into the recipient, thereby to form a seal.

Advantageously, the conduit includes a tapered plug for carrying the protuberance and the recess.

Alternatively, the protuberance and the recess may be carried in a tapered bore in the recipient.

Another alternative is to provide the recess on the plug or recipient and the protuberance on the recipient or plug.

According to another aspect of the present invention, a connector for connecting a conduit to a recipient, comprises a plug carrying at least one protuberance and at least one recess disposed adjacent to the protuberance, said protuberance being of a hardness sufficient either to cold work part of the recipient into the recess or to be cold worked into the recess on insertion of the plug into the recipient.

Preferably, the protuberance comprises a knifeedge. Advantageously, cross-sectional area of the recess is equal to or greater than that of the knifeedge above the line or taper on the plug, so that when cold flow of material of the recipient is caused by insertion of the plug into the recipient, cold flow will continue until the plug taper meets that of the wall.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a vertical section of a plug and a recipient, Figure 2 shows a detail of Figure 1, Figure 3 shows a connector for an electrical line, and Figure 4 shows a connector for a gas feed.

Reference is directed firstly to Figure 1, in which a recipient is indicated by 1 and a plug for sealing insertion into the recipient by 2. The plug 2 is formed with protuberances 4 in the form of knife-edges. Just further down the taper than the knife-edges, recesses 5 are located. The recipient wall 1 contains a tapered bore 6. The bore has an edge region 6 which is cold worked in a manner to be explained below.

Reference is now directed to Figure 2, in which like reference numerals to Figure 1 are used for like parts. Figure 2 shows the knife-edge/recess of Figure 1 in more detail. From Figure 2, it can be seen that the knife-edge to the left of the figure is a knife-edge with a single angle 7, the knife-edge having a height 8. A knife-edge 9 to the right of the figure has a double angle knife-edge, which angles are indicated by 10 and 1 1. In both cases, the cross-sectional area of the recess is equal to or greater than that of the knife-edge above the line of the taper, indicated by 14, so that cold flow of material which is displaced by the knife-edge, as will be described below, continues until the plug taper meets that of the wall.

Reference is now directed to Figure 3, in which like reference numerals to Figures 1 and 2 are used for like parts. In Figure 3, a ceramic cable insulator is indicated by 16. Electrical lead throughs for cables are indicated by 17. Since the plug 2 in Figure 3 can be worked on away from the recipient, the ceramic insulator can be secured within the plug by silver solder or low melting point glass indicated by 18. Likewise, the electrical cables can be secured to the ceramic insulator.

Reference is now directed to Figure 4, which shows a plug containing a gas pipe feed. A gas pipe is indicated by 19. The gas pipe is brazed or silver soldered within a bore 20 inside the plug.

Insertion of the plug into the recipient is now described. Where the material of the recipient 1 is softer than that of the plug material and since the knife-edge protrudes from the shape of the taper, on insertion of the plug into the tapered hole, the knife-edge is forced into the wall producing cold flow of the wall material into the recesses 5, immediately below the knife-edges 4. As was mentioned above, the cross-sectional area of the recess is equal to or greater than that of the knifeedge above the line of the taper, so that cold flow of material 6 from the recipient displaced by the knife-edge continues until the plug taper meets that of the wall.

Design of the knife-edge is a compromise of several factors. Knife-edge size, shape and angle 7 depend on the plug and recipient material being used, and the operational environment of the seal.

A square knife-edge gives the most rigid shape but requires a high insertion force. Reducing the angle from ninety degrees down to say fifteen degrees reduces the insertion force but at the expense of knife-edge stiffness, and a more difficult machining operation. Use of a double angle on the knife-edge increases the stiffness, but at the expense of ease of machining.

Knife-edge height 8 is limited by the taper angle, the length of the plug, and the number of knife-edges on a given plug. A typical plug for use for example on aluminium, would have a taper angle of twelve to fifteen degrees and two knifeedges with heights in the range of quarter to one millimetre and edge angle between forty-five and seventy-five degrees.

Cold flow of the recipient material 6 into the knife-edge fills up any surface imperfections in the knife-edge surface finish. Flow of the recipient material into the recess below the knife-edge produces a locking action and increases the resistance of the seal to vibration and temperature cycling, particularly with knife-edge angle significantly less than ninety degrees. Cold welding between the material of the knife-edge and the recipient wall material will occur and form a permanent bond. Coating of the knife-edge with a suitable metal, for example copper may assist in increasing the degree of cold welding that occurs with an aluminium recipient.

In connection with the applications of the seal which are shown in Figures 3 and 4, the vacuum seals between ceramic insulator and steel plug and lead throughs are made by standard techniques, for example metallisation of the ceramic followed by brazing or the use of low melting point glasses. The seal is made by applying hydraulic pressure to the outer portion of the plug until a pre-determined pressure is reached. At this point, the tapers of the plug and recipient hole are in contact and the knife-edges have penetrated to their maximum depth.

The feed pipe of Figure 4 is welded or brazed to the plug.

For large diameters, a seal can be formed by pressing a tapered ring into a tapered recess formed between the main body of the recipient and a flange or other body, knife-edges being formed on the inner and outer sections of the tapered ring.

In some embodiments of the present invention, the knife-edge might itself be worked into a recess. The seal and connector as described above find application, for example, in vacuum plant or in installations where differing fluid pressures exist on either side of the seal, for example in undersea applications.

From the above description, it can be seen that an improved seal and connector incorporating such seal is provided.

Claims (8)

1. A seal for sealing a conduit to a recipient, comprising at least one protuberance disposed on the conduit or recipient and a recess disposed on the conduit or recipient, the protuberance being cold worked into the recess or cold working material of the recipient or conduit into the recess on insertion of the conduit into the recipient, thereby to form a seal.

2. A seal as claimed in Claim 1, in which the conduit includes a tapered plug for carrying the protuberance and the recess.

3. A seal as claimed in Claim 1, in which the protuberance and the recess are carried in a tapered bore in the recipient.

4. A connector for connecting a conduit to a recipient, comprising a plug carrying at least one protuberance and at least one recess disposed adjacent to the protuberance, said protuberance being of a hardness sufficient either to cold work part of the recipient into the recess or to be cold worked into the recess on insertion of the plug into the recipient.

5. A connector as claimed in Claim 4, in which the protuberance comprises a knife-edge.

6. A connector as claimed in Claim 4 or 5, in which the cross-sectional area of the recess is equal to or greater than that of the knife-edge above the line or taper on the plug, so that when cold flow of material of the recipient is caused by insertion of the plug into the recipient, cold flow will continue until the plug taper meets that of the wall.

7. A seal substantially as hereinbefore described and as shown in the accompanying drawings.

8. A connector substantially as hereinbefore described and as shown in the accompanying drawings.