GB2554353A

GB2554353A - Sealing device for sealing a mineral-insulated cable, mineral-insulated cable and method for sealing the cable

Info

Publication number: GB2554353A
Application number: GB1616035.0A
Authority: GB
Inventors: Gajdarus Tomás
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2016-09-21
Filing date: 2016-09-21
Publication date: 2018-04-04
Also published as: WO2018054559A1; GB201616035D0

Abstract

A sealing device 16 for sealing the space 14 between the outer sheath 11 or a support tube (31, Fig 7) of a mineral-insulated electric cable 10 and at least one wire 12 of the cable comprises a sealing plate 17 made of or containing an electrically isolating material and having at least one through-hole 18, each for passing through one wire of the cable. At the edge 20 of each through-hole is a ring element 19 made of a metal or an alloy and providing an inner contact surface 21 for generating a positive substance jointing (eg soldering, brazing or welding) between the ring element and the wire. The plate may have a fixing ring 23 to attach to the sheath, which may be a tube of greater length than the thickness of the plate (see Fig 3). The ring elements may be conical, or may be tubes of different lengths (see Fig 5). The cable may be a thermocouple element.

Description

(56) Documents Cited:

GB 0597607 A (71) Applicant(s):

Continental Automotive GmbH

Vahrenwalder Strasse 9, 30165 Hannover, Germany (72) Inventor(s):

Tomas Gajdarus (58) Field of Search:

INT CL H02G

Other: Online: WPI, EPODOC (74) Agent and/or Address for Service:

Continental Automotive GmbH

PO BOX 22 16 39, 80506 Munich, Germany (54) Title of the Invention: Sealing device for sealing a mineral-insulated cable, mineral-insulated cable and method for sealing the cable

Abstract Title: Sealing device for sealing a mineral-insulated cable (57) A sealing device 16 for sealing the space 14 between the outer sheath 11 or a support tube (31, Fig 7) of a mineralinsulated electric cable 10 and at least one wire 12 of the cable comprises a sealing plate 17 made of or containing an electrically isolating material and having at least one through-hole 18, each for passing through one wire of the cable. At the edge 20 of each through-hole is a ring element 19 made of a metal or an alloy and providing an inner contact surface 21 for generating a positive substance jointing (eg soldering, brazing or welding) between the ring element and the wire. The plate may have a fixing ring 23 to attach to the sheath, which may be a tube of greater length than the thickness of the plate (see Fig 3). The ring elements may be conical, or may be tubes of different lengths (see Fig 5). The cable may be a thermocouple element.

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Description

Sealing device for sealing a mineral-insulated cable, mineral-insulated cable and method for sealing the cable

The invention is concerned with a sealing device for sealing a mineral-insulated electric cable. The sealing device can seal a space between an outer sheath of the cable and at least one wire arranged inside the outer sheath. The invention also comprises the mineral-insulated cable that is sealed at at least one end by the inventive sealing device. Finally, the invention comprises a method for sealing an end of a sheath of a mineral-insulated cable .

A mineral-insulated cable (MIC) is an electric cable with an outer sheath that can be of tubular shape and that can be made of metal. Inside the outer sheath at least one electrically conductive wire can be arranged and the space between the at least one wire and the outer sheath is filled with an electrically insulating mineral, like e.g. magnesium oxide powder or aluminum oxide. The insulating mineral can be a powder. For example, a thermocouple cable can be provided in the form of a mineral-insulated cable. After cutting a mineral-insulated cable into length, the open ends of this cable must be sealed in order to keep the mineral powder inside the sheath and to prevent humidity from intruding the cable.

A mineral-insulated cable with an appropriate sealing is described in US 5,917,150 A. However for sealing the end of the mineral-insulated cable, sealing material must be inserted into the open end of the sheath and for obtaining the bonding between the sealing material and the sheath, the end must be heated such that the sealing material melts inside the sheath. This process is difficult to control.

A sealed mineral-insulated cable is also described in US 6, 229, 093 BI, wherein the sealing of the end of the sheath of the cable comprises a liquid-tight sleeve for each wire projecting out of the sheath of the cable. However, for providing such sleeves, a sealing material must be applied to the wires and melted in order to seal the space between the wires and the sleeve. As sealing material, glass or epoxy raising or spinel is used. This requires the placing of the loose sealing material at the end of the mineral-insulated cable and melting the sealing material together with the end of the mineral-insulated cable which is a complex process.

It is an object of the present invention to provide a sealing for an end of a mineral-insulated electric cable, wherein applying the sealing shall be made possible with few and simple production steps .

The object is achieved by the subject matter of the independent claims. Advantageous developments with convenient and non-trivial further embodiments of the invention are specified in the following description, the dependent claims and the figures .

The invention provides a sealing device for a mineral-insulated electric cable (or short: mineral-insulated cable). The sealing device is for sealing the space between the outer sheath of the cable and the at least one wire arranged or running inside the outer sheath. The sealing device comprises a sealing plate made of or is at least comprising an electrically isolating material. The sealing plate comprises at least one through-hole. Each through-hole is for passing through one single wire of the cable. In other words, it is assumed that the wires of the cable are longer than the surrounding sheath. If the sealing plate may be placed onto the open end of the sheath, the at least one wire may be stuck through a respective through-hole of the sealing plate. After placing the sealing plate with through-holes onto the open end of a mineral-insulated cable, the sealing plate must be fixed to the cable. To this end, the invention provides a ring element at each through-hole. The ring element is arranged around a respective rim or edge of the through-hole. The ring element itself can be fixed or connected to the sealing plate. If a wire is stuck through the through-hole of the sealing plate, the wire is automatically stuck through the ring element or surrounded by the ring element. Each ring element is made of a metal or an alloy and provides an inner contact surface for generating a bonding or jointing between the ring element and the wire. The bonding between the ring element and the wire is a positive substance jointing like it can be generated by soldering, brazing or welding the wire to the ring element. Thus the sealing plate is jointed or bonded to the wire by means of the ring element and a positive sub-stance jointing (substance-to-substance bond). This seals the space between the sealing plate and each wire of the mineral-insulated cable against humidity and/or gas.

The inventive sealing device provides the advantage that the sealing material, i.e. the material the sealing plate is made of, does not have to be positioned or placed inside the sheath and melted afterwards. Instead, the sealing material is provided in the form of a ready-made or finished sealing plate that can be placed at the end of the open mineral-insulated cable without the need of a melting process . Instead, the sealing plate is connected with the at least one wire of the cable by means of soldering, brazing or welding, which is a simpler process compared to melting glass or ceramics.

The invention also comprises optional embodiments that provide features which afford additional technical advantages.

As was just explained, instead of melting the sealing material of the sealing plate, the sealing is obtained by connecting each ring element to the wire that runs through the ring element. In order to provide a reliable sealing, each ring element preferably comprises or is made of one of nickel (Ni), nickel silicon (Nisi) , nickel chromium silicone (NiCrSi). These materials are especially suited for connecting the ring elements to thermocouple wires .

Preferably, one or several or each ring element is shaped as a tube that protrudes over a surface of the sealing plate. In other words, the sealing ring does not end at the surface of the sealing plate, but provides a tube or pipe in which the wire can be arranged. Such a tube provides a mechanical support for the wire that is projecting out of the sheath.

Preferably one or several or each tube is cone shaped in that an outer diameter of the tube decreases with distance to the surface of the sealing plate. In other words, the tube is thinner at the far end compared to the near end of the tube directly adjacent to the surface of the sealing plate. This provides the advantage for soldering, brazing or welding a wire to the tube.

In one embodiment at least two of the tubes are of different length .

With regards to the sealing plate, the electrically isolating material of the sealing plate preferably consists of or comprises at least one of a glass, a ceramic, and a glass ceramic. These materials are heat resistant such that exposing the mineral-insulated cable to heat will not loosen or destroy the sealing.

The sealing plate should also be fixed to the sheath thus that humidity and/or gas cannot intrude into the cable through a gap between the sealing plate and the sheath. Preferably at an outer rim of the sealing plate a fixing ring is provided. The fixing ring is connected to the outer rim of the sealing plate. Thus between the fixing ring and the sealing plate no intrusion of humidity and/or gas is possible. Further, the sealing ring provides a contact surface for generating a positive substance jointing between the fixing ring and the sheath of the cable. Such a positive substance jointing can be provided by e.g. soldering, brazing or welding or gluing. In other words, the sealing plate may be placed on the open end of the sheath like a lid or cover. By means of the fixing ring the sealing device may then be connected or fixed to the rim of the sheath.

The fixing ring may be made of or comprises a metal or an alloy. This allows for soldering, brazing or welding the fixing ring to the sheath.

Preferably, a thickness or length of the fixing ring is greater than a thickness or height of the sealing plate. The length of the fixing ring is the elongation of the fixing ring along the direction perpendicular to the diameter of the fixing ring. The fixing ring overlaps the sealing plate, it provides a collar that is a tube or a sleeve or a fitting or a support for the sheath when putting the sealing plate over the open end of the sheath. The contact area between the sheath and the fixing ring is increased for a more reliable bonding between the sealing device and the sheath.

So far, it has been assumed that the fixing ring of the sealing device should be directly connected to the sheath of the cable. However, the sheath of the cable may be arranged inside a support tube. The support tube may provide mechanical support or stabilization for the sheath. For example, the support tube may be made of or comprise steel. Using a support tube provides the advantage that a smaller diameter of the sheath may be used for providing the same stiffness of the cable as compared to a cable without a support tube and a larger diameter of the sheath instead. With regard to the support tube, in one embodiment of the invention the fixing ring provides a contact surface for generating a positive substance jointing between the fixing ring and the support tube, instead of the sheath as described above. Accordingly, if the thickness of the fixing ring is greater than a thickness of the sealing plate, the fixing ring may form a collar for the support tube, instead of the sheath as described above. Fixing the sealing device to the support tube instead of directly fixing it to the sheath provides the advantage that a cavity or space may be provided between the end of the sheath and the sealing device. The cavity may be filled with e.g. additional sealing material or with additional mineral powder or it may be empty.

As was already described, the ring elements at each through-hole and the fixing ring at the outer rim of the sealing plate may comprise metal and/or an alloy. Preferably, each ring element and the fixing ring are electrically insulated against each other by the sealing plate. Thus, no extra measures need to be undertaken in order to electrically insulate the sheath and the wires of the mineral-insulated cable in the region of the end of the cable.

In contrast to the prior art the sealing device is not produced or manufactured by melting the sealing material while it is already arranged inside the open end of the sheath. Instead, it is preferred that the sealing device is provided in a ready-made or pre-manufactured form that is independent of the cable. In other words, the sealing device may be produced first and afterwards placed on the open end of the mineral-insulated cable.

This latter step results in a mineral-insulated cable that is also part of the invention. The inventive cable comprises the outer sheath and the at least one wire arranged inside the sheath. The outer sheath may be made of or comprise a metal or an alloy. For example, the sheath can be made of steel or copper or Inconel. The at least one wire may be part of a thermocouple. An electrically insulating mineral, like, e.g., magnesium oxide powder or aluminum oxide powder, is arranged between each wire and the sheath. A respective end of the at least one wire protrudes out of an end of the sheath. For sealing this arrangement, the end of the sheath is sealed by means of an embodiment of the inventive sealing device. The respective end of the at least one wire is passed through or stuck through a respective ring element of a respective through-hole of the sealing plate of the sealing device. Each wire is soldered or brazed or welded to the respective ring element. Alternatively, the wire may be glued to the ring element.

Preferably, a material of the respective ring element of each through-hole has a CTE (coefficient of thermal expansion) that matches the CTE of the end of the wire that it is connected to. The matching means that the CTE of the ring element is larger or equal or smaller than the CTE of the wire. Thus, heating the arrangement of wire and ring element will not result in e.g. a crack or gap between the wire and the ring element. In other words, the CTEs can be chosen according to the performance needed.

Preferably, the mineral-insulated cable is a thermocouple element. Thus the cable is a robust thermo-sensor that is sealed against humidity and/or gas at the so-called cold-end side of the thermocouple .

For applying the sealing device to a mineral-insulated cable, the following inventive method can be used. The method is for sealing an end of a sheath or a support tube of a mineral-insulated cable, wherein a respective end of at least one wire protrudes out of the end of the sheath. The method comprises providing a sealing device according to the invention, moving the protruding end of the at least one wire through a respective ring element of a respective through-hole of the sealing device and arranging the sealing device at the end of the sheath. Thus, the sealing plate of the sealing device covers the end like a lid. Further, each wire which running through a respective ring element is attached to its ring element by way of soldering or brazing or welding such that a gap or space between the ring element and the wire is sealed.

The invention also comprises further embodiments of the inventive method that comprise features as they are already described in connection with the inventive sealing device. For this reason, the corresponding features of the embodiments of the method are not described here again.

In the following an exemplary implementation of the invention is described. The figures show:

Fig. 1 a schematic illustration of an embodiment of the inventive mineral-insulated cable;

Fig. 2 a schematic illustration of a sealing device provided in the cable of Fig. 1;

Fig. 3 a schematic illustration of another embodiment of the cable;

Fig. 4 a schematic illustration of a sealing device provided in the cable of Fig. 3;

Fig. 5 a schematic illustration of another embodiment of the cable;

Fig. 6 a schematic illustration of a sealing device provided in the cable of Fig. 5.

Fig. 7 a schematic illustration of another embodiment of the cable with a support tube;

Fig. 8 a schematic illustration of a sealing device provided in the cable of Fig 7.

The embodiment explained in the following is a preferred embodiment of the invention. However, in the embodiment, the described components of the embodiment each represent individual features of the invention which are to be considered independently of each other and which each develop the invention also independently of each other and thereby are also to be regarded as a component of the invention in individual manner or in another than the shown combination. Furthermore, the described embodiment can also be supplemented by further features of the invention already described.

In the figures elements that provide the same function are marked with identical reference signs.

Fig. 1 shows a mineral-insulated cable 10 that can be, e.g., a thermocouple element. The cable 10 can comprise an outer sheath 11 that can be made of a metal or an alloy. The sheath 11 can be made of, e.g., steel or Inconel (R) . The sheath 11 can have the shape of a tube. Inside the sheath 11, wires 12 can be arranged, like, e.g., wires of a thermocouple. At an end 13 of sheath 11 the wires 12 protrude out of the sheath 11. Thus, the wires 12 can be connected to extension wires (not shown). A space 14 between wires 12 and sheath 11 is filled with an insulating mineral 15 . The mineral 15 can be provided in the form of a powder. The mineral 15 can be, e.g., aluminum oxide or magnesium oxide.

In order to seal the end 13 in order to protect the mineral 15 against humidity, a sealing device 16 is fixed to the end 13. The sealing device 16 alone is shown in Fig. 2. The sealing device 16 comprises a sealing plate 17 for covering or closing or sealing the open end 13 of sheath 11. The sealing plate 17 can be made of glass or ceramics. For each wire 12 the sealing plate 17 provides a through-hole 18. In or at each through-hole 18 a ring element 19 can be arranged or provided that can be attached, e.g., to an inner rim 20 of each through-hole 18. The inner rim 20 represents an edge of the through-hole 18. Each ring element 19 is of the basic shape of a hollow cylinder through which the protruding end of the wire 12 can be pushed or stuck. Inside each ring element 19 a contact surface 21 is provided. Each ring element 19 can be made of nickel or nickel silicone or nickel chrome silicone or another alloy that is compatible to wire 12 with regards to CTE and their electrical compatibility. The compatibility can be found in simple experiments and depends on the planned operational conditions of the cable 10. The contact surface 21 allows for producing a mechanical bonding between the ring element 19 and the wire 12 inside ring element 19. For example, the wire 12 and the ring element 19 can be welded or soldered or brazed together.

An outer rim 22 of the sealing plate 17 can be surrounded by a fixing ring 23. The fixing ring 23 can comprise a metal and/or an alloy. The fixing ring 23 can be fixed to the sheath 11 by means of a mechanical bonding 24 similar to the mechanical bonding 24 of the wire and the ring element 19. For example, the fixing ring 23 can be welded or brazed or soldered to the sheath 11.The mechanical bonding 24 provides a watertight sealing such that no humidity and/or gas can intrude the sheath 11 and reach the mineral 15.

The ring elements 19 can be of the shape of a tube with a length 25 greater than a thickness 26 of the sealing plate 17. Thus the ring elements 19 provide a support tube for the end of the wire 12 .

Further, an outer surface 27 of each ring element 19 can be cone shaped thus that the mechanical bonding 24 between the wire 12 and the ring element 19 can be produced by welding or soldering or brazing with less heat energy at a far end 28 of the ring element 19 with regard to sealing plate 17.

Fig. 3 shows a mineral-insulated cable 16 that is built in a comparable way with regard to the mineral-insulated cable of Fig.

1. For this reason, only the elements that differ are explained.

The cable 10 shown in Fig. 3 and the corresponding sealing device 16 shown in Fig. 4 differ from the embodiment shown in Fig. 1 and Fig. 2 in that a length or thickness 28 of the fixing ring 23 is larger or greater than the thickness 26 of the sealing plate 17. Thus, a collar 29 is provided by fixing ring 23 such that the end 13 of sheath 11 is supported or covered or surrounded by the collar 29. The mechanical bonding 24 between sheath 11 and fixing ring 23 can be made more robust as a larger contact surface 30 is available as compared to the embodiment of Fig. 1 and Fig. 2.

In Fig. 5 a mineral-insulated cable 10 is shown that is based on the embodiment of Fig. 3. The sealing device 16 of the cable 10 of Fig. 5 is shown in Fig. 6.

The difference between the embodiments of Fig. 5 and Fig. 6 on one side and Fig. 3 and Fig. 4 on the other side is that the ring elements 19 are provided as tubes with different length 25 in the embodiment of Fig. 5 and Fig. 6.

Thus, the mineral-insulated cable 10 as shown in Fig. 1, Fig. 3 and Fig. 5 can be sealed at an open end 13 by means of a sealing device 16 according to Fig. 2, Fig. 4 and Fig. 6. Each sealing device 16 is a termination element that consists of one external ring 23 with the same dimensions as the end 13 of the cable or sheath 11 with two tubes as ring elements 19 to pass wires or conductors going through. The elements can be welded to fix the sealing device 16 to the wires 12 and the sheath 11.

This provides a simple way to seal a mineral-insulated cable by an extension part that can be manufactured independently and can be provided as ready-made or pre—manufactured part. A further advantage is that by choosing the material of the ring elements 19 and of the fixing ring 23, CTEs can be adapted to the materials used for the wires 12 and the sheath 11. Moreover, as no melting of sealing material (like glass or ceramics) is needed close to the mineral powder (like magnesium oxide) of the mineral-insulated cable, no gas evaporates from the mineral powder which would result in bubbles inside the molten sealing material.

Fig. 7 illustrates a cable with a support tube 31 for mechanically supporting the sheath 11. The sheath 11 is arranged inside the support tube 31. The support tube 31 and the sheath 11 may be provided as two coaxially arranged cylinders that touch each other. A sealing device 16 may be fixed or connected to the support tube 31 in the already described manner. The sealing device 16 may be arranged at a distance to sheath 11 such that a gap or free space or cavity 32 is provided between the sealing device 16 on one side and the end 13 of the sheath 11 on the other side. Fig. 8 shows the sealing device 16 used for the cable 10 of Fig 7.

Overall, the example shows how a mineral-insulated cable can be sealed by a pre-manufactured or pre-assembled termination part comprising glass or ceramics.

Claims

Patent claims

1. Sealing device (16) for sealing a space (14) between an outer sheath (11) or a support tube (31) of a mineral-insulated electric cable (10) and at least one wire (12) arranged inside the outer sheath (11), the sealing device (16) comprising a sealing plate (17) made of or containing an electrically isolating material, wherein the sealing plate (17) comprises at least one through-hole (18) , each for passing through one wire (12) of the cable (10) , characterized in that a ring element (19) is arranged at a respective edge (20) of each through-hole (18), wherein each ring element (19) is made of a metal or an alloy and provides an inner contact surface (21) for generating a positive substance jointing between the ring element (19) and the wire of the cable (10).

2. Sealing device (16) according to claim 1, wherein each ring element (19) comprises or is made of one of Ni, Nisi and NiCrSi .

3. Sealing device (16) according to any of the preceding claims, wherein one or several or each ring element (19) is shaped as a tube that protrudes over a surface of the sealing plate (17).

4. Sealing device (16) according to claim 3, wherein one or several or each tube is cone shaped in that an outer diameter of the tube decreased with distance to the surface of the sealing plate (17).

5. Sealing device (16) according to claim 3 or 4, wherein at least two tubes of different length (25) are provided.

6. Sealing device (16) according to any of the preceding claims, wherein the electrically isolating material of the sealing plate (17) consist of or comprises at least one of a glass, a ceramic, and a glass ceramic.

7. Sealing device (16) according to any of the preceding claims, wherein at an outer rim (22) of the sealing plate (17) a fixing ring (23) is provided, wherein the fixing ring (23) is connected to the outer rim (22) of the sealing plate (17) and provides a contact surface (30) for generating a positive substance jointing between the fixing ring (23) and the sheath (11) or the support tube (31) of the cable (10).

8. Sealing device (16) according to claim 7, wherein the fixing ring (23) is made of or comprises a metal or an alloy.

9. Sealing device (16) according to claim 7 or 8, wherein a thickness (28) of the fixing ring (23) is greater than a thickness (26) of the sealing plate (17) such that the fixing ring (23) forms a collar (29) for the sheath (11) or the support tube (31).

10. Sealing device (16) according to any of the claims 7 to 9, wherein each ring element (19) of the at least one through-hole (18) and the fixing ring (23) are electrically insulated by the sealing plate (17) .

11. Sealing device (16) according to any of the preceding claims, wherein the sealing device (16) is provided in a pre-manufactured form that is independent of the cable (10).

12. Mineral-insulated cable (10) comprising:

- an outer sheath (11) and

- at least one wire (12) arranged inside the sheath (11) , wherein the electrically insulating mineral (15) is arranged between each wire (12) and the sheath (11) and wherein a respective end of the at least one wire (12) protrudes out of an end (13) of the sheath (ID , characterized in that the end (13) of the sheath (11) is sealed by means of a sealing device (16) according of any of the preceding claims, wherein the respective end of the at least one wire (12) is stuck through a respective ring element (19) of a respective through-hole (18) of a sealing plate (17) of the sealing device (16) and is soldered or brazed or welded to the respective ring element (19).

13. Mineral-insulated cable (10) according to claim 12, wherein a material of the respective ring element (19) has a CTE that matches a CTE of the end of the wire (12) that it is connected to .

14. Mineral-insulated cable (10) according to claim 12 or 13, wherein the cable (10) is a thermocouple element.

15. Method for sealing an end (13) of a sheath (11) or a support tube of a mineral-insulated cable (10), wherein a respective end of at least one wire (12) protrudes out of the end (13) of the sheath (11), the method comprising:

- providing a sealing device (16) according of any of the claims 1 to 11,

- moving the end of the at least one wire (12) through a respective ring element (19) of a respective through-hole (18) of the sealing device (16) and arranging the sealing device (16) at the end (13) of the sheath (11),

- soldering or brazing or welding each ring element (19) to the respective end of the at least one wire (12) that is stuck through the ring element (19) and thus sealing a space between the ring element (19) and the wire (12).

Intellectual

Property

Office

Application No: GB1616035.0 Examiner: Paul Nicholls