DK143623B - SEAL HEAD FOR A TREATMENT BEARING FOR A CABLE OR SIMILAR SUBJECT - Google Patents

Description

(19) DENMARK

| J | (12) SUBMISSION WRITING o «U3623B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 4656/78 (51) | nt.ci.3 H 01 ® 13/14 (22) Filing day 19 · Oct. 1978 // F 16 J 15 / 4-6 (24) Race day 19 · Oct. 1978 (41) Aim. available Apr 22 1979 (44) Presented 14. S ep. 1981 (86) International application no. "(86) International filing day (85) Transfer day" (62) Master application no. "

(30) Priority Oct 21 1977, 773155, PI

(71) Applicant OY NOKIA AB, 0C101 Helsinki 10, FI.

(72) Inventor Pekka Erik Laupiainen, FI.

(74) International Patent Bureau.

(54) Sealing cow by for a treatment = pipe for a cable or similar item.

BACKGROUND OF THE INVENTION The present invention relates to a sealing head for an internally pressurized treatment tube for a cable or similar elongate blank, comprising a carrier that can be secured to the end of the treatment tube and a spring-loaded gasket having a central opening for the cable. passage and a closed control chamber designed in the carrier which encloses the package and is adjustably connected to a pressure medium source I to bring the control chamber under the influence of the pressure medium to exert a radial, compressive force on the outer circumference of the package to regulate the package. opening.

For example, by vulcanizing an extruded insulating coating on the surface of an electrical cable, this is axially passed through a treatment tube filled with a gas or liquid under pressure. In order to close the pressure-loaded space in the treatment tube, a sealing head of the above type is placed at its end so that the cable to be treated passes through the gasket placed in the sealing head.

It has previously been proposed to use a tapered gasket or seal in the sealing head and to adjust the diameter of the central aperture, i.e. the tightness of the gasket to the surface of the passing cable, by axially compressing the tapered portion of the gasket by a metal ring of complementary shape. The necessary compressive force can be provided by means of compressed air cylinders and a rotary ring. This regulation is cumbersome to perform and a remote control is difficult to arrange. A further disadvantage is that the gasket or seal cannot be replaced during the treatment process.

From published German patent application 2,304,515 it is known to radially compress the conical part of the gasket by means of a resilient ring hose which encloses the conical part and which with its outer circumference abuts a fixed plant and is connected to a pressure medium source for inflating the hose.

Since the treatment tube should be pressurized during the vulcanization of the coating on the cable passing through the treatment tube, its outlet end must be closed by means of a sealing head before the vulcanization begins. In order for the coated cable to pass through the gasket in the sealing head, this gasket must be arranged to substantially follow or join the outside of the cable. The joining between a drawline which initially serves to pull the cable through the treatment tube, and the cable itself, however, is so inaccurate and has such an irregular shape that when passing through the package it causes leakage and thus a detrimental reduction of the pressure in the treatment tube. Therefore, using known sealing heads, it has first been possible to close the treatment tube tightly, and thus to begin the vulcanization after the coated cable has reached the sealing head. This results in considerable losses, as the unvulcanized part of the coated cable has had to be discarded. Since the length of the treatment tube can be as much as 100 m, it is clear that the discarding of a cable part of similar length is of economic importance, especially in the case of high-voltage high-voltage cables.

The object of the present invention is to provide a sealing head which eliminates the above-mentioned drawbacks and allows to provide a seal or barrier to the treatment tube and to maintain the tightness also during the passage of the joint between the draw line and the cable through the sealing head. Further, it is an object of the invention to provide a sealing head which permits replacement of a gasket while the cable passes through the sealing head.

To this end, the sealing head according to the invention is characterized in that at least two resilient sealing means are arranged in the carrier in the direction of movement of the cable and that in the carrier for each sealing means there is a separate enclosing control chamber, which control chambers are individually adjustable. way is connected to a pressure medium source, in which an annular space is formed between the sealing means, which is externally limited by the carrier.

The invention is based on a co-operation between two sealing means or gaskets, first, namely during the start of a cable treatment process, density is provided against the smooth exterior of a trussline whose outer diameter is substantially equal to or slightly smaller than the outer diameter of the cable coating. and then, namely, when the cable has reached the sealing head, against the coating of this cable, without the pressurized gas or liquid in the vulcanization tube being able to leak from it as the joint or transition between the draw line and the cable passes through the sealing head. Conveniently, the first sealing means or the first gasket, calculated in the direction of movement of the cable, may be adjusted by means of the pressure medium for the passage of the cable coating, while the sealing means or the gasket following in the direction of movement may be adjusted after the passage of the draw line. When the forward end of the cable has reached the first sealing member or first seal, its diameter is adjusted after the passage of the cable coating. Hereby, density is first created by the last pack, then by the first pack and then finally by both packings. The pressure-tight coarse bounded by the carrier between the gaskets ensures that the pressure in the treatment tube cannot dissipate if the first gasket is not yet fully sealed, or if the transition between the drawline and cable should cause leakage in the gaskets. These should be axially spaced greater than the transition between the draw line and the cable.

Thus, a sealing head according to the invention makes it possible to close and pressurize the treatment tube as well as to begin the vulcanization of the cable coating immediately after initiation of the coating extrusion.

By connecting the gap between the gaskets in a controllable manner to another source of pressure medium, one can reduce the medium pressure required for each of the gaskets in the control chambers by regulating the pressure prevailing in the space between the gaskets.

By assembling the sealing head of axially consecutive annular elements, as further specified in claim 3,. For example, a gasket is replaced during the treatment process as the sealing member or gasket closest to the gasket to be replaced can be closed through a sufficiently high medium pressure in the associated control chamber.

A gasket in the form of a flat sealing plate is easy and inexpensive to produce, since no form is required for manufacture, as is the case for front seals.

The invention is explained in more detail below with reference to the drawing, in which: FIG. 1 shows an axial section in an embodiment of a sealing head according to the invention and a part of an associated treatment tube as well as a cable; FIG. 2 shows an axial section in another embodiment of the sealing head, and FIG. 3 is a top view of the sealing head locking device.

In the drawing FIG. 1, a treatment tube 1 with a sealed head 2 and a treated cable 3 running in the direction of the arrow A is shown, for example the treatment tube may be a vulcanization tube as shown in US-A-4,036,129.

The sealing head has a carrier 4 with a central passage channel 5. In the carrier there are arranged at axially spaced apart two annular sealing plates or gaskets 6 and 7, consisting of elastic material, the planes of which are perpendicular to the axis of the passage channel. These sealing plates or gaskets have an aperture 8 which substantially corresponds to the diameter of the cable. The plates are supported on both sides by support rings 9 in the carrier.

In the carrier there is for each sealing plate or packing an annular, surrounding, closed control chamber 10 or 11, which in the illustrated embodiment is constituted by an annular, flexible hose 12 which fits exactly into a housing 13 formed in the carrier.

Each control chamber is connected by means of a connecting piece 14 and a conduit 15 through a pressure control valve 16 to a pressure medium source 17, which in this case is assumed to be a source of compressed air. Hereby, in each of the control chambers, a desired pressure can be provided which exerts through the hoses a compressive force F towards the outer circumference of the seals for radially compressing them. By changing the pressure in the control chambers, the density of the gaskets against the outside of the cable can be adjusted.

A gap 18 formed between the gaskets is connected by means of a conduit 19 through a pressure control valve 20 to the inner space of the treatment tube 1, so that the pressure prevailing in the gap 18 can be regulated to, for example, half of the pressure in the treatment tube. Thereby, the compressive force to be exerted against the two seals can be reduced.

The FIG. 2 differs in particular from the embodiment shown in FIG. 1 in the design of the control chambers 30 and 31 for the sealing plates or gaskets 6 and 7, the respective chambers according to FIG. 2 is separately formed as an annular, closed chamber 33 in the carrier. A closed, resilient cylindrical ring 32. is provided in each of these chambers. Through this ring, the pressure in the control chamber exerts a radial compressive force F against the sealing plate or gasket. The ring 32 ensures the tightness of the seal head against the pressure in the treatment tube.

In the embodiments of FIG. 1 and 2, the carrier consists of separate, axially consecutive elements 4A, 4B and 4C joined together, and the control chambers 10, 11 and 30, 31, respectively, are formed between two elements 4A and 4B, 4B and 4C, respectively. The sealing head is provided with a locking mechanism 22 with two pivotable locking arms 23 for the inner element pair 4A and 4B and two pivotable locking arms 24 for the outer element pair 4B and 4C.

The locking arms include locking pins 25. Hereby, for example, the outer element pair 4B, 4C of the carrier can be opened for replacement of the sealing plate or gasket 7 during the course of the treatment process, provided that the sealing plate or gasket 6 is closed tightly during the replacement time.

In order to allow replacement of the sealing plates or gaskets 6, 7 and the supporting rings 9 while the cable extends through the sealing head, the relevant elements are two-part.

The figures of the drawing and the accompanying explanation merely illustrate the idea of the invention. As far as the details are concerned, a sealing head according to the invention can vary considerably within the scope of the claims. Thus, instead of compressed air, a pressurizing fluid can also be used as a pressurized medium.