WO2001025666A1

WO2001025666A1 - Swivel coupling sealing means

Info

Publication number: WO2001025666A1
Application number: PCT/NO2000/000322
Authority: WO
Inventors: Rune Weltzien
Original assignee: Rf-Procom A.S
Priority date: 1999-10-01
Filing date: 2000-10-02
Publication date: 2001-04-12
Also published as: AU7817900A; NO994922L; NO994922D0

Abstract

In a coupling device (1, 2) to be used in surroundings with a high pressure and possibly an aggressive or harmful surrounding fluid, a sealing (12) is safeguarded against pressure from the surrounding medium by providing a corresponding pressure from the rear side. Therefore, in an interface area between mutually rotatable parts (1, 2) of the coupling, there is provided an inside chamber (23) for a hydraulic fluid, e.g. oil, and this hydraulic fluid is given the same pressure as the surroundings via a diaphragm which constitutes a division in a pressure transfer chamber (14, 16) divided in two parts, an inner part (14) thereof communicating with the oil-filled chamber (23), and an outer part (16) thereof communicating with the surroundings via an opening (15).

Description

SWIVEL COUPLING SEALING MEANS

The present invention relates to a sealing means for a so-called swivel coupling. In particular, the invention relates to a sealing device for a coupling consisting of two coupling pieces on respective sides of a dividing point of a split line or device that may be situated in surroundings with a high pressure, one of the coupling pieces being rotatable relative to the other about an axis through both of them, and the interface between the two coupling pieces is provided with a sealing to prevent influence from the surroundings on the inside part of the interface. Rotating couplings or swivel couplings are well known in several connections. As an example, electrical couplings of the type with a collector ring and a brush, are well known. In many situations it is necessary that one part, for example a cable, must be able to allow rotation movement, and it is then possible to insert a swivel coupling that splits the cable. Depending on what type of cable one is dealing with, and what sort of environment this cable will be situated in, the swivel coupling must then comprise special connector parts or coupling pieces with elements providing good connection from one cable part to the other.

In a hydrophone streamer towed in water in order to pick up reflected seismic signals from rock formations below the sea bed, special regulator devices for floating depth are included, i.e. so-called "birds". These devices are equipped with "wings" to be tilted by means of electromotors, in order to adjust cable floating depth. (It is important to be able to control floating depth, due to disturbing signal reflexes directed down from the sea surface, and floating depth is a parameter that will be included in the processing in order to remove such disturbances.) Sideways steering is also necessary, to be able to adjust the position, e.g. relative to similar neighbour streamers. For this reason, among other reasons, the "birds" must be rotatably mounted to the cable, and it is then of importance to be able to transfer electric current to the device from an anterior cable segment, through a rotating coupling. However, since such a cable is in a submerged condition, the rotating coupling is subject to pressure from surrounding seawater, and if seawater penetrates in through the coupling, the result may be destruction of the collector ring/brush system as well as other inside parts.

Also in connection with underwater lines for fluid transfer, especially in connection with underwater hydrocarbon exploitation, it is necessary to utilize swivel couplings. Also in this case it is important that seawater does not seep in to pollute the fluid flow. It is also important to protect for instance quick coupling elements situated in the coupling interface, against penetrating seawater.

The present invention has been provided to solve these problems, and, to be noted, not only in connection with "birds" in streamer cables and oil/gas conducting lines, but for any rotatable coupling in which it is important to protect internal parts in the coupling interface, against penetration of a fluid from the outer environment due to pressure. Further, this is related not only to hoses, lines and similar devices to be connected via a swivel coupling, but any devices coupled in such a manner and located in an external pressure environment.

In accordance with the invention, the problem is solved by a sealing device of the special type stated in the introduction, and the sealing device in accordance with the invention is characterized in that one of the coupling pieces is equipped with a chamber containing a hydraulic fluid, at least one channel from the chamber to the inside of the sealing, and, to the chamber from the surroundings, a connecting channel that contains a partition diaphragm, for pressurizing the hydraulic fluid from the surroundings via the diaphragm.

Preferably, the chamber may have a means for pressurizing, for providing superpressure in the fluid. Preferably, the fluid is an oil.

In one embodiment, the line is an electric line, and the inside part of the interface includes a collector ring device.

In another embodiment, the line is a fluid flow line, and the inside part of the interface includes a quick-coupling to a rotating inner sleeve. In a further embodiment of the invention, the line is an optical fibre line, and the inside part of the interface includes a rotatable optical connector.

In a further embodiment, the line is a combined line that comprises at least two elements in a group constituted by the elements electric line, fluid flow line and optical fibre line. In a further embodiment, the split device is a hydrophone streamer section comprising a floating depth regulating device, and the inside part of the interface includes a collector ring device.

Furthermore, the split device may be arranged in such a manner that a line engages a "fixed" termination, i.e., the device may comprise the termination part of the line and a fixed, complementary termination part for the line. However, in principle a line may of course equally well lie still in a reference system, while a termination device rotates, or both parts may rotate mutually as well as relative to a surrounding reference system. In another embodiment, the split device may be a ship's hull with a propeller shaft and a propeller, the two coupling pieces then being the propeller shaft and a hull area that includes a lead-through opening for the propeller shaft. The inside part of the interface is then the space inside the hull, and an outer part of the connecting channel then passes through the hull area close to the lead-through opening.

In the above, "dividing point" shall be construed to be the general location where e.g. two cables meet to be connected together in order to constitute an extended cable line, or the general location where two part devices meet to be connected together in order to constitute a complete device. Hence, the "dividing point" is "the location of an interface".

"Surroundings" and "surrounding environment" is intended to mean an outside liquid or gas environment that is harmful to construction details on an inside of the coupling, or harmful to the transfer characteristics of the coupling (i.e. detrimental to a transmitted signal, transferred energy or transferred material through the coupling).

In the following, the invention will be explained in more detail by describing some embodiments, and in this connection it is referred to the appended drawings, where fig. 1 shows a swivel coupling with a sealing device in accordance with a first embodiment of the invention, for an electric transmission device, fig. 2 shows a swivel coupling with a sealing device in accordance with a second embodiment, for transfer of fluids, fig. 3A shows a floating depth regulating device for a streamer cable, with a swivel coupling and a sealing device in accordance with an embodiment of the invention, fig. 3B shows a cross section through the device shown in fig. 3A, figs. 3C, 3D, and 3E show certain details of the device appearing in fig. 3A, fig. 4 shows a propeller shaft bushing in a ship's hull, with a swivel coupling and a sealing device in accordance with a further embodiment of the invention, and figs. 5A, 5B and 5C show the sealing chamber principle that is common to all embodiments of the invention.

A first embodiment of the invention appears in fig. 1. The purpose of this swivel coupling is to be able to transfer electric current or electric signals between a part 1 substantially at left in the figure, which part can be regarded as a stationary part for simplicity (also referred to as a stationary swivel housing), and a part 2 that is rotatable relative to the first mentioned part (the second part referred to as a rotatable housing). This is possible by means of slip rings/collector rings, in accordance with a previously known principle. Contact terminals for connection from both sides are shown by reference numerals 17, 18. A ball bearing for the rotatable housing 2 is shown by reference numeral 5, arranged on the outside of an axially extended section of part 2. Ball bearing 5 absorbs vertical and axial forces in connection with rotation against the stationary housing 1. Reference numeral 6 indicates a locking nut for a distance sleeve shown by reference numeral 7. Reference numeral 11 refers to a stationary and fixed sealing housing for collector rings, and collector ring and brush bridge are indicated by reference numeral 19. The distance sleeve 7 engages and locks ball bearing 5 and collector ring housing 11 in a fixed position, contacting housing 1. Special notice is made with regard to a mechanical special sealing in a chamber indicated by reference numeral 12, because this is the proper sealing between stationary part 1 and rotatable part 2. This is the sealing that first and foremost is subject to pressure from the surroundings, since seawater under pressure will be able to seep in through the narrow space between part 1 and part 2, toward the sealing in chamber 12. It is important that seawater, or more generally, a surrounding fluid medium that may do harm to inside details, is prevented from penetrating past the sealing in chamber 12. Internally in part 1 there is arranged a pressure transfer chamber that is filled with a hydraulic (i.e. substantially incompressible) fluid, e.g. oil. One part 14 of the pressure transfer chamber communicates with the interface between part 1 and part 2, at the inside of chamber 12. In other words, directly behind the sealing in chamber 12, there is oil. This oil is of a protective type, it is not electrically conductive, and it does not mix with the outer fluid medium (seawater). In order to maintain a correct oil counter-pressure, the pressure transfer chamber has a diaphragm 13 of annular shape, dividing the chamber in two parts 14 and 16, of which 14 is an oil side in direct communication with the inner chamber 23, and chamber part 16 is in direct communication with the surrounding medium via opening 15. Hence, the pressure prevailing in the surrounding medium (seawater) and that is dependent on depth, is transferred to the oil in the inner chamber via diaphragm 13. The annular pressure transfer chamber 14, 16 is arranged inside a circular ring 20 that is attached by means of screws 21 and a sealing ring 22. Reference numerals 3 indicate sealing rings for support flanges mounted against respectively stationary and rotatable swivel housings 1 , 2. Reference numeral 10 indicates two conductor connections from contact terminals 17 and 18 at the respective support flanges, to the collector ring means 19. Reference numeral 4 indicates a sleeve clamp nut for a cable 26. Reference numeral 24 shows a threaded section, where a service end cap has been screwed into swivel housing 1 ,

Thus, the novelty of the swivel coupling at hand is that the inner chamber 23 is filled by a hydraulic fluid, in particular oil, and the fluid pressure in inner chamber 23 is adapted to the outer pressure by letting the outer fluid medium enter through slit opening 15 to push against diaphragm 13 which in its turn moves toward the "oil side" 14 and increases oil pressure. This works in accordance with a principle termed "external pressure equalizing". If the pressure continues to increase when the swivel coupling reaches a greater depth, the diaphragm deflection will increase correspondingly, to compensate for increased pressure, and the oil pressure will increase also. The idea behind this is that when a small super-pressure is used inside the internal oil-filled chamber 23, it will not be possible for seawater to pass the sealing in chamber 12.

In fig. 2 appears another embodiment that is adapted for a fluid transfer line. In this figure, in which a new set of reference numerals is used, reference numeral 1 indicates a housing part assumed to be stationary, while a rotatable and axially extended housing part is indicated by reference numeral 2. Numeral 3 designates sealing rings for support flanges mounted against the rotatable housing 2 and the stationary housing 1 , respectively, and reference numeral 4 designates a flange nut to be tightened around a flange coupling 17 outside sealing ring 3. Rotatable housing 2 is supported rotatably in the stationary housing 1 by means of a ball bearing 5. Ball bearing 5 situated outside the axially extended part of rotatable housing 2, absorbs vertical and axial forces during rotation. Reference numeral 6 indicates a locking nut for a distance sleeve 7 engaging and locking ball bearing 5 in a fixed position, contacting housing 1.

The stationary housing 1 contains a quick-coupling (of high pressure type), generally indicated by reference numeral 19, including sealing details. Outside the quick coupling there is a mechanical sealing comprising a bellows enclosing a spring. In the quick-coupling a stationary inner part 9 contacts a rotatable part 8, the rotatable part 8 of the quick-coupling being an integral part of the rotatable swivel coupling part 2. Reference numeral 18 designates a trigger channel for the quick-coupling, working in accordance with a well known principle, which needs no further explanation here. The quick-coupling has an inner sealing ring 10, and additionally a mechanical special sealing 11 is arranged for outer slide sealing, which special sealing also works in accordance with a previously known principle, not to be described further here.

In the same manner as in the case regarding fig. 1 , a surrounding fluid pressure (seawater pressure) against the swivel coupling, will also in this case subject the main sealing 12 to a problematic pressure through the narrow opening between housings 1 and 2. (Sealing 12 is a special sealing of a mechanical type, but PTFE material is considered used on the contact surfaces in question.) Therefore, in the inner part of the stationary housing 1 there is arranged a chamber 20 containing a protective hydraulic fluid, in particular oil. Chamber 20 provides an oil environment on the inside of the special sealing 12. In the same manner as in the previous case, an inlet from the surroundings (e.g. seawater of depth dependent pressure) is arranged in the stationary housing 1 , to an outer chamber 16. The outer chamber is delimited by an annular diaphragm 13 that also delimits an inner chamber 14 which is in direct communication with the inner chamber 20 that contains a hydraulic fluid (oil). (The outer chamber 16 and the inner chamber 14 constitute together a pressure transfer chamber.) The pressure transfer chamber 14, 16 is delimited by a ring (like the ring 20 in fig. 1 ) attached by means of screws 21 , and is sealed by a sealing ring (like reference numeral 22 in fig. 1 ). Hence, an outer pressure can be transferred via the diaphragm to the hydraulic liquid in the inner chamber, and further past ball bearing 15 to the chamber with special sealing 12. Thereby, the pressure across special sealing 12 is equalized/balanced. It is also possible to arrange several diaphragm chambers that each contains a diaphragm and has an inlet from the surroundings to the outer surface of the diaphragm. The diaphragm or diaphragms may be provided with attached balancing springs.

Of course, it is also possible to increase the pressure in the hydraulic fluid to provide a small superpressure, so as to protect even better against penetration of e.g. seawater through the special sealing 12. This may e.g. be implemented by means of an internal reservoir space with an accumulator. It is also possible to implement a combination of the arrangements mentioned above, for use in a joint/coupling of a so-called umbilical cable that comprises a fluid line as well as signal lines, i.e electrical and/or optical signal lines. The principles and detailed arrangements mentioned above, can easily be used in a coupling for such a combined cable or for coupling an umbilical to a fixed side.

In fig. 3A appears an embodiment of the invention that can be used in connection with a seismic streamer cable. Also in this case, another and separate set of reference numerals is used. The figure shows a section of such a streamer cable that is a section for controlling the streamer floating depth and/or sideways position, and this is effected by means of a "bird" with wings, shown in the figure as a part underneath the actual cable. In the cable section in question, appearing centrally in the figure, a central part 5 appears, which part can be perceived as a fixed part, i.e. it is coupled in a fixed manner to adjacent parts of the cable, while the "bird" hanging below, is mounted to an outer sleeve 4 that is rotatable about an axis that is common to part 5 and part 4. For transfer of power and control signals for operating wings etc., a collector ring system is provided for, shown in the area just above the "electronics" box. The area in which the collector rings are situated, must be protected, and this area is filled by e.g. oil, like in the previously mentioned cases. In order to protect the bearings of interest, which bearings are indicated on both sides of outer part 4, against penetration from the outer pressure medium (that is seawater), there is provided also in this case an additional, two-part chamber with a separating diaphragm, shown at right in the stationary inner part. The surrounding medium is let into one part of the two-part chamber, and the inner part of the chamber is in fluid communication with the inner area that contains the hydraulic liquid (oil). Hence, a rear pressure is provided for the sealings also in this embodiment.

Of course, also in this embodiment it is possible to complete the arrangement with a pressurizing means that provides an additional superpressure for the hydraulic fluid.

In the following, the elements in fig. 3A are explained in more detail: Reference numeral 1 shows the end housing of the bird, reference numeral 2 shows a ball bearing for supporting the rotatable housing (ref. 4), reference numeral 3 shows a jamb nut for attaching the cable to the bird, reference numeral 4 shows the rotating bird housing, reference numeral 5 shows the center pipe containing an electronics box 20 with cabling 17, multi-contacts 18 and cables in the main seismic cable 19, reference numeral 6 shows a surface hatch for the rotatable bird housing 4 with access to collector rings 7 and springs 9, as well as cabling 8, reference numeral 7 shows collector rings, reference numeral 8 shows a cable from the collector rings toward bird motor 11 in the lower bird part 21 , reference numeral 9 shows springs for collector ring brushes, reference numeral 10 shows a watertight offshore snap-lock connector for transfer of power between the rotatable bird housing 4 and the lower bird part 21 , reference numeral 11 shows the bird motor, reference numeral 12 shows a transfer link from the bird motor 11 toward elevator 13, reference numeral 13 shows an elevator for adjusting the depth of the streamer in the sea, reference numeral 14 shows an opening for water to the pressure transfer chamber with a diaphragm 2C in fig. 3C, reference numeral 15 shows a special sealing in the form of a mechanical sealing, implemented here in a modified embodiment with pressure equalization, reference numeral 16 shows a T track lock for the lower bird part, reference numeral 17 shows a line connection through the bird and between cable sections, reference numeral 18 shows a multi-connector for connecting the bird to the streamer cable sections, reference numeral 19 shows a part of a cable inside the streamer cable, reference numeral 20 shows an electronics unit for power distribution and signal transmission between streamer sections, and reference numeral 21 shows the lower bird part that contains motor 11 and transfer link 12 as well as support and attachment for elevator 13.

In the figure appears a bird that is mounted in between streamer cable sections 22 and clamped to both sides of a bird end housing 1 by means of the jamb sleeve nut 3.

The rotating center part of bird housing 4 rotates around center pipe 5 on a ball bearing 2 inserted between center pipe 5 and rotating bird housing 4. Connection between streamer sections is established by means of internal cables 17 through the center pipe 5, which cables are connected to multi pin connectors with sealings in both ends of center pipe 5, and corresponding multi pin plugs 18 in seismic cables provide connection to internal cables 19 in seismic cables 22. An electronics box 20 transfers signal and current to collector rings and brushes 7, whereupon a cable 8 forwards current and control signals to the bird motor 11 via a watertight offshore connector 10 with a quick-coupling. The bird motor 11 is connected to the elevator 13 via a transfer link 12, thereby to enable change of elevator angle and consequently adjust the streamer depth in the water. The lower bird part 21 that contains motor 11 , transfer link 12 and support for the elevator 13, is attached to the rotatable bird housing 4 by means of a T track lock at the forward edge of bird 16, and by means of offshore connector 10 with a snap-lock. This simplifies dismantling of the lower part when the streamer cable is to be reeled into a drum onboard a vessel.

Fig. 3B shows a section through the rotatable housing 4, with a power cable 8 from collector rings 7, with a transmission to bird motor 11 that by means of link 12 changes the angle of elevator 13. Reference numeral 2 designates ball bearing on the center pipe shown by reference number 5.

Fig. 3C shows a segment of the pressure transfer chamber with water inlet opening 14, diaphragm 2C, oil-filled chamber 2D and channel through bird housing 4, further a channel past ball bearings 2 toward special sealing 15 that is pressure equalized with the water pressure toward the sealing opening toward the waterside, shown to the right of the sealing, and the oil pressurizing the left side of the sealing by means of the channel past the ball bearings 2 as previously mentioned. The special sealing 15 that is a mechanical type sealing, in accordance with a well known principle, will experience the same pressure on both sides of the sealing ring, so that water penetration will not be possible.

The special sealing will be described further in connection with a separate figure 5A. Fig. 3D shows the pressure transfer chamber, where a circular ring 17 is dismantled from the rotatable bird housing 4.

Reference numeral 16 shows an attachment bolt, and such attachment bolts are mounted circularly along the circumference of the circular ring chamber part 17. The diaphragm 2C has a rubber coating forming a sealing between the rotatable housing 4 and the ring chamber part 17, and in this manner establishing an annular pressure transfer chamber that transfers water pressure via diaphragm 2C to the oil present in chamber 22 and toward special sealing 15, where the oil applies a pressure against sealing rings equal to the oppositely directed water pressure on the opposite side of the mechanical special sealing, which side exhibits an opening toward the sea.

Fig. 3E shows an enlarged segment drawing of the attachment 16 of the lower bird part 21 in the rotatable center housing 4 by means of a T track lock with a front opening on the bird center part 4. The lower bird part 21 is pushed into this T track lock, and thereafter the rear part is pushed upward, so that the watertight offshore connector 10 with a snap-lock will lock the lower part to the rotatable top part 4. The snap-lock enables quick dismantling of the lower part 21 from the top part 4 when the streamer cable is reeled onto a cable drum.

The advantages of this type of bird, is that the operator can rely on power to the bird motor from a cable, not from batteries, which is the present solution.

Power from the cable implies improved continuity, without costly operation breakdowns and discharged batteries.

The bird can easily be dismantled from the streamer when the cable is reeled onto the cable drum. The front part of the bird may have the shape of a ship's bow, and such a shape will help to avoid flotsam sticking to the bird body. (If too much flotsam becomes attached to the bird, the bird may finally be torn off from the streamer.)

In fig. 4 appears another embodiment of the invention, viz. in connection with a propeller shaft bushing in a ship's hull. Also in this case, a separate set of reference numerals is used:

Fig. 4 shows a segment drawing of a ship's propeller shaft 1 , onto which a wear sleeve 2 has been mounted and secured by means of a locking ring 3, and at the same time an expanding sealing mass 4 has been molded in between sleeve 2 and shaft 1.

Reference numeral 5 designates a sealing chamber having an outer sealing ring 6 of steel, and an inner sealing ring 7 with "Tordon" Teflon material mounted therein, which assembly is described in fig. 5A that deals with the actual sealing.

Reference numeral 8 designates an end lid for the sealing chamber , that together with intermediate chamber 9 forms an integral sealing chamber held together by bolts 10, and wherein sealings 11 caulk between end lid 8 and intermediate chamber 9. The intermediate chamber 9 has an outside threaded support indicated by reference numeral 13, and is screwed into support flange 12 which is fixed to the ship's stern post 14 by means of fixing bolts 15, and gaskets 16 establish sealing between stern 14 and support flange 12.

Inside the support flange 12, a circular bellows 17 has been inserted, which bellows can be pressurized through opening 18, using hydraulic oil or pressurized air. The bellows 17 will expand in all directions, and finally seal against the shaft inside the chamber where the bellows 17 has been mounted, and it will then be possible to dismantle the sealing chamber end lid 8 for replacement/check of the sleeve sealing, without dismantling the shaft or entering the ship in a boat yard.

Reference numeral 21 is a pressure tank for internal separation of the water side 22 and the oil side by means of a diaphragm 27.

The water side has a pipe connection 24 with an opening 20 to the sea. The oil side 23 has a pipe connection 25 with a pipe thread toward the end lid 8 of the sealing chamber. Since the water pressure propagates through opening 20 to the water side 22 of the diaphragm 27, this pressure will provide a force that is transferred to the oil side 23 of the diaphragm, which side is filled by oil. This increasing hydrostatic pressure propagates to the sealing ring 7, and forces this ring toward sealing ring 6 which is subject to the same water pressure on the opposite side, via opening 19. A balance in hydrostatic forces is established, resulting in no liquid transfer from the water side to the oil side. The special sealing with a new type of mechanical seal with Teflon sealing rings mounted into steel rings 6 and 7, is described in more detail below, in the description regarding fig. 5A.

In fig. 4 we find a shaft sealing with external pressure equalization, and in which in-seeping water at position 19 enters a sealing chamber, in which water subjects a diaphragm area to a hydrostatic pressure, and where the diaphragm is fixed by vulcanization to a steel ring. An oppositely directed sealing ring has packing rings mounted fixedly into a steel ring, which is in its turn attached to the diaphragm by vulcanization. This side of the sealing chamber is oil-filled up to the oil chamber in pressure tank 21. When the pressure tank water side 22 transfers pressure toward this sealing 7 via the pipe connection 25, there is established a balance in pressure on respective sides of the sealing, and liquid cannot move from the water side to the oil side or vice versa.

The advantage of this type of sealing, is that it is quite capable of resisting water penetration to the ship's interior.

Furthermore, the sealing can be dismantled for inspection, possibly sealing rings can be replaced without pulling the ship into a boat yard. The sealing needs a minimum of maintenance.

The inner chambers and the channel therebetween can be equipped with a pressure alarm sensor for monitoring the pressure condition therein. An abnormal pressure increase will provide an alert if leakages should arise, or if a defect should appear in a diaphragm between the seawater side and the interior side with the hydraulic liquid.

The pressure equalizing principle across a mechanical sealing with PTFE slide material will eliminate maintenance between class inspections of shafts for propeller operation in connection with propulsion machinery and current variants of bow thrusters, and for azimuth propeller operation. Further, installation of a header tank for pressurizing sleeve sealings may possibly be eliminated, with installation and maintenance saving effects resulting, relative to the conventional installations used today. It is possible to achieve a virtually maintenance-free sealing, safeguarded against surprising leakages. The selection of materials when using segment rings makes it possible to change sealing rings without pulling out the shaft, which results in saving of expenses if unforeseen damages should arise.

The special sealing chamber that is a central feature in the present invention, appears more clearly in fig. 5A, 5B and 5C. Also with regard to these figures, a separate set of reference numerals is used.

In fig. 5A appears an enlarged segment of the sealing chamber, in which a new and modified type of mechanical sealing having equal areas A1 and A2, will subject the sealing rings 3 to an equal pressure. This pressure on diaphragm 4 is established by the external water pressure, that through opening S (see also ref. 19, fig. 4 and ref. 14, fig. 3C) applies pressure to the diaphragm 4 (2C in fig. 3C), which diaphragm transmits this movement and applies pressure to the oil in chamber P1 (2D in fig. 3C). The hydrostatic pressure transmitted from the pressure transfer chamber that includes a diaphragm, enters the sealing chamber (15, fig. 3C) and applies a pressure force P1 to diaphragm 4 in fig. 5A, of given area A1. The diaphragm is arranged inside an enclosing circular sleeve 6 with sealing rings 7 therearound inside the sealing chamber 12. This sleeve 6 is stationary, and does not rotate. The diaphragm 4 is attached to the closed end of the sleeve, and a steel ring 2 is mounted on the diaphragm, and Teflon sealing slide rings 3 are attached inside the steel ring 2. A bore 24 conducts oil inbetween a channel in the steel ring and toward the Teflon sealing rings. This sealing liquid has the same pressure as the water pressure in chamber P2. When the sealing rings are subject to a leakage, equal pressures will prevent fluid transfer from chamber P2 toward chamber P1.

These Teflon rings 3 slide toward an oppositely directed steel ring 1 , attached to (vulcanized to) a diaphragm 4 in the sealing chamber side P2 that is in communication with the sea through an opening labeled S, at an arrow close to reference numeral 9. The diaphragm in chamber P2 has the same area A2 as the diaphragm in the chamber labeled P1. When both chambers have equal diaphragm areas and the same hydrostatic pressure that propagates to chambers p1 and p2, the forces P1 and P2 will be the same upon respective diaphragm areas, and we have two oppositely directed, equal pressure forces as well as hydrostatic pressures.

This can be expressed by means of the following formula: P1 x A1 = P2 x A2 wherein P1 = pressure in chamber 1 , A1 = area of diaphragm sealing 1 , P2 being the pressure in chamber 2, while A2 is the area of the diaphragm sealing.

The diaphragm 4 in chamber P2 is fixed by vulcanization to a steel ring that slides against sealings 3. Further, the diaphragm is locked against an axial sleeve by means of locking ring 9, shown in a expanded segment drawing in fig. 5C, wherein an o-ring 7 seals against the axial sleeve, as well as a hydrostatically influenced sealing 8 that expands due to pressurizing (labeled P in fig. 5C) and is in contact with the axial sleeve 20. Additional packers 7 provide sealing for the stationary sleeve 6 arranged in chamber P1. The sealing rings 3 in figs. 5A and 5B are made from Teflon material, having a precision ground slide surface that slides against steel ring 1 in fig. A, and they will, in accordance with a well known principle for mechanical sealing, provide such sealing. A spring 5 having the same spring force in chambers P1 and P2, and with a spring guide board 10 in fig. 5A, maintains a constant force against the diaphragms 4, that transmit these oppositely directed pressures toward the sealing rings. This pressure helps to ensure pressure balance between chambers P1 and P2.

Thus, the common feature of the embodiments described above, which feature is the most important one for the invention, is that a diaphragm will be influenced by any external increase in pressure, and compensate for the increase by applying a pressure load on the hydraulic fluid inside the swivel housing, and the internal pressure will therefore be equal to the outside pressure. Thereby, the important sealings will be safeguarded. The types of swivel couplings exemplified here, will, with regard to the sealing system, be useful at any water depth. The above description of the invention is merely exemplary, as already explained hereabove, and it must be underlined that the invention, in its most general form, comprises all embodiments of that which is stated in the appended claim 1.

Claims

PATENT CLAIMS

1. A sealing means for a coupling consisting of two coupling pieces on respective sides of a dividing point for a split line or device that may be situated in surroundings with an enhanced pressure, one coupling piece being rotatable relative to the other about an axis through both coupling pieces, and the interface between the two coupling pieces being provided with a sealing to prevent influence on the internal part of said interface, from the surroundings, characterized in that one of said coupling pieces is equipped with a chamber containing a hydraulic fluid, at least one channel from said chamber to the inside of said sealing, and to the chamber from the surroundings a communication channel containing a partition diaphragm, for pressurizing the hydraulic fluid from the surroundings via said diaphragm.

2. The sealing means of claim 1, characterized by a pressurizing means connected to said channel, said chamber or said communication channel inside said diaphragm, for providing a superpressure in the fluid.

3. The sealing means of claim 1, characterized in that the fluid is an oil.

4. The sealing means of claim 1, characterized in that said line is an electric line, and that the inside part of said interface includes a collector ring means.

5. The sealing means of claim 1 , characterized in that the line is a fluid-conducting line, and that the inside part of said interface includes a quick-coupling to a rotating inner sleeve.

6. The sealing means of claim 1 , characterized in that the line is an optical fiber line, and that the inside part of said interface includes an optical rotating connector.

7. The sealing means of claim 1 , characterized in that the line is a combined line comprising at least two elements of a group constituted by the elements electrical line, fluid-conducting line and optical fiber line.

8. The sealing means of claim 1 , characterized in that the split device is a hydrophone streamer section comprising a floating depth regulating unit, and that the inside part of said interface includes a collector ring means.

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9. The sealing means of claim 1 , characterized in that the split device is constituted by a termination part of a line and a fixedly arranged, complementary termination part, wherein the line termination part is swivel-coupled to the fixed termination part, or wherein the line i5 termination part is fixed and the fixed termination part is rotatably arranged, or wherein both said parts are mutually rotatable and rotatable relative to a fixed reference system.

10. The sealing means of claim 1 ,

20 characterized in that the device is a ship's hull with a propeller shaft and a propeller, the two coupling pieces being the propeller shaft and a hull area that includes a through opening for said propeller shaft, the inside part of said interface being the inner space of the hull, and an outer part of said communication channel passing through the hull area close to said through opening.

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