WO1989008934A1

WO1989008934A1 - Electrical connectors

Info

Publication number: WO1989008934A1
Application number: PCT/GB1989/000234
Authority: WO
Inventors: Alan David Webb
Original assignee: Alpha Thames Engineering Limited
Priority date: 1988-03-09
Filing date: 1989-03-09
Publication date: 1989-09-21
Also published as: EP0428515A1; GB8805601D0; DE68918861D1; EP0428515B1

Abstract

An electrical connector suitable for supply of power to electrical equipment which is installed and used underwater comprises a housing (1) filled with a liquid and accommodating an enclosure (2) also containing a liquid and at least one electrical contact (12). A pin of a plug is inserted through a valve (4) and into the enclosure (2) via a conduit (3) to provide an electrical connection with the electrical contact (12). Upon insertion of the plug, a push rod (19) actuates a valve (17) to evacuate substantially all of the liquid in the enclosure (2) into a gas-filled chamber (16) and the gas in the chamber (16) is displaced into the enclosure (2), such that the electrical connection within the enclosure (2) operates in a substantially liquid-free atmosphere.

Description

ELECTRICAL CONNECTORS

This invention relates to electrical connectors and in particular to electrical connectors for supply of power to electrical equipment which is installed and used underwater. Various types of electrical connectors for this purpose are currently available, and they can generally be divided into two basiccategories in which the electrical connection has to be made or broken in air, or alternatively it can be made or broken underwater.

The first category of electrical connectors are more usually associated with such items of equipment as underwater television camera systems, electrical supplies to diving bells or enclosed well head remote control systems. These electrical connectors vary in rating and complexity from relatively simple single or twin line connectors of the type to be found in divers ' umbilicals for telephone communications to the fifty- four pin waterproof connectors used at the tether cable terminations of remote controlled, free swimming submersibles. These connectors intended for electrical make and break in air generally have water¬ tight enclosures and rely on "0" ring seals to exclude the water from the live parts of their construction, and they are also pressure sensitive in that they have to be rated for use at specific maximum ambient pressures .

The second category of electrical connector may take the form of one of a number of different constructions. One construction consists of a positive displacement design, in which the insertion of a plug pin into a socket with an interference fit is intended to displace the water within the socket tube. This construction relies upon close tolerances and the correct choice of body material to ensure a resilient interference fit. For short underwater missions, this electrical connector is very effective, but it has 1 size limitations, and an earth fault can occur if a speck of grit is trapped during insertion of the plug pin. When this construction is used for long term underwater installation, there may be some difficulty 5 in breaking apart a connector of this type.

Furthermore, as with other known types of electrical connectors, with this construction only a limited number of make and break cycles is possible before wear on the interfitting components allows leakage of 10 water, and consequent failure of the electrical connector. For this reason, they are only usually used either for applications involving single electrical connections, or for comparatively non-vital, low voltage, low current equipment. They may however 15 be used in the connection of the electrical components of diving bell umbilicals to the bell body penetrators, but in this case, all vital life support connections are normally duplicated, and power supplies are equipped with earth leakage interruptor relays to 2.0. prevent failures of insulation from causing a safety hazard.

Another type of underwater mateable electrical connector has a moulded rubber body, the resilience of which is relied upon to isolate water trapped in 25 cavities, which contain electrically conductive metal, within the rubber moulding. This design is effective for small multi-conductor connectors, but it also has size limitations and is prone to grit entrapment. There is an additional disadvantage, in 30 that corrosion can occur wherever trapped water is permanently in contact with the metal parts. With this type of connector, it can also be very difficult, if not impossible, for a diver to separate the components against the pressure of water, even at 35 relatively shallow depths. 1 Another known type of electrical connector is the pressure balanced type, which operates by introducing an insulating liquid, such as oil, into the connector to isolate the conducting pins or sockets from the „ 5 water. These connectors may have an oil- filled electrical contact chamber and a piston arrangement to maintain a constant volume of oil within the connector body. Different arrangements of this oil-filled type connector have been manufactured for use with very high 10 voltages and power capacities. However, they are relatively expensive, require close manufacturing tolerances and contain many component parts.

Another oil-filled type connector relies upon the difference in specific gravity of the filling oil and 15 surrounding water to trap the insulating liquid around the conducting metal. As the connector plug is inserted into the socket, the oil level in the socket alters and a reservoir built into the socket body accommodates the excess oil, until the plug is removed 20 from the socket. This electrical connector is very simple and is available for all sizes and applications, but it is essential that it be mounted with a vertical axis. Depending upon the specific application, the socket can be installed with its open end either 25 directed downwards or upwards, and a filling oil of specific gravity either lighter or heavier than the surrounding water is selected. With this connector it is possible, though not recommended, to make and break live electrical circuits underwater, and to leave the 3σ socket open to the water with power still connected thereto. As this connector is pressure balanced and does not rely upon seals, it is relatively easy for operation in any water depth.

In yet another known oil-filled electrical 5 connector, the plug has a single pin with any number of ring contacts along its length, and the socket is fixedly mounted on equipment on the water or sea bed with its open socket mouth directed upwards . The _j_ socket is filled with an insulating oil, which is heavier than the surrounding water. To prevent debris dropping into the socket, the mouth is closed with a buoyant valve ball trapped inside, which is dislodged

5 by the plug pin, as it starts to be inserted into the socket. This arrangement is not dependent on a specific orientation and, as the internal socket contact body can be loosely located within the outer casing, alignment of the pin is readily achieved,

_I__Q which permits the plug to be installed upon equipment, such as a wellhead, by lowering it down guide wires. Thus this device can be installed without the use of divers.

The plug contains an oil reservoir, which can be

X5 filled with heavy oil that is decanted down into the socket after complete mating to top up the oil level in the socket if necessary. This is however very unlikely to be necessary, as the connector is completely closed after mating, but with repeated

20 plug withdrawals a trace of oil tends to be removed each time. Along the length of the plug is an O-ring sealed hydraulic circuit connection, which aligns with a hydraulic circuit in the socket body. In. both plug and socket, the hydraulic ports are closed by

25 spring-loaded valves to prevent fluid loss when the plug and socket are disconnected. By design, these valves can only open under the socket filling oil, and so surrounding water cannot enter the hydraulic pipework or equipment.

30 This construction forms a composite electrical and hydraulic power connector complete with communications circuits, that can operate in almost any water depth without manned intervention. The bodies of the components are largely of plastics materials, which eliminates any corrosion problems and so long term installation can be considered. It can be used for high or low power circuits, on either, or both AC or DC supplies. However, all of these oil- filled connectors suffer from the problem of ingress of water molecules or droplets into the oil upon mating of the connector parts, which can cause short- circuiting, as well as corrosion of metal parts leading to degradation and eventual failure of the connector.

An alternative type of electrical connector, which contains an insulator, has the socket body filled with a grease, which is held in place behind a rubber membrane. When the plug pins are inserted through carefully manufactured slit-holes in the membrane, the grease is displaced thereby distorting the membrane slightly. As the pins are removed, grease is drawn in behind to fill the void left by the pins in the socket body and the membrane reverts to its original dimensions. This electrical connector is very effective for small power applications, but has a ^■physical size limitation. As with the oil-filled connectors, this device can also be operated live underwater. However, also like the oil-filled connectors, this device has the problem of ingress of water molecules or droplets into the grease during mating of the connector parts.

An entirely different type of electrical connector which is based upon inductive coupling techniques, has also been developed. This connector is essentially a magnetic circuit which is split into two halves at the mating face. Coils are wound around each half, and when assembled the unit is virtually a 1/1 transformer. This connector can have the positive advantage of not having live metal in contact with water, when electrical connection is made or broken underwater. It does, however, only work on an AC circuit, and although very suitable for communications circuits, it has a distinct power capacity limitation and a significant power loss. Various versions have been made and marketed, but transmission efficiencies of greater than 80% are rare . These electrical connectors are relatively heavy and bulky, and are very susceptible to loss of efficiency if grit is trapped between the mating faces, which can also cause serious overheating problems in power circuits. The iron core has to be protected from water corrosion, and this is usually achieved by applying a thin protective membrane, which has to be within the magnetic path, consequently causing loss of efficiency. Also, being of necessity very thin, this membrane is accordingly prone to damage. It is an object of the present invention to provide an improved electrical connector suitable for use in underwater electrical connections, which does not suffer from the disadvantages associated with electrical connectors which have been available hitherto for this purpose.

Accordingly the present invention consists in an electrical connector for use in making underwater electrica connections comprising an electrical socket including an enclosure containing a liquid and at least one electrical contact, and an electrical plug for insertion into said socket t provide an electrical coupling between the or each electric contact and the plug, and being characterised by means for evacuating substantially all of the liquid from said enclosure by insertion of said electrical plug. In order to permit disconnection of the electrical connector, means are provided for balancing the pressure of the enclosure with that of the surrounding water, i.e. ambient pressure.

Preferably, the evacuating means include valve means connecting said enclosure to a gas-filled chamber maintaine at a pressure, e.g. atmospheric pressure, below the pressure within said enclosure, said valve means being actuable to permit the flow of said liquid, e.g. under the influence of gravity, from said enclosure into said chamber by the action of inserting said plug. The valve means may also permit gas from the chamber to flow into the enclosure during said evacuation of the liquid from the enclosure.

In a preferred embodiment, the valve means may be actuated by means of a push rod, which is connected at one end to the valve means and the other end of which projects outwardly from said connector. The projecting end of the push rod may be located so that, just prior to final engagement or location of the plug, the projecting end engages the plug body to actuate the valve means . The enclosure conveniently has a valved inlet for the plug which may comprise a conduit opening at one end into the enclosure and sealingly closed at its other end by valve means, the valve means being operable by a pin of the plug to enable the pin to be inserted into the enclosure via the conduit. Advantageously, the socket components are immersed in a liquid contained within an outer housing. The socket preferably .includes means for replenishing the enclosure with liquid from within the housing prior to disconnection of the socket from, the plug. The replenishing means may comprise valve means coupled to the enclosure.

The chamber is preferably filled with air and the enclosure is filled with a liquid which suitably has one or more of the following properties, i.e. dielectric, non-diesel substantially incompressible, and environmentally acceptable. One example of such a liquid is an oil. Alternatively an inert gas may be used instead of air.

The present invention thus provides an electrical connector, wherein the electrical connection operates in a substantially liquid-free atmosphere, thereby overcoming the problems caused by invading water molecules or droplets. The electrical connector, in accordance with an embodiment of the invention, can also be re-usable and has generous alignment and orientation tolerances for mating purposes. Preferably, the plug, rather than the socket, is mounted on the seabed or an underwater structure, as this has no moving parts or seals, which may require maintenance thereby minimizing the need for retrieval, although this can be relatively easily achieved if necessary. The electrical socket is also suitable for transit through an air/water interface prior to mating with the plug pin.

The electrical connector may also be constructed from corrosion resistant materials to inhibit corrosive degradation of the connector.

In order that the invention may be more readily under¬ stood an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 shows a cross-sectional view of an electrical socket of an electrical connector, in accordance with the invention,..

Figure 2 shows an enlarged view in more detail of a valve part of the electrical socket, and

Figure 3 shows a cross-sectional view of an electrical plug of the electrical connector.

With reference to Figures 1 and 2, there is shown an electrical socket, the components of which are immersed in a. liquid, for example oil, filling an outer housing 1 supported in a lifting frame 30. Prior to the socket being immersed underwater, this oil is poured into the housing 1 through holes closed by drain/filling plugs 32. The housing 1 contains an annular chamber 33, which is partitioned into two regions 34 and 35 by a pressure-compensating diaphragm 24. Also prior to the socket enclosure being filled with oil, oil is poured into the region 35 through holes closed by crud caps 38 so that the diaphragm 24 is moved into the illustrate position to enable it to function as described hereinafter. During filling of the oil, the lifting frame 30 is held up by at least one prop 39, which is moved to the position illustrated by dashed lines in Figure 1. All of the socket components are made from a corrosion-resistant material, such as a glass reinforced plastics material or a polyester resin, stainless steel,etc,or a combination thereof. The socket includes an enclosure 2 having an inlet conduit 3, connected at one end into the enclosure and having a ball valve 4 at its other end. Along the length of the conduit 3 are two O-ring seals 5 and two scraper rings 6. The ball valve 4 consists of a valve ball 7 lodged between two flexible membrane seals 8,9, so as to seal apertures 10,11, respectively formed in the membrane seals. The enclosure 2 and inlet 3 are filled with a liquid, preferably in the form of oil, through drain/filler cap 32a. The enclosure 2 also contains a contact 12 which can be electrically connected to an external power source, via an electrical lead cable 13.

Two further conduits 14,15 are connected at one of their ends into the enclosure 2 and at their other ends into a chamber 16, which is sealed by a pressure transfer valve

17 and is filled with a gas, preferably air, at a pressure . approximately equal to atmospheric pressure. The valve 17, which is shown enlarged and in more detail in Figure 2, includes a spring 18, which is compressed by upward movement of a push rod 19, the upward movement being effected by force exerted on end 19a of the rod, which projects externally of the socket. Once the force exerted on the rod end has been removed, the push rod 19 returns to its initial position under the action of the spring. Referring now also to Figure 3, an electrical plug consists of a pin 20 connected into a plug body 21, into which an electrical lead cable 22 is inserted. Electrical coupling of the electrical contact 12 in the socket is achieved by insertion of the pin 20 into the socket. The pin 20 enters the socket by penetrating the membrane seals 8,9 through the apertures 10,11 which dislodges the valve ball 7 into a space 23 in the inner conduit 3, and by furthe penetration, the pin pushes through scraper rings 6. Entrapped oil in front of the pin is driven through the conduit 3 into the enclosure 2 , and hence through the open transfer valve 17 into the housing 1, via conduit 14, valve passage 40 and valve holes 41 and 42. Oil fro the housing then flows into region 34 of the annular chamber 33 via passages 36 and 37, which causes the diaphragm 24 to flex an thereby compensate for the increase in volume of the oil within the housing 1. When correctly inserted, the tip of the pin 20 engages with the contact 12 to form the electrica coupling.

As the socket approaches the plug body 21, the rod end 19a, and thus the push rod 19, is pushed upwards by shoulder 25 of the plug body locating in recess 25a formed in the ba of the socket. This activates the pressure transfer valve 17, causing the 0-ring seals 5 to seal around the pin 20 and the oil, together with any water droplets contained therein, in the enclosure 2 to flow, under gravity, into th chamber 16 via conduit 14. Air contained in the chamber 16 is simultaneously displaced from the chamber into the enclosure via the conduit 15. By this action an air atmosphere is provided within the enclosure 2, which is substantially liquid-free. As the socket body rests on the plug shoulders, the lifting frame 30 continues downward movement to operate a flip latch 26 in readiness for disconnection procedure.

The pin 20 is positively retained in the socket by the pressure differential between the interior of the enclosure 2 and the surrounding water pressure, and the oil from the enclosure 2 remains in the chamber 16.

To disconnect the plug and socket, the lifting frame 30 is lifted by lifting equipment, which raises the flip latch 26 and hence the push rod 27 which thus operates a pressure release valve 28, by lost motion between the housing and the socket body. The pressure release valve seals another chamber 31 connected by conduit 29 into the enclosure 2 and containing clean oil. By operating the valve 28, the clean oil passes into the enclosure 2 and air in the enclosure compresses accordingly, to equalize the enclosed pressure to outside ambient pressure. Because the oil in the housing 1 is at the surrounding ambient water pressure, as the oil in the chamber 31 passes into the enclosure 2, oil from the housing passes through non-return poppet valve 42 in the bottom of the chamber 31 to re-fill the chamber 31. A balance in the pressure is thus re-instated and O-ring seals 5 are relieved and the socket can be lifted completely from the plug. Upon recovery of the socket, the socket body is inverted with the valves 18 and 28 open and the drain/fillin plugs 32 and 32a removed to allow all the fluids to drain ou Also, a return spring may be provided in the conduit space 23 to return the valve ball 7 to its seating upon removal of..the plug pin 20. A different number of seals may be provided in the inlet conduit 3. For example, the membrane seal 8 may be omitted and/or only one 0-ring seal may be provided at 5.

Although the electrical connector in accordance with one embodiment of the invention, has been described with the socket located over the plug, the connector may be inverted, in which case the valve ball is formed from a material which is lighter than the oil or other liquid contained in the socket, so that it floats up within the oil into its valve seating.

Whilst particular embodiments of the invention have been described, other modifications will be envisaged withou departing from the scope of the invention. For example, a liquid other than oil may be used in the enclosure and inlet of the socket. Also, a gas other than air, such as an inert gas, may be contained in the gas chamber. In this respect, it is necessary to select a liquid and a gas, which do not undergo spontaneous combustion when under pressure. In the embodiment described there is one contact only for clarity and simplicity. However, depending upon circuit configurati two or more contacts could be arranged spaced along the pin of the plug and similarly within the socket. For larger power circuits additional plug and socket assemblies may be required. In another embodiment the chamber for containing clean oil may be omitted so that during disconnection of the plug and socket, oil passes into the enclosure 2 directly from the housing 1.

Furthermore, alternative pressure-compensating means ma be used instead of a diaphragm. For example, a cylinder and piston-type hydraulic compensating reservoir may be used Instead of the ball valve, alternative valve means, such as a gravity-operated tapered plug valve, may be used to seal the end of the conduit 3 and also be operable by the plug p

Repetitive connection and disconnection of the plug an socket may be achieved by the socket being provided with a plurality of gas chambers and transfer valves.

In high-voltage connection systems, signalling can be achieved using fibre optics. In this application, optical fibre connections may be included within the electrical connector, in which case the liquid contained within the socket should be compatible with these connections.

Claims

1. An electrical connector for use in making underwater electrical connections comprising an electrical socket including an enclosure (2) containing a liquid and at least one electrical contact (12), and anelectricalplug (20,21) for insertion into said socket to provide an electrical coupling between the or each electrical contact (12) and the plug (20,21), and being characterised by means (14,15,17) for evacuating substantially all of the liquid from said enclosure (2) by insertion of said electrical plug (20,21).

2. An electrical connector as claimed in claim 1, wherein means (24,26,27,28) are provided for balancing the pressure of the enclosure (2) with that of the ambient pressure in order to permit disconnection of the socket and the plug (20,21) .

3. An electrical connector as claimed in claim 1 or 2, wherein the evacuating means (14,15,17) include valve means (17) connecting said enclosure (2) to a gas-filled chamber (16) maintained at a pressure below the pressure within said enclosure (2), said valve means (17) being actuable to permi the flow of said liquid from said enclosure (2) into said chamber (16) by the action of inserting said plug (20,21).

4. An electrical connector as claimed in claim 3, wherein the pressure within said chamber (16) is maintained at atmospheric pressure.

5. An electrical connector as claimed in claim 3 or 4, wherein said liquid flows from said enclosure (2) into said chamber (16) under the influence of gravity.

6. An electrical connector as claimed in claim 3,4, or 5, wherein the valve means (17) may also permit gas from the chamber (16) to flow into the enclosure (2) during said evacuation of the liquid from the enclosure (2).

7. An electrical connector as claimed in any one of claims 3 to 6, wherein the valve means (17) is actuated by means of a push rod (19) which is connected at one end to the valve means (17) and the other end (19a) of which projects outwardly from said connector.

8. An electrical connector as claimed in claim 7, wherein the projecting end (19a) of the push rod (19) is located so that, just, .prior to final engagement or location of the plug (20,21), the projecting end (19a) engages the plug bod (21) to actuate the valve means (17) .

9. An electrical connector as claimed in any preceding claim, wherein the enclosure (2) has a valved inlet (3) for the plug (20,21) comprising a conduit (3) opening at one en into the enclosure .(2) and sealingly closed at its other end by valve means (4), the valve means (4) being operable by a pin (20) of the plug (20,21) to enable the pin (20) to be inserted into the enclosure (2) via the conduit (3) .

10. An electrical connector as claimed in any preceding claim, wherein the socket components are . immersed in a liquid contained within an outer housing (1).

11. An electrical connector as claimed in claim 10, wherein the socket includes means (28,29) for replenishing the enclosure (2) with liquid from within the housing (1) prior to disconnection of the socket from the plug (20,21) .

12. An electrical connector as claimed in claim 11, wherein the replenishing means (28,29) comprises valve means (28) coupled to the enclosure (2).

13. An electrical connector as claimed in any preceding claim, wherein said liquid has one or more of the following properties, i.e. dielectric, non-diesel, substantially incompressible, and environmentally acceptable.

14. An electrical connector as claimed in any preceding claim, wherein said liquid is an oil.

15. An electrical connector as claimed in any one of claims 3 to 14, wherein said gas is air.

16. An electrical connector as claimed in any one of claims 3 to 14, wherein said gas is an inert gas.

17. An electrical connector as claimed in any preceding claim, wherein the connector is constructed from corrosion resistant materials.

18. An electrical connector as claimed in any preceding claim, wherein the plug (20,21) is adapted to be mounted on the sea-be.dor an underwater structure and said socket is arranged to be lowered over, and lifted from, the plug (20,21).