GB2208191A - Sealed electrical connector - Google Patents

Abstract

An electrical connector comprises electrical socket-type contacts (12) to each of which is respectively connected an electrical cable core element. An inner sheath (16) surrounds the contacts (12). An outer earhing sheat (10, 26) also surrounds the contacts (12) and is a push-fit onto the inner sheath (16). A seal (23) is provided between an inwardly projecting annular ledge on the outer sheath (26) and an outwardly projecting annular ledge on the inner sheath (16). The outer sheath (10, 26) is held in position on the inner sheath (16) by means of a flange (1) which engages an annular ledge on the outer sheath (10) and can be clamped to a receiving complementary connector. <IMAGE>

Description

IMPROVEMENTS IN ELECTRICAL CONNECTORS.

This invention relates to electrical connectors.

The invention is particularly applicable to plug and socket type connectors for use in hazardous and/or corrosive environments.

Known plug and socket type connectors which are designed for use in hazardous and/or corrosive environments are required to have their electrical connections substantially protected as far as possible from the surrounding environment during and/or after the electrical connection is made. In the first place this is to reduce the risk of an explosion and in the second place to prolong the life of the components.

The above problems are clearly exacerbated when the connectors are designed for high power applications.

While known sealed plug-socket connectors use sealing components, they are complex devices which are difficult and therefore expensive to manufacture.

Furthermore, wall sections have been designed following tests on materials of ferrous or non-ferrous metals to find that a diametrical tubular section not less than 3mm thickness can withstand a point impact energy of 30 joules at a distance of 150mm from an inside diameter of IOmm. Therefore, all wall sections subject to possible impact have been designed accordingly, with a point of impact length taken into consideration.

Materials of various types can be used for the connectors depending upon environmental conditions but the most popular material is gunmetal.

It is an object of the present invention to provide a protected plug-socket connector which is less complex to construct than know protected plug sockets.

According to the present invention, there is provided an electrical connector comprising an electrical contact, means for securing an electrical cable to the electrical contact, an electrically conducting outer earthing sheath surrounding the electrical contact, an inner sheath surrounding the electrical contact, an inner sheath fitted, at least partially inside the outer sheath and sealing means located between the inner and outer sheaths.

Preferably the outer sheath is a push fit onto the inner sheath.

Preferably the outer sheath is provided with a radially extending retaining flange.

Preferably the retaining flange, when provided, is separate from the outer sheath and is formed with an aperture through which the outer sheath is received, a first abutment on the outer sheath engaging a second abutment on the flange which extends into the aperture.

Preferably, part of the outer surface of the outer sheath is formed with a screw thread which is adapted to receive a sealing collar which, in use, forms a seal around the outer cable sheath.

The push fit concept of the outer sheath onto the inner sheath eliminates the need for special machining for keying purposes which would be essential in a single component design. This feature simplifies the assembly procedure for the connector as a whole as the internal components thereof are exposed before the connector is mated with its complementary connector.

When the connector is mated the flange is slipped over the external sleeve and clamped to a corresponding portion on the complementary connector.

The invention can be put into practice in several ways two of which will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a cross-section through a female socket according to the present invention; Figure 2 is an end view of the socket of Figure 1; Figure 3 is an end view of an alternative socket arrangement to that in Figure 2; Figure 4 is a cross-section of an alternative cable seal to that in Figure 1; Figure 5 is a cross-section through a male plug according to the present invention which is adapted to fit the female socket of Figure 1; Figure 6 is an end view of the socket of Figure 4; Figure 7 is a view of the other end of the plug in Figures 5 and 6; and Figure 8 is view of the end illustrated in Figure 7 illustrating an alternative pin arrangement.

Referring to the Figures 1 to 4 of the drawings, a gland nut 2, ferrule 3 and seal ring 4 are arranged at one end of a connector according to the invention to form a seal around a cable. The sealing arrangement is the subject of our patent application number 8711083 and will not be described in detail here.

The gland nut 2 is threaded onto one end of a body 26 of the connector. A flange 1 forms a running fit on a barrel sleeve 10 on which the body 26 is mounted.

An armour wire portion 35 of the cable is radially splayed out and clamped to the surface of a screen clamp 24 by means of a wire clamp ring 27 which is urged toward the clamp 24 by tightening bolts 22.

A cable core screening component 36 of the cable is received in holes in the screen clamp 14, having been twisted into suitable bundles. Again, the screening component is retained in place by the tightening bolts 22.

This collective screening to earth of each individual core at the socket and at the other end of the cable produces a parallel earthing circuit to ensure equipotential electrical bonding to prevent electrical shock and a reduction in common mode electrical noise interference at the exposed cable core surface.

The exposed core pieces of the cable are received into separate socket-type contact tubes 12 supported in a main insulating body 15. The cores are secured in place by two socket screws 11. Alternatively the cores may be crimped or soldered in position. Each of the contact tubes 12 are formed with four angularly spaced slots in their periphery. Each contact tube 12 also recessed in the insulating body 15 and incorporates a circular spring metal clip 14 which urges the slotted tube 1 2 into electrical contact with a mating plug to provide a high pressure, low sliding resistance, contact connection.The power contact tube 12 also incorporates an "0" ring seal 13 which is in sealing engagement with the outer surface of the tube and the surrounding surface of the insulator 15 to prevent the ingress of water and other contaminants when the socket receives a complementary plug.

The insulator 15 also incorporates internal perforated screens 34, which are moulded therein, and an internal screen pin 33.

The outer surface of the insulator 15 is shrouded in a metallic barrel 16. A seal is created between the insulator 15 and the barrel 16 by means of a further "0" ring seal 21 which prevents the ingress of water and/or dust therebetween. The barrel 16 and insulator 15 have mating complementary key and key way which require the pair to maintain a specific relative position when they are press fitted together under the application of pressure during assembly of the socket.

The metallic barrel 16 is formed with an outer surface machined to a close tolerance which, when the complementary plug portion is connected to the socket, provides a close tolerance fitting with an internal surface of a body portion of the plug. The tolerance is designed to provide a specified flame path or minimum experimental safe gap to prevent flame transmission when the socket and associated plug are to be used in explosive atmospheres.

The barrel sleeve 10 comprises a collar which abuts a complementary portion on the barrel 16 such that the one is a press fit onto the other during assembly.

A key way is formed in the outer surface of the barrel sleeve 10 which engages a complementary formation in the inner surface of the barrel 16.

The body 26 of the connector is screw threaded onto the outer surface of the barrel sleeve 10 and an "0" ring seal 23 is held between an inwardly projecting annular ledge on the body 26 and an outwardly projecting ledge on the barrel sleeve 10. Once the body is tightened onto the barrel sleeve, and the seal is created by the "0" ring between the two, a set screw 9 in the body 26 is tightened to bear on the barrel sleeve 10 to secure them in their relative postions.

An insulated keeper 8, comprising a tubular length of insulating material, spaces the power contact tubes 12 from the screen clamp 24. As the screen clamp 24 is mounted on the barrel sleeve 10 it urges the keeper 8 toward the tubes 12 maintaining the tubes 12 in position at one end of the connector. The keeper also ensures that there is insulation between the tubes 12 and the screen clamp 24.

Turning now to Figures 5 to 8 a plug according to the invention for connection to the socket described above is of similar design. The body 43 is bolted to the face of a piece of equipment to which the electrical cable is to be connected. The face is formed with a suitable hole through which a cable can be secured to the plug extends.

An insulator 415 inside a body portion 41 of the connector supports four electrical pins 47 and 410.

The pins 47 and 410 extend from cavities in each of which a cable core is fitted. Each cable is retained in place by means of a set of screws 44. Alternatively the cables can be soldered or crimped in place. The insulator 415 also incorporates internal perforated screens 419 which are integrally moulded therein together with a central screen connector pin 420.

When the pins 47 and 410 are mated with the contact tubes in the socket by push fitting, the inner surface of the body 43 of the connector around the pins creates a close tolerance fit with the outer surface of the barrel 16.

An "0" ring 412, forming an interface seal, is located between the insulator 415 and the adjacent inner surface of the body 43 which prevents dust and/or liquid contaminants, such as water, ingressing therebetween.

Between the outer surface of each connecting pin 47 or 410 and the surrounding insulator 415 there is a further "0" ring seal which prevents dust and/or liquid contaminants, such as water, ingressing the plug therethrough. An insulated keeper 416 is braced against the equipment face and maintains the connecting pins and insulator assembly in place in the body 43.

An earth screen contact 417, in the form of a cross with a central hole, is a tight push fit over the internal screen pin 420 to provide the earth to the equipment face. The screen contact 417 is secured in this position by cap screws 42 which are received in the body 43 of the connector.

An interface seal 411 is inserted in the front face of the insulator 415 to seal between the mating portions of the plug and socket when connected together.

A metallic earth spring contact 48 of tubular construction is located in the space in the body 43 of the connector into which the connecting socket enters.

The spring 48 incorporates a series of slots. Each finger thus created between the slots bears radially inwardly onto the barrel 16 of the mating socket.

As stated above, a plug-socket connector according to the present invention is particularly suited to high power applications in hazardous and/or corrosive environments. Typically rating specifications are the 50amps current rating, 5.2 k amps (R.M.S.) symmetrical current rating at 1500C for 1 second, asymmetrical peak fault current rating of 13.2 K Amps (Peak), a MVA rating of 3.7 MVA, a maximum voltage rating of 1100 volts and/or a Comparative Tracking index of 400-600 CTI.

By the symmetrical fault current rating is meant that value when the voltage crest is approaching its maximum value which gives rise to sustained heating effects. The plug and socket is therefore designed to be capable of accepting this fault current without damage or melting of components for the time and temperature specified.

By asymmetrical peak fault current rating is meant that value occurring momentarily when the voltage crest is approaching zero, which gives rise to dynamic bursting effects on cable connections, this design caters safely for this effect without damage.

By the comparative tracking index is meant that British Standards which takes into account the possibility of the worst environmental conditions for electrical tracking such as coal, dust and damp.

A plug and socket according to the invention is suitable for submersion up to 450 lbs/sq in. water pressure.

It is also suitable for momentary point impact loads of 30 joules. Such plugs and sockets provide fast replaceable interface connection joints of bolted or screwed connection. They are simple in construction and thus advantages in fitting manufacturing and assembly by press fitting. Furthermore, plugs and sockets according to the invention provide integral electrical noise interference control as well as a cable retention by displacement seal and improved electrical characteristics. Moreover, plugs and sockets of this type provide 50 amp rating at 1100 volts whilst still incorporating screening.

Claims (6)

1. An electrical connector comprising an electrical contact, means for securing an electrical cable to the electrical contact, an electrically conducting outer earthing sheath surrounding the electrical contact, an inner sheath also surrounding the electrical contact, the inner sheath being fitted, at least partially, inside the outer sheath, and sealing means located between the inner and outer sheaths.

2. A connector as claimed in claim 1, wherein the outer sheath is a push fit onto the inner sheath.

3. A connector as claimed in claim 1 or 2, wherein the outer sheath is provided with a radially extending retaining flange.

4. A connector as claimed in claim 3, wherein the retaining flange is separate from the outer sheath and is formed with an aperture through which the outer sheath is received, a first abutment on the outer sheath engaging a second abutment on the flange which extends into the aperture.

5. A connector as claimed in any of the preceding claims, wherein part of the outer sheath is formed with a screw thread which is adapted to receive a sealing collar which, in use, forms a seal around the outer cable sheath.

6. An electrical connector substantially as specifically described herein with reference to Figure 1 in conjunction with Figure 2 or 3, or Figures 5 and 6 in conjunction with Figure 7 or 8 of the drawings.