GB2355348A - Coupling for hazardous areas - Google Patents

Abstract

A coupling comprises a connector and a counterpart wherein mating faces of the connector and the counterpart are provided with engaging formations which form a chamber to enclose the contacts 65,64 of the connector and counterpart while the contacts are engaged (figure 8) and also during separation of the contacts (figure 11). The formations telescope during disconnection of the connector and counterpart to contain any hazard inside the connector and the telescoping sleeves provide flame paths 26, 54. The connector may conform to Exd and Exe protection.

Description

2355348 IMPROVEMRNTS IN CONNECTORS This invention relates to connectors,

and is more particularly concerned with plug and socket connectors f or use in hazardous areas where there is danger of sparks causing explosions.

In such hazardous areas, it is commonly necessary to electrically isolate the piece of equipment being used if it is required to disconnect, and perhaps remove, the equipment from the trunk/spur or splice to which it is connected. This can have a disadvantageous effect in that power supplies and communication links to other, perhaps essential, equipment is unnecessarily interrupted. Attempts have been made to arrive at a connector arrangement for a piece of electrical equipment in which a switch element is incorporated into the connector arrangement but this is seen to disadvantageously complicate the construction, and reduce the reliability and operation of the connector. Also, successful use of such connector arrangements requires specific manual manipulation of the switch arrangement and should this not occur the likelihood of an explosion arising is greatly increased.

The present invention therefore seeks to provide for a connector having advantages over known connectors which are particularly arranged for use in hazardous areas and having one or more advantages over such known connectors.

According to the present invention there is provided a connector comprising releasably engagable first and second portions each having respective first and second engagement formations and respective first and second electrical contacts, the first and second engagement formations being arranged to be brought into engagement during establishment of contact between the first and second electrical contacts and being arranged to be released subsequent to the separation of the said first and second contacts, wherein the said engagement formations serve to define a chamber which is arranged to enclose the contacts between the said first and second contacts when in contact and during the separation 2 thereof.

The connector is particularly advantageous in that the first and second portions of the connector can simply be separated, and thus the electrical contact between the first and second contacts broken whilst located in a hazardous area since, at the sime when the contacts are separated and remain in a literally close proximate, i.e. the time period in which a spark might arise, the contacts and thus the source of the potential spark, are enclosed within the chamber formed by the engagement formation, which flameproof chamber serves to prevent passage of any explosion caused within the chamber f-rom being propagated to an external combustible medium within the hazardous area.

Advantageously, the first and second engagement formations comprise telescoping sleeve members. Preferably, the electrical connector of at least one of the first and second portions is located so as to be recessed relative to the outer end of the sleeve.

Advantageously, co-operating surfaces of the first and second engagement formations are of the first and second engagement surfaces are arranged to define a flamepath for the said chamber.

Preferably, at the time the chamber is opened to the hazardous environment during separation of the connector, the first and second contacts are arranged to be separated by a predetermined distance.

The plug and socket connectors of the present invention are intended particularly for use with fieldbus devices in zone I or 2 hazardous areas. However, the use of the plug and socket connector is not limited to fieldbus systems. It can also be used for other components that require "'live' connect ion/di s connection in hazardous areas, for example power supplies, 4 to 20 mA instrumentation, remote 1/0, etc.

It is an advantage of the present invention to provide a plug and socket where an instrument or other device can be removed from a trunk/spur or splice without having to electrically isolate, i.e. de- energise, the trunk/spur or 3 splice. The plug and socket of the present invention can also advantageously allow for faster assembly and dismantling of the instrument or device to/from the trunk/spur or splice for maintenance purposes, etc.

It is also advantageous that the plug and socket of the present invention can be arranged to connect directly to an instrument or to a junction/equipment box or enclosure. Power is supplied to the socket only. The plug supply is isolated when the plug and socket are parted.

According to another aspect of the present invention as provided a connector comprising a first portion arranged for releasable connection to a second portion for the connection of respective first and second electrical contacts, the connected portions serving to form an enclosure for isolating the contacts from the local environment of the connector, the first portion having a body with electrical leads extending outwardly from an aperture thereof, the said aperture being sealed by means of an encapsulant.

In order that the invention may be more fully understood, one presently preferred embodiment of plug and socket in accordance with the invention will now be described by way of example and with reference to the accompanying drawings. In the drawings:

Fig. 1 is a schematic diagram showing the plug and socket both connected and parted; Figs. 2a, 2b and 2c are an exploded diagrammatic view, a side view and an end view of the plug assembly of the connector of the present invention; Figs. 3a, 3b and 3c are an exploded diagrammatic view, a side view and an end view of the socket assembly of the connector of the present invention; Figs. 4a and 4b show two schematic examples of the mounting/ location of the connector of the present invention, into a transmitter and into junction boxes; 35 Fig. 5 is a general arrangement schematic drawing showing methods of protection and IP rating for a connector in accordance with the present invention; 4 Fig. 6 shows the creepage and clearance distances in the plug and socket of the connector of the present invention; Fig. 7 is a tran ' sverse section through the connector; Fig. 8 is a longitudinal section through the connector 5 taken along the line A-A in Fig. 7; Fig. 9 is a sectional view similar to Fig. 8 but showing the plug/socket shortly before the contacts are broken; Fig. 10 is a sectional view similar to Figs. 8 and 9 but showing the plug/socket broken; Fig. 11 is a sectional view similar to Fig. 8, 9 and 10, showing the plug/socket nearing separation.

Fig. 12 is a transverse section through the socket assembly; and Fig. 13 is a longitudinal section taken along the line D-D of Fig. 12 showing the internal earth details.

Referring first to Fig. 1, this shows the plug and socket schematically. In the upper part of Fig. 1 the plug 10 and the socket 12 are shown connected. In the lower part of Fig. 1 they are shown parted. The plug 10 has a main cable entry 14 and a main cable entry compartment - providing Exd protection 16. Within the connected unit there is a contact compartment also arranged to provide for - Exd protection 18. The socket 12 includes an instrument /enclosure connection again allowing for Exd protection 20. From this instrument /enclosure connection 20 extend flying leads 22.

When the plug 10 and socket 12 are parted, the contacts of the plug are exposed and have no protection. The contacts of the socket are also exposed but are arranged to provide for Exe protection.

Referring now to Fig. 2a, this shows an exploded view of the plug assembly of the connector which can be seen in side and end view from Fig. 2b and 2c. The plug assembly comprises a plug body 24 of copper alloy or stainless steel. From this there extends an external flame path 26, for example more than 12.5 mm long. There is a mating internal flame path on the socket face and is described later with reference to Fig. 3a. The plug assembly also comprises a plug collar 28, also of copper alloy or stainless steel. A snap ring 30 retains the glug collar 28 on the plug body 24. A neoprene or silicone seal 32 is provided between the plug body and plug collar. This seal 32 is arranged to mate with the socket. A plug cover 34 may be provided optionally, to be a screw f it into the open end of the plug collar 28. A screw 36 secures a chain to the cap of the plug cover 34. At the other end of the plug assembly there is provided an injection moulded insulator 38. The plug gland adaptor 42 is of copper alloy or stainless steel. The plug gland adaptor 42 has a f lame path 44. A number of gold-plated copper alloy crimp terminal pins 46 extend from the insulator 38. The broken line 48 indicates the boundary between Exd protection and Exe protection. The plug assembly has Exd protection when mated with the socket. A stainless steel set screw 50 is fitted through a hole in the plug collar 28 to secure the plug to the srocket.

Referring now to Fig. 3a, this shows an exploded view of the socket assembly of the connector which can be seen in side and end view f rom. Figs. 3b and 3a. The socket assembly comprises a socket body 52 of copper alloy or stainless steel. The socket body 52 has an internal flame path 54 which mates with the flame path 26 on the plug face. At the one end of the socket body 52 there extends a flame path 56. From that end of the socket assembly extend four wires 58 which are held in place by a potting encapsulant 60. Into the other end of the socket body 52 is fitted an injection moulded insulator 62 which is keyed and clipped to the socket body, offering protection for crimp sockets and a key location for the plug.

Also provided are three gold-plated copper alloy crimp terminal sockets 64. Within the socket body 52 is fitted an i'nternal earth bracket 66 which is held in place by drive rivet 68. Also provided is a socket cap 72, of copper alloy or stainless steel, which is secured to the socket body 52 by way of copper alloy or stainless steel set screws 76. The broken line 78 indicates the division between Exd protection and Exe protection. The socket assembly has Exd protection 6 when mated with the plug.

When the plug and socket are connected, i.e. are fully assembled, the protection method for the electrical contacts will be by way of flameproof Exd arrangement. When the plug and socket have been disconnected (after the contacts have broken within the explosion/f lame proof protection), the protection for the exposed socket contacts will be by way of an Exe arrangement. The plug and socket when separated and where the socket is connected to an Explosion/flame proof enclosure should maintain the Flameproof protection for that enclosure. This will also apply to increased safety enclosures where the "ingress protection' (IP rating) must be maintained. The main cable entry compartment protection will be Flameproof when connected, and unprotected when parted, as shown in Fig. 1. The plug and socket can only be parted by the use of a special tool.

Fig. 4 illustrates the mounting/location of the connector in various ways. Fig. 4a shows its mounting directly into an explosion/flame proof device (transmitter) Fig. 4b shows its mounting into an Exd junction box, and Fig. 4c shows its mounting directly into an Exe or type n junction box with an earthing strip. In Fig. 4a the plug and socket are shown connected and parted in the two views. The incoming cable 80 to the plug is via a cable gland 82. In Fig. 4b the socket has an internal earth 84 and an earthing post 86. In Fig. 4c the junction box is indicated at 88 and there is provided an earthing strip 90.

In the plug and socket of the present invention the plug/socket and cable entry compartment should be designed to have a free volume of less than 100 cubic centimetres. This allows for shorter flame paths where explosion/flame proof protection is employed. For the plug and socket compartment, the volume calculation must be considered to be where the conducting pins have just separated. For Exd enclosures (that the plug and socket could be attached to) an internal volume of greater than 2000 cubic centimetres is frequently encountered.

7 Gaskets and seals can be used to increase ingress protection (IP rating.) but they must not interrupt the flame path at any point. This is applicable to cylindrical joints and to threaded connections. The flame path length must be 5 maintained.

Fig. 5 is a general arrangement schematic diagram, showing the plug and socket connected and disconnected in the respective views. The flame paths are indicated, and also the limits of Exd and Exe protection in both the connected and disconnected states. This illustrates that as the plug and s. ocket are drawn apart, the connector pins disconnect from each other while still within a flame proof chamber. This means that any spark or explosion caused upon disconnection of the connector pins will be contained within the flame proof chamber.

One of the considerations which must be taken into account in relation to the electrical specification of the connector is the creepage/ clearance distances. This is illustrated in Fig. 6. Here the plug and socket are positioned side by side. The dimensions A are the distance from the electrical contact to free space (protection from contact to a conductive or earthed surface) The dimensions B are the distance between electrical contacts. The dimensions C are the distance between the electrical contacts and the outer casing.

Figs. 7 to 11 illustrate the features of the plug and socket arrangement interrelate as they are moved apart.

Figs. 8-11 represent longitudinal sectional views of the connector shown in end view in Fig. 7: the sections being taken with the longitudinal sections being taken along the lines arrows a- a in Fig. 7.

The connector arrangement illustrated in Figs. 8-11 employs the plug and sockets described and illustrated previously with references to Figs. 2 and 3 and so similar reference numerals have been employed.

Turning f irst to Fig. 8 the plug and socket are shown in complete mating contact in which a plug collar 28 is fully 8 tightened over the external surface of the sleeve defining the internal flame path 54 such that the electrical contacts 64, 65 of the socket and plug respectively are in full contact.

Illustrated in Fig. 9 is a view of the connector 5 arrangement once a disconnection procedure has commenced. Such a procedure commences with the rotation of the plug collar 28 which, in view of its co-operation with threaded outer surface of the sleeve defining the internal flame path 54 of the socket, serves to move the plug and socket in relative directions away from each other. The distance for movement that has occurred as illustrated in Fig. 9 is shown by up arrows X which illustrates the degree to which the plug and socket have started to separate. With continued turning of the plug collar 54 the relative positions illustrated in Fig. 10 are encountered at which the relative distance for movement is again illustrated by arrows X and here it is shown that the electrical connectors 64, 65 are now separated so as to break the electrical connection between the two parts, i.e. the plug and socket, of the connector. A particularly important aspect of the present invention is illustrated most clearly in Fig. 10 since it will be appreciated that, while the electrical connector 64, 65 are now disconnected, they are nevertheless still maintained within an enclosed chamber formed due to the over lapping of the plug collar 54 and the and the annular sleeves defining the flame paths 26, 54. Thus, any spark that might occur subsequent to separation of the electrical contacts 64, 65 will be contained within the chamber defined by the aforementioned sleeves and so will not escape into the hazardous area in which the connector is located. Advantageously, the manner of engagement between at least two of the services defining the said chamber comprises an Ex d f lame path. In accordance with the illustrated embodiment, the outer surf ace of the sleeve 62 and inner surface of the sleeve 26 of the plug and the outer surface of the sleeve 62 of the socket are arranged to mate so as to define an Ex d flame path.

Fig. 11 shows the plug and socket arrangement in 9 accordance with the illustrated embodiment of the present invention upon further separation of the plug end socket: which separation is again illustrated by arrows X.

As will be appreciated from the degree of overlap of the flame paths 26, 54 the relative positions of the plug and socket are approaching a situation of complete separation which, in the illustrated example, coincides with the opening of the aforementioned chamber to external conditions within the hazardous area. In an accordance with an important further feature of the present invention, the relative separation between the vertical contact 64, 65 of the connector and as illustrated by arrows Y are such as to offer Ex e protection since the separation illustrated by arrows Y is a predetermined amount providing for such protection at the time that the aforementioned chamber becomes open.

As mentioned, to clarify the construction of this e mbodiment further, a transverse view of the socket assembly 17 illustrated in Fig. 12, whereas Fig. 13 illustrates a longitudinal section.

Also illustrated with reference to Fig. 8 is an encapsulant insert 60 which serves to seal the feed-through cabling extending out of the back of the socket which is part of the safety of the connector arrangement and, for example, its use in an Exd/e enclosure. This has a particular advantage of allowing for the use of lower-cost feed-through cabling than might otherwise be required.

All will be appreciated in essence, the invention lies in a plug and socket connector which is designed so that the plug and socket can be separated while the connector is"live" in a hazardous area, for power and fieldbus circuits.

Key to illustrations in drawings Ficr. 1 14 - Main cable entry 16 - Main cable entry compartment - Exd 18 - Contact compartment - Exd Instrument/enclosure connection Exd 22 - Flying leads A - Instrument /enclosure connection Exd B - Contacts exposed - EXd C - Contacts exposed - no protection Ficr 4 A Power/Signal input 84 socket internal earth 86 Earthing post Ficr. 4B Earthing strip Ficr 5 A - Exd cable gland B - Flame paths C - Limits of Exe protection D - Limits of Exd protection 25 E Limits of Exd protection F - Explosion at the contacts Ficr. 13 A Connection wire (soldered) 30 B - Internal earthing bracket D - Drive rivet

Claims (11)

1. A connector comprising releasably engagable f irst and second portions each having respective first and second engagement formations and respective first and second electrical contacts, the first and second engagement formations being arranged to be brought into engagement during establishment of a contact between the f irst and second electrical contacts and to be released subsequent to the separation of the said f irst and second contacts, wherein the said engagement formations serve to define a chamber which is arranged to enclose the contacts when in contact and during the said separation thereof.

2. An electrical connector as claimed in claim 1, wherein the first and second engagement formations comprise telescoping sleeve members.

3. A connectors as claimed in claim 2 wherein the electrical connector of at least one of the said f irst and second portions is located so as to be recessed relative to the outer end of the sleeve.

4. A connector as claimed in any one of claims 1-3, wherein cooperating surfaces of the said first and second engagement formations are arranged to define a flamepath for the said chamber.

5.. A connector as claimed in claim 4 when the f lame path 25 comprises an Ex d f lame path.

6. A connector as claimed in any one of claims 1-5 wherein the dimensions and respective locations of the first and second contacts relative to the first and second engagement formations are such that, at the time of opening of the said chamber during separation of the connector, the first and second contacts are s eparated by a predetermined distance.

7. A connector as claimed in claim 6, wherein the said predetermined distance is arranged to provide for Ex e protection.

8. A connection as claimed in any one of claims 1-7, wherein the first and second portions comprise a plug and socket member respectively.

13.

9. A connector as claimed in any one of claims 1-8, wherein the said first and second portions are arranged to be completely separable.

10. A connectors as claimed in any one of claims 1-9, wherein 5 at least one of the first and second portions is arranged to have electrical through-leads which are sealed at a point of exit f rom the said f irst or second portion by means of an encapsulant.

11. An electrical connector substantially as hereinbefore 10 described, with reference to, and as illustrated in Figs. 1, 4, 5, 6 and Figs 2, 3, 7-13 of the present application.