CORROSION PROTECTION OF OPPOSITELY POLARISED ELECTRICAL CONDUCTORS

Abstract: Corrosion protection of oppositely polarised electrical conductors is provided by means of a physical barrier between oppositely polarised conductors in data connectors and telephone line jacks. The physical barrier is preferably provided by the board of a double-sided printed circuit board. Other preferred embodiments include running conductors within channels and using a barrier of silicone based gel. The invention also provides a barrier to isolate a line jack unit from the contaminating environments that are known to be associated with line jack units located within back boxes that are sunk into the wall of a building.

Description: CORROSION PROTECTION OF OPPOSITELY POLARISED ELECTRICAL CONDUCTORS. The present invention relates to methods for the elimination or * minimisation of electrolytic and other corrosion. The invention has particular 5 application to connectors and their associated apparatus, and more particularly to data connectors and telephone line jacks. The problem of corrosion in connector systems, causing costs associated with down-time, engineer's expenses and customer dissatisfaction is well known. Corrosion in connector systems is often 0 caused by moisture and/or contaminants, particularly ionic contaminants, which are present in the environment of the connector. This problem is exacerbated in modern systems which often have a very small separation between oppositely polarised metal parts such as jack contacts, printed circuit board conductors and component leads. 5 The problem of corrosion is particularly associated with line jack units installed within a back box which, for aesthetic reasons, is sunk into the wall of a room. In new buildings back boxes may be installed into freshly built and plastered walls. Line jack units are then wired and fitted to the back boxes with minimum delay, and often before the building materials have fully 0 dried. As a result, contaminants known to be present in the building r materials have an increased likelihood of mobility, and thus, an increased likelihood of causing corrosion in the line jack unit. Very high corrosion failure rates of line jack units installed in this way often result. A number of solutions to corrosion problems have been adopted, 5 including most notably for printed circuit based systems, the application of a conformal coating to the printed circuit board. This is a relatively costly process requiring careful control to avoid coating areas such as jack contacts which would otherwise suffer contact reliability problems. It is also not always totally effective in eliminating corrosion, and is not usually suitable for use with connector systems which are not based on printed circuit boards. The present invention arises from the appreciation that arrangements of oppositely polarised conductors such as those found in connector systems may be required to operate in environments in which they may be brought into contact with ionic contaminants which are known to promote corrosion. This is known to be the dominant cause of failure in printed circuit board based telephone line jack units. The present invention has the object of providing methods of reducing or eliminating corrosion in connector systems particularly connector systems which are of particular applicability in data and telephone jack products. According to the invention there is provided a connector system comprising at least one pair of conductors and corrosion inhibiting means physically separating the conductors. The corrosion inhibiting means may take any suitable form and preferably is provided by a physical barrier between two conductors. The conductors include signal lines of the type on a printed circuit board for example. According to a second aspect of the invention there is provided a method of eliminating or reducing electrolytic corrosion of conductors in a connector system to which oppositely polarised signals are to be connected whereby a physical barrier is provided between the conductors. In particular, the physical barrier is provided between conductors which in use will be oppositely polarised. k A printed circuit board preferably provides a physical barrier between 5 the signal lines by having a line of each such pair on either side of the board so that the printed circuit board is double-sided. Alternatively, the physical separation may be achieved by means of having the signal lines run within channels formed for example in a plastic moulding. A lid for such a moulding may be provided so that each line runs 0 in a sealed cavity. As an alternative, the lines may be moulded into a suitable material such as plastic. In a further embodiment of the invention the physical barrier comprises a substance such as silicone based gel which covers the conductors. Preferably such substance completely covers the conductors 5 in the connector when no plug is inserted i.e. when not in use, and is moved away from the contacts or a portion of the conductors when a plug is inserted and returns to cover the conductors completely when the plug is removed. In a connector system comprising a line jack unit and a metal back 0 box sunk into a wall the back box and the line jack unit constitute said « conductors. Preferably the corrosion inhibiting means is provided by a barrier between the back box and line jack unit. According to a third aspect of the invention therefore there is provided line jack apparatus comprising a line jack unit having conductors, a metal 5 back box and a physical barrier, whereby said barrier is provided between the line jack unit and the metal back box, said barrier forming an enclosure around the conductors of the line jack unit and said barrier being impervious to ionic contaminants. According to a further aspect of the invention there is provided a method of inhibiting corrosion of a line jack unit located within a metal back box comprising the provision of a physical barrier impervious to ionic contaminants between the line jack unit and the back box, said barrier forming an enclosure around conductors of the line jack unit. With this arrangement the physical barrier protects the conductors of the line jack unit from moisture and contaminants in the surrounding environment. In a preferred embodiment the barrier clips to the rear of the line jack unit to form a seal effective against the ingress of moisture and contaminants. The physical barrier is provided with a hole for entry of a cable for connection to the line jack unit. The hole may be grommeted for example. Preferably a seal is provided between the cable and the walls of the hole to seal the conductors of the line jack unit from the surrounding environment. Preferably said barrier is of a plastics material. The materials PVC, ABS or polystyrene are particularly preferred. A preferred embodiment of the invention comprises a telecommunications connector having a first pair of signal lines which may be oppositely polarised, perhaps at 0 and -50 Volts DC if connected to a public switched telephone network. A means is provided for the physical separation of these oppositely polarised lines in order to avoid electrolytic corrosion. Specific embodiments of the invention will now be described in detail and by way of example only with reference to the accompanying drawings in which:- * Figure 1 is a schematic plan view of a printed circuit based line jack 5 unit of the invention; Figure 2 is a schematic plan view of a lead frame based line jack unit of the invention; Figure 2a is an expanded view of the section marked A of Figure 2; and Figure 3 is a side view of a further embodiment of connector according to the invention. Figure 4 is an expanded side view of a line jack unit and back box showing how the physical barrier of the invention is fitted between the line jack unit and the back box. 5 Figure 5 is a view showing the front of the physical barrier shown in Figure 4. Figure 1 shows an example of a printed circuit based line jack unit, utilising a double sided printed circuit board, and incorporating a pair of insulation displacement connection (IDC) strips. The full line represents a 0 conductor line on the upper side of the printed circuit board and the dashed « line represents a conductor on the under side. Suppose that terminal 2 is connected to 0 Volts, and terminal 5 is connected to -50 Volts. Other printed circuit board conductors are omitted for clarity. Electrolytic corrosion as a result of contamination by ionic compounds is minimised by the 5 physical barrier of the printed circuit board. Figure 2 shows an example of a lead frame based line jack unit in which the conductors C run within channels G in the plastic moulding. A lid for the moulding may be provided and may be provided with parts which may be connected together to provide sealed cavities for each conductor. These cavities will provide protection from contaminants known to promote corrosion. By extension, and with similar corrosion inhibiting effect, such conductors could be moulded into an assembly such that each conductor is surrounded by plastic. Figure 3 shows an example of a jack in which conductors C are held at opposite electrical polarities. In this example, a physical barrier B is provided by the inclusion of a substance which covers all of the oppositely polarised conductors when no plug is inserted, is moved away from the contacts when a plug is inserted, and returns to cover the conductors completely once more when the plug is removed. This substance may take the form of a silicone based gel. Figure 4 shows a line jack unit 0 of the type to be installed within a back box 12. A barrier 14 in the form of a partial enclosure is clipped onto the rear of the line jack unit. The barrier is provided by a plastic fitting. Together the line jack unit 10 and the barrier 14 clipped thereto enclose the conductors of the line jack which would otherwise be exposed to moisture and contaminants originating in the surrounding environment of the back box. The combined line jack unit 10 and barrier 14 is secured to the back box which will have been previously sunk unto the wall. It will be appreciated that the present invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.

Claims: CLAIMS 1. A connector system comprising at least one pair of conductors and corrosion inhibiting means physically separating the conductors. 2. The connector system of claim 1 wherein corrosion inhibiting means is provided by at least one barrier between the conductors. 3. The connector system of claim 2 comprising a printed circuit board printed with at least one conductor on both faces of the board, whereby said barrier is provided by said board. 4. The connector system of claims 2 or 3 comprising at least one conductor within a channel, whereby said barrier is defined by part of the wall of the channel. 5. The connector system of claim 4 wherein a lid is provided to cover said channel. 6. The connector system of any preceding claim wherein at least one conductor runs in a sealed cavity. 7. The connector system of any preceding claim wherein at least one conductor is moulded into plastic. 8. The connector system of claims 2 to 7 wherein said barrier comprises a silicone based gel. 9. The connector system of claim 8 wherein the gel is moveable to enable a plug to contact at least one conductor and wherein the gel is movable to cover said one conductor when the plug is disconnected from said at least one conductor. 10. A method of eliminating or reducing electrolytic corrosion of conductors in a connector system to which oppositely polarised signals are to be connected whereby a physical barrier is provided between the conductors. 11. The method of claim 10 wherein the physical barrier is provided between conductors which in use will be oppositely polarised. 12. Line jack apparatus comprising a line jack unit having conductors, a metal back box and a physical barrier, whereby said barrier is provided between the line jack unit and the metal back box, said barrier forming an enclosure around conductors of the line jack unit and said barrier being impervious to ionic contaminants. 13. The line jack apparatus of claim 12 wherein said barrier is of a plastics material. 14. A method of inhibiting corrosion of a line jack unit located within a metal back box comprising the provision of a physical barrier impervious to ionic contaminants between the line jack unit and the back box, said barrier forming an enclosure around conductors of the line jack unit. 15. The method of claim 14 wherein said barrier is of a plastics material.

Inventors: ODLEY RICHARD AUSTIN, ODLEY, RICHARD, AUSTIN
Applicants: AUSTIN TAYLOR COMMUNICAT LTD, ODLEY RICHARD AUSTIN, AUSTIN TAYLOR COMMUNICATIONS LIMITED, ODLEY, RICHARD, AUSTIN
Application year: 1995
Main classification: H01R13
IPC codes: H01R13, H05K1