GB2327125A

GB2327125A - Gas sensor with electrical connection socket

Info

Publication number: GB2327125A
Application number: GB9714380A
Authority: GB
Inventors: Peter John Sewell
Original assignee: City Technology Ltd
Current assignee: City Technology Ltd
Priority date: 1997-07-08
Filing date: 1997-07-08
Publication date: 1999-01-13
Also published as: GB9714380D0

Abstract

A gas sensor assembly comprises a housing (1) in which is mounted a gas sensor for generating an electrical signal on a set of connecting pins (7) extending from one end of the housing. A cap (10) is positioned over the one end of the housing, the cap having an aperture (12) aligned with the connecting pins and through which an electrical socket can be inserted so as to mate with the connecting pins (7). The cap (10) includes a locking device (6) for retaining the electrical socket in the aperture.

Description

GAS SENSOR ASSEMBLY The invention relates to a gas sensor assembly of the kind comprising a housing in which is mounted a gas sensor for generating an electrical signal on a set of connecting pins extending from one end of the housing; and a cap positioned over the one end of the housing, the cap having an aperture aligned with the connecting pins and through which an electrical socket can be inserted so as to mate with the connecting pins. Such assemblies are hereinafter referred to as of the kind described.

Sensors of the kind described are marketed by City Technology Limited under the trade names CiTiceL, MediceL, AO2 and MOX. This assembly incorporates an electrochemical gas sensor although the invention is applicable to a wide variety of different types of gas sensor. A problem which has been encountered with these known gas sensor assemblies is that they have relatively complex construction and need to make use of a special "molex" type connector to provide the connector pins. This connector provides a friction lock for the electrical socket and has to be carefully mounted on a printed circuit board.

In accordance with the present invention, a gas sensor assembly of the kind described is characterised in that the cap includes a locking device for retaining the electrical socket in the aperture.

We have developed a modified gas sensor assembly in which the locking device is provided by the cap instead of being provided separately on the printed circuit board.

This results in a significant cost saving since the molex type connector is no longer required. Furthermore, preferably the locking device is integrally formed with the rest of the cap, for example the cap could comprise a onepiece moulding of plastics or other suitable material. The cost of fabricating the cap in both the old and new designs is substantially the same and so a significant cost saving results.

A further problem which can occur with the known device is the ingress of dirt, dust and moisture through the aperture which can result in damage to the printed circuit board and other electrical components. Preferably, therefore, the cap further comprises a wall extending across the aperture and having holes through which the connecting pins extend. Such a wall can be easily fabricated if the cap is made as a one piece moulding with the result that the ingress of dust, dirt and moisture is substantially prevented while at the same time the appearance of the product is enhanced since the printed circuit board can no longer be seen through the aperture.

In some cases, the cap may be integrally formed with the housing or welded or otherwise secured, for example glued or snap fitted, to the housing during manufacture.

Preferably, however, the cap is detachably mounted to the housing so as to allow access to the printed circuit board in case of faults and also to ease manufacture.

An example of a gas sensor assembly according to the invention will now be described and contrasted with a known gas sensor assembly with reference to the accompanying drawings, in which: Figure 1 is a side elevation, partly in section, of a known gas sensor assembly; and, Figure 2 is a view similar to Figure 1 but of an example of a gas sensor assembly according to the invention.

The sensors to be described are oxygen sensors and make use of an electrochemical gas sensor well known in the art. The invention is equally applicable to toxic gas sensors. The known sensor which is shown in Figure 1 comprises a housing 1 within which the sensor components are mounted, the housing having an externally screwthreaded spigot 2 to enable the sensor to be connected to a conduit carrying a gas to be monitored. The other end of the housing 1 opposite the spigot 2 supports a printed circuit board 3 which carries an electrical circuit of a conventional form and includes three contacts (not shown) on a surface 4 facing away from the housing 1. A typical form of circuit on the pcb 3 is described in our British Patent Application No. 9708604.5. A Molex type 6410 series friction lock connector 5 is secured to the printed circuit board 3. The connector 5 is formed as a plastics moulding having a friction lock tab 6 projecting away from the printed circuit board 3 and supporting a set of three connecting pins 7 (only one visible in Figure 1). The pins 7 are arranged in a line one behind the other as seen in Figure 1. Each pin 7 is electrically connected to a respective contact on the printed circuit board 3.

A plastics cap 8 is mounted to the housing 1 as a force fit or screw fit, the cap 8 having a central aperture 9 into which the pins 7 and friction lock tab 6 extend.

In use, an electrical socket (not shown) having three apertures aligned with the pins 7 is inserted through the aperture 9 so that the pins 7 are received in the apertures of the socket, the socket being pushed onto the pins 7 causing the friction lock tab 6 to be urged to the right as seen in Figure 1 against its resilience so as to lock the socket in place.

As explained above, this known construction is relatively complex and expensive to fabricate and there is also the risk of the ingress of dust, dirt and moisture through the aperture 9.

Figure 2 illustrates an example of an assembly according to the invention and those components which are the same as those shown in Figure 1 have been given the same reference numerals and will not be further described.

In this case, a cap 10 is provided in the form of a onepiece plastics moulding, the cap 10 having a central tubular section 11 which is square in plan. The tubular section 11 opens outwardly at 12 to enable an electrical socket to be inserted while the other end of the section 12 is closed by a wall 14 having a set of three holes 13 for receiving respective ones of the pins 7. The wall 14 closely engages the bases of the pins 7 as can be seen in Figure 2 and rests on the surface 4 of the printed circuit board when the cap 10 is mounted to the housing 1. A friction lock tab 6 integrally formed with the wall 14 extends alongside the pins 7 so that when a socket is inserted into the tubular section 11 and receives the pins 7, the tab 6 is urged to the right against its resilience so as to hold the socket in position.

As will be appreciated, the wall 14 substantially prevents the ingress of dust, dirt and moisture through the cap while at the same time supporting the pins 7, the tab 6 being integrally formed with the cap so as to simplify its overall structure. The wall 14 also hides the pcb from view.

The gas sensor can have any conventional construction including a two or three electrode electrochemical gas sensor.

Claims

1. A gas sensor assembly comprising a housing in which is mounted a gas sensor for generating an electrical signal on a set of connecting pins extending from one end of the housing; and a cap positioned over the one end of the housing, the cap having an aperture aligned with the connecting pins and through which an electrical socket can be inserted so as to mate with the connecting pins characterised in that the cap includes a locking device for retaining the electrical socket in the aperture.

2. An assembly according to claim 1, wherein the locking device comprises a resilient tab which is urged under its resilience into engagement with the socket.

3. An assembly according to claim 1 or claim 2, wherein the connecting pins extend into the aperture of the cap.

4. An assembly according to any of the preceding claims, wherein the cap further comprises a wall extending across the aperture and having holes through which the connecting pins extend.

5. An assembly according to any of the preceding claims, wherein the locking device is integrally formed with the rest of the cap.

6. An assembly according to any of the preceding claims, wherein the cap comprises a one-piece moulding of, for example, plastics.

7. An assembly according to any of the preceding claims, wherein the cap is detachable from the housing.

8. A gas sensor assembly according to any of the preceding claims, wherein the gas sensor comprises an electrochemical gas sensor.

9. A gas sensor assembly substantially as hereinbefore described with reference to the example shown in Figure 2 of the accompanying drawings.