GB2231430A - Security sensor - Google Patents

Abstract

A housing 1 for a security sensor is in the form of a shallow rectangular box. The rear surface 3, which is held by the mounting of the housing against a base member such as a door or window whose vibrations are to be detected, is formed with channels 5 for condensation to flow through. They are preferably skew to the sides of the box and have flared, curved ends, leaving land areas 2 which may be wholly or partly within the plan area of the housing. <IMAGE>

Description

"Improvements relating to Security Sensors" This invention relates to security sensors.

It was developed for those which are attached to doors or windows to signal vibrations generated by an attempt to break in, but it is probably equally applicable to other types of sensor, such as passive infra-red.

The sensors of our VIPER-(RTM) System and others like it are housed in small shallow rectangular units which are screwed to the window frame.

It is not practical to make them waterproof, and although recommendations can be made for them to be placed at a high level, they are often fixed low down where condensation on the inside of the window can gather. Water can then penetrate the housing and make the sensor malfunction, or even permanently damage it.

It is the aim of this invention to try to eliminate this problem.

According to the present invention there is provided a housing for a security sensor adapted to be fixed with its rear surface against a base member, that rear surface having channels therein to form, in conjunction with said member, passages for water to pass from one side or end of the housing to the other.

For a vibration sensor, the base member will most likely be a door or window whose vibrations are to be detected.

As mentioned above, the housing is conventionally of rectangular form, and normally it would be set with its longitudinal axis horizontal or vertical. Preferably, therefore, the passages will be aslant to this longitudinal axis so that, whichever of the two normal ways the housing is fixed, there will be a downward incline of the passages.

In order to promote easy flow, the ends of the channels may be divergent and the land areas left by them may have curved contours, particularly at those ends. Also, they will preferably be mostly within the outer periphery of the rear surface.

For a better understanding of the invention, one embodiment will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a rear plan view of a sensor housing, and Figure 2 is a section on the line II-II of Figure 1.

A sensor housing 1 is of rectangular form and its rear face has land areas 2 proud of a surface 3 by lmm or more. The surfaces of the land areas are flat to abut firmly against a substantial area of window frame, for example, and the housing is secured by means of screws through holes 4.

Adjacent land areas form channels or grooves 5 which, in this example, are at 600 to the longitudinal axis of the housing and extend from one side to the other. The corners, at least, of the land areas 2 are rounded so that the ends of the channels diverge.

Also the land areas are set back in from the longitudinal edges, except for one short length at one end, to form a peripheral overhang.

When in position, whether the longitudinal axis is horizontal or vertical, water may initially gather partly under the overhang as illustrated at 6 in Figure 2, but it will not accumulate to any significant degree. As soon as the bead is of a certain size, its own weight will overcome any surface tension and force it to drain through the passages formed by the channels 5 in conjunction with the window frame or other base. Escaping droplets are indicated at 7.

Claims (6)

-CLAIMS

1. A housing for a vibration sensor adapted to be fixed with its rear surface against a base member, that rear surface having channels therein to form, in conjunction with said member, passages for water to pass from side or end of the housing to the other.

2. A horsing as claimed in Claim 1, wherein the rear surface is generally rectangular and the passages are aslant to the sides thereof.

3. A housing as claimed in Claims 1 or 2, wherein the ends of the channels are divergent.

4. A housing as claimed in Claims 1, 2, or 3, wherein the land areas left by the channels have curved contours.

5. A housing as claimed in any preceeding Claim, wherein the land areas left by the channels are all substantially within the outer periphery of the rear surface.

6. A housing for a vibration sensor substantially as hereinbefore described with reference to the accompanying drawing.