GB2253879A - Security clip for commodity meters - Google Patents

Abstract

A clip 32 for securely fastening a ZVEI optical head 28 to the ZVEI optical port 24 of an electricity meter, for use where the head forms part of a permanent connection between the meter and a separate prepayment unit, is provided with two resilient legs 36 which fit over and embrace the head. The lower ends of the legs are bent upwardly and outwardly, and spring into and engage in undercuts 29 provided in the wall of the ZVEI port into which the head fits. Once in place, the clip can be removed only by cutting off one of its legs, so that its accidental or inadvertent removal is effectively prevented. <IMAGE>

Description

COMMODITY METERS This invention relates to commodity meters and to commodity metering systems incorporating such meters, and is more particularly but not exclusively concerned with an electricity metering system of the kind described in our United Kingdom Patent Application No. 2 236 003.

The electricity metering system described in our United Kingdom Patent Application No. 2 236 003 comprises an electronic electricity meter having an optical port, known as a ZVEI port, via which the measurements made by the meter can be accessed, and a separate prepayment unit having an optical link which communicates with the meter by way of a ZVEI optical head secured to the ZVEI port.

Although the meter and prepayment unit are both arranged to detect unauthorised disconnection of the optical link and to respond appropriately, it is desirable to ensure that the optical link cannot easily be disconnected accidentally, but can be readily disconnected and reconnected by authorised personnel of the commodity supplier. It is therefore an object of the present invention to provide a commodity meter having an optical link which possesses these desirable characteristics.

According to the present invention, there is provided a commodity meter having an optical port via which optical signals can be directed into and received from the meter by an optical head secured to the port, wherein the port includes a shallow recess for receiving and at least partially locating the input/output face of the optical head, said recess having at least two generally oppositely disposed undercuts in its wall, and wherein the head is held in the recess by a clip which fits over the head and has at least two resilient legs which embrace the head and whose ends are bent upwardly and outwardly to spring into and engage in respective ones of the undercuts when the clip is pressed down over the head, whereby to prevent removal of the clip without the severance of at least one of the legs or other permanent damage to the clip.

Typically, the input/output face of the optical head and the recess are both circular, and the optical head has an electrical lead projecting radially therefrom: in this case, the clip advantageously includes a bifurcated portion which projects over the head from the portion of the clip interconnecting the two legs and towards the recess, so as to fit over and engage the electrical lead, whereby such engagement and the engagement of the bent over ends of the two legs in the undercuts serves to prevent rotation of the optical head in the recess.

Advantageously, the clip is made in a single piece, preferably from a non-magnetic resilient material such as stainless steel, brass or a beryllium copper alloy.

Convenientally, the recess is formed as an aperture in a flat plastics plate, which is bonded to a window in the front of the meter over the optical signal emitter and receiver of the optical port.

The invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is an exploded perspective view of an electricity meter in accordance with the present invention; and Figures 2 and 3 are plan and side views respectively of a clip forming part of the meter of Figure 1.

The meter shown in the drawing is indicated generally at 10, and is of the kind described in our aforementioned United Kingdom Patent Application No.

2 236 003. The meter 10 comprises a case 12 having in its front face a transparent window 14, through which a display 16, typically an LCD, shows the number of units of electricity metered by the meter.

Also visible through the window 14, via a circular aperture 18 in a flat square plastics plate 20 bonded to the window with a mild steel washer 21 coaxially disposed in the aperture, are the optical emitting and receiving elements 22, 23 of a ZVEI optical port generally indicated at 24. The aperture 18 and the window 14 together form a shallow recess 26, which serves to receive and at least partially locate the input/output face of a generally circular-section ZVEI optical head 28. The head 28 includes a permanent magnet (not shown), which holds the head in the recess 26 by virtue of the magnetic attraction between this magnet and the washer 21.

The wall of the recess 26 is provided, in diametrically opposed regions thereof aligned with a diagonal of the plate 20, with two very short radially extending blind grooves 29 whose blind ends are undercut.

The head 28 contains optical receiving and emitting elements (not shown) which are aligned, as will hereinafter become apparent, to cooperate with the emitting and receiving elements 22, 23 in the meter 10, and has an electrical input/output lead 30 for transmitting electrical signals between the emitting and receiving elements in the head and a prepayment unit (not shown) of the kind described in our aforementioned United Kingdom Patent Application No. 2 236 003: the nature of these signals and of the various optical emitting and receiving elements are described in more detail in that application.

In accordance with the present invention, to prevent accidental removal of the head 28 from the recess 26, the head is more securely held in the recess than can be achieved by the aforementioned magnetic attraction by a one piece spring clip 32.

As can be seen in Figures 1 to 3, the clip 32 is made from a non-magnetic spring material such as stainless steel, and comprises a yoke 34 which bears on the back of the head 28, and two legs 36 which extend' over and embrace diametrically opposed side surfaces of the head. The clip 32 also has a bifurcated portion 40 extending downwardly over the head 28 from the yoke 34 to define a slot 42 which fits over and engages the electrical lead 30: the angle between the portion 40 and the nearest leg 36 is about 45".

The ends 38 of the legs 36 are bent outwardly and upwardly, the two bends being substantially flush with the aforementioned input/output face of the head 28 when the clip 32 is fully pressed home on the head 28. The orientation of the bifurcated portion 40 of the clip 32 with respect to the legs 36 is such that when the clip is fitted over the head 28 with the slot 42 in the bifurcated portion 40 engaging the electrical lead 30, and the head is correctly aligned in the recess 26, the bent over ends 38 of the legs are aligned with the blind grooves 29 in the wall of the recess. So pressing the clip 32 downwardly onto the head 28 causes the bent over ends 38 of the legs to enter the grooves 29.The tops of the blind ends of the grooves 29 initially compress the bent over ends 38 of the legs 36 towards the legs, but further downward movement enables the bent over end 38 to spring into and engage the undercut regions of the blind ends of the grooves. At this point, the head 28 is locked in the recess 26, and cannot be withdrawn or rotated without cutting off at least one of the legs 36 or otherwise permanently damaging the clip 32.

Thus the consumer in whose premises the meter 10 is installed is most unlikely to remove the head 28 from the meter accidentally (and if he removes it deliberately, the supply of electricity will be cut off, as explained in our aforementioned patent application). The electricity suppliers personnel, on the other hand, can carry a supply of spare clips, which are relatively inexpensive, and can thus readily cut off one clip if it is desired to remove the head 28 from the meter 10, and refit using a new one.

Several modifications can be made to the described embodiment of the invention. For example, the clip 28 can have more than two legs, and it can be made of springy materials other than stainless steel, for example brass or a beryllium copper alloy. Also, the permanent magnet in the head 28 and the washer 21 can be omitted if desired. Finally, the invention is applicable to commodity meters other than electricity meters, for example gas meters and water meters.

Claims (6)

1. A commodity meter having an optical port via which optical signals can be directed into and received from the meter by an optical head secured to the port, wherein the port includes a shallow recess for receiving and at least partially locating the input/output face of the optical head, said recess having at least two generally oppositely disposed undercuts in its wall, and wherein the head is held in the recess by a clip which fits over the head and has at least two resilient legs which embrace the head and whose ends are bent upwardly and outwardly to spring into and engage in respective ones of the undercuts when the clip is pressed down over the head, whereby to prevent removal of the clip without the severance of at least one of the legs or other permanent damage to the clip.

2. A meter as claimed in claim 1, wherein the input/output face of the optical head and the recess are both circular, and the optical head has an electrical lead projecting radially therefrom, and wherein the clip includes a bifurcated portion which projects over the head from the portion of the clip interconnecting the two legs and towards the recess, so as to fit over and engage the electrical lead, whereby such engagement and the engagement of the bent over ends of the two legs in the undercuts serves to prevent rotation of the optical head in the recess.

3. A meter as claimed in claim 1 or claim 2, wherein the clip is made in a single piece.

4. A meter as claimed in claim 3, wherein the clip is made from a non-magnetic resilient material such as stainless steel, brass or a beryllium copper alloy.

5. A meter as claimed in any preceding claim, wherein the recess is formed as an aperture in a flat plastics plate, which is bonded to a window in the front of the meter over the optical signal emitter and receiver of the optical port.

6. A commodity meter substantially as herein described with reference to the accompanying drawings.