Improvements in or relating to meter switches

Abstract: A switch assembly for an electricity meter comprising two parts, one of which parts (2) includes a fixed contact (12) and a meter output terminal (13) and the other of which parts (1) includes a moving contact (8) and a meter input terminal (3), the moving contact being coupled to the input terminal via a conductive spring (7) on which it is supported and which serves in use both to carry switch current and to bias the moving contact towards the fixed contact, and via a meter shunt (5) adapted so as to receive in use, sensor conductors so that current supplied via the switch from the input terminal to a consumer via the output terminal can be sensed for measurement purposes.

Description: This invention relates to electricity meter switches and to electricity meters which embody them. More especially, but not exclusively, it relates to switches for modular electricity meters of a kind described in our co-pending British patent application numbers 9509304.3 (F21093), 9501772.9 (F21069), and 9424461.3 (F21667), which include a mains isolating switch. Modular meters of the kind described as aforesaid, comprise a basic meter module which includes a mains electricity isolating switch effective to isolate a consumer circuit from a supply circuit. The switch may be manually operated and/or it may be operated by an actuator in an 'add-on' module, fitted to the basic module to extends its functionality. Thus, as explained in our co-pending patent applications, the basic module may include for example a manually operated switch and be converted to a pre-payment meter by the addition of an 'add-on' module, which is arranged to receive electricity credit tokens and which includes a switch actuator operable automatically when credit is exhausted to cause the switch to disconnect a consumer from an electricity supply. It is apparent that a switch for modular and other electricity meters should be robustly constructed and yet be simple and comparatively inexpensive to fabricate. One object of this invention therefore is to satisfy these requirements. GB-A-2,070,862 (Bosch) provides an electrical switch forming part of a relay. The switch includes moving contacts and fixed contacts which are mounted on an angled contact bracket. This contact bracket includes two laterally projecting connection arms defining a region therebetween which comprises a measuring resistor. According to the present invention there is provided a switch assembly for an electricity meter, the switch assembly comprising; a first part including a fixed contact and a first meter terminal; a second part including a moving contact and a second meter terminal; a conductive spring which supports the moving contact and which, in use, carries switch current; and a meter shunt connecting the conductive spring to the second meter terminal, the shunt being adapted so as to receive, in use, sensor conductors so that current supplied from the first meter terminal to a consumer via the second meter terminal can be sensed for measurement purposes and whereby the conductive spring comprises a narrowed portion between the moving contact and the meter shunt to facilitate spring flexure. Other embodiments of the invention are defined in the dependent claims. One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which, FIGURE 1 is a generally schematic perspective view of parts for a single pole electricity meter switch; FIGURE 2 is a perspective view of the parts shown in Figure 1 from a different angle; FIGURE 3 is a perspective view of the parts shown in Figures 1 and 2, assembled in a meter housing and shaded for ease of identification, and FIGURE 4 is a perspective view of the parts shown in Figures 1, 2 and 3, assembled in a meter housing which includes a switch actuator. Referring now to the drawings, wherein corresponding parts of the various Figures bear, as appropriate, the same numerical designation, a contact assembly for a single pole meter switch comprises two parts 1 and 2. The part 1 includes a flat copper metal strip input terminal 3, which is bent orthogonally and which is electrically and mechanically connected by a means of brazing points 4 to a flat copper alloy shunt 5. The shunt 5 is connected by brazing points 6 to a copper alloy leaf spring 7 which supports a moving switch contact 8. To facilitate brazing of the points 4 and 6, the parts may first be 'part pierced', so that they mutually locate. Although in this example, brazing points are used, to effect electrical connection, it will be appreciated that in alternative embodiments the parts may be welded, hard soldered or screwed together so as to provide the necessary electrical connection, and mechanical strength. The shunt 5 includes grooves 9 to which conductors are connected which couple the shunt to a measurement circuit (not shown). Grooves 10 are also provided in which conductors are soldered which serve to provide power for other parts of the electricity meter. In order to facilitate flexure of the leaf spring 7, a narrowed neck 11 is formed between the shunt 5 and the moving contact 8. The moving contact 8 is arranged to co-operate with a fixed contact 12, which is supported on a copper strip output terminal 13 which is bent orthogonally so that the fixed and moving contacts 12 and 8 respectively align. Strip material from which the output terminal 13 formed is provided at an end thereof remote from the terminal 13, with a spring connector 14, as shown in Figure 2, which, as will hereinafter be explained, serves to provide electrical connection via a complimentary plug part (not shown) of an 'add-on' module (not shown). As can be best be seen in Figure 3, the terminals 3 and 13 are arranged to lie flat in a housing body 15 so that they are mutually parallel and lie in substantially the same plane. In use of a meter of which the housing forms a part, input and output conductors are introduced through apertures 16 and 17 respectively in the housing 15 and clamped into position by means of screws 18 against the input and output terminals 3 and 13 respectively. Apertures 19 and 19a in the housing are provided for input and output neutral conductors respectively, which are secured by means of clamping screws 20. Connection of the neutral conductors is not central to the present invention, since the meter incorporates single pole switching only. As shown in Figure 4, a mechanical switch actuator 21 is provided which is arranged to effect switch operation so as to open or close the contacts 8 and 12 against the biasing force provided by the leaf spring 7. Additionally the switch may be operated by an actuator (not shown), which is contained in an 'add-on' module (not shown) fitted to the basic meter module to extend functionality, as described in our co-pending patent applications. The actuator (not shown) is arranged to operate in the direction of an arrow 22 so as to make contact with a switch operating member 23 which operates through a lever 24 to effect switch operation in a manner similar to operation as effected by the switch actuator 21. Although the 'add-on' module and parts associated therewith are not described in detail, they are described in our co-pending patent applications to which attention is directed.

Claims: A switch assembly for an electricity meter, the switch assembly comprising:- a first part (2) including a fixed contact (12) and a first meter terminal (13); a second part (1) including a moving contact (8) and a second meter terminal (3); a conductive spring (7) which supports the moving contact and which, in use, carries switch current; and a meter shunt (5) connecting the conductive spring to the second meter terminal, the shunt being adapted so as to receive, in use, sensor conductors so that current supplied from the first meter terminal to a consumer via the second meter terminal can be sensed for measurement purposes; and whereby the conductive spring comprises a narrowed portion between the moving contact and the meter shunt to facilitate spring flexure. A switch assembly according to claim 1, wherein the first and second meter terminals comprise output and input terminals respectively. A switch assembly according to claim 1 or 2, which forms a part of a single pole switch. A switch assembly according to any one of the preceding claims, wherein the conductive spring comprises a strip metal leaf spring. A switch assembly according to claim 4, wherein the strip metal leaf spring comprises a copper alloy. A switch assembly according to any one of the preceding claims, wherein the meter shunt comprises strip metal to which the second meter terminal and the conductive spring are electrically connected, the second meter terminal and the conductive spring being spaced apart by the meter shunt. A switch assembly according to claim 6, wherein the meter shunt comprises copper alloy strip material. A switch assembly according to claim 6 or 7, wherein the meter shunt includes grooves (9) to which conductors are connected for coupling the meter shunt to a measurement circuit. A switch assembly according to any one of the preceding claims, wherein the second part further includes grooves (10) to which conductors serving to provide power for other parts of an electricity meter are soldered. A switch assembly according to any one of the preceding claims, wherein the second meter terminal comprises strip metal. A switch assembly according to claim 10, wherein the strip metal comprises flat copper strip material. A switch assembly according to any one of claims 9 to 10, wherein the moving and fixed contacts comprise a silver alloy material. A switch assembly according to any one of claims 9 to 11, wherein the first meter terminal comprises strip metal. A switch assembly according to claim 13, wherein the strip metal comprises flat copper strip material. A switch assembly according to claim 13 or 14, wherein one end of the first terminal is arranged to serve as an output terminal connector and the other end of the first terminal is adapted to define an electrical socket connector for receiving a complimentary plug of a meter 'add-on' module, the fixed contact being supported by the metal strip at a position intermediate between its ends. A switch assembly according to claim 15, wherein the electrical socket connector comprises a spring connector (14). An electricity meter including a switch assembly according to any one of the claims 12 to 16, wherein the first and second meter terminals are supported in spaced apart relationship within a meter housing so that strip metal of respective terminals lies substantially co-planar, both terminals being bent orthogonally with respect to this plane so that the moving contact aligns with the fixed contact to facilitate switch operation and aligns with a switch actuator (21) which in use is used to effect switch operation against the biasing force of the conductive spring.

Inventors: ROTHWELL NEIL, ROTHWELL, NEIL
Applicants: SIEMENS METERING LTD, SIEMENS METERING LIMITED
Application year: 1996
Main classification: G01R11
IPC codes: H01H1, H01H9