The present invention relates to a meter unit and to a method of releasing a terminal cover portion of a meter unit.

Currently in domestic and commercial premises electricity, gas, water and air quality/usage, for example, are monitored using separate stand-alone meters. Particularly in commercial premises the electricity usage of several devices or appliances, hereinafter referred to generally as "loads", is often monitored using separate meters for each load. In such cases, in order to derive valuable data about the energy usage of each load it is necessary to collate metered values manually, and subsequently enter the data manually on a computer for processing.

More sophisticated electricity meters are configured to send data automatically to a data logging device which may be local, or may be reached via a communications device, for example over the telephone line, or the internet.

A previously considered example of electricity meter brings together a fixed number of metering units and combines them in a unitary housing, together with a common visual display and processing means to manipulate and present the data collected by the individual metering units. Cables are used to carry the measurement signals from current detectors located locally at each load. The combined multi-meter load is particularly suited to modern premises in which the electrical supply enters the building at a single location, and is controlled from a single control panel. Meter units must be electrically connected to wires carrying a signal representative of the current being drawn by the load. For this purpose the unit is provided with at least one pair of electrical terminals.

The unit typically has a protective casing, both to keep the terminals free from dust and also to prevent accidental contact with the terminals by an operative. To provide access to the terminals the casing typically has a removable cover.

However, careless operatives sometimes fail to replace the terminal covers, which can then become misplaced. Furthermore, the removal and replacement of terminal covers can be fiddly as the modules are often installed in cabinets with very little space around them and the wires which are to be connected to the terminals are carried in trunk conduits which pass close by the terminal cover, leaving little space for manipulating it.

Preferred embodiments of the present invention aim to address at least some of the aforementioned shortcomings in the prior systems.

The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto.

According to the invention there is provided a meter unit having an electrical terminal for electrical connection to a wire or cable, the meter unit having a case comprising a case body and a terminal cover portion moveable between a first position in which the terminal is substantially covered, preventing access thereto, and a second position in which the terminal is substantially uncovered, permitting access thereto, wherein in the second position the terminal cover portion is retained in engagement with the case body.

In a preferred arrangement movement of the terminal cover portion between the first and second positions includes relative sliding movement.

The terminal cover portion and the case body may slide relative to each other between the first and second positions by engagement of one or more lugs in one or more slots, the lugs being part of one of the case body and terminal cover portion and the slots being part of the other of the case body and the terminal cover portion. In a preferred arrangement the at least one lug is formed in the case body and the at least one slot is formed in the terminal cover portion.

In a particularly preferred arrangement the terminal cover portion is moveable between the second position and a third position relative to the case body. Preferably the terminal cover portion is moveable from the second position to the third position after a limit of the relative sliding motion is reached.

In a particularly preferred arrangement the terminal cover portion is movable between the second and third positions by relative pivoting movement between the terminal cover portion and the case body.

Preferably the terminal cover portion is retained in engagement with the case body in the third position. The terminal cover portion may be retained in the third position by engagement of at least one of the one or more lugs with at least one of the one or more slots. The terminal cover portion may be arranged to be retained in the first position by a retaining latch means. The retaining latch means may be actuated to release the terminal cover portion from retention in the first position. In a preferred arrangement the retaining latch means may be actuated by depression of a button.

The retaining latch means may comprise biasing means arranged to urge the terminal cover portion at least partly towards the second position when the retaining latch means is actuated to release the terminal cover portion from retention in the first position.

The biasing means may comprise spring means, and preferably comprises a sprung clip.

The meter unit may comprise a plurality of electrical terminals and may comprise a plurality of terminal cover portions . The invention also includes a method of releasing a terminal cover portion on a case of an electrical meter unit, in order to gain access to an electrical terminal of the meter unit, the method comprising sliding the terminal cover portion from a first position, in which the terminal is substantially covered, preventing access thereto, to a second portion in which the terminal is substantially uncovered, permitting access thereto, wherein in the second position the terminal cover portion is retained in engagement with the case body.

The method may include pivoting the terminal cover portion from the second position to a third position.

Preferably the method comprises actuating a latch means to release the terminal cover portion from retention in the first position. The method may include pressing a button to actuate the latch means.

The method may comprise any combination of the features or limitations referred to herein, except a combination of such features as are mutually exclusive.

A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a schematic perspective view of modular metering apparatus including individual meter units according to an embodiment of the invention;

Figure 2 shows a meter unit of Figure 1 in more deta Figure 3 is a schematic side view of part of the unit of Figure 2, with a terminal cover portion in a first position; Figure 4 is a schematic side view of the unit of Figure 3 , with the terminal cover portion in a second position; and

Figure 5 is a schematic side view of the unit of Figures 3 and 4, with the terminal cover unit in a third position.

Referring to Figure 1 this shows modular metering apparatus generally at 10, comprising a master module 12, slave modules 14a to 14f, and a communications module 16. Together the modules 12, 14 and 16 make up a modular metering apparatus for metering electricity from plural loads (not shown) such as, in the case of a large food retail premises, chill or freeze display cabinets.

Each of the slave modules includes plural electricity meters for measuring electricity used by a load. The loads may be located remotely from the apparatus 10 and each one has a current detector that feeds a low-voltage signal back to the meter via a cable (not shown) . The slave modules are connected to one another and to the master module by an internal bus through which data and power are carried between the modules.

The master module 12 comprises the hub of the system and communicates on a bespoke internal bus with the slave modules to interface/measure/collect/detect/monitor data relevant to an individual site/application. The master module is arranged to periodically pull data from each slave making it available to a user as though sourced from a single device. An LCD display unit 18 presents the data to a user. The master module also houses a 32-bit microprocessor (not shown) which, with custom firmware, is used to manipulate the data gathered from the slave modules making the data ready for external systems. Concentrating data in this way reduces the time and resource required for external systems to collect and manipulate a range of energy management data.

Figure 2 shows an individual module, or meter unit 14 which forms part of the apparatus 10. The individual modules connect together by a releasable snap-fit engagement and each clips on, at its rear, to a DIN rail (not shown) .

The unit 14 comprises a robust case body 22 of thermoplastics material. Within the body 22 are first and second electricity meters (not shown) respectively having first and second sets of terminals for connecting to cables (not shown) , each leading to a remotely located load. The first and second sets of terminals are located beneath first and second (i.e. upper and lower) terminal cover portions 24 and 26 which, as will be described below, are moveably mounted on the case body 22. In Figure 2 both the upper and lower terminal cover portions are in the closed position, covering the terminal contacts within the case body 22 and preventing access thereto. The terminal cover portions 24 and 26 include respective release latches 24a and 26a which are used to release the terminal cover portions from the closed position. Other features of the unit 14 include sprung clips 28 which are for connecting the unit to an adjacent module/unit in the apparatus 10, and a communications connector 30 for connecting to the power/data bus in the apparatus 10. A release button 32 is operable to release the unit 10 from its engagement with the adjacent modules in the apparatus 10. Turning to Figures 3 to 5, these show schematically the terminal cover portion 24 in various positions in relation to the case body 22.

In Figure 3 both the upper and lower terminal cover portions 24 and 26 are in a first, closed position. In this position the terminal contacts within the case body 22 are covered and are not accessible by an operative. To release the terminal cover portion 24, its release latch 24a (shown in Figure 2) must be depressed. This is done by pressing a face of the latch which acts as a button. The terminal cover portions are arranged to move slidably on the case body and are sprung mounted so that when the release latch is depressed the terminal cover portion springs outwards from its locked position.

Figure 4 shows the terminal cover portion in a second position. Here the release button 24a has been depressed and the terminal cover portion has been urged away from its closed position. The terminal cover portion 24 has been made to slide further horizontally with respect to the case body to a maximum extent, as shown in the figure. The sliding movement is achieved by engagement of a pair of lugs (not shown) inside the case body with a pair of corresponding elongate slots 34, one either side, on the terminal cover portion 24. At the limit of the sliding movement, as shown in Figure 3, the terminal cover portion is able to pivot in relation to the case body, with the slots 34 pivoting upon the lugs (not shown) . Figure 5 shows the terminal cover portion after it has been pivoted in relation to the case body. The terminal cover portion is retained on the case body and cannot be removed, and thereby possibly misplaced by an operative. In the configuration shown in Figure 5 an operative has full, unhindered access to the terminals within the case body.

When the terminal cover portion is to be returned to the closed configuration shown in Figures 2 and 3 the movements are reversed, so that the terminal cover portion is first pivoted to the horizontal position shown in Figure 4, and is then slid along the case body until the closed position is reached, with the resistance of the spring being overcome in the final stages of the sliding movement before automatic securing of the latch. The operation of the lower terminal cover portion 26 mirrors that of the upper portion 24, in that upon depressing the release latch 26a the terminal cover portion 26 may first be slid outwards from the case body and may then be pivoted upwards.

The apparatus described above provides terminal cover portions that are easy to use and whose movement takes up little space, whilst providing maximum access in the open position. The spring loading of the terminal cover portions provides immediate visual feedback to an operative, showing that the terminal cover portion has been opened.

The terminal cover portion described above can be used on the slave modules, or on the master module or a

communications module, and the term "meter unit" is used generally herein to refer to any of the components of a metering apparatus or system which require a terminal cover .

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.