Field of invention:
The present invention relates to an enclosure for housing energy meter  particularly  an enclosure for housing energy meter for measuring consumption of the electricity.

Background of invention:
Energy meter is being used in electric energy distribution system and is located at the subscriber’s or customer’s premises. The energy meter measures the amount of electric energy consumed by the subscriber/customer.

Various components of the energy meter are encased/enclosed inside a casing/enclosure in order to provide protection to the components and to enhance the ease of mounting of the energy meter at the user’s premises. Further  it is also desired from an enclosure to avoid unauthorized access of the components. By avoiding such unauthorized access of the components of the energy meter  tampering to the meter can be avoided.

The enclosure of the energy meter is made in two or three parts and the parts are joined together. Figures 1 and 2 illustrate conventionally used energy meter enclosure which includes a meter base for mounting an energy metering unit and a terminal block  a meter cover and a terminal cover. In some of the conventional construction of the enclosure  the terminal block is integrated with the meter base. Referring to figure 2  the energy metering unit comprises a printed circuit board (PCB) consists of electrical/electronic components/circuit for measuring energy consumption and plurality of terminals for making electrical connection with the said energy metering unit. The terminal block mounted on the meter base is used for accessing the terminals of energy metering unit for making electrical connections. As can be observed from figure 2  the meter base is a vertical base i.e. it remains in vertical position when energy meter is mounted for metering purpose. As shown in figure 2  the meter cover is secured on meter base so as to cover the energy metering unit and the terminal cover is secured to the meter base so as to cover the terminal block. The terminal cover is secured with the meter base by means of single or multiple screws.
As described in the previous paragraph  one of the requirements in a meter is to prevent access to the internals of the meter. Traditionally this has been achieved by use of lead or plastic seals on meters. However these seals are easily duplicated. To overcome this problem the meters cover and base is typically welded ultrasonically to prevent unscrupulous access to the meter.

The energy metering unit comprises electrical/electronic circuit and components which causes another requirement for the energy meter that the energy meter must be immune to strong electrostatic discharges (ESD) produced externally on the meters. Often fraudsters try to degrade or damage the electronic circuits by discharging high voltage electric sparks on the meter enclosure. Traditionally this is protected by means of shielding inside the meters which diverts the spark energy to ground paths.

In conventional meter  two or more shields are required to protect meter form all three sides (Top  left and right)  where there are air gaps formed at due to assembly of two different parts at the adjoining edges. This additional shield is constructed using a conductive wire (typically 1-2 mm diameter) placed inside the meter over periphery but terminated to ground on PCB to discharge the ESD. Incorporating additional shields does not give complete protection against ESD and requires additional manufacturing and assembling process steps with additional cost.

Referring to figure 1  an air gap G1 is formed between the meter base and the meter cover at their adjoining edges. Similarly  another air gap G2 is formed between the terminal cover and the meter base at their adjoining edges. As can be observed from figures 1 and 2  the air gap G1 can be a direct access to the electrical/electronics components/circuit of the metering unit. Therefore  the air gap G1 formed between the meter base and meter cover makes the energy metering unit vulnerable to the ESD.

Objects of the present invention:
The main object of the present invention is to provide an enclosure for energy meter.
Another object of the present invention is to overcome at least one of the problems associated with the conventional/existing enclosure for energy meter.
Still another object of the present invention is to provide an enclosure for energy meter with less number of joints so as to minimize various problems associated with the conventional/existing enclosure for energy meter.

Summary of the invention:
Accordingly  the present invention provides an enclosure for an energy meter  said enclosure comprising:
a top cover comprising a top wall and a side walls defining a hollow chamber  and an opening located opposite to the top wall for accessing the said chamber;
a terminal block assembly comprising
a horizontal plate comprising two opposing upper and lower surfaces for mounting an energy metering unit and terminal block respectively;
the chamber is shaped and sized so as to receive and accommodate the energy metering unit mounted on the horizontal plate and once the energy metering unit accommodated in the chamber  the horizontal plate of the terminal block assembly is secured with the top cover thereby closing the opening of the chamber.

In an embodiment of the present invention  the energy metering unit comprises a printed circuit board (PCB) comprising of electrical/electronic components/circuit for measuring energy consumption and plurality of terminals for making electrical connection.

In another embodiment of the present invention  the PCB is vertically mounted on the upper surface of the horizontal plate.

In still another embodiment of the present invention  the lower surface is provided with apertures for accessing the terminals through the terminal block for making electrical connections.

In yet another embodiment of the present invention  the top cover comprises:
peripheral back walls extending outwardly from the periphery of the opening; and
peripheral cross walls and peripheral longitudinal walls around outer periphery of the peripheral back wall thereby forming an envelop surrounding the opening and the back wall.

In a further embodiment of the present invention  the horizontal plate is shaped and sized so that the horizontal plate is located below the peripheral back wall and inside the envelop formed by the peripheral cross walls and peripheral longitudinal walls thereby closing the opening.

In a further more embodiment of the present invention  the terminal assembly is secured with the top cover by means of one or more side locks.

In one more embodiment of the present invention the side locks are strengthened by metallic plate which is inserted in the top cover.

In another embodiment of the present invention  the side locks comprises snaps  and the terminal assembly comprises support plates which extend vertically from the top cover and provided with slots to cooperate with the snaps for securing the terminal assembly with the top cover.

In still another embodiment of the present invention  the top cover is provided with slots for accessing the slots provided on the support plates of the terminal assembly for snaps of the side locks.

In yet another embodiment of the present invention  the terminal assembly comprises a vertical plate mounted vertically on the horizontal plate for covering and supporting the PCB.

In a further embodiment of the present invention  comprising a terminal cover is hingedly secured with the terminal assembly for covering the terminal block.

In another embodiment of the present invention  the vertical plate of the terminal assembly is provided with a first pair of hinge post and terminal cover is provided with a second pair of hinge post which cooperates with the first pair of hinge post for securing the terminal cover with the terminal assembly.

In still another embodiment of the present invention  the first pair of hinge post is provided with detents and the second pair of hinge post is provided with protrusions to cooperate with the detents for hingedly securing the terminal cover with the terminal assembly.

In one more embodiment of the present invention  the top cover is provided with a window for projecting there through the first pair of hinge post.

Brief description of the figures:
Figure 1 illustrates a conventional enclosure for an energy meter.
Figure 2 illustrates an exploded view of the enclosure shown in figure 1.
Figures 3 and 4 illustrate exploded view of enclosure for energy meter according to an embodiment of the present invention.

Figure 5 illustrates an exploded view of the terminal assembly showing snap type side locks for securing terminal assembly with the top cover.
Figure 6 illustrates the assembled view of enclosure for an energy meter according an embodiment of the present invention.
Figures 7 and 8 illustrate an enclosure comprising a terminal cover according an embodiment of the present invention.
Figure 9 illustrates assembled view enclosure for energy meter according to an embodiment of the present invention.

Detailed description of the invention:
The present invention will now be described with reference to Figures 3-8.

Figure 3 illustrates an exploded view of an enclosure for an energy meter according to an embodiment of the present invention. Referring to figure 3 and 4  as shown in figures 3 and 4  the enclosure (E) comprises a top cover (1) and a terminal assembly (2). The top cover (1) has a top wall (3) and four side walls (4) which define a hollow chamber (5) and an opening (6) located opposite to the top wall (3) for accessing the chamber (5). As shown in figures 3 and 4  the top cover (1) comprises peripheral back wall (7) extending outwardly from the periphery of the opening (6). The top cover also comprises peripheral cross wall (8) and peripheral longitudinal wall (9) around outer periphery of the peripheral back wall (7) thereby forming an envelop (En) surrounding the opening (6) and the peripheral back wall (7).

The terminal assembly (2) may be used for mounting energy metering unit and a terminal block (10) of the energy meter. As described in previous paragraphs  the energy metering unit comprises a printed circuit board (PCB) (11) comprising of electrical/electronic components/circuit for measuring energy consumption and plurality of terminals for making electrical connection. The terminal assembly (2) comprises a horizontal plate (12) for mounting the energy metering unit. As shown in figures 3 and 4  the horizontal plate (12) comprising an upper surface (13) and a lower surface (14) located opposite to the upper surface (13). In other words  the upper surface (13) and the lower surface (14) are two opposing surface of the horizontal plate (12). The PCB (11) is vertically mounted on the upper surface (13) of the horizontal plate (12). For this purpose  an edge of the PCB (11) may be mounted on the upper surface (13) of the horizontal plate (12). In an embodiment of the present invention a cradle (not shown in figures) may be secured on the horizontal plate (12) using screws and the PCB (11) may be mounted vertically on multiple bosses of the cradle.

The terminal block (10) is mounted on the lower surface (14) of the horizontal plate (12) for accessing terminals of the energy metering unit for making electrical connections. For this purpose  the horizontal plate may be provided with plurality of apertures for accessing the terminals of the energy metering unit through the terminal block. The terminal block may be integrated with the horizontal plate.

Referring to figure 4  the chamber of the top cover (1) is shaped and sized so as to receive and accommodate the PCB which is vertically mounted on the terminal assembly through the opening. The peripheral back wall (7) is shaped and sized so that the horizontal plate (12) can be located or supported below the peripheral back wall (7); and the peripheral cross walls (8) and the peripheral longitudinal walls (9) are shaped and sized so as to completely envelop edges of the horizontal plate (12).

As can be observed from figure 4  original dimension (i.e. length (L) and breadth (B)) of the opening (6) is extended by width (w) of the peripheral back wall so that the opening (6) has extended dimensions (i.e. length (L’) is about L+2w and breadth (B’) is about (B+2w). Dimension (length (l) and breadth (b)) of the horizontal plate (12) is smaller than the extended dimensions (L’  B’) of the opening (6) (i.e. l < L’ and b < B’) so that the horizontal plate (12) can be received inside the envelop formed by the peripheral cross walls (8) and the peripheral longitudinal walls (9). The dimension (length (l) and breadth (b)) of the horizontal plate (12) is larger than the original dimensions (L  B) of the opening (6) (i.e. L < l and B< b) so that the horizontal plate (12) may be supported below the peripheral back wall (6).

As can be observed from figure 4  the peripheral back wall (6) may be provided with one or more locating pins (15) and the horizontal plate (12) may be provided with corresponding locating slots (15’) for receiving the locating pins for locating the horizontal plate (12) of the terminal assembly below the peripheral back wall (7) inside the envelop formed by the peripheral cross wall (8) and longitudinal wall (9).

Once the horizontal plate (12) is located below the peripheral back wall (7) with the help of locating pins (15)  the terminal assembly (2) may be secured with top cover (1). For this purpose  one or more side locks may be provided for securing the terminal assembly (2) with the top cover (1). As shown in figures 4 and 5  two snap-type side locks (16) comprising snaps (s) are provided for securing the terminal assembly (2) with the top cover (1). Referring to Figure 5  the terminal assembly (2) is provided with corresponding slots (17) which are adapted to cooperate with the snaps (s) of the snap-type side locks (16).

For disposing such slots (17) on the terminal assembly  support plates (18) are provided which are extending vertically from the horizontal plate (12). For accessing the slots (17) on the terminal assembly (2)  the side walls (4) of the top cover (2) are provided with slots (19) corresponding to the slots (17) of the terminal assembly (2). The slots (19) disposed on the side walls (4) may be surrounded by surrounding wall so as to define a pocket (P) for receiving the side lock (16). Once the side lock received in the pocket (P) so as to prevent easy access of the side lock (16).

Figure 6 shows the terminal assembly (2) secured with the top cover (1) with the help of side locks (16). As can be observed from figure 6  the snaps (s) of the side locks (16) remains inside the chamber (5) and can not be accessed from outside.

Referring to figures 5 and 6  the energy metering unit is received in the chamber (5) through the opening (6) and completely accommodated inside the chamber (5). Further  the opening (6) is completely closed by the horizontal plate (12) which is located below the peripheral back wall (7) and the edges of the horizontal plate (12) are covered by the envelop formed by the peripheral cross wall (8) and peripheral longitudinal wall (9). As can be clearly observed that there is no air gap exist which can be accessible for external electrostatic discharge (ESD). Even  if some clearance exists between the horizontal plate (12) and the peripheral back wall (7) or peripheral cross wall (8) or peripheral longitudinal wall (9)  the same can not be accessed for ESD from outside. Further  the electrical/electronics components of energy metering unit are located on upper portion of the PCB vertically mounted on the horizontal plate so that these components are lies away from the clearance which may exist between the horizontal plate (12) and the peripheral back (7) wall or peripheral cross wall (8) or peripheral longitudinal wall (9) thereby further reducing the chances of access of these component for external ESD.

Referring to figure 4  a vertical plate (20) may be mounted on the horizontal plate (12) for covering the PCB. The vertical plate (20) may also be used for indicating meter-rating  brand name/logo  meter identification information e.g. meter type  serial no.  rated voltage  current  manufacturer information etc. The vertical plate (20) of the terminal assembly (2) may be provided with a hole (H) for installing a spring loaded push button (21) electrically connected with the PCB (11). A meter display (22) may be mounted under the vertical plate (20). As can be observed from figures 4  5 and 6  the vertical plate (20) is completely received inside the chamber (5). The top cover may be made of transparent plastic material so that the display can be read from outside.

As can be observed from figure 6  the terminal block (10) remains outside the enclosure so that the terminals can be accessed for making electrical connections of the PCB (11). The terminal block (10) may be covered with a terminal cover (23). Figures 7 and 8 illustrate a terminal cover (23) which is hingedly secured with the terminal assembly (2). For this purpose  the vertical plate (20) of the terminal assembly (2) is provided with a first pair (24) of hinge post and the terminal cover (23) is provided with a second pair (25) of hinge post which cooperates with the first pair (24) of hinge post to hingedly secure the terminal cover (23) with the vertical plate (20). The first pair (24) of hinge post may be provided with detents and the second pair (25) of hinge post may be provided with protrusions which are received in the detents for hingedly securing the terminal cover (23) with terminal assembly (2). Since the vertical plate (20) completely remains inside the chamber (5)  the top cover (1) may be provided with a window (W) (as shown in figure 5) through which the first pair (24) of hinge post extends from the vertical plate (20) outside the chamber (5) as shown in figure 6. The window (W) may be shaped and sized so that the push button installed in the hole of the vertical plate can be accessed through the window as shown in figure 6.

Figure 9 shows an assembled view of the enclosure for energy meter of the present invention.

As can be observed from figure 3-8  the construction of the enclosure does not require a separate meter base. The top cover (1) is covered from five sides and the opening (6) is closed by the horizontal plate (12) of the terminal assembly (2) which makes the manufacturing simpler and cheaper. The construction of the enclosure described with reference to figure 3-8  high degree of protection against ingress of dust and water can be achieved without the use of any additional gasket or sealing material because there is no partition in the top cover (or top cover is single piece part). As the top cover (1) of the meter is a single part construction which covers the electrical/electronic components mounted on the PCB (11) from five sides (i.e. from top and four sides) without any air discharge paths or air gaps  the enclosure provides high immunity from external Electrostatic Spark Discharges without use of any shielding to cover the air gaps and for diverting the ESD to the ground paths. In an alternate embodiment of the present invention  a metallic shield (M) may be mounted on the PCB (11) (as shown in figure 4) to provide a second level of protection from ESD after the first level of protection provided by the construction of the enclosure of the present invention. As can be noticed  only one metallic shield is required in the enclosure of the present invention. The construction and manufacturing of the single metallic shield is relatively simpler.

In the enclosure of the present invention  there is no need for ultrasonic welding. The construction of the enclosure of the present invention is a tamper proof construction in which accessing internal components are very difficult. Further  enclosure of the present invention may be provided with means to leave a visible evidence of tampering if attempted. In the enclosure both the side locks once fitted at proper place  the snaps of the side locks are not accessible from outside and therefore  only way to open the meter is to break the side locks. However  in attempt to break the side locks  the pocket which receives the side lock will also get damaged leaving visible evidence of opening the meter enclosure. In another embodiment  a metal plate may be inserted to strengthen the side lock from inside in the top cover. The side locks may be provided with manufacturer’s identification mark so that if the side locks are broken and duplicated the same can be identified easily.

The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention  will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention.

We claim:

1. An enclosure for an energy meter  said enclosure comprising:
a top cover comprising a top wall and a side walls defining a hollow chamber  and an opening located opposite to the top wall for accessing the said chamber;
a terminal assembly comprising
a horizontal plate comprising two opposing upper and lower surfaces for mounting an energy metering unit and terminal block respectively;
the chamber is shaped and sized so as to receive and accommodate the energy metering unit mounted on the horizontal plate and once the energy metering unit accommodated in the chamber  the horizontal plate of the terminal member is secured with the top cover thereby closing the opening of the chamber.

2. An enclosure for an energy meter as claimed in claim 1  wherein the energy metering unit comprises a printed circuit board (PCB) comprising of electrical/electronic components/circuit for measuring energy consumption and plurality of terminals for making electrical connection.

3. An enclosure for an energy meter as claimed in claim 2  wherein the PCB is vertically mounted on the upper surface of the horizontal plate.

4. An enclosure for an energy meter as claimed in claim 2  wherein the lower surface is provided with apertures for accessing the terminals through the terminal block for making electrical connections.

5. An enclosure for an energy meter as claimed in claim 1  wherein the top cover comprises:
peripheral back walls extending outwardly from the periphery of the opening; and
peripheral cross walls and peripheral longitudinal walls around outer periphery of the peripheral back wall thereby forming an envelop surrounding the opening and the back wall.

6. An enclosure for an energy meter as claimed in claim 5  wherein the horizontal plate is shaped and sized so that the horizontal plate is located below the peripheral back wall and inside the envelop formed by the peripheral cross walls and peripheral longitudinal walls thereby closing the opening.

7. An enclosure for an energy meter as claimed in claim 1  wherein the terminal assembly is secured with the top cover by means of one or more side locks.

8. An enclosure for an energy meter as claimed in claim 1  wherein the side locks are strengthened by metallic plate inserted in the top cover.

9. An enclosure for an energy meter as claimed in claim 7  wherein the side locks comprises snaps  and the terminal assembly comprises support plates which extend vertically from the top cover and provided with slots to cooperate with the snaps for securing the terminal assembly with the top cover.

10. An enclosure for an energy meter as claimed in claim 9  wherein the top cover is provided with slots for accessing the slots provided on the support plates of the terminal assembly for snaps of the side locks.

11. An enclosure for an energy meter as claimed in claim 2  wherein the terminal assembly comprises a vertical plate mounted vertically on the horizontal plate for covering the PCB.

12. An enclosure for an energy meter as claimed in claim 2  further comprising a terminal cover is hingedly secured with the terminal assembly for covering the terminal block.

13. An enclosure for an energy meter as claimed in claim 2  wherein the vertical plate of the terminal assembly is provided with a first pair of hinge post and terminal cover is provided with a second pair of hinge post which cooperates with the first pair of hinge post for securing the terminal cover with the terminal assembly.

14. An enclosure for an energy meter as claimed in claim 1  wherein the first pair of hinge post is provided with detents and the second pair of hinge post is provided with protrusions to cooperate with the detents for hingedly securing the terminal cover with the terminal assembly.

15. An enclosure for an energy meter as claimed in claims 1-13  wherein the top cover is provided with a window for projecting there through the first pair of hinge post.

16. An enclosure for an energy meter substantially as herein described with reference to the accompanying drawings.