The present invention relates to cover assemblies and in particular, but not exclusively, to cover assemblies for low voltage network boxes. Low voltage network boxes, commonly referred to as link boxes, facilitate the distribution of electricity from Distribution Network Operators (DNO's) to their customers. The local area network grid is typically segmented through 3-phase underground link boxes, each containing removable solid links to permit segmentation of the network for fault isolation. Once a fault has been isolated, redundancies in the network setup and appropriate switching measures are provided to ensure a relatively uninterrupted continuation of the supply to customers.

Unfortunately, the current approach to fault detection relies very much on customers reporting an issue with their current supply, with DNO's having no way of actively monitoring the health of their existing link box network infrastructure. This problem is exacerbated by the need to replace existing link boxes as they come to the end of their expected lifespan. With the sheer number of link boxes on the existing network outweighing the rate at which they can be replaced, DNO's require a way in which to monitor and prioritise the replacement of some link boxes over others.

Adjunct to the problem of ageing link boxes, is the problems caused by penetration of ground water and build-up of condensation within the link box. The combination of moisture and live electrical components may result in a dangerous build-up of heat and pressure, with recent incidents resulting in explosive failure of the link box. Placement of link boxes at and below street level therefore represents a serious risk to the general public, adding to the growing need to identify and monitor the health of each link box. The present invention therefore seeks to provide a link box cover assembly for detecting a temperature within the link box and capable of signalling DNO's of any increase in detected temperature.

According to a first aspect of the present invention there is provided a cover assembly for a link box, the assembly comprising: a removable lid; a sensor means; a signal generating means for generating a data signal, connected to the sensor means; a signal transmitting means connected to the signal generating means for wirelessly transmitting the data signal; and an electrical power source for supplying electrical power to the signal generating means and the signal transmitting means; wherein the assembly is configured to generate and transmit a signal in response to sensing a predefined condition by the sensor means.

The planar lid is sized for use with both new and existing or "legacy" link boxes. The link box cover is relatively easy to replace, without requiring access to the link box itself. The sensor, signal generating and transmitting means are integrally formed within the lid to allow for ease of replacement as a single piece. Replacement of the link box covers can be implemented at a rate much faster than the rate at which link boxes themselves can be replaced, providing a more immediate solution to the problem of monitoring the health of the link box network.

Preferably, the sensor means comprises a temperature sensor for detecting a temperature within the link box and is configured to generate and transmit the signal if the detected temperature exceeds a predetermined threshold value.

Detected temperature is used as a proxy for the health of the link box, with increases in temperature indicating failure of the link box. Monitoring the increase/ decrease in temperature of each link box provides a way to monitor the health of the link box network and ultimately prioritise the replacement of link boxes that are more at risk of failure. It is also preferred that a further signal is generated and transmitted once the detected temperature falls below the predetermined threshold value. Preferably, the assembly is configured to power down after a predetermined time following generation and transmission of the signal so as to preserve battery life.

In addition, it is preferred that the signal comprises data identifying the link box as well as data relating to the detected temperature. It is also preferred that the sensor means is mounted on the undersurface of the lid. This allows the sensor to be best placed for detecting temperature within the link box.

In addition, it is preferred that the sensor means is housed within a protective shield. In the event of failure, the housing protects the sensor means long enough for a signal to be generated and transmitted to the DNO. Preferably, the signal is a Short Message Service (SMS) signal. This allows the generation and transmission of the signal to 'piggy-back' on the existing and reliable SMS communication network infrastructure.

In accordance with a second aspect of the present invention there is provided a system comprising a cover assembly as described above, further comprising means for receiving the signal and means for processing the signal.

In accordance with a third aspect of the present invention, there is provided a link box fitted with a cover assembly of the first aspect, or a system according to the second aspect, of the present invention.

A specific 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 part exploded, cross-sectional view of an embodiment of a cover assembly and link box, in accordance with the present invention;

Figure 2 is a part exploded, perspective view of the cover assembly of Figure 1 ; Figure 3 is a top view of the cover assembly of Figure 1 ; Figure 4 is a cross-sectional view of the cover assembly of Figure 1 ; and

Figure 5 illustrates a display of the link box health network system in accordance with the present invention.

Figure 1 illustrates a link box 100 of generally conventional form which comprises a metal housing 102, which, in use, is typically buried below ground level within a link box chamber 104 and whose upper end is closed off by a removable link box cover 106. The housing 102 is in the shape of an open-topped metal rectangular box and comprises a rectangular base wall 108 with enclosing parallel, planar side walls 1 10, parallel, planar front and rear walls 1 12 extending perpendicularly from the base wall 108, and the open upper end of the box is closed off by a removable bell lid 1 14, defining an enclosure therein for housing electrical switching/ connecting and disconnecting components (not shown). The bell lid 1 14 is sized to overhang the enclosing walls 1 10, 1 12 of the housing 102 and is formed from a heavy cast iron material to prevent easy access to the electrical components within.

The housing 102 is provided with opposed cable inlets/ outlets 116, 1 18 formed on the face of the front and rear walls 112 of the housing (it will be appreciated that the terms "inlet' and "outlet' as used herein are not intended to indicate direction in the sense of load and supply).

In order to install to the link box 100, an access chamber 104 is constructed. The chamber 104 is excavated to a depth sufficient to allow the link box to be completely buried below ground level. The chamber is lined with pre-fabricated concrete elements, bricks or like and is provided with a recessed portion 124 formed around the upper periphery of the chamber for accommodating a link box cover frame 126.

As best seen in Figure 2, the link box cover frame 126 is rectangular and comprises two parallel short end portions 128 and two parallel long side portions 130 extending perpendicularly to the end portions, with each portion comprising a base wall 132 and a side wall 134 extending perpendicularly from the base wall 132, whereby the base walls 132 form a continuous, inwardly projecting lip. As best illustrated in Figure 1 , the outer faces of the base wall 132 and side wall 134 of each portion 128, 130 meet to form an outwardly projecting obliquely angled edge 136 extending around the periphery of the frame 126. When the frame 126 is in abutment with the recess 124 formed around the periphery of the link box chamber 104, the obliquely angled edge 136 facilitates retention of the frame 126 within a layer of mortar located in the recess 124 in use thereby securing the frame 126 to the link box chamber 104.

The link box cover 106 as seen in Figure 2 is the shape of a rectangular metal tray. The cover comprises a rectangular base wall 138 and four upstanding enclosing walls 140, each extending outwardly from a respective edge of the base at an oblique angle to the plans of the base wall 138 to define a volume 142 therein. As illustrated in Figures 1 , 3 and 4, a concrete mixture 144 is set within the volume to provide weight to the link box cover 106.

In use, the link box cover 106 is lowered on top of the frame 126 and held in place under the weight of the concrete mixture within the tray. As best illustrated in Figure 3, the upper face 140 of the link box cover 106 comprises four apertures 146, located along the longer sides 148 in the upper face 140 of the cover. The apertures 146 are provided in respective hollow metal fixings which are cast into the concrete mixture during manufacture, in the conventional manner, and are used in conjunction with conventional manhole keys to facilitate lifting of the link box cover 106 to gain access to the link box chamber 104. The recessed portion 124, link box cover frame 126 and link box cover 106 are sized such that when the link box cover 106 is secured on top of the frame 126, its upper face 140 is flush with ground level.

Referring now to Figure 4, the link box cover 106 further comprises, on its underside, a smart control unit 150 comprising a temperature sensor assembly 170 communicatively coupled to a network interface 154 having Short Message Service (SMS) capability. The smart control unit is housed within a protective cover 156, mounted to the underside of the link box cover 106 to protect the control unit in the event of a failure of the link box. The link box cover 106 further comprises an anti-vandal relay antenna 158, communicatively coupled to the network interface 154 via an antenna cable 160. The relay antenna is mounted within a steel insert 162 formed within the volume 142 of the link box cover 106. The steel insert 162 is positioned such that when the relay antenna 158 is mounted, its uppermost surface is flush with the upper surface of the link box cover 106.

The control unit further comprises a printed circuit board (PCB) 174 on which a programmable electronic control 168 is mounted and is communicatively connected to the network interface 154. The controller 168 is configured to generate an SMS signal which is transmitted by the relay antenna 158 whenever the detected temperature within the link box chamber exceeds/ falls below a predetermined threshold value. The controller 168 is powered by a battery 152. When the detected temperature exceeds/ falls below the predetermined threshold value, the sensor assembly 170 is configured to electrically connect the battery 152 to the controller 168 thereby supplying power to the network interface 154. Similarly, after a predetermined period after the detected temperature exceeds/ falls below the predetermined threshold value, the sensor assembly 170 is configured to electrically disconnect the power source 152 from the controller 168, thereby turning off the power supply 152 to the network interface 154.

The controller 168 has integrated functionality, including but not limited to, power management and communication control. The controller 168 is provided with a unique identifier which is associated with, and therefore identifies, the particular link box 100 and its location. In this embodiment, when the detected temperature within the link box chamber 104 exceeds the predetermined threshold value, power is supplied to the controller 168 and network interface 154 and a first input is provided to the controller 168. The controller, in response, causes the network interface 154 to generate an SMS signal which is transmitted via the antenna relay 158. The antenna 158 relays the SMS signal to an SMS gateway (not shown) which may route the SMS signal to a central server (not shown) and/ or directly to a mobile device of a network grid engineer. The SMS signal includes the unique identifier of the link box 100, its location and the detected temperature value. The SMS signal my also include additional information such as information relating to the remaining power supply level of the battery 152. The controller 168 is configured to cause the network interface 154 to generate an SMS signal every time the detected temperature increases above the predetermined threshold value. Once the detected temperature falls below the predetermined threshold value, the controller 168 causes the network interface 154 to generate a final confirmatory SMS signal, after which the controller 168 and network interface 154 enter a dormant mode, in order to preserve battery life.

Once the SMS signal has been relayed from the antenna 158 and routed through the SMS gateway to the server, the server is updated to reflect the new information associated with the identified link box 100. In response to receiving the information, the server may be configured to prompt a person responsible for maintaining the link box 100 via a display means such as a screen 172 as illustrated in Figure 5 or via any other means including, but not limited to, e-mail 170 or SMS text message.

In this way, temperature increases within the link box chamber, often indicating failure of the link box, are detected in real time, allowing for immediate action to be taken.

The present description is for illustrative purposes only and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope of the present disclosure. For example, the system might be configured to allow bi-directional transmission of signals between the control unit and the central server. In a bi-directional wireless system, additional hardware such as a receiver may be included in the control unit. Moreover, although the control unit has been described as being powered off when the detected temperature within the link box chamber is below a predetermined threshold value, the control unit may have a continuous supply of power. Furthermore, the link box cover may be secured to the frame by way of anti-tamper fastener means.

In addition, mounting of the control unit 150 is not limited to the undersurface of the link box cover 106 and can be placed at any position within the link box 100. For example, the control unit 150 can be mounted on a wall of the chamber 104 or, freely placed within the chamber 104. This allows for ease of assembly of the weighted link box cover 106 to slide into place, on top of the frame 126 without damaging the control unit 150.

Further still, the network interface 154 may generate and transmit the SMS signal directly to the SMS gateway whenever the detected temperature within the link box chamber 104 exceeds/ falls below a predetermined threshold value such that no antenna relay is required. In addition, the network interface 154 may have increased wireless functionality including, but not limited to, Infrared (IR) communication, Wi-Fi, WiMax, radio and Bluetooth capability. Furthermore, the battery 152 may be supplemented with or replaced entirely with a continuous power supply.

While the sensor assembly has been described with specific reference to a single temperature sensor, other types of sensors may be employed including, but not limited to, smoke detectors, pressure sensors and humidity sensors, the number and placement of which within the link box cover can be varied. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.