Background

Metal detectors are used in industry, such as the food and pharmaceutical industries, to check products for metal contaminants. Metal may enter the products from parts, such as nuts and bolts, lost by the processing machinery or metal fragments from mechanical wear of the machinery. Metal detectors may also be used to prevent intentional sabotage of products with metal contaminants.

A typical metal detector for use in an industrial process comprises a non-conductive former with an aperture and several coils of wire surrounding the aperture. The coils can be used to detect when magnetically or electrically conductive materials pass through the aperture. A housing surrounds the former and coils and a volume between the housing and the former is filled with a potting material. The potting material increases the density of the detector, reducing the detector’s sensitivity to vibrations and variations in temperature and may increase a sensitivity of the detector.

The housing is typically a thick case made from panels of a conductive material such as a stainless steel or aluminium. The housing can be constructed from metal panels that are welded together to form a rigid housing. The housing is conductively joined to a material which forms an electrostatic screen on the interior of the aperture of the former. The electrostatic screen is conductively joined with the housing to ensure sensitive operation of the detector.

There are several disadvantages associated with such prior art detectors. Such detectors are expensive to manufacture, partly due to the cost of producing the housing. Additionally, the housing being formed from thick metal does not adhere well to the potting material, as stresses generated during the curing of the potting material may cause fissures, thereby allowing spaces or voids to be formed between the potting material and the housing. This may increase the susceptibility of the detectors to vibration and therefore reduces the sensitivity of the detectors. Finally, cracks and imperfections can form in the join between the electrostatic screen and the housing reducing the performance of the detector. It is an object of embodiments of the present invention to at least mitigate one or more of the problems of the prior art.

Summary of the Invention

According to aspects of the present invention, there is provided apparatus and methods as set forth in the appended claims.

According to an aspect of the present invention, there is provided a metal detector, comprising a former having an aperture through which objects may be passed in use, one or more coils arranged around the former to surround the aperture, a plurality of outwardly extending ribs supported upon the former, at least some of the plurality of ribs being arranged to extend from an intermediate position about the former, each rib having an outer surface defining a support, a conductive cover arranged upon the support.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only, with reference to the accompanying figures, in which:

Figure 1 shows a schematic diagram of a former with an aperture surrounded by a plurality of coils, in accordance with an embodiment of the present invention;

Figure 2 shows a schematic diagram of a former surrounded by a plurality of ribs and a flange surrounding the aperture, in accordance with an embodiment of the present invention;

Figure 3 shows a schematic diagram of interlocking ribs, in accordance with an embodiment of the present invention;

Figure 4 shows a schematic diagram of a portion of a cover according to an embodiment of the present invention; Figure 5 shows a schematic diagram of the former surrounded by a plurality of ribs, where the cover is surrounds some of the plurality of ribs, in accordance with an embodiment of the present invention; and

Figure 6 shows a schematic diagram of the former surrounded by a plurality of ribs, where the cover surrounds the plurality of ribs, in accordance with an embodiment of the present invention.

Detailed Description of Embodiments of the Invention

Embodiments of the present invention provide an apparatus and method of manufacture of a metal detector. The metal detector may be constructed outwardly, therefore, the metal detector will be described in this order with reference to Figures 1 to 6.

The metal detector comprises a former 100 with an aperture 110, as shown in Figure 1. The former 100 may be made from a non-conductive material, such as a plastic or a fibre reinforced composite although other materials may be used. In an embodiment shown in Figure 1, the former 100 comprises linear sides which form a rectangular shape, although, the former 100 may be arranged in any suitable shape. When in use, a conveyor belt may be arranged to run through the aperture 110 to pass objects through the detector. Alternatively, the detector may be used in a gravity-based system where a conveyor belt is not required to pass objects through the aperture. Other arrangements for passing objects through the detector may also be envisaged. The aperture 110 in the embodiment of Figure 1 is rectangular, although any suitable shape may be used for the aperture 110. The aperture 110 has a central longitudinal axis 120 and throughout the present specification, references to axial, radial and circumferential directions are relative to the longitudinal axis 120.

The former 100 has an interior surface 170 on the inside of the aperture 110 and an outer surface 180 forming an exterior of the former 100. The former 100 may be continuous, such that there are no gaps extending from the interior surface 170 to the outer surface 180. On the outer surface 180, one or more coils 130 are arranged around the former 100 to surround the aperture 110. Each coil is formed from electrically conductive wire wrapped around the former 100. The coils 130 may have a central axis which is parallel to, or coincident with the central longitudinal axis of the aperture 110. The coils 130 may lie upon the outer surface 180 of the former 100 or may be in some embodiments situated within grooves 140 extending into the outer surface 180 of the former 100. In some embodiments, each coil 130 may be positioned in a respective groove around the former 100. The grooves 140 may ensure accurate positioning of the coils 130 around the former 100 and the coils 130 may be secured within the grooves 140, such as using an adhesive.

The coils 130 may comprise one or more transmitting coils and one or more receiving coils. In some embodiments, the coils 130 comprise a plurality, such as two, receiving coils although other numbers may be envisaged. The receiving coils may be located on either side of the one or more transmitting coils. The receiving coils may be located at equal distances from the transmitting coil. The one or more transmitting coils may be connected to a high frequency generating circuit (not shown) so that, in use, the coil produces an alternating electromagnetic field. The field from the transmitting coil may induce a voltage in each receiving coil. The receiving coils may be arranged such that the voltage induced in each coil is substantially equal. The presence of a conductive material within the aperture 110 disrupts the field of the transmitting coil and different voltages are measured in one or more of the receiving coils. The receiving coils may be arranged so that the voltage, when no conductive material is present in the aperture 110, substantially cancel out. As such a non-zero voltage indicates the presence of a conductive object within the aperture 110. In an alternative embodiment, the arrangement of the coils may differ. The coils 130 may comprise a plurality of transmitting coils, such as two, arranged on either side of a receiving coil. The transmitting coils may be connected to one or more high frequency generating circuits. The transmitting coils may be arranged such that, when in use, the voltage induced in the receiving coil is zero when no conductive material is present in the aperture 110. As such, a non-zero voltage indicates the presence of a conductive object within the aperture 110.

The coils 130 extend away from the former 100, as shown in Figure 1, and ends of the coils may be received within an electronics bay (not shown) associated with an apparatus of the metal detector 100. The electronics bay may contain monitoring equipment. The monitoring equipment monitors the voltage of the coils 130 to detect when metal passes through the detector.

The interior surface 170 of aperture 110 may be covered with a layer of conductive material which may include carbon. The material forms an electrostatic screen 630 on the interior surface 170 of the former 100. The conductivity of the material used to form the electrostatic screen 630 may block the alternating electric field generated by the transmitting coil but not significantly affect the alternating magnetic field generated by the transmitting coil. The electrostatic screen 630 may be used on the interior surface 170 of the former 100 to stabilise the capacitance between the coils and the products passing, in use, through the aperture 110.

In an embodiment, the material used to form the electrostatic screen 630 may be applied as a paint, which may contain carbon. When dry, a paint, such as carbon paint, is a brittle material and cracks may form in the dry paint. In an embodiment, a covering or sealing layer, such as of varnish, may be applied onto the carbon paint to protect the paint from damage. In another embodiment, the covering or sealing layer to protect the paint may be a thick protective polyurethane or epoxy coating. Alternatively, in another embodiment, the aperture may be covered with a plastic liner, to protect the paint. The liner may be arranged such that is does not touch the carbon paint. The coating or sealing layer or plastic lining may be chosen to meet the hygiene standards of food agencies for use in metal detectors. Any alternative conductive material capable of forming an electrostatic screen 630 may be used on the interior surface 170 of the former 100, including wire patterns etched on circuit boards and metal mesh. Non-magnetic metals may be used in the electrostatic screen 630. Any alternative conductive material may also be protected by the covering or sealing layer or plastic liner.

Supported on the outer surface 180 of the former 100 are a plurality of ribs 210, 220, as shown in Figure 2. The plurality of ribs are arranged to extend outwardly from the former 100 relative to the longitudinal axis 120. The ribs 210, 220 may be directly supported on the former 100. In an embodiment shown in Figures 2 and 3, each of the ribs 210, 220 may be formed from thin sheet material, such as plastic or fibre reinforced polymer, although other materials may be used. The ribs 210, 220 may comprise a first face 270, 275 and an opposing second face (not shown). The ribs 210, 220 may comprise an inner surface 260, 265 and an outer surface 250, 255. The inner surface 260, 265 may be supported on the outer surface 180 of the former 100. The ribs 210, 220 are arranged around the outer surface 180 of the former 100 to provide a support structure around the former 100 without obstructing the aperture 110. In an embodiment, the ribs 210, 220 may be formed from a material sufficiently rigid to be self-supporting which may provide increased strength. Each rib 210, 220 may be any suitable shape and material such that the plurality of ribs 210, 220 when arranged about the former 100, provide a support structure. The ribs 210, 220 may be supported in features 150 about the outer surface 180 of the former 100, where the features 150 may be blind apertures, grooves or another structure configured to support the ribs 210, 220.

In an embodiment illustrated in Figures 2 and 3, the ribs comprise a plurality of sets of ribs arranged in different orientations. The ribs in the embodiment shown in Figures 2 and 3 are sheet-like and generally planar, but in an alternative embodiment, the ribs may be formed as a frame or structure comprising an outer surface supported on members extending from the former. In some embodiments the ribs 210, 220 comprise a first set of ribs 210 and a second set of ribs 220. Each set of ribs 210, 220 may be supported in respective features 150, 160 about the exterior of the former 100. In one embodiment, the first set of ribs 210 are supported on the former 100 in a first set of grooves 150 and the second set of ribs 220 are support on the former 100 in a second set of grooves 160. The grooves 150, 160 may fully or partially span the former 100 in any direction relative to the longitudinal axis 120. The first set of ribs 210 and the first set of grooves 150 may be arranged along an axis generally parallel to a longitudinal axis 120 of the aperture 110. The second set of ribs 220 and the second set of grooves 160 may be arranged along an axis generally perpendicular to a longitudinal axis 120 of the aperture 110, i.e. along the transvers axis of the aperture 110. The ribs 210, 220 may be arranged to be spaced apart about the former 100. As such, at least some of the ribs extend from an intermediate position 212 about the former, as well as proximal to the aperture 110 openings 211. In an embodiment at least some of the first set of ribs 210 may be configured to interlock with at least some of the second set of ribs 220. In the embodiment shown in Figures 2 and 3, the two sets of ribs 210, 220 may have opposing slots 215, 225. The slots 215, 225 may be configured to interlock the two sets of ribs 210, 220. The slots 215, 225 may be formed in the outer surface 250 of the first set of ribs 210 and the inner surface 265 of the second set of ribs 220 or the slots 215, 225 may be formed in the outer surface 255 of the second set of ribs 220 and the inner surface 260 of the first set of ribs 210. The slots 215, 225 may be configured so that the outer surface 250 of the first set of ribs 210 is flush with the outer surface 255 of the second set of ribs 220 when the ribs 210, 220 are interlocked, thereby defining a single outer support surface in at least two orientations. Each set of ribs 210, 220 may be supported by grooves 150, 160 in the former 100 as well as by the other set of ribs 210, 220. In an embodiment, the first set of ribs 210 and the second set of ribs 220 may be configured to interlock in a unique way such that there is only one way in which the sets of ribs may be assembled, thereby aiding assembly of the detector 100. In some embodiments, the features 150, 160 in the former 100 and each of the ribs may be marked, such as labelled or colour-coded to identify where each rib should be supported on the former. In this way, the arrangement of the ribs 210, 220 may reduce the construction cost and complexity of the detector.

At least some of the first set of ribs 210 and at least some of second set of ribs 220 may be fused together. The fusing may occur once the ribs 210, 220 are assembled about the former 100. The sets of ribs 210, 220 may be fused together at locations about the ribs where the ribs 210, 220 interlock. The ribs 210, 220 may be fused together. The fusing may use a welding or bonding technique, such as using an adhesive.

In an embodiment, there may be one or more apertures 213, 214, 222 through the faces 270, 275 of each rib. The apertures 213, 214, 222 allow a potting material to flow between the ribs 222, 210 as discussed in more detail below. The apertures 213, 214, 222 may be fully contained within each face 270, 275 of the ribs 222, 213 i.e. the aperture be entirely surrounded by the rib, or may extend inward from the edge of the faces 270, 275 of the ribs 214. The rib shape and the arrangement of apertures shown in Figures 2 and 3 is for illustrative purposes and other arrangements may be envisaged. The ribs 210, 220 may be any appropriate shape configured to be supported on the former 100 and provide a support structure. The outer surface 250, 225 of the ribs 210, 220 may be smooth or curved as well as the straight as illustrated in the embodiments shown in the Figures. The apertures may be of any shape including, but not limited to, circular, semi-circular, rectangular or triangular. The apertures 213, 214, 222 may be distributed across the ribs in any pattern. The apertures 213, 214, 222 which extend past the edge of the ribs 214 may be in the first set 210 and/or the second set of ribs 220 as well as on the radially outward edge of the ribs as well as the radially inward edge of the ribs.

The ribs 210, 220 form a structural support by which a highly conductive cover 600 may be supported upon the former 100. The outer surface 250 of each rib 210, 220 defines a support on which the highly conductive cover 600 is arranged. The cover 600 may be supported directly on the ribs 210, 220. The cover 600 may be bonded to the ribs 210, 220. The first set of ribs 210 and the second set of ribs 220 may perpendicularly-interlock at generally 90 degrees, as shown in Figures 2 and 3. This arrangement can provide the ribs 210, 220 with strength required to support the cover 600. However, the orientation of ribs 210, 220 described with respect to the embodiments shown in Figures 1 to 3 is for illustrative purposes only. Any suitable orientation or arrangement of the ribs 210, 220 on the former 100 may be used. The ribs 210, 220 may interlock at any angle such that the ribs 210, 220 may support the cover 600. The ribs 210, 220 may extend between the former 100 and the cover 600.

Figure 4 shows a portion 400 of the conductive cover 600 according to an embodiment of the invention. The conductive cover 600, illustrated in Figure 6, may comprise one or more cover portions 400. The cover portion 400 may be configured to cover generally half of the outer surface of the ribs. The cover portion 400 may be cross-shaped with an aperture 530 corresponding to the shape of the aperture 110 in the former 100. The cover portion 400 may be formed from sheet material. The sheet material may be a foldable material. The cover portion 400 may comprise a plurality of planar sections 500 having folds 520 there-between. The cover portion 400 may be cut from a 2D sheet and may be scored with lines to form folds 520 i.e. where a fold line is formed in the sheet material. In an alternative embodiment, the sheet material may be able to bend such that the cover portion 400 contains curves rather than folded edges.

In an embodiment shown in Figure 5, the cover portion 400 is arranged on the outer surface of the ribs 210, 220. The sheet material may be arranged upon the ribs 210, 220 with folded edges 520 that enable the cover portion 400 to follow the contours of the ribs 210, 220. In an alternative embodiment, the sheet material may be able bend such that the cover portion 400 contains curves rather than folded edges which enable the cover to follow the contours of the ribs 210, 220.

The one or more cover portions 400 may form the cover 600, as illustrated in the embodiment of Figure 6. Once arranged upon the ribs 210, 220 the complete conductive cover 600 forms a conductive surrounding for the ribs 210, 220. The joins 510 in the cover may be fused together. Fusing techniques such as soldering, welding or another appropriate fusing technique to form a conductive joint 610 may be used.

The conductive cover 600 arranged upon the support, defined by the outer surface of the ribs 210, 220, may be formed from a foldable or bendable sheet material. The conductive cover 600 may be formed from a highly conductive sheet material. The conductive cover 600 may be formed from a non-magnetic material. The sheet material may be a metal sheet. The metal sheet may be aluminium, brass or cooper, although other conductive foldable materials may be used. A thin material may be chosen for the cover, such as up to approximately 2mm, or 1 mm in thickness, to allow the cover to contract or expand with changes in temperature and to reduce a weight of the detector.

The conductive cover 600 is arranged to make electrical contact with the electrostatic screen 630 on the interior surface 170 of the aperture 110. A conductive join 620 between the electrostatic screen 630 and the conductive cover 600 improves the stability of the metal detector.

A flange 230 may be used in some embodiments to form a conductive join 620 between the conductive cover 600 and the electrostatic screen 630. The flange 230 may be formed from a conductive material. The material used for the flange 230 may be a metal, for example, copper or aluminium. The flange 230, shaped according to the aperture 110, may be arranged around at least a portion of the aperture 110, as illustrated in Figure 2 according to an embodiment of the invention. The flange 230 may be attached to the former 100.

In the embodiment shown in Figures 4 and 5, the flange 230 may be arranged to be flush with the interior surface 170 of the aperture 100. The flange 230 may extend away from the former 100 to be joined with the conductive cover 600. The flange 230 may be joined to the conductive cover 600 using soldering, welding or another appropriate fusing technique to form a conductive joint 620. The material forming the electrostatic screen 630 may extend onto the flange 230 reducing the likelihood of cracks or imperfections forming. The conductive cover 600 may extend perpendicular to the interior surface 170 of the former 100, therefore, the flange 230 facilitates a conductive connection between the electrostatic screen 630 on the interior surface 170 of the former 100 and the conductive cover 600. In some embodiments, the flange 230 may be rigidly attached to the former 100 to reduce movement between the former 100 and the cover 600. The rigid attachment may be achieved by fusing, such as bonding, which may be achieved with an adhesive. The rigid attachment may further reduce a likelihood of cracks forming in the electrostatic screen 630 on the joint between the former 100 and the conductive cover 600.

The joints 610, 620 between cover sections 500 and between the conductive cover 600 and the former 100 may be fluid tight. A potting material may be located in the volume between the former 100 and the conductive cover 600. The potting material may provide the detector with a high mass to improve the sensitivity of the detector by reducing vibrations and temperature changes in the detector. The potting material may be epoxy resin, foam, concrete or an alternative suitable material.

The potting material may be introduced through a closeable aperture (not shown) located in the conductive cover 600. The aperture in the cover may be conductively sealed once the potting material has been inserted. The material may enter the volume between the former 100 and the conductive cover 600 as a flowable material, such as a fluid. The apertures 213, 214, 222 in the ribs 210, 220 are configured to allow the potting material to fill substantially all the volume such that no air pockets remain. The semi-circular apertures 214 shown in the embodiment of Figure 2 to 4 allow the potting material to make contact against the former 100.

During the process of inserting the potting material, the potting material may increase in temperature during the curing cycle due to an exothermic chemical reaction. The potting material may then contract at a later stage of the curing process as it solidifies and its temperature decreases. The conductive cover 600 may be configured to deform in a controlled manner during the potting process. The conductive cover 600 may return generally to its original shape at the end of the potting process allowing the conductive cover 600 to adhere to the solidified potting material ensuring high sensitivity of the detector. Alternatively, the conductive cover 600 may be designed to acquire a new shape at the end of the potting process which also allows the conductive cover 600 to adhere to the solidified potting material.

The conductive cover 600 may be formed from a thin metal sheet, as discussed previously, which may be flexible in response to the changing temperature of the potting material. The conductive cover 600 may expand when the potting material is at a high temperature and contract when the potting material cools. Indentations may be formed in the conductive cover 600 in the areas between the ribs 210, 220 when the potting material cools.

The conductive cover 600 may be bonded to the ribs 210, 220 to help control or reduce deformation of the cover 600 during the potting process. The support of the conductive cover 600 provided by the ribs 210, 220 may be sufficient to allow the potting process to be performed without significant distortion or deformation to the conductive cover 600. Once the potting compound has solidified and adhered to the conductive cover 600, the support of the conductive cover 600 provided by the ribs 210, 200 is no longer required.

A case (not shown) may be arranged to enclose the conductive cover 600 providing an additional outer layer to the detector. The case may additionally enclose the electronics bay. The case may be spaced apart from the conductive cover 600 to allow a volume to exist there-between. The volume between the conductive cover 600 and the case may be filled with a second potting material. The material may be the same or different to that used to fill the volume between the former 100 and the conductive cover 600. The case may be made from stainless steel. Mouldings may be added to the conductive cover 600 or the case. The mouldings may be decorative mouldings to improve the aesthetics of the design.

At least part of an outer surface of the detector may be covered by a coating. The coating may cover the conductive cover 600 or the case in different embodiments, as appropriate. The coating may be a paint or a layer of epoxy. The epoxy may be a food-grade epoxy. The epoxy may be applied as an airless gel coating. The epoxy may be used when the conductive cover 600 or case is made from aluminium. The coating of epoxy can provide a low-cost finish for the conductive cover 600, case or detector.

The described invention provides a metal detector at a lower cost than metal detectors of the state of the art. The ribs provide a support structure which allows a low-cost cover formed of sheet material to be used. The cover may be joined without requiring welding to be used, relatively low cost and low skilled labour methods such as soldering may be used instead. Additionally, the ribs and the cover may be cut to 0.1 mm tolerances leading to smaller performance variations between detectors. Furthermore, the use of a flange 230 to connect the cover to the electrostatic screen 630 provides an improving joint, less prone to forming cracks in the electrostatic screen 630.

The metal detector of the present invention may be manufactured using the following method.

First, the former 100 is provided with an aperture 110 through which objects may be passed when the detector is in use. The set of features 150, 160, such as blind apertures of grooves, may be created about the outer surface 180 of the former 100 configured to support the plurality of ribs 210, 220. Additionally, grooves 140 may be created in the outer surface 180 of the former 100 to receive the one or more coils

130. Once the former 100 has been provided, the one or more coils 130 are arranged around the former 100 to surround the aperture 110. The coils 130 may comprise the transmitting coil and the receiving coils. The coils may extend away from the former 100 to be received by the electronics bay. The coils 130 may be arranged such that they are situated within grooves 140 on the outer surface 180 of the former 100. The coils may be secured in the grooves with an adhesive.

Once the coils 130 have been arranged around the former 100 the plurality of outwardly extending ribs 210, 220 are supported on the former 100. The ribs 210, 220 extend outwardly relative to the central axis 120. The plurality of ribs 210, 220 are supported such that at least one of the plurality of ribs extends from an intermediate position 212 along the former 100. Supporting the ribs 210, 220 on the former 100 may comprise supporting a first set of ribs 210 in an axis generally parallel to the longitudinal axis 120 of the former 100. Supporting the ribs 210, 220 on the former 100 may further comprise supporting a second set of ribs 220 arranged along an axis generally perpendicular to the longitudinal axis 120 of the former 100, i.e. along the transvers axis of the aperture 110. Additionally, supporting the plurality of ribs 210, 220 on the former 100 may comprise locating at least some of the plurality of ribs 210, 220 in features 150 about the outer surface 180 of the former 100.

At least some of the first set of ribs 210 may be interlocked with at least some of the second set of ribs 220. At least some of the first set of ribs 210 may be fused together with at least some of the second set of ribs 220. The first set of ribs 210 and the second set of ribs 220 may be configured to interlock in a unique way such that there is only one way in which the sets of ribs may be assembled. In an embodiment, the features in the former 100 and each of the ribs are labelled to identify where each rib should be located on the former 100.

Prior to supporting the ribs 210, 220 on the former 100, the one or more apertures 213, 214, 222 may be created through each rib. Additionally, the opposing slots 215, 225 may be formed in the first set of ribs 210 and the second set of ribs 220 to facilitate interlocking the ribs. The plurality of ribs 210, 220 comprises the outer surface 250 defining a support and, once the ribs 210, 220 are supported on the former 100, the conductive cover 600 may be arranged upon the support. The conductive cover 600 may be bonded to the ribs 210, 220 to control the deformation of the cover 600 during the potting procedure.

The conductive cover 600 may be composed of the several cover sections 500. The conductive cover 600 may be formed from the sheet material which may be metal. The material may be folded along scored lines or bent to follow the contours of the ribs 210, 220. The cover sections 500 may be folded around a jig to ensure consistency between manufactured detectors. The joins 510 in the cover 600 may be fused using soldering, welding or another appropriate fusing technique to form a conductive joint 610. Before, the conductive cover 600 is arranged upon the support, the flange 230 may be arranged around at least a portion of the aperture 110. The flange 230 may be attached to the former 100.

Once the conductive cover 600 is arranged on the support, the volume between the former 100 and the conductive cover 600 may be filled with the potting material. The potting material may be inserted through an aperture (not shown) on the conductive cover 600. Once the potting material has been inserted, the aperture may be closed and conductive joints created between the aperture and the conductive cover 600.

Once the potting material has been inserted, the interior surface 170 of the aperture 110 may be covered with the layer of conductive material to form the electrostatic screen 630. The material may extend on to the flange 230 from the interior surface of the aperture 110 to provide a conductive join 620 between the conductive cover 600 and the electrostatic screen 630. Once the electrostatic screen 630 has been created the aperture 100 may be coated with the covering or sealing layer or plastic lining.

Additionally, the method may comprise attaching the electronics bay to the conductive cover 600. The case may be arranged to enclose the conductive cover 600 or the conductive cover 600 and the electronics bay. The volume between the case and the conductive cover 600 may then be filled with a second potting material. Furthermore, mouldings may be added to the conductive cover 600 or the case to improve the aesthetics of the design. The steps in the method may be performed in any order suitable of producing the metal detector of the present invention.

It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program. Still further, embodiments of the present invention may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.