NZ528129A - Inductive signal transfer transformer for electric fence signalling - Google Patents

Abstract

An inductive high voltage isolation signal transfer device for use in signalling along electric fence systems and isolating the high voltage fence pulses from the output, includes a pair of axially aligned insulation shrouded coils, one serving as an input with terminals 2 and the other as an output with terminals 10, and coupling a signal by magnetic induction between the input and output terminals. The respective shrouds are configured to fit together to set the separation distance between the coils. This ensures that the coupling between the coils does not have to be calibrated after assembly and that the terminals are separated and isolated in accordance with specified isolation standards.

Description

iwiecruai Office of NT - 7 SEP 2004 PATENTS FORM NO. 5 Fee No. 4: $250.00 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No: 528129/530414 Dated: 9 September 2003 / 23 December 2003 SIGNAL TRANSFER DEVICE WE Gallagher Group Limited, a new Zealand of Kahikatea Drive, Hamilton, New Zealand hereby declare the invention for which I/We pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: 1 SIGNAL TRANSFER DEVICE TECHNICAL FIELD This invention relates to a signal transfer device for electronic circuits whilst maintaining electrical separation between the circuits.

In particular, but not limited to, this device is intended for use in electrified fence applications.

BACKGROUND ART Electric fence systems are well known within the farming industry and are used extensively for containing stock within a defined area, or to deter animals from 10 entering areas where they are not wanted - such as for example crops, roadways, buildings, dangerous terrain and so forth.

Electric fence systems are also used extensively to provide security barriers to deter or stop intruders from entering or leaving prohibited areas such as for example power stations, military installations, prohibited government buildings, or 15 prisons.

Some electric fence systems can be quite small (such as where a single length of wire is used to separate an area for strip grazing), however the majority of systems are quite extensive and generally consist of a large single network which can have several kilometres of wire connected to the energiser.

In security applications several sections of electric fence maybe independently monitored.

Energisers are typically connected to the mains power however there are a great number of energisers that are battery powered or even solar powered. 2 James & Wells ref: 122236/16 There is a need within the electric fence industry for an improved electrical separation system between the electrical input circuit and the output circuit connected to the fenceline, particularly in relation to the required separation distance that complies with the required IEC safety standards 60335-2-76, and its 5 National country derivatives, which at the same time allows circuitry which can monitor fenceline parameters.

In the past a variety of different methods have been used, the most common of which has used Photonics.

There are significant difficulties with these, specifically with regard to alignment and 10 the need for in-circuit calibration.

Obviously the integrity of the electric fence is paramount as a single breach will be enough to allow the passage of animals or intruders past the fence.

Historically the only method of determining the integrity of the fence was for an operator to walk along the fenceline checking for damage including the possibility 15 of the fence being cut, or for the presence of objects lying against the fence - such as fallen trees or other vegetation.

Due to the very nature of the electric fence system the wire is exposed to all types of adverse conditions, including extreme weather conditions, contact from animals or machinery such as tractors etc and in the case of security fencing they may 20 have been compromised by having an insulating material thrown over them in order for intruders to pass by them, or the wires may have been cut.

There have been many attempts to improve this situation, particularly with the advent of remote monitoring units which are intended to be situated on the fenceline at some distance from the energiser and to report back to the energiser 25 with some information with respect to the fenceline parameters. 3 James & Wells ref: 122236/16 United States Patent No. 4297633 discloses such a system which has a number of remote units (responders) that are situated at various points along the fence network away from the energiser.

The responder reports back to the energiser after each energiser pulse, or after a 5 preset number of pulses, the return signal form gives an indication of the fence's effectiveness at that immediate point.

If the fenceline parameters fall below a preset level then an alarm will be activated.

Another of these systems is disclosed in New Zealand Patent No. 500355. This system consisted of a hand held monitoring unit that when placed in contact with 10 the electrified fence will send an electrical signal along the fenceline in order that the base unit (generally the energiser) can read the transmitted signal and determine certain fenceline parameters from these results.

New Zealand Patent No. 514126 discloses a monitoring system for an electric fence, where a base station (energiser) includes a communication module that 15 contains a recorded message. This message can be automatically transmitted to the operator by mobile phone, landline or radio transmission in order to inform the operator of the fault condition on the fenceline.

In some instances the operator can transmit a code to the base station in order to turn off the base station or to turn it back on again.

It should be understood that all such methods which use the fenceline for communications require both the transmitter and the receiver to be attached to the fence with sufficient electrical isolation from the high-voltage pulses to ensure safety and also to prevent the possibility of dangerous mains power being present on the fence due to an equipment failure. 4 James & Wells ref: 122236/16 Following is a list of the current methods for measuring the signals that are propagated along an electric fence system (whilst maintaining the required level of electrical isolation laid down in the IEC safety standards 60335-2-76). 1. Photonics (opto-isolators) - generally in the form of Light Emitting Diodes 5 photo transistors, photo detectors and other light sensitive electronic devices. These are used extensively in the current range of energisers that are available as they are quite small and allow signals to be passed without any electrical connection between the circuits. 2. Capacitance plates. 3. Windings incorporated in the output pulse transformers.

Each of these systems are far less than ideal as they are limited by inherent problems and characteristics.

The problems associated with Photonics systems include:- non-linear signal transfer characteristics, a large variation in performance between devices 15 (therefore post-production calibration is required before these devices can be installed in an electric fence system), signal transfer characteristics vary with temperature, signal transfer characteristics will also vary over time as the unit ages, these devices also have a poor dynamic operating range.

The systems incorporating Capacitance plates are limited by at least the following 20 problems:- The Capacitance plates required are large and take up a lot of room in the energiser casing, they are also expensive to manufacture and their accuracy depends upon the earthing systems. Their signal transfer characteristics are not repeatable between different power supply distribution systems.

James & Wells ref: 122236/16 Some of the problems associated with sensing windings incorporated in the output pulse transformers are as follows:- These systems generally have non-linear signal transfer characteristics and, due to their coupling to the primary winding circuit, the sensing windings are 5 unable to make any other measurements on the secondary circuit - such as fence return voltage, earth loss voltage etc., also these systems are not suitable for the transfer of out of band communication signals through the pulse transformer.

Another significant problem with the aforementioned systems is that when a field 10 failure occurs, replacement components need to be recalibrated in situ before they can be used again.

This generally means that the unit must be returned to the factory so that the repaired unit can be recalibrated.

In all of the above examples there simultaneously exists the need for the input 15 circuitry to be separated from the output circuitry in accordance with the standards laid out in IEC 60335-2- 76. The aforementioned examples do not all address this issue, or where they do, then they require calibration when incorporating the data transfer application. This calibration is currently undertaken in the factory or service centre. In some cases, such as component replacement field calibration is 20 desirable but is not practical.

There are many applications of electric fence systems where two-way communications are highly desirable. This has particular relevance to large electric fence systems and to security applications. 6 James & Wells ref: 122236/16 Therefore there is a need within the electric fence industry for an improved system that complies with the required electrical separation standards of IEC safety standards IEC 60335-2-76 and which also allows a reliable method for monitoring fenceline parameters through signal transfer without calibration, and which is 5 impervious to thermal drift or aging, and is not compromised by such things as, but not limited to, high energy pulses typically experienced on electric fences.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their 10 authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components 20 or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent 25 from the ensuing description which is given by way of example only. 7 James & Wells ref: 122236/16 DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided a signal transfer device which includes, at least two signal transfer elements, where the signal transfer device is 5 constructed so there is a fixed separation distance between an unprotected input terminal and an unprotected output terminal of the signal transfer device, wherein one signal transfer element is configured to generate a magnetic field and one signal transfer element is configured to sense the generated magnetic field, the signal transfer device being characterized in that the signal transfer elements are 10 located substantially along a common axis with no electrical connection between the signal transfer elements.

According to an additional aspect of the present invention there is provided a signal transfer device substantially as described above which includes, a signal transfer device which includes, at least two signal transfer elements, 15 where the signal transfer device is constructed so there is a sufficient separation distance between unprotected input terminal and an unprotected output terminal of the signal transfer device to meet the minimum regulatory isolation creepage distance and insulation breakdown voltage between a primary circuit and a fence circuit, and one signal transfer element is configured to generate a magnetic field 20 and one signal transfer element is configured to sense the generated magnetic field, the signal transfer device being characterized in that the signal transfer elements are located substantially along a common axis with no electrical connection between the signal transfer elements.

According to a further aspect of the present invention there is provided a signal 25 transfer device, which includes 8 James & Wells ref: 122236/16 at least two signal transfer elements, wherein the signal transfer device is constructed so there is a sufficient separation between an unprotected input terminal and an unprotected output terminal of the signal transfer device to meet the minimum isolation creepage distance and insulation breakdown voltage 5 specified by IEC60335 between the primary circuit and the fence circuit, and one signal transfer element is configured to generate a magnetic field and one signal transfer element is configured to sense the generated magnetic field, characterised in that the signal transfer elements are located substantially on a common axis with no 10 electrical connection between the signal transfer elements.

It should be appreciated that in preferred embodiments of the present invention the signal transfer element may include a bobbin onto which a conducting winding is located and which has a pair of terminals located at one distal end of the bobbin for connection into a circuit.

It should also be appreciated that in preferred embodiments of the present invention the bobbin assembly may be encapsulated within an insulating shroud which electrically isolates the winding along at least part of its length up to the area that is fitted with the terminals.

It should be appreciated however that in some embodiments of the present 20 invention the bobbin is wound with windings which have an insulated exterior surface. These windings can provide the same level of electrical isolation as a shroud.

It should also be noted that the bobbin isolates both the primary and the secondary coils from a hollow centre of the bobbin. 9 James & Wells ref: 122236/16 It should also be appreciated that although in preferred embodiments of the present invention the signal transfer elements of a single signal transfer device are axially aligned along a single axis, but in some embodiments of the present invention the signal transfer elements may be offset from one another although 5 may still be considered substantially axially aligned.

Preferably the present invention may be adapted to provide a signal transfer device configured or adapted to block high voltage pulses present at an input terminal and to pass data signals through to an output terminal.

In a preferred embodiment the signal transfer device may include a core aligned 10 along the common axis of the signal transfer element. In the further preferred embodiment such a core may be inserted into a hollow centre of a bobbin or bobbins of signal transfer elements incorporated into the signal device provided.

In the further preferred embodiment the signal transfer device may include a magnetic core. However those skilled in the art should appreciate that non-15 magnetic cores may also be provided if required.

The use of a bobbin with a hollow central region allows the body of the bobbin to isolate a conducting winding wire from a core inserted through the centre of the bobbin.

It should be appreciated that throughout the present specification the term "bobbin" 20 should be understood to mean a cylindrical former around which an electrical winding is placed.

However in some embodiments the bobbin can be constructed with a non-circular cross-section, examples of which could be a square former, a triangular former, an oval former, etc.

James & Wells ref: 122236/16 It should also be appreciated that throughout the present specification the term "shroud" should be understood to mean an insulated cover that fits around the wound bobbin along at least part of the windings.

Throughout the present specification the term "axially aligned" should be 5 understood to mean that a common axis is used or there is no substantial difference in the axis of each of the main components.

In operation, the present invention generates a magnetic field in one signal transfer element, a percentage of which is sensed by the complimentary signal transfer element.

This allows for a level of signal transfer from one circuit to another without any physical or electrical connection between the circuits.

It should be appreciated that in some embodiments the present invention a third signal transfer element may be incorporated into the signal transfer device in order that a representation of the original signal can be used in a further circuit, such as 15 a monitoring circuit, feedback circuit, or to an additional output circuit.

According to another aspect of the present invention there is provided a signal transfer device, including two signal transfer elements, wherein the signal transfer elements are substantially axially aligned, providing a substantially linear transfer signal response across the 20 operational range of the present invention, characterised in that the present invention is installed without the need for any form of calibration. 11 James & Wells ref: 122236/16 According to another aspect of the present invention there is provided a signal transfer device, including two coil assemblies, wherein each of which is configured to include a bobbin onto which a conducting winding is located, and two shrouds, wherein each shroud is configured to fit over the windings of a coil assembly, characterised in that in operation, the coil assemblies are substantially axially aligned with one another.

A signal transfer device configured as discussed above may provide a preset level 10 of electrical isolation between the core assemblies provided.

In some preferred embodiments of the present invention the signal transfer device includes a magnetic core.

In preferred embodiments of the present invention the terminals are configured as "blade" terminals that are pushed into complementary socket terminals fitted to a 15 printed circuit board or any other similar device to which the present invention is to be connected.

In preferred embodiments of the present invention the shrouds are configured to fit together securely in a manner in which the relative positioning of the two coil assemblies will be substantially the same and highly repeatable.

It should be appreciated that this will ensure that the signal transfer level does not vary significantly between different examples of the same signal transfer device. 12 James & Wells ref: 122236/16 It should also be appreciated that in preferred embodiments of the present invention the coil assemblies abut each other in a substantially mirrored orientation wherein the shrouds fit together in secure arrangement in order to ensure that the coupling between the coils remain substantially constant.

In a preferred embodiment all signal transfer elements incorporated into the signal transfer device may be substantially identical. In such instances high volume manufacturing techniques may be employed to produce a significant volume of signal transfer elements, where two or more of these elements can be used in the provision of single signal transfer device. This configuration of the present 10 invention substantially simplifies the manufacturing process involved and may also reduce the cost of manufacturing the resulting signal transfer device.

It should be appreciated that in most preferred embodiments of the present invention, the separation distance between signal transfer elements may determine the strength of magnetic field sensed by a signal transfer element. In some 15 embodiments, the thickness of the bobbin and/or the shroud sections that are located between the coils will be used to govern the coupling level between the coils, and hence the magnetic field strength sensed by a signal transfer element.

However, this should not be seen to be limiting the present invention in any way as in some other preferred embodiments a spacer may be inserted between the 20 bobbins, and/or the bobbins and shrouds can be constructed in a manner where they do not intrude between the end faces of the coils. For example, in some instances a spacer may be inserted between the bobbins of at least two adjacent signal transfer elements, or alternatively the spacer may be inserted between the shrouds of two adjacent signal transfer elements. 13 James & Wells ref: 122236/16 It is envisaged that in most embodiments of the present invention where there is no magnetic core fitted, the magnetic coupling between the coils will be in the region of only one percent or less.

Once again, this should not be seen to be a limitation on the present invention in 5 any way as in other embodiments the coil assemblies can be constructed in a manner wherein the coupling level is one percent or greater.

In embodiments of the present invention that include a magnetic core the level of coupling between the coils can be orders of magnitude greater than those embodiments without a magnetic core.

It should also be appreciated that in embodiments of the present invention where a magnetic core is not required, that a non-magnetic core can be used to assist in the correct alignment of the coil assemblies.

Although in preferred embodiments of the present invention, the coil assemblies abut each other at an end face and do not physically overlap in any manner, this 15 should not be seen to be limiting the present invention as in other embodiments it is equally feasible for one coil assembly to be inserted within a void constructed within the bobbin of other coil assembly and on the same central axis.

This configuration can be utilised to increase the level of coupling between the coils, particularly when no magnetic core is present.

In a preferred embodiment the shroud may be configured to provide an external cover for a bobbin and may also include an internal core receiver where the body or main section of a bobbin are located between these two components or elements. The bobbin may be sandwiched between the internal core receiver and exterior cover of the shroud, there by allowing the shroud to isolate the conducting 14 James & Wells ref: 122236/16 winding held by the bobbin from a core inserted through a hollow internal core receiving component.

In a further preferred embodiment at least one end of the shroud's core receiving component may be closed. In such embodiments a pair of shrouds provided for 5 adjacent signal transfer elements may encapsulate or enclose a core, there by isolating the conducting windings involved from the core within the interior core receiving sections of the shrouds.

In a further preferred embodiment the bobbin provided may include at least one partition or channels formed along its length. These partitions may divide up the 10 group of windings applied to the top surface of the bobbin into a set or fixed number of winding banks. The provision of such partitions allows for the accurate and highly repeatable winding of conductors across the surface of the bobbin. Reducing the space in which a winding is to be applied in turn will aid the accuracy with which the winding can be laid down onto a bobbin. This is of advantage in the 15 case of the present invention to ensure effective isolation distances are provided across the windings applied, and also to ensure a consistent voltage drop across the entire length of windings.

It should be understood that the present invention can be used in a variety of applications where a signal transfer is required without any direct electrical contact.

One major area for use of the present invention within an electrical fence energiser is to transfer a measurement signal from the secondary circuit that is connected to the fence, to the primary circuit that is connected to the mains while maintaining the level of isolation for safety required by international standard IEC60335-2 and its national derivatives.

Another major area for use of the present invention will be to facilitate two way James & Wells ref: 122236/16 signal communications along a length of an energised fenceline, wherein one coil assembly is connected to a transceiver circuit and the other coil assembly is connected to the fenceline circuit.

With the use of the present invention, sampling of the high voltage energiser pulse 5 (which is necessary to monitor the performance of the energiser and/or fenceline), can be done without the need for complicated and costly high voltage measuring circuits, or for circuits to step down the voltage in order that the pulse can be safely monitored, as the relatively low coupling available in most embodiments of the present invention without the inclusion of a magnetic core, will reduce the induced 10 voltage to a level where relatively low voltage measuring equipment can be used.

It should also be appreciated that in some embodiments of the present invention separate signal transfer devices are used for the transmission of, and for the reception of, signals when connected to the fenceline.

It can be seen from the foregoing that the present invention has several distinct 15 advantages over all the current systems available, whilst still conforming with the IEC Standards 60335-2-76.

One major advantage over the opto-couplers currently used within the art is that the present invention is impervious to the effects of changing temperature, aging, change in signal response over the operational range etc.

Opto-couplers are notorious for being unstable in their performance as well as being non-linear over a signal range.

This means that each opto-coupler system has to be aligned manually as well as each system having to be calibrated and the software used with the system will need to increase the measured signals as the opto-couplers have a non-linear 25 response. 16 James & Wells ref: 122236/16 Whereas, with the present invention there is a linear transfer signal response and therefore the output will have a direct correlation to the input level. This not only means that no individual calibration of each signal transfer device is necessary, but also that no linearisation will be required for its operation.

As stated previously, the present invention meets the requirements of IEC 60335-2-76 standard as there is at least a 30mm separation between the unprotected input and unprotected output connectors as the whole of the coil assemblies are enclosed within the protective and insulating shroud (the IEC 60335-2-76 Standard currently requires a 30mm minimum creepage distance).

It should be appreciated that in all preferred embodiments of the present specification the bobbins and the shrouds are constructed of a suitably durable insulating material which is chosen to also conform with the latest IEC standards (typically not less than 20kV isolation), whilst allowing the coil assemblies to remain in close proximity to each other, or they may even be abutted, and therefore 15 enables the magnetic coupling between the coils, that is necessary for the transfer of electrical signals.

Another significant advantage of the present invention is that due to its simplicity of construction and installation, in-field fault finding by engineers will be made much more straightforward as no calibration will be required for repaired equipment and 20 therefore it will not have to be returned to the factory, also the engineers undertaking the fault finding will have to carry less stock than would be previously required.

BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the following 25 description which is given by way of example only and with reference to the 17 James & Wells ref: 122236/16 accompanying drawings in which: Figure 1 is a diagrammatical representation of the cross-sectional view of a preferred embodiment of the present invention with the bobbin and shroud separated; Figure 2 is a diagrammatical representation of a cross-sectional view of a preferred embodiment of the present invention with the shroud fitted over the bobbin, and Figure 3 is a cross sectional representation of one preferred embodiment of the present invention where Figure 3a shows a complete signal 10 transfer device without an integral core fitted, and Figure 3b shows the same device with a core fitted.

Figure 4 are block diagrams showing the typical connection of the present invention into: 4(a) a measurement circuit, 4(b) a transceiver circuit, and 4(c) a circuit with separate transmitter and receiver Figure 5 is a cross section representation of one alternative embodiment of the present invention which includes a bobbin on a number of partitions spaced along the length of the bobbin.

BEST MODES FOR CARRYING OUT THE INVENTION With reference to the figures, there is illustrated a signal transfer device (generally 20 indicated by arrow 1) as configured in accordance with a preferred example of the present invention.

The signal transfer device (1) consists of two main sub-assemblies which are formed from a bobbin (2) and a shroud (3). 18 James & Wells ref: 122236/16 The bobbin (2) is constructed of a conductor coil former (4) onto which the conductor coils (5) are wound, an end face (6) and a backing plate (7), both of which ensure the correct location of the conductor coils (5).

The other side of the backing plate (7) is joined to a mounting block (8).

The mounting block (8) has a locator pin (9) to ensure that the bobbin (2) is correctly located within the circuit to which it is connected.

The mounting block (8) has two connector terminals (10) to which either end of the conductor coils (5) are terminated.

The backing plate (7) has at least one conductor channel (11) through which 10 conducting connector terminals are passed from the conducting coils (5) to the terminals (10). It should be noted that for clarity these connector terminals are omitted from the drawings.

The shroud (3) consists of an outer sheath (12) that is connected to an inner sheath (13) in a configuration so that when the shroud (3) is fitted over a bobbin 15 (2), then the conductor coil former (4), the end face (6) and the conductor coils (5) fit in the integral void (conductor void, 14), that is formed between the inner sheath (13) and the outer sheath (12) of the shroud (3).

The inner sheath (13) is constructed of such dimensions that it will fit snugly within the void (15) within the centre of the conductor coil former (4).

The inner sheath (13) is constructed with a central void (16) constructed of the appropriate dimensions for the insertion of a core (18) (magnetic or otherwise) if desired.

Figure 3a shows a complete signal transfer device (1) wherein the two bobbin (2) and shroud (3) assemblies are connected together at their distal end faces from 19 James & Wells ref: 122236/16 the circuit connectors (10) and figure 3b shows the same configuration with the insertion of a ferrite core (18).

The shroud (3) also includes a number of lugs (17) that are designed to firmly locate within the complementary sockets (not shown for clarity) of the 5 corresponding shroud (3) of the other side of the signal transfer device (1).

An example of the operation of the present invention for measuring fenceline and/or energiser performance is as follows: One signal transfer element (2,3) is connected to the high-voltage fenceline via a high impendence component (19), the other side of the signal transfer element 10 (2,3) is connected to earth (25).

The complementary signal transfer element (2,3) within the signal transfer device (1) is connected between earth and the input to a low-voltage measurement circuit (20).

The two signal transfer elements (1) are connected together by using the lugs (17) 15 on their shrouds (3) to ensure a secure fit. There will be no high permeability core (18) fitted as only a small fraction of the fenceline signal is required for accurate measurement.

Examples of the operation of the present invention (1) for transferring communication signals bi-directionally are as follows: In systems where a communications transceiver (21) is used (transmitter (22) and receiver (23) in one package) then only one signal transfer device (1) is necessary.

The input/output signal connection (26) of the transceiver (20) is connected to one terminal of one of the signal transfer elements (2,3) with the other connection being grounded (25).

James & Wells ref: 122236/16 The other signal transfer element (2,3) is connected between earth (25) and a high impedance component (19) (the other side of which is connected to the fenceline (24).

The core (18) is fitted if necessary to improve the coupling of low-level signals.

In systems that require separate transmitter (21) and receiver (23) circuits then two signal transfer devices (1) will be connected in parallel, one of which will be connected to a communications signal transmitter (22) and the other to a communications signal receiver (23) in the same manner as in the previous example for a transceiver (21).

These examples clearly show that there is no electrical connection between the signal transfer elements (2,3) of a signal transfer device (1), this isolates the measurement (20) or communications circuits (21,22,23) from the high-voltage fenceline (24) pulses whilst enabling the accurate transfer of signals to and from the fenceline (24).

Figure 5 is a cross section representation of one alternative embodiment of the present invention which includes a bobbin with a number of partitions spaced along the length of the bobbin.

In the embodiment shown with respect to Figure 5 the bobbin (2) has a number of partitions (30) formed along its length. These partitions divide up or implement banks of wound conductor coils (5) distributed along the length of the bobbin. As can be seen from Figure 5 even and reproducible layers of windings are trapped in the relatively small banks provided by the partitions (5). This ensures a consistent voltage drop across the entire the length of the bobbin (2) and also provides for a consistent manufacturing of reproducible banks of conductor coils (5).

Aspects of the present invention have been described by way of example only and 21 James & Wells ref: 122236/16 it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof. 22 James & Wells ref: 122236/16

Claims (20)

WHAT WE CLAIM IS:

1. An inductive electrical signal transfer device which includes at least two inductive electrical signal transfer elements, where the inductive electrical signal transfer device is constructed so that there is a separation distance between an unprotected input terminal and an unprotected output terminal of the inductive electrical signal transfer device, wherein one inductive electrical signal transfer element is configured to generate a magnetic field and one inductive electrical signal transfer element is configured to produce a signal in response to the generated magnetic field, wherein the inductive electrical signal transfer elements are located substantially along a common axis with no electrical connection between the signal transfer elements, and wherein at least one inductive electrical signal transfer element is encapsulated by an insulating shroud, wherein two shrouds are configured to fit together to set the separation distance between the two inductive electrical signal transfer elements.

2. An inductive electrical signal transfer device as claimed in claim 1 wherein the distance between the input terminal and output terminal of the transfer device maintains a safe level of electrical isolation as defined by International Standard IEC60335-2-76.

3. An inductive electrical signal transfer device as claimed in claim 1 or claim 2 wherein the transfer device is adapted to block high voltage pulses present at an input terminal and to pass data signals through to an output terminal. 23

4. An inductive electrical signal transfer device as claimed in any previous claim wherein all inductive electrical signal transfer elements incorporated into the inductive electrical signal transfer device are substantially identical.

5. An inductive electrical signal transfer device as claimed in any previous claim wherein a terminal of a inductive electrical signal transfer element is provided by a blade terminal.

6. An inductive electrical signal transfer device as claimed in any previous claim wherein the inductive electrical signal transfer device includes a core aligned along the common axis of the inductive electrical signal transfer elements.

7. An inductive electrical signal transfer device as claimed in claim 6 wherein a magnetic core is provided.

8. An inductive electrical signal transfer device as claimed in claim 6 wherein a nonmagnetic core is provided.

9. An inductive electrical signal transfer device as claimed in any previous claim wherein a inductive electrical signal transfer element includes a bobbin onto which a conducting winding is located, said conducting winding being associated with a pair of terminals located at one end of the bobbin.

10. An inductive electrical signal transfer device as claimed in claim 9 wherein the bobbin is provided by a cylindrical former.

11. An inductive electrical signal transfer device as claimed in either claim 9 or claim 10 wherein the bobbin isolates the conducting winding from a core inserted through the centre of the bobbin. /nf®'/ectoa7£-—» )LEd 13. 14. 15. 16. 17. 18.

An inductive electrical signal transfer device as claimed in any one of claims 9 to 11 wherein an insulating shroud isolates the conducting winding from a core inserted through the centre of a bobbin.

An inductive electrical signal transfer device as claimed in every one of claims 9 to 12 wherein the separation distance between inductive electrical signal transfer elements determines the strength of magnetic field sensed by a inductive electrical signal transfer element.

An inductive electrical signal transfer device as claimed in claim 11 wherein the thickness of the shroud determines the strength of magnetic field sensed by a inductive electrical signal transfer element.

An inductive electrical signal transfer device as claimed in any one of claims 9 to 14 which includes a spacer inserted between the bobbins of at least two adjacent signal transfer elements.

An inductive electrical signal transfer device as claimed in any one of claims 12 to 15 which includes a spacer inserted between the shrouds of at least two adjacent inductive electrical signal transfer elements.

An inductive electrical signal transfer device as claimed in any one of claims 9 to 11 wherein a bobbin is wound with conductive windings said windings having an insulated exterior surface.

An inductive electrical signal transfer device as claimed in any one of claims 9 to 17 wherein a bobbin includes at least one partition.

An inductive electrical signal transfer device which includes, at least two inductive electrical signal transfer elements, where the inductive electrical signal transfer device is constructed so there is a sufficient separation 25 distance between unprotected input terminal and an unprotected output terminal of the inductive electrical signal transfer device to meet the minimum regulatory isolation creepage distance and insulation breakdown voltage between a primary circuit and a fence circuit, and one inductive electrical signal transfer element is configured to generate a magnetic field and one inductive electrical signal transfer element is configured to produce a signal in response to the generated magnetic field, the inductive electrical signal transfer device being characterized in that the inductive electrical signal transfer elements are located substantially along a common axis with no electrical connection between the signal transfer elements, and wherein at least one inductive electrical signal transfer element is encapsulated by an insulating shroud, wherein two shrouds are configured to fit together to set the separation distance between the two inductive electrical signal transfer elements.

20. An inductive electrical signal transfer device which includes, two coil assemblies wherein each of the coil assemblies includes a bobbin onto which a conducting winding is located, and two shrouds wherein each shroud is configured to fit over the windings of a coil assembly, and wherein said two shrouds are configured to fit together to set the separation distance between the two inductive electrical signal transfer elements, the inductive electrical signal transfer device being characterized in that the coil assemblies are substantially axially aligned with one another. 26 An inductive electrical signal transfer device substantially as herein described with reference to and as illustrated by the accompanying drawings and/or examples. GALLAGHER GROUP LIMITED by its Attorneys / JAMES & WELLS ZptUQl 2$ m.z. Jai^200? 27 I