WO2014135850A2

WO2014135850A2 - Cable structure and connection assembly method

Info

Publication number: WO2014135850A2
Application number: PCT/GB2014/050611
Authority: WO
Inventors: David Robert Smith
Original assignee: Contour Electronics Limited
Priority date: 2013-03-04
Filing date: 2014-03-03
Publication date: 2014-09-12
Also published as: GB2511495B; WO2014135850A3; GB201303763D0; GB2511495A

Abstract

An electrical cable is proposed, comprising a conductive core, first and second insulation layers, made from materials having differing and complementary properties in appropriate ratios to provide necessary mechanical, dielectric and fire resistance properties. A method of assembling a cable and connector assembly for use in high voltage, pressurised, sterile environments is also proposed.

Description

CABLE STRUCTURE AND CONNECTION ASSEMBLY METHOD

The present invention relates to an electrical cable and a related connector assembly. In particular the invention relates to an arrangement of layers of insulation around a conducting element for an electrical cable, suited in particular to medical uses. The invention further relates to a method of assembling conductors and insulating members to create an electrical connector assembly particularly suited to medical uses. Background to the Invention

Electrical devices are increasingly used in medical fields. The implementation of electrical and electronic devices which are suited to the highly sterile and potentially high-risk areas of use associated with surgery and treatment of patients, in particular with keyhole surgery techniques, present new problems. In relation to the present invention, a need has been identified for a cable which meets a number of requirements of a particular medical application in which the cable must be highly flexible, sufficiently durable and resistant to a number of factors such as, heat sources, fire and gamma radiation, which may be encountered in particular surgical applications. Further, any conductor of the cable and conducting elements in the assembly will be charged to very high voltages, in the region of ten thousand volts and higher. This brings further challenges in relation to leakage of static charge through any insulation used, and the associated dangers of a shock to a patient, or at least equally importantly, potential shock to staff or medical professionals operating on a patient. In the past, medical grade cables have been proposed which can meet certain requirements relating to radiation resistance or flexibility, but it has been challenging to find a sufficient balance of dimensions, durability, resistance to charge leakage and mechanical strength. Further, methods of connecting parts of an electrical connector assembly together in a sufficiently sterile, durable, reliable manner whilst providing resistance to current or static charge leakage, and an air-tight seal are desirable. Summary of the Invention

In consideration of the drawbacks of the prior known cables, the present invention proposes an electrical cable comprising: a conductive core;

a first insulation layer; and

a second insulation layer;

the first insulation layer comprising LLDPE; and

the second insulation layer comprising PVC.

It has been found that a first insulation layer comprising LLDPE (linear low density polyethylene) combined with a second insulation layer comprising PVC (polyvinyl chloride) can advantageously provide the required combination of mechanical strength, resistance to leakage of static charge, flexibility, and resistance to heat or fire and gamma-radiation / EtO Sterilisable, whilst providing the desired sterile properties for medical uses.

The first insulation layer may be LLDPE and may be within the second insulation layer, which may be made from PVC. This arrangement allows the LLDPE to provide mechanical strength and dielectric strength to resist static leakage and high voltage creepage, while the PVC in an outer layer can provide resistance to fire and gamma radiation and the necessary sterile or sterilisable properties. By combining the two materials in the described manner, a cable of sufficiently low diameter and high flexibility can be created, which has a sufficiently high resistance to high voltage creepage or static leakage and mechanical stresses.

The PVC layer may be combined with or replaced by polyurethane (PU), or thermoplastic elastomer (TPE). The principal advantages associated with the present invention have been identified as being associated with the use of PVC, although the above materials can also be advantageous in the situations and configurations described.

Alternative materials which may be used in combination with or in place of LLDPE may include high-density polyethylene (HDPE), low density polyethylene (LDPE), fluoropolymers, such as FEP (fluorinated ethylene propylene), ETFE (Ethylene tetrafluoroethylene), PTFE (polytetrafluoroethylene) or polypropylene. However, the principle advantages of the invention have been found to be associated with the use of LLDPE for the desired mechanical and dielectric properties, which can also be found in HDPE or LDPE or the other materials described herein for the first insulation layer.

Various configurations for the cable of the present invention can be envisaged, which can meet the desired requirements for outer diameter, strength, flexibility, dielectric strength and suitability for medical applications.

The outer diameter of the conductive core may be in the range of 13% to 35% of the overall diameter of the cable.

The first layer may have a thickness in a range of around 17% to around 68% of the cable radius.

The second layer may have a thickness in a range of around 17% to around 68% of the cable radius.

The thickness of the second, outer, layer may be of greater thickness than that of the first, inner, layer. This can allow the inner layer to provide a degree of mechanical strength and dielectric resistance, without hindering the flexibility of the cable, while the outer layer, having a greater thickness, can provide further mechanical strength and the necessary fire and radiation resistance. The outer layer may be made from a material which is more elastic than the inner layer, more deformable or having a lower modulus of elasticity than the inner layer. This can allow for greater deformation, as necessary, at outer parts of a cable to take place in a more deformable material, to increase the flexibility of the overall cable, whilst the inner layer provides mechanical strength and resistance to high voltage creepage and static leakage.

The outer diameter of the conductive core may be around 25% to 35% of the overall diameter of the cable. The outer diameter of the first layer may be around 45% to 60% of the overall diameter of the cable and the outer diameter of the second layer may be the overall diameter of the cable.

In a particular example, the outer diameter of the conductive core may be around 0.8mm, the thickness of the first layer may be around 0.4mm and the thickness of the second layer may be around 0.7mm. This arrangement has been found to be particularly beneficial in examples where an outer diameter of the overall cable of around 3mm is desirable and these dimensions have been found to provide the required dielectric resistance, fire resistance, resistance to gamma radiation and mechanical strength. A section through a diameter of the cable may comprise approximately 15% conductive core, 17% LLDPE and 68% PVC. In this manner, when a section is cut through an diameter of a cable, and a line is drawn along that diameter, 15% of the line drawn through the diameter will be in the conductive core, 17% will be in LLDPE and 68% will be in PVC, where the outer layers will be present in two separate parts on opposite sides of the conductive core. Therefore, two thicknesses of each layer in the cable adds up to the percentage figures for the LLDPE and the PVC.

A section through a diameter of the cable may alternatively comprise 20% conductive core, 23% LLDPE and 57% PVC. Alternatively, the section through a diameter of the cable may comprise 25% conductive core, 29% LLDPE and 46% PVC. Alternatively, a section through a diameter of the cable may comprise around 30% conductive core, 35% LLDPE and 35% PVC.

The above arrangements can be advantageous in providing a desired mixture of mechanical strength, flexibility of the cable, and meeting criteria for approved medical grade standards, as well as resistance to fire and gamma radiation.

A section through the conductive core may comprise between around 38 to 61 strands of any wire size from 0.05mm diameter to 0.1 mm diameter. These diameters may also be interpreted as 44AWG and 38AWG, respectively.

AWG stands for American Wire Gauge and is a well-known term of reference for wire sizes. Choosing the appropriate number of strands of a particular diameter in the core allows the necessary flexibility and mechanical strength requirement to be met. If too many cores or cores of too great a diameter are used in the cable, then the flexibility can be hindered whilst if too few strands, or strands of too small a diameter are used, then the mechanical strength of the cable may be hindered. An appropriate balance of these properties is therefore desirable.

Alternative arrangements which can be advantageous include a section through the conductive coil comprising between around 37 to 20 strands of any wire size from 0.064mm to 0.127mm (42AWG to 36AWG).

Further advantageous arrangements have been found to comprise around 19 to 7 strands of any wire size from 0.08mm to 0.16mm (48AWG to 34 AWG). Further, a further advantageous arrangement includes a section through the core comprising at least seven strands of any wire size from 0.16mm to 0.321 mm (34AWG to 28AWG).

As will be apparent, an electrical cable substantially described herein with reference to the drawings is arranged in such a manner that it can balance the numerous requirements in certain high voltage medical uses in which a sufficient degree of resistance to high voltage creepage or static leakage is required, in combination with a balance of mechanical strength and flexibility and resistance to fire and gamma radiation, whilst meeting the necessary standards for medical use.

Further difficulties brought about by the numerous requirements of equipment suitable for medical uses occur when it is necessary to connect cables suitable for medical use to other conductors and/or insulating materials, while providing suitable dielectric, mechanical properties in materials suitable for use in medical applications. In addressing the difficulties experienced when connecting such materials, the present invention provides a method of assembling a high voltage cable and connector assembly, comprising the steps of:

applying a primer to an outer part of insulation of an insulated cable;

applying glue to the connecting sleeve and/or the primed insulation and the primed insulator sleeve;

applying heat to the insulator sleeve over primed parts of the insulated cable and connecting sleeve to connect the insulator sleeve to the insulation of the insulated cable;

applying a primer to the outer part of the insulator sleeve;

applying a primer to inner walls of an opening in a connector hub;

placing the connector hub over primed parts of the insulator sleeve; and applying a glue between the connector hub and the insulator sleeve.

Two insulated cables may be crimped or other wised joined together and this may include the use of a connective sleeve. The connecting sleeve is optional, but preferred for best performance of the invention, and may be referred to as a splice crimp. The connector hub may be referred to as a cable hub. The connector assembly and assembly method described herein may be used with any of the cables or cable structures described herein. Applying heat to the insulator sleeve is also an optional step, necessary only if the insulator sleeve is to be heat shrinked to the connector assembly.

The principal difficulties overcome by the assembly method and related connector assembly of the present invention arise because of the importance of creating a reliable and impermeable connection between insulation of an insulated cable and an insulator sleeve for covering at least a part of a conductor element and/or a connector hub connected to the sleeve or insulation of the cable. Certain materials, and in particular the materials of the present invention, used for insulation of a cable and insulator sleeves are generally very difficult to glue together and, as such, multiple method steps are required to ensure a reliable and correctly sealed connection between the different elements. A particular combination of steps performed in the present invention allow a reliable connection to be created, whilst minimising costs associated with buying custom manufactured parts. The multiple priming steps involved help to ensure that the mechanical properties of the overall connector assembly meet the required standards, while the overall connector assembly is also sufficiently resistant to high voltage creepage or static leakage, has the desired mechanical properties and reduces the dependence on particular custom prepared elements for connecting the connector assembly together.

The insulator sleeve may be a heat-shrinkable sleeve and heat may be applied to the heat-shrink sleeve to connect the insulator sleeve to primed and/or glued parts of the insulation of the insulated cable and of the connecting sleeve. This step helps to ensure a tight fit between the elements whilst allowing the primed and glued elements to stick together sufficiently.

The method may further comprise connecting a conductor element of the insulated cable to a second conductor element. This can allow a change of materials of the conductor to be implemented along its length. In particular medical uses, it is advantageous for a conductor element which is used near the body to be made from stainless steel, whilst a conductor element of the insulated cable may be constructed from a cheaper and more flexible material, such as copper, which can increase the utility of the overall connector assembly.

The conductor element of the insulated cable may be connected to the second conductor element by a splice joint, or by a crimped metallic element. This can give the desired mechanical strength whilst avoiding the need for any solders, which solders can result in messy operations which are not necessarily suited to medical applications.

The method may further comprise placing the connector assembly in a vertical orientation such that gravity encourages glue into the interface between the connector hub and the insulator sleeve.

The glue may be applied to the outside of the splice joint or crimped element holding the conductive parts together, to enable appropriate bonding to the insulator sleeve.

The insulation of the insulated cable may comprise PVC, which has advantageous fire and gamma radiation properties, but which is difficult to glue to certain materials, in a clean manner suitable for medical use.

The insulation sleeve may comprise flouropolymer or polyolefin heat shrinkable tubing. These materials are particularly beneficial because of their exceptional dielectric properties, chemical inertness and low flammability ratings.

The insulator cable may comprise a conductor made of a first metal and a second conductor element may be made from a second metal different from the first, these different metals may be a copper conductor, which may be used in the insulated cable, while a stainless steel second conductor element may be used in parts of the connector assembly which are to be used near or in the human body.

The method may therefore include connecting a conductor element of an insulated cable to a second conductor element.

The method may comprise applying heat to the heat-shrink sleeve to shrink the heat-shrink sleeve onto the insulated cable and the connecting sleeve.

The method described herein therefore provides numerous benefits and advantages, for medical uses in particular. The resulting high voltage cable and connector assembly provides improved strength, flexibility and adaptability to the desired medical use, whilst minimising costs by reducing any need for overly complex components.

A high voltage cable and connector assembly may therefore comprise: a primer applied to an outer part of insulation of an insulated cable;

a primer applied to an inner wall of an insulator sleeve; glue applied to the connecting sleeve and/or the primed insulation and the primed insulator sleeve inner wall;

the insulator sleeve glued over primed parts of the insulated cable and of the connecting sleeve;

a primer applied to the outer part of the insulator sleeve;

a primer applied to inner walls of an opening in a connector hub;

the connector hub disposed over primed parts of the insulator sleeve; and

a glue applied between the connector hub and the insulator sleeve.

The connector hub may have a profile having a first portion arranged to co-operate with a diameter of the outer diameter of the insulator cable while a second part of the connector hub may have a diameter arranged to co-operate with the outer diameter of the insulator sleeve. These two parts of the connector hub may have a diameter change located between them. This point of diameter change may be arranged such that the insulator cable is held remote from the distal end of the connector hub, the distal end being arranged for connection to a catheter tube. This may be achieved with connection means, which connection means may be a screw thread, bayonet connection or other rotatable connection. A push-fit or other lockable connection means may further be included. The connector assembly may be arranged to provide an airtight seal between the connector hub and the insulator sleeve and between the insulator sleeve and cable insulation and connecting sleeve. A primer may be included on the outer surface of an insulator sleeve for covering at least a part of a conducting element.

Detailed description of preferred embodiments of the invention

Specific examples of the present invention will now be described in relation to the following figures in which:

Figure 1 shows a cross-section through a cable of the present invention;

Figure 2 illustrates a first step in an assembly method of the present invention;

Figure 3 shows a second step in an assembly method of the present invention; Figure 4 shows a further step in an assembly method of the present invention;

Figure 5 shows a further step in an assembly method of the present invention;

Figure 6 shows a further step in an assembly method of the present invention;

Figure 7 shows a further step in an assembly method of the present invention;

Figure 8 shows a further step in an assembly method of the present invention;

Figure 9 shows a connector hub suitable for use in an assembly method of the present invention;

Figure 10 shows a further step in an assembly method of the present invention; and

Figure 1 1 shows a further step in an assembly method of the present invention.

Figure 1 shows a cross-section through an electrical cable of the present invention. The cable 1 comprises a conductive core 1 1 , which may be comprised of separate strands 12 of conductive material, which may be a metal such as copper or any other suitable conductive material. The cable further comprises an inner layer of insulation 13 which has a thickness 131 and an outer diameter 132. The cable further comprises an outer layer of insulation 14, which has a thickness 141 and an outer diameter 142, which may be the outer diameter of the cable. A section through a diameter of the cable can be drawn along line 15. Along such a line, certain portions of the line will be in outer layer 14 of insulation and the total amount on that diameter 15 will be made up of the two opposite parts 151 of the outer layer. Similarly, two opposing parts 152 of the inner insulation layer 13 will also be present on the diameter 15. A further part of the line 15 within insulation layer 30 will be occupied by the conductive core 1 1 . The thicknesses of the insulation layers 131 and 141 can advantageously be configured according to the proportions and ratios described herein. The outer diameters can also be configured according to the ratios and dimensions described herein. The diameter, number, and size of threads in the conductive core 1 1 can also be configured as described herein to provide the desired advantages of the invention.

Proposed materials for the inner layer 13 and outer layer 14 of the cable 1 are LLDPE and PVC, respectively. However, the PVC layer may be replaced with polyurethane (PU), or thermoplastic elastomer (TPE). The principal advantages associated with the present invention have been identified as being associated with the use of PVC, although the above materials can also be advantageous in the situations described herein.

Alternative materials which may be used in place of LLDPE may include high-density polyethylene (HDPE), low density polyethylene (LDPE), fluoropolymers, such as FEP (fluorinated ethylene propylene), ETFE (Ethylene tetrafluoroethylene), PTFE (polytetrafluoroethylene) or polypropylene. However, the principle advantages of the invention have been found to be associated with the use of LLDPE for the desired mechanical and dielectric properties, which can also be found in HDPE or LDPE.

Figure 2 illustrates a first process step in which a high voltage cable and connector assembly 2 of the present invention may be connected. The insulated cable 21 can be joined to a conductor element 22. It has been found that using a splice crimp 23 improves the strength of this connection whilst avoiding the need for complex and messy soldering solutions, which can also contaminate the necessarily sterile products used in medical applications. An insulation layer 24 may be disposed over conductor 22 and an end of the conductor 22 distal from the splice crimp 23 may be exposed, such that a high voltage applied to the conductor via the insulated cable 21 can be exposed to the atmosphere at a distal end of the connector assembly. In certain applications, it is advantageous to expose this element to the atmosphere in the cavity inside a patient whilst keyhole surgery is being carried out.

Figure 3 illustrates the detail of the connector assembly 2 shown in Figure 2. A glue may be applied to splice crimp 23 and a suitable glue is a cyanoacrylate adhesive, which is designed for the bonding of plastics where very fast fixing and heat resistance is required. A primer may not be necessary on splice crimp 23.

A primer and/or cyanoacrylate adhesive may be applied to a region 31 of the insulation of insulated cable 21 over a chosen distance, which may, for example, be 10mm in certain applications. A suitable primer is one which is designed to make polyolefin and other low energy surfaces suitable for bonding with cyanoacrylate adhesives, such as Loctite™ 7701 , which uses aliphatic amine as the principal active ingredient for priming the surface to be primed. The same or a different primer and/or cyanoacrylate adhesive may be applied over region 32, optionally over a distance of around 4mm to prepare the insulation of insulated cable 21 and the insulated cable 24 for connection.

Figure 4 illustrates an insulator sleeve 4 which can be used with the present invention. The sleeve may be made from a heat-shrinkable material. A primer can be applied to the internal surfaces of a first end 41 of sleeve 4. The primer may further be applied to a second end 42 of sleeve 4, the first part 41 to which primer is applied may be of greater length than the second part 42 to which primer is applied. This may be advantageous when one material, such as the material of the insulated cable 21 is more difficult to glue with sufficient mechanical strength than a second material, such as the material of insulated cable 24. Primer is generally applied around the whole outer circumference of the relevant parts of sleeve 4.

Figure 5 illustrates a subsequent method step in which the insulator sleeve 4 has been placed over splice crimp 23 and the primed part of the insulated cable 21 and the insulated cable 24.

Figure 6 shows a detailed representation of the insulator sleeve 4 in place over the connection and it can further be seen that a transition region 41 is provided, in which there is a change in diameter from the larger diameter associated with the insulated cable 21 , to a smaller diameter section 44 associated with the splice crimp 23. A further diameter change 45 to a larger diameter section 46 associated with the diameter of insulator sleeve 24 may be present, which may be of smaller diameter than the outer diameter over of the part of sleeve 4 located over insulated wire 21 , but greater in diameter than splice crimp 23.

Figure 7 illustrates locations where a primer may be applied to any or all of mid-section 44 of insulator sleeve 4 or larger or smaller diameter sections 47 and 46, respectively, as well as two transition portions 43 and 45 of the sleeve. Any or all of these parts may have primer applied to them to prepare them for connection to a connector hub in subsequent method steps. Figure 8 illustrates a connector hub 8 which has been placed into the connector assembly in the direction of arrow 81 . In this way, a first end 82 of connector hub 8 may have a larger diameter opening than a second end 83 of connector hub 8. The opening in second end 83 of connector hub 8 may be configured to substantially match or correspond to an outer diameter of insulated cable 24 whilst first end 82 may have an opening whose diameter is configured to match an outer diameter of a larger section 47 of sleeve 4, so that bonding occurs between the connector hub 8 and the insulator sleeve 4. In certain embodiments, the distance 84 from a first end 82 of the connector hub to an end of the insulator sleeve may be 6mm plus or minus 2mm.

Figure 9 shows a connector hub 8 in cross-section, so that internal features of the connector hub can be seen. First end 82 may have an internal chamfer 821 which may assist in guiding a glue placed in a chamfer into the internal diameters of the connector hub. The connector hub may have a first, largest diameter internal section 85, which may be considered to have a diameter matching the greatest outer diameter of sleeve 4. The connector hub 8 may comprise an internal diameter transition portion 86, which transitions to a smaller diameter section 87. This smaller diameter may be configured to substantially correspond to the outer diameter of the insulator sleeve part 46 of Figure 7, which covers the connecting sleeve. The connector hub may further comprise a smaller diameter opening 88, which may be configured to correspond to the outer diameter of the insulated cable 24. The connector hub may therefore have first and/or second and/or third internal diameter sections, corresponding to first and/or second and/or third outer diameters of the cable and connector sleeve. This arrangement can assist in efficient gluing of the relevant parts of the internal diameter of the connector hub to the outer diameters of the connector sleeve and insulator sleeve. All of these features can assist in providing the necessary air-tight seal from first end 82 of hub 8 to second end 83 of hub 8. This is especially important when the connector hub is being used to connect to a catheter which is inserted into an inflated cavity within a body of a person, which may be under positive internal pressure, to keep the cavity inflated. Connector means 89 may be provided on a connection portion of the connector hub. Such means may comprise a screw thread, a push-fit, a bayonet type locking portion, or any suitable locking means which may be configured to provide an airtight connection between the connector hub and item to which it will be connected, such as a catheter.

Figure 10 illustrates the connector assembly 2 of the present invention viewed from first end 82 of connector hub 8. Chamfered edge 81 can be seen as indicated in the Figure and, in a subsequent step in the method, a glue can be placed in the chamfered area. A suitable glue is a cyanoacrylate adhesive which is designed for the bonding of plastics where very fast fixing is required and tight bond gaps are present. One or more of the assemblies 2 of the invention can then be placed in an upright position as illustrated in Figure 1 1 , to allow the glue applied to first end 82 of the connector hub to flow into the inner diameters 85, 86, 87 and 88 of the hub to glue the connector hub to the connector sleeve and/or the insulated cable 24 as appropriate. It will be evident that the methods and product described herein overcome numerous disadvantages associated with prior art methods of cable assembly and address in particular certain particular requirements associated with medical uses with high voltage conductors in a pressurised environment. An appropriate assembly and production method can therefore be produced and implemented in which the costs and complexity of the methods and material used are minimised, whilst meeting the various technical requirements of a desired use of the resulting product.

Claims

1 . A method of assembling a high-voltage cable and connector assembly, comprising the steps of:

applying a primer to an outer part of insulation of an insulated cable;

applying glue to the primed insulation and the insulator sleeve;

applying the insulator sleeve over primed parts of the insulated cable to connect the insulator sleeve to the insulation of the insulated cable;

applying a primer to the outer part of the insulator sleeve;

applying a primer to inner walls of an opening in a connector hub;

2. A method according to claim 1 , wherein the insulator sleeve is a heat- shrinkable sleeve and heat is applied to the heat-shrink sleeve to connect the insulator sleeve to primed parts of the insulation of the insulated cable and of a connector sleeve.

3. A method according to claim 1 or claim 2, further comprising connecting a conductor element of the insulated cable to a second conductor element.

4. A method according to any of claims 1 to 3, wherein the conductor element of the insulated cable is connected to a second conductor element by connecting sleeve, preferably by a splice joint.

5. A method according to any of claims 1 to 4, further comprising placing the connector assembly in a vertical orientation such that gravity encourages glue into the interface between the connector hub and the insulator sleeve.

6. A method according to any of claims 1 to 5, wherein glue is applied to the outside of the splice joint.

7. A method according to any of claims 1 to 6, wherein the insulation of the insulated cable comprises PVC.

8. A method according to any of claims 1 to 7, wherein the insulated cable comprises fluoropolymer.

9. A method according to any of claims 1 to 8, wherein the insulated cable comprises a conductor made of a first metal and a second conductor element is made from a second metal different from the first metal.

10. A method according to claim 9, wherein the insulated cable comprises a copper conductor and the second conductor element comprises stainless steel.

1 1 . A method according to any of claims 1 to 10, connecting a conductor element of an insulated cable to a second conductor element of a second insulated cable.

12. A method according to any of claims 1 to 1 1 , applying heat to the heat shrink sleeve to shrink the heat shrink sleeve onto two insulated cables.

13. A method of assembling a high-voltage cable and connector assembly substantially as described herein with reference to the figures.

14. A high-voltage cable and connector assembly substantially as described herein with reference to the figures.

15. A high-voltage cable and connector assembly comprising:

a primer applied to an outer part of insulation of an insulated cable;

glue applied to the insulator sleeve and/or the primed insulation of the insulated cable;

the insulator sleeve glued over primed parts of the insulated cable;

a primer applied to the outer part of the insulator sleeve;

a primer applied to inner walls of an opening in a connector hub; the connector hub disposed over primed parts of the insulator sleeve; and

a glue applied between the connector hub and the connecting sleeve.

16. A high-voltage cable and connector assembly according to claim 15, wherein the connector hub has an inner profile having a first portion arranged to co-operate with a diameter of the outer diameter of the insulator cable.

17. A high-voltage cable and connector assembly according to claim 15 or claim 16, wherein a further part of the connector hub has a diameter arranged to co-operate with the outer diameter of the insulator sleeve.

18. A high-voltage cable and connector assembly according to any of claims 15 to 17, wherein two parts of the connector hub have a diameter change located between them, the diameter change arranged such that the insulator cable is held remote from the distal end of the connector hub, the distal end being arranged for connection to a catheter tube.

19. A high-voltage cable and connector assembly according to any of claims 15 to 18, further comprising with connection means for connection of the hub to a catheter tube.

20. A high-voltage cable and connector assembly according to any of claims 15 to 19, wherein the assembly is arranged to provide an airtight seal between the connector hub and the connector sleeve and/or between the connector sleeve and cable insulation and insulator sleeve.

21 . An electrical cable comprising:

a conductive core;

a first insulation layer; and

a second insulation layer;

the first insulation layer formed from a first material comprising at least one of HDPE, LLDPE, LDPE, a flouropolymer or polypropylene; and the second insulation layer formed from a second material comprising at least one of PVC, TPE or Polyurethane.

22. An electrical cable according to claim 2, wherein the first insulation layer is within the second insulation layer.

23. An electrical cable according to claim 21 or claim 22, wherein the outer diameter of the conductive core is in the range of around 13% to 35% of the overall diameter of the cable.

24. An electrical cable according to any of claims 21 to 23, wherein the first insulation layer has a thickness in the range of around 17% to around 68% of the cable radius.

25. An electrical cable according to any of claims 21 to 24, wherein the second insulation layer has a thickness in the range of around 17% to around 68% of the cable radius.

26. An electrical cable according to any of claims 21 to 25, wherein a thickness of the second, outer, insulation layer is greater than a thickness of the first, inner, insulation layer.

27. An electrical cable according to any of claims 21 to 26, wherein:

a. the outer diameter of the conductive core is around 25% to 35 % of the overall diameter of the cable;

b. the outer diameter of the first layer is around 45% to 60% of the overall diameter of the cable; and

c. the outer diameter of the second layer is 100% of the overall diameter of the cable;

28. An electrical cable according to any of claims 21 to 27, wherein:

a. the outer diameter of the conductive core is around 0.8mm;

b. the thickness of the first insulation layer is around 0.4mm; and c. the thickness of the second insulation layer is around 0.7mm.

29. An electrical cable according to any of claims 21 to 28, wherein a section through a diameter of the cable comprises:

15% conductive core;

17% the first insulation layer; and

68% the second insulation layer.

30. An electrical cable according to any of claims to 21 to 29, wherein section through a diameter of the cable comprises:

20% conductive core;

23% the first insulation layer; and

57% the second insulation layer.

31 . An electrical cable according to any of claims 21 to 30, wherein a section through a diameter of the cable comprises:

25% conductive core;

29% the first insulation layer; and

46% the second insulation layer.

32. An electrical cable according to any of claims 21 to 31 , wherein a section through a diameter of the cable comprises around:

30% conductive core;

35% the first insulation layer; and

35% the second insulation layer.

33. An electrical cable according to any of claims 21 to 32, wherein a section through the conductive core comprises:

between around 38 to 61 strands of any wire size from around 0.05mm in diameter to around 0.1 mm diameter.

34. An electrical cable according to any of claims 21 to 33, wherein a section through the conductive core comprises:

between around 37 to 20 Strands of any wire size from 42AWG to 36AWG.

35. An electrical cable according to any of claims 21 to 34, wherein a section through the conductive core comprises:

between around 19 to 7 Strands of any wire size from 40AWG to 34AWG.

36. An electrical cable according to any of claims 21 to 35, wherein a section through the conductive core comprises:

at least 7 strands of any wire size from 34AWG to 28AWG.

37. An electrical cable substantially as described herein with reference to the drawings.

38. A high-voltage cable and connector assembly according to any of claims 15 to 20, comprising a cable according to any of claims 21 to 37.