阅读说明：本技术 电隔离器 (Electrical isolator ) 是由 D.V.L.福尔克纳 A.D.泰勒 于 2019-12-13 设计创作，主要内容包括：提供一种电隔离器,所述隔离器包括：第一流体载运构件；第二流体载运构件,所述第二流体载运构件与所述第一流体载运构件间隔开以形成间隙；电阻性、半导电或非导电部件,所述电阻性、半导电或非导电部件跨越所述间隙延伸并且被结合到所述第一流体载运构件和所述第二流体载运构件,以便在所述第一流体载运构件与所述电阻性、半导电或非导电部件之间以及在所述第二流体载运构件与所述电阻性、半导电或非导电部件之间提供不透流体的密封；以及增强型复合材料,所述增强型复合材料包围所述第一流体载运构件、所述第二流体载运构件和所述电阻性、半导电或非导电部件。(Providing an electrical isolator, the isolator comprising: a first fluid carrying member; a second fluid carrying member spaced apart from the first fluid carrying member to form a gap; a resistive, semi-conductive or non-conductive member extending across the gap and bonded to the first and second fluid-carrying means so as to provide a fluid-tight seal between the first fluid-carrying means and the resistive, semi-conductive or non-conductive member and between the second fluid-carrying means and the resistive, semi-conductive or non-conductive member; and a reinforced composite material surrounding the first fluid-carrying means, the second fluid-carrying means and the resistive, semi-conductive or non-conductive components.)

1. An electrical isolator, comprising:

a first fluid carrying member;

a second fluid carrying member spaced apart from the first fluid carrying member to form a gap;

a resistive, semi-conductive or non-conductive member extending across the gap and bonded to the first and second fluid-carrying means so as to provide a fluid-tight seal between the first fluid-carrying means and the resistive, semi-conductive or non-conductive member and between the second fluid-carrying means and the resistive, semi-conductive or non-conductive member; and

a reinforced composite material surrounding the first fluid-carrying means, the second fluid-carrying means and the resistive, semi-conductive or non-conductive components.

2. The electrical isolator of claim 1, wherein material is provided in the gap between the first and second fluid-carrying means and bonded to the resistive, semi-conductive or non-conductive component and the first and second fluid-carrying means.

3. The electrical isolator of claim 2, wherein the first fluid carrying member terminates in a first flange extending radially outward therefrom and the second fluid carrying member terminates in a second flange extending radially outward therefrom, and the material extends between the first flange and the second flange.

4. An electrical isolator as claimed in claim 1, 2 or 3, wherein the resistive, semi-conductive or non-conductive component is bonded to the first and second fluid-carrying means by a bonding material provided between the resistive, semi-conductive or non-conductive component and the first fluid-carrying means and between the resistive, semi-conductive or non-conductive component and the second fluid-carrying means.

5. An electrical isolator as claimed in any preceding claim, wherein the resistive, semi-conductive or non-conductive component comprises an annular gasket extending coaxially with the first and second fluid-carrying members.

6. The electrical isolator of claim 5, wherein a first cutout is formed in the first fluid carrying member,

a second cut-out portion is formed in the second fluid carrying member, and

the annular gasket is received in the first and second cut-out portions such that a radially inner surface of the annular gasket is substantially flush with radially inner surfaces of the first and second fluid carrying members.

7. An electrical isolator as claimed in any preceding claim, wherein the reinforced composite material comprises:

a circumferentially wound fiber reinforced polymer layer extending circumferentially around the first fluid carrying component, the second fluid carrying component and the resistive, semi-conductive or non-conductive component; and

a helically wound fiber reinforced polymer layer extending helically around the first fluid carrying means, the second fluid carrying means and the resistive, semi-conductive or non-conductive component.

8. An electrical isolator as claimed in any preceding claim, wherein each of the first and second fluid-carrying members comprises a curved portion such that the curved portions of the first and second fluid-carrying members form a substantially oval shape or convex portion extending radially outwardly from the first and second fluid-carrying members.

9. The electrical isolator of claim 8, wherein the gap is located at a radially outermost portion of the oval shape or the protruding portion.

10. An electrical isolator as claimed in claim 8 or 9, wherein the resistive, semi-conductive or non-conductive components are shaped so as to conform to the shape of the first and second fluid-carrying means.

11. The electrical isolator of claim 10, wherein the resistive, semi-conductive, or non-conductive member further comprises a radial protrusion extending radially outward therefrom into the gap.

12. An electrical isolator as claimed in claim 8, 9 or 10, wherein a composite material having low electrical conductivity is provided in the gap extending between the first and second fluid carrying members.

13. A hydraulic or fuel system comprising an electrical isolator as claimed in any preceding claim.

14. A method of making an electrical isolator, the method comprising:

bonding first and second fluid carrying means to a resistive, semi-conductive or non-conductive component extending across a gap between the first and second fluid carrying means so as to provide a fluid-tight seal between the first and resistive, semi-conductive or non-conductive components and between the second fluid carrying means and the resistive, semi-conductive or non-conductive components; and

forming a reinforced composite material surrounding the first fluid-carrying means, the second fluid-carrying means and the resistive, semi-conductive or non-conductive component.

15. The method of claim 14, wherein forming the reinforced composite comprises:

wrapping a fiber-reinforced polymer around the first fluid-carrying member, the second fluid-carrying member, and the resistive, semi-conductive, or non-conductive component;

before, during or after said winding of the fibre reinforced polymer, providing a resin mixture so as to form a fibre reinforced polymer and resin mixture extending around the first fluid carrying means, the second fluid carrying means and the resistive, semi-conductive or non-conductive component; and

curing the fiber-reinforced polymer and the resin mixture.

Technical Field

The present disclosure relates generally to electrical isolators and, more particularly, to electrical isolators used in hydraulic fluid lines or fuel lines of vehicles or machines, such as aircraft. An electrical isolator may be used to connect two fluid carrying members, such as pipes, hoses or tubes, for example, pipes carrying hydraulic fluid or fuel.

Background

Aircraft and other vehicles contain a large number of fluid transport systems, specifically hydraulic and fuel systems that include fluid transport components such as pipes. Such parts are typically metallic or composite materials and have good electrical conductivity.

Devices are incorporated into such systems to form electrical isolators between the metallic components thereof. These isolators prevent the build-up of static electricity by safely dissipating the build-up of static electricity and also prevent excessive current flow through the system, for example due to a lightning strike. Both of these events can lead to fire hazards if such isolators are not present in the system.

When incorporated into a fluid delivery system, the electrical isolator also needs to act as a secure channel for the fluid. In certain systems, such as hydraulic systems or hydraulic fluid lines in aircraft, the isolators need to be able to withstand high pressures, in addition to other load and environmental factors.

The present disclosure is directed to balancing the above factors to provide electrical isolation functionality within a pressurized fluid system.

When used in particular, but not exclusively, in aircraft, it is also desirable to make the electrical isolator as small and light as possible.

US 2017/0103832 a1 discloses an electrical isolator for use in a fluid delivery system. The electrical isolator comprises a first fluid-carrying member, and a second fluid-carrying member spaced apart from the first fluid-carrying member; a resistive, semi-conductive or non-conductive component located between and sealed with respect to the first and second fluid-carrying means, wherein the resistive, semi-conductive or non-conductive component is adapted to transport fluid flowing from the first fluid-carrying means to the second fluid-carrying means; a reinforced composite material surrounding the first fluid carrying member, the second fluid carrying member and the resistive, semi-conductive or non-conductive component, wherein the reinforced composite material is continuous and may provide a conductive path between the first and second fluid carrying members, wherein the reinforced composite material comprises a fibre and resin mixture and the resin mixture comprises a resin and a conductive additive. O-ring seals provided in grooves machined into the first and second fluid carrying means are used to seal the resistive, semi-conductive or non-conductive component relative to the first and second fluid carrying means.

In typical electrical isolators, expensive multi-part one-way seals are used to provide a seal between the fluid carrying component and the resistive, semi-conductive or non-conductive component or gasket.

Disclosure of Invention

According to an aspect of the present disclosure, there is provided an electrical isolator comprising:

a first fluid carrying member;

a second fluid carrying member spaced apart from the first fluid carrying member to form a gap;

a resistive, semi-conductive or non-conductive member extending across the gap and bonded to the first and second fluid-carrying means so as to provide a fluid-tight seal between the first and resistive, semi-conductive or non-conductive members and between the second fluid-carrying means and the resistive, semi-conductive or non-conductive members; and

a reinforced composite material surrounding the first fluid-carrying means, the second fluid-carrying means and the resistive, semi-conductive or non-conductive components.

The above isolator uses a combination between the resistive, semi-conductive or non-conductive component and the first and second fluid-carrying means thereof to provide a fluid-tight seal between the first fluid-carrying means and the resistive, semi-conductive or non-conductive component and between the second fluid-carrying means and the resistive, semi-conductive or non-conductive component, such that, in use, fluid can flow from the first fluid-carrying means to the second fluid-carrying means without leakage. In isolators according to the present disclosure, there is no need to provide separate sealing components, such as conventional hydraulic seals used in known electrical isolators, which require grooves to be machined into portions of the electrical isolator and are typically expensive and time consuming to assemble. Furthermore, the conventional hydraulic seals may sometimes be improperly assembled, resulting in leaks that may be detected only after the isolator has been fully assembled, the reinforced composite material has cured, and the isolator has been tested.

In addition to the above, because resistive, semi-conductive or non-conductive components are incorporated into the first and second fluid-carrying means in an electrical isolator according to the present disclosure, the resistive, semi-conductive or non-conductive components and the first and second fluid-carrying means are fixed in place relative to each other such that no additional means are required to hold the resistive, semi-conductive or non-conductive components and the first and second fluid-carrying means in place when forming the reinforced composite.

In addition to the above, in prior art arrangements using seals such as O-rings, internal fluid pressure in the electrical isolator may force the seal through a small gap, potentially causing the seal to permanently deform or compress and thus fail. The seal provided by incorporating a spacer according to the present disclosure may help reduce deformation or crushing of the seal by mechanically supporting some of the contact surfaces of the seal. By bonding to the resistive, semi-conductive or non-conductive member and the first and second fluid carrying means, relative movement between the bonding and the resistive, semi-conductive or non-conductive member and the first and second fluid carrying means is reduced such that deformation or crushing of the seal provided by the bonding is less likely to occur.

In addition to the above, an electrical isolator according to the present disclosure implements an electrical isolator that is fluid-tight at the required pressures to be provided in a shorter axial length than has previously been possible. The electrical isolator of the present disclosure is also lighter and less expensive to produce than known electrical isolators that use conventional hydraulic seals.

In addition to the above, the electrical isolator of the present disclosure uses a reinforced composite material surrounding the first fluid carrying means, the second fluid carrying means and the resistive, semi-conductive or non-conductive components while providing a conductive path through the reinforced composite material, but without providing a gap between the first fluid carrying means and the second fluid carrying means. This provides a means to effectively dissipate charge buildup and electrically isolate the junction between two fluid transport devices while providing a fluid tight joint.

The reinforced composite material surrounds the first and second fluid-carrying means, but typically only its ends, such as closest to the resistive, semiconductive or nonconductive component. The reinforced composite may be a continuous tube extending from the first fluid carrying member (or end thereof) through the gap to the second fluid carrying member (or end thereof).

In any aspect of the disclosure, material may be provided in a gap between the first and second fluid-carrying members, and may be bonded to the resistive, semi-conductive or non-conductive component and the first and second fluid-carrying members. The material may be bonded to the first and second fluid-carrying members and the resistive, semi-conductive or non-conductive component using an adhesive.

The material may have a low electrical conductivity such that the material acts as an electrical isolator between the first and second fluid-carrying members.

Further, the materials may be used to minimize relative movement of the respective portions of the electrical isolator under pressure.

In any aspect of the present disclosure, the material may be an elastomer, and more preferably, the material may be a fluoroelastomer.

In any aspect of the disclosure, the first fluid carrying member may terminate in a first flange extending radially outward therefrom, and the second fluid carrying member may terminate in a second flange extending radially outward therefrom, and the material may extend between the first flange and the second flange. The first and second flanges may provide a greater radial extent to support material on either side thereof, such that a greater amount of material may be provided between the first and second fluid carrying members than would otherwise be possible.

In any aspect of the present disclosure, the resistive, semi-conductive or non-conductive component may be bonded to the first and second fluid-carrying means by a bonding material provided between the resistive, semi-conductive or non-conductive component and the first fluid-carrying means and between the resistive, semi-conductive or non-conductive component and the second fluid-carrying means. In this example, the seal may be provided by a bonding material extending over part or the entire extent of the mating surfaces of the resistive, semi-conductive or non-conductive components and the respective first and second fluid-carrying members.

In any aspect of the disclosure, the bonding material may be flexible so as to accommodate relative movement between the resistive, semi-conductive or non-conductive component and the first and second fluid-carrying members, for example due to their different rates of thermal expansion and contraction. Providing a flexible bonding material may prevent delamination and increase the fatigue life of an isolator according to the present disclosure.

In any aspect of the present disclosure, the bonding material may comprise an adhesive, preferably a fuel resistant adhesive, or a flexible adhesive or a fuel resistant flexible adhesive.

In any aspect of the present disclosure, the bonding material may comprise a sealant material or an injection molded elastomeric material.

In any aspect of the disclosure, the resistive, semi-conductive or non-conductive component may comprise an annular gasket extending coaxially with the first and second fluid-carrying members.

In any aspect of the present disclosure, a first cutout may be formed in the first fluid carrying member,

a second cut-out portion may be formed in the second fluid carrying member, and

an annular gasket may be received in the first and second cut-out portions such that a radially inner surface of the annular gasket is substantially flush with radially inner surfaces of the first and second fluid carrying members. By having the radially inner surface of the annular gasket substantially flush with the radially inner surfaces of the first and second fluid carrying members, the fluid flow through the electrical isolator in use may be optimised.

In any aspect of the present disclosure, the reinforced composite may include:

a circumferentially wound fiber reinforced polymer layer extending circumferentially around the first fluid carrying component, the second fluid carrying component and the resistive, semi-conductive or non-conductive component; and

a helically wound fiber reinforced polymer layer extending helically around the first fluid carrying means, the second fluid carrying means and the resistive, semi-conductive or non-conductive component.

The layer of circumferentially wound fibers (also referred to as "hoop" fibers) provides additional pressure resistance to the electrical isolator. The hoop fiber is wound at a high angle to the axis of the structure so that it winds in a very tight spiral (or in some cases even directly on itself, i.e., at ninety degrees to the axis). Thus, the hoop fiber does not expand under radial pressure and therefore strongly resists radial loads, i.e. it is pressure resistant. Such electrical isolators with circumferential fiber layers better accommodate the high pressures of hydraulic systems.

While circumferential fibers are well suited to provide pressure resistance, they are not well suited to hold electrical isolators together because they do not provide much strength in the axial direction. However, the helically wound fiber layer (which in one example may be provided radially outward from the circumferential fibers) provides axial strength.

Circumferential fibres here mean fibres with a high winding angle (the angle which the fibre makes with the axis of the part (usually mounted on a mandrel) during winding), typically 80 to 90 degrees, more preferably at least 85 degrees.

Helical fibres here mean fibres with a low winding angle, typically between 30 and 70 degrees. It is often difficult to wind the fibers at angles below about 30 degrees, while angles above 70 degrees do not provide the desired axial strength. However, lower angles are still possible, down to substantially 0 degrees if fiber placement can be achieved. It is even possible to use true axial fibers instead of helical fibers (i.e. fibers at an angle of 0 degrees to the axis, i.e. parallel to said axis), but the placement of such fibers is difficult.

In some aspects of the disclosure, the first and second fluid-carrying components and resistive, semi-conductive or non-conductive components may comprise a cylindrical component having a constant cross-section along its axial extent. However, the shape of the first and second fluid carrying means and resistive, semi-conductive or non-conductive components may be altered to optimise the weight of the electrical isolator in view of internal stresses applied to the electrical isolator in use. Thus, in any aspect of the present disclosure, each of the first and second fluid carrying members may comprise a curved portion such that the curved portions of the first and second fluid carrying members form a substantially oval shape or convex portion extending radially outwardly from the first and second fluid carrying members.

In any aspect of the present disclosure, the gap may be located at a radially outermost portion of the oval shape or the bulge.

In any aspect of the present disclosure, the resistive, semi-conductive or non-conductive component may be shaped so as to conform to the shape of the first and second fluid-carrying means.

In some examples of the disclosure as discussed above, electrical isolation between the first and second fluid-carrying members may be provided by an elastomer. In an alternative example, the resistive, semi-conductive or non-conductive member may further comprise a radial protrusion extending radially outward therefrom into the gap. Thus, the radial protrusion may provide electrical isolation between the first and second fluid carrying members.

In another alternative example, a composite material having low electrical conductivity may be provided in a gap extending between the first and second fluid carrying members. The composite material may be used to provide electrical isolation between the first and second fluid-carrying members and resist movement therebetween.

In another alternative example, resistive, semi-conductive or non-conductive components may extend radially outside the first and second fluid carrying means such that no isolation material is provided in a gap extending between the first and second fluid carrying means.

In another aspect of the present disclosure, a hydraulic or fuel system is provided that includes the electrical isolator of any of the above examples.

In another aspect of the present disclosure, there is provided a method of making an electrical isolator, the method comprising:

bonding first and second fluid carrying means to a resistive, semi-conductive or non-conductive component extending across a gap between the first and second fluid carrying means so as to provide a fluid-tight seal between the first and resistive, semi-conductive or non-conductive components and between the second fluid carrying means and the resistive, semi-conductive or non-conductive components; and

forming a reinforced composite material surrounding the first fluid-carrying means, the second fluid-carrying means and the resistive, semi-conductive or non-conductive component.

Using the method of the present disclosure provides a simple and cost-effective method of making an electrical isolator. Because the first and second fluid-carrying means are bonded in position relative to the resistive, semi-conductive or non-conductive components prior to forming the reinforced composite, there is no need to use external compressive forces or other means to hold portions of electrical isolators in place while forming the reinforced composite. In contrast, in prior art isolators that use hydraulic seals, a compressive force is required to hold portions of the isolator in place until after the reinforced composite is fully formed.

Additionally, the method of bonding the first and second fluid carrying means to the resistive, semi-conductive or non-conductive component provides a simpler, less expensive and less time consuming method of forming a seal between components than in prior art isolators using hydraulic seals.

In any aspect of the method of the present disclosure, forming the reinforced composite may comprise:

wrapping a fiber-reinforced polymer around the first fluid-carrying member, the second fluid-carrying member, and the resistive, semi-conductive, or non-conductive component;

providing a resin mixture so as to form a fiber reinforced polymer and resin mixture extending around the first fluid carrying member, the second fluid carrying member and the resistive, semi-conductive or non-conductive component before, during or after winding the fiber reinforced polymer; and

curing the fiber-reinforced polymer and resin mixture.

In the method of the present disclosure, resin may not leak into the first and second fluid-carrying means from reinforced composite material provided radially externally of the first and second fluid-carrying means prior to the curing step, as sealing is provided by the bond between the first fluid-carrying means and the resistive, semi-conductive or non-conductive component and between the second fluid-carrying means and the resistive, semi-conductive or non-conductive component. Thus, there is no need to provide separate environmental seals between the first fluid carrying means and the resistive, semi-conductive or non-conductive components and between the second fluid carrying means and the resistive, semi-conductive or non-conductive components as in known electrical isolators using hydraulic seals.

In any aspect of the method of the present disclosure, the wrapping a fiber reinforced polymer around the first fluid carrying member, the second fluid carrying member, and the resistive, semi-conductive, or non-conductive component may comprise:

circumferentially winding a circumferentially wound fiber reinforced polymer around the first fluid carrying component, the second fluid carrying component, and the resistive, semi-conductive, or non-conductive component; and

winding a helically wound fiber reinforced polymer extending helically around the first fluid carrying means, the second fluid carrying means and the resistive, semi-conductive or non-conductive component.

It will be appreciated that the circumferentially wound fiber reinforced polymer and the helically wound fiber reinforced polymer may be provided in a variety of different arrangements including (but not limited to): providing a circumferentially wound fiber reinforced polymer in a first layer and providing the helically wound fiber reinforced polymer in a second layer extending around the first layer; or the helically wound fibre-reinforced polymer is provided in a first layer and the circumferentially wound fibre-reinforced polymer is provided in a second layer extending around the first layer.

Drawings

Various non-limiting examples will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 shows a cross-section through an electrical isolator above a centerline of the electrical isolator according to a first example of the present disclosure;

FIG. 2 shows a cross-section through an electrical isolator above a centerline of the electrical isolator according to a second example of the present disclosure;

FIG. 3 shows a cross-section through an electrical isolator above a centerline of the electrical isolator according to a third example of the present disclosure;

FIG. 4 shows a cross-section through an electrical isolator above a centerline of the electrical isolator according to a fourth example of the present disclosure;

FIG. 5 shows a cross-section through an electrical isolator above a centerline of the electrical isolator according to a fifth example of the present disclosure; and

fig. 6 shows a cross-section through an electrical isolator above a centerline of the electrical isolator according to a sixth example of the present disclosure.

Detailed Description

The present disclosure relates to electrical isolators that may be used in aircraft hydraulic systems or hydraulic fluid lines to provide a stronger fluid-carrying structure while controlling induced electrical currents (e.g., due to lightning) and dissipating static electrical charges. It will be understood that the drawings show a cross-section through an exemplary electrical isolator above a centerline of the electrical isolator. A cross-section (not shown) through the electrical isolator below the centerline of the exemplary electrical isolator of the figure would be a mirror image of the cross-section shown above the centerline.

Fig. 1 illustrates an electrical isolator or fluid carrying element 10 according to an example of the present disclosure.

The electrical isolator 10 forms part of a fluid delivery network (e.g., a hydraulic fluid network in an aircraft). Fluid, such as hydraulic fluid, may flow through electrical isolator 10 in the direction of arrow 100.

The electrical isolator 10 includes a first fluid carrying member or tube 12 and a second fluid carrying member or tube 14. Both the first tube 12 and the second tube 14 may be metallic and may include end fittings for attachment to other tubular components in the fluid-carrying system. In the illustrated example, the first conduit 12 and the second conduit 14 have the same structure. The first and second conduits 12, 14 are opposed and spaced apart from each other to provide a gap G therebetween.

In the illustrated example, the first and second conduits 12, 14 are tubular, i.e., cylindrical and have a circular cross-section. Other shapes and cross-sections are possible. Although the first and second conduits 12, 14 are shown in fig. 1 as extending coaxially about the axis a-a, this is not necessary, and examples are contemplated in which the axes of the first and second conduits 12, 14 are angled with respect to one another. For example, the angle may be less than 90 degrees, 60 degrees, 30 degrees, 15 degrees, 10 degrees, or 5 degrees.

The first and second conduits 12, 14 include radially inner axial surfaces 18 and radially outer axial surfaces 20 spaced therefrom in a radial direction to form a wall thickness of the first and second conduits 12, 14. Both the first duct 12 and the second duct 14 terminate in a flange 16 that extends radially away from the axis a-a and beyond the radially outer axial surface 20. Thus, the flange 16 provides a radial surface 26 as an end face of the first and second conduits 12, 14.

Cut-outs are formed in the radially inner axial surfaces 18 of the first and second conduits 12, 14 extending from their open ends away from the opposite conduit and around the circumference of the conduit so as to form a substantially annular cut-out. The radial surface 22 delimits the end of said cut-out and engages the radially inner axial surface 18.

An annular gasket 24 formed of a resistive, semi-conductive or non-conductive material is provided to fit within the cut-out portions in the first and second conduits 12, 14 such that a radially inner surface 25 of the annular gasket 24 extends substantially flush with the radially inner axial surface 18 of the first and second conduits 12, 14. It will be appreciated that the annular gasket 24 extends between the first and second conduits 12, 14 to maintain a gap G therebetween. The gap G between the first and second conduits 12, 14 is sized to provide electrical isolation between the first and second conduits 12, 14. In one example, the size of the gap G may be defined by the expected electrostatic and electrical requirements of the isolator. In a preferred example, the gap G between the first and second metal pipes 12, 14 should be at least 3 mm.

A minimum gap between the first and second conduits at their wet surfaces is also required. This may generally be provided by the axial length of the annular gasket 24 extending between the wetted surfaces of the respective first and second conduits 12, 14, and may be about 3.81 cm (1.5 inches). However, it will be appreciated that the required gap will depend on the size and intended use of the particular isolator, and may be defined by its intended electrostatic and electrical requirements. Thus, in an alternative example of the present disclosure, the minimum gap between the first and second conduits at the wet surfaces thereof may be about 1.27 cm to about 2.54 cm (about 0.5 inches to about 1 inch).

In the example shown in fig. 1, the minimum gap between the first and second conduits at their wet surfaces is bounded by the axial length of the annular gasket 24. Thus, it will be appreciated that the electrical isolator of the example may be made significantly shorter in the axial direction than has been possible in the past, as the molded fluoroelastomer seal and reinforced composite 30 may be provided to extend over no more than the axial extent of the annular gasket 24. Furthermore, the example electrical isolator may have a reduced weight and be less expensive and time consuming to produce than previously known electrical isolators.

A material (e.g., fluoroelastomer 28) is molded to fill the gap G between the flanges 16 of the first and second conduits 12, 14. Many such materials may be provided in place of the fluoroelastomer if the rigid or flexible material provides suitable electrical isolation properties and if the material does not react with the fluid medium flowing through the isolator. In one example, a material similar to Dow Corning 730 FS resistant sealant arc resistance =124 can be used. When chemically compatible with other materials used in the isolator, a molding material such as PEEK or Nitrile may be used. In another preferred example, PR-1770 class A fuel tank sealant may be used.

When in place, the material or fluoroelastomer 28 forms an annular shape and is bonded to the radially outer surface of the annular gasket 24 and the radial surface 26 defined by the respective flanges 16 of the first and second conduits 12, 14. It will be appreciated that the molded fluoroelastomer serves to hold the first and second conduits 12, 14 together and the annular gasket 24 to the first and second conduits 12, 14. Thus, the molded fluoroelastomer 28 provides a fluid-tight seal between the annular gasket 24 and the first and second conduits 12, 14.

The molded fluoroelastomer also typically has a hardness and rigidity suitable for minimizing the radial or hoop stresses and movement experienced between the first and second conduits 12, 14 and the annular liner 24.

In accordance with the present disclosure, a reinforced composite 30 is positioned about the first pipe 12, the second pipe 14, and the fluoroelastomer 28. The reinforced composite 30 may consist of, or consist essentially of, a fiber and resin mixture. The fibers may be glass fibers, carbon fibers or polyamide fibers. The resin mixture may include a resin that may have a thermoset (e.g., epoxy) or thermoplastic (e.g., polyaryletherketone "PEEK") construction.

The reinforced composite 30 may be continuous and cover all of the first conduit 12, the second conduit 14, and the fluoroelastomer 28 without air gaps and/or other materials therebetween. The first and second pipes 12, 14 may include a surface coating or treatment, and the surface coating or treatment may be the only material between the first or second pipe 12, 14 and the reinforced composite 30.

The reinforced composite 30 extends axially past the flanges 16 of the first and second pipes 12, 14. Thus, the inner diameter of the reinforced composite 30 gradually decreases as the reinforced composite 30 extends past and beyond the flange 16, providing a hemispherical outer profile that may be optimized for the internal pressure experienced by the isolator. In some examples, the isolator may have an outer profile comprising parallel central sections radially outward from the gap G, the outer profile narrowing at its ends.

The resin mixture includes conductive additives, such as carbon black and/or carbon nanotubes, and varying amounts of conductive additives can be incorporated into the resin mixture to achieve the desired conductivity for a particular application.

The reinforced composite allows the electrical isolator to withstand the higher internal pressures it will be subjected to when used in a hydraulic system without leakage. To achieve optimal resistance to both radial and axial forces applied to the electrical isolator, the reinforced composite may include fibers wound circumferentially around the pipe and fluoroelastomer (for radial forces) and fibers wound helically around the pipe and fluoroelastomer (for axial and some radial forces). In one example of the present disclosure, the reinforced composite includes a circumferentially extending layer or layers of a circumferentially wound fiber reinforced polymer around a first fluid carrying component, a second fluid carrying component, and a resistive, semi-conductive or non-conductive component, and a helically wound layer or layers of a helically wound fiber reinforced polymer extending helically around the circumferentially wound layer of fiber reinforced polymer, the first fluid carrying component, the second fluid carrying component, and the resistive, semi-conductive or non-conductive component.

The layer of circumferentially wound fibers (also referred to as "hoop" fibers) provides additional pressure resistance to the electrical isolator. The hoop fiber is wound at a high angle to the axis of the structure so that it winds in a very tight spiral (or in some cases even directly on itself, i.e., at ninety degrees to the axis). Thus, the hoop fiber does not expand under radial pressure and therefore strongly resists radial loads, i.e. it is pressure resistant. Such electrical isolators with circumferential fiber layers better accommodate the high pressures of hydraulic systems.

While circumferential fibers are well suited to provide pressure resistance, they are not well suited to hold electrical isolators together because they do not provide much strength in the axial direction. However, the helically wound fiber layer provides axial strength.

Circumferential fibres here mean fibres with a high winding angle (the angle which the fibre makes with the axis of the part (usually mounted on a mandrel) during winding), typically 80 to 90 degrees, more preferably at least 85 degrees.

Helical fibres here mean fibres with a low winding angle, typically between 30 and 70 degrees. It is often difficult to wind the fibers at angles below about 30 degrees, while angles above 70 degrees do not provide the desired axial strength. However, lower angles are still possible, down to substantially 0 degrees if fiber placement can be achieved. It is even possible to use true axial fibers instead of helical fibers (i.e. fibers at an angle of 0 degrees to the axis, i.e. parallel to said axis), but the placement of such fibers is difficult.

A method of forming the electrical isolator of fig. 1 will now be described.

A first conduit 12 and a second conduit 14 may be provided. The first conduit 12 and/or the second conduit 14 may form part of a network of conduits, or each conduit may comprise an end of a larger conduit. Electrical isolator 10 may be part of a hydraulic conduit network (e.g., a hydraulic system or hydraulic fluid conduit in an aircraft) that operates at greater than 1000 psi, 2000 psi, or 3000 psi.

Annular gaskets are inserted into the cut-away portions of the first and second conduits 12, 14 so as to extend along and between the first and second conduits 12, 14 and provide a gap G between the first and second conduits 12, 14. The fluoroelastomer 28 is then molded into the gap G between the flanges 16 of the first and second conduits 12, 14. Thus, when in place, the fluoroelastomer 28 forms an annular shape and is bonded to the radially outer surface 27 of the annular gasket 24 and to the radial surface 26 defined by the respective flanges 16 of the first and second conduits 12, 14. In a preferred example, the fluoroelastomer is injection molded and an adhesive is applied to the radially outer surface 27 of the annular gasket 24 and the radial surface 26 defined by the respective flanges 16 of the first and second conduits 12, 14 to bond the fluoroelastomer thereto.

To provide reinforcement, the reinforced composite 30 is positioned around the first pipe 12, the second pipe 14, the annular liner 24, and the fluoroelastomer 28.

To form the composite material 30, fibers (e.g., polymer fibers) are pulled through a bath containing a resin mixture, and the fiber and resin mixture may then be wrapped around the first tube 12, the second tube 14, the annular liner 24, and the fluoroelastomer 28 until the fiber and resin mixture exhibits sufficient thickness and covers the desired axial extent of the first tube 12, the fluoroelastomer 28, and the second tube 14. The orientation of the fibers can be controlled, for example, using an automated lap coating process. The resin mixture includes a conductive additive. Different amounts of the conductive additive may be added and mixed into the resin contained in the tank to alter or change the conductivity of the reinforced composite 30.

It is also possible to use fibrous materials that have been saturated with resin to form the composite material 30 rather than drawing the fibers through a resin bath as described above.

The fiber and resin mixture is cured to form the reinforced composite 30. Once cured, the reinforced composite material serves to hold the components of the electrical insulator 10 together to provide strength and resistance to the passage of high pressure fluids through the electrical insulator 10.

The method may further include passing the fluid through electrical isolator 10, i.e., from first conduit 12 to second conduit 14 via annular gasket 24, at a pressure greater than 1000 psi, 2000 psi, or 3000 psi. The method may further include passing the fluid through electrical isolator 10 at a test pressure of 30,000 psi or more, i.e., from first conduit 12 to second conduit 14 via annular gasket 24.

Fig. 2 illustrates an electrical isolator or fluid carrying element 210 in accordance with an alternative example of the present disclosure, wherein the shape of the electrical isolator has been modified to reduce internal stresses in components of the electrical isolator and the weight thereof.

In the illustrated example, the first and second conduits 212, 214 are tubular, i.e., cylindrical and have a circular cross-section.

The first and second conduits 212, 214 include a radially inner axial surface 218 and a radially outer axial surface 220 spaced therefrom in a radial direction, thereby forming a wall thickness of the first and second conduits 212, 214. Both the first and second conduits 212, 214 include end portions 234 having a cross-section forming a curved shape extending radially outward away from an axis a-a along which the first and second conduits 212, 214 extend. When assembled such that the first and second conduits 212, 214 are opposed with a gap G therebetween, the cross-sections of the curved ends 234 of the first and second conduits 212, 214 form an arc, as seen in fig. 2. Thus, the ends of the first and second annular conduits 212, 214 extend toward each other and form a substantially oval shape or bulge extending radially outward from the first and second annular conduits 212, 214.

Cut-away portions are formed in the radially inner axial surfaces 218 of the first and second conduits 212, 214 that extend away from the opposing conduit from the open ends thereof. The radial surface 222 defines an end of the cut-out in each of the first and second conduits 212, 214 and engages the radially inner axial surface 218.

An annular gasket 224 formed of a resistive, semi-conductive or non-conductive material is provided to fit within the cut-out portions in the first and second conduits 212, 214 and to extend between the first and second conduits 212, 214 to maintain a gap G therebetween. As seen in fig. 2, the annular gasket 224 of this example is shaped to conform to the curved shape of the ends of the first and second conduits 212, 214. In a preferred example, the gap G between the first and second conduits 212, 214 should be at least 3 mm.

The fluoroelastomer 228 is molded to fill the gap G between the opposing end faces 236 of the first and second conduits 212, 214. Thus, when in place, the fluoroelastomer 228 forms an annular shape and is bonded to the radially outer surface of the annular gasket 224 and to the end faces 236 of the first and second conduits 212, 214. It will be appreciated that the molded fluoroelastomer serves to hold the first and second conduits 212, 214 together and the annular gasket 224 to the first and second conduits 212, 214. Thus, the molded fluoroelastomer 228 provides a fluid-tight seal between the annular gasket 224 and the first and second conduits 212, 214. The molded fluoroelastomer generally has a hardness and rigidity suitable for minimizing the shifting and hoop stresses experienced between first conduit 212, second conduit 214, and annular liner 224. In one non-limiting example, the molded fluoroelastomer may comprise a Dow Corning 730 solvent resistant sealant white 90 ml tube. This material cures into a strong, flexible rubber, has good adhesion to many substrates, and is stable and flexible between-65 ℃ (-85 ° F) and 260 ℃ (500 ° F). Which retains its properties upon exposure to fuels, oils and solvents. The material properties are as follows:

● durometer/hardness: 40A

● flash point: > 214F

● Rt tack free time: 25 minutes

● basic chemical: fluorosilicone

● dielectric strength: 331V/mil

● elongation: 200 percent of

● peel strength: 15

● operating temperature: -65 to 260C

● tensile strength: 300

● bulk resistance: 2.1X 10(13) ohm-cm

In alternative examples, DAI-EL fluoroelastomers from DAIKIN or Greene Tweed FPH sealing materials may be used.

In accordance with the present disclosure, the reinforced composite 230 is positioned about the first pipe 212, the second pipe 214, and the fluoroelastomer 228 in a manner similar to that described with respect to fig. 1.

The reinforced composite 230 extends axially past the bulges formed by the first and second conduits 212, 214 to meet the radially outer axial surfaces 220, 220 of the first and second conduits 212, 214. Thus, the inner diameter of the reinforced composite 230 gradually decreases as the reinforced composite 230 extends past and beyond the bulge.

As seen in fig. 2, the radially outer surface 238 of the fluoroelastomer 228 may be concave, as the fluoroelastomer naturally shrinks away from the surface to which it is bonded during the production process. The concave surface 238 of the fluoroelastomer 228 may reduce the accuracy with which reinforcing fibers may be wrapped around the pipe and the fluoroelastomer when forming the reinforced composite 230. In this regard, the radially outer surface 238 of the fluoroelastomer 228 may be configured to provide a substantially planar surface.

It will be appreciated that the electrical isolator of fig. 2 may be formed by the method described above with respect to fig. 1.

Fig. 3 shows an electrical isolator or fluid carrying element 310 according to an alternative example of the present disclosure, wherein the shape of the electrical isolator has been modified to reduce internal stresses in components of the electrical isolator and the weight thereof in a manner similar to the example of fig. 2.

In the illustrated example, the first and second conduits 312, 314 are tubular, i.e., cylindrical and have a circular cross-section.

The first and second conduits 312, 314 include radially inner axial surfaces 318 and radially outer axial surfaces 320 spaced therefrom in a radial direction to form a wall thickness of the first and second conduits 312, 314. Both the first conduit 312 and the second conduit 314 include an end 334 that is shaped in a manner similar to that in the example of fig. 2. However, in contrast to the example of fig. 2, the end faces 336 of the first and second conduits 312, 314 are angled, the end faces extending inwardly toward one another as they approach the radially inner surfaces of the respective first and second conduits 312, 314.

Cut-outs are again formed in the radially inner axial surfaces 318 of the first and second conduits 312, 314.

As in the example of fig. 2, an annular gasket 324 formed of a resistive, semi-conductive or non-conductive material is provided to fit within the cut-out portions in the first and second conduits 312, 314.

As seen in fig. 3, the seal between the first and second conduits 312, 324, 314 is formed by bonding a radially outer surface 340 of the annular gasket 324 to a radially inner surface 342 of the cut-out portions in the first and second conduits 312, 314. In one example, an annular liner may be coated with an adhesive film and then overwound with a composite material such that the adhesive bonds to the liner and composite material during curing.

The low conductivity glass composite 343 is formed in the gap between the end faces 336 of the first and second conduits 312 and bonds the radially inner surface of the low conductivity glass composite 343 to the radially outer surface 340 of the annular liner 324. In one example, the glass fibers may be wrapped around the annular liner 324 in the gap to form the first few layers of circumferential glass fibers in a non-conductive (low carbon) resin. The fibers may then be overwound with conductive glass fibers and the fibers and resin may then be cured. If it is desired to avoid carbon resin escaping, a partial cure may be performed for the first few layers of hoop glass fibers in a non-conductive (low carbon) resin, followed by overwinding and then providing a final cure.

The reinforced composite 330 is again positioned around the first conduit 312, the second conduit 314, and the low-conductivity glass composite 343 in a manner similar to that described with respect to fig. 2.

A method of forming the electrical isolator of figure 3 will now be described.

A first conduit 312 and a second conduit 314 may be provided. The first conduit 312 and/or the second conduit 314 may form part of a network of conduits, or each conduit may comprise an end of a larger conduit. Electrical isolator 310 may be part of a hydraulic conduit network (e.g., a hydraulic system or hydraulic fluid conduit in an aircraft) that operates at greater than 1000 psi, 2000 psi, or 3000 psi.

A bonding material, such as an adhesive, sealant material, or injection molded elastomeric material, is applied to the radially outer surface 340 of the annular gasket 324, which is then inserted into the cut-away portions of the first and second conduits 312, 314 to provide a gap between the first and second conduits 312, 314 and form a seal between the first conduit 312, the annular gasket 324, and the second conduit 314.

A glass composite 343 is then formed in the gap G between the ends of the first and second conduits 312, 314.

To provide reinforcement, the reinforced composite 330 is positioned around the first conduit 312, the second conduit 314, the annular liner 324, and the glass composite 343 in the manner described with respect to fig. 1.

The method may further include passing the fluid through electrical isolator 310, i.e., from first conduit 312 to second conduit 314 via annular gasket 324, at a pressure greater than 1000 psi, 2000 psi, or 3000 psi.

Fig. 4 illustrates an electrical isolator or fluid carrying element 410 according to an alternative example of the present disclosure, wherein the shape of the electrical isolator has been modified to reduce internal stresses in components of the electrical isolator and the weight thereof in a manner similar to the example of fig. 2 and 3.

In the illustrated example, the first and second conduits 412, 414 are tubular, i.e., cylindrical and have a circular cross-section.

The first and second conduits 412, 414 include radially inner axial surfaces 418 and radially outer axial surfaces 420 spaced therefrom in a radial direction to form a wall thickness of the first and second conduits 412, 414. Both the first conduit 412 and the second conduit 414 include an end 434 that is shaped in a manner similar to that in the example of fig. 2.

Cut-outs are again formed in the radially inner axial surfaces 418 of the first and second conduits 412, 414.

As in the example of fig. 2, an annular gasket 424 formed of a resistive, semiconductive or non-conductive material is provided to fit within the cut-out portions in the first and second conduits 412, 414. In the example shown in fig. 4, the cross-section of the axially central portion of the annular gasket 434 forms an arc so as to form an oval shape or convex portion 444 extending radially outward from a first cylindrical portion 446 provided at one end of the annular gasket 434. A second cylindrical portion 448 is provided adjacent the projecting portion 444 at the other end of the annular gasket 424. The annular insert 424 also includes a radial projection 450 extending radially outward from the radially outermost portion of the projection 444. The radial projections 450 are shaped to fill the gap between the ends 434 of the first and second conduits 412, 414. Thus, in this example, the radial protrusion 450 provides the desired isolation in the first and second conduits 412, 414.

As seen in fig. 4, the seal between the first and second conduits 412, 424, 414 is formed by bonding a radially outer surface 440 of the annular gasket 424 to a radially inner surface 442 of the cut-out portions in the first and second conduits 412, 414. PR-1770 class a fuel tank sealant or the like may be used. The end faces 436 of the first and second conduits are also bonded to corresponding surfaces of the radial projection 450.

The reinforced composite 430 is again positioned around the first conduit 412, the second conduit 414, and the annular liner 424 in a manner similar to that described with respect to fig. 2.

A method of forming the electrical isolator of figure 4 will now be described.

A first conduit 412 and a second conduit 414 may be provided. The first conduit 412 and/or the second conduit 414 may form part of a network of conduits, or each conduit may comprise an end of a larger conduit. Electrical isolator 410 may be part of a hydraulic conduit network (e.g., a hydraulic system or hydraulic fluid conduit in an aircraft) that operates at greater than 1000 psi, 2000 psi, or 3000 psi.

A bonding material, such as an adhesive, sealant material, or injection molded elastomeric material, is applied to the radially outer surface 440 of the annular gasket 424 and the side surfaces of the radial projections 450. The annular gasket 424 is then inserted into the cut-out portions of the first and second conduits 412, 414 to provide a gap (filled by the radial projection 450) between the first and second conduits 412, 414 and form a seal between the first and second conduits 412, 424 and 414.

To provide reinforcement, the reinforced composite 430 is positioned around the first conduit 412, the second conduit 414, and the annular liner 424 in the manner described with respect to fig. 1.

The method may further include passing the fluid through electrical isolator 410, i.e., from first conduit 412 to second conduit 414 via annular gasket 424, at a pressure greater than 1000 psi, 2000 psi, or 3000 psi.

Fig. 5 illustrates an electrical isolator or fluid carrying element 510 according to an alternative example of the present disclosure. Electrical isolator 510 of fig. 5 is contemplated for use in lower pressure environments. Aerospace applications, automotive applications, industrial applications, and home applications may use isolators that are subjected to much lower pressures. In some applications, the fuel pressure may be less than 125 psig, with about 45 psig being typical in some automotive applications.

As in the previous example, electrical isolator 510 includes a first fluid carrying member or conduit 512 and a second fluid carrying member or conduit 514. The first and second conduits 512, 514 are cylindrical and opposed and spaced apart from each other along the axis a-a to provide a gap G therebetween.

First and second conduits 512, 514 include a radially inner axial surface 518 and a radially outer axial surface 520 spaced therefrom in a radial direction, thereby forming a wall thickness of first and second conduits 512, 514. Both first conduit 512 and second conduit 514 terminate in a tapered end surface 552.

An annular liner 524 formed of a resistive, semiconductive or nonconductive material is provided to extend across portions of the first conduit 512, across the gap G and across portions of the second conduit 514. The seal between the first conduit 512, the annular gasket 524, and the second conduit 514 is formed by bonding a radially inner surface 554 of the annular gasket 524 to a radially outer surface 520 of the first and second conduits 512, 514.

In accordance with the present disclosure, the reinforced composite 530 is positioned around the first conduit 512, the second conduit 514, and the annular liner 524 in a manner similar to that previously described.

The reinforced composite 530 extends axially past the ends of the annular liner 524 and engages the first and second conduits 512, 514. Thus, the inner diameter of the reinforced composite 530 gradually decreases as the reinforced composite 530 extends past and beyond the end of the annular pad 524.

A method of forming the electrical isolator of figure 5 will now be described.

A first conduit 512 and a second conduit 514 may be provided. First conduit 512 and/or second conduit 514 may form part of a network of conduits, or each conduit may comprise an end of a larger conduit.

A bonding material, such as an adhesive, sealant material, or injection molded elastomeric material, is applied to the radially inner surface 554 of the annular gasket 524. The radially inner surface 554 of the annular gasket 524 is then positioned in mating engagement with the radially outer surfaces of the first and second conduits 512, 514 to provide a gap between the first and second conduits 512, 514 and to form a seal between the first conduit 512, the annular gasket 524, and the second conduit 514.

To provide reinforcement, the reinforced composite 530 is positioned around the first conduit 512, the second conduit 514, the annular liner 524 in the manner described with respect to fig. 1.

The method may further include passing fluid through electrical isolator 510 at a pressure of between about 30 psig and 150 psig, i.e., from first conduit 512 to second conduit 514 via annular gasket 524.

In an alternative example shown in fig. 6, a long annular backing tube 624 having a substantially constant radius over its longitudinal extent to form an outer surface 690 extending substantially parallel to the backing tube 624 may be overwound using a simply wound composite material. The simply wound composite forms a reinforced composite 630 and the pipe may then be cut to the desired length if desired. This further simplifies the production of the electrical isolator according to the example and provides a low cost solution for lower pressures with square corners that is not weight optimized.

To provide the desired functionality of the electrical isolator, the radially outer layer of the reinforced composite 630 may be electrically conductive while the radially inner portion of the reinforced composite is electrically non-conductive. Cup-shaped metal contacts (not shown) may then be provided that extend from each of the first and second conduits 612, 614 to contact the conductive radially outer layer of the reinforced composite 630.

While the present disclosure has been described with reference to various examples, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the disclosure set forth in the appended claims.