GB2244179A - Antistatic connection of hose assembly - Google Patents

Abstract

A hose assembly (10) includes a hose (11) internally furnished with a helically wound reinforcing conducting wire (12), a tailpiece (14) at the end of the hose and a seal annulus (21) urged into sealing relationship with the hose (11) and the tailpiece (14) by means of a ferrule (18), a tail (20) of the inner wire (12) being led through the seal annulus (21) and secured in electrically conducting relation with the tailpiece (14), desirably to provide a visible indication that there is electrical continuity between the inner wire (12) and the tailpiece (14). Inner and outer conducting wires may be connected together in the assembly in such a way that the connection may be broken for testing continuity of each wire individually. <IMAGE>

Description

HOSE ASSEMBLIES This invention relates to hose assemblies which are used for conveying industrial fluids of low conductivity, such as light petroleum distillates, and which comprise a length of flexible hose which is wrapped internally and, optionally, externally with a helical reinforcing wire which serves to provide an electrically conducting path from end to end of the hose assembly and also serves as reinforcement for the usually, laminated synthetic plastics or rubber material of the hose. At the end, the hose is connected to a hose coupling which includes: a tailpiece which is disposed within the hose end; an external ferrule and annular seal which, with the tail piece, forms a fluid tight seal with the hose and means for connecting to a comparable or similar coupling.

From the point of view of hazards associated with flammable vapours and in order to prevent the build-up of static electricity generation along the hose, it is essential that the coupling is in electrically conductive relationship with both the inner wire and the outer wire. Bonding to earth is achieved through the coupling of the assembly.

Heretofore, this has been achieved.in#the aforesaid hoses by ensuring that the tailpiece has an inner part which is in engagement with the inner wire, such inner part being possibly threaded helically to engage the inner wire and having an end part which is externally smooth and which is sealed relative to the end of the hose by means of an annular seal arrangement. Swaging of the ferrule onto the tailpiece causes the end part of the hose to be sealed relative to the tailpiece and the inner part of the tailpiece to be firmly urged against the wire so as to be in electrical contact therewith. Similarly, the outer wire is clamped by an inner part of the ferrule so as to achieve electrical continuity with the tailpiece, by means of a metallic strip fitted within the ferrule therewith.

As has been mentioned, if electrical continuity between either the inner wire or the outer wire and the coupling should be broken, the assembly becomes very dangerous, from the point of view of any accumulated static charge being unable to dissipate to earth. Breakage of the electrical connection can occur through breaking of the wire (fairly rare and usually only a problem in relation to the inner wire, any break in the outer wire usually being seen fairly quickly) or a failure to make or maintain the electrical connection between the inner or outer wire and its part of the coupling. For example, the engagement between the outer wire and the ferrule can be rendered non conducting by oxide or lubricant film on the ferrule, or between the inner wire and the tailpiece for similar reasons.In many cases, the inner wire has a protective, non electrically conductive or semi conductive coating which has to be removed over a part of the length of the wire to make full electrical contact with the tailpiece.

Electrical contact between this small part of the inner wire and the tailpiece can be broken by corrosion or entry of material being conveyed.

It is an object of the present invention to provide a method of making a hose assembly which reduces the possibility of loss of electrical continuity along the hose, and between it and its coupling.

According to the invention there is provided a method of making a hose assembly including providing a length of hose which is internally furnished with a helically wound reinforcing conducting wire, placing a tailpiece within one end of the hose, engaging a seal annulus with an end portion of the hose and urging the seal into sealing relationship with the hose and the tailpiece by means of a ferrule, wherein a tail of the inner wire is led through the seal annulus and secured in electrically conducting relation with the tailpiece.

The seal annulus will usually be of a deformable plastics or rubber material and can have a solid nose and a pair of skirts defining an annular slot in which said end portion of the hose is engaged and sandWiched during swaging. In this case an aperture can be provided in the nose of the seal for passage of said wire tail.

A portion of the wire tail can lie adjacent the inner skirt.

The material of the annulus may be sufficiently plastic to flow around the wire tail and form an adequate seal between it and the annulus and hose end.

However, this will not normally be the case, as the material of the annulus has to be sufficiently strong to form a good physical bond between the tailpiece and the ferrule for the simple physical strength of the assembly. Preferably, therefore, seal material is provided which will deform to seal completely any gaps between the wire and the hose and the seal annulus.

Desirably the sealing material deforms plastically.

The sealing material can be in the form of a short length of tubing surrounding the tail of the inner wire one or more annular sealing rings surrounding the tail or one or more strips of a suitable material laid along side the tail. We have found that two strips of PTFE material laid along side the tail are quite satisfactory.

Desirably the free end of the tail is attached to the tailpiece so as to be externally visible. This enables the physical connection of the tailpiece to the wire to be visibly inspected.

Connection can be by means of a wire clamp such as a socket and grubscrew, or can be a simple soldered or comparable connection. However, in order to reduce the possibility of damage to the connection between the wire and the tailpiece in use, it is desirable that the connections should be within the material of the tailpiece. It is desirable, therefore, that the tailpiece be provided with an inwardly extending reinforcement projection or lug accommodating the wire clamp formation. The wire clamp formation can comprise a pair of intersecting apertures arranged at an angle to each other, one forming a socket for the wire and the other receiving a clamping screw such as a grubscrew. In this sort of connection it is important to provide reinforcements internally of the tailpiece, otherwise the material of the tailpiece could be weakened beyond its minimum strength.

Further, it would be impossible to apply a rotatable annular coupling nut to the tailpiece before assembly.

As has been mentioned, the electrical continuity connection between the outer wire and the ferrule and hence to the tailpiece is usually less of a problem.

However, the connection between the ferrule and the tailpiece is not always continuous and for this reason it is desirable to provide a tail on the outer wire, bring the tail back through the ferrule at the exterior diameter of the sealing annulus and connect that to the tailpiece in a manner similar to the tail on the inner wire.

To accommodate the tails the ferrule can be provided with diametrically opposite notches in its outer flange diameter at the seal end.

In the case of a tailpiece which includes a coupling member which does not have an annular, larger diameter nut, it is possible for the lug to be provided on the outside of the tailpiece, thus avoiding any need to reduce the internal cross-sectional area of the tailpiece.

If so desired, an electrically insulating member can be provided to ensure electrical separation between the outer flange of the ferrule and the metal of the tailpiece, electrical connection being between the tailpiece and the ferrule being maintained, in normal practice, by the connection between the two wires and the tailpiece. With separable connections between the two wires and the tailpiece it is possible, with the inclusion of this insulator to isolate the inner and outer wire conducting paths and electrically test them independently for continuity of the hose assembly. This can be very important when an internal wire may break or become disconnected without there being any visible sign thereof.

Instead of the outer wire being connected in the same way as the inner wire, it is possible for the connection between the ferrule and the outer wire to be relied upon for electrical continuity by terminating the outer wire within the ferrule and for a metal strap to be provided between the ferrule and the tailpiece which provides electrical connection.

This strap can form part of a disconnectable system for testing as aforesaid.

The invention includes a hose assembly made by the method aforesaid.

The invention still further provides a hose assembly including a length of hose ' having an internal and an external reinforcing conducting wire helix, a tailpiece engaging inside an end portion of the hose and an external ferrule swaged to compress a seal and an end portion of the hose, between the ferrule and the tailpiece, means being provided to electrically isolate the ferrule and the tailpiece, and electrical connection being made between the inner wire and the tailpiece and the outer wire and the ferrule, an electrical connection between the ferrule and the tailpiece being provided, which connection can be broken in order to allow the inner wire/tailpiece continuity and the outer wire/ferrule continuity to be tested independently.

Connection between the inner wire and the tailpiece and the outer wire and the ferrule can be independantly tested by the methods described earlier.

The invention will be described further, by way of example, with reference to the accompanying drawings where: Figure 1 is a cross sectional view illustrating one end of a preferred hose of the invention; Figure 2 is a cross section on the line 11-11 of Figure 1; Figure 3 is an enlarged cross sectional view illustrating a sealing annulus used in the hose of Figure 1; Figures 4 and 5 are enlarged fragmentary cross sectional views taken on the line lV-lV illustrating its condition before and after swaging respectively; Figure 6 is a view similar to that of Figure 1 but illustrating a second aspect of the invention; Figure 7 is a cross sectional view on the line Vll-Vll of Figure 6; Figure 8 is a view similar to Figure 10 but illustrating a second aspect of the invention; Figure 9 is a cross sectional view on line lX-lX of Figure 8;; Figure 10 shows a further view comparable to Figure 1 but illustrating a further modification in that the coupling fitted to the hose assy is an alternative design (cam locking coupling); Figure 11 is a cross sectional view of line Xl-Xl of Figure 10; Figure 12 shows a modified tailpiece for use with the invention; Figure 13 is a fragmentry view in the direction of arrow A in Figure 12; and Figure 14 is a view comparable to that of Figure 13 but showing a variation.

Referring now to Figures 1 to 9, it will be seen that a first preferred hose assembly 10 of the invention includes a length of hose 11 having inner and outer reinforcing conducting helical wires 12 and 13. The hose assembly 10 can be a free hose assembly, in which case it will have a fitting at each end.

Alternatively, the assembly can extend from a container or other apparatus, in which case it can be permanently attached at one end and have a fitting only at the other end. Normally, however, the assembly 10 will have a fitting at each end and, hereinafter, the assembly 10 is described as though it does have a fitting at each end.

At each end of the hose 11 a conducting metal tailpiece 14 is inserted. As seen, on the tailpiece 14 is a helical screw formation 15 for engagement with the inner wire 12. This formation is not essential, although it does help the strength of the fitting. The tailpiece 14 forms part of a coupling 16 which, as well as the tailpiece 14 includes a connection means such as a loose annular nut 17 of conventional form.

These e is sealed to the tailpiece 14 by inwardly swaging a metal ferrule 18, which has a generally cylindrical body and an inturned flange 1% by reducing its external diameter.

Sealing is achieved by means of a seal annulus 21 which is shown in cross section in Figure 3. Whe annulus 21 has a front, generally solid, nose 22 and inner and outer annular skirts 23, 24 defining between them an annular slot 25 which receives an end portion of the hose 11. Upon swaging of the ferrule 18 the seal annulus 21 is compressed into sealing engagement with the hose 11 and the tailpiece 14. Although the material of the annulus is deformable, it does form a significant part of the mechanical bond between the coupling and the hose 11 and therefore cannot be too soft.

In accordance with a preferred method of the invention a tail 20 is formed on the inner wire 12 and is straightened to extend parallel to the axis 26.

During assembly the tail 20 is passed through the annular slot 25 and through a hole 27 formed in the nose 22. Because of the aforesaid lack of flowability of the material of the annular seal 21, it is usually necessary to provide some additional sealing material to fill the interstices which could be formed between the tail 20 and the end of the hose 11 and the skirt 23. This can take the form of a sleeve of deformable plastics or rubber, one or more sealing rings, a settable compound or the like. Desirably however a pair of strips 28 of deformable PTFE are used to form this seal. Figures 4 and 5 illustrate the formation of the seal. It will be seen from Figure 5 that during the swaging operation the strips 28 are compressed and deformed completely co fill any interstices which may be formed between the wire tail 20 and the adjacent component.

After passing through the aperture 27 the tail 20 passes through a notch 29 formed in the flange 19 of the ferrule 18 whereafter, the tail 20 is bent (see Figure 2) and inserted into a socket 30 which has been formed in a lug 31 internally formed (usually by casting) with the tailpiece 14. The lug 31 also accommodates a threaded aperture 32 which intersects the socket 30 and in which a grubscrew 33 is provided securely to clamp the wire tail to the lug 31 and form a secure electrical connection between it and the tailpiece 14.

This connection can be replaced by a soldered brazed or swaged or other electrically conductive connection if necessary, it being important not to reduce the thickness of the metal of the tailpiece to such a degree as would impair its pressure resistance or hoop strength.

Desirably, and as best seen at the bottom of Figure 1, the outer wire 13 is treated in a comparable way. A tail 34 is formed, led outside the sealing annulus 21 to a notch 35 in the flange 19 and secured to a lug 36 in the same way as the tail 20 secured to the lug 31.

Figures 10 and 11 are Figures very similar to Figures 1 and 2 and they illustrate how the invention can be applied to a cam locking coupling (a female type is illustrated but the invention is equally applicable to a male coupling). In this case it is not necessary to slide the nut 17 over the tailpiece 38 because of the nature of the coupling. Thus, the lugs 31 and 36 can be replaced with external lugs 39 and 40 which, together with the grubscrew 41 serves exactly the same purpose as the lugs 31 and 36 in relation to the wire tails 42, 43 in that they form a secure electrical connection between them and the coupling. In relation to Figures 10 and 11 as the remaining parts of the construction are comparable in every way to the similar parts of Figures 1 and 2 no further description has been included.

Figures 6 and 7 illustrate two possible variations to the construction which is shown in Figs.

1 and 2. In the hose assembly 44 shown the hose 45 is secured to a tailpiece 46 by a ferrule 47 with the interposition of seal annulus 48. An inner tail 49 is sealed and connected to the tailpiece 46. However, this construction differs from that shown in Figure 1 in that the outer wire 50 is terminated within the ferrule and connected to the ferrule 47 by contacting the interior surface, and connection between the ferrule 47 and the tailpiece 46 is effected by means of a releasable strap 51. This strap 51 forms an electrical connection between the ferrule 47 and the tailpiece 46. The connection can be disconnectable by being soldered or brazed at the tailpiece end and secured by a clamp strap 52 to the ferrule, or in any comparable way, the clamp strap being removable.

Figures 6 and 7 also illustrate the important second aspect of the invention. In the hose assembly 44 the inner wire is electrically connected by its tail 49 to the tailpiece 46 and the outer wire 50 is connected to the tailpiece 46 either by a tail (not shown) or by the strap 51. In either case, the connection between the tailpiece and the ferrule 47 can be broken. Between the ferrule 47 and the tailpiece 46 is provided insulating means which, in this instance is in the form of a stepped ring 53.

Alternatively a shrunk insulating sleeve can be used.

This ensures that the ferrule 47 and outer wire 50 and the tailpiece 46 and inner wire 49 are electrically separate when the connection (such as 51) has been disconnected. This allows the continuity of the internal helix wire and the two tailpieces and the electrical continuity of the two ferrules and the outer helix wire to be tested independently. This is particularly important in the case of the inner helix which can, sometimes, break without that break being externally detectable.

In Figures 8 and 9 is shown a hose assembly 54 which is comparable to the hoses in Figures 6 and 7 and that shown in Figures 10 and 11. Here, the hose assembly 54 has a tailpiece 55 which has a cam fitting 56. Thus, it has external lugs 57 comparable to lugs 39 and 40. Over and above Figures 10 and 11, however, it has an insulating ring 58 comparable to the ring 53 in Figure 6. It will be appreciated that the hose shown in Figures 8 and 9 is comparable to the hose shown in Figures 6 and 7 except that it has both inventions applied to a cam locking coupling.

As has been mentioned, the method of the invention produces a hose assembly which has a greatly reduced possibility of there being electrical isolation between either its outer wire and its ferrule and coupling and its inner wire and the tailpiece. In addition, there is also provided the additional possibility of electrically isolating the inner and outer wires so that the electrically continuity can be independently tested once a simple interconnection between them has been disconnected.

The invention is not limited to the precise details of the foregoing and variations can be made thereto.

For example, many different forms of seal can be employed and the sealing method is applicable to hose assemblies having flanged ends or any other convenient type of connecting members.

Figures 12 to 14 illustrates one possible variation in the way of secureing the wire tails. In Figure 12 is shown a tailpiece 59 (note that here it is the female swival tailpiece which is illustrated but it will be appreciated, of course, that any tailpiece can be so treated) which, instead of the large internal lugs 30, 31 is provided with shallow internal lugs 60 which allows the formation of a slot 61 in the outer surface of the tailpiece. The wire tail (not shown) can be arranged to be disposed in the slot and soldered or brazed thereto. Figure 13 shows the slot 61 suitable to accommodate a single wire and it will be appreciated that a further slot 61 is provided on the diametrically opposite side of the tailpiece 59 or alternatively at any angle less than 1800. However, as illustrated in Figure 14 the relatively narrow slot 61 can be replaced by a wider slot 62 and both wire tails can be soldered in the same slot 62.

The slots 61, 62 can be either cast or machined into the tailpiece.

Claims (28)

1. A method of making a hose assembly including providing a length of hose which is internally furnished with a helically wound conducting wire, placing a tailpiece within one end of the hose, engaging a seal annulus with an end portion of the hose and urging the seal into sealing relationship with the hose and the tailpiece by means of a ferrule, wherein a tail of the inner wire is led through the seal annulus and secured in electrically conducting relation with the tailpiece.

2. A method as claimed in claim 1, wherein the seal annulus is of a deformable plastics or rubber material.

3. A method as claimed in claim 1 or 2 wherein the annulus has a solid nose and a pair of skirts defining an annulur slot in which said end portion of the hose is engaged and sandwiched during swaging.

4. A method as claimed in claim 3, wherein an aperture is provided in the nose for passage of said wire tail.

5. A method as claimed in claim 3 or 4, wherein a portion of the wire tail lies adjacent the inner skirt.

6. A method as claimed in any of claims 1 to 5 wherein the material of the annulus is sufficiently plastic to flow around the wire tail and form an adequate seal between it and the annulus and hose end.

7. A method as claimed in any of claims 1 to 5, wherein sealing material is provided which will deform to seal completely between the wire and the hose and the annulus.

8. A method as claimed in claim 7, wherein the sealing material deforms plastically.

9. A method as claimed in claim 7 or 8, wherein the sealing material is in the form of a short length of tubing surrounding the tail.

10. A method as claimed in claim 7 or 8, wherein the sealing material is in the form of one or more annular sealing rings surrounding the tail.

11. A method as claimed in claim 7 or 8, wherein the sealing material is composed of one or more strips of a suitable material.

12. A method as claimed in claim 11, wherein the sealing material is two strips of PTFE material laid along side the tail.

13. A method as claimed in any of claims 1 to 12, wherein the free end of the tail is attached to the tailpiece so as to be externally visible.

14. A method as claimed in any of claims 1 to 13, wherein connection is by means of a wire clamp.

15. A method as claimed in claim 14 wherein the wire clamp is a socket and grubscrew, or a single soldered or comparable connection.

16. A method as claimed in claim 13 or 14, wherein the connection is within the material of the tailpiece.

17. A method as claimed in claim 16, wherein the tailpiece is provided with an inwardly extending reinforcement projection accommodating the wire clamp formation.

18. A method as claimed in claim 13 to 17, wherein formation comprises a pair of intersecting apertures arranged at an angle to each other, one forming a socket for the wire and the other receiving a clamping screw such as a grubscrew.

19. A method as claimed in any of claims 1 to 18, wherein there is provided a tail on the outer wire, the tail is led back through the ferrule at the exterior of the sealing annulus and connected to the tailpiece in a manner similar to the tail on the inner wire.

20. A method as claimed in any preceding claim, wherein to accommodate the tails, the ferrule is provided with spaced notches in its outer flange.

21. A method as claimed in any of claims 1 to 14 or claim 20, wherein the tailpiece includes a coupling member which does not have an annular, larger diameter nut, a lug being provided on the outside of the tailpiece for the wire anchorage.

22. A method as claimed in claim 19 or any claim dependent therefrom, wherein an electrically insulating member is provided to ensure electrical separation between the outer flange of the ferrule and the metal of the tailpiece, electrical connection between the tailpiece and the ferrule being maintained, in normal practice, by the connection between the two wires and the tailpiece.

23. A method as claimed in claim 19 or 22, wherein the connection between the ferrule and the outer wire is relied upon for electrical continuity, a strap being provided between the ferrule and the tailpiece to provide electrical connection.

24. A method as claimed in claim 23 when dependent from claim 22, the strap forming part of a disconnectable system for testing.

25. A hose assembly made by the method of any preceding claim.

26. A hose assembly including a length of hose, internal and external reinforcing and conducting wire helices, a tailpiece engaging inside an end portion of the hose and an external ferrule swaged to compress a seal and an end portion of the hose between the ferrule and the tailpiece, means being provided electrically to isolate the ferrule and the tailpiece, and electrical connection being made between the inner wire and the tailpiece and the outer wire and the ferrule, an electrical connection between the ferrule and the tailpiece being provided, which connection can be broken in order to allow the inner wire/tailpiece continuity and the outer wire/ferrule continuity to be tested independently.

27. A method of making a hose assembly substantially as hereinbefore described with reference to the accompanying drawings.

28. A hose assembly substantially as described with reference to the accompanying drawings.