BACKGROUND TO THE INVENTION High pressure flexible hoses typically consist of a reinforcing core of fibres or wires, encased in a resilient material such as rubber or plastics. To form connections between hoses or to connect the hose to a valve or other termination, it is conventional to swage on to the end of the hose, a metal coupling. The coupling is typically formed with an annular socket into which the hose end is inserted, the coupling then passing through one or more swaging dies to compress the walls of the socket into engagement with the hose wall, to form a fluid tight connection. The inner walls of the socket may be provided with annular ribs which bite into the resilient material to improve the connection. Such hoses are typically used in the oil industry, for example for hoses associated with oil drilling and production rigs, and for tanker connections.

Typical hose end terminations are relatively short and are swaged or crimped onto the hoses with a machine, which is often a specially tooled hydraulic press. In one form of swaging, the swaged end fittings are pushed or pulled through a die, essentially a hole in a strong fixture. The end fitting initially has a larger diameter than the hole in the die, but by pushing or pulling the end fitting through the die, the end fitting diameter is plastically deformed to a smaller diameter. In some

variants, the internal diameter of the end fitting may be swaged by drawing a dolly which is larger than the bore of the end fitting, through the bore of the end fitting, to plastically deform the inside member of the end fitting outward, thus clamping the end fitting onto the pipe or hose. Crimped end fittings are similar in design to swaged end fittings, but are formed in a machine that has a number of punches that simultaneously squeeze the end fitting outer diameter down to crimp it onto the pipe or hose. Swaged and crimped end fittings are relatively similar, thus, either or both are referred to herein as "swaged"or"crimped"interchangeably, including variants of the swaging and crimping process that achieve the result of plastically deforming the end fitting to grip or hold the pipe or hose. Swaged terminations are relatively inexpensive and quickly installed, but have a limited tensile capacity. For small hose diameters this is not a severe limitation, however, the tensile load on the hose wall, resulting. in the end cap load, is proportional to the pipe internal diameter area, while the strength of the wall increases approximately with the hose circumference. This results in tension in the wall increasing geometrically faster then the strength of the wall. While the tensile capacity of swaged or crimped fittings can be extended to some extent by increasing their length, eventually the conventional swaged or crimped end fitting design reaches a limit. Thus, as diameter and pressure envelope capability increases, a different type of coupling is required. In particular, swaged end fittings are problematic at higher pressures for hoses employing thermoplastic materials because the latter are essentially super-cooled liquids. Whilst thermoplastics materials may appear to be solids, they flow like viscous liquids when loaded in tension or shear. Since swaged end fittings traditionally transfer the entire tensile load from the end fitting to the hose wall via shear, at higher pressures and temperatures the

hose wall gradually slides out from the end fitting.

Another problem with such fittings is leakage from the inside. This can result because the internal pressure tends to push the pipe wall away from the inner sleeve or insert of the annular socket. When the pressure exerted by the inner sleeve or insert drops sufficiently, the internal fluid leaks along the interface between the inner sleeve or insert and the pipe wall.

Flexible pipes, in contrast conventionally use expensive custom designed and machined end fittings, with each structural layer being carefully terminated. Such end fittings also normally have venting systems that convey gasses built up inside the pipe to the outside of the end fittings. The flexible pipe end fittings are not susceptible to the creep failure phenomena (hose sliding out), which plague hose fittings, but are much larger and more expensive than swaged or crimped end fittings.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a coupling for use with a flexible pipe or hose and for high pressure service, the coupling having inner and outer sleeves between which a hose or pipe end is to be disposed and secured, and wherein a seal is provided to prevent leaks between the inner sleeve and the pipe or hose. The inner and outer sleeves are both deformable for gripping the hose or pipe end securely therebetween. The seal is provided at the inner sleeve and at the end thereof away from the hose or pipe end, that is at the opening of the annular socket.

The seal may include one or more 0-rings, or alternatively a self-energising seal. The seal may be integral with the inner sleeve, and in the form of a self-energising seal. A self-energizing seal is a seal

designed such that increased pressure in the fluid results in a tighter seal.

Preferably such a coupling may comprise an end fitting, the inner and outer sleeves being secured together at one end of each thereof. At said one end connection means may be provided. The inner and outer sleeves define an annular socket opening at the other end thereof into which the hose or pipe can be inserted, with the inner sleeve being deformable radially outwards and the outer sleeve being deformable radially inwards.

A venting system may be included to evacuate gases which in use of the coupling permeate through a wall of the flexible pipe or hose, and to exhaust said gases to an external system or vent them to the ambient surroundings.

Preferably the external wall of the inner sleeve and the internal wall of the outer sleeve are provided with teeth for gripping the hose or pipe internal and external walls, respectively.

Outwardly-directly circumferential ribs may be provided on the inner sleeve, which ribs are shaped in longitudinal cross-section as teeth directed away from said other end of the inner sleeve, and the teeth becoming progressively sharper along the length of the socket away from the other end.

If the coupling is for use with a hose or pipe having a reinforcing layer, the teeth may be such that in use of the coupling the teeth extend into the reinforcing layer, whereby to improve gripping of the hose or pipe.

According to another aspect of the present invention there is provided a method of securely connecting a

flexible pipe or hose for high pressure service to a coupling therefore, the coupling having deformable inner and outer sleeves between which an end of the hose or pipe is to be disposed and secured, including the steps of disposing the end of the hose or pipe between the sleeves with a seal provided between the inner sleeve and the hose or pipe, and deforming both of said sleeves towards the respective surface of the pipe or hose in such a manner that the average diameter of the pipe or hose over the length thereof within the coupling is not increased, and such that the pipe or hose is gripped securely there between.

The deformation may be achieved by swaging using a. two- step process in which the inner sleeve is swaged outwardly towards the hose or pipe, and the outer sleeve is swaged inwardly towards the hose or pipe in separate operations. The inner sleeve may be swaged outwardly before the outer sleeve is swaged inwardly.

Alternatively, the inner sleeve may be swaged outwardly and the outer sleeve is subsequently swaged inwardly.

The method may further include the step of measuring the internal diameter of the hose or pipe during the deformation process, whereby to provide an indication of the degree of deformation of the inner or outer sleeves, whichever was deformed last, whereby to facilitate control of the process for achieving reproducibility of manufactured connections. Alternatively, the method may include the step of measuring the pressure during deformation, whereby to provide an indication of degree of deformation and thereby to facilitate control of the process for achieving reproducibility of manufactured connections. Strain gauges or pressure sensitive materials may be used for measuring the pressures.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described with reference to the accompanying drawings in which Figure 1 is a partial cross-sectional view of a fitting before swaging, with the hose end inserted; Figure 2 is a partial cross-sectional view of the inner part of the coupling of Figure 1; Figure 3 is an enlarged sectional view of the ribs of the component shown in Figure 2; Figure 4 is a view corresponding to Figure 1, showing the start of the first stage of a swaging process, Figure 5 is a view similar to that of Figure 4, but illustrating the configuration before commencement of the second stage of the swaging process; Figure 6 is a cross sectional view of a fitting before swaging or crimping and with a hose inserted in the annular socket thereof; Figure 7 shows an enlarged sectional view of a number of the ribs of the component of Figure 6, with a first embodiment of sealing means, and Figure 8 shows an enlarged sectional view of one rib of the component of Figure 6 and a second embodiment of sealing means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring firstly to Figures 1 to 3, an unswaged fitting comprises two components which are welded together to define between them an annular socket 1 into which a hose end 2 is inserted. The inner component 3 has at one end an externally screw threaded connection and at the other a section of reduced diameter having external circumferential ribs evenly spaced there along. Each rib 4 is shaped in cross-section like a tooth directed away from the entrance to the socket, with the teeth becoming

progressively sharper or more pointed away from the entrance, as can be seen in Figure 3. The first rib 4a nearest to the entrance to the socket has a relatively rounded profile, while the last rib 4j, furthest from the entrance, has a sharp toothed profile. The diameters of the peaks of the ribs may increase slightly along the length of the fitting, so that the first rib 4a also has the smallest diameter, while the last rib 4j has the greatest diameter. This is indicated in the drawings in particular in Figure 3 by the dashed line. This ensures that, after swaging, the inward force exerted on the hose by the fitting increases progressively away from the entrance to the socket, thereby reducing the sharp transition between the swaged and free portions of the hose.

The ribs 4 are may also be dimensioned such that the spaces between them are substantially equal in volume to that of the ribs, whereby material displaced by each rib from the inner surface of the hose during swaging can flow into the spaces between the ribs, initially filling the space without significant compression of the material. For large diameter pipes and high pressure use, it has however been found necessary to swage the fitting to a greater degree than this, as is discussed in the following.

The outer component 5 of the fitting has circumferential ribs 6 which are inwardly directed within the socket 1, and may also shaped so that the spaces between the ribs are substantially equal in volume to that of the adjacent ribs. Again, in profile the ribs 6 have a toothed configuration with the teeth angled away from the entrance to the socket 1.

The hose is typically of the type having one or more reinforcing layers 7 between layers of electrometric or

thermoplastic material. The reinforcing layer material may be comprised of metal tapes wound in opposite directions, so as to overlap, or metal wires or ceramic or other fibres braided or otherwise provided within the hose wall.

The fitting comprises two tubular components which can conveniently be formed from steel tube, machined internally and externally to provide the desired profile.

The two components are then welded together to provide the structure illustrated in Figure 1 or Figure 6. The inner tube 3 could be initially formed by forging, although machining would still be necessary to provide the external ribs, or at least to finish the ribs to the desired profiles. The outer tube 5 may possibly be manufactured by deforming a thinner tube, as opposed to machining a relatively thick-walled tube. A range of different outer components of different inner diameters may be required to accommodate variations in the dimensions of the hose, for example hoses with different wall thickness for different operating pressures, or to compensate for manufacturing tolerances. It may also be necessary to provide coupling having different inner component diameters, where variations in internal diameter require this.

A hole 8 is provided through the outer component of the fitting, at the end thereof remote from the socket entrance. This serves to allow escape of air from the socket during swaging, as described hereinafter. To prevent ingress of moisture in use, the hole 8 will need to be sealed. It may be possible to position the hole such that the displacement of the hose in the socket due to the swaging action will block the hole at the completion of swaging.

In an alternative arrangement, venting means may be provided in place of a simple hole 8, to allow escape of gases and to prevent ingress of moisture or air. This may be desirable if permeation of gas or liquid from within the tube enters the reinforcing layer.

Alternative sealing methods are described hereinafter.

Allowing this gas or liquid to vent from the end of the hose will serve to prevent pressure build up within the hose wall, possibly leading to delaminating. A further possibility would be the addition of a pressure detector at the vent, or in place of it, to provide a warning of pressure increases which may be due to leakage within the hose.

Referring now to Figures 4 and 5, the assembly of the fitting with the hose comprises three main steps: insertion of the hose end 2 into the socket in a correctly-sized coupling; internal swaging of the inner part 3 of the coupling into engagement with the inner surface of the hose ; and then external swaging of the outer part 5 of the fitting into engagement with the external surface of the hose. The dimensions of the fitting are ideally selected such that the hose is a sliding fit within the socket. However, to accommodate variations in the external dimensions of the hose resulting from normal manufacturing tolerances, it may be preferred to use a standard fitting dimensioned to accommodate hose within the tolerance range, and selecting different swaging dies according to the actual internal and external diameters of the hose.

The fitting is first mounted over a shaft 10 of a ram (not shown) which passes through an abutment plate 11 against which the end of the fitting rests. The swaging tool proper, 12, may be screw threaded onto the shaft 10 or formed integrally therewith, and is disposed so as to come to rest against the inner end of the inner part of

the fitting. If necessary, the shaft is adjusted in position to bring the tool into contact with the fitting, as shown in Figure 4. The hose is then inserted into the socket over the tool 12 until a pre-marked length is within the socket. The ram is then operated to pull the tool through the fitting until the internal clearance of the threaded portion of the fitting permits the fitting to be removed from the tool 12.

The final step of the method is illustrated in Figure 5.

A swaging die 13, which may be in two parts, is positioned around the hose and with its wider entrance part receiving the socket end of the fitting. A pushing ram (not shown in its entirety) has a cup 14 at the end thereof into which the threaded end of the fitting is located. The ram is then extended to push the fitting through the swaging die 13, swaging the outer part of the fitting into contact with the outer surface of the hose.

As can be appreciated from the description and drawings the two-stage swaging process comprising swaging initially from the inside of the fitting and subsequent swaging from the outside of the fitting, results in a particularly secure connection between the fitting and the hose, and this is achieved without increasing the average diameter of the hose over the length of the fitting. For high pressure use this is particularly desirable. The fittings when mounted on the hoses or pipes have a larger tensile capacity than hitherto.

Whereas the above description refers to swaging fittings on to hoses, they may alternatively be crimped thereto.

The swaging process is preferably such that a higher degree of swaging is obtained than was the case with previous fittings. In order to be able to swage the fittings in a reproducible manner, it is advisable to include some form of manufacturing process control. This

may involve measuring the deflection of the inner sleeve member 3 or the outer sleeve member 6. Whereas the above double swaging process performs the internal swaging first, it is alternatively possible to provide the external swaging first. The deflection of the inner sleeve or the outer sleeve would then be measured for whichever element was deformed last, for the manufacturing process control. The measurement of the deflection may comprise measuring the internal diameter or alternatively measuring the pressures involved in the swaging or crimping process. In the latter case strain gauges or pressure sensitive materials may be employed to determine the amount of squeeze and thus be employed in a process control method.

In order to prevent leakage of the material contained within the hose during use thereof, by passage between the interface between the inner-most surface of the hose and the outer-most surface of the inner sleeve, it is proposed to place at least one seal thereat. In the embodiment illustrated in Figure 7, such a seal may be comprised by a separate element such as an 0-ring seated in a trough between two adjacent ribs. In Figure 7 an 0- ring 21 is disposed in a trough 25 between two adjacent ribs 23 and 24. An annular groove may be machined to provide a seat for the seal 21. If required for higher reliability, a second 0-ring 27 can be disposed between ribs 24 and 28. Such 0-rings may be of polymeric or elastomeric materials.

An alternative embodiment of sealing means is illustrated in Figure 8. This is a simple self-energising seal and is comprised by an annular slot 29 machined into the end of the inner sleeve 3 as illustrated, together with a grooved portion 30 at the outer surface of the sleeve 3.

The tubular element 31, thus formed, will be urged, by pressure within the pipe entering annular space 29, in

the direction to force the portion 30 against the inner surface of the hose. Whereas this arrangement of self- energising seal is formed integrally with the sleeve 3, it could alternatively be formed as a separate element.

Such a self-energising seal will produce a greater sealing effect for higher pressures within the pipe.

As will be appreciated from the above, the end fittings proposed by the present invention include a number of specialised features which allow their use in terminating high pressure hoses or flexible pipe. They are relatively low cost and can be quickly installed. In addition they provide a larger tensile capacity than conventional swaged or crimped fittings. Whereas the specific embodiments described above have particularly profiled teeth, being sharper towards the interior of the annular socket, this is not the only possibility. Other profiles may alternatively be used. It is also possible to employ teeth which, when the fitting is mounted on the hose or pipe, extend into the reinforcing layers thereof, partly deforming them to improve the grip. Whereas the invention has been described in terms of end fittings for hoses or pipes, it is correspondingly applicable to couplings for hoses or pipes. A coupling may be employed to join two hoses or pipes or to join a hose or pipe to another member, the latter coupling thus being in the form of an end fitting.