GB2307663A - Method and apparatus for flaring ends of plastics tubes - Google Patents

Abstract

Apparatus, for forming flared ends on plastic tubes comprising a heater 2 with an aperture 5 for receiving one end of the tube, a second aperture 32 for receiving a flared end forming element 7 where the end forming element 7 is mounted so as to be operable to controllably advance towards the end of the tube and substantially close the second aperture 32 as it advances towards the end of the tube. A method for fixing a tube wire support to a tube and fitting is also described and claimed. an aperture or slot 29, Fig 6 an end fitting 19, passing the end of the wire into the interior of the end fitting and through the aperture or slotting the wire into the slot so that the end of the wire is accessible from the outside of the end fitting and fixing the wire to the end fitting. The end fitting comprises an aperture or slot for receiving tube wire.

Description

TUBE FLARING APPARATUS This invention relates to a method and apparatus for plastic tube flaring and, more particularly, but not exclusively, to apparatus for flaring the ends of helically convoluted thermoplastic tubes.

Methods of forming convoluted plastic tubes are known. In US patent specification 3327039, a method of producing spirally corrugated hoses which is fabricated of plastic material is described. Such a hose or tube is utilised where flexibility and elasticity are required in a tube having a relatively thick wall. The method generally describes use of a grooved mandrel over which a tube is placed to be forced into the grooves by a groove forming member. Similar methods are disclosed in UK patent application number 2126685, UK patent number 1543586 and US patent number 4134958.

Generally, tube materials are carefully chosen to suit the particular chemical or physical requirements of the application. Chemical inertness is required in many applications where the materials being transported through the tubing may react with the walls of the tubing.

Typically, an inert plastic such as PTFE is chosen for this kind of application. However, in some applications several lengths of tube must be joined end to end and the clamps which are utilised to join the respective ends of the tubes interrupt the continuous internal plastic lining and provide areas for undesirable chemical reactivity.

The problem is addressed by placing the securing clamps on the outside of the tubes and flaring the respective ends of the tubes to be joined so that the flared ends are approximately at right angles to the axis of the tube. The flared ends of the adjoining tubes are then clamped together between the flat end faces of the respective clamps. This method maintains a continuous internal plastic lining between adjoining tubes but the flaring of the ends is problematic and it commonly results in tube splitting. Furthermore, it is difficult to flare the ends of the tubes at the ideal angle of 90" as, due to elastic memory, they tend to relax a little when cold after being released from their final clamp.

Heat sources such as hot air guns and/or heated 'flaring' pegs have been used to provide heat but this is generally insufficient, not consistent around the circumference of the tube and not easily controllable particularly in the case of the 'flaring' pegs. A further problem is that these methods may cause damage to either the internal tubing or the flared ends.

In particular, one method uses an internal 'expandable' clamp(s) with an integral flaring mechanism. The clamp is fastened within the end of the tube and sandwiches the tube between the internal clamp and the external securing clamp.

The internal clamp provides a secure base from which the 'flaring' mechanism is pulled down to force the tube end in a flared manner against the end face of the securing clamp.

It is possible to gradually adjust the flaring mechanism and this allows the flaring process to be performed gradually and controllably so the chance of splitting the flared end is reduced. However, in order to secure the internal clamp(s) considerable frictional forces are exerted by the clamp against the internal diameter of the tube which can cause damage to the internal tube. This is a particular problem when the tube is helically convoluted as the clamps themselves must also fit within this configuration in order to avoid tube damage. Furthermore, external visual examination may be insufficient to see any damage to the tube.

A further method avoids some of these problems by first deconvoluting helical tubes. The method then includes the step of manually pressing the tube end against one or more fixed frusto-conical 'flaring' pegs in turn - to gradually flare the end - before clamping the flared end against a suitable peg. The method succeeds in avoiding damage to the internal circumference of the tube but the likelihood of splitting the flared end increases due to the manual forces applied by the flaring pegs being difficult to measure or control. Furthermore, it is difficult to support the entire length/weight of a hose assembly whilst the flaring process is taking place. In addition, it is difficult to ensure that the external end clamp will remain axially fixed with respect to the internal tube during the flaring process as it is pushed away from the end being flared by the forces involved.

The present invention addresses these problems.

According to a first aspect of the present invention, there is provided apparatus for forming flared ends on plastic tubes comprising: a heater, the heater having a first aperture for receiving an end of a tube to be heated, and a second aperture for receiving a flared end forming element; the end forming element is mounted so as to be operable to advance controllably towards the end of the tube and substantially close the second aperture as it advances towards the end of the tube.

Advantageously, this allows the end of the tube to be formed whilst maintained within the preset temperature range as the temperature of the oven is more easily maintained due to closure thereof by the advancing forming element.

In addition, the controlled heating allows the tube to be deconvoluted, if necessary, prior to the flare formation steps.

Furthermore, the heating means may be easily controlled during the flaring process and there is thus little chance of splitting the ends. In particular, the axial movement of the forming element improves heat control during the forming process. In addition, the heater unit is itself axially movable with respect to the tube and this gives a very rapid introduction of controlled heat to the end of the tube to be flared.

The apparatus does not require any internal clamps and it therefore avoids internal damage to the tube.

Preferably, an end fitting, close fitting with the tube and having a flat end face, which may be an annular flange, at its forward end is placed over the end of the tube so that the flat end face forms a plate against which the tube is flared by a forming element. A suitable preset amount of tube protrudes from the end-fitting for this purpose.

Preferably, two clamps are operable to hold the tube and the end fitting in a predetermined relative position so as to maintain the preset protruding amount of tube during flaring.

The clamps may be axially adjustable which allows optional axial adjustment of the tube prior to flaring. This improves control of the length of tube to be flared.

Prior to formation, the clamps are locked into position and this prevents the end-fittings moving with respect to the tube. Furthermore, the tube clamp holds the entire length of hose securely.

Where the tube liner has a helically configured surface, it is often preferable to be able to 'pull' the protruding tube back into the end-fitting a little (RHS to LHS as per Figure 1) once it has been deconvoluted (but prior to the flaring process), as this ensures that the completed flared end blends consistently with the internal tube at the edge where they meet.

This invention advantageously provides a simple means of achieving this, whether or not the tube has an external wire support.

Where there is NO external wire support, this movement can be provided by means of suitable threaded axial adjustment between the end-fitting and tube clamps (see Figure 1).

This is achieved without loosening them.

Where there is an external wire support (which is threaded from inside to outside through an end-fitting), the clamp holding the tube (and/or external braid) may be loosened sufficiently to allow the tube to be pulled back (in a helical manner) the requisite axial amount; before being tightened again ready for 'flaring'.

Typically, the forming element is frusto-conical and at least a second forming element having a larger apex angle is also utilised so that a gradual flaring operation can be performed. Usually, there are several forming elements.

The forming elements may be located on a carousel for easy changeover after the reciprocating action of the previous forming element. After the action of the forming elements is completed, the partially flared tube end is tightly clamped between the flat face of the end fitting and a mating flat face of a second end fitting. After cooling a 90" flared end or flange is formed at the end of the tube which is completely heat set.

The tube may be smooth bore or helically convoluted in form.

Advantageously, the invention provides a single continuous process producing stable stress free flared plastic tubes.

The product is already heat set upon cooling and requires no further treatment in order to stabilise the product.

Typically, the tube heating means circumferentially surrounds the tube end so that the tube may be heated over its whole circumference prior and/or during flare formation.

The invention provides a single continuous process for forming heat set flared tubes.

Where a hose assembly has an external helical wire support this must be secured at each end fitting by suitable and appropriate means. What is particularly important is that the wire or the method of fixing the wire does not damage the internal plastic tube either before, during or after securement.

It is preferable to secure the wire to the end-fitting by a permanent method such as welding as this adds to the working parameters of the finished product (ie increased working pressure and/or vacuum rating).

It is also preferable to have the external wire fastened inside the end-fitting as this allows the finished hose assembly to be more durable when in use, as the wire provides both ends with circumferential protection against the end fittings which reduces wear during use. This is particularly the case at the inner edge of the end fitting which by repeatedly pressing against the tube during flexion ultimately causes tube failure, typically, by a puncture or "kink" near to one (or both) of the endfittings.

Preferably, the end forming element is shaped so that as it is advanced towards the end of the tube so that a front portion of the end forming element passes through the second aperture, a rear portion of the end forming element acts to maintain the second aperture substantially closed.

Preferably, the end forming element or its front portion, is frustoconical in shape. The outer diameter of the frusto-conical portion is preferably just less than the diameter of the second aperture so that the frusto-conical portion can as it approaches the aperture substantially close it.

There may be a continuous wall depending from and having substantially the same dimensions as the outermost periphery of the front portion of the end forming element is provided so that when the front portion of the end forming element is advanced past the second aperture into the heater, the continuous depending wall substantially closes the second aperture.

Preferably, there is a frusto-conical shaped front portion of the end forming element is integral with a cylindrically shaped block extending to the rear of the front portion, and in which the outer diameter of the block is just smaller than the diameter of the second aperture so that as the block passes through the second aperture, the second aperture remains substantially closed.

Preferably, the heater is designed to heat the end of the tube to within a predetermined temperature range which is sufficient to cause a chosen tube material to at least partially lose its elastic memory.

Preferably, the heater comprises controllable heating elements.

Preferably, the end forming element, or its front portion, is controllably heatable.

Preferable, the heater, first and second apertures, and end forming element are substantially axially aligned along the longitudinal axis of the tube. The alignment is preferably to within plus or minus 5".

Preferably, the heater is axially moveable with respect to the tube.

An end fitting close fitting with the tube may be provided, having a flat end face at its forward end is placed over the end of the tube so that the flat end face forms a plate against which the tube is flared by the end forming element. The flat end face may comprise an annular flange.

A heat resistant gasket may be placed over the end of the tube adjacent to the flat end face of the end fitting so that the gasket forms a surface against which the tube is flared by the end forming element.

Preferably, the end fitting is arranged so that a predetermined amount of tube protrudes from the end fitting when it is placed over the end of the tube.

First and second clamps may be provided to hold the end fitting and tube respectively in a predetermined relative position so as to maintain the predetermined protruding amount of tube during flaring.

The first and second clamps are preferably axially moveable with respect to one another whereby axial adjustment of the tube so as to improve control of the length of tube to be flared is provided. The clamps are preferably lockable in position preventing the end fitting moving with respect to the tube during flaring. One or more vertical and/or horizontal hose supports may be provided to the rear of the second clamp. The vertical and/or horizontal hose supports are axially moveable with respect of the tube and/or vertically adjustable.

The tube, heater, end forming elements and, if provided, clamps and hose supports are preferably substantially axially aligned by means of a alignment rail on which these are mounted. Preferably, one or more of the clamps can be adjusted so that once a helically convoluted tube has been deconvoluted, the tube can be drawn back away from the end fitting so that the predetermined amount of tube protruding from the end fitting for flaring is achieved.

In a preferred embodiment, at least a second end forming element having a larger apex angle than the first end forming element in the instance where this is frustoconical in shape so that a gradual flaring operation can be performed. Preferably, the first and second, and if present the further, end forming elements are located on a rotatable carousel for easy changeover after the reciprocating action of the previous end forming element.

Preferably, a second end fitting or other clamping means having a mating flat face is provided so that after flaring the partially flared tube end can be tightly clamped to the flat face so as to form a 90" flared end of flange at the end of the tube. This may have a protruding end, preferably with tapered sides and dimensioned for insertion into the tube and centering the tube in the end fitting before the partially flared tube is clamped to the mating end fitting.

In a preferred embodiment, the heater circumferentially substantially surrounds the tube end so that the tube end may be heated over its whole circumference prior to and/or during flare formation. The tube may be heated within its whole circumference by means of heating elements within the end forming element.

The tube and if provided, tube support wire may be helically convoluted and the tube may be braided.

According to a second aspect of the present invention, there is provided a method of fixing a tube wire support to a tube end fitting comprising the steps of: forming an aperture or slot in the end fitting suitable for receiving a tube wire; passing the end of the wire into the interior of the end fitting and through the aperture, or slotting the wire into the slot, so that the end of the wire is accessible from the outside of the end fitting; and fixing the wire to the end fitting.

Advantageously, the second aspect of the invention allows the wire to be fitted close to the outer end of the end fitting which maximises the tube protection provided by the wire and also maximises the tensile strength of the bond between the end fitting and the tube. Such a welding position would not be possible, without risking damage to the tube, without the invention.

Preferably, the wire is welded to the end fitting after the wire has been cut back so that it is substantially flush with the exterior surface of the end fitting. Typically, the size of the aperture is dimensioned to be close fitting with the wire. Most preferably, the wire is passed through the aperture prior to tube flaring whilst the cutting, and welding operations, are carried out after tube flaring.

Preferably, the method further comprises the step of: cutting the wire close to the hole or slot where it exits the end fitting; and/or welding the end of the wire to the end fitting and/or if a slot is provided, welding the wire to a collar introduced to the end fitting so as to form an aperture with the slot.

The collar may be cylindrical and positioned about the tube. The wire may be welded to the end fitting after the wire has been cut back so that it is substantially flush with the exterior surface of the end fitting. The size of the aperture or slot is preferably dimensioned to be close fitting with the wire. The wire is preferably passed through the aperture or into the slot prior to tube flaring, whilst the cutting, and welding operations, are carried out after tube flaring.

According to a further aspect there is provided an end fitting having an aperture or slot for receiving tube support wire. The end fitting may be provided with a collar for forming the slot into an aperture. The tube end fitting with an aperture or slot is preferably for use in the second aspect of the present invention.

According to a further aspect there is provided, a plastic tube having an external support wire having at least one end fitting with an aperture or slot receiving an end of the support wire from the inside of the end fitting. The tube and support wire may be helically convoluted and/or braided.

Generally, the end-fittings may be flanged; male/female threaded fittings, or any other suitable flat-faced fittings.

The hoses may be externally braided or unbraided. Where they are braided, this has to be securely fastened to the inner end of each external end-fitting using suitable metallic collars which are typically hydraulically 'swaged' onto the end-fittings - trapping the braid between them.

The 'flaring' process may take place either prior to, or subsequent to the 'swaging process' where the hoses have no external wire (be they smooth-bone or convoluted). But where they do have an external support wire, the 'flaring' process MUST be completed first. Then, the wire is trimmed to length and welded (or otherwise suitably fastened) to the end-fitting. Only then can the 'swaging' process take place.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a side view of apparatus in accordance with the present invention; Figure 2 shows an end view of apparatus in accordance with the present invention; Figure 3a shows a partial side view of the primary vice in accordance with the present invention; Figure 3b shows a plan view of the primary vice during tube flaring in accordance with the present invention; Figure 4 shows end and side views of an end fitting in accordance with the second and third aspect of the present invention; Figure 5a shows a tube with support wire prior to unwinding of the end of the support wire and deconvolution; Figure 5b shows a tube after the wire has been passed through an aperture in the wall of the end fitting and a partially flared end; and Figure Sc shows a tube after clamping. The insert shows an end fitting with a slot and collar arrangement.

Figure 6 also shows an alternative end fitting with the collar and slot arrangement.

Turning to Figure 1, an apparatus 1 for tube flaring is shown. A heater 2 with heating elements 3 forms an enclosure which substantially surrounds the protruding end 25 of tube 16. End 25 passes into heater 2 through aperture 5 when heater 2 is moved into the position shown in dotted lines.

An end fitting or stub-end 19 is positioned about tube 16.

End-fitting 19 includes an annular rim 24. An iris shutter 11 can be closed in so that shutter 11 and rim 24 substantially close aperture 5 of heater 2.

A frusto-conical shaped principle former 7 is axially aligned within approximately 5 of the longitudinal axis of tube 16, end fitting 19, aperture 5 and a second aperture 32. The outer diameter of principle former 7 is just slightly smaller than aperture 32 so that as principle former 7 is moved towards aperture 32 it substantially closes it. A wall or cylindrical block 8 is provided in one preferred embodiment to the rear of principle former 7 so that as former 7 is advanced into heater 2, wall or block 8 ensures that aperture 32 remains closed.

Heater 2 is positioned on an axially moveable mount 4.

Similarly, principle former 7 is mounted on a carousel 9 which is also axially moveable. Thus, principle former 7 can be advanced towards end 25 of tube 16 by moving carousel 9. In addition, fine adjustment of the position of former 7 is provided by an adjustable arm which connects former 7 to carousel 9. A secondary former 10 is also provided on carousel 9, in one embodiment. This can be rotated into position in axial alignment with tube 16 by rotating carousel 9. Principle former 7 has a conical shape with an angle approximately equal to 90 . Secondary former 10, whose position can also be finally adjusted, has a cone with an angle of approximately 1300. For certain applications only one former is required. In other applications secondary and even tertiary formers and so on may be required.

Tube 16 comprises external over-braid 18 and includes external helical wire support (not shown in figure 1) and an inner plastic tube 17. The wire support is normally situated between the braid and the tube. Tube 16 is held in position at end 25 by primary vice 12 which is normally fixed axially, though it can be moveable.

A secondary vice 13 holds over-braid 18 back from the end of the tube and is usually axially moveable or it can be axially fixed. Where it is axially moveable a threaded clamping arrangement 33 can be used to adjust the distance between the vices.

A third set of supports 14 is provided to maintain the tube 16 in a stable position during the flaring process.

Supports 14 are normally axially and vertically adjustable.

An axis of flaring 22 or longitudinal axis through apparatus 1 can be described. All the components of the apparatus are aligned within around 5 of this axis.

Typically, the supports, clamps, heater and carousel are mounted on a rail or other aligning mechanism so that lateral adjustment (into or out of the paper in Figure 1) so as to align these elements axially is automatically achieved.

Turning to Figure 2, primary vice 12 is provided with means to tighten up the clamps in the form of threaded rod and bolts arrangement 23. The vices can be opened to allow insertion and removal of the stub-end or end fitting 19 and the PTFE hose or tube. Clamps 20 within primary vice 12 are size matched to accommodate the end fitting 19. The adjustable door or iris 11 of heater unit 2 is also seen.

The adjustable door or iris 11 on the heater has an inner diameter approximately equal to the outer diameter of the end fitting or stub-end 19 at its widest point.

Turning to Figure 3a, it can be seen that end face 24 of end fitting 19 is normally within 5 of a plane perpendicular to the axis of flaring 22. When completed, the flared tube end 25 lies at 90" to the axis of flaring.

Adjustment means 23 provide for tightening or loosening of clamps 20 about end fitting 19.

Turning to Figure 3b, protruding tube end 25 is shown partially flared. Each different end fitting and tube size requires the use of different or adjusted clamps 20 so that the end fitting and tube can be securely held.

Turning to Figure 4, the end fitting is seen in more detail. Here, a hole 26 inclined at an angle with respect to a radii extending from axis 22 to end fitting 19, is shown. The hole 26 is inclined because the helical wire support around the tube leaves the tube at a tangent. The helical wire support is passed through hole 26, cut off close to the opening of hole 26 and welded to the end fitting. When the wire is welded to the end fitting 19, any wire which protrudes above the surface of the stub-end may need to be ground down by suitable means prior to "swaging" taking place. The outer diameter of the hole 26 through the end fitting is larger than the outer diameter of the wire which is pushed or threaded through it.But the hole is not so large as to allow particulates from the welding of the wire to the stub-end, to pass through it and to damage the internal tubing. The distance X of the hole from the rear side of the end fitting is equal to approximately one to two pitches of the convoluted tube which is to be passed inside the end fitting.

Turning to Figure 5a, the convoluted plastics PTFE tube 16 with an external helical wire support 27 is illustrated in cross section passing through end fitting 19. The pitch of the tubing is P. Plastic tube 27 is shown protruding through the flat face 24 of the end fitting 19 and has not yet been deconvoluted, nor has the external wire 27 been removed. Also, the end fitting has no hole drilled through it in this embodiment. It is preferred however that the plastics tube is deconvoluted, the external wire is removed and the stub-end has a hole or slot.

Turning to Figure 5b, it can be seen that protruding end 25 has been deconvoluted and partially flared to an angle of approximately 45O with respect to a plane perpendicular to the axis of flaring 22. Primary flaring can cause the angle to be as small as 25 , though this is normally achieved after a second or subsequent flaring. It can be seen that the wire is removed from tube 16 up to two or three convolutions behind the flat face of end fitting 19.

Here the end of external wire 27 has been passed through hole 26.

Turning to Figure 5c, end fitting 19 is mated with a second end fitting 119 by clamping force 31. Tubing 16 is deconvoluted to within approximately one pitch of the tubing from the flared face in this embodiment. In the inset, it can be seen that as alternative to a hole 26, a slot 29 and optionally collar 28 can be provided. Wire 27 is passed through slot 29 prior to collar 28 being threaded along the wire to be welded to end fitting 19.

A planar gasket of heat resistant material such as a fibrous material resistant to 200"-300"C is provided between the flared end 25 of tube 16 and flat face 24 of end fitting 19. The provision of this gasket between the flared end 25 and end face 24 provides "give" when two end fittings 19, 119 are clamped together.

The mating clamp used to form the completed flared end to an angle of 90" from a partially flared end is of similar size to the end fitting 19 to which it is to be fastened, or it may indeed be another stub-end 119 as shown in the figure. In Figure 5c, no hole is shown in the end fitting because the tube does not have an external wire. Where external wire is provided, a hole or slot 29 will be preferred to secure it to the end fitting.

The clamping force needs to be great enough and disposed about the end fitting to hold the flared end securely in place over 360" between the flat faces of the stub-end and its mating clamp. However, the clamping force should not be so great as to damage the plastics tube and flared end.

A gasket 30 helps reduce the possibility of such damage.

Turning to Figure 6, a perspective view of an end fitting 19 with a slot 29 and collar 28 which is slid towards and welded to the stub-end is provided. In this way, the collar and slot form an aperture, though the wire can, in this embodiment, be easily slid into the slot before the collar is brought up to the end fitting.

Heater 2 includes heating elements whose power output can be controlled from 0-100%. The principle former may also be heated so that its outer frusto-conical surface is controllably heated. The elements within the principle former 7 may be distributed evenly beneath the frustoconical surface or these may be distributed so that particular portions of the frusto-conical surface can be heated to a greater or lesser extent than other areas of the surface.

The method of carrying out an embodiment of the invention is as follows.

Securely fasten the end-fitting (at the end being flared) into the primary vice using suitable sized clamps. Ensure that the flat-face of the end-fitting is held as shown in Figures 3a and 3b, to get the best finished flared end.

Securely fasten the tube into the secondary vice, using the correctly sized clamps.

Note: Where the tube is externally covered by over-braid two options are available.

1. Pull braid back to the left hand side of the vice and apply clamps directly against the tube and/or 2. Wrap protective tape around the tube prior to the clamps being applied. This allows both the braid and the tube to be securely located without the braid damaging the internal tube.

Distance between the vices is typically 0 to 12".

The heater unit is moved axially until the "door" on its LHS forms a vertical plane with the flat-face of the endfitting as denoted by the dashed lines in Figure 1.

The hole left at the RHS of the heater unit is blocked by axially locating the "principal" former in a position which fills it in.

The principal former is the first to be used in the flaring process. Its total angle is typically approximately 90".

The "secondary" tube vice is loosened and the tube is pushed through the end-fitting (LHS to RHS), until the require length of tube protrudes from its flat-face. This vice is then tightened to hold the tube securely in place (note: where the external wire passes through the end fitting - the LHS to RHS movement of tube will also be accompanied by rotation of the tube, i.e. helical movement).

The heater unit is turned on at a suitable power output and the protruding tube is heated until: 1 for convoluted tube, the convolutions are completely removed and sufficiently soft to be flared or 2 for smooth tube it has at least partially lost its elastic-memory (and is soft enough to be flared).

For hoses with convoluted linings it may be preferable to temporarily loosen the secondary vice after deconvolution so that the tube can be pulled back a little to the LHS before the flaring process is begun to remove the excess tube length resulting from the deconvolution.

Alternatively, where external wire is not present, the tube may be moved axially by means of a suitable thread arrangement (2).

With experience time/power output figures can be established for different sizes and types of tubing. Care must be taken not to over heat the tube during any part of the process.

The "principal" former (total angle typically 90 ) is then moved axially to the LHS until it touches the protruding tube end which is "held" in place. The hot tube expands a little allowing the principal former to be moved slowly further to the LHS inside it, by controlled gradual means.

To visually observe the process, the heater can be moved axially to the RHS as required, and of course be moved back into position to heat the tube end. This easy axial movement of the heat source makes it much easier to ensure that too much heat is not absorbed by the tube during the deconvoluting/flaring process.

Eventually the principal former cannot move any further to the LHS as it presses the tube against the external endfitting. Care has to be taken not to axially split the end of the tube being flared by applying excessive axial movement too quickly. Heat output needs to be carefully controlled.

The principal former is pulled back to the RHS beyond the heater unit (along the flaring axis). The carousel is then rotated so that the next suitable former lies along the flaring axis, facing the end to be further flared. It is moved axially to the LHS until it touches the partially flared tube end which is still held firmly in place.

One, or several formers may be fitted to the carousel.

Typically two are used.

This former (which may be the final one required) may typically have a total angle of approximately 1300. It is again moved further to the LHS until it again cannot move further as it presses the tube against the external end fitting.

This former is then moved to the RHS until it substantially clears the heater unit. The heater unit is also moved to the RHS leaving approximately 6-12" of clear space to the RHS of the partially flared end. The heater is switched off.

The partially finished flared end is now tightly clamped against the flat-face of a similarly sized end-fitting, which is manually positioned by the operative performing the task. The flaring process is now complete and the securely clamped end is left to cool. Typical cooling time is approximately 0-30 minutes. See Figures 5b and 5c.

When the clamped end is removed, what remains is a heatstabilised permanently formed 90" flared tube end.

This method and apparatus allows the tasks of deconvolution and/or flaring to be performed; easily, quickly, consistently and cheaply without needing to move or touch the hose assembly, once it has been correctly situated and secured in the apparatus. Critically, it provides a method for flaring ends with a reduced likelihood of splitting or damaging the tube during the operation.

Check before starting: 1.1 That the correct clamps are fitting to both the primary and secondary vices (ie that their respective internal diameters correspond to the overall diameters of the end-fitting and the tubing they will securely locate).

1.2 The horizontal and vertical supports (where needed) are correctly: 1.2.1 height and width adjusted to accommodate hose and 1.2.2 axially adjusted to support hose and end-fittings.

1.3 That the heater unit is correctly "centred" with respect to the axis along with the "flaring" process takes place. That the correct "door" is fitted on the left hand side of the heater to ensure that the end-fitting at the flaring-end can just "fit" through its centre. That the heater is plugged in, set to the correct power output figure and ready for use.

1.4 That all "formers" fixed to the rotating carousel are "centred" along the "flaring" axis.

1.5 That both sets of clamps are "centred" along the axis of flaring.

1.6 The door on the LHS of the heater may preferably have means to adjust the size of its internal hole - to accommodate fittings with different outer diameters (O/Ds).

1.7 The door on the RHS of the heater will preferably have an o/d slightly greater than the maximum o/d of the formers.

In order to form the end-fitting for use in the second aspect of the invention, a hole is drilled through the endfitting at suitable distance from its pipe end. See Figure 4. "Suitable distance" is typically approximately equal to 1-3 convolutions of pitch of tube chosen.

The hole is just large enough to accommodate the o/d of wire chosen.

The tube is twisted through the stub-end and the end of the wire is threaded through the hole so it protrudes out from it. When the flaring process is completed the wire left over is cut off. The remainder which is now just sticking through is "spot-welded" to the stub-end. Taking care not to damage the internal tube. See Figure 5b. The wire is now secured.

Claims (46)

1. Apparatus for forming flared ends on plastic tubes comprising: a heater, the heater having a first aperture for receiving an end of a tube to be heated, and a second aperture for receiving a flared end forming element; the end forming element is mounted so as to be operable to advance controllably towards the end of the tube and substantially close the second aperture as it advances towards the end of the tube.

2. An apparatus according to claim 1, in which the end forming element is shaped so that as it is advanced towards the end of the tube so that a front portion of the end forming element passes through the second aperture, a rear portion of the end forming element acts to maintain the second aperture substantially closed.

3. An apparatus according to claim or 1 or 2 in which, the end forming element or its front portion, is frusto-conical in shape.

4. Apparatus according to claim 3, in which the outer diameter of the frusto-conical portion is just less than the diameter of the second aperture so that the frusto-conical portion can as it approaches the aperture substantially close it.

5. Apparatus according to any of the claims 2 to 4, in which a continuous wall depending from and having substantially the same dimensions as the outermost periphery of the front portion of the end forming element is provided so that when the front portion of the end forming element is advanced past the second aperture into the heater, the continuous depending wall substantially closes the second aperture.

6. Apparatus according to claim 5, in which a frusto conical shaped front portion of the end forming element is integral with a cylindrically shaped block extending to the rear of the front portion, and in which the outer diameter of the block is just smaller than the diameter of the second aperture so that as the block passes through the second aperture, the second aperture remains substantially closed.

7. Apparatus according to any preceding claim in which the heater is designed to heat the end of the tube to within a predetermined temperature range which is sufficient to cause a chosen tube material to at least partially lose its elastic memory.

8. Apparatus according to any preceding claim in which the heater comprises controllable heating elements.

9. Apparatus according to any preceding claim in which the end forming element, or its front portion, is controllably heatable.

10. Apparatus according to any preceding claim in which the heater, first and second apertures, and end forming element are substantially axially aligned along the longitudinal axis of the tube.

11. Apparatus according to claim 10 in which the alignment is to within plus or minus 5".

12. Apparatus according to claim 10 or 11, in which the heater is axially moveable with respect to the tube.

13. Apparatus according to any preceding claim which an end fitting close fitting with the tube and having a flat end face at its forward end is placed over the end of the tube so that the flat end face forms a plate against which the tube is flared by the end forming element.

14. Apparatus according to claim 13 in which the flat end face comprises an annular flange.

15. Apparatus according to claim 13 or 14, in which a heat resistant gasket is placed over the end of the tube adjacent to the flat end face of the end fitting so that the gasket forms a surface against which the tube is flared by the end forming element.

16. Apparatus according to any of claims 13 to 15, in which the end fitting is arranged so that a predetermined amount of tube protrudes from the end fitting when it is placed over the end of the tube.

17. Apparatus according to any claims 13 to 16, in which first and second clamps are provided to hold the end fitting and tube respectively in a predetermined relative position so as to maintain the predetermined protruding amount of tube during flaring.

18. Apparatus according to claim 17, in which the first and second clamps are axially moveable with respect to one another whereby axial adjustment of the tube so as to improve control of the length of tube to be flared is provided.

19. Apparatus according to claim 18, in which the clamps are lockable in position preventing the end fitting moving with respect to the tube during flaring.

20. Apparatus according to any of claims 17 to 19, in which one or more vertical and/or horizontal hose supports are provided to the rear of the second clamp.

21. Apparatus according to claim 20, in which the vertical and/or horizontal hose supports are axially moveable with respect of the tube and/or vertically adjustable.

22. Apparatus according to any preceding claim in which the tube, heater, end forming elements and, if provided, clamps and hose supports are substantially axially aligned by means of a alignment rail on which these are mounted.

23. Apparatus according to any of claims 17 to 22, in which one or more of the clamps can be adjusted so that once a helically convoluted tube has been deconvoluted, the tube can be drawn back away from the end fitting so that the predetermined amount of tube protruding from the end fitting for flaring is achieved.

24. Apparatus according to any preceding claim, in which at least a second end forming element having a larger apex angle than the first end forming element in the instance where this is frusto-conical in shape so that a gradual flaring operation can be performed.

25. Apparatus according to claim 24 in which the first and second, and if present the further, end forming elements are located on a rotatable carousel for easy changeover after the reciprocating action of the previous end forming element.

26. Apparatus according to any preceding claim in which a second end fitting or other clamping means having a mating flat face is provided so that after flaring the partially flared tube end can be tightly clamped to the flat face so as to form a 90" flared end of flange at the end of the tube.

27. Apparatus according to any preceding claim in which the heater circumferentially substantially surrounds the tube end so that the tube end may be heated over its whole circumference prior to and/or during flare formation.

28. Apparatus according to any preceding claim in which the tube is heated within its whole circumference by means of heating elements within the end forming element.

29. Apparatus according to any preceding claim, in which a mating element having a flat surface for clamping to a partially flared tube end to form a 90 degree angle is provided.

30. Apparatus according to claim 29, in which the mating element includes a tapered protruding portion which fits inside the end of the tube to centre the tube within the end fitting.

31. Apparatus according to any preceding claim in which the tube and if provided, tube support wire are helically convoluted.

32. Apparatus according to any preceding claim, in which the tube is braided.

33. A method of fixing a tube wire support to a tube end fitting comprising the steps of: forming an aperture or slot in the end fitting suitable for receiving a tube wire; passing the end of the wire into the interior of the end fitting and through the aperture, or slotting the wire into the slot, so that the end of the wire is accessible from the outside of the end fitting; and fixing the wire to the end fitting.

34. A method according to claim 33, further comprising the step of: cutting the wire close to the hole or slot where it exits the end fitting.

35. A method according to claim 33 or 34 further comprising the step of: welding the end of the wire to the end fitting and/or if a slot is provided, welding the wire to a collar introduced to the end fitting so as to form an aperture with the slot.

36. A method according to claim 35, in which the collar is cylindrical and positioned about the tube.

37. A method according to any of claims 33 to 36, in which the wire is welded to the end fitting after the wire has been cut back so that it is substantially flush with the exterior surface of the end fitting.

38. A method according to any of claims 33 to 37, in which the size of the aperture or slot is dimensioned to be close fitting with the wire.

39. A method according to any of claims 33 to 38, in which the wire is passed through the aperture or into the slot prior to tube flaring, whilst the cutting, and welding operations, are carried out after tube flaring.

40. Apparatus according to any of claims 1 to 32, or a tube end fitting, in which the end fitting has an aperture or slot for receiving tube support wire.

41. Apparatus or an end fitting according to claim 40 in which the end fitting is provided with a collar for forming the slot into an aperture.

42. A plastic tube having an external support wire having at least one end fitting with an aperture or slot receiving an end of the support wire from the inside of the end fitting.

43. A plastic tube according to claim 42, in which the tube and support wire are helically convoluted and/or braided.

44. Apparatus for forming flared ends on plastic tubes substantially as described herein with reference to and/or as illustrated in the accompanying figures.

45. A method for forming flared ends on plastic tubes substantially as described herein with reference to and/or as illustrated in the accompanying figures.

46. An end fitting for forming flared ends on plastic tubes substantially as described herein with reference to and/or as illustrated in figures 3a, 3b, 4, 5a, 5b, Sc or 6.