GB2390566A

GB2390566A - Improved shaping of thermoplastic tubes

Info

Publication number: GB2390566A
Application number: GB0215799A
Authority: GB
Inventors: Andrew Howard John Miller
Original assignee: TFX Group Ltd
Current assignee: TFX Group Ltd
Priority date: 2002-07-09
Filing date: 2002-07-09
Publication date: 2004-01-14
Also published as: GB0215799D0

Abstract

A method and apparatus for forming a bend 1a-1f in a thermoplastics tube 1 employs a bending head 2 to form a bend at a pre-determined position. A feed device 3 feeds the tube 1 to the bending head 2. The tube 1 is heated by an infra-red radiation source 12 emitting radiation having a wavelength of 750nm to 2500nm and is cooled by low temperature (subzero) nitrogen to retain the desired bend configuration. A programmable microprocessor controller 4 controls the feeding, bending, heating and cooling operations in a pre-determined sequence to form the bend 1a-1f to the required shape at the pre-determined position. Multiple bends 1a-1f can be formed of different sizes (radius) in the same or different planes.

Description

IMPROVED METHOD AND APPARATUS FOR SHAPING

THERMOPLASTIC TUBES

This invention concerns thermoplastic tubes and provides an improved 5 method and apparatus for forming such tubes into a required shape. As used, herein, the term 'tube' includes hoses, pipes and similar conduits whether of single or multi-layer construction and is fo be construed accordingly in following description and claims.

Thermoplastic tubes are used in many applications for transporting fluids and are commonly used in the automotive field as connections for vapour,

vent, hydraulic, fuel, coolant or oil lines. In such applications, the tube is often required to be of a specific shape or configuration including one or more bends.

UK Patent No. 2 249 750-B discloses a method and apparatus for shaping a thermoplastic tube by contactless heating a pre-formed bend region of the tube with infra-red radiation to soften the thermoplastic material to conform to the required bend configuration. The tube is then cooled to 20 set the thermoplastic material in the required bend configuration whilst the tube is supported on a former.

The heating cycle is controlled by switching one or more remote infra-red radiation sources on and off to provide a pulsed emission of infra-red 25 radiation to heat gradually the bend region of the tube to the required temperature. Pulsing the infra-red radiation is used to allow the heat input to be distributed around the bend region by conduction and prevent burning or blistering the surface of the tube.

The method and apparatus disclosed in UK Patent No. 2 249 750-B can be used to form tubes of complex shape with multiple bends by] simultaneously heating and cooling discrete bend regions of the tube.

This requires the tube to be pre-formed to the required shape using 5 several farmers and providing sources of infra-red radiation and cooling fluid for each bend region. This adds to the manufacturing costs and is generally only suitable for small bore tubes that can be pre- formed without distorting (kinking) the tube wall to alter the cross- section and change the flow characteristics of the tube.

UK Patent Application No. 2 342 309-A discloses a method and apparatus for shaping a thermoplastic tube in which the tube is pre-heated in the region where a bend is to be formed. The pre-heated region is then conformed to the required bend shape between a pair of relatively 15 movable formers while maintaining a pressure differential between the inside and outside of the tube to prevent the tube wall distorting (kinking) in the bend region. The tube is then cooled to set the thermoplastic material in the required bend configuration.

20 The method and apparatus disclosed in UK Patent Application No. 2 342 309-A can also be used to form tubes of complex shape with multiple bends but a pair of relatively movable formers is required for each bend.

As a result, it is not possible to form a large number of bends at the same time. This adds to manufacturing costs and increases production times. i A further disadvantage of the method and apparatus disclosed in both UK Patent No. 2 249 750-B and UK Patent Application No. 2 342 309-A is that production is relatively labour intensive requiring the tubes to be loaded and unloaded individually. This adds significantly to 30 manufacturing costs and also increases production times, especially where

the method and apparatus have to be specially designed to comply with health and safety standards to reduce the risk of injury to the operator. I The present invention has been made from a consideration of the 5 problems and disadvantages of the known methods and apparatus for shaping thermoplastic tubes discussed above.

It is an object of the present invention to provide an improved method and apparatus for shaping thermoplastic tubes which can produce tube 10 configurations having one or more bends in a simple manner.

It is a particular desired object of the present invention to provide an improved method and apparatus for shaping thermoplastic tubes which is less labour intensive than the existing methods and apparatus discussed 15 above.

It is yet another preferred object of the present invention o provide an improved method and apparatus for shaping thermoplastic tubes which can produce multiple bends in one or more planes to form tubes of complex 20 shape.

It is a still further desired object of the present invention to provide an improved method and apparatus for shaping thermoplastic tubes which is capable of being automated. i Other objects and advantages of the invention will be apparent from the description hereinafter of exemplary embodiments of the invention.

According to a first aspect of the invention there is provided a method of 30 forming a bend in a tube of thermoplastic material by contactless heating

of the tube before or after bending the tube to a desired bend configuration and cooling the tube to retain the desired bend configuration characterized in that the contactless heating is effected by emission of infra-red radiation having a wavelength in the range 750nm to 2500nm.

By employing infra-red radiation from the near end of the spectrum, we have found that the thermoplastic material can be rapidly heated to the required temperature for conforming the tube to the desired bend configuration. More particularly, the infra-red radiation can pass through the thermoplastic material so that the heat energy input to the tube is distributed in the circumferential direction. As a result, pulsing the radiation source to allow the heat energy input to be distributed around 15 the tube can be avoided.

In this way, heating to the required temperature may be effected by a continuous burst of infra-red radiation without burning or blistering the surface of the tube. As a result, it may be possible to reduce cycle times 20 significantly resulting in improved efficiency and increased productivity.

The heating may be controlled either by exposing the tube for a pre-

determined time or in response to the surface temperature of the tube or a combination of time and temperature.

Heating may be further enhanced by arranging for infra-red radiation passing through the tube to be reflected back into the tube. In this way, the heat energy input to the thermoplastic material on the side of the tube remote from the radiation source may be increased. As a result, heating

efficiency may be improved and a more uniform distribution of the heat energy input to the tube may be achieved in the circumferential direction.

Preferably, the cooling is effected by a low temperature cooling fluid 5 passed over the tube and/or passed through a former in contact with the tube. In a preferred arrangement, the cooling fluid is a sub-zero gas such as nitrogen. By employing a sub-zero gas as the cooling medium, we have found that the tube can be rapidly cooled to set the thermoplastic I material in the required bend shape without degrading the thermoplastic 10 material. In this way, cycle times may be further reduced resulting in additional improvements in efficiency and productivity.

According to a second aspect of the invention there is provided a method of forming a bend in a tube of thermoplastics material by heating of the IS tube before or after bending the tube to a desired bend configuration and cooling the tube to retain the desired bend configuration characterized in that the step of cooling the tube is effected by the use of a cooling fluid having a temperature below 0 C.

20 Preferably, the cooling fluid is sub-zero gaseous nitrogen. The cooling fluid may be passed over the surface of the tube to cool the tube directly.

Alternatively or additionally, the cooling fluid may be passed across a surface in contact with the tube to cool the tube indirectly. For example, the cooling fluid may be passed through a former on which the tube is 25 held in the required bend configuration.

The tube may be heated by any suitable means and is preferably arranged for contactless heating, for example by infra-red radiation or hot air or other convenient heat source remote from the tube.

According to a third aspect of the invention there is provided a method of forming a bend in a tube of thermoplastics material comprising heating the tube before or after bending the tube to a desired bend configuration and cooling the tube to retain the desired bend configuration characterized 5 in that the steps of heating, cooling and bending the tube are controlled in a predetermined sequence via programmable control means.

The programmable control means may be electronic control means such as a microprocessor programmed with the predetermined sequence to control 10 the bending operation with the heating and cooling to form or retain the desired bend configuration.

The steps of heating, cooling or bending the tube may be repeated to form several bends for providing tubes of complex shape with multiple bends.

15 The bends may be of the same or different size and may be formed in the same or different planes.

According to a fourth aspect of the invention there is provided apparatus for forming a bend in a thermoplastics tube comprising a bending head, 20 means for feeding a tube to the bending head to form a bend at a pre-

determined position, means for heating the tube before or after forming the bend, and means for cooling the tube to set the thermoplastic material to retain the bend shape characterized in that the apparatus further comprises programmable control means for controlling the bending head, 25 feeding means, heating means and cooling means in a pre- determined sequence to form the bend to the required shape at the pre- determined position. The control means may be electronic control means such as a 30 programmable microprocessor for controlling positioning of the tube at

the bending head, actuation of the bending head to form the bend and operation of the heating and cooling means to set the bend shape.

The control means may be operable to form successively a plurality of 5 bends to produce tubes of complex shape for any desired application.

The bends may be of different size and shape and may be formed in different directions and/or lie in the same or different planes.

The control means may be responsive to sensors for controlling the 10 bending operation in accordance with an input of the desired bend shape to the control means. The input to the control means may be via a control panel or any other suitable means, for example a computer.

The bending head may comprise a pair of relatively movable farmers for 15 bending the tube to form the required bend shape. Preferably, one of the farmers is stationary during the bending operation and has a profile for I forming the inner radius of the bend and the other former is rotatable around the stationary former to bend the tube to the required bend shape.

20 The farmers may be shaped to enclose the tube at the point of bending.

For example, the farmers may be provided with grooves in the outer surface matching the profile of the tube. In this way, the farmers provide external support for the tube at the point of bending to maintain substantially the cross-section of the tube. Some tubes may also require 25 internal support during the bending operation and this may conveniently be achieved by providing a pressure differential between the inside and the outside of the tube.

The heating means may be of any suitable type and is preferably arranged 30 for contactless heating the surface of the tube. A preferred heat source is

infra-red radiation with infra-red radiation in the near part of the spectrum, for example having a wavelength in the range 750nm to 2500nm, being especially preferred for rapid heating of the tube.

5 The cooling means may be of any suitable type and is preferably arranged for cooling the surface of the tube directly or indirectly. A preferred cooling medium is a low temperature gas, for example sub-zero nitrogen, for rapid cooling of the tube.

10 The invention will now be described in more detail, by way of example only with reference to the accompanying drawings, wherein: Figure 1 shows a thermoplastic tube having multiple bends in three planes formed by the method and apparatus of the present invention; Figure 2 shows diagrammatically apparatus embodying the present invention; Figure 3 shows diagrammatically the apparatus of Figure 2 turned 20 through 90 about the longitudinal axis; Figure 4 shows diagrammatically formation of a bend using the apparatus of Figures 2 and 3; 25 Figure 5 shows diagrammatically the position of the tube for forming the next bend using the apparatus of Figures 2 and 3; and Figure 6 shows diagrammatically a modification to the apparatus of Figures 2 to 5.

Referring first to Figure 1 of the drawings, a thermoplastic tube 1 is shown having six bends la-if formed between the ends la, lh to produce a complex configuration in three planes x, y and z. 5 The tube I may be for an automotive vapour, vent, hydraulic, fuel, coolant or oil line and may be of single or multi-layer construction employing any suitable materials for the intended application as will be familiar to those skilled in the art. The detailed construction and materials from which the tube 1 is made form no part of this invention 10 and will not be described in detail.

Referring now to Figures 2 to 4 of the drawings, apparatus for forming the tube 1 to the shape shown in Figure 1 is depicted schematically and comprises a bending head 2 and a feed device 3 for advancing the tube 1 15 to the bending head 2.

The bending head 2 and feed device 3 are operable under the control of a programmable microprocessor controller 4 for automatically feeding and bending the tube 1 to produce the desired configuration according to data 20 input to the controller 4. The controller 4 also controls operation of means 5 for heating the tube 1 and means 6 for cooling the tube 1.

The feed device 3 is arranged to receive a length of tube 1 from a loading station (not shown) in which a plurality of tubes can be stored for 25 delivery to the feed device 3 under the control of the controller 4.

The bending head 2 comprises a pair of farmers 7, 8 between which the tube 1 is located during the bending operation.

The former 7 forms the inner radius of the bend to be formed and is i stationary during the bending operation. The former 8 forms the outer radius of the bend to be formed and is carried by a movable arm 9.

5 The former 8 is movable towards and away from the former 7 in the direction of arrow A (Figure 2) and is rotatable around the former 7 in the direction of arrow B (Figure 3) under the control of the controller 4.

The feed device 3 comprises a pair of clamps 10, 11 arranged to 10 hold/release the tube 1 under the control of the controller 4. The clamp 10 adjacent to the bending head 2 is stationary and the clamp 11 is mounted on a carriage (not shown) for reciprocating movement in the direction of arrow C (Figure 2) towards and away from the clamp 10 for advancing the tube 1 to the bending head 2.

The means 5 for heating the tube 1 comprises an infra-red radiation source 12 arranged to heat a section of the tube 1 in which the bend is to be formed. In this embodiment, the infra-red source 12 is arranged to heat the tube 1 at the bending head 2.

Alternatively or additionally, the infra-red radiation source may be arranged to heat the tube 1 before the bending head 2, for example at the feed station 3 between the clamps 10,11.

25 The infra-red radiation source 12 comprises one or more emitters such as a lamp (not shown) for emitting infra-red radiation in the near part of the spectrum, typically having a wavelength in the range 750nm to 2500nm.!

We have surprisingly found that infra-red radiation of this form produces rapid heating of the thermoplastic material of the tube 1 to the required temperature without burning or blistering the surface of the tube 1.

5 More particularly, near infra-red radiation can pass through the thermoplastic material of the tube 1 so that the tube 1 can be uniformly heated to the required temperature by a continuous burst of radiation.

This reduces the time to heat the tube 1 compared to the use of a pulsed emission of infra-red radiation. As a result, the processing time can be 10 reduced.

The benefits and advantages resulting from the use of near infra-red radiation to heat the tube 1 can be further enhanced by providing a reflective surface on the opposite side of the tube to the infra-red source 15 12. In this way infra-red radiation passing through the tube 1 is reflected back to heat further the tube 1 and provide a further reduction in the processing time.

The means 6 for cooling the tube 1 comprises a source 13 of cooling fluid 20 arranged to direct cooling fluid over the tube 1 to set the thermoplastics material in the new configuration of the bend just formed.

In this embodiment, the source 13 comprises one or more nozzles (not shown) and the cooling fluid is sub-zero gaseous nitrogen or other low 25 temperature fluid for rapidly cooling the tube 1.

Alternatively or in addition to directing cooling fluid over the tube l, the cooling fluid may be passed through the former 7 which is made of a high thermal conductivity material such as aluminium for cooling the tube 1 by 30 conduction.

Operation of the apparatus to form the tube 1 of Figure 1 will now be described. 5 First, a straight tube 1' of the required length for the intended product is loaded into the loading station. Typically, the loading station will contain a plurality of tubes 1' for continuous production of tubes 1 of the desired shape. 10 The controller 4 is programmed either by inputting appropriate data via a control panel (not shown) of the shape of the tube 1 to be formed or by selecting a program already stored in the memory of the controller or loading a program from a source, e.g. a computer or disc, into the memory of the controller 4.

Typically, the program will include details of the bends to be formed, the temperature the tube is to be heated to, the distance the tube must be advanced for each bend, the radius of the bends and the plane in which the bend is to be formed relative to other bends.

The production cycle to form the tube 1 is initiated via the controller 4 to cause a tube 1' to be delivered from the loading station to the feed device 3. For this, the clamp 11 may be moved to engage the tube 1' a preset distance from the front end.

The clamp 11 may then move towards the clamp 10 to feed the tube 1' to position the front end at the required position relative to the bending head 2 to form the first bend. The clamp 10 is then closed to grip the tube 1 and the clamp 11 withdrawn to its initial position (Figure 2).

) The former 8 is then moved to locate the tube 1' between the former 8 and former 7 (Figure 3). The former 8 is then swept around the former 7 to produce the desired bend configuration (Figure 4).

5 The farmers 7, 8 are formed with grooves 14, 15 in the peripheral surfaces that co-operate to enclose the tube 1' at the point of bending to provide external support for maintaining the cross-section of the tube 1' during the bending operation. The tube 1' may also be supported internally by fluid pressure eg compressed air to prevent the tube wall 10 distorting (kinking).

The tube 1' is held between the clamp 10 and the formers 7, 8 in the desired configuration of the bend to be formed. The tube 1' is then rapidly heated to soften the thermoplastic material of the bend region by a 15 continuous burst of infra-red radiation from source 12 having a wavelength in the range 750nm to 2500nm to the near part of the spectrum. The temperature to which the tube 1' is heated is controlled so that the 20 plastic material of the tube 1' is softened to conform to the new shape of the bend without melting. The heating may be controlled by timing the burst of radiation or by detecting the temperature of the surface of the tube 1' and switching the radiation source 12 off when a pre-determined temperature is detected.

The tube 1' is then rapidly cooled by sub-zero gaseous nitrogen applied to the outer surface of the tube 1' from the source 13 and/or passed through the former 7 to set the thermoplastic material and retain the bend configuration.

i The former 8 is then retracted and the clamp 10 released allowing the tube 1' to be fed forwards by the clamp 11 to position the next section of the tube 1' at which a bend is to be formed relative to the former 7.

5 The clamp 11 may be rotatable about the longitudinal axis of the tube as indicated by the arrow D (Figure 5). In this way, the tube 1' can be positioned for forming the next bend in a different direction and/or a different plane. For example, Figure 5 shows the tube 1' advanced to the position for forming the next bend and rotated through 180 to form the 10 bend in the opposite direction to the first bend.

The tube 1' is then formed to the required configuration of the next bend and the bend configuration set by rapidly heating and cooling the tube 1' as before. In this way a series of bends can be formed successively until 15 the desired final configuration of the tube 1 is obtained.

As will be understood, the whole shaping process is controlled automatically via the controller 4 to produce the desired tube configuration. On completion of the shaping process, the formed tube 1 20 is ejected into a hopper (not shown) or other suitable collector for formed tubes 1.

A new tube 1' to be shaped is delivered to the feed device 3 from the loading station and the cycle repeated to form the next tube 1. In this 25 way, a plurality of tubes 1 can be produced automatically and the operator is only required to load lengths of pipe into the loading station and remove former pipes from the hopper.

As will be appreciated, the above-described apparatus enables tubes to be 30 formed to any desired configuration accurately and reliably. An

important feature of the invention is the facility for rapid heating and cooling the bend region of the tube to allow the tube to be set in the new bend configuration and reduce cycle times thereby improving productivity. Referring now to Figure 6, there is shown a modification to the apparatus of Figures 2 to 5 in which the former 7 comprises a plurality (not shown) of formers 7a-7d of different diameter stacked one on top of the other.

The stack of farmers 7a-7d is vertically movable to position any selected 10 one of the formers 7a-7d in the stack for co-operating with the former 8 to produce a bend of the desired configuration.

In this way, the range of bends that can be formed is increased and the apparatus can automatically change over between the farmers 7a-7d 15 during a production cycle without requiring an operator to change the former 7. As a result, multiple bends of different size can be formed as desired by appropriate programming of the controller 4.

It will be understood the invention is not limited to the embodiment 20 above-described. For example, the section of the tube to be formed to a desired bend shape may be heated prior to the bending operation. The heating may be effected with the tube located at the bending head (Figure 2).

25 Alternatively, the tube may be heated prior to advancing to the bending head, for example by positioning an infra-red radiation source between the clamps 10,11. In this way, the steps of bending the tube and heating the tube for forming the next bend may be carried out simultaneously so as to reduce further cycle times and improve efficiency.

I Other changes and modification that can be made to the apparatus will be apparent to those skilled in the art and are deemed within the scope of the invention.

Claims

1. Apparatus for forming a bend in a thermoplastics tube comprising a bending head, means for feeding a tube to the bending head to form a 5 bend at a pre-determined position, means for heating the tube before or after forming the bend, and means for cooling the tube to set the thermoplastic material to retain the bend shape, and programmable control means for controlling the bending head, feeding means, heating means and cooling means in a pre-determined sequence to form the bend 10 to the required shape at the pre-determined position.

2. Apparatus according to claim 1 wherein the control means is electronic control means for controlling positioning of the tube at the bending head, actuation of the bending head to form the bend and 15 operation of the heating and cooling means to set the bend shape.

3. Apparatus according to claim 2 wherein the control means is operable to form successively a plurality of bends to produce tubes of complex shape.

4. Apparatus according to claim 2 or claim 3 wherein the electronic control means is a programmable microprocessor.

5. Apparatus according to claim 3 or claim 4 wherein bends are of 25 different size and/or are formed in different directions and/or lie in the same or different planes.

6. Apparatus according to any one of the preceding claims wherein the control means is responsive to sensors for controlling the bending

operation in accordance with an input of the desired bend shape to the control means.

7. Apparatus according to claim 6 wherein the input to the control 5 means is via a control panel.

8. Apparatus according to claim 6 wherein the input to the control means is via a computer.

10

9. Apparatus according to any one of the preceding claims wherein the bending head comprises a pair of relatively movable formers for bending the tube to form the required bend shape.

10. Apparatus according to claim 9 wherein one of the farmers is 15 stationary during the bending operation and has a profile for forming the inner radius of the bend and the other former is rotatable around the stationary former to bend the tube to the required bend shape.

11. Apparatus according to claim 9 or claim 10 wherein the farmers 20 are shaped to enclose the tube at the point of bending.

12. Apparatus according to claim 11 wherein the farmers are provided with grooves in the outer surface matching the profile of the tube.

25

13. Apparatus according to any one of claims 9 to 11 wherein a set of stationary farmers of different diameter is provided and the movable former is co-operable with any selected one of the stationary farmers.

14. Apparatus according to claim 13 wherein the set of stationary formers is arranged in a movable stack for aligning the selected former with the movable former.

5

15. Apparatus according to any one of the preceding claims wherein the heating means is arranged for contactless heating the surface of the tube.

16. Apparatus according to claim 15 wherein the heating means is 10 infra-red radiation.

17. Apparatus according to claim 16 wherein the infra-red radiation has a wavelength in the range 750nm to 2500nm.

15

18. Apparatus according to any one of the preceding claims wherein the cooling means is arranged for cooling the surface of the tube directly or indirectly.

19. Apparatus according to claim 18 wherein the cooling means is a 20 low temperature gas.

20. Apparatus according to claim 19 wherein the gas is sub-zero nitrogen. 25

21. Apparatus according to any one of the preceding claims wherein the feeding means includes a device for gripping the tube and advancing the tube to the bending head.

22. Apparatus according to claim 21 wherein the gripping device includes a clamp means arranged to hold/release the tube under the control of the programmable control means.

5

23. Apparatus according to claim 22 wherein the clamp means comprises a stationary clamp adjacent to the bending head and a movable clamp mounted on a carriage for reciprocating movement towards and away from the stationary clamp for feeding the tube to the bending head.

10

24. Apparatus according to any one of the preceding claims wherein the feeding means is arranged to receive the tube from a loading station for delivery to the bending head.

25. Apparatus for forming a bend in a thermoplastics tube substantially 15 as hereinbefore described with reference to Figures 2 to 5 of the accompanying drawings.

26. Apparatus for forming a bend in a thermoplastics tube substantially as hereinbefore described with reference to Figures 2 to 5 of the 20 accompanying drawings as modified by Figure 6 of the accompanying drawings.

27. A method of forming a bend in a tube of thermoplastic material comprising the steps of feeding a tube to a bending head to form a bend at 25 a pre-determined position, heating the tube before or after forming the bend, and cooling the tube to set the thermoplastic material to retain the bend shape, wherein the feeding, bending, heating and cooling are controlled in a pre-determined sequence by programmable control means to form the bend to a required shape at the pre-determined position.

28. A method according to claim 27 wherein the heating is contactless by emission of infra-red radiation having a wavelength in the range 750nm to 2500nm from a radiation source remote from the tube.

5

29. A method according to claim 28 wherein the contactless heating of; the tube is effected by a continuous burst of infra-red radiation to heat the tube to a required temperature.

30. A method according to claim 28 or claim 29 wherein the 10 contactless heating of the tube is controlled either by exposing the tube for a predetermined time or in response to the surface temperature of the tube or a combination of time and temperature.

31. A method according to any one of claims 28 to 30 wherein the 15 contactless heating of the tube is enhanced by arranging for infra-red radiation passing through the tube to be reflected back into the tube.

32. A method according to any one of claims 27 to 31 wherein the 9 cooling is effected by a low temperature cooling fluid passed over the 20 tube and/or passed through a former in contact with the tube.

33. A method according to claim 32 wherein the cooling fluid is a gas having a temperature below 0 C.

25

34. A method according to claim 33 wherein the gas is nitrogen.

35. A method according to any one of claims 27 to 34 wherein the bending operation is controlled with the heating and cooling to form and retain the desired bend configuration.

36. A method according to claim 35 wherein the steps of heating, cooling or bending the tube are repeated to form several bends for providing tubes of complex shape with multiple bends.

5

37. A method according to claim 36 wherein the bends are of the same or different size.

38. A method according to claim 37 wherein the bends are formed in the same or different planes.

39. A method according to any one of claims 27 to 38 wherein the tube is formed to the required shape between two relatively movable formers.

40. A method according to claim 39 wherein one of the formers is 15 stationary and the other former is movable during the bending operation.

41. A method according to claim 40 wherein a plurality of stationary farmers are provided and the movable former is co-operable with any selected one of the stationary farmers for forming the required bend 20 shape.

42. A method of forming a bend in a tube of thermoplastic material substantially as hereinbefore described with reference to Figures 1 to 5 the accompanying drawings.

43. A method of forming a bend in a tube of thermoplastic material substantially as hereinbefore described with reference to Figures 1 to 5 the accompanying drawings as modified by Figure 6 of the accompanying drawings.

44. A thermoplastics tube having a bend formed by the apparatus of claims I to 26.

45. A thermoplastics tube having a bend formed by the method of 5 claims 27 to 43.

46. A method of forming a bend in a tube of thermoplastic material by contactless heating of the tube before or after bending the tube to a desired bend configuration and cooling the tube to retain the desired bend 10 configuration characterized in that the contactless heating is effected by emission of infra-red radiation having a wavelength in the range 750nm to 2500nm.

47. A method of forming a bend in a tube of thermoplastics material by 15 heating of the tube before or after bending the tube to a desired bend configuration and cooling the tube to retain the desired bend configuration characterized in that the step of cooling the tube is effected by the use of a cooling fluid having a temperature below 0 C.

20

48. A method of forming a bend in a tube of thermoplastics material comprising heating the tube before or after bending the tube to a desired bend configuration and cooling the tube to retain the desired bend configuration characterized in that the steps of heating, cooling and bending the tube are controlled in a predetermined sequence via 25 programmable control means.