GB2126685A - Convoluted plastics tube - Google Patents

Abstract

Method and apparatus for producing helically convoluted plastics tube comprising the steps of positioning a preformed plain flexible tube over a mandrel, bringing the mandrel and a convolution forming head (18) together in relative rotary motion whereby to form convolutions in the tube, and applying a convolution retaining element (24) in a helical manner to the tube. <IMAGE>

Description

SPECIFICATION Hose production This invention relates to a method and apparatus for producing helically convoluted flexible hose.

In our UK Patent No. 1543586 there is disclosed an apparatus for the production of helically convoluted flexible tube which includes a mandrel and a convolution forming tool, the mandrel being non-rotatable but movable axially through said tool, said tool being rotatable around said mandrel and being provided with a helical guide formation adapted to receive a convolution retaining element whereby in use the combined rotation of the tool and helical feed of the convolution retaining element serves to cause axial movement of the mandrel through the tool as the convolution retaining element is helically formed round the tube contained in the mandrel.

We have now found helically convoluted flexible hoses can be produced on modified forms of the above apparatus.

In general, a method of producing helically convoluted plastics tube comprises the steps of positioning a preformed plain flexible tube over a mandrel, bringing the mandrel and a convolution forming head together in relative rotary motion whereby to form convolutions in the tube, and applying a convolution retaining element in a helical manner to the tube.

Apparatus according to the invention comprises a rotatable mandrel and a convolution forming tool, the tool and the mandrel being adapted for rotation relative to one another and axial motion relative to one another, the apparatus optionally further comprising means for feeding a convolution retaining element into the convolutions of the tube formed by the convolution forming tool.

The means of feeding a convolution retaining element into the convolutions in the tube formed by the convolution forming tool is optional in that it need not necessarily form part of the apparatus but the application of a convolution retaining member may be done as a separate, subsequent operation. Whether the convolution retaining element is applied simultaneously with the formation of the convoluted hose, or is a subsequent step, it will normally be necessary to produce a commercially acceptable hose.

According to another aspect of the present invention there is provided an apparatus which comprises a non-rotatable mandrel and a convolution forming tool, the tool being adapted for rotation relative to the mandrel, and the two being adapted for relative axial motion, means for feeding a convolution retaining element into the convolutions of the tube formed by the tool being provided at a subsequent work station to the tool.

The convolution retaining element may conveniently comprise a metal wire which is wound into the helical convolutions of the convoluted tube serving to hold the tube in place against deformation arising from subsequently applied pressure, heating, or any elastic or plastic relaxation of the tube material. The convolution retaining element is preferably applied on the apparatus of the invention and may be applied simultaneously with the forming of the convolutions by the convolution forming tool, or maybe applied 'downstream' of the convolution forming tool into the newly formed convolutions.

The spacing between the convolution forming tool and the application of the convolution retaining element will be largely determined by the characteristics of the material from which the tube is formed which in turn determines how long the convolutions produced by the convolution forming tool retain their shape before the application of the convolution retaining element.

In the apparatus of the present invention, the mandrel is rotatable and generally the convolution forming tool will be held against the rotation and the mandrel rotated. However, it is equally possible that both the mandrel and the convolution retaining tool be rotated, the only stipulation being that there is relative rotary movement between the two so that the convolution forming tool will produce convolutions on the tube held on the mandrel.

The tubes from which the hoses produced in the practice of the invention are formed are of flexible, usually impervious material and are preferably of a plastics material. Plastics material tubes have little torsional rigidity in thin section and also have, to varying degrees dependent upon the grade and type of plastics material, the ability to regain their original shape after cold deformation, known as plastic or elastic memory.

It has been found that by using a cyindrical mandrel internal to the plastics material tube, which is capable of accepting the torsional forces applied whilst the convolution forming tool is rotated relatively to the tube, the torsional weakness of the tube is overcome to the extent that an otherwise unconvolutable tube can be convoluted readily without suffering collapse due to the applied torque.The natural resilience of many plastics materials would not permit permanent convolutions of any significant depth to be formed even when produced using a cylindrical mandrel in this way and it has been found that a convolution retailing element, for example a wire bead, applied into the root of the convolutions either immediately after the convolutions are formed, or shortly thereafter, before the tube has had an opportunity to relax back towards its original shape, allows the convolutions to be retained. Without the convolution retailing element the tube would relax to such an extent that the convolutions produced by the convolution forming tool would become extremely shallow or disappear completely, particularly in service where internal pressures and elevated temperatures hasten this effect.The convolutions may be heat set but again it is generally necessary to have a convolution retaining element present throughout heat setting stage so as to stabilise the plastics material until after it has been heat set. Thus, in the latter case, while it is necessary in the initital forming of the tube to use a convolution retaining element this may in certain circumstances, be removed subsequently to a heat stabilisation step although normally it is more convenient even where heat setting is used to leave the convolution retaining element in place.

The tube used in the practice of the invention will generally be of plastics material and may, for example, comprise polyethylene, polypropylene, polyvinylchloride, polyester, nylon, or, preferably, polytetrafluoroethylene (PTFE). The tube's internal diameter relative to the external diameter of the mandrel will be such as to permit convolutions to be formed and this matter is discussed more fully in the above mentioned UK 1543586.

Furthermore, tubes manufactured on the apparatus according to the invention may be used as such or may be further coated for example with a braid or other coating as desired.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic elevational view of an apparatus according to UK 1543586; Figure 2 is a similar diagrammatic view to figure 1 of an apparatus in accordance with the present invention; Figure 3 (a) and (b) is a view of the apparatus similar to figure 1 in which the convolution retaining element is applied at a subsequent stage; and Figure 4 (a) and (b) is a similar view to figure 2 of an apparatus in which the convolution retaining element is applied at a subsequent stage.

Referring to the drawings, figure 1 illustrates an apparatus generally in accordance with UK 1543586 and this comprises a mandrel 10 held against rotation in a clamp 12 fixed to the machine frame 14. A plastics material tube 16 is located on the mandrel and fixed thereto at one end. The mandrel and tube pass through a convolution forming tool 18 which is rotated about the mandrel and tube by means of a rotating head 20. Associated with the tool 18 is a means 22 for feeding the convolution retaining element, in this case a metal wire 24, from a storage spool 26. The mandrel 10 moves axially through the tool 18 producing the convoluted and wired hose 28.

In figure 2 an apparatus in accordance with the invention is illustrated in which the convolution forming tool 18 is clamped relative to the frame 14 and the mandrel 10 is rotated by the rotating head 20, while being moved axially with respect to the head 18. Convolution retaining wire 24 is fed in as before producing the finished hose 28.

In figure 3 an apparatus similar to figure 1 produces convolution in the tube 16, and the convoluted tube 16a is then, in a subsequent operation, wound with retaining wire 24 to produce the finished hose 28.

In figure 4 an apparatus similar to that shown in figure 2 produces convolutions in the tube, and the convoluted tube 16a is then wrapped in convolution retaining wire 24 to produce the finished tube 28.

In yet another variant, a tube 16a convoluted according to figure 3 (a) or 4 (a) may have the convolution retaining element 24 wrapped round it on an apparatus in which the mandrel 10 is held against rotation and the means for applying wire 24 is rotated about the mandrel.

Other forms and variants of the apparatus and method of operating it will be apparent from the above and are within the scope of the present invention. Reference has been made to our UK Patent 1543586 and the apparatus and method disclosed therein is specifically disclaimed.

Claims (Filed on 1/9/83) 1. A method of producing helically convoluted plastics tube comprising the steps of positioning a preformed plain flexible tube over a mandrel, bringing the mandrel and a convolution forming head together in relative rotary motion whereby to form convolutions in the tube, and applying a convolution retaining element in a helical manner to the tube.

2. An apparatus which comprises a rotatable mandrel and a convolution forming tool, the tool and the mandrel being adapted for rotation relative to one another and axial motion relative to one another, the apparatus optionally further comprising means of feeding a convolution retaining element on to the convolutions of the tube formed by the convolution forming tool.

3. An apparatus which comprises a nonrotatable mandrel and a convolution forming tool, the tool being adapted for rotation relative to the mandrel, and the two being adapted for relative axial motion, means for feeding a convolution element into the convolutions of the tube formed by the tool being provided at a subsequent work station to the tool.

4. An apparatus as claimed in claim 2 in which the convolution retaining element is applied simultaneously with forming the convolutions by the convolution forming tool.

5. An apparatus as claimed in claim 2 in which the convolution retaining element is applied downstream of the convolution forming tool.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. after it has been heat set. Thus, in the latter case, while it is necessary in the initital forming of the tube to use a convolution retaining element this may in certain circumstances, be removed subsequently to a heat stabilisation step although normally it is more convenient even where heat setting is used to leave the convolution retaining element in place. The tube used in the practice of the invention will generally be of plastics material and may, for example, comprise polyethylene, polypropylene, polyvinylchloride, polyester, nylon, or, preferably, polytetrafluoroethylene (PTFE). The tube's internal diameter relative to the external diameter of the mandrel will be such as to permit convolutions to be formed and this matter is discussed more fully in the above mentioned UK 1543586. Furthermore, tubes manufactured on the apparatus according to the invention may be used as such or may be further coated for example with a braid or other coating as desired. The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic elevational view of an apparatus according to UK 1543586; Figure 2 is a similar diagrammatic view to figure 1 of an apparatus in accordance with the present invention; Figure 3 (a) and (b) is a view of the apparatus similar to figure 1 in which the convolution retaining element is applied at a subsequent stage; and Figure 4 (a) and (b) is a similar view to figure 2 of an apparatus in which the convolution retaining element is applied at a subsequent stage. Referring to the drawings, figure 1 illustrates an apparatus generally in accordance with UK 1543586 and this comprises a mandrel 10 held against rotation in a clamp 12 fixed to the machine frame 14. A plastics material tube 16 is located on the mandrel and fixed thereto at one end. The mandrel and tube pass through a convolution forming tool 18 which is rotated about the mandrel and tube by means of a rotating head 20. Associated with the tool 18 is a means 22 for feeding the convolution retaining element, in this case a metal wire 24, from a storage spool 26. The mandrel 10 moves axially through the tool 18 producing the convoluted and wired hose 28. In figure 2 an apparatus in accordance with the invention is illustrated in which the convolution forming tool 18 is clamped relative to the frame 14 and the mandrel 10 is rotated by the rotating head 20, while being moved axially with respect to the head 18. Convolution retaining wire 24 is fed in as before producing the finished hose 28. In figure 3 an apparatus similar to figure 1 produces convolution in the tube 16, and the convoluted tube 16a is then, in a subsequent operation, wound with retaining wire 24 to produce the finished hose 28. In figure 4 an apparatus similar to that shown in figure 2 produces convolutions in the tube, and the convoluted tube 16a is then wrapped in convolution retaining wire 24 to produce the finished tube 28. In yet another variant, a tube 16a convoluted according to figure 3 (a) or 4 (a) may have the convolution retaining element 24 wrapped round it on an apparatus in which the mandrel 10 is held against rotation and the means for applying wire 24 is rotated about the mandrel. Other forms and variants of the apparatus and method of operating it will be apparent from the above and are within the scope of the present invention. Reference has been made to our UK Patent 1543586 and the apparatus and method disclosed therein is specifically disclaimed. Claims (Filed on 1/9/83)

1. A method of producing helically convoluted plastics tube comprising the steps of positioning a preformed plain flexible tube over a mandrel, bringing the mandrel and a convolution forming head together in relative rotary motion whereby to form convolutions in the tube, and applying a convolution retaining element in a helical manner to the tube.

2. An apparatus which comprises a rotatable mandrel and a convolution forming tool, the tool and the mandrel being adapted for rotation relative to one another and axial motion relative to one another, the apparatus optionally further comprising means of feeding a convolution retaining element on to the convolutions of the tube formed by the convolution forming tool.

3. An apparatus which comprises a nonrotatable mandrel and a convolution forming tool, the tool being adapted for rotation relative to the mandrel, and the two being adapted for relative axial motion, means for feeding a convolution element into the convolutions of the tube formed by the tool being provided at a subsequent work station to the tool.

4. An apparatus as claimed in claim 2 in which the convolution retaining element is applied simultaneously with forming the convolutions by the convolution forming tool.

5. An apparatus as claimed in claim 2 in which the convolution retaining element is applied downstream of the convolution forming tool.