WO1996014200A1

WO1996014200A1 - Method of manufacturing resilient tubing

Info

Publication number: WO1996014200A1
Application number: PCT/NZ1995/000115
Authority: WO
Inventors: Mark Alexander Jenkins
Original assignee: Mark Alexander Jenkins
Priority date: 1994-11-07
Filing date: 1995-11-03
Publication date: 1996-05-17
Also published as: GB2309005A; AU3939695A; CA2204730A1; GB2309005B; GB9709261D0

Abstract

A method for the manufacture of clear corrugated or convoluted tubing from a resilient material such as polyurethane. The method of forming the tubing is in accordance with conventional manufacturing techniques used for corrugated or convoluted tubing but is characterised by a permanent non-stick coating such as a tetrafluoroethylene polymer being applied to the surfaces of the die blocks.

Description

METHOD OF MANUFACTURING RESILIENT TUBING

This invention relates to a method of manufacturing resilient tubing.

The manufacture of resilient corrugated or convoluted tube or hose is well known and there are many and varied uses to which such a product may be put. For example, this type of tubing or hosing is commonly used in the medical and healthcare industries for supply of anaesthetic or for ventilating purposes. In such environments the material from which the tubing is formed must be approved for the purpose by the regulating authorities. It must also be able to be sanitised and/or sterilised.

In the medical and healthcare industries there is a move toward the use of clear or transparent tubing and this has lead to manufacturing difficulties. These difficulties include the selection of a suitable plastics material which meets the approval of the regulating authorities yet is one which can be readily moulded in an effective and economic manner.

One of the main difficulties associated with manufacture of such tubing for this purpose from a suitably approved plastics material is caused by the material tending to not release from the moulding die blocks. While it is known to use silicon based mould release material experience shows that such silicon based releases are not suitable with the class of plastics material which needs to be used to achieve the requirements of being clear, able to be sanitised/sterilised and can withstand the rigours of the environment in which the tubing is used. Also typical means used to prevent sticking of rubber material in the die blocks when forming corrugated rubber tubing are not suitable when making such tubing from an elastomeric material such as polyurethane.

I have now developed a manufacturing method which overcomes or at least goes some way to overcoming the manufacturing problems referred to above.

Broadly, the present invention consists of a method of moulding a corrugated or convoluted tube from resilient material, the method being characterised by applying a non¬ stick coating to the die blocks used in the moulding of the tubing. In the preferred form of the invention the non-stick coating is a permanent coating.

In the preferred form of the invention the non-stick coating is a tetrafluoroethylene polymer such as Teflon (registered trade mark). The Teflon as used in the preferred form of the invention is able to withstand heat (typically temperatures in the order of 190 C are present when the die blocks contact, ie close over, the hot smooth walled tube). My experimental work to date has established that a Teflon coating of the type used for the coating of the cooking surface of an appliance such as a frying pan is quite suitable.

According to the invention the method of manufacturing by moulding a corrugated or convoluted tube is in accordance with well known techniques whereby an extruded smooth walled tube formed of a plastics material is passed between cold die blocks. These die blocks close about the hot smooth walled tube and the tube is moulded into the corrugated or convoluted form by locating a ventilated torpedo within the tube and forcing the tube into the suitably configured heated die blocks by passing of compressed air through the torpedo. According to the invention the surfaces with which the plastics material comes into contact during the moulding procedure is coated with the non-stick material, eg Teflon. The thickness of the non-stick material can be in the order of 0.020 to 0.030mm.

The material which I have selected for the manufacture of the resilient tubing is Texon, an extrusion grade polyurethane manufactured by Bayer AG. This material is used for medical applications and is both FDA approved and has a National Sanitisation Approval. The material provides a clear hose which even after use and sanitisation/sterilisation remains clear and resilient.

When the hose is used for the delivery of anaesthetic it is necessary that the hose be able to be sterilised by autoclaving and hence for such hose I have chosen Texon Grade DB7 1018. However, for general healthcare use such as for ventilating where the hose only needs to be sanitised or disinfectable I have chosen Texon Grade 990A.

Resilient or flexible plastics tubing of corrugated or convoluted form and meeting the requirements of the medical or healthcare industry can be manufactured in clear form in accordance with my invention. The use of the non-stick coating on the surfaces of the die blocks with which the plastics material makes contact during the moulding procedure has enabled me to manufacture in an effective and economic manner. My invention therefore provides for the first time a method of manufacturing such tubing without the problems which have previously faced a manufacturer endeavouring to achieve tubing having the aforementioned characteristics and meeting the medical/healthcare industry requirements.

With hoses of the type to which the present invention relates, it is often necessary to provide a cuff at each end of the hose. According to the present invention the cuff can be over moulded on the formed hose and in the preferred form the cuff is moulded from a polyurethane but one having a different hardness to that from which the tube is made. Once again to prevent the cuff from sticking in the injection mould, the moulding surfaces of the injection moulding tool are coated with a permanent non-stick coating namely tetrafluoroethylene (eg Teflon).

Claims

CLAΪMS

1. A method of moulding a corrugated or convoluted tube from resilient plastics material the method being characterised by applying a non-stick coating to the die blocks used in the mouldings of the tubing.

2. The method of claim 1 wherein the non-stick coating is a permanent coating.

3. The method of claim 1 or 2 wherein the non-stick coating is a tetrafluoroethylene polymer.

4. The method of claim 3 wherein the non-stick coating is Teflon (registered trade mark).

5. The method of any one of the preceding claims wherein the resilient plastics material is an elastomeric plastics.

6. The method of any one of claims 1 to 4 wherein the resilient plastics material is polyurethane.

7. The method of claim 5 or 6 wherein the resilient plastics material is one which complies with FDA and/or Material Sanitisation requirements.

8. The method of any one of the preceding claims wherein an end of the corrugated or convoluted tube is further placed in an injection moulding tool and an over moulded cuff is formed one said end, the moulding surfaces of the injection moulding tool also being coated with a permanent non-stick coating.

9. The method of claim 8 wherein the non-stick coating is a tetrafluoroethylene polymer.

10. The method of claim 9 wherein the over moulded cuff is formed from a polyurethane of a harder grade than that used to form the tube.

11. A flexible plastics tubing of corrugated or convoluted form when formed using the method of any one of the preceding claims.

12. A die block used for the manufacture of corrugated or convoluted tubing from a resilient plastics material characterised in that a non-stick permanent coating is applied to the moulding surfaces.

13. Die block as claimed in claim 12 wherein the non-stick coating is a tetrafluoroethylene polymer.