GB2026929A

GB2026929A - Making catheters

Info

Publication number: GB2026929A
Application number: GB7831178A
Authority: GB
Original assignee: LJM REINFORCED PLASTICS Ltd
Current assignee: LJM REINFORCED PLASTICS Ltd
Priority date: 1978-07-26
Filing date: 1978-07-26
Publication date: 1980-02-13

Abstract

A method of making an oral airway for medical use in which an extruded plastics tube (10) is blow moulded to produce a longitudinally curved main portion (22) with an enlarged cavity portion (28) at one end thereof. The tube is cut transversely (B-B) through the other end to provide a throat end opening to the airway and transversely (A-A) through the enlarged cavity portion to provide a mouth end opening to the airway, the part (16) of the enlarged cavity portion remaining attached to the main portion (22) providing a peripheral flange for engagement with the teeth or lips of the patient. Two adjoined oral airways can be formed simultaneously. <IMAGE>

Description

SPECIFICATION Method of making oral airways This invention relates to oral airways for medical use, and more particularly to an improved method of making them.

An oral airway is a tube which is inserted into the oral (i.e. oro-pharyngeal) passage of a patient who is recovering from anaesthesia, so as to prevent his tongue from closing the oral passage while he is unconscious and provide an airway past the tongue.

The tube is curved so as to conform generally to the shape of the oral passage, and is provided with a flange at the outer end to engage the lips or teeth of the patient to prevent the tube from being swallowed, and it is usually provided with a hard insert sleeve adjacent the flange to prevent the patient from biting through the tube. The tube is usually made of plastics or rubber, and the insert is conveniently made of nylon.

Hitherto, for many years, such airways have been made of rubber by a dipping process or of plastics by an injection moulding process. The dipping process required a mandrel, usually of steel, which was dipped into the latex bath in conventional manner; the rubber tube then being stripped from the mandrel. This process was slow and cumbersome, and hence relatively costly, and was generally superceded by the injection moulding process. Here, a split mould with a loose core has to be used, which is expensive to produce, and is subject to considerable wear and frequent breakdowns, so that the process is still somewhat expensive as a result of mould costs and down-time in the use of the mould.

Also, since only certain types and grades of plastics are suitable for medical use, in practice the tubes are injection moulded from ethylene-vinyl acetate copolymer (e.v.a.), which is a compromise between the physical and medical requirements for the product and the suitability of the material for injection moulding.

The present invention provides a process for making an oral airway for medical use, which comprises blow-moulding a plastics tube to the desired generally curved shape for the airway, and trimming the ends to provide a through passage for air with a peripheral flange at one end for engagement with the teeth or lips of the patient. Preferably the internal cross-section of the airway is a little larger at the end portion adjacent the flange so as to receive a hard insert sleeve which is located axially in one direction by the smaller cross-section of the rest of the tube and in the other direction by an inward lip formed around the opening to the passage during the moulding process.

It has been found that this method of making an airway can actually be quicker than injection mould ing since it requires a shorter cycle time; that it imposes less wear on the mould, with consequently less down-time; that the mould is less expensive to make; and that it is suitable for moulding polyvinyl chloride (p.v.c.), thereby producing a better finished article in the optimum medical grade of material, rather than the compromise material of e.v.a.

In order that the invention may be more clearly understood, one embodiment will now be described with reference to the accompanying drawings, wherein: Figure 1 shows a perspective view of an oral airway, Figure 2 shows a median cross-section through a mould on the line ll-ll of Figure 3, and Figure 3 shows an axial cross-section on the line Ill-Ill of Figure 2 during moulding.

Referring to Figure 1 of the drawings, the airway comprises a curved plastics tube 10 with a mouth opening 12 at one end and a throat opening 14 at the other end. A peripheral flange 16 is provided around the mouth end. A hard nylon insert sleeve 18 is received in the mouth end portion which has a slightly larger internal cross-section, whereby the smaller cross-section of the rest of the tube keeps the insert at the mouth end. The insert is retained by a small inward lip 20 around the mouth opening.

This lip is resiliently deflectable for insertion of the sleeve 18, but prevents its accidental removal.

Referring to Figures 2 and 3; the mould for blow-moulding is made in two parts which divide along the line Il-Il of Figure 3 (so that Figure 2 shows a side view of one part of the mould). The mould cavity has a main region 22 corresponding to the desired external shape of the airway. At the throat end the mould cavity is radiused at 24 leading to a small end cavity portion 26. At the mouth end the mould cavity has a larger end cavity portion 28 which terminates in an inlet 30 for the freshly extruded plastics tube with a central core 32 provided with a nozzle 34 for compressed air (or other gas).

A p.v.c tube 36 is extruded, preferably with a longitudinal curvature to assist in conforming to the curvature of the mould, and the two mould parts are brought together around the tube, as shown in Figure 3. The leading end of the tube is thus closed by being flattened between the mould parts. Then compressed air is introduced into the tube through the nozzle 34, causing the still molten tube to expand to fill the cavity, as shown in Figure 2 and in dot-dash lines in Figure 3. The mould parts are then separated and the chilled moulded tube is removed and the ends trimmed by cutting on the lines A-A and B-B, leaving a smooth rounded end around the throat opening and the flange 16 around the mouth opening. The mould also provides the small inward lip 20 at the mouth opening. The hard insert sleeve is thereafter inserted in the usual way.

If desired, two airways can be moulded at the same time by providing a longer mould cavity, as indicated in dot-dash lines in Figure 2, with two main regions 22 separated by a common cavity region 28, a small cavity portion 26 being provided at one end only, the inlet 30 taking its place at the other end. In this way the rate of production of airways can be considerably increased. By arranging the main regions 22 in the manner indicated, they provide a substantially continuous axial curvature, so that extrusion of a curved tube can still be advantageously employed. A similar effect could be produced by arranging the main regions so that they are joined through a common small cavity portion 26, the inlet 30 being at the mouth end of one of the airways as in Figures 2 and 3, the mould closing the tube in the cavity portion 28 at the mouth end of the other of the airways. More than two airways could be simultaneously produced in like fashion, the mould cavities for the separate airways being arranged end-toend as described.

Claims

1. A process for making an oral airway for medical use, which comprises blow-moulding a plastics tube to the desired shape for the airway, with a longitudinally generally curved main portion and a enlarged cavity portion at one end thereof, and cutting through the tube transversely at the other end of the main portion to provide a throat end opening to the airway, and cutting the tube trans verselythrough said enlarged cavity portion to provide a mouth end opening to the airway, the part of said enlarged cavity portion remaining attached to the main portion providing a peripheral flange for engagement with the teeth or lips of the patient.

2. A process according to claim 1 wherein the throat end of the main portion has a region of reducing cross-section through which the transverse cut at that end is made.

3. A process according to claim 1 or claim 2 wherein the main portion has an enlarged internal cross-section in the region adjacent said flange so as to receive a hard insert sleeve which can be located axially in one direction by the smaller cross-section of the rest of the main region and in the other direction by an inward lip formed around the opening to the passage during the moulding process.

4. A process according to any one of the preceding claims wherein the closing of the mould seals the throat end of the tube, the fluid under pressure for expanding the tube being injected into the tube from the other end.

5. A process according to any one of claims 1, 2 and 3 wherein a plurality of airways are produced in a single blow moulding process from a single length of plastics tube, the mould providing mould cavities for the separate airways arranged end-to-end and adjacent mould cavities joined by an intermediate cavity.

6. A process according to claim 5 wherein said intermediate cavity provides a single said enlarged cavity portion common to both of the adjacent airways.

7. A process for making an oral airway for medical use, substantially as herein described with reference to the drawings.

8. An oral airway for medical use comprising a longitudinally curved tube for insertion into the oral passage of a patient and having a throat opening at one end and a mouth opening at the other end with an out-turned peripheral flange around the mouth opening to engage the lips or teeth of the patient, the tube being blow-moulded from plastics material.