GB2181055A - Disposable syringe - Google Patents

Abstract

A resiliently compressible variable volume casing having particular application as a disposable syringe. The casing (1) defines a chamber (1a) and is provided at one end region thereof with an aperture (2) for permitting transfer of a substance to and from the chamber. The casing is in the form of a bellows and has a wall including a plurality of fold regions (6) between which are respective bellows portions (7, 7a). The casing is configured so that there is a substantial reduction in ''dead space'' or the air entrapped in the casing, when the bellows is compressed. This is achieved by one or more of the following: 1) forming the bellows portions so that when the bellows is compressed there is a bellows portion the periphery of which lies wholly within or wholly without the peripheries of its adjacent bellows portions; 2) providing the casing with a member mounted with respect to the casing and such that, when the bellows is compressed, the member occupies a major portion of the internal volume of the casing; and 3) forming the bellows portions each with concave and convex surface so that a concave surface of one bellows portion mates with the convex surface of the adjacent bellows portions. The reduction of ''dead space'' in the compressed casing, and the almost complete elimination of air which follows, mean that the casing is particularly useful for the storage of substances for which contact of air is to be avoided. The aperture may be formed as a hollow needle receiving portion particularly adapted to receive a hypodermic needle, so that the casing may be used as a syringe either to remove body fluids or to administer medication.

Description

SPECIFICATION Disposable syringe This invention relates to a disposable syringe.

Routine venesection for the collection of blood samples is one of the most frequent of clinical procedures. At present, the syringes in use are of a plunger-in-barrel design and require the use of two hands by the clinician in order to withdraw blood. This means that a tourniquet is required to ensure that the vein is accessible. Further, when the blood sample has been taken, it must be transferred to a storage vial, since the plunger in barrel design is ill suited to the storage of fluid. Also, the disposable syringes in common use require precision moulding, and are relatively expensive.

There have been proposed several syringes using variable volume bellows; however, none of these syringes have been commercially produced, and it is felt that there are two main reasons for this: the problem of "dead space" when using a bellows type product; and the problems associated with manufacturing a completely compressible and expandable bellows.

The problem of "dead space" arises as a result of the air still entrapped in a completely compressed bellows. This can cause difficulties as air may become entrapped in a fluid being taken from or administered to a patient, with possible adverse effects. There is a British Standard which sets out the requirement of maximum dead space for conventional syringes as follows: Syringe size Maximum volume of dead space ml ml 1 0.07 2 0.07 5 0.07 10 0.10 20 0.15 30 0.17 50 0.20 Figs. 1a and 1b of the accompanaying drawings show a portion of a conventional bellows, in cross-section, respectively expanded and completely compressed: generally about 15% of the total volume will be "dead space" when compressed.

Concerning the manufacture of such products, problems have previously arisen in obtaining a bellows which is compressible to a maximum extent, and then returns substantially completely to its original form.

Thus, there has not hithertofore been provided an inexpensive, disposable syringe which can be used for both administering fluids to, and collecting fluids from, a patient, and which can also serve as a storage means.

According to one aspect of the present invention there is provided a disposable syringe comprising a resiliently compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with a hollow needle receiving portion for receiving a needle and whose interior is in communication with the chamber, the casing being in the form of a bellows and having a wall defining a plurality of fold regions between alternate ones of which are respective bellows portions, wherein the bellows portions are so configured that, when the bellows is compressed, the periphery of each bellows portion lies wholly within or wholly without the periphery of its adjacent bellows portion(s).

According to another aspect of the present invention there is provided a disposable syringe comprising a resiliently compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with a hollow needle receiving portion for receiving a needle and whose interior is in communication with the chamber, the casing being in the form of a bellows, wherein the hollow needle receiving portion is an injection moulded portion, and the bellows is a blow moulded portion.

According to a further aspect of the present invention there is provided a method of manufacturing a syringe as defined in either of the preceding paragraphs, which method comprises firstly forming the needle receiving portion by an injection moulding process and subsequently forming the bellows by a blow moulding process.

When the syringe is in use, with a needle in place on the receiving portion, to administer a fluid contained in the chamber, pressure on the casing causes the wall to be compressed to reduce the volume of the casing, whereby the fluid is administered through the needle, and, when the syringe is in use to withdraw a fluid from a patient, the wall is compressed to reduce the volume of the chamber, and subsequently released to permit the fluid to be drawn from the patient into the chamber. Thus, only one hand is required to operate the syringe.

Preferably the syringe is moulded as a single unit.

The syringe can be manufactured in a sealed form with a fluid for administration being contained in the chamber.

The receiving portion may be provided with a releasable sealing means whereby the syringe, when not in use, can serve as a vial.

Preferably, the casing is provided with markings to indicate the capacity of the bellows portions.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:~ Figures la and 1b show respectively, in part, a conventional bellows expanded and compressed; Figures 2a and 2b shows respectively, in part, the bellows according to one embodiment of the present invention expanded and compressed, Figure 3 and 4 show a syringe in the expanded and compressed states respectively; Figure 5 is a plan view of the syringe of Fig. 3; Figure 6 and 7 show syringes of different capacities from that shown in Figs. 3 to 5; and Figure 8 shows a partial cross-section through another form of syringe having an eccentrically mounted needle receiving portion.

Figs. 3, 4 and 5 shows a syringe in accordance with one embodiment of the present invention. The syringe has a casing 1 with a protrusion 2 manufactured with a Luer (or any other) lock universal-sized needle-adapter portal 3. For example the adapter portal may be as described in BS 1263. The needle adapter portal 3 is provided with a hollow syringe needle 4 (Fig. 6) when the syringe is to be used, the interior of the needle communicating, via the adapter portal 3, with an interior chamber defined by the casing 1. The casing 1 has a circular base 5 (Fig. 5), and defines a chamber.

The casing 1 is constructed so as to have fold regions: in Fig. 3 these take the form of fold lines, between alternate ones 6 of which are defined bellows portions 7, 7a. Alternate bellows portions have different widths, the width being measured perpendicular to the longitudinal axis of the bellows, along a fold region intermediate said alternate fold regions. For example, as shown in Fig. 3, bellows portion 7a is slightly wider than adjacent bellows portion 7. In Fig. 3, the difference is exaggerated for the sake of clarity, and in an embodiment having a wall thickness of 0.75mm and an internal volume of 10ml. may be about 0.75mm.The effect of this alternating size bellows construction on the compressibility of the bellows is illustrated diagrammatically from a comparison of Figs. 1 b and 2b, from which it can be clearly seen that the air entrapped in the compressed bellows is substantially less in Fig. 2b. In fact, using this arrangement, the wasted internal space can be reduced to about 1/10to of conventional bellows, and may be as low as 1% of the volume. Further, the compressed height of the bellows is reduced by about 50%, that is the compressed height of a conventional bellows may be about twice that of a bellows of the same volume in accordance with an embodiment of this invention.

In Fig. 2b the dimensions are as follows: a =0.75mm b=7mm c =0.65mm The compressibility of the bellows, and its ability to return substantially completely to its original form after compression, is also affected by the manner in which the bellows is manufactured. It has been found surprisingly that a technique currently in use for the manufacture of plastics bottles can be used with great success to manufacture a substantially completely resilient bellows container. This technique is described in, for example, GB 1493453 and 1502338. This method involves the so-called injection stretch-blow technique, which is carried out as follows. At the start of each stetch-blow cycle, an injection die having the shape of the required syringe head fits tightly onto a ring nozzle. The injection mould produced in this way is filled in the first operation with the required amount of plastic stock for a tube which, after cooling, forms the finished syringe head. Following a conventional injection moulding process, the injection die moves upwards drawing a tube of plastic while a quantity of plastic stock, dependent on the speed at which the tube is drawn, is fed from the ring nozzle. On one side, gripped in the injection mould, and on the other in the ring nozzle, a tubular parison with precisely controlled wall thickness is thus formed. After the parison has been drawn, it is enclosed in two halves of a blow mould which is constructed to form a tight seal against the injection die and the nozzle. The syringe is then blown using a conventional blow moulding process to form the final product.By combining the advantages of injection moulding and blow moulding, a resilient product having an accurately formed syringe head can be manufactured.

Further, the accurate formation of the alternating size bellows construction is permitted.

The base 5 of the casing 1 may be provided with labels to identify either the patient under venesection or the fluid being injected. The syringe may be manufactured in a range of sizes in order to allow the collection or delivery of precise fluid volumes. Those having a capacity of 5, 10 and 20 ml. are shown in Figs. 3, 6 and 7 respectively.

In order to further assist in the delivery of precise fluid volumes, each bellows portion is constructed to have a capacity of, for example, 2 ml, and the value is marked on the wall of the casing so that an immediate indication of the quantity of fluid contained in the casing can be given.

For collecting a blood sample from a patient, the vein can be made accessible using one hand, while suction is attained by pressing the base 5 of the casing 1 with the other hand to its fully compressed state. A slow controlled recoil is then effected under the control of the thumb of the operator whereby the volume of the interior chamber is slowly increased to draw blood from a a patient through the needle into the chamber.

Conversely, when using the syringe for injections to administer a drug, the interior chamber of the casing 1 can be filled with the drug to be administered, the drug being expelled by pressure applied slowly to the base 5 of the casing 1 by the operator.

Fig. 8 shows a partial cross-section of a syringe manufactured according to the arrangement shown in Figs. 2a and 2b and having an eccentrically mounted needle portal 3. Figure 8 shows the internal chamber 1a. The base 5 may carry markings indicating the patient's name and the nature of the fluid in the syringe.

It will be appreciated that the construction of the bellows need not be such as to provide for a regular alteration between the width of bellows portions, but that it would be possible to achieve a reduction in the amount of dead space by other arrangements in which the periphery of each bellows portion lies wholly within or wholly without the periphery of its adjacent bellows portion(s).

Uses of the syringe extend to all uses currently performed by standard syringes, including venesection or arterial collection of blood specimens, and intravenous or intramuscular injections.

The syringe would normally be sterile-packed for immediate use with a removable end cap over the needle portal to allow the syringe to be sealed for transport of specimens.

The syringe described above further has the advantages that it can be manufactured as a single moulded unit for a fraction of the cost of conventional syringes, and may be operated with considerable control using only one hand. A syringe of this kind may also be pre-packaged with anticoagulant or chelating agents for specific chemopathological or haematological applications, and could serve as a sample vial for the blood withdrawn. Furthermore, such simple syringes could come pre-packed with specific therapeutic fluids, thereby precluding the need for expensive vial packaging and the effort of filling the syringe. Savings in time and expense would be substantial.

A A particular advantage of the syringe acting as a container is that it obviates the need for using crystalline substances (for adding water, saline solution etc.) and the drugs can be preproduced in ready-to-use form. Since hospitals have refrigeration facilities, temperature sensitive drugs can be stored "on site". Further, the syringes may be manufactured of a plastics material which has an additive giving UV light shielding to the plastics material for the protection of photosensitive drugs. Expiry dates for the drugs may be marked on the base of the syringe in the usual way. The storage of drugs "on site" and in a convenient form for administration is particularly important where the administration of the drug is to be carried out immediately.

The syringe could also be used for administering drugs to animals in the field of agriculture or veterinary science.

Claims (10)

1. A disposable syringe comprising a resiliently compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with a hollow needle receiving portion for receiving a needle and whose interior is in communication with the chamber, the casing being in the form of a bellows and having a wall defining a plurality of fold regions between alternate ones of which are formed respective bellows portions, wherein the bellows portions are so configured that, when the bellows is compressed, the periphery of each bellows portion lies wholly within or wholly without the periphery of its adjacent bellows portion(s).

2. A syringe as claimed in claim 1, in which the casing is such that, following compression of the syringe under pressure, when the pressure is released, the volume of the chamber returns substantially completely to its original value under its own resilience.

3. A syringe as claimed in claim 1 or 2, which has been moulded as a single unit.

4. A syringe as claimed in claim 3 in which the needle receiving portion is an injection moulded portion and in which the bellows comprise a blow moulded portion.

5. A disposable syrgine comprising a resilient compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with a hollow needle receiving portion for receiving a needle and whose interior is in communication with the chamber, the casing being in the form of a bellows, wherein the hollow needle receiving portion is an injection moulded portion, and the bellows being a blow moulded portion.

6. A syringe as claimed in any preceding claim, in which the receving portion is provided with a releasable sealing means whereby the syringe, when not in use, can serve as a vial.

7. A disposable syringe substantially as hereinbefore described with reference to, and as shown in, Figs. 2a, 2b and 3 to 8 of the accompanying drawings.

8. A method of manufacturing a syringe according to claim 3 or 5, which method comprises firstly forming the needle receiving portion by an injection moulding process and subsequently forming the bellows by a blow moulding process.

9. A method as claimed in claim 8, in which the blow moulding process is carried out using a parison integral with the injection moulded portion.

10. A method claimed in claim 8 or 9, substantially as herebefore described with reference to the accompanying drawings.