DISPOSABLE SYRINGE

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: TITLfi OF THE INVENTION DISPOSABLE SYRINGE Field of the invention This invention relates to a resiliently compressible variable volume casing, for example for use with a hypodermic needle as a disposable syringe. Background to the invention 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 and/or testing vial, since the plunger in barrel design is ill suited to the storage or testing of fluid. Also, the disposable syringes in common use require precision moulding, and are relatively expensive. Of course, syringes are also used to administer medicament. 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 three main reasons for this: the problem of "dead space" when using a bellows type product; the problems associated with manufacturing a completely compressible and expandable bellows; and the problem of controlling sufficiently accurately the amount of medicament administered. The problem of "dead space" arises as a result of the air still entrapped even 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 It is believed that the prior proposed bellows type syringes have not been commercially developed because they have not been able to meet these requirements. UK 1095316 discloses a bellows type syringe having a casing forming a plurality of bellows portions, in which the end wall of the end bellows portion has a reduced structural stiffness whereby it can be collapsed completely against the other wall of the end bellows portion under an axial force. To. ensure that the force is applied axially, a stud or plunger is formed with the end wall. The syringe is designed to indicate whether it has been correctly inserted prior to injection of its contents into a patient. UK 1095316 does not address the problem of "dead space", and it is apparent that this will remain a problem with the syringe described therein. Further, the manufacture of the syringe with the necessary plunger is awkward. Brief description of the drawings Figures la and lb show respectively, in part, a conventional bellows expanded and compressed; Figures 2a and 2b show respectively, in part, the bellows according to one embodiment of the present invention expanded and compressed, Figure 3 and 4 show a casing in the expanded and compressed states respectively; Figure 5 is a plan view of the casing of Figure 3; Figure 6 and 7 show syringes of different capacities from the casings shown in Figures 3 to 5; Figure 8 shows a partial cross-section through another form of syringe having an eccentrically mounted needle receiving portion; Figure 9 shows a partial cross-section through another form of casing having different diameter bellows portions; Figure 10 shows a casing with concave and convex bellows portions surfaces; Figures 11 and 12 show a syringe with an arrangement to control delivery of fluid from the syringe; and Figure 13 shows a syringe with a housing for enabling a continuous controlled delivery of fluid from the syringe. Figures la and lb of the accompanying 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. Summary of the invention According to a first aspect of the present invention there is provided a resiliently compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with an aperture for permitting transfer of a substance to and/or from the chamber, the casing being in the form of a bellows and having a wall including a plurality of fold regions between which are respective bellows portions, wherein the bellows portions are so configured that, 'when the bellows is compressed there is a bellows portion the periphery of which lies wholly within or wholly without the peripheries of both its adjacent bellows portions. " Preferably there is a set of such bellows portions, so that each bellows portion has a periphery lying wholly within or wholly without its neighbouring bellows portion(s) . According to a second aspect of the invention there is provided a resiliently compressible variable volume casing defining a chamber, the casing being in the form of a bellows and being provided at one end region thereof with an aperture for permitting transfer of a substance to and/or from the chamber and there being a member mounted with respect to the casing and such that, when the bellows is substantially fully compressed, the member occupies a major portion of the internal volume of the casing. Preferably, the member is circularly cylindrical and is formed integrally with said end region of the casing. That end or the opposite end region is preferably formed as a substantially flat base. In the described embodiment, the member operates as a piston to occupy most of the internal volume of the casing when the bellows is compressed. The aperture can be formed as a hollow needle receiving portion for receiving a syringe needle whereby, with a syringe needle attached to the hollow needle receiving portion, the casing can serve as a syringe. Alternatively, the aperture can be formed to communicate with an elongate flexible cannula having a needle at its distal end. According to a third aspect of the invention there is provided a resiliently compressible variable volume casing defining a chamber, the casing having an aperture to permit transfer of a substance to and/or from the chamber and being in the form of a bellows, the casing having a wall including a plurality of fold regions between which are. respective bellows portions, each bellow portion having first and second surfaces, the first surface of a bellows portion contacting the second surface of its adjacent bellows portion when the bellows is compressed, wherein the first surfaces are convex and the second surfaces are concave in such a manner that the first and second contacting surfaces mate when the bellows is compressed. According to a fourth 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. It will be appreciated that the casing could incorporate the features of any or any combination of the first to fourth aspects of the invention. According to a fifth aspect of the present invention there is provided a method of manufacturing a casing as defined in any of the preceding paragraphs, which method comprises firstly forming the aperture providing end region by an injection moulding process and subsequently forming the bellows by a blow moulding process. In a preferred embodiment, there is 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. When the casing is in use as a syringe with a needle in place at the aperture or needle receiving portion, to administer a fluid contained in the chamber, pressure on an end region of 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 aperture may be provided with a releasable sealing means whereby the casing, when not in use as a syringe, can serve as a vial. When the casing has a substantially flat base, it is ideally suited for storage or for insertion into testing equipment to test the contents thereof. Preferably, the casing is provided with markings to indicate the capacity of the bellows portions. These markings can be formed on a mould used to manufacture the bellows portions so as to be impressed on the casing. The invention also provides an arrangement for delivering a desired quantity of a fluid, the arrangement including: a resiliently compressible variable volume casing defining a chamber and having at one end region thereof an aperture for delivery of fluid from the chamber, the casing being in the form of a bellows and having a plurality of fold regions between which are respective bellows portions; and ' a housing secured or adapted to be secured to the casing and provided with a plurality of protrusions arranged to latch the bellows portions as the bellows is compressed. The casing can be made in accordance with any or any combination of the first to fifth aspects of the invention. Description of the preferred embodiment 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 Figures 3 to 13 of the accompanying drawings. Figures 3, 4 and 5 show a casing in accordance with one embodiment of the present invention. The casing 1 has a hollow needle receiving portion 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 when the syringe is to be used (see Figure 6), 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 flat circular base 5 (Figure 5), so that the casing can be stored upright when in use as a vial. The casing 1 is constructed so as to have fold regions: in Figure 3 these take the form of fold lines 6, between which are defined bellows portions 7, 7a. In the embodiment of Figures 3 to 5, the alternate bellows portions have different widths, the width being measured perpendicular to the longitudinal axis of the bellows, along a fold region 6a intermediate said bellows portion defining fold regions 6. For example, as shown in Figure 3, bellows portion 7a is slightly wider than adjacent bellows portion 7. In Figure 3, the difference is exaggerated for the sake of clarity. In an embodiment having a wall thickness of 0.75mm and an internal volume of 10ml. the difference 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 Figures lb and 2b, from which it can be seen clearly that the air entrapped in the compressed bellows is substantially less in Figure 2b. In fact, using this arrangement, the wasted internal space can be reduced to about 1/10th 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 Figures 2a and 2b the dimensions are as follows: a = 0.75mm b = 7mm c = 0.65mm When the bellows is fully compressed, even with the reduced height attainable using alternating bellow portions of different diameters, there may still be some air trapped inside the casing, that is there is still some "dead space". This dead space is reduced further with the embodiment of Figure 8 which shows a partial cross-section of a syringe without alternating bellows portions and having an eccentrically mounted needle portal 3. Figure 8 shows the internal chamber la. The base 5 may carry markings indicating the patient's name and the nature of the fluid in the syringe. In this embodiment the casing has formed integrally therewith a circularly cylindrical member or piston 8. This piston 8, when the bellows is compressed, occupies most of the internal column of the compressed casing 1, thereby reducing significantly the "dead space". There will only remain as insignificant amount of air in the portal 3. The height h of the piston, as measured along the longitudinal axis of the casing, is such that it is just less than the compressed height h of the bellows (Figure 7). It may be that for casings of certain capacities, and as shown in Figure 8, it is possible to dispense with the "alternating bellows" configuration, and merely to use a "dead space" reducing piston such as piston 8. As shown in Figure 8, the needle receiving piston 3 is placed offcentre to permit formation of the piston 8 at the needle ' receiving end of the casing. It would be possible to provide alternatively or additionally a piston 8' formed integrally with the base 5, as shown in Figure 9. In Figure 9 the needle receiving portion 2 is shown centrally of the casing, and the casing has an "alternating bellows" construction. It will be appreciated that it is also possible, referring to Figure 8, to place the needle receiving portion 2 centrally of the piston 8, instead of in the illustrated offset position. Another way in which the dead space can be reduced is to manufacture the casing so that the bellows portions each have an convex surface and a concave surface, as shown in Figure 10. Figure 10 illustrates a casing having a bellows type casing l 1 , with each bellows portion 7 ' having an upper convex wall 9 and a lower concave wall 10. With this arrangement, when compressed, the upper convex wall 9 of a lower bellows portion 7 fits readily into, or mates with, the lower concave wall 10 of the adjacent upper bellows portion, hence serving to permit further compressibility. As an alternative to manufacturing the bellows with a concave, convex configuration, it would be possible to arrange for the lower wall of each bellows portion to be slightly more resilient than the upper wall, so that the upper wall of the bellows portion would tend to deform the lower wall of the adjacent bellows portion. Of course, the lower surfaces could be convex, while the upper surfaces are concave. The concave/convex arrangement could be applied to the alternating configuration as shown in Figure 10, with or without the "dead space" reducing piston 8. 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 stretch-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 or the concave/convex construction is permitted. As a result of the blow moulding process, the wall thickness of the larger diameter bellows portions is marginally thinner than that of the smaller diameter bellows portions. The piston 8 can be formed by altering the blow mould accordingly. The base 5 of the casing 1 may be provided with labels to identify either the patient under venesection or the fluid being injected. This enables the syringe to be labelled much more easily than conventional hypodermics. The casing 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 Figures 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 fixed capacity of a given number of millilitres, 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 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. The volume of fluid administered to a patient is dependent on the pressure applied to the syringe. The delivery of a precise quantity of fluid when using the casing as a syringe to administer medicament is assisted by the configuration of each bellows portion as a known volume of fluid. With the arrangement of Figure 11, this is utilised by providing a housing 11 having a plurality of ratchets or teeth 12a, 12b, etc formed along the internal wall of the housing. The housing 11 has an upper closure member 13, preferably formed integrally with the wall of the housing and which is fixedly secured to the needle receiving portion 2 of the casing 1. In operation, the base 5 of the casing 1 is pushed towards the needle receiving end of the casing, which can be done with the thumb of the hand used to hold the casing. As the lowest bellows portion 7a moves upwardly in Figure 10, it catches on the upper surface of the lowermost ratchet 12a, making an audible clicking noise. By counting the number of clicks, administration of a desired amount of medicament can be achieved. Such a system would be particularly useful for a blind person who regularly has to self administer a drug such as insulin. Alternatively, the housing could be made transparent to enable the compression of the bellows to be monitored visually, the ratchets providing a useful control to avoid over administration. With the housing 11 of Figure 10, the spacing of the ratchets increases slightly along the housing wall since the lowermost ratchet only has to accommodate one bellows portion, whereas the next ratchet must accommodate two bellows portions, and so on. The region nearest the delivery end of the casing is free of ratchets to accommodate the fully compressed bellows. Instead of the housing, there could be a single strip 18 with a plurality of teeth 20 to perform the same function, as shown in Figure 12. Such a strip has an aperture 19 to fit over the needle receiving portion 2. The strip could have a plurality of teeth or a single tooth at one predetermined quantity. As shown in Figure 13, the syringe can be used as part of a controlled continuous drug delivery system to replace the rather cumbersome hypodermic system currently used. In this case a plate 14 is fixed to the needle receiving portion 2. An open ended housing 15 having a base 16 secured to the base 5 of the casing 1 is arranged for movement relative to the plate 14. The plate 14 serves to secure the syringe in a delivery system (not shown), which includes a drive means (shown diagrammatically as a spring 7) acting on the casing 1 in the direction of arrow A to compress the bellows. Any suitable controllable drive means could be used. 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 there is a bellows portion the periphery of which lies wholly within or wholly without the peripheries of both its adjacent bellows portions. 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 casing described above further has the advantages, when for use as a syringe, that it can be manufactured as a single, unbreakable, moulded unit for a fraction of the cost of conventional syringes, and may be operated with considerable control using only one hand. This one hand control reduces the likelihood of damage to a patient. 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 particular advantage of the casing when used as a container is that, because of the elimination of air in the compressed state, 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 facilites, temperature sensitive drugs can be stored "on site". Suitable materials for the casing include thermoplastic polymers such as nylon polymers, polyethylene, polypropylene, surgical grades of polyvinylchloride, and ethylenevinylacetate. Further, the casing 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 casing 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. The casing can be manufactured so cheaply that it can be disposed of after use. However, if required, it can be sterilised using e.g. gamma radiation, or in an autoclave, for reuse.

Claims: 1 CLAIMS : 1. A resiliently compressible variable volume casing defining a chamber, the casing being in the form of a 5 bellows and being provided at one end region thereof with an aperture for permitting transfer of a substance to and/or from the chamber and there being a member mounted with respect to the casing and such that, when the bellows is substantially fully compressed, the member X0 occupies a major portion of the internal volume of the casing. 2. A resiliently compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with an aperture for permitting transfer 15 of a substance to and/or from the chamber, the casing being in the form of a bellows and having a wall including a plurality of fold regions between which are respective bellow portions, wherein the bellows portions are so configured that, when the bellows is compressed, 20 there is a bellows portion the periphery of which lies wholly within or wholly without the peripheries of both its adjacent bellows portions. 3. A casing as claimed in claim 4, wherein there is a set of such bellows portions, so that each bellows 25 portions has a periphery lying wholly within or wholly without the peripheries of its neighbouring bellows portion(s) . 4. A casing as claimed in claim 2 or 3, wherein there is a member mounted with respect to the casing and such 30 that when the bellows is compressed the member occupies a major portion of the internal volume of the casing. 5. A resiliently compressible variable volume casing defining a chamber, the casing being provided at one end region thereof with an aperture for permitting transfer 35 of a substance to and/or from the chamber, the casing being in the form of a bellows and having a wall including a plurality of fold regions between which are respective bellows portions, each bellows portion having first and second surfaces, the first surface of a bellows portion contacting the second surface of its adjacent bellows portion when the bellows is compressed, the first surfaces being concave and the second surfacesbeing convex in such a manner that the first and second contacting surfaces mate when the bellows is compressed. 6. A casing as claimed in claim 2, 3 or 5, wherein there is a member mounted with respect to the casing and such that when the bellows is substantially fully compressed the member occupies a major portion of the internal volume of the casing. 7. A casing as claimed in claim 1 or 6, in which the member is circularly cylindrical. 8. A casing as claimed in claim 1, 6 or 7, in which the member is formed integrally with said end region of the casing. 9. A casing as claimed in any preceding claim, wherein the aperture is formed as a hollow needle receiving portion for receiving a syringe needle whereby, with a syringe needle attached to the hollow needle receiving portion, the casing can serve as a syringe. 10. 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. 11. A method of manufacturing a casing as claimed in any preceding claim, which method comprises firstly forming the aperture providing end region by an injection moulding process and subsequently forming the bellows via a blow moulding process. 12. An arrangement for delivering a desired quantity of a fluid, the arrangement including: a resiliently compressible variable volume casing defining a chamber and having at one end region thereof an aperture for delivery of fluid from the chamber, the casing being in the form of a bellows and having a plurality of fold regions between which are respective bellows portions; and a housing secured or adapted to be secured to the casing and provided with a plurality of protrusions arranged to latch the bellows portions as the bellows is compressed. SUBSTITUTESHEET

Inventors: COLGATE DAVID JOHN, RICHARDS PETER WILLIAM, SPONSEL WILLIAM ERIC, COLGATE, DAVID, JOHN, RICHARDS, PETER, WILLIAM, SPONSEL, WILLIAM, ERIC
Applicants: AXIPAC LTD, AXIPAC LIMITED
Application year: 1986
Main classification: A61M5
IPC codes: A61M5