Method of manufacturing a plastic cartridge

Abstract: A plastic cartridge for use as a pre-filled cartridge comprising a hollow cylindrical barrel (1) having a top end (6) and a bottom end (2) both of which are open. The bottom end (2) is sealed by a stopper (3) and the top end (6) by a plastic cap (7). The cap (7) comprises a hypodermic needle (27), or an integrally moulded fitting (12) adapted to receive a hypodermic needle, and a closure (9) which is frangibly connected and integral with the cap (7) so that upon application of a removal force on the closure (9) the closure (9) can be separated from the cap (7) thus revealing the hypodermic needle or the hypodermic needle fitting (12) and the contents of the cartridge. Also the prefilled syringe is described and a method for manufacturing the pre-filled cartridge.

Description: Technical field of the invention The present invention relates to a method for manufacturing a plastic pre-filled cartridge to be used in a prefilled syringe. Background of invention Many syringes in common use today utilize a glass or plastic pre-filled cartridge. Such cartridges are conventionally sealed at one end by a rubber stopper membrane which is sealed against the outside of the cartridge by a metal cap. The metal cap is crimped onto the end of the cartridge thus ensuring an effective seal at the end of the cartridge remote from the rubber stopper. One example of such a syringe is described in AU-A-73632/81. Cartridges of the type described are conventionally filled with an injectable medium and may then be autoclaved to ensure the sterility of the contents. In use, these cartridges are inserted into a syringe holder designed to allow expression of the contents of the cartridge. For example, metal barrelled syringes having a fitting at one end to accept a double sided needle and a plunger at the other end have previously been in use. These syringes are intended for multiple use and must be stored in a sterilizing cabinet after each use. Furthermore, they suffer from the disadvantage that they are heavy and large. The size of the syringe is a particular disadvantage as these syringes are intimidating for patients. Also in use are disposable syringe bodies to which there is fixed a double sided needle. When these disposable syringe bodies are used a pre-sterilized cartridge is inserted into the syringe body. The double sided needle is adapted to puncture the rubber membrane at the end of the cartridge barrel and a plunger rod is used to expel the contents of the cartridge. The cumbersome nature of prior syringe assemblies has lead to various alternative assemblies being investigated with a particular view to designing a simple disposable syringe and cartridge. For example, in Australian patent specification 468,624 there is described a disposable syringe assembly having a barrel moulded from plastics material. This syringe however continued the use of double ended needles and required the use of an external shell for the mounting of the cannula. An alternative arrangement also using a double ended needle is disclosed in AU-A41625/78. This syringe assembly utilized a double ended needle encased within a housing which was retained in a hub socket within which the needle housing was adapted to move. On the application of an inward force on the needle housing a diaphragm adjacent the hub was punctured by the rearward needle to reveal the contents of the cartridge for injection. This development also suffered from the disadvantage of having to provide an internal diaphragm within the cartridge and the use of a double ended needle. Similar use of a puncturable diaphragm in conjunction with a spike for revealing the contents of a pre-filled syringe can be seen by reference to AU-A27579/77. It has also been common practice to utilize a needle guard and these guards have usually conveniently slipped over the needle fitting (for example see Fig. 1 of AU-B86910/82). Such needle guards are usually frictionally fitted over the needle fitting. In WO86/03126 there is disclosed a syringe which incorporates a retaining clip to hold a separate needle fitting in position over the end of an injection body having a specially moulded needle fitting seat. The retaining clip incorporates a protective sheath which is frangibly connected to the body of the clip. However, the syringe assembly described in WO86/03126 suffers from the disadvantage of requiring a specially moulded seat for retaining the hypodermic needle fitting and a retaining clip to hold the needle in place. This limits use of the syringe to needles which can be fitted into the moulded seat and sealing requires the use of a separate sealing ring. DE-C-809 698 describes an ampoule for a syringe wherein the head of the ampoule is made of a rigid material and a body rigidly connected thereto which is made of an elastic material or made of a rigid material and provided with a stopper at the bottom end. A groove is provided on the rigid head of the ampoule above the seat for the needle whereby the groove provides a weakened line where the tip of the head could be broken off. The tip of the head functions as a closure of the ampoule against the environment and has to be broken off before a needle can be arranged on the head or before the ampoule could be emptied into a syringe. The head of the ampoule and its tip is protected from contamination by a protection cap made of bacteria-proof cellulose material, in particular paper. This protection cap is glued to the thicker part of the tip of the ampoule. US-A-3 406 686 and US-A-3 375 825 describe a method of assembling a prefilled syringe of the above described type. The assembling method is performed in several steps and in different environments, some of which are aseptic. In the above mentioned documents the cartridges have been manufactured and partly assembled before they have been sterilized all in different steps. The cartridge has then been aseptically filled and closed. This way of manufacturing a cartridge of the above mentioned type is naturally difficult and expensive as it requires several different steps, some of which can be complicated. The prior methods also requires that the materials used in the different parts of the cartridge can be sterilized, e.g. are autoclavable. A cartridge manufactured in accordance with the present invention to be used in a prefilled syringe as described below represents a unique product for use in delivering injectable substances. It provides many improvements over the cartridges in present use. In particular the cartridge described does not suffer through use of multiple components such as metal caps and rubber membranes. As there is no rubber membrane the practitioner does not have to use a double sided needle. This overcomes two problems associated with the standard cartridges, namely blocked needles due to a core of rubber becoming lodged in the needle and leaking at the point of needle entry through the rubber membrane due to a bent needle. A further advantage is the use of the cartridge in a simple disposable prefilled syringe unit which is not as heavy, large and intimidating as existing syringes. The invention The present invention encompasses a method of manufacturing a cartridge unit. According to the invention the method for manufacturing a prefilled cartridge comprises the following steps: a) injection moulding a cartridge barrel having a top end and a bottom end both of which are open, in an aseptic environment; b) injection moulding a plastic cap including an integrally moulded fitting adapted to receive a hypodermic needle and a closure which is frangibly connected with said cap in said aseptic environment; c) introducing into said aseptic environment a pre-sterilized stopper; d) fitting the pre-sterilized stopper into the bottom end of the cartridge barrel in said aseptic environment; e) aseptically filling the said cartridge with an injectable medium in said aseptic environment; and f) sealingly attaching said cap to the cartridge barrel in the said aseptic environment, as described in claim 1. The cartridge cap is preferably affixed to the cartridge barrel by welding it to the barrel. Butt welding or ultrasonic welding techniques can be usefully employed to effect this fixation. Preferably, an overcap is also injection moulded in the aseptic environment as well. This component is fixed over the top of the cartridge cap after the cartridge cap has been affixed to the cartridge barrel. The overcap can alternatively be supplied to the aseptic environment in a pre-sterilized form. Further preferred embodiments of the method according to the invention are clear from the dependent claims 2 to 5. The barrel which is used in the present invention may be made of any rigid plastics material. For example, a translucent or transparent plastics material such as polyethylene terephthalate, polyamide, polypropylene or TPX may be used. Other suitable materials are well known to those skilled in the art. Most preferably, polypropylene is used as this material is of relatively low cost, has clear finish and is a well tested material for containing pharmaceutical substances. The cartridge manufactured according to the method of the invention can be used in existing syringe barrets (with the necessary modifications) or can itself be used as a component part of a syringe unit. In use the cartridge/syringe unit is assembled by inserting the plunger rod into the stopper sealing the bottom end of the cartridge. The closure forming part of the cartridge cap is then removed by applying an appropriate force thereto and a hypodermic needle is then applied to the needle fitting on the cartridge cap (where required). A single sided needle is adequate but the closure must be removed prior to application of the hypodermic needle. Removal of the closure reveals the contents of the cartridge. Application of a force against the plunger rod causes positive forward movement of the stopper in the cartridge barrel thus causing expression of the injectable through the hypodermic needle. In this form there is provided an all plastic (other than cannula) hypodermic syringe which is easy to use and which is disposable after a single use. According to the invention a cartridge barrel and cartridge cap are injection moulded in an aseptic environment, a pre-sterilized stopper is introduced into the aseptic environment and is fitted into the bottom end of the cartridge barrel to seal same The cartridge barrel is then aseptically filled with the proposed injectable medium and then sealed by affixing the cartridge cap to the top end of the filled cartridge barrel. Brief Description of the Drawings A preferred embodiment of the invention is hereafter described with reference to the following drawings in which: Figure 1 is a cross-sectional exploded view of a cartridge produced in accordance with a method of present invention having a luer slip needle fitting. Figure 2 is a cross-sectional exploded view of a syringe unit utilizing the cartridge shown in Figure 1. Figure 3 is a cross-sectional assembled view of a syringe unit utilizing the cartridge shown in Figure 1. Detailed Description of the Drawings In Figure 1 there is shown a cartridge barrel 1. Cartridge barrel 1 is made of a plastics material, most preferably polypropylene. At the bottom end of barrel 1 there is an open end 2 into which there is inserted a stopper 3. Stopper 3 is adapted to move within barrel 1 whilst retaining a fluid tight seal. To this end, stopper 3 is preferably made of rubber and has two sealing rings 3a and 3b. At its top end cartridge barrel 1 has a neck 4 of smaller diameter than the rest of the cartridge barrel body. At the end of neck 4 there is provided a flange 5. At the end of the neck portion there is provided an upper annular face 6a, an outer neck wall 5a and an abutment shoulder 5b. At the edge of upper annular face 6a, there is provided a cartridge end rib 31. The cartridge barrel 1 is open at the top end at open end 6. A cartridge cap 7 is provided, which is adapted to be sealingly attached to the neck 4 of cartridge barrel 1. Cartridge cap 7 is shown in greater detail in the enlargement "A" to Figure 1. This cap has an annular shoulder 8 adapted to clip over flange 5 on neck 4. When the cap is clipped into place over neck 4 the inside face 13a of depending peripheral skirt 13 contacts outer neck wall 5a and annular shoulder 8 clips over and is in contact with abutment shoulder 5b on the neck (see Figure 1). A X-formed closure fitting 9 is integrally attached to the cartridge cap 7 to ensure complete evacuation of the contents of cartridge barrel 1. An annular rib 10 is provided on the underside of the top 11 of cartridge cap 7. This annular rib 10 is provided on the lower part of the top 11 of cartridge cap 7 and is located so that it abuts against the top of the neck 4 and laps the side of cartridge end rib 31 when the cartridge cap 7 is clipped onto the top of cartridge barrel 1. A standard luer slip finish 12 is provided as part of cartridge cap 7. Assembly of the cartridge is preferably as follows. The cartridge cap and overcap are injection moulded from sterile plastic material, the injection moulding machine being situated in an aseptic area. Cartridge barrel 1 is stoppered with a pre-sterilized stopper at the open end 2 and is then aseptically filled. After the cartridge has been filled the cartridge cap 7 is clipped onto neck 4, annular shoulder 8 seating beneath flange 5 and in contact with abutment shoulder 5b. A fluid tight seal is ensured by welding cartridge cap 7 to cartridge barrel 1. In the embodiment shown this is effected by ultrasonic welding. A welding horn is placed on top 11 above annular rib 10 and cartridge end rib 31 and a welding anvil is placed under the bottom lip 14 of depending peripheral skirt 13. Ultrasonic welding causes annular rib 10 and cartridge end rib 31 to melt and form a broad sealing ring between cartridge cap 7 and the top of neck 4. In use, closure 9 is severed from the top of cartridge cap 7 revealing the contents of the cartridge and exposing the luer slip finish 12 for attachment of a standard needle fitting having a luer finish. This cartridge may be used in syringe assemblies which are presently available (with minor adjustments to the top end of the assembly to accommodate the cartridge cap) or as a component in a disposable syringe unit. A disposable syringe unit utilizing the cartridge illustrated in Figure 1 is shown in an exploded view in Figure 2. Where used as a component part of a syringe unit it is necessary that the cartridge be fitted with a finger grip and a plunger rod. Preferably the finger grip is a plastic sleeve shaped component having a flange sufficiently wide for accommodating a finger on either side of the cartridge barrel. Such a finger grip is also preferably made of an elastomer such as polypropylene, polyethylene of polyethylene terephthalate. The finger grip is adhered to the side of the cartridge, preferably by welding same to the plastic cartridge barrel. The plunger rod may have a variety of moulded ends, such as a screw thread to allow positive aspiration; or a blunt end to allow self aspiration during injection. The opposite end of the plunger rod may conveniently have a spanner fitting moulded into it for removing the cape closure. The spanner fitting at the end of the plunger rod is advantageous as it allows the user to employ the mechanical advantage provided by the length of the plunger rod. In the preferred embodiment of the invention used in a disposable syringe unit a finger grip 15 is provided at the bottom end of the cartridge body. The finger grip 15 has a hollow sleeve 16 shaped to fit over the end of cartridge barrel 1. The finger grip may be adhered to the cartridge barrel 1 but is preferably welded thereto. Finger grip 15 is provided with an arm 17 which protrudes over opposite sides of sleeve 16 to provide a gripping area 18 on either side of cartridge barrel 1. A plunger rod 19 is also provided and has a moulded end 20 adapted to fit into a recess 21 provided in stopper 3. An alternative to the moulded end 20 as shown in Figure 2 is to provide a screw thread fitting at the end of plunger rod 19 adapted to screw into a corresponding screw thread in recess 21. At the opposite end of plunger rod 19 there is provided a spanner fitting 22 of X-formed shape adapted to co-operate with closure 9. A handle 23 is located at the end of plunger rod 19 so to enable pressure to be applied to plunger rod in the axial direction of the cartridge barrel 1. A protective cap 24 is provided at the top end to fit over and protect the cap 7. Figure 3 shows the above described syringe unit in an assembled condition utilizing a modified cap and overcap 25. As illustrated cap 7 is clipped onto the neck 4 of cartridge barrel 1. The closure 9 on cap 7 comprises an integral stem 26. Overcap 25 is clipped over the top of cap 7, stem 26 and neck 4 and is located so that it abuts against the top of the neck 4 and laps the side of cartridge end rib 31 when the cartridge cap 7 is clipped onto the top of cartridge barrel 1. A standard luer slip finish 12 is provided as part of cartridge cap 7. In use the plunger rod 19 is inserted into recess 21 in stopper 3. In the embodiment shown in Figure 3, a lateral force is applied to overcap 25. This force acts upon stem 26 thus causing closure 9 to snap off the top of needle fitting 12. Once closure 9 has been broken off cap 7, needle fitting 12 is exposed for receiving a needle having a luer slip configuration. The removal of closure 9 also exposes the contents of cartridge barrel 1 for injection. The hypodermic needle 12a once fitted, sealingly fits over the luer slip on cap 7 and positive pressure on plunger rod 19 causes stopper 3 to advance in cartridge barrel 1 causing the injectable medium to be expressed through hypodermic needle 12a. In use the embodiment shown in Figure 2 operates in the same way as shown in Figure 3 except that the closure is removed by snap action preferably with the aid of spanner fitting 22 at the end of plunger rod 19. In each of the embodiments described herein it is possible using the cartridge of the present invention to provide a disposable syringe which is easy to use and simple in application. There is no need to use a separate syringe holder and the cartridge can be provided to practitioners in a partially assembled condition with the finger grip already attached to the cartridge barrel. The only separate components being a plunger rod and additionally a standard hypodermic needle in the case of those embodiments illustrated in Figures 2 and 3. Each of the above mentioned embodiments are preferably completely manufactured in an aseptic environment to ensure the sterility of the injectable medium. For example in the embodiment illustrated in Figure 3, cartridge barrel 1 is injection moulded in an aseptic environment. Stopper 3 is then delivered to the aseptic environment in a pre-sterilized condition and inserted into the bottom end 2 of cartridge barrel 1. The cap 7 is also injection moulded in the aseptic environment. The cartridge barrel is stoppered then filled with the pre-sterilized injectable medium and is the capped by the injection moulded cap 7. The cap 7 is then welded or otherwise adhered to cartridge barrel 1. Overcap 25 is also injection moulded in the aseptic environment and is fitted over the closure 7 and neck 4 prior to removal of the cartridge from the aseptic conditions. When manufactured as described above it is important that the polymer beads used for the injection moulding process be pre-sterilized prior to injection moulding of the component parts of the cartridge. Finger grip 15 and plunger rod 19 can be injection moulded outside of the aseptic environment as they are not placed in direct contact with the injectable medium. Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into constructions and parts previously described without departing from the spirit or ambit of the invention as described in the appended claims.

Claims: A method for manufacturing a plastic pre-filled cartridge which comprises: a) injection moulding a cartridge barrel having a top end and a bottom end both of which are open, in an aseptic environment; b) injection moulding a plastic cap including an integrally moulded fitting adapted to receive a hypodermic needle and a closure which is frangibly connected with said cap in the said aseptic environment; c) introducing into the aseptic environment a pre-sterilized stopper; d) fitting the pre-sterilized stopper into the bottom end of the cartridge barrel in the aseptic environment; e) aseptically filling the said cartridge with an injectable medium in said aseptic environment; and f) sealingly attaching said cap to the cartridge barrel in the aseptic environment. A method according to claim 1 wherein the cap is sealingly attached to the top end of the cartridge barrel (1) by welding it to the barrel in the aseptic environment. A method according to claim 2 wherein the cap is welded to the top end of the cartridge barrel by using ultra sonic welding. A method according to claim 1 or 2 wherein there is additional provided an overcap (25) which is injection moulded in the aseptic environment and which is placed over the cap after the cap has been sealingly attached to the top end (4) of the cartridge barrel (1). A method according to claims 1 or 2 wherein an additional overcap (25) is pre-sterilized and inserted into the aseptic environment and placed over the cap (7) after the cap has been sealingly attached to the top end (4) of the cartridge barrel (1).

Inventors: KIMBER MICHAEL BROWNING, KIMBER, MICHAEL BROWNING
Applicants: ASTRA AB, ASTRA AKTIEBOLAG
Application year: 1989
Main classification: A61M5
IPC codes: A61M5