A DISPOSABLE SYRINGEThis invention relates to a disposable syringe which may be used only once.
In many situations it is desirable to prevent the transmission of disease and infection which may result from the re-use of syringes, possibly by several people.
According to the present invention from one aspect, there is provided a disposable syringe comprising:an elongate hollow member which is provided with an orifice into which a needle may be fitted;a partition which is slidably mounted within the hollow member, forms a seal between chambers within the hollow member on opposite sides of the partition and comprises a first, frangible portion and a second portion;;a plunger which is received in the hollow member and which comprises an end portion which is engageable with the second portion for urging the partition to slide within the hollow member in a direction away from the orifice and is engageable with the first portion for urging the plunger both to slide within the hollow member in a direction towards the orifice and also to break the first portion and create a passageway between said chambers, which passageway is open if said plunger is removed from engagement with said first portion.
According to the present invention from another aspect there is provided a disposable syringe that may be used only once, comprising:a cylindrical tubular member, one of whose ends terminates at a narrowing into which a needle may be fitted and into the other end of which a plunger is received, the plunger being provided with a cylinder having at least one sealed joint wherein:the cylinder is hollow and has two bases and in its interior is located an end conical portion of the plunger by means of which and during an injection one of the bases is perforated at a zone opposite the end of the plunger, the conical portion providing an enlargement which presents displacement of the conical portion out of the interior of the cylinder; and the other base of the cylinder has at least one opening so that after said perforation is made, the sealed tightness of the syringe is broken, making it impossible for said syringe to effect a second suction.
The present invention will now be described, by way of example, with reference to the accompanying drawing in which:Figure 1 is a sectional view of a syringe according to an example of the present invention ready for suction;Figure 2 is a sectional view of such a syringe during injection;Figure 3 is a sectional view of such a syringe after injection.
The syringe 1 represented in the Figures comprises an outer cylindrical tubular member 2, one of whose ends terminates at an axial narrowing 3 providing an orifice in which a needle, which is not shown, could be fitted.
A generally cylindrical partition member 4 defined by a cylindrical surface 5, two caps 6 and 7 and two collars 13 is slidably mounted within the tubular member 2 in such a way that an air-tight seal is formed at at least one of the interfaces between the collars 13 and the tubular member 2. The cap 6 is provided with a plurality of passageways 8 passing through the cap and a passageway through which a plunger 10, which is slidable with respect to the partition member 4, extends.
The plunger is provided with an end portion 9 at or near the end of the plunger closest to the axial narrowing and the end portion includes a conical head 12 and a flange 15.
Cap 7 is provided with a frangible portion 11 which is sited in such a position that it may be perforated by the conical head when the plunger is slid with respect to the partition member 4. The flange 15 is sufficiently large not to pass through the passageway or through the frangible portion 11 and forms a seal across the site of the frangible portion 11 when it is pressed in place thereon.
As shown in Figure 1, when the syringe is first to be used the plunger 10 is slid relative to the tubular member 2 and to the partition member 4 in a direction away from the axial narrowing 3 (as indicated by the arrow in that Figure) until the flange 15 bears upon the cap 6. Further movement of the plunger 10 relative to the tubular member 2 and away from the axial narrowing 3 forces the partition member 4 to slide in the tubular member and, by virtue of the fact that the member 4 imposes an air-tight seal between the chambers on opposite sides of cap 7, the substance which it is desired to inject may be sucked through the axial narrowing.
To perform the injection and expel from the syringe the substance which it is desired to inject, the plunger 10 is slid relative to the tubular member 2 and to the partition member 4 in a direction towards the axial narrowing (as indicated by the arrow in Figure 2) until the tip of the conical head 12 meets and perforates the frangible portion 11 and the flange 15 bears upon the cap 7 and forms a seal across the site of the perforated portion as shown in Figure 2. Further movement of the plunger 10 relative to the tubular member and towards the axial narrowing urges the flange against the cap 7 so as to further improve the seal over the site of the perforated portion and forces the partition member to slide in the tubular member.By virtue of the fact that the partition member and the end portion 13 with the flange 15 impose an air-tight seal between the chambers on opposite sides of face 7, the substance which it is desired to inject may be expelled through the axial narrowing.
If an attempt is made to re-use the syringe and the plunger is again slid relative to the tubular member 2 and to the partition member 4 in a direction away from the axial narrowing 3 (as indicated by the arrow inFigure 3), the end portion 13 will move away from the cap 7, uncovering the perforated portion 16, until the flange is brought to bear upon the cap 6 as shown inFigure 6. Further movement of the plunger relative to the tubular member and in a direction away from the axial narrowing will again force the partition member 4 to slide in the tubular member but because the chambers on opposite sides of the partition member 4 are connected through passageways 8 and the perforated portion 16 nothing may be sucked through the axial narrowing in normal use. The syringe- is therefore unserviceable after only one use.