Syringe

The present invention relates to a syringe in which a predetermined quantity of medication can be stored to be dispensed in predetermined doses as required.

In medicine, for example for diabetic patients, or in dentistry, for example for anaesthetic purposes, individual disposable syringes are provided, each being used for one dose of the injection required. It is clear that this is a wasteful and costly procedure, particularly since in most cases the same quantity of medication is required for each injection.' Furthermore, it is often desirable that the physician ,fills a syringe with the quantity of medication sufficient for. the entire course of treatment and adjusts the syringe so that the patient, upon each actuation of the syringe will always inject only the required dose.

US-A-2 646 042 describes a syringe for storing medication and 20 dispensing dosed quantities thereof comprising:

a housing;

a storage chanter within said housing;

a dose chamber in said housing in direct communication with said 25 storage chamber;

first piston means for initially introducing a fluid into said storage chamber and subsequently for introducing by pressure a predetermined volume of the fluid into said dose chamber; and second piston means for expelling the volume of fluid from the dose chanter;

said first piston means being in direct communication with the storage chamber and operable to vary the volume thereof for a selective increase in the volume to permit the inflow of fluid therein, and for a selective reduction in the volume for generating an increase of pressure therein;

said second piston means being in direct communication with said dose chamber and mounted for outward movement in response to an increase in the volume of fluid in said dose chamber and for manual Inward movement;

means associated with said second piston means for indicating the volume of fluid in said dose chamber;

said first and second piston means being coaxial, said first piston means having an inner end and an outer end, said second piston means extending axially through said first piston means 10 with the inner end of the second piston means in said dose chamber and the outer end of the second piston means at the outer end of said first piston means;

means for preventing relative movement between said first piston means and said housing when said second piston means is moved to 15 expel fluid from the dose chamber;

sealing means mounted adjacent, the outlet opening of said storage chamber and selectively openable to allow fluid movement therethrough.

This known syringe enables a predetermined quantity of a medicament to be introduced therein at aqy given time but requires constant control by the user.

It is an object of this invention to provide a syringe which is 25. adapted to store a quantity of medication for multiple injections and with which predetermined doses of this medication can be expelled.

The present invention is a syringe characterised in that said 30 means for preventing relative movement comprises engaged screw thread means on and between said first piston means and said housing arranged such that rotational movement of said first piston means'relative to said housing will effect a longitudinal movement of said first piston means relative to said housing and 35 the storage chamber therein;

said means for indicating the volume of fluid in said-dose chamber comprises a tubular handle received over said second piston means and having calibrations thereon; means on said handle to adjustably limit outward movement of said second piston means; and said dose chanter is defined by an elongate sleeve opening through the inner end of said first piston means, said second piston means being received in said sleeve, said means to adjustably limit outward movement of said second piston means comprising a nut adjustably mounted on said sleeve and engaged ’ for rotation by the interior of said tubular handle, said handle being longitudinally slidable over said nut, and abutment means on said handle engageable with the nut, as adjusted, to limit outward movemeht of said handle and said second piston means,

Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings in which:

Figures 1, 2 and 3 show longitudinal schematic sections of three embodiments of the syringe according to the invention, the embodiment of Figure 3 being shown on a larger scale.,

Figure 3a shows the radial calibration provided on the embodiment of Figure 3.

The syringe shown in Figure 1 has an outer syringe housing 1 provided with an outlet opening 2 at the closed end and a circumferential flange 3 at the open end, a short internal thread 4 also being provided at this open end. A cylindrical casing 5, having an external thread 7 along its length, is rotatably mounted within housing 1, the inner end 6 of the casing 5 _י constituting a piston. At its end opposite to the inner end 6, the casing 5 is provided with a circumferential flange 8. The casing 5 has an axially extending cylindrical sleeve 9a which merges with end 6 and in which a piston 10 is longitudinally movable by its rod 11. This rod 11 is enclosed by a tubular handle 12 which extends into an annular well 13 in casing 5 surrounding sleeve 9a. The tube 12 is arranged to engage the rod 11 such that it can be moved therewith. The tube 12 is linearly , , calibrated at 14 as indicated.

The syringe works as follows:

A two way hypodermic needle (not shown) which is double-sided, is attached in the conventional manner to a cap 15 which covers the end of outlet opening 2 with the interposition of an elastic washer 16, the needle penetrating said washer. By rotating casing 5 relative to housing 1, the space 17 therein between its ends and the end 6 will be filled. Now the said needle is withdrawn. The filling process of space 9 is continued by rotating casing 5 towards opening 2 whereby owing to the pressure within space 17, piston 10 together with handle 12 will move in a direction opposite to that of arrow X and fill sleeve 9 also until the calibration 14 indicates a certain predetermined dose. Now in order to dispense said pre- . determined dose a second hypodermic needle which is a finer one is attached and penetrates washer 16 in order to inject a smaller, but predetermined dose. This is effected by pushing handle 12 in the direction of anow X, a stop (not shown) preventing this movement after the end of piston 10 has reached the end 6 of casing 5. After the needle is , removed, piston 10 will remain in its position until a further injection is made. At this time casing 5 will be screwed into housing 1 up to the point where the proper calibration 14 will be shown again and this will force piston 10 into the direction opposite to the arrow thereby filling sleeve 9 with the proper dose.

In the embodiment of the syringe shown in Figure 2 the parts which have the same reference numerals as those in Figure 1 are the same and operate simiarly and will not be further described. The additional part in this case is a threaded ring 18 which is screwed into threaded and calibrated handle 12 to serve for fixing a predetermined fixed dose. This syringe works as follows:

The filling of space 17 and 9 is carried out in the same way as of Figure 1, the difference being that the movement of the piston 10 and handle 12 in the direction of arrow Y is continued until the piston 10 reaches stop 19 in casing 5. Thus the entire sleeve 9 is filled. Ring 18 is now rotated on handle 12 up to the calibration which indicates the required dose and when the injection is to take place handle 12 is pushed to the right in a direction opposite to that of arrow Y until ring 18 meets flange 8 whereby sleeve 9 will be emptied by a quantity corresponding to the required dose.

In the embodiment of the syringe of Figure 3 the parts which are the same or similar to those of Figures 1 and 2 will not be particularly described. It is a particular feature of this syringe that it can be used to repeatedly administer a fixed dose. For this purpose the tubular handle 12 has a hexagonal internal cross-section, a hexagonal nut 20 being housed in its inner end and being held therein by an internal flange 12a. Thus, the handle 12 can freely move axially and when rotated will force the nut 20 to rotate. The tubular wall of sleeve 9a is provided with an external thread along its length adapted to be screwingly engaged by the nut 20. The circumferential flange 8 is provided with radial calibrations 8a, ten being shown here, the relationship between calibration 14 and calibration 8a being similar to that used in a micrometer.

The syringe works as follows;

A two way hypodermic needle (not shown) which is double-sided, is attached in the conventional manner to a cap 15 which covers the end of outlet opening 2 with the interposition of sealing means in the form of an elastic washer 16, the needle penetrating this washer 16. A storage chamber 17 is defined between the inner end 6 of the casing 5 and the closed end of the housing 1.

Medicament is introduced into this storage chamber 17 through the outlet opening 2 via the washer 16, and the double-sided needle, by retracting the first piston 6. The piston 6 is retracted by rotating the casing 5 relative to the housing 1 by way of the screw threads 4 and 7. When the storage chamber 17 has received the desired amount of medicament, normally an amount equivalent to several doses, the outlet opening 2 is closed by removal of the needle,, thereby providing a sealed container.

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When a dose Is to be administered, the handle 12 is rotated to thus rotate the nut 20 until the desired calibration 14 appears against the flange 8. Now the casing 5 is rotated, the outlet 2 remaining closed, with the internal pressure generated forcing 5 the medicament into a dose chamber 9. This movement of the medicament into the dose chamber 9 will move the piston 10 together with the handle 12 in an outward direction, the piston 10 being stopped in its movement when flange 12a meets the nut 20 such that a predetermined dose will be filled in the chamber 9.

In order to dispense said predetermined dose a second hypodermic needle, which is a finer one, is attached and penetrates washer 16. An amount of medicament equal to the predetermined dose within the dosfc chamber 9 is then injected. This is effected by pushing handle 12 inwardly to drive the piston 10 inwardly. This 15 inward driving of the second piston 10 moves the dose amount of medicament from the chamber 9 to the chamber 17, at the same time discharging an equal amount of medicament through the outlet opening 2. The provision of screw threads between the first piston 6 and the housing 1 prevents movement of the first piston 20 6 during the outward and inward movement of the second piston

10. A stop (not shown) prevents further movement after the end of the piston 10 has reached the end 6 of the casing 5.

After the needle has been removed, the piston 10 will remain in 25 its position until a further injection is made. At this time the casing 5 will again be screwed into the housing 1 forcing piston 10 outwardly thereby filling dose chamber 9 with the required dose. The next dosage will now be exactly that of the first one. Since the calibration 14 may be difficult to read, 30 calibration 8a will show a more accurate reading.

The profile of the internal wall of the handle 12 may have any other shape than that described, e.g. square or any other geometric shape, or a circular nut may be provided with

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,'־8־ י . . ''.?. .''.;A.' diametrically opposed lugs which engage in diametrically opposed elongated ;slits in the wall of the handle 12.

The calibrations may be raised, so that the syringe can be used by the blind.