JET INJECTOR FOR MASS INOCULATION

Abstract: A needleless jet injector device (100) for use with separate storage tanks of gas and medicament, the device (100) comprising a body having a gas inlet for connection to the gas storage tank and a medicament inlet for connection to the medicament storage tank, an active chamber for receiving medicament and having a jet nozzle (1) through which the medicament is discharged, the active chamber further receiving a piston head (3) movable to force the medicament through the nozzle (1) upon movement of the piston head (3) in the chamber towards the nozzle (1), the piston head (3) being connected to a piston (9) movable within a gas chamber (24) within the body, and means (14, 15, 20) for selectively allowing gas to enter the gas chamber (24) so as to move the piston (9) and the piston head (3) to discharge medicament through the nozzle (1).

Description: JET INJECTOR FOR MASS INOCULATION BACKGROUND OF THE INVENTION The present invention pertains to needleless injectors and more particularly to a needleless jet injector for mass inoculation. SUMMARY OF THE INVENTION It is an object of the present invention to provide a jet injector which facilitates mass administration, by injection, of veterinary or human medication from a bulk supply. Accordingly, the invention provides, in a first aspect, a needleless jet injector device for use with a supply of gas under pressure and medicament, the device comprising a body having a gas inlet for said gas and a medicament inlet for said medicament, a first chamber communicating with said medicament inlet and having an outlet, a jet nozzle communicating with said outlet so as to receive medicament, under pressure, for injection, a second chamber communicating with said gas inlet, a first piston at least partly defining said first chamber and movable to vary the volume thereof so as to deliver a dose of medicament under pressure to said outlet, a second piston at least partly defining said second chamber and movable to vary the volume thereof, connection means coupling the first and second pistons so that movement of said second piston causes movement of said first piston, medicament flow control means to operatively restrict flow of the medicament from the medicament inlet to said first chamber, and control means to regulate the flow of gas to said second chamber to cause movement of said second piston and therefor movement of said first piston. In a preferred embodiment, the medication is carried by a backpack which supplies the injector. The injector preferably automatically reloads a medication cylinder upon the release of a trigger mechanism at the completion of each injection. It is preferred that the dosage be readily adjustable by means of a piston stroke adjuster. BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of a jet injector according to the present invention will now be more fully described, by way of example, with reference to the drawings, of which: Figure 1 is a cross-sectional view of one embodiment of a jet injector according to the present invention; and Figure 2 is a perspective view of the injector of Figure 1 and a backpack used to carried medicament and propellant. DETAILED DESCRIPTION OF THE DRAWINGS As shown in figure 1, a needleless jet injector 100 comprises a nozzle 1 through which a high pressured jet is discharged. During the delivery stroke of a delivery piston 3, a check valve 2 opens, allowing medication to pass through the nozzle 1. The check valve 2 closes on the intake stroke of the piston 3 to prevent air from being drawn into the interchangeable medication cylinder 22. As the piston 3 reciprocates, medication is alternately drawn into the cylinder 22 and discharged through the nozzle 1. A medication transfer tube 4 enables medication to be transferred from a medication receiver 6 to the medication cylinder 22. A check valve 5 closes on the delivery stroke of the piston 3 preventing medication from passing back into the receiver 6. The check valve 5 opens on the intake stroke of the piston to allow medication to flow from the receiver 6 to the cylinder 22. The medication receiver 6 is a chamber within the body of the injector which receives and holds medication from an external source such as a backpack. To ensure that the rear portion of the cylinder (in which the piston rod 8 resides) is open to atmospheric pressure during both intake and delivery strokes, a cylinder vent 7 is provided through the rear of the medication cylinder. The piston rod 8 connects the delivery pi ton 3 to a CO- piston 9. When a pressurized gas such as C0 2 is released from the C0 receiving chamber 13 it passes through a C0 2 release valve 14 (if open) and into a C0 2 chamber 24. A collar stop 10 is provided in the chamber 24 for limiting and adjusting the return stop position of the piston 9. A worm and rack mechanism 11 responds to rotation of the stroke adjuster 12, moving the stop 10 forward and backward in a linear fashion thereby altering the stroke of the piston 9. The CO- release valve 14 is opened by actuation of the trigger and lever mechanism 20 acting through the release valve actuator 15. Opening the CO- release valve 14 allows pressurized gas to travel from the receiving chamber 13, into the delivery chamber 24 and hence into the working portion of the cylinder 23 for the purpose of displacing the piston 9. A release valve actuator 15 is provided which, upon upward deflection of the trigger and lever mechanism 20, opens the C0 2 release valve 14 and closes the C0 2 cylinder vent valve 16. With the trigger and lever mechanism 20 still held in the upward deflected position, the release valve actuator 15 allows the release valve 14 to close, stopping the flow of pressurized gas into the delivery chamber 24 at the completion of the delivery stroke. The cylinder vent valve 16 opens upon the release of the trigger and lever mechanism 20 and allows the cylinder 23 to be vented to the atmosphere via the cylinder port 17, lever port 18 and handle vent 19. At the completion of the delivery stroke, a transfer valve 21 opens and allows pressurized gas to fill the return chamber 25. Upon release of the trigger end lever mechanism 20 the cylinder vent valve 16 opens and the cylinder 23 is vented to atmosphere which in turn allows the pressurized gas in the return chamber 25 to drive the piston 9 back to the collar stop 10. With the return travel of the piston 9, the piston 3 draws medication into the medication cylinder 22. As shown in figure 2, a trigger operated jet injector needleless syringe 100 according to the teachings of the present invention may be used in conjunction with a backpack harness 101. The harness 101 may be used to support a medicament cylinder 102 and a liquid carbon dioxide cylinder 103. The contents of the medicament and C0 2 cylinders are discharged through a manifold 104 and through separate hoses 105, 106 to the respective intake ports of the injector 100. The backpack harness may consist of a rigid mounting frame which includes waist and shoulder straps which can be adjusted to the wearer's needs. The CO- and medicament manifold(s) may either be attached to the harness or separately attached to each of the cylinders. The pressurized gas cylinder, preferably a carbondioxide cylinder, will be a high pressure cylinder containing approximately 2.5 kilograms of liquid carbon dioxide which is used as the pressure medium for actuating the piston 9. The medicament cylinder may be an unpressurized vessel of light weight material to contain the particular medicament used in a particular inoculation program. Like the pressurized gas cylinder it is readily replacable and refillable. Both the medicament cylinder 22 and nozzle 1 of the injector 100 are replacable. The cylinder may be tailored to suit the correct dosage of a particular medicament. The nozzle contains a very fine bore which, on release of the piston under the gas pressure, will create a high pressure, high velocity jet. The nature of the high velocity jet through the fine bore creates wear within the bore and after a period of time, this wear will reduce the efficiency of penetration of the medicament. The nozzle is therefore readily replacable in the field at the first sign of reduced efficiency which will be noticable by wetting of the skin surface. The injector portion 100 may be provided in two or more sizes utilising the same operating principles. A larger robust unit is particularly suited to mass inoculation of sheep, cattle, pigs and other animals. A smaller unit is more suitable for the mass inoculation of children and adults. A major benefit of this invention is the fully automatic reloading and recharging for rapid multiple injections. The unit is fully adjustable in both dosage and charge for difference thickness skins and different sizes of animals. Because it is a needleless syringe, it completely eliminates the problem of cross contamination or infection which exists with mass inoculation with multiple use needles. While the present invention has been described with reference to particular mechanical components and details of construction, these should be understood as having been provided by way of example and not as limitation to the scope of the invention.

Claims: CLAIMS 1. A needleless jet injector device for use with a supply of gas under pressure and medicament, the device comprising a body having a gas inlet for said gas and a medicament inlet for said medicament, a first chamber communicating with said medicament inlet and having an outlet, a jet nozzle communicating with said outlet so as to receive medicament, under pressure, for injection, a second chamber communicating with said gas inlet, a first piston at least partly defining said first chamber and movable to vary the volume thereof so as to deliver a dose of medicament under pressure to said outlet, a second piston at least partly defining said second chamber and movable to vary the volume thereof, connection means coupling the first and second pistons so that movement of said second piston causes movement of said first piston, medicament flow control means to operatively restrict flow of the medicament from the medicament inlet to said first chamber, and control means to regulate the flow of gas to said second chamber to cause movement of said second piston and therefor movement of said first piston. 2. A needleless jet injector device according to claim 1, wherein the medicament flow control means comprises a one way valve between the first chamber and the nozzle to allow medicament to pass out from the first chamber through the nozzle but to prevent air being drawn back into the first chamber. 3. A needleless jet injector device according to either claim 1 or claim 2, wherein said body is provided with a medicament storage chamber coupled to receive medicament from the medicament inlet and an outlet connected to the first chamber. 4. A needleless jet injector device according to claim 3, further comprising a one way valve between the first chamber and the medicament storage chamber to allow medicament to pass from the medicament storage chamber to the first chamber but to prevent passage back into the medicament storage chamber. 5. A needleless jet injector device according to any preceding claim, wherein said body is provided with a gas storage chamber coupled to receive gas from the gas inlet and an outlet connected to the second chamber. 6. A needleless jet injector device according to claim 5, wherein said control means comprises a release valve between the second chamber and the gas storage chamber to allow gas to pass from the gas storage chamber to the second chamber. 7. A needleless jet injector device according to claim 6, further comprising a trigger means for releasing the release valve upon actuation of the trigger means. 8. A needleless jet injector device according to any preceding claim, wherein the connection means is movable in a cylinder, the cylinder being provided with a vent to atmosphere. 9. A needleless jet injector device according to any preceding claim, further comprising means for adjusting the amount of travel of the first and second pistons so as to thereby adjust the amount of medicament discharged through the nozzle. 10. A needleless jet injector device according to claim 9, wherein said means for adjusting comprises a movable collar arranged within the second chamber against which collar the second piston abuts when at a rearmost posi ion of its stroke. 11. A needleless jet injector device according to claim 10, wherein the collar is movable forwards and rearwards by means of a worm screw arrangement to thereby move the first piston within the first chamber to decrease or increase the volume of the first chamber and hence the amount of medicament therein. 12. A combination of a needleless jet injector device according to any preceding claim and a backpack containing a gas storage tank and a medicament storage tank connected to the gas inlet and the medicament inlet, respectively. 13. A combination according to claim 12, further comprising a manifold between the gas storage tank and the gas inlet and the medicament storage tank and the medicament inlet. 14. A combination according to either claim 12 or claim 13, wherein the backpack is provided with a frame and straps for mounting the backpack on a user.

Inventors: ROSENZWEIG PETER ELLIOTT, ROSENZWEIG, PETER, ELLIOTT
Applicants: SY QUEST INT LTD, SY-QUEST INTERNATIONAL LIMITED
Application year: 1991
Main classification: A61M5
IPC codes: A61M5