United States Patent 3802430

A disposable pyrotechnically powered injector comprising a barrel formed to receive an ampule, an ampule having a plug at one end and an orifice at the other and containing a selected medicament, a plunger activated gas generating pyrotechnic charge, and a gas operated piston positioned in the barrel and adapted to drive the plug within the ampule and thereby discharge the medicament under high pressure through the orifice.

Schwebel, Paul R. (Van Nuys, CA)
Arnold, Leonard G. (Encino, CA)
Application Number:
Publication Date:
Filing Date:
Primary Class:
International Classes:
A61M5/30; A61M5/303; A61M5/20; A61M5/31; (IPC1-7): A61M5/30
Field of Search:
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US Patent References:
3335722Hypodermic device1967-08-15Lowry et al.
3308818Injection cartridge1967-03-14Rutkowski
2669230Injection apparatus1954-02-16Smoot
2575071Explosive-operated device1951-11-13Rockwell
2514401Land mine1950-07-11Liljegren
2322245Ypodermic injector and method of use thereof1943-06-22Lockhart
2322244Hypodermic injector1943-06-22Lockhart

Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Recla, Henry J.
Attorney, Agent or Firm:
Finkel, Robert Louis
With the foregoing in mind, what I claim as my invention is

1. A disposable deflagratory powered injector comprising:

2. The deflagratory powered injector of claim 1 wherein said firing mechanism includes:

3. The deflagratory powered injector of claim 2 wherein:

4. The deflagratory powered injector of claim 3 wherein said resilient means is a spring carried by the plunger and exerting expansive force between said plunger and the firing pin.


The subject invention relates generally to disposable needleless injectors and, more particularly, to a pyrotechnically powered hypodermic injector adapted to inject any desired medicament from a pre-packaged ampule through the skin in a fine, high pressure stream.

Many prior art devices disclose the concept of employing high pressure gas in lieu of the common hypodermic syringe and needle for the subcutaneous injection of fluid medicaments such as vitamins, vaccines, anaesthetics, and the like. Typical of these are the injectors shown in U.S. Pat. Nos. issued to Smoot 2,605,763; Lawshe, et al. 2,645,223; Brown 2,646,798; Dickinson, Jr. 2,667,874; Suttermeister 2,680,439; Copen 2,687,728; Morando 3,115,133; Lowry, et al. 3,335,722; and Clark 3,527,212. The advantages claimed for such devices are too well known to require reiteration.

The prior art teaches the storage of a propellant gas, such as CO2, under pressure in a cartridge or in a cavity formed in the injector body. The fluid medicament is usually stored in an ampule, which may be inserted into the injector, or in a cavity in the injector itself. Various means are provided to puncture the pressure vessel and release the stored gas. The gas either acts on a piston or mixes with the medicament to drive the fluid through a small orifice which creates the injected high velocity stream. In one prior art device the propulsive gas is pre-mixed with the medicament. Lowry, et al. U.S. Pat. No. 3,335,722 utilizes conventional explosive cartridges to propel a specially designed plunger in a reuseable injector; however, as it points out, direct explosive action has heretofore been considered unsuitable for hypodermic injectors.

The subject invention utilizes a single-shot preloaded pyrotechnic charge or deflagrant to propet a piston-actuated high velocity fluid injection system. The gas-producing deflagrant is activated by a primer, which in turn is ignited by a firing pin having a manually released spring-operated trigger mechanism. A frangible retaining member secures the firing pin in place to protect against accidental premature discharge.

The barrel of the injector is adapted to receive a pre-packaged ampule containing the desired medicament. The ampule is provided with an internal plug at the end received by the barrel of the injector and with one or more orifices in its other end.

When the triggering mechanism is activated the gas generated by the pyrotechnic charge drives a piston positioned in the mouth of the barrel against the plug, forcing the latter into the ampule and discharging the medicament with sufficient velocity to pierce the skin. Means are provided within the barrel to prevent the propulsive gas from entering the ampule and contaminating the medicament, and to impede the release of this gas into the atmosphere. In a preferred embodiment of the invention, these results are achieved by mounting the piston at the end of expansible bellows adapted to receive and contain the propulsive gas generated by the pyrotechnic charge.

From the foregoing brief summary it will be understood that one of the principal objects of the subject invention is the provision of a needleless hypodermic injector of simple construction which may be easily and inexpensively produced so as to be economically disposable after use. Another object is the provision of a compact, lightweight and durable injector which may be conveniently packed for transportation and storage under the widest possible range of conditions. Still another object is the provision of a needleless hypodermic injector in which the propulsive force is furnished by gas generated by a pyrotechnic charge at the time of use, thereby eliminating the need for the more conventional specially constructed heavy-duty gas storage vessels of the prior art injectors.

The invention has for another object the inclusion in a gas operated hypodermic injector of means to preclude the possibility of contamination of the injected medicament by the propulsive gas and to avoid the possibility of injecting the gas itself under the skin.

The design and construction of the actuating mechanism of the invention provide positive protection against both accidental discharge and misfiring.

Finally, the injector the subject invention is particularly well adapted to permit the standardization of packaging for substantially all known injectible medicaments.

Further objects and advantages will become apparent to the reader upon consideration of the following detailed description of several preferred embodiments of the subject invention as illustrated in the accompanying drawing in which:


FIG. 1 is a side sectional view of a preferred embodiment of the subject invention prior to discharge;

FIG. 2 is a similar view of the embodiment illustrated in FIG. 1 at the time of discharge;

FIG. 3 is a front end view of the embodiment illustrated in FIG. 1;

FIG. 4 is a partially cut away side view of a modified form of the subject invention; and

FIG. 5 is a partially cut away view of another modified form of the invention.

Wherever practicable a single numeral is used for the same or functionally similar features in the several figures.


Referring to the preferred embodiment depicted in FIGS. 1 and 2, the disposable needleless pyrotechnically powered hypodermic injector consists essentially of a cylindrical casing 11 having a hollow barrel 12 with an annular sleeve 13 at its end adapted to receive an ampule 14 containing a selected liquid medicament 15. Casing 11, ampule 14 and the various other components of the injector hereinafter described may be formed of any metal or plastic material having suitable strength, rigidity, resilience and chemical resistance. Cooperating means such as detents 16 and spiral grooves 17 may be provided to secure ampule 14 releasably to the end of barrel 12.

One end of ampule 14 is seated by means of a plug 18, and the other end is provided with passages 19 terminating in orifices 21. While a single discharge passage and orifice will suffice, it has been determined that a plurality of outlets covering a small area of skin are more effective and result in less pain and trauma to the patient. The optimum configuration is presently believed to be five passages having their orifices arranged as illustrated in FIG. 3. The end of ampule 14 is rounded outwardly and the central region 22 surrounding orifices 21 is recessed. A removeable protective cap 23 is sterilized and slipped over the end of ampule 14 to serve as a seal for passages 19 and a cover for the end of the ampule itself.

At the rear end of barrel 12 casing 11 is provided with an encapsulated pyrotechnic propellant charge 25, such as "AM584" manufactured by the Bermite Division of Tasker Industries, having a uniform, progressive rate of burning over the required impulse period of 130-250 milliseconds. A primer 26 is positioned to ignite pyrotechnic charge 25 when primer 26 is activated by firing pin 27 located in axial passage 28 within casing 11.

Firing pin 27 is mounted on the face of a disc 29 preferably of a frangible plastic having an annular rim 31 extending radially outwardly therefrom. The rim 31 of disc 29 is retained in an annular recess 32 formed in the inner wall of passage 28 by means of an end cap 32.

A plunger 36 is inserted into the bore of end cap 32 so that its shank 38 abuts the rear face of disc 29 and its head 39 extends outwardly of end cap 32. Resilient expansion means such as spring 41 exert in expansive force between head 39 of plunger 36 and the rear face of disc 29.

One end of expansive bellows 42 is sealed around the encapsulated pyrotechnic propellant 25 and adapted to receive all of the gases produced by charge 25 within its chamber 43. The opposite end of bellows 42 is sealed by piston 44. Piston 44 is adapted to butt against the rear face of plug 18 when ampule 14 is secured to the end of barrel 12.

In operation, with ampule 14 in place on barrel 12 protective cap 23 is removed and discarded and the tip of ampule 14 is pressed lightly against the skin 45 of the person to be injected.

Sufficient force is applied to head 39 of plunger 36 in the direction of disc 29 to rupture annular rim 31 and thereby release disc 29. Under the combined influence of the manual force exerted on plunger 36 and the resilient force exerted by spring 41, firing pin 27 is thrust into primer 26, igniting the latter and thereby igniting pyrotechnic charge 25. The rapidly expanding gas generated by charge 25 quickly fills chamber 43 within bellows 42 and drives piston 44, and plug 18 before it, into ampule 14. Preferably the front face of plug 18 is shaped to conform with the front wall of the medicament containing chamber within ampule 14. Bellows 42 is adapted to permit piston 44 to drive plug 18 the full length of the chamber within ampule 14 and against the front wall of this chamber, thereby insuring that all of the medicament 15 within this chamber is discharged through passages 19 and orifices 21 in a fine stream with a sufficiently high velocity to pierce the skin 45.

By selectively varying the quantity and strength of propellant charge 25, the expansive characteristics of bellows 42, the resiliency and frictional properties of piston 44 and plug 18, the dimensions of barrel 12 and ampule 14, and the number, size and design of passages 19 and orifices 21, the dosage, depth of penetration and various other injection perameters can readily be established at the time of manufacture.

The embodiment of the invention illustrated in FIG. 4 is substantially identical with that of FIG. 1, except that the former does not employ expansible bellows 42 to contain the gas produced by propellant charge 25. Instead, an annular groove or manifold 51 is provided in the inner wall of barrel 12. Manifold 51 is ported to the atmosphere through a duct 52 terminating in a metering orifice 53 in the outer wall of casing 11. An O-ring 54 is seated in an annular recess in the inner wall of the barrel 12 between manifold 51 and the end of barrel 12.

Piston 44 is of a length such that its rear end extends rearwardly of manifold 51 when it comes to rest after driving plug 18 the entire length of the chamber within ampule 14. In this configuration the O-ring prevents any of the propulsive gas generated by charge 25 from by-passing piston 44 and contaminating the medicament 15 within ampule 14, and manifold 51, duct 52 and metering orifice 53 insure that any gas trapped between piston 44 and the inner wall of barrel 12 will be discharged slowly into the atmosphere.

The embodiment of FIG. 5 is similar to that of FIG. 4, except that the former utilizes a packing gland 61 within a discharge port 62 in the wall of barrel 12 to bleed the propellant gas generated by charge 25 after it has imparted its thrust impulse to piston 44.

With each of the three embodiments, once the contents of ampule 14 have been discharged the entire injector is intended to be discarded.