US3688765A

US3688765A - Hypodermic injection device

Info

Publication number: US3688765A
Application number: US863583A
Authority: US
Inventors: Jack S Gasaway
Original assignee: Jack S Gasaway
Current assignee: DARDIN FRANCIS E
Priority date: 1969-10-03
Filing date: 1969-10-03
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05

Abstract

A needleless hypodermic device including a body carrying a compressed-gas cartridge in one end and an ampul of fluid to be injected at the opposite end, the ampul having a nozzle portion projecting beyond the body and provided with an aperture of predetermined size, and having a plunger movable to force the fluid from the ampul through the aperture. A cylinder in the body carries a tubular member and is spring-biased toward the cartridge for penetrating the cartridge and releasing the gas to drive a piston which, in turn, moves the plunger to exhaust the fluid. A trigger retains the cylinder in a cocked position until time of use.

Description

United States Patent Gasaway [151 3,688,765 [451 Sept. 5, 1972 [54] HYPODERMIC INJECTION DEVICE [72] Inventor: Jack S. Gasaway, 2005 Barranca,

Newport Beach, Calif. 92660 [22] Filed: Oct. 3, 1969 [21] App1.No.: 863,583

[52] US. Cl ..128/173 H, 128/218 A, 124/11 [51] Int. Cl. ..A61m 05/30 [58] Field of Search..128/173, 173 11,218 R,218 A,

FOREIGN PATENTS OR APPLICATIONS Primary ExaminerJoseph S. Reich Attomey-Gausewitz & Carr [57] ABSTRACT A needleless hypodermic device including a body car- 5 References Cited rying a compressed-gas cartridge in one end and an ampul of fluid to be injected at the opposite end, the

UNITED STATES PATENTS ampul having a nozzle portion projecting beyond the 2,764,977 10/1956 Ferguson ..128/173 H body and Provided with an aperture of predetemlined 2,547,099 4/1951 Smoot ..128/173 11 Size, and having a p g movable to force the fl 2,650,591 9/1953 Love ..118/173 H from the ampul through the aperture. A cylinder in 2,691,374 10/1954 McKibben et a1. ..128/272 the body carries a tubular member and is spring- 2,704,543 3/1955 Scherer ..128/173 I-I biased toward the cartridge for penetrating the car- 2,737,946 3/1956 H6111, J1. ..128/173 H {ridge and releasing the gas to drive a piston which in MaICOIm ..124/1 I tum moves the plunger to exhaust the A trigger 3,131,692 5/1964 Love R x retains the cylinder in a cocked position until time of 3,378,007 4/1968 Poulsen ..128/272 X 3,464,412 9/ 1969 Schwartz ..128/272 X 2,507,276 4/ 1970 Burgess ..128/173 R 17 Claims, 4 Drawing Figures awe .41

PA'TENTEDSEP 5 I972 .SHEEI 1 0f 2 INVENTOR. Jack 5 awn 4y V PATENTEDSEP 51972 SHEET 2 0F 2 INVENTOR. JACK 5: 6:454W4 I-IYPODERMIC INJECTION DEVICE BACKGROUND OF THE INVENTION:

1. Field of the Invention:

This invention pertains to hypodermic injection devices.

2. The Prior Art: v

It has been recognized that medications and other substances may be injected beneath the skin without the use of a needle by being forced through the epidermis in a high-pressure jet. This has patient acceptance because a needle is not required and the injection causes little or no pain. Devices which have been marketed for providing this type of injection; however, have been large and expensive units adapted to retain large quantities of medicament for repeated injections. They have not been portable, nor adapted for self-administration by the patient. Such cumbersome and expensive units have meant that the use of pressure-injecting devices has been limited. Some smaller compressed gas-powered injection devices have been proposed, but they have been relatively difficult to use and generally somewhat complex and expensive. In particular, prior devices have lacked a convenient way for replacement of gas cartridges used for driving the fluid to be injected, and for providing replacement supplies of medicament. Sterilization has been a problem, and there has been no satisfactory way of varying quantities of the fluid to be injected nor the size of the opening through which the jet is discharged.

SUMMARY OF THE INVENTION:

The present invention provides a small, simple and relatively low-cost pressure hypodermic injecting device which may be approximately the size of a fountain pen. It is powered by a gas cartridge, which is readily installed in the device or removed when it is spent. Similarly, the medicament or other material is in a self-contained, presterilized, sealed ampul that is disposed of after each use. The ampul includes a nozzle portion providing a discharge aperture of the proper size. It contains a measured amount of fluid, providing an appropriate quantity of whatever material is to be injected, with a plunger in the ampulsealing its end and providing the means for forcing the material through the discharge aperture. The plunger may be positioned at different depths in the ampul, depending upon the amount of fluid it contains.

Between the ampul and the gas cartridge is a cylinder that is reciprocative between a position remote from the cartridge and one adjacent it. The cylinder carries a tubular member extending rearwardly therefrom that punctures the cartridge when the cylinder is moved to the position adjacent the cartridge, causing the gas from the cartridge to enter the cylinder. This drives a piston in the cylinder through a stroke which, in turn, forces the plunger to move the length of the ampul to discharge the material through the ampul outlet opening. The body of the device reinforces the ampul structurally, and the ampul and plunger are provided with semispherical end walls which help direct all of the material from within the ampule to and through the discharge opening. A spring biases the cylinder toward the cartridge, while a releasable trigger holds it in the retracted position until the injection is to take place.

The device is cocked readily by sliding two sections of the boy of the device relative to each other, which causes the cylinder to be moved with one section to its retracted position, while the trigger device on the other section drops behind an end flange on the cylinder, holding the cylinder in the retracted position. Bayonet connections are provided for the two body sections and for the end caps that hold the cartridge and the ampul. This facilitates removal of the used ampul and cartridge, loading of replacements, and the cocking of the device for the next injection. The simplicity of operation and safety of the device make it adaptable for use by those requiring self-administered injections. It is not limited to injection through the skin, but may be used wherever fluid is to be injected.

BRIEF DESCRIPTION OF THE DRAWING:

FIG. 1 is a plan view of the hypodermic device of this invention;

FIG. 2 is a longitudinal sectional view taken on line 2-2 of FIG. 1, with the device in the cocked position;

FIG. 3 is a view similar to FIG. 2, but with the device in the released position; and

FIG. 4 is an enlarged transverse sectional view taken along line 4-4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

The hypodermic device of this invention includes a body 10 having a generally cylindrical exterior. At its forward end (to the left as illustrated) there is a portion 11 of the body 10 which is of reduced exterior diameter. This portion of the body is received within the re arward end of a tubular body member 12 having an outer diameter the same as that of the principal portion of the 7 body 10. The tubular member 12 is connected to the body 10 by a bayonet lock, which includes opposed slots through the rearward portion of the member 12 having longitudinal portions 13 and lateral portions 14 at right angles to the longitudinal portion. Lugs 15 project radially outwardly from the forward portion of the body 10 into the bayonet slots.

Within the body 10 is an elongated cylindrical chamber 17, which receives a tubular cylinder 18 of smaller diameter. A the forward end 1 1 of the body 10 is a member 19 having an axial opening 20 that substantially complementarily and slidably receives the circumferential surface of the cylinder 18. The member 19 includes a radial flange portion 21 in which is the opening 20. The member 19 extends rearwardly into a recess provided therefor in the forward end portion 11 and is secured therein by conventional means such as a force fit as shown, or by threads or the like similar to that shown at 29. A compression spring 23 circumscribes the cylinder 18 and bears against the flange 21 interiorly of the annular portion 21 of the member 19. The opposite end of the spring 23 engages an exteriorly projecting radial flange 24 on the rearward end of the cylinder 18, thereby biasing the piston 18 rearwardly, or to the right as illustrated.

The forward end of the cylinder 18 extends through an opening 25 in a radial wall 26 in the tubular member 12 adjacent the member 19, and is adapted to enter a cylindrical chamber 27. A member 28 at the forward end of the cylinder 18 in the chamber 27 has an annular externally threaded portion 29 mating with threads in the forward interior portion of the cylinder. A radial flange 30 projects radially outwardly of the threaded portion 29 and beyond the circumferential surface of the cylinder 18. An axial opening 32 through the member 28 slidably receives an elongated piston 33 extending forwardly from the cylinder 18. Enlarged circular discs 34 and 35 are mounted on the forward end of the piston 33 beyond the member 28.

At the rearward end of the piston 33 is a pair of spaced radial flanges 36 and 37 between which is an O- ring 38 providing a seal with respect to the wall of the cylinder 18. A relatively light compression spring 39 bears against the flange 36 at one end and the end of member 28 at the other, thereby biasing the piston 33 toward the right to the position of FIG. 2, where the flange 37 engages the wall forming the cylinder head 40 at the right-hand end of the cylinder 18.

An axial opening 42 extends through the cylinder head 40 and with a press fit receives one end of a tubular firing pin 43 that projects rewardly axially beyond the cylinder 18. The rearward end 44 of the tubular firing pin 43 is chamfered so that it provides a convergent outer edge. The firing pin 43 extends into a cylindrical opening 46 through a transverse wall 47 of the body 10 at the rearward end of the chamber 17. On the opposite side of the wall 47 is a cylindricalchamber 49 closed at its outer end by a hollow cap member 50. The latter member extends over a rearward end portion 51 of the body, which is of reduced outside diameter, and has opposed bayonet slots 52 receiving lugs 53 on the body for locking the cap 50 to the end of the body 10. An ring 54 at the inner end of the cap member 50 provides a seal with respect to the body 10. Therefore, the chamber 49 is sealed except for the opening 46 through the wall 47.

Within the chamber 49 is a cartridge 56 containing a compressed gas, such as carbon dioxide. The cartridge 56 includes an end wall 57 adjacent the wall 47 of the body 10, having a frangible axial portion 58 of reduced thickness located adjacent the convergent end portion 44 of the firing pin 43.

At the opposite end of the device, the chamber 27, which at its rearward portion is defined by the tubular member 12, extends also into a hollow forward closure member 60. The latter member includes an end wall 61, through which extends an opening 62 at the longitudinal axis of the injector unit. The member 60 is provided with opposed lugs '63 which extend into bayonet slots 64 in the tubular member 12 to attach the member 60 to the member 12. An O-ring 65 seals the connection between the members 60 and 12.

Within the chamber 27 beyond the end of the piston 33 is an ampul 67, suitably made of glass or plastic. The exterior of the ampul 67 is substantially complementary to the adjacent portions of the chamber 27 and to the opening 62 through the end wall 61. The ampul has an integral forward nozzle end portion 68 which extends through the opening 62 and projects slightly beyond the end wall 61. A small opening 69 extends through the projecting portion 68 of the ampul 67, leading to an interior chamber 70, which receives the medicament or other fluid which is to be expelled upon operation of the hypodermic device. A removable covering (not shown) may be included over the nozzle end 68 to maintain it in a sterile condition.

The chamber 70 includes a thin circumferential wall 71 of circular cross section and a semispherical forward wall 72. This provides an inward taper at the nozzle end to the centrally positioned opening 69.

In the rearward portion of the ampul 67 is a plunger 74 having a semispherical forward section 75 which is opposite from and complementary to the wall 72 of the ampul 67. The ampul is entirely filled with the fluid to be injected, there being no air present beyond the plunger 74. The plunger 74 is provided with annular grooves 76 to define annular ribs 77 complementary to the circumferential wall 71 of the ampul and sealingly engage it. The plunger 74 preferably is of rubber or of a plastic material that will readily form a seal with the wall 71 of the ampul and retain the fluid. The outer or rearward end 78 of the plunger 74 presents a radial surface adjacent the forward end of the piston 33.

A longitudinal slot 80 is provided in the body 10, extending radially inwardly at its rearward end to the chamber 17. Within the slot 80 is a detent member 81 rotatable relative to the body 10 about a transverse pin 82. A trigger button 83 projects radially outwardly beyond the circumferential surface of the body 10 at the forward end of the member 81 on one side of the pin 82. A small compression spring 84 is located beneath the forward end of the member 81, engaging the bottom of the slot 80. This biases the member 81 in a clockwise direction as the device is shown in FIG. 2. The detent member 81 includes a radially inwardly projecting and forwardly facing shoulder'85 at its rearward end, on the opposite side of the pin 82, which extends radially inwardly into the rear end portion of the chamber 17 and engages the abutment provided by the rearward surface of the flange 24 on the cylinder 18. This holds the cylinder 18 in the retracted, leftward position of FIG; 2 against the force of the compression spring 23.

In use of the hypodermic device of this invention, the tip portion 68 of the ampul 67 is placed in contact with the skin where the injection is to be made. Then the trigger button 83 is depressed, rotating the detent member 81 in a counter-clockwise direction. This moves the shoulder 85 away from the flange 24 of the cylinder 18. Consequently, the compression spring 23 drives the cylinder rearwardly from the position shown in FIG. 2 to that of FIG. 3, where the flange 24 strikes the wall 47 at the end of the chamber 17. The wall 47 forms an abutment that limits the rearward movement of the cylinder 18. This movement of the cylinder 18 causes the beveled end 44 of the tubular firing pin 43 to pierce the wall 58 of the cartridge 56, and the member 43 enters the cartridge. This provides a path for the compressed carbon dioxide or other gas to flow out of the cartridge 56 through the tubular member 43 and the passageway 42 in the cylinder head 40 into the interior of the cylinder 18. There, the pressurized gas bears against the end of the piston 33, moving the piston 33 forwardly relative to the cylinder 18. The forward end of the piston 33 engages the rearward surface 78 of the plunger 74, pushing the plunger the length of the ampul 67 to the position of FIG. 3. This drives the medicament or other fluid from the interior of the ampul 67 through the outlet opening 69 at a high velocity. The jet of fluid produced in this manner is injected through the epidermis of the patient.

The fact that the semispherical plunger surface 75 is complementary to the end wall 72 of the ampul 67, together with the location of the nozzle opening 69 at the center of the wall 72, helps assure that the entire contents of the ampul 67 are exhausted as the piston 33 is driven through its stroke. During the movement of the plunger 74, the wall of the chamber 27 reinforces the ampul structurally so that it is not broken by the pressure built up within it.

When the piston 33 reaches the end of its stroke, its rearward end passes a radial port 87 in the wall of the cylinder 18. This allows any excess gas to bleed outwardly through the port 87, into the chamber 17 and, by way of the slot 80, to the atmosphere. This vents the unit to atmospheric pressure, and assures that the compressed gas cannot enter the ampul 67.

After the piston 33 has reached the forward end of its stroke and the pressure behind it has been relieved, the spring 39 returns the piston to its retracted position, where it engages the cylinder head 40. The forward closure member 60 then may be removed by separating its bayonet connection to the tubular member 12, allowing the spent ampul to be removed from the open rearward ends of the member 60 and discarded. A new fully-charged ampul then may be inserted into the member 60, which is reattached to the forward end of the tubular member 12.

The device then is recocked for its next use. To accomplish this, the body and tubular member 12 are given relative rotation to position the lugs at the forward ends of the longitudinal portions 13 of the bayonet slots in the member 12, as shown in FIG. 1. Then, the members 10 and 12 are moved axially relative to each other to partially move the member 12 away from the body member 10. As this movement takes place, the lugs 15 slide in the longitudinal portions 13 of the bayonet slots, which limit the amount of separation of the members 10 and 12. With the cylinder 18 having been driven rearwardly by the spring 23 to the position of FIG. 3, the flange 30 of the member 28, which is attached to the cylinder, is brought into engagement with the end wall 26 of the member 12. This causes the cylinder 18 to move axially rearwardly with the member 12 relative to the body member 10. The detent member 81, on the other hand, is attached to the body member 10, so that there is longitudinal movement between the cylinder 18 and the detent 81. As this occurs, the outwardly inclined inner surface 89 at the end of the detent adjacent the shoulder 85 slides over the edge of the cylinder flange 24. Ultimately, this movement brings the rearward end of the flange 24 past the shoulder 85 of the detent 81. The spring 84 then causes the detent 81 to rotate downwardly in back of the flange 24, holding the cylinder 18 in the retracted, cocked position of FIG. 2. After the cylinder has been moved to the cocked position, the tubular member 12 is moved back onto the body member 10, and the parts are rotated to bring the lugs 15 into the transverse portions 14 of the bayonet slots to hold the members 10 and 12 in their assembled position.

With the cylinder 18 moved back to the cocked position, the tubular firing pin is removed from the compressed-gas cartridge 56, being retracted into the opening 46 in the end wall 47 between the chambers 17 and 49. After this, the bayonet connection for the cap member 50 is separated so that, upon removal of the cap 50, the cartridge 56 can be removed. An unused sealed compressed-gas cartridge then is replaced in the chamber 59 and the cap member 50 is returned to the connected position. The hypodermic device then is completely ready for reuse.

Knurled portion 90, 91, 92 and 93 are provided on the exteriors of the members 10, 12, 50 and 60, respectively, to facilitate the rotational and axial movement given these parts during the preparation of the device for use. The provisions of a compressed-gas cartridge for powering the unit and replaceable sealed ampuls for containing the liquid to be injected, together with the easily operated bayonet connection and the mechanical arrangements for the various parts, mean that it is an extremely simple procedure to make the device ready for reuse. The entire sequence in operating the device can be accomplished quite easily and rapidly.

For economy of manufacture, it is preferred to make the ampuls 67 of a single length regardless of the quantity of fluid that is to be accommodated. For lesser amounts of fluid, the plunger is initially positioned further into the ampul, still acting as the rearward closure for retaining the fluid.

The ampuls may be made with different sizes of nozzle openings 69 to suit the viscosity of the fluid retained and the type of injection that is to be made. Typically, the ampuls may provide openings of 0.003,0.005 and 0.008 inch diameters. The depth of penetration will increase with the diameter of the nozzle opening for a given fluid, while larger diameters are needed for fluids of greater viscosity. With the nozzle being a part of the replaceable ampul rather than a portion of the permanent structure of the injection device, it is a simple matter to provide precisely the needed size of discharge opening for each injection to be made.

I claim 1. A pressure-operated injection device comprising a body,

an ampul carried by said body,

a fluid to be injected retained in said ampul,

said ampul having a portion projecting outwardly of said body, said portion having an aperture therethrough of predetermined size,

a plunger in said ampul remote from said aperture, means for moving said plunger in said ampul for forcing said fluid through said aperture for injecting said fluid into an adjacent object, said means for moving said plunger including a compressed-gas cartridge, a cylinder, and a piston in said cylinder movable by said gas, means for releasing gas from said compressedgas cartridge and conducting gas into said cylinder, said piston including means for engaging said plunger and moving said plunger with said piston, said cylinder being movable relative to said body, between a first position remote from said compressed-gas cartridge and a second position adjacent said compressed-gas cartridge,

resilient means biasing said cylinder toward said second position,

and releasable means for holding said cylinder in said first position, said cylinder including means for entering said compressed-gas cartridge when said cylinder is in said second position for thereby providing said means for releasing gas from said compressed-gas cartridge.

2. A device as recited in claim 1 in which said means for entering said compressed-gas cartridge includes a tubular member communicating with said cylinder, projecting outwardly therefrom, and movable with said cylinder, said compressed-gas cartridge having a frangible portion adjacent said tubular member,

said frangible portion being engageable by said tubular member upon said movement of said cylinder from said first position to said second position for severing said frangible portion and causing said tubular member to enter said compressed-gas cartridge and conduct said gas from said compressed-gas cartridge to said cylinder.

3. A device as recited in claim 1 in which i said body includes two relatively movable portions,

one of said portions including means engageable with said cylinder when said cylinder is in said second position for moving said cylinder to said first position upon movement of said one portion relative to the other of said portions of said body.

4. A hypodermic device comprising a body,

means on said body for retaining a quantity of compressed gas, said means including a frangible portion for permitting the escape of said gas,

means on said body for retaining a quantity of fluid to be injected by said device, said means retaining said fluid having an outlet aperture for discharging said fluid, and a plunger movable for forcing said fluid through said aperture,

a cylinder on said body,

said cylinder being reciprocative relative to said compressed-gas retaining means between a first position remote from said compressed gasretaining means and a second position adjacent said compressed gas-retaining means,

a tubular means providing communication with the interior of said cylinder and relatively movable therewith, said tubular means being engageable with said frangible portion when said cylinder is moved from said first position to said second position,

whereby said tubular means severs said frangible portion for conducting said compressed gas to the interior of said cylinder,

a piston in said cylinder,

said piston having a portion adjacent said plunger, said piston being movable by said compressed gas when said compressed gas is so conducted into said cylinder for moving said plunger and discharging said fluid through said aperture, resilient means biasing said cylinder toward said second position, and releasable detent means for holding said cylinder in said first position. 5. A device as recited in claim 4 in which said means for retaining said compressed gas includes a cartridge, said body having a chamber receiving said cartridge, said chamber having a wall having an opening adjacent said frangible portion, said tubular means extending into said opening. 6. A device as recited in claim 4 in which said means for retaining said fluid includes an ampul, said body including a chamber substantially complementarily receiving said ampul, whereby said chamber provides reinforcement for said ampul, said chamber having an opening therethrough, said ampul having an integral portion projecting beyond one end of said body through said openmg, said portion of said ampul having said aperture for discharging said fluid. I 7. A device as recited in claim 6 in which said ampul includes a wall opposite from said plunger, said aperture extending from said wall to said integral portion of said ampul, said wall being inwardly tapered toward said aperture for facilitating the flow of said fluid through said aperture, said plunger having a surface adjacent said wall which is substantially complementary to said wall. 8. A device as recited in claim 7,in which said surface and said wall are substantially semispherical. 9. A device as recited in claim 4 in which said resilient means for biasing said cylinder toward said second position includes a compression spring circumscribing said cylinder, said cylinder having an abutment extending radially outwardly from the periphery thereof engaged by said compression spring at one end of said spring, said body having a shoulder engaged by the opposite end of said compression spring. 10. A device as recited in claim 4 including in addition a compression spring in said cylinder circumscribing said piston, said piston having an abutment engaged by one end of said spring, said cylinder having an abutment engaged by the opposite end of said spring,

whereby said spring urges said piston to a retracted position away from said plunger. 1 1. A device as recited in claim 4 in which said cylinder includes a vent opening through the wall thereof intermediate the ends of said cylinder, whereby when said piston has traveled a predetermined distance said vent opening is uncovered for permitting escape of excess compressed gas through said vent opening. 12. A device as recited in claim 4 in which said body is in at least two sections,

said sections being movable between a first position of relative adjacency and a second position of relative separation, said detent means being carried by one of said sections,

the other of said sections having means engageable withsaid cylinder for moving said cylinder therewith to said first position when said sections are moved to said position of relative separation for permitting said detent means to engage said cylinder and retain said cylinder in said first position. 13. A device as recited in claim 12 in which said sections include bayonet means interconnecting the same for permitting said movement between said position of relative adjacency and said position of relative separation, said bayonet means including portions for holding said sections in said position of relative adjacency. 14. A device as recited in claim in which said body includes a cap defining at least a portion of said chamber for said cartridge, said cap being removable from said body. 15. A device as recited in claim 14 in which said 5 body and said cap include bayonet connecting means for permitting rapid attachment and release of said cap for installation and removal of said cartridge.

16. A device as recited in claim 6 in which said body includes a cap defining at least a portion of said chamber for said ampul, said cap being removable from said body.

17. A device as recited in claim 16 in which said body and said cap include bayonet connecting means for permitting rapid attachment and release of said cap for installation and removal of said ampul.

Claims

1. A pressure-operated injection device comprising a body, an ampul carried by said body, a fluid to be injected retained in said ampul, said ampul having a portion projecting outwardly of said body, said portion having an aperture therethrough of predetermined size, a plunger in said ampul remote from said aperture, means for moving said plunger in said ampul for forcing said fluid through said aperture for injecting said fluid into an adjacent object, said means for moving said plunger including a compressed-gas cartridge, a cylinder, and a piston in said cylinder movable by said gas, means for releasing gas from said compressed-gas cartridge and conducting gas into said cylinder, said piston including means for engaging said plunger and moving said plunger with said piston, said cylinder being movable relative to said body between a first position remote from said compressed-gas cartridge and a second position adjacent said compressed-gas cartridge, resilient means biasing said cylinder toward said second position, and releasable means for holding said cylinder in said first position, said cylinder including means for entering said compressed-gas cartridge when said cylinder is in said second position for thereby providing said means for releasing gas from said compressed-gas cartridge.

2. A device as recited in claim 1 in which said means for entering said compressed-gas cartridge includes a tubular member communicating with said cylinder, projecting outwardly therefrom, and movable with said cylinder, said compressed-gas cartridge having a frangible portion adjacent said tubular member, said frangible portion being engageable by said tubular member upon said movement of said cylinder from said first position to said second position for severing said frangible portion and causing said tubular member to enter said compressed-gas cartridge and conduct said gas from said compressed-gas cartridge to said cylinder.

3. A device as recited in claim 1 in which said body includes two relatively movable portions, one of said portions including means engageable with said cylinder when said cylinder is in said second position for moving said cylinder to said first position upon movement of said one portion relative to the other of said portions of said body.

4. A hypodermic device comprising a body, means on said body for retaining a quantity of compressed gas, said means including a frangible portion for permitting the escape of said gas, means on said body for retaining a quantity of fluid to be injected by said device, said means retaining said fluid having an outlet aperture for discharging said fluid, and a plunger movable for forcing said fluid through said aperture, a cylinder on said body, said cylinder being reciprocative relative to said compressed-gas retaining means between a first position remote from said compressed gas-retaining means and a second position adjacent said compressed gas-retaining means, a tubular means providing communication with the interior of said cylinder and relatively movable therewith, said tubular means being engageable with said frangible portion when said cylinder is moved from said first position to said second position, whereby said tubular means severs said frangible portion for conducting said compressed gas to the interior of said cylinder, a piston in said cylinder, said piston having a portion adjacent said plunger, said piston being movable by said compressed gas when said compressed gas is so conducted into said cylinder for moving said plunger and discharging said fluid through said aperture, resilient means biasing said cylinder toward said second position, and releasable detent means for holding said Cylinder in said first position.

5. A device as recited in claim 4 in which said means for retaining said compressed gas includes a cartridge, said body having a chamber receiving said cartridge, said chamber having a wall having an opening adjacent said frangible portion, said tubular means extending into said opening.

6. A device as recited in claim 4 in which said means for retaining said fluid includes an ampul, said body including a chamber substantially complementarily receiving said ampul, whereby said chamber provides reinforcement for said ampul, said chamber having an opening therethrough, said ampul having an integral portion projecting beyond one end of said body through said opening, said portion of said ampul having said aperture for discharging said fluid.

7. A device as recited in claim 6 in which said ampul includes a wall opposite from said plunger, said aperture extending from said wall to said integral portion of said ampul, said wall being inwardly tapered toward said aperture for facilitating the flow of said fluid through said aperture, said plunger having a surface adjacent said wall which is substantially complementary to said wall.

8. A device as recited in claim 7 in which said surface and said wall are substantially semispherical.

9. A device as recited in claim 4 in which said resilient means for biasing said cylinder toward said second position includes a compression spring circumscribing said cylinder, said cylinder having an abutment extending radially outwardly from the periphery thereof engaged by said compression spring at one end of said spring, said body having a shoulder engaged by the opposite end of said compression spring.

10. A device as recited in claim 4 including in addition a compression spring in said cylinder circumscribing said piston, said piston having an abutment engaged by one end of said spring, said cylinder having an abutment engaged by the opposite end of said spring, whereby said spring urges said piston to a retracted position away from said plunger.

11. A device as recited in claim 4 in which said cylinder includes a vent opening through the wall thereof intermediate the ends of said cylinder, whereby when said piston has traveled a predetermined distance said vent opening is uncovered for permitting escape of excess compressed gas through said vent opening.

12. A device as recited in claim 4 in which said body is in at least two sections, said sections being movable between a first position of relative adjacency and a second position of relative separation, said detent means being carried by one of said sections, the other of said sections having means engageable with said cylinder for moving said cylinder therewith to said first position when said sections are moved to said position of relative separation for permitting said detent means to engage said cylinder and retain said cylinder in said first position.

13. A device as recited in claim 12 in which said sections include bayonet means interconnecting the same for permitting said movement between said position of relative adjacency and said position of relative separation, said bayonet means including portions for holding said sections in said position of relative adjacency.

14. A device as recited in claim 5 in which said body includes a cap defining at least a portion of said chamber for said cartridge, said cap being removable from said body.

15. A device as recited in claim 14 in which said body and said cap include bayonet connecting means for permitting rapid attachment and release of said cap for installation and removal of said cartridge.