Hypodermic injection device having cannula covered with resilient sheath

Abstract

A hypodermic injection device comprising a cartridge holder having a cylindrical body open at one end and closed at the other end, the closed end being provided with an aperture, a cartridge including an ampoule with attached cannula within the holder, the cannula being directed toward the holder's closed end, the ampoule including a cylindrical sleeve slidably carrying a piston, the sleeve being open at one end and having a necked portion at the other end to receive a hub mounting the cannula, fluid medicament in the sleeve between the piston and cannula, a spring power assembly for moving the cartridge forward and for injecting the fluid medicament carried in the ampoule, a safety assembly for controlling actuation of the spring power assembly, and a resilient sheath covering the cannula to maintain the cannula in sterile condition.

Description

SUMMARY OF THE INVENTION

This invention relates to injection devices of the gun type wherein spring power means drives an ampoule and cannula to insert the cannula and then inject the medicament. The cannula is provided with a resilient sheath to maintain the cannula in sterile condition at all times prior to injection.

In the device of this invention, the ampoule and attached cannula are slidably carried in a cylindrical holder which is closed at the end housing the cannula except for an aperture through which the cannula passes when the unit is actuated. A spring power assembly drives a plunger which engages the ampoule to drive the ampoule and cannula forward causing the cannula to travel out through the aperture in the closed end of the cylindrical holder and to enter the locus which is to receive the fluid medicament. Continued movement of the plunger, after placing of the cannula in the locus, forces a piston in the ampoule forwardly to inject the medicament. During this action, the resilient sheath positioned on and over the cannula is held within the closed end of the cylindrical holder and is pierced by the end of the cannula as it proceeds forwardly. As the cannula continues forward, the sheath is compressed between the closed end of the cylindrical holder and the cannula hub. This action continues until the cannula is fully extended, at which time the sheath is not quite fully compressed, thus making it possible for the sheath to act as a shock absorber at all times during forward travel of the cannula. Toward the end of injection, the forward travel of the power spring is such that its energy is less than that now stored in the compressed sheath. Therefore, a slight retraction of the cannula occurs during the terminal portion of the injection.

In view of the foregoing, it is an object of this invention to provide a gun type injection device with a resilient cannula sheath for maintaining the cannula in sterile condition at all times prior to actuation.

It is another object of this invention to provide a gun type injection device with a resilient cannula sheath to act as a shock absorber during operation of the device.

It is a further object of this invention to provide a gun type injection device wherein the cannula is covered by a resilient sheath which upon being compressed when the device is actuated will react to retract the cannula a small distance during the terminal portion of injection.

IN THE DRAWINGS

FIG. 1 is a longitudinal broken away view, partly in section, illustrating the sheath as applied to the cannula when the injection device is in ready position;

FIG. 2 is a view similar to FIG. 1, showing the compressed sheath after firing of the injection device with the cartridge fully projected and just prior to the forward movement of the plunger and injection of the medicament; and

FIG. 3 is a view similar to FIG. 2, illustrating a slight retraction of the cannula from the fully extended position of FIG. 2 which retraction occurs during the terminal portion of the injection.

DETAILED DESCRIPTION OF THE INVENTION

The single embodiment of this invention illustrated in FIGS. 1-3 is merely one example of the injection apparatus that can advantageously use the cannula sheath arrangement of this invention.

The device comprises an outer cylindrical sleeve 100 having an inturned shoulder 110 at one end and an annular groove 113 in the inner wall adjacent the other open end. A cartridge assembly 106 is assembled in the shouldered end of the outer sleeve 100. The cartridge assembly 106 includes a cartridge holder sleeve 104 fitted within the sleeve 100 and having a decreased forward end portion 153 forming a shoulder 154 which fits against seat 112 provided by outer sleeve shoulder 110. The extreme forward end portion 156 of the holder sleeve 104 is tapered to form a small circular aperture.

The cartridge 135 includes an ampoule cylinder 136 with liquid medicament 146 there within and a piston 148 at one end with a cannula 150 at the other end. The ampoule cylinder 136 has a necked portion 80 with a diameter less than that of the cylinder 136 and terminates in an enlarged annular flange. The cannula 150 is secured to a cannula hub 81 which in turn is affixed to the enlarged flange on the necked portion 80. More specifically, cannula hub 81 comprises a reduced diameter portion 84 which is secured to cannula 150 and an intermediate body 86 connected to enlarged body 88. The enlarged body 88 fits over and is secured to the annular flange of the necked portion 80 of the ampoule cylinder. Within the neck of the ampoule cylinder 136, between the inner end of the cannula 150 and the medicament, there may be interposed a fluid pressure rupturable diaphragm generally like that described in U.S. Pat. No. 3,391,695 to Sarnoff.

The cartridge assembly 106 is assembled in the outer sleeve 100 with the cannula 150 spaced from the apertured end of the holder 104. The overall length of the ampoule 135 and cannula 150 is such that it is all contained within the holder sleeve 104, as illustrated in FIG. 1.

The outer sleeve 100 is of such length that it accommodates the cartridge assembly 106 in one end and receives the gun assembly 200 in the other to complete the device. The gun assembly 200 comprises an inner gun sleeve 101 having an out turned flange 103 which fits up against the end of the cartridge holder sleeve 104 when the gun assembly is inserted in the outer sleeve 100. The other end of the inner gun sleeve 101 is centrally apertured to form a hole 120. The rear outer face 122 of the inner gun sleeve 101 is planar and perpendicular to the longitudinal axis of the sleeve for a purpose to be brought out later.

A plunger 162 fits within the out turned flange end of the inner gun sleeve 101. This plunger has a cylindrical body portion 163 and a circular head portion 164 of a diameter larger than the body portion 163 and generally slightly less than that of the piston 148 in the ampoule 135. The head 164 has an opening which is sized to align and correspond to the through hole 166 in the plunger body 163. The plunger head 164 is provided with a plurality of circumferentially spaced, radially extending tabs 168. These tabs 168 form a diameter greater than that of the plunger head 164 so that the tabs will engage the end of the ampoule cylinder 136. Longitudinal slots 172 are formed in the plunger head 164 immediately behind the tabs 168. These slots are sized so that they will accommodate the tabs 168 when they are later broken off or bent rearwardly in the operation of the device. These slots extend throughout the length of the head behind the tabs.

Referring to FIGS. 1 and 2, a locking detent 176 is fitted through the hole 166 in the plunger 162 and has a central body portion 178 with outwardly extending lugs 180 on one end fitting an annular shoulder 182 of the plunger head 164. The other end of the locking detent 176 is provided with four equally spaced, longitudinally extending springy detent arms terminating in frusto-conical detent heads 186. This locking detent 176 maintains the plunger 162 and inner gun sleeve 101 in assembled position with a coil spring 138 compressed therebetween as follows: A coil spring 138 is positioned over the plunger body 163 and abuts the plunger head 164 at one end and the inner face of the end wall of the inner sleeve 101 at the other. Upon compressing of the coil spring 138 sufficiently, the detent heads 186 will be cammed inwardly by engaging the periphery of the end wall opening 120 and pass therethrough whereupon the bases of the detent heads 186 will come to rest on the planar face 122 of the inner gun sleeve 101 to retain the plunger and inner gun sleeve in assembled condition with the coil spring 138 compressed therebetween. When desired, the rear planar surface 122 of the inner sleeve 101 may be overlaid with a metal washer 127, in which case it is advantageous to provide a guide and holding flange 128 to surround the opening 120. The flange 128 is provided with a lip portion to retain the washer in place.

As illustrated in FIGS. 1 and 2, the inner gun sleeve 101 has a plurality of longitudinally extending raised ribs 129 running from the flange 103 approximately one-half the length of the said sleeve. An outer gun sleeve 192 fits over inner gun sleeve 101 and is sized to frictionally engage ribs 129. The outer sleeve 192 has a closed end 194 with a central aperture 196 from which extends a frusto-conical cam surface 198 sized and shaped to cooperate with frusto-conical detent heads 186 to cam said heads radially inwardly. The outer gun sleeve 192 is provided with a circumferential locking rib 199 which fits in groove 113 in the outer sleeve 102 to retain the gun assembly 200 in position in said outer sleeve. It should be noted that the length of outer gun sleeve 192 is slightly less than that of the inner gun sleeve 101 so as to make certain that there will be space between the inner wall of the outer gun sleeve 192 and the flange 103 of the inner gun sleeve 101 so that the two gun sleeves may move relative to each other to cam frusto-conical detent heads 186 inwardly in operating the device.

In order to make certain that the frusto-conical detent heads 186 are not accidentally cammed inwardly, a safety pin assembly is provided. This safety pin assembly comprises a cap 142 having a cylindrical sleeve 143 sized to fit over the end portion of outer gun sleeve 192. A safety pin 144 extends inwardly from the center of the cap 142 into the opening formed by the inner portions of the detent heads 186 to thereby prevent inward movement of said detent heads. The cap 142 is provided internally with a plurality of spacer abutments 145 to assure proper positioning of the cap on the outer sleeve 192.

As shown in FIG. 1, resilient sheath 250 is positioned over the cannula 150 such that the open end of the sheath fits over and around cannula hub portion 84 and abuts the shoulder 82 formed by hub portions 84 and 86. The length of the sheath is such that its closed end is slightly beyond or spaced from the end of cannula 150. In order to make certain that the sheathed cannula is maintained in proper alignment with aperture 158, a plurality of ribs 157 is formed on the inner face of tapered holder portion 156 surrounding said aperture. Thus, the end of the sheath 250 is held in necessary alignment by bearing against the converging section of the ribs 157.

Upon the actuation of the injection device, the cartridge assembly 106 moves forward whereby the sheath 250 is compressed between the cannula end of the cartridge holder sleeve 104 and the hub shoulder 82, as illustrated in FIG. 2. The cannula sheath, in being compressed, acts as a shock absorber to gradually absorb some of the energy provided by the power spring 138 as it drives the cartridge assembly 106 forward. It should be noted that at no time, even when the cannula is fully extended, is the sheath compressed to such an extent that it would act as a solid and thereby provide no shock absorbing in such a condition.

When the cannula 150 is fully extended as shown in FIG. 2, the cannula sheath 250 will be compressed the greatest amount hence the largest reactionary force will exist in the compressed sheath in such position. As illustrated in FIG. 2, the cartridge 135 has completed its travel under the force of spring 138 and the forward movement of piston 148 commences under the action of spring 138 to start the injection cycle. The size of the sheath is such that in the maximum compressed condition, as in FIG. 2, the forces stored in the sheath are greater than those in spring 138 when it has reached a point just short of full piston travel. At this point the compressed sheath 250 takes over and causes the cartridge 135 and attached cannula 150 to retract slightly, as shown in FIG. 3, while the last stage of injection takes place. It is at this stage that the forces of the compressed sheath and the spring 138 are counterbalanced.

The importance of the sheath 250 and its multiple features is even more important when consideration is taken of the fact that most of the ampoule cylinders (i.e. cylinder 136 of the device illustrated) are made of glass and hence are subject to breakage under certain amounts and types of shock. The shock absorbing feature enjoyed by the use of the cannula sheath of this invention contributes substantially to overall quality and reliability. Furthermore, the covering of the cannula with the sheath provides greater ease in assembly since it is not necessary to maintain any of the inner portions of the holder and associated elements in sterile condition.

The type of material from which the sheath 250 can be made varies substantially. Even so, the preferred material would be one having good resilient characteristics such as various types of rubber and synthetics. Shelf life is also important. By this it is meant that the material should retain its characteristics over a substantial period of time and under varied conditions.

Claims

What is claimed is:

1. In a hypodermic injection device comprising a gun, a cartridge holder in operative relationship to the gun, a cartridge within the holder, said gun comprising a sleeve open at one end thereof, a plunger positioned within the sleeve, spring power means acting on said plunger tending to move it out the open end of the sleeve, restraining means cooperating with said plunger to prevent plunger movement, safety means acting on said restraining means to render it inoperative, said cartridge holder comprising a hollow shell acting as a prolongation of the gun sleeve, said cartridge including an ampoule comprising a hollow cylindrical sleeve, a piston slidably positioned in one end thereof and means mounting a cannula extending from and closing off the other end, a fluid within the cylindrical sleeve between the piston and the cannula, the cartridge fitting within the cartridge holder with the free end of the cannula within the end of the holder remote from the gun, the improvement comprising:

a resilient sheath covering the cannula, said sheath having a closed end and an open end, the length of the sheath being sized such that when assembled on the cannula the closed end of the sheath is not pierced by the cannula end, and means for preventing forward movement of the closed end of the sheath whereby when the power means forces the cartridge forward the cannula will pierce the closed end of the sheath and deliver the fluid medicament from the ampoule sleeve.

2. The invention as set forth in claim 1 and wherein the resilient sheath comprises a resilient cylinder having a closed and an open end, the length of the sheath being sized such that the closed end thereof is spaced from the cannula end.

3. The invention as set forth in claim 1 and wherein the resilient sheath is so sized that upon forward movement of the cartridge, the sheath will be compressed between the cannula hub and the forward end of the cartridge holder and act as a shock absorber.

4. The invention as set forth in claim 3 and wherein the size of the resilient sheath is such that it is never fully compressed, even when the cartridge is fully extended.

5. The invention as set forth in claim 4 and wherein means are provided in the forward end of the cartridge holder for centrally positioning the closed end of the resilient sheath in the cartridge holder.

6. The invention as set forth in claim 1 and wherein the resilient sheath is so sized that when it is compressed by the full extension of the cartridge under action of the power means the reactionary energy stored in the compressed sheath will overcome the force of the power means and retract the cannula a small distance.

7. The invention as set forth in claim 3 and wherein the cylindrical sleeve is made of glass.