Hypodermic Injection Device With Shock Absorbing Spring

Abstract

A hypodermic injection device is provided comprising a cylindrical holder closed at one end and slidably carrying an ampoule with attached cannula facing the closed end of the holder, medicament is provided in the ampoule between the cannula and the piston in the ampoule, a gun spring assembly is associated with the holder and in operative association with the ampoule to force the ampoule and attached cannula forward thus driving the cannula out of the closed end of the holder and into the locus of injection, and a counterbalancing spring is positioned in the holder between the closed end thereof and the cannula end of the ampoule to counteract the gun spring force.

Description

This application is an improvement on copending application Ser. No. 105,728, filed Jan. 11, 1971, and entitled "Gun Type Hypodermic Injector With Rapid Cartridge Displacement Within Holder" now U.S. Pat. No. 3,712,301.

SUMMARY OF THE INVENTION

This invention relates to a hypodermic injection device and more particularly to a gun type device wherein spring power drives the ampoule and cannula to insert the cannula and then inject the medicament, additional spring means are provided to counteract said spring power to provide shock absorbing, better dispersion of medicament and safety with regard to insertion of the cannula.

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. A helical spring is positioned around the cannula and abuts the closed end of the holder and the cannula end of the ampoule. A gun spring drives a plunger which engages the ampoule to drive the ampoule and cannula forward causing the cannula to pierce the closed end of the holder and to enter the locus which is to receive the medicament. During the movement of the ampoule, the helical spring is compressed sufficiently to produce a counter force stopping the ampoule. The plunger continues to move forward pushing the piston in the ampoule to eject the medicament through the cannula. This continued movement of the plunger dissipates the energy of the gun spring and allows the helical spring to overcome same and push the ampoule rearwardly thus retracting the cannula.

The counterbalancing effect provided by the helical spring is valuable in that if the cannula strikes a hard surface while being inserted, this resistance coupled with the force of the compressed helical spring, will cause the cannula to stop entry and possibly retract depending on the depth of penetration of the cannula which obviously will be a measure of the relative spring forces at any given position.

In view of the foregoing, it is an object of this invention to provide a gun type hypodermic injection device having spring means to counterbalance the gun spring power employed to insert the cannula and inject the medicament.

It is another object of this invention to provide a gun type hypodermic injection device as above wherein the counter-balancing spring means serves to retract the needle during injection to provide greater dispersion of the medicament.

It is yet another object of this invention to provide a gun type hypodermic injection device as above wherein the counter-balancing spring means serves as a shock absorber to control forward movement of the ampoule under the force of the gun spring.

It is a still further object of this invention to provide a hypodermic injection device wherein the counterbalancing spring serves to prevent injury to the user by employing the counter-balance spring force to assist in preventing further penetration of the cannula when it strikes a solid spot by providing an opposing force to counteract that of the gun spring.

IN THE DRAWINGS

FIG. 1 is a cross-sectional view of the hypodermic injection device of this invention as it is stored;

FIG. 2 is a cross-sectional view of the device after the gun spring has forced the cannula out the closed end of the holder and has completed its outward travel;

FIG. 3 is a cross-sectional view similar to FIG. 1 illustrating a second embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

One form of this invention is illustrated in FIGS. 1 and 2 of the drawings. In this embodiment 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 opening which is closed by a cannula pierceable stopper 158 that hermetically seals this end of the cartridge holder 104.

The cartridge 135 includes an ampoule cylinder 136 with liquid medicament 146 therewithin 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 sleeve 82 which in turn is affixed to the enlarged flange in the necked portion 80. More specifically, cannula sleeve 82 comprises a reduced diameter portion 84 which is secured to the cannula 150 and an enlarged body 86 forming a shoulder 88. The enlarged body 86 fits over and is secured to the annular flange on 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 stoppered end of the holder 104. The piston end of the ampoule cylinder 136 is retained in place within the holder sleeve 104 by resilient contact between the exterior surface of the ampoule 136 and an annular bead 160 on the inner wall of the holder sleeve 104 adjacent its open end. This bead 160 hermetically seals the ampoule cylinder at its piston end and frictionally retains it in position within the holder sleeve 104. The diameter of the exterior of the ampoule cylinder 136 is less than the internal diameter of the holder sleeve 104 throughout the major length of said holder sleeve so that once the ampoule cylinder is moved forward and is free of the annular head 160 and the cannula 150 has pierced the stopper 158, the ampoule 135 will move freely in the holder sleeve. The gas in front of the ampoule will readily flow therepast in the annular space between the ampoule cylinder and the inner wall of the holder sleeve 104 as the ampoule travels forward. By this method of sealing, the cannula 150 may be maintained in a sterile environment until use is made of the device. It should be noted that the forward interior of the holder sleeve 104 is contoured to form a seat 161. 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 on 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 there-between. 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 illustrated in FIGS. 1 and 2 a spring means 210 is positioned within the cartridge holder 104 between ampoule cylinder 136 and the inner closed end of the holder 104. More particularly, the spring means 210 comprises a helical spring 212 positioned around cannula 150 and interposed between the closed end of the holder 104 and flat end portion 214 of the ampoule cylinder 136 surrounding the necked portion 80. It should be noted that a resilient washer 218 is positioned between the spring 212 and the flat end portion 214 of the ampoule cylinder 136. The helical spring 212 is sized to fit down into the reduced end portion 153 of holder 104.

The embodiment illustrated in FIG. 3 of the drawings is similar to that of FIG. 1 except for the helical spring arrangement. In this embodiment the helical spring 212 surrounds the cannula 150 abutting against shoulder 88 of the cannula sleeve 82 and the closed end of the holder 104. The function is identical in both embodiments.

The function of the spring means 210 is threefold: namely, to act as a shock absorber, as a safety feature and as a means for retracting the cannula a small amount after complete projection thereof.

The device is delivered to the user in the form shown in FIG. 1. For use, initially the safety pin 144 is removed and then the forward end of the device is applied to the patient at the locus desired. Subsequently, when the outer gun sleeve 192 is thrust toward the locus, a telescoping action takes place between the outer and inner gun sleeves. An advantage of the arrangement is that the outer sleeve 100 is long and the injection device may be grasped very conveniently along substantially its entire length to operate it.

Telescoping action of the gun sleeves causes the frusto-conical cam surface 198 to cam the detent heads 186 together, whereby they become smaller in diameter than the opening 120, and the spring 138 becomes effective to advance the plunger 162. In the initial movement, the plunger tabs 168 engage the end of the ampoule 136 and force it forwardly off the bead 160 and upon further travel forces the cannula 150 through stopper 158 into the position illustrated in FIG. 2. At this point, the ampoule cylinder 136 has substantially fully compressed spring 212 and cannula 150 fully introduced whereby further travel of the plunger 162 causes tabs 168 to be sheared off and fall back into slots 172 so that the plunger may continue to move forward by engaging the ampoule piston 148 to force the medicament out of the cannula 150.

It should be noted that the spring 212 is sized such that it will stop travel of the ampoule 135 short of the holder shoulder 161 to thereby obviate any possibility of breaking of the ampoule by hard impact thereon. This is the shock absorbing feature of the spring previously mentioned.

Additionally, the spring affords a safety feature as follows: Obviously, in the initial movement of the ampoule 135 under the force of gun spring 138, this spring must have sufficient power to overcome spring 212. Balancing of these spring forces is a critical matter. Spring 138 must have enough stored energy to force the cannula 150 into the desired position and depth for introduction of the medication. On the other hand, spring 212 upon compression by the ampoule 135 as it moves forward must build up sufficient resistance such that the movement of the ampoule will stop short of the holder shoulder 161.

Obviously, as the ampoule moves toward the end of the holder 104, the force of spring 138 diminishes and that being built up in spring 212 increases. Thus a counterbalancing effect is achieved. This counterbalance is important as a safety feature. For example, in the use of the device if the projecting cannula in its movement should strike a solid mass, the sudden impact coupled with the counter effect of the spring 212, will be sufficient to cause the cannula to stop and perhaps retract depending on the amount of projection that had taken place at the specific instant of impact. This would avoid injury to the user which is a major consideration.

The third important feature of the spring 212 is the retraction of the cannula after it has been fully projected under the force of gun spring 138. As set forth previously in describing the operation of the device, it will be recalled that the gun spring 138 drives the ampoule 135 forward to force the cannula 150 out the end of the holder and into the locus of application of the medicament. This complete forward movement of the cannula and ampoule is illustrated in FIG. 2 wherein the spring 212 has been compressed to its maximum compression. At this point, the gun spring continues to push the plunger and engaged piston forward to force the medicament out the cannula. As the plunger continues forward to cause the piston to eject the medicament, the reduction in force of spring 138 is overcome by spring 212 and the cannula 150 commences to retract slightly as the latter part of the ejection of the medicament is taking place. This retraction as the medicament is being injected provides good dispersion to decrease the time required for the medicament to take effect.

In view of the foregoing, it is now apparent that the hypodermic injection device of this invention is a substantial step in the producing of a foolproof and safe self-injection device having a wide area of use.

Claims

I claim:

1. In a hypodermic injection device comprising a gun, a cartridge holder having a closed end and 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, a puncturable seal closing off the end of the holder remote from the gun, 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 closed end of the holder, the improvement comprising:

shock absorbing and retracting spring means interposed between the cannula end of the cartridge and the closed end of the cartridge holder, said shock absorbing and retracting spring means being sized whereby it is compressed by the cartridge and acts as a shock absorber as said cartridge moves under the force of the spring power means until the cannula is fully projected into the patient, the shock absorbing and retracting spring means being further characterized by having a compressed spring force when the cannula is fully projected into the patient and injection begins under the continuing expansion of the spring power means to overcome the force of the spring power means and retract the cannula while injection continues and is completed.

2. The invention as set forth in claim 1 and wherein the shock absorbing and retracting means comprises a coiled spring positioned around the cannula between the cannula end of the cartridge and the closed end of the cartridge holder.

3. The invention as set forth in claim 2 and wherein the coiled spring is a helical spring.

4. The invention as set forth in claim 1 and wherein the hollow cylindrical ampoule sleeve is necked down at its cannula end to form a cylindrical projection of reduced diameter, an annular flange formed on the end of said projection, and a cannula sleeve connected to the cannula and fitting over the flange to secure the cannula to the ampoule and further wherein the shock absorbing and retracting spring means comprises a helical spring fitting around the cannula and abutting that portion of the ampoule cylinder around the cylindrical portion of reduced diameter and the closed end of the cartridge holder.

5. The invention as set forth in claim 1 and wherein the hollow cylindrical ampoule sleeve is necked down at its cannula end to form a cylindrical projection of reduced diameter, an annular flange formed on the end of said projection, and a cannula sleeve connected to the cannula, said cannula sleeve having a portion secured to the cannula and an enlarged portion fitting over and secured to the flange and further wherein the shock absorbing and retracting spring means comprises a helical spring fitting around the cannula and abutting the enlarged portion of the cannula sleeve and the closed end of the cartridge holder.

6. The invention as set forth in claim 4 and wherein a resilient washer is positioned between the helical spring and the ampoule cylinder.