US3403679A - Hypodermic injection apparatus with a secondary capsule-collapsing means - Google Patents

Description

3,403,679 NDARY K. SINCLAIR ETAL HYPODERMIC INJECTION APPARATUS WITH A SECO Oct. 1, 1968 CAPSULE-COLLAPSING MEANS Filed Dec. 10, 1965 2 Sheets-Sheet l FIG. 2%

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HYPODERMIC INJECTION APPARATUS WITH A SECONDARY CAPSULE-COLLAPSING MEANS Filed Dec. 10, 1965 2 Sheets-Sheet 2 qg ssg g/lfi :5 In pnta s B I f y %0rneys United States Patent 3,403,679 HYPODERMIC INJECTION APPARATUS WITH A SECONDARY CAPSULE-COLLAPSING MEANS Kenneth Sinclair, Winterslow, and Cyril Daniel Watson, Idmiston, England, assignors to The Secretary of State For Defence in Her Britannic Majestys Government of the United Kingdom of Great Britain and Northern Ireland, London, England Filed Dec. 10, 1965, Ser. No. 512,884 Claims priority, application Great Britain, Dec. 11, 1964, 50,617/ 64 6 Claims. (Cl. 128-218) ABSTRACT OF THE DISCLOSURE A hypodermic syringe includes a syringe casing, a liquid-containing sealed collapsible capsule housed in the casing, and a main spring which, when released, partially compresses the capsule. A needle within the capsule punctures the forward end of the capsule and injects liquid into the body of the user. A secondary spring between the casing and the capsule urges the front end of the capsule in a rearward direction against the action of the main spring until the collapse of the capsule is completed.

The invention relates to hypodermic injection apparatus mainly for the self administration of therapeutic or prophylactic agents or for veterinary work. The intention relates more particularly to injection apparatus or syringes in which a hypodermic needle is housed within the apparatus before an injection operation is performed and which are used for intra-muscular injections well into the flesh.

Hypodermic syringes previously known or used have a hypodermic needle supported within a liquid-containing chamber which may be a tube or a sealed collapsible capsule located within the forward end of the casing of the syringe. In these hypodermic syringes a plunger is dis posed within the casing behind the chambers which when released is driven ctorward by a spring to drive the point of the needle through the end of the chamber and into the skin of the user, and thereupon cause the ejection of the liquid through the needle and into the flesh.

In these spring-loaded automatic hypodermic syringes the discharge of liquid from the needle must take place while the needle is actually penetrating into the flesh and the discharge is substantially completed by the time the needle has completed its course. Powerful actuating springs are employed in order to effect a rapid injection and minimise pain, and its has been found in practice that the discharge of liquid from these devices can be seriously impeded so that incomplete dosage can often result when, as is usual and desirable, the injection is given into a muscle, and the needle comes into unrelenting contact with the facia of gristle which is found between layers of muscle and is thereby blocked and the further discharge of liquid prevented.

An important object of the present invention is to reduce the frequency of these maloperations which could have serious or fatal consequences, and to provide an automatic self-injection device which can be relied on to give a full and effective dose when used for intramuscular injections.

The length of the needle must be just shorter than that of the chamber so that when the liquid-containing tube or capsule is compressed it is rapidly punctured and the liquid can be ejected through the needle without any risk of the chamber bursting or the device being prevented from operating. The needle thus enters the flesh to a depth just less than the length of the needle and the liquid containing chamber and this depth of penetration may in various cir- "ice cumstances be greater than what is desirable or necessary, for example, if an injection were to be self administered with known injectors of this type by a person suffering a partial mental or physical collapse or having thin muscles the needle could hit a bone, and since the needle is usually injected with high force and velocity by the spring serious bone damage could result.

Another important object of the present invention is to minimise these hazards and provide an elfective, automatic self-injection hypodermic syringe which is as far as possible safe to use even by unskilled users in a state of partial mental or physical collapse.

Further objects of the invention are to provide such a safe automatic self-injection syringe which at the same time is easy to operate even by one hand and which cannot be contaminated before use.

It is a particular object of the invention to provide an effective and safe automatic self-injection syringe which can be reloaded with a liquid-containing collapsible capsule which can be sealed with its contents sterilized before use.

Another object of the invention is to provide a capsuleloaded automatic self-injection syringe which can operate rapidly and thus minimise pain and which yet can reliably provide a full dose of liquid.

In a hypodermic syringe in accordance with the present invention, a sealed, cylindrically corrugated capsule is utilized whose rigidity is diminished by the piercing of the seal by the needle and the collapse of the capsule from its initial prior-to-use condition to a partially collapsed condition. The collapse of the capsule is brought about by employing the usual main spring which has to be released by a release mechanism to drive the rear end of the capsule forward, but in addition it has been (found possible to incorporate a secondary spring in the syringe to act against the forward end of the capsule and modify the action of the needle in such a manner that, although liquid is still discharged as the needle penetrates into the flesh, the hazard of needle blockage is substantially eliminated and the overall penetration of the needles is reduced.

It will be appreciated that the provision of a release mechanism which can release two detached springs acting on the far ends of a capsule would be a most undesirable complication in a compact instrument of this type and a further advantageous feature of a hypodermic syringe in accordance with the invention is that a release mechanism is not required to hold the secondary spring prior-to-use.

The main spring must have initially a greater loading than that of the secondary spring so that when released it can drive the capsule against the skin of the user and commence the collapse of the capsule and penetration of the needle into the flesh against the reaction of the opposing secondary spring. The rate and initial loading of the main spring must however be such that the loading of the main spring decreases to that of the opposing secondary spring before the capsule is fully collapsed and the needle fully advanced into the flesh. Because of the inertia in the rapidly moving capsule and spring system the needle overshoots the position it would be in when there is static equilibrium between the two opposing springs. Consequently the complete collapse of the capsule is effected by a simultaneous advance of both springs which involves a small but vital reciprocation and hence slight withdrawal of the needle before the injection of liquid is completed, from its limit of penetration when the system overshoots the final equilibrium position.

The secondary spring as a result performs two functions. Firstly it withdraws the needle a little. If and when the needle impinges on gristle facia during its throw it will be rapidly withdrawn sufliciently to relieve pressure on the facia and prevent this from blocking the needle. Secondly it limits the maximum penetration of the needle and thus decreases the likelihood of the needle contacting the bone. The injector is thus rendered both more effective and safer to use than its predecessors. By judicious choice of the throws and strengths of the main spring means and the secondary spring and of the prior-to-use position of the capsule in the casing either the maximum penetration of the needle can be considerably limited so that the injection may be simply hypodermic rather than intramuscular or the amount of withdrawal of the needle from maximum penetration can be increased.

According to a feature of the invention, the forward end of the capsule is held by the secondary spring in a position to the rear of the forward end of the casing, and the main spring means has also suflici-ent loading, when released, to drive the whole capsule forward to contact the body of the user positioned at the forward end of the syringe, and thereby to increase the loading of the secondary spring. Thus in operation, the capsule can acquire a considerable momentum before it strikes the skin, which facilitates the injection of the needle.

By a feature of the invention the device is rendered even safer, particularly when used by people suffering a state of partial mental or physical collapse.

According to this feature of the invention, the syringe uses a collapsible capsule having a non-collapsible tubular rear end portion which is driven by the main spring means and a member positioned in the entrance to the said rear end portion and which bears on the head end of the needle to hold it away from the rear end of the capsule, the member being displaceable by the head of the needle if the needle is subjected to a given resistance to its travel on contacting a solid obstacle, so that if the rear end portion of the capsula continues to be driven forward by the main spring means the member is displaced into the rear end portion and the point of the needle is not driven into the obstacle.

According to a further feature of the invention the displaceable member inside the capsule is a cup-shaped plunger having a fluted wall Whose maximum outside diameter is just greater than the bore of the non-collapsible rear end portion of the capsule, whereby when the cupshaped plunger is subjected to a given force the fluted wall buckles inwards and the member may be driven into the rear end portion.

According to another feature of the invention, the said main spring means and the release mechanism comprise a compression spring, a main plunger having a sleeve part located within the casing and having a recess, a detent body integral with the casing and having a detent which can engage in the recess in the plunger, a member having a push button projecting from the rear end of the casing and a shaft within the casing for holding the detent in engagement with its recess in the plunger, the shaft having a recessed portion which can be aligned with the detent when the push button is pressed whereby the detent can move out of engagement with its recess and the plunger and main compression spring released.

According to yet another feature of the invention the casing is detachable into two parts, a rear part housing the main spring and the release mechanism and a forward part housing the capsule and the secondary spring, so that after use of the syringe the casing may be so detached and the main spring reloaded and the spent capsule replaced with a new one.

One construction of a hypodermic syringe in accordance with the invention will now be described with reference to the accompanying drawings of which:

FIGURE 1 is a sectional elevation of a syringe as loaded with a liquid filled capsule prior-to-use;

FIGURE 2 is a sectional elevation of the syringe at a particular moment during operation;

FIGURE 3 is an outline and part-sectional elevation of the syringe showing its configuration after use; and

FIGURE 4 is a sectional elevation of a liquid-containing capsule.

As shown in FIGURE 1, the syringe has a casing which is detachable into two parts, a forward housing 1 and a rear housing 2, having bores 3 and 4 in each respectively. The bore 3 has opposing steps 5 and 6 located respectively further from and nearer to the joint in the housings 1 and 2, and the bore 4 has a step 7 at its forward end.

A tubular capsule carriage 8 has an external flange 9 at one end and an internal flange at the other, and is arranged within the forward housing 1 with the flange 9 resting on the step 6 so that the remainder of the carriage 8 is forward of the flange 9. A secondary spring 11 is housed in an annular space between the capsule carriage 8 and the bore 3 between the step 5 and the flange 9. The length of the carriage 8 is such that the free end of the forward housing 1 extends beyong the flange 10 in the position described. The capsula carriage 8 is thus movable away from the step 6 and against the spring 11. A capsule 12, with a pot 13 sealed onto one end to form a non-collapsible rear end portion of the capsule, is located within the capsule carriage 8 with its forward end resting on the flange 10.

A tubular main carriage 14 has an internal flange 15 at its forward end and an external flange 16 having detent holes 17 at the other. The external diameter of its body is such that it will travel within the capsule carriage 8 while its flange 16 is arranged to travel within the bore 4 of the rear housing 2 and the flange 15 passes over the pot 13 and bears on to the end of the capsule 12. A tubular top hat-shaped plunger 18 inside the main carriage 14 also fits over the pot 13 with its external flange resting on the internal face of the flange 15. A main spring 19 is located within the carriage 14 and has one end bearing on the external flange of the plunger 18 and the other on the face of a detent body 20 fixed at the rear end of the rear housing 2. The initial loadings and the rates of the two springs 11 and 19 are such that the loading of the main spring 19 will decrease during use to equal the consequential loading of the secondary spring 11 before the capsule 12 is fully collapsed. The initial loading of the main spring 11 must be suflicient to rapidy move the capsule 12 forward to the skin, increasing the loading of the secondary spring 11 at the same time, and partially collapse the capsule. The final equilibrium position of the two springs is that shown in FIGURE 3.

The detent body 20 has an axial bore 21 and its external shape also forms an annular space, within the rear housing 2, in which may travel the external flange 16 of the main carriage 14, and which is connected to the bore 21 by detent holes 22 corresponding to the holes 17 in the flange 16 so that the added length of a hole 17 and 22 is less than or equal to their diameter. A push button 23 extending into the detent body 20 has a spindle 24 with an annular recess 25 whose depth is equal to or greater than the thickness of the flange 16 of the main carriage 14. A seating 26 is attached to the spindle 24 where it protrudes through the detent body 20 into the rear housing 2. A release spring 27 is provided, housed within the main spring 19 and having its ends bearing on the seating 26 and the end of the plunger 18.

The spindle 24 slides within the bore 21 of the detent body 20, and the function of the release spring 27 is to retain the push button 23 in a loaded position prior-to-use with the button protruding rearwards from the detent body 20 and the rear housing 2, and with the spindle 24 opposite and covering the detent holes 22. The recess 25, being between the spindle 24 and the button 23, also protrudes from the end of the detent body 20. Balls 28 of diameter just less than or equal to the added length of the holes 17 and 22 are held in the added holes 17 and 22 by the bore 4 and the spindle 24. Thus the balls 28, backed by the spindle 24, hold the main carriage 14 and hence the main spring 19 in the compressed position. A protective cap 29, retained by a recess between the detent body 20 and the rear housing 2, serves to prevent accidental firing of the syringe as a result of knocks etc.

The collapsible construction of the capsule 12 is more clearly shown in FIGURE 4, which also shows the pot 13 sealed on to the rear end of the capsule. A cup-shaped member 30 is lodged in the mouth of the pot 13 and has an longitudinally fluted wall 31 the maximum outside diameter of which is just greater than the bore of the pot 13. The flutes are constructed so that on application of a given force to the member 30 by the needle, the wall 31 is deformed and the member is driven into the pot 13. The well formed in the member 30 by the walls 31 communicates with the interior of the pot 13 by a hole 32. The head of a hollow needle 33 rests in the well in the member 30 and is retained in a position along the axis of the capsule 12 with its point resting against the forward face of the capsule by a retaining ring 34. The cylindrically corrugated wall of the capsule 12 is made of tin.

The capsule is almost filled with a solution, leaving only the well of the member 30 around the head of the needle 33 and the interior of the pot 13 containing air. Liquid solution being incompressible, the presence of some air allows the commencement of capsule collapse, and the penetration of the needle 33 into the skin before ejection of the solution and the continuation of solution ejection after the capsule 12 has been fully collapsed. The capsule unit is thus self-contained and it can be supplied as a refill to the syringe, with its contents sterilised. The capsule fits into the syringe in the position shown in FIGURE 1 with a rubber pad 35 acting as a locating cushion between the forward end of the capsule and the internal surface of the flange of the capsule carriage 8. The pad 35 also protrudes through the flange 10 to rest on the skin during firing.

When the syringe is required for use the protective cap 29 is removed and the syringe is held, thumb over the button 23 with the forward end against a fleshy part of the body. The button is pressed so as to bring the recess 25 opposite the detent holes 22 in the detent body 20. The balls 28 are impelled to the recess 25 and the main carriage 14 moves rapidly forward by the expansion of the main spring 19 acting on the external flange of the plunger 18. The capsule 12 together With its liquid contents is arranged in its initial state to be stiffer than the comparatively unloaded secondary spring 11, and because of this and the inertia of the system the expansion of the main spring 19 moves the capsule 12 and the capsule carriage 8 with the main carriage 14, compressing the spring 11, until the pad 35 contacts the skin. Normally, by this time capsule 12 has started to collapse and the needle 33 has pierced the end wall, because of relative inertia and the loading of the secondary spring 11, further movement of the forward end of the capsule 12 is then prevented, and the capsule 12 continues to collapse under the force of the main spring 19 and the point of the needle 33 pierces the rubber pad 35 and enters the skin. The disposition of the injector parts is now as shown in FIGURE 2. The injection of solution commences and continues as the main spring 19 continues to expand and the capsule 12 is further collapsed and the needle 33 drive deeper into the flesh. The main spring 19 overshoots the equilibrium position of the two opposing springs 11 and 19 and through the reaction of the secondary spring 11, acting through the carriage 8, the spring-capsule system reciprocates rapidly causing slight withdrawals of the needle as the two opposing springs act in consort to complete the collapse of the capsule. The rearward movement of the forward end of the capsule caused by the secondary spring limits the maximum penetration of the needle. The final disposition of the injector parts is then as shown in FIG- URE 3. The final discharge of liquid is aided by expansion of the small volume of air in the capsule initially compressed by the commencement of the capsules collapse, and the withdrawal of the needle prevents the needle from being blocked by gristle facia.

If the syringe is inadvertently used at a part of the body where the penetrating depth of the needle is greater than the depth of the flesh, and the needle is caused to strike a bone, the sudden loading on the needle is transmitted to the cup-shaped member 30, whose wall 31 then buckles and allows the pot 13, driven by the main spring 19, to ride over the member without causing any further force to be applied to the needle. The injection of solution will, however, continue.

The syringe may be reloaded with a fresh capsule after use by detaching the forward housing 1 from the rear housing 2 and pushing the collapsed capsule 12 rearwards from its carriage 8. The main carriage 14 is pushed into the rear housing 2 to compress the springs 19 and 27 so that when detent holes 17 and 22 are again opposite each other as in FIGURE 1 the release spring 27 will force the button 23 outwards. This causes the balls 28 to leave the recess 25 and move into the combined holes 17 and 22 and grip the main carriage 14 in the prior-to-use position by means of the spindle 24. The cap 29 is then replaced over the button 23. A new capsule 12 with pad 35 fitted is dropped into the carriage 8 of the housing 1 and the two housings 1 and 2 are again joined. The syringe is then loaded, ready for use, as shown in FIGURE 1.

A particular syringe as illustrated in the drawings and described above has the following specification. It is 4.72" long, and uses a tin-walled capsule 1.897" long. The capsule has a non-collapsible pot just under /2" in length and its collapsible portion collapses to just under /2 in length. Its main spring 19 is 3.94" in free length, has an initial loading of 18.7 lbs. and a rate of 9 lb./in., while the secondary spring 11 is 1.95" in free length, has an initial loading of 8.55 lbs, and a rate of 14 A lb./in. The resulting maximum penetration of the needle is limited to approximately /4".

We claim:

1. A hypodermic syringe for making injections in the body of a user, comprises a syringe casing, a liquid-containing sealed collapsible capsule having a puncturable forward end and which is housed in a forward end of the casing, main spring means located in the casing behind the capsule and acting on a rearward end of the capsule, a release mechanism in the casing for retaining the main spring until it is released, a hypodermic needle through which liquid can pass and which prior to use is disposed through almost the full length of the interior of the capsule with its point directed to the forward end of the cap sule, a secondary spring set between the casing and the forward end of the capsule so as to be able to urge the forward end of the capsule in a rearward direction, the main spring means having sufficient power and throw, when released, to drive the rearward end of the capsule forward against the reaction of the secondary spring and to compress and partially collapse the capsule and inject the needle and some liquid therethrough into the body of the user, and the secondary spring being sufficiently powerful to thereupon drive the forward end of the capsule rearward against the action of said main spring means until the collapse of the capsule is completed.

2. A hypodermic syringe for making injections in the body of a user, comprises a syringe casing, a liquid-containing sealed collapsible capsule having a puncturable forward end and which is housed in a forward end of the casing with its forward end behind the forward end of the casing, main spring means located in the casing behind the capsule acting on a rearward end of the capsule, a release mechanism in the casing for retaining the main spring until it is released, a hypodermic needle through which liquid can pass and which prior to use is disposed through almost the full length of the interior of the capsule with its point directed to the forward end of the capsule, a secondary spring set between the casing and the forward end of the capsule so as to be able to urge the forward end of the capsule in a rearward direction, the main spring means having sulficient power and throw,

when released, to drive the whole capsule forward whilst increasing the loading of the secondary spring, and to continue to drive the rearward end of the capsule forward against the reaction of the secondary spring, compressing and collapsing the capsule while injecting the needle and some liquid therethrough into the body of the user, the secondary spring being sufficiently powerful to thereupon drive the forward end of the capsule rearward against the action of said main spring means until the collapse of the capsule is completed.

3. A hypodermic syringe according to claim 2 and whose capsule has a non-collapsible tubular rear end portion which is driven by the main spring means and a member positioned in the entrance to the said rear end portion and which bears on the head end of the needle to hold it away from the rear end of the capsule, the member being displaceable by the head of the needle if the needle is subjected to a given resistance to its travel on contacting a solid obstacle, so that if the rear end portion of the capsule continues to be driven forward by the main spring means the member is displaced into the rear end portion and the point of the needle is not driven into the obstacle.

4. A hypodermic syringe according to claim 3 and wherein the displaceable member inside the capsule is a cup-shaped plunger having a fluted wall whose maximum outside diameter is just greater than the bore of the noncollapsible rear end portion of the capsule, whereby when the cup-shaped plunger is subjected to a given force the fluted wall buckles inwards and the member may be driven into the rear end portion.

5. A hypodermic syringe according to claim 2, wherein the said main spring means and the release mechanism comprise a compression spring, a main plunger having a sleeve part located within the casing and having a recess, a detent body integral with the casing and having a detent which can engage in a recess in the plunger, a member having a push button projecting from the rear end of the casing and a shaft within the casing for holding the detent in engagement with its recess in the plunger, the shaft having a recessed portion which can be aligned with the detent when the push button is pressed whereby the detent can move out of engagement with its recess and the plunger and main compression spring released.

6. A hypodermic syringe according to claim 2 and wherein the casing is detachable into two parts, a rear part housing the main spring and the release mechanism and a forward part housing the capsule and the secondary spring, so that after use of the syringe the casing may be so detached and the main spring reloaded and the spent capsule replaced with a new one.

References Cited UNITED STATES PATENTS 2,752,918 7/1956 Uytenbogaart 128-218.2

FOREIGN PATENTS 915,262 1/1963 Great Britain. 964,585 7/ 1964 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

W. E. KAMM, Assistant Examiner.

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