JPH11319091A - Manufacture of hypodermic syringe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hypodermic syringe which remarkably holds back production costs and moreover, achieves excellent safety. SOLUTION: This method is to manufacture a hypodermic syringe for injecting vaccine liquors or the like which includes a housing, a plunger assembly slidably supported by the housing, a hollow needle drawn from the housing and a needle cover covering the needle and the needle between injection processes is supported by the plunger assembly while being pulled into the housing. In this case, there are a process wherein at least two housing member pieces 1a and 1b composing the housing and the needle cover 4 composing the housing is connected together by a hinge 41, a process wherein the plunger assembly integrated with the hollow needle is fitted into the housing member pieces 1a and 1b so that the hollow needle is housed into the needle cover 4 and a process of joining the housing member pieces 1a and 1b and the needle cover 4 together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a hypodermic syringe, and more particularly to a method of manufacturing a hypodermic syringe having a retractable needle.

[0002]

BACKGROUND OF THE INVENTION As is well known, following international interest in the spread of AIDS virus, it has been recognized that one major form of transmission of this virus is through contact with or use of syringes contaminated with AIDS virus. Have been.

[0003] In a conventional hypodermic syringe,
The needle remains exposed after use of the syringe. Therefore,
After the syringe has been used, it may be accidentally punctured by the needle. As a result, if the patient is a carrier of AIDS virus, infection by AIDS virus may occur. Also, disposal of used syringes is a dangerous operation because the exposed needle and any one of the syringes can be contaminated with disease.

Another disadvantage of conventional hypodermic syringes is that the syringes are easily reused. For intravenous drug addicts, a single syringe is often shared by many. This significantly increases the chance of becoming infected with AIDS virus. If one of those people is a carrier of AIDS virus, this syringe will infect other people with the virus.

[0005] Syringes have been developed in which the needle is retracted after the syringe has been used. One example of such a syringe is, for example, Australian Patent Application 1308
No. 8/88. This leading syringe is in much the same manner as a conventional syringe having a hollow needle extending from one end of a cylindrical housing and a plunger assembly extending from the other end of the housing to displace a piston supported within the housing. It is configured. A means is provided on the piston for engaging one end of the needle at the end of the injection process. The needle is then withdrawn by withdrawing the piston through the housing. Alternatively, the needle is supported by one means that allows it to be retracted after the injection process.

By the way, in the above-mentioned prior art, the needle remains exposed at the end of the injection until the retracting means is operated. Thus, there is still the possibility of accidental contact with the needle immediately after the syringe has been used. Also, because the plunger assembly must be retracted after the injection, or the needle support must be actuated to retract the needle, the user neglected or retracts the needle. There may not be enough time, so the needle remains exposed after use of the syringe, thereby negating the benefit of the retraction means.

[0007] Thus, the present inventor has proposed a highly safe hypodermic syringe which can be retracted during the injection stroke of the syringe in order to minimize the possibility of accidental contact with the needle first. (PCT / AU90 / 0029)
5). This hypodermic syringe mainly includes a piston shaft, a piston head, a cylinder, a luer lock fitting, a needle, and a needle cover.
This hypodermic syringe is pre-filled with the drug so that it can be used immediately when it arrives at hand.At the time of use, twist the needle cover at the tip and remove it, and at this point it is ready to inoculate the patient. The feature is that safety is considered so that the needle is not accommodated in the main body and goes out.

[0008]

However, in the case of this improved type of hypodermic syringe, there is a problem that the cost is increased due to the large number of parts. The present invention has been made in view of such circumstances, and at least two housing member pieces constituting a housing and a needle cover are joined by a hinge, and a plunger assembly integrated with a needle is provided in the housing member piece. The needle is inserted into the needle cover so that it is stored in the needle cover, and each housing member and the needle cover are joined so that the needle is stored in the needle cover. An object of the present invention is to provide a method for manufacturing a syringe.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a housing, a plunger assembly slidably supported by the housing, a hollow needle contained within and extending from the housing, and a needle. Comprising a needle cover for injecting an inoculant liquid, wherein the needle is supported by the plunger assembly and retracts into the housing during an injection stroke. Hinge connecting the at least two housing member pieces and the needle cover to each other, and fitting a plunger assembly integrated with the needle into the housing member piece so that the needle is housed in the needle cover; Joining the housing member pieces and the needle cover to each other.

[0010] In the present invention, it is preferable that the joining between each housing member piece and the needle cover is performed by, for example, ultrasonic welding of a contact portion of both. In the present invention, it is preferable to have safety means for capturing the needle in the housing after the completion of the injection stroke. Wherein the plunger assembly has an elongate shaft having a piston at one end thereof, the needle extending from its opposite end and communicating with a longitudinal shaft passage completely passing through the shaft and the piston. It is preferable to have a passage.

The housing is preferably an elongated body portion having a cylindrical chamber therein for slidably supporting the piston, and an elongated safety shroud portion for accommodating the needle therein. And a room.

The safety means referred to above comprises a shoulder adjacent to the needle hole and provided in the needle chamber, which complements the tip of the needle when the needle is retracted from outside into the needle chamber. When the needle is not constrained in the needle cover, it deviates from the linear alignment with the needle chamber. The longitudinal axis of the needle is deflected at an angle from the longitudinal axis of the shaft when the needle is unconstrained.

[0013] The safety means further or alternatively has a nullification chamber in the body portion at the end of the housing. The nullification chamber is adjacent to the cylindrical chamber to receive a piston after the injection is completed. Also, a displaceable diaphragm is located at or adjacent the junction of the cylindrical chamber and the nullification chamber to separate and seal the nullification chamber from the cylindrical chamber. The diaphragm,
As the piston enters the nullification chamber, it is displaced by the piston. That is, the protruding piston portion of the inclined end surface of the piston pushes the diaphragm, and pushes the diaphragm into the invalidation chamber.

In the present invention, a needle cover is formed integral with and detachable from the distal end of the safety shroud portion, the distal end having a frangible embrittlement adjacent to the needle cap, whereby the needle is closed. The cover is twisted away from the tip to expose the needle portion secured therein.

In the present invention, the plunger assembly preferably has at least one handle member (trigger) extending laterally from the axis at or adjacent to an opposite end thereof, and has an elongated elongate shape. A directional slot is provided in the housing, thereby allowing the or each handle member to extend outwardly from the housing. A peripheral wall preferably extends along at least a substantial portion of the periphery of the or each longitudinal slot.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) Reference is made to FIGS. 1A, 1B and 2. FIG.
Here, FIG. 1A is a longitudinal sectional view of the hypodermic syringe according to the first embodiment, and FIG. 1B is a sectional view taken along line XX of FIG. 1A and in which the hollow needle is retracted. , FIG. 2 shows FIG. 1 (A),
The exploded view of the hypodermic syringe of (B) is shown. However, FIG.
(A) and (B) illustrate the hypodermic syringe as being supplied prior to use with the hollow needle retracted within the housing. It is also conceivable that the hypodermic syringe is supplied with the hollow needle protruding and the syringe pre-loaded with the inoculum liquid.

The hypodermic syringe includes a housing 1 and a plunger assembly 2 slidably supported within the housing.
And a hypodermic or hollow needle 3 integral with and extending from the plunger assembly 2 and a needle cover 4. A hollow needle 3 is integrally attached to the plunger assembly 2. Therefore, the plunger assembly 2 and the hollow needle 3 are
Move together as a single assembly. At the tip of the needle cover 4, silicone sealing is adhered to keep hygiene in the sealed cylinder so that unnecessary things are not mixed.

The housing 1 is elongated and has a body portion 6 defining an elongated chamber 5 therein. The cross section of the room 5 is circular to define a cylindrical room. A safety shroud 7 extends from one end of the body portion 6.
The safety shroud 7 has a needle chamber 8 for accommodating the hollow needle 3 therein. The chamber 5 and the needle chamber 8 communicate to form a single continuous chamber for receiving the plunger assembly 2 integrated with the hollow needle 3. The safety shroud 7 and the body part 6 are connected to each other to form the elongate housing 1 of the syringe. The body part 6
Being substantially cylindrical, the safety shroud 7 is tapered to define the distal end of the housing 1.
The hollow needle 3 usually protrudes from the safety shroud 7, and the protruding portion is protected by a needle cover 4 integral with the safety shroud 7.

The plunger assembly 2 has a piston head 9 at one end and a plunger arm 11 made of, for example, magnesium, which is partially a trigger 10 at the other end.
The plunger arm 11 has a rubber piston 12 mounted on the head 9. The plunger assembly 2 has a hollow needle 3 mechanically caulked along its longitudinal direction. This portion can be formed by using a UV-actuated adhesive and fixing the hollow needle even with a plastic material. For example, a V-shaped notch 9a is provided at the end edge of the piston head 9, and a convex portion 12a is provided on the peripheral surface of the piston 12 on the side where the hollow needle 3 is located. 12a is fitted in the notch 9a. This prevents the plunger assembly 2 from rotating when using the syringe. The main surface of the piston 12 opposite to the hollow needle 3 is inclined so that a diaphragm described later can be pushed after the use of the syringe. Further, a hole (not shown) for passing the hollow needle 3 is formed in the center of the piston 12.

Preferably, the longitudinal axis of the plunger arm 11 is at least substantially parallel to the longitudinal axis of the housing 1 when the plunger assembly 2 is supported by the housing 1. These longitudinal axes can also be virtually aligned. The hollow needle 3 preferably projects from said opposite end of the plunger arm 11. Both longitudinal axes of the hollow needle 3 and the plunger arm 11 are
When the syringe is used, it is at least substantially aligned. In the case of this embodiment, the longitudinal axis of the hollow needle 3 is
For example, 1 relative to the longitudinal axis of the plunger arm 11
° has been deflected. The hollow needle 3 has a longitudinally extending needle passage completely therethrough to allow the passage of the inoculum liquid.

The trigger 10 has at least one member extending from the plunger arm 11 at least substantially transversely with respect to its longitudinal axis. Preferably,
Two such triggers 10 are provided to extend laterally from plunger arm 11 in opposite directions. Each trigger 10 is, for example, a simple lateral arm, or has a curved and flattened shape to form a finger support as shown in the drawings.

The wall of the safety shroud 7 has a trigger 10
A longitudinal slot 13 is provided for each trigger 10 to allow the wings to extend outwardly from the housing 1. This allows the longitudinal displacement of the plunger assembly 2 and the hollow needle 3 to be controlled from outside the housing 1.
The length of the slot 13 is such that the hollow needle 3 is maximally protruded or maximally retracted and the trigger 10 preferably abuts the peripheral edge of the slot 13 in either of the two needle positions Is enough to forgive. The trigger 10 is formed of a high-strength, low-weight material such as magnesium metal in order to guarantee sufficient strength, but is not limited thereto, and may be a resin or the like.

The piston 12 is slidably housed within the elongated chamber 5 and in sealing contact with the wall of the chamber 5. The piston 12 has a piston face 14 that extends at least substantially laterally with respect to the longitudinal axis of the plunger arm 11. Body part 6 with said elongated room 5
A ring-shaped groove is formed in the inner wall at the end of the main body 6, and a diaphragm 15 which forms a liquid storage chamber together with a part of the main body 6 and the piston 12 is provided in the groove. Here, members that come into contact with the inoculum liquid, such as the diaphragm 15 and the piston 12, are those approved by the Food and Drug Administration. The medicine is covered with a cap 17 which forms a nullification chamber 16 together with a part of the main body 6 and the diaphragm 15.

When the hollow needle 3 is completely retracted, it is accommodated in the needle chamber 8 of the safety shroud 7. The hollow needle 3 is stretched by pulling the trigger 10 toward the opposite side (rear end side) of the hollow needle 3. The forward movement of the plunger assembly 2 displaces the piston 12 away from the diaphragm 15, thereby reducing the volume of the liquid holding space 20 in the liquid receiving chamber. To retract the hollow needle 3, the trigger 10 is displaced away from the tip of the safety shroud 7, retracts the hollow needle 3 back into the safety shroud 7, and moves the piston 12 to the diaphragm 15.
Displace toward.

The tip of the hollow needle 3 is initially accommodated in the needle cover 4 and is accommodated in the safety shroud 7 after use.
In this embodiment, for example, the needle cover 4 is formed integrally with the safety shroud 7. The needle cover 4 can be easily separated from the safety shroud 7 by twisting. Such a configuration helps to prevent the hollow needle 3 from becoming contaminated prior to the actual use of the syringe. In addition, it visually indicates that the syringe has been used or otherwise tampered with.

After the tip of the hollow needle 3 is exposed by removing the needle cover 4, the trigger 10 is pulled to the opposite side of the hollow needle 3 so that the inoculum liquid in the liquid storage chamber passes through the passage of the hollow needle 3. Injected into the affected area of the patient. As the hollow needle 3 is further extended from the housing 1, the volume of the liquid storage chamber in the syringe decreases.

Next, the liquid is injected by displacing the housing 1 towards the penetration point of the hollow needle 3. This is accomplished with one hand by engaging one or more fingers with a trigger 10 extending from the housing 1 and placing a palm or thumb on the rear end of the housing 1. By pushing the rear end of the housing 1 with the palm or thumb in the direction of the trigger 10, the volume of the liquid receiving chamber is reduced, thereby forcing the liquid through the hollow needle 3 into the injection area. During the injection stroke, the hollow needle 3 is retracted systemically and returns into the housing 1.

At the front end of the needle chamber 8, the hollow needle 3 is completely retracted into the housing 1 at the end of the injection and in order to prevent or make it difficult for the syringe to be reused,
A shoulder 19 is provided as a safety measure. The needle tip is captured by the shoulder 19 when the hollow needle 3 is completely retracted into the needle chamber 8. The hollow needle 3 is slightly offset from the axial direction of the plunger arm 11 to facilitate the capture of the needle tip 3.

The hollow needle 3 has an "offset bias".
, Whereby the longitudinal axis of the hollow needle 3 is constantly deviated at a specific angle from the longitudinal axis of the shaft when the hollow needle 3 is unconstrained. The bias angle is, for example, 1.
0 degrees. When the plunger assembly 2 is supported inside the cylindrical chamber 5, the longitudinal axis of the shaft is parallel and aligned with the longitudinal axis of the needle chamber 8 before or during use of the syringe. Is done. Accordingly, the hollow needle 3 is biased against the offset bias, so that spring tension is maintained in the hollow needle 3 before and during use of the syringe.

If the hollow needle 3 returns into the completely retracted needle chamber 8, the hollow needle 3 no longer leaves the needle chamber 8. Due to the offset bias, the hollow needle 3 realigns away from the longitudinal axis of the needle cover 4 and the needle tip disengages from the linear alignment with the needle cover 4 and is captured in the needle chamber 8 behind the shoulder 19. Is done. If an attempt is made to extend the hollow needle 3 again, the needle
Engage with 19 to prevent the extension of the hollow needle 3.

Another safety measure is provided to prevent or make it difficult for a person using the syringe to intentionally leave a small part of the hollow needle 3 out after injection and to enable the syringe to be reused. Have been. This safety means is a nullification chamber 25 provided at the end of the main body 6. The nullification chamber 16 is cylindrical and communicates with the cylindrical chamber 5 and has a longitudinal axis aligned with the longitudinal axis of the main cylindrical chamber 5. Accordingly, a substantially annular shoulder (or wall) 20 is provided between the cylindrical chamber 5 and the nullification chamber 16. The end of the housing 1 is sealed by a cap 21, thereby closing off the open end of the nullification chamber 16.

The diaphragm 15 abuts or adjoins an annular shoulder 20 to separate and seal the nullification chamber 16 from the cylindrical chamber 5. In the present embodiment, the diaphragm 15 is
It is tightly fitted in the invalidation chamber 16 in the position as shown. Peripheral edge of diaphragm 15 and invalidation chamber 16
The frictional force between the wall and the wall secures the diaphragm 15 in place. Although not shown, a shallow undercut may be provided in the wall of the invalidation chamber 16 so that the periphery of the diaphragm 15 is accommodated therein.

The piston 12 has a peripheral wall 22 which sealingly engages the wall of the cylindrical chamber 5 when a syringe is used. The peripheral wall 22 is chamfered to define a frustoconical wall. The diameter of the piston 12 preferably increases gradually towards the piston face. Preferably, at least the peripheral wall 22 of the piston 12 is resilient so that when the piston 12 is supported in the cylindrical chamber 5 it is compressed to maintain a sealing engagement. In this embodiment, the peripheral wall 22 has an annular groove for receiving an independent sealing means such as an O-ring to maintain the piston 12 in a sealing engagement with the cylindrical chamber 4.

Prior to use of the syringe, the needle tip of which is initially protected in the needle cover 4, the piston 12 is located at a distance from the diaphragm 15, as shown in FIG. In the configuration in which the diaphragm 15 is supported by the elastic means,
The piston 12 at least partially pushes the diaphragm 15 into the invalidation chamber 16. Then, as the hollow needle 3 is extended, the piston 12 retreats from the cylindrical chamber 5.

During the injection stroke, the piston 12 has a diaphragm
Retreat toward 15. At the end of the injection stroke, as shown in FIG. 4, the piston 12 pushes the diaphragm 15 to displace it. When the diaphragm 15 is shown and fitted in the invalidation chamber 16, the piston surface 14 of the diaphragm 15 is inclined to assist in detachment of the diaphragm 15. This inclined portion pushes up the diaphragm 15, and the diaphragm 15 is released. The end of the injection is clearly felt because of the reduced resistance to movement of the trigger 10 felt by the user as the diaphragm 15 is displaced. Displacement of the diaphragm 15 causes a loss of compressive force in the cylindrical chamber 5 and a loss of function of the syringe. Further, as the piston 12 enters the nullification chamber 16, the hollow needle 3
Is completely retracted from the outside into the needle chamber 8 and the hollow needle 3 is
To catch behind.

The chamfered peripheral wall 22 also serves as the nullification chamber 16
Help guide the piston 12 inside. This is piston 12
As it reaches the annular shoulder 20, the nullification chamber of the piston 12
This is because the expansion of 16 and the shape of the chamfered peripheral wall 22 of piston 12 cause piston 12 to "pull" into nullification chamber 16. This rearward pulling effect further ensures that it is difficult to prevent the hollow needle 3 from being completely retracted after use of the syringe.

The hypodermic syringe having the above-described configuration is manufactured as follows. That is, first, as shown in FIG. 5, the two housing member pieces 1a and 1b that constitute the housing 1 and the needle cover 4 are joined together by a hinge (hinge) 41 by a molding method to be integrated. . Next, the plunger assembly 2 integrated with the hollow needle 3 and having the piston 12 attached to one end thereof is moved while the needle cover 4 is moved so that the hollow needle 3 is housed in the needle cover 4. 1a. Then, each housing member piece 1
a, 1b and the needle cover 4 were joined by ultrasonic welding of their joints. Subsequently, a predetermined amount of the inoculant liquid was filled into a cylindrical portion formed by a part of the main body 6 of the housing 1 and a part of the piston 12. Further, after the diaphragm 15 was disposed at a predetermined position of the cylinder main body 6, a cap 17 was mounted on the end of the main body 6 to form a nullification chamber 16, thereby producing a hypodermic syringe.

The hypodermic syringe of the above configuration is used in the following manner. 1) The syringe is supplied with the hollow needle 3 enclosed in a needle cover 4 and a safety shroud 7 to prevent contact of the hollow needle 3 and thus contamination. In addition, a required amount of the inoculant medicinal solution is filled in advance in the liquid storage chamber constituted by the wall of the elongated room 5, the piston and the diaphragm 15.

2) First, the needle cover 4 is threaded and cut off from the safety shroud 7 to expose the needle tip. Needle cover 4
The removal of also indicates that the syringe has not been used or tampered with yet.

3) Next, after inserting the hollow needle 3 into the affected part of the patient, the trigger 14 is moved toward the opposite side of the hollow needle 3 from the needle tip, so that the inoculum main liquid in the liquid storage chamber is hollow. It is injected into the affected part through the needle passage of the needle 3.

4) As the inoculation of the patient progresses,
At the end of the injection movement, the safety shroud 8 advances along the hollow needle 3 to a position where the tip of the safety shroud 7 contacts the skin of the patient. Since the diaphragm 15 must be displaced, a distinct resistance is felt at the end of the injection insertion stroke, thereby informing the user that the dose has been administered.

5) By continuing the compression stroke, the syringe is destroyed when the aforementioned resistance is felt, thus rendering the syringe useless and secure. Since the hollow needle 3 is completely retracted into the safety shroud 7 and completely shielded as it leaves the patient's skin, there is no means to contact the hollow needle 3.

6) The two housing member pieces 1a, 1b and the needle cover 4 are joined by a hinge 41 to be integrated, and then integrated with the hollow needle 3 and the piston 12 is attached to one end of the plunger assembly. 2 is fitted into the housing member 1a so that the hollow needle 3 is housed in the needle cover 4, and the housing members 1a, 1b and the needle cover 23 are joined by ultrasonic welding of their joints. Since it is manufactured, assembling can be remarkably facilitated and cost can be reduced as compared with a conventional hypodermic syringe composed of many parts.

7) After filling the liquid containing chamber with the liquid to be inoculated from the rear of the cylinder without closing the cap 17, it is necessary to inhale the medicine as in the prior art in order to cap the cap 17 on the rear end of the housing. And can be filled quickly in large quantities.

8) Since the plunger arm 11 is formed of magnesium, a) it is possible to produce with a short cycle time in the die casting process, and b) the needle is quickly fastened by a mechanical caulking method without a special adhesive. It has the advantages that it can be fixed, c) thin and strong parts can be made with minimum raw materials, and d) it can be amortized after use.

[0046]

As described above in detail, according to the present invention, at least two housing member pieces constituting a housing and a needle cover are joined by a hinge, and the plunger assembly integrated with the needle is provided. By fitting into the housing member pieces and joining the housing member pieces and the needle cover so that the needles are housed in the needle cover, it is possible to provide a hypodermic syringe excellent in safety while significantly reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a hypodermic syringe according to one embodiment of the present invention.

FIG. 2 is an explanatory view of a plunger assembly in which a hollow needle is swaged.

FIG. 3 is a perspective view for explaining a use state of the hypodermic syringe in FIG. 1;

FIG. 4 is a view for explaining a method of manufacturing the hypodermic syringe of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Plunger assembly, 3 ... Hollow needle, 4 ... Needle cover, 5 ... Slender room, 6 ... Body part, 7 ... Safety shroud, 8 ... Needle room, 12 ... Piston, 13 ... Trigger, 14 ... longitudinal slot, 15 ... diaphragm, 16 ... disable chamber, 17 ... cap.

Claims (11)

[Claims] 1. A housing comprising: a housing; a plunger assembly slidably supported by the housing; a hollow needle accommodated in the housing and extending from the housing; and a needle cover covering the needle. A method for manufacturing a hypodermic syringe for injection of an inoculant liquid, wherein the needle is supported by the plunger assembly and retracts into the housing during an injection stroke, at least two housing members constituting the housing Joining the piece and the needle cover with a hinge, fitting the plunger assembly integrated with the needle into the housing member piece so that the needle is housed in the needle cover, and removing each housing member piece and the needle cover. A method of manufacturing a hypodermic syringe. 2. The method for manufacturing a hypodermic syringe according to claim 1, wherein the joining of each of the housing member pieces and the needle cover is performed by ultrasonic welding of a contact portion between the two. 3. The method for manufacturing a hypodermic syringe according to claim 1, further comprising safety means for capturing the needle in the housing after completion of an injection process. 4. The plunger assembly has a plunger arm having a piston head at one end and a trigger portion at the other end, and a piston mounted on the head of the plunger arm. The method for producing a hypodermic syringe according to claim 1, wherein: 5. A needle chamber, wherein said housing is an elongated body portion and slidably supports said piston, and an elongated safety shroud portion is a needle chamber for accommodating said needle inside a front end and inside. 5. The method for producing a hypodermic syringe according to claim 4, comprising: 6. The needle chamber has a shoulder that captures the tip of the needle when the needle is retracted into the needle chamber, and the needle is aligned with the needle chamber when not locked in the needle chamber. 6. The method for producing a hypodermic syringe according to claim 5, wherein the hypodermic syringe deviates from the alignment relationship. 7. The method of manufacturing a hypodermic syringe according to claim 6, wherein the longitudinal axis of the needle is deflected at an angle from the longitudinal axis of the shaft when the needle is unconstrained. . 8. The safety means having a nullification chamber in the body portion at the end of the housing, the nullification chamber being adjacent to the cylindrical chamber for receiving the piston after completion of an injection. The method for producing a hypodermic syringe according to any one of claims 5 to 7, wherein 9. A displaceable diaphragm is located at or adjacent to a junction between the cylindrical chamber and the nullification chamber to partition and seal the nullification chamber from the cylindrical chamber; 9. The method of claim 8, wherein the diaphragm is displaced by the piston as it enters the nullification chamber. 10. A piston having a projection on a needle-side end face thereof, an elongated shaft at one end of a plunger assembly having a piston head for fitting with the piston, and the projection of the piston being fitted into the head. 5. The method for manufacturing a hypodermic syringe according to claim 4, wherein a notch is provided. 11. The hypodermic syringe according to claim 4, wherein the end face of the piston opposite to the needle side is inclined, and the piston pushes up the diaphragm when the needle is pushed back. Method.