HK1184738B - Syringe assembly - Google Patents

Abstract

An injection device comprises a syringe extendible against a spring bias from a retracted position in a housing to a projecting injecting position. A spring biased plunger has collapsible elbows which, when the plunger is released, initially engage the end of the syringe to drive it to the projecting position, whereupon arresting of the syringe movement causes the elbows to collapse inside the syringe to allow the plunger to engage and drive the bung.when the projection is protruded from the projection part, the collapsible elbows is protruded outwardly from the slit, therefore the projection area is provided with a first circumference, which is larger than the circumference of the upper or the lower solid part. When the projection area is on a contraction position, the collapsible elbows can contract toward the inside of the slit, therefore the projection area is provided with a second circumference similar to the circumference of the upper and lower solid part.

Description

Syringe assembly

The present application is a divisional application filed based on a divisional application of PCT application having an application date of 2005-6-23, an application number of 200580020958.6, and an invention name of "improvement on automatic injection device" (application number 201010576413.6 filed on 2010-12-1, and an invention name of "improvement on automatic injection device").

The above-mentioned PCT application claims priority from the prior application GB0414054.7, the disclosure of which is incorporated herein by reference.

Background

There are many forms of automatic injection devices which, when operated, cause the needle of a syringe to move forwardly, thereby extending the needle from the guard housing, before the syringe is driven through the needle to express a dose of liquid. It is important to attempt to ensure that the syringe is moved bodily forward to expose the needle before pressurizing the contained liquid so that dripping from the needle does not occur before the actual injection occurs. It is an object of the present invention to provide a mechanism that operates in this desired manner.

Disclosure of Invention

According to the present invention there is provided an injection device for ejecting a dose of liquid from an injection needle at one end of a syringe located within a housing of the device, the syringe being movable by a plunger on release of a drive bias member at one end of the housing to move the syringe from a first position in which the needle is shielded by the housing to a second position in which the needle projects from the other end of the housing, the plunger being rod-shaped and having a flexible projection centrally located in a longitudinal direction, the flexible projection being located beyond the other end of the syringe prior to release of the drive bias member, such that primary motion (primaryovement) of the plunger under the bias of the drive bias member causes the projection to bear against the other end of the syringe to move the syringe from the first position to the second position, further movement of the syringe is then prevented, which causes the flexible portion to contract inwardly into the syringe, thereby allowing the plunger to move within the syringe by a secondary motion (second piston) into contact with and acting on the bung, thereby compressing the liquid within the syringe and causing the liquid to be expelled through the needle of the syringe.

With such an arrangement, the protrusion will remain in its protruding position (so as to move the syringe from the first position to the second position) until the force increases to an extent that allows the protrusion to collapse inwardly, whereby the piston can subsequently move within the syringe to cause liquid to be expressed through the syringe.

The projection may comprise one or more flexible elbows projecting beyond the normal outer circumference of the rod, but which may be compressed within the outer circumference. It may be in the form of two elbows defined either side of a longitudinal slot in the rod. The elbow may be pre-formed as a pair of arms at either side of the longitudinal slit between upper and lower solid portions (solidport) of the rod.

Preferably the injection device will include a return bias member (return bias member) acting between the syringe housing and the other end of the syringe to keep the syringe retracted within the housing until the drive bias member is released.

One or more of the biasing members disposed within the housing may be in the form of a coil spring.

Drawings

The invention may be carried into practice in a number of ways and a preferred embodiment thereof will now be described with reference to the accompanying drawings, in which:

figure 1 is a cross-sectional view through an injection device of the present invention prior to use; and

fig. 2 and 3 are similar views showing a subsequent stage of operation of the injection member.

Detailed Description

The injection device shown in the figures comprises a syringe 1 located within a protective housing 2. The syringe comprises 3, 3 incorporating a liquid formulation held in place by a plug (bung) 4 and having an injection needle 5 through which the liquid formulation can be ejected through the injection needle 5 by pressurising the plug 4. 3 have an enlarged head 6. The piston 7 is biased forwardly by a coil spring 8, however, the piston 7 is held in the locked position (fig. 1) until a trigger (trigger), shown schematically at 11, is actuated to release the piston and spring 8. Before use, the syringe 1 is held retracted within the housing 2 by the coiled spring 9.

It will be seen that the piston 7 is rod-shaped having a central portion defining a pair of projecting elbows 10. The pair of protruding elbows 10 may be pre-formed as part of the molded piston 7. The raised elbows 10 are flexible, which allows them to move inwardly, resulting in this portion of the rod having a similar circumference as the rest of the rod. It can be seen from figure 2 that when the piston is released and biased by the spring 8, the expanded region formed by the elbow 10 bears against the head 6 of the housing 3 and provides sufficient force to compress the spring 9 until the head 6 abuts the top of the housing 2 whereupon further movement of the housing 3 is prevented. The continued bias provided by spring 8 then causes elbow 10 to be compressed inwardly as elbow 10 enters the interior of 3. With the elbow 10 in the contracted state, the plunger can then move relatively easily within the 3 to act on the bung 4 and thereby cause the contents of the syringe to be ejected through the needle 5.

The illustrated construction of the piston 7 provides several technical advantages. It may be integrally molded. Moreover, the retracting movement of the protruding elbow provides a means to provide the appropriate injection force to drive the needle into the skin to the appropriate depth, while subsequently providing a relatively low resistance against the inner wall of the syringe container (syringeconjugate), so that the main thrust of the spring corresponding to the remainder of its stroke is applied to the bung 4. It will be appreciated that other contracting protrusion configurations may be used in place of the contracting elbows.

Claims (10)

1. An injector piston for an injector assembly of an injection device, the injector piston being rod-shaped and comprising:

the upper solid part is provided with a solid part,

a lower solid portion having a stopper operable to move a syringe of the syringe assembly and to transmit a discharge force to one end of the stopper, an

A central portion between upper and lower solid portions, the central portion having a raised area comprising two flexible elbows disposed centrally between the upper and lower solid portions of the piston and on either side of a single longitudinal slit aligned with a longitudinal centerline of the piston, wherein when the raised area is in a raised position the flexible elbows project outwardly from the longitudinal slit to enable inward collapse of the raised area of the piston, and when the raised area is in a collapsed position the flexible elbows contract inwardly toward the longitudinal slit to enable the raised area of the central portion to have a second perimeter length similar to the perimeter lengths of the upper and lower solid portions.

2. The syringe plunger of claim 1, wherein:

the raised area of the syringe piston is configured to drive the syringe from a first position relative to a housing of an injection device to a second position relative to the housing such that an injection needle of the syringe protrudes from the housing.

3. The syringe plunger of claim 1, wherein:

the raised area of the syringe piston is in a raised position prior to entry into the syringe and the raised area is in a retracted position within the syringe to apply an expulsion force to the stopper.

4. The syringe plunger of claim 1, wherein:

the syringe piston is integrally molded.

5. An automatic injection device comprising:

a housing;

a syringe connected at one end to an injection needle, the syringe being slidably mounted within the housing for movement between a first position relative to the housing in which the injection needle is shielded by the housing and a second position relative to the housing in which the injection needle projects from the housing;

a stopper slidably mounted in the syringe and movable to expel liquid through the injection needle; and

a rod-shaped piston, the rod-shaped piston comprising:

the upper solid part is provided with a solid part,

a lower solid portion having one end operable to move the plug and transfer the expulsion force to the plug, an

A central portion between the upper and lower solid portions, the central portion having a raised area comprising two flexible elbows disposed centrally between the upper and lower solid portions of the piston and on either side of a single longitudinal slit aligned with a longitudinal centerline of the piston, wherein when the raised area is in a raised position the flexible elbows project outwardly from the longitudinal slit to enable inward collapse of the raised area of the piston, and when the raised area is in a collapsed position the flexible elbows contract inwardly toward the longitudinal slit to enable the raised area of the piston to have a second perimeter length similar to the perimeter lengths of the upper and lower solid portions; and

a drive biasing member disposed at one end of the housing and operable to move the piston toward the other end of the housing.

6. The injection device of claim 5, wherein:

the raised area of the piston is configured to drive the syringe from a first position relative to the housing to a second position relative to the housing such that an injection needle of the syringe protrudes from the housing.

7. The injection device of claim 5, wherein:

the raised area of the piston is in a raised position prior to entry into a syringe and the raised area is in a retracted position within the syringe to apply an expulsion force to the stopper so as to compress a fluid within the syringe and cause the fluid to be expelled from the syringe.

8. The injection device of claim 5, further comprising:

a return biasing member acting between the other end of the syringe and the housing to retain the syringe in the first position relative to the housing until the drive biasing member is released.

9. The injection device of claim 5 or 8, wherein:

one or more biasing members disposed within the housing are in the form of coil springs.

10. The injection device of claim 5, wherein:

the piston is integrally molded.