Hypodermic Syringe With Radially Movable Blocking Elements

Abstract

A hypodermic syringe comprising a liquid container and a needle connected thereto at one end, which assembly is incorporated in a housing, the liquid container being bounded at the other end by a piston, and an operating mechanism being present to exert a force on the piston, one or more blocking elements being present for locking the operating mechanism or the piston against movement relative to the liquid container, the housing showing a diameter transition such that when the blocking elements pass along it, they are moved radially so that the blocking is removed and the piston penetrates into the liquid container so that the liquid flows out through the needle.

Description

The invention relates to a hypodermic syringe comprising an assembly of liquid container and a needle connected thereto at one end, which assembly is incorporated in an elongate housing so as to be movable, the other end being bounded by a piston fitting in said container, the housing being bounded on the side of the needle by a wall through which the needle can, but the liquid container cannot, pass, an operating mechanism being furthermore present to exert a force on the piston.

A hypodermic syringe of the above-described type is known from the French Pat. specification No. 1,342,358. In this hypodermic syringe a pressure is exerted on the piston by means of a pre-tensioned spring after unlocking the operating mechanism. As a result of this, the assembly of liquid container and needle is moved to the outside while at the same time a diaphragm which separates the liquid from the needle can be broken in that the liquid becomes under pressure so that the liquid starts flowing out.

A drawback of this known hypodermic syringe is that the liquid can already be pressed out of the liquid container before the needle has penetrated sufficiently far into the part of the body to be treated.

It is the object of the invention to mitigate this drawback and to provide a hypodermic syringe in which the instant at which the pressing-out of the liquid out of the liquid container begins is determined unambiguously by the construction of the syringe.

In order to realize the end in view, the hypodermic syringe according to the invention is characterized in that one or more blocking elements are present which can be moved at right angles to the longitudinal direction of the housing and which block the operating mechanism or the piston against movement relative to the liquid container, the wall of the housing showing, at least over those parts of its circumference over which the blocking elements extend, a diameter transition which is situated at a distance from the upper edge of the liquid contained at most corresponding to the length of the needle, all this in such manner that in passing said transition the said elements move radially and the blocking is removed, after which the piston can penetrate into the liquid container and the liquid flows out through the needle.

Upon exerting a force by the operating mechanism in the hypodermic syringe according to the invention, first the assembly of liquid container and needle is moved over such a distance that the needle has reached the desirable depth of penetration, after which, when the transition edge provided in the housing is passed, the blocking is removed and the piston presses the liquid out of the liquid container. In this manner the instant of flowing-out of the liquid is fully determined by the design of the housing.

The blocking elements may have a variety of constructions; one example is constituted by pawl segments incorporated in a groove of the piston or a pressure member cooperating therewith, said pawl segments being forced by springs against the wall of the housing, their configuration being such that upon passing the diameter transition they are forced inwards over such a distance that they become located inside the wall of the liquid container.

In a favorable embodiment of the hypodermic syringe according to the invention the blocking elements are formed by annular segments bearing individually on the upper edge of the liquid container and engaging with their outer annular surface the wall of the housing, the inner annular surface of said segments being at least partly bevelled and having a smallest diameter smaller than the inside diameter of the liquid container, the piston and a pressure member, respectively, cooperating therewith of the operating mechanism comprising a bevelled surface which bears against the bevelled surface of the annular segments, the diameter at the said diameter transition becoming larger so that the annular segments can move outwards and are released from the piston and the pressure member, respectively.

In a further favorable embodiment of the hypodermic syringe according to the invention the blocking elements are constituted by outwardly springing lugs which are connected to the piston or a pressure member cooperating therewith and which face the liquid container with their free end and in the untensioned condition have a larger diameter than the wall of the liquid container, the piston and the pressure member, respectively, having space for receiving said lugs when they are compressed, said lugs comprising, on their surface bearing on the edge of the liquid container, a collar which falls within the liquid container and comprising a bevel on their side facing the inner wall of the housing, the diameter of the housing at the area of the said diameter transition becoming smaller so that when the lugs move along said transition they are forced inwards.

In another favorable embodiment of the hypodermic syringe according to the invention the blocking elements are likewise formed by outwardly springing lugs connected to the piston or the pressure member, but in this embodiment their free end is remote from the liquid container and which lugs, in the untensioned condition, have a larger diameter than the wall of the liquid container, the piston and the pressure member, respectively, having space for receiving said lugs when they are compressed, said lugs comprising a surface which bears on the edge of the liquid container, the part of the lugs situated between said surface and their free end being bevelled on the side facing the wall of the housing, the diameter of the housing at the area of the said diameter transition becoming smaller so that when said lugs are moved along it they are forced inwards.

In the two last-mentioned embodiments the pressure member and the piston and the lugs connected thereto, respectively, may be formed as one assembly, for example, of a synthetic resin.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which

FIG. 1 diagrammatically shows a hypodermic syringe comprising a pressure member provided with blocking lugs.

FIG. 2 diagrammatically shows a hypodermic syringe in which the piston is provided with blocking lugs which with their free ends are remote from the liquid container.

FIG. 3 diagrammatically shows a hypodermic syringe which comprises separate blocking segments which can be moved radially.

Reference numeral 1 in FIG. 1 denotes a housing which is constructed of two parts 2 and 3. An assembly of liquid container 4 and needle 5 connected thereto is arranged in said housing so as to be movable. The lower side of the liquid container 4 is closed by a diaphragm 6 which bursts when the liquid comes under pressure. The upper side of the liquid container is closed by a piston 7. A pressure member 8 constructed as a cup spring cooperates with the piston 7. A compression spring 9 is present between the pressure member 8 and the upper side of the part 3 of the housing. The pressure member 8 is locked against movement by means of a locking member 10 which is connected thereto and which comprises legs 11 on its upper side. On their outside the legs 11 comprise a bevel 12 which bears on an edge of the part 3 of the housing with flat sides 13.

A slidable sleeve 14 which comprises a conical bore 15 which can cooperate with the bevel 12 of the legs 11 is situated around the part 3 of the housing. In order to prevent an unintentional actuation of the syringe a pin 16 is present which projects in the space between the legs 11 in such manner that said legs cannot be compressed. The pin 16 is affixed to a cap 17 with which the pin can be removed.

The pressure member 8 comprises resilient lugs 20 which bear on the upper edge of the liquid container 4 with their free end 21. The free end 21 comprises a collar 22 which falls within the liquid container. From the free end 21 the lugs have a bevel 23. At the area of the lugs 20 the part 3 of the housing comprises axial grooves in which the lugs 20 are situated. These grooves extend up to the position 24 where they change to a smaller diameter via a bevel 50.

The operation of this hypodermic syringe is as follows: First of all the cap 17 with pin 16 is removed. The housing 14 is then moved downwards relative to the part 3 of the housing, the legs 11 being squeezed by conical bore 15 so that the edges 13 are released and the member 10 with pressure member 8 is forced downwards by the spring 9. Since the pressure member 8 presses on the liquid container 4 by means of the lugs 20, said container is also moved downwards, the needle 5 penetrating the wall of the housing. At the instant, the needle has substantially entirely left the housing, the lugs 20 pass the diameter transition 24. Said lugs 20 are forced inwards so that they are released from the edge of the liquid container 4, and the pressure member forces the piston 7 downwards and the liquid is pressed out of the liquid container. During the lowering of the liquid container 4 by means of the pressure member 8, the lugs 20 exert no extra frictional force on the wall of the part 3 of the housing because the lugs 20 with collar 22 engage behind the edge of the liquid container 4 so that the lugs 20 cannot move outwards.

In this manner a hypodermic syringe is obtained in which the instant at which the pressing-out of liquid begins is determined unambiguously by the position of the diameter transition bevel 50.

A seal 25 is present between the liquid container 4 and the part 2 of the housing, so that prior to use the compartment 26 in which the needle 5 is present is fully closed so that the needle can be stored in a sterile atmosphere.

FIG. 2 shows a hypodermic syringe which corresponds in general with the syringe shown in FIG. 1 and in which therefore corresponding components are referred to by the same reference numerals. The difference from the syringe shown in FIG. 1 is that the piston 7 is provided with lugs 30 which are remote from the liquid container with their free end. A horizontal surface 31 of each of said lugs 30 bears on the edge of the liquid container 4, while from said surface the lugs 30 extend upwards at an angle over a part 32. The pressure member 8 is constructed so that it bears again against the piston 7 and is furthermore provided with recesses in which the lugs 30 will bear upon compression, In this manner it is achieved that when the operating mechanism is actuated first the whole assembly of liquid container 4 and needle 5 is moved. When the bevel 50 of the grooves are passed, the lugs 30 are pressed inwards so that the piston 7 in the liquid container starts moving and the liquid is pressed out.

FIG. 3 shows again a hypodermic syringe as is shown in FIGS. 1 and 2 in which the blocking elements are formed by separate annular segments 40 a horizontal surface 41 of which bears on the edge of the liquid container 4. The outer annular surface of said segments bears against the inner wall of the part 3 of the housing, while the inner annular surface is provided with an inclined part 42 which has a smaller diameter than the inside diameter of the liquid container. The pressure member 8 has a diameter which is slightly smaller than that of the liquid container and, with a bevelled surface 43, engages the surface 42 of the annular segments. At the area 24 the part 3 of the housing changes into the part 2 of the housing which has a slightly larger diameter. When actuating the operating mechanism of this syringe also, first the liquid container and the needle are moved by means of the pressure member because the annular segments lock the pressure member and the liquid container. When the annular segments 40 pass the edge 24 they are forced outwards as a result of the forces exerted on the inclined surface 42 so that they are released from the pressure member. The pressure member then presses on the piston so that the liquid starts flowing out.

From the above it may be obvious that the invention provides a hypodermic syringe in which the sequence of movement of the liquid container with needle and piston is entirely determined by the design of the housing and blocking elements cooperating therewith.

Claims

What is claimed is:

1. A hypodermic syringe comprising a cylindrical liquid container, a needle connected to one end thereof, a piston slidably fitting in the other end of the liquid container, a medicament in the container between the needle and piston, an elongate cylindrical housing slidably carrying said container, a pressure member slidably positioned in the housing adjacent the piston end of the container, transversely movable positive blocking means engaging the edge of the container at the piston end and controlling relative movement of the container and the piston therein by the pressure member, spring means for forcing the pressure member toward the needle end of the housing, stop means on the needle end of the housing, transition means on the inner surface of the housing between said blocking means and said stop means for causing the blocking means to move out of engagement with the container whereby the pressure member will force the piston toward the needle to eject the medicament in said container.

2. The invention as set forth in claim 1 and wherein the pressure member has a head portion sized to slidably fit within the container, the housing comprises an upper portion and a lower portion of larger inner diameter and further wherein the transversely movable positive blocking means comprises annular elements bearing on the edge of the cylindrical container at the piston end and in engagement with the inner wall of the upper portion of the housing, the inner face of each annular element sloping downwardly and inwardly and terminating inwardly of the container wall to form a circular opening of smaller diameter than the head portion of the pressure member, the head portion of said pressure member engaging said inner faces whereupon movement of the pressure head moves the cylindrical container toward the lower housing portion, upon reaching the lower housing portion the pressure head portion forces the blocking elements outwardly to allow the pressure head to engage the piston and upon continued movement eject the medicament from the container.

3. The invention as set forth in claim 1 and wherein the housing comprises an upper portion and a lower portion, said lower portion having a plurality of axial grooves in its inner wall, the transversely movable positive blocking means comprising a plurality of lugs extending radially from the pressure member and fitting in the aforesaid grooves, said lugs each having a flat lower face engaging the edge of the container adjacent the piston end and a downwardly and inwardly sloping outer face, the lower end of each of the grooves being provided with an inwardly and downwardly sloping bevel termination, whereupon downward movement of the pressure head the outer faces of the lugs engage the bevel terminations and cause the lugs to move inwardly so as to force the flat lower faces of the lugs off the container edge and allow the lugs to be forced radially inwardly to slide within the container and engage the piston to eject the medicament.

4. The invention as set forth in claim 1 and wherein the housing comprises an upper portion and a lower portion having a plurality of axial grooves in its inner wall, the transversely movable positive blocking means comprising a plurality of lugs connected to the piston and fitting in the aforesaid grooves, each lug having an intermediate horizontal flat face engaging the edge of the container adjacent the piston end, the upper portion of each lug extending into its respective groove, the lower end of each of the grooves being provided with an inwardly and downwardly sloping bevel termination, whereupon downward movement of the pressure member the upper portion of the lugs will engage the bevel terminations and be forced inwardly removing the flat face lug portion from the edge of the container and allowing the piston to then be moved to eject the medicament.