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1. (WO1990006142) SERINGUE HYPODERMIQUE
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HYPODERMIC SYRINGE

FIELD OF THE INVENTION
This invention relates to an hypodermic syringe for use in administrating subcutaneous or intravenous injections to persons and animals. While not limited thereto, the invention has particular application for use in hazardous situations in which the patient may possibly or actually be infected with a fatally lethal and incurable virus, microvirus or bacteria.
BACKGROUND OF THE INVENTION
Hypodermic syringes are well-known in the art, including pre-sterilized syringes having a protective cap over the cannula or needle, and which is to be removed immediately prior to administering an injection. The cover is intended subsequently to be replaced over the needle after use of the syringe.
However, at this point, the cannula or needle of the syringe has become contaminated by its use on the patient, and, the needle or cannula itself is potentially lethal, in that it then is a carrier of the virus, micro-virus, or bacteria. Careless handling of cap, or, in the absence of the protective cap, can result in the user unintentially being pricked, scratched or cut by the sharpened end of the needle, this resulting in infection of the user.

Numerous proposals have been made to avoid this occurrence, but none has been entirely successful.
Sudden retraction of the needle into the syringe by spring force as has been prior proposed, can cause splattering of contaminants on the needle onto the hands of the user, and possibly into the user's eyes in the event that a visor is not worn by the user. Also, the impact of retraction of the needle under spring force can cause an impact on the syringe, resulting in accidental dropping of the syringe, with possible dangerous consequences.
Other prior proposals involved a manually retractable and manually extendable needle guard. However, such needle guards require that they be forced manually into the extended position in order to break the holding force of a resiliently engaged retaining member. If the user's hand should slip off the needle guard during the extension of the needle guard, there again is the possibility of the user's hand being impaled by the unprotected needle.

SUMMARY OF THE INVENTION
It is an object of this invention to materially reduce the hazards to the user in using a hypodermic syringe, by providing a syringe assembly having an axially slidable needle guard that is retractable under manual force, and then lockable in retracted position by rotation of the needle guard relative to the syringe. Optionally, a spring is provided within the needle guard, and against the bias of which the needle guard is retractable.
Thus, according to the present invention, in order to ready the sterilized syringe for use, the user must grasp the barrel of the syringe with one hand, and then grasp the needle guard with the other hand, subsequent to which the needle guard is rotated relative to the barrel of the syringe into a position in which the needle guard can be slid axially of the barrel of the syringe.
Having reached the fully retracted position of the needle guard, the needle guard can then be rotated by the user relative to the barrel of the syringe in order to lock the needle guard in its retracted position.
Having used the syringe to effect either an injection on the patient, or withdrawal of blood, the user then rotates the needle guard in an opposite direction to free it for movement longitudinally of the barrel of the syringe, and then, further rotates the needle guard to lock it in an extended position relative to the barrel of the syringe. This forward movement of the needle guard to its extended position can be under the assist of a spring reacting between the needle guard and the barrel of the syringe. If such a spring-assist is provided, then, movement of the needle guard to its extended position proceeds under the manual control of the user, in that the barrel of the syringe is at that time grasped by one of the user's hands, and, the needle guard is at that time being grasped by the other of the user's hands.
Thus, both of the user's hands are located out of proximity to the sharpened end of the cannula or needle, and in a location of maximum safety.
In one preferred embodiment of the invention, either the barrel of the syringe or the needle guard is formed to be other than circular in cross-section, specifically, it is formed to be elliptical, and the needle guard is formed of a resilient plastics material which is capable of resilient deformation under the application of pressure laterally thereof.

The syringe barrel is provided with an axially and circumferentially extending slide track, the circumferentially extending portions of the slide track incorporating either indents or projections for cooperation with a projection formed internally of the needle guard. In this embodiment, the projection on the needle guard is located on the minor axis of either the syringe barrel, or the needle guard. By the application of lateral pressure to the needle guard at the location of the major axis, the minor axis is caused to extend and permit free passage of the projection on the inner surface of the needle guard either out of the indent in the syringe barrel, or over the axially extending step in the syringe barrel.
Further, optionally, a biasing spring can be provided internally of the needle guard which is compressed on retraction of the needle guard, and which acts to move the needle guard to its extended position upon release of the latch between the syringe barrel and the needle guard, and, to a position in which the needle or cannula of the syringe is again contained completely within the needle guard. Also, optionally, the needle guard is closed by a removable cap, and is further closed by a frangible diaphragm which is punctured by the syringe-needle upon retraction of the needle guard.
Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which

DESCRIPTION OF THE DRAWINGS
Figure 1 is a front elevation of the syringe of the present invention, showing the needle guard in cross-section;
Figure 2 is a view similar to Figure 1, but showing the needle guard in a retracted position;

Figure 3 is a fragmentary cross-section through the barrel of the syringe taken on the line 3-3 of Figure 2;
Figure 4 is a transverse cross-section through the syringe taken on the line 4-4 of Figure 2, and illustrating the cross-section of a needle guard of elliptical cross-section; and
Figure 5 is a cross-sectional view corresponding with Figure 4 and showing the needle guard when compressed in the direction of its major axis .

DESCRIPTION OF THE PREFERRED EMBODIMENTS
The syringe of the present invention includes, as is conventional, a barrel 10 within which a plunger is axially slidable, the plunger having been omitted for the purpose of clarity. Extending axially from the barrel 10 is a hollow needle or cannula 12, which is secured in the end of the barrel 10 in any convenient manner, such as the barrel 10 having been molded in-situ about one end of the needle 12.
Positioned externally of the syringe barrel 10 is a needle guard 14, the needle guard 14 preferably being formed of a resilient and compliant plastics material, conveniently a vinyl material, the needle barrel 10 being formed from a substantially rigid plastics material such as a polymethacrylate .

Extending axially of the syringe barrel 10 is a slide track indicated generally at 16, the slide track including an axially-extending linear portion 18 which merges into arcuate circumferentially extending portions 20 at its opposite ends.
Each of the circumferentially extending portions 20 include a radial projection 22, extending axially of the syringe barrel, or, in the alternative, an indentation can be provided in substitution for the radial projection.
Located internally within the needle guard 14 is a radially inwardly extending projection 24 of a form complimentary to the slide track 16, the projection 24 being moveable along the slide track 16 in order to permit retraction of the needle guard 14 from the extended position shown in Figure 1 to the retracted position shown in Figure 2.
Optionally, a compression spring 26 is positioned internally of the needle guard 12 and reacts against one end of the needle guard and the juxtaposed end of the syringe barrel. The purpose of this spring 26 is to ensure that the needle guard 14 is moved to an extended position at all times other than when it is intentionally latched in the retracted position.
Conveniently also, the needle guard is provided with a removable closure cap 28, and, is provided with a frangible diaphragm 30 underlying the cap 28, the diaphragm 30 being puncturable by the needle 12 upon retraction of the needle guard 14.
As more clearly illustrated in Figures 4 and 5, the needle guard 14 is formed for it to be other than circular. As illustrated in Figure 4, the needle guard is formed elliptical in transverse cross-section, with the projection 24 lying on the minor axis of the ellipse, and the major axis extending perpendicularly thereto. The projection 24 either is received within an indentation in each of the circumferentially extending portions 20 of the slide track 16, or, is positioned behind a radially-outwardly extending projection 22 formed within each of the circumferentially extending portion 20.
Thus, in an initial condition, and as illustrated in Figure 1, the projection 24 is pressed radially inwardly into contact with the bottom wall of the slide track 16, and, without regard to whether it is received within an indentation, or positioned behind a radially outwardly extending projection 22, the projection 24 acts to lock the needle guard 14 against both rotational movement about the axis of the syringe barrel 10, or, movement axially thereof.
As is illustrated in Figure 5, the application of manual pressure along the major axis of the needle guard 14 in the direction of the arrows P-P will cause movement of the projection 24 in a direction radially outwardly of the axis of the syringe barrel 10, into a position in which it is either moved out of engagement within an indentation in the needle barrel 10, or, into a position in which it clears the radially outwardly extending projection 22.
The needle guard 14 is at that time freed for rotation relative to the syringe barrel 10, this movement being guided by the projection 24 riding within the circumferentially extending portion 20. Having reached the end of its permissible travel, the projection 24 then becomes aligned with the axially extending portion 18 of the slide track 16, this permitting the needle guard 14 to be retracted from the position shown in Figure 1 to the position shown in Figure 2. This retraction is effected against the bias of the spring 26, in the event that such a spring is provided. In the event that the user should release the needle guard 14 prior to its being latched in a retracted position, then, the needle guard 14 will be returned to its initial position.
Having traversed the axial length of the axial portion 18 of the slide track 16, the user can then latch the needle guard 14 in the retracted position illustrated in Figure 2 by rotating the needle guard 14 in an opposite direction to cause the projection 24 to pass over or into the radial, projection 22 or an indentation corresponding with that provided at the opposite end of the slide track. This latching will proceed automatically upon rotation of the needle guard relative to the barrel under the resilience of the needle guard 14, which inherently will attempt to return to its elliptical conformation as illustrated in Figure 4.
After use of the syringe, the needle guard 14 is unlatched in exactly the same manner as that previously described. This unlatching, requires that the syringe assembly be grasped by both hands of the user, and effectively maintains the user's hands isolated from the needle 12, which at that time is possibly contaminated.
As will be appreciated, various modifications in the structure illustrated can be effected without departing from the scope of the invention as defined in the appended claims. For example, if the needle 12 is a short needle, then, the slide track can be arranged as a scroll cam with projections or indentations at its opposite ends, such that rotation of the needle guard relative to the barrel 10 will automatically cause retraction of the needle guard 14 against the bias of the spring 26, the spring 26 being available to return the needle guard 14 to its extended position at any time prior to latching of the needle guard in its retracted position. Further, as will be readily appreciated, instead of being arranged such that a reverse rotational movement of the needle-barrel is required, the respective opposite circumferentially extending portions 20 of the slide track 16 could be oppositely extending such that one-half turn is required to unlatch the needle guard from its extended position, and, one-half turn in the same direction is required to re-latch the needle guard when in its retracted position.