Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2002-06-12
2004-04-06
Casler, Brian L. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S198000
Reexamination Certificate
active
06716197
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a needle retracting mechanism for a hypodermic syringe, comprising a body with a needle retraction chamber, which body in a first end is adapted to receive injectant from a syringe barrel and in a second end slidingly supports a needle which by means of a force from a pretensioned actuator is retractable into the needle retraction chamber, the actuator being releasable by response to the injectant.
The invention also relates to a needle holder for a hypodermic syringe, which needle holder comprises a needle retracting mechanism.
The invention also relates to a hypodermic syringe comprising a barrel and a plunger, which syringe comprises a needle retracting mechanism.
BACKGROUND OF THE INVENTION
Needles of used syringes constitutes a risk, both by themselves and as a source to contagion. Re-use of syringes constitutes a particular risk for contagion.
Most syringes are disposable syringes with a standardised fitting which can mate corresponding standardised fittings of syringe needles. This standardised fitting enables a wide range of combinations of various syringe sizes and needle sizes. A common standardised fitting is the Luer fitting.
Various safety syringes, in which the needle is retracted after use are known.
U.S. Pat. No. 5,122,118 describes an automatic needle retracting syringe in which a gelatine capsule retains a helical spring. Upon contact with the liquid injectant, the gelatine capsule weakens and allows the spring to retract the needle into the body of the syringe.
U.S. Pat. No. 5,049,133 describes a manual needle retracting syringe in which a spring which can retract the needle into the body of the syringe is releasable by moving the plunger to trigger a plurality of teeth-shaped hinges.
U.S. Pat. No. 5,188,614 describes a protective casing for use with a hypodermic syringe. A dual component foaming agent is disposed in the casing. When the components are mixed together they form an expanding and hardening plastic foam. Upon pressing the syringe into the casing subsequent to the ejection of fluid from the syringe, the foaming agents are activated and the expanding foam forces the syringe and syringe needle rearwardly within the casing, and encapsulates the used needle within the casing and foam.
WO-A-9 205 818 describes an automatic needle retracting syringe in which a spring which forces the needle into the plunger is released by pressing the plunger into the barrel after use.
WO 98/30261 describes a needle holder for use in combination with a syringe and a needle. The needle holder is provided with an expandable element and retention means for the expandable element. Contact between the expandable element and an injectant causes the expandable element to expand and retract the needle into the needle holder. The invention also relates to a syringe comprising the needle holder.
Prior art automatic needle retracting syringes which function by a response to the injectant, i.e. water, are generally encumbered with an unreliable and unpredictable release of the actuator.
Prior art manual needle retracting syringes are generally encumbered with the drawback that the force which is required to release the actuator is so large that using the safety syringe is felt cumbersome.
In some of the above mentioned safety syringes the needle and the retracting mechanism are integrated in the syringe barrel. There is therefore no possibility of combining variable syringe sizes with various needle sizes, which means that a greater number of syringe variants must be held in stock to satisfy all needs. Logistically this is a big problem.
A favourable material which respond to the injectant is alginate, which loses its mechanical strength and eventually dissolves in water. Alginate items are formed by extrusion or moulding. The resulting items are fragile and mechanically weak, which means that they easily deform or break. From a mechanical point of view, alginate is therefor not a preferable material.
SUMMARY OF THE INVENTION
The object of the invention is to provide an improved safety syringe in which the above problems are reduced or eliminated. Another object is to provide a safety syringe with both an automatic and a manual needle retracting mechanism. A further object is to provide an automatic needle retracting syringe in which alginate is suitable as material in the injectant responding item.
The objects are achieved by a needle retracting mechanism, a needle holder and a hypodermic syringe according to the preamble, which are characterized by the features of the claims.
In a first aspect the invention thus relates to a needle retracting mechanism for a hypodermic syringe, comprising a body with a needle retraction chamber, which body in a first end is adapted to receive injectant from a syringe barrel and in a second end slidingly supports a needle which by means of a force from a pretensioned actuator is retractable into the needle retraction chamber. The needle retraction chamber is provided with a funnel-shaped entrance opening, which widens out towards a retainer for the actuator and needle. The retainer comprises a compressible portion which in a retaining position is bigger than the entrance opening and abuts funnel-shaped sides of the entrance opening, and in a compressed release position is smaller than the entrance opening, and thus can enter the entrance opening. The pretensioned actuator forces the retainer into the funnel-shaped entrance opening, i.e. the actuator forces the compressible portion towards the release position. The compressible portion is, however, kept in the retaining position by a spacer. The spacer is made from a material which after some time in contact with the injectant loses its mechanical strength.
In storage no injectant is present, and the spacer maintains its mechanical strength and shape, which means that the compressible portion of the retainer is maintained in its retaining position.
When the syringe is filled with an injectant, a contact between the spacer and the injectant takes place, which after some time causes the spacer to lose its mechanical strength. The spacer then no longer maintain the compressible portion of the retainer in its retaining position, and the actuator therefore forces the compressible portion into the release position, and into the entrance opening. The width of the needle is smaller than the entrance opening, and both the needle and the retainer is forced through the entrance opening and into the needle retraction chamber. It is thus provided an automatic release of the needle retraction.
Preferably the compressible portion of the retainer comprises elastic arms which in first ends are integral with a base portion of the retainer and in second ends are moveable between the retaining position and the release position. The second ends of the elastic arms preferably have oblique end faces, corresponding to the funnel-shaped sides of the entrance opening. Further the elastic arms preferably have mountings for the spacer.
When the compressible portion of the retainer is in the retaining position and keeps the actuator in place, a force from the funnels-shaped sides of the entrance opening attacks the compressible portion of the retainer. This force is counteracted by a force from the compressible portion of the retainer, which force is a resultant of the force from the actuator and a force between the compressible portion and the spacer. Assuming no friction, the forces which act between the funnel-shaped entrance opening and the compressible portion of the retainer are perpendicular to the funnel-shaped sides. Depending on the angle of the funnel-shaped sides, which is a matter of design choice, the force between the compressible portion and the spacer can be made much smaller than the force from the actuator.
Practically there will be a friction between the funnel-shaped sides of the entrance opening and the compressible portion of the retainer, but still the force between the compressible portion and the spacer can be made much smaller than the force from the
Casler Brian L.
Han Mark K.
Syringus AS
Young & Thompson
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