US 6,572,584 B1 · Retractable syringe with reduced retraction force

Abstract

A tamperproof retractable non-reusable syringe has a one piece hollow outer body with a barrel for a slidable plunger, a transition zone and a smaller diameter nose portion. An elongated needle holder and spring combination is installable from the rear of the outer body, guided into the nose portion and held by cooperating inwardly and outwardly facing surfaces oriented in the direction of retraction at the most constricted part of the transition zone where the nose begins. The plunger has an opening with a dislodgable stopper for receiving parts of the retraction mechanism. The stopper and the head of the needle holder are of significantly reduced diameter from the injection fluid chamber to resist blowing out prematurely. In one embodiment the head of the needle holder is surrounded by a separable retainer member which is slidingly removed by contact with the tip of the plunger after the stopper is mostly or fully removed to avoid cumulation of force required for retraction after the injection.

Claims28

Dependent claims

A reduced force syringe plunger handle for use in retracting a retractable syringe of the type having an elongated hollow syringe barrel having a front end portion containing a retraction mechanism activated by forward movement of the plunger relative to the barrel, the retraction mechanism comprising a rearwardly biased needle holder held by a separable retainer member lodged in the front end portion of the barrel, the retainer member having first and second sides oppositely disposed relative to a longitudinal axis through the barrel, the syringe plunger handle having a tubular body reciprocatably mounted in the barrel, the tubular body having a head comprising a front tip configured to contact and separate the retainer member from the needle holder by forward movement of the plunger relative to the barrel thereby releasing the needle holder for retraction, wherein the improvement comprises:

the front tip of the plunger having a longitudinally varying front surface comprising a first forwardly extending side configured to contact and move the first side of the retainer member relative to the needle holder and the barrel, and a second forwardly extending side disposed rearwardly of the first forwardly extending side, the second forwardly extending side configured to thereafter contact and move the second side of the retainer member relative to the needle holder and the barrel when the plunger is moved forwardly relative to the barrel, thereby reducing the plunger force required to activate the retraction mechanism.

A reduced force syringe plunger handle for use in retracting a retractable syringe having a long axis and a transversely positioned retainer member in a retraction mechanism having a retractable needle, comprising:

an elongated tubular syringe plunger having an end cap for depression of the plunger at a back end and a head portion at a front end of the plunger, the head portion having a plunger seal for sealingly slidingly in a syringe barrel;
the syringe plunger having a tubular wall containing a retraction cavity within the syringe plunger, the tubular wall extending forwardly into the head portion;
the head portion having a forwardly extending hollow tip portion defining an opening through the tip portion leading into the retraction cavity;
the hollow tip portion having a contact surface at the front of the plunger which varies axially in forward extension at different angular locations with respect to said opening, wherein one portion of the contact surface is configured to push first against the transversely positioned retainer member before the rest of the contact surface engages the retainer member thereby tilting the retainer member during retraction of the retractable needle;
whereby the plunger force required for release of the retainer member from the retractable needle is reduced as compared to a plunger having a generally transverse contact surface and the same retainer member and retraction mechanism.

2 more elements

A method of reducing plunger retraction force in a retractable syringe of the type having a barrel, a syringe plunger which reciprocates axially in the barrel and a front mounted retraction mechanism in the barrel having a retractable needle being held in position in the barrel by means of a transverse retainer which is separated from the retractable needle by contact between the front tip portion of the plunger and the transverse retainer when the plunger is moved forward after an injection to push the retainer off the retractable needle and allow retraction, comprising the step of:

providing a plunger having a front edge on the front tip portion configured to push on one portion of the retainer before pushing on the rest of the retainer when the plunger is pushed forward at the end of an injection;
pushing the plunger forward to bring the front edge of the tip portion in contact with the transverse retainer member;
and
tilting the transverse retainer with respect to the retractable needle while it is being separated from the retractable needle by forward movement of the plunger.

1 more element

A method of reducing plunger retraction force in a retractable syringe of the type having a barrel, a syringe plunger which reciprocates axially in the barrel, and a front mounted retraction mechanism in the barrel having a retractable needle being held in position by means of a transverse retainer with an outside edge in contact with the inside surface of the front of the barrel wherein the transverse retainer is separable from the retractable needle upon forward movement of the plunger after an injection is made whereby a front tip portion of the plunger pushing against the retainer moves the retainer forward in the front of the barrel thereby freeing the retractable needle, comprising the steps of:

providing a plunger having a front edge on the front tip portion configured to slide one portion of the outer edge of the transverse retainer with respect to the front of the barrel before beginning to move the rest of the retainer with respect to the front of the barrel when the plunger is pushed forward at the end of an injection;
and
pushing the plunger forward to bring the front edge of the tip portion in contact with the transverse retainer member;
and
moving one portion of the transverse retainer with respect to the front of the barrel before moving the rest of the transverse retainer during forward movement of the plunger while the retractable needle is being separated from the transverse retainer.

2 more elements

Dependencies are inferred from the claim text.

Retractable syringe with reduced retraction force

Life of this patent

Retractable syringe with reduced retraction force

Life of this patent

Abstract

Claims28