One-use retracting syringe with positive needle retention

In a syringe of one use having a syringe barrel having a needle for injection of fluid extended from the front of the barrel and a movable handle extending from the back of the barrel, mounted for limited reciprocation in the barrel, the movable handle including a front end portion having a piston in sliding sealed contact with the interior of the barrel wherein the piston establishes a variable fluid chamber for injection fluid in the barrel, a back end portion of the handle having a thumb cap for applying thumb force to the handle and positive locking structure in the barrel which limits a second rearward movement of the handle after a first rearward movement of the handle to fill the variable fluid chamber with injection fluid and a first forward movement of the handle to inject the fluid, the improvement comprising:

• the needle is a retractable needle mounted in a retraction structure in the front of the barrel with the needle extended in its unretracted position and biased for retraction in a retraction direction;
• the front end portion of the handle is adapted to operate the retraction structure to retract the needle, the front end portion having a needle retention chamber and said piston behind the variable fluid chamber to receive the retracted needle;
• the needle retention chamber having a front end and a diametrically enlarged section;
• the positive locking structure is a stop positioned to limit rearward movement of needle retention chamber to within the confines of the barrel by contact with said enlarged section of the needle retention chamber;
• the handle is a two part handle having a back end portion which separates from the front end portion if the needle retention chamber is attempted to be pulled past the stop by pulling on the back end portion of the handle;
• and
• wherein the syringe is not subject to reuse even if the needle is not retracted after use.

A retracting syringe of one use having an operating handle which cannot be removed from the syringe barrel after one use, comprising:

• an elongated hollow syringe barrel having a front end and an open back;
• a retractable needle retractably mounted in a retraction structure located in the front end of the syringe barrel and biased for retraction in a rearward direction;
• a movable handle in the syringe barrel having a front end portion having a piston in sliding sealed contact with the interior of the barrel, a back end portion having a cap at the back end for applying thumb force to the handle, and a needle retention chamber in the front end portion of the handle for receiving the retractable needle;
• positive locking structure located within the syringe barrel to limit movement of the handle in a rearward direction and prevent its removal from the syringe barrel after one use;
• whereby the retracted needle after use is safely contained in the needle retention chamber within the syringe barrel and cannot be removed by manipulation or withdrawal of the plunger.

A syringe of one-use, comprising:

• an elongated hollow syringe barrel having a front end portion and an open back end;
• a needle mounted in the front end portion of the barrel;
• a two part movable handle mounted for reciprocation in the barrel, the handle having a head portion in front having a piston in sliding sealed contact with the interior surface of the barrel and a handle portion releasably connected to the head portion;
• a lock mounted in the barrel that allows said head portion to pass the lock when the head and handle portion are inserted into said open back and a force is applied to the handle portion in a forward direction;
• the handle portion being separated from the head portion when the handle portion is pulled back after having passed the lock in a forward direction, said separation occurring by release of the handle portion from the head portion due to resistance of the lock without breaking of the separating parts.