One-Use retracting syringe with positive needle retention

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(57) Abstract : A retracting syringe (10) of one use has a plunger (38, 40) comprising a handle portion (38) and a needle retention portion (400) forward of the handle portion (38) which serves as the plunger (38, 40) and preferably also serves to trigger the re- traction mechanism (20) when the handle (38) is moved forward beyond the forward end-of-injection position. The positive locking structure (66) in the syringe barrel (12) permits one withdrawal of the handle (38) in the-rearward direction to fill the variable fluid chamber (56) and one movement in the forward direction to empty the variable fluid chamber (56) but thereafter limits the rearward ovement of the needle retention chamber (40) and/or the handle (38) to ensure that the syringe (10) cannot be reused even if the user fails to trigger the retraction device 9200 to retract the needle (18).