safety retractable syringe with selective trigger, the present invention relates to a medical device comprising a hollow cylindrical body, a central rod, a plunger, a needle adapter and a lock body in which the locking body It is made of flexible polymeric material； the hollow cylindrical body is provided with a locating groove, a large sealing ring and a zero line； the central rod is provided with a pull jaw and a tray； the needle adapter is provided with an annular locating claw, an inner sealing ring and a recoil ring； The locking body is supplied with a sealing tray, a sealing coil, a locating ring and a stopper. the sealing tray and large sealing ring, sealing coil and inner sealing ring engagement engage each other to make up the sealing structure. When the locating ring engages the pull-jaw and is then pulled back by the core rod, the needle adapter is retracted together into the hollow cylindrical body by adjusting the sealing coil and the recoil ring. The stopper may be placed in an internal cavity in the annular locating jaw of the needle adapter to determine the annular locating jaw in the hollow cylindrical body. Therefore, the locking body can perform three functions and simplify the structure. Since a distance trigger 1 is preset, when the front piston sealing line overlaps the zero line, a selective trigger of the safety mechanism can be obtained.seringa com retração de segurança e gatilho seletivo, a presente inovação refere-se a um aparelho médico, que compreende um corpo cilíndrico oco, uma haste central, um êmbolo, um adaptador da agulha e um corpo da fechadura, no qual o corpo de bloqueio é feito de material polimérico flexível； o corpo cilíndrico oco está provido de uma ranhura de localização, um grande anel de vedação e uma linha zero； a haste central está provida com uma garra de puxar e uma bandeja； o adaptador de agulha é provida de uma garra de localização anelar, um anel de vedação interior e um anel de recuo； o corpo de bloqueio é forneci
