Safety syringe for mixing two-component medicaments

A mixing syringe for two-component medicaments comprising:

• (A) a cartridge housing having a first end and a second end, said cartridge housing having a substantially cylindrical cartridge housing bore;
• (B) a slidable cartridge disposed in said cartridge housing bore and having a first end, a second end, and a temporary sealing barrier disposed between said first and second ends and separating a cartridge bore of said cartridge into a cylindrical medicament solvent charge chamber and a cylindrical medicament charge chamber,
• said cartridge housing having means connected thereto, for breaching said temporary sealing barrier,
• said cartridge being suitable for separately storing a medicament solvent charge and a medicament charge in said medicament solvent charge chamber and said medicament charge chamber, respectively, said charges to be mixed to form a medicament to be expelled from said cartridge;
• (C) a piston disposed within said first end of said cartridge and being slidably seated in said cartridge bore;
• (D) a needle housing assembly rigidly attached to said cartridge and contained wholly within said cartridge housing;
• (E) an injection needle which is containable wholly within said cartridge housing, which can be extended to a position in which at least a portion of said needle extends outside of said cartridge housing,
• said needle being fixedly attached to said needle housing assembly and extending therethrough for injecting mixed medicament;
• (F) a puncturable end cap, said end cap sealing said second end of said cartridge housing;
• and
• (G) means for retracting said needle to reside completely within said cartridge housing after the expulsion of said medicament from said syringe;
• said means for breaching the temporary sealing barrier between chambers of said slidable cartridge comprising a pushrod having an anchoring end and a puncturing end wherein said anchoring end is connected to said cartridge housing, said pushrod extending from said cartridge housing toward said cartridge puncturable end stopper;
• said needle assembly housing having a pushrod aperture for freely guiding said pushrod therethrough so that said puncturing end of said pushrod resides in close proximity to and in alignment with said puncturable cartridge end stopper.