Automatic pharmaceutical dispensing syringe

摘要

An automatic pharmaceutical dispensing syringe (2), includes a main barrel (4) having hollow interior (18) sized to house a conventional pharmaceutical cartridge (16) and needle (6). A cap (6) at one end (8) of the main barrel is used to rotate a threaded dosing screw (158) housed within the main barrel. The dosing screw is permitted to move axially within the main barrel. The dosing screw threads (156) engage similar threads (146) on an elongate piston driver (140) which abuts the cartridge piston (152). A brake pad (194) secures the piston driver to the main barrel while the cap is rotated to select the desired dose. Doing so causes the dosing screw to move axially relative to the piston driver to compress an injection spring (174). The injection sequence is begun by placing the distal end (114) of an outer sleeve (10) surrounding the main barrel against the patient and pressing a trigger (130). This permits a needle insertion spring (106), captured between the main barrel and the outer sleeve, to drive the main barrel, cartridge and needle assembly distally, thus driving the needle into the patient. Only at the end of travel does the brake pad release the piston driver to permit the injection spring to drive the piston driver against the piston thus forcing the pharmaceutical through the needle and into the patient.