Power operated aspirating hypodermic syringe

A disposable gas pressure operated hypodermic syringe for automatically inserting a hypodermic needle into tissue, drawing a vacuum in said needle, and finally injecting medicament into the tissue, comprising:

• an elongated tubular main housing having a sealed first end, being the triggering end, and a second end, being the needle end;
• a source of compressed gas housed in a first end portion of the main housing;
• an elongated unitary tube slidably supported in the main housing and extending from a first end which is proximate the source of compressed gas when the syringe is in the preset condition to a second end which is foreshortened from the second end of the main housing by the length of an extensible portion of the hypodermic needle, substantially;
• a sliding valve member having a cylindrical head and a cylindrical stem, said cylindrical stem having a diameter less than that of the head, said valve member cylindrical head having a hermetic fit in a reduced cross sectional portion of the elongated unitary tube, and the stem portion having a hermetic fit with a further reduced cross sectional portion of the elongated unitary tube, said sliding valve member being situated in the elongated unitary tube proximate the source of compressed gas;
• a medicament chamber supported in the elongated unitary tube between the sliding valve member and the second end of said elongated unitary tube;
• a piston closing the end of the medicament chamber facing the sliding valve member;
• a hypodermic needle supported in the second end of the elongated unitary tube proximate the medicament chamber, said hypodermic needle having an elongated end portion housed in and facing the second end of the main housing;
• manual means for releasing the compressed gas into the first end of the main housing to propel the elongated unitary tube to the second end of the main housing and to insert the elongated end portion of the hypodermic needle into tissue;
• means for admitting gas pressure to the head of the sliding valve member on the side facing the medicament chamber, means for restricting the movement of the sliding valve member to a selected rate of travel, the movement of the stem of said sliding valve producing a vacuum in the medicament chamber thereby effecting the function of aspirating, means controlled by the sliding valve member when it has completed the aspiration stroke, substantially, for admitting gas pressure into the medicament chamber to inject the medicament into tissue.