Disposable safety syringe having a retractable needle cannula and cannula lock

A disposable safety syringe having a retractable needle cannula and comprising:

• a hollow cylinder having proximal and distal ends and containing a supply of fluid to be administered to a patient;
• a double ended hypodermic needle cannula, a first end of said cannula extending into the interior of said cylinder, and the opposite end of said cannula extending outwardly from said cylinder for administering an injection;
• means for releasably retaining said cannula at the distal end of said cylinder;
• a plug located within said cylinder to be positioned at the distal end thereof, such that the first end of said cannula penetrates said plug;
• a piston located at the proximal end of said cylinder in spaced axial alignment with said plug, whereby the fluid in said cylinder is received in the space between said piston and said plug;
• and
• means to move said piston distally through said cylinder and towards said plug to expulse the fluid from said cylinder via said cannula and to connect said piston to said plug, and to move said piston proximally through said cylinder to relocate said plug to a relatively proximal position within said cylinder and correspondingly withdraw said cannula from said retaining means for retraction completely within said cylinder.

A safety syringe having a retractable needle cannula and comprising:

• a hollow cylinder having proximal and distal ends and containing a supply of fluid to be administered to a patient;
• a double ended hypodermic needle cannula, a first end of said cannula extending into the interior of said cylinder, and the opposite end of said cannula extending outwardly from said cylinder for administering an injection;
• means for removably retaining said cannula at the distal end of said cylinder;
• a plug located at the distal end of said cylinder;
• a piston located at the proximal end of said cylinder in spaced axial alignment with said plug, whereby the fluid in said cylinder is received in the space between said piston and said plug;
• and
• means to move said piston axially and reciprocally through said cylinder, such that a distal movement of said piston through said cylinder and towards said plug expulses the fluid from said cylinder via said cannula and causes said plug and said piston to be penetrated by the first end of said cannula, and a proximal movement of said piston through said cylinder removes said cannula from said retaining means and relocates said cannula and the plug penetrated thereby towards the proximal end of said cylinder such that said cannula is withdrawn completely within said cylinder.