Portable drug delivery device including pump with tapered barrel

A syringe pump for pressurizing a fluid drug to be dispensed and administered to a patient, comprising:

• a barrel having an outlet end and a side wall;
• a piston reciprocable in the barrel and in sliding contact with the side wall of the barrel for pressurizing fluid in the barrel;
• and
• spring means engaged with the piston for urging it in a direction toward the outlet end to pressurize the fluid;
• wherein
• said barrel side wall is tapered between its ends so that it has a larger diameter at its outlet end, whereby the frictional resistance between the piston and barrel side wall becomes less as the spring expands and the piston moves toward the outlet end, the degree of taper being chosen so as to substantially compensate for decreased force imparted by the spring means as it expands, resulting in a constant force on the fluid during the entire length of travel of the piston in the barrel, whereby the flow rate of the fluid drug administered to the patient remains constant during an entire dispensing cycle.

A liquid drug delivery device for administering a drug to a patient at a constant and predetermined flow rate during a dispensing cycle, comprising:

• pump means for pressurizing the drug in liquid form;
• conduit means connected with the pump means for conveying the pressurized drug to the patient;
• and
• restrictor means fluidly connected with said pump means for regulating the flow rate of drug pressurized by the pump means and conveyed by the conduit means, said pump means having means for maintaining a constant pressure on the drug during an entire dispensing cycle to thereby obtain a constant flow rate of the drug during the dispensing cycle.