Sealing arrangement for syringe

Abstract

A syringe containing a high water content product and for use in a drug infusion system is provided. The syringe includes a plunger carrying front and rear o-rings made of a diene rubber compound such as chlorobutyl rubber or bromobutyl rubber to impart very low gas permeability characteristics to the o-rings. The plunger may be molded as a single part or in two parts. If molded as one part with radially-engaging mold portions, the seal glands in the plunger may include parting lines from the mold. If molded as two parts with axially-engaging mold portions, the front seal gland may include a sealing surface and under cut that has no parting line. The orings may be surface treated with a lubricant to improve sealing where the molding process gives rise to parting lines in the seal glands.

1 . A syringe for use in a drug infusion system, the syringe comprising:
 a barrel having a tapered front end, a rear end, and a cylindrical wall defining an outer surface and an inner surface, the rear end of the barrel being open, and the front end of the barrel including an orifice;   a plunger within the barrel, the plunger including a continuous contact surface at a front end of the plunger, a rear end of the plunger having an outer cylindrical surface including a tapered outer surface at the rear end of the plunger, a deflectable tab, a blind bore having an inner cylindrical wall portion defining a continuous even cylindrical surface extending from an entrance of the blind bore to a plunger seat, a front seal gland extending circumferentially around the plunger between the front end of the plunger and the rear end of the plunger, and a rear seal gland extending circumferentially around the plunger between the front seal gland and the rear end of the plunger, the tapered outer surface increasing in diameter from a surface of the rear seal gland to the rear end of the plunger;   a front o-ring positioned in the front seal gland, and creating a gas-tight seal between the inner surface of the barrel and the plunger; and   wherein the front o-ring is sized to maintain the gas tight seal through a temperature change within a temperature range of −25° C. to 40° C.