A stopper includes a main body portion defining an open rearward end configured to receive the plunger rod, an engagement portion provided along an inner circumference of the main body portion configured to engage at least a top portion of the plunger rod, a closed front end forming a flexible roof, and a first perimetrical skirt extending around an outer circumference of the main body portion toward the closed front end of the main body portion. When fluid pressure is increased inside the syringe barrel during an injection, the flexible roof expands in a radial direction toward an inner wall of the syringe barrel, the first perimetrical skirt is forced against the inner wall of the syringe barrel, and an engagement between the plunger rod and the engagement portion forces the main body portion to expand in the radial direction toward the inner wall of the syringe barrel.

A stopper adapted for attachment with a plunger rod for use within a syringe barrel is disclosed. The stopper includes a main body defining an open rearward end and a closed front end. The open rearward end is adapted to receive a front forward end attachment portion of the plunger rod. The stopper also includes a core member integrally formed with the main body adjacent the closed front end. The core member includes a nose portion having a conical tip configured for entering an outlet opening of the syringe barrel. The closed front end of the stopper has a profile configured to cooperate with an internal surface of the syringe barrel wall to prevent reflux and reduce dead space within the barrel.

An anti-reflux syringe assembly having a reservoir for containing a fluid, the reservoir having a cylindrical side wall, an open distal end, and a proximal end having a proximal end wall provided at its axial center with a through opening; a piston slidable in leaktight manner in the reservoir, the piston having a distal end adapted to connect to a plunger passing through the open distal end of the reservoir, and a proximal end having a proximal end wall. The proximal end walls of the reservoir and of the piston are conical, and the proximal end wall of the reservoir forms an angle and the proximal end wall of the piston forming an angle , with 3<<5.

There is provided drug delivery devices comprising a drug container assembly with a needle and automatic needle insertion and drug delivery mechanisms. Aspects of the devices described include a noise-generation mechanism to indicate the completion of drug delivery, a mechanism for triggering drug delivery following needle insertion, front-end activation of the device and a safety mechanism for covering the needle after use and methods of assembly of the devices.

A dual chamber syringe facilitates selective drug mixing, dosing, and administration, as well as pre- or post-administration flushing with a single syringe instrument. A syringe barrel incorporates an outlet, as well as variable-volume, primary and secondary fluid chambers, separated by a floating stopper. The floating stopper defines a dome-shaped split septum with a central slit at its apex. The split septum is a bi-stable valve, closing the central slit by compression in its meridial dimension when the septum is in a first, relaxed state, and opening the central slit when the septum is buckled or flipped under tension in the meridial dimension in a second state. Buckling of the septum wall is caused solely by differential fluid pressure applied by a single plunger, without physical contact of the septum with any other structure within the syringe.