Patent ID: 7563252

Claim:
An injection device for causing a dose of liquid to be ejected, said device comprising: a housing; a syringe located within said housing, the syringe comprising a container and a needle at one end of the container through which the dose of liquid is to be ejected; a plunger, the syringe being movable by said plunger, upon release of an actuating bias member at one end of the housing, to move the syringe, from a first position wherein the needle is shrouded by the housing, to a second position wherein the needle projects from the housing, the plunger having an end positioned within said container of the syringe; and a surrounding and gripping flexible O-ring carried by said plunger, said O-ring rests against an enlarged head of the container, such that a primary movement of the plunger, under a bias of the actuating bias member, transmits a frictional force to the O-ring with the result that the container is moved by and with the O-ring linearly from said first to said second position, whereupon arresting of further movement of the container results in a frictional grip between the plunger and the O-ring being overcome, thus enabling the plunger to move by a secondary movement relatively to the O-ring, further into the container, into contact with and to act upon a plug within the container to compress the dose of liquid within the syringe and cause expression of the dose of liquid through the needle.