Dispersion multichamber auto-injector

An auto-injector comprising a medicament cartridge assembly, a stressed spring assembly, and means mounting said assemblies together in cooperating relation so as to provide an exterior housing having a needle extending end,

• said medicament cartridge assembly including a container having one end disposed adjacent the needle extending end of said housing, first piston means mounted in a storage position within said container in spaced relation with the one end thereof for movement therein from the storage position thereof through an operative stroke in a direction toward the one end thereof, a hollow hypodermic needle having a sharpened end and an opposite inlet end portion disposed within said container in a storage position to be moved therefrom by and with said first piston means during the operative stroke thereof, closure means enclosing the sharpened end of said needle and the one end of said container disposed in a position to be penetrated by the sharpened end of said needle when said needle is moved with said first piston means, a first liquid medicament within said container in a storage position between said first piston means and said closure means, second piston means mounted in a storage position within said container in spaced relation with respect to the storage position of said first piston means for movement from the storage position thereof through an operative stroke in a direction toward said closure means, a second liquid medicament in said container disposed in a storage position in motion transmitting relation between said second piston means and said first piston means in sealed relation with respect to said first liquid medicament,
• the operative relation of said first liquid medicament and said needle between said first piston means and said closure means when in said storage positions within said container being such that when said first piston means is moved through the operative stroke thereof said needle is moved by said first piston means so that (1) during an initial portion of the movement of said needle with said first piston means the sharpened end of said needle penetrates through said closure means beyond the needle extending end of said housing and into the skin of a user without significant passage of said first liquid medicament from the sharpened end of the needle and (2) during the remaining portion of the movement of the needle with the first piston means, the first liquid medicament is moved into the inlet end of the needle and out of the sharpened end thereof and into the tissue of the user as the sharpened end moves inwardly of the skin into a full depth position,
• said stressed spring assembly including spring means, releasable means for retaining said spring means in a stressed storage position, and releasing means operable in response to a predetermined manual actuating procedure to release said releasable means so that said spring means moves said second piston means through the operative stroke thereof during an initial portion of which said first piston means is moved through the operative stroke thereof,
• said medicament cartridge assembly including bypass means operable in response to the movement of said first piston means through a final portion of the operative stroke thereof to allow a subsequent remaining portion of the operative stroke of said second piston means to move said second liquid medicament beyond said first piston means through said needle and out of the sharpened end thereof generally after the sharpened end has reached its full depth position.