Patent ID: 7744561

Claim:
A needleless injection device, comprising: a cylinder for medicament having an injection nozzle at a forward end thereof and an opening at its rearward end; a piston sliding in the cylinder through said open end, in use, to drive the medicament through the nozzle; a ram to drive the piston into the cylinder and having a longitudinal axis; and an energy accumulator to drive the ram when discharged and disposed between the ram and a discharge assembly, a rear end of the ram extending into said discharge assembly; wherein the discharge assembly comprises a retention member fixed in the assembly, said retention member having a plurality of retention elements spaced around and adapted to locate on the ram when in a charged position of the ram, and a release ring surrounding said retention elements to prevent radial outward displacement thereof and discharge of the ram; wherein axial displacement of said release ring releases said retention elements and causes discharge of the ram by said accumulator; wherein said retention elements are integral with said retention member and each has an enlarged head which can move into and out of engagement with a groove or recess on the ram by deformation of the material of said retention member; and wherein said retention member comprises a collet having radially spreadable fingers that are flexible and bias radially-inwardly, and wherein said collet in use moves between said first position in which said fingers engage with said ram and said second position in which said fingers spread radially out of engagement with said ram.