Needleless injector wand assembly

A needleless injector wand assembly comprising

• a tubular barrel;
• a first chamber at a front, discharge end of said barrel for receiving an injectable liquid from a source thereof;
• a nozzle on the front end of said barrel for discharging liquid from the first chamber;
• a plunger slidable in the barrel for movement between a retracted position in which liquid is drawn into the first chamber and an extended position in which the liquid is discharged through said nozzle;
• a second chamber in said barrel rearwardly of and separated from said first chamber;
• a piston slidable in said second chamber for movement under fluid pressure between an extended position in which it moves the plunger to the extended position and a retracted position in which it moves the plunger to a retracted position;
• a third chamber in said barrel surrounding said second chamber for alternately receiving gas under pressure from said second chamber during movement of the piston from the retracted to the extended position, and for introducing the gas under pressure to said second chamber during movement of said piston from the extended to the retracted position;
• a breach plug closing a rear end of said barrel including a first passage for receiving a gas under pressure from a source thereof, and carrying the gas to a rear end of the piston to cause the piston to move from the retracted to the extended position, and a second passage for carrying the gas under pressure to and from said third chamber to cause said piston to alternately move from the retracted to the extended position and from the extended to the retracted position;
• and
• a pair of tubes connected to a rear end of said breach plug for carrying gas under pressure to and from said breach plug.