| 主权项 |
1. A needleless injector comprising:
a barrel for receiving an injectable liquid from a source thereof; a holder including a first end extending into said barrel, a central passage for conveying liquid and a cylindrical sleeve at a second end extending out of said barrel; a disposable, plastic nozzle removably mounted on the cylindrical sleeve of said holder for discharging liquid from said holder and barrel, said disposable nozzle including an elongated tubular body having a tapered front discharge end; a passage extending through said body for discharging liquid received from said holder; an annular recess in a rear end of said body for receiving the holder sleeve; and a resilient detent extending outwardly from an inner wall of said annular recess for extending into a notch in a front end of the holder sleeve when the nozzle is mounted on the holder; a plunger slidable in said barrel for movement between a retracted position in which liquid is drawn into said barrel between said holder and said plunger and an extended position in which liquid is discharged through said holder and disposable nozzle; a piston separate from said plunger slidable in said barrel movable under fluid pressure to move said plunger to an extended, liquid discharge position; a retractor connected to said piston in said barrel for moving said plunger to the retracted position when said piston is retracted; a coupler connecting said retractor to said plunger permitting sliding of said piston in said barrel against said plunger to move the latter to the extended position, and for drawing the plunger to the retracted position when the piston and retractor are moved in a direction away from said holder and nozzle to the retracted position; a first valve for introducing fluid under pressure into said barrel alternately on one side of said piston to move the piston and plunger from the retracted to the extended position to discharge liquid through said holder and nozzle, and on a second side of said piston to return the piston and plunger to a retracted position in which injectable liquid is drawn into the barrel between said holder and said plunger; a trigger for operating said first valve to cause said plunger to move from the retracted to the extended position and then back to the retracted position each time the trigger is operated; and a stop in a second end of said barrel remote from said one end for limiting movement of the piston when the plunger and piston move to the retracted position. |
