LIQUID-INJECTION INSTRUMENT WITHOUT NEEDLE, IN PARTICULAR FOR USE IN DENTISTRY

摘要

A liquid-injection instrument without needle comprises an elongated body in two separable parts placed end to end. The first, so-called medical part comprises at least one cavity receiving a liquid-tight cell which contains the injection liquid and has a movable base which, when displaced, forces liquid from the cell towards at least one variable-volume dosing chamber in the said first part which communicates with a nozzle provided with an injector capable of forming a narrow jet of liquid following forcible expulsion of liquid from the dosing chamber. The second, so-called motor part comprises a pneumatically controlled mobile assembly which effects alternating movements. The mobile assembly comprises a working piston (52-233-420) and a control and propulsion spring (62-241-444) which acts on the piston when gradually compressed by the movement of a plunger (52-276-445) caused by the pressure of compressed air in a gas-tight chamber (51-287) in the body. The movement of the plunger continues until the spring is suddenly released and is accompanied by depressurization of the compressed air, ensuring rapid movement of the piston and expulsion of the liquid from the dosing chamber (38-243-430), after which the plunger returns to its initial position.