Quality of Service Definition

A nozzle structure is provided for injecting a flowable medium into a die or mold, specifically for injecting hot wax into a die. The nozzle structure comprises a generally tubular housing an intermediate portion of which is submerged in a reservoir of hot wax with the discharge end of the housing extending beyond the reservoir. A nozzle plug is reciprocatably mounted in the hollow of the housing with a major portion of the plug being frustoconical and coacting with a complementary portion of the housing to provide a valve. Movement of the plug toward the discharge end prevents the ejection of wax and movement of the plug in the opposite direction permits the ejection of hot wax because the hot wax in the reservoir is under pressure and there is a direct flow from the reservoir through the valve in the nozzle plug when the same is open. Because of the mating conical surfaces, the wax flow begins slowly and increases gradually and continuously to full flow. The wax flow is laminar, and turbulence and splashing of wax in the die is avoided. The nozzle contains an evacuating system, so that no wax is left in the nozzle after the injection cycle is completed. As a consequence, the wax injected into the die is always fresh from the reservoir, uniform in temperature, and uniform in viscosity. This, of course, results in a greatly improved pattern finish and appearance.