| 摘要 |
<p>A metering/dispensing head (10) and system for dispensing small doses of liquid nitrogen into individual filled cans (16) proceeding from a filling station to a closing station. The head includes a nozzle member (32) to which a source of liquid nitrogen under pressure is connected via pipe (12). The lower plane surface (72) of that member cooperates in close sliding relationship with the upper plane surface (70) of a rotary valve disc (40) around which are spaced triangular apertures (68). A small clearance separates those cooperating surfaces, but is of such a size as to effectively prevent loss of liquid nitrogen when the valve disc closes off a downwardly-pointing outlet nozzle (80) which opens into the lower surface of the nozzle member. A jet of liquid nitrogen exiting from said nozzle when uncovered by a said aperture in the valve disc injects a filled can moving beneath the nozzle member with a metered quantity of liquid nitrogen. The nozzle opens into a circular cavity (82) formed in the under side of the nozzle member. The pressure of gaseous nitrogen in that cavity when the nozzle is closed by the valve disc isolates the valve disc from the low temperature liquid nitrogen. The valve disc is exposed to the same atmospheric conditions as the filling station, and is maintained thereby substantially at room temperature. Adjustment of the position of the nozzle radially relative to the valve disc adjusts the size of the said doses of liquid nitrogen.</p> |
