| 摘要 |
The present fluid level controlled automatic shutoff valve is comprised of a tubular housing with an axial bore which has an upstream closure, a downstream opening, and an annular piston seat at the downstream opening. A movable piston is positioned in the bore, and biased to a retracted position by a tension spring connected between the piston and the closure of the bore. A plurality of channels on the wall of the housing extend between an upstream end of the housing and the bore. The channels terminate in venturis downstream of the piston in the retracted position. The shutoff valve is positioned in a fluid dispensing device. When pressurized fluid is delivered through the dispensing device, the fluid is directed through the channels and out the venturis at high speed and low pressure. Before the fluid level in a container being filled reaches an open lower end of the dispensing device, the pressures between the upstream and downstream ends of the piston are balanced by air flowing into downstream opening of the bore from the open lower end of the dispensing device. When the fluid level reaches the open lower end of the dispensing device, the air flow is cut off, and the low pressure fluid from the venturis pulls the piston into the seat at the downstream opening of the bore. Fluid flow is shut off.
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