| 摘要 |
A dispensing valve assembly and system for viscous materials includes a dispensing valve including a valve casing with an interior chamber, a dispensing port and a longitudinal valve passageway. An inlet port intersects the valve passageay and connects to a source of material to be dispensed. A valve element is slidably received in the passageway and includes a drive shaft portion, an elongated piston head portion and a waisted portion. Seals are provided to seal against the piston head, and the valve element reciprocates over a cycle so that the waisted portion periodically interrupts the first seal allowing material to flow into the chamber and out of the dispensing port. As the valve element closes, a seal is again established to shut off material flow. Continued advancement retracts the piston head further from the chamber to create a negative pressure that draws back material from the dispensing portion to cause a clean cut off of flow. A metering port and a metering cylinder may be employed.
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