| 摘要 |
Valve assemblies are provided that are adapted and configured to quickly start up and shut off a spray or liquid flow. Exemplary valve assemblies according to the present disclosure effectively minimize and/or prevent dripping from occurring during the start up and shut off of the valve assembly, and/or at times when flow through the valve assembly is suspended. A non-constant clearance between a spring-biased piston and an elongated member is provided, and an elastic member seals therebetween. As the elastic member interacts with the piston in different clearance regions, variable frictional forces are applied to the piston. In further exemplary embodiments, the surface area for force application from the upstream side exceeds the surface area for application of force from the downstream side. The disclosed valve assemblies have a variety of applications, including spray or liquid flow applications that include nozzles and orifices, such as fuel supply applications, agricultural applications and spray drying applications.
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