Take the case of fast curing low-viscosity materials (100 cps), such as cyanoacrylate adhesives, which may need to be discharged. That is to say, the dispensing valve used for gluing must be able to prevent the fluid from blocking the passage due to curing during the feeding cycle. At the same time, the valve must be able to separate the air-driven moving parts from the wet parts. Glue valves for water or low viscosity fluids should be able to ensure that the fluid can still circulate at low pressure, i.e. gravity supply.
Suitable rubber valves include pinch valves, needle valves or diaphragm valves. Viscosities of medium and low viscosity liquids are similar to those of emulsion substances. Pressurized storage containers for supplying such fluids require degassing and stirring functions. Short tubular valves and lifting valves with backdraft function are suitable for such dispensing viscous fluids. Medium viscous fluids can also be pneumatic needle valves. For corrosive materials and abrasive fillers with high viscosity (500,000 cps), they have high strength and resistance. Aerodynamic rubber valves for corrosive and wear-resistant sealing components are suitable, and the higher the wear degree of materials, the more frequent the maintenance cycle of rubber valves.
When the dispensing viscosity is like gel or silica gel, the glue container is usually 0.1 gallons of barrel or 1-5 gallons of cylinder. The cylinder gum dispensing fluid pushes the pressure plate through the pneumatic pump, and the extruded glue supplies the rubber valve through the high pressure pipe. It should be noted that there will be a phenomenon called tunneling effect in the pneumatic gum dispensing syringe, that is, only the intermediate fluid can be pumped out. Especially if the rubber package is not specially designed for automatic dispensing, this phenomenon will be more prominent.