High-speed liquid dispensing modules

[0011]The present invention provides apparatus and methods for dispensing a heated liquid. In accordance with the principles of the present invention, an apparatus for dispensing a liquid includes a liquid distribution manifold capable of heating the liquid, a dispenser body capable of receiving a flow of the liquid from said liquid distribution manifold, and a pneumatic actuator. The dispenser body is equipped with a flow-control mechanism having a first condition in which the flow of the liquid is discharged from the dispenser body and a second condition in which the flow of the liquid is blocked. The pneumatic actuator has a solenoid valve equipped with an air outlet, an air piston housing, an air cavity disposed within the air piston housing and having an air inlet, and an air piston operatively positioned for movement within the air cavity. The air piston is operatively coupled with the flow-control mechanism for providing the first and second conditions. The solenoid valve is capable of controlling a flow of pressurized fluid to the air cavity and is mounted in abutting, thermally-conductive contact with the air piston housing so that the air outlet and air inlet are substantially coextensive. A thermally insulating shield is positioned between the pneumatic actuator and the liquid distribution manifold. The shield is capable of reducing the transfer of heat from the liquid distribution manifold to the pneumatic actuator.

If the heated liquid cools below a threshold temperature, it may not remain flowable and/or molten or may not have the desired properties when applied on the substrate.

If the operating temperature rises above a certain threshold temperature, the solenoid valve cannot operate properly and may malfunction, suffer permanent damage, or fail.

It follows that simply spacing the solenoid valve from the housing containing the air cavity with a nipple or a length of tubing is not an adequate solution for reducing the heating of the solenoid valve in those dispensing applications requiring a cycle time of 9 milliseconds or less.

The transfer of heat from the dispenser body and the distribution manifold also reduces the useful lifetime of the solenoid valve.

Therefore, equipping a solenoid valve with high-temperature seals permits the valve to operate over a larger temperature range but presents a significant liability for high-speed dispensing operations.

Moreover, even if a solenoid valve is equipped with such high-temperature seals, it still cannot operate reliably if heated above about 225° F.