Abstract text

Methods and apparatus for dispensing liquid material provide the option to dispense precise and repeatable quantities or volume of material over a wide range of viscosities. In one embodiment, a metering chamber is provided that can be filled and emptied at the same time so as to eliminate time delays between dispensing operations. The material may be under pressure and that pressure is used to fill and empty a metering chamber. In another embodiment, a control device is provided with a metering chamber wherein the control device operates to switch pressurized fluid between two passages to the metering chamber. In a more specific embodiment, the control device may be, for example, a valve, and more specifically in one embodiment a pneumatically actuated spool valve