Combination gravimetric and volumetric dispenser for multiple fluids
A combination gravimetric and volumetric fluid dispenser which includes a scale linked to a controller. The controller is linked to a plurality of two stage valves which control the dispensing of large quantities of base materials. The controller is also linked to a plurality of nutating pumps which together with the controller controls the dispensing of smaller quantities of additive materials. The base material dispensing valves include stepper motor actuators having multiple steps per revolution and are under the control of an analog signal from a controller. The base material dispensing valve is opened or closed via a rod that is slidably raised or lowered upon rotation of the drive shaft of the stepper motor actuator.
1. A valve and control mechanism for use in a fluid dispensing system, comprising:
a stepper motor capable of receiving an analog signal from a controller;
the stepper motor being coupled to a threaded shaft that is coupled to a slidable rod for raising and lowering a first end of the slidable rod, the slidable rod comprising a second end that serves as a low flow plug of a two-step valve; and
an optical sensor for communicating the position of the valve to the controller;
wherein the stepper motor comprises a drive shaft that is coupled to the threaded shaft through a flexible coupling; and
a coupling device linking the threaded shaft to a bracket which couples the threaded shaft to the slidable rod, the mechanism further comprising an anti-rotation bearing that slides between a plurality of support shafts, thereby preventing unintended rotation of the coupling device.
2. The valve and control mechanism of claim 1 , wherein the stepper motor actuator has about 400 steps per revolution.
3. The valve and control mechanism of claim 1 , wherein a driver unit is employed between the stepper motor actuator and the controller.
4. The stepper motor actuator in combination with the two-step valve of claim 1 , wherein the threaded shaft has a pitch of ten threads per inch.
5. The valve and control mechanism of claim 1 , further comprising thrust bearings for supporting the threaded shaft.
6. The valve and control mechanism of claim 1 wherein the two-step valve is for dispensing a base material for paint.