Dispensing – Automatic control – Of dispensers with fluid pressure discharge assistance
Reexamination Certificate
1998-08-07
2001-09-25
Bomberg, Kenneth (Department: 3754)
Dispensing
Automatic control
Of dispensers with fluid pressure discharge assistance
C222S062000, C222S064000, C222S069000, C222S288000, C222S399000, C222S444000
Reexamination Certificate
active
06293429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a variable-rate, digitally-controlled fluid metering device for use in applications such as, for example, mixing of fluids, injecting variable volumes of fluid into fluid streams, spraying chemicals in process lines, cooling of rooftops, livestock, poultry etc. The invention also relates to the use of the fluid metering device in spray irrigation systems.
2. Description of the Related Art
Conventional methods vary emitter size or pressure to regulate flow rates of fluids, which can cause problems because of limited range of pressures and flows, changed pattern radius, and changed distribution uniformity within the pattern. For sprinkler systems, problems occur because of changed pattern radius and changed distribution uniformity within the pattern. For injection of fluid treatment agents, nozzles usually have relatively small passages for low volume flow rates, which are highly prone to plugging if small sized particulate matter is present in the injection fluids. Furthermore, in systems such as, for example, agricultural irrigation systems, it is desirable to discharge precise amounts of fluids regardless of pressure variations. Standard sprinklers in agricultural irrigation systems, use fixed-orifice designs, which have corresponding pressure-flow relationships. By design, the flow rate of a given sprinkler at a given pressure is fixed. In movable irrigation systems, application depths are altered in practice by altering the travel rate of the sprinkler over the ground. Constant-speed machines use time-proportional control, meaning they must stop periodically to reduce average travel velocity. Intermittent motion degrades the uniformity of application, and the uniformity is worse for smaller sprinkler pattern radii. Alignment control of multi-span center pivot and linear-move machines superimposes another start/stop pattern on inner towers. Some standard sprinklers are used in a time-proportional, switched mode. Solenoid valves turn the supply on and off in a controllable sequence. The control variable is the length of time the water is on relative to the cycle time. The dynamics of the solenoid are a limiting factor and the uniformity of application may not be adequate.
U.S. Pat. No. 5,134,961 (Giles et al) discloses a device for controlling volumetric flow through pressure atomization sprays. Each nozzle is connected to a direct acting, in-line solenoid valve which is connected to a liquid supply at constant pressure. The valve is excited by square wave pulses of variable frequency and duty cycle to reciprocate between its fully open and closed positions and thereby control the flow rate over a range without changing the droplet size and spray pattern.
U.S. Pat. No. 4,867,192 (Terrell et al) discloses an apparatus for controlling irrigation water pH by blending a minute stream of sulfuric acid into a flowing water stream. The sulfuric acid pumps are variable displacement, positive displacement pumps which are electrically driven and controlled by a controller through electrical circuits.
U.S. Pat. No. 5,271,526 (Williams) discloses a programmable additive controller which controls the flow of fluid additives. A flowmeter is connected to a solenoid control valve for measuring flow of fluid. The controller opens and closes the valve and incorporates an input for required quantities of additive to be added each cycle. This system has a minimum injection per cycle of about 5 or fewer cc's per cycle. A comparator in the controller compares a required quantity with signal output indicating flow through the flowmeter. The difference between actual flow and target flow is continuously sent so that the target flow is continuously adjusted up or down when necessary to compensate for the previous difference.
While various devices have been developed for variable flow of fluids, there still remains a need in the art for a more effective and accurate device for delivering fluids at variable flow rates. The present invention provides a variable-flow rate, digitally-controlled fluid metering device that can use any type of emitter for delivering fluids at a wide range of flow rates by controlling the pulse rate for a given reservoir volume. The controllable range of flow rates can be expanded by replacing with different sized reservoirs. The present invention is different from prior art devices and solves some of the problems associated with the prior art devices. The present invention allows the use of large orifice emitters for delivering low volumes of fluids which allows the use of low quality fluids and/or reduces filtration steps and clogging of emitters.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a digitally-controlled device that allows variable flow rates of fluids with positive displacement.
A further object of the present invention is to provide a fluid metering device with a flow rate that is a linear combination of cycle time when cycle time is short enough that the reservoir of the device does not fill or empty completely.
Another object of the present invention is to provide a device where the instantaneous flow rate from zero to maximum is controlled by a limited duration pulse.
Another object of the present invention is to provide a fluid metering device where flow rate is proportional to the number of pulses.
Further objects and advantages of the invention will become apparent from the following description.
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patent: 4867192 (1989-09-01), Terrell et al.
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patent: 5156179 (1992-10-01), Peterson et al.
patent: 5246164 (1993-09-01), McCann et al.
patent: 5271526 (1993-12-01), Williams
patent: 5294023 (1994-03-01), Ioannides et al.
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C. Camp and E. Sadler, 1994 International Winter ASAE Meeting, Dec. 13-16, 1994.
Camp Carl R.
Evans Dean E.
Sadler Edward John
Usrey Lonnie J.
Bomberg Kenneth
Fado John D.
Poulos Gail E.
Silverstein M. Howard
The United States of America as represented by the Secretary of
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