Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
2000-02-07
2001-05-22
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C251S129070, C251S129170
Reexamination Certificate
active
06234202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a latching, dynamically balanced, three-way fluid control valve.
2. Description of Related Art
Insecticides are commonly distributed onto a field by a sprinkler system that is mounted to a truck. The sprinkler system has a plurality of spray nozzles that are coupled to a source of pressurized insecticide. The fluid is typically sprayed from both sides of the vehicle to maximize the spray radius of the system. When moving along the perimeter of a field it is not always desirable to spray from both sides of the truck. For this reason, it is desirable to provide a number of control valves that allow the operator to control the flow of fluid from the nozzles.
Fluid control valves typically contain a spool that controls the flow of fluid between a number of ports located in the valve housing. The flow of fluid between the ports is determined by the position of the spool. By way of example, in a three-way valve, when the spool is in one position a supply port is in fluid communication with an outlet cylinder port. When the spool is in a second position the cylinder port is in fluid communication with a return port. The position of the spool is typically controlled by a solenoid(s).
The spools have a number of channels or grooves that align the ports of the valve housing. The channels are relatively narrow and are susceptible to clogging, particularly when used in an agricultural environment that has a relatively large amount of dirt and dust. Additionally, the narrow channels produce a relatively large pressure drop across the valve. It would be desirable to provide a three-way fluid control valve that is not susceptible to clogging and does not produce a significant pressure drop across the valve.
Solenoid controlled fluid valves typically require a continuous supply of power to actuate the solenoids. The requirement for continuous power increases the power supply and energy consumption of the system. Additionally, spool valves are dynamically unbalanced such that the solenoids must overcome the pressure of the working fluid to move the spool. The additional work required to overcome the fluid pressure consumes more power and reduces the energy efficiency of the system. Therefore it would be desirable to provide a solenoid actuated three-way control valve that is dynamically balanced, is not susceptible to clogging, does not produce significant pressure drops, and can be actuated without a continuous supply of power.
SUMMARY OF THE INVENTION
The present invention is a latching, dynamically balanced, fluid control valve. The valve includes a housing which has a supply port, a cylinder port and a return port. Fluid communication between the supply port and the cylinder port is controlled by a first valve that opens and closes a first valve port of the housing. Fluid communication between the supply port and the cylinder port is controlled by a second valve that opens and closes a second valve port. The valves and ports provide relatively large valve openings that are not susceptible to clogging and do not produce significant pressure drops in the valve.
The first and second valves are connected to a transfer tube that is coupled to a solenoid and a return spring. The solenoid can be actuated to move the tube and valve from a first position, which allows fluid communication between the cylinder port and the supply port, to a second position that allows fluid communication between the cylinder port and the return port. The spring returns the valves to the first position. The solenoid is actuated by short digital pulses that latch the transfer tube and valves into position. The solenoid and spring are sealed by a pair of seals that each have an effective area which is approximately equal to the effective area of the valves. Each seal is located opposite from a valve seat so that opposing fluid pressures are applied to the seal and the valve. The opposing pressures create a net force on the transfer tube that is approximately zero, thus providing a balanced fluid valve that requires less energy to actuate.
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Blakely , Sokoloff, Taylor & Zafman LLP
Michalsky Gerald A.
Sturman BG, LLC
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