Fluid handling – Combined
Reexamination Certificate
2000-03-24
2001-10-23
Chambers, A. Michael (Department: 3753)
Fluid handling
Combined
C251S368000, C417S012000, C417S038000
Reexamination Certificate
active
06305416
ABSTRACT:
BACKGROUND OF THE INVENTION
Electrically operated pumps are used to supply water from wells and to boost the pressure of municipal water systems. Such pumps are operated by electric motors under the control of a pressure sensitive switch. Some prior art systems operate by keeping a reservoir tank substantially filled with water. In such a system, the pump motor turns on when pressure drops below a pre-set value and turns off when the pressure reaches another higher pre-set value. The duty cycle for the electric motor in such a system is high, with numerous transitions from off to on and off again.
Alternative systems are known in which the pump runs when there is a demand for water and is off when the demand ceases. U.S. Pat. Nos. 5,190,443 and 5,509,787 are directed to actuators which control a pump based on demand. In these two patents, the interplay of hydrostatic and hydrodynamic forces moves a shuttle member which alternately opens and closes a passageway to allow pressure to communicate with a pressure-activated switch for controlling the pump motor. Another design as set forth in U.S. Pat. No. 3,871,792 utilizes a combination of hydrodynamic forces and spring forces to control a switch operate the pump motor. In particular, the configuration set forth in the '792 patent requires two springs, one to control the moving member of a poppet valve and another spring to control the motion of a flexible diaphragm. The design is also complicated by first and second internal auxiliary passageways to provide for pump motor control.
SUMMARY OF THE INVENTION
In one aspect, the invention is a hydraulic actuator comprising an actuator body which includes an inlet, at least one outlet, a port communicating with a pre-charged diaphragm tank, and a port communicating with a pressure switch. The actuator body includes a movable member which, in a first position, fills the inlet port and provides fluidic communications with the pressure switch. In a second position, the movable member opens the inlet's port and seals the pressure switch port. The actuator further comprises a spring disposed within the actuator body, which urges the movable member towards the first position. The movable member includes a bypass which provides fluidic communication between the inlet and interior of the actuator body when the movable member is in the first position. The actuator may include a check valve assembly, which, in an open position, allows fluidic communication from the pressure switch to the actuator valve.
In a preferred embodiment, the movable member comprises a lubricious material or a lubricous coating. The lubricious material or coating may be a fluoropolymer such as Teflon™ or an acetal such as Delrin™. Other appropriate fluoropolymers include fluorinated ethylene propylene, perfluoroalkoxy copolymers, and ethylene-tetrafluoroethylene copolymers. Other appropriate lubricious coatings include diamond, diamond-like coatings, silver, metal oxides and fluorides, molybdenum sulfide, tungsten sulfide, carbon, graphite, titanium nitride, nickel alloys, parylenes, poly(vinylpyrrolidone), silicone, boron nitride, polyimides, or plasma vapor deposited polymers.
In another aspect, the invention is a hydraulic actuator comprising an actuator body which includes an inlet, at least one outlet, a port communicating with a pre-charged diaphragm tank, a port communicating with a pressure switch, and a passageway communicating with the port which communicates with the pressure switch and an interior of the actuator body. The actuator body includes a movable member which seals the inlet port and provides fluidic communication with the pressure switch when it is in a first position. In a second position, the movable member opens the inlet port and seals the pressure switch port. The actuator further comprises a spring disposed within the actuator body which urges the movable member toward the first position. The movable member includes a bypass which provides fluidic communication between the inlet and an interior of the actuator body which the movable member is in the first position. The actuator may further include a support member which includes a transverse passageway in fluidic communication with an axial passageway, wherein the axial passageway communicates with the port which communicates with the pressure switch. The support member may include plurality of spaced apart seals. The movable member may include a passageway which enables fluidic communication between the interior of the actuator body and the port in communication with the pressure switch when the movable member is in the first position.
The bypass may comprise at least one groove oriented longitudinally with respect to the movable member, which is cut into a surface of the movable member, or the by-pass may comprise at least one channel drilled through a base portion of the movable member. The movable member may include an axial passageway which enables fluid communication between the port which communicates with the pressure switch and the interior of the actuator body when the movable member is in the first position. When the movable member is in the first position, it may be seated in a recess in the actuator body and may seal the inlet port by means of an o-ring seated in the recess. A flow rate of greater than 2.5 gal/min through the inlet may exert a force on the movable member greater than that exerted by the spring. The minimum flow rate to overcome the force of the spring may be 2, 1.5, 1, or 0.5 gal/min. The actuator may further include a support member which guides the movable member in a sliding motion. The support member may include a transverse passageway which is in fluidic communication with an axial passageway, which in turn communicates with the port communicating with the pressure switch. The movable member may include a passageway which enable fluidic communication between the transverse passageway and the interior of the actuator body when the movable member is in the first position.
REFERENCES:
patent: 3871792 (1975-03-01), Gritz
patent: 5190443 (1993-03-01), Valdes
patent: 5509787 (1996-04-01), Valdes
Beekhuis Stefan
Joerg Wolf
Lombari Robert
Snel Fred
Chambers A. Michael
Choate Hall & Stewart
Flexcon Industries
Rosen Valarie B.
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