Motors: expansible chamber type – Cyclically operable – Working member controlled motive fluid for distributor motor
Reexamination Certificate
2002-10-21
2004-05-18
Lazo, Thomas E. (Department: 3745)
Motors: expansible chamber type
Cyclically operable
Working member controlled motive fluid for distributor motor
C137S625630, C091S350000
Reexamination Certificate
active
06736046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pilot control valve that achieves a continuous and consistent pumping rate for a reciprocating pump. More particularly, the pilot control valve of the present invention relates to a pilot control valve that controls the flow of control fluid to a piston, valve or the like to drive a reciprocating device such as a chemical or glycol injection pump. The pilot control valve of the present invention controls such flow through a pneumatic valve mechanism having a movable valve member and a plurality of slide valves slideably engaging the movable valve member. By selectively communicating and venting pressurized control fluid through a plurality of control fluid conduits, the pilot control valve of the present invention provides for increased pressurization and venting of the control fluid acting on the piston to increase the pumping speed of the reciprocating device.
2. General Background
There are various prior art devices known for controlling reciprocating pumps. Many prior art devices use a mechanical control mechanism to drive the piston of the reciprocating pump, but these mechanisms have been unreliable either because they require a number of failure- and/or wear-prone components or because they can stall or vary in stroke frequency in response to varying operating conditions frequently encountered in practical usage. One pilot control valve invention using pneumatic valve control and improving on these prior art devices is the pilot control valve invention disclosed in U.S. Pat. No. 6,183,217 B1, entitled “Pilot Control Valve for Controlling a Reciprocating Pump” which issued on Feb. 6, 2001.
The pilot control valve disclosed in U.S. Pat. No. 6,183,217 B1 changes the directional flow of control fluid to a piston coupled to the pilot control valve to drive a reciprocating device. More specifically, the pilot control valve of U.S. Pat. No. 6,183,217 B1 includes a valve member shiftable within a valve body between a first or “downstroke” position and a second or “upstroke” position. When in its first position, the valve member allows communication of pressurized control fluid supplied to the valve body to the lower surface of the piston to initiate movement of the piston from its first or “downstroke” position to its second or “upstroke” position. The pressurized control fluid is communicated to the lower surface of the piston through a first pressurized fluid conduit extending along the length of the valve body outside of the valve body. As the piston reaches its second position, a vent in a rod attached to the piston allows control fluid acting on the valve member retaining the valve member in its first position to depressurize and vent from the valve body. The pressurized control fluid is vented from the valve body through a fluid exhaust conduit extending out of the valve body. As such control fluid is depressurized and vented, pressurized control fluid acts on the valve member to initiate movement of the valve member from its first position to its second position. As the valve member moves from its first position to its second position, a slide valve portion of the valve member advances with the valve member from a first position to a second position. In its second position, the valve member through the positioning of the slide valve portion precludes communication of control fluid to the lower surface of the piston and allows communication of pressurized control fluid to the upper surface of the piston causing the piston to return to its first position. The pressurized control fluid is communicated to the upper surface of the piston through a second pressurized fluid conduit extending along the length of the valve body but within the valve body. As the piston returns to its first position, the vent in the piston rod allows the pressurized control fluid acting on the upper surface of the piston to act on the valve member to move the valve member back to its first position. As the valve member returns to its first position, the slide valve portion of the valve member also returns to its first position. In its first position, the valve member through the positioning of the slide valve portion precludes communication of the control fluid to the upper surface of the piston and allows the pressurized control fluid to vent through a fluid exhaust conduit. The valve member through the positioning of the slide valve portion also allows communication of the control fluid through the first pressurized fluid conduit to the lower surface of the piston and the process is repeated over and over. The duration of each cycle is varied by adjusting a backpressure valve that varies the rate that the control fluid acting on the piston is depressurized and vented from the valve body during each cycle. This process is repeated over and over to achieve a consistent pumping rate for the reciprocating device that uses only pneumatic valve control.
The pilot control valve of U.S. Pat. No. 6,183,217 B1 overcame the prior art devices by improving reliability by controlling the communication of control fluid to a piston included with a reciprocating device using pneumatic valve control rather than a mechanical control mechanism. Although the pilot control valve disclosed in U.S. Pat. No. 6,183,217 B1 has significant advantages, there is still a need for a pilot control valve that delivers a greater volume of control fluid at an increased pressure to drive reciprocating devices at increased stroke rates. Furthermore, there is a need for a pilot control valve that can be tuned to prevent stalling under differing pressure, viscosity, and/or compressibility properties of the control fluid. Finally, there is a need to reduce the operating impact stresses on the pilot control valve by more smoothly transitioning the valve member from its first position through its second position. Such improved performance would need to be achieved without sacrificing reliability and by still providing for the complete control of the piston in a pneumatic manner.
SUMMARY OF THE INVENTION
The pilot control valve of the present invention represents an improvement over the pilot control valve of U.S. Pat. No. 6,183,217 B1 for most reciprocating device applications because it increases the stroke rate of the reciprocating device, it prevents stalling, it increases the tolerance of the reciprocating device to varying properties of the control fluid, it reduces the likelihood of freezing of the control fluid, and it reduces the impact stresses on the valve member, but still relies solely on pneumatic valve control. These improvements are realized with an actual increase in reliability.
Similar to the pilot control valve of U.S. Pat. No. 6,183,217 B1, the pilot control valve of the present invention is positioned above the piston included with the reciprocating device to provide linear, reciprocating force using compressible or non-compressible pressurized control fluid to drive the piston. The pilot control valve of the present invention controls the communication of the control fluid to the piston using pneumatic valve control.
More specifically, the pilot control valve of the present invention includes a valve member shiftable within a valve body between a first or “downstroke” position and a second or “upstroke” position. When in its first position, a pair of slide valves slideably engaging the valve member allow communication of control fluid supplied to the valve body to the lower surface of the piston to initiate movement of the piston from its first position to its second position. Simultaneously, the slide valves allow the control fluid acting on the upper surface of the piston to vent through exhaust ports located in the valve body. The pressurized control fluid is communicated to the lower surface of the piston through a first pair of pressurized fluid conduits extending along the length of the valve body. The pilot control valve of U.S. Pat. No. 6,183,217 B1 delivered pressurized control fluid to the upper surface of the piston t
Elliott Andrew C.
Guccione, Sr. Ray A.
Checkpoint Fluidic Systems International, Ltd.
Jones Walker
Lazo Thomas E.
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