Check valve system

Details Check valve system Check valve system

1999-07-29

2001-12-11

Walberg, Teresa (Department: 3742)

Pumps

Motor driven

Fluid motor

C417S225000, C417S345000

Reexamination Certificate

active

06328542

ABSTRACT:

TECHNICAL FIELD
The present invention relates to valves and, more particularly, to check valve systems for use with intensifier pumps.
BACKGROUND INFORMATION
Hydraulic intensifier pumps are widely used in applications requiring the delivery of a high pressure jet of fluid. An intensifier pump includes a pump cylinder, a hydraulic working piston, a product intensifier piston, an inlet for the hydraulic working fluid, an inlet for the product fluid to be pressurized, and an outlet for the pressurized fluid. In operation, lower pressure hydraulic fluid is applied to the comparatively large working piston. The working piston, in turn, drives the smaller intensifier piston. The ratio of the hydraulic and product piston areas is the intensification ratio. The hydraulic pressure is multiplied by the intensification ratio to produce an increase in pressure.
The fluid to be intensified typically is delivered to the intensifier via an inlet check valve from a low pressure fluid supply pump. The fluid supply pump generally is able to generate sufficient pressure to overcome the tension of an internal poppet spring within the check valve, opening the check valve when the intensifier is in the retraction cycle and allowing product fluid to be delivered to the intensifier cylinder. When the piston begins its advance cycle to expel the pressurized fluid, the higher pressure of the intensified product fluid overcomes the lower supply pressure, closing the inlet check valve and thereby preventing backflow of the intensified fluid into the low pressure supply side of the pump. Many intensifier systems incorporate two or more single acting, single ended intensifier pumps, or two double intensifier pumps, that advance and retract on an alternating basis to provide a substantially continuous fluid jet. When one product intensifier piston retracts, the other advances. The relative timing of the advance and retraction cycles is carefully controlled to provide a substantially constant fluid pressure. Nevertheless, intensifier systems incorporating multiple single or double-acting intensifier pumps typically exhibit minor pressure fluctuations.
For industrial applications requiring precise fluid delivery, pressure fluctuation can be highly undesirable. For example, in processing of dispersions, emulsions, liposomes, and the like, the total amount of work, or energy, being applied is a function of both the mechanical power, or shear, and the time the product is in the shear zone. Further, in order to effectively process dispersions, the energy level must be sufficiently high and uniform to disperse agglomerate structure. A gradient of energy levels being applied to a dispersion, a result of processes having pulsation, will result in some of the product being subjected to insufficient processing. Continued processing of the product, under conditions where pulsations exist, cannot compensate for the gradient of energy levels that is less than the energy level required. Other applications that suffer from pulsation include the processing and pumping of coating solutions to a coating process such as a dual layer coating die.
SUMMARY
The present invention is directed to a high pressure check valve system useful with an intensifier pump. The check valve system is particularly useful in an intensifier pump system designed to be pulsation free, or “pipless.” The check valve system includes a controller that controls the check valve based on the position of a piston within the intensifier pump barrel. The present invention also is directed to an intensifier pump system incorporating such a check valve system, as well as a method for controlling a check valve and an intensifier pump system based on the position of a piston within the intensifier pump barrel.
A system and method, in accordance with the present invention, preferably senses a continuous position of one or more intensifier pistons during operation. The term “continuous position,” as used herein, means the position of a hydraulic working piston or product intensifier piston at one of several points along the path traveled by the piston, in contrast to sensing merely a single termination or proximity point, e.g., at the end of a cycle. Continuous position sensing allows anticipation of different events along the path traveled by the piston, such as the start or end of a cycle. In some embodiments, however, use of a proximity sensor may be acceptable.
The position of the product intensifier piston may be sensed directly. Alternatively, the position of the hydraulic working position may be sensed as an indication of the position of the product intensifier piston. In other words, the position of the hydraulic working piston will provide an indirect indication of the position of the product intensifier piston. The system and method operate to selectively open and close associated inlet check valves based on the sensed position to carefully control the delivery of product fluid to each intensifier pump. Active control of the check valves based on continuous piston position allows more precise timing of fluid delivery in relation to advance, retraction, and preload stages of the piston cycle. Anticipation of the onset of piston advance and retraction cycles can improve valve response time, providing an actively controlled “smart” valve. Valve operation can be made more efficient, and can be tuned according to the characteristics of the valve and the product fluid.
With this check valve system and method, the operation of an intensifier pump can provide more uniform fluid pressure. For example, check valves associated with multiple single acting and double acting intensifier pumps can be coordinated to provide a continuous, steady, high pressure flow of product fluid with minimal pressure fluctuation. In addition, the check valves can be actively controlled with an actuator to provide increased initial closing force, increased seating pressures, and increased opening and closing speeds. Also, in some embodiments, actuation speed can be dynamically controlled by controlling the characteristics of the valve actuator. The result is a check valve having an accelerated response time, allowing precise synchronization with the intensifier piston.
With improved response time, the inlet check valve can be opened more quickly to increase the amount of fluid pumped to the intensifier cylinder during the retract cycle. In addition, the check valve can be closed more quickly, minimizing valve leakage upon initiation of the advance cycle of the intensifier piston. The inlet check valve can be particularly useful for applications involving the delivery of pigmented dispersions having higher viscosity levels or particulate structures. Active control based on continuous piston position permits the system to compensate for changes in the characteristics of the product being processed through the inlet check valves.
Knowledge of the continuous position of the product intensifier piston enables anticipation of an event such as, for example, the end of the advance cycle or the start of the retract cycle. This anticipation advantage allows check valve actuation to be finetuned according to intensifier pump operation. Also, negative effects on valve hysteresis resulting from product fluid characteristics such as high viscosities and particulate structures can be compensated by tuning check valve actuation. With relatively large opening and closing forces and active actuation, the valve system is able to function positively when encountering high viscosity dispersions having a wide particle size distribution, and need not be subject to a fixed spring bias response.
In one embodiment, the present invention provides a system for controlling the flow of fluid to an intensifier pump, the system comprising a check valve housing defining an inlet for communication with a fluid supply, an outlet for communication with the intensifier pump, and a fluid flow channel extending between the inlet and the outlet, a valve poppet that is movable within the fluid flow channel to open and close th

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