Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
1999-09-01
2001-07-24
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
36
Reexamination Certificate
active
06264432
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to pumps, and more particularly to a method and apparatus for controlling a pump.
BACKGROUND OF THE INVENTION
Often, it is necessary in an industrial or other process to inject a measured quantity of a flowable material into a further stream of material or a vessel. Metering pumps have been developed for this purpose and may be either electromagnetically or hydraulically actuated. Conventionally, an electromagnetic metering pump utilizes a linear solenoid which is provided half-wave or full-wave rectified pulses to move a diaphragm mechanically linked to an armature of the solenoid.
FIGS. 1 and 2
illustrate a conventional control strategy for an electromagnetic metering pump
15
(shown in FIG.
3
). A solenoid
16
(also shown in
FIG. 3
) is electrically powered at a sufficient level to provide a pumping force at maximum air gap (i.e., zero stroke) which will meet or exceed the maximum fluid force expected to be encountered. The electric power is also delivered at maximum power level at all other stroke positions.
As illustrated in
FIG. 3
, the stroke length of the metering pump
15
is conventionally controlled by a mechanical stroke length adjustment control
17
comprising a screw
18
and a handle
19
. Typically, an operator of the pump manually sets the stroke length by turning the handle
19
, thereby adjusting the screw
18
to a position corresponding to the desired stroke length.
Moreover, the metering pump is ordinarily primed by operating a priming button disposed external to the pump. To prime in this manner, the operator first manually adjusts the mechanical stroke length adjustment control
17
via the handle
19
to the position associated with a maximum stroke length and then pushes the external prime button, which in turn causes the pump to run at its maximum pumping rate.
Several problems, however, arise during the operation of the conventional metering pump. First, the heat that is generated by the electrical powering of the solenoid typically results in the need for components that can tolerate same, such as plastic and metal enclosures and other plastic and metal parts and/or larger solenoids with more copper windings. In addition, the extra forces applied to the armature in light of the maximum power that is applied result in the need for relatively heavier return springs and components to counteract residual magnetism and allow the armature to return in time for the pump diaphragm to do suction work. Still further, sound levels are increased owing to the banging of the armature at the end of the stroke when pumping against lower force levels, and further due to the striking of the armature against a stroke adjustment stop at the end of each suction stroke under the influence of the heavy return spring. Service life is typically short owing to the mechanical stresses that are encountered.
In addition, the conventional mechanical stroke length adjustment control
17
can be inaccurate owing to a lack of precision of the parts and wear.
Moreover, the priming devices present in even the most sophisticated metering pumps are not capable of automatically detecting a loss of prime. Rather, the operator must independently detect that a loss-of-prime condition has arisen. In addition, conventional metering pumps do not automatically return to the originally programmed stroke settings or pump operating conditions after priming or repriming.
SUMMARY OF THE INVENTION
In an effort to overcome these problems, a new control methodology has been implemented that automatically and electronically controls stroke length, stroke velocity and pump priming, while delivering power to the coil as a function of the position of the pump element, thereby substantially reducing the amount of wasted force and energy and the amount of heat produced.
More particularly, in accordance with one aspect of the present invention, a control for a pump having a movable pump element movable over a stroke length which is controllably variable in response to electrical power applied to a power unit comprises a sensor for detecting an operational characteristic of the pump and a circuit responsive to the sensor. The circuit modulates electrical power applied to the power unit in dependence upon the detected operational characteristic of the pump to control the stroke length of the movable pump element.
Preferably, the power unit comprises a solenoid having a coil. Also preferably, the pump element comprises an armature and the sensor comprises a position sensor for detecting the position of the armature. In addition, power is applied to the pump during a suction stroke for controlling the stroke length.
In accordance with another embodiment, the sensor comprises at least one pressure transducer which senses a pressure differential. The circuit may comprise a driver circuit that is coupled to the coil for applying electrical power thereto. A programmed processor is responsive to the sensor for controlling the driver circuit such that electrical power is delivered to the coil in dependence upon the position of the armature.
In accordance with another embodiment, the control may further comprise a keypad coupled to the circuit for inputting a pump parameter and a display also coupled to the circuit for displaying a plurality of pump parameters.
In alternative embodiments, the pump may comprise an electromagnetic metering pump or a hydraulic metering pump.
In accordance with a further aspect of the present invention, a control for an electromagnetic metering pump having a movable pump element movable over a stroke length which is controllably variable in response to electrical power applied to a solenoid comprises a position sensor for detecting a position of the movable pump element and a driver circuit responsive to the sensor and modulating electrical power applied to the solenoid. Power is applied to the solenoid during a suction stroke in dependence upon the detected position of the pump element to control the stroke length of the movable pump element.
In accordance with yet another aspect of the present invention, a method of controlling the stroke length of a pump having a coil and an armature alternately movable in suction and discharge strokes within a range of positions comprises the steps of detecting the position of the armature and providing electrical power to the coil in dependence upon the position of the armature.
In accordance with yet another aspect of the present invention, a control for a metering pump having a movable pump element movable over a stroke length which is controllably variable in response to electrical power applied to a power unit comprises a sensor for detecting an operational characteristic of the pump and a circuit responsive to the sensor. The circuit modulates electrical power applied to the power unit in dependence upon the operational characteristic of the pump element to automatically prime the pump.
In accordance with yet another aspect of the present invention, a control for a metering pump having a movable pump element movable over a stroke length which is controllably variable in response to electrical power applied to a solenoid comprises a position sensor for detecting a position of the pump element and a driver circuit responsive to the sensor. The driver circuit modulates electrical power applied to the solenoid in dependence upon the position of the pump element to automatically prime the pump. The pump element is movable in suction and discharge strokes and the circuit includes means for increasing power applied to the power unit during a suction stroke when a detected pump element velocity is greater than a certain magnitude. The circuit further includes means for reapplying power to the power unit during a subsequent discharge stroke to prime the pump.
In accordance with yet another aspect of the present invention, a method of automatically priming a pump having a coil and an armature movable within a range of positions in suction and discharge strokes comprises the steps of detecting
Kilayko Enrique L.
Ryan Liam
Fastovsky Leonid
Liquid Metronics Incorporated
Walberg Teresa
LandOfFree
Method and apparatus for controlling a pump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for controlling a pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for controlling a pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2526760