Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
2001-05-17
2003-09-09
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S044110, C417S413100
Reexamination Certificate
active
06616413
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to method devices and system for fluidic pumps. More particularly it pertains to/gas pumps, gas flow control and fluid level sensing. This invention optimizes the efficiency of electromagnetic reciprocating pumps such as those described in U.S. Pat. No. 4,154,559, U.S. Pat. No. 4,170,439, and U.S. Pat. No. 5,052,904 (among others) by control of the pump driving frequency and drive current. Energy savings are realized in the pump operation by eliminating off-nominal pump drive conditions. In practice, electromagnetic reciprocating pumps are driven by the continuous 60 Hz sinusoidal AC service available from utility power companies (50 Hz in some countries other than the US). In their design and manufacture they are made to pump most efficiently at or near the utility power frequency when they are operating at or near the nominal conditions of their intended application range. As conditions vary from the nominal, efficiency and flow also vary. Off nominal pump performance may become so compromised that flow ceases well before the pump capacity is exceeded.
The Problem
The problems with prior art pumps is that they do not automatically optimize. By driving these pumps with periodic pulses rather than continuous sinusoidal current or by appropriately interrupting a continuous sinusoidal drive current, an opportunity is created in the interval when the drive current is off to monitor the voltage produced in the electromagnet coil by the returning motion of the magnet near the core poles. The voltage waveform thus produced can be analyzed to derive steering information for control of the drive frequency and drive current to optimize pump operation for varying conditions that fall within the pump performance limits. In addition, the voltage waveform can be analyzed to indicate the back pressure or pump load. For a given drive current, this indication has a consistent relationship to the height of the fluid column into which the pump is operating (based on the Least Squares Fit analysis, this relationship is linear). Thus the pump not only operates as a pump, but also as a level sensor. This method is scaleable and is applicable to similar pumps with higher or lesser capacities than those intended for the patent examples given above.
BRIEF SUMMARY OF THE INVENTION
The invention is the modification of the drive method for electromagnetic reciprocating pumps such as those described inter alia by Enomoto U.S. Pat. No. 4,154,559, by Hase U.S. Pat. No. 4,170,439, and by or Itakura U.S. Pat. No. 5,052,904. By driving these pumps with periodic, pulsed current rather than continuous sinusoidal current, an opportunity is created in the interval between the drive pulses to monitor the voltage produced in the coil by the motion of the magnet(s) near the core poles.
All the prior art know to the applicant his attorney or the examiner has been made of record in the parent application to which this is a continuation in part. The invention enables electromagnetic reciprocating pumps to be used to sense the pumping load and, thus, fluid levels. The invention enables control of electromagnetic reciprocating pumps to deliver flow at a constant rate under varying pumping load conditions (varying fluid column heights into which the pump is operating).
REFERENCES:
patent: 4022174 (1977-05-01), Brinkman
patent: 4154559 (1979-05-01), Enomoto
patent: 4170439 (1979-10-01), Hase
patent: 4792293 (1988-12-01), Wang
patent: 4899582 (1990-02-01), O'Dougherty
patent: 5052904 (1991-10-01), Itakura et al.
patent: 5066204 (1991-11-01), Point et al.
patent: 5193986 (1993-03-01), Grant et al.
patent: 5494415 (1996-02-01), Morita
patent: 5520517 (1996-05-01), Sipin
patent: 5630710 (1997-05-01), Tune et al.
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