Pump control systems
AssigneeWaters Associates, Inc.
InventorsLouis Abrahams, Burleigh M. Hutchins, Jr., James L. Waters
Life of this patent
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Abstract
A compact pumping system especially useful in liquid chromatography wherein comprising a liquid path which is fully flushed on each stroke of a pump, a pump which provides substantially pulse-free flow, a pressure-sensor integrated into said flow path and operably connected to the control circuit of a bifilar stepping motor. This circuit is so designed that the driving current applied to the motor is only that required to pump the liquid. The avoiding of heat associated with a greater current is particularly important in forming a compact package of motor and pump for use in liquid chromatography.
Claims37
In a liquid delivery system of the type comprising a pump and outlet useful for supplying from said outlet a liquid under pressure the improvement wherein there is interposed between said pump and a discharge port from said delivery means 1) a pressure-sensing means and 2) flow-control means operably communicating between said pressure-sensing means and a motor drive means for said pump, said control means operably interacting with said drive means to control the flow-output of said pump by controlling the speed of said motor;
- wherein said flow-control means comprises A) Bourdon-type tube, the interior of which forms a flow path for substantially all said liquid B) means for sensing displacement of said tube in response to pressure of the liquid therein, and C) motor control means comprising said sensing means and a motor drive means for said pump;
- wherein said Bourdon-type tube is enclosed within a housing and mounted between a light source and a light-sensing said light source and sensing means forming said displacement-sensing means, and also forming means to provide an input signal to said motor control means;
- and
- wherein said Bourdon tube is bent to form two substantially parallel segments of a single conduit.
In a liquid delivery system comprising a pump, a motor drive for said pump and discharge port for supplying a compressible liquid under different pressure, the improvement wherein said liquid delivery system comprises
- 1. interposed between said pump and said discharge port, a liquid pressure-sensing means, and
- 2. motor control means operably communicating between said pressure-sensing means and said motor drive means, said motor control means forming means to control the flow-output of said pump by controlling the speed said motor in response to the pressure-sensed by said pressure-sensing means, and
- 3. wherein said motor control means comprises means to modify motor speed in response to pressure, said control means forming means to continuously compensate for compression of said liquid being pumped, and to maintain a substantially constant output of liquid despite changes in compression of said liquid with varying pressure.
A liquid delivery system as defined in claim 5 wherein said means to compensate for compression comprises means to speed up the motor, in response to said pressure-sensing means detecting increased pressure.
A pumping process for supplying a compressible liquid under different pressures, said process utilized in conjunction with a pump, a motor drive for said pump, and discharge port, the improvement including the steps of
- 1. sensing pressure of said liquid at a point between said pump and said discharge port,
- 2. controlling the speed of said motor in response to the pressure-sensed by said pressure-sensing means, and
- 3. wherein said controlling step comprises a) modifying motor speed in response to said pressure, and b) continuously compensating for compression of said liquid being pumped, thereby maintaining a substantially constant output of liquid despite changes in compression of said liquid with varying pumping pressures.
Dependencies are inferred from the claim text.