Method for monitoring fluid flow from a volumetric pump
First Claim
1. A method for determining whether fluid is flowing from a positive displacement pump, which includes an outlet valve that opens to allow fluid to flow past it during a pumping cycle, when a fluid pressure within the pump reaches a predefined cracking pressure, comprising the steps of:
- producing a signal indicative of a movement of the outlet valve from a closed position to at least a partially open position that allows fluid to flow from the pump in response to the fluid pressure within the pump exceeding the predefined cracking pressure;
establishing an electrical threshold for the signal;
comparing the signal to the threshold; and
determining that fluid is not flowing from the pump based upon the relative magnitudes of the signal and the threshold.
2 Assignments
0 Petitions
Accused Products
Abstract
A method for determining if fluid is being displaced by a volumetric pump. The volumetric pump (30) includes an inlet cracking valve (46) and an outlet cracking valve (52) disposed on opposite sides of a plunger (48) used to displace fluid by compressing flexible tubing (34). During a pumping segment of a pumping cycle for the volumetric pump, the outlet cracking valve is closed with a cracking force that compresses the flexible tubing until the pressure of the fluid displaced by the plunger exceeds a cracking pressure, at which time the outlet cracking valve opens to enable fluid flow from the volumetric pump. A cracking flexure (182) provides the cracking force. As the outlet cracking valve opens in response to the fluid pressure exceeding the cracking pressure, a flow detector (54) mounted to the cracking flexure responds to the stress generated in the cracking flexure thereby, producing a signal indicative of fluid flow from the volumetric pump. Since a compressible gaseous fluid in the pumping portion of the flexible tubing does not develop the cracking pressure, the flow detector also provides an indication when a source of liquid (31) for the volumetric pump has run dry. The method comprises the steps of processing the signal to determine if it exceeds a predefined threshold that varies as a function of the rate at which the pump is set to deliver fluid.
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Citations
20 Claims
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1. A method for determining whether fluid is flowing from a positive displacement pump, which includes an outlet valve that opens to allow fluid to flow past it during a pumping cycle, when a fluid pressure within the pump reaches a predefined cracking pressure, comprising the steps of:
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producing a signal indicative of a movement of the outlet valve from a closed position to at least a partially open position that allows fluid to flow from the pump in response to the fluid pressure within the pump exceeding the predefined cracking pressure; establishing an electrical threshold for the signal; comparing the signal to the threshold; and determining that fluid is not flowing from the pump based upon the relative magnitudes of the signal and the threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for determining whether a liquid is flowing from an outlet of a positive displacement pump having an outlet valve that only opens to allow a fluid to flow from the pump when a pressure developed by the fluid exceeds a predefined cracking pressure, comprising the steps of:
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a. applying a spring bias force to the outlet valve to develop a force that closes the outlet valve until the pressure of the fluid within the pump overcomes the force, causing the outlet valve to open sufficiently so that fluid flows from the pump; b. sensing a movement of the outlet valve as fluid in the pump flows through the outlet valve after the pressure of the fluid exceeds the cracking pressure, forcing the outlet valve open, and by sensing the movement, producing a signal proportional to the opening of the outlet valve; and c. in response to the signal, determining whether the liquid is flowing from the pump through the outlet valve. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification