05039279 is referenced by 69 patents and cites 18 patents.

A flow detector for use in a volumetric pump to determine if fluid is being displaced by the 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 passage exceeding the cracking pressure, a flow detector (54) comprising in one preferred embodiment a strain gauge (198) 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. Other types of sensors, including an optical sensor (300), and a linear variable displacement transformer (LVDT) (318) are alternatively used for sensing movement of an outlet valve arm (180) as fluid flows from volumetric pump (30). 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.

Sensor for detecting fluid flow from a positive displacement pump
Application Number
Publication Number
Application Date
March 15, 1990
Publication Date
August 13, 1991
Michael W Lawless
Boulder Creek
Vernon R Natwick
Los Altos
Christensen O Connor Johnson & Kindness
Abbott Laboratories
F04B 49/10
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