Patent ID: 9623165
Date: 2017-04-18
CPC Classifications: A61M,F17D

Claim:
1. A cassette for pumping a treatment solution through a dialyzer in a dialysis system, said cassette comprising: a body, a hydraulic manifold which is defined inside the body and configured for fluid communication with a first hydraulic connector on the body, the first hydraulic connector being arranged for connecting the dialyzer to the cassette, a pneumatic manifold which is defined inside the body and configured for fluid communication with a first pneumatic connector on the body, the first pneumatic connector being arranged for connecting the cassette to a pneumatic pressure source, a set of solution pumps including an upstream solution pump and a downstream solution pump, each solution pump of the set of solution pumps including a pump cavity which is defined inside the body for fluid communication with the hydraulic and pneumatic manifolds, a calibration cavity connected for fluid communication with a bypass line that extends between the upstream and downstream solution pumps, and a valve arrangement which is operable to selectively communicate the pump cavity with the hydraulic and pneumatic manifolds so as to, during the operation of the respective solution pump, reciprocate an interface in the pump cavity and thereby displace the treatment solution through the hydraulic manifold, wherein each of the pump cavities defines, during operation of the respective solution pump, said interface as a direct gas-to-liquid interface in the pump cavity between a gaseous substance admitted via the pneumatic manifold and the treatment solution admitted via the hydraulic manifold, and wherein the cassette is operable in a calibration phase, in which the valve arrangement is operable to cause one of the upstream or downstream solution pumps to perform an emptying stroke that moves the direct gas-to-liquid interface from an upper reference level to a lower reference level so as to push the treatment solution into the bypass line, cause the other of the upstream or downstream solution pumps to perform a filling stroke that moves the direct gas-to-liquid interface from a lower reference level to an upper reference level so as to draw the treatment solution from the bypass line, and selectively establish fluid communication between the bypass line and the calibration cavity during the emptying and filling strokes so as to transfer a known or measurable calibration volume between the calibration cavity and the pump cavity of the upstream solution pump or the downstream solution pump, wherein a level detector is operable to measure a level change corresponding to the calibration volume in said pump cavity of the upstream solution pump or the downstream solution pump.