Patent ID: 9724453
Date: 2017-08-08
CPC Classifications: A61M,F04B

Claim:
1. A breast pump system comprising: an expression unit for coupling to a breast to obtain milk in response to an applied pressure change; a vacuum pump configured to be run continuous; a passageway pneumatically coupling the expression unit to the vacuum pump; a solenoid valve pneumatically coupled to the passageway, said solenoid valve including a magnetic member arranged to move alternately between (i) a first position at which the passageway is pneumatically sealed from ambient air flow, thereby enabling the vacuum pump to reduce a pressure in the expression unit to a predetermined negative pressure without exceeding a safety limit, and (ii) a second position at which the passageway is open to ambient air flow, thereby enabling the vacuum pump to pump ambient air to the expression unit to increase the pressure in the expression unit from the predetermined negative pressure; a power source arranged to supply electrical power to the solenoid valve; and a controller configured to detect a change in an inductance of the solenoid valve that is indicative of the magnetic member moving from the first position to the second position and to control an operation of at least one of the solenoid valve and the vacuum pump in dependence on detection of said change in the inductance, where the controller is adapted to switch off the vacuum pump when the controller does not detect the change in the inductance of the solenoid valve within a predetermined time period wherein switching off the vacuum pump stops a further increase in negative pressure in the expression unit beyond the predetermined negative pressure exceeding the safety limit, where the controller is further adapted to switch off the vacuum pump when the controller does not detect the change in the inductance of the solenoid valve within the predetermined time period that corresponds to a period (i) beginning as the magnetic member is moving to its second position which results in the change in the inductance and (ii) ending subsequent to the magnetic member having fully moved into its second position, but prior to a current in the solenoid valve increasing to a stable level.