Patent ID: 9700239
Date: 2017-07-11
CPC Classifications: A61B,A61G

Claim:
1. A method of detecting a change in occupancy status of a fluidizable bed extending longitudinally between a head end and a foot end and having a distribution plenum and a fluidizable medium, the method comprising: determining an unloaded plenum pressure value corresponding to an absence of a load on the bed; determining a loaded plenum pressure value corresponding to a presence of an occupant on the bed, wherein the unloaded plenum pressure and the loaded plenum pressure are determined using a pressure sensor that is installed either inside the plenum or a conduit that connects a blower with the plenum such that the entirety of the sensor is situated inside the plenum or conduit, wherein the plenum is continuously open to atmosphere through the fluidizable medium when the unloaded plenum pressure and the loaded plenum pressure are measured by the pressure sensor; calculating a reference value as a sum of the unloaded plenum pressure value and a predetermined fraction of a difference between the loaded and unloaded plenum pressure values, wherein the unloaded plenum pressure value corresponds to pressure in the plenum when the fluidizable medium is in a fluidized state and a load is not being supported by the fluidized medium, and the loaded plenum pressure value corresponds to fluid pressure in the plenum when the fluidizable medium is in the fluidized state and a portion of the occupant is supported by the fluidized medium with another portion of the occupant being supported by a nonfluidizable section of the bed that is pivotable upwardly and downwardly relative to a fluidizable medium container that contains the fluidizable medium, the nonfluidizable section being situated adjacent the head end of the fluidizable bed and the fluidizable medium container being configured so that the fluidizable medium occupies a space extending from the nonfluidizable section to the foot end of the fluidizable bed; detecting a current pressure value in the plenum; and issuing a signal in response to the current pressure value being equal to or less than the reference value.