Patent ID: 7596823

Claim:
Lying-down means comprising a mattress ( 1 ) with a plurality of air chambers ( 2 ) in grid arrangement and each having at least one air connecting means ( 6 ) a plurality of controllable valves ( 3 ) each associated with a respective one of the air chambers for pumping in air into the air chamber and letting out air from the air chamber, a plurality of sensors, one of said sensors being a pressure sensor, a control unit ( 4 ) connected with the sensors and individually controlling the valves ( 3 ) in dependence on output signals of the sensors and an air source ( 7 ) connected with the valves, wherein the air source ( 7 ) comprises a piston ( 15 ) driven by a linear motor ( 14 ) and reciprocatingly movable in a piston housing ( 16 ) having a pump chamber, wherein the control unit ( 4 ) controls the valves ( 3 ) in such a way that a valve for pumping in or letting out air is open during the upward or downward movement of the piston only if the pressure in the respective air chamber corresponds with the air pressure prevailing in the pump chamber, and wherein the piston housing has the pressure sensor, the pressure sensor having an output signal supplied to the control unit for enabling the control unit to ensure that the valve for pumping in or letting out air is open during the upward or downward movement of the piston only if the pressure in the respective air chamber corresponds with the pressure prevailing in the pump chamber of the piston housing.