Abstract: A hydraulic actuating unit for raising a hospital bed includes a reservoir, a hydraulic piston cylinder device the cylinder of which has its ends connected to the reservoir through a supply conduit that contains a hydraulic plunger pump with suction and pressure valve means and through a return conduit which contains an orifice in a normally closed relief valve. A branch conduit leads to a hydraulic liquid accumulator from the supply conduit at a location between the cylinder and pressure valve means. A multiple pilot operated check valve of the differential type is provided in the branch conduit towards the accumulator. The largest and smallest end faces of the differential spool member are subject to the pressure in the branch conduit while the differential area of the spool member is subject to the pressure in a conduit which leads from the return conduit at a location between the orifice and the relief valve.