Cylinder device for a hydraulic lifting device with distance measurement, hydraulic lifting device, chassis and mobile device

A mobile medical device comprising a chassis with a hydraulic lifting device for lifting the chassis, wherein the chassis has castors which come into contact with the ground for moving the chassis on the ground, and wherein the hydraulic lifting device comprises a cylinder device, the cylinder device comprising:

• a housing, a piston rod axially movable relative to the housing, and a support foot attached to the piston rod, wherein the support foot is configured to lift the chassis off the ground when the cylinder device is actuated;
• and
• a distance measuring device which detects axial movement of the piston rod relative to the housing, wherein the distance measuring device comprises a rotary element, a movement transmission element and a sensor unit;
• wherein the rotary element is disposed in the housing in such a way that a rotary movement of the rotary element relative to the housing is possible and an axial movement of the rotary element relative to the housing is prevented;
• wherein the piston rod comprises the movement transmission element, the movement transmission element translating an axial movement of the piston rod into a rotary movement of the rotary element;
• and
• wherein the sensor unit is attached to the housing and the sensor unit detects the rotary movement of the rotary element which is converted into a distance travelled by the piston rod,
• wherein an immobilization state of the piston rod is a state in which the piston rod is held in an extended position in which the chassis is lifted from the ground;
• wherein the sensor unit detects a retraction of the piston rod during the immobilization state;
• and
• wherein the retraction of the piston rod during the immobilization state is compared with predefined tolerances to detect an unintentional lowering of the chassis.