Braking device for braking an elevator car of an elevator installation

A braking device for braking an elevator car of an elevator installation, the elevator installation including an elevator shaft connecting several floors of a building to one another, a vertical rail arranged in the elevator shaft, the elevator car being moveable in the elevator shaft between the floors, and the elevator car having the braking device pressing a brake lining against the rail to brake the elevator car, the braking device comprising:

• a spring element exerting a spring force on the brake lining pressing the brake lining against the rail;
• a master unit having a master housing and a master piston arranged in the master housing, the master piston being displaceable along a master axis and, together with the master housing, enclosing a master volume filled with a first portion of a brake fluid, a size of the master volume depending on a position of the master piston along the master axis;
• a slave unit having a slave housing and a slave piston arranged in the slave housing, the slave piston being displaceable along a slave axis and, together with the slave housing, enclosing a slave volume filled with a second portion the brake fluid, a size of the slave volume depending on a position of the slave piston along the slave axis, wherein a counterforce compensating for the spring force is exerted on the slave piston by increasing the slave volume, the slave piston being coupled to the brake lining such that the counterforce is transmitted to the brake lining in a direction opposite to the spring force;
• a hydraulic line connecting the master volume to the slave volume;
• an actuator adapted to displace the master piston along the master axis;
• an expansion tank containing a third portion of the brake fluid;
• a control valve adjustable between a blocking position and a flow position, the control valve having a first control valve connection connected to the expansion tank and a second control valve connection connected to the master volume and/or the slave volume, the first control valve connection and the second control valve connection being separated in the blocking position and connected together in the flow position, wherein a sum of the master volume and the slave volume is constant when the control valve is in the blocking position.