Safety device, safety system, and method for supervising safety of an elevator system

A safety device for supervising safety of an elevator, the safety device comprising:

• at least one connection interface for receiving data about an absolute position of an elevator car of the elevator in an elevator shaft of the elevator;
• a device adapted to calculate a velocity of the elevator car based on the absolute position data;
• a device adapted to monitor motion of the elevator car in order to keep the motion of the elevator car within an allowed motion limit curve;
• and
• a device adapted to control at least one stopping device if the motion of the elevator car exceeds the allowed motion limit curve;
• wherein the allowed motion limit curve is a function of the absolute position.

A method for supervising a safety system of an elevator, the method comprising:

• measuring motion data of an elevator car of the elevator in an elevator shaft of the elevator on a continuous basis;
• calculating a velocity of the elevator car using the motion data;
• controlling motion of the elevator car using a safety device in order to ensure that the motion of the elevator car remains within an allowed motion limit curve;
• and
• stopping the elevator car using the safety device if the motion of the elevator car exceeds the allowed motion limit curve;
• wherein the motion data includes an absolute position of the elevator car in the elevator shaft, and
• wherein the safety device comprises at least one stopping device.