Method and an elevator system for defining an elongation of an elevator car suspension device

An elevator system, comprising:

• an elevator car;
• an elevator car suspension device configured to suspend the elevator car and a counterweight in an elevator shaft;
• an elevator service device;
• and
• an elevator safety control device,
• wherein the elevator safety control device is configured to periodically obtain a value representing an overtravel distance of the elevator car, to thus obtain a plurality of periodically obtained values representing the overtravel distance of the elevator car,
• wherein the elevator safety control device or the elevator service device is configured to define elongation of the elevator car suspension device based on the plurality of periodically obtained values representing the overtravel distance of the elevator car, wherein the elevator safety control device or the elevator service device is further configured to
• define a longtime trend of the overtravel distance based on the plurality of periodically obtained values representing the overtravel distance, and
• define a particular time frame during which a length of the elevator car suspension device is to be adjusted, based on the defined longtime trend,
• wherein each periodically obtained value representing the overtravel distance is obtained by
• overcoupling a final limit switch arranged to the elevator shaft above a top floor of a plurality of floors in the elevator shaft,
• driving the elevator car upwards from the top floor until the counterweight comes into contact with a buffer at a bottom of the elevator shaft, and
• determining a distance travelled by the elevator car from the top floor up to a position in the elevator shaft that corresponds to detection of an indication that the counterweight comes into contact with the buffer,
• wherein the distance corresponds to the overtravel distance of the elevator car, and
• wherein the indication that the counterweight comes into contact with the buffer is detected based on
• detection of a change in a torque of a hoisting motor of a hoisting machine configured to drive the elevator car, or
• detection of a movement of the buffer via a switch coupled to the buffer.

A control device for an elevator system, the elevator system including an elevator car, a counterweight, and an elevator car suspension device configured to suspend the elevator car and the counterweight in an elevator shaft, the control device comprising:

• a memory storing computer program code;
• and
• a processor configured to execute the computer program code to perform a method, the method comprising:
• periodically obtaining a value representing an overtravel distance of the elevator car, to thus obtain a plurality of periodically obtained values representing the overtravel distance of the elevator car, and
• defining an elongation of the elevator car suspension device, based on the plurality of periodically obtained values representing the overtravel distance of the elevator car,
• selectively transmitting one or more signals, based on the defined elongation of the elevator car suspension device, to
• cause an instruction to adjust a length of the elevator car suspension device to be provided, and/or
• provide an instruction to cause the elevator car to be taken out of service, defining a longtime trend of the overtravel distance based on the plurality of periodically obtained values representing the overtravel distance, and
• defining a particular time frame during which a length of the elevator car suspension device is to be adjusted, based on the defined longtime trend,
• wherein each periodically obtained value representing the overtravel distance is obtained by
• overcoupling a final limit switch coupled to the elevator shaft above a top floor of a plurality of floors in the elevator shaft,
• driving the elevator car upwards from the top floor until the counterweight comes into contact with a buffer at a bottom of the elevator shaft, and
• determining a distance travelled by the elevator car from the top floor up to a position in the elevator shaft that corresponds to detection of an indication that the counterweight comes into contact with the buffer,
• wherein the distance corresponds to the overtravel distance of the elevator car, and
• wherein the indication that the counterweight comes into contact with the buffer is detected based on
• detection of a change in a torque of a hoisting motor of a hoisting machine configured to drive the elevator car, or
• detection of a movement of the buffer via operation of a switch coupled to the buffer.