The present invention relates to the field of elevator technology and more
particularly to a detection system monitoring an abnormal moving situation for an
elevator car and/or a counterweight.
BACKGROUND OF THE INVENTION
One of the most popular elevator designs is still the roped traction elevator. In
current versions of such type having the car linked to a counterweight via a
suspension roping, the roping is guided in kind of loop over a traction sheave
which is driven by motor force to move the car either up or down. Therewith a
movement of the counterweight is linked in opposite direction, meaning that in
case the car travels down the counterweight goes up, and vice versa. Said roping
can be of a round rope type or a flat belt. As regards the counterweight, it weighs
about the same as the empty car filled to 40-percent of its rated capacity. In other
words, when the car is 40 percent full (an average amount), the counterweight and
the car are perfectly balanced. The purpose of this balance is to conserve energy
and ensure adequate friction between the suspension roping and traction sheave.
With equal loads on each side of the sheave, it only takes a little bit of force to tip
the balance one way or the other. To put it another way, the balance maintains a
near constant potential energy level in the system as a whole. The friction between
this roping and the traction sheave is critical in elevators. In normal operation
conditions the friction between the ropes and the traction sheave is large enough

CLAIMS
1. Method for monitoring the run of a roping (13) interconnecting a car
(10) and a counterweight (12) of an elevator and for detecting an abnormal
operation condition during the drive of a drive pulley (14) intending therewith
the car and the counterweight to be moved by said roping, wherein the roping
(13) is running on its way from the car (10) to the drive pulley (14) via at least
one diverting pulley (16, 17) and on its way from the counterweight (12) to
the traction drive pulley (14) via at least one diverting pulley (18),
characterized in that the rotation of at least two of said pulleys (14, 16, 17; 18)
is monitored by sensing their rotation, wherein the rotation data are analysed
in view of a mutual correlation indicating unobstructed advancing of the car
(10) or counterweight (12) or both, and detecting therewith an abnormal
situation when detecting an absence of such correlation.
2. Method according to claim 1,
characterized in that a stopping of the run of the elevator is initiated as a
20 response of an abnormal difference in the mutual rotation data.
3. The method according to claim 1 or 2,
characterized in that it further comprises launching an alarm as a response to a
detected abnormal operation condition.

4. A computer program comprising a program code adapted to cause the
method according to any of claims 1 – 3 being executed on a data-processing
system.
5. System for monitoring the run of a roping (13) interconnecting a car
(10) and a counterweight (12) of an elevator and for detecting an abnormal operation condition during the drive of a drive pulley (14) intending therewith the car and the counterweight to be moved by said roping, the system
comprising
- at least one diverting pulley (16, 17) coupled to the car, the drive pulley
(14) and at least one diverting pulley (18) coupled to the counterweight,
wherein the at least two pulleys (14, 16, 17; 18) are equipped with sensors
sensing their rotation, respectively
- a control unit configured to receive the sensor data and to analyse them by
monitoring a mutual correlation indicating therewith unobstructed
advancing of the car (10) or counterweight (12) or both.
6. The system according to preceding claim 5,
characterized in that the system is configured to stop the run of the elevator as
a response of the detection of an abnormal difference in the mutual
correlation.
7. The system according to one of preceding claims 5 or 6,
characterized in that the system is configured to launch an alarm as a response
to a detected abnormal difference in the mutual correlation.