Patent Description:
Tensile support structures, such as coated steel belts or wire ropes containing metal cords, are used to move an elevator car up and down within an elevator shaft or hoistway. Because the condition of the tensile support structure is critical to the safety of the operation of the elevator, there is a need to determine the remaining strength level of the tensile support and detect if the remaining strength level falls below a minimum threshold.

The strength of a tensile support structure can be reduced by normal operation of the elevator over time. The primary source of the degradation in the strength of the support structure is the cyclic bending of the support structure around sheaves as the elevator is moved up and down in an elevator shaft or hoistway. The degradation of a support structure is normally not uniform along the length of the support structure, but rather, focused to areas of the support structure that are subjected to high levels or severities of bending cycles.

Some electrical characteristics, such as electrical resistance or impedance, of the cables, cords or tension members in the support structure will vary as the cross-sectional areas of the tension members decrease. Accordingly, it is possible to determine the remaining support strength of the support structure based on the electrical characteristics of the tension members thereof. There currently are some monitoring systems which employ a resistance-based inspection scheme to monitor the resistance of support structures, and thus, the remaining strength thereof. In such systems, a measured electrical resistance is compared to a predetermined resistance threshold such that if the resistance threshold is exceeded, the belt is evaluated for potential repair or replacement. The resistance threshold is determined taking selected factors into account, including an expected elevator system traffic pattern. Such monitoring systems are known for example in <CIT>, <CIT>, <CIT> and <CIT>. <CIT> discloses a method of wear detection of a support structure of an elevator according to the preamble of claim <NUM> and a monitoring system for a support structure of an elevator car according to the preamble of claim <NUM>.

According to a first aspect of the present invention, a method of wear detection of a support structure of an elevator system according to claim <NUM> is provided.

The one or more indicators may include a count of elevator car starts from a selected landing floor of the elevator system.

The monitoring system may be operably connected to a main controller of the elevator system, the main controller providing the count to the monitoring system.

The one or more indicators may include load weight data of the elevator car.

The monitoring system may be operably connected to a load weight sensor of the elevator car to provide the load weight data to the monitoring system.

The threshold resistance may be re-determined at one or more selected intervals.

The selected interval may change over a service life of the support structure.

The electrical resistance may be remeasured at one or more selected measurement intervals.

The method may include one or more of remeasuring the electrical resistance, repairing the support structure or retiring the support structure if the measured electrical resistance exceeds the resistance threshold.

According to a second aspect of the present invention, a monitoring system for a support structure of an elevator car of an elevator system according to claim <NUM> is provided.

The monitoring unit may be configured to redetermine the threshold resistance at one or more selected intervals.

The measurement unit may be configured to remeasure the electrical resistance at one or more selected measurement intervals.

According to a third aspect of the present invention, an elevator system according to claim <NUM> is provided.

The one or more indicators may include one or more of a count of elevator car starts from a selected landing floor of the elevator system, or load weight data of the elevator car.

The support structure may be one of a rope or a belt.

The present invention relates to monitoring of support structures. While <FIG> describes one possible support structure, in particular a tensile support structure, namely belts or ropes used to suspend and/or drive components of an elevator system, the present invention could be used with other support structures. Other exemplary support structures include belts or jacketed cords as used in exercise machines, jacketed cables as used with cranes, or any other multistrand wire or rope being used in tension. Referring now to <FIG>, an elevator system <NUM> is shown in schematic fashion. It is to be understood that the version of the elevator system10 shown in <FIG> is for illustrative purposes only and to present background for the various components of a general elevator system.

As shown in <FIG>, the elevator system <NUM> may include a car <NUM> coupled to a counterweight <NUM> by a support structure <NUM>. The support structure <NUM> may extend over a traction sheave <NUM> that is driven by a machine <NUM>. Traction between the sheave <NUM> and the support structure <NUM> may drive the car <NUM> and counterweight <NUM> through the hoistway. Operation of the machine <NUM> may be controlled by a main controller <NUM>. The elevator system <NUM> may further include a monitoring system <NUM> in electrical communication with, and/or disposed in a location proximate to, the support structure <NUM> and configured to detect the condition of the support structure <NUM> by measuring, for example continuously or intermittently, the resistance thereof.

Turning to <FIG>, one exemplary support structure <NUM> is provided in the form of a belt having a plurality of individual tension members <NUM> in a jacket coating <NUM>. The tension members <NUM> may include conventional steel wires formed into strands and/or cords, or any other supportive material having an electrical resistance. The jacket coating <NUM> may comprise one or more materials suitable for promoting traction with the traction sheave <NUM>, such as polyurethane or elastomeric materials. The jacket coating <NUM> may additionally comprise an electrically insulative material suitable for prohibiting electrical communication therein. The operational condition or state of one or more (including each) tension member <NUM> of the support structure <NUM> of <FIG> may be determined using a resistance-based inspection scheme, wherein, for example, the remaining life of the one or more tension members <NUM> of the support structure <NUM> may be determined in terms of the increase in the resistance of the tension members <NUM> relative to a baseline value (for example measured during initial installation of the support structure <NUM> in the elevator system <NUM>. The overall operational condition or state of a support structure <NUM> could be monitored continuously or intermittently for any substantial increase in resistance. The support structure <NUM> may also be monitored for any wear in the jacket coating <NUM> by, for example, detecting for any contact or electrical short between exposed tension members <NUM> and electrically conductive idler or fraction sheaves <NUM>. In one possible arrangement, the individual tension members <NUM> may be connected in series so as to minimize the number of monitored resistances and provide one effective resistance per support structure <NUM>. The effective resistance of a support structure <NUM> may be indicative of the actual resistance, or any multiple, fraction or scale thereof, exhibited by the support structure <NUM>. As shown by the ends of an exemplary support structure <NUM> of <FIG>, the tension members <NUM> may be coupled or shorted together at alternating and respective ends using connectors <NUM> so as to electrically connect the tension members <NUM> associated with one support structure <NUM> in series form. Other arrangements, such as monitoring one or more tension members <NUM> in parallel or a combination of parallel and serial monitoring of subsets of the tension members <NUM>, are also possible.

Referring to <FIG>, the monitoring system <NUM> is electrically connected to one or more tension members <NUM> of the support structure <NUM>. Although described below with respect to tension members <NUM>, the monitoring system <NUM> could be connected to one or more strands or individual wires of the tension members <NUM>. The monitoring system <NUM> is connected to support structure <NUM> at a suitable location, for example, at an end of the support structure <NUM> located at an upper end of the hoistway of the elevator system <NUM>. It is to be appreciated, though, that this location is merely exemplary and other locations for connecting the monitoring system <NUM> to the support structure <NUM> are contemplated within the scope of the present invention.

During operation, an electrical current is applied through the tension members <NUM>. A resulting voltage allows for determination of an electrical resistance of the tension member <NUM>. This measured resistance is compared to an initial resistance of the tension member <NUM> measured or established during the initial installation of the support structure <NUM> to the elevator system <NUM>. A change in the electrical resistance of the tension member <NUM>, typically an increase in resistance, indicates wear of the tension member <NUM>. The change in electrical resistance is compared to one or more thresholds, and when the threshold is exceeded, action may be taken by the elevator system <NUM>, including but not limited to, notifying the maintenance provider, sounding of an alarm, and/or stopping operation of the elevator system <NUM>.

Referring again to <FIG>, wear of the tension member <NUM> depends of the traffic pattern of the elevator car <NUM> along the hoistway <NUM>, being cycles of passage of portions of the tension member <NUM> over the traction sheave <NUM>. As such, when determining the resistance threshold, the monitoring system <NUM> utilizes an actual traffic pattern of the elevator car <NUM>. Utilization of the actual traffic pattern of the elevator car <NUM> when determining the resistance threshold allows for a more accurate and less conservative determination of the resistance threshold, thereby potentially extending the useful service life of the support structure <NUM>, compared to a traditional measurement system in which does not take into account an actual traffic pattern of the elevator car. Such a determination results in a more conservative estimation, and thus support structures <NUM> may be retired from service prior to their useful service life being exhausted.

The actual traffic pattern is determined via intercommunication between the monitoring system <NUM> and other components of the elevator system <NUM>. For example, the main controller <NUM> may count quantities of starts at each floor landing <NUM> of the hoistway <NUM>. Each start at a particular floor landing <NUM> equates with a passage of a particular portion of the support structure <NUM> over the traction sheave <NUM> of the elevator system <NUM>. Further, the monitoring system <NUM> may be connected to a load weight sensor <NUM> of the elevator car <NUM>, with the sensed load weights being indicative of tensile loads on the support structure <NUM>, in particular a suspension portion <NUM> of the support structure <NUM> between the traction sheave <NUM> and the elevator car <NUM>.

Referring now to <FIG>, a method of operating an elevator system <NUM>, in particular evaluating a condition of the support structure <NUM>, is illustrated. In block <NUM>, the support structure <NUM> and monitoring system <NUM> are installed in the hoistway <NUM>. At block <NUM>, an electrical resistance of at least one tension member <NUM> of the support structure is measured by the monitoring system <NUM>. At block <NUM>, an electrical resistance threshold is established based on an actual traffic pattern of operation of the elevator system <NUM>. In some embodiments, the actual traffic pattern is determined via communication between the monitoring system <NUM> and the main controller <NUM> and/or the load weight sensor <NUM>. At block <NUM>, the measured electrical resistance is compared to the electrical resistance threshold, with the result of the comparison indicative of wear of the at least one tension member <NUM>.

If the measured electrical resistance is below the electrical resistance threshold, at block <NUM> the elevator system <NUM> is operated for a selected time interval, for example one month or one year. The stated time intervals are merely exemplary, however, and other time intervals may be utilized. When the time interval is complete, the electrical resistance is remeasured at block <NUM>, and the actual traffic pattern of operation of the elevator system <NUM> over the time interval may be utilized to modify the electrical resistance threshold at block <NUM>. One skilled in the art will readily appreciate that the electrical resistance of the support structure <NUM> may be measured at measurement intervals that vary over the service life of the support structure. The measured electrical resistance is compared to the electrical resistance threshold at block <NUM> and if the measured electrical resistance exceeds the resistance threshold, the support structure <NUM> is evaluated further at block <NUM> for further action, which includes remeasurement of the electrical resistance, or repair or replacement of the support structure <NUM>. If the measured electrical resistance of the support structure <NUM> does not exceed the resistance threshold, the elevator system <NUM> is again operated for a selected interval at block <NUM>. It is to be appreciated that the selected interval may remain constant, or alternatively may change relative to previous selected intervals. For example, early in the life of the support structure <NUM>, the selected interval may be relatively long, and may decrease when the support structure <NUM> nears its projected end of service life.

Referring now to <FIG>, a method of wear detection of the support structure <NUM> is illustrated. At block <NUM>, an electrical resistance of at least one tension member <NUM> of the support structure is measured by the monitoring system <NUM>. At block <NUM>, an electrical resistance threshold is established based on an actual traffic pattern of operation of the elevator system <NUM>. In some embodiments, the actual traffic pattern is determined via communication between the monitoring system <NUM> and the main controller <NUM> and/or the load weight sensor <NUM>. At block <NUM>, the measured electrical resistance is compared to the electrical resistance threshold, with the result of the comparison indicative of wear of the at least one tension member <NUM>.

Utilizing actual traffic patterns of operation of the elevator system <NUM> in determination of the resistance threshold for use in electrical resistance-based evaluation of the support structure <NUM>, reduces uncertainty in establishing the resistance threshold, thus extending useful service life of the support structure <NUM> and reducing associated costs and maintenance time.

While the present invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the scope of the appended claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the appended claims.

Claim 1:
A method of wear detection of a support structure (<NUM>) of an elevator system (<NUM>), comprising:
measuring (<NUM>, <NUM>) an electrical resistance of at least one tension member (<NUM>) of a support structure (<NUM>) via a monitoring system (<NUM>), the supporting structure (<NUM>) being operably connected to an elevator car (<NUM>) and one or more sheaves (<NUM>) of an elevator system (<NUM>);
characterized in that the method further comprises:
determining (<NUM>, <NUM>) a threshold resistance utilizing one or more indicators of an actual traffic pattern of the elevator car (<NUM>) along a hoistway (<NUM>), being cycles of passage of portions of the tension member (<NUM>) over the one or more sheaves (<NUM>);
comparing (<NUM>, <NUM>) the measured electrical resistance to the threshold resistance, the result of the comparison indicative of wear of the at least one tension member (<NUM>); and wherein:
if the measured electrical resistance does not exceed the threshold resistance, operating (<NUM>, <NUM>) the elevator system (<NUM>) for a selected time interval; and
if the measured electrical resistance exceeds the threshold resistance, evaluating (<NUM>, <NUM>) the support structure (<NUM>) for further action, which includes remeasurement of the electrical resistance, or repair or replacement of the support structure (<NUM>).