Patent Description:
Elevator sheaves include a surface that engages the roping and, therefore, is subject to wear over time. Various approaches have been used in the industry to address such wear. For example, plastic sheave liners have been used to establish a desired level of traction. Plastic sheave liners tend to introduce less wear on the elevator roping. Replacing plastic sheave liners is more economical than replacing or reconditioning an entire sheave.

Regardless of the type of sheave or liner, excessive wear should be avoided to prevent damage to the sheave. If a sheave or liner wears too much, the sheave may need to be repaired or discarded, which introduces additional cost and requires taking the elevator out of service while the situation is rectified. The industry standard technique for determining an amount of wear requires a mechanic to observe and measure the condition of the sheave. That approach is time consuming and can only reasonably be done infrequently. <CIT> discloses a sheave monitor.

According to a first aspect of the present invention an elevator sheave wear monitoring device is provided as claimed in claim <NUM>.

In some embodiments the second indication corresponds to a request or a command to shut down an associated elevator system.

In some embodiments the at least one detector is situated to detect the position of the elevator roping near a location where contact between the elevator roping and the sheave begins or ends.

In some embodiments the at least one detector is situated to detect the position of the elevator roping relative to a center of the sheave.

In some embodiments the at least one detector comprises an optical sensor.

In some embodiments the at least one detector comprises a proximity sensor.

In some embodiments the at least one detector comprises a contact sensor.

According to a second aspect of the present invention a method of monitoring elevator sheave wear is provided as claimed in claim <NUM>.

In some embodiments the detecting is performed by at least one detector situated to detect the position of the elevator roping at a location where contact between the elevator roping and the sheave begins or ends.

<FIG> schematically illustrates selected portions of an elevator system <NUM>. An elevator car <NUM> is coupled to a counterweight <NUM> by roping <NUM>. Although not shown in detail in <FIG>, the roping <NUM> includes a plurality of tension members, such as round steel ropes or flat belts. The roping <NUM> follows a path defined, at least in part, by sheaves <NUM>. At least one of the sheaves <NUM> is a traction sheave associated with a machine (not illustrated) that selectively causes movement of the roping <NUM> to control the movement and position of the elevator car <NUM> for providing elevator service to passengers.

At least one wear detector <NUM> is situated near one of the sheaves <NUM>, which is the traction sheave in this example. The wear detector <NUM> detects a position of the roping <NUM> that is indicative of an amount of wear on the sheave <NUM> surface that engages the roping <NUM> as the roping <NUM> at least partially wraps around the sheave <NUM>. The detector in this example is situated to detect a position of the roping <NUM> near a location where contact between the sheave <NUM> and the roping <NUM> begins or ends, depending on the direction the roping <NUM> is moving as the elevator car <NUM> moves. In the illustrated example, the wear detector <NUM> is situated to detect the position of the roping <NUM> along a line that corresponds to a tangent to the location of initial or final contact between the roping <NUM> and the sheave <NUM>. In the illustrated embodiment, the wear detector <NUM> detects a position of the roping <NUM> relative to a center <NUM> of the sheave, which is an axis of rotation of the sheave <NUM>.

In the illustrated example embodiment, a processor <NUM>, which comprises a computing device and memory, receives indications from the wear detector <NUM> regarding the position of the roping <NUM>. The processor <NUM> is configured to determine when the detected location of the roping <NUM> corresponds to an amount of wear on the sheave <NUM> that satisfies at least one criterion. The processor <NUM> is configured to provide an indication when the detected roping position indicates an amount of wear that exceeds a threshold. The indication may be useful as a notification that the sheave <NUM> or its liner needs attention because of the amount of wear. One feature of the illustrated arrangement is that the processor may be programmed or configured to perform more detailed analysis or to provide more detailed outputs than just an indication of the sheave needing maintenance or a need to shut down the elevator system.

Other embodiments do not include a separate processor. In some such embodiments, a passive switch is activated based on the wear detector <NUM> detecting a wear condition of the sheave that requires attention. The passive switch may activate an indicator that the sheave requires attention in the near future or it may cause a shut-down of the elevator system if the amount of detected wear is significant enough to warrant shut-down. In other embodiments, the wear detector is configured to provide an output that corresponds to or indicates the detected wear condition of the sheave.

<FIG> illustrates a portion of the sheave <NUM> and shows how each of the ropes is received in a groove <NUM> in a sheave liner <NUM>. A thickness of the liners <NUM> or the radius of the sheave <NUM> dictates the position of the roping in the illustration. Over time the sheave liners <NUM> will wear and the roping <NUM> will be situated closer to the center of the sheave <NUM> (e.g., lower according to the drawing). The wear detector <NUM> in this example is configured to detect when the roping position corresponds to different amounts of wear. A first threshold <NUM> corresponds to a first amount of wear and a second threshold <NUM> corresponds to a second, greater amount of wear. The wear detector <NUM> in this embodiment detects the position of the roping <NUM> and provides an output to the processor <NUM> that indicates whether the roping <NUM> is in a position corresponding to the first threshold <NUM> or the second threshold <NUM>.

<FIG> includes a flow chart diagram <NUM> that summarizes a method of monitoring wear on the sheave <NUM>. At <NUM>, the wear detector <NUM> detects the position of the roping <NUM>. In embodiments that include the processor <NUM>, the wear detector <NUM> provides a corresponding indication to the processor <NUM>. At <NUM>, a determination is made whether the detected position of the roping <NUM> corresponds to wear on the sheave <NUM> (or the liners <NUM>) exceeds the first threshold <NUM>. This may be accomplished by the wear detector <NUM> or the processor <NUM>, depending on the particular embodiment. If the roping position does not correspond to wear sufficient to meet or exceed the first threshold <NUM>, then the process continues at <NUM>. The wear detector <NUM> may continuously provide an output of the detected roping position or periodically detect the position and provide a corresponding output.

If the roping position corresponds to wear exceeding the first threshold <NUM>, a determination is made at <NUM> whether that position of the roping has been consistent enough to indicate wear exceeding the first threshold. This determination is a way of filtering out any movement of the roping, such as vibration, that may falsely indicate sheave wear. Such movement of the roping will not be continuous or consistent over time and the illustrated method includes the determination at <NUM> to verify when a detected roping position is based on the wear condition of the sheave <NUM> rather than some other condition in the elevator system <NUM>.

Situating the wear detector <NUM> to detect the roping position as close as possible to the place where contact between the sheave <NUM> and the roping <NUM> begins or ends tends to minimize false positive detections that may be caused by rope or belt movement that is due to roping sway or vibration.

The determination at <NUM> is made by the processor <NUM> in some embodiments. In others, the wear detector <NUM> has a time delay function or feature that will delay an output from the wear detector <NUM> until a sufficient time has passed that the roping remains in a location corresponding to sheave wear.

For example, when a detected roping position corresponds to sheave wear that exceeds the first threshold <NUM> for only a few seconds or the signal from the wear detector <NUM> is not constant, the decision at <NUM> is negative and the process returns to detecting the roping position at <NUM>.

If the detected roping position consistently corresponds to sheave wear exceeding the first threshold within predetermined parameters, then whether the detected roping position corresponds to sheave wear exceeding the second threshold <NUM> is determined at <NUM>. If the second threshold is not exceeded, then the wear detector <NUM> or the processor <NUM> provides a first indication at <NUM>. The first indication provides information regarding the condition of the sheave such as an amount of wear that requires attention or scheduling a liner replacement in the near future.

When the position of the roping <NUM> corresponds to wear exceeding the second threshold <NUM>, a determination is made whether that roping position has been consistent enough to indicate actual wear at <NUM>. Again, there may be temporary conditions in the elevator system <NUM> that tend to cause movement of the roping, such as vibration or sway, that may result in the roping <NUM> temporarily moving into a position that could be incorrectly interpreted as resulting from sheave wear. The determination at <NUM> filters out such temporary roping positions to eliminate false positive determinations of wear exceeding the second threshold <NUM>.

When the roping position corresponds to wear exceeding the second threshold <NUM>, the method includes providing a second indication at <NUM>. In some embodiments, the second indication at <NUM> corresponds to a request for sheave maintenance or liner repair as soon as possible. In some embodiments, the second indication may be or request a command to shut down the elevator system until the sheave <NUM> is inspected and serviced.

In some embodiments, the wear detector <NUM> will include more than one detector with each of them associated with a particular wear threshold. Other embodiments include a wear detector that is configured to provide an indication of the location over a sufficient distance or number of locations in a manner that indicates whether the amount of wear has reached more than one threshold.

Some embodiments include an optical sensor that detects the position of the roping <NUM>. For example, <FIG> schematically shows an optical sensor <NUM>. In one embodiment, the optical sensor includes a laser diode <NUM> and a receiver or deflector <NUM> situated so that the roping <NUM> interrupts the light beam <NUM> of the laser diode <NUM> when the sheave wear reaches a selected threshold. In some embodiments, multiple light beams are used with each beam aligned with a respective threshold.

Another example type of optical sensor <NUM> includes a camera that provides image information regarding the position of the roping <NUM> and, therefore, the wear condition of the sheave <NUM>. For example, the camera would be situated in place of the laser diode <NUM> and the receiver or deflector <NUM> would be replaced with a reference image or background that would be interrupted or otherwise appear different in an image from the camera when the roping <NUM> position changes because of sheave wear.

Other embodiments of the wear detector <NUM> include at least one proximity sensor or at least one contact sensor. The embodiment shown in <FIG> includes at least one roller <NUM> situated to be contacted by the roping <NUM>. A sensor <NUM> provides an output when the roller <NUM> rotates as a result of contact with the roping <NUM> during elevator car movement. The roller <NUM> is supported by brackets <NUM> in a position where the roping <NUM> will normally not contact the roller <NUM> until the sheave or its liner has worn an amount corresponding to a selected threshold. In some such embodiments, the output of the sensor <NUM> indicates wear depending on an amount of time that the roller <NUM> has been rotating with longer times indicating increasing wear.

Those skilled in the art who have the benefit of this description will realize what sensor type and arrangement will best meet their particular needs.

Claim 1:
An elevator sheave wear monitoring device, comprising at least one detector (<NUM>, <NUM>, <NUM>) situated to detect a position of elevator roping (<NUM>) that is indicative of a condition of a sheave (<NUM>) that the roping (<NUM>) at least partially wraps around, the at least one detector (<NUM>, <NUM>, <NUM>) providing an output corresponding to the detected position of the elevator roping (<NUM>) and indicating an amount of wear of the sheave that exceeds at least one threshold; and
further comprising a processor (<NUM>) configured to:
determine when the detected position of the elevator roping (<NUM>) indicated by the at least one detector (<NUM>, <NUM>, <NUM>) indicates an amount of wear of the sheave (<NUM>) that exceeds at least one threshold, and
provide an indication that the amount of wear exceeds the at least one threshold;
characterized in that the processor (<NUM>) is further configured to determine an amount of time that the detected position of the elevator roping (<NUM>) indicates the amount of wear of the sheave that exceeds the at least one threshold, and
provide the indication only if the determined amount of time exceeds a predetermined minimum, and further characterized in that:
the at least one threshold comprises a first threshold and a second threshold, and
the processor (<NUM>) is configured to
determine whether the detected position of the elevator roping (<NUM>) indicated by the at least one detector indicates an amount of wear of the sheave (<NUM>) exceeds the first threshold;
determine whether the detected position of the elevator roping (<NUM>) indicated by the at least one detector indicates an amount of wear of the sheave that exceeds the second threshold; and
provide the indication by
providing a first indication when the amount of wear exceeds the first threshold but not the second threshold, and
providing a second indication when the amount of wear exceeds the second threshold.