Patent Application
20120097487
The present disclosure generally relates to elevators and, more particularly, relates to systems for detecting the derailment of a movable element within an elevator.
In modern society, elevators have become ubiquitous machines for transporting people and cargo through buildings of multiple stories. Upon their advent, cities immediately had the option of building upwardly as opposed to only outwardly, thereby contributing to the modern high-rise city landscape and current urban planning models.
Today, the levels of the highest buildings in the world continue to grow, with buildings over one-hundred stories being commonplace; the limits for skyscrapers are being pushed to one hundred and fifty floors or more. That increased height creates multiple new challenges and magnifies existing ones for elevator designers. For example, in a building of such height, is not uncommon for the building at its apex to sway back and forth in excess of three feet or more. Accordingly, each of the mechanical components of the building, including the elevator, must be built to withstand such lateral motion. This is particularly true in areas prone to high winds or earthquakes, where building sway could be even more severe.
One challenge created by the sway of very high buildings has been to provide a mechanism by which the derailment of the elevator car, counterweight, or other moving component can be easily detected with minimal false readings. For years, such detection systems have primarily consisted of a so-called “ring and string” device wherein an electric conductor such as a wire string is extended vertically through the hoistway of the elevator and held at electrical potential. The string is typically mounted only at the top and bottom of the hoistway. A sensing ring is in turn physically mounted to a movable element in the hoistway, such as the counterweight. The sensing ring completely circumscribes the electrical conductor but in spaced relation thereto. When installed and properly aligned, as the counterweight moves up and down on the rail, the sensing ring does not come in contact with the electrical conductor, even with a moderate level of building sway. However, if the counterweight becomes derailed, the sensing ring will contact the electrical conductor. Because the conductor is held at potential, the contact between the ring and the conductor closes a circuit, directing current to flow from the conductor into the counterweight, which in turn is detected by the derailment detection system of the elevator.
As building heights have steadily increased, the sway component mentioned above tends to cause more false readings in the derailment detection system than is desired by the end-user. In particular, even when the counterweight or the movable element within the hoistway are properly mounted on the rails of the system, if the building encounters significant sway either due to high winds or otherwise, the rails on which the movable element is mounted will tend to sway with the building, and in turn cause the sensor itself to sway. However, the electrical conductor stays fixed within the hoistway, in which it is attached only at its top and bottom, so that when the rail and counterweight sway, the ring can potentially contact the wire or electrical conductor, resulting in improper activation of the elevator derailment detection system. This not only inconveniences the end-user in that the elevator will stop or otherwise become less than fully operational, but also results in added expense in terms of maintenance costs for the building.
In accordance with one aspect of the disclosure, an elevator derailment detection system is therefore provided. The system may include a movable element slidably mounted on a rail, an electrical conductor extending through a hoistway and held at electrical potential, a plurality of mounting brackets connecting the electrical conductor to a fixed element within the hoistway, and a sensor connected to the movable element. The sensor may include a sensing head having a non-continuous perimeter partially surrounding and in spaced relation to the electrical conductor.
In accordance with another aspect of the disclosure, a method of reducing false trips on an elevator derailment detection system is disclosed comprising extending an electrical conductor through an elevator hoistway provided in a building, holding the conductor at electrical potential, connecting the electrical conductor within the hoistway such that the electrical conductor moves substantially in concert with the hoistway as the building sways, and mounting a sensor to a movable element slidably mounted within the hoistway. The sensor may include a sensing head at least partially surrounding, and in spaced relation to, the electrical conductor.
In accordance with another aspect of this disclosure, an elevator derailment detection system is disclosed comprising a hoistway, a rail extending within the hoistway, a counterweight slidably mounted on the rail, an electrical conductor extending vertically through the hoistway and held at electrical potential, a plurality of mounting brackets connecting the electrical conductor to the rail, and a sensor connected to the counterweight and including a sensing head having a non-continuous perimeter substantially surrounding, and in spaced relation to, the electrical conductor.
These and other aspects of the disclosure will become more apparent upon reading the following disclosure when taken in conjunction with the accompanying drawings.
While the present disclosure is susceptible to various modifications and alternative obstructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to be limited to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the present disclosure.
Referring now to
As shown in
In order to move the car 30 and thus the passengers and/or cargo loaded thereon, a motor 36 is provided typically at the top of hoistway 22. Connected to the motor 36 is an electronic control 38 which in turn is connected to a plurality of operator interfaces 40 provided on each floor to call the elevator car 30, as well as operator interfaces 42 provided on each car 30 to allow the passengers thereof to dictate the direction of the car 30. Mechanically extending from the motor 36 is drive shaft 44, which in turn is connected to a pulley or a sheave 46. Trained around the sheave 46 is a cable or a belt 48 which forms a continuous loop about lower sheave 50. The cable 48 is in turn connected to counterweight 32 and car 30. Of course, multiple different embodiments or arrangements of these components are possible with a typical system including multiple belts 48 as well as various arrangements for the motor and sheaves of the elevator system 20.
Referring now to
In addition to the mounting brackets 60 and 62 at the top and bottom of the hoistway 22, a plurality of intermediary mounting brackets 64 are connected to fixed elements within the hoistway 22 as well. Similar to mounting brackets 60 and 62, intermediary mounting brackets 64 electrically isolate the electrical conductor 52 from the rest of the elevator system 20. This can be achieved by manufacturing the mounting brackets 60, 62, 64 from electrically insulative materials such as plastic or the like. By using the intermediary brackets 64 in combination with the top and bottom mounting brackets 60, 62, as the rails 28 sway, the electric conductor 52 sways substantially in concert with the rails 28, the importance of which will be described in further detail below.
Referring to
By providing the sensing head 72 in a G-shaped configuration or some other form having a non-continuous perimeter 73 with an opening 74, as the counterweight or other movable element moves up and down on its respective rail, the sensing head 72 can move past the intermediary mounting brackets 64 without contact. For example, in other embodiments, the sensing head 72 could be provided in a U-shape, C-shape, or in any other form having a non-continuous perimeter. In order to facilitate the respective motions of the sensing head 72 past the intermediary mounting brackets 64, the intermediary mounting brackets 64 could include a canted or L-shaped distal end 75.
It is also important to note that regardless of its shape, the sensing head 72 is normally held in spaced relation from the electric conductor 52. In other words, when the elevator system 20 is installed properly and aligned, and the building is not swaying and the movable element is not derailed, the sensing head 72 should not be in contact with the electrical conductor 52. Rather, the sensing head 72 should be spaced from and partially surrounding the electrical conductor 52, at a distance sufficient to avoid conduction of electricity from the electrical conductor 52 through the sensing head 72 and thus to the rest of the elevator system 20, causing a false trip or other indication of derailment.
Based on the foregoing, it can be seen that if the building 24 is subjected to a significant degree of sway, the rails 26 and 28 of the elevator system 20 will in turn sway with the building 24. In prior systems, the electric conductor of the derailment detection system, which typically would be fixed at only the top and bottom, would not sway with the rails 26, 28, and thus the electric conductor would actually contact the sensing head and thereby generate an alarm or safety trip within the system suggesting that the movable element had become derailed from its respective rail. This in turn would cause the elevator system 20 to shut down or otherwise be at less than peak efficiency until the alarm was resolved. However, with the present disclosure, as the electric conductor 52 is secured to the rails or other fixed element by intermediary mounting brackets 64 at spaced intervals 76, as shown in
Importantly though, if the movable element such as the counterweight 32 does in fact become derailed from its respective rail due to high winds the building may be experiencing, an earthquake, or the like, even with the electric conductor 52 moving in concert with the rails, the counterweight or any other movable element will move away from the rail a distance sufficient to cause the sensing head 72 to come into contact with electrical conductor 52, thereby closing the circuit and generating a derailment signal as desired, such as by a ground fault sensor 78 or the like.
While not a steadfast relationship, the inventors have found that by providing the spaced intervals 76 at approximately 200 feet (60.96 meters) apart, the electric conductor 52 will move substantially in concert with the rail 26 and 28 as the building sways under normal conditions. In other embodiments, the spaced intervals can of course be at other distances. The graphs provided in
Turning now to
Based on the foregoing, it can be seen that the present disclosure provides for a mechanism by which derailment of a movable element within elevator system, such as a counterweight or an elevator car, can be accurately detected with minimal false trips even when the building is of significant height and is experiencing significant sway or other movement due to high winds, earthquakes, or other causes.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US09/51153 | 7/20/2009 | WO | 00 | 12/20/2011 |
