Patent Application
20130081905
Typical elevator systems can include an elevator car attached to a counterweight by roping. A drive machine, which includes a motor and a brake, rotates and acts (typically by traction) on the roping (that could be round ropes or flat belts) that engages the machine to move the elevator car and counterweight up and down an elevator hoistway, transporting passengers or cargo from one floor to another. An elevator controller controls operation of the elevator system. The drive machine is typically located at the top of the hoistway.
When an elevator call is registered, the controller sends a signal to the drive machine to raise or lower the car to the call floor, and then apply the brake on the machine as the elevator approaches the call floor. One possible brake for the drive machine is a clutch brake, which consists of a fixed plate, a movable plate, springs and an electromagnet for moving the movable plate, and a liner located between the fixed plate and the movable plate and attached to a shaft which rotates with the drive machine when the elevator car is being moved. When braking is needed, the movable plate is moved towards the fixed plate by springs, bringing the liner into contact with both the movable plate and the fixed plate. The frictional forces from the contact of the fixed plate, the liner and the movable plate stop the rotational movement of the liner. As the liner is connected to the shaft, this stopping translates to the shaft and the drive machine, and stops the movement of the elevator car. When the elevator needs to move again, the controller sends a signal, and current is sent to the electromagnet to pull the movable plate away from the liner and the fixed plate, allowing rotational movement of the liner and shaft, and movement of the car.
Whenever the electromagnets are not energized, the springs force the movable plate toward the fixed plate, and bring the liner into contact with the plates.
There are various circumstances (both before and after installation of the machine in the elevator hoistway) in which the electromagnets may not be energized, for example, during transportation of the machine to the job site or while the machine resides at the job site awaiting installation in the hoistway. After installation, the electromagnets are not energized, for example, during power loss to the building or the elevator system, during periods of inactivity of the elevator system, or while the elevator system is in a “sleep mode.”
Under certain conditions, prolonged contact between the liner and the plates may cause the liner to stick to the moveable plate and/or the fixed plate. When subsequently energizing the electromagets, the liner may not disengage from the moveable plate and/or the fixed plate. Without disengagement of the liner and plate(s), the machine may not be able to operate since the liner/plate sticking prevents the shaft from rotating. In an installed elevator system, the controller will sense the inability of the machine shaft to rotate, and shut down the elevator system. A technician must then visit to resolve the issue.
With machineroomless elevator systems (in which the machine resides in the hoistway rather than in a conventional machine room), this brake sticking scenario can prove difficult and/or time consuming to remedy. A technician typically accesses the machine in the hoistway by travelling on the top of the car until it reaches the top of the hoistway. With the machine inoperative, the technician must find another way to access the machine in the hoistway.
An elevator brake component used in a friction brake of an elevator includes a metal plate that is frictionally engaged with another brake component when the elevator brake is engaged. The plate includes a non-stick finish on the metal plate on a surface of the plate that is frictionally engaged when the elevator brake is engaged by the other brake component.
Motor 12 is connected to shaft 14 to rotationally drive shaft 14. Shaft 14 also connects to sheave 20 (alternatively, sheave 20 could be an integral part of shaft 14) and liner 26. Fixed plate 24 is part of housing 18 in this embodiment. Movable plate 28 (which could be an annular disk or formed from multiple segments as seen in
To move an elevator car up and down in a hoistway, controller 34 sends drive signals through wiring 34A to motor 12 to rotationally drive shaft 14 about axis 16. Rotation of shaft 14 is translated to sheave 20, which rotates and, typically through traction, drives the roping to raise or lower the elevator car and counterweight, depending on which way drive signals sent to motor cause motor to rotationally drive shaft 14.
Brake assembly 22 is connected to rotating shaft 14 through liner 26, for example, using splines 25A on shaft 14 that engage grooves 25B on a hub of the liner 26. This connection causes liner to rotate with shaft 14. The brake assembly 22 also secures to the non-rotating portion of the machine 10, for example by fastening the housing 32 of the brake assembly 22 to the housing 18 using bolts.
When the elevator is in operation and controller 34 is sending drive signals through wiring 34A to motor 12 to rotationally drive shaft 14, controller 34 also sends current through wiring 34B to electromagnet 33 to produce a magnetic field that causes movable plate 28 to move axially toward brake housing 32. The movement of movable plate away from fixed plate 24 allows liner 26 to rotate with shaft 14. When braking is desired, for example when elevator car approaches a desired destination, controller 34 stops sending current to electromagnet 33, and movable plate 28 then moves axially towards liner 26 due to the force of springs 30. Springs 30 move movable plate 28 axially away from the brake housing 32 so that movable plate 28 pushes liner 26 into contact with fixed plate 24 and movable plate 28. The resulting friction from the contact with fixed plate 24 and movable plate 28 stops liner 26 from rotating. This stopping of rotation is translated to shaft 14, sheave 20 and the roping, resulting in stopping of movement of the elevator car up or down in the hoistway.
As will be discussed in further detail below, fixed plate 24 and/or the movable plate 28 has a finish thereon that reduces the likelihood of liner 26 sticking to the plates 24, 28.
As mentioned above, when elevator car is moving up or down in the hoistway, shaft 14 rotates, rotating liner 26. During that time, electromagnet 33 receives current, moving movable plate 28 away from liner 26, allowing liner 26 to rotate freely. When car is stopped, current to electromagnet 33 is stopped, and movable plate 28 is moved axially towards liner 26 by springs 30. This movement moves liner 26 into contact with one side of fixed plate 24 and with one side of movable plate 28. The friction between the surfaces of liner 26 with one side of fixed plate 24 and one side of movable plate 28 stops the rotational movement of liner 26. Due to the splined connection 25, rotational movement of shaft 14 is also stopped. This stopping of rotational movement of shaft 14 then stops the movement of car up or down within the hoistway. Movable plate 28 is moved axially against the compressive force of springs 30 toward electromagnet 33 by current flowing through electromagnet 33. When there is a loss of power to the elevator system, no current is sent through electromagnet 33, and movable plate 28 is released to be moved towards liner 26 by springs 30. This ensures that movable plate 28 is moved axially towards liner 26, to stop car movement in the event of a loss of power to the elevator system.
In some instances, when plates 24, 28 and liner 26 are moved together to frictionally stop movement of the elevator car, certain conditions cause the plates 24, 28 and liner 26 to stick together, preventing further elevator movement. This frequently occurs in humid climates or in situations where the elevator is used infrequently, such as in sports stadiums where games may be played only once per week. This also may occur when shipping an elevator brake assembly, where it may come into contact with moisture through the shipping process or while waiting to be installed. When the fixed plate 24, liner 26 and movable plate 28 have been held together by springs 30 for prolonged periods of time (for example a week or more between games in the case of a sports stadium) or for weeks during shipping and/or exposed to moisture, the plates can stick to liner 26, and can remain stuck together even after the electromagnet 33 receives current to move movable plate 28 away from fixed plate 24 and liner 26. When this happens, the elevator sends an error signal back to the controller, and a technician must come to inspect the problem. This often results in having to replace the entire braking assembly, resulting in an extended period of time in which the elevator is unable to be used and in high replacement costs.
The current invention seeks to solve this problem by inclusion of a finish (which should be interpreted to include the use of a material) on at least the side of fixed plate 24 and/or movable plate 28 that comes into contact with liner that reduces the likelihood of liner 26 sticking to the plates 24, 28. Preferably, the finish eliminates any sticking between liner 26 and plates 24, 28. However, it is still within the scope of this invention for the finish to reduce sticking between liner 26 and plates 24, 28 (measured by torque) below the level of sticking with conventional materials. Either possibility previously discussed (i.e. eliminating or reducing sticking) is hereinafter referred to as being non-stick. This non-stick finish can be done in several ways, depending on the material which fixed plate 24 and movable plate 28 are made of. If fixed plate 24 and movable plate 28 are made of regular steel, the plate is given a low-roughness finish and coated with black oxide. To achieve the low-roughness finish the steel plate can be placed in a tumbler with abrasive materials such as rocks and sand. It can be spun around or tumbled in the tumbler to bring the surface of the plate into contact with the abrasive materials. The abrasive materials rid the steel plate of micro peaks that occur when forming the plate, thereby lowering the roughness of the surface of the plate. The plate then gets a black oxide coating for corrosion resistance. This low-roughness steel plate with black oxide generally results in a roughness of about 0.12 Ra to about 0.25 Ra. Alternatively, fixed plate 24 and movable plate 28 can be made of stainless steel with the non-stick finish being a mirror finish. The roughness of the stainless steel plate with a mirror finish can be about 0.03 Ra to about 0.07 Ra.
The non-stick finish on at least the side of fixed plate 24 and/or movable plate 28 that comes into contact with liner 26 greatly reduces the possibility of sticking of the plates 24, 28 in brake assembly 22, even in the situations where sticking was prevalent such as situations of infrequent elevator use and elevators in humid climates. This reduces both the time during which the elevator is inoperable and the cost of replacing the brake in which the plates stuck. Additionally this invention can help eliminate the need to replace brake assemblies that have been exposed to moisture during the shipment process, causing them to be stuck together even before the first use.
Shaft 40 connects to a sheave and motor (not shown) to rotate therewith to move elevator car up and down in a hoistway. Shaft 40 connects to plate 38 so that plate 38 rotates with shaft 40 (much in the same way as shaft 14 and liner 26 of
When a signal to brake is sent from controller (not shown), braking assembly 42 operates clutches 44A, 44B to clamp down on both sides of brake plate 38 to stop the rotation of brake plate 38 through frictional force. This stopping of the rotation of brake plate 38 stops the rotational movement of shaft 40, stopping the movement of the elevator car in the hoistway.
When the brake is exposed to moisture or when the brake has been engaged for a period of time, sticking sometimes occurs between brake plate 38 and clutches 44A, 44B, preventing clutches 44A, 44B from releasing. This prevents brake plate 38 and shaft 40 from rotating, therefore preventing elevator to move within the hoistway. This sticking often results in the need to replace the brake, adding expense and inconvenience of the elevator being out of service for a period of time. By using a brake plate with a non-stick finish according to the current invention in disk brake assembly 36, incidents of sticking are greatly reduced or eliminated. The non-stick finish can be a mirror finish for brake plate 38 made of stainless steel, resulting in a roughness of about 0.03 Ra to about 0.07 Ra. The non-stick finish can also be a low-roughness finish with black oxide for brake plate 38 made of steel, resulting in a roughness of about 0.12 Ra to about 0.25 Ra.
In summary, replacing the brake plate of an elevator brake assembly with a brake plate with non-stick finish according to the current invention greatly reduces the likelihood of the brake plate sticking in an elevator braking assembly. This reduces the expense of replacing brakes which have become stuck, as well as keeps elevators running smoothly without service interruptions, even in situations where an elevator may sit with the brake engaged and the car not moving for a week or more (such as at a sports stadium). Furthermore, this eliminates some of the restrictions on shipping of brakes which do not include brake plates with the non-stick finish according to the current invention, including having to ensure the brake assembly is kept away from moisture on ships and out of elements such as rain prior to installation within a hoistway.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. For example, a different type of brake (other than the ones shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/US2010/038639 | Jun 2010 | US | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US10/38639 | 6/15/2010 | WO | 00 | 12/12/2012 |
