Conveyors: power-driven – Conveyor or accessory therefor specialized to convey people – With means to control the operation of the section
Reexamination Certificate
2000-08-11
2001-07-31
Bidwell, James R. (Department: 3651)
Conveyors: power-driven
Conveyor or accessory therefor specialized to convey people
With means to control the operation of the section
C198S322000
Reexamination Certificate
active
06267219
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a passenger conveyor system, and more particularly to a safety system including a communication bus that connects safety related components.
A typical passenger conveyor, such as an escalator or moving walk, includes a truss, a plurality of sequentially connected treadplates traveling through a closed loop path within the truss, and a machine for driving the treadplates.
Escalators and moving walks include devices such as sensors for monitoring speed, sensors for detecting missing treadplates, devices for monitoring wear; actuators for utilizing special purpose devices and output devices, such as traffic lights. Each of these devices includes a combination of interface devices, i.e., sensors, switches or actuators, that are connected to a central control. To assure the continued operation of the sensors typical passenger conveyers include a safety system that monitors and responds to each sensor.
Conventional escalator safety systems are implemented using a Safety Chain which is a serial circuit of the switches and contacts. The Safety Chain operates relays (or contactors) that handle the power to the escalator motor. An operation of any contact within the chain will disconnect the motor or drive from the main power supply. The serial connections of the contacts and the bridging for inspection leads to a long chain which requires higher voltages to minimize the effects of voltage losses along the chain.
Because the Safety Chain is wired in serial, a failure cannot be specifically identified. During maintenance and inspection, it is sometimes necessary to include bridges in the Safety Chain by hand for testing and error searching. Manual installation and removal of the bridges is time consuming and labor intensive. Further, the serial connection renders remote checking difficult.
Therefore it has been determined that a need exists for an improved safety system which lowers part count and manufacturing costs, all while improving operability.
SUMMARY OF THE INVENTION
An escalator system designed according to this invention improves inspection and diagnostic work, promotes safe escalator operation, and enables safe degradation when an unsafe condition is detected. The safety system includes a communications bus which facilitates the exchange of control and data signals between a microprocessor based safety controller or “bus master”. Various other components including bus nodes designed to interface with sensors, contacts, and switches along with detectors, components, and other safety equipment ensure the safe operation of the escalator system.
The software controlled bus master operates a communications bus which has bus nodes throughout the entire escalator system. The bus nodes are periodically polled to ascertain the status of the sensors, contacts, and switches connected to the bus nodes. The microprocessor may operate in one of several different modes such as maintenance, inspection, normal operations, degraded operations, and emergency operations. When appropriate, the bus master generates output signals to the escalator control system and the escalator drive and brake system.
If an unsafe condition occurs, the bus master generates the appropriate outputs to be conveyed to the escalator control and drive systems. The safety controller may activate devices to arrest the escalator's motion. The bus master and associated components provide an electronic safety system which can be centrally managed, greatly improves installation time, quality, manufacturing costs, and operational characteristics.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.
REFERENCES:
patent: 5697485 (1997-12-01), Abraham et al.
patent: 5785165 (1998-07-01), Stahlhit et al.
patent: 5886497 (1999-03-01), Zaharia
Gewinner Jürgen
Henkel Reinhard
Spannhake Stefan
Bidwell James R.
Carlson Gaskey & Olds P.C.
Otis Elevator Company
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