Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes control for power source of drive-means
Reexamination Certificate
1998-12-22
2001-07-03
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes control for power source of drive-means
C187S394000
Reexamination Certificate
active
06253879
ABSTRACT:
TECHNICAL FIELD
This invention relates to an elevator speed determining and monitoring device and method. More specifically, this invention relates to a device, and a method for its use, which determines an overspeed condition of an elevator car and provides an electronic signal corresponding thereto.
BACKGROUND OF THE INVENTION
Elevators are presently provided with a plurality of braking devices which are designed for use in normal operation of an elevator, for example to hold the elevator car in place where it stops at a landing, and which are designed for use in emergency situations such as arresting the motion of a free-falling elevator car.
One such braking device is provided to slow an overspeeding elevator car, that is one which is travelling over a predetermined rate. Such braking devices typically employ a governor device which triggers the operation of safeties. In such elevator systems a governor rope is provided which is looped over a governor sheave at the top of the hoistway and a tension sheave is at the bottom of the hoistway and is also attached to the elevator car. When the governor rope exceeds the predetermined rate of the elevator car the governor grabs the governor rope, pulling two rods connected to the car. The rods pull two wedge shaped safeties which pinch the guide rail on which the elevator car rides thereby braking and slowing the elevator car.
The device and method employed in determining an overspeed condition of an elevator car is important to the proper working of the safety braking system. In conventional systems the speed of an elevator car may be monitored through the governor rope, governor sheave, tension sheave or mechanical linkages which operate the safeties. For instance, the governor sheave described above typically employs a centrifugal device which when an overspeed condition is reached engages a brake producing drag on the governor rope and thereby activating the safeties. The governor rope rotates a governor, at a rate of rotary speed that relates to the linear speed of the elevator car. The governor has fly weights that move outwardly with increasing speed as a result of increasing centrifugal force. When the elevator exceeds a predetermined speed the fly weights trip an overspeed switch which allows a set ofjaws to grip the rope and activate the safeties. In other systems a tachometer is attached to a secondary cable attached to the sheave and employed to monitor an overspeed condition of the elevator car and activate the safeties.
A disadvantage of the prior art systems is the wear which occurs to the rope and governor systems. The greatest problem with this type of wear is that it is often visually undetectable. In addition when an overspeed condition occurs the elevator is required to be taken out of service until a mechanic is available to reset the governor unit and release the safeties.
Another disadvantage of a governor rope assembly is the required maintenance and hoistway space required. The governor rope, sheaves and linkages must be periodically cleaned, lubricated and replaced. All maintenance requirements are considered burdensome to those skilled in the art, and therefore an undesirable feature. As such there is a need to eliminate a governor rope assembly and a further need for an accurate device and method to monitor and determine an overspeed condition of an elevator car without a governor rope assembly. In light of this need there exists a further need for an accurate, non-contact, continuous and instantaneous device and method of detecting an overspeed condition of an elevator.
DISCLOSURE OF THE INVENTION
Therefore, it is an object of the present invention to provide an improved method and apparatus for detecting an overspeed condition of an elevator car.
In accordance with the present invention, an overspeed condition of an elevator is detected by determining the speed of the elevator using a radar speed sensor. The speed sensor continuously monitors the speed and direction of an elevator in an accurate, noncontact continuous and instantaneous manner without using a rope assembly governor system of the prior art. In an embodiment of the present invention the speed sensor is mounted to an elevator car and directs a transmitted signal at a portion of the hoistway or rail. In another embodiment the speed sensor is mounted to the ceiling or bottom of the hoistway and directs the transmitted signal at the elevator car. The speed sensor receives a return signal and produces a speed signal indicative of the speed and direction of the elevator car. The speed signal is received by a microprocessor which compares the speed signal to a predetermined threshold value corresponding to an overspeed condition. When an overspeed condition exists the microprocessor produces an overspeed signal enabling a safety brake system to slow the elevator.
The foregoing and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of the invention, as shown in the accompanying drawings.
REFERENCES:
patent: 4318456 (1982-03-01), Lowry
patent: 4662481 (1987-05-01), Morris et al.
patent: 4880082 (1989-11-01), Kahkipuro et al.
patent: 5052523 (1991-10-01), Ericson
patent: 5065845 (1991-11-01), Pearson
patent: 5151562 (1992-09-01), Fujita et al.
patent: 5223680 (1993-06-01), Schmidt-Milkau et al.
patent: 5306882 (1994-04-01), Gerwing et al.
patent: 5323877 (1994-06-01), Mori
patent: 5377786 (1995-01-01), Nakagawa
patent: 5393941 (1995-02-01), Mizuno et al.
patent: 5487450 (1996-01-01), Gerber
patent: 5644111 (1997-07-01), Cerny et al.
patent: 5648644 (1997-07-01), Nagel
patent: 5648645 (1997-07-01), Arpagaus et al.
patent: 5736695 (1998-04-01), Hoepken
patent: 5883345 (1999-03-01), Schonauer et al.
patent: 0712804 (1996-05-01), None
patent: 0543154 (1997-09-01), None
patent: 0812796 (1997-12-01), None
patent: 0856485 (1998-01-01), None
patent: 0841282 (1998-05-01), None
patent: 0662445 (1999-04-01), None
patent: 3124688 (1991-05-01), None
patent: 4246079 (1992-09-01), None
patent: 4365771 (1992-12-01), None
patent: 5147852 (1993-06-01), None
patent: 5262472 (1993-10-01), None
patent: 6255949 (1994-09-01), None
patent: 8198543 (1996-08-01), None
patent: 9040317 (1997-02-01), None
patent: WO9842610 (1998-10-01), None
Otis Invention Disclosure No. OT-4556 entitled Mechanical Resetting for Switch (Apolo Governor) dated Apr. 27, 1999.
Skalski Clement Alexander
Vecchiotti Alberto
Otis Elevator Company
Salata Jonathan
LandOfFree
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