Railways – Car-carried propulsion system – Electric
Reexamination Certificate
1999-07-23
2001-09-04
Le, Mark T. (Department: 3617)
Railways
Car-carried propulsion system
Electric
C104S292000
Reexamination Certificate
active
06283039
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a conveying system that uses a linear motor for conveying works, assembly components, or other articles to be conveyed.
2. Description of the Related Art
Conveying apparatuses have been extensively used that employ rollers or belts to carry works, assembly components, or other articles to be conveyed. Especially in the case of a conveying apparatus that employs a belt, in order to stop only a particular article in transfer at a predetermined position, the article has to be forcibly restrained, inevitably producing friction between the belt and the article. Further, the accuracy of positioning at the stop point is not very high.
In recent years, linear motor type conveying systems have been proposed and used as the conveying systems for clean rooms, nuclear power stations, physical distribution, etc. A linear induction motor is capable of carrying considerably heavy articles and it is therefore being used as a typical motor used for conveyance. The linear induction motors, however, are considered unsuited for applications that require accurate positioning at stop points.
The conventional conveying systems employing belts or rollers have difficulties in the aspect of the control of dust, carrying speed, maintenance, service life, and positioning control. The linear induction motor type is also disadvantageous in positioning control. The linear motors that allow the braking characteristics thereof to be adjusted have been requiring power be fed to a moving unit thereof, so that the moving unit is likely to produce dust.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a conveying system employing a linear motor that permits accurate stop positioning.
It is another object of the present invention to provide a conveying system employing a linear motor that has a passive moving assembly to minimize dust produced.
To achieve the above objects, according to one aspect of the present invention, there is provided a conveying system using a linear motor, comprising a passive moving assembly of a linear motor, which is loaded with an article to be conveyed, a scale provided on the moving assembly, a rail for guiding the moving assembly, a sending drive coil disposed at a sending station associated with the rail, a receiving drive coil disposed at a receiving station associated with the rail, which is positioned away from the sending station, a contactless sensor which is disposed at least at the receiving station and which detects the scale, drivers for driving the sending and receiving drive coils, and control means to which information regarding the moving assembly from the sensor is connected, and which drives the respective drivers to accelerate and send the moving assembly, then to stop at a predetermined position at the receiving station following non-energization travel.
The moving assembly has a permanent magnet, and said linear motor can be a linear DC motor.
A combination of the scale and the contactless sensor may be a combination of a linear scale and a photoelectric sensor, or a combination of a magnetic scale and a magnetic sensor or other positioning sensor.
The control means is configure to cause the driver to send the moving assembly at a predetermined sending speed that matches a load of the moving assembly and the length of a non-energized travel passage.
The control means reads the linear scale by the sensor after the moving assembly is received at the receiving station to detect the speed of the moving assembly, compares the detected speed with a reference receiving speed, and corrects the speed of the moving assembly so as to position and stop the moving assembly at a predetermined position. The sending station and the receiving station are provided with the same capability and can be interchangeably operated under the control by the control means.
A plurality of the sending and receiving drive coils are disposed to construct an assembly line. The moving assembly can be intermittently moved for positioning after the moving assembly is received and stopped at the receiving station. The moving assembly is returned from the receiving station to the sending station.
REFERENCES:
patent: 4652800 (1987-03-01), Fukuwatari
patent: 4665349 (1987-05-01), Matsuo
patent: 4690066 (1987-09-01), Morishita et al.
patent: 4718621 (1988-01-01), Horimouchi et al.
patent: 4800818 (1989-01-01), Kawaguchi et al.
patent: 5251741 (1993-10-01), Morishita et al.
patent: 6118245 (2000-09-01), Sienz et al.
patent: 0 400 663 (1990-12-01), None
Kajioka Morimasa
Takayanagi Shin-ichi
Frank Robert J.
Kelemen Gabor J.
Le Mark T.
Minebea Co. Ltd.
Venable
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