Paper making and fiber liberation – Apparatus – Electric controls or systems
Reexamination Certificate
1999-03-12
2001-03-13
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Apparatus
Electric controls or systems
C162S265000, C192S01200R, C192S084210, C310S092000, C310S103000
Reexamination Certificate
active
06200426
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to paper machines, and, more particularly, to couplings for transmitting rotational power to rolls, cylinders, pulleys and/or gears in paper machines.
2. Description of the Related Art
A paper machine such as a paper-making machine or off-line coater includes a plurality of rotatable driven elements, such as rolls, cylinders, pulleys and/or gears. Such rotatable driven elements are rotatably driven using a drive unit such as an electric motor, pump, etc. It is known to directly or indirectly connect the drive unit with a rotatable driven element using mechanical interconnections such as shafts, chains, belts, etc. It is also known to use a mechanically operated coupling such as a slip clutch with a plurality of pressure plates, etc. Such mechanical clutches have the disadvantage of wearing over time and thus requiring repair and/or replacement.
It is also known to use a magnetic coupling to interconnect a drive unit with a rotatable driven element in a paper machine. The magnetic coupling includes a first rotor carrying a plurality of permanent magnets and a second rotor carrying a plurality of electrical conductors. Rotation of the permanent magnets relative to the electrical conductors causes the generation of counter electro-magnetic fields which provide a rotatable output torque to drive the rotatable driven element. Such a magnetic coupling has the advantage of not wearing over time since the rotors do not physically wear against each other, when compared with a mechanical type clutch.
A disadvantage of a magnetic coupling as described above is that the permanent magnets have a substantially constant magnetic flux, which in turn results in a magnetic field with a substantially constant and finite strength. The efficiency of the magnetic coupling and transmitted torque can be only slightly varied within the operating range of the magnetic coupling.
What is needed in the art is a coupling or clutch which may be used to drive a rotatable driven element in a paper machine which allows the transmitting torque and/or efficiency of the clutch to be varied and controlled.
SUMMARY OF THE INVENTION
The present invention provides a controllable electro-magnetic clutch for providing controlled rotational speed and/or slip to rolls, cylinders, pulleys and/or gears in a paper machine.
The invention comprises, in one form thereof, a paper-making machine or an off-line coater including a rotatable drive unit and a rotatable driven element in the form of a roll, cylinder, pulley and/or gear. A clutch includes a rotatable input shaft coupled with the rotatable drive unit. At least one drive rotor is connected with the input shaft, and includes a plurality of magnetic coils. Each magnetic coil includes a coil winding. At least one driven rotor is positioned axially adjacent to at least one of the drive rotors. Each drive rotor includes a plurality of angularly spaced electrical conductors which are positioned adjacent to at least one of the drive rotors. A rotatable output shaft is coupled with the driven rotor and the rotatable driven element. A source of modulated direct current power is coupled with each of the magnetic coils, whereby a magnetic flux generated by the drive rotor and a coupling force between the drive rotor and the driven rotor can be varied.
An advantage of the present invention is that the coupling force between the rotatable drive unit and the roll, cylinder, pulley and/or gear can be varied.
Another advantage is that slip can be controlled in the coupling.
Yet another advantage is that the modulated direct current voltage to the magnetic coils can be provided in a number of simple and easily controllable ways.
REFERENCES:
patent: 4449617 (1984-05-01), Sakakiyama et al.
patent: 6031309 (2000-02-01), Nishimura
Nguyen Dean T.
Taylor & Aust P.C.
Voith Sulzer Paper Technology North America Inc.
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