Fluid sprinkling – spraying – and diffusing – Slinger or splasher; or deflector rotated relative to effluent – Disc impeller type or bowl-like slinger or deflector
Patent
1994-12-06
1996-05-21
Weldon, Kevin P.
Fluid sprinkling, spraying, and diffusing
Slinger or splasher; or deflector rotated relative to effluent
Disc impeller type or bowl-like slinger or deflector
B05B 310
Patent
active
055181805
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of Invention
A rotary atomizer and a method of operating it.
The invention relates to a rotary atomizer of the kind in which a disc- or wheel-shaped atomizing device is secured to one end of a shaft which is connected with the rotor of a high frequency asynchronous electric motor. The operating speed of the motor is controlled by a frequency converter to impart to the shaft a rotational speed substantially higher than the first critical speed of the shaft and atomizing device.
2. Prior Art
In general, rotary atomizers in which the atomizing disc or wheel is directly driven by a high speed electric motor is known, e.g. from Keith Masters: "Spray Drying Handbook", 5th Edition, New York 1991, page 218. These offer the advantage that a gear transmission between the drive motor and the atomizer is not required. In some prior art atomizers of this kind a comparatively short rigid shaft carrying the atomizing device at its lower end has been coupled with the rotor of the high frequency motor.
With such a design, the necessity to operate the atomizer within a speed range safely below the first critical speed of the shaft and the atomizer wheel sets limits to the diameter range of atomizer wheels, for which a direct high frequency motor drive can be successfully used when the circumferential velocity required for atomization is to be achieved.
From U.S. Pat. No. 4,713,146 it is known to operate rotary atomizers at rotational speeds higher than the first critical speed of the rotating parts by a rather complicated shaft design involving incorporation of spring means between inner and outer shaft members to permit flexible pivotal motions of the shaft during start and stop of the atomizer.
SUMMARY OF INVENTION
From this background, it is the object of the invention to provide a rotary atomizer of the kind described which to a much lesser extent suffers from the described limitations and may thus be successfully used for a far wider range of rotary atomizers down to small-scale atomizers with a power consumption of 1 kW and with a smaller wheel diameter down to, e.g. 90 mms or less and which provides flexibility of the shaft with a simple design of the rotary system.
According to the invention this object is achieved by a design characterized in that the shaft and the rotor are designed as one integral unit with the rotor surrounding a part of the shaft remote from said one end, said shaft and rotor unit being radially supported only by radial bearings at either end of said part of the shaft.
By operating the atomizer at the supercritical rotational speed the atomizing device will be self-aligning during operation, and the whole system will be less sensitive to dynamic imbalances caused by tolerances or imperfections in the atomizer wheel geometry and/or irregularities in the feeding of the product to be atomized.
The design of the shaft and the rotor of the high frequency motor as one integral unit offers the advantage of a very compact design which is particularly useful in small-size atomizers designed to handle feed volumes down to about 50 liters per hour. However, the invention is in no way limited to such applications but may successfully be put into operation for a substantial range of wheel diameters up to large size atomizer wheels having a diameter of 350 mms or more and designed for a product handling capacity of 200 tons per hour or more.
The invention furthermore relates to a method of operating a rotary atomizer of the kind in which a disc- or wheel-shaped atomizing device is secured to one end of a shaft which is directly connected with the rotor of a high frequency asynchronous electric motor, the operating speed of which is controlled by a frequency converter to impart to the shaft a rotational speed substantially higher than the first critical speed of the shaft and atomizing device.
According to the invention this method is characterized in that with the shaft and the rotor designed as an integral unit with the rotor surrounding a part of the shaft remote fr
REFERENCES:
patent: 3749315 (1973-07-01), Crathern
patent: 4275838 (1981-06-01), Fangmeyer
patent: 4368849 (1983-06-01), Farmery
patent: 4450785 (1984-05-01), Meisner
patent: 4609148 (1986-09-01), Gill
patent: 4713146 (1987-12-01), Ek
Niro Holding A/S
Weldon Kevin P.
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