FERROFLUID SEALING OF ROTARY SHAFTS
The simplest traditional MFS construction is comprised of a ring permanent magnet with two magnet conducting ring poles. The gap between the shaft and the poles is filled with sealing fluid (magnetic fluid) with a help of a syringe. This procedure performed by syringe as the gap is not easily accessible.
In a self-filling seal of the pole there are ring bulges on the inner surface. Ferrofluid is held in the gap between these bulges in non-operational mode. This gap is considerably wider than a radial working gap between the poles and the shaft which is to be sealed. Inserting the shaft into magnet system causes relocation of magnet flow and ferrofluid is thus drawn into the working gap.
PC DRIVES DUST PROTECTION
Ferrofluid is successfully used for dust protection. Magnet field holds it in a ring gap. between rotating shaft and static casing. Magnetic fluid prevents dust particles from penetration.
RADIAL FERROFLUID-BASED BEARING
Ring magnet embraces non-magnet shaft and forms axisymmetric magnet field around it. The gap between the shaft and the bearing is filled with ferrofluid. As the shaft shifts along the axis it is affected by centering force.
Shaft centering is done in both static and dynamic modes. The bearing ensures low friction rotation of the shaft.
INERTIAL ACCELEROMETER
Cylindrical magnet is put into non-magnet cylindrical casing with ferrofluid. Magnet is inertial mass of the sensor.
Without acceleration magnet is situated in the center of non-magnet casing. Affected by acceleration force the magnet shifts, its motion detected by motion sensor.
High sensitivity of the sensor is provided by low friction between magnet and casing.
LIQUID-STAGE METER
Liquid-stage meter is a vertical tube made of non-magnet material with external floating ring magnet. The gap between the magnet and the tube is filled with ferrofluid.
As the volume of the fluid changes the floating magnet moves freely along the tube.
As the floating magnet moves ferrofluid lubricant moves along with it ensuring its economical consumption.
INERTIAL DAMPER
Non-magnet casing filled with ferrofluid is mounted on the shaft. Permanent magnet levitates in ferrofluid in the central part of non-magnet casing.
Centering force acts upon the magnet as a result of accidental radial shift. When the shaft rotation accelerates or slows down damper casing rotation deviates from magnet rotation speed which turns on a mechanism of ferrofluid friction that damps hostile vibration.
DYNAMIC LOUDSPEAKER
The problem of moving coil heat removal can be solved by filling the gap around the coil by fluid with heat conductivity higher than that of air. However regular fluid would normally leave the gap as loudspeaker is moved.
Due to the fact that there forms strong enough non-uniform magnet field in the gap, ferrofluid stays within the gap despite any shock or motion applied to it which resolves the problem of heat removal.
CENTERING OF THE WORKING COIL OF LOUDSPEAKER
Working coil of loudspeaker is located in magnet system gap with non-uniform magnet field. The minimal intensity of the field is in the center of the gap. As the coil shifts aside centering force emerges. As a result the coil settles symmetrically against the vertical axis of magnet system and has no possibility of accidental contact with polar tips.
Centering of working coil by ferrofluid improves frequency characteristics of loudspeaker.
SEPARATING MATERIALS BY FERROFLUID
Non-magnet particles of various densities fall down the layer of ferrofluid between the poles of electric magnet. Outside magnet field all particles sedimentate. When the magnet is turned on the particles separate according to their density: the light ones stay and aggregate on the surface of ferrofluid and the heavy ones sedimentate and get into intake unit.
Separation mode may be adjusted by varying non-uniformity of the magnet field.
BIOSEPARATORS AND ANALYZERS WITH MAGNETITE APPLICATION
The method of bacteria and protozoa detection in environment, fodder, water and food specimens is based on the application of uniform paramagnetic microscopic particles, whose surfaces are covalently coherent with purified antibodies tolerant to different strains of human and animals pathogenic flora. Subjected to the incubation process antibodies covered the particles get in contact with principal bacteria applied to magnetic particle.
Under the action of magnetic field magnetic particles are gathered in one place and easily get out of the medium. Then, to wash out the particles, the complex „particle-bacteria“ sequentially drops down to different test tubes before the final resuspension for further processing and detection.
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