Classifying – separating – and assorting solids – Sifting – Plane sifters
Patent
1995-11-07
1998-05-12
Bollinger, David H.
Classifying, separating, and assorting solids
Sifting
Plane sifters
209315, 209319, 209329, 209341, 209354, 209355, 2093665, B07B 128
Patent
active
057494711
DESCRIPTION:
BRIEF SUMMARY
This invention relates to improvements in a known type of vibrating screen for sizing granular materials such as gravel, sand, crushed stone, etc., in which an oblong screen body is movable in relation to a frame by a motor powered vibrator mechanism which is connected to the screen body. In these known screens, oscillating movements are imparted to the screen body by the vibrator mechanism; there is an upper screen deck and one or more lower screen decks; there are successively decreasing screen openings for each lower deck; the decks are inclined downward from the feed end toward the discharge end; each screen deck is composed of a plurality of component screens arranged one after the other; each component screen is provided with a screening element such as metal wire cloth or netting; and, the component screens are arranged with successively decreasing inclinations relative to the horizontal plane.
OBJECT OF THE INVENTION
The objects of the present invention are to obtain a vibrating screen which, under limitation of its dimensions and weight, has a high capacity and makes it possible to produce a plurality of accurately separated product fractions and which also, due to the mentioned limitations, has a low acquisition cost and is easy to transport.
In brief, the stated objects have been attained by fitting the vibrating screen in accordance with the invention with a vibrator mechanism with a directional throw in combination with a specific arrangement of the inclination of the different screen decks, in addition to which a width-saving tensioning of the screen cloths or nettings is made possible by means of a specific tensioning arrangement.
BACKGROUND
In crushing and screening plants, for example for the production of concrete ballast or asphalt material, the development has gone towards increasing capacity demands in combination with demands for the production of accurately sized, short product fractions, i.e. fractions having a small span between the upper and lower fraction limits. A typical example of such fractions, and of an application of the vibrating screen in accordance with the present invention, is the dividing of a feed material 0-16 mm into the fractions 0-4, 4-8, 8-11.2 and 11.2-16 mm. An additional typical prerequisite is that the capacity of the screen should be at least 150-200 metric tons per hour and, furthermore, that it should be easily portable in order to make it possible also to exploit smaller material deposits in an economical way. For the last-mentioned prerequisite, in addition to the transportability and, thereby, the transport cost, the acquisition cost of the screen is also of importance.
Even discounting the demand for transportability, it is a great advantage to be able to keep the dimensions of the screen as small as possible. Large and heavy screens with large vibrating masses imply severe strains on the screen body and require a meticulously correct dimensioning and balancing of same. Furthermore, heavily dimensioned bearings are required for the vibrator mechanism, which bearings cannot endure a high speed, i.e. a high stroke frequency of the vibrating movement. The acceleration or throwing effect on the material to be screened is thereby impaired. Furthermore, the screens are of course more expensive in acquisition and require more energy for their operation.
A typical example of a screen in accordance with the invention which is adapted to the above-mentioned production prerequisites is a multideck screen having an effective width of the screen decks of 1800 mm and an effective length of same of 3300 mm. Even larger width and length measures can come into the question for the obtaining of higher capacities.
It is known earlier to divide a screen deck into a plurality of component screens having a successively decreasing inclination in the direction towards the discharge end of the screen. This arrangement results in different transport speeds of the material to be screened along the different component screens, which is advantageous for the screening effic
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Bollinger David H.
Svedala-Arbra AB
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