Classifying – separating – and assorting solids – Sifting – Elements
Patent
1985-06-04
1987-05-12
Bashore, S. Leon
Classifying, separating, and assorting solids
Sifting
Elements
209342, 209396, 209405, 209674, 210389, B07B 112, B07B 130
Patent
active
046647902
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for screening wooden chips or similar particular materials and to a screening apparatus for carrying out the method.
A known screening apparatus includes a chute arranged upon a bottom frame, the chute being provided with an upper bottom which includes a screening grid consisting of mutual parallel screening rods, and is vibrated relative to the frame by a vibrating device. The bottom frame is provided with longish carrier elements, which are arranged to project upwardly between the screening rods so that gaps are created between the rods. When the chute is vibrating, e.g., is oscillating in a plane in its longitudinal direction, the screening rods perform a to-and-fro movement relative to the carriers, by which particulate materials with a piece size less or equal to the width of the gaps fall through the screening grid and are be picked up on a lower bottom arranged on the chute.
It has appeared that the known device has a range of application limits to certain kinds of particulate materials and that it has a limited capacity. Thus it is desired to widen the range of application of the apparatus and to increase the capacity within given limitations.
SUMMARY OF THE INVENTION
The purpose of the present invention is to satisfy the wishes mentioned above. The purpose has been achieved by an invention which is constituted by a method for screening with a screening apparatus which partly includes the same members as the known screening apparatus and which is characterized in that the carrier elements are brought to vibrate partly relative to the bottom frame and partly relative the chute with the screening rods, by which the chute preferably vibrates in the same plane as the carriers. In particular, the relative movement between the screening rods and the carriers is controlled by a mutual phase displacement, e.g., by separate vibration of each.
The invention also includes a screening apparatus which is characterized in that the carrier elements are movably arranged on the frame. Preferably, the carrier elements are connected to the frame by struts which include a spring device. The vibrating movement of the carrier elements thereby is effected by a vibration device which is attached to any of the struts. The vibration movement of the chute and the screening rods is effected by a vibration device attached on the frame and which is connected with the chute. The vibration device thereby preferably is constituted by a crank device which is driven by an electrical motor.
In an alternative embodiment of the invention, the carrier elements and the chute are vibrated by crank devices attached to the frame, whose crank motion is controllable for adjusting of a mutual phase displacement of the two vibration movements.
The carrier elements are provided with a mass, which is considerably less than the one of the chute, by which the carrier elements can be brought to vibrate moe easily and with a higher frequency than the chute. By this an intensive movement in the particulate materials to be screened will be achieved at the gap between the carrier elements and the screening rods, by which an effective screening will be achieved. The higher frequency of oscillation of the carrier elements also has proved to prevent clogging of the screening grid.
The screening method in accordance with the invention is not limited to a division of particulate materials into two fractions. By providing the chute with several bottoms, a division in several fractions can be achieved. The method is in particular useful for screening wooden chips, but is not limited to this kind of particulate materials. The method also can be used to separate gravel from wooden chips and the like.
The invention will be better understood by reference to the attached drawings which show an embodiment of the inventive apparatus for screening wooden chips.
DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically shows a preferred embodiment of the inventive screening ap
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Bashore S. Leon
Lithgow Thomas M.
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