Classifying – separating – and assorting solids – Sorting special items – and certain methods and apparatus for... – Separating means
Patent
1998-01-14
2000-09-05
Nguyen, Tuan N.
Classifying, separating, and assorting solids
Sorting special items, and certain methods and apparatus for...
Separating means
209479, 209694, 209930, B07C 900
Patent
active
061129070
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus and a method for separating material, in particular waste material. Such material is normally in a co-mingled state and can consist of newspapers, cardboard, plastic bottles, glass, organic waste and other such items. The sorting of waste material is a major problem and many different systems have been developed in order to extract various components of the waste. For example, it is possible to extract metal components of the waste using magnetic or eddy current separators where appropriate. However, most existing systems can effectively sort only a limited number of types of waste and the present invention is directed at the provision of a system which can improve on this.
We have found that objects may be separated if placed on a carrier surface and that carrier surface is provided with a movement in the plane of the carrier surface. This effect can be partially accounted for because different objects experience different frictional forces and, therefore, are accelerated and decelerated by differing amounts.
Further certain objects may momentarily leave the carrier surface at which point air resistance becomes a dominant factor. In certain circumstances objects may bounce along the carrier surface and this can cause separation. The effect can be particularly pronounced if the movement of the carrier surface is such that resonance occurs so that certain objects only (or more frequently) contact the table when it is moving in one particular direction. The physical properties of the objects and the carrier surface will effect the natural frequency with which an object will bounce.
Both the velocity and acceleration with which the carrier surface moves are important in the separation process. Objects have a co-efficient of limiting friction and co-efficient of dynamic friction. These co-efficients depend on the composition and nature of surface of the object concerned. When the carrier surface is given a certain acceleration, the limiting friction will be overcome for some objects but not others. Those objects whose limiting friction is not overcome, will remain stationary relative to the carrier surface. If the limiting friction is overcome for a particular object, that object will then move with a certain velocity relative to the carrier surface. A frictional force, however, will still act on this object, and this force will be dependent on the object's co-efficient of dynamic friction. This frictional force will tend to decrease the relative velocity between the carrier surface and the object concerned. A moving object which is in contact with the carrier surface will always experience a force in the direction in which the table is moving. Therefore, if the table spends longer moving in one direction than another, each object will experience a force for a greater period of time in one direction than the other. This can have the effect of providing different objects with different velocities and thereby yield separation.
When objects leave the carrier surface the distance that they travel will depend on their momentum and the air resistance that they experience. The mass, density, surface area and the surface characteristics of the objects are therefore important. Different objects will leave the carrier surface dependent on its velocity and acceleration. If the surface spends longer travelling one direction than another, objects will tend to pick up more speed in that direction.
The separation effect can be enhanced by providing the carrier surface with variable acceleration so that, at different times, the limiting friction for different objects is overcome.
The separation may be amplified by using a carrier surface having a variable slope. Objects which have obtained a large velocity in a certain direction will tend to proceed in that direction. Objects with lesser velocities, will spend longer on the slope and therefore gain a higher velocity down the slope due to the action of gravity. The slope of the carrier surface can also encourage certain components
REFERENCES:
patent: 1141852 (1915-06-01), Sutton et al.
patent: 4583645 (1986-04-01), Yamamoto
patent: 4978011 (1990-12-01), Gorlitz et al.
Biomass Recycling Ltd.
Browning Clifford W.
Nguyen Tuan N.
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