PRIOR ART The eccentric assembly, which determines the cone crusher workability, is the most heavily working unit in it. It consists of a body, manufactured of steel, with an immovable cone gear-wheel joint either to upper or lower edge of it. The inner surface is treated with an angular eccentricity towards the outer surface and determines the trajectory of motion of movable cone axis. Inner and outer surfaces of the body are formed as supports for rolling or plain bearings.

Important drawback of eccentric assembly unit in cone crusher with rolling bearings, for which they have not found application in practice, is the high cost of necessary large-dimensional rolling bearings, which make the eccentric unit more complicated, require high precision of manufacture and assembly of working parts [1].

Cone crushers with plain bearings are manufactured in two variants: -circular pouring of the inner surface of the body of eccentric assembly unit and outer surface along an axis of 240-270 with antifrictional material, usually babbit [2] ; -manufacturing of plain bearings as changeable bronze or steel bushes with babbit pouring [3, 4].

An eccentric assembly unit in cone crushers most similar in its technical nature is the one, described in [3]. It consists of a body with an immovable cone gear-wheel joint to one of its ends. The inner surface is treated with an angular eccentricity towards its outer surface. Inner bushing, which is used as a plain bearing for shank of the shaft of movable cone of crusher, is connected immovably to inner surface of the body. The bushing is manufactured of bronze or steel, poured on the working surface with babbit. Outer surface of the body is born in a second plain bearing, manufactured as a second bushing of bronze or steel with babbit. The inner bushing is cylindrical or cone with an angular eccentricity.

The outer bushing is usually cylindrical. In the process of fragmentation of processed in the crusher material, the eccentric unit is the one, which takes the difference of periodically changing forces of fragmentation, originating between the movable and immovable cones of the crusher. This involves fast wearing of plain bearings, realized as bushings, made of bronze or steel, which on its own behalf rises the cost of exploitation.

Manufacture of plain bearings of low dimensions from plastics is known [5].

Manufacture of plain bearings of large dimensions from plastic material to be used in cone crushers is unknown.

The object of the present invention is to create an eccentric assembly unit in cone crusher with increased longevity and reduced exploitation cost.

SUMMARY OF THE INVENTION The object of the present invention is an eccentric assembly unit in cone crusher, consisting of a body, the form of which is similar to cylindrical one, with a connected to one of its ends an immovable cone gear-wheel. The inner surface is treated with an angular eccentricity towards the outer surface. Bushing, which is used as a plain bearing for shank of the shaft of movable cone of crusher, is connected immovably to inner surface of the body. Outer surface of the body is born by a second plain bearing, used as a second plain bearing. The second bushing is connected immovably to corpus of the crusher. First and second plain bearings are manufactured from plastic material of the type of semi- crystalline engineering plastics, for example, polyamides (PA), polyethyleneterrephtalate and polyacetal (POM) or their modification.

Inner surface of the first plain bearing, realized as bushing is cylindrical. It is treated with an angular eccentricity.

It is possible the inner plain bearing to be realized a cone bushing.

BRIEF DESCRIPTION OF DRAWINGS The present invention is described in more details with reference to the drawings, where: Figure 1 presents a longitudinal section along the axis of first embodiment of the eccentric assembly unit in cone crusher; Figure 2 presents a longitudinal section along the axis of second embodiment of the eccentric assembly unit in cone crusher.

DETAILED DESCRIPTION OF THE INVENTION The eccentric assembly unit in cone crusher, shown in fig. 1, consists of body, which has a shape near to the cylindrical shape, manufactured of steel, a cone gear wheel is joined immovably to one of the ends. Inner surface of the body 1 is treated with an angular eccentricity towards its outer surface. A bushing 3, which serves as a plain bearing for the shank of shaft of movable cone of crusher, not shown in the figure, is connected immovably to the outer surface of body 1. The body 1, together with the gear wheel 2 and bushing 3 is born by its outer surface by a second bushing 4, which is bond immovably to corpus of crusher, not shown in the figure. The two bushings 3 and 4 are of cylindrical shape. Both plain bearings, realized by bushings 3 and 4 are manufactured of plastic material of the type of semi-crystalline engineering plastics, for example PA, PETP, POM and their modifications.

The second embodiment of the eccentric assembly unit in the cone crusher, shown in figure 2 differs from those, shown in figure 1 in the fact that inner surface of body 1 is a cone-shaped and the first bushing 3 is also cone-shaped.

In the process of fragmentation of the processed in the crusher material the eccentric assembly is the unit that takes the reaction of periodically changing forces of fragmentation, originating between the movable and immovable cones of the crusher, however as the bushings 3 and 4 are manufactured of plastic material of the above- mentioned type with increased longevity, because: -the coefficient of friction of steel into plastic material is constant in a wide temperature range and is lower than the coefficient of friction of bronze/babbit in steel, which provides reduced working temperature of plain bearing, accident-free work in dusty and/or moist medium and/or insufficient lubrication of friction surfaces ; -these materials do not allow wearing of friction metallic surfaces, for example, shank of shaft of movable cone and outer surface of body; -increased resistance towards all types of lubricating agents, oil products and organic diluters and for that reason the last do not contaminate from separate splits or oxides formed in the process of work.

Increased longevity of bushings 3 and 4 brings to reduction of exploitation cost, which are additionally reduced by easier and cheaper manufacture of bushings 3 and 4 of plastic material, in comparison to bushings made of metal. Reduced exploitation cost, on its behalf, brings to reduced cost for realization of technological operation fragmentation in the process of material processing.

The first embodiment of the useful model, shown in figure 1, is realized and analyzed by the authors under working conditions. The bushing 3 of dimensions outer diameter 644 mm, inner diameter 561 mm and length 820 mm is manufactured of modified (thermally stabilized) PA. After 6 months of continuous exploitation the wearing of the working diameter of bushing 3 is even along its whole length and is within the boundaries of 0.15 mm to 0.20 mm. There is no wearing on shank of shaft of movable cone, to the contrary, polishing is observed. For comparison, a bushing of highly quality bronze, having the same dimension, put in the same working conditions has exploitation life of 3 to 4 months. Often this life is reduced just to several days. Price of bushing of the above mentioned plastic material is 1.5 to 2 times lower than price of bronze bushing, which brings to reduced exploitation cost.

REFERENCES 1. Muizemnek J. A., Kalunov G. A. etc."Cone crushers", M., Machinostroenie 1970, p. 98, (in Russian) 2."Manual on mechanics of ore shafts", Dachenko, A. C., Nedra 1978 1978, p.366-367, fig. IV. 35 ; 3. Cone crusher model Kubria of the German company KRUPP; 4. Muizemnek J. A., Kalunov G. A. etc."Cone crushers", M., Machinostroenie 1970, p. 96, (in Russian) 5. RU-2086817.