TECHNICAL FIELD

The present invention concerns gyratory crushers. More particularly the invention concerns an axial thrust bearing of a gyratory crusher.

BACKGROUND ART

Gyratory crushers comprise a vertical eccentric shaft with an inclined inner hole therein. A main shaft, to which a supporting cone is attached, and which is supported to the frame at its upper part by means of an upper supporting bea¬ ring, is mounted in the hole. The supporting cone is sur¬ rounded on its sides by the frame of the crusher, an element acting as a wearing part called outer crushing head being attached to the frame. An element acting as a wearing part called inner crushing head is attached to the supporting cone. The inner and outer crushing heads, together, form a crushing chamber, where the feed material is crushed. When the eccentric shaft is rotated, the main shaft and, together with it, the supporting cone get to an oscillating movement, whereby the gap between the inner and outer head at each point varies during the working cycle. The smallest gap during the working cycle is called the setting of the crusher, and the difference between the minimum and maximum gap is called the stroke of the crusher.

Through the magnitude of the setting and the stroke of the crusher, i.a. the particle size distribution of the produced crushed material and the production capacity can be in- fluenced.

Presently, a gyratory crusher can be adjusted by means of a hydraulic system, so that the main shaft can be moved vertically in relation to the frame. This makes it possible to change the setting so that the size of the final product corresponds to the desired one and/or to maintain the same setting when the crushing heads wear.

Below the main shaft, there is a thrust bearing com¬ bination. At the lower end of the main shaft, there is a bearing plate made of bearing metal, said bearing plate having

usually a convex lower surface. A corresponding plate made of bearing metal, said plate having a convex upper surface, is attached on top of an adjusting piston, located below the main shaft, or, in some embodiments, onto the bottom of a cup- formed plunger piston acting as an adjusting piston. Lubri¬ cating grooves have been machined onto the bearing plates for lubrication oil. Between the bearing plates, there is usually an intermediate plate made of steel, following the surfaces of the bearing plates and having thus in general two concave surfaces. The bearing metal is an alloy softer than steel, e.g. bronze.

Either one of the bearing plates can also have a plane surface, whereby the corresponding surface of the intermediate plate is naturally also a plane surface. A disadvantage of the thrust bearing construction of prior art is that the different coefficients of thermal expansion of the metals change the geometry of the bearing surfaces in different ways. This causes local increase of surface pressure in the bearings. This, in turn, causes extra heat, whereby the surfaces change their shape even more. Thereby the local surface pressure is further increased, and finally the bearing may be destroyed.

A disadvantage of the prior art is also the fact, among others, that the bevelled edges of the lubricant grooves machined into the bearing metal softer than steel, wear in use. This can finally lead to an insufficient formation of lubricant film between the bearing surfaces, which also can cause the bearing to be destroyed.

A further disadvantage of the prior art is that a lot of bearing metal is needed. The bearing metal is usually material more expensive than steel, whereby one disadvantage of the bearing based on prior art is its high cost. Ad¬ ditionally, in several embodiments the most useful bearing material is lead bronze, so that the use of a bearing based on the prior art causes work hygienic and environmental problems because of the high consumption of toxic lead.

Patent publication SE 138 423 discloses an axial bearing of a crusher, in one embodiment of which the intermediate plate is entirely of bronze, and the opposite surfaces above

and below it are made of steel. In that case, too, there is the problem of the different coefficients of thermal expansion of the metals, and the different deformations of the curved surfaces. Another embodiment described in the publication shows a bearing, where the bearing material used for the intermediate plate is laminated textile impregnated with phenolic resin. The centre part of the intermediate plate is entirely of this impregnated textile material, surrounded by an enforcing ring of metal.

DISCLOSURE OF THE INVENTION General description

What has now been invented, is an axial thrust bearing combination in accordance with claim 1, and a gyratory crusher in accordance with claim 7. Some preferred embodiments of the invention are stated in other claims.

Most essential to the invention is that at least one surface of the intermediate plate is plated with a bearing metal layer, and that the opposite surface against this bearing metal layer is made of a harder material than this bearing material. Most preferably, the bearing metal plating is attached by exploding to the surface of the steel heart of the intermediate plate.

Explosive welding for connecting materials with each other is known in the art. Plating with explosion method means that the piece to be plated is placed onto a base, and a plating plate is placed above it, at a distance from the part to be plated. The explosive is ignited and the plating plate hits to the surface of the part to be plated. The surfaces are totally welded to each other.

The construction of the massive bearing made of bearing metal has been changed so that the frame of the intermediate plate is manufactured of steel or a material having correspon¬ ding strength characteristics, and a bearing metal plate is joined therewith at least on one side, but preferably on both sides. The convex, concave or plane bearing plate on the upper and lower sides, provided with lubrication grooves, is correspondingly manufactured of steel or a material having corresponding strength characteristics.

A separate plate below can also be replaced by the upper surface of the piston with lubrication grooves, or in some embodiments with the upper surface of a cup-formed plunger piston provided with lubrication grooves. The construction in accordance with the present invention has the advantage that the different thermal expansions of the steel and the bearing metal can be better controlled, when only a thin bearing metal plating is used on the intermediate plate made of steel, instead of massive bearing metal plates. A sufficient thickness of the plating is, depending on the type of the crusher and the crushing process, from ca. 10 mm even to l mm. Additionally, the wearing of the lubrication grooves on the surface of the steel or a material having corresponding strength characteristics is minor. Further, the use of bearing metals is less, and thereby the production costs are decreased.

The lower bearing plate can be eliminated, and thus the construction is more simple.

One further advantage is gained when the invention is applied to a crusher, where the massive adjusting piston is replaced by a thin-bottomed, cup-formed adjusting piston, onto the bottom of which the main shaft is supported via an axial bearing. When in this kind of a crusher, the thickness of the bearing surface is added to the thickness of the bottom of the piston, the bottom will be stiffer and more robust, however, without increasing the total height of the crusher. It is, in addition, easier to arrange the safety valve of the hydraulic adjustment system to the thicker bottom of the adjusting piston. Thus, in an overload situation, the adjustment pressure oil can be led from below the adjusting piston to the axial and radial bearings of the crusher, thus providing additional lubrication or cooling for the bearings, especially required in the overload situation. Description of drawings The enclosed drawings form a part of the description of the invention.

Figure 1 illustrates a gyratory crusher.

Figure 2 illustrates one embodiment of a thrust bearing combination in accordance with the present invention.

Example

A gyratory crusher has a spindle shaft comprising a main shaft 1 and a conic crushing head 3, mounted onto a supporting cone 2. An inclined hole of an eccentric shaft 4 causes during the working cycle a forced oscillating movement narrowing and widening the crushing gap 5 between the crushing heads making the stones to crush between them. The smallest value of the crushing gap 5 during a working cycle is called the setting of the gyratory crusher. The setting is changed by means of a hydraulic adjusting device by leading pressure medium to a space 7 below a piston 6, whereby the spindle shaft raises upwards thus decreasing the setting. Correspondingly, by removing pressure medium from the space 7, the spindle shaft

I descends downwards and the setting is increased. The lower end of the main shaft is leaning against the upper surface of the adjusting piston, or in some embodiments, against the upper surface of the cup-formed bottom of the adjusting piston via a thrust bearing 9. Between the inner surface of the piston 6 and the outer surface of the eccentric shaft 4, there is a radial bearing 8. Between the inner surface of the eccentric shaft and the spindle shaft 1, there is a radial bearing 10' . The crusher is surrounded by a frame 11' .

The thrust bearing combination 9 makes it possible to accomplish a forced oscillating movement of the main shaft of the gyratory crusher. The thrust bearing combination 9 of figure 2 comprises an intermediate plate 10, the upper surface

II of which is a part of a concave spherical surface, against which rests an upper bearing 12 correspondingly formed as a part of a convex spherical surface and mounted at the lower end of the main shaft. The plane lower surface 13 of the intermediate plate 10 of the thrust bearing combination is supported by the corresponding plane bearing surface 14 of the upper surface of the piston bottom. Of the surfaces 11 and 13 of the intermediate plate, at least one is plated with a bearing metal plating. The upper bearing 12 is made of steel or a material with corresponding strength characteristics, as well as the bearing surface 14 of the piston bottom.

In the piston, there is a channel 15, the lower end of which opens to the pressure medium chamber 7. The other end of the channel opens to an opening in the middle of the inter¬ mediate plate 10. At the lower end of the channel 15, there is a safety valve 18, which opens only when the pressure in the chamber 7 exceeds a given value. When the crushing pressure exceeds the given value, the safety valve 18 relieves the pressure from the chamber 7 to the axial bearing 9 of the main shaft, thus providing for it the required additional lubrication.

Correspondingly, the additional lubrication can also be led to the radial bearing of the crusher, via the other branch 16 of the channel 15 and a lubricant chamber 17.

In the embodiment of figure l, the lower bearing surface 14 is on a separate part attached to the bottom of the piston.

The bearing surface 14 has a convex form, whereby the lower surface of the intermediate plate 10 against it has correspon¬ dingly a concave form.

The convex bearing surface 12 attached to the lower end of the main shaft, made either of steel or a material with corresponding strength characteristics, can also be manufac¬ tured as one piece with the main shaft.

The other surface of the intermediate plate can also be left unplated, and it can be provided with oil grooves, and the corresponding surface of the bearing part can be plated with bearing metal.

The bearing metal forms only a thin layer on the core part of the intermediate plate. The volume of the core part is at least 50 %, preferably at least 70 %, eventually even at least 99 % of the total volume of the intermediate plate. The bigger the share of the core part, the better the strength and the loading capacity of the intermediate plate, and the better the thermal expansion of the intermediate plate corresponds to the thermal expansion of the surfaces against it. Most preferably the core part extends to the edge of the opening in the intermediate plate.