EP0804965A1 - Milling surface - Google Patents

Abstract

The grinder track consists of a series of segments (16,18) mounted on a turntable and forming a circular grinding surface beneath rollers which grind material as it is poured onto the track. The segments are fitted to a machineable steel sole (20) with outer (26) and inner (24) edges forming recesses for them. The segments are made from a material with a high resistance to wear, such as cast iron or chrome, or of ceramic inserts in metal matrices. They are fixed to the sole by screws (42) and wedging bushes (40). In addition, the sides of the sole recesses have chamfered surfaces which act as dovetail joints for the segments.

Description

The present invention relates to a track for shredders consisting of several segments supported by a rotary table and forming at least one circular raceway evolving below grinding rollers to grind material poured onto the track.

A grinder of the kind targeted by the present invention is, for example, described in patent EP 0476496 B1. There are also double track mills with two concentric raceways which run beneath two pairs of grinding rollers. The tracks, both those with a single raceway and those with a double raceway, are generally made up of separate segments or segments juxtaposed, which allows easier handling of these elements of limited weight because you have to know that the weight total of a whole track can be of the order of a few tens of tonnes. In addition, in the event of accidental deterioration of a track segment, it can be replaced individually without the need to replace the entire track.

The major problem with grinder tracks is wear. Due to the abrasive nature of the material to be ground, the segments are, in fact, exposed to rapid and intense wear and must be made of very hard chromium cast iron. On the other hand, the segments must undergo very precise machining in order to be fixed correctly on the table of the crusher and protect it against any degradation likely to occur during service. These requirements are not mutually compatible, the machining of a chrome cast iron track is very difficult and very expensive.

The wear of the tracks with double raceway is, moreover, irregular insofar as the internal raceway wears out faster than the external raceway. The shapes of the wear profiles of the raceways are also different, which leads to differences in the grinding efficiency of one raceway compared to the other and reduces the efficiency of the mill. Generally, it is the state of wear of the inner race which is decisive for the replacement of the segments and it is often necessary to replace a track or a segment while its region forming the outer raceway could still be used for some time.

The object of the present invention is to provide a new track for shredders which makes it possible to remedy these drawbacks, in particular to provide a track with better resistance to wear and a track which manifests more uniform wear.

To achieve this objective, the invention proposes a track for shredders of the kind described in the preamble which is characterized in that each segment consists of a machinable steel sole with an outer edge and an inner edge defining a housing for a segment wear having high wear resistance and removably attached to the sole, the upper surface of the wear segment forming the race or tracks.

Thanks to the design of the added wear segments, it is possible to choose harder and more wear-resistant materials for these without being limited in the choice by the need for precise machining of the base. Thus, not only can ferrous alloys such as chromium cast iron be used for the wear segments, but also composite parts with a metal matrix and extremely hard inserts, for example in various ceramics.

Likewise, it is possible to choose for the sole an easily machinable steel since the sole is not subjected to grinding wear. The sole can therefore be machined in optimal conditions to be fixed correctly on the rotary table which must remain in perfect condition.

The wear segments can be fixed to the sole using screws and clamps.

The edges of the sole may have bevelled parts forming dovetail attachments with the wear segments.

In the event of wear, it is sufficient to replace the added wear segments, the sole being able to remain in place. The fixing of these segments by screws and clamps allow an easy and easy replacement.

Since the soleplate can remain in place, it effectively protects the table against possible impacts with the wear segments when these are replaced.

According to an advantageous embodiment, the track can comprise a series of interior wear segments and a series of exterior wear segments defining two concentric raceways while each sole has a protruding central rib in an arc of a circle separating the interior segments. outer segments.

In this case the inner segments and the outer segments can be replaced separately and the outer segment, more particularly, can remain in place until the outer race is completely worn. It is also possible to choose a harder material for the inner segments in order to ensure uniform wear of the two raceways.

In general, the invention offers the possibility of choosing different materials for each of the wear segments and of regularizing the general wear profile by choosing a harder material where the track wears the most and make the wear profile more uniform, which has a great influence on the performance of the mill.

• la Figure 1 représente schématiquement une coupe radiale à travers une piste annulaire selon la présente invention et
• la Figure 2 représente schématiquement une coupe radiale à travers la semelle.

Other features of the invention will emerge from the detailed description of a preferred embodiment presented below, by way of illustration, with reference to the appended figures in which:

• FIG. 1 schematically represents a radial section through an annular track according to the present invention and
• Figure 2 schematically shows a radial section through the sole.

The track shown in Figure 1 and generally designated by the reference 10 is fixed on a rotary annular table not shown. It has on its upper face two concentric annular raceways, of concave section, more specifically an internal raceway 12 and an external raceway 14 which evolve below two pairs of grinding rollers not shown with convex running surface .

The two raceways 12 and 14 are defined in a series of internal wear segments 16 respectively a series of external wear segments 18, these segments being made of very wear-resistant material. The different segments are fixed in housings defined in a sole 20 (see also Figure 2) which can also be segmented and which is made of treated steel to obtain good mechanical properties and be easily machinable.

The sole 20 has a flat base 22 with an inner edge 24 and an outer edge 26 delimiting with a median projecting rib 28 in an arc of a circle the locations of the wear segments 16 and 18. The inner and outer edges 24 and 26 comprise, preferably, inclined corners 30 respectively 32 cooperating with corresponding beveled corners of the segments 16 and 18 to define solid dovetail fasteners of the wear segments.

The wear segments may have, on their lower surface, cells 34 into which pins 36 penetrate through the sole 20 to ensure correct positioning of the segments when they are put in place and to prevent any displacement. relative to the wear segments relative to the sole, under the action of the engine torque transmitted by the sole and the segments to the bed of material to be ground and to the rollers.

The fixing and tightening of the segments 16 and 18 can be ensured by screws 38 and clamps 40 in the middle region and by the dovetail housings 30 and 32 on the periphery of the sole 20.

If the invention has been described in detail with reference to Figures 1 and 2 in the context of its advantageous application to a track with two raceways, it should be noted that it is not limited to this application and that it also brings many benefits to single-track tracks.

Claims (6)

Track for shredders consisting of several segments supported by a rotary table and forming at least one circular raceway evolving below grinding rollers for grinding material spilled on the track, characterized in that each segment consists of a sole (20) of machinable steel with an outer edge (26) and an inner edge (24) defining a housing for a wear segment having a high resistance to wear and removably fixed on the sole (20), the upper surface of the wear segment forming the race or tracks. Track according to claim 1, characterized in that the wear segments are fixed to the sole (20) using screws (38, 42) and clamps (40). Track according to claim 1, characterized in that the edges of the sole (20) have bevelled parts (30, 32) forming dovetail fastenings with the wear segments. Track according to any one of claims 1 to 3, characterized in that it comprises a series of internal wear segments (16) and a series of external wear segments (18) defining two concentric raceways (12 , 14) and in that each sole (20) has a projecting central rib (28) in an arc separating the inner segments (16) from the outer segments (18). Track according to any one of claims 1 to 4, characterized in that the wear segments are made of chromium cast iron. Track according to any one of Claims 1 to 4, characterized in that the wear segments are composite parts with a metal matrix or with ceramic inserts with high wear resistance.

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