CA2412314C - Impeller for centrifugal crushers with vertical axis and method for making same - Google Patents

Abstract

Throw shoe for centrifugal-type crushers with a vertical shaft. Initially, i.e. when it is first used, this throw shoe (1) is not provided with pockets or cavities, but it is provided on its working side (5) with a reinforcement structure (4) made out of a composite material, obtained from an iron-based alloy and highly wear-resistant ceramic tiles, said reinforcement structure being formed in situ when the throw shoe is being cast by infiltration of the liquid metal used to form the body of the piece in a mass of ceramic tiles and binder. The working wear automatically results in the formation of pockets or cavities which, by filling up with the crushed material, exert a protection function against shocks.

Description

THROW SHOE FOR CENTRIFUGAL-TYPE CRUSHERS
WITH A VERTICAL SHAFT AND METHOD OF PRODUCTION
Object of the invention [0001] The present invention relates to a throw shoe (also called impacter or impeller), which is intended for so-called VSI-crushers (Vertical Shaft Impacter), i.e.
centrifugal-type crushers with a vertical shaft and a reinforcement structure.

Technological background of the invention [0002] The aforementioned crushers are well known in the prior art and widely used for crushing rock aggregates, among others in quarries and cement works.

[0003] The document WO 99/47264 and other documents cited in that publication refer to such crushers.

[0004] Those documents indicate that centrifugal-type crushers comprise a cylindrical housing containing a rotary table, which is supported by a vertical bearing and which comprises means to rotate the table about the central shaft of the crusher. The crusher comprises a series of throw shoes or impacters fixed onto the rotary table, as well as a series of anvils located on the inner vertical wall of the cylindrical housing, around the rotary table.

[0005] Throw shoes usually have a parallelepiped shape, generally made of cast iron and affixed to the rotary table of the crusher. The side of the throw shoe which is turned toward the rotation axis of the table is called the nose of the throw shoe, while the side which is parallel to the anvils fixed to the cylindrical housing forms the exit side of the throw shoe.

[0006] The front side of the throw shoe, called the working side, is the one encountering the material to be crushed and preceding the rear side in the rotation direction of the throw shoe.

[0007] This front working side of the throw shoe may be provided with one or more cavities, which do not run through the whole structure of the throw shoe and which form pockets, these pockets fill up with material when the crusher is rotating and thus protect the throw shoe from shocks and erosion due to the material that has accumulated in the pockets.

[0008] During the crushing operation, the material to be crushed is poured into the centre of the rotary table by known means. Due to centrifugal force and to the impact with the working side, the material is thrown towards the anvils, against which it is crushed before it drops, in crushed form, at the bottom of the crusher from where it is removed. While the material is being thrown, the throw shoes are subjected to very high stresses and consequently to rapid wear.

[0009] Thanks to the accumulation of material in the pockets, the use of pocket throw shoes considerably increase the working lifetime of the throw shoes in certain applications.

[0010] In this type of throw shoe, it is observed that the wear preferentially occurs around the exit edge of the pockets, i.e. where the abrasion due to the particles thrown by the centrifugal force is highest.

[0011] The above-mentioned document WO 99/47264 and other documents therein cited display protections or reinforcements meant to avoid or reduce such erosion effects.

[0012] The specific solution put forward by WO 99/47264, i.e. the production of a throw shoe with one or several pocket(s) with an essentially parallelepiped form, consists in creating on the whole periphery of the pocket(s)' or on part of said periphery a reinforcement structure made out of a composite material, obtained from an iron-based alloy and highly erosion-resistant ceramic tiles. That structure, which is formed in situ during the casting of the throw shoe by infiltration of the liquid metal used to form the body of the piece in a mass of ceramic tiles and binder, has proved particularly effective to ensure an increased working lifetime of the throw shoe.

[0013] Although this type of production provides considerable technical progress and technological advantages, some limitations or difficulties have appeared.

[0014] First of all, the support made out of ceramic tiles and binder has to be perfectly infiltrated by the metal in order to obtain effective turnover.

[0015] The width of the metal on either side of the support should be large enough to ensure sufficient infiltration of the ceramic component of the reinforcement structure. Which means that a large width of the walls of the composite piece must be provided, which has the consequence of limiting the dimension of the pockets. Thus, the width of the ceramic reinforcement also has to be controlled in order to improve the infiltration; this limitation of the width of the reinforcement makes it less effective and more fragile.

[0016] Moreover, in the case of throw shoes with one pocket as well as throw shoes with several pockets, the pockets are empty when the throw shoes are first used and unprotected by the material to be crushed.

[0017] During that first use, the thin walls are particularly exposed to impacts due to the biggest aggregates or to alien material (steel pieces, shovel teeth, etc.).

[0018] This can lead to the breaking of the most fragile reinforced walls, which seriously damages the piece and often requires its replacement very soon after the first use.

(0019] In the case of crushers with a vertical shaft, the wear profile is generally hard to control because the working conditions depend on different parameters, which change with time: supplying particle size, aggregate abrasiveness, etc.

[0020] With the solution disclosed in WO 99/47264, a change in the form of the pockets induces a complete change of the cast models and pit boxes, with no possibility to predict the obtained result.

[0021] Moreover, these operations are very expensive and result in important time losses.

[0022] Furthermore, when the profile of the pockets has to be changed, there is also a limitation in the form because of the above-mentioned infiltration difficulty.

[0023] Finally, the wear of throw shoes in VSI-crushers is all the same a major problem because the abrasion and shocks are excessively severe. To increase the working lifetime of the throw shoes is a constant concern.

Object of the invention [0024] The invention aims to solve the above-mentioned problems, and in particular to further improve the performances of throw shoes by making the most of the inner advantages of the throw shoes production technology described in WO 99/47264.

Summary of the invention [0025] The invention proposes a throw shoe intended for centrifugal-type crushers with a vertical shaft, which unlike the ones disclosed in the aforementioned prior art,'does not deliberately and initially, i.e. when first used, comprise cavities or pockets, but which comprises on its working side a composite reinforcement structure obtained from an iron-based alloy and highly wear-resistant ceramic tiles, said composite reinforcement structure being formed in situ during the casting of the throw shoe by infiltration of the liquid metal used to form the body of the piece in a mass of ceramic tiles and binder.

[0026] Said reinforcement structure is provided on the working side according to a suitable geometrical disposition in order to let the metal locally (i.e. in the zones without reinforcement structure) show on the working surface, so that the working wear automatically results in the formation of pockets or cavities, which exert a protection function against shocks by filling up with crushed material, while at the same time maintaining the reinforcement structure at the upper periphery of the pockets thus formed, i.e. on the working surface.

[0027] The throw shoe thus produced can entirely solve the aforementioned problems.

[0028] As far as the infiltration difficulties are concerned, the quantity of metal available to infiltrate the support is according to the invention all the metal constituting the piece, instead of only the metal constituting a single wall. Moreover, a larger reinforcement can be introduced where it is judged necessary, because the infiltration conditions are enhanced due to the bigger mass of liquid metal.

[0029] The fact that the pockets are not formed from the start totally avoids the risk due to the presence of thin walls during the first use, because large enough walls can be produced.

[0030] In the embodiment according to the invention, only the profile of the reinforcement has to be changed if the form'of the pockets needs to be changed, which highly lowers the costs and furthermore offers better possibilities of form and conception. Moreover, it is possible to cast the piece without using one or more sandpits in order to form the pocket(s), which considerably reduces production costs.

[0031] Finally, the technique according to the invention can noticeably increase the working lifetime because as soon as the pockets start to form, autoprotection occurs due to the material retained in the pockets being formed.
The process of the formation of the pockets is slowed down and when they are fully formed, all the time needed for the formation has saved up working lifetime.

[0032] As a summary, the invention integrates all the specific advantages described in WO 99/47264 of a reinforcement structure, made out of a composite material and formed in situ by infiltration of a liquid metal in a ceramic mass with the ease and advantages of the production of a piece, with no obligation to provide one or several pocket(s).

[0033] The process used is particularly simple to carry out, it simply consists in fixing a ceramic wear-resistant cover, preferably in the form of a mass of a binder and ceramic tiles from alumina and zirconia, at the bottom of a mould by conventional means such as gluing, mechanical fixing, nails, screws, cramping shaft or others depending on the desired geometrical disposition to allow the subsequent formation of one or several pocket(s) by wear, and then in casting the metallic mass used to form the body of the throw shoe.
When this metal infiltrates the ceramic mass, it ensures its perfect connection to the cast piece during the cooling of the piece. The piece is then removed from the mould and, after possible finishing (trimming, etc.), the throw shoe can be directly used.

[0034] Other characteristics and advantages of the invention will be clearly understood thanks to the following description, with reference to the attached drawings.

Brief description of the drawings [0035] In the different drawings enclosed herewith, - Figure 1 is a perspective view of a pocket throw shoe according to the prior art, with a ceramic reinforcement infiltrated by metal;
- Figure 2 is a perspective view of a throw shoe without pockets according to the present invention with the same kind of reinforcement;
- Figure 3 is a longitudinal section view of a throw shoe according to Fig. 2 with the evolution line of the profile of the pockets during their formation.

Detailed description of a preferred embodiment of the invention [0036] Identical reference numbers are used in the different figures for identical or similar constituent elements.

[0037] A conventional throw shoe 1 according to Fig.l comprises one or several pocket(s), in this case the cast pockets 2 and 2', before the throw shoe 1 is used. This throw shoe advantageously comprises reinforcements 4 in infiltrated ceramic. The nose 6 of the throw shoe and the exit side 7 of the throw shoe, which are usually highly solicited, can comprise additional reinforcements, such as reinforcement 8 represented on Fig.l.

[0038] In the case of the embodiment represented on Fig.2, the throw shoe 1 is designed before it is used as a full piece, without pockets on its working side 5 but provided with cast reinforcements 4. These reinforcements can be arranged, as represented on Fig.2, according to a form and disposition similar to those provided on Fig.l, if one wishes to form two pockets in service. Of course, according to the desired aims, other forms and dispositions are possible.

[0039] Fig.3 shows the evolution in service (Progression I, II and III) of the profile of the pocket being formed, due to the presence of the reinforcements 4 before the piece is first used.

[0040] The middle reinforcement, which separates the pockets 2 and 2' and which is shared by them, is represented on Fig.l as presenting the same width as the corresponding middle reinforcement of Fig.2 (and Fig.3).
In the case of the embodiment of Fig.1, the width is however limited because it is particularly difficult in this case to totally infiltrate the ceramic material in this mass by the metal, whereas this difficulty does not occur in the case of Fig.2 because of the "full"
character of the piece formed by casting.

[0041] The invention thus brings a simple solution to different technical problems of throw shoe production, in particular a larger liberty of conception thereof.
Moreover, the execution of the recommended technique is inexpensive. The cost of additional casting to be used is largely compensated by the added working lifetime, the ease of execution and the fact that no specific means are required for forming the pockets while casting the piece.

[0042] Additional reinforcements for the nose and the exit side of the throw shoe, such as the one represented by reference number 8 on Fig.1, can also be provided in the embodiment of the invention, notably of Fig.2 and 3.
For the sake of clarity of the drawing, they are not represented therein.

Claims (7)

1. Throw shoe for centrifugal-type crushers with a vertical shaft, characterised in that it does not initially comprise, i.e. when it is first used, any cavity or pocket, but is provided on its working side (5) with a reinforcement structure (4) which is made out of a composite material, obtained from an iron-based alloy and highly wear-resistant ceramic tiles, said composite reinforcement structure being formed in situ during the casting of the throw shoe by infiltration of the liquid metal used to form the body of the piece in a mass of ceramic tiles and binder.

2. Throw shoe according to Claim 1, characterised in that said reinforcement structure (4) is provided on the working side (5) according to a suitable geometrical disposition in order to let the metal locally show on the working surface (5), so that the working wear automatically results in the formation of pockets or cavities which, by filling up with crushed material, exert the protection function against shocks while at the same time maintaining the reinforcement structure at the upper periphery of the pockets thus formed, i.e. on the working surface.

3. Throw shoe according to Claim 2, characterised in that it comprises a reinforcement structure (4), the form and disposition of which are such that it results in the formation of at least one pocket during working wear.

4. Throw shoe according to Claim 3, characterised in that it comprises a reinforcement structure (4), the form and disposition of which are such that it results in the formation of at least two pockets during-working wear.

5. Throw shoe according to any one of the claims 1-4, characterised in that the ceramic tiles are alumina-based and zirconia-based tiles.

6. Method for producing a throw shoe according to any one of the claims 1-5, characterised in that, depending on the desired geometrical disposition in order to allow the subsequent formation of one or several pocket(s) by wear, a cover of wear-resistant ceramic, which can be infiltrated by a molten metal, is fixed at the bottom of a mould, in that the metallic mass used to form the body of the throw shoe is then cast, so that it shows on the working surface in the zones left without ceramic material, and in that, after connecting the cover of infiltrated ceramic material with the metallic mass by cooling, the piece forming the throw shoe is removed from the mould.

7. Use of the throw shoes according to any one of the claims 1-5 or obtained by the process according to Claim 6, in centrifugal-type crushers with a vertical shaft by progressively forming pockets by working wear of its constituent material unprotected by the reinforcement structure on the working side.