Crushing members for crushers

Abstract: A crushing member as a roll (A) cooperates with another crushing member in a crusher for crushing material which is nipped in between opposed crushing surfaces of the members. The crushing members have at least in the parts thereof providing their crushing surfaces first and second blocks (1 and 2) arranged alternately in the direction (X) in which material is nipped in and having different wear resistances. The blocks (2) of less wear resistance wear after initial use to provide recesses between the blocks (1) which increase nipping in of material and thus throughput.

Description: The present invention relates to crushing, or pulverising members as defined in the pre-characterizing part of claim 1, which are known from JP-17-55-9389 and which are used in crushers or pulverisers of the type in which the material is fed into a nip between surfaces of crushing members, thereby to be crushed. Crushers of this type include, e.g. roll crushers, cone crushers, ring roll mills, vertical roller mills, edge runners, etc. The crushing members comprise rolls, rollers, table liners, etc. which form the crushing surfaces in such crushers, and are represented by A and B in this specification. Further the crushing surface with which the crushing member A is provided is represented by a and that which the crushing member B is provided with by b , respectively, in this specification. Heretofore, various materials such as iron ore, coal, coke, graphite, converter slag, blast furnace slag, limestone, clinker, rock etc. have been crusted by roll crushers, cone crushers, ring roll mills, vertical roller mills, etc. The crushing principle involved in the functioning of these crushers will now be described with reference to Figures 1 to 4 of the accompanying drawings, of which Figure 1 relates to a roll crusher; Figure 2 to a cone crusher; Figure 3 to a ring roll mill; and Figure 4 to a vertical roller mill. In a roll crusher as shown in Figure 1, a pair of rolls A and B having cylindrical surfaces a and b are counter rotated to effect crushing of the material by compression and shearing exerted between both rolls A and B. In a cone crusher as shown in Figure 2, the material is crushed by compression and shearing in a crushing space formed between a spindle A having a truncated cone outer surface which gyrates, while rotating about its own axis, and a fixed anvil B having an inverse truncated cone inner surface b . In a ring roll mill as shown in Figure 3, a plurality of rolls (typically from 2 to 6) each having a cylindrical surface are gyrated at a high speed to thrust the rolls onto the fixed ring B having an inner cylindrical surface b by the centrifugal force, thereby effecting crushing of material therebetween. In a vertical roller mill as shown in Figure 4, two crushing rollers B each having a cylindrical surface b are pressed onto a plane surface a of a crushing table A while the latter is rotated, so that material which is fed onto the table A near the centre thereof is crushed by the compression, impact and shearing action by the table A and the rollers B, while being transferred outward by the centrifugal force. The rollers B and the table A are not restricted to the cylindrical surfaces b and the plane surface a , but may include a combination of a table liner with a ring groove and a ring roller fitted thereinto. One way of increasing the output per unit time in the above crushers is to produce a situation for facilitating the nipping in of the material between the crushing members A and B (for example, between a roller and a table liner, between a roll and a ring, and between a spindle and an anvil of a cone crusher). Taking a ring roll mill as an example, when new product rolls A begin to be used, the crushing efficiency is low, depending on the type of material. This is because the crushing surface a of the roll A is plane cylindrical and smooth, resulting in inadequate nipping-in. Then as uneven wear begins occurring on the rolls A, after operating them for a while, a crushing efficiency rise has been often experienced. On this ground, as a means for enhancing the crushing efficiency, the crushing surface of the roll A of a ring roll mill has been initially provided with striped protrusions 4 such as shown in Figure 5 of the accompanying drawings. Such a means is not limited to rolls of ring roll mills, and may be employed in the form of providing rolls of roll pulverisers with a wavy or serrate shape. Also the spindle surface of some cone crushers is serrate and several lines of striped protrusions are provided on the rollers or table liner of vertical roller mills etc. Initially providing the crushing surfaces a and b with striped protrusions 4 has the effect of increasing the pulverising efficiency from the beginning of crushing, thereby augmenting the output tonnage per hour. This is believed to result from the fact that these protrusions function to improve nipping-in. However, high striped protrusions 4, if provided on the crushing surfaces a and b of the crushing member will cause vibration and noise and, therefore, the height of the striped protrusions 4 should be naturally subject to limitation. Accordingly, the striped protrusions 4, immediately after starting the operation, will wear away, thus actually failing to attain significant efficiency in increasing the crushing efficiency. US-A-3339055 cited during examination relate to a roll crusher rebuilding apparatus which deposits circumferentially spaced apart transverse welds to provide hardfacing strips on the surface of a roll in accordance with the so-called skip-welding technique. Of late, the cost of operating crushing machines has notably increased due to the increases in power cost for crushers, the cost of consumable members and, further, in the labour cost expended for their replacement. When high priced materials are crushed, the high cost therefor may be absorbed by the added values, but generally, the materials requiring crushing are low-priced and with such materials presently there is available no means to enable absorption of high crushing costs other than by increasing the output per unit time. In view of the situation hereabove described, an object of the present invention is to provide a crushing member which enables crushing efficiency to rapidly increase after starting a crushing operation and, thereafter, to be maintained for an appreciable period. The invention provides a crushing member in accordance with claim 1. The portions need not be arranged alternately exactly in the direction in which the material is nipped in but may be arranged in a direction having an angle of from 0 to 45 degrees to this direction. The width of the first portions of higher wear resistance is larger than the width of the second portions. The first portions of higher wear resistance may be separately formed portions which are fitted between and secured to adjacent second portions. Alternatively, the first portions of higher wear resistance may have been formed in situ between adjacent second portions. In this case, they may have been formed in situ by for example overay welding, padding by spray coatings, or by casting. The crushing member may comprise a body comprising the portions of lower wear resistance formed integrally with a substrate portion of the member. Alternatively, the crushing member may comprise a substrate portion to which said second portions are secured. In the illustrated embodiments the elongate portions are substantially rectangular in cross-section. In order that the invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to Figures 6 to 16 of the accompanying drawings, of which: Figure 6 is a perspective view of a crusher roll for a roll crusher or ring roll mill: Figure 7 is an enlarged, developed view of a portion of the side edge of the roll in Figure 6 prior to use. Figure 8 is a similar view to Figure 7 but after some use of the roll: Figure 9 is a perspective view of another roll: Figure 10 is a perspective view of another roll: Figures 11 and 12 are views similar to Figure 7 showing variations of roll constructions: Figures 13 and 14 are longitudinal side sections of a roll showing the roll before and after use in a ring roll mill: Figure 15 is a perspective view of another roll; and Figure 16 is a view similar to Figure 7 of the roll of Figure 15. Although the invention is applicable to all forms of crushing members referred to above, it will be described in relation to a crushing member in the form of a roll for use in a roll crusher or ring roll mill. Referring now to Figure 6, it will be understood that in use of the illustrated roll A material is crushed by being nipped in between the crushing surface a of the roll A and the crushing surface of another crushing member (not shown in this figure). The direction X in which the material is nipped in between the crushing surfaces is in the roll circumferential direction. On the roll A, as shown in this figure, two types of blocks 1 and 2 which are different in wear resistance are alternately arranged in at least the surface layer part in the direction X in which the material is nipped in, or in the roll circumferential direction. These blocks form respective elongate portions of the roll A, in the part thereof providing its crushing surface a . The blocks 1 and 2 are initially substantially level at the crushing surface, as shown in Figure 7, but when crushing material with roller A with blocks 2 inferior to blocks 1 in wear resistance, wear will occur sooner on the top crushing surface of blocks 2 having lower wear resistance than on the blocks 1 having higher wear resistance, automatically forming recesses of depth ℓ, as shown in Figure 8. As this situation is brought about, the nipping-in of the material is improved and the crushing efficiency is abruptly elevated; thereafter, a constant level production efficiency will be continuously maintained, until the blocks 1 having higher wear resistance are worn away to their usable limit. Thus once recesses with the specified depth ℓ are formed, the top of the block 2 having lower wear resistance will undergo wear to the same extent as the wear on the block 1 having higher wear resistance. As a consequence, the recesses will maintain the same depth thereafter. The recesses are automatically produced on use of the roll, and by being so formed have a non-slip contour, which will rarely cause noise or vibrations to be produced. It should be noted that in the following description, a wear resistant block 1 designates the block 1 having higher wear resistance of the aforementioned blocks 1 and 2, and a spacer block 2 the block 2 having lower wear resistance. In the following, working variations of the invention will be described in detail. With regard to the arrangement of the wear resistant blocks 1 and the spacer blocks 2, as shown in Figure 6, basically, they should exist in the surface layer of either crushing member A or B, but they may extend to an intermediate part thereof, or further - as shown in Figure 9 - they may extend throughout the crushing member. From the standpoint of cost, they should preferably be limited to a surface part of a depth such that the amount of the high priced wear resistant blocks 1 used may be reduced. When the crushing surface members A and B are rollers, the peripheral direction of the circumferential surface of the roll is the direction X in which the material is nipped in between the crushing surfaces a and b ; therefore, blocks 1 and 2 are also alternately arranged in the peripheral direction of the roll circumference. Also on the spindle A and anvil B in cone crushers, the ring B in ring roll mills and the rollers B in vertical roller mills, as shown in Figures 1 to 4, the peripheral direction of the crushing surfaces a and b is the direction X in which the material is nipped in; in this direction blocks 1 and 2 are alternately arranged; on the table A of a vertical roller mill, the circumferential direction of the crushing surface a (plane surface) is the direction X in which the material is nipped in and the blocks 1 and 2 are arranged alternately in this direction, or as it were, radially. When blocks 1 and 2 are alternately arranged, as shown in Figure 6, the direction of their arrangement Y may not necessarily be in complete agreement with the direction X in which the material is nipped in on the crushing surfaces a and b , but it may be at an angle of  to the direction X in which the material is nipped in, as shown in Figure 10. In this instance,  should preferably be smaller than 45 degrees. If it exceeds 45 degrees, the crushing efficiency will decline and a shearing force will be exerted between the crushing members A and B, resulting in an increase in mixing capacity. The structure of blocks 1 and 2 being alternately arranged may be selectively employed in a part where wear would otherwise be most marked, as shown in the later-described Figure 15. The wear resistant blocks 1 are blocks of a material showing adquate wear resistance, as used in the surface layer part of the crushing members A and B. The blocks 1 may be formed of, e.g. ceramics, high chrome cast iron, sintered hard alloys, various types of tool steels, cermet base alloys, etc. Blocks 1 may be pre-moulded and fitted and secured in respective grooves formed between adjacent spacer blocks 2, 2 as indicated in Figure 7 making use of an adhesive, soldering, bolts or other mechanical means, etc. Alternatively, blocks 1 of a hardened metal may be formed by casting wear resistant molten metal in each recess, or, as shown in Figure 11, may be built up by a hardened weld metal formed by various types of padding (including plasma powder overlay welding). In the case where the blocks 1 are formed in situ the hardened padding method is preferable as the selection of the hardened alloy suitable as the material is easy, for example, since by using plasma powder padding, any desired alloy may be readily formed by altering mixture of alloy powders, and further, since any part of the hardened alloy which has worn unevenly may be readily repaired by further padding. As plasma powder working is relatively easy, maintenance and repair is facilitated. When casting or padding, penetration of the hardened metal should be minimised to maintain the difference in wear resistance substantially throughout the widths of the blocks 1 and 2. The weld penetration lines 5 of the spacer blocks 2 should desirably be kept straight so far as practical. The wear resistance of the wear resistant blocks 1 substantially governs the life of the crusher members A and B. The spacer blocks 2, besides being integrally formed with the substrate part 3 of the crushing members A and B with the same material as the substrate part 3, may be formed separately from the substrate part 3 and attached, as shown in Figure 12, by welding, soldering, adhesive or other mechanical joining methods, or by various surface hardening overlay welding or plasma powder padding, flame spray coated padding, etc. In the case of the substrate part 3 being formed as a separate body from the blocks 2, the material of the spacer blocks 2 may be altered relative to the material of the substrate part 3 (e.g. to SKD6 tool steel, high speed steelflat bars, etc.), to lessen the wear resistance difference between it and the wear resistant blocks 1. As for the difference in wear resistance between the wear resistant blocks 1 and the spacer blocks 2, if it is small, the depth of the recesses formed between blocks 1 will be very small, resulting in low material nipping-in efficiency. Conversely, if it is large, distinctive recesses will be formed, thus enhancing the material-mipping-in efficiency, but adversely causing noise or vibration, On this ground, with regard to the wear resistance of the spacer block 2, a 10-90% reduction in wear resistance from the wear resistant block is desirable, as evaluated in terms of the reciprocal of the later described wear factor. Referring to Figure 7 the height H of the wear resistant blocks 1 and the spacer blocks 2 or, in other words, the thickness of the portion which they occupy, should desirably be 3mm or more. If it is less than 3mm, generally, it is difficult to ensure long life of the crushing surfaces a and b , irrespective of their materials. If H is high, however, the proportion of the wear resistant block relative to the whole of the crushing surface members A and B will increase, resulting in higher cost. It should desirably be limited to below 60mm. The top crushing surfaces of both blocks 1 and 2 should basically be on a common surface in their preoperation state, but even if there are some differences in level between them, the spacer blocks will wear on commencement of use of the member producing the abovementioned recesses. Thus no particularly serious problems will be raised. The width w of the spacer blocks 2 is smaller than the width W of the wear resistant blocks 1. This is because, if w exceeded W, the significance of providing the wear resistant block 1 would lessen, resulting in reduction in the durability of the crushing members A and B. Moreover, vibration and noise problems would arise. If w were extremely small relative to W, however, the effect of improving the material nipping-in function would decline. The width w is at least 0.1 x W and less than 1.0 W. The widths w and W should be chosen according to the size of the material to be crushed. Thus if the material size is small, w and W both should be small to enhance material nipping-in. The provision of the recesses due to wear of the blocks 2 has the effect of improving material nipping-in, but on the other hand, if the depth of the recesses is large, they may cause vibration or noise. An investigation conducted by the present inventors revealed that depths less than 0.5mm have small effect on the nipping-in, and that depths in excess of 15mm increase the possibility of vibration and noise being produced. The depths of the recesses is governed mainly by the difference in wear resistance between the wear resistant blocks 1 and the spacer blocks 2 but is also influenced by with width w of the spacer blocks 2. Accordingly, in order to obtain the desired recess depth, both the difference in wear resistance and w are adjusted. Figures 13 and 14 show the cross-section of a conventional roll of a ring roll mill used for crushing graphite respectively before and after the operation therewith. As the roll material 14% manganese steel type JIS-ScMnHll was used, and the roll had a life of approximately four months, during which time the following operational characteristics were noted. Before about 20 days had elapsed after operation with new rolls commenced, crushing efficiency was low, the rate of throughput being approximately 7 t/hr, but thereafter crushing efficiency gradually increased, to 14 t/hr at a maximum, giving approximately twice as high crushing efficiency. This results from the fact that because the newly produced roll had a smooth cylindrical outer surface, material nipping-in was inadequate, but after a lapse of 20 days, uneven wear on the roll surface and the resultant wavy surface had the effect of improving material nipping-in, resulting in increase in the amount of the material crushed per unit time. After a lapse of about four months, as shown in Figure 14, wear greatly increased, and more particularly an uneven wear occurred across the width of the roll to a depth of 20mm maximum at the centre thereof, resulting in a notable reduction in crushing efficiency, necessitating roll replacement notwithstanding adequate thickness remaining at both roll ends. In order to test for confirmation of the effect of increasing initial output and extending life in service by providing blocks of different wear resistance arranged alternately at the surface of a crushing member, as shown in Figures 15 and 16, spacer blocks 2 were provided by welding molten metal on the roll circumferential surface at intervals of 20-25mm in its peripheral direction and finished with a grinder to a rectangular sectional shape with height 5-6mm and width 5-8mm; thereafter, between each two of them, a molten metal which was superior to the aforementioned molten metal in wear resistance was formed into beads as the wear resistant blocks 1. Table 1 gives the component composition, hardness and wear resistance of the welding rod used at that time. The wear resistance is represented by wear factor (amount of wear given with that of SS41 as 100). ABRASODUR-16 has a 2.0 wear factor, which means that it has a wear resistance 50 times as high as that of SS41, and ABRASODUR-43 further four times as high a wear resistance as -16. Since on the roller, wear occurs symmetrically about the central part, as seen in the width direction of the roller, the 10-15mm width parts at both ends of the roll where no wear occurs are left and inside of them the wear resistant blocks 1 and the spacer blocks 2 are arranged. It will be understood that the wear factor is a comparative value of relative wear on the basis of abrasion test values as measured in a laboratory. In actual applications measured values will, of course, be somewhat different from them. Applied part Welding Rod Type C Cr Nb Mo Hardness Wear Factor Spacer block ABRASODUR - 16 4.0 9.0 - 2.0 HRC 60 2.0 Wear resistant block ABRASODUR - 43 5.5 22.0 8.0 - HRC 60 0.5 As the rolls formed in this way were put to use, the crushing efficiency rose to 14 t/hr after a lapse of only three days of operation. Further, their service life was extended from the conventional four months to eight months, during which time the production efficiency was continuously maintained at 14 t/hr and no problems of noise and vibration occurred. From the above description it will be appreciated that providing a crushing member with two types of blocks differing in wear resistance alternately arranged at least in its surface layer part causes recesses to be automatically formed in the blocks which are inferior in wear resistance, thereby improving material nipping-in; the life of the crushing member itself is governed by the block having higher wear resistance, so that the crushing member as a whole shows very high durability; further, while in use of the blocks, the recesses are kept constant in depth in correspondence with the difference in their wear resistance; accordingly, over the whole of their durable period, proper crushing efficiency is maintained and since these recesses are automatically formed, noise and vibration resulting from the recesses is not as pronounced as in the case where the recesses are provided between striped protrusions as shown in Figure 5.

Claims: A crushing member (A,B) for cooperation With another member (B,A) in a crusher for crushing material which is nipped in between opposed crushing surfaces (a.b) of the members (A,B), said crushing member (A,B) having a crushing surface (a.b) comprising first elongate surface portions and second elongate surface portions of lower wear resistance than said first elongate surface portions which first and second elongate surface portions are arranged alternately relative to the direction (X) in which, in use, material is nipped in, said first elongate surface portions being provided by first elongate portions (1) and said first elongate portions being disposed in recesses between second elongate portions (2) providing said second elongate surface portions, characterized in that the width (w) of the second elongate portions is at least 0.1 times and less than 1.0 times the width (W) of the first elongate portions (1) and that, the difference in wear resistance between the first and second elongate portions and said widths (w and W) are such that, in use, the depth (ℓ) of recesses which are formed by wear between said first elongate portions and said second elongate portions is maintained at the same value in the range from 0.5 to 15 mm. The crushing member as claimed in claim 1, wherein the portions (1,2) are arranged alternately in a direction (Y) having an angle of from 0 to 45 degrees to the direction (X). The crushing member as claimed in claim 1 or 2, wherein the first portions (1) of higher wear resistance are separately formed portions which are fitted between and secured to adjacent second portions (2). The crushing member as claimed in claim 1 or 2, wherein the first portions (1) of higher wear resistance have been formed in situ between adjacent second portions (2). The crushing member as claimed in claim 4, wherein said first portions have been formed in situ by overlay welding, padding by spray coatings, or by casting. The crushing member as claimed in any one of claims 1 to 5, wherein the member comprises a body comprising the portions (2) of lower wear resistance formed integrally with a substrate portion (3) of the member. The crushing member as claimed in any one of claims 1 to 5, wherein the member comprises a substrate portion (3) to which said second portions (2) are secured. The crushing member as claimed in any one of the preceding claims, wherein said elongate portions (1,2) are substantially rectangular in cross-section.

Inventors: KAWATSU HAJIME, KAWATSU, HAJIME
Applicants: ING SHOJI CO, I N G SHOJI CO., LTD.
Application year: 1987
Main classification: B02C4
IPC codes: B02C2, B02C4, B02C15