AU629579B2 - Apparatus for reconditioning table of roller mill - Google Patents

Description

i. ii ^rar~"Yn-~xl"Y 629579 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION NAME ADDRESS OF APPLICANT: Kurimoto, Ltd.

12-19, Kitahorie 1-chome Nishi-ku Osaka Japan Consolidated Metal Services, Inc.

700 East 10th Street Cattanooga Tennessee 37401 United States of America NAME(S) OF INVENTOR(S): Toshiyuki ASHIDA Hisao YOSHIDA Shigeaki SUGIOKA ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Apparatus for reconditioning table of roller mill rtt I I The following statement is a full description of this invention, including the best method of performing it known to me/us:- 45967/89

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la BACKGROUND OF THE INVENTION 7 1. Field of the Invention The present invention relates to an apparatus for reconditioning a table of a roller mill whose crushing surface is worn away and receded as a result of operation at a working site, and, more particularly, to an apparatus capable of reconditioning a table of the roller mill at the working site.

Description of prior art: 18 S 19 21 0 22 23 0:0 24 26 27 0 0 28 00 0 0 29 31 32 33 34 36 37 38 Generally in the roller mill, as shown in Figure 4, a plurality of rollers are biased onto, and turn on, the crushing table, rotating horizontally so that the rollers are pressed against the upper surface of the table. An object to be crushed is charged from above the crushing chamber and brought from the center of the table to the outer periphery thereof due to centrifugal force, then the object is crushed between the rollers and the table by compressively sliding movement downward, and output to the outside. This type of roller mill has been widely used in processing coal, cement clinker, blast furnace slag, etc., and exhibits high efficiency compared with drum type mills such as ball mills.

In the roller mill, however, a problem exists in that both the rollers and the table are unavoidably worn away and recede. It may be said that this is not a substantial disadvantage if all crushing surfaces are regularly or evenly worn away, because the relation between the rollers and the table remains relatively similar. Actually, however, the surfaces of the rollers and the table suffer from individual and irregular abrasion or wear and tear 459i67/89 T: 1,0- 2 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 S: 20 4 t 1 t 21 22 I 23 4,94 S 24 26 27 28 29 31 32 33 34 36 37 i 38 respectively, and therefore the crushing condition originally established becomes different from what is expected. As a result, the mill cannot maintain a required efficiency and its performance declines.

Figure 5 illustrates such abrasion, in which a crushing space C is formed between the roller R and the table T.

Both roller and table suffer from abrasion in the process of charging the object S to be crushed from the right side to the left side and discharging the object in the form of powder P. Thus, the worn roller and table recede to the lines A. It may be said that, because an impetus is given at all times to the roller downwardly by a trunnion mechanism, the required distance between the two crushing surfaces can be maintained so long as the abrasion remains within a certain level, and the crushing performance may not be substantially affected as long as the abrasion remains within that level. However, when the mill is further operated and the abrasion reaches the lines B, the space near the charging port not serving as a crushing space becomes narrower than the space formed between the crushing faces serving as the crushing space. The configuration of the crushing space is thereby changed, and the crushing performance declines sharply.

in To correct such a decline i crushing yield, it has been conventional either to remove the worn out roller and replace it with a new spare roller or to give a padding to the worn circumferential surface to recover the original 0 -c-e.

crushing su.ae. One of the latter reconditioning techniques was disclosed in Japanese Patent Application Publication (examined) No. Sho 58-10143. The applicant also proposed one of such techniques in Japanese Patent Application No. Sho 63-61643.

In the reconditioning by padding (welding), the rollers can be removed with relative ease by reason of the construction of the roller mill. On the other hand, removal of the table is very troublesome, and work almost equivalent to complete disassembly is required.

As a result, the time of interruption or downtime Flg 4 i. -i 3 t

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1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 S23 24 26 27 28 29 30 31 32 33 34 36 37 38 necessary for disassembly, padding and reassembly is considerable and, usually, circumstances at the site of a crushing operation cannot allow such a long downtime in view of the required rate of operation. It is, therefore, conventional to adopt a second best or provisional method in which, as illustrated in Figure 4, a liner made of abrasion resistant metal such as high chromium cast iron is engageably applied to the upper side of the table, so that the liner along may be changed when abrasion of the liner has reached the level of affecting the crushing yield after continuous crushing operation.

Furthermore, because the vertical roller mill is generally a large-sized apparatus, it is difficult to form a round table of a single material beforehand,. For that reason, first a plurality of fan-shaped segments are separately formed, and then the segments are assembled into a round table at the place where the apparatus is installed and the crushing operation is carried out. As a result, there is a join between one segment and the other, which brings about another problem: this Join often invites such drawbacks as abnormal abrasion, depression or protuberance, resulting in noise and vibration, and eventually negatively affecting the performance of the roller mill. In such a large-sized roller mill, it may be possible to recondition the worn segment of the liner by manual welding. It takes, however, a very long time and much labour for removal, padding and reattaching of the liner, resulting in interruption of operation over a long period. In addition, the cause of the mentioned drawback at the Joins between segments still remains after completing the reconditioning of the worn segment, which may amplify all the more the negative affect due to the join on the performance of the mill.

Generally, the vertical roller mill is not put into operation as an isolated unit, but is used in association with other adjacent apparatus of a whole plant to perform a specific overall process. For that reason, it is quite inconvenient and uneconomical that crushing performance t i.

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-4declines from day to day as the shape and size of crushed grains varies from what is required: the decline eventually impairs the functioning of the entire plant.

SUMMARY OF THE INVENTION The present invention was made to solve the above discussed problems and has an object of providing an apparatus for reconditioning a worn table of a roller mill which is capable of reconditioning the worn and receded portion of the table simply, easily and with high performance without removal of the table, and by which the problems due to the divided crushing surface and pertinent to the large-sized mill are overcome.

The invention accordingly provides an apparatus for reconditioning a worn surface of a rotatable table of a roller mill comprising: drive means capable of being operatively coupled into the driving mechanism for the table to control the rotation of the table, in place of 20 its normal drive; an automatic continuous welding machine 0 adapted to be located near the rotating table and having coa welding torch which is moveable over said worn surface °in the radial direction during each rotation of the table for reconditioning thereof by welding and means for continuously feeding a flexible welding wire to said V welding torch when it is reconditioning said worn surface L i by welding; and control means for controlling the position of the welding torch so that it is moveable over j. said worn surface as aforesaid; said drive means, control means and automatic continuous welding machine being moveable and/or transportable to and from the site of a table to be reconditioned.

In the preferred embodiment, a separate drive means is mounted intermediate of the regular driving mechanism and the table (comprising electric motor, motor shaft, coupling, reduction gear, worm, rotary shaft, etc.), 920729,gjndail25,kurlet,4 substituting the regular drive with the drive means while leaving the table surface which has been worn away and receded due to crushing operations, and rotation of the table is controlled by the drive means.

As the drive means is preferably adapted to freely control the number of revolutions, the table is rotated in such a manner as to provide an optimum welding speed and to thereby enable the torch attached to the welding machine to carry out welding under the most desirable conditions. Generally, the speed of rotation of the table during the crushing operation is largely different from a typical ideal welding speed (peripheral velocity).

Moreover, there is a difference between the inner and outer peripheral velocities under the same speed of rotation, and it is thus difficult to achieve a welding speed satisfactory for every aspect. This difficulty can be easily overcome by embodiments of the invention. That is, as the speed of rotation is reduced according to the advance of the welding seam from inner periphery to outer periphery, a predetermined desirable welding condition can be maintained from start to finish.

f Abrasion of the table is not even, as mentioned above, and recession due to abrasion usually shows irregular curves. The torch included in the welding machine is preferably attached to the front end of the welding machine and can follow exactly the irregular curves, forming a required electric arc. The receded depth is almost constant in the circumferential direction by reason of the construction of the vertical roller mill. Accordingly, adjustment of peripheral velocity according to diametrical movement can be done by changing the speed of rotation of the table, while vertical adjustment according to variation of the receded depth can be done by changing the attitude of the torch; thus any desirable welding condition being

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Il i-i 7 6 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 ;19 S 20 21 22 23 24 26 27 28 aGe 29 a 31 32 33 i. 34 36 37 38 maintained at all times.

In addition, the automatic welding machine, drive means for rotation of the table, control panel including toots controller thereof, necessary tll-, etc. are preferably transportable and can be accommodated in a stout box suitable for easy transportation from one place to the other.

As a result of the foregoing construction and function of the invention, reconditioning work on a tab'.e at a crushing operation site, which has been heretofore considered almost impossible, has now been achieved, and the reconditioned table recovers its original operation performance like a new table. The time necessary for the reconditioning work is rather short, which means that the problem of operation rate due to interruption of operation to carry out reconditioning work is largely reduced.

Preferably, only one welding seam is continuously formed like a groove of disk filling up old seam thereby forming a plain crushing surface of the table. This means that a new desirable element is added to the table, whose performance may be superior to that of a new table without such an additional element.

The apparatus of the invention can be satisfactorily applied to both vertical and horizontal roller mills.

Other objects and advantages of the invention will become apparent in the course of the following description, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A and B are respectively a front view and a side view of part of an embodiment (drive control of the table) in accordance with the present invention; Figure 2 is a front view of the embodiment (attitude control of torch); Figure 3 is a front view of another part of another embodiment; Figure 4 is a sectional front view of a vertical roller I ~I e j 1 mill; 2 F i 3 the pr 3 4 6 7 and igure 5 is a partially sectioned front view to explain ior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT d 7 S8 Qa s a

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f i ,i ,6 11 12 13 14 16 17 18 19

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20 21 S 22

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i. 23 4' 24 rriL 26 27 it 28 S1,t 29 30 it 31 32 t 33 t 34 36 37 38 Figures 1A and B show an embodiment of the invention, in which A is a front view of a section related to rotation control of the table and B is a side view thereof. A DC variable motor 1 is connected to a second reduction gear 4 through a first reduction gear 2 and a coupling 3 both directly connected to the DC variable motor 1 so that a sufficiently reduced speed of rotation is transmitted to a sprocket 5. The DC motor 1 is freely variable within a range of 1:30 to achieve an optimum welding condition, and the revolution is transmitted from the sprocket 5 to the rotation shaft of the table of the roller mill by way of a chain link. It is also possible to employ belts and pulleys instead of the chain link.

Submerged arc welding is generally employed to carry out welding on the table at the operation site. It is also possible to employ other welding methods such as carbon dioxide gas arc welding, plasma arc welding or the like to the extent that they may be adequate for full automatic welding. In this embodiment, open arc welding using a combination wire is employed because of the simplicity of the apparatus as well as its convenience with respect to the reconditioning work at the operation site. Because it is most popular that a table (liner) is made of a white pig iron containing 25% of chromium, in view of enhanced abrasion resistance, the portion to be reconditioned is desirably padded with the same material.

For the purpose of defining the welding deposit with this material and enabling the wire to carry out automatic continuous welding, a flux cored wire is used in this embodiment. More specifically, the wire has a hollow axial center which is filled with desired additive powder such as chromium, carbon, etc. The wire itself has a flexibility, 8 7 1 2 3 4 6 i 7 8 9 11 12 13 14 16 17 18 S 19 1 20 21 I '1 22 23 I 24 o 24 26 27 28 (I 29 31 32 4 4 33 34 36 37 38 and forms a component substantially the same as the base metal by reaction at the time of welding. It is most preferable that a plurality of welding heads is mounted and generates arcs simultaneously, thereby performing a welding amount two or three times more than ordinary welding.

Figure 2 shows an embodiment of the welding torch control. In the drawing, the torch 6 facing the worn and receded portion of the table T moves horizontally on a rack gear 7 mating at the bottom of a travelling beam. A carriage 8 and a base 9 support and hold the whole apparatus. A wire feed mechanism 10 is disposed at the rear. The wire feed mechanism principally comprises a wire feed motor 11, a wire feeder 12 and a wire strainer 1.3, and feeds the top end of the torch with the wire at a desired speed in a certain ratio. Roughly speaking, the table T is worn away almost linearly, and there is no extremely curved surface portion. Accordingly, when the table makes one turn and a line of bead is placed on the entire circumference, the rack gear 7 is actuated to advance the top end of the torch by one bead toward the center of the table and stop it there, the table then turns once more and a line of bead is placed on the entire circumference. In this way, adjustment of height of the torch is not so crucial, and manual adjustment by the operator is sufficient.

Figure 3 shows another embodiment, in which table T has an originally circular arc-shaped large crushing surface and, therefore, the worn and receded surface will also be an irregular curved one. To meet this, it is preferably to turn the top end of the torch instead of the horizontal movement by rack gear employed in the foregoing first embodiment. Specifically, in Figure 3, the welding torch 6 and the wire feed mechanism 10 are fixed onto a supporting base (not illustrated) with a supporting bar 14, and the entire wire feed mechanism can be oscillated round the center axis established by the connection part mounted on the supporting bar 14. When completing one bead of welding by rotating the table through one turn, the inclination of the top end of the torch is automatically (otherwise

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1 2 3 4 6 7 i 8 9 I 10 i 11 12 13 i 14 V 16 17 18 19 21 22 I 23 c 24 26 27 28, 29 31 32 33 34 36 37 38 i 9 manually) turned by a required angle so as to keep its attitude perpendicular to the surface to be welded. For the purpose of assisting such a function, a wire conduit tube is flexibly hung from above so as to feed constantly a certain length of wire irrespective of turning the top end, as illustrated in Figure 3.

Having described our invention as related to the embodiment shown in the accompanying drawings, it is our intention that the invention is not limited by any of the details of description, but rather be constructed within the spirit and scope as set forth in the appended claim.

Claims (2)

1. 2. Apparatus according to claim 1 wherein said welding torch is pivotally mounted above said table for effecting a rotational traverse of the table complementary to said worn surface when the latter is concave, the torch projecting substantially normally to the surface throughout said traverse.
2. 3. An apparatus for reconditioning a table of a roller mill substantially as hereinbefore described with reference to the accompanying drawings. Dated this 28th day of July, 1992 KURIMOTO, LTD. and CONSOLIDATED METAL SERVICES, INC. By their Patent Attorneys Davies Collison Cave