CA1212365A - Trimetal pulverizer roll and a method of manufacture thereof - Google Patents
Trimetal pulverizer roll and a method of manufacture thereofInfo
- Publication number
- CA1212365A CA1212365A CA000431137A CA431137A CA1212365A CA 1212365 A CA1212365 A CA 1212365A CA 000431137 A CA000431137 A CA 000431137A CA 431137 A CA431137 A CA 431137A CA 1212365 A CA1212365 A CA 1212365A
- Authority
- CA
- Canada
- Prior art keywords
- roll
- set forth
- grinding
- pulverizer
- coal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C15/00—Disintegrating by milling members in the form of rollers or balls co-operating with rings or discs
- B02C15/04—Mills with pressed pendularly-mounted rollers, e.g. spring pressed
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C15/00—Disintegrating by milling members in the form of rollers or balls co-operating with rings or discs
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C15/00—Disintegrating by milling members in the form of rollers or balls co-operating with rings or discs
- B02C15/004—Shape or construction of rollers or balls
- B02C15/005—Rollers or balls of composite construction
Abstract
A TRIMETAL PULVERIZER ROLL AND A METHOD OF MANUFACTURE THEREOF
ABSTRACT OF THE DISCLOSURE
A pulverizer, i.e., grinding, roll (18) of the type that is particularly suited for embodiment in a bowl mill (10) wherein the roll (18) coacts with another surface (14) within the mill (10) to effect the pulverization therewithin of a material such as coal. The subject roll (18) embodies a trimetal form of construction. More specifically, the core material, i.e., the first or inner layer (50), of the trimetal roll (18) consists of a relatively soft material that is noted for its good machinability. The next, i.e., second or intermediate, layer (52) of the trimetal roll (18) comprises a material that has medium wear-resistant qualities. The last, i.e., third or outer, layer (54) of the trimetal roll (18) comprises a material having highly abrasive resistant qualities. In addition, there is provided a method of manufacturing such a trimetal roll (18).
ABSTRACT OF THE DISCLOSURE
A pulverizer, i.e., grinding, roll (18) of the type that is particularly suited for embodiment in a bowl mill (10) wherein the roll (18) coacts with another surface (14) within the mill (10) to effect the pulverization therewithin of a material such as coal. The subject roll (18) embodies a trimetal form of construction. More specifically, the core material, i.e., the first or inner layer (50), of the trimetal roll (18) consists of a relatively soft material that is noted for its good machinability. The next, i.e., second or intermediate, layer (52) of the trimetal roll (18) comprises a material that has medium wear-resistant qualities. The last, i.e., third or outer, layer (54) of the trimetal roll (18) comprises a material having highly abrasive resistant qualities. In addition, there is provided a method of manufacturing such a trimetal roll (18).
Description
; A TRIMETAL PULVERIZER ROLL AND A METHOD OF MANUFACTURE THEREOF BACKGROUND OF THE INVENTION
This invention relates to rolls, and more specTfically to a trimetal pulverizer roll of the type that is intended to be used in bQwl mills for purposes of effecting the pul-verization therein of material such as, for example, coal and to a method ox manufacturing such a trimetal pulverizer roll.
An essential component of any steam generation system of the type, which u~i1izes pulverized coal as a fuel, is the apparatus in which the coal is pulveri7ed in order to render it suitable for such usage. Although the prior art ls replete with examples of vari OU5 types of apparatus that have been employed for purposes of accomplishing coal pulverization, 15 one form of apparatus, which in particular has frequently been ; used for th7s purpose, is that commonly referred to as a bowl mill. The latter obtains its name principally from the fact that the pulverization, i.e., gr7nding, of the coal that takes place therewithin occurs on a grinding surface, which insofar as configuration is concerned resembles somewhat a bowl.
For an exemplary showing of a prior art form of bowl mill, reference may be had to U.S. Patent No. 3,465,971, which is assigned to the same assignee as the present invention.
Patent No. 3,465,971 contains a teaching of both the nature of the construction and the mode of operation of a bowl mill that is suitable for use for purposes of effecting the ~2~3~i~
pulverization of the coal that is used to fuel a coal-fired steam generator. As set forth in this patent, the essential components of such a bowl mi11 are a body portion, i.e., housing, within which a grinding table is mounted for rotation, a plurality of grinding rolls that are suppsrted in equally spaced relation one to another, the plurality of grinding rolls are suitably arranged in such a manner so as to coact with the grinding table such that coal ~Ihich is disposed on the surface of the grindTng table is capable of being ground, i.e., pulverized, by the rolls, coal supply means for feeding to the surface of the grinding table the coal which is to be pulverized in the bowl mill, and air supply means for providing to the interior of the body portion the air that is required in ths operatlon of the bowl mill.
In order to satisfy the demands for pulverized coal of a coal-fired steam generation system that embodies a conventional form of construction, there commonly exists a need to employ a plurali+y of bowl mills of the type which are shown in the aforereferenced patent. In this regard, note is further made here of the fact that in terms of capacity each of these bowl mills may have a capacity of up to one hundred tons per hour of pulverized coal. In addition to possess;ng the capability of operating a its maximum capacity, each of these bowl m711s must also be capable of operating at less than full capacity, i.e., at some percentage thereof, e.g., 25%, 50~, 75%, etc. Finally, these bowl mills must also be capable of use with a variety of types of coal that have dissimilar grinding characteristics.
With further reference to the aforementioned patent, the mode of construction of the grinding rolls that are depicted therein is such that each grinding roll is designed to be mounted on a shaft-like member. As a result the grinding rolls are each capable of movement relative to the surface of the grinding table. To effect the assembly of the grinding roll with the aforesaid shaft-like member, each ; grinding roll preferably has a through passage formed through the center thereof. The function of this +hrough passage is to enable the shaft-like member to be positioned therewithin in mounted relation thereto. Accordingly, in order to facilltate the task of providing the grinding roll with such a through passage, it is desirable that the grinding roll be composed of a material thaw is characterized by its ease of machinability, i.e., a relatively soft material such as gray iron.
On the other hand, in addition to it being desirable to form the grlnding roll of a material that is relativeiy soft, there exists also a need for at least the external, i.e., outer, surface of the grinding roll to consist of a material that is characterT~ed by its good wear-resistant qualitles. The primary reason for this is that the grinding rolls in the course of effecting the pulverizatTon of material therewith are of necessTty subjected to a harsh abrasive action, the latter being occasioned by virtue of the nature of the material that is being pulverized as well as by virtue of the manner in which th1s pulverization takes place. The result, therefore, is that the grinding rolls exhibit a susceptibllTty to being rendered unusable in a relatively short period of time. That is, the rolls are found to have a relatively short operating Itfe. Fur obvious reasons, it is desirable thaw such a result be avoided, if possible. As is known to those who are sk711ed in this art, the wear, which the grindTng rolls that are employed in bawl mills actually experience Ts influenced principally by the grinding characteristTcs of the materTal that is being pulverized as well as by the productive output of the bowl mill, i.e., the amount of material that is being pul~erTzed in the bowl mill in a given period of time.
hen the external, 7.e., outer, surface of the pulverTzer, i.e., grinding, roll becomes sufficiently worn so as to preclude any further use thereof for purposes of effectTng the pulverTzatTon of materTal therewith, the remaining portions of the roll are normal still functional.
. .
That ls, the grinding roll but for its worn external surface would still be serviceable. Thus, from the standpoint of achieving economies of manufacture, it would be desirable, if possible, to effect a resurfacing of the external surface of the grinding roll such that the latter might once again be utilized for the pulverization of material rather than necessitating that the worn grinding roll be replaced by one that is entirely new. Further to this point, one would normally expect that the cost of reconditioning, i.e., resurfacing, the outer surface of a worn grinding roll would be significantiy less than the cost associated with the manufacture of an entirely new grinding roll.
In additTon to the relative cost of resurfacing the external, i.e., outer, surface of a worn grinding roll as contrasted to the cost of manufacturing an entirely new grinding roll, there also exists the matter of the operating Iife which ts achievable w7th a resurfaced worn grinding roll ; as contrasted to that which is obtainable with an entirely new grinding roll. Namely, Tn order to be economically feasible it is desirable that the operating life of a resurfaced worn grinding roll be approximately equivalent to that which one would obtaTn from a new grlnding roll. what is, any savings which are achievable from making use of a resurfaced worn grTnd7ng roll as contrasted to employTng an entirely new grind7ng roll should not be d7ssipated as a consequence of the fact that the operat7ng 17fe of a worn gr7nd7ng roll is such that several resurfac7ngs thereof are required in order to real7ze the same operat7ng life that can be realized w7th a gr7nding roll that is totally new. To summarize, if in the interest of obtaining comparable operating lives, muItiple resurfac7ngs would have to be had of the worn gr7nd7ng roll such that the cost thereof would probably equal, 7f not exceed, the cost of prov7d7ng an ent7rely new gr7nding roll, then, the advantages accruing from reus7ng a worn gr7nd7ng roll v7s-a-vis replacing the latter with a new grinding roll would undoubtedly not be real7zed.
. ; ' .
This invention relates to rolls, and more specTfically to a trimetal pulverizer roll of the type that is intended to be used in bQwl mills for purposes of effecting the pul-verization therein of material such as, for example, coal and to a method ox manufacturing such a trimetal pulverizer roll.
An essential component of any steam generation system of the type, which u~i1izes pulverized coal as a fuel, is the apparatus in which the coal is pulveri7ed in order to render it suitable for such usage. Although the prior art ls replete with examples of vari OU5 types of apparatus that have been employed for purposes of accomplishing coal pulverization, 15 one form of apparatus, which in particular has frequently been ; used for th7s purpose, is that commonly referred to as a bowl mill. The latter obtains its name principally from the fact that the pulverization, i.e., gr7nding, of the coal that takes place therewithin occurs on a grinding surface, which insofar as configuration is concerned resembles somewhat a bowl.
For an exemplary showing of a prior art form of bowl mill, reference may be had to U.S. Patent No. 3,465,971, which is assigned to the same assignee as the present invention.
Patent No. 3,465,971 contains a teaching of both the nature of the construction and the mode of operation of a bowl mill that is suitable for use for purposes of effecting the ~2~3~i~
pulverization of the coal that is used to fuel a coal-fired steam generator. As set forth in this patent, the essential components of such a bowl mi11 are a body portion, i.e., housing, within which a grinding table is mounted for rotation, a plurality of grinding rolls that are suppsrted in equally spaced relation one to another, the plurality of grinding rolls are suitably arranged in such a manner so as to coact with the grinding table such that coal ~Ihich is disposed on the surface of the grindTng table is capable of being ground, i.e., pulverized, by the rolls, coal supply means for feeding to the surface of the grinding table the coal which is to be pulverized in the bowl mill, and air supply means for providing to the interior of the body portion the air that is required in ths operatlon of the bowl mill.
In order to satisfy the demands for pulverized coal of a coal-fired steam generation system that embodies a conventional form of construction, there commonly exists a need to employ a plurali+y of bowl mills of the type which are shown in the aforereferenced patent. In this regard, note is further made here of the fact that in terms of capacity each of these bowl mills may have a capacity of up to one hundred tons per hour of pulverized coal. In addition to possess;ng the capability of operating a its maximum capacity, each of these bowl m711s must also be capable of operating at less than full capacity, i.e., at some percentage thereof, e.g., 25%, 50~, 75%, etc. Finally, these bowl mills must also be capable of use with a variety of types of coal that have dissimilar grinding characteristics.
With further reference to the aforementioned patent, the mode of construction of the grinding rolls that are depicted therein is such that each grinding roll is designed to be mounted on a shaft-like member. As a result the grinding rolls are each capable of movement relative to the surface of the grinding table. To effect the assembly of the grinding roll with the aforesaid shaft-like member, each ; grinding roll preferably has a through passage formed through the center thereof. The function of this +hrough passage is to enable the shaft-like member to be positioned therewithin in mounted relation thereto. Accordingly, in order to facilltate the task of providing the grinding roll with such a through passage, it is desirable that the grinding roll be composed of a material thaw is characterized by its ease of machinability, i.e., a relatively soft material such as gray iron.
On the other hand, in addition to it being desirable to form the grlnding roll of a material that is relativeiy soft, there exists also a need for at least the external, i.e., outer, surface of the grinding roll to consist of a material that is characterT~ed by its good wear-resistant qualitles. The primary reason for this is that the grinding rolls in the course of effecting the pulverizatTon of material therewith are of necessTty subjected to a harsh abrasive action, the latter being occasioned by virtue of the nature of the material that is being pulverized as well as by virtue of the manner in which th1s pulverization takes place. The result, therefore, is that the grinding rolls exhibit a susceptibllTty to being rendered unusable in a relatively short period of time. That is, the rolls are found to have a relatively short operating Itfe. Fur obvious reasons, it is desirable thaw such a result be avoided, if possible. As is known to those who are sk711ed in this art, the wear, which the grindTng rolls that are employed in bawl mills actually experience Ts influenced principally by the grinding characteristTcs of the materTal that is being pulverized as well as by the productive output of the bowl mill, i.e., the amount of material that is being pul~erTzed in the bowl mill in a given period of time.
hen the external, 7.e., outer, surface of the pulverTzer, i.e., grinding, roll becomes sufficiently worn so as to preclude any further use thereof for purposes of effectTng the pulverTzatTon of materTal therewith, the remaining portions of the roll are normal still functional.
. .
That ls, the grinding roll but for its worn external surface would still be serviceable. Thus, from the standpoint of achieving economies of manufacture, it would be desirable, if possible, to effect a resurfacing of the external surface of the grinding roll such that the latter might once again be utilized for the pulverization of material rather than necessitating that the worn grinding roll be replaced by one that is entirely new. Further to this point, one would normally expect that the cost of reconditioning, i.e., resurfacing, the outer surface of a worn grinding roll would be significantiy less than the cost associated with the manufacture of an entirely new grinding roll.
In additTon to the relative cost of resurfacing the external, i.e., outer, surface of a worn grinding roll as contrasted to the cost of manufacturing an entirely new grinding roll, there also exists the matter of the operating Iife which ts achievable w7th a resurfaced worn grinding roll ; as contrasted to that which is obtainable with an entirely new grinding roll. Namely, Tn order to be economically feasible it is desirable that the operating life of a resurfaced worn grinding roll be approximately equivalent to that which one would obtaTn from a new grlnding roll. what is, any savings which are achievable from making use of a resurfaced worn grTnd7ng roll as contrasted to employTng an entirely new grind7ng roll should not be d7ssipated as a consequence of the fact that the operat7ng 17fe of a worn gr7nd7ng roll is such that several resurfac7ngs thereof are required in order to real7ze the same operat7ng life that can be realized w7th a gr7nding roll that is totally new. To summarize, if in the interest of obtaining comparable operating lives, muItiple resurfac7ngs would have to be had of the worn gr7nd7ng roll such that the cost thereof would probably equal, 7f not exceed, the cost of prov7d7ng an ent7rely new gr7nding roll, then, the advantages accruing from reus7ng a worn gr7nd7ng roll v7s-a-vis replacing the latter with a new grinding roll would undoubtedly not be real7zed.
. ; ' .
2;~5 _5_ It has been known in the prior art to resurface a worn grinding roll. Further, the results obtainable therefrom have proven to be generally satisfactory. Most often, this resurfacing has been in the form of providing the external surface of the worn grinding roll with a suitably dimensioned layer of weld metal. In view of this experience which the prior art has had with the resurfacing of a worn grinding roll, there have been attempts made at provid7ng the external surface of new grlnding rolls with a hard facing.
Unfortunately, however, such attempts applied to new grinding rolls have not heretodate met with much success.
The motivation behind the attempt to effect a resurfacing of new grinding rolls has largely resided in the desire to extend the operating life thereof. One of the major reasons for seeking to extend the operating life of new grinding rolls i5 that it would enable the period to be ; extended between when shutdowns are required to accomplish the removal of worn grTndlng rolls and the replacement thereof wTth new grinding rolls. Furthermore, when consideration is given to the fact that each bowl mill normally embodtes three grTnding rolls, each of which periodically must be removed and replaced when 7t becomes worn, as well as the fact that a plurality of bowl mills are commonly emptoyed to provide the requisite amount of pulverized coal to a coal-fired steam - 25 generation system, the magnTtude of the problem that is presented by the need to effect a shut down of the bowl mill for purposes of accomplishing the removal and replacement of worn grindTng rolls while concomitantly ensuring that the power generation system retains the capability to provide continuous uninterrupted service should be readily apparent.
In addition to the above there 7s also the matter of the expend7ture of t7me and effort along with the cost per se that 7s associated with the act of removTng and replacing a worn grinding roll. Obv70usly, therefore, if one were to be successful in achieving a reduction in the frequency with which grinding rolls are required to be replaced as a
Unfortunately, however, such attempts applied to new grinding rolls have not heretodate met with much success.
The motivation behind the attempt to effect a resurfacing of new grinding rolls has largely resided in the desire to extend the operating life thereof. One of the major reasons for seeking to extend the operating life of new grinding rolls i5 that it would enable the period to be ; extended between when shutdowns are required to accomplish the removal of worn grTndlng rolls and the replacement thereof wTth new grinding rolls. Furthermore, when consideration is given to the fact that each bowl mill normally embodtes three grTnding rolls, each of which periodically must be removed and replaced when 7t becomes worn, as well as the fact that a plurality of bowl mills are commonly emptoyed to provide the requisite amount of pulverized coal to a coal-fired steam - 25 generation system, the magnTtude of the problem that is presented by the need to effect a shut down of the bowl mill for purposes of accomplishing the removal and replacement of worn grindTng rolls while concomitantly ensuring that the power generation system retains the capability to provide continuous uninterrupted service should be readily apparent.
In addition to the above there 7s also the matter of the expend7ture of t7me and effort along with the cost per se that 7s associated with the act of removTng and replacing a worn grinding roll. Obv70usly, therefore, if one were to be successful in achieving a reduction in the frequency with which grinding rolls are required to be replaced as a
3~
consequence of their having become worn, cost savings could be realized in terms of the time and sffort that is required to be expended to effect such replacement. There has been shown to exist in the prior art a need for a new and improved form of grinding roll that is characterized by the fact that this new grinding roll possesses a significantly longer operating life than that commonly found to be possessed by prior art forms of grinding rolls, In addition, a need has been demonstrated for a new and improved method for manufacturing such a new and improved form of grinding roll.
It is, therefore, an object of the present inventTon to provide a new and improved form of pulverizer roll.
It is another object of the present invention to provide such a pulverizer roll which is characterized in that it embodies a trimetal mode of construction.
It is still another object of the present invention to provide such a trimetal pulverTzer roll that is primarily intended to be employed in a bowl mill for purposes of effecting the pulverization therewithin of a material such as coal.
A further object of the present invention is to provide such a trlmetal pulverizer roll that is distinguishable by its relatTvely long operating life.
A still further object of the present invention is to provide such a trimetal pulverizer roll having a first portion thereof that is characterized by its ease of machinability, a second portion thereof that is characterized by the fact that it exhibits medium wear-resistant qualit7es, and a third portion thereof that is characterized by the fact that it exhibits highly abrasive resistant qualities.
Yet another object of the present invention is to provide such a trimetal pulverizer roll that while being readily employable in a bowl mill yet also enables significant cost savings to be realized through the use thereof insofar as the operation of the bowl mTII is concerned.
'I ,; ' ' -- ~L2123~
Yet still another object of the present inventton is to provide a new and improved method of manufacturing such a trimetal pulverizer roll.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention there is provided a pulverizer, i.e., grinding roll of the type that is particularly suited for employment in a bowl mill. When mounted in the bowl mill, the subject roll is designed to be operatlve to coact with another surface of the bowl mill in order to accomplish the pulverization within the bowl mill of material such as coal. To this end, the subject roll embodies a trimetal form of construction. More speciflcally, the subJect roll incorporates a first, i.e., 7nner, portion whtch is made of material that is characterized by its ease of machinability, as for example, gray iron.
Further, this inner portion has formed therethrough a passage which is suitably dimensioned for receiving therewithin a shaft-like member on which the roll is designed to be mounted in supported relation thereto. Next, the subject roll Tncorporates a second, i.e., intermediate, portion of material that 7s suitably supported in adhered relation on the inner portion. This intermediate portion, which is substantially un7form in thickness, is composed of a material that is voted for Tts medium wear~resistant qualities such as a material like Raymix, the latter being obtainable from applicant's assignae. Lastly, the subject roll incorporates a third, i.e., outer, port70n that is suitably supported in adhered relation on the intermediate portion. This outer portion is substantially uneven in thickness. That is, those areas of the outer portion of the subject roll that are known to wear most rapidly are provTded with a thicker thickness of material. Finally this outer portion is composed of a highly abrasive resistant material such as a weld overlay material.
In'accordance with another aspect of the present invention there is provided a method of manufacturing such a tri~etql pulverizer, i.e., grinding roll. The subject method ~23~
includes the steps of forming from a material that is characterized by its ease of machinability a body having the general configuration of a roll, providing through the center of the body a suitably dimensioned through passage capable of having a shaft-like support member positioned therewithin in mounted relation thereto, affixing in supported relation to the body a first substantially uniform layer of material having medium wear-resistant characteristics, and affixing in supported relation to the first layer of material a second substantially nonuniform layer of material having highly abrasive resistant characteristics.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a side elevational view partly in section and with some parts broken away of a bowl mill embodying pulverizer rolls constructed in accordance wifh the present invention and manufactured in accordance with the method of the present invention;
Figure 2 is a sectional view on an enlarged scale of a pulverizer roll constructed in accordance with the present invention and manufactured in accordance with the method of the present inventlon; and Figure 3 is a sectional view on an enlarged scale of a pulverized roll constructed in accordance with the present invention and manufactured in accordance with the method of the present invention, illustrating in exaggerated form +he uneven nature of the thickness of the outer portion of the pulverizer roll.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing, and more particularly to F7gure l thereof, there is depicted therein a pulverizing bowl m711, generally designated by reference numeral 10.
Inasmuch as the nature of the construction and the mode of operation of pulverizing bowl mills per se are well-known to those skilled in the art, it is, therefore, not deemed necessary to set forth herein a detailed description of the bowl mill lO, which is illustrated in Figure l. Rather, it is Z3~5 g deemed sufficient for purposes of obtaining an understanding of a pulverizing bowl mill lO, which is capable of being equipped with pulverizer rolls constructed in accordance with the present 7nvention and manufactured by means of the present inventton, that there merely be presented herein a generalized description of the nature of the construction and the mode of operation of the components of the pulverizing bowl mill lO.
For a more detailed description of the nature of the construction and the mode of operation of the components ot the pulverizing bowl mill lO, which are not described in depth herein, one may have reference to the prior art, e.g., U.S.
Patent No. 3,465,971, which issued September 9, 1969 to J. F.
Dalenberg et al., and/or U.S. Patent No. 4,002,299, which issued January ll, 1977 to C. J. Skalka.
ReferrTng further to Figure l of the drawing, the pulverizing bowl mill lO, as illustrated therein, includes a substantially closed separator body 120 A grinding table 14 is mounted on a shaft 16, which in turn is operatively connected to a suitable drive mechanTsm (not shown), so as to be capable of being rotatably driven thereby. With aforedescrTbed components arranged within the separator body 12 in the manner depicted in Figure 1 of the drawing, the grtnding table 14 Ts designed to be driven in a clockwise direction.
Continuing with description of the pulverizing bowl mill 10, a plurality of pu3verizer, i.e., grinding, rolls 18, preferably three in number in accord with conventional practice, are suitably supported within the interior of the separator body 12 so as to be spaced equidistantly one from another around the circumference of the latter. The nature of the construction as well as the method by which each of the grinding rolls 18 is manufactured comprises the subject matter that forms the essence of the present invention. A
description of the nature of the construction of the grinding rolls 18 as well as a description of the method by which such a grinding roll 18 is manufactured will be found set forth i5 --1 o--hereinafter. First, however, note is made here of the fact that in tha interest of maintaintng clarity of illustration in the drawing only one grinding roll 18 has been shown in Figure 1.
As further regards +he grinding rolls 18, each of the latter, as best understood with reference to Figure 1 of the drawing, is preferably supported on a suitable shaft (not shown) such as to be rotatable relative thereto. Moreover, the grinding rolls 18 are also each suitably supported in a manner yet to be described for movement relative to the upper surface, as viewed wtth reference to Figure 1, of the grinding table 14. To this end, each of the grinding rolls 18 has cooperatively associated therewith a hydraulic means, gensrally designated in Figure 1 by reference numeral 20.
Each of the hydraulic means 20, as will be described more fully hereinafter, is operafive to establish a hydraulic loading on the grlnding roll 18 that is associated therewith.
The effect of this loading is to cause the roll 18, which is subject thereto, to exert the requisTte degree of force on the coal that is disposed on the grinding table 14, and thereby accomplish the desired pulverTzation of this coal.
The material, e.g., coal, that is to be pulverized in the bowl mtll 10 is fed thereto by means of any suitable conventional form of feed means. By way of exempllfication in this regard, one such feed means that may be employed for this purpose is a belt feeder means (not shown). Upon being discharged from the feed means (not shown), the coal enters the bowl mill 10 by means of a coal supply means, generally designated by reference numeral 22, with which the separator body 12 is suitably provided. In accordance with the embodiment of the pulverizing bowl mill 10 illustrated in Figure 1, the coal supply means 22 includes a suitably dimensioned duct 24 having one end thereof, which extends outwardly of the separator body 12 and preferably terminates in a funnel-like member (not shown). The latter mamber (not shown) is suitably shaped so as to facilitate the collection lZ~Z~5 "
of the coal particles entering the bowl mill 10, and the guiding thereafter of these coal particles into the duct 24.
To this end, as shown 7n Figure 1 of the drawing, the duct end 26 preferably is suitably supported within the separator body 12 through the use of any suitable form of conventional support means (not shown) such that the duct end 26 is coaxially aligned with the shaft 16 that supports the grinding table 14 for ro+ation, and is located in spaced relation to a suitable outlet 28 provided in the classifier, generally designated by reference numeral 30, through which the coal flows in the course of being fed onto the surface of the grinding table 14.
In accord wlth the mode of operation of pulverizing bowl mills that embody the form of construction depicted in FTgure 1, a gas such as air is utilized to effect the conveyance of the coal from the grinding table 14 through the interior of the separator body 12 for discharge from the pulver7zing bowl mill 10. The air that is made use of in this regard enters the separator body 12 through a suitable opening (not shown) formed therein for this purpose. From +he aforesa7d opening snot shown) in the separator body 12, the aTr flows to a multiplicity of annular spaces 32 suitably - formed between the circumference of the grinding table 14 andthe inner wall surface of the separator body 12. The air upon - 25 exiting from the annular spaces 32 is deflected over the grinding table 14 by means of suitably positioned deflector means (not shown). One such form of deflector means (not shown), which is suitable for use for this purpose in the bowl mill 10 of Figure 1 comprises the subject matter of U.S.
Patent No. 4,234,132 which issued to applicant on November 18, 1980, and which is assigned to the same assignee as the present applicatTon.
While the air is flowing along the path described above, the coal which is dTsposed on the surface of the grinding table 14 is being pulverized by the action of the ; grinding rolls 18. As the coal becomes pulverized, the ~z~
partlcles are by centrifugal force thrown outwardly away from the center of the grinding table 14. Upon reaching the region of the circumference of the grinding table 14, the coal particles are picked up by +he air exiting from the annular spaces 32 and are carried along therewith. The combined flow of air and coal particles is thereafter captured by the deflector means (not shown), which has been referred to previously hereinabove. The deflector means (not shown), in turn, is operative to cause this combined flow of air and coal particles to be deflected over the grinding table 14.
This necessitates a change in direction in the path of flow of this combined stream of air and coal particles. In the course of effecting this change of direction, the heaviest coal partTcles, because they have more inertia, become separated from the air stream> and fall back onto the surface of the grinding table 14, whereupon they undergo further pulverization. The lighter coal particles, on the other hand, because they have less inertTa continue to be carried along in the air stream.
After leaving the influence of the aforedescribed deflector means (not shown), the combined stream consisting of air and those coal particles that rematn entrained therein flows to the classifier means 30 to which reference has been had herein previously. In accord with conventional practice and in a manner which is well-know~ to those skilled in this art, the classifier 30 operates to effect a further sorting of the coal particies that remain in the air stream. Namely, those particles of pulverized coal, which are of the desired parttcle size, pass through the classifier 30 and along with the air are discharged therefrom and thereby from the bowl mill 10. This discharging of the coal particles is effected through the outlets 34 with which the bowl mill 10 is suitably provided for this purpose.
On the other hand, those coal particles, which in size are larger than desired, are returned to the surface of - the grinding table 14 whereupon they undergo further ~Z3~
pulverization. Thereafter, these coal particles are once again subjected to the process that has been described above.
That 7s, these particles are thrown outwardly of the grinding table 14, are picked up by the air exiting from the annular spaces 32, are carried along with the air to the deflector means (not shown), are deflected back over the grinding table 14 by the deflector means (not shown), the heavier particles drop back onto the grinding table 14, the lighter particles are carried along to the classifier 30, and finally those particles which are of the proper size pass through the classifier 30 and exit from the bowl mill 10 through the outlets 34.
ConsiderTng further the matter of the pulverizing action to which the coat disposed on the upper surface, as viewed with reference to Figure 1, of the grinding table 14 is subjected by the grinding rolls 18, the amount of force that must be exerted on the latter in order to effect the desired degree of pulverizatton of the coal mill vary depending on a number of factors. For example one important consideration in this regard is the nature of the coal itself. That is, the amount of force required to pulverlze the coal will be a function of the grindability of the coal to be pulverized, ire., the grinding characteristics of the latter. Another important factor in determining the amount of force that the grinding rolls 18 must exert to accomplish the desired degree of pulverization of the coal is the depth to which the coal is disposed on the grinding table 14, which in turn is a function of the outpu+ rate at which the bowl mill 10 is being operated.
As best understood with reference to Figure 1 of the drawing, the amount of grinding force which the grinding rolls 18 apply to the coal on the grinding table 14 is a function of the amount of force with which the grinding rolls 18 are biased into engagement with the coal on the table 14. In accord with the nature of the construction shown in Figure 1, ; the grinding roll 18 depicted therein, which is suitably 36~
mounted for rotation on a shaft (not shown), is suitably supported so a: to be pivotabie about the pivot pin 36 into and out of engagement with the coal that is disposed on the grinding table 14. Although only one grinding roll 18 is shown in Figure 1 and although this discussion is directed fo this one grinding roll 18, it is to be understood that as has been mentioned previously hereinbefore the bowl mill 10 is normally provided with three such grinding rolls 18.
Therefore, this discussion is intended to be equally applicable to each of these three grinding rolls 18.
Continuing with the matter of the force exerted by the gri.nding roll 18~ the latter in accord with the nature of the construction illustrated in Figure 1 is designed to be biased hydraulically into and out of engagement with the coal that is on +he grinding table 14. More specifically, to this end the hydraulic means 20 is cooperatively associated with the grinding roll 18~ As depicted in Figure 1, the hydraulic means 20 includes a cylinder 38 suitably mounted to the exterior wall surface of the separator body 12. Wlthin the cylinder 38, a piston 40 is suitably supported for movement therewithin. Attached to the piston 40 is a piston rod 42 of sufficient length so as to extend into the interior of the separator body 12 whereupon the free end of the piston rod 42 engages an upstanding member 44 that comprises a portion of the support means for the grtnding roll 18. A suitable opening 46 Ts formed in the separator body 12 to enable the piston rod 42 to project into the interior of the latter. In a manner well-known to those skilled in the art of hydraulics, the cylinder is filled with a suitable hydraulic fluid, such that a hydraulic pressure is applied by the fluid to both faces of the piston 40. The hydraulic fluid which fills the - cylinder 38 is provided thereto from a suitable source thereof (not shown).
Accordingly, the extent to which the free end of the piston rod 42 projects into the interior of the separator body 12 for engagement with the member 44 is a function of the ~Z~ 5 difference in hydraulic pressure, which is applied to the faces of the piston 40. In turn, the extent to which the free end of the piston rod 42 extends into the interior of the separator body 12 determines the extent to which the grinding roll 18 is hydraulically biased into engagement with the coal on the grinding table 14, and concomitantly the amount of grinding force being applied to the coal by the grinding roll 18. That is, the piston rod 42 is fixedly attached to one face of the piston 40 such that as the piston 40 moves in response to the difference in hydraulic pressure being applied - to the faces thereof, the piston rod 42 moves along therewith. It is to be understood in this connection that the opening 46 provided in the separator body 12 through which the piston rod 42 passes is equipped with suitable sealing means (not shown) operative to prevent the leakage through the openlng 46 of hydraulic fluid from the cylinder 38 to the interior of the body 12.
By way of exemplification, the more the free end of the piston rod 42 extends into the interior of the separator body 12, the more it will cause the member 44 to move in a clockwise direction, as viewed with reference to Figure 1, abouf the pivot p7n 36, and thereby have the effect of increasing the amount of grinding force that the grindlng roll 18 exerts on the coal that is on the grinding table 14.
Conversely, the less the free end of the piston rod 42 projects into the interior of the separator body 12, the less clockwise movement there will be of the member 44 about the pivot pin 36, and thus the less grinding force the roll 18 will exert on the coal that is disposed on the table 14.
Lastly, in accord with the preferred form of construction, the hydraulic means 20 is provided with an accumulator 48. The.function of the latter is to obviate any potentially damaging consequences that might otherwise flow from the occurrence of some form of transient operating condition. For example, should some foreign object be introduced into the bowl mill 10 along with the coal that is 121Z3~i~
to be pulverized, and should this foreign object become disposed on the grinding table 14, the effect of the grinding roll 18 engaging this foreign object would be to raise the roll 18 away from the table 14, to would be to cause the roll 18 to move about the pivot pin 36 in a counterclockwise direction, as viewed with reference to Figure 1. As a consequence of this action, the member 44 would be made to apply a force against the free end of the piston rod 42 tending to cause the piston 40 to move in a direction away from the wall surface of the separator body 12. further, as the piston 40 moves in this manner, the hydraulic fluid located in that portion of the cylinder 38 towards which the piston 40 is moving would tend, absent the presence of the accumulator 48, to resist the movement of the piston 40. This could result in damage being incurred by the various components that are operatively associated with the grTnding roll 18.
Accordingly, the function of the accumulator 48 is to permit hydraulic fluid to flow thereinto as the fluid ts being forced from the cylinder 38 by the advancing piston 40.
- However, as soon as the grinding roll 18 passes over the foreign object, the grTnding roll 18 Ts once again restored to-its normal position, i.e., nontransient condition. This occurs by vtrtue of the flow from the accumulator 48 tnto the cyltnder 38 of the hydraultc flutd whtch had been made to flow tnto the former from the latter, because of the counterclockwtse movement, as vtewed with reference to Figure 1, of the grinding roll 18 about the pivot pin 36 caused by the ra7sing of the roll 18 as the latter engaged and passed over the foretgn object located on the table 14.
For purposes of setttng forth a detatled descrtptton of the structural nature of a pulvertzer roll 18 constructed tn accord wtth the present tnventton as well as the method by whtch such a pulvertzer roll 18 ts manufactured tn accord wtth the present invention, reference will now be had parttcularly to Ftgures 2 and 3 of the drawing. It is important to take note here of the fact that Figure 2 in contrasf fo Figure 3 is intended to simpiy provide a general illustration of a pulverizer, i.e., grtnding, roll 18 constructed in accord with the present invention. Figure 3, on the other hand, as will be more fully set forth hereinafter, illustrates with more partTcularly the specific details of construction of 2 pulverizer roll 18 that is manufactured in accordance with the present inventionO
With the above as a frame of reference, it can be seen prom Figures 2 and 3 that the grinding roll 18 embodies a trimetal form of construction. More specifically, as best understood with reference to Figures 2 and 3, the grinding roll 18 embodies a main body portion, generally designated by reference numeral 50, that embodies the overall configuration of a roll. In addition to the body portion 50, the grinding roll 18 further embodies two other dissimilar portions of materlal arranged Tn layered relation to each other as well as to the body portion 50. To th7s end, one of these two portions, i.eO, that denoted generally by the reference numeral 52 in F7gures 2 and 3 of the drawing, is suitably positioned Tn superimposed relation ,o the body portion 50 of the grinding roll 18. Similarly, the other of the aforereferenced two portions, i.e., that denoted generally by the reference numeral 54 in Figures 2 and 3 of the drawing, is suitably positioned in super7mposed relation to the port70n 52.
As further regards the body portion 50 of the grinding roll 18, the latter in accord with the best mode embodiment of the invention is made of a relatively soft, easily machinable material, such as gray iron Moreover, w7th particular reference to Figures 2 and 3 it can be seen therefrom that the body portion 50 has a passage 56 formed entirely therethrough at substantially the center thereof.
The through passage 56 is suitably dimensioned so as to be carable of receiving therewithin in assembled relation thereto -; the shaft-like member (not shown) to which re$erence has ~Z~Z3~
previously been made hereinbefore, and on which the grinding roll 18 is suitably supported so as to be capable of functioning in the manner described above and as shown in Figure 1.
Next, with regard to the portion 52, i.e., the intermediate layer, with which the trimetal pulverizer roil 18 is provided, in accord with the best mode of the invention this portion 52 preferably comprises a material that is noted for its medium wear-resistant qualities. In this regard, a material that has been found suitable for use for this purpose is a material referred to by the name Raymix. Raymix, which has a known composition, can be obtained from the Monongahela plant of applicant's assignee. The reasons why a material having such qualities is selected for use in this context, and the manner in which the portion 52 consisting of Raymix preferably is adhered to the body portTon 50 will be found set forth with more particularity hereinafter.
The last, i.e., portion 54, of the three portions, which collectively comprise the trimetal pulverizer roll 18 preferably consists, in accord with the best mode embodiment of the tnventton, of a material that is characterized by the fact that it is highly abrasive resistant. One material, which ls suitable for use in this regard, is that known to those skilled in this art as nihard. As in the case of the portion 52 the reasons for employing a material to form the portion 54, i.e., the outer layer of the trime+al pulverizer roil 18 that has the characteristics described above, and the manner in which the portion 54 is affixed to the portion 52 will be found set forth hereinafter with more particularlity.
Suffice it to say at this point, however, that the reasons for constructing the grinding roll 18 from a plurality of dissimilar materials that are arranged in a layered array are as a result of recognition being had first to the fact that there is a need to provide the body portion 50 with the through passage 56, and secondly to the fact +hat the outer surface of the pulverizer roll 18 is subjected to a harsh ~2123~5 _19_ abrasive action in the course of effecting the pulverization of coal. The result, therefore, is that on the one hand it is desirable that the body portion 50 be made of a relatively soft, easily mach:nable material so as to facilitate the formulation therein of the through passage 56. In contradistinction to this, there is a need for at least the outer surface, i.e., that encompassed by the intermediate layer, i.e., portion 52, and fhe outer layer, i.e., portion 54, to be made of materials that are characterized by their capability to resist wear, and in particular that kind of wear which is occasioned by abrasive action.
Insofar as concerns the illustratTons that comprise Figures 2 and 3 of the drawing, as was noted previously herein, Figure 2 is simply intended to illustrate in a general fashion the nature of the construction in accord with the present Invention of the pulverizer, i.eO, grinding, roll 18.
Figure 3, on the other hand, Ts intended to illustrate a grinding roll 18 constructed in accordance with the present invention whereTn therein is depicted in exaggerated fashion the fact that the outer layer, i.e., portion 54, embodies an uneven thickness in contradistinction to the intermediate layer, l.e., portion 52, whtch is of substantially uniform thickness. More speciflcally9 the external surface of the outer portion 54, i.e., that denoted by the reference numeral 58 in Figure 3 Ts provided with a specific configuration which is intended to constitute a replication of the wear pattern that a pulverization, i.e., grinding, roll 18 develops as a consequence of its being utilized to effect the pulverization of a material such as coal within a bowl mill 10. That is, the external surface 58 of the outer portion 54 of the grinding roll 18 is suitabiy configured such that those areas thereof which based on past experience it can be anticipated will be subjected to the greatest degree of wear are made to have a thicker thickness of material, e.g., nihard, thereat.
The intent in doing so is to attempt to achieve a uniform wear rate of the outer portion 54 by means of providing more 3~
~20-material in those areas whereat it is expecfed that the roll 18 will experrience the most wear based on past experience applied to the use to which the roll 18 is intended to be put. To summarize, the outer portion 54 of the pulverizer, i.e., grinding, roll 18 is 7ntentionally made to have a nonuniform thickness such that more material is provided in those areas whereat more wear is predicted to take place, and less material is provided in those areas whereat less wear is expected to occur.
Next, a description will now be had of the method by which in accord wTth the present invention the pulverizer, i.e., grinding, roll 18 is preferably manufactured. This will then be followed by a description of the benefits that flow from the use of a pulverizer roll 18 which embodies a trimetal form of construction. Insofar as the method of manufacture of the pulverizer roll 18 ls concerned, in accord with the best mode embodiment of the invention a centrifugal casting process is employed for this purpose. Proceeding with the description of the subject method, in accord with the first step thereof the requisite amount of material, e.g., Raymix, needed to form the 7ntermediate portion 52 of the pulverizer roll 18 is poured in known fashion into a suTtable mold. In accordance with the known techniques of centrifugal casting, the Raymix under the influence of centrifugal force moYes outwardly within the mold and forms a layer thereof in abutting engagement to the inner surface of the mold. Once the intermediate portion 52 of the pulverizer roll 18 is formed, the next step in accord with the subject method is to effect the pouring into the mold of the requisite amount of material, e.g., gray iron, to form the inner, i.e., body, portion 50 of the pulverizer roll 18. In accord once again with fhe known techniques of centrigual casting, the gray iron under the influence of centrifugal force forms a layer in abutting engagement with +he inner surface of the interme=iate portion 52. A suitable bonding agent is preferably utTlized to cause the outer surface of the inner portion 50 to adhere to the 23~5 inner surface of the intermediate portion 52. After the pulverizer roll 18 has been partially formed in the aforedescribed manner, the partially formed roll 18 is removed from the aforereferenced mold and the outer surface of the intermediate portion 52 to the extent deemed necessary is prepared for receipt thereon of the outer portion 54. This is followed by the affixation of the outer portion 54 to the intermediate portion 52. To this end, in accord with the best mode embodTment of the method of manufacture of the present invention, the outer portion 54 is provided in the form of a weld overlay. Moreover, as described previously hereinbefore, the outer portion 54 preferably is applied in the form of a nonuniform thTckness of material such that the thicker thickness thereof is located in those areas whereat it is believed, based on the use to which it is known the pulverizer roll 18 will be put9 the greatest wear will be experienced.
it is to be noted here that in accord with the method described above, the through passage 56 is formed through substantially the center of the body portion 50 during the casting process. Thus, the need to machine such a passage 56 therethrough is obviated except for any minor machining that may be required to prepare the passage 56 for the receipt therein of the shaft-like member (not shown) on which the pulverizer roll 18 is designed to be mounted in supported relation thereto.
Attention will now be directed to the matter of the benefits that flow from the use of a pulverizer roll that embodies a trimetal form of construction. To this end, those benefits which are to be found enumerated hereinafter are presented by way of exemplification and not limitation.
First, the pulverlzer roll 18 by virtue of its trimetal form of construction embodies a body portion 50 that is capable of being made from a material that is relatively easy to work thereby enabling economies of manufacture to be realized from the use for this purpose of this material, e.g., gray iron.
; Secondly, the pulverizer roll 18 that embodies a trime~al ~lZ3~
structure has an external surface that consists of an outer portion 54 which consists of a relatively hard, i.e., highly abrasive resistant material such as nihard that is capable of resisting the abrasive action produced in the course of effecting the pulverization therewith of a material such as coal. Moreover7 because of the fact that the outer portion 54 is provided with a thicker thickness of material in the areas which are most subject to wear, the pulverizer roll 18 is characterized by the fact that the outer portTon 54 wears more slowly, i.e., wears more uniformly. That is, before the outer portion 54 wears through in those areas which are subject to the greatest wear, a more uniform wearing of the entire outer portion 54 is realized.
In addition, it is most important to note here that the external surface of the pulverizer roll 18 is not composed of simply the outer portion 54. But rather the external surface further comprises the intermediate portion 52, which also consists of a material having wear-resistant qualities, e.g., Raymix. As a consequence, even when the outer portion 54 is worn through, the pulverizer roll 18 still remains serviceable in that the intermediate portion 52 is also capable of performing the wear-resisting function. It is of course true that the material which comprises the lntermediate portion 52 ts not as hard, i.e., is not as abrasive resistant as the outer portion 54. Nevertheless, the pulverizer roll 18 is still capable of being used with the intermediate portion 52 exposed, i.e., serving, as the pulverizing surface. The significance of this is that continued usage may be made of the pulverizing roll 18.
Namely, no longer is it necessary to immediately replace pulverizer rolls when the outer surface thereof wears through for fear of damagTng the roll, i.e., so to preclude the resurfacing of the worn roll. In contradisttnction, with the pulverizer roll 18 of the present invention it is possible most frequently, to await the next scheduled shutdown of the bowl mill 10 in order to effect the removal and replacement of the roll 18 after the outer portion 54 thereon has worn through. This is because the intermediate portion 52 serves as an adequate surface to effect the continued pulverization therewith of coal within the bowl mill 10. Normally, the life of~the intermediate portion 52 Defore it also wears through is such as to enable a sufficient period of time to expire to reach the next scheduled shutdown of the bowl mill 10.
Another advantage that derives from the use of d7ssimilar materTals for the intermediate portion 52 and the outer portion 54 is that it is possible to visually recognize when the outer portion 54 has worn through in one or more places This visual indication is had by noting the different appearance, e.g., color, etc. of each of the two dissimilar materials, i.e., the Raymix of intermediate portion 52 and the ! 15 nihard of outer portion 54. To further enhance this visual recognitton, it is possible to color with a suitable medium, e.g., red paint, the outer surface of the intermediate portion 52 so as to prov7de the latter w7th a read71y viewable surface before the outer port70n 54 7s affixed thereto.
In summary, not only does the pulver7zer roll 18 constructed 7n accordance with the present invention prov7de a roll that has a measurably longer operat7ng life than do the rolls wh7ch have heretofore been constructed in accordance with the teachings of the prior art, but also the pulverizer roll 18 7s characterized by the fact that even when the outer port70n 54 thereof becomes worn through, by v7rtue of the pressnce of the intermed7ate portion 52 cont7nued usage may be made of the pulver7zer roll 18 for effecting the puiver7zat70n of a mater7al without the roll 18 sustaining damage thereto.
This obv7ates the need to experience many of those shutdowns of the bowl mill 10 which have been occasioned heretofore by the need to accomplish the removal and replacement of a pulverizer roll that had been constructed in accordance with the teachings of the prior art. Lastly, by providing the outer portion 54 with a nonuniform th ! ckness, addittonal wear ; is obtainable from the pulverizer roll 18 before the outer ~2~Z~65 portion 54 thereof wears through; namely, those areas of he outer portion 54 which experience shows are subjected to the greatest wear are provided with the thickest layer of material.
Thus, in accordance with the present invention there has been provided a new and improved form of pulverizer roll.
Moreover, the pulverizer roll of the present invention is characterized in that it embodies a trimetal mode of construçtion. In addition, in accord with the present invention a trimetal pulverizer roll is provided that is primarily intended to be employed in a bowl mill for purposes of effecting the pulverization therewithin of a material such as coal. Further, the +rimetal pulverizer roll of the present invention is distinguishable by its relatively long operating life. Additionally, in accordance with the present invention a trimetal pulverizer roll 7s provided whTch has a first portion thereof that is characterized by its ease of machinability, a second portion thereof that is characterized by the fact that 7t exhibits medium wear-reststant qualities, and a third portion thereof that is charac-terized by the fact - that it exhlbits htghly abrasive resistant qualities. Also, the trimetal pulverizer roll of the present invention while being readily employable in a bowl mill yet also enables significant cost savings to be realized through the use thereof insofar as -the operation of the bowl mill is concerned. Furthermore, in accord with the present invention a new and improved method of manufacturing such a trimetal pulverizer roll is provided.
While only one embodiment of my invention has been shown, it will be appreciated that modifications thereof, some of which have been al!uded to hereinabove, may still be readily made thereto by those skilled in the art. 1, therefore, intend by the appended claims to cover the modifications alluded to herein as well as all the other modifications, which fall wlthin the true spirit and scope of my invention.
What is claimed is:
consequence of their having become worn, cost savings could be realized in terms of the time and sffort that is required to be expended to effect such replacement. There has been shown to exist in the prior art a need for a new and improved form of grinding roll that is characterized by the fact that this new grinding roll possesses a significantly longer operating life than that commonly found to be possessed by prior art forms of grinding rolls, In addition, a need has been demonstrated for a new and improved method for manufacturing such a new and improved form of grinding roll.
It is, therefore, an object of the present inventTon to provide a new and improved form of pulverizer roll.
It is another object of the present invention to provide such a pulverizer roll which is characterized in that it embodies a trimetal mode of construction.
It is still another object of the present invention to provide such a trimetal pulverTzer roll that is primarily intended to be employed in a bowl mill for purposes of effecting the pulverization therewithin of a material such as coal.
A further object of the present invention is to provide such a trlmetal pulverizer roll that is distinguishable by its relatTvely long operating life.
A still further object of the present invention is to provide such a trimetal pulverizer roll having a first portion thereof that is characterized by its ease of machinability, a second portion thereof that is characterized by the fact that it exhibits medium wear-resistant qualit7es, and a third portion thereof that is characterized by the fact that it exhibits highly abrasive resistant qualities.
Yet another object of the present invention is to provide such a trimetal pulverizer roll that while being readily employable in a bowl mill yet also enables significant cost savings to be realized through the use thereof insofar as the operation of the bowl mTII is concerned.
'I ,; ' ' -- ~L2123~
Yet still another object of the present inventton is to provide a new and improved method of manufacturing such a trimetal pulverizer roll.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention there is provided a pulverizer, i.e., grinding roll of the type that is particularly suited for employment in a bowl mill. When mounted in the bowl mill, the subject roll is designed to be operatlve to coact with another surface of the bowl mill in order to accomplish the pulverization within the bowl mill of material such as coal. To this end, the subject roll embodies a trimetal form of construction. More speciflcally, the subJect roll incorporates a first, i.e., 7nner, portion whtch is made of material that is characterized by its ease of machinability, as for example, gray iron.
Further, this inner portion has formed therethrough a passage which is suitably dimensioned for receiving therewithin a shaft-like member on which the roll is designed to be mounted in supported relation thereto. Next, the subject roll Tncorporates a second, i.e., intermediate, portion of material that 7s suitably supported in adhered relation on the inner portion. This intermediate portion, which is substantially un7form in thickness, is composed of a material that is voted for Tts medium wear~resistant qualities such as a material like Raymix, the latter being obtainable from applicant's assignae. Lastly, the subject roll incorporates a third, i.e., outer, port70n that is suitably supported in adhered relation on the intermediate portion. This outer portion is substantially uneven in thickness. That is, those areas of the outer portion of the subject roll that are known to wear most rapidly are provTded with a thicker thickness of material. Finally this outer portion is composed of a highly abrasive resistant material such as a weld overlay material.
In'accordance with another aspect of the present invention there is provided a method of manufacturing such a tri~etql pulverizer, i.e., grinding roll. The subject method ~23~
includes the steps of forming from a material that is characterized by its ease of machinability a body having the general configuration of a roll, providing through the center of the body a suitably dimensioned through passage capable of having a shaft-like support member positioned therewithin in mounted relation thereto, affixing in supported relation to the body a first substantially uniform layer of material having medium wear-resistant characteristics, and affixing in supported relation to the first layer of material a second substantially nonuniform layer of material having highly abrasive resistant characteristics.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a side elevational view partly in section and with some parts broken away of a bowl mill embodying pulverizer rolls constructed in accordance wifh the present invention and manufactured in accordance with the method of the present invention;
Figure 2 is a sectional view on an enlarged scale of a pulverizer roll constructed in accordance with the present invention and manufactured in accordance with the method of the present inventlon; and Figure 3 is a sectional view on an enlarged scale of a pulverized roll constructed in accordance with the present invention and manufactured in accordance with the method of the present invention, illustrating in exaggerated form +he uneven nature of the thickness of the outer portion of the pulverizer roll.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing, and more particularly to F7gure l thereof, there is depicted therein a pulverizing bowl m711, generally designated by reference numeral 10.
Inasmuch as the nature of the construction and the mode of operation of pulverizing bowl mills per se are well-known to those skilled in the art, it is, therefore, not deemed necessary to set forth herein a detailed description of the bowl mill lO, which is illustrated in Figure l. Rather, it is Z3~5 g deemed sufficient for purposes of obtaining an understanding of a pulverizing bowl mill lO, which is capable of being equipped with pulverizer rolls constructed in accordance with the present 7nvention and manufactured by means of the present inventton, that there merely be presented herein a generalized description of the nature of the construction and the mode of operation of the components of the pulverizing bowl mill lO.
For a more detailed description of the nature of the construction and the mode of operation of the components ot the pulverizing bowl mill lO, which are not described in depth herein, one may have reference to the prior art, e.g., U.S.
Patent No. 3,465,971, which issued September 9, 1969 to J. F.
Dalenberg et al., and/or U.S. Patent No. 4,002,299, which issued January ll, 1977 to C. J. Skalka.
ReferrTng further to Figure l of the drawing, the pulverizing bowl mill lO, as illustrated therein, includes a substantially closed separator body 120 A grinding table 14 is mounted on a shaft 16, which in turn is operatively connected to a suitable drive mechanTsm (not shown), so as to be capable of being rotatably driven thereby. With aforedescrTbed components arranged within the separator body 12 in the manner depicted in Figure 1 of the drawing, the grtnding table 14 Ts designed to be driven in a clockwise direction.
Continuing with description of the pulverizing bowl mill 10, a plurality of pu3verizer, i.e., grinding, rolls 18, preferably three in number in accord with conventional practice, are suitably supported within the interior of the separator body 12 so as to be spaced equidistantly one from another around the circumference of the latter. The nature of the construction as well as the method by which each of the grinding rolls 18 is manufactured comprises the subject matter that forms the essence of the present invention. A
description of the nature of the construction of the grinding rolls 18 as well as a description of the method by which such a grinding roll 18 is manufactured will be found set forth i5 --1 o--hereinafter. First, however, note is made here of the fact that in tha interest of maintaintng clarity of illustration in the drawing only one grinding roll 18 has been shown in Figure 1.
As further regards +he grinding rolls 18, each of the latter, as best understood with reference to Figure 1 of the drawing, is preferably supported on a suitable shaft (not shown) such as to be rotatable relative thereto. Moreover, the grinding rolls 18 are also each suitably supported in a manner yet to be described for movement relative to the upper surface, as viewed wtth reference to Figure 1, of the grinding table 14. To this end, each of the grinding rolls 18 has cooperatively associated therewith a hydraulic means, gensrally designated in Figure 1 by reference numeral 20.
Each of the hydraulic means 20, as will be described more fully hereinafter, is operafive to establish a hydraulic loading on the grlnding roll 18 that is associated therewith.
The effect of this loading is to cause the roll 18, which is subject thereto, to exert the requisTte degree of force on the coal that is disposed on the grinding table 14, and thereby accomplish the desired pulverTzation of this coal.
The material, e.g., coal, that is to be pulverized in the bowl mtll 10 is fed thereto by means of any suitable conventional form of feed means. By way of exempllfication in this regard, one such feed means that may be employed for this purpose is a belt feeder means (not shown). Upon being discharged from the feed means (not shown), the coal enters the bowl mill 10 by means of a coal supply means, generally designated by reference numeral 22, with which the separator body 12 is suitably provided. In accordance with the embodiment of the pulverizing bowl mill 10 illustrated in Figure 1, the coal supply means 22 includes a suitably dimensioned duct 24 having one end thereof, which extends outwardly of the separator body 12 and preferably terminates in a funnel-like member (not shown). The latter mamber (not shown) is suitably shaped so as to facilitate the collection lZ~Z~5 "
of the coal particles entering the bowl mill 10, and the guiding thereafter of these coal particles into the duct 24.
To this end, as shown 7n Figure 1 of the drawing, the duct end 26 preferably is suitably supported within the separator body 12 through the use of any suitable form of conventional support means (not shown) such that the duct end 26 is coaxially aligned with the shaft 16 that supports the grinding table 14 for ro+ation, and is located in spaced relation to a suitable outlet 28 provided in the classifier, generally designated by reference numeral 30, through which the coal flows in the course of being fed onto the surface of the grinding table 14.
In accord wlth the mode of operation of pulverizing bowl mills that embody the form of construction depicted in FTgure 1, a gas such as air is utilized to effect the conveyance of the coal from the grinding table 14 through the interior of the separator body 12 for discharge from the pulver7zing bowl mill 10. The air that is made use of in this regard enters the separator body 12 through a suitable opening (not shown) formed therein for this purpose. From +he aforesa7d opening snot shown) in the separator body 12, the aTr flows to a multiplicity of annular spaces 32 suitably - formed between the circumference of the grinding table 14 andthe inner wall surface of the separator body 12. The air upon - 25 exiting from the annular spaces 32 is deflected over the grinding table 14 by means of suitably positioned deflector means (not shown). One such form of deflector means (not shown), which is suitable for use for this purpose in the bowl mill 10 of Figure 1 comprises the subject matter of U.S.
Patent No. 4,234,132 which issued to applicant on November 18, 1980, and which is assigned to the same assignee as the present applicatTon.
While the air is flowing along the path described above, the coal which is dTsposed on the surface of the grinding table 14 is being pulverized by the action of the ; grinding rolls 18. As the coal becomes pulverized, the ~z~
partlcles are by centrifugal force thrown outwardly away from the center of the grinding table 14. Upon reaching the region of the circumference of the grinding table 14, the coal particles are picked up by +he air exiting from the annular spaces 32 and are carried along therewith. The combined flow of air and coal particles is thereafter captured by the deflector means (not shown), which has been referred to previously hereinabove. The deflector means (not shown), in turn, is operative to cause this combined flow of air and coal particles to be deflected over the grinding table 14.
This necessitates a change in direction in the path of flow of this combined stream of air and coal particles. In the course of effecting this change of direction, the heaviest coal partTcles, because they have more inertia, become separated from the air stream> and fall back onto the surface of the grinding table 14, whereupon they undergo further pulverization. The lighter coal particles, on the other hand, because they have less inertTa continue to be carried along in the air stream.
After leaving the influence of the aforedescribed deflector means (not shown), the combined stream consisting of air and those coal particles that rematn entrained therein flows to the classifier means 30 to which reference has been had herein previously. In accord with conventional practice and in a manner which is well-know~ to those skilled in this art, the classifier 30 operates to effect a further sorting of the coal particies that remain in the air stream. Namely, those particles of pulverized coal, which are of the desired parttcle size, pass through the classifier 30 and along with the air are discharged therefrom and thereby from the bowl mill 10. This discharging of the coal particles is effected through the outlets 34 with which the bowl mill 10 is suitably provided for this purpose.
On the other hand, those coal particles, which in size are larger than desired, are returned to the surface of - the grinding table 14 whereupon they undergo further ~Z3~
pulverization. Thereafter, these coal particles are once again subjected to the process that has been described above.
That 7s, these particles are thrown outwardly of the grinding table 14, are picked up by the air exiting from the annular spaces 32, are carried along with the air to the deflector means (not shown), are deflected back over the grinding table 14 by the deflector means (not shown), the heavier particles drop back onto the grinding table 14, the lighter particles are carried along to the classifier 30, and finally those particles which are of the proper size pass through the classifier 30 and exit from the bowl mill 10 through the outlets 34.
ConsiderTng further the matter of the pulverizing action to which the coat disposed on the upper surface, as viewed with reference to Figure 1, of the grinding table 14 is subjected by the grinding rolls 18, the amount of force that must be exerted on the latter in order to effect the desired degree of pulverizatton of the coal mill vary depending on a number of factors. For example one important consideration in this regard is the nature of the coal itself. That is, the amount of force required to pulverlze the coal will be a function of the grindability of the coal to be pulverized, ire., the grinding characteristics of the latter. Another important factor in determining the amount of force that the grinding rolls 18 must exert to accomplish the desired degree of pulverization of the coal is the depth to which the coal is disposed on the grinding table 14, which in turn is a function of the outpu+ rate at which the bowl mill 10 is being operated.
As best understood with reference to Figure 1 of the drawing, the amount of grinding force which the grinding rolls 18 apply to the coal on the grinding table 14 is a function of the amount of force with which the grinding rolls 18 are biased into engagement with the coal on the table 14. In accord with the nature of the construction shown in Figure 1, ; the grinding roll 18 depicted therein, which is suitably 36~
mounted for rotation on a shaft (not shown), is suitably supported so a: to be pivotabie about the pivot pin 36 into and out of engagement with the coal that is disposed on the grinding table 14. Although only one grinding roll 18 is shown in Figure 1 and although this discussion is directed fo this one grinding roll 18, it is to be understood that as has been mentioned previously hereinbefore the bowl mill 10 is normally provided with three such grinding rolls 18.
Therefore, this discussion is intended to be equally applicable to each of these three grinding rolls 18.
Continuing with the matter of the force exerted by the gri.nding roll 18~ the latter in accord with the nature of the construction illustrated in Figure 1 is designed to be biased hydraulically into and out of engagement with the coal that is on +he grinding table 14. More specifically, to this end the hydraulic means 20 is cooperatively associated with the grinding roll 18~ As depicted in Figure 1, the hydraulic means 20 includes a cylinder 38 suitably mounted to the exterior wall surface of the separator body 12. Wlthin the cylinder 38, a piston 40 is suitably supported for movement therewithin. Attached to the piston 40 is a piston rod 42 of sufficient length so as to extend into the interior of the separator body 12 whereupon the free end of the piston rod 42 engages an upstanding member 44 that comprises a portion of the support means for the grtnding roll 18. A suitable opening 46 Ts formed in the separator body 12 to enable the piston rod 42 to project into the interior of the latter. In a manner well-known to those skilled in the art of hydraulics, the cylinder is filled with a suitable hydraulic fluid, such that a hydraulic pressure is applied by the fluid to both faces of the piston 40. The hydraulic fluid which fills the - cylinder 38 is provided thereto from a suitable source thereof (not shown).
Accordingly, the extent to which the free end of the piston rod 42 projects into the interior of the separator body 12 for engagement with the member 44 is a function of the ~Z~ 5 difference in hydraulic pressure, which is applied to the faces of the piston 40. In turn, the extent to which the free end of the piston rod 42 extends into the interior of the separator body 12 determines the extent to which the grinding roll 18 is hydraulically biased into engagement with the coal on the grinding table 14, and concomitantly the amount of grinding force being applied to the coal by the grinding roll 18. That is, the piston rod 42 is fixedly attached to one face of the piston 40 such that as the piston 40 moves in response to the difference in hydraulic pressure being applied - to the faces thereof, the piston rod 42 moves along therewith. It is to be understood in this connection that the opening 46 provided in the separator body 12 through which the piston rod 42 passes is equipped with suitable sealing means (not shown) operative to prevent the leakage through the openlng 46 of hydraulic fluid from the cylinder 38 to the interior of the body 12.
By way of exemplification, the more the free end of the piston rod 42 extends into the interior of the separator body 12, the more it will cause the member 44 to move in a clockwise direction, as viewed with reference to Figure 1, abouf the pivot p7n 36, and thereby have the effect of increasing the amount of grinding force that the grindlng roll 18 exerts on the coal that is on the grinding table 14.
Conversely, the less the free end of the piston rod 42 projects into the interior of the separator body 12, the less clockwise movement there will be of the member 44 about the pivot pin 36, and thus the less grinding force the roll 18 will exert on the coal that is disposed on the table 14.
Lastly, in accord with the preferred form of construction, the hydraulic means 20 is provided with an accumulator 48. The.function of the latter is to obviate any potentially damaging consequences that might otherwise flow from the occurrence of some form of transient operating condition. For example, should some foreign object be introduced into the bowl mill 10 along with the coal that is 121Z3~i~
to be pulverized, and should this foreign object become disposed on the grinding table 14, the effect of the grinding roll 18 engaging this foreign object would be to raise the roll 18 away from the table 14, to would be to cause the roll 18 to move about the pivot pin 36 in a counterclockwise direction, as viewed with reference to Figure 1. As a consequence of this action, the member 44 would be made to apply a force against the free end of the piston rod 42 tending to cause the piston 40 to move in a direction away from the wall surface of the separator body 12. further, as the piston 40 moves in this manner, the hydraulic fluid located in that portion of the cylinder 38 towards which the piston 40 is moving would tend, absent the presence of the accumulator 48, to resist the movement of the piston 40. This could result in damage being incurred by the various components that are operatively associated with the grTnding roll 18.
Accordingly, the function of the accumulator 48 is to permit hydraulic fluid to flow thereinto as the fluid ts being forced from the cylinder 38 by the advancing piston 40.
- However, as soon as the grinding roll 18 passes over the foreign object, the grTnding roll 18 Ts once again restored to-its normal position, i.e., nontransient condition. This occurs by vtrtue of the flow from the accumulator 48 tnto the cyltnder 38 of the hydraultc flutd whtch had been made to flow tnto the former from the latter, because of the counterclockwtse movement, as vtewed with reference to Figure 1, of the grinding roll 18 about the pivot pin 36 caused by the ra7sing of the roll 18 as the latter engaged and passed over the foretgn object located on the table 14.
For purposes of setttng forth a detatled descrtptton of the structural nature of a pulvertzer roll 18 constructed tn accord wtth the present tnventton as well as the method by whtch such a pulvertzer roll 18 ts manufactured tn accord wtth the present invention, reference will now be had parttcularly to Ftgures 2 and 3 of the drawing. It is important to take note here of the fact that Figure 2 in contrasf fo Figure 3 is intended to simpiy provide a general illustration of a pulverizer, i.e., grtnding, roll 18 constructed in accord with the present invention. Figure 3, on the other hand, as will be more fully set forth hereinafter, illustrates with more partTcularly the specific details of construction of 2 pulverizer roll 18 that is manufactured in accordance with the present inventionO
With the above as a frame of reference, it can be seen prom Figures 2 and 3 that the grinding roll 18 embodies a trimetal form of construction. More specifically, as best understood with reference to Figures 2 and 3, the grinding roll 18 embodies a main body portion, generally designated by reference numeral 50, that embodies the overall configuration of a roll. In addition to the body portion 50, the grinding roll 18 further embodies two other dissimilar portions of materlal arranged Tn layered relation to each other as well as to the body portion 50. To th7s end, one of these two portions, i.eO, that denoted generally by the reference numeral 52 in F7gures 2 and 3 of the drawing, is suitably positioned Tn superimposed relation ,o the body portion 50 of the grinding roll 18. Similarly, the other of the aforereferenced two portions, i.e., that denoted generally by the reference numeral 54 in Figures 2 and 3 of the drawing, is suitably positioned in super7mposed relation to the port70n 52.
As further regards the body portion 50 of the grinding roll 18, the latter in accord with the best mode embodiment of the invention is made of a relatively soft, easily machinable material, such as gray iron Moreover, w7th particular reference to Figures 2 and 3 it can be seen therefrom that the body portion 50 has a passage 56 formed entirely therethrough at substantially the center thereof.
The through passage 56 is suitably dimensioned so as to be carable of receiving therewithin in assembled relation thereto -; the shaft-like member (not shown) to which re$erence has ~Z~Z3~
previously been made hereinbefore, and on which the grinding roll 18 is suitably supported so as to be capable of functioning in the manner described above and as shown in Figure 1.
Next, with regard to the portion 52, i.e., the intermediate layer, with which the trimetal pulverizer roil 18 is provided, in accord with the best mode of the invention this portion 52 preferably comprises a material that is noted for its medium wear-resistant qualities. In this regard, a material that has been found suitable for use for this purpose is a material referred to by the name Raymix. Raymix, which has a known composition, can be obtained from the Monongahela plant of applicant's assignee. The reasons why a material having such qualities is selected for use in this context, and the manner in which the portion 52 consisting of Raymix preferably is adhered to the body portTon 50 will be found set forth with more particularity hereinafter.
The last, i.e., portion 54, of the three portions, which collectively comprise the trimetal pulverizer roll 18 preferably consists, in accord with the best mode embodiment of the tnventton, of a material that is characterized by the fact that it is highly abrasive resistant. One material, which ls suitable for use in this regard, is that known to those skilled in this art as nihard. As in the case of the portion 52 the reasons for employing a material to form the portion 54, i.e., the outer layer of the trime+al pulverizer roil 18 that has the characteristics described above, and the manner in which the portion 54 is affixed to the portion 52 will be found set forth hereinafter with more particularlity.
Suffice it to say at this point, however, that the reasons for constructing the grinding roll 18 from a plurality of dissimilar materials that are arranged in a layered array are as a result of recognition being had first to the fact that there is a need to provide the body portion 50 with the through passage 56, and secondly to the fact +hat the outer surface of the pulverizer roll 18 is subjected to a harsh ~2123~5 _19_ abrasive action in the course of effecting the pulverization of coal. The result, therefore, is that on the one hand it is desirable that the body portion 50 be made of a relatively soft, easily mach:nable material so as to facilitate the formulation therein of the through passage 56. In contradistinction to this, there is a need for at least the outer surface, i.e., that encompassed by the intermediate layer, i.e., portion 52, and fhe outer layer, i.e., portion 54, to be made of materials that are characterized by their capability to resist wear, and in particular that kind of wear which is occasioned by abrasive action.
Insofar as concerns the illustratTons that comprise Figures 2 and 3 of the drawing, as was noted previously herein, Figure 2 is simply intended to illustrate in a general fashion the nature of the construction in accord with the present Invention of the pulverizer, i.eO, grinding, roll 18.
Figure 3, on the other hand, Ts intended to illustrate a grinding roll 18 constructed in accordance with the present invention whereTn therein is depicted in exaggerated fashion the fact that the outer layer, i.e., portion 54, embodies an uneven thickness in contradistinction to the intermediate layer, l.e., portion 52, whtch is of substantially uniform thickness. More speciflcally9 the external surface of the outer portion 54, i.e., that denoted by the reference numeral 58 in Figure 3 Ts provided with a specific configuration which is intended to constitute a replication of the wear pattern that a pulverization, i.e., grinding, roll 18 develops as a consequence of its being utilized to effect the pulverization of a material such as coal within a bowl mill 10. That is, the external surface 58 of the outer portion 54 of the grinding roll 18 is suitabiy configured such that those areas thereof which based on past experience it can be anticipated will be subjected to the greatest degree of wear are made to have a thicker thickness of material, e.g., nihard, thereat.
The intent in doing so is to attempt to achieve a uniform wear rate of the outer portion 54 by means of providing more 3~
~20-material in those areas whereat it is expecfed that the roll 18 will experrience the most wear based on past experience applied to the use to which the roll 18 is intended to be put. To summarize, the outer portion 54 of the pulverizer, i.e., grinding, roll 18 is 7ntentionally made to have a nonuniform thickness such that more material is provided in those areas whereat more wear is predicted to take place, and less material is provided in those areas whereat less wear is expected to occur.
Next, a description will now be had of the method by which in accord wTth the present invention the pulverizer, i.e., grinding, roll 18 is preferably manufactured. This will then be followed by a description of the benefits that flow from the use of a pulverizer roll 18 which embodies a trimetal form of construction. Insofar as the method of manufacture of the pulverizer roll 18 ls concerned, in accord with the best mode embodiment of the invention a centrifugal casting process is employed for this purpose. Proceeding with the description of the subject method, in accord with the first step thereof the requisite amount of material, e.g., Raymix, needed to form the 7ntermediate portion 52 of the pulverizer roll 18 is poured in known fashion into a suTtable mold. In accordance with the known techniques of centrifugal casting, the Raymix under the influence of centrifugal force moYes outwardly within the mold and forms a layer thereof in abutting engagement to the inner surface of the mold. Once the intermediate portion 52 of the pulverizer roll 18 is formed, the next step in accord with the subject method is to effect the pouring into the mold of the requisite amount of material, e.g., gray iron, to form the inner, i.e., body, portion 50 of the pulverizer roll 18. In accord once again with fhe known techniques of centrigual casting, the gray iron under the influence of centrifugal force forms a layer in abutting engagement with +he inner surface of the interme=iate portion 52. A suitable bonding agent is preferably utTlized to cause the outer surface of the inner portion 50 to adhere to the 23~5 inner surface of the intermediate portion 52. After the pulverizer roll 18 has been partially formed in the aforedescribed manner, the partially formed roll 18 is removed from the aforereferenced mold and the outer surface of the intermediate portion 52 to the extent deemed necessary is prepared for receipt thereon of the outer portion 54. This is followed by the affixation of the outer portion 54 to the intermediate portion 52. To this end, in accord with the best mode embodTment of the method of manufacture of the present invention, the outer portion 54 is provided in the form of a weld overlay. Moreover, as described previously hereinbefore, the outer portion 54 preferably is applied in the form of a nonuniform thTckness of material such that the thicker thickness thereof is located in those areas whereat it is believed, based on the use to which it is known the pulverizer roll 18 will be put9 the greatest wear will be experienced.
it is to be noted here that in accord with the method described above, the through passage 56 is formed through substantially the center of the body portion 50 during the casting process. Thus, the need to machine such a passage 56 therethrough is obviated except for any minor machining that may be required to prepare the passage 56 for the receipt therein of the shaft-like member (not shown) on which the pulverizer roll 18 is designed to be mounted in supported relation thereto.
Attention will now be directed to the matter of the benefits that flow from the use of a pulverizer roll that embodies a trimetal form of construction. To this end, those benefits which are to be found enumerated hereinafter are presented by way of exemplification and not limitation.
First, the pulverlzer roll 18 by virtue of its trimetal form of construction embodies a body portion 50 that is capable of being made from a material that is relatively easy to work thereby enabling economies of manufacture to be realized from the use for this purpose of this material, e.g., gray iron.
; Secondly, the pulverizer roll 18 that embodies a trime~al ~lZ3~
structure has an external surface that consists of an outer portion 54 which consists of a relatively hard, i.e., highly abrasive resistant material such as nihard that is capable of resisting the abrasive action produced in the course of effecting the pulverization therewith of a material such as coal. Moreover7 because of the fact that the outer portion 54 is provided with a thicker thickness of material in the areas which are most subject to wear, the pulverizer roll 18 is characterized by the fact that the outer portTon 54 wears more slowly, i.e., wears more uniformly. That is, before the outer portion 54 wears through in those areas which are subject to the greatest wear, a more uniform wearing of the entire outer portion 54 is realized.
In addition, it is most important to note here that the external surface of the pulverizer roll 18 is not composed of simply the outer portion 54. But rather the external surface further comprises the intermediate portion 52, which also consists of a material having wear-resistant qualities, e.g., Raymix. As a consequence, even when the outer portion 54 is worn through, the pulverizer roll 18 still remains serviceable in that the intermediate portion 52 is also capable of performing the wear-resisting function. It is of course true that the material which comprises the lntermediate portion 52 ts not as hard, i.e., is not as abrasive resistant as the outer portion 54. Nevertheless, the pulverizer roll 18 is still capable of being used with the intermediate portion 52 exposed, i.e., serving, as the pulverizing surface. The significance of this is that continued usage may be made of the pulverizing roll 18.
Namely, no longer is it necessary to immediately replace pulverizer rolls when the outer surface thereof wears through for fear of damagTng the roll, i.e., so to preclude the resurfacing of the worn roll. In contradisttnction, with the pulverizer roll 18 of the present invention it is possible most frequently, to await the next scheduled shutdown of the bowl mill 10 in order to effect the removal and replacement of the roll 18 after the outer portion 54 thereon has worn through. This is because the intermediate portion 52 serves as an adequate surface to effect the continued pulverization therewith of coal within the bowl mill 10. Normally, the life of~the intermediate portion 52 Defore it also wears through is such as to enable a sufficient period of time to expire to reach the next scheduled shutdown of the bowl mill 10.
Another advantage that derives from the use of d7ssimilar materTals for the intermediate portion 52 and the outer portion 54 is that it is possible to visually recognize when the outer portion 54 has worn through in one or more places This visual indication is had by noting the different appearance, e.g., color, etc. of each of the two dissimilar materials, i.e., the Raymix of intermediate portion 52 and the ! 15 nihard of outer portion 54. To further enhance this visual recognitton, it is possible to color with a suitable medium, e.g., red paint, the outer surface of the intermediate portion 52 so as to prov7de the latter w7th a read71y viewable surface before the outer port70n 54 7s affixed thereto.
In summary, not only does the pulver7zer roll 18 constructed 7n accordance with the present invention prov7de a roll that has a measurably longer operat7ng life than do the rolls wh7ch have heretofore been constructed in accordance with the teachings of the prior art, but also the pulverizer roll 18 7s characterized by the fact that even when the outer port70n 54 thereof becomes worn through, by v7rtue of the pressnce of the intermed7ate portion 52 cont7nued usage may be made of the pulver7zer roll 18 for effecting the puiver7zat70n of a mater7al without the roll 18 sustaining damage thereto.
This obv7ates the need to experience many of those shutdowns of the bowl mill 10 which have been occasioned heretofore by the need to accomplish the removal and replacement of a pulverizer roll that had been constructed in accordance with the teachings of the prior art. Lastly, by providing the outer portion 54 with a nonuniform th ! ckness, addittonal wear ; is obtainable from the pulverizer roll 18 before the outer ~2~Z~65 portion 54 thereof wears through; namely, those areas of he outer portion 54 which experience shows are subjected to the greatest wear are provided with the thickest layer of material.
Thus, in accordance with the present invention there has been provided a new and improved form of pulverizer roll.
Moreover, the pulverizer roll of the present invention is characterized in that it embodies a trimetal mode of construçtion. In addition, in accord with the present invention a trimetal pulverizer roll is provided that is primarily intended to be employed in a bowl mill for purposes of effecting the pulverization therewithin of a material such as coal. Further, the +rimetal pulverizer roll of the present invention is distinguishable by its relatively long operating life. Additionally, in accordance with the present invention a trimetal pulverizer roll 7s provided whTch has a first portion thereof that is characterized by its ease of machinability, a second portion thereof that is characterized by the fact that 7t exhibits medium wear-reststant qualities, and a third portion thereof that is charac-terized by the fact - that it exhlbits htghly abrasive resistant qualities. Also, the trimetal pulverizer roll of the present invention while being readily employable in a bowl mill yet also enables significant cost savings to be realized through the use thereof insofar as -the operation of the bowl mill is concerned. Furthermore, in accord with the present invention a new and improved method of manufacturing such a trimetal pulverizer roll is provided.
While only one embodiment of my invention has been shown, it will be appreciated that modifications thereof, some of which have been al!uded to hereinabove, may still be readily made thereto by those skilled in the art. 1, therefore, intend by the appended claims to cover the modifications alluded to herein as well as all the other modifications, which fall wlthin the true spirit and scope of my invention.
What is claimed is:
Claims (17)
1. A pulverizer roll of the type suitable for use in a bowl mill for purposes of effecting the pulverization therewithin of a material such as coal comprising:
a.) a first portion formed of a material characterized by its ease of machinability, said first portion having a through passage formed therein suitably dimensioned so as to be capable of receiving therewithin a member operative for effecting the mounting thereon of the pulverizer roll in supported relation thereto;
b.) a second portion formed of a material noted for its medium wear-resistant qualities, said material of said second portion being different from said material of said first portion, said second portion being adhered to said first portion in layered relation thereto; and c.) a third portion formed of a material noted for its highly abrasive resistant qualities, said material of said portion being different from both said material of said second portion and said material of said first portion, said third portion being affixed to said second portion in layered relation thereto.
a.) a first portion formed of a material characterized by its ease of machinability, said first portion having a through passage formed therein suitably dimensioned so as to be capable of receiving therewithin a member operative for effecting the mounting thereon of the pulverizer roll in supported relation thereto;
b.) a second portion formed of a material noted for its medium wear-resistant qualities, said material of said second portion being different from said material of said first portion, said second portion being adhered to said first portion in layered relation thereto; and c.) a third portion formed of a material noted for its highly abrasive resistant qualities, said material of said portion being different from both said material of said second portion and said material of said first portion, said third portion being affixed to said second portion in layered relation thereto.
2. The pulverizer roll as set forth in Claim 1 wherein said material of said first portion comprises gray iron.
3. The pulverizer roll as set forth in Claim 2 wherein said first portion comprises a layer of substantially uniform thickness of gray iron.
4. The pulverizer roll as set forth in Claim 1 wherein said material of said second portion comprises Raymix.
5. The pulverizer roll as set forth in Claim 4 wherein said second portion comprises a layer of substantially uniform thickness of Raymix.
6. The pulverizer roll as set forth in Claim 1 wherein said material of said third portion comprises nihard.
7. The pulverizer roll as set forth in Claim 6 wherein said third portion comprises a layer of nonuniform thickness of nihard with the thickest thickness of nihard being located at those areas of said third portion that are predicted to be subject to the greatest wear.
8. The pulverizer roll as set forth in Claim 1 wherein the dissimilarity between said material of said third portion and said material of said second portion enables a visual recognition to be had of when said third portion has worn through.
9. A method of manufacturing a pulverizer roll having a trimetal form of construction and of the type suitable for use in a bowl mill for purposes of effecting the pulverization therewith of a material such as coal comprising:
a.) forming from a material characterized by its ease of machinability a first portion;
b.) providing the first portion with a passage extending therethrough substantially at the center thereof;
c.) forming from a material noted for its medium wear-resistant qualities a second portion;
d.) adhering the second portion on the first portion in layered relation thereto;
e.) forming from a material noted for its highly abrasive qualities a third portion; and f.) affixing the third portion on the second portion in layered relation thereto.
a.) forming from a material characterized by its ease of machinability a first portion;
b.) providing the first portion with a passage extending therethrough substantially at the center thereof;
c.) forming from a material noted for its medium wear-resistant qualities a second portion;
d.) adhering the second portion on the first portion in layered relation thereto;
e.) forming from a material noted for its highly abrasive qualities a third portion; and f.) affixing the third portion on the second portion in layered relation thereto.
10. The method as set forth in Claim 9 wherein the first portion is formed as a layer of substantially uniform thickness of gray iron.
11. The method as st forth in Claim 10 wherein the first portion is formed by means of a centrifugal casting process.
12. The method as set forth in Claim 9 wherein the second portion is formed as a layer of substantially uniform thickness of Raymix.
13. The method as set forth in Claim 12 wherein the second portion is formed by means of a centrifugal casting process.
14. The method as set forth in Claim 9 wherein the third portion is formed as a layer of nonuniform thickness of nihard with the thickest thickness of nihard being located at those areas that are predicted to be subjected to the greatest wear.
15. The method as set forth in Claim 14 wherein the third portion is formed as a weld overlay.
16. The method as set forth in Claim 9 wherein the second portion is adhered to the first portion through the use of a bonding agent.
17. The method as set forth in Claim 9 wherein the third portion is affixed to the second portion by means of welding.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44685082A | 1982-12-06 | 1982-12-06 | |
| US446,850 | 1982-12-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1212365A true CA1212365A (en) | 1986-10-07 |
Family
ID=23774053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000431137A Expired CA1212365A (en) | 1982-12-06 | 1983-06-24 | Trimetal pulverizer roll and a method of manufacture thereof |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0110191A2 (en) |
| JP (1) | JPS59109254A (en) |
| KR (1) | KR840006915A (en) |
| AU (1) | AU2210183A (en) |
| CA (1) | CA1212365A (en) |
| ES (1) | ES527602A0 (en) |
| ZA (1) | ZA836139B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60209268A (en) * | 1984-04-03 | 1985-10-21 | 川崎重工業株式会社 | Vertical mill |
| IN166426B (en) * | 1986-02-24 | 1990-05-05 | Combustion Eng | |
| AU629243B2 (en) * | 1989-09-14 | 1992-10-01 | Kurimoto, Ltd. | Method for manufacturing a crushing roller and method for using the roller |
| US5346148A (en) * | 1993-03-16 | 1994-09-13 | The Babcock & Wilcox Company | Asymmetric pulverizer tire |
| CN102544632A (en) * | 2010-12-07 | 2012-07-04 | 中国电子科技集团公司第十八研究所 | Anti-blocking lithium air battery |
| CN112846477B (en) * | 2020-12-29 | 2022-06-28 | 瓯锟科技温州有限公司 | Device for compounding powder and metal plate |
-
1983
- 1983-06-24 CA CA000431137A patent/CA1212365A/en not_active Expired
- 1983-08-19 ZA ZA836139A patent/ZA836139B/en unknown
- 1983-11-04 EP EP83111022A patent/EP0110191A2/en not_active Withdrawn
- 1983-11-10 KR KR1019830005329A patent/KR840006915A/en not_active Application Discontinuation
- 1983-11-28 ES ES527602A patent/ES527602A0/en active Granted
- 1983-12-05 JP JP58228604A patent/JPS59109254A/en active Pending
- 1983-12-05 AU AU22101/83A patent/AU2210183A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| ZA836139B (en) | 1984-04-25 |
| ES8506206A1 (en) | 1985-07-01 |
| JPS59109254A (en) | 1984-06-23 |
| KR840006915A (en) | 1984-12-04 |
| AU2210183A (en) | 1984-06-14 |
| ES527602A0 (en) | 1985-07-01 |
| EP0110191A2 (en) | 1984-06-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |