US3807803A - Cutter chain having bits sets cutting different advance levels - Google Patents

Abstract

A cutter chain utilized on a cutter bar assembly contains sets of bits on alternate block links. One set of bits is adopted to cut a kerf portion at a different level of advance than the other set of bits.

Description

United States Patent [191 Rollins et al.

[ 1 Apr. 30, 1974 CUTTER CHAIN HAVING BITS SETS CU'I'IING DIFFERENT ADVANCE LEVELS [76] Inventors: Lester G. Rollins, 650 Forest La.;

Glenn S. McDowell, 601 Wiley Ave., both of Franklin, Pa. 16323 [22] Filed: Mar. 22, 1973 [21] Appl. N0.: 343,926

Related US. Application Data [62] Division of Ser. No. 158,037, June 29, 1971, Pat. No.

[52] US. Cl. 299/84 [51] Int. Cl. E2lc 25/34 [58] Field of Search 299/82-84 [56] References Cited UNITED STATES PATENTS 3,307,875 3/1967 McDowell 299/84 X 2,125,296 8/l938 Joy 299/84 Primary Examiner-Emest R. Purser [57] ABSTRACT A cutter chain utilized on a cutter barassembly contains sets of bits on alternate block links. One set of bits is adopted to cut a kerf portion at a different level of advance than the other set of bits.

7 Claims, 7 Drawing Figures PATENTEMPR-somw 3.807 803 sum 10F 2 FIG 2 PArEmsumso m4 3.801.803

SHEET 2 BF 2 FIG: 4

CUTTER CHAIN HAVING BITS SETS CUTTING DIFFERENT ADVANCE LEVELS This is a division, of application Ser. No. 158,037, filed June 29, 1971 and now U.S. Pat. No. 3,752,534.

BACKGROUND OF THE INVENTION Cutter bar chains presently in use are operative in making a penetrating cut (deep kerf) in a mineral face by initially sumping the cutting chain directly into the face and then moving the cutting chain transversely of the sump cut either horizontally or vertically within the mineral face, hereinafter referred to as shearing. In sumping, only the cutter bits traveling over the forward end of the cutter bar penetratethe working face of the mineral vein, while in shearing essentially all the cutter bits traveling along one complete side of the cutter bar act upon the working face of the mineral vein. Thus, a much larger number of cutter bits are engaged in cutting the coal at any one time in the shearing operation than are engaged in cutting during the sumping operation.

As is well known, the operator of a coal cutting machine which supports and drives a cutter chain can control the force with which the cutter bar assembly is thrust against a mineral face. With such a cutting chain the rate at which a cutter bar assembly can be physically urged 'into a mineral vein may be determined by the capability of the cutter bits to penetrate mineral. The capability of bits to penetrate the mineral is in turn determined by the penetrating force available per bit out of the total number of bits simultaneously engaged in cutting a kerf in a mineral vein. Obviously the force per bit must be sufficient to penetrate and dislodge the mineral being cut. Thus, since more bits are utilized at one time in shear throughout the length of the working portion of the cutter bar, it is the force requirement per bit in shear that determines the optimum bit spacing or pitch of the cutter bits. Should too many bits be utilized in shear the force per bit is reduced and may cause reduced cutting and production of undesirable fines because of shallow bit penetration even though the same number of bits per foot of chain could be used advantageously in sumping, since, with the short length of chain in use during sumping the force available per bit is higher during sumpingdue to the small number of bits engaged with thecoal at any one time. Accordingly, the penetrating rate for sumping of prior cutter bars is limited by the pitch between the bits which is determined by the shear requirements only and operators are limited in their penetrating rate of sump because of the bits spaced per shear requirements. Because of the greater force per bit available during sump, in prior devices operators quite often sumped the cutter chains at a penetrating rate greater than normal i.e. faster than the bit spacing would effectively produce without interference cutting, thereby causing non-cutting portions of the chain (blocks and links) to engage the solid mineral and cause chain damage.

Prior configurations having primary and secondary cutter bits have been utilized to assist in the cutting operation of a cutter chain, but such prior devices are not of a configuration to solve the problem of increasing normal sumping speed without decreasing shearing speed as is done in the present invention. U. S. Pat. No. 2,832,579'of A. L. Barrett issued Apr. 29, 1958 defines half pitch arrangement of secondary bits at a lower level of advance, positioned between the primary bits, cannot be realized with the Barrett structure.

SUMMARY OF THE INVENTION According to the present invention there is provided a novel cutter chain configuration having one set of primary cutter bits, in a conventional bit pattern suitable for a cutter bar, positioned in bit blocks located on primary links along the chain at a primary level of advance in a manner to engage the mineral working face during both sumping and shearing operations and a second set of cutter bits, in a like conventional cutter bar bit pattern, positioned on cutter blocks located on secondary links positioned intermediate respective primary cutterbits along the chain at a secondary level of advance in a manner to engage the mineral working face as secondary bits to assist the primary bits only during the high rate of penetration achieved during sumping operation. Other provisions of this invention will be more apparent when taken in conjunction with the following detailed description and the accompanying drawings therein;

FIG. I is an end view of a portion of the novel cutter chain of this invention showing the bit positions of one complete bit pattern in a particular embodiment of the chain of this invention;

FIG. 2 is a side elevational view of a section of the novel chain of FIG. 1 showing the relative positioning of two primary and two secondary links and respective cutter bits;

FIG. 3 is a sectional view of a secondary link taken substantially on line 33 of FIG. 2 looking in the direction of the arrows;

. FIG. 4 is an end elevational view of one of the primary links of FIG. 1;

FIG. 5 is a side elevational view of the link shown in FIG. 4; 7

FIG. 6 is a schematic representation of a portion of a mineral vein with a kerf produced therein according to the action of a device of a prior art coal cutting machine; and

FIG. 7 is a fragmentary view of a portion of a mineral vein having a kerf produced therein by the device of the present invention.

DESCRIPTION FIG. 2 illustrates a portion of a-single cutter chain generally indicated at 10 with a plurality of primary or block links 12 and in intermediate positions connecting or secondary links 14 respectively carrying primary bit blocks 16 with primary bits P such as 18 and 19 (FIGS. 1, 2 and 4) and secondary bit blocks 20 carrying secondary cutter bits S such as 21 and 22 as seen in FIGS. 2 and 3,

In the present invention the primary bit blocks 16 provided with a set of primary bits P in a conventional double arcuate bit pattern 17, are spaced from each other by what would normally in the prior art have been a full chain pitch with a connecting link 14 connected between each pair of the primary.links 12 by means of pintles such as 24 in the standard method of providing a cutter chain. In the present invention however, the connecting or secondary links 14 of the single end type (best seen in FIG. 3 and at the right hand end of FIG. 2 where the single end portion 15 positionable between the saddle end portions 13 of the primary links 12 may be seen) carry the set of secondary bits S such as 21 and 22 in the bit blocks in place of the ordinary non-cutting connector links of prior art chains. Thus chain 10 provides successive bits at half the standard pitch or bit spacing of prior art chains of the same pitch length.

By locating the secondary bit blocks 20 intermediate the usual primary bit blocks 16 the number of cutter bits per unit chain length, of a given pitch, has been doubled. The set of secondary bits S such as 21 and 22 are arranged in a conventional double arcuate cutter bar bit pattern 23 best seen in FIG. 1 at a secondary level of advance below the level of the double arcuate bit pattern 17 of the primary bits P by an amount sufficient so that during a shearing operation only the primary bits P, such as 18 and 19, engage the working face of the mineral vein. During a sumping operation, where the penetrating rate of travel into the working face is greater, the secondary bits S, such as 21 and 22, will assist the primary bits in cutting kerf when arranged in the proper patterns.

Utilizing both the primary bits and secondary bits in a sump operation the optimum penetrating rate of the cutter .bar is increased substantially over the optimum rate of prior art chains. It is to be noted that the optimum sumping rate of this description will be taken to mean the greatest penetration rate which will notcause contact of the bit block or other chain parts with solid mineral in the vein or in other words the optimum rate of penetration is limited to an advance equal to the length of bit extension before pattern repeat.

This limitation is due to the fact that the penetration rate is equal to the rate of advance of the chain into the mineral and if the advance per pattern is more than the length of the bit extension interference cutting will occur since, it is obvious that before the second bit in a given orbit arrives a certain part of the chain will be rubbing on that part of the mineral still unmined, in solid form, with excessive wear on the chain parts and excessive production of fines which are undesirable as will hereinafter appear.

As an example; in a chain having a 9 bit pattern and a pitch of 7 inches between bits in the direction of travel, if the chain speed is 700 feet per minute there will be a time 1/20 of a second elapsed in traveling one pitch 7 inches. The result is that the 9 pitch pattern will repeat every 9/20 of one second and during that time the advance at a sump speed of 18 feet per minute would be approximately l-l l/l6 inches. With the standard bit extension (free height above the bit block) of 1% inches it can be seen that the above mentioned 18 feet per second sumping speed is approximately the maximum allowable under the definition of optimum rate of advance.

With the primary and secondary bits of the present invention we have the potential to generate two surfaces within the kerfs simultaneously, one of which leads the other by approximately inch, and with the cooperative action of the primary and secondary bits it has been found possible to use a 7 pitch bit pattern for the primaries with a 6 pitch bit pattern for the secondaries. Also, with the cooperative action of the secondary bits with relation to the primary bits the pattern effectively repeats twice as often so that we have the following relationship. With an actual penetration rate of 36 feet per minute and a 7 inches pitch we find a penetration rate of 9/25 inch per pitch, which on a 7 pitch pattern would figure out to be over 2% inches per pattern as a penetration rate. At first glance this seems to be far above the earlier defined optimum rate, however, when it is realized that the secondary bits make the pattern repeat effectively twice as often we find that we have a rate of approximately 1 5 1 inches penetration per pattern for each type of bit in sumping which on a 1% inches bit extension gives us optimum penetration at 36 feet per minute or more and is even farther removed from interference cutting than above described prior sumping at 18 feet per minute. Comparing the optimum penetration of prior machines at 18 feet per minute with the optimum penetration possible with the primary and secondary bits of this invention are more than 35 feet per minute gives one a good idea of the advantages inherent in the primary and secondary bit arrangement of this invention essentially doubling the optimum sump rate.

It is to be realized that, as far as penetrating force is concerned, the coal cutters even of prior art were capable of sumping speeds much greater than 18 feet per minute but only at the cost of a great amount of interference cutting with damage to the chains and other deleterious results as above mentioned. When the optimum cutting rate of the chain is maintained at 36 feet per minute or more as with the present invention there is much less temptation for the operator to disregard the possibility of damage and high rate of wear and go ahead with a maximum sumping rate regardless of consequences.

As a cutter is commonly used, the penetration rate in shearing, that is cutting with the full length of the side of the bar (hereinafter the shearing rate) has in the past been limited to a maximum of 4 to 6 feet per minute with the prior art bit pattern as above described, namely, 7 inches pitch and 9 pitch repeat pattern. At the higher penetration rate of 6 feet per minute with a chain speed of 700 feet per minute we would again find 1/20 of a second for a chain travel of one pitch or 9/20 of a second per pattern and at a shearing rate of 6 feet per minute penetration would equal approximately 9/16 inch penetration per pattern. Since this penetration is far below the optimum of 1% inches per pattern as described earlier, the limitations on a penetration rate in shear must be due to an entirely different set of factors from those found for the optimum sumping rate.

It is to be noted that the total force available for advancing the bar in shear is limited by the amount of side thrust available, from the machine on which the bar is mounted, before the machine will overturn or skew in the cut. It should also be noted that the total amount of force will be. divided between the number of bits in contact with the elongated kerf being developed in a shear cut. For an I 1 foot bar at a pitch of 7 inches there would be approximately 19 bits engaged at any one time in a shear cut. Thus the total force from the machine would be divided by 19 in arriving at a total penetrating force per bit and a greater number of bits i.e., a shorter pitch chain or the double number of bits of this invention would only decrease the penetration force per bit with an increase in production of fines and probably with an inferior cutting rate if all bits were in fact cutting. The secondary bits being at lower level of advance as hereinafter set forth do not significantly engage the unmined mineral during shear cutting. Therefore this invention provides the double number of bits for sumping while not increasing the number of bits actively engaged in the shear cut.

However, it has also been found that the maximum shear rate in easily penetrated materials is closely related to the ability to clear the cut material out of the kerf to allow the bar to swing into new cutting positions rather than having anything to do with the amount of force supplied per bit, within reasonable limits. In recognition of these considerations it was felt necessary to provide means. for carrying the cut material out of the kerf as rapidly as possible and to that end there was provided on each of the primary links a coal moving or kerf sweeping conveying lug such as that shown at 26. The conveying lug 26 as actually used is a transversely extending slightly tapered sweeping member extending outwardly from the side of each primary link on the side thereof opposite the side on which the respective primary bit block 16 is mounted and extending outwardly a major portion of the distance defined by the most outward extending cutter bit as 'best seen in FIG. 1. As an example, but not limitative upon the application of this invention, a chain such as that illustrated, producing a 7 inches kerf has been found to operate very satisfactorily with lugs extending out to a position 2% inches from the centerline of the chain to produce a sweep area 5 /2 inches broad within the 7 inches kerf. Since as this chain was used there was little evidence of interference of the lugs with the side of the kerf and practically no wear on the lugs it is felt that a closer approach to the full width of the kerf might well give better results. The height of the lug as shown in the typical example of FIGS. 1 and 4 is approximately 1 /2 inches below bit height to allow for the rate of advance being limited only by the bit extension rather than by possible interference with the lugs 26. Although the lugs 26 have been shown on one side only of each primary link 12 there is no basic reason why these lugs could not be used on both sides of the link with simply a cutout area being provided for the bit blocks 16 on the opposite side of the primary links 12 and there is further no basic reason why these lugs or others like them could not be used on either or both sides of the secondary links 12 and such variations are within the scope of the instant invention. Referring again to FIG. 1 it will be noted that the broken line representation of the lug 26 on the righthand side of the chain as viewed in FIG. 1 is a representation of the normal position of the lugs 26 on the primary links supporting the leftward slanting and extending primary bits as seen in FIG. 1.

Therefore it is to be noted that the chain of this invention has two advantages over prior art chains in the act of shear cut, namely, that the secondary bits not being in position to contact the solid minerals do not reduce the penetrating force per bit but because of their positions and that of the bit blocks 20 supporting them they provide a very good apparatus for conveying out the broken pieces of mineral after the primary bits have loosened it from the mineral vein. Secondly the conveying lugs 26 being on the sides opposite the bit blocks are in perfect position for clearing the kerf, particularly of fines which might otherwise block the advance of the bar. As a result of these two advantageous features it has been found possible to attain a shear speed substantially greater than that of prior art chains.

In the range of 8 to 10 feet per minute there would be a penetrating rate of about A inch per pattern with a 7 inches pitch, 7 bits per pattern, and a bit speed 'of 700 feet per minute so that the secondary bits at a level of advance inch behind the primary bits will not be significantly engaged by the solid mineral. Thus as related to shear it is to be seen that the chain of this invention giving a possible 8 to 10 feet per minute shear rate will far exceed the capabilities of earlier chains found to be in the range of 4 to 6 feet per minute. It has also been found that fewer fines are produced because of the better tooth penetration which gives breaking action rather than the grinding and dust formation of lesser bit penetration.

The operation of the chain of this invention is to be appreciated as-the method of cutting into a coal vein comprising the cutting of a single kerf portion by the end of a cutter bar being sumped into the vein at a rate of advance employing both the primary and the secondary bits to generate arcuate kerf surface portions. The sumping action to be followed by shearing action, sidewise relative to said kerf portions, at a rate slow enough to employ only the primary bits in arcuate kerf surface formation. Simultaneously at least with the shearing action the coal cuttings would be conveyed out of the kerf rapidly enough to avoid cuttings build-up and interference with bar shearing action.

Although the invention is shown and described herein with a particular bit pattern of one secondary bit located intermediate adjacent primary bits along the length of the chain, it is not necessary to limit the bit configuration to such a pattern. Other bit patterns and distribution may be utilized with both primary and secondary bits wherein the secondary bits are utilized -in sump only. An alternate examplecan be that of having more secondary bits (such as 2) located between adjacent primary bits to further increase the sumping speed.

FIGS. 6 and 7 illustrate one of the great advantages of the cutter chain of this invention resident in the presence of both the cutter blocks on the secondary links and particularly of the lugs 26v on the primary links. With a cutter chain of the prior art it has been found that after operation of the chain through a kerf 30 in a mineral vein in the mining of a place 38 by undercutting for shooting, there remains within the kerf 30 an extensive pile of dust as at 34, varying in thickness from approximately 40 to 50 percent of the height of the kerf, at the open end of the kerf, to percent filling of the kerf at the back of the place 38 in the remote portion of the kerf away from the open face 36.

In contrast to the situation illustrated in FIG. 6 showing prior art chain action, the chain 10 of the present invention having been used to form a kerf 40, seen in FIG. 7 extending inwardly into a vein 42 from an open face 46 shows a deposit of dust and fines indicated at 44 as being approximately 10 to 15 percent of the height of the kerf even at the back of the place rather than the 40 percent to 100 percent filling of the prior art as seen in FIG. 6.

In view of the above described (FIG. 6) situation it has been common practice to double cut the mineral to provide two full kerfs in order to have sufficient clear kerf to allow expansion of the coal when shot. This amount of clear kerf is obtained by single cutting with the chain 10 of this invention.

As a result of the small amount of dust left in the kerf 40 by the chain 10 it has been found that the number of shot charges for bringing down the normal amount of coal may be reduced in the case of the kerf 40 from the normal 9 shot charges to to 7 shot charges with the open kerf of FIG. 7 produced by the chain 10 of the present invention.

In addition to the savings in hole formation and explosives it has been found that because of better fracturing especially toward the back part of the mining place (shown at 48 in FIG. 7) the loading machine, not having to dig out unfractured or nearly solid coal can load the place in approximately 25 percent less time than with former cutting and shooting operations.

Thus the present invention can be characterized as a method of mechanically cutting a kerf in a solid vein to provide an open space for explosive breakage to take place which method leaves no more than filling of the kerf with dust or fines after the kerf has been cut by the chain 10 of the present invention.

Although the method and apparatus hereinbefore described has been generally related to coal mining it is to be realized that both method and apparatus are applicable to mining various frangible minerals i.e. easily penetrated materials similar to soft coal, such as salt, trona or the like.

What is claimed is:

1. An endless cutter bar chain utilized on a cutter bar assembly for cutting a deep kerf in a mineral vein comprising: a plurality of connected links; a first set of bits in a cutter bar bit pattern mounted on certain of said links; a second set of cutter bits in a cutter bar bit pattern mounted on other of said links with each of said other of said links being interspersed between said certain links; said first set of bits being located to generate an arcuate kerf surface portion at a first level of advance and said second set of bits being located to generate a second arcuate kerf surface portion at a second level of advance substantially below said first level of advance only when said chain is operating on such a cutter bar which is being sumped into such a mineral vein at optimum rate; and said first and second sets of bits are respectively located in a manner that only said first set of cutter bits will generate a kerf surface portion when said chain is operating on such a cutter bar which is being sheared through such a mineral vein.

2. An endless cutter .chain as specified in claim 1 wherein the bits of said first set of bits are spaced apart by one full chain pitch and the bits of said second set of bits are located between said bits of said first set of bits and spaced one-half pitch therefrom.

3. An endless cutter bar chain utilized on a cutter bar assembly for cutting a deep kerf in a mineral vein comprising: a plurality of spaced block links; at least one connecting link disposed intermediate each adjacent pair of block links; a first set of bits in a first bit pattern mounted on said block links; a second set of bits in a second bit pattern mounted on said connecting links; and one of said bit patterns being located to cut a kerf portion below the kerf portion cut by the other of said bit patterns. I

4. A cutter chain as specified in claim 3 wherein only one of said connecting links are disposed intermediate each adjacent pair of block links and said one of said bit patterns is said first bit pattern.

' 5. A cutter chain as specified in claim 3 additionally comprising a material conveying means on certain of said links.

6. A cutter chain as specified in claim 5 wherein said conveying means is a laterally extending lug portion on each block link.

7. A cutter chain as specified in claim 3 additionally comprising a kerf sweeping means on certain of said links for continuously clearing broken mineral out of a kerf formed by said chain during mineral cutting operation thereof.

Claims (7)

1. An endless cutter bar chain utilized on a cutter bar assembly for cutting a deep kerf in a mineral vein comprising: a plurality of connected links; a first set of bits in a cutter bar bit pattern mounted on certain of said links; a second set of cutter bits in a cutter bar bit pattern mounted on other of said links with each of said other of said links being interspersed between said certain links; said first set of bits being located to generate an arcuate kerf surface portion at a first level of advance and said second set of bits being located to generate a second arcuate kerf surface portion at a second level of advance substantially below said first level of advance only when said chain is operating on such a cutter bAr which is being sumped into such a mineral vein at optimum rate; and said first and second sets of bits are respectively located in a manner that only said first set of cutter bits will generate a kerf surface portion when said chain is operating on such a cutter bar which is being sheared through such a mineral vein.

2. An endless cutter chain as specified in claim 1 wherein the bits of said first set of bits are spaced apart by one full chain pitch and the bits of said second set of bits are located between said bits of said first set of bits and spaced one-half pitch therefrom.

3. An endless cutter bar chain utilized on a cutter bar assembly for cutting a deep kerf in a mineral vein comprising: a plurality of spaced block links; at least one connecting link disposed intermediate each adjacent pair of block links; a first set of bits in a first bit pattern mounted on said block links; a second set of bits in a second bit pattern mounted on said connecting links; and one of said bit patterns being located to cut a kerf portion below the kerf portion cut by the other of said bit patterns.

4. A cutter chain as specified in claim 3 wherein only one of said connecting links are disposed intermediate each adjacent pair of block links and said one of said bit patterns is said first bit pattern.

5. A cutter chain as specified in claim 3 additionally comprising a material conveying means on certain of said links.

6. A cutter chain as specified in claim 5 wherein said conveying means is a laterally extending lug portion on each block link.

7. A cutter chain as specified in claim 3 additionally comprising a kerf sweeping means on certain of said links for continuously clearing broken mineral out of a kerf formed by said chain during mineral cutting operation thereof.

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