US3752534A - Coal cutting using more teeth for sumping than shearing - Google Patents

Abstract

A method for cutting a deep kerf in a vein of frangible mineral whereby a cutter bar is sumped into a mineral vein at a rate to cut by all bits in a sequential plurality of bit patterns and then the cutter bar is traversed to shear at a rate such that only a portion of the bits in a sequential plurality of bit patterns are cutting to extend the kerf.

Description

United States Patent [1 1 Rollins et al.

' Aug. 14, 1973 COAL CUTTING USING MORE TEETH FOR SUMPING THAN SHEARING [76] Inventors: Lester G. Rollins, 650 Forest Ln.;

Glenn S. McDowell, 601 Wiley Ave., both of Franklin, Pa. 16323 [22] Filed: June 29, 1971 [21] App]. No.: 158,037

521 u.s.c|....'. 299/10, 299/84 51 im. 01. l B 21c 25/34 [58] Field of Search ..2'99/1o-"1"8,824538-90; 175/89, 90

[56] References Cited UNITED STATES PATENTS 3,307,875 3/1967 McDowell 299/10 1,469,132 9/1932 Wilson 299/83 3,180,687 4/1965 l-lorton..... 2,832,579 4/1958 Barrett 54,833 5/1866 Locke et ll 299/10 Primary Examiner-Emest R. Purser Att0meyE. Wallace Breisch ABSTRACT A method for cutting a deep kerf in a vein of frangible mineral whereby a cutter bar is sumped into a mineral vein at a rate to cut by all bits in a sequential plurality of bit pattems and then the cutter bar is traversed to shear at a rate such that only a portion of the bits in a sequential plurality of bit patterns are cutting to extend the kerf.

4 Claims, 7 Drawing Figures PAIENIEmumma 3.752.534 sum 1 0F 2 LESTER a. ROLL/NS a GLENN s. MCDOWELL J: INVENTORS COAL CUTTING USING MORE TEETH FOR SUMPING THAN SHEARING BACKGROUND OF THE INVENTION Cutter bar chains presently in use are operative in making a penetrating cut (deep kerl) 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 penetrate the 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 hit 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 undersirable 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 hit is higher during sumping due to the small number of bits engaged with the coal 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 cutterchairs 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 a primary and secondary bit arrangement for coal cutting, however, since all of the bits of the Barrett device are spaced at the standard cutter bit pitch no more than the normal number of cutter bits is present in the Barrett device and the advantages inherent in applicants 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 cutter bits 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 3--3 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;

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 suchas I8 and 19 (FIGS. 1, 2 and 4) and secondary bit blocks 20 carrying secondary cutter bits S such as 21 and22 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 secondarylinks .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 20 in place of the ordinary non-cutting connector links of prior art chains. Thus chain 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 unitchain 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 not cause 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 bits in the direction of travel, if the chain speed is 700 feet per minute there will be a time one-twentieth 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 1/16 inches. With the standard bit extension (free height above the bit block) of l-3/4 inches it can be seen that the above mentioned 18 feet per second sumping speed is approximately the maximum alowable 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 five-eighths 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 nine twenty-fifths inches per pitch, which on a 7 pitch pattern would figure out to be over 2-1/2 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 ll/4 inches penetration per pattern for each type of bit in sumping which on a l-3/4 inches bit extension gives us optimum penetration at 36 feet per minute or more and is even farther removed from in terference 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 optimm 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-inch 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 one-twentieth of a second for a chain travel of one pitch or nine-twentieths of a second per pattern and at a shearing rate of 6 feet per minute penetration would equal approximately nine-sixteenths inch penetration per pattern. Since this penetration is far below the optimum of l-3/4 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 1 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 fmes 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 [imitative upon the applica' tion 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 2-3/4 inches from the centerline of the chain to produce a sweep area 5 -l/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 l-l/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 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 ad vance 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 one-half 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 five-eighths 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 buildup 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 example can 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 pres ence of both the cutter blocks on the secondary links and particularly of the lugs 26 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 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.

I 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 percent 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:

l. A method of cutting a slot in a mineral vein by an elongated cutter bar having a cutter chain carrying bits arranged in a sequential plurality of bit patterns and movable in an orbital path around an elongated supporting means at a selected orbital velocity comprising: sumping such a cutter bar while the cutter chain is orbiting at a selected velocity into a mineral vein at a rate to cut a portion of such a slot by all bits in each sequential plurality of bit patterns; moving such a cutter bar transversely of the longitudinal axis thereof, while said cutter chain is orbiting at said selected velocity, at a rate to transversely extend such a portion by a plurality of bits in each sequential plurality of bit patterns with such plurality of bits being less than the number of bits in a bit pattern.

2. A method as specified in claim 1 wherein all of said bits in a bit pattern is at least twice as great-as said plurality of said bits in a bit pattern.

3. A method as specified in claim 1 wherein the rate of sumping said cutter bar is greater than the rate of the transverse movement of said cutter bar.

4. A method as specified in claim 1 additionally comprising simultaneously with said moving said cutter bar transversely conveying the mineral cuttings from said slot at a rate to prevent build up of such mineral cuttings in said slot.

l l II i l a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 52', 4 Dated August 14 1973 hwentofls) LESTER G. ROLLINS a GLENN 3. MC DOWELL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column claims 1 and 2 should read as follows:

1. A method of cutting a slot in a mineral vein by an elongated cutter bar having a cutter chain carrying bits arranged in asequential pluralityof bit patterns and movable in an orbital path around an elongated supporting means at a selected orbitalvelocity comprising: sumping such a cutter bar while the cutter chain is orbiting at a selected velocity into a mineral vein at a rate to cut a portionof such a slot by all bits in each sequential plurality of bit patterns; moving such a cutter bar transversely of the longitudinal axis thereof, awhile said cutter chain is orbiting at said selected velocity,

at a rate to tra'nsversely extend such a portion by a plurality of bits in said each sequential plurality of bit patterns with i said plurality of bits being less than the number ofbits in said each sequential plurality of bit patterns.

'2. A method as specified inclaim 1 wherein said all bits in each sequential plurality of bit patterns is substantially twice as great as said plurality of bits. i

Signed and I sealed this 5 y Of 97M:-

(SEAL) Attest:

113mm?) I LF E Q J c. MARSHALL DANN Attestlng 9 Commissioner of Patents FORM PC3-1050 (10-69) usccwmpbc 5037 4259 u.s. covsnuumr rnm'nueorrlcs: I!" man-3:1,

Claims (4)

1. A method of cutting a slot in a mineral vein by an elongated cutter bar having a cutter chain carrying bits arranged in a sequential plurality of bit patterns and movable in an orbital path around an elongated supporting means at a selected orbital velocity comprising: sumping such a cutter bar while the cutter chain is orbiting at a selected velocity into a mineral vein at a rate to cut a portion of such a slot by all bits in each sequential plurality of bit patterns; moving such a cutter bar transversely oF the longitudinal axis thereof, while said cutter chain is orbiting at said selected velocity, at a rate to transversely extend such a portion by a plurality of bits in each sequential plurality of bit patterns with such plurality of bits being less than the number of bits in a bit pattern.

2. A method as specified in claim 1 wherein all of said bits in a bit pattern is at least twice as great as said plurality of said bits in a bit pattern.

3. A method as specified in claim 1 wherein the rate of sumping said cutter bar is greater than the rate of the transverse movement of said cutter bar.

4. A method as specified in claim 1 additionally comprising simultaneously with said moving said cutter bar transversely conveying the mineral cuttings from said slot at a rate to prevent build up of such mineral cuttings in said slot.

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