Universal ripper miner

A universal ripper miner used to cut, collect and transfer material from an underground mine working face includes a cutter head that is vertically movable in an arcuate cutting cycle by means of drive members, such as hydraulically actuated pistons. The cutter head may support a circular cutter bit having a circular cutting edge that may be indexed to incrementally expose a fresh cutting edge. An automatic indexing system is disclosed wherein indexing occurs by means of a worm gear and indexing lever mechanism. The invention also contemplates a bi-directional bit holder enabling cutting to occur in both the upstroke and the downstroke cutting cycle. Another feature of the invention discloses multiple bits arranged in an in-line, radially staggered pattern, or a side-by-side pattern to increase the mining capacity in each cutting cycle. An on-board resharpening system is also disclosed for resharpening the cutting edge at the end of cutting stroke position. The aforementioned improvement features may be used either singly, or in any proposed combination with each other.

TECHNICAL FIELD 
The present invention relates generally to excavation systems which can 
cut, collect and transfer the cut material and, more particularly, to 
improvements to ripper miners relating to single and bi-directional cutter 
bits, multiple bits and on-board bit sharpening. 
BACKGROUND ART 
FIG. 1A is an illustration of our universal ripper miner disclosed in U.S. 
Pat. No. 4,501,448 to Roger J. Morrell and David A. Larson, assigned to 
the United States of America as represented by the Secretary of the 
Interior. Our prior ripper miner machine includes two hydraulically 
operated pistons 201 and 202 with their movable and extendable piston rods 
203 an 204, respectively, being attached to the cutter head 206. At one 
end, the pistons are pivotally attached by roller shafts 220 and 221 to 
the machine's main frame 205 and at the other end to the movable cutter 
head by roller shafts 222 and 223. A center shaft 207 allows the cutter 
head 206 with its drag bit 208 to rotate in an arcuate path as the 
attached two piston rods are reciprocated by a power source within their 
respective movable pistons. The cutter head rotates in an arcuate vertical 
path through approximately 185.degree. during its cutting swing or cycle. 
As the rock is cut loose from the face by drag bit 208, the cuttings are 
continuously collected in the hopper 209 section of the cutter head which 
moves in unison with the drag bit. At the end of the cutting swing, an 
opening 210 in the hopper allows the cuttings to drop through chute 211 
into an external bin 212. From this bin, the cuttings are fed onto a 
conventional conveyor 213 and moved to the end of the machine and then 
into the mine haulage system. After each vertical cutting upswing, the bit 
is returned to its original starting position. The main frame 205 and 
cutter head are then rotated horizontally by the rotary table 214 into 
position for the next cutting swing. The roof jack assembly 215 pushes 
against the roof to lock the machine firmly in place during the cutting 
operation. After the bit has cut across the entire face of the heading, 
the main frame and cutting head are advanced forward (i.e., to the left in 
FIG. 1A) for the next cutting cycle by the two advance pistons 225 and 
226. These pistons slide the entire machine, which is mounted to the base 
plate 219, along the walking beams 217 and 218. After three to four 
advance cycles, the machine is raised up off of the ground by jacks (not 
shown) the advanced pistons retracted, and the machine is ready for 
another series of cutting advances at a new location to the right or left 
of its previous cutting cycle. Thus, it is to be noted that the machine 
advances forward between a series of individual cutting cycles and the 
machine is rotated horizontally after each of its individual cutting 
cycles or swings. 
The drag cutter 208 consists of a bit insert and a bit holder, the bit 
holder resisting the cutting forces and holding the bit insert in place. 
The bit insert does the actual rock cutting. It is held in place on the 
holder by bolting, or by clamping or brazing. The bit insert has only one 
cutting edge requiring frequent resharpening, depending upon the hardness 
of rock being mined, causing down time during resharpening. 
It is accordingly one object of the present invention to provide a cutter 
bit for mining machines generally, and the ripper miner disclosed above in 
particular, that has multiple cutting edges. 
Another object of the invention is to provide the multiple cutting edge bit 
with a capability of being easily and quickly indexed upon the bit holder 
to expose a fresh cutting edge. 
Another object of the invention is to provide a bit indexing system that 
automatically indexes the bit to expose a fresh cutting edge without 
manual intervention. 
As mentioned above, our prior universal ripper miner disclosed in FIG. 1A 
is only capable of cutting operation in the upstroke. Thereby, valuable 
mining time is lost each time the cutter head 206 reaches its upper end of 
cutting stroke through the period it is lowered by pistons 201 and 202 to 
its bottommost position where it is repositioned to execute the next 
upward cutting stroke. 
Another object of the present invention is to provide a cutter head of a 
mining machine with a bi-directional cutter enabling the machine to mine 
rock in both upward and downward cutting strokes. 
Another object of the invention is to provide a mining machine in general, 
and our ripper miner disclosed above in particular, with a bi-directional 
cutter that mines rock in both the upstroke and the downstroke and which 
has the further capability of utilizing a cutting bit with multiple 
cutting edges. 
Still a further object of the present invention is to provide a cutter head 
with a multi-holder arrangement allowing a plurality of bits to be mounted 
upon the cutter head to improve mining efficiency. 
Still a further object of the invention is to provide an on-board bit 
resharpening system that is capable of sharpening the cutter bit(s) at the 
end of an upward or downward cutting cycle. 
DISCLOSURE OF THE INVENTION 
A ripper miner, in accordance with the invention, comprises a cutter head 
having a cyclical cutting cycle traversing an arcuate angle in a generally 
vertical plane. The cutter head is mounted to a machine frame and means is 
provided for moving the cutter head with respect to the frame. 
In accordance with one improvement feature of the present invention, there 
is provided a circular cutting bit having a circular cutting edge movable, 
about a central axis of rotation, to selectively expose a fresh cutting 
edge for improved cutting efficiency. In one embodiment, the circular 
cutter is formed with a bottom cylindrical recess receiving a cylindrical 
mounting hub formed in an upper surface of the bit holder. Thusly 
received, a hold down bolt secures the circular cutter to the bit holder. 
Loosening of the bolt permits rotation of the circular bit to expose the 
fresh edge. 
In another embodiment, the circular cutter may be provided with an 
automatic indexing system for partially rotating the circular bit to 
expose a fresh cutting edge. In this embodiment, the circular bit is 
secured to an indexing shaft with a hold down bolt engaging the upper end 
of the shaft projecting upwardly from the mounting hub. A lower end of the 
indexing shaft is journalled within the bit holder and includes a worm 
gear in meshing contact with a worm extending transversely within a cavity 
formed within the bit holder. One end of the worm extends through a side 
wall of the bit holder and is connected to an indexing lever, via a 
ratchet and spring return mechanism. The indexing lever extends along a 
side wall of the cutter head to engage a stationary member on the machine 
frame as the cutter head approaches an end of cutting stroke position. 
Such engagement causes the indexing lever to rotate the worm screw through 
a predetermined angular interval, causing corresponding rotation of the 
circular cutting edge through the worm gear and indexing shaft. 
A partial circular cutter bit is also disclosed wherein the bit is formed 
with a semicircular cutting edge. The bit body is secured to the bit 
holder with plural hold down bolts. 
In accordance with another improvement feature of the present invention, 
the cutting head may be provided with a bi-directional bit holder 
pivotally secured to side walls of the cutter head and equipped with upper 
and lower bits engageable with a mining surface in the upstroke and 
downstroke, respectively, of the cutter head. In addition to the 
conventional opening in the cutter head located upwardly adjacent the bit 
holder to receiving cuttings in the upstroke, there is provided a second 
opening located downwardly adjacent the bit holder to receive cuttings in 
the downstroke. A deflector scraper may be pivotally mounted to the cutter 
head side walls to extend beneath the downstroke opening, ensuring that 
cuttings generated in the downstroke are directed into the cutter head. 
In accordance with another improvement feature of the present invention, 
multiple bit holders may be mounted upon the cutter head to provide a 
plurality of bits that may be arranged in various configurations. In one 
such configuration, a plurality of bits are arranged in an in-line 
vertically spaced pattern with their bit cutting edges being located in 
progressively radially outward locations so that the next in-line bit cuts 
progressively deeper into the rock face during the upstroke or downstroke. 
The bits may also be arranged in a side-by-side pattern to increase the 
effective width of the cut. 
In an alternate embodiment, a single bit holder may be used to mount a 
plurality of bits in individual bit holders in a desired pattern to suit 
rock conditions. The single, multi-bit holder may include a pair of 
support side walls to which the individual bit holders are mounted. 
In accordance with yet another feature of the present invention, there is 
disclosed a bit resharpening system that comprises a motor driven grinding 
wheel mounted to the machine frame and equipped with a feed mechanism 
adapted to advance the grinding wheel into grinding contact with the bit 
cutting edge as the bit holder reaches an end of cutting stroke position. 
The improvement features discussed above may be used separately, together, 
or in any combination with each other. 
It will be readily seen by one of ordinary skill in the art that the 
present invention fulfills all of the objects set forth above. After 
reading the foregoing specification, one of ordinary skill will be able to 
effect various changes, substitutions of equivalents and various other 
aspects of the invention as broadly disclosed herein. It is therefore 
intended that the protection granted hereon be limited only by the 
definition contained in the appended claims and equivalents thereof.

BEST MODE FOR CARRYING OUT THE INVENTION 
The present invention is directed towards multiple improvements made to the 
universal ripper miner disclosed in our prior U.S. Pat. No. 4,501,448 
issued to Roger J. Morrell and David A. Larson on Feb. 26, 1985, the 
disclosure of which is hereby expressly incorporated by reference herein. 
The improvements according to the present invention discussed infra, 
relate to improved cutting bits mounted to a cutter head 10 of the type 
disclosed in our aforesaid '448 patent. The five improvements comprise the 
structure and use of a circular cutter, bit indexing, bi-directional 
cutters, multiple cutters and on-board bit resharpening. The five 
improvements can be used singly, altogether, or in any desired combination 
thereof. The use of these improvements does not change the basic operation 
of the universal ripper miner disclosed in the '448 patent and, if 
desired, these improvements may be incorporated into other types of 
excavating machines as will occur to one of ordinary skill in the art 
based upon a review of the present disclosure. 
CIRCULAR CUTTER 
The ripper miner (not shown) of the type disclosed in our '448 patent and 
the cutter head 10 thereof may be provided with a circular cutter 12 of 
the type depicted in FIGS. 1-3. Circular cutter 12 includes a bit 12' 
formed with a circular shaped cutting edge 12a (in the top plan view of 
FIG. 3) formed with appropriate rake and clearance angles 14 and 16 and of 
a material that has the ability to cut rock anywhere along its circular 
edge. More specifically, the circular bit 12' can have a positive, zero or 
negative rake angle 14 and can have a full 360.degree. circular edge or a 
partial circular edge 18 as depicted in FIGS. 4, 5, 6 and 7. The improved 
cutting efficiency of these circular edges (i.e., full or partial) will be 
realized in both cases. Circular cutter bits 12 can be constructed of heat 
treated tool steel and can have a cutting edge composed of a tungsten 
carbide or other hard material. The cutters 12 can be made in a variety of 
sizes, with different attack, rake and clearance angles to suit any 
cutting condition. 
More specifically, the circular cutter bit 12' is formed with cylindrical 
top and bottom recesses 20 and 22 in upper and lower surfaces thereof, 
respectively. The top cylindrical central recess receives a hold down bolt 
24 and washer 26 for securing the circular cutter 12 to the bit holder 28 
by interfitting the bottom recess 22 with a cylindrical mounting hub 30 
projecting upward from the bit holder 28. An outer annular surface 32 of 
the circular cutter 12 is of frustoconical shape that is supported on the 
cutter bit holder 28 by mounting hub 30. The surfaces 32,34 advantageously 
permit rotation of the circular bit 12 on the mounting hub 30 upon 
loosening of the hold down bolt 24 to expose a fresh cutting edge. 
Circular cutter 12 provides several important advantages. One advantage is 
the improved cutting efficiency which tests have shown to be up to twice 
as energy efficient as conventional cutters. Another important advantage 
is the continuous cutting edge 12a that the circular bit 12' provides, 
allowing the bit to be incrementally rotated through 360.degree. to 
incrementally expose fresh cutting edges before resharpening is required. 
This rotation can be done manually by loosening the hold down bolt 24 as 
described above or by a cutter bit indexing system of the type described 
below. 
As mentioned above, the hub 30 may be integrally formed in an upper surface 
of the bit holder 28, or welded or otherwise secured thereto. The hub 30 
serves both to secure the bit 12 and to provide rotation or indexing 
motion about its central longitudinal axis 36. 
FIGS. 4-7 are illustrations of a partial circular bit 40 having a partial 
circular cutting edge 18 (in top plan view of FIG. 6) flushly mounted 
within an upper recess 42 of the bit holder 44 by means of plural hold 
down bolts 46. The attack angle of both the full and partial circular bits 
are respectively defined by the mounting hub 30 (FIG. 1) or bottom seating 
surface 42 (FIG. 4) of the bit holders 28,44. 
BIT INDEXING 
The ripper miner such as disclosed in our '448 patent can be provided with 
bit indexing which is the ability to rotate the bit 12 in order to keep a 
sharp cutting edge in contact with the rock. As the bit 12 cuts rock, its 
edge 12a gradually dulls which adversely affects energy efficiency, bit 
forces and dust generation. The greatest bit wear occurs primarily at the 
point of the cutting edge 12a in deepest contact with the rock. The 
remainder of the cutting edge is relatively unworn. On a bit with several 
cutting edges or continuous cutting edges, it would be desirable to rotate 
the bit a small amount to present a sharp cutting edge to the rock. After 
all cutting edges are worn, the bit can be resharpened. 
The full circular bit 12 of FIGS. 1-3 may have its continuous cutting edge 
12a progressively exposed by indexing the bit around the mounting hub 
central longitudinal axis 36 either manually or automatically. For manual 
indexing, the central hold down bolt 24 is loosened and the bit 12 is 
rotated about the mounting hub 30 while in full seating engagement 
therewith to expose a fresh sharp cutting edge. The hold down bolt 24 is 
then re-tightened. This type of manual indexing occurs where the need for 
resharpening is infrequent. 
FIGS. 8-10 are illustrations of an automatic bit indexing system 50 that is 
preferred for use when the requirement for bit indexing is frequent. With 
reference to FIG. 10, the automatic bit indexing system 50 comprises a 
gear drive 52 including an indexing shaft 54 extending through the 
mounting hub 30 to which shaft the circular bit 12 is secured with the 
hold down bolt 24. A worm gear 56 is mounted to a lower end portion 57 of 
the indexing shaft 54 within an interior housing cavity 60 located within 
the bit holder 28. The worm gear 56 meshes with a worm screw 62 journalled 
in side housing portions 64 of the bit holder 28 (FIG. 9) and is rotated 
by an indexing lever 66 secured to one end of the worm screw projecting 
outwardly from the bit holder 28 via a rachet and spring return mechanism 
70. The indexing lever 66 projects away from the bit 12 along the cutter 
head 10. 
The automatic bit indexing system 50 is adapted to operate automatically as 
the bit 12 reaches the end of a cut and is out of contact with the rock 
surface. For example, as depicted in FIG. 8, the indexing lever 66 may be 
activated by contact with a stationary member 72 on the machine frame 74 
of the ripper 76 with such contact causing the lever to rotate about the 
longitudinal axis 78 of the worm screw 62 through a predetermined angular 
interval with co-rotation of the worm screw causing corresponding rotation 
of both the worm gear 56 and indexing shaft 54 and thereby the bit itself. 
The indexing lever 66 resets automatically from position A to position B 
as the cutter head 10 begins its cut by rotating about the center shaft 80 
of the ripper, i.e., as the indexing lever moves out of contact with the 
stationary member 72. 
It is within the scope of this invention to reset the indexing or ratchet 
lever 66 with, for example, weights. Also, the gear drive 52 can be 
powered independently by a separate motor providing rotative torque to the 
worm screw 62 with automatic operation through a series of limit switches, 
or manual operation by an operator actuating the motor. 
The manual and automatic bit indexing systems advantageously save valuable 
production time by reducing the time required to change worn bits. The 
indexing systems also ensure that a sharp bit is available for cutting. 
While the design of the indexable bit is subject to modification (i.e., it 
need not necessarily be a circular bit) the bit nonetheless must have 
multiple cutting edges. These bits must be resharpened when all of their 
cutting edges are worn, using either conventional sharpening methods or 
the automatic sharpening system discussed infra. 
BI-DIRECTIONAL CUTTER 
FIGS. 11-14 are illustrations of bi-directional cutters that can be mounted 
to the ripper miner to provide a capability of cutting both on the 
upstroke (as in the '448 patent) and the downstroke to effectively double 
the production rate of the ripper miner by eliminating the non-productive 
time associated with the non-cutting downstroke. As depicted in FIG. 12, 
an opening 85 is provided in the cutter head 10 above the bit arrangement 
87 to receive cuttings generated during the upstroke and such an opening 
is disclosed in the universal ripper miner of the '448 patent. Preferably, 
a second opening 90 is provided in the cutter head below the bit 
arrangement 87 to receive cuttings generated during the downstroke. To 
direct the cuttings into the head 10, a deflector-scraper 92 may be 
pivotally mounted at a lower end of the opening 90 with a pivot shaft 94 
extending between housing side walls 96 of the cutter head. The 
deflector-scraper 92 is arranged so that its scraping edge 98 rests 
against the rock surface 100 being mined in the downstroke to direct 
cuttings into the opening 90. Preferably, the deflector-scraper blade 92 
is arranged so that its scraper edge 98 traverses an arcuate path that is 
located radially inwardly of the arcuate path circumscribed by the bits. 
In this manner, contact between scraper edge 98 and the wall being cut by 
the bit arrangement 87 in the upstroke is avoided. 
The bi-directional cutter 87 may be either pivoted or non-pivoted with 
single or double bit inserts. The pivoted type with a single bit 
arrangement is depicted in FIG. 11 and the pivoted type with a double bit 
arrangement is depicted in FIGS. 12 and 13. In both arrangements, the bit 
holder 102 has an inwardly extending portion 104 between and pivotally 
secured to the cutter head housing side walls 96 by means of a retainer 
pin 106. The holder 102 projects outwardly from the side walls 96 through 
an opening 108 that limits pivotal movement in the upstroke and downstroke 
about the pivot pin 106. 
More specifically, with reference to the single bit embodiment of FIG. 11, 
the inwardly extending portion of holder bar 10 of a height H1 that is 
less than the corresponding height H2 of the opening 108 formed by edges 
of the side walls through which the holder extends. The upper and lower 
edges 110 and 112 define stop surfaces against which corresponding upper 
and lower surfaces 104a and 104b of portion 104 of the holder bar 102 abut 
in the upstroke and downstroke respectively. The width of the opening in 
the cutter head 10 only slightly exceeds the corresponding width of 
portion 104 of the holder bar 102 to provide guiding surfaces maintaining 
the movement of the holder in a vertical plane about the retainer pin 106. 
The bit holder 102 includes a dirt shield 114. 
The single bit is schematically depicted in FIG. 11 and may obviously take 
various forms, such as the full circular bit configuration of FIGS. 1-3, 
or the partial circular bit of FIGS. 4-7. 
In the FIG. 12 embodiment of the double bit bi-directional cutter, a 
U-shaped receiver 115 welded to the cutter head housing side walls 96 has 
upper and lower interior contact surfaces 117 and 119 limiting the range 
of movement of the bit holder 120 in the upstroke and downstroke 
positions. The holder 120 includes a collar portion 122 substantially 
corresponding to the upwardly projecting portion 28a,44a of bit holders 
28,44 against which portion either the partial or full circular bits can 
abut as per FIGS. 1 or 4. Although a pair of upper and lower partial 
circular cutter bits are depicted in FIGS. 12-14, it will be understood 
that the full circular cutter bits of FIGS. 1-3 may be utilized in either 
the FIG. 11 or 12 embodiment of the invention. 
The bit inserts used in the above-identified bi-directional cutters can be 
made in a variety of shapes and sizes and with any desired rake or 
clearance angle. These bits can be attached to the bit holder by the usual 
bolts or clamps and, in the case of the double bit arrangement, either bit 
can be replaced independent of the other. The bi-directional cutters of 
FIGS. 11-14 may be used in conjunction with any other (or all) of the 
other improvements identified herein. 
MULTIPLE CUTTERS 
The ripper miner may be equipped with more than one cutter bit to either 
improve productivity or maintain productivity in very hard rock. The 
number, shape and mounting pattern of these cutter bits can vary to suit 
conditions, as will occur to one of ordinary skill in the art upon review 
of the following. However, the cutters are preferably mounted in such a 
way as to produce a full depth of cut in a single pass. Thereby, the 
operation of the ripper miner is the same irrespective of whether a single 
cutter or multiple cutters are used. 
If sufficient power is available to the cutter head, then multiple cutters 
can be used to increase the productivity of the ripper miner. This 
situation will normally occur in softer, non-abrasive type rocks. In hard 
rock, it may not be possible to operate a cutter at full depth due to the 
presence of high cutter forces that could cause breakage or unacceptable 
high wear of the cutter bits. In this case, several cutters, each taking a 
portion of the cutter load, will facilitate maintenance of full production 
while keeping the cutters from being overloaded or damaged. 
Multiple cutters may be installed on the ripper miner in several different 
ways. With reference to FIGS. 15 and 17, for example, and in accordance 
with one embodiment of the invention, the cutter head includes a plurality 
of similar bit holders 130 that may be bolted at 131 to reinforced 
mountings 132 in the cutter head 10 in vertically spaced, in-line 
relationship to each other with an opening 134 formed in the cutter head 
side walls 96 above each bit to receive the cuttings. Preferably, the bits 
12 are arranged in line with bit cutting edges 12a being located in 
progressively radially outward locations so that the next in-line bit 
(e.g., 12') cuts progressively deeper into the rock. These radially 
displayed locations are apparent from FIGS. 15 and 17. The bits 12 can 
also be arranged in a side by side pattern as depicted in FIG. 16 to 
increase the effective width of the cut. In the side by side arrangement, 
each bit 12 preferably has the same depth of cut. The bits may also be 
arranged in an echelon pattern, a V-shaped pattern, etc., as will occur to 
one of ordinary skill based upon a review of this disclosure. The bits can 
also be replaced independently of one another and can be resharpened as 
required. 
The bit holder 130 may also take the form of bit holders 28 or 44 depicted 
in FIGS. 1-7. 
In an alternative embodiment depicted in FIGS. 18 and 19, a single bit 
holder 140 may be used to mount a plurality of bits 12 in individual bit 
holders 142 (which may be bit holders 28 or 44) in a desired pattern to 
suit rock conditions. The single, multi-bit holder 140 of FIG. 18 contains 
a plurality of bits mounted in the in-line pattern of FIGS. 15 and 17. The 
individual holders 142 are bolted at 143 to a pair of support walls 144 
which in turn are secured to side walls 96 of the cutter head 10 with 
bolts 146. The individual bits 12 are secured to their respective holders 
142 with bolts 24 in either the manner described above or by the use of 
fastening means that will easily occur to one of ordinary skill. 
ON-BOARD RESHARPENING OF BITS 
The ripper miner has the ability to resharpen its bits without removing 
them from the machine. The ability to keep the bits sharp is important to 
the success of the cutting method. Because the ripper miner has one, or at 
the most a few bits, it becomes a practical matter to sharpen these bits. 
The benefits of a sharp cutting bit are many and important. These include 
less cutting forces acting on the bit, greater energy efficiency, less 
dust generation, and reduced time required for bit changes. The ability to 
resharpen in hard rock mining is even more important as bits dull rapidly 
and only sharp bits are able to cut hard rock effectively. 
A preferred method of resharpening is shown in FIGS. 20-22 although the 
exact mechanism can vary somewhat. The primary features are a grinding 
wheel 150 which has the correct angle and shape and is the appropriate 
composition for grinding tool steel, tungsten carbide, or other bit 
materials. The grinding wheel 150 is rotated at high speed by an 
appropriate motor 152 and jets 154 of cooling and cleaning liquid 
preferably to keep the bit clean and cool during sharpening. FIGS. 21 and 
22 illustrate resharpening of a single bit 12 of partial circular shape, 
however, the method can be used for multiple bits, full circular bits and 
for bits of different shapes. 
The resharpening process will normally take place at the end of, or at the 
start of, the cutting stroke when the bit 12 is out of contact with the 
rock surface. At this point, the resharpening assembly which is mounted on 
the frame 74 of the mining machine is moved into the correct orientation 
to the bit and the rotating grinding wheel 150 is moved across the 
clearance edge 12a of the bit. This process removes the flat surface on 
the clearance side of the bit and restores the bit to its original 
sharpness. Normally, only a few hundredths of an inch will be removed 
during each resharpening cycle although this can be adjusted to suit wear 
conditions. The bits can be resharpened until they can no longer cut 
clearance for the bit holder. Depending on the bit and holder design, this 
can range up to several inches. The resharpening process is expected to 
take only a few seconds to accomplish and can be less frequently and as 
desired, e.g., at the end of each cutting stroke. 
The resharpening assembly 155 comprises a grinding wheel 150 with its 
rotation motor 152, a feed mechanism schematically shown at 154a which 
sets the amount to be removed during each pass, and a mechanism containing 
guides 156 (which may be mounted to the motor) to move the wheel across 
the bit 12 in the desired path. Details of this assembly, the number of 
such assemblies and their locations may vary to suit the number and type 
of bits used and the configuration of the ripper miner. 
COMPOSITE CUTTING SYSTEM 
The improvement features discussed supra may be used separately, together, 
or in any combination with each other. FIG. 23 is an illustration of four 
improvements used together in a single cutting system. For example, there 
are provided three individual bit holders 160, 165 and 170 with bit 
holders 160 and 170 being substantially identical to each other with a 
full circular bit 12 and the automatic indexing system 50 depicted in 
FIGS. 8-10. The lower circular bit on bit holder 170 is mounted to cut 
material in the downstroke while the upper full circular bit in holder 160 
cuts only in the upstroke. The bit holders 160 and 170 are stationarily 
mounted to a frame arrangement 175 that may be bolted at 177 between side 
walls 96 of the cutter head 10. 
The intermediate holder 165 incorporates top and bottom full circular bits 
in the bi-directional cutting arrangement analogous to the FIG. 12 
embodiment. The intermediate holder 165 also includes an automatic 
indexing system 50 of the type disclosed in FIGS. 8-10. 
The composite cutting system of FIG. 23 is an illustration of but one way 
to combine the individual improvement features but are not intended to 
limit the scope of the present invention. The combinations disclosed above 
and obvious variations thereof may be used to achieve the desired 
performance in virtually any cutting conditions. 
From the foregoing descriptions of the preferred embodiments of our 
improvements to the universal ripper miner such as disclosed in our '448 
patent, it should be clear that its operation contemplates several types 
of improvements designed to be used with our universal ripper miner 
without requiring any change in its basic operating principles. It will 
also occur to one of ordinary skill in the art that the individual 
improvements disclosed herein, either individually or in any desired 
combination, may be incorporated into other types of mining machines.