Patent Application
20090256413
The present invention pertains to a cutting bit for impingement of earth strata. More specifically, the present invention pertains to a cutting bit for impingement of earth strata wherein the cutting bit, which exhibits excellent wear resistance and impact resistance, encounters less resistance and exhibits better rotational properties and longer useful tool life than prior cutting bits.
Heretofore, cutting bits (e.g., rotatable cutting bits) used for mining, trenching and construction applications including a road planing applications comprise an elongate steel cutting bit body. Such cutting bits also comprise a hard (e.g., cemented (cobalt) tungsten carbide) insert affixed to the axial forward end of the cutting bit body. The bore of a holder (or block) retains (in a rotatable fashion or in a non-rotatable fashion) the cutting bit at its axial rearward end. During operation such as, for example, in a road planning application, a driven drum carries a plurality of holders, each of which in turn, carries a cutting bit. The drum drives the cutting bit into impingement with the earth strata (e.g., asphaltic material of a highway) thereby breaking or disintegrating the earth strata into pieces. Since the cutting bit, and especially the cutting bit body, experience severe forces, it is very desirable that the cutting bit body possess optimum properties (e.g., wear resistance and impact resistance) suitable to withstand such a severe operating environment for an acceptable duration.
Heretofore, the typical cutting bit body used in a cutting bit for mining and construction applications has an elongate steel body that presents a relatively wide collar wherein the collar is the portion of the cutting bit body that has the greatest transverse dimension. In the case of a cutting bit with a cutting bit body of a generally cylindrical geometry, the collar is the portion that has the greatest diameter. The collar is relatively wide because the cutting bit body must have a sufficient amount of strength (or impact resistance) and wear resistance.
While the cutting bits that have the wide collar function in a satisfactory fashion, there is a drawback with these cutting bits. This drawback is that the wide collar presents a greater volume or mass of material of the cutting bit that must pass through the earth strata. This results in an increase in the resistance the cutting bit encounters upon impingement of the earth strata. Such an increase in resistance results in an increase in energy necessary to break up the earth strata, which increases fuel consumption and overall operating costs, as well as decreases or reduces overall operational efficiency for the specific application. In the case of a road planing bit, the bit impinges roadway materials such as, for example, asphaltic material. Thus, it would be highly desirable to provide an improved cutting bit that does not encounter as much resistance upon impingement of the earth strata as earlier cutting bits. By providing such a cutting bit, the fuel consumption and overall operating costs will decrease and the overall operational efficiency will increase.
As mentioned above, a cutting bit with a wider profile encounters more resistance upon impingement of the earth strata. By encountering more resistance, the cutting bit exhibits a higher rate of wear, which, in turn, causes the cutting bit to become blunter thereby reducing the overall cutting efficiency. An operator must replace more often cutting bits that experience a higher rate of wear as opposed to cutting bits that experience a lower rate of wear. In the case of a road planing application, and there can be a great amount of time spent to change out an entire set of road planing bits on a road planing drum. Thus, it would be highly desirable to provide a cutting bit that exhibits a slimmer profile thereby encountering less resistance upon impingement of the earth strata. Such a cutting bit with a slimmer profile would exhibit a lower rate of wear thereby taking a greater amount of time to become blunter, and hence, increase the overall operational efficiency of the cutting or mining or road planing operation in.
In a coal mining operation, it is most desirable if the coal is broken in to larger pieces or chunks. By doing so, fewer small particulates and fines such as, for example, coal dust, are generated during the coal mining operation. This is a desirable result since there is concern over the excessive generation of small particulates such as coal dust. In the case where the cutting bit presents a wider profile or geometry, there is the tendency for the cutting bit to pulverize the coal upon impingement, which generates small particulates. The use of a cutting bit with a wider profile results in a higher incidence of generating small particulates due to the increased resistance of the cutting bit impinging the substrate (e.g., vein of coal). Therefore, it would be highly desirable to provide an improved cutting bit that upon impingement of the earth strata (or substrate) does not result in the excessive generation of small particulates and fines such as, for example, coal dust. Further, it would be highly desirable to provide such an improved cutting bit that actually reduces the amount of small particulates and fines generated during a coal mining operation.
In the process of a cutting bit impinging the earth strata, it is desirable that the cutting bit exhibit acceptable strength or impact resistance and wear resistance. Impact resistance is desirable because the earth strata can be inconsistent in that it may contain hard anomalies. For example, in a mining operation the earth strata may contain rocks or the like in a formation of softer coal or minerals. In a road planing operation such as planing asphaltic roadway material, the cutting bits may impact a manhole cover or the life during the course of the planing operation. In a trenching operation, the cutting bits may encounter rocks or other very hard regions. Wear resistance is necessary because of the highly abrasive nature of the earth strata (e.g., asphaltic material).
During the process of a rotatable cutting bit impinging the earth strata, it is very beneficial that the rotatable cutting bit freely rotate about its central longitudinal axis. Free rotation about its central longitudinal axis maintains the geometric symmetry of the cutting bit about its central longitudinal axis, which typically results in a longer useful tool life. It would be highly desirable to provide an improved cutting bit that freely rotates about its central longitudinal axis. It would also be highly desirable to provide an improved cutting bit that possesses an inherent capability to rotate freely about its central longitudinal axis.
It is apparent that it would be very desirable to provide an improved cutting bit that encounters less resistance upon impingement of the earth strata, and yet exhibits acceptable strength or impact resistance and wear resistance. It is also apparent that it would be very desirable to provide an improved rotatable cutting bit that is freely rotatable to maintain its geometric symmetry about its central longitudinal axis. It is further apparent that it would be highly desirable to provide an improved cutting bit that exhibit an inherent capability to rotate freely about its longitudinal axis.
In one form thereof, the invention is a cutting bit for impinging earth strata. The cutting bit comprises a highly wear-resistant elongate cutting bit body that has an axial forward end and an axial rearward end, an enlarged dimension head portion at the axial forward end and a reduced dimension shank portion at the axial rearward end. The highly wear-resistant elongate cutting bit body has a maximum transverse dimension and a longitudinal axial length. The cutting bit has a superhard insert affixed to the head portion at the axial forward end of the cutting bit body. The cutting bit exhibits a slimness ratio comprising the ratio of the maximum transverse dimension to the longitudinal axial length wherein the slimness ratio ranging between about 0.15 and about 0.60.
In another form thereof, the invention is a cutting bit for impinging earth strata. The cutting bit comprises a highly wear-resistant elongate cutting bit body that has an axial forward end and an axial rearward end, an enlarged dimension head portion at the axial forward end and a reduced dimension shank portion at the axial rearward end. At least a part of the highly wear-resistant elongate cutting bit body comprises a hard component-matrix composite material to provide wear resistance. The cutting bit has a hard insert affixed to the head portion at the axial forward end of the cutting bit body.
In yet another form thereof, the invention is a cutting bit for impinging earth strata. The cutting bit comprises a highly wear-resistant elongate cutting bit body that has an axial forward end and an axial rearward end, an enlarged dimension head portion at the axial forward end and a reduced dimension shank portion at the axial rearward end. The highly wear-resistant elongate cutting bit body has a maximum transverse dimension and a longitudinal axial length. The highly wear-resistance cutting bit body comprises a substrate, and at least a part of the substrate has a hardfacing layer thereon. The cutting bit has a hard insert affixed to the head portion at the axial forward end of the cutting bit body. The cutting bit exhibits a slimness ratio that comprises the ratio of the maximum transverse dimension to the longitudinal axial length wherein the slimness ratio ranges between about 0.15 and about 0.25.
In still another form thereof, the invention is a cutting bit for impinging earth strata. The cutting bit comprises a highly wear-resistant elongate cutting bit body that has an axial forward end and an axial rearward end, an enlarged dimension head portion at the axial forward end and a reduced dimension shank portion at the axial rearward end. The highly wear-resistant elongate cutting bit body carries a wear rotator to provide wear resistance. The cutting bit has a hard insert affixed to the head portion at the axial forward end of the cutting bit body.
In another form thereof, the invention is a cutting bit for impinging earth strata. The cutting bit comprises a highly wear-resistant elongate cutting bit body that has an axial forward end and an axial rearward end, an enlarged dimension head portion at the axial forward end and a reduced dimension shank portion at the axial rearward end. The highly wear-resistant elongate cutting bit body has a maximum transverse dimension and a longitudinal axial length. The cutting bit has a hard insert affixed to the head portion at the axial forward end of the cutting bit body. The cutting bit has a slimness ratio comprising the ratio of the maximum transverse dimension to the longitudinal axial length wherein the cutting bit exhibits a slimness ratio ranging between about 0.15 and about 0.25.
The following is a brief description of the drawings that form a part of this patent application:
Referring to the drawings,
The rotatable cutting bit 20, which has an overall axial length equal to dimension A-I, and comprises an elongate cutting bit body 22, which is a highly wear-resistant cutting bit body, that has a central longitudinal axis A-A about which the cutting bit 20 rotates during operation. The cutting bit body 22 has an axial forward end 24 and an opposite axial rearward end 26. There is an enlarged dimension head portion (see bracket 30) at the axial forward end 24 and a reduced dimension shank portion (see bracket 32) at the axial rearward end 26. In this specific embodiment, the highly wear-resistant elongate cutting bit body 22 is made of a hard component-matrix composite material. However, as an alternative, the cutting bit body maybe made of any one of a cemented carbide or a substrate with a coating layer wherein the coating layer being a material selected from the group consisting of hardfacing including hardfacing applied by a plasma transferred arc process, polycrystalline diamond, diamond (e.g., a CVD diamond film), cubic boron nitride, and polycrystalline cubic boron nitride.
One should appreciate that a highly wear-resistant elongate cutting bit body exhibits a wear resistance greater than the wear resistance of a cutting bit body made from steel compositions typically used heretofore to make cutting bit bodies.
Cutting bit body 22 further contains at its axial forward end 24 a valve seat-style socket 34 adapted to receive a hard insert 40 so that the hard insert 40 affixes to the head portion 30 at the axial forward end 24 of the cutting bit body 22. Although the hard insert 40 will be described in more detail hereinafter, the hard insert can be made from material selected from the group including a hard component-matrix composite material, and a substrate with a coating layer wherein the coating layer being a material selected from the group consisting of hardfacing including hardfacing applied by a plasma transferred arc process, polycrystalline diamond (PCD), diamond, cubic boron nitride, and polycrystalline cubic boron nitride (PcBN). The hard insert may also be made from other hard materials known to those in the art to be suitable to function as a hard insert in a cutting bit. There should be an appreciation at the above materials are also suitable for use as the hard insert (or superhard insert) in other specific embodiments disclosed herein. There should also be an appreciation that some of the materials are what those skilled in the art consider to be superhard materials. Superhard materials include polycrystalline diamond, diamond (e.g., a CVD diamond film), cubic boron nitride, and polycrystalline cubic boron nitride. A superhard insert is an insert made from a superhard material.
Shank portion 32 contains an annular groove 36 near the axial rearward end 26 of the cutting bit body 22 wherein the groove 36 is adapted to receive a resilient retainer 38. When the cutting bit 20 is inserted into the bore of a holder or block (not illustrated) typically used to carry a cutting bit, the resilient retainer 38 expands in a radial outward direction to frictionally engage the wall of the bore and thereby rotatably retain the cutting bit within the bore. There should be an understanding that the cutting bit 20 may use other known ways to retain the cutting bit within the bore of the holder.
As disclosed by the broken away portion of the cutting bit body 22 adjacent to the axial forward end 24 thereof, all of the elongate cutting bit body 22 is made of a hard component-matrix composite material. The hard component-matrix composite material is disclosed in U.S. Pat. No. 6,984,454 to Majagi entitled WEAR-RESISTANT MEMBER HAVING A HARD COMPOSITE COMPRISING HARD CONSTITUENTS HELD IN AN INFILTRANT MATRIX, that is assigned to Kennametal Inc., and is hereby incorporated in its entirety by reference herein. Although it will become apparent from the description hereinafter, it is contemplated that as an alternative, only a portion of the cutting bit body rather than the entire cutting bit body could be made of the hard component-matrix composite material. Further, there should be an appreciation that reference to the term hard component-matrix composite material (or a like term) refers to the material disclosed and described in U.S. Pat. No. 6,984,454 to Majagi.
Although more specific compositions are set forth below and in U.S. Pat. No. 6,984,454, the hard component-matrix composite material comprises a plurality of discrete hard constituents and matrix powder of hard particles and an infiltrant alloy bonded together to form the hard component-matrix composite. A more detailed description of the hard constituents, the matrix powder and the infiltrant alloy is set forth hereinafter.
In reference to the geometry of the cutting bit body 22 as illustrated in
Based upon the above dimensions, there should be an appreciation that the ratio between the maximum transverse dimension of the head portion to be axial length of the cutting bit body (E/B) can vary within a specified range. More specifically, one preferred range for the ratio E/B is between about 0.26 and about 0.32. A specific value for the ratio E/B is 0.29. However, there should be an appreciation that the E/B slimness ratio could range between about 0.150 to about 0.600. There is the contemplation that the slimness ratio could be between about 0.150 and about 0.250 and between about 0.150 and about 0.200.
One can see that the specific embodiment of the cutting bit as illustrated in
Table B sets forth dimensions along the line of the dimensions in Table A, except that the cutting bits pertain to a construction tool and a trenching tool. The construction tool cutting bit body is a model RZ25 construction tool made and sold by Kennametal Inc. of Latrobe, Pa. 15650. The trenching cutting bit body is a model TS2 trenching tool made and sold by Kennametal Inc. of Latrobe, Pa. 15650.
Referring to
The axial rearward portion 54 has an axial forward end 56 and an axial rearward end 58. The axial rearward portion 54 contains an annular groove 60 adjacent to the axial rearward end 58, as well as a conically-shaped portion 62 adjacent to the axial forward end 56. One should appreciate that the geometry of the axial forward end 56 of the axial rearward portion 54 may be something other than of a conical geometry. For example, the geometry of the axial forward and 46 may be dendritic, planar, or non-planar wherein the objective is to increase the amount of surface area over which the axial rearward portion 54 contacts the axial forward portion 64. Typically, in the case when an infiltration method is utilized to bonded together these two components, the bonding strength increases with an increase in the surface area over which the two components are in contact. A resilient retainer 63 is within the groove 60. Resilient retainer 63 functions in a fashion like that of retainer 38.
The axial forward portion 64 has an axial forward end 66 and an axial rearward end 68. The axial forward portion 64 contains a cylindrical socket 72 at the axial forward end 66 and a conically-shaped socket 70 at the axial rearward end 68. A hard insert 73, which can comprise a superhard material such as, for example, polycrystalline diamond, polycrystalline cubic boron nitride, contains an axial forward conical portion 74 and an axial rearward cylindrical portion, which presents a plurality of radially projecting axial serrations 75. The hard insert 73 affixes within the cylindrical socket by press fitting wherein the tool body surrounding the socket 72 deforms upon entry of the hard insert 73 into the socket 72 to frictionally retain the insert in the socket. However, there should be an appreciation that other methods could affix the hard insert 73 within the socket 72 wherein these other methods can include without limitation brazing, gluing and shrink fitting. Further, even though in this specific embodiment insert 73 projects past the axial forward end 66, there should be an appreciation that the insert 73 may be flush with the surface of the axial forward end 66. In addition, there should be an appreciation that the shape of the hard insert 73 could take on any one of a number of different geometries. For example, rather than the axial forward portion of the hard insert 73 being generally conical, it could present a geometries such as shown by hard insert 134 in
The conical socket 70 in the axial forward portion 64 receives the conical portion 62 of the axial rearward portion 54 so that the axial forward portion 64 affixes by brazing or the like to the axial rearward portion 54. There should be an appreciation that other methods could affix the axial forward portion 64 to the axial rearward portion 54 wherein these other methods can include without limitation gluing, press fitting, shrink fitting and other mechanical means. In addition, an infiltration process such as disclosed in U.S. Pat. No. 6,984,454 to Majagi is appropriate to use to affix together the axial forward portion 64 to the axial rearward portion 54. In such an arrangement, one could position the steel axial rearward portion 54 in a mold and position the components of the hard component-matrix composite about the conical portion 62 of the axial rearward portion 54 and then infiltrate the same so as to metallurgically join the axial forward portion 64 to the axial rearward portion 54.
Referring to
One can appreciate that the specific embodiment of the cutting bit as illustrated in
Referring to
The axial rearward portion 84 has an axial forward end 86 and an axial rearward end 88. Axial rearward portion 84 has a head portion 94 with an enlarged diameter collar and a reduced diameter shank portion 87. The axial rearward portion 84 contains an annular groove 95 in the shank 87 adjacent to the axial rearward end 88. The axial rearward portion 84 contains a large diameter socket 90 in the axial forward end 86 thereof. A small diameter socket 92 is in the bottom surface of the large diameter socket 90. A resilient long retainer 96 is carried within the groove 95. Retainer 96 functions in a fashion generally like retainer 38 in that it expands in a radial outward direction to frictionally engage the wall of the bore in the holder.
The assembly further includes a washer 98 wherein
The axial forward portion 100 has an axial forward end 102 and an axial rearward end 104. The axial forward portion 100 contains a cylindrical socket 106 at the axial forward end 102. A generally cylindrical post 108 projects from the axial rearward end 104. A plug-style hard insert 109, which can comprise a superhard material such as, for example, polycrystalline diamond, polycrystalline cubic boron nitride, affixes by brazing or the like (or in the alternative can be affixed by methods that include without limitation gluing, press fitting, shrink fitting and other mechanical means) within the cylindrical socket 106. The sockets 90 and 92 in the axial rearward portion 84 receive the axial forward portion 100 (including the post 108 being received within the socket 92) so that the axial forward portion 100 affixes by brazing or the like (or in the alternative can be affixed by methods that include without limitation gluing, press fitting, shrink fitting and other mechanical means) to the axial rearward portion 84. There should be an appreciation that an infiltration process such as disclosed in U.S. Pat. No. 6,984,454 to Majagi is appropriate to use to affix together these components. In such an arrangement, one can position the steel component (i.e., the axial rearward portion 84) in a mold, and then position the components of the hard component-matrix composite that form the axial forward potion 100 about the steel component and infiltrate the same thereby metallurgically joining the components (i.e., axial rearward portion 84 and axial forward portion 100) together.
Referring to
In reference to the geometry of the cutting bit body 200, the axial length of the entire cutting bit body is equal to the dimension “I”. The axial length of the axial forward portion 208 is equal to the sum of the dimension “J” and “K” and the axial length of the axial rearward portion 210 is equal to dimension “L”. The axial forward portion 208 presents a generally frusto-conical shape wherein the minimum transverse dimension (or diameter) is equal to dimension “N” and the maximum transverse dimension (or diameter) is equal to dimension “M”. The maximum transverse dimension of the axial forward portion 208 exists at the collar of the cutting bit body. A fillet provides a transition between the frusto-conical surface and the collar. The transverse dimension of the axial forward portion gradually increases in the axial rearward direction at an angle equal to dimension “S”. The transverse dimension (or diameter) of the axial rearward portion 210 is constant and is equal to dimension “O”. Table B below sets forth selected dimensions and ranges of dimensions from the specific embodiment of the cutting bit body 200.
Based upon the above dimensions, there should be an appreciation that the ratio between the maximum transverse dimension of the head portion to be axial length of the cutting bit body (M/I) can vary within a specified range. More specifically, the specific ratio M/I is 0.325. One preferred range of M/I is between about 0.250 and about 0.450. There is the contemplation that the M/I ratio can range between as low as about 0.150 to as high as about 0.600. There is the expectation that an especially preferred range of M/I is between about 0.150 and about 0.250 with an even more preferred range between about 0.150 and about 0.200.
In reference to the specific embodiment illustrated by
Referring to
The shank portion 120 contains a groove 130 that receives a resilient retainer 132. Retainer 132 functions like the retainer 38 of the first specific embodiment of the cutting bit 20.
Head portion 118 contains a plurality of recesses 126 that are generally cylindrical in shape. Recesses 126 exhibit a somewhat random orientation; however, recesses 126 may exhibit a specific intentional pattern to provide specific wear properties or characteristics. A cylindrical discrete rotator wear member 128 affixes by brazing or the like (or in the alternative can be affixed by methods that include without limitation gluing, press fitting, shrink fitting and other mechanical means) into each one of the recesses 126. In this embodiment, a portion of the surface of each one of the discrete rotator wear members 128 extends past the surface of the head portion 118 so as to present an exposed rotator (or side or lateral) surface. There should be an appreciation and that the discrete rotator wear members 128 may also be flush with the surface of the head portion 118 or, as an alternative, be recessed within the recesses 126 relative to the surface of the head portion 118.
The discrete wear rotator members may be made of a hard material such as, for example, cemented (cobalt) tungsten carbide or the hard component-matrix composite material or cubic boron nitride, polycrystalline diamond material or polycrystalline cubic boron nitride. Further, there should be an appreciation that the discrete wear rotator members can comprise a volume or mass of hard coating (e.g., PCD) either on the surface or in the recesses or a weld bead either on the surface or in the recesses of the head portion 118. The rotator wear members facilitate the rotation of the cutting bit about its central longitudinal axis and a description of this feature is set forth hereinafter.
Still referring to
Referring to
Head portion 148 contains a plurality of recesses 156 that are generally triangular in shape. Recesses 156 exhibit an orientation comprising two rows about the circumference of the head portion 148. However, as mentioned above, the recesses do not have to present a specific orientation in that the recesses can be randomly contained in the cutting bit or have an orientation that is asymmetric about the central longitudinal axis. There is the contemplation that the recesses may be in a helical or spiral orientation. A discrete rotator wear member 158 affixes by brazing or the like (or in the alternative can be affixed by methods that include without limitation gluing, press fitting, shrink fitting and other mechanical means) into each one of the recesses 156. In this embodiment, a portion of the surface of the discrete rotator wear member 158 extends past the surface of the head portion 148 so as to present an exposed surface. Further, there should be an appreciation that the discrete wear rotator members can comprise a volume or mass of hard coating (e.g., PCD) either on the surface or in the recesses or a weld bead either on the surface or in the recesses of the head portion. The rotator wear members facilitate the rotation of the cutting bit about its central longitudinal axis and a description of this feature is set forth hereinafter. There is the expectation of an enhancement to the rotation of the cutting bit when the rotator wear members are in a helical or spiral arrangement.
Still referring to
Referring to
Head portion 178 contains a plurality of recesses 186 that are generally rectangular in shape. Recesses 186 are oriented in a row about the circumference of the head portion 178. A discrete rotator wear member 188 affixes by brazing or the like into each one of the recesses 186. In this embodiment, a portion of the surface of the discrete rotator wear member 188 extends past the surface of the head portion 178 so as to present an exposed surface. Further, there should be an appreciation that the discrete wear rotator members can comprise a volume or mass of hard coating (e.g., PCD) either on the surface or in the recesses or a weld bead either on the surface or in the recesses of the head portion. The rotator wear members facilitate the rotation of the cutting bit about its central longitudinal axis and a description of this feature is set forth hereinafter.
In reference to the rotator wear members contained in the specific embodiments of
Referring to
Referring to the specific embodiments illustrated in
In reference to the centrifugal force generated to the heavier perimeter weighting of the head portion of the cutting bit, the discrete rotator wear members are at the periphery or perimeter of the head portion of the cutting bit. This is illustrated in
In reference to the impingement of the debris upon the side or lateral surfaces of the discrete rotator wear members, during operation, the cutting bit impinges the earth strata to break the earth strata into pieces. These pieces 200 impinge against the exposed surfaces (e.g., the side surfaces or lateral surfaces of the rotator wear members) 189 of the discrete rotator wear members 188 to facilitate the rotation of the cutting bit about its central longitudinal axis.
As the operation continues the head portion experiences abrasive wear to increase the amount of exposed surface of the discrete rotator wear members. This is shown in
It can thus be seen that each one of the cutting bits of
Referring to
The cutting bit 220 further includes a mediate wear region generally designated as 244. In this embodiment, the mediate wear region 244 includes an inner split ring 246 that has an interior surface 248 and an exterior surface 250, as well as a forward surface 251. The mediate wear region 244 further includes an outer split ring 252 that has an interior surface 254 and an exterior surface 256, as well as a rearward surface 258. These rings typically comprise two pieces.
When assembled to the cutting bit body, the inner ring 246 is closest to the reduced diameter section 234 so that the interior surface 248 contacts and affixes to the interior surface 236 of the reduced diameter section 234 and the forward surface 251 contacts and affixes to the forward transverse surface 238. The interior surface 254 of the outer ring 252 contacts and affixes to the exterior surface 250 of the inner ring 246, and the rearward surface 258 contacts and affixes to the rearward transverse surface 240. These rings (246, 248) affix to one another and the cutting bit body by brazing or the like (or in the alternative can be affixed by methods that include without limitation gluing, press fitting, shrink fitting and other mechanical means).
In this specific embodiment, the inner ring 246 is made of the hard component-matrix composite material and the outer ring 252 is made of steel. The inventors contemplate that the outer ring could be made of the hard component-matrix composite material and the inner ring could be made of steel. The inventors further contemplate that the inner and outer rings could be made of the hard component-matrix composite material of different compositions. There is the contemplation that a plasma transferred arc process can be useful to deposit hard material to form the inner ring 246. The plasma transferred arc process is used to use a metallic coating to a substrate in order to prove its resistance against where and/or corrosion. During the process, metal powder is fed into a molten weld puddle generated by a plasma arc at a high temperature (e.g., 20,000° C.). An exemplary plasma transferred arc system is available through PLASMA Team Snc (see internet website: http://www.plasmateam.com).
There should be an appreciation that an infiltration process such as disclosed in U.S. Pat. No. 6,984,454 to Majagi is appropriate to use to affix together these rings. In such an arrangement, one can position the one of the rings in a mold, and then position the components of the hard component-matrix composite about the steel component and infiltrate the same thereby metallurgically joining the components together. Further, there should be an appreciation that the entire mediate wear region could be made of the hard component-matrix composite material using the infiltration techniques.
The axial rearward portion 228 contains a groove 230 that receives a resilient retainer 232. Retainer 232 functions like the retainer 38 of the first specific embodiment of the cutting bit 20.
Referring to
The socket 370 in the mediate wear region 356 receives the axial forward portion 354 and the socket 372 in the mediate wear region 356 receives the axial rearward portion 358. The axial forward portion 354 and the axial rearward portion 358 each affix by brazing or the like (or in the alternative can be affixed by methods that include without limitation gluing, press fitting, shrink fitting and other mechanical means) to the mediate wear region 356. Hot isostatic pressing (HIP) or rapid omnidirectional compaction (ROC) techniques can make the mediate wear region 356. The mediate wear region 356 can comprise a hard material such as, for example, the hard component-matrix composite material and any one of the following materials: a matrix material (e.g., nickel steel) were in the hard components include cast carbides, spherical cast carbide, and macrocrystalline carbides. There is also the expectation that the hard components may comprise polycrystalline diamond.
Referring to
The forward socket 308 in the mediate wear region 302 receives the axial forward portion and the rearward socket 310 in the mediate wear region receives the axial rearward portion. The axial forward portion and the axial rearward portion each affix by brazing or the like to the mediate wear region. There should be an appreciation that an infiltration process such as disclosed in U.S. Pat. No. 6,984,454 to Majagi is appropriate to use to affix together these components. In such an arrangement, one can position the steel component in a mold, and then position the components of the hard component-matrix composite about the steel component and infiltrate the same thereby metallurgically joining the components together.
In reference to the PCD insert 297, it has an axial forward PCD region 330 of polycrystalline diamond material and a backing region 332 that provide support for the PCD region. The axial forward PCD region 330 presents a conical geometry. U.S. Pat. No. 6,344,149 to Oles, which is hereby incorporated by reference herein, discloses techniques to make the PCD insert. While most all of the axial forward PCD portion may comprise polycrystalline diamond, there should be an appreciation that the axial forward PCD region may comprise a conical backing with a layer of PCD thereon.
Referring to
The highly wear-resistant cutting bit body 502 has an enlarged head portion 508 adjacent the axial forward end 504 thereof and a reduced shank portion 510 adjacent to the axial rearward end 506 thereof. A collar 512 separates the head portion 508 from the shank portion 510. The collar 512 has a maximum transverse dimension “BB”. The rotatable cutting bit 500 has a retainer 514 at the axial rearward end 506 of the highly wear-resistant cutting bit body 502. The rotatable cutting bit 500 has a superhard insert 516 at the axial forward end 504 of the highly wear-resistant cutting bit body 502. The superhard insert 516 extends a distance “CC” past the axial forward end 504 of the highly wear-resistant cutting bit body 502. The slimness ratio of BB/AA, i.e., the ratio of the maximum transverse dimension to the axial length, is about 0.150.
There should be an appreciation that the cutting bit of the present invention provides an increase in useful tool life for a number of reasons. The use of a superhard material for the hard insert at the axial forward end of the cutting bit enhances the penetration of the cutting bit into the earth strata or substrate. This feature by itself increases the useful tool life of the cutting bit. The use of a cutting bit body that exhibits enhanced wear resistance lengthens the time the cutting bit body to maintain its structural integrity. Like for a hard insert comprising a superhard material, this feature by itself increases the useful tool life of the cutting bit.
The combination of the use of a superhard material for the hard insert in combination with a cutting bit body that exhibits enhanced wear resistance provides for an exceptional increase in the useful tool life of the cutting bit. More specifically, heretofore, the use of a superhard hard insert in connection with a conventional cutting bit body possesses the imitation that the useful life of the cutting bit body terminates prior to the termination of the useful life of the superhard insert. The typical consequences of the superhard insert, which still possesses useful tool life, becomes detached from the cutting bit body upon the cutting bit body wearing past its useful life. However, in the case of the combination of a superhard insert and a cutting bit body with enhanced wear resistance, the cutting bit body maintains its structural integrity thereby providing support to the superhard insert for a longer time. Thus, the termination of the useful life of the cutting bit body with enhanced wear resistance more closely matches the termination of the useful tool life of the superhard insert. The appropriation of the beneficial properties of the superhard insert and the cutting bit body with enhanced wear resistance results in a cutting bit exhibits enhanced useful tool life.
Some of the components of the cutting bits are made of steel. In reference to steel alloy compositions, the steel alloys listed in Table 1 are suitable for the manufacture of steel alloy components of cutting bits. While Table 1 lists suitable steel alloys, there should be appreciation that steel alloys other than those set forth in Table 1 below may be suitable for use in the manufacture of the cutting bit.
In reference to the composition of the cemented tungsten carbide useful for the hard inserts at the axial forward end of the cutting bit, the cemented tungsten carbides may be any one of a number grades of cemented tungsten carbide that are suitable for impingement of earth strata. These cemented tungsten carbide grades may include grades that comprise between about 0.01 weight percent and about 35 weight percent cobalt with the balance tungsten carbide (the average grain size varies between about 0.01 microns and about 25 microns) and recognized impurities, as well as in the alternative various additives (e.g., the carbides, nitrides and/or carbonitrides of the elements (except for tungsten) of Group IVa, Va, and VIa of the Periodic Table). Typical grades of cemented (cobalt) tungsten carbide have a hardness of less than or equal to about 88.5 Rockwell A. An exemplary grade of cemented tungsten carbide comprises the following about 6 weight percent cobalt with the balance tungsten carbide (average grain size ranging between about 4 microns to 10 microns) and recognized impurities, and has a hardness equal to about 89.5 Rockwell A. Other grades of cobalt-bonded cemented carbides (and their properties) are disclosed in the article by Santhanam et al., entitled “Cemented Carbides” Metals Handbook Volume 2, 10th Edition Properties and Selection, wherein this article is hereby incorporated in its entirety by reference herein.
In reference to the hard component-matrix composite material, it comprises a plurality of discrete hard constituents (described hereinafter) wherein these hard constituents are held within a matrix. The matrix comprises a mass of matrix powder that comprises different kinds of hard particles and/or powders, and an infiltrant alloy that has been infiltrated into the mass of the matrix powder and the hard constituents under the influence of heat and sometimes under additional environmental influences such as, for example, in a pressure or in a vacuum. Furthermore, the infiltrant alloy may be infiltrated into the mass of hard constituents and matrix powder under various atmospheres (e.g., argon, helium, hydrogen, and nitrogen).
The hard constituents may comprise sintered cemented carbide members (which hereinafter may be called sintered cemented carbide members) that can be of various geometric shapes such as, for example, triangular. As one option, the hard constituent can present a specific pre-determined shape depending upon the specific application. As an alternative, a hard sintered cemented carbide member could be crushed to obtain hard constituents wherein the hard constituents are crushed particles of a larger size wherein the particle size is measured by mesh size (e.g., −80+120 mesh).
As one option, the hard constituents can be selectively positioned within the matrix of the hard composite which typically occurs in the mold prior to infiltration. It is contemplated that the hard constituents may cover between about 0.5 percent to about 90 percent of the surface area of the wear-resistant hard member. There is no intention to restrict the invention to the specific positioning of the hard constituents in the hard composite. For example, the hard constituents may be uniformly (or non-uniformly or randomly) distributed throughout the volume of the hard composite.
By mentioning the above specific hard constituent, there is no intention to limit the scope of the invention to this specific hard constituent. It is contemplated that other materials would be suitable for use as the hard constituents in the hard composite. In this regard, the following materials would appear to be suitable for use as hard constituents in the hard composite: sintered cemented tungsten carbide wherein a binder includes one or more of cobalt, nickel, iron and molybdenum; coated sintered cemented tungsten carbide wherein a binder includes one or more of cobalt, nickel, iron and molybdenum, and the coating comprises one or more of nickel, cobalt, iron and molybdenum; one or more of the carbides, nitrides, and borides of one or more of titanium, niobium, tantalum, hafnium, and zirconium; one or more of the coated carbides, coated nitrides, and coated borides of one or more of titanium, niobium, tantalum, hafnium, and zirconium wherein the coating comprises one or more of nickel, cobalt, iron and molybdenum; chromium carbides; coated chromium carbides; coated silicon carbide wherein the coating comprises one or more of nickel, cobalt, iron and molybdenum; and coated silicon nitride wherein the coating comprises one or more of nickel, cobalt, iron, copper, molybdenum or any other suitable metal; and coated boron carbide wherein the coating comprises one or more of nickel, cobalt, iron, copper, molybdenum, and any other suitable metal.
The matrix powder can comprise a crushed cemented carbide particle. The crushed cemented carbide particles may be present in a size range for these crushed cemented carbide particles equal to −325+200 mesh. Another size range for these crushed cemented carbide particles is −80+325 mesh. The standard to determine the particle size is by using sieve size analysis and the Fisher sub-sieve size analyzer for −325 mesh particles. One composition for the crushed cemented carbide particles is cobalt cemented tungsten carbide wherein the cobalt ranges between about 6 weight percent and about 30 weight percent of the cobalt cemented tungsten carbide material and tungsten carbide is the balance of the material. Another preferred composition for crushed cemented carbide particles is cobalt cemented tungsten carbide wherein the cobalt ranges between about 0.2 weight percent and about 6 weight percent of the cobalt cemented tungsten carbide material and tungsten carbide is the balance of the material.
By mentioning specific compositions, there is no intention to limit the scope of the invention to these specific cemented carbides. It is contemplated that other cemented carbides (e.g., chromium carbide) would be suitable for use as the crushed cemented tungsten carbide particles in the hard composite. In this regard, the carbides could be different from tungsten carbide (e.g., titanium carbide and chromium carbide) and the binder could be different from cobalt (e.g., nickel). It is further contemplated that the crushed cemented carbide particles may vary in composition throughout a particular hard composite depending upon the specific application. It is also contemplated that certain hard materials other than cemented carbides may be suitable to form these particles.
The matrix powder may also contain crushed cast carbide particles wherein one size range for these particles is −325 mesh. Another size range for these particles is −80 mesh. One composition for these particles is cast tungsten carbide. It is contemplated that the crushed cast carbide particles may vary in composition throughout a particular hard composite depending upon the specific application. It is further contemplated that other cast carbides or hard materials are suitable for use in place or along with the crushed cast carbide particles.
The matrix powder may further include in addition to crushed cemented carbide particles and/or crushed cast carbide particles, any one or more of the following: crushed carbide particles (e.g., crushed tungsten carbide particles that have a size of −80+325 mesh), steel particles that have an exemplary size of −325 mesh, carbonyl iron particles that have an exemplary size of −325 mesh, cemented carbide powder, and coated (e.g., nickel coating) cemented carbide particles, and nickel-coated tungsten carbide particles (−80+325 mesh).
It is desirable that the infiltrant alloy has a melting point that is low enough so as to not degrade the hard constituents upon contact therewith during the infiltration process. Along this line, the infiltrant alloy has a melting point that ranges between about 500 degrees Centigrade and about 1400 degrees Centigrade. It is contemplated that the infiltrant alloys may have a melting point that ranges between about 600 degrees Centigrade and about 800 degrees Centigrade. It is further contemplated that the infiltrant alloys may have a melting point that ranges between about 690 degrees Centigrade and about 770 degrees Centigrade. It is still further contemplated that the infiltrant alloys may have a melting point below about 700 degrees Centigrade. Exemplary general types of infiltrant alloys include copper-based alloys such as, for example, copper-silver alloys, copper-zinc alloys, copper-nickel alloys, copper-tin alloys, and nickel-based alloys including nickel-copper-manganese alloys. Exemplary infiltrant alloys are set forth in Table 2 herein below.
By mentioning specific infiltrant alloys in Table 2, there is no intention to limit the scope of the invention to infiltrant alloys with these specific compositions and/or properties. As one alternative, the composition of the infiltrant alloy could be within the range of 5-40 weight percent nickel, 5-40 weight percent manganese and the balance copper.
Referring to an exemplary hard component-matrix composite material, the hard particles in the hard composite may comprise 100 percent crushed nickel cemented chromium carbide particles. The nickel could comprise between about 3 weight percent and about 25 weight percent of the cemented carbide with chromium carbide comprising the balance. The preferred composition of the cemented carbide is about 15 weight percent nickel and the balance chromium carbide. The particle size of the crushed cemented (nickel) chromium carbide particles can range between about −325 mesh and about +80 mesh. The infiltrant alloy can comprise between about 60 weight percent and about 80 weight percent of the hard composite and the crushed nickel cemented chromium carbides can comprise between about 20 weight percent and about 40 weight percent of the hard composite.
Referring to another exemplary hard component-matrix composite material, it can also be made from the compositions set forth in Table 3 below. The matrix powder is Mixture No. 2 taken from Table 4 hereof. The hard constituents are crushed nickel cemented chromium carbide wherein the nickel is present in an amount of 15 weight percent. The particle size of the crushed cemented (nickel) chromium carbide particles can range between about −325 mesh and about +80 mesh. The titanium diboride (TiB2) particles have a particle size equal to −325 mesh. The infiltrant alloy was the copper-based alloy A-I set forth in Table 1. The infiltrant alloy comprised between about 60 weight percent and about 70 weight percent of the hard composite.
In yet another example of the hard constituent-matrix composite, there are a plurality of sintered cemented carbide members that typically have a composition of 10 weight percent cobalt and the balance tungsten carbide. The matrix powder typically includes tungsten carbide, chromium carbide, as well as cobalt and nickel in the form of a binder alloy for the carbides and/or a coating on the carbides. One typical infiltrant alloy has a composition (weight percent) of copper(53%)-nickel(15%)-manganese(24%)-zinc(8%) and a melting point equal to about 1150 degrees Centigrade.
Another exemplary composition for the hard constituent-matrix composite material comprises hard constituents that comprise one or more sintered carbides wherein these carbides include tungsten, titanium, niobium, tantalum, hafnium, chromium and zirconium. The matrix powder typically comprises one or more sintered carbides, crushed sintered carbides, cast carbide, crushed carbides, tungsten carbide powders and chromium carbide powders. The infiltrant alloy has a composition (weight percent) of copper(53%)-nickel(15%)-manganese(24%)-zinc(8%) and a melting point equal to about 1150 degrees Centigrade.
In still another exemplary composition, the hard constituents that comprise crushed cemented tungsten carbide having a particle size equal to −80+120 mesh. The cemented carbide is cobalt cemented tungsten carbide where the cobalt is present in an amount of 10 weight percent. The hard composite further contains a matrix powder that could be any one of the matrix powders set forth in Table 2 through Table 6 hereof, but preferred a matrix powder may be any one of Matrix Powders Nos. 1 through 3 set forth in Table 4 hereof. The ratio by weight of the matrix powder to the infiltrant alloy is about 40:60 by weight. In some applications, the hard constituent crushed cemented tungsten carbide particles (−80+120 mesh) range between about 2.5 volume percent and about 40 volume percent of the hard composite with the balance comprising matrix powder and infiltrant alloy. However, there are some applications in which the crushed cemented tungsten carbide particles range between about 2 volume percent to about 4 volume percent of the hard composite. There are also other applications in which the crushed cemented tungsten carbide particles range between about 30 volume percent and about 40 volume percent of the hard composite.
In yet another exemplary embodiment, the hard constituents may comprise one or more sintered carbides wherein these carbides include tungsten, titanium, niobium, tantalum, hafnium, chromium and zirconium. The matrix powder typically comprises one or more sintered carbides, crushed sintered carbides, cast carbide, crushed carbides, tungsten carbide powders and chromium carbide powders. The infiltrant alloy has a composition of copper(53%)-nickel(5%)-manganese(24%)-zinc(8%) and a melting point equal to about 1150 degrees Centigrade.
The hard constituent-matrix composite material can comprise crushed cemented tungsten carbide having a particle size equal to −80+120 mesh. The cemented carbide is cobalt cemented tungsten carbide where the cobalt is present in an amount of 10 weight percent. The hard composite further contains a matrix powder that could be any one of the matrix powders set forth in Table 4 through Table 8 hereof, but preferred a matrix powder may be any one of Matrix Powders Nos. 1 through 3 set forth in Table 4 hereof. The ratio by weight of the matrix powder to the infiltrant alloy is about 40:60 by weight. In some applications, the hard constituent crushed cemented tungsten carbide particles (−80+120 mesh) range between about 2.5 volume percent and about 40 volume percent of the hard composite with the balance comprising matrix powder and infiltrant alloy. However, there are some applications in which the crushed cemented tungsten carbide particles range between about 2 volume percent to about 4 volume percent of the hard composite. There are also other applications in which the crushed cemented tungsten carbide particles range between about 30 volume percent and about 40 volume percent of the hard composite.
In some embodiments, the hard constituents can also comprise cemented carbides, silicon carbides, boron carbide, aluminum oxide, zirconia and other suitable hard materials. The matrix powder typically comprises one or more of crushed tungsten carbide, crushed cemented tungsten carbide, crushed cast tungsten carbide, iron powder, tungsten carbide powder (the tungsten carbide made by a thermit process or from co-carburized tungsten carbide), chromium carbide powder, spherical cast carbide powder and/or spherical sintered carbide powders. The infiltrant alloy has a composition of copper(53%)-nickel(15%)-manganese(24%)-zinc(8%) and a melting point equal to about 1150 degrees Centigrade.
Examples of specific matrix powders (Mixtures Nos. 1 through 20) are set forth in Tables 4 through 8 hereinafter. In reference to the composition of the matrix powders, it should be appreciated that the crushed tungsten carbide component or the crushed cast tungsten carbide component may be substituted, in whole or in part, by spherical sintered tungsten carbide and/or spherical cast tungsten carbide particles. In some cases the spherical sintered tungsten carbide and/or spherical cast carbide particles (or powders) could be used 100% in combination or alone as the hard constituents in the matrix powders.
Additional examples of the hard constituent-matrix composite material are set forth hereinafter. One such example of the hard constituent-matrix composite material comprises sintered cobalt (10 weight percent cobalt) cemented tungsten carbide members and the matrix powder comprised Mixture No. 1 in Table 4 and the infiltrant alloy comprised (in weight percent) a Cu(53%)-Ni(15%)-Zn(8%)-Mn(24%) alloy described above. The matrix powder comprised 40 weight percent and the infiltrant alloy comprised 60 weight percent of the combination of the matrix powder and the infiltrant alloy. Depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 95 weight percent with the balance of the hard composite comprising the matrix powder and the infiltrant alloy. In the alternative and depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 90 percent of the surface area of the hard composite.
For yet another example of the hard constituent-matrix composite material, it comprised a sintered cobalt (6 weight percent cobalt) cemented tungsten carbide member. The matrix powder comprised Mixture No. 4. The infiltrant alloy comprised in weight percent) a Cu(53%)-Ni(15%)-Zn(8%)-Mn(24%). The matrix powder comprised 45 weight percent and the infiltrant alloy comprised 55 weight percent of the combination of the matrix powder and the infiltrant alloy. Depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 95 weight percent with the balance of the hard composite comprising the matrix powder and the infiltrant alloy. In the alternative and depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 90 percent of the surface area of the hard composite.
Still another example of the hard constituent-matrix composite material is a composition that comprises sintered cobalt (6 weight percent cobalt) cemented tungsten carbide cylindrical members. The matrix powder was Mixture No. 3 as set forth in Table 1. The infiltrant alloy comprised (in weight percent) a Cu(53%)-Ni(15%)-Zn(8%)-Mn(24%). The matrix powder comprised 40 weight percent and the infiltrant alloy comprised 60 weight percent of the combination of the matrix powder and the infiltrant alloy. Depending upon the specific application the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 95 weight percent with the balance of the hard composite comprising the matrix powder and the infiltrant alloy. In the alternative and depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 90 percent of the surface area of the hard composite. For some applications, the cemented tungsten carbides may be present in a range between about 1 percent to about 5 percent of the surface area. For other applications, the cemented tungsten carbide members may be present in a range between about 70 percent and about 90 percent of the surface area.
Another example of the hard constituent-matrix composite material comprises nickel-coated sintered cobalt (10 weight percent cobalt) cemented tungsten carbide members. The matrix powder comprised Mixture No. 4 from Table 1. The infiltrant alloy comprised (in weight percent) a Cu(53%)-Ni(15%)-Zn(8%)-Mn(24%). The matrix powder comprised 45 weight percent and the infiltrant alloy comprised 55 weight percent of the combination of the matrix powder and the infiltrant alloy. Depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 95 weight percent with the balance of the hard composite comprising the matrix powder and the infiltrant alloy. In the alternative and depending upon the specific application, the cemented tungsten carbide members were present in a specified amount between about 1 weight percent and about 90 percent of the surface area of the hard composite. For some applications, the cemented tungsten carbide members may be present in a range between about 1 percent to about 5 percent of the surface area. For other applications, the cemented tungsten carbide members may be present in a range between about 70 percent and about 90 percent of the surface area.
It is apparent from the above description that applicants have invented an improved cutting bit In the process of a cutting bit impinging the earth strata, it is desirable that the cutting bit exhibit acceptable strength or impact resistance and wear resistance. Impact resistance is desirable because the earth strata can be inconsistent in that it may contain hard anomalies. For example, in a mining operation the earth strata may contain rocks or the like in a formation of softer coal. In a trenching operation, the cutting bits may encounter rocks or other very hard regions. In a road planing operation such as planing asphaltic roadway material or concrete roadway material, the cutting bits may impact a manhole cover or the life during the course of the planing operation. Wear resistance is necessary because of the highly abrasive mature of the earth strata (e.g., asphaltic material).
It is apparent that the present invention provides an improved cutting bit that freely rotates about its central longitudinal axis. It is also apparent that the present invention provides an improved cutting bit that possesses an inherent capability to rotate freely about its central longitudinal axis.
It is further apparent that the present invention provides a cutting bit that exhibits a slimmer profile thereby encountering less resistance upon impingement of the earth strata. Such a cutting bit with a slimmer profile would exhibit a lower rate of wear thereby taking a greater amount of time to become blunter, and hence, increase the overall operational efficiency of the cutting or mining operation in. Such a cutting bit with a slimmer profile can be achieved by the use of a superhard insert in combination with a highly wear-resistant elongate cutting bit body. There should be an appreciation that the superhard insert is used in the cutting bit typically exhibits longer useful life than a conventional cemented (cobalt) tungsten carbide hard insert. This is especially the case when the superhard insert is used in conjunction with the highly where-resistant elongate cutting pick body. Such a cutting bit with a slimmer profile can also be achieved by the use of a highly wear-resistant elongate cutting bit body in conjunction with a hard insert.
It is also apparent that the present invention provides an improved cutting bit that upon impingement of the earth strata (or substrate) does not result in the excessive generation of small particulates and fines such as, for example, coal dust. There is an advantage connected a cutting bit that actually reduces the amount of small particulates and fines generated during a coal mining operation.
It is apparent that it would be very desirable to provide an improved cutting bit that encounters less resistance upon impingement of the earth strata, and yet exhibits acceptable strength or impact resistance and wear resistance. It is also apparent that it would be very desirable to provide an improved rotatable cutting bit that is freely rotatable to maintain its geometric symmetry about its central longitudinal axis.
The patents and other documents identified herein are hereby incorporated by reference herein. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. There is the intention that the specification and examples are illustrative only and are not intended to be limiting on the scope of the invention. The following claims indicate the true scope and spirit of the invention.
