MULTI-INSERT CUTTER BIT

Abstract: A cutter bit is disclosed having a shank with a forward working portion and multiple inserts mounted on the forward working portion. One of the inserts is a lead insert facing and projecting foremost in the direction of rotation or travel of the bit. A clearance face is provided rearwardly of the load insert so as to reduce the rubbing action that occurs between the cutter bit and the material formation to be removed. The lead insert can be a laminated insert with a metal shim between individual inserts. Another insert is located rearwardly of the lead insert in the clearance face of the bit and projects out of said clearance face to control the wear of the clearance face during the life of the cutter bit. A cutting edge may be formed on the wear controlling insert projecting from the clearance face.

Description: This invention concerns cutter bits for the mining industry and is especially concerned with long wall mining bits used in removing coal, potash or trona formations. Cutter bits used in mining operations are comprised of a shank for insertion into a toolholder with a forward working portion on the shank for engagement with the material formation. An individual insert of hard wear resistant material has been provided on the forward working portion to cut into the coal or mineral formation and to enhance the life of the bit as it removes the mineral formation. With long wall mining bits, the insert is positioned to face the direction of rotation of the bit and has a cutting edge on the insert impacting the mineral formation. A clearance face is provided behind the insert to reduce the rubbing of the forward working portion against the mineral formation as the bit passes through the formation. A plurality of the cutters are usually mounted on a drum that typically might be rotated at 60 revolutions/minute while the drum is driven into and along a face of a coal formation at about 20 to 40 feet/minute (6―12 m/min.). The forward working portion of the cutter bits usually penetrate the coal formation by up to two to four inches. The coal formation is removed by the cutting, picking, and hammering of the cutter bits as the drum rotates and is moved along the face. A cutter bit with a hard resistant insert block whereon a cutting edge is formed, is known from US-A-2 521 089. The cutting edge has sides tapering outwardly toward the shank of the cutter bit when viewed from the front. In the clearance face behind the cutting edge a second, similar insert block is mounted. This second insert block has its cutting edge lying flush with the clearance face and is provided as a spare insert block which becomes effective in the event the front insert block is damaged to such an extent that the second insert block is exposed to the material being worked. In a cutter bit known from DE-B-1 203 714, a wear resistant weld is applied to the clearance face behind the cutting edge formed on a hard wear resistant cutting plate. The wear resistant weld protrudes from the clearance face. Typically, in long wall mining of coal formations, the drum may pass along a face of a coal seam with operator access to the drum occurring only at the end of each pass. As the cutter bit becomes used, wear develops across the forward working portion of the bit extending from the leading cutting edge of the insert rearwardly across the clearance face. The reduced clearance increases the rubbing and abrasion of the forward working portion against the coal formation, generating excessive heat frequently causing the insert to fail due to heat checking. As the wear scar develops across the clearance face of the bits, machine power consumption rises, sometimes stalling the machine. The cutting edge of the insert on the cutter bits faces in the direction of rotation of the bit and, when viewed from a front view, the cutting edge tapers outwardly toward the shank and is preferably V-shaped or U-shaped with the V or the U opening toward the shank of the bit. It is desirable to keep this configuration for the life of the bit rather than to let the cutting edge wear to a flat. When the cutting edge does wear to a flat, not only is more power required, but more dust is also created in the mine. It is an object of the present invention to provide a cutter bit that is more durable than previous mining bits. It is a further object of the present invention to enhance the life of the cutter bits by reducing the heat generated by the rubbing of the clearance face against the coal formation. It is still a further object of the present invention to enhance the life of the cutter bits by minimizing the propagation of cracks due to heat checking of the carbide. It is still a further object of the present invention to enhance the life of the cutter bit by controlling the wear of the clearance face so as to provide a self-sharpening cutter bit. It is a further object of the present invention to make the life of the cutter bit more predictable, enabling bit changes to be made at the end of a pass, when the cutter drum is more accessible. Brief Summary of the Invention The present invention as defined in the claims involves a cutter bit having a shank for insertion into a toolholder and a forward working portion having multiple inserts with at least a lead cutting insert having a cutting edge for removing hard and abrasive mineral formations. The inserts are composed of a hard wear resistant material, such as a cemented carbide, and a leading insert is mounted on the forward working portion of the bit and faces and projects foremost in the direction of intended travel of the bit. A clearance face is located rearwardly of the hard wear resistant leading insert to reduce rubbing against the mineral formation as it is being removed. According to the present invention, the leading insert may be a single piece of carbide or a laminated insert having at least two or more individual inserts bonded to the cutter body. Further, according to the present invention, an additional insert is mounted in the clearance face behind the insert and have a cutting edge thereon. The multiple inserts enhance the life of the bit by reducing wear of the forward working portion behind the leading insert and preserving the taper on the forward working portion of the bit. The benefit of maintaining the taper on the forward working portion is to create a self-sharpening effect and reduce the heat generated by the friction of the bit passing through the coal or mineral formation. This reduces failure of the inserts due to heat checking and the wear resistant properties of the inserts will be more fully utilized. The additional insert mounted on the clearance face protrudes beyond the clearance face and may have a cutting edge of its own at the beginning of the life of the bit. The additional insert controlling the wear pattern of the clearance face helps reduce the wear on the leading insert and create the self-sharpening effect which reduces the power required per unit volume of mineral or coal produced. The additional insert placed in the clearance face comprises forming a recess in the clearance face behind the leading insert and fastening in the recess an insert of hard wear resistant material that projects above the clearance face, preferably a wear resistant cemented hard metal carbide although other materials, such as ceramics, diamonds, hardfacing materials, etc., are contemplated. The recess formed in the clearance face may take the form of a cylindrical hole, a series of cylindrical holes, an elongated slot, or slots, or an additional insert attached to a surface behind the direction of travel of the leading insert. Along with the possible cutting edge on the additional insert in the clearance face, the present invention further contemplates the leading insert comprising at least two inserts with cutting edges placed in an adjacent relation to one another so that if one insert fails the second insert presents its cutting edge to the material to be removed. The preferable mode is arranging at least two inserts with cutting edges as described together to form a laminated insert on the forward working portion of the bit with at least two individual inserts brazed to a metal shim. The cutting edges of the individual inserts are arranged facing the direction of rotation of the bit and so positioned one behind the other that if the leading cutting edge either wears away or fractures the following cutting edge comes into operation against the mineral formation. The leading cutting edge is preferably thicker and narrower than the following cutting edge so as to provide greater wear resistance at the center of the cutting edge. The preferred mode according to the present invention is to mount at least one cylindrical insert in the clearance face and have their uppermost tips project above the leading cutting tip and intersect a line that forms an included angle of six degrees with a plane perpendicular to the longitudinal area of the bit and passing through the apex of the cutting edge of the leading insert. Preferably, the individual cutting inserts are comprised of a cemented metal carbide material and have a metal shim member dividing the two inserts. The carbide inserts are brazed to the metal shim member and the entire assembly is brazed in a pocket formed on the forward working position of the cutter bit. In a preferred mode, it is believed that the leading insert is comprised of a tough impact resistant carbide material and the others are comprised of a wear resistant carbide material. The exact nature of the present invention will become more clearly apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which: Figure 1 is a partially cut away side view of a cutter bit according to the present invention. Figure 1A is a top view of a cutter bit according to the present invention. Figure 2 is a side view of one embodiment of a multi-insert cutter bit according to the present invention. Figure 2A is a partial top view of the cutter bit of Figure 2. Figure 3 is still another embodiment of the multi-insert cutter bit of the present invention. Figure 4 is an end view of a cutting insert according to the present invention. Figure 4A is a side view of a cutting insert according to the present invention. Referring to the drawings somewhat more in detail, shown in Figure 1 is a partially cut away view of a cutter bit 105 having a flat rectangular shank portion 12 and a forward working portion 14 with a sloped or curved clearance face 24. Mounted on the forward working portion 14 is a cutting insert 108 having a cutting edge 18 formed on the insert 108. The insert is usually comprised of a hard wear resistant material, such as a cemented hard metal carbide material, and is brazed in a pocket 20 formed on the forward working portion 14. The direction of travel of the bit 105 is indicated as at arrow 22 with the bit 105 being driven against a formation to be reduced. Located rearwardly of the direction of travel of the cutting edge 18 is the clearance face 24 on forward working portion 14. Clearance face 24 is configured so as to reduce the rubbing of the rearmost part of the forward working portion 14 of cutter bit 10 as it is driven through the mineral formation. The bit 105 in Figure 1 is shown inserted into block 106 and has a foremost carbide compact 108 and a second carbide compact 110 located rearwardly of the forwardly facing compact 108. Compact 110 is cylindrical in nature but has a flat 111 placed on its forward side such that a cutting edge 112 is created on the compact. The cutting edge 112 is located on an approximately four to six degree line drawn along the back rake of the bit 105. The angle can be demonstrated by constructing a plane perpendicular to the longitudinal axis of the shank of the bit and passing it through the apex of the cutting edges of the leading insert. Testing of these bits has revealed that the clearance face wears on an approximately four to six degree angle when compared to a horizontal line parallel to the base block 106 into which the bit 105 is inserted. It is, therefore, believed that the cutting edge of the trailing insert 110 should be placed on a line of approximately four to six degrees from the clearance face so that it may have a cutting action similar with the foremost compact 108 while also preventing wear along the clearance face. The positive angle shown, although preferably varying from four to six degrees, could vary more depending upon the feed of the cutting drum down the face of the coal to be cut. It has been found that, for most feeds, four to six degrees is preferable, but the faster the drum feeds down the coal face, the greater the angle will have to be in order to achieve optimum cutting. A further modified bit 120 is shown in holder 122 in Figure 2. This bit has a leading insert 124, a second cylindrical insert 110 as described in Figure 1 and a third cylindrical insert 126, with each of the inserts 110 and 126 having a flat produced thereon such that a cutting edge 112 and 128 are provided on the inserts. Again, as shown, the inserts 110 and 126 have their cutting edges 128 and 112 located on a line tilted approximately four to six degrees along the clearance face of the bit 120 because it is believed desirable to have all the inserts simultaneously perform a cutting action when in use. Figures 1A and 2A show top views of Figures 1 and 2, respectively. In Figure 1A, forward insert 108 is shown along with a cylindrical insert 110 having a cutting edge 112. Similarly, in Figure 2A, a top view is shown having the insert 110 with a cutting edge 112 and an insert 126 even behind insert 110 having a further cutting edge 128. Again, it is desirable to place all the cutting edges near or on a line of six degrees from a tangential line 125. In Figure 3, a further modification is shown with the third insert 126 shown in its position. However, insert 127 is now shown as a cylindrical plug, when viewed in side, tapering from top to bottom and inserted in hole 129 and brazed in place with braze 131. By placing insert 127 in the bit in this fashion, it is believed that, as the insert wears down, it, itself, has a self-sharpening effect in that the tapered section always presents a fresh cutting edge to the material to be cut. Shown in Figure 4 is the insert 131 shown in end view as a cylindrical plug and tapering from one end to the other. Figure 4A shows the insert 131 in side view, again having a taper from one end to the other. Shown in Figure 2, the included angle of six degrees can be constructed by forming a plane perpendicular to the longitudinal axis of the shank of the bit 120 and passing it through the uppermost tip of the foremost cutting insert 124. The six degree line shown in Figure 2 then intersects that plane and has the cutting points 112 and 128 either in line or adjacent to the six degree angle. In Figure 5 and 5A is shown a leading insert 92 mounted in front of a second insert 94 with each of the inserts brazed to an individual shim member 96 mounted on the forward part of the clearance face 98 of the cutter bit 100. Immediately behind insert 94 are located two cylindrical inserts 102 and 104 which project from the clearance face and form the hard wear resistant means which will aid in maintaining a tapered cutting edge 106 on the cutter bit 100 as previously described. Individual carbide inserts 92 and 94 form a composite or laminated insert with each being brazed to metal shim member 96. Preferably, the inserts 92 and 94 are formed of a cemented hard carbide material and are brazed to a steel shim member 36. The hard wear resistant means is preferably comprised of a hard wear resistant cemented metal carbide material. The advantage of the composite or laminated insert is that some materials that are hard and wear resistant, such as a cemented hard metal carbide, are subject to failure due to heat checking. By making the leading insert a composite of at least two individual inserts connected to a shim, or connected to each other as by brazing, the temperature differential across each carbide insert is reduced which, in turn, reduces the tendency for heat checking and, further, if cracks in the individual carbide members do develop, then propagation is arrested by the metal shim or braze connection separating the two individual inserts 92 and 94.

Claims: 1. In a cutter bit (105, 120) having shank means (12) and abutment means for insertion into a toolholder (106), a forward working portion (14) on said shank means for engagement with the material to be cut, hard wear resistant means (108, 124) with a first cutting edge on said forward working portion, said cutting edge having sides tapering outwardly toward said shank means (12) when viewed from the front, a clearance face (24) behind said cutting edge, and an insert (110, 126) of hard wear resistant material having a cutting edge (112, 128) and mounted in said clearance face (24) centrally behind said hard wear resistant means, characterized in that said insert (110, 126) is narrower than said hard wear resistant means (108, 124) and has an end portion projecting above the clearance face and over the hard wear resistant means (108, 124) so as to reduce the rate of wear and maintain the taper of said first cutting edge during the life of the bit, the cutting edge (112, 128) being formed on the end portion of said insert (110, 126) such that a part of said cutting edge passes through or is located adjacent a first plane forming a positive included angle with a second plane formed perpendicular to the longitudinal axis of the shank (12) of the bit and passing through the tip of said hard wear resistant means on said forward working portion, said angle being the greater the faster the cutting machine, e.g. a cutting drum, is to be fed into the material to be excavated. 2. The bit according to claim 1 in which the mounting of said insert (110) comprises an elongated slot extending rearwardly from the direction of rotation of the bit and located behind said hard wear resistant means, and an elongated insert mounted in said slot. 3. The bit according to claim 2 in which said hard wear resistant material is comprised of cemented hard metal carbide. 4. The bit according to claim 1 in which said hard wear resistant means forming said cutting edge comprises at least two discrete wear resistant inserts and means for holding said inserts together, each of said inserts having a cutting edge that, when viewed from the front, tapers outwardly toward the shank of the bit. 5. The bit according to claim 4 in which said means for holding said inserts together comprises a shim member between said two inserts and means for fastening said inserts to said shim member. 6. The bit according to claim 1 in which the mounting of said insert (110) comprises forming a first cylindrical recess in said clearance face and mounting an elongate cylindrical insert of hard wear resistant material in said recess. 7. The bit according to claim 6 which further comprises a second cylindrical recess formed in said clearance face behind said first circular recess and a second elongate cylindrical insert (126) mounted in said second recess. 8. The bit according to claim 4 which further comprises the cutting edge of the first discrete insert forming the hard wear resistant means is narrower than the cutting edge of the second discrete insert forming the hard wear resistant means when the two discrete inserts are viewed from the front. 9. The bit according to claim 1 which further includes said first and second planes forming an included angle of approximately four to six degrees. 10. The bit according to claim 9 which further includes at least two inserts (110, 126) mounted in said clearance face (24), each of said two inserts having a cutting edge (112, 128) and the tips of said cutting edges each located in or adjacent to said first plane. 11. The bit according to claim 1 in which said insert (110, 126) in said clearance face comprises an elongate cylindrical plug member. 12. The bit according to claim 11 in which said plug member has a planar flat (111) formed thereon and said flat (111) intersects one end of the plug member to form a cutting edge (112, 128). 13. The bit according to claim 12 which further comprises the plane of said flat (111) tapering away from the center line of said plug member as it extends away from said cutting edge.

Inventors: HUTZELL, CLYDE G., MCKENNA, ALEX G.
Applicants: KENNAMETAL INC.
Application year: 1983
Main classification: E21C35
IPC codes: E21B10, E21C35