Shearing Cutter on a Degradation Drum

Abstract

In one aspect of the present invention, a pick comprises a forward end and rearward end. The forward end comprises a shearing cutter and the rearward end comprises a shank. The shank and the shearing cutter are arranged co-axially about a central axis. The shearing cutter is supported by an enlarged section that narrows towards the shearing cutter and that has a greater cross section than the shank along a plane substantially perpendicular to the central axis. The shearing cutter comprises a flat surface that is substantially perpendicular to the central axis.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 11/424,806 filed on Jun. 16, 2006. This application claims priority to U.S. application Ser. No. 11/424,806, which is herein incorporated by reference for all that it teaches.

BACKGROUND OF THE INVENTION

The present invention relates to a cutting tool that may be used in asphalt, mining, excavation, and other industries. In asphalt or concrete milling, an array of cutting tools supported by a drum may engage the paved surface causing both the paved surface to degrade, and the tools to wear. Typically, conical cutting elements are used in milling. These conical cutting elements are rotationally supported by a block or drum on a milling drum. The blocks are generally adapted to hold the picks at an offset angle such that the picks will rotate as they engage the formation. Rigidly fixed shearing cutters have also been used in the milling drum prior art.

U.S. Pat. No. 5,235,961 to McShannon, which is herein incorporated by reference for all that it contains, discloses a carbide mineral cutting tip with a solid carbide body having at least one front face, at least one top face, a bottom seating face, a rear face, and side faces, the rear face being provided at the end of an extended tail portion of the tip, whereby the front-to-rear length of the tip approximates to twice the depth of the tip represented by the top-to-bottom length of the front face. The invention also includes a mineral cutter pick provided with such a tip.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a pick comprises a forward end and rearward end. The forward end comprises a shearing cutter and the rearward end comprises a shank. The shank and the shearing cutter are arranged co-axially about a central axis. The shearing cutter is supported by an enlarged section that narrows towards the shearing cutter and that has a greater cross section than the shank along a plane substantially perpendicular to the central axis. The shearing cutter comprises a flat surface that is substantially perpendicular to the central axis.

The pick may be secured within a holder attached to a drum. The shank may be rotatably secured within a bore and may be rotatable about a central axis of the shank. The forward end may be tapered towards the shearing cutter. The shearing cutter may comprise cemented metal carbide. The shearing cutter may also comprise a super hard material bonded to cemented metal carbide at a non-planar interface, the super hard material forming the flat surface. The super hard material may comprise an axial thickness greater than the thickness of the cemented metal carbide. The shank may be press fit into the bore of the holder. The shearing cutter may be brazed to a carbide bolster that progressively increases in diameter from the forward end. The shearing cutter may be bonded to a carbide bolster attached to a rotating shield.

The pick may be incorporated in a milling machine. The pick may be incorporated in mining machine. The shearing cutter may comprise a flat edge, rounded edge, chamfered edge, double chamfered edge, or combinations thereof. The pick may also be incorporated in a trenching machine.

In another aspect of the present invention, a degradation drum comprises a pick secured to an outer surface of the drum through a block rigidly mounted to the outer surface. The block comprises a bore with an inner surface, the shank being secured within the bore. At least one pick comprises a shearing cutter comprising a flat surface. The shearing cutter and the shank are co-axially arranged about a central axis. The flat surface of the shearing cutter is substantially perpendicular to the central axis. At least one shearing cutter may be positioned proximate a longitudinal edge of the drum. The bore may be substantially aligned with a length of the block and may be substantially coaxial with the central axis of the pick. The pick may be laterally offset from the direction of rotation of the drum. The pick may be offset at an angle of 7 to 15 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of an embodiment of a degradation drum suspended underside of a pavement milling machine.

FIG. 2 is a perspective diagram of an embodiment of a degradation drum.

FIG. 3 is a cross-sectional diagram of an embodiment of a pick.

FIG. 4 is a cross-sectional diagram of an embodiment of a degradation drum engaged with a portion of a pavement.

FIG. 5 is a cross-sectional diagram of another embodiment of a pick.

FIG. 6 is a cross-sectional diagram of another embodiment of a pick.

FIG. 7 is a detailed diagram of another embodiment of a degradation drum.

FIG. 8 is a detailed diagram of another embodiment of a degradation drum.

FIG. 9 is a cross-sectional diagram of another embodiment of a pick.

FIG. 10 is a cross-sectional diagram of another embodiment of a pick.

FIG. 11 is a cross-sectional diagram of another embodiment of a pick.

FIG. 12 is a cross-sectional diagram of an embodiment of a shearing cutter.

FIG. 13 is a cross-sectional diagram of another embodiment of a shearing cutter.

FIG. 14 is a cross-sectional diagram of another embodiment of a shearing cutter.

FIG. 15 is a cross-sectional diagram of another embodiment of a shearing cutter.

FIG. 16 is a cross-sectional diagram of another embodiment of a shearing cutter.

FIG. 17 is an orthogonal diagram of an embodiment of a mining machine.

FIG. 18 is a perspective diagram of an embodiment of a trenching machine.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIG. 1 is a cross-sectional diagram that shows a plurality of picks 101 attached to a driving mechanism, such as a rotatable drum 102 attached to the underside of a pavement milling machine 103. The milling machine 103 may be an asphalt planer used to degrade man-made formations 104 such as pavement prior to placement of a new layer of pavement. The picks 101 may be attached to the drum 102, bringing the picks 101 into engagement with the formation 104. A holder, such as a block welded or bolted to the drum 102, is attached to the driving mechanism and a shank of the pick 101 is inserted into the holder. The holder may hold the picks 101 at an angle offset from the direction of rotation, such that the picks 101 engage the formation 104 at a preferential angle. Arrow 105 discloses the milling machine's direction of travel.

Referring to FIG. 2, a rotary degradation drum 102 for harder pavements, such as concrete is disclosed. The degradation drum 102 may comprise a plurality of picks 200 disposed adjacent to each other, thereby covering most of the outer surface of the drum 102. In some embodiments, the drum 102 may comprise as many as 400 picks. The plurality of picks 200 may comprise shearing cutters 210.

Shearing cutters 210 may have advantages over pointed picks. For instances, the shearing cutters 210 may take a shallower depths of cut into the formation. This makes the shearing cutters 210 less aggressive and requires a greater specific energy than pointed cutters. But this may be advantageous when the pick is enhanced with a brittle cutting material such as sintered polycrystalline diamond or cubic boron nitride. While efficiency is lost, the life of the shearing cutter 210 is believed to be longer. Thus, the overall performance of the drum 102 may improve for harder formations. Preferably, the picks' shanks are rotatably secured within the drum's holders, and the picks 200 with shearing cutters 210 are laterally offset to encourage the picks 200 to rotate upon engagement with the formation. This rotation spreads the wear around the shearing cutter's entire circumference instead of localizing wear on a specific side. The picks 200 may be offset at an angle of 7 to 15 degrees from the direction of rotation of the drum 102. The picks 200 disposed in the center region of the drum 102 may be offset less than picks 200 disposed away from the center region of the drum 102. Picks 220 positioned at the longitudinal ends of the drum 102 may be angled to cause the cutter to rotate as the pick 220 not only engages the depth of cut, but also as the cutter engages the wall formed by the cut as the cutter is entering the cut.

FIG. 3 discloses a cross-sectional diagram of an embodiment of a pick 200. The pick 200 may comprise a forward end and a rearward end. The forward end may comprise the shearing cutter 210 and a rearward end may comprise a shank 300 that is adapted to fit within the bore of the drum's holder or block. The shank 300 and the shearing cutter 210 are arranged co-axially about a central axis of the pick 200. The shearing cutter 210 is supported by an enlarged section of the pick 200 that narrows towards the shearing cutter 210. The tapered end may prevent the forward end of the pick 200 from coming into contact with the formation especially when the negative rake angle is small as in the case of shearing cutters 210. The enlarged section has a greater cross section than the shank 300 along a plane that is substantially normal to the central axis.

The shearing cutter 210 may comprise shear cutter bonded directly to a cemented metal carbide core 380 press fit into a bore 310 formed in the forward end of the pick 200. In some embodiments, the core 380 may be segmented and the distal most segment may support a superhard cutting material such as sintered polycrystalline diamond or cubic boron nitride. The shearing cutter 210 may comprise a flat surface 330 that forms a cutting edge with the cutter's cylindrical side. The flat surface 330 may be substantially perpendicular to the axis of the shank 300.

The pick 200 may comprise a gap 340 of 0.010 to 0.115 inches between the outer surface of the shank 300 and the inner surface of the holder 350. The gap 340 may assist the pick's free rotation. Preferably, the gap 340 is small enough to prevent dirt and debris from entering while cutting the formation. Preferably, the shank 300 comprises at least two diameters joined by a transition region. The multiple diameters are believed to reduce bending forces in the shank 300. Bending forces may also be reduced by lengthening the shank 300 and the holder's bore. The pick 200 may comprise a washer 360 intermediate the forward end and the rearward end. The washer 360 may allow the rotation of the pick 200 for a long period of time. The washer may be constructed of steel. The shank 300 and the holder 350 may be held together by a snap ring mechanism 370.

FIG. 4 discloses a rotatable shearing cutter 210 in contact with a formation 104. The shearing cutter 210 scrapes a thin layer of formation 104 off during each pass. This is opposed to pointed cutters that are more aggressive. Pointed cutters may induce fractures which usually propagate through the formations. Since the pointed cutters are imparting more energy into the formation per pass, pointed cutters tend to wear faster. In softer formations, typically made of asphalt, a carbide or superhard material enhanced pointed cutter may be robust enough. However, in harder formations like asphalt formations that incorporate extremely hard rock or concrete pavement, the traditional approach of using a pointed cutter may be costly. By changing the shape of the cutter to be less aggressive, the impact force experienced by the cutter is less, thereby extending the cutter's life.

The shearing cutters 210 may degrade the formation 104 at a negative rake angle. The rake angel is measured by the angle formed against the tangent of the cut's curvature and the flat surface of the shearing cutter 210. Preferably, the angle is negative 10 to 20 degrees for concrete jobs of average hardness. More preferably, the angle is 15 degrees.

FIG. 5 is a cross-sectional diagram of another embodiment of a pick 200. In some embodiments, the shearing cutter 210 may comprise a super hard material 550 bonded to cemented metal carbide 500 at a non-planar interface 510. The super hard material 550 may form the flat surface 520. The super hard material 550 may comprise a material selected from a group comprising diamond, polycrystalline diamond, natural diamond, synthetic diamond, vapor deposited diamond, silicon bonded diamond, cobalt bonded diamond, thermally stable diamond, polycrystalline diamond with a binder concentration of 1 to 40 weight percent, infiltrated diamond, layered diamond, monolithic diamond, polished diamond, course diamond, fine diamond, cubic boron nitride, diamond impregnated matrix, diamond impregnated carbide, metal catalyzed diamond, or combinations thereof.

Preferably, a sintered polycrystalline diamond is used. The sintered diamond is formed by subjecting a plurality of diamond crystals to high pressure and high temperature. A catalyst is generally used to lower the activation energy required to form new diamond to diamond bonds between the diamond crystals resulting in a polycrystalline diamond geometry. Sintered diamond is preferred over vapor deposited diamond because vapor deposited diamond is generally not as dense as sintered diamond. Generally, vapor deposited diamond is easier to bond to object, but it exhibits anisotropic properties by having greater impact resistant in certain directions. Sintered diamond, on the other hand, is more isotropic by having high impact resistance in from all directions.

Referring to FIG. 6, shearing cutter 210 may be bonded to a cemented metal carbide bolster 600 that increases in diameter moving away from the forward end. The carbide bolster 600 may resist abrasion at the forward end of the pick 200.

FIG. 7 discloses a rotary degradation drum 102 specifically tailored for asphalt milling. The drum 102 may comprise a plurality of rotary picks 200 arranged in a helical array. The picks 200 may comprise shearing cutters 210. The drum 102 may comprise fewer picks 200 for asphalt milling in comparison to concrete milling, thereby increasing the impact forces per pick.

FIG. 8 discloses a drum with both pointed cutters and shear cutters. In some embodiments, the shearing cutter 210 may be positioned proximate the longitudinal edge of the drum 102 while the pointed cutters are located along the length of the drum 102. In some embodiments, the shear cutters 210 may prevent sides of the drum 102 from coming into contact with formation. In other embodiments, the pointed and shear cutters may be combined in other arrangements. For example, a shear cutter 210 may be positioned to follow a pointed cutter, thereby, subjecting some formation area to both cutting mechanism. Here, the pointed cutting element aggressively impacts the formation with the force being focused just in front of the pointed cutter's apex. The pointed cutter penetrates easier and induces fractures through the area. The shear cutter 210 follows and opens the cut wider than the pointed cutter. Thereby, removing the fractured area easier since the formation is weakened from the induced fractures. It is believed that this combination may be synergistically remove more formation material together than either cutting mechanism may remove on its own.

FIG. 9 discloses the forward end with a carbide bolster 900 attached to a rotating shield 910 and a rearward stationary end comprising a shank 920. A bearing between the shield and the shank may provide free rotation. In some embodiments, the rotation may be restricted to reduce the differential movement between the parts and preventing erosion between them.

FIG. 10 discloses the forward end of the pick 200 comprising shearing cutter 210 attached to a cemented metal carbide 380. The shearing cutter 210 and the cemented metal carbide 380 may comprise same diameter. The shearing cutter 210 may comprise a superhard cutting material such as sintered polycrystalline diamond or cubic boron nitride. In some embodiments, the shearing cutter 210 may comprise a cemented metal carbide 380 as illustrated in FIG. 11. The shearing cutter 210 bonded to the cemented metal carbide 380 may be press fit into a bore 310 formed in the forward end of the pick 200. The cemented metal carbide 380 may comprise a greater axial thickness than the shearing cutter 210.

FIGS. 12-16 disclose different shear cutters 210 comprising a super hard material 550 bonded to cemented metal carbide 500. The bonding between the super hard material 550 and the cemented metal carbide 500 may comprise planar interface, non-planar interface, or combinations thereof. The shearing cutters 210 may comprise flat edge 1000, rounded edge 1001, chamfered edge 1002, double chamfered edge, or combinations thereof. The shearing cutters 210 with flat edge 1000 may perform well in soft formations while the shearing cutters 210 with rounded and chamfered edge may perform better in hard formations by changing the direction that resultant force loads are induced into the cutter. In some embodiments, the edge may comprise multiple chamfers that are at different angles with the flat. These different chamfers are preferably contiguous. In some embodiments, the chamber may not be uniform. FIG. 15 discloses a cutter with a carbide that narrows towards the super hard material. FIG. 16 discloses two flats both capable of cutting the formation. The diameter of the distal most flat 1003 comprises a small diameter than the more proximal flat 1004, so the more proximal flat 1004 may widen a cut formed by the more distal flat 1003. In some embodiments, the super hard material 550 may comprise an axial thickness greater than the thickness of the cemented metal carbide 500. In some embodiments, the super hard material 550 may comprise an axial thickness smaller than the thickness of the cemented metal carbide 500. In other embodiments, the super hard material 550 may comprise an axial thickness equal to the thickness of cemented metal carbide 500.

FIG. 17 discloses a mining machine 1700 incorporating the present invention. The picks 101 may degrade a coal steam 1720 or a steam made of another valuable material or mineral.

FIG. 18 discloses a trenching machine 1800 comprising a plurality of picks 101 on a rotating chain 1810. The rotating chain 1810 rotates in the direction of the arrow 1850 and cuts the formation forming a trench while bringing the formation cuttings out of the trench to a conveyor belt 1830 which directs the cuttings to a side of the trench. The rotating chain 1810 is supported by an arm.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.

Claims

1. A pick, comprising:

a forward end and rearward end;

the forward end comprising a shearing cutter and the rearward end comprising a shank;

the shank and the shearing cutter are arranged co-axially about a central axis;

the shearing cutter is supported by an enlarged section that narrows towards the shearing cutter and that has a greater cross section than the shank along a plane substantially perpendicular to the central axis; and

the shearing cutter comprising a flat surface that is substantially perpendicular to the central axis.

2. The pick of claim 1, wherein the pick is secured within a holder attached to a drum.

3. The pick of claim 1, wherein the shank is rotatably secured within a bore and is rotatable about a central axis of the shank.

4. The pick of claim 1, wherein the forward end is tapered towards the shearing cutter.

5. The pick of claim 1, wherein the shearing cutter comprises cemented metal carbide.

6. The pick of claim 1, wherein the shearing cutter comprises a super hard material bonded to cemented metal carbide at a non-planar interface, the super hard material forming the flat surface.

7. The pick of claim 6, wherein the super hard material comprises an axial thickness greater than the thickness of the cemented metal carbide.

8. The pick of claim 1, wherein the shank is press fit into the bore of the holder.

9. The pick of claim 1, wherein the shearing cutter is brazed to a carbide bolster that progressively increases in diameter from the forward end.

10. The pick of claim 1, wherein the shearing cutter is bonded to a carbide bolster attached to a rotating shield.

11. The pick of claim 1, wherein the pick is incorporated in a milling machine.

12. The pick of claim 1, wherein the pick is incorporated in mining machine.

13. The pick of claim 1, wherein the shearing cutter comprises a flat edge, rounded edge, chamfered edge, double chamfered edge, or combinations thereof.

14. The pick of claim 1, wherein the pick is incorporated in a trenching machine.

15. The pick of claim 1, wherein the pick comprises a negative rake angle of 15 degrees approximately.

16. A degradation drum, comprising:

a pick secured to an outer surface of the drum through a block rigidly mounted to the outer surface;

the block comprising a bore with an inner surface, the shank being secured within the bore;

at least one pick comprising a shearing cutter comprising a shearing cutter comprising a flat surface;

the shearing cutter and the shank are co-axially arranged about a central axis; and

the flat surface of the shearing cutter is substantially perpendicular to the central axis.

17. The drum of claim 16, wherein the at least one shearing cutter is positioned proximate a longitudinal edge of the drum.

18. The drum of claim 16, wherein the bore is substantially aligned with a length of the block and is substantially coaxial with the central axis of the pick.

19. The pick of claim 16, wherein the pick is laterally offset from the direction of rotation of the drum.

20. The pick of claim 16, wherein the pick is offset at an angle of 7 to 15 degrees.