Cutter Bit And Method Of Causing Rotation Thereof

Abstract

A method and apparatus for turning a cutter bit in a continuous mining machine by providing one or more projections coupled to the bit having sufficient length so that when the cutter bit is in operation, material dislodged by the cutter bit, when falling, will impact the projections. The impact will generate a torque about the axis of the cutter bit causing the cutter bit to rotate a few degrees about the axis. Continual impact of the projections will provide continuous turning of the bit thereby increasing its useful life.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improvements in the cutter bits used in continuous mining machines. The invention relates particularly to a method for providing continuous turning of the cutter bit in order to even the wear of the cutter bit thereby prolonging its life.

2. Description of the Prior Art

Many attempts have been made in the past in an effort to solve the uneven wear of cutter bits used in continuous mining machines. These cutter bits are mounted either in rotating drums along the periphery of the drum so that the axis of the bit is normal to the axis of the drum, or on a series of parallel chain-type drives such that the axis of the bits is always normal to the surface of the chain. The continuous mining machines cause the bits to move into the material being mined and tear away said material. If the bits are stationary only one surface will contact the material continuously. The single surface will wear excessively causing the bit to fail in a short period of time by wearing away the metal supporting the hardened tungsten carbide tip. A typical cutter bit is disclosed in the U.S. Pat. to A. B. Bower, Jr. No. 3,476,438. This patent, along with the U.S. Pat. to J. K. Maddock No. 3,361,481 and a French patent to Gerald Wayne Elders 1,483,463, are illustrative of patents relating to cutter bits used in continuous mining machines. These patents all are directed toward methods of continuously rotating the bits by providing rib extensions along the outer conical surface of the bit so that friction of the rib against the material being cut will cause rotation of the bit.

SUMMARY OF THE INVENTION

The present invention contemplates a method and apparatus for rotating a cutter bit not by the use of friction against the surface being cut, but rather by impact of the bit by falling material dislodged by the cutter bit.

In order to provide a means for rotating the bit by impact, novel projections are mounted on the bit and extend radially from the bit. The projections are of sufficient length so that material being dislodged above the bit will fall striking the projections. The forces thus transferred to the projections will cause a torque about the axis of the cutter bit imparting rotation thereto. Many types of configurations are possible which will suffice to cause impact rotation of the cutter bit. The projections can be mounted directly to the bit by welding or keyed to the bit mechanically.

It is, therefore, an object of this invention to provide a method for rotating a cutting bit in an effort to extend the life of the bit.

It is a further object of this invention to use the forces generated by falling mined material as a means of developing sufficient torque to cause continuous turning of a cutter bit in a mining machine thereby providing even wear of the bit cutting surface resulting in an extended useful life of the cutter bit.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side view of the cutter bit illustrating the preferred impact arms;

FIG. 2 is a front view of FIG. 1;

FIG. 3 is a perspective view of FIGS. 1 and 2;

FIG. 4 illustrates the method of operation of the impact arms;

FIG. 5 is a modified impact arm mounting which is removable from the cutter bit, with the bit shown in dotted lines;

FIG. 6 is a cross-sectional view of the impact arm ring shown in FIG. 5;

FIG. 7 is a perspective view of a modified impact arm ring with the cutter position defined by dotted lines; and

FIGS. 8 through 14 illustrate various modifications of the impact ring shown in FIGS. 2 through 7.

SPECIFIC DESCRIPTION OF THE FIGURES

Referring to all of the FIGURES, but in particular to FIGS. 1 through 4, a cutter bit generally referred to by the number 20 is shown. The cutter bit has a shank portion 21 and a conical cutting portion 22 axially formed with shank 21. A hardened material insert 23 is mounted in conical head 22 so that a portion of insert 23 projects from head 22. Insert 23 is generally made from tungsten carbide-type materials, and is preformed to a sharpened point to enhance the cutting of the bit.

A mounting for the cutter bit is generally referred to by number 24, and is shown in dotted lines since it forms no part of this invention, but is included to illustrate the method for holding the bit only. The bit normally is anchored or secured in the mounting 24 by means of a pin 25; however, other means are also normally employed such as a ring having a plurality of dimples positioned to engage the holes for pins 25 in the mounting. A circumferential groove 26 is formed behind the head 22, and is generally used to assist in removing the bit once it becomes worn. A shoulder 27 acts as a bearing surface for the bit during use.

To a standard bit is mounted a plurality of impact arms 30 which in the embodiment shown in FIG. 1 are attached to shoulder 27, and normal to the surface of the shoulder. The impact arms can be mounted by welding, brazing or any other suitable means or forged directly during the manufacture of the cutter bit. Impact arms 30 can be made of any suitable material such as iron, steel, or other metals which can take an impact from falling material without breaking or bending severely. The length of the impact arms can vary greatly; however, the efficiency of the impact arms will increase with their length. For example, referring to FIG. 2, the radius labeled R which is the distance between the axis of the shaft 21 and the tip of the impact arm can have a minimum just slightly larger than the diameter of the shoulder 27 and a maximum preferred length which does not exceed the diameter of the mounting 24.

The force generated (useful in rotating the shaft 21) is dependent on the weight of the material impacting arm 30 and the distance or radius R where the impact occurred on arm 30. Thus, the longer the arm, the greater the rotational force generated by the falling material. The maximum length of arms 30, of course, depends on the diameter of the rod forming the impact arms 30 and the mechanical strength of the rod. Thus, if the rods were beyond the maximum diameter of mounting 24, the coal or mined material could bend the rod back over mounting 24 causing the arms to jam thereby preventing rotation of the cutter bit. Furthermore, if the arms are too long, they could be easily bent and their effectiveness reduced or eliminated. In addition, the length of impact arms 30 is determined by the closeness of the adjacent cutter bits. The arms should not interfere with the rotation movement of adjacent cutting bits. If arms 30 are too short, the material will have little to impact, thereby reducing the chances of impact and, in addition, the radius R will be minimum, thereby generating the minimum force possible. The preferred embodiment uses arms which extend out to the diameter of mounting 24.

OPERATION

The operation of the arms can be better understood by referring to FIG. 4. A cutter bit 20 is moving in the direction of the arrow 32. As it moves, it breaks away material 33a, 33b or 33c. For example, if 33b should impact arms 30a at point 34, a force will be generated about the axis of cutter bit 20 in the direction of arrow 35. Mined material 33c will likely impact arms 30c since it is moving in the direction of arrow 36. If material 33c impacts arms 30c a rotational force will be generated in the direction of arrow 35c. Mined material 33a as it falls will probably impact arm 30a or one of the two arms 30b or 30d if these arms have moved into a position under material 33a. From the description of the operation, it can be observed that the falling material will probably not cause a complete rotation of cutter 20, but will cause a partial rotation. However, the random impact of the falling material on the impact arms will cause a continual rotation of bit 20, resulting in what amounts to a continuous rotation in both directions, clockwise and counterclockwise. The continual rotation will cause equal wear on all sides of the cutter bit cone 22 and equal wear on sharpened hard insert 23. Since the softer metal on cone 22 will wear away first, insert 23 will always be exposed as a cutting element. Since it is rotating, more or less, continuously (regardless of its direction), the point on insert 23 will remain fairly round. That is, it will not sharpen to a chisel shape which is likely if the bit ceases to rotate.

In an embodiment incorporating this invention which was successfully tested, a bit having a shaft diameter 21 of fifteen-sixteenths inch and a shoulder diameter 27 of 11/4 inch had impact arms mounted on the shoulder comprising 1/4 inch diameter mild steel rods with a radius R of 11/4 inch.

A second embodiment was successfully tested using the same rods 30 as above and the same radius R with the rods mounted in the circumferential groove 26.

A third embodiment was successfully tested where the rods 30 were one-fourth inch in diameter, radius R was 11/8 inch and the rods were bent forward approximately 20.degree. to increase the impact probability. From the above tests, it was determined that bits without impact means averaged approximately 64 hours of continuous use while bits with impact arms made as described above operated 104 hours and were still useable.

MODIFIED IMPACT ARMS

Referring to FIGS. 5 and 6, a modified impact arm is illustrated and essentially comprises a disc 40 having an axial opening 41 of a size sufficient to permit the disc to pass over the shank 21 of cutter 20. A pair of notches 42 is formed in the opening 41 and engages a raised portion 43 which cooperates with the notch 42 to prevent turning of disc 40. A plurality of impact arms 44 are formed extending from disc 40. The impact arms of this embodiment are bent at an angle .theta. in order to increase the probability of impact. Obviously, the arms need not necessarily be bent. However, any configuration which increases the probability of impact is preferred over other embodiments. A notch 42 is illustrated in this embodiment. It is well within the skill of the art to incorporate any method which would prevent ring 40 from turning on shaft 21. In fact, the ring could be welded to the shaft. The advantage of the embodiment shown in FIGS. 5 and 6, however, is that the ring can be used for a plurality of cutter bits in succession; that is, once a bit becomes unserviceable, the ring can be removed and placed on a new bit. The ring in this embodiment is shown mounted behind shoulder 27. It is obvious that the ring can be mounted over shoulder 27 or in the circumferential groove 26. Many ways can be devised for attaching the ring to the cutter bit so that it can be released and reused and yet will not turn on shaft 21 once the cutter bit is put into service. Four impact arms are shown in the embodiment of FIG. 6. It is obvious that many types of impact arms can be used and more than four or less than four impact arms 44 can be incorporated. If less than four are used, efficiency of the system may be impaired to some extent when compared to the performance of a cutter bit having four impact arms.

ADDITIONAL MODIFICATIONS

The embodiments shown in FIGS. 7 through 14 illustrate some of the ways the impact arms can be designed or formed in order to accomplish the purposes of this invention. It should be understood that the embodiments illustrated in these FIGURES can either be welded to the cutter bit or mounted releasably to the cutter bit as illustrated in FIGS. 5 and 6. FIGS. 7 and 8 illustrate impact arms which have notches 50 cut about the periphery and extensions 51 which may be mounted to the arms 52, or formed with arms 52 by forging, turning, casting or other well-known manufacturing methods. The projections 51 can also be formed by merely being bent up from the arms 52. The impact arms can then be attached to the cutter bit as previously described.

FIG. 8 illustrates that there can be at least two impact arms or four impact arms -- two being illustrated by dotted lines. The impact arms shown in FIGS. 9 and 10 are formed by merely dimpling or creasing a ring using a hydraulic press or other well-known means. It is obvious, of course, the impact arms above-described can also be easily cast. The arms shown in FIG. 11 consist of a disc 60 having a plurality of projections 61 about the outer diameter of disc 60. The impact ring shown here can easily be formed by molding, forging, turning or any other well-known system.

The impact arms shown in FIG. 14 are similar to that shown in FIG. 11 except the projections are radial and formed in the surface of a disc 60. The impact arms shown in FIGS. 12 and 13 are obviously formed by cutting disc 60 and bending up radial portions to form impact arms. It is obvious that many conceivable impact arms can be constructed which operate on the basic principle that falling material will cause a rotational force to be applied to a cutter bit if the material strikes a projection attached to the cutter bit. The main criteria for rotating the bit essentially consists in providing projections from the cutter bit surface having sufficient length not only to cause a sufficient rotating force being imparted to the cutter shaft when the arms are impacted by falling material, but also having the arms sufficiently placed and oriented and in sufficient number so that there is a high likelihood that falling material will strike the arms.

These and other features of this invention will become apparent when reference is made to the drawings and the accompanying specification and claims.

Claims

What I claim is:

1. In a continuous mining machine, a method for turning a cutter bit having a cylindrical shaft, a cutter head and one or more extended projections coupled thereto of a distance as measured from the axis of said cutter bit at least twice the radius of said shaft, comprising,

a. passing said cutter bit through material to be mined, thereby breaking some of said material free above said cutter bit so that said material falls past said cutter bit;

b. placing said one or more extended projections under at least a portion of said falling material, whereby said falling material impacts one or more of said projections causing said bit to turn.

2. In a cutter bit having a cylindrical shaft, a shoulder formed on one end of said cylindrical shaft and a cutting head formed to said shoulder, an improvement to said rotation of said cutter bit comprising a plurality of spaced projections extending radially from said shoulder by a distance as measured from the axis of said cutter bit at least twice the radius of said shaft for imparting a rotational force about the axis of said shaft by impact to said projections.

3. A device as described in claim 2, wherein said means coupled to the cutting head for imparting a rotation comprises a plurality of rods welded to the cutting head and substantially radial to the axis of said cutting head.

4. A device as described in claim 2 wherein the length of said rods radially extend from the cutting head on a radius of 11/2 inches from the axis of said cutting head.

5. A device as described in claim 2 including a cutter bit holder having an outer diameter, wherein said plurality of rods extends to the outer diameter of said cutter bit holder.

6. In combination with a cutter bit for a cutter bit holder said cutter bit having a shaft and a cutter head axially formed with the shaft, an improvement comprising means provided on said cutter bit and extending normal to said cutter bit by a distance as measured from the the axis of said cutter bit greater than twice the radius of said shaft in a manner to provide an impact surface whereby mined material when falling will impact said impact surface causing rotation of said cutter bit.

7. A device as described in claim 6 wherein said means comprises a plurality of rods attached to the outer surface of said cutter bit and extending normal to the outer surface thereof.

8. An impact rotation means for a cutter bit comprising a disc having an external diameter greater than the external diameter of said cutter bit, and having an axial opening therethrough, means for coupling said cutter bit to said disc through said opening, and impact receiving means formed in said disc in a manner to project from the surface of said disc.

9. A device as described in claim 8, wherein said means for coupling said cutter bit to said disc through said opening comprises welding said disc around said opening to said cutter bit.

10. A device as described in claim 8, wherein said means for coupling said cutter bit to said disc through said opening comprises forming an engaging means in said opening and a mating engaging means on said cutter bit to prevent relative rotation of said cutter bit of said impact rotation means.

11. A device as described in claim 8, wherein said impact means comprises a plurality of raised portions on the surface of said disc.

12. A device as described in claim 8 wherein said impact means comprises forming a plurality of pairs of radial slots in said disc, and bending the portion of said disc between said pairs of slots at an angle with the surface of said disc.

13. A device as described in claim 8 wherein said impact means comprises forming a plurality of radial slots in said disc, and bending portions of said disc adjacent said slot at an angle with said disc surface.