Mining or in situ disintegration of hard material – Cutter tooth or tooth head
Reexamination Certificate
2002-04-01
2004-07-20
Kreck, John (Department: 3672)
Mining or in situ disintegration of hard material
Cutter tooth or tooth head
C299S102000, C299S106000, C299S104000
Reexamination Certificate
active
06764140
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for locating a cutting bit on a rotary drum used to cut earth, rock, pavement and the like and, in particular, to an improved cutting lacing method and cutter bit assembly.
2. Background
This invention is directed to locating a plurality of offset points with reference to a peripheral surface or portions of a peripheral surface. Although the invention is to such locating it is believed easier to understand with reference to cutter bits for rotating drums of a coal mining machine for which the invention was initially developed. The methods and apparatus apply to positioning cutter bits on chains for trenchers as well. Inasmuch as the principles of this invention in locating bit points (i.e., the points of the bits) applied to rotary cutting drums, the prior methods and apparatus for locating cutter bits on a rotary drum are discussed for the sake of simplicity in understanding the invention. Diameters and lengths of a cutter drum section vary so that, while the procedures discussed are the same, the tools and aids utilized will vary to compensate for the variations in drum diameter. It is also to be noted that a drum section carries various bit blocks at various locations which receive the bits, and pedestals upon which the bit blocks are mounted. The geometry of the bit blocks and bits is known and, for a specific combination, fixed. Accordingly, such bits and drums are described herein as the presently preferred embodiment of the invention.
In materials mining and in other fields in which a large volume of hard materials must be cut, it is typical to employ an apparatus which includes a vertically moveable horizontal axis cutting drum having cutting bits attached thereto. By virtue of the engagement of the cutting bits which are mounted on the rotating cutting drum with the surface to be cut, material is removed from such surface for further processing.
Due to the substantial forces generated during the cutting operations, the cutting bits must be securely mounted on the cutting drums, but must also be readily removable for replacement. In one prior art form of cutting bit holding apparatus, a cutting bit having an elongated cylindrical shank and a hard cutting tip at one end is retained in a cutter bit holder block which is usually welded directly to the cutting drum or a drum pedestal. A shank receiving bore in the bit holder block is adapted for receiving the shank of the cutting bit therethrough.
Cutter drums vary in design for various mining machines including drums manufactured by a specific manufacturer. As is known, a cutting drum may consist of elongated drum sections, end sections and ring sections between the drum and end sections. The drum, end, and ring segments form a cutter head with various cutter head designs being utilized. Regardless of the design of a cutter head or cutting chain, it is necessary that the cutter head or chain cut its own clearance. That is, the bits on the cutter head cut and break the coal, rock or earth such that the cutter head can be moved forward into a coal seam. In this regard, it is to be noted that coal is a fragile material and that the path of movement of a cutter bit through a coal seam to cause coal breakage is an important aspect of proper lacing of the cutting bits on a drum or cutter chain. Also, each section of a cutter head must carry cutter bits to cut its own clearance. A cutter head which cannot cut clearance for itself is not an acceptable mining machine.
In the mining of coal, it is accepted practice to arrange cutter bits on a traveling or rotating member, such as a cutter chain or a rotating drum, such that the cutting edges or tips of the cutter bits travel through separate paths in the coal seam to be mined. There are various factors regarding the cutting of coal seams which are evaluated by various manufacturers of mining machinery in locating cutter bits on a rotating member including, but not limited to, the hardness and abrasiveness of the material being excavated. The locating of the cutter edges or cutting tip points of a cutter bit is referred to as the “lacing” of a cutter chain or drum and varies among various machinery manufacturers; however, all machinery manufacturers want as accurate locating of the cutter edge or tip point as is possible under the various manufacturing processes.
In the mining and construction industry, the accuracy in connecting a bit holder block to a drum is critical in achieving the designed lacing for the drum. The contact of the conical tip of a cutter bit and the earth strata enhances the rotation of the cutting tool during the road planing operation. The conical tip that actually impinges and rubs against the surface of the earth strata together with the angle of attack enhances or reduces the rotation of the cutting tool. For instance, an increase in the distance that the contact is away from the central longitudinal axis of the hard insert results in an increase in the extent to which such contact encourages rotation of the cutting tool. The angle of attack for cutter bits is designed to optimize rotation of the cutter bit, hence any variation from the designed angle of attack results in a change in the designed rotation characteristics of the cutter bits. Reduced rotation of the cutting tool causes the cutting tool bit to become unevenly worn on one side, for instance, and the cutting bit quickly becomes damaged and inoperative. Such bit holder blocks on rotary drums must be removed and attached back onto the drum. It is well-known in the industry that the accurate lacing of the cutter bits onto a drum is important to the performance of the mining/construction drum. Therefore, the cutter tips must be accurately welded onto the cutting drum or chain. As will be appreciated, such failures of cutter bits are quite costly because the cutting apparatus must be removed from service in order that the remaining portion of the cutter bit can be removed away from the cutting drum and a replacement cutter bit attached.
The typical road milling drum of the past comprises a generally cylindrical drum with a plurality of road milling bit-block assemblies attached to a pedestal or directly to the surface of the drum. More specifically, the holder block, which rotatably holds the bit, is welded to the pedestal or surface of the drum.
In the construction industry for road milling it is essential that that each bit impinges on the road substrate at an exclusive discrete point so that the points of impact span the length of the drum. Typical impact point spacing for road milling has been about 0.625 inches.
In the prior art, methods of locating cutter bit blocks to mining and construction drums have included automated systems that use programmed machines for positioning and welding the blocks in their proper position. U.S. Pat. Nos. 4,897,904 and 4,947,535 disclose automated equipment that places and fixes the tip point with respect to a rotatable drum. The tip point is held in its programmed position at a preselected position by an automated arm having a gripper for grasping the cutter bit holder block. The holder block is welded onto the preselected position. Such automated lacing equipment is expensive and requires skilled technicians to ensure proper programming for the lacing and maintenance of the manufacturing equipment.
When bit holder block location pins were forged perpendicular to the forge parting lines, they were consistent and located the blocks very accurately. For instance, Kennametal' C10AMC block in the Kennametal Road Planing catalogue, catalogue number BO
1-1
(12)D1, illustrates a block with perpendicular cylindrical pins which effectively positioned a block on the drum. Also see the prior art perpendicular locating pins in U.S. Pat. No. 5,842,747.
A different method to manufacture (forge) bit holder blocks has been developed recently. This new method of forging produces blocks having the block shape shown in
FIG. 1
at
10
and marketed in Kennametal' 2001 “Road
Carson, Jr. Duane E.
Frear Joseph
Stiffler Stephen P.
Kennametal Inc.
Kreck John
Weldon Kevin P.
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