Patent Application
20140167487
The disclosure relates to cutter drums for mining equipment. More specifically, the disclosure relates to rotary cutter drums for continuous mining machines, also known as continuous cutter modules and cutter modules.
Highwall mining is applied in harvesting coal, minerals, ores or other materials in seams or veins under an overburden, which may be accessed from an exposed edge of the seam or vein. Highwall mining is applicable where a continuous mining machine can be placed in a cut or trench to extend a cutter module, followed by a train of conveyor segments (or units) as the cutter module advances, into a substantially horizontal shaft under the overburden. Usually a train of segments for Highwall mining comprises a cutter module, a train of conveyor segments, provided with a conveyor for transporting mined material from and to opposite adjacent conveyor segments in the train of conveyor segments and a drive for the cutter module and conveyors. U.S. Pat. No. 7,717,522 describes a conveyor segment for use in a train of conveyor segments for Highwall mining.
The cutter drum is one of the most important wear items on a continuous mining machine. The cutter drum constitutes an important limit on the machine's excavation (sump) speed and efficiency. Improvements to cutter drum designs that make them last longer, allow them to apply greater forces to the seam drive (tunnel) face, and/or can improve the economics of excavating seam drives with a continuous mining machine.
In some circumstances, environmental conditions in the mining area near or at the cutter module can hamper efficient mining. For example, a very low (thin seam) mining shaft with ample shear-up and limited cutter-drum cutting space can decrease the mining capacity due to limited roller bearing capacities and cutting vibrations at the expense of mined material. In addition, such circumstances may also cause damage to parts of the mining equipment like cutter drives, x-pair tapered roller bearings, seals, gear boxes, and shear arms. U.S. Pat. No. 7,997,659 describes a rotary cutter for tunnel boring machine which can be used in low mining shaft applications.
An embodiment of the present disclosure relates to a rotary cutter including a cutter drum having bore and a bit coupled to an exterior surface of the cutter drum. The rotary cutter also includes a shaft positioned inside the bore, the shaft having a flat passageway extending along a longitudinal axis of the shaft and a bearing portion disposed on an exterior surface of the shaft.
Another embodiment of the present disclosure relates to a rotary cutter having a cutter drum having a first bore, the bore having a first inner portion having a first diameter and a second inner portion having a second diameter wherein the second diameter is greater than the first diameter. The rotary cutter further includes a cutting bit coupled to the cutter drum, a bearing having a second bore, the bearing disposed in the first bore, and a shaft positioned inside the second bore, the shaft having a flat passageway extending along an axis of the shaft and a bearing portion disposed on an exterior surface of the shaft, the bearing portion being in contact with the bearing. In addition, the rotary cutter includes an oil reservoir disposed in the second inner portion between the cutter drum and the shaft, the oil reservoir being filled with a lubricating fluid, wherein the lubricating fluid passes along the passageway from the oil reservoir to a surface where the bearing portion of the shaft contacts the bearing.
Yet another embodiment of the present disclosure relates to a mining machine having a frame and a shaft coupled to the frame, the shaft having a flat passageway extending along an axis of the shaft and a bearing portion disposed on an exterior surface of the shaft. The mining machine further includes a bearing disposed on the shaft, a portion of the bearing being in contact with the bearing portion of the shaft and a cutter drum disposed on the bearing, the cutter drum rotating with respect to the shaft. The mining machine also includes a cutting bit coupled to the cutter drum.
Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.
The shaft 20 is substantially cylindrical in shape and is sized and configured to have a portion of the shaft 20 fit inside of the cutter drum 24. The shaft 20 is crowned such that the diameter of the shaft 20 at the center 38 of the shaft 20 is slightly larger than the diameter of the ends 40 of the shaft 20. When the shaft 20 bows under forces that will be thrust on the cutter drum 24 during cutting operations, the end 40 of the shaft 20 nearest the applied force will remain approximately flat along the portions of the shaft 20 that are in contact with the bearing hubs 22, which results in more even loading of the bearing hubs 22 which allows for greater forces to be placed on the cutter drum 24. Four longitudinal passageways 42 are disposed the shaft 20 (shown in
The shaft 20 is coupled to the frame 10 using a combination of the end caps 14, the splines 32 and the slots 34 such that forces from the cutter drum 24 are transferred to the bearing hub 22, and then to the shaft 20, and then in turn to the frame 10. The mounting of each end of the rotary cutter 12 to the frame 10 minimizes the deflection of the rotary cutter 12 under a given load as compared to a cantilever mounting arrangement.
Two bearing hubs 22 are used in the rotary cutter 12. One bearing hub 22 is disposed on each end 40 of the shaft 20. For ease of description, only one bearing hub 22 and end 40 will be described as both ends 40 are substantially similar. The bearing hub 22 is cylindrical in shape and is hollow. The bearing hub 22 is of a robust thick wall design to provide roundness backup tolerances which may be useful when the bearing is coated. In the illustrated embodiment an interior portion 41 of the bearing hub 22 and a shoulder of the bearing hub 22 are laser hardened. The bearing hub 22 is sized and configured to be disposed in an interior portion of the cutter drum 24. Threads 51 (illustrated in
The cutter drum 24 is substantially cylindrical and is hollow. As best seen in
Two inner bearings 26 and two keys 28 are used in the rotary cutter 12. One inner bearing 26 and key 28 is disposed on each end 40 of the shaft 20. For ease of description, only one inner bearing 26 and key 28 will be described as both ends of the rotary cutter 12 are substantially similar. The inner bearing 26 is substantially in the shape of a ring and is coupled to the shaft 20 using the key 28 such that the key 28 inhibits the inner bearing 26 from rotating with respect to the shaft 20, but does not inhibit the inner bearing 26 from moving longitudinally along an axis of the shaft 20. In an alternative embodiment more than one key 28 is used to couple the inner bearing 26 to the shaft 20. The inner bearing 26 is sized and configured such that it is inhibited from entering the center interior portion 44 of the cutter drum 24. In the illustrated embodiment the inner bearing 26 is a thrust (shouldered) style bearing, the inner bearing 26 interfacing with the bearing hub 22 which is a sleeve (journal) style bearing. In an alternative embodiment the inner bearing 26 may be an axial or thrust or common ball roller or tapered roller bearing. The inner bearing 26 in the illustrated disclosure is coated with a moly-bronze coating.
The seal assembly 30 (best seen in
The assembly of the rotary cutter 12 will now be described. Each end of the rotary cutter 12 is a minor image of the other end, so only the assembly of a single end will be described. First, one or more keys 28 and the inner bearing 26 are placed onto the shaft 20, the key 28 serving to inhibit the inner bearing 26 from rotating with respect to the shaft 20. At this point the shaft 20 may be inserted into the cutter drum 24 and then one or more keys 28 and the inner bearing 26 are placed onto the opposite side of shaft 20. Next the bearing hub 22 and seal assembly 30 may be assembled to the shaft 20, while the bearing hub 22 and seal assembly 30 are simultaneously inserted into the opposite side of the cutter drum 24. A bolt 62 can then be inserted through an opening on the cutter drum 24 into the indentation 53 in order to align the bearing hub 22 and allow floating movement to follow shim tolerances with the cutter drum 24 and duo-cone seal retainer ring 52. The bolt 62 also inhibits the cutter drum 24 from rotating with respect to the bearing hub 22. Next the duo-cone seal retainer ring 52, including the resilient member 60, is placed on the shaft 20 and into cutter drum 24. After that the toric elements 56 and metal to metal seal 58 are placed onto the shaft 20, the toric elements 56 and metal to metal seal 58 being placed between the shaft 20 and the duo-cone seal retainer ring 52. In the next step the sprocket 16 is coupled to the cutter drum 24 using screws, bolts, dowel pins or the like. Next the frame 10 is placed onto the splines 32 of the shaft 20. A seal 36 is placed between the frame 10 and the end cap 14. The end cap 14 is then inserted into the hollow portion 35 of the shaft 20 and the end cap 14 is coupled to the frame 10 using screws, bolts, tack-welds or the like. Other embodiments may be assembled in a similar, or different, fashion.
When fully assembled, the rotary cutter 12 includes an oil reservoir 64 (best seen in
The rotary cutter 12 and frame 10 have industrial applicability on tunnel boring machines, continuous mining machines and other mining machines where they can be used to crush and remove rock for mining or other purposes. The rotary cutter is one of the most important wear items on a continuous mining machine, and constitutes an important limiting factor of a mining machine's excavation speed and efficiency. The rotary cutter 12 disclosed herein lasts longer and requires less maintenance than prior art rotary cutters, resulting in a faster and more efficient rotary cutter.
The rotary cutter 12 uses sleeve (journal) and shouldered (thrust) bearings, as has been described herein, instead of tapered roller bearings as have been used in the past on rotary cutters. The sleeve bearing system is much more compact than the tapered roller bearing. The use of a sleeve bearing system permits the shaft 20 and the cutter drum 24 to occupy a proportionally larger portion of the total annular space or volume of the rotary cutter 12. The resulting larger cutter drum 24 may permit the rotary cutter 12 to last longer in operation, minimizing the amount of maintenance needed, and increasing the overall efficiency or excavation speed of the rotary cutter 12. Substituting sleeve bearings for tapered roller bearings is also useful in assembly as the tapered roller bearings typically require precise operations during assembly to preload. The sleeve bearing does not require steps to preload. The use of the bearing hub 22 in combination with the inner bearing 26 allows for the shaft 20 to float with respect to the bearing hub 22 and inner bearing 26, which does not result in damage to the rotary cutter 12 when the shaft 20 and/or cutter drum 24 expand or contract axially due to temperature changes. The seal assembly 30 also allows for axial tolerance gaps that may result from such thermal changes.
The shaft 20, cutter drum 24 and/or other components may flex during operation of the rotary cutter 12, resulting in a pressure differential between the two sides of the seal assembly 30. If the pressure differential rises too high, oil can squirt past the seal assembly 30, or foreign materials may be drawn past the seal assembly 30 from outside of the rotary cutter 12. To help prevent this possibility, shaft 20 includes passageways 42 which help oil move from one side of the rotary cutter 12 to the other, opposite side to relieve oil pressure differentials.
Lubricating oil or fluid is sent from the oil reservoir 64 via passageways 42 to lubricate bearing areas such as the bearing hub 22, the inner bearing 26 and the seal assembly 30. Lubricating oil or fluid stored in the oil reservoir 64 serves to reduce the temperature of the lube oil near bearing surfaces during rotary cutter 12 operation which in turn helps maintain the temperature of the seal assembly 30, bearing hub 22 and inner bearing 26 below maximum levels. In addition, lubricating oil or fluid stored in the oil reservoir 64 serves to dampen vibrations that occur during operation of the rotary cutter 12.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed rotary cutter drum apparatus. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed rotary cutter drum apparatus. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
