The United States of America As Represented by the Secretary of

Other

Wallace W Roepke

Richard J Wilson

David P Lindroth

Sterling J Anderson

Kelly C Strebig

Bradley V Johnson

Patrick J Cain

Joseph W Rasmussen

A longwall mining machine comprises a rotatable cutting head having a configuration in the form of an equilateral triangle viewed along its axis of rotation and formed with a continuous auger along the outer surface of the head. Cutter bits are located on apexes of the auger. The cutting head is mounted on a boom adjacent the longwall and is geared to produce an eccentric Cardan motion to the head causing the cutter bits to follow a substantially square trajectory in a plane normal to the axis of rotation of the head. Production of coal dust is minimized by deep linear vertical and horizontal cuts extending downwardly from roof to floor. During rotation of the head, cut coal is augered outwardly from the longwall and dropped into a conveyor for removal to a collection area.

Triangular shaped cutting head for use with a longwall mining machine

A rotatable mounting block with a coal cutter bit which reduces the amount of wear to the bit. The cutter bit is fixed within the bore of a bit holder and moves in unison therewith within the mounting block. Positive rotation of the holder/bit is provided by a ratchet sleeve and pawl which interact with spiral slots on the lower extending end of the bit holder. The pawl prevents rotation of the ratchet sleeve in one direction (downward) so that the cutter bit will rotate during movement into the mounting block's bore as inwardly facing sleeve teeth are cammed in the slots of the bit holder. On the upward stroke of the bit/holder within the mounting block, the ratchet sleeve is free to rotate as a strong Belleville spring--also in the mounting block--forces them upward to the original position.

Mounting block to rotate coal cutter bits

A method of augmenting the cutting operation of a cutter bit to reduce the cutting energy required and to reduce the respirable dust generated during the cutting operation. During the cutting operation of coal with a continuous mining machine greater than 90 percent of the primary respirable dust generated occurs in the crushing zone around the tip of bit. By applying a high pressure (2,500 to 5,000 psi) spray of water at or near the center of the cutting tip, as the tip touches the coal, tests have shown very substantial reductions in the airborne respirable dust generated and that there is lubrication and cooling at the cutter tip/mineral interface to provide for reduced sumping forces and lowered methane ignition potential.

Dust controlling method using a coal cutter bit

A coal mining apparatus and its method of use in which a continuous mining machine removes and transfers cut material reducing airborne respirable coal dust generated in the cutting and collection process. The conventional high speed head rotating with the bits going forward at the top is replaced by a triangular shaped dished out linear cutting head rotating with the bits mounted at the apexes going rearward at the top. This produces a box cut in the mine face with a square cross-section. After the head has made a box cut by sumping the full head diameter beginning at the mine floor, it is sheared upwardly producing a linear shear cut. This shear step is at a constant depth equal to the complete cutting head diameter. The modified cutting head is used as part of the loading and transfer mechanism. This is accomplished by reversing its direction of rotation and cutting on the upstroke from floor to roof so that the head acts as a bucket collecting the cut coal, then transferred to an adjacent transport system which allows the cut coal to be loaded and conveyed away from the mine face without further dust generation due to free fall fracture on the floor or intermediate handling by a dust generating gathering head mechanism. To insure that the coal is consistently discharged at the proper position, a movable bridge conveyor and follower assembly is used with the cutting head.

Automatic face transfer linear cutting rotary head continuous mining

A method of operating a machine having a constant depth linear cutting head which is retrofitted to a continuous mining machine replacing the rotary head. By altering the usual configuration of the cutting head from the high speed rotating type with a large number of bits, as is currently being used, to one employing a non-rotary type head with 10 percent or less of the usual number of bits, and also operating a combined sumping and shearing action without the bits exiting the coal face being cut, less respirable dust is produced at the mine face. In addition to decreasing the dust and amount of menthane gas - when coal is mined - which is liberated, our method also produces more coal on the average for each cut in the mine face by deeper constant depth cuts in the 3- to 6-inch range by first sumping into the mine face and then shearing the face, without withdrawing or rotating the point attack bits. Sumping may begin near the mine face roof or floor and shearing may be in either a vertical or horizontal direction with or without the aid of high pressure water. One modification calls for shearing with two opposite cutting heads moving towards the mine face center.

Method of operating a constant depth linear cutting head on a

The triangular-shaped rotary head mounted on an eccentrically driven shaft rotates at a low speed in a path determined by a ring/pinion gear ratio, such that cutting tools mounted on the apices of the triangular-shaped rotary head follow a square path entering the face of the coal seam to be cut at a top corner and making a long linear vertical cut at a constant depth of approximately one and one-half times the diameter of the rotary head greatly reducing dust generation and methane ignition potential, while increasing productivity.

Linear cutting rotary head continuous mining machine

A vibrating wire gage for use with a mine rockbolt. The wire is anchored within the hollow portion of a cylindrical gage body that has an adjustable lower member. Rotation of the adjustable member changes the tension in the wire and as a result its frequency of vibration. Forces acting on the bolt imbedded in the rock cause the gage body to deform as well as its wire since the upper end of the gage body is held to a rockbolt anchored firmly within the earth. By noting variations in the frequency of the wire from an initial setting, the change in the amount of force the rockbolt is under can be determined. A rotatable pick can be inserted through a hole in the lower adjustable member to mechanically pluck the wire. The readout of the vibrations from the plucked wire may be accomplished by a mechanics stethoscope held against the gage or by an electrically operated pickup head which engages the vibrating wire.

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Excelsior, MN, United States of America

Wallace W Roepke