David P Lindroth, 84Lakeville, MN

4062595, Dec 13, 1977

Oct 15, 1976

5/732676

Wallace W. Roepke - Excelsior MN
David P. Lindroth - Apple Valley MN
Richard J. Wilson - Minneapolis MN

The United States of America as represented by the Secretary of the
Interior - Washington DC

E21C 2724
E21C 3520

299 18

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.

5003144, Mar 26, 1991

Apr 9, 1990

7/506054

David P. Lindroth - Apple Valley MN
Roger J. Morrell - Bloomington MN
James R. Blair - Inver Grove Heights MN

The United States of America as represented by the Secretary of the
Interior - Washington DC

H05B 680

219 1055A

An apparatus for the sequential fracturing and cutting of subsurface volume of hard rock (102) in the strata (101) of a mining environment (100) by subjecting the volume of rock to a beam (25) of microwave energy to fracture the subsurface volume of rock by differential expansion; and , then bringing the cutting edge (52) of a piece of conventional mining machinery (50) into contact with the fractured rock (102).

4012077, Mar 15, 1977

Jul 2, 1976

5/702373

Wallace W. Roepke - Excelsior MN
David P. Lindroth - Apple Valley MN
Joseph W. Rasmussen - Minneapolis MN

The United States of America as represented by the Secretary of the
Interior - Washington DC

E21C 2724

299 76

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.