US2810565A - Drives for automatic mining machines of the planer type - Google Patents

Drives for automatic mining machines of the planer type Download PDF

Info

Publication number
US2810565A
US2810565A US451504A US45150454A US2810565A US 2810565 A US2810565 A US 2810565A US 451504 A US451504 A US 451504A US 45150454 A US45150454 A US 45150454A US 2810565 A US2810565 A US 2810565A
Authority
US
United States
Prior art keywords
conveyor
drive
drives
mining
mining device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US451504A
Inventor
Dommann Gunther
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US451504A priority Critical patent/US2810565A/en
Application granted granted Critical
Publication of US2810565A publication Critical patent/US2810565A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21CMINING OR QUARRYING
    • E21C29/00Propulsion of machines for slitting or completely freeing the mineral from the seam
    • E21C29/04Propulsion of machines for slitting or completely freeing the mineral from the seam by cable or chains
    • E21C29/14Propulsion of machines for slitting or completely freeing the mineral from the seam by cable or chains by haulage cable or chain pulling the machine along the working face
    • E21C29/16Winches or other means for pulling cable or chain
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00Machine element or mechanism
    • Y10T74/19Gearing
    • Y10T74/19014Plural prime movers selectively coupled to common output

Definitions

  • This invention relates to improvements in drives for automatic mining machines. It more particularly relates to an improved drive for an automatic mining machine provided with a longitudinally extending conveyor and a device movable back and forth along the conveyor for removing mineral such as coal and depositing same in the conveyor.
  • Such machines for the mining and/or loading of mineral such as coal are known.
  • Such machines for use in long wall mining may consist of a longitudinally extending conveyor which is positioned along and adjacent to the mine face.
  • a coal removing device is moved back and forth along the conveyor for removing coal from the mine face and depositing the same in the conveyor.
  • the conveyor and mining device may be continuously advanced.
  • the conveyor may have an upper trough shaped portion through which flights of scrapers move.
  • the scrapers may be connected at each end to endless chains or the like which are rotated. The coal is deposited in the trough and continuously conveyed by means of the scraper flights.
  • a planer cutting head is drawn back and forth along the forward longitudinal side of the conveyor, preferably in guided relation thereto by means of a flexible traction element such as a chain.
  • the planer cutter head cuts in each direction of movement and has an inclined surface somewhat in the shape of a plow which guides the cut coal into the conveyor.
  • a common drive may be provided for operating the conveyor and pulling the mining device, such as the planer cutter, back and forth along the conveyor. Since, as is well known, the starting friction is greater than the running friction, the power required to start the scraper flight of the conveyor is generally about three times the power required to operate the same. As the power installation must be suflicient to start the conveyor, the same has a large power reserve which is not utilized during operation.
  • the mining device may be connected to the drive with a disengageable coupling which makes possible temporary stoppage of the mining device.
  • the entire power of the drive is available for driving the conveyor and may be utilized for the initial starting of the same.
  • the excess power is utilized for operation of the mining device by engaging the coupling again.
  • the traction element of the mining device such as the chain which pulls the planer head is driven in all cases for any given direction of motion from only one end of the conveyor, even if identical driving stations are provided at both ends of the 2,810,565 Patented Oct. 22, 1957 "ice 2 conveyor.
  • the forces necessary to pull the mining device, such as the planer cutting head, are, therefore, exerted completely through a single drive gear.
  • the entire suspended chain must be centralized at this point.
  • a back and forth motion of the mining device is only possible by changing the driving'station and not by changing the direction of operation of the drive gears since the conveyor is always driven in a single direction.
  • the traction element such as the chain, must be conducted from one drive station to the other.
  • a subdivision of the drive of the mining machine by the insertion of a reversal station between the ends of the conveyor is thus not possible. This, however, in practical operation is a serious disadvantage, particularly when operating on long wall mine faces which are traversed by faults.
  • the traction element such as the chain, extends over the entire length of the conveyor whereas the mining device, such as the planer cutting head, will only be operated over a part of the conveyor length as, for example, between the fault and the driving station.
  • the extension of the traction element over the length of the conveyor prevents the manual preparatory work in the fault zone and endangers the additional support which is generally necessary at that place.
  • the conveyors and the mining device as, for example, the planer cutting head, are provided with separate drives, the above mentioned disadvantage is eliminated.
  • the pulling of the traction element of the mining device, such as the chain can be efiected simultaneously from drive stations positioned at each end of the conveyor. back and forth motion is effected by reversing the direction of operation of the sprocket wheels. In this connection, the pulling forces exerted by both drive members are reduced so that only one half of the force is exerted by each drive. In this connection, the insertion of intermediate reversing stations or drives is possible. ingly, separate plows can. operate along different sections of a single continuous conveyor. With separate drives, however, the drive for the conveyor must have an increased power sufficient to start the same. This power is, of course, not utilized and wasted during normal operation.
  • One object of this invention is a drive for a conveyor and mining device of a type described above which incorporates the advantages of the two above mentioned systems, while eliminating the disadvantages thereof.
  • a separate drive is provided for the conveyor and for the mining device such as the planer cutting head.
  • the drive for the conveyor is preferably a direct drive.
  • the drive for the mining device is an indirect drive which may be connected to assist in the driving of the conveyor for its starting.
  • the drive for the mining device is preferably connected thereto through a disengageable coupling.
  • the mining device drive may be constructed so that the same is reversable or may be connected to drive the mining device through a reversing gear.
  • An automatic locking device is preferably provided which prevents a coupling of the conveyor drive and the mining device drive when the same are operating in opposite directions of rotation.
  • the motor 1 drives the drive drum 3 of the conveyor 4 through the gearing 2. As the drive drum 3 rotates, the chains which pass over each end thereof carry along the scraper flights which convey the coal.
  • the motor 1 is preferably so dimensioned and powered that it has sufficient power to operate the conveyor 4 during all the normal operating conditions, but does not have sufficient power to initially start the same in operation. Therefore, in operation of the conveyor, the power of the motor 1 is fully utilized and there is no excess power which is wasted.
  • the motor 5 on the other side of the conveyor through the gearing 6 drives the sprocket wheel 7 over which the chain 8 passes.
  • the chain 8 in turn drives the shaft 13 by means of the sprocket wheel 9.
  • the shaft 13 thus rotates with the motor 5 and contains two disengageable fluid couplings 10 and 14 at each end.
  • the disengageable fluid coupling 10 when engaged causes the shaft 13 to drive the sprocket wheel 11 which in turn actuates the endless traction element 12 in the form of a chain to which the mining device, such as a planer cutting head, is attached.
  • the disengageable fluid coupling 14- when engaged causes the shaft 13 to drive the sprocket wheel 15.
  • the sprocket wheel 15 is in turn connected by means of a chain 16 to the sprocket wheel 17 which is mounted on the shaft 18.
  • the fluid coupling 10 is disengaged so that the shaft 13 will not drive the sprocket Wheel 11 and the fluid coupling 14 is engaged so that the shaft 13 will drive the sprocket wheel 15.
  • the motors 5 and 1 are then started.
  • the motor 1 through the gearing 2 directly drives the shaft 18 and the drive drum 3.
  • the motor 5 through the gearing 6, sprocket wheels 7 and 9 and chain 8, drives the shaft 13.
  • the shaft 13 in turn drives the sprocket Wheel 15, the chain 16, sprocket Wheel 17, the shaft 18 and thus the drum 3.
  • the combined powers of the motors 1 and 5 are thus exerted on the conveyor and the motor 5 supplements the power of the motor 1 so that sufficient power is exerted on the drum 3 to overcome the initial starting friction and bring the conveyor to its operating speed.
  • the additional power of the drive 5 is not required and the coupling 14 is disengaged so that the motor 1 solely drives the conveyor.
  • the coupling 10 may then be engaged so that the mining device, such as the planer cutting head, is drawn back and forth along the conveyor by means of the chain 12 driven over the sprocket wheel 11.
  • a drive for an automatic mining machine provided with a longitudinally extending conveyor and a mining device pulled back and forth along said conveyor by a flexible traction element, which comprises a first drive motor, means connecting said first drive motor to the conveyor for the driving actuation thereof, a second drive motor, first disengageable means connecting said second drive motor to said conveyor for the driving actuation thereof, and second disengageable means connecting said second drive motor to said flexible traction element for the driving actuation thereof.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Milling, Drilling, And Turning Of Wood (AREA)

Description

Oct. 22, 1957 G. DOMMANN Filed Aug. 23, 1954 vi rill/ll!!! IIIIIIIJ DRIVES FOR AUTOMATIC MINING MACHINES OF THE PLANER TYPE INVENTOR GUNTHER DOMMANN ATTORNEYS United States Patent DRIVES FOR AUTOMATIC MINING MACHINES OF THE PLANER TYPE Giinther Dommann, Wethmar, near Lunen, Germany Application August 23, 1954, Serial No. 451,504
4 Claims. (Cl. 2628) This invention relates to improvements in drives for automatic mining machines. It more particularly relates to an improved drive for an automatic mining machine provided with a longitudinally extending conveyor and a device movable back and forth along the conveyor for removing mineral such as coal and depositing same in the conveyor.
Automatic mining machines for the mining and/or loading of mineral such as coal are known. Such machines for use in long wall mining may consist of a longitudinally extending conveyor which is positioned along and adjacent to the mine face. A coal removing device is moved back and forth along the conveyor for removing coal from the mine face and depositing the same in the conveyor. As the coal is removed from the face, the conveyor and mining device may be continuously advanced. The conveyor may have an upper trough shaped portion through which flights of scrapers move. The scrapers may be connected at each end to endless chains or the like which are rotated. The coal is deposited in the trough and continuously conveyed by means of the scraper flights.
One embodiment of such an automatic mining machine known as a coal planer, a planer cutting head is drawn back and forth along the forward longitudinal side of the conveyor, preferably in guided relation thereto by means of a flexible traction element such as a chain. The planer cutter head cuts in each direction of movement and has an inclined surface somewhat in the shape of a plow which guides the cut coal into the conveyor.
In mining planers and other similar mining machines, a common drive may be provided for operating the conveyor and pulling the mining device, such as the planer cutter, back and forth along the conveyor. Since, as is well known, the starting friction is greater than the running friction, the power required to start the scraper flight of the conveyor is generally about three times the power required to operate the same. As the power installation must be suflicient to start the conveyor, the same has a large power reserve which is not utilized during operation.
In units provided with a common drive for the conveyor and mining device such as the planer cutter, the mining device may be connected to the drive with a disengageable coupling which makes possible temporary stoppage of the mining device. In this manner, the entire power of the drive is available for driving the conveyor and may be utilized for the initial starting of the same. When the conveyor is in operation, the excess power is utilized for operation of the mining device by engaging the coupling again.
In devices as described above with a common drive for the conveyor for the mining device, the traction element of the mining device such as the chain which pulls the planer head is driven in all cases for any given direction of motion from only one end of the conveyor, even if identical driving stations are provided at both ends of the 2,810,565 Patented Oct. 22, 1957 "ice 2 conveyor. The forces necessary to pull the mining device, such as the planer cutting head, are, therefore, exerted completely through a single drive gear. using a chain as a traction element, the entire suspended chain must be centralized at this point. A back and forth motion of the mining device, such as the planer cutter head, is only possible by changing the driving'station and not by changing the direction of operation of the drive gears since the conveyor is always driven in a single direction. In order to effect this reversing, the traction element, such as the chain, must be conducted from one drive station to the other. A subdivision of the drive of the mining machine by the insertion of a reversal station between the ends of the conveyor is thus not possible. This, however, in practical operation is a serious disadvantage, particularly when operating on long wall mine faces which are traversed by faults. The traction element, such as the chain, extends over the entire length of the conveyor whereas the mining device, such as the planer cutting head, will only be operated over a part of the conveyor length as, for example, between the fault and the driving station. The extension of the traction element over the length of the conveyor, however, prevents the manual preparatory work in the fault zone and endangers the additional support which is generally necessary at that place.
If the conveyors and the mining device as, for example, the planer cutting head, are provided with separate drives, the above mentioned disadvantage is eliminated. The pulling of the traction element of the mining device, such as the chain, can be efiected simultaneously from drive stations positioned at each end of the conveyor. back and forth motion is effected by reversing the direction of operation of the sprocket wheels. In this connection, the pulling forces exerted by both drive members are reduced so that only one half of the force is exerted by each drive. In this connection, the insertion of intermediate reversing stations or drives is possible. ingly, separate plows can. operate along different sections of a single continuous conveyor. With separate drives, however, the drive for the conveyor must have an increased power sufficient to start the same. This power is, of course, not utilized and wasted during normal operation.
One object of this invention is a drive for a conveyor and mining device of a type described above which incorporates the advantages of the two above mentioned systems, while eliminating the disadvantages thereof. This and still further objects will become apparent from the following description read in conjunction with the drawing which shows a diagrammatic plan view of an embodiment of a drive in accordance with the invention.
In accordance with the invention, a separate drive is provided for the conveyor and for the mining device such as the planer cutting head. The drive for the conveyor is preferably a direct drive. The drive for the mining device is an indirect drive which may be connected to assist in the driving of the conveyor for its starting. The drive for the mining device is preferably connected thereto through a disengageable coupling. The mining device drive may be constructed so that the same is reversable or may be connected to drive the mining device through a reversing gear. An automatic locking device is preferably provided which prevents a coupling of the conveyor drive and the mining device drive when the same are operating in opposite directions of rotation. With two drives for the mining device provided with couplings reversing gears for moving the mining device in each direction of motion, the same are advantageously so connected with each other that they may be shifted from one direction to the other jointly.
When
The
Accord- Referring to the embodiment as shown in the drawing, the motor 1 drives the drive drum 3 of the conveyor 4 through the gearing 2. As the drive drum 3 rotates, the chains which pass over each end thereof carry along the scraper flights which convey the coal. The motor 1 is preferably so dimensioned and powered that it has sufficient power to operate the conveyor 4 during all the normal operating conditions, but does not have sufficient power to initially start the same in operation. Therefore, in operation of the conveyor, the power of the motor 1 is fully utilized and there is no excess power which is wasted.
The motor 5 on the other side of the conveyor through the gearing 6 drives the sprocket wheel 7 over which the chain 8 passes. The chain 8 in turn drives the shaft 13 by means of the sprocket wheel 9. The shaft 13 thus rotates with the motor 5 and contains two disengageable fluid couplings 10 and 14 at each end. The disengageable fluid coupling 10 when engaged causes the shaft 13 to drive the sprocket wheel 11 which in turn actuates the endless traction element 12 in the form of a chain to which the mining device, such as a planer cutting head, is attached. The disengageable fluid coupling 14- when engaged causes the shaft 13 to drive the sprocket wheel 15. The sprocket wheel 15 is in turn connected by means of a chain 16 to the sprocket wheel 17 which is mounted on the shaft 18.
In operation, in order to start the conveyor 4, the fluid coupling 10 is disengaged so that the shaft 13 will not drive the sprocket Wheel 11 and the fluid coupling 14 is engaged so that the shaft 13 will drive the sprocket wheel 15. The motors 5 and 1 are then started. The motor 1 through the gearing 2 directly drives the shaft 18 and the drive drum 3. The motor 5 through the gearing 6, sprocket wheels 7 and 9 and chain 8, drives the shaft 13. The shaft 13 in turn drives the sprocket Wheel 15, the chain 16, sprocket Wheel 17, the shaft 18 and thus the drum 3. The combined powers of the motors 1 and 5 are thus exerted on the conveyor and the motor 5 supplements the power of the motor 1 so that sufficient power is exerted on the drum 3 to overcome the initial starting friction and bring the conveyor to its operating speed. Once at its operating speed, the additional power of the drive 5 is not required and the coupling 14 is disengaged so that the motor 1 solely drives the conveyor. The coupling 10 may then be engaged so that the mining device, such as the planer cutting head, is drawn back and forth along the conveyor by means of the chain 12 driven over the sprocket wheel 11.
I claim:
1. A drive for an automatic mining machine provided with a longitudinally extending conveyor and a mining device pulled back and forth along said conveyor by a flexible traction element, Which comprises a first drive motor, means connecting said first drive motor to the conveyor for the driving actuation thereof, a second drive motor, first disengageable means connecting said second drive motor to said conveyor for the driving actuation thereof, and second disengageable means connecting said second drive motor to said flexible traction element for the driving actuation thereof.
2. Drive according to claim 1 including a rotatable shaft connected for rotation with said second drive motor, and in which said first disengageable means includes a disengageable coupling connected to said shaft and said second disengageable means includes a second disengageable coupling connected to said shaft.
3. Drive according to claim 1 in which said seconddrive motor is a reversible drive motor.
4. Drive according to claim 1 in which said means connecting said second drive motor to said flexible traction element includes a reversing gear.
References Cited in the file of this patent UNITED STATES PATENTS 1,397,893 Kay Nov. 22, 1921 2,071,778 Walne Feb. 23, 1937 2,282,597 Archer May 12, 1942 2,360,753 Anderson Oct. 17, 1944 2,388,385 Cortlidge Nov. 6, 1945 2,595,336 Corsentino May 6, 1952 2,689,013 Dean et a1 Sept. 14, 1954 2,689,621 Donley Sept. 21, 1954 2,689,716 Bainbridge Sept. 21, 1954 2,691,514 Lobbe Oct. 12, 1954
US451504A 1954-08-23 1954-08-23 Drives for automatic mining machines of the planer type Expired - Lifetime US2810565A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US451504A US2810565A (en) 1954-08-23 1954-08-23 Drives for automatic mining machines of the planer type

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US451504A US2810565A (en) 1954-08-23 1954-08-23 Drives for automatic mining machines of the planer type

Publications (1)

Publication Number Publication Date
US2810565A true US2810565A (en) 1957-10-22

Family

ID=23792489

Family Applications (1)

Application Number Title Priority Date Filing Date
US451504A Expired - Lifetime US2810565A (en) 1954-08-23 1954-08-23 Drives for automatic mining machines of the planer type

Country Status (1)

Country Link
US (1) US2810565A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3335622A (en) * 1964-10-19 1967-08-15 Gewerk Eisenhuette Westfalia Selective drive transmission
US3863522A (en) * 1971-06-30 1975-02-04 John Gibson Chain tensioning devices and drive assemblies for mining
US4346938A (en) * 1979-09-22 1982-08-31 Halbach & Braun Hauling and cutting plant
US4503731A (en) * 1980-09-17 1985-03-12 Anderson Strathclyde Plc A.F.C. Drive gearbox
US4605122A (en) * 1983-11-22 1986-08-12 Dowty Meco Limited Scraper chain conveyor

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1397893A (en) * 1920-10-12 1921-11-22 Kay Harry Driving-gear especially for groups of rolls
US2071778A (en) * 1935-08-31 1937-02-23 William R Walne Diesel drive for oil wells
US2282597A (en) * 1938-09-02 1942-05-12 Nat Supply Co Well drilling plant
US2360753A (en) * 1941-06-17 1944-10-17 American Well & Prospecting Co Universal speed control for multiple prime movers
US2388385A (en) * 1943-08-02 1945-11-06 Goodman Mfg Co Material gathering and loading machine
US2595336A (en) * 1948-02-09 1952-05-06 Corsentino Pete Power transmission mechanism for farm implements
US2689013A (en) * 1947-03-28 1954-09-14 Greyhound Corp Control for two-engine vehicles
US2689716A (en) * 1948-02-12 1954-09-21 Huwood Mining Machinery Ltd Mining plow and conveyer apparatus
US2689621A (en) * 1947-09-13 1954-09-21 Four Wheel Drive Auto Company Truck with interrelated multiple prime movers, power take-off couplings, and operating controls therefor
US2691514A (en) * 1947-06-14 1954-10-12 Gewerk Eisenhuette Westfalia Planer type coal mining and loading machine

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1397893A (en) * 1920-10-12 1921-11-22 Kay Harry Driving-gear especially for groups of rolls
US2071778A (en) * 1935-08-31 1937-02-23 William R Walne Diesel drive for oil wells
US2282597A (en) * 1938-09-02 1942-05-12 Nat Supply Co Well drilling plant
US2360753A (en) * 1941-06-17 1944-10-17 American Well & Prospecting Co Universal speed control for multiple prime movers
US2388385A (en) * 1943-08-02 1945-11-06 Goodman Mfg Co Material gathering and loading machine
US2689013A (en) * 1947-03-28 1954-09-14 Greyhound Corp Control for two-engine vehicles
US2691514A (en) * 1947-06-14 1954-10-12 Gewerk Eisenhuette Westfalia Planer type coal mining and loading machine
US2689621A (en) * 1947-09-13 1954-09-21 Four Wheel Drive Auto Company Truck with interrelated multiple prime movers, power take-off couplings, and operating controls therefor
US2595336A (en) * 1948-02-09 1952-05-06 Corsentino Pete Power transmission mechanism for farm implements
US2689716A (en) * 1948-02-12 1954-09-21 Huwood Mining Machinery Ltd Mining plow and conveyer apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3335622A (en) * 1964-10-19 1967-08-15 Gewerk Eisenhuette Westfalia Selective drive transmission
US3863522A (en) * 1971-06-30 1975-02-04 John Gibson Chain tensioning devices and drive assemblies for mining
US4346938A (en) * 1979-09-22 1982-08-31 Halbach & Braun Hauling and cutting plant
US4503731A (en) * 1980-09-17 1985-03-12 Anderson Strathclyde Plc A.F.C. Drive gearbox
US4605122A (en) * 1983-11-22 1986-08-12 Dowty Meco Limited Scraper chain conveyor

Similar Documents

Publication Publication Date Title
US2810565A (en) Drives for automatic mining machines of the planer type
US2105504A (en) Method of mining coal
US2205013A (en) Material moving apparatus
US2381109A (en) Gathering and loading machine
US2564038A (en) Coal digger
US2689717A (en) Plow mining method and apparatus
US1930016A (en) Mining machine
US2060226A (en) Mining machine
US2732056A (en) Loader-conveyor apparatus
US1585694A (en) Apparatus for loading material
US3378303A (en) Method and apparatus for controlling loading machines in underground mining
US2254181A (en) Material moving apparatus
US2169424A (en) Mining system
US1489600A (en) Mining and loading machine
US4453774A (en) Driving arrangement for longwall mining machines
US1836250A (en) Mining apparatus
US1785959A (en) Mining apparatus
US2131179A (en) Mining machine feeding mechanism
US3066924A (en) Auger type mining machines
US3892184A (en) Drive arrangements for mining machines
US1169842A (en) Mining-machine.
US2161835A (en) Mining machine transmission mechanism
US2783036A (en) Cutter head for boring type continuous miner
US2041714A (en) Mining apparatus
US2292970A (en) Kerf-cutting machine