a combination machine for simultaneous cutting of minerals or rocks from a solid mass and loading them into transportation facilities. Machines designed for extracting minerals are called cutter-loaders; those used for driving underground shafts are called entry-driving machines; and those used for driving preparatory coal shafts to develop the working face are called cutting (driving) machines. Cutting-loading machines are most widespread in the coal industry, although today they are also being increasingly widely used for the extraction of other minerals, such as potassium and rock salts, manganese, and rare earths.
Cutting-loading machines were created as a result of the design development of the coal-cutting machine. Efficient cutting-loading machines were produced in the USSR in 1932 (the wide-web cutter-loader designed by A. I. Bakhmutskii and the IaR model designed by V. G. Iatskikh and G. I. Romenskii for cutting coal from slightly inclined thin seams). The first efficient cutting-loading machines were made in Great Britain in 1935 (the wide-web Mecco-Moore cutter-loader) and in Germany in 1938 (the Eichhoff and Rein Preus-sen wide-web machine).
A cutting-loading machine consists of a working member (for breaking down—that is, the fracturing of the rock mass); a loading member, whose task is, in many cases, performed by the working member (for loading the broken rock for transportation); a propulsion mechanism; drive motors; gears; control members; and devices for dust suppression (sprinkling systems) and collection.
There are several types of cutter-loader working members, which are distinguished according to design and cutting methods: bar members, which consist of one or more cutting-chain jigs that break up the rock by means of a system of cutting slits, with subsequent fracturing of the blocks between the slits, or by cutting from the face surface; drum members (with vertical or horizontal rotation), which break up the rock by cutting from the surface of the face; auger members (with horizontal rotation), which break up the rock by cutting from the surface of the face and feed the broken pieces along the axis of the auger onto a conveyer; crown members, which break up the rock by cutting from the face surface with a rotating crown equipped with cutters; drill members, which break up the rock by cutting out thin concentric slits, with subsequent fracturing and conveyer loading of the interslit pillars; planetary members, which break up the rock by cutting from the surface of the face, with cutters working over an area in a planetary motion; and milling members, which break up the rock by means of a system of burrs (including disk burrs). The working members of cutter-loaders may also be of the combination type (for example, drill and drum or planetary and auger).
Depending on the design and loading method, the loading members of cutting-loading machines are subdivided into scraper conveyers (including flexible conveyers) and conveyers with bracket scrapers (ring loaders), as well as those that operate in combination with so-called raking claws; and bucket loaders, which usually empty the rock onto a belt transfer mechanism.
Depending on the design and mode of operation, cutter-loaders may be pulley-operated (a cable or welded link chain) and may ride on rails, wheels, pneumatic tires, or tracks or may be equipped with a hydraulic step feed. Cutter-loaders are usually powered by surface air-cooled or water-cooled asynchronous squirrel-cage electric motors fed by an AC current of 380 to 4,160 volts. Experimental work is being conducted on the use of frequency-controlled (thyristor drive) electric motors. The transfer mechanisms of cutter-loaders consist of power reduction gears and positive-displacement hydraulic drives with a pump and hydraulic power ram or hydraulic engine.
Cutter-loaders are used for long and short working faces (longwalls and chambers, respectively). For long working faces combines are classified according to their cutting method as wide-web (1.2 to 2.4 m) and narrow-web (up to 1.0 m). The first wide-web cutter-loader to be used on an industrial scale was the Donbass model. This machine was equipped with a bar working member, a ring scraper loader, and a cable-operated transfer mechanism. The wide-web Kirovets cutter-loader, with a bar working member and a ring scraper loader, was widely used for mining very thin, slightly inclined seams (0.6–0.9 m thick). The main disadvantages of wide-web cutter-loaders are the impossibility of utilizing mechanized supports and the absence of a support-free space near the working face, which is essential for the use of a movable face conveyer. For this reason, a basically new trend began to develop in the 1950’s, in addition to the further development of wide-web cutter-loaders—the design of narrow-web cutter-loaders that operated mainly in combination with a flexible scraper face conveyer that could be moved without dismantling.
The narrow-web cutter-loader with a drum working member was first used in industry in Great Britain in 1945–47 (the Undertown model cutter-loader). In the USSR, the machines most widely used for cutting slightly inclined seams were the narrow-web 2K-52, IK-101, KSh-lKG, and 1K-58M cutter-loaders with auger-type working members, the model MK-67 cutter-loader with a drum working member, model BK-52 with a drill working member and, for steeply sloping seams, the KT and UKR-1K (Temp) cutter-loaders with a drum working member (see Table 1). Anderson-Boys auger-type narrow-web cutter-loaders and Trepan Schierer combination drill- and drum-type narrow-web cutter-loaders are widely used in the mines of Great Britain, and Eichhoff model EDW-200 and EDW-130L auger-type narrow-web cutter-loaders are widely used in West Germany. Narrow-web cutter-loaders of similar design have also been developed in France. Poland, Czechoslovakia, and Japan.
|Table 1. Specifications of Soviet lot-produced narrow-web coal cutting-loading machines|
|Thickness of seam (m)...............................||1.1–1.8||1.35–2.85||0.75–1.2||0.7–1.3||0.45–0.85||0.6–1.5||0.9–1.4||2.0–3.2|
|Slope angle of seam (deg).........................||0.35||0–15||0–15||0–20||45–90||45–90||0–20||0–20|
|Type of working member.....................................||auger||auger||auger||vertical drum||horizontal drum||horizontal drum||drill||auger|
|Grip of working member (m).....................||0.63–0.8||0.63||0.63–0.8||0.8||0.9||0.9–1.0||0.63–0.8||0.63|
|Cutting speed (m/min)................................||3.07–3.84||2.4–2.7||2.5–2.9||2.05–2.44||1.83–1.72||1.9||2.2–2.6||2.45–1.9|
|Feed rate (m/min).......................................||0.0–6.0||0.3–4.0||0–4.5||0–4.5||0.36–1.27||0–3.0||0–4.5||0–2.0|
|Tractive force offeed (tons-force)......................................||to 15||to 15||to 15||to 15||—||—||to 15||to 20|
|Total available power (kW)........................||105||110||105||105||32||50||80–125||150|
|Basic dimensions (m)length.......................................................||5.92||6.5–7.1||5.8||5.5||5.1–5.3||4.9||6.3||5.5|
|Rated capacity (tons/min)....................................||1.8–3.5||2.0–3.8||1.2–1.8||2–2.5||0.8–1.0||to 2.5||2.3–3.4||to 5.0|
The development and introduction of narrow-web cutter-loaders have permitted the use of flexible, movable face conveyers and enhanced the prospects for the use of mechanized supports. The daily output capacity of narrow-web cutter-loaders may be as high as 3.000–5,000 tons of coal. Cutter-loaders for short faces have found their widest application in the American coal industry. A shortwall cutter-loader also functions simultaneously as an entry driving machine for driving shafts into a mineral layer. The machines most widely used in the USA for working short faces are the tread-mounted Joy cutter-loaders, with drum and drill units in combination with bar working members. These machines are high-powered (240–400 kilowatts) and have high output capacities (6–14 tons per minute) and caterpillar drive. They are made for use in flat and slightly inclined seams 0.9 to 3.0 m thick.
Entry-driving machines are classified according to use (for driving shafts in coal or other mineral and in rock), according to the cross-sectional shape of the working area (rectangular, trapezoidal, circular, or arched), and according to the direction of cutting (for horizontal and inclined workings). The first entry-driving machine to be used industrially in Soviet mines was the PK-2 machine, with a bar working member, which is similar in design to the German Streckenbagger machine. The most widely used model in the coal industry of the USSR is the PK-3 machine, with a crown working member in the form of a rotating tapered cutting head. The cutting head is moved during fracturing of the coal at the face by means of hydraulic power rams. This machine is designed for driving entries with a cross-sectional area of 8–12 sq m. The design of the PK-3 entry-driving machine served as a basis for the development of similar models in the USSR (type 4PU for underground shafts with a cross-sectional area of 4–8 sq m and the PK-9R for shafts with a cross-sectional area of 7–16 sq m) and abroad (the Brattby machine in Great Britain and the Eichhoff model EV-100 in West Germany). The Karaganda 7/15 entry-driving machine, with a planetary working member that has made possible entry-driving rates of more than 3,000 m per month in coal, was developed in the USSR for rapid entry driving. The first machine to be used industrially for the driving of entries in rocks of low toughness was the ShBM entry-driving machine, with a cutter working member that breaks up the rock by cutting and fracturing and is equipped with a hydraulic step feed. These machines are well adapted for extracting potassium salts. Machines with a milling working member and a hydraulic step feed have been developed for driving entries (including tunnels) in tougher rock. The best-known of these is the Robbins entry-driving machine, which is manufactured in the USA. Machines with a similar working member (disk burrs) were developed in the USSR for driving shafts in rock (the TOR-6, lasinovatets. and MPG-3 models).
The KN-2U cutting machine, with a bar working member. was developed in the USSR for cutting shafts in coal seams 0.8–1.2 m thick and 2.6 m wide with an angle of inclination up to 18°.
Efforts are being made in the USSR to perfect and develop new types of cutting-loading machines, such as cutter-loaders for narrow-web and highly efficient mining of thin and thick seams, cutting machines for cutting operations in thin seams, and machines for driving entries into hard rock. The main trends in the development of cutting-loading machines are an increase in available power and output capacity, broadening of the areas of application with regard for the total range of mining and geological conditions, improvement of the quality of the coal extracted, increased reliability and extended life of machines, large-scale introduction of hydraulic drive and automatic control facilities, greater safety and improved working conditions (leading disconnection, reliable dust suppression and collection, and so on), and maximum standardization of units and components.
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