A continuous miner is a mining machine that produces a constant flow of ore from the working face of the mine. The machine continuously loads coal with a cutting steel drum and conveyor system. Continuous miners, which began to take off in the 1940s, now make up of 45 percent of the underground coal mine production.
Today, continuous miners are being developed as driverless machines controlled via remote control.
IN THE BEGINNING
The first ripper-type continuous miner appeared in the early 1900s but was not successful. The first successful machine was built by an American, Harold Silver, in 1943 and was used for work in the Consolidated Coal & Coke Co. mine. In 1946 the machine attracted the interest of Joy Manufacturing Co., w
hich purchased the patents for the machine and developed two prototypes. They became known as the JCM models and were used for mining projects beginning in 1948.
By the 1950s, a series of continuous miners had been produced and manufactured by Joy Manufacturing. The company’s 3JCM model was so successful it stayed in production for the next 18 years with 212 being produced. This miner was beneficial in that it could adapt to different mining conditions; however, it had many drawbacks, including its complex structure, which made it difficult to clean, and its slow mining rate, which was attributed to the small area provided for face cutting.
Continuous miners were also developed as a borer type machine. The borer type continuous miner was first produced in the form of the Colmol model in 1948. The Colmol was able to provide low-boring intensity of 400 tons per day with a 48-inch seam capacity. Jeffrey Mining Co. quickly scooped up the patents for this machine. When Jeffery took over the prototypes and used them to construct its own models, it featured machines with horsepower as high as 150 to 190. Not to be outdone, Marietta, Goodman and Joy all produced larger machines with more work capacity.
Marietta was acquired by Clarkson Manufacturing Co., and was later acquired itself by National Mine Service in 1957. Larger borers began to 
be produced after the acquisition, namely the Marietta 675, consisting of 375 horsepower and able to cut seven feet, six inches high by 13 feet wide. The prototype was increased to 450 horsepower. The weight was increased to 57 tons and the machine became a prime potash miner at 250 tons, this time capable of cutting eight feet high and 25 feet wide. The rotor was operated by a 400 horsepower motor, proving to be a tough contender for other manufacturers to beat.
Goodman developed the Type 500 in 1954. The Type 500 could cut seven feet high and 13.5 feet wide; its rotors were each driven by a 400-pound motor. The machine’s total weight was 73,000 pounds
Joy also developed a larger miner when it produced the 2BT and the 2BT6, which was powered by a 510 horsepower motor and weighed 52 tons.
Another type of miner was the auger head miner, a device with dual augers, first built in 1955. Produced by A.G. Wilcox, it was built primarily for low-seam applications. Jeffrey Manufacturing began producing a similar model in the 1950s. The 100-L, built in 1960, consisted of a chassis with a height of 20.5 inches. Although Jeffrey ceased production of the auger head, Wilcox (now a subsidiary of Fairchild Inc.) continued to produce them.
Oscillating head ripper miners also made an appearance in the 1950s. Invented by E.M. Arentzen, president of Lee Norse Co., the Roadmaster was a machine featuring rotating cutter wheels that turned horizontally while engaged in a downward direction. The initial machine was mounted on rubber tires and evolved to crawler tracks by 1951. These machines gradually grew in size and became more complex over time. Joy countered this with its 8 CM and 9 CM miners, complete with hydraulic oscillation and triple bit rings. These miners were most successful in the 1960s, with the other types of miners experiencing steady declines.
The drum head type continuous miner was introduced in 1967 by Jeffrey Manufacturing Co. The first version was known as the Heli Miner, with a 14-foot wide, non-oscillating cutter head. Joy, National Mine Service, and Lee Norse also produced this type of miner. The most successful in the early 1970s were Lee Norse’s Norse 10 and Norse 11 models.
Remote-controlled and Robotic Miners
Today’s miner can extract at least 38 tons of coal per minute, depending on the thickness of the seam, although manufacturers are constantly beating the record.
Modern day continuous miners are remote-controlled and customized for different mining conditions. The number of robotic miners operated via computer controls is increasing, eliminating the need for an operator in this sometimes dangerous task.
The remote-controlled continuous miner is likely to continue paving the path of the future, with the Mining Safety and Health Administration employing resources to ensure the efficient operation of this type of machine. With remote-controlled machines gaining widespread popularity, as evidenced by the 699 units that were in operation in the U.S. in 2004 alone, more safety and health concerns involving their use have been brought to the attention of the industry.
Phil Robertson, Editor
