working principle
The working principle of the electric drill is that the motor rotor of the electromagnetic rotary or electromagnetic reciprocating small-capacity motor performs the magnetic field cutting work operation, and drives the working device through the transmission mechanism to drive the gear to increase the power of the drill bit, so that the drill bit scrapes the surface of the object and better penetrates the object. .
Brief history
The birth of the world's power tools began with electric drill products. In 1895, Germany's Fein developed the world's first DC electric drill. The weight of this electric drill is 14 kg. The outer casing is made of cast iron and can only be drilled 4 mm on the steel plate. Hole. Then there was a three-phase power frequency (50 Hz) electric drill, but the motor speed did not exceed 3000 r/min.
In 1914, a single-phase series-excited motor-driven electric drill appeared, with a motor speed of more than 10,000 r/min.
In 1927, an intermediate frequency electric drill with a power supply frequency of 150-200 Hz appeared. It has the advantages of high single-phase series-excited motor speed and simple and reliable three-phase power frequency motor, but it needs to be powered by medium frequency current. Use is limited.
In the 1960s, there was a battery-free electric drill with a power cord using a nickel-cadmium battery. In the mid-to-late 70s, charging time was also shortened due to lower battery prices, and such electric drills were widely used in Europe, America, and Japan.
The electric drill was originally made of cast iron as the outer casing, and then changed to aluminum alloy as the outer casing. In the 1960s, thermoplastic engineering plastics were used in electric drills and achieved double insulation of electric drills.
Electronic speed drills also appeared in the 1960s. The electric drill uses an element such as a thyristor to form an electronic circuit, and adjusts the rotational speed by the depth at which the switch knob is inserted, so that the electric drill can be used according to the object to be processed (such as different materials, diameter of the drilled hole, etc.). Choose a different speed.
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