Attic platform installation tool for storage shelf and mezzanine floor
The birth of the world's power tools began with electric drill products. In 1895, Germany developed the world’s first DC drill. This electric drill weighs 14 kilograms. The housing is made of cast iron and can only drill 4 mm holes in steel plates. . A three-phase power frequency (50Hz) drill followed, but the motor speed failed to exceed 3000r/min.
In 1914, an electric drill driven by a single-phase series motor appeared. The motor speed reached 10,000 r/min or more.
In 1927, an intermediate-frequency drill with a power supply frequency of 150-200 Hz appeared. It not only has the advantages of high speed of single-phase series motor, but also has the advantages of simple and reliable three-phase power frequency motor, but it needs power supply with medium-frequency current. Use is limited.
In the 1960s, a cordless drill with a power cord using a nickel-cadmium battery was introduced. By the late 1970s, due to lower battery prices and shorter charging times, this kind of electric drill was widely used in Europe, America and Japan.
The electric drill originally used cast iron as the outer shell, and later used an aluminum alloy as the outer shell. In the 1960s, thermoplastic engineering plastics were applied on electric drills and double insulation of electric drills was realized.
In the 1960s, electronic speed control drills also appeared. This kind of electric drill uses thyristors and other components to form electronic circuits. The depth of rotation of the switch knobs is used to adjust the rotation speed, so that the electric drill can be used according to different objects (such as different materials, size of drill holes, etc.), Choose a different speed.