Power Tools Structure

The power tool is composed of a casing, a transmission mechanism, a working head, a handle, a power switch and a power connection component. The basic structure is as shown in the figure below.

power tools structure 

1—Motor 2—Shell 3—Transmission mechanism 4—Working head 5—Handle 6—Power switch 7—Power connection assembly 8—Radio disturbance suppressor


  1. Motor

Motors for power tools mainly include single-phase series excitation motors, three-phase, single-phase power frequency and three-phase intermediate frequency (150-400HZ) asynchronous cage motors and permanent magnet DC motors. Single-phase series-excited motors have high rotation speed, small size, large starting torque, and can be used for both AC and DC. It is the most used type of motor in power tools.

The three-phase power frequency cage asynchronous motor has simple structure, convenient manufacture and maintenance, fixed speed, reliable operation and durability, and is mostly used for high-power electric tools and portable electric tools. The three-phase intermediate frequency cage asynchronous motor not only has the advantages of the three-phase power frequency cage asynchronous motor, but also has the advantages of high speed and small size of the single-phase series excitation motor.

Permanent magnet DC motors are generally used in household power tools, and are made into a type without power cords, which are directly powered by nickel-cadmium batteries. They also have the advantages of high efficiency, low starting current, and simple structure, but the power is small.


  1. Shell

The shell plays the role of support and protection, and has the characteristics of high strength, light weight, heat resistance, harmonious and pleasing color, and well-proportioned and generous shape.

Generally it’s made of engineering plastics or aluminum alloys. The engineering plastic material is reinforced nylon or polycarbonate. The application of engineering plastics not only reduces the weight of power tools, but also improves the safety of power tools.


  1. Transmission Mechanism

The transmission mechanism is mainly used to transmit energy, decelerate speed and change the direction of motion.

In order to meet the needs of various processing operations, the movement modes of the power tools working head include rotation, reciprocation, impact and vibration, etc., as well as compound movement of both impact and rotation.

Transmission gears are the most widely used transmission forms in power tools, including spur gears, helical spur gears, spur and spiral bevel gears, internal gears, harmonic gears, etc. The characteristics of the transmission are: high speed, large speed ratio, and most of the modules are between 0.6 and 1.5mm. The strength of the gear must not only meet the requirements of long-term full-load operation and overload, but also ensure that it can withstand braking torque and impact force several times larger than full-load.


  1. Working Head

The working head of the electric tool is the tool, cutting tool, abrasive tool and other working tools and their clamping parts for various processing of the workpiece. Cutting tools include all kinds of drill bits, taps, drills, saw blades, etc. Abrasive tools include various shapes and sizes of grinding wheels, abrasive cloths, grinding heads, etc. Throwing tools are all kinds of throwing wheels. There are also nut sleeves, screwdrivers (screwdriver), expander, etc.


  1. Handle

The handle include double horizontal handle, rear support handle, pistol handle, rear straight handle, etc. according to different use requirements and structures.

Some small and micro tools, such as electric punching shears, electric shearing machines, micro screwdrivers, etc., do not have special handles, and can be operated directly by holding the shell.

Some tools are also provided with auxiliary handles at the front end to reduce the operator's labor intensity.

There are two types of connection between the auxiliary handle and the power tool housing, the threaded connection type and the clamp clamping type.

Threaded connection type is to connect the handle directly to the housing of the electric tool through the connection thread on the handle.

The clamp type connection is a connection that is made into a clamp shape at the connection end of the handle, and the neck of the electric tool is clamped by the clamp.


  1. Power Switch and Interference Suppression Components

The structure of switches for electric tools mostly adopts two-pole bridge double-break contacts, and there is an instantaneous action mechanism to make the contacts quickly turn on and off. The hand-operated switch can automatically reset and cut off the power supply, and some are also equipped with a self-locking mechanism. The speed control switch generally adopts a combination of thyristor and electronic circuit to achieve the functions of speed regulation, speed control, and opening and closing circuits.

Most of the switches for power tools are installed in the handle, which requires small size, compact structure, safety and reliability, and cannot be replaced by ordinary switches.

Devices for suppressing radio disturbances are installed in the handle or housing.

Combination capacitors and inductance choke coils are used to suppress the disturbance of single-phase series excitation or AC and DC power tools to TV and radio.


  1. Power Connection Components

The power connection component is composed of a power plug, a flexible cable or cord, and a power cord sheath, etc., and is used to connect the power tool with the power grid. Most of the flexible cables or cords are light rubber-sheathed flexible cables or plastic-sheathed cables.

In Class I power tools, the protective grounding wire is specified as a green-yellow two-color wire

No protective grounding wire is allowed in Class II and III power tools.

Flexible cables or cords should be securely clamped and sheathed at the point of entry into the power tool. The sheath is made of insulating materials such as rubber and thermoplastic.

Class II power tools must use reinforced insulation power plugs, which are non-reconnectable power plugs in which the power plug and the flexible cable or cord are molded into one.

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