Electric wrench refers to an electric tool for tightening and loosening bolts and nuts. It is a tool for tightening high-strength bolts. It is used for initial tightening, final tightening and initial tightening of torsional shear high-strength bolts in the construction of large hexagon head high-strength bolts for the installation of steel structure bridges, plant buildings, chemical industry and power generation equipment, as well as occasions with strict requirements on the torque or axial force of bolt fasteners.

定转矩电动扳手是一种能自动控制转矩的电动扳手。它适用于需要用高强度螺栓连接的桥梁结构、大型钢塔、钢结构厂房、冶金设备的构架、大型起重机架、矿井钢架等工程中及大型柴油机、发电设备、化工设备中，要求恒定的夹紧力连接的螺栓也可用定转矩扳手来紧固。

Constant torque electric wrench is an electric wrench that can automatically control torque. It is applicable to bridge structures, large steel towers, steel structure plants, frames of metallurgical equipment, large crane frames, mine steel frames and other projects that need to be connected with high-strength bolts, as well as large diesel engines, power generation equipment and chemical equipment. Bolts requiring constant clamping force can also be tightened with constant torque wrenches.

特别在现代桥梁建设中，定转矩电动扳手是实现以“栓焊梁”代替“铆焊梁”的有效工具。这对简化工地安装工序、降低建桥成本、减轻劳动强度，从而加速桥梁建设具有较大的意义。

Especially in modern bridge construction, the constant torque electric wrench is an effective tool to realize the replacement of "rivet welded beam" with "bolt welded beam". This is of great significance to simplify the site installation process, reduce the bridge construction cost, reduce the labor intensity, and accelerate the bridge construction.

定转矩电动扳手的转矩以电气装置来进行控制。这种电动扳手具有耗电量少、噪声小、调节灵活、能自动停机、转矩稳定等优点。

The torque of constant torque electric wrench is controlled by electrical device. The electric wrench has the advantages of low power consumption, low noise, flexible adjustment, automatic shutdown, stable torque and so on.

电动扳手是装卸螺纹联接件的手持式电动工具，广泛应用于汽车、拖拉机、电机电器、动力机械、阀门、水泵、纺织机械等制造业的装配工作中，在化工、水泥预制件、塑料成型等作业中则用于生产流程中装拆真空罐、反应釜和水泥模板、带螺纹塑料件的脱模工作；也可用在铁道、桥梁、建筑等工程中作水泥轨枕、桁架节点、角钢脚手架等结构的安装、检修和拆换工作。

Electric wrench is a hand-held electric tool for loading and unloading threaded connectors. It is widely used in the assembly of automobiles, tractors, motors and electrical appliances, power machinery, valves, water pumps, textile machinery and other manufacturing industries. In chemical industry, cement prefabricated parts, plastic molding and other operations, it is used for the assembly and disassembly of vacuum tanks, reactors and cement templates in the production process Demoulding of threaded plastic parts; It can also be used for the installation, maintenance and replacement of cement sleepers, truss joints, angle steel scaffolds and other structures in railways, bridges, buildings and other projects.

当螺母的端面与工件端面接触后，阻力矩急剧上升，转动的螺旋槽使滚珠带着主动冲击块克服摩擦力和工作弹簧的压力向后移动，使主动冲击块与从动冲击块互相啮合的牙脱离啮合。此时，从动冲击块不移动，而主动冲击块继续向后移动。在转过从动冲击块的牙后，由于工作弹簧的作用使主动冲击块瞬时前移，并沿螺旋槽产生一个角加速度，主动冲击块撞击从动冲击块，两牙产生碰撞。然后螺旋槽又使滚珠和主动冲击块后移，脱离啮合。这样周而复始产生一次又一次的碰撞，获得所需的冲击力矩，使螺母紧固。

When the end face of the nut is in contact with the end face of the workpiece, the resistance moment rises sharply, and the rotating spiral groove makes the ball move backward with the active impact block to overcome the friction and the pressure of the working spring, so that the teeth meshed between the active impact block and the driven impact block are disengaged. At this time, the driven impact block does not move, but the active impact block continues to move backward. After turning the teeth of the driven impact block, the active impact block moves forward instantaneously due to the action of the working spring, and an angular acceleration is generated along the spiral groove. The active impact block impacts the driven impact block, and the two teeth collide. Then the spiral groove moves the ball and the active impact block backward and out of engagement. In this way, collisions occur again and again to obtain the required impact torque and tighten the nut.

如将电源开关接到反转位置即可拧出螺母。双重绝缘单相串励电动扳手在操作手柄上装有两只开关。一只为工作开关，是操纵起动和停止的；另一只是专门为改变电枢正反转而设置的，两只开关不可接反。

If the power switch is connected to the reverse position, screw out the nut. The double insulated single-phase series excitation electric wrench is equipped with two switches on the operating handle. One is a working switch, which operates start and stop; The other one is specially set to change the forward and reverse rotation of the armature, and the two switches cannot be connected reversely.