MD-type electric hoist widely used in electric single-girder crane , electric single girder overhead cranes, electric hoist gantry cranes and hoists used alone dynamic suspension rail electric hoist, as can mention two kinds of lifting speed, you can try to hang and assembly bits and other occasions to make slow, but in general when using fast lifting, the use of more flexible, more extensive use of the occasion.
2 The drive mechanism
Like electric hoist with CD, MD electric hoist is also used conical rotor motor, different in that its use of fast and slow two-motor drive. Which uses ZDS1, dual motor powered by two motors of different power (ie power ratio decreasing by other two motors) ZD1-and ZDM1 type connection is made through the gears. When the power is turned on and not connected to the motor is usually a slow speed main motor, the main motor of the fan wheel and the toothed braking wheel brake pressing contact with an output of one of the transmission gear, the torque generated by the motor vice through the shaft extended gear to the output stage of the main motor gear, output by the main motor shaft to get slow. When the speed of the main motor power connector is usually when the main motor produces an axial magnetic force to overcome the force of the brake spring, the main motor of the fan wheel and a toothed wheel brake disengaged, the main rotor of the motor starts running immediately, get constant speed.
3 Braking structural features
By the MD-type electric hoist structure can be seen as the main motor brake is not fixed, the constant, slow lifting, the load torque is transmitted the same way: hook hoist drum shaft main motor reducer Main motor brake (brake wheel with teeth) main and auxiliary motor gears deputy vice motor brake motor shaft at normal speed when lifting, the main motor is running but the motor is not running, Vice load torque from the main motor brake bear, and eventually through the main and auxiliary motor gears passed to Vice motor braking device; during slow lifting, the Deputy motor running, as the main motor shaft, the main motor load torque is then transmitted to the Vice brake motor brakes commitments, we can see that the motor brake is deputy MD electric hoist normally, the final brakes slow work, and its importance is self-evident.
4. Accidents performance
In the inspection work, on several occasions found that MD-type electric hoist slow motor bolts loose, the city also several outbreaks of slow motor and slow motor coupling bolts fall fall accident. Electric hoist at high altitude, difficult to find in the ground manipulator motor connection loose; and in the manipulation, the manipulation of mostly note hanging objects, rarely pay attention to the danger of coming down from above; single girder cranes and hoist the majority follow the ground using a portable controller manipulation, officers followed hanging objects, is in the fall just below the motor, so once a fall occurs very dangerous.
5 Stress Analysis
In common 5MD electric hoist, for example, it uses ZDS10.8/7.5 dual turbine drive, including a station for constant speed 7.5 kw main motor and a lifting platform ZDM21-4-type power 0.8kw slow hoisting motor with a deputy. Shown in Figure 1, slow motor and electric hoist used between the flange body, with ordinary M8 coarse thread bolt.
Vice motor main parameters: Power 0.8kw, rated speed 1380r/mm, static brake torque 8.34N / M. Vice motor mounting flange bolts set the force analysis:
(A) primary and secondary electrical work, the Deputy motor mounting flange came by brake load torque reaction.
(2) main and auxiliary motor brake, rear flange face of inaction by the motor torque effect, static braking torque should be greater than the work load torque.
(3) but also by the deputy motor flange weight resulting bending moment and shear force. In the action of the load, the general compression bolt is coupled parts must meet, between the joining surfaces to generate sufficient clamping force, by the frictional engagement surface to balance the external load, with the coupling surface does not slip, in order not to occur loose lapse.
7 Conclusion
Slow with ordinary bolt main motor and when (the bolt and wall of the hole there is a gap), its working principle is: the bolt preload, the clamping force is generated between the joints, relying on friction to resist lateral external load. Therefore, to regularly inspect the bolt and sturdiness.
