What is the principle of hanging steel wire rope of mine hoist?

Friction hoist is the most commonly used type of hoist in coal mine deep well transportation, and multiple steel wire ropes are installed for tension transportation. The steel wire rope is easy to be worn, rusted or even broken after long-time operation. According to the coal mine safety regulations, the steel wire rope shall be replaced in time. For the wire rope replacement process of multi rope friction hoist, it is also a work process with high professional and technical requirements. At present, the commonly used replacement and recovery methods of hanging wire rope are mainly divided into winch method and old rope with new rope method. Both methods have their own engineering characteristics, but they also have certain technical defects, which can not effectively ensure the safety and reliability in the wire rope recovery process. When recovering the steel wire rope, the main problem is that the steel wire rope will have centrifugal force under the torque force, resulting in the winding between the steel wire ropes: when manually pulling the recovered steel wire rope, the steel wire rope must be blocked and cut. This method has low safety and is not economical for the cost investment of manpower and material resources. Therefore, a device that can continuously recover the steel wire rope is designed, which can reduce the internal torsion of the steel wire rope, prevent winding, reduce the work cost, and finally achieve the purpose of protecting the safety of operators.

1 torsion mechanism of steel wire rope

1.1 structural characteristics of steel wire rope

Before designing the steel wire rope recovery device, it is necessary to understand the internal structure of the steel wire rope before designing a targeted recovery device. The steel wire rope used by the hoist can be divided into two categories. When the twisting direction of the steel wire and the rope strand is inconsistent, this type is the alternating twisting steel wire rope; on the contrary, when the twisting direction of the steel wire and the rope strand is consistent, this type is the same twisting steel wire rope. The two types of steel wire rope structures are completely different in technical characteristics. The appearance of the cross twisted steel wire rope is relatively rigid, the surface roughness is large, and it has strong bending stress, but the recovery force after being stressed is good; The outer surface of the same direction lay steel wire rope is smooth and the bending stress is weak, so this type of steel wire rope is relatively soft and has a long service life 4. At the same time, the hoisting wire rope mainly adopts the single-layer strand structure, and the structural diagram is shown in Figure 1.

1.2 torsion principle of steel wire rope

Understanding the torsion principle of steel wire rope is the premise of designing steel wire rope recovery device. When the mine is lifted vertically, the hoist must pass through the crown wheel when pulling the steel wire rope. At this time, the steel wire rope will be frequently bent in both positive and negative directions. Whether the steel wire rope is lifted or lowered, it will make the steel wire rope bend at the crown wheel. The load on the section of the steel wire rope during bending is mainly related to the tensile load on the section, the load on the terminal, the mass per unit length, the distance from the lower end of the section and other factors. In the process of practical application, in order to ensure the bending stress balance of the steel wire rope, the same number of steel wire ropes will be arranged in the left and right directions, so that the rotation direction of the steel wire rope has stability. The commonly used steel wire rope layout is shown in Figure 2 on the following page.

2 design scheme of steel wire rope recovery device

2.1 design idea

The recovery device shall have the function of follow-up and stop, and the speed can be controlled in time: the recovery device shall be equipped with a flexible support structure, which can replace the rope disc at any time and reduce the quality of the rope disc; the most important design needs to reduce the torsion of the steel wire rope, prevent the winding of the steel wire rope, and effectively reduce the centrifugal force: the parameters of the recovery device shall be set according to the design idea. The drive motor power is 125KW, the drive voltage is 380V, the recovery speed is 0~10m/min, and the maximum recovery length is 800m.

When the recovery device rewinds the steel wire rope, it shall be consistent with the speed at which the steel wire rope leaves the drum. Although the speed of the recovery device can be adjusted, the rope feeding speed is generally 0~5m/min

2.2 overall scheme

The steel wire rope recovery device is mainly divided into three modules: drive module, clamping module, rope arrangement and torque release module. The drive module is mainly used to output power to realize that the recovery device can recover the steel wire rope; the clamping module is the rope disc support function module, which can facilitate the installation and disassembly of the rope disc; the main function of the rope arrangement and torque release module is to ensure the safety of the steel wire rope in the recovery process. Based on the design of the overall scheme, the overall structure of the recovery device is designed as shown in Figure 3.

2.3 functional structure design of recovery device

2.3.1 driving mechanism

The design of driving mechanism mainly includes power device design and chain drive design. Jd-2 drawworks is used as the driving device of the power unit. The drawworks shall be explosion-proof, with a rated speed of 1550

r/min。 The power is transmitted to the drive shaft through the sprocket to drive the rotation of the recovery device. The power output enables the working load to output power at the most appropriate position. The small sprocket model of the recovery device is 16A with 32 teeth, and the large sprocket model is 16A with 45 teeth.

The design of chain drive is mainly to ensure that the chain will not be broken under the low-speed motion state of the recovery device when the steel wire rope is recovered.

2.3.2 clamping mechanism

The clamping mechanism can realize rapid clamping of the rope disc. When the piston is about to be ejected, it will inject hydraulic oil to give a certain clamping force to the rope disc. In case of failure of the automatic device, it can also use the manual method as the temporary hydraulic source, and can effectively control the lateral movement of the clamping plate. The tailstock is also a key component of the tightening mechanism. The tailstock is equipped with a support platform and a support column. Installing the tailstock on the base can have enough space to remove the rope disc. The structure diagram of the clamping mechanism is shown in Figure 4.

2.4 model structure establishment

The SolidWorks modeling software is used to establish the three-dimensional model diagram of the wire rope recovery device, and the relevant mechanical loads are applied. At the same time, the boundary conditions consistent with the actual working conditions are designed to constrain the wire rope recovery device. The structure model mainly reduces the friction resistance through the chain transmission, and realizes that the torsion speed of the steel wire rope is in a reasonable range. The clamping device mainly uses the balance bar to connect with the base, which realizes a larger working space for the operator and does not affect the support rope disc. The structure diagram of the simulation model of the wire rope recovery device is shown in Figure 5.

3. Analysis of working performance of steel wire rope recovery device

3.1 dynamic simulation analysis

According to the actual working conditions, the dynamics of the recovery device is simulated and analyzed after the load parameters are applied to the simulation model. Figure 6 on the following page shows the force between the twine disc and the paddle shaft. When the twine disc starts to rotate, the paddle shaft will drive the full load twine disc to rotate in a short time, so the force of the paddle shaft to push the twine disc will change dramatically. It can be seen that at 0.34s, the maximum force reaches 7444n. As the rope reel reaches the predetermined speed, the force with the shift rod gradually stabilizes around 3000n. Since the friction force of the steel wire rope bearing the bottom plate is 1000N, the winding radius when the coil is full is 900mm, and the eccentricity of the paddle shaft is 300mm, it can also be calculated that the driving force of the paddle shaft in the stable state is 3000n. It shows that the retraction device reduces the torsional force of the steel wire rope, and the centrifugal force is also reduced accordingly, so that the steel wire rope can be stabilized in the recovery process.

3.2 modal analysis of rack

Because the recovery device is easy to make the whole frame vibrate when pulling the steel wire rope, the modal analysis of the frame is also particularly important. The recovery device shall be started by inching frequently under heavy load conditions. Due to the heavy weight of the rope disc and the large impact on the rack, it is necessary to calculate the excitation frequency of the rope disc to the rack during startup to avoid resonance and damage to the rack during startup. As shown in Figure 7, it can be concluded that the frequency corresponding to the maximum amplitude is 2.34hz, indicating that the impact of the rope reel on the rack is a low-frequency impact, which is lower than the natural frequency of the rack. It indicates that the recovery device will not cause resonance during inching operation and can operate smoothly.

4 Conclusion

The dynamic and modal analysis of the new steel wire rope recovery device is carried out through the finite element simulation technology. The test results show that the designed recovery device can meet the engineering needs of replacing steel wire rope.