For multi-rope friction hoists, non-hot-melt materials are more suitable for use as Friction pulley lining blockmaterials. The factors that affect the friction coefficient of the lining block include surface condition, load pressure, wire rope creep speed and ambient temperature.

According to the working principle of the multi-rope friction hoist, the friction liner (hereinafter referred to as the liner) installed on the cylinder shell of the friction wheel (master wheel) of the hoist is a very important part of the friction hoist to drive the wire rope and lift the load. The friction performance of important parts directly affects the working capacity, working efficiency and safety of the hoist.

1 、lining block material

There are two main purposes of the liner: one is to increase the friction between the friction wheel and the wire rope to improve the working capacity and safety of the hoist; the other is to act as an isolation pad to isolate the shell and the wire rope to avoid direct contact between the two Friction with each other to protect the shell and prolong the service life of the wire rope. From the purpose of the liner, it can be seen that the material used to make the liner should have two main characteristics: one is that the friction performance is good, that is, the friction coefficient with the wire rope should be high and stable; the other is that the wire rope should not be damaged, that is, the hardness of the liner should be low.于wire rope. Around these two characteristics, the cushion materials used in the early days were mostly natural materials, such as wood, leather, rubber and aluminum alloy. With the development of the chemical industry, people gradually began to use synthetic materials, such as polyvinyl chloride, polyurethane rubber, and resin materials. According to the chemical properties of the material, the gasket material can be divided into two types: hot-melt type and non-hot-melt type. Polyvinyl chloride and polyurethane are hot-melt materials. There are many types of polyurethane due to its different types and components, and there are certain differences in performance. The polyester polyurethane used to make the liner is characterized by good toughness and wear resistance. However, polyurethane materials have their insurmountable weaknesses. For example, the melting point is low, generally only more than 100 degrees, and it is difficult to ensure the friction performance of the liner under accidental circumstances; especially the thermal conductivity is very poor (it is sufficient to be used as a refrigerator insulation material). The frictional heat accumulation and local temperature increase will affect the friction coefficient; the transverse rigidity is poor, the deformation is large after the force, and the fatigue fracture is prone to; avoid ultraviolet radiation, short aging cycle and poor cutting performance. Non-hot-melt materials are materials that will not melt when heated until they burn. Compared with hot-melt materials, non-hot-melt materials have many advantages, such as not melting when heated, and can ensure the friction performance of the liner in unexpected situations; the friction coefficient is high and stable, and the temperature is less affected; the hardness is high, and the transverse rigidity Good, the deformation is small after being stressed, and fatigue fracture is not easy to occur; it has strong chemical resistance, anti-aging ability, long life and good cutting performance. The resin-based gaskets that are frequently used in China are non-hot-melt materials with excellent friction properties. According to the working characteristics of the multi-rope friction hoist, it should be said that non-hot-melt materials are more suitable for use as gasket materials.

2、Working conditions of the liner

The working conditions of the gasket mainly include four aspects: surface condition, load pressure, wire rope creep speed and ambient temperature, and are also four main factors affecting the friction coefficient of the gasket.

2.1、Surface condition When the liner is working, due to the influence of many factors at the site of use, the surface of the rope groove will have different states, such as dry, water or grease, but it is often not a simple one, but several states. Put it together, such as grease and water, and it is also contaminated by mineral powder, especially in the state of grease. The mineral powder is stuck by the grease and attached to the steel wire rope, and participates in the work of the friction surface. Groundwater is the direct cause of water dripping, and grease is the antiseptic of the steel wire rope, which sticks from the wire rope when the liner is in contact with the wire rope. In most cases in our country, the liner works with steel wire rope anti-corrosion grease and water. This state is the worst of all surface conditions and has the greatest adverse effect on the friction coefficient of the liner. Of course, the grease mentioned here is not ordinary anti-corrosion grease, but special steel wire rope anti-corrosion grease for friction lifting, referred to as friction grease. Tests have shown that, under normal circumstances, the friction coefficient of the liner under different surface conditions is different, and the friction coefficient under the greased state is the lowest. Therefore, the friction performance of the liner is inseparable from the surface state. Generally speaking, the friction coefficient of the gasket, unless otherwise specified, should refer to the friction coefficient in the greased state.

2.2、 load pressure

The liner is subjected to pressure from the wire rope when it is working, and this pressure varies greatly depending on the location of the liner. Generally speaking, the pressure (or specific pressure) refers to the average pressure, which is calculated according to the projected area of the rope groove. Different specifications and models of elevators have different pressures on their gaskets, but the average pressure is generally around 2.0 MPa, and the maximum is less than 3.0 MPa.

2.3 、The creep speed of the wire rope

During normal operation, relative sliding between the liner and the wire rope is not allowed. If sliding occurs, it is considered as a failure of the friction pair, which is likely to cause accidents. However, because the wire rope is an elastic body, according to the elastic body transmission theory, the wire rope will elastically slide or creep on the pad. Due to the difference in elasticity of the wire rope, the difference in tension, and the different operating speed, the creep speed of the wire rope is different for different specifications of hoists.

Research shows that: the creep speed of the wire rope has a certain effect on the friction performance of the liner. From the perspective of speed influence, the increase of the creep speed will appropriately increase the friction coefficient of the liner, but the wear will increase.

2.4、 ambient temperature

my country has a vast territory. The outdoor temperature in winter and summer should be normal from -30-+40℃, while the indoor temperature should be controlled within the range of 0-30℃.

The working environment of the liner is generally indoor, but the steel wire rope closely connected with it is different. For the tower hoist, the wire rope must pass from the machine room to the shaft through the open shaft tower. For floor hoists, the wire rope must be completely exposed through the outdoors to reach the shaft, and the wire rope will be exposed to the sun and rain. In contrast, the working environment of the wire rope is much harsher, but because the liner is always in contact with the wire rope, its friction performance will be affected to a certain extent by the temperature of the wire rope, especially when the surface of the wire rope is greased. some.

3、Performance requirements of the gasket

The use of the liner clearly shows that the coefficient of friction is the most important performance parameter of the liner. From the perspective of use, the liner should have the following three main properties:

(1) The friction coefficient should be high. According to the current level of the domestic gasket manufacturing industry, many friction coefficients should be above 0.25.

(2) The friction coefficient should have the characteristics of increasing with the increase of the creeping speed of the wire rope, so as to ensure the convergence of the sliding speed when abnormal sliding is caused by an accident.

(3) Good thermal stability. When unexpected conditions cause abnormal sliding, the surface temperature of the liner rope groove cannot be melted when the temperature rises, and the friction coefficient should remain stable.

In addition, the liner should have sufficient strength, uniform internal organization, no defects, oil and water resistance, long-term exposure to grease and water, and stable performance, without damaging the wire rope, without polluting the environment, harmful to human health, and cutting Good performance etc.

4、 conclusion

The pad is as important to the multi-rope friction hoist as the tire is to the car. Without it, the hoist cannot effectively drive the wire rope to work. The performance of the liner is related to the parameter level of the whole hoist. The poor performance of the liner makes the hoist unable to run safely and reliably. Therefore, the liner is paid much attention to at home and abroad, and research is constantly being carried out.