With the development of industrialization, rubber sheathed flexible cable, with its stable electrical performance, excellent mechanical and physical properties, especially soft characteristics, has been the main equipment installation cable used in various mobile occasions. At present, in the mining process of large-scale open-pit coal mine and metal mine, large-scale gravel and sharp objects often hit the cable, and the cable is often subject to great drag force in the process of moving with large-scale mining equipment. Therefore, the drag type rubber sleeve cable relies on special structural design to reduce the impact of external torsion force on the sheath material, so as to improve the service life of the cable The first choice for the installation and use of equipment in dragging occasions.
In the case of frequent dragging and friction, the reduction of cable life is often caused by the abrasion of the sheath from the outside to the inside, causing damage to the insulated core, so the life of the sheath directly affects the service life of the cable. The traditional sheath thickness of the towed cable is divided into two parts, and the structure of braiding layer is added between the two layers of sheath to increase the binding force of the inner and outer sheath. The braiding layer adopts the material with certain elastic force to buffer the reaction of the cable sheath in the process of stress, so as to improve the service life of the cable.
The former realization of the sheath is divided into two parts. Naturally, the thickness of each layer of sheath will be thin, which greatly improves the difficulty of process realization. Therefore, the selection of rubber material in the extrusion die is particularly important. In general, the production of ordinary rubber sheathed cable is realized by providing greater pressure to fill the cable core through the ratio of mold core and mold. Generally, the mold core will choose a larger angle to reduce the angle of mold sleeve (see Figure 1). The angle difference between the mold core and mold sleeve is generally controlled at about 15 ℃. The extrusion pressure of rubber material is controlled by the angle difference to squeeze the material when it is compacted On the surface of cable core. The thickness of the internal and external protection of the towed cable is relatively thin, and the production of rubber material is extrusion production. During the production of external protection, the rubber material acts on the cable core at the extrusion die mouth, and when the pressure is too large, it is easy to cause the accumulation and extrusion of the internal sheath, resulting in clamping phenomenon.
In order to solve the above problems, we have done many theoretical design and practical demonstration. By improving the angle difference between the core and the mold sleeve, we can solve the problem that the external protection pressure is too large for the internal protection, and greatly improve the continuous production capacity of this kind of cable.
The improved module is shown in Figure 2:
Figure 1: die drawing before improvement
The mould parameters before improvement: α = 110 ℃, β angle is generally 89 ℃, angle difference (α - β) is generally 21 ℃,
Figure 2: improved mold drawing
The improved α angle is generally 89 ℃, β angle is generally 68 ℃, and the angle difference (α - β) is generally 21 ℃. This mode of die matching is to reduce α angle and β angle. According to the mechanical analysis, this angle matching can reduce the pressure on the inner sheath when the outer sheath is extruded, which can ensure the extrusion of the sheath well.
After practice, it can be extruded well, and the sheath surface is smooth, there is no slub and so on, which effectively solves the problem of clamping die.