Conical picks of mining machines with increased utility properties – selected construction and technological aspects

doi:10.46544/ams.v26i2.02

Abstract

Shearers and roadheaders are commonly used to extract useful mineral deposits, especially hard coal, and for drilling roadways in underground mines, tunnels and other underground buildings in civil engineering. As the primary working process of this type of machines, mechanical mining of rocks is carried out by cutting. These machines' working units are equipped for this purpose with picks, usually conical (point-attack). They have the form of an axially symmetrical body consisting of a steel shaft and a tip usually made of tungsten carbide, connected by a hard brass solder. Due to the possibility of spontaneous rotation in the pick holders and even wear and tear of their tip around the entire perimeter, conical picks have a much longer service life compared to radial picks. Their life, especially when cutting hard and sharp abrasive rocks, is, however, still unsatisfactory. Rapid wear of the picks leads to a decrease in mining efficiency, an increase in this process's energy consumption, and an increase in dynamic surplus to which the cutting machine is subject. Among many forms of wear and tear of the conical picks, attention was paid to the problem of asymmetrical abrasive wear of the tips, pulling out the connection of the soldered pick tip and fatigue breaking of the pick shafts in the transition zone of the shank into the shoulder. The article presents original propositions of modification of the construction of the roadheaders/shearers conical pick shafts and the method of fixing the tip in the pick shaft in order to increase their operational durability significantly. The technologies and devices necessary to manufacture conical picks of the proposed structure were described. The developed modifications significantly contribute to the improvement of functional properties, including the reliability of conical picks, used in particular for hard rock mining.

Highlights

Modern longwall shearers used for mining coal and other minerals mined in longwall systems, as well as roadheaders used for drilling roadways in underground mines, tunnels and other underground buildings, are commonly equipped with conical picks armed with tips usually made of tungsten carbides (Fig. 1a & b)
The conical picks with the described modification retain the same external dimensions as conventional picks, which allows their use in existing cutting heads/drums of mining machines
One of the reasons for accelerated operational damage to mining machines conical picks is blocking the rotation of the picks around their axis during cutting

Summary

Introduction

Modern longwall shearers used for mining coal and other minerals mined in longwall systems, as well as roadheaders used for drilling roadways in underground mines, tunnels and other underground buildings, are commonly equipped with conical (point-attack) picks armed with tips usually made of tungsten carbides (Fig. 1a & b). Another type of operational damage to the conical picks f the mining machines is fatigue fracture of the pick shanks (Luo et al, 2010; Lu et al, 2018) (Fig. 3). The wear of the pick shaft's head does not have to be directly the result of the rock mining process but, for example, the friction of the pick against the spoil characterized by high abrasiveness and recirculation of this spoil (Underground Mining, 2020).

Results

Conclusion