Vol 33 Iss. 1

The task of integrated mechanization of coal excavation at coal mines still remains unsolved. Moreover, not everyone clearly understands what should be meant by integrated mechanization. Often the concept of integrated mechanization is substituted by the concept of continuous or complete mechanization. However, continuous or complete mechanization means the use of mechanization in all parts of the production process; integrated mechanization should be called such an organization of the production process in which the work of all parts, and therefore the entire mine as a whole, is subject to the rhythm of the main mining machines, the rhythm of machines and mechanisms working in the faces. Only then will the greatest efficiency be ensured for mining machines – their highest productivity, their best use. What rhythm of work of downhole machines should be considered as the guiding one, what should be considered as the main and most promising in the work of mining machines. In the coal mining industry for a long time for the production of cutting, cutting machines have been used; for breaking coal – blasting; and the loading of coal onto the conveyor until recently was carried out manually. Specially designed loading machines did not justify their purpose. For joint mechanization of cutting, breaking and loading operations, mining combines – the first mechanisms of integrated mechanization – were created.

One of the most important technical problems of mining industry development is the problem of transportation of large volumes of rock mass. The solution of this problem should provide a significant increase in the productivity of transportation plants. The newest transport equipment should satisfy a number of other requirements, the most important of which are: a) increase of labor productivity at transport works; b) increase of reliability of transport work and complete elimination of delays in work of excavation machines due to transport; c) decrease of cost of transportation of bulk cargoes; d) all possible introduction of automatic control of transport complexes; e) increase of service life of transport mechanisms and replacement of the most expensive and scarce materials used for their manufacture; f) reduction of weight and facilitation of assembly and transportation of transport installations . Of exceptional importance is the creation of productive and reliable installations for transportation of huge volumes of bulk cargoes during large hydraulic engineering construction and at modern open-pit mines equipped with the latest mining machines of high productivity and power.

One of the currently widely used methods of calculation of belt conveyors consists in a preliminary calculation, the initial position of which is the approximately determined value of power on the drive shaft of the conveyor, and in the final calculation - the method of determining the tension in characteristic points of the contour of the traction body. In this method, the accuracy of the final calculation depends on the accuracy with which the preliminary calculation determines the weight of a linear meter of belt. The practice of calculations shows that in a number of cases the error in preliminary determination of belt weight can reach a significant value, as a result of which the final calculation turns out to be insufficiently accurate.The main errors in the preliminary calculation are as follows: 1) the maximum tension of the belt is determined by a formula that is not valid for all cases encountered in practice; 2) the weight of moving parts of the conveyor is taken tentatively.

Delivery of coal from the mine face in most cases is carried out by several scraper conveyors forming a conveyor line. The start-up of such a line should be carried out by alternately switching on the conveyors in the sequence reverse to the coal flow. To reduce the voltage drop in the network, the sequential start of motors should be made with a certain time delay. Conveyors should be stopped in the sequence corresponding to the direction of coal flow. In recent years, coal mines have done a lot of work on the transfer of area conveyor lines to remote control. However, remote control of scraper conveyors with the help of magnetic starters, even in the case of their electrical interlocking, does not eliminate the operations of sequential time delayed start of motors and monitoring the work of conveyors. Therefore, remote control does not cause reduction of labor intensity of works on maintenance of conveyor installations. For complete elimination of these works it is necessary to supplement the system of remote control with automatic devices providing sequential start of motors with a timedelay and control over the state of electrical and mechanical parts of each conveyor, i.e. it is necessary to realize automated remote control of conveyor line.

Loading machines with bucket working body UMP-1, PPM-2, PML-5, EPM-2 (Table 1) and others, due to mobility and versatility, have received in the mining industry the widest distribution. They are the main loading machines when sinking excavations in strong rocks. There are a lot of unsolved problems in the complex study of loading machines operation. Thus, the literature lacks comprehensive data on the study of the main resistances to penetration of the working body of the machine, there is no methodology for the calculation of loading machines. However, on the study of the processes occurring during the digging of soils and bulk materials by the working bodies of earthmoving machines, there are valuable materials that can be used in the development of theoretical provisions and in the practice of loading machines.

The process of scooping or gripping the rock mass with a bucket, which is to some extent in a disturbed state of adhesion between the particles, is one of the links in the chain of processes for the extraction of minerals. However, it has not received sufficient coverage in the technical literature. Related areas, such as the theory of soil cutting, are also comparatively poorly developed. Research works on loading machines do not go further than the registration of the mode of operation of machines, do not investigate the compliance of the machine to the face, do not analyze the individual stages of loading and therefore cannot give justification to the theoretical concept of the loading process, the magnitude and nature of possible forces and calculation methods of newly designed loading machines. Experiments with models of the elements of the working organs of loading machines (published so far) are only the first steps in the systematic study of the scooping process, since the conditions of the experiments cannot correspond to the actual operating environment of loading machines.

The problems of kinematics and dynamics of the shovel of loading machines are represented by several works of domestic technical literature and few substantial foreign works. Among them the most interesting are the articles by S. G. Kalmykov, who compared the kinematics and dynamics of three types of rolling handles (shovels), determined the force in the handle chain and the power consumed by loading machines, and K. A. Lokhanin, who justified the design changes in the loading machine associated with the replacement of pneumatic motors with electric ones. At the same time, K. A. Lokhanin considered the kinematics and dynamics of the shovel. The starting point of these theoretical studies is the independence of the number of revolutions of the motor shaft from the load during the shovel movement. The result of this simplification, which makes us abstract from the relationship existing in any engine between the load and the number of revolutions, is a huge error in the calculations.

The development of mechanization of coal and rock loading processes in preparatory excavations requires further improvement of loading machines and increasing the efficiency of their work. For this purpose, it is necessary to consider the validity of the principles of machine operation, to establish the expediency of the design of the working element and to outline the direction of their further development. As a criterion for comparing the principles of operation of the working element of loading machines, we take the trajectory of its movement and the direction of movement at the time of penetration into the pile of blasted material. The existing loading machines can therefore be subdivided into three groups: 1) the trajectory of movement of the working element coincides with the vertical plane, the penetration into the heap of material occurs from below; 2) the trajectory of movement is in a plane close to the horizontal plane; the moment of penetration and separation of material from the heap is characterized by lateral (flank) movement; 3) the trajectory of movement coincides with the vertical plane; penetration into the heap of material occurs from above.

The proposed article presents the results of research on the interaction of forces during the operation of the scraper during the period of scooping the material and establishes the main technical parameters of rope scrapers. As an initial formula characterizing the process of digging of soils (or the process of scooping of bulk materials) by buckets of earthmoving machines, we take the well-known formula of N. G. Dombrovsky (see the article).

With the modern development of mining electrical engineering, a series-wound DC motor is used as a traction motor on mine electric locomotives. It best satisfies the requirements of mine electric locomotives when operating on mine haulage tracks. At present mine haulage tracks are characterized by very weak top structure, sharply variable gradients, the presence of curves of small radius and in some cases waterlogged and contaminated rails. Such condition of haulage tracks, naturally, leads to deterioration of rolling stock operation, rapid wear of running parts of electric locomotives and mine cars — to increased resistance to movement of the entire train. Working conditions of the traction motor of mine electric locomotives usually have a sharply variable load value. Static resistance to motion often takes negative values. In the presence of other additional resistance to motion, the traction motor actually operates all the time in transient modes — in acceleration and deceleration.

The weight of the train in the calculations of mine electric locomotive traction is taken by the lowest value determined from the conditions of the adhesive weight of the electric locomotive, heating of traction motors and braking of the train. One of the above conditions in each specific case, depending on the main technical parameters of the electric locomotive and transportation conditions, is limiting and determines the size of the train. In the case under consideration, of the main technical parameters of the electric locomotive, the parameters of the adhesive weight , continuous tractive force and continuous speed of the electric locomotive are of decisive importance. It is obvious that a rational ratio between the values of these parameters is of considerable interest, since it makes it possible, other things being equal, to allow a larger train size.

The signaling, centralization and interlocking devices used in domestic mines operate at voltages from 12 to 250 volts - in the range of the low voltage scale. As the operating experience has shown, the reliability of signaling, centralization and interlocking devices does not depend on the voltage at which these devices operate. The safety of operation of signaling, centralization and interlocking devices, from the point of view of their maintenance, is in inverse dependence on the voltage value. But, taking into account that signalling and control systems are low-voltage stationary installations, the fulfillment of safety rules, which eliminate the possibility of accidents at high voltage values, during their operation does not cause significant difficulties. The main factor determining the optimality of the voltage value of signalling systems is the economic costs of power supply. In this case the most favorable voltage value will also be the optimal one for these specific conditions.

The practical significance of the question of the method of determining the value of the longitudinal slope of trenches and their cross-section is to reduce the amount of work on the construction of main trenches, which on average for quarries are about 10-15% of the total amount of earthworks, and in absolute figures reach several million cubic meters. At an average cost of 1 m³ of 8-10 rubles, even an insignificant reduction in excavation works will reduce capital expenditures for quarries by several million rubles. For this purpose, three main technical parameters related to trench design were analyzed: longitudinal slope, determined by the volume of mining operations (freight turnover), type of traction, type of locomotive, and operating conditions of the quarry tracks; width of the trench base, which is set depending on the track gauge, the number of railroad tracks to be laid and water drainage conditions; slope angles set depending on the geotechnical properties of the soils in which the trench is excavated .

The introduction of automation into the main and auxiliary production processes is currently the most important direction of further development of mechanization of the Soviet mining industry. The workers engaged in this issue face two main tasks: 1) wide introduction into production of the achievements already available in this field, tested by the practice of work of individual enterprises; 2) finding ways to further expand the scope of application of automated methods of work and improve the equipment used for this purpose. Transfer to automatic operation of various still unautomated units of the complex of electromechanical equipment of mines requires solving a number of problems associated with the creation of special types of equipment, schemes and equipment for automatic control, monitoring and regulation. It is possible to automate in principle the operation of almost all mine mechanical installations, but the automation of some of them is achieved relatively easily, and others, even well-proven under conventional non-automatic methods of operation, - only with the use of very complex schemes and a large number of additional equipment and control equipment.

The issue of selecting rational sizes (capacity) of mine cars for underground transportation has been discussed in the domestic mining literature for twenty years. In the first period of development of mechanization of mining industry, when our plants were just starting to master the serial production of cars and electric locomotives, it was necessary to set the problem and its solution, which could provide answers to the questions put forward by designers about what should be the main dimensions of the cars designed by them. Attempts to solve the question in this plane were reflected, for example, in the works of A. V. Nekoz and A. I. Milovanov. Later, when the serial production of several types of cars and electric locomotives was mastered and the unification of carswas carried out, which established a certain minimum of their standard sizes, there was a need to solve the question of choosing the size of the car in a different plane. Now this question began to be put forward not by designers, who by that time had created a number of standard cars and thus basically fulfilled their task, but by design engineers. They were interested in another question: how to choose the mostadvantageous one for the given operating conditions from among the available standard cars.