INTRODUCTION

In modern conditions for an intensification of productions in various industries shock mechanisms are widely used. They receive the greatest application as executive powers of cars, especially in the chisel technics. Creation and introduction of pneumatic boring cars of shock action allows to carry out with certain degree of efficiency drilling process in breeds with fortress factor f=8- 20 on a scale of the professor of M.Protodjakonov. However these cars have a number of essential lacks. The main things from them – low EFFICIENCY and high cost of consumed pneumoenergy. The general EFFICIENCY of pneumatic boring cars – defined as the relation of the capacity transferred to a chinks, to power consumption of compressor installation – for mine conditions remains at rather low level.

The boring cars equipped with hydraulic mechanisms of rotation and blow, have several times bigger EFFICIENCY, than pneumatic, and work from the electric system. Besides, wide application of hydraulic cars allows to avoid expenses for building of powerful compressor installations and difficult, the big extent, pneumonetworks, gives the big economic effect. Essentially and that metal consumption of hydraulic cars, as a rule, on 15-30 % more low, than pneumatic. So, the research and developmental works directed on creation and introduction in manufacture of hydraulic cars of shock action, have great value.

1 ACTUALITY OF THEME

In connection with shortage of the electric power and considerable difficulties which test mines, questions of creation of power saving up technologies and cars become especially actual.

The comparative analysis of power expenses at application of pneumatic and hydraulic energy shows that use of hydraulic energy is more expedient.

The basic consumers of the electric power on mines are compressor installations. They consume 50-60 % generalmine expense of the electric power. Even insignificant decrease in consumption of compressed air gives rather notable economy of the electric power. Among the main consumers of pneumoenergy it is possible to name jackhammers. Besides the pneumoenergy significant amount is lost in a network.

Thus, application of hydraulic impact devices on mines instead of the pneumatic will reduce the expense of the electric power and will provide additional economic benefit.

2 SCIENTIFIC AND PRACTICAL VALUE

Scientific value of work consists in an establishment of laws of working process of a hydrohammer, a substantiation and a choice of a range of rational parameters for maintenance of the maximum EFFICIENCY of the device.

Practical value of work consists in working out of imitating algorithm of working process of a hydrohammer and the program for the personal computer; an establishment of possibility of use of the device of giving of a hydrohammer for a combine «URAL-10А».

3 THE PURPOSE AND RESEARCH PROBLEMS

The purpose master’s works is the establishment of laws of working process of cars of hydroshock action of high capacity, optimisation of parameters and a choice on this basis of the most corresponding basic scheme for hydrohammer construction. For object in view achievement it is necessary to solve following primary goals:

1. To consider and make the comparative analysis of existing cars of shock action of high capacity;
2. To analyse various block diagrammes of hydroimpact devices and to choose the scheme which can be used for a hydrohammer;
3. To carry out the analysis of working process of a hydrohammer for what to define key parameters, to make the analysis of the basic types of the basic schemes taken as a principle of designs of hydrohammers, to choose the most corresponding for hydrohammer construction, and also to make mathematical and imitating models;
4. To optimise device parameters;
5. To analyse the hydraulic scheme helldriver for use of the device of giving of a hydrohammer.

4 THE REVIEW OF EXISTING MODELS OF THE HYDROHAMMER

4.1 The review of existing models of the hydrohammer developed in the world

The design of new generation of hydrohammers D-600, D-550 series "Delta" (in a working out stage are D-250, D-150) is based on effect use "a liquid spring" which has no wide application in world practice of manufacture of hydrohammers. The working element a hammer simultaneously serves as the piston for accumulation of energy of hydrosystem at returnable movement after blow fulfilment. Recycling of an impulse of reverse motion of the worker firing-pin in useful energy of "a liquid spring", making back and forth motion, allows to exclude pneumatic chambers from hydraulic system of a percussion instrument.

The hydrohammers of series of Delta appeared as a result of long researches during work in the most difficult terms and improvements during many years. An equipment of new generation of Delta is consonant with all types of modern power-shovels.

From recent time a company to "Tradition-K" entered in the number of producers of hydrohammers - one of the largest salespeople of a build equipment at the market of Russia which trades in these aggregates already 10 years. Now a firm produces three models of hydrohammers - Delta-5, SMG-200 and SMG-300. The model of SMG-200 is unique that among hydrohammers occupies transitional position between easy and middle categories. Sure, successful compromise: SMG-200 can be assembled on power-shovels with the range of working mass 4...14 t. The hydrohammer of SMG-300 is developed on the base of hydrohammers of SP-71, SP-71A, MG-300 taking into account their exploitation build organizations.

On the drawing 4.1.1 The basic scheme of a hydrohammer of Finnish firm Junttan

Drawing 4.1.1 – The basic scheme of a hydrohammer of Finnish firm Junttan

4.2 The review of existing models of the hydrohammer developed in Ukraine

All-union research and project-designer institute of mining by a hydraulic method. Hydropercussion hammer of double-action.

A hammer consists of corps with a string-course, step piston-firing-pin (D1>d2), slide-valve of step form (d1>d2), working instrument. In a piston-firing-pin there is opening for connection of lower cavity with the area of discharging (by an atmosphere) and with an overhead cavity at switching of slide-valve accordingly in overhead or lower position. In addition, in the wall of piston-firing-pin there is opening for hydraulic connection of cavity of slide-valve with an overhead cavity (by the area of feed) and area of rarefaction.

A hydropercussion hammer works as follows. An overhead cavity through openings is reported with a lower cavity. A liquid from a pump from a cavity through openings enters cavity. Piston-firing-pin under the action of the uncompensated loadings of pressure of liquid and begins to rise. Thus opening is recovered a string-course and the volume of liquid in a cavity appears reserved. It prevents moving of slide-valve upwards from the action of the uncompensated loadings of pressure of liquid. As soon as opening goes out from under a string-course, a cavity unites with the area of rarefaction. A slide-valve moves upwards to support, connecting here through openings cavity with the area of rarefaction. A piston-firing-pin, continuing to move upwards, is braked to the complete stopping with effort from pressure of liquid on the circular topside of ledge of piston, and then under the action of hydropercussion impulse dispersed downward and buffets on an instrument. To beginning of blow opening is included in a cavity above a piston and hydraulically connects the internal cavity of piston with the area of feed. A slide-valve under the action of difference of efforts on-the-spot greater string-course moves downward to support and connects cavities again. A piston-firing-pin begins to rise. The cycle of work of hydropercussion hammer repeats oneself further.

Hydropercussion hammer of double-action , including a corps and step piston-firing-pin with built-in in it a slide-valve, different that, with the purpose of simplification of construction and increase of reliability of work, in the wall of piston-firing-pin above the overhead butt end of slide-valve opening is executed, hydraulically alternately relating the internal cavity of piston with the areas of feed and rarefaction.

5 CHOICE OF THE BASIC SCHEME OF THE HYDROHAMMER

The hydrohammer can be developed on the basis of one of three block diagrammes: the scheme with the operated chamber of a forward stroke, the scheme with the operated chamber of reverse motion, the scheme with two operated chambers. The preliminary analysis of the above-stated block diagrammes has allowed to establish, the scheme with the operated chamber of reverse motion as dispersal piston is carried out by the liquid stream which pressure exceeds brought (рmax> р0) is perspective that provides intensive dispersal firing-pin, increase of pretonic speed and energy of individual blow. However, for realisation of the scheme the hydrodrummer should be equipped working GPA and the return valve. In view of lacks and advantages of the scheme, for the subsequent analysis we accept the device on the basis of the block diagramme with operated chambers of reverse motion. The basic scheme of a hydroimpact device is presented on dr. 5.1.

Drawing 5.1 – the Basic scheme of a hydroimpact device with the operated chamber of reverse motion

6 MATHEMATICAL MODEL OF THE HYDROHAMMER

The hydraulic shock mechanism working in system of a volume hydrodrive represents difficult hydrodynamic system which is characterised by a great number (more than 20) factors. For comprehensive investigation of its functioning, a choice of the cores of constructive and working parameters, for revealing of rational modes, great number carrying out is necessary Experiments. And carrying out of each experience will be interfaced to manufacturing of separate knots and device details. The most effective way of the decision is mathematical. In this connection The problem of the mathematical description of working process of the basic scheme of a hydrohammer, for the purpose of working out of imitating algorithm and the program is put. The given approach will allow to investigate great volume of variants and to make a choice of optimum parametres of system without Carrying out of labour-consuming experiments.

The core is the knot of the drummer which piston makes back and forth motion under the influence of pressure forces on its working surfaces. The equation of movement of the piston looks like:

where — Weight of the piston; - Coordinate of position of the piston; - Pressure of a liquid in corresponding working chambers; - The areas of working surfaces of the piston in corresponding chambers; - The force of a friction created Rubber consolidations (rings) of the piston.

Mobile element of knot of the distributor is the piston-valve which equation of movement looks like:

where — Weight of the piston-valve; - Piston coordinate; - Pressure of a liquid in corresponding working chambers; - The areas of working surfaces; - Force of a friction.

Thus, for definition of a condition of system the decision of the differential equations of movement of the piston and the valve taking into account the functional factors set by algebraic and integrated dependences is necessary. The received system of the equations cannot be solved analytically because of essential nonlinearity of boundary conditions, therefore the decision is carried out numerically by imitating modelling of working process.

7 SIMILARITY CRITERIA DEFINITION

The finding of dimensionless criteria of similarity allows to establish interrelation between the factors influencing working process of a hydrohammer, for the purpose of the subsequent optimisation of working process.

The following dependence of target parameter N on entrance parameters is established:

The quantity of fundamental physical variables which characterise process, is equal m=13. The quantity of units of dimensions which is necessary for expression of dimensions of variables, is equal k=3. Difference m - k=10. Working process of a hydrohammer can be described ten dimensionless combinations:

From last expression follows that as criteria of similarity following dimensionless complexes can be accepted:

; ; ; ;

; ; ;

; ; .

CONCLUSION

Experience of creation of hydraulic hammers confirms their clear advantages before pneumatic:

1. Maintenance of high power frequency indicators;
2. Possibility of work as the hinged equipment, for example, instead of a ladle of a dredge, a tractor, the bulldozer, etc.;
3. Possibility of maintenance of work in system of a hydrodrive of the basic car (a dredge, a tractor, the bulldozer);
4. Increase к.п.д.;
5. Decrease in operational expenses;
6. noise and dust content Reduction.

Now the hammers using as a working liquid mineral oils are widely known. There is data about possibility of work of some kinds of the similar equipment on water oil emulsion. The problem of working out of a complex destructive agency of the mineral including mechanical shock influence on a face is considered actual. In this connection the question on creation of the hydraulic hammer, capable to work on technical water sees rather important. Availability of this working liquid in the conditions of mine, an open-cast mine and mine does of this kind hydrohammers attractive to use at mineral extraction, for carrying out of preparatory and auxiliary works.

LIST OF THE USED LITERATURE

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At writing of the given abstract a master’s work has not been finished yet. Date of the work’s final end is on December, 1st, 2010. Full text of work and materials on a theme can be received from the author or her supervisor after the named date.