CONTENT

Introduction

1. Prior art

2. Object of the invention

3. Summary

Literature

Introduction

For agricultural land’s processing the disk harrows of different types and embodiments are being applied in which bearing assemblies with frictionless bearings are being used. The important issue for agricultural production is land’s processing and preparation for its future use. The better land will be prepared the more favorable terms will succeed for growing and getting the future harvest. The bearing assemblies are the main elements of machines and mechanisms. Bearing assemblies account nearly 30% of machine’s cost in general [1].

One should mention that all the assemblies of agricultural machine, including bearing assemblies, are exploited in very difficult conditions when machine performs its function. These conditions are characterized by significant dust level, high temperature of environment in summer time, high dynamic burdens. The dust, penetrating in the bearing assembly through the compaction, mixes with the lubricant, thickens it and turns into hard conglomeration which cottars rolling body of bearing. All these factors negatively affect the durability of bearing assemblies, which don’t elaborate its standard operation time and before the appointed time substitute with new under emergency. So the operating life of disk harrow to scheduled repair reduces from 500-700 to 150-200 work hours because of loss of bearing’s durability.

Similar conditions were observed by researchers on the coal pits. It is fixed that the frictionless bearing of band conveyor’s rolls get gumming in dusty environment since after 30 hours of work. Moreover the resistance coefficient to roll’s rotation rises from 0, 07 to 0, 41. According to this reason the operating time of conveyor rolls falls down from 12…18 months to 5…7 [6].

1. Prior art

The issue of reliability enhancement (safety margin, durability, maintainability) of bearing assembly was taken up by some research and educational institutes. For instance, Bauman Moscow state technical university: at the lifting-transport machines department scientists showed that the most rational and possible way of enhancing the durability of bearings is the substitution of single-strand radial ball bearings into identically-sized double-strand globular ball bearings. The effectiveness of such substitution predefined by enhancing in 3...8 times as much of bearings resort, which are used in conditions of rings misalignment by practically the same cost that the single-strand bearings. Besides, such bearings have the resistance coefficient to rotation in 1,5…3,0 as lower than single-strand have.

The issue of construction and reliability improvement of bearing assemblies is taken up by such research institutes as Skochinsky mining institute; educational institutes as Donetsk national technical, Dnepropetrovsk mining academy and others. The illustration of it is the article of O.V. Budishevsky, N.A. Sklyarov. About the improvement of bearing functionality [3], the textbook “Technical diagnosis of mechanical equipment” (authors V.M. Kravchenko, V.A. Sidorov, V.Y. Sedush), where types and reasons of bearing damage are widely represented. The same theme is covered in the journal “Lifting-transport technics” (V.A. Sidorov) [5].

So “Donetskugleremont”Ltd. (I.M. Mytko, N.A, Sklyarov) and Donetsk national technical university (K.I. Chebanenko, V.V. Adadurov) offered to use the metal-fluoroplastic slider bearings instead of ball bearings in rolls of shaft belt conveyers.

On the picture 1 one can see the scheme of metal-fluoroplastic.

Picture 1 – Metal-fluoroplastic

Fluoroplastic covering advantageously differs from other polymeric coverings for the meanings of friction coefficients represented in the table 1.

Table 1 – Friction coefficients of polymeric materials with steel

MATERIAL	Size of friction coefficients
	Dry friction	Water lubrication	Oiling
Organic   glass	0,57	-	-
Textolite	0,51	0,31	0,21-0,18
Caprone	0,46	0,30	0,22-0,08
Nylon	0,43	0,21	0,18
Polyethylene of low pressure	0,197	0,197	0,115
Fluoroplastic	0,049	-	0,027

Metal-fluoroplastic slider bearings are the bearings of boundary (dry) friction, working without lubrication. They are widely used in the helicopter screws, automobiles like KAMAZ, loons etc.

Metal-fluoroplastic has all the operating capabilities near the best that makes it the most versatile in its qualities. The most valuable qualities are: these bearings can work in air, water, acid and other environments. In work time, without lubrication, metal-fluoroplastic assumes very big unit loadings (near to 350 MPa), keeps working capacity in the wide range of temperatures (from -250°С till +300°С), it has the same heat conductance and coefficient of thermal expansion as steel has. On the working face of metal-fluoroplastic there appeared no static electricity and fretting corrosion that makes possible to use it in highly explosive environments.

2. Object of the invention

The aim of our work is the development of construction of disk harrow bearing assembly of enhanced durability.

On the base of foregoing it is obvious that for our aim’s realization it is reasonably to use metal-fluoroplastic slider bearings by means of frictionless bearings substitution and by estimation of possibility of its use in disk harrow.

As a basis for our aim’s realization was taken and examined the disk harrow Discover XL 60 (pic. 2) of well-known world firm in making the agricultural and land processing technics KUHN.

Picture 2 – Disk harrow Discover XL 60 (frames: 22, cycles: infinite, delay: 25 ms, file size: 559 kB)

The technical characteristics of the disk harrow Discover XL 60 are given in the table 2.

Table 2 – The technical characteristics of the disk harrow Discover XL 60

Grasp width, m	7,00
Disk number, piece	60
Disk diameter, mm	660
Disk thickness, mm	8
Assemblage	Hydraulic
Transport width, m	<3
Bearing assembly number	16
Strips	560/60-2,5
Mass without rolls, kg Mass with rolls, kg	7090 8540
Maximal capacity of machine (kVT/hp)	210/285

One of the most important elements for disk harrow work is mounting bearing assembly (pic. 3), which must take the huge loadings in time of dry unprepared land processing. It must be securely enclosed from dust and abrasive particles ingression into bearings, have a possibility to take big dynamic overloads when the disk get on the stony ground or ground with roots and stubble.

The construction and geometrical sizes of the bearing assembly of the disk harrow Discover XL 60 are given on the picture 4.

Picture 3 – Bearing assembly draft

Picture 4 – Bearing assembly with metal-fluoroplastic bearing draft

3. Summary

The offered bearing assembly of the disk harrow is given on the picture 5. In the carcass of the bearing assembly 1 on the through axis 2 fabricated the metal-fluoroplastic bearing 3. From both sides the bearing is protected with labyrinth compaction 4 from dust ingression, which are from one side in the carcass of the bearing assembly 1 and, from other side, in the cover 5, which is fixed to the carcass with six bolts 6. Metal-fluoroplastic bearing in its turn consists of metal carcass and pressed in it metal-fluoroplastic barrel (look pic. 1). The carcass of the bearing is of barrel-like shape for the possibility of self-installing in cases of crabbing.

The checking of the metal-fluoroplastic bearings workability was in time of bench and commissioning (shaft) tests of the trial batch of rolls (30 pieces) of the belt conveyors, which are equipped with the bearings of the same type and number of the serial made rolls of the Krasnoluchensk machine-building plant with the frictionless bearings. The results of the commissioning tests are given in the table 3.

Table 3 – The results of the commissioning tests of the trial batch of rolls