Design parameters of circular multidirectional spherical knife tools

. The aim of the research is to justify the design and geometric parameters of spherical blade working tools for preparing the soil for sowing gourds. The scheme of spherical knife working body is given. The basis of the working body is the thickness of the flange, the crevice of the spherical knife, the depth of treatment, the height of the knife element. Analytical dependences for determining the basic parameters of spherical knife working bodies are obtained. Theoretical researches show that for quality ripping of soil with minimal traction resistance the diameter of spherical blade working elements must be 400 mm, thickness of blade 15 mm, number of knives in blade must be 12 units. The length of the spherical blades is 110 mm.


Introduction
Asia leads the world in the production of melons.About 77% of the cultivated area of these crops is concentrated here.Europe accounts for 9.5%, America and Africa for 7% each of the world's cultivated area of melons.It should be noted that in recent years, against the background of reduction of areas under melons in Africa, they steadily increase on other continents.The most significant growth is observed in Asia.
Over the past 20 years, the world consumption of vegetables, gourds and fruits has been growing by an average of 5-7% per year.Uzbekistan not only meets the needs of its population, but also exports agricultural products and has great potential in this area.One of the conditions for effective melon cultivation is high-quality soil preparation for sowing.
For its qualitative performance it is necessary to take into account the peculiarities of applied technologies and natural-production conditions of the region.In Uzbekistan, on average, there are 320 sunny days a year, there is a consistent change of seasons, which creates optimal conditions for growing high-quality varieties of melons.Therefore, the gifts of the generous Uzbek land -melons have become a real brand and are famous all over the world.

Materials and methods
In the current stage of disc tillage machines, solid or notched discs with a constant curvature of their surface are used.Working tools with variable surface curvature are usually not used.In this connection we also use knife elements with constant curvature of the blades.The tool is mounted with a zero angle of attack.To increase the processed surface of the field, the blade elements are installed on the disc with the curvature directed in different directions from the plane of their attachment.Blades are sharpened on the outer and inner sides of the blade elements.Recommended angle of blade sharpening

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. The width of the knife element in terms of its strength is taken 40 mm.In connection with the installation of knife elements on the disk alternately, where directed curvature in different directions from the plane of their mounting on the flange, the width of the capture of such a working body will be 10 cm.On a flange of the working body, it is possible to arrange 12 knife elements, taking into account their geometric dimensions and fixing.In this case 6 of them will be directed by the curvature in different directions (figure 2).
where kn n -number of knives on the disc;  -kinematic parameter of the knife disk; A  -center corner of the point the nose of the knife touches the surface of the ground, degree; Thus, the traction resistance of the battery of knife discs will be expressed by the dependence: The maximum possible number of knives on the disk (figure 5) will be determined from the geometric parameters of the knife and the disk on which they are fixed: he length of the base (fastening part) of the knife, mm.

Fig. 5. Geometric parameters of the knife disk
Based on the geometric parameters of the knife (figure 3), the length of its base can be represented by the dependence: where ex R -outer radius of the blade disc, mm.
Then the maximum possible number of knives on the disk, taking into account will be determined by the dependence: , , The resulting fractional value of the number of knives kn n knife must be rounded down to a whole value.
The most important task in the operation of knife disk batteries is to minimize the energy consumption for chopping the surface layer of the sown soil.This is achieved by influencing the soil of the knife disc working elements while fulfilling the condition of stable cutting with sliding: ) 90 where kn  -cutting angle, degree;  -angle of external friction of the blade on the soil with stubble residues, degree.

Results and discussion
Based on preliminary one-factor experimental studies, the most significant factors determining the design parameters of disc-shaped multidirectional spherical knife working tools were identified.These include: disc diameter, number of knives, and distance between the knife discs.The limits of variation of these parameters were also determined.The quality of soil tillage, i.e. its crumbling, was used as a criterion for evaluating the functioning of the working body.
When cultivating the soil in the sowing area with disc-shaped multidirectional spherical blade tools, the following performance indicators were obtained, shown in figures 6 -7.6 and 7, that with all possible values of the diameter of the working body and the number of blade elements the optimal distance between the discs in the batteries is 11 cm.

Conclusions
Based on the data in Figure 6, we can conclude that the rational size of the working bodies are: the diameter of the disc blade 400 mm, the number of knives on a disk of 12 pieces and the distance between the discs in the battery 11 cm.In this case, the required quality of presowing tillage (K=80%) is not achieved in all cases of disk loosener use.This indicates the need to use additional working elements in the design of the combined tillage device.

Fig. 1 .
Fig. 1.Geometric dimensions in the equatorial section of the spherical knife blades The basic geometric parameters of the spherical knife working tool include its diameter, radius of curvature, half of the angle at the apex of the disc sector.As additional, the angle of the sharpening cone ω and sharpening angle i. Define them as follows.For 5  k and a working depth of 8 cm we have a blade diameter of 400 mm.From dependence 1, the radius of curvature of the knife element is 455 mm.The thickness of the blade element is 3.2 mm.Taking into account the safety margin, we accept mm 4 

Fig. 2 .
Fig. 2. Rotary tillage tool with spherical blade elements For strip tillage in the sowing area it is necessary to combine blade tools in batteries.The diagram of such a battery is shown in figure 3.

Fig. 3 .
Fig. 3. Diagram of the disk battery with multidirectional spherical knife elements

t- 2023 Fig. 4 .
Fig.4.Geometric parameters of the knife disk bladeThe component of the traction resistance of the soil on the side surface of the blade, taking into account its geometric parameters, will be determined by the dependence:

Fig. 6 .
Fig. 6.Response surface (tillage quality) as a function of diameter kd D of the disc−shaped,

Fig. 7 .
Fig. 7. Map of response level lines (tillage quality) depending on diameter kd D of the disc-shaped,