Seedless watermelon is a wonderful flower in modern plant breeding. The number of triploid seedless watermelons grown in China is high and the quality is excellent. It is a world leader and its cultivated area and total output are also among the highest in the world. However, in the production process, seedless watermelons have the problem of low seed collection, low germination rate and low seedling rate. One of the main reasons is that the seed coat of seedless watermelon seeds is thick, and there are mechanical obstacles to seed coat, resulting in difficulty in germination and poor consistency of germination. The production often uses “broken shell†germination. Unbroken seed germination rate is only 20% to 30%, after shelling can be increased to more than 90%. At present, the method of artificial shelling is generally used: The teeth are lightly twisted, the wire clamp is lightly clamped, or the small knife is slanted to cut the umbilicus on both sides. This mode of operation is relatively primitive, with low production efficiency, high labor intensity, and high production costs, hindering the further industrialization of the seedless watermelon industry. Especially in recent years, the domestic labor price has been rising, increasing the cost of seedless watermelon seeding. Therefore, the development of seedless watermelon automatic sheller instead of the original artificial shell has important practical value, and at the same time to further develop the seedless watermelon industry Conditions. This paper mainly uses the seed table to analyze the watermelon seed, the design of seedless watermelon seed crusher seeding device and the main physical characteristics of the seedless watermelon seed are measured, and it is designed for seedless watermelon seed crusher seed metering device. Provides a theoretical basis for design. Related Instruments: Semi-automatic Nitrogen Determinator Distiller Graphite Box,Graphite Gear Box,Molded Graphite Box,Parts For Graphite Gearbox CARBONS TECH&CREATION(HENAN) INDUSTRY CO.,LTD , https://www.kymoldedgraphite.com
Many countries in the world have studied the physical characteristics of seeds of different varieties. There are many researches on the physical characteristics of rice and rape seeds in China. Yang Ling et al. and Zhang Guihua et al. respectively studied rice coated seeds, and mainly used the research results to conduct research on seeders. Zhao Jinhui et al. performed research on the physical characteristics of rapeseed and rapeseed seeding devices. Xie Lijuan conducted some research on the mechanical properties of lotus seeds. Extensive research has been conducted on edible watermelon seeds in foreign countries; however, there are few domestic research literatures. Dong Youli and Zhou Hongjie conducted experimental analysis and analysis on the compressed shell breaking of edible watermelon seeds. At present, there are no relevant reports on the relevant physical properties of seedless watermelon seeds at home and abroad.
1 Materials and Methods
1.1 Materials There are three common seedless watermelon seeds: black cattle, honey red and flower skin. The moisture content was 7.11%, 6.98%, and 6.69%, respectively. Before the experiment, the watermelon seeds were manually selected, and the seeds with the diseases, damages, and shapes and sizes were excluded.
1.2 Methods The experiment was completed at the Agricultural Materials Laboratory of Hunan Agricultural University from July 1st to August 1st, 2010. The basic physical parameters (thousands of grain quality, triaxial size) and mechanical properties (angle of repose and sliding friction coefficient) of different varieties of seedless watermelon seeds were determined.
1.2.1 Measurement of 1000-mass The measurement was performed using an electronic scale (accuracy: 0.01 g), and each sample was repeated 5 times.
1.2.2 Measurement of triaxial dimensions Three-axis length (L), width (W), and thickness (T) measurements were performed on seeds using a micrometer (accuracy: 0.01 mm). During the measurement, 100 seeds of different varieties were randomly selected; the same category was measured at different positions 5 times, and the maximum value was taken as the measurement value, and the measurement result was taken as the average value.
1.2.3 True Density Measurement The true seed density is measured using the immersion method. The pycnometer method in the immersion method has the advantages of simple instrument, convenient operation and reliable results. Using the pycnometer method, the immersion solution was a toluene solution; each species was performed 10 times and the average value was taken. Volume (V) is calculated as V = [( Mt- Mp )- (Mts-Mps) ]/Ït (1) where Mt-Pycnometer + Toluene mass (g); Mp-Pyramid mass (g ); Mts - pycnometer + seed + toluene mass (g); Mps - pycnometer + seed mass (g); Ït - toluene density. The true density is calculated as Ïts= (Mps-Mp) /V (2) The angle of repose is measured using a ruler. The instrument used is shown in Figure 1. The measuring instrument is mainly composed of a base, a seed height bar, a vernier scale, a chassis, a circular diameter ruler, and a funnel. Among them, the bracket is marked with a scale and can be moved up and down to control the drop height of the grain. During the test, the brackets on the left and right sides of the funnel shall be kept at the same level so as to adjust the height of the bottom of the funnel to the chassis. The straight line between the center of the funnel and the center of the chassis is perpendicular to the chassis, ensuring that the sample falls in the center of the chassis. The chassis and funnel can be freely changed so that the angle of repose of different samples can be measured. Given diameter D, measured separately for H, the angle of repose α = arctan( 2H/D), where H is the stack height and D is the bottom diameter of the stack. Repeat 5 times and average it. 
The method of measuring the static sliding friction factor slope meter is shown in Fig. 2. The bottom plate of the angle of repose measuring instrument (as shown in Fig. 1) is adjusted by a gear and a rack to a certain height, which is an inclined surface. The seed to be measured is placed on the inclined surface, and the height of the inclined surface is gradually adjusted through the gear adjusting mechanism to gradually increase the inclination of the inclined surface. β, when the seed is slid along the slant, the slant angle is recorded by the protractor. The slant angle β is the slant angle β; repeat 5 times and take the average value. Static sliding friction factor (μ) is calculated as μ = tanβ ( 3) 
2 Results and Discussion
2.1 Geometric physical properties The experimental results of geometric and physical properties are shown in Table 1, including the results of experimental measurements and standard deviations. The measurement results ranged from 9.13 to 10.06 mm in length; 6.41 to 6.77 mm in width; and 2.18 to 2.22 mm in thickness. Among them, the three-axis size of honey-red was the largest, which was 10.06,6.77,2.22mm respectively; the average values ​​of three-axes three-axes were 9. 50,6. 58,2. 20mm. From the experimental results in Table 1, it can be seen that the geometrical dimensions of the three varieties are not much different; 3 The triaxial dimensions of the varieties are smaller than the geometric parameters of the edible watermelon seeds. The triaxial dimensions of the seedless watermelon seeds directly affect the flowability and filling properties of the watermelon seeds in the seeding device, and are the primary parameters to be considered when determining the structure shape of the seed metering device and the structure of the seeding device. Basically the same three The shaft size facilitates the design of the metering device. 
2.2 Thousands of mass and true density parameters The experimental results are shown in Table 2, the measured values ​​and standard deviations. The red honey has a mass of 67. 33g, the heaviest; black cattle's true density is 902.45kg / m3, the largest. The specific gravity characteristics of the three cultivars did not differ greatly. The average grain weight and true density were 61. 52g, 900. 20kg / m3; The average true density is slightly greater than the consumption of watermelon. 
2.3 Mechanics physical characteristics The static sliding friction factor represents the sliding performance between the material and the contact surface. Different materials have different sliding surfaces at different contact surfaces. The results of mechanical and physical properties are shown in Table 3. 
From the results in Table 3, it can be seen that the static sliding friction factor of the seedless watermelon seeds and the wood board is the largest, and the static sliding friction factor of the glass is the smallest, and the static sliding friction factor of the painted iron plate is slightly larger than the static sliding of the plastic board. Friction factor. Among them, the sliding friction coefficient (3.96) of honey red and wood is the largest, and the sliding friction factor (0.41) of black cattle and glass is the smallest. According to Razavi's results, the sliding friction factor of edible watermelon seeds is slightly smaller than that of seedless watermelon seeds; but the sliding friction factor of seedless watermelon seeds is much larger than that of coated seeds and rapeseed seeds. The greater the friction factor of the seed, the greater the inclination of the seed guide of the seedless watermelon seed box, and the requirement that the position of the seed hole be increased when the seed meter discharges the seed. When the static sliding friction factor is too large, the fluidity of the seeding is not good, affecting seeding. Therefore, in the design, guide plates with lower static sliding friction factors should be selected. From Table 2, it can be seen that the static sliding friction coefficient of the seedless watermelon seed and the wood board is the largest and the design is not suitable for the selection; the static sliding friction factor with the glass is the smallest, theoretically the best choice, but the general glass is easy Broken, processing connection is difficult. Therefore, painted iron plates and plastic plates are more suitable for parts such as seed boxes and seed feeders that come into contact with the seeds.
The angle of repose reflects the internal friction and scattering properties of the bulk material. The larger the angle of repose, the greater the internal friction force and the less scattered, the harder the seeds flow in the box, the difficulty in taking the seed from the box when the seeds are arranged, and the increase in the friction between the watermelon seeds during the scattering. The greater the damage rate. As shown in Table 3, black cattle had the largest angle of repose (27.91°), followed by honey red (25.73°) and flower bud (22.15°). The average of 3 varieties was 25. 26°, less than rape seeds and coated seeds.
3 Conclusions The main physical characteristics of seedless watermelon seeds were obtained by experimental measurement method. The results of the study have made up for the blank of physical parameters of seedless watermelon seeds.
The determination of the triaxial size of the triploid watermelon seed can provide basis for designing the hole shape and hole size of the seed metering device; and the determination of the frictional characteristics provides a theoretical calculation for the setting of the seed metering speed and the selection of the movement form. in accordance with.
The static sliding friction angle between the triploid watermelon seed and the wooden board, the paint iron plate, the plastic plate and the glass is different. The different static sliding friction angles are the dip angle of the seeding plate of the seed metering device, the hole or the groove of the seed metering device The location requires different angles. Therefore, while considering the seeding agencies to meet the work requirements, we must also make seedlings meet agronomic requirements. The experiment found that the water content had a significant influence on the physical characteristics of seedless watermelon seeds. In the next work, the research will focus on the effect of water content on the physical characteristics of seedless watermelon seeds and the study of mechanical properties of broken shells.