## 3 Key Components Design
### Sorting Mechanism  
In the process of vibrating jujubes, some leaves will fall as well, which is not conducive to the collection of winter jujubes. Secondly, the size of the winter jujube has a great influence on its selling price, so fruit farmers will classify the winter jujubes by size and sell it in package. However, manual sorting is time-consuming and laborious [21]. In view of this problem, we designed an automatic sorting mechanism to realize the size classification of winter jujubes and the removal of leaves. The mechanism is shown in Figure 10. The sorting mechanism consists of two symmetrical sorting boxes, which can rotate with each other to surround the jujube tree in the middle. The side of the sorting box is equipped with a blower, which can blow the jujube leaves out of the box. Under the blower, there is a layer of soft network arranged in a strip. Due to the heavy mass of winter jujubes, they can continue to fall through the soft network, while the leaves that are not blown out of the box during the falling process are separated so that they cannot pass through the soft network for their light mass. There is a layer of screen plate under the soft network which is installed through slots for easy replacement, and the angle between it and the base plane is \(20^{\circ}\). There are square holes with a fixed size on the screen plate, and small winter jujubes will fall into the small jujube storage box through square holes. The larger winter jujubes cannot pass through the square holes and roll into the large jujube storage box along the inclined screen plate under the action of gravity. When jujube is small enough but not aligned to the hole for sorting, it also slides on the screen plate, and drops from the hole below during the slide. The screen plates with different size square holes were designed for fruit famers to choose according to the actual size of the winter jujubes.  
Figure 10: Sorting mechanism diagram: (1) Screen plate; (2) soft network; (3) jujube leaves export; (4) blower; (5) jujubes export; (6) the large jujube storage box; (7) the small jujube storage box.  
Figure 9: Umbrella skeleton design diagram: (1) Fixed block; (2) first rod; (3) sliding block; (4) rotation spindle; (5) pin; (6) limit block; (7) connecting rod; (8) second rod.  
In the process of blowing out jujube leaves, the wind speed of the blower has a great influence on the removal of leaves, and the mathematical modeling analysis is performed. The falling process of jujube leaves is affected by both gravity and blow force. The blow force can be obtained by Equation (22).  
\[F_{c}=Q\Delta v=v^{2}s \tag{22}\]  
where, \(F_{c}\) is the blow force, N; \(Q\) is flow, m\({}^{3}\)/s; \(\Delta v\) is the wind speed difference value, m/s; \(v\) is the wind speed, m/s; \(s\) is the leaf area, m\({}^{2}\).  
The jujube leaves are falling free in the vertical direction, and the drop time can be determined by the free fall formula:  
\[h=\frac{1}{2}\text{g}t^{2} \tag{23}\]  
where, \(h\) is the vertical falling distance, m; \(t\) is the falling motion time, s.  
The jujube leaves are accelerated in the horizontal direction, and the motion distance can be obtained by Equation (24).  
\[l=\frac{1}{2}a_{c}t^{2}=\frac{1}{2}\frac{F_{c}}{m_{l}}\frac{2 lt}{\text{g}}= \frac{v^{2}sh}{m_{l}\text{g}} \tag{24}\]  
where, \(m_{l}\) is the mass of jujube leaf, kg; \(a_{c}\) is the transverse acceleration, m/s\({}^{2}\).  
In order to obtain the parameters used in the formulas, we measured the mass and area of 200 jujubes and leaves, respectively. Then, we recorded the measurement data and calculated the average value. Finally, winter jujube mass \(m_{l}=0.01\) kg, is the smallest and largest projected area of jujube leaves in vertical wind direction \(S_{\text{max}}=3\times 10^{-4}\) m\({}^{2}\), \(S_{\text{min}}=0.6\times 10^{-4}\) m\({}^{2}\). According to the above equation, the wind speed for blowing out jujube leaves can be obtained at 20.41-45.64 m/s.