## 3 Design of Main Working Parts
### The Transmission System  
The transmission system of the combined machine for transplanting outcrop of Codonopsis with a micro ridge covered with film is shown in Figure 16.  
Figure 16: Schematic diagram of transmission system of combined machine. 1. Coupling. 2. Trenching shovel. 3. Seedbed preparation device. 4. Driving shaft of seedling-casting device. 5. Driven shaft I. 6. Ground wheel. 7. Seedling-casting device. 8. Driven shaft II. 9. Chain drive. 10. Gearbox. 11. Cutter shaft. 12. Rotary tillage soil-cutting set. 13. Hanging frame. 14. Film-spreading roller. 15. Soil-covering disk.  
Figure 15: Structural diagram of film-covering device. 1. Adjusting rod of film-spreading roll. 2. Film-hanging rod. 3. Plastic film. 4. Mulching area on furrow. 5. Rain-collecting surface. 6. Seedlings. 7. Film side outcrop. 8. Film-spreading roll. 9. Connecting rod of film-spreading roll. 10. Connecting frame of film-hanging rod. 11. Frame.  
In the field operation, the machine adopts the three-point suspension mode at the rear of the four-wheel tractor and drives the trenching shovel to complete the trenching and ridgesing of the seedbed. At the same time, as the machine progresses, the seedbed preparation device collects soil from the ridge and furrow and forms two V-shaped seedbeds. While the machine moves forward, the ground wheel is driven to rotate to input the power to the drive shaft of the seedling-casting device through the chain drive. When the driving shaft of the seedling-casting device rotates, it drives the seedling-casting device to move. The seedling-casting device is linked with the driving shaft of seedling-casting device, driven shaft I, and driven shaft II to complete the manual placement of seedlings. The power output shaft of the tractor inputs the power to the rotary tillage knife from the gearbox through the coupling, then the rotary tillage knife cuts the soil on the seedlings' soil-covering belt and throws the soil onto two V-shaped seedbeds. Meanwhile, the mulching film rotates synchronously with the hanging frame, and the spreading film roller mulches the film evenly and makes sure the seedlings outcrop on the edge of the film. Then, 4 soil-covering disks work together to cover the seedlings and press the film.  
In order to meet the agronomic requirements of seedling plant spacing, when the ground wheel rotates for one round, the driving shaft of the seedling-casting device rotates \(n\) times, then  
\[\frac{z_{1}z_{3}}{z_{2}z_{4}}=n \tag{30}\]  
where \(z_{1}\) is the number of sprocket teeth of the ground wheel shaft, which is set to be 27; \(z_{2}\) is the number of input sprocket teeth of the intermediate shaft, which is set to be 13; \(z_{3}\) is the number of output sprocket teeth of the intermediate shaft, which is set to be 26; \(z_{4}\) is the input sprocket teeth of driving shaft of the seedling-casting device, which is set to be 12.  
When the ground wheel rotates for 1 round, the number of seedlings (\(n_{1}\)) delivered by each seedling-casting device is  
\[n_{1}=n\pi d(1+\varepsilon)/D \tag{31}\]  
where \(d\) is the diameter of the driving shaft of the seedling-casting device, which is 100 mm; \(D\) is the spacing between the seedling plates of the seedling-casting device, which is taken to be 40 mm; \(\varepsilon\) is the slip rate of the seedling-casting device, which is 3%.  
From Equation (31), it can be calculated that the seedling spacing \(X\) is  
\[X= \pi d_{1}/n_{1} \tag{32}\]  
\(d_{1}\) is the diameter of the ground wheel (510 mm).  
By calculating Formulas (31) and (32), it can be obtained that when the ground wheel rotates for 1 round, the number of seedlings delivered by each seedling-casting device \(n_{1}=36\), seedling spacing \(X=44\) mm.