*3.2. Design of the Collection Devices*

Collection is one of the key processes required to finish the harvesting of dandelion seeds. The collection devices mainly include the disturbing roller, collection cover, negativepressure blowers, and the height-regulating device. The 3D structure of the collection devices is illustrated in Figure 3. Dandelion seeds with pappi detach from plants after being disturbed by the disturbing roller and then collect to the collection cover using negative-pressure blowers, thus completing their collection [17,18]. The design solves problems of difficulty collecting dandelion seeds with pappi, high labor intensity, and low harvesting efficiency.

**Figure 3.** 3D structure of the collection devices. 1. Fan fixing bracket; 2. Disturbing roller; 3. Electrical machine; 4. Collection cover; 5. Height-regulating device; 6. Fan blades.

3.2.1. Design of the Disturbing Roller

The disturbing roller is one of the core components of the collection devices. The collection quality, to a great extent, is influenced by the device [19,20]. Figure 4 illustrates the 3D structure of the disturbing roller, which mainly consists of a drive motor, a support frame, a rotation shaft, and spring-teeth; it is driven by the motor.

**Figure 4.** The 3D structure of the disturbing roller. 1. Electrical machine; 2. Spring-teeth; 3. Rotation shaft; 4. Support frame.

In this article, the diameter range of 4~6 cm was obtained by measuring the crown balls of 100 dandelion plants. The maximum diameter of 6 cm was used as the design basis; that is, the minimum horizontal length of the elastic teeth is 6 cm. At the same time, in order to better make the downed seeds move to the lower part of the fan, the head of the spring teeth is bent. The horizontal length of the bent spring teeth is 2 cm, and the horizontal length of the spring teeth is at least 6 cm. In this paper, when designing the horizontal spacing of the spring teeth, the minimum diameter of the crown ball was measured to be 4 cm, so the horizontal distance between the two spring teeth should be set to be less than 4 cm. In order to better facilitate contact between the disturbance roller and the crown ball, we designed the horizontal distance between the spring teeth to be 2 cm, ensuring that at least two spring teeth have contact with the crown ball at the same time and improving the shooting ability of the spring teeth. After analyzing the shape of the spring teeth of a wheat combine harvester and baler, it was determined that they have a cylindrical shape; therefore, the spring teeth designed in this paper are spring steel with a diameter of 6 mm. The spring teeth are evenly arranged on the disturbance roller with a horizontal spacing of 2 cm, and the horizontal length of the spring teeth is 6 cm.

As shown in Figure 5, when collecting dandelion seeds the disturbing roller first disturbs dandelion plants to loosen the connection between the plants and seeds or to cause seeds to detach from the plants. Negative-pressure blowers are then used to finish the collection. It can be seen from Figure 5b that in order to improve the collection efficiency, it is necessary to position the spring-teeth just below the blowers and rotate them by 90◦. For this to be effective, the advance time *t*<sup>1</sup> of the harvester needs to be equal to the period of rotation *t*<sup>2</sup> of the disturbing roller.

$$t\_1 = \frac{R}{V} \tag{1}$$

$$t\_2 = \frac{\frac{\pi}{2}}{2\pi N} = \frac{1}{4N} \tag{2}$$

where *<sup>V</sup>*, *<sup>R</sup>*, and *<sup>N</sup>* represent the forward speed of the harvester (m·s<sup>−</sup>1), radius of rotation of the disturbing roller (m), and rotational speed of the disturbing roller (rpm), respectively.

It is calculated that

$$N = \frac{V}{4R} \tag{3}$$

According to Equation (3), to make spring-teeth appear just below the blowers after the rotation of 90◦ intended to enhance the collection effect, the rotational speed of the disturbing roller should be related to the radius of rotation of the disturbing roller and the forward speed of the harvester.

**Figure 5.** Schematic diagram of perturbation process. (**a**) After the perturbation process. (**b**) During disturbing the process. (**c**) Before the perturbation process. Screen, V and R, represent the forward speed of the harvester (m·s<sup>−</sup>1) and radius of rotation of the disturbing roller (m).

The radius of rotation of the disturbing roller needs to be designed according to the diameter of the spherical seed heads of dandelion. It can be seen from Table 2 that the diameter of spherical seed heads is 4~6 cm; that is, the radius of rotation of the disturbing roller is

$$R = r + d\tag{4}$$

where *R* is the radius of rotation of the disturbing roller (m); *r* is the radius of the rotation shaft of the disturbing roller (m); and *d* denotes the diameter of the spherical seed heads of dandelion plants (m).

The diameter of the rotation shaft of the disturbing roller is set to be 3 cm by comprehensively considering the feasibility of the entire design and the dimension reliability of the disturbing roller. That is, *R* ≥ 4.5 cm, then *R* = 5 cm, the horizontal length of the spring-teeth is 3.5 cm, and the diameter of the rotating shaft of the disturbing roller is 3 cm. Under these conditions, the rate of rotation of the disturbing roller is only related to the forward speed; that is, the rate of rotation of the disturbing roller *N* is 5*V* (where *V* is the forward speed).

At the same time, the selection of materials for producing spring-teeth on the disturbing roller is also critical. At present, the most widely used materials for producing spring-teeth include metals, plastics, and nylons. Compared with other materials, metal spring-teeth are hard and heavy; plastic spring-teeth are light while having poor toughness, which is likely to damage dandelion plants; and nylon spring-teeth are light, which reduces the load on the motor, and they are also highly elastic, tough, and hard to break, showing good performance for their cost. Considering this, nylon was selected to produce spring-teeth on the disturbing roller.
