How does a rice and wheat thresher improve threshing efficiency and reduce grain breakage through optimized drum structure?
Publish Time: 2025-11-19
In combined rice and wheat harvesting or segmented operations, the threshing process is crucial in determining the quality and loss rate of the harvested grain. Traditional threshers often face a dilemma: increasing drum speed or impact force to improve threshing efficiency often leads to increased grain breakage; conversely, reducing impact force results in incomplete threshing and increased entrainment losses. The rice and wheat thresher, through systematic optimization of its drum structure—including spike/rough bar layout, zoned drum speed control, dynamic adjustment of concave plate gap, and coordinated airflow design—successfully achieves a delicate balance between "highly efficient threshing" and "low-loss grain protection," significantly improving operational quality and economic benefits.
The drum is the core working component of the thresher, and the threshing elements mounted on its surface directly act on the ear of grain. Addressing the fragile nature of rice and the toughness of wheat, modern threshers employ a zoned, composite drum design: the front section features sparsely spaced, obtuse-angled spikes or short-grooved bars for gentle combing and initial grain separation, avoiding high-speed impact; the rear section uses densely packed, high-strength grooved bars or spirally arranged spikes to forcefully thresh any remaining grains. This progressive threshing path, characterized by "loose at the front, tight at the back, combing before beating," ensures a threshing rate of over 98% while keeping grain breakage below 1.5%, far superior to traditional uniform drum structures.
2. Variable Speed and Flexible Transmission: Dynamically Adapting to Operating Conditions
Drum speed directly affects the impact force. While a fixed high speed improves efficiency, it can easily cause over-crushing when processing crops with high moisture content or uneven maturity. Advanced threshers incorporate continuously variable or intelligent speed control systems that automatically adjust the drum speed based on feed rate and crop moisture sensor feedback. For example, the speed automatically decreases to 600–800 rpm in the early morning when dew is heavy, focusing on gentle threshing; during the dry afternoon hours, it increases to over 1000 rpm for enhanced threshing. Some models also employ flexible couplings or buffer belt drives to absorb impact energy during momentary overload, preventing the grains from being crushed by "hard impact."
3. Concave Plate Gap and Eccentric Drum Design: Optimizing Threshing Space and Action Time
The gap between the drum and the concave plate determines the residence time and force intensity of the crop in the threshing zone. Traditional fixed gaps are difficult to adapt to the differences in ear shape among different varieties. Optimization solutions include:
Adjustable Concave Plate Mechanism: The inlet and outlet gaps are adjusted in real time via a handle or hydraulic device to achieve a wedge-shaped channel with a "wide inlet and narrow outlet," allowing the crop to be threshed gradually under pressure;
Eccentric Drum Arrangement: The drum shaft is slightly offset from the center of the concave plate, forming a dynamic gap that decreases from large to small, extending the effective threshing stroke and reducing the impact of a single, severe blow.
This design allows the grains to be separated at a lower impact frequency, significantly reducing mechanical damage.
4. Airflow Assistance and Negative Pressure Suction: Timely Removal of Threshing Material to Avoid Repeated Impact
If threshed kernels remain in the drum area, they will be repeatedly impacted by incompletely threshed ears, causing secondary breakage. Modern threshers integrate directional airflow ducts and negative pressure suction ports below the drum. Utilizing lateral airflow generated by a fan or localized negative pressure, threshed kernels and light impurities are quickly blown/sucked away and sent to the cleaning system. This not only reduces the residence time of kernels in the high-energy zone but also lowers the drum load, indirectly allowing for gentler threshing parameters.
5. Upgraded Materials and Surface Treatment: Wear-Resistant and Friction-Reducing for Long-Term Stability
Drum components, due to long-term friction with straw and chaff, are prone to wear and deformation, leading to a decline in threshing performance. High-performance threshers use high-manganese steel spikes and surface-welded tungsten carbide or ceramic-coated textured bars, achieving a hardness of HRC55 or higher, extending service life by 2-3 times. Simultaneously, key contact surfaces are polished or micro-textured to reduce the coefficient of friction, minimizing kernel scratches and adhesion.
The optimization of the rice and wheat thresher drum structure is a sophisticated engineering practice that integrates agronomic characteristics, mechanical dynamics, and intelligent control. It no longer relies on brute force for threshing, but instead achieves an intelligent operational logic of "threshing everything that needs threshing and protecting everything that needs protecting" through structural zoning, dynamic control, spatial optimization, and airflow coordination. Against the backdrop of increasing national emphasis on reducing grain loss, this type of drum technology innovation, centered on low breakage and high purity, is providing solid support for ensuring national food security and improving the modernization level of agricultural machinery.
