Pneumatic Sowing Machine Hollow Drum Compensation
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Solution Overview
Problem
The existing pneumatic precision seed drill's housing expansion under pressure leads to displacement of its components, causing inconsistent seed delivery due to changing distances between the separating device and its drive, resulting in missing or double seed spots, and requiring tight manufacturing tolerances to mitigate these issues.
Innovation Solution
A design where the drive shaft is sealed within the hollow drum, allowing the drum to be separated by a parting plane with a seal, maintaining constant distance between the perforated disk and the discharge line, and enabling adjustable alignment to compensate for housing expansion, with a removable cover for easy maintenance and adjustable seed delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the housing is permanently connected in two parts, then the structural integrity is improved, but the housing expansion under pressure causes component displacement and changes distances between the separating device and discharge line, worsening seed delivery precision
Solution Approach 1:
The housing is divided into two separable parts: a stationary housing part and a removable cover. The hollow drum is also separable by a parting plane between the rotary plate and perforated disc. This segmentation allows the housing to be assembled and disassembled, enabling adjustment and maintenance while maintaining structural integrity during operation.
Solution Approach 2:
The drive shaft is designed to be guided through the perforated disc with a sealing element, allowing the hollow drum to expand slightly under pressure without causing rigid constraint displacement. The sealing element accommodates the expansion dynamically while maintaining the seal, preventing the component displacement that would occur with permanently connected parts.
2Manufacturing precision
If tight manufacturing tolerances are used for the separating device, then the effect of housing expansion is reduced, but the manufacturing complexity and cost increase
Solution Approach 1:
By segmenting the hollow drum into separable components (rotary plate and perforated disc) with a parting plane, the design allows for easier manufacturing and assembly. The sealing element at the parting plane accommodates tolerances and expansion, reducing the need for extremely tight tolerances across all components.
Solution Approach 2:
The drive shaft guidance through the perforated disc with a sealing element changes the system from a rigid fixed-distance configuration to a flexible sealed configuration. This allows the distance to remain effectively constant while accommodating housing expansion, reducing manufacturing tolerance requirements.
3Reliability
If the hollow drum is designed as a closed structure, then the pneumatic sealing is improved, but the maintenance accessibility and seed hopper emptying become difficult
Solution Approach 1:
The hollow drum is segmented with a parting plane that allows separation between the rotary plate and perforated disc. The removable cover provides additional access points. This segmentation maintains pneumatic sealing during operation (when assembled) but allows easy disassembly for maintenance and seed hopper emptying.
Solution Approach 2:
The sealing element is pre-installed at the parting plane to ensure pneumatic sealing is established before operation begins. This preliminary sealing action maintains the closed structure's integrity during pressurized operation while allowing easy removal for maintenance.
4Device complexity
If a gear ring is used to drive the separating device, then the drive mechanism is simplified, but the housing design becomes less compact and the drive shaft alignment becomes more sensitive to expansion
Solution Approach 1:
The gear ring is removed from the design. Instead, the drive shaft is guided directly through the perforated disc with a sealing element, eliminating the intermediate gear ring component and simplifying the drive mechanism while improving housing compactness.
Solution Approach 2:
The sealing element acts as an intermediary between the drive shaft and the hollow drum interior. It allows the drive shaft to pass through the perforated disc while maintaining pneumatic sealing, enabling direct drive without a gear ring and reducing the housing's length requirement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design ensures consistent seed delivery by maintaining a constant distance between the perforated disk and the dispensing line, improves the pneumatic precision seed drill's operation, and simplifies maintenance by allowing adjustments to compensate for manufacturing tolerances and housing expansion, reducing the risk of seed delivery errors.
Implementation Method 1
The otherwise closed housing is connected to the blower and thus subjected to excess pressure, so that a pressure difference develops between the housing and the interior of the singling device. The pressure difference ideally ensures that one seed adheres to the side wall of the singulating device per perforation.
Implementation Method 2
a drive shaft is guided through at least one of these side walls and the hollow drum is sealed against the drive shaft by means of a sealing element
Implementation Method 3
the separation plane lies between the rotary plate and the perforated disc and is sealed by a seal in the unseparated state
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a pneumatic single-grain sowing machine, comprising: a closed housing (1); a rotatably driven separating device (3), which has circularly arranged perforations (7A); a fan, by means of which a pressure difference can be produced between the housing (1) and the interior of the separating device (3), the separating device (3) thus being designed to separate seed by means of the perforations (7A) with the aid of the pressure difference, the separating device (3) being designed as a closed hollow drum having two side walls arranged at a distance from each other. The aim of the invention is to create a separating device (3) that is designed to compensate slight housing expansions. This aim is achieved, according to the invention, in that a drive shaft (9, 9') is fed through at least one of said side walls, in that the hollow drum is sealed against the drive shaft (9, 9') by means of a sealing element, in that the hollow drum can be divided by a dividing plane, in that the hollow drum is formed by a rotary plate (6) and by a perforated disk (7) having the perforations (7A), that the dividing plane lies between the rotary plate (6) and the perforated disk (7) and is sealed by a seal (10) in the undivided state, and in that, after the interruption of the pressure difference, the separated seed is accelerated by the pressure difference in the dispensing line (8).