Center Overlap Sickle Guard with Adjustable Ledger
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Solution Overview
Problem
Existing crop cutting devices face challenges in achieving proper shearing action, especially in tough cutting conditions, due to issues with blade overlap and alignment at the center of the cutter bar, leading to wear and poor cutting efficiency.
Innovation Solution
A crop cutting device design featuring a center overlap arrangement where the inboard ends of the sickle bars are positioned to overlap at the center of the cutter bar, with a center knife guard having adjustable ledger surfaces to ensure proper alignment and contact between the blades and guards, allowing for efficient cutting without crop accumulation between blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional pointed guards with integral construction are used, then the guard structure is simple and easy to manufacture, but the blade alignment and shearing action are poor especially in tough cutting conditions
Solution Approach 1:
The guard is divided into separate components: a base piece attached to the cutter bar defining the ledger surface, and a separate nose piece that projects forwardly. This segmentation allows independent adjustment and positioning of each component to achieve proper blade alignment while maintaining manufacturing simplicity.
Solution Approach 2:
The nose piece is made adjustable relative to the base piece, allowing dynamic adjustment of the guard geometry to accommodate different cutting conditions and blade positions. This enables optimization of shearing action while maintaining a simple overall structure.
2Reliability
If hold-down members are used to press blades against ledger surface, then cutting contact is improved, but the device complexity and number of adjustments increase
Solution Approach 1:
The hold-down function is merged with the existing guard structure by making the nose piece adjustable and pressable against the blade. This combines the guiding function of the guard with the hold-down function, eliminating the need for separate hold-down members and reducing overall device complexity.
Solution Approach 2:
The nose piece serves multiple functions: it guides the blade, protects the front edge, and provides adjustable pressure to maintain blade contact with the ledger surface. This multi-functionality reduces the number of separate components needed.
3Strength
If stub guard with wide front edge is used for strength, then guard durability is improved, but crop engagement causes deflection and poor cutting
Solution Approach 1:
The nose piece has an asymmetric geometry with a wide base for strength and a tapered or pointed forward projection for crop guidance. This asymmetric design provides both structural strength at the base and efficient crop engagement at the forward edge, eliminating the trade-off between strength and cutting efficiency.
Solution Approach 2:
Different parts of the nose piece have different geometric properties optimized for their specific functions: the base provides strength and structural support, while the forward projection provides crop guidance and minimal interference with the cutting action.
Data Source
AI summary
The center sickle overlap arrangement of a sickle type mower for a cutter bar that include a pair of sickles for reciprocating motion where each sickle is essentially half the length of the cutter bar for reduced forces and vibrations for high speed cutting. In the center, the sickle blades overlap at only guard and the blade of one sickle is inverted and co-operates with a top ledger surface of the associated guard so that both the blades are in proper shearing arrangement with the respective guard ledgers. Further the top ledger surface is adjustable to allow clearance adjustment to ensure tight clearance between all sickle cutting surfaces and guard ledgers. Further the arrangement ensures that all crop is cut between sickle sections and guard ledgers rather than between a pair of sections on the opposing sickles.