Bell Crank Mechanism for Work Machine Bucket Stability
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Solution Overview
Problem
In wheel loaders with a Z-bar link system, the bucket's lower surface tilts excessively when lifted to the top position, causing accidental dumping during earth and sand loading operations, which prevents planned height dump loading.
Innovation Solution
The work machine design includes a bell crank mechanism with specific angle constraints (θ ≤ 176° and α ≤ 72.3°) to maintain the bucket's lower surface at a minimal lowering angle (ω ≤ 4.5°) when lifted, ensuring the bucket remains horizontal and preventing earth and sand from spilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bucket is mounted to the boom end and lifted to the top position in a conventional Z-bar link system, then the bucket can be positioned at the top for dumping, but the lowering angle of the bucket front end increases excessively causing accidental dumping
Solution Approach 1:
The invention changes the geometric parameters of the bell crank mechanism by constraining the angle θ between the first line segment (connecting boom pivot and connecting link pivot) and the second line segment (connecting tilt cylinder pivot and bell crank pivot) to be 176° or less. This parameter change ensures that the lowering angle of the bucket front end is maintained at 4.5° or less when the bucket is at the top position, preventing accidental dumping while maintaining operational capability
2Adaptability or versatility
If the fork is combined with the Z-bar link to enable fork attachment, then the attachment angle can be kept substantially constant, but the bucket lowering angle at top position increases causing dumping issues
Solution Approach 1:
The invention optimizes the bell crank angle parameter θ to 176° or less, which simultaneously achieves two objectives: maintaining substantially constant attachment angle for both bucket and fork attachments (improving adaptability) and limiting the bucket lowering angle at top position to 4.5° or less (improving reliability). This parameter optimization resolves the contradiction between attachment versatility and bucket stability
Data Source
AI summary
In a work machine 1, an angle θ formed by a first line segment L1 connecting a pivot position Y of a bell crank 11 on a boom 10 and a pivot position X of the bell crank 11 on a connecting link 13, and a second line segment L2 connecting the pivot position Y of the bell crank 11 on the boom 10 and a pivot position W of the bell crank 11 on the tilt cylinder 12 on a bucket 20 side is 176 (deg) or less, an angle α formed by the second line segment L2 and a line segment L3 connecting the pivot position W of the bell crank 11 on the tilt cylinder 12 and a pivot position Z of the tilt cylinder 12 on a working structure is 72.3 (deg) or less, and, in a case where the bucket 20 is set at a top position, a lowering angle ω of a front end of a lower surface of the bucket 20 is 4.5 (deg) or less.