Bell Crank Geometry for Wheel Loader Bucket Angle Control
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Solution Overview
Problem
Wheel loaders face issues with the bucket's angle changing excessively during loading operations, leading to interference with dump trucks and unintended dumping of earth and sand, especially when the bucket is lifted to a maximum height, due to the bell crank's position relative to the fork or bucket.
Innovation Solution
The design includes a bell crank positioned halfway along the boom with specific angle constraints (θ ≤ 206.5° and α ≤ 73.2°) to maintain the bucket's lower surface horizontal at maximum height, preventing interference with dump trucks and ensuring efficient loading by controlling the downward angle (ω ≤ 10°) using a tilt cylinder and connecting link configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the bucket is lifted to maximum height position without operating the tilt cylinder, then the bucket reaches the loading height, but the lower surface of the bucket becomes greatly tilted downward toward the distal end
Solution Approach 1:
The bell crank acts as an intermediary mechanism between the boom and the bucket. By positioning it halfway along the boom and configuring the connecting links, it mediates the motion transmission to maintain the bucket's lower surface substantially horizontal at maximum height, preventing excessive tilting while allowing rapid lifting.
2Length of moving object
If the distal end of the lower surface of the bucket at maximum height is tilted downward, then the bucket can be positioned higher, but the bucket contacts with the loading space of the dump truck or the earth and sand drop onto the ground
Solution Approach 1:
The invention changes the geometric parameters of the Z-shaped link mechanism, specifically setting the angle θ formed by the bell crank links to satisfy 170° < θ ≤ 206.5° and the angle α between the tilt cylinder and bell crank to satisfy 0° < α ≤ 73.2°. These parameter changes ensure the bucket maintains proper orientation at maximum height, preventing contact with the dump truck and unintended dumping.
3Stability of the object's composition
If the bell crank is positioned lower to maintain bucket angle, then the bucket angle is controlled, but the lower end of the bell crank interferes with the load vehicle during loading operation
Solution Approach 1:
The bell crank is positioned in the longitudinal direction halfway along the boom, utilizing the longitudinal dimension of the boom structure. This spatial arrangement allows the bell crank to be positioned at a height that controls the bucket angle while its lower end does not interfere with the load vehicle during loading operations.
4Productivity
If the tilt cylinder is used to adjust the bucket angle for load leveling, then the loading efficiency is improved, but the device complexity increases
Solution Approach 1:
The Z-shaped link mechanism with the bell crank configured at specific angles provides automatic angle compensation as the boom elevates. The mechanism self-adjusts to maintain the bucket's lower surface substantially horizontal at maximum height without requiring manual operation of the tilt cylinder, thereby improving productivity while avoiding the complexity of additional control operations.
Data Source
AI summary
An angle formed on a side of a bucket by a first line segment that connects a first pivot region of a bell crank relative to a boom and a second pivot region of the bell crank relative of a connecting link and a second line segment that connects the first pivot region and third a pivot region of the bell crank relative to a tilt cylinder is no more than 206.5°. An angle formed by the second line segment and a line segment that connects the third pivot region and fourth a pivot region of the tilt cylinder relative to a structural body is, in a fork-attached state, no more than 72.3°. When a pivot region of the fork relative to the boom is substantially 1.5 m from the ground, a lower end of the bell crank is located higher than a lower end of the fork.