Pre-stressed Inner Shell Boom Assembly for Excavator Frame Lift
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Solution Overview
Problem
The weight and structural limitations of steel booms in machines like hydraulic excavators restrict their optimization, especially in long booms where the frame lifts from the ground under heavy loads, and the need to accommodate varying operational loads is not adequately addressed.
Innovation Solution
A load carrying member with an outer shell and a pre-stressed inner shell, where a pin is used to increase the spring rate of the inner shell, allowing for adjustable stress distribution and improved structural stability, using materials like high-strength steel and carbon fibers, and incorporating a movable pin mechanism for dynamic stress adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a long steel boom is used to increase the working range, then the boom provides structural stability, but the weight of the boom increases excessively causing the frame to lift from the ground
Solution Approach 1:
The boom is divided into two separate shells (outer shell and inner shell) that can be manufactured independently and then assembled together. This segmentation allows each shell to be optimized for specific functions while reducing the overall weight compared to a single solid steel boom of equivalent strength.
Solution Approach 2:
The boom employs a composite structure with an outer shell and an inner shell made from different materials or material configurations. This composite approach enables the boom to achieve the required structural stability and load-bearing capacity with reduced weight compared to traditional solid steel construction.
2Strength
If the boom structure is made heavier to accommodate heavy loads, then the load-bearing capacity increases, but the frame lifts from the ground surface during operation
Solution Approach 1:
The pin mechanism enables dynamic adjustment of the inner shell's spring rate, allowing the boom to adapt its structural characteristics based on the actual load conditions. This dynamic adjustment allows the boom to provide high load-bearing capacity when needed while maintaining lower overall weight for normal operations, preventing frame lift.
Solution Approach 2:
The spring rate of the inner shell can be adjusted by changing the position or configuration of the pin, thereby altering the structural parameters of the boom to match different load requirements. This parameter adjustment allows optimization of the strength-to-weight ratio for various operating conditions.
3Ease of manufacture
If a fixed steel boom structure is used, then manufacturing is straightforward, but the ability to accommodate different operational loads is limited
Solution Approach 1:
The inclusion of a movable pin mechanism transforms the fixed boom structure into a dynamically adjustable one. The pin can be repositioned to change the spring rate of the inner shell, enabling the boom to adapt to different load conditions while maintaining a relatively simple manufacturing process for the individual components.
Solution Approach 2:
The dual-shell structure with an adjustable pin serves multiple functions: it provides structural support, enables load adaptation, and allows for spring rate adjustment. This multi-functionality is achieved within a manufacturing framework that remains relatively straightforward for each component.
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
The solution enhances the boom's ability to handle varying loads by increasing its spring rate and structural stability, reducing the risk of frame lift and optimizing boom design, enabling more efficient operation across different load conditions.
Implementation Method 1
The inner shell is disposed within the outer shell and configured according to a predetermined curvature, whereby the inner shell is pre-stressed
Implementation Method 2
A pin is disposed through the outer shell and in contact with the inner shell and configured to increase a spring rate of the inner shell
Data Source
AI summary
The present disclosure provides a load carrying member for a machine. The load carrying member includes an outer shell, an inner shell disposed within the outer shell. The inner shell is pre-stressed. The load carrying member also includes a pin disposed through the outer shell and in contact with the inner shell to add stress to the inner shell during operation of the machine.