Closed Center Hoist Valve Snubbing Position
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Solution Overview
Problem
Existing truck hoist valve systems, particularly those with variable displacement pumps, lack control over engagement between the truck bed and frame during lowering, and incorporating features like restricted flow positions is complex, often leading to elaborate valve designs and implementation challenges.
Innovation Solution
A closed-center truck hoist valve with a snubbing position is introduced, which places the cap end and rod end of the hydraulic cylinder in restricted flow communication with the tank, allowing for controlled lowering and cushioning of the truck bed as it approaches the frame, while maintaining a four-position valve configuration without adding extra positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a variable displacement pump system with float position is used, then the truck bed can move freely relative to the frame during travel, but control over engagement between the truck bed and frame during lowering is reduced
Solution Approach 1:
The valve system dynamically transitions between different flow restriction states. The float position allows free movement during travel, while the lowering position provides controlled engagement during bed lowering. This dynamic adaptability resolves the contradiction by providing different control characteristics for different operational phases.
Solution Approach 2:
The system changes the flow restriction parameter based on operational needs. During travel, the float position minimizes restriction for free movement. During lowering, the system transitions to a restricted flow state to control engagement. This parameter change allows the system to optimize performance for each operational mode.
2Reliability
If a fixed displacement pump system with five-position valve is used, then control over engagement between truck bed and frame is improved, but the valve becomes more elaborate with more positions
Solution Approach 1:
The four-position valve performs multiple functions that would traditionally require more positions. The center position provides both holding and float capabilities, while the lowering position incorporates snubbing function. This multi-functionality reduces the number of positions needed while maintaining comprehensive control.
Solution Approach 2:
The patent merges the holding and float functions into the center position, and combines lowering with snubbing control in the lowering position. This consolidation of functions reduces the total number of valve positions from five to four while preserving all necessary control capabilities.
3Object-affected harmful factors
If snubbing position is added to control engagement, then impact force during lowering is reduced, but the valve design becomes more complex
Solution Approach 1:
The snubbing function provides beforehand cushioning by restricting flow during the lowering process. This gradual flow restriction cushions the impact before the truck bed contacts the frame, preventing sudden shock loads. The cushioning effect is built into the lowering position itself, eliminating the need for separate cushioning mechanisms.
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 provides enhanced control over the truck bed's engagement with the frame during lowering, preventing damage by reducing impact force and allowing for flexible operation, while maintaining system pressure and avoiding pressure buildup, thus addressing the limitations of variable displacement pump systems.
Implementation Method 1
a cap end line configured for placing the cap end in restricted flow communication with the tank
Data Source
AI summary
A valve for controlling a hydraulic cylinder on a work machine may include a raising position configured for placing a pump in fluid communication with a cap end of the hydraulic cylinder. The valve may also include closed center position configured for closing off fluid communication to the cap end line and the rod end line. The valve may also include a lowering position configured for placing the pump in fluid communication with the rod end of the hydraulic cylinder. The valve may also include a snubbing position configured for placing the cap end in restricted flow fluid communication with the tank and for placing the rod end in restricted flow fluid communication with the tank.