Forklift Hydraulic Pressure Relief with Height-Based Threshold Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current single-stage hydraulic pressure relief systems on material handling vehicles are set to relieve pressure at a constant threshold, leading to oversized hydraulic components and increased costs, as they are sized for worst-case scenarios rather than intended uses, which can result in higher costs and inefficiencies.
Innovation Solution
A hydraulic control system with multi-stage pressure relief, including high and low pressure relief valves and a variable pressure relief valve, which adjusts pressure thresholds based on the height of the fork assembly, allowing for more precise sizing of hydraulic components and reduced costs by providing lower pressure relief at higher elevations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-stage pressure relief system is used with a constant pressure threshold, then the system can ensure safety at maximum operating pressure, but the hydraulic components become oversized and costs increase
Solution Approach 1:
The pressure relief system is segmented into multiple stages with different pressure thresholds. A first pressure relief valve operates at a lower pressure threshold for normal operating conditions, while a second pressure relief valve operates at a higher pressure threshold for maximum load conditions. This segmentation allows each valve to be sized appropriately for its specific operating range, preventing oversized components while maintaining safety across all operating conditions.
Solution Approach 2:
The system dynamically switches between different pressure relief thresholds based on operating conditions. The control system activates the first pressure relief valve at lower pressures during normal operation and activates the second pressure relief valve at higher pressures during maximum load conditions. This dynamic adaptation allows the system to optimize component sizing for intended uses rather than worst-case scenarios only.
2Reliability
If hydraulic components are sized for worst-case scenarios, then safety is ensured, but costs and inefficiencies increase
Solution Approach 1:
Different parts of the hydraulic system are designed with different pressure ratings corresponding to their specific operating conditions. The first pressure relief valve and its associated components are sized for normal operating pressures, while the second pressure relief valve and its components are sized for maximum operating pressures. This local optimization allows components to be manufactured at appropriate sizes for their intended use rather than all components being oversized for worst-case scenarios.
Solution Approach 2:
The system changes the pressure threshold parameter based on operating conditions by switching between two different pressure relief valves. This allows the hydraulic system to operate efficiently at lower pressures during normal conditions while maintaining the capability to handle maximum pressures when needed, thereby reducing overall system costs without compromising safety.
3Device complexity
If a constant pressure threshold is used for relief, then the system design is simple, but component sizing becomes inefficient
Solution Approach 1:
The pressure relief system is divided into segments with different pressure thresholds that correspond to different operational phases. This segmentation improves operational efficiency by allowing the system to operate at optimal pressure levels for each phase rather than being constrained by a constant high pressure threshold, thereby reducing energy consumption and improving overall productivity.
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 multi-stage pressure relief system allows for more efficient use of hydraulic components, reducing costs by enabling the sizing of components for intended loads and elevations, thereby improving the operational efficiency and cost-effectiveness of material handling vehicles.
Implementation Method 1
The high pressure relief valve is configured to provide fluid communication from the supply passage to the reservoir when a pressure upstream of the high pressure relief valve exceeds a high pressure threshold
Implementation Method 2
The low pressure relief valve is configured to provide fluid communication from the supply passage to the reservoir when a pressure upstream of the low pressure relief valve exceeds a low pressure threshold
Implementation Method 3
The low pressure control valve is moveable between a control valve open position where fluid communication is provided from the supply passage to the low pressure relief valve and a control valve closed position where fluid communication is inhibited from the supply passage to the low pressure control valve
Implementation Method 4
The variable pressure relief valve is configured to provide fluid communication from the supply passage to the reservoir when a pressure upstream of the variable pressure relief valve exceeds a variable pressure threshold. The variable pressure threshold is set by the controller based on a height of the fork assembly
Data Source
AI summary
A method of controlling a hydraulic control system of a material handling vehicle is provided. The method includes detecting an elevated height of a fork assembly, determining if the elevated height is above a first predetermined height threshold, and actuating a first low pressure control valve from a control valve closed position to a control valve open position to provide fluid communication from a supply passage to the first low pressure relief valve when the elevated height is above a first predetermined height threshold.