Hydraulic Swing-Back Prevention with Neutral Pressure Locking
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Solution Overview
Problem
Existing swing-back preventing apparatuses for hydraulic actuators fail to effectively prevent operation due to undesired loads when the differential pressure between ports is zero, leading to unwanted operation during stops, especially on inclined surfaces.
Innovation Solution
A swing-back preventing apparatus with a piston that moves between offset and neutral positions based on differential pressure, using communication passages and biasing members to control fluid flow, ensuring the communication passages are blocked at neutral positions to prevent unwanted operation, and utilizing flow rate control spools to maintain communication between ports regardless of pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the communication passage is open at neutral position to allow hydraulic actuator movement, then the hydraulic actuator can operate freely, but undesired load causes unwanted operation when stopped on inclined surfaces
Solution Approach 1:
The communication passage is designed to dynamically change its state between open and closed based on piston position. When the piston is at the neutral position, the communication passage is closed to prevent unwanted operation. When the piston moves to offset positions during normal operation, the communication passage opens to allow free operation. This dynamic state change resolves the contradiction between operational freedom and stop stability.
2Reliability
If the piston remains at neutral position to prevent swing-back, then the hydraulic actuator cannot respond to operational commands, but if the piston moves to offset position, the communication passage opens causing unwanted operation
Solution Approach 1:
The system prepares the communication passage to be closed before unwanted operation can occur. By closing the communication passage when the piston is at the neutral position, the system preliminarily prevents swing-back phenomena. When operational commands are given, the piston moves to offset positions, which preliminarily opens the communication passage to enable responsive operation.
3Reliability
If the communication passage is always closed to prevent unwanted operation, then swing-back is prevented, but the hydraulic actuator cannot perform pumping operation
Solution Approach 1:
The communication passage transitions from a static closed state to a dynamic state that opens when needed. During pumping operations, the piston moves to offset positions, which opens the communication passage to allow hydraulic fluid flow and enable pumping capability. During stop periods at neutral position, the communication passage remains closed to prevent unwanted operation, thus resolving the contradiction between reliability and 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
Effectively prevents hydraulic actuators from operating due to undesired loads by quickly establishing and maintaining zero differential pressure, thereby suppressing swing-back phenomena and improving assembly efficiency by reducing the number of parts.
Implementation Method 1
a piston (22) which moves to a position corresponding to a differential pressure between a liquid pressure of the first port (31) and a liquid pressure of the second port (32)
Implementation Method 2
a pair of biasing members (27L, 27R) which act against the liquid pressure of the first port (31) and the liquid pressure of the second port (32) and bias the piston (22) to return to a neutral position
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a swing-back preventing apparatus capable of preventing a hydraulic actuator in a stop state from operating by undesired load. The swing-back preventing apparatus includes a housing, a piston, and a pair of biasing members. First and second spaces are formed between the piston and the housing, and the piston includes a pair of communication passages that are communicable with first and second spaces. When the piston is located at a first offset position, the first space is blocked from a first port. When the piston separates from the first offset position, the first space is connected to the first port. When the piston is located at a second offset position, the second space is blocked from a second port. When the piston separates from the second offset position, the second space is connected to the second port. When the piston is located at a position on the first offset position side of a neutral position, a first communication passage is connected to the first space. When the piston is located in a range from the neutral position to the second offset position, the first communication passage is blocked from the first space. When the piston is located at a position on the second offset position side of the neutral position, a second communication passage is connected to the second space. When the piston is located in a range from the neutral position to the first offset position, the second communication passage is blocked from the second space.