Pneumatic Pilot Valve Hysteresis via Slide Valve
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Solution Overview
Problem
Current pneumatically operated 4-way valve systems often fail to create desired hysteresis due to variables like system volume and leaks, which prevent the pressure above the poppet valve from dropping, resulting in the pilot valve not snapping open.
Innovation Solution
An additional slide valve is introduced to restrict the inlet above the poppet valve, creating a pressure drop that forces the valve to snap open, ensuring hysteresis is achieved without affecting the flow once the valve is actuated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a storage spring and poppet valve system is used to create hysteresis, then the valve can be pneumatically detented, but the system becomes sensitive to pressure drop variables such as system volume and leaks
Solution Approach 1:
A slide valve is introduced as an intermediary component between the actuation pin and the poppet valve. This slide valve controls the pressure drop across the poppet valve by restricting the inlet passage, ensuring reliable snap action while isolating the system from sensitivity to volume and leak variables.
Solution Approach 2:
The invention changes the pressure parameters by creating a controlled pressure drop across the slide valve. This pressure drop is maintained regardless of system volume or leaks, ensuring consistent snap action. The slide valve restricts the inlet passage to maintain this pressure differential until actuation occurs.
2Reliability
If the inlet passage is restricted to create pressure drop for snap action, then hysteresis is improved, but flow capability may be reduced
Solution Approach 1:
The slide valve is designed to move dynamically between two positions: a restricted position during normal operation that creates pressure drop for snap action, and an open position during actuation that removes the restriction to allow full flow. This dynamic movement resolves the contradiction between flow restriction and flow capability.
Solution Approach 2:
The slide valve is positioned in advance to restrict the inlet passage, creating the necessary pressure drop before actuation occurs. When the actuation pin pushes the slide valve, the restriction is removed preliminarily prepared, ensuring both snap action and subsequent full flow capability.
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
This solution allows for proper snap action and increased hysteresis in the pneumatically detented valve, independent of the pneumatic circuit, ensuring consistent valve operation.
Implementation Method 1
An additional slide valve is added to the pilot valve that restricts the inlet of the pilot valve above the poppet valve that creates a pressure drop
Implementation Method 2
the storage spring can expand back out to its nominal length and snap the valve open, creating the desired hysteresis
Implementation Method 3
the air pressure above the poppet valve is higher then the pressure bellow it, which is usually atmospheric pressure. This differential pressure creates a net force that keeps the valve closed
Data Source
AI summary
The 4-way valve used to control the operation of a pneumatic motor can be pneumatically operated such as by a pilot valve. The pilot valve (20) works by creating a restriction at the high-pressure air/signal port (22) regardless of the pressure drop up-stream of the pilot valve (20) while still allowing for adequate flow once the valve (20) is actuated. An additional slide valve (24) is added to the pilot valve (20) that restricts the inlet 30 of the pilot valve (20) above the poppet valve (28) that creates a pressure drop, see FIG. 3. The extra pressure drop forces the valve (20) to snap open once the actuator pin (32) contacts the poppet valve (20) to create the hysteresis. Once the valve (20) snaps open, the slide valve (24) moves to uncover the high-pressure ports (22), removing the restriction to ensure that the main 4-way (10) fully actuates.