Pneumatic Valve Interlock Using Air Spring Feedback
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Solution Overview
Problem
Existing pneumatic drive control systems face challenges in preventing sudden automatic changes in switching position without an input signal, particularly due to spring breakages in pilot valves, which can lead to unintended operation of pneumatic drives and undetected errors, requiring complex and costly solutions for safety and error detection.
Innovation Solution
A structurally simple valve arrangement with two electro-pneumatically pilot-controlled directional control valves, where one valve's preliminary stage has an external control connection and an air spring that can be acted upon and vented by the other valve, ensuring that both valves must switch together to change the state of the working connections, and incorporating check or throttle devices to prevent unintended movements and detect errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electro-pneumatically pilot-controlled valve is used, then the control structure is simple, but a spring breakage in the pilot valve can cause unintended automatic switching of the pneumatic drive
Solution Approach 1:
The single valve is segmented into two series-connected directional control valves (first valve 4 and second valve 12), where each valve must switch for the pneumatic drive to change position. This segmentation prevents unintended switching because both valves must be actuated simultaneously, eliminating the risk of automatic switching due to spring breakage in a single pilot valve.
2Reliability
If a redundant valve arrangement with two series-connected valves is used, then safety against unintended switching is improved, but error detection capability deteriorates because individual spring breakages cannot be detected
Solution Approach 1:
A feedback mechanism is implemented where the second valve 12 controls the air spring 19 of the first valve 4. During normal operation, the air spring provides counterpressure to the main stage 6 of the first valve. If a spring breakage occurs in the first pilot valve 7, the feedback mechanism causes the air spring to expand, which can be detected through pressure sensors or position sensors, enabling error detection while maintaining the safety of the redundant valve arrangement.
3Difficulty of detecting and measuring
If electronic monitoring measures and position sensors are integrated, then error detection capability is improved, but device complexity and costs increase significantly
Solution Approach 1:
Instead of using electronic monitoring measures and position sensors, the invention uses purely pneumatic means for error detection. The air spring 19 connected to the second valve 12 provides a pneumatic feedback mechanism that automatically indicates errors through pressure changes. This pneumatic approach achieves error detection capability while avoiding the complexity and high costs associated with electronic sensors and monitoring systems.
4Difficulty of detecting and measuring
If the second valve acts upon the air spring of the first valve, then error detection is enabled through pneumatic feedback, but the valve arrangement complexity increases
Solution Approach 1:
The control functions of the two valves are merged through the air spring connection. The second valve 12 not only controls the second working connection 2 but also simultaneously controls the air spring 19 of the first valve 4. This merging of functions allows error detection to be achieved without adding separate monitoring systems, as the same pneumatic connection serves dual purposes: controlling the valve and providing error feedback.
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 arrangement effectively prevents sudden automatic changes in the switching position of pneumatic drives during errors, allows for reliable error detection, and maintains operational safety while reducing complexity and costs by using commercially available pneumatic components.
Implementation Method 1
a second, each electro-pneumatically pilot-controlled directional control valve (12), wherein one or both directional control valves (4, 12) is/are arranged upstream of the working connections (1, 2) for their loading and venting, wherein the preliminary stages of both directional control valves (4, 12) are designed to automatically reset
Implementation Method 2
electro-pneumatically pilot-controlled valves with an electrically directly actuated preliminary stage (pilot valve, pilot valve) and a main stage (main valve) which is pneumatically actuated indirectly via the preliminary stage
Data Source
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AI summary
The aim of the invention is to provide a valve arrangement for controlling pneumatic drives, with protection against sudden unprompted changes to the initial switching position without reception of an input signal there is a fault in a restoring element of a pilot stage, and subsequent effective fault detection by purely pneumatic means. According to the invention, the valve arrangement comprises a first and a second working connection (1; 2) that can be connected to a drive and a first and a second electropneumatically pilot-operated directional control valve, one or both directional control valves being mounted upstream of the working connections (1; 2) for action upon and ventilation of same. The pilot stages of both directional control valves are designed as self-restoring entities and the second direction control valve is designed to alternate between a rest position and a switching position. The pilot stage of the first directional control valve has an external control connection (8, 8') which can be acted upon by the second directional control valve to achieve its switching position and can be ventilated by the second directional control valve to achieve its rest position. The second directional control valve has an air spring (19) as a restoring element for the main stage (14) and said air spring can be acted upon and ventilated externally via the first directional control valve. A change of state between action upon or ventilation of the air spring (19) takes place once the first directional control valve is in a switching position and only when the first directional control valve changes switching state. A change of state between action upon or ventilation of a working connection (1; 2) takes place after an action upon or ventilation which is brought about when the second directional control valve is in the switching position and only when the second directional control valve is in the rest position.