Piezo-Actuated Snap Disc Switch for Redundant Signal Verification
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Solution Overview
Problem
Existing mechanical infeed movement conversion devices, such as those using snap-action disks, fail to provide a reliable redundant electrical switching signal, especially when the snap-action disk wears out due to frequent switching, leading to unreliable operation in safety-critical applications.
Innovation Solution
Integration of a piezo element with the actuating element to generate a redundant electrical pulse upon snap-action disk activation, ensuring a temporally unambiguous verification of the switching signal by measuring the actuation force reduction when the disk snaps through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a snap-action disk is used to generate an electrical switching signal, then the device can be operated with a simple mechanical actuation mechanism, but the reliability of the switching signal deteriorates due to wear from large numbers of switching movements
Solution Approach 1:
The switching signal generation is segmented into two independent components: the original snap-action disk contact system and a new piezoelectric sensor system. Each component can detect the switching event independently, and both signals are processed together to provide redundant verification, thereby maintaining operational simplicity while improving reliability.
Solution Approach 2:
A piezoelectric sensor is introduced as an intermediary element that detects the mechanical stress change when the snap-action disk snaps through. This intermediary converts the mechanical event into an electrical signal without interfering with the original contact-based switching mechanism, providing an additional verification pathway.
2Reliability
If redundant verification of the switching signal is implemented, then the reliability of the electrical device control is improved, but the device complexity increases due to additional sensors and signal processing
Solution Approach 1:
The piezoelectric sensor is integrated into the existing actuating element structure, merging the redundant detection function with the existing mechanical components. The sensor is positioned to directly measure the stress change during snapping, eliminating the need for separate mounting structures or complex mechanical linkages.
Solution Approach 2:
The piezoelectric sensor replaces the need for additional mechanical verification mechanisms (such as duplicate contacts or mechanical linkages) by using a purely electrical sensing approach based on piezoelectric effect. This substitution reduces mechanical complexity while providing the required redundant verification.
3Productivity
If the snap-action disk is used for frequent switching operations, then the productivity of the device is improved, but the wear of the snap-action disk increases leading to signal failure
Solution Approach 1:
The piezoelectric sensor is pre-installed and calibrated to detect the characteristic stress pattern of the snap-action disk before wear occurs. This preliminary detection capability allows the system to identify wear-related signal degradation early and switch to relying more on the piezoelectric signal, preventing complete system failure.
Solution Approach 2:
The evaluation device continuously monitors both the contact-based switching signal and the piezoelectric sensor signal, providing feedback on the health and reliability of each detection pathway. This feedback mechanism allows the system to adaptively weight the reliability of each signal source based on their current condition, ensuring robust operation even as components wear.
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 provides a redundant verification mechanism for the electrical switching signal, enhancing reliability and safety by instantaneously generating a second electrical pulse coupled to the snap-through event, thereby ensuring accurate and timely control of electrical devices.
Implementation Method 1
at least one piezo element is attached to the actuating element, that the snap-action disk snapping through is detected by the piezo element and that the piezo element generates an electrical pulse
Data Source
Figure 1a~1b
Figure 2~3
Figure 4
AI summary
In a device (1) for converting a mechanical feed movement into an electrical switching signal (12) for an electrically operated machine tool or other electrical device, consisting of: - a housing (3) in which at least one recess (4) is incorporated, - an actuating element (5) axially guided in the recess (4) of the housing (3), - a snap disc (9) held pre-tensioned in the housing (3), which is convex in the direction of the actuating element (5) in the unactuated state, and - a circuit board (10) arranged in the housing (3) on which at least one electrical switching contact (11) is provided,The actuator (5) is designed to be positioned in the direction of the snap disc (9) and aligned with it. The actuator (5) is designed to verify the switching signal (12) triggered by the snap disc (9) immediately by an electrical pulse as a second redundant switching signal (12). The electrical device should only be switched by the evaluation and control unit when the switching signal (12) of the snap disc (9) and the second electrical pulse are present. This task is accomplished by attaching at least one piezoelectric element (21) to the actuator (5). The actuation of the snap disc (9) is detected by the piezoelectric element (21), and the piezoelectric element (21) generates an electrical pulse (22) which is output to an evaluation and control unit (13). This unit simultaneously measures the electrical switching signal (12) of the snap disc (9) and evaluates it to generate an electrical switching signal (12).