Safety Switch Welding Detection via Magnetic Field Actuation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetically operated safety switches, such as reed switches, can become welded closed, allowing unauthorized access to machinery by bypassing the safety mechanism, as they can be inadvertently or intentionally closed by external magnets, compromising the safety function.
Innovation Solution
A method and apparatus that utilize an electromagnet to periodically test the state of the magnetically operated switch by establishing a magnetic field to move it from a closed to an open configuration, monitoring electrical characteristics to determine if the switch has been welded closed, and preventing power supply if necessary, ensuring the switch remains open and safe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a magnetically operated switch (reed switch) is used to control the safety switch, then the safety switch can be operated conveniently by closing the door to bring the magnet into proximity with the reed switch, but the reed switch may become welded closed due to large current flow, compromising safety
Solution Approach 1:
The patent divides the circuit control function into two separate switches: a reed switch for magnetic actuation and a normally open switch for circuit control. This segmentation isolates the reed switch from high current flow, preventing welding while maintaining magnetic operation capability.
Solution Approach 2:
The patent introduces a normally open switch as an intermediary between the reed switch and the power circuit. This intermediary switch handles the high current flow to the motor, while the reed switch only controls the switching signal, protecting the reed switch from welding.
2Ease of operation
If a reed switch is used in the safety switch, then the switch can be closed by bringing a magnet into proximity, but a user can circumvent the safety switch by placing a magnet adjacent to the reed switch to close it without closing the door
Solution Approach 1:
The patent combines two switching mechanisms: the reed switch for magnetic actuation and a normally open switch mechanically linked to the door closure. Both switches must be closed simultaneously for the circuit to operate, merging magnetic control with mechanical verification to prevent circumvention.
Solution Approach 2:
The patent implements feedback by requiring that door closure (mechanical action) and magnetic field presence (magnetic action) both trigger switch closure. The system verifies both conditions are met before allowing motor operation, providing feedback that prevents unauthorized activation.
3Speed
If the reed switch is positioned close to the magnet for effective operation, then the magnetic field strength is sufficient to close the reed switch, but the reed switch is vulnerable to welding from large current flow
Solution Approach 1:
The patent segments the circuit into a control circuit (with the reed switch) and a power circuit (with the normally open switch and motor). The reed switch operates in the low-current control circuit, maintaining fast switching response, while the high-current power circuit is handled by the normally open switch, preventing welding.
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 unauthorized access by reliably detecting and addressing the welding issue, maintaining the safety switch's functionality and ensuring the machinery is not operated when the door is open, thus enhancing safety standards.
Implementation Method 1
The electromagnet is arranged to establish a magnetic field when energised and the magnetic field is arranged to move the magnetically operated switch from a closed configuration to an open configuration
Implementation Method 2
A magnet is provided on a door to the machine guard and is positioned such that, when the door to the machine guard is closed, the magnet is adjacent to and in close proximity with the reed switch. Closure of the door brings the magnet into proximity with the reed switch, which causes the reed switch to close.
Data Source
AI summary
A safety switch configured to determine whether a magnetically operated switch which forms part of the safety switch has been welded closed. The safety switch is configured to establish a first magnetic field in the vicinity of the magnetically operated switch. The magnetic field is arranged to move the magnetically operated switch from a first configuration to a second configuration. The safety switch monitors the state of the magnetically operated switch to determine if the magnetically operated switch has been moved by the first magnetic field, thereby determining if the magnetically operated switch has been welded closed.