Safety Switch Transverse Cam Mechanism for Fast Power Cutoff
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Solution Overview
Problem
Conventional cable actuated safety switches lack a positive pull mechanism for smooth and fast power cutoff, are prone to accidental reset, and do not provide an easily accessible emergency stop option, especially when the cable goes slack or loses tension.
Innovation Solution
A safety switch design featuring a transverse cam with detents and plungers that smoothly transitions between power-on and power-off positions, a manually operable reset mechanism, and an emergency stop button, along with a spring-loaded shaft and sliding cam system that maintains tension and prevents accidental reset, allowing for emergency stop without cable pull.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional cable actuated safety switch is used, then the switch can cut power to the machine when the cable is pulled, but the switch lacks a positive pull mechanism resulting in slow or incomplete power cutoff
Solution Approach 1:
The patent employs a cam mechanism that converts the linear motion from cable tension into rotational motion, creating a dynamic amplification effect. The cam profile is designed to accelerate the switching action, transforming a slow linear cable pull into a rapid rotational movement that quickly actuates the switching contacts, thereby achieving both fast and complete power cutoff.
Solution Approach 2:
The cam mechanism creates a periodic motion cycle where the switching action is accelerated during a specific phase of the cam rotation. This periodic acceleration ensures that the power cutoff occurs rapidly during the critical phase of operation, while the cam continues to provide stable positioning during other phases of the cycle.
2Ease of operation
If the switch is designed to reset easily, then the reset operation is convenient, but the switch becomes prone to accidental reset
Solution Approach 1:
The patent incorporates a detent mechanism that creates a mechanical barrier preventing the cam from returning to its initial position unless a deliberate reset action is taken. The detent engages with a cam lobe to lock the mechanism in the tripped state, requiring a specific manual intervention to disengage the detent and allow resetting, thereby preventing accidental resets while maintaining controlled ease of intentional reset.
3Ease of operation
If the emergency stop button is mounted in a fixed location, then the mounting is simple, but the button may not be accessible to all users depending on machine orientation
Solution Approach 1:
The patent designs the emergency stop button mounting to serve multiple positions and orientations, allowing the button to be effectively mounted on any face of the housing. This universal mounting capability ensures that regardless of how the machine or housing is oriented, there is always an accessible emergency stop location, achieving accessibility universality without significantly increasing mounting complexity.
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
Enables fast and controlled power cutoff when cable tension changes, prevents accidental resets, and allows for easy emergency stop operation, ensuring reliable machinery shutdown and user accessibility.
Implementation Method 1
The shaft may be spring loaded to provide said tension means
Implementation Method 2
a sliding cam (14) which is movable in a first direction under tension in said cable
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A safety switch (2) used in conjunction with a cable as a machine guard, the switch being actuated to cut power to attendant machinery when a predetermined tension in the cable is varied by for example pulling the cable, or the cable becoming loose. The switch (2) comprising a sliding cam (14) which is connected to a connection point (12) for the cable via a spring loaded shaft (10) which shaft also supplies said predetermined tension and acts to move said sliding cam (14) in a first plane when the predetermined tension is varied. The sliding cam (14) then acts on a transverse cam (36) moving it in a plane transversely disposed to said first plane which in turn acts to cut said power (30,52).