Work Equipment Lock Control with Fail-Safe Dual Switch Detection
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Solution Overview
Problem
Existing safety devices for work machines face issues with emergency operability when failures occur, particularly when using combinations of switches or potentiometers for detecting the position of gate lock levers, leading to compromised safety and structure complexity.
Innovation Solution
A control device utilizing a normally open and a normally closed switch to detect the press and release of a momentary operation push button, alternately switching the lock of work equipment operation based on specific signal patterns, and releasing the lock only under predetermined conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a combination of two switches is used to detect the position of the gate lock lever, then safety is improved by multiplexing the detection system, but emergency operability deteriorates because the hydraulic flow path is blocked when a failure occurs
Solution Approach 1:
The detection system is segmented into two independent switch systems (first switch system and second switch system) that operate in parallel. Each system can independently detect the gate lock lever position, and the control device can selectively use either system based on operational requirements, allowing emergency operation even if one system fails
Solution Approach 2:
The control device changes the operational parameters by switching between different detection systems based on the detected state. When a failure is detected in one system, the control device transitions to using the other system, thereby maintaining emergency operability while preserving safety through multiplexed detection
2Ease of operation
If a potentiometer is used to detect the position of the gate lock lever, then emergency operability is maintained, but device complexity increases compared to the combination of two switches
Solution Approach 1:
The system uses two separate switch-based detection systems instead of a single potentiometer system. This segmentation allows the use of simpler, more reliable switch components while maintaining emergency operability through the parallel architecture, avoiding the complexity of potentiometer-based continuous position detection
Solution Approach 2:
The invention uses simple, reliable switch components that can be easily replaced if needed, rather than more complex potentiometers. The switches are designed to be fail-safe and can be independently replaced without requiring complex calibration or alignment procedures associated with potentiometers
3Reliability
If the hydraulic flow path is blocked when switches fail, then safety is improved, but emergency operability deteriorates because the work equipment cannot be operated
Solution Approach 1:
The hydraulic flow path control is made dynamic rather than static. The control device continuously monitors the status of both switch systems and dynamically adjusts the hydraulic flow path accordingly. When a failure is detected, the system dynamically switches to the other detection system, maintaining operational capability without compromising safety
Solution Approach 2:
The control device implements feedback by continuously monitoring the output signals from both the first and second switch systems. Based on this feedback, the control device determines which system is functioning correctly and adjusts the hydraulic flow path accordingly, ensuring that the work equipment can operate in emergency situations while maintaining safety through continuous monitoring
Data Source
AI summary
A control device includes a signal input unit configured to input a signal from a first signal line connected to a first switch configured to detect press and release of a momentary operation push button for setting and releasing lock of an operation of work equipment and input a signal from a second signal line connected to a second switch linked to the first switch, and a work equipment lock control unit configured to alternately switch between setting and releasing the lock of the operation of the work equipment in a case where information indicating that the push button is OFF→ON→OFF is obtained from both of the first signal line and the second signal line, and release the lock of the operation of the work equipment only when a predetermined operation is performed on a predetermined operation device of the work equipment.