Usage Lock Safety Circuit for Power Tools
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Solution Overview
Problem
Existing use locks for power tools require users to hand over their personal transponders for service, making them vulnerable to misuse if stolen, and lack a mechanism to limit unauthorized usage.
Innovation Solution
A safety circuit that allows temporary operation with a service code, which increments a counter with each use, switching to a permanent non-operating state after a predetermined count, requiring an operating code for continued use, and resets with each valid operating code entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a personal transponder is used for user authentication, then access control security is improved, but the device becomes vulnerable to misuse when the transponder is stolen for service purposes
Solution Approach 1:
The authentication system is segmented into two distinct code types: service codes for maintenance personnel and user codes for authorized users. This segmentation allows the system to differentiate between service operations and normal usage, preventing misuse of service access while maintaining security for both groups.
Solution Approach 2:
A counter mechanism is introduced as an intermediary between service code authentication and full device operation. The counter limits the number of times a service code can be used, acting as a mediator that temporarily permits service access while ultimately preventing prolonged unauthorized usage.
2Ease of repair
If a service code allows temporary operation for maintenance, then ease of service is improved, but unauthorized users can operate the device multiple times if they obtain the service code
Solution Approach 1:
The service code authorization is made dynamic through the counter mechanism. The authorization status changes from permitted to blocked based on the number of uses. This dynamic adjustment allows flexible service access initially while automatically tightening security after a predetermined number of operations.
Solution Approach 2:
The system changes the authorization parameter from static (service code always valid) to dynamic (service code valid only for N times). By modifying the validity parameter of the service code based on usage count, the system enables service accessibility while preventing unlimited unauthorized operations.
3Reliability
If the counter value is set low to prevent misuse, then security against unauthorized usage is improved, but testing opportunities during servicing are reduced
Solution Approach 1:
The counter is set to a low value that provides sufficient security (blocking after minimal uses) while still allowing enough operations for essential service tasks. The counter value is optimized to be just enough for service needs but insufficient for productive misuse, achieving security through partial authorization.
Data Source
Figure 1~2
AI summary
The tool e.g. angle grinder (1), has a safety switch (20) switching a drive motor (2) i.e. combustion motor, into a ready state or into an external operating state based on received signals of a radio frequency identification device (RFID) transmitting and receiving unit (18). The unit receives operation and service codes. The switch switches the motor into a temporary service state during reception of the allowed service codes. A counter is incremented during reception of the service codes. The switch switches the motor into a permanent external operation state after reaching a preset count.