Plug Connection Locking Mechanism for Power Tool Cable Safety
Solution Overview
Problem
The plug-in connection in hand-held power tools, such as hammer drills, represents a mechanical weak point that can lead to exposure of wires or live contacts if damaged, necessitating an overload protection mechanism to ensure safe disconnection and easy replacement of the supply cable.
Innovation Solution
A two-part supply cable with a detachable plug connection featuring a locking mechanism that engages and disengages based on tensile load, incorporating a pin, spring-loaded blocking body, and connecting link to securely lock and unlock the connection, ensuring electrical safety and ease of replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If a detachable plug connection is used in the supply cable, then the supply cable can be replaced easily, but the plug connection becomes a mechanical weak point that may expose wires or live contacts
Solution Approach 1:
The supply cable is divided into two separate sections: a machine-side section with a female connector and a network-side section with a male connector. This segmentation allows the cable to be replaced easily while maintaining a secure connection interface through the detachable plug connection.
Solution Approach 2:
A locking mechanism with a locking element and locking cam is implemented in the plug connection before any potential damage can occur. This locking mechanism prevents premature disconnection and provides overload protection that forces the connection to open in a controlled manner only when excessive tensile load is applied, preventing wire exposure or live contact exposure.
2Reliability
If a locking mechanism is added to prevent premature disconnection, then connection reliability improves, but the device complexity increases
Solution Approach 1:
The locking mechanism is designed to be self-actuating through a spring element that automatically engages the locking element with the locking cam when the connectors are mated. The spring provides the necessary forcing action to engage the locking elements without requiring additional actuators or complex control systems, thereby maintaining simplicity while ensuring reliable locking.
3Ease of operation
If the locking mechanism requires manual operation, then ease of operation is maintained, but the forcing action needed for unlocking may interfere with manual control
Solution Approach 1:
The locking cam is designed with an asymmetric profile that requires forcing action in only one direction (axial tensile load) to disengage the locking element, while allowing easy manual rotation in the opposite direction for normal locking and unlocking operations. This asymmetric design decouples the manual operation from the forced unlocking mechanism, enabling users to operate the locking mechanism with little effort under normal conditions while still providing automatic overload protection when excessive tensile load is applied.
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
The solution provides secure electrical disconnection and easy replacement of the supply cable, preventing exposure of wires and ensuring user safety by automatically opening the connection under excessive load, allowing safe handling and maintenance.
Implementation Method 1
A spring-loaded blocking body engages in the connecting link. The pin can be inserted in one opening without any effort and pushed by a rotary movement to behind the blocking body by a rotary movement. In the event of a low tensile force, the blocking body prevents the pin from being able to emerge at the second opening.
Implementation Method 2
The pin can be inserted in one opening without any effort and pushed by a rotary movement to behind the blocking body by a rotary movement. The connecting link can have a path running monotonously along the axis between the second opening and the spring-loaded blocking body.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The tool i.e. drill hammer (1), has an electric motor (5) driving a tool support (2), and a two-part supply cable (18) with a portion (21). The portion is mechanically attached within a machine housing (17). Another portion of the supply cable is coupled at the former portion outside the machine housing by a detachable plug-in connection (20). A locking mechanism rotatably locks the detachable plug-in connection around an axle and releases the detachable plug-in connection with tensile stress above a threshold value along the axle. Halves of the mechanism contain a pin.