Electric Tool Switch With High-Current Fuse Protection
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Solution Overview
Problem
Power tools with increasing performance parameters face significant electrical load risks, particularly high short-circuit currents that can lead to safety hazards like overheating and fire, due to component malfunctions or wear, which existing technologies struggle to mitigate effectively.
Innovation Solution
Incorporating a high-current fuse or overcurrent device in the switch circuit arrangement that interrupts the electrical voltage supply independently, using a bi-metal component for mechanical opening, or electronic components like MOSFETs to safely shut down the power tool in case of a short-circuit, ensuring safe operation even with defective power semiconductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-current fuse or overcurrent device is added to the switch circuit arrangement, then safety against short-circuit currents is improved, but device complexity increases
Solution Approach 1:
The fuse and overcurrent device are integrated directly into the switch housing and circuit arrangement, combining multiple safety functions within the existing switch structure rather than adding separate external components. This merging approach provides comprehensive short-circuit protection while minimizing the increase in overall device complexity.
2Productivity
If fully electronic switching elements like power semiconductors are used, then productivity and performance are improved, but reliability deteriorates due to inability to switch off when defective
Solution Approach 1:
The fuse and overcurrent device act as intermediary safety components that independently interrupt the circuit when defects occur in the power semiconductor. These intermediary elements provide a fail-safe mechanism that overrides the defective electronic switching element, ensuring the power tool can be safely shut off even when the primary electronic switching component fails.
3Ease of manufacture
If mechanical contacts are used in the switch, then ease of manufacture is improved, but reliability worsens due to contact wear and chatter
Solution Approach 1:
The patent replaces traditional mechanical contact-based switching with fully electronic switching elements (power semiconductors like MosFETs). This substitution eliminates the mechanical contacts that suffer from wear and chatter, improving reliability. The electronic switching elements are controlled by circuit arrangements that detect fault conditions and interrupt the circuit electronically without mechanical contact degradation.
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 effectively minimizes the risk of user endangerment by ensuring safe shutdown and preventing electrical shorts, reducing contact wear and chatter, and providing a fail-safe mechanism for power tools, especially in fully electronic switches without mechanical contacts.
Implementation Method 1
a bi-metal component, which may be prestressed, so that a high short-circuit current and the resulting strong heating of the bi-metal component result in a snapping opening of the contact
Implementation Method 2
The fuse can be arranged in a compact arrangement in the housing of the switch... when a short-circuit current occurs, the electrical voltage supply to the electric motor is interrupted independently of the actuating member
Data Source
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AI summary
The invention relates to an electric and/or electronic switch (1), in particular for an electric tool (15) comprising an electric motor (17), such as a battery-powered and/or mains electric tool, for example drill, grinder, saw, plane, angle grinder or similar, and a circuit arrangement (6, 6') for switching on and/or switching off the electrical current supply to the electric motor (17). The circuit arrangement (6, 6') can consist of a contact system with a fixed contact and a movable switching contact that co-operates with the latter. The circuit arrangement (6, 6') consists of electronics comprising a power semiconductor that can be switched between a blocking or a conductive state. In addition, the circuit arrangement (6, 6') has an actuating organ (5) for activating the switching operation in the circuit arrangement (6, 6'). A circuit-breaker (11) of the high-current type is associated with the circuit arrangement (6, 6'), in such a way that if a short-circuit occurs, the electrical current supply to the electric motor (17) is interrupted independently of the actuating organ (5). In addition or alternatively, the circuit arrangement (6, 6') can have an overload unit (11) in such a way that in the event of a failure of the circuit arrangement (6, 6'), the electrical current supply to the electric motor (17) is interrupted by the overload unit (11).