Power Tool Brake Interlock for Missing Accessory Prevention
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Solution Overview
Problem
Existing power tools lack a reliable mechanism to prevent operation when accessories such as auxiliary handles or covers are not attached, potentially leading to unsafe usage.
Innovation Solution
A power tool design incorporating a braking mechanism and a restricting member that ensures the tool accessory remains in a braked state unless an accessory is properly attached, using a mechanical arrangement without detectors to prevent operation when an accessory is not attached, regardless of the switch state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detector and controller are used to prohibit rotation when accessory is not fitted, then safety is improved, but device complexity increases
Solution Approach 1:
The patent replaces electronic detectors and controllers with a purely mechanical restricting member system. The restricting member is directly actuated by the accessory itself through mechanical contact, eliminating the need for sensors and electronic control circuits while achieving the same safety function of preventing operation when the accessory is missing.
Solution Approach 2:
The accessory serves a dual function: it is both the tool component and the activating element for the safety mechanism. When the accessory is installed, its physical presence directly actuates the restricting member to release the brake, without requiring separate detection systems. The system uses the accessory's own installation state to control operation.
2Device complexity
If a mechanical blocking element is used to prohibit operation when accessory is not fitted, then device complexity is reduced, but reliability of operation restriction may be insufficient
Solution Approach 1:
The braking mechanism is engaged in advance before the accessory is installed. The restricting member is positioned to block the brake-releasing member's movement path prior to accessory installation. Only after the accessory is properly fitted does the restricting member move to allow brake release, ensuring operation is prohibited beforehand when the accessory is missing.
Solution Approach 2:
The restricting member acts as a mechanical intermediary between the accessory installation state and the brake-releasing member. It translates the physical presence or absence of the accessory into corresponding positional states that directly control whether the brake can be released, providing a reliable mechanical linkage for safety control.
3Ease of operation
If the brake-releasing member movement path is not blocked, then ease of operation is improved, but safety is compromised when accessory is not fitted
Solution Approach 1:
The restricting member dynamically changes position based on accessory installation. When the accessory is installed, the restricting member moves to a position that allows the brake-releasing member to move freely for normal operation. When the accessory is absent, the restricting member automatically returns to a blocking position, preventing brake release. This dynamic adjustment maintains ease of operation when safe while ensuring safety when the accessory is missing.
Data Source
AI summary
A power tool includes a motor configured to provide driving force to a tool accessory, a braking mechanism disposed on a driving-force-transmission path from the motor to the tool accessory and configured to put a brake on driving of the tool accessory, at least one attachment portion configured such that an accessory is removably attachable thereto, and a restricting member configured to be directly or indirectly pressed and displaced by the accessory when the accessory is attached to any one of the at least one attachment portion. In a state in which the accessory is not attached to any of the at least one attachment portion, the restricting member is located at a preventive position at which between-members abutment prohibits releasing of a braked state effected by the braking mechanism.