Power Tool Locking Mechanism Prevents Inadvertent Motor Start
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Solution Overview
Problem
Existing electric power tools can inadvertently switch on the motor due to the unlocking position of the tool locking device, which poses a safety risk and requires a solution to prevent this while being economically manufactured.
Innovation Solution
A locking mechanism that is actuated by a single locking lever, allowing the safety element to be reliably locked in its safety or release position, preventing erroneous manipulation and integrating the locking of the working tool with the braking device, using a cam surface for stable control and eliminating the need for a spring, and made of plastic for cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a braking device mechanically connected with the safety element is used, then rapid braking of the working tool is achieved, but inadvertent switching-on of the motor remains possible
Solution Approach 1:
The locking mechanism merges the safety element retention function with the existing braking device by integrating a locking member that engages with the braking device housing. This combination ensures that the safety element cannot be inadvertently moved from the safety position, preventing unintended motor activation while maintaining the rapid braking capability through the same mechanical linkage.
Solution Approach 2:
The locking member acts as an intermediary element between the safety element and the braking device housing. It provides a form-fit connection that mechanically prevents the safety element from moving out of position, thereby mediating the control between the user's intent and the motor activation while adding a layer of safety without requiring complex electronic systems.
2Reliability
If a locking mechanism with multiple components is used to prevent inadvertent switching on, then safety is improved, but manufacturing cost increases
Solution Approach 1:
The locking mechanism is segmented into distinct functional components: a locking member with a head portion and engagement portion, a groove in the braking device housing, and a spring. This segmentation allows each component to be manufactured separately using standard processes and then assembled, reducing overall manufacturing complexity and cost compared to a monolithic design.
Solution Approach 2:
The locking mechanism uses inexpensive materials and simple geometries that can be manufactured cost-effectively. The locking member and groove design allows for easy production using standard molding or machining processes, and the spring is a common, low-cost component. This approach prioritizes cost-effective safety over premium materials or complex assembly.
3Ease of operation
If the safety element can be freely moved between positions, then ease of operation is improved, but inadvertent actuation increases
Solution Approach 1:
The locking mechanism dynamically adapts to the safety element's position through the spring-loaded locking member. When the safety element is in the safety position, the locking member engages with the groove to prevent movement. When intentionally released, the spring allows the locking member to disengage, enabling controlled movement. This dynamic behavior maintains ease of intentional operation while preventing erroneous manipulation.
Solution Approach 2:
The locking member is pre-positioned to engage with the groove, creating a preliminary constraint that prevents the safety element from moving unintentionally. This preliminary anti-action counteracts any inadvertent forces or slips that might cause erroneous actuation, while still allowing deliberate user action to overcome the locking mechanism through the release mechanism.
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 prevents inadvertent motor switching on, ensuring safe operation by locking the safety element in its intended position, simplifying user handling, and reducing manufacturing costs through a cost-effective design.
Implementation Method 1
The locking mechanism has a locking member engageable in a groove provided in the braking device
Implementation Method 2
using a cam surface for stable control and eliminating the need for a spring
Data Source
AI summary
An electrical power tool includes a locking device (31) for securing the working tool (3) on a motor-driven shaft (2; 200), a device (10) for braking the shaft (2), a safety element (8) connected with the braking device (10) and an actuation switch (7) and having a safety position that corresponds to the braking position of the braking device (10) and a non-actuation position of the switch (7) in which the switch (7) cannot turn the shaft-driving motor (M) on, and a release position that corresponds to the release position of the braking device (10) and an actuation position of the switch (7), and a locking mechanism (21) operatively connected with the safety element (8) and the locking device (31) and displaceable between a locking position which corresponds to an unlocking position of locking device (31) and in which the safety element (8) is retained in its safety position, and a release position in which the locking device (31) is in its locking position, and the safety element (8) occupies its release position.