Chainsaw Trigger and Lockout Layout for One-Handed Control
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Solution Overview
Problem
Existing handheld gardening tools with trigger and operation member switches are difficult to operate simultaneously due to their relative positions, making it challenging to control the tool with one hand.
Innovation Solution
A chainsaw design featuring a trigger lever with a lockout lever and restricting portion that allows easy operation by preventing unintentional rotation, combined with a power switch placement that facilitates one-handed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple operation members (trigger, first operation member, second operation member) are arranged on a single operating lever, then the control mechanism is integrated, but it becomes difficult to operate them simultaneously with one hand due to their relative positions
Solution Approach 1:
The operating lever is divided into functionally independent segments: the trigger lever body for cutting control, the lockout lever for safety interlock, and the operation portion with projection for power switch control. Each segment can be operated independently by different fingers, enabling simultaneous multi-function control with one hand.
Solution Approach 2:
The operation portion is positioned in a different spatial dimension (inside the main body case) relative to the trigger lever body (protruding from main body case). This three-dimensional arrangement allows fingers to access and operate multiple controls simultaneously without interference, resolving the two-dimensional crowding problem on the operating lever surface.
2Ease of operation
If the trigger lever is made freely rotatable to improve operability, then ease of operation increases, but unintentional rotation and accidental activation occur reducing safety
Solution Approach 1:
The lockout lever is positioned to engage with the trigger lever body in advance, preventing rotation before operation begins. The restricting portion similarly pre-limits the rotation range. These preliminary constraints ensure that intentional activation requires deliberate user action rather than accidental movement.
Solution Approach 2:
The lockout lever acts as an intermediary safety mechanism between the user's hand and the trigger lever body. It must be deliberately disengaged or pressed before the trigger lever can rotate, providing a secondary confirmation step that prevents accidental activation while maintaining operational ease when intentionally activated.
3Reliability
If the projection portion is positioned to engage with the restricting portion for safety, then accidental rotation is prevented, but the structure becomes more complex
Solution Approach 1:
The restricting portion is integrated into the main body case structure rather than being a separate component. The projection portion on the operation portion works with this integrated feature to provide rotational restriction. This merging approach provides safety functionality without adding discrete parts, maintaining structural simplicity.
Data Source
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AI summary
A working machine is provided that includes a working portion and a main body portion including a main body case, an operation mechanism and a power switch. The operation mechanism includes a trigger lever, a lockout lever, and a restricting portion. The trigger lever includes a trigger lever body, and an operation portion including a projection portion. When an external force toward the main body case is applied to the trigger lever body, the projection portion of the operation portion comes into contact with the restricting portion and the trigger lever body comes into contact with the lockout lever, so that the trigger lever body is configured to be prevented from rotating relative to the main body case. When the working machine is viewed from a normal direction of a flat surface while being placed on the flat surface, a rotation center of the trigger lever body overlaps with the power switch.