Handle Blocking Lever Layout for One-Handed Tool Actuation
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Solution Overview
Problem
Handheld work apparatuses with safety levers require simultaneous operation of blocking and actuating levers, which can be inconvenient and unintuitive, often necessitating a loss of grip on the handle for proper operation.
Innovation Solution
The apparatus is designed with a handle and levers arranged such that the blocking lever can be operated by the thumb and the actuating lever by the index finger, allowing ergonomic operation without requiring a longitudinal movement of the thumb, and includes a spring unit and wing elements for easy access and balanced restoring forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blocking lever and actuating lever are arranged for simultaneous operation, then the safety function is ensured, but the ease of operation deteriorates as the operator may have to relinquish their firm grip on the handle
Solution Approach 1:
The operation sequence is segmented into two distinct steps: first pressing the blocking lever with the thumb to release the safety block, then pressing the actuating lever with the index finger to activate the motor. This segmentation allows each lever to be operated independently in sequence, maintaining safety while improving ease of operation.
Solution Approach 2:
The blocking lever is designed to be pressed first as a preliminary action before the actuating lever can be operated. The thumb presses the blocking lever to move the safety block away from the actuating lever's pivot path, preparing the system for subsequent actuation by the index finger.
2Device complexity
If the rotational axis of the blocking lever is arranged parallel to the longitudinal axis of the handle, then the structure is simplified, but the ease of operation deteriorates as the thumb must move in longitudinal direction and grip must be relinquished
Solution Approach 1:
The rotational axis of the blocking lever is arranged asymmetrically at an angle of 10° to 60° relative to the longitudinal axis of the handle, rather than being parallel. This asymmetric arrangement allows the thumb to press the blocking lever using only a pivot movement within the natural thumb range, eliminating the need for longitudinal thumb movement and maintaining firm grip on the handle.
3Ease of operation
If the levers are arranged for one-handed operation, then the ease of operation is improved, but the reliability may deteriorate if the operator cannot maintain firm grip
Solution Approach 1:
The operation is segmented into two sequential steps performed by different fingers: the thumb presses the blocking lever first, then the index finger presses the actuating lever. This segmentation ensures that the motor is only activated after the safety blocking function has been deliberately released, maintaining reliability even during one-handed operation.
Solution Approach 2:
The thumb's pressing of the blocking lever serves as a preliminary safety confirmation action before the index finger can activate the motor. This preliminary action ensures that the operator intentionally releases the safety block, preventing accidental activation while maintaining ease of one-handed operation.
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
Enables ergonomic and intuitive operation of the work apparatus, allowing for easy actuation with minimal grip adjustment and maintaining a secure hold, suitable for both right- and left-handed users.
Implementation Method 1
a spring unit for the blocking lever acts in combination with a contour on the blocking lever... the spring unit, adjacent in the lower portion of the contour, biases the blocking lever in the direction of the blocking position
Data Source
AI summary
The invention is directed to a handheld work apparatus having a work tool. The work apparatus defines a longitudinal plane and includes a handle having a longitudinal axis. The blocking lever is mounted so as to be pivotable about a rotational axis. The blocking lever blocks the actuating lever in a blocking or disable position and enables the actuating lever for actuation in at least one operating enable position. In the direction of view perpendicular to the longitudinal plane, the longitudinal axis of the handle and the rotational axis of the blocking lever conjointly define an angle (α). The angle (α) lies in a range of from 10° to 60°.