Offset Blade Loppers with Four-Bar Linkage for Safe Branch Cutting
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Solution Overview
Problem
Conventional lopping shears pose a safety risk when cutting large branches above the user's head, as the blades extend in the direction of the handles, making it difficult to stand directly below the branch without the cut branch falling on the user.
Innovation Solution
The design features elongate handles with an offset blade configuration, where a static blade and an articulated blade are connected via a link, allowing the blades to rotate relative to each other, creating a four-bar linkage that positions the cutting and shearing edges outside the handle axis, enabling safe cutting of branches without the risk of them falling on the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the blades extend in the direction of the handles (conventional configuration), then the cutting action is straightforward and mechanically simple, but the user cannot stand directly below the branch without risk of the cut branch falling on the user
Solution Approach 1:
The patent applies dimensionality change by offsetting the blades from the handle axis, moving the cutting action from a linear extension along the handle axis to a lateral position perpendicular to the handle axis. This allows the user to stand below the branch while the blades cut to the side, eliminating the safety hazard of branches falling on the user.
Solution Approach 2:
The patent employs asymmetry in the blade configuration where the blades are positioned offset from the handle axis rather than symmetrically aligned with it. This asymmetric arrangement creates a four-bar linkage mechanism that provides both safety benefits and effective cutting action.
2Object-affected harmful factors
If the blades are offset from the handle axis, then safety is improved and branches fall to the side, but the mechanical linkage becomes more complex with additional components
Solution Approach 1:
The patent segments the cutting mechanism into distinct components: a first blade connected to the handle, a second blade offset from the handle axis, and a four-bar linkage system connecting them. This segmentation allows each component to perform its specific function while maintaining overall system coherence.
Solution Approach 2:
The patent introduces a four-bar linkage as an intermediary mechanism between the handle and the offset blade. This intermediary translates the linear motion of the handle into the rotational motion required for the offset blade to achieve cutting action, bridging the gap between simple handle operation and complex offset cutting geometry.
3Force
If the blades are positioned perpendicular to the handle axis, then cutting force is reduced and mechanical advantage is improved, but the blade geometry becomes more complex
Solution Approach 1:
The patent employs dynamics by allowing the blades to rotate relative to each other during the cutting stroke. The four-bar linkage enables the blades to change their orientation dynamically, achieving optimal cutting angles throughout the motion cycle rather than maintaining a fixed geometry.
Solution Approach 2:
The patent changes the geometric parameters of the blade system by positioning the blades perpendicular to the handle axis and allowing rotational movement. This parameter change optimizes the mechanical advantage and reduces the cutting force required while the four-bar linkage accommodates the geometric complexity.
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
This configuration allows users to safely cut branches and limbs while maintaining balance and weight distribution, as the blades are offset, enabling branches to fall to the side, reducing the force needed to cut and providing mechanical advantage for cutting through bones during field dressing.
Implementation Method 1
A four-bar linkage assembly is defined by portions of the extension link, the link, the articulated blade, and the static blade. The four-bar linkage further includes an input link, a fixed link, a coupler link, and an output link.
Implementation Method 2
providing mechanical advantage for cutting through bones during field dressing
Data Source
AI summary
Loppers include first and second elongated handles that are both directly connected and indirectly connected through a linkage assembly. The first handle has a static blade having a concave shearing edge extending generally transverse from the longitudinal axis of the first handle. The second handle has a curved end portion that curves toward the first handle and is pivotally secured to the static blade. An articulated blade has a convex cutting edge and is rotatably secured to the static blade. A link connects the curved end portion to an end of the articulated blade. Movement of the second handle relative to the first handle pivots the curved end portion about the static blade, thereby moving the cutting edge relative to the shearing edge via the link. The static blade and articulate blade are offset from the handles and extend generally transverse to the longitudinal axis of the first handle.