Utility Knife Blade Retention via Pivot Torque
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Solution Overview
Problem
Existing utility knives with replaceable blades often have complex structures and inconvenient operation, leading to accidental blade detachment due to inflexible locking mechanisms, posing a safety hazard.
Innovation Solution
A blade holder with a notch on the blade and a retaining member that engages through a locking part, where the pivot axis is positioned to create a counterclockwise torque when the blade is pulled, combined with a spring member for stable retention and an unlocking structure using a thumbwheel or rotatable disc for easy blade replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tilting lock rod mechanism is used to constrain and replace blades, then blade replacement is enabled, but the structure becomes complicated and the lock rod may tilt under external force causing accidental blade detachment
Solution Approach 1:
The locking part is preliminarily positioned to engage with the notch on the blade before use. The spring member preliminarily applies elastic force to ensure the locking part is ready to engage or remains engaged with the notch, preventing accidental detachment while enabling easy replacement when needed.
Solution Approach 2:
The patent changes the physical state of the locking mechanism by introducing a spring member that dynamically adjusts the position and engagement force of the locking part. This allows the system to transition between a constrained state (during use) and an unlocked state (during replacement) based on applied forces.
2Reliability
If the pivot axis is positioned higher or aligned with the line of action force, then the structure is simpler, but the locking part cannot generate sufficient engagement force to prevent accidental detachment
Solution Approach 1:
The patent employs asymmetric positioning of the pivot axis relative to the line of action force. The pivot axis is deliberately positioned offset from the direct line of force, creating a moment arm that generates rotational torque. This asymmetric arrangement converts linear pulling forces into rotational engagement forces, enhancing the locking action without requiring additional complex components.
Solution Approach 2:
The patent transitions from a one-dimensional linear force transmission to a two-dimensional rotational mechanism. By positioning the pivot axis offset from the line of action, the system utilizes rotational torque (a different dimensional aspect) to enhance engagement stability, transforming the nature of the force application rather than simply increasing linear force.
3Ease of operation
If a complex tilting mechanism is used for blade replacement, then blade constraint is achieved, but the operation becomes inflexible and inconvenient
Solution Approach 1:
The patent introduces dynamic characteristics to the locking mechanism through the spring member and the offset pivot axis. The system can dynamically respond to applied forces: under normal use conditions, the spring maintains engagement; when external force is applied during replacement, the mechanism dynamically transitions to an unlocked state. This dynamic behavior provides both stability during use and flexibility during replacement.
Solution Approach 2:
The locking mechanism is designed to be self-actuating through the spring member and offset pivot geometry. When external force is applied to remove the blade, the mechanism automatically transitions from locked to unlocked state without requiring separate actuating components. The spring and geometric arrangement cause the locking part to naturally disengage when needed, making the system self-service and highly adaptable.
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 prevents accidental blade detachment by ensuring stable engagement of the locking part with the notch, allowing for simple and flexible operation, reducing the risk of safety hazards during blade replacement.
Implementation Method 1
a spring member (10) is also mounted on the axle pin (13) of the blade holder (2) and exerts elastic force on the retaining member (8)
Implementation Method 2
the line of said action force extends over the axis location so that it exerts on the retaining member a counterclockwise torque around the axis
Data Source
AI summary
The invention discloses a utility knife preventing its blade from accidental detachment. Prior utility knives may lose constraint on the blade due to tilting of the retaining member when the blade receives external force from the blade holder pulling outward, causing the blade to detach accidentally from the blade holder. In the present invention, the line of the action force in the engagement area of blade and retaining member extends over the axis of axle pin where the retaining member is mounted, so that when the blade receives external force pulling it outward from the blade holder, a counterclockwise torque is formed to the retaining member to allow the retaining member constrain the blade more tightly and thus prevent the blade from accidental detachment.