Locking Pliers Pivot Pin Clearance for Stable Grip
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Solution Overview
Problem
Conventional locking pliers require continuous user force to maintain a firm grip on a workpiece due to unstable sliding engagement of pivot pins with oval slotted apertures, which can lead to deviations in gripping force and stability.
Innovation Solution
The locking pliers feature a pivot pin with a diameter not greater than 0.8 times the pivot hole's diameter, allowing for an annular trajectory within the hole's contour sections, providing stable engagement and maintaining grip without continuous user force through a biasing member and toggle locking mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pivot pin is tightly fitted in an oval slotted aperture to prevent movement, then the gripping force stability is improved, but the aperture cannot be made precisely and the first pivot pin cannot move rearward when the jaws are operated to the closed locked position
Solution Approach 1:
The invention transitions from a static tight fit to a dynamic loose fit with controlled movement. The pivot pin is intentionally made loose in the pivot hole, allowing it to move along an annular trajectory within the hole during jaw operation, while still maintaining stable engagement through friction and contact with contour sections of the hole.
Solution Approach 2:
The invention changes the dimensional parameters by making the pivot hole diameter larger than the pivot pin diameter (with a specific ratio relationship). This parameter change allows the pivot pin to move freely within the hole while maintaining stable engagement, resolving the contradiction between movement capability and stability.
2Reliability
If the pivot hole diameter is made equal to or only slightly larger than the pivot pin diameter to reduce movement, then the gripping force stability is improved, but the pivot pin cannot trace an annular trajectory for stable engagement with contour sections
Solution Approach 1:
The invention establishes a specific parameter relationship where the pivot hole diameter is a defined multiple (0.8 times or less) of the pivot pin diameter. This quantitative parameter change enables the pivot pin to trace an annular trajectory while maintaining stable engagement with the contour sections, achieving both movement capability and engagement stability.
3Force
If continuous user force is applied to maintain a firm grip, then the gripping force is improved, but the user cannot operate the pliers without continuous effort
Solution Approach 1:
The invention enables the locking pliers to maintain gripping force automatically once locked, without requiring continuous user effort. The pivot pin's engagement with the contour sections of the pivot hole creates friction and mechanical interlocking that self-maintains the gripping force, making the system self-sustaining after initial activation.
Solution Approach 2:
The invention utilizes the annular trajectory and circular contour sections of the pivot hole to create a self-locking mechanism. The curved path and circular geometry enable the pivot pin to naturally engage and lock into position, maintaining gripping force through geometric constraints rather than continuous external force.
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 design ensures a firm and stable gripping force on workpieces without continuous user input, as the pivot pin's engagement with the hole's contour sections generates friction to counteract the biasing force, maintaining the jaws in a locked and tightened position.
Implementation Method 1
the pivot pin's engagement with the hole's contour sections generates friction to counteract the biasing force, maintaining the jaws in a locked and tightened position
Implementation Method 2
A biasing member engages with the fixed handle and the movable jaw, with the fixed handle and the movable jaw subject to a tensional force of the biasing member
Data Source
AI summary
A locking pliers includes a fixed handle. A fixed jaw is connected to the fixed handle. A movable jaw cooperates with the fixed jaw and includes movable and fixed pivoting regions. A movable handle is pivotally connected to the movable pivoting region. A movable pivot unit includes a pivot pin engaging with the fixed handle and the fixed pivoting region, and a pivot hole is disposed in one of the fixed handle and the fixed pivoting region and configured and dimensioned to loosely receive the pivot pin. The pivot hole has a first diametrical size and the pivot pin has a second diametrical size not greater than 0.8 times the first diametrical size. A biasing member engages with the fixed handle and the movable jaw.