Tool-less Trigger Guard for AR15 Receiver
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Solution Overview
Problem
The existing trigger guard installation for AR15/M16 lower receivers requires forceful insertion of a roll pin, which often damages the thin mounting tabs, a common breakage point during assembly.
Innovation Solution
A tool-less trigger guard design using a cross pin with a spring engagement mechanism that fits within the mounting openings, eliminating the need for impact force and reducing the risk of tab damage, along with optional elastomeric buffers for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a roll pin is hammered or pressed into the mounting holes to attach the trigger guard, then the trigger guard can be securely fastened to the lower receiver, but the thin mounting tabs on the lower receiver are at high risk of breaking
Solution Approach 1:
The pin diameter is changed from being larger than the hole diameter (traditional roll pin) to being equal to or slightly smaller than the hole diameter. This parameter change eliminates the need for forceful insertion while maintaining secure attachment through the spring engagement mechanism.
Solution Approach 2:
A spring engagement means is introduced as an intermediary element between the pin and the mounting holes. The spring provides a compliant connection that secures the trigger guard without requiring impact forces that would damage the mounting tabs.
2Reliability
If a roll pin with larger diameter than the mounting hole is used, then the pin can be self-retaining after forceful insertion, but specialized tools and impact force are required for installation
Solution Approach 1:
The pin diameter parameter is changed to match or slightly exceed the hole diameter, allowing direct insertion without impact tools. The self-retaining capability is achieved through the spring engagement mechanism rather than through oversizing the pin.
Solution Approach 2:
The spring engagement means automatically secures the pin in place through its elastic properties, making the installation process self-completing without requiring specialized tools or additional operations beyond simple insertion.
3Ease of operation
If a pin with diameter equal to or slightly larger than the mounting hole is used, then installation can be simplified, but the pin may not be self-retaining without additional engagement mechanisms
Solution Approach 1:
The pin and spring engagement means are merged into a single integrated component. The spring is formed as part of the pin structure, combining the fastening function with the self-retaining function in one element.
Solution Approach 2:
The integrated spring engagement means automatically provides self-retaining capability through its elastic deformation as the pin is inserted, eliminating the need for separate retention mechanisms or additional installation steps.
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 secure and damage-free installation and removal of the trigger guard without specialized tools, ensuring the integrity of the mounting tabs and providing a stable, adjustable fit.
Implementation Method 1
A deflectable spring means is operably positioned in the transverse opening to be deflected when the pin is inserted in the transverse opening and to engage the spring engagement means on the mounting pin when the mounting pin reaches a preselected position.
Implementation Method 2
At least one elastomeric buffer member may be positioned on the trigger guard member to contact a surface of the receiver when installed to prevent movement between the installed trigger guard and the receiver.
Data Source
AI summary
Provided is a trigger guard for an AR15-type firearm lower receiver, attachable and removable without application of impact force. It includes an elongated trigger guard member having forward and rear ends with a rear transverse opening positioned to align with mounting openings on the receiver. A mounting pin has a size no greater in cross-section than that of the mounting openings on the receiver and a spring engagement means thereon. A deflectable spring means is operably positioned in the transverse opening to be deflected when the pin is inserted in the transverse opening and to engage the spring engagement means on the mounting pin when the mounting pin reaches a preselected position.