Two-piece trigger and spring retention system

What is this patent about?

’309 is related to the field of firearm trigger mechanisms and, more specifically, to modular trigger assemblies designed for simplified installation and maintenance. Traditional triggers are often unitary components secured by cross-pins that require significant disassembly of the firearm frame to service. The background context of the invention addresses the need for a trigger system that can be easily removed or replaced without disrupting the primary functional connections between the trigger bar and the firing mechanism.

The underlying idea behind ’309 is a modular two-piece trigger architecture that utilizes a torsionally loaded internal spring to both bias the trigger and facilitate a tool-less retention system. By splitting the trigger into an upper mounting component and a lower user-interface component, the design allows the mechanical pivot and spring housing to remain functionally integrated while the external finger piece can be serviced. The key insight is the use of a spline connection to join these pieces, ensuring that torque is efficiently transferred from the user's finger to the internal firing linkage.

The claims of ’309 focus on a trigger assembly comprising an upper trigger piece with a cylindrical portion that houses a torsional spring within an internal recess. The independent claims specify that the lower trigger piece is mounted around this cylindrical portion, while the spring extends outward to engage a trigger bar. Crucially, the claims describe a retention mechanism where the cylindrical portion and the spring itself abut against retaining lips within the firearm frame, allowing the assembly to be held in place without traditional transverse pins.

In practice, the invention works by nesting the coil base of the spring inside the upper trigger piece, with one end of the spring fixed to the trigger and the other arm pressing against the trigger bar. This creates a self-contained unit that can be snapped into the frame's annular grooves. To remove the assembly, a user applies an upward force to clear the retaining lips and rotates the unit forward through a bottom opening in the frame. This pin-less mounting allows the trigger to be disconnected from the trigger bar via a simple slip-fit pin-and-bore interface.

This approach differs from prior solutions by eliminating the need for secondary fasteners like screws or pins that typically secure a trigger to the frame. By integrating the spring into the mounting geometry, the design reduces the total part count and the spatial footprint within the firearm housing. The use of a tapered spline between the upper and lower pieces further differentiates the invention, providing a robust, press-fit engagement that prevents mechanical play while allowing the lower trigger piece to be swapped or serviced independently of the internal firing components.