Door Sag Prevention Retainer and Bolt System
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Solution Overview
Problem
Pre-hung doors tend to sag in door frames due to unsupported lock sides and the use of staples and adhesive tape, which can damage the door's appearance.
Innovation Solution
Supporting both sides of the door with a retainer and bolt system, where the lock side is secured to the lock jamb using a molded plastic retainer and bolt with a spur to prevent easy withdrawal, without modifying the door or jamb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lock side of the door is unsupported, then the door can be installed with simple hinges and staples, but the door tends to sag in the frame
Solution Approach 1:
The patent introduces a retainer as an intermediary component that connects the door to the lock jamb. The retainer includes a body with a recess that receives a bolt, and the bolt engages with the lock jamb to provide support. This intermediary mechanism enables the door to be supported on the lock side without requiring complex modifications to the door or jamb structures.
2Productivity
If tapes and staples are used to close the door, then the door can be secured quickly, but the appearance of the door is marred
Solution Approach 1:
The patent extracts the door closing function from the temporary fastening methods (staples and tapes) and implements it through a permanent structural solution. The retainer and bolt system provides both support and closing functionality, eliminating the need for visible staples or tapes on the door surface.
Solution Approach 2:
The retainer acts as an intermediary that provides both structural support and door closing functions. The recess in the retainer body receives the bolt, and together they secure the door to the lock jamb, replacing the need for appearance-damaging fasteners while maintaining installation efficiency.
3Stability of the object's composition
If a retainer and bolt system is used to support the lock side, then door sagging is prevented, but the device complexity increases
Solution Approach 1:
The patent segments the support function into two distinct components: the retainer body and the bolt. The retainer body includes a recess that receives the bolt, and the bolt engages with the lock jamb. This segmentation allows each component to have a specific function while working together to provide overall door support, making the system easier to manufacture and install.
Solution Approach 2:
The patent applies local quality by concentrating the support function at the lock side of the door where it is most needed. The retainer and bolt system is installed only at the lock jamb, providing targeted support without requiring complex modifications throughout the entire door structure.
4Ease of operation
If the bolt can be easily withdrawn from the jamb, then installation and removal are simple, but the door support reliability is reduced
Solution Approach 1:
The patent applies asymmetry in the bolt design where one end of the bolt has a spur that engages with the lock jamb. The spur prevents the bolt from being easily withdrawn while still allowing for intentional installation and removal. This asymmetric feature provides directional resistance to withdrawal forces while maintaining ease of operation during proper installation and maintenance.
Data Source
AI summary
An accessory for preventing a pre-hung door from sagging in a door frame comprised of a retainer for supporting one side of the door on a lock jamb of the frame and a bolt which is slideable in the frame for preventing the door from rotating in the frame. The retainer has a “U” shaped portion which receives a lock jamb and an adjoining cylindrical portion which engages a bore in a door. The bolt is an elongated slender member having an enlarged end portion which engages a pocket in the lock jamb and a spur which resists a withdrawal of the bolt from the lock jamb.