Security Latch for Swing Bar Door Guard
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Solution Overview
Problem
Existing swing bar door guards can be defeated by inserting a stiff member to push the swing bar clear of the arm, allowing unauthorized access when the door is slightly ajar.
Innovation Solution
A security latch with a T-configured post and cross-member that fits between the swing bar members, requiring rotation to secure the swing bar in place, and frictional securing to prevent easy manipulation, along with rotational stops to limit the post's movement to 90 degrees, ensuring the cross-member remains effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a swing bar door guard is used to prevent door opening, then door security is improved, but the device can be easily defeated by inserting a stiff member to push the swing bar clear
Solution Approach 1:
The security latch is segmented into distinct functional components: a post with cross-member forming a T-configuration, a plate for mounting, and rotational stopping means. This segmentation allows each component to perform its specific function - the T-shape provides both passage and blocking capabilities, while the stopping means limits rotation to prevent defeat mechanisms
Solution Approach 2:
The post with cross-member acts as an intermediary element between the swing bar and the defeating mechanism. It allows the swing bar to pass through in the unlocked state but blocks the insertion of stiff members that would otherwise push the swing bar clear, thereby mediating between security requirements and operational accessibility
2Stability of the object's composition
If the post is frictionally secured in the plate, then rotational stability is improved, but some effort is required to rotate the post
Solution Approach 1:
The frictional securing mechanism changes the parameter of rotational resistance dynamically. When the post is installed, friction provides high rotational stability to prevent unauthorized rotation. When legitimate operation is needed, sufficient force can overcome this friction to allow rotation to the blocking position, balancing stability and operability
3Manufacturing precision
If rotational stops are provided to limit post rotation to 90 degrees, then the cross-member positioning is improved, but the device complexity increases
Solution Approach 1:
The rotational stopping means creates an asymmetric rotational constraint, allowing rotation in one direction up to 90 degrees while preventing rotation beyond this limit. This asymmetric design ensures the cross-member can be positioned correctly to block the swing bar while maintaining simplicity through geometric constraints rather than complex mechanical mechanisms
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
Prevents the swing bar from being opened from the opposite side by requiring effort to rotate the post and cross-member, enhancing security by making unauthorized access more difficult and noisy, thus providing additional time for intervention.
Implementation Method 1
The post is preferably frictionally secured in the plate from which it extends, thus requiring some slight effort to rotate the post and its cross-member
Data Source
AI summary
A security latch for a swing bar door guard having a break away rotatable cross-member to further secure the swing bar so as to permit a minimal gap between the door and doorway when the door is opened while the cross-member extends through the swing bar retaining arm passage and is rotated lengthwise across the span to secure the swing bar. The minimal gap inhibits the introduction of a tool into the span along the midsection of the swing bar that could be used to pry the swing bar members apart to release the knob of a swing bar retaining arm.