Forced-Entry-Resistant Sash Lock With Screwless Snap-Fit Housing
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Solution Overview
Problem
Existing sash window locks are vulnerable to forced entry from the exterior, and they require screws for installation, which can be inconvenient and may not provide adequate security against unauthorized manipulation.
Innovation Solution
A sash lock design that snaps into the meeting rail without screws, featuring a housing, shaft/handle member, cam member, and secondary cam with a detent mechanism, which includes a cantilevered arm to prevent forced entry by inhibiting counter-rotation of the cam, ensuring secure locking without fasteners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional sash lock with screws is used, then the installation is secure, but the installation process is inconvenient and time-consuming
Solution Approach 1:
The patent removes the screws and fastening holes from the lock housing, extracting the fastening function entirely. The housing is designed to snap directly into the meeting rail without any external fasteners, eliminating the installation steps involving screws while maintaining secure attachment through the snap-fit mechanism with retaining lugs and grooves.
2Reliability
If a traditional sash lock is used, then the structure is simple, but it is vulnerable to forced entry from the exterior
Solution Approach 1:
The patent applies preliminary anti-action by designing the cam mechanism so that the cam cannot be rotated from the exterior side. The cam is positioned and constrained within the housing such that any attempt to manipulate it from outside met with resistance before the locking action can be compromised, preventing forced entry attempts from succeeding.
Solution Approach 2:
The patent introduces an intermediary element in the form of the cam mechanism that translates the handle rotation into locking action. This cam acts as a mediator between the user's locking action and the actual engagement with the keeper, providing mechanical advantage and preventing direct manipulation of the locking components from the exterior.
3Productivity
If a screwless snap-in design is used, then the installation is easy and quick, but the security against unauthorized manipulation may be compromised
Solution Approach 1:
The patent segments the locking function into distinct components: the snap-fit housing for secure attachment, the cam mechanism for locking action, and the handle for user interaction. This segmentation allows each component to be optimized independently - the housing provides quick snap-in installation while the cam and handle provide secure anti-manipulation protection.
Data Source
AI summary
A forced-entry-resistant sash lock includes a housing, shaft/handle member, cam member, and secondary cam. When the cam member is in the unlocked position, rotating the shaft causes secondary cam rotation initially being independent of the cam member, and subsequently the secondary cam's first contact surface contacts the cam member's first contact surface causing co-rotation of the cam member and engagement of its cantilevered arm's first engagement surface with an interior housing wall's first engagement surface to cause deflection of the arm, and continued shaft rotation returns the cantilevered arm to the undeflected position, whereat forced counter-rotation of the cam member towards the unlocked cam member position is prevented by the contact between the first contact surface of the secondary cam and first contact surface of the cam member and contact between the second engagement surface of the cantilevered arm and the second engagement surface of the interior wall.