Flush Casement Window Lock with Over-Center Linkage
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Solution Overview
Problem
Existing casement window locks have a high profile due to internal driving mechanisms, and they lack features to prevent back driving, which limits their design in achieving a flush mount and secure operation.
Innovation Solution
A low-profile casement window lock design that incorporates a lifter and restrictor arm to shift pivot points, combined with an over-center linkage, allowing the handle to rotate fully while maintaining a flush appearance and preventing back driving by using a fork component and lifter in slidable communication, with the lifter moving vertically relative to the fork and the handle pivoting on multiple points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a traditional lock handle with internal driving mechanism is used, then the locking function is achieved, but the profile height becomes large (20-25mm protrusion)
Solution Approach 1:
The locking mechanism is divided into separate functional components: a handle that pivots independently, a lifter that moves vertically, and a fork component that drives the lock bar. This segmentation allows each component to be optimized for its specific function while reducing the overall profile height requirement
Solution Approach 2:
The lifter acts as an intermediary component between the handle and the fork component. It translates the handle's pivoting motion into vertical movement that drives the fork horizontally, enabling a compact arrangement that reduces profile height from 20-25mm to approximately 8mm
2Ease of operation
If the handle pivots directly to drive the fork component, then the mechanism is simple, but the handle cannot be fully reversed and back driving is possible
Solution Approach 1:
The mechanism uses dynamic motion transformation through multiple pivoting points and an over-center linkage. The handle pivots about two different points during operation, and the linkage passes through an over-center position that naturally prevents back driving while enabling complete handle reversal
Solution Approach 2:
The linkage geometry is designed asymmetrically with specific pivot point locations and linkages of different lengths. This asymmetric configuration creates the over-center action that provides mechanical advantage in one direction while preventing reverse motion, enabling both full handle reversal and back driving prevention
3Length of moving object
If the lock mechanism is designed for flush mounting (8mm profile), then aesthetics and security are improved, but the internal mechanism becomes more complex
Solution Approach 1:
The mechanism transitions from a primarily horizontal motion (traditional lock handles) to a combination of vertical and horizontal motion. The lifter moves vertically while the fork moves horizontally, utilizing two dimensions of motion to achieve compact profile height while maintaining functional complexity
Data Source
AI summary
A low profile actuating window lock for casement windows having a handle actuate a lifter that slides vertically on a fork component in slidable communication with the window lock casing, the handle pivotable about the lifter and pivotable about a restrictor arm that pivots relative to the casing, allowing the handle to rotate fully from the locked position to the unlocked position with low clearance from the window frame. The pivot points of the handle, lifter, restrictor arm configuration allow for an over center linkage that prevents back driving the casement window lock.