Mortise Lock Backset Reduction via Pivoting Nut Flap
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Solution Overview
Problem
Mortise locks for narrow door frames, such as balcony doors with large glass surfaces, face challenges in minimizing the backset (distance between the forend and the rotation axis) due to the need for holes in the lock housing and a fixed connection between the nut and latch, limiting the minimization of the backset and increasing manufacturing costs and maintenance efforts.
Innovation Solution
The lock design incorporates a control pin interacting with a control link in the housing, allowing the nut flap to fold over the link, reducing the necessary distance between the control pin and axis of rotation, and uses a leaf spring for latch retention, eliminating the need for additional complex parts like springs or gears, and a gear device with teeth on the nut's neck to reduce the lock's depth and installation space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed connection between the nut and latch is used, then the latch can be pressed into the housing, but the backset cannot be minimized and the positioning of the rosette breakthrough is impeded
Solution Approach 1:
The patent replaces the fixed connection between the nut and latch with a dynamic, movable connection. The nut flap can pivot relative to the nut, and the control pin moves within the control link's guide opening. This dynamic connection allows the latch to be pressed into the housing reliably while enabling the nut to be positioned closer to the forend, minimizing the backset.
Solution Approach 2:
The patent divides the previously fixed nut-latch connection into separate, movable components. The nut flap is separable from the nut through the pivot connection, and the control pin is separable from the control link through the guide opening. This segmentation allows independent optimization of each component's position and function, enabling smaller backset while maintaining reliable latch operation.
2Length of moving object
If the nut is positioned closer to the forend to minimize backset, then the backset is reduced, but the distance between the control pin and axis of rotation becomes insufficient for required latch lift
Solution Approach 1:
The patent resolves the insufficient control pin distance by utilizing a different geometric configuration. Instead of relying solely on the radial distance from the axis of rotation, the control link's guide opening extends in a direction that provides the necessary leverage for latch lift. The control pin travels along an extended path within the guide opening, effectively increasing the mechanical advantage without increasing the backset.
Solution Approach 2:
The control link serves as an intermediary between the control pin and the latch mechanism. It translates the limited motion of the control pin (constrained by the small backset) into the required latch lift through its guide opening geometry. This intermediary component enables the system to achieve the necessary latch stroke despite the reduced distance between the control pin and axis of rotation.
3Reliability
If additional complex parts like springs or gears are added to ensure proper nut flap positioning, then the positioning reliability is improved, but the device complexity and manufacturing costs increase
Solution Approach 1:
The patent employs a self-service mechanism where the control link's guide opening automatically guides the control pin into the correct position during operation. The geometry of the guide opening inherently ensures proper positioning of the nut flap relative to the driver and engagement surface, eliminating the need for additional positioning springs, gears, or other complex components. The system self-regulates through the kinematic constraints of the guide opening.
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
This design achieves a smaller backset with fewer components, reducing manufacturing costs and maintenance, while ensuring reliable latch operation and secure locking mechanisms, allowing for efficient production and minimizing errors.
Implementation Method 1
the latch is designed as a reverse latch and is held in the housing by a movable retainer, the movable retainer formed by a leaf spring arranged in a recess in the housing
Implementation Method 2
a spring-mounted latch
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The lock (1) has a housing, a rotatably supported bolt (2) and a bolt flap (4) supported at the bolt in a pivotable manner over a bearing. The bolt flap has an attachment that acts together with an engagement surface of an elastically supported latch (3). The bolt flap has a control pivot that acts together with a control connecting rod in the housing. Holes are formed in the housing for fastening the lock to a door frame, and recesses (22, 23) are formed in a flat spring (19), where one of the recesses comprise a side section that serves as an end stop for a lock pushing rod.