Latch Bolt Indicia and Sweep Geometry for Door Strike Adjustment
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Solution Overview
Problem
Installation and proper engagement between the latchbolt and strike in latch mechanisms, particularly in exit devices for glass doors, are problematic, leading to issues with force requirements and security due to the flexibility of glass and typical latchbolt configurations.
Innovation Solution
A latchbolt with visible indicia indicating minimum and maximum desired extension distances, a non-flat sweep side for retraction, and beveled edges to prevent point contact and reduce retraction force, facilitating adjustment and secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the latchbolt protrudes too far into the strike, then the engagement security is improved, but too much force is required to retract the latch
Solution Approach 1:
The latchbolt incorporates a non-flat sweep side with specific geometric features (angled surface, radius, and chamfer) at localized regions. This creates different surface qualities along the latchbolt: the sweep side provides engagement security while the chamfered edge reduces retraction force by creating a mechanical advantage during the retraction stroke.
Solution Approach 2:
The latchbolt includes a radius (curved surface) at the sweep side to facilitate smooth engagement with the strike plate. This curved geometry allows the latchbolt to roll or glide into the strike rather than making abrupt contact, reducing the force required for both engagement and retraction while maintaining secure positioning.
2Force
If the latchbolt does not protrude far enough into the strike, then the force required to retract the latch is reduced, but the door may be opened with sufficient force even if the latch is not retracted
Solution Approach 1:
The invention optimizes specific geometric parameters of the latchbolt including the sweep side angle, radius dimension, and chamfer size. By carefully selecting these parameters, the latchbolt achieves the minimum required protrusion distance into the strike for secure engagement while limiting the maximum protrusion to reduce retraction force requirements.
3Device complexity
If a typical latchbolt configuration is used, then the device complexity is reduced, but point contact with the strike plate causes scoring and increases retraction force
Solution Approach 1:
The latchbolt replaces the traditional sharp-edged configuration with a rounded radius at the sweep side. This curved geometry distributes contact pressure across a larger area of the strike plate during engagement, preventing point contact scoring. The radius acts as a bearing surface that rolls into the strike, reducing both wear and retraction force.
Solution Approach 2:
The invention converts what would traditionally be a harmful sharp edge into a beneficial rounded radius. The curved sweep side that might seem to add complexity actually simplifies the engagement process by providing smooth rolling contact, reducing wear on the strike plate, and decreasing the force required for operation.
4Ease of manufacture
If the latchbolt has a flat face, then the manufacturing is simplified, but point contact with the strike plate opening increases retraction force requirements
Solution Approach 1:
The latchbolt maintains a flat face for the majority of its surface area, which is easy to manufacture. However, localized regions are modified with specific geometric features including the sweep side radius and chamfered edge. This combination allows the bulk of the latchbolt to be simple and easy to manufacture while the localized features provide the mechanical advantage needed to reduce retraction force.
Data Source
AI summary
A door latch slide for engagement with a strike plate in a doorjamb. The door latch slide comprises a latch slide body engageable with an actuator device mounted on the door for moving the latch slide toward and away from the strike plate, the latch slide body being adjustable with respect to the door to adjust extension distance toward the strike plate. A latchbolt extends from the latch slide body and has a non-flat sweep side for contacting an outside of the strike plate to cause retraction of the latchbolt away from the strike plate as the door is closing and an opposite flat face for contacting an inside of an opening in a face of the strike plate to prevent the door from opening when the latchbolt is extended toward and into the strike plate opening. The latchbolt has a pair of indicia on at least one side thereof, one of the indicia indicating a minimum desired distance for extension of the latchbolt into the strike plate opening and the other of the indicia indicating a maximum desired distance for extension. The latch slide may be adjusted during installation of the actuator device by visually extending the latchbolt into the strike plate opening, moving the latch slide body toward or away from the strike plate until the strike plate face is between the pair of indicia on the latchbolt, and setting the latch slide body with respect to the actuator device so that the latchbolt when extended maintains the strike plate face between the pair of indicia on the latchbolt.