Anti-Barricade Lockset With Clutched Spindle Rotation Limits
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Solution Overview
Problem
Conventional locksets can be barricaded from the egress side, preventing authorized individuals from retracting the deadbolt, particularly in institutions like mental health facilities, due to limitations in anti-barricade mechanisms.
Innovation Solution
An anti-barricade mechanism with a turnhub, spindle, and clutch mechanism that limits rotation to a predetermined angular range, allowing unobstructed locking and unlocking while preventing barricading attempts by exceeding a threshold torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lockset is used, then the door can be locked and unlocked normally, but a person on the egress side can prevent the door from opening by holding the thumbturn in place, barricading the door
Solution Approach 1:
The lockset mechanism transitions from a static connection between thumbturn and deadbolt to a dynamic system with variable engagement states. The anti-barricade mechanism allows the connection to be established or disconnected based on operational conditions, enabling normal operation while preventing barricading attempts.
Solution Approach 2:
The system changes the engagement parameter between the thumbturn and deadbolt based on detected conditions. When a barricade attempt is detected (thumbturn held in position), the engagement parameter changes from connected to disconnected, allowing the deadbolt to be actuated independently of the thumbturn position.
2Ease of operation
If the spindle is allowed to rotate freely, then the deadbolt can be extended and retracted, but the spindle can rotate more than 360 degrees causing over-travel and potential damage
Solution Approach 1:
The stops are positioned to engage the spindle before it can rotate beyond the safe angular range. This preliminary action prevents over-travel by establishing mechanical limits in advance, protecting the mechanism from damage while allowing full operational rotation.
3Productivity
If the anti-barricade mechanism allows unobstructed deadbolt retraction, then authorized individuals can open the door, but the mechanism must detect and respond to barricade attempts in real-time
Solution Approach 1:
The anti-barricade mechanism incorporates feedback through the interaction between the thumbturn, spindle, and stops. When the thumbturn is held in a position that would prevent normal deadbolt retraction, the mechanism detects this condition through the engagement state of the stops and responds by allowing independent deadbolt actuation.
Data Source
AI summary
An example lockset generally includes a housing, a bolt, a turnhub, and a spindle. The bolt is mounted in the housing for movement between an extended position and a retracted position. The turnhub is rotatably mounted in the housing and engaged with the bolt. Rotation of the turnhub in a bolt-extending direction drives the bolt toward the extended position, and rotation of the turnhub in a bolt-retracting direction opposite the bolt-extending direction drives the bolt toward the retracted position. The spindle engaged with the turnhub, is operable to exert torque on the turnhub in the bolt-retracting direction, and is selectively operable to exert torque on the turnhub in the bolt-extending direction. The housing includes a pair of stops configured to limit rotation of the spindle to a predetermined angular range.