Thermally Responsive Door Strike for Fire Locking
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Solution Overview
Problem
Existing door strikes fail to effectively prevent door opening during elevated temperatures, such as in fire conditions, and lack a reversible mechanism to restore normal operation after temperature normalization.
Innovation Solution
A thermally responsive door strike with a deformable element that changes configuration at elevated temperatures to prevent door opening, and reverts to its original configuration upon cooling, allowing for reversible operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solenoid or air actuated piston is used to actuate the locking member, then the door can be opened under normal conditions, but the door cannot be automatically held locked during elevated temperature conditions such as fires
Solution Approach 1:
A thermally responsive element is introduced as an intermediary component between the actuating mechanism (solenoid or piston) and the locking member. This element remains inactive under normal conditions but automatically activates during elevated temperature conditions to prevent the locking member from being actuated, thereby holding the door locked without requiring complex additional controls
Solution Approach 2:
The thermally responsive element is designed to automatically respond to temperature changes without external control. When exposed to elevated temperatures such as during a fire, the element self-activates to block the actuating mechanism, ensuring the door remains locked. When temperatures return to normal, the element automatically resets, restoring normal operation without manual intervention
2Reliability
If intumescent material is used to fill internal voids in the door strike, then the door strike is incapacitated during high heat, but the system becomes non-reversible requiring disassembly and reinstallation
Solution Approach 1:
The system transitions from a static, irreversible intumescent material configuration to a dynamic, reversible configuration using a thermally responsive element that can change state with temperature. The element dynamically adapts its position or properties based on temperature conditions, allowing the door strike to be incapacitated during fire and automatically restored when temperatures normalize, eliminating the need for disassembly and reinstallation
3Use of energy by moving object
If the biasing spring force is kept slightly more than the force required to return the locking member to locking position, then the energizing current can be kept low, but the system lacks the capability to prevent actuation during elevated temperatures
Solution Approach 1:
The thermally responsive element serves as a mediator that works in conjunction with the low-force biasing spring system. Under normal conditions, the minimal spring force allows easy actuation with low current. During elevated temperatures, the thermally responsive element blocks the actuating mechanism, preventing door opening regardless of the low spring force, thus maintaining both energy efficiency and fire safety
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
The door strike effectively prevents door opening during high-temperature events, such as fires, while ensuring the door can be reopened once temperatures return to normal, thereby aiding in fire containment and occupant safety.
Implementation Method 1
a deformable element that changes configuration at elevated temperatures
Implementation Method 2
a single solenoid which has a winding of a conductor which, when electrically energized, actuates an armature
Implementation Method 3
an armature which has a locking member connected thereto and biased by a spring
Data Source
AI summary
In one aspect the present invention provides a door strike which prevents the opening of an associated door when the door strike has been heated to an elevated temperature of at least about 1000° F., preferably when the door strike is at higher temperatures such as are present during a fire in a building structure. The door strike includes a thermally responsive element which retards the normal operation of the door strike when it is at an elevated temperature. A further aspect of the invention is a method for controlling the undesired spread of a fire or smoke between adjacent spaces separated by the door wherein a fire or smoke condition exists in at least one of these spaces, via the provision of a door strike having a thermally responsive element which retards the normal operation of the door strike when it is at an elevated temperature.