Fireproof Door and Window Lock With Heat-Deteriorating Shoulder Unit

Resolve Bottlenecks,
Find Innovative Solutions
Generate Solutions

Solution Overview

Problem

Existing fireproof doors and windows are vulnerable to accidental opening during early stages of a fire due to human error, as conventional locks made of metallic alloys melt or deform under high temperatures, compromising flame confinement.

Innovation Solution

A lock for fireproof doors and windows featuring a boxlike body with a guiding and supporting element for an elastic member, where a shoulder unit made of material that deteriorates at a predefined temperature ensures the bolt remains engaged, preventing accidental opening by maintaining the door or window closed until components seize due to heat-induced deformations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional lock made of metallic alloys is used in fireproof doors and windows, then the lock can be easily manufactured and operated, but it melts or deforms under high temperatures causing accidental opening

Engineering Contradiction:
Improvelock reliability during fireVSAvoidlock strength at high temperature
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The lock is divided into multiple functional components: a bolt for engagement, an elastic member for maintaining engagement force, and a guiding and supporting element with a shoulder unit for controlling bolt movement. This segmentation allows each component to perform its specific function independently, ensuring reliable operation during fire conditions.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The elastic member acts as an intermediary between the bolt and the guiding and supporting element. It transmits and maintains the engagement force on the bolt, ensuring that the bolt remains firmly engaged in the jamb selvage even under thermal stress, preventing accidental opening.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Strength

If the lock components are made of heat-resistant materials to prevent deformation, then the lock maintains strength at high temperature, but the device complexity and manufacturing cost increase

Engineering Contradiction:
Improvelock strength at high temperatureVSAvoidlock structure complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The guiding and supporting element is designed with a shoulder unit that changes its functional parameters under thermal conditions. The shoulder unit's geometry is specifically configured to control the elastic member's action at different temperatures, allowing the lock to maintain engagement without requiring entirely heat-resistant materials for all components.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The elastic member provides self-service by automatically maintaining engagement force on the bolt through its inherent elasticity. This eliminates the need for additional active components or complex control mechanisms, keeping the device simple while ensuring reliable operation during fire conditions.

Inventive Principle:
Principle #25Self-service

3Ease of manufacture

If a simple and inexpensive lock design is used, then the manufacturing cost is low, but the lock may be tampered with or accidentally opened during early stages of fire

Engineering Contradiction:
Improvelock manufacturing simplicityVSAvoidresistance to accidental opening
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The elastic member is pre-loaded to continuously exert engagement force on the bolt, keeping it firmly seated in the jamb selvage before any thermal event occurs. This preliminary action ensures that the lock is inherently resistant to accidental opening or tampering from the outset, without requiring complex additional mechanisms.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The design accepts that metallic components will eventually deform under extreme heat, but converts this potential harm into a beneficial timing mechanism: the intumescent sealant fails first at lower temperatures, and only after that does the metallic lock components begin to deform at higher temperatures, ensuring fire containment is maintained as long as possible.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

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 lock ensures the door or window remains securely closed during the early stages of a fire, avoiding accidental openings and maintaining integrity until the lock components deform, while being cost-effective and having a space occupation equivalent to traditional locks.

Implementation Method 1

a bolt which is kept elastically in a configuration of partial protrusion from said boxlike body

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

said shoulder unit being constituted by material that can deteriorate above a predefined threshold temperature

Methodology Applied
Scientific EffectThermal deterioration: Melting

Data Source

PatentEP4441321B1Lock for fireproof doors and windows
Publication Date: 2025.09.24 CISA SPA
  • EP4441321B1 patent drawingFigure 1
  • EP4441321B1 patent drawingFigure 2
  • EP4441321B1 patent drawingFigure 3

AI summary

A lock (1) for fireproof doors and windows comprising a boxlike body (2) for containing movement means (3) for a bolt which is kept elastically in a configuration of partial protrusion from the boxlike body (2). The movement means are controlled by an element which can be actuated manually, such as a handle, a knob, a key, and the like. The lock (1) comprises a guiding and supporting element, which is integral with at least one portion of the box-like body (2), for an elastic member (4) which is kept in a fully deformed configuration by means of a shoulder unit (5), which can be coupled rigidly to the guiding element, against which one end (4a) of the elastic member (4) abuts. The shoulder unit (5) is constituted by material that can deteriorate above a predefined threshold temperature: upon the deterioration of the unit (5), the elastic member (4) assumes a less deformed configuration in which one of its ends (4a) abuts, even indirectly, against a portion of the bolt, forcing it into an arrangement of partial protrusion from the boxlike body (2).