Offset-Rebate Window Frame for Slim Stable Mullions

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Solution Overview

Problem

Existing window and door frames with integrated panels and sashes are bulky and aesthetically unappealing due to robust locking bars, compromising stability and manufacturing costs.

Innovation Solution

A frame design featuring a surround divided by a bar connected at two points, with a first circumferential rebate on the outer side and a second on the inner side, and inclined surfaces rotated relative to each other, allowing panels and sashes to be offset, resulting in a slimmer profile while maintaining stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If robust locking bars are used to securely hold panels and stop casement windows, then stability and reliability are improved, but the frame's appearance deteriorates due to large and prominent locking bars

Engineering Contradiction:
Improvestability of panel and sash holdingVSAvoidaesthetic appearance of frame
Core Design Contradiction:
ReliabilityVSShape

Solution Approach 1:

The rebate is positioned in a different spatial dimension (on the outer side of the frame) rather than on the inner side where locking bars would be visible. This dimensional relocation allows the locking mechanism to function effectively while being concealed from view, resolving the contradiction between structural reliability and aesthetic appearance.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The locking function is extracted from the visible inner side of the frame and relocated to the outer side through the rebate structure. The rebate itself becomes the primary locking feature, eliminating the need for prominent internal locking bars that compromise aesthetics.

Inventive Principle:
Principle #2Taking out (Extraction)

2Shape

If the frame is designed to be slim for aesthetic appeal, then visual appearance is improved, but the stability and reliability of accommodating panels and sashes deteriorates

Engineering Contradiction:
Improveslim profile of frameVSAvoidstability of panel and sash accommodation
Core Design Contradiction:
ShapeVSReliability

Solution Approach 1:

The locking and securing functions are relocated to the outer dimension of the frame through the rebate structure. This allows the inner frame profile to remain slim and aesthetically pleasing while the outer rebate provides the necessary structural depth for reliable panel and sash accommodation.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The frame exhibits different qualities at different locations: the inner profile remains slim for aesthetics, while the outer rebate area provides increased depth and structural strength for reliable panel and sash holding. This localized differentiation resolves the contradiction between overall slimness and local stability requirements.

Inventive Principle:
Principle #3Local quality

3Reliability

If locking bars are made large and robust to provide required stability, then reliability is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:
Improvestability of frame structureVSAvoidcomplexity of locking mechanism
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The complex internal locking bar mechanism is extracted and replaced by a simpler rebate structure on the outer frame. The rebate provides inherent mechanical interlocking capability without requiring additional robust locking components, thereby reducing device complexity and manufacturing cost while maintaining reliability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The rebate structure serves multiple functions simultaneously: it provides the mechanical interlocking for panels and sashes, defines the opening geometry, and eliminates the need for separate robust locking bars. This self-sufficient design reduces overall system complexity and manufacturing requirements.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4685328A1Frame, window comprising a frame and door comprising a frame
Publication Date: 2026.01.28 ART OF ELEMENTS GMBH
  • EP4685328A1 patent drawingFigure 1A~1B
  • EP4685328A1 patent drawingFigure 1C~1D
  • EP4685328A1 patent drawingFigure 2A~2B

AI summary

The invention relates to a frame, preferably made of wood, comprising a frame (1) and at least one bar (2) which is connected to the frame (1) at two connection points (3) to divide the frame (1) into at least two areas, wherein at least one first area is formed with a first circumferential rebate (4) for receiving a panel and wherein at least one second area is formed with a second circumferential rebate (5) for receiving a sash, wherein the frame comprises an inner side and an outer side opposite the inner side, wherein the first circumferential rebate (4) is arranged on the outer side, the second circumferential rebate (5) is arranged on the inner side and at least two corresponding inclined surfaces (6) are formed between the connection points (3) and the bar (2), wherein the inclined surfaces (6) are arranged rotated relative to each other.Furthermore, the invention relates to a window comprising a frame and a door comprising a frame.