Concealed Piano Hinge Geometry for Flush Door Surfaces

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Solution Overview

Problem

Conventional piano hinges have visible interlocking portions that pose aesthetic and contamination issues.

Innovation Solution

A piano hinge design with a continuous and planar first front face that aligns with the door plane, hiding all hinge knuckles, allowing a 150-degree rotation without contact between extension and second front face, and featuring angled second front faces to create a gap for motion, with hidden hinge knuckles and flush mating surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional piano hinges are used, then strong hinge function is achieved, but visible interlocking portions create aesthetic and contamination issues

Engineering Contradiction:
Improvehinge strengthVSAvoidaesthetic and contamination issues
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The visible interlocking portions (hinge knuckles) are extracted from the aesthetic view by positioning them on the rear face of the door assembly, hidden from the front view. The front face displays a continuous panel surface without visible hinge components, separating the functional elements from the aesthetic surface.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The hinge mechanism is repositioned from a two-dimensional visible interface to a three-dimensional configuration where the interlocking portions are located on the rear face, creating depth and hiding the mechanical elements from the front aesthetic view.

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

2Object-affected harmful factors

If the first front face is made continuous and planar to hide hinge knuckles, then aesthetic appearance is improved, but the hinge mechanism requires precise geometric configuration to maintain motion capability

Engineering Contradiction:
Improveaesthetic appearanceVSAvoidgeometric configuration complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The second front face is configured at a non-right angle relative to the second jamb face, creating an asymmetric geometry that forms a gap between the second front face and the second jamb face. This asymmetric design allows the first hinge portion to rotate into the gap while maintaining the continuous planar appearance of the first front face.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The hinge assembly is segmented into distinct functional zones: the first front face provides the continuous aesthetic surface, the second front face creates the motion gap, and the hinge knuckles provide the mechanical interlocking. Each segment serves its specific function while working together as an integrated system.

Inventive Principle:
Principle #1Segmentation

3Ease of operation

If the extension contacts the second front face to limit motion, then the hinge rotation is constrained, but the extension must be precisely positioned to avoid contact during normal operation

Engineering Contradiction:
Improvemotion controlVSAvoidextension positioning precision
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The extension is designed to potentially contact the second front face to limit motion, but the gap configuration allows normal operation without contact. The contact serves as a mechanical stop only when needed, providing motion control through a design that normally operates without requiring precise avoidance positioning.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentEP4015750B1Piano hinges
Publication Date: 2025.11.26 BE AEROSPACE INC
  • EP4015750B1 patent drawingFigure 1
  • EP4015750B1 patent drawingFigure 2~3
  • EP4015750B1 patent drawingFigure 4

AI summary

A piano hinge can include a first hinge portion (101) configured to attach to a first door edge, the first portion having a first front face (103), a first jamb face (105) extending rearward from the first front face, and one or more first hinge knuckles (107) extending from either or both of the first front face and the first jamb face. The first front face can be configured to extend over the one or more first hinge knuckles in a lateral direction such that the first front face hides the one or more first hinge knuckles behind first front face.