Welded Steel Door Hem Joint Concealing Welds
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The pan-and-lid metal door design faces issues with assembly bottlenecks and material costs due to the reliance on adhesive for bonding, which can lead to assembly strength compromises and susceptibility to twisting or racking, especially when the adhesive is not properly applied or fails under impact.
Innovation Solution
A welded steel door design featuring a pan with flanges and a lid where the lid's edges are hemmed and secured with projection spot welds, providing a robust construction that hides weld marks and allows for a streamlined manufacturing process similar to the pan-and-lid design, while maintaining strength comparable to perimeter-channel designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive bonding is used to join pan and lid, then material costs are reduced and assembly is simplified, but assembly strength is compromised and the door becomes susceptible to twisting or racking
Solution Approach 1:
The patent combines mechanical interlocking (projection and recess) with adhesive bonding in a hybrid joining system. The projection on the pan fits into a recess on the lid, providing immediate mechanical strength, while adhesive is applied to the bonding surface to supplement the connection. This merging of mechanical and chemical bonding methods resolves the contradiction by achieving both ease of manufacture and high assembly strength.
2Productivity
If adhesive bonding is used to join pan and lid, then manufacturing process is streamlined, but the door is susceptible to twisting or racking until adhesive sets
Solution Approach 1:
The patent incorporates temporary support members that are positioned between the pan and lid during assembly to prevent twisting or racking before the adhesive sets. These support members maintain the geometric stability of the door assembly during the critical curing period, allowing the streamlined adhesive bonding process to proceed without compromising structural integrity. After curing, the temporary supports are removed.
3Strength
If mechanical interlocking is used without adhesive, then assembly strength is improved, but manufacturing complexity increases due to unbalanced assembly flow
Solution Approach 1:
The patent segments the joining process into distinct functional elements: a projection element on the pan, a corresponding recess on the lid, adhesive application zones, and temporary support positions. This segmentation allows each component to be prepared and assembled independently in a balanced workflow, reducing assembly process complexity while maintaining strong mechanical interlocking throughout the door assembly.
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 solution enables efficient and balanced assembly with improved aesthetics and productivity, as the welds secure the door effectively, preventing racking and eliminating the need for post-welding treatments, while maintaining comparable strength to perimeter-channel designs.
Implementation Method 1
a plurality of welds securing the lid to the pan, the welds extending between the portion of the top surface of the lid folded back on itself of each hem and the respective lid engaging surface of each flange
Data Source
AI summary
A welded steel door including a pan having a bottom surface forming a first face of the door and flanges extending on opposite edges thereof forming opposite side edges of the door, the flanges having a lid engaging surface spaced from the bottom surface, a lid having a top surface forming a second face of the door opposite the first face, opposite edges of the top surface each having a hem mated with a respective lid engaging surface of each flange, the hem including a portion of the top surface folded back on itself, and a plurality of welds securing the lid to the pan. The welds extend between the portion of the top surface of the lid folded back on itself of each hem and the respective lid engaging surface of each flange and are thereby concealed.