Sheet Metal Shell Corner Fastening for Lateral AC Strength
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Solution Overview
Problem
Housings for room air conditioners/heat pumps lack lateral strength, leading to breakage during shipment, and existing methods to enhance strength, such as screwing, often result in spaces between sheet metal pieces due to misalignment and threadable connections, reducing structural integrity.
Innovation Solution
A method of punching holes in the corners of a shell so that screws engage only the innermost sheet metal, eliminating misalignment and space formation, by using an assembly machine to clinch and punch holes that ensure threaded engagement with the innermost flange or shell brace, but not the outermost sheet metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If screws are inserted in each corner to provide lateral strength, then lateral strength is improved, but space forms between sheet metal pieces due to threadable engagement, reducing connection strength
Solution Approach 1:
The patent extracts the screw engagement from the outermost sheet metal layer and redirects it to engage only the innermost sheet metal layer. This is achieved by positioning the punch to create holes that pass through the outermost layer without threading into it, while the screw threads engage exclusively with the innermost layer. This separation eliminates the space formation problem that occurs when screws attempt to thread into multiple overlapping layers simultaneously.
2Strength
If screw holes are formed during stamping and folding, then lateral strength can be provided, but screw holes do not line up due to tolerances in folding
Solution Approach 1:
The patent performs the hole punching operation after the shell assembly is completely formed through stamping and folding operations. Rather than pre-punching holes in flat sheet metal before forming, the punch creates holes in the three-dimensional assembled shell, ensuring that holes in multiple layers are automatically aligned because they are punched at the same location on the finished structure. This eliminates alignment problems caused by folding tolerances.
3Ease of manufacture
If clinching is used to hold the shell together, then manufacturing is simplified, but the shell has very little lateral strength and corners tend to break
Solution Approach 1:
The patent merges two fastening methods: clinching and screw fastening. The shell corners are initially clinched together to provide basic structural integrity and positioning, then screws are added through the punched holes to provide enhanced lateral strength. This combination allows the manufacturing process to retain the simplicity of clinching while adding the strength benefits of screw fastening at critical corner locations.
Data Source
AI summary
A method of manufacturing a shell from sheet metal for a room air conditioner/heat pump is shown. The sheet metal is stamped and formed to a U-shaped rectangular shell with open ends and a shell brace. Flanges on the outer edge of the U-shaped rectangular shell overlap at corners with (a) adjacent flanges or (b) the shell brace. Both the U-shaped rectangular shell and shell brace are inserted into an assembly machine where the corners are clinched and punched. The outermost flange at each corner is punched to a fixed diameter, but the innermost flange or the shell brace is only punched to a conical shape. Screws are inserted at each corner that pass through the fixed diameter to threadably engage only the conical shape of the innermost flange or shell brace.