Pot-Shaped Pressure Vessel Screw Joining via Resistance Welding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing pot-shaped pressure vessels, such as air spring pots for vehicles, face challenges in precise positioning and alignment of screws due to production tolerances, leading to axial errors and potential leaks, especially when using friction welding or metal-active gas-shielded welding, which can result in pressure-tightness issues.
Innovation Solution
A method involving screws with a tapering connecting section extending around the circumference, inserted through apertures in the pot's bottom from the inside, allowing for precise orientation and resistance welding without welding filler metal, ensuring accurate alignment and pressure-tight closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction welding is used to join screw heads to the bottom of the pot, then the screws can be firmly joined to the bottom, but the screws cannot be precisely positioned in the correct position relative to the hole pattern and may have incorrect orientation due to production tolerances
Solution Approach 1:
The screw shank is inserted through the aperture from the inside of the pot before the joining process, allowing the screw to be pre-positioned and oriented correctly relative to the hole pattern. This preliminary insertion ensures that the screw axis is aligned with the aperture center, compensating for potential production tolerances in the bottom surface orientation.
Solution Approach 2:
Instead of joining the screw head to the outside of the bottom (conventional approach), the screw is inserted from the inside of the pot through the aperture, and the joining process occurs with the screw shank protruding from the outside. This inversion allows the screw to be positioned from the inside where precision is easier to achieve, while the head remains on the outside for proper alignment with the hole pattern.
2Reliability
If the bottom of the pot is made closed and pressure-tight, then pressure containment is improved, but screws must be attached from the outside requiring depressions or troughs that complicate the design and may still result in protruding screw heads
Solution Approach 1:
The screw is inserted through the aperture from the inside of the pot before the final joining step. This preliminary insertion allows the screw to be positioned and oriented correctly while the aperture remains open, maintaining the pressure-tight integrity of the bottom structure without requiring additional depressions or troughs.
Solution Approach 2:
The screw insertion process extracts the need for external screw head attachment and associated depressions. By inserting the screw from the inside through the aperture, the design eliminates the complexity of external head mounting while maintaining a closed, pressure-tight bottom structure.
3Strength
If metal-active gas-shielded welding is used to join screw heads to the inside of the bottom, then screws can be firmly joined, but welding filler metal can cause uncontrolled cooling leading to incorrect positioning of screw shanks and potential porosity or air inclusions
Solution Approach 1:
The invention extracts the problematic welding filler metal from the joining process by using resistance welding instead. This eliminates the uncontrolled cooling effect that causes incorrect positioning of screw shanks and prevents porosity or air inclusions, while still achieving firm joining of the screw to the bottom.
Solution Approach 2:
The invention replaces the metal-active gas-shielded welding process with resistance welding. This substitution eliminates the harmful effects of welding filler metal and uncontrolled cooling, providing more precise control over the joining process and screw shank positioning.
4Reliability
If screw heads are attached to the outside of the bottom, then the bottom can be made closed, but the screw heads protrude from the outside requiring additional depressions or troughs that complicate manufacturing
Solution Approach 1:
The invention inverts the conventional approach by inserting the screw from the inside of the pot through the aperture rather than attaching the head from the outside. This inversion allows the screw shank to protrude from the outside for proper alignment with the hole pattern, while the aperture in the bottom maintains the closed, pressure-tight structure without requiring additional depressions or troughs.
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
This approach reduces the reject rate in series production, maintains precise screw orientation, prevents porosity and air inclusions, and allows for compact screw head designs, enabling cost-effective and accurate manufacturing of pressure vessels with improved pressure-tightness.
Implementation Method 1
The connecting section of the screw is joined to the edge of the aperture, in particular by resistance welding
Data Source
AI summary
A method for manufacturing a pot-shaped pressure vessel, in particular an air spring pot for a vehicle, comprises the following steps: providing a pot, which comprises a bottom, which comprises at least one aperture, providing at least one screw, which comprises a head and a shank, inserting the shank of the at least one screw through the aperture from an inside of the pot, so that the shank of the screw protrudes from an outside of the bottom, and firmly joining the screw to the bottom of the pot. In the transitional area from the head to the shank at least one screw comprises a connecting section tapering from the head to the shank and extending all round the circumference. In inserting the shank through the aperture the connecting section is brought to bear against the edge of the aperture, and the connecting section is joined to the edge of the aperture along its bearing contact with the latter.