| 摘要 |
A perforated metal center tube is provided for use within an oil, fuel, or hydraulic filter. The tube is fabricated from a perforated metallic sheet formed into a cylinder in which opposite edges thereof are mutually engaged with one another to form a longitudinal multi-layered lockseam. The lockseam is mechanically clinched to inhibit slippage of the mutually engaged edges without the need for welding, soldering or otherwise chemically or adhesively bonding the lockseam. A series of circumferential beads are provided at spaced locations along the length of the tube to provide structural reinforcement. Each bead is formed through lockseam without generating slippage or disengagement of the first and second edges relative to one another. The beads advantageously provide the tube with sufficient structural integrity to withstand typical filtration pressures, with a metallic sheet of relatively thin gauge.
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