Extension Spring-Custom-made Universal-Swivel-Hook (movable-hook) Tension Spring

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1. Performance
   • Uniform Corrosion-Safe Tension – Formed from 304 austenitic stainless wire Ø1 – 5 mm and solution-annealed, the springs deliver stable modulus and ≥60 % residual elastic energy even after 1 000 h salt-spray exposure.
   • High Elastic Limit – Cold-worked coils reach 1 250–1 600 MPa tensile strength; dual stress-relief at 300 °C holds permanent set below 2 % after 100 000 full-stroke cycles.
   • Swivel-Hook Versatility – Precision-milled universal hooks rotate 360 ° to self-align under load, eliminating side-bending and extending service life when anchor points are offset.
   • Custom Force Curve – Free lengths 30 – 400 mm and coil outside diameters Ø10 – 35 mm allow preload tuning from 25 N to 1 200 N; variable-pitch options reduce initial pull force while preserving maximum extension travel.
2. Application Scenarios & Assembly Requirements
   • Access Panels & Machine Guards – Maintain consistent closure pressure yet permit quick removal; swivel hooks compensate for misaligned latch pins.
   • Automotive & Marine Components – Withstand road salt, humidity and temperature swings from –40 °C to +120 °C in throttle linkages, seat return mechanisms, and deck-lid assists.
   • Medical & Food Equipment – Non-magnetic 304 alloy meets hygiene standards for lab centrifuges, packaging jaws, and commercial dishwashers.
   • Fitting Guidelines
   – Eyelet/Pin Diameter: 0.75 × wire Ø to minimise local stress.
   – Extension Limit: cap stroke at 85 % of elastic range to retain ≥95 % initial load through life.
   – Hook Seating: allow ≥30 ° free rotation or use clevis ends to exploit swivel capability.
3. User-Friendly Operation
   • Plug-and-Play Hooks – Detachable, reversible hooks install without tools; spring body can be replaced in situ while re-using existing swivels.
   • Kink-Free Packaging – Supplied on reusable reels or in anti-static trays with coil separators, preventing tangles and preserving preload accuracy.
   • Color-Band Coding – Heat-shrink markers on each spring indicate wire size and rate, streamlining line-side selection and maintenance audits.
   • Clean-Room Ready – Ultrasonically washed and nitrogen-packed; compatible with IPA wipe-down or autoclave cycles up to 135 °C (uncoated versions).
4. Quality & Longevity
   • ISO 9001 / IATF 16949 Production – In-line laser gauges keep coil pitch tolerance within ±0.05 mm and load tolerance within ±6 %.
   • Shot-Peened Fatigue Resistance – Compressive surface stresses boost cycle life by >25 % versus non-peened counterparts; laboratory tests show <3 % load fade after 1 000 000 extensions.
   • Custom Surface Finishes – Options include passivation (ASTM A967), black oxide, electropolish, or PTFE dry film (<8 µm) to tailor friction, reflectivity, or biocompatibility without altering spring rate.
   • Full Traceability – Laser-etched codes link each spring to 3.1 material certificates, furnace charts, and individual load/deflection graphs, ensuring audit-ready documentation for aerospace, medical, and food-processing applications.