Helical Extension Springs

Precision Extension Springs

Helical Extension Springs

Helical Extension Springs are used to provide pulling force. These springs are typically made of round wire and will generally have hooks/loops on the ends for attachment to the application. Extension springs can be made with many different configurations of ends for attaching including but not exclusive to machine hooks, cross over center hooks/loops, special shaped hooks, extended hooks and pig tail end configurations. The typical extension spring design will have some initial tension (force that keeps the coils together). There is also a “Draw Bar” spring assembly design that acts as a extension spring but has a positive stop that limits the amount of extension that you can achieve.  These assemblies are made with wire forms and a compression spring and are used when you need to have some movement at certain forces but cannot be allowed to extend beyond a point and will then act as a rigid link.

Sizes and shapes include round, square rectangular, shaped and many others.  Extension springs can be made from many different wire types:

  • Stainless steel
  • Carbon
  • High-temp nickel alloy
  • Copper

Customer Case Study – Extension Springs

A customer was designing a precision solenoid valve that required a very precise spring force and initial tension requirement, which meant that the tolerances would need to be very tight to achieve the performance required.  This was a matter of utilizing the best wire type, diameter and using the best manufacturing process to control the spring diameter’s tension and lengths, but the tolerances were so little that each spring had to be fine tuned.  This was a matter of adjusting the initial tension to each spring after it was manufactured by loading the spring onto the electronic load tester and extending each out to specific length’s to end up with the precise initial tension required on each spring.  This application had a more challenging specification which was a matter of how it was going to be attached on one end. One end of the application had a very small area for any end hook configuration and that area was not much more than twice the wire diameter.  This made it impossible to design anything other than a pig tail configuration but there still was no room for any type of hook that could be formed from that wire diameter on the pig tail and meet the maximum hook stress allowed before that hook would start to yield. To solve the problem this customer’s engineering department worked together with the Orlando Spring engineering department to develop a ground-in dove tail groove.  The final product resulted in the groove being ground into the pigtail end of that spring and used for the attachment method for that end.

For your next helical extension springs project please reach us on our Contact Us page or call us at (562) 594-8411.