FAQ
Frequently Asked Questions about Constant Force Springs
- What is a ‘Constant Force Spring’?
- How do I apply these springs?
- What is a typical application for a Constant Force Spring?
- What are the advantages of Constant Force Springs?
- What materials is constant force springs manufactured from?
- Do constant force springs have good environmental resistance?
- What is the lowest temperature a constant force spring can operate in?
- What is the highest temperature a constant force spring can operate in?
- What is the maximum strength from a constant force spring?
- What can I do to achieve higher forces?
- Is a standard range of springs available?
- Can I get springs manufactured to suit my particular application?
- How do I increase fatigue life?
- What can I do to get a higher life and higher load in a tight space?
- What do I need to know to specify a Constant Force Spring?
- How do I mount the spring?
- Are the springs easy to handle?
- Do the springs have a shelf life?
- What endforms are available?
- Can you make springs with Variable force?
1 What is a ‘Constant Force Spring’?
A constant force spring is produced from flat steel strip, it has uniform cross section throughout its length and is coiled to a constant diameter, when extended the spring will recoil with constant power.Springs from 2mm wide up to 100mm wide can be produced with thickness from 0.05mm to in excess of 0.7mm.
2 How do I apply these springs?
Springs can simply be extended to exert a constant force; reverse wound onto a drum as a spring motor to create a constant torque or where space is limited centrally wound as a power spring to create near constant torque.3 What is a typical application for a Constant Force Spring?
Extended springs are used for counterbalancing or for feeding components, staples in a staple gun, items in a point of sale display or applying constant loads to a commutator brush etc. Motor springs are used for cable retraction and power generation etc. Power springs are used for retracting seat belt webbing, tape measures and dog leads etc as well as in seat recliner and window regulator mechanisms.4 What are the advantages of Constant Force Springs?
Apart from exerting a constant force which means consistent performance, the springs are much easier to handle than a conventional wire spring, they can be extended up to 50 times there original length making them very easy to package5 What materials is constant force springs manufactured from?
Stainless Steel (301S21) is commonly used for many applications as well as a high carbon material that has been patented (a specialised heat treatment process)6 Do constant force springs have good environmental resistance?
Stainless steel springs have very good resistance in general atmospheric conditions but may be adversely affected when exposed to certain chemicals which may lead to hydrogen embrittlement and premature fatigue failure. Carbon steel springs should be protected with a suitable rust inhibitor depending on the application. For more details please visit www.spiroflex.com or contact the Spiroflex sales department.7 What is the lowest temperature a constant force spring can operate in?
Sprioflex products are used on Satellite applications where temperatures fall below –40 Degrees without any detrimental affect on product performance.8 What is the highest temperature a constant force spring can operate in?
Temperatures in excess of 150 DegC may cause the springs to relax and lose power; it is recommended that applications where the springs may be subject to elevated temperatures be tested thoroughly to confirm the suitability of this technology before application.9 What is the maximum strength from a constant force spring?
Spiroflex can produce standard range products with a force of 150N or torque of 10NM; special design springs could be produced with double these forces.10 What can I do to achieve higher forces?
The power is proportional to the cross section of the material and the diameter to which it has been coiled; coiling a strip to tighter diameter will increase force.11 Is a standard range of springs available?
Yes, visit www.spirioflex.com for details or call the Spiroflex sales department for details. Standard range springs are generally available from stock.12 Can I get springs manufactured to suit my particular application?
Yes, Spiroflex will design and produce special products from a production run of one to a batch of several million.13 How do I increase fatigue life?
The fatigue life is related to the thickness of the strip and the diameter to which it has been coiled, typical fatigue life will range from 5,000 to 100,000 cycles depending on spring design.Coiling a strip to a larger diameter will increase life, this needs to be balanced with the effect on force and the Spiroflex sales team can help you design a suitable component.
