Constant force springs
Constant force springs provide a steady load across their full range of motion, making them ideal for applications that demand controlled, repeatable movement. Known for their ability to extend with a constant force, they’re widely used in window balance systems, medical devices, and counterbalance mechanisms.
As a trusted global manufacturer, Lesjöfors offers both standard and custom constant force springs. Our engineers tailor dimensions, materials, mounting methods, and finishes to suit each application, delivering durable, precisely crafted components backed by decades of expertise.
Technical specifications
- Thickness:
50 - 800 mm
- Materials:
Stainless steel strip and Spring steel strip
- Load range:
Approximately 7 - 93 kg
- Coiled diameter range:
380 - 1700 mm
What are constant force springs?
Constant force springs are also known as constant load springs. They are made from flat strip material and formed to a set curvature that creates the required pull force for the application. These springs can extend without compromising performance and can be mounted in various ways.
Product range & stock availability
Stock constant force springs
Lesjöfors offers one of the industry’s most comprehensive ranges of stock constant force springs. Choose from various lengths, end details, cycle life, and force ratings to suit your build.
As a leading constant force spring manufacturer, we provide quality and reliability. Our global distribution network provides fast delivery and local support.
Custom constant force springs
Every application is different with unique design needs. Customize your constant force spring by defining the strip width, pull force, and travel, then choose the mounting style to fit your application.
Our custom solutions are built for performance, safety, and long-term durability. Backed by a global engineering and distribution network, you can expect to receive quality parts with fast turnaround times.
Mounting methods for constant force springs
We offer several constant force spring options to suit different applications:
Cavity
A cavity-mounted spring uses a stationary spool for controlled extension, with simplified assembly but increased friction from continuous surface contact.
Conduit
A conduit-style spring mounts on a rotating drum or shaft, enabling smooth extension in compact systems with restricted linear travel.
Back-to-back
Two opposing springs unwind in opposite directions, improving stability, reducing torsion, and supporting long extension requirements with balanced output.
Tandem
Two springs mounted in sequence increase total force and operating range when back-to-back arrangements are not possible.
Laminar
Multiple interwound springs deliver higher force in limited space, ideal for short extensions requiring elevated load capacity.
Leading constant force spring manufacturers
Lesjöfors constant force coil springs are built for precision, safety, and long service life. Each spring uses flat strip material formed to a defined curvature for stable, repeatable force. Production control and careful selection ensure smooth motion in demanding applications. Expert consultation is available for special dimensions and versions.
- Stable, consistent pull from engineered strip geometry
- Flexible installation for partial or full extension
- Quality support and consultation for bespoke projects
How do constant force springs work?
A constant force spring is a pre-stressed flat strip wound into tight coils. As the free end is pulled, the strip uncoils and straightens, while the curve at the coil remains almost unchanged – keeping the pull steady through most of the stroke. The force depends on the strip’s thickness, width, and coil diameter.
These springs operate without performance loss and can be installed for partial or full extension. Typical applications include window balance systems, weight counterbalances in aerospace and defense, and medical devices where smooth, repeatable motion is essential.
Constant force spring materials
Constant force springs must deliver steady pull, even in challenging or hygienic environments, and material choice plays a fundamental role in performance.
At Lesjöfors, we manufacture constant force springs from durable strip materials, formed with precision for stable force and smooth travel. Stainless steel options provide strong corrosion resistance, while tailored finishes improve wear protection in demanding settings. With careful control of strip size and coil design, every spring is built for consistent, dependable performance.
Trusted in medical devices and electronics
Co-creating the future of medical springs for the healthcare industry
Our components support a wide range of medical devices, from autoinjectors to wearable health monitors. Learn how our spring technologies enhance safety, reliability, and performance across medical applications.
Leading the way in spring technology for electronics
From small springs to stampings and pressings, Lesjöfors supplies compact, high-precision components engineered for the demands of the electronics industry. Learn how our solutions support innovation and reliability across the sector.
Related products
Power springsPower springs
Flat spiral power springs for controlled torque and compact retraction, up to 2 mm thick.
Spiral torsion springsSpiral torsion springs
Formed from strip material up to 12 mm thick, for rotational torque applications.
Dynamic gas springsDynamic gas springs
Dynamic gas springs with speed and damping controlled by a cylinder wall slot.
FAQs
Resources and support
- Learn more about Lesjöfors
About Lesjöfors
- Contact our team of experts
Contact and support
- Explore FAQs and advice
FAQs & technical advice