CSS Constant Tension Spring

Concord Shading Systems (CSS) manufactures a proprietary Constant Tension Spring Systems for custom window shading applications. As window shade manufacturing becomes more sophisticated and shade technology gravitates towards cordless operation CSS’ reputation of innovation allows us to deliver spring assemblies that simply work the first time and for a long time with some of the highest life cycles in the industry.

CSS utilizes standard stainless steel springs for all of our Constant Tension Spring Systems. CSS manufactures constant force spring systems, also called constant tension springs. CSS constant force springs:

  • Offer high force output with very small space requirements
  • Provide long linear reach with minimal force buildup
  • Store power indefinitely when extended

Constant force springs are typically specified and engineered with the following in mind:

  • Materials – Type 301 stainless steel typically produces the best part at the lowest cost. High-carbon steel, Inconel and other materials are suggested when required.
  • Life in total estimated number of cycles – the life of the constant force spring is very predictable. A life cycle is an extension and retraction of either the whole spring or any portion of it. A low estimate of the life will lead to early failure. A high estimate (the more common error) makes the spring larger and more expensive than is necessary.
  • Force requirements – the force of the spring should be equal to the requirement of the application. The normal tolerance for a constant force spring is +/-10% Available space – For any force value there are several material thickness and width combinations that can be used. The natural coil diameter depends upon the thickness, life, and force required. A constant force spring does not extend tangent of the coiled body of the spring.
  • Our cord is a super-strong fiber made from Ultra-High Molecular Weight Polyethylene; which is 15 times stronger than steel and up to 40% stronger than aramid fibers.  The cord is also resistant to moisture, UV light and chemicals.

Concord Shading offers constant tension springs for order in the following tensions:

PART NUMBER Force – LB. Force – kg. Cord travel in Inch Cord travel in cm. Cycles
CS/W6.1-300 3.5 LB 1.6 kg. 170 “ 430 cm. 9000
CS/W6.1-400 3.5 1.6 kg. 220 “ 560 cm. 9000
CS/V8.1-300 7 LB 3.2 kg. 170 “ 430 cm. 4000
CS/V8.1-400 7 LB 3.2 kg. 200 “ 510 cm. 4000
CS/W8.1-300 5 LB 2.3 kg. 170 “ 430 cm. 6000
CS/W8.1-400 5 LB 2.3 kg. 200 “ 510 cm. 6000
CS/X6.1-300 2.5 LB 1.2 kg. 170 “ 430 cm. 12000
½” springs
CS/W6.05-300 2.5 LB 1.2 kg. 170 “ 430 cm. 9000
* all pull force readings are approximate
* Cord travel can be increased with modification, up to 280 inches . or 710 cm.