Constant Force Spring Explanation – Part 1

What differentiates the constant force spring from the conventional extension and compression (round wire) spring? Hooke’s Law states that the extension of a spring is directly proportional to the load applied to it. Therefore, the further an extension spring is extended, the greater the force.

The graph below shows that constant force springs are not bound by Hooke’s Law, and they provide a constant force over the length of travel. We can categorize the springs that we produce as:

  • Constant Force
  • Gradient Positive
  • Gradient Negative

constant force spring comparison chart

In this blog, we’re focusing on the standard constant force spring to give you better insight into its advantages and unique characteristics.

How Are Constant Force Springs Made?

On extremely long designs, there’s a mechanical advantage to the changing diameters, and the force increases as the spring extends. However, this amount of increase is minimal compared to extension springs and can be negated if necessary.

The life cycle of a constant force spring is set by the diameter of a certain thickness of the steel. See our previous blog concerning life cycles for more information on the subject.

Understand Different Types of Constant Force Springs

A constant force spring can be utilized to apply a linear extension force. At Vulcan Spring, our trademark name for this type of spring is Conforce®. When discussing a linear extension, we specify the force in lbs. (Kg, N, etc.) of pull force. This spring is used to push or pull one or more objects, or to counterbalance an object throughout its travel length.

An alternate version of this spring is called a constant torque spring. Our trademark name for this type of spring is Contorque®. When discussing the torque spring, we work in inch-lbs. (NM etc.) of torque. This spring is wound onto an output spool providing rotational torque and is commonly used to wind up cable, provide torque in toys, and other applications requiring rotational torque.

By designing a constant force spring into a product, the engineer can save space and provide for the correct amount of force required for the design.

Your Complete Source for Custom Springs

Contact us with any questions you have about our extensive custom spring solutions. Our experienced team can design and manufacture the right springs for all types of commercial, industrial, and manufacturing applications. We partner with engineers, contract manufacturers, and designers to produce springs for medical equipment, retail displays, and residential and commercial windows. If you already know what types of springs you need, head over to our online store.

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