Design and Function of a Twin Spring or Motor Brush Spring

One of the most unique spring designs produced by Vulcan is called a twin spring.  Its name is derived from the characteristic of having two springs formed from the same strip of stainless steel material.  These custom springs are intended to work together, in unison, doubling the force of a single spring.  Twin springs are a version of a Conforce® spring, providing constant force throughout the travel length.

The area between the two coils is referred to as the saddle area, which is formed to fit over the part or component that is being pushed.  The saddle can also be cut-out to provide access to the component and is best designed when assigned a dimension to fit over that specific part.  It can be located at different heights between the coils for ease of assembly or as an indicator for direction.

Twin springs are used in a wide range of applications where available space is limited and a relatively strong force is required.  Medical devices and surgical mechanisms incorporate this design to push or feed surgical staples in disposable skin staplers.  Electric motors utilize the twin spring to provide a constant force on the carbon brush, extending the life of the motor and increasing reliability and overall quality. These springs are also referred to as electric motor brush springs.

Most twin spring designs are derived from our 3,000 life cycle chart (Chart T).  This chart can be found in our design guide.

This is only one option and higher life cycle designs can be designed and produced.  The length of material contained in each side coil must be long enough to encompass the maximum extension plus a minimum of 1.5 coils remaining.  Additional length is added for the saddle width.

For more information please contact us.

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