Variable force springs, also known as constant force springs, are a type of spring that provides a constant force throughout its range of motion. These springs are commonly used in applications such as clock mechanisms, retractable safety belts, and window shades. In this article, we will explore how variable force springs work, their construction, and the various applications in which they are used.
Construction of Variable Force Springs
Variable force springs are typically constructed using a flat ribbon of spring steel. The steel is wound around a mandrel and then heat-treated to create a helical spring. The spring is then mounted onto a reel or drum, which allows it to extend and retract as needed. A common feature of variable force springs is that they have a curved shape, which allows them to provide a constant force throughout their range of motion.
How Variable Force Springs Work
Variable force springs work by utilizing the inherent properties of the spring steel. When a variable force spring is extended, the spring steel ribbon is wound around the drum or reel. As the spring extends, the steel ribbon unwinds from the drum, and the spring force increases. The opposite occurs when the spring is compressed; the steel ribbon winds around the drum, and the spring force decreases.
The curved shape of variable force springs allows them to maintain a constant force throughout their range of motion. This is because the curvature of the spring steel ribbon ensures that the force is distributed evenly across the entire length of the spring. As a result, the spring is able to provide a consistent amount of force regardless of its extension or compression.
Applications of Variable Force Springs
Variable force springs are used in a wide range of applications across various industries. One common application is in clock mechanisms. Variable force springs are used to provide the torque needed to wind the clock\’s mainspring. They are also used in retractable safety belts and window shades to provide a constant force throughout their range of motion.
Variable force springs are also used in the medical industry. They are used in surgical instruments to provide a constant amount of force when retracting tissue. Additionally, they are used in orthodontic appliances to provide the necessary force to move teeth into their correct position.
Conclusion
Variable force springs are a versatile type of spring that provides a constant force throughout their range of motion. Their construction using a flat ribbon of spring steel allows them to be wound onto a reel or drum, providing the necessary extension and retraction. Their curved shape ensures that the force is distributed evenly, maintaining a constant force regardless of their extension or compression. As a result, they are used in a wide range of applications across various industries.
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