Traditional power springs and preloaded springs

source：Qianye Precision time：2022-9-14

Traditional power springs and preloaded power springs are fabricated from spring steel bars to provide torque. Spring steel is a low alloy, medium carbon steel or high carbon steel with a very high yield strength. Objects made of spring steel can return to their original shape despite significant bending or twisting. Power springs use flat (unstressed) steel windings, while pre-stressed power springs use pre-stressed steel to produce a larger range of usable torque than conventional power springs.

During the manufacturing process, the spring is wound into the retaining ring or the customer’s housing (the retaining ring is pictured below). When ready for final installation, carefully install the spring into its housing with the outer end attached to the outer edge and the inner end attached to the mandrel (see photo below). During operation, the housing or mandrel will be fixed while the other component is free to rotate. Depending on the requirements of your specific design, it may be beneficial to use a fixed mandrel/free box or free box/fixed mandrel arrangement.

These springs are typically used to retract the cord or cable of the spool. You might see it in lawn mowers, retractable lanyards, or dog leashes. This is also the type of spring used to drive many mechanical clocks and timers, which is why they are sometimes called “clock springs”. The load provided by the spring increases with the cross-sectional area of the material. The number of turns the spring can provide depends on the space available between the mandrel and the housing and the overall length of the spring. All preloaded power springs need to be preloaded from their free state to reach their effective operating range.

We already know the basics of power springs. Here are the issues to avoid in power spring design:

1. Mandrel and housing

A common problem we see from customer requests is undersized housing and oversized mandrel designs. Small boxes and large mandrels will not result in a qualified power spring design. This can cause various problems. Each time the mandrel and housing rotate relative to each other, the spring material moves. As the spring is wound, the outer coil moves toward the middle, engaging the spring more to provide torque in the opposite direction. As spring unfolds, the outer coil returns to its natural state. The travel of the spring material from outside to inside is critical to delivering torque. If this space is limited, performance suffers.

2. Underestimate weight.

If you plan to use a spring to push, pull, or otherwise push a component that contains a spring, you need to consider the weight of that spring. When you increase the torque and turns required for a power spring, you will inevitably increase the size of the spring. By increasing the size of the spring, you will also design a heavier spring. A heavier spring will require more torque to overcome the added weight. Heavy power springs or very strong springs with limited range of motion due to fewer turns available.

3. Maximum constant torque of the power spring.

A common misconception is that the maximum torque that can be specified for a spring is seen throughout its entire range of rotation (number of turns). The preloaded power spring spring needs several turns, called the acceleration period, to reach the useful range, which we call the “useful turns”. When winding a small number of turns, the spring will provide less torque than the maximum. When discussing your spring design with Qianye Precision, be sure to pay attention to the torque value required within your working range so that we can design a torque curve that suits your needs. The final maximum torque specification may exceed the torque required for the application.

4. Forgetting about installation

When designing spring boxes and mandrels, it can be critical to avoid situations that require “blind” assembly or complex fits between springs and assembled components. This has the potential to slow down the final assembly of the product.

Whether you need standard power springs or customized power springs, you can contact Shenzhen Qianye Precision Metal Co., Ltd. to use professional technology to meet your specified requirements, and design, develop, and proof products according to your needs, so that your products can be found The best solution to meet your application needs.