Design of Constant Force Spring in Spool Damper

source：Qianye Precision time：2022-9-14

When powered by a damped constant force spring mounted on the spool, there are several key principles that influence the design of linear motion applications. These principles support robust and consistent performance of products in a variety of applications, including automotive and aircraft interiors, industrial machine components, and many other user interface applications.

The example components shown above will be cited as examples of the various design principles detailed below. This example assembly has a sliding drawer (shown in red) powered by a constant force spring mounted on a spool (spool in green; constant force spring shown in yellow) running within a mounting base (shown in grey), such as a central Console a car. A ratchet or door latch mechanism (not shown) can be implemented to allow the tray to be locked in place with a single press by the user. This example is a typical set of applications used in the automotive industry.

1. Preload spring

When a constant force spring is in its free state, it does not exert any force. As the spring stretches, the spring force rapidly increases from zero to nominal load. However, to avoid including this “accelerated” part of the work envelope, the design can use preloading. An example of preloading is shown in the figure below. Note that although the mechanism is retracted, the depicted spring is extended.

To include preload in the design, ensure that the spring extends a distance equal to the outer diameter of the coil during assembly in order to engage the mounting feature. Therefore, at the beginning of the operating range, the spring has extended far enough to reach the rated load. Note that the picker does not affect the preload length.

2. Spool – install constant force spring

The ideal fitting for a constant force spring on the spool should be tight enough to prevent the spring ring from sliding or spinning on the spool diameter. To ensure a good fit, Qianye Precision usually recommends increasing the spool diameter by 12%. For example, if the nominal spring ID is 1.00″, a 1.12″ spool diameter is recommended.

Spool design also affects ease of assembly. The simplest design for assembly purposes is a plain cylindrical spool with a hole through the shaft for the shaft. The exclusion of flanges, although sometimes not feasible, allows for faster and simpler assembly.

When dealing with the physical enclosure of the components inside the system, be sure to leave enough room for the natural movement of the springs. Not having enough space to limit this movement can result in noise and excessive friction within the system. In cases where the thickness and length combine to form a larger outer diameter (outer diameter), the outer diameter can be used in place of the inner diameter to ensure sufficient space.

3. Constant force spring

Qianye Precision provides standard and customized options to meet the various needs of customers. The image below shows two types of constant force springs from the many options we offer.

Constant force springs can apply a variety of design features to meet space constraints, optimize assembly motion, and effectively reduce part count, thereby reducing material and labor costs. These can be applied along with other principles to achieve assembly designs that meet requirements and exceed expectations.

Shenzhen Qianye Precision Metal Co., Ltd. is designed for customer-specific applications. Using professional technology to meet your specified requirements, we sincerely recommend that customers obtain consulting services from our R&D engineers in the early stage of product introduction and development. Design, develop, and sample products according to your needs, so that your products can find the best solution to meet your application needs.