Do you know what springs are used as stop mechanisms?

We often find that the spring we make is wrongly used as a stop mechanism in the design. This design defect can occur in all types of springs, including constant force spring, constant torque spring and power spring.

For example, consider a simple cable extension product in which the spring retracts the cable into the housing. If the spring is completely wound before the cable is fully deployed, the spring will be used as a stop mechanism. This action will damage the function of the spring and components and should be avoided at all costs. Here are some useful tips when considering the stop mechanism.

Constant Force Spring Application:  Initial designs often show the inner end of a Constant Force Spring attached to its’ spool. This is not necessary.  If the spool is larger than the natural spring diameter, the spring will automatically fit tightly on the spool.  In the case when a screw is attached to the spool, additional concerns arise.  If the spring is pulled tight on the screw,  a hump will result that will not only make the retraction difficult but will cause a fracture point and reduce life cycles. To avoid this, we recommend that the spool maintain 1-1/2 wraps of spring material at the furthest extension.  If these additional wraps are not practical in the design, another method of stopping the rotation is required.

Constant Torque Spring Applications:   This type of motor spring is commonly used to retract a cable or to keep a constant torque rotational force on a spool.  It is extremely important not to use the end of the spring as a stop.  The cable should be fully extended with at least 1-1/2 wraps on of spring material remaining on the storage spool.  Likewise, the spring should be pre-wound so that when the cable is fully retracted there is still one or more wraps on the output spool.  If this is not practical in the design, another method of stopping the rotation is required.  An example of how to accomplish this is shown below.

Power Spring Applications: Similar to the constant torque spring, a power spring, or a pre-stressed power spring, will a retract cable or provide rotational torque.  There are commonly two points of attachment for a power spring: the case and the arbor.  Again, it is necessary to avoid operating the spring near either end.  The spring should be pre-wound at least one full turn and not allowed to unwind past that point.  If not pre-wound the recommended amount, the spring will perform poorly and ultimately fail.  Winding the spring completely will cause constant pulling on the outer end. In-kind, the spring will not function properly or even fail when allowing it to unwind. This may be avoided by stopping rotation a turn or two before the spring is fully wound.

In order to optimize your design, we suggest you contact the engineers of Precisione di Qianye.

 Shenzhen Qianye Precision Metal Co., Ltd. was established in 2006 to supply high-quality stainless steel springs for many fields. Through continuous efforts, it has obtained 20 patent certificates and 4 copyrights of spring equipment software granted by the State Intellectual Property Office, creating an enviable industry influence. The company designs and manufactures a wide range of power springs, constant force springs, constant torque springs, variable force springs and motor brush springs. Qianye works closely with customers to develop customized solutions to meet their personalized needs. In order to provide better services, it has been continuously investing in production technology and supply chain. The company itself is a manufacturer of stainless steel raw materials. Due to the support of raw materials, the production of spring products is not limited by materials; Can develop and manufacture special material requirements; In addition, the delivery time is also greatly shortened. Quality is the top priority. Qianye has passed ISO9001, ISO14001 and national high-tech enterprise certification, and attaches great importance to staff training. Its spirit is to “treat people with sincerity and create things with sincerity”, and strive for excellence.