Power springs

The traditional form of the strip spring is the power spring.  

The special feature of the MAXIMO power spring is that the combination of winding forward and then back increases the power density, making maximum use of the available material properties.

Spring characteristics

The power spring has a rising torque characteristic curve.
Figure below shows a typical spring characteristic curve for a power spring.



The spring characteristic can be divided into three ranges: pretension (initial tension), working range and reserve.

This torque is required to wind the spring up (blue line) - mechanical energy introduced.

The torque returned by the spring (orange line) - mechanical energy recovered.

The energy lost by the spring due to friction.  
This is shown in the diagram by the difference between the extraction line and the retraction line.  
The hysteresis defines the efficiency of the power spring during operation.

Pretension (initial tension): 
In this range, the power spring shows a steep increase in torque. The power spring should not be operated in the steep rise range, as higher bending stresses will have a considerable negative impact on the service life of the spring.

Working range:
The working range is the middle range of the characteristic curve. In this range, the rise in the torque curve is even, with an almost linear characteristic.

The number of reserve revolutions serves to protect the spring. If the spring is wound up too far or up to the block, it may be damaged.

A range of measures can be used to influence the spring characteristics.
In addition to the spring dimension itself, lubrication and a spring support also have a positive impact on the spring characteristics.