Definition
As the name suggests, the fixed force spring is a spring that can maintain a constant elasticity in the corresponding stroke, also called a constant force spring, and its use is linear motion, generally using its resilience. English name: constant spring.
Advantages: Compared with ordinary compression or stretching spring, its elasticity is very constant, and it can output the elasticity close to the straight line, ensuring that the product will not change because of the change of the elasticity during use. In the narrow and long space, the space can be reduced as much as possible, which improves the possibility for the beautiful design of the product. The graph is as follows:
Disadvantages: Because it is used in a straight line, its space must require a certain length to play its role, relative to the scroll spring, its life is significantly shorter, generally only 2,000 to 5,000 times.
The application of fixed force spring
1, lifting fan
Compared with the old design that relies on screws to fix the fan head, it can be easily lifted and lowered after using the fixed force spring, and it can be easily fixed in the halfway position, making the fan more beautiful and convenient. At present, this kind of design has been sold abroad for many years, and the design is quite mature.
2, liquid crystal display
In the process of the display getting larger and higher requirements, the old display can only adjust the Angle of the front and back obviously can not meet the requirements, and now the display can rotate 360°, can tilt back and forth, can slide up and down, almost everything. The function of sliding up and down and stopping at any point is achieved by using the fixed force spring. Through its balanced elasticity, it can hold the display head stably in any position to prevent sliding. At present, the world's PC giants all use this new design, so that it is more and more perfect in function.
3, sliding doors and Windows
In the European and American markets, sliding doors and Windows have been popular, and its upward sliding force is from the fixed force spring, through the resilience of a set of fixed force springs on both sides, can make glass doors and Windows easily slide upward, reducing its heavy resistance.
4. Supermarket vending racks
In order to enable guests to see the goods on the shelf are very neat and beautiful, often need salespeople to organize the shelves, now in some high-end shopping malls, began to use automatic push shelves, as long as the goods in front of the out, the goods behind the automatic push, that is to ensure the beautiful and tidy, but also save time, And to achieve this function is the use of fixed force spring vending rack.
5, motor carbon brush pressing device
Since the ordinary carbon brush device uses a compression spring, the compression spring gradually attenuates when it is used to the end, so that the carbon brush can not press the rotating shaft with a constant force, reducing the performance of the motor, and the fixed force spring with a double curl design can always give the carbon brush with a constant elasticity from beginning to end, so that the performance of the motor is always stable.
Fixed force spring material
Selection SUS301 series is the preferred material for fixed force spring, this material has high hardness, high tensile strength, smooth surface, good rust resistance, easy processing on the side...... Making this material almost the best choice for fixed force springs. Its hardness can reach about Hv600 (after low temperature heat treatment), the tensile strength can reach more than 1665Mpa, the nickel content is between 6.0 and 8.0, to ensure its good anti-rust performance.
Of course, if the use of the environment is more harsh, in the ultra-high temperature or ultra-low temperature environment, you can also choose SJ101 series of wide temperature and high strength constant elastic alloy, at high temperatures can still maintain high strength, constant elasticity, low expansion coefficient. However, its material unit price is expensive, and it is generally not used.
Fixed force spring design
Fixed force spring design is generally considered from two places:
1. Performance
The two most important properties, one is the elastic value, the other is the life. The thicker the general material, the wider the width, the higher the elasticity. In the same size of the material, the smaller the crimp inner diameter, the higher the elasticity, and vice versa. On the contrary, under the same production conditions, the thinner the material, the better its life, in the same size of the material, the smaller the crimp inner diameter, the shorter the life, and vice versa.
2. Installation space
Generally according to the installation space to set the outer diameter value of the fixed force spring, sometimes in the case of the use of the shaft, but also take into account the inner diameter value, the general fixed force spring outer diameter can not be greater than the installation space, otherwise it will produce friction, affect the use of.