At present, various types of constant-force spring hangers and supports designed and manufactured both in China and abroad use GB1239 cylindrical helical compression springs as the elastic energy-storage element. Because these springs have low stiffness and an ineffective power ratio as high as 65%, the resulting products are bulky and heavy, difficult to manufacture, and inconvenient to install during construction. This is especially true for heavy-load, large-displacement models, where sourcing raw materials and manufacturing the cylindrical helical compression springs is difficult, directly affecting product performance and use. In recent years, combined cylindrical helical compression springs have been adopted domestically and internationally to increase spring stiffness. Although the overall volume and weight of the product series have been reduced to some extent, the inherent problems of high ineffective power, large size, heavy weight, and poor performance have still not been fundamentally solved.
Overview of Shenzhen Leading Spring Co., Ltd.’s constant-force springs. The constant-pressure spring hanger and support is a brand-new product successfully developed to overcome many shortcomings of traditional constant-force spring hanger and support products. It is an upgraded replacement for various constant-force spring hanger and support products. The constant-pressure spring hanger and support series uses an energy-storage assembly composed of GB/T 1972 series disc springs. By applying the variable-arm lever principle within the drive mechanism, it converts small deformation and an approximately linearly varying load into a constant load, and amplifies the small deformation step by step. For the vertical-displacement type constant-pressure spring hanger and support, forces are decomposed and recombined during displacement to achieve vertical displacement of the supported load.
The key component of the brush holder is the constant-pressure spring. The manufacturing process requirements for this spring are relatively strict. The general manufacturing process is as follows:
- Cutting: Cut the stainless-steel strip into lengths according to the drawing dimensions. The strip length should be consistent with the rolling direction of the steel strip. Clean it with industrial alcohol and dry it. No oil or dirt may remain, to avoid affecting the heat-treatment quality.
- Coiling: Coil the cleaned strip onto a mandrel into a spiral form, then place it into a retaining ring. The inner diameter of the retaining ring should be slightly smaller than the spring’s outer diameter, because after heat treatment the spring will rebound slightly when removed. The mandrel diameter used for coiling should also be slightly smaller than the required inner diameter of the spring. To ensure spring quality and service life, the ratio of mandrel diameter to spring strip thickness is recommended to be in the range of 30–50.
- Heat treatment: Place the spring together with the retaining ring into the container of the heat-treatment equipment. First evacuate the container, then raise the temperature to 520 °C and hold for 2.5 hours. Then cool to 50 °C. Open the vacuum container, remove the spring from the retaining ring, reverse the spring, and perform a spring load (pressure) test.