Design and manufacture a complete set of constant force springs for a variety of applications in almost all industries, from medical care to aerospace and general household products. The constant force spring is different from the traditional spiral wound spring. They are made of pre tensioned high-yield metal strips (usually stainless steel) rather than wires.
Constant force springs are classified as “tension springs”. When winding, the metal strip resists uncoiling with nearly constant resistance. When extended, the internal stress of the metal resists any load force at a nearly constant rate. Once the spring extends to a length of 1.25 times its diameter, it reaches full load and produces a nearly constant force. According to the size of the spring and the load it supports, the fatigue life cycle of the constant force spring is between 2500 and 1000000 times.
Constant force springs are commonly used in automotive engineering, aerospace engineering, medical and retail. Some common applications are: Cable retractor, motor, spacecraft, fitness equipment, door closer, hose retriever, nuclear magnetic resonance scanner, X-ray machine, point of sale display, toys, furniture accessories, retractable tape measure or dog line, retractable vacuum cleaner line, etc.
Material selection is important, as is the thickness and width of the metal strip. The most commonly used metal is grade 301 stainless steel because it can make consistent high-quality and strong constant force springs. Other materials are available, such as high carbon steel, Inconel, etc., which may be more suitable for springs that need to resist high load forces.
To select or manufacture the correct spring, you must know the approximate initial force or load to overcome when the spring reaches the “constant force” stage. The higher the initial load, the larger the spring diameter you need.
In addition, the spring end details need to be designed to be fixed or connected to the components that will curl and unfold.
To determine the size of a constant force spring, certain guidelines must be followed. To calculate the total length of the spring strip, the following formula can be used: total length = circumference wound on the drum + initial deflection + maximum working deflection (ID x π x 1.5) + I F + W F.
External factors will limit the life cycle of constant force spring.
For example, debris or particles can clog the system, slowing or hindering coiling and deployment. If the spring mechanism is open to the element or is often in contact with corrosive fluid, corrosion may occur, affecting the movement of the spring. Extreme temperatures can also affect spring operation. This may be of particular concern in aerospace engineering.
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