Tension helical springs, also known as extension springs, are comprised of tightly wound helical coils that are designed to operate in the direction of the tension. The spring stretches to a particular length when a force is applied to it. These springs have hooks at both its ends, and are attached to the product. When components attached to the spring are pulled apart from either sides, the spring tries to hold itself together to resist pulling, thereby causing the springing action. When no force is applied, the loops of spring are touching a hook, or loop on the other end. These springs are generally used to deliver return force to the components that are extended.
The coils of spring are wound around the initial tension. The initial tension is a force that holds coils together. Or initial tension is a measure of the initial force applied, and the starting point of the separation of coils. The initial tension can be easily manipulated to meet the desired load requirements of any application. The initial tension of the spring can be easily controlled during the cold coiling process. In this process, the wire is shaped into a spring using an automated coiling machine. Also, the extension springs achieve more flexibility during the cold coiling process than hot coiling.
There are no solid stops to prevent overloading in extension springs. Hence, stress levels are much lower for extension springs than other spring types. Drawbar spring is a typical type of extension spring with an in-built definite stop, which will carry a static load after attaining a maximum length. These springs are ideal for potential overload conditions. One of the most common applications of the drawbar spring is supporting a porch spring.
Various types of hooks or ends are used to attach tension helical springs to the source of attachment. Some common types include German loops, extended hooks, English loops, side hooks, short hooks, straight torsion ends, straight offset, extended hook and screw plug, etc. Also, these springs can be availed in a wide array of dimensions from small sized springs for medical devices to large springs used in off-road machinery. Also, these springs can be availed in metric or inch designs.
Tension helical springs are manufactured from diverse range of materials such as copper alloys, stainless steel, cold drawn steel, titanium alloy, various types of wires, etc. These springs are used for diverse applications such as garage doors, farm machinery, washing devices, trampolines, carburetors, door locks, etc.