- Introduction
A spring is an elastic object that stores mechanical energy. Springs are typically made of spring steel. There are many spring designs. In everyday use, the term often refers to coil springs.
When a conventional spring, without stiffness variability features, is compressed or stretched from its resting position, it exerts an opposing force approximately proportional to its change in length (this approximation breaks down for larger deflections). The rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve. An extension or compression spring’s rate is expressed in units of force divided by distance, for example or N/m or lbf/in. A torsion spring is a spring that works by twisting; when it is twisted about its axis by an angle, it produces a torque proportional to the angle. A torsion spring’s rate is in units of torque divided by angle, such as N·m/rad or ft·lbf/degree. The inverse of spring rate is compliance, that is: if a spring has a rate of 10 N/mm, it has a compliance of 0.1 mm/N. The stiffness (or rate) of springs in parallel is additive, as is the compliance of springs in series.
Springs are made from a variety of elastic materials, the most common being spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication. Some non-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosion resistance and beryllium copper for springs carrying electrical current (because of its low electrical resistance).
2. Tension Spring / Extension Spring
Extension springs are springs attached at both ends to other components. When these components move apart, the spring pulls them back together. You might consider, for example, the springs attached to +the sides of a trampoline. These allow the trampoline give when someone jumps on it but return the trampoline to its original position.
Tension springs are extension springs that can withstand a high amount of tension, meaning that they can withstand the pull of very strong loads. Tension springs can be custom ordered and designed to suit the specific purposes of any load or project.
What is a Tension Springs or Close Coiled Springs?
Tensions springs are designed to create a specific pull force when extended to a particular length. In other words, the amount of pull created by a tension spring can be calibrated to correlate to a particular amount of stretch. Coiled tension springs can be produced to have a certain amount of initial tension that has to be surpassed before the spring will stretch at all. This means that there is either a spring available or that can be custom created for all your engineering needs.
The tensile springs are provided with hooks or loop as shown Figure. These loops may be made by turning whole coil or half of the coil. In a tension spring, large stress concentration is produced at the loop or other attaching device of tension spring. Tension springs are attached to something at both ends, the springs create resistance and build up potential energy. How tight a spring’s coils are determined its initial tension.
In addition to tension, springs can be customized for specific needs because they vary according to body length, extended length, maximum load, finish, material and the types of ends. This means that tension springs are manufactured in a wide array of sizes, tensions and other specifications for a variety of uses, but tension springs are easily customizable for a specific project.
Tension springs are also called as closely coiled springs. The spring wire is coiled so close that the plane containing each turn is nearly at right angles to the axis of the helix and the wire is subjected to torsion. The helix angle of these springs are very small, it’s usually less than 10°. The major stresses produced in helical springs are shear stresses due to twisting. The load applied is parallel to or along the axis of the spring.
What Are Some Common Uses of Tensions Springs in Engineering?
Because they are easily customizable, tension springs have a wide variety of applications:
- Garage doors are controlled by tension springs. These large springs make garage doors relatively easy to open while preventing them from slamming shut.
- Many automobiles use tension springs in a variety of ways, most commonly in carburetors.
- Vise-grip pliers use tension springs. Vise-grip pliers can be locked into a certain position and used much like a vise grip. It is tension springs that keep this grip tight.
- Clothes washers rely on tension springs. Tension springs keep a washer’s tub balanced.
- Farm machinery uses tension springs, much as automobiles do. Tension springs are also used in specialty equipment.
- Medical devices often employ tension springs in a number of ways. Surgical lights, stretchers, and many hand-held medical devices rely on tension springs.
Although this list is basic, it is easy to see that tensions springs are used in the engineering of a variety of products.
Springs and tension springs specifically are an important component in many mechanical systems and, therefore, are essential to the engineering of these systems. The many variables of a tension spring mean that it is relatively easy to find a premade spring to suit the specifications of a specific project. If a premade tension spring is not readily available, custom made tension springs can be created.
3. Wave Spring
This is a Smalley wave spring in an industrial application. The crest-to-crest spring applies force to keep a seal and prevent leakage from one pressurized side of a rotary union to the other.
There are almost as many variations of wave springs as there are spring applications. Although often out of sight, these springs are essential in many motion-control applications—including gear assemblies, actuators, rotary unions, and different kinds of clutches—and consumer applications as well.
As an alternative to other coil springs, wave springs occupy 30 to 50% of the compressed height space of comparable round-wire springs with the same deflection and load specifications. Manufacturers typically make wave springs from a single filament of flat wire formed in continuous precise coils with uniform diameters and waves … most commonly out of 17-7pH hardened stainless steel. Manufacturers make the springs with either plain ends (for wavy) or squared-flat ends (with shim ends)
Wave springs operate as load bearing devices. They take up play and compensate for dimensional variations within assemblies. They can produce a range of forces whereby loads build either gradually or abruptly to reach a predetermined working height. This establishes a precise spring rate in which load is proportional to deflection.
Other wave-spring variations
Some manufacturers offer single, nested, and multi-turn wave springs. A single-turn wave spring with overlapping ends saves axial space so that more space is given for travel. The spring clings to the bore, which saves more radial space. The overlapping ends prevent radial jamming because a circumferential movement is allowed. The spring ends could move against each other so that the specification load at work height is always given.
A wave spring, also known as coiled wave spring or scrowave spring, is a spring made up of pre-hardened flat wire in a process called on-edge coiling (also known as edge-winding). During this process, waves are added to give it a spring effect. The number of turns and waves can be easily adjusted to accommodate stronger force or meet specific requirements.
Advantages
A wave spring has advantages over a traditional coiled spring or a washer
- Axial space can be reduced by up to 50%. As a result, the overall size of the assembly becomes smaller, reducing weight and production cost.
- The load in an axial direction is 100% transferable.
- One multi-turn wave spring replaces multiple stacked wave washers. This eases installation and reduces maintenance times.
- A wave spring can accommodate higher thrust load within the axial space as only the wire size, number of waves, wave height and number of turns need to be adjusted to accommodate higher thrust loads.
Varieties
Multiple types of wave spring are available: Single-turn wave springs include gap single-turn and overlap single-turn type. Multi-turn wave spring types, include shim-end and plain-end types. The nested wave spring incorporates smaller waves within larger ones.
