What is a Spring? (Mechanical Spring)
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.
A metal wire spring that functions in a spring mechanism that compresses, extends, rotates, slides, pulls, and exerts force when an equal or greater force is applied. A spring mechanism can exert pressure, rotational force, or pulling strength in a variety of ways.
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.
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).
What is the function of Spring?
The Function of Springs are:
- To absorb the shock or vibration as in-car springs, railway buffers, etc.
- To measure the forces in a spring balance.
- Apply forces in brakes and clutches to stop the vehicles.
- Spring is also used to store the energy as in clocks, toys, etc.
- Spring can control the motion of cams and followers by maintaining contact between two elements.
Types of Springs
The most common spring types include:
- Compression Springs
- Extension Springs
- Torsion Springs
- Constant Force Springs
- Belleville Springs
- Drawbar Springs
- Volute Springs
- Garter Springs
- Flat Springs
- Gas Springs
- Air Springs
1. Compression Springs
A compression spring is an open-coil helical spring that offers resistance to a compressive force applied axially. They are usually coiled at a constant diameter, though they can be coiled in other needed forms such as conical, concave (barrel), convex (hourglass), or various combinations of these.
Compression springs are used to resist force and/or store energy, depending upon the application
2. Extension Springs
Extension springs absorb and store energy as well as create a resistance to a pulling force. These springs are normally attached at both ends to other components and when these components move apart, the spring tries to bring them back together again. It is the initial tension that determines how tightly together the spring is coiled.
This initial tension can be manipulated to achieve the load requirements of a particular application. Designs normally have hooks, eyes, or other interface geometry at the ends which attach to the opposing components. They are frequently used to provide a return force to components that extend in an actuated position.
3. Torsion Springs
Torsion springs are helical springs that exert a torque or rotary force. The ends of a torsion spring are attached to other components, and when those components rotate around the center of the spring, the spring tries to push them back to their original position.
Although the name implies otherwise, torsion springs are subjected to bending stress rather than torsional stress. They can store and release angular energy or statically hold a mechanism in place by deflecting the legs about the body centerline axis.
This type of spring is normally a closed wound but can have a pitch to reduce friction between the coils. They offer resistance to twist or rotationally applied force. Depending on the application, torsion springs can be designed to work in a clockwise or counter-clockwise rotation, thus determining the direction of the wind.
4. Constant Force Springs
The extension type of Constant Force Spring represents the most basic, yet most versatile, type of constant force spring. It is a pre-stressed flat strip of spring material that is formed into virtually constant radius coils around itself or on a drum.
When the strip is extended (deflected) the inherent stress resists the loading force, the same as a common extension spring, but at a nearly constant (zero) rate. A constant torque is obtained when the outer end of the spring is attached to another spool and caused to wind in either the reverse or the same direction as it is originally wound.
The full rated load of the spring is reached after being deflected to a length equal to 1.25 times its diameter. Thereafter, it maintains a relatively constant force regardless of extension length. The load is basically determined by the thickness and width of the material and the diameter of the coil.
5. Belleville Springs
Belleville springs, or washers, resemble a slightly tapered disc, and for this reason, are also known as disc springs. They are used in conjunction with fasteners like bolts for pre-tensioning purposes. Typically, a bolt is inserted in a Belleville spring and then attached to a substrate.
Belleville springs are available in a variety of material options, including 17-7 PH stainless steel, 301 stainless steel, beryllium copper, H13, phosphor bronze, ZC plated, and ZY plated.
6. Drawbar Springs
Drawbar springs are excellent for use in potential overload situations and offer a built-in safety feature that, upon fracturing, will continue to carry a static load. In a drawbar spring, the load is applied at the ends of long steel loops which pass through the spring’s center and are hooked around the opposite end, thus compressing the spring upon loading. A common application of the drawbar spring is used when supporting a porch swing.
7. Volute Springs
A volute spring is a compression spring in the form of a cone (somewhat like a classical volute). Under compression, the coils slide past each other, thus enabling the spring to be compressed to a very short length in comparison with what would be possible with a more conventional helical spring.
The shape of the initial spring steel (or other material) is a “V”, with the ends of the V at either end of the wound spring (which forms a distorted cylinder, of wider diameter at the center), and the bottom point of the V at the center.
Such springs can frequently be found as a component of garden secateurs. Short posts anchored in each side of the handles and inserted into each narrow end of the spring, keep the spring in position.
8. Garter Springs
A garter spring is a coiled steel spring that is connected at each end to create a circular shape and is used in oil seals, shaft seals, belt-driven motors, and electrical connectors. Compression garter springs exert outward radial forces, while extension garter springs exert inward radial forces.
The manufacturing process is not much different from the creation of regular coiled springs, with the addition of joining the ends together. Like most other springs, garter springs are typically manufactured with either carbon steel or stainless steel wire.
9. Flat Springs
Flat springs are flat strips of material that, when deflected by an external load, store and release energy. These types of springs are small, stamped metal components that function as a spring by controlling deflection within small or restricted spaces.
Flat springs are made from strip stock bent into shape. Spring materials range from high-carbon steels to copper alloys to titanium to high-temperature alloys, depending on the application.
10. Gas Springs
A gas spring is a type of spring that, unlike a typical mechanical spring that relies on elastic deformation, uses compressed gas contained within an enclosed cylinder sealed by a sliding piston to pneumatically store potential energy and withstand the external force applied parallel to the direction of the piston shaft.
Common applications include automobiles (where they are incorporated into the design of struts that support the weight of the hatchback tailgate while they are open) and office chairs. They are also used in furniture, medical and aerospace applications.
Much larger gas springs are found in machines that are used in industrial manufacturing (the press tooling industry), where the forces they are required to exert often range from 2500N to 400,000N (forty tonnes).
11. Air Springs
Air springs are air pressurized bellow or bladder type devices of a variety of shapes and sizes and are used for providing actuation, shock absorption, and vibration isolation. Key specifications include the intended application, type, style, physical dimensions, mounting type, as well as features.
Air springs are used primarily in machine applications such as vehicle suspensions for shock absorption and as machine mounts for vibration isolation. They are available in a variety of types and sizes based on load requirements and application.
Other uses include lifting, compressing, tilting, etc. Air springs used for vibration isolation are also known as air cushions.
Application of Springs
- To apply forces and control motion, as in brakes and clutches.
- Measuring forces, as in the case of a spring balance.
- Storing energy, as in the case of springs used in watches and toys.
- Reducing the effect of shocks and vibrations in vehicles and machine foundations.
Advantages of Spring
- Mostly we use spring to avoid vibration because the sudden vibrations in a car may effect the human and it cause vomiting.
- To avoid vibrations in machines.
- To apply forces and control motion in clutches and brakes
- It helps in storing energy as in case of watches and toys.
- It has high durability.
- Spring has the ability of stored energy inside it.
- It is easy to design and cheaper to produce.
- Spring is a maintenance-free device.
Disadvantages of Spring
- If the deflection of the spring exceeds some critical value then the spring will buckle.
- It is difficult to replace the spring.
- Once the spring is damaged it is difficult to repair.