Compression springs

Introduction

Springs are used in a variety of ways in many industries around the world. The compression spring was one of the first springs to be invented and it has become, by far, one of the most studied type.

Compression springs are open-coiled springs which are wound in a helical shape. They are designed to oppose compression, meaning they can push back when they are pushed on. Helically-wound compression springs are the most common configuration and have an extensive range of uses.

Compression springs are typically positioned over a rod or fitted into a hole. When the spring is subject to pressure caused by weight pressing on its axis, it compresses and becomes shorter. As the spring compresses, it gains a potential to push back in an effort to return to its original position.

History of Use

Compression springs are one of the key components of many pieces of equipment that we use on a daily basis, but their origins date back more than 600 years. Compression springs were first used in door locks, to ensure that only one specific type of key could be used to unlock the door.

It wasn’t long before compression springs were used in the world’s first spring powered clock. This was a success, but it took time before scientists became interested. The most famous of these scientists was Robert Hooke, who developed a law that defined the nature of the compression spring; Hooke’s law.

Hooke’s law states that the force that a spring exerts is directly proportional to its extension. This is important, as it provides an understanding of the amount of force that is required for the spring to compress or extend in a certain application. This changed how springs were used and is the reason they are so common now.

Pacemakers

Small springs are typically used in applications where quality control and minute actions are key. For example, in watchmaking or, in the medical industry. Medical instruments require the most precise objects for them to work efficiently, especially if they are to be used to aid humans. An example of this is springs used in pacemakers.

Oil Rigs

Oil rigs are some of the most robust man-made structures, but they must also endure some of the world’s fiercest and harshest weather conditions. As such, they need to use components that help maintain their shape, no matter what the weather. For underwater piping, garter springs – a specific type of compression spring - are used to ensure no water/oil leaks in/out of the pipes. The reason for this is that garter springs provide an inward radial force, ideal for securing a joint.

Suspension Systems

Springs can provide an extension or a compression, depending on the situation. For example, if a heavy load is applied to a compression spring, it will compress in such a way that is proportional to the force.

Because of this, compression springs can be used to hold heavy loads without affecting another structure. An example of this is in suspension systems; compression springs, as well as important hydraulic components in vehicle suspension systems, help to act as shock absorbers, which is important when driving.

Other Applications

The force produced by compression springs makes them an excellent vessel for storing energy, ideal for numerous applications. They are used in everyday items, such as pens, vehicles, and mobile phones.

Compression springs can be manufactured in any size, with varying degrees of stiffness, known as spring rate.

Larger compression springs with greater spring rate are used in stamping presses in the printing industry and in other appliances, such as lawn mowers. Smaller compression springs are found in medical devices, small electronic devices, precision instruments and tools. They are commonly used in automotive, aerospace, and consumer applications.

Some of the most common applications for these types of springs include the following:

• Valves
• Vehicles
• Door locks
• Railways
• Ballpoint pens
• Firearms
• Wheelchairs
• Turbines
• Engines
• Mining and drilling
• Toys
• Electronics

Materials Used for Compression Springs

Choosing the right material for compression springs is crucial. These materials need to have the ability to flex when a force is applied without breaking. For this reason, not all metals are adequate. Springs need to store energy and release it when required; this amount of energy is dependent on the size and material of the spring.

Some of the most frequently used materials for compression springs include:

• High carbon steels – The most common materials for springs, high carbon steels are suitable for both lower and higher stress applications, due to their tensile strength. Carbon steels can also receive additional protection against corrosion with a pre-galvanised coating.
• Stainless steels – When the application calls for a high degree of corrosion and heat resistance, stainless steel is often the solution. These alloys come in different grades, suitable for a variety of uses.
• Alloy steels – Chrome vanadium and chrome silicon are alloy steels ideal for chock loads, like engine valve springs.
• Non-ferrous alloys – Cold-drawn copper alloys are the materials of choice when excellent electrical conductivity, high temperatures and high resistance to corrosion are a concern.
• Hot temperature alloys – Materials such as nickel and chromium alloys are suitable for applications that require good resistance to corrosion at high temperatures.

Strength and Stress

Stress is determined by a spring’s dimensions and its load bearing deflection requirements. The type of stress on a coil is referred to as torsion. As the coil is compressed, the surface of the coil exposed to pressure is subject to the greatest stress but, as the spring deflects, the rest of the spring takes on more stress. This is known as a range of operating stress.

Types and Uses

Conical, hourglass, and barrel-shaped are all types of compression springs used in applications requiring low solid, increased stability, or resistance to surging. These types of spring have a small solid height, designed so each active coil fits within the next coil, resulting in the solid height being equal to one or two thickness of wire. This is useful where the solid height is limited.

Variable rate springs offer a constant uniform pitch and have an increasing force rate. The larger coils gradually begin to bottom as a force is applied.

Being the most common type of spring, the most common consumers are engineering companies, the defence industry, and vehicles.

Related articles on Designing Buildings Wiki

• Compression vs Wave Springs.
• Die springs.
• E-spring.
• Flat springs.
• How door locks work.
• Key qualities of springs.
• Spring materials.
• The importance of gas springs.
• Tension springs v torsion springs.
• Using springs in construction to prevent disaster.
• Large and Hot Coiled Compression Springs
• The Difference Between Tension and Torsion Springs
• The Multiple Uses of Compression Springs
• The Uses of Wire Forms Within the Construction Industry
• Types of spring.

--European Springs and Pressings Ltd 15:24, 18 Oct 2017 (BST)