Closed coil spring

Types of Closed Coil Spring

• Compression Springs

  The most common type of closed coil spring is the compression spring. Closed coil compression springs are designed to receive axial loads and compress when weight or tension is applied. Such coil springs are widely used in applications like machine parts, in mattresses or cushion seats, automotive suspensions, and even in electronic devices such as TV remote controls and some batteries.

• Tension (Extension) Springs

  A closed coil tension spring is similar to a compression spring, except that it is designed to withstand tensile or pulling forces. These springs are positioned with their coils tightly closed to prevent them from unwinding. As a result, closed coil extension springs stretch and try to return to their original length. Tension springs are commonly employed in mechanisms that require pulling forces. The applications include spring-loaded doors, mechanical actuators, or catches.

• Torsion Springs

  Torsion springs store and release rotational energy, unlike tension and compression springs. These springs have coils that are not just closed but also shaped to impart torque. Torsion springs are twisted along their axis. When the coil unwinds or twists back, the spring exerts a torsional force. In many cases, the coils of a torsion spring are closed to prevent wire from slipping off during application. Such springs are usually used in clothespins, door hinges, and other mechanical locks and levers.

• Flat Springs

  Unlike helical or coiled designs, flat springs take a different shape, although some designs feature closed coils. These springs are mainly in the form of a flat strip or a ribbon-like coil. Though some flat springs have coils that are closed at the ends, which gives rise to a helical design but in a flatter format. In this regard, the closed end provides some features of a helical spring and some features of a flat spring. Leaf suspension systems and certain electronic components, such as pressure switches, commonly use flat springs.

What Makes a Closed Coil Spring Durable

• Material Composition

  Closed coil springs are usually manufactured from high-strength steel alloys such as stainless, carbon, or chrome-silicon steel, as well as titanium and aluminum alloys, for durability. Such a composition allows them to endure repeated loading cycles without any permanent deformation. Sometimes, tension or extension springs are made from non-ferrous metals to prevent rust and corrosion.

• Coil Shape and Design

  The design of closed coil springs, especially the coils, helps make the spring more durable. Springs with a more significant diameter or broader coils have better flexibility and carrying capacity, which makes them more durable. Conversely, very tight coils may lead to metal fatigue sooner. Moreover, tension springs enclose their coils to prevent uncoiling.

• Heat Treatment Processes

  Heat treatment processes enhance the strength of the materials used in closed coil springs. The common processes include quenching and tempering and annealing.

• Stress Distribution

  Typically, closed coil springs are designed to have the ends of their coils closed and ground flat for even load distribution. This design minimizes the concentration of stress at specific points. Furthermore, the grinding of the coil ends allows for proper seating within the intended fixtures. As such, this reduces the chances of incorrect positioning and the resulting unnecessary misalignment. This coherent design reduces mechanical wear and tear and increases durability.

• Corrosion Resistance

  Closed coil springs that are corrosion and rust-resistant have increased durability. This is because corrosion degrades the integrity of the metal, thus weakening the spring. Stainless steel, titanium, and surface-treated coils provide longer lasting durability, especially in adverse environments.

• Spring Relaxation

  Over time, conventional springs lose their ability to return to their original shapes. However, closed coil springs manufactured with anti-relaxation features can endure long hours of load without permanently deforming the spring material.

Industrial Applications of a Closed Coil Spring

• Automotive Industry

  Springs are extensively used in the automotive industry for suspension systems, shock absorbers, and other components. Several closed coil springs, such as compression springs and extension coil springs, are often incorporated into car seats to offer needed comfort.

• Aerospace Applications

  Aerospace Engineering incorporates springs in actuators, landing gears, and other critical mechanisms that require lightweight yet robust components. In such delicate industries, they mostly use titanium or heat-treated steel springs that can endure extreme temperature variations and high mechanical loads.

• Machinery and Equipment

  Springs find wider usage in heavy machinery and industrial equipment such as closed coil compression springs in control valves, sheaves, pulleys, and so on. In this and other mechanical engineering fields, springs are critical elements in maintaining equilibrium and absorbing shocks.

• Electronics and Consumer Goods

  Closed coil spring ingenuity is not limited to heavy industrial and automobile space. Closed coil springs, especially tension springs, are widely used in everyday life electronics such as remote controls, internal switches, and more. Additionally, cloths pegs and some mechanical keyboards use these springs. Moreover, compression springs are the main feature in mattresses to provide comfort and support.

• Industrial Tools

  Divers industrial tools, particularly hand tools like pliers, clamps, and wedges, take advantage of closed coil springs to return the tools to an open position after use. Moreover, power tools like nail guns and drills have integrated springs in the mechanisms that drive the bits or nails.

• Medical Devices

  Pneumatic and hydraulic actuators, as well as pressure and other medical devices, commonly incorporate closed coil springs due to their dependability. In medical equipment, such as the mechanical components and instruments used in diagnostic and therapeutic procedures, these springs are critical in maintaining precision and reliability.

• Seismic Protection

  As mentioned, closed coil springs, particularly the coil spring dampers, are applied in seismic protection applications. Suspension systems in buildings and bridges are equipped with these springs to absorb ground motion energy during an earthquake. This application, however, requires high durability and elasticity to minimize loads on structures during seismic events.

How to Choose a Closed Coil Spring

• Load Capacity

  The first consideration when choosing a closed coil spring is the amount of load it has to carry at any given time. Compression springs are meant to bear loads, while extension springs are meant to pull loads. Torsion springs, on the other hand, are mostly for rotational loads. Therefore, knowing the nature of the load is critical in narrowing down to the appropriate spring.

• Spring Rate

  Spring constant or resides (usually represented by ‘k’) is defined as the distance a coil spring will compress or stretch per unit load. In an extension coil spring, it refers to how much it will stretch when a force is applied. In a compression spring, it describes how much it will compress when a weight is added. Simply put, spring rate is used to measure the stiffness of a given coil spring.

• Travel Distance

  Travel distance is the total movement or compression a spring undergoes when load is applied. Different applications have different requirements. Some need longer travel distance coil springs, while others need shorter ones. For example, car suspension or mattress coils require longer distances since the load in those applications is dynamic. In contrast, travel distance requirements in electronics and precision tools are much shorter.

• Material and Environment

  A closed coil spring may be subjected to varying environmental conditions, simultaneously as mechanical loads. Therefore, the material used to make the spring should be able to withstand all those conditions. For instance, if the application will be used outdoors or under conditions that may result in corrosion, use a closed coil tension spring made of stainless steel or surface-treated alloy steel. Additionally, in industries like aerospace, springs are made of titanium alloys due to their non-magnetic properties, as well as being lightweight but strong.

• Space Constraints

  Some applications have very limited spaces for components to fit. Hence, in such applications, the only consideration should be the coil diameter and length of the spring. Even with these limitations, do not compromise on the above-stated measures. Adequate load capacity, suitable materials and environmental resistance, and appropriate spring rate and travel distance should all be put into consideration, even with the limited space.

• Cost and Manufacturing Precision

  The type of material, design, and overall properties of the spring invariably affect the price. So will the method employed to manufacture the spring. Precision-engineered springs are more costly but offer better performance and consistency than less precise or mass-produced ones. In applications where the performance of the spring is critical, the cost may not be a hindrance, especially if safety is at stake. However, in applications where the utilization is one-off or for low-load mechanics, one might prefer cost-effective alternatives as long as they satisfy the minimum functional demands.

Q and A

Q1: How does a closed coil spring differ from an open coil spring?

A1: As its name suggests, a closed coil spring has coils that are closely wound together. This means that the last coil of the spring is tightly wound to give it a closure. An open coil spring, on the other hand, has coils that are loosely wound. This means that the coils do not touch each other. Because of this distinction, closed coil springs are used in tension, torsion, and compression, while open coil springs are used in applications requiring low springing forces.

Q2: How is a closed coil compression spring made?

Production of a closed coil compression spring begins with coiling wire around a cylindrical tool to form the coil shape. The ambient air containing oxygen and other gases is pumped into the coil to provide the needed pressure that will keep the spring in the form of a coil as it solidifies. Once the coil has been shaped and solidified, the ends are trimmed, ground, and sometimes closed to give it a good even surface. The spring is then heat-treated, possibly coated, and finally inspected for quality before being packed.

Q3: What are the signs that a closed coil spring is bad?

Some of the common ways to tell if a spring is bad include a visible distortion in the shape of the spring, such as bent coils, gaps between coils, or wrong spring height. Others are broken or fractured wires, corrosion and rust if made with materials that are prone to rust, exerting weaker forces than normal, or making abnormal noises when in use. Furthermore, excessive wear on the components around the spring, abnormal oscillation and bouncing, or vehicle tilting to one side, among others, are also strong indicators that a spring is bad.

Q4: What are the advantages of a closed coil spring?

Some of the advantages of closed coil springs include efficient energy storage and release, giving linear motion to mechanical processes. In automotive and industrial contexts, they absorb shocks, reduce vibrations, maintain ride height, and improve handling, providing stability and support in such applications. Because of closure in tension or extension springs, they fix the position of the coils and enable easier installation, thus making it less complicated to replace a bad spring. They are also cost-effective, since they have a wide variety of applications with different load capacities.

Q5: How to determine whether one has the right spring for their application?

The right spring for an application has to satisfy the requirements of load or weight to be supported, spring rate or how much the spring can stretch, and travel distance or the length of the spring when fully extended. A good indication of the best spring for one's application is to look for one that has absorbed the weight or load with minimal accompanying motion. If the motion is negligible, the spring is good enough not to bounce around or shake excessively.