Spring Choice Matters: What it Means for Equipment Manufacturers and Device Makers

Springs may not be at the top of a designer’s mind when working on an application, but they are essential in many applications.

The sizes and types available vary greatly and their choice is influenced by application parameters and industry requirements. Manufactured from many different materials that must often meet international standards, they can be coiled, wire-formed or stamped by presses to achieve the desired spring shape and properties.

Spring Types

This article will look at the choices of springs in the automotive, healthcare and medical, and agricultural industries. The types commonly used are:

Belleville washer, also known as a coned-disc spring, conical spring washer, disc spring, Belleville spring or cupped spring washer, is a conical shell that can be loaded along its axis either statically or dynamically.

Compression springs are usually of a coil type and offer resistance to a force tending to compress a spring.

Constant-force springs exert a constant force over their range of motion and do not obey Hooke's law. Generally they are constructed as a ribbon of spring steel that rolls up when relaxed.

Extension springs, also known as a tension spring, are designed to store energy and exert a specified pull force when extended to a specific length.

Power springs, also known as clock springs, store and release large amounts of rotational energy in the form of torque.

Torsion springs work by torsion or twisting. When twisted, they exert torque in the opposite direction proportional to the amount they are twisted.

Wave springs, also known as coiled wave springs, are made up of pre-hardened flat wire in a process called on-edge coiling or edge-winding that add a wave to give them a spring effect.

Automotive Springs

Springs are utilized throughout a vehicle’s interior, exterior and within the engine.

Compression springs are used in anti-lock brake systems and fuel injectors along with locks, pumps and valves. The most common form is a straight cylindrical formed from round wire but they are also used in other complex shapes, such as hourglass, conical, barrel, square, ovate, rectangular or with reduced ends that are produced from round or flat wire.

Extension springs are used in what are termed foundation brake components; the brake-assembly components at the wheels of a vehicle.

Power springs are used in retractor mechanisms such as those found in seatbelts.

Torsion springs are used as couplings between concentric shafts such as in a motor pump assembly and are typically found in single coil or double coil forms.

Coil springs are often found in heavier trucks, specifically on the front suspension between the upper and lower control arms. These springs are suitable to carry heavy loads and are therefore also used within the air brake assembly.

Belleville washers are used in clutch and brake mechanisms as well as in transmissions.

Healthcare and Medical Springs

Within the healthcare and medical industry, springs can be found in devices as diverse as x-ray machines, bed lift mechanisms, and drug infusers. There are a multitude of different types of springs to accommodate the myriad of applications. While some springs dampen force and perform a pushing action, others oppose extension by pulling themselves back together.

Compression springs are used in prosthetic limbs to enhance performance or when a squeezing action is needed, such as in a surgical stapler.

Extension springs are used in stretchers, surgical lights, and a number of small handheld devices.

Constant force springs, either motor type (drum take-up) or extension type (strip end connection) are often found in surgical instruments and MRI machines.

Wave springs are sometimes specified in place of conventional round wire compression springs. Generally, wave springs occupy 30-50 percent of the compressed height space of comparable round wire springs, offering more deflection with the same load specifications. They are used in drug delivery devices, especially EpiPens or insulin pens, as well as in support prosthetics and orthotics.

Many of these healthcare and medical applications are hygienic and require production in cleanrooms. In addition, shoulder-to-shoulder engineering can be instrumental in helping device makers to go from initial design through to market. Spring suppliers should also be able to offer a range of finishes and surface coatings to enhance application performance.

Agricultural Springs

In agricultural applications, springs are found in many types of farming equipment from seed meters and harvesters to irrigation systems, mowing equipment and tractors. They need to be reliable in extreme temperatures, often have to accommodate working effectively in dirty environments and handle pressure loads.

Compression springs are needed to support a variety of the load requirements of an agricultural setting and are used widely in irrigation, such as in pop-up sprinkler heads.

Spring clips and pins are used to support farmers in properly attaching tractor hitches.

Specialized springs and wire forms are found in hydraulic systems, planters, and cutters.

Tines are heavy wire forms on machines that work the field soil.

Torsion springs, extension springs, and other types of springs are often used in combination within various gas-powered handheld lawn equipment.

In Summary

Springs play an important role in the automotive, healthcare and medical, and agricultural industries, impacting performance and helping provide optimal operating scenarios. However, it is vital that the correct type of spring is chosen from the large variety of types on the market.

Here, an overview of the most common types of springs and their applications has been given. To ensure the best performance in every case, though, each individual application should be investigated and in most cases a custom solution will be required.