A spring is a mechanical device designed to store and release energy. Springs exhibit elasticity, deforming under a load and returning to their original shape once the load is removed. This characteristic allows them to absorb shock, maintain force, or provide motion in countless applications.
Springs Designed for Compression
Compression springs are open-coiled helical springs specifically engineered to resist compressive forces. When a pushing load is applied, these springs shorten, storing potential energy within their structure. They regain their original shape and length as the load is reduced or removed, releasing the stored energy. These springs can be cylindrical, the most common shape, or take on other forms like conical, barrel (convex), or hourglass (concave) shapes. Conical designs allow coils to nest within each other, reducing solid height and sometimes offering a progressive spring rate.
The wire used to create compression springs can have various cross-sections, including round, square, or rectangular. Applications for compression springs are widespread, ranging from small household items like pens to larger industrial machinery. They are found in automotive suspension systems, helping absorb road shocks, and within door locks to provide the necessary tension. Compression springs are also used in electronics, medical devices, and in automobile seats for comfort.
Springs Designed for Extension
Extension springs are designed to absorb and store energy by resisting a pulling force. These springs elongate when a tensile load is applied, and they typically feature tightly coiled helical bodies. Unlike compression springs, their coils usually touch in their free, un-stretched state, holding an initial tension that helps them return to their original length. This initial tension can be adjusted to meet specific load requirements.
To facilitate attachment, extension springs commonly have hooks, loops, or other interface geometries at their ends. These end configurations can vary widely, including open hooks, extended hooks, or threaded inserts, each serving specific functional needs. Extension springs are utilized in numerous everyday items that require a pulling force or a return mechanism. Common applications include garage door assemblies, where they help lift heavy doors, and trampolines, where they contribute to the bouncing action. They also appear in vise-grip pliers, washing machines, and various toys.
Springs Designed for Torsion
Torsion springs are mechanical devices crafted to store and release rotational energy. They exert a twisting or rotational force, known as torque, when their ends are twisted along their axis. These springs typically appear as helical coils with legs extending from the main body, which are connected to mechanical components. As one end rotates around the spring’s axis, the coil tightens, accumulating potential energy.
When the twisting force is released, the torsion spring unwinds and rebounds elastically, discharging the stored energy and exerting a rotational force in the opposite direction. These springs are commonly used in applications requiring angular movement or a static holding force. Examples include door hinges, garage door mechanisms that counterbalance the door’s weight, clothespins, and certain automotive assemblies.
Flat and Specialty Springs
Beyond the common helical designs, other spring types are engineered for specific functions and spatial constraints.
Leaf Springs
Leaf springs are a type of flat spring characterized by their layered structure, typically consisting of several bowed strips of metal stacked together. These are commonly employed in vehicle suspension systems, absorbing vertical loads and cushioning impacts. Their design distributes stress over multiple leaves, providing durability for heavy-duty applications.
Belleville Washers
Belleville washers, also known as disc springs, are conical washers designed to provide significant force in a small space. When compressed, their conical shape flattens, offering high load capacity with minimal deflection. These springs can be stacked in various configurations to achieve different load and deflection characteristics, suitable for applications requiring high loads and precise force.
Wave Springs
Wave springs feature a unique wavy or serpentine shape rather than a traditional coil. This design allows them to provide spring force in a compact axial space, making them suitable for applications where radial space is limited. Their compact nature helps reduce assembly size and weight in many mechanical systems.
Constant Force Springs
Constant force springs are pre-stressed strips of material coiled tightly, often resembling a roll of tape. They are designed to exert a nearly constant force over a long range of extension or retraction. This makes them useful in applications where a consistent pulling or lifting force is needed, such as counterbalancing mechanisms, window sash balances, or automatic return systems.
Volute Springs
Volute springs are typically conical springs made from flat strip material, wound such that each coil nests within the next. This construction results in a very robust spring with a high load capacity and excellent shock absorption, often found in heavy machinery or railway applications where durability and significant compression resistance are needed.
Gas Springs and Other Elastic Devices
Gas springs operate on a different principle compared to traditional mechanical springs. Instead of relying on the elastic deformation of metal, they utilize compressed gas, typically nitrogen, contained within a sealed cylinder. A piston rod connected to a piston moves within this cylinder, and the compressed gas exerts force as the piston is displaced. This mechanism allows gas springs to provide controlled motion and damping.
The force generated by a gas spring is proportional to the pressure of the gas inside, and this pressure pushes the piston rod to extend or compress. While mechanical springs store energy through physical deformation, gas springs store energy pneumatically. They are often preferred for applications requiring smooth, controlled movement over a distance, such as supporting car trunks and hoods, adjusting office chairs, or enabling the movement of medical beds. Gas springs can also offer advantages like a constant force output over their stroke and the ability to be locked in certain positions.