Spring Types

COMPRESSION SPRINGS

compression_springs2compression_springsHelical compression springs are designed and used to resist applied compressive forces or to store energy in the push mode. Compression springs are the most common spring configuration and are found in many applications such as the automobile, aerospace and consumer goods.

The most widely used form of compression spring is the straight cylindrical spring made from round wire; however, shaped wire may be used, such as square or rectangular. Many other forms are produced. Conical, barrel, hourglass or straight cylindrical with or without variable spacing between coils are available.
 
Such configurations are used to reduce solid height, buckling and surging, or to produce nonlinear load deflection characteristics. Energy storage is greater for round wire compression springs than for rectangular wire compression springs and can be increased by nesting. Rectangular wire is used to reduce solid height or increase the space efficiency of the design. Most die springs are made from rectangular wire for this reason. It should also be noted that most compression springs have closed and ground ends, although there are other end configurations available depending on the particular application.


In applications where space is limited and particularly where solid height is restricted, springs designed from rectangular wire are often used. These springs are commonly referred to as die springs. Die springs store more energy in a smaller space than equivalent round-wire springs. Even though stress distribution around the rectangular cross section is not as uniform as the round wire section, the energy storage capacity is higher because more material can be incorporated into the allocated space

  
EXTENSION SPRINGS

While many applications require springs that dampen force and perform a pushing action, others require springs that oppose extension by pulling themselves back together. Extension springs, also called tensile springs, are found in many applications, such as a common household stapler, trampolines, garage doors and various types of spring tensioning devices.

Extension springs are typically made with initial tension, which forces the coils to press against each other in the unloaded position. Extension springs are typically installed with an initial tension that stretches the spring until the coils are close to separating. After the initial tension has been applied, the extension spring deflects only if it receives a load greater than the initial tension.

Extension springs have hooks on their ends to attach them to the application. Various hook styles and configurations are available depending on the particular application.
 
Helical extension springs do not normally have set removed. Furthermore, unlike compression springs, extension springs do not have a solid stop to prevent overloading. For these reasons, design stresses are generally lower for extension than compression springs. A special type of extension spring, know as a drawbar spring, has a solid stop. It is essentially a compression spring with special hooks.

TORSION SPRINGS

Helical torsion springs are used to apply a torque or store rotational energy are commonly referred to as torsion springs. The two most common types are single and double-bodied springs.

Torsion springs are found in clothespins, window shades, counterbalance mechanisms, ratchets, hinges and various other machine components. They are also used as couplings between concentric shafts such as in a motor pump assembly. Torsion springs are generally mounted around a shaft or arbor, and must be supported at three or more points.
 
Torsion springs are stressed in bending. If possible, a torsion spring should always be loaded in a direction that causes the body diameter to decrease. The residual forming stresses are favorable in this direction, but unfavorable when the spring is loaded in a direction that increases the body diameter. Unless there are unfavorable residual stresses in the end bends, spring makers normally heat-treat these springs at a low temperature to stabilize the end positions rather than fully stress-relieve them. If the direction of loading tends to increase body diameter, the spring maker should be advised to stress-relieve the springs.

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