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About Extension Springs
Extension springs, also referred to as “tension
springs,” are made to counter extension. Extension springs are often
fully compressed prior to being used. Hooks, eyes or other sorts of connectors
are attached to their respective ends and are used to connect to the components
that utilize the spring. Extension springs store energy and exert a pulling
force. When components move apart, the spring attempts to bring them back
together. Extension spring end configurations vary widely and include
threaded inserts, extended twist loops, crossover center loops, expanded
or reduced eyes and rectangular, or "teardrop-shaped," ends.
Two types of extension springs are constant force springs and drawbar
springs. Whereas standard extension springs are made of wound wire and
are in a helical pattern, constant force springs are made of tightly wound
bands of pre-hardened spring or stainless steel strip. This steel band
has a fixed bend so that each curve of the strip wraps tightly on its
inner neighbor. Constant force springs are well-suited to long extensions
with little or no load increase. Drawbar springs have steel loops that
pass through the center of the spring and are hooked around the opposite
end. This configuration leads to the compression of the spring upon loading,
making drawbar springs ideal for potential overload situations. The design
of drawbar springs offers a definite stop that will continue to carry
a static load after reaching the maximum extended length.
Because extension springs do not have solid ends, they have trouble handling
overload situations. The point of fracture or malfunction is almost always
at one of the ends of the spring, not in the middle helix. The stresses
applied to the hooks will depend on the bend or shape of the connecting
device because certain styles can handle differing weight amounts. Extension
springs are found in common items such as cassette players, garage doors
and toys. Other applications include automotive interiors and exteriors,
garage door assemblies, trampolines, washing devices, farm machinery,
etc. Extension springs can be small enough for use in medical devices
and large enough to be utilized in off-road machinery brake springs.
Finding the proper hook or eyelet style is crucial to the peak performance
of an extension spring. Spring manufacturers will also need to know the
wire diameter of round wire or the dimensions of rectangular wire, when
selecting extension springs. It is also necessary to determine the number
of coils required and the initial tension. Figure out the maximum outside
diameter, minimum inside diameter and the length, including the length
of the inside hooks. It is also important to determine the maximum extended
length or distance of travel and the end configuration (hook gap). Finally,
specify whether or not a finish is needed.
Featured
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Types
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are flat metal doughnuts whose insides are higher than the outsides.
While not a coiled spring, mounting a bunch of belleville washers together
forms a very strong spring.
- ,
also known as “power,” “motor” or “flat
coil springs,” are made from wide, flat stock and are used in
clocks, retractor reels and other machinery. Clock springs are coiled
up like the shell of a snail and have the ability to store great amounts
of rotational energy.
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are made by wrapping wire around a cylinder in a helical pattern. Coil
springs are the most standard type and shape of spring.
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are open coiled, helical springs that offer resistance to compressive
loading.
- have a cone-shaped design that provides a solid height
that is lower than a regular spring. Conical compression springs also
provide near constant spring rate.
-
are a special variety of extension springs that are well-suited for
long extensions with no load build-up.
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are a form of compression springs that are engineered to give predetermined
pressure at a given compression reliably and consistently.
-
are a type of extension springs in which steel loops pass through the
center of the spring, hooking at the opposite end. The load is applied
to the loop, compressing the spring.
-
include a wide range of springs manufactured from flat strip material
which, on being deflected by an external load, will store and then release
energy.
-
are either helical extension or compression springs that are typically
used in oil seals. The ends of garter springs are connected so that
each spring becomes a circle and exerts radial forces.
-
provide controlled motion and speed for elements, such as lids and doors,
that open and close. There is normally a gas, such as nitrogen, in the
chamber to provide absorption.
- ,
also called “spiral springs,” are the most common type of
spring and can be used in torsion, tension, extension or compression.
- ,
also called “semi-elliptical” or “cart springs,”
have a slender arc-shaped form. Leaf springs are a simple form of spring
used mostly in heavy vehicles, such as vans, trucks and railway carriages.
-
have fewer leaves whose thicknesses vary from the center to the ends
of the spring, following a parabolic curve. Contact between the coils
is made only at the ends and at the center.
- ,
also called “clock” or “motor springs,” store
and release rotational energy in the form of torque.
- ,
also referred to as “spiral torsion” or “brush springs,”
operate without any contact between the coils.
-
exert pressure along a path which is a circular arc, providing torque.
The wire itself is twisted when the spring is compressed or stretched.
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