| Compression
Springs are coil springs wound with spacing between the coils
so that they can be compressed from their free length to a shorter
operating length to store energy or provide a force. Typical
applications for compression springs are to provide pressure,
as in an electrical contact spring; to resist the movement of
another component, as in a pressure gage; to return another
component to a desired position, as in a door latch; or to store
and release energy, as in a toy dart gun. Compression springs
fall into the following general categories based on their overall
shape:  click to view larger imageCylindrical,
Straight or Standard - All coils are the same diameter.
These are the most common and least expensive compression
springs. They are produced on high speed, automatic spring
coilers that can produce up to 300 parts per minute. The ends
can be either open or closed and they can be ground flat,
although grinding significantly increases the cost and is
often unnecessary for small wire sizes. For more on end
types click here.
Conical
or Tapered - Coil diameter decreases from one
end of the spring to the other. These springs are often
used when
there is not enough room for a cylindrical spring. They can
be made so that the smaller coils telescope down into
the
larger coils as the spring is compressed so that the spring
 click to view larger imagecan operate in a smaller axial space. Conical springs
can
also be made so that the load vs. deflection curve gets steeper
as the spring is compressed and the larger diameter coils
bottom out or “go solid”.
Barrel
or Convex - Tapered so that both ends are smaller
than the middle. These springs can have some of the same advantages
as a conical spring with the added advantage that they are
symmetrical. The reduced ends may also aid in automatic assembly
or may help keep the spring centered around a smaller diameter
shaft.
Hourglass
or Concave - Tapered so that both ends are larger
than the middle. These springs can have some of the same advantages
as a conical spring with the added advantage that they are
symmetrical. The enlarged end coils may also help keep the
spring centered on a larger diameter hole.
Variable
Pitch - Wound with a varying amount of space between
the coils. This technique can be used to produce springs
with
a non-linear load vs. deflection curve, or to add closed
coils in the center of the spring to reduce tangling.
Preset
– Springs that will operate at a stress level that exceeds
the elastic limit of the material can be preset by compressing
a spring to solid height. This process removes any permanent
deformation due to exceeding the elastic limit of the material
and builds in beneficial stresses near the wire surface, with
an apparent increase in the elastic limit. |