241 and 242. Laminated or Carriage Springs, used on carriages to take up the jolts of the wheels in passing over uneven roads. 241 shows the elliptical form, and 242 the semi-elliptical form. They are built up of flat spring metal strips.

243. Watch or Clock Spring, used to drive a watch or clock train. The spring is formed of a flat spring metal strip, wound into a flat coil.

244. Ribbon Spring

A strip of flat spring metal mounted to exert a torsional pressure.

245. Spiral Spring

A length of round spring wire wound into spiral form. This spring could be used either as a tension or as a compression spring, though usually it has the form shown in Figure 247 when used as a tension spring. A spiral spring should never be extended or compressed more than one-third of its length.

246. Sear Spring

This spring gets its name from its use in gun locks for causing the sear to catch in the notch of the tumbler. However, the spring is here shown as holding apart the arms of a compass.

247. Tension Spiral Spring

A spiral spring which tapers toward the ends so that the pull will come centrally" on the spring, thus giving an even tension and avoiding side strains.

248. Flat Or Leaf Spring

A strip of flat spring metal used chiefly as a compression spring. A spring of this type is apt to lose its resiliency after continued use.

249. Disk Spring

A compression spring made up of a series of dished disks or plates.

250. Helical Spring

This spring differs from the spiral spring, Figure 245, in that it is formed by being wrapped around a cone, whereas a spiral spring is formed by being wrapped around a cylinder. The helical spring may safely be compressed until it lies flat like a clock spring.

251. Volute Spring

A compression spring formed by coiling a flat spring ribbon into a helix.

252. Furniture Spring

A compression spring comprising a double helical spring used in furniture to support the cushioned backs or seats of chairs. This spring is also used in bed springs.