Springs

• Spring


  An elastic object used to store mechanical energy, usually made of hardened steel
• Materials used for springs

  • High carbon steel
  • Alloy stainless steel
  • Stainless steel
  • Copper alloy
  • Nickel-base alloy
• Springs


  • Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication
• Uses of springs


  • To absorb energy or shock loads
  • To act as a source of energy
  • To produce a pressure or force in surfaces of clutches and to keep cam follower in contact with the cam
  • To absorb vibration
  • To act as load-measuring device and instruments
• Tension/Extension spring


  The spring is designed to operate with a tension load, so the spring stretches as the load is applied to it
• Compression spring


  The spring is designed to operate with a compression load, so the spring gets shorter as the load is applied to it
• Torsion spring


  The load applied to the spring is a torque or twisting force, and the end of the spring rotates through an angle as the load is applied
• Types of springs based on shape

  • Coil spring
  • Flat spring
• Types of coil springs

  • Compression coil spring
  • Tension coil spring
  • Flat compression coil spring
• Types of springs based on how the load force is applied

  • Cantilever spring
  • Coil spring or helical spring

  
• Compression springs


  Designed to become shorter when loaded, their turns (loops) are not touching in the unloaded position, and they need no attachment points
• Tension or extension springs


  Designed to become longer under load, their turns (loops) are normally touching in the unloaded position, and they have a hook, eye or some other means of attachment at each end
• Volute spring


  A compression spring in the form of a cone, designed so that under compression the coils are not forced against each other, thus permitting longer travel
• Hairspring or balance spring


  A delicate spiral torsion spring used in watches, galvanometers, and places where electricity must be carried to partially-rotating devices such as steering wheels without hindering the rotation
• Leaf spring


  A flat springy sheet, used in vehicle suspensions, electrical switches, bows

  
• Belleville washer or Belleville spring


  A disc shaped spring commonly used to apply tension to a bolt (and also in the initiation mechanism of pressure-activated landmines)
• Gas spring


  A volume of gas which is compressed
• Mainspring


  A spiral ribbon shaped spring used as a power source in watches, clocks, music boxes, windup toys, and mechanically powered flashlights
• Progressive rate coil springs


  A coil spring with a variable rate, usually achieved by having unequal pitch so that as the spring is compressed one or more coils rests against its neighbour
• Rubber band


  A tension spring where energy is stored by stretching the material
• Helical compression spring end treatments

  • Plain
  • Plain & Ground
  • Squared
  • Squared and Ground
• Springs made from smaller wire (less than approximate 0.020 in, or 0.5mm) are usually squared only
• In unusual cases, the ends may be ground without squaring, or they may be left with plain ends, simply cut to length after coiling. Used for low application
• Free length


  The length that the spring assumed when it is exerting no force
• Solid length


  The spring is collapsed to the point where all coils are touching
• Compressed length


  The length of spring to which deflection occurred, including operating length (Lo) and installed length (Li)
• Spring rate, k


  The relationship between the force exerted by a spring and its deflection. Any change in force divided by the corresponding change in deflection
• Spring Index, C


  The ratio of the mean diameter of the spring to the wire diameter. Dm/Dw. It is recommended that C be greater than 5.0, with typical machinery springs having C value ranging from 5-12
• For less than 5, the forming of the spring will be very difficult and the severe deformation required may create cracks in the wire
• The stresses and the deflections in springs are dependent on C, and a larger C will eliminate the tendency for a spring to buckle
• Pitch, P


  The axial distance from a point on one coil to the corresponding point on the next adjacent coil
• Pitch Angle


  The larger the pitch angle, the steeper the coils appears to be. Most practical designs produce a pitch angle less than 12o. If the angle is greater than 12o, undesirable compressive stresses develop in the wire
• Virtually any elastic material can be used for a spring. However, most mechanical applications use metallic wire – high-carbon steel, alloy steel, stainless steel, brass, bronze, beryllium copper, or nickel-base alloys
• Wahl's factor, K


  This term accounts for the curvature of the wire and the direct shear stress in the analysis of helical compression springs
• Do


  Outside diameter
• Di


  Inside diameter