Constant Supports

A Constant Effort Spring Supports preferred when the use of variable effort support maybe not be appropriate for the following reasons:

  1. The vertical movement is too great for variable effort support (approx. > 75mm)
  2. Only a slight change in load is acceptable (e.g., close to sensitive equipment)
  3. Space considerations prevent the use of variable effort supports.

The Constant Effort Spring Supports is based on a simple mechanical principle: To produce a constant supporting effort, the load moment about the central pivot must be counterbalanced by an equal spring moment throughout the travel range (see diagram).

Constant Diagram

constant diagram cpa

The constant effort support designed and manufactured by CPA incorporates the latest design concepts to produce support which provides an essentially constant supporting effort throughout the total travel of the unit. In addition, the robust and simple construction of the well-proven C&P design using a bell-crank lever has been enhanced to include universal locking of the load arm.

With a cylindrical spring housing of substantial construction and several support configurations to suit the position relative to steelwork and available space, the unit can be installed in many arrangements. In addition, the spring housing prevents the ingress of foreign bodies such as construction debris, thus reducing the danger of damage or restriction of the unit’s function.

The universal locking mechanism allows the load arm to be locked in any position for a hydrostatic test, maintenance and decommissioning. The locking is done at the load arm so that excessive loadings are not transferred to the spring tension rod and spring coil. The threaded rods used for universal locking are removed once the support has been installed and stowed on the side of the spring housing.


  1. The standard range of CPA constant effort supports constructed to accommodate loads between 8kg and 33500kg with a typical range of travels between 40mm and 610mm in 10mm increments.
  2. Constant effort supports are manufactured having a maximum deviation of +/-5% of the specified load.
  3. Universal Locking of the load arm is provided as standard.
  4. Upper and lower travel stops are incorporated in all units to prevent excessive overtravel.
  5. All supports are fitted with a visible travel scale.
  6. Supports are supplied with hot-dip galvanized finish as standard.
  7. Spring coils are supplied plastic-coated as standard.
  8. Screw Threads are ISO-metric coarse pitch series (6mm pitch series above size M64).


  1. Special Constant Supports can be designed for higher loadings or travels than are covered by the standard range.
  2. Supports can be designed for hydrostatic tests more than twice the operating load.
  3. Supports can be supplied with a unique paint finish or manufactured from corrosion-resistant materials.