The NEG'ATOR® extension spring represents the most basic, yet most versatile, type of constant force spring. It is a prestressed flat strip of spring material which is formed into virtually constant radius coil around itself or on a drum. This straightened length of spring actually stores the spring's energy through its tendency to assume its natural radius.

The full rated load of the spring is reached after being deflected to a length equal to 1.25 times its diameter. Thereafter, it maintains a relatively constant force regardless of extension length. Load is basically determined by the thickness and the width of the material and the diameter of the coil.

Fatigue life of NEG'ATOR springs ranges from 2,500 cycles to over a million cycles depending upon the load and size of the spring. Working deflections of 50 times the drum diameter can be achieved. A wide variety of mounting configurations can be used such as cavity mounts, multiple (or laminated) spring mounts, etc., depending on the application. End connections can also be varied to fit the design parameters. Hunter Spring's engineers can help you select a spring design to meet your space, life cycle, load, and operation requirements.
In addition, the NEG'ATOR constant force spring is the key component to the NEG'ATOR spring motor assembly, commonly found in counterbalance applications.

• Low force gradient over entire deflection range
• Extremely long linear extensions possible
• Maximum force generated at initial deflection
• Permits smaller package size due to inherent compact size and light weight
• Variety of material can be use

The SPIR'ATOR® constant torque spring is a design breakthrough offering many advantages over conventional prestressed power springs. Alternating layers of eye and spring element produce fewer initial prewinds. The result is much more economical spring comprised of thinner, shorter, narrower materials. Improved performance results from the torque increase in the initial turns; this produces a flatter torque curve over the entire working range of the spring.

The SPIR'ATOR prestressed spiral spring is produced by reverse winding a NAG'ATOR on an arbor or case or, when linear motion is required, through use of pulley and cable attachment.

The unique design of this encapsulated spring yields a compact power source which operates with higher working stress and can provide more than twice as many revolutions as a conventional power spring in the same size case. With torque and deflection being equal, a SPIR'ATOR generally requires 20% less space than a power spring. Most importantly, this power package creates a low torque gradient. SPIR'ATOR torque springs and power springs are used in Hunter Spring reels, common found in applications requiring a fast, economical solution to product design problems where counterbalancing, retrieving, returning, or other long deflection functions are required.

• Higher prestressing generally permits use of thinner material thus smaller package size than comparable power spring
• Low force gradient yields usable torque throughout operating range
• Normal residual stresses
• Variety of material can be use