This invention concerns a helical spring with a spring wire made of thermosetting plastic in which are embedded reinforcing fibers that run at an angle of approximately 45.degree. to the longitudinal axis of the spring wire.
The invention also concerns a process for producing such a helical spring in which a spring wire made of a thermosetting resin and reinforcing fibers embedded in it are wound into a helical spring and the resin is then cured.
Helical springs are frequently used in machinery elements that maintain the force fit between two elements in motion or in case of wear. The motion of an element leads to the motion of the spring in the same direction, which causes large inertial forces, particularly in case of high-frequency oscillations and high-amplitude vibrations. To keep these inertial forces small, the mass of the helical spring should be as small as possible.
For this reason, attempts have been made to make helical springs of fiber composite materials, particularly of carbon fiber-reinforced plastic, since mass reductions of up to 70% are possible with this material. Such springs are built up in layers of carbon fiber rovings wound at an angle of 45.degree. to the longitudinal axis of the spring wire. High mechanical and thermal stresses are produced during this buildup, because of which breakage or creeping of the fibers can occur (U.S. Pat. No. 4,260,143).
It is the purpose of this invention to produce a helical spring made of fiber composite material of this type, particularly of carbon fiber-reinforced plastic, that has strength characteristics that are improved over those of the helical springs of this type known heretofore.
USPTO Backgrounds
USPTO Backgrounds