Composite gear having a permanent compressive stress at the root portion of each tooth

摘要

The composite gear 10 includes a body portion 28 having a plurality of teeth 14. The gear 10 is formed by placing it in a suitable tool 30 such that a compressive stress (hoop stress) 32 is exerted on the teeth 14 adjacent the root portion of each tooth (fig 3A). A portion of the gear adjacent the teeth is wrapped with a resin fibrous material 22,24 that is allowed to cure while the compressive stress 32 is maintained on the gear. When the resin fibrous material 22,24 has at least substantially cured and the gear 10 is removed from the tool 30, a permanent compressive stress is formed at the root portion adjacent each tooth. The compressive stress counteracts the tension stress that is experienced at the root portions of the teeth when the gear is in use, thus significantly strengthening (i.e., toughening) the gear and increasing its fatigue life. This allows smaller and lighter gears to transmit the same forces as larger prior art gears. The invention may be applied to different types of gearing including spur, ring or bevel gears. The fibrous material may be glass, Kevlar ¹, boron or carbon.