| 摘要 |
A low profile, externally controlled, variable pitch fan blade hub assembly is disclosed which is especially useful in high humidity environments such as are encountered in the fan induced, hot air discharge section of an industrial water cooling tower. The hub housing has central hub means including a member which is telescoped over the drive shaft therefor to limit the overall height of the assembly. The hub member is biased axially of the hub by a series of peripherally located springs contained within the housing. A fluid such as air may be introduced into the housing under pressure to shift the hub unit in a direction against the spring bias thereon. The housing has a plurality of radially extending bores each of which rotatably receives a respective fan blade axle provided with an elongated arm on the innermost end thereof within the housing positioned such that a cam follower on each arm is received in a cam track forming a part of the hub unit. As the hub unit shifts in the housing in response to introduction of pressurized fluid or release of fluid from the housing, concomitant swinging of the cam follower arm rotates the blade axles to simultaneously vary the pitch of the fan blades. Recessing of the hub unit springs in the housing and the use of a plurality of such springs around the circumference of the hub unit assures uniformity of spring bias on the hub unit without impairment of the moisture sealing integrity of the hub housing.
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