| 摘要 |
<p>A screw compressor of the kind incorporating at least two rotors, one male and one female rotor, provided with helically extending lands and grooves. Conventional rotors are usually made of metal. The male rotor may be made of plastics material by moulding of a blank to be machined finely and with precision by cutting tools. The female rotor, on the other hand, has rather narrow lands, and a sufficient strength and shape permanence is, according to general practice, obtainable only if it is made of metal, preferably steel. The object of the invention is to provide a screw compressor having rotors which can be manufactured in an easier way than before. For this purpose the female rotor (1) is injection moulded from a plastics material having a modulus of elasticity of at most 25000 N/mm<2>. The lands (3) of the female rotor have a thickness (a) which is so adapted to the modulus of elasticity of the plastics material as to allow the lands to be deflected resiliently when clashing with the other rotor (2), as a result of dimensional deviations of the order likely to occur during hardening or curing of the plastics material, or at prevailing temperature variations, but not as a result of the pressure exerted by the working fluid. Due to the injection moulding the surface smoothness is fine enough to make subsequent finishing unnecessary and damages caused by lack of machining are avoided because of the resilient deflecting of the lands of the female rotor when clashing with the other rotor.</p> |
