文档介绍：Available online at hanism
and
Machine Theory
Mechanism and Machine Theory 43 (2008) 812–828
ate/mechmt
Study on the tooth profile for the screw claw-type pump
Chiu-Fan Hsieh *, Yii-Wen Hwang, Zhang-Hua Fong
Department of Mechanical Engineering, National Chung-Cheng University, 168 San-Hsing, Ming-Hsiung, Chia-Yi 621, Taiwan, ROC
Received 20 April 2006; received in revised form 25 May 2007; accepted 29 June 2007
Available online 13 August 2007
Abstract
In this paper, a profile of claw-type rotor is designed by means of the theory of gearing and the equation of undercut-
ting. The designed profiles are suitable for straight rotor lobes if using in a machine with radial suction and discharge ports.
Besides, for the twin-screw rotors with claw-shape, we develop a methodology to verify the drawbacks of gas sealing in the
design of US patent 6,129,535, US patent 6,139,297 and UK patent 2,292,589. Our numerical results indicate that these
patents are unlikely to produce efficient gas sealing between twin-screw rotors. Thus, we propose two modified designs
to improve gas sealing and reduce carryover.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Claw-type rotor; Gas sealing; Carryover
1. Introduction
The dry vacuum pumps, which generates no oil and gas during operation, is useful for vacuum exhausting
in semiconductor fabrication equipment, particularly in new or high-technology industries, like vacuum heat
treatment, nuclear research, micro electro mechanical systems (MEMS), nanotechnology, precision manufac-
turing or national defence technology must be manufactured in vacuum environments.
Roots rotor is used in positive displacement vacuum pump, and it has better pumping ratio in the medium
vacuum. In the geometric design for a rotor, Wang, Fong and Fang [1] proposed design constraints for five-arc
Roots vacuum pumps, including the conditions for avoidance of tooth undercutting and carryover. They stud-
ied that if the centre of the