The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 15, 2014
Filed:
Jul. 28, 2011
Hideki Fujimoto, Shizuoka, JP;
Hitoshi Nishimura, Shizuoka, JP;
Hideki Fujimoto, Shizuoka, JP;
Hitoshi Nishimura, Shizuoka, JP;
Hitachi Industrial Equipment Systems Co., Ltd., Tokyo, JP;
Abstract
A multi-stage oil-free screw compressor includes: a suction throttle valve for controlling air intake into the compressor; a piston assembly for operating the suction throttle valve; and a structure for supplying a working pressure to the piston assembly. In order to reduce startup load at the time of startup of the compressor, the suction throttle valve is fully closed while a secondary side of a compressor body is opened to the atmosphere. When a negative pressure and the air pressure, that provide the working pressure, are used for slightly opening the suction throttle valve in order to switch the compressor to a loaded mode after a motor for driving the compressor is accelerated to its top speed, the air pressure is provided by a control pipe line that is defined by the same pipe line that forms a drain pipe line. This permits the control pipe line to be opened to the atmosphere as needed during the startup time. Thus is provided the oil-free screw compressor achieving improved startup reliability.