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:
May. 12, 1987
Filed:
Jul. 23, 1985
Hitachi, Ltd., Tokyo, JP;
Abstract
An operation control system of a rotary displacement type vacuum pump capable of reducing a starting torque of the vacuum pump includes a suction regulating valve and a pressure sensor for monitoring suction pressure located in a suction passage of the vacuum pump, an inverter electrically coupled to a variable speed electric motor for driving the vacuum pump and a control unit. The control unit is operative, when the vacuum pump is started, to keep the suction regulating valve in a closed position until the value of suction pressure monitored by the pressure sensor reaches a predetermined upper limit value and to gradually increase the rpm. of the variable speed electric motor. The control unit is further operative to produce a signal for increasing or decreasing the rpm of the variable speed electric motor so as to bring the value of suction pressure monitored by the pressure sensor to the vicinity of a predetermined lower limit value.