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:
Feb. 10, 1981
Filed:
Mar. 01, 1978
David N Shaw, Unionville, CT (US);
David J First, Carlisle, MA (US);
Dunham-Bush, Inc., West Hartford, CT (US);
Abstract
An electronic control system for sequential actuation of a four-way solenoid valve is used to selectively load and unload a slide valve control for a screw compressor. The electronic control system is responsive to output air pressure and pulses a four-way solenoid valve to selectively load and unload the system so that it will maintain system pressure within a preselected deadband. Selective pulsing of the four-way solenoid valve is used to gate hydraulic fluid to load and unload chambers separated by a piston coupled to a slide valve which shifts longitudinally and changes the capacity of the screw compressor. The control system senses output line pressure, and when a limit pressure is exceeded, a dump solenoid valve and fast-unload system is actuated to entirely unload the system of air pressure until reduced to a level below the set deadband. The control circuit also monitors current to the motor which drives the screw compressor. When the motor current is above a normal limit, further loading of the compressor is inhibited. If the current continues to rise, indicating a decrease in voltage available for power, the compressor is driven to an unloaded state until the current matches the preset normal limits. By use of electronic control for selective pulsing of the four-way solenoid valve, energy savings are realized by maintaining operation within a narrow deadband of operation.