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:
Jun. 13, 1989
Filed:
Aug. 24, 1988
Tony J Wood, West Salem, WI (US);
American Standard Inc., New York, NY (US);
Abstract
A solenoid valve used as an expansion valve in a refrigeration circuit has an opening that varies as a function of the pulse width of a high frequency PWM (pulse width modulated) control signal. A transistor controls the electrical current delivered to the solenoid valve. The PWM control signal rapidly cycles the transistor on and off at a constant frequency that is sufficiently high to prevent the valve from having enough time within a cycle to move between fully open and closed. As a result, the valve balances at an intermediate position determined by the relative lengths of the on and off periods of each pulse cycle. The relative on-off pulse widths, often referred to as, 'duty cycle', is varied in response to a temperature sensor to control the flow of refrigerant through the refrigeration circuit. The duty cycle is also adjusted to compensate for any variations in the supploy voltage applied across the solenoid valve.