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:
Jul. 13, 1993
Filed:
Nov. 15, 1991
John A Benevelli, Burbank, IL (US);
Michael L Murray, Franklin Park, IL (US);
Duane C Drinkwine, Berwyn, IL (US);
Lab-Line Instruments, Inc., Melrose Park, IL (US);
Abstract
A temperature-controlled environmental chamber includes a resistance heater controlled by a solid state relay and a refrigeration unit including an electronically controlled suction throttling valve connected in the refrigerant line between the evaporator and the inlet of the compressor. A temperature controller senses the temperature in the chamber and compares it to a set point temperature and outputs a pulse-width modulated control signal indicative of the difference between the two temperatures. The control signal directly controls the heater relay for substantially continuous variation between minimum and maximum heating conditions. The control signal is converted to an analog signal for controlling the throttling valve of the refrigeration unit for substantially continuous variation between maximum and minimum cooling conditions, so that the amount of cooling provided is inversely proportional to the amount of heating provided. A hot gas bypass is provided for maintaining a minimum input pressure on the condenser and a refrigerant bypass is provided to maintain the input temperature of the compressor below a predetermined maximum.