Electronic anti-ice control

Claim 2

An electronic device for preventing the formation of ice crystals in a cold air supply, said device comprising: first means for measuring the wet bulb temperature of the air supply and forming a first signal that is related to the wet bulb temperature, second means for measuring the dry bulb temperature of the air supply and forming a second signal that is related to the dry bulb temperature, third means for comparing said first and second signals and forming a third signal whenever the wet bulb temperature is substantially equal to or higher than the dry bulb temperature, and fourth means responsive to the presence of said third signal to add heat to the air supply so that the ice crystals do not form.

Claim 3

The device of claim 1 wherein: fifth means are included for detecting when the dry bulb temperature is above the freezing point of water and for preventing said third means from forming said third signal whenever the dry bulb temperature is above the freezing point of water.

Claim 4

The device of claim 1 wherein: means are provided for preventing the dry bulb temperature from falling below a predetermined minimum.

Claim 5

The device of claim 1 wherein: said first signal as produced by said first means is a first analogue voltage which is directly related to the wet bulb temperature, said second signal as produced by said second means is a second analogue voltage which is inversely related to the dry bulb temperature, said first voltage is at the 0 level when the wet bulb temperature is slightly below the freezing temperature of water while said second voltage is at the 0 level when the dry bulb temperature is substantially at the freezing temperature of water, and said third signal is a third voltage produced by adding said first and second voltages and said third means includes a diode for blocking the third voltage from said fourth means whenever said third voltage indicates that said wet bulb temperature is substantially below the dry bulb temperature.

Claim 6

A control system for an air conditioning unit comprising: a source of cold air; a source of warm air; first means for combining the cold and warm air; electronic means for sensing the wet bulb temperature and said dry bulb temperature of said combined air and producing a control voltage when the wet bulb temperature is approximately equal to said dry bulb temperature; a screen disposed within said first means so that the combined air flows through said screen; a valve disposed to control the flow of at least one of said sources of air; a fluid pressure regulator for producing a fluid pressure that is related to said control voltage coupled thereto; second means having a movable member that moves in response to said fluid pressure, third means for mechanically coupling said movable member to said valve so that the opening of said valve varies when said movable member moves; and fourth means coupling the air pressure produced on the upstream side of said screen to one side of said movable member and for coupling the air pressure produced on the downstream side of said screen to the other side of said movable member to cause said valve to warm the temperature of the combined air when a pressure differential appears across the screen.

Claim 7

A control system for an air conditioning unit comprising: a source of cold air; a source of warm air; first means for combining the cold and warm air; electronic means for sensing the wet bulb temperature and said dry bulb temperature of said combined air and producing a control voltage when the wet bulb temperature is approximately equal to said dry bulb temperature; a screen disposed within said first means so that the combined air flows through said screen; a valve disposed to control the flow of at least one of said sources of air; a fluid pressure regulator for producing a fluid pressure that is related to said control voltage coupled thereto; second means having a movable member that moves in response to said fluid pressure, third means for mechanically coupling said movable member to said valve so that the opening of said valve varies when said movable member moves; and fourth means coupling the air pressure produced on the upstream side of said screen to one side of said movable member and for coupling the air pressure produced on the downstream side of said screen to the other side of said movable member to cause said valve to warm the temperature of the combined air when a pressure differential appears across the screen.

Claim 8

The system of claim 5 wherein: fifth means are included for detecting when the dry bulb temperature is above the freezing point of water and for preventing said third means from forming said third signal whenever the dry bulb temperature is above the freezing point of water.

Claim 9

The system of claim 5 wherein: sixth means are provided for preventing the dry bulb temperature from falling below a predetermined minimum.

Claim 10

In the control system of claim 5 wherein said electronic means includes: first measuring means for measuring the wet bulb temperature of the air supply and forming voltage that is related to the wet bulb temperature, second measuring means for measuring the dry bulb temperature of the air supply and forming a second voltage that is related to the dry bulb temperature, and means for comparing said first and second signals and forming said control voltage whenever the wet bulb temperature is approximately equal to the dry bulb temperature.

Claim 11

The system of claim 8 wherein: said first voltage is a first analogue voltage which is directly related to the wet bulb temperature, said second voltage is a second analogue voltage which is inversely related to the dry bulb temperature, said first voltage is at the 0 level when the wet bulb temperature is slightly below the freezing temperature of water while said second voltage is at the 0 level when the dry bulb temperature is substantially at the freezing temperature of water, said comparing voltage is produced by adding said first and second voltages and said third means includes a diode for blocking the third voltage from said fourth means whenever said third voltage is at a negative value.

Claim 12

A control system for an air conditioning unit comprising: a first duct to supply a flow of cold air; a second duct to supply a flow of warm air; a third duct to receive and combine the flow of cold air from said first duct and the flow of warm air from said second duct; means operably associated with said third duct to sense the wet bulb temperature and the dry bulb temperature of the combined cold air and warm air in said third duct and generating a signal when the wet bulb temperature is approximately equal to or higher than said dry bulb temperature; valve means operably associated with said second duct to increase the flow of warm air to said third duct in response to the signal produced by said wet bulb and dry bulb temperature sensing means to prevent the formation of ice within said third duct.

Claim 13

A control system for an air conditioning unit comprising: a first duct to supply a flow of cold air; a second duct to supply a flow of warm air; a third duct to receive and combine the flow of cold air from said first duct and the flow of warm air from said second duct; means operably associated with said third duct to sense the wet bulb temperature and the dry bulb temperature of the combined cold air and warm air in said third duct and generating a signal when the wet bulb temperature is approximately equal to or higher than said dry bulb temperature; valve means operably associated with said second duct to increase the flow of warm air to said third duct in response to the signal produced by said wet bulb and dry bulb temperature sensing means to prevent the formation of ice within said third duct.

Claim 14

The control system for an air conditioning unit of claim 10 wherein said wet bulb and dry bulb temperature sensing means includes means to prevent the generating of the signal whenever the dry bulb temperature is above the freezing point of water.

Claim 15

The control system for an air conditioning unit of claim 10 and in addition an icing screen disposed within said third duct and a differential pressure responsive means operably associated with said valve means and said icing screen to increase the flow of warm air should any ice form on said icing screen.