Air conditioning bypass control

Claim 2

An air conditioning system comprising: an evaporator for cooling air in a passenger compartment; a compressor for pressurizing refrigerant discharged from said evaporator; a condenser for cooling refrigerant discharged from said compressor; valve means for expanding refrigerant discharged from said condenser to a low pressure condition prior to its introduction into said evaporator; a defrost control valve assembly fluidly connected between said compressor and said evaporator and opened in response to a predetermined evaporator refrigerant temperature to direct hot refrigerant from said compressor directly into said evaporator for defrosting; said defrost control valve including a housing with a cylinder and a piston valve within said cylinder reciprocal between closed and open positions; one end of said piston valve being exposed to refrigerant pressure from said compressor outlet which exerts an opening force upon said piston valve; the other end of said piston valve forming a variable volume control chamber with said housing; said piston having a small diameter bleed port extending between said ends to said control chamber to transmit refrigerant pressure from the compressor outlet to said control chamber thus equalizing the pressure forces acting on the ends of the piston which normally maintains said piston in its closed position; said housing forming an enclosure connected to said control chamber by a passage and having an inlet and an outlet fluidly connected respectively to said evaporator and the inlet of said compressor; valve means for blocking said passage when in a closed position; bimetal spring means within said enclosure and connected to said valve member for moving said valve member into an open position in response to a predetermined evaporator refrigerant temperature corresponding to frost accumulation on said evaporator whereby said open passage decreases refrigerant pressure in said control chamber to permit a pressure force on said first end of said piston to move it into an open position permitting hot refrigerant to pass directly to said evaporator for defrosting.

Claim 3

An air conditioning system comprising: an evaporator for cooling air in a passenger compartment; a compressor for pressurizing refrigerant discharged from said evaporator; a condenser for cooling refrigerant discharged from said compressor; valve means for expanding refrigerant discharged from said condenser to a low pressure condition prior to its introduction into said evaporator; a defrost control valve assembly fluidly connected between said compressor and said evaporator and opened in response to a predetermined evaporator refrigerant temperature to direct hot refrigerant from said compressor directly into said evaporator for defrosting; said defrost control valve including a housing with a cylinder and a piston valve within said cylinder reciprocal between closed and open positions; one end of said piston valve being exposed to refrigerant pressure from said compressor outlet which exerts an opening force upon said piston valve; the other end of said piston valve forming a variable volume control chamber with said housing; said piston having a small diameter bleed port extending between said ends to said control chamber to transmit refrigerant pressure from the compressor outlet to said control chamber thus equalizing the pressure forces acting on the ends of the piston which normally maintains said piston in its closed position; said housing forming an enclosure connected to said control chamber by a passage and having an inlet and an outlet fluidly connected respectively to said evaporator and the inlet of said compressor; valve means for blocking said passage when in a closed position; bimetal spring means within said enclosure and connected to said valve member for moving said valve member into an open position in response to a predetermined evaporator refrigerant temperature corresponding to frost accumulation on said evaporator whereby said open passage decreases refrigerant pressure in said control chamber to permit a pressure force on said first end of said piston to move it into an open position permitting hot refrigerant to pass directly to said evaporator for defrosting.

Claim 4

An air conditioning system comprising: an evaporator for cooling air in a passenger compartment; a compressor for pressurizing refrigerant discharged from said evaporator; a condenser for cooling refrigerant discharged from said compressor; valve means for expanding refrigerant discharged from said condenser to a low pressure condition prior to its introduction into said evaporator; a defrost control valve assembly fluidly connected between said compressor and said evaporator and opened in response to a predetermined evaporator refrigerant temperature to direct hot refrigerant from said compressor directly into said evaporator for defrosting; said defrost control valve including a housing with a cylinder and a piston valve within said cylinder reciprocal between closed and open positions; one end of said piston valve being exposed to refrigerant pressure from said compressor outlet which exerts an opening force upon said piston valve; the other end of said piston valve forming a variable volume control chamber with said housing; said piston having a small diameter bleed port extending between said ends to said control chamber to transmit refrigerant pressure from the compressor outlet to said control chamber thus equalizing the pressure forces acting on the ends of the piston which normally maintains said piston in its closed position; said housing forming an enclosure connected to said control chamber by a passage and having an inlet and an outlet fluidly connected respectively to said evaporator and the inlet of said compressor; valve means for blocking said passage when in a closed position; bimetal spring means within said enclosure and connected to said valve member for moving said valve member into an open position in response to a predetermined evaporator refrigerant temperature corresponding to frost accumulation on said evaporator whereby said open passage decreases refrigerant pressure in said control chamber to permit a pressure force on said first end of said piston to move it into an open position permitting hot refrigerant to pass directly to said evaporator for defrosting.

Claim 5

An air conditioning system comprising: an evaporator for cooling passenger compartment air; a compressor for pressurizing refrigerant discharged from said evaporator; a condenser for cooling refrigerant discharged from said evaporator; a combination expansion valve and defrost control valve assembly including a housing with an expansion valve portion fluidly extending between said condenser and said evaporator for expanding refrigerant to a lower pressure condition; said housing further having a defrost control valve portion opening in response to a low refrigerant temperature corresponding to frost accumulation on said evaporator to direct hot refrigerant from said compressor directly into said evaporator for defrosting purposes; said defrost control valve portion having a cylinder and a piston valve within said cylinder reciprocal between closed and open positions; one end of said piston valve being exposed to refrigerant pressure from said compressor outlet to exert a fluid force upon said piston valve; the second end of said piston valve forming a variable volume control chamber with said housing; said piston having a small diameter bleed port therethrough extending between said first and second piston ends for transmitting refrigerant pressure from the compressor outlet to said control chamber thereby equalizing refrigerant pressures acting against said first and second ends; said housing forming an enclosure connected by a passage to said control chamber and having an inlet and an outlet fluidly connected respectively to said evaporator and said compressor; a needle valve member adapted to move between open and closed positions with respect to said passage; bimetal spring means within said enclosure operatively connected to said needle valve member for movement between open and closed positions in response to changes in refrigerant temperature of said evaporator corresponding to frost accumulation on said evaporator whereby said bimetal spring means moves in response to a predetermined low refrigerant temperature to open said passage and change the refrigerant pressure within said control chamber to move said piston into an open position for directing hot refrigerant to said evaporator.

Claim 6

An air conditioning system comprising: an evaporator for cooling passenger compartment air; a compressor for pressurizing refrigerant discharged from said evaporator; a condenser for cooling refrigerant discharged from said evaporator; a combination expansion valve and defrost control valve assembly including a housing with an expansion valve portion fluidly extending between said condenser and said evaporator for expanding refrigerant to a lower pressure condition; said housing further having a defrost control valve portion opening in response to a low refrigerant temperature corresponding to frost accumulation on said evaporator to direct hot refrigerant from said compressor directly into said evaporator for defrosting purposes; said defrost control valve portion having a cylinder and a piston valve within said cylinder reciprocal between closed and open positions; one end of said piston valve being exposed to refrigerant pressure from said compressor outlet to exert a fluid force upon said piston valve; the second end of said piston valve forming a variable volume control chamber with said housing; said piston having a small diameter bleed port therethrough extending between said first and second piston ends for transmitting refrigerant pressure from the compressor outlet to said control chamber thereby equalizing refrigerant pressures acting against said first and second ends; said housing forming an enclosure connected by a passage to said control chamber and having an inlet and an outlet fluidly connected respectively to said evaporator and said compressor; a needle valve member adapted to move between open and closed positions with respect to said passage; bimetal spring means within said enclosure operatively connected to said needle valve member for movement between open and closed positions in response to changes in refrigerant temperature of said evaporator corresponding to frost accumulation on said evaporator whereby said bimetal spring means moves in response to a predetermined low refrigerant temperature to open said passage and change the refrigerant pressure within said control chamber to move said piston into an open position for directing hot refrigerant to said evaporator.