Insulating glass with capacitively coupled heating system

• US 5,852,284 A
• Filed: 01/07/1997
• Issued: 12/22/1998
• Est. Priority Date: 01/07/1997
• Status: Expired due to Term

• Current Assignee: Libbey-Owens-Ford Co. (Eaton Corporation PLC.)
• Original Assignee: Libbey-Owens-Ford Co. (Eaton Corporation PLC.)
• Inventors: Gerhardinger, Peter F., Teder, Rein S., Millett, Fred A.
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US08/779,470
• Time in Patent Office: 714 Days
• Field of Search: 219/203, 219/219, 219/520, 219/522, 219/532, 219/536, 219/541, 219/542, 219/218, 219/497, 219/499, 219/510, 219/543, 49/70
• US Class Current: 219/522
• CPC Class Codes: F25D 21/04 Preventing the formation of frost or condensate
• CPC Class Codes: F25D 2400/02 Refrigerators including a heater
• CPC Class Codes: H05B 1/0236 for vehicles
• CPC Class Codes: H05B 2203/016 Heaters using particular connecting means
• CPC Class Codes: H05B 2203/035 Electrical circuits used in resistive heating apparatus
• CPC Class Codes: H05B 3/84 Heating arrangements specially adapted for transparent or reflecting areas, e.g. for demisting or de-icing windows, mirrors or vehicle windshields

Abstract

A glass heating system includes a low emissivity sheet of coated glass and a capacitor for capacitive coupling the coated glass to a power source. The low emissivity glass is economical to produce and provides superior thermal properties. The low emissivity glass has a low sheet resistance and is coupled to one or more capacitors to increase the impedance of the circuit and reduce the power dissipation by the coated glass. The exact amount of power to be delivered to the coated glass can be varied by changing the capacitor. The low emissivity glass has improved thermal characteristics for use in insulating glass doors for freezers and refrigerators. In a two-paned insulating glass door, the capacitor can be conveniently mounted in the frame of the door or in the space between the two panes.

Claims

1. A heated glass system for heating glass sheet surfaces, said heated glass system comprising:

a sheet of glass having a generally rectangular shaped configuration;

a transparent, conductive coating applied to a surface of said sheet of glass, said coating having a hemispheric emissivity of less than 0.50;

a pair of bus bars mounted along opposite edges of said sheet of glass and electrically connected to said conductive coating, said bus bars each including a connector for connecting said bus bar to an alternating current power supply to form a circuit through said conductive coating; and

a capacitor connected in series between one of said bus bars and the power supply, said capacitor increasing an impedance of the circuit to reduce current flowing through and to reduce power dissipated by said conductive coating.

2. The heated glass system defined in claim 1, wherein said conductive coating is tin oxide.

3. The heated glass system defined in claim 1, wherein said conductive coating is indium tin oxide.

4. The heated glass system defined in claim 1, wherein said conductive coating is zinc oxide.

5. The heated glass system defined in claim 1, including at least one additional capacitor selectively connected into the circuit between one of said bus bars and the power supply, and including a control device for controlling the connection of at least one of said capacitor and said at least one additional capacitor into the circuit to change the impedance of the circuit.

6. The heated glass system defined in claim 5, wherein the control device is a switch for changing the connections of said capacitor and said at least one additional capacitor between one of an individual, parallel, and series connection in the circuit.

7. The heated glass system defined in claim 1, wherein said conductive coating has a hemispheric emissivity in the range from 0.15 to 0.43.

8. The heated glass system defined in claim 7, wherein said conductive coating is a pyrolytic low emissivity coating.

9. An insulating glass unit comprising:

a first sheet of glass and a second sheet of glass, each sheet of glass including an unexposed surface and an outer surface;

a conductive coating applied to the unexposed surface of said first sheet of glass, said conductive coating having a hemispheric emissivity of less than 0.50;

a frame secured around a periphery of said first and second sheets of glass for maintaining the glass sheets in parallel, spaced-apart relationship with the unexposed surfaces facing each other;

a pair of bus bars mounted along opposite edges on the unexposed surface of said first sheet of glass and electrically connected to said conductive coating, said bus bars each including a connector for connecting said bus bar to an alternating current power supply to form a circuit through said conductive coating; and

a capacitor mounted on said frame and connected in series between one of said bus bars and the power supply, said capacitor increasing an impedance of the circuit to reduce current flowing through and to reduce power dissipated by said conductive coating.

10. The heated glass system defined in claim 9, including at least one additional capacitor selectively connected into the circuit between one of said bus bars and the power supply, and including a control device for controlling the connection of at least one of said capacitor and said at least one additional capacitor into the circuit to change the impedance of the circuit.

11. The heated glass system defined in claim 10, wherein the control device is a switch for changing the connections of said capacitor and said at least one additional capacitor between one of an individual, parallel, and series connection in the circuit.

12. The insulating glass unit defined in claim 9, wherein said conductive coating has a hemispheric emissivity in the range from 0.15 to 0.43.

13. The insulating glass unit defined in claim 9, wherein said conductive coating is a pyrolytic low emissivity coating.

14. The insulating glass unit defined in claim 9, wherein said capacitor is mounted on a circuit board and the circuit board is positioned in said frame.

15. The insulating glass unit defined in claim 9, wherein said frame includes a spacer positioned between said first and second sheets of glass at the periphery of said sheets of glass, said capacitor being mounted within a space inside the spacer.

16. The insulating glass unit defined in claim 9, wherein said frame includes a spacer positioned between said first and second sheets of glass at the periphery of said sheets of glass, said capacitor being mounted on said spacer in a space between the unexposed surfaces of said first and second sheets of glass.

17. The insulating glass unit defined in claim 9, including a conductive coating applied to the unexposed surface of said second sheet of glass, said conductive coating having a hemispheric emissivity of less than 0.50, and including a pair of bus bars mounted along opposite edges on the unexposed surface of said second sheet of glass and electrically connected to said conductive coating, said bus bars each including a connector for connecting said bus bar to an alternating current power supply to form a circuit through said conductive coating and wherein said bus bars on said first sheet of glass and said bus bars on said second sheet of glass are connected to said capacitor.

18. A refrigerated cabinet door adapted to be movably mounted on a refrigerated cabinet, said door comprising:

a first sheet of glass adapted to be positioned adjacent the ambient environment of the refrigerated cabinet and a second sheet of glass adapted to be positioned adjacent the interior of the refrigerated cabinet, each sheet of glass including an unexposed surface and an outer surface;

a conductive coating applied to the unexposed surface of said first sheet of glass, said conductive coating having a hemispheric emissivity of less than 0.50;

a frame secured around a periphery of said first and second sheets of glass for maintaining the glass sheets in parallel, spaced-apart relationship with the unexposed surfaces facing each other;

a pair of bus bars mounted along opposite edges on the unexposed surface of said first sheet of glass and electrically connected to said conductive coating, said bus bars each including a connector for connecting said bus bar to an alternating current power supply to form a circuit through said conductive coating; and

a capacitor mounted on said frame and connected in series between one of said bus bars and the power supply, said capacitor increasing an impedance of the circuit to reduce current flowing through and to reduce power dissipated by said conductive coating.

19. The heated glass system defined in claim 18, including at least one additional capacitor mounted on said frame and selectively connected into the circuit between one of said bus bars and the power supply, and including a control device for controlling the connection of at least one of said capacitor and said at least one additional capacitor into the circuit to change the impedance of the circuit.

20. The insulating glass unit defined in claim 18, wherein said conductive coating has a hemispheric emissivity in the range from 0.15 to 0.43.

21. The insulating glass unit defined in claim 18, including a conductive coating applied to the unexposed surface of said second sheet of glass, said conductive coating having a hemispheric emissivity of less than 0.50, and including a pair of bus bars mounted along opposite edges on the unexposed surface of said second sheet of glass and electrically connected to said conductive coating, said bus bars each including a connector for connecting said bus bar to an alternating current power supply to form a circuit through said conductive coating and wherein said bus bars on said first sheet of glass and said bus bars on said second sheet of glass are connected to said capacitor.