SAFETY DEVICE FOR MULTI-PANE GLASS REFRIGERATOR DOORS

• US 3,655,939 A
• Filed: 11/16/1970
• Issued: 04/11/1972
• Est. Priority Date: 11/16/1970
• Status: Expired due to Term

• Current Assignee: Michael E. Stromquist
• Original Assignee: Michael E. Stromquist
• Inventors: Stromquist, Michael E.
• Primary Examiner(s): Albritton, C. L.
• Application Number:
  US05/089,882
• Time in Patent Office: 512 Days
• Field of Search: 219/202,203,213,214,218,496,519,522 200/84N 62/248,275 49/70 52/173,616
• US Class Current: 219/218
• CPC Class Codes: H05B 1/0236 for vehicles
• 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 safety device for a multi-pane electrically heated glass refrigerator door. The glass unit forms a pressurized chamber. A pressure sensor and associated circuit breaking means removes electrical power from the door when damage to the unit causes the pressure within the chamber to vary.

Claims

1. In a refrigerated cabinet door adapted to be heated by a source of electrical energy, the combination comprising:

at least two glass panels;

means for sealing said panels in mutually spaced relationship to define at least one sealed chamber therebetween, said chamber being normally maintained at a predetermined pressure different from atmospheric;

an electrically conductive coating adhered to the interior surface of one of said panels within said chambers;

means for electrically connecting spaced portions of said coating to opposite sides of the source of electrical energy;

means responsive to the pressure within said chamber for providing an output signal when said pressure varies from said predetermined pressure;

means responsive to said output signal to disconnect said conductive coating from the source of electrical energy.

2. The combination of claim 1 wherein said means for electrically connecting said coating to the source of energy comprises:

first and second electrodes adhered to the surface of said conductively coated panel in spaced relationship.

3. The combination of claim 2 wherein said means for electrically connecting said coating to the source of electrical energy further comprises:

a first normally closed relay contact connected between said first electrode and one side of the source of electrical energy.

4. The combination of claim 3 wherein said means for electrically connecting said coating to the source of electrical energy further comprises:

a second normally closed relay contact connected between said second electrode and the other side of the source of electrical energy.

5. The combination of claim 3 wherein said means responsive to said output signal comprises:

a relay contact activator responsive to the receipt of said output signal to open said relay contact and disconnect said first electrode from said source of electrical energy.

6. The combination of claim 4 wherein said means responsive to said output signal comprises:

a relay contact activator responsive to the receipt of said output signal to open said relay contacts and disconnects said first and second electrodes from said source of electrical energy.

7. In a multi-pane glass refrigerated cabiNet door wherein the glass panes are joined around their peripheral edges in spaced relation to form a chamber isolated from the external atmosphere, and wherein an electrically conductive coating adheres to the interior surface of one of the glass panes within the isolated chamber, and wherein at least two electrode means are adapted to connect spaced portions of said coating to opposite terminals of a source of electrical energy, a safety device comprising:

means for normally maintaining said chamber at a predetermined pressure different than atmospheric pressure;

a pressure sensor operatively positioned within said chamber to sense the pressure therein, said sensor providing an output signal when the sensed pressure varies from the predetermined pressure condition; and

means responsive to the receipt of said output signal to disconnect the electrode means from said source of electrical energy.

8. The glass refrigerated cabinet door defined in claim 7 wherein the chamber is normally at an elevated pressure with respect to the external atmosphere, said pressure sensor being responsive to a reduction in sensed pressure, to provide said output signal.

9. The glass refrigerated cabinet door defined in claim 7 wherein said chamber is normally at a pressure below the external atmospheric pressure, said pressure sensor being responsive to an increase in sensed pressure to provide said output signal.