U.S. patent application number 09/909262 was filed with the patent office on 2003-04-03 for energy-free refrigeration door and method for making the same.
Invention is credited to Cording, Christopher R..
Application Number | 20030062813 09/909262 |
Document ID | / |
Family ID | 25426915 |
Filed Date | 2003-04-03 |
United States Patent
Application |
20030062813 |
Kind Code |
A1 |
Cording, Christopher R. |
April 3, 2003 |
Energy-free refrigeration door and method for making the same
Abstract
The present invention provides a refrigeration door, and method
for making the same, for controlling condensation, providing
thermal insulation, with a desired amount of visible transmittance,
without using electricity to heat the door. The energy-free
refrigeration door of the present invention includes a door frame
housing and an insulating glass unit comprising inner, middle and
outer sheets of glass. A first sealant assembly disposed around the
periphery of the inner and middle sheets of glass forms a first
chamber between the inner and middle sheets of glass. A second
sealant assembly disposed around the periphery of the middle and
outer sheets of glass forms a second chamber between the middle and
outer sheets of glass. A gas, such as krypton, air, or argon is
held in the first and second chambers. The outer sheet of glass and
inner sheet of glass each have an unexposed surface that faces the
middle sheet of glass. A low emissivity coating is disposed on the
unexposed surfaces of the inner and outer sheets of glass so that
the glass door as a whole has a U value that prevents formation of
condensation on the outer surface of the outer sheet of the glass
door, without the application of electricity to heat the door,
while also providing the desired evaporation rate of condensation
from the inner side of the inner sheet of the glass door.
Inventors: |
Cording, Christopher R.;
(Kingsport, TN) |
Correspondence
Address: |
ROTHWELL, FIGG, ERNST & MANBECK, P.C.
1425 K STREET, N.W.
SUITE 800
WASHINGTON
DC
20005
US
|
Family ID: |
25426915 |
Appl. No.: |
09/909262 |
Filed: |
July 19, 2001 |
Current U.S.
Class: |
312/405 |
Current CPC
Class: |
A47F 3/0434 20130101;
E06B 3/6715 20130101 |
Class at
Publication: |
312/405 |
International
Class: |
A47B 096/04 |
Claims
What is claimed is:
1. A refrigeration door adapted to be mounted on a refrigerating
compartment, said door comprising: an inner sheet of glass
including a first surface and a second surface, said first surface
of said inner sheet being disposed adjacent the interior of the
refrigerating compartment; an outer sheet of glass including a
first surface and a second surface, said first surface of said
outer sheet being disposed adjacent the exterior environment of the
refrigerating compartment; a middle sheet of glass disposed between
said inner and outer sheets of glass; a first sealant assembly
disposed around the periphery of said inner sheet of glass and said
middle sheet of glass for maintaining said inner sheet and said
middle sheet in spaced-apart relationship from each other; a second
sealant assembly disposed around the periphery of said middle sheet
of glass and said outer sheet of glass for maintaining said middle
sheet and said outer sheet in spaced-apart relationship from each
other; a first low emissivity coating adjacent the second surface
of said inner sheet of glass; a second low emissivity coating
adjacent the second surface of said outer sheet of glass; said
inner sheet, outer sheet, middle sheet, first sealant assembly,
second sealant assembly, and said first and second low emissivity
coatings forming an insulating glass unit having a U value
substantially equal to or less than 0.2 BTU/hr-sq ft-F
substantially preventing the formation of condensation on said
first surface of said outer sheet of glass without the application
of electricity for heating said first surface of said outer sheet
of glass; and a frame secured around the periphery of said
insulating glass unit.
2. The refrigeration door of claim 1, further comprising: a first
chamber defined by said inner sheet of glass, said middle sheet of
glass, and said first sealant assembly; a second chamber defined by
said middle sheet of glass, said outer sheet of glass, and said
second sealant assembly; and a gas disposed in said first and
second chambers.
3. The refrigeration door of claim 2, wherein: said inner, said
middle, and said outer sheets of glass have a thickness
substantially equal to one eighth of an inch; said inner and said
middle sheets of glass being spaced apart a distance substantially
equal to one half inch; and said middle and said outer sheets of
glass being spaced apart a distance substantially equal to one half
inch.
4. The refrigeration door of claim 2, wherein at least one sheet of
glass is formed of Comfort Ti-PS.
5. The refrigeration door of claim 2, wherein said first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 1.73 Btu/hr-ft-F.
6. The refrigeration door of claim 5, wherein: said inner, said
middle and said outer sheets of glass having a thickness
substantially equal to one eighth of an inch; said inner and said
middle sheets of glass being spaced apart a distance substantially
equal to one half inch; and said middle and said outer sheets of
glass being spaced apart a distance substantially equal to one half
inch.
7. The refrigeration door of claim 2, wherein said gas in said
first chamber and said second chamber are the same.
8. The refrigeration door of claim 2, wherein said gas in said
first chamber and said second chamber are not the same.
9. The refrigeration door of claim 2, wherein said gas is selected
from the group consisting of argon, krypton, and air.
10. The refrigeration door of claim 1, wherein said insulating
glass unit has a U value substantially equal to or less than 0.16
BTU/hr-sq ft-F.
11. The refrigeration door of claim 1, wherein said outer sheet and
said inner sheet each have an emissivity substantially equal to or
less than 0.05.
12. The refrigeration door of claim 1, wherein said outer sheet and
said inner sheet each have an emissivity substantially equal to or
less than 0.03.
13. The refrigeration door of claim 1, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.04.
14. The refrigeration door of claim 1, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.01.
15. The refrigeration door of claim 1, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.0025.
16. The refrigeration door of claim 2, wherein said first and
second low emissivity coatings are selected from the group
consisting of a titania based silver and fluorine doped tin
oxide.
17. The refrigeration door of claim 2, wherein said first and
second low emissivity coatings are applied with a process selected
from the group consisting of sputter coating, pyrolytic coating and
spray coating.
18. The refrigeration door of claim 2, wherein said frame is formed
from a material selected from the group consisting of extruded
plastic, aluminum, and fiber glass.
19. The refrigeration door of claim 1, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus twenty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
seventy degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent; and wherein said first surface of said outer sheet of
glass is substantially free of condensation.
20. The refrigeration door of claim 1, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus forty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
eighty degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent; and wherein said first surface of said outer sheet of
glass is substantially free of condensation.
21. The refrigeration door of claim 1, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than zero degrees Fahrenheit; the temperature of the
exterior environment is substantially equal to or greater than
seventy two degrees Fahrenheit; and the humidity in the ambient
environment is substantially equal to or greater than sixty
percent; and wherein said first surface of said outer sheet of
glass is substantially free of condensation.
22. The refrigeration door of claim 2, wherein at least one sheet
of glass is formed of Comfort E2.
23. The refrigeration door of claim 1, wherein said first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 1.73 Btu/hr-ft-F.
24. The refrigeration door of claim 1, wherein said first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 1.51 Btu/hr-ft-F.
25. The refrigeration door of claim 1, wherein said first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 0.84 Btu/hr-ft-F.
26. A refrigeration door adapted to be mounted on a refrigerating
compartment, said door comprising: an inner sheet of glass
including a first surface and a second surface, said first surface
of said inner sheet being disposed adjacent the interior of the
refrigerating compartment; an outer sheet of glass including a
first surface and a second surface, said first surface of said
outer sheet being disposed adjacent the exterior environment of the
refrigerating compartment; a middle sheet of glass disposed between
said inner and outer sheets of glass; a first sealant assembly
disposed around the periphery of said inner sheet of glass and said
middle sheet of glass for maintaining said inner sheet and said
middle sheet in spaced-apart relationship from each other; a second
sealant assembly disposed around the periphery of said middle sheet
of glass and said outer sheet of glass for maintaining said middle
sheet and said outer sheet in spaced-apart relationship from each
other; a first low emissivity coating adjacent the second surface
of said inner sheet of glass; a second low emissivity coating
adjacent the second surface of said outer sheet of glass; said
inner sheet, outer sheet, middle sheet, first sealant assembly,
second sealant assembly, and said first and second low emissivity
coatings forming an insulating glass unit having an emissivity
substantially equal to or less than 0.04 substantially preventing
the formation of condensation on said first surface of said outer
sheet of glass without the application of electricity for heating
said first surface of said outer sheet of glass; and a frame
secured around the periphery of said insulating glass unit.
27. The refrigeration door of claim 26, further comprising: a first
chamber defined by said inner sheet of glass, said middle sheet of
glass, and said first sealant assembly; a second chamber defined by
said middle sheet of glass, said outer sheet of glass, and said
second sealant assembly; and a gas disposed in said first and
second chambers.
28. The refrigeration door of claim 27, wherein: said inner, said
middle, and said outer sheets of glass have a thickness
substantially equal to one eighth of an inch; said inner and said
middle sheets of glass being spaced apart a distance substantially
equal to one half inch; and said middle and said outer sheets of
glass being spaced apart a distance substantially equal to one half
inch.
29. The refrigeration door of claim 27, wherein at least one sheet
of glass is formed of Comfort Ti-PS.
30. The refrigeration door of claim 27, wherein said gas is
selected from the group consisting of argon, krypton, and air.
31. The refrigeration door of claim 26, wherein said insulating
glass unit has a U value substantially equal to or less than 0.16
BTU/hr-sq ft-F.
32. The refrigeration door of claim 26, wherein said outer sheet
and said inner sheet each have an emissivity substantially equal to
or less than 0.05.
33. The refrigeration door of claim 26, wherein said outer sheet
and said inner sheet each have an emissivity substantially equal to
or less than 0.03.
34. The refrigeration door of claim 26, wherein said insulating
glass unit has a U value substantially equal to or less than 0.2
BTU/hr-sq ft-F.
35. The refrigeration door of claim 26, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.01.
36. The refrigeration door of claim 26, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.0025.
37. The refrigeration door of claim 27, wherein said low emissivity
coatings are selected from the group consisting of a titania based
silver and fluorine doped tin oxide.
38. The refrigeration door of claim 27, wherein said low emissivity
coatings are applied with a process selected from the group
consisting of sputter coating, pyrolytic coating and spray
coating.
39. The refrigeration door of claim 27, wherein said frame is
formed from a material selected from the group consisting of
extruded plastic, aluminum, and fiber glass.
40. The refrigeration door of claim 26, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus twenty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
seventy degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent; and wherein said first surface of said outer sheet of
glass is substantially free of condensation.
41. The refrigeration door of claim 26, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus forty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
eighty degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent; and wherein said first surface of said outer sheet of
glass is substantially free of condensation.
42. The refrigeration door of claim 26, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus zero degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
seventy-two degrees Fahrenheit; and the humidity in the ambient
environment is substantially equal to or greater than sixty
percent; and wherein said first surface of said outer sheet of
glass is substantially free of condensation.
43. The refrigeration door of claim 27, wherein at least one sheet
of glass is formed of Comfort E2.
44. The refrigeration door of claim 26, wherein said first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 1.73 Btu/hr-ft-F.
45. The refrigeration door of claim 26, wherein first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 1.51 Btu/hr-ft-F.
46. The refrigeration door of claim 26, wherein first sealant
assembly and said second sealant assembly each have a heat transfer
rate substantially equal to or less than 0.84 Btu/hr-ft-F.
47. A refrigeration door having an outer surface and adapted to be
mounted on a refrigerating compartment, said door comprising: a
first sheet of glass; a second sheet of glass; a first sealant
assembly disposed around the periphery of said first sheet of glass
and said second sheet of glass for maintaining said first sheet and
said second sheet in spaced-apart relationship from each other; a
first low emissivity coating adjacent a surface of said first sheet
or said second sheet of glass; said first sheet and second sheets
of glass, said first sealant assembly, and said first low
emissivity coating forming an insulating glass unit having a U
value substantially equal to or less than 0.2 BTU/hr-sq ft-F; and a
frame secured around the periphery of said insulating glass
unit.
48. The refrigerator door of claim 47, further comprising: a third
sheet of glass; a second sealant assembly disposed around the
periphery of said second sheet of glass and said third sheet of
glass for maintaining said second sheet and said third sheet in
spaced-apart relationship from each other; and wherein said
insulating glass unit further includes said third sheet of glass
and said second sealant assembly.
49. The refrigeration door of claim 48, further including a second
low emissivity coating adjacent a surface of said first sheet, said
second sheet, or said third sheet of glass.
50. The refrigeration door of claim 49, wherein the U value of said
insulating glass unit is effective to substantially prevent the
formation of condensation on the outer surface of the door without
the application of electricity for heating the outer surface when
the interior temperature of the refrigerating compartment is
substantially equal to or less than zero degrees Fahrenheit; the
temperature of the exterior environment is substantially equal to
or greater than seventy-two degrees Fahrenheit; and the humidity in
the ambient environment is substantially equal to or greater than
sixty percent.
51. The refrigerator door of claim 47, wherein the U value of said
insulating glass unit is effective to substantially prevent the
formation of condensation on the outer surface of the door without
the application of electricity for heating the outer surface when
the interior temperature of the refrigerating compartment is
substantially equal to or less than minus zero degrees Fahrenheit;
the temperature of the exterior environment is substantially equal
to or greater than seventy-two degrees Fahrenheit; and the humidity
in the ambient environment is substantially equal to or greater
than sixty percent.
52. The refrigeration door of claim 51, further comprising: a first
chamber defined by said first sheet of glass, said second sheet of
glass, and said first sealant assembly; and a gas disposed in said
first chamber.
53. The refrigeration door of claim 52, wherein said first sealant
assembly has a heat transfer rate substantially equal to or less
than 1.73 Btu/hr-ft-F.
54. The refrigeration door of claim 43, wherein said gas is
selected from the group consisting of argon, krypton, and air.
55. The refrigeration door of claim 47, wherein said insulating
glass unit has a U value substantially equal to or less than 0.16
BTU/hr-sq ft-F.
56. The refrigeration door of claim 47, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.04.
57. The refrigeration door of claim 47, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.01.
58. The refrigeration door of claim 47, wherein insulating glass
unit has an emissivity substantially equal to or less than
0.0025.
59. The refrigeration door of claim 47, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus twenty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
seventy degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent; and wherein the outer surface of the door is substantially
free of condensation.
60. The refrigeration door of claim 47, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus forty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
eighty degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent; and wherein the outer surface of the door is substantially
free of condensation.
61. A refrigeration door having an outside surface and adapted to
be mounted on a refrigerating compartment, said door comprising: a
first sheet of glass; a second sheet of glass; a first sealant
assembly disposed around the periphery of said first sheet of glass
and said second sheet of glass for maintaining said first sheet and
said second sheet in spaced-apart relationship from each other; a
first low emissivity coating adjacent a surface of said first sheet
or said second sheet of glass; said first sheet and second sheets
of glass, said first sealant assembly, and said first low
emissivity coating forming an insulating glass unit having an
emissivity substantially equal to or less than 0.04 substantially
preventing the formation of condensation on the outside surface of
the refrigeration door without the application of electricity for
heating said outer surface; and a frame secured around the
periphery of said insulating glass unit.
62. The refrigerator door of claim 61, further comprising: a third
sheet of glass; a second sealant assembly disposed around the
periphery of said second sheet of glass and said third sheet of
glass for maintaining said second sheet and said third sheet in
spaced-apart relationship from each other; and wherein said
insulating glass unit further includes said third sheet of glass
and said second sealant assembly.
63. The refrigeration door of claim 62, further including a second
low emissivity coating adjacent a surface of said first sheet, said
second sheet, or said third sheet of glass.
64. The refrigeration door of claim 61, further comprising: a first
chamber defined by said first sheet of glass, said second sheet of
glass, and said first sealant assembly; and a gas disposed in said
first chamber.
65. The refrigeration door of claim 64, wherein said first sealant
assembly has a heat transfer rate substantially equal to or less
than 1.73 Btu/hr-ft-F.
66. The refrigeration door of claim 65, wherein said gas is
selected from the group consisting of argon, krypton, and air.
67. The refrigeration door of claim 61, wherein said insulating
glass unit has a U value substantially equal to or less than 0.16
BTU/hr-sq ft-F.
68. The refrigeration door of claim 61, wherein said insulating
glass unit has a U value substantially equal to or less than 0.20
BTU/hr-sq ft-F.
69. The refrigeration door of claim 61, wherein said insulating
glass unit has an emissivity substantially equal to or less than
0.01.
70. The refrigeration door of claim 61, wherein insulating glass
unit has an emissivity substantially equal to or less than
0.0025.
71. A method of manufacturing a refrigeration door component having
an outer surface, said method comprising the steps of: providing a
first sheet of glass providing a second sheet of glass; providing a
first low emissivity coating adjacent a surface of said first sheet
of glass or said second sheet of glass; disposing a first sealant
assembly around the periphery of said first sheet of glass and said
second sheet of glass to maintain said first sheet and said second
sheet in spaced-apart relationship from each other; and said first
sheet of glass, said second sheet of glass, and said first sealant
assembly forming an insulating glass unit having a U value
substantially equal to or less than 0.2 BTU/hr-sq ft-F
substantially preventing the formation of condensation on the outer
surface of the refrigeration door component without the application
of electricity for heating the door component.
72. The method of claim 71, wherein said first sheet of glass, said
second sheet of glass, and said first sealant assembly define a
first chamber; and further comprising the step of disposing a gas
in said first chamber.
73. The method of claim 71, further comprising the steps of:
providing a third sheet of glass; disposing a second sealant
assembly disposed around the periphery of said second sheet of
glass and said third of glass for maintaining said second sheet and
said third sheet in spaced-apart relationship from each other; and
wherein said insulating glass unit further includes said third
sheet of glass and said second sealant assembly.
74. The method of claim 73, wherein said third sheet of glass
includes a low emissivity coating adjacent a surface of said third
sheet of glass.
75. The method of claim 71, wherein said first sheet of glass is
formed of Comfort Ti-PS.
76. The method of claim 71, wherein said first sealant assembly has
a heat transfer rate substantially equal to or less than 1.73
Btu/hr-ft-F.
77. The method of claim 76, wherein: said first and said second
sheets of glass having a thickness substantially equal to one
eighth of an inch; and said first and said second sheets of glass
being spaced apart a distance substantially equal to one half
inch.
78. The method of claim 71, further including the step of disposing
said insulating glass unit in a door frame.
79. The method of claim 72, wherein said gas is selected from the
group consisting of argon, krypton, and air.
80. The method of claim 71, wherein said insulating glass unit has
a U value substantially equal to or less than 0.16 BTU/hr-sq
ft-F.
81. The method of claim 71, wherein said insulating glass unit has
an emissivity substantially equal to or less than 0.04.
82. The method of claim 71, wherein said insulating glass unit has
an emissivity substantially equal to or less than 0.01.
83. The method of claim 71, wherein said insulating glass unit has
an emissivity substantially equal to or less than 0.0025.
84. The method of claim 71, wherein said low emissivity coating is
selected from the group consisting of a titania based silver and
fluorine doped tin oxide.
85. The method of claim 71, wherein said low emissivity coating is
applied with a process selected from the group consisting of
sputter coating, pyrolytic coating and spray coating.
86. The method of claim 72, wherein said first sheet of glass is
formed of Comfort E2.
87. The refrigeration door of claim 73, wherein said first and
second sealant assemblies have a heat transfer rate substantially
equal to or less than 1.73 Btu/hr-ft-F.
88. The refrigeration door of claim 71, wherein said first sealant
assembly has a heat transfer rate substantially equal to or less
than 1.51 Btu/hr-ft-F.
89. The refrigeration door of claim 71, wherein said first sealant
assembly has a heat transfer rate substantially equal to or less
than 0.84 Btu/hr-ft-F.
90. A method of manufacturing a refrigeration door component having
an outer surface, said method comprising the steps of: providing a
first sheet of glass; providing a second sheet of glass; providing
a first low emissivity coating adjacent a surface of said first
sheet of glass or said second sheet of glass; disposing a first
sealant assembly around the periphery of said first sheet of glass
and said second sheet of glass to maintain said first sheet and
said second sheet in spaced-apart relationship from each other; and
said first sheet of glass, said second sheet of glass, and said
first sealant assembly forming an insulating glass unit having an
emissivity substantially equal to or less than 0.04 substantially
preventing the formation of condensation on the outer surface of
the refrigeration door component without the application of
electricity for heating the door component.
91. The method of claim 90, wherein said first sheet of glass, said
second sheet of glass, and said first sealant assembly define a
first chamber; and further comprising the step of disposing a gas
in said first chamber.
92. The method of claim 90, further comprising the steps of:
providing a third sheet of glass; disposing a second sealant
assembly disposed around the periphery of said second sheet of
glass and said third of glass for maintaining said second sheet and
said third sheet in spaced-apart relationship from each other; and
wherein said insulating glass unit further includes said third
sheet of glass and said second sealant assembly.
93. The method of claim 92, wherein said third sheet of glass
includes a low emissivity coating adjacent a surface of said third
sheet of glass.
94. The method of claim 90, wherein said first sealant assembly has
a heat transfer rate substantially equal to or less than 1.73
Btu/hr-ft-F.
95. The method of claim 90, further including the step of disposing
said insulating glass unit in a door frame.
96. The method of claim 91, further including the step of disposing
said insulating glass unit in a door frame.
97. The method of claim 96, wherein said gas is selected from the
group consisting of argon, krypton, and air.
98. The method of claim 90, wherein said insulating glass unit has
a U value substantially equal to or less than 0.2 BTU/hr-sq
ft-F.
99. The method of claim 90, wherein said insulating glass unit has
an emissivity substantially equal to or less than 0.01.
100. The method of claim 90, wherein said insulating glass unit has
an emissivity substantially equal to or less than 0.0025.
101. The refrigeration door of claim 92, wherein said first and
second sealant assemblies have a heat transfer rate substantially
equal to or less than 1.73 Btu/hr-ft-F.
102. The refrigeration door of claim 90, wherein said first sealant
assembly has a heat transfer rate substantially equal to or less
than 1.51 Btu/hr-ft-F.
103. The refrigeration door of claim 90, wherein said first sealant
assembly has a heat transfer rate substantially equal to or less
than 0.84 Btu/hr-ft-F.
104. A substantially transparent insulating glass unit having an
outer surface and being for use with a refrigerating compartment
residing in an exterior environment and having an interior
refrigerating compartment; said insulating glass unit door
comprising: a first sheet of glass; a second sheet of glass; a
first sealant assembly disposed around the periphery of said first
sheet of glass and said second sheet of glass for maintaining said
first sheet and said second sheet in spaced-apart relationship from
each other; a first low emissivity coating adjacent a surface of
said first sheet or said second sheet of glass, and said first
sheet of glass, said second sheet of glass, and said first sealant
assembly providing the insulating glass unit with a U value
effective to substantially prevent the formation condensation on
the outer surface without the application of a electricity to heat
the outer surface of the insulating glass unit when the interior
temperature of the refrigerating compartment is substantially equal
to or less than zero degrees Fahrenheit; the temperature of the
exterior environment is substantially equal to or greater than
seventy degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent.
105. The door of claim 104, further comprising: a third sheet of
glass; and a second sealant assembly disposed around the periphery
of said second sheet of glass and said third of glass for
maintaining said first sheet and said second sheet in spaced-apart
relationship from each other.
106. The door of claim 105, further including a second low
emissivity coating adjacent a surface of said first sheet, said
second sheet or said third sheet of glass.
107. The door of claim 106 wherein the insulating glass unit has a
U value that substantially prevents the formation condensation on
the outer surface when the interior temperature of the
refrigerating compartment is substantially equal to or less than
minus forty degrees Fahrenheit; the temperature of the exterior
environment is at substantially equal to or greater than eighty
degrees Fahrenheit; and the humidity in the exterior environment is
substantially equal to or greater than sixty percent.
108. The door of claim 106, wherein said low emissivity coating is
effective to cause the insulating glass unit to have a U value
substantially equal to or less than 0.2 BTU/hr-sq ft-F.
109. The refrigeration door of claim 105, wherein said first
sealant assembly and said second sealant assembly each have a heat
transfer rate substantially equal to or less than 1.73
Btu/hr-ft-F.
110. The refrigeration door of claim 104, wherein the insulating
glass unit has a U value substantially equal to or less than 0.16
BTU/hr-sq ft-F.
111. The refrigeration door of claim 104, wherein said first sheet
or second sheet has an emissivity substantially equal to or less
than 0.05.
112. The refrigeration door of claim 104, wherein the insulating
glass unit has an emissivity substantially equal to or less than
0.04.
113. The refrigeration door of claim 104, wherein the insulating
glass unit has an emissivity substantially equal to or less than
0.01.
114. The refrigeration door of claim 104, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus twenty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
seventy degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent.
115. The refrigeration door of claim 104, wherein the interior
temperature of the refrigerating compartment is substantially equal
to or less than minus forty degrees Fahrenheit; the temperature of
the exterior environment is substantially equal to or greater than
eighty degrees Fahrenheit; and the humidity in the exterior
environment is substantially equal to or greater than sixty
percent.
116. The refrigeration door of claim 105, wherein said first
sealant assembly and said second sealant assembly each have a heat
transfer rate substantially equal to or less than 1.73
Btu/hr-ft-F.
117. A refrigeration unit including an insulated enclosure defining
a compartment, a cooling system, and a door adapted mounted on an
opening of said compartment, said door having an outer surface and
comprising: a first sheet of glass; a second sheet of glass; a
first sealant assembly disposed around the periphery of said first
sheet of glass and said second sheet of glass for maintaining said
first sheet and said second sheet in spaced-apart relationship from
each other; a first low emissivity coating adjacent the a surface
of said first or said second sheet of glass; said first sheet,
second sheet, first sealant assembly, and said first low emissivity
coating forming an insulating glass unit having a U value
substantially equal to or less than 0.2. BTU/hr-sq ft-F
substantially preventing the formation of condensation on the outer
surface of the door without the application of electricity for
heating said first surface; and a frame secured around the
periphery of said insulating glass unit.
118. The door of claim 117, further comprising: a third sheet of
glass; and a second sealant assembly disposed around the periphery
of said second sheet of glass and said third of glass for
maintaining said second sheet and said third sheet in spaced-apart
relationship from each other.
119. The refrigeration door of claim 117, further comprising: a
first chamber defined by said first sheet of glass, said second
sheet of glass, and said first sealant assembly; a second chamber
defined by said middle sheet of glass, said outer sheet of glass,
and said second sealant assembly; and a gas disposed in said first
and second chambers.
120. The refrigeration door of claim 118, wherein said first
sealant assembly and said second sealant assembly each have a heat
transfer rate substantially equal to or less than 1.73
Btu/hr-ft-F.
121. The refrigeration door of claim 117, wherein the refrigeration
door has an emissivity substantially equal to or less than
0.04.
122. The refrigeration door of claim 117, wherein the refrigeration
door has an emissivity substantially equal to or less than
0.01.
123. The refrigeration door of claim 117, wherein said first
sealant assembly has a heat transfer rate substantially equal to or
less than 1.73 Btu/hr-ft-F.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates, generally, to refrigeration
doors and, in particular, to an energy-free refrigeration door
providing condensation control, thermal insulation, and a desired
amount of visible transmittance. More particularly, the
refrigeration door of the present invention achieves these desired
characteristics through the application of a low-emissivity
coating, without electrically heating the door. Throughout this
application the term "refrigeration door" is meant to refer to a
door used for freezers, refrigerators and similar units and
cabinets. In addition, for purposes of this application the term
"energy-free" (as in energy-free refrigeration door) means that
electricity is not applied to the glass to heat the glass.
[0003] 2. Discussion of the Background
[0004] Refrigeration doors for commercial freezers, refrigerators
and the like are typically constructed of glass to allow the
customer to view the products placed therein for sale without
opening the door. However, when condensation forms on the glass
(sometimes referred to as "fogging"), the customer is not able to
see through the door to identify the products inside, which is
undesirable from the standpoint of the customer and the store owner
or retailer as well.
[0005] Moisture condenses on the outside of the glass refrigeration
door because the surface temperature of the outside of the glass is
reduced below the ambient temperature in the store by the colder
refrigerated interior of the freezer or refrigerator. When the
temperature of the surface of the glass drops below the dew point
of the air in the store, moisture condenses on the surface of the
glass. In addition, when a door is opened in a humid environment,
the innermost sheet of glass, which forms the inside of the door,
is also momentarily exposed to the ambient air of the store and
condensation may form on the inside of the door as well. The
condensation on the inside of the glass door also occurs because
the temperature of the inside of the glass door is below the dew
point of the ambient store air to which it is exposed.
[0006] As previously indicated, condensation on the glass door,
which may become frost, prevents the customer from seeing the
products for sale through the glass door. Consequently, when
condensation or frost is on the glass door, the customer must
perform the unpleasant task of opening the refrigeration door to
identify the contents inside, which is impractical in a store with
a large number of freezers or refrigerators. Not only is opening
every refrigeration door tedious and time consuming from the
customer's perspective, it is undesirable from the retailer's
standpoint as well since it significantly increases the energy
consumption of the retailer's freezers and refrigerators, thereby
resulting in higher energy costs to the retailer.
[0007] There are various industry performance standards which
refrigeration doors are required to comply with in order to be
acceptable. In the United States, much of the industry requires
freezer doors (but not refrigerator doors) that prevent external
condensation when used in an environment with an outside
temperature of eighty degrees Fahrenheit (80.degree. F.), an
outside relative humidity of sixty percent (60%), and an inside
temperature of minus forty degrees Fahrenheit (-40.degree. F.).
Other countries have different requirements.
[0008] As is well known in the art, a typical refrigeration door is
comprised of an insulating glass unit (IGU) housed in a door frame.
The IGU in a refrigeration door is, typically, comprised of two or
three sheets of glass sealed at their peripheral edges by a sealant
assembly, generally referred to as an edge seal. In an IGU
comprised of three sheets of glass, two insulating chambers are
formed between the three sheets of glass. In an IGU comprised of
two sheets of glass, a single insulating chamber is formed.
Typically, IGUs for refrigerators are constructed of two sheets of
glass, while IGUs for freezers employ three sheets of glass. Once
sealed, the chambers are often filled with an inert gas such as
argon, krypton, or other suitable gas to improve the thermal
performance of the IGU.
[0009] Most conventional approaches to preventing or reducing
condensation in a refrigeration door involve supplying energy to
the door by including a conductive coating on one or more of the
glass surfaces of the IGU for electrically heating the glass. The
purpose of heating the glass is to maintain the temperature of the
glass above the dew point of the warmer ambient air of the store.
By heating the glass above the dew point, the undesirable
condensation and frost are prevented from forming on the glass in
the door, providing a clear view through the glass to the interior
of the refrigeration compartment.
[0010] In a door consisting of a three-paned IGU, an unexposed
surface of one or two of the sheets of glass is coated with a
conductive material. The conductive coating is connected to a power
supply by two bus bars or other electrical connectors mounted on
opposite edges of the glass. As current passes through the coating,
the coating heats, thereby heating the glass sheet to provide a
condensation-free surface. The coating on the IGU of a
refrigeration door is normally applied to the unexposed surface of
the outermost glass sheet. However, because condensation sometimes
forms on the inside of the inner sheet of glass, the unexposed
surface of the innermost sheet of glass may also be coated for
heating to prevent condensation.
[0011] There are numerous drawbacks and problems associated with
these conventional heated refrigeration doors of the prior art.
First, heating the door incurs an energy cost above and beyond the
energy costs of the cooling system. In a standard size commercial
freezer, the additional cost to heat a freezer door is
substantial--based on current electrical utility pricing, such
additional costs can be $100 per year or more for each freezer.
Considering that many stores utilize multiple freezers, with some
supermarkets and other food retailers utilizing hundreds of
freezers, the cumulative energy costs associated with such heated
freezer doors are significant.
[0012] Second, excess heat from conventional heated refrigeration
doors will migrate to the refrigeration compartment, creating an
additional burden on the cooling system, which results in still
greater energy costs. Third, if the power supplied to the door for
heating is too low, is turned off, or is shut down due to a power
outage, condensation and/or frost will form on the glass. If the
power dissipation is too high, unnecessary additional energy costs
will be incurred. In order to reduce the occurrence of these
problems, such heated glass doors often require precise control of
the door heating system. In order to achieve the necessary precise
control of the door heating system, an electrical control system is
required, which results in increased design and manufacturing
costs, as well as substantial operational and maintenance
costs.
[0013] Fourth, these electrically heated glass doors present a
safety hazard to customers and a potential risk of liability and
exposure to retailers and refrigeration system manufacturers. The
voltage applied to the glass door coating is typically 115 volts
AC. The shopping carts used by customers in stores are heavy and
metal. If the shopping cart strikes and breaks the glass door,
electricity may be conducted through the cart to the customer,
which could cause serious injury or even death.
[0014] U.S. Pat. No. 5,852,284 and U.S. Pat. No. 6,148,563 disclose
applying a voltage to a glass coated with a conductive coating
(which may be a low emissivity coating) to control the formation of
condensation on the outer surface of the glass door. The conductive
coating, such as a low emissivity coating, provides a resistance to
the electricity, which produces heat, while also providing
desirable thermal characteristics. However, the refrigeration doors
disclosed in these patents suffer from the previously described
drawbacks and problems associated with all electrically heated
refrigeration doors.
[0015] In addition to being used for conductivity, such low
emissivity coatings have been employed as another means for
reducing condensation on refrigeration doors. Specifically, one
method of increasing the insulating value of glass (the "R value"),
and reducing the loss of heat from the refrigeration compartment,
is to apply a low emissivity (low E) coating to the glass. A low E
coating is a microscopically thin, virtually invisible metal or
metallic oxide layer(s) deposited on a glass surface to reduce the
emissivity by suppressing radiative heat-flow through the glass.
Emissivity is the ratio of radiation emitted by a black body or a
surface and the theoretical radiation predicted by Planck's law.
The term emissivity is used to refer to emissivity values measured
in the infrared range by American Society for Testing and Materials
(ASTM) standards. Emissivity is measured using radiometric
measurements and reported as hemispherical emissivity and normal
emissivity. The emissivity indicates the percentage of long
infrared wavelength radiation emitted by the coating. A lower
emissivity indicates that less heat will be transmitted through the
glass. Consequently, the emissivity of a sheet of glass or of an
IGU impacts the insulating value of the glass or IGU as well as the
heat conductivity (the "U value") of the glass or IGU. The U value
of a sheet of glass or of an IGU is the inverse of its R value.
[0016] In a multi-pane IGU, the emissivity of the IGU, which is the
combined emissivity of the sheets of the glass that form the IGU,
may be approximated by multiplying the emissivity of all the sheets
of glass together. For example, in a two-sheet IGU with each sheet
of glass having an emissivity of 0.5, the total emissivity would be
0.5 multiplied by 0.5 or 0.25.
[0017] While low E coatings have been applied to IGUs used in
refrigeration doors both with and without electrically heating the
doors, such coatings and IGUs are not capable of controlling
condensation and providing the required thermal insulation through
the broad range of temperatures and environments in which such
refrigeration doors are utilized without applying electricity to
heat the doors. More specifically, notwithstanding the use of such
low E coatings, refrigeration doors that are not heated have failed
to provide condensation control in applications in which the
interior temperature of the refrigeration compartment is
substantially near or below freezing.
[0018] Thus, notwithstanding the available electrically heated and
low emissivity coated refrigeration doors, there is a need for a
refrigeration door: (1) that provides the necessary condensation
control and thermal insulation over a broad range of temperatures
and environments; (2) with the desired amount of visible
transmittance; (3) that avoids unnecessary energy costs and undue
burden on the cooling system by eliminating the need for supplying
electrical power to heat the door; (4) that does not require an
expensive and complex electrical control system, thereby minimizing
design, manufacturing, operation, and maintenance costs; and (5)
that does not present a safety hazard to customers and a potential
risk of liability and exposure to manufacturers and retailers.
SUMMARY OF THE INVENTION
[0019] The primary objective of the present invention is to
overcome the deficiencies of the prior art described above by
providing an energy-free refrigeration door with condensation
control, thermal insulation, and a desired amount of visible
transmittance.
[0020] Another key objective of the present invention is to provide
a refrigeration door that does not employ electrical energy in
order to reduce condensation on the glass.
[0021] Another key objective of the present invention is to provide
a refrigeration door that controls condensation and that does not
transfer significant heat to the interior of the freezer or
refrigerator, thereby further burdening the cooling system and
increasing energy costs.
[0022] Still another objective of the present invention is to
provide a refrigeration door with condensation control that is
easier and more economical to manufacture, operate, and maintain
than the prior art refrigeration doors and systems.
[0023] Yet another objective of the present invention is to provide
a refrigeration door with condensation control that is easier to
design, operate, and maintain.
[0024] Another objective of the present invention is to provide a
method for making a refrigeration door with condensation control
that does not use electricity to heat the glass to control the
condensation.
[0025] Yet another objective of the present invention is to provide
a refrigeration door with an emissivity of less than 0.04.
[0026] Still another objective of the present invention is to
provide a refrigeration door with an emissivity of approximately
0.0025.
[0027] Yet another objective of the present invention is to provide
a refrigeration door with a U value of less than 0.2 BTU/hr-sq
ft-F.
[0028] Still another objective of the present invention is to
provide a refrigeration door with a U value of approximately 0.16
BTU/hr-sq ft-F.
[0029] The present invention achieves these objectives and others
by providing an energy-free refrigeration door, and method for
making the same, comprising a door frame housing an insulating
glass unit comprising inner, middle and outer sheets of glass. A
first sealant assembly disposed around the periphery of the inner
and middle sheets of glass forms a first chamber between the inner
and middle sheets of glass. A second sealant assembly disposed
around the periphery of the middle and outer sheets of glass forms
a second chamber between the middle and outer sheets of glass. A
gas, such as krypton, air, or argon is held in the first and second
chambers. The outer sheet of glass and inner sheet of glass each
have an unexposed surface that faces the middle sheet of glass. A
low emissivity coating is disposed on the unexposed surfaces of the
inner and outer sheets of glass so that the glass door as a whole
has a U value that prevents formation of condensation on the outer
surface of the outer sheet of the glass door, without the
application of electricity to heat the door, while also providing
the desired evaporation rate of condensation from the inner side of
the inner sheet of the glass door.
[0030] Further features and advantages of the present invention, as
well as the structure and operation of various embodiments of the
present invention, are described in detail below with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The accompanying drawings, which are incorporated herein and
form part of the specification, illustrate various embodiments of
the present invention and, together with the description, further
serve to explain the principles of the invention and to enable a
person skilled in the pertinent art to make and use the invention.
In the drawings, like reference numbers indicate identical or
functionally similar elements.
[0032] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0033] FIG. 1 depicts a refrigeration system employing the present
invention.
[0034] FIG. 2. depicts a refrigeration door according to the
present invention.
[0035] FIG. 3 is an illustration of a partial cross-sectional view
of a refrigeration door according to the present invention.
[0036] FIG. 4 is an illustration of a partial cross-sectional view
of a refrigeration door according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] In the following description, for purposes of explanation
and not limitation, specific details are set forth, such as
particular coatings, coating processes, sheet thicknesses, seal
assemblies, number of sheets, sheet spacings, and methods for
assembling the door, etc. in order to provide a thorough
understanding of the present invention. However, it will be
apparent to one skilled in the art that the present invention may
be practiced in other embodiments that depart from these specific
details. Detailed descriptions of well-known coatings, coating
processes, sealant assemblies, and methods for assembling the door
are omitted so as not to obscure the description of the present
invention. For purposes of this description of the invention, terms
such as external, internal, outer, and inner are descriptions from
the perspective of the inside of the freezer or refrigerator
compartment as is evident from the figures.
[0038] Testing, as well as computer modeling, has shown that a U
value (the conductivity of transfer of heat through the glass) of
approximately 0.2 BTU/hr-sq ft-F is required for the refrigeration
door to prevent condensation on the outside of the glass under the
performance requirements for the United States industry as
described above. As discussed, however, when the door is opened,
condensation may form on the inside of the inner sheet of glass of
the door because the temperature of the inner surface of the sheet
is below the dew point of the more humid ambient store air to which
it is exposed. The condensation, however, will dissipate once the
door is closed as the moisture evaporates into the freezer or
refrigerator compartment.
[0039] While the condensation is present on the inside of the door,
the contents of the freezer or refrigerator are not visible through
the door. Consequently, the speed of the evaporation, which
determines the length of time during which the condensation is
present, is an important design criterion. The more heat that is
transferred through the glass door to the inner surface of the
glass door, the faster the condensation on the inside of the door
will evaporate. However, increased heat transfer through the door
also results in increased energy costs from the cooling system.
Consequently, the optimal U value of the glass door will be driven
by numerous factors including the difference between the outside
and inside temperatures, the glass thickness, the spacing, the
gas(es) used in the chamber(s) of the IGU, the number of sheets,
the spacer material, the ambient humidity, the absorption
coefficient of the coating in the far infrared spectrum, as well as
the desirable time for evaporation of the condensation. In
addition, the costs associated with the selected components (i.e.,
the gas, the sealant assembly, the glass, etc.), the energy costs,
and other factors are also design considerations. The preferred
embodiment described below provides a U value of 0.16 BTU/hr-sq ft
F that prevents condensation on the outside of the door, while
permitting enough heat to penetrate through the door from the
ambient external environment to allow condensation on the inside of
the door to evaporate in a reasonable amount of time. Some
refrigeration system manufacturers require that the condensation
evaporate within a few minutes and others require evaporation
within one minute. The time required for the condensation to
evaporate will vary according to the amount of time the door is
open, the humidity in the store, the refrigeration system
compartment temperature, the refrigeration system contents, the
heat transferred through the door (which is dependent on the U
value), and other factors.
[0040] In the preferred embodiment of the present invention, as
shown in FIG. 1, a refrigeration system 5 includes a plurality of
transparent refrigeration doors 10 with each having a handle 11. As
will be discussed in more detail below, each refrigeration door 10
includes an IGU 50 mounted in a frame 55. The interior of the
refrigeration system includes a plurality of shelves 6 for holding
merchandise to be seen through the door. Referring to FIG. 2, the
refrigeration door 10 of the present embodiment is mounted to the
opening of the refrigeration system with a hinge, which allows the
door to open outwards.
[0041] As discussed above, the refrigeration door 10 includes an
IGU 50 housed in a frame 55. As shown in FIG. 3, the IGU 50 is
comprised of an outer sheet of glass 60, a middle sheet of glass
65, and an inner sheet of glass 70. The IGU 50 is housed in frame
55 and also includes a first sealant assembly 90 that extends
around the periphery of the inner surface 62 of the outer sheet 60
and the outer surface of the middle sheet 65 of glass to define a
substantially hermetically sealed insulated outer chamber 92.
Similarly, a second sealant assembly 95 extends around the
periphery of the outer surface 72 of the inner sheet 70 and inner
surface of the middle sheet 65 of glass to define a substantially
hermetically sealed insulated inner chamber 94.
[0042] The outer surface 61 of the outer sheet of glass 60 is
positioned adjacent the external ambient environment 7. In other
words, the outer surface 61 of the outer sheet 60 is exposed to the
environment in which the refrigerator or freezer resides. The inner
surface 62 of the outer sheet 60 forms part of, and is exposed to,
the outer chamber 92.
[0043] In this preferred example embodiment, the outer sheet 60 is
one eighth of an inch thick, tempered, and the inner surface 62 of
the outer sheet 60 is coated with a low emissivity coating 63.
Specifically, in this embodiment, the low E coating is a
sputter-coated low E coating that includes an ultra-hard titania as
the base layer to ensure a high level of thermal performance and a
high visible transmittance. This particular sputter coated glass
can be tempered after the coating and offers high visible light
transmission without high levels of color tinting. The outer
surface 61 of outer sheet 60 is not coated. In this embodiment, the
outer sheet 60 may, for example, be a sheet of Comfort Ti-PS glass,
one eighth of an inch thick, manufactured by AFG Industries, Inc.
of Kingsport, Tennessee, which has a low E coating providing an
emissivity of 0.05. As is well-known in the art, the Comfort Ti-PS
is cut to the appropriate size, tempered, and edged before being
integrated into the IGU 50.
[0044] The middle sheet of glass 65 is positioned between the outer
60 and inner 70 sheets of glass and forms part of the outer chamber
92 and the inner chamber 94. The middle sheet 65 is spaced one half
inch from the outer sheet 60 and inner sheet 70 and is a one eighth
of an inch thick, uncoated, sheet of tempered glass.
[0045] The inner sheet of glass 70 is positioned adjacent the
interior of the freezer or refrigerating compartment 9, with its
inner surface 71 exposed to the interior of the compartment 9. The
outer surface 72 of the inner sheet 70 forms part of, and is
exposed to, the inner chamber 94. The outer surface 72 of the inner
sheet 70 of glass is also coated with a low emissivity coating 73.
In this embodiment, the coating 73 on the outer surface 72 of the
inner sheet 70 is the same as that described above with respect to
the coating 63 of the inner surface 62 of the outer sheet 60. The
inner surface 71 of inner sheet 70 is not coated. In this
embodiment, the inner sheet 70 may also, for example, be a sheet of
Comfort Ti-PS, one eighth of an inch thick, manufactured by AFG
Industries, Inc., which has the described characteristics and
coating.
[0046] In this example embodiment, the chambers 92 and 94 are both
filled with air. In alternative embodiments, each chamber may be
filled with a different gas and the chambers could be filled with
krypton, argon, or other suitable gas.
[0047] The sheets 60, 65 are held apart by a first sealant assembly
90 which extends around the periphery of the sheets 60, 65
maintaining the glass sheets in parallel, spaced-apart relationship
creating chamber 92 between the sheets 60, 65, while also sealing
the chamber 92 from the external environment. Likewise, the sheets
65, 70 are held apart by a second sealant assembly 95 which extends
around the periphery of the sheets 65, 70 maintaining the glass
sheets in parallel, spaced-apart relationship creating chamber 94
between the sheets 65, 70, while also sealing the chamber 94 from
the external environment. The sealant assemblies 90, 95 maintain a
one half inch space between the outer sheet 60 and middle sheet 65
and inner sheet 70 and middle sheet 65, respectively.
[0048] The sealant assemblies 90, 95 of the present embodiment are
preferably, warm edge seals. "Warm edge" is used to describe an
insulating glass sealing assembly that reduces heat loss better
than conventional aluminum spacers and sealant combinations. Each
of the sealant assemblies 90, 95 of this embodiment includes its
own spacer and desiccant, which replaces the need for a separate
sealant, metallic spacer, and desiccant, and has a heat transfer
rate of 0.84 Btu/hr-ft-F (sometimes referred to as a K value). The
sealant assemblies 90, 95 in this embodiment are a composite
extrusion containing a combination of polyisobutylene sealant, hot
melt butyl sealant, desiccant matrix, rubber shim and a vapor
barrier. Suitable sealant assemblies of this type are manufactured
and sold by TruSeal Technologies of Beachwood, Ohio, under the name
"Comfort Seal."
[0049] Referring to FIG. 3, IGU 50 is shown. IGU 50 is comprised of
glass sheets 60, 65, and 70 integrated by sealant assemblies 90 and
95. IGU 50 is installed in frame 55 in any suitable manner
well-known to those skilled in the art. The frame 55 is made from
extruded plastic or other suitable well-known frame materials, such
as extruded aluminum, fiber glass or other material. If, in an
alternative embodiment the frame 55 is formed of aluminum or other
material, the door may require heating along its edges to ensure
condensation control around the edges of the door.
[0050] Referring to FIG. 1, a refrigeration system 5 is shown. The
door frame 55 is coupled to the refrigeration compartment 8 in any
suitable fashion as is well known in the art, such as a single door
long hinge, multiple hinges, or in a slot for sliding the door open
and closed. In addition, the frame may include a door handle 11 or
other suitable actuating means as is appropriate for the
application. The refrigeration system 5, of which the door 10 forms
a part, may be any system used for cooling a compartment, such as
that disclosed in U.S. Pat. No. 6,148,563, which is hereby
incorporated herein by reference.
[0051] The above preferred embodiment provides a refrigeration door
with a U value of 0.16 BTU/hr-sq ft-F (and emissivity of 0.0025),
which has been found to be suitable for freezer door applications
requiring the performance standards identified above with respect
to the United States industry. A U value of 0.16 BTU/hr-sq ft-F
permits the refrigeration door to easily meet the required
performance standards, while also allowing enough heat to penetrate
through the door from the external ambient environment to evaporate
condensation formed on the inside of the door in a reasonable time
period. In addition, the preferred embodiment provides a visible
light transmittance of sixty-six percent (66%).
[0052] As an alternative to the Comfort Ti-PS glass, other low E
coated glass may be used, such as, for example, Comfort Ti-R,
Comfort Ti-AC, Comfort Ti-RTC, and Comfort Ti-ACTC, all of which
are available from AFG Industries, Inc., which like Comfort Ti-PS,
are titania/silver based low E coated glass manufactured by AFG
Industries, Inc. Another suitable type of glass is Comfort E2,
which is coated with a pyrolytic process and is a fluorine doped
tin oxide low E coated glass, one eighth of an inch thick, and
which is manufactured by AFG Industries, Inc. Comfort E2 is
suitable for some of the less stringent performance standards
because of its higher emissivity.
[0053] The U value of the refrigeration door 10 is determined by a
number of design factors including the number of sheets of glass,
the thickness of the sheets, the emissivity of the IGU, the spacing
between the sheets, and the gas in the chamber(s). In the three
pane refrigeration door 10 of the preferred embodiment described
above, the U value of 0.16 BTU/hr-sq ft-F is accomplished using air
as the gas being held in the chambers, glass thicknesses of one
eighth of an inch on all sheets, one half inch spacing, and an IGU
emissivity of 0.0025. However, each of these factors can be varied
resulting in numerous permutations of values that could be combined
to provide the same U value. In addition, other applications may
require a smaller or larger U value depending on the environment,
costs constraints, and other requirements or considerations.
[0054] A number of computer simulations have been performed to
determine the U values of numerous IGUs for use in refrigeration
doors 10 with a range of values of each of the various design
parameters combined in different permutations. The table below
includes the design parameters and corresponding calculated U
values for a number of three pane IGU configurations. In addition
to the design parameters listed in Table 1 below, all of the three
pane IGU U value calculations were computed with each pane being
one eighth of an inch thick, and a total of two sides of the three
panes being low E coated. Tempering of the glass does not
significantly effect the calculated performance values.
1TABLE 1 Spacing between Sheets Gas in Type of Emissivity of U
value (inches) Chambers Coating IGU (Btu/hr-sq ft-F) 1/2 air Ti-PS
0.0025 0.16 {fraction (5/16)} air Ti-PS 0.0025 0.22 1/2 argon Ti-PS
0.0025 0.12 {fraction (5/16)} argon Ti-PS 0.0025 0.17 1/2 krypton
Ti-PS 0.0025 0.11 {fraction (5/16)} krypton Ti-PS 0.0025 0.11 1/2
air CE2 0.04 0.20 {fraction (5/16)} air CE2 0.04 0.26 1/2 argon CE2
0.04 0.17 {fraction (5/16)} argon CE2 0.04 0.21 1/2 krypton CE2
0.04 0.15 {fraction (5/16)} krypton CE2 0.04 0.15
[0055] In each of the tables included herein, "Ti-PS" refers to the
low E coating of AFG Industries' Comfort Ti-PS glass and "CE2"
refers to the low E coating of AFG Industries' Comfort E2 glass,
both described above. In addition, the U values in the tables are
calculated as "center of the glass" values, because the computer
simulation does not have the capability to consider the sealant
assembly. Consequently, there are no sealant assembly data or
design criteria listed in the tables.
[0056] In an alternative two pane embodiment of the present
invention shown in FIG. 4, the IGU 50 includes an outer sheet 60
and inner sheet 70 of glass, the frame 55, and a sealant assembly
90. In this two-pane embodiment, both the outer sheet 60 and inner
sheet 70 are one eighth of an inch thick and include the same low E
coating as described in the first embodiment, which is titania
based silver low E coating. Again, both the outer sheet 60 and
inner sheet 70 may, for example, be a sheet of Comfort Ti-PS glass,
one eighth of an inch thick, manufactured by AFG Industries, Inc.
The coated sides of the sheets 60 and 70 are on the unexposed
surfaces of the sheets, sides 62 and 72, respectively, which form
part of the chamber 92. In addition, the same sealant assembly 90
described above (the Comfort Seal) may be used and acts to provide
a spacing of one half inch between the outer 60 and inner 70 sheets
of glass.
[0057] Table 2 below includes design parameters and the
corresponding calculated U values for a number of two pane IGUs. In
addition to the design parameters listed in the table below, all of
the two pane calculations were computed with each pane being one
eighth of an inch thick, and a total of two sides of the two panes
being low E coated. Tempering of the glass does not significantly
effect the calculated performance values.
2TABLE 2 Spacing between Sheets Gas in Type of Emissivity of U
value (inches) Chambers Coating IGU (Btu/hr-sq ft-F) 1/2 air Ti-PS
0.0025 0.29 {fraction (5/16)} air Ti-PS 0.0025 0.36 1/2 argon Ti-PS
0.0025 0.23 {fraction (5/16)} argon Ti-PS 0.0025 0.28 1/2 krypton
Ti-PS 0.0025 0.22 {fraction (5/16)} krypton Ti-PS 0.0025 0.20 1/2
air CE2 0.04 0.32 {fraction (5/16)} air CE2 0.04 0.39 1/2 argon CE2
0.04 0.27 {fraction (5/16)} argon CE2 0.04 0.31 1/2 krypton CE2
0.04 0.26 {fraction (5/16)} krypton CE2 0.04 0.24
[0058] In alternative embodiments, any suitable type of coating
processes may be employed including pyrolytic (e.g., as in the
Comfort E2), which is often referred to as chemical vapor
deposition (CVD), spray, and sputter coating (e.g., as in the
Comfort Ti-PS). Furthermore, these processes may be applied using
well-known off-line or on-line manufacturing methods as is suitable
and appropriate for the quantity and type of production and
process. Likewise, any suitable low E coating may be employed
including silver based, titania based, or fluorine doped tin oxide
coating.
[0059] Although the embodiments described above include low E
coatings on the unexposed surfaces of two sheets of glass, other
embodiments of the present invention might include a low E coating
applied to only one sheet of glass on either side, or on both
sides. Likewise, in other embodiments the middle sheet of glass (of
a three pane embodiment) may include a low E coating on either side
(or both sides) instead of, or in addition to, coatings on the
inner sheet 70 and outer sheet 60 of glass.
[0060] In yet another three pane embodiment, the inner sheet of
glass 70 does not have a low E coating on either side of the sheet
of glass 70. Likewise, in an alternative to the two sheet
embodiment described above, the low E coating is present on only
one sheet, or on both sides of both sheets. In general, the number
of sheets that have the low E coating and the side (or sides) that
have the coating is a design choice. The total emissivity of the
IGU, which along with other factors determines the U factor of the
door, is more important with respect to the thermal performance
than which side or sides of which sheet(s) are coated. In addition,
although the embodiments described herein have emissivities of less
than or equal to 0.04 for refrigeration door applications, using a
high performance gas (such as krypton) may enable an IGU with an
emissivity of slightly more than 0.04 to provide the necessary
condensation control in some circumstances.
[0061] In other embodiments, other sealant assemblies may be
employed including for example, an all-foam, non-metal assembly
such as the Super Spacer, manufactured by EdgeTech, Inc, which has
a heat transfer rate of approximately 1.51 Btu/hr-ft-F. Another
suitable sealant assembly is the ThermoPlastic Spacersystem (TPS)
manufactured by Lenhardt Maschinenbau GmbH, which has a heat
transfer rate of approximately 1.73 Btu/hr-ft-F.
[0062] The spacing in the above disclosed embodiments is one half
inch. However, while the preferred spacing ranges between five
sixteenths of an inch to one half inch, other embodiments of the
invention may use spacings up to three quarters of an inch. In
addition, while the above disclosed embodiments employ glass one
eighth of an inch thick that is tempered (except for the middle
sheet), other embodiments may use untempered glass or thicknesses
that are greater than, or less than, one eighth of an inch.
[0063] The design parameters of an embodiment of the present
invention will be determined, in part, by the application or
intended use of the embodiment. More specifically, the exterior
ambient temperature, interior temperature, and exterior ambient
humidity (and associated dew point) are important factors in
determining the necessary U value for the design, which in turn,
determines the design parameters (type of glass, emissivity, number
of sheets, gas, etc.).
[0064] The left five columns of Table 3 below provide a list of
calculated U values for various applications of the intended use
and includes the exterior temperature, interior temperature,
exterior humidity, and calculated dew point for each U value. In
addition, the right three columns of Table 3 provide an embodiment
of the invention that will provide the necessary U value.
3TABLE 3 Calculated U Values for Various Environmental Parameters
IGU Design Variables Dewpoint Maximum for Satisfying Identified
Exterior Interior U Value (Outside Relative U Value Temp Temp Btu/
Glass T) Humidity Glass Spacing Gas In Deg F. Deg F. hr-sq ft-F Deg
F. Percent (Two Sheets) Inches Chambers 80 -40 0.19 64.9 60.1 Ti-PS
3/8 air 72 0 0.27 57.4 60 CE2 {fraction (5/16)} air 80 -40 0.15
67.6 66.0 CE2 3/8 krypton 80 -40 0.18 65.7 61.8 CE2 3/8 argon 80
-40 0.25 60.3 51.1 CE2 3/8 air 80 -40 0.16 67.3 65.3 CE2 1/2
krypton 80 -40 0.17 66.5 63.5 CE2 1/2 argon 80 -40 0.20 64.1 58.5
CE2 1/2 air 80 -40 0.11 70.6 73.1 Ti-PS 3/8 krypton 80 -40 0.14
68.6 68.3 Ti-PS 3/8 argon 80 -40 0.19 65.0 60.3 Ti-PS 3/8 air 80
-40 0.12 70.2 72.1 Ti-PS 1/2 krypton 80 -40 0.13 69.4 70.2 Ti-PS
1/2 argon 80 -40 0.17 66.7 64.0 Ti-PS 1/2 air 72 -10 0.18 61.2 68.9
CE2 3/8 argon 72 0 0.18 62.1 71.1 CE2 3/8 argon 72 10 0.18 63.0
73.4 CE2 3/8 argon 70 0 0.18 60.3 71.4 CE2 3/8 argon 80 0 0.18 69.2
69.7 CE2 3/8 argon 90 0 0.18 78.1 68.3 CE2 3/8 argon 70 -20 0.21
55.5 60.1 CE2 3/8 air 86 -22 0.11 77.5 75.9 Ti-PS 3/8 krypton 80
-40 0.19 65.0 60.3 CE1 1/2 air 70 32 0.18 63.4 79.6 CE2 3/8 argon
80 32 0.18 72.2 77.2 CE2 3/8 argon 90 32 0.18 81.0 75.0 CE2 3/8
argon
[0065] The design parameters of Table 3 identify the type of glass
(which is one eighth of an inch thick), the spacing between sheets,
and the gas in the chambers. In addition, all of the IGUs of the
Table 3 include a third, non-coated sheet of glass that is one
eighth of an inch thick, and that is disposed between the two
sheets of glass identified in the table. CE1 in the Table 3 refers
to Comfort El, which has an emissivity of 0.35 and is sold by AFG
Industries, Inc.
[0066] The foregoing has described the principles, embodiments, and
modes of operation of the present invention. However, the invention
should not be construed as being limited to the particular
embodiments described above, as they should be regarded as being
illustrative and not as restrictive. It should be appreciated that
variations may be made in those embodiments by those skilled in the
art without departing from the scope of the present invention.
[0067] While the application of the present invention has been
described in the application of a refrigerator or freezer door,
other applications might include vending machines, skylights, or
refrigerated trucks. In some of these applications, condensation on
the second or colder side of the glass may not be an issue because
the glass is not in a door that is periodically opened exposing the
cold glass to a more humid environment. As a result, the key
factors in designing the glass are economics (i.e., the energy
costs and the cost of the glass and its installation), visible
transmittance, durability, and other considerations.
[0068] While a preferred embodiment of the present invention has
been described above, it should be understood that it has been
presented by way of example only, and not limitation. Thus, the
breadth and scope of the present invention should not be limited by
the above described exemplary embodiment.
[0069] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *