U.S. patent number 3,775,992 [Application Number 05/272,410] was granted by the patent office on 1973-12-04 for method and apparatus for making clear ice.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to James A. Bright.
United States Patent |
3,775,992 |
Bright |
December 4, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS FOR MAKING CLEAR ICE
Abstract
A clear ice maker has a stationary open-top tray for containing
a predetermined quantity of water. A grid has a plurality of
open-bottom, open-top ice mold cavities and flexible filler means
between the cavities to displace substantially all of the water
into the cavities when the grid is in the tray. The side and bottom
walls of the tray are heated to keep the water adjacent thereto
from freezing. Air at below-freezing temperatures is directed over
the open top of the tray and grid to freeze water into clear ice
starting at the interface between the air and the water in the
cavities and continuing downwardly toward the bottom wall of the
tray. Harvesting mechanism periodically removes the grid and clear
ice from the tray before the air has frozen the water in the
cavities to the bottom wall of the tray; and then twists the grid
to release the clear ice into a storage bucket.
Inventors: |
Bright; James A. (Dayton,
OH) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
23039681 |
Appl.
No.: |
05/272,410 |
Filed: |
July 17, 1972 |
Current U.S.
Class: |
62/73; 62/353;
62/351 |
Current CPC
Class: |
F25C
1/24 (20130101); F25C 2305/022 (20130101) |
Current International
Class: |
F25C
1/22 (20060101); F25C 1/24 (20060101); F25c
005/08 () |
Field of
Search: |
;62/353,351,73,356 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wayner; William E.
Assistant Examiner: Tapolcai, Jr.; William E.
Claims
What is claimed is:
1. A clear ice maker comprising tray means adapted to contain a
body of water and having an open top, a grid in said tray means for
supporting clear ice to be formed thereon and having a poor heat
conducting characteristic, said tray means adapted to provide the
lower portion of said body of water with an above-freezing
temperature to maintain it in a liquid state, refrigerating means
adapted to expose the surface of said body of water at said open
top to below-freezing ambient air for a sufficient period to start
the freezing of a surface layer of ice on said body of water and to
continue the freezing thereof progressively downwardly in
supporting engagement with said grid, and means adapted to remove
said grid and the ice supported by said grid from said tray means
before said ice extends to the bottom of said tray means.
2. A clear ice maker comprising tray means adapted to contain a
volume of water in a refrigerated ambient, a grid in said tray
means for supporting clear ice to be formed thereon and having a
poor heat conducting characteristic, said grid on the inside
thereof having a cube forming cavity defining the top surface of
said volume of water with said refrigerated ambient, heating means
adapted to provide the lower portion of said volume of water with
an above-freezing temperature to maintain it in a liquid state,
refrigerating means adapted to expose said volume of water to
below-freezing ambient air along said top surface for a sufficient
period to start freezing a surface layer of ice on said volume of
water in said cube forming cavity and to continue the freezing
thereof progressively downwardly in supporting engagement with said
grid, means adapted to periodically automatically remove said grid
and the ice supported by said grid from said tray means before said
ice extends to the bottom of said tray means, and means connected
to the bottom of said tray means for supplying make-up water to
said tray means during the periodic removal of said ice to restore
said volume of water to the volume contained in said tray means
before the freezing of said surface layer of ice was started.
3. A method of making clear ice adjacent a support comprising
containing a body of water adjacent said support, heating the lower
portion of said body of water to above-freezing temperature whereby
to retain said lower portion in a liquid state, distributing a flow
of air at below-freezing temperature uniformly over the top surface
of said body of water for a sufficient period to start the freezing
of a surface layer of ice on said body of water and to continue the
freezing thereof progressively downwardly in supporting
relationship with said support, and periodically removing said
support and the ice supported thereby before the ice extends to the
bottom of said body of water whereby to avoid the entrapment of gas
and minerals entrained in said body of water.
4. A method of making clear ice on a support having a poor heat
conducting characteristic and storing said clear ice in a
receptacle in a freezer comprising containing a body of water
adjacent said support, heating the lower portion of said body of
water to above-freezing temperature whereby to retain said lower
portion in a liquid state, distributing a flow of air at
below-freezing temperature uniformly over the top surface of said
body of water for a sufficient period to start the freezing of a
surface layer of ice on said body of water and to continue the
freezing thereof progressively downwardly in supporting engagement
with said support, periodically removing the support and the ice
supported thereon before the ice extends to the bottom of said body
of water whereby to avoid the entrapment of gas and minerals
entrained in said body of water, and moving said support and the
ice supported thereon during the periodic removal thereof through
said flow of air at a rate sufficient to dry said ice before it is
stored in said receptacle.
5. A clear ice maker comprising a grid in a tray adapted to contain
water, means for exposing the bottom side of said tray to
above-freezing temperatures whereby to retain a lower portion of
water in said tray in a liquid state, means exposing the top
surface of water in said tray to below-freezing temperatures for a
sufficient period to start the freezing of a portion of said water
from said top surface down into clear ice, said grid on the inside
thereof having a cube forming cavity defining the top surface of
said water and on the outside thereof a void formed by said cavity,
said void filled sufficiently with filler material to displace
substantially all of the water from the tray into the cavity, said
filler material having an anti-stick characteristic with respect to
ice and said tray to provide easy removal of the grid and clear ice
from the tray, means for periodically removing the grid and clear
ice from said tray before the clear ice extends a sufficient
distance toward the bottom side of said tray to entrap gas and
minerals which may be entrained in said water, and means for
releasing said clear ice from said grid.
6. A clear ice maker comprising a warpable grid in a tray adapted
to contain water, heating means for heating the bottom side of said
tray to above-freezing temperatures to retain a lower portion of
water in said tray in a liquid state throughout the clear ice
making process, fan means distributing sub-freezing air over a top
planar surface of water in said tray for a sufficient period to
initiate the freezing of clear ice along the interface between said
air and said top planar surface and to continue the freezing of
clear ice downwardly in said grid, said grid on the inside thereof
having cube forming cavities of inverted truncated pyramidal shape
defining in an upper portion of said cavities the top surface of
water in said tray and on the outside thereof voids formed by said
cavities, said voids filled sufficiently with filler material to
displace substantially all of any water in the tray from the tray
into the cavities, said filler material and said grid having an
anti-stick characteristic with respect to ice and said tray to
provide easy removal of the grid and clear ice cubes from the tray
and the clear ice cubes from said grid, means for periodically
removing the grid and clear ice cubes from said tray before the
freezing of clear ice downwardly reaches said lower portion of
water in said tray and entraps in said cubes any gas and minerals
which may be entrained in said lower portion of water, and means
for warping said grid to release said clear ice cubes therefrom,
said filler material having a characteristic of flexibility to
distribute forces uniformly throughout said grid when the grid is
removed from the tray and warped to release the clear ice
cubes.
7. The clear ice maker of claim 6 wherein said grid is
polypropylene and said filler material is RTV silicone rubber.
8. The clear ice maker of claim 6 wherein the top surface of water
adapted for freezing as clear ice is at least 65 square inches,
said fan means is distributing air having a sub-freezing
temperature of substantially minus 10.degree. F. to minus
12.degree. F. at substantially 10 to 15 cubic feet per minute, and
said removing means includes a timer controlling the removal of the
grid and clear ice cubes from said tray substantially once every
two and one-half hours.
9. In combination, a domestic freezer, a clear ice maker in said
freezer comprising a warpable grid in a tray adapted to contain
water, heating means energizable for heating the bottom side of
said tray to above-freezing temperatures to retain a lower portion
of water in said tray in a liquid state throughout the clear ice
making process, fan means operable for cooling said freezer to
substantially 0.degree. F. and for distributing sub-freezing air at
substantially minus 10.degree. F. to minus 12.degree. F. over a top
planar surface of water in said tray for a sufficient period to
initiate the freezing of clear ice along the interface between said
air and said top planar surface and to continue the freezing of
clear ice downwardly in said grid, said grid on the inside thereof
having a cube forming cavity defining in an upper portion of said
cavity the top surface of water in said tray and on the outside
thereof a void formed by said cavity, said void filled sufficiently
with filler material to displace substantially all of any water in
the tray from the tray into the cavity, and control means
deenergizing said heating means when said fan means is not
operating for distributing said sub-freezing air to reduce heat
dissipated in said freezer.
10. A clear ice maker in a freezer comprising a tray having side
and bottom walls adapted to contain a body of water, a grid in said
tray having cavity-forming means for displacing the body of water
contained by said walls into the cavity, fan means distributing
sub-freezing air over the top planar surface of said body of water
in said grid cavity for a sufficient period to initiate the
freezing of clear ice in said grid cavity along the interface
between said air and said top planar surface and to continue the
freezing of clear ice downwardly in said grid cavity, and a bucket
for storing said clear ice in said freezer and being removable from
said freezer, heating means energizable to maintain said body of
water in a liquid state adjacent said tray below the freezing clear
ice, harvesting mechanism for removing said grid and clear ice from
said tray before the freezing of clear ice downwardly in said grid
cavity reaches the bottom wall of said tray and depositing said
clear ice in said bucket, said heating means comprising a first
heater for the sidewall of the tray and a second heater for the
bottom wall of the tray, and control means providing for continuous
energization of said first heater and energization of said second
heater only when said bucket is full of clear ice or removed from
said freezer whereby to maintain said body of water below the
freezing clear ice at substantially 36.degree. F.
11. The clear ice maker of claim 10 wherein said first and second
heaters are vinyl covered resistance wire retained in a foil
sandwich between said side and bottom walls of the tray on the
outside thereof and a layer of foam insulation.
12. In combination with an insulated cabinet wall defining a
freezer compartment adapted to contain air at subfreezing
temperatures, a clear ice maker in said freezer compartment, said
clear ice maker comprising a tray on the inside of said insulated
cabinet wall having side and bottom tray walls adapted to contain
water therein at a predetermined level, cooling means supplying air
at sub-freezing temperatures to the top surface of water contained
in said tray at said predetermined level for a sufficient period to
start freezing an upper portion of said water from said top surface
downwardly into clear ice, heating means maintaining a bottom
portion of said water in a liquid state adjacent said bottom tray
wall, and water fill means for refilling said tray with water to
said predetermined level when the upper clear ice portion is
removed from said tray, said fill means including a reservoir
adapted to contain water therein in a liquid state at said
predetermined level and means for maintaining water in said
reservoir at said predetermined level, said reservoir being on the
outside of said insulated cabinet wall substantially in the same
horizontal plane as said tray, and conduit means interconnecting
said reservoir and said tray from connections with said reservoir
and tray below said predetermined level to place said reservoir in
liquid flow communication with the bottom portion of water in the
tray whereby water is supplied from said reservoir to said tray
through said conduit means until the water level in said tray and
reservoir is common at said predetermined level.
13. The combination of claim 12 wherein the connection of said
conduit means with said tray is in heat transfer relationship with
said heating means whereby water in the conduit means on the inside
of said insulated cabinet wall remains in a liquid state.
14. The combination of claim 12 wherein the heating means and the
connection of said conduit means with said tray are foamed in place
by insulation on the outside of said tray walls.
Description
This invention relates to a method and apparatus for making clear
ice and, more particularly, to such apparatus for domestic
refrigerators.
Clear ice has been a desire of users and a goal of manufacturers
for years. Apparatus for making clear ice, however, has been
cumbersome and suited only to commercial manufacture of ice.
Heretofore, no one has simplified clear ice makers to the point
where they are suitable in size, cost and operation to the
relatively small confines of the freezer in a domestic
refrigerator.
Accordingly, it is an object of this invention to make clear ice in
a manner similar to that by which skim ice is formed on the surface
of a puddle or pool by below-freezing air in winter.
It is also an object of this invention to provide a clear ice maker
wherein clear ice is formed on a removable, poor heat-conducting
support downwardly from an exposed surface on a body of water
whereby to force gas and minerals entrained in said body of water
ahead of the clear ice and into a remaining non-frozen portion of
the body of water.
Another object of this invention is a method of making clear ice
along an interface between below-freezing air and a body of
purified water in a freezer.
Another object of this invention is a method of making clear ice by
conversion along an interface between below-freezing air and a body
of purified water in a freezer.
A specific object is the provision of a method and apparatus for
making clear ice in a container in the freezer of a domestic
refrigerator by containing water in a tray, heating the bottom of
the tray to keep the lower portion of the water in a liquid state,
freezing the top portion of the water starting at the interface
between the water and freezer air and continuing to freeze water
downwardly toward the bottom of the tray, and periodically removing
the frozen clear ice portion before it extends sufficiently toward
the bottom of the tray to entrap gas and minerals in the water.
A more specific object is the provision of a method and apparatus
for making clear ice in a container in a domestic refrigerator and
storing said clear ice in a receptacle in a freezer comprising
containing water in a tray, heating the bottom of the tray to keep
the lower portion of the water in a liquid state, freezing the top
portion of the water by distributing a flow of below-freezing air
thereover starting at the interface between the water and the
below-freezing air and continuing to freeze water downwardly toward
the bottom of the tray, periodically removing the frozen clear ice
portion before it extends sufficiently toward the bottom of the
tray to entrap gas and minerals in the water, and moving the clear
ice portion during its periodic removal through said below-freezing
air slow enough to dry said clear ice portion before it is stored
so that it will not stick to other clear ice portions in said
receptacle during storage thereof.
Another object of this invention is the provision in the clear ice
making apparatus of the last object for forming the clear ice in
block-like cubes.
Another object of this invention is the provision in the clear ice
maker of the foregoing objects of a warpable grid in a
water-containing tray, the inside of said grid having cube forming
cavities of inverted truncated pyramidal shape and the outside of
said grid between said cavities being filled with an anti-stick
material to displace substantially all of the water from the tray
into the cavities and provide easy removal of the grid and clear
ice from the tray, said anti-stick material also being flexible to
distribute forces uniformly throughout said grid when the grid is
removed from the tray and warped to harvest the clear ice.
A still further object of this invention is a clear ice maker in a
freezer comprising a tray containing a body of water and fan means
distributing sub-freezing air over the top surface of said body of
water whereby to initiate the freezing of clear ice along the
interface between said air and said top surface, heating means to
maintain said body of water in a liquid state adjacent said tray
below said clear ice, and control means to deenergize said heating
means when said fan is not blowing sub-freezing air over the top
surface of said body of water, thereby to reduce heat dissipated in
said freezer.
A still further object of this invention is a clear ice maker in a
freezer comprising a tray containing a body of water, a grid in
said tray displacing said body of water into cavities in said grid,
fan means distributing sub-freezing air over the top surface of
said body of water in said grid whereby to initiate the freezing of
clear ice along the interface between said air and said top
surface, and a bucket for storing said clear ice, heating means to
maintain said body of water in a liquid state adjacent said tray
below said clear ice, harvesting mechanism for removing said grid
from said tray and depositing said clear ice in said bucket, said
heating means comprising a first heater for the sidewall of the
tray and a second heater for the bottom wall of the tray, and
control means providing for continuous energization of said first
heater and energization of said second heater only when said bucket
is full of clear ice or not in said freezer.
It is also an object of this invention to provide in the clear ice
maker of any of the foregoing objects a tray and grid combination
containing a body of water having an exposed top planar surface
area of substantially 65 square inches in a freezing ambient
(0.degree. F.) for initial freezing as clear ice and a timer for
initiating the removal of said grid from said tray and the
harvesting of said clear ice substantially every two and one-half
hours.
Another object in the clear ice maker of this invention is the
provision of common liquid level seeking fill means including a
tray inside the freezer and a float-controlled reservoir outside
the freezer in liquid-flow communication through a tube connected
to the bottom wall of said tray.
A further object in the clear ice maker of this invention is the
provision of a stationary container comprising a tray adapted to
contain on the inside thereof a body of water with a relatively
large top surface area exposed to a freezing ambient (0.degree. F.)
for initial freezing as clear ice, insulation surrounding the side
and bottom walls of said tray on the outside thereof and heaters
sandwiched between the insulation and the tray for exposing the
body of water below said clear ice to an above-freezing ambient
(36.degree. F.).
Another object is the provision in the clear ice maker of this
invention of a stationary container comprising an insulated and
heated tray adapted to contain a body of water with a relatively
large area top surface portion exposed in the freezer of a domestic
refrigerator, fan means adapted to distribute air to said top
surface coextensively with said top surface at a quantity of
substantially 10 to 15 cubic feet per minute and at a temperature
of substantially minus 10.degree. F. to minus 12.degree. F. to
freeze the top surface portion only into clear ice, and harvesting
mechanism for moving said clear ice from said tray through said air
at a rate sufficient to dry said clear ice before it is stored.
Further objects and advantages of the present invention will be
apparent from the following description, reference being had to the
accompanying drawings wherein a preferred embodiment of the present
invention is clearly shown.
IN THE DRAWINGS
FIG. 1 is a fragmentary section through the freezer compartment of
a domestic refrigerator showing in side elevation the automatic
clear ice maker of this invention;
FIG. 2 is a front elevational view taken along line 2--2 in FIG. 1
with parts broken away to provide a schematic representation of the
clear ice harvesting cycle;
FIG. 3 is a sectional view taken along line 3--3 in FIG. 2;
FIG. 4 is a fragmentary sectional view taken along line 4--4 in
FIG. 3 and showing a portion of the water fill system;
FIG. 5 is a sectional view taken along line 5--5 in FIG. 3 and
showing an insulated and heated water containing tray;
FIG. 6 is a fragmentary sectional view taken along line 6--6 in
FIG. 4;
FIG. 7 is a perspective view of a side by side refrigerator freezer
showing the clear ice maker of this invention installed in a
portion of the freezer compartment;
FIG. 8 is a perspective view of the clear ice maker of this
invention in an ice harvesting mode;
FIG. 9 is a sectional view with parts broken away taken along line
9--9 in FIG. 3 to show the ice harvesting mechanism and weight
sensing means;
FIG. 10 is a side elevational view with parts broken away taken
along line 10--10 in FIG. 9;
FIG. 11 is a sectional view of the ice harvesting mechanism taken
along line 11--11 in FIG. 10 to show the ice making cycle timer and
drive mechanism;
FIG. 12 is a perspective view from the front side with parts broken
away to show ice harvesting mechanism for moving the ice grid and
weight sensing means for sensing, first, the presence of an empty
ice storage bucket and, secondly, a predetermined load of ice in
the bucket;
FIG. 13 is a perspective view of the ice harvesting mechanism from
the back side to show the ice making cycle timer and drive
mechanism;
FIG. 14 is a sectional view of a water fill system suitable for use
with this invention;
FIG. 15 is a pictorial representation of the elec-trical control
system of this invention; and
FIG. 16 is a schematic wiring diagram.
GENERAL
In accordance with the teachings of this invention and with
particular reference to FIG. 7, a domestic refrigerator 20 is
shown. The refrigerator is of the side by side type wherein a right
side portion encloses a refrigerated food compartment 22 and the
left side portion encloses a lower freezer portion 24 for storing
frozen foods and an upper freezer portion 26 enclosing the clear
ice maker of this invention shown generally at 28. A vertical full
length door 30 may be used to close both the upper and lower
freezer compartments 24, 26.
In general, the clear ice maker 28 (FIGS. 1 and 8) includes a tray
and heater assembly 34, an ice cube grid 36, an ice storage bucket
assembly 38, a weight sensing means 39 for bucket and ice, an ice
harvesting mechanism 40, and a water fill system 42.
TRAY AND HEATER ASSEMBLY
The tray and heater assembly 34 (FIGS. 4 and 5) is supported by
bracket means 46 from a sidewall 48 of the freezer compartment 26.
The assembly includes a drawn sheet metal housing 50 forming on one
side thereof a water containing tray 52 having a sidewall 54 and a
bottom wall 56 and on the other side thereof a cavity filled with
freon-filled urethane foam insulation 58. A pair of heaters 60, 62
surround the tray 52. Heater 60 is adapted for heating all four
sidewalls 54 of the tray and thereby normally exposes the bottom
side of the tray (beneath the ice) to above-freezing temperature.
This retains that portion of water along the bottom side of the
tray in a liquid state. For this purpose, heater 60 is comprised of
90.8 inches of vinyl covered resistance wire rated at 115 volts,
6.5 - 7.5 watts, 250 ohms per foot reference.
Heater 62 is adapted for supplying additional heat to the tray
bottom wall 56 under certain circumstances to keep ice from
freezing all the way down to the bottom wall, and is comprised of
41.7 inches of vinyl covered resistance wire rated at 115 volts,
2.8 - 3.2 watts, 1,268 ohms per foot reference.
Heater 60 is sandwiched between a sheet 66 of 0.005 aluminum foil
and a sheet 68 of 0.002 aluminum foil. Similarly, bottom wall
heater 62 is sandwiched between a sheet 70 of 0.005 aluminum foil
and a sheet 72 of 0.002 aluminum foil. The mating edges of foil
sheets 66 and 68 are heat-sealed as are the mating edges of foil
sheets 70 and 72. Both heater assemblies 60 and 62 are foamed in
place between the tray and the urethane foam.
Also foamed in place is a tray fill tube 76 of polypropylene in
heat transfer relation to heater 62 to prevent freeze-up and
adapted to supply water to fill tray 52 through the bottom wall 56
of the tray. Electrical leads may enter the freezer through tubing
77.
WATER FILL SYSTEM
The water fill system 42 will now be described with reference to
FIGS. 1 and 4. In general, water is supplied to tray 52 from a
reservoir 78 defined by a water valve housing 80 attached to the
back wall 82 of the refrigerator 20 behind the freezer compartment
26. Water in reservoir 78 communicates with tray 52 through outlet
84 in the reservoir housing and tubing or conduit means 86
connecting outlet 84 with tray fill tube 76 through a protector
tube base 90 (FIG. 4). Water contained in tray 52 seeks a common
level with water in reservoir 78. Thus, the desired fill level in
the tray is achieved by predetermining the water level in reservoir
78.
To control the level of water in reservoir 78, water valve housing
80 includes a float 94 pivotally attached at 96 to a wing hinge
bracket 98. Top wall 100 of housing 80 carries a water valve
assembly 102 including a water inlet 104 and a water outlet 106. A
domestic supply of purified water may be connected to the inlet
104. Valve pin 108 (slidably supported on three ribs 109) has a
rubber valve portion 110 adapted for closing against a valve seat
112. At the lower end of assembly 102, a valve pin actuator 114
pivots about axis 116 in response to the upward force of float 94
at one end 120 as balanced against a water level adjustment
mechanism 122 at the other end 124. Water level may be adjusted by
a remote knob 125 turning worm gears 126, 128 against spring
130.
The water level is adjusted at 125 in a manner to shut off the
water supply at 110, 112 when the water level A (FIGS. 2 and 14)
exists in both reservoir 78 and tray 52. In general, a fresh charge
of water is supplied to tray 52 during an ice harvesting cycle when
grid 36 is out of the tray. It should be noted that water level A
will be raised to water level B when the grid is in the tray. The
grid is constructed in a manner to displace substantially all water
from the tray into the grid cavities for making clear ice. In this
way, the water so displaced is available to form cubes in the grid
cavities and, accordingly, does not form an adhesive film of ice
between the grid and tray which resists the separation of grid and
tray at the start of an ice harvesting cycle.
ICE CUBE GRID
Ice cube grid 36 (FIGS. 2, 3 and 8) has characteristics of poor
heat conduction and good flexibility at low temperature with good
ice release and return memory. It is comprised of a polypropylene
housing 140 defining cavities 142 for a plurality of ice cubes.
Each cavity 142 has an inverted truncated pyramidal shape. On the
outside of the housing between the cavity forming portions thereof,
a flexible filler 146 of RTV silicone rubber fills the space
between the cube forming cavities on the outside of grid 36. The
filler material should have an anti-stick characteristic to aid in
the release of the grid from the tray during ice harvesting. It
should be sufficiently flexible to distribute forces throughout the
grid when the grid is warped for harvesting cubes. Aside from these
characteristics, the filler 146 serves to force water in the tray
upwardly into the cube forming cavities of the grid. Thus, with the
grid in place in the tray (FIG. 2, solid line), water level A will
become water level B.
ICE STORAGE BUCKET ASSEMBLY
The ice storage bucket assembly 38 will be described with reference
to FIGS. 1 and 2. An ice container 150 of high impact polystyrene
rests on a steel wire shelf 152. The shelf pivots about a support
foot 154 on the bottom wall 156 of freezer portion 26 and includes
an upright bracket 158 at the rear thereof which hangs from a
weight sensing means 39 in a manner to keep the back 160 of the
shelf spaced from the freezer wall 156. The ice container or bucket
150 is built up with a high wall 170 to catch the cubes falling
from the grid 36 above. In general, the weight sensing means 39
will in one mode reflect the presence of ice container 150 on shelf
152 and, in another mode, the presence of a full load of ice cubes
within the container 150.
WEIGHT SENSING MEANS
The weight sensing means 39 (FIGS. 9 and 15) is comprised of a
nylon weigh shaft 176 having a hooked portion 178 for gripping a
loop in the upright shelf bracket 158. The weigh shaft is connected
to a stainless steel container weigh bar 188 which pivots about 198
and is electrically connected to terminal 190 by resting thereon.
An ice weigh bar 192, also stainless steel, is disposed above the
container weigh bar and pivots about a brass pin 194. The other end
of ice weigh bar 192 normally rests in electrically conducting
relationship against a brass weigh bar stop and terminal 196. The
container weigh bar includes a terminal 198 which cooperates with
terminal 196 to comprise a weigh switch. Another terminal 200 is
disposed above the ice weigh bar 192 and is normally out of
electrical contact with the weigh bar. In brief, the presence of
container 150 on shelf 152 will cause the weigh shaft 176 to pull
down in a manner to cause container weigh bar 199 to touch ice
weigh bar 192 and complete a circuit between terminals 198 and 196.
When container 250 fills up with a predetermined full load of ice
cubes, the further downward movement of weigh shaft 176 will cause
container weigh bar 188 to force ice weigh bar 192 out of
electrical contact with terminal 196 and into electrical contact
with terminal 200. For additional details of the weight sensing
mechanism suitable for use with this ice maker, reference may be
had to my (Invention File A-17,153).
HARVESTING MECHANISM
The harvesting mechanism 40 will now be described with reference to
FIGS. 9, 10, 11, 12 and 13. With particular reference to FIGS. 12
and 13, the harvesting mechanism is comprised of a box-like plastic
casing 210 defining a compartment 212 for the grid pivoting and
twisting gears on one side of a gear mounting plate 214. On the
other side of the mounting plate 214, the housing is divided into a
drive compartment 216 and a timer compartment 218.
The means for pivoting or removing and twisting or warping grid 36
are disposed in gear compartment 212. A cam and crank gear 220 is
rotatably mounted on plate 214 and is rotatably driven from the
other side of the plate by a pair of worm gears 222, 224 which are,
in turn, driven by drive motor assembly 226. The cam and crank gear
220 is comprised of a cam portion 230 and a gear portion 232. The
cam 230 cooperates with a holding switch 234 through a switch
actuator 236 so that the holding switch is closed when the switch
actuator 236 rides the outer periphery of the cam. In the position
of FIG. 12, switch actuator 236 is disposed in a notched portion of
the cam periphery to open switch 234. Gear 232 directly drives a
timer gear 240 and includes a crank portion 242 in a slot 244 of
segment gear 246. Thus, one rotation of crank and cam gear 220 will
cause the segment gear 246 to rock back and forth about its pivot
point 250.
The segment gear is drivably connected to grid drive gear 252 which
extends outside the mechanism casing 210 where a D socket 254 is
adapted for connection with a similarly shaped stud on grid 36 as
at 256 (FIG. 3).
Timer gear 240 is pivotally mounted on mounting plate 214 and
extends therethrough for directly driving ball timer 260. In
general, and with reference to FIG. 11, ball timer 260 is comprised
of a pivotable timer switch arm 262 including a magnetic slug 264
disposed adjacent the normally non-magnetic periphery 266 of a
circular housing 268. The housing includes a diametrical void 270
filled with a viscous fluid. Within the void and suspended by the
viscous fluid is a steel ball 272.
An ice making cycle is timed by the time it takes for ball 272 to
fall by gravity through the viscous fluid to the diametrically
opposite position adjacent magnetic slug 264 where its presence
will attract the slug magnetically and close a timer switch 280
(FIG. 16) between terminals 282 and 284 (FIG. 15). For additional
details of the ball timer, reference may be had to my (Invention
File A-17,151).
OPERATION
An ice making cycle in accordance with the teachings of this
invention will now be described. Water level in reservoir 78 is
adjusted by means of water level adjustment 125 to provide a
predetermined water level A when grid 36 is not in tray 52. Once
the adjustment is made, water valve 110, 112 will be opened and
closed by the action of float 94 and lever 114 to rapidly return to
this water level during the time that grid 36 is being rotated out
of tray 52 during an ice harvesting cycle.
With grid 36 in tray 52, substantially all of the water comprising
water level A will be forced through the open bottom of each grid
cavity 142 to form a water level B near the top of the grid
cavities. This water level B will provide in the embodiment shown a
water depth of approximately 1 inch in the tray. Fan means 285
(FIG. 16) blows air through and includes a duct 290 on the back
wall of the freezer compartment 26 which distributes a quantity (10
to 15 cubic feet per minute) of below-freezing air (minus
10.degree. F. to minus 12.degree. F.) uniformly over the exposed
top planar surface (water level B) of the water in the grid
cavities. The air is cooled by refrigerating or cooling means
including a compressor 286 and a temperature responsive cold
control 289 for controlling fan means 285 and compressor 286. The
refrigerating means may include a defrost arrangement including a
defrost heater 287 and limiter switch 288 in series with a defrost
timer contact 299. Additional distribution may be accomplished by
suitable means such as adjustable louvers 292 at the duct 290.
A skim of clear ice (FIG. 3) starts to form at water level B along
the top planar surface of water filling each cube cavity 142. Ice
thickens from this top surface progressively downwardly. During the
generation of this ice, heater 60 is energized to heat the body of
water in each tube cavity below the ice forming along the top
surface of the body of water in each cube cavity. During the time
that ice is progressively freezing from the top surface of each
cube cavity toward the bottom wall 56 of tray 52, ball 272 in timer
260 is falling toward magnetic slug 264. When the slug is attracted
to the ball, timer switch 280 closes (FIG. 16). This occurs when
the clear ice is in the form of a cube 296 approximately one-half
inch thick. With the ice maker in a 0.degree. F. freezer and the
refrigerator in a 70.degree. F. room ambient, compressor 286 in the
freezing system normally operates 60 - 70 percent of the time.
These parameters provide for freezing clear ice one-half inch thick
in about two and one-half hours. Thus, timer 260 is designed so
that the ball 272 will taken two and one-half hours to close timer
switch 280. The saturation of the body of water with gas and
minerals is a factor in determining this freezing rate. In general,
the more saturated the water is, the slower the freezing rate
should be for clear ice.
Assuming ice container 150 is in place on shelf 152 and timer
switch 280 closes, a circuit will be completed between terminal 198
and terminal 196 and motor 226 will be energized. In response to
the operation of motor 226 through worm gears 222, 224, cam and
crank gear 220 will start to rotate. The first function occurs when
cam 230 through switch actuator 236 closes holding switch 234. The
holding switch assures completion of a harvesting cycle by forming
a shunt circuit around timer switch 280. This is necessitated by
the opening of switch 280 as timer housing 268 starts to rotate and
moves ball 272 away from magnetic slug 264.
With reference to FIGS. 2 and 3, grid 36 starts to rotate with
substantially one-half inch cubes 296 of clear ice in the top
portion only of each cavity 142. Unfrozen water 298 beneath the
cubes remains in tray 52 in a liquid state. Tray housing 50
includes an upstanding flange 300 journalling a stud 302 projecting
from one corner of the grid. A stud at the same corner on the
opposite end of the grid (not shown) fits in the D socket 254 of
grid drive gear 252. As grid 36 rotates from the installed position
X (FIG. 2) through the upright position Y to the harvesting
position Z, the grid will engage a raised boss 304 which halts the
pivoting motion of the grid at its outer end. However, the
harvesting mechanism continues to drive the grid causing the end
nearest the driving mechanism to continue rotation to warp the grid
in a manner to release clear ice cubes 296 from the grid. The
released cubes fall into the ice container 38 therebelow.
The time it takes to move the grid from position X to position Z is
predetermined as approximately 5 minutes. During this time the
exposed surface of each clear ice cube 296 in the grid is exposed
to the cold dry air in the 0.degree. F. freezer. This air in this
amount of time drys the cube surface before the cube is released
from the grid and stored in the container. Since the cubes are dry
when stored, they tend not to stick together.
After the cubes are harvested, the continued rotation of crank 232
operating through its crank 242 in the slot of segment gear 246
will return the grid to its installed position X.
When the container 150 is full of ice, this added weight will,
through the weight sensing means 39, close a circuit between
terminal 198 and terminal 200 to energize the tray bottom heater
62. This added heat will prevent ice forming in the grid from
freezing all the way to the bottom of the tray.
It is also desirable to reduce heat dissipated in the freezer by
deenergizing the tray side and bottom heater 60 when sub-freezing
air is unavailable in the freezer. For this purpose (FIG. 16),
heater 60 is placed in parallel with fan means 286 and compressor
286 so that it will be deenergized when cold control 287 is
satisfied and the circuit opened.
While the embodiment of the present invention as herein disclosed
constitutes a preferred form, it is to be understood that other
forms might be adopted.
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