Information
-
Patent Grant
-
6612118
-
Patent Number
6,612,118
-
Date Filed
Wednesday, February 6, 200222 years ago
-
Date Issued
Tuesday, September 2, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 062 74
- 062 135
- 062 233
- 062 347
-
International Classifications
-
Abstract
The ice maker herein works in the conventional manner wherein a refrigeration system provides for cooling of the evaporator. Water is first circulated over the evaporator as the evaporator is cooled. A temperature sensor is located in a water recirculating system and a microprocessor monitors the temperture of the circulating water. Once a predetermined non-freezing temperature is reached, for example 40 degrees Fahrenheit, water circulation is stopped. However, the compressor continues to run and cool the evaporator for a predetermined period of time to a desired lower temperature. The pump is then turned on and water again circulated over the evaporator initiating the ice making cycle. This process insures that ice adheres to the evaporator and does not prematurely slough off and/or result in the formation of slush.
Description
FIELD OF THE INVENTION
The present application relates generally to ice making machines, and specifically to controls and sensors as used therein.
BACKGROUND
Ice making machines are well known in the art, and typically include an ice cube making mechanism located within a housing along with an insulated ice retaining bin for holding a volume of ice cubes produced by the ice forming mechanism. In one type of ice maker a vertically oriented evaporator plate is used to form a slab of ice characterized by a plurality of individual cubes connected by ice bridges there between. As the slab falls from the evaporator plate into the ice bin, the ice bridges have a tendency to break forming smaller slab pieces and individual cubes. As is well understood, the ice slab is formed by the circulating of water over the cooled surface of the evaporator plate, the plate forming a part of a refrigeration system including a compressor and a condenser. Water that is not initially frozen to the evaporator falls into a drip pan positioned below the evaporator and is pumped there from back over the evaporator. After sufficient time has elapsed, ice of a desired thickness will form on the evaporator.
Of critical importance to ice makers of this general type, is knowing when the ice is of the desired thickness to be harvested. Once the harvest point is reached, the making of ice is discontinued by stopping the flow of water over the evaporator and the cooling thereof. The evaporator plate is then heated, typically by the use of hot gas from the refrigeration system. The ice slab then melts slightly releasing its adhesion to the plate so that it can fall into the bin positioned there below. Various controls have been proposed and used over the years to signal the harvest point.
Occasionally, however, the proper functioning of such harvest controls can be interfered with by the imperfect formation of ice on the evaporator. For example, it is known that under certain high ambient conditions, for example, ice can initially form on the evaporator that is not well adhered thereto. Such ice can prematurely fall from the evaporator prior to reaching the desired harvest point. This ice can be in the form of pieces of hard ice or can even comprise a slush. This “volunteer harvest” ice can fall into the drip pan and cause disruption of the recycling flow of the water by interfering with the operation of the pump that provides therefor, and can also block or otherwise compromise the operation of the ice harvest detection equipment. In either case, proper operation of the ice maker can be interfered with resulting in premature ice harvest, lack of harvest, damage to the ice maker and the like. Accordingly, it would be desirable to have an ice maker that prevents improper ice formation that results in premature falling thereof from the evaporator.
SUMMARY OF THE INVENTION:
The ice maker herein works in the conventional manner wherein a refrigeration system provides for cooling of the evaporator. Water is first circulated over the evaporator as the evaporator is cooled. A temperature sensor is located in the water recirculating system and a microprocessor monitors the temperture of the circulating water. Once a predetermined temperature is reached, for example 40 degrees Fahrenheit, water circulation is stopped. However, the compressor continues to run and cool the evaporator for a predetermined period of time, such as, one minute. The pump is then turned on and water again circulated over the evaporator initiating the ice making cycle.
Those of skill will appreciate that the first cycling of the water permits the cooling thereof to a relatively cold temperature, but above freezing so that ice is not formed on the evaporator. After the first water circulating is stopped the evaporator is permitted to cool down to a temperature at which it is ready to form ice. Therefore, the control of the present invention insures that the water and the evaporator are both at sufficiently low temperatures such that initiation of ice formation will result in strong adherence of ice to the evaporator. As a result thereof, “slushing” or the formation of otherwise poorly adhered ice, is prevented.
DESCRIPTION OF THE DRAWINGS
A better understanding of the structure, function, operation and advantages of the present invention can be had by referring to the following detailed description which refers to the following drawing figures, wherein:
FIG. 1
shows a perspective view of an ice maker mounted atop an ice storage bin.
FIG. 2
shows a partial cross-sectional view of the interior of the ice maker.
FIG. 3
shows a schematic representation of the ice maker.
FIG. 4
shows an enlarged view of the ice maker control board.
FIG. 5
shows an enlarged partial cross-sectional view of the water pan and pressure fitting.
FIG. 6
shows a flow diagram of the control strategy of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The ice maker of the present invention is seen in
FIG. 1
, and referred to generally by the numeral
10
. Ice maker
10
includes an exterior housing
12
and is positioned atop an insulated ice retaining bin
14
. As is further understood by referring to
FIGS. 2 and 3
, and as is conventional in the art, ice maker
10
includes a vertical ice forming evaporator plate
16
, a condenser and fan
18
and a compressor
20
connected by high pressure refrigerant lines
21
a
and low pressure line
21
b
. As is also well understood, the refrigeration system herein includes an expansion valve
22
and a hot gas valve
24
. A water catching pan
26
is positioned below evaporator
16
and includes a partial cover
27
. A water distribution tube
28
having a water inlet
29
extends along and above evaporator
16
. A water supply solenoid valve
30
has an inlet connected to a source of potable water, not shown, and an outlet line
31
supplying water to pan
26
. A water pump
32
provides for circulating water from outlet
32
b
thereof to inlet
29
of distribution tube
28
along a water line
34
. A solenoid operated dump valve
36
is fluidly connected to line
34
and serves, when open, to direct water pumped thereto to a drain, not shown. An evaporator curtain
37
is pivotally positioned closely adjacent evaporator
16
and includes a magnetic switch
38
for indication when it has moved away from evaporator
16
to an open position indicated by the dashed line representation thereof. For purposes of clarity of the view of
FIG. 2
, the various fluid connections of pump
32
, dump valve
36
and water supply valve
30
are not shown, such being represented in schematic form in FIG.
3
.
As particularly seen in
FIG. 4
, and also by referring to
FIG. 2
, an electronic control board
40
is located within a separate housing
41
at a position remote and physically isolated from pan
26
and evaporator
16
. Control board
40
includes a microprocessor
42
for controlling the operation of ice maker
10
. Board
40
includes a pressure sensor
44
, such as manufactured and sold by Motorola, Inc. of Phoenix, Ariz., and identified as model MPXV5004G. As understood by also viewing
FIG. 5
, a plastic pneumatic tube
46
, shown in dashed outline, is connected to sensor
44
and on its opposite end to a cylindrical air cup or fitting
48
. Those of skill will understand that housing
41
includes a cover, not shown, that provides for the enclosing and protection of control
40
and sensor
44
therein and through which tube
46
passes prior to connecting to sensor
44
.
A temperature sensor
47
, as for example manufactured by Advanced Thermal Products, Inc., St. Marys, Pa., and identified as an NTC thermistor, is fluid tightly secured in water circulating tube
34
. Specifically, tube
34
has a T-fitting portion into which sensor
47
is tightly inserted. A clamp
47
′ is secured around the perimeter of the “T” portion of tube
34
thereby providing for fluid tight securing of sensor
47
therein. Sensor
47
is electrically connected to microprocessor
42
of control board
40
.
A Fitting
48
resides in pan
26
at the bottom thereof and is press fit within a circular ridge
49
that is formed as an integral molded portion of the bottom surface of pan
26
. Fitting
48
includes an outer housing
48
a
defining an inner air trapping area
48
b
and a tube connecting portion
48
c
. Four water flow openings
50
exist around a bottom perimeter of housing
48
a.
The operation of the present invention can be better understood by referring to the flow diagram of
FIGS. 6A and 6B
wherein the basic operation of the present invention is shown. At start block
51
power is provided to control
40
. At block
52
compressor
20
is turned on and substantially simultaneously at block
54
fill valve
30
and dump valve
36
are opened. Thus, cooling of evaporator
18
begins and water flows into pan
26
. At decision block
56
, once a predetermined pump-on water level is reached in pan
26
, as indicated by the level line represented by the letter P in
FIG. 5
, circulatory water pump
32
is turned on at block
58
. The pump-on point is sensed by sensor
44
. In particular, as water fills pan
26
, water flows through holes
50
of fitting
48
. As that occurs, air trapped in area
48
b
is slightly compressed and forced into tube
46
which communicates such pressure increase to sensor
44
. That pressure is then input as a voltage to microprocessor
42
which assigns a numerical value thereto corresponding to a pressure scale. Therefore, when the predetermined pressure value is sensed that corresponds to the pressure at level P, pump
32
is turned on. Because of the fluid connections of pump
32
and dump valve
36
, the action of pump
32
serves to move any water in pan
26
to valve
36
causing the draining away thereof. Thus, a minimum water level, indicated by the level line represented by the letter M in
FIG. 5
, is sensed in the same manner as described above for level P. When that predetermined volume of the water has been removed from pan
26
, pump
32
is stopped at block
62
. As the water supply valve remains on, the level in pan
26
begins to rise and when the P level is again sensed at block
64
, then at block
66
, pump
32
is re-started and fill valve
30
closed. As dump valve
34
remains open, water will again be pumped from pan
26
. At block
68
control
40
again senses for the attainment of the M level. When that occurs, then, at block
70
, water pump
32
is stopped, dump valve
34
is closed and fill valve
30
is opened. It can be appreciated that blocks
52
-
68
serve as a dump cycle whereby any contaminants that have accumulated in pan
26
are agitated by the action of pump
32
and the inflow of water and are twice flushed in this manner and removed from the system.
At block
72
control
40
monitors for the attainment of a maximum fill level for pan
26
indicated by the level line denoted by letters MX. When this highest pressure level is sensed, then at block
74
fill valve
30
is closed. At block
76
, the pump is turned on and the water is again circulated over evaporator
16
. Temperature sensor
47
monitors the temperature of the circulating water at block
78
and when that temperature reaches 40 degrees Fahrenheit, the pump, at block
80
, is turned off. At decision block
82
a period of time, such as one minute is allowed to time out. It will be understood that during this time the evaporator is allowed to further cool down as the compressor is continuing to run. At block
84
, the circulating pump is turned back on and the water again flows over the evaporator. A ten second clock is set at block
86
, and when that has timed out, fill valve
30
is opened. at block
88
. It will be understood by those of skill that action of pump
32
will serve to fill fluid line
34
and distribution tube
28
which will slightly lower the level of water in pan
26
below that of the desired maximum water volume indicated by level MX. Thus, fill valve
30
is opened at block
88
, to replenish that volume as is determined at block
90
. At block
92
, fill valve
30
is closed when the desired starting maximum level MX is again attained.
At this point pump
32
is operating to flow water over evaporator
16
as such is being cooled by the action of compressor
20
, condenser and fan
18
and expansion valve
22
, all as operated by control
40
. As ice forms on evaporator
16
, the water level in pan
26
goes down as does the pressure sensed by sensor
44
. When a predetermined harvest water level is reached, as indicated by the level line denoted H, a corresponding predetermined pressure value is sensed by control
40
at block
94
. When the harvest point is indicated, pump
32
is stopped and hot gas valve
24
is opened at block
96
, causing evaporator
16
to warm resulting in the release of the ice slab formed thereon. Of course, those of skill will understand that other heating means known in the art could be employed, such as, an electrical heater integral with the ice forming evaporator. As is well understood, when the slab of ice falls from evaporator
16
, curtain
37
is opened and switch
38
is closed, signalling to the control
40
, at block
98
, the release of the ice slab from evaporator
16
, i.e. that the curtain is open. The hot gas valve is then closed at block
100
. As is also known, to insure that the slab of ice has fallen into bin
12
and is no longer in the vicinity of evaporator
16
, at block
96
, the control herein awaits the remaking of switch
38
, block
102
, which occurs when curtain
36
is free to swing back to its normal closed position unobstructed by any ice. At block
104
the control returns to start and initiates a further ice making cycle.
Those of skill will appreciate that the above control process is described in the context of the operation of a particular ice making machine. However, the essential steps of the control method of the present invention require that a volume of water be circulated over the evaporator while the evaporator is being cooled in order to pre-cool the water to a predetermined non-freezing point. In other words, the object during the pre-cool is not to form any ice. This pre-cooling is accomplished by the use of a temperature sensor that tracks the temperature of the circulated water and signals when the predetermined non-freezing temperature is reached. The circulation of the water is then stopped, but the cooling of the evaporator is continued in order to pull the temperature thereof down to a colder temperature. After the evaporator has a chance to cool further, the ice making cycle is then initiated by re-starting the circulation of the pre-cooled water. Those of skill will appreciate that the above described process insures that both the circulating water and the evaporator are both sufficiently cold such that at the initiation of the ice making cycle the first ice to be formed will be securely held to the evaporator. Thus, “slushing” or other undesired formation of ice that prematurely falls from the evaporator, is prevented.
Naturally, the temperature to which the volume of water is first cooled and the period of time that the circulation of the water is subsequently turned off while the evaporator is allowed to cool without the water circulating over it, are matters of design choice for those of skill in the art based on such variables as size and type of refrigeration components, typical ambient conditions, volume of ice made per cycle, etc. In the embodiment described herein, it was found sufficient to bring the evaporator down to a temperature of approximately seven degrees Fahrenheit. In the preferred embodiment of the present invention, a period of time was experimentally determined that will be sufficient in most all conditions to assure that the evaporator is brought to that desired low initiating of ice making temperature of 7 degrees Fahrenheit. In a further embodiment, either a temperature sensor
110
located at the outlet of evaporator
16
or a pressure sensor
112
along the suction line
21
b
of compressor
20
, both being connected to control
42
, can be used to directly sense, or determine by correlation to temperature and pressure, respectively, when the evaporator is at the desired initiating of ice making temperature. Of course, use of either of sensors
110
or
112
add cost, although do provide for more accuracy. It will be understood by those of skill that directly sensing or determining the evaporator temperature permits a modification of the previously described method of the present invention. In particular, after the volume of water is brought to the desired non-freezing temperature and the circulation of that water is stopped, the cooling of the evaporator is continued until the evaporator is determined to be at the desired initiating of ice making temperature, after which circulation of the water is re-initiated. In this manner an average period of time is not selected that assumes that the evaporator is at that desired temperature, rather that temperature is determined directly.
Claims
- 1. A method for controlling an ice maker, the ice maker having a refrigeration system for providing cooling of an ice forming evaporator, and a water circulatory system for circulating water over the evaporator for forming ice thereon as the evaporator is cooled by the refrigeration system, the method comprising the steps of:circulating a volume of water over the evaporator while cooling the evaporator and while sensing the temperature of the circulated volume of water, stopping the circulating of the volume of water when a predetermined nonfreezing temperature of the water is sensed, continuing to cool the evaporator after the stopping of the circulating of the volume of water for a period of time to permit further cooling of the evaporator, re-starting circulating of the volume of water over the evaporator for initiating an ice making cycle.
- 2. A method for controlling an ice maker, the ice maker having a refrigeration system for providing cooling of an ice forming evaporator, and a water circulatory system for circulating water over the evaporator for forming ice thereon as the evaporator is cooled by the refrigeration system, the method comprising the steps of:circulating a volume of water over the evaporator while cooling the evaporator and while sensing the temperature of the circulated volume of water, stopping the circulating of the water when a predetermined nonfreezing temperature of the volume of water is sensed, continuing to cool the evaporator after the stopping of the circulating of the volume of water while sensing the temperature of the evaporator and re-starting circulating of the volume of water over the evaporator for initiating an ice making cycle when a predetermined initiating of ice making temperature of the evaporator is sensed.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5582018 |
Black et al. |
Dec 1996 |
A |
5653114 |
Newman et al. |
Aug 1997 |
A |
6125639 |
Newman et al. |
Oct 2000 |
A |