Refrigeration – Automatic control – By congealed removable product condition
Reexamination Certificate
1999-09-30
2002-01-01
Doerrler, William (Department: 3744)
Refrigeration
Automatic control
By congealed removable product condition
C062S351000
Reexamination Certificate
active
06334318
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an automatic ice making apparatus for use in a home refrigerator.
BACKGROUND ART
In a first example of conventional automatic ice making apparatus, the state of freeze of water is determined by a thermostat mounted on an ice making tray, and the thermostat is used for sensing the temperature and for switching over an electric heater or an ice discharging motor, for example. In such automatic ice making apparatus, the operation temperature of the thermostat is set generally to about minus 10° C. When the thermostat is operated at a temperature of about minus 10° C., a contact of switch of the thermostat is closed to energize the electric heater mounted on the ice making tray, so that the ice making tray is heated, the surface of ice contacted to the ice making tray is melted, and the ice is removed from the ice making tray.
The ice discharging motor for use in an ice discharging mechanism is energized at the same time of the switching over of the thermostat by the switching function thereof, however, the motor is deenergized when a claw for discharging ice is brought into contact with the ice, and then the motor is energized when the ice is removed from the ice making tray to discharge the ice from the ice making tray. It is a matter of course that the ice discharging motor is of the type to be remained in the deenergized state for a while.
The hysteresis property is applied to the thermostat in order to separate positively the ice from the ice making tray. That is, the switch contact of the thermostat is turned ON at about minus 10° C. and turned OFF at about plus 10° C. Due to the hysteresis property, when the temperature of the ice making tray is elevated to about plus 10° C., the switch contact of the thermostat is turned OFF to deenergize the electric heater.
A cam for operating two limit switches is provided on the ice discharging motor. One of the limit switches serves as to turn ON or OFF an electromagnetic valve for supplying water. The other of the limit switches is connected in parallel with the switch contact of the thermostat, so that the ice descharging motor is rotated continuously even if the switch contact of the thermostat is turned OFF. After the ice has been discharged perfectly, the ice discharging motor is still rotated, and the electromagnetic valve is energized by the cam and the limit switch for a period of time determined by the number of rotation of the motor and the figure of the cam so as to supply water.
Then the ice discharging motor is deenergized and the water supply is stopped. The above is a cycle of the ice making.
In a second example of the conventional automatic ice making apparatus, the state of freeze of water is determined by such a control system that the temperature of an ice making tray is detected by using a thermistor mounted on the ice making tray as a temperature sensor, and an output voltage of the thermistor is compared to a predetermined value and judged by a comprator whether the temperature of the ice making tray is higher or lower than the predetermined temperature. The automatic ice making apparatus of this system is similar basically to the first example of the conventional automatic ice making apparatus except that in the second example of the automatic ice making apparatus a semiconductor switch is used as a power switch for the electric heater and the motor.
FIG. 5
shows a conventional ice making means comprising an ice making tray
11
provided with a thermostat
12
and a heater
13
, and an ice discharging motor
14
for an ice discharging mechanism provided with an ice discharging claw
15
, a cam
16
, a contact LS
1
for the cam
16
, a cam
17
and a contact LS
2
for the cam
17
, wherein ice
18
in the ice making tray
11
can be discharged by rotating the claw
15
. Further, water is supplied from a water supply pipe
19
into the ice making tray
11
through an electromagnetic valve
20
.
When the ice
18
of a predetermined quantity is discharged by the ice discharging mechanism and stored in an ice storing box
21
, a sensor
22
detects the ice stored in the ice storing box
21
to stop the power supply from a power source
23
so as to stop temporarily the ice making operation.
When the amount of the ice in the ice storing box
21
is reduced, the power is supplied from the power source
23
to start the ice making operation.
In a state shown in
FIG. 5
, the amount of the ice in the ice storing box
21
is reduced, the ice making operation is started, a predetermined quantity of water is supplied into the ice making tray
11
, and the electromagnetic valve
20
is deenergized. In this state, the thermostat
12
is turned OFF, so that no power is applied to the heater
13
and the motor
14
. When the water in the ice making tray
11
is frozen and the thermostat
12
is turned ON, the heater
13
and the motor
14
are energized, so that the ice
18
contacted with the ice making tray
11
is melted and discharged into the ice storing box
21
by the claw
15
rotated by the motor
14
in the ice discharging mechanism. The rotation of the motor
14
is continued, so that the contact LS
1
is turned ON by the cam
16
. As a result, the electromagnetic valve
20
is operated to start the water supply, a quantity of water corresponding to the angular position of the motor
14
is supplied, and the ice making operation is restarted. The above motions are repeated until the sensor
22
for sensing the ice stored in the ice storing box is turned OFF.
In the conventional automatic ice making apparatus thus far described, the setting temperature of the ice making tray for freezing water positively is set to a value lower than a value required actually to freeze water so as to have a large play in consideration of the fluctuation in temperature in a freezing chamber, in mounting condition of the temperature sensor or the like. Accordingly, the conventional apparatus has such a defect that an ice making time becomes long, because a long time is required until the temperature of the ice making tray is lowered more than the temperature at which the temperature sensor is operated.
This problem will now be explained detail.
FIG. 1
shows ice making operation steps, temperature variations of the ice making tray and freezing states of water in one cycle of ice making operations of a general automatic ice making apparatus. First of all, the temperature of the ice making tray is maintained at a constant value substantially between a state that water on the ice making tray is frozen partially and a state that the water is frozen perfectly, because the ice making tray absorbs the heat of condensation.
After the freezing of water is completed, the temperature is lowered, because no heat of condensation is generated. When the temperature sensor detects the freeze of water, the electric heater is energized to elevate the temperature of the ice making tray, so that the ice contacted with the ice making tray is melted, and the ice is discharged to finish one cycle of the ice making operation.
In order to reduce the ice making time in the conventional automatic ice making apparatus, the setting value of a freeze judging temperature is approached as near as possible to the actual freezing temperature. However, the output value of the temperature sensor for the ice making tray, which may be maintained constant substantially while the water is condensed is fluctuated according to the temperature in the freezing chamber and the mounting condition of the temperature sensor or the like. Accordingly, a play according to the fluctuation must be necessary in the temperature setting. This results in the time until the sensor judges the freeze of water becomes about twice a time required for freezing the water actually in the automatic ice making apparatus practically used.
As stated in the first example of the prior art, the energization of the heater is controlled by the thermostat and accordingly a play must be added in the setting temperature similar to the control of the heater
Ando Hitoshi
Kuroda Eiji
Nakayama Atsuo
Niwa Yasushi
Toida Naoko
Ali Mohammad M.
Doerrler William
Japan Servo Co. Ltd.
Nilles & Nilles S.C.
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