Information
-
Patent Grant
-
6700102
-
Patent Number
6,700,102
-
Date Filed
Wednesday, October 23, 200221 years ago
-
Date Issued
Tuesday, March 2, 200420 years ago
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Inventors
-
Original Assignees
-
Examiners
-
CPC
-
US Classifications
Field of Search
US
- 219 494
- 219 491
- 219 511
- 219 501
- 219 497
- 219 483
- 219 486
- 219 481
- 219 510
- 034 269
- 034 524
- 034 549
- 034 553
- 034 526
- 236 46 R
- 236 40
- 318 781
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International Classifications
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Abstract
A control circuit for a clothes dryer operating with a 120 volt power supply compensates for changes in the ambient temperature to compensate for premature advancement of the dryer timer motor during an automatic drying cycle. The control circuit has a thermally biased low outlet thermostat and a thermally biased high outlet thermostat which control the energization of a heater in the dryer. The low outlet thermostat and the high outlet thermostat each open circuit at respective lower and higher predetermined temperatures when the outlet air flow from the dryer drum reaches the lower or higher respective predetermined temperatures to thereby de-energize the heater and advance the timer motor. The control circuit includes a thermally biased ambient thermostat that is normally open and unbiased, and that switches control of the heater energization from the low output thermostat to the high outlet thermostat when thermally biased and when the ambient temperature rises above a predetermined ambient temperature. The ambient thermostat becomes thermally biased when the low output thermostat is open circuited. Both the low and high output thermostats are normally thermally biased during the automatic drying cycle and are un-biased during user time selected drying cycles so that the low and high temperature thermostats cycle on and off at higher temperatures than they would during the automatic drying cycle.
Description
FIELD OF THE INVENTION
The present invention relates to an automatic clothes dryer and in particular to an electric control circuit for use during an automatic clothes drying cycle which provides ambient temperature compensation.
BACKGROUND OF THE INVENTION
Clothes dryers are known to employ an operating thermostat responsive to the exhaust air temperature from the dryer to cycle the dryer heater on and off during the drying cycle to maintain the temperature in the dryer within a set range. Small heating elements may be placed adjacent the thermostat to provide a thermal bias. The provision of a thermal bias causes the thermostat to operate at a lower exhaust air temperature and is commonly used to lower the maximum exhaust air temperature at which the operating thermostat reacts.
While the use of thermally biased thermostats is known in the art, these thermostats have been used in automatic dryer applications where 240 volts is applied across the thermostats and dryer heater coils to deliver energy to heat the clothes to temperatures well above ambient. However, in small and mid-size clothes dryer applications where lower voltages of 110 to 120 volts and currents of 15 amps are employed, an automatic dryer operation has not been an energy efficient feature because the thermostats typically cause the dryer heating elements to automatically cycle on and off at too low of an outlet temperature. As a result, the dryers either have to apply heat to the clothing for periods longer than necessary or terminate the drying cycle when the clothes are still wet. This inefficient automatic drying operation problem is further enhanced when the ambient temperature around the dryer is relatively high resulting in a small temperature difference between the ambient temperature and the temperature at which the outlet dryer cycles on and off. As a result, automatic drying cycles have not been offered for all small and mid-sized dryers operating with 120 volt power sources. Instead, these dryers are provided with a time selected drying operation where the dryer operates at about 140° F. for the time specified by the user before entering a cool down period.
Accordingly, there is a need for an energy efficient, ambient responsive, automatic dryer control circuitry suitable for use with small and mid-sized clothes dryers capable of operating with 120 volt power supply.
SUMMARY OF THE INVENTION
The present invention relates to a clothes dryer operating with a 120 volt power supply and having an automatic control circuit that compensates for changes in the ambient temperature to compensate for premature advancement of the dryer timer motor during an automatic drying cycle. The control circuit comprises a low outlet thermostat and a high outlet thermostat which control the energization of a heater in the dryer. The low outlet thermostat and the high outlet thermostat each open circuit at respective lower and higher predetermined temperatures when the outlet air flow from the dryer drum respectively reaches the lower or higher predetermined temperatures to thereby de-energize the heater and advance the timer motor. The control circuit includes an ambient thermostat that switches control of the heater energization and timer motor advancement from the low output thermostat to the high outlet thermostat when the ambient temperature rises above a predetermined ambient temperature. The control circuit provides for more energy efficient drying in an automatic drying cycle for small and mid-size dryers operating with a 120 volt power source.
The ambient thermostat preferably has an internal biasing heater or resistor that is energized to permit the ambient thermostat to switch between the low output thermostat and the high output thermostat when the predetermined ambient temperature is reached. Preferably, the internal biasing heater of the ambient thermostat is energized when the low output thermostat is open circuited.
In accordance with a further preferred aspect of the present invention, both the low and high output thermostats each have internal biasing heaters that are normally energized during the automatic drying cycle and are de-energized during time selected drying cycles so that the low and high temperature thermostats cycle on and off at higher temperatures than they would during the automatic drying cycle.
In accordance with an aspect of the present invention there is provided a control circuit for controlling the operation of a clothes dryer having a dryer drum, a drum air inlet and a drum air outlet permitting an air stream to flow into and out of the dryer drum, a heater for heating the air stream before the air stream passes into the dryer drum, and a control circuit for controlling energization of the heater during an automatic drying cycle.
The control circuit comprises:
a supply line and a neutral line adapted for connection to a 120 volt power supply source;
a series connection across the supply line and the neutral line of a low output temperature thermostat, a high output temperature thermostat and the heater, the low output temperature thermostat opening at a first predetermined temperature and the high output temperature thermostat opening at a second predetermined temperature higher than the first predetermined temperature thereby controlling energization of the heater;
a timer motor connected between the supply line and a first point located between the high output temperature thermostat and the heater, the timer motor advancing to end the automatic drying cycle during periods when either one of the low output temperature thermostat and high output temperature thermostat is open;
an ambient thermostat for sensing ambient temperature and being electrically connected in parallel with the low outlet thermostat and in series with the supply line and a second point between the low output temperature thermostat and the high output temperature thermostat, the ambient thermostat providing a bypass circuit around the low temperature thermostat when a predetermined ambient temperature is reached; and,
wherein, the low output temperature thermostat opens when the temperature of the air stream exiting out of the drum reaches the first predetermined temperature to control cycling on and off of the heater and to control the advancement of the timer motor, and wherein control cycling on and off of the heater and control of advancement of the timer motor in response to the high output temperature thermostat opening at the second predetermined temperature occurs when the first outlet thermostat is bypassed out of circuit by the ambient thermostat.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the nature and objects of the present invention reference may be had to the following detailed description when taken in conjunction with the accompanying electrical diagrammatic drawings wherein:
FIG. 1
is a side view of a clothes dryer having the control circuit of the present invention; and,
FIG. 2
is a schematic wiring diagram showing circuitry for the control circuitry of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
Referring to
FIG. 1
there is shown a clothes dryer
10
having a rotating drum
12
mounted therein. The rotating drum
12
has an open front through which access can be gained through door
14
of the dryer
10
for the insertion and removal of clothing and other articles from the drum
12
.
The clothes dryer
10
has a rear panel
16
provided with a series or plurality of louvers
18
through which air may be drawn into the interior of the dryer
10
. The airflow is shown by arrows
20
passing through the louvers, through a series of openings
23
in the rear end head
22
of the dryer drum
12
through front ducting
24
and out through exhaust ducting
26
that defines an exhaust air stream path. Motor
28
rotates blower
30
to draw the air
20
through the drum
12
. The motor
28
through pulley
35
and belt
33
also causes the rotation of the dryer drum
12
.
A heater housing assembly
32
is mounted by suitable bolts
34
to the rear panel
16
of the dryer
10
. The heater assembly
32
is adjacent the end head
22
of the drum
12
. The heater assembly
32
has a rear wall
36
that is spaced from the rear end head
22
. The heater assembly has an electrical heating element
50
mounted on insulators
54
. It should be understood that an alternative construction for the dryer drum
12
and heater assembly
32
may comprise a stationary rear end head with a heater box mounted to the rear end head for supplying heated air into the dryer drum. Further, the drum shows an axial air flow therethrough and alternatively the air flow may return through an outlet exhaust in the rear wall of the dryer drum.
An ambient temperature thermostat
58
is shown mounted below the heater assembly
32
of the electric dryer. This thermostat
58
is designed to open when the ambient temperature of the air flow into the dryer drum exceeds about 25° C. Second and third temperature thermostats
60
,
62
are mounted in the dryer outlet air duct to respond to a rise in the temperature of the air exiting the clothes dryer drum
12
.
On top of the dryer
10
is a control panel
66
which includes control dials
64
, or touch sensitive key pads, for controlling the operation of the dryer
10
. It should be understood that these dials are utilized to provide for automatic control of the dryer
10
through a warm up cycle, one or more drying cycles and a cool down cycle. These dials can also select timed drying cycles.
Referring to
FIG. 2
the control circuit of the present invention in relation to an electric dryer is shown. A 120 volt power source is fed to terminal
150
designated as L
1
The neutral terminal is shown at
159
. Terminal
150
is connected to one pole
156
of timer motor control switches
153
and
158
. The terminal
154
of switch
153
is connected to ambient thermostat
58
and a low output thermostat
60
. Terminal
160
of timer control switch
158
is connected to timer motor
108
and to terminal
164
of motor start switch
166
. Low output thermostat
60
is connected in series with high output thermostat
62
which in turn is connected in series with heater
50
. These three devices,
60
,
62
and
50
are found in series branch
47
connected between the supply line
150
and neutral line
159
. Also connected in the series branch between resistance heater
50
and thermostat
62
is safety thermostat
80
. Safety thermostat is set to open should the dryer drum air inlet temperature exceeds the maximum preset inlet air temperature.
Pole
168
of start switch
166
is connected to pole
116
of centrifugal switch
110
which in turn is connected to “run” winding
118
of the blower and drum drive motor
28
. The other end of run winding
118
is connected to terminal
114
which is connected to terminal
126
of door switch
122
. The other terminal
124
of switch
122
is connected to neutral terminal
159
.
Pole
164
of start switch
166
is also connected to pole
126
via poles
107
and
111
of belt break switch
109
. The blade
126
of centrifugal switch
110
is shown in its “start” position, i.e. bridging poles
116
and
128
. Pole
128
is connected to “start” winding
130
of motor
28
. The other end of start winding
130
is connected to terminal
114
.
The timer motor
108
is connected to switch
170
which toggles between poles
172
and
174
. Switch
170
is ganged with switch
178
at the bottom of the circuit drawing and the functioning of these switches for a timed drying cycle selection is discussed hereinbelow. However, in the positions shown for switches
170
and
178
, the control circuit is in the timed drying cycle selection where the dryer operates for a predetermined amount of time during which the heater
50
is cycled on and off controlled by either of outlet thermostats
60
or
62
and timer motor
108
continuously advances. When the switch
170
is connected to pole
174
, switch
178
is also closed and connected to pole
180
. In this arrangement, the timer motor
108
is in an automatic dry cycle and is connected to series branch
47
at point
191
. The timer motor
108
does not advance as long as the heater coil
50
remains energized from L
1
.
As the clothes begin to dry, the temperature of the air exiting the drum begins to increase and outlet thermostats
60
and
62
together with the ambient thermostat
58
control energization of heater coil
50
. In the control circuit, the ambient thermostat
58
is connected from pole
154
between the outlet thermostats
60
and
62
at point
190
. The ambient thermostat
58
has an internal biasing heater (resistor)
59
connected across pole
154
and point
190
between outlet thermostats
60
and
62
. The outlet thermostats
60
and
62
each have respective internal biasing heaters
61
,
63
. Internal biasing heater
61
is connected from a point
190
between the low output thermostat
60
and the high outlet thermostat
62
to the neutral terminal
159
through switch
178
. Internal biasing heater
63
is connected between point
191
in the series branch
47
to the neutral terminal
159
through switch
178
.
During the automatic dry setting, the level of energization (i.e. current flow along series branch
47
and through) heater coil
50
is controlled by the closed or open states of thermostats
58
,
60
and
62
. The following describes the functioning of the present invention as it relates to an “automatic” cycle for the 120 volt dryer.
The preferred aspect of the present invention is in the use of a biasable low drum outlet control thermostat
60
to provide the automatic cycling required for the automatic cycle at low ambient temperature below 25° C. and, a biasable, normally open, ambient air thermostat
58
, to switch from the biasable low drum outlet control thermostat
60
to a biasable regular drum outlet thermostat
62
, when the ambient temperature around the dryer is above 25° C. Both the outlet thermostats
60
,
62
are positioned to sense the temperature of the air exiting the dryer drum
12
. The ambient air thermostat
58
is positioned to sense the temperature of the air entering the dryer cabinet
10
.
When the dryer is operated on an automatic cycle in an ambient temperature of 15 to 25° C., the low outlet thermostat
60
and the high outlet thermostat
62
are closed at the beginning of the cycle. The timer contact or switch
170
is open to pole
172
and is closed to pole
174
. Also switch
178
is closed to pole
180
. As a result, the internal biasing heaters
61
and
63
of both the low outlet temperature thermostat
60
and the high outlet temperature thermostat
62
are energized. The ambient thermostat
58
is open and its internal biasing heater
59
is not energized since the low outlet temperature thermostat
60
is closed and same voltage is applied to both sides of the biasing heater
59
.
As the drying cycle advances, the clothes humidity goes down and the temperature of the air exiting the drum
12
goes up. At a certain predetermined temperature, established as the proper calibration of its sensing disc and the proper wattage level of internal biasing heater
61
, the low outlet temperature thermostat
60
opens. When thermostat
60
opens, the dryer heating element
50
and the internal biasing heaters
61
and
63
of both the low outlet temperature thermostat
60
and high outlet temperature thermostat
62
are de-energized. Also, the internal biasing heater of the ambient thermostat
58
is energized.
The calibration of the ambient thermostat
58
and its internal biasing heater
59
are calibrated so that, when the ambient temperature is below 25° C., the thermostat
58
remains open. After a period of time, since the dryer heating element
50
is off, the temperature of the air exiting the drum will go down and the low outlet temperature thermostat
60
, with its own internal biasing heater
61
de-energized, closes. The dryer heating element
50
and the internal biasing heaters
61
and
63
of the low outlet temperature thermostat
60
and the high outlet temperature thermostat
62
become re-energized.
When the low outlet temperature thermostat
60
is open and the timer switch
170
is closed to pole
174
, the timer motor
108
advances extra space. When the low outlet temperature thermostat
60
closes the timer motor
108
stops. This cycling open and closed of the low outlet temperature thermostat
60
and the corresponding timer
108
continues until the timer
108
advances to the cool down cycle and then to the “off” position. With the proper calibration of the thermostats
58
,
60
, and
62
, the timer
108
advances to the “off” position when the clothes load reach the proper degree of dryness.
With the same “automatic” cycle selection, if the ambient temperature is above 25° C., the opening of the low outlet temperature thermostat
60
would occur sooner and thermostat
60
stays open longer before closing again. To prevent the timer motor
108
from advancing to the “off” position too soon and the dryer stopping when the clothes are still too damp, the present invention further comprises a high outlet temperature thermostat
62
that operates in co-operation with the ambient thermostat
58
. Thus, when the ambient temperature is above 25° C., the automatic drying cycle runs initially as described above, however, when the low outlet temperature thermostat
60
opens, the internal biasing heater
59
of the ambient thermostat
58
becomes energized and after a short while, the ambient thermostat
58
closes before thermostat
60
cycles closed. When the ambient thermostat
58
closes, the dryer heating element
50
and the internal biasing heaters
61
and
62
of both the low outlet temperature thermostat
60
and the high outlet temperature thermostat
62
are energized. This prevents closing of the low outlet thermostat
60
. The dryer heater
50
continues to heat the air entering the dryer drum
12
until the temperature of the air exiting the drum
12
reaches a second higher predetermined temperature that causes the biased high outlet temperature thermostat
62
to open. Once the thermostat
62
opens, the cycling of the heating element
50
and timer motor
108
advancement continues with opening and closing of the thermostat
62
until the end of the drying cycle is reached. The control circuit now cycles at a higher temperature associated with the higher temperature at which thermostat
62
opens, when biased, compared to the lower temperature at which thermostat
60
opens, when biased. With the circuit cycling at a higher temperature, the clothes are properly dried even though the dryer
10
is operating in higher ambient air temperature.
It should be understood that when the “automatic” cycle is selected, the dryer automatically stops when the clothes load is dried but, to get the automatic cycle termination, the thermostats
60
and
62
must cycle on-off to get the timer motor
108
to advance. With the 120 volt dryer, the energy input is relatively low and the low outlet temperature thermostat
60
and the high outlet temperature thermostat
62
are set to cycle at relatively low temperatures. If it was not for the automatic termination requirement, there would be no need to cycle the heater on-off at these low temperatures. Therefore, to further improve the drying performance, the present invention further provides another preferred feature that automatically prevents this low temperature cycling of the thermostats
60
and
62
when the “timed” cycle is selected. That is when a user sets the drying time for the dryer to operate. In the “timed” selection, the timer controlled contact or switch
178
is open from pole
180
and, as a result, no current flows through internal biasing heaters
61
and
63
. Accordingly, the low outlet temperature thermostat
60
and the high outlet temperature thermostat
62
are no longer biased and the exhaust air temperature from the dryer drum
12
has to reach a higher temperature before the low outlet temperature thermostat
60
and the high outlet temperature thermostat
62
start cycling.
Claims
- 1. A control circuit for controlling the operation of a clothes dryer having a dryer drum, a drum air inlet and a drum air outlet permitting an air stream to flow into and out of the dryer drum, a heater for heating the air stream before the air stream passes into the dryer drum, and a control circuit for controlling energization of the heater during an automatic drying cycle, the control circuit comprising:a supply line and a neutral line adapted for connection to a 120 volt power supply source; a series connection across the supply line and neutral line of a low output temperature thermostat, a high output temperature thermostat and the heater, the low output temperature thermostat opening at a first predetermined temperature and the high output temperature thermostat opening at a second predetermined temperature higher than the first predetermined temperature thereby controlling energization of the heater; a timer motor connected between the supply line and a first point located between the high output temperature thermostat and the heater, the timer motor advancing to end the automatic drying cycle during periods when either one of the low output temperature thermostat and high output temperature thermostat is open; an ambient thermostat for sensing ambient temperature and being electrically connected in parallel with the low output thermostat and in series with the supply line and a second point between the low output temperature thermostat and the high output temperature thermostat, the ambient thermostat providing a bypass circuit around the low temperature thermostat when a predetermined ambient temperature is reached; and, wherein, the low output temperature thermostat opens when the temperature of the air stream exiting the drum reaches the first predetermined temperature to control cycling on and off of the heater and to control the advancement of the timer motor, and wherein control cycling on and off of the heater and control of advancement of the timer motor in response to the high output temperature thermostat opening at the second predetermined temperature occurs when the first outlet thermostat is bypassed by the ambient thermostat.
- 2. The clothes dryer of claim 1 wherein the ambient thermostat is normally open and is thermally biased by a first electrical biasing heater connected across the ambient thermostat which when energized permits the ambient thermostat to close at said predetermined ambient temperature, and the opening of the low output temperature thermostat further energizing the first electrical biasing heater to permit closing of the ambient thermostat when the predetermined ambient temperature is reached and thereby bypass the low output temperature thermostat.
- 3. The clothes dryer of claim 2 wherein the low output temperature thermostat has a second biasing heater connected from the series branch at the second point between the low output temperature thermostat and high output temperature thermostat to the neutral line to be energized during the automatic drying cycle, and the high output temperature thermostat having a third biasing heater connected from the series branch at the first point between the high output temperature thermostat and the heater to the neutral line to be energized during the automatic drying cycle.
- 4. The clothes dryer of claim 3 further including first and second switches responsive to a user selecting a timed drying cycle for respectively switching the timer motor from a first connection to the first point to a second connection to neutral line to permit continuous advancement of the timer motor and for opening a third connection between the second and third biasing heaters to the neutral line so as to raise the temperatures at which the low output temperature thermostat and high output temperature thermostat open to respectively higher third and fourth predetermined temperatures.
- 5. A clothes dryer adapted to be connected to a 120 volt power supply source and having a dryer drum, a drum air inlet and a drum air outlet permitting an air stream to flow into and out of the dryer drum, a heater for heating the air stream before the air stream passes into the dryer drum, and a control circuit for controlling the dryer though an automatic drying cycle, the control circuit comprising:a supply line and a neutral line adapted for connection to the 120 volt power supply source; a series branch connecting in series a low output temperature thermostat, a high output temperature thermostat and the heater across the supply line and the neutral line to control energization of the heater, the low output temperature thermostat and high output temperature thermostat being mounted in the dryer to sense the temperature of the air stream passing out of the drum, and the low output temperature thermostat opening at a first predetermined temperature that is less than a second predetermined temperature at which the high output temperature thermostat opens; a timer motor connected between the supply line and the series branch at a first point of the series branch located between the high output temperature thermostat and the heater, the timer motor advancing to end the automatic drying cycle during period when either one of the low output temperature thermostat and high output temperature thermostat is open; a thermally biased ambient thermostat mounted in the dryer for sensing ambient temperature, normally being in an open position, being electrically connected in parallel with the low output thermostat and in series with the supply line and a second point between the low output temperature thermostat and the high output temperature thermostat, the thermally biased ambient thermostat having a first electrical biasing heater connected across the thermostat which heater when energized permits the ambient thermostat to close when a predetermined ambient temperature is reached; and wherein, the low output temperature thermostat opens when the temperature of the air stream passing out of the drum reaches the first predetermined temperature to control cycling on and off of the heater and to control the advancement of the timer motor, and the opening of the low output temperature thermostat further energizing the first electrical biasing heater to permit the closing of the ambient thermostat when the predetermined ambient temperature is reached to bypass the low output temperature thermostat in the series branch, to control cycling on and off of the heater and to control the advancement of the timer motor in response to the high output temperature thermostat opening at the second predetermined temperature.
- 6. The clothes dryer of claim 5 wherein the low output temperature thermostat has a second biasing heater connected from the series branch at the second point between the low output temperature thermostat and high output temperature thermostat to the neutral line to be energized during the automatic drying cycle, and the high output temperature thermostat having a third biasing heater connected from the series branch at the first point between the high output temperature thermostat and the heater to the neutral, line to be energized during the automatic drying cycle.
- 7. The clothes dryer of claim 6 further including first and second switches responsive to a user selecting a timed drying cycle for respectively switching the timer motor from a first connection to the first point to a second connection to neutral line to permit continuous advancement of the timer motor and for opening a third connection between the second and third biasing heaters to the neutral line so as to raise the temperatures at which the low output temperature thermostat and high output temperature thermostat open to respectively higher third and fourth predetermined temperatures.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2364219 |
Nov 2001 |
CA |
|
US Referenced Citations (14)