U.S. patent number 3,651,579 [Application Number 04/604,757] was granted by the patent office on 1972-03-28 for drier control.
This patent grant is currently assigned to The Maytag Company. Invention is credited to Thomas R. Smith.
United States Patent |
3,651,579 |
Smith |
March 28, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
DRIER CONTROL
Abstract
This invention is directed to a control for determining the
moisture content of articles. Electrodes are positioned to be
bridged by samples of articles in a treatment apparatus. In at
least one embodiment, a capacitor is connected in circuit with the
electrodes so that the charge thereon varies with the moisture
content of the material as measured by the resistance of the
material between the electrodes. A trigger circuit containing an
electrical breakdown device having an effectively infinite
resistance in one condition, as, for example, a neon lamp, provides
a signal when the material achieves a predetermined moisture
content. A switch responds to the signal for operating a
control.
Inventors: |
Smith; Thomas R. (Newton,
IA) |
Assignee: |
The Maytag Company (Newton,
IA)
|
Family
ID: |
26986672 |
Appl.
No.: |
04/604,757 |
Filed: |
December 27, 1966 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
329155 |
Dec 9, 1963 |
10191971 |
|
|
|
22323 |
Apr 14, 1960 |
|
|
|
|
Current U.S.
Class: |
34/532 |
Current CPC
Class: |
G05D
22/02 (20130101); D06F 34/08 (20200201); D06F
2105/28 (20200201); D06F 2101/00 (20200201); D06F
2105/62 (20200201); D06F 58/38 (20200201); D06F
34/18 (20200201); D06F 2103/10 (20200201) |
Current International
Class: |
D06F
58/28 (20060101); G05D 22/02 (20060101); G05D
22/00 (20060101); F26b 019/00 () |
Field of
Search: |
;34/45,48,53 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Favors; Edward G.
Parent Case Text
This application is a division of copending application Ser. No.
329,155, filed Dec. 9, 1963, which is now U.S. Pat. No. 3,613,254,
issued Oct. 19, 1971, the latter of which is a continuation of
application Ser. No. 22,323, filed Apr. 14, 1960, now abandoned.
Claims
I claim:
1. A moisture sensing control for use with ap-paratus for drying
material and operative to control said apparatus in accordance with
the moisture content of said material, said moisture sensing
control comprising, an electric circuit including spaced
electrodes, said electrodes arranged to be bridged by said material
so that the resistance between said electrodes varies as the
moisture content of the material, means connected in circuit with
said electrodes for applying a DC potential across the electrodes
that increases as said resistance increases, a neon lamp pulser
connected in circuit with said electrodes and responsive to a
predetermined potential across the electrodes to pass a pulse, a
relay, and means connected in circuit with said relay and
responsive to the pulse to pass a control signal to the relay for
operating the relay.
2. A moisture sensing control for use with apparatus for drying
material and operative to control said apparatus in accordance with
moisture content of said material, said moisture sensing control
comprising, an electrical circuit including a source of DC voltage
connected in said circuit, spaced electrodes electrically connected
in circuit with said DC voltage source and having a DC potential
impressed thereon, said spaced electrodes adapted to be bridged by
the material being dried so that the DC potential across said
electrodes is dependent upon the moisture content of said material,
a capacitance in parallel circuit relationship with said electrodes
so that the charge thereon increases as the moisture content of the
material between said electrodes decreases, neon lamp signal
generating means connected in circuit with and responsive to a
predetermined function of the charge of said capacitance for
producing a signal, switch means operative in response to said
signal to be switched from one operational state to another, and
control means connected with and operated by the change in
operational state of said switch means to effect a control
function.
3. In a moisture sensing control adapted for use with an apparatus
in which material of varying moisture contents is treated and in
which said control is operative to indicate when the material
during the treatment attains a certain moisture content based upon
random samples, the combination comprising, spaced-apart electrodes
connected to an electrical potential and adapted to contact the
material being treated and to complete a circuit therethrough,
means for presenting random portions of the material into bridging
contact with said electrodes in order that the electrical
resistance of representative samples of the material is shunted
across said electrodes, integrating circuit means including
capacitance for developing a charge which is a function of the
integration over a time period of the electrical resistance of the
samples of the material contacting and bridging said electrodes,
trigger circuit means responsive to a predetermined function of the
charge on said capacitance for producing a signal when the material
has developed a certain moisture content, said trigger circuit
means including in circuit with said capacitance electrical
breakdown means having a normally effectively infinite resistance
operable until said capacitance developes substantially said
predetermined charge for providing effective regulation of said
trigger circuit means and operable after said predetermined charge
is developed on said capacitance for changing to a low resistance
to produce said signal, and control circuit means responsive to
said signal for providing a control function.
4. The moisture sensing control of claim 3 in which said electrical
breakdown means includes a neon lamp.
5. In a moisture sensing control adapted for use with an apparatus
in which material of varying moisture contents is treated and in
which said control is operative to indicate when the material
during the treatment attains a certain moisture content based on
random samples, the combination comprising, spaced-apart electrodes
connected to an electrical potential and adapted to contact the
material being treated and to complete a circuit therethrough,
means for presenting random portions of the material into bridging
contact with said electrodes in order that the electrical
resistance of representative samples of the material is shunted
across said electrodes, control circuit means operable for
effecting a control function upon the material attaining a certain
moisture content, trigger circuit means including in circuit with
said electrodes electrical breakdown means having an effectively
infinite resistance in one condition and operable for providing
effective regulation of said control circuit means, integrating
circuit means including capacitance in circuit with said electrodes
for developing a potential which is a function of the integration
over a time period of the electrical resistance of the samples of
the material contacting and bridging said electrodes, said
electrical breakdown means being responsive to a certain function
of the potential across said capacitance and operable from a first
condition to a second condition at said certain moisture content
for actuating said control circuit means.
6. The moisture sensing control according to claim 5 in which said
electrical breakdown means comprises a neon lamp.
7. In a moisture sensing control adapted for use with an apparatus
in which material of varying moisture contents is treated and in
which said control is operative to indicate when the material
during the treatment attains a certain moisture content based on
random samples, the combination comprising, spaced-apart electrodes
connected to an electrical potential and adapted to contact the
material being treated and to complete a circuit therethrough,
means for presenting random portions of the material for bridging
contact with said electrodes in order that the electrical
resistance of representative samples of the material is shunted
across said electrodes, control circuit means operable for
effecting a control function upon the material attaining a certain
moisture content, circuit means including in circuit with said
electrodes electrical breakdown means having an effectively
infinite resistance in one condition and operable between first and
second conditions for providing effective regulation of said
control circuit means, means for developing an electrical analog
which is a function of the integration of the moisture contents of
the random portions of the material contacting and bridging said
electrodes, said electrical breakdown means being responsive to a
certain value of said electrical analog for operation from said
first condition to said second condition at said certain moisture
content for actuating said control circuit means.
8. The moisture sensing control of claim 7 in which said electrical
breakdown means includes a diode device.
9. The moisture sensing control of claim 7 in which said electrical
breakdown means includes a two element neon tube.
10. In a moisture sensing control adapted for use with an apparatus
in which material of varying moisture contents is operative to
indicate when the material during the treatment attains a certain
moisture content based on random samples, the combination
comprising, spaced-apart electrodes connected to an electrical
potential and adapted to contact the material being treated and to
complete a circuit therethrough, means for presenting random
portions of the material for bridging contact with said electrodes
in order that representative samples of the material are shunted
across said electrodes, control circuit means operable from a first
posture to a second posture to initiate termination of operation of
said apparatus upon the material attaining a certain moisture
content, circuit means including in circuit with said electrodes a
signal generating diode means operable between first and second
conditions for providing effective regulation of said control
circuit means, means for developing an electrical analog which is a
function of the integration of the moisture contents of the random
portions of the material contacting and shunting said electrodes,
said signal generating diode means being responsive to a certain
value of said electrical analog for operation from said first
condition to said second condition at said certain moisture content
for actuating said control circuit means to said second posture
whereby initiation of termination of operation of said apparatus is
effected.
11. The moisture sensing control according to claim 10 in which
said signal generating diode means comprises a neon lamp.
12. A control for determining moisture content of material,
comprising, an electric circuit including a voltage divider network
one part of which is provided with a known resistance and the other
part of which includes spaced electrodes adapted to be bridged by a
material the resistance of which varies as its moisture content
varies, a capacitor in circuit with the electrodes so the charge
thereon is a function of the resistance between the electrodes, a
two element glow lamp connected in circuit with said capacitor and
responsive to a predetermined function of the charge on the
capacitor to produce a signal, normally nonconducting switching
means responsive to and actuated by said signal to a conducting
condition, and control means connected in circuit with said
switching means and operated by the current passed by the switching
means.
13. The control according to claim 12 in which said two-element
glow lamp is a neon lamp.
14. A moisture sensing control for use with apparatus for drying
material and operative to control said apparatus in accordance with
moisture content of said material, said moisture sensing control
comprising, spaced electrodes adapted to be bridged by the material
being dried so that the electrical potential across said electrodes
is dependent upon the moisture content of said material, means
connected in circuit with and operative to apply a DC potential
across said electrodes, a capacitance connected in parallel with
said electrodes so that the charge thereon increases as the
electrical resistance of the material between said electrodes
increases, glow lamp signal generating means connected in circuit
with said capacitance and operative in response to a predetermined
function of the charge on said capacitance to produce an electrical
signal, and control means responsive to said signal to pass current
of sufficient magnitude to effect a control function.
15. The moisture sensing control according to claim 14 in which
said glow lamp signal generating means comprises a neon lamp.
16. A moisture sensing control for use with apparatus for drying
material and operative to control said apparatus in accordance with
the moisture content of said material, said moisture sensing
control comprising, sensing means arranged for engagement with the
material being dried to complete a sensing circuit and the
potential of said sensing means being determined by current flow
through said material, means connected in circuit with and
operative to apply a DC voltage to said sensing means, a
capacitance connected in circuit with said sensing means for
accumulating a charge which increases as the moisture content of
said material decreases, glow lamp signal generating means
connected in circuit with said capacitance and operative in
response to a predetermined function of the charge on said
capacitance to produce a signal, control means for said apparatus,
and means connected in circuit with said control means and
responsive to said signal to actuate said control means to effect a
control function.
17. The moisture sensing control according to claim 16 in which
said glow lamp signal generating means comprises a neon lamp.
18. In a moisture sensing system adapted for use with a material
drying apparatus and operative to indicate when the material during
a drying operation contains a certain moisture content based on
random samples, the combination comprising, spaced-apart electrodes
connected to an electrical potential and adapted to contact the
material being treated for completing a circuit therethrough, means
for presenting random portions of the material for bridging contact
with said electrodes in order that the electrical resistance of
representative samples of the material is shunted across said
electrodes, control means connected to said electrodes and
including electrical breakdown means having first and second
electrical conditions in which one of said electrical conditions
presents an effectively infinite resistance, said control means
further including integration means operable for integrating the
moisture contents of the random portions of the material contacting
and bridging said electrodes, one of said electrical breakdown
means and said integration means being responsive to a function of
the electrical resistance across said electrodes for actuating the
other to condition said control means for initiating termination of
said drying operation, and termination means responsive to said
control means for initiating termination of said drying operation
at said certain moisture content.
19. The moisture sensing system according to claim 18 in which said
electrical breakdown means comprises a neon lamp.
20. In a moisture sensing system as defined in claim 18 wherein
said integration means includes a capacitor.
21. In a moisture sensing system as defined in claim 20 wherein
said electrical breakdown means includes a glow lamp having a
condition of normally effectively infinite resistance in the
presence of wet material at said electrodes and operable to the
other electrical condition responsive to said capacitor in the
presence of material having said certain moisture content for
actuating said control means to initiate termination of said drying
operation.
22. In a moisture sensing system as defined in claim 18 wherein
said integration means includes motor driven means.
23. In an apparatus for drying fabrics operable through a cycle of
operation, a drum for containing said fabrics, means for rotating
said drum to tumble said fabrics, means for drying said fabrics in
said drum, electrodes for contacting and completing an electrical
circuit through said tumbled fabrics, said electrodes spaced apart
a fixed distance adapted to receive therebetween the fabrics being
dried so that the electrical resistance between said electrodes
varies with the electrical resistance condition of the fabrics
therebetween, means for applying electrical voltage to said
electrodes, means for instituting said cycle of operation of said
apparatus, means responsive to a predetermined electrical
resistance condition of said fabrics contacting said electrodes for
generating a control voltage, a gaseous discharge device for
producing a light when said control voltage attains a predetermined
value, a light responsive device positioned to be illuminated by
the light produced in said gaseous discharge device, and means
controlled by said light responsive device for initiating
termination of the cycle of operation.
24. In an apparatus according to claim 23 further characterized in
that said gaseous discharge device is a neon lamp.
25. A moisture sensing control for use with apparatus for treating
material and operative to control said apparatus in accordance with
the moisture content of said material comprising, an electric
circuit including spaced electrodes adapted to engage random
portions of said material and further including means for applying
a potential across said electrodes, said electrodes arranged to be
bridged by said material so that the potential between said
electrodes varies as a function of the moisture content of the
material bridging the electrodes, electrical breakdown means
connected in circuit with said electrodes and responsive to a
predetermined potential across said electrical breakdown means
which is a function of the potential across the electrodes to
operate from a first electrical condition to a second electrical
condition, said electrical breakdown means having an effectively
infinite resistance in one of said first and second electrical
conditions, and means responsive to operation of said electrical
breakdown means to said second condition for effecting a control
function.
26. The moisture sensing control according to claim 25 in which
said electrical breakdown means comprises a neon lamp.
27. A moisture sensing control for use with apparatus for drying
material and operative to control said apparatus in accordance with
moisture content of said material, said moisture sensing control
comprising, spaced electrodes adapted to be bridged by the material
being dried so that the electrical potential across said electrodes
is dependent upon the moisture content of said material, means
connected in circuit with and operative to apply a potential across
said electrodes, a capacitance connected in circuit with said
electrodes so that the charge thereon varies as a function of the
electrical resistance of the material between said electrodes,
electrical breakdown means connected in circuit with said
capacitance and operative in response to a predetermined potential
across said electrical breakdown means as a function of the charge
on said capacitance to generate an electrical signal, said
electrical breakdown means operable between first and second
electrical conditions and having an effectively infinite resistance
in one of said first and second electrical conditions, and control
means responsive to said signal to effect a control function.
28. The moisture sensing control according to claim 27 in which
said electrical breakdown means comprises a neon lamp.
Description
This invention relates to a control system in a machine for drying
fabrics, and more particularly, to a system for automatically
controlling termination of the drying operation after the fabrics
have reached a predetermined degree of dryness.
Most of the conventional driers, especially of the home laundry
type, regulate the drying period by a manually adjustable timer
which is preset by the operator. The duration of the drying
operation depends upon the judgment, or guess, of the operator as
to the proper period for the desired degree of dryness. The results
are inconsistent overdrying, underdrying, or, in the case of some
fabrics, incomplete drying of particular pieces.
Heretofor, numerous control systems for domestic clothes driers
have been attempted in an effort to obtain automatic termination of
the drying operation in a domestic clothes drier after the fabrics
have reached the desired dryness. One of the major problems facing
any automatic control system is the difficulty in obtaining
consistently completely dried loads of mixed fabrics as found in
the home laundry, since different fabrics vary in their moisture
retentivity. In addition, some fabrics have both light and heavy,
thin and thick sections, to further complicate the problem.
One previous system has used the change in conductivity of the
fabrics as the moisture is removed in order to discontinue
operation of a drying machine at the moment electrical conductivity
of the fabrics, as sensed directly between conductors in the drum,
attains a predetermined value. This type of control causes
premature shut-off of the machine before the clothes are completely
dry, especially with mixed loads, which frequently occur in the
home, because some of the pieces dry long before others and the wet
pieces when enclosed in, or shielded by, drier pieces causes
instantaneous premature shut-off of the machine. In this type of
control, since the drier operates only if a damp fabric is
continuously contacting the electrodes, if at any moment none of
the electrodes, or probes, within the drier drum contact a damp
piece, the control will operate immediately to institute
termination of drying. For this reason the control is unreliable,
and unsatisfactory.
In other control systems, the humidity of the air within the drier
is measured to determine when the drying operation should be
terminated, instead of direct measurements of the electrical
conductivity of the fabrics. Humidity determinations are an
unreliable index of the condition of the fabrics, and control
systems dependent thereon contain an inherent deficiency.
In still other systems attempts have been made to control the
termination of the drying period by thermostats in the drier. In
these systems the thermostats operate to shut-off the heaters when
the temperature within the drying cabinet rises above a set value
which occurs when most of the clothes have been dried. Again, the
control does not insure that all of the fabrics have been
dried.
It is an object of the present invention to provide a control
system for a clothes drier responsive to the dry condition of the
fabrics being treated. It is a further object of the invention to
provide a system for controlling termination of a drying operation
that is responsive to the isolated fabrics in a load, so as to
obtain reliable shut-off of the drying operation. It is a still
further object of the invention to provide a system whereby direct
response of the control to the dryness or conductivity of fabrics
is made practical or feasible for home laundry clothes driers. It
is another object of the invention to provide a control system
having a manually operable preselection adjustment which initiates
termination of the drying operation when the clothes have reached
the manually preselected condition of dryness, for example, when
the fabrics are in damp dry condition suitable for ironing. Further
objects and advantages of this invention will become evident as the
description proceeds and from an examination of the accompanying
drawings which illustrate several embodiments of the invention and
in which similar numerals refer to similar parts throughout the
several views.
In the Drawings:
FIG. 1 is a view in vertical section, partly broken away,
illustrating a drier which incorporates the control system of the
invention;
FIG. 2 is a bottom view of one of the baffles shown in the drum of
the drier in FIG. 1, illustrating the location of the
electrodes;
FIG. 3 is a schematic diagram of a preferred circuit employing the
principles of the control system of the present invention;
FIG. 4 is a schematic diagram of a modified form of circuit which
may be used as a control employing the principles of the
invention;
FIG. 5 is a schematic diagram of a modified from of circuit which
may be used as a control employing the principles of the invention;
and
FIG. 6 is a schematic diagram of a modified form of circuit which
may be used as a control employing the principles of the
invention.
Briefly described, the invention relates to a control system in
which conductors, electrodes, or probes, directly contact fabrics
being dried, and control termination of the drying operation after
their electrical resistance, or conductivity, dependent upon their
condition of dryness, exceeds a predetermined value for a
predetermined time.
In FIG. 1 of the accompanying drawings is shown a clothes drier
having a base frame 10 which serves as a support for upstanding
channel base members 11 and 12 which together with cross piece 14
support the hollow blower housing casting 17. Housing 17 includes a
tubular portion 21, a divider wall 20 having a rearwardly flared
inner portion defining an intake into an impeller chamber, and
radially directed longitudinal webs 22 which converge toward each
other to provide a retainer member 23. A passageway 26 is located
between the tubular portion 21 and the bearing retainer member 23
which transverses the supporting webs 22.
Journalled within member 23 is a revoluble drum drive shaft 31
which projects from both ends of the housing 17. Affixed to drum
drive shaft 31 at the rear of the cabinet is a large pulley 33
which is driven by motor 34 through motor pulley 36, main drive
belt 37, a speed reduction system (not shown) and belt 40.
The opposite or forward end of the drum drive shaft 31 is rigidly
connected to the drum spider member 46 which has radiating spokes
51 that support rim 52. A heat resistant sealing member 54
encircles the front periphery of blower housing 17 and the circular
shoulder 55 located on the rear portion of drum spider 46.
A horizontally mounted tumbling drum 60 has a rear wall 61 which is
secured to rim 52 for support and rotation by shaft 31. Rear drum
wall 61 is imperforate except for a central exhaust opening 62.
The periphery of rear wall 61 is flanged to form a supporting
shoulder for the imperforate cylindrical side wall 65 which carries
the clothes elevating vanes 66 for tumbling clothing within drum 60
during rotation of the latter member. Cylindrical side wall 65 is
connected to the front drum wall 67.
Front wall 67 has a centrally located access opening 68 and a
circular perforate portion 69 located concentrically to access
opening 68. This perforate portion 69, formed by several concentric
rows of holes, serves as the air intake into drum 60.
The cabinet 70 which is fastened to base frame 10 and which
encloses the entire drying mechanism has an access opening 71
aligned to drum access opening 68 thereby allowing both of openings
68 and 71 to receive the door gasket 72. The door 73 is hinged and
forms an airtight seal with gasket 72.
Fastened to cabinet 70 is the shroud or cowling member 74. Located
between shroud 74 and the front drum wall 67 is an open coil
electric heating element 75 which extends completely around the
inside of cowling member 74 to raise the temperature of air passing
through perforate portion 69 in the front drum wall 67. It will be
understood that a gas heater may be used in place of the electrical
element.
Air flow into drum 60 through the perforate area 69 and into the
blower housing 17 is produced by rotation of the revoluble impeller
member 76 located in blower housing 17. Fan pulley 77 is connected
to the driving motor 34 by main drive belt 37. The blower housing
casting 17 supports a cycling thermostat 78 which is connected in
series with the heating element 75 in order to maintain the
interior of drum 60 at the proper selected drying temperature. In
practice, this switch is set to open at approximately
135.degree..
Also connected in series with the heating element 75 is the high
limit switch 79 which is mounted on an upper part of shroud member
74 so as to disconnect heating element 75 from its source of power
in case the temperature near the front of the drum should rise
above a predetermined selected temperature during the operation of
the clothes drier, for instance, in the event of reduced air flow
through drum 60.
In order to measure the electrical conductivity or resistance for
determining the condition of dryness of the fabrics, electrodes or
probes 80, 81 are mounted within the drum 60. In the form shown,
the electrodes are spirally wound about each of the drum baffles 66
to provide a maximum amount of contacting or probing surfaces
exposed to the fabrics placed within the drum. As best illustrated
in FIG. 2, the electrodes are preferably set in recesses or grooves
in the baffles to prevent shorting therebetween by metallic objects
sometimes attached to the fabrics, for example, metal buttons,
clips, buckles, and the like. It will be realized that different
forms of electrodes, or probes, may be used, although the type
disclosed herein is preferred.
Electrical energy is supplied to electrode 80 by lead 84 that is
connected to brush 85 which engages the stationary slip ring 86
while the drum 60 is rotating. The slip ring 86 may be supported on
an electrically insulative band 87 mounted on housing 17. Slip ring
86 is in turn connected to a lead 90 which runs to the control unit
92. Electrode 81 may also be supplied with electrical energy of the
opposite polarity to electrode 80 by lead 83 that may be connected
to a similar arrangement of brushes and slip rings. It is
preferred, however, to ground electrode 81 to the rotatable drum
60, so that it is supplied by current from lead 91 which is also
grounded to the framework of the drier.
The automatic control unit 92 may be secured to the upper portion
of the cabinet. Leads 90, 91 enter the control unit and are
connected to the control circuit to be described hereinafter.
It will be noted that the baffles 66 are formed of electrically
nonconductive material in order to insulate the electrodes.
However, the electrodes are electrically shorted by contacting the
wet fabrics during tumbling. Ordinarily, a plurality of baffles 66
are mounted within the drum 60, each of which is provided with
electrodes 80, 81, and the respective electrodes of all the baffles
connected in parallel.
Referring now to FIG. 3 which illustrates the automatic control
circuitry, there is shown diagrammatically a timing cam stack 94
for controlling the drying operation. The cam stack has five cam
switches 95 to 99 in which cam switch 95 controls the heater, cam
switch 96 the timer motor, cam switch 97 the drive motor, cam
switch 98 the sensing circuit, and cam switch 99 the damp dry
setting.
It will be noted that the cam stack has "regular dry" and "damp
dry" settings, either of which may be preselected through manual
operation of a knob (not shown) by the operator. It should be clear
that the cam stack may include other selections, for example, for
wash and wear fabrics, air fluff, and special loads.
The cam stack 94 is advanced by a timer motor mechanism 102 in 3
minute intervals, each of which three minute interval is
represented by the vertical lines in the cam stack 94 in the
drawing. The shaded areas in the drawing indicate that the circuit
is completed, while the blank portions mean that the circuit is
open at the time interval and for the cam switch specified.
The drier is energized by a conventional three wire system
represented by power lines L.sub.1, L.sub.2 and N. The heater is
connected between L.sub.1 and L.sub.2 for 220 volts AC by circuit
from L.sub.1 through cam switch 95, line 105, thermostat switch 78,
high limit switch 79 to one side of the heater 75. The other side
of the heater is connected to power line L.sub.2 through
centrifugal switch 104 in motor 34. Centrifugal switch 104 is
normally open. When motor 34 is rotated switch 104 is centrifugally
closed to energize heater 75.
The timer motor 102 is energized by a circuit from power line
L.sub.1, on-off switch 100, cam switch 96, line 106 to one side of
the timer motor 102. The other side of the timer motor is connected
to power line N.
The drive motor is energized by a circuit from power line L.sub.1,
on-off switch 100, cam switch 97, line 107 to one side of the motor
34. The other side of the motor 34 is connected to power line
N.
The sensing circuit is energized by a circuit from power line
L.sub.1, on-off switch 100, cam switch 98, line 108.
The sensing circuit has a selenium half-wave rectifier 112
connected on one side to line 108 through line 111. The other side
of the rectifier 112 is connected to capacitor 115 through a series
resistor 113. The other side of the capacitor 115 is connected to
power line N through series resistor 116. It will be noted that the
electrodes 80, 81 within the drum are connected across the
capacitor 115 by lines 90, 91. When the capacitor is charged by the
DC circuit from the rectifier 112, it may be discharged by any
conducting material placed across, and shorting, the electrodes 80,
81.
A gaseous discharge tube, such as a neon lamp 120 is connected
across capacitor 115. Neon lamp 120 normally has an infinite
resistance, however, when the charge on the capacitor 115 reaches a
predetermined value, the gas is ionized and the circuit is
conducted therethrough to produce visible discharge.
A light sensitive cell 122 is positioned to detect the discharge of
the neon lamp 120. One side of the light sensitive cell 122 is
connected by line 134 to line 108, and the other side of the light
sensitive cell is connected to relay 125 through line 123. The
other side of the relay 125 is fastened to power line N. Normally,
when dark, the light sensitive cell 122 has a very high resistance.
However, when it detects light, its resistance is greatly reduced
and completes the circuit to energize relay 125.
Relay 125 operates switches 126 and 127. Switch 126 completes a
holding circuit in order to maintain the relay 125 energized after
the photo-electric cell 122 has been excited through the discharge
of neon lamp 120. The holding circuit is from line 108 to line 128
through switch 126 to one side of the relay 125. The other side of
the relay is connected to power line N.
Switch 127 controls the timer motor 102. When switch 127 is closed
the timer motor is energized by a circuit from line 107, line 129,
switch 127, line 130 to one side of timer motor 102. The other side
of the timer motor 102 is connected to power line N.
It will be seen that the capacitor 115 is charged by a DC circuit
through the rectifier 112 and series resistance 113, 116 to power
line N. The rate at which the capacitor 115 is charged depends,
among other factors, upon the value of resistors 113, 116. It has
been found that if the power between L.sub.1 and N is 110 volts 60
cycle alternating current, the capacitor 115 may be a 6 microfarads
paper condenser and the total resistance of 113 and 116 is 31
megohms, or 30 and 1 megohms, respectively. The neon lamp in this
arrangement may be designed to fire at 68 to 76 volts.
As the capacitor 115 is slowly charged through resistors 113, 116,
it is also discharged through electrodes 80, 81 when the clothes
are wet. However, as the clothes are dried, the average rate of
discharge diminishes to a point at which the charge on the
condenser reaches an amount which will fire the neon lamp 120. This
operates the relay 125 through the photo-electric cell 122.
It will be apparent that resistors 113, 116 may be connected on the
same side of capacitor 115. However, for safety reasons, it is
better to divide the total resistance between the two sides of the
capacitor.
From the foregoing, it is believed that the operation of the device
is apparent. The operator opens the door 73 of the drier and
inserts the fabrics in the drum 60. Next the cam timer is manually
set to "regular dry" position and the on-off switch 100 closed.
When the timer is set to the beginning of the "regular dry"
position, the heater line 105 is connected to power line L.sub.1
through cam switch 95. Also timer motor line 106, drive motor line
107 and sensing circuit line 108 are all connected to power line
L.sub.1, if the on-off switch 100 is closed through cam switches 96
to 98, as indicated by the shaded areas in the cam stack 94. The
drive motor 34 rotates the drum 60 to tumble the clothes therein by
baffles 66. After a certain rotational speed is achieved by the
drive motor 34, switch 104 is centrifugally operated to close the
circuit to the heater 75.
The timer drive mechanism 102 when energized advances the cam stack
94 every 3 minutes. It will be noted that the timer drive mechanism
102 is maintained in energized position for a total of 6 minutes
after which it is de-energized by the cam switch 96, as indicated
by the blank area in the third 3 minute interval. When the timer
drive mechanism is de-energized, continued operation of the drier
is under control of the sensing circuit. The timer drive mechanism
remains de-energized and the drier continues to operate until the
timer drive mechanism is again energized to terminate the drying
operation through actuation of the sensing circuit. With the timer
drive mechanism de-energized, the drier operation continues with
the heater energized and the drive motor rotating to tumble the
fabrics within the drum 60.
As long as the clothes remain wet, or sufficiently damp to
effectively discharge the capacitor 115, the drying operation is
maintained. Although the capacitor 115 is charged by the rectifier
and through resistors 113, 116 it continues to be discharged by the
fabrics shorting electrodes 80, 81. However, when the moisture is
removed, the fabrics achieve increased electrical resistance and
the charge on the capacitor 115 begins to accumulate. The build up
of the charge on capacitor 115 reaches a predetermined amount over
a predetermined period of time of sufficient duration for all of
the clothes within the drum to contact the electrodes during
tumbling. Thus, if a damp fabric has been entrapped in dry fabrics,
as the drum continues to rotate, the damp piece will eventually
contact the electrodes 80, 81 and discharge the capacitor 115 to
prevent termination of the drying operation. On the other hand, if
the pieces are all dry, termination of the drying operation will be
initiated.
One of the important features of the present invention is the time
integration of the effective average resistance of the fabrics
which fall across the probes with a predetermined average value
necessary for initiating termination of the drying period. This
reduces the occasion for premature termination of the drying
operation.
After all of the fabrics have achieved a predetermined resistance
for a predetermined period of time, the neon lamp 120 discharges.
This excites light sensitive cell 122 to complete the circuit to
the relay 125. When relay 125 is energized, it is maintained
energized through the circuit completed through switch 126. The
relay also completes a circuit through switch 127 to again energize
the timer drive mechanism 102. The timer drive mechanism then
begins to run through the remainder of the open interval in the
timer cam switch 96 and for two additional 3 minute periods making
a total of approximately 6 minutes. It should be noted that at the
end of the first additional 3 minute interval the heater circuit is
de-energized at the end of the second 3 minute interval all
remaining circuits are de-energized by the timer cam stack 94 and
the drying cycle discontinued.
The additional 3 minute heating period insures that the clothes
will be completely dry, even in the folds or thick portions which
are often found in fabrics of the home laundry. The last 3 minute
period of operation without heat obtains a cooling period to bring
the temperature of the clothes down to a comfortable handling
temperature.
In the event the operator desires the clothes to be damp dry, a
condition suitable for ironing, the timer cam stack 94 is manually
positioned to "damp dry." In this position, operation of the device
is similar to "regular dry" with two exceptions. The cam switch 99
connects resistor 131 in parallel to resistor 113. The circuit is
completed by a line 132, cam switch 99, and line 109 to one side of
resistor 131. The other side of resistor 131 is connected in
parallel to resistor 113. Resistor 131, has, for example, a value
of 330,000 ohms. This means that the total resistance in series
with the capacitor 115 is substantially reduced. Thus, the
capacitor 115 is charged at a greater rate. The increased rate at
which the capacitor 115 is charged results in the neon lamp 120
being fired at a time when the resistance through the clothes as
sensed by the electrodes 80, 81 indicates the clothes are still
damp. The charge on the capacitor 115 accumulates more rapidly
through the reduced value of the total resistance and overtakes the
discharge through the electrodes at an earlier fabric resistance,
so that the clothes are partially damp when the neon tube is
discharged.
As in the instance of the "regular dry" position, in the "damp dry"
position the relay 125 also completes a circuit through switch 127
to again energize the timer drive mechanism 102. The timer drive
mechanism 102 then begins to run through the remainder of the open
interval in the timer cam switch 96 at which time all circuits are
de-energized. In this way, the clothes in the damp dry position are
subjected to less heat before the drive motor is stopped, so that
they contain the desired amount of moisture.
FIG. 4 shows a modified form of sensing circuit which may be
employed in the control of FIG. 3. A rectifier 135 is connected on
one side to a power line 133. The other side of the rectifier 135
is connected to the capacitor 136 through a series resistor 137.
The other side of the capacitor 136 is connected to the power line
134.
The electrodes 141, 142, located within the drum of the drier, are
connected across the capacitor 136 by lines 143, 144. When the
capacitor 136 is charged by the DC circuit from the rectifier 135,
it will be discharged by any conducting material placed across the
electrodes, such as wet fabrics.
A gaseous discharge tube 138 and a relay 139 are connected between
lines 143, 144 across the capacitor 136. The relay contacts 145,
146, normally open, are closed when the relay 139 is energized when
the gaseous tube 138 becomes conductive. Contact 145 is in series
with a holding circuit to maintain the relay 139 closed after the
gaseous tube 138 has fired. Contact 146 connects the timer motor
147 of the control circuit to the power line 134. The other side of
the timer motor is connected to the power line 133.
In operation, the sensing circuit of FIG. 4 operates to fire the
gaseous tube 138 when the resistance of the clothes, as determined
by the electrodes 141, 142, reaches a predetermined value. During
the time the clothes are tumbled, the capacitor 136 is gradually
charged by a DC circuit through the rectifier 135 and through the
series resistance 137 at a rate which is less than the discharge
from the capacitor through the electrodes 141, 142 when the clothes
are wet, however, when the clothes reach a predetermined dryness
the capacitor 136 is charged faster than it is discharged through
the electrodes. When the capacitor charge accumulates to a
predetermined value, the discharge tube fires to energize relay
139. The relay is kept energized by holding circuit through relay
switch 145. Relay switch 146 completes the circuit to the timing
motor 147 which initiates the termination of the drying
operation.
An alternative form of sensing circuit is shown in FIG. 5 in which
a half-wave rectifier 162 is connected on one side to power line
160. The other side of the rectifier 162 is connected to a
capacitor 161. The opposite side of the capacitor 161 is connected
to a rotor switch 164. Rotor switch 164 has a switch blade 165
rotated by a drive mechanism (not shown). The switch blade 165
successively and alternately engages contacts 166, 167 and 168.
Switch contact 166 is connected to the other side of the power line
161' so that when the switch blade engages contact 166, capacitor
161 is charged through the rectifier 162. The switch blade, as it
continues to rotate, opens the circuit to the power line 161' and
contacts the contact 167 which connects the capacitor 161 across
electrodes 169, 170, located within the drum of the clothes drier,
in order to contact the tumbling clothes. If the clothes are wet
the capacitor will be discharged through the electrodes 169, 170,
when switch blade 165 engages contact 167. Delay time of switch
blade 165 on contact 167 may be varied to obtain the desired
dampness of the clothing. On the other hand, if the clothes are
dry, the capacitor will retain its charge.
The switch blade 165 next touches contact 168 which places the
capacitor 161 across the circuit which has in series a gaseous tube
172 and relay 173. If the charge on the capacitor 161 is nil, or
only of small value, because it has been discharged through the
clothes, the gaseous tube is undisturbed. However, if the capacitor
161 has built up a certain charge, as determined by the value of
the gaseous tube 172, the tube 172 will fire and energize relay
173. When the relay 173 is energized, contacts 174, 175 are closed.
Contact 174 completes a holding circuit to maintain the relay
energized, while contact 175 energizes the timing motor 176 to
initiate termination of the drying operation.
The sensing circuit of FIG. 5 is the subject matter of U.S. Pat.
No. 3,221,417, issued Dec. 7, 1965 assigned to the same
assignee.
Yet another form of the sensing circuit is shown in FIG. 6 of the
drawing. In the sensing circuit of FIG. 6, a motor 180 is connected
to power lines 178 and 179. Motor shaft 184 of motor 180 drives a
shaft 181 through a slip clutch 182. The slip clutch has a movable
clutch face 185 splined on motor shaft 184 for longitudinal
movements along its axis. An opposite clutch face 186 is
non-rotatably secured to the shaft 181.
A variable resistance 187 has a movable arm 188 driven by shaft
181. The variable resistance is connected at one end to line 191.
The movable arm 188 is connected to power line 178 through line
190, so that the resistance in line 191 is changed from a high
value to nil as the arm is rotated clockwise.
When the shaft 181 is rotated it moves against the bias of spring
195, which may be accomplished by winding a cable secured to wheel
194 and spring 195. When the shaft 181 is released, it is rotated
counter-clockwise and returned to starting position by the spring
195.
A three element gaseous tube 199 is connected in series with a
solenoid 200 between the power lines 178, 179. The gaseous tube
normally is not conducting, however, when its grid 198 receives a
positive potential it becomes conducting. A pair of electrodes 196
and 197 are connected between the grid 198 and the cathode 201 of
the three element gaseous tube. A grid resistor 202 is in series
with the grid and electrode 196. As long as the clothes are wet and
electrically conducting, a current flows between the electrodes
196, 197 to apply a positive potential to the grid 198 which
permits the gaseous tube 199 to conduct current between the power
lines 178, 179 to energize the solenoid 200. However, when the
clothes are dry and non-conducting, the grid receives a negative
potential which does not permit the tube to fire, so that the
solenoid 200 remains de-energized.
The lever 207 is normally urged clockwise about pivot pin 209 by a
spring 208, so that the friction face 185 splined on the motor
shaft 184 contacts friction face 186 on shaft 181. However, when
the armature 205 is moved by the solenoid 200 through energization
of the solenoid 200, the friction face 185 is disengaged from
friction face 186 by movement of the lever 207 in a
counter-clockwise direction.
A relay 210 is mounted in the line 191 having contacts 211, 212.
Contact 211 completes a holding circuit, and contact 212 connects
timer 213 to the power line.
Operation of the sensing circuit shown in FIG. 6 is as follows. The
relay 210 remains de-energized since it has in series therewith
resistance 187. Motor 180 is constantly rotating and when the
clutch 182 is engaged, the arm 188 is turned to decrease the
resistance in series with the relay 210 to nil. However, as long as
the clothes are wet, the gaseous tube 199 will fire to energize
solenoid 200 and disengage the clutch 182 through operation of the
solenoid armature 205. Lever 207 then moves against the bias of
spring 208 to disengage clutch 182 and spring 195. If isolated
clothes come into contact with the electrodes before the arm 188 of
resistance 187 has swung completely around to short out the
resistance 187, the clutch is disengaged to permit the spring 195
to move the resistance arm to full value. It is evident that the
resistance 187 can also be eliminated and the time of movement of
the arm 188 from a "0" position to a contact with line 191 used to
provide the time delay. When the clothes become completely dry, the
clutch is engaged fro a period of time sufficient for the arm 188
to swing in to contact line 191, thereby effectively eliminating
the resistance 187. The relay 210 is then energized to close
contacts 211, 212. Contact 211 maintains the relay energized, while
contact 212 energizes a timing motor 213 which initiates the
termination of the drying operation.
In the drawings and specification there has been set forth a
preferred embodiment of the invention, and although specific terms
are employed, these are used in a generic and descriptive sense
only, and not for purposes of limitation. Changes in form and the
proportion of parts, as well as the substitution of equivalents are
contemplated, as circumstances may suggest or render expedient,
without departing from the spirit or scope of this invention as
further defined in the following claims.
* * * * *