United States Patent [19]
[11] Patent Number:
Koehler
[45]
[54]
ELECTRONIC CYCLE TIMER FOR A
HOUSEHOLD APPLIANCE
[75] Inventor: Gerald C. Koehler, Peru, Ill.
[73] Assignee: Worldtronics International, Inc.,
Oglesby, Ill.
[21] App]. No.: 641,789
Aug. 16, 1984
[22] Filed:
[51] Int. Cl.‘ .............................................. .. A23F 0/00
[52] U.S. Cl. ........................................ .. 368/9; 99/281;
99/283; 219/441; 219/492
[53]
Field of Search ............... .. 99/280, 281, 337, 338;
219/492, 441; 368/9, 10
[56]
References Cited
U.S. PATENT DOCUMENTS
4,330,702
4,406,217
5/1982 Cheng ................................. .. 99/281
9/1983 .Oota .................................... .. 99/280
4,468,406 8/1984 d’Alayer O’Costemore
d’Arc .................................. .. 99/280
FOREIGN PATENT DOCUMENTS
2101471
1/1983
United Kingdom ................ .. 99/280
Primary Examiner—Bernard Roskoski
Attorney, Agent, or Firm—Leydig, Voit & Mayer, Ltd.
[57]
ABSTRACT
An electrical timer for a household appliance typically
Date of Patent:
Jan. 28, 1986 '
has an integrated circuit including‘ an internal presetta
ble clock registering the time of day, an internal register
storing a presettable activation time, and a gate generat
ing an activation signal when an activation enable signal
is present and the clock registers the activation time. To
prevent an activation signal from being generated on a
daily basis without manual intervention, a bistable cir
cuit is provided to generate the activation enable signal
in response to a cycle enable signal received from the
appliance operator. The bistable circuit is set to activate
the activation enable signal upon receipt of the cycle
enable signal, and is reset by the activation enable signal
to disable the activation enable signal. For a coffee
maker, the bistable circuit is preferably reset by the
activation signal at the active-to-inactive transition sig
nalling the end of brewing. To reject electrical noise
pulses, the bistable circuit preferably has a response
time of at least approximately ?ve milliseconds. Prefera
bly the cycle enable signal is generated by a three posi
tion switch having “on” and “off’ positions which acti
vate and deactivate the activation signal regardless of
the time of day, and a middle “automatic” position. In
this case the bistable circuit is set when the switch is
moved from the automatic position to the off position.
Alternatively a separate push-button switch generates
the cycle enable signal.
" V
20 Claims, 1 Drawing Figure
“18:05
DISPLAV
23.
20
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4,566,802
VSS
ALARM
COLON
CLOCK 10
V00
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ON
HOUR MINv §1ET O'F
BREWING
DEVICE
SETTING\\
i 1
swncnss,
,7 /7 I 1701/7 1
‘ ‘s7
,eBREW
TIME
V
17
AUTO
C
F] MANUAL
0"
j \,5
CYCLE
ENABLE A
46
44
ENABLE
42
50
4/
CYCLE /
ENABLING
CIRCUIT, 4U
45
49
1
4,566,802
2
DESCRIPTION OF THE PREFERRED
ELECTRONIC CYCLE TIMER FOR A
HOUSEHOLD APPLIANCE
EMBODIMENT
Turning now to the drawings, there is shown in FIG.
1 a coffee maker generally designated 10 including an
BACKGROUND OF THE INVENTION
electronic cycle timer generally designated 11 accord
ing to the present invention. For the brewing of coffee,
The present invention relates generally to electronic
timers, and speci?cally to an electronic timer which
activates a household appliance at a preset time of day.
a cover 12 in the top portion 13 of the coffee maker 10
is opened to gain access to a water reservoir (not
For automatic activation of household appliances
such as coffee makers, electronic cycle timers have been
shown). After ?lling the reservoir with a certain
amount of water, the cover 12 is replaced. Ground
coffee and a coffee ?lter (not shown) are placed in a
tray 14 which is inserted below the top portion 13. An
used which generate an activation signal at a preset time
each day. Such an electronic timer basically consists of
an integrated circuit which is manufactured in high
internal heater or brewing device (not shown) is then
activated to heat the water in the reservoir and to drip
the hot water through the coffee in the tray 14. By the
force of gravity, the brewed coffee drips from a center
hole (not shown) in the tray 14, and is received in a flask
15.
In. contrast to the old fashioned percolator-type cof
fee maker, the drip-type coffee maker 10 does not boil
the brewed coffee. Consequently, the brewed coffee
volume and is used in digital alarm clocks. The inte
grated circuit includes an internal presettable clock
registering the time of day, an internal register storing a
presettable activation time, and a gate generating an
activation signal when an activation enable signal is
present and the clock registers the activation time. A
timer for a coffee maker also typically includes a three
position switch having an “off” position, an “auto
matic” position, and an “on” position which enables the
retains many of the subtle ?avors which are otherwise
coffee maker regardless of the time of day.
lost or destroyed by excessive heat which is applied in a
Underwriters Laboratories has expressed concern 25 perculator. The drip-type coffee maker 10 has recently
enjoyed considerable commercial success as a house
with the operation of coffee makers in the automatic
hold appliance as a result of consumers becoming aware
mode. About seventy ?res per year have been attributed
of these advantages.
to unattended coffee makers. Presumably a ?re is very
The drip-type coffee maker 10, however, has the
unlikely for one cycle after the coffee maker has its
water reservoir ?lled. Repeated operation with an 30 disadvantage that the brewing process is slower than
that required for an old fashioned percolator. During
empty water reservoir, however, increases the likeli
the morning rush, household consumers usually do not
hood of having a ?re. Therefore, Underwriters Labora
have time to wait while the coffee is brewing in the
tories is considering a requirement that an automatic
timer must not repeatedly activate a coffee maker when
the coffee maker is unattended.
drip-type coffee maker. So that a consumer may arise
35 each morning to ?nd a fresh, hot supply of brewed
SUMMARY OF THE INVENTION
The primary object of the invention is to provide an
economical cycle timer accepting a manual cycle enable
signal for the control of a household appliance.
Another object of the invention is to provide a cycle
timer accepting a manual cycle enable signal and which
uses a conventional alarm clock integrated circuit.
coffee awaiting, the electronic timer 11 is set to start the
brewing process before the consumer arises. Of course,
the consumer has the responsibility of previously load
ing the coffee maker 10 with water and ground coffee
before retiring in the evening.
To enable the consumer to set the timer 11, the timer
has a digital display for indicating the time of day and
the activation time, and push buttons 17 for setting the
correct time of day and the desired activation time. The
Still another object of the invention is to provide an 45
timer also has an indicator light 19 for signaling that the
' economical cycle timer which obtains a cycle enable
coffee maker 10 is activated for brewing, and a slide
signal from a three position switch including an “off”,
“automatic”, and “on ” position.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention
will become apparent upon reading the following de
tailed description and upon reference to the drawings in
switch with “of ’, “automatic”, and “on” positions.
It is thought to be unsafe to operate the coffee maker
10 without ?rst ?lling the unit with at least a certain
amount of water. The water ensures thatthe tempera
ture of the heating element or brewing device (not
shown) in the coffee maker 10 will not exceed the boil
ing point of water. If temperatures in the coffee maker
10 exceed the boiling point of water, there is a very
which:
FIG. 1 is a perspective view of a coffee maker includ 55 small but ?nite chance that a ?re may occur.
ing the electronic timer of the present invention; and
FIG. 2 is a schematic circuit diagram of a preferred
embodiment of the invention.
While the invention is susceptable to various modi?
cations and alternative forms, a speci?c embodiment 60
thereof has been shown by way of example in the draw
ings and will herein be described in detail. It should be
understood, however, that the intention is not to limit
the invention to the particular form disclosed, but, on
According to a basic aspect of the present invention,
the electronic timer 11 ensures that an'unattended cof
fee maker 10 is not repeatedly activated. After ?lling
the coffee maker with water and ground coffee, the user
must supply a cycle enable signal, for example, by tog
gling the slide switch 18. Otherwise, the timer 11 will
not activate the coffee maker for brewing.
Turning now to FIG. 2, there is shown a schematic
circuit diagram of the electronic timer 11. The basic
the contrary, the intention is to cover all modi?cations, 65 timing functions are performed by a standard alarm
equivalents, and alternatives falling within the spirit and
clock integrated circuit 20 which drives the display 16.
scope of the invention as de?ned by the appended
Preferably the alarm clock integrated circuit is a type
claims.
TMS 3450 manufactured by Texas Instruments, Inc.
3
4,566,802
4
the relay 32 does not result in any signi?cant ?uctuation ,
and the display is a four digit seven segment duplex
LED common‘cathode display such as part number
SL-l008023T.‘ The colon of the display 16 is separately
in the voltage supplied to the alarm clock integrated
circuit.
As described above, the alarm clock integrated cir- ‘
driven by the alarm clock integrated circuit 20 through
cuit 20 activates the brewing device 31 when the switch
18 is in the automatic position and whenever the time
a 150 ohm resistor 21‘.
The alarm clock integrated circuit 20 requires a 12
volt power supply to its V35 and —VDD inputs. The
power is provided by a transformer 22 excited by house
registered by the internal clock of the integrated circuit
20 coincides ‘with the activation time stored in the inte-, ‘
hold current from an, electricalicord 23. The trans
former 22 is center tapped to provide oppositely phased .
multiplexing signals to the display 16 through respec
tive 10 ohm resistors‘24 and 25, and a clocking signal to
the integrated circuit 20 through a 510 K ohm resistor
26. The alternating voltage from‘the secondary of the
transformer 22. is recti?ed by directional diodes 27,‘ 28,
29 (part no. 1N400l) and ?ltered by a 1000 microfarad,
16 VDC capacitor 30 to provide 12 volts to the V35 and
VDD inputs to the integrated circuit 20. The integrated
circuit 20 has separate hour, minute and set inputs
which are selectively connected to +V$5 through the
time setting switches 17.
grated circuit. In accordance with an important aspect.
of the present invention, to prevent an activation signal
from being generated on a daily basis withoutmanual
intervention, a cycle enabling circuit generally desig- ‘
nated 40 generates the activation enable signal BREW
ENABLEin response to a cycle enable signal received
from the user. The cycle enabling circuit 32 includes a
bistable circuit determining the logic state of the activa- ‘
tion enable signal BREW ENABLE. The bistable cir- ‘
cuit is set upon the occurrence of the cycle enable signal .
being received from the user, to activate the activation
enable signal BREW ENABLE. The bistable circuit is
reset when the integrated circuit 20 generates an active
activation signal ‘BREW. In othenwords, each time that
The alarm clock integrated circuit 20 has an internal
clock registering the time of day which is set so that the
display 16 indicates the current hour and minute. by
the brewing device 21 is activated, the user must there- t
after intervene by generating a cycle enable signal, to
depressing the respective hour and minute time setting 25 permit the integrated circuit 20. to reactivate the brew
ing device 31lat a later time.
As shown in FIG. 2, the bistable, circuit comprises a
switches‘17a, ‘17b. The integrated circuit 20 also has an
internal register storing an activation time presettable to
a desired time by continually closing the set switch 17c
~.and then selectively closing the hour and minute
switches 17a; 17b. Moreover, the integrated circuit 20
pair of complementary bipolar transistors including an
NPN transistor 41, part number 2SC945, and a PNP
transistor 42, part number 2SA733, which are intercon
nected in a regenerative fashion. In a ?rst state, both
transistors 41 and 42 are conductive or active, and in a
- has a gate generating an activation or BREW signal
;., upon the coincidence of the time of day registered by
the internal clock, the preset‘activation time, and an
second state both transistors are non-conductive or ‘
activation enable signal which is received on an OFF, ‘
input. The activation signal for the particular alarm
since toggling of the switch 18 from the automatic posi
tion to the off position breaks the connection from
+V5$ to the emitter of PNP transistor 42,.thereby ren
clock integrated circuit 20, is active low and is thus,
,, designated BREW ENABLE. The three position
11,SWltCh 18, when set to the OFF position, applies +V5$
dering the transistor 42 non-conductive. Hence, tog-1
’ to the OFF input of the integrated circuit 20 so thatthe
,IBREW‘ ENABLE signal becomes inactive, thereby
dissabling the BREW ‘signal. The ON position of the
inactiven The three position switch ‘18 ‘functions as, a
means for receiving from the user a cycle enable signal
40
gling of the switch .18 will set the transistors 41 and 42 l
to their inactive or non-conductive states. Alterna- .
tively, a separate switch could be provided to receive 1
from the user a cycle enable signal independent of the
switch 18 applies +VSS to the ON output of the alarm
clock integrated ‘circuit 20 to thereby override and
activate the BREW signal regardless of whether the
gate in the alarm clock integrated circuit 20 activates 45
for example, could connect the, emitter of the PNP
the BREW signal.
The BREW. signal is used to activate the heating
push-button switch sets the transistors 41; and 42 to their
slide switch 18.‘A normally closed push-button switch,
transistor 42 to +V5S so that manual activation of the, .
current from the line cord 23, a relay 32 is provided to
turn the brewing device 310m and off in response to the
non-conductive states.
It should be noted that the transistors 41 and 42. are
interconnected via resistors 43, 44 and 45. ‘The collector ‘
of the NPN transistor 41 is connected to the base of the. .
‘ BREW signal. An ‘NPN bipolar transistor 33 is used to
PNP transistor 42 through the resistors 43 and 44,‘
excite the coil of the relay 32 in response to the rela
tively low level ,BREW‘signal. The relay driver transis
which are each 20 K; ohms. The collector of the PNP ‘
transistor 42 is connected to the base of the NPN tran- ‘
tor 33 is preferably a type 1402C transistor and has a 6.8
K1 ohm series resistor 34 and a 4.7 K ohm shunt resistor
35 connected to its base. The coil of the relay 32 has a
sistor 41 through the resistor 45 which is 4.7 K ohms.
The NPN transistor 14 also has a 20 K ohm load. resistor
46 connecting its collector to +VSS and a 4.7 K ohm
damper diode 36 part number 1N4l48. The indicator 19
is a light emitting diode (LED) exciting through a 1.5 K
43-47 in cooperation with the transistors 41‘, ‘42 ensure
ohrn current limiting resistor 37. The LED 19 and resis
tor 37 are connected across the coil of the relay 32 to
that the transistors“ and 42 are either both in their ‘
conductive or active states or‘are both in their non-con
element or brewing device 31 in the coffee maker‘ 10.
Since the brewing device 31 is operated by household
resistor 47 connecting its base to - VDD. These resistors
signal activation of the brewing device 31. The relay 32
ductive or inactive states. Asnoted above, this bistable a
is a 9 volt relay and is powered through a separate
recti?er circuit,including a directional diode 38, part
circuit is set to its second or inactive state when the user ‘
number 1N400l, and a 470‘ microfarad electrolitic ca
to its ?rst or active state by the BREW signal, an elec
toggles the switch 18.‘ So that the bistable circuit isreset
pacitor 39.‘ Since separate respective diodes and ?lter
trolytic capacitor 48 typically 1 microfarad. connects
capacitors are used to provide power to the alarm clock
the base of the NPN transistor 41 to the collector of the .
relay driver, transistor 33.: In particular, the ‘bistable ,
integrated circuit 20 and the relay 32, the operation of
5
4,566,802
circuit is set to its ?rst or conductive state at the very
6
circuit is set upon the occurrence of the cycle
enable signal being received from the user to
generate an active activation enable signal, and
end- of brewing when the BREW signal changes from
an active to an inactive state. In other words, when the
BREW signal goes low thereby turning off the relay
driver transistor 33, the collector of the relay driver
transistor 33 goes high so that a pulse is coupled
said bistable circuit is automatically reset by said
activation signal to generate an inactive activa
through the capacitor 48 to turn on the NPN transistor
41 which in turn activates the PNP transistor 42.
hold appliance from being reactivated unless a
cycle enable signal is thereafter received from
tion enable signal thereby preventing said house
It is a noteworthy safety feature that the bistable
the user.
.
circuit is reset by the BREW signal at the very end of 10
2. The electronic timer as claimed in claim 1, wherein
brewing. The toggling of the switch 18 by the user is
said cycle enabling means further includes means for
intended to indicate that water has been added to the
resetting said bistable circuit upon the occurrence of the
coffee maker in anticipation of another brewing cycle.
active-to-inactive transition of said activation signal.
This, of course, is done after any previous brewing
3. The electronic timer as claimed in claim 1, wherein
cycle. Hence, the cycle enabling circuit 40 preferably
said bistable circuit includes means for establishing a
cancels any cycle enable signal received from the user ' predetermined reponse time of at least approximately
during the brewing cycle. Thus, safety is enhanced by
?ve milliseconds so that said bistable circuit is not set or
resetting the bistable circuit at the end of a brewing
reset by said respective cycle enable signal and activa
cycle and not before.
tion signal unless said signals are present for a time
The cycle enabling circuit 4,0 also has a few other 20 duration of at least said predetermined response time
features which ensure reliable operation. A diode 48 is
thereby rejecting noise.
used to connect the collector of the transistor 42 to the
4. The electronic timer as claimed in claim 1, wherein
OFF input of the integrated circuit 20 in order to ensure
said means for receiving from the user a cycle enable
that the OFF input of alarm clock integrated circuit can
signal comprises a multi-position switch having a ?rst
never reset the bistable circuit. Of greater importance is 25 position wherein said activation signal is disabled re
a capacitor 50, typically 0.5 microfarads, which limits
gardless of said means for generating an activation sig
the response time of the bistable circuit to no greater
nal, a second position wherein said activation signal is
.. than 5 milliseconds. The capacitor 50 functions as a
responsive to said cycle enabling means, and a third
position wherein said activation signal is active regard
memory element to hold the state of the bistable circuit
in the event of electrical noise pulses which are re
less of said means for generating an activation signal,
ceived, for example, from the line cord 23.
In view of the above, an economical cycle timer for a
household appliance has been disclosed which accepts a
manual cycle enable signal and which uses a conven
wherein said cycle enable signal is active to set said
bistable circuit when said multi_-position switch is in a
position other than said second position, and cannot set
said bistable circuit when said multi-position switch is in
tional alarm clock integrated circuit. A cycle enabling
said second position.
circuit ensures that the appliance is not repetitively
5. The electronic timer as claimed in claim 1, wherein
activated when the appliance is unattended. The cycle
said integrated circuit is a conventional alarm clock
enabling circuit includes only a hand full of low cost
integrated circuit and said cycle enabling means is an
parts and receives a cycle enable signal from the usual
electronic circuit external to said integrated circuit.
on-automatic-off switch so that the safety feature only 40 6. The electronic timer as claimed in claim 5, wherein
slightly increases the cost of the electronic timer.
said bistable circuit includes a pair of complementary
What is claimed is:
transistors, the input of each transistor being responsive
1. An electronic timer for activating a household
to the output of the other transistor thereby establishing
appliance for a limited duration upon the occurrence of
a ?rst state wherein the transistors are both active and a
a selected time of day, said timer having an integrated 45 second state wherein the transistor are both inactive,
circuit including
and wherein said bistable circuit further comprises a
(a) an internal clock registering the time of day and
capacitor for maintaining the state of said bistable cir
means for setting the registered time to the correct
cuit to establish a predetermined response time for re
jecting noise.
local time,
(b) an internal register storing a preset activation time 50
preset activation time when an activation enable
7. The electronic timer as claimed in claim 6, wherein
the time constant of said capacitor is at least approxi
mately ?ve milliseconds.
8. The electronic timer as claimed in claim 6, wherein
said transistors are bipolar transistors, the collector of
each transistor is connected to the base of the other
transistor through at least one resistor, and said capaci
signal is present,
tor has a ?rst terminal connected to a terminal of one of
wherein the improvement comprises means for
said resistors.
9. The electronic timer as claimed in claim 8, wherein
and means for setting the activation time to a se
lected time, and
(0) means for generating an activation signal for said
limited duration upon the coincidence of the time
of day registered by the internal clock and the
preventing said household appliance from being
activated on a daily basis in the absence of man 60 said ?rst terminal of said capacitor is connected through
ual intervention including, in combination,
a ?rst one of said resistors to the base of one of said
means for receiving from the user a cycle enable
transistors and through a second one of said resistors to
signal, and
cycle enabling means for generating the activation
enable signal in response to the cycle enable
signal, said cycle enabling means including a
bistable circuit determining the logic state of the
activation enable signal, wherein said bistable
the collector of the other of said transistors.‘
10. The electronic timer as claimed in claim 8,
65 wherein said means for receiving from the user a cycle
enable signal includes a switch connecting the emitter
of a ?rst one of said transistor to a respective power
supply voltage, and said cycle enabling means includes
7
4,566,802
8
16. The electronic timer as claimed in claim 14,‘
wherein the bistable circuit includes an interconnected
a capacitor applying the activation signal to the base of
one of said transistors.
pair of complementary bipolar transistors.
11. The electronic timer as claimed in claim 8,‘
wherein said cycle enabling means includes a diode
17. The electronic timer as claimed in claim 16,‘
wherein toggling of the multi-position switch sets the ‘
feeding the activation enable signal from the collector
bistable circuit by interrupting the flow of current
of one of said transistors to said integrated circuit, and
wherein said electronic timer includes a switch having a
?rst contact connected to said diode and said integrated
through at least one of said transistors.
18. The electronic ‘timer as claimed in claim 16,
wherein the bistable circuit is reset by an electrical pulse
coupled through a capacitor to a base of one of said
transistors.
circuit and a second contact connected to a supply
voltage overriding said cycle enabling means.
12. An electronic timer for activating a brewing de
19. An electronic cycle timer for activating a coffee
vice in a coffee‘ maker for a limited duration upon the
occurrence of ‘a selected time of day, said electronic
maker for a limited duration upon the occurrence of a
selected time of day, said timer having an integrated
circuit including
timer comprising, in combination, an alarm clock inte
grated circuit clocking the time of day, receiving at
enable signal and generating an alarm signal for activat
ing said brewing device for said limited duration when
enabled by said enable signal and the time of day is
(a) an internal clock registering the time of day and
means for setting the registered time to the correct.
local time,
(b) an internal register storing a preset activation time
coincident with a preset alarm time, time setting
switches for setting the time of day and said alarm time
and means for setting the activation time to a se
lected time,
for said integrated circuit, a digital display indicating
the time of day clocked by said integrated circuit, a
(c) means for generating a brew signal to activate said
coffee. maker for said limited duration upon the
multi-position switch having an “off’ position for dis
abling said brewing device, an “automatic” position,
and an “on” position for activating the brewing device
regardless of whether the time of day is coincident with
the alarm time, and a bistable circuit for generating the
enable signal for the integrated circuit and preventing
said brewing device from being activated on a daily
basis in. the absence of manual intervention, said bistable
coincidence of the time of day registered by the
circuit being manually set to generate an active enable
signal when the multi-position switch is toggled from
the. automatic position, and being automatically reset to
disable the enable signal in response to activation of the 35
brewing device thereby preventing said brewing device
from being reactivated unless a cycle enable signal is
thereafter received from the user.
13. The electronic timer as claimed in claim 12,
werein the bistable circuit is reset at the end of brewing.
14. The electronic timer as claimed in claim 12,
wherein the bistable circuit includes a capacitor for
internal clock and the preset activation time when
a brew enable. signal is present,
wherein the improvement comprises‘ means for
preventing said coffee maker from being acti- ‘
vated on a daily basis in the absence of manual
intervention including, in combination, a switch
for receiving from the user a cycle enable signal,
and a bistable circuit for generating the brew
enable signal in response to the cycle enable
signal, said bistable circuit being set to one state
activating the brew enable signal .upon the oc
currence of the cycle enable signal, and being
automatically reset to the other state by said
brew signal to disable the brew‘ enable signal
thereby preventing said coffee maker from being
reactivated unless a cycle enable signal is there-‘
after received from the user.
limiting the response time of the bistable circuit thereby
20. The electronic timer as claimed in‘claim 19,:
wherein said bistable circuit includes. an interconnected
providing noise immunity.
pair of complementary transistors and a capacitor for
15.‘ The electronic timer as claimed in claim 14, 45 limiting the response time of said bistable circuit to
thereby reject electrical noise pulses.
wherein the response time of the bistable circuit is at
*
I3‘
*
ilk
ill‘
least 5 milliseconds.
55
60
65
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