Abstrict
An electric heater circuit for an electric heater includes a set
of heater coils for generating heat, a normally closed temperature
sensitive switch for deactivating the heater coils when the temperature
inside the electric heater exceeds a predetermined threshold temperature,
a normally closed tilt sensitive switch for deactivating the heater
coils in response to tilting movement of the electric heater beyond
a predetermined amount relative to a normal upright position, a
light and buzzer combination for providing signals when either the
temperature sensitive switch is opened as a result of the temperature
inside the electric heater exceeding the predetermined threshold
temperature or the tilt sensitive switch is opened as a result of
tilting movement of the heater beyond the predetermined amount relative
to the normal upright position, fan and an adjustable thermostat.
Claims
What is claimed is:
1. An electric heater circuit for an electric heater comprising:
a. heater coil means for generating heat,
b. a temperature sensitive switch for reducing the amount of current
flowing through the heater coil means when the temperature inside
the electric heater exceeds a predetermined threshold temperature,
the temperature sensitive switch being normally closed,
c. a tilt sensitive switch for reducing the amount of current flowing
through the heater coil means in response to tilting movement of
the electric heater beyond a predetermined amount relative to a
normal upright position, the tilt sensitive switch being normally
closed, and
d. signal means coupled in parallel with said temperature sensitive
switch and said tilt sensitive switch for providing a signal directly
in response to either the temperature sensitive switch being opened
as a result of the temperature inside the electric heater exceeding
the predetermined threshold temperature or the tilt sensitive switch
being opened as a result of tilting movement of the heater beyond
the predetermined amount relative to the normal upright position.
2. The electric heater circuit of claim 1 and further including
an adjustable thermostat.
3. The electric heater circuit of claim 2 and further including
a motor operated fan.
4. The electric heater circuit of claim 3 and wherein the circuit
includes a capacitor.
5. The electric heater circuit of claim 4 and wherein the signal
means includes a lamp and a buzzer.
6. The electric heater circuit of claim 5 and wherein the adjustable
thermostat and tilt sensitive switch are a single unit.
7. An electric heater circuit for an electric heater comprising:
a. heater coil means for generating heat,
b. a temperature sensitive switch for deactivating the heater means
when the temperature inside the electric heater exceeds a predetermined
threshold temperature, the temperature sensitive switch being normally
closed,
c. a tilt sensitive switch for deactivating the heater means in
response to tilting movement of the electric heater beyond a predetermined
amount relative to a normal upright position, the tilt sensitive
switch being normally closed, and
d. signal means coupled in parallel with said temperature sensitive
switch and said tilt sensitive switch for providing a signal directly
in response to either the temperature sensitive switch being opened
as a result of the temperature inside the electric heater exceeding
the predetermined threshold temperature or the tilt sensitive switch
being opened as a result of tilting movement of the heater beyond
the predetermined amount relative to the normal upright position.
8. An electric heater circuit for an electric heater comprising:
a. input means for connecting the electric heater circuit to a
source of power,
b. a temperature sensitive switch coupled between the input means
and the heater means responsive to temperature inside the electric
heater, the temperature sensitive switch being normally closed,
the amount of current passing through the heater means depending
in whether the switch is open or closed,
c. a tilt sensitive switch coupled between the input means and
the heater means responsive to tilting movement of the electric
heater, the tilt sensitive switch being normally closed, the amount
of current passing through the heater means depending on whether
the switch is open or closed, and
d. a signal means for providing a signal directly in response to
either the temperature sensitive switch being opened or the tilt
sensitive switch being opened.
9. An electric heater circuit for an electric heater comprising:
a. heater coil means for generating heat,
b. a tilt sensitive switch for controlling the amount of current
flowing through the heater coil means, said tilt sensitive switch
reducing the amount of current flowing through the heater coil means
in response to tilting movement of the electric heater beyond a
predetermined amount relative to a normal upright position, and
c. signal means under the control of said tilt sensitive switch
for providing a signal directly in response to the heater being
tilted beyond said predetermined amount relative to the normal upright
position.
10. The electric heater circuit of claim 9 and further including
an adjustable thermostat for controlling the amount of current flowing
through the heater coil means.
11. The electric heater circuit of claim 9 and further including
a motor operated fan for circulating air around and through the
electric heater.
12. The electric heater circuit of claim 9 and wherein the circuit
includes a capacitor having a very high impedance relative to the
impedance of the signal means.
13. The electric heater circuit of claim 9 and wherein the signal
means includes a lamp and a buzzer.
14. The electric heater circuit of claim 9 and wherein the adjustable
thermostat and tilt sensitive switch are a single unit.
15. The electric heater circuit of claim 9 and wherein the tilt
sensitive switch is a two position switch and is normally closed.
16. The electric heater circuit of claim 15 and wherein the tilt
sensitive switch comprises a pendulum and a pair of contacts.
17. The electric heater circuit of claim 9 and further including
a resettable thermal fuse for reducing the current flowing through
the heater coil means when the temperature exceeds a predetermined
threshold.
18. The electric heater circuit of claim 17 and wherein the signal
means is also under the control of said resettable thermal fuse
switch.
19. The electric heater circuit of claim 18 and wherein the resettable
thermal fuse is a two position switch, one position being open and
the other position being closed.
20. The electric heater circuit of claim 19 and further including
a plug for connecting the electrical heater circuit to an external
power source and a multi-position input switch means for connecting
the plug to said heater coil means, the motor operated fan and the
signal means.
21. The heater circuit of claim 9 and wherein said signal means
is in a circuit in parallel with said tilt sensitive switch.
22. The heater circuit of claim 9 and wherein the heater circuit
is an analog circuit.
Description BACKGROUND OF THE INVENTION
The present invention relates generally to an electric heater and
more particularly to an electrical circuit for an electric heater
which includes a heater coil, a signal indicator, a first switch
for simultaneously deactivating the heater coil and activating the
signal indicatator when the temperature inside the heater exceeds
a predetermined value and a second switch for simultaneously deactivating
the heater coil and activating the signal indicator means when the
electric heater is tilted beyond a predetermined angle.
As used herein, the term "deactivating the heater coil"
means reducing the current flow through the heater coil means so
that the heat generated is negligible, at most. Also, the term "activating
the signal indicator means" increasing the current flow through
the signal indicator so that it is energized and outputting a detectable
signal.
The need exists for a heater circuit for an electric heater which
includes an arrangement for essentially turning off the heater in
the event the heater is either overheated or tipped over and at
the same time activating an alarm to indicate one (or both) of these
faults has occurred.
The present invention accomplishes this in a unique manner with
a minimum number of parts.
SUMMARY OF THE INVENTION
An electric heater circuit for an electric heater constructed according
to the teachings of the present invention includes heater means
for generating heat, a temperature sensitive switch for deactivating
the heater means when the temperature inside the electric heater
exceeds a predetermined threshold temperature, the temperature sensitive
switch being normally closed, a tilt sensitive switch for deactivating
the heater means in response to tilting movement of the electric
heater beyond a predetermined amount relative to a normal upright
position, the tilt sensitive switch being normally closed, and signal
means for providing a signal when either the temperature sensitive
switch is opened as a result of the temperature inside the electric
heater exceeding the predetermined threshold temperature or the
tilt sensitive switch is opened as a result of tilting movement
of the heater beyond the predetermined amount relative to the normal
upright position.
Various features and objects advantages will appear from the description
to follow. In the description, reference is made to the accompanying
drawing which forms a part thereof, and in which is shown by way
of illustration, a specific embodiment for practicing the invention.
This embodiment will be described in sufficient detail to enable
those skilled in the art to practice the invention, and it is to
be understood that other embodiments may be utilized and that structural
changes may be made without departing from the scope of the invention.
The following detailed description is, therefore, not to be taken
in a limiting sense, and the scope of the present invention is best
defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings wherein like reference numerals represent like
parts:
FIG. 1 is a schematic of an electric heater circuit for an electric
heater constructed according to the teachings of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, there is shown in FIG. 1 a schematic
of an electric heater circuit for an electric heater constructed
according to the teachings of the present invention, the electric
heater circuit being identified by reference numeral 11.
Heater circuit 11 includes an input plug 12 which may be connected
to an external power source (not shown). Plug 12 has a pair of poles
12-1 and 12-2.
Heater circuit 11 includes a heater section 13 having first, second
and third heater coils labelled 15, 17 and 19, respectively. Heater
circuit 11 also includes a motor operated electric fan 21 that circulates
air around and through electric heater 11 to increase its effectiveness.
Fan 21 can operate at either a high speed or a low speed.
Heater coils 15, 17 and 19 and electric fan 21 are controlled by
a selector switch 23. Selector switch 23 is five position rotary
type switch that includes five terminals labelled 25, 27, 29, 31
and 33. Terminal 33 is connected to a first pole 12-1 of plug 12.
When the rotary element (not shown) is in position 1, terminal 33
is not electrically connected to any of terminals 25, 27, 29 and
31 and the electric heater is in an "off" mode (i.e. neither
heater section 13 nor fan 21 are "on"). When the rotary
element is in position 2, terminal 33 is connected to terminal 25.
In this position, heater section 13 is in an "off" mode
and electric fan 21 is in a high power mode. When the rotary element
is in position 3, terminal 33 is connected to terminal 27, in which
case heater section 13 is in an "off" mode and electric
fan 21 is in a low power mode. When the rotary element is in position
4, terminal 33 is connected to terminals 27, 29 and 31 in which
case, electric fan 21 is in a low power mode and the heater section
13 is in a high heat mode. When the rotary element is in position
5, terminal 33 is connected to terminals 27 and 29, electric fan
21 is in a low power mode and heater section is in a low heat mode.
Heater circuit 11 further includes a tip thermostat 35, a permanent
thermal fuse 37, a resettable thermal fuse 39, a signaling circuit
41, a power lamp 43, a capacitor 45 and a signaling circuit test
switch 47.
Tip thermostat 35 is a combination tip sensor 35-1 and adjustable
thermostat 35-2. The adjustable thermostat 35-3 is used to manually
set the temperature above which heater section 13 is activated (i.e.
turned on). The tip sensor 35-1 is used to detect tilting movement
of the electric heater (not shown) in which the heater circuit 11
is mounted beyond a predetermined angle and cause heating circuit
13 and fan 21 to be deactivated (i.e. turned off) when such tilting
movement is detected. The adjustable thermostat 35-2 of tip thermostat
35 includes a pair of contacts 49 and 51 and a control 53. Contact
49 is mounted on a movable arm 55 while contact 51 is mounted on
a fixed arm 57. Contacts 49 and 51 are normally closed. The tip
sensor 35-1 of tip thermostat 35 includes a pair of contacts 59
and 61 and a pendulum 63. Contact 59 is mounted on a movable arm
65 while contact 61 is mounted on a fixed arm 67. Contacts 59 and
61 are normally closed.
Tip thermostats are well known in the art and are made in various
constructions. See for example U.S. Pat. No. 3,201,548 and U.S.
Pat. No. 3,936,786.
Permanent thermal fuse 37 is a two terminal device, the terminals
being labelled 69 and 71. Permanent thermal fuse 37 is normally
closed. Permanent thermal fuse 37 is used to permanently deactivate
heater section 13 and fan 21 when the temperature inside the electric
heater exceeds a predetermined temperature.
Resettable thermal fuse 39 temporarily disables heater section
13 and fan 21 when as long as the temperature inside the electric
heater is in excess of a predetermined (set) temperature and includes
a pair of contacts 73 and 75, contact 73 being mounted on a movable
arm 77. Contacts 73 and 75 are normally closed. Resetable thermal
fuse 39 and permanent thermal fuse 37 are connected in series between
pole 12-2 of plug 12 and fixed arm 67 in tip thermostat 35.
The temperature at which fuse 37 permanently deactivates heater
13 and fan 21 is higher than the temperature at which fuse 39 temporarily
deactivates these elements.
Signaling circuit 41 includes an alarm lamp 79 and a buzzer 81
which are connected in parallel. Signaling circuit 41 is used to
indicate that the electric heater has been tilted beyond the predetermined
angle (i.e. contacts 59 and 61 in tip switch 35-2 are opened) or
that the temperature inside the electric heater is in excess of
a predetermined temperature (i.e. contacts 73 and 75 are open) or
both. Signaling circuit is activated as will hereinafter be explained.
Power lamp 43 is used to indicate there is power in electric circuit
11 i.e. the electric circuit is "on".
Test switch 47 is used to determine if signaling circuit 41 is
operable and includes a pair of contacts 83 and 85 mounted on fixed
arms 87 and 89 and a contact 91 mounted on a movable arm 93 to which
is attached a button 95. Contact 91 is normally in contact with
contact 85.
Capacitor 45 is sized so as to have an impedance that is much higher
than that of the heater coils 15, 17 and 19. Also, power lamp 43
is sized so as to have a very high impedance relative to the impedance
of signaling circuit 41.
Heater circuit 11 operates in the following manner.
Assume, for illustrative purposes, selector switch 23 is in the
high heat position (i.e. the rotary element is in position 4).
If the temperature in the room where the electric heater is situated
is lower than the temperature setting on adjustable thermostat 35-2
and there are no faults (i.e. the temperature inside the heater
is not excessive; that is, not higher than the setting on fuse 39
and the heater is not tipped over), then adjustable thermostat 35-2,
tip sensor 35-1, permanent thermal fuse 37 and resettable thermal
fuse 39 will all be closed. Current will flow through power lamp
43, adjustable thermostat 35-2, tip sensor 35-1, permanent thermal
fuse 37, resetable thermal fuse 39, fan 21 and coils 15, 17 and
19 capacitor 45 and signaling circuit 41. The current passing through
coils 15, 17 and 19 will be sufficient to heat up coils 15, 17 and
19 and give off heat and the current passing through power lamp
43 and fan 21 will be sufficient to activate the components. On
the other hand, the current passing through signaling circuit 41
will not be sufficient to cause lamp 79 to light up or buzzer 81
to sound. The current passing through capacitor 45 will be negligible.
If the temperature in the room exceeds the setting on adjustable
thermostat 35-2, both occurrences, then adjustable thermostat 35-2
will open. If there are still no faults (i.e. excessive internal
temperature or tilting over) then tip switch 35-1 and the two fuses
37 and 39 will still be closed. In this case, current will still
flow through power lamp 43, capacitor 45 and coils 15, 17 and 19,
fan 21 and signaling circuit 41. However, since the impedance of
capacitor 45 is much larger than the impedance of heater coils 15,
17 and 19, and fan 21 the amount of current flowing through coils
15, 17 and 19 and fan 21 will be negligible, at most and there will
essentially be no heat generated and the fan will not be "on".
The amount of current flowing through lamp 79 and buzzer 81 will
still be negligible (i.e. not enough to turn either one of these
elements on) and the amount of current flowing through lamp 43 will
not be sufficient to turn it on.
If the temperature in the room stays below the temperature setting
on adjustable thermostat 35-2 and the unit is tipped beyond the
predetermined angle set on tip sensor 35-1, then pendulum 63 will
swing over and cause contacts 59 and 61 to open. Current will flow
through signaling circuit 41, power lamp 43, fan 21 and heater coils
15, 17 and 19. Since adjustable thermostat 35-2 is closed, only
a negligible current will flow through capacitor 45. Since power
lamp 43 has a very high impedance relative to signalling circuit
41, most all of the current will flow through signalling circuit
41 rather than power lamp 43. Thus, lamp 43 will not be lit. Also,
because the impedance of buzzer 81 is much higher than the resistance
of the heater coils only negligible current will go through coils
15, 17 and 19. As a result, lamp 79 will light and buzzer 81 will
sound. If the temperature inside heater 11 exceeds the temperature
sitting on fuse 39, then the same results will occur except that
resettable thermal fuse 39 will open rather than tip switch 35-1.
If a fault (excessive internal temperature or excessive tilt) occurs
while adjustable thermostat 35-2 is open then sufficient current
will flow through capacitor 45 to activate lamp 79 and buzzer 81
but not to generate more than negligible heat from coils 15, 17
and 19 and fan 21 will not "on".
If selector switch 23 is moved to a low heat position the same
results will occur for each case noted above except that no current
will flow through coil 15.
If selector switch 23 is in either one of the "fan-only"
positions, no current will flow through any of the heater coils.
Any resulting faults will "turn off" fan 21.
As can be appreciated, tip sensor 35-1 simultaneously deactivates
heater circuit 13 and fan 21 and activates lamp 79 and buzzer 81
when it is opened and fuse 39 simultaneously deactivates heater
circuit 13 and fan 21 and activates lamp 79 and buzzer 81 when it
is opened.
By way of example only, the following are values of certain components
in heater circuit 11.
Heater circuit 13 . . . 9.6 ohms (Impedance)
Capacitor 45 . . . 0.5 uf (250 VAC)
Buzzer 81 . . . 2.8 Kohms (Impendance)
Alarm Lamp 79 . . . 105 Kohms (Impendance)
Power Lamp 43 . . . 105 Kohms (Impedance)
The embodiment of the present invention is intended to be merely
exemplary and those skilled in the art shall be able to make numerous
variations and modifications to it without departing from the spirit
of the present invention. All such variations and modifications
are intended to be within the scope of the present invention as
defined in the appended claims.
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