Abstrict
A portable electric heater which can be used with different power
supplies and can also be used as a lamp. The heater includes a compact
housing having a top panel and a bottom panel and at least two removable
heating elements mounted within the housing. The heater may be connected
to different electrical power supplies having different voltages.
A switch is provided to connect one or the other of the two heating
elements to the electrical power supply, depending on the voltage
of the power supply. An adjustable thermostat is provided to turn
off the heating elements to prevent the heater from overheating.
The heating elements may be light bulbs in which case the heater
also includes a sliding door which may be opened in order to use
the heater as a lamp.
Claims
What is claimed is:
1. An electric heater comprising:
a housing;
at least two removable heating elements mounted within the housing;
connecting means adapted to connect the heater to at least two
electrical power supplies having different voltages;
a first switch connected to the two heating elements and to the
connecting means, said switch including means for selectively supplying
electrical power to one of the heating elements at a time, depending
on the voltage of the power supply connected to the connecting means;
adjustable thermostat for turning off the heating elements when
said elements reach a predetermined temperature; and
a second switch which bypasses the thermostat.
2. The electric heater of claim 1, wherein the housing has a top
panel and further comprising a movable door mounted in the top panel
having an open position in which the heater is used as a lamp and
in the open position the second switch is activated to bypass the
thermostat.
3. The electric heater of claim 2, wherein the movable door has
a contacting member which closes the second switch when the movable
door is in the open position.
4. The electric heater of claim 1, wherein a top panel of the housing
has a movable door and the heater can be used as a light when the
door is in an open position.
5. The electric heater of claim 1, wherein the first switch has
a first position in which power of a first voltage is provided to
a first of the two heating elements and a second position in which
power of a second voltage is provided to a second of the two heating
elements, wherein the first voltage and the second voltage are different.
6. The electric heater of claim 5, wherein the first switch is
positioned at the first position when the source of electric current
is 115 volts and positioned at the second position when the source
of electric current is 12 volts.
7. The electric heater of claim 6, wherein the first switch in
the first position causes the electric current to be directed to
a 115 volt heating element and in the second position causes the
electric current to be directed to a 12 volt heating element.
8. The electric heater of claim 1, wherein the removable heating
elements are positioned in sockets which are adapted to receive
both light bulbs and heating cartridges.
9. The electric heater of claim 1, wherein the removable heating
elements are light bulbs.
10. The electric heater of claim 1, wherein the removable heating
elements are wound coil heating cartridges.
11. The electric heater of claim 1, wherein the connecting means
is adapted to connect to a household power supply, a car lighter
jack and a battery. time.
12. An electric heater comprising:
a housing;
at least two removable heating elements mounted within the housing;
connecting means adapted to connect the heater to at least two
electrical power supplies having different voltages;
a first switch connected to the two heating elements and to the
connecting means, said switch including means for selectively supplying
electrical power to one of the heating elements at a time, depending
on the voltage of the power supply connected to the connecting means;
adjustable thermostat means for turning off the heating elements
when said elements reach a predetermined temperature; and
wherein the two heating elements are mounted on a plate which is
rotated in the housing to allow access to the heating elements.
13. An electric heater comprising:
a housing;
first and second removable heating elements mounted within the
housing;
a power supply connector for connecting the heater to first and
second electrical power supplies having different voltages;
a first switch connected to the first and second heating elements
and to the power supply connector, said first switch selectively
supplying electrical power to the first removable heating element
from the first electrical power supply and supplying electrical
power to the second removable heating element from the second electrical
power supply, wherein the first switch supplies power only to one
of the first and second heating elements at a time; and,
a lock for locking the first switch in a first position or a second
position to prevent inadvertent motion of the first switch.
14. The electric heater of claim 13, further comprising an adjustable
thermostat which turns off the first and second heating elements
when the heating elements reach a predetermined temperature and
bypass switch for bypassing the adjustable thermostat so that the
heater can be used as a lamp.
15. The electric heater of claim 1, further comprising a lock for
locking the first switch in a first position or a second position
to prevent inadvertent motion of the first switch.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a portable resistance heater,
and more particularly to a low wattage heater and lamp assembly
for use in a wide variety of heating and lighting applications.
2. Description of the Related Art
Portable electric resistance heaters are used in any number of
indoor and outdoor applications. Conventional portable resistance
heaters such as space heaters include an electric heating element
made of a material with a high electrical resistance. Space heaters
may also include a fan for circulating air heated by the electric
heating element and a thermostat for controlling the temperature
of the heater. However, conventional portable heaters are large
and cumbersome. They are also expensive to operate because of the
amount of electricity used by the heating element and the fan.
There is currently a need for a compact, low powered electric heater
which can be used by outdoor workers and sportsmen as both a heater
and a lamp. There is also a need for a heater which is adaptable
to a variety of power supplies so that it can be used even when
there is no electric outlet available.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention meets these needs by providing a low powered,
compact, electric heater which can be adapted to be used with different
power supplies and can also be used as a lamp. The present invention
can be used by outdoor workers, hunters, fishermen, campers, boaters,
snowmobilers, other outdoor sportsmen, travelers sleeping in their
cars, truck drivers sleeping in their trucks, and outdoor workers.
An electric heater according to a preferred embodiment of the invention
includes a housing having a top panel and a bottom panel and at
least two removable heating elements mounted within the housing.
A connecting means is provided for alternatively connecting the
heater to at least two power supplies having different voltages.
A first switch connects one or the other of the two heating elements
to the connecting means for supplying power, depending on the voltage
of the power supply. An adjustable thermostat is provided to turn
off the heating elements when said elements reach a predetermined
temperature.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The invention will be described in greater detail with reference
to the accompanying drawings in which like elements bear like reference
numerals, and wherein:
FIG. 1 is a top view of the electric heater according to a first
embodiment of the invention;
FIG. 2 is a front view of the electric heater of FIG. 1;
FIG. 3 is a right side view of the electric heater of FIG. 1;
FIG. 4 is a cross-sectional view of the electric heater of FIG.
1 taken under the cover;
FIG. 5 is a top view of the electric heater according to a second
embodiment of the invention;
FIG. 6 is a cross-sectional view of the embodiment of FIG. 5 taken
under the cover of the heater;
FIG. 7 is a cross-sectional view of a third embodiment of the invention
taken under the cover; and
FIG. 8 is a schematic diagram of the embodiment of FIGS. 1-4.
DETAILED DESCRIPTION
With reference the first embodiment of the present invention illustrated
in FIGS. 1-4, the portable electric heater includes a housing 10
containing two electric heating elements 12, 14, which may be in
the form of conventional electric light bulbs, positioned within
the housing. The housing 10 is preferably provided with a top cover
16, a bottom cover 18 and side walls 20. The top cover 16 is preferably
removably mounted, for example, by screws 22 so that the cover may
be removed for maintenance. The bottom cover 18 may be either permanently
mounted or removable.
The top cover 16 is provided with an opening 24 which is covered
by a sliding door 26. A pair of tracks 28 are mounted on the top
cover 16 and receive the sliding door 26. The door 26 slides along
the tracks 28 between an open position in which the device can be
used as both a lamp and a heater and a closed position in which
the device is used only as a heater. A stop 30 is provided at an
edge of the sliding door 26 and projects into the interior of the
housing. The stop 30 strikes the sides of the opening 24 and prevents
the door from sliding out from under the tracks 28. The stop 30
may be a screw or any other member which projects from the bottom
of the door 26. The stop 30 may also project from the top of the
door 26 and can be used as a handle for moving the door. The sliding
door 26 allows the heater to be used as a lamp by sliding the door
into an open position, thus exposing the heating elements 12, 14.
The housing 10 is preferably formed from sheet metal. However, other
materials which can withstand the heat of the heating elements without
warping or melting may also be used.
Within the housing 10, two different voltage sockets 32, 34 are
provided for receiving heating elements 12, 14. The sockets 32,
34 are mounted on a dividing wall 36 which extends from one side
of the housing to the other. Two holes are formed in the dividing
wall 36 into which the sockets 32, 34 are received. The first socket
32 is preferably adapted to receive a conventional 115 volt bulb
or heating element and the second socket 34 is preferably adapted
to receive a conventional 12 volt bulb or heating element. In the
preferred embodiment of the present invention the heating elements
12, 14 are small commercially available light bulbs having wattages
from 25 to 40 watts. The heating elements 12, 14 are subject to
burning out after a period of time and may be removed and replaced
either through the opening 24 or by removing the top cover 16.
Alternatively, in the embodiment illustrated in FIGS. 1-4, the
dividing wall 36 may be mounted in the housing 10 by three screws
70, 71, 72 with two of the screws 70, 71 positioned on the front
side of the housing and one screw 72 on the back side of the housing.
With this arrangement the lower screw 71 can be removed and the
dividing wall 36 including the sockets 32, 34 and the heating elements
may be rotated on the two remaining upper screws 70, 72 to allow
the heating elements 12, 14 to slide easily into the sockets 32,
34 through the opening 24.
A voltage selection switch 38 is provided which is set to select
either 115 volts or 12 volts depending on the available power supply.
A second switch 39 which functions as an on/off switch is provided
above the voltage selection switch 38. Preferably, the switches
38, 39 are single pole, double throw slide switches, each having
three leads. The leads of the voltage selection switch in the embodiment
of FIGS. 1-4, cannot be seen in FIG. 4 because they are located
directly below the leads of the on/off switch 39.
However, the second embodiment of the present invention which is
illustrated in FIGS. 5 and 6 does not include an on/off switch.
Therefore, the voltage selection switch 38 can be seen more clearly
in the embodiment of FIG. 6. The first lead 42 of the switch 38
is connected to the 115 volt socket 32, the second or middle lead
44 is connected to the power supply 40, and the third lead 46 is
connected to the 12 volt socket 34. The switch 38 is manually movable
between two positions which alternatively supplies power to the
first socket 32 or the second socket 34 depending on the voltage
of the power source used. In the two switch embodiment of FIGS.
1-4, the second or middle lead 44 of the voltage selection switch
38 is connected through the on/off switch 39 to the power supply.
The voltage switch 38 is mounted within the housing with a sliding
portion extending through a side wall of the housing 10. The side
wall of the housing may be marked with 115 V and 12 V, and ON and
OFF to indicate the two switch positions of the two switches 38,
39.
Although it is possible to run the 115 volt heating element on
a lower voltage power supply such as 12 volts, the 12 volt heating
element cannot be run on a higher voltage power supply without causing
the heating element to burn out. Therefore, the voltage switch 38
is preferably provided with a lock 74 for preventing inadvertent
switching during use which will cause the lower voltage heating
element to burn out. The lock 74 includes a plate which is attached
to the switch 38 and a wing nut which is tightened to prevent movement
of the plate and the switch 38. A washer 75 may be provided under
the wing nut which prevents the wing nut from contacting the switch
38 as the wing nut is rotated.
A power supply cord 40 enters the housing 10 through a bushing
41 which attaches the power supply cord 40 securely to the housing.
The bushing 41 includes a pair of set screws 43, one of which can
be seen in FIG. 4, positioned on opposite sides of the bushing on
the inside of the housing. The set screws 43 are tightened on an
insulating covering of the power supply cord 40 to hold the cord
in place.
Although, the invention has been described as including 115 volt
and 12 volt heating elements, it should be understood that other
voltage heating elements and power sources may be used. Power may
be supplied to the heater from a variety of power sources. When
the heater 10 is powered by a 115 volt power source such as household
current, the switch 38 is positioned to direct the current to the
115 volt heating element 12. When the heater is powered by a 12
volt source, the switch 38 is positioned in the second position
to direct the current to the 12 volt heating element 14.
A fuse (not shown) is preferably provided external to the heater
in the power supply cord 40. Alternatively, a fuse may be mounted
within the housing 10 of the heater.
The heater according to the first embodiment includes a thermostat
48 which controls the temperature of the heater by turning the heating
elements 12, 14 on and off when the heater reaches a predetermined
temperature. The simplest form of automatic temperature control
uses bimetallic contacts which open and close the circuit to the
heating elements 12, 14 in response to temperature. The thermostat
48 has a knob 50 which extends from a side wall of the housing 10
and two bimetallic arms 52, 54. The lower arm 54 is connected to
a post 56 which is mounted on the knob 50. The post 56 extends through
an opening in the upper arm 52 which is large enough to prevent
any contact between the upper arm 52 and the post 56. The lower
arm 54 is electrically connected to the power supply and the upper
arm 52 is electrically connected to the heating elements.
Contact elements 58 are mounted on the upper and lower bimetallic
arms so that the contact elements contact each other to complete
the electrical circuit and provide current to the heating elements.
When the temperature of the heater increases, the bimetallic arms
bend and are moved away from one another, causing the contact elements
58 to move out of contact with one another which turns off the heater.
Rotation of the knob 50 moves the lower arm 54 up and down to regulate
the temperature at which the thermostat 48 will turn the heater
off. The knob 50 preferably has a pointer 75 on an external surface
and the side wall of the housing is preferably marked with temperature
markings so that the temperature may be set. Although, the thermostat
is preferably of the type described above, other small scale thermostats
which perform the function of regulating the temperature of the
heating elements and preventing the heater from overheating may
also be used.
When light bulbs are employed as heating elements 12, 14, the heater
can be used as a lamp by opening the sliding door 26 on the top
cover 16 of the housing. A screen may also be provided which covers
the opening 24 when the sliding door 26 is in an open position.
When the sliding door 26 is in the open position, the stop 30 operates
to close a thermostat bypass switch 60 by closing a contact lever
62. The bypass switch 60 has two leads which are connected to the
lead to the upper and lower arms 52, 54 of the thermostat. When
the bypass switch 60 is moved into the closed position by the stop
30, the thermostat is bypassed so that the heating element is not
turned on and off when the heater is used as a lamp.
A second embodiment of the present invention is illustrated in
FIGS. 5 and 6. The second embodiment includes many of the same elements
and features as the first embodiment and the corresponding elements
are provided with corresponding reference numerals. According to
the second embodiment of the present invention, the sockets 32,
34 are mounted on a dividing wall 36' which extends from one side
of the housing to the other. The dividing wall 36' has a stepped
shape to accommodate the two sockets 32, 34 of different voltages.
The dividing wall 36' of the second embodiment is not movable. In
addition, the embodiment of FIGS. 5 and 6 differs from the first
embodiment in that the switch 60 is in a different orientation.
However, the switch 60 operates in the same manner as the switch
of the first embodiment.
The heater according to the second embodiment is preferably provided
with an adapter or a set of adapters 66 which allow the heater to
be plugged into a household outlet, a car lighter jack, or run directly
off a battery. This set of adapters may also be provided for the
other embodiments which are disclosed. In addition, the set of adapters
may include an on/off switch and a fuse (not shown) which may be
provided between the power source and the heater. Alternatively,
an on/off switch and a fuse may be mounted within the housing 10
of the heater.
In a third embodiment of the present invention, the heating elements
may be wound coil heating cartridges 68, as shown in FIG. 3, such
as those disclosed in U.S. Pat. No. 2,831,951, which is incorporated
herein by reference. The heating cartridge for use in the present
invention includes a helical resistance wire wound on a central
core and surrounded by insulating material and a sheath. The heating
cartridge is provided with leads which may be adapted to conform
to the sockets of the present invention. When heating cartridges
are used the sliding door 26 and the bypass switch 60 may be eliminated
because the heater will not be used as a lamp. The heating cartridges
may be replaced by removing the top cover 16. This third embodiment
provides the same advantage of the first and second embodiments
of providing a compact heater which may be powered by a variety
of power supplies.
The portable heater according to all of the embodiments of the
present invention is convenient due to its compact size. The top
and bottom covers of the housing are preferably about 2.75 by 4.50
inches and the entire housing is less than 1.50 inches in depth.
This small size allows the heater to be easily transported and used
in situations where a conventional space heater would be too large
such as inside a car or even inside a coat pocket. The fact that
the heater can be used as a lamp avoids the necessity of carrying
a separate lamp.
While the invention has been described in detail with reference
to the specific embodiments thereof, it will be apparent to one
skilled in the art that various changes and modification can be
made, and equivalents employed, without departing from the spirit
and scope of the invention.
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