Note: Descriptions are shown in the official language in which they were submitted.
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Our Reference: 8LN-104-A
PATENT
VARIABLE LOW INTENSITY INFRARED NEATER
FIELD OF THE INvErsinmsr
[0001] This invention relates to an apparatus and method for healing an
enclosed
space with a variable low intensity infrared heater.
PACKGROUND OF MB INVENTION
[0002] Gas fired infrared beaters typically are used in large industrial
settings. A gas
heater bums natural gas, propane, or similar combustible gases and the
combustion
by-products or exhaust gases are passed through a radiant heating tube which
becomes hot and radiates energy waves therefrom. Reflectors are often used to
reflect the energy waves toward the desired location usually toward the floor
where
the infrared energy waves are converted into heat. These low intensity
infrared
heaters generally operate at full capacity when not in an off condition with
the result
that the burner constantly cycles between its on condition and its off
condition, thus
making it difficult to control heating levels.
[0003] There have been some attempts to create a two-stage heater by
utili7ing a
single gas flow control assembly with two pressure settings with a single
speed
blower. The problem with this system is that even though the gas pressure, and
therefore the gas volume, is varied between the two stages, the blower
speed.is
constant. As a result at both high and low stages the volume of air is the
same.
Therefore there is either too much air for a low stage or too little air for
the high
stage resulting in low efficiency combustion. Practically, since these systems
idle
most of the time at low stage, the excess air results in low efficiency
operation and a
great amount of wasted energy. Further, since a single gas flow control
assembly
valve is utilized, it is difficult to achieve an accurate setting for either
the high or low
level operation.
SUMMARY 12-M a13) =nal
[0004] This invention is directed to the provision of improved, MI=
efficient radiant
heater.
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[0005] The radiant heater of the invention is of the type including a
burner having an
inlet for receiving an air and gas mixture and an exhaust for emitting exhaust
gases
generated by combustion of the air and gas mixture within the burner; an
elongated
radiant heating tube having an inlet for receiving the exhaust gases emitted
by the
burner; a gas valve for controlling the flow of gas to the burner; and a
blower for
controlling the flow of air to the burner.. According to the invention, the
blower
comprises a two-stage blower having a low speed for delivering a low air flow
te the
burner and a high speed for delivering a high air flow to the burner. This
arrangement allows for a proper and fixed air/gas ratio for both high- and low-
stage
operation of the burner.
[0006] According to a further feature of the invention, the blower
includes an eleetzie
motor having a low winding corresponding to the blower low speed and a high
winding corresponding to the blower high speed. This arrangement provides a
ready
and efficient means of providing the two levels of blower operation.
[0007] According to a further feature of the invention, the gas flow
control assembly
includes a two-regulator assembly or a two-valve assembly, each having a
different
setting, one a low setting for delivering a low gas flow to the burner and the
other
having a high setting for delivering a high gas flow to the burner. This
atrsmgement,
utilizing a two-stage blower in combination with a two-stage gas flow control
assembly, allows for precise control of the desired air/gas ratio for both
high- and
low-level operation.
[0008] According to a further feature of the invention, the valve
assembly includes
two valves for independently controlling gas flow from a source to the burner.
This
arrangement allows for precise control of the gas flow volumes provided in the
high
and low level operational stages.
[0009] The invention also provides a method of heating a room with an
infrared
heater of the type including a burner having an inlet for receiving an air and
gas
mixture and an exhaust for emitting exhaust gases generated by combustion
within
the burner; and an elongated radiant heating tube having an inlet for
receiving the
exhaust gases emitted by the burner.
[0010] According to the invention methodology, a two-stage gas valve is
provided
having a low setting for delivering a low gas flow to the burner and a high
setting for
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delivering a high gas flow to the burner. A two oblige blower is provided
having a
low speed for delivering a low air flow to the burner and a high speed for
delivering
a high air flow to the burner; and the blower is operated at the low speed
when the
gas flow control assembly is operaiing at the low setting and at the high
speed When
the regulator is operating at the high setting. This methodology allows
precise
air/gas ratios to be provided at both the high- and low-level operational
stages of the
burner.
[0011] According to a further feature of the invention methodology, a
temperature set
point is defund for the room, a progronmed temperature differential is
defined, the
temperature of the room is monitored, and the burner is ignited when the roam
temperature is less than the temperature set point. A temperature threshold is
defined
as the temperature set point minus the temperature differential. The blower is
operated at the high level when the room temperature is equal to or below the
temperature Threshold, and the blower is operated at the low level when the
room
temperature is greater than the temperature threshold and lower than the set
point
temperature. This arrangement provides a ready and convenient means of
providing
high level operation when the room is relatively cold relative to the set
point
temperature and providing low level operations when the room temperature is
dose
to the set point temperature.
[0012] According to a further feature of the invention methodology, the
regulator is a
two-stage regulator and the method includes the further step of operating the
regulator at a high level when the blower is operating at the high level and
operating
the regulator at a low level when the blower is operating at the low level.
This
methodology allows precise air/gas ratios to be provided at both the high end
low
level operational stages of the burner.
[0013] According to a further feature of the invention methodology the gas
flow
control assembly has either of two valves or two regulators operating in
parallel and
the method includes the step of opening one valve or regulator and closing one
valve
or regulator when the regulator is operating at the low level and opening both
valves
or regulators when the gas flow control assembly is operating at the
highõlevel. It is
understood that also one valve or regulator could provide a higher flow such
that one
valve or regulator is used for the low setting and the other for a high
sitting. This
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methodology allows for precise control of the volume of gas delivered at both
the low
level and the high level operational stages.
[0013a] In accordance with another aspect of the present invention, there
is provided
an infrared heater comprising: a housing having an interior and an exterior; a
burner positioned within the interior of the housing, the burner having an
inlet
- for receiving air and gas and an exhaust for emitting exhaust gases
generated by
combustion of a mixture of the air and the gas within the burner; an elongated
radiant heating tube extending from the housing having an inlet for receiving
the exhaust gases emitted by the burner and for emitting heat; a two position
gas flow control assembly for controlling the flow of gas to the burner at a
low
setting and at a high setting; and a blower positioned on the exterior of the
housing the blower receiving inlet air and directing the inlet air into the
housing
to the inlet of the burner wherein the blower comprises a two stage blower
having a low speed for delivering a low air flow to the burner when the gas
control assembly is at its low setting and a high speed for delivering a high
ai -
flow to the burner when the gas control flow assembly is at its high setting.
[0013b] In accordance with a further aspect of the present invention,
there is provided
an infrared heater comprising: a housing having an interior and an exterior; a
burner positioned within the interior of the housing, and fix receiving and
combusting an air and gas mixture to generate exhaust gases; a radiant heating
tube receiving the exhaust gases from the burner and converting the exhaust
gases into radiant heat; a two stage gas flow control assembly operative to
deliver gas to the burner at either a low level or a high level; and a two
stage
blower positioned on the exterior of the housing operative to deliver air to
the
burner at either a low level or a high level.
[0013c] In accordance with a further aspect of the present invention,
there is provided a
method of heating a room with an infrared heater of a type including a housing
having and interior and an exterior and a burner positioned within the housing
and having an inlet for receiving air and gas. and an exhaust for emitting
exhaust gases generated by combustion within the burner, and an elongated
radiant heat tube extending from the housing and located in the room to be
heated and having an inlet for receiving the exhaust gases emitted by the
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burner, a two stage gas regulator having a low setting for delivering a low
gas
flow to the burner and a high setting for delivering a high gas flow to the
burner; and a two stage blower positioned on the exterior of the housing and
having a low speed for delivering a low air flow to the inlet of the burner
and a
high speed for delivering a high air flow to the inlet of the burner, wherein
the
method comprises the steps of; (i) operating the blower at the low speed while
operating the regulator at the low setting to heat the room; and (ii)
operating the
blower at the high speed while operating the regulator at the high setting to
heat
the room.
[0013d] In accordance with a further aspect of the present invention,
there is provided a
method of heating a room with an infrared heater of a type including a housing
having an interior and an exterior and a burner positioned within the housing
and having an inlet for receiving an air and gas mixture and an exhaust for
emitting exhaust gases generated by combustion within the burner, an elongated
radiant heating tube extending from the housing and having an inlet for
receiving the exhaust gases emitted by the burner, a gas flow control assembly
for controlling the flow of gas to the burner, and a two stage blower
positioned
and the exterior of the housing for controlling the flow of air to the burner,
the
method comprising the steps of: defining a temperature set point of the room;
defining a programmed temperature differential; monitoring the temperature of
the room; igniting the burner when the room temperature is less than the
temperature set point; defining a temperature threshold as the temperature set
point minus the temperature differential: operating the blower at the high
level
when the room temperature is equal to or below the temperature threshold: and
operating the blower at the low level when the room temperature is greater
than
the temperature threshold and lower than the set point temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The description herein makes reference to the accompanying
drawings
wherein like reference numerals refer to like parts throughout the several
views, and
wherein:
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[0015) Figure 1 is a perspective view of a radiant heater according to the
invention;
[0016] Figure 2 is a cross section of the heater schematically showing
reflected energy
waves;
[0017] Figure 3 is a side elevational view of the heater;
[0018] Figure 4 is a fragmentary, cross-sectional, somewhat schematic view
of the
heater;
[0019] Figure 5 is a cross-sectional view taken on line 5-5 of Figure 4;
[0020] Figure 6 is a detail cross-sectional view of a gas flow control
assembly utilized
in the heater;
[0021] Figure 6A is a detail cross-sectional view of an alternate gas flow
control
assembly utilized in the heater, and
[0022] Figure 7 is a flow chart showing the operation of the heater.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023) The infrared heater 10 of the invention, broadly considered,
includes a housing
12, a radiant tube 14, a reflector 16, a burner 18 (shown only in Fig. 4), a
blower 20, a
gas flow control assembly 22, and a controller 24 (shown only in Fig. 3).
[0024) Housing 12 has a box like sheet metal configuration.
[0025] Radiant tube 14 is elongated and includes an inlet end 14a secured
to a front
wall 12a of housing 12, in communication with a wall aperture 12b as shown in
detail
in Fig. 4. Radiant tube 14 also includes an exhaust end 14b as shown in Fig.
3.
[0026) Reflector 16 has an inverted U configuration in cross-section, is
suitably
supported in spaced overlying relation to tube 14, and is generally
coextensive with
tube 14.
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[0027] As shown in Figs. 4 and 5, burner 18 is elongated and generally
tubular, has a
venturi configuration, and includes an inlet end 18a positioned in housing 12
proximate wall 12a and an outlet end 18b positioned in the inlet end 14a of
tuba 14
and centered concentrically within the tube by a plundity of circumferentially
spaced
spokes or vanes 18c.
[0028] Blower 20 is a centrifugal blower and includes a housing 26 and an
electric
motor 28 mounted on a side wall 26c of the housing and driving the blower
scroll or
impeller in a known manner. Housing 26 includes an air inlet 26a and an air
exhaust
26b communicating with an aperture 12c in housing rear wall 12d whereby
actuation
of the blower discharges pressurized air into theinterior of the housing 12.
[0029] Motor 28tis a two-speed motor having a high winding and a low
winding so
that the blower comprises a two-stage blower having a low speed for delivering
a low
air flow to housing 12 and burner 18 and a high speed for delivering a high
air flow
to housing 12 and burner 18. Motor 28 may for example comprise a 1/25 HP, 110
V
AC single phase 60 ha motor and may be operative to deliver a low air flow of
25
CFH and a high air flow of 50 CFH.
[0030] Gas flow control assembly 22 may be supported within housing 12 on
housing
lower wall 12e and comprises either a two-stage regulator or a two-stage valve
with
the 'two stages achieved by the use of two independent valves 30 and 32 as
shown in
Figs. 4 and 6 or two regulators 202 and 204 arranged in parallel within a
common
housing as shown in Fig. 6A.
[0031] Valve 30 includes a gas inlet 30a, a redundant solenoid valve 30b,
a main
valve 30c controlled by a spring 30d and a diaphragm 30c, a gas outlet 30f, a
cep
screw 30g. an adjustment screw 30h, and a vent 301.
[0032] Valve 32 is identical to valve 30 as indicated by the Ince
reference numbers
32a-32i. =
[0033] Main valves 30e and 32c are controlled in known manner by
solenoids and
each valve is moveable between first and second positions corresponding to the
valve
being 100% closed and 100% open respectively.
[0034] In the assembled burner package shown in Fig. 4, blower 20 is
mounted on
rear housing wall 12d with the blower outlet 26b aligned with housing Wall
aperture
12o. The regulator assembly 22 is mounted on housing lower wall 12e within
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housing 12, A gas inlet line 34 passes through housing rear wall 124 and
thereafter
bifurcates to form a first branch 34a cororaunkating with the inlet 30a of
valve 30
and a second branch 34b communicating with the inlet 32a of valve 32. Branch
gas
outlet lines 36a and 36b communicate respectively with the outlet 30f of valve
30
and the outlet 32f of valve 32 and thereafter converge to form gas outlet line
36,
which extends within housing 12 to a free end 36e fixedly and centrally
secured to an
annular disk 38a positioned at the inlet end 18a of burner 18 and clf.Bnivig
apluT2Jity
of perforations 38a shown in Fig. 5.
[0035] Controller 24, shown in Fig. 3, may be mounted on housing 12 and
Is
connected by a lead 40 to a two-stage thermostatic plobe 42 carried by housing
12.
The controller 24 provides a reading of room temperature from the probe 42 to
regulator 22 by a lead 44 and to the high and low windings of motor 21 of
blower 20
by a lead 46.
[0036] With respect to the general overall operation of the heater, gas
is supplied to
the interior of burner 18 via line 36, and sins supplied to the burner 18 via
blower 20
with the air from the blower 20 entering into the interior of the vented
through the
perforations 38a for mixture with the gas. Air also passes into tube inlet end
14a
outwardly of the venturi for passage through vanes 18c, which act to invert a
mid to
the air to facilitate the air/gas mixing. It will be understood that ignition
is
accomplished in a known =MX= by a pilotless direct spark utilizing an ignition
module (not shown) and that burner operation is monitored and controlled in a
known manner by an ignition detection control (not shown).
[0037] The specific operation of the invention heater is best understood
with reference
to Figure 7. The flow sequence for the invention heater begins by dcf2ning a
set
point temperature T. and a programmed differential (It and comparing these
values to
the room temperature Tr as determined by the thermostatic probe 42 and as
recognized by controller 24. This comparison is shown at step 100 in Figure 7.
If
the room temperature Tr is less than the set point temperature To the
thermostat calls
for heat in step 102. If the room temperature 1; is greater than or equal to
the set
' point temperature Tv the controller will turn the unit off as shown in
stet:904. Once
the thermostat calls for heat in step 102, the controller calculates whether
the room
temperature T. is less than or equal to the temperature set point T. minus the
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programmed differential du or whether the room temperature Tr is greater than
the
temperature set point T11:121)111S the programmed differential de. This
calculation is
shown as step 106.
[0038] If the room temperature Tr is less than or equal to the
temperature set point Ts
minus the programmed differential de, the controller, as sliown in step 108,
commands a high gas flow rate from the gas regulator by energizing solenoids
to
move both valves 30c and 32o to their second, fully-opened positions, and
commands
a high air flow rate from the blower by energizin' g a relay 109 (shown in
Fig. 3) in a
sense to power the high winding of blower motor 28. The heater 10 is now in a
high
output mode as shown in step 110 and then loops back to step 100 to
.continuously
monitor the room temperature Tr relative to the set point temperature T.
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00393 If the room temperature T, is greater than the set point
temperature T, minus
the programmed differential de in step 106, the controller, as shown in step
112,
eon:upends a low gas flow rate from the gas regulator by energizing solenoids
to
move valve 30c to the second, open position and move valve 32c to the first,
closed
position, and commands a low air flow rate from the blower by energizing the
relay
109 in a sense to power the low vvindingiof the blower motor 28. The heater 10
is
now in a low output mode as shown in step 114 and then loops back to step 100
to
continuously monitor the room temperature T, for comparison with the
temperature
set point Ts. It will be understood that if the heater is initially operated
at the high
output level, when the room temperature Tr reaches the set point temperature
Ts
minus the temperature differential du the controller will operate to place the
heater in
the low output mode by switching the blower motor 28 to the low winding and
closing valve 32c. When the room temperature eventually readies the set point
temperature irs = the controller shuts off the heater and allows the blower to
stay on
for a few minutes to purge any flue gases left in the system.
[0040] With reference to Figure 6A, another preferred two-stage gas
regulator 200 is
illustrated. Gas flow control assembly 200 may for example be of the type
available
from White Rogers of St. Louis, MO sold under the brand name Two Stage Gemini.
As shown, the gas flow control assembly includes a low-fire regulator 202 and
a
high-fire regulator 204. Low-fire and high-fire regulators 202 and 204 work In
combination with main valve 206 to provide two-stage gas control. The
regulator
body includes an inlet 208 and associated inlet pressure tap 210 and inlet
screen 212.
Gas exits the assembly 200 at outlet 214. Outlet 214 includes an associated
outlet
pressure tap 218 and outlet screen 216. The assembly 200 includes a control
gas
orifice 220 and associated orifice opening 222. Main valve 206 is biased by
diaphragm 224 in a manner known to those of skill in the art. The assembly 200
includes a vent 226 and redundant solenoid 228.
[0041] It is understood by those of skill in the art that the assembly
illustrated in
Figure 6A could be substituted for the assembly illustrated in Figure 6. In
particular,
where Figure 6 illustrates an assembly in which valves 30o and 32e selectively
cooperate to provide two levels of gas flow, Figure 6A illustrates an assembly
in
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Which low-fire regulator 202 and high-fire regulator 204 operate to deliver
two gas
flows.
[0042] When the temperature drops below the set point, yet still stays
above the set
point temperature minus the programmed differential, the low stage of the
heater
comes back on until the thermostat is satisfied. The system idles around the
set point
on the low stage, on and off, preventing any overshoot effect with otherwise a
high
heating inertia. HOWOVOT, if there is a sudden drop in the room temperature
for any
reason the heater Fumes on with high stage allowing a fast recovery.
[0043] The invention, by utilizing a two-stage blower and a two-stage gas
flow
control assembly, allows for a proper and fixed air/gas ratio for both the
high and low
output levels. This arrangement has the advantages of saving energy by
operating
with optimum gas/air ratios at all times; saving energy by reducing the
temperature
overshoots due to the high heat inertia; reducing wear and tear on the
components by
eliminating utmecessary cycling of the unit on high heat; providing accurate
constant
rate for each stage due to the two independent valves or regulators; allowing
for a
higher differential between the two stages due to the independent regulator
adjustment; and reducing the cost of the heater by elbeinatietg the need for
en
expensive. continuously variable blower motor providing a continuously
variable
blower speed.
[0044] The gas flow control assemblies disclosed in the present
embodiments provide
a much more accurate two-stage flow control as compared to the gas flow
control
assemblies of the prior art.
[0045] While the invention has been described in connection with what is
presently
considered to be the most practical and preferred embodiment, it is to be
understood
that the invention is not to be limited to the disclosed embodiments but, on
the
contrary, is intended to cover various modifications and equivalent =easements
included within the spirit end scope of the appended claims, which scope Is to
be
accorded the broadest interpretation so as to encompass all such modifications
and
equivalent structures as is permitted under the law.
