U.S. patent number RE38,453 [Application Number 09/534,235] was granted by the patent office on 2004-03-09 for infant incubator.
This patent grant is currently assigned to Hill-Rom Services, Inc.. Invention is credited to Joseph J. Lessard, Robert M. McDonough, Peter Schumann, Jan F. Wenstrup.
United States Patent |
RE38,453 |
Lessard , et al. |
March 9, 2004 |
Infant incubator
Abstract
An infant incubator in which the heater for heating the air
circulated through the incubator and the speed of the fan which
forces air across the heater to circulate through the incubator are
controlled to increase the temperature of the heated air and
delivery of the heated air to the space in which an infant has been
placed for treatment when an access door of the incubator has been
opened. The increase in temperature and delivery of the heated air
is caused by a sensor which senses when the access door is
opened.
Inventors: |
Lessard; Joseph J. (Horsham,
PA), McDonough; Robert M. (Hatfield, PA), Wenstrup; Jan
F. (Doylestown, PA), Schumann; Peter (Richboro, PA) |
Assignee: |
Hill-Rom Services, Inc.
(Batesville, IN)
|
Family
ID: |
31891573 |
Appl.
No.: |
09/534,235 |
Filed: |
March 23, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
703793 |
Aug 27, 1996 |
05730355 |
Mar 24, 1998 |
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Current U.S.
Class: |
237/3; 237/14;
454/195 |
Current CPC
Class: |
A61G
11/00 (20130101); G05D 23/1931 (20130101); A61G
2203/46 (20130101) |
Current International
Class: |
A61G
11/00 (20060101); G05D 23/19 (20060101); A01K
031/20 () |
Field of
Search: |
;237/3,14,15 ;454/195
;219/400,385,386 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Boles; Derek
Attorney, Agent or Firm: Barnes & Thornburg
Claims
What is claimed:
1. An infant incubator comprising: a hood having an access door in
a wall thereof; a base upon which said hood is mounted and having a
deck which with said hood defines an enclosure and has openings
through which air enters and leaves said enclosure; a heater within
said base for heating the air; a fan for supplying air to said
heater and heated air from said heater into said enclosure through
at least one of said openings and for returning air from said
enclosure to said heater through at least one of said openings;
sensing means responsive to movement of said access door for
sensing when said access door is opened; and control means
responsive to said sensing means for: (a) increasing the heat
generated by said heater, and (b) increasing the speed of said
fan
when said access door is opened.
2. An infant incubator according to claim 1 wherein said sensing
means include: (a) a magnetic reed switch mounted to said base, and
(b) a magnet mounted to said access door of said hood movable with
said access door into and out of the range of said magnetic reed
switch.
3. An infant incubator according to claim 2 further including a
first temperature sensor positioned in said enclosure for sensing
the temperature of the air within said enclosure and a second
temperature sensor adapted for attachment to the skin of an infant
being treated in the incubator.
4. An infant incubator according to claim 3 wherein said control
means are also responsive to said first temperature sensor and said
second temperature sensor for controlling: (a) the amount of
increased heat generated by said heater and the time period over
which said increased heat is generated, and (b) the amount of
increased speed of said fan and the time period said fan is
operated at said increased speed.
5. Apparatus for controlling the temperature of an infant incubator
comprising: a heater for heating air circulated within an
incubator; a fan for circulating heated air within the incubator;
sensing means responsive to at least one of: (a) movement of an
access door for sensing when the access door is opened, (b) the
temperature to which an infant being treated in an incubator is
exposed, and (c) the temperature of the skin of an infant being
treated in an incubator; and control means responsive to said
sensing means for controlling: (a) the heat generated by said
heater, and (b) the speed of said fan.
6. Apparatus according to claim 5 wherein: (a) said sensing means
include: (1) a magnetic sensor responsive to movement of an access
door of an incubator for sensing when the access door is opened,
(2) a first temperature sensor responsive to the temperature to
which an infant being treated in an incubator is exposed, and (3) a
second temperature sensor responsive to the skin temperature of an
infant being treated in an incubator, and (b) said control means
are responsive to: (1) magnetic sensor for increasing: (i) the heat
generated by said heater, and (ii) increasing the speed of said fan
when said access door is opened, and (2) at least one of: (i) said
first temperature sensor, and (ii) said second temperature sensor
for controlling: (i) the amount of increased heat generated by said
heater and the time period over which said increased heat is
generated, and (ii) the amount of increased speed of said fan and
the time period said fan is operated at said increased speed.
7. Apparatus according to claim 6 wherein said magnetic sensor
includes: (a) a magnetic reed switch mounted to a base of an
incubator, and (b) a magnet mounted to an access door of an
incubator and movable with the access door into and out of the
range of said magnetic reed switch.
8. An infant incubator according to claim 1 wherein: (a) said
access door is in a front wall of said hood, (b) said hood has a
second access door in a rear wall of said hood, and (c) said deck
has: (1) openings extending along said front wall and said rear
wall through which air enters said enclosure, and (2) an opening
extending along a third wall of said hood and through which air
leaves said enclosure.
9. An infant incubator comprising: a hood having a first access
door in a front wall thereof and a second access door in a rear
wall thereof; a base upon which said hood is mounted and having a
deck which with said hood defines an enclosure and has first and
second openings extending along said front wall of said hood and
said rear wall of said hood, respectively, through which air enters
said enclosure and only one opening extending along a third wall of
said hood through which air leaves said enclosure; a heater within
said base for heating the air; a fan for supplying air to said
heater and heated air from said heater into said enclosure through
said first opening and said second opening and for returning air
from said enclosure to said heater through said opening extending
along said third wall; sensing means responsive to movement of said
first access door and movement of said second access door for
sensing when either of said access doors is opened; and control
means responsive to said sensing means for increasing at least one
of: (a) the heat generated by said heater, and (b) the speed of
said fan
when either of said access doors is opened.
10. An infant incubator according to claim 3 further including: (a)
a third temperature sensor for sensing ambient temperature outside
the incubator, (b) an alarm indicator for developing an alarm
indication when at least one of: (1) a difference in actual infant
skin temperature and a predetermined set point exceeds a
predetermined threshold, and (2) a difference in actual air
temperature within said hood and a predetermined set point exceeds
a predetermined threshold, and (c) means responsive to said third
temperature sensor for delaying an alarm indication by said alarm
indicator by a time period dependent upon the ambient temperature
if at least one of: (1) a difference in actual infant skin
temperature and a predetermined set point exceeds a predetermined
threshold, and (2) a difference in actual air temperature within
hood and a predetermined set point exceeds a predetermined
threshold, exists and such difference is caused by the operator of
the incubator changing operation of the incubator.
11. An infant incubator according to claim 3 wherein: (a) said
sensing means include a third temperature sensor for sensing
ambient temperature outside the incubator, and (b) said control
means are responsive to said third temperature sensor for: (1)
controlling the heat generated by said heater, and (2) controlling
the speed of said fan after said access door has been closed.
12. Apparatus according to claim 5 further including: (a) a third
temperature sensor for sensing ambient temperature outside an
incubator, (b) an alarm indicator for developing an alarm
indication when at least one of: (1) a difference in actual infant
skin temperature and a predetermined set point exceeds a
predetermined threshold, and (2) a difference in actual air
temperature within the hood of an incubator and a predetermined set
point exceeds a predetermined threshold, and (c) means responsive
to said third temperature sensor for delaying an alarm indication
by said alarm indicator by a time period dependent upon the ambient
temperature if at least one of: (1) a difference in actual infant
skin temperature and a predetermined set point exceeds a
predetermined threshold, and (2) a difference in actual air
temperature within a hood of an incubator and a predetermined set
point exceeds a predetermined threshold, exists and such difference
is caused by the operator of the incubator changing operation of
the incubator.
13. An infant incubator according to claim 5 wherein: (a) said
sensing means include a third temperature sensor for sensing
ambient temperature outside the incubator, and (b) said control
means are responsive to said third temperature sensor for: (1)
controlling the heat generated by said heater, and (2) controlling
the speed of said fan after said access door has been closed.
14. An infant incubator according to claim 9 wherein said sensing
means include: (a) a magnetic reed switch mounted to said base, and
(b) a magnet mounted to said access door of said hood movable with
said access door into and out of the range of said magnetic reed
switch.
15. An infant incubator according to claim 14 further including a
first temperature sensor positioned in said enclosure for sensing
the temperature of the air within said enclosure and a second
temperature sensor adapted for attachment to the skin of an infant
being treated in the incubator.
16. An infant incubator according to claim 15 wherein said control
means are also responsive to said first temperature sensor and said
second temperature sensor for controlling: (a) the amount of
increased heat generated by said heater and the time period over
which said increased heat is generated, and (b) the amount of
increased speed of said fan and the time period said fan is
operated at said increased speed. .Iadd.
17. An infant incubator comprising: a hood having an access door in
a wall thereof; a base upon which said hood is mounted and having a
deck which with said hood defines an enclosure filled with air;
openings through which air enters and leaves said enclosure; an
electrical heating system within said base for supplying heated air
into said enclosure through at least one of said openings to raise
the temperature of the air within the enclosure and for returning
air from said enclosure through at least one of said openings; and
a source of electrical power connected to said electrical heating
system when said access door is opened for increasing the rate of
temperature increase of the air in the
enclosure..Iaddend..Iadd.
18. The incubator of claim 17, wherein the electrical heating
system comprises an electrical heater for warming up the air prior
to the supplying of heated air to the enclosure through the at
least one of the openings..Iaddend..Iadd.
19. The incubator of claim 18, wherein the electrical heating
system comprises an electrical fan for increasing the flow of
heated air supplied to the enclosure through the at least one of
the openings..Iaddend..Iadd.
20. The incubator of claim 17, wherein the electrical heating
system comprises an electrical fan for increasing the flow of
heated air supplied to the enclosure through the at least one of
the openings..Iaddend..Iadd.
21. The incubator of claim 17, including an temperature sensor
located in the incubator and responsive to a temperature of an
infant located in the incubator to connect the source of electrical
power to said electrical heating system when the sensed temperature
drops below a desired value..Iaddend..Iadd.
22. The incubator of claim 17, including an temperature sensor
located in the incubator and responsive to a temperature of the air
in the incubator to connect the source of electrical power to said
electrical heating system when the sensed temperature drops below a
desired value..Iaddend..Iadd.
23. The incubator of claim 22, including an temperature sensor
located in the incubator and responsive to a temperature of an
infant located in the incubator and the air in the incubator to
connect the source of electrical power to said electrical heating
system when either of the sensed temperature drops below a desired
value..Iaddend..Iadd.
24. An infant incubator comprising: a deck, a hood defining an
enclosure with the deck; at least one access door coupled to the
hood for movement relative thereto between an open position and a
closed position; a sensor operatively coupled to the access door
and configured to indicate the position of the access door relative
to the hood; and an electric fan configured to circulate air within
the enclosure, the fan being operatively coupled to the sensor so
that the fan operates at a fan speed..Iaddend..Iadd.
25. The infant incubator of claim 24, wherein the speed of the fan
increases when the access door moves away from the closed
position..Iaddend..Iadd.
26. The infant incubator of claim 24, wherein the sensor is a
magnetic reed switch mounted to the hood and further comprising a
magnet mounted to the access door, and wherein the magnet is
positioned to lie adjacent to the magnetic reed switch when the
access door is in the closed position, and wherein the magnetic
reed switch is the control for the connection..Iaddend..Iadd.
27. The infant incubator of claim 26, wherein the magnetic reed
switch provides a signal in response to the position of the access
door and further comprising a fan control processing module coupled
to the magnetic reed switch and coupled to the fan, the fan control
processing module being configured to control the speed of the fan,
the fan control processing module receiving the signal from the
magnetic reed switch and controlling the speed of the fan in
response thereto..Iaddend..Iadd.
28. The infant incubator of claim 24, further comprising a heater
configured to heat the air going into the enclosure, the heater
being operatively coupled to the sensor so that the heater
generates heat in response to the position of the access
door..Iaddend..Iadd.
29. The infant incubator of claim 28, wherein the sensor provides a
position signal in response to the position of the access door, a
temperature sensor providing a temperature signal in response to
the temperature of the air within the enclosure, a controller
coupled to each of: the sensor, the temperature sensor, the heater,
and the fan, and wherein the controller controls the heat generated
by the heater and the speed of the fan in response to the position
signal and the temperature signal..Iaddend..Iadd.
30. The infant incubator of claim 29, further comprising a second
temperature sensor coupled to the controller and providing an
ambient temperature signal in response to the temperature outside
of the enclosure, a third temperature sensor coupled to the
controller and providing an infant temperature signal in response
to the temperature of an infant being treated within the enclosure,
and wherein the controller controls the heat generated by the
heater and the speed of the fan in response to the position signal,
the temperature signal, the ambient temperature signal, and the
infant temperature signal..Iaddend..Iadd.
31. The infant incubator of claim 30, wherein the controller
includes an alarm control, an alarm indicator coupled to the alarm
control, and wherein the alarm indicator providing an alarm
indication in response to the position signal, the temperature
signal, the ambient temperature signal, and the infant temperature
signal..Iaddend..Iadd.
32. The infant incubator of claim 24, further comprising a
temperature sensor configured to indicate the temperature outside
of the enclosure, the fan being operatively coupled to the
temperature sensor so that the fan operates at a fan speed
responsive to the temperature outside of the
enclosure..Iaddend..Iadd.
33. An infant incubator comprising: a hood having at least one
access door in a wall thereof; a deck which with said hood defines
an enclosure and openings through which air enters and leaves said
enclosure; a heater; a first air passageway leading from the heater
to at least one of the openings; a second air passageway extending
from another one of the openings in the enclosure to the inlet of
the heater; a fan in one of said passageways; an electric power
source input connected to the fan through a control; a door
position sensor coupled between said door and said control to
activate the control when said access door is opened to increase
the speed of said fan..Iaddend..Iadd.
34. The incubator of claim 33, also including a connection from the
power supply control to the heater, and wherein the sensing means
increases the flow of power to the heater when said access door is
opened..Iaddend..Iadd.
35. Apparatus for controlling the temperature of an infant
incubator comprising: an incubator enclosure having at least one
access door; a heater; a circulation passageway leading from the
heater into the enclosure and from the enclosure into the heater; a
fan in the circulation passageway; a power source input connected
to the fan and heater through a control; the control connecting the
power source to the fan and heater when at least one of: a) a door
open or shut position indicator indicates the access door is
opened; b) a first temperature sensor measuring the skin
temperature of an infant in the enclosure sensing a temperature
below that desired; and c) a temperature sensor measuring the
temperature of the air in the enclosure below that
desired..Iaddend.
Description
TECHNICAL FIELD
The present invention relates, to infant incubators and, in
particular, to apparatus for regulating the heating of the air
which is circulated through an infant incubator and introducing the
heated air into the space in which an infant is placed for
treatment.
BACKGROUND OF THE INVENTION
The most common way for regulating the heating of the air which is
circulated through an incubator is to control the power delivered
to the heater. An alternative approach, although not as common, is
to control the speed of a fan which forces air across the heater
and through the incubator. Typically, a temperature sensor, located
in the space in which an infant is placed for treatment, and a
temperature sensor, attached to the infant, serve as the control
for establishing and maintaining the desired temperature of the air
to which the infant is exposed.
Incubators have access doors which, when opened, permit access to
an infant by those attending to the infant. When an access door is
opened, the ambient air can enter the incubator space in which the
infant has been placed and change the conditions of the air to
which the infant is exposed. As a result, incubators have been
arranged with openings extending along the access doors through
which incubator air passes to develop warm air curtains which are
intended to serve as shields to inhibit the ambient air from
entering the space in which the infant has been positioned.
Some incubators are arranged to sense either the access door being
opened or a change in temperature in the space in which the infant
has been placed and change the heating and delivery of the air
which is circulated through the incubator to compensate for the
change in conditions by the entry of the ambient air.
SUMMARY OF THE INVENTION
An infant incubator, constructed in accordance with the present
invention, includes a hood having an access door in a wall thereof
and a base upon which the hood is mounted and having a deck which
with the hood defines an enclosure. The deck has openings through
which air enters and leaves the enclosure. Also included in this
incubator are a heater within the base for heating the air and a
fan for supplying air to the heater and heated air from said heater
into the enclosure through at least one of the openings and for
returning air from the enclosure to the heater through at least one
of the openings. An infant incubator, constructed in accordance
with the present invention, further includes sensing means
responsive to movement of the access door for sensing when the
access door is opened and control means responsive to the sensing
means for increasing the heat generated by the heater and
increasing the speed of said fan when the access door is
opened.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of an incubator constructed
in accordance with the present invention.
FIG. 2 is a top view of the heater and fan portions of the FIG. 1
incubator.
FIG. 3 is a side view of a sensor unit, constructed in accordance
with the present invention, by which opening and closing of an
access door of an incubator is sensed.
FIG. 4 is a block diagram of the sensor and temperature control
portions of an incubator constructed in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, an infant incubator, constructed in accordance
with the present invention, includes a hood 10 having an access
door 12 in a wall 14 thereof. This incubator also has a base 16
upon which hood 10 is mounted and having a deck 18 which with the
hood defines an enclosure.
Deck 18 has openings through which air enters and leaves the
enclosure. For the infant incubator illustrated in FIG. 1 and being
described, access door 12 is in a front wall of hood 10 and the
hood has a second access door 20 in a rear wall 22 of the hood.
Deck 18 has openings 24 and 26 extending along front wall 14 and
rear wall 22, respectively, of hood 10. As shown by the arrows in
FIG. 1, air enters the enclosure defined by hood 10 and deck 18
through openings 24 and 26 and leaves this enclosure through a
third opening 28 extending along a third wall 29 of the hood.
When access door 12 is opened, the air passing through opening 24
in deck 18 forms a warm air curtain which serves as a barrier and
reduces the effect of the ambient temperature outside the incubator
on the enclosure defined by hood 10 and deck 18. Similarly, a warm
air curtain is formed at opening 26 in deck 18 when access door 20
is opened.
An infant incubator, constructed in accordance with the present
invention, preferably includes a first inner wall 30 and a second
inner wall 31, respectively, secured to and movable with front
access door 12 and rear access door 20. Inner walls 30 and 31
reduce radiant heat losses when the respective access doors are
closed and serve to carry warm air, introduced through openings 24
and 26 in deck 18, to the top of hood 10 as indicated by the
arrows.
An infant incubator, constructed in accordance with the present
invention, also includes a heater within base 16 for heating the
air circulated through the incubator and a fan for supplying air to
the heater and heated air from the heater into the enclosure
defined by hood 10 and deck 18 through at least one of the openings
in the deck and for returning air from this enclosure to the heater
through at least one of the openings in the deck. Referring to FIG.
2, a heater 32 is positioned in a first compartment 34 in the base
of an incubator. A fan 36 is positioned in a second compartment 38
in the base of the incubator. As fan 36 turns, air is forced past
heater 32 and conducted through suitable ducting into the enclosure
defined by hood 10 and deck 18 of FIG. 1 and drawn from this
enclosure through suitable ducting to the fan for
recirculation.
An infant incubator, constructed in accordance with the present
invention, also includes sensing means responsive to movements of
access doors 12 and 22 for sensing when one or both of these access
doors is opened, responsive to the temperature in the enclosure
defined by hood 10 and deck 18 for measuring the temperature of
this enclosure, and responsive to the skin temperature of an infant
being treated in the incubator for measuring the skin temperature
of the infant. These sensing means include, as shown in FIG. 3, a
magnetic sensor composed of a magnetic reed switch 40 and a magnet
42 responsive to movement of an access door, a first temperature
sensor 44, shown in FIG. 1, responsive to the temperature to which
an infant being treated in an incubator is exposed, and a second
temperature sensor, identified in FIG. 1 by reference numeral 46,
responsive to the skin temperature of an infant being treated in
the incubator.
Referring to FIG. 3, which shows the sensing means for access door
12 of hood 10, the sensing means for each door include magnetic
reed switch 40 mounted to base 16 and magnet 42 mounted to the
access door and movable with the access door into and out of the
range of the magnetic reed switch. After access door 12, with
magnet 42, is moved a predetermined amount, for example 15 degrees,
the magnet comes within the range of magnetic reed switch 40 and
the magnetic reed switch is actuated. When access door 12 is closed
and magnet 42 moves out of the range of magnetic reed switch 40,
the magnetic reed switch opens.
It is common practice to measure the temperature of the enclosure
defined by hood 10 and deck 18 and the skin temperature of an
infant being treated in an incubator and to use such temperature
measurements to regulate the temperature in the enclosure.
An infant incubator, constructed in accordance with the present
invention, also includes control means responsive to the magnetic
sensor 40, 42 for increasing the heat generated by heater 32 and
increasing the speed of fan 36 when an access door is opened. The
control means are also responsive to the first temperature sensor
44 and the second temperature sensor 46 for controlling the amount
of increased heat generated by heater 32 and the time period over
which the increased heat is generated and the amount of increased
speed of fan 36 and the time period the fan is operated at the
increased speed.
Referring to FIG. 4, as one or both of the access doors of an
incubator are opened, the magnetic reed switch 42 or 48 associated
with the open door or doors closes and signals are supplied to
inputs to a heater control processing module 50 and a fan control
processing module 52 which, in turn, develop control signals which
are supplied from outputs of heater control processing module 50
and a fan control processing module 52 to heater 32 and a fan 36
for increasing the heat generated by heater 32 and increasing the
speed of fan 36 when an access door is opened. As one or both of
the access doors in opened, there is no immediate effect on the air
temperature within hood 10 at the location of temperature sensor 44
nor on the skin temperature of the infant at the location of skin
temperature sensor 46. Yet it is known that the air temperature in
the vicinity of the infant drops when one or both of the access
doors is opened. Consequently, the magnetic sensors associated with
the access doors "over-ride" the usual control function of air
temperature sensor 44 and skin temperature sensor 46 to increase
the heat generated by heater 32 and to increase the speed of fan 36
when an access door is opened. When the effect of the access door
being opened is sensed by air temperature sensor 44 and by skin
temperature sensor 46, control of heater 32 and fan 36 returns to
air temperature sensor 44 and skin temperature sensor 46 and the
amount of increased heat generated by heater 32 and the time period
over which the increased heat is generated and the amount of
increased speed of fan 36 and the time period the fan is operated
at the increased speed are controlled by air temperature sensor 44
and skin temperature sensor 46 in the usual manner.
It is common practice to include in an infant incubator an alarm
indicator when either the difference in actual infant skin
temperature and a predetermined set point exceeds a predetermined
threshold or the difference in actual air temperature within hood
10 and a predetermined set point exceeds a predetermined threshold.
Typically, the alarm indication is delayed a prescribed period of
time if the difference between the measured effect and the
predetermined set point is due, for example, to a change caused by
the operator of the incubator. For example, a significant drop in
the skin temperature of the infant due to a change in the condition
of the infant or a significant drop in the temperature of the air
in the hood due to a failure in the air heating unit, each of which
would cause the thresholds to be exceeded, should be alarmed
immediately. In contrast, for example, opening an access door or
raising the predetermined set point for the temperature of the air
within the hood or raising the predetermined set point for the skin
temperature of the infant, each of which can cause the difference
in actual infant skin temperature and a predetermined set point to
exceed a predetermined threshold or the difference in actual air
temperature within the hood and a predetermined set point to exceed
a predetermined threshold, should not be alarmed and would, in the
absence of a delay in the alarm indication, indicate an alarm
condition. Therefore, sufficient time is provided before an alarm
condition is indicated for the incubator to stabilize when a
condition, which might otherwise indicate an alarm condition, is
created by the operator of the incubator.
Preferably, an incubator, constructed in accordance with the
present invention, includes a third temperature sensor 52, shown in
FIGS. 1 and 4, for sensing the ambient temperature outside the
incubator and controlling the delay, if any, in actuation of an
alarm indicator 54, shown in FIG. 4, when the difference between
the actual infant skin temperature and a predetermined set point
exceeds a predetermined threshold or the difference in actual air
temperature within hood 10 and a predetermined set point exceeds a
predetermined threshold. Ambient temperature can be a factor which
determines rate at which readings of skin temperature and
temperature of the air within the hood recover from readings
affected by operator induced changes. Consequently, the control
means include an alarm control module 56 which is responsive to
ambient temperature sensor 52 for controlling alarm indicator 54 to
delay actuation of the alarm indicator depending upon the ambient
temperature. For example, the lower the ambient temperature, the
longer the delay in actuation of alarm indicator 54 after an open
access door is closed.
In addition, ambient temperature sensor 52 can be used to control
the heater 32 and fan 36 speed and this is indicated in FIG. 4 by
the connections between ambient temperature sensor 52 and heater
control processing module 48 and fan control processing module 50.
Because ambient temperature can affect the temperature of the air
within hood 10, the ambient temperature, at the time an access door
is closed, can be another input to controlling heater 32 and fan
36. A range of ambient temperatures can be established by which the
power delivered to heater 32 and the speed of fan 36 can be set to
be dependent upon the particular ambient temperature at the time
the access door was closed.
While there have been described preferred embodiments of the
present invention, it should be obvious to those skilled in the art
that various modification and changes can be made without departing
from the true spirit and scope of the invention.
* * * * *