U.S. patent application number 15/152680 was filed with the patent office on 2016-09-08 for humidifier for respiratory apparatus.
The applicant listed for this patent is ResMed Limited. Invention is credited to Jack Wei CHENG, Ronald James HUBY, Paul Jan KLASEK, Alexander VIRR.
Application Number | 20160256657 15/152680 |
Document ID | / |
Family ID | 39364106 |
Filed Date | 2016-09-08 |
United States Patent
Application |
20160256657 |
Kind Code |
A1 |
KLASEK; Paul Jan ; et
al. |
September 8, 2016 |
HUMIDIFIER FOR RESPIRATORY APPARATUS
Abstract
A flexible tape heater (110) in a patient conduit (112) may be
used to heat the flow of gas in the patient conduit (112) that is
delivered to the patient mask (116). The thin, flat and extended
nature of the flexible tape heater (110) may enhance heat transfer
with the gas flow whilst also providing low impedance to the gas
flow. Heating of the gas may facilitate the desired temperature and
humidity to be reached for the gas delivered to the patient by the
respiratory apparatus. The flexible tape heater (110) may be placed
in the patient conduit (112) such that the flexible tape heater
(110) is twisted or bent about one or more of the flexible tape
heater's (110) three axes. Additionally these configurations may be
used to enhance the turbulent mixing of the water vapour produced
in the humidification chamber (114) with the gas flow.
Inventors: |
KLASEK; Paul Jan; (Sydney,
AU) ; VIRR; Alexander; (Gosford, AU) ; HUBY;
Ronald James; (Sydney, AU) ; CHENG; Jack Wei;
(Sydney, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ResMed Limited |
Bella Vista |
|
AU |
|
|
Family ID: |
39364106 |
Appl. No.: |
15/152680 |
Filed: |
May 12, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12312207 |
Apr 30, 2009 |
|
|
|
PCT/AU2007/001715 |
Nov 8, 2007 |
|
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15152680 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2205/3368 20130101;
A61M 2230/04 20130101; A61M 2205/3334 20130101; A61M 16/1075
20130101; A61M 2205/6018 20130101; A61M 16/161 20140204; A61M
16/1085 20140204; A61M 16/0003 20140204; A61M 2016/0027 20130101;
A61M 2205/14 20130101; A61M 16/0875 20130101; A61M 2205/3375
20130101; A61M 16/06 20130101; A61M 16/0057 20130101; A61M 16/0816
20130101; A61M 16/108 20140204; A61M 16/0825 20140204; A61M
2205/6054 20130101; A61M 16/16 20130101; A61M 16/109 20140204; A61M
16/1095 20140204 |
International
Class: |
A61M 16/10 20060101
A61M016/10; A61M 16/06 20060101 A61M016/06; A61M 16/08 20060101
A61M016/08; A61M 16/00 20060101 A61M016/00; A61M 16/16 20060101
A61M016/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2006 |
AU |
2006906224 |
Claims
1. A respiratory apparatus for delivering gas to a patient,
including: a PAP device generating a supply of pressurised gas to
be delivered to the patient; a humidifier for vaporizing water and
delivering water vapour to humidify the gas; a gas flow path
leading from the PAP device to the humidifier and from the
humidifier to a patient interface; and a heater in thermal contact
with one or more of the gas and the water, wherein the heater
comprises an elongate heating filament in the form of a tape.
2. A respiratory apparatus according to claim 1 wherein the gas
flow path includes a first portion between the PAP device and the
humidifier and a second portion between the humidifier and the
patient interface, and wherein the heating filament extends along
at least part of both said first and second portions of the gas
flow path.
3. A respiratory apparatus according to claim 1 wherein said
heating filament is in thermal contact with both the gas in the gas
flow path and the water in the humidifier.
4. A respiratory apparatus according to claim 1 wherein the heating
filament has an intermediate portion which is in contact with the
water in the humidifier.
5-39. (canceled)
40. A humidifier for respiratory apparatus, comprising: a first
respiratory gas passage for receiving gas from a PAP device; a
humidification chamber adapted to contain water for vaporization; a
second respiratory gas passage for delivering humidified gas from
the humidification chamber to a patient interface; and and a heater
in thermal contact with one or more of the gas and the water,
wherein the heater comprises an elongate heating filament in the
form of a tape.
41. A humidifier according to claim 40, wherein the heating
filament extends along at least part of both said first and second
respiratory gas passages.
42. A humidifier according to claim 40, wherein the heating
filament is in thermal contact with the water in the humidification
chamber.
43. A respiratory apparatus for delivering gas to a patient,
including: a PAP device generating a supply of pressurised gas to
be delivered to the patient; a gas flow path leading from the PAP
device to a patient interface; and a heater in thermal contact with
the gas within the gas flow path, wherein the heater comprises an
elongate heating filament in the form of a tape.
44-46. (canceled)
47. A respiratory apparatus for delivering gas to a patient,
including: a PAP device generating a supply of pressurised gas to
be delivered to the patient; a gas flow path leading from the PAP
device to a patient interface; and one or more sensors or control
elements for sensing or controlling properties of the gas, wherein
the sensors or control elements are located along an elongate
filament in the form of a tape in contact with the gas in the gas
flow path.
48. A humidifier for respiratory apparatus, comprising a container
for holding a body of water, apparatus for passing a respiratory
gas flow over the surface of the water to humidify the gas flow,
and a heater supported so as to preferentially heat the water
adjacent said surface.
49. A humidifier according to claim 48, wherein the heater is
supported so as to float adjacent the surface of the water.
50. A humidifier according to claim 49, wherein the heater is
supported by an inherent buoyancy of the heater.
51. A humidifier according to claim 49, wherein the heater is
supported by a buoyant support body.
52-62. (canceled)
63. A humidifier for respiratory apparatus, comprising a first
respiratory gas passage for receiving gas from a PAP device, a
humidification chamber, a second respiratory gas passage for
delivering humidified gas from the humidification chamber to a
patient interface, and a heater in thermal contact with one or more
of the gas and the water, wherein the heater comprises an elongate
heating filament extending along at least part of both said first
and second respiratory gas passages.
64. A humidifier according to claim 63, wherein the heating
filament is in thermal contact with water in the humidifier
chamber.
65. A humidifier according to claim 63, wherein the heating
filament comprises two or more separately controllable heating
zones within the respiratory apparatus.
66. (canceled)
67. (canceled)
68. A respiratory apparatus for delivering gas to a patient,
including: a PAP device generating a supply of pressurised gas to
be delivered to the patient; a humidifier for vaporizing water and
delivering water vapour to humidify the gas; a gas flow path
leading from the PAP device to the humidifier and from the
humidifier to a patient interface; and a heater in thermal contact
with one or more of the gas and the water, wherein the heater
comprises two or more controllable heating zones within the
respiratory apparatus.
69. A method of controlling one or more characteristics of a gas
being delivered by a respiratory apparatus to a patient, including
the steps of: providing a humidifier apparatus containing water;
providing a heater in contact with one or more of the gas being
provided to the patient and the water in the humidifier apparatus,
said heater having two or more controllable heater zones; and
controlling the heater zones to control the one or more
characteristics of the gas within the different zones of the
respiratory apparatus to provide gas to the patent with the desired
one or more characteristics.
70. A respiratory apparatus according to claim 69, wherein said one
or more characteristics includes one or more of temperature,
humidity, gas flow, gas velocity or pressure.
71. A method of increasing patient comfort during start-up
humidification of a gas being delivered by a respiratory apparatus
to a patient, including the steps of: providing a heater, in
contact with a gas being provided to the patient along a gas flow
path and in contact with water in a humidifier apparatus; and
commencing heating of the gas in the gas flow path and heating of
the water in the humidification apparatus, such that the patient is
initially provided with heated gas while the temperature of the
water in the humidification apparatus is being increased to the
operating temperature.
72. (canceled)
73. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to humidification and heater
arrangements used to control the humidity of breathable gases used
in all forms of respiratory apparatus ventilation systems including
invasive and non-invasive ventilation, Continuous Positive Airway
Pressure (CPAP), Bi-level therapy and treatment for sleep
disordered breathing (SDB) conditions such as Obstructive Sleep
Apnea (OSA), and for various other respiratory disorders and
diseases.
[0003] 2. Description of Related Art
[0004] Respiratory apparatus commonly have devices to alter the
humidity of the breathable gas in order to reduce drying of the
patient's airway and consequent patient discomfort and associated
complications. The use of a humidifier placed between the positive
airway pressure (PAP) device (or flow generator) and the patient
mask, produces humidified gas that minimizes drying of the nasal
mucosa and increases patient airway comfort. In addition in cooler
climates, warm air applied generally to the face area in and about
the mask, as may occur inadvertently by a leak, is more comfortable
than cold air.
[0005] Many humidifiers types are available, although the most
convenient form is one that is either integrated with or configured
to be coupled to the relevant respiratory apparatus. While passive
humidifiers can provide some relief; generally a heated humidifier
is required to provide sufficient humidity and temperature to the
air so that patient will be comfortable. Humidifiers typically
comprise a water tub having a capacity of several hundred
milliliters, a heating element for heating the water in the tub, a
control to enable the level of humidification to be varied, a gas
inlet to receive gas from the PAP device and a gas outlet adapted
to be connected to a patient conduit that delivers the humidified
pressurized gas to the patient's mask.
[0006] Typically, the heating element is incorporated in a heater
plate which sits under, and is in thermal contact with the water
tub.
[0007] The humidified air may cool on its path along the conduit
from the humidifier to the patient, leading to the phenomenon of
"rain-out", or condensation, forming on the inside of the conduit.
To counter this, it is known to additionally heat the gas being
supplied to the patient by way of a heated wire circuit inserted
into the patient conduit which supplies the humidified gas from the
humidifier to the patient's mask. Such a system is illustrated in
Mosby's Respiratory Care Equipment (7.sup.th edition, 2004, ISBN
0-323-02215-4) at page 97.
[0008] Such a heating method for the patient conduit may only
provide poor heat transfer due to the wire locating itself along
the conduit wall rather than in the main gas stream. A wire will
also only give poor turbulent mixing due to its low profile. As a
result heat transfer may be poor and the mixing of water vapour and
gas may also be poor.
[0009] Alternatively the heating wire circuit may be located in the
wall of the patient conduit. Such a system is described in U.S.
Pat. No. 6,918,389.
[0010] U.S. Pat. No. 6,918,389 describes a number of humidifier
arrangements for supplying low relative humidity, high temperature
humidified gas to the patient. Some of these arrangements include
pre- or post-heating of the gas to reduce the relative
humidity.
[0011] None of these prior art devices provides an entirely
satisfactory solution to the provision of comfortable humidified
gas to the patient, nor to the ease of construction, the hygiene
requirements and to the energy and patient comfort requirements at
startup.
SUMMARY OF THE INVENTION
[0012] The present invention aims to provide an alternative
humidifier arrangement which overcomes or ameliorates the
disadvantages of the prior art, or at least provides a useful
choice.
[0013] In one form, the invention provides a respiratory apparatus
incorporating a heater tape.
[0014] In a further form the invention provides a humidifier
incorporating a floating heater plate.
[0015] In a further form, the invention provides a humidifier
arrangement for respiratory apparatus, including an elongate
filament heater in contact with the gas path in the regions before
and after the humidification chamber. Preferably, the filament
heater in further contact with a body of water in the
humidification chamber.
[0016] Optionally, heating of the filament is divided into two or
more separately controllable zones.
[0017] In further form, the invention provides a humidity and/or
temperature or other sensing or control apparatus for use with
respiratory apparatus, including a heating filament in thermal
contact with the gas and/or water, wherein the filament is in the
form of an elongate tape. Preferably, the tape is flexible, and may
in one embodiment be passed along the bore of the patient gas
conduit, or incorporated into the conduit wall.
[0018] In a further form, the invention provides a humidifier for
use with respiratory apparatus, including a heater in contact with
water in the humidification chamber, and where the heater floats or
otherwise rises and falls with changes in the water level in the
humidification chamber.
[0019] A further form of the invention provides a method of
humidifying a gas being delivered by a respiratory apparatus to a
patient. The method includes the steps of [0020] providing a heater
in contact with the gas being provided to the patient along a gas
flow path and in contact with the water in a humidifier apparatus;
and [0021] providing two or more separately controllable heating
zones within the respiratory apparatus.
[0022] A further form of the invention provides a method of
increasing patient comfort during the start-up of humidification in
the respiratory apparatus. The method includes the steps of: [0023]
providing a heater in contact with a gas being provided to the
patient along a gas flow path and in contact with water in a
humidifier apparatus; and [0024] commencing heating of the gas in
the gas flow path and heating of the water in the humidification
apparatus, such that the patient is initially provided with heated
gas while the temperature of the water in the humidification
apparatus is being increased to the operating temperature.
[0025] Preferably, the step of heating the gas in the gas flow path
includes the step of heating of a part of the gas flow path
upstream of the humidification chamber such that passage of the
heated gas through the humidifier apparatus provides an initial
degree of humidification.
[0026] Further forms of the invention are as set out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Further preferred embodiments of the invention will now be
described with reference to the accompanying drawings, in
which:
[0028] FIG. 1 is a schematic side sectional view of the patient
conduit with a flexible tape heater in an embodiment of the present
invention;
[0029] FIG. 2 is an alternative embodiment of FIG. 1 where the
flexible tape heater is in a helical configuration;
[0030] FIG. 3: is an alternative embodiment of FIG. 2 where the
flexible tape heater is twisted about its longitudinal axis;
[0031] FIG. 4 is a schematic perspective view of another embodiment
of the flexible tape heater;
[0032] FIG. 5 is a transverse cross-sectional view of the patient
conduit showing an embodiment of the flexible tape heater connected
to the conduit wall.
[0033] FIG. 6 is another view of the connector embodiment of FIG. 5
where the wall connector is disengaged.
[0034] FIG. 7 schematically illustrates a flexible tape heater and
humidification arrangement comprising multiple zones within a
respiratory apparatus.
[0035] FIG. 8 is a schematic side sectional view of the
humidification chamber with an embodiment of the floating heater
tape;
[0036] FIG. 9 is a perspective sectional view of another embodiment
of a floating heater tape having a helical construction;
[0037] FIG. 10 is a plan view of another embodiment of a floating
heater tape wound in a horizontal spiral;
[0038] FIG. 11 is a perspective view of an embodiment of a floating
heater plate secured to a floating support grid;
[0039] FIG. 12 is side sectional view of another embodiment of FIG.
11, along the plane indicated by 12 on FIG. 11, where the floating
heater plate has a rippled or dimpled surface;
[0040] FIG. 13 is a perspective view of another embodiment of the
floating heater plate located within a buoyant ring.
[0041] FIG. 14 is a plan, cross-sectional view of another
embodiment of the floating heater plate.
[0042] FIG. 15 is a vertical, cross-sectional view of the
embodiment of FIG. 14.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Flexible Tape Heater
[0043] FIG. 1 illustrates the use of a flexible tape heater 110 as
a heating filament within a patient conduit 112 of a respiratory
apparatus. The patient conduit 112 is located between the
humidification chamber 114 and the patient interface, e.g. mask
116. The patient conduit 112 serves the purpose of conveying the
flow of gas from the humidification chamber 114 (partially shown)
to the patient mask 116 in respiratory apparatus. The
humidification chamber 114 in turn receives pressurized gas from a
PAP device (not shown) or flow generator or blower. The
humidification chamber 114 is a humidifier that vaporizes water to
humidify the gas flow to the patient.
[0044] The flexible tape heater 110 in the patient conduit 112 may
be used to heat the flow of gas in the patient conduit 112. The
thin, flat and extended nature of the flexible tape heater 110 may
enhance heat transfer with the gas flow whilst also providing low
impedance to the gas flow. Heating of the gas may facilitate the
desired temperature and humidity to be reached for the gas
delivered to the patient by the respiratory apparatus.
[0045] FIGS. 2 and 3 illustrate that the flexible tape heater 110
may be placed in the patient conduit 112 such that the flexible
tape heater 110 is twisted or bent about one or more of the
flexible tape heater's 110 three axes. FIG. 2 is a helical
configuration for the flexible tape heater 110. FIG. 3 illustrates
a longitudinal axis twist configuration for the flexible tape
heater 110.
[0046] The use of these twisted, helical or other configurations
described above increases the length of the flexible tape heater
110 in the patient conduit 112 and thus the available surface area
for heat transfer between the gas flow and the surface of the
flexible tape heater 112. Additionally these configurations can be
used to enhance the turbulent mixing of the water vapour produced
in the humidification chamber 114 with the gas flow.
[0047] In another embodiment an alternate flexible tape heater (not
shown) may be combined with the wall of the patient conduit 112 in
order to provide heating to the wall to prevent condensation.
Optionally an additional flexible tape heater 110 may be used
within the patient conduit 112 to provide increased heating to the
gas flow. In addition the patient conduit 112 may be insulated or a
heated conduit as in the prior art in order to reduce heat loss and
minimize consequent water condensation or "rain-out" within the
patient conduit 112. The insulation could be an outer sleeve or
wrapping about the patient conduit 112. The outer sleeve or
wrapping could be foam, fabric or an air space in the case of a
double walled conduit.
[0048] In an alternate embodiment the patient conduit 112 may be
formed by making a helix of the flexible tape heater 110 and
joining the edges of the flexible tape heater 110 to form the
patient conduit 112.
[0049] The flexible tape heater 110 may be sufficiently flexible so
that in use flexing of the patient conduit 112 is not restricted.
The flexibility of the flexible tape heater 110 may also be
sufficient to enable insertion and removal of the flexible tape
heater 110 within the patient conduit 112, while being sufficiently
stiff so that the flexible tape heater 110 may be inserted into the
patient conduit 112 and will support itself in a desired position
and not collapse against a wall or to one end of the patient
conduit 112. Additionally the stiffness should preferably be
sufficient so that the flexible tape heater 110 will not flutter in
the gas stream to produce an unwanted audible noise.
[0050] In situations where the flexible tape heater 110 is exposed
to water the flexibility of the flexible tape heater 110 may allow
it to shed precipitates such as Calcium Carbonate (lime scale etc)
and various other precipitates commonly found in and derived from
mineralized or "hard water". A polytetrafluroethylene (PTFE,
"Teflon") coating upon the flexible tape heater 110 may also
improve the ability to shed precipitates.
[0051] FIG. 4 illustrates one embodiment of the flexible tape
heater 110, in which the heater is a heating element 410.
[0052] In one embodiment, the heating element 410 is formed by
printed circuit techniques applied to a surface of a flexible
substrate sheet (not shown) such as kapton, silicone rubber,
all-polyimide, PTFE. Included in the printed circuit techniques
which may be used are etched foil, printing and vacuum deposition
techniques.
[0053] Another sheet of the substrate material or other suitable
sheet material is then laid upon the substrate sheet with the
heating element 410. The two sheets are then adhered or fused
together to encapsulate and/or seal the heating element 410 and
form a flexible tape heater 110. The Thermofoil.TM. range of the
type of flexible heaters by Minco of Minneapolis USA, described at
www.minco.com, are examples of commercially available strip heaters
which may be modified for use in the present application.
[0054] An alternative embodiment to produce a flexible tape heater
110 is to use a laminator, such as a twin silicon roller laminator,
to encapsulate a heating element 410, which may be in the form of
wire or ribbon, within two tapes of polycarbonate film. The
resulting tape may for example have dimensions ranging from 1 to 10
mm wide and 0.1 to 1 mm thick, although other sizes may be used.
Dimensions of about 0.2 to 0.5 mm in thickness and about 5 mm wide
are preferred for use in the patient conduit 112.
[0055] Alternative profiles or geometric structures for the
flexible tape heater 110 may include: [0056] The transverse
cross-section of the flexible tape heater may be rectangular,
elliptical or arbitrary. [0057] The surface of the flexible tape
heater 3 may be rough or smooth or dimpled. [0058] One or more
surfaces of the flexible tape heater 3 may be rippled.
[0059] In other embodiments the laminating films or encapsulating
sheets used to make the flexible tape heater 110 may be of
materials such as polyester, polypropylene or any suitable and
approved substance for respiratory medicine use. Alternatively,
multiple laminating films, sheets or coating films may be used to
create a composite strip having the desired properties whilst
retaining the desired compatibility with respiratory medicine use
for the outer surface. Other conductors may also be present between
each of these multiple layers, for example so as to form multiple
heating circuits, such as to allow multiple heating zones along the
length of the flexible tape heater 110.
[0060] A heating element 410 of wire or ribbon may have any
suitable transverse cross-section, for example circular, elongate
or rectangular. The heating element 410 may for example consist of
a resistive conductor.
[0061] The arrangement of the heating element 410 between the
laminating films or sheets may be any ordered or disordered
arrangement that increases the heat transfer of the flexible tape
heater 110 to the surrounding media, be it gas or liquid. The
heating element 410 may also have a positive thermal coefficient
(PTC) for resistance such that heating decreases as the temperature
increases towards a desired temperature.
[0062] Alternatively the heating element 410 may have a negative
thermal coefficient to allow sensing of the temperature or heat
transfer of the heating element 410 or surrounding media.
[0063] In other embodiments there may be multiple heating element
circuits (not shown) within a flexible tape heater 110. The
multiple heating elements may be connected in series or parallel.
The use of these multiple heating circuits within a flexible tape
heater 110 enables additional heating to be applied as required in
the operation of the respiratory apparatus.
[0064] In another embodiment one or more sensors 412 may be
included within the flexible tape heater 110 to monitor
characteristics of the gas flow within the respiratory apparatus
system. In one embodiment the sensor 412 may monitor air
temperature using a sensor such as a thermocouple, platinum
resistance thermometer or thermistor with its attendant signal
connection 414. It is preferred that the sensor 412 active area
(not shown) would be flat with a thickness of less than about 2 mm,
and preferably less than 1 mm.
[0065] One or more control elements 416 may be included within the
flexible tape heater 110 to control characteristics of the gas flow
within the respiratory apparatus system. The control element's
connection 418 may be separate or multiplexed with the sensor's 412
signal connection 414.
[0066] Other active and passive circuit components such as surface
mount circuit components (not shown) may also be incorporated
within the flexible tape heater 110 as necessary for the proper
functioning of the sensing, controlling or heating functions of the
flexible tape heater 110. All the circuit components described may
exist on a single layer within the flexible tape heater 110 or may
be spread over multiple layers of the flexible tape heater 110.
[0067] For the flexible tape heater 110 the circuit components all
preferably have the common physical feature that they are of a
small enough dimension to enable them to be accommodated in the
overall profile of the flexible tape heater 110 and co-located with
the heating element 410.
[0068] The range of sensor 412 and control element 416 components
that may be used is shown by way of example in the following:
[0069] Relative and absolute humidity sensors 412. [0070]
Temperature sensors 412 with a positive temperature coefficient
(PTC) or negative temperature coefficient (NTC) in the form of a
thermistor. Alternatively the PTC property may be intrinsic to the
heating element 410 so that the flexible tape heater 110 is self
limiting and the heating element 410 is also acting as a control
element 416. Thermocouples, platinum resistance thermometers and
the like may be used to produce an actual temperature value signal
for control and monitoring. [0071] Directional flow sensing of the
gas may realized by using at least two independently controlled
heating sections spaced along the flexible tape heater each
comprising a temperature sensor (e.g. thermistor). The two or more
heating sections are controlled and the temperatures sensed to
detect the direction of gas flow. [0072] Hot wire anemometry for
gas flow velocity sensing 412. In an alternate embodiment, a
portion at least of the heating element 410 may form the hot wire
element for the anemometry sensing system. In use, by way of
example, the variation in resistance of the portion of the heating
element 410 may provide a measure of gas flow velocity. [0073]
Ambient pressure sensing 412, e.g. inspiratory vs. expiratory
pressures. [0074] Two pressure sensors 412 located respectively at
thicker and thinner sections of the flexible tape heater 110 may
provide a gas flow rate indication due to the venturi tube effect.
A relationship between the outputs of the two pressure sensors 412
provides an indication of gas flow rate or velocity quantities. The
venturi tube effect being imparted respectively by the thicker and
thinner sections of the flexible tape heater 110 constricting and
dilating the gas flow path in the patient conduit 112. [0075] The
pressure sensors 412 may be any one that a person skilled in use of
electronic and mechanical pressure sensors or transducers may
select that is suitable for the purpose. The pressure sensors 412
may be configured to form a differential pressure sensor for two or
more locations within the respiratory apparatus. [0076] Control
elements 416 that make use of the output from a sensor 412, such as
for temperature, to control, by way of example a transistor/power
controller which regulates the current applied to a heating element
410. A person skilled in the art of electronic control design and
manufacture may select from any one of many widely available
techniques and devices for control. [0077] Electromagnetic
communication protocols via miniature aerials and receivers, e.g.
`Bluetooth`. Aerials for transmitting and receiving information may
be located for example in the flexible tape heater 110, the wall of
the patient conduit 112, or an active vent system (not shown), or
within the other components of a respiratory apparatus (not shown).
In another embodiment the aerials could be of a dimension as
allowed by the length of the flexible tape heater 110 or the
patient conduit 112. [0078] Power supply to a flexible tape heater
110 may be in a similar manner to the electromagnetic communication
described above. In this embodiment the transmitting and receiving
aerials or inductive coils would be adapted for power
transmission.
[0079] The flexible tape heater 110 may also comprise one or more
micro-tubes 420 to allow remote sensing away from the PAP device
and/or humidification chamber 114. The micro-tubes may for example
provide pressure, noise/snore and/or cardiological signal sensing.
By way of example the micro-tubes may be attached to the side of
the flexible tape heater 110 or encapsulated within by one of the
manners described above. The micro-tube 420 may have diaphragm 421
at its end that may act as a pressure sensor. The micro-tube's 420
length serving to communicate the mechanical/acoustic pressure
signal when the micro-tube 420 wall is comparatively stiff compared
with the diaphragm 421. In yet another embodiment a portion of the
micro-tube 420 wall (not shown) may serve as a diaphragm for
pressure sensing. The use of a micro-tube 420 for pressure signal
communication or as part of the pressure sensor may provide the
benefit of avoiding flow noise within the patient conduit 112 and
other areas in the respiratory apparatus.
[0080] In an alternate embodiment the micro-tube 420 may be
configured as a differential pressure sensor for two or more
locations within the respiratory apparatus. The configuration
chosen for one or more micro-tubes 420 may be any one that a person
skilled in the use of mechanical and electronic pressure sensors
may select that is suitable for the purpose.
[0081] In FIG. 4 a tape connector 422 is shown joining two flexible
tape heaters 110, 110' to each other. The joining of a number of
flexible tape heaters 110 may be to allow electrical and other
sensing and controlling communications between the flexible tape
heaters 110 as well as power supply. The joining may also offer a
way of securing in position a flexible tape heater 110 within a
respiratory apparatus. The tape connector 422 may be any one of the
connectors widely available or readily designed and manufactured by
a person skilled in the art such that the tape connector 422 is
adapted to allow the various embodiments of the flexible tape
heater to operate from one flexible tape heater 110 to another
flexible tape heater 110'.
[0082] FIGS. 5 and 6 illustrate a wall connector 510, 512 which
allows the flexible tape heater 110 to attach to the wall 514 of
the patient conduit 112 or other suitable internal wall of the
respiratory apparatus. The attachment to the wall may be for
securing the position of the flexible tape heater 110 or to allow
the flexible tape heater 110 to operate with another flexible tape
heater 110' and/or to a base unit 716, described below with
reference to FIG. 7. Where the wall may have internal electrical
wires (not shown), electro-optical fibres (not shown) and
mechanical tubes (not shown) to allow a number of flexible tape
heaters 110 to operate with each other or the base unit 716 (FIG.
7). The wall connector 510, 512 preferably comprises of compatible
male 510 and female 512 connectors which may make an electrical,
communications and/or mechanical connection between the flexible
tape heater 110 and the wall 514. FIG. 5 shows the male 510 and
female 512 wall connectors as a ball and socket arrangement in an
engaged configuration, FIG. 6 shows the male 510 and female 512
wall connectors separated. The male 510 and female 512 connectors
may be interchangeable in position and engaging action with a
mixture of male or female components as a person skilled in the art
of connectors may design and manufacture. Preferably the connectors
510, 512 reversibly lock the flexible tape heater 110 in position
on the conduit wall 514 such that they may also be disengaged. The
connectors 510, 512 may be used at any location along or around a
wall of the respiratory apparatus.
[0083] The connectors described with reference to FIGS. 4, 5 and 6
may also have Identification-Communication-Memory (ICM) chips 424
as illustrated in FIG. 4. The ICM chips 424 allow the
identification and communication of the operating parameters of a
flexible tape heater 110 to another flexible tape heater 110'
and/or to a base unit 716 described below with reference to FIG. 7.
For example, the flexible tape heater 110 may communicate regarding
itself as well as detect and report regarding other components that
are attached to the respiratory apparatus such as the patient mask
116 type or the patient conduit 112 type or an active vent system
(not shown). The information thus gathered by the flexible tape
heater 110 may then be sent to the base unit 716 (FIG. 7). The ICM
chip 424 system may consist of in part a radio frequency
identification chip (RFID) to store and communicate the heating
element 410, sensor 412 and control element 416 identification and
operating parameters. The base unit 716 (FIG. 7) may have a
capability to communicate with the RFID chip and adjust its
operation and control of the respiratory apparatus accordingly.
Such a system has been described in the Australian Patent
Application No. 2005907200 "Identification System and Method for
Mask and Ventilator Components." the contents of which are
incorporated herein by reference. The communication may also be
used to control an active vent system (not shown).
[0084] The heating element 410, sensing 412 and control element 416
components described above may be located anywhere along a flexible
tape heater 110 or distributed or divided amongst a number of
flexible tape heaters 110 as appropriate to their function. For
example a thermocouple temperature sensor 412 may be located on a
flexible tape heater 110 at the end adjacent the patient mask 116
to enable closed loop temperature control based on the gas
temperature delivered to the patient mask 116.
[0085] In an alternative embodiment a temperature sensor (not
shown) may be located in or in the vicinity of the patient mask 116
but separated from the flexible tape heater 110. However the
temperature sensor may communicate with the flexible tape heater
110 in one of the manners described above to enable closed loop
control of the temperature of the gas delivered to the patient.
[0086] In yet another alternative embodiment different flexible
tape heaters 110 may be used for sensing, monitoring and/or
controlling the system. Such flexible tape heaters may not include
a heating element 410, but instead incorporate one or more other
circuit components for sensing 412 and controlling 416. For example
a respiratory apparatus may contain two or more flexible tapes, one
or more undertaking a heating function and one or more undertaking
a sensing and/or controlling function.
[0087] The sensing and control methods and devices described above
allow closed loop control to be used for optimizing gas delivery to
the patient mask 116 so that it is at the desired temperature and
humidity. Alternatively a simple open loop system may be used where
driving voltages or currents for a heating element 410 may be, by
way of an example, from 0.1 to 50 v direct current or the power
equivalent for alternating current, for example from 0.1 to 50 W.
The sensing and control may also control the level of intentional
gas leak from an active vent system, depending on the amount of
pressure being supplied. For example as the ventilator pressure
increases the active vent system may be controlled to reduce the
level of its intentional leak to an acceptable level.
[0088] Additionally, the sensors 412 and/or control elements 416
may be used for compliance or statistical data gathering.
[0089] Furthermore, the different components of the flexible tape
heater 110 embodiments described herein may be used as stand alone
components in a respiratory apparatus not employing a humidifier
114, and such arrangements are within the scope of the
invention.
[0090] A flexible tape heater 110 as thus described would be easily
removable from the patient conduit 112 or other sections of a
respiratory apparatus to enable cleaning, maintenance or
replacement. The flexible tape heater 110 also offers efficient
heating with the option of sensing 412 and control element 416
components being easily incorporated into the flexible tape heater
110.
Multiple Zone Heating.
[0091] FIG. 7 illustrates a respiratory apparatus which makes use
of three flexible tape heaters 110, 110', 110'' that are of the
same general construction and use as the flexible tape heater 110
embodiments described above.
[0092] A PAP device 710 supplies gas supplied from an ambient
temperature supply which may be the air in the room or augmented or
replaced by a specific gas supply such as oxygen. A flexible tape
heater 110'' is located in a humidifier conduit 712 which connects
the PAP device 710 with the humidification chamber 114. The
flexible tape heater 110'' located in the humidifier conduit 712
may serve to pre-heat the gas entering the humidification chamber
114 as well as providing any one of the sensing or controlling
features described in the above embodiments of the flexible tape
heater 110.
[0093] The humidifier conduit 712 may be a tube or a short
connecting fixture forming a short conduit. In addition the
humidifier conduit 712 may be rigid or flexible as required for the
operation of the PAP device 710 with the humidification chamber 114
and/or the operation of the flexible tape heater 110''. The
flexible tape heater 110'' is connected to a controller/power
supply 714. The controller/power supply 714 supplies power and
communication with any heating element 410, sensor 412 or control
element 416 of the flexible tape heater 110''.
[0094] Optionally the controller/power supply 714 may be combined
with the PAP device 710 to form a base unit 716.
[0095] The flexible tape heater 110'' located in the humidifier
conduit 712 is connected with a second flexible tape heater 110'
located within the humidification chamber 114. The connection
between the two flexible tape heaters 110', 110'' may be by the
tape connector 422 described above with respect to FIG. 4. The
flexible tape heater 110' located in the humidification chamber 114
receiving its connection to the controller/power supply 714 via the
flexible tape heater 110'' located in the humidifier conduit
712.
[0096] In an alternate embodiment the flexible tape heater 110'
located in the humidification chamber 114 may be connected to the
controller/power supply 714 via a wall connector 510, 512 as
described above with respect to FIG. 5 and located within the
humidification chamber 114. The wall connector 512 being connected
to appropriate communication cables and/or tubes (not shown) to the
controller/power supply 714.
[0097] The flexible tape heater 110' located in the humidification
chamber 114 may be wholly or partially within a liquid water 718
body of the humidification chamber 144. The water 718 is provided
as a source of water vapour for the humidification of gas passing
through the humidification chamber 114. The flexible tape heater
110' may heat the water in the humidification chamber 114 via the
use of its heating element 410. The flexible tape heater 110' may
also provide any one of the sensing or controlling features
described in the above embodiments of the flexible tape heater 110
for the humidification chamber 114.
[0098] In an alternate embodiment the flexible tape heater's 110'
may be located wholly above the water surface 720. In such a
position water vaporization may be imparted via radiation heating
and/or convective heating by the flexible tape heater 110' as well
as heating the gas within the humidification chamber 114.
[0099] A flexible tape heater 110 may also be located in the
patient conduit 112 as described above. The flexible tape heater
110 in the patient conduit 112 may be connected via a tape
connector 422' to the flexible tape heater 110'' in the
humidification chamber 114 and thence to the controller/power
supply 714 as described above. In an alternate embodiment the
flexible tape heater 110 in the patient conduit 112 may be
connected with the controller/power supply 714 via a wall connector
510, 512 (as described above with respect to FIG. 5) located within
the patient conduit 112.
[0100] The flexible tape heater 110 may provide additional heating
of the humidified gas in the patient conduit 112 via the use of its
heating element 410. The flexible tape heater 110 may also provide
any one of the sensing or controlling features described in the
above embodiments of the flexible tape heater 110 for the patient
conduit 112.
[0101] The flexible tape heaters 110, 110', 110'' thus may comprise
multiple heating circuits, so that each of the three heater zones
may be operated independently or in concert. Where the humidifier
conduit 712, the humidification chamber 114 and the patient conduit
112 each respectively form a heating, controlling and sensing zone
within a respiratory apparatus. The controller/power supply 714
being able to individually and collectively heat, control and sense
within each zone. In yet another embodiment a flexible tape heater
110 may have multiple heating elements 410 along it so that
temperature and humidity profiles are possible along a flexible
tape heater 110 and the regions it occupies in a respiratory
apparatus.
[0102] In an alternative embodiment one or more of the flexible
tape heaters 110, 110', 110'' may not be of the type described
above but another suitable heating element. For example, the
flexible tape heater 110'' within the humidifier conduit 712 may be
formed as a simple wire heater or other conventional heater type
rather than as a flexible tape heater 110 of the type described
herein.
[0103] The use of the arrangements described above may give the
advantages of: [0104] A single inter-connected heating, controlling
and sensing system which may be internal to the patient conduit
712, the humidification chamber 114 and the patient conduit 112;
[0105] The complete heater, sensor and control system may be
removed simply as one connected unit for cleaning, maintenance or
replacement; [0106] The interconnection of the flexible tape
heaters 110, 110', 110'' and the zones facilitates a high degree of
closed loop control for temperature and humidity of the gas
delivered to the patient. [0107] The ability to sense temperature
and humidity at different sections of the patient conduit 112 in
order to control the condensation at various sections in the
patient conduit 112. [0108] The different components of the heater
and/or sensing/control system may be used in combination or
separately within a conventional humidifier and an associated
respiratory apparatus. For example the flexible tape heater 110 may
also be used to heat the patient conduit 112 together with a
conventional humidifier with a heating base plate. Alternatively a
flexible tape heater 110' may be used to heat the body of water 718
within the humidification chamber 114 together with a heated or
insulated wall patient conduit 112, as described above. [0109] The
ability to install multiple heaters in parallel and series at any
location of the respiratory apparatus. The multiple heaters may
exist as multiple flexible tape heaters 110 and/or multiple heating
elements 410 within a flexible tape heater 110. This may allow, for
example, `super` heating during the beginning operation of the
respiratory apparatus when the body of water 718 requires time to
reach the desired temperature. The temporary extra heating of the
air with multiple heaters would increase the capacity of the air to
take up the cooler water. This may be controlled or profiled in
response to the temperature of the water in the body of water 718
to provide the appropriate level of humidity.
[0110] For the respiratory apparatus the placement of the three
flexible tape heaters 110, 110', 110'' and the timing and sequence
of their use allows the gas comfort features of temperature and
humidity to be managed by allowing the separate, staggered
production of: [0111] Heating of an ambient gas that has a low
absolute humidity. [0112] Water vaporization. [0113] Heating of the
gas that has an increased absolute humidity (after the
humidification chamber 114).
[0114] The following example of use illustrates an advantage in the
operation of the preferred embodiment of FIG. 7.
[0115] Particularly in winter and colder climates the patient
respiratory gas requires increases in the supplied levels of gas
temperature and humidity. In the preferred embodiment the aim of
the system from a cold start-up is to rapidly deliver warm gas
initially and then increase humidity over time as the humidifier
warms up. This approach allows the patient to receive comfortable
warm air closely followed by an increasing relative humidity,
before there is an onset of any adverse symptoms of low humidity
respiratory assistance.
[0116] For a cold start in a winter climate the three heater system
of FIG. 7 may thus operate in the following manner for the
preferred embodiment. Firstly, the cool ambient temperature gas
from the PAP device 710 is warmed by using the flexible tape heater
110'' in the humidifier conduit 712 with optional additional
heating being provided by the flexible tape heater in the patient
conduit 110. This initially provides warm but relatively dry air to
the patient. However, it is noted that some humidity will be taken
up by the warmed gas passing over the water 718 in the humidifier
114.
[0117] As the warmed gas flow begins to absorb appreciable water
vapour from the unheated water 718 in the humidification chamber
114, the flexible tape heater 110 in the patient conduit 112 may
begin or increase its heating in order to prevent `rain-out`
condensation in the patient conduit 112. The initial warming of the
gas with the flexible tape heater 110'' in the humidifier conduit
712 has the advantage of immediately commencing a degree of
humidification, as a simple "pass-over" operation, whilst the
flexible tape heater 110' in the humidification chamber 114 is
still warming up the water. The heat for vaporization in the simple
"pass-over" operation being provided by the heated gas from the
humidifier conduit 712.
[0118] As the flexible tape heater 110' in the humidification
chamber 114 begins to warm the water surface and rapidly increase
the absolute humidity in the gas passing through the humidification
chamber 114 to achieve the desired level of humidification, the
flexible tape heater 110 in the patient conduit 112 would adjust
its heating to maintain the absolute humidity by preventing
condensation in the patient conduit 112. The flexible tape heater
110 may also serve to maintain the desired gas temperature in the
patient conduit 112. The flexible tape heater 110'' in the
humidifier conduit 712 may have a heating profile based on the
level of heating of the body of water 718 in the humidification
chamber 114, the heating profile being the rate of heating of the
gas flow in a period of time that can be provided by changing the
power to the flexible tape heater 110'' in the humidifier conduit
712 or the structural configuration of the flexible tape heater
110''. In some circumstances there may be more effective control of
the humidity by controlling the gas temperature as opposed to
heating the water.
[0119] An additional advantage of this operational embodiment is
that it may allow reduced power consumption at humidification start
up so that the respiratory apparatus may be able to be operated by
direct current power supply or a portable power supply. Also,
satisfactory operation may still be obtained when two or more
flexible tape heaters 110 are multiplexed, one flexible tape heater
110 is operated at a time but there is cycling in operation between
two or more flexible tape heaters 110.
[0120] In addition the various flexible tape heater 110
configurations may be used to provide zones of differing gas flow
and/or acoustic properties along the patient conduit 112 or the
respiratory apparatus as a whole, FIG. 7.
[0121] It may be desirable to modify the acoustic impedance
properties of the patient conduit 112 using the flexible tape
heater 110 for the following: [0122] the generation or reduction in
white noise. (broad frequency spectrum noise); [0123] the damping
or filtering of a particular acoustic noise frequency component/s,
e.g. structure-borne or air-borne PAP device tonal noise; [0124]
enhancement of the propagation of patient respiratory acoustic
signals through the patient conduit 112 and to the base unit 716
for monitoring and diagnosis.
[0125] The alteration of acoustic impedance properties using the
flexible tape heater 110 may be achieved by the choice of the
materials making up the flexible tape heater 110 and by the
configurations described above for the flexible tape heater 110 in
the patient conduit 112, and additionally as shown in FIGS. 1 to
3.
Floating Heater
[0126] In FIG. 8 a humidification chamber 114 arrangement utilizing
a floating heater tape 810 is illustrated. The floating heater tape
810 floats in the body of water 718 in the humidification chamber
114 such that a substantial portion of the floating heater tape 810
is immersed but is still adjacent to the water surface 720 so as to
heat preferentially that part of the water near the surface
720.
[0127] The floating heater tape 810 may comprise a length of
flexible tape heater 110 of similar construction and use to that
discussed in the above embodiments. This has the significant
advantage that the heater for both applications is robust to gas or
water immersion, since a floating heater tape 810 may be partially
immersed in water during the respiratory apparatus' operation,
either unintentionally as the body of water 718 increases or
decreases in volume or by tilting of the humidification chamber
114, or intentionally to maintain the temperature of the water
vapour in the gas of the humidification chamber 114.
[0128] The respective upstream and downstream ends of the floating
heater tape 810, respectively located in the humidifier conduit 712
and the patient conduit 112, may have tape connectors 422, 422' so
that the floating tape heater 810 may connect with other flexible
tape heaters 110 as described in the above embodiments for the
respiratory apparatus with respect to FIG. 7. For an alternate
embodiment, wall connectors 510, 512 may be used instead of the
tape connectors 422, as described above with respect to FIGS. 5 and
6.
[0129] The floating heater tape 810 may be adapted to float either
by the inherent buoyancy of the floating heater tape 810, by
surface tension effects, or may be supported in a manner which
keeps the heater near the water surface regardless of changes in
the water level. Inherent buoyancy may be obtained by choice of
materials or structure, for example voids (not shown) within the
floating heater tape 810. A support grid (not shown) may be used to
support the floating tape heater near or at the water surface 710.
The support grid may also be used as an aid in general positioning
of the flexible heater tape 810 within the humidification chamber
114.
[0130] FIGS. 9 and 10 illustrate a number of exemplary embodiments
that the floating heater tape 810 may have within the
humidification chamber 114. FIG. 9 illustrates a floating heater
tape 810 which has been wound into a helix. In this embodiment the
floating heater tape 810 may intrinsically float such that a
sufficient portion of the floating heater tape 810 is immersed in
the body of water 718. FIG. 10 illustrates another embodiment where
the floating heater tape 810 may be wound in a horizontal
spiral.
[0131] The preceding embodiments for the floating heater tape 810
represent a number of defined configurations whereas in use the
floating heater tape 810 may assume a combination of the defined or
undefined configurations. For example a long helix which continues
as a spiral, combining FIGS. 9 and 10. Additionally, the floating
tape heater 810 configuration may be spiraled or otherwise formed
so as to be partly immersed in the body of water 718 so that it
heats both the water near the air and the air near the water, in
the proximity of the water surface 720, to produce a stratified
zone of heat to improve water uptake into the gas for
humidification.
Floating Heater Plate
[0132] FIG. 11 illustrates a floating heater plate 1110 constructed
in a similar manner to the floating heater tape 810, described
above, but with a plate form rather than a tape form. The floating
heater plate 1110 is shown as a circular disc; however it is to be
appreciated that the floating heater plate may be formed in any
desired shape.
[0133] The floating heater plate 1110 may be secured to a floating
support grid 1112 or other buoyancy device (not shown), for example
a buoyant plastics material. The floating support grid 1112 may
facilitate the floating heater plate 1110 to be positioned just
below the water surface 720 so as to allow sufficient contact with
the water to cause vaporization.
[0134] FIG. 12 shows another embodiment of the floating plate
heater 1110 where the plate form is rippled or dimpled in a regular
or irregular fashion. The rippling and/or dimpling provides valleys
which may allow pockets of water to accumulate on the upper surface
of the floating heater plate 1110. In this embodiment, the floating
heater plate 1110 may be naturally buoyant, so that floating heater
plate 1110 may float without the need for a support grid 1112 or
other buoyancy device.
[0135] In an alternative embodiment shown in FIG. 13, the floating
heater plate 1110 is located within a buoyant ring 1310 that allows
a shallow bath of water (not shown) to be present above floating
heater plate 1110. Apertures 1312 through the buoyant ring 1310
allow water to flow onto the upper surface of the floating heater
plate 1110 so that a shallow bath of water is formed. The buoyant
ring 1310 with the floating heater plate 1110 floats at the water
surface 720 of the body of water 718 of a humidification chamber
114. Connections 422, 422', 510 to the floating heater plate 1110
are made through the buoyant ring 1310.
[0136] FIG. 14 shows another embodiment where the floating heater
plate 1110 may also be additionally supported and positioned within
the humidification chamber 114 by the use of one or more suspension
arms 1410. FIG. 14 is a cross-sectional plan view of the
humidification chamber 114 with the floating heater plate 1110. The
suspension arms 1410 may be flexibly attached to a suspension line
1412, located where a wall 1414 and a ceiling (not shown) of the
humidification chamber 114 meet. The suspension arms 1410 project
generally downwards to the floating heater plate 1110. The
suspension arms 1410 flexibly attach 1416 preferably to the
circumference of a buoyant float 1418 which supports the floating
heater plate 1110. Alternatively the suspension arms 1410 may
flexibly attach to any other convenient point upon the floating
heater plate 1110 or the buoyant float 1418. The suspension arms
1410 may individually comprise of semi-rigid plastic material in a
sheet, bar or tape shape. Alternatively the suspension arms 1410
may comprise of lengths of wire or plastic filaments or the same
materials in a helical or spring arrangement to form a suspension
arm.
[0137] A thermal sensor 1420 and a thermal protection switch 1422
is located with the floating heater plate 1110 or may be
incorporated within the floating heater plate 1110 in the manner of
the sensor 412 and the control element 416 described with respect
to the flexible tape heater 110 embodiments above.
[0138] The one or more suspension arms 1410 may support the
connections 422, 422', 510 between the floating heater plate 1110,
the thermal sensor 1420, the thermal protection switch 1422 and the
controller/power supply 714.
[0139] A position post 1424 is located axially through the center
of the floating heater plate 1110 and the buoyant float 1418. The
position post 1424 may guide the floating heater plate 1110 as well
as providing position information about the water surface 720 or
the floating heater plate 1110 to the controller/power supply
714.
[0140] FIG. 15 illustrates a vertical cross-sectional view of the
FIG. 14 embodiment. This embodiment differs from that of FIG. 7 in
that the PAP device 710 and controller/power supply 714 are located
as one top unit 1510 on top of the humidification chamber 114. In
this configuration the gas flow from the PAP device 710 is directed
(as indicated by the arrows) by two humidifier conduits 712 onto
the water surface 720. However in alternate embodiments one or more
humidifier conduits 712 may be used in a similar manner. Humidified
gas exiting the humidification chamber 114 is via the patient
conduit 112 as shown.
[0141] In use the suspension arms 1410 with the buoyant float 1418
allow the floating heater plate 1110 to rise and fall with the
water surface 720. In the embodiment illustrated in FIGS. 14 and 15
the suspension arms 1410 operate such that the floating heat plate
1110 rotates (or twists) about an axis corresponding to the
location of the position post 1424. In the alternative embodiments
of the suspension arms 1410 described above the floating heater
plate 1110 may only move vertically without rotation. The
suspension arms 1410 with the position post 1424 maintain the
desired position of the floating plate heater 1110 with respect to
the water surface 720 within the humidification chamber 114.
Preferably the depth of water above the floating heater plate may
be from 1 to 5 mm and more preferably 3 to 4 mm. The operation of
the suspension arms 1410 with the position post 1424 may continue
even if the humidification chamber is tilted up to 20 degrees from
the vertical. This offers the advantage that the floating heater
plate 1110 may continue to be at least partially immersed in water
so as to vaporize sufficient water for humidification when the
humidification chamber is tilted from the vertical at large
angles.
[0142] In yet another embodiment the suspension arms 1410 may
project from the side walls 1414 of the humidification chamber 114
and attach to the floating heater plate 1110 or buoyant float 1418
as described above. In another alternate embodiment the position
post 1424 may be absent, the suspension arms 1410 providing the
function of the position post 1424.
[0143] The above described embodiments of the floating heater tape
810 and floating heater plate 1110 may be more power efficient in
generating water vapour, and more effective in quickly achieving
the desired water surface temperature for humidification at
start-up of the apparatus. This may be due to the effective heat
transfer to the water surrounding the heating element 410. In
addition, the water adjacent to the water surface 720 is heated
preferentially for vaporization rather than heating the whole body
of water 718 from the bottom up of the humidification chamber 114
as in the case of a heater being located at the bottom of the body
of water 718.
[0144] Although the invention has been herein shown and described
in what is conceived to be the most practical and preferred
embodiments, it is recognized that departures can be made within
the scope of the invention, which is not to be limited to the
details described herein but is to be accorded the full scope of
the appended claims so as to embrace any and all equivalent
assemblies, devices and apparatus.
[0145] In this specification, the word "comprising" is to be
understood in its "open" sense, that is, in the sense of
"including", and thus not limited to its "closed" sense, that is
the sense of "consisting only of". A corresponding meaning is to be
attributed to the corresponding words "comprise, comprised and
comprises where they appear.
[0146] It will further be understood that any reference herein to
known prior art does not, unless the contrary indication appears,
constitute an admission that such prior art is commonly known by
those skilled in the art to which the invention relates.
* * * * *
References