AU427405B2 - Improvements in. or relating to humidifying means - Google Patents

Description

1 3 1 34 no This invention PoCleis to tTumidifying means. In huiidifyin_ means, for use, for example for humidifying and heating air or gases which is to be breathed

by a patient undergoing artificial respiration, there is a need for a humidifying means which is capable of having

portions thereof readily sterilised, while yet enabling

adequate and accurate control of the temperature, and the

saturation of the air passed through the humidifying means.

In order to control the temperature and the humidity of the

air at any selected temperature, elaborate and sophisticated

controls are necessary, usually electronic, and of.course

such electronic apparatus may not be immersed in water, for

example, for the purpose of sterilising.

It is, therefore, an object of the present invention in one aspect to provide humidifying apparatus which is simple to construct yet effective in use, and which will at least go

a considerable.way towards meeting the foregoing desiderate or which will at least provide the public with a useful

choice.

Accordingly, in one aspect, the invention consists in apparatus for humidifying and heating air, said apparatus

comprising a container for water to be converted into

water vapour at a desired temperature, said container being adapted to be heated externally, and being adapted to be

removed from the source of heat for the purpose of

sterilisation or other purposes, cover means for said

container, adapted to provide an air space above the level of water, heat transfer means adapted to be mounted within

said container and comprising conducting means adapted to

conduct heat to evaporating surfaces in said air space

above the level of water in said container, air inlet means

adapted to admit gases into said air space, vapour transfer means adapted to transmit vapour from said air space to

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13,134/70 gases passing therethrough, gas ana vapour outlet means,

heating means separate from said container, means for

maintaining said container in thermal contact with said

heating means, and control means to sense the temperature

of the water contained in said container, the construction

and arrangement being such that, in use, on said' container

being heated by said heating means, such heat will be

transferred by conduction through said conducting means to

said evaporating surface in'said air space for transfer

into the gas.es passing through said air space so that a

mixture of water-vapour and gases can be transferred from

said air space, said heat control means being adapted to

control the temperature and, therefore, the moisture content

of such gases transferred from said air space.

We have also found that it is desirable to provide

further heating means in a tube forming part of humidifying

means and which connects the humidifying source to, for

example, a patient to whom humidified gases are to be

provided. Previously it had been thought that spiral electric heating means were necessary to maintain adequate

heating, but such heating means are complicated and expensive

to produce.

It is therefore, an object of the present

invention in a further aspect, to provide humidifying

apparatus which'will obviate or minimise the foregoing

disadvantage in a simple yet effective manner or which will

at least provide the public with a useful choice.

421, 4

13,1 34/70 One preferred form of the invention will now be

described with reference to the accompanying drawings in

which:- Figure 1 is a perspective exploded view of a

humidifying apparatus according to the invention, with a

delivery module, a humidifying module and a heater module

shown detached one from the other, Figure 2 is a plan view of the construction shown

in Figure 1 with the delivery module detached. Figure 3 is a section on the line A-A Figure 2, and,

Figure 4 is a wiring diagram for the heating and

control apparatus utilised in the humidifying apparatus

shown in Figures 1 to 3.

427, 405

13,134 no Referring to the drawings, the humidifying apparatus

shown in Figures 1 to 3, is referred as a matter of

convenience in the following into a delivery module 1, a

humidifying module 2, and a heater module 3. The delivery

module 1 comprises a cap member 4, having an inlet 5 for humidified gases e.g. air and oxygen hereinafter referred to

simply as air, and an added outlet 6, the outlet 6 being connected to a tube 7 which has within it a heating element

8 in the form of a wire hairpin, that is to say, the wire

extends from a terminal unit 9 or near to the opposite end

of the tube 7, and then returns to the terminal unit .9. The terminal unit 9 is supplied through a cable

connected to the heater module 3 as will be described further

later. The cap 4 also includes a water filler cap 11 which

may be removed for adding water to a container 12 forming

part of the humidifying module 2, as will be described further

later. The air inlet 5 of the cap 4 fits on an air outlet

13, leading from the humidifying module 2. This module

will now be described in detail. The container 12 is preferably of transparent

material has an open mouth 14, and a disc bottom 15, the disc bottom being substantially flat so as to have a

considerable bearing surface on a heating plate 16 forming

part of the heater module 3. The container 12 is provided

with lugs 17 and 18. A cover 19 is provided, having the

air outlet 13 above mentioned, and also having an air inlet-

The cover 19 is also preferably of a transparent

material so that water levels.can be examined within the

container 12, and the cover is sealed to the container 12

by an 0-ring 21. It is a feature of the invention that the

container 12 may not be over-filled without it being clearly

obvious to the attendant, since filling to the level of the

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13,1 34/70 open-mouth 14 will cause overflow into the space 22,

between the cover and the container 12, so that the container

may be readily filled with a predetermined amount of water i.e. to the level of the mouth 14. It is to be noted that the inlet 20 is an inlet for air and other gases, e.g.

added oxygen to be humidified.

Mounted within the container 12 are conducting means which, preferably, comprise a scroll 23 of preferably

metal e.g. aluminium plate of a suitable gauge, e.g. 12g.,

and having a sufficient number of turns as to provide

adequate evaporating surface area, to evaporating means or

vapour transfer means associated with the scroll.comprising,

e.g. blotting paper 24 placed in contact with the surface of the scroll in the air space.25 in the cover 19 above

the open mouth 14 of the container 12, with the blotting

paper also dipping into the water. We have been surprised by the fact that there has been adequate transfer

of heat from the floor of the container to the scroll.

The air space and the filled water space are about equal in volume in use. The cover 19 is fixed to the container 12 by the cover 19 also having lugs 26 and a ring

27 has an annulus 28 and lugs 29, the annulus 28 pressing

against the lugs 26 and the lugs 29 engaging below the

lugs 17 of the container. The ring is given a twist action in use so that spaces, not shown, between the lugs 29 can

pass over the lugs 17 for separating the cover from the

container.

This completes the container, and it will be seen from this description that the container and its cover are

of extremely simple construction which may be removed readily, and may be sterilised or otherwise dealt with without hindrance by temperature control deyices or other

features which would otherwise prevent adequate sterilisation.

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13,1 34 no As stated above, the heater module 3 includes a The heater plate 16 having a heating element 31 therein. bolts heater plate 16 is mounted on springs 32 with holding are 33, and for example, three such spring mountings provided. The purpose.of this is to ensure that there is 15 of the close contact between the plate 16 and the bottom

container 12. Normally, the plate 16 stands proud of onto the plate members 34, but when the container is pressed 35 by a 16, and the lugs 18 held onto the heater module body lugs 38 ring 36 having a flange and annulus 37 which has the body engaging with further lugs 39, forming a part of

Again rotation of the ring 36 engages or disengages the lugs 38 and 39. In order to control the temperature of the water is provided in the container 12, a temperature sensing device thus a in contact with the bottom 15 of the container, heating plate thermistor 40 is mounted in an opening in the 41. Thus 16 being insulated therefrom by a heat insulant with the the thermistor is arranged to be in close contact bottom plate 15, and we have found thst to a satisfactory in the extent this enables close control of the temperature of that water of container 12, while yet permitting removal container for sterilising purposes. Indicating lights are provided to indicate for example lights satisfactory operation of the apparatus and lens 44 42 and 43 are provided arranged to shine through a 35, there which is a transparent plate fitted in the body lights and being a green filter 45 interposed between the 44. the lens/347 A main switch 46 controls supply to the a clamp 48 which equipment and a thumb screw 47 forms part of being may be fixed to a standard to prevent the apparatus

knocked over.. 42 405

13,13 4 no Turning now to the circuit shown in Figure 4, that

C-ircuit is dividied into blocks or modules comprising a tube

heater control module generally referenced 48, a heater

-thermostat module 49, a-power control module 50 and other

exssociated equipment which will be referred to further in

-the following.

A transformer 51 supplies current at suitable 'Voltages. In particular, it supplies 24v. to the heater

%tire 8. The transformer 51 also has a 19v. supply 52, which

'will be referred to later.

The hose heater control module 48 comprises a bridge rectifier circuit having rectifiers 52 and. 72 supplying

41 silicon controlled rectifier 53. A variable resistance

54 enables control of the supply to the tube heater 8

manually, and a pre-set control 55 is a trimmer control

normally pre-set to adjust the phase shift of the supply to

a 900 phase shift, that is to say, supplying minimum supply current to the heater 8. The thermostat control module 49 is supplied from

-the 19v. tap 56 and has a bridge circuit comprising resistors 58, 59 and 60 which are fixed resistors, and in the fourth

arm of the bridge, there is the thermistor 40 together with

a calibrating variable resistor 61.* The bridge is supplied through a resistance 63 and regulated by a zener diode 62

supplying a balanced voltage feed into the differential input

of an operational amplific, 64, for example a mu A741C as made by Pair-child Semi-conductors Inc. The amplified drive

from the amplifier 64 supplies a reed relay 65, the contacts

of which are shown at 66, and will be referred to later. A

positive feed back is given through lead 66a, and resistor 67

to the non inverting input 68 of the amplifier 64 for the purpose of giving added stability resulting in a small

differential to be used in operation.

a 427, 405

4 70 1 3.1 3 The power module'50 is fed at the input voltage,

e.g. 230 volts 50Hz and the heating element referenced 31 in Figure 3 is divided into two sections 33A and 33B in the

wiring diagram. These elements are supplied through a

Triac 69 which is triggered by operation of the switch

contacts 66 which apply a signal to the gate 67 of the

Triac. It is a particular feature of the invention that

the arrangement of the reed relay 65 is such that the low voltage circuits are electrical isolated from the mains

voltage circuits of which the contacts 66 of the reed relay

form part. The resistor 70 is provided to control the.

potential applied to the gate 67 to eliminate random and spurious triggering of the Triac 69. Display units are provided to indicate operation of

the circuitry, and as mentioned above the bulbs 42 and 43 are

arranged to show through the green filter 45 when operation

is normal, thus the lights 42 and 43 form the load of a

silicon controlled rectifier 71. The operation is as follows

and refers to the positive half-cycle of the 24v line 57.

Owing to the turn-on delay of the S.C.R. 53, the potential

at the junction of diodes 52 is such that S.C.R. 71 will be turned on prior to the turn on of S.C,R. 53. If for any

reason, pin 73 is at zero potential relative to lead 74,

the S.C.B. 71 will not turn on, and, consequently, lights

42 and 43 will not be illuminated. Since the supply is

still connected through lead 75, the potential' atthe anode

of S.C;R. 71 will go positive, and through diode 76 will

charge the capacitor 77, forward biasing diode 78 which is connected through lead 79 to the inverting input 80 of the

amplifier 64. This turns the amplifier off, thus removing

power by opening contacts 66 of the reed relay Consequently, the heater does not come on under these

circumstances. The potential at pin 73 can be zero either

9 427.405

13,134/7n through the hose .ieater 8 being open circuited or not plugged in. Resistor 81 is connected in the circuit to ensure that

if there is any reasonably high resistance across the heater

terminals 9, the safety features will still operate.

Resistor 82 is provided to ensure that the safety features

will still operate, even if lamps 42 and 43 are open

circuited. Resistors 83 are provided to assist in lengthening the life of the bulbs by restricting current

surges when switching on.

In the case of over-heat conditions, when a back up thermostat 84 closes, it either open circuits the fuse

or the element section 33. This reduces power to the heater circuitry and, as a result of this, there is a circuit

through the red neon lights 86 indicating this malfunction, This circuit is now a high-resistance circuit, because the

added resistors 87 are of a high value and, consequently, the power is reduced.to transformer 51 through lead 88

because of such high resistance in series with the transformer

primary. Because of the feed through the transformer primary, the neon lights 86 remain illuminated even though the switch 84 may reopen, until either fuse 85 or the heater section 33 has been repaired.

The tube 7 is connected to auxiliary apparatus, for example, a mouthpiece or other device through which air

may be supplied to a patient undergoing artificial respiration. A suitable type of heating element for-the hair pin or hair pins 8 would be the resistance wire utilised for

electric blanket manufacture.

The energy supplied to the resistance wire 8, in the tube is, of course controlled so that in use the increase

in temperature of the air to be breathed which is

imparted by the resistance element is selected to be equal

427. 405

13.13 no to or exceed the temperature drop which occurs in the

air so heated in its passage between the output of-the

humidifying means and the patient's body, and in any event,

the temperature increase is adjusted to ensure that the

air is-delivered to the patient at no more than a maximum

desired temperature. The tube 7 is selected so that it

has reasonable flexibi.lity, having regard to the use for which it is intended, and the tube wall has a reasonable

thickness and/or insulating properties so that the

heat from the heating element is contained within the tube.

rather than being dissipated from the outer wall of the

tube. A suitable material is aplasticised PVC.

In the foregoing, it can be seen that a humidifying

apparatus is provided in which the humidifying module can

be readily detached from the heating module, for

sterilisation filling, changing of the blotting paper,

ox for other servicing or other requirements, very simply and very quickly. The safety devices result in operation

which will have a considerable regard to the patient's.

safety, the construction being such that should one. module

fail, other modules. are cut off from the electrical supply

or the electrical supply is reduced so that the patient gets

simply saturated air and other gases, e.g. oxygen at room

temperature which is preferable to his obtaining overheated

air.

421, 405

Claims (1)

13,134/70 The claims defining the invention are as follows: Apparatus for humidifying and heating air, said apparatus comprising a container for water to be converted

into water vapour of a desired temperature, said container

being adapted to be heated externally, and being adapted to be removed from the source of heat for the p-rpose of -sterilisation or other purposes, cover means for said

container adapted to provide an air space above the level of water, heat transfer means adapted to be mounted within

said-container and comprising conducting means adapted to conduct heat to evaporating surfaces in said air space above the level.of water in said container, air inlet means

adapted'to admit gases into said air space, vapour transfer

means adapted to transmit vapour from said air space to gases passing therethrough, gas and vapour outlet means,

heating means separate from said container, means for

maintaining said container in thermal contact with said heating means, and control means to sense the temperature

of the water contained in said container, the construction

and arrangement being such that, in use, on said container being heated by said heating means, such heat will be

transferred by conduction through said conducting means to said evaporating surface in said air space for transfer into

the gases passing through said air space so that a mixture ofwater vapoui and gases can be transferred from said air

space, said heat control means being adapted to control the

temperature and, therefore, the moisture content of such faseas transferred from said air space. 3 1 t.7IS 9 2. Apparatus as claimed in Claim 1, wherein said container is provided with a cover, the cover having

sufficient volume as to provide an air space above the container, the construction and arrangement being such that over filling of the container is not readily possible.

12 427, 405

13.1 34 no 3. Apparatus as clailed in Claim 1 or Claim 2, wherein

said container and said cover are of transparent material.

4. Apparatus'as claimed in any one of the preceding scroll, claims, wherein said conducting means comprise a floor the base of said scroll being adapted to rest on the from the of said container, so that heat may be conducted

floorr said container to said scroll.... j

said scroll Apparatus as claimed in Claim 4, wherein absorbent is.faced'on'one or bth surfaces with water material such as blotting paper.

6. Apparatus as claimed in any one of the preceding mounted on a claims, wherein said heating means is spring is adapted heating module, and the bottom of said container means in a to be pressed against the spring mounted heating heating manner such that there is good contact between the

means and the bottom of the container. said 7. Apparatus as claimed in Claim 6, wherein heating container is adapted to be pressed against said against .means by a ring having a flange adapted to.press lugs lugs on said container, and said ring having further module, adapted to engage lugs associated with said heating pressure. rotation of thb ring engaging lugs to cause such

8. Apparatus as claimed in Claim 7, wherein tho cover said container for said container is adapted to be held to on the by a ring having a flange adapted to engage lugs

cover, and said ring having flanges adapted to engage of said flanges associated with said container, rotation cover to ring causing engagement of said lugs to hold the the container. cover 9. Apparatus as claimed in Claim 8, wherein said adjacent is sealed to said container by an 0-ring between

walls of the cover and the container. So 427, 405

13.134 Apparatus as claimed in any une of the preceding

claims wherein a tube is provided adapted to carry gases

and vapour from said gas and vapour outlet means through

auxiliary apparatus into the body of a patient undergoing

assisted or artificial respiration said tube carrying an

insulating electrically energizable heating wire or wires

arranged longitudinally of said tube.

11. Apparatus as claimed in Claim 10 wherein heat

control means are provided to control the heat supplied

to said further heating means, said heat control means

comprising .abridge rectifyiig circuit controlling a

ilicon controlled rectifier, and having manual and pre-set

controls so that the energy supplied to said further heating

means is adjustable.

12. Apparatus as claimed in Claim 11, wherein indicating

lights are provided, adapted toindicate correct operation

of said further heating means, and a monitoring circuit is

provided adapted to extinguish said lights when the further.

heating means is open-circuited, or has a sufficiently

high resistance as to prevent normal operation.

13. Apparatup as claimed in Claim 11, wherein said

monitoring control comprises a connection to the bridge

heat control circuit connecting to the gate of a silicon

controlled rectifier or.the like device, adapted to cut off

the supply of power to the lights under conditions of

mal-operation. 14 427. 405

13.134/no 14. Apparatus as claimed'in any one of the preceding

claims, wherein a thermostat control circuit is provided

so comprising a thermostat such as a thermistor, arranged

as to have an operative part thereof firmly in contact with

the bottom of said container-, and which is heat.insulated

from said heating element, said thermistor being adapted to

control the supply of electricity to said heating element to

.control the temperature of the water in said container.

Apparatus as claimed in Claim 14 wherein said

therdstor is connected in a bridge circuit, the balancing

voltage of which is fed into the differential input of an

operational amplifier, the output from which controls a relay,

the contacts of which control the supply of electricity to

said heating means.

16. Apparatus as claimed in Claim 15 when dependent on

Claim 10 wherein the supply of power to said further heating

means is controlled through a silicon controlled rectifier the

gate of which is controlled from a phase shifting circuit

and said phase shifting circuit is connected to a bridge also

connected to a further silicon controlled rectifier which

controls a v.tage supplied to a condenser which on being

charged to a predetermined voltage operates said operational.

amplifier to control said relay so as to switch off the supply

of electricity to said heating means, the circuit connections

427, 405

13,1 34/70 and arrangement being such that should said further

heating means be open circuited or have a high resistance

such high resistance prevents turning on of said further

silicon controlled rectifier to said predetermined level.

17. Apparatus as claimed in Claim 14 or Claim 15 wherein

the control of power to said heating means is effected

by the contacts of said relay controlling the gate of a

double diode device such as a Triac, the output of which

in turn controls the voltage supplied to said heating

elements.

18. Apparatus as claimed in Claim 17 wherein a back up

thermostat is provided connected through a group of

warning lights and resistors to the source of power,

said lights being also connected to a dividing point in said.

electric heating element which divides the element into two

parts, open circuiting of a fuse in the circuit or one part of

said heating elements reducing the supply of power to the

remaining part of said heating element and cutting off the

supply of power to said further heating means.

19. Apparatus for humidifying and heating air when

constructed, arranged and operable substantially as described

with reference to the accompanying drawings.

-16- 427,405

13,1 341rio of August 1972 Dated this First -day FISHER PAYKEL LIMITED the Applicant Patent Attorneys -for SPRUSON FERGUSON

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131334 no

427.405

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