Patent Description:
The present invention relates generally to electrical heaters and particularly to integrated electric heaters for use in heating fluids. More particularly, the present invention relates to in-molded heaters for heating fluids within containers. The electrical heater may be used in a range of devices including, for example, humidification devices, electric jugs, other fluid warming containers, fans and the like. The heater may be used in a respiratory humidification device.

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 and the patient mask produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort.

Many humidifier types have been proposed, including humidifiers that are either integrated with, or configured to be coupled to, the respiratory apparatus. Independent humidifiers have also been proposed. While passive humidifiers can provide some relief, generally a heated humidifier is required to provide sufficient humidity and temperature to the air so that the patient will be comfortable.

Humidifiers typically comprise a water tub having a capacity of several hundred millilitres, 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 gas conduit that delivers the humidified, pressurized flow of breathable gas to the patient's mask.

Commonly, humidifier tubs are attached either directly to a humidifier control base or to a system base, or cradle, that facilitates the correct assembly of the PAP device with the humidifier. Generally, the humidifier control base or the system base, or cradle, comprises a heating plate that contacts the base of the humidifier tub to facilitate heating of the water within the humidifier tub.

<FIG> depicts a prior art humidifier device <NUM> with a control base <NUM>, which comprises a heater plate <NUM>. A water tub <NUM> comprising an air inlet <NUM>, an air outlet <NUM> and a heat conductive tub base <NUM>, is adapted to sit upon the heater plate <NUM> of the control base <NUM>. The base systems typically comprise a spring loaded heater plate <NUM> on to which the water tub <NUM> is attached. The spring loaded heater plate <NUM> ensures good thermal contact with the tub base <NUM> of the water tub <NUM>, although some thermal losses occur between the heater plate <NUM> and the water tub <NUM>. For example, the Fisher & Paykel HC200™ system and the Respironics RemStar™ heated humidifier have spring loaded heater plates. However, such spring loaded heater plates can provide a friction force against insertion of the water tub, which may make installation of the water tub difficult for some users, especially older or frail users.

The water in the water tub <NUM> is heated via thermal conduction between the heater plate <NUM> and the tub base <NUM> of the water tub <NUM>. The tub base <NUM> is commonly formed of aluminium or stainless steel. The tub base <NUM> is generally formed as a separate component of the water tub <NUM> and sealingly coupled to the upper portion of the water tub, for example using adhesives or a stamped rolled edge. For example, see Applicant's <CIT>. This results in multiple components that require assembly during manufacture of the humidifier and increase the size and weight of the device. Furthermore, the assembled construction provides an increased risk of leakage between the sealed components.

Other forms of heaters are known but have rarely, or not at all, been used in commercially available respiratory humidifiers to date. One example is induction heaters as described in Applicant's <CIT>. Flexible layered heaters are also known and have been used in a range of applications including defogging mirrors, screens for televisions, video cameras & mobile phones and blanket heaters. For example, printed thick film heating elements that comprise conductive and resistive inks, such as carbon ink or silver ink, have been used. <FIG> shows the general construction of a printed thick film heating element <NUM> comprising a first film substrate layer <NUM> with a conductive and resistive inks layer <NUM> printed thereon and then a second film <NUM>. The two films <NUM>, <NUM> are laminated together with a pressure sensitive adhesive sandwiching the ink layer <NUM>. The films are typically thermoplastic or thermoset polymers such as polyester or polyimide. Such flexible layered heaters may be attached to the required surfaces to provide the required heating function.

Many products are provided with labels attached to their surfaces. Labels are commonly used to provide decorative designs, branding, texture, instructions, warnings and other such graphical material to products. There are many different forms of product labels and techniques for attaching such labels to objects. In-mold labeling is a method used to attach the labels to the surface of a molded object wherein the label is attached within the wall of a molded object. In-mold labeling is used with blow molded and injection molded products such as toys, containers for cleaning products, motor oil, beverages and the like. The label is printed onto a film using known printing techniques such as flexography, offset, screen or hot stamping printing. <CIT>) describes a process for in-mold labeling.

<FIG> illustrates the general construction of an in-mold label <NUM> where a graphic <NUM> is printed upon a film <NUM>. The formed printed film <NUM>, <NUM> is placed and held within an open mold with the film <NUM> surface adjacent to the mold. The mold is closed and the hot mold resin <NUM>, such as a plastic polymer, is extruded or injected into the mold to form the desired object shape with an integrally molded label. The film <NUM> is generally comprised of a polypropylene or polyethylene copolymer that comprises a heat-activated adhesive that facilitates attachment of the printed film within the wall of the molded object.

Conventional humidifiers have the disadvantage of many different components that require assembly and increase weight. The assembly of different components and the use of heater plates and tubs with conductive base plates provides an increased risk of water leakage. The present invention seeks to address one or more of these disadvantages or at least provide a reasonable alternative.

<CIT> relates to a modular fluid heating apparatus which may be assembled from a plurality of modular heating components. Each modular heating component includes a first molded section defining a first opening therethrough and a second molded section defining a second opening therethrough. The first and second openings are aligned to form a fluid tight passage through the modular heating component. A resistance heating element is secured between the first and second molded sections in the enclosed area. The resistance heating element includes a supporting substrate having a first surface thereon and an electrical resistance heating material fastened to the first surface of the supporting substrate. The passages may be aligned <NUM>° to direct the fluid passing through the fluid heating apparatus into at least a portion of the collection area.

An aspect of the invention is directed to a heater element that provides safe and effective heat. Another aspect of the invention provides a heater element that is molded within a container during manufacture. A further aspect relates to an in-mold heater element comprising a polymer film having electrically conductive ink printed upon at least one surface. In another aspect the electrically conductive ink is carbon and/or silver ink. In a further aspect the polymer film is a polyester, polyimide, polycarbonate or polypropylene.

Another aspect is related to a heater element comprising a polymer film having an electrically conductive ink printed upon at least one surface wherein the polymer film is molded into at last one surface of the molded object. In an additional aspect, the heater element comprises electrical connectors fastened to the electrically conductive ink to provide power and/or control signals. In a further aspect, the heater element comprises sensors such as a temperature sensor for controlling the temperature of the heater element. Yet another aspect includes a thermal fuse to provide a protection system to protect against over heating of the heater element.

Another aspect of the invention relates to a method for manufacturing an object comprising an in-molded heater element. In a further aspect the object is formed by injection molding. In an alternative aspect the object is formed by extrusion molding.

Another aspect of the invention relates to a method for manufacturing a humidifier comprising an in-mold heater element. In a further aspect the humidifier has a reduced number of parts and/or simple assembly process.

Yet another aspect of the invention relates to a respiratory humidifier comprising a heater formed from an in-mold heater element.

Still another aspect of the invention relates to an electrical heater having simple electrical connections.

According to one sample embodiment of the invention, a heater element comprises a first polymer film having an electrically conductive circuit provided upon a surface. The first polymer film is electrically insulating and is molded into at least one surface of a molded object.

According to another sample embodiment of the invention, a method of manufacturing an in-mold heater element comprises i) providing an electrically conductive circuit on a first surface of a first polymer film; ii) placing the first polymer film including the electrically conductive circuit in a mold such that a second surface of the first polymer film opposite the first surface is adjacent the mold; and iii) insert molding resin to form a predetermined molded shape such that the first polymer film is incorporated within at least one surface of the molded shape.

According to a further sample embodiment of the invention, a humidifier comprises a tub configured to contain a supply of water; and a heater comprising a first polymer film having an electrically conductive circuit provided upon a surface. The first polymer film is electrically insulating and the tub is formed of molded resin and the heater is molded at least partially within the resin.

According to a still further sample embodiment of the invention, a method of humidifying a flow of pressurized breathable gas comprises passing the flow of pressurized breathable gas over a supply of water contained in a tub, wherein the tub is formed of molded resin and a heater comprising a first polymer film having an electrically conductive circuit on a first surface is molded at least partially within the resin.

According to yet another sample embodiment of the invention, a molded object comprises a heater element, the heater element comprising a first polymer film having an electrically conductive circuit upon a surface. The first polymer film is molded into at least one surface of the molded object. A control system configured to control a temperature of the heater element.

Other aspects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of this invention.

Sample embodiments of the present invention will be described in relation to the attached drawings, in which:.

<FIG> illustrates the general construction of an in-mold heater element <NUM> formed according a method of the invention. A conductive ink <NUM>, such as carbon ink or silver ink, is printed upon the surface of a film <NUM>. The combined printed film and heater element <NUM> is then placed within an open mold with the film <NUM> adjacent the mold. The mold is closed and mold resin <NUM> is injected or extruded into the closed mold to form the desired object. The resulting molded object has a printed film heater element <NUM> molded within the wall of the object.

In one embodiment the film <NUM> is a thermoplastic or thermoset polymer material such as polyester, polyimide, polycarbonate, polypropylene or other polymers that provide good thermal conductivity together with electrical insulation properties and mechanical protection of the printed ink. The film is thick enough to provide a stable film for the printed ink while still providing sufficient heat transfer. The film may have a thickness between <NUM> to <NUM>, for example between <NUM> to <NUM>.

In a further sample embodiment shown in <FIG>, a second film <NUM> may be used to sandwich the conductive ink <NUM> to provide a protective layer between the conductive ink <NUM> and the molding resin <NUM>. The second film <NUM> may also be formed from a thermoplastic or thermoset polymer material. The second film <NUM> may be electrically insulating, similarly to the film <NUM>. Alternatively, the second film <NUM> may be resistive or conductive as described in more detail below.

In another sample embodiment shown in <FIG>, a second layer <NUM> of protective ink is printed over the conductive ink <NUM> to provide a protective layer.

The electrically conductive ink may be carbon ink or silver ink or any other suitably electrically conductive ink. The conductive ink is generally printed in a thickness of about <NUM> to <NUM>, for example about <NUM> to <NUM>. However, larger or smaller conductive ink thicknesses are considered within the scope of the invention. In a sample embodiment, the electrically conductive ink is printed on to the film using a screen printing process. However, it should be appreciated that other printing processes may be used, for example etching.

The pattern of the conductive ink affects the distribution of the heat and the resistance in the circuits. The pattern of the electrically conductive ink applied to the film may be adjusted to provide different power densities. The thickness, width, length, and material properties (resistivity/conductivity) of the electrically conductive ink pattern determines the resistance in the circuit. A thicker or wider ink pattern has lower resistance than thinner or narrow ink patterns, whereas the resistance increases with increasing lengths of the conductive ink pattern.

In a sample embodiment, the ink pattern is designed to provide a given resistance to allow a particular voltage to be applied to the circuit. For example, the electrically conductive ink may be applied in a series of parallel bands linked with a perpendicular band, for example at bands periphery, or the ink may be applied as a single continuous circuit.

<FIG> illustrates an ink pattern having a series of linked parallel bands. The arrows represent the electrical connections that are made to the ends of the circuit. It is to be understood that this is only a sample and other ink patterns are considered within the scope of the invention.

The conductive ink circuits may include a combination of conductive inks such as carbon and silver ink to provide different resistance properties within the heating element. Carbon ink has a much higher resistance compared to silver ink. For example, carbon ink <NUM> may be used to form the series of parallel bands, as shown in <FIG>, and silver ink <NUM> may be used to link the carbon ink bands <NUM> at their periphery.

<FIG> illustrates an ink pattern having a single continuous circuit. As in <FIG>, the arrows represent the electrical connections that are made to the ends of the circuit. It is also to be understood that this is only a sample of a continuous circuit and other ink continuous patterns are considered within the scope of the invention.

In a further sample embodiment, the conductive ink circuit may also include other conductive element components such as metal bands to link a series of conductive ink bands, or for the electrical connections. <FIG> shows a heater element <NUM> comprising a first layer of film 42a having a conductive ink <NUM> printed thereon and a metal layer <NUM> laid over the ink <NUM> on the first layer of film 42a. A second film 42b is laminated to retain the metal layer <NUM>. Any conductive metals or alloys may be used, for example copper, gold and nickel chrome, or any other electrically conductive metal.

Although various sample heater element embodiments have been described with respect to the use of conductive inks, it should be appreciated that the heater element circuit may be formed of, for example, conductive or resistive polymer film or an overmolded layer instead of, or in addition to, the conductive ink. For example, as shown in <FIG>, the heater element <NUM> may include a circuit formed of a conductive or resistive polymer film <NUM> that may be stamped to provide the circuit pattern. The conductive or resistive polymer film <NUM> circuit may be provided on a polymer film <NUM> to form a stamped film heater element <NUM>.

As shown in <FIG>, the heater element circuit may be formed by overmolding <NUM> the pattern of the circuit onto the film <NUM> to form an overmolded film heater element <NUM>. The overmold layer <NUM> may be formed of a resistive or conductive material.

Referring to <FIG>, heater element <NUM> and control circuit therefor may be formed by any combination of conductive ink <NUM>, conductive or resistive polymer film <NUM>, and/or overmolding <NUM>. It should be further appreciated that the heater element <NUM> and control circuit may be used, for example, with the metal layer described above with respect to <FIG>. The heater element circuit and/or the control circuit may be formed of multiple layers of conductive ink, conductive or resistive polymer film(s), and/or overmolding to control the thermal properties.

Referring to <FIG>, the heater element circuit may be formed of conductive ink(s) <NUM>, and a film or foil <NUM> may locate, connect, and/or thermally protect a thermal sensor <NUM>, <NUM>, e.g. a thermistor. The thermal sensor may then be overmolded <NUM> to control the thermal properties of the sensor, and/or to insulate the sensor from the water of a humidifier tub.

As shown in <FIG>, the heater element may be either a printed film heater element <NUM>, a stamped film heater element <NUM>, and/or an overmolded heater element <NUM> and may be formed in a shape, for example a spiral, that is configured to cause differential heating to thereby cause water currents to form. For example, the heater element may be configured to create a swirling flow. As another example, the heater element may be formed with portions causing differential heating in areas of a humidifier where water flow may tend to be reduced, or stagnant, compared to other portions of the humidifier.

In the embodiments discussed above, any suitable molding resin may be used, including such resins as polycarbonate, polycarbonate ABS blends such as Astaloy™, polyethylene and polypropylene. The molded object <NUM> may be formed using extrusion molding or injection molding techniques or any other appropriate molding techniques. The molded object <NUM> comprising the in-mold heater <NUM> of the invention, including the printed film heater element <NUM>, the stamped film heater element <NUM>, and/or the overmolded heater element <NUM>, may be made into any desired shape and may be used for a range of heating applications, for example, water baths, heaters, heating racks, syringe heaters, humidifiers, heated containers such as battery heaters and other suitably moldable objects and products.

In one sample embodiment, the in-molded heater element <NUM> is formed within a humidifier device, for example in a respiratory humidifier device <NUM>. <FIG> shows an embodiment of the in-mold heater element <NUM> of the invention used in a respiratory humidifier device <NUM>. The conductive ink <NUM> is printed onto a film <NUM> and the subsequently formed printed ink film heater element <NUM> is molded into the base and/or sides of a humidifier tub <NUM> during the molding of the humidifier tub <NUM>. In this embodiment the humidifier tub <NUM> comprises an upper portion <NUM> and a lower portion <NUM>. The lower portion <NUM> comprises the in-mold heater element <NUM> at the base of the humidifier tub <NUM>. However, it should be appreciated that the in-mold heater element <NUM> may be formed in any portion of the humidifier tub <NUM>, for example in the sides, base, top or combinations thereof.

In another sample embodiment shown in <FIG>, an in-mold printed heater element <NUM> may be used to heat the air passing through the humidifier to enhance the moisture uptake by the air, or to adjust the temperature of the delivered air.

The upper portion <NUM> of the humidifier tub <NUM> comprises an air inlet <NUM> and an air outlet <NUM>. However, the air inlet <NUM> or air outlet <NUM> or both may be located in the lower portion <NUM>. The upper portion <NUM> may be formed as a removable lid to allow ease of cleaning and/or filling of the tub with water. Alternatively the upper portion <NUM> may be permanently fastened to the lower portion <NUM>, for example by welding or gluing or any other techniques known to sealingly fasten components. A seal may be used between the upper portion <NUM> and the lower portion <NUM> to reduce the risk of water leakage. The joint between the upper portion <NUM> and the lower portion <NUM> may be located above the maximum water fill line of the humidifier tub <NUM> to reduce the likelihood of water leakages from the humidifier tub <NUM>.

Electrical connections <NUM> provide power to the in-mold heater element <NUM> may be formed as part of the molding process within the humidifier tub, as described in more detail below. In a sample embodiment, the electrical connections <NUM> are attached to a power source and/or control source and are located above the maximum water fill line of the humidifier tub.

The molded respiratory humidifier may be configured as a stand-alone humidifier device or designed as an integrated device for attachment to a related product such as a PAP device, for example in a similar manner to the ResMed S8™ PAP device and the HumidAire™ 3i humidifier device. It should be appreciated that the in-mold heater elements may be molded into any appropriately molded object that requires a heater element.

A sample humidifier tub embodiment is shown in <FIG>, in which the in-mold heater element <NUM> is not located within the inner surface of the humidifier tub <NUM> but on an exterior surface of the tub <NUM>. In this embodiment, the in-mold heater element <NUM> may be molded into the exterior surface of the base of the tub <NUM> as described above or the heater element <NUM> may be a printed ink film heater element <NUM> in the form of a thick film heater that is attached to the base of the tub <NUM>, for example using adhesives. To prevent access to the heater element <NUM>, the tub <NUM> also comprises a base cover <NUM> that is attached to the base of the tub <NUM>. In one embodiment the base cover <NUM> is sealed at contact points <NUM> to the allow ease of cleaning of the tub, for example in a dishwasher, without disturbing the heater element <NUM>. A cavity <NUM> is formed between the heater element <NUM> and the base cover <NUM> to provide insulation. Insulating material may be inserted into the cavity <NUM> to prevent the heat transferring to the base cover <NUM>. This embodiment allows easy access to electrical connections as they are provided on the exterior surface of the tub.

Another sample embodiment for a humidifier tub is shown in <FIG>. In this embodiment, the humidifier tub <NUM> is molded with an open base. A heater element <NUM> is located in the base of the humidifier tub <NUM> and a base cover <NUM> is attached to the base of the humidifier tub <NUM>. The base cover <NUM> may be attached to the base of the humidifier tub <NUM> using a clamp <NUM> around the bottom perimeter. A seal <NUM> may be located between the humidifier tub <NUM> and the base cover <NUM> to prevent water leakage. The clamp <NUM> may permanently attach the base cover <NUM> to the humidifier tub <NUM>, for example using an adhesive or rolled edge clamp. Alternatively, the clamp <NUM> may allow removal of the base cover <NUM> for cleaning or disinfecting purposes. In this embodiment, the clamp <NUM> may be in the form of a screw-on or press-fit arrangement or one or more clips. Furthermore, the clamp <NUM> may be formed as an integral part of the base cover <NUM>, for example in the form of a screw-on base cover (not shown). The heater element <NUM> may be molded into the base cover <NUM> as described above or positioned in the base of the humidifier as a laminated heater element <NUM>. The laminated heater element <NUM> may be attached to the base cover <NUM>, for example using adhesives, or positioned above the base cover <NUM> to provide a cavity <NUM> under the laminated heater element <NUM>. The laminated heater element <NUM> may provide the internal base of the humidifier tub <NUM> such that water in the tub cannot flow under the laminated heater element <NUM>. In this embodiment, the cavity <NUM> under the heater element may provide an insulating layer to protect the base cover <NUM> from excess heat. Alternatively, the laminated heater element <NUM> may be positioned within the humidifier tub <NUM> to allow water to flow on both sides of the heater element <NUM> allowing heating of water on both sides of the heater element <NUM>.

The in-mold heater element <NUM> requires electrical connections for operation of the heater element. Access to at least a portion of the in-molded heater element <NUM> or a connector attached to the heater element <NUM> is required at a suitable external position of the molded object (e.g. humidifier tub), to enable connection to a power supply unit. The electrical connector construction must establish an electrical connection between the heater element circuit, e.g. conductive ink, conductive or resistive polymer film, and/or overmolding, and an electrical contact.

In a sample embodiment, the electrical connections are molded into the object together with the heater element during the molding process. The electrical connections may be via a direct contact to the heater circuit or via connection to additional components, such as electrical wire or a metal contact. <FIG> show sample embodiments for the electrical connection. In all embodiments, the film <NUM> comprising the heater element circuit, e.g. printed conductive ink layer <NUM> of printed ink film heater element <NUM>, is shown molded into the mold resin <NUM>.

<FIG> show examples of direct access <NUM> to the in-mold heater element <NUM>, e.g. to the conductive ink <NUM>, for direct contact to an electrical tab or connector, for example on a base unit or stand unit. The in-mold heater element <NUM> would be placed upon a complementary shaped tab or connector that may be connected to a power supply unit or electrical plug. In <FIG>, the molded resin <NUM> is shaped to form the recess <NUM>. In contrast, in <FIG>, the film <NUM> and the conductive ink <NUM> are exposed in a section of the mold such that no mold resin <NUM> is formed on a portion of the printed films.

<FIG> show the use of additional components for the electrical connection. <FIG> shows an electrical wire <NUM> fastened to the conductive ink <NUM> on the film <NUM>. The electrical wire <NUM> may be fastened to the conductive ink <NUM> on the film <NUM> using techniques for fastening electrical connections, such as crimping or terminal blocks. Alternatively the fastened electrical wire <NUM> may include a rigid mechanical contact connector, for example a plug and socket type connector, such as a spade or bullet connector, for the connection to the conductive ink <NUM> on the film <NUM>. The electrical wire <NUM> is fastened to the conductive ink <NUM> on the film <NUM> prior to the molding step with the mold resin. Thus, the electrical connection and electrical wire <NUM> is molded into the molded object together with the conductive ink <NUM> on the film <NUM>. In another sample embodiment, illustrated in <FIG>, a conductive material <NUM>, such as a metal contact, is fastened to the conductive ink <NUM> on the film <NUM> and the conductive material <NUM> is exposed on the outer surface of the molded object <NUM> to provide a direct electrical contact for a complementary electrical contact on a base or stand unit as described above for embodiments shown in <FIG>.

<FIG> shows a humidifier tub <NUM> having a heater element <NUM> molded into the molded humidifier tub <NUM>. The heater element <NUM> may be a printed ink film heater element <NUM> and be formed in the base <NUM> of the humidifier tub <NUM> and extend up at least one of the sidewalls <NUM>. The sidewall <NUM> is molded with the heater element <NUM> to provide an external access for the electrical power and control connections above and/or away from the water W in the humidifier tub <NUM>. <FIG> shows an alternative arrangement for providing access for the electrical connections where the heater element <NUM> is molded through the humidifier tub sidewall <NUM>. The heater element <NUM> is shown on the upper surface of the sidewall <NUM>, however it may also be provided on the lower surface.

The electrical connector for the molded object, e.g. humidifier tub, may be formed using features of the in-molded heater element <NUM>, e.g. a printed ink film heater element <NUM>. <FIG> shows an embodiment of a connector region. The connector region comprises a film <NUM> having the conductive ink layer <NUM> printed thereon and then having a further layer of metal <NUM> laid over the conductive ink layer <NUM>. The molded resin <NUM> is added around the heater element <NUM> to form the molded object, e.g. humidifier tub. In this design, the molded resin <NUM> is formed on the internal surface of the object and the heater element <NUM> is on the external surface. The molded resin <NUM> provides the structural and physical support for the electrical connection. The molding may also be designed to provide guiding assistance when the heater element connector is engaged with the power supply connector. The metal layer <NUM> may be exposed on the external surface to provide a conductive contact connector.

<FIG> show an example of a mating connector design. The in-mold heater element <NUM>, e.g. a printed ink film heater element <NUM> as described above, is formed within an exposed surface of the molded object <NUM>. A complementary shaped connector portion is formed in the power supply unit <NUM>. A spring contact <NUM> on the power supply unit <NUM> provides electrical connection to the exposed contact, e.g. metal layer <NUM>, on the heater element <NUM> in the molded object <NUM> when the molded object <NUM> is inserted in direction <NUM> into the power supply unit <NUM>. <FIG> shows a cross-section of the contact portions of the molded object. The shape of the molded connector region may be used to provide alignment for the connectors. The alignment portions may be formed in different shapes as indicated by <NUM> and <NUM>.

<FIG> shows another sample embodiment for the electrical connector construction to provide an electrical connection between the heater element and an electrical contact. In this embodiment, an electrical connector <NUM> having a pin-like structure <NUM> with a head portion <NUM> that is inserted through the molded object <NUM> and the in-mold heater element <NUM>, e.g. a printed ink film heater element <NUM>. The pin portion <NUM> of the electrical connector <NUM> is inserted from the interior of the molded object <NUM> until the head portion <NUM> is positioned against an internal surface of the molded object <NUM>. In one embodiment, the electrical connector <NUM> is molded into the molded object <NUM> during manufacture. In an alternative embodiment, the electrical connector <NUM> is inserted after the molded object <NUM> is made. The electrical connector <NUM> contacts the heater element circuit, e.g. conductive ink layer <NUM>, as it passes through the wall of the molded object <NUM>. The molded object <NUM> may also be designed to expose the film <NUM> on the outer surface such that a portion of the conductive ink <NUM> is exposed on the external surface. A securement unit <NUM> is attached to the pin portion <NUM> of the electrical connector <NUM> to provide an increased electrical conductive interface 42a and to secure the electrical connector <NUM> in position. The securement unit <NUM> may be in the form of a screwed, riveted or glued adaptor, or the like. Seals <NUM> may be provided to ensure a secure and safe connection. The electrical connector may be above the water level in a humidifier tub.

The level of heating by the in-mold heater elements may be controlled using a temperature sensor such as a thermistor or thermocouple. In a sample embodiment shown in <FIG>, the in-mold heater <NUM> includes one or more thermistors <NUM>, <NUM> electrically in series with the power supply and the printed conductive ink <NUM> on the film <NUM>. Depending upon the application, a positive temperature coefficient (PTC) thermistor or a negative temperature coefficient (NTC) thermistor may be used to control the level of heating. For example, a PTC thermistor operates to decrease the heating power to the heater element as the temperature increases towards the desired temperature. A PTC thermistor may be used in a respiratory humidifier device.

A temperature sensor <NUM>, or thermistor, or conductive thermoplastic elastomer (PTC-TPE) with PTC electrical properties may be molded into the molded object <NUM> together with the heater element circuit, e.g. conductive ink <NUM>, on the film <NUM>, as shown in the sample embodiment depicted in <FIG>.

In another sample embodiment shown in <FIG>, a thermal fuse <NUM> may be incorporated with the conductive ink <NUM> on the film <NUM> in a proximity close to the surface of the heater <NUM> to guard against overheating.

Referring to <FIG>, a humidifier tub <NUM> may include an in-mold heater element comprising, for example, a stamped film heater element <NUM> including a stamped resistive or conductive polymer film <NUM> and the polymer film <NUM>. The tub <NUM> may also include an overmold material <NUM> that separates portions 43a, 43b, 43c of the polymer film <NUM>. When the water level W is above the overmold material <NUM>, the water forms a conductive circuit with the portions 43a, 43b, 43c of the polymer film <NUM>, as shown in <FIG>. When the water level W is below the overmold material <NUM>, the conductive path between the portions 43a, 43b, 43c is broken. The polymer film <NUM> may thus be used as a water level sensor. For example, an amp meter may be connected to the polymer film <NUM>. When the water level W falls below the overmold material <NUM>, the conductive path is broken and the amp meter will detect the absence of current. It should be appreciated that the electrically conductive ink may be used instead of, or in addition to, the polymer film <NUM>. It should also be appreciated that the polymer film <NUM> may be replaced by, for example, a conductive ink foil.

According to another sample embodiment shown in <FIG>, the humidifier tub <NUM> may include a printed ink film heater element <NUM> that comprises a conductive ink <NUM> and a polymer film <NUM>. The humidifier tub <NUM> may also include an overmolded material <NUM> formed over the heater element <NUM>. As shown in <FIG>, the overmolded material <NUM> may include a mound(s), or "volcano(es)", 57a that is formed above the remainder of the overmolded material <NUM>. The mound 57a may include, for example, another heater, including another printed ink film heater <NUM> or a stamped film heater <NUM>, thermistors <NUM> or <NUM>, temperature sensors <NUM> or <NUM>, and/or thermal fuse(s) <NUM>. The additional heater element <NUM> or <NUM> may be electrically conductive when the water level W is above the overmolded mound(s) 57a, as shown in <FIG>, and electrically non-conductive when the water level W is below the mound(s) 57a, as shown in <FIG>. Thus, the mound(s) 57a may allow the additional heater element <NUM> or <NUM> to operate as a water level sensor as described above. Similarly, the thermistors <NUM> or <NUM> and/or the temperature sensors <NUM> or <NUM> may act as a water level sensor. For example, when the water level falls below the overmold mound(s) 57a, a large temperature differential may be sensed that indicates the water level has dropped below the mound(s) 57a.

In another sample embodiment shown in <FIG>, a temperature sensor <NUM> may be positioned adjacent the base of a humidifier tub and may be used to provide an indication of the water level. For example, if the water level is very low the heater element will heat up very rapidly. Other sensors, such as humidity sensors, may also be included within the molded object on the heater element to provide an indication of the level of humidification. Sensors may be loaded on to the heater element in contact with the conductive ink using conductive adhesives and covered with an epoxy for protection. Temperature sensors molded into different portions of a molded object may also provide an indication of the flow rate by detecting the temperature and rate between two temperature sensors.

Referring to <FIG>, a humidifier tub may comprise a lower portion <NUM> and an upper portion <NUM>. The upper portion <NUM> may comprise an air inlet <NUM> and an air outlet <NUM>. The lower portion <NUM> may comprise a printed film heater element <NUM>, although it should be appreciated that the heater element may be a stamped film heater element or an overmolded film heater element as described above.

The lower portion <NUM> may comprise a plurality of temperature sensors <NUM>, <NUM>, <NUM>, <NUM>. As the water level in the lower portion <NUM> goes down, each sensor <NUM>, <NUM>, <NUM>, <NUM> will be successively exposed to air flow through the humidifier. The change in the detected temperature, from water to air flow, provides an indication of the water level.

Referring to <FIG>, the heater element <NUM> may extend along a side wall of the lower portion <NUM> of the humidifier tub <NUM> and include a plurality of sensors <NUM>, <NUM>, <NUM>, <NUM> provided in the heater element to provide an indication of the water level. The heater element <NUM> will heat up more rapidly in areas not exposed to water in the lower portion <NUM> and the sensors in the areas of the heater element not exposed to water will indicate higher temperatures. It should also be appreciated that the circuit of the heater element <NUM> may also include, for example, a thermistor and/or a thermal fuse, as described in relation to other embodiments. It should be further appreciated that the heater element may be a stamped film heater element or overmolded film heater element as also described above.

Referring to <FIG>, the humidifier tub <NUM> may comprise the upper portion <NUM> and the lower portion <NUM>. The upper portion may also comprise a thermal sensor, or sensors, <NUM>, <NUM>, <NUM>. The thermal sensor(s) <NUM>, <NUM>, <NUM> may be placed above the water level, for example a maximum fill level defined in the lower portion <NUM>, to detect a temperature of the air in the upper portion <NUM>. If the air temperature exceeds a predetermined temperature, for example <NUM>, the power provided to the heater element <NUM> may be controlled to lower the air temperature.

It should be appreciated that the heater element <NUM> may be provided in a base of the lower portion <NUM>, as shown in <FIG>, or the heater element <NUM> may be configured as in <FIG>. It should further be appreciated that any positive number of temperature sensors <NUM>, <NUM>, <NUM> may be provided, and temperature sensors may be provided at multiple locations in the upper portion <NUM> of the humidifier tub <NUM>. For example, a temperature sensor may be provided at the inlet <NUM> and/or the outlet <NUM> to provide control of the heater element. As the inlet air temperature changes, the power supplied to the heater element <NUM> may be controlled to maintain a predetermined temperature at the outlet.

The film may also include a water level sensor. For example, a water level sensor including cathodic probes or a thermal gradient using temperature sensors, may be included in the molded object, e.g. humidifier tub. The sensors would rely on the thermal relationship between the heater and the water, and the ability to mold the shape of the molded object to accommodate the mechanical requirements of the humidifier. A humidity sensor(s), either an absolute and/or a relative humidity sensor may be provided in the humidifier to allow for control of the heater element. Such a control system is disclosed in, for example, <CIT> and <CIT> and April <NUM>, <NUM>, respectively.

The heaters may also be zoned. For example, the heaters may be provided on the film or overmolded material to include a water heating section and an air heating section. Each heater in each zone may include separate sensing, control, and/or thermal protection elements provided on the film. The zoning may also be horizontal for sensing and heating. Horizontal zoning would allow heating of the surface of the water only to improve warm up time and reduce energy losses.

In addition to temperature sensors molded into the molded object via the film or overmolded material, an electronic circuit, or circuits, may be provided on the film or overmolded material and molded into the molded object. For example, switching control elements may be provided on the film or overmolded material to recover heat losses that would normally be dissipated. The recovered heat may be used to heat the water in the humidifier chamber.

The power supply may be a stand alone power supply unit or incorporated within a supplementary device, such as PAP device that provides the power and electrical control systems for the device comprising the in-mold heater, such as an integrated humidifier device. Alternatively, the power supply unit forms a component of a humidifier device.

The use of in-mold heater elements may provide a number of advantages over conventional heating technologies, including lower cost, ease of manufacture, reduced weight and increased efficiency. For example, the ability to mold the heater element within the molded object results in a reduction in the number of components and the time and complexity of assembly of the complete object. Hot plate and heat conductive plates are no longer required but are combined as the in-mold heater element performs the equivalent function. Such reductions may also lead to a significant cost savings. Furthermore, as the heater element may be included exactly where the heating is required there may be an increase in heating efficiency and response time. Molding the heater elements within the molded object also minimizes the chance of leakage in molded objects designed to hold fluids, such as humidifiers.

For a respiratory humidifier, the use of an in-mold heater element may have some significant benefits. For example, the humidifier may no longer require a cradle or chassis unit, which conventionally includes the hot plate and the structural features to secure the humidifier tub to ensure good thermal contact between the humidifier tub base and the hot plate. A humidifier tub base seal is no longer required and leakage problems should be reduced, or minimized. These lead to component cost savings and simplified assembly making the humidifier unit less expensive to manufacture. The incorporation of the heater element within the molded humidifier tub can provide enhanced safety and protection against exposure to hot heating elements, especially when the humidifier is in use.

Claim 1:
A humidifier tub (<NUM>, <NUM>, <NUM>, <NUM>) for a respiratory apparatus configured to deliver pressurized breathable gas to a patient's airways, the humidifier tub comprising:
a container comprising a base (<NUM>) and a side wall (<NUM>) defining a reservoir for containing a supply of liquid to be evaporated, the container being made of a first material; and
an in-molded heating element (<NUM>) molded at least partially inside the container and covered by a layer (<NUM>),
wherein the layer is an electrically insulating polymer film and is formed from a second material different from the first material, and
wherein an electrically conductive circuit is provided on the layer.