1. Field
The present disclosure pertains to an infrared emitter usable in an IR gas detection system, the infrared emitter having enhanced efficiency and/or longevity.
2. Description of the Related Art
Infrared emitters formed on substrates having low thermal conductivity are known. Infrared electromagnetic radiation is emitted from such an emitter by an emissive layer disposed on the substrate. Electrical current is provided to the emissive layer by electrical leads disposed on the substrate. Generally, the substrate has a thickness of at least about 0.005 inches. Rather than attempting to reduce the thermal mass of the emitter as a whole, conventional infrared emitters tend to be formed with what was previously perceived to be a balanced level of thermal mass.
Accordingly, one or more aspects of the present disclosure relate to an infrared emitter. In some embodiments, the emitter comprises a substrate, a heating element, and a dispersive layer. The substrate has a first surface and a second surface opposite the first surface, and is substantially planar. The heating element is disposed on a portion of the first surface of the substrate, and is configured to emit infrared electromagnetic radiation in response to an electrical current being introduced thereto. The dispersive layer is disposed on the first surface of substrate, has a thickness of less than about 40 μm, covers at least about 70% of the first surface, and is formed from a material having a thermal conductivity of at least 110 W/m ° C.
Yet another aspect of the present disclosure relates to a method of emitting infrared electromagnetic radiation. In some embodiments, the method comprises connecting a heating element with a power supply, the heating element being disposed on a substrate having a first surface and a second surface opposite the first surface, the substrate being substantially planar, the heating element being disposed on the first surface of the substrate and being configured to emit infrared electromagnetic radiation in response to an electrical current being introduced thereto, the heating element being connected with the power supply by a pair of leads disposed on the substrate, the pair of leads being configured to connect the heating element to a power supply to facilitate introduction of an electrical current to the heating element; directing an electrical current from the power supply through the heating element via the leads; emitting electromagnetic radiation from the heating element responsive to the electrical current; and dissipating heat from the substrate through a dispersive layer disposed on at least 70% of the first surface of the substrate, the dispersive layer being formed from a material having a thermal conductivity of at least about 110 W/m ° C.
Still another aspect of present disclosure relates to an infrared emitter. In some embodiments, the emitter comprises means for carrying components of the emitter, the means for carrying having a first surface and a second surface opposite the first surface, the means for carrying being substantially planar; means for emitting infrared electromagnetic radiation disposed on a portion of the first surface of the means for carrying, the means for emitting being configured to emit infrared electromagnetic radiation in response to an electrical current being introduced thereto; and means for dissipating heat disposed on at least 70% of the first surface of the means for carrying, the means for dissipating being formed from a material having a thermal conductivity of at least about 110 W/m ° C.
These and other objects, features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the disclosure.
As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other.
As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
The principles of the infrared emitter described herein can be employed in transducers for outputting: (a) a signal proportional in magnitude to the concentration of carbon dioxide flowing through an airway adapter in a patient-to-mechanical ventilator circuit, and (b) a reference signal. These signals can be ratioed in the manner disclosed in for example, one or more of U.S. Pat. Nos. 4,859,858; 4,859,859; and/or 5,369,277, which are hereby incorporated by reference in their entirety into the present application, to provide a third signal dynamically representing the concentration of the carbon dioxide flowing through the airway adapter. An exemplary airway adapter and a complementary transducer are shown in
The illustrated airway adapter 22 is designed for connection between an endotracheal tube inserted in a patient's trachea, and/or some other subject interface appliance, and the plumbing of a mechanical ventilator or other generator of a pressurized flow of breathable gas, and transducer 24 is in this instance employed to measure the expired carbon dioxide level of a medical patient, and/or levels of other gases.
Referring to
The central section 34 of airway adapter 22 provides a seat for transducer 24. An integral, U-shaped casing element 42 positively locates transducer 24 endwise of the adapter and, also, in that transverse direction indicated by arrow 44 in
To: (a) keep the gases flowing through airway adapter 22 from escaping through apertures 46 and 48 without attenuating the infrared radiation traversing optical path 50, and (b) keep foreign material from the interior of the airway adapter, the apertures are sealed by windows 52 and 54. Windows 52 and 54 may be formed from infrared transmissive materials, such as sapphire or other transmissive materials.
That casing 26 of transducer 24 in which the source unit 28 and detector unit 30 are housed has first and second end sections 58 and 60 with a rectangularly configured gap 62 therebetween. With the transducer assembled to airway adapter 22, the two sections 58 and 60 of transducer casing 26 embrace those two inner side walls 64 and 66 of airway adapter central section 34 in which energy transmitting windows 52 and 54 are installed.
Optically transparent windows 68 and 70 are installed along optical path 50 in apertures 72 and 74 provided in the inner end walls 76 and 78 of transducer housing 26. These windows allow the beam of infrared radiation generated in unit 28 in the left-hand end section 58 of transducer housing 26 to pass airway adapter 22 and from the airway adapter to the detector unit 30 in the right-hand section 60 of the transducer housing. At the same time, windows 68 and 70 keep foreign material from penetrating to the interior of the transducer casing.
An infrared emitter 80 is held by infrared emitter unit 28, and is configured to emit infrared electromagnetic radiation responsive to an electrical current being applied thereto.
A dispersive layer 93 is disposed on upper surface 92 of substrate 90. Dispersive layer 93 is formed from a material having a high thermal conductivity and low electrical conductivity. Its thermal conductivity is of at least about 100 W/m ° C., of at least about 120 W/m ° C., of at least about 145 W/m ° C., and/or other thermal conductivities. Its electrical conductivity is less than 0.01/Ωm, or less than 0.005/Ωm, and/or other electrical conductivities. Dispersive layer 93 is configured to disperse heat from substrate 90 during use. In some embodiments, dispersive layer 93 covers at least about 70% of upper surface 92, at least about 80% of upper surface 92, at least about 90% of upper surface 92, and/or other proportions of upper surface 92. Dispersive layer 93 can be up to about 50 μm thick, up to about 40 μm thick, up to about 30 μm thick, up to about 20 μm thick, and/or have other thicknesses.
Two electrical leads 94 and 96 are disposed above upper surface 92 of substrate 90. In the exemplary infrared radiation emitter 80 illustrated in
Leads 94 and 96 are formed from a material having a relatively high electrical conductivity and a relatively high thermal conductivity. For example, leads 94 and 96 may have an electrical conductivity of at least about 4.5×106/Ωm. Leads 94 and 96 may have a thermal conductivity of at least about 145 W/m ° C. Without limitation, leads 94 and 96 may be formed from one or more of gold, copper, silicon, and/or other materials. Leads 94 and 96 may be bonded to emitter 80. This may be performed through a printing process. The thickness of leads can be up to 20 μm. The thickness can also be controlled to be less than 10 μm and the leads can be spread at least 1 mm from the heating element on the first surface of the substrate to serve as the heat dissipating layer at the same time.
A heating element 102 is superimposed on leads 94 and 96, and is disposed on upper surface 92 of substrate 90. Heating element 102 is a thick film or layer of an emissive, electrically resistive material. By way of non-limiting example, heating element 102 may be formed by firing an ink that includes a large proportion of platinum and has an operating temperature between about 250° C. and about 700° C.
In some embodiments, heating element 102 is about 0.070 inch long. Two ends 104 and 106 of heating element 102 overlap about 0.020 inch onto leads 94 and 96 of emitter 80. Thus, the total overlap may constitute between about 50% and about 60% of the total area of heating element 102.
During operation, leads 94 and 96 connect heating element 102 with a power supply such that a current from the power supply is applied to heating element 102 through leads 94 and 96. Overlaps in the range just described tend to keep the current density at the interfaces between heating element 102 and leads 94 and 96 from becoming too high, which may cause heating element 80 to fail by burnthrough or fatigue cracking of heating element 80.
On a back surface 108 of substrate 90, a backing layer 110 is disposed. Backing layer 110 covers at least substantially all (e.g., all or substantially all) of back surface 108. Backing layer 110 effectively dissipates heat from substrate 90 during operation. Backing layer 110 may have a thickness less than about 0.00004 inches. Backing layer 110 may have a thermal conductivity of not less than about 145 W/m ° C. Backing layer 110 may be formed from one or more of gold, copper, silicon, and/or other materials.
By virtue of one or more of, among other things, a reduced thermal conductivity of substrate 90, a reduced thickness of substrate 90, increased electrical conductivity of leads 94 and 96, increased thermal conductivity through dispersive layer 93, and/or the addition of backing layer 108, the efficiency of infrared emitter 80 may have a reduced thermal mass and/or may dissipate heat more quickly than conventional emitters. For some conventional heated elements (IR emitters), a certain temperature or temperature modulation needs to be attained for gas detection. This temperature or temperature modulation is the result of dynamic thermal heating and conduction of the IR emitter. With the design and structure of infrared emitter 80, enhanced power efficiency and temperature modulation through the control and balance of pulse energy delivery, thermal mass, thermal insulation and/or heat conduction. The trough temperature during the modulation at a duty cycle may be reduced by the design of infrared emitter 80 up to 60%. The improved power efficiency and delivery may reduce the power consumption, prolong the operation lifetime infrared emitter 80, and/or provide other enhancements such as to afford greater tolerance and optical loss. The improved temperature and temperature modulation may improve the signal to noise ratio, reduce the need of power consumption, and/or provide other enhancements.
At an operation 122, a heating element is connected with a power supply. In some embodiments, the heating element the same as or similar to heating element 102 (shown in
At an operation 124, an electrical current is directed through the heating element to induce heating in the heating element. In some embodiments, operation 124 is performed by a pair of leads the same as or similar to leads 94 and 96 (shown in
At an operation 126, infrared electromagnetic radiation is emitted responsive to the electrical current. In some embodiments, operation 126 is performed by a heating element the same as or similar to heating element 102 (shown in
At an operation 128, heat is dissipated from the heating element. The dissipation of heat from the heating element may increase modulation amplitude, reduce power consumption, enhance longevity, and/or provide other enhancements. In some embodiments, operation 128 is performed by a dispersive layer and/or a backing layer the same as or similar to dispersive layer 93 and/or backing layer 110 (shown in
In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination.
Although the description provided above provides detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the disclosure is not limited to the expressly disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present disclosure contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.
This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/IB2012/056755, filed on Nov. 27, 2012, which claims the benefit of U.S. Provisional Patent Application No. 61/565,582, filed on Dec. 1, 2011. These applications are hereby incorporated by reference herein.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2012/056755 | 11/27/2012 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2013/080122 | 6/6/2013 | WO | A |
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