The invention relates generally to filter assemblies for filtering a gas stream and, more particularly, to filter assemblies having an integrated heat source.
The higher incidence and awareness of airborne diseases (e.g., SARS, Avian Flu) have made the filtration of exhaled gas for patients on mechanical ventilation a requirement in some healthcare environments. Exhaled gases can commonly reach a ventilator unit at 37 C and near 100% relative humidity. Accordingly, in-line filters used in such applications need to be able to withstand moisture. The administration of inline aerosol medications can also result in the filter elements being similarly subjected to moisture. Wetting of filter elements can weaken and lead to breaches in the filter media of such filter elements. Wet filter elements also have higher flow resistance which can make it more difficult for the patient to force air through a filter element (through exhalation or inhalation).
Another concern is condensation formation in the ducting or tubing associated with ventilation devices and the negative effects of such condensation on components (e.g., without limitation, flow sensors) downstream of a filter element. In order to avoid such condensation, it is desirable to raise the temperature of the gases flowing within the ventilation devices.
As such, it is desirable to place a bacteria filter in the exhalation gas pathway that can maintain its integrity and low flow resistance when subjected to moisture, while simultaneously increasing the temperature of the exiting gas to prevent rainout within the ventilation device
Known devices heat the filter housing in attempting to keep the filter elements dry and increase the temperature of the exhaled gases. Such devices are generally inefficient, as a portion of the energy applied is typically lost to the surrounding environment rather than being used to heat the media and gas. Because the increase in gas temperature is limited due to such losses, condensation can still occur downstream of the filter. Additionally, known devices often allow moisture to collect on the filter media.
There is thus room for improvement in the area of filters and filter assemblies used in filtering of exhalation gases.
In one embodiment, the invention provides a filter assembly for filtering a gas stream, comprising: a number of filter elements each structured to be disposed in the gas stream; and a heating element for heating each of the number of filter elements. The heating element being structured to be disposed in the gas stream for directly heating the gas stream as the gas stream passes therethrough. The heating element may comprise a porous structure that is structured to accommodate the gas stream passing therethrough. The heating element may be arranged in a generally planar structure. The heating element may be generally thin and flexible and arranged in a generally non-planar structure and may comprise a carbon fiber heating element. The number of filter elements may be spaced a distance from the heating element. The number of filter elements may be in direct communication with the heating element. The number of filter elements may be disposed downstream from the heating element. The number of filter elements may comprise a first filter element and a second filter element and the heating element may be disposed between the first filter element and the second filter element. The filter assembly may be structured to be disposed in a gas stream comprising exhalation gases.
Another embodiment provides a method of filtering a gas stream. The method comprises: directly heating the gas stream as the gas stream passes through a heating element, filtering the gas stream as the gas stream passes through a number of filter elements disposed in the gas stream, and heating each of the number of filter elements with the heating element. The heating element may comprise a porous structure that accommodates the gas stream passing therethrough. The heating element may be arranged in a generally planar structure. The heating element may be generally thin and flexible and arranged in a generally non-planar structure. The heating element may comprise a carbon fiber heating element. The number of filter elements may comprise a first filter element and a second filter element and the heating element may be disposed between the first filter element and the second filter element. The filter assembly may be disposed in a gas stream comprising exhalation gases. The number of filter elements may be spaced a distance from the heating element. The number of filter elements may be in direct communication with the heating element. The number of filter elements may be disposed downstream from the heating element.
The accompanying drawings illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the principles of the invention. As shown throughout the drawings, like reference numerals designate like or corresponding parts.
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.
As employed herein, the statement that two or more parts or components are “coupled” together shall mean that the parts are joined or operate together 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).
Heating element 18 preferably comprises a thin, sheet-like, generally flexible, porous structure such as, without limitation, a carbon fiber heating element. A carbon fiber heating element resembles a sheet of fabric, and can be woven such that it is porous to gas flow. The carbon fibers of heating element 18 are electrically conductive and generate heat when a voltage differential is placed across them.
The structure of heating element 18 allows it to be disposed directly in gas stream 12. Additionally, such structure also allows for the heating element 18 to be disposed in close proximity to, and preferably in direct contact with, the filter media 20, 22 of the first and second filter elements 14, 16, and thus provide heat directly to the filter media 20, 22. Thus, when humid gases flow through the filter assembly 10, as shown by arrows 12 in
It is to be appreciated that placement of the heating element 18 directly in the gas stream 12 provides for more uniform heating of the gas stream 12 than known designs that heat the housing through which the gas stream passes, thus not uniformly heating the gas. Additionally, such placement of the heating element 18 within the gas stream 12 more efficiently utilizes the heating element 18 in transferring heat energy to the gas stream 12 instead of the conduit 11 and/or related housings (not shown).
The design of filter assembly 10 may be varied in order to provide optimum filtration properties for varied conditions. For example,
It is to be appreciated that although the fluid supply 60 is shown in
While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, deletions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as limited by the foregoing description but is only limited by the scope of the appended claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB09/55528 | 12/4/2009 | WO | 00 | 6/15/2011 |
Number | Date | Country | |
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61139666 | Dec 2008 | US |