Title

CPAP Filter

Field of the Invention

This invention relates to filters for gas streams. In particular, the invention relates to in-line filters for gas-delivery devices for delivering gasses to patients.

Background

There are a number of commercial devices available for delivering breathable gas to a patient for the treatment of sleep disordered breathing. For example, in the treatment of obstructive sleep apnoea, air is often delivered at continuous positive air pressure (CPAP) wherein air is supplied continuously at a pressure greater than ambient to the nose of a sleeping patient through a mask to keep the patient's airways open for effective respiration.

It is important for that the air and other gases delivered for treatment of sleep- disordered breathing to be as pure as possible and not to include particulate contaminants such as dust and micro-organisms, both of which could result in unintended consequences for a patient. It is known to filter the input air for a CPAP gas-delivery system, such as that which is described in patent application WO 2007/045017 and other systems and devices as known in the art. What is needed is a gas filter for a CPAP device that is effective in removing impurities but is also easy to remove for cleaning and replacement as needed.

Brief Description of the Figures

Figure 1 shows a side perspective view of an embodiment of the components of a gas filter.

Figure 2 shows a side perspective view of an embodiment of gas filter system.

Figure 3 shows a transverse section of a gas filter being positioned in a receptacle.

Figure 4 shows a transverse section of a gas filter positioned for operation.

Summary of the Invention

Currently available gas filters for CPAP devices and other gas-delivery devices incorporate substantially parallel faces of filters that are inserted into receptacles having substantially parallel engaging faces. It is an object of the invention to provide a gas filter that is effective for removing particulate matter from a gas stream but also easy to remove for cleaning or replacement. The present invention provides a filtering means that is tapered from the insertion end to the opposite end and a receptacle for the filtering means that is similarly tapered. This arrangement provides an effective filter that is easy to insert into its receptacle, the receptacle having a complementary shape and dimension. The material of the filtering means may be any appropriate material known in the art to be useful for removing particulate matter resulting in minimal loss of efficiency of filtration while enhancing the insertion and removal of the filter from its receptacle.

In one aspect the invention provides a filter system for a gas stream, the filtering means having a first end and second end, the first end forming a substantially obtuse angle with a side of the filtering means and the second end forming a substantially acute angle with the side of the filtering means and a receptacle having a complementary shape for engaging the filtering means. The filtering means may have at least a portion of a side tapering substantially smoothly from the first substantially obtuse angle to a spaced portion of the side of the filtering means. The filtering means may taper from the first end to the second end, the taper being smooth or stepped.

In second aspect, the invention provides a filter system for a gas stream, comprising a filtering means having a trapezoidal shape; and a receptacle having a complementary shape for engaging the filter. The filter system may be located in the air stream of a gas-delivery device for delivering gas to the nose of a subject.

In a third aspect, the invention provides a filter system for a gas stream, comprising a filtering means having a first end smaller in cross section than a second end; and a receptacle having a complementary shape for engaging the filter means. A portion of a side of the filter means may tapers substantially smoothly from. The filter system of may be located in the gas stream of a gas-delivery device for delivering gas to the nose of a subject.

In a further aspect, the invention provides a method of filtering the gas in a gas- delivery device for delivering gas to the nose of a subject, comprising the steps of; engaging a filtering means having a generally trapezoidal shape into a receptacle of complementary shape; and placing the resulting filtering system in the path of the gas stream of said gas-delivery device.

Detailed Description of the Drawings and Most Preferred Embodiments

In this document a reference to "comprising" is a reference to "including", where both words are used in a context that is not limiting. The invention is most easily understood with reference to the accompanying figures. It will be understood that the figures are intended to be illustrative embodiments of the invention and that the scope of the invention as defined in the claims includes further embodiments not so illustrated. For example, the preferred embodiment of the invention has a trapezoidal shape. The scope of the invention includes embodiments with conical shapes and other suitable shapes.

Figure 1 shows in side perspective view a filter 2 and receptacle 1 which comprise a filter apparatus for a gas-delivery system. A first end 3 of the filter 2 has a first width or cross sectional area, which tapers along an outer surface 7 to a second insertion end 4 having a second width of the filter 2. It can be seen in Figure 1 that the outer surfaces of the insertion end and the side walls form a generally obtuse angle and the inner surfaces of the corresponding walls of the receptacle 1 form a corresponding angle while the surface of the distal end of the filter and the side surfaces form a generally acute angle. The receptacle 1 has a corresponding width at a first end 5 which tapers along a side surface 8 to a second corresponding width 6. The taper of the side walls may be stepped as well as smooth, as long as the insertion end of the filter is smaller in width or cross sectional area than the distal end 3. Figure 1 shows that both sides 7, 9 of the filter 2 taper from the first end to the second end. The scope of the invention includes that a single side of the filter to be tapered from the first end to the second end. Alternatively, the filter may be generally cone-shaped. The taper results from the insertion end 4 forming an acute angle with the side 7. Preferably, both sides 7 of the filter taper to the insertion end 4. The receptacle 1 has a corresponding taper to the filter 2 from a first end to a second end. This enables the filter to be easily inserted into the receptacle as indicated in the direction of the arrow for a snug fit.

As shown in Figure 2, in operation the pathway of air flow, indicated by the arrow 13, is substantially perpendicular to the end of the filter 2 through the opening of the receptacle and through the material of the filter 2.

Preferably the filter is an essentially trapezoidal shape when viewed from an end of the filter and receptacle provide a simple but effective means to filter air but which is simple and easy to remove for cleaning and replacement. Alternatively, the invention includes embodiments where there sides of the shape are stepped in width, reducing from one end to the insertion end.

The most effective filtration is achieved if the clearance 14, shown in Figure 3, between the outside surface of the filter 2 and the inside surface of the receptacle 1 is minimised. Preferably the outside surfaces of the filter 2 are essentially smooth planes. This arrangement helps to minimise any channelling or air flow around the edges of the filter in passing through the receptacle. Any channelling reduces the effectiveness of the filtration. Preferably, there is interference between the engagement surfaces 9 of the filter 2 with the inside surfaces 15 of the receptacle 1 when the filter is in position for operation as shown in Figure 4. Such interference minimises any channelling of the air so that the air flows through the filter and particulate matter is filtered.

The taper of the filter most advantageously requires little insertion force in engaging the filter with its receptacle. The maximum force required to position the filter occurs as the filter engages the inside faces 15 of the receptacle.