GB2450735A

GB2450735A - Filter Unit Assembly and Method of producing Oxygen Enriched Air

Info

Publication number: GB2450735A
Application number: GB0713030A
Authority: GB
Inventors: Frederick Ian Wood
Original assignee: AIR SAFETY Ltd
Current assignee: AIR SAFETY Ltd
Priority date: 2007-07-05
Filing date: 2007-07-05
Publication date: 2009-01-07
Anticipated expiration: 2027-07-05
Also published as: GB2450735B; GB0713030D0

Abstract

A filter unit assembly (1) intended particularly for use on an item of medical equipment, e.g. an oxygen concentrator. The assembly (1) comprises: <SL> <LI>(a) a housing (2) having at least one air inlet (7) and having an air outlet (10) in communication with a tubular connector (11) projecting from the exterior of the housing, and <LI>(b) a filter element (13) mounted within the housing (2) and arranged in the path of air flow from the inlet (7) to the outlet (10). </SL> The or at least one inlet (7) comprises a tube (6) extending at least partly within the housing (2) so as to reduce the noise generated by the filter unit assembly (1) when filtering air.

Description

AIR FILTER ASSEMBLY

The present invention relates to an air filter assembly intended particularly (but not necessarily exclusively) for filtering air to be supplied to a machine such as an item of medical equipment for treating or otherwise processing air.

Numerous items of medical equipment (e.g. oxygen concentrators) require a constant flow of clean air to operate and be reliable. Small particles and dust must be removed from the air before it enters the equipment and this is achieved by means of an air filter assembly. Assemblies for use in medical equipment are usually constructed with a plastics moulded case and a filtering media such as a pleated filter and/or a foam pad. Typically the outlet from the filter assembly is through a sleeved connector and at least one inlet aperture is moulded in the housing.

Thus for example (and as indicated above) such filters are used in oxygen concentrators which may be used for providing oxygen-enriched air to a person (usually based at home) with respiratory problems. Such concentrators are an alternative to the use of an oxygen cylinder and are able to supply oxygen-enriched air as and when required, as opposed to a cylinder which may ultimately become depleted and require replacement. Such oxygen concentrators require a clean supply of air to be supplied to a molecular sieve (or other separation arrangement within the concentrators) which functions to provide for oxygen enrichment of the air (by depletion of its nitrogen content). Air filter assemblies for use in oxygen concentrators are disclosed for example in US 6,866,700 B2 (AG Industries). * ** * * *

In addition to filtering the air, the air filter assembly is also required to act as a silencer to reduce noise generated by the machine from escaping to atmosphere. To ***.

$ .. this end, the filter assembly may incorporate a medium such as felt or acoustic foam * to reduce noise. However the silencer function of the air filter assembly is generally : ** partly negated by the fact that the inlet opening has a smaller cross-sectional area than the outlet, which causes the airflow to accelerate. Unfortunately this can also * generate noise.

It is therefore an object of the present invention to obviate or mitigate the above mentioned disadvantages.

According to a first aspect of the present invention there is provided a filter unit assembly comprising (a) a housing having at least one air inlet and having an air outlet in communication with a tubular connector projecting from the exterior of the housing, and (b) a filter element mounted within the housing and arranged in the path of air flow from the inlet to the outlet wherein the or at least one inlet comprises a tube extending at least partly within the housing.

Preferably the or at least one tube has an inlet mouth configured to "funnel" air into the tube, i.e. to provide a smoothed air flow from the tube.

According to a second aspect of the present invention there is provided a filter unit assembly comprising (a) a housing having at least one air inlet and having an air outlet in communication with a tubular connector projecting from the exterior of the housing, and . (b) a filter element mounted within the housing and arranged in the path of air flow from the inlet to the outlet * ** * * S ::::: wherein the or at least one inlet comprises a tube having an inlet mouth * configured to "funnel" air into the tube.

We have found that the provision of the inlet tubes, as defined for the first and second aspects of the invention, serves to reduce the noise generated by the filter unit assembly when filtering air on a machine such as an oxygen concentrator (or other machine filter unit). The noise reduction effect is enhanced for the case where the tube has an inlet mouth configured to "funnel" air into the tube.

In preferred embodiments of the invention, the tubes have an inlet mouth which is defined by walls that are radiused as seen in cross-section so as to provide for the smoothed ("funnelled") air flow.

The tube is of preferably of circular internal cross-section but other formations are possible. The internal cross-section of the tube may be constant along the length of the latter or may taper in a direction inwardly of the housing.

In particularly preferred embodiments of the invention, the or at least one tube has a Iength:diameter ratio in the range 4-6:1, e.g. about 5:1.

In one preferred construction of filter assembly in accordance with the invention the or at least one inlet tube extends wholly within the housing and may for example be formed in the body of the housing. In the latter case the filter element (such as a pleated filter element) may be received in a cavity defined partly by the tube formed in the body of the housing.

In a further embodiment of the invention (a) the housing is defined by a wall arrangement and first and second ends, * said first end being formed with at having at least one aperture for providing an air inlet to the housing and said second end having an air outlet in communication with a S...

* : tubular connector projecting from the exterior of said second end, S.. * S. * S S S.. S * S * S S S.

(b) the filter element is tubular and is mounted at one end thereof on the interior of said second element so as to surround said air outlet, the other end of the filter element being spaced from the second end and there being a clearance between the filter element and the wall arrangement of the housing, and (c) there is a blanking element mounted on said other end of the filter element.

Filter assemblies in accordance with the invention are eminently suitable for use in filtering air supplied to items of medical equipment such as an oxygen concentrator. It will be appreciated that for all applications of the filter assembly air enters "directly" into the housing, by which we mean that the air is drawn into the tubes from the atmosphere without the filtered assembly having an inlet connector to a source of air that is to be filtered.

Further features of the invention are set out in the appended claims.

The invention will be further described by way of example only with reference to the accompanying drawings, in which: Figs la and lb are respectively a cut-away view and a top plan view of one embodiment of a first embodiment of filter unit assembly in accordance with the invention; Figs 2a and 2b, Figs 3a and 3b, and Figs 4a and 4b are similar to Figs la and I b but showing respectively second, third and fourth embodiments of filter unit assemblies in accordance with the invention; and * . * *** :. Fig 5 is a cut-away view of a fourth embodiment of filter unit assembly in accordance with the invention. S..

S * .. * . . *5S * S. S * S* *.

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The filter unit assembly 1 shown in Fig Ia comprises a two-piece plastics housing 2 comprised of: (a) an integrally moulded plastics shell (of generally circular-section) formed with waIls 3 and 4, and a circular plate 5 (which with the wall 4 provides a first end for the housing 2) from the inner surface of which project three air inlet tubes 6 positioned symmetrically around the periphery of plate 5, each tube leading from a respective aperture 7 in the plate 5; and (b) an end cap member 8 (providing a second end for the housing 2) located by means of its peripheral lip 9 over that end of the shell opposite to the plate 5, the end cap member 8 being formed with an air outlet 10 (of greater cross-sectional size than the apertures) associated with a tubular connector element 11 (for mounting the assembly on an air filtration apparatus).

As shown in the drawings, walls 3 converge towards each other in a direction going away from end cap member 8 to a junction region 12 so as to form a frustoconical body for the housing 2. At the junction region 12, the walls 3 meet the walls 4 which in turn converge at a shallower angle towards the end plate 5, thereby forming a frustoconical (first) end for the housing 2..

Provided within the housing 2 is a tubular filter element 13 which is located in position at the outlet end of the housing 2 between two concentric annular ridges 14 and 15 provided on the inner surface of end cap member 8, the ridge 14 being positioned so as closely to encircle the air outlet 10. The filter element comprises a pleated filter I 3a surrounded by a woven pre-filter layer I 3b (for removing "coarse" *:::* particles from the air flow. The external diameter of tubular filter element 13 is such *. that an annular space 16 is defined between the filter element 13 and wall 3. At its *...

end opposite outlet 10, the tubular filter element 13 is provided with a circular end cap member 17 (provided for blanking that end of the filter element 13) which is S..

approximately at the level of the junction region 12. The overall diameter of circular * *a * e * **. S S. * * S * S *S end cap member 17 is such that an annular gap 18 is defined between the end cap member 17 and the junction region 12.

It will be further appreciated from the drawing that a chamber 19 is defined by the end plate 5, the end cap member 17 and the walls 4.

As indicated above, and in accordance with the invention, there are three air inlet tubes 6, each one being associated with a respective inlet aperture 7. The tubes are moulded integrally with end plate 5 and project perpendicularly from its inner surface into the chamber 19, terminating short of the end cap member 17. In the embodiment illustrated in Fig la, each tube 16 is generally cylindrical (although may have a slight taper going in a direction inwardly of the housing). Typically the tube 16 will have a length of about 30mm and a diameter of about 6mm although other length:diameter ratios may be employed.

The apertures 7 are configured to "funnel" air into the tubes 7 and thereby avoid sharp edges which could contribute to noise. In the illustrated embodiment, this "funnelling" is achieved by virtue of the bounding walls 20 of the aperture being radiused when seen in cross-section so that the upper end of the aperture 6 (i.e. at the outer surface of plate 5) is of lesser diameter than the lower end with there being a smooth transition for air flow into the tube. This arrangement provides for a smoothed air flow entering the tube.

In use, the filter assembly I is mounted by means of its connector 11 on any oxygen concentration unit or other apparatus to which filtered air is to be delivered.

During an air filtration operation the air to be filtered passes through the apertures 7 and the tubes 6 into the chamber 19 prior to passing through the gap 18 into the *:::: annular space 16. Subsequently the air passes radially inwardly through the filter * ::: : element 13 and through the outlet 10 for an oxygen concentration operation. S..

The tubes 6 and apertures 7 serve to provide noise reduction as compared to a similar apparatus but in which tubes 6 are omitted. This is achieved by virtue of the S. S

SI S.

configuration of the apertures 7 allowing air to be "funnelled" into the tubes 6 which themselves keep the noise within the filter and ensuring that the air enters the filter smoothly.

Reference is now made to Fig 2 which shows a further embodiment of filter unit. For convenience, like reference numerals in Figs I and 2 denote the same parts.

It will be seen that the embodiment of Fig 2 is generally similar to that of Fig 1 save that the junction region 12 is positioned somewhat above the end cap member 17 and the frustoconical walls 4 are replaced by a radiused edge 21 providing a transition from wall 3 to plate 5.

Additionally, the end plate 5 is provided centrally with a tubular support member 22 which serves to reduce movement of the unit formed by the tubular filter and the end cap member.

Fig 3 shows a further embodiment of filter unit which is very similar to that illustrated in Fig 2 save for the configuration of the radiused edge 21.

Fig 4 shows a further embodiment of filter unit constructed in accordance with the principles described above. In this case, the air inlets 5 are formed in the radiused edge 21 of the end region rather than the end plate 5.

Reference is now made to Fig 5 which shows a further embodiment of filter assembly 100. As compared to the generally cylindrical embodiments of Figs 1-4, the filter assembly 100 shown in Fig 5 is of a somewhat more "cuboid" construction and has a body 101 in which is moulded an inlet tube 102 which is formed in accordance *:::* with the principles described more fully above, particularly in relation to Fig 1. As clearly shown in Fig 5, tube 102 leads to a chamber 103 from which air is able to pass through a pleated filter element 104 (the upper end of which is received in a * compartment defined partly by the tube 102) and then through an acoustic foam pad S..

* 105 before passing to the air outlet 106. * S. * 5 S *S. S

S S 55 * *.

Claims

1. A filter unit assembly comprising (a) a housing having at least one air inlet and having an air outlet in communication wrh a tubular connector projecting from the exterior of the housing, and (b) a filter element mounted within the housing and arranged in the path of air flow ftorn the inlet to the outlet wherein the or at least one inlet comprises a tube extending at least partly within the housing.

2. An assembly as claimed in claim 1 wherein the or at Least one tube has an inlet mouth configured to "funnel1' air into the tube,

3. A filter unit assembly comprising (a) a housing having at least one air inlet and having an air outlet in communication with a tubular connector projecting from the exterior of the housing, and (b) a filter element mounted within the housing and arranged in the path of air flow from the inlet to the outlet wherein the or at least one inlet comprises a tube having an inlet mouth configured to "funnel" air into the tube.

4. An assembly as claimed in claIm 2 or 3 wherein said inlet mouth of the

III

rube is defined by walls that are radiused as seen in cross-section, *

I **. . I. S * S S * *1

5. An assembly as claimed in any one of claims 1 to 4 wherein the or at least one tube is of circular cross-section,

6. An assembly as claimed in any one of claims 1 to 5 wherein the or at least one tube is of constant internal cross-section along its length.

7. An assembly as claimed in any one of claims I to 5 wherein the internal cross-section of the or at least One tube tapers in a direction inwardly of the liousing.

8. An assembly as claimed in any one of claims 1 to 7 wherein the or at least one tube has a length;diarneter ratio in the range 4-6:1.

9. An assembly as claimed in claim 8 wherein the or at least one tube has a lerigth:diameter ratio of about 5:1.

10. An assembly as claimed in any one of claims I to 9 wherein the at least one tube extends wholly within the housing.

11. An assembly as claimed in claim 10 comprising a tube that is formed in the body of the housIng

12. An assembly as claimed in claim 11 wherein the filter element is received in a cavity defined partly by said tube provided lxi the body of the housing.

13 An assembly as claimed in claim 12 wherein the filter element is a pleated filter element. * S *5

14. An assembly as claimed in claim 13 additionally comprising an acoustic foam pad downstream of the filter element. 5.

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: .. iS. An assembly as claimed in an one of claims ito 9 wherein 4.S u S. S * S S * I. (a) the housin is defined by a wall arrangement and first and second ends, said first end being formed with at having at least one aperture for providing an air inlet to the housing and said second end having an air outlet in comniun.icatjon with a tubular connector projecting from the exterior of said second end, (b) the alter clement is tubular and is mounted at one end thereof on the interior of said second element so as to surround said air outlet, the other end of the filter element being spaced from the 8econd end and there being a clcarnce between the filter element and the wall arrangement of the housing, and (c) there is a blanking elenient mounted on said other end of the filter element.

16. An assembly as claimed in claim 15 wherein the or each tube is otT-set from the centre of the first end of the housing.

17. An assembly as claimed in claim 15 or 16 wherein there are a plurality of tubes.

18 An assembly as claimed in claim 17 wherein the tubes are disposed symmetrically around the centre of the first end of the housing.

19. An assembly as claimed in any One of claims 15 to 18 wherein there are three tubes.

20, An assembly as claimed in any one of claims 15 to 19 wherein the or *: .s each rube is located at least partly in a chamber defined within the housing between I...

the blanking element and the first end of the housing PSI. * II p. ,

21. Aji assembly as claimed in claim 20 wherein the or each tube extends : ,,. wholly in the chamber, U.. * S. S * S. * **

22. An assembly as claimed in any one of claims 15 to 21 wherein the each or each tube is provided in an end plate formation of the housing.

23. An assembly as claimed in any one of claims 15 to 21 wherein the or each tube is provided in a radiused portion of the fIrst end,

24. An assembly as claimed in claim 20 or 21 wherein an abutment member is provided in the head space to Limit axial movement of the tubular filter element,

25. The use of a filter assembly as claimed in any one of claims 1 to 24 wherein an item of medical equipment requiring a flow of filtered air.

26. The use as claimed in claim 25 wherein the medical equipment is an oxygen concentrator.

27. A method of producing oxygen-enriched air comprising filtering air with a filter assembly as claimed in any one of claims 1 to 24 and passing the filtered air to means for enriching Its oxygen content. * ** *1 * * *s S... * I S.. *..*

SI *5 5

I I. p * . S S.. * *5 I p p. * S.