WO2007090011A2

WO2007090011A2 - Engine air intake barrier filter system for aircraft

Info

Publication number: WO2007090011A2
Application number: PCT/US2007/060910
Authority: WO
Inventors: Joseph L. Wilson
Original assignee: Aerospace Filtration Systems, Inc.
Priority date: 2006-01-30
Filing date: 2007-01-23
Publication date: 2007-08-09
Also published as: WO2007090011A3

Abstract

An inlet barrier filter system (11) is mountable on an aircraft (13) and is disposed for filtering air prior to intake into an engine of the aircraft. The filter system (11) generally includes a filter element (21) having filter media (31) and a flexible border (35). A rigid frame (23) may be mounted on the aircraft (13). The filter element (21) may be sized and shaped to be received in the rigid frame (23). A retainer system (25) may retain the filter element (21) after it is installed in the frame.

Description

WSTR 8483.1 PCT

ENGINE AIR INTAKE BARRIER FILTER SYSTEM FOR AIRCRAFT

FIELD OF THE INVENTION

[0001] The present invention is directed to barrier filter systems, and more particularly to barrier filter systems for filtering intake air of aircraft engines.

BACKGROUND OF THE INVENTION

[0002] Prior art barrier filter systems for aircraft are shown, for example, in co-assigned U.S. Pat. Nos. 6,595,742 and 6,824,582, and Pat. App . No. 10/823,934, all of which are incorporated herein by reference. Filter systems typically comprise a replaceable filter assembly including a rigid retention frame installed around the filter media. After a period of use, the filter assembly is removed from the aircraft, cleaned, and then reinstalled in the aircraft. The rigid frame around the filter media is useful because it helps ensure that the media will maintain its shape, even under the high air flow in the air intake stream of an aircraft. The rigid frame may also facilitate, among other things, storage and cleaning of the filter. However, the prior art filter assembly is relatively expensive, due at least in part to the rigid frame. Additionally, if the filter assembly must be curved to conform to the aircraft, special tooling is required to manufacture the filter element.

SUMMARY OF THE INVENTION

[0003] One aspect is directed to an inlet barrier filter element for mounting on an aircraft for filtering air prior to intake into an engine of the aircraft. The filter element comprises flexible filter media and a WSTR 8483.1 PCT

flexible border extending around the filter media. The filter element is generally flat prior to installation and is capable of bending upon mounting on the aircraft to conform to the aircraft.

[0004] In another aspect, an inlet barrier filter system is mounted on an aircraft and is disposed for filtering air prior to intake into an engine of the aircraft. The filter system generally comprises a filter element including filter media and having a flexible border. A rigid frame is mounted on the aircraft. The filter element is sized and shaped to be received in the rigid frame. A retainer system is mountable on the frame for retaining the filter element after it is installed in the frame .

[0005] Various refinements exist of the features noted in relation to the above-mentioned aspects of the present invention. Further features may also be incorporated in the above-mentioned aspects of the present invention as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present invention may be incorporated into any of the above- described aspects of the present invention, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig. 1 is a perspective, partially cut-away view of a portion of an example helicopter including one embodiment of a filter system.

[0007] Fig. 2 is an exploded view of the filter system. WSTR 8483.1 PCT

[0008] Fig. 3 is a section view of a retainer system of one embodiment.

[0009] Fig. 4 is a perspective view of a filter element of the system.

[0010] Corresponding reference characters indicate corresponding parts throughout the drawings .

DETAILED DESCRIPTION OF THE DRAWINGS

[0011] Referring to Figs. 1-3, an inlet barrier filter system 11 of one embodiment is mounted in an aircraft engine air inlet 12. The type of aircraft and engine is not important to this invention, but the aircraft shown is a portion of a helicopter 13 having a jet engine 15. The system 11 is disposed for filtering air prior to intake into the engine to inhibit harmful particles from contacting and thereby damaging the engine. In this embodiment, the system is disposed in the air inlet, though other configurations are contemplated within the scope of the invention. The filter system 11 generally comprises a flexible filter element 21, a rigid frame 23, and a retainer system 25.

[0012] The flexible filter element 21 includes a suitable filter media 31. In one embodiment, the filter media 31 is capable of achieving high particle removal efficiencies. In this embodiment, the media has a face velocity range of between 15 to 50 feet per second (fps) . The pressure drop across the media will range from .6 inches of water at 15 fps to 5.6 inches of water at 50 fps. The filter media 31 is suitably made of a lightweight material that will also be resistant to damage by water and other liquids it may encounter in operation. Suitable filter media includes paper, woven cotton, WSTR 8483.1 PCT

polyester or felt. The media may include a grid fabric having a plurality of layers. The filter media 31 may be strengthened by a stainless steel screen (not shown) which encloses all or a portion of the filter media. To improve the filter efficiency for finer particles, the filter media 31 may be impregnated with oil that not only improves particle removal, but also helps resist moisture absorption by the filter media rendering it waterproof. The media of this embodiment is also pleated. Various other configurations, including other filter media and unpleated media are contemplated within the scope of the invention .

[0013] The filter element 21 has a flexible border 35 attached around the outer edges or border of the media 31. In this embodiment, the flexible border 35 includes a potting material, e.g., a polysulphite, polyurethane or other polymeric, or an epoxy, among other suitable materials. The potting material helps to seal the border around the filter element 21 and forms a perimeter to facilitate mounting, e.g., the installer can grasp the filter element by the potting material and install it in the aircraft. Other materials for the border are contemplated.

[0014] As shown in Fig. 4, the filter element 21 of this embodiment is generally planar or flat as manufactured and prior to installation. The element can be manufactured using inexpensive tooling (not shown) that is generally flat or planar. In other words, the manufacturing process, and the tooling used therein, does not impart any curvature to the filter element. The manufacturing process is therefore easier and less expensive . WSTR 8483.1 PCT

[0015] The potting material can be attached or formed around the filter media 31 in the tooling. When the filter element is ready to be installed on the aircraft, the flexible filter element can be deflected or bent significantly to conform to the aircraft. In one embodiment, the element 21, or portions thereof, can be bent or flexed to a radii of less than 20 inches, and in other embodiments flexed even further to less than 15 inches or even less than 10 inches in radius.

[0016] The rigid frame 23 that receives the filter element 21 is suitably mounted on the helicopter 13 (it may be original equipment or retrofit on existing aircraft, and can take a variety of configurations) . In this embodiment, the frame 23 includes a plurality of border members 41 (e.g., four as shown) that support the border 35 of the filter element 21. More particularly, the cross-section (Fig. 3) of each border member 41 includes a wall 43, a flange 45 extending perpendicularly therefrom, and a small inwardly turned lip 47. Optionally, the frame 23 can include cross-members 49 (giving it a "window pane" look) . The border members 41 may be formed separately, or integrally as one piece.

[0017] The retainer system 25 of this embodiment includes a retainer plate 51 having an inwardly turned lip 53 extending from the plate. The wall, flange, plate and the respective lips of this embodiment retain or capture the border 35 of the filter element 21. The system 25 also includes suitable fasteners 55, e.g., screws, extending through respective holes 57 in the plate 51 and the border members 41 of the frame 23. However, many other configurations of the frame and retainer system are contemplated . WSTR 8483.1 PCT

[0018] A small seal 61 extends along the flange 45 of this embodiment to facilitate sealing around the border 35 of the element 21. The seal is designed so that the filter element can be readily removed from the frame without damage. Many other sealing configurations are contemplated. For example, the seal may be a light adhesive applied between the border members and the border 35 of the filter element 21. The adhesive is light enough to allow for easy removal of the filter element 21. The seal may also form part of the retainer system 25.

[0019] The frame 23 of this embodiment is adjacent the contour or outer moldline 65 of the aircraft. Thus, the rigid frame 23 and retainer plate 25 of this embodiment are curved to conform to the moldline 65. The filter element 21, and especially the border 35 of the filter element, is flexible to conform to the curve. In some cases, the filter element 21 is resilient as well. Thus, the filter system 11 of this embodiment conforms to the outer moldline 65 of the helicopter 13, and the filter element 21 may form part of the outer moldline of the helicopter. Other configurations are contemplated, including those where the border members are not curved and where the frame is located downstream in the air intake system so that it is not adjacent the moldline.

[0020] The filter element can be easily manufactured flat, and is also flexible so that it is capable of being installed in a curved frame on the aircraft. The filter element is inexpensive because less expensive tooling may be used, thereby decreasing the cost of the filter element. If the filter element were manufactured in a curved but rigid configuration, the tooling required to WSTR 8483.1 PCT

assemble the filter element would be significantly more expensive .

[0021] In some embodiments of the present invention, the filter element is so inexpensive as to be "disposable", meaning that rather than cleaning the filter after it becomes dirty as has been the practice with prior art aircraft filters of this type, the filter is discarded without cleaning- However, the filter element may also be cleaned or otherwise refurbished within the scope of this invention .

[0022] When introducing elements of various aspects of the present invention or embodiments thereof, the articles ^""a", "an", "the" and "said" are intended to mean that there are one or more of the elements- The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of "top" and "bottom", "front" and "rear", "above" and "below" and variations of these and other terms of orientation is made for convenience, but does not require any particular orientation of the components.

[0023] As various changes could be made in the above constructions, methods and products without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Further, all dimensional information set forth herein is exemplary and is not intended to limit the scope of the invention unless stated otherwise .

Claims

WSTR 8483.1 PCTWhat is claimed is:

1. An inlet barrier filter element for mounting on an aircraft for filtering air prior to intake into an engine of the aircraft, the filter element comprising flexible filter media and a flexible border extending around the filter media, wherein the filter element is generally flat prior to installation and capable of bending upon mounting on the aircraft to conform to the aircraft .

2. The filter system of claim 1 wherein the filter element is capable of bending to a radius less than 20 inches without damaging the element.

3. The filter system of claim 1 wherein the filter element can bend to a radius less than 10 inches without damaging the element.

4. The filter system of claim 1 wherein the media has a face velocity of from 15 to 50 feet per second.

5. The filter system of claim 1 wherein the media causes a pressure drop of no more than 0.6 to 5.6 inches of water.

6. The filter system of claim 1 wherein the flexible border includes flexible potting material.

7. The filter system of claim 1 wherein the filter element includes pleated cotton media. WSTR 8483.1 PCT

8. The filter system of claim 7 wherein the media is dry.

9. The filter system of claim 7 wherein the media is wet.

10. The filter system of claim 1 wherein the filter element includes pleated paper media.

11. An inlet barrier filter system mounted on an aircraft and disposed for filtering air prior to intake into an engine of the aircraft, the filter system comprising: a flexible filter element including flexible filter media and a flexible border around the media; a rigid frame mounted on the aircraft; and a retainer system for retaining the filter element in the frame ; wherein the flexible filter element flexes to conform to the rigid frame mounted on the aircraft.

12. The filter system of claim 11 wherein the filter element is bent to a radius less than 20 inches.

13. The filter system of claim 11 wherein the media has a face velocity of from 15 to 50 feet per second.

14. The filter system of claim 11 wherein the media causes a pressure drop of no more than 0.6 to 5.6 inches of water. WSTR 8483.1 10

PCT

15. The filter system of claim 11 wherein the rigid frame includes a plurality of border members for supporting the border of the element and includes cross- members extending between the border members for supporting areas of the filter element spaced from the border.

16. The filter system of claim 15 wherein at least two of the border members are curved, the filter element being flexible to conform to the curve.

17. The filter system of claim 11 wherein the frame is adjacent the outer moldline of the aircraft, and a resilient, curved outer surface of the filter element conforms to the outer moldline.

18. The filter system of claim 11 in combination with the aircraft and wherein the aircraft is a helicopter.

19. The filter system of claim 11 wherein borders of the retainer system and the frame include opposing supports for capturing the flexible border therebetween.

20. The filter system of claim 19 further comprising a seal supported by one of the supports and engaging the border for facilitating sealing around the border of the filter element.

21. The filter system of claim 20 further wherein the retainer system includes an adhesive seal between the rigid frame and the filter element.