GB2131319A

GB2131319A - Filter element

Info

Publication number: GB2131319A
Application number: GB08234642A
Authority: GB
Inventors: John Charles Field
Original assignee: COSWORTH ENG
Current assignee: COSWORTH ENG
Priority date: 1982-12-03
Filing date: 1982-12-03
Publication date: 1984-06-20

Abstract

An annular filter element for the air intake of an I.C. engine comprises a filtering layer of flexible foam plastics supported by a layer of semi-rigid foam plastics (30), the latter being for example polyurethane foam, impregnated to increase its hardness and having relatively large pores. The element is made by bending a strip comprising the two layers, bonded or stitched together, to cylindrical form and bonding or stitching the abutting ends. The axial ends of the filtering layer extend beyond the layer (30) and may be chamferred at (40, 41) to make seals with the enclosing housing when axially compressed. The outer, upstream face of the filtering layer has circumferential grooves (22). <IMAGE>

Description

SPECIFICATION Filter device and filter assembly for use therein This invention relates to a filter device and to a filter assembly for use therein. More particularly, but not exclusively, the invention relates to a filter device and to a filter assembly for use therein, to filter air for supply to the air intake of an internal combustion engine of a motor vehicle.

There is known from U.S. 3,491,891 a filter device incorporating a filter assembly comprising a filter element of flexible porous foam plastics material supported by a filter element support screen having a foraminous side wall. In this filter assembly, the support screen is made of perforated sheet metal and is provided at its upper and lower ends with a rubber-like lip which is interposed between said ends and upper and lower inwardly directed ridges of the filter element which overlie said ends of the screen.

The object of the invention is to provide a filter device and a filter assembly for use therein which is more economical to manufacture than is the filter device and filter assembly of the U.S. Specification.

According to one aspect of the invention, we provide a filter assembly comprising a filter element of flexible porous foam plastics material supported by a filter element support screen having a foraminous side wall, wherein the support screen comprises a semi-rigid porous foam plastics material.

The foam plastics material may comprise a reticulated polyurethane foam which has been impregnated to increase the hardness thereof to an extent adequate to support the filter element.

The screen may have a compression resistance of at least 0.51bs per linear centimetre and preferably at least 0.851bs per linear centimetre.

The filter element may be bonded to the support screen, for example by adhesive or otherwise secured thereto.

The adjacent surfaces of the screen and filter element may be rectilinear in longitudinal crosssection.

The filter element may be deeper than the screen so as to project beyond the top and bottom ends of the screen.

The filter element and screen may together define a shoulder, preferably an orthogonal shoulder, at the top and bottom ends thereof.

Alternatively, the filter element may have upper and lower surfaces which are inclined towards the screen.

The outer surface of the filter element may be provided with at least one peripherally extending channel or rib and preferably a plurality of alternat ing channels and ribs.

The filter element may, in transverse crosssection, describe a closed figure and the screen may be disposed within the filter element.

The closed figure may be a circle and the filter element and screen, in their "at rest" condition comprise concentric cylinders.

The or each channel or rib may extend around said closed figure so that where the closed figure is a circle, the or each channel or rib is of annular configuration.

The filter element may have a frusto-conical recess at the upper and lower ends thereof, the radially and longitudinally inner end of the recess terminating at the adjacent end of the screen.

According to another aspect of the invention, we provide a filter device incorporating a filter assembly according to the first aspect of the invention, wherein the assembly is disposed in a housing having top and bottom walls which are in sealed relationship with the top and bottom ends of the filter element.

The top and bottom ends of the filter element may be in sealed relationship with the top and bottom walls by virtue of parts of the filter element which extend beyond the screen being compressed as a result of the distance between the top and bottom walls being less than the depth of the filter element and the non-projecting parts of the filter element being prevented from at least substantial compression by being bonded to the screen.

The assembly may be disposed in said housing in an 'at rest' shape or may be deformed from an 'at rest' shape.

The assembly may be cylindrical when disposed in said housing or may be deformed from an "at rest" cylindrical shape to another shape such as a rectangular shape or semi-cylindrical shape when disposed in said housing.

When the filter assemblies, in transverse crosssection, describe a closed figure, the housing may have a side wall interconnecting said top and bottom walls and there may be fluid passage means through the side wall and through at least one of said top and bottom walls whereby fluid can flow between said openings through the filter element and screen.

The invention will now be described in more detail by way of example only, with reference to the accompanying drawings, wherein: Figure l is a plan view of a filter assembly embodying the invention; Figure 2 is a section on the line 2-2 of Figure 1 to an enlarged scale; Figure 3 is a plan view of a filter assembly of a second embodiment of the invention; Figure 4 is a section on the line 4-4 of Figure 3 to an enlarged scale, different to that of Figure 2; Figure 5 is a cross-section through a filter device embodying the filter assembly illustrated in Figures 1 and 2; and Figure 6 is a fragmentary sectional view showing a modification of Figure 4.

Referring now to Figures 1,2 and 5, a filter device comprises a housing 10 having top and bottom walls 11, 12 respectively of circular configuration interconnected bya cylindrical sidewall 13 which is permanently secured to the bottom wall 12, for example by welding, and is removably connected to the top wall libya rod 14 with which a nut 15 is threadedly engaged to clamp the top wall 11 against the upper end of the side wall 13.

The housing 10 is, of course, of essentially conventional construction and is provided, in conventional manner, with an air inlet opening 16 and an air outlet opening 17 in the bottom wall 12.

Disposed within the housing 10 is a filter assembly 20, best illustrated in Figures 1 and 2. The filter assembly 20 comprises a filter element 21 and a support screen 30. The filter element is made by taking an essentially rectangular strip of flexible polyurethane foam material of appropriate pore size, in the present example a 60 pores per inch reticulated foam and of the desired thickness, width and length and forming two parallel longitudinally extending channels 22 therein of desired configuration.

In the present example, the bottom wall of each channel 22 has a central portion 23 parallel to the general plane of the inner and outer surfaces 24 and 25 respectively and side portions 27 which are inclined at an angle of 300 to said planes and join side walls 28 of the channel which are perpendicular to said planes.

The inner surface 25 of the strip is bonded by adhesive to a support screen 30 made of semi-rigid polyurethane foam made by impregnation of a recticulated polyurethane foam to increase the hardness thereof to the necessary degree to give the desired extent of semi-rigidity. In the present example, the screen 30 is made of such a polyurethane foam having ten pores per inch and one example of a suitable material is that sold under the Trade Name BULPREN HC although of course other semi-rigid foam plastics material may be used.

The strip of material from which the screen is made is likewise rectangular but is of less depth than the strip of which the filter element is made so as to provide orthogonal shoulders 31 at the top and bottom surfaces 32,33 respectively of the screen, so that the top and bottom surfaces 34,35 respectively of the filter element are spaced further apart than the top and bottom surfaces 32, 33 of the screen.

The thus bonded together assembly of screen and filter element is then formed into a cylindrical shape as shown in Figure 1, and the adjacent longitudinal end surfaces are bonded together by a suitable adhesive as indicated at 36 in Figure 1.

If desired, instead of securing the filter and screen together and/or said end surfaces together by adhesive bonding, any other suitable securing means may be provided such as stitching.

The resulting cylindrical filter assembly is positioned within the housing 10 in its "at rest" cylindrical form so as to be co-axial with the wall 13. The top wall 11 is then placed in position and the nut 15 tightened to compress the parts of the filter element projecting above the end surfaces 32,33 of the screen against the top and bottom walls 11 and 12 thereby providing a seal. As shown in Figure 5, the projecting part deforms so that a portion thereof becomes trapped between the top and bottom wall and the adjacent surface 32,33 of the screen, thereby ensuring a good seal.

The channels 22 increase the surface area of the intake side of the filter.

If desired, the housing 10 may be of other shape than cylindrical, for example it may be of rectangular box configuration, and may be provided with guide flanges on the top and bottom walls so that the filter assembly is deformed from its "at rest" cylindrical configuration to a configuration conforming to that of the housing.

If desired, the filter assembly may be disposed between end walls 11 and 12 in the form of end caps and the filter assembly may be provided with a separate side wall 13 or may be unprovided with a side wall.

If desired, the screen may be disposed externally of the filter element, the filter element being suitably contoured to permit of bonding and, if desired, a filter element may be disposed on each side of the screen so as to sandwich the screen therebetween.

Further if desired, the assembly may comprise further layers and may comprise more than one support screen.

Referring now to Figures 3 and 4 there is illustrated an alternative embodiment which is the same as the embodiment described hereinbefore except for the configuration of the projecting parts of the filter element, and hence the same reference numerals have been used in Figures 3 and 4 as were used in Figures 1 and 2 to refer to the corresponding parts.

In this embodiment, the filter element is provided with a frusto-conical recess 40, 41 at the top and bottom thereof, the radially and longitudinally inner ends 42,43 respectively thereof terminating at the adjacent upper and lower end 32,33 respectively of the screen 30. The recesses 40,41 have a frustoconical half angle of 450 and the overall height of the filter element to the radially and longitudinally outer ends of the recesses 40,41 extend from their associated end surfaces 32, 33 a distance which is approximately five times greater in the embodiment of Figures 3 and 4 than the embodiment of Figures 1 and 2. For example, in Figures 1 and 2 the extent of projection may be 3.2mm whilst in the element of Figures 3 and 4the distance may be 16mm.

When a filter assembly as illustrated in Figures 3 and 4 is incorporated in a housing as illustrated in Figure 5, the projecting upper and lower parts of the filter element are deformed and again provide a good seal with the upper and lower walls of the housing, the part of the filter element bonded to the support screen 30 being uncompressed.

In a modification of the assembly shown in Figure 3, the ends 32, 33 of the screen are inclined so as to be continuous with the end surfaces of the further element as shown in Figure 6.

In the embodiments described hereinbefore, the support screen is of a material which has a compression resistance at 25% compression or 25KPa and in practice, a filter assembly having an internal diameter of 165mm is able to support a total applied load of 141bs.

It will be appreciated however that the support screen may be made of other material than that described hereinbefore so long as the semi-rigid support screen material is sufficiently rigid to support the filter material and provide a good seal. A compression resistance of 0.51b per linear centimetre and preferably at least 0.851b per linear centimetre.

Because the support screen is made of a foam plastics material, which is simply bonded to the foam plastics filter material, and because it is merely necessary to cut out strips of appropriate dimen sions, laminate the strips together and bend them round to form a cylindrical configuration, the cost of manufacture of a filter assembly and hence of a filter device incorporating the assembly embodying the present invention is considerably more economical than the cost inveolves in manufacturing a filter assembly and hence filter device as described in U.S.

Specification 3,491,891. This is because the expense of obtaining a stock material of perforated sheet metal is avoided, together with the greater expense of cutting such material to size than is incurred in cutting plastics material to size, as well as avoiding the need to provide rubber end strips.

Although the filter assemblies described above are cylindrical, if desired a filter assembly embodying the invention may be of any desired shape, including for example, a planar lamina or a rectangular shape, made, for example, by securing four planar laminas together in a rectangular configuration.

CLAIMS (Filed on 22 Nov 83.) 1. A filter assembly comprising a filter element of flexible porous foam plastics material supported by a filter element support screen having a foraminous side wall, wherein the support screen comprises a semi-rigid porous foam plastics material.

2. An assembly according to Claim 1 wherein the foam plastics material comprises a reticulated polyurethane foam which has been impregnated to increase the hardness thereof to an extent adequate to support the filter element.

3. An assembly according to Claim 1 or Claim 2 wherein the screen has a compression resistance of at least 0.51bs per linear centimetre.

4. An assembly according to Claim 3 wherein the screen has a compression resistance of at least 0.851bs per linear centimetre.

5. An assembly according to any one of the preceding claims wherein the filter element is bonded to the support screen by adhesive.

6. An assembly according to any one of the preceding claims wherein the adjacent surfaces of the screen and filter element are rectilinear in longitudinal cross-section.

7. An assembly according to any one of the preceding claims wherein the filter element is deeper than the screen and projects beyond the top and bottom ends of the screen.

8. An assembly according to Claim 7 wherein the filter element and screen together define a shoulder at the top and bottom ends thereof.

9. An assembly according to Claim 7 wherein the filter element has upper and lower surfaces which are inclined towards the screen.

10. An assembly according to any one of the preceding claims wherein the outer surface of the filter element is provided with at least one peripherally extending channel or rib.

11. An assembly according to any one of the preceding claims wherein, in transverse crosssection, the filter element describes a closed figure and the screen is disposed within the filter element.

12. An assembly according to Claim 11 wherein the closed figure is a circle and the filter element and screen, in their "at rest" condition comprise concentric cylinders.

13. An assembly according to Claim 11 or Claim 12 where appendant to Claim 10 wherein the or each channel or rib extends around said closed figure so that where the closed figure is a circle, the or each channel or rib is of annular configuration.

14. An assembly according to any one of the preceding claims wherein the filter element has a frusto-conical recess at the upper and lower ends thereof, the radially and longitudinally inner end of the recess terminating at the adjacent end of the screen.

15. A filter assembly substantially as hereinbefore described with reference to and as shown in Figures 1,2 and 5 or Figures 3 and 4 or Figure 6 of the accompanying drawings.

16. A filter device incorporating a filter assembly according to any one of Claims 1 to 15 wherein the assembly is disposed in a housing having top and bottom walls which are in sealed relationship with the top and bottom ends of the filter element.

17. A device according to Claim 16 wherein the top and bottom ends of the filter element are in sealed relationship with the top and bottom walls by virtue of parts of the filter element which extend beyond the screen being compressed as a result of the distance between the top and bottom walls being less than the depth of the filter element and the non-projecting parts of the filter element being prevented from at least substantial compression by being bonded to the screen.

18. A devie according to Claim 16 or Claim 17 wherein the assembly is disposed in said housing in an 'at rest' shape.

19. A device according to Claim 16 or Claim 17 wherein the assembly is disposed in said housing by deforming the assembly from an 'at rest' shape.

20. A device according to Claim 18 wherein the assembly is cylindrical when disposed in said housing.

21. A device according to Claim 19 wherein the assembly is deformed from an "at rest" cylindrical shape to a rectangular shape.or semi-cylindrical shape when disposed in said housing.

22. A device according to any one of Claims 16 to 21 wherein the filter assembly, in transverse crosssection, decribes a closed figure, the housing having a side wall interconnecting said top and bottom walls and there being fluid passage means through the side wall and through at least one of said top and bottom walls whereby fluid can flow between said openings through the filter element and screen.

23. A filter device substantially as hereinbefore described with reference to and as shown in Figures 1,2 and 5 or Figures 3 and 4 or Figure 6 of the accompanying drawings.

24. Any novel feature or novel combination of features disclosed herein and/or shown in the accomcanyinq drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. sions, laminate the strips together and bend them round to form a cylindrical configuration, the cost of manufacture of a filter assembly and hence of a filter device incorporating the assembly embodying the present invention is considerably more economical than the cost inveolves in manufacturing a filter assembly and hence filter device as described in U.S. Specification 3,491,891. This is because the expense of obtaining a stock material of perforated sheet metal is avoided, together with the greater expense of cutting such material to size than is incurred in cutting plastics material to size, as well as avoiding the need to provide rubber end strips. Although the filter assemblies described above are cylindrical, if desired a filter assembly embodying the invention may be of any desired shape, including for example, a planar lamina or a rectangular shape, made, for example, by securing four planar laminas together in a rectangular configuration. CLAIMS (Filed on 22 Nov 83.)

1. A filter assembly comprising a filter element of flexible porous foam plastics material supported by a filter element support screen having a foraminous side wall, wherein the support screen comprises a semi-rigid porous foam plastics material.