Filter arrangement

A filter arrangement is described in which fuel flows through a filter member in a radially outward direction. A sleeve surrounds the filter element and defines, with the filter member, an air collection chamber. One or more small openings are provided in the sleeve whereby air is permitted to escape from the air collection chamber at a controlled rate.

This invention relates to a filter for use in removing contaminants from a
 supply of fuel to an engine, the filter being particularly suitable for
 use in filtering contaminants from a supply of diesel for a compression
 ignition internal combustion engine.
 In a known filter arrangement, a pleated filter member is located within a
 substantially cylindrical housing. The filter member is folded so that, in
 cross-section, the filter member is of star-like form. An axially
 extending perforated tube is located within the housing, the tube being
 arranged to receive fuel from a fuel tank. In use, fuel flows from the
 fuel tank to the axially extending tube. The fuel passes through the
 perforations of the tube to the filter member. The filter member prevents
 continued movement of contaminants carried by the fuel whilst permitting
 the fuel to pass through the filter member to a chamber adjacent in inner
 surface of the housing wall. The filtered fuel can then flow to an outlet
 from where it is supplied to a high pressure fuel pump. A suitable pump
 may be located either upstream or downstream of the filter to supply fuel
 to or draw fuel through the filter.
 This type of filter arrangement may alternatively be used with fuel being
 supplied from the fuel tank to the chamber adjacent the housing wall, the
 fuel flowing in a radially inward direction through the filter member
 towards the axially extending tube. The clean fuel reaching the tube is
 then supplied to a high pressure fuel pump or other device.
 The fuel supplied to the filter often carries with it a considerable amount
 of air. Where fuel flows from the outside of the filter member towards the
 axially extending tube, it is known to provide an arrangement whereby the
 air is collected and removed as required through a bleed outlet.
 Alternatively, an arrangement may be provided whereby air is allowed to
 continue with the flow of fuel at a controlled rate, the quantity of air
 permitted to flow with the fuel being sufficiently low that operation of
 the high pressure fuel pump or other devices downstream of the filter is
 not affected.
 It is an object of the invention to provide a filter arrangement of the
 type in which fuel flows in a radially outward direction, and in which air
 is permitted to continue with the flow of fuel at a controlled rate.
 According to the present invention there is provided a filter assembly
 comprising a housing, a filter member located within the housing, the
 housing including an inlet arranged to permit dirty fuel to be supplied to
 a central chamber within the filter member and an outlet arranged to
 permit clean fuel to be removed from an outer chamber surrounding the
 filter member, and a sleeve surrounding an upper part of the filter member
 and defining with the filter member an air collection chamber, at least
 one small opening being provided whereby air is permitted to flow at a
 controlled rate from the air collection chamber to the outer chamber.
 The filter member is conveniently of generally cylindrical form.
 The filter member and sleeve conveniently form part of a filter cartridge
 which further comprises an upper support plate and a lower support plate,
 the support plates being secured to one another by an axially extending
 tubular member, the filter member engaging the support plates to
 substantially prevent contaminant flow between the filter member and the
 support plates. The sleeve conveniently depends from the outer periphery
 of the upper support plate, the lower edge of the sleeve being axially
 spaced from the lower support plate.
 The invention further relates to a filter cartridge for use in such a
 filter arrangement.

The filter assembly illustrated in the accompanying drawing comprises a
 generally cylindrical housing 10 having an inlet port 12 and an outlet
 port 14. The inlet port 12 communicates with a downwardly extending, axial
 tube 16 which is integral with the housing 10.
 A filter cartridge 18 is located within the housing 10, the filter
 cartridge 18 comprising an upper annular support plate 20 and a lower
 annular support plate 22. The support plates 20, 22 are interconnected by
 a perforated tubular member 24. A filter member 26 surrounds the tubular
 member 24, the filter member 26 being located between the upper and lower
 support plates 20, 22. The filter member 26 conveniently takes the form of
 a pleated paper member, but it will be understood that other materials are
 suitable, for example felt or a sintered material or spun synthetic
 fibres.
 Radially outward of the filter member 26 is located a tubular sleeve 28
 which is connected at its upper end to the outer periphery of the upper
 support plate 20. As illustrated in the accompanying drawing, the lower
 edge of the sleeve 28 is axially spaced from the lower support plate 22.
 Thus a region 30 is defined through which fuel is permitted to flow, in
 use, to escape from the filter cartridge 18.
 The sleeve 28 is radially space from the outer edge of the filter member
 26, thus a chamber 32 is defined between the sleeve 28 and the filter
 member 26, the chamber 32 acting, in use, as an air collection chamber. As
 shown in the drawing FIGURE, a major lower portion of the sleeve is
 substantially imperforate, and a minor upper portion of the sleeve
 includes at least one opening 34. The small openings 34 are of dimensions
 such that air collected in the air collection chamber 32 is permitted to
 escape through the openings 34 at a controlled rate.
 The filter cartridge 18 is sealed within the housing 10, an O-ring 36 being
 located upon an annular wall 40 provided on the lower wall of the housing
 10, the O-ring 36 engaging the outer periphery of the lower support plate
 22, an O-ring 38 providing a seal between the tube 16 and the upper end of
 the tubular member 24. Although not illustrated, the housing 10 may take
 the form of a two part housing comprising a cup and a lid, the inlet and
 outlet ports 12, 14 being carried by the lid. Where such an arrangement is
 provided, separation of the lid from the cup permits replacement of the
 filter cartridge 18, the action of securing the lid to the cup
 appropriately sealing the filter cartridge 18 to the housing 10.
 A pair of drain openings 42 are provided in the lower wall of the housing
 10, the openings 42 being located adjacent, but on opposite sides of the
 annular wall 40. A screw-threaded plug 44 is arranged to close the
 openings 42. In use, any water droplets which collect in the lower end of
 the housing 10 can be drained by removing or releasing the plug 44, the
 water flowing from the housing 10 through the openings 42.
 In use, the inlet port 12 is connected to a suitable source of fuel and the
 outlet port 14 is connected to a high pressure fuel pump. Fuel flows from
 the source through the inlet port 12 and tube 16 to a central chamber
 defined by the perforated tubular member 24. Fuel is able to flow through
 the perforations of the member 24, the fuel flowing through the filter
 member 26 in a generally radial direction whilst contaminants carried by
 the flow of fuel are collected by the filter member 26. The fuel at the
 outer periphery of the filter member 26 flows downwardly, passing through
 the space 30 to a chamber defined between the outer surface of the sleeve
 28 and the inner surface of the housing 10. The clean fuel from this outer
 chamber is able to flow upwardly towards the outlet port 14 from where it
 is supplied to the pump.
 Air carried by the supply of fuel to the filter cartridge 18 tends to flow
 upwardly as the fuel flows in the radially outward direction through the
 filter member 26, the air being collected within the air collection
 chamber 32 upon exiting the filter member 26. The air collected within the
 air collection chamber 32 is able to escape at a predetermined rate
 through the openings 34, the air continuing as a stream of small bubbles
 with the flow of fuel through the outlet port 14. As the air flows as a
 stream of small bubbles, the flow of air is not detrimental to the
 operation of devices downstream of the filter arrangement. It will be
 appreciated that although the openings 34 are illustrated as being located
 in an upper part of the side wall of the sleeve, the openings could be
 provided in the part of the sleeve which is coplanar with the upper
 support plate.