GB2292897A - Fuel filter - Google Patents

Abstract

A fuel filter element includes a casing (10) within which is mounted an inner tube (11) and between which and the casing is mounted an annular filter medium (12). Fuel in use flows downwardly through the tube and then upwardly through the filter medium to an outlet (19). At the lower end of the filter medium is a lower apertured support plate (13) and at the upper end there is mounted a support plate (14) of annular and inverted trough like form. Apertures (21) are formed in a rim portion of the trough through which fuel flows to the outlet and at the apex of the trough in a bleed orifice (23) which allows air to escape from the trough into the outlet in a controlled manner. <IMAGE>

Description

FUEL FILTER This invention relates to fuel filter elements of the kind having an outer casing, an inner tube which extends within the casing, a filter medium which is located between the outer wall of the tube and the inner wall of the casing and upper and lower annular support plates which extend between the casing and the tube to support the filter medium, the plates being perforated to allow fuel flow through the filter medium.

Such filter elements are well known in the art and have two forms namely one being where in use the element is clamped between upper and lower housing parts. The upper housing part defines a fuel inlet connection and a fuel outlet connection and the lower housing part defines a bowl which affords communication between the lower end of the tube and the perforations in the lower support plate. The two housing parts and the filter element are clamped by a central bolt which extends with clearance through the tube. The upper housing part defines an annular chamber open to the perforations in the upper support plate and communicating with one of said connections. In addition the upper housing part defines a central spigot which locates in sealing relationship in the upper portion of the tube, the spigot being hollow and communicating with the other of said connections.The other form of element is for use where the element is in screw thread engagement or is otherwise secured to a housing part similar to the aforesaid upper housing part. The role of the lower housing part is effected by a bowl portion which is an integral part of the casing of the element.

The present invention is concerned with a filter element in which the fuel flows upwardly through the filter medium so that the chamber in the upper housing part, is connected to the outlet connection. With this arrangement air which is entrained with the fuel will pass through the filter medium and collect in the chamber and will then be discharged through the outlet connection. The filter element or filter unit in which the element is mounted, in use is located downstream of a high pressure fuel injection pump and such pumps are designed to cope with air entrained with the fuel.If however large quantities of air are suddenly supplied to the pump its operation can be impaired and the object of the present invention is to provide a filter element of the kind specified which is capable of trapping the air and releasing it in manageable quantities into the fuel stream leaving the element.

According to the invention in a fuel filter element of the kind specified the upper support plate is of inverted trough shape and is provided with an air bleed orifice at or near the apex of the trough to allow air to flow at a restricted rate from the trough, fuel flow apertures being provided adjacent the rim of the trough at a position below said air bleed orifice.

Examples of filter elements in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic side elevation of one example of a filter unit shown in association with an upper housing part, Figure 2 is a view similar to Figure 1 showing another example of the filter element, Figures 3 and 4 are top views of the filter elements shown in Figures 1 and 2, Figure 5 is a view similar to Figures 1 and 2 showing a further example and Figure 6 is a view similar to Figures 3 and 4 but relative to the example of Figure 5.

Referring to Figure 1 of the drawings the filter element comprises a hollow cylindrical casing 10 in which is positioned a tube 11 and located between the outer surface of the tube 11 and the inner surface of the casing is a filter medium 12 which is conveniently formed from at least two strips of filter paper wound about the tube 11, the longitudinal edges of the paper being coated on one side so that as winding takes place a series of pockets generally of V shape in cross section are formed.

At the lower end of the filter element there is provided a lower annular support plate 1 3 which is secured to or is an integral part of the casing 10. The support plate acts to locate the lower end of the tube 11 and is perforated to allow fuel flow into the lower end of the filter medium. At the upper end of the filter element there is provided an upper annular support plate 14 which is shaped in a special way to be described. The filter element in use, is assembled to an upper housing part 15 which carries lugs not shown whereby it can be secured to a suitable support and the upper housing part defines a central depending spigot 16 which locates within the upper end of the tube 11. Conveniently the spigot carries a sealing ring to establish a fuel tight connection with the tube.

The spigot is hollow and is connected to a fuel inlet 1 7. The assembled filter unit includes a lower housing part (not shown) which defines a space to permit the fuel flow as indicated by the arrows 18 and conveniently the upper and lower housing parts are interconnected by a bolt which when tightened, clamps the filter element between the two housing parts. Seals are provided to prevent leakage of fuel.

The upper housing part defines an outlet 19 and this communicates with an annular chamber 20 defined in the upper housing part. In use, when fuel is supplied through the inlet the fuel flow takes place down the tube 11, up through the filter medium into the chamber 20 and then through the outlet 19. The filter medium acts to retain contaminate contained within the fuel.

As shown in Figure 1, the upper support plate 14 is shaped to define an inverted trough and part has a plurality of apertures 21 formed in the inner rim of the trough adjacent the upper end of the tube 11 and these apertures permit flow of fuel into the chamber 20. Air which passes through the filter medium collects in the annular space 22 which is defined by the trough and the air is allowed to leak from this space in a controlled manner through an orifice 23 into the chamber 20. The air flows from the chamber 20 through the outlet 19 in a controlled manner and at a rate which the pump downstream of the filter unit can cope with.

In the arrangement shown in Figure 1 the inner portion of the upper support plate slopes downwardly towards the upper end portion of the tube 11 and defines the openings 21. In the arrangement shown in Figure 2 it is the outer portion of the upper support plate which slopes downwardly towards the casing 10 and is provided with the fuel flow openings 21a.

In the arrangement shown in Figure 5 the upper support plate is shaped to inverted "U" section with sloping inner and outer portions extending towards the tube and the casing respectively. In this arrangement two series of fuel flow appertures are provided in the sloping parts of the support plate.

Claims (2)

1. A fuel filter element comprising an outer casing, an inner tube which extends within the casing, a filter medium located between the inner wall of the casing and the outer surface of the tube and upper and lower support plates which extend between the casing and the tube to support the filter medium the plates being apertured to allow fuel flow upwardly through the filter medium, the upper support plate being formed to inverted trough shape and being provided with an air bleed orifice at or near the apex of the trough to allow air to flow at a restricted rate from the trough, the apertures being provided in a rim portion of the trough at a position below said air bleed orifice.

2. A fuel filter element according to claim 1 in which said apertures are formed in the inner and outer rim portions of the trough.