Claims:We Claim:

1. A filter cartridge (101) for a fuel filter (100), the filter cartridge (101) comprising a housing (102) and at least 3 layers of filter element placed coaxially, a first layer (103) of filter element comprising a hydrophobic material placed around the housing (102); characterized in that filter cartridge (101) :
a second layer (104) of filter element comprising a hydrophilic material wound around the outer wall of the housing (102), the length of the second layer (104) is equal to the length of the first layer (103);

a third layer (105) of filter element comprising a tube, a hydrophobic mesh wound around the tube, the tube placed inside the interior walls of the housing (102), the length of the tube is greater than the length of the first layer (103) and the second layer (104).

2. The filter cartridge (101) for a fuel filter (100) as claimed in claim 1, where the tube is affixed inside the inner wall of the housing (102) such that the tube is not in contact with the inner wall of the housing (102).
, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed

Field of the invention
[0001] The present disclosure relates to a filter cartridge for a fuel filter.

Background of the invention
[0002] Fuel Filter placed in the fuel line of a vehicle, filters out dust and water particles from the fuel. If these substances are not removed, they cause rapid wear and failure of the fuel pump and injector components, due to their abrasive action on the high-precision components used in modern injection systems. The filter element is conventionally made into filter cartridges. These filter cartridges are made of multiple layers of semi-permeable paper placed perpendicular to fuel flow. The emission norms in Bharat Stage VI standard require that water separation efficiency in a diesel filter for new and for clogged condition for passenger vehicles be more than 95% and 85% respectively.

[0003] Patent no. US 9,718,005B2, “Fuel filter of an internal combustion engine, and filter element of a fuel filter” discloses a fuel filter for fuel, in particular diesel fuel, of an internal combustion engine. A housing has at least one fuel inlet for the fuel to be cleaned, at least one fuel outlet for cleaned fuel, and at least one water outlet for water which has been separated from the fuel. The filter element is arranged in the housing said filter element seemingly separating the fuel inlet from the fuel outlet. The filter element has a filter medium which is designed as a hollow body and which can be permeated from the inside to the outside or from the outside to the inside in order to filter the fuel. The filter element has a coalescing medium designed as a hollow body for separating water contained in the fuel. The coalescing medium is arranged downstream of the filter medium in the flow path of the fuel, around said filter medium, or in the interior delimited by the filter medium. The coalescing medium includes at least one regenerated-fiber coalescing system consisting of a coalescing material which is suitable for coalescing water and which has at least 20 wt. % of regenerated fibers, preferably at least 50 wt. %.

Brief description of the accompanying drawings
[0004] An embodiment of the invention is described with reference to the following accompanying drawings:
[0005] Fig. 1 depicts a filter cartridge (101) for a fuel filter (100).

Detailed description of the drawings

[0006] Figure 1 depicts a filter cartridge (101) for a fuel filter (100). The filter cartridge (101) comprises a housing (102) and at least 3 layers of filter element placed coaxially. A first layer (103) of filter element comprises a hydrophobic material placed around the housing (102). The most important non-limiting feature of the filter cartridge (101) is a second layer (104) and a third layer (105) of filter element. The second layer (104) of filter element comprises a hydrophilic material wound around the outer wall of the housing (102). The length of the second layer (104) is equal to the length of the first layer (103). The third layer (105) of filter element comprises a tube. A hydrophobic mesh is wound around this tube. The tube is placed inside the interior walls of the housing (102). The length of the tube is greater than the length of the first layer (103) and the second layer (104). The tube is affixed inside the inner wall of the housing (102) such that the tube is not in contact with the inner wall of the housing (102).

[0007] In an embodiment the first layer (103) is placed in a manner such that the contact angle between the water droplets in the fuel and the first layer (103) is more than 90 degree. The first layer (103) is in the form of an accordion-folded hydrophobic material. The radial distance between the first layer (103) and the inner wall of the housing (102) is at least 5 millimeters (mm). The second layer (104) comprises multiple wounds of a 0.6mm hydrophilic material around the inner wall of the housing (102). The radial distance between the second layer (104) and first layer (103) is zero i.e. they are in contact with each other. The third layer (105) of filter element layer (herein referred as the tube) is placed in such a manner that it has a contact angle between 105 to 135 degrees with the water droplets.

[0008] In an embodiment the tube is affixed inside the inner wall of the housing (102) using a glue. In another embodiment of the invention described above the tube is affixed inside the inner wall of the housing (102) using a rib structure provided in the housing (102). In an embodiment of the invention described above, the first layer (104) of the filter element comprising the hydrophobic material is composed of two layers of a synthetic filter paper media. The second layer (104) comprising hydrophilic layer is composed of a coalesce media. For example this coalesce media can be but is not limited to an 80% Viscose and 20% Polyester material. The third layer (105) i.e. the tube having the hydrophobic mesh is made up of a material such as but not limited to a Polyethylene Terephthalate (PET).

[0009] The filter cartridge (101) as disclosed above comprises three stages of filtration provided by the three layers of filter element. Figure 2 depicts the process of water filtration. The first layer (103) of the filter element being hydrophobic media repels the water droplets presents in the fuel. Water droplets with size as low as 10µm are screened out. The second layer (104) is a hydrophilic layer, which coalesces water droplets of size as low as 10µm into larger droplets of size 300µm. These larger droplets of water (111) coalesce together and exit the second layer (104). The third layer (105) is the tube comprising the hydrophobic mesh. The hydrophobic mesh repels these larger water droplets (111) and they are separated from the fuel by the principle of gravity roll down. The principle of gravity roll down means that water droplet size being heavier than fuel rolls down on the repelling hydrophobic mesh by gravity principle.

[0010] Another very important non-limiting feature of the present invention is the length of the tube. The length of hydrophobic tube is more than the first layer (103) and the second layer (104). Due to this increased length, water droplets after coalescing from the second layer (104), roll down onto the hydrophic mesh of the tube till the water droplet (111) moves out of the housing (102) of the filter cartridge (101) and enter the region below the housing (102) where water droplet cannot be drawn back into hydrophobic tube. The increased length of the tube makes the gravity roll down effect more pronounced and increases the efficiency of water separation.

[0011] This idea to develop a filter cartridge (101) for a fuel filter (100) increases the water separation efficiency of the fuel filter. In the conventional filters, due to equal length of the three layers smaller water droplets get drawn back into the hydrophobic tube. The increased length of the third layer i.e. the tube, addresses this problem making separation of water from fuel more efficient. In addition the particular arrangement of the layers of the filter element and their configuration helps achieve a water separation efficiency of =95% in new condition and = 85% in clogged condition. This lowers the content of water in the fuel. Lower water content in fuel prevents the deterioration fuel injection components due to corrosion and erosion which otherwise occur due to water entering into these components.

[0012] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the filter cartridge (101) for a fuel filter (100) are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.