Claims:We Claim:
1. A fuel filter (10), comprising:
a housing (105);
a cover (110) having a fuel inlet (115) and a fuel outlet (120) and covering the housing (105) at a flow end of the housing (105);
a filtering material (130) located inside the housing (105), dividing a housing volume into a filtered portion (135) and an unfiltered portion (140);
a tube (145) extending axially inside the filtered portion (135) of the housing (105) for conveying filtered fuel from the filtered portion (135) to the fuel outlet (120);
characterized in that:
a hole (150) in the tube (145), for enabling movement of air from the filtered portion (135) of the housing (105) to the fuel outlet (120).

2. The fuel filter (10) as claimed in Claim 1, wherein the hole (150) is located in proximity to the cover (110).

3. The fuel filter (10) as claimed in Claim 2, wherein the hole (150) is located at a level to which the filtering material (130) extends on a side of the cover (110).

4. The fuel filter (10) as claimed in Claim 2, wherein the hole (150) is located beyond a level to which the filtering material (130) extends on a side of the cover (110).

5. The fuel filter (10) as claimed in Claim 1, wherein a diameter of the hole (150) is 0.8 mm.

6. The fuel filter (10) as claimed in Claim 1, further comprising an end cap (165) disposed radially between the cover (110) and the filtering material (130), wherein the end cap (165) comprises an aperture (170), the aperture (170) forming an airflow passage between the unfiltered portion (140) of the housing (105) and the filtered portion (135) of the housing (105).

7. The fuel filter (10) as claimed in Claim 6, wherein a diameter of the aperture (170) is 0.8 mm.

, Description:FIELD OF THE INVENTION
[0001] This invention relates to a fuel filter.

BACKGROUND OF THE INVENTION
[0002] Filters are used in vehicles for reducing particulate impurities in the fuel, before the fuel is finally injected into the cylinders for combustion. The fuel filter is normally fitted in the low-pressure circuit between the electric fuel pump and the high pressure pump in the engine compartment. The filters have filtering elements inside the housing to enable filtering the fuel. Air is introduced into the fuel filter by the incoming fuel, which sometimes gets locked inside the filter and poses difficulties for the filtered fuel to move out of the filter. This leads to non-availability of the filtered fuel when needed for the engine. DE 19616493 discloses a fuel filter with a tube disposed axially to enable the egress of the filtered fuel after filtration. The tube optimally reaches the level of the filtered fuel in the filter and enables drawing in the filtered fuel through the tube out of the filter. But the tube does not enable the air inside the filter to be transported out of the filter.

BRIEF DESCRIPTION OF DRAWINGS
[0003] Embodiments of this disclosure is explained in principle below with reference to the drawings. The drawings are:
[0004] FIGURE 1 shows a cross section of a fuel filter.

DETAILED DESCRIPTION
[0005] FIGURE 1 shows a cross section of a fuel filter 10.
[0006] The fuel filter 10 comprises a housing 105 and a cover 110 having a fuel inlet 115 and a fuel outlet 120 and covering the housing 105 at a flow end 125 of the housing 105. The fuel filter 10 also has a filtering material 130 located inside the housing 105, dividing a housing volume into a filtered portion 135 and an unfiltered portion 140. The filter 10 also comprises a tube 145 extending from the cover 110 axially inside the filtered portion 135 of the housing 105 for conveying filtered fuel from the filtered portion 135 to the fuel outlet 120. The fuel filter 10 is characterized in that, there is a hole 150 in the tube 145 for enabling movement of air from the filtered portion 135 of the housing 105 to the fuel outlet 120. The working of the tube 145 and the hole 150 will be explained hereinafter.
[0007] The housing 105 of the filter 10 provides shape for the filter 10 and support for the components of the filter 10. The filtering material 130 enables filtering the fuel, as the fuel inside the filter 10 moves from the unfiltered portion 140 to the filtered portion 135. The constituents of filtering material 130 and the working of the same is understood by a person of ordinary skill in the art. As the filtered fuel in the filtered portion 135 reaches a free end 155 of the tube 145, the filtered fuel can be sucked in or pass through the tube 145 to the fuel outlet 120, which will be explained hereinafter. The housing volume indicated above refers to a volume inside the housing 105 that can be filled with fuel and emptied.
[0008] The hole 150 can be located in proximity to the cover 110. More specifically, the hole 150 can be located at a level to which the filtering material 130 extends on a side of the cover 110. On the other side, the filtering material 130 extends on to the other end of the housing 105 as well. Alternatively, the hole 150 can also extend beyond the level to which the filtering material 130 extends on the side of the cover 110. The level, in the context of the instant application, refers to a plane or a planar level that can be for disposing or locating components. As an example, the hole 150 can be located at a distance of 120 mm from the free end 155 of the tube 145. This distance of 120 mm is just an example and can take any other value as well, depending on the size of the filter 10. The advantage of having the hole 150 at the level to which the filtering material 130 extends on the cover 110 side or beyond the above level is that the hole 150 is accessible to the entire air column inside the filtered portion 135. In other words, if the hole 150 is situated at a level which is between the level to which the filtering material 130 extends on the cover 110 side and the free end 155 of the tube 145, then the hole 150 may not be accessible to the air between the level of the hole 150 and the level to which the filtering material 130 extends on the cover 110 side.
[0009] The cover end 160 of the tube 145 refers to the end of the tube 145 that is attached to the cover 110. And the free end of the tube 155 refers to the end of the tube 145 that is free, or opposite the cover end 160. The filtered fuel enters the tube 145 through the free end 155 of the tube 145. The advantage of having the tube 145 is that the tube 145 enables drawing in the filtered fuel out of the filter 10 even at lower pump speed.
[0010] The hole 150 has a diameter of 0.8 mm. This hole size of 0.8 mm is the optimum size for removing air in the filtered portion 135 for lower pump speeds. Optimal removal of air in the filtered portion 135 increases the level of the filtered fuel in the filtered portion 135.

[0011] The fuel filter 10 further comprises an end cap 165 disposed radially between the cover 110 and the filtering material 130, wherein the end cap 165 comprises an aperture 170, wherein the aperture 170 forms an airflow passage between the unfiltered portion 140 of the housing 105 and the filtered portion 135 of the housing 105. The end cap 165 is glued radially to the filtering material 130. The end cap 165 forms a lower portion of the cover 110 which is adjacent the flow end 125 of the housing when fitted onto the housing 105. The end cap 165 extending radially refers to a circumferential disposition of the end cap 165 over the flow end 125 of the housing 105. The flow end 125 of the housing 105 is so called as the fuel inlet 115 and the fuel outlet 120 are adjacent the said end.
[0012] The aperture 170 has a diameter of 0.8 mm. This diameter of 0.8 mm enables maintaining optimum filtration efficiency through the filtering material 130, as the air in the unfiltered portion 140 is enabled to flow through the aperture 170 thereby facilitating improved usage of a surface of the filtering material 130 for filtration of fuel.
[0013] The working of the fuel filter 10 is explained hereinafter. The unfiltered or impure fuel flows into the filter through the fuel inlet 115 and fills the unfiltered portion 140 of the housing 105. From the unfiltered portion 140, the fuel flows through the filtering material 130 and flows to the filtered portion 135. The filtered portion 135 contains the filtered fuel to be delivered out of the filter 10. The filtered portion 135 generally starts getting filled up from the bottom of the filter 10 or close to the free end 155 of the tube 145, as the fuel generally flows to the bottom of the filter 10 in the unfiltered portion 140 due to gravity, before getting filtered. Along with the fuel, air also gets introduced into the filter 10 through the fuel inlet 115 and some of the air passes through the filtering material 130 to the filtered portion 135. However, if the filtering material 130 is wet with fuel, it is difficult for the air to pass through the filtering material 130. The hole 150 in the tube 145 and the aperture 170 in the end cap 165 are for removing the air from the filtered portion 135 and the unfiltered portion 140 respectively, which will be explained hereinafter.
[0014] Generally, upon filtration of the fuel by the filtering material 130, the filtered fuel starts collecting at the bottom of the filter 10 in the filtered portion 135 and the remaining portion of the filtered portion 135 is filled with air which needs to be removed. If the level of filtered fuel in the filtered portion 135 is above the free end 155 of the tube 145, then the air in the filtered portion 135 will find it difficult to exit the filter 10 through the fuel outlet 120. The hole 150 which is in proximity to the cover 110 serves to enable the air to exit the filtered portion 135. The other advantage of continuously removing the air from the filtered portion 135 is that the unobstructed flow of filtered fuel from the filtered portion 135 is enabled, leading to a reduction in instances of long cranking. As the filtered fuel flows through the tube 145 to the fuel outlet 120, the flowing fuel creates a low pressure zone inside the tube 145 near the hole 150 compared to the pressure outside the tube 145 in the filtered portion 135. This enables the air from the filtered portion 135 to flow into the tube 145 and travel along with the filtered fuel to the fuel outlet 120.
[0015] As explained above, once the filtering material 130 is wet with fuel, the air from the unfiltered portion 140 will not be able to pass through the filtering material 130. This air in the unfiltered portion still has to be removed from the filter 10. The unfiltered portion 140 of the housing 105, apart from extending peripherally in the housing 105 radially beyond the filtering material 130, also extends between the filtering material 130 and the end cap 165, which is in a direction perpendicular to the peripheral extension of the unfiltered portion 140 described above. The aperture 170 is disposed on the end cap 165 and forms an airflow passage between the unfiltered portion 140 of the housing 105 and the filtered portion 135 of the housing 105. An airflow passage, in the context of the instant application refers to a passageway for conveying air from one side to another side.
[0016] The air in the unfiltered portion 140 passes through the aperture 170 to the filtered portion 135 and is sucked into the tube 145 through the hole 150 to be removed out of the filter 10. Hence, the air from both the filtered portion 135 and the unfiltered portion 140 is sucked in through the tube 145 to be removed from the filter 10.
[0017] The filter 10 can be used to filter diesel and find applications in vehicles using diesel as fuel.
[0018] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. Any modification in the embodiments are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.