Field of the invention
[0001]This invention relates to a fuel filter with an air vent screw.
Background of the invention
[0002] Passenger car and Lightweight segment vehicles focuses on mileage hence prefer lightweight products, and in particular a lightweight fuel filter. This requirement lead to the development of the plastic fuel filter, which is compared to metal fuel filter. Fuel system is mainly divided to FPC (Fuel Pressure Controller) and FCU (Fuel Control unit) based fuel system. FCU based system has overflow valve and air venting system in built, but in FPC system, it should be provided in the fuel filter. In FPC based system the main problem or issue to be solved is the entrapped air in the fuel tank, which will be in the form of dissolved air/gas in fuel. During the operation, in-tank fuel pump supplies the fuel at 3-5 bar pressure range to the fuel filter. In the filter, the dissolved air/gas will be separated from the fuel due to density difference and air being lighter in weight stays at the top most area of the fuel filter. This entrapped air must be vented from the filter before effecting the functionality of the fuel system.
[0003] A Prior art document WO2016154510 discloses an air separator including a vessel defining a hollow interior chamber having an inlet for receiving fuel from a fuel source and an outlet for fluidic communication with an engine. An air-bleed receives and removes a quantity of undesired gas, which is in fluidic communication with a discharge port. Further, a filter media for contact with fuel received and a conduit for delivering fuel passing through the filter media to the outlet. The air separator removes gas from the fuel prior to passage through the outlet to the engine, with the gas passing through the air-bleed. The air bleed includes a fluidic mixing alcove for passage of the gas through the discharge port. The air separator is between the transfer pump and the engine.
Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and
illustrated in the accompanying drawing:

[0005] Figure 1 illustrates a fuel filter in a fuel supply system, in accordance with an embodiment of the invention;
[0006] Figure 2 illustrates a sectional view of an air vent screw in accordance with the present invention.
Detailed description of the embodiments
[0007] Fig.1 illustrates a fuel filter in a fuel supply system, in accordance with one embodiment of the invention. The fuel filter 12 comprises an inlet 14 and an outlet 16 made on a filter head 13. The fuel filter 12 further comprises a slot 18 formed in the filter head 13 and an air vent screw 20 fitted in the slot 18 of the fuel filter 12. The air vent screw 20 comprises a first portion 22, a second portion 23 and a third portion 24. The first portion 22 has larger dimensions than the second portion 23 and the third portion 24.
[0008] Further the construction of the fuel supply system and the components of the systems is explained as follows. The fuel supply system 10 comprises a fuel tank 40 and a fuel pump 42 adapted to pump the fuel from the fuel tank 40. The system 10 comprises a high-pressure fuel pump 44 connected to the fuel filter 12. The fuel from the fuel tank 40 is pumped into the high-pressure fuel pump 44 via the fuel filter 12. From the high-pressure pump 44, the pressurized fuel is made to flow into a common rail system (not shown). The fuel having the impurities is filtered in the fuel filter 12 and the filtered fuel from the outlet 16 of the fuel filter 12 flows into the high-pressure pump 44.
[0009] A filter element (not shown) is positioned in a cylindrical shape in the fuel filter 12. The fuel from the inlet 14 flows into an area between an inner surface of the fuel filter 12 and an outer surface of the filter element. The filtered fuel flows out from the fuel filter 12 via the outlet 16. However, the shape of the filter element is not restricted to the cylindrical shape, but can be any other shape that is known in the person skilled in the art.

[0010]The fuel filter 12 comprises a top portion and a bottom portion wherein the top portion acts as the filter head 13 to hold the filter element when assembled into the fuel filter 12. The fuel filter 12 further comprises an over flow valve 46 formed in proximity to the inlet 14 in the filter head 13. An excess amount of fuel flows out from the over flow valve 46 back into the fuel tank 40.
[0011] In the conventional fuel filters, the air vent screw 20 is made of either one of the following materials comprising a metal and a plastic. According to one embodiment of the present invention, the air vent screw 20 is made of a plastic material. The second portion 23 of the air vent screw 20 has larger dimensions than the third portion 24. For instance, the first portion 22 has larger circumference than the second portion 23 and the third portion 24 and the second portion 23 has larger circumference than the first portion 22.
[0012]Figure 2 illustrates a sectional view of an air vent screw in accordance with the present invention. The first portion 22 acts a holder for screwing /unscrewing the screw into the fuel filter 12. For instance, the first portion 22 is made as a knob kind of structure for holding the air vent screw 20. The second portion 23 comprises a threaded portion 23(a) made corresponding to a threaded portion 18(a) of the slot 18 in the fuel filter 12. The slot 18 made in the fuel filter 12 receives a portion of the air vent screw 20 during the screwing of the air vent screw 20 into the filter head 13.
[0013]The second portion 23 further comprises a double sided through hole 26 and a passage 28 formed from the hole 26 extended up to an open end of the first portion 22. It is to be understood that, the type of the hole 26 is not restricted to the double sided through hole 26 but can be any other type of hole that is known in the state of the art. The passage 28 is formed perpendicular to the hole 26 and is extended up to the open end of the first portion 22.

[0014]An air fuel mixture formed in the fuel filter 12 is adapted to flow into the atmosphere through the hole 26 and the passage 28, when the air vent screw 20 is unscrewed from the fuel filter 12. As mentioned above, the passage 28 in the screw is made perpendicular to the 26 for the air fuel mixture to flow out into atmosphere.
[0015]The third portion 24 comprises a groove 32 accommodating a flexible seal ring 34. The shape of the groove 32 and the seal ring 34 is made radial according to one embodiment of the invention. The seal ring 34 is adapted to seal/close the slot of the fuel filter 12 when the air vent screw 20 is screwed into the slot 18 of the filter head 13. The seal ring 34 is made of a flexible material chosen from a group of materials comprising a rubber, a plastic, a film, a glass fiber.
[0016]A method of working of the air vent screw is explained as follows. During any one of the scenarios comprising the filling of the fuel, either at the first filling of the fuel in an OEM plant or when the fuel is completely exhausted or during repair of any of the fuel pipes or replacement of the fuel filter 12. In the above-mentioned scenarios, the air is accumulated on the top portion of the fuel filter 12 due to the density difference between air, diesel and water. This causes delay / late cranking of the engine / vehicle and damages the components of the fuel supply system 10.
[0017]The air vent screw 20 is manually operated (opened /closed) to remove the air fuel mixture from the fuel filter 12. When the air vent screw 20 is fitted in the filter head 13, the seal ring 34 of the air vent screw 20 seals the slot area of the filter head 13, thus not allowing flow of the air fuel mixture formed at the top portion in the fuel filter 12.
[0018]To release the air fuel mixture accumulated at the top portion of the fuel filter 12, the air vent screw 20 is removed from the slot 18 of the filter head 13. When the air vent screw 20 is unscrewed from the fuel filter 12, the flexible seal ring 34 is compressed and is pulled towards the open end of the slot 18, such that, the movement of the flexible seal ring 34 creates an upper flow path and a lower flow path for the air fuel mixture to move.

[0019]The air fuel mixture flowing in the above-mentioned flow paths, moves towards the double through hole 26 and then into the passage 28. From the passage 28, the air fuel mixture flows out into the atmosphere, thus clearing the accumulated air in the fuel filter 12. During this process, the air vent screw 20 is not removed completely from the filter head 13.
[0020]With the above-mentioned new design of the air vent screw 20, the efficiency of the fuel filter 12 is increased. The effective removal of the air fuel mixture from the fuel filter 12 helps in reduction in the damage of the fuel supply system 10 and sudden stopping of the vehicle.
[0021] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

We Claim:
1. A fuel filter (12) in a fuel supply system (10), said fuel filter (12) comprising:
- an inlet (14) and an outlet (16) made on a filter head (13);
- a slot (18) formed in said filter head (13);
- an air vent screw (20) fitted in said slot (18) of said fuel filter (12); characterized in that:
said air vent screw (20) comprising a first portion (22), a second portion (23) and a third portion (24), said first portion (22) has larger dimensions than said second portion (23) and said third portion (24).
2. The fuel filter (12) as claimed in claim 1, wherein said second portion (23) of said screw has larger dimensions than said second portion (24).
3. The fuel filter (12) as claimed in claim 1, wherein said first portion (22) acts a holder for screwing /unscrewing said screw (20) into said fuel filter (12).
4. The fuel filter (12) as claimed in claim 1, wherein said second portion (23) comprises a threaded portion (23(a)) made corresponding to a threaded portion (18(a)) of said slot (18) in said fuel filter (12).
5. The fuel filter (12) as claimed in claim 1, wherein said second portion (23) comprises a double sided through hole (26) and a passage (28) formed from said hole (26) extended up to an open end (30) of said first portion (22).
6. The fuel filter (12) as claimed in claim 5, wherein an air fuel mixture adapted to flow into the atmosphere through said hole (26) and said passage (28), when said air vent screw (20) is unscrewed from said fuel filter (12).
7. The fuel filter (12) as claimed in claim 5, wherein said passage (28) in said screw (20) is made perpendicular to said hole (26) for said air fuel mixture to flow out into atmosphere.

8. The fuel filter (12) as claimed in claim 1, wherein said third portion (24) comprises a groove (32) accommodating a flexible seal ring (34) , said seal ring (34) adapted to seal/close said slot (18) of said fuel filter (12) when said air vent screw(20) is screwed into said filter head (13).
9. The fuel filter (12) as claimed in claim 1, wherein said seal ring (34) is made of a flexible material chosen from a group of materials comprising a rubber, a plastic, a film, a glass fiber.