CLIAMS:We Claim:
1. A screw plug assembly (9) for an overflow valve (8) of a fuel metering unit, said screw plug assembly (9) comprising a screw plug (12) with a bore adapted to seal said overflow valve (8); and
a control bolt (14) inserted within a bore defined within said screw plug (12), said control bolt (14) biased against an end of a spring member (16) in a manner such as to facilitate adjusting a pre-load acting on said spring member (16).
2. The screw plug assembly (9) for an overflow valve (8) of a fuel metering unit in accordance with Claim 1, wherein said control bolt (14) has a plurality of screw threads defined on its outer periphery.
3. The screw plug assembly (9) for an overflow valve (8) of a fuel metering unit in accordance with Claims 1 and 2, wherein a plurality of screw threads are defined in the bore of said screw plug (12), said plurality of screw threads defined in the bore of said screw plug (12) mesh with the plurality of screw threads of said control bolt (14).
4. The screw plug assembly (9) for an overflow valve (8) of a fuel metering unit in accordance with Claim 1 wherein said control bolt (14) comprises a flanged portion (18) defined on said control bolt (14), said flanged portion (18) adapted to seal said overflow valve (8).
5. The screw plug assembly (9) for an overflow valve (8) of a fuel metering unit in accordance with Claim 1 wherein said control bolt (14) includes a notched portion (20) defined on said control bolt (14), said notched portion (20) facilitates rotating said control bolt (14).
6. The screw plug assembly (9) for an overflow valve (8) of a fuel metering unit in accordance with Claim 1 wherein said control bolt (14) includes a seal (22) located in a recess in said control bolt (14) and said screw plug (12), said seal (22) facilitates sealing said control bolt (14) against said screw plug (12).
7. An overflow valve (8) of a fuel metering unit, said overflow valve (8) includes a screw plug assembly (9) comprising a screw plug (12) with a bore adapted to seal said overflow valve (8); and
a control bolt (14) inserted within the bore defined within said screw plug (12), said control bolt (14) biased against an end of a spring member (16) in a manner such as to facilitate adjusting a pre-load acting on said spring member (16).
8. A fuel metering unit, said fuel metering unit comprising:
an overflow valve body (10) integrated within a housing of said fuel metering unit;
a screw plug assembly (9) adapted to seal said overflow valve body (10);
characterized in that
a screw plug (12) with a bore coupled to said overflow valve body (10), said screw plug (12) adapted to seal said overflow valve body (10);
a control bolt (14) inserted within said bore defined within said screw plug (12), said control bolt (14) biased against an end of a spring member (16) in a manner such as to facilitate adjusting a pre-load acting on said spring member (16).
9. The fuel metering unit in accordance with Claim 8 wherein said control bolt (14) has a plurality of screw threads defined on its outer periphery.
10. The fuel metering unit in accordance with Claim 8 and 9 wherein a plurality of screw threads are defined in the bore of said screw plug (12), said plurality of screw threads defined in the bore of said screw plug (12) mesh with the plurality of screw threads of said control bolt (14).
,TagSPECI:Field of the invention
[0001] This invention relates to an overflow valve in a fuel metering unit.
Background of the invention
[0002] An overflow valve is used in a conventional fuel metering unit. The overflow valve used in the conventional fuel metering unit is inserted within the fuel metering unit and screwed on to a clamping device that is integrated within the fuel metering unit. A plug is disposed within the overflow valve and is in contact with a spring member. The plug facilitates sealing the overflow valve, thereby preventing escape of fuel while the overflow valve is operational. Due to the plug remaining in a stationary position, it is not possible to adjust the pre-load acting on the spring member when the pressure of fuel acts on the overflow valve. In order to adjust the pre-load acting on the spring member, a plug which is adaptable to be extended within the overflow valve is required.
[0003] Indian Patent Application Number 2014/CHE/6026 describes an overflow valve used in a fuel metering unit. The overflow valve includes a plug that is disposed within the overflow valve. The plug facilitates sealing the overflow valve, thereby preventing escape of fuel while the overflow valve is operational. A spring member is disposed within the overflow valve and is in contact with the plug of the overflow valve. A ball is disposed within the overflow valve and is in contact with the spring member of the overflow valve. The spring member is located in the overflow valve of the fuel metering unit in a manner such that one end of the spring member abuts the plug while the opposite end of the spring member is in contact with the ball.
Brief description of the accompanying drawings
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0005] Figure 1 illustrates an overflow valve in a fuel metering unit in one embodiment of the invention.
Detailed description of the embodiments
[0006] Figure 1 illustrates a screw plug assembly 9 for an overflow valve 8 of a fuel metering unit. The screw plug assembly 9 comprises a screw plug 12 with a bore adapted to seal the overflow valve 8. A control bolt 14 is inserted within a bore defined within the screw plug 12. The control bolt 14 is biased against an end of a spring member 16 in a manner such as to facilitate adjusting a pre-load acting on the spring member 16.
[0007] In addition, an overflow valve 8 of a fuel metering unit is described. The overflow valve 8 includes a screw plug assembly 9 comprising a screw plug 12 with a bore adapted to seal the overflow valve 8. A control bolt 14 is inserted within the bore defined within the screw plug 12, the control bolt 14 biased against an end of a spring member 16 in a manner such as to facilitate adjusting a pre-load acting on the spring member 16.
[0008] Further, a fuel metering unit is described. The fuel metering unit comprises an overflow valve body 10 integrated within a housing of the fuel metering unit. A screw plug assembly 9 is adapted to seal the overflow valve body 10. A screw plug 12 with a bore is coupled to the overflow valve body 10, the screw plug 12 adapted to seal the overflow valve body 10. A control bolt 14 is inserted within the bore defined within the screw plug 12, the control bolt 14 biased against an end of a spring member 16 in a manner such as to facilitate adjusting a pre-load acting on the spring member 16.
[0009] The fuel metering unit includes the housing of the fuel metering unit. The housing includes an inlet that is in flow communication with a feed pump. The inlet is adapted to receive fuel from the feed pump. The housing of the fuel metering unit includes an outlet that is in flow communication with a high pressure pump. The fuel metering unit includes the overflow valve 8 that is integrated within the fuel metering unit. The overflow valve 8 is positioned within an opening defined within the fuel metering unit during the manufacturing phase of the fuel metering unit. Specifically, the overflow valve 8 is integrated within the housing and is not mechanically detachable from the housing of the fuel metering unit.
[00010] The overflow valve 8 comprises an overflow valve body 10 having an inlet 15 and an outlet 19. A screw plug assembly 9 which is disposed within the overflow valve 8. The screw plug assembly 9 facilitates sealing the overflow valve 8 thereby preventing escape of fuel while the overflow valve 8 is operational. A spring member 16 is disposed within the overflow valve 8 and is in contact with a portion of the screw plug assembly 9 of the overflow valve 8. A calotte 17 is disposed within the overflow valve 8 and is in contact with the spring member 16 of the overflow valve 8. The calotte 17 facilitates preventing fuel entry within the overflow valve 8 by closing the inlet 15 of the overflow valve body 10 while the flow metering unit is non-operational. The spring member 16 is located in the overflow valve 8 of the fuel metering unit in a manner such that one end of the spring member 16 abuts the portion of the screw plug assembly 9 while the opposite end of the spring member 16 is in contact with the calotte 17.
[00011] The construction of the screw plug assembly 9 is now described. The screw plug assembly 9 includes a screw plug 12. The screw plug 12 includes screw threads defined on its outer periphery. The screw threads defined on the outer periphery of the screw plug 12 mesh with screw threads provided on an inner portion of the overflow valve body 10. The screw plug 12 includes a bore provided within the body of the screw plug 12.
[00012] A control bolt 14 is inserted within the bore provided within the body of the screw plug 12. The control bolt 14 has screw threads defined on its outer periphery. The screw threads defined on the outer periphery of the control bolt 14 mesh with the screw threads defined on the bore of the screw plug 12. A notch 20 is provided on an upper surface of the control bolt 14. The control bolt 14 may be rotated by inserting an allen key in the notch 20. When rotated in a clockwise direction by means of the allen key, the control bolt 14 is displaced against the screw plug 12 in a direction such that force acting on the spring member 16 increases. Therein, the control bolt 14 compresses the spring member 16, thereby facilitating pre-loading the spring member 16. When rotated in an anti-clockwise direction by means of the allen key, the control bolt 14 is displaced in a direction such that the force acting on the spring member 16 reduces. Therein, the control bolt 14 decompresses the spring member 16, thereby decreasing the pre-load acting on the spring member 16.
[00013] The control bolt 14 includes a flanged portion 18. The flanged portion 18 is provided on the control bolt 14 and is proximate to the spring member 16. The flanged portion 18 facilitates sealing the overflow valve body 10 to prevent fuel from escaping from the overflow valve body 10 via the bore within which the screw plug assembly 9 is inserted.
[00014] A seal 22 is located in a recess provided on the control bolt. Specifically, the seal 22 is provided at an interface of the screw plug 12 and the control bolt 14. The seal 22 prevents fuel in the overflow valve body 10 from escaping through the interface between the screw plug 12 and the control bolt 14.
[00015] The principle of working of the screw plug assembly 9 for an overflow valve of a fuel metering unit is now explained as an example. The control bolt 14 may be rotated by inserting the allen key within the notch 20 and rotating the notch 20 it in the clockwise direction. Therein, the control bolt 14 is displaced relative to the screw plug 12 and against the biasing force of the spring member 16 such that the control bolt 14 applies a pre-load on the spring member 16. The amount of pre-load acting on the spring member 16 may be precisely controlled by a user depending on a specific application. The pre-load acting on the spring member 16 causes the spring member 16 to be displaced at a lower force than what would be normally required to displace the spring member 16 when pressurized fuel is channelled to the overflow valve 8. The spring member 16 is designed to compress, thereby allowing fuel to enter the chamber in which the spring member 16 is housed under a specified operating pressure that is lower than what would be normally required when the spring member 16 is not pre-loaded. When the pressure of fuel entering the fuel metering unit via the inlet 15 exceeds the specified operating pressure, the spring member 16 gets compressed. The compression of the spring member 16 causes the calotte 17 to move downwardly, thereby channelling fuel into the overflow valve 8. Excess fuel that is channelled to the fuel metering unit is channelled to the fuel tank via the outlet 19.
[00016] The above described overflow valve 8 that is integrated within the housing facilitates pre-loading the spring member 16, thereby operating the overflow valve 8 at a lower operating pressure of pressurized fuel.
[00017] 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. The scope of this invention is limited only by the scope of the claims. Many modification and changes in the embodiments aforementioned are envisaged and are within the scope of this invention.