Field of the Invention
The present invention relates to a fuel cap for fuel tank of a motor vehicle. More particularly, the present invention relates to a fuel cap which is able to maintain the required air pressure within a fuel tank and avoid fuel spillage out of the fuel tank during running of a motor vehicle.
Background
Fuel tank of a motor vehicle should be able to withstand an absolute air pressure of 1.3bar inside it without any leakage. However, the fuel tank is prone to leakage of air through several openings, mainly which are present in the fuel cap. Therefore, it is utmost necessary to provide a fuel cap which does not have any points of leakage and is able to maintain a high air tightness function with respect to fuel filler neck.
Although, fuel cap for a fuel tank of a motor vehicle is a simple part yet complex in design. Moreover, fuel caps present conventionally are not able to withstand air tightness at absolute pressure of 1.3bar inside the fuel tank and has some points of leakages from where the air pressure is able to release to the environment outside. The following paragraphs explain in detail how various components are assembled together to form a conventional fuel cap.
The fuel cap present in the prior art comprises of a cylindrical body which forms core of the fuel cap and all other components are fixed around it. Cylindrical body constitutes of three portions top portion, middle portion and bottom portion. The top and middle portions are cylindrical in shape and are split by a circular portion. The circular portion has two clearances that are spaced 180° symmetrical to each other. The top portion of cylindrical body comprises of plurality of projections and recesses that extend from circular portion to top end of the top portion. However, the clearances present on the circular portion continue as recesses till top end of top portion of the cylindrical body. The middle portion of the cylindrical body has two projections which are spaced 180° symmetrical to each other. Starting from left edges on the clearances present in the circular portion they run downward across its length to end at the lower edge of the middle portion of the cylindrical body. Just above the lower edge the middle portion has
two rectangular openings that are spaced 180° symmetrical from each other and 90° symmetrical to projection present on the middle portion. A lock assembly is housed inside the top and middle portions of the cylindrical body. Rotating a key in the lock moves its levers present so as to push an actuator out of one of the two rectangular openings.
The bottom portion of the cylindrical body is also cylindrical in shape and is separated from the middle portion by a main circular plate. This main circular plate has two engagement projections which are spaced 180° symmetrical to each other. The bottom portion houses breathe-in breathe-out assembly.
The recesses and clearances formed on top portion and circular portion respectively of the cylindrical body allow insertion of two pairs of ribs spaced 180° symmetrical to each other on inside surface of cylindrical trunk portion of the body cover. Thus, these recesses and clearances allow insertion of the body cover from top portion on to the middle portion thus making its trunk portion finally rest on the middle portion. Also, each rib in both pairs of ribs is at a small distance from each other. This small distance acts as a channel for breathe-in breathe-out of air. The lower end of the trunk portion has a step towards its inner surface. This step houses a seal ring and seals gap present between the cylindrical body and the body cover. However, due to o-geometry of the seal ring, it is unable to completely seal the air gap. The air present inside the fuel tank may escape from the space available around it, thus unable to completely seal the air gap.
The body cover further comprises of a circular plate which is placed near the top end of the trunk portion. The outer edge of this circular plate is tapered and is complimentarily engaged inside circular mouth of the turning handle. The inner edge of this circular plate is joined to a frustum like surface thus narrowing in diameter and finally meeting the trunk portion. The outside slope of this frustum like surface comprises of four steps spaced 90° symmetrical to each other. The circular plate is further provided on the bottom side surface thereof with a pair of downwardly extending anti-rotation projections. The width of anti rotation projections is equal to the clearance provided between the ribs of the fuel filler port. A circular seal member with diameter a bit less than the circular plate
thereof is accommodated on the bottom surface of the circular plate. The circular seal member has two openings which allow the anti-rotation projections to project out of it.
The trunk portion of the body cover is encompassed by a coiled spring which is further encased inside a locking member. The coiled spring rests between upper surface of the main circular plate and lower surface of a step provided on inside surface near the top edge of the locking member.
The locking member is a cylindrical component and its top surface rests below the circular seal ring. Also, the top surface of the step provided on inside surface near to top edge of the locking member rests below the four steps that are spaced 90° symmetrical to each other on the outside slope of a frustum like surface of the body cover. The locking member on its outside surface has two locking projections which are spaced 180° symmetrical to each other. The locking projection has four edges right edge, left edge, top edge and bottom edge. The right edge is a bit longer than the left edge therefore providing an inclination on the top edge. This inclined top edge helps easier movement of locking member under the tapered locking ribs present on the inside of the mouth of the fuel filler neck. The lower end of the locking member engulfs the main circular plate present between the middle and bottom portions of the circular body. The main circular plate has two engagement projections which fit inside the lower end of the locking projection present on the locking member. However, due to free space available in the locking projection the fuel cap does not fit properly on to the mouth of the fuel filler neck. Also, this improper fitment leads to release in required pressure inside the fuel tank. Further, this also leads to leakage of fuel from the space provided in the fuel cap. Therefore, there is a need to develop a fuel cap which properly abuts the mouth of fuel filler neck and is able to maintain required air pressure inside the fuel tank. Also the need is to develop a fuel cap which does not allow any leakage of fuel from the fuel tank.
Objects of the Invention
A primary object of the present invention is to provide an improved fuel cap for fuel tank of a motor vehicle which overcomes at least some of the problems faced by existing fuel caps.
Another auxiliary object of the present invention is to provide a fuel cap for fuel tank of a motor vehicle which is able to maintain air tightness at absolute air pressure of 1.3bar inside the fuel tank and does not allow air to escape out to the open atmosphere.
Summary of the Invention
Accordingly, the present invention relates to a fuel cap to be secured intermittently to a fuel filler neck attached to an inlet of a feed oil pipe, comprising a cylindrical body comprising a top portion, a middle portion and a bottom portion, the said top portion being separated from the middle portion by a circular portion and the said middle portion being separated from the bottom portion by a main circular plate; a body cover encircling the middle portion of the cylindrical body, the said body cover comprising a cylindrical trunk portion and a circular plate located on a top end of the cylindrical trunk portion, the said circular plate being provided with a pair of anti-rotation projections on a bottom surface thereof; a turning handle being affixed to the circular plate of the body cover and encircling the top portion of the cylindrical body; a circular seal member accommodated by the bottom surface of the said circular plate of the body cover; and a cylindrical locking member encasing the cylindrical trunk portion of the body cover, the said cylindrical locking member comprising a pair of locking projections on an outside surface thereof; characterized in that each of the said locking projection of the cylindrical locking member is provided with a pair of beams on an inner surface thereof that terminate at a predetermined distance from a bottom end of the locking projection, and the said predetermined distance being equal to 10% to 100% of the length of the main circular plate separating the middle portion of the cylindrical body from the bottom portion of the cylindrical body.
According to another aspect of the present invention, the fuel cap is described wherein the main circular plate comprises of a pair of engagement projections engaged within predetermined distance provided in the locking projections.
According to yet another aspect of the present invention, the fuel cap further comprising a seal ring mating with a step provided on inner side surface of a lower end of the body
cover, a lower end of the middle portion and upper surface of the main circular plate, wherein the cross section of said seal ring being dependent upon mating surfaces.
According to one more aspect of the present invention, the fuel cap is described wherein said seal ring having a rectangular cross section with a pair of flanges, each flange being on its top and bottom surfaces.
According to another aspect of the present invention, the fuel cap is described wherein said flange is selected from the group comprising triangular flange, circular flange, trapezoidal flange or rectangular flange.
According to yet another aspect of the present invention, the fuel cap is described wherein top portion of the cylindrical body comprises of plurality of projections and
recesses.
According to one more aspect of the present invention, the fuel cap is described wherein circular portion separating top portion from middle portion of cylindrical body comprises of a pair of clearances.
According to another aspect of the present invention, the fuel cap is described wherein the middle portion of the cylindrical body has two projections which start from left edges of the clearances present in the circular portion and run across middle portions length to end at a lower edge of the middle portion of the cylindrical body.
According to yet another aspect of the present invention, the fuel cap is described wherein cylindrical trunk portion of the body cover comprises of two pair of ribs on inner surface thereof.
According to one more aspect of the present invention, the fuel cap is described wherein the circular plate of the body cover is connected to top part of cylindrical trunk portion by a frustum like surface.
According to another aspect of the present invention, the fuel cap is described wherein the turning handle comprises of a circular mouth having plurality of projections and recesses on inner surface thereof, said plurality of projections and recesses complimentary to plurality of projections and recesses provided on top portion of the cylindrical body.
According to yet another aspect of the present invention, the fuel cap is described wherein said seal member is provided with a pair of openings that allow the pair of anti-rotation projections on the bottom surface of the circular plate to project out.
According to one more aspect of the present invention, the fuel cap is described further comprising a coiled spring encompassing the trunk portion of the body cover and encased inside the locking member.
According to another aspect of the present invention, the fuel cap is described wherein the top and middle portion of the cylindrical body comprises a lock assembly and an actuator in their inner area thereof.
According to yet another aspect of the present invention, the fuel cap is described wherein the bottom portion of the cylindrical body houses a breathe-in breathe-out assembly.
According to one more aspect of the present invention, the fuel cap is described wherein said pair of ribs on inner surface of cylindrical trunk portion lies on right edge of two projections present on the cylindrical body in a securing-started stage.
According to another aspect of the present invention, the fuel cap is described wherein said pair of ribs on inner surface of cylindrical trunk portion lies on left edge of two projections present on the cylindrical body in a securing-finished stage.
According to yet another aspect of the present invention, a fuel cap as claimed in claim 1, wherein an upper edge of the said locking projection is metallic.
Brief Description of the Drawings
The invention itself, together with further features and attended advantages, will become
apparent from consideration of the following detailed description, taken in conjunction
with the accompanying drawings. One or more embodiments of the present invention are
now described, by way of example only, with reference to the accompanied drawings
wherein like reference numerals represent like elements and in which:
Figure 1a illustrates an isometric view of the fuel cap.
Figure 1b illustrates bottom view of the fuel cap.
Figure 2 is an exploded perspective view of the fuel cap.
Figure 3 is a sectional view of the fuel cap showing various components as assembled
together.
Figure 4 illustrates a cut-out view showing pair of beams present on inner surface of the
locking projection.
Figure 5a illustrates a perspective view of locking member according to prior art.
Figure 5b illustrates a perspective view of locking member according to present
invention.
Figure 6a shows a sectional view of seal member.
Figure 6b shows a sectional view across line A-A' of seal member as shown in figure 6a.
Figure 7a illustrates unlock position and lock position of the fuel cap.
Figure 7b illustrates one of the views of fuel filler neck.
Figure 8a illustrates a perspective view of the fuel cap when it is in the securing-started
stage.
Figure 8b illustrates a perspective view of the fuel cap when it is in the securing-finished
stage.
Figure 9 illustrates a test set up for testing the ability of fuel cap to maintain a required air
pressure inside a fuel tank.
Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Detailed description of the Invention
While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention as defined by the appended claims.
Before describing in detail embodiments it may be observed that the novelty and inventive step that are in accordance with the present invention reside in the construction of fuel cap, accordingly, the drawings are showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such setup or device. In other words, one or more elements in a system or apparatus proceeded by "comprises... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus. The following paragraphs explain present invention with respect to fuel cap 1 to be secured to a fuel filler neck attached to an inlet of a fuel pipe.
Fig. la is an isometric view of the fuel cap 1. The figure further shows some parts of the fuel cap 1 such as turning handle 6 with a cylindrical opening 61 in center containing a lock assembly 10.

Fig. lb illustrates a bottom view of the fuel cap 1. The figure further shows some parts of the fuel cap 1 such as main circular plate 241, bottom portion 24 of the cylindrical body extending beyond main circular plate 241, engagement projections 242 present in the main circular plate 241 and placed inside locking projections 52 of the locking member 5, circular plate of the body cover 3 engulfed inside an outside edge of the turning handle 6.
Fig. 2 illustrates an exploded view of various parts comprised in a fuel cap 1 and fig. 3 illustrates an assembled fuel cap. The following paragraphs explain in detail how these components are assembled together to form a unitary structure to form a fuel cap 1.
The fuel cap 1 of the present invention comprises of a cylindrical body 2 which forms core of the fuel cap 1 with all other components assembled around it. The cylindrical body 2 comprises of top portion 21, middle portion 23 and bottom portion 24. The top 21 and middle portions 23 are split by a circular portion 22 and middle and bottom portion 24 are split by a main circular portion 241. This circular portion 22 has two clearances 221 that are spaced 180° symmetrical to each other. The top portion 21 of cylindrical body 2 comprises of plurality of projections and recesses 211 that extend from circular portion 22 to top end of the top portion 21. However, the clearances 221 continue as recesses till top end of this top portion 21. The middle portion 23 has two projections 231 which start from left edges on the clearances 221 and run across its length to end at the lower edge of the middle portion 23.
The bottom portion 24 of the cylindrical body 2 extends beyond the main circular plate 241. The main circular plate 241 has two engagement projections 242 that are spaced 180° symmetrical to each other. The bottom portion 24 houses breathe-in breathe-out assembly 9.
A body cover 3 comprising of a cylindrical trunk portion 31 and circular plate 32 is fitted on to the middle portion 23 of the cylindrical body 2. The cylindrical trunk portion 31 has two pair of ribs on inner surface thereof which are spaced 180° symmetrical to each other. The recesses 211 and clearances 221 formed on top portion 21 and circular portion 22
respectively of the cylindrical body 2 allow insertion of the these two pairs of ribs, thus the body cover 3 on to the middle portion 23. A circular plate 32 is located at the top end of the trunk portion 31. The inner edge of this circular plate 32 is joined to a frustum like surface 322 thus narrowing in diameter and finally meeting the trunk portion 31. The outside slope of this frustum like surface 322 comprises of four steps 324 spaced 90° symmetrical to each other. The circular plate 32 is further provided on the bottom side surface thereof with a pair of downwardly extending anti-rotation projections 323.
A circular seal member 33 with diameter a bit less than the circular plate 32 thereof is accommodated on the bottom surface of the circular plate 32. The circular seal member 33 has two openings 331 which allow the anti-rotation projections 323 to project out of it. This seal member 33 is tightly secured on to the cylindrical opening or the mouth of the fuel filler neck.
A turning handle 6 is affixed to the circular plate 32. More particularly, the turning handle has a circular mouth and a cylindrical opening 61. The circular mouth is snap fitted on top of the circular plate 32. The cylindrical opening 61 has plurality of projections and recesses on its inner surface thereof. These pluralities of projections and recesses are complimentary to projections and recesses 211 present on the top portion 21 of the cylindrical body 2 and therefore are helpful in tight fitment of turning handle 6. The top edge of this cylindrical opening 61 is curved towards inside to accompany an o-ring 62 which seals any air gap present between the top edge of the cylindrical opening 61 and turning handle 6.
A cylindrical locking member 5 encases the cylindrical trunk portion 31 of the body cover 3. The top surface of the locking member 5 rests below the circular seal member 33. Also, the top surface of a step 51 provided on inside surface near to top edge of the locking member 5, rests below the four steps that are spaced 90° symmetrical to each other on the outside slope of a frustum like surface 322 of the body cover 3. The locking member 5 on its outside surface has two locking projections 52 which are spaced 180° symmetrically to each other. These locking projections 52 are provided with a pair of
beams on their inner surface thereof. These beams terminate at a predetermined distance from a bottom end of the locking projection. This predetermined distance is equal to 10% to 100% of the length of the main circular plate 241 dividing middle and bottom portion of the cylindrical body 2. Further, the main circular plate 241 is provided with a pair of engagement projections 242 that engage within the locking projections 52. More particularly, these engagement projections 242 engage within the predetermined distance provided in the locking projections 52. Thus, this engagement of engagement projections 242 in the locking projections 52 helps in tight fitment of fuel cap 1 on to the mouth of the fuel filler neck. More particularly, the circular seal member 33 tightly abuts the mouth of the fuel filler neck, thus leaving no space for any release of air pressure present within the fuel tank or the fuel itself.
A seal ring 4 which has a rectangular cross section is accommodated on top surface of the main circular plate 241. More particularly, the lower end of the trunk portion 31 which rests on top surface of the main circular plate 241 has a step 311 towards its inner surface so as to accommodate a seal ring 4. The rectangular cross-section 41 occupies all the space that is present in the step 311. Moreover, a flange 42 is provided on top and bottom surface of the seal ring to rule out any possibility of space being left out. The flange 42 may be either of triangular, trapezoidal, circular or rectangular in shape.
The trunk portion 31 of the body cover 3 is encompassed by a coiled spring 7. More particularly the coiled spring 7 is encased inside the locking member 5. More precisely, the coiled spring 7 rests between upper surface of the main circular plate 241 and lower surface of a step 51 provided on inside surface near to top edge of the locking member 5.
A lock assembly 10 is housed inside the top 21 and middle portions 23 of the cylindrical body 2. Also, an actuator is placed below the lock assembly in the middle portion of the cylindrical body. There are two rectangular openings 232 on the lower part of the middle portion 23 which are 90° symmetrical to the two projections 231. These rectangular openings 232 allow the actuator to project out in the locked condition.
Also, a breathe-in breathe-out assembly is housed within the lower portion 241 of the cylindrical body 2.
Fig. 4 illustrates a fuel cap 1 wherein a cut-out portion of the locking projection 52 is shown. The cut-out portion shows a pair of beams on the inner surface of the locking projections. These beams terminate at a predetermined distance '1' from a bottom end of the locking projection 52. This predetermined distance T is equal to 10% to 100% of the length of the main circular plate 241 dividing middle and bottom portion of the cylindrical body 2.
Figure 5a and 5b illustrate cylindrical locking member 5 of the prior art and that of the present invention respectively. It can be seen from figure 5a in prior art the pair of beams present in inner surface of the locking projection 52 were placed away from the main circular plate 242. Figure 5b illustrates locking member 5 wherein the pair of beams terminate at a predetermined distance '1' from the bottom end of the locking projection 52.
Figures 6a and 6b illustrate a seal ring 4 present on inside of a step 311 wherein the step 311 is present towards inner surface of lower end of the trunk portion 31 of the cylindrical body 2. The seal ring 4 provides a seal between the lower end of the cylindrical body 2 and upper surface of the main circular plate 241. The cross section of the seal ring depends upon the mating surfaces it is surrounded with. However, in a preferable embodiment as shown in figure 6b the seal ring has a rectangular cross-section 41. The rectangular cross-section 41 occupies all the space present in the step 311 provided on inner surface of the lower edge of the body cover 3, thus providing a better seal. Moreover, a flange 42 is provided on upper and lower surface of the ring to rule out any possibility of escape of air present inside the fuel tank. The flange 42 may be either of triangular, trapezoidal, circular or rectangular in shape.
Fig. 7a illustrates securing operation of the fuel cap 1 to a fuel filler neck. The fuel cap 1 is secured to the fuel filler neck provided towards inner side surface thereof with a pair of
locking ribs made integral therewith by having locking projections 52, which are provided on the locking member 5, crawl into the lower portion of the ribs, and engaging the locking projections 52 with the lower portion of the ribs.
Figure 7b illustrates fuel filler neck wherein the locking rib is shown to have its lower edge tapered. The movement of locking projection 52 across this tapered edge contracts the coiled spring 7 thus axially moving locking member 5 with respect to cylindrical body 2.
At securing-started stage as illustrated in fig. 8a the anti-rotation projections 323 provided below the circular plate of the body cover 3 are in line with the locking projection provided on the locking member 5. The fuel cap 1 when inserted into the fuel filler neck allows anti-rotation projections 323 and locking projections 52 to crawl into the clearance provided between the locking ribs in the fuel filler neck. While, the anti-rotation projections 323 remain in the clearance between the ribs, the locking projections 52 crawl downwards so that the right corner of the top inclined surface of each locking projection 52 rests below the initial edge of the locking ribs. Also, at securing-started stage each pair of ribs provided on inner surface of the trunk portion 31 of the body cover 3 lie between right edge of the projection 231 and left edge of the rectangular opening 232 of the middle portion 23 of the cylindrical body 2. In order to securely lock the fuel cap 1 on the fuel filler neck, the turning handle 6 of the fuel cap 1 is rotated in clockwise direction, thus rotating the engagement projections 242 present on the main circular plate 241 on the cylindrical body 2. Engagement projections 242 rotate locking projections 52 as they are securely placed inside them. The locking ribs provided on the inner side surface of the fuel filler neck are tapered at their lower edge as illustrated in fig. 7b, so that when the upper edge of the locking projection moves below the locking ribs, the coiled spring 7 present between the lower surface of the step 51 provided near the upper edge of the locking member 5 and the upper surface of the main circular plate 241 provided on the cylindrical body 2 thereof, is contracted. Thus, the force applied by movement of locking projection 52 against the tapered lower edge of the locking ribs provided on the fuel filler neck cause contraction of coiled spring 7. Further, the
contraction of coiled spring 7 is responsible for axial movement of locking member 5 with respect to cylindrical body 2, thus urging the circular seal member 33 to fit tightly against the mouth of the fuel filler neck. Also, the position of the ribs present on inner surface of the body cover 3 is now changed and they lie between the left edge of the other projection and right edge of the rectangular opening 232. This stage is known as securing finished stage of the fuel cap 1 as illustrated in fig. 8b. Thereafter, a key is inserted inside the lock provided in the fuel cap 1. The rotation of the lock levers by the key, allow an actuator 1001 to project out of one of the rectangular openings 232 provided on middle portion 23 of the cylindrical body 2 of the fuel cap 1. Thus, this movement of actuator 1001, out of one of the openings 232 makes one of the pair of ribs now lie between right edge of the actuator 1001 and left edge of the projection 231, causing the fuel cap 1 to be securely locked to the fuel filler neck, thus terming this stage as a lock position hereafter. In lock position, a person would not be able to rotate the fuel cap 1 in anti-clockwise direction without unlocking it. Thus, the operation of fuel cap 1 starting from securing-started stage to the lock position not only tightly secures the fuel cap 1 to mouth of fuel filler neck but also makes it impossible to open the fuel cap 1 without unlocking it.
Figure 9 illustrates a test setup for testing the ability of fuel cap 1 to maintain the required air pressure within a fuel tank. As told before in the background section that it is one of the requirements to maintain an absolute air pressure of 1.3bar within a fuel tank. Therefore, the fuel cap 1 needs to be air tight so that it is able to maintain such a pressure. Consequently, fig. 9 shows a test set up where the fuel cap 1 is tested for its ability of maintaining a constant absolute air pressure of 1.3bar inside a fuel tank. Following steps explain this test in detail:
1. Firstly, the breathe-in breathe-out vent of the fuel cap 1 is sealed.
2. The fuel cap 1 is then placed on the mouth of fuel filler neck.
3. The turning handle 6 of the cap 1 is moved in clockwise direction so as to change its position from aligned position to misaligned position. The cap now cannot be removed from fuel filler neck without rotating it in anti-clockwise direction.
4. Thereafter, the cap is locked by a key so as to restrict any movement of cap in anti-clockwise direction.
5. There are two gauges present in this set up for measuring air pressure. First gauge is present on the air inlet to measure the air pressure being applied form the inlet side and the second is present on the filler pipe so as to measure the its internal pressure. Now, an absolute air pressure of 1.3bar is applied from air inlet side. Now the second gauge should show an absolute air pressure of 1.3bar.
6. Thereafter, a one way valve present between the first gauge and the filler pipe is closed so that no air can diffuse towards air inlet side.
7. Subsequently, the air inlet is also closed so that the first pressure gauge shows a zero reading.
8. Now, there's a wait period of 5 minutes during which the reading on second pressure gauge is observed. If the reading does not falls below 1.3bar, it means that the fuel cap 1 shows meets the standard requirement.
It has been seen from the above test setup that the fuel cap 1 as developed in the present invention is able to maintain an air pressure of 1.3 bar inside a fuel filler tank. Therefore, meeting the standard requirement set for motor vehicles.
The foregoing detailed description has described only a few of the many possible implementations of the present invention. Thus, the detailed description is given only by way of illustration and nothing contained in this section should be construed to limit the scope of the invention.

We Claim:
1. A fuel cap to be secured intermittently to a fuel filler neck attached to an inlet of a
feed oil pipe, comprising:
a cylindrical body comprising a top portion, a middle portion and a bottom
portion, the said top portion being separated from the middle portion by a circular
portion and the said middle portion being separated from the bottom portion by a
main circular plate;
a body cover encircling the middle portion of the cylindrical body, the said body
cover comprising a cylindrical trunk portion and a circular plate located on a top
end of the cylindrical trunk portion, the said circular plate being provided with a
pair of anti-rotation projections on a bottom surface thereof;
a turning handle being affixed to the circular plate of the body cover and
encircling the top portion of the cylindrical body;
a circular seal member accommodated by the bottom surface of the said circular
plate of the body cover; and
a cylindrical locking member encasing the cylindrical trunk portion of the body
cover, the said cylindrical locking member comprising a pair of locking
projections on an outside surface thereof;
characterized in that each of the said locking projection of the cylindrical locking
member is provided with a pair of beams on an inner surface thereof that
terminate at a predetermined distance from a bottom end of the locking
projection, and
the said predetermined distance being equal to 10% to 100% of the length of the
main circular plate separating the middle portion of the cylindrical body from the
bottom portion of the cylindrical body.
2. A fuel cap as claimed in claim 1, wherein the main circular plate comprises of a pair of engagement projections engaged within predetermined distance provided in the locking projections.
3. A fuel cap as claimed in claim 1, further comprising:
a seal ring mating with a step provided on inner side surface of a lower end of the body cover, a lower end of the middle portion and upper surface of the main circular plate, wherein the cross section of said seal ring being dependent upon mating surfaces.
4. A fuel cap as claimed in claim 3, wherein said seal ring having a rectangular cross section with a pair of flanges, each flange being on its top and bottom surfaces.
5. A fuel cap as claimed in claim 4, wherein said flange is selected from the group comprising triangular flange, circular flange, trapezoidal flange or rectangular flange.
6. A fuel cap as claimed in claim 1, wherein top portion of the cylindrical body comprises of plurality of projections and recesses.
7. A fuel cap as claimed in claim 1, wherein circular portion separating top portion from middle portion of cylindrical body comprises of a pair of clearances.
8. A fuel cap as claimed in claim 1, wherein the middle portion of the cylindrical body has two projections which start from left edges of the clearances present in the circular portion and run across middle portions length to end at a lower edge of the middle portion of the cylindrical body.
9. A fuel cap as claimed in claim 1, wherein cylindrical trunk portion of the body cover comprises of two pair of ribs on inner surface thereof.
10. A fuel cap as claimed in claim 1, wherein the circular plate of the body cover is connected to top part of cylindrical trunk portion by a frustum like surface.
11. A fuel cap as claimed in claim 1, wherein the turning handle comprises of a circular mouth having plurality of projections and recesses on inner surface thereof, said plurality of projections and recesses complimentary to plurality of projections and recesses provided on top portion of the cylindrical body.
12. A fuel cap as claimed in claim 1, wherein said seal member is provided with a pair of openings that allow the pair of anti-rotation projections on the bottom surface of the circular plate to project out.
13. A fuel cap as claimed in claim 1, further comprising a coiled spring encompassing the trunk portion of the body cover and encased inside the locking member.
14. A fuel cap as claimed in claim 1, wherein the top and middle portion of the
cylindrical body comprises a lock assembly and an actuator in their inner area
thereof.
15. A fuel cap as claimed in claim 1, wherein the bottom portion of the cylindrical body houses a breathe-in breathe-out assembly.
16. A fuel cap as claimed in claim 1, wherein said pair of ribs on inner surface of cylindrical trunk portion lies on right edge of two projections present on the cylindrical body in a securing-started stage.
17. A fuel cap as claimed in claim 1, wherein said pair of ribs on inner surface of
cylindrical trunk portion lies on left edge of two projections present on the
cylindrical body in a securing-finished stage.
18. A fuel cap as claimed in claim 1, wherein an upper edge of the said locking projection is metallic.