Seals-caps for fuel tanks

A seal cap, particularly for fuel tanks, is provided, having a body comprising a cylindrical prolongation directed toward a fuel tank spout, in which fits a wing supporting element, such wings travelling along a helicoidal gradient located inside the spout, a seal gasket preferably being welded between a shoulder of the element and the lower edge of the cylindrical prolongation, and a U-shaped ring being pushed against the gasket by a spring means which rests upon the inner side of the cap.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the manufacture of seal-caps having 
constant torque and a flat gasket, to be used particularly for automobile 
fuel tanks or crankcases. 
2. Description of the Prior Art 
At present, such caps are equipped with flat rubber gaskets which do not 
provide a positive seal and are not easy to put on and remove. 
In fact, the caps must meet certain other requirements which involve design 
compromises which have not proved very satisfactory. 
A perfect seal requires a strong tightening torque to screw on the cap. 
Easy mounting would therefore entail gas leaks in some cases. 
This invention aims at eliminating the difficulties outlined herein while 
allowing for a constant force of compression of the cap gasket onto the 
spout into which fuel is introduced, thus assuring an excellent seal, 
without modifying the torque to be exerted upon the cap while it is being 
screwed on. The seal is also assured by a flat gasket made of an 
elastomer, which is easy to manufacture and is low in cost.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referrng now more specifically to the drawings and particularly to FIG. 1, 
there is shown a cap-body 1, preferably made of a synthetic material, the 
fuel tank spout 2 onto which it is applied, and the helicoidal gradient 3 
of spout 2, along which the upper section of the two wings 4 of the cap 
travel. 
The body of cap 1 comprises an internal cylindrical prolongation 5 directed 
toward the spout, into which fits an element 6 supporting wings 4. The 
element 6 has a shoulder 7 facing a lower edge 8 of the cylindrical 
prolongation 5, with a natural or synthetic flat rubber gasket 9 being 
tightly wedged between those two tightening means. 
A U-shaped ring 10, concentric with prolongation 5, is supported by the 
gasket 9. Inside of ring 10 is placed a flat spring 11, or according to 
the embodiment of FIG. 4, several helicoidal springs 12. 
The seal of the spout 2 is assured by the gasket 9 whose inner edge is 
compressed between the shoulder 7 of element 6 and the edge 8 of 
prolongation 5. These two pieces are linked in an appropriate position by 
any suitable means such as clamping, welding, ultra-sound, etc. The outer 
edge of gasket 9 is pushed against spout 2 by the force of springs 11,12. 
This is achieved with constant force, through ring 10. The ring 10, moving 
along the axis of the cap against springs 11,12, balances the pushing in 
of the cap as wings 4 describe the helicoidal gradient 3 located inside 
spout 2. This arrangement thus enables one to exert a practically constant 
rotational couple upon the cap during the whole operation of sealing the 
spout. 
When the wings 4 of element 6 of the cap are stopped at the end of gradient 
3 (with the height of ring 10 and characteristics of gradient 3 having 
been defined accordingly), ring 10 comes into contact with the bottom side 
of cap 1, thus preventing any additional progress past the stopping point. 
From the preceding, it can be seen that the device of the present invention 
enables a tight seal, though it only requires a limited, constant 
tightening torque, requiring no particular effort to bring the cap in 
locked position. 
Moreover, this is obtained with a simple flat rubber gasket which can be 
stamped out and is therefore relatively inexpensive to produce, compared 
to heretofore provided means for fulfilling the same function. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is therefore to be understood 
that within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described herein.