Cap with valve

A cap with valve of the invention comprises a cap body having a fluid flow path with a stepped portion, a seal member disposed in the fluid flow path of the cap body and having outer and inner lip elements and making only the outer lip element abut on the stepped portion of the cap body, a support plate fixing the seal member and urging it to the stepped portion of the cap body and having a fluid flowing hole at the center, and a valve plate abutting on the inner lip element of the seal member and biased to close inner circumference of the inner lip element. An annular groove is formed at inner periphery of an opposite surface of the seal member to the support plate, and a stepped portion corresponding to the annular groove is formed on the support plate, thereby the seal member is fitted and fixed to the support plate through the annular groove and the stepped portion. A recess is formed on at least one of rear surface of the outer and inner lip elements and the support plate so that gap is produced at whole circumference of rear surface of the outer and inner lip elements of the seal member and the support plate at the non-pressed state of the seal member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a cap with valve, such as a fuel cap or a 
radiator cap for automobiles, which is installed to an aperture of a 
container such as a fuel tank or a radiator and adjusts pressure in the 
container by flowing fluid such as air out of the container or into the 
container from outside when the pressure in the container is positive or 
negative. 
2. Description of the Prior Art 
FIG. 1 shows structure of a cap with valve in the prior art, for example, a 
fule cap to be installed to a filler neck of an automobile. 
A fuel cap (hereinafter referred to as "cap") 1 in FIG. 1 is installed to a 
filler neck 10 of a fuel tank. A cap body 2 has a flow path 2a for fluid 
such as air and a stepped portion 2b formed on inner circumference of the 
flow path 2a. An annular seal member 3 is disposed in the flow path 2a and 
provided with lip elements 3a, 3b projecting in the same direction at 
outer and inner peripheries respectively, and the outer lip element 3a 
only is adapted to abut on the stepped portion 2b of the cap body 2. A 
support plate 4 is also disposed in the flow path 2a and provided at the 
center with a fluid flowing hole 4a so that the whole rear surface of the 
seal member 3 is adhered and the seal member 3 is biased by a spring 7 and 
urged to the stepped portion 2b of the cap body 2. Further, a valve plate 
5 is disposed in the flow path 2a and abuts on the inner lip element 3b of 
the seal member 3 so that inner circumference of the inner lip element 3b 
is biased closable by a spring 8. In the cap 1, when pressure in the fuel 
tank is positive, the valve plate 6, the seal member 3 and the support 
plate 4 are elevated against the biasing force of the spring 7, and since 
the outer lip element 3a of the seal member 3 and the stepped portion 2b 
of the cap body 2 are separated from each other, fluid such as air in the 
tank flows through the gap between the outer lip element 3a and the 
stepped portion 2b. On the contrary, when the pressure in the fuel tank is 
negative, the valve plate 5 is lowered against the biasing force of the 
spring 8, and since the inner lip element 3b of the seal member 3 and the 
valve plate 5 are separated from each other, fluid such as air flows in 
the tank through the gap between the inner lip element 3b and the valve 
plate 5. 
In this constitution of the prior art, however, in order that fluid such as 
air flows into or out of the tank at low pressure of 0.03.about.0.15 
Kg/Cm.sup.2 using the springs 7, 8 having low spring constant, the outer 
and inner lip elements 3a, 3b, the stepped portion 2b of the cap body 2, 
the valve plate 5, the rear surface of the seal member 3 and the support 
plate 4 must be high in surface precision (particularly undulation 
precision) and severe quality control is required for manufacturing the 
parts. 
In order to fix the seal member 3 to the support plate 4 in the cap 1 of 
the prior art, means such as adhesion, welding of plating is utilized and 
therefore much process number is required to assemble the seal member 3 to 
the support plate 4 and the assembling cost becomes high. 
Further in the cap 1 of the prior art, respective parts are assembled to 
the cap body 2 in sequence of the spring 8, the valve plate 5, the support 
plate 4 with the seal plate 3 fixed thereto, the spring 7, and the spring 
shoe plate 6. Since the outer and inner lip elements 3a, 3b of the seal 
member 3 are formed on the same plane in the conventional cap 1, when the 
valve plate 5 is assembled the valve plate 5 is positioned at upper side 
of the stepped portion 2b of the cap body 2 on account of the biasing 
force of the spring 8. When the support plate 4, the spring 7, the spring 
shoe plate 6 and the like are assembled later, the assembling may be 
effected in the state that outer circumference of the valve plate 5 
remains to catch the stepped portion 2b of the cap body 2. This will cause 
the wrong assebling. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a cap with valve wherein a gap is 
formed at non-pressed state between whole circumference of rear surface of 
outer and inner lip elements in a seal member, even if surface precision 
is slightly low at parts such as a stepped portion of a cap body, outer 
and inner lip elements in the seal member and rear surface thereof, the 
support plate or a valve plate, the undulation can be absorbed by the gap 
and high seal performance of the valve can be maintained and the operation 
is possible even at low pressure, and the seal member can be fitted and 
assembled to the support plate thereby the assembling of the seal member 
to the support plate becomes easy and the cost becomes low. 
Above object can be attained by a cap with valve comprising a cap body 
having a stepped portion on inner circumference of a fluid flow path, a 
seal member disponsed in the fluid flow path of the cap body and having 
lip elements projecting in the same direction at outer and inner 
peripheries respectively and making only the outer lip element abut on the 
stepped portion of the cap body, a support plate fixing the seal member 
and urging it to the stepped portion of the cap body and provided at the 
center with a fluid flowing hole, and a valve plate abutting on the inner 
lip element of the seal member and biasing inner circumference of the 
inner lip element closable, wherein a recess is formed on at least one of 
rear surface of the outer and inner lip elements and the support plate so 
that gap is produced between whole circumference of rear surface of the 
outer and inner lip elements and the support plate at nonpressed state of 
the seal member, an annular groove is formed at inner periphery of 
opposite surface of the seal member to the support plate, the support 
plate is formed with a stepped portion corresponding to the annular groove 
of the seal member, and the annular groove of the seal member is fitted to 
the stepped portion of the support plate thereby the seal member is fixed 
to the support plate. 
Another object of the invention is to provide a cap with valve, wherein the 
valve plate is disposed lower than the stepped portion of the cap body at 
assembling state of the valve plate, and when each member is assembled 
after assembling the valve plate, the valve plate is prevented from 
catching the stepped portion of the cap body so as to eliminate the wrong 
assembling of the valve plate or the like. 
Above object can be attained by a ring body used as a seal member and 
having step difference so that the inner lip element is disposed lower 
than the outer lip element. 
Above object is also attained in a constitution that the valve plate is 
biased through a spring by a spring shoe extending from lower side of the 
stepped portion of the cap body and provided at the center with a fluid 
flowing hole, the valve plate has a plurality of locking legs being 
engageable with the fluid flowing hole of the spring shoe, during the 
assembling, at first the locking legs are engaged with the fluid flowing 
hole of the spring shoe, the valve plate is previously disposed lower than 
the stepped portion of the cap body, various members are assembled to the 
cap body and then the locking legs are detached from the fluid flowing 
hole of the spring shoe and the valve plate is arranged at prescribed 
position. 
Further in addition to above constitution, the support plate is biased 
through the spring by the spring shoe plate installed on inner 
circumference of the fluid flow path of the cap body and provided at the 
center with the fluid flowing hole, the support plate has a plurality of 
locking legs being engageable with the fluid flowing hole of the spring 
shoe plate, during the assembling, the spring is previously interposed and 
the support plate is assembled through the locking legs to the spring shoe 
plate, the valve plate is assembled to the spring shoe as already 
described, and the spring shoe plate is fitted to the fluid flow path of 
the cap body, and then the locking legs of the valve plate and the support 
plate are detached from the fluid flowing hole of the spring shoe and the 
spring shoe plate respectively so as to arrange various members in 
prescribed position, thereby the efficient assembling of various members 
can be attained.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A cap 11 with valve as a first embodiment of the invention is a fuel cap to 
be installed to a filler neck 20 of a fuel tank for an automobile. The cap 
11 is composed of a cap body 12 made of plastic material such as 
polyacetal in nearly cylindrical form, and an upper cover 19 made of 
plastic material such as nylon in disc-like form and fitted to a flange 32 
on upper end of the cap body 12 and provided with a grasping portion 19a. 
In order to prevent overtightening of the cap 11 to the filler neck 20, 
the upper cover 19 is formed at rear surface with a ratchet projection 
19b, and a resilient finger 32a is formed at outer circumference of the 
flange 32 of the cap body 12 and provided at top end with a locking pawl 
32b being engageable with the ratchet projection 19b. 
A thread 33 for installing the filler neck 20 is provided on outer 
circumference of the cap body 12, and a seal ring 34 is installed on 
outside of lower surface of the flange 32. 
A flow path 12a for fluid such as air in the tank is formed on inside of 
the cap body 12, and a stepped portion 12b is formed on inner 
circumference of the flow path 12a. 
A seal member 13 of elastomer, a support plate 14 of plastic material such 
as polyacetal, a valve plate 15, a spring shoe plate 16 and coil springs 
17, 18 are arranged in the flow path 12a. 
As clearly seen in FIG. 4, the seal member 13 is a ring body comprising an 
outer lip element 13a and an inner lip element 13b projecting in the same 
direction at edge of outer and inner circumferences respectively, and step 
difference is formed so that the inner lip element 13b is disposed at 
lower side of the outer lip element 13a. Recesses 13d, 13d are formed on 
whole circumference of rear surface of the outer and inner lip elements 
13a, 13b in the seal member 13 so that gap h is produced between the seal 
member 13 and the support plate 14 as hereinafter described at non-pressed 
state. Opposite surface of the seal member 13 to the support plate 14 as 
hereinafter described is formed at inner circumferential edge with a thick 
portion 13e being slightly thick in the seal member axial portion and an 
annular groove 13c. 
The support plate 14 is a ring body formed with a fluid flowing hole 14a at 
the center and with a stepped portion 14b corresponding to the annular 
groove 13c of the seal member 13. The annular groove 13c fitted to the 
stepped portion 14b thereby the seal member 13 is fixed to the support 
plate 14. In this constitution, the assembling is simple and the cost can 
be reduced in comparison to conventional fixing method using an adhesive 
or the like. 
Lower end of the coil spring 17 abuts on rear surface (upper surface) of 
the support plate 14 fixing the seal member 13, and upper end of the coil 
spring 17 is restricted by the spring shoe plate 16 of disc-like form 
fixed by undercut to upper inner circumference of the fluid flow path 12a 
in the cap body 12, thereby the outer lip element 13a in the seal member 
13 is urged to the stepped portion 12b of the cap body 12. A fluid flow 
path hole 16a is formed at the center of the spring shoe plate 16. 
The valve plate 15 of disc-like form to constitute the seal surface is 
biased by the coil spring 18 and abuts on the inner lip element 13b in the 
seal member 13, and closes inner circumference of the inner lip element 
13b. Lower end of the coil spring 18 is restricted by the spring shoe 12c 
extending from lower side of the stepped portion 12b in the cap body 12. A 
fluid flow path hole 12d is formed at the center of the spring shoe 12c. 
Valve operation of the cap 11 in the first embodiment will now be 
described. 
When pressure in the tank is positive, as shown in FIG. 6, the support 
plate 14 fixing the seal member 13 against the biasing force of the spring 
17 is elevated, and the outer lip element 13a of the seal member 13 and 
the stepped portion 12b of the cap body 12 are separated from each other 
so as to produce a gap between the outer lip element 13a and the stepped 
portion 12b, thereby fluid such as air in the tank flows through the fluid 
flowing hole 12d of the spring shoe and the fluid flowing hole 16a of the 
spring shoe plate and between the resilient finger 32a and the upper cover 
19 into the atmosphere. In this case, the inner lip element 13b of the 
seal member 13 remains to abut on the valve plate 15. If the pressure in 
the tank becomes normal afterwards, the support plate 14 is lowered by the 
biasing force of the spring 17 and makes the outer lip element 13a of the 
seal member 13 abut on the stepped portion 12b of the cap body 12. 
On the contrary, when the pressure in the tank is negative, as shown in 
FIG. 7, the valve plate 15 is lowered against the biasing force of the 
spring 18 and the inner lip element 13b of the seal member 13 and the 
valve plate 15 are separated from each other so as to produce a gap 
between the inner lip element 13b and the valve plate 15, thereby fluid 
such as air flows between the resilient finger 32a and the upper cover 19 
and through the fluid flowing hole 16a of the spring shoe plate, the fluid 
flowing hole 14a of the support plate and the fluid flowing hole 12d of 
the spring shoe into the tank. In this case, the outer lip element 13a of 
the seal member 13 remains to abut on the stepped portion 12b of the cap 
body 12. If the pressure in the tank becomes normal afterwards, the valve 
plate 15 is elevated by the biasing force of the spring 18 and abuts on 
the inner lip element 13b of the seal member 13. 
As already described, pressure in the tank becomes positive or negative and 
fluid such as air flows out of or into the tank, and then the pressure in 
the tank becomes normal and the outer lip element 13a and the inner lip 
element 13b in the seal member 13 are urged to the stepped portion 12b of 
the cap body 12 and the valve plate 15 being respective seal surfaces, 
thereby gap h is produced between whole circumference of rear surface of 
the outer and inner lip elements 13a, 13b and the support plate 14 at 
non-pressed state. Even if surface precision is not so high in the outer 
and inner lip elements 13a, 13b and the stepped portion 12b, the valve 
plate 15 being respective seal surfaces, rear surface of the seal member 
13, the support plate 14 and the like, the error can be absorbed by the 
gap h and high performance is obtained, and if the springs 17, 18 of low 
spring constant are used, the operation is possible even at low pressure. 
In the first embodiment, in order to form air gap h between whole 
circumference of rear surface of the outer and inner lip elements 13a, 13b 
of the seal member 13 and the support plate 14 at non-pressed state, the 
recesses 13d, 13d are provided on rear side of the outer and inner lip 
elements 13a, 13b in the seal member 13, but recesses may be provided at 
side of the support plate 14. 
Further in the first embodiment, the seal member 13 is formed to have the 
step difference so that the inner lip element 13b is disposed lower than 
the outer lip element 13a. However, the outer and inner lip elements 13a, 
13b may be formed on the same level as long as gap h is formed between the 
support plate 14 and whole circumference of the outer and inner lip 
elements 13a, 13b at non-pressed state and the annular groove 13c is 
formed to be fitted to the prescribed stepped portion 14b of the support 
plate 14. 
If the inner lip element 13b is disposed lower than the outer lip element 
13a as shown in the first embodiment, when the valve plate 15 is 
assembled, the spring 18 can have such length that the valve plate 15 is 
disposed not higher than the stepped portion 12b of the cap body 12 but 
lower than the stepped portion 12b, thereby when various members are 
assembled after assembling the valve plate 15 there is no fear of 
assembling at the state that the valve plate 15 catches the stepped 
portion 12b of the cap body 12. 
In order to prevent the wrong assembling of the valve plate 15 or the like 
further and to assemble respective members simply and efficiently, 
constitution of the second embodiment as shown in FIG. 8 and FIG. 9 may be 
used. 
A cap 21 in the second embodiment like the cap 11 in the first embodiment 
comprises a cap body 22, a seal member 23, a support plate 24, a valve 
plate 25, a spring shoe plate 26, and coil springs 27, 28, wherein the 
support plate 24 is formed with a plurality of locking legs 24c projecting 
upwards from periphery of a fluid flowing hole 24a of the support plate 24 
and being engageable with a fluid flowing hole 26a of the spring shoe 
plate 26, and the valve plate 25 is formed with a plurality of locking 
legs 25a projecting downwards and being engageable with a fluid flowing 
hole 22d of a spring shoe 22c in the cap body 22. 
Assembling of various members to the cap body 22 in the cap 21 of the 
second embodiment is performed as follows (refer to FIG. 9): 
The support plate 24 fixing the seal member 23, the spring 27 and the 
spring shoe plate 26 are previously assembled by engaging the locking legs 
24c of the support plate 24 with the fluid flowing hole 26. 
The valve plate 25 is assembled to the spring shoe 22c of the cap body by 
engaging the locking legs 25a with the fluid flowing hole 22d of the 
spring shoe through the spring 28, and the spring shoe plate 26 assembling 
the support plate 24 is fixed by undercut to prescribed position on upper 
end of the cap body 22. 
And then the locking legs 25a, 25c of the valve plate 25 and the support 
plate 24 are narrowed towards inside by elastic deformation and detached 
from the fluid flowing holes 22d, 26a in engaged state respectively, 
thereby each member is arranged to prescribed position by the biasing 
force of the springs 27, 28. 
Accordingly, such constitution eliminates the wrong assembling of each 
member, and each member can be assembled simply and efficiently.