Air-tight cap for bottle

The present invention relates to an extremely useful air-tight cap for bottle, and more particularly an air-tight cap adapted for use in a so-called positioning container wherein a bottle of a non-circular cross section such as a polygonal or oval form is closed by a cap of a same cross section when it is brought to a determined positional relationship with respect to said bottle and capable of achieving tight closure of the cap in such determined position to maintain air tightness and to completely prevent the leak of the content by means of a structure capable of achieving maximum packing effect.

BACKGROUND OF THE INVENTION 
In general injection molded plastic caps for bottles are inevitably 
associated with certain dimensional fluctuations particularly in the screw 
thread portion thereof, depending upon the material used and the 
contraction resulting from cooling after the molding step. 
Such a cap, when used in combination with such positioning container as 
mentioned above, is therefore apt to result in an incompletely air-tight 
closure in the determined closing position due to the dimensional errors 
in the screw thread portion, thus often giving rise to leakage of the 
content. 
SUMMARY OF THE INVENTION 
The present invention is a cap provided therein with a packing of 
sufficient elasticity and deformability for ensuring close contact with 
the opening of the container, whereby a secure closure and air-tightness 
is achieved even with an injection molded plastic cap having certain 
dimensional error in the screw thread portion thereof when it is brought 
to a determined closing position with respect to the container.

DETAILED DESCRIPTION OF THE INVENTION 
In the attached drawing showing an embodiment of the present invention, 
there are shown a packing 1, a cap inner member 2, a cap outer member 3, a 
cap 4 composed of said packing, cap inner member and cap outer member, and 
a container 5. 
The packing 1 is provided with a closing portion 11 of an inverted 
truncated conical shape to be fitted into and maintained in close contact 
with a neck 51 of the container 5, the side wall 11a of said closing 
portion 11 being connected to an annular hollow elastic portion 12 of a 
semi-circular cross section of which upper part is inwardly curved. Said 
elastic portion is provided at the outer lower periphery thereof with an 
annular projection 13 to be brought into pressure contact with the top 
face of said neck 51. The packing is further provided on the central inner 
face of said closing portion 11 with a vertical cylindrical support 14 
having a flange 14a at the upper end thereof, and is entirely formed by an 
elastic soft plastic material. 
The cap inner member 2 comprises an upper wall portion 21 provided at the 
center thereof with a circular opening 22 for receiving the cylindrical 
support 14 of said packing 1, said opening 22 being provided along the 
periphery thereof with a seat ring portion 23 to engage with the flange 
14a of said cylindrical support 14, and a female thread 24 provided on the 
internal peripheral wall extended under said upper wall portion to engage 
with a male thread 52 provided on the opening 51 of the container. 
The cap outer member 3 is shaped in a cap form to be fitted on said cap 
inner member 2. 
The cap of the present invention is formed by fitting and securing said cap 
inner member 2 in said cap outer member 3 and inserting the cylindrical 
support 14 of the packing 14 upwards through the circular opening 22 of 
said cap inner member 2, thereby maintaining the packing 1 in a suspended 
state by means of engagement of the flange 14a with the seat ring 23. 
On a shoulder at the bottom portion of the neck 51 of the container 5 and 
on the bottom face of the cap 4 coming into contact with said bottom 
portion when said cap is fitted on said opening, there is provided a 
positioning structure composed of a lug a and an engaging recess b 
therefor for maintaining said cap and opening at a determined positional 
relationship (cf. FIGS. 4a and 4b). 
When the cap 4 is placed on said neck 51 for fitting on the container 5, 
the closing portion 11 of the packing 1 is inserted as shown in FIG. 1 
into said neck, with the inclined side wall 11a and annular projection 13 
of said packing 1 being respectively brought into contact with the inner 
wall and the top face of said neck. 
Upon rotation of the cap outer member 3 to advance the screw engagement of 
the cap along the male thread 52 of the neck 51, the upper wall portion 21 
of the cap inner member 2 descends against the elasticity of the elastic 
hollow portion 12 of the packing 1 while compressing the annular portion 
of said packing 1 until the mutual engagement of positioning structures a 
and b is achieved, where the screwing is completed to realize complete 
closure of the opening 51. 
The hollow elastic portion 12 of the packing, being connected to the 
inclined side wall 11a of the closing portion 11 and formed into an 
annular shape with a semi-circular cross-section with an inwardly curved 
upper part, is structurally sufficiently resilient and has sufficient 
elasticity and deformability achieved by the constituent material, and 
thus is suitably pressed by the upper wall portion 21 of the cap inner 
member 2. In the compressed state as shown in FIG. 3b, the resulting 
repulsive force inversely biases the cap inner member 2 upwards, thus 
further ensuring tight and firm closure of the cap 4. 
At the same time the closing portion 11 of the inverted truncated conical 
shape and the annular projection 13 are firmly pressed respectively 
against the inner face and the top face of the neck 51, thus achieving 
additional air-tightness. 
Besides the elastic hollow portion 12 recovers the original shape 
immediately when the cap is removed and can therefore endure repeated 
uses. 
As explained in the foregoing, the cap of the present invention, capable of 
achieving a complete closure through suitable adjustment of cap fitting 
with compensation of dimensional error in the screw threads by means of 
the hollow elastic portion formed in the packing, is most adapted for use 
in the positioning containers of various shapes as shown in FIG. 5 for 
achieving secure and firm closure regardless of the presence of certain 
dimensional errors in the injection molding of the screw threads, and this 
is ideal for containers requiring the positioning of the cap for closing. 
The positioning structure explained in the foregoing is by no means limited 
to that composed of a lug and an engaging recess as shown in FIGS. 4a and 
4b but may be composed of other suitable mechanisms.