Pull-tab for easy-to-open container lid

A pull-tab for an easy-to-open can container is mounted on a lid provided at an opening of a partially-open type container that contains a liquid such as a refreshing beverage. The pull-tab is fixed by a rivet at a predetermined portion of a removable portion surrounded by a score provided on the lid. A dish-like or bowl-like recessed portion is formed around the peripheral edge of a rivet insertion hole of the pull-tab. The peripheral edge of the rivet insertion hole is turned upward along the peripheral wall of the recessed portion to form a horizontally turned portion. A reinforcing edge is provided around the entire peripheral edge of the pull-tab with the exception of the distal end portion at a portion thereof at which the rivet insertion hole is provided. The length of this portion at which no reinforcing edge is provided is made smaller than the outer diameter of the recessed portion. Therefore, it is possible to efficiently prevent the pull-tab coming off the rivet when the container is opened. It is also possible to reduce the thickness of the pull-tab.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a lid mounted on an open portion of a 
container body that contains a liquid such as a refreshing drink, and, 
more particularly, to a pull-tab for an easy-to-open container lid which 
is mounted on the lid. 
2. Description of the Prior Art 
Conventional easy-to-open containers of the above-described type are 
classified as being one of two types, a partial-open-type and a 
full-open-type. In such an easy-to-open container, a panel portion of the 
lid of the container is provided with a score defining a removable 
portion. To remove the removable portion from the panel portion of the lid 
and thereby open the easy-to-open container, the score is ruptured by the 
action of gripping and pulling upward a gripping portion of a pull-tab 
that is fixed to the lid by means of a rivet formed integrally therewith 
at a predetermined portion of the removable portion surrounded by the 
score, with the end of the pull-tab opposite the gripping portion acting 
as a support. 
Recently, the pull-tabs have been made thinner with a view to promoting 
conservation of resources. To cope with this tendency, it was proposed in 
the specification of Japanese Patent Publication No. 12358/1970 that the 
rigidity of the pull-tab may be increased in order to prevent it from 
coming off the rivet by forming the portion surrounding a hole in the 
pull-tab through which the rivet is inserted into a bowl-like 
configuration. It was also disclosed in the specification of Japanese 
Utility Model Publication No. 421/1980 that a horizontally turned portion 
may be provided by turning the peripheral edge of the rivet insertion hole 
of the pull-tab upward so as to prevent the pull-tab from coming off the 
rivet. Further, Japanese Utility Model Laid-Open No. 98326/1983 proposes 
making the length of the distal end of the pull-tab where no turned 
reinforcing edge is provided to be smaller than the outer diameter of the 
recessed portion provided at the peripheral edge of the rivet insertion 
hole so as to provide sufficient strength to allow the container to be 
opened even if the thickness of the pull-tab is small. 
The above-described proposals each have their own advantages, and are 
effective in providing a pull-tab having a thin wall. However, each of 
them also has its own problems: for example, the pull-tab disclosed in the 
specification of Japanese Patent Publication No. 12358/1970 has the 
disadvantage that the pull-tab readily comes off the rivet when the 
container is opened. Japanese Utility Model Publication No. 421/1980 
involves the disadvantage that it requires a large amount of opening force 
even though it is effective in reducing the likelihood of the pull-tab 
coming off. The pull-tab disclosed in Japanese Utility Model Laid-Open No. 
98326/1983 also suffers from the problem that the pull-tab readily comes 
off. Thus, there have been limitations in regard to the desire to reduce 
the thickness of a pull-tab. 
SUMMARY OF THE IDNVENTION 
Accordingly, an object of the present invention is to provide an improved 
pull-tab for an easy-to-open container which enables efficient prevention 
of the tendency for a pull-tab to come off a rivet, and which enables the 
thickness of a pull-tab to be reduced. 
The above-described object and other objects of the present invention can 
be attained by providing a pull-tab for an easy-to-open container which is 
fixed by a rivet to a predetermined portion of a removable portion 
surrounded by a score provided on a lid, which comprises: one end having a 
hole through which the rivet is inserted; a dish-like or bowl-like 
recessed portion formed around the peripheral edge of the rivet insertion 
hole; a horizontally turned portion formed by bending the distal end of 
the peripheral recessed portion upward along a peripheral wall portion of 
the rivet; a gripping portion provided at the other end of the pull-tab 
away from the one end at which the rivet insertion hole is provided; and a 
reinforcing edge provided around the entire peripheral edge of the 
pull-tab with the exception of a distal end portion thereof at the one end 
at which the rivet insertion hole is formed, wherein the length of the 
portion at which no reinforcing edge is provided is made smaller than the 
outer diameter of the recessed portion.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An easy-to-open container 1 shown as a plan view in FIG. 1 is a so-called 
partial-open type can container having a lid 2 that is partially opened 
(at a removed portion 4 which is to be described later). The lid 2 has a 
flange 2a at its peripheral edge which is double seamed with the edge of a 
can body. Part of a panel portion 2b of the lid 2 is surrounded by a score 
3 to form a removable portion 4. A rivet 5 is integrally formed with the 
end of the removable portion 4 (at the central portion of the lid panel 
portion 2b) in such a manner that it protrudes upward. 
A pull-tab 6 according to the present invention is provided on the lid 
panel 2b with part thereof being supported by the rivet 5. More 
specifically, the pull-tab 6 has a rivet insertion hole 7 at one end 
thereof. The peripheral edge of the rivet insertion hole 7 is bent upward 
along a peripheral recessed portion 5a of the rivet 5 to form a 
horizontally or upwardly inclined turned portion 8, as shown in FIG. 3. 
The peripheral edge of the rivet insertion hole 7 of the pull-tab 6 is 
also provided with a dish-like recessed portion 9, as shown in FIG. 3, 
which functions to increase the rigidity of the peripheral edge of the 
insertion hole. The proximal end of the recessed portion 9 acts as a 
support fulcrum when the pull-tab 6 is pulled up. 
The pull-tab 6 also has a gripping portion 6a at the other end thereof 
which serves as a portion gripped by a finger and lifted up when the 
container is opened. The entire inner peripheral edge of the gripping 
portion 6a as well as the entire outer periphery of the pull-tab 6 with 
the exception of a distal end portion 6b thereof are turned downward to 
form a reinforcing edge 10 (FIG. 2). A portion of the pull-tab 6 at which 
no reinforcing edge 10 is formed (the distal end portion 6b) corresponds 
to a seamed portion at which the pull-tab is coupled to an adjacent one 
when pull-tabs are sequentially formed from a moving material wound in a 
coil-like shape Thus, the length b of the portion at which no reinforcing 
edge is formed (the distal end portion 6b) is made smaller than an outer 
diameter a of the recessed portion 9 (b&lt;a). 
As will be understood from the foregoing description, since the peripheral 
edge of the rivet insertion hole of the pull-tab is provided with a 
dish-like or bowl-like recessed portion according to the present 
invention, the rigidity of the peripheral edge of the rivet insetion hole 
can be increased, and, at the same time, the force required to open the 
removable portion can be reduced because the proximal end of the dish-like 
or bowl-like recessed portion acts as a support. Further, since the length 
of the distal end portion of the pull-tab at which no reinforcing edge is 
formed is set at a value which is smaller than the outer diameter of the 
recessed portion, sufficient strength is provided for opening the 
container. Further, since the peripheral edge of the rivet insertion hole 
of the pull-tab is turned upward to form the horizontally turned portion, 
coming off of the pull-tab from the rivet can be prevented. Thus, the 
present invention makes possible the provision of a thin pull-tab which 
can overcome the problems of prior art.