Childproof closure for large containers

A screw top container lid defines child-proof opening means which are especially suitable for use with container lids of large size. The container lid has a top wall and a peripheral wall with an inner surface, typically with screw threads for attachment to a container lip. The inner surface of the peripheral wall also defines a ratchet for engagement with corresponding ratchet on a container when the lid is applied to it, to permit screw-threaded rotation of the lid in a tightening direction to seal the lid on the container in a closed condition, but to prevent counterrotation of the lid to permit removal from the container. A portion of the peripheral wall defines removable tear strip means. The tear strip carries at least some of the ratchet of the peripheral wall, with the result that a container carrying the lid in its closed condition may be opened by removing the tear strip to facilitate counterrotation of the lid. Desirably, a second portion of the ratchet of the peripheral wall remains after removal of the tear strip, to maintain a lock that normally prevents counterrotation. This ratchet portion may be in one or more sections, and may be proportioned to permit manual flexing thereof out of engagement with the corresponding ratchet of the container, so that the lid may be manually removed, but once again locked upon reapplication of the lid. By this means, its child-proof characteristic remains even after opening.

BACKGROUND OF THE INVENTION 
It is of course necessary to store many materials such as toxic chemicals 
in a container which cannot be opened by children, and innumerable designs 
of child-proof containers are present in the prior art. However, most of 
these designs relate to small containers, and are generally impractical 
for use with respect to larger containers. 
In accordance with this invention, a containersystem is provided in which a 
screw top lid contains a child-proof closure for limiting access to the 
container. As one feature of the invention, the container lid may be of a 
design to permit positive reclosing after opening, while still retaining a 
locked characteristic which remains generally unopenable for smaller 
children. However, the container may be easily and manually opened by an 
adult user. Since the container can be relocked, it may be used to reseal 
volatile and toxic substances after initial opening. 
DESCRIPTION OF THE INVENTION 
In this invention, a screw-top container lid is provided which defines a 
top wall and a peripheral wall carried about the top wall. The peripheral 
wall has an inner surface that defines screw-thread attachment means. 
In accordance with this invention, the inner surface of the peripheral wall 
also defines ratchet means for engagement with corresponding ratchet means 
on a container when the lid is applied thereto, the ratchet means being 
proportioned to permit screw-threaded rotation of the lid in a tightening 
direction so that the lid can be sealed on the container in closed 
condition. However, counterrotation of the lid is prevented by the 
interengaging ratchet means, to prevent its removal from the container. 
A portion of the peripheral annular wall of the lid defines removable tear 
strip means, with the tear strip means carrying at least some of the 
ratchet means. Thus, a container carrying the lid in closed condition may 
be opened by removing the tear strip means, to thus facilitate the 
counterrotation and consequent removal of the lid from the container. 
Preferably, not all of the ratchet means on the peripheral wall is carried 
on the tear strip means, so that a second portion of the ratchet means 
remains after removal of the tear strip means. The peripheral wall of the 
lid defines a free edge, the peripheral wall being preferably flexible to 
permit outward, manual flexing of portions of the edge and adjacent wall 
portions. It is desirable for the second portion of the ratchet means to 
be positioned near enough to the free edge of the peripheral wall to 
permit disengagement of that second portion of the ratchet means from the 
corresponding ratchet means on the bucket upon outward flexing of an edge 
portion. 
Thus, that second portion of the ratchet means which is positioned in 
spaced relation to the tear strip means may be sized and positioned to 
permit its manual disengagement by a single user, by outward manual 
flexing of the edge portions. Then, it becomes possible to counterrotate 
the lid, while the remaining second ratchet portions are so outwardly 
flexed, to open the container after removal of the tear strip means. 
However, while the tear strip means are present, such outward manual 
flexing does not release the container lid for counterrotation, since at 
least some of the ratchet means on the lid will remain in engaging 
relation with the corresponding ratchet means on the container. 
Accordingly, the container lid is childproof because one must first tear 
away the tear strips. Then, the remaining second ratchet portion or 
portions on the peripheral wall of the container lid are preferably sized 
so that only adult hands can disengage all of them from the corresponding 
ratchet portions on the container, to permit counterrotation of the 
container lid for opening. 
The second portion of the ratchet means which are spaced from the tear 
strip means may be a single portion if desired, but preferably consist of 
a pair of diametrically opposed ratchet sections. However, any other 
desired arrangement may be used, if susceptible to essentially complete 
disengagement by the user by manual outward flexing of portions of the 
peripheral wall. 
Preferably the peripheral wall is of annular shape, disposed about the 
entire container lid. Also, an inner, annular wall may be carried by the 
lid in substantially concentric relation with the peripheral wall, to 
define an annular slot which is proportioned to receive a container lip, 
to provide an improved seal between the container lip and the lid.

DESCRIPTION OF SPECIFIC EMBODIMENTS 
Referring to the drawings, container 10 is shown to be a wide-mouthed, 
tapered bucket, defining an annular strengthening rib 12 about its outer 
surface. Container 10 defines a lip 14 which is proportioned to carry lid 
16 in screw-threaded relation thereon, typically making use of several 
multiple-start screw threads 18 of generally conventional design on the 
peripheral wall 20 of lid 16, and equally conventional, corresponding 
screw threads 22 projecting outwardly from the area of bucket lip 14. 
Typically, three or four multiple start threads 18, 22 may be provided for 
a short lid rotation of less than 180 degrees, as the lid is applied to 
and removed from container 10. 
As shown in FIG. 4, lid 16 defines a top wall 17 having an annular step 19, 
which may be used to define an area to receive the bottom end of another 
bucket 10 for stacking of the buckets with their lids in place. Peripheral 
wall 20 may surround an inner, annular wall 24 which is carried by lid 16 
in substantially concentric relation with peripheral wall 20, to define an 
annular slot 26, which is proportioned to receive container lip 14. Thus, 
a gentle pressure seal may be provided between inner annular wall 24 and 
the inner area adjacent bucket lip 14, for sealing purposes. Also, if 
desired, the top of lip 14 may seal against the uppermost end of slot 26 
for added sealing. Radial stiffening ribs 25 may connect between inner 
wall 24 and the underside of lid 16 for strengthening purposes. 
In accordance with this invention, the inner surface of peripheral wall 20 
also defines ratchets 28, details of which are seen in FIGS. 5 and 6. When 
lid 16 is in its screw-threaded, closed position on container 10, ratchets 
28 are engaged with corresponding ratchets 30, which are preferably 
positioned in an annular band about the entire outer periphery of 
container 10. 
FIG. 6 is intended to show the detailed shape of both ratchets 28 and 30, 
and how, as is a well-known principle for ratchets, each individual 
ratchet 32 is a structure of generally pyramidal cross-section having a 
long side 34 and a short side 36, typically perpendicular to each other, 
with both sides 34, 36 being typically in acute angle relation to the 
plane of the wall 37 that carries them. As shown in FIG. 5, ratchets 28, 
30 are positioned with their respective long sides 34 facing in opposite 
directions, so that the respective long sides 34 of ratchets 28, 30 can 
meet. Thus, it becomes relatively easy for the respective ratchets 28, 30, 
by simple mechanics, to rotate, with peripheral wall 20 moving in a 
counterclockwise direction relative to container 10, flexing slightly as 
it moves. However, it is much more difficult for peripheral wall 20 to 
move in the opposite direction with respect to container 10, because in 
permitted counterclockwise motion the respective long walls 34 slide by 
each other by lever action, but with clockwise motion, the shorter walls 
36 interengage at a steeper angle to inhibit such motion. Thus, lid 16 may 
be manually rotated on the screw threads 22 of container 10 into closed 
condition, but it cannot be opened again by counterrotation under normal 
circumstances. 
In the specific embodiment shown, container lid 16 defines a pair of tear 
strips 32, 34, each defining a tear tab 36 of generally conventional 
design, to permit breaking away of one end of each tear strip 32, 34 and 
then tearing of the tear strip circumferentially along line of weakness 
38, with each tear strip typically extending about 120 to 170 degrees 
about the periphery of lid 16 to a breakaway section 38 that is typically 
present to permit removal of each torn-away tear strip from the remainder 
of lid 16. 
The remaining sections 40, 42 of peripheral wall 20 typically are of 
essentially identical design, and are not removed by the removal of tear 
strips 32, 34. These sections 40, 42 are sized to permit manual outward 
flexing of the free edges 44 thereof, as shown in phantom in FIG. 4, to 
permit complete disengagement, of the second portion of ratchet segments 
28a that remain on sections 40, 42 after tear strip removal, from the 
corresponding ratchets 30 carried on container 10. Thus, when the 
remaining sections 40, 42 are so flexed outwardly by the hands, it becomes 
possible to unscrew lid 16 from container 10 with the necessary rotation 
for separation of the two members being typically substantially less than 
one turn, typically about one quarter turn. 
When it is desired to reattach the screw top lid 16 to container 10, one 
simply may conventionally screw it back on the container, since the 
remaining second ratchet sections 28 do not seriously interfere with the 
application of lid 16 as they engage with added ratchet section 30, while 
the lid is screwed on. However, the remaining second ratchet sections 28 
still inhibit unscrewing of lid 16, unless one flexes sections 40 and 42 
outwardly as described above. 
Thus, the opened container still retains some of its childproof locking 
function after opening, since sections 40, 42 can be sized to make it 
substantially impossible for the small hands of even a strong child to 
outwardly flex all of sections 40, 42 sufficiently to disengage all of the 
remaining second ratchet portions 28 from corresponding ratchet 30 on the 
bucket. 
Preferably, corresponding ratchet 30 on the bucket is a continuous, annular 
shape, while the portions of ratchet 28, carried on peripheral wall 
sections 40, 42, are separated by ratchet-free spaces 50 between the 
ratchet portions 28 defined on peripheral wall 20. This makes easier the 
breaking away of the tear strips at tear strip opening portions 36 and the 
corresponding tear-off of the tear strips at ends 38. 
If desired, the tear strip may comprise a single strip that extends around 
most of the periphery of peripheral wall 20, leaving only a single portion 
of free edge 44 which is not torn away by the tear strip, so that only one 
section needs to be flexed outwardly to rotate lid 16 off of container 10. 
Additionally, other configurations of tear strips and untorn portions 
having a segment of free edge 44 may be provided as desired. 
Accordingly, the container of this invention provides a screw- threaded lid 
capable of tightly sealing the container. At the same time, the opening 
process, while not difficult, exhibits childproof, protective 
characteristics, which protective characteristics are not lost by the 
initial opening of the container. Thus, the screw- threaded lid may be 
once again locked on the container after opening. The invention of this 
application is particularly useful with respect to large-mouthed 
containers, having a diameter on the order of four inches or more, while 
many childproof closures are only useful when their diameter is small. 
The above has been offered for illustrative purposes only, and is not 
deemed to limit the scope of the invention of this application, which 
invention is as defined in the claims below.