 |
Description  |
|
|
BACKGROUND OF THE INVENTION
The present invention relates to improvements in disposable liners for
containers, and, in one particular aspect, to unique and improved
impervious skin-tight plastic liners, for paint buckets and the like,
which retain a desired shape despite thinness of side and bottom walls
resulting from vacuum-forming from thermoplastic sheet material, and which
may be readily inserted into and removed from a container because of
venting afforded by side-wall ribs, and which may be releasably snaplocked
in place and kept free of drip and pour contaminations by a relatively
stiff overhanging rim having several indentations.
It has of course been generally well known to line containers with
inexpensive disposable plastic liners, and the common soft flat plastic
bags which may be opened and draped over and inside wastebaskets and the
like comprise one familiar example. Imperviousness, and ease of cleaning
and disposing of contents have been prime considerations, and liquid-proof
linings have been provided for such diverse items as foamed-plastic
containers (U.S. Pat. No. 3,144,167), garbage pails (U.S. Pat. No.
1,484,606), and drums for chemicals (U.S. Pat. No. 3,167,210). The latter
patent, involving closed drums with top filler necks, disclosed fluted
ribbing to impart stiffness to side walls of a plastic drum liner, and, in
another case (U.S. Pat. No. 3,940,052), the base of a drum liner has been
made stiff, and, in a yet further case (U.S. Pat. No. 3,027,444), a liner
fitted within a fiber industrial drum has been caused to have
progressively increasing thickness from top to bottom. Holes near the
upper end of a flexible bag have served to vent a garbage can while it was
being lined (U.S. Pat. No. 2,092,969), and a collapsible paint bucket and
its liner have both been collapsed in a controlled manner to exclude air
as the contents diminished (U.S. Pat. No. 3,173,573). Flexible bags,
reinforced with a metal frame and having an upper tie-off, have also been
proposed for lining a paint container and sealing a brush in place (U.S.
Pat. No. 3,905,476). It has further been known to frictionally fit and
hold the rim of a plastic cup lid (U.S. Pat. No. 4,026,459).
Professional decorators routinely employ open-topped metal paint buckets of
predetermined sizes to hold desired quantities of paint, and, although
such containers are relatively inexpensive, their costs are not
negligible, and substitute non-metallic construction material such as
paperboard has been introduced in an effort to reduce investments in such
items. In accordance with the present teachings, a conventional sturdy
metal paint bucket may be used and re-used, over and over again, without
need for intermediate cleaning or drying, and without regard for color or
other contaminations, by fitting the bucket with a very thin low-cost
disposable plastic liner. Although it might at first seem to be a
straightforward matter to implement such a concept, there are numerous
complications which interfere. For example, the thin pliable-bag type
liner, which immediately comes to mind, is bothersome to open, handle and
fit in place, and it tends to wrinkle, to sag from its intended position,
and to tear and puncture readily. If, on the other hand, the liner is made
rather stiff, it tends also to be thicker and more costly to make, and it
resists seating and unseating if it is of tight form-fitting proportions.
Further, any leakage between the bucket and liner, such as may occur as
the result of brush-wiping and dripping, tends to cause the two to adhere
and can lead to need for bothersome cleaning to prevent subsequent
contaminations and poor fit of other liners.
SUMMARY OF THE INVENTION
The present invention is aimed at creating improved lined containers, for
paint and the like, which facilitate set-ups and clean-ups and promote
multiple uses of such containers, without entailing great expense. In a
preferred embodiment, a sheet of thermoplastic material which is of at
least a predetermined thickness is heated and vacuum-drawn to a seamless
bucket-like shape of liner wherein an upper rim of substantial thickness
encircles a very much thinner frustro-conical sidewall portion, the latter
being blended with a substantially flat bottom. Distributed about the
sidewall portion, which is otherwise perfectly smooth, are several
inwardly-projecting hemicylindrical hollow ribs which run vertically fully
from the bottom to the underside of the rim, and these ribs constitute the
only irregularities between the external frustro-conical outline of the
liner and the internal frustro-conical outline of a paint bucket within
which it is to be mated. The vertically-stiffening effects of the ribs
complement the circularly-stiffening effects of the upper rim, the latter
not only being thicker than the bottom and side walls but also being of a
U-shaped cross-section and overhanging the smaller rim of a cooperating
bucket by a sufficient amount to preclude leakage under the lining from
under the rim. Spaced indentations around the rim serve to lock with a
bucket rim and prevent the liner from moving unintentionally once it is
fitted into place.
Accordingly, it is one of the objects of this invention to provide novel
and advantageous thin plastic liners, for paint pails and the like, which
are of low-cost self-sustaining form and which have venting and
strengthening ribs facilitating their use.
Another object is to provide a unique and improved disposable skin-tight
plastic liner for a container, in which a relatively thick upper rim
strengthens the liner circularly and both overhangs and interfits with a
container rim.
BRIEF DESCRIPTION OF THE DRAWINGS
Although those aspects of the present invention which are considered to be
novel are expressed in the appended claims, further details as to
preferred practices and as to further objects and features thereof may be
most readily comprehended through reference to the following description
when taken in connection with the accompanying drawings, wherein:
FIG. 1 provides a pictorial view of an improved container liner in
accordance with certain of the present teachings;
FIG. 2 is a pictorial view of a paint bucket and a cooperating liner of the
form shown in FIG. 1, together with arrows representing venting and a
direction of relative movement;
FIG. 3 illustrates a cross-section of the liner, taken along section line
3--3 in FIG. 1;
FIG. 4 is a cross-sectional detail of a portion of mated rims of a liner
and bucket such as appear in FIGS. 1 and 2; and
FIG. 5 is a cross-sectioned detail of another portion of mated rims of a
liner and bucket, taken at an indentation position such as that designed
by section line 5--5 in FIG. 1.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
Having reference to the drawings, wherein like reference characters
designate identical or corresponding components and units throughout the
several views, and more particularly to FIGS. 1 and 2 thereof, one
embodiment of an improved plastic liner, 6, intended for use with a metal
paint pail 7 of conventional form and dimensions, is shown to have a
generally frustro-conical configuration. Typically, such a common open
five-quart metal paint bucket will have an upper rim diameter of about 8
1/2 inches, a lower-end diameter of about 7 1/2 inches, an inside depth of
about 6 inches, and an outwardly-rolled rim, 8, having about a 3/16 inch
diameter. The liner 6 has complementary dimensions, enabling it to mate
snugly within the bucket, in skintight relationship except for certain
features thereof which are discussed hereinafter.
For purposes of producing a liner which is seamless, somewhat rigid
circularly about the top, and sparing of material and related cost, the
preferred processing is that of vacuum-forming. In practice of that
technique, sheet thermoplastic material of a relatively substantial
thickness (such as 0.030 inch) is heated and vacuum-drawn into a mold
cavity, with the resulting upper circular rim 6a retaining very nearly the
same original sheet thickness (such as 0.025-0.030 inch) and the
cylindrical side wall 6b and substantially flat bottom 6c having about
0.005 inch thickness 9 which is only about one-sixth that of the rim
thickness 10 (FIGS. 3 and 4). Examples of suitable plastic material are
polyethylene, polypropylene, polystyrene and rigid vinyl, and the material
may be selected to be clear, translucent, opaque or colored. Thinness of
the side wall is perfectly satisfactory, because the lining will then tend
to flex into a desirable clinging skin-tight relationship with the bucket
interior; however, that same thinness results in structural weakness
allowing the side walls to collapse and/or crack easily, and, further, the
close air-blocking fit makes it difficult to seat the liner fully into the
bucket, or to withdraw it after it has been seated. It is for the latter
reasons that several vertical venting ribs 11 are formed at equi-angularly
spaced positions around the side wall 6b. Four such ribs are shown for the
illustrated embodiment, and it should be noted that these project radially
inwardly, and that they are of hollow hemicylindrical cross-section, and
that they have substantially the same wall thinness, 9a, as the thinness 9
of the side wall elsewhere (FIG. 3), and that all of the venting ribs
extend fully from the bottom of the pail (11a, FIG. 1) to the underside
(11b, FIG. 1) of the rim 6a. Such ribs may be relatively shallow in the
radial direction, with a radial protrusion 11c of but about 1/8 inch and
an arcuate span 11d of about 3/8 inch being sufficient to accomplish the
intended results in the case of the liner for a five-quart pail under
discussion. With such ribs, the side wall 6b is advantageously stiffened,
in the vertical direction, and a plurality of such liners can be stacked
in fully mated relationship with their ribs aligned, for compact storage
and shipment. When such a liner, 6, is dropped into a metal paint bucket,
7, and gravitates slowly into place as suggested by arrow 12 in FIG. 2,
the entrapped air escapes by way of the vents afforded by ribs 11, as
suggested by arrows 13, and the liner will therefore settle into the
intended position without remaining raised or requiring hand-pressing into
place or leaving creases or wrinkles. Similarly, when such a liner has
once been dropped in place, it may thereafter be readily lifted from the
bucket, with or without some contents which may remain in the liner,
inasmuch as air will be drawn in through the venting ribs to allow the
skin-tight bottom and side walls to pull away from the interior of the
bucket.
A conventional bead or rim 8 about the top of a paint bucket is rolled in
the radially outward direction, and the relatively stiff and thick rim 6a
of a liner is intended to seat upon the bucket rim and to cover it. Rim 6a
not only has the aforementioned 6:1 ratio of thickness in relation to side
wall thickness but is also drawn downwardly, to fit about the bucket rim
8, and thence outwardly and again downwardly, at 6d (FIG. 4), such that it
overhangs bucket rim by a significant radial distance 6e and a significant
axial distance 6f, which may be about 1/8 inch and 1/4 inch, respectively.
The outwardly-and-downwardly extending folded-back rim 6a effectively
prevents drippings from brush wipings and pourings, from leaking between
the liner and bucket, where their presence would defeat purposes of the
lining. Distances such as those mentioned suffice to prevent capillary and
other surface-tension effects from drawing paint or other liquid contents
between the bucket rim and the liner.
It is also preferred that the liner be held secure against unintended
separation from the bucket, as might occur during pouring because the
venting ribs will allow the liner to fall out readily, and that it be
restrained against unintended angular movement, such as might occur during
stirring and/or brush wiping as the inwardly-projecting venting ribs are
encountered. Such needs are satisfied by incorporating several
equally-spaced arcuately-elongated inwardly-directed indentations, 6g,
into the liner rim 6a. As is shown in FIG. 5, such indentations protrude
inwardly, at 6g, just below the level at which a metal bucket rim is to be
encountered, and the somewhat flexible liner rim 6a must flex outwardly to
accommodate the snap-fitting of those indentations as a liner is being
pressed fully into place. Once so fitted, the indentations serve to hold
the liner frictionally against accidental displacements axially and
angularly.
The liner rim 6a (FIG. 4) may advantageously be terminated in a
radially-extending annular margin, as is represented by dashed-linework
6h, rather than in the second downwardly-extending cylindrical margin 6d.
Trim of excess material following vacuum forming is facilitated when the
periphery of the rim extends radially. Drippings from the margin will not
be likely to leak between the liner and bucket when spacings such as those
already mentioned herein are preserved in the case of the
radially-extending margin.
Although the container described in connection with this specification has
been that of one size of metal bucket or pail for paint, the same
invention may also be practiced with specifically-different containers for
other materials. In other sizes, for example, paint containers may have
handle ears disposed upwardly very near their rims, and the overhanging
plastic liner rim may then be partly interrupted at such sites to afford
needed clearance. More numerous venting ribs will of course afford greater
axial stiffness, for larger-size liners. Accordingly, it should be
understood that the specific embodiments and practices herein described
have been presented by way of disclosure rather than limitation, and that
various modifications, combinations and substitutions may be effected by
those skilled in the art without departure in spirit or scope from this
invention in its broader aspects and as set forth in the appended claims.
* * * * *
|
|
 |
|
 |
Description |
|
