Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to disposable lids for
disposable drinking vessels, which lids may be secured to the
rim of a corresponding drinking vessel to prevent spills and/or
to retain heat.
Disposable cup lids are usually made of plastics
material and are produced in very large numbers from a die to
form a lip on the lid which mates with a rim of the cup or glass
with which it is to be used. Advantageously, such covers have
openable and reclosable tabs to permit access to the cup or
glass for drinking from it. A desirable cup lid is one of which
the tab may be opened, retained open so that it does not
interfere with the use of the cup for drinking purposes, does
not have to be disposed of separately, and may also be
reclosable.
Various attempts have been made in the past to produce
such lids. For example, U.S. Patent Nos. 3,977,559 (LOMBARDI),
August 31st 1976, and 4,473,167 ~BAILEY) September 25th 1984,
disclose stamped out tabs in drinking cup lids, which tabs hinge
with respect to the lid to open and close. No means is shown for
securing the tabs in the open position and they are apparantly
free to flap against the user's face in use. U.S. Patent No.
4,502,608 (MILLS) March 5th 1985, discloses a somewhat similar
tab but this tab is not hinged but wholly removable. Thus the
container is not reclosable but the nuisance of a flapping tab
is not present. U.S. Patent No. 3,994,411 ((ELFELT et al)
November 30th 1976, discloses a hingable tab which may be
retained in the open position by slotting a portion of the tab
into a slit through the lid. U.S. patent No7 4,629, 088 (DURGIN)
December 16th 1986, discloses a tear strip which may be hinged
back to latch into a shallow tab shaped nest. Overhanging
detents are provided at the edges of the socket to hold the tab.
U.S. Patent No. 4,460,103 (RAMA et al) July 17th 1984, discloses
a hingable tab which does not extend to the edge of the lid but
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comprises a hingable panel in the plane of the lid. The panel is
provided with a peg which fits into a socket in the lid to hold
the panel in open position by friction. U.S. Patent No.
4,202,459 (DEPARA~ES) May 13th 1980, and-U.S. Des. Patent No.
259,403 (FRAZIER) June 2nd 1981, disclose a lid having a
hingable tab. That part of the lip of the lip which lifts with
the tab lodges in a similarly shaped groove to hold the tab
open.
All the tabs mentioned are formed by cuts into the
plastics material of the lid either as full lines or broken
lines.
It is desirable that there should, at least initially
before any tear strip is first opened, be an integral lip around
the lid for mating with a corresponding rim of the cup or glass.
Such an integral lip when mated with the rim of the cup may
exert some tension in the resulting band around the rim thereby
resulting in good sealing with the rim. Cuts through this band
to define a tear strip may at least weaken the band and, hence,
are undesirable. Some of the previous lids are provided with
radial strengthening ribs to mitigate this.
Moreover, a curved section of lid lodged in a
similarly curved socket therefor, may be lodged mainly by
friction. It may be desirable to improve such lodgement.
However, it is important that details of the die
should be as simple as possible and that extra steps of
manufacture, such as stamping cuts defining tear strips should
be minimised or even eliminated.
According to the present invention there is provided a
disposable substantially circular lid for a drinking vessel
comprising;
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a generally planar cover formed from resiliently deformable,
oriented, plastics sheet material and having a peripheral lip
comprising in a lower surface of the cover to engage a
corresponding rim of the vessel;
a tear strip in the lid comprising a minor portion of the lip
and a corresponding section of the cover, the strip being
adapted to tear inwardly from the periphery of the lid in the
direction of orientation of the plastics sheet material;
a manually grippable tab of the strip extending outwardly of
the lid having side edges joining the lid at an angle thereto
and defining, in the apex of each angle, starting points for
tearing; and
a groove located on a chord of the circular lid and diametrically
opposite said minor portion of the lip and adapted to receive
said minor portion of lip, the minor portion of the lip being
manually resiliently deformable and the groove being shaped such
that some deformation of the lip portion is necessary for it to
fit into the groove whereby the lip portion is biased against the
sides of the groove in gripping relation.
The starting points for tearing may be defined only by
the apex of each angle, but there~is no objection to providing a
cut or "nick" in the relevant apex to facilitate tearing even
more.
Preferably the minor portion of the lip is manually
resiliently deformable and the groove is shaped such that some
deformation of the lip portion is necessary for it to fit into
the groove. The resulting bias of the lip portion against the
sides of the groove may increase the holding force between them.
Suitably the groove is substantially straight. However, if a
straight groove is made during forming, the resulting groove
tends to be slightly off-straight due to deformation in cooling.
It is preferred that any such deformation is calculated to
counter the curve of the minor portion of lip.
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Preferably a stop is provided to reduce the
possibility of the tear strip being torn too far back and
possibly being entirely torn away from the lid in error.
Conveniently, such a stop may be a chordal groove extending
across the tear strip perpendicular to a radius of the lid
bisecting the tab. Such a groove may also act as a hinge for the
tear strip.
The groove to receive the minor portion of lip is
suitably of similar length and width to that portion of lip. The
portion of lip, since it formed part of the periphery of the
circular lid, is arcuate and thus requires some deformation to
squeeze it into a straight groove or another shape of groove
other than its exact complement. Once located in the groove,
the lip is biased to return to its arcuate form and its ends
may bear against a wall of the groove, thus providing more than
the frictional grip of exactly similarly shaped parts.
Channels or strengthening ribs may be provided on
either surface of the cover.
A lid according to the invention may be formed from
extruded oriented plastics material sheet. If the plastics
material is orientable, the direction of orientation is in the
direction of extrusion and is imposed on the sheet during
extrusion. In this case, the tear strip itself may be integral
with the cover with no provision being made for marking the tear
lines with perforations or full or broken cuts if the direction
of desired tearing is aligned with the direction of orientation
of the extruded plastic sheet.
An embodiment of the invention will now be described
by way of example with reference to the drawings, in which
Figure 1 is a perspective view of an embodiment of the
invention;
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Figure 2 is a plan view of the lid shown in Figure l;
Figure 3 is a section on the line III-III of Figure 2
but with the tear strip lifted;
Figure 4 is a sketch similar to that of Figure 3 but
showing a section of a slightly different lid;
Figure 5 is a diagrammatic sketch showing latching
mechanism in the unlatched position; and
Figure 6 is a similar diagrammatic sketch to that of
Figure 4 but showing the latching mechanism in the latched
position.
Referring to the drawings, a lid 11 covers a cup 10
which has a rim 15. The rim 15 mates with peripheral lip 13
of the lid 11.
The cup 10 may be of any convenient material, for
example, of polystyrene foam for hot drinks and of waxed paper
with a rolled rim 15 for cold drinks or of molded plastics
material.
The lid 11 may be formed from resiliently deformable
plastics sheet material, conveniently extruded plastics sheet
material having an orientation in the direction of extrusion.
Such orientation tends to happen naturally and, in most cases, is
more difficult to avoid than to provide.
Provision of a tear strip 40 without the necessity of
perforations or full or broken cuts to define its edges, makes
use of the almost inevitable property of orientation possessed
by the sheet from which the lid 11 is formed. A manually
grippable tab 42 extends outwardly of the periphery of the lid
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11 from the edge of the lip 13. Preferably, the tab 42 connects
with the lip through angles each having a sharp apex 44.
Convenien~ly each angle may be about 90 .
When tab 42 is gripped and pulled upwardly and
backwardly in the general direction of arrow 14, the stresses at
the apices 44 of the angles at which the tab 42 joins the lip
may be sufficient to initiate tearing. However, if desired, cuts
or nicks may be provided at these apices to help facilitate
tearing. Thereafter, the line of tearing generally follows the
direction of orientation of the plastics material with the
result that the tear strip 40 is formed as a segment of the lid
without any especial provision of tear lines. If non-oriented
plastics material is used, such tear lines should be provided.
It is an preferable feature of the present invention
to provide a lid having a lip 13 mating with a rim 15 of the
drinking vessel without perforated or cut lines for defining and
lifting an access strip to the vessel. Perforated or cut lines
in the lip area represent areas of weakness and may detract from
the band strength and resulting sealing of the lip with the
rim.
A short chordal groove 22 is provided across the tear
strip vertically to the direction of tear. This groove 22 may be
formed in the forming operation. It acts as both a hinge for
bending back tear strip 40 and as at least a partial stop to
reduce any tendency of the tear strip to tear too far. When
tearing reaches groove 22, the operator is at least aware of an
irregularity in the smoothness of tearing and should exert no
further tearing force.
The tear strip 40 may be bent back about the groove 22
so that a minor arcuate portion 46 of lip 13 moves towards the
upper surface of the lid 11 in the direction of arrow 14 in
Figure 1. A latching groove 19 is located to receive the arcuate
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portion 46 of lip 13. Groove l9 has a length sufficient to
receive portion 46 and its shape is such that the arcuate
portion 46 must be deformed slightly in order to fit into it,
and possibly the groove 19 itself deforms slightly fitted when
the available portion 46 is fitted into it. As shown groove l9
is substantially straight and its width is such as to receive
the slightly deformed portion 46.
Groove 19 is normally formed to be straight but
deformation during cooling usually results in lack of
straightness. It may be an advantage if such lack of
straightness slightly counters the curve of arcuate portion 46.
This is best seen in Figure 5.
Once portion 46 is located in groove l9 it is biased
to return to its undeformed state and thus the groove l9
confines it firmly in its lodged position. Figure 5 shows a
diagrammatic sketch of the undeformed portion 46 superimposed
upon the groove 19 with a counter curve to arcuate portion 46
which is shown in broken lines. Figure 6 shows a similar view
but with the portion 46 lodged in groove 19. Arrows 48 show the
direction of forces between the portion 46 and the groove l9
which result in rim securement of the portion 46 in groove 19.
When it is desired to close the tab it may be manually
disengaged from groove 19 and moved in the direction of the
arrow 31 shown in Figure 3 to re-engage the rim 15.
Conventional reinforcing ribs, for example, ribs 2
may be provided.
Although the invention has been described with
reference to specific embodiments, it will be appreciated that
modifications and changes may be made without departing from the
spirit and scope of the claims.
