Note: Descriptions are shown in the official language in which they were submitted.
_ACKGROUND OF THE INVENTION
The present invention relates to a molded
closure cap for sealing a container and more particularly
to a closure cap which is formed in a molding operation
where portions of the cap are formed of one p]astic and where
other portions are ~ormed of another plastic The same molding
dies or plungers are used with different nozzles for the two
plastic materials.
There are a number of plastic closure caps
which are presently formed by a molding operation where the
container engaging threads and other portions are formed in
a single mold. Most closure caps of this type are formed from
one type of plastic material which is used ~or the complete
closure. Other closure caps are made of two or more plastic
materials and the different portions are formed by successi~ely
activated plungers or dies.
The closure cap of the present invention uses
different plastic materials for the hard and softer portions
of ~he cap such as softer plastic materials for the sealin~
portions of the closure cap. The invention, however, includes
a molding method and means where a single mold is used but
where the differing plastic materials are supplied to the
single molding means through separate noz~les and during
successiYe spacing motions of the molding dies or plunger.
Thus, the present invention includes
improYed closure molding means where differing plastics hith
differing characteristics are used in the molding operation
hithout a change of the molding ~lunger or dies.
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According]y, an object of the present invention is to
p;-ovide an improved method and means for forming a closure
cap having portions formed of plastic materials of differing
characteristics and to the improved closure thus formed.
Another object of the present invention is to provide
an improved method and means of molding.
Apparatus and a method for molding articles from a plurality
of differing plastics comprises spaced molding heads each
including mold dies, means for holding the heads in one position
to form a first cavity, a plastic injector nozzle positioned
to communicate with said first cavity, means for moving the
heads in a second position forming a second cavity communicating
with said first cavity, and a second plastic injection nozzle
positioned to communicate with said second cavity.
Further objects of the invention will become apparent
upon an understanding of the illustrative embodiments described,
or will be indicated in the appended claims, and various advantages
not referred to herein will occur to one skilled in the art
upon employment of the invention in practice.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention has been chosen
for purposes of illustration and description and is shown
in the accompanying drawings, forming a part of the specification,
wherein:
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Fig. 1 is a front elevational view, partially
cut away, of a closure cap in accordance with the present
invention .
Fig. 2 is a front elevational view, partially
cut away, of the closure cap of Fig. 1 in sealing engagement
with a container.
Figs. 3 and 4 are enlarged sectional views
illustrating successive positions of the molding elements
of the apparatus in performing the molding operation of the
invention.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
Figs. 1 and 2 illustrate a preferred embodiment
of a molded closure cap 1 manufactured by the apparatus and
method of the invention. The closure cap 1 has a molded outer
shell 2 including container engaging means which are continuous
threads 3 in the embodiment illustrated but which may be lugs
or other suitable containing engaging members. The outer
shell ~ is molded of a relatively rigid plastic such as
polypropylene or copolymers thereof or high density polyethylene.
These plastics are available in formulations which provide
a relatively rigid and form retaining closure cap shell including
the cover 4 and the dependent skirt 5 with the threads 3
formed on the inner surface of the skirt 5.
In order to provide for a tight seal with a
glass or plastic container 6, including a seal which will
contain pressure or provide a vacuum seal, an inner sealing
member 7 is formed on the under surface of the closure cap
~ d
cover 4 of a relatively softer plastic capable of conforming
to and thereby creating a tight seal with the rim 8 of the
container 6. The preferred cross section of the sealing
member 7 includes container engaging members such as the
flared ribs or fingers 9 positioned to engage the outer
and inner corners of the container rim 8 finish. The central
portion of the sealing member 7 may be reinforced, as
illustrated, with a thickened center 10. In other embodiments
this central thickening may take the form of a plug adopted to
provide a stopper-like seal with the container mouth.
In the preferred embodiment of the closure 1
as illustrated, the closure cover 4 is shown with a concave
shape. This shape of the cover is useful, particularly for
pressure packages, where the internal pressure on the closure
cap cover 4 tends to force it towards a flat shape rather than
causing it to bulge outwardly. A number of plastic materials
are useful for the sealing member 7 including low density
polyethylene. The outer surface of the closure cap skirt S
is knurled at 11 for facilitating the gripping of thè closure
cap 1 during application and removal.
Figs. 3 and 4 illustrate a preferred apparatus
for and method of molding closure caps of the general type
described above. This preferred apparatus and method molds
the closure cap including the harder outer shell and the
softer inner plastic sealing member in successive injection
operations within a unitary molding head with the two different
plastics being injected through spaced injection nozzles
in an upper die member and with controlled spacing operations
for forming the separate portions being provided ~or bv
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relative movement of portions of the molding apparatus.
The general method and the related apparatus
will now be described generally with reference to Figs. 3
and 4 which are enlarged cross sections of the molding apparatus.
There is an upper molding head 12 which is
fixedly mounted. It includes a nozzle mounting portion 13
and cooperating members 14 and 15. Die member 14 includes
a pair of nozzle mounting appertures 16 and 17 and nozzle
outlets 18 and 19. The molding surface 28 of a plunger 26
is shaped to form a cavity in combination with the lower
surface 22 of the member 14 to form the sealing member 7.
The second die 15 fastened to the lower surface of the first
die 14 includes an annular surface 24 defining the closure
cap skirt 5. The ~ower molding head 25 is movable mounted
and includes the central molding die or plunger member 26
with the thread molding surfaces 27 encircling its upper
portion and with its top 28 being appropriately shaped to
provide the desired lower surface on the sealing member 7.
The lower molding head 25 includes additional
die members for sealing the underside of the cap skirt 5
for the molding operation including ring-like members 29
and 30.
The molding operation will now be described
with particular reference to Figs. 3 and 4 which show the
positions of the molding members 12 and 25 during the
successive injections of plastic through the two nozzle
outlets 18 and 19.
Thus, Fig. 3 illustrates the lower molding
head 25 in its raised position with a tight engagement
. Z ~ Lj
between the plunger 26 and upper die member 14 in a position
defining the sealing member 7. The softer plastic for the
sealing member 7 is injected from nozzle outlet 18 into
the sealing member cavity.
When this injection is finished, the entire
lower die head 25 is lowered (Fig, 4) the exact distance
which corresponds to the closure cap cover 4 thickness. The
nozzle outlet 19 is used to fill the resulting cavity comprising
the closure cap cover 4 and skirt portion 5, This cavity
is defined by the upper die member 14, the top of the
sealing member 7, the die member 15, plunger 26 and die
member 29,
When these in,jections are completed, a
finished closure cap 1 has been molded comprising the entire
harder outer shall 2 and the softer inner sealing member 7.
The lower molding plunger is now dropped a distance exceeding
the closure cap 1 height and the molding plun~er 26 is
unscrewed from the closure 1 permitting the closure to be
wiped clear.
Other sequences of relative motion may be
used to open two successively communicating cavities to
permit the injection of differing plastics without requiring
a die change other than relative movement of die portions.
It will be seen that an improved
method and means has been described for rapidly molding
articles such as plastic closure caps and the like formed
of two or more plastics of differing characteristics. A
preferred closure cap formed of a plurality of plastic
materials has also been described which is advantageously
manufactured by means of the method and apparatus described.
As various changes may be made in the form,
construction and arrangement of the invention and without
departing from the spirit and scope of the invention, and
without sacrificing any of its advantages, it is to be
understood that all matter herein is to be interpreted as
illustrative and not in a limiting sense.
