Note: Descriptions are shown in the official language in which they were submitted.
1~1002Z
The present invention relates to the moulding of plastic
drums.
The present invention is particularly directed to the
production of a plastic drum disclosed in copending application
No. 307,777 filed on even date herewith and entitled All Plastic
Blow Molded Drum.
In the above referenced copending application, an all
plastic blow molded drum is disciosed and includes a tubular out-
wardly bilged body having an integral upper and bottom closed end
each provided with outwardly extending ribs arranged and dimen-
sioned to permit stacking of one drum on top of another similar
drum. The upper rib is interrupted with a sealable drain opening
disposed in one of the interruptions and a vent opening disposed
in the other of such interruptions. A radial circumferentially
extending rib on the drum body is located near the upper end and
bottom end with each rib provided with a laterally extending
flange extending in the direction of the neighboring end, thereby
defining a recess for accommodating surfaces of a drum moving
device such as a hook or parrot beak lifting device. The radial
ribs with lateral flange serve as rolling hoops and extend out-
wardly in a radial direction an amount substantially the same as
that of the bilge of the tubular body side wall whereby the cen-
tral portions of neighboring drums can touch one another in
transport without the upper and lower flanges hooking over or on
each other.
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1110Q22
The present invention provides a method of molding the
foregoing all plastic drum.
The present invention also provides a method of blow
molding an all plastic drum and at the same time form an outwardly
extending projection thereon by a compression molding technique.
According to the present invention therefore there is
provided a method of moulding a plastic drum having at least one
outwardly extending projection comprising the steps of: extruding
a tubular parison of resin material having a predetermined wall
thickness with at least one section thereof having an additional
amount of resin of increased thickness for formation of each pro-
jection and at the same time assure a predetermined wall thick-
ness of the drum adjacent each projection no less than that at
the remaining portions of the drum to avoid having a zone of weak-
ness at each such location with the extrusion being programmed
to locate each section of additional thickness to facilitate the
~ formation of each of the projections; utilizing a longitudinally
split blow molding for cooperating and forming the selected drum
configuration and blow molding the parison into the selected drum
configuration when the parison is disposed interiorly of the
closed split blow mold, the parison being thus blown into the
selected drum configuration during the blow molding cycle and
such blowing being continued for a predetermined period of time
to assure the formation of the selected drum configuration and
the predetermined wall thickness adjacent the projections;
utilizing compressionmolds formingpart ofthe blowmold withsurfaces
of thecompression moldforming thecompression moldcavity beinglongi-
tudinally reciprocalin essentiallythe samedirection asthe longitu-
dinal axisof theblow mold,capturing apredetermined amounto~ the
additional resinin eachof theopen compressionmold cavitiesupon blow-
ing ofthe parison;and compressionmolding thepredetermined additional
amount ofresin intoeach ofthe projections UpOII longitudinallyrecip-
rocating thecompres-
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ll~OQ2Z
sion mold into its closed posi~ion, and at the same time assuring
the predetermined wall thickness adjacent each projection, the
compression molding of the projection taking place during the
blow molding cycle and after the initiation of the blow molding
cycle.
Desirably the tubular parison has at least two sections
thereof with an additional amount of resin of increased thick-
ness for the formation of at least two outwardly extending pro-
jections on said drum.
In a particular aspect thereof the present invention
provides a method of molding a plastic drum having at least two
outwardly extending projections comprising the steps of: extruding
a tubular parison of resin material having a predetermined wall
thickness with at least two sections thereof having an additional
amount of resin of increased thickness for formation of the pro-
jections and at the same time assure a predetermined wall thick-
ness of the drum adjacen~ the projections no less than that at
the remaining portions of the drum to avoid having a zone of
weakness at such locations with the extrusion being programmed
to locate each section of additional thickness to facilitate the
formation of each of the projections; utilizing a longitudinally
split blow molding for cooperating and forming the selected drum
configuration and blow molding the parison into the selected
drum configuration when the parison is disposed interiorly of
the closed split blow mold, the parison being thus blown into
the selected drum configuration during the blow molding cycle
and such blowing being continued for a predetermined period of
time to assure the formation of the selected drum configuration
and the predetermined wall thickness adjacent the projections;
utilizing at least one compression mold with surfaces of the
compression mold forming the compression mold cavity being longi-
tudinally reciprocal in essentially the same direction as the
- 3a -
111002Z
longitudinal axis of the blow mold, capturing a predetermined
amount of the additional resin in each of the open compression
mold cavities upon blowing of the parison; and compression mold-
ing the predetermined additional amount of resin into each of
the projections upon longitudinally reciprocating the compression
mold into its closed position, and at the same time assuring the
predetermined wall thickness adjacent the projection, the compres-
sion molding of the projection taking place after the initiation
of the blow molding cycle.
The present invention will be further illustrated by
way of the accompanying drawings in which:
Figure 1 is a side elevational view of an all plastic
blow molded drum produced in accordance with the present invention;
Figure 2 is a top plan view thereof;
Figure 3 is a side elevational view of an open blow mold
and compression mold shown in section with certain parts broken
away and removed and with a lowered parison between the open molds;
Figure 4 shows the blow mold closed about the parison
with the blow pin cooperating in introducing fluid under pressure
to expand the parison into the configuration of the blow mold
cavity while the compression mold is open;
Figure 5 is a similar view showing the compression mold
closed after the blow molding cycle is initiated and while it
continues;
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l 11100;~2
Figures 3A, 4A and 5A are enlarged fragmentary sectional
views of a part of the compression mold showing (i) the parison
with extruded thickened sections spaced from but adjacent the
open compression mold prior to blow molding (Figure 3A),
(ii) the parison blown into the configuration of the closed
blow mold with the thickened section forced into the cavity of
the open compression mold (Figure 4A) and (iii) the compression
mold closed to form the outwardly extending projection on the
exterior of the blown drum during the blowing cycle (Figure 5A);
LO and
Figure 6 is a longitudinal sectional view of the drum
with outwardly extending projections formed in accordance with
the present invention.
111~)022
DETAILED DESCRIPTION
A drum 10 molded according to the present invention in-
cludes a body 12 of tubular configuration provided with an
integrally formed bottom closed end 14 and an upper closed
end 16. In order to facilitate the manipulation and handling
of the drum, radially extending ribs 18a and 18b are formed
integrally with the tubular body 12. Each rib 18a and 18b
extends circumferentially around the periphery of the tubular
body 14 and includes laterally extending flanges 20a and 20b,
respectively. In addition, each rib defines a recess 22a and
22b, respectively, which advantageously receive and accommodates
surfaces of either a chain hoo~, parrot beak hook or lifting
device conventionally employed for moving drums. In addition
to the undercut or reinforcing qusset, the pres~nt invention
lS contemplates the formation of other forms of laterally extend-
ing projections requiring compression molding as a supplement
to blow molding as part of a single operation without the need
of any secondary operation, especially in the field of
manufacturing all plastic drums, containers or the like.
In manufacturing the drum 10, a parison 24 is initially
extruded, dropped or otherwise formed. Incident to the forma-
tion of the parison, predetermined sections 26 and 28 are pro-
vided with additional resin forming a heavy or thickened zone
in section. The programming of a parison with a heavy section
is a technique well known in the blow molding industry. The
parison 24 will be disposed between the open blow mold 30 then
opened compression molds 36 and 38. The compression molds form
part of the blow mold and extend from the cavity surfaces de-
fining the tubular body 12 and bottom closed end 14 and upper
closed end 16 ~see Fi~ure 3).
lllOO;~Z
The longitudinally split blow mold 30 is closed about
the lowered parison 24 again in a manner well kno~n to those
skilled in the art. In this connection, reference is made to
commonly assigned U.S. Patent Nos. 3,212,129 and 3,266,390 for
details of blow molding of plastic drums. Upon the closing
of the blow mold 30, the internal blowing cycle commences to
force the parison of predetermined thickness outwardly against
the surfaces of the blow mold to assume the desired configuration
of drum (see Figure 4).
The thickened sections 26 and 28 are blown into the
expanded compression mold cavity 32 and 34, respectively, formed
by the respective retracted sections of the compression molds 36
and 38. The movable compression mold section are reciprocal
in a longitudinal direction in any one of many ways including
the illustrated hydraulic piston-cylinder assembly 40 and 42,
respectively. Immediately following the initiation of the
blowing cycle, the compression molds 36 and 38 are closed about
the respective thickened sections 26 and 28. The actuation of
the compression molds follows a suitable time delay in order
20 to permit the expansion of the parison against the surfaces of
the blow mold. In a practical application of the present in-
vention, the compression molds are closed approximately five
seconds after the start of the blowing cycle. The length of
blowing cycle will vary depending upon the wall thickness of
the drum. In connection with the practical embodiment, the
blowing cycle extended over a period of approximately three
minutes for a drum of approximately 55 gallons having a wall
thickness of approximatel~ a minimum of 1/8" with the thic~ness
increasing to about 3/8" adjacent the ribs 18a and 18b. The
30 closed compression molds 36 and 38 will advantageously form
the ribs 18a and 18b, respectively.
Upon the completion of the molding cycle, the compres-
lllOOX2
sion molds 36 and 38 retract to their original position.
`Thereafter, the press opens to open the split blow mold to
permit the finished drum 10 to be removed.
The shape and location of the ribs 18a and 18b are
determined by the configuration of the compression mold cavity
and the positioning of the compression mold within the side
walls of the blow mold.
As previously explained the ribs 18a and 18b may
also be in the form of rolling hoops or reinforcing gussets re-
quiring the use of the supplemental compression molding technique.These projections can extend completely around the circum-
ferential periphery ofthe side wall of the drum or can be
stratigically placed in a given area to provide a handle or
hand grip. By the same token, the radial projection need not
be at about 90 to the side wall of the drum, but may extend
anywhere between 30 and 90 to the side wall.
It should be understood that in addition to the manu-
factu~e of drums and containers the present invention is equally
applicable to the formation of any other tYpe o~ hollow article.
.
6 -
111~ 2Z
Thus the several aforenoted objects and advantages are
most effectively attained. Although a single somewhat pre-
ferred embodiment of the invention has been disclosed and
described in detail herein, it should be understood that this
invention is in no sense limited thereby and its scope is to
be determined by that o$ the appended claims.
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