Note: Descriptions are shown in the official language in which they were submitted.
~074S14
This invention provides an improved method and apparatus
for making blown plastic containers which have a hollow
handle on one side with the handle of one-piece construction
with the body of the container~ The container is formed on
an injection molding machine with a special pre-blow mold
having a cavity into which a part of a parison is displaced
to form a handle portion of the partially blown container.
This handle portion which is hollow and curved along its
outer edge region to the shape of the final handle, is then
collapsed or compressed over a portion of its area.
The compressed area comprises the area between the body
of the partially blown container and the outer part of the
handle portion which will constitute a hollow bail handle
of the final product. The compressed part of the handle
portion is sheared from the remainder of the partislly
blown container and this shearing operation is performed
while the molten material of the parison is still hot enough
to seal over the lines where the compressed plastic is
separated from the hollow portions of the partially blown
container. These hollow portions are the handle along its
entire length and the body portion to which the handle con-
nects.
The blowing mold in which the parison is initially
blown to form the partially blown container is of special
construction. It has a plunger, shaped to the area which is
to be compressedg and has a complementary support on the
opposite side of the area that is to be compressed. The
plunger and the support are both movable so as to apply
force to opposite sides of the area of the handle portion
which is to be compressed between them. After compressing
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the plastic between the plunger and the support so as to make
it no longer hollow, the plunger and support are then moved
in such a way as to shear the compressed area from the re-
mainder of the handle portion, which is still hollow~ and
from the side of the partially blown container.
The sheared material is moved downward in the die and
the apparatus has means for stripping the sheared material
from the support so that it can be discharged to a waste
receptacle and leave the support clear for operation on a
second partially blown container.
The plunger and the support form portions of the wall
of the cavity space into which plastic is displaced to make
the handle portion.
Another feature used in the preferred embodiment of the
invention is the stretching of the parison for a substantial
distance lengthwise of the core rod on which the parison is
formed. This stretching is preferably done after an initial
blowing of the parison to free it from friction against the
core rod and the stretching is preferably formed by the pres-
sure of the blowing fluid that is introduced into the parison.
The blow mold in which the container is partially blown
is preferably made with a diameter only slightly greater than
the diameter of the original parison so that the initial
blowing in the first blow mold does not expand the diameter
or the circumference to any great degree but does the conseO
quential stretching of the plastic for axial orientation in a
lengthwise direction where the cavity of the mold is sibstan-
tially longer than the parison.
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In order to prevent sagging of the extended end of the
parison, while in the first blow mold and during transfer
from the first blow mold to a second blow mold, the preferred
embodiment of the invention has a core rod with an end por-
tion which telescopes into the main portion of the core rod.
During stretching of the parison, the end of the core rod,
which is telescoped into the main portion, is extended to a
length approaching that of the partially blown parison so as
to provide a support, if necessary, for the end of the parison
which is beyond the original end of the core rod.
In the preferred embodiment, the partially formed con-
tainer and its hollow handle are transferred to a second
blow mold with a cavity shaped to the final contour of the
container and in a subsequent blowing step, in this second
blow mold, the partially blown container and handle are ex-
panded to their final shape and size.
Other objects, features and advantages of the invention
will appear or be pointed out as the description proceeds.
In the drawing, forming a part hereof, in which like
reference characters indicate corresponding parts in all the
views:
Figure 1 is a diagrammatic top plan view of injection
blow molding apparatus for making the containers with handles
in accordance with this invention;
Figure 2 is a fragmentary, greatly enlarged, sectional
view on the line 2-2 of Figure l;
Figure 3 is a diagrammatic, isometric view of the first
blowing mold shown in Figures 1 and 2;
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Figure 4 is a fragmentary, diagrammatic and greatly
enlarged view through the core rod when expanded as in the
first blowing mold; the view being taken along the line 4-4
of Figure 3; and
Figure 5 is a greatly enlarged sectional view taken
on the line 5-5 of Figure 1.
Figure 1 shows an injection blow molding machine 10
having an injection station comprising a mold 12; a first
blowing station comprising a blowing mold 14; a second blow-
ing station comprising a blowing mold 16 and a fourth station
comprising a stripper 18~ These stations are located at 90
angular spacing around an indexing head 20 which rotates about
a center shaft 22. Indexing head 20 has four faces corres-
ponding to the operational stations with the molds 12, 14, 16
and the stripper 18.
A core rod 24 extends from each of the faces of the
indexing head 20. Only one core rod 24 is shown for each
face; but it will be understood that conventional blow mold-
ing machines have a plurality of core rods extending from
each face and the core rods 24 are merely representative of
core rods for carrying a parison and workpiece successively
from one operational station to the next.
Molten plastic from a plasticizer 26 is injected into
the mold 14 to coat the core rod 24 with a parison in accord-
ance with conventional practice.
When the mold 12 opens, the indexing head 20 eotates
90 and carries the core rod 20 to the next operational
station where the core rod and the parison are inserted into
a mold 14.
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Figure 2 shows the special construction of the first
blow mold 14. This mold 14 has an upper section 30 and a
lower section 32. The lower section 32 is connected to a
fixed platen 34; and the upper section 30 moves up and down
to open and close the mold in the conventional manner. The
mold 14 has a cavity 36 which is of unusual construction.
On one side of the core rod 24, the left side in Figure 2,
the cavity 36 extends for a substantial distance to form
what may be termed a handle portion 38 of the cavity 36.
Part of the wall of this cavity portion 38 is formed by the
lower end of a generally semi-circular plunger 40, which
slides up and down in a guideway 42 of the same cross sec-
tion as the plunger 40.
A part of the lower surface of the handle portion 38
of the cavity is formed by the top surface of a support 44
located at the upper end of a piston rod 46. The cross sec-
tion of the support 44 is substantially the same as that of
the plunger 40. The support 44 slides in a guideway 42a
which is actually a continuation of the guideway 42. The
piston rod 46 is moved up and down by a cylinder-and-piston
motor 48.
In the operation of the mold 14, the blowing of the
parison expands it to the walls o the cavity 36, including
the handle portion 38 of the cavity~ but the cavity preferably
contains air on the outside of the parison during the blowing
operation. This air is preferably subject to some pressure
during the blowing so as to act as a barrier to the expan-
sion of the parison and preferably the compressing of the
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air in the cavity around the outside of the parison is suffi-
cient to hold the plastic slightly spaced from the cavity wall
or in only light contact with the wall so as to provide for
lengthwise stretching of the parison in the body portion of
the cavity 36 as will be explained in connection with Figure 3.
The cavity 36 is substantially smaller than the intended
final cross section of the container and the parison, par-
tially blown to form a container, is indicated in Figure 2 by
the reference character 50.
When the plastic of the partially blown container 50
has reached the limits imposed by the cavity of the mold 14,
and any barrier pressure within the mold, the plunger 40 and
support 44 apply pressure to opposite sides of the area of
the handle portion which is to be removed from the mold 14.
Figure 2 shows the entire handle portion of the partially
blown container 50 to be hollow; and it should be understood
that in the molding of the parison on the core rod in the
injection mold 12 (Figure 1) there is more plastic applied
to the side of the parison which will confront the handle por-
tion 38 in the mold 14. Thus in the first blowing of the con-
tainer 50, there is ample plastic to expand into the handle
portion 38 of the cavity without causing a substantial reduc-
tion in the thickness of the wall across the handle portion 38.
After the partial blowing of the container 50 in the
mold 14, the plunger 40 and support 44 apply pressure to
opposite sides of the hollow center portion in the handle por-
tion 38 of the mold cavity and collapse this hollow portion
so that the upper and lower parts of the handle portion, be-
tween the plunger 40 and support 44 are pressed into contact
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with one another.
The plunger 40 continues to move downward and to press
the support 44 downward until the support 44 reaches the
broken line position indicated in dotted lines. In this
lowered position, the support 44 is in line with a discharge
outlet 54 opening through a side of the lower mold section 32.
There are two openings 56 through the support 44. Pins 58
extend upward from a fixed plate 60; and these pins 58 are
in line with the openings 56 and small enough to extend
through the openings 56 and protrude above the top of the
support 44 when the support is in its lowermost position, as
indicated by broken lines in Figure 2.
The material sheared from the handle portion of the
partially bLown container 50 is indicated in broken lines by
the reference character 62. The pins 50 hold this sheared
plastic 62 against further downward movement as the support
44 completes its downward stroke~ Thus the sheared plastic
62 is stripped from the support 44, as shown in Figure 2.
A blast of air through a passage 64, which opens into the
guideway 42a, blows the sheared plastic 62 out of the lower
section 32 of the mold through the discharge outlet 54. This
construction for stripping and discharging the sheared plas-
tic 62 is merely representative of means for removing the
sheared plastic from the mold 14~
Figure 3 is a diagrammatic showing of the mold 14 with
the cavity 36 extending for a substantial distance beyond a
plane 68 which marks the limit to which the parison extended
in the mold cavity 36 prior to blowing of the parison.
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An end wall 70 of the cavity 36 determines the extent to
which the partially blown parison can extend during the
blowing operation in the mold 14. There is an air inlet
passage 72 leading to the cavity 36 for supplying air for the
barrier or cushion against total expansion in the cavity 36,
as previously explained. There is an air outlet 74 at the
far end of the cavity 36 which is ad~ustable to control the
rate of escape of air from the cavity and the resulting cush-
ioning effect. This ad~ustment is effected by a needle valve
76 on the exhaust outlet 74.
The plastics of the partially blown container 50 is
stretched in the direction of the length of the core rod 24
as a result of air introduced into the interior of the parison
while the plastic of the parison is free to expand all the way
to the end face 70 of the mold 36; or just short of the end
face as a result of the cushion of air caused by the supply
of air under pressure through the inlet 72 at a slightly
higher rate than the discharge of air from the outlet 74.
This air cushion prevents the plastic from pressing against
the side wall of the cavity 36 with sufficient friction to
prevent expansion and stretching of the parison lengthwise
along substantially the full length of the cavity 36.
Figure 4 is a diagram~atlc showing of the end portion
of the core rod 24. The main body of the core rod, toward
its outer end is a tubular structure 78. There is an end
portion 80 of the core rod which telescopes into the tubular
structure 78 as shown in Figure 4. A check valve 82 in an
end face of the end portion 80 prevents plastic from entering
the core rod during the in~ection of the parison over the
core rod.
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The telescoping end portion 80 has a piston 84 closing
its open cross section at one location; and when air is in-
troduced into the core rod 24 behind the piston 84, the piston
84 pushes the telescoping end portion 80 forward to extend
the length of the core rod so that there is a support for
the partially blown parlson or container 50 while in the
mold 14 and during transfer of the partially blown container
50 to the second blowing mold 16 (Figure 1).
Figure 4 also shows a tube 86 which extends through an
opening in the piston 84 and this tube 8~ extends back to a
source of compressed air which is used for blowing the pari-
son on the core rod independently of any movement of the
telescoping end portion 80.
Whenever the pressure behind the piston 84 is relieved,
a spring 88, connected at opposite ends to the piston 84
and to a fixed pin 90 in the core rod, retracts the teles-
coping portion 80 back into the main body of the core rod 24.
Referring again to Figure 3, a bail handle 92 is shown
extending from one side of the partially blown container 50.
A clearance between the mid portion of the handle 92 and the
wall of the partially blown container 50 is indicated by the
reference character 94. This clearance provides room for
the insertion of the fingers of a human hand between the
main grip portion of the handle 92 and the wall of the fi-
nally blown container 50. In the final blowing in the second
blow mold this clearance 94 is reduced somewhat if the cavity
of the second blow mold permits further expansion of the dia-
meter of the handle 92, as is preferably the case. The clear-
ance 94 remains sufficient, however, for the admission of the
fingers of the hand of a person lLfting the final container.
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Figure 5 shows the container blown to its final cross
section and indicates by the reference character 50a. The
handle 92, blown to a slightly larger cross section, is indi-
cated by the re~erence character 92a.
The mold 16 has a cavity 96 with a handle portion 97
shaped to the desired final contour of the handle 92a. It
will be understood that the cavity 97 must be shaped to re-
ceive the handle portion 92 of the partially blown container
50.
The second blow mold 16 opens in the manner conven-
tional with other blow molding apparatus and the indexing
head 20 (Figure 1) turns 90 to carry the core rod 24 and the
container 50a to the strlpper station lô at which the con-
tainer SOa is pushed off the core rod 24, in accordance with
conventional practice. The neck 99 of the container is han-
dled at all of the operational stations in the manner con-
ventional for blow molding containers with threaded or unthread-
ed neck portions.
The preferred embodiment of the invention has been
illustrated and described, but changes and modifications can
be made and some features can be used in different combina-
tions without departing from the invention as defined in the
claims.
