Note: Descriptions are shown in the official language in which they were submitted.
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HOLLOW ARTICLE FORMING APPARATUS AND METHOD
BACKGROUND OF THE INVENTION:
Field of the Invention:
This invention relates to apparatus and methods
for forming hollow articles of hardenable plasticiæed mate-
rials, and particularly to apparatus and techniques for
forming such articles by blow molding. The present applica-
tion is a division of my application Serial No. 369,926,
filed February 2, 1981, which in turn, was a division of
my application Serial No. 283,048, filed July 19, 1977.
Discussion o_ Reported Developments
The production of hollow articles such as contain-
ers, by the blow molding of plasticized materials is an
art that has been practiced for many years; glass is a
material that has been successfully blow molded on a com-
mercial scale. In apparatus that has been used for forming
glass containers, a gob of molten glass is placed in a pari-
son mold and a plunger is pressed into the glass to form
a parison that is supported in a neck mold. Then the neck
ring, with the parison attached, is transferred to a blow
molding cavity, where a blowing head inflates the parison
into the shape of a finished container~
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3~1
After the advent of synthetic thermoplastic poly-
hydrocarbon materials, came efforts to produce hollow con-
tainers from such materials. In one of the earliest com-
mercial efforts, extrusion blow molding, which began in
the 1930's, a tubular parison is extruded and thereafter
the softened parison is placed in an opened split blow mold
that, when closed, clamps both ends of the tube together.
Various means are utilized to inflate the tube while it
is inside the blow mold, to Eorm a finished object. This
method has several drawbacks, a primary one being that the
amount of material consumed, for each container made, is
relatively high because the portions of plastic material
that are pinched off from each end of the tube by the blow
mold are lost. These portions are either discarded or are
reground and remelted for subsequent reuse. These factors
have an adverse impact on materials and processing costs.
Materials costs are an especially important factor now because
rapidly rising petroleum prices have forced up the costs
of the thermoplastic resins that are commonly used in con-
tainer production.
A second commercially practiced process for makinghollow plastic articles is injection blow molding. In this
process, a preform is formed on a preform core by inject-
ing plasticized material under high pressure into an injec-
tion cavity in which the core has been placed. Such sys-
tems avoid the loss of the pinched-off portions of material
that are inherent in the extrusion blow molding process,
provide better control of article weight, and yield a better
neck finish on the article, but in turn have other drawbacks
First, the machines for carrying out this process
are costly. The basic injection press must be capable of
developing at least several tons of pressure and such presses
are expensive to make. Also, the cost of tooling (i.e.,
cores, blow cavities, neck rings, etc.) for these machines
is high, because it must be made to very close tolerances
so that the formation of flash on the parison is avoided.
Flashing occurs when the resin, which is injected under
high pressure, is forced between mating parts of the tooling
and is undesirable because it is carried over to the finished
container, with the result that the container is either
discarded or must undergo additional processing to remove
the flash; the amount of material used to form each con-
tainer is also unnecessarily increased. Such tooling can
easily be rendered useless by slight damage to the tools
resulting from accidents or mishandling.
In addition, to provide a small cross section
of material that is easily severed after the injection step,
the plasticized material is injected through a very small
gate or opening in the injection cavity. In order to obtain
a sufficient flow of resin through the gate, the resin must
be heated to a point at which the viscosity is relatively
low and it must be subjected to high pressure, usually on
the order of 15,000 to 20,000 psi or higher. ~hen injection
molding relatively stiff resins, such as high nitrile barrier
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resins (the materials that are currently considered in the
forefront with respect to containers for pressurized fluids,
for exampler carbonated beverages), injection pressures
in the range of 2~,000 psi are used. These high pressures
cause the resin to flow through the gate at high velocity
and this generates additional heat that raises the tempera-
ture of the resin above its melt temperature. This can
cause deterioration of thermo-sensitive resins and results
in visual blemishes, such as local opacity or discoloration,
or mechanical blemishes, such as locally reduced wall thick-
ness or voids, in the finished product. The rise in the
temperature of the resin also increases machine cycle time
because additional time is necessary to reduce the tempera-
ture of the preform to an optimum blow molding temperature.
Another undesirable result of the use of high injection
pressures is that it induces an uneven stress distribution
in the preform, especially in the part of the preform near
the gate, this leads to difficulties in inflating the pre-
form evenly and also to weakened portions in the finished
article.
Injection blow molding also has limitations with
respect to the maximum size of container that can be eco-
; nomically produced. Machine cycle time is lengthened be
cause the relatively larger volume of resin necessary to
form the larger preform must be injected through the verynarrow gate into the injection cavity. Moreover, injection
presses capable of developing sufficient injection pres-
sure over the relatively larger area involved are very costly.
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5;~
Thermo-forming is another container production
process that has been used commercially. In the more con-
ventional forms of thermo-forming apparatus that have been
used, a sheet or web of thermoplastic material is drawn
across the mouth of an article-forming cavity. A plunger
forces the thermoplastic material into the cavity, some-
times aided by a vacuum drawn in the cavity or by blowing
air introduced through the plunger. This process has ser-
ious drawbacks from the standpoint of material utilization,
because a major portion of the web from which the article
is drawn is not used and is discarded as scrap.
U.S. Patent No. 3,602,946 discloses an improved
thermo-forming technique in which a pad of thermoplastic
material from which the article is to be formed is molded
under low pressure, the periphery of the pad being received
in a transfer ring. A thin-walled article is formed from
the pad of thermoplastic material by a plunger that forces
the material into a forming cavity. Even by this process,
however, a significant portion of the pad of thermoplastic
material remains adhered to the transfer ring after the
article is formed, and this material represents waste that
- is not used in the formation of the article.
Efforts have been made to mold preforms using
low pressure molding techniques. In one type of equipment,
a ram is used to introduce a quantity of plasticized mate-
rial, through a relatively large opening, into a preform
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ca~ity that contains a preform core. Examples of this arrangement are
îllustrated in United States Patent No. 3,172,929 to Santelli and United
States Patent No. 3,170,871 to Ninneman et al. It should be noted that in
these arrangements, the ram Eorms a portion of the bottom wall of the preform
cavity; if the volume of the charges of plasticized material is not very
closely controlled, preforms having differing bottom wall thicknesses9 and
thus differing blowing characteristics, are produced on each cycle, with a
resulting non-uniformity of the finished articles.
Other attempts have involved compression molding the preform by
pressing a preform core into a charge of plasticized material placed in a
preform cavity. See United States Patent 3,337,910 to West and United
States Patent No. 3,375,533 to Criss. It is believed to be very difficult
to produce fully packed preforms having uniform blow molding characteristics
by these means. If attempts are made to make the volume of the charge equal
to the volume of the preform mold space, on a statistical basis, some of the
charges will ~e of lower volume and an incomplete preform will result. If
the cavity is overcharged by a volume of material greater than that of the
mold space, then the incidence of flashing or uneven wall thickness of the
preform is likely to increase.
SUMMARY OF THE INVENTION
According to the present invention, there is provided apparatus
for feeding a charge of plasticized material to a forming cavity, comprising
a source of plasticized material, a nozzle means for feeding plasticized
material from the source to the forming cavity, means for effecting relative
axial movement between the forming cavity and the nozzle, whereby the nozzle
is positioned inside the forming cavity and means for effecting relative
separation of the forming cavity and the nozzle at a first rate while plasti-
cized material flows from the nozzle, the means for effecting relative
separation including means for effecting the relative separation at a second
rate higher than the first rate.
S'~l
According to an exemplary molding method and apparatu~ embodylng
the invention, a charge of plasticized material i8 placed in a preform cavity
member. By relative movement together of the preform cavity member
- 6a -
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. ~,~
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and the preform core, the preform core is introduced into
the preform cavity, resulting in formation of an unpacked
preform. Camming surfaces associated with the preform cav-
ity can be used to close neck rings surrounding the base
of the preform core.
After the preform cavity, preform core and neck
ring segments have been brought together to define a pre-
form mold space, a quantity of plasticized material is urged
under pressure into the preform mold space to form a com-
pletely packed preform. The preform is thereafter blowmolded into the shape of the desired finished article.
A symmetrical, void-free charge of plasticized
material in the preform cavity is assured by ~irst placing
the source of plasticized material near the bottom of the
preform cavity and then progressively feeding the charge
of plasticized material into the preform cavity as relative
separation of the preform cavity and the source of plasti-
cized material is effected.
The neck mold actuating mechanism of the neck
mold associated with a preform core strips the finished
article from the core by first moving the closed neck mold
longitudinally with respect to the core. Thereafter, the
actuating mechanism causes the neck mold segments to move
laterally outwardly from the longitudinal axis of the core
to release the neck of the finished article.
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DESCRIPTION OF THE PREFERRED EMBODIMENT:
Fig. 1 is a front elevational view of one embodi-
ment of apparatus in accordance with the invention, having
a single forming station.
Fig. 2 is a partial plan view of the apparatus
illustrated in Fig. 1.
Fig. 3 is an end view of the apparatus shown in
Fig. 1, taken from the end adjacent the forming station.
Fig. 4 is a sectional view of a preform cavity
block, with a preform core received in the preform cavity.
Fig. 5A is a front elevational view of a preform
core and neck ring mechanism showing various positions of
the parts.
Fig. 5B is an end view of the core and neck ring
assembly shown in Fig. 5A.
Fig. 6 is a schematic view of article discharge
apparatus.
Fig. 7 is a schematic diagram of a hydraulic con-
trol circuit for moving the plasticizer with respect to
the preform cavity.
S~21
Figs. 8A through 8M illustrate schematically the
sequence of operation of apparatus of the type shown in
Fig. 1.
Fig. 9 illustrates a second embodiment in which
a single plasticizing element serves two forming units.
Description of the Apparatus shown in Figs. 1-8
In accordance with the embodiment shown in Fig.
1, the apparatus includes a source of plasticized material
12, for example, a maxalating screw plasticizer, that i5
mounted on base 11 and that defines a charging station.
Also mounted on the base 11 is a forming unit 13 at which
preforms and finished articles are formed.
Referring to Figures 1 and 2, a shuttle 14 is
slideably mounted on a pair of guides 15 that are mounted
on the base. The shuttle 14 is moved laterally between
the charging station and the forming station by suitable
means, such as a hydraulic cylinder 16. In Figure 1, the
shuttle is shown positioned at the charging station and
in Figure 2 the shuttle is shown positioned at the forming
station.
The shuttle 14 has a generally centrally disposed
aperture in which is freely disposed a preform cavity block
17. The cavity block includes preform cavity 18 that defines,
in part, the exterior shape of the preform. As mentioned,
the cavity block 17 is freely received in the shuttle 14
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and is retained on the shuttle by a peripheral flange 17a.
Shuttle 14 also has affixed thereto a receiving tube 19.
It should be noted, as shown in Figure 1, that when the
preform cavity 18 i5 positioned at the charging station,
the receiving tube 19 is positioned at the article forming
station.
With reference to Figures 1, 2 and 3, the plasti-
cizer 20 is mounted for vertical movement with respect to
the base 11. The mounting arrangement for the plasticizer
20 includes the base 25 secured on the base 11 and a pair
of upstanding guide bars 21 that are mounted on the base
25. The plasticizer 20 is mounted to move vertlcally on
the guide bars 21 by hydraulic motor units, 22 that are
slideably mounted on the guide bars 21. A hydraulic con-
trol circuit for effecting movement of the plasticizer 20
along the guide bars 21 will be discussed below in connec-
tion with Figure 7.
The plasticizer 20 moves vertically to position
the nozzle 23 a short distance from the bottom oE the pre-
form cavity 18 and to withdraw the nozzle 23 from the cavity18. Alternatively, the plasticizer could be held in fixed
position and the preform cavity block moved relative to
the fixed nozzle to accomplish filling of the cavity in
the manner hereinafter more fully explained. ~eans similar
to those disclosed herein for moving the plasticizer could
be employed for moving the preform cavity block vertically
at the charging station.
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The plasticizer 20 includes a feed hopper 24 for
feeding resin in particulate form to the plasticizer.
Again reEerring to Figures l, 2 and 3r the form~
ing unit 13 includes a press comprised of vertical tie bars
26 that extend between a lower fixed platen 27 and an upper
fixed platen 28. A moveable platen 29 is slideably mounted
for movement in vertical directions on the tie bars 26.
A hydraulic cylinder 31 is utilized to move the platen
29 vertically along the tie bars 26.
As shown in Figure l, a mounting plate 32 is mounted
above the upper fixed platen 28 and carries a hydraulic
cylinder 33, the function of which will later be described
in connection with the description of Figures 5A and 5B.
Depending from the bottom of upper fixed platen
28 is a neck ring and core assembly 34 which is also discussed
further below. It should be noted that in order to give
a full view of the assembly 34 in Fig. l, the figure does
not include one of the blow molding cavity parts and its
mounting structure.
Referring to Fi~ures 2 and 3, blow splits 36a,
36b are readily removably mounted on plates 30a and 30b
respectively. The plates 30a and 30b are mounted for trans-
verse sliding movement with respect ~o mounting bases 37a,
37b respectively by suitable means, for example, slideable
guides 39a, 39b that are received in slide bearings mounted
on the bases 37a, 37b. The plates 30a, 30b are moved toward
and away from core 62 by suitable means, such as hydraulic
cylinders 38a, 38b respectively. As shown in Fig. 3, the
blow splits 36a, ~6b are closed about core 62 to ~orm a
blow molding cavity in which an article, such as a container,
is formed.
With certain types of resins, particularly those
having a relatively high viscosity at melt temperatures,
as the nozzle 23 is withdrawn from the preform cavity 18,
a string of plastic material follows the nozzle as it is
withdrawn ~rom the charge of plasticized material deposited
in the cavity 18. It is desirable to sever this string,
and one means of doing so is illustrated by the severing
unit 40 shown in Figure 2. The unit 40 includes a heated
element 41, for example, a nichrome wire that is connected
to a source of electrical current (not shown) that heats
the wire 41. The wire 41 extends between opposed arms 42.
The wire 41 is caused to sweep beneath the nozzle 23 by
a suitable means, such as a solenoid 43 that is drivingly
engaged with the arms 42.
As previously mentioned, the cavity block 17 is
rreely received in the shuttle 14. In this manner, the
cavity block 17 can be driven vertically upwardly out of
the shuttle 14. This latter-mentioned operation is carried
out when the shuttle 14 is positioned against the stops
44 (Figure 2), i.e., when the preform cavity 18 is posi-
tioned with its longitudinal axis in vertical alignment
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with the longitudinal axis of the core and neck mold unit
34. The vertically moveable platen 29 carries on its upper
face a locking block 47. The locking block 47 has a cross-
sectional peripheral configuration that is compatible with
a locking recess 48 in the base of the cavity block 17.
Thus, as the cavity block 17 is carried by the shuttle 14
over the platen 29, the locking block 47 is received in
the recess 48 and the cavity block is firmly coupled to
the sliding platen 29. When the foregoing has been accom-
plished, the hydraulic cylinder 31 is caused to first movevertically upwardly to drive the cavity block 17 and thus
preform cavity 18 toward the core and neck ring unit 34;
like~ise, the hydraulic cylinder 31 can be caused to move
the platen 29 downwardly, thereby withdrawing the cavity
block 17 and causing it to be once again supported in the
shuttle 14.
Referring to Figure 2, it should be noted that
means are provided for locating the cavity block 17 with
respect to the shuttle 14. In the preferred embodiment,
such location is accomplished by means of a locating pin
45 upstanding from the shuttle 14 and a complementary recess
49 in the flange 17a of the cavity block 17. Thus, when
the cavity block 17 is drawn downwardly onto the shuttle
14, the position of the cavity 17 is located by the pin
45, which prevents rotation of the cavity block 17 in the
shuttle 14.
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Figure 4 is a cross~sectional view showing a core
and neck ring assembly 34, with the core positioned in the
preform cavity 18. In Figure 4, the preform cavity block
17 has been driven upwardly from the shuttle 14 so that
the core 62 is received in the preform cavity 1~. The pre-
form cavity block 17 has removeably secured therein a pre-
form cavity member 5~ in which is formed the preform cavity
18. The cavity member 50 has a bore 52 formed in the lower
portion thereof. In the bore 52 is slideably mounted a pis-
ton 51 that is retained in the bore 52 by suitable meanssuch as a snap ring 53. Piston 51 carries an extending
portion 54 that is slideably received in and that conforms
to the cross-sectional configuration of the recess 55 that
communicates with the preform cavity 18.
The preform cavity block also includes an inlet
conduit 5b for admitting a fluid under pressure, such as
air, into the chamber in the cavity block 17 formed beneath
the piston 51. Pressurized fluid introduced through conduit
56 bears against the piston 51 and forces it upwardly, there-
2~ by causing the extension 54 to move into the recess 55,
for purposes to be later explained.
Cavity block 17 can also be provided with appro-
priate means for providing a heat exchange fluid to the
preform cavity member 50. In the arrangement shown in Fig-
ure 4, an inlet conduit 57 carries the heat exchange fluidto an annular chamber 58 formed between the preform cavity
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block 17 and the cavity member 50. The heat exchange fluid
is exhausted from the chamber 58 by an outlet conduit 59.
In this manner, plasticized material in the preform cavity
18 can be brought to and maintained at a desired tempera-
ture.
It should also be noted that in the top portionof the cavity member 50 there is formed a tapered surface
60, the function of which will hereinafter be discussed.
Referring again to Figure 4, the core and neck
ring assembly 34 includes a core member 62 mounted in a
core mounting base 63. The core mounting base 63 is in
turn removeably secured to the fixed upper platen 28. The
core 62 is mounted for limited sliding movement relative
to the mounting base 63 for purposes as will hereinafter
be explained,
Preferably, means are provided for supplying a
heat exchange fluid to the core. In the arrangement shown
in Figure 4, a centrally disposed tube 64 is disposed within
the hollow interior of the core 62. Heat exchange fluid
is supplied to the tube 64 via an inlet conduit 65 that
is in fluid communication with the tube 64. The fluid flows
through the tube 64 and exits therefrom at the end adjacent
the tip of core 62, and then travels upwardly in spaces
61 formed between the outside wall of the tube 64 and the
inside surface of the core 62, to an exhaust conduit 66.
35'hl
The upper fixed platen 28 also includes a conduit
67 for supplying blowing gas, usually air, under pressure
to a conduit 68 in the core mounting base 63. The blowing
gas flows from the conduit 68 through passageway 69 formed
between the core 62 and the core mounting block 63. It
should be realized that the blowing gas is supplied to the
core when the core has been removed from the preform cavity
18 and is disposed in a blowing cavity. A blowing gap is
provided between the shoulder 105 on the core 62 and the
portion 106 of the mounting block 63. The blowing gas travels
from the spaces 69 through channels ~not shown) and exits
through the blowing gap formed between the core and the
core mounting block. In this manner, the preform is in-
flated against the interior walls of the blowing cavity.
Preferably, the core and neck ring assembly 34,
the preform cavity member 50, and the blow splits 36a, 36b
are all readily demountable from their respective mountings
so that a changeover to different tooling is easily effect-
ed. In this manner, the apparatus can form a variety of
shapes and sizes of finished articles.
Referring to E`igures 5A and 5B, there is shown
a preferred mechanism for actuating the neck mold segments
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70a, 70b. As previously mentioned, segments 70a, 70b are
mounted on neck ring mounting blocks 71at 71b, respectively.
In turn, the neck ring mounting blocks 71a, 71b are slide-
ably mounted on track members 75a and 75b. The track mem-
bers 75a, 75b include outwardly extending tracks 76 on which
the neck ring mounting blocks 71a and 71b are slideably
received.
The track members 75a and 75b are each af~ixed
to one of the arms of a yoke member 72. The yoke member
72, as shown in Figure 5A, is mounted for vertical movement
with respect to the upper fixed platen 28. As shown in
Fig. 5B, pairs of guide blocks 81a and 81b slideably receive
the yoke member 72 in the gap between the guide blocks.
Means are provided for effecting transverse move-
ment of the neck ring sections 70a, 70b toward and awa~
from the longitudinal axis of core 62 and also for effecting
movement of neck ring sections 70a, 70b in directions paral-
lel to the longitudinal axis of the core 62. The embodi-
ment illustrated in Figs. 5A and 5B includes a camming means
comprised of opposed pairs of camming blocks 77a and 77b
that are mounted in depending relationship from fixed platen
28. Each of the camming blocks includes a cam track 78a,
78b, respectively. In each of the cam tracks, a cam fol-
lower 79a, 79b is received. The cam followers 79a, 79b
are attached to the neck ring mounting blocks 71a, 71b,
respectively. It should be noted that each of the cam tracks
78a, 78b includes a first portion that i5 substantially
s~
vertically disposed and a second portion that is angularly
disposed with respect to the first portion and which di-
verges outwardly with respect to the longitudinal axis oE
the core 62.
The yoke 72 is connected to the hydraulic cylinder
33 (Figs. l and 3) by a drive linkage comprised of rod 73
and clevis 74. Also, resilient driving elements, such as
compression springs 82 extend between the tangs 83 mounted
on yoke 72 and the top surface of fixed platen 28.
Referring to Fig. 5A, the operation of the neck
ring actuating mechanism is explained. In the full line
position of the yoke 72, the segments 70a, 70b and the cam
followers 79a, 79b, the yoke 72 is in its uppermost posi-
tion, as are the cam followers 79a, 79b, in their respective
cam track 78a, 78b. In this position, the neck ring seg-
ments 70a, 70b are fully closed about the base of core 62
and define in conjunction therewith, a neck ring mold for
forming the neck of an article. These various parts are
preferably held in this position by an upward force on the
yoke 72 developed by the hydraulic cylinder 33.
It should be noted that the foregoing describes
the position of the various parts at the time the preform
is being Eormed, as will later be described, and at the
time that the preform is being blow molded into its final
shape.
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Subsequent to the formation of the container in
the blow cavity, the sections of the blow cavity are separated
and the finished container is then stripped from the core
62. This is accomplished by causing the hydraulic cylinder
33 to exert a downward force on the rod 73, and thus a down-
ward force on the yoke 72. This causes the yoke 72 to move
downwardly with respect to the fixed platen 28, thereby
also causing track members 75a, 75b to move downwardly.
This in turn causes neck ring mounting blocks 71a, 71b to
move downwardly, as, it will be recalled, the blocks 71a,
71b are mounted on the track members 75a, 75b respectively.
It should be realized that as the neck ring mount-
ing blocks 71a, 71b move downwardly with respect to the
fixed platen 28, the cam followers 79a, 79b move in the
cam tracks 78a, 78b respectively. During an initial portion
of the travel of the yoke 72, the cam followers 79a, 79b
move substantially vertically, and in parallel fashion,
in the first portions of the cam track 78a, 78b. As a re-
sult of this, the neck ring segments 70a, 70b are moved
longitudinally, with respect to the core 62, but do not
separate laterally away from the longitudinal axis of the
core. This results in stripping the neck of the container
from the base portion of the core and freeing it for subse-
~uent removal from the core. This stage of movement is
shown in the intermediate single dotted phantom line posi-
tion of Figs. 5A and 5B.
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As the yoke member 72 continues downwardly, the
cam followers 79a, 79b enter the outwardly diverging por-
tions of the cam tracks 78ar 78b and neck ring mounting
blocks 71a, 71b and therefore, the neck ring segments 70a,
70b are caused to move both downwardly and laterally out-
wardly with respect to core 62~ as shown by the double dotted
phantom line position of Figs. 5A and 5B. This action frees
the neck of the container from the undercut portions of
the neck rings 70a, 70b and the finished article is free
to fall ~rom the core 62.
In the embodiment of Fig. 1, the finished container
falls into receiving tube 19 that includes (as shown in
Fig. 6) a swingable bottom wall 86 that is pivotally mounted
at the bottom end of tube 19 by suitable means, as for ex-
ample, pivot pins 87. The bottom wall member 86 can bepivoted to the full line position shown in Figure 6 by a
suitable camming structure, such as pin 88 on chute 89.
When this occurs, a finished container within receiving
tube 19 is free to fall by gravity to the chute 89 mounted
on base 11 (See Fig. 1) and from there into a suitable re-
ceiving device.
As the neck ring parts 70a, 70b are opened, as
previously described, it should be realized that ~he compres-
sion springs 82 are compressed by the advancing yoke 72.
After the finished article is free of the core 62, the hy-
draulic cylinder 33 is deactivated and the compression springs
82 are free to drive yoke 72 upwardly. The length of springs
82 is such that the yoke 72 is not returned to the full
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line position shown in Figure 5A, but rather, the yoke 72
is driven to a point at which the neck ring parts 70a, 70b
remain slightly open. In this condition, the neck ring
parts 70a, 70b are positioned so that when the preform cavity
block 17 is driven upwardly, as previously described, the
tapered surface 60 of the cavity member 50 closes the neck
ring segments about the core 62.
As previously mentioned, the plasticizer 20 is
mounted for vertical movement with respect to base 11.
A preferred hydraulic circuit for effecting vertical move-
ment of the plasticizer 20 is schematically shown in Fig.
7. As previously noted, the plasticizer 20 is mounted on
the base 11 by means of upstanding guide rods 21, on which
are slideably received hydraulic cylinders 22. Each guide
rod 21 includes, enclosed within a cylinder 22, a fixed
piston member 93 that defines two fluid pressure chambers
in each cylinder 22, an upper chamber above the piston 93
and a lower chamber below the piston 93.
For purposes of discussion of the hydraulic control
circuit shown in Fig. 7, it will be assumed that the plasti-
cizer 20 is at its upper vertical limit of travel and is
about to move vertically downwardly to introduce the nozzle
23 into the preform cavity 18. The solenoid operated 3-
position two-way valve 90 is energized so as to position
valve section B between the pressure and tank lines P and
T and the conduits 98 and 94 respectively. Hydraulic fluid
under pressure supplied by pump P flows through section
,:
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B of the valve ~0 to conduit 94 and in turn, through conduit
100 to conduit 97, through check valve 96, through conduit
95, to the lower chamber of the cylinder 22. This causes
the cylinder 22 to be driven downwardly on guide rod 21,
thereby lowering the plasticizer 20. Appropriate limit
switches are provided to stop downward movemen~ of the plas-
ticizer 20 when the tip of the nozzle 23 is spaced a small
distance from the bottom of the preform cavity. It should
be noted that during this time, the full line pressure from
pump P has been supplied to the bottom chamber of cylinder
22 and that therefore ~he downward movement of the plasti-
cizer 20 is relatively rapid. Fluid contained in the upper
chamber of cylinder 22 exhausts from the chamber through
conduit 94, valve section B of valve 90 to tank.
After the nozzle has been positioned in close
proximity to the bottom of the preform cavity 18, the flow
of plasticized material from the nozzle 23 into the cavity
18 is initiated. As the flow of plasticized material con-
tinues, the plasticizer 20 i5 drawn slowly upwardly. It
has been found desirable to correlate the rate of withdrawal
of nozzle 23 with the flow rate of the plasticized material
from nozzle 23 during most of the filling phase, such that
the tip or orifice of the nozzle is maintained near (usually
within an eighth of an inch for most materials) the upwardly
2~ advancing level of the charge of plasticized material being
deposited in the cavity 18. Less viscous resins, such as
the polyolefins, flow relatively easily from the nozzle
so that the level of the charge is slightly above the tip
of the nozzle during filling. The more viscous or "stiff"
resins, such as the high nitrile types, flow relatively
more slowly ~rom the nozzle, and thus the tip of the noz-
zle is usually spaced slightly above the level of the charge.
In this manner, a substantially symmetrical, void-free charge
of plasticized material is reliably deposi~ed in the cavity
18.
At this point, it should be noted that very impor-
tant advantages result from arrangements wherein the charge
of plasticized material is placed in a cavity as heretofore
described. Most important of these is that the maximum
temperature to which thermoplastic materials must be raised
is substantially below that necessary in injection blow
molding. Because the plastici~ed material freely issues
from the orifice of a nozzle that has a cross-sectional
area at least several times larger than that of the gate
in an injection mold, the viscosity of the plasticized mate-
rial deposited can be relatively high; thus the viscosity
of the material does not have to be lowered by raising its
temperature as is necessary in injection blow molding.
For example, the temperature of the high nitrile barrier
resins previously mentioned, must be raised to above A10F
and in some instances close to 450F, to achieve flow char-
acteristics adequate for injection molding a preform. These
temperatures are very close to the temperatures at which
some materials degrade. In comparison, when using these
high nitrile resins in the process herein disclosed, charges
are deposited in the preform cavity at temperatures in the
-23-
t~j~f~3l
range of 350-380F. sy reason of the lowered temperature
of the plasticized material, the risk of degrading these
thermo-sensitive materials is greatly reduced. With respect
to other thermoplastic resins, for example, polyethylene,
polypropylene, PVC, SAN, the charge can be deposited in
the cavity at temperatures very close to the ideal forming
and blowing temperatures of these materials. This reduces
or eliminates the need for thermal conditioning of the charge
and preform, thereby reducing machine cycle time and decreas-
ing the energy requirements of the apparatus.
It should be noted that, when the flow of plasti-
cized material is initiated, the valve 90 is energized to
position section A of this valve between the pressure and
tank conduits, and lines 94 and 98~
In this mode, line pressure from conduit P is
delivered through valve section A to conduit 94 and thence
into the upper chamber of the cylinder 22. This causes
the plasticizer 20 to rise vertically. However, it should
be noted that the exhaust of fluid from the lower chamber
of the cylinder 22 is controlled by a three-position sole-
noid valve 91. During the time that the plasticizer 20
is feeding a charge into the preform cavity 18, the valve
section A of valve 91 is positioned to connect conduit 101
to conduit 99. Thus, the fluid exhausted from cylinder
22 flows through conduit 95, through conduit 101, through
valve section A, through conduit 9g, to a variable fluid
flow restrictor 92 and thence through valve section A of
-24-
5~
valve 90 to tank. The flow restrictor 92 limits the flow
rate of fluid through conduit 99 and thereEore causes the
cylinder 22 to rise slowly. The flow restrictor 92 is a
type that is readily ad]ustable to yield a range of fluid
flow rates through conduit 98. By means of this adjust-
ment, the rate of rise of the nozzle 23 can be regulated
in accordance with the flow rate of the plastici~ed material
from nozzle 23, thereby maintaining the ti~ of the nozzle
near the level of the charge being introduced into the pre-
form cavity. It should be noted that fluid flow from thelower chamber of cylinder 22 through conduit 97 is prevented
by check valve 96.
When the plasticizer 20 has finished delivering
a charge of plasticized material, the valve 91 is actuated
to position valve section B so that conduit 101 is in fluid
communication with conduit 99. Thus, fluid exhausted from
the lower chamber of cylinder 22 flows through conduit 9S,
through conduit 101, through valve section B of valve 91,
through conduit 99, through conduit 100, through conduit
94 and through valve section A of valve 90 to tank. In
this manner, the variable flow restrictor 92 is bypassed
and fluid can exhaust more quickly from the bottom chamber
of cylinder 22. As a result, the plasticizer 20 rises rela-
tively quickly, drawing the nozzle 23 clear of the preform
cavity 18.
s~
Machine Operating Cycle
Reference is made to Figs. 8A - 8M that illustrate
one operating cycle of the apparatus described above.
In Fig. 8Ar the apparatus is shown with the shuttle
14 positioned so that the longitudinal axis of preform cav-
ity 18, is aligned with the longitudinal axis of nozzle
23. The receiving tube 19 is disposed beneath the core
and the neck ring unit 34. It should be realized that dur-
ing a normal operating cycle, a completed article is being
formed and released at the forming station 13 during the
sequence depicted in Figs. 8A through 8D.
Fig. 8B is a partial view of the apparatus illus-
trating downward movement of the plasticizer 20 to position
the tip of the nozzle 23 a short distance from the bottom
of preform cavity 18. During this time, the nozzle 23 has
entered the cavity 18 quickly as previously described in
connection with the hydraulic control circuit of Fig. 7.
After downward movement of the plasticizer 20 is terminated,
plasticized material is caused to issue from the nozzle
23 and enters the recess 55 and begins filling the bottom
of the preform cavity 18.
Fig. 8C shows the nozzle 23 of the plasticizer
as it is being withdrawn relatively slowly as the plasti-
cized material is deposited in the preform cavity 18. The
speed of ascent of the plasticizer 20 is controlled by the
~3~
variable flow restrictor 92 so that the tip of no~zle 23
is maintained near the upwardly advancing level of the charge
of plasticiæed material, for example, a short distance d,
above the level of the charge, as shown. The speed of ascent
is made variable so that differences in flow rates among
various resins and differences in charge volumes can be
accommodated, yet the positioning of the tip of the noz71e
near the level of the charge, while the charge is deposited,
is maintained.
Referring to Fig. 8D, after a predetermined volume
of plasticized material has been deposited in the preform
cavity 18, the hydraulic control circuit shown in Fig. 7
is activated to its fast rise mode and the nozzle 23 is
quickly withdrawn from the preform cavity 18. If a plas-
ticized material that has a tendency to "string" is being
used, after the nozzle 23 has been withdrawn from the pre-
form cavity 18, the solenoid 43 (Fig. 2) is energized so
that hot wire 41 is caused to sweep beneath the nozzle and
sever any material extending between the charge and the
nozzle 23.
It should be noted that progressively feeding
the charge of plasticized material from the bottom of the
preform cavity 18 upward, ensures that no air is occluded
in the charge as it is deposited in the cavity. Further,
a symmetrically shaped charge is evenly deposited in cavity
18. Both of these features contribute to the reliable forma-
tion of the preform.
-27-
~3~
Fig. 8E shows that the shuttle 14 has moved along
guides 15 to position the preform cavity 18 directly beneath
the core 62. It should be realized that the receiving tube
19, that contained a finished article from the previous
blow molding step, has moved from under the core 62 and
has released the article, as described in connection with
Fig. 6. It should also be realized that the locking block
47 attached to moveable plate 29 has entered the locking
recess 48 of cavity block 17, thereby firmly coupling the
cavity block 17 to the moveable plate 29. At this time,
moveable plate 29 is driven upwardly, as by hydraulic cylinder
31 (Figs. 1 and 3) thereby driving the cavity block 17 toward
the core and neck ring assembly 34.
Fig. 8F is a view of the apparatus depicted in
Fig. 8E looking in the direction of arrows V. In this view,
the preform cavity block 17 is shown as having partially
completed its upward travel, with the core 62 just enter-
ing the preform cavity 18. It should be noted that the
neck ring parts 70a and 70b remain slightly open about the
base of the preform core 62.
Fig. 8G is a view of the apparatus taken along
the same line as Fig. 8F. In this view, the tapered surface
60 of the preform mold cavity has closed the neck ring parts
70a and 70b about the core 62 so that a complete preform
mold space is defined in the continuous space between the
core, the preform cavity 18 and the neck ring mold prior
to the time that the level of the resin has reached the
neck mold
-2~-
5~
It should be noted that, up to this time, no mold-
ing pressure has been placed on the plasticized material
in the preform cavity; the plasticized material has freely
advanced upwardly into the annular space between the core
and the preform mold cavity. The only stress induced into
the plasticized material during this part of the cycle is
frictional stress resulting from flow between core and cavity
surfaces. Also plasticized material remains in the recess
55 in the preform mold cavity, as shown in Fig. 4.
It should further be realized that, as the core
62 advances into the charge of plasticized material, because
of the absence of pressure on the plasticized material,
the core is not deflected by a pressure differential occur-
ring within the mold cavity. Rather, the hydraulic forces
are equalized and the tendency ~or the core to deflect is
eliminated.
Figure 8H shows the moveable platen 29 at its
upper limit of vertical travel. At this point, the preform
cavity block 17 has pushed the neck ring assembly vertically
upward to its upper limit of travel as shown in the full
line position of Figs. 5A and 5B and the core is introduced
to its maximum extent into the preform cavity. At this
time, the plate 29 imparts a clamping force to hold the
preform mold member 50 and core assembly 34 together under
pressure. After this clamping force is applied, fluid under
pressure is supplied via conduit 5~ to the chamber beneath
piston 51, which causes upward movement of piston 51, there-
-29-
~3~
by causing extension or ram 54 (Fig. 4) to enter the recess
55 and force plasticiæed material frcm recess 55 into the
preform mold space. The plasticized material, under pressure,
comyletes the filling and packing of the preform mold space.
The pressure that must be placed on the resin ~y the ram
54 varies, depending upon the material being processed.
For materials such as the polyolefins, pressures of 300
psi or less have been used; for "stiff" materials such as
the nitrile resins, pressures in the range of 4000-5000
psi are used. The ram 54 advances in recess 55 until the
pressures on both sides of the ram, that resulting from
the pressure of the material in the cavity and that derived
from the pressurized fluid on piston 51, are in equilib-
rium. Preferably, at this point, the top surface of the
ram is spaced a short distance below the bottom wall of
the preform cavity. The equilibrium pressure varies, de-
pending on the resin being processed.
An important advantage of the equipment just des-
cribed is that the preform mold cavity is fully defined
before the plasticized material is placed under pressure.
This avoids flashing of the plasticized material, especially
in the region of the neck mold. Because the final Eorming
pressure is relatively low, the tolerances between mating
preform molding tools can be significantly reduced from
the tolerance levels required in injection molding tools.
This latter factor substantially reduces tooling manufactur-
ing costs. Also, because the final forming operation of
-30-
3~Z~
the preform is carried out under low press~re, there is
a reduction in undesirable pressure-induced stress concen-
trations in the preform.
As the foregoing steps were carrîed out, the charge
s of plasticized material and the preform were bein~ tempera-
ture conditioned for optimum blow molding by the circula-
tion of heat exchange fluids about the preform cavity and
in the core.
Referring to Fig. 8I, after the formation of a
complete preform on the core 62, the plate 29 moves down-
wardly and carries with it the preform cavity block 17.
Once the cavity block 17 has been lowered away from the
core 62, the blow mold parts 36a and 36b are brought together
about the core 62, which now carries a complete preform.
Fig. 8J shows the next step of the sequence in
which the shuttle 14 has moved to position the preform cavity
block 17 once again beneath the nozzle 23 of the plasticizer
20 and the receiving tube 19 beneath the core 62. While
the foregoing has been carried out, blowing gas has been
introduced into the core 62 and the preform is inflated
against the walls of the blow cavity.
Fig. 8K is a view of the apparatus shown in Fig.
8J, the view being taken in the direction of arrows X-X.
s~
This view is taken showing the position of blow cavity sec-
tions 36a and 36b about the core 62 and prior to movement
of yoke 72 downwardly.
Fig. 8L, a view taken in the same direction as
Fig. 8K, shows the initial movement of the yoke 72 downwardly
with accompanying movement of the cam followers 79a, 79b
from the starting position (shown in phantom line) downwardly
in the initial portion of the cam tracks 78a, 78b. During
this movement, the neck ring segments 70a, 70b remain closed
about the neck of the finished container C. As the neck
ring sections are moved downwardly, they carry the finished
container C downwardly and move it longitudinally with re-
spect to the core 62. This results in stripping the neck
of the container C from the core 62.
Fig. 8M shows a continuation of the movement of
yoke 72 and neck ring segments 70a and 70b. During this
phase of operation, the cam Eollowers 79a, 7gb are moved
into the outwardly diverging sections of the cam tracks
78a, 78b respectively. This causes the neck ring segments
70a, 70b to be moved laterally outwardly with respect to
the core 62, allowing the finished container C to disengage
from the undercut portion of the neck ring segments and
to fall by gravity into the receiving tube 19. The finished
container C is retained in the tube 19 by the pivoted bottom
wall 86.
-32-
3S2~
In the foregoing description, the sequence of
operation is controlled by a control system utilizing con-
ventional limit switches and timers to control the initia-
tion, duration, and termination of the vario~ls phases of
operation; the design of a suitable system is believed to
be within the skill of the ordinary artisan in this art.
Description of Fi~. 9 Embodiment
Turning to Fig. 9, the apparatus shown therein
functions essentially in the same manner as previously des-
cribed with respect to the Figure 1 embodiment. Two formingstations 13 and 13' are disposed on each side of a plasti-
cizer 20. The forming stations are substantially as described
with respect to the embodiment of Fig. 1. In this apparatus,
the shuttle 14 carries ~wo preform cavity blocks 17 and
17' and two receiving tubes 19 and 19'.
As shown in Fig. 9, the spacing between the preform
cavity block 17 and 17' is such that when one of the cavity
blocks is positioned to receive the nozzle 23 of the plasti-
cizer 20, the other is positioned at a forming station in
position to form a preform on a core. In this manner, whilea finished container is formed at one of the forming stations,
a prerorm can be formed on the core at the other forming
station. In this design idle time of the plasticizer is
reduced and output can be substantially doubled over the
embodiment shown in Fig. 1.
-33-
3~
In this embodiment, a different arrangement is
utilized for removing finished containers from the appara-
tus. Each of the receiving tubes, 19, 19' has an opening
103, 103' at the bottom thereof. The size of the openings,
S 103, 103' is sufficient so that a finished container can
be pushed laterally out of the receiving tubes 19, 19' by
a suitable ejecting element (not shown) through the open-
ings 103, 103' onto a belt conveyor 102.
Conclusion
From the foregoing discussion, it can be seen
that many benefits and advantages are present in the inven-
tion disclosed herein; some of which are:
--The amount of material used for each container
is precisely controlled, with substantially no waste occur-
ring;
--The manufacturing costs of the equipment and
tooling is kept low by eliminating the requirements for
developing high clamping and injection pressures;
--The ease of processing thermoplastic materials
is increased, the risk of temperature-induced degradation
of such materials is decreased, and machine cycle times
are reduced, by the deposit of a viscous, relatively low
-34-
3~1
temperature charge that is at a temperature substantially
lower than that necessary for injection molding of such
materials;
--The range of article sizes that can be economi-
cally produced by the apparatus, in relation to both machinecost and processing cost, exceeds that of other systems;
--Even materials difficult to process, such as
the nitrile barrier resins, can be processed directly to
form finished containers, without the need for intermediate
conditioning steps.
