Note: Descriptions are shown in the official language in which they were submitted.
~3~ 2a3
The invention relates to improvements in
methods of and in machines for making hollow plastic
articles, and more particularly to improvements in
methods of and in machines for making blow molded
articles of thermoplastic material. Still more
particularly, the invention relates to improvements in
methods and machines which can be resorted to with
advantage Eor the making of stretch blow molded articles,
namely articles which are obtained as a result of
mechanically effected biaxial stretching and
pneumatically effected expansion of thermoplastic ~,~
parisons in the cavities of blow molds.
A stretch blow molding machine normally
comprises several molds which define cavities for
reception of thermoplastic parisons. The molds cooperate
with nozzles which serve to inject into the parisons
metered quantities of a pressurized fluid, and with
mechanical stretching devices which lengthen the parisons
prior, during or subsequent to expansion with pressurized
fluid. In many presently known machines, the molds are
mounted on a turntable which is indexible about a
vertical axis so that the molds advance seriatim past a
charging station where the cavities of the molds receive
thermoplastic parisons. The parisons are thereupon
subjected to a mechanical biaxial stretching aetion and
are expanded with a compressed fluid to assume a shape
conforming to the surfaces bounding the cavities of the
respective molds. As a rule, conversion of parisons into
hollow plastic articles (e.g., bottles) is completed not
later than when the respective mold completes about
-- 2 --
f ^: ``
: :`
2, ~ 3
three-fourths of a full revolution about the axis of the
turntable. The thus obtained plastic articles are
removed form the cavities of the respective molds so that
each mold is empty not later than when it reaches the
charging station.
An advantage of the just outlined conventional
method and machine is that the articles can be turned out
at regular intervals. The machine will turn out n = 4
articles per revolution of the turntable if the latter
supports four equidistant molds.
The speed at which the turntable can be indexed
about the vertical axis depends upon several parameters.
One of these parameters is the interval of time which is
required to convert the parison in the cavity of a mold
into a stretch blow molded article. In addition, the
period of time which elapses for each full revolution of
the turntable depends upon the length of the interval
which is required to insert a parison into the cavity of
a mold and upon the length of the interval which elapses
to remove a freshly formed hollow article from the
respective mold. Thus, if the turntable is in continuous
rotary motion, the speed of such movement is dependent
upon at least three variablesO On the other hand, if the
turntable is driven in stepwise fashion, the length of
intervals of dwell is determined by the periods of time
which are needed for insertion of parisons and for
removal of hollow articles whereas the speed of movement
of the stepwise driven turntable between successive
stoppages depends upon the period of time which is
required to complete the mechanical stretching and the
- 3 -
pneumatic blowing operation, i.e., the conversion of a
parison into a hollow article, as well as upon maximum
permissible acceleration and deceleration of the molds.
The turntable cannot be subjected to abrupt acceleration
or deceleration because this could adversely affect the
positions of parisons in the respective mold cavities.
The peripheral speed of the continuously or
intermittently rotating turntable is inversely
proportional to its diameter. All of these factors
prevent a conventional stretch blow molding machine from
turning out a large, or even a relatively large, number
of articles per unit of time.
~ nother drawback of stretch blow molding
machines which employ continuously or intermittently
rotating turntables for the molds is that the supplying
of hot waterl coolant, compressed fluid, electric current
and parisons to as well as removal of hollow articles
from the cavities of molds presents numerous problems.
For example, it is necessary to provide means for
conveying electric current between stationary and mobile
parts, and the same holds true for the means which serve
to supply a pressurized fluid (e.g., compressed air) for
expansion of parisons in the cavities of the respective
molds, to supply hot water and to supply a suitable
coolant. Additional serious problems arise in connection
with the sealing of paths for the flow of pressurized
fluid into the parisons which are confined in the
cavities of moldsO The electrically operated monitoring
and signal generating devices on the turntable must
transmit signals to stationary parts outside of the
.. l' j .;',, .. :. . :. . ..
turntable. All this contributes to the bulk, cost and
complexity of conventional machines.
S~ill another drawback of conventional machines
is that they cannot simultaneously produce two or more
different types of hollow stretch blow molded articles.
Thus, each and every mold is provided with the same
cavity and each mechanical stretching device is the same
as all other devices. On the other hand, the demand for
blow molded hollow thermoplastic articles of all sizes
and shapes has grown beyond all expectations so that
there exists and urgent need for methods and machines
which can be relied upon to turn out large numbers of
such articles per unit of time. One of the reasons for
growing popularity of hollow thermoplastic articles is
that their making and disposal are satisfactory for -~
- ecological reasons.
One feature of the present invention resides in -
the provision of a method of manipulating thermoplastic
parisons and blow molded articles ~including stretch blow
molded articles). The method comprises the steps of
feeding parisons to a distributing station, positioning a
plurality (namely at least two) of blow molds around the
distributing station, transferring discrete parisons from
the distributing station into discrete molds, converting
parisons in the respective molds into blow molded
articles, and removing the articles from the respective
molds.
; The step of removing an article from a mold can
immediately precede the step of transferring a parison
into such mold, i.e., the step of introducing a parison
.
-- 5 --
s~ ~ 3
into the then empty cavity o a mold can follow,
practically instantaneously, the evacuation of a freshly
formed article from ~he same mold.
Each step of converting a parison in one of at
least two molds can take place simultaneously with the : `
step of transferring a parison into the other of the at
least two molds, and vice versa.
The transferring step can include conveying the
parisons along an arcua~e path, particularly along an
endless annular path (such as a circular path) prior to
entry of parisons into molds. The removing step can
include transporting articles from the respective molds
toward or away from the center of the annular path.
The positioning step can include placing the
`: molds in a circle around the distributing station, and
the transferring step can include clamping the parisons
at the distributing station and delivering the thus
clamped parisons to the molds.
The removing step can include lifting articles
out of the respective molds,
In accordance with a presently preferred
embodiment, the method further comprises the step of
holding the molds against movement relative to the
distributing station in the course of the feeding,
transferring, converting and removing steps (~or example,
the molds ean be fixedly mounted on a stationary
support), and the step of transferring a parison into one
of the molds can take place simultaneously with
conversion of a parison into an article in another mold.
The transferring and removing steps can include
-- 6 --
.--~
J ~ ~
preferably continuously moving at least one conveyor
between the distributing station and the molds t and
providing the at least one conveyor with first facilities
(e.g., first tongs) for accepting parisons at the
distributing station and for inserting parisons into
molds, and with second facilities (e.g., second tongs) ;~-
for accepting articles from molds. ` ~-
The transfPrring step can further include ~ ~delivering parisons from the distributing station to the ~ "
molds in a predetermined sequence (i.e., in accordance
with a predetermined pattern), and the removing step can
further include evacuating articles from molds in a
predetermined sequence.
The transferring step can involve the use of ;
mobile tongs for discrete parisons, and the removing step
can include lifting articles out of the respective molds
and delivering lifted articles to an article storing
and/or evacuating facility (e.g., to a belt conveyor for
plastic bottles, vials or like containers).
It is also possible to select the transferring
step in such a way that it involves simultaneously
withdrawing a plurality of parisons from the distributing
station. The removing step can include simultaneously
removing articles from at least two molds.
The transferring step can include pneumatically
transferring (either by suction or with a pressurized
fluid) parisons from the distributing station to the ~--
molds. Analogously, the removing step can include `~
pneumatically conveying (by suction or with a pressurized
fluid~ articles from the molds to storage or to a
~ J~
take-off conveyor. Alternatively, the transferring step
can include conveying parisons by gravity feed, and
the removing step can include evacuating articles from
the respective molds by gravity feed. It is also
possible to rely on a combination of gravity feed and
pneumatic conveying, either for transfer of parisons to
the molds and/or for the removal of articles from the
respective molds.
Another feature of the invention resides in the
provision of a machine for manipulating thermoplastic
parisons and blow molded articles, particularly stretch
blow molded articles. The improved machine comprises
means defining a distributing station, means for feeding
parisons to the distributing station, a plurality of blow
molds which are disposed around thé distributing station,
means for transferring parisons from the distributing
station into molds for conversion into blow molded
articles, and means for removing articles from the molds.
The machine further comprises a support for the molds.
The support can be stationary, and the transferring means
;~ can be mounted for movement relative to the distributing
station and relati~e to the molds on the support.
Alternatively, the machine can comprise means (such as a
mobile support in the form of a turntable) for moving the
molds relative to the distributing station. The moving
means can define for the molds a predetermined path, and
the transferring means of such machine can comprise means
for delivering parisons into molds in a first portion of
the path. The removing means of such machine preferably
comprises means for evacuating articles from molds in a
- ~
~ ~ r~ 3
different second portion of the path.
The transferring means (e.g., in the form of
one or more chutes) can be s~ationary relative to the
support. Alternatively, the machine can employ ~ -
transferring means which is movable relative to -the
support. The movable transferring means can comprise
tonys for parisons and means for moving the tongs between
the distributing station and the molds. The arrangement
can be such that the transferring means is equipped with
tongs for simultaneous retention of two or more parisons.
The means for moving the tongs can be designed to move
the tongs at an at least substantially constant speed. -~
The removing means can be provided on the transferring
means or vice versa. ~-
: . , .
In accordance with a presently preferred
embodiment, the transferring means comprises tongs for
parisons and means for moving the tongs between the
distributing station (where the tongs receive parisons)
and the molds (where the tongs are relieved of parisons).
Such machine can further comprise means for controlling
the moving means. The transferring means of this machine
can comprise a lever having a plurality of arms and means -
for pivoting the lever about a predetermined axis which
is disposed between the arms. The tongs are provided on ;
one of the arms, and the removing means is provided on
another arm. The controlling means can comprise means
for circulating the axis along a substantially circular ;
path about the distributing station. Each of the arms
can include a first portion or section which is pivotable
about the axis and a second portion or section which i9
_ g _
:
.,
. :
~ - \
pivotable and/or otherwise movable relative to the first
portion or section. The tongs and the removing means are
carried on the second portions or sections o the
respective arms. The controlling means can be designed
to maintain the removing means in register with an
article-containing mold and to simultaneously maintain
the tongs in register with a parison at the distributing
station.
The molds of the improved machine are open-and-
shut molds. Each such mold can comprise a plurality of
sections which define a cavity for parisons and blow
molded articles. At least one section of each mold is
movable relative to at least one other mold section
between an open position in which a parison is insertable
into or an article is removable from the cavity, and a
closed position in which the parison or the article is
confined in the cavity. Means is provided for moving the
at least one section of each mold between open and closed
positions, and the machine further comprises means for
controlling the operation of such moving means. The
controlling means can comprise cam and follower means.
In order to simplify the controlling means, the latter
preferably further comprises a rotor or other suitable
means for moving the cam means relative to the molds.
Such cam means can include at least one endless cam which
surrounds the distributing station. The rotor is
preferably driven to rotate about an axis at the
, i distributing station. Such rotor can include a
horizontal end wall and an annular wall which is mounted
on or is integral with the end wall. The cam and
-- 10 --
. ,.. , .. : . , . , . ~ .. .. ... ~
,,
S3
follower means of the controlling means can include a cam
and follower unit on the end wall to move the one section ~ ~-
of each mold between open and closed positions, and the
annular wall of the rotor can be provided with or can -~
carry one or more additional cam and follower units to
regulate the operation of means for converting parisons
into hollow articles.
Each cam can constitute a groove cam.
The converting means can include valves which
serve to admit pressurized fluid into parisons in the
cavi~ies of molds and means for actuating the valves.
Such actuating means can receive motion from a follower
which tracks one of the cams on the annular wall of the
rotor. The actuating means can comprise holders for the
valves and means for reciprocating the holders and their
valves relative to the parisons in the cavities of the --
molds in response to rotation of the rotor and resulting
displacement of the followers tracking the cams. Each
holder can be provided with means for sealing the
parisons in their mold cavities to prevent the escape of
gaseous fluid from parisons when the valves are open.
The converting means can further include means
for mechanically stretching parisons in the cavities of
the molds, and such stretching means can receive motion
from the follower tracking one of the cams on the annular
wall of the rotor. The converting means of such machine
can further comprise a step-up transmission which is
interposed between the stretching means and the
respective follower. Such transmission can comprise an
input element which is operatively connected (e.g., by a
,. :
-- 11 --
::
2 ~ 3
motion transmitting link~ with the respective follower,
an output element which is operatively connected with the
respective stretching means, and an intermediate element
which receives motion from the input element and serves
to transmit motion to the output element in such a way
that the extent of movement of the output element exceeds
the extent of movement of the input element. At least
one element of the transmission can include a belt and
pulley drive. The belt and pulley drive of the
intermediate element can be designed in such a way that
it comprises a larger-diameter pulley which is driven by
the input element, a smaller-diameter pulley which serves
to drive the output element, and an endless Elexible
element which is trained over the pulleys. The
transmission can Eurther comprise a friction-operated
coupling device between the input element and the
respective follower and~or a friction-operated coupling
device between the output element and the stretching
means.
The cam which controls the actuating means for
the valves can be provided with a single lobe which is
tracked by followers to effect an opening of the
respective valves. The flanks of the lobe can make with
the remaining portion of the cam angles of 100-135
degrees, preferably angles at least close to 135 degrees.
That cam on the annular wall of the rotor which
initiates opening and closing of the valves is preferably
installed at a levPl below the cam which controls the
movements of the mechanical stressing means. The cam
which controls the movements of the stretching means
- 12 -
: - ~.. , . : . :. :.: : . ::.:: : .
. ~ ,: . . . : . ,- .: .:: . . : .. , : . .
~^
~33:~?~3
preferably includes a first section at a level below a
second section. The first section is tracked by the
respective follower in one position (e.g., inoperative
position) of the stretching means, and the second section
is tracked when the stretching means for a mold assumes
another position (e.g., ~he operative position). The
length of the first section can equal or approximate the
length of the second section. Gradual transitions are
preferably provided between the first and second
sections, and such transitions can be inclined relative
to the two sections at angles of between 40 and 60
degrees.
The transferring means can comprise at least
one chute for parisons. Such chute can have a slope
which is sufficient to ensure that a parison which enters
the chute can slide by gravity feed toward the cavity of
an open mold. It is also possible to provide means for
pneumatically and/or mechanically conveying parisons
along one or more chutes from the distributing station to
the cavities of open and empty molds. For example, the
transferring means can comprise a chute for each mold.
Each such chute has an upper end portion adjacent the ~ `
distributing station and a lower end portion adjacent the
respective mold. Such transferring means can further
comprise gates or other suitable means Eor releasably
locking the lower end portions of the chutes so ~s to
ensure that a parison can leave the respective chute only
, when the adjacent mold is open and its cavity is ready to
receive a parison.
The molds can form a complete ring around the
- 13 -
; ` ~
- ~,
distributing station. Alternatively, ~he machine can
comprise only two, three or another relatively small
number of molds. The distributing s~ation can be located
at or close to the center of the circular array of molds.
The novel features which are considered as
characteristic of the invention are set forth in
particular in the appended claims. The improved
machine itself, however, both as to its construction and
its mode of operation, together with additional features
and advantages thereof, will be best understood upon
perusal of the following detailed description of certain
specific embodiments with reference to the accompanying
drawing.
FIG~ 1 is a schematic plan view of a machine
which embodies one form of the invention and operates
with a ring-shaped array of stationary molds;
FIG. 2 is a schematic elevational view of a
second machine wherein the molds are mounted on a rotary
support in the form of a turntable;
FIG. 3 is a schematic plan view of a third
machine with stationary molds and with a combined parison ~-J
transferring and article removing device;
FIG. 4 is an enlarged fragmentary vertical
sectional view substantially as seen in ~he direction of
arrows from the line IV-IV of FIG. 3;
FIG. 5 is a developed view of two cams in the
machine of FIGS. 3 and 4;
FIG. 6 is a schematic plan view of a third
machine wherein the means for transferring parisons to
~he cavities of molds comprises a set of stationary
- 14 -
. . ,, i, ~,,.. , .. -. ~ ,,,: - , -
:~ ,: - - -.. -.. :,
~.
~3~2~.~
chutes; and
FIG. 7 is a similar schematic plan view of a
fourth machine wherein the transferring means comprises a
single chute which can be moved around the parison
distributing station.
Referring first ~o FIG. 1, there is shown a
stretch blow molding machine including a plate-like
support 1 for a set of molds 6 forming a ring 5 around a
parison distributing station 2. Parisons 22 are fed to
the station 2 by an endless belt conveyor 27
substantially radially of the array of molds 6, and ~-~
finished stretch blow molded articles 9 are removed from
molds 6 by a removing device 10 for delivery to a
take-off station 3, namely onto the upper reach of an
endless belt conveyor 8. The machine further comprises a
transferring device 15 which serves to transfer parisons
22 from the station 2 to selected molds 6, for example,
in a predetermined sequence. Still further, the machine
comprises parison converting means including means for
mechanically stretching parisons 22 in the cavities of
the respective molds 6 and means for admitting into the
parisons metered quantities of a pressurized fluid ~such
as compressed air) to ensure that the shape of each
article 9 will conform to the shape of the surface
bounding the cavity in the respective mold 6.
The distributing station 2 occupies or is close
to the center 4 of the circular array 5 which is formed
by the molds 6, and the take-off station 3 is outwardly
adjacent a marginal portion 7 of the support 1. The
conveyor 8 at the station 3 can deliver articles 9 to a
2 ~ ~
magazine. The removing device 10 is designed to lift
articles 9 out of the respective mold cavities and to
thereupon move the lifted articles along an arcuate or
other path on their way toward the conveyor 8 at the
take-off station 3. The illustrated removing device 10
is mounted for angular movement about an upright pivot
member 11 which is adjacent the marginal portion 7 of the
support 1 close to the take-off station 3. The free end
of the removing device 10 carries tongs or grippers 12
which can engage a finished article 9 for delivery onto
the conveyor 80 The illustrated removing device 10
includes a composite elongated arm which is assembled of
several articulately connected sections or portions
(portions 13 and 14 are shown in FIG. 13 so that it can
move its tongs 12 toward and into register with the
cavities of selected molds 6. Once an article 9 has been
lifted out of the cavity of the respective mold 6, the
removing device 10 is caused to turn about the axis of
the pivot member 11 in order to move the tongs 12 above
the adjacent receiving end of the continuously or
intermittentl~ driven conveyor 8 at the take-off station
3. The machine can be equipped with two or more removing
devices 10 each of which is positioned and designed to
remove articles 9 from the cavities of an adjacent group
of two or more molds 6. Alternatively, or in addition
- thereto/ the ring-shaped array 5 of molds 6 can be caused
to turn about the distributing station 2 so as to move
successive or selected molds 6 into the range of tongs 12
on the composite arm 13+14 of the removing device 10.
The transferring device 15 comprises tongs 24
- 16 -
~ 3 3 ~ 2 i j
at the free end 23 of an elongated composite arm 16 which
is turnable about a vertical axis deined by an upright
pivot member 18 mounted in a bearing 17 within the array
5 of molds 6. The arm 16 is assembled of several
portions or sections (two are shown in FIG~ 1, as at 20
and 21) which are articulakely connected to each other by
one or more joints 19. Such design of the transferring
device 15 enables its tongs 24 to accept a parison 22 at
the distributing station 2 and to transfer the thus
accepted parison into the cavity of a selected mold 6.
The means for opening and closing the jaws of the tongs
24 is or can be of conventional design and is not
specifically shown in the drawing. The same holds true
for the means for opening and closing the jaws or claws
of the tongs 12 forming part of the removing device 10.
It goes without saying that the machine further comprises
suitable means for pivoting the arm 16 of the
transferring device 15 about the axis of the pivot member
18 and for increasing or reducing the distance between
the pivot member 18 and the claws of the tongs 24 in
order to enable the device 15 to accept parisons 22 at
the station 2 and to deliver the thus accepted parisons
into the unoccupied cavity of a selected mold 6.
The molds 6 are preferably designed in such a
way that biaxial stretching or lengthening of parisons 22
precedes pneumatic expansion of the parisons to complete
the conversion of a parison into a hollow article 9,
e.g., a bottle, a vial or an analogous con-tainer for
flowable media. FIG. 1 shows that each mold 6 comprises
two sections 25, 26 at least one of which is movable ;~
~.
:
- 17 -
\
~ ~3 ~
relative to the other so as to assume an open position
(in which the tongs 24 can introduce a parison 22 in~o
the respective cavity or the tongs 12 can remove a
finished article 93 or a closed position in which the
parison 22 is properly confined in the cavity and is
ready to be acted upon by the stretching means as well as
to receive a requisite quantity of a compressed gaseous
fluid.
In accordance with one presently preferred
embodiment, the molds 6 are stationary, iOe., they are
not movable relative to and/or with the support 1. It is
then necessary to design the transferring device or
devices 15 in such a way that parisons 22 can be
transferred from the station 2 into the cavity of any one
: of the ring-shaped array 5 of molds 6, and that the
removing device or each removing device 10 can lift a
inished article 9 from `any selected mold 6. The
effective length of the arms of the illustrated devices
10 and 15 can be changed within a range which is
necessary to ensure that the tongs 12 can be moved
between the take-off station 3 and any selected mold 6,
and that the tongs 24 can be moved between the
distributing station 2 and any selected mold 6. This
applies, of course, if the machine of FIG. 1 employs a
single transferring device 15 and a single removing
device 10. The manner in which the tongs 24 on the arm
16 of a transferring device 15 can pick up parisons 22
from the feeding conveyor 27 for introduction into the
cavity of a selected mold 6, and in which the removing
device 10 can lift articles 9 out of mold cavities for
- 18 -
~ `
:;
~ 3 ~ 3
transport to the conveyor 8 at the take-off station 3 can
be seen in FIG. 2.
The molds 6 of FIG. 2 are mounted on a support
in the form o a turntable 49 which is rotated by a gear
transmission 150 receiving motion from a variable-speed
electric or other suitable motor 1510 The turntable 49
moves successive or selected molds S to a first location
where the arm 16 of the transferring device 15 delivers
parisons 22 which are taken off the feeding conveyor 27, `
and to a second location where the molds 6 are opened or
are already open so as to enable the removing device 10
to lift the articles 9 out of the respective mold `
cavities and to transfer the thus lifted articles onto
the conveyor 8 at the take-off station 3. The molds 6
can be indexed to the two locations one after the other
or in any desired sequence. It is also possible to
provide two or more locations for delivery of parisons 22
thereto and to provide two or more locations for removal ;
of articles from mold cavities. An advantage of the
machine of FIG. 2 is that it can accommodate a large
number of molds 6. MoreovPr, this machine renders it
possible to employ a transferring device 15 with two or
more arms 16 tonly one shown) or with a single arm or
two or more tongs 24 (not shown) for simultaneous
insertion of parisons 22 into two or more molds 6.
Analogously, the removing device 10 can be designed for
simultaneous removal of articles 9 from two or more mold
cavities.
Another advantage of the machine of FIG. 2 is
that it can be equipped with substantially stationary
-- 19 --
~33.~2~
transferring and removing devices 15 and 10,
respectively. Thus, the distances which must be covered
by the tongs of the transferring device 15 and by the ,,
tongs o the removing device 10 are much shorter than the
distances which such tongs must cover in the machine of
FIG. l wherein the molds 6 are mounted on a stationary or
fixed support l. However, the versatility of the machine
of FIG. 2 can be considerably enhanced if the devices lO
and 16 are movable relative to the turntable 49 so that
they can readily reach any selected mold 6 on the
turntable. By superimposing the movements of the devices
lO, 15 upon the movements of the turntable 49, the
machine of FIG. 2 renders it possible to increase the
output by reducing to a minimum the length of intervals
which elapse for evacuation of freshly formed articles 9
from the respective mold cavities (as soon as the
parison-converting step in a cavity is completed) and by
reducing the length of intervals which are required to
introduce parisons into freshly emptied molds 6. The
turntable 49 can be maintained in motion during
insertion of parisons 22 into and during removal of
articles 9 from mold cavities, especially if the
turntable supports a large number of molds so that its
peripheral speed is relatively low.
FIG. 3 shows a modified machine with three
equidistant open-and-shut molds 6 disposed in a circle
about a distrihuting station 63 for parisons 22. The
transferring device 15 of FIGS. l and 2 is replaced with
a different transferring device including a conveyor in
the form of a lever 52 having two arms extending to
- 20 -
~ 3 ~ r~ ~
opposite sides of a vertical fulcrum 51 which is movable
along an endless path indicated by a phantom-line circle
62. Each arm is composed of several portions or
sections. Thus, one of the arms includes a first portion
or section 53 connected to the fulcrum 51 and a second ~ ~:
portion or section 54 connected to the first section 53
by a pivot member 56. The free end o:E the section 54
carries tongs 55 for removal of parisons 22 from the
distributing station 63. The other arm of the lever 52
includes a first portion or section 57 mounted on the
fulcrum 51 and a second portion or section 59 which is
articulately connected to the section 57 by a pivot
member 58. The free end of the section 59 carries tongs
60 for removal of articles 61 from the cavity of the
adjacent mold 6. The tongs 60 is movable up and down so
as to lift and article 61 out of the cavity of the
adjacent mold 6.
The lever 52 can turn about the axis of the
fulcrum 51 while the latter travels along the endless
circular path 62. The means Eor moving the fulcrum 51
along such path is not shown in FIG. 3. The portions or
sections 54 and 59 can pivot relative to the respective
portions or sections 53, 57 while the fulcrum 51 is at a
standstill and/or while the fulcrum 51 travels along the
path 62. The direction in which articles 61 can be
removed from the machine of FIG. 3 is indicated by an
arrow A. The tongs 60 can deposit articles 61 on a
conveyor which moves in the direction of arrow A and
perform the function of the conveyor 8 of FIGS. 1 and 2.
The arrangement is preferably such that the lifting of a
.
- 21 -
~"j ~
~ 3~2~3
finished article 61 from the respective mold cavity takes
place simultaneously with the engagement of a parison 22
at the distributing station 63 by the tongs 55. Once the
introduction of a parison 22 into an open mold 6 is
completed, the sections 25, 26 of such mold are closed
and the stretching and blowing operations can begin to
convert the parison into an article 61. The molds 6 are
mounted on a ring-shaped wall member 102 resting on a
support 1. The feeding conveyor for parisons 22 is
indicated by arrow B.
FIG. 4 shows the means 64 for controlling the
movements of mold sections 25, 26 between open and closed
positions and the means for converting parisons 22 into
articles 61 as well as the means for controlling the
opening and closing means for the mold sections 25, 26
and the operation of the converting means.
The controlling means 64 comprises three cam
and cam follower units 65, 66 and 67. The unit 67 serves
to open and close the sections 25, 26 of the molds 6, the
unit 66 serves to regulate the admission of pressurized
fluid into parisons 22, and the unit 65 serves to
initiate and control movements of stretching members 78
which increase the length of parisons 22 in the cavities
of the respective molds 6. The controlling means 64
further includes a cupped rotor 68 which has a horizontal
end wall or bottom wall 70 and an annular wall 69
extending upwardly from the end wall 70 and having in its
external surface 72 two groove cams 74, 75 forming part
of the units 65, 66, respectively. A groove cam 71 in
the underside 73 of the end wall 70 forms part of the
- 22 -
-
unit 67. The hub 112 of the cupped rotor 68 is rotatable
in antifriction bearings or in other suitable bearings
113 carried by the support 1.
The support 1 carries the aforementioned ring-
shaped wall member 102 for all three molds 6, or a
discrete upright wall member 102 for each of the three
molds. The wall member or members 102 movably support
roller followers of the cam and follower units 65, 66 and
67. The cam 74 receives a roller follower 84 and the cam
75 receives a roller follower 83. The means 76 for
moving the parts of the converting means in response to
rotation of the cupped rotor 68 relative to the wall
member or wall members 102 (i.e., relative to the molds
6) includes a set of links, levers and like parts which
receive motion from the followers 83 and 84. It will be
noted that the cam 75 for the follower 83 is located at a
level below the cam 74 for the follower 84.
The upper follower 84 transmits motion to a
compressed-gas connection 77 carrying a holder and
actuating means 114 for a valve 200 which must be opened
in order to admit pressurized fluid (such as compressed
air~ into the parison 22 in the cavity of the respective
mold 6. The holder 114 has means for sealingly engaging
a nipple 80 of the parison 22 to prevent uncontrolled
escape of pressurized fluid during pneumatic expansion of
the parison in the cavity of the mold 6. The valve 200
is opened in automatic response to lowering of the holder
114 by the follower 83 into sealing engagement with the
nipple 80.
The follower 84 initiates and controls the
,:
- 23 -
1~
- ~
~ ~3~
movements of a stretching member 78. A discrete
stretching member 78 and a discrete holder 114 is
provided for each of the molds 6.
The holder 114 which is shown in FIG. 4 is
connected to one end of a pivotable lever 79 which is
mounted on the wall member 102, as at 81, and the shorter
arm of which is connected to a motion transmitting link
82 receiving motion from the follower 83 in the cam 75.
Relatively small up-and-down movements o the motion
transmitting link 82 result in much larger up-and-down
movements of the holder 114 and valve 200. The valve 200
opens automatically when the holder 114 is lowered into
sealing engagement with the nipple 80-of the parison 22
in the adjacent mold 6. When the admission of a
requisite quantity of pressurized fluid is completed, the
cupped rotor 68 causes the follower 83 to pivot the lever
79 in a counterclockwise direction (as seen in FIG. 4) so
that the holder 114 is lifted above and away from the
nipple 80 and the valve 200 closes automatically to
terminate the admission of pressurized fluid into the
parison 22 (which by then is converted into an article
61). The unit 67 thereupon effects an opening of the
respective mold 6 so that the tongs 60 can lift the
article 61 out of the mold cavity preparatory to transfer
onto the conveyor which advances articles 61 in the ~: :
direction of arrow A.
The follower 84 in the cam 74 is connected with
a motion transmitting link 85 which, in turn, can ~ ;
transmit motion to the input element 87 of a step-up
transmission 86. The latter further includes an output
- 24 - :~
:` :
'..~'~
~33~
element 88 and an intermediate element or transmission
89. The output element 88 can move an entraining member
99 for the stretching member 78 at the respective stretch
blow molding station. The purpose of the intermediate
element 83 of the transmission 86 is to transform
relatively short displacements of the input element 87
into longer movements of the output element 88 and
stretching member 78.
A friction-operated coupling device 94 is
provided between the motion transmitting link 85 and the
input element 87 of the transmission 86~ The input
element 87 is a belt drive having two toothed pulleys 90,
91 and an internally toothed belt 93 which is trained
over these pulleys. The friction-operated coupling
device 94 engages the external surface of the belt 93.
Such external surface is rough to ensure adequate
engagement with the coupling device 94. The latter is or
can include a friction pad provided on the motion
transmitting link 85 and bearing against the external
~o surface of the belt 93.
The output element 88 of the transmission 86
also comprises two toothed pulleys 97 and an endless
internally toothed belt 98 which is trained over these
pulleys. The belt 98 transmits motion to the entraining
member 99 for the stretching member 78.
The intermediate element 89 of the transmission
86 comprises a large-diameter pulley 95 which is coaxial `
with and is non-rotatably connected to the pulley 90 of
the input element 87, and a smaller-diameter pulley 97
(e.gO~ an extension of the upper pulley of the output
- 25 -
.
: :~: : .
,. ~ ~ ~ , . .,. . . , . :
~ 3
element 88~ which transmits torque to the output element
88. An internally toothed endless belt 96 is trained
over the pulleys 95 and 97 of the element 89 to ensure
that the stretching member 78 covers a relatively long
distance in response to a relatively short upward or
downward movement of the coupling device 9~. The
entrainin~ member 99 can be a functional equivalent of
the coupling device 94, i.e., it can comprise a rough-
surfaced friction pad which bears against the rough
external surface of the endless toothed belt 98 of the
output element 88 to move the stretching member 78 up or
down, depending upon ths configuration of that portion of
the cam 74 which is then tracked by the follower 84. The
entraining member 99 can be fixedly secured to the
stretching member 78.
FIG. 4 shows a parison 22 during conversion
into an article 61. The stretching member 78 is shown in
a retracted position in which its lower end is spaced
apart from the bottom wall of the biaxially stretched ~ :
parison 22. The valve 200 is open and admits compressed
gaseous fluid into the interior of the parison 22 while
the nipple 80 is sealingly engaged by the holder 114. :
The latter can comprise one or more sealing rings which
directly engage the nipple 80 of the parison 22 in the
cavity of the adjacent mold 6. It is clear that the
stretching member 78 is fully extracted from the freshly
finished article 61 before the latter is lifted out of or
otherwise removed from the cavity of the respective mold .
6. ~t such time, the follower in the cam 71 at the
underside of the end wall 70 of cupped rotor 68 maintains
- 26 -
: .
-
~33~
the sections 25, 26 of the mold 6 in open positions.
The lower end portion of the motion
transmitting link 82 of FIG. 4 is guided by a coulisse
100 on the wall member 102, and a second coulisse 101 is
provided for the lower end portion of the motion
transmitting link 85. The illustrated wall member 102 is
assumed to constitute a circumferentially complete or
composite enclosure (see FIG. 3) surrounding the three
molds 6 which, in turn, surround the distributing station
63 and the path 62 for movement of the fulcrum 51 for the
combined parison transferring and article removing lever
52. As mentioned above~ a discrete pair of motion
transmitting members 82, 85 is provided for each mold 6O
Howev~r, the cupped rotor 68 and its endless annular cams
71, 74, 75 are common to the three molds 6. The
configuration of two of these annular cams is shown in
developed view in FIG. 5, namely that of the cam 74 and
that of the cam 75.
The configuration of cams 74 and 75 is such
that they do not effect an abrupt acceleration or
deceleration of the motion transmitting links 82, 85 at
~: the three blow molding stations. It is preferred to
~ ensure that the movements of the links 82, 85 are carried
: out at a constant rate which can be readily achieved by
appropriate selection of configuration of the cams 74 and
75. As shown in FIG. 5, the cam 75 has a single lobe 103
which causes the corresponding follower 83 to lower a
holder 114 into engagement with the nipple 80 of the
adjacent parison 22 when the lobe 103 reaches the
respective mold 6 while the rotor 68 rotates about its
- 27 -
~ ~ 2 ~ 3
vertical axis. The flanks 104, 105 of the lobe 103
preferably make with ~he plane of the end wall 70 and
with the remaining portion 106 of the cam 75 angles of
100-150, most preferably angles of close to or exactly
135.
The cam 74 has a first section 112 at a lower
level and a second section with ~nd portions 107, 108 at
a higher second level. The section 112 is tracked by a
roller follower 84 when the respective stretching member
78 is maintained in raised position. The transitions
between the two sections 107-108 and 112 of the cam 74
are preferably smooth and gradual and can make with the
- plane of the end wall 70 angles of 40-60 degrees. These
transitions are or can be mirror images of each other.
The maximum height of th~ lobe 103 of the cam -~
75 and the difference between the levels of the two
sections 107-108 and 112 of the cam 74 determine the
extent of vertical movement of the holders 114 and of the
stretching members 78, respectively. As a rule, sùch
differences will be relatively small in order to avoid
excessive acceleration of the motion transmitting links
, . ~ .. .
82 and 85.
FIG. 4 further shows a gear 168 which forms
,.,~ ,.~ ., "
part of the means for driving the cupped rotor 68 about
its vertical axis. Only three molds 6 have been shown in
FIG. 3 for the sake of clarity; the machine of FIGS. 3
and 4 can comprise two, four or more molds without
departing from the spirit of the invention.
The conveyor 27 of the means for feeding
parisons 22 to the station 2 or 63 can be installed at a "~ ~ `
:, .
.,:: : :
' ~
' ~: -
- 28 -
:: .
-
~ 3 ~
level above the support 1. However, it is also possible
to install the feeding means at a level beneath the
support for the molds 6 and to provide suitable means
(e.g., a ~echanical elevator or a suction generating
device, not shown) for lifting parisons 22 from the level
of feeding means beneath the support 1 to a level above
the support so that they can be engaged by the tongs 12
or 5s.
FIG. 6 shows that a mobile transferring device
(such as the device 15 of FIG. 1) can be replaced by a
transferring device 28 including a set of stationary
chutes or troughs 29 each having an upper end at the
distributing station 2 and a lower end 30 at the
respective mold 6. Each chute 29 defines a channel
wherein a parison 22 can slide by gravity from the
station 2 toward the respective mold 6. The lower ends
30 of the chutes 29 are provided with disengageable
(e.g., retractible) locking or arresting devices or gates
31 which arrest the parisons 22 adjacent the respective
molds 6 and are automatically retracted as soon as the
cavity of the adjacent mold is ready to receive a fresh
parison, i.e., as soon as the removal of a freshly formed
article is completed.
A parison 22 can leave the discharge end of the
feeding conveyor 27 by gravity alone and/or with
assistance from suitable mechanical or pneumatic means,
e.g., nozzles which discharge compressed air and effect
the transfer of parisons from the conveyor 27 into
selected chutes 29 and/or promote the advancement of
parisons in the chutes. Disengagement (e.g., retraction)
- 29 -
~33~2~
of locking devices 31 can take place in automatic
response to opening of the respective molds 6, or with a
certain delay following such opening so as to provide an
interval of time for evacuation of a freshly formed
article 9 or 61 from the mold cavi~y before the locking
device 31 opens or is retracted in order to enable the
parison 22 to leave the chute 29 and to enter the
adjacent mold cavity.
FIG. 7 illustrates a por~ion of a further
stretch blow molding machine wherein the means for
transferring parisons 22 into selected molds 6 comprises :~
a single chute 33 having an upper end 32 adjacent the
distributing station 2 and a lower end provided with a
locking device 35. The upper end 32 can turn about a :
vertical axis 34 so that the locking device 35 advances
- along an arcuate path adjacent the ring-shaped array of
molds 6 which surround the station 2 and are fixedly
mounted on the support 1. The means for turning~the
single chute 33 about the axis 34 can comprise a stepping
motor or any other suitable means which can index the
chute 33 through angles of desired magnitude so as to ~ :
move the locking device 35 adjacent that mold 6 wherein
the cavity is ready to receive a parison 22. The
indexing means is operated in accordance with a :~
predetermined program. The arrangement may be such that
opening of a mold 6 automatically entails a movement of
the locking device 35 to proper position for opening and ~:
, admission of a parison 22 into the cavity of such mold, ~:
preferably with an automatic delay which is needed to
allow for evacuation of the freshly formed article from - -~;:
- 30 -
11 3 ~ 3 ~
such mold.
Parisons 22 can slide off ~he chute 33 and into
the adjacent mold cavities by gravity feed (i.e., due to
appropriate selection of inclination of the channel in
the chute 33), or such admission of parisons into the
mold cavities can be assisted by properly distributed and
oriented nozzles which discharge jets of compressed air
or another suitable fluid. Mechanical introducing means
can be used in addition to or in lieu of nozzles for
compressed air or another gaseous fluid.
Referring again to FIG. 1, the removing device
10 may but need not necessarily be outwardly adjacent the
support 1 for the molds 6. For example, the removing
device can be movably installed in the area 4 within the
ring-shaped array 5 of the molds 6. Such modification is
analogous to that which is shown in FIG. 3 wherein the
lever 52 forms part of the means for transerring
parisons 22 into molds 6 as well as of the means for
removing articles 61 from the cavities of the molds. An
advantage of the arrangement which is shown in FIG. 3 is
that the removing means including the tongs 60 is nearer
to all of the molds 3 than the removing device 10 of FIG.
1. On the other hand, the device 10 of FIG. 1 exhibits
the advantage that it can be moved out of the way so that
it does not interfere with the delivery of parisons 22 by
the feedin~ conveyor 27 and/or with transfer of parisons
22 from the distributing station 2 to the cavities of the
molds 6.
It is further possible to modify the improved
machine in such a way that the take-off station 3 is
- 31 -
~,, " ~ " ~
, . ~ , . . . .
,~,, . : . .. . .
~3~2 ~3
located in the space 4 within the ring-shaped array 5 of
molds 6 which surround the distributing s~ation 2 or 63.
For example, the support 1 of FIG. 1 can be provided with
an opening (not shown) and the tongs 12 are then movable
to a position above such openin~ to release an article 9
which descends through the opening to be intercepted by a
collecting receptacle beneath the support 1 or to descend
onto a conveyor performing the function of the conveyor 8
of FIG. 1. Still further, it is possible to provide a
conveyor or articles 9 or 61 at a level above the
station 2 and to equip the removing device 10 with
suitable means for raising freshly removed articles 9 to
the level of such overhead conveyor to which the articles
can adhere by suction or on which the articles can be
held in any other suitable way. The just described mode
of removing articles 9 or 61 exhibits the advantage that
the removing device 10 or its equivalent must cover
relatively short distances from the cavities of the molds
6 to the take-off station at a level above the station 2.
All embodiments of the improved method and all
embodiments of the improved machine exhibit the advantage -~
that the number of blow molded articles which can be
turned out per unit of time is higher than in heretofore
known machines and in accordance with heretofore known
methods. The reason is that the parisons 22 are
invariably delivered to a central location within the
array of molds, irrespective of whether the molds are
stationary or are caused to circulate around the parison
distributing station. The output of the improved machine
is high even if the molds are caused to orbit stepwise
`:`
lr~ 3
around the distributing sta-tion so that they are
stationary during insertion oE parisons into and/or
during removal of finished articles from the mold
cavities. It is also wi~hin the purview of the invention
to maintain the molds 6 in motion during insertion of
parisons and/or during removal of finished blow molded
articles.
An important advantage of that embodiment of
the improved machine which employs stationary molds
(including the machines shown in FIGS. 1 and 3 to 7) is
that such mounting of molds simplifies the admission of
pressurized fluid, heating liquid, coolant and the
supplying of electrical energy to various electrically
operated or current-consuming parts on or adjacent the
molds. This will be readily appreciated since the
conduits which supply pressurized fluid to the holders
(such as 114) of valves (such as 200) need not include
stationary and moving parts; they can extend all the way
from a stationary source of pressurized fluid to the
respective holders. All that is necessary is to employ
relatively short flexible conduits which enable the
holders 114 to move up and down to an extent which is
necessary to properly engage their sealing elements with
the nipples 80 of the parisons 22 and to permit
convenient evacuation of blow molded articles from the
mold cavities. Moreover, the construction of means for
moving the holders 114 and the stretching members 78
, relative to the molds 6 is simpler and less expensive if
such moving means are associated with stationary molds.
It has been found that the life span of sealing elements
- 33 -
~,3~,2~i3
which are used in conjunction with stationary molds is a
multiple of the life expectancy of sealing elements
which are used to prevent uncontrolled escape of
pressurized fluid in machines wherein the molds are in
motion during conversion of parisons into hollow
articles.
Stationary molds are desirable on the
additional ground that this simplifies the design of
parts which supply heating and cooling fluids
(particularly water) to the molds. It has been found -~
that the versatility and availability factor of the
improved machine can be increased hundertfold by
resorting to a set of stationary molds with a centrally
located parison distributing station. Similar
observations apply for the economy of operation of the `~
improved machine. A machine with stationary molds is
surprisingly simple, compact and reliable. The controls
are simple and inexpensive, and the energy requirements
are much lower than those of a conventional machine with
orbiting molds. Moreover, the controls are more reliable
and their operation is much more accurate than in
machines with orbiting moldsO
A further important advantage of the improved
machine, irrespective of whether it employs stationary or
mobile molds, is that it can be readily set up to turn
out two or more different types of blow molded articles
in a simultaneous operation. This can be achieved by
using identical parisons or by using two or more
different types and/or sizes of parisons. The regulation
of converting operation is sufficiently simple and
- - 34 -
2 ~ ~ ;
reliable to ensure that the wall thickness of each blow
molded article matches or closely approximates a desired
optimum wall thic~ness. This renders it possible to
achieve considerable economies as concerns the
consumption of thermoplastic material because the
quantity of material which is needed for the making of
discrete articles can be calculated in advance with a
high degree of accuracy.
Since the controls (including detectors,
sensors, adjusters, gauges and others) which are used in
a machine with stationary molds are not subjected to
extensive stresses and can be fixedly mounted adjacent
the parts to be monitored, the machine of the present
invention can employ high-quality detectors, sensors and
like parts which can monitor the operation of the machine
with a heretofore unmatched degree of accuracy.
Therefore, the operation of the improved machine can be
regulated by a computerized controlling system. ~owever,
it is equally within the purview of the invention to
provide the machine with semiautomatic or with manually
operable controls. Irrespective of the nature of
selected controls (whether programmed, semiautomatic or
manual), the machine renders it possible to individually
select optimum heating and/or cooling for each mold, to
individually select the periods of confinement of
parisons in the cavities of discrete molds, to
individually regulate the extent of biaxial stretching of
parisons if the improved machine constitutes a stretch
blow molding machine, and/or to otherwise individually
select any and all parameters which influence th~ quality
::
- 35 -
~ 3 3 ~
of products and the output of the machine. For example,
the controls of the machine can render it possible to
individually select the temperature profiles for discrete
molds 6 in order to take into account ~he nature oE
thermoplastic material of (different) parisons which are
fed for delivery to certain molds. If the machine of the
present invention is used for the making of bottles or
like containers, it can turn out high-quality bottles the
weight of which is less than the weight of similarly
dimensioned bottles which are produced in conventional
machines by between 5 and ~0 percent.
Each of the illustrated machines can be
operated in such a way that the introduction of a parison
22 into an empty mold 6 takes place immediately upon
completed removal of a freshly formed article 9 or 61.
This is possible regardless of whether the machine
employs stationary molds or a set of molds which orbit
about the parison distributing station. When the molds
are caused to orbit, the just described mode oE inserting
parisons 22 and of removing articles 9 or 61 reduces the
necessary number of interruptions of orbital movement of
the molds because each interruption can be used for
insertion oE at least one parison as well as for removal
of at least one article~ A reduction of the number of
interruptions of orbital movement of the molds
contributes to smoother operation of the machine, to a
higher output of the machine and to greater
predictability of the converting step because the
parisons in the cavities of the molds need not be
accelerated and decelerated as often as in presently
- 36 -
2 ~ 3
known machines with orbiting molds.
The placing of the parison distributing station
2 or 63 at or close to the center of the array of
stationary or orbiting molds 6 also exhibits a number of
important advantages. Thus, when the parisons are
supplied in accordance with heretoEore known proposals,
the station to which fresh parisons are delivered to -~
assume a position close to the molds is located outside
of the annulus of orbiting molds. Therefore, it is
invariably necessary to slow down or to actually arrest
the mold which is about to receive a parison, and the
same holds true for removal of finished articles from the
cavities of molds in conventional machines. Repeated
acceleration and deceleration of molds necessitates
the provision of numerous controls and entails
considerable wear upon the moving parts. Moreover, and
as already pointed out above, conventional machines are -~
not suited for simultaneous production of two or more ;~
different types of blow molded articles because this
would even further complicate the controls and the
regulation of supply of electrical energy, heating
liquid, coolant and pressurized gaseous fluido
The machines which are shown in FIGS. 1 and 3
to 7 exhibit the additional advantage that the mass of
moving parts (such as of the devices 10, 15 of FIG. 1,
the lever 52 of FIG. 3 and the chute 33 of FIG. 7) is a
minute fraction of the combined mass of molds and their
rotary support. This reduces the energy requirements of
the means for moving such parts and renders it possible
to move the parts at a speed which is much higher than -
- 37 -
~ ~3~2~
that of a turntable with a large number of molcs thereon9
Moreover, the intervals which are requ.ired for j,
acceleration or dec01eration of a transferring and/or
removing device are much shorter than those which elapse
for acceleration or deceleration of a large number of
molds which are mounted on a rotary support.
- 38 -
