Note: Descriptions are shown in the official language in which they were submitted.
~32~7~9
The present invention relates to injection
molding machines and relates, in particular, to such
machines having the capability of operating a plurality
of molds arranged in series. In particular, the
invention is concerned with a process for opening and
closing molds in an injection molding machine, and an
improved clamping cycle.
This Application is a divisional of Canadian
Patent Application, Ser. NoO 589,420 filed Jan. 27/89.
The prior art shows injection molding machines
having the capability of operating a plurality of molds
arranged in series. For example, U.S. Patent No.
3,707,342, issued to A. Lohman on December 26, 1972 ;
shows two molds spaced apart in tandem with a dual
noz~le injection unit positioned therebetween to fill
the two molds alternately. No provision is made for
separate means to stuff the molds.
U.S. Patent No. 3,898,030, issued August 5, 1975
to T.G. sishop~ entitled Injection-Mold Clamping Unit
Having Alternately Ejecting Die Assemblies, describes
that latches 80A and 80B are used to couple separable
mold halves 56A and 58A whereby single clamping and
ejection units are used for both molds.
U.S. Patent No. Re 28,721, reissued to J.J.
Farrell on February 24, 1976, entitled Time Saver
Plastic Draw-Back Valve Assembly, describes a primary
reciprocating-screw
-1- ~ :.'
~1 '
i32871~ ~7-423
injection unit 12 and an auxiliary injection piston 50
with a valve 52 for divertinq molten plastic 10w from
t~e primary unit to the secondary unit thereby isolatinq
the primar~ unit and permittin~ the secondary unit to
"stu~" mold 32.
O~her pertinent machine patents include PCT
Publication No. W0 86/011~6, dated February 26, 1986 and
We~t German Patent No. ~428780, da~ed Marc~ 13, 1986.
In addition, the prior art shows stack and sandwiah
mold arran~ements wherein the molfl cavity plate~ are
digposed ~ack to back separated by an inte~ral hot
runner. ~epxeeentative of staak mold arran~emen~s are
U..S. Patent ~08. 3,7~3,040, 3,973,892 an~ 4,400,341.
Stack or sandwic~ mold arrangementfi are well known in
the artl however, their draw backs lnaluae a le~ than
optimum operat~nq cycle and lack o~ versati~ity ln
component~.
~ dditional publications of interest are U.S. Patent
No. ~,752,207, issued June 21, 19~8 to ~aaden, including
a related brochure entitled "~TU~RE - Twin~Statlon
In~ection-Mouldinq Machlne3" an~ a brochure b~ Stork
Plastics Machinery entitled "Stork rJ-Type In~ection
M~uldin~ Mach~ne".
- -2-
,
~ 32 8~1 9 ~7-423
The '207 patent and related Stubbe brochure
(publis~ed October 1986) show a ~oose neck connection
between a plastic injection uni.t and a distributor
carried by a movable platen.
The Stork brochure ~publi~hed on or about 1985)
shows an injection unit disposed perpendicular to the
mold clamp unit axis.
Moreover, there i9 a disadvantaqe in combini.n~ a
hot runner wi.th mold element~ as a sin~le piece part.
Such an arrangement necessita~es replacement o a
complete multiple elem~nt mold and ho~ runner as a unit
when one wishes to ~han~e molds. Whereas when ~he mold
elements are separable from the hot runner ~ystem, i~ ls
merely necessary ~o remove mold elements while ~he hot
runner remains a machine fixturq.
U.S. Patent ~lo. 4,539,171 ~o ~orensen is al~o of
interest. In the '171 patent, ~hermoplastic material i8
transferred from an injection unit to a sandwich mold by
means of a so-called snorkel 30 and a cooperatin~ noz~le
16. The snorkel and nozzle make a connection to provide
a conduit for thermoplastic material. The snorkel and
nozzle move relative to another alon~ a common axis :~
which i~ parallel to an~ spaced ~rom central axi~ 13
alon~ which clampinq platens 10 an~ 11 rec~procata.
.
132~7~
In accordance with one aspect of the invention
there is provided in an injection molding machine
having a plurality of molding stations arranged in
tandem where each station includes at least one mold,
each mold comprising a pair of cooperating mold halves,
fixed and movable platens supporting the mold halves, a
single primary clamping means and a plurality of
secondary clamping means for opening and closing the
molds in accordance with a plurality of permutations
and combinations at the direction of a programmed
clamping control means, a process for opening and
closing molds comprising the steps of closing all molds
by means of the primary clamping means, clamping the
mold halves of each mold individually by the secondary
clamping means, connecting the primary clamping means
to the molds at all stations by means of a serial
connection with secondary clamping means, unclamping a
f irst pair of mold halves at a f irst mold station, and
separating the mold halves at the first station by
moving the remaining molds at the remaining stations by
means of the primary clamping means and the serial
connection.
In accordance with another aspect of the
invention there is provided in a method of molding
articles sequentially at two different molding stations
each having a mold where both stations are within a
single unitary injection molding machine, the maahine
_4_
, - ,.
-" 172~719
being operable to inject material at a primary
injection pressure and at a secondary injection
pressure, an improved clamping cycle comprising the
steps of arranging the molds of two molding stations A
and B in series, clamping the molds of both stations A
and B to oppose a primary injection pressure, clamping
the mold at station B to oppose a secondary injection
pressure, injecting molten plastic into the mold at
station B solely, releasing the primary injection
pressure on the molds of both stations A and B, again
clamping the molds of both stations A and s to oppose
the primary injection pressure, again clamping the mold
at station A to oppose the secondary injection
pressure, injecting molten plastic into the mold at
station A solely, and again releasing the primary
injection pressure on the molds of both stations A and
B whereby the molds at stations A and B are clamped
under secondary injection pressure independently.
A further feature of the invention is to provide
a primary clamping system operable to clamp all mold
stations simultaneously. A single primary clamp means
cooperating with and making a series connection with a
plurality of secondary clamp means is operable in
response to a clamp control unit to open and close
molds at a plurality of tandemly arranged mold stations
in accord with various permutations and combinations.
-" ~328719
It is a further feature of the invention to
provide an independent secondary clamping system
operable to clamp platens of a given mold station
directly and selectively or, in the alternative,
operable to clamp mold halves of said given station
directly and selectively.
It is a further feature of the invention to mount
secondary clamps directly upon the mold platens.
A feature of this invention is a novel molding
sequence in which a part molded at a station A, for
example, which is serviced by a primary and a secondary
injection means may be of entirely different size and
structural complexity than another part molded at a
station B. In accordance with this feature, filling
and stuffing of the mold at station B may be
accomplished sequentially by a single injection means.
A still further feature of the invention is that
two parts requiring generally equal cooling periods may
be molded at two tandemly arranged stations using a
single primary clamp means. The single primary clamp
means acting upon two stations in the same time
interval that would be required if the parts were -
molded successively at the two mold stations utilizing
primary and secondary clamp means.
-6--
1~28719
In contrast to the above prior art disclosures,
there is disclosed herein an injection molding machine
having a plurality of molding s-tations with a plurality
of machine accessories arranged in various combinations
developing a sequence of operations calculated to
reduce molding cycle time per part particularly when
molding large parts, such as large containers or
autobody parts.
There is particularly described herein an
injection molding machine which enables the mold
assemblies to be operable independently of each other
and to be readily separable from the machine.
A further feature disclosed herein is the
provision of a plurality of mold stations arranged in
series and separated by a discrete, central, movable
machine platen.
A further feature disclosed herein is the
provision of structure for transferring molding
compound from an injection unit to a manlfold
distributor block along a path which is perpendicular
to the clamping axis or the longitudinal machine axis.
A still further feature disclosed herein is the
provision of seal means for sealing the injection unit
nozzle to the distributor block orifice along an axis
I which is perpendicular to the clamping axis.
I
-
~32~719
A further feature disclosed herein is the
incorpora-tion in the central movable platen of a
distributor communicating with whatever mold halves may
be attached to the central platen.
' A further feature disclosed herein is the
provision of a check valve in the distributor block to
prevent leakage of resin when the injection unit nozzle
is not in sealing contact with the distributor block
orifice.
A further feature disclosed herein is the
provision of a central movable platen with individual
manifold sections on opposite sides of the platen
operable to feed moldable resin to mold halves carried
by the central platen under the control of valve means
positioned upstream of the central platen. The central
movable platen may be cored for cooling and the
manifold sections isolated from the platen by an
insulating air gap.
A further feature disclosed herein is the ;
provision of valve means in the manifold distributor
block operable to place the injection unit and/or a
packing unit in communication with the individual
manifolds, selectively.
A further feature disclosed herein is the
provision of power means for effecting and maintaining
the seal between the manifold distributor block and the ~ `
13 2 8 r~
, ~ ,
injection unit nozzle where the power means operates
along a path which is perpendicular to the mold
clamping axis.
A further feature disclosed herein is the
provision of a plurality of mold stations arranged in
series and separated by a discrete, central, movable
machine platen.
A still further feature disclosed herein is the
feeding of molten plastic into a plurality of
individual mold cavities at different, serially
arranged mold stations utilizing a single primary
injection means and one or more secondary injection
means to fill and pack (stuff) each said mold cavity in
sequence thereby increasing overall productivity of
individual molds.
A further feature disclosed herein is the use of
primary injection means dually as a mold cavity ~ ;~
"filler" and a mold cavity "stuffer".
~A further feature disclosed herein is a novel
sequencing system for utilizing primary and secondary ~
,,:
injection means to inject molten plastic into a ~-
plurality of mold stations clamped by a single, primary
clamping means, where the primary injection means
performs both, a mold filling and stuffing function at
one station
1~ ~
: ' :
. ,
~3~871,9
A further feature disclosed herein is the
provision of an injection molding machine in which one
or more primary injection means are mounted on a fixed
or movable platen with track means facilitating motion
of the units, to and fro, along the longitudinal axis
(x axis) of the machine.
A still further feature disclosed herein is the
incorporation, into a multi-station injection molding
machine, of a parts removal device or robot which is
operable to remove parts molded in reverse or in
identical orientation at each station.
A further feature disclosed herein is the
provision of a secondary injection means mounted on a
movable platen whose design lends itself to a wide -
variety of mounting locations on said movable platen,
i.e. top, side or bottom of said movable platen.
A further feature disclosed herein is the
provision of an injection molding machine on a single
rame means comprising at least two injection means and
at least four mold stations arranged in series.
-9a- -
~7-423
132~7~
An injection molding machine embracing ~eature~
described herein includes, in one comblnation or
another, a main frame, fixed and movable platens to
support mold halves and primary and secondary clamp
means. The secondary clamp mean~ are usually attached
to the mold platens, however, i~ nece~sary they may also
be mounted directly on mold halves that are attached to
the pla~ens.
A distributing manifola iB incorporated in a
central movahle platen includin~ valve means or
~irectin~ molten plas~ic to oppose~ mola s~atlon. The
manifoLd includes a connec~ion to a primary injection
means and to a seconflary in~eat~on means with
appropria~e valve means ~or controllin~ flow ~rom the
primary injection means.
In an alternative embodiment o~ the machine, the
primary in~ection means is pro~rammed to melt su~icient
plastic to fill two molds. A irst mold is then filled
by the primary injection mean~ and stuffe~ by a
secondary in~ection means. Next, molten plastic flow i~ ~;
directed to a second mold station where the filling of
the molfl as well as the ~tu~fin~ Btep i8 performed
solely by the primary in~ection mean~. In thl~
embodiment the clampin~ ~unction may be 601ely by the
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~3~7~9 87-~23
. ..
primary clamp means or by the primary clamp means in
combination with ~econdary clamps, depending upon size,
configuration and relative coolinq rates o~ the
respective molded parts.
Further, the machine includes ejection means and a
parts remover (robot) which operates on rec~ilinear
coordinates to move from moldinq station to molding
station along a ~irst axi3 and into and ou~ of an open
mold alon~ a ~econ~ axi 8 .
Product may be molded in the same or in rever~e
orientation with appropriate modification of tlle part3
remover and the flow path of the molten plastic.
In rever~e orientation, the remover hea~3 carries
flual "plck up" elements, while product molded in same
orientation is ~rasped by a remover head wlth a ~in~le
pick up.
In certain ~ituatlon~, the ~ize and compLexlty o~
th~ mol~ed parts require the use of a plurality o~
primary injection means adapted to cooperate with a
plurality of secondary injection means to insure
complete ~illing an~ stuf~ing the corresponding mold
cavity in a qiven mold station.
A ~urther embodiment o~ the mac~in0 takes the orm
of a double capacity unit. In thi~ arrangement, there
` ~
~328719 87-423
are four molding -qtations, two primary injection means
and two central platen~, each incorporating a
~istributor.
o~her features an~ advantages o~ the preisent
invention wi.ll become more apparent from an examination
of the s~cceeding speci~icatlon when read in conjunction
with the appended drawings, in which:
.
~RIF,F DESCRIPTION OF THE DRAWI~C~S
Flg. 1 showici A side view o~ a typical lay out of
- t~e sequential molding machine of thie pre~ent invention
with the distributor block bro~en away for clarity:
Fig. 2 is a view aimilar to Fig. 1 showing the
oppoeite moldin~ station open with the molded part ~ .
poised for removal:
Fig. 3 is an additional side ~iew ~howing both mold
stations in the closed condition with primary anfl :~
secondary clamp mean~i In operation:
- Fiq. 4 is a side of the machine with the moldefl .
part~i remover or robot in an open mold retrieving a part;
Fig. 5 is a top plan view of the illustration of
Fi~
Fig. 6 is similar to Fi~. 5 showing the robot in
the opposite moldinq stationJ
-12-
13287~9 87-~23
, ,
Fig. 7 i~ a plot of the machine sequence o~
operation charti.ng the position of the various mac~ine
accessories against the step by step generation o~ the
molded parts
Pig~. 8, 9 and 10 show an alternative arrangement
of primary and secondary injection means ~erving two
molding stations;
Fi~. ].1 is a plan view of an injection molfling
machine with an alternative ~econdary or parting line
clamp ~tructure,
Fi~. 12 is a schematic illustration of details of
the structure and moun~inq mean~ o t~e alternative
. seconaary clamp o~ Flg. 11;
¦ Fi~. 13 is a plan view of a ma~hine modification in
w~ich a plurality of primary injection means are :
utilized in combination with a plurali~y o~ di~tributor
block~ anA corre~ponding aecondary in~ection mean~
Fig. 14 is a side view of an additional machine
modi~ication showing double sets o~ primary and
secondary injection means and robots ~ervicing ~our mold
stationss
Fi~. 15 is a char~ fletailing the opera~ing sequence
o~ the machine o~ Fiq. 14;
. -13~
~: ' .
~7-423
~328'~19
Fi~. 16 i.s a side view o an altexnative machine
arrangement facilitating molding piece parts in the same
physical orientation using a single primary in~ection
means
Fi~. 17 is similar to Fiq. 16 modified to use two
primary injection units;
Fi~. 18 is a cycle chart for the Fi~ 18
modi~icationt
Fig. 19 is a plan view o a modi~led molding
machine with por~ions broken away to illustrate an
al~ernative manifold structure,
Fiq. 20 is a plan view of a portion of Fiq. 19,
enlarged, showinq the hot runner sy~tem, the in~ection .
unit ~extruder), the injection unit nozzle clamp means
and mold halvesS
Fig. 21 iB a view similar to Fig. 20 showinq the
in~ection untt in po~ition to ~upply mol~able material ~. :
to the hot runner 6ystem with the injection unit nozzle
clamped to the hot runner ~ystem,
Flg. 2~ is an elevational view of the ri~ht side of
Fiq. ~1 showing the valve means for switclling molding
material to manifold sections, the nozzle clamping means
and a packing cylin~er or ~tuffer, and,
Fi~. 23 ls a ~ectlonal view, enlarqed, a~ viewed in
the plane of the line 5-5 o Fiq. 20 and in the
-14-
~7 - a~2 3
~328~19
direction o~ the arrows, s~owing the seal between the
nozzle and the manifold distributor block and showing
the valve means.
DE~AILED DESCRIPTION OF THE PREFER~D EMBODI~EN~
Referring ~o Figs. 1, 2 and 3, a basic embodiment
of the injection moldinq machine o~ the present
invention is disclosed comprising molding stations A and
B havin~ es~ential aacessories deining a primary clamp
section 11, a ~econflary clamp sectiort 12, a primary
molten plastic injection section 13 anfl a secondary
injection section 14. Either ~he primary and/or
3econdary injection unit may be o~ the reciprocating
screw type or pi_ton type.
Molds 16 and 17, frequen~ly of diferent
configura~ions, comprise mol~ halves 18 and 19 and 21
and 22, respectively.
Mold halves 19 and 21 are mounted on central
movable platen 26 and halves 18 and 22 are mounted on
movable platen 24 ana ~ixed platen 27, respectively.
Platens 23 and 27, fixed to the machine frame 31,
upport tie bars 28 and 29 in the usual and cu~tomary
ashi on .
'
- --].5--
i ~7-~23
132~719
Pla~en 24 i9 connected to primaxy clamping pi~ton
32 and is reciprocated thereby sliding on tie b~rs 28
and 29.
~, Central platen 26 is also movable on tie bars 28
ana 29 and i~ releasably connected to movable platen 24
and fixe~ platen 27 by ~econdary clamping mean0 12 in a
manner which will be explained in qreater ~etail as this
:' ... .
specification proceeds.
Machine section 14 includes a di~tribution block 33
incorporated in platen 26, wi~h heating ~lemente 34,
~. molten plastic supply channel 36 and sel~ctor valve 37
¦ ~~or diverting compound ~low from station A to ~tation B
and vice ver~a.
~ he Ai~tributor blocX 33 terminates in a cylinder
~8 ~aving a pis~on 39 an~ a reservoir 41.
A ~econ~ c~annel 42, adapted to make a connection
with a reaiprocatin~ primary in jection ~ection 13, a~ i8
most apparent in Fi~. 2, include6 a shut off valve 42
for cu~ting off molten plas~ic ~low from the primary
injection means.
With the plston 39 in the retracted po~ition, a~
shown in Fig. 1, the molten pla3tic advanced by the
~i injection section 13 opera~e3 to ~ill the mold cavity to
which 0elector valv- 37 is ~et ~tation B in ~ and
~imultaneously ills reservoir or accumulator 41. ~1pon
~:
~ ' '
~ -16-
87-~23
~32871~
closure o~ ~hut of valve 43, i~olating the injection
section 13, actuati,on of the piston 39 i9 operable to
"stuf~" t~e mold cavity to which molten plastic was
inltially directed.
~ bviously the reservoir can be reestablished and
rechar~ed upon retraction of the piston 39 in
preparation to char~e the opposite mold cavity.
Typically, the injection section 13 include~ a
plasticizing-i.n~ection unit re~erred to in the ar~ a~ a
reciprocating-screw extruder.
Fi~s. 4, 5 and 6 are similar to Flg~. 1, 2 and 3
and ~how de~aila o~ one em~odiment o~ the ~econdary
clamp means and the structure and operation o~ the ~
molded parts removal unit or robot. ,
Referrinq to Fig. 4, the parts removal-unit
operate~ automa~iaally in tlmed ~quencei in rohot ~ -
~ashion, and includes a first Leq 44 which reciprocates ~;
under control of power unit 46 alon~ the lon~itudinal
axis (x axis) o~ the machine guided by a track (not ~ '
shown). ~he power unit 46 i8 supported by ~ixe~ platen
27. `
When the part removal head 48 is in register with
an open mold, such as t~e open mold at station A ~n Fiq.
4, a second ley 4~ i9 actuated by suitable power mean~
to advance the head alon~ a eeaond axis (~ axis) into
17
' ~
~7-~23
~28719
re~ister with finished part P. The part is then ejeated
from core 51 by ejector pins 52, in well known fa~hion,
and picked up by the head.
The head 48 is provided with a source of vacuum and
a valve operable to direc~ vacuum to the part side of
the head where upon the part P is grasped and drawn away
from the core by the head. The heafl i6 retracted
automatically and the part P released to an appropriate
container (not shown) for packa~ing or further
processing, as the ca~e may be.
Fig~. 5 and 6 are top plan views o~ the
illu~tration of Fig. 4 anfl show details and operation o~
one embodiment of the secondary clamp sea~ion indlcated
generally by the re~erence numeral 12.
Pairs o~ opposed arms S3 and 54, ixed to central
platen 26, are formed with notche~ 56 and 57 and cam
~ace~ 5~ and 59. The notche~ are enga~sfl by ~og~ or
lu~s 61 and 62 having mating cam faces 63 and 64. The
lu~s 61 anfl 62, operable to reciprocate in timefl
sequence un~er the control of pl~ton-cylinder ~ssemblies
66 and 67, are mounted on the movable platen 24 and
fixed platen 27, xespectively.
As mold halves of a given mold station approach
their closed po~ition, the lu~s move into matlng notche~
..
. . .
~7-~23
~328719
and the mating cam faces engage one another to drive the
mold halves into ti~ht face to face contact holdin~ the
~old halves sealea during cavity stuffing and subsequent
cooling period independently of the primary clamp means
in a manner and according to an operating ~equence set
forth in the cycle chart of Fi~. 7.
Fiq. 6 shows the part removal head 48 in place in
the open mold at ~tation s poisefl to retract ~rom the
mold to transfer part P out of ~he machine.
In thi~ po~ition t~e vac~um o~ the head 48 ha~ ~een
diverted fro~ the ri~ht side of the head to the left
side of the head as viewed in Fiq. 6 to accompli~h the
part pick up at station s.
Referrin~ in de~ail to Fig. 7, a plot showing a
typical molding cycle of the machine of Figs. 1 ~hrough
6 is lai~ out coordinately where t~e y axis i8 a
~che~ule of sequenti~l positions o~ the variou~ m~chin~
components or accessories for stations A and B, and the
x axis i8 a schedule of the proqres~ of the part through
the molding ~teps.
The chart is read in the following fashion:
startin~ at the upper left hand corner at the polnt
in~icatea by the letter S, one 'IpiC~8 Up'l the moldinq
cycle by notin~ the small c~rcle~ extendin~ alon~ t~e y
axis w~ich indica~e that primary clamp 11 is open,
-19~
1 .
87-~23
13287~9
injection section 13 is back (to the right in Fig. 4),
the injection section 13 i.6 plasticizing, shut o valve
~3 is closed, secondary injecti.on section 1~ (stu~fer
piston 38) is retracte~, selector valve 37 i~ open to
station ~, secondary clamp section 12 is clamplng
R tation A, secondary clamp 12 at station B is free
(open), ejector pins 52 are retracted at station A,
ejector pins 52 are forward tejecting) at station B,
robot or pick up hea~ 48 ha~ moved alon~ machine x axi~
to station B and along t~e z axis into the mold at
~tation ~.
~ eferring to the point x at the lower lef~ corner
o~ the chart of ~iq. 7, i~ i~ apparent when the variou~
mac~ine elements are in the po~ition~ ~uat indicated by
"reading" the char~ a molfled part is coolin~ in it~ mold
at ~tation A and ~he robo~ or pick up head 48 i~
positioned in ~e open moLd at station B.
The chart is read in the manner de~cribed
incrementally from le~t to right, the machine having
produced two part~ P upon arriving at end E of a
complete cycle.
Referring now to Fi~s. 8, 9 and 10, an alternative
embodiment of the primary and seconaary injection means
i~ ~isclosed schematically. In thi~ arrangement molding
stations A and B are serviced by an in~sction unit 68
-20-
~328719 87-~23
and secondary injection unit 69. A selector valve 71,
(qhown as a two way valve but which ma~ be a three way
valve) disposed in ~istributor block 72 within platen
70, i8 operable to ~ivert the flow of molten plastic
from injection unit 68 to the mold at station B as
indicated schematically in Fi~. 9 or to the mol~ at~;
s~ation A as indicat~d sc~ematically in Fi~. 10. Thus, ~ .
operation of the injec-tion unit in the Fi~. 9 :~
arrang~ment delivers molten plastic simultaneously to
the mold o~ station B an~ to the seaon~ary in~ection
unit 69. At ~he appropriate interval ~elector valve 71 : :
directs the mol~en plastic to mol~ station A wllile
in~ection continues into station B rom the 6econdary
in~ection unit, The signlflcance o~ this arr~n~ement i~
that (1) the primary in~ection unit is pro~rammed to
prepare sufficient plastic to satisfy the molas of both .
mold stations A and Bt (2) the s~condary in~ection unit
69 completes injection into the mold at ~tation B a~ter ~ ~
selector valve 71 shifts the flow of plastic to station ~ :
A; ~3) molten plastic i5 delivered directly to ~tation A
~rom the primary injection unit to comPlete the :~
in~ection, whereby either the primary and/or secondary
unit may serve as a stuffer. For example, as a
variation of this embodiment one may also stu~f station
A with ~econdary in~ection unit 69 wi~h appropriate
valving,.
. -21-
~; - . -. ~ :
87 - 42 3
13287~9
Either the primary or ~econdary in~ection uni~s may
be of the reciprocating screw type or the piston type~
Injection pressure of molten plastic into a mold
cavity to fill a mold cavity is fre~uently of a level
ranging from 15,000 to 21,000 psi and injection pressure
to "hold or stuf" the cavity to com~ensate or
shrinkage is frequently of the order of 6,000 psi.
~ he~e pre~ure levels can be develope~ by prlmaxy
and/or secondary in~ection means.
When piece part~ molfled at ~tations A and B have
substantia]ly uniform or equal cooling period~,
secondary clamping mean~ (parting line clamps) can be
eliminated and the molds of sta~ion A and B are held
clamped by the primary clamping unit and both molds are
opened simultaneou~ly.
In situation~ where the cooling periods are unequal
it is ne~e~sary to u~e part~ng line clamps in ad~ition
to primary clamp.
Referring now to Fig~. ll and I2, an alternatlve
design for a secondary clampin~ unit i~ di~losed
wherein partin~ line clamp elements 73 and 74 are shown
mounted on mold halves 75 as at 76 shown in Fi~s. 11 and
12. The units at station A and s~ati.on ~ are of
iden~ical structure. There~ore, only one modi~ie~
seoondary clamping unit will he described~
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The clamp elements 73 and 74 are opera~ed by a
pi~ton-cylinder arran~ement 77 on opposite side6 of a
mold station such as is shown at s~ations A and B in
Fig. 11. Matinq mold halves are ~ormed with eut out~ or :
recesses 81 and 82 fitted with hardened inserts 83 and
84 secured to mold halves by bol ts 87 and 88. Each
insert is formed with a taper matin~ with a ~-
corresponding taper on the complementary elamps 73-74.
Actuation of the e~linder unit 77 moves the clamps on
opposite sides o~ the moLd~ along a piston rod 86 (fixed
to a mold half as at 76) ~rom a retraete~ posi~ion of
Fig. 12 to an operatinq position shown ln Fi~. 11
driving the ~old halves into fAee to faee contaet under
very high compressive stress.
~ote that the parting line elamp ~truatur~ of Figs. ;~
11 and 12 i6 moun~ed directly on the mold halves and
operates directly on the mol~ halves, in contrast to the
seeondary clamp strueture described previously whicll i9
mounted on the mold platens and operates direetly on the
mold platens.
Obviously, any of a number of arrangements may be
devised in mounting the seeondary clampin~ arrangement
on the mold halves as engineering and other design
eonsiderations dletate.
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` 132~719
I Referring to Fig. 13, a ~urther alternative
'~ embodiment of the injection molding machine is disclosea
wherein the open mold configuration at station B
represents a large, complex part. In order to insure
adequate flllin~ and stu~fin~, a machine modification is
arranged wherein a plurality of primary injection units
~1, 92 and 93 are mounted on the top of fixed platen
94. Suitable tracks 96 are provided for advancin~ tl~e
injection unit~ to and ~ro to make appropriate
connection with matin~ ~econdary in jection units ox
~tuf~ers 97, 98 and 99 incorpora~ed in a central movable
~ platen 101. Thus, in operation ~he primary injection
.' unit~ and cooperating ~tu~er units are operable
individually or collectively in various combinat~ons and
permutation~ a~ de~ign complexi~y o~ the molded part~
aictat~ .
Obviou~ly, the po~ition and number of the primary
injection and cooperating stuffer unit~ is a matter of
choice con~istent with part retrieval, overall length o~
machine, ~loor space and so ~orth.
Fig. 14 illustrates a double capacity ~achine in
which there are four molding stations A, B, ~ and D, two
oppo~ed primary in~ection extruder3 10~ and 103 with ~wo
central mold platens 104 and 106 each incorporatin~ a
secondary extru~ion unit~ or stuX~ers 107 and 108, in
.~
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~L32871~ ~
the fashion and for the purpo~e previously described,
for servicing mold stations ~ and C on the left and mold
stations B and A on the right, respecti~e]y. ~he
reference numerals ]09 and 111 designate mold part
removal units or robot~. Naturally, each mold station
could have a plurality of molds as required.
Hereagain, the location of primary injecting units
i8 a ma~tex of ~e~ign choice based on machine ~ize
lim~'tations and available operating ~pace.
~ he machine con~i~uration o~ Fi~. 14 show~ the
mold~ open at stations A and D while the molds at
station~ R and C are closed.
This confiquration is developed in the following
~ a gh i on .
I Assume tha~ the primary clamping means actuated by ~-
piston 32 has moved all movable platens 24, 104, 25 and
lOfi to the r~ht a~ainst stationary platen 27 clo~lng
all molds at stat1ons A, a, C an~ D with all secondary
clamps 12-12 latched.
11pon an appropriate signal from the clamp control
~Figure 5), the secondary clamp 12 at ~tation A i~
relea~e~ while the secondary clamp~ 12 a~ s~ation~ B, C
and D remain latched.
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~2~719
The piston 32 i~ ordered to move to the left. This
occurrence opens ~he mold at ~tation A and dog 117
secured to movable platen 25 moves ~rom the da~hed line
position to the solid line position to abut stop 118.
Contact between the dog 117 and stop 11~ stop~
movable platen 106 in the position shown in Fig. 14 and
blocks further separation of mold halves at station A.
Upon the occurrence o~ t~e above-noted abutment and
in timefl se~uence, the secondary clamp at station D i8 . . :
unlatched 80 that upon continued motion of the piAton 32
to the left the mold at station D opens to complete
development of the mold layout shown in Fiq. 14, i.e.
molds at Rtation~ A and ~ are open and mol~s at station~
B and C remain clo~e~ and clamped.
Aqain starting from a closed mold position at
,
stations A, B, C and D, ~he molds at station~ ~ an~ C
are openefl in similar fashion in response to the
appropriate si~nals ~rom the clamp control unit.
Fig. 15 is an operating schedule showing the
sequential positions o~ the various machine accessories
as the double capacity unit o~ Fi~. 14 operates to
produce ~our molded parts per cycle.
Fig. 16 shows a machine arrangement in which a
single primary injection unit i5 utilized to mold parts
at ~tations A and B where each part i8 molded in th~
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13287~
same physical and ~patial orientation. Si~niicantly,
in this arrangement, the robot head require~ only a
single pick up unit in that each mold part iB graaped
while dlsposed in t~e same orientation.
In this machine configuration a segment of the
molten pla~tic flow channel leading to ~ta~ion B i~
carried by and reciprocates with the central platen 104
and is separa~le ~rom ~he flow channel serv~ng station A
as ~hown by the re~erence numeral 100. The ~low
channels opera~e to ~upply the mold at ~tation B when
valve~ 112 and 113 are open and ~alve 114 ia alosed.
Ater injection and suitable holdin~ at station B valves
. and 113 are clos~d, valve 114 is opened and molten
plastic i~ injected into the mold a~ sta~ion A at the
¦ appropriate time in ~he molding cycle. In order to
I ~acilitate ~his arrangement, a conical cut out 116 1
j ~ormed in the stationary platen 119.
¦ Dependinq, ~or example, upon the s~milarity of
molded parts anfl cooling time required, use of a
~econdary injection unit or stuffer i~ optional.
Correspondin~ly, u~e oE secondary clamp units iB al80 an
optional acces~ory. The necess~ty ~or secondary
clampin~ unit~ depends primarily on ths relative cooling
rate~ o~ the part~ m~lde~ at each ~ation.
1` .
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~328719 a7-~23
Fig. 17 shows a modification of the arran~ement o
Fig. 16 in which two primary injection units are
utilized, one ~ervicin~ molding station A and the
another servicing station B. In this arrangement,
stuffer unit~ are unnecessary in that the primary
injection units act dually to perform the mold filling
and mold ~tufing function.
Fig. 18 i~ a chart of the molding cycle of Fi~. 17
indicating the various posi~ions of maahine accessories
fluring the course of moldin~, coolin~ and e~ecting piece
parts ~rom stations A and B ~equentially.
When using more than one injec~ion means, ~iferent
resins may be injec~ed into ~ eren~ mold aavities or
di~erent resins may be coinjected in the ~ame mold
cavity to gain a layered waLl ~ruature.
DE S CR I PT I O N OF T HE ALTE R NAT I VE EM BOD I M ENT
Referring now to Figs. 19-23, a modified in~ection
moldin~ mac~ine indicated ~enerally by the reference
numeral 111 includes fixed platens 112 and 113, carried
by a base frame supporting pairs of tie rods 116-116 and
117-117 in the usual and customary ~ashion. A movable
oentral pla~en, in~icated generaLly at P, incorporating
a hot runner ~y~tem compri3es a manlfold distributor
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~a28719
block 120, moldable material switching valve means 121,
manifold mean~ de~ining manifold section5 122 and 123,
and mold halves 124 and 126 supported by said central
platen
Central platen P is movable in coo~eration wit~
movakle platen 127 to open and close mold hal~es at mold
stations indicated at A and B to mold articles, such as
At C.
The clamps 128, 129, 131 and 132 operate ~o ~eal
and maintain close con~act between mold halves durinq
molding in controllefl ~eq~ence.
Note that manifold section~ 122 and 123 s~raddle
and are supported removably by movable central platen
136.
Except ~or suitable fastenlng means and ~pacer~
~not shown), the manifold sectlon~ 122 and 123 are
isolated from the central platen 136 by an insulatinq
air gap indicated by the reference numeral lOS.
Frequent~y, it is desirabla to includè cooling
coils in the central platen 136 to prevent ove~eatin~ ;;
and attendant expansion o~ the platen leading to siezing
t~ the tie rods 116-116 and 117-117.
Cooling of the central platen 136 in combina~ion
with the insulating air gap 105 protects the manifold
sections 122 and 123 from overheating.
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~32g71~
Mold ha].ves 124 and 126 are also supported by ~he
central platen 136 and the manifold section~ 122 and 123
are sealed against respective-mold halves 124 and 126
about the periphery o~ mold openings 106 by seaL means
defining a raised annulus or boss as indica~ed by the
reference numerals 100 and 101.
Mani~olfl dis~ributor block 120, connected ~o the
central plat~n 36, include~ molding material ~witc~ing
valve 121 and provide~ ~upport for an injection unit
nozzle clampin~ mean~ in~icated generally by the
~e~erence numeral 142.
An injection unit in the o~m of an extruder 143,
movably ~upporte~ b~ means (not shown), i8 movable from
the po~ition shown in Fig. 20 to an in~ection position
indicated in Fi~. 21, alon~ a Fath or axi~ indicated by
the reference nume~al 144. The axis 144 is generally
parallel to the injection mol~ing machine axis (mol~
clamping axis~ indicated by the reference numeral 146.
When the injection unit 143 is in the in~ection
position (Fi~. 21), nozzle 147 i~ aligned with and
commUnicates wit~ ori~ice 1~8 o~ manifold di~tributor
bloclc 120.
A seal, indicated at S~ ig. 23~, is-e~fected by
the contact hetween 6urface 149 o~ mani~old di3~rlbutor
bloclc in~ert 151 and sur~ace 152 of noz le insert 153.
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~ he seal i~ maintained by no~zle clamping means 142
defining, in this embodiment of the invention, cylinder
154 with cooperating piston 156 secured to,the manifold
~istributor block 120 by rods 157. The nozzle clamping
means acts alon~ axis 160, whlch is perpendicular to
machine or clamping axis 14~.
Switching valve means 121, upstream of the manifol~
mean3, defining a spool valve i8 operatefl in cyclic
fashion in ~ynchronism with ~he molding cycLe ~o switch
moldable material to appropriate maniold sea~ion 122
and 123 via condults 133 and 13~ (Fi~. 23). The 8pool
valve 121 is rec~proaated by valve opera~ng ayllnder ~ -
159 (Fi~. 22), a~ indicated by the arrow 161 oP Fiq. 23.
Ball clleck valve 162 i~ provided in moldable
material flow path 163 to prevent leakage when the
nozzle i~ unalamped and the seal between the no~le and ~:
the manifold di~tributor block i~ broken.
A stu~fer or packer unit 164 is located upstream o
the spool valve 121 and communicates with the flow path
163 via conduit 16fi. ~:
I~ is anticipated ~hat the ~troke of the in~ection ;
unit 143 in moving ~rom the position o~ Fiq. 20 to the
injectlon position of Fi.g. ?.1 will vary from one molding
set-up to another dependinq upon the "buil~ up" or
~ thickne~s of the mold halve~. ~
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~32871~
That is, the injec~ion poi3ition will vary along the
machine axis depending upon ~he dimensions o the mold
halves in the closed position measured alon~ the
lon~itudinal or clamping axiis o~ the machine.
The stroke o~ the injection unit is also
advanta~eous in that it provides access for a robot or
other automatia molded article retrieval device to enter
open mold halve~i to ~rasp and remove a mold~A ~r~icle C.
It iq ~o be understood that the invention i~ not
limited to the illustrations described and shown hereln,
whiah are deemed to be merely illustrative of the best
modes of carrying out the invention, and which are
susceptible of modificat~on of form, i~ize, arrangement
o parts anA detall~ o~ ope*atlon. The invention rather
is lntende~ to encompass all such modi~ication~ w~lch
are wlthin it~ spirit and scope as defined by ~he claims.
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