Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates to an injection molding
machine and is more particularly concerned with an openable
and closeable injection nozzle mounted at the discharge end
of the plasticizing cylinder which forms part of a
plasticizing unit. The nozzl~ is axially coupled to the
plasticizing cylinder and has a discharge opening which may
be closed by a valve needle controlled by a power mechanism,
such as a hydraulic piston-and-cylinder unit. At least one
of force-transmitting linkage means comprises joints at both
ends and is connected to the valve needle.
In known injection molding nozzles of the above
outlined type, the valve needle is arranged coaxially with
the valve body and may be operated by a control cylinder
with the intermediary of a two-arm lever. Such an
arrangement which is disturbing the thermal symmetry of the
nozzle is shown, for example, in French Patent No. 1,439,001
(Figures 7 and 8), in German Utility Model No. 7,020,969
(Figures 5-7) and in German Patent No. 23 36 099. Such
injection molding nozzles are also disclosed in Canadian
Patent Application No. 561,670 filed March 16, 1988.
It is a disadvantage of the above-outlined prior
art arrangement that because of the use of a two-arm lever,
the nozzle channel cannot be arranged coaxially with the
axis of injection. Rather, the plasticized synthetic
material is injected into the discharge zone of the
injection nozzle from the plasticizing chamber of the
plasticizing cylinder through detour channels, arranged
radially offset to the injection
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axis Because of the multiple change in the direction of
flow of the plasticized material and because of the cross-
sectional configuration of the detour channels, a sig-
nificant pressure drop is usually experienced. When the
needle valve of the nozzle is ~irectly actuated by the control
cylinder (as shown in Figures 5-7 of German Utility Model No.
7,020,969), the needle valve is in direct engagement with the
piston of the control cylinder which is situated coaxially
to the flow channel. The coaxial arrangement of the control
cylinder, however, requires that the plasticizing cylinder be
laterally offset relative to the discharge nozzle. Conse-
quently, a throughout linear flow channel extending from the
plasticizing cham~er of the plasticizing cylinder to the
nozzle outlet cannot be constructed regardless of whether the
valve needle is actuated by means of a lever or directly by
a coaxial control cylinder: the construction of such a
nozzle channel is impeded either by the force-transmitting
lever or by the control cylinder. Thus, for this reason, in
each instance, flow channels are required which have portions
oriented transversely to the axis of injection.
Furthermore, closeable injection nozzles are known,
whose spring-biased valve needles are arranged at an angle to
the injection axis, such as shown in Figure 3 of French
Patent N~. 1,439,001 and in German Utility l~lode] No. 1,79~,444.
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In such closeable nozzles, the nozzle valve opens when the
pressure of -the synthetic material exceeds a predetermined
limit. Consequently, in such nozzles the preconditions for a
control by computer program are missing.
SUMMARY OF l~E INVENTION
It is an object of the invention to provide an improved injection
nozzle of the above-outlined type, including its driving mechanism mana-
ged by programm which injection nozzle may be used at low technical ex-
0 penditure by choi~e as closeable nozzle or as "open" nozzle with the samecharacteristical construction of the M ow channel caused by hydrodynamic
and thermotechnicalreasons and to change the injection nozzle together
with the plas-ticizing cylinder automatically without exchanging is driving
mechanism from the injection unit. It is noted that by "open" nozzle
there is meant a nozzle construction whose noz-zle body has a
nozzle channel which is coaxial to the axis of injection and
is not provided with a nozzle closing mechanism. Such open
' nozzl~s operate in conjunction with a decompressing device
which relieves the plastic material in the plasticizing
cylinder of an excess pressure before the plasticizing unit
is moved away from the injection mold assembly. Such a
pressure relief prevents an undesired escape of the plastic
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material. Open nozzles are widely used beeause of their
versatility and beeause of their reliable, disturbanee-free
`operation.
Injection molding nozzles whieh are of the closeable
type are, however, indispensable in performing eertain
speeific tasks. Thus, such nozzles permit a high injection
molding speed at the beginning phase of the injecting
operation at the time when the plasticized material in the
plasticizing eylinder is, prior to opening the nozzle, at a
eertain pressure.
The above-outlined objeet and others to beeome apparent
as the speeifieation progresses, are aceomplished by the
invention, aeeording to which, briefly stated, the nozzle
body has a eoaxial nozzle channel which extends up to the
nozzle opening and through which the plastie material may
flow freely and further, the valve needle whieh is provided
for closing the nozzle ehannel at the nozzle opening is
longitudinally slidably reeeived in a bore whieh is arranged
.. ..
at an acute angle to the nozzle channel, at least one of the
force-transmitting linkage means guided respectively connec-
ted to the power means by coupling means, the power means com-
prise an axis of symmetry, which is arranged at an angle ~ the
valve needle and securing means mounted on the carrier block
lock respectively release the plasticizing cylinder to respec-
tively from the carrier block.
.. , .. , . . , ., _ ,, . ,,, . . _ _ . _ ., . _ . _ .. . .. ,, ., . " . ., . , . ,, ., .. , , , , .,, , .. . .. _ . .
-, : ., .. , -- ., .. . .: . , .
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Although the axis of symmetry of the power cylinder has a rela-
tively high angle to the axis of the valve needle, it is avai-
lable to transmit a motion of the power means, which motion is
parallel to the axis of injection in a c~osing motion or in an
opening motion of the valve needle without bending the valve
needle. Further,it is possible to arrange the power cy].inder~
which can be disconnected.at the carrier block radially dis-
placed from the axis of injection withoutmanaging the valve
needle in the nozzle body with a force-transmitting lever, which
disturbes the thermical symmetry and the flow of the synthetic
material through the nozzle. Furthermore, it is not necessary
.as usually experienced in prior art constructions, to change
the drive direction of the power cy]inder in an inverted motion
of the valve needle by an intermediate member. Such an arrange-
ment of the force-transmission of the power cylinder allows to
transmit the upstroke of the power cylinder to the closing mo-
tion of the valve needle. Additionally the closeable nozzle
may be usable as an "open" nozzle, when the valve need]e is
situated in a permanent]y open position.
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The shut-off nozzle structured according to the inven-
tion is adapted for a particularly rational mass manufacture
if the valve needle slides directly in the guide bore
provided in the nozzle body; that is, if the dihmeter of the
valve needle corresponds substantially to the inner diameter
of the guide bore. such a direct guidance of the valve
needle in the nozzle body has furthermore the advantage that
without appreciable weakening of the nozzle body, valve
needles of smaller diameter may be used which facilitates the
control of the valve needle because significantly smaller
forces are needed for maintaining the nozzle closed. This
applies particularly to a reliable hydraulic closing of the
nozzles in case the plasticized material in the shut-off
nozzle has a very high pressure, for example, up to 2800
bar. In case the control cylinder is arranged parallel to
the axis of injection, a force reorientation towards the
valve needle is feasible without generating stresses in the
force-transmitting members or in the valve needle in case the
force reorientation is effected by a cardan joint system.
In case a customer - for example, to save costs -
requests delivery of a plasticizing assembly only with a
permanently open nozzle, the nozzle construction according to
the invention makes i~ possible to couple a nozzle body -
which has no guide bore - to the p]asticizing cylinder in the
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same manner as a nozzle b~dy which includes a guide bore.
It is to be noted that a particular design of the force-
transmitting members according to another feature of the
invention causes the valve needle - upon charging the
rearward, larger piston face of the hydraulic cylinder - to
be moved into its closed position. As a result, and also by
1~ virtue of the small diameter (for example, 4 mm) of the
valve needle, even if a relatively small control cylinder is
used, a reliable closing of the nozzle opening is possible
even at very high pressures of the plasticized material.
According to another feature of the invention the securing
means of the power cylinder can be managed by the same driving
cylinder securin~ the plasticizing cylinder to the carrier block.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a side elevational view, partially in
section, of an injection molding assembly incorporating a
preferred embodiment of the shutoff nozzle according to the
invention, illustrated in a half-open position.
Figure 2 is a sectional side elevational view of one
part of Figure 1, illustrated on an enlarged scale.
Figure 3 is a sectional side elevational view of one
part of Figure 2, illustrated on an enlarged scale.
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Figure 4 is a sectional elevational view illustrating an
inserted nozzle structured differently from the nozzle
construction shown in Figure 3.
Figures 5, 6, 7, 7a and 8 are perspective views, on an
enlarged scale, of various components of the preferred
embodiment.
Figure 9 is an enlarged front elevational view of the
preferred embodiment.
DESCRIPTION OF THE PREFERRED E~30DIMENT
Turning to Eigures 1 and 2, the plasticizing cylinder 11
which forms part of the plasticizing assembly and which is
equipped with a heating device 30 is received, at its
rearward portion llb in a central bore lOa of a carrier block
10. In the carrier block 10, the plasticizing cylinder 11 is
immobilized in its working position by a locking device 33.
The locking device 33 comprises a radially slidable upper
bolt 33' and a radially slidable, two-part lower bolt 33 " ,
33''' which move in a vertical direction on the rearward end
of the carrier block 10. The lower bolt 33'' 33''' has a
bore in which there is received a piston-and-cylinder unit
~control piston 14) for controlling a valve needle 73 of a
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shutoff nozzle V mounted at the front end of the plasticizing
cylinder 11. The valve needle 73 may have a diameter of
4 mm. By virtue of this arrangement, the radial locking and
unlocking motion of the lower bolt 33'', 33''' which carries
with it the control cylinder 14, is utilized for coupling
and uncoupliny the control cylinder to and from the operat-
ing linkage of the valve needle 73, as will be described in
greater detail later.
The carrier block 10 which is integrated into the
injection molding unit is movable, together with the plas-
ticizing cylinder 11, in linear guides into engagement with
or away from a firmly clamped injection mold assembly (not
shown).
The closing stroke or opening stroke of the control
cylinder 14 is transmitted to the valve needle 73 by means of
a switch rod 82, an actuating rod 77 and an intermediate
member 88. The switch rod 82 and the actuating rod 77 are
connected with one another by means of a clamping member 80
as illustrated in particular in Figure 9. The switch rod 82
has at its end a thread 82a, by means of which it is con-
nected with the clamping member 80. By rotating the switch
rod 82 with the aid of a wrench inserted in a hexagonal
recess 82b, the switch rod 82 may be axially adjusted
relative to the clamping member 80 and thus the sliding path
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of the valve needle 73 may be adjusted to perform an optimal
shut off. The clamping member 80 and the switch rod 82 may
be immobilized in their set relative position by means of a
clamping screw 81 which bridges a gap 80a, splitting the
threaded bore 80b in which the threaded end 82a of the
switch rod 82 is received. As it may be observed by com-
paring Figures 2 and 9, the actuating bar 77 passes through
the clamping member 80 in the zone of a bore and a slot 80c
and may be tightened to the clamping member 80 after ap-
propriate adjustmen_ by means of a screw 81' which bridgesthe slot 80c. Also referring to Figure 6, a spherical head
77a situated at the frontal end of the actuating bar 77 is
received in a spherical socket 88b of the rod-like force-
transmitting intermediate member 88 to thus form a ball
joint. The intermediate member 88 surrounds with its frontal
end a rearward spherical head 73c of the valve needle 73 to
constitute a further ball joint. The spherical socket 88b in
the rearward enlarged portion 88a of the intermediate member
88 is laterally open for the introduction or removal of the
spherical head 77a of the actuating rod 77. In the spherical
socket 88b the spherical head 77a of the actuating rod 77 is
secured by means of a lateral locking element 88c. The
intermediate member 88 extends approximately in an axial
alignment with the valve needle 73.
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The actuating bar 77 is held by means of a pivot ring 76
which surrounds the frontal end of the plasticizing cylinder
11 with a clearance. The pivot ring 76 is articulated to
the plasticizing cylinder 11 in the vicinity of the uppermost
generatrix y (Figure 2) on either side thereof for a pivotal
motion to make possible the closing and opening of the
shutoff nozzle V by means of the valve needle 73. For this
purpose, two threaded bolts 89 which are oriented radially to
the plasticizing cylinder 11 and which are threadedly con-
nected with the pivot ring 76, extend by means of sphericalheads 89a into corresponding spherical pivotal bearings llc
of the plasticizing cylinder 11, as shown in Figure 3. In
this manner, the pivot ring 76 is pivotal between limits
about a horizontal pivot axis. The distance m (Figure 9) of
the pivot axis s-s of the pivot ring 76 from the approximate-
ly horizontally extending actuating bar 77 corresponds
approximately to the outer diameter of the plasticizing
cylinder 11. In this manner, the pivot ring 76 forms a
relatively long pivotal lever so that upon small closing or
opening swinging movements of the pivot ring 76 there is
obtained an approximately horizontal motion of the actuating
rod 77. The threaded bolts 89 are immobilized in their set
working position by means of securing nuts 90. For support-
ing the actuating bar 77, the latter passes through a bearing
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bore 76b provided in the pivot ring 76 and situated,in the
vertical symmetry plane z-z, as shown in Figure 9. The
bearing bore 76b has two frustoconical sections 76b' which
merge into one another along an inner circumferential ]ine
76b'' as shown in Figure 7a.
Referring in particular to Figure 8, the nozzle body 70
has a coaxial, linear nozzle channel 70a which extends to the
nozzle opening 70a'' and which permits an entirely free flow
of the synthetic material therein. The valve needle 73 which
is arranged to close or open the nozzle channel 70a at the
noz~le opening 70a'' is received in a guide bore 70e which
extends at an acute angle to the nozzle channel 70a. The
nozzle body 70 is a one-piece component and is provided with
a planar engagement face 70m. The diameter of the valve
needle 73 corresponds to the inner width of the guide bore
70e which intersects the nozzle channel 70a behind the nozzle
opening 70a'' at the frontal end of a narrowed outlet end
portion 70a'. During the control motions of the valve needle
73 - which has, as shown in Figure 6, a valving part 73a and
a guide part 73b - the outer needle surface glides, with a
close sliding fit, directly on the inner surface of the guide
bore 7Oe.
The inner diameter of the coupling bore lle of the
plasticizing cylinder 11 corresponds to the diameter of a
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coupling thread 72a of a hollow screw 72. The latter is
provided with a radial flange 72c. The coupling thread 72a
of the hollow screw 72 engages an inner thread of the
coupling bore lle. In this rnanner, the annular, planar,
5 precision-ground sealing face (engagernent face) 70m of the
radial flange 70k may be pressed against a corresponding
sealing face lla of the plasticizing cylinder 11, while the
hollow screw 72 axially presses against the annular shoulder
70h of the nozzle body 70 with an engagement face 72b. An
axial clamping of the radial flange 70k of the nozzle body 70
with the plasticizing cylinder 11 is effected subsequent to a
positionally correct adjustment of the nozzle body in such a
manner that the valve needle 73 and the force-transmitting
elements are oriented symmetrically to the vertical symmetry
plane z-z. The nozzle bore 70a has a funnel-like tapering
inlet portion 70a''' into which extends the conical terminus
of the displacement body 86.
By actuating the control cylinder 14, the valve needle
73 may be placed into its shutoff position or open position.
As it may be observed in Figure 1, a coil spring 26 surrounds
the switch bar 82. The coil spring 26 exerts its spring
force on the switch bar 82 by virtue of engaging a snap~ring
87 seated in a circumferential groove of the switch bar 82
and also engaging an arming element 51 of the plasticizing
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cylinder 11. By virtue of this arrangement, the spring-
biased valve needle 73 is maintained in its shutoff position
even if the switch bar 82 is disconnected from the control
cylinder 14.
The plasticizing cylinder 11 which may be axially
immobilized in the bore lOa of the carrier block 10 by means
of the radially and vertically guided locking bolts 33', 33''
and 33"', may be set free by virtue of a rearward motion of
the carrier block 10, for example, for the purpose of the
feed screw. Such an arrangement is disclosed in United
States Patent No. 4,708,622, issued November 24, 1987. The
control cylinder 14 is arranged at the carrier block 10 and
shifts in unison with the carrier block 10 during the
rearward releasing travel thereof.
The assembly for effecting an automatic coupling between
the switch bar 82 and the piston rod of the control cylinder
14 comprises, as may be observed in Figure 1, a coupling
portion 14b which is arranged on the switch rod 82 and a
coupling portion 17 which is arranged on the piston rod of
the control cylinder 14. In the coupled state, the two
coupling parts 14b and 17 interengage so that an automatic
disconnection of the coupling is achieved by the vertical
motion of the locking bolt assembly 33', 33'' and 33'''
during the unlocking motion thereof. The coupling assembly
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is accommodated in a niche T of the carrier block 10. The
-- ~switch bar 82 is guided approximately parallel to the
injection axis a-a in the arming elements 50, 52 of the
plasticizing cylinder 11 by means of sliding bushings 57.
The plasticizing cylinder 11 has a two-part cover 18
whose lower part 18'' shrouds the switch rod 82 and whose
upper part 18'' has a hoist ring 53. soth cover parts are
secured to the arrning element 51 of the plasticizing cylinder
11. The head of a lower securing screw 54 has a centering
cone. During the transport of the plasticizing unit, the
. conical securing screw 54 may extend into a corresponding
centering opening of the setting faces of the transport
devices. After a~program-controlled unlocking of the
plasticizing cylinder 11 and after its axial immobilization,
the plasticizing cylinder 11 may be set free from the carrier
block 10 by virtue of the latter being pulled off the
plasticizing cylinder 11 by a hydraulic mechanism. Upon such
an occurrence, the connecting plugs 29' of a connector plate
28' of the carrier block 10 are separated from the connecting
plugs 29 of a connector plate 28 of the plasticizing cylinder
11 .
With particular reference to Figure 4, as noted earlier,
the plasticizing cylinder 11 may be, if desired, provided
with a nozzle body 170 which has an external configuration
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identical to the ahove-described nozzle body 70 but which
has no guide bore. As may be observed particularly in
Figures 3 and 4 in conjunction with Figure 8, the nozzle
bodies 70, 170 are selectively securable in the working
position by a pin 71 which extends into the nozzle body 70
and the plasticizing cylinder 11 for preventing relative
rotations. As may be observed particularly in Figures 3 and
4, the flow channels 70a of the selectively used nozzle body
70 (for a shut-off nozzle ~) or 170 (for an open nozzle O)
are concentrically arranged to a heating coil 79 so that
upon control of the selectively used nozzles V or 0, there
will be achieved identical initial thermal conditions in the
flow passage 70a. As seen in Figure 2, the rearward
terminal portion 77a of the actuating bar 77 passes through
an opening 50a of the adjoining arming element 50.
It will be understood that the above description
of the present invention is susceptible to various
modifications, changes and adaptations, and the same are
intended to be comprehended within the meaning and range of
equivalents of the appended claims.
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