Note: Descriptions are shown in the official language in which they were submitted.
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Description
Cross Reference to Related Applications
This aLpplication claims the priority of Applications 195 31
328, filed on August 25, 1995, and 195 42 453, filed on November
S 14, 1995, the disclosure contents of which is herewith also
explicitly made the subject matter of the present invention.
Technical F'ield
The invention relates to an injection molding unit for a
lC machine for the injection molding of plastics for the processing of
plasticizable compounds according to the preamble of claim 1.
State of the Technology
EP-A 576 925 discloses an injection molding unit of this type
wherein a carrier block is seated so as to be axially displaceable
with respect to a stationary mold carrier. The linkage between
carrier block and stationary mold carrier takes place via
electromech.anical spindle drives nested one behind the other, the
latter comprising a drive unit configured as a hollow shaft motor
for the application of the nozzle to the injection mold and an
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injection unit which produces the axial movement of the conveying
screw within the plasticizing cylinder during injection. A rotary
motor is also provided on an injection bridge for the rotation of
the conveying screw. By way of the only guidance which, however,
does not take place symmetrically with respect the injection axis,
guide rails are provided on the machine base, on which rails at
least the carrier block is guided. By nature, a precise guidance
does not occur when the spindle nut of the hollow shaft motor is
applied against the spindle which is connected to the stationary
mold carrier in a manner fixed against rotation. Further guide
elements are not provided. The serial arrangement of drive unit
and injection unit results in a large structural length of the
injection molding unit since the paths of movement of the two units
are strung one behind the other. In the event of a defect of one
un:it, at least one 'beam' must be detached with both units, thus
resulting in unnecessary additional work and additional costs.
DE-C 43 17 998 also discloses to arrange a drive unit for the
application of the nozzle and an injection unit symmetrically with
respect to the injection axis. Electric motors serve as drives
2i~ which, via belt drives, drive hollow shafts of drive unit and
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in-jection unit which are nested inside one another. Here, too,
both units can only be replaced together and separate guide
elements are not provided with the exception of the guide strips
which are loosely mounted on the machine base.
DE-C 41 30 287 discloses the lengthening of a conventional
plasticizing cylinder by means of inserts. In this manner, the
length/diameter ratio (L/D ratio) of the conveying means can be
changed. This is necessary in cases where the output of the
in-jection molding machine must be increased, e. g., to supply the
1() plasticized compound with an increased thermal output.
Summary of the Invention
On the basis of this state of the technology, it is the object
of the present invention to modify an injection molding unit of the
generic type cited at the outset in such a way that, in a favorable
manner, this results in an improved guidance of the injection
molding unit.
This object is accomplished by an injection molding unit
having the characteristics of claim 1.
The only point which is connected with the stationary mold
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carrier and which is thus stationary at least in the direction of
the injection axis, namely the articulation point of the longer
part of spindle and spindle nut, is used for a guiding function in
that, in its end region, the longer part is simultaneously
configured as a guide beam. Compared to the 'mere' guidance of the
carrier block on the spindles of the spindle drives, this offers
the advantage of a considerably more precise guidance with greater
positional accuracy.
Brlef Description of the Drawings
Fi(~. 1 A partially cut side view of an injection molding unit
which rests against the stationary mold carrier,
Fig. 2 a view of the injection molding machine according to Fig.
l from the right,
Fi~. 3 a section according to line 3-3 of Fig. 1,
Fig. 4 a side view of the injection molding unit according to
Fig. 1 in a further embodiment wherein the guide region
is supported by a supporting element,
Fig. 5 a view of the injection molding unit according to Fig. 4
2l~ from the right,
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Fig. 6 a view of the injection molding unit according to Fig. 4
having a rotary motor which is identical in structure to
the injection motors,
Fig. 7 a section through a hollow shaft motor.
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Detailed Description of Preferred Embodiments
The invention is now described in greater detail by way of
exc~mple with reference to the attached drawings. The embodiments,
however, are merely examples which are not intended to limit the
concept of the invention to a specific physical arrangement.
The injection molding unit serves to meter and inject
plasticized material such as, e. g., plastic materials, powdered
compounds and ceramic compounds into a mold cavity 80 of a mold M
which can be fastened with a part on a stationary mold carrier 35
1'; of a mold closing unit. During the injection, the injection
molding unit rests against the mold M with a nozzle D. Figures 1
to 3 illustrate the fundamental design of the injection molding
unit of an i.njection molding machine for plastics, on which design
the further embodiments are also based.
The injection molding unit has a carrier block 10' by means of
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which the injection molding unit is substantially supported on a
machine frame 81. The support takes place by way of insertion of
tw~ strips 62' which are provided with guide rails 19 on their
upper side. On the guide rails, a carrier block 10' on guide shoes
79 can be moved toward the stationary mold carrier 35 and away from
t:he same by means of at least one spindle drive A. Nevertheless,
the entire injection molding unit including its support can be
moved or pivoted as a structural unit detached from the machine
ba,e, e. g., for injection into the parting plane. A spindle 31'
1~ as a longer part and a spindle nut 78 as a shorter part of the
spindle dri-ves A can be moved relative to one another, while it is
po,sible to connect the spindle nut with the axially displaceable
carrier block 10' and the spindle 31' with the stationary mold
carrier 35 in a manner fixed against rotation. At least one hollow
shaft motor 73 drives the spindle nut 78 of the spindle drive A for
the application of the nozzle D to the mold M, optionally via an
integrated planetary gear.
Both spindle drives can be actuated separately by hollow shaft
motors. The expenditure of a motor per drive must be compared with
the advantage that all drives can be reliably submitted to a
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function test in the manufacturing company and can then be supplied
as a structural unit to the injection molding unit.
In addition to these spindle drives, at least one, preferably
two further spindle drives E are provided which have spindles 18'
and nuts 11 as parts that are movable relative to one another. One
part of these two parts is arranged on the injection bridge 25' and
the other on the carrier block 10'. When these spindle drives E
are operated by means of the injection motors 51', the injection
bridge moves relative to the carrier block such that the conveying
means 72 is moved axially in a plasticizing unit 17.
The p~Lasticizing unit comprises a plasticizing cylinder 36
which is arranged on the front side of the carrier block 10'. If
a ,-onveying screw is arranged as conveying means 72, a rotary motor
52', 52" is further arranged such that it drives the conveying
screw in the injection axis s-s. If only a conveying piston is
provided, t:his conveying means also penetrates the carrier block
10' and is seated on the injection bridge 25', but a rotary motor
is not necessary in this case.
For the rotation of the conveying means 72 configured as
conveying screw, the rotary motor 52' is arranged transversely to
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the injection axis s-s, preferably rising upward, so that the
injection molding unit becomes shorter. Therewith the center of
gravity of the injection molding unit is moved further toward the
center. A favorable rotational speed/torcIue characteristic for the
5 conveying means 72 can be accomplished via a gear 26', preferably
a bevel gear.
In the embodiments, the longer part of spindle and spindle nut
of the spindle drive A for the application of the nozzle D is
extendea as a stable guide element throughout the injection molding
unit. There, it has a guide region 31a'. This guide region serves
for the precise and positionally accurate guidance of the carrier
block 10' by means of sliding bearings 33a and also of the
injection bridge 25' by means of sliding bearings 33b.
S:imultaneously, the mass that needs to be moved for the application
of the nozz]e is reduced due to the dual function of the spindle
3'L' of the hollow shaft motor 73.
The dual function of the spindle is accomplished by way of
breaking up the combination of injection unit and drive unit which
exists in t,he state of the technology. But with this it is
possible at the same time to now configure the injection motor and
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the rotary motor as a standard motor and to provide them with a
largely ide:ntical structure, thus, as a side effect of the improved
guidance, simultaneously resulting in a cost reduction for the
design of the entire injection molding unit.
In the embodiment of Figures 1 to 6, the guide region is part
of a spindle which thus represents the longer part of the spindle
drive. But, in principle, the function of spindle and spindle nut
is interchangeable. Thus, Fig. 7 illustrates a hollow shaft motor
wherein the longer part is a tube 110 with insic;e profiling into
1~ which plunges a rod 111 with a spindle head llla. In this sense,
the spindle head llla is a 'nut' having an outside profiling which
in Fig. 7 c~operates with the inside profiling of the tube 110 via
cylindrical rolling bodies or spherical rolling bodies 112.
However, a direct transmission without rolling bodies would also be
possible. ]Iere, the tube 110 represents the rotor 21 of the hollow
shaft motor 22; the interior chamber R can be ventilated via the
vent 23. I:E the tube 110 were to be extended, the thus illustrated
hollow shaft motor could also assume the guide function with this
t:ube as the longer part of the spindle drive, as is illustrated in
Figures 1 to 6.
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Accorcing to Figs. 2 and 3, the guide regions 31a' are
arranged in a horizontal plane symmetrically with respect to the
pl~sticizi~g unit 17. In wing regions 25c' are arranged the
further sp-ndle drives E and therewith also the drive motors 51'.
l'hese are also arranged symmetrically with respect to the
plasticizi~g unit, but in a plane having an angle with respect to
t:he horizortal. The injection motors 51' are arranged to be fixed
against rc_ation on the injection bridge 25' and rotate the
spindles 1~3' which cooperate with nuts 11 arranged to be fixed
1~ against ro~ation which are disposed in wing regions lOb' of the
carrier block 10'. Stops 63' are disposed at the end of the
spindles 1-3'. Each injection motor 51' is associated with a
planetary c~-ar 51a'. In the embodiments according to Figs. 1 to 5,
this only permits to configure the injection motors 51' and the
r-otary motor 52' to have the same structure because the occurring
forces in -ough approximation are at a ratio of 2:1; but with an
arrangemen~ of the rotary motor 52' according to Fig. 6, a
planetary crear 26" can be used as a gear that is identical in
structure to the planetary gears 51a'.
The integrated planetary gears 26", 51a' permit the use of
- 10 -
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larger spindles, which must be equated with a longer service life
of the drive. At the same time, a larger pitch can be accomplished
on the spindles so that an optimization is possible in that the
torque can be set to be relatively high and the rotational speed
can be reduced at the same time. This also serves to increase the
service life.
The carrier block 10' can be moved on the spindle 31' up to a
stop 32'. In its front region, the spindle 31' is held in a
holding plate 27. This holding plate is connected with the strips
lC 62' on whic]~L the carrier block 10' is guided at the level of the
machine frame 81. In order to further enhance the stability of the
entire injection molding unit, a three-dimensional frame is formed
irL the two last embodiments of Figures 4 to 6 by means of strip 62'
arLd holding plate 27 in that a supporting plate 82 is provided
1~ which then supports the guide region 31a' of the spindle 31' of the
spindle drives A also in the rear region. In this manner, a stable
seating is aLccomplished, the injection molding unit is prevented
from tipping in the rear region and vibrations are combated
effectively which counteract the service life of the entire unit.
This stability is advantageous when the injection molding unit is
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displaced or pivoted, e. g., for injecting into the parting plane
or when the injection molding unit is moved to a depot for
maintenance.
Replaceable adapters 13 are arranged between the one part of
', the spindle drive A and the carrier block 10' or between this one
part and the stationary mold carrier 35. They are disposed in the
a-a axis o: the spindle 31'. The adapters 13 form at least
portions of _eams into which plunge the spindles 31' of the spindle
drives A or which they penetrate. The adapters 13 can
simultaneously serve as a guide for the plasticizing unit 17. The
adapters are usually supplied in their shortest and thus most
favorable er~odiment for transport when they are delivered to the
customer. ::~ it is necessary for the customer, e. g., to improve
the mixing results or the cluality of the material to be
plasticized a longer L/D ratio of the conveying means 72 can be
accomplisheci by replacing the adapters 13 by longer ones or by
stringing adapters 13 one behind the other. The adapters can be
sllpplied , e. g., by the manufacturer in a length which corresponds
to an L/D rGtio of 5 so that the conventional L/D ratio can be
increased from 20 to 25 by stringing two adapters one behind the
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other. It is possible to seat the adapters or the spindles 31' on
a carrier i.n the region of the stationary mold carrier 35, which
carrier can be displaced laterally or upward on the stationary mold
carrier 35 in order to thus make the injection molding unit
accessible to a linear sprue, as is disclosed in DE-C 42 27 336.
This does not break up the connection with the stationary mold
carrier 35 in the direction of the injection axis s-s.
It is understood that this description can be subjected to a
great variety of modifications, changes and adjustments which are
in the range of equivalents with respect to the attached claims.
