Note: Descriptions are shown in the official language in which they were submitted.
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Injection Moulding Machine
The present invention relates to an injection-moulding machine
with a double C-shaped machine frame and a fixed as well as a
hydraulically or electro- mechanically movable die platten, at
least one additional force element being provided in an
arrangement that is symmetrical with respect to force in order
to balance out the bending moment that deforms the machine
frame and is generated when the mould is closed, this
preferably being a hydraulic ram that is acted upon by a force
that corresponds to or is proportional to the closing force
that is exerted exerted by the first force element.
Such injection moulding machines are generally known. The die
plattens of these known machines are connected to each other
by beams so as to absorb the axial forces that occur during
the injection process, the movable mould carrier optionally
being supported so as to the movable on these beams.
DE-AS-llO9 356 describes an injection moulding machine with a
multi-part frame that incorporates two solid cast transverse
members that are connected to each other by a plurality of
longitudinal beams that extend in the mould-closing direction;
these beams serve to absorb the mould-closing forces. The
longitudinal beams are arranged in a middle area of the
transverse members, whereas beyond this middle area, on one
side there is a fixed die platten as well as a die platten
that can be moved by a first force element; on the other side
there is an additional hydraulically powered force element
that is arranged so as to be symmetrical with respect to
force; this is used to balance out the bending moments that
are exerted on the longitudinal beams by the first force
element.
In addition, DE-Al-25 28 153 describes a single-column press
with an upper and a lower frame that are in the form of arms
that are secured to a vertical column-type frame, and between
which there are a fixed die platten and also a die platten
that can be moved by a first force element. In order to
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compensate for the bending moments that deform the multi-part
frames, an additional element is provided in an arrangement
that is symmetrical with respect to power and which can be
acted upon simultaneously with the first force element.
DE-Ul-92 12 480 describes an injection moulding machine with a
single-part frame that supports a fixed die platten and a die
platten that can be moved by a force element, this being
supported--so as to be able to rotate--transversely to the
axial direction of the force that is applied. The tipping
ability of the die plattens that is achieved thereby ensures
that these are always parallel, even in the face of great
closing force.
JP 57209799 (Patents Abstracts of Japan, Volume 7, No. 68)
describes a shaping machine in which the two transverse arms
are connected through screw connections to the ends of a
longitudinal arm, there being a mould-closing device and a
compensating ram between the transverse arms, these being
arranged so as to be symmetrical with respect to force in
reference to the longitudinal arm, so that the turning moments
exerted by the two rams balance each other out.
It is the task of the present invention to create an injection
moulding machine of the type described in the introduction
hereto, in which the parallelity of the die plattens is
ensured during the mould-closing procedure.
A further task of the present invention is to prevent any
bending of the double C-longitudinal arm in double C-shaped
machine frames.
The present invention solves this problem in that the
longitudinal arm of the double C-shaped machine frame is
formed in one piece with the transverse arms thereof.
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As a result of this configuration, it is possible to eliminate
the beams that usually absorb the axial forces; because of the
arrangement of additional force elements, in particular on the
hydraulic rams that act on the frame, the sum of the forces
and bending moments acting on the frames can be reduced to
zero and the frame can be kept free of distortion. In a
particular, this is so because the bending moments generated
by the closing force, in particular in the longitudinal
direction of the frame, can be balanced out, at least by the
force that counter-balances the closing force.
According to a development of the present invention, all the
hydraulic rams are arranged on the machine frame and have axes
that preferably run parallel to each other, which means that
despite a readily accessible form closing unit, a
distortion-free machine frame is guaranteed.
According to a further development of the present invention,
the hydraulic rams are arranged on the inside of the arm in
particular the longitudinal arm of the double C-shaped frame,
and they operate in the same direction.
In another embodiment, the hydraulic rams that move the die
plattens and the additional hydraulic rams work in different
directions.
In another development of the present invention all the
hydraulic rams can be connected to a common feed system, or
else be supplied from different feed systems.
According to the present invention it is also possible to
develop the injection moulding machine such that the fixed die
platten is connected to a an additional platten that is
arranged on the opposite arm; and such that the two plattens
are articulated in each instance onto the particular
corresponding arm.
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According to another development of the present invention,
provision can also be made such that the hinges lie in the
axial direction of the hydraulic ram that operates the movable
platten; and such that the two plattens that are hinged to
each other are connected by way of an additional beam, this
then serving as a guide for the movable die platten.
In a preferred embodiment, the injection moulding machine is
characterized especially in that the two plattens that are
hinged together, the additional beam, the movable die platten,
and the hydraulic ram that operates this form a connected and
coherent closing frame.
The present invention will be described below on the basis of
the drawings appended hereto. Figures 1 to 8 show different
embodiments of the injection moulding machine according to the
present invention, identical parts bearing the same reference
numbers in each case.
Figure 1 shows an embodiment with a double C-shaped frame, two
arms 2, 3 being arranged on a pedestal 1, the arm 2
accommodating the fixed die platten 4 and the other arm 3
accommodating the mobile die platten 5. The pedestal 1 also
supports an injection unit that delivers the moulding
material. The die plattens 4, 5 support the mould halves 8,
8a.
The movable die platten 5 is connected to a hydraulic ram 9
that functions as a closing mechanism and this moves the die
platten and generates the required press force; this is
arranged on one side of the beam 13, i.e., the double
C-longitudinal arm, and is parallel to this. In addition,
another hydraulic ram 10 is fitted between the two arms 2, 3,
and this is arranged on the other side of the beam 13, and is
similarly parallel to this. The hydraulic rams 9, 10 are
supplied from a common hydraulic line 6, and act in opposite
directions.
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Thus, the arrangement of the additional hydraulic ram 10 is
symmetrical with respect to force, so that the moment that is
generated when the hydraulic ram 9 is working is balanced
out,and these sum of all the moments is zero.
In order to fulfill the equation to the effect that the sum of
all the forces and moments acting in the machine frame is
equal to zero, according to the present invention, in this
system, if the axial Z 1, Z 2 are unequally spaced away from
the mid-line axis m, the piston surface of the rams 9, 10
must be made unequally large or an element that reduces the
pressure must be incorporated in one ram line, or one of the
two rams must be supplied from a dedicated and independent
pressure supply system. In any case, what is achieved is that
pure tensile forces are effective in the beam 13, and this is
not loaded with moments; this is achieved by matching the
force that is exerted by,the ram 10 to the closing force that
is generated by the ram 9.
The arm 2 is secured rigidly to the pedestal 1, in contrast to
which the arm 3 is connected to the pedestal by way of a
groove-pin combination 12 so as to be axially movable, if
necessary in order to prevent rotation of the beam 13. It is
preferred that the groove be in the form of an elongated hole.
Figure 2 shows a modification of the embodiment shown in
figure 1; in this, the arms 2, 3 are articulated onto the beam
13. The two hydraulic rams 9, 10 are arranged on both sides
of the beam 13, on the inner side of the arm 3, the beam
passing through the die platten 5, said beam serving as a
guide element for the movable die platten 5.
A further embodiment is shown in Figure 3; in this, the frame
2 is configured as a one-piece C-shaped frame. The two
hydraulic rams lie parallel to each other and parallel to the
C-long arm, although they are supplied from different pressure
pumps, not shown herein.
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As is shown in Figure 4, it is also possible to arrange the
hydraulic rams 9, 10 so that they oppose each other, when the
additional hydraulic ram 10 that is used to equal out the
bending moment is arranged on the outer side of the arm 2, and
the bale 14 passes through both arms 2, 3 or else encloses
them; this then clamps the parts together.
Figure 5 shows an embodiment in which the two arms 2, 3 are
connected to a beam 13 that is articulated onto them, as is
shown in Figure 2. However, each of the two arms is separated
from the pedestal 1 by an additional hydraulic ram 10', 10",
the direction of their axes being perpendicular to that of the
hydraulic ram 9 that activates the movable die platten 5.
This configuration, too, guarantees that only tensile forces
act on the beam 13, and also ensures that the die plattens 4
and 5 are parallel, since the sum of all the moments and
forces can be held to zero by simply counterbalancing the
forces of the hydraulic rams 10', 10".
Figure 6 shows an arrangement of the injection moulding
machine that corresponds to the one shown in Figure 1, this
being a vertical arrangement.
Figure 7 shows an injection moulding machine in which the
movable die platten 5 is not activated directly by the
hydraulic ram 9, but is arranged on the movable arm 3. The
hydraulic ram 9 is located on the outer side of the arm 3 and
the piston rod is secured to the inside of the arm 2. It
moves the arm 3 against the additional hydraulic ram 10. The
movable die platten 5 is thus moved indirectly by way of the
arm 3, which slides on the pedestal 1. In this arrangement,
the hydraulic rams 9, 10 are supplied separately. This
version requires no additional beam 13.
In the embodiment that is shown in Figure 8, the beam 13
passes through the arm 3 and is secured rigidly to the inner
side of the arm 2. A locking device 14 is arranged on the
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outer side of the arm 3. The mould is closed by the ram 10
and then the beam 13 is locked automatically by the locking
device 14. Then the two rams 9 , 10, which are arranged in
parallel, build up the closing pressure.
Naturally, the embodiments described above can be used not
only for injection moulding machines, but, essentially, for
presses that are used to shape different materials.
A further embodiment is shown in Figure 9. In this version,
in addition to the fixed die platten 4, there is an additional
platten 17, each of these plattens being connected to the
corresponding arm 2, 3 through hinged 16 that are on the axis
of the hydraulic ram 9 and thus on the effective axis of the
closing force F1. The fixed plattens 4, 17 are both connected
by way of an additional beam 15. The die platten 5 that is
moved by the hydraulic ram 9 slides along the additional beam
15 and uses this as a guide.
This configuration decouples the closing frame formed by the
plattens 4, 5, 17, the additional beam 14, and the hydraulic
ram 9, from the frame, and this ensures a further improvement
in ensuring that the die plattens are parallel, particularly
when the mould is being closed, even if the arms do spread
apart slightly.
Even though the present invention has been described above on
the basis of embodiments in which a hydraulic cylinder-piston
assembly 10 was used to apply the counter-force, the present
invention is not restricted thereto. What is important is the
fact that this involves a powered force element that can be
activated simultaneously with the closing ram 9, with a force
that is equal to or proportional to the closing pressure.
Thus, the force element can be configured, for example, as an
electrically powered ballscrew or threaded spindle.
