Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
Mould-closina unit for an infection mouldina machine
Reference to related aaplications
The present application claims the priority of the German patent application
198
12 741.3, filed on March 24, 1998, the disclosure of which is hereby expressly
made the subject matter of the present application.
Field of the invention
The invention relates to a mould-closing unit for an injection moulding
machine to
process plastics materials and other plasticizable masses such as powdery or
ceramic masses in accordance with the preamble of claim 1, this mould-closing
unit having a mould height adjustment device.
By "mould height" is here understood the height of the mould which is measured
in the closing direction and which corresponds to the distance between the
move-
able mould carrier and the stationary mould carrier when the mould is closed.
Adjusting devices of this kind are first of all necessary in injection
moulding ma-
chines in which the closing movement and the building-up of the locking
pressure
takes place via a toggle joint, since the support plate for the toggle joint
has to be
positioned in relation to the integrated injection moulding tool in such a way
that
as the tool or the mould is closed, the toggle joint is expanded and thus can
apply
its maximum locking pressure in each cycle. Furthermore mould height adjusting
devices are necessary to optimize the closing path, when moulds with variable
mould height are used on the same machine.
Prior Art
From PATENT ABSTRACTS OF JAPAN, vol. 16, No. 471 (M-1318),1992-09-
30)and JP 04 169216 A is known a mould-closing unit, underlying the preamble
of claim 1 and having a mould height adjustment. This mould height adjustment
is
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-c-
used as usual in connection with a toggle joint as the closing mechanism. On
the
moveable mould carrier, an electromagnetically actuatable fixing device is pro-
vided and on the support element for the toggle joint mechanism a fixing
device is
provided which may be actuated manually to detachably fix the support element.
If when the moveable mould carrier is fixed and the support element detached,
the closing motor driving the toggle joint is actuated, the support element is
dis-
placed into the necessary position for the new mould height, in which the
locking
pressure can be applied with the toggle joint in an expanded position. The
support
element is not fixed in a positive manner, and thus after a plurality of
cycles at
least the precision suffers in the repeated application of the locking
pressure.
Above all however this mould height adjustment has no influence on the opening
path to open the mould, since this is dependent on the movement of the toggle
joint and not on the position of the support element.
Mould-closing units with mould height adjustments are known in which there are
provided on bars, which are mostly fixed to the stationary mould carrier and
serve
to guide the moveable mould carrier, threaded portions which are connected
with
nuts. These nuts are driven via a separate drive to adjust the mould height.
The
nuts have on their outer side a ring gear, such that they can be actuated
either
with a ring gear or with a toothed belt. (US-A 4,281,977; Brochure "Elektra S-
Serie" (p.5) of the company Ferromatic Milacron Maschinenbau GmbH, 79364
Malterdingen). During an injection cycle the support element for the moveable
mould carriers is hold in position by the nuts. Hence, the closing mechanism
moves only the movable mould carrier, whereas the support element is
stationary.
Only when the mould height shall be altered, the support element is moved
along
the guide elements. This is generally the case, when the mould is changed.
For adjusting the mould height and locking a support plate for the closing
mecha-
nism, the company Engel Vertriebs GmbH, A-4311 Schwertberg, Austria has a
known way of providing the bars with grooves and fixing to these grooves two
half-nuts by moving the half-nuts in a radial direction towards one another
until
they come into contact with the grooved region of the guide bars.
Furthermore, from the company Husky Injection Moulding Systems there is a
known way of achieving locking of this kind with a bayonet fastening. For this
pur-
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pose, the bar has regions into which a closing piston can engage, as well as
re-
gions along which the moveable closing piston can slide radially on the guide
bars. By turning the closing piston, a positive-locking effect is caused, such
that at
least a portion of the locking pressure can also be applied to this piston
simulta-
neously.
From DE 24 29 570 B1 is known an injection moulding machine in which two
pressure cylinders are used to close the mould. One pressure cylinder serves
to
displace the moveable mould plate, a further cylinder to apply the locking
pres-
sure. Correspondingly, even during the injection moulding cycles, two plates
are
moved jointly as the moveable mould carrier. A support element which is adjust-
able with an alteration of the mould height is not provided. The fixing device
is
only actuated when the piston of the cylinder has completed its stroke
movement
and in addition now the locking pressure is to be applied via the piston.
From DE 42 43 735 C2 is known a two-plate machine in which, in order to
achieve the mould closure, the moveable mould plate is drawn towards the sta-
tionary mould carrier. The moveable mould carrier is separable from the guide
bars which are necessary during the application of the locking pressure and
can
be locked to same. However once the locking has been accomplished, it is only
the closing cylinder which is responsible for the mould closing movement and
the
application of the locking force. Alteration and thus optimization of the
locking
pressure is thus not possible.
In parallel proceedings, the document DE 30 42 712 C2 was cited, the object of
which is completely different however, since there, on engagement grooves of
the
guide bars, a locking mechanism for the protective bolt is triggered and
locked,
which covers the mould tentering space.
Summary of the invention
Proceeding from this prior art, the object underlying the present invention is
to
create a mould-closing for many uses.
This object is achieved by a mould-closing unit with the features of claim 1.
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Associated with the moveable mould carrier is a fixing device, such that the
moveable mould carrier can be fixed in any way in its current position. If the
lock-
ing of the drive is detached from the bars, the drive can be adjusted with its
re-
spective support relative to the bars, such that~a mould height adjustment
occurs.
Herein is not essential, whether the injection moulding machine is a two-plate-
system, wherein the closing mechanism is arranged on the stationary mould car-
rier, or a three-plate-system, wherein a separate support element is provided
for
the closing device. Since the drive device usually used for a main axis can
now be
used for a subordinate function, an additional drive for the adjustment of the
mould height can be dispensed with. Additional guide elements are not
necessary
since the guide elements which are present anyway, generally the tie bars, can
be
used. Through the use of the mould height adjustment device, however, in each
- cycle the pressure build-up times can be reduced in the order of several
tenths of
seconds.
Thus where higher forces have to be applied constantly, i.e. in the standard
op-
erational state, a positive connection is provided which can be detached as re-
quired to adjust the mould height. In the other region, in which the moveable
mould carrier only has to be fixed for a short time, in order to effect the
adjust-
ment of the mould height, the moveable mould carrier can, on the other hand,
be
fixed on the guide elements or on the machine base merely by a non-positive
connection.
In both cases, but above all in the positive operational connection, collet
chucks
are used to this end. The collet chucks have the advantage, that as a result
of the
secure clamping, clamping free from play between the guide elements and in par-
ticular the support element is guaranteed, since unlike the known threaded ad-
justments, no thread play has to be taken into account. By this means, the
preci-
sion of the whole injection moulding machine can be simultaneously increased
despite the existing mould height adjustment. For safety, the devices are so
con-
structed that the basic function of injection moulding is always adjusted
automati-
cally under the effect of resilient means.
Further advantages will be apparent from the subclaims.
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Short descriation of the figures
Fig. 1 a schematic representation of an injection moulding machine in side
view, in operation
Fig. 2 the injection moulding machine according to Fig. 1 with clamped move-
able mould carrier,
Fig. 3 a representation as per Fig. 1 in operation with adjusted support ele-
meet,
Figs. 4,5 the collet chuck of the clamping device for fixing the spacing a in
the
open and closed position,
Figs. 6,7 the fixing device on the moveable mould carrier in open and clamped
position,
Fig. 8 an embodiment of an injection moulding machine without any bars,
Detailed description of preferred embodiments
The invention will now be explained in greater detail with examples, referring
to
the attached drawings. The examples of embodiment are only examples and do
not limit the inventive concept to a certain physical arrangement.
Fig. 1 shows schematically an injection moulding machine for processing
plastics
materials and other plasticizable masses, which has an injection moulding unit
S
and a mould-closing unit F. The mould-closing unit has a stationary mould
carrier
10, whose position e.g. in relation to the machine base is fixed and in the
present
case is indicated by a fixed bearing. Furthermore, a moveable mould carrier is
provided which in the present case is a constructional unit consisting of the
clamping plate 23, the cylinder 25 with piston rod 26 of drive D and a backing
plate 24. Mould clamping plate and backing plate are braced with one another,
such that a precise unit guided on guide elements 12 is produced which forms
the
moveable mould carrier 11 and has a pre-determined fixed length. The mould
clamping plate 23 of the moveable mould carrier 11 and the stationary mould
car-
rier 10 enclose between themselves the mould teetering space R. In this mould
teetering space, injection moulds M of variable height can be used, as in
particu-
lar Fig. 1 and Fig. 2 make clear. According to the height of the injection
mould M,
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the spacing a between the moveable mould carrier 11 and the stationary mould
carrier 10 is greater or smaller. The height of the mould which determines
this
spacing a is measured in the closing direction s-s.
To move the moveable mould carrier, a drive D is provided which moves the
moveable mould carrier in the closing direction s-s towards the stationary
mould
carrier 10 and away from it again. A part of this drive D is in this
embodiment,
besides the cylinders 25, the piston rod 26. In the present case of a three-
plate-
system (stationary mould carrier, moveable mould carrier, support element) the
piston rod 26 is supported on the support element 21. It is also conceivable
to
dispose the closing mechanism on the stationary mould carrier and thus obtain
a
two-plate system, the device for fixing the spacing a being then allocated as
clamping device 13 to the stationary mould carrier 10. Furthermore, the drive
D,
which is hydraulic here, can also be e.g. electromechanical or pneumatic.
Guide elements 12 configured as tie bars reach through the stationary mould
car-
rier 10 and the moveable mould carrier 11 in Figs. 1 to 3. They serve as a
guide
for the moveable mould carrier 11 during its movement and can, as will be gone
into later, also serve as a guide for the support element 21 during its
movement.
For this purpose, only one portion 12a of the guide element 12 is necessary,
so
that with other guiding of the moveable mould carrier 11 the rest of the guide
ele-
ment can be dispensed with (Fig. 8). The support element 21 is in this embodi-
ment mounted moveable in relation to the machine base in the closing direction
s-
s, and this is indicated by the symbol for the corresponding moveable bearing
arrangement. The guide elements 12 have at least one portion 12a with which
the
clamping device 13 between the stationary mould carrier 10 and moveable mould
carrier 11 comes into operational connection, as soon as the desired spacing a
is
set.
In addition, a fixing device 14 is allocated to the moveable mould carrier 11
which,
on actuation, fixes the moveable mould carrier 11 in its respective position.
This
fixing can be on the guide elements 12, as in the embodiment, however fixing
the
moveable mould carrier to the machine base or to another suitable stationary
lo-
cation is also conceivable. As soon as the moveable mould carrier has been
fixed,
the drive D, which is generally a component of the closing device for moving
the
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moveable mould carrier 11 and for applying the locking pressure, can be
actuated
when the fixing device 14 is actuated and the clamping device 13 is out of
opera-
tional connection, in order to move the support element 21 along its guide,
here
along portions 12a of the guide elements 12, and thus to alter the spacing a
for
the following injection cycles. This is shown by 1=igs. 1 to 3.
In Fig. 1 the clamping device 13 is fixed on the guide elements 12. Simultane-
ously the fixing device 14 is open as the spacing between the clamping jaws
and
the guide elements 12 in Fig. 1 makes clear. In this state, the moveable mould
carrier can be moved along the guide elements by drive D, which produces an
optimization in respect of the spacing a of the small mould M shown in Fig. 1.
In Fig. 2 a larger injection mould M is transferred into the mould tentering
space
R. Here the support element 21 is still in the position of Fig. 1. It becomes
clear
that in this state no satisfactory opening movement can be brought about for
the
injection mould M. Therefore, as indicated by the arrows, the fixing device 14
is
locked, by which means the moveable mould carrier is held secure in its
position.
Then the clamping device 13, which is allocated to each guide element 12, is
un-
locked. If drive D is now actuated, there is no movement of the moveable mould
carrier because it is clamped. Instead, the support element 21 is now moved in
the closing direction s-s, such that a position of the support element as per
Fig. 3
is produced, which position is adapted to the corresponding mould height. In
order
to make an injection moulding process possible again, the support element 21
is
locked with the clamping element 13 and the fixing device 14 is unlocked. Now
the further process of manufacturing injection moulded parts can take place,
adapted to the altered mould height.
To be precise, the spacing a between the stationary mould carrier 10 and the
moveable mould carrier 11 is adjusted by drive D, which in a small injection
mould
with a small mould height, has to cover a larger movement path than in an
injec-
tion mould with a large mould height. However if an unaltered movement path of
the moveable mould carrier 11 is assumed, an alteration of spacing a takes
place,
as a comparison between Figs. 1 and 3 shows. However the spacing between
support element 21 and stationary mould carrier 10 has also changed as has the
distance b of the guide elements 12 projecting beyond the support element. To
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this extent, one could also talk about an adjusting device to adjust the
length b of
the projecting guide elements 12, optimizing the amount of oil with an
unaltered
movement path of drive D.
Naturally, the fixing device 14 has to be arranged only on any part of the
move-
able mould carrier, and it can comprise a single or a plurality of fixing
devices. In
the embodiment they are arranged on the backing plate 24, however they can
also be arranged directly on the mould clamping plate 23. It must just be
ensured
that the movement of the moveable mould carrier can be temporarily prevented
by the fixing device.
Portion 12a of the guide element 12 has an altered cross-section, it being in-
tended that this cross-section alteration should contribute to making possible
a
positive operational connection with the clamping device 13 to fix the spacing
a. A
positive connection free from play is desired at this location, since high
forces
have to be applied during the injection cycle, to which the clamping device 13
must be equal. The cross-sectional alteration can be grooves or, in this
embodi-
ment, a thread 12b. A thread has the advantage that it can be manufactured
very
precisely as a result of continuous manufacturing in thread cutting. The
fixing de-
vice 14 on the other hand is fixed in a non-positive manner, since this device
is
open during the injection cycle and only low forces are applied during the
secon-
dary function of the adjustment of the mould height. In this respect the non-
positive connection is adequate for this purpose.
Figs. 4 and 5 show preferred embodiments of the clamping device 13 to fix spac-
ing a free from play. As clamping device 13, an actuating element 15 for a
first
collet chuck 38 is provided which element is disposed coaxially to the guide
ele-
ments 12 in the region of portion 12a. The collet chuck has a threaded bush 16
which enters positive operational connection with the thread 12b of portion
12a
when the collet chuck is actuated. The clamping device 13 is so constructed
that it
automatically remains in the locked position under the force of a resilient
means
22 held on pins 37. Unlocking to adjust the mould height or to adjust spacing
a
takes place under the effect of a hydraulic medium. This hydraulic medium is
led
via the hydraulic connection 29 into the annular hydraulic chamber 27. As a
com-
parison between Fig. 4 and Fig. 5 shows, the application of this hydraulic
medium
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leads to an axial movement of the annular piston 17 against the force of the
resil-
ient means 22. During this movement, the conical portion 17a of the annular
pis-
ton 17 moves out of engagement and the conical region 16a of the collet chuck
38
moves into engagement. Consequently, the threaded bush 16 is expanded by the
cone ring 31 and a relative movement between support element 21 and guide
element 12 is rendered possible. If the hydraulic pressure in the hydraulic
cham-
ber 27 is reduced, as a result of the resilient means 22 mounted in recess 21
a of
the support element 21, resetting of the annular piston 17 into a position as
per
Fig. 5 comes about. In this movement, the cone ring 31 connected via fastening
means 32 to the annular piston 17 is also moved axially with said piston. On
the
other hand, the movement of the (double) annular piston 17 is ended by the
coni-
cal region 16b and the conical portion 17a coming together. The hydraulic cham-
ber 27 is also limited in an axial direction by a closing element 33.
Figs. 6 and 7 show the fixing device 14. This fixing device 14 has a second
collet
chuck 19, which is disposed in the embodiment coaxially to a guide element 12
and is fixed on the moveable mould carrier 11, or more precisely on the
backing
plate 24 in a recess 24a. The fixing device has a housing 36 which encloses a
hydraulic chamber 28 radially towards the outside, to which chamber hydraulic
medium can be applied via a hydraulic connection 30. The second collet chuck
19
has a conical region 19a which causes the clamping with a conical portion 18a
of
the hydraulically actuated annular piston 18. The return into the non-clamped
po-
sition takes place under the effect of an additional resilient means 20. As a
com-
parison between Figs. 6 and 7 shows, the movement of the annular piston is lim-
ited on the one hand by a stop on the housing 36 and on the other hand by the
conical portion 18a and conical region 19a coming into contact with one
another.
The elastic means 20 is mounted in a closing element 34 which is connected to
the housing 36 via securing means 35.
Fig. 8 shows a further embodiment in which the piston rod 26 of drive D serves
as
the guide element, and comes into positive operational connection with the
clamping device 13 via a portion 26a which in this respect can be equated with
the previously-mentioned portion 12a.
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Fig. 8 also shows that use of clamping device 13 and fixing device 14 is also
pos-
sible on a machine without bars, in which instead of tie bars, a force
transmission
element 40 guides the forces occurring during injection moulding around the
mould tentering space R to achieve better accessibility. This force
transmission
element, possibly also multipart, is hinged on' one hand to the stationary
mould
carrier 10. On the other hand, drive D is supported on its opposite end 42
associ-
ated with the moveable mould carrier 11. Here the clamping device 13 can be
provided which co-operates with portion 26a. If the clamping device 13 is open
and the fixing device 14 engaging on the guide element 41 is locked, the drive
D
can displace portion 26a of the piston rod 26 relative to the clamping device.
Thus
altered movement paths of the moveable mould carrier are produced for subse-
quent injection cycles.
