U.S. patent application number 11/060218 was filed with the patent office on 2005-10-20 for method and device for producing a composite component.
Invention is credited to Borst, Peter, Dettinger, Juergen, Kuttler, Werner.
Application Number | 20050232803 11/060218 |
Document ID | / |
Family ID | 34684102 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050232803 |
Kind Code |
A1 |
Kuttler, Werner ; et
al. |
October 20, 2005 |
Method and device for producing a composite component
Abstract
A method for producing a sintered material/plastic composite
component is described. The method includes: (a) placing a sintered
material component in an injection-molding device which has a lower
die, an upper die and at least one slide; (b) elastically pressing
the slide against the placed-in sintered material component; (c)
moving the lower die and upper die together, the elastically
pressed slide being clamped in between in order to fix the position
of the slide, and a mold cavity being formed, in which the sintered
material component is arranged, and (d) injecting plastic into the
mold cavity, so that the sintered material/plastic composite
component is formed.
Inventors: |
Kuttler, Werner;
(Moessingen, DE) ; Borst, Peter; (Unlingen,
DE) ; Dettinger, Juergen; (Unterensingen,
DE) |
Correspondence
Address: |
DECHERT LLP
P.O. BOX 10004
PALO ALTO
CA
94303
US
|
Family ID: |
34684102 |
Appl. No.: |
11/060218 |
Filed: |
February 16, 2005 |
Current U.S.
Class: |
419/9 |
Current CPC
Class: |
B29C 45/332 20130101;
B29C 45/14639 20130101; B29C 2045/14098 20130101; B29C 45/14778
20130101; B29C 45/14836 20130101; B29C 45/14065 20130101; B29C
33/123 20130101; B29K 2705/00 20130101 |
Class at
Publication: |
419/009 |
International
Class: |
B22F 007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2004 |
DE |
10 2004 008 450.5 |
Claims
What is claimed is:
1. A method for producing a sintered material/plastic composite
component, comprising: (a) placing a sintered material component in
an injection-molding device which has a lower die, an upper die and
at least one slide, (b) elastically pressing the slide against the
placed-in sintered material component, (c) moving the lower die and
upper die together, the elastically pressed slide being clamped in
between in order to fix the position of the slide, and a mold
cavity being formed, in which the sintered material component is
arranged, and (d) injecting plastic into the mold cavity, so that
the sintered material/plastic composite component is formed.
2. The method as claimed in claim 1, the slide being guided during
the elastic pressing operation by a control surface until contact
is made with the sintered material component or shortly before, so
that the slide is brought up to the placed-in sintered material
component at low speed.
3. The method as claimed in claim 2, the slow approach of the slide
taking place simultaneously with the moving together of the lower
die and the upper die.
4. The method as claimed in claim 1, the slide being kept latched
in a retracted position before the sintered material component is
placed in.
5. The method as claimed in claim 1, the slide being pressed by the
upper die or the lower die against a mating portion of the other
die.
6. The method as claimed in claim 5, the mating portion being
formed by an insert which is fixed on the die concerned and is made
of a more elastic material than the material of the upper die or
the lower die.
7. The method as claimed in claim 5, the material pairing of the
mating portion and the slide being chosen such that high static
friction is achieved.
8. The method as claimed in claim 5, the mating portion being
inclined in the direction of the mold cavity at an angle of less
than 10.degree., in particular less than 7.degree., and the slide
being formed with a corresponding slope on its corresponding
contact surface.
9. The method as claimed in claim 1, the slide being displaceably
mounted on one of the two dies.
10. The method as claimed in claim 1, the slide having a clearance
through which a control pin can be led.
11. The method as claimed in claim 10, a relative movement between
the control pin and the slide taking place in dependence on the
relative movement between the upper die and the lower die.
12. The method as claimed in claim 10, the control pin being
elastically prestressed and displaced against the prestressing
direction by a push rod during the moving together of the dies.
13. The method as claimed in claim 10, the slide being kept in a
retracted position by a latching engagement of the control pin on
one edge of the clearance.
14. The method as claimed in claim 10, the speed of the inward
movement of the slide in the direction of the mold cavity being set
up by a control surface of the control pin.
15. The method as claimed in claim 1, the mold cavity for forming
the sintered material/plastic composite component being defined in
the lateral direction by a plurality of slides which are all
elastically prestressed in the direction of the mold cavity.
16. A device for producing a sintered material/plastic composite
component, comprising a lower die, an upper die and at least one
slide, which together define a mold cavity for placing in a
sintered material component, wherein the device is an
injection-molding device, the slide being elastically prestressed
in the direction of the mold cavity and mounted with respect to the
lower die and the upper die in such a way that the position of the
slide can be fixed such that it lies against the sintered material
component by pressing the dies together.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to methods and systems for
producing a sintered material/plastic composite component. More
particularly, the present invention relates to producing such a
composite component using a system having a lower die, an upper die
and at least one slide, which together define a mold cavity for
placing in a sintered material component.
BACKGROUND OF THE INVENTION
[0002] A sintered material/plastic composite component (hereafter
"composite component") refers to a workpiece in which a sintered
material component is made to bond with a plastic molding compound,
which is subsequently attached to the sintered material component
with interlocking and frictional engagement (after the curing of
the plastic). It is at the same time intended to be possible also
to include one or more further components of any other material in
this process, so that the further component is also incorporated in
the composite of the sintered material component and plastic with
interlocking and frictional engagement. A sintered material
component includes at least one of sintered metal component; a
sintered ceramic component or the like.
[0003] A typical method for producing a composite component
comprises bonding the plastic with the sintered material component
(and possibly one or more further components) in a pressureless
manner as part of a casting process. Pressureless casting has an
advantage that, in spite of the brittleness of the sintered
material component, a composite component can be produced without
running the risk of the sintered material component being destroyed
thereby.
[0004] However, such a pressureless casting process has a
disadvantage that it is comparatively slow and does not represent
great process reliability. Furthermore, the chance of cavities not
being completely filled (formation of voids) is not ruled out.
[0005] Therefore, the injection-molding method is generally
preferred in mass production. However, this method has not so far
been used in connection with sintered material components because
the pressure prevailing during the injection molding has the
tendency to destroy the sintered material component.
[0006] If the injection-molding method is applied, a composite
component is therefore generally produced by a combination of a
non-sintered compact steel component and plastic (and possibly one
or more further components).
[0007] For example, it is known for the production of injection
valves for modern diesel engines to produce a composite component
on the basis of this method.
[0008] This involves initially producing a magnetic pot from a
compact steel with high precision. A grinding step and an eroding
step are among the steps thereby performed. On account of the
generally inferior magnetic properties of compact steel, it may
therefore be necessary to provide complex incisions to improve the
magnetic properties of the magnetic pot.
[0009] Also produced is a coil component, in which a coil is wound
around a plastic coil former, two terminal pins being cast,
injection molded or inserted into the coil former with interlocking
engagement. The terminal pins are then electrically connected to
ends of the wound coil.
[0010] This coil component is inserted into an annular opening of
the magnetic pot, the terminal pins being led through bushings, so
that they protrude from the opposite side.
[0011] Subsequently, this arrangement is inserted into an injection
mold and the remaining cavities between the coil component and the
magnetic pot are filled with injected plastic in order to enclose
the coil component captively in the magnetic pot. Subsequently,
finishing (flash removal, possibly grinding, etc.) may also be
performed if need be.
[0012] A compact steel/plastic composite component of this type can
be used as a stator for a solenoid valve which is, for example,
part of a unit-injector system for modern diesel engines. In this
case, a solenoid valve needle is led through a central clearance in
the magnetic pot and can be adjusted in the axial direction when
current is supplied to the coil component.
[0013] The magnetic pot made of compact steel is comparatively
expensive to produce.
SUMMARY OF THE INVENTION
[0014] It is accordingly the object of the present invention to
provide methods and systems for producing a composite component
with which the composite component can be produced at lower
cost.
[0015] This object is achieved by a method for producing a sintered
material/plastic composite component. The method includes: (a)
placing a sintered material component in an injection-molding
device which has a lower die, an upper die and at least one slide;
(b) elastically pressing the slide against the placed-in sintered
material component; (d) moving the lower die and upper die
together, the elastically pressed slide being clamped in between in
order to fix the position of the slide, and a mold cavity being
formed, in which the sintered material component is arranged; and
(e) injecting plastic into the mold cavity, so that the sintered
material/plastic composite component is formed.
[0016] The above object is also achieved by the device mentioned at
the beginning for producing a sintered material/plastic composite
component, the device being an injection-molding device and the
slide being elastically prestressed in the direction of the mold
cavity and mounted with respect to the lower die and the upper die
in such a way that the position of the slide can be fixed such that
it lies against the sintered material component by pressing the
dies together.
[0017] With the method according to the invention or the
injection-molding device according to the invention it is possible
to produce a composite component at low cost.
[0018] On the one hand, a sintered material component is less
expensive than a compact steel component, which only obtains the
correct shaping by means of complex working steps. Furthermore, a
sintered material component generally has much better magnetic
properties than a compact steel component, so that composite
components with favorable magnetic properties can be produced.
[0019] The measure of elastically pressing the slide against the
sintered material component placed into the mold cavity achieves
the effect of compensating in each case for the relatively great
tolerances of sintered material components. The position of the
slide optimally lying directly against the sintered material
component is subsequently fixed by moving the lower die and the
upper die together. Only after that is the actual injection-molding
operation carried out.
[0020] The fact that the slide lies directly against the sintered
material component and is fixed in this position by the upper die
and the lower die means that, in spite of the comparatively high
injection-molding pressure, there is no risk of the sintered
material component being damaged in this process.
[0021] This is so because it has been found that previous attempts
to produce a sintered material/plastic composite component failed
for the following reasons. Until now, injection-molding devices
have been constructed in such a way that, for the lateral
delimitation of the mold cavity, a slide is displaced into a fixed
position, defined by a stop, to form the mold cavity. On account of
the comparatively great tolerances of sintered material components,
there is the risk of the mold cavity formed in this way either
being too small (the sintered material component is then damaged by
the slide), or too large (the sintered material component is then
destroyed by the pressure of the injected plastic molding
compound).
[0022] The measure of elastically "docking" the slide such that it
lies directly against the sintered material component achieves the
effect of compensating for these tolerance problems. The risk of
the sintered material component being destroyed is avoided.
[0023] The object is accordingly achieved completely.
[0024] It goes without saying that, whenever a sintered material
component is referred to in the present context, either a sintered
material component on its own or (as in the aforementioned example
of the solenoid valve) an arrangement comprising a sintered
material component and a further component is to be understood.
[0025] It is of particular benefit in the case of the method
according to the invention if, during the elastic pressing
operation, the slide is guided by a control surface until contact
is made with the sintered material component or shortly before, so
that the slide is brought up to the placed-in sintered material
component at low speed.
[0026] This measure avoids the slide colliding at excessive speed
with the placed-in sintered material component on account of the
elastic prestressing. As a result, damage to the sintered material
component is avoided in this phase of the method according to the
invention.
[0027] It is at the same time of particular benefit if the slow
approach of the slide takes place simultaneously with the moving
together of the lower die and the upper die.
[0028] As a result, the process can be carried out in an optimized
way in terms of timing. It is also possible to mechanically couple
the approach of the slide and the moving together of the dies.
[0029] According to a further preferred embodiment, the slide is
kept latched in a retracted position before the sintered material
component is placed in.
[0030] This sets up a defined position of the slide, in which the
slide is at an adequate distance from the mold cavity to place in
the sintered material component.
[0031] It is also preferred if the slide is pressed by the upper
die or the lower die against a portion of the other die.
[0032] This brings about direct fixing of the slide between the
lower die and the upper die. The slide can consequently be securely
kept in the position in which it is lying against the sintered
material component.
[0033] At the same time, it is of particular benefit if the mating
portion of the other die is formed by an insert which is fixed on
the die concerned and is made of a more elastic material than the
material of the upper die or the lower die.
[0034] While the dies are generally produced from a high strength
steel alloy, the insert is produced from a somewhat more elastic
material. However, the insert also generally consists of a metal,
for example a steel alloy with a hardness or elasticity which is
comparable to that of copper. This achieves the effect that no
excessive stresses, which may for example lead to bearing damage or
the like, occur during the pressing together of the upper die and
the lower die and the accompanying fixing of the slide.
[0035] According to a further preferred embodiment, the material
pairing of the mating portion and the slide is chosen such that
high static friction is achieved.
[0036] Accordingly, secure positional fixing of the elastically
pressed slide can be achieved even with a comparatively low contact
pressure of the lower or upper die.
[0037] Furthermore, it is advantageous if the mating portion is
inclined in the direction of the mold cavity at an angle of less
than 10.degree., in particular less than 7.degree., and if the
slide is formed with a corresponding slope on its corresponding
contact surface.
[0038] This measure achieves the effect that a kind of self-locking
occurs between the mating portion and the contact surface of the
slide as soon as the slide is pressed between the upper die and the
lower die even with a comparatively small force. Even when very
high injection-molding pressures occur in the interior of the mold
cavity (greater than 1000 bar), it can be reliably ensured in this
way that the slide is fixed in its position.
[0039] Such a high operating pressure in the injection-molding
method is required in the case of parts that are subjected to
particularly high loading, in order to set up a reliable
process.
[0040] Furthermore, it is advantageous if the slide is displaceably
mounted on one of the two dies.
[0041] In this case it is possible to dispense with mounting it
independently of the upper die and the lower die, which would
generally lead to a much more complex construction. It is
particularly preferred at the same time if the slide is
displaceably mounted on the die, which for its part is formed in
such a way that it is movable with respect to the other die.
[0042] As a result, the mold cavity is largely exposed when the
dies are open, so that automated placement of the sintered material
component is possible in a simple way.
[0043] It is of particular benefit furthermore if the slide has a
clearance through which a control pin can be led.
[0044] This measure makes it possible for the slide to be kept in a
retracted position by the control pin when the dies are open.
[0045] It is of particular benefit in this case if a relative
movement between the control pin and the slide takes place in
dependence on the relative movement between the upper die and the
lower die.
[0046] This makes it possible for the relative movements to overlap
in terms of timing. In this way, short cycle times can be
achieved.
[0047] Furthermore, it is advantageous if the control pin is
elastically prestressed and is displaced against the prestressing
direction by a push rod during the moving together of the dies.
[0048] The push rod may be provided for example on the die on which
the slide is not mounted. When the dies are moved together, the
push rod keeps the control pin almost fixed as it were while the
dies move toward each other. As a result, at the same time a
relative movement between the control pin and the slide is set
up.
[0049] According to a further preferred embodiment, the slide is
kept in a retracted position by a latching engagement of the
control pin on one edge of the clearance.
[0050] The latching engagement is in this case designed in such a
way that it cannot be released either during the elastic
prestressing of the slide or by the prestressing of the control
pin.
[0051] The release of the latching connection may take place for
example by the push rod mentioned above.
[0052] Furthermore, it is advantageous if the speed of the inward
movement of the slide in the direction of the mold cavity is set up
by a control surface of the control pin.
[0053] To be more precise, the speed setting takes place by the
interaction between the surfaces of the control pin on the one hand
and of the slide (or a clearance of the slide) on the other
hand.
[0054] This measure makes it possible to avoid the slide advancing
too quickly in the direction of the mold cavity when the latching
is released, on account of the elastic prestressing, which could
have the consequence of destroying the sintered material component
or jamming the injection-molding device.
[0055] Overall, it is also advantageous if the mold cavity for
forming the sintered material/plastic composite component is
defined in the lateral direction by a plurality of slides which are
all elastically prestressed in the direction of the mold
cavity.
[0056] This makes it possible to create a largely freely definable
mold cavity in the direction of the direction of movement of the
slides. Furthermore, a greater number of slides makes it possible
to avoid stress peaks or notch stresses occurring in the region
between the contact surface between the respective slide and the
sintered material component.
[0057] It goes without saying that the features mentioned above and
still to be explained below can be used not only in the combination
respectively specified but also in other combinations or on their
own without departing from the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWING
[0058] Exemplary embodiments of the invention are explained in more
detail in the description which follows and are represented in the
drawing, in which:
[0059] FIG. 1 shows a schematic plan view of an injection-molding
device, according to one embodiment of the present invention for
carrying out the method, according to one embodiment of the present
invention;
[0060] FIG. 2 shows a schematic side view of the injection-molding
device of FIG. 1;
[0061] FIG. 3 shows a cross-sectional view of a sintered material
component in the form of a magnetic pot for a solenoid valve;
[0062] FIG. 4 shows a cross-sectional view of a coil component for
the solenoid valve, the coil component being insertable into an
annular clearance of the magnetic pot of FIG. 3;
[0063] FIG. 5 shows a schematic sectional view of an
injection-molding device, according to one embodiment of the
invention for carrying out the production method, according to one
embodiment of the invention;
[0064] FIG. 6 shows a plan view of the slide arrangement of the
injection-molding device of FIG. 5;
[0065] FIG. 7 shows a representation of a slide and an assigned
control pin of the injection-molding device of FIGS. 5 and 6 in a
state before the lower die and the upper die are moved together;
and
[0066] FIG. 8 shows a view comparable to FIG. 7 at a later point in
time during the moving together of the dies.
DETAILED DESCRIPTION OF THE INVENTION
[0067] In FIGS. 1 and 2, a first embodiment of the
injection-molding device according to the invention is designated
generally by 10.
[0068] The injection-molding device 10 has a lower die 12 and an
upper die 14. In the case of this embodiment, the lower die 12 is
immovably formed and is for example firmly anchored to the
floor.
[0069] The upper die 14 is mounted movably in the vertical
direction in relation to the lower die 12.
[0070] The injection-molding device 10 also has a slide 16 movably
mounted in the horizontal direction.
[0071] The lower die 12, the upper die 14 and the slide 16 together
form a mold cavity 20, which in the present exemplary embodiment is
approximately cylindrically formed.
[0072] As FIG. 1 in particular reveals, in this case the lateral
surface of the cylinder is partly formed by the lower die 12. A
further part of the lateral surface of the cylindrical mold cavity
20 is formed by a front region of the slide 16.
[0073] The injection-molding device 10 serves for producing a
sintered material/plastic composite component (hereafter "composite
component" for short). A composite component of this type is to be
understood as meaning a component which is created by making a
sintered material component bond with plastic with interlocking
and/or frictional engagement. In the present case, the plastic is
bonded with the sintered material component by means of the
injection-molding method. Furthermore, the composite component may
have a further component, which is bonded with the sintered
material component or the plastic with interlocking and/or
frictional engagement by means of the injection-molding method. The
additional component may itself in turn be a composite
component.
[0074] The slide 16 is elastically prestressed in the horizontal
direction, in the direction of the mold cavity 20, by means of a
spring 24 (or some other elastic device).
[0075] This elastic prestressing causes the slide 16 to place
itself against a sintered material component 22 placed into the
cavity 20, to be precise with a specific pressing force 26. The
pressing force 26 is to be chosen such that the slide 16 is pressed
against the sintered material component 22, so that a compensation
for tolerance takes place. On the other hand, the pressing force 26
is to be chosen such that the relatively brittle sintered material
component 22 is not destroyed.
[0076] As soon as the slide 16 is pressed elastically against the
sintered material component 22 placed into the mold cavity 20, the
upper die 14 is lowered onto the lower die 12. As a result, the
mold cavity 20 is also closed off in the upward direction. On the
other hand, the slide 16 is clamped in between the lower die 12 and
the upper die 14 and in this way is fixed in its position.
[0077] In this case, the upper die 14 exerts a specific pressing
force 28 on the slide 16. The pressing force 28 is adequate to
avoid the slide 16 being displaced into the mold cavity 20 on
account of the injection-molding pressure during the injection of
the plastic.
[0078] This ensures that the slide 16 "supports" the sintered
material component 22 during the actual injection-molding
operation. This avoids deformations of the sintered material
component 22, which could lead to rupture on account of the brittle
material properties.
[0079] It should be noted that the pressure in the interior of the
mold cavity 20 during the injection-molding operation may lie in
the range of 1000 bar or more. The pressing force 28 must
accordingly be significant, in order to ensure that the slide 16
does not change its position on account of this operating pressure.
This can be backed up by measures such as suitable selection of the
material pairings, by surface treatment at the contact points
between the dies 12, 14 and the slide 16, etc.
[0080] In the case of the embodiment of FIGS. 1 and 2, the slide 16
is mounted on the upper die 14 and its spring 24 is supported on
the upper die 14. It goes without saying, however, that the slide
16 could generally also be mounted and supported on the lower die
12. It is also generally possible to provide means for the mounting
and supporting of the slide 16 that are independent both of the
lower die 12 and of the upper die 14.
[0081] In FIG. 2 it can also be seen that the sintered material
component 22 has an inner clearance, into which plastic is injected
during the injection-molding process. Accordingly, the
injection-molding operating pressure acts in the radial direction
(horizontally) outward. Consequently, the slide 16 serves for
directly supporting the sintered material component 22 in the
radial direction. It is generally also conceivable, however, for a
slide 16 to act radially inward on a sintered material component,
in order to support an operating pressure which acts radially
outward on the sintered material component 22.
[0082] Represented in FIGS. 3 and 4 are the component parts of a
sintered material/plastic composite component which is preferably
produced by the method according to the invention or the
injection-molding device 10 according to the invention.
[0083] The composite component has on the one hand a sintered
material component 22', which is represented in FIG. 3. The
sintered material component 22' is formed as a magnetic pot 30 for
the stator of a solenoid valve. The magnetic pot 30 is generally
cylindrically formed and has a central clearance 32 passing through
it. The clearance 32 is designed for receiving an actuator (for
example a valve needle) of the solenoid valve.
[0084] The sintered material component 22' also has an annular
clearance 34, which is aligned concentrically in relation to the
central clearance 32. The annular clearance does not extend over
the entire axial length of the magnetic pot 30.
[0085] Also provided in the magnetic pot 30 are two bushings 35,
which extend from the bottom of the annular recess 34 to the
opposite extreme end of the magnetic pot 30. Of the two bushings
35, only one is represented in FIG. 3.
[0086] FIG. 4 shows an electrical coil element 36. The coil element
36 has an approximately annular plastic body 38, around which a
coil 40 is wound. Furthermore, the coil element 36 has two contact
pins 42 (only one of which is represented in FIG. 4). The contact
pins 42 extend from the plastic body 38 downward in the axial
direction and are electrically connected to opposite ends of the
coil 40.
[0087] It is evident from joint consideration of FIGS. 3 and 4 that
the coil element 36 can be inserted into the annular clearance 34,
the contact pins 42 being led through the bushings 35, so that the
contact pins 42 protrude with respect to the assigned extreme end
of the magnetic pot 30.
[0088] In order to fasten the coil element 36 securely and
captively on the magnetic pot 30, the coil element 36 is
injection-molded in the magnetic pot 30 by means of the method
according to the invention.
[0089] In other words, the arrangement comprising the magnetic pot
30 (sintered material component 22') and the coil element 36
inserted in it is inserted into the mold cavity 20 of an
injection-molding device according to the invention (for example
according to FIGS. 1 and 2). Subsequently, a slide 16 is
elastically pressed against the magnetic pot 30 from the outside.
The position of the slide 16 is fixed in this state, in that the
dies 12, 14 are moved toward each other. This is followed by the
actual injection-molding operation, in which cavities between the
coil body 36 and the magnetic pot 30 are completely filled under
pressure. Furthermore, it is also possible thereby for attachments
or the like to be formed on, which protrude with respect to the
magnetic pot 30 and for example support the contact pins 42 to
prevent them from being bent away.
[0090] The composite component produced in this way then serves as
a stator for a solenoid valve. In this case, the coil arrangement
36 is fixed on the magnetic pot 30 in an operationally secure
manner for a long service life (even if there are great
vibrations).
[0091] In FIGS. 5 and 6, a further embodiment of an
injection-molding device according to the invention is designated
generally by 50.
[0092] The injection-molding device 50 is constructed in principle
in a way similar to the injection-molding device 10 of FIGS. 1 and
2 and operates on the same functional principles. Fundamentally the
same injection-molding method is also applied. Accordingly,
elements corresponding to one another are provided with the same
reference numerals or reference numerals corresponding to one
another. Hereafter, only the differences between the two
injection-molding devices 10, 50 are discussed. The description of
the injection-molding device 10 is intended also to apply in
addition to the injection-molding device 50.
[0093] The injection-molding device 50 has a static lower die 12
and, vertically movable with respect to it, an upper die 14. The
upper die 14 is movable in relation to the lower die 12 along
guiding axes, which are schematically designated in FIG. 5 by
52.
[0094] As can be seen in particular in FIG. 6, the
injection-molding device 50 has four slides 16A, 16B, 16C and 16D,
which in plan view are arranged in the form of a cross. The slides
16A to 16D delimit the lateral cylinder surface of a generally
cylindrically formed mold cavity 20'. A sintered material component
(for example the magnetic pot 30 with the inserted coil element 36)
placed into the mold cavity 20' is accordingly delimited in the
radial direction on all sides by the four slides 16A to 16D.
[0095] The four slides 16A to 16D are mounted movably in the
horizontal direction on the upper die 14. Furthermore, the four
slides 16A to 16D are in each case elastically prestressed by a
spring 24A to 24D on the upper die 14.
[0096] The slides 16A to 16D also have in each case a clearance 54
passing vertically through them.
[0097] Fastened on the lower die 12 are push rods 56, which
protrude upward with respect to a surface on which the slides 16
rest when the mold cavity 20' is closed. This state is represented
in FIG. 5.
[0098] The push rods 56 pass through the clearances 54 and extend
to slightly above an upper side of the respective slides 16. In the
horizontal direction, however, the push rods 56 do not touch the
slides 16. Accordingly, it is ensured in the state shown in FIG. 5
that the slides 16 are unhindered by the push rods 56 as they are
pressed by their springs 24 elastically against a placed-in
sintered material component 22.
[0099] Aligned with the push rods 56 in the horizontal direction,
control pins 58A to 58D are mounted on the upper die 14 (only the
control pins 58A and 58B are represented in FIG. 5). The control
pins 58 are prestressed in the vertical direction by means of
suitable springs 60A to 60D in the direction of the lower die 12.
The control pins 58 are in this case mounted displaceably with
respect to the upper die 14 in vertical guides of the upper die 14.
The prestressing of the springs 60 has the effect that the control
pins 58 rest on the push rods 56. However, in the injection-molding
position represented in FIG. 5, the control pins 58 are not
touching the slides 16.
[0100] In the injection-molding position represented in FIG. 5,
furthermore, it is ensured by a pressing force (not represented) of
the upper die 14 with respect to the lower die 12 that the slides
16A to 16D are fixed in their position, to be precise in the
position in which they have been elastically pressed against a
sintered material component 22 before their position is fixed.
[0101] In the injection-molding position represented in FIG. 5, an
injection-molding operation in which plastic is injected into the
mold cavity 20' via a runner (not represented) in the
injection-molding method can accordingly take place. The operating
pressure thereby occurring is supported via the outer wall of the
sintered material component 22 on the positionally fixed slides 16A
to 16D in the radial (horizontal) direction.
[0102] In FIGS. 7 and 8, it is additionally shown how the slides 16
interact with the control pins 58 when the injection-molding device
30 is transferred from an opened state into a closed state. The
operation of only one slide 16 is described hereafter, although the
operation described takes place at the same time for all four
slides 16A to 16D.
[0103] In the opened state of the injection-molding device 50, that
is when the upper die 14 is lifted off from the lower die 12, the
control pin 58 has penetrated into the clearance 54 of the slide
16.
[0104] A beveled control surface 62 is provided on the radially
outer surface of the clearance 54. The control surface ends in a
control edge 64 lying in the vertically mid-way region of the
clearance 54. The clearance 54 is offset underneath the control
edge 64.
[0105] On the side facing the control surface 62, the control pin
58 is provided with a correspondingly beveled control surface 66. A
clearance is formed in the control surface 66, so that a detent 68
is formed. In this state represented in FIG. 7, the detent 68
engages behind the control edge 64 of the slide 16. The slide 16 is
accordingly latched in a set-back position. The slide 16 is
accordingly anchored on the upper die 14 in a retracted position.
The retracted position is offset by a distance A radially or in the
horizontal direction with respect to the injection-molding position
as it is shown in FIG. 5.
[0106] The upper die 14 can be lifted off to the extent that the
end edge of the control pin 58 comes away from the oppositely lying
end edge of the push rod 56. The upper die 14 is lowered onto the
lower die 12, as is represented by an arrow 78. When this happens,
at a certain point in time the control pin 58 strikes the push rod
56 (cf. FIG. 7). As it travels further in the direction 78, the
latching of the detent 68 and the control edge 64 is released by
means of the push rod 56. On account of the spring 60, however, the
control pin 58 is generally in contact with the push rod 56. As the
lowering continues, the control pin 58 is forced more and more out
of the clearance 54. At the same time, the spring 24 presses the
slide 16 radially inward (pressing force 26 in FIG. 8). As a
result, the control surfaces 62 and 66 come into contact against
each other. On account of the beveling, the slide 16 is thereby
gradually moved radially (horizontally) inward toward the mold
cavity 20'. As soon as the push rod 56 has forced the control pin
58 completely out of the clearance 54, the slide 16 comes away from
the control pin 58 and is pressed by the pressing force 26 alone
onto a sintered material component 22 placed into the mold cavity
20.
[0107] When the injection-molding device 50 is opened (arrow 76 in
FIG. 5), the relative movement of the control pin 58 and the slide
16 takes place in the reverse sequence. On account of the pressing
force of the spring 60, the control pin 58 is pressed into the
clearance 54 and, on account of the contact of the control surface
66 against the control surface 62, moves the slide 16 radially
outward, until finally the latching of the detent 68 and the
control edge 64 is achieved.
[0108] In FIG. 5 it is also shown that an insert of another
material, which is provided generally with the reference numeral
70, is in each case inserted in the lower die 12 underneath the
respective slides 16A to 16D. The insert 70 is produced from a
material (for example metal) which is formed such that it is more
elastic than the material of the dies 12, 14. This achieves the
effect that the slides 16 are pressed together with a certain
elasticity during the pressing together of the upper die 14 on the
lower die 12. This avoids excessive stresses. The material of the
insert 70 may have, for example, an elasticity similar to
copper.
[0109] Also provided in the upper die 14 is a central insert 72,
which delimits the mold cavity 22' from the upper side. For similar
reasons, the central insert 72 may be produced from a material
other than that of the dies 12, 14.
[0110] In FIG. 5 it is also shown that an ejector 74 can be led
through the upper die 14 in order to press the formed composite
component onto the lower die 12 and hold it on the latter while the
upper mold 14 is raised after an injection-molding operation.
* * * * *