CH622985A5

CH622985A5 - Cold-runner mould for processing thermosets

Info

Publication number: CH622985A5
Application number: CH1104477A
Authority: CH
Inventors: Hat Auf Nennung Verzichtet Erfinder
Original assignee: Bucher Guyer Ag Masch
Priority date: 1977-09-09
Filing date: 1977-09-09
Publication date: 1981-05-15

Abstract

The two mould halves (1, 2) heated to curing temperature bear against one another at the mould parting plane in the closed position. In the fixed mould half (1) a manifold insert (4) is provided which has a central feed channel (5) and manifold channels (6) which radiate away from the feed channel (5). The manifold insert (4) is held at a temperature lower than the curing temperature, so that the moulding compound in the channels (5, 6) does not cure. The movable mould half (2) possesses recesses (13) which are open towards the mould parting plane (3). Said recesses form passages to the mould cavities (14). These passages and the manifold channels (6) have sections (19) overlapping in the mould parting plane (3). The passages are provided with constricted openings (15) to the mould cavities (14). The workpieces (18) can be removed from the movable mould half (2), and the sprues in the passages (13) can be removed, by means of ejectors (16, 17). Since the passages (13) lie in the mould parting plane (3) and these passages (13) have narrow openings (15) to the mould cavities, the sprues can be easily removed. <IMAGE>

Description

       

  
 



   Im Bereiche der Verbindung der Verteilerkanäle mit den Durchlässen weisen vorzugsweise letztere einen gegenüber dem Querschnitt der ersteren verengten Querschnitt auf, wobei das Ablösen der erstarrten Angüsse von der fliessfähigen Formmasse in den Kaltkanälen erleichtert und das Austreten der Formmasse aus der beim Öffnen der Form freiwerdenden Mündung dieser Kanäle vermindert wird. So kommt es auch beim Schliessen der Form nicht dazu, dass fliessfähige Formmasse zwischen den  



     Formhälften    eingequetscht wird. Das Gesagte trifft im vermehrten Masse zu, wenn die Verteilerkanäle einen sich längs der Formtrennebene zu den Durchlässen erstreckenden Endabschnitt aufweisen. Dabei kann vorzugsweise der Verteilereinsatz einen über die Formtrennebene vorstehenden Endteil aufweisen, welcher in eine Ausnehmung der beweglichen Formhälfte eingreift und welcher die Verteilerkanäle zumindest teilweise aufnimmt, wobei die bewegliche   Formhälfte    und der Endteil miteinander zusammenwirkende Dichtungsflächen aufweisen. Diese   Dich-    tungsflächen können konisch oder pyramidenförmig ausgebildet sein, so dass das Austreten der Formmasse beim Übergang von den Verteilerkanälen in die Durchlässe auf alle Fälle vermieden wird.



   Weitere Besonderheiten und Vorteile der vorliegenden Erfindung ergeben sich aus der nachfolgenden Beschreibung, in welcher anhand der Zeichnung ein Ausführungsbeispiel des Erfindungsgegenstandes näher erläutert wird. Die Zeichnung zeigt in einem senkrecht zur Formtrennebene gelegten Schnitt einen Teil eines Kaltkanalwerkzeuges. Das dargestellte Werkzeug besitzt die Formhälften 1 und 2, welche in der gezeigten geschlossenen Stellung des Werkzeuges an der Formtrennebene aneinander anliegen. Die Formhälften 1 und 2 werden auf Härtungstemperatur beheizt. In der feststehenden Formhälfte ist ein Verteilereinsatz 4 vorgesehen, der einen zentralen Zuführungskanal 5 und die von diesem strahlenartig erstreckende Verteilerkanäle 6 in sich schliesst.

  Der Verteilereinsatz 4 ist durch den Temperierer auf einer gegenüber der Härtungstemperatur niedrigeren Temperatur gehalten, so dass die Formmasse in dem zentralen Zuführungskanal 5 und in den Verteilerkanälen 6 nicht aushärtet. Die Verteilerkanäle 6 erstrecken sich in der Formtrennebene 3 zwischen einem Basisteil 41 und einem Endteil 42 des Verteilereinsatzes 4. Der Basisteil 41 und der Endteil 42 sind voneinander getrennte Teile, welche aneinander ebenfalls in der Formtrennebene anliegen und miteinander durch nicht dargestellte Schrauben oder dergleichen lösbar verbunden sind. Im Bereiche der Verbindung des zentralen Zuführungskanals und der Verteilerkanäle weist der Endteil 43 einen Verteilerkegel 7 auf.

  Der Endteil 42 greift in eine Ausnehmung 8 der beweglichen Formhälfte 2 ein, wobei die konische Mantelfläche 9 des Endteiles von einer entsprechenden Fläche 10 der Ausnehmung 8 umschlossen ist. Diese Flächen liegen insbesondere im Bereiche der Mündung der Verteilerkanäle dichtend aneinander auf. Durch Ausnehmungen 11 des Verteilereinsatzes 4 wird der Wärmeübergang von den beheizten Formteilen auf den Verteilereinsatz verringert. Letzterer weist Kanäle 12 auf, durch welche das zum Temperieren des Einsatzes dienende Fluidum strömt.



   Die bewegliche Formhälfte 2 besitzt zur Formtrennebene 3 hin offene Ausnehmungen 13, welche die Durchlässe zwischen den Verteilerkanälen 6 und den mit 14 bezeichneten Formnestern bilden, wobei - wie aus der Zeichnung bei 19 ersichtlich - die Durchlässe und Verteilerkanäle sich in der Formtrennebene überlappende Endabschnitte aufweisen. Der Anschaulichkeit halber weisen in der linken bzw. in der rechten Hälfte der Zeichnung die Formnester 14 und die Ausnehmungen 13 unterschiedliche Formen auf, um zu verdeutlichen, dass diesbezüglich dem Fachmann praktisch unbeschränkte Möglichkeiten zur Verfügung stehen. Wesentlich ist nur, dass die Durchlässe verengte Mündungen zu den Formnestern aufweisen. Aus der linken Hälfte der Zeichnung ergibt sich dies von selbst, da dort ein sogenannter Filmanguss vorgesehen ist, wobei der Durchlass 13 eine bandartige Form besitzt.

  In der rechten Hälfte der Zeichnung ist ein Tunnelanguss dargestellt und die verengte Mündung zum Formnest ist hier mit 15 besonders bezeichnet. Im Bereiche der Formnester befinden sich Ausstosser 16, wie dies allgemein üblich ist.



  Weitere Ausstosser 17 sind im Bereiche der Durchlässe vorgesehen. Mit den   Ausstossenn    16 können die Werkstücke 18 aus der beweglichen Formhälfte entfernt werden, nachdem die Form geöffnet worden ist. Die Ausstosser 17 dienen dabei dazu, die Angüsse zu entfernen, welche durch die sich in den Durchlässen befindende und dort ausgehärtete Masse gebildet wurden. Diese Angüsse sind in der Zeichnung der Anschaulichkeit halber nicht dargestellt. Desgleichen lässt die Zeichnung die sich in den Verteilerkanälen befindliche fliessfähige Formmasse nicht erkennen.



  Dank dieser Auslassung ist es besser ersichtlich, dass die Mündung 19 der Durchlässe zu den Verbindungskanälen einen gegen über letzteren geringeren Querschnitt aufweist.



   Die Wirkungsweise dieses Werkzeuges ergibt sich im wesentlichen bereits aus dem eingangs Gesagten, so dass hier nur das Wesentliche wiederholt zu werden braucht. Wird die Formmasse durch den Zuführungskanal 5, die Verteilerkanäle 6 und die Durchlässe 13 in die Formnester 14 eingebracht, so beginnt sie dort und auch in den Durchlässen sofort auszuhärten, wobei die Fliessfähigkeit der Formmasse in den Verteilerkanälen voll erhalten bleibt, zumal letztere von den Formnestern durch die Durchlässe räumlich getrennt sind. Man könnte die Sache auch so sehen, dass die Durchlässe 13 heisse Endabschnitte der kalten Verteilerkanäle bilden. Unmittelbar nach dem Aushärten wird die Form geöffnet und es werden die Ausstosser 16 und 17 betätigt.



  Dies kann - wie erwähnt - in der Weise geschehen, dass die Werkstücke von den Angüssen an der dafür vorgesehenen Sollbruchstelle getrennt werden. Dazu kommt es nicht nur, wenn die Ausstosser zeitlich gestaffelt betätigt werden, man kann dies auch durch eine entsprechende Ausbildung der Mündung der Durchlässe zu den Formnestern erreichen. Ein Beispiel dafür lässt die rechte Seite der Zeichnung erkennen, wo der Durchlass 13 mit dem Formnest durch eine zu diesem hin konisch verengende Mündung verbunden ist. Selbst bei gleichzeitiger Betätigung der Ausstosser 16 und 17 kommt es hier zu einer Trennung, da der in der Mündung 15 entstandene kleine Zapfen vom Werkstück 18 abgeschert und mit dem Anguss aus dem Durchlass 13 ausgeworfen wird.



   Die räumliche Trennung zwischen den kalten Verteilerkanälen.



  und den Formnestern und die dabei entstehende erweiterte Wärmeüberganszone ermöglicht es, die unterschiedlichen Temperaturen für die kalten und die warmen Werkzeugteile, dort wo diese Temperaturen hersschen müssen, genauer einzuhalten. Es ist mithin einfacher, im Bereiche der Formnester für die Einhaltung einer Temperatur von ca   1800 C    und im Bereiche der Kaltkanäle für die Niederhaltung der Temperatur auf ca   1100 C zu    sorgen.



  Abgesehen von dem dadurch erreichten störungsfreien Betrieb lässt sich dadurch die Qualität der Werkstücke und die Produktivität der Maschine erhöhen. 



  
 



   In the area of the connection of the distribution channels to the passages, the latter preferably have a cross section which is narrower than the cross section of the former, the detachment of the solidified sprues from the flowable molding compound in the cold channels being facilitated and the molding compound escaping from the opening of the mold which is released when the mold is opened Channels is decreased. Thus, even when the mold is closed, there is no flowable molding compound between the



     Mold halves is squeezed. What has been said applies to an increasing extent if the distributor channels have an end section which extends along the mold separation plane to the passages. The distributor insert can preferably have an end part projecting beyond the mold parting plane, which engages in a recess in the movable mold half and which at least partially receives the distributor channels, the movable mold half and the end part having mutually cooperating sealing surfaces. These sealing surfaces can be conical or pyramid-shaped, so that the molding compound is prevented from escaping during the transition from the distribution channels into the passages.



   Further special features and advantages of the present invention result from the following description, in which an embodiment of the subject matter of the invention is explained in more detail with reference to the drawing. The drawing shows part of a cold runner mold in a section perpendicular to the mold parting plane. The tool shown has the mold halves 1 and 2, which bear against one another at the mold parting plane in the closed position of the tool shown. The mold halves 1 and 2 are heated to the curing temperature. A distributor insert 4 is provided in the fixed mold half, which encloses a central feed channel 5 and the distributor channels 6 which extend radially therefrom.

  The distributor insert 4 is kept at a temperature which is lower than the hardening temperature by the temperature control unit, so that the molding compound does not harden in the central feed duct 5 and in the distributor ducts 6. The distributor channels 6 extend in the mold parting plane 3 between a base part 41 and an end part 42 of the distributor insert 4. The base part 41 and the end part 42 are parts which are separate from one another and which likewise abut one another in the mold parting plane and are detachably connected to one another by screws or the like, not shown are. In the region of the connection of the central feed channel and the distribution channels, the end part 43 has a distribution cone 7.

  The end part 42 engages in a recess 8 of the movable mold half 2, the conical outer surface 9 of the end part being enclosed by a corresponding surface 10 of the recess 8. These surfaces lie sealingly against one another, in particular in the region of the mouth of the distribution channels. The heat transfer from the heated molded parts to the distributor insert is reduced by recesses 11 in the distributor insert 4. The latter has channels 12 through which the fluid used for tempering the insert flows.



   The movable mold half 2 has recesses 13 which are open towards the mold parting plane 3 and which form the passages between the distributor channels 6 and the mold nests denoted by 14, wherein - as can be seen from the drawing at 19 - the passages and distributor channels have overlapping end sections in the mold parting plane. For the sake of clarity, the mold cavities 14 and the recesses 13 have different shapes in the left or right half of the drawing, in order to make it clear that the person skilled in the art has practically unlimited possibilities in this regard. It is only essential that the passages have narrowed mouths to the shape nests. This is obvious from the left half of the drawing, since a so-called film gate is provided there, the passage 13 having a band-like shape.

  In the right half of the drawing, a tunnel gate is shown, and the narrowed mouth to the mold nest is designated 15 here. In the area of the mold cavities there are ejectors 16, as is common.



  Further ejectors 17 are provided in the area of the passages. With the ejections 16, the workpieces 18 can be removed from the movable mold half after the mold has been opened. The ejectors 17 serve to remove the sprues which were formed by the mass located in the passages and hardened there. For the sake of clarity, these sprues are not shown in the drawing. Likewise, the drawing does not show the flowable molding compound located in the distribution channels.



  Thanks to this omission, it is easier to see that the mouth 19 of the passages to the connecting channels has a smaller cross section than the latter.



   The mode of operation of this tool essentially results from what was said at the beginning, so that only the essentials need to be repeated here. If the molding compound is introduced through the feed channel 5, the distributor channels 6 and the passages 13 into the mold nests 14, it begins to harden there and also in the passages, the flowability of the molding compound in the distributor channels being fully retained, especially since the latter from the mold nests are spatially separated by the passages. It could also be seen in such a way that the passages 13 form hot end sections of the cold distribution channels. Immediately after curing, the mold is opened and the ejectors 16 and 17 are actuated.



  As mentioned, this can be done in such a way that the workpieces are separated from the sprues at the intended breaking point. This not only occurs when the ejectors are actuated in a staggered manner, but can also be achieved by appropriately designing the mouth of the passages to the mold nests. An example of this can be seen on the right-hand side of the drawing, where the passage 13 is connected to the mold cavity by means of an opening which narrows conically towards it. Even when the ejectors 16 and 17 are actuated at the same time, there is a separation since the small pin formed in the mouth 15 is sheared off the workpiece 18 and ejected from the passage 13 with the sprue.



   The spatial separation between the cold distribution channels.



  and the mold nests and the resulting extended heat transfer zone make it possible to more precisely maintain the different temperatures for the cold and hot tool parts, where these temperatures have to be. It is therefore easier to maintain a temperature of approx. 1800 C in the area of the mold cavities and to keep the temperature down to approx. 1100 C in the area of the cold runners.



  In addition to the trouble-free operation achieved as a result, the quality of the workpieces and the productivity of the machine can be increased.

Claims

PATENT CLAIMS 1. Cold runner mold for processing thermosets, with molded parts heated to the curing temperature and with a distributor insert kept at a lower temperature, the channels of which communicate with the mold nests, characterized in that the distributor channels are connected to the mold nests by passages extending essentially in the mold separation plane .

2. Tool according to claim 1, characterized in that the passages and the distribution channels have overlapping end sections in the mold parting plane.

3. Tool according to claim 2, characterized in that the passages are formed by recesses of one mold half which are open towards the mold parting plane.

4. Tool according to one of claims 1 to 3, characterized in that the passages have narrow openings to form a predetermined breaking point intended to form nests.

5. Tool according to claim 1, characterized in that ejectors are provided in the region of the passages.

6. Tool according to claim 4, characterized in that in the region of the connection of the distributor channels with the passages the latter have a cross section which is narrowed compared to the cross section of the former.

7. Tool according to claim 4, characterized in that the distributor channels have a section extending along the mold parting plane to the passages.

8. Tool according to claim 7, characterized in that the distributor insert has an end part removably attached to a base part, the distributor channels being provided between the end part and the base part and the movable mold half and the end part having mutually cooperating sealing surfaces.

9. Tool according to claim 8, characterized in that the sealing surfaces are conical or pyramid-shaped.

10. Tool according to one of claims 1 to 6, characterized in that the distributor channels are connected to a feed channel, a distributor cone being provided at the connection point.

The invention relates to a cold runner tool for processing thermosets, with molded parts heated to the curing temperature and with a distributor insert kept at a lower temperature, the channels of which communicate with the mold nests.

In the processing of thermosets, previously used tools also hardened the molding compound in the distribution channels, so that each time a shot was made, a distribution channel sprue occurred. In order to avoid the resulting loss of material, the distribution channels in tools of the type mentioned at the outset are accommodated in a special distributor insert which is kept at a lower temperature than the moldings heated to the curing temperature, in such a way that the molding compound retains its flowability. Even with careful tool design, however, it could not be prevented that in the end area of the so-called cold runners, i.e. where these channels open into the mold cavities, the mass occasionally solidified occasionally, in individual cases. Trouble-free, especially automatic operation was not possible.

In order to avoid this problem, a tool was developed in which the distributor is designed as a unit that is movable relative to the other molded parts, in which the distributor channels open into protruding sprue nozzles, which are pressed against the mold when the molding compound is shot in, but immediately thereafter through it Moving back the whole distribution unit can be separated. Apart from the considerable mechanical effort, the problem of the hardening of the mass in the injection nozzles could not be solved with the last certainty with this system. New problems even arose from the fact that material escaping from the injection nozzles in their retracted position was squeezed when the distributor unit was brought up to the molded part in question.

Attempts have also been made to prevent the cold channels from being blocked by plugs of solidified material which form in the ends of the cold channels by preventing the channels from being narrowed in the manner of a nozzle in their end region. In the case of a sufficiently large clear width of the channel opening, there is in fact no blockage due to solidified molding compound. However, there is the further disadvantage that the solidification front in the region of the wide channel opening does not necessarily coincide with the surface of the workpiece to be produced, but rather more or less the wide mouth of the cold runner bulges out, so that the workpiece is raised and cannot be easily tolerated. Reworking the workpieces to remove such ridges is costly and the reject rate is accordingly high.

However, this means material losses which, as is understood from what has been said above, arise precisely from the endeavor to avoid the material losses caused by the distributor sprues.

The purpose of the present invention is to create a tool in which these disadvantages do not occur, so that workpieces can be produced in automated operation with practically no waste. The object of the invention is to spatially separate the distributor insert containing the cold runners from the mold nests. According to the invention, this object is achieved in that the distributor channels are connected to the mold nests by passages which extend essentially in the mold separation plane.

The molding compound in the openings is exposed to the hardening temperature so that defined sprues are created on the workpiece. The associated loss of material is, however, immaterial since the passages only have to have a small volume. The removal of the sprues from the workpiece is unproblematic, especially if the passages have narrow openings to the mold nests intended to form a predetermined breaking point.

Since the passages extend essentially in the mold parting plane, they are separated from the cold runners when the mold is opened and the sprue can easily detach from the molding compound in the cold runners, irrespective of how largely the solidification front in the mouth of the Cold runner intervenes, since this only affects the shape of the sprues, ie the shape is affected by pieces already lost. The passages can be formed by recesses in one half of the mold and this can have ejectors in the area of the passages, so that when the mold is opened, the gates can be repelled simultaneously with the workpieces for which ejectors are of course provided anyway.

The ejectors for the sprues on those for the workpieces can also be actuated in a staggered manner, so that the sprues are separated from the workpieces as soon as they are ejected.