DE3514251A1 - Process for producing an article from a core and an outer layer of thermoplastics - Google Patents

Abstract

In a process for injection moulding an article with a core and an outer layer of thermoplastics, which article has at least two dome-shaped walls connected by a plate, the plastics are injected one after the other through injection openings (41, 42) into regions (24, 25), corresponding to the dome-shaped walls, of a mould cavity (23) under conditions of throughput, duration and synchronisation of the start of injection such that, at a specific time (t3) the total volume of plastic injected for the outer layer corresponds to the specified volume of this plastic in the finished article and the individual volumes correspond to the distribution of the total volume in the finished article, and such that, at a respective time (t5, t4), the volume of plastic injected for the core corresponds to a specified distribution of a predetermined volume of this plastic in the finished article, the plastic streams also filling the region (26) of the mould cavity (23) corresponding to the joining plate. <IMAGE>

Description

DIPL.-ING. GERHARD PULS (19J2-I97l)

35U251

D-8000 MUNICH 90 IA-59 264 SCHWEIGERSTRASSE 2

Cibie Proiecteurs phone: (089) 66 20ji

^j telegram: protectpatent

telex: 524070

TELEFAX: VIA (089) Z 71 So 63 (Hl) description

Process for the production of an article from a core and an outer layer made of thermoplastics

The invention relates to a method for injection molding articles made of plastic.

Its purpose is to improve the procedure known as "two-component injection molding", which, in the production of an article from a core or inner part and a skin or outer layer made of plastics, consists in that:

- a die corresponding to the article or in

corresponding mold cavity is produced,

- A liquid plastic for the skin or outer layer is injected into this mold cavity, the injected volume of which is substantially equal to the volume of this material in the finished article which 5 but in the immediate vicinity of the injection opening in Mold cavity remains to the extent that this limits a volume that is the total volume of the article, the is to be generated corresponds to,

- then into the mold cavity, that is, into the

still flowable plastic for the outer layer, a pre- *

lumen plastic is injected for the core, which corresponds to the volume of this material or material in the finished Article corresponds, so that this plastic compound for the Core by putting in the plastic compound for the outer layer

thermoplastic / 2

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which causes migration or flow in the mold cavity, generally after the injection is complete the plastic for the core is completely lined with the plastic for the outer layer, - the hardening of at least the plastic for the skin causes or is caused in order to be inside the Mold cavity to obtain a rigid article,

- and the article or product obtained is removed from the mold.

The parameters of such an injection molding process, i.e. the choice of plastics, temperatures and pressures for injection molding, changing the viscosities in order to have a continuous lining of the mold cavity with the Plastic for the outer layer in the injection molding of the Obtaining plastic for the core or the inner layer without interruption is generally known to the person skilled in the art.

So far, however, this method of working has only been used for the production of simply shaped and smaller articles, for which the determination of the various parameters mentioned above remained possible in order to avoid any cracking of the plastic masses for the outer layer when injection molding the 5 plastic for the core and to avoid a homogeneous To ensure distribution of the two plastic masses in the mold cavity, and also the use of a single one Injection opening remained possible for both plastic compounds.

However, once the shape of the item to be manufactured became more complicated and its dimensions larger, one encountered problems of insufficient homogeneity or uniformity in the distribution of the two plastic masses in the mold cavity and the discontinuity of one and / or the other plastic compound, because certain areas of the mold cavity from the only injection opening for the

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Plastic masses were difficult to access.

For the production of complex shaped and / or bulky articles, a mode of operation is known in which several injection openings are provided for one and the same mold cavity; this way of working leads to the Use of only one plastic compound that is simply intended to fill the mold cavity with good results; she However, it is difficult to transfer it to two-component injection molding as soon as it is as homogeneous as possible seeks simultaneous presence of two plastic compounds in the entire mold cavity in order to obtain articles, which have a continuous core that is as homogeneous as possible with a skin or outer layer is coated or encased.

The aim of the invention is to provide a method by means of which the two-component injection molding, such as defined above, in a single mold cavity with multiple injection ports is enabled to produce an article to produce, which has at least two arched walls, each to at least one axis that they intersect, are rotationally symmetrical and which are connected to one another by a flat partition. As a non-limiting one One example is the production of several reflectors in one piece for motor vehicle headlights are determined, and each reflector constitutes one of the curved walls. In DE-OS 33 24 018 is already indicated, as with the help of the two-component injection molding method in the case of such a reflector, the contradicting requirements regarding smooth surface and good resistance to mechanical and thermal stresses through suitable selection of thermoplastics for the core (or soul) and the skin (or cladding layer)

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and thanks to a special way of working during injection molding, this known method however only on the manufacture of a single reflector or one in terms of the simple shape and the dimensions of a comparable article.

The method according to the invention is characterized in that that the following steps are carried out one after the other:

(a) Manufacture or choose a die or

a tool or mold cavity which / which has at least two arched zones, each of which is arched to the aforesaid Walls are complementary and each of which is at least approximately rotationally symmetrical to an axis, which it cuts in a cutting area; as well as a flat intermediate zone complementary to said one Partition wall is and connects said arched zones with one another, with an injection port in each of the said intersection zone is provided;

(b) each of the injection ports is connected an equal source of liquid plastic for the skin or skin and injected under pressure through each the injection openings this thermoplastic material in the mold cavity under such conditions of the amount, the duration and the synchronization of the start of the injection molding through the various injection openings, that at the same time through the various openings in the mold cavity as much volumes of thermoplastic Plastic for the skin or outer layer has been introduced so that it essentially accumulates correspond to a predetermined volume of thermoplastic material for the outer layer in the desired article and taken individually, correspond to a predetermined distribution of this predetermined volume, whereupon one then At this point the injection molding stops and the injection ports from the source of the thermoplastic Separates plastic for the outer layer;

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(c) Immediately and simultaneously close each of the injection ports to an equal source of fluid thermoplastic material for the core and injects this thermoplastic material under pressure through each of the injection ports into the mold cavity; injection molding is then interrupted through each of the openings and separates these openings from the source of thermoplastic resin for the core to such Time that at this time and through these openings in the mold cavity a volume of thermoplastic Plastic has been introduced for the core, which has a predetermined distribution of a predetermined volume thermoplastic material for the core in the desired article corresponds, with the volumes of the material for the skin or outer layer and for the core or inner layer in the intended article and theirs Distribution are so predetermined that in the intermediate zone continuously outer layer material, injected through the various openings on the one hand as well as core material injected is present through the various openings on the other hand;

(d) at least the skin material is hardened or hardened to form a rigid article to obtain;

5 (e) remove the article from the mold cavity

or demold the article.

The fact that at the same time the injection of the thermoplastic material for the skin or outer layer through all injection openings are ended and injection of the thermoplastic material for the core is started, it is best to produce the same conditions everywhere as the thermoplastic for the Core during the injection process, the migration of the thermoplastic Plastic for the skin inside the mold cavity and its lining causes it while by observing the predetermined volumes and

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AO

divisions in the specified type ensures that there is a steady course of both the in the intermediate zone Skin as well as the core. This choice of the intermediate zone of the mold cavity as the area in which the from the thermoplastics for the skin and for the core continuously fed to various injection openings run, makes it possible to ensure this steady course under optimal conditions, on the one hand to the the simple geometry of this zone and, on the other hand, the fact that this zone is made of both plastics can be reached from the injection openings on a path that is as straight as possible. Furthermore it is in that special case that the article produced consists of several reflectors defined by its curved walls, It is more advantageous that any deficiencies or defects that may be present, which occur more in the outer layer than in the core, are present on the intermediate wall free of optical functions, which passes through the intermediate zone of the mold cavity is formed than in the zones or areas that form the actual reflectors.

Even in the frequent case that the arched walls and of course the corresponding zones or areas make up or enclose different volumes of the mold cavity, it is easy to achieve the simultaneous Completion of the injection of the thermoplastic material for the outer layer in step b) by the plastic or the material for the outer layer through the various injection openings with essentially identical delivery and injected during different time periods determined by the distribution of the for the entire article provided volume of thermoplastic material on the various injection openings are predetermined and by staggering the start of injection through the various openings.

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It will be noted that upon completion of step c) described above, one at each injection port in the mold cavity Zone thermoplastic for the core is present, which is not thermoplastic for the Outer layer is wrapped. If necessary, advantageously between stage c) and stage b) the injection openings are each reconnected to the source of thermoplastic material for the outer layer and thus re-injecting this material under pressure into the mold cavity through each of the openings will. In the article obtained, the core is then completely enveloped by the outer layer.

For this purpose, a line can advantageously be provided in step a) in each intersection area, which opens into the mold cavity opposite the corresponding injection opening, as well as a piston inside this line, that delimits or closes the mold cavity towards the latter and that between an injection position and a position behind the injection position is movable. One then holds the plunger during the Steps b) and c) in the injection position and brings it after step c) and during the re-injection of the thermoplastic material for the outer layer in the back position. In this way you can by choosing a suitable piston stroke between an injection position and its previous position as well as by suitable choice of these two positions the thermoplastic material for the outer layer again immediately following the thermoplastic material injected in step b) for the outer layer inject if necessary. Generally, by withdrawing the plunger and re-injecting of thermoplastic material for the outer layer in the injection openings at the end of stage c) existing thermoplastic material for the core "he-

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flushed out "and the injection openings with thermoplastic Plastic for the outer layer are filled in order to immediately repeat them for step b) of a subsequent one Prepare work cycle.

The method according to the invention will now be described with reference to the attached Drawing explained in more detail. 1 and 2 show perspective views of an article,

which can be produced according to the invention, that is, an article which in a block two

Includes reflectors for automobile headlights;

3 shows a device for injection molding this article, in section through a plane which includes the axes of the mold cavity corresponding to the optical axes of the two reflectors;
FIG. 4 shows part of the device along the line IV-IV in FIG. 3; FIG.
Fig. 5 is a diagram showing the various phases of the

Injection molding explained;

6 shows the detail VI of FIG. 3 after the injection of the thermoplastic material has ended for the core on a greatly enlarged scale. 25th

The invention is described below with reference to the implementation of an article comprising two reflectors; however, it is by no means limited to the manufacture of such articles and those skilled in the art can easily make the changes that adapt the procedure to each (desired) configuration of the item can.

In the example illustrated by the drawing, as shown in FIGS. 1 and 2, the article 1 is exposed two curved walls or surfaces 2 and 3 arranged side by side and composed of an intermediate wall 4,

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the dome-shaped walls or surfaces 2 and 3, which make up the reflectors in the finished product, with each other connects.

The wall 4 is flat and delimited by two approximately flat and rectangular sides 11 and 12 parallel to one another, which are connected to one another by an edge 13. These Wall 4 is intended, for example, to hold the article 1 and, with it, that of the walls 2 and 3 existing reflectors on a body part of the

Ensure motor vehicle by blending into the general outline of the body. *
or flange-like plate

The (arched or dome-shaped) walls 2 and 3 protrude on the same side 11 of the wall 4. The wall 2 is limited by two sides 5 and 6, which form a paraboloid of revolution around the same axis 7, which is the optical The axis of the corresponding reflector is defined and, as not shown, directed perpendicular to the wall 4 or, as shown, can be directed obliquely to the wall 4. Pages 5 and 6 are flush with pages 12 and 11 approximate ellipses 14 and 15. The paraboloid of revolution, which defines each of them, intersects the axis 7, around which the wall 2 an opening 16 with the axis 7 having a rotationally cylindrical circumference which is intended to receive a lamp. Wall 2 is in bounded in the same way by two sides 8 and 9, which form a paraboloid of revolution about an axis 10 which is parallel runs to the axis 7; these sides 8 and 9 close flush with sides 12 and 11 along approximate ellipses 17 and 18 on. The paraboloids that make up pages 8 and 9 define the wall 3, intersect the axis 10, but the Wall 3 is pierced around this latter (axis) by an opening 19 which is intended to receive a lamp and the one has to the axis 10 rotationally cylindrical circumference. The obtained with the help of the procedure described below

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tene article has uninterrupted walls 2 and 3, that is, walls without the openings 16 and 19, which according to must be attached to the demolding of the article. The injection molding process described below provides one Article whose domed or dome-shaped walls 2 and 3 intersect their axes 7 and 10, respectively.

To produce such an article according to the invention, an injection molding tool 20 such as shown in fig.

This tool 20 is made up of two parts 21 and 22 together, which are arranged side by side and form a solid unit during injection molding, the mold cavity 23, which corresponds to the desired article 1, with the exception of the openings 16 and 19, and which corresponds to Demoulding can be separated from each other.

The die or the mold cavity 23, which is in this way by the two side by side and firmly together connected tool halves 21 and 22 of the tool 20 is limited, has two arched or dome-shaped Zones or areas 24 and 2 5 which are connected to one another by a flat intermediate area 26. the Zones 24 and 25 correspond to the walls 2 and 3 without the openings 16 and 19 and have the same rotational symmetry like the latter (walls) around the respective axes

27 and 28 of the tool, the two axes 27 and 28 occupying the same relative positions as the Axes 7 and 10 of the desired item. The zones or Areas 24 and 25 intersect the respective axes 27 and

28 in a corresponding intersection area 29 and 30. The intermediate zone 26 in turn corresponds to the wall 4.

The tool half 21 advantageously has for this purpose

LA-59 264 -> r -

an approximately flat side 31, on the one hand for the connection is intended with the tool half 22 and on the other hand to form the side 12 of the wall 4, two Protuberances which define convex sides 32 and 33 and are stormed to form the respective sides 5 and 3; and comprises the tool half 22 recessed in a side 34 which is adapted to the side 31 around the die 23, when the tool halves 21 and 22 are united to define such a die 23, a stepped side 36, which is intended to shape the side 11 and, by its abutment 37 on the side 34, the edge 13 of the area 4. The side or surface 36 for its part has two recessed concave sides or surfaces 39 and 40 which are intended to do so are to shape the respective sides or surfaces 6 and 9. The sides or faces 31 and 36 define the zone 26 between the zones 24 and 25 of the mold cavity 23.

In each of the areas or zones 29 and 30 and more precisely at the interface of the side or surface 39 with the

Axis 27 and at the interface of the side or surface with axis 28 open into the mold cavity 23, the respective injection openings 41 and 42, which are arranged in the mold half 22.
25th

The two injection openings 41 and 42 are defined through one end of the associated channel 50 or 51 of an associated nozzle 43 or 44, which is in a corresponding Bore 45 and 46 of the tool half 22 is mounted, the nozzles 43 and 44 of which are fixed at least during the injection stages.

The channels 50 and 51, in this way via the injection ports 41 and 42 open into the tool or mold cavity 23, also open outside this Tool cavity 23, that is, on the outside of the

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Tool 20 into an inlet opening 52 or an inlet opening 53.

Means for making the connection, for example with screws 47 and 48 provided on the nozzles 43 and 44 are, connect the latter to a manifold block 49 in such a way that with the inlet opening 52 an outlet opening 54 of the block 49 communicates with the inlet opening 53 and an outlet opening 55 of the block.

Each of these outlet openings 54 and 55 consists of one End of a corresponding channel 56, 57, which also has an end 58, 59 which extends into a corresponding bore 60, 61 of the distributor block 49 engages.

The respective ends 69 and 69 of the other two channels 70, 71, which are also in the manifold block 49 are arranged and also each have a different end 72, 73 with which they are in the Hole 61 open or engage.

In each of these channels 70 and 71, one end such as 74 opens a respective inlet channel 75, 76, the one in the distributor block 49 is attached and further a second end like 77, which has an inner channel like 78 of a corresponding Connecting piece such as 79, firmly connected to the block 49 by suitable means such as 80, for example Screws, with a corresponding injection molding head such as 81 a corresponding source 82, 83 of a liquid and joins pressurized thermoplastic material,

The sources 82 and 83 for the flowable, under pressure standing thermoplastic are of any 5 known design for injection molding and therefore not shown here in detail.

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Once the sources 82 and 83 for the flowable and pressurized thermoplastic material are in Operation are, the channels 75 and 70 of the manifold block 49 up to the ends 6 8 and 72 of the channel 70 with flowable and pressurized thermoplastic from the source 82 is filled while the channels 76 and 71 to the ends 69 and 73 of the channel 71 with flowable and pressurized thermoplastic Plastic from the source 83 can be filled.

The entry of one or the other thermoplastic material into the channel 56 and / or into the channel 57 is selectively by rotating a stopcock 64 about an axis 164 inside the bore 60 of the manifold block 49, and / or a cock 65 about an axis 165 in the interior of the bore 61 of this distributor block regulated.

The execution of the cock plugs (or three-way cocks) 64 and 65 for this Purposes, as well as the relative arrangement of the ends 58, 68, 69 in the side 62 of the bore 60 as well as that of the ends 59, 72, 73 in the side 63 of the bore 61 can easily be determined or fixed by a person skilled in the art.

Thus, by rotating the plug 65 about the axis 165 bring this plug into the bore 61 mainly in three positions, namely:

- A first position A, in which any connection between the channel 57 on the one hand and the channels 70 and on the other hand, as well as still being interrupted between these channels 70 and 71;

a second position B obtained by rotating the plug 65 from the first position; in this position B is the channel 57 and with it the injection opening 42 in connection with source 82; the end 73 of the channel 71, however, is preferably still

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closed by the plug 65;

a third position C obtained by turning the plug 65 with respect to the first position A in reverse Sense to the sense that leads to the second position B; of the plug 65 then connects the injection port 42 with the source 83; the channel 70, however, is closed.

The position of the plug 65 in one of these directions with respect to the axis 165 with respect to the manifold block 49 can be effected using any known manner, for example under the action of a cylinder or a spindle 94, the / these one with the manifold block 49 has a firmly connected body 95 and a shaft 96 which is connected to the plug 65 via a handle 97 is.

In exactly the same way, the plug 64 can by rotating about the axis 164 in the interior of the bore 60 under the action of means such as a cylinder or a spindle 98/3 / die acts on the plug 64 via a handle 99, regardless of the actuation of the plug 65 by the cylinder or the spindle 94, can be brought into three positions, that is:

a first position A 'in which the plug 64 interrupts any communication between the channels 56, 70 and 71;

- In a second position B ¹ , in which the plug 64 brings the end 58 of the channel 56 and the end 68 of the channel 70 in connection with one another, but continues to interrupt any connection between the ends 58 of the channel 56 and the end 69 of the channel 71 to bring injection port 41 into communication with source 82;

- In a third position C, in which the plug connects the end 58 of the channel 56 with the end 69 of the channel 71 brings in connection and on the other hand the connection between

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the end 58 of the channel 56 and the end 68 of the channel 70 interrupts to the injection port 41 in communication with to bring the source 83.

It can be seen that it is possible in this way, as desired, thermoplastic plastic from one or the other inject the other of the sources 82 and 83 through one or the other of the injection ports 41 and 42, by interrupting this injection at will.

Advantageously, the injection heads such as 81 are identical and the different channels of the manifold block 49 that Connections such as 79 and the nozzles 43 and 44 and the plug 64 and 65 are dimensioned so that regardless of the contemplated injection port 41 and 42 and independently from the sources 82 and 83 under consideration, the establishment of communication between an injection port and a source establishes between them a circle whose developed length is identical to an equally identical usable cross-section or passage cross-section; this changes the injection conditions of the openings 41 and 42 are unified, regardless of whether one is plastic compound from the source 82 or Plastic compound injected from the source 83.

By the arrangement of the injection openings 41 and 42 along the axes 27, 28 of the dome-shaped zones or areas 24, 25 of the tool cavity 23, preferably in the concave sides 39, 40, which delimit this tool cavity 23 in the tool half 22, an optimal one Distribution of the injected plastic mass ensured.

Preferably, in addition, as shown, each of the injection openings 41, 42 along the respective Axis 27, 28, that is, in each of the convex surfaces

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32, 33 of the mold cavity 23 in the corresponding intersection area 29, 30 with this axis 27, 28 a line 100, 101 be arranged, in which an associated piston 102, 103 can move back and forth.

The two lines 100, 101 are each in two sections divided, each by an outer peripheral surface are limited, which extends rotationally cylindrical to the corresponding axis 27, 28, that is, in a first Section 104, 105 adjacent to the mold cavity 23 a diameter which is larger than the corresponding injection openings 41, 42 in the transverse direction to the corresponding one Axis 27, 28, and in a second section 106, 107 with a smaller diameter, which is attached to the first Connected via a shoulder or projection 108, 109 and opens outside the tool 20, more precisely outside of the tool half 21, opposite the nozzle 43 along the axis 27 and the nozzle 44 along the axis 28.

The two pistons 102 and 103 each have the shape of a flat disk, are transverse to the corresponding axis 27, 28 arranged with a diameter which is substantially equal to the diameter of the corresponding peripheral sides or areas of sections 104 and 105 of the conduits 100, 101, so that the piston 102 in the section 104 of the Line 100 can slide along axis 27, the piston 103 can slide inside the section 105 of the conduit 101 along the axis 28 and in this way the volume of the mold cavity 23 in the intersection 29 of the zone 24 with the axis 27 or in the intersection 30 of the zone with the axis 28 can be varied.

For this purpose, the pistons 102 and 103 are preferably less thick than along the corresponding axis 27, 28 the corresponding section 104, 105 of the line 100, 101 is wide along this axis.

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Both pistons 102, 103 are firmly connected at one end a corresponding shaft 110, 111 sliding along the associated axis 27, 28 is arranged in the line 100, 101 corresponding to it, more precisely in the Section 106, 107 of the respective line, which is the smallest Has diameter. This shaft 110, 111 has otherwise, outside of the tool half 21, a second end which is firmly connected to the shaft 112, 113 a cylinder or a spindle 114, 11 5, which continues a body 116, 117, which with the tool half 21 is firmly connected. The two cylinders 114 and 115 can be regulated or controlled independently of one another be to at will the corresponding piston 102, 103 especially in one or the other of the two positions bring to. In a first position, called the injection position, the piston 102 is completed by a Page 118, which is directed towards the interior of the mold cavity 23, whose side 32 or forms, based on this side a protrusion along axis 27; The piston is in the other of the two positions, called the retracted position withdrawn along the axis 27 in the interior of the section 104 with respect to its injection position. In the same Way, the piston 103 is completed by a side 119, which is directed towards the interior of the mold cavity 23, the side 33 thereof, or forms one with respect to this side

Projection along axis 28 in an injection position, and is retracted in a retracted position in the interior of section 105 along axis 28 with respect to the injection position.
30th

Such an injection molding tool is used in accordance with the method according to the invention as follows.

In a first stage in the implementation of the method, the two tool halves 21 and 22 are manufactured or

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simply selected the ones that are suitable to put together the mold cavity 23 to form the desired Article 1; the two tool halves 21 and 22 then become the tool 20 united. In the example shown here, the walls 2 and 3 of the article 1 are clearly different Volumes, for example the wall 2 with a larger volume is intended to be a reflector for a low beam headlamp to form, while the wall 3 with a smaller volume is intended to be a reflector for To form a high-beam headlight, and as a result, the zone 24 of the cavity 23 has a larger volume than zone 25.

The assembly described with reference to FIGS. 3 and 4 is then carried out by removing the nozzles 43 and 44 be assembled on the one hand with the manifold block 49 connected to the injection heads such as 81 of the sources 82 and 83 is connected, and on the other hand with the mold half 22 to determine the injection openings 41 and 42. The two cock plugs 64 and 65 then take the position A, A 'through the action of the cylinders 94 and 98, in which any connection between the respective channels 56, 70, 71 and the channels 57, 70, 71 is prevented and the Cylinders 114 and 115 bring and hold pistons 102 and 103 in their injection position.

After the entire channels have been cleaned or rinsed, flowable thermoplastic material fills under Pressure from source 82 enters inlet channel 75 and channel 70 of block 49 while also being more flowable thermoplastic resin under pressure from source 83 fills inlet channel 76 and channel 71, in both Cases up to the bores 60 and 61, in which the cones 64 and 65 provide insulation from the ends 58, 59 of the Channels 56, 57, which lead to the injection openings 41, 42, hold in an upright position. The manifold block 49 is by means

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maintained for heating 84 at a suitable temperature, the flowability of the two thermoplastics ensures. These heating means 84 are, for example, electrical resistors, as shown but also be of a different nature. In other words, the source 82 provides a thermoplastic material, which has been brought to a temperature above its plasto-elasticity temperature; the source 83 provides a thermoplastic material, which is also at a temperature above its temperature the plasto-elasticity has been brought, and the block 49 is with the means 84 at a temperature above that held at the highest of these two temperatures of plasto-elasticity. These temperatures are known to the person skilled in the art; 5 They depend on the type of thermoplastic used and the fillers that may be present and the pressures to be maintained during injection molding, and these parameters are therefore not described in more detail.

The thermoplastic resin provided by source 82 is intended to be used to form the skin or wrapping or coating. To form the top layer of the article 1, while the plastic supplied from the source 83 is intended to the To identify the core or inner part of this article. 25th

Fig. 5 explains the various phases or stages of the actual injection molding process, which can then begin.

The times are plotted on the abscissa and the positions of the chicks 64 and 65 on the ordinate, as above described above.

The starting point in time at which the in 3 is completed and the thermoplastics supplied from sources 82 and 83 have been completed the channels 75 and 70 or 76 and 71 up to the bores

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Fill 60 and 61 and the pistons 102 and 103 assume their injection position. At time t, with the aid of the cylinder 98, the plug 64, which is combined with the zone 24 of the mold cavity 23, that is to say with the dome-shaped zone of this mold cavity which occupies the largest volume, is brought into its position B ¹ in which it brings the confluence end 58 of the channel 56 into communication with the end 68 of the channel 70, whereby the thermoplastic material for the skin or outer layer then enters the zone 24 of the mold cavity 23, with a throughput regulated by the injection pressure, which is determined by a person skilled in the art , and through the useful cross-section or flow cross-section in the channels 70, 56, 50 and in the Ku-? ken 64. At a later point in time t ₂ , the "

Chick 65 brought with the help of the cylinder 94 in its second position B, in which it is the junction end 59 of the Line 57 brings the end 72 of the line 70 in communication and it then begins to fill the zone 25 of the Mold cavity 23 via the injection opening 42 with a throughput or an amount that takes into account the dimensions described above is the same as the throughput or the amount with which the zone is filled of the mold cavity 2 3 has started and then continued. For this purpose, the inlet channel 75 just like the channel 78 of the connecting piece 79 has a flow cross-section or a useful cross-section that at least twice where is large as that of the line

Then, at the same point in time t _3, the two chicks 64 and 65 are returned to their starting position A ¹ , A with the aid of the cylinders 98 and 94, in which they isolate the channels 56 and 57, that is to say the injection openings 41 and 42 from the channels 70 and 71 and consequently also with respect to the two sources 82 and 83.

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The shift or the distance between the two times t ₁ and t 2, at which the filling of the zone with the larger volume and the filling of the zone 25 with the smaller volume begins, can easily be determined by the person skilled in the art in such a way that to this Time t, via the injection openings 41 and 42, respective volumes of the thermoplastic material for the skin or outer layer have been introduced into the mold cavity 23, which, cumulated, i.e. taken together, essentially correspond to a given volume of this thermoplastic material in the desired article 1 and which, taken individually, correspond to a predetermined distribution of this predetermined volume.

Immediately after the injection of this thermoplastic material for the skin, that means practically for the Time t, the two chicks 64 and 65 are simultaneously brought into their third position C, C, in which they in each case the confluence end 58 of the channel 56 and the confluence end 59 of the channel 57 with the channel 71, that is connect to the source 83 of the thermoplastic resin for the core; injecting it into the mold cavity 23 then begins simultaneously via the two injection openings 41 and 42. Taking into account the dimensional features given above and the fact that the channel 76, like the channel (corresponding to the channel 78) of its connecting piece (corresponding to the connecting piece 79) with the source 83 a useful cross-section or have a flow cross-section which is at least twice as large as that of the channel 71 the thermoplastic material for the core with an equal throughput through the injection port 41 and over the injection port 42 is introduced.

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The zone 25 with a smaller volume is therefore filled faster than the zone 24 with a larger volume, and at a point in time t. by means of the cylinder 94, the plug 65 is brought into its first position A in order to interrupt the injection into the zone 25; At a later point in time t, the plug 64 is then likewise ^{brought into its first position A 1} with the aid of the cylinder 98 in order to also interrupt the injection into the zone 24 of the mold cavity 23. Taking into account the dimensional features described above, the injection quantity into zone 24 of mold cavity 23 is not affected by the completed injection into zone 25.

The time t. is set so that between t ₃ and t.

A volume of thermoplastic material for the core has been introduced via the injection opening 42 into the zone 25 of the mold cavity 23, which volume corresponds to a predetermined distribution of a predetermined total volume of this thermoplastic material in the desired article 1; the time t ,. is determined so that between t ₃ and tr a volume of thermoplastic material has also been introduced into the zone 24 of the mold cavity 23 which corresponds to such a predetermined distribution of the volume of the thermoplastic material for the core in the desired article.

The total volumes of the plastics injected in this way for the skin and for the core and the distribution these volumes between the two injection openings 41 and 42 are predetermined so that at the time t. that via the injection opening 42 into the zone 25 of the Mold cavity 23 introduced material for the core and for the skin, the material introduced first for the skin is displaced by the subsequently introduced material for the core, into the zone 26 of the mold cavity

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23 arrive, and that at time t, - the thermoplastic Material for the core and the thermoplastic material for the skin, which through the injection port 41 in the Zone 24 of the mold cavity have been introduced, with the core material introduced later being introduced first Skin material elongated, also get into this zone 26, in order to create a continuity here on the one hand in the thermoplastic To ensure material for the core and on the other hand in the thermoplastic material for the skin, as shown in Fig. 6, in which the thermoplastic material for the core is 120 and the thermoplastic material is designated by 121 for the skin.

Taking into account the same throughput through the openings 41 and 42, regardless of whether the source 82 or 83 is in operation, a person skilled in the art can easily determine the shifts that this takes place between the times t 1 and t_ on the one hand and the times t and tr on the other should be adhered to by determining the injection times t, - t ,, t ₃ - t ", t. - t ~, tr - t ,, of the various thermoplastics through the various injection openings 41, 42.

At time t ₅ the channels 51 and 57 on the one hand and the channels 50 and 56 on the other hand are filled with core material; This means on the one hand with regard to the injection openings 41 and 42 that the thermoplastic material for the core is not completely enveloped by the thermoplastic material for the skin, and on the other hand that before repeating the injection cycle just described, in the one with the injection of the thermoplastic material for the skin is started, the channels 50, 51, 56, 57 must be cleaned of all traces of thermoplastic material for the core.

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As a result, according to a preferred embodiment of the method according to the invention, at a point in time t _g immediately following the point in time t-, for example simultaneously with the aid of the cylinders 98 and 94, the cock plugs 64 and 65 are moved into their second position B ¹ , B again to bring the junction end 58 of the channel and the junction end 59 of the channel 57 in communication with the channel 70 and via this with the source 82 for the thermoplastic material for the skin and this material is again injected via the injection openings 41 and 42, up to a time t ₇ which is determined in such a way that at least the thermoplastic material for the skin has replaced the thermoplastic material for the core in the channels 50, 51, 56, 57, and this injection is interrupted at time t_ by the stopcock plugs and 65 with the help of the cylinders 98 and 94 are brought back to their starting position A ¹ , A, in which they any connection between the injection openings 41 and 42 on the one hand and the sources 82 and 83 on the other hand interrupt. This flushing or cleaning is facilitated by a movement of the pistons 102 and 103, under the action of the cylinders 114 and 115, from their original injection _{position, which they assumed at time t fi} , to their retracted position, which they assume at time t ₇ .

Then, in a manner known per se, at least the thermoplastic material of the skin or outer layer and optionally harden the thermoplastic material of the core or cause this hardening by the Mold 20 can cool or it cools, so that in its cavity 23 a rigid article receives; then the two tool halves 21 and 22 are separated from one another to produce the article obtained to remove from the mold cavity 23 or to demold it.

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In order to obtain the article shown in FIGS. 1 and 2, the openings 16 and 19 must then be created.

The pistons 102 and 103 are then returned to their injection position with the aid of the cylinders 114 and 115 reassembling the tool halves 21 and 22 to form a mold cavity 23; this is again the Point in time t, which can be followed by the injection stages described above. The heating of block 49 with the means 84 ensures that the thermoplastics from the injection heads such as 81 to the injection openings like 41 and 42 are kept flowable outside the injection phases.

By means of the measures according to the invention it is achieved in a particularly advantageous manner that each of the two reflectors is formed exclusively from the quantities of plastic that have been injected through the injection opening belonging to the reflector in question. The flange-like plate 4, which connects the two reflectors to one another, on the other hand, is formed by quantities of plastic which have been injected partly through one injection opening and partly through the other of the two injection openings. Therefore, streaks or other discernible irregularities on the surface of the outer layer ₍ which could be caused by the meeting of the plastic flows injected through the two injection openings, if at all, only occur in the area of the flange-like plate 4, where they are harmless, but not in the area of the one or the other reflector.

The present invention has been described with reference to the manufacture of an article having only two domed or dome-like walls connected to one another by a flange-like plate, e.g.

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with twin reflectors; is the procedure described however, it is not limited to such a case, and those skilled in the art will easily recognize that one can only use an appropriate one Mold cavity 23 and arranging so many injection openings, such as dome-shaped walls are provided, can create more complex articles. The transfer of the shifts between the injections through the two openings 41 and 42 in the event that a larger number of injection openings is provided, belongs to the area of 0 professional ability and is therefore not outside of it of the scope of the present invention, which generally allows numerous variants of execution without thereby leaving their framework.

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Claims (5)

PATENTANWÄLTE ctk-incfkanz tuectkofv * · WUESTHOFF-v. PECHMANN-BEHRENS-GOETZ "-» »l.freda ™ ESthoff DIPL.-ING. GERHARD PULS (19J2-I971) EUROPEAN PATENT ATTORNEYS dipl.-chem. Dr. E. Freiherr von pechmann DR.-ING. DIETER BEHRENS 3 ζ 1 UJ 5 1 DIPL.-ING .; DIPL.-VIRTSCH.-ING.XUPERT GOKTZ LA-59 264 D-8000 MUNICH 90 Note: CIBIfi PROJECTEÜRS SCHWEIGERSTRASSE 2 phone: (089) 66 ao 51 TELEGRAM: PROTECTPATENT .ELEX: 51 fax: via (089) 2 71 60 63 (in) claims 1. Method of making an article from a Core and an outer layer by injection molding of thermoplastics in one of the desired article Corresponding mold cavity, one after the other with a flowable thermoplastic material for the outer layer and a flowable thermoplastic material is injected for the core, at least the outer layer solidify left and the rigid article obtained is demolded, f characterized in that one for Her- ^ position of an article (1) which has at least two dome-like walls (2, 3), both of which are at least approximate are rotationally symmetrical to a respective axis (7, 10) which they intersect and which one with the other are connected to one another by a flange-like plate (4), in particular twin reflectors for motor vehicle headlights, the following steps are carried out in succession: a) a mold cavity (23) is manufactured or selected, which has at least two dome-like zones (24, 25) which correspond to the dome-like walls (2, 3) and both of them are at least approximately rotationally symmetrical to a respective axis (27, 28) and these are in a cutting area (29, 30) cut, as well as a flat intermediate zone (26), which corresponds to the flange-like plate (4) and the two dome-like zones (24, 25) connects to one another, and the one in each of the intersection areas (29, 30) Has injection port (41, 42); / 2 , A-59 264 -2- 35Η251 b) the two injection openings (41, 42) are connected to a source (82) for flowable thermoplastic material for the outer layer and this thermoplastic material is injected through each of the injection openings (41, 42) under pressure into the mold cavity (23) under such conditions Throughput, the duration and the synchronization of the start of injection through the injection openings (41, 42) that at a certain point in time (t ^) through the various injection openings (41, 42) in the mold cavity (23) volumes of the thermoplastic material for the Outer layer have been introduced which, taken together, essentially correspond to a predetermined volume of thermoplastic material for the outer layer in the desired article (1) and which, taken individually, correspond to a predetermined distribution of this predetermined volume, whereupon at the time (t ₃ ) interrupts the injection process and the injection openings (41, 42) from the source (82 ) for thermoplastic the outer layer separates; c) immediately thereafter, both injection openings (41, 42) are connected to a source (83) for flowable thermoplastic material for the core and this thermoplastic material is injected under pressure into the mold cavity (23) via each of the injection openings (41, 42); then the injection process is interrupted via each of the injection openings (41, 42) and the injection openings (41, 42) are separated from the source (83) for thermoplastic material of the core at a respective point in time (t _g , t.), in such a way that to At this point in time (t_, t-), a volume of thermoplastic material of the core has been introduced into the mold cavity (23) via the injection openings (41, 42), which corresponds to a predetermined distribution of a certain volume of thermoplastic material for the core in the desired article ( 1) corresponds, whereby the volumes of plastic for the outer layer and plastic for the core in the desired article (1) and their distributions are specified so that in the / 3 ΊΑ-59 264 - 3 - 35-251 Intermediate area (26) on the one hand forms a continuous layer of plastic for the outer layer (121), injected via the two injection openings (41, 42) and, on the other hand, a continuous layer of plastic for the core (120) _f injected via the two injection openings (41, 42) ; whereupon at least the outer layer (121) is allowed to harden in a manner known per se and the rigid article (1) is removed from the mold.
10 2. The method according to claim 1, characterized in that when the dome-like walls (2, 3) form different volumes, step b) is carried out by the plastic compound for the outer layer through the injection openings (41, 42) with substantially the same throughput and for different periods of time (t ₃ - t 1 - t 1) by staggering the start of injection through the injection openings (41, 42) (against each other). 3. The method according to claim 1 or 2, characterized in that in step a) injection openings (41, 42) in the concave areas (39, 40) of the mold cavity (23). 4. The method according to any one of claims 1 to 3, characterized characterized in that between stage c) and stage d) the injection openings (41, 42) are again connects to the source (82) for thermoplastic material for the outer layer and again this plastic through the injection openings (41, 42) under pressure into the Injected mold cavity (23), then this re-injection is interrupted and the injection openings (41, 42) from the Source (82) for the thermoplastic material separates the outer layer. / 4 , Λ-59 264 -4- 35U25J 5. The method according to claim 4, characterized in that in step a) in each cutting area (29, 30) provides a line (100, 101) which is opposite the corresponding injection opening (41, 42) in the mold cavity (23) opens, and in the interior of these lines (100, 101) each have a piston (102, 103) which the mold cavity (23) closes off towards the lines (100, 101) and which is movable between an injection position and a withdrawn position related to on the injection position, behind this, and that the pistons (102, 103) during stages b) and c) in the injection position and after step c) and during said re-injection in FIG holds withdrawn position. 7234