JP4410602B2 - Hot runner mold for sandwich molding and sandwich molding method using the same - Google Patents

Description

  The present invention relates to a hot runner mold used in an injection molding machine, and in particular, at the time of sandwich molding in which a skin layer is formed with one resin and a core layer is formed with the other resin using two kinds of resins. According to the hot runner mold used. The present invention also relates to a sandwich molding method using such a hot runner mold.

  8 and 9 show an example of a conventional mold for sandwich molding (Patent Document 1).

  The mold shown in FIG. 8 includes a gate 77, a first hot runner 71, a second hot runner 72, a valve chamber 73, a valve body 74, and the like. A valve chamber 73 is provided in front of the gate 77, and a valve body 74 is accommodated in the valve chamber 73. A flow path 75 is formed at the center of the valve body 74, and an annular flow path 76 is formed between the inner peripheral surface of the valve chamber 73 and the outer peripheral surface of the valve body 74. The resin flow path that allows the annular flow path 76 and the gate 77 to communicate with each other can be opened and closed by the advancement and retreat of the valve element 74. FIG. 8 shows a state in which the valve body 74 has advanced to block the flow path.

  In the sandwich molding procedure, first, as a first operation, a skin resin is supplied to the first hot runner 71 and injected from the gate 77 to the cavity 78 through the annular flow path 76 to form a skin layer. Next, as a second operation, the core resin is supplied to the second hot runner 72 while continuing to inject the skin resin (or the injection is stopped), and from the gate 77 to the cavity 78 via the flow path 75. The core layer is formed inside the already formed skin layer by injection.

  FIG. 8 shows a state at the time when the second operation is almost finished. By pushing the valve body 74 forward and pressing it against the seat surface 73a, the space between the annular flow path 76 and the gate 77 is blocked. Only resin for injection is injected.

  Finally, the injection of the core resin is stopped as a third operation, and the injection of the skin resin is continued (or restarted), and only the skin resin is passed through the hot runner 71 and the annular flow path 76 to the cavity 78. The mold is filled with the resin in a state where the entire outer surface of the molded product is covered with the resin for skin, and the injection process is completed.

  In the third operation of the mold shown in FIG. 8, the valve body 74 is retracted and the skin resin is supplied from the annular flow path 76. Since this resin flows to both the gate 77 and the flow path 75, it is difficult to reliably flow the skin resin into the cavity 7 and cover the gate with the skin resin unless the flow into the flow path 75 is restricted. Become. Therefore, in this case, it is necessary to provide a backflow prevention mechanism on the nozzle side of the forming machine upstream from the mold. On the other hand, in the modification shown in FIG. 9, by providing a valve body 79 in the flow path 75 at the center of the valve body 74, it is possible to block the flow path of the core resin. Yes.

  Here, the third operation for injecting only the skin resin at the end is an operation for covering the entire outer surface of the part with the skin resin. At the same time, the skin in the hot runner mold for sandwich molding is used. This also serves as a cleaning operation in which the core resin remaining in the flow path downstream from the joining portion of the resin for the core and the resin for the core is replaced with the resin for the skin. If the core resin remains in this part, when only the skin resin is injected in the first operation in the next molding cycle, the remaining core resin is mixed into the skin layer, and the color mixture portion Will cause molding defects.

  A conventional hot runner mold for sandwich molding does not have a function of blocking the flow path to the gate alone. In the case of the mold shown in FIGS. 8 and 9, the third operation is performed with the flow path to the gate 77 open until the end. Therefore, in order to prevent such molding defects due to the occurrence of the color mixture portion, the third operation is performed. In order to secure a sufficient amount of the resin for skin to be injected in this operation, it was necessary to set molding conditions that increased the resin. However, when molded under such conditions, the skin resin not only covers the surface of the gate portion, but further enters the core layer to form a five-layer portion in the vicinity of the gate.

For this reason, in sandwich molding under the molding conditions as described above, not only the filling ratio of the core layer cannot be increased, but also the skin resin is press-fitted into the almost full mold at high pressure in the final stage. In addition, the skin resin wraps a part of the already formed skin layer inside the core, and as a result, the skin layer of the surface layer portion is thinned so that the core resin can be easily seen from the outside. It was.
Japanese Patent Laid-Open No. 04-316818

  The present invention has been made to solve the above-described problems in conventional sandwich molding, and the object of the present invention is to provide a skin resin and a core resin immediately before the gate at the final stage of sandwich molding. A mold that can perform a cleaning operation for replacing the resin for the core remaining in the flow path downstream from the junction with the resin for the skin separately from the operation for filling the resin for the skin into the cavity of the mold, and An object of the present invention is to provide a sandwich molding method using this.

The hot runner mold for sandwich molding of the present invention is
A hot runner mold for performing sandwich molding using the first and second resins,
A gate opening in the cavity inner wall;
A valve chamber provided upstream of the gate;
A rod-shaped valve body that is housed in the valve chamber and opens and closes the gate by moving in the axial direction in the valve chamber;
A first port and a second port that open to the inner peripheral surface of the valve chamber;
A first sprue and a second sprue provided on the back of the mold,
The first runner from the first sprue to the first port,
A second runner from the second sprue to the second port,
Have
In the part adjacent to the tip of the valve body, an annular first flow path is formed between the outer peripheral surface of the valve body and the inner peripheral surface of the valve chamber,
Inside the valve body, a second flow path is formed that opens from the side surface of the valve body to the tip through the inside and opens to the valve chamber at a position offset from the central axis of the gate,
When the valve body is in the retracted position, the gate is opened and at the same time the first port is connected to the first flow path, thereby forming a flow path to the gate through the first port, the first flow path, and the valve chamber, Furthermore, the second port is connected to the second flow path, thereby forming a flow path to the gate through the second port, the second flow path, the valve chamber,
When the valve body is in the forward position, the valve is connected to the first port, the flow path leading to the valve chamber via the first flow path, and the flow path leading to the valve chamber via the second port, second flow path. The tip of the body is inserted into the gate and is formed so as to block the flow path to the cavity.

  Using the above hot runner mold for sandwich molding, sandwich molding can be performed as follows.

  In the above procedure, when the core resin is supplied from the second flow path into the mold, the operation of supplying the skin resin can be stopped.

  As described above, in the hot runner mold for sandwich molding of the present invention, even when the gate is closed, the skin resin flow path and the core resin flow path are connected upstream of the gate. Therefore, by closing the gate when the resin is filled in the cavity, the core resin remaining in the flow path downstream from the joining point of the skin resin and the core resin immediately before the gate is replaced with the skin resin. The cleaning operation can be performed separately from the operation of filling the skin resin into the cavity.

  Furthermore, by configuring the rod-shaped valve body so that the rotation angle around the axis can be switched in the valve chamber, the flow path in the mold can be switched as described below.

  That is, when the valve body is in the retracted position at the first rotation angle, the gate is opened, and at the same time, the first port is connected to the first flow path, whereby the gate passes through the first port, the first flow path, and the valve chamber. The second port is connected to the second flow path, thereby forming a flow path to the gate through the second port, the second flow path, and the valve chamber.

  When the valve body is in the forward position at the first rotation angle, the flow path leading to the valve chamber via the first port and the first flow path and the flow path reaching the valve chamber via the second port and the second flow path are connected. The tip of the valve body is inserted into the gate while the state is kept, and the flow path to the mold is closed.

  On the other hand, when the valve body is in the retracted position at the second rotation angle, the gate is opened and the second port is connected to the first flow path, whereby the second port, the first flow path, the valve chamber The first port is connected to the second flow path through the first port, the second port, and the flow path to the gate through the first port, the second flow path, and the valve chamber.

  When the valve body is in the forward position at the second rotation angle, the flow path reaching the valve chamber via the second port and the first flow path is connected to the flow path reaching the valve chamber via the first port and the second flow path. The tip of the valve body is inserted into the gate while the state is kept, and the flow path to the cavity is closed.

  If the rod-shaped valve body is configured in this way, it is possible to easily switch between the following two injection modes by switching the rotation angle around the axis of the valve body.

  That is, in the first mode, the skin resin is supplied into the cavity through the first runner, the first port, and the first flow path, and the core resin is supplied to the second runner, the second port, and It is supplied into the cavity through the second flow path.

  On the other hand, in the second mode, the skin resin is supplied into the cavity through the second runner, the second port, and the first flow path, and the core resin is supplied to the first runner, the first It is supplied into the cavity through one port and the second flow path.

  In the hot runner mold for sandwich molding of the present invention, a plurality of on-off valves composed of the valve body and the valve chamber may be provided. In that case, it is possible to finely adjust the cross-sectional structure of the sandwich molded product by appropriately setting the timing of the operation of moving the valve body of each on-off valve to the retracted position and the operation of moving to the forward position for each on-off valve. It becomes possible.

  According to the hot runner mold for sandwich molding of the present invention, the core filling rate of the sandwich molded product can be increased and the appearance quality can be increased.

(First example)
FIGS. 1 to 4 show an example of a hot runner mold for sandwich molding according to the present invention. Here, FIG. 1 is a cross-sectional view including the central axis of the mold, FIG. 2 is a cross-sectional view of the AA portion of FIG. 1, and FIGS. 3 and 4 are partial enlarged cross-sectional views of the gate portion and the on-off valve. In the figure, 1 is a first sprue, 2 is a second sprue, 3 is a first runner, 4 is a second runner, 6 is a gate, 7 is a cavity, 10 is an on-off valve, 11 is a valve chamber, 13 is a valve body, Reference numeral 17 denotes a first flow path, 18 denotes a second flow path, 27 denotes a first port, and 28 denotes a second port.

  The hot runner mold is formed by superposing four plates 21 to 24 and includes two sprues 1 and 2 and two runners 3 and 4. In this example, the first sprue 1 and the second sprue 2 are formed on the right surface of the plate 21, the gate 6 is formed on the left surface of the plate 23, and the cavity 7 is formed between the left surface of the plate 23 and the right surface of the plate 24. ing.

  An on-off valve 10 is provided adjacent to the gate 6 and upstream thereof. The on-off valve 10 includes a valve chamber 11, a rod-shaped valve body 13, a hydraulic actuator 15, and the like. The valve chamber 11 is provided inside the plates 23 and 22 and is connected to the back of the gate 6. A valve body 13 is accommodated in the valve chamber 11. The valve body 13 is incorporated in the plates 22 and 23, and the rear end of the valve body 13 is connected to the piston of the actuator 15.

  The first runner 3 penetrates the plate 21 and the plate 22, reaches the left surface of the plate 22, bends sideways, passes through a flow path formed between the left surface of the plate 22 and the right surface of the plate 23, and 11, and is connected between the first sprue 1 and the gate 6.

  Similarly, the second runner 4 passes through the plate 21 and the plate 22, reaches the left surface of the plate 22, bends sideways, and passes through a flow path formed between the left surface of the plate 22 and the right surface of the plate 23. The second sprue 2 and the gate 6 are formed so as to reach the valve chamber 11.

  3 and 4 are partially enlarged cross-sectional views of the gate 6 and the on-off valve 10. As described above, the valve chamber 11 is provided behind the gate 6, and the rod-shaped valve body 13 is accommodated therein. The downstream ends of the first runner 3 and the second runner 4 open to the inner peripheral surface of the valve chamber 11 to form a first port 27 and a second port 28, respectively.

  The shaft portion of the valve body 13 is fitted to the inner peripheral surface of the valve chamber 11, and the distal end portion of the valve body 13 is formed with a smaller diameter than the shaft portion. An annular space is formed between the inner peripheral surfaces. Furthermore, a nose portion 13 a that fits with the gate 6 is formed at the most distal portion of the valve body 13. The first flow path 17 reaches the tip of the valve body 13 through this annular space, and connects the first port 27 and the gate 6. Inside the valve body 13, a second flow path 18 is formed from the side surface of the valve body 13 to the tip portion. The second flow path 18 includes an opening 18a extending from the side surface of the valve body 13 to the central axis thereof, a hole-shaped flow path 18b passing through the central axis of the valve body 13, and the nose portion at a position offset from the central axis. The small-diameter flow path 18c opened near 13a is connected in order, and the second port 28 and the gate 6 are connected. 3 and 4 (cross-sectional views), only one small-diameter channel 18c is illustrated, but a plurality of small-diameter channels 18c are arranged in the circumferential direction.

  Here, FIG. 3 shows a state in which the valve body 13 is moved backward by the actuator 15 and the gate 6 is opened. In this state, the first runner 3 is connected to the gate 6 via the first port 27, the first flow path 17 and the valve chamber 11, and the second runner 4 is connected to the second port 28, the second flow path 18 and the valve. It is connected to the gate 6 through the chamber 11.

  On the other hand, FIG. 4 shows a state in which the valve body 13 is advanced by the actuator 15 and the gate 6 is closed. In this state, the nose portion 13 a at the tip of the valve body 13 is inserted into the gate 6 and the gate 6 is closed, but the first runner 3 is connected to the valve chamber 11 via the first port 27 and the first flow path 17. The second runner 4 remains connected to the valve chamber 11 via the second port 28 and the second flow path 18.

  As described above, the gate 6 is closed by inserting the nose portion 13 a at the tip of the valve body 13 into the gate 6. Even in this state, the first runner 3 and the second runner 4 are both connected to the valve chamber 11. As a result, the resin can flow backward from one to the other. That is, this operation enables cleaning in which the resin in the valve chamber 11 is replaced with one resin.

  FIG. 5 shows an outline of the nozzle portion of the injection apparatus to which the above mold is connected. This nozzle includes two nozzle tips 51 and 52. These nozzle chips are connected to a first injection unit 55 and a second injection unit 56, respectively, via a connecting block 54. Inside the connection block 54, a flow path 57 for sending the first molten resin from the first injection unit 55 to the first nozzle chip 51, and a second from the second injection unit 56 to the second nozzle chip 52. A flow path 58 for feeding the molten resin is provided.

  A first injection unit 55 is connected to the first sprue 1 (FIG. 1) of the hot runner mold for sandwich molding via the first nozzle tip 51, and the first sprue 2 (FIG. 1) is connected to the first sprue 2 (FIG. 1). A second injection unit 56 is connected via the second nozzle tip 52.

  Next, the procedure for sandwich molding by connecting the injection apparatus shown in FIG. 5 to the mold shown in FIGS.

  First, the valve body 13 is retracted (FIG. 3), the first injection unit 55 (FIG. 5) is activated, and the skin resin is introduced from the first sprue 1 into the mold (first operation). This operation corresponds to an operation of opening a valve gate of a hot runner mold for molding only one ordinary resin and starting injection. The skin resin flows into the cavity 7 through the first sprue 1, the first runner 3, the first port 27, the first flow path 17 and the gate 6. The skin resin contacts the inner surface of the cavity 7 and is cooled to form a skin layer (solidified layer on the surface).

  At this time, even if the second flow path 18 and the second runner 4 are connected to each other, the backflow prevention valve provided on the second injection unit 56 side or the screw retraction preventing device provides the second skin resin. Is prevented from entering the channel 18 side.

  After a predetermined amount of the resin for skin is fed into the cavity 7, the first injection unit 55 is stopped (or left activated), and the second injection unit 56 (FIG. 5) is started. The core resin is introduced from the second sprue 2 into the mold (second operation). The core resin passes through the second sprue 2, the second runner 4 and the second port 28, enters the second flow path 18 formed in the valve body 13, and then passes through the small diameter flow path 18 c. It enters the front of the body 13 and flows into the cavity 7 through the center of the gate 6.

  The resin that enters the cavity 7 at this stage is already in a molten state because the skin resin previously fed into the cavity 7 has already begun to form a skin layer (solidified layer) by contacting the inner surface of the cavity 7. It will flow through the central part that is kept. As a result, a molded article having a sandwich structure is formed. Further, if the first injection unit 55 remains activated, the skin resin sent from the first flow path 17 is wrapped in the core resin sent from the second flow path 18 from the periphery. 6, the skin resin spreads in the cavity 7 so as to replenish the already formed skin layer, and the core resin flows inside the skin layer to form a core portion, sandwich structure The molded product is formed. If the skin resin is supplied in an amount sufficient to form the skin layer over the entire surface of the molded product, the core resin fed later will break through the skin layer and appear on the surface. Absent.

  Thereafter, the second injection unit 56 is stopped, the first injection unit is restarted (or left activated), and the skin resin is transferred from the first injection unit 55 to the gold through the first sprue 1. Introduce into mold (third action). As a result, only the skin resin is sent into the cavity 7 to completely cover the outside of the molded product.

  After the cavity 7 is filled with the resin, the valve body 13 is moved forward to close the gate 6 (state shown in FIG. 4). This operation is the same as the operation of terminating injection and closing the valve gate with a normal hot runner mold for molding only one resin. In the case of sandwich molding, the skin resin just before the gate and the core resin are merged so that the core resin is not mixed into the skin resin injected in the first operation of the next molding injection process. It is necessary to perform cleaning in which the resin in the portion downstream from the position to be completely replaced with only the skin resin.

  As shown in FIG. 4, even if the nose portion 13 a at the tip of the valve body 13 is inserted into the gate 6 and the flow path to the cavity 7 is shut off, the first runner 3 still has the first port 27 and the first flow path 17. Since the second runner 4 is connected to the valve chamber 11 via the second port 28 and the second flow path 18, the skin resin is transferred to the first injection unit 55 from the first injection unit 55. If the operation of supplying the valve chamber 11 through the sprue 1 is continued, the skin resin flows backward from the valve chamber 11 through the small-diameter channel 18c to the second channel 18 side, and is downstream from the junction of both resins. This resin can be completely replaced with a skin resin. Therefore, even after the gate 6 is closed, the skin resin supply operation is continued for the time required for cleaning, and then the first injection unit 55 is stopped. Thus, one injection process for sandwich molding is completed.

  As described above, since the cleaning operation in the valve chamber 11 is performed separately from the filling of the skin resin into the cavity 7 with the gate 6 closed, a product defect caused by the cleaning operation (i.e., The occurrence of a thinning of the skin layer in the vicinity of the gate, etc.) is prevented, and the core filling rate can be increased.

  Next, it is assumed that the second resin supplied from the second flow path as the core resin is switched to use as the skin resin by using the mold (FIGS. 1 to 4). The situation will be described.

  As described above, the state upstream of the gate 6 at the end of the final injection process before switching is that the cavity 7 is filled with resin, the valve body 13 is advanced, the gate 6 is closed, and then the skin immediately before the gate is used. Cleaning is performed by replacing the resin downstream of the position where the resin and the core resin are merged with only the skin resin, and the skin resin passes through the small-diameter channel 18c from the valve chamber 11 to the second channel 18 side. It is in a state of backflow.

  Therefore, after the switching, first, a discarding operation for discharging the resin flowing back to the second flow path 18 side is necessary. In the molding after the disposal is completed, the second resin newly used for skin flows into the valve chamber 11 from the flow path 18c, and flows into the cavity 7 through the gate 6 (first operation). This comes into contact with the inner surface of the cavity 7 and is cooled to form a second resin skin layer. After a predetermined amount of the resin for skin is fed into the cavity 7, the first injection unit 55 is activated and the first resin to be newly used for the core is introduced from the first flow path 17. The core layer is formed by flowing in the center portion where the molten state is still maintained (second operation). In this case, if the skin resin continues to be supplied from the second flow path 18, it is mixed with the core resin upstream of the gate 6 and does not replenish the skin layer. Stop.

  In the third operation in which only the skin resin is injected to completely cover the outside of the molded product with the skin resin, only the second injection unit 56 is activated again, and the second resin used for the skin is used again. Send. The tip of the valve body 13 at this time is filled with the first resin introduced as the core resin introduced in the previous second operation, and a plurality of small area flows are contained therein. The second resin is sent from the path 18c. The resin sent from the gate 6 to the cavity 7 is replaced only with the second resin, but the first resin used for the core is completely in the valve chamber 11 at the tip of the valve body 13. It cannot be eliminated and remains.

  After the cavity 7 is filled with the resin, the valve body 13 is advanced to close the gate 6, and the resin in the downstream portion from the joint portion of both resins in the valve chamber 11, which is the final step of the third operation, is used as the skin resin. The replacement cleaning operation is a flow from the plurality of small-diameter flow paths 18c to the large cross-sectional flow path 17, so that the remaining core resin completely flows back to the flow path 17 side over the entire cross-sectional area. It cannot be excluded.

  Since this phenomenon is repeated throughout each injection process, it is impossible to prevent the core resin from being mixed in the skin layer injected at the beginning of the injection process. That is, sandwich molding using the second channel side for the skin is impossible, and in this embodiment, molding for replacing the skin resin and the core resin cannot be performed.

(Second example)
6 and 7 show another example of a hot runner mold for sandwich molding according to the present invention. These drawings are enlarged sectional views of the gate 6 and the on-off valve 10. In addition, this metal mold | die is the same as the metal mold | die previously shown in FIGS. 1-4 except having added the mechanism for rotating the valve body 13. As shown in FIG. Accordingly, a cross-sectional view including the entire mold is omitted, and common constituent elements are denoted by the same reference numerals and description thereof is omitted.

  In the figure, 35 represents a rotation actuator, 36 represents a rack, and 37 represents a pinion. In the mold shown in this example, the rotation actuator 35 is operated, and the rotation angle around the axis of the valve body 13 can be switched by 180 degrees via the rack 36 and the pinion 37.

  FIG. 6 shows a state in which the rotation angle of the valve body 13 is at the first angle and the valve body 13 is in the retracted position. This state represents the same state as FIG. 3 described above. In this state, the gate 6 is opened, and at the same time, the first port 27 is connected to the first flow path 17, and the second port 28 is connected to the first port 28. It leads to the two flow paths 18. Thus, the first sprue 1, the first runner 3, the first port 27, the first flow path 17, the flow path to the gate 6 through the valve chamber 11, the second sprue 2, the second runner 4, the second A flow path reaching the gate 6 through the port 28, the second flow path 18 and the valve chamber 11 is formed.

  If the valve body 13 is moved to the forward position while the rotation angle of the valve body 13 is fixed in this state, the same state as in FIG. 4 is obtained, and the nose portion 13a at the tip of the valve body 13 is inserted into the gate 6. The first runner 3 is connected to the valve chamber 11 via the first port 27 and the first flow path 17, and the second runner 4 is connected to the valve via the second port 28 and the second flow path 18. The state connected to the chamber 11 is maintained.

  FIG. 7 shows a state where the rotation angle of the valve body 13 is at the second angle and the valve body 13 is in the retracted position. In this state, the gate 6 is opened, and at the same time, the second port 28 is connected to the first flow path 17, and the first port 27 is connected to the second flow path 18. As a result, the second sprue 2, the second runner 4, the second port 28, the first flow path 17 and the flow path to the gate 6 through the valve chamber 11, the first sprue 1, the first runner 3, and the first port. 27, a flow path to the gate 6 through the second flow path 18 and the valve chamber 11 is formed.

  When the valve body 13 is moved to the forward position while the rotation angle of the valve body 13 is fixed in this state, the nose portion 13a at the tip of the valve body 13 is inserted into the gate 6 and the gate 6 is closed. 3 is connected to the valve chamber 11 via the first port 27 and the second flow path 18, and the state where the second runner 4 is connected to the valve chamber 11 via the second port 28 and the first flow path 17 is maintained.

  By using such a mold, sandwich molding in which the skin resin and the core resin are exchanged, which was impossible in the previous example (FIGS. 1 to 4), becomes possible. In the following, the sandwich resin that used the first resin supplied from the first runner 3 for the skin and the second resin supplied from the second runner 4 for the core was finished, and the skin resin was used. And a method for replacing the core resin, that is, a sandwich in which the second resin supplied from the second runner 4 is used for skin and the first resin supplied from the first runner 3 is used for core A method for switching to molding will be described.

  The state upstream of the gate 6 at the end of the final injection process before switching is that only the first resin that has been used as a skin until then is valved from the first runner 3 through the first port 27 and the first flow path 17. From the state sent to the tip of the body 13 (the state of FIG. 6), the valve body 13 is advanced, the nose portion 13a is fitted to the gate 6 and the gate is closed, and then the skin resin and core immediately before the gate Cleaning is performed by replacing the resin in the downstream portion from the position where the resin for the resin joins with only the resin for the skin, and the skin resin flows backward from the valve chamber 11 to the second channel 18 side via the small-diameter channel 18c. It is in a state.

  In the first injection process after switching, the valve body 13 is moved backward (state shown in FIG. 6), and before the second injection unit 56 is activated, the rotation actuator 35 is operated to rotate the valve body 13 180 degrees. Let Thus, the second port 28 is connected to the first flow path 17 (state shown in FIG. 7). Thereafter, the second injection unit 56 is activated, and the second resin newly used for the skin is supplied to the gate 6 via the second runner 4, the second port 28, and the first flow path 17. Supply (first operation).

  At this time, the first flow path 17 includes the first resin used for the skin in the previous sandwich molding (the amount supplied in the last half of the final third operation and the valve body at the start of this injection). When 13 is retracted, the amount of leakage from the small-diameter flow path 18c remains, but these are discharged when the skin resin is injected for the first time. Therefore, the first molded product after switching is defective molding in which the core resin is mixed in the skin layer, but from the second molding, molding using only the second resin as the skin layer is possible.

  Therefore, while continuing this molding, the resin used for the core to be charged into the first injection unit is switched from the first resin to the third resin, and the first runner 3 and the second resin in the mold are switched. After all of the resin in the flow path 18 is replaced with the third resin, the third resin supplied from the first injection unit 55 is used for the skin if the valve body 13 is rotated again to return to the state shown in FIG. The third sandwich used can be performed. In this way, molding can be performed in which the resin is sequentially switched.

  In the case of a mold having a plurality of gates, such as for a large molded product, sandwich molding can be similarly performed by providing an on-off valve corresponding to each gate. At that time, the valve bodies 13 of the on-off valves 10 provided in the respective gates may be operated simultaneously, but depending on the difficulty of resin flow due to the shape, the opening start of the valve body 13 of any on-off valve 10 may be delayed. It is also possible to operate with a time difference so as to speed up the closing start. That is, by setting at least one of the operation timing for retreating the valve body and the operation for advancing the valve body, a deviation in the arrival timing of the resin flowing inside the cavity 7 to the flow end is determined. Can be reduced, molding defects can be reduced, and the core filling rate of sandwich molding can be increased.

The figure which shows an example of the hot runner metal mold | die for sandwich molding of this invention AA section sectional view of the mold shown in FIG. Enlarged sectional view of the mold gate and on-off valve shown in FIG. 1 (with the gate open) Enlarged sectional view of the mold gate and on-off valve shown in FIG. 1 (with the gate closed) The figure which shows the outline | summary of the injection apparatus connected to the hot runner metal mold | die for sandwich molding of this invention Partial expanded sectional view which shows the other example of the hot runner metal mold | die for sandwich molding of this invention (state of the 1st rotation angle) Partial expanded sectional view which shows the other example of the hot runner metal mold | die for sandwich molding of this invention (state of a 2nd rotation angle) Sectional drawing which shows an example of the conventional hot runner metal mold | die FIG. 8 is an enlarged cross-sectional view showing a modification of the hot runner mold shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st sprue, 2 ... 2nd sprue, 3 ... 1st runner, 4 ... 2nd runner, 6 ... gate, 7 ... cavity, 10 ... on-off valve 11 ... Valve chamber, 13 ... Valve body, 13a ... Nose part, 15 ... Actuator, 17 ... First flow path, 18 ... Second flow path, 18a ... Opening Part, 18b ... hole-like flow path, 18c ... small diameter flow path, 21, 22, 23, 24 ... plate, 27 ... first port, 28 ... second port, 35・ ・ ・ Rotation actuator, 36 ・ ・ ・ Rack, 37 ・ ・ ・ Pinion, 51 ・ ・ ・ First nozzle tip, 52 ・ ・ ・ Second nozzle tip, 54 ・ ・ ・ Connection block, 55 ・ ・ ・First injection unit, 56 ... second injection unit, 57, 58, 75, 76 ... flow path, 71 ... One hot runner, 72 ... second hot runner, 73 ... valve chamber, 73a ... seat surface, 74 ... valve body, 75 ... through hole, 76 ... annular flow path, 77 ... Gate, 78 ... Cavity, 79 ... Valve.

Claims (7)

A hot runner mold for performing sandwich molding using the first and second resins,
A gate opening in the cavity inner wall;
A valve chamber provided upstream of the gate;
A rod-shaped valve body that is housed in the valve chamber and opens and closes the gate by moving in the axial direction in the valve chamber;
A first port and a second port that open to the inner peripheral surface of the valve chamber;
A first sprue and a second sprue provided on the back of the mold,
The first runner from the first sprue to the first port,
A second runner from the second sprue to the second port,
Have
In the part adjacent to the tip of the valve body, an annular first flow path is formed between the outer peripheral surface of the valve body and the inner peripheral surface of the valve chamber,
Inside the valve body, a second flow path is formed that opens from the side of the valve body to the tip through the inside and opens to the valve chamber at a position off the central axis of the gate,
When the valve body is in the retracted position, the gate is opened and at the same time the first port is connected to the first flow path, thereby forming a flow path to the gate through the first port, the first flow path, and the valve chamber, Furthermore, the second port is connected to the second flow path, thereby forming a flow path to the gate through the second port, the second flow path, the valve chamber,
When the valve body is in the forward position, the valve is connected to the first port, the flow path leading to the valve chamber via the first flow path, and the flow path leading to the valve chamber via the second port, second flow path. A hot runner mold for sandwich molding, characterized in that the tip of the body is inserted into a gate to close the flow path to the cavity. A hot runner mold for performing sandwich molding using the first and second resins,
A gate opening in the cavity inner wall;
A valve chamber provided upstream of the gate;
A rod-shaped valve body that is housed in the valve chamber, opens and closes the gate by moving in the axial direction in the valve chamber, and can switch the rotation angle around the axis in the valve chamber;
A first port and a second port that open to the inner peripheral surface of the valve chamber;
A first sprue and a second sprue provided on the back of the mold,
The first runner from the first sprue to the first port,
A second runner from the second sprue to the second port,
Have
In the part adjacent to the tip of the valve body, an annular first flow path is formed between the outer peripheral surface of the valve body and the inner peripheral surface of the valve chamber,
Inside the valve body, a second flow path is formed that opens from the side of the valve body to the tip through the inside and opens to the valve chamber at a position off the central axis of the gate,
When the valve body is in the retracted position at the first rotation angle, the gate is opened, and at the same time, the first port is connected to the first flow path, thereby reaching the gate through the first port, the first flow path, and the valve chamber. A flow path is formed, and the second port is connected to the second flow path, thereby forming a flow path that reaches the gate through the second port, the second flow path, and the valve chamber,
When the valve body is in the forward position at the first rotation angle, the flow path leading to the valve chamber via the first port and the first flow path and the flow path reaching the valve chamber via the second port and the second flow path are connected. The tip of the valve body is inserted into the gate and the flow path to the flow path to the cavity is blocked,
When the valve body is in the retracted position at the second rotation angle, the gate is opened, and at the same time, the second port is connected to the first flow path, thereby reaching the gate through the second port, the first flow path, and the valve chamber. A flow path is formed, and further, the first port is connected to the second flow path, thereby forming a flow path that reaches the gate through the first port, the second flow path, and the valve chamber,
When the valve body is in the forward position at the second rotation angle, the flow path reaching the valve chamber via the second port and the first flow path is connected to the flow path reaching the valve chamber via the first port and the second flow path. A sandwich-molding hot runner mold characterized in that the tip of the valve body is inserted into the gate and the flow path to the cavity is closed while the state is maintained. A method for performing sandwich molding using the hot runner mold for sandwich molding according to claim 1 or 2,
First, the valve body is moved to the retracted position, and the skin resin is supplied from the first flow path into the cavity.
Next, while continuing the operation of supplying the skin resin, the core resin is supplied from the second flow path into the cavity,
Next, while continuing the operation of supplying the skin resin, the supply of the core resin is stopped,
After the cavity is filled with resin, the valve body is moved to the forward position and the gate is closed while continuing the operation of supplying the skin resin.
In this state, after the skin resin is caused to flow backward from the first flow path to the end of the second flow path, the supply of the skin resin is stopped. A method for performing sandwich molding using the hot runner mold for sandwich molding according to claim 1 or 2,
First, the valve body is moved to the retracted position, and the skin resin is supplied from the first flow path into the cavity.
Next, the operation of supplying the skin resin is stopped, and the core resin is supplied from the second flow path into the cavity.
Next, the supply of the core resin is stopped and the operation of supplying the skin resin is resumed.
After the cavity is filled with resin, the valve body is moved to the forward position and the gate is closed while the operation of supplying the skin resin is continued.
In this state, after the skin resin is caused to flow backward from the first flow path to the end of the second flow path, the supply of the skin resin is stopped. A method for performing sandwich molding using the hot runner mold for sandwich molding according to claim 2, comprising:
By switching the rotation angle around the axis of the valve body between the first rotation angle and the second rotation angle,
The skin resin is supplied into the cavity through the first runner, the first port, and the first flow path, and the core resin is supplied into the cavity through the second runner, the second port, and the second flow path. The first mode to supply,
Resin for skin is supplied into the cavity through the second runner, the second port and the first flow path, and the resin for core is supplied into the cavity through the first runner, the first port and the second flow path. A second mode of supply;
A sandwich molding method characterized by switching between the two.   The hot runner mold for sandwich molding according to claim 1 or 2, comprising a plurality of on-off valves composed of the valve body and the valve chamber.   A sandwich molding method using the sandwich molding hot runner mold according to claim 6, wherein the plurality of on-off valves are moved to a retracted position and to an advanced position. A sandwich molding method characterized in that at least one of the operation timings is arbitrarily set so that the plurality of on-off valves can operate with a time difference.

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