JP2005138414A - Hot runner mold for sandwich molding and sandwich molding method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot runner mold for sandwich molding having a simple constitution as compared with a conventional mold and constituted so as to prevent the leakage of a molten resin from a gate after a molded product is taken out. <P>SOLUTION: This hot runner mold for sandwich molding is constituted so as to perform sandwich molding using first and second resins and equipped with the gate 6, a valve chamber 11, a rod-shaped valve disc 13, first and second runners 3 and 4 and first and second ports 27 and 28. An annular first flow channel 17 is formed between the outer peripheral surface of the valve disc 13 and the inner peripheral surface of the valve chamber 11 and a second flow channel 18 is formed in the valve disc 13. This second flow channel 18 is opened to the valve chamber 11 at the leading end part of the valve disc 13 being a position offset from the center axis and, when the valve disc 13 is allowed to retreat, the gate 6 is opened and the first port 27 is connected to the first flow channel 17 while the second port 28 is connected to the second flow channel 18. When the valve disc 13 is allowed to advance, the gate 6 is closed and the first port 27 is closed by the side surface of the valve disc 13 while the terminal of the second flow channel 18 is closed by a sheet surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hot runner mold used in an injection molding machine, and in particular, not only two types of resins (for example, combinations of different types of resins such as polystyrene and polyethylene, but also the same resin may have different colors). The same is applied to the hot runner mold used in sandwich molding in which the skin layer is formed with one resin and the core portion is formed with the other resin. 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.

  In normal sandwich molding, the core resin is injected from the center of the gate 77 into the cavity 7 through the second hot runner 72 and the flow path 75. The skin resin is injected into the cavity 78 from the peripheral portion of the gate 77 through the first hot runner 71 and the annular flow path 76. By pressing the valve element 74 against the seat surface 73a, the flow path (ring-shaped flow path 76) of the resin for skin can be blocked (the state shown in FIG. 8).

  However, in this mold, the core resin flow path (flow path 75) is not blocked. Therefore, the phenomenon that the core resin leaks from the gate 77 after the molded product is taken out cannot be prevented.

  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. However, this mold requires two drive means to drive the valve body 74 and the valve body 79, so that the structure becomes complicated and large, and the blocked resin flow path for the core Since the amount of resin remains in the part downstream from the blocking point, that is, in the path from the valve element 79 to the gate 77, the phenomenon that the resin leaks out from the gate 77 after the molded product is taken out is completely prevented. There was a problem that could not be done.

  In addition, as a method to increase the productivity of sandwich molding, when molding of the required production volume is completed, the second resin that has been used for the core until then is used as the resin for the skin. In the meantime, the first resin that was used for the skin until then is used as the core, and the first resin is changed to the third resin in the resin flow path, Sandwich molding is continued, and after the resin replacement is completed, a third molded product is produced by switching the third resin used for the core in the second molded product to be used as a skin resin. Continuous automatic resin change (color change) molding is performed, but this is not possible with a hot runner mold.

  In addition, the operation | movement which changes resin with the metal mold | die shown in FIG.8 and FIG.9 is as follows.

  In the final state of each injection process, the injection of the core resin is stopped and only the skin resin is injected so that the core resin is not mixed in the skin layer injected at the beginning of the next injection process.

  Accordingly, the first resin injected from the first hot runner 71 is used for the skin, and the second resin injected from the second hot runner 72 is used for the core. When switching to sandwich molding using the second resin for skin, the first resin is filled between the flow path 76, the tip of the valve body 74 and the valve chamber 73, and the downstream end of the flow path 75 is discharged. After returning to the reverse flow state, the valve element 74 is pressed against the seat surface 73a to block the skin resin flow path (annular flow path 76). At this time, the resin between the front end of the valve element 74 and the seat surface 73a is pushed out to both the flow path 76 and the flow path 75 side, but since it is all skin resin, there is no problem. Since the first resin is mixed only in the downstream end outlet portion of the flow path 75, the second resin existing in the second hot runner 72 and the flow path 75 can be obtained by performing cleaning for discharging the resin in this portion. Can be used for the skin layer.

  However, the injection process after switching to use the second resin for the skin is the state near the gate at the end of the injection process in which only the skin resin is injected by stopping the injection of the core resin in the final stage In other words, the second resin flows back into the flow path 75, between the tip of the valve body 74 and the valve chamber 73 and to the flow path 76. At this time, the cross-sectional area between the tip of the valve element 74 and the valve chamber 73 and the flow path 76 is larger than the cross-sectional area of the downstream end outlet of the flow path 75, and the flow spreads over the entire circumference in the circumferential direction. Since it is a road, it does not flow over the entire circumference but flows partially, and the first resin and the second resin remain mixed on the distal end surface of the valve body 74. In such a state, when the valve body 74 is pressed against the seat surface 73a, the resin in which the first resin and the second resin existing between the tip of the valve body 74 and the seat surface 73a are mixed together is the flow path 76 and the flow path. It will be pushed to both sides.

In such a state, the first resin (or the mixture of the first resin and the third resin) is used as the skin resin (second resin) injected from the flow path 75 in the first operation of the next injection step. Resin) is mixed, resulting in molding defects. Since this flow behavior is repeated every shot, sandwich molding in which the resin injected from the second hot runner 72 and the flow path 75 is used for the skin cannot eliminate the mixing of the core resin in the skin layer, It is inevitable that the molding will be defective.
Japanese Patent Laid-Open No. 04-316818

  The present invention has been made in view of the problems of the conventional sandwich molding hot runner mold as described above, and the object of the present invention is to have a simple configuration as compared with the conventional sandwich molding hot runner mold. An object of the present invention is to provide a hot runner mold for sandwich molding in which molten resin does not leak from the gate after the molded product is taken out.

  Furthermore, an object of the present invention is to provide a hot runner mold for sandwich molding that can be continuously and automatically replaced with resin in the same manner as a normal cold runner mold.

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 moves in the axial direction in the valve chamber to open and close the gate;
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 portion 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, and the valve chamber,
When the valve body is in the forward position, the first port is closed at the side of the valve body, and the tip of the valve body is inserted into the gate so that the first flow path and the second flow path are closed simultaneously. It is characterized by being.

When sandwich molding is performed using the above mold, the valve body is operated as follows:
That is, first, the valve body is moved to the retracted position, and the skin resin is supplied from the first flow path into the mold. Next, the core resin is supplied from the second flow path into the mold while the operation of supplying the skin resin is continued. Next, the supply of the core resin is stopped while the operation of supplying the skin resin is continued. After the cavity is filled with the resin, the supply of the skin resin is stopped and the valve body is moved to the advanced position to close the gate.

  Alternatively, the supply of the skin resin may be stopped halfway, and only the core resin may be supplied into the mold. In that case, first, the valve body is moved to the retracted position, and the skin resin is supplied from the first flow path into the mold. Next, the supply of the skin resin is stopped, and the core resin is supplied from the second flow path into the mold. Next, the supply of the core resin is stopped and the supply of the skin resin is resumed. After the cavity is filled with the resin, the supply of the skin resin is stopped, and the valve body is moved to the advanced position to close the gate.

  Preferably, the second flow path is configured so as to be always connected to the second port regardless of the position of the valve body in the axial direction.

  Further, preferably, the rod-shaped valve body is configured to be able to switch the rotation angle around the axis in addition to the axial movement in the valve chamber. In that case, the flow path inside the mold is configured as follows.

  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 first port is closed at the side surface of the valve body, and the tip of the valve body is inserted into the gate so that the first flow path and the second flow path are simultaneously It 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. Further, the first port is connected to the second flow path, whereby a flow path reaching the gate through the first port, the second flow path, and the valve chamber is formed.

  When the valve body is in the forward position at the second rotation angle, the second port is blocked by the side surface of the valve body, and the tip of the valve body is inserted into the gate so that the first flow path and the second flow path are simultaneously It is blocked.

  Also in this case, preferably, the second flow path is configured so as to always be connected to the second port regardless of the position of the valve body in the axial direction.

  As described above, when the valve body is configured so that the rotation angle in the valve chamber can be switched, the rotation angle around the axis of the valve body is set to the first rotation angle and the first rotation angle. By switching between the two rotation angles, the skin resin supply path and the core resin supply path can be switched between the first mode and the second mode as follows. That is, in the first mode, the skin resin is supplied into the mold 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 the It supplies in a metal mold | die through a 2nd flow path. On the other hand, in the second mode, the skin resin is supplied into the mold through the second runner, the second port, and the first flow path, and the core resin is supplied to the first runner and the first It supplies in a metal mold | die through a port and said 2nd flow path.

  The hot runner mold for sandwich molding of the present invention has a simple structure as compared with the conventional one. Moreover, according to the hot runner mold for sandwich molding of the present invention, the molten resin does not leak from the gate after the molded product is taken out.

  Further, when the rotation angle around the axis of the valve body can be switched in the valve chamber, the skin resin can be supplied from either the first runner or the second runner. Correspondingly, the core resin can be supplied from either the second runner or the first runner. Accordingly, the skin resin supply source (specifically, the injection unit) and the core resin supply source (specifically, another injection unit) can be arbitrarily replaced. That is, sandwich molding in which the skin resin and the core resin are exchanged at any time is possible, and continuous automatic resin change (color change) becomes possible.

(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 partially enlarged cross-sectional views of the gate 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 is formed so as to reach 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. Further, 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 It is connected to the gate 6 through the valve 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 first port 27 is blocked by the side surface of the valve body 13, and the first runner 3 and the first flow path 17 are blocked. Further, the nose portion 13a at the tip of the valve body 13 is inserted into the gate 6 and the gate 6 is closed, whereby the first flow path 17 and the second flow path 18 are simultaneously blocked.

  In this example, the second runner 4 and the second flow path 18 are always connected regardless of the position of the valve body 13 in the axial direction. Therefore, when the valve body 13 is advanced to close the gate 6, the resin in the valve chamber 11 can be removed by flowing back to the second runner 4 side via the second flow path 18.

  As described above, the first flow path 17 (used as a flow path for the skin resin) and the second flow path 18 (used as a flow path for the core resin) by a single operation of moving the valve body 13 forward. ) Can be closed at the same time. Therefore, it is possible to prevent a phenomenon that the resin remaining in the valve chamber 11 leaks from the gate 6 after the molded product is taken out.

  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 sandwich hot runner mold via a first nozzle tip 51, and a second sprue 2 (FIG. 1) is connected to the second sprue 2 (FIG. 1). The second injection unit 56 is connected via the nozzle tip 52.

  Next, a procedure for performing sandwich molding by connecting the injection apparatus shown in FIG. 5 to the mold shown in FIGS. 1 to 4 will be described.

  First, the valve body 13 is moved backward (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. 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, the second flow of the skin resin is prevented by the backflow prevention valve provided on the second injection unit 56 side or the screw retreat prevention device. Intrusion to the road 18 side is prevented.

  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. 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. If the first injection unit 55 remains activated, the skin resin sent from the first flow path 17 passes through the gate 6 while wrapping the core resin sent from the second flow path 18 from the surroundings. Then, 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, and a sandwich-structure molded product is formed. It 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 55 is started again (or while it is started), and the skin resin is transferred from the first injection unit 55 to the gold through the first sprue 1. Introduce into the mold. 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 resin, the first injection unit 55 is stopped and the valve body 13 is advanced to shield the gate 6. This operation is the same as the operation of terminating injection with a normal hot runner mold for molding only one resin and closing the valve gate, and this is the end of one injection process.

  Next, the situation when it is assumed that the second resin used for the core has been switched to use as the skin resin using the above-described mold (FIGS. 1 to 4) 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 for the skin until then passes from the first runner 3 through the first port 27 and the first flow path 17 to the valve body. In this state, the valve body 13 is moved forward while the nose 13a is fitted to the gate 6 to seal the gate. The first resin removed from the front of the valve body 13 by the advance of the valve body 13 flows back to the second flow path 18 side because the opening 18a is always in communication with the second port 28. Therefore, in the first injection step after switching, the valve body 13 is retracted, the second injection unit is started, and only the second resin that is newly used for skin is injected from the second flow path. The first resin that flows backward is mixed in the downstream end of the second flow path 18, but after this is discharged, only the second resin is allowed to flow.

  At this time, the second resin newly used for the skin flows from the small-diameter flow path 18c near the center of the flow path, but flows into the cavity 7 through the gate 6 as the second flow path 18. Since this is only the second resin supplied from, this is brought into contact with the inner surface of the cavity 7 and cooled to form a skin layer of the second resin. After a predetermined amount of skin resin is fed into the cavity 7, the first injection unit is activated and the first resin to be used for the core is newly introduced from the first flow path 17, and is still in a molten state. The core portion is formed by flowing in the central portion where the above is maintained. In this case, if the skin resin is continuously supplied from the second flow path 18, it is mixed with the core resin upstream of the gate 6 and does not supplement the skin layer, so the second injection unit 56 is stopped.

  In order to completely cover the outside of the molded article with the skin resin, in the final stage of the injection process in which only the skin resin is injected, only the second injection unit 56 is activated again, and the second resin used for the skin is used. Send. At this time, the tip of the valve body 13 is filled with the first resin used as the core resin introduced in the previous step, and the small diameter of the small area close to the center of the flow path Since the second resin is sent from the flow path 18c, the resin sent from the gate 6 to the cavity 7 is replaced with only the second resin. The first resin used for use cannot be completely eliminated and remains. Therefore, when the cavity 7 is filled with the resin and the injection process is finished, the second injection unit 56 is stopped and the valve body 13 is advanced, so that the reverse flow flows into the second flow path 18 through the small diameter flow path 18c. The resin to be used is a mixture of the first resin and the second resin.

  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 flow path side for the skin is impossible, and in the above mold (FIGS. 1 to 4), 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 to FIGS. 1-4 except having added the mechanism for rotating the valve body 13. 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 rotary 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 where 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, the first port 27 is connected to the first flow path 17, and the second port 28 is further connected to the second 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.

  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 first port 27 is blocked by the side surface of the valve body 11 and the nose portion 13a at the tip of the valve body 13 is closed. Inserted into the gate 6, the gate 6 is closed, and the first flow path 17 and the second flow path 18 are simultaneously closed.

  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 second port 28 is closed on the side surface of the valve body 11 and the nose portion 13a at the tip of the valve body 13 is closed. Inserted into the gate 6, the gate 6 is closed, and the first flow path 17 and the second flow path 18 are simultaneously closed.

  By using such a mold, it is possible to perform sandwich molding in which the skin resin and the core resin are exchanged, which is impossible in the previous example (FIGS. 1 to 4). 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 for the skin until then is the valve from the first runner 3 through the first port 27 and the first flow path 17. The valve body 13 is moved forward from the state sent to the distal end portion of the body 13 (the state shown in FIG. 6), and the nose portion 13a is fitted to the gate 6 to seal the gate. At this time, the first resin removed from the front of the valve body 13 by the advancement of the valve body 13 flows back to the second flow path 18 side because the opening 18a is always connected to the second port 28.

  In the first injection step 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 a second resin to be newly used for skin is supplied to the gate 6 via the second runner 4, the second port 28, and the first flow path 17.

  At this time, in the first flow path 17, the first resin used for the skin in the previous sandwich molding (the amount not removed at the time of the final gate seal and the valve body 13 is retracted at the start of this injection). In this case, the portion leaked from the small-diameter flow path 18c remains, but these are removed 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 the molding is continued in this state, the resin used for the core to be put into the first injection unit is switched from the first resin to the third resin, and the first runner 3 in the mold and After all the resin in the second flow path 18 has been replaced with the third resin, the third resin supplied from the first injection unit 55 can be obtained by rotating the valve body 13 again to return to the state shown in FIG. Can be used for the third sandwich molding. 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 arbitrarily setting at least one of the operation of retracting the valve body and the operation of moving the valve body, the arrival timing of the resin flowing inside the cavity 7 to the flow end is shifted. By reducing the number, 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. FIG. 2 is a cross-sectional view of the mold shown in FIG. FIG. 2 is a partially enlarged cross-sectional view of the mold gate and the on-off valve shown in FIG. FIG. 2 is a partially enlarged cross-sectional view of the mold gate and the 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. The 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). The partial expanded sectional view (state of the 2nd rotation angle) which shows the other example of the hot runner metal mold | die for sandwich molding of this invention. Sectional drawing which shows an example of the conventional hot runner metal mold | die. The expanded sectional view which shows the modification of the hot runner metal mold | die 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, and 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 portion 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. In addition, 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, the first port is closed at the side of the valve body, and the tip of the valve body is inserted into the gate so that the first flow path and the second flow path are closed simultaneously. A hot runner mold for sandwich molding characterized by being made.   The hot runner mold for sandwich molding according to claim 1, wherein the second flow path is always connected to the second port regardless of the position of the valve body in the axial direction. A method for performing sandwich molding using the hot runner mold for sandwich molding according to claim 1, comprising:
First, the valve body is moved to the retracted position, and the skin resin is supplied from the first flow path into the mold,
Next, while continuing the operation of supplying the skin resin, the core resin is supplied from the second flow path into the mold,
Next, while continuing the operation of supplying the skin resin, the supply of the core resin is stopped,
After the cavity is filled with the resin, the supply of the skin resin is stopped, and the valve body is moved to the advanced position to close the gate. A method for performing sandwich molding using the hot runner mold for sandwich molding according to claim 1, comprising:
First, the valve body is moved to the retracted position, and the skin resin is supplied from the first flow path into the mold,
Then, the supply of the skin resin is stopped, and the core resin is supplied from the second flow path into the mold,
Next, the supply of the core resin is stopped and the supply of the skin resin is resumed.
After the cavity is filled with the resin, the supply of the skin resin is stopped, and the valve body is moved to the advanced position to close the gate. 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 can be accommodated in the valve chamber, opens and closes the gate by moving in the axial direction in the valve chamber, and switches the rotation angle around the axis in the valve chamber, and opens to the inner peripheral surface of the valve chamber A first port and a second port;
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 portion 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 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. Further, 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 first port is closed at the side surface of the valve body, and the tip of the valve body is inserted into the gate so that the first flow path and the second flow path are simultaneously 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. Further, the first port is connected to the second flow path, thereby forming a 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 second port is blocked by the side surface of the valve body, and the tip of the valve body is inserted into the gate so that the first flow path and the second flow path are simultaneously Being configured to be blocked,
Features hot runner mold for sandwich molding.   The sandwich according to claim 5, wherein the second flow path is always connected to either the first port or the second port regardless of the position of the valve body in the axial direction. Hot runner mold for molding. A method for performing sandwich molding using the hot runner mold for sandwich molding according to claim 5, comprising:
By switching the rotation angle around the axis of the valve body between the first rotation angle and the second rotation angle,
The resin for skin is supplied into the mold through the first runner, the first port, and the first flow path, and the resin for the core is fed through the second runner, the second port, and the second flow path before the gold A first mode for feeding into the mold;
The resin for skin is supplied into the mold through the second runner, the second port, and the first flow path, and the resin for the core is fed through the first runner, the first port, and the second flow path before the gold A second mode for feeding into the mold;
A sandwich molding method characterized by switching between the two.

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