JP2004114614A - Hot runner mold for sandwich molding and sandwich molding method using the mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot runner mold which can be used in sandwich molding. <P>SOLUTION: The mold has two sprues 1 and 2 and two runners 3 and 4. A gate 6 is provided to the inner wall of a cavity 7, and a switching valve 10 is installed adjacent to the gate 6 on the upstream side of the gate 6. The first sprue 1 connects the first sprue 1 and the switching valve 10, and the second sprue 2 connects the second sprue 2 and the switching valve 10. The switching valve 10 has the first position for connecting the first and second runners 3 and 4 simultaneously to the gate 6, the second position for connecting only the first runner 3 to the gate 6 and cutting off the second runner 4 from the gate 6, and the third position for cutting off the first and second runners 3 and 4 simultaneously from the gate 6. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hot runner mold used in an injection molding machine, and particularly to sandwich molding in which two types of resins are used to form a skin layer with one resin and a core with the other resin. The present invention relates to a hot runner mold used for: The present invention also relates to a sandwich molding method using such a hot runner mold.
[0002]
[Prior art]
In the cold runner mold, since the resin solidified in the runner is left on the molded product, it takes time to remove the resin, and there is a problem in the yield of the raw material. In order to solve such a problem, a hot runner mold has been developed. In the hot runner mold, by maintaining the temperature in the runner at a value that keeps the resin in a molten state, it is possible to take out only a molded product without a solidified runner portion. However, since the hot runner mold has a relatively long runner portion, it is difficult to use it for sandwich molding as described later, and only the cold runner mold is used for sandwich molding.
[0003]
FIG. 8 shows an outline of a conventional hot runner mold. The hot runner mold is configured by stacking a plurality of plates 71 to 74. In this example, a sprue 75 is formed on the right surface of the plate 71, a gate 77 is formed on the left surface of the plate 73, and a cavity 78 is formed between the left surface of the plate 73 and the right surface of the plate 74. The runner 76 is formed so as to start from the inside of the plate 71, penetrate the plate 72 and reach the inside of the plate 73, and connects between the sprue 75 and the gate 77. An injection device is connected to the sprue 75.
[0004]
If an injection device 80 for sandwich molding is connected to such a conventional hot runner mold as shown in FIG. 8, the following problem occurs.
[0005]
The injection device 80 for sandwich molding includes a first injection unit 81, a second injection unit 82, a nozzle 83, and the like. The nozzle 83 includes therein a first flow path 84 for feeding the resin for skin and a second flow path 85 for feeding the resin for core. The second flow path 85 is formed on the central axis of the nozzle 83, and the first flow path 84 has an annular cross-sectional shape and is formed so as to surround the periphery of the second flow path 85. The first flow path 84 is connected to the first injection unit 81 on the upstream side, and the second flow path 85 is connected to the second injection unit 82 on the upstream side. The first flow path 84 and the second flow path 85 join immediately before the discharge port of the nozzle.
[0006]
At the time of sandwich molding, first, an appropriate amount of skin resin is injected from the first injection unit 81 into the mold via the first flow path 84. Next, the resin for the skin and the resin for the core are simultaneously injected into the mold through the first flow path 84 and the second flow path 85, respectively. In the state of the two layers, the nozzle 83 feeds the sprue 75 through the discharge port. However, while passing through the relatively long runner 76, the two resins are mixed. For this reason, it was difficult to perform sandwich molding using a conventional hot runner mold.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the problems when sandwich molding is performed using the hot runner mold as described above, and an object of the present invention is to provide a hot runner mold that can be used during sandwich molding. Is to provide a type.
[0008]
[Means for Solving the Problems]
The hot runner mold for sandwich molding of the present invention,
A hot runner mold for performing sandwich molding using two types of resins,
A gate opening on the inner wall of the cavity,
A switching valve provided adjacent to and upstream of the gate;
A first sprue and a second sprue provided on the back of the mold,
A first runner for introducing a first molten resin into the cavity from the first sprue through the switching valve and the gate,
A second runner for introducing a second molten resin from the second sprue into the cavity through the switching valve and the gate,
According to the hot runner mold for sandwich molding of the present invention, a path through which the first molten resin is introduced and a path through which the second molten resin is introduced are each provided with the first runner. And the second runners are individually provided and are joined immediately before the gate, so that the first molten resin and the second molten resin do not mix before reaching the gate. Furthermore, since the switching valve is provided at the junction of the first runner and the second runner, the resin fed into the cavity can be accurately switched, and when the mold is opened after the end of the injection, the molten resin flows from the gate. Can be prevented from leaking out.
[0009]
In the hot runner mold for sandwich molding of the present invention, the gate may be provided at a plurality of locations on the inner wall of the cavity, depending on the size and shape of the product to be molded. In that case, a switching valve is provided adjacent to each gate and upstream thereof.
[0010]
For example, the switching valve can be constituted by first and second opening / closing mechanisms that are driven independently of each other. In that case, the first opening / closing mechanism is provided between the first runner and the gate, and the second opening / closing mechanism is provided between the second runner and the gate.
[0011]
Preferably, a switching valve capable of switching between three positions is used. In that case, at the first position, both the first runner and the second runner are simultaneously connected to the gate. In the second position, only the first runner is connected to the gate, and the second runner is disconnected from the gate. In a third position, both the first runner and the second runner are simultaneously disconnected from the gate.
[0012]
Preferably, the switching valve includes a valve chamber provided on the upstream side of the gate, a rod-shaped valve element housed in the valve chamber, and the like. A downstream end of the first runner and a downstream end of the second runner are opened on the side surface of the valve chamber. The valve body has a first flow path that passes between the outer peripheral surface of the valve body and the side surface of the valve chamber and reaches the distal end of the valve body, and a valve body that passes through the inside of the valve body from the outer peripheral surface of the valve body. A second flow path leading to the tip is formed.
[0013]
In this case, the flow path is switched between the first position, the second position, and the third position by driving the valve body in the front-back direction with respect to the gate in the valve chamber. . Specifically, at the first position, the first runner is connected to the first flow path, and the second runner is connected to the second flow path. In the second position, the state between the second runner and the second flow path is shut off while the first runner is connected to the first flow path. In the third position, both between the first runner and the first flow path and between the second runner and the second flow path are shut off.
[0014]
Alternatively, the switching valve includes a valve chamber provided on the upstream side of the gate, a rod-shaped first valve body housed in the valve chamber and having a through-hole on an axis passing through the center of the gate, and the through-hole. And a rod-shaped second valve body incorporated therein. A downstream end of the first runner and a downstream end of the second runner are opened on the side surface of the valve chamber. The first valve body has a first flow path that reaches between the outer peripheral surface of the first valve body and the side surface of the valve chamber and reaches the tip of the first valve body, A second flow path is formed from the outer peripheral surface to the tip of the first valve body via the through hole.
[0015]
In this case, by driving the first valve body (or the first valve body and the second valve body) in the valve chamber in the front-back direction with respect to the gate, the first position, the first position, The flow path is switched between the second position and the third position. Specifically, at the first position, the first runner is connected to the first flow path, and the second runner is connected to the second flow path. In the second position, the state between the second runner and the second flow path is shut off while the first runner is connected to the first flow path. In the third position, both between the first runner and the first flow path and between the second runner and the second flow path are shut off. Furthermore, the gate can be closed by projecting the second valve body forward from the through hole.
[0016]
Note that, depending on the type of the product to be molded or the method of operating the injection unit connected to the mold, the second position, that is, the first position, among the first, second, and third positions described above. The state where only the runner is connected to the gate may be omitted.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
1 and 2 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, and FIG. In the drawing, 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 a switching valve, 11 is a valve chamber, 12 Represents a valve body.
[0018]
This hot runner mold is configured by stacking 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. Is formed.
[0019]
A switching valve 10 is provided adjacent to and upstream of the gate 6. The switching valve 10 includes a valve chamber 11, a rod-shaped valve body 12, a hydraulic actuator 15, and the like. The valve chamber 11 is provided inside the plate 23 and is connected behind the gate 6. The distal end portion of the valve element 12 is housed in the valve chamber 11. The valve element 12 passes through the plate 22, and the rear end of the valve element is connected to the actuator 15. The actuator 15 is incorporated inside the plate 21 and the plate 22.
[0020]
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, The first sprue 1 and the gate 6 are formed so as to reach the valve chamber 11.
[0021]
Similarly, the second runner 4 penetrates the plate 21 and the plate 22, reaches the left surface of the plate 22, bends laterally, and forms 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 pass through and reach the valve chamber 11.
[0022]
FIG. 3 shows an enlarged cross-sectional view of the gate 6 and the switching valve 10. As described above, the valve chamber 11 is provided behind the gate 6 and houses the distal end portion of the valve element 12 therein. The downstream ends of the first runner 3 and the second runner 4 open to the side surfaces of the valve chamber 11, respectively. A first flow path 17 and a second flow path 18 are formed at the tip of the valve element 12. The first flow path 17 reaches the distal end of the valve body 12 through a gap between the outer peripheral surface of the small diameter portion provided at the distal end of the valve body 12 and the side surface of the valve chamber 11. The second flow path 18 is formed inside the distal end portion of the valve element 12, enters the center of the valve element 12 from the outer peripheral surface of the valve element 12, and reaches the distal end of the valve element 12 through the center of the valve element 12. You.
[0023]
By driving the valve body 12 in the valve chamber 11 in the front-rear direction with respect to the gate 6, the flow path can be switched. In this example, the switching of the flow path is performed between three positions. Here, the state shown in FIG. 3 corresponds to the first position. In the first position, the valve body 12 is at the retreat limit, the first runner 3 is connected to the gate 6 via the first flow path 17 and at the same time the second runner 4 is connected to the second flow path 18 FIG. 4 a, which is connected to the gate 6 via, shows the state in the second position. In the second position, the valve element 12 is in the intermediate position, only the first runner 3 is connected to the gate 6 via the first flow path 17, and the second runner 4 is shut off from the gate 6. FIG. 4b shows the state in the third position. In the third position, the valve body 12 is at the forward limit, and both the first runner 3 and the second runner 4 are simultaneously disconnected from the gate 6.
[0024]
FIG. 5 shows an outline of a nozzle portion of an injection device to which the hot runner mold is connected. This nozzle has two nozzle tips 51 and 52. These nozzle chips are connected to a first injection unit 55 and a second injection unit 56 via a connection block 54, respectively. Inside the connection block 54, a flow path 57 that sends the first molten resin from the first injection unit 55 to the first nozzle chip 51, and a second flow path from the second injection unit 56 to the first nozzle chip 52 A flow path 58 for feeding the molten resin is provided.
[0025]
A first injection unit 55 is connected to the first sprue 1 of the hot runner mold (FIG. 1) via a first nozzle tip 51, and a second nozzle tip 52 is connected to the second sprue 2. The second injection unit 56 is connected via the.
[0026]
Next, a procedure for performing sandwich molding using the hot runner mold shown in FIGS. 1 to 4 will be described.
[0027]
First, the switching valve 10 is set to the second position (FIG. 4A), the first injection unit (55, FIG. 5) is started, and the skin resin is introduced from the first sprue 1 into the mold. The skin resin flows into the cavity 7 through the first runner 3, the first flow path 17, and the gate 6. The resin for skin is cooled by contacting the inner surface of the cavity 7, and a solidified layer (skin layer) is formed on the outer side.
[0028]
After a predetermined amount of the skin resin is fed into the cavity 7, the switching valve 10 is switched to the first position (FIG. 3), the second injection unit (56, FIG. 5) is activated, and the core resin is started. From the second sprue 2 into the mold. Thereby, the resin for the skin continuously flows into the cavity 7, and at the same time, the resin for the core flows into the cavity 7 via the second runner 4, the second flow path 18, and the gate 6.
[0029]
At this time, the core resin enters the cavity 7 from the second channel 18 formed inside the valve body 12, through the valve chamber 11 and the center of the gate 6. On the other hand, the resin for the skin enters the valve chamber 11 from the first flow path 17 formed on the outer periphery of the valve body 12, passes through the gate 6 in a state where the resin for the core is wrapped from the periphery, and enters the cavity 7. . The skin resin is replenished to the already formed skin layer and spreads into the cavity 7. The core resin flows inside the skin layer.
[0030]
As described above, when the core resin enters the cavity 7, the skin resin that has been fed into the cavity 7 first comes into contact with the inner surface of the cavity 7 and has already started to form a solidified layer (skin layer). Then, the core layer resin flows into the central portion where the molten state is still maintained, and a molded article having a two-layer sandwich structure is formed. Therefore, if the resin for the skin is supplied in an amount sufficient to form the skin layer over the entire surface of the molded article, the core resin supplied later will break through the skin layer and appear on the surface. There is no.
[0031]
Thereafter, the switching valve 10 is again switched to the second position (FIG. 4A) to shut off the second flow path, stop the second injection unit (56, FIG. 5), and remove only the resin for the skin. It is introduced into the mold from one sprue 1. Thereby, the resin for skin is replenished into the cavity 7 and completely covers the outside of the molded product.
[0032]
After the cavity 7 is filled with the resin, the switching valve 10 is switched to the third position (FIG. 4B) to shut off the first flow path 17 and stop the first injection unit (55, FIG. 5). I do. This completes one injection step.
[0033]
As a modification of the above method, when injecting the core resin, the injection of the skin resin may be interrupted. In that case, after switching the switching valve 10 to the first position (FIG. 3), the operation of the first injection unit (55, FIG. 5) is stopped. As a result, only the core resin flows into the cavity 7 via the second flow path 18 and the gate 6.
[0034]
Also, as a modification of the above method, only the first injection unit (55, FIG. 5) is activated with the switching valve 10 at the first position (FIG. 3), so that only the skin resin is molded. It can also be sent inside. In that case, the switching valve 10 does not need to have the second position (a state in which only the first runner 3 is connected to the gate 6 and the second runner 4 is shut off from the gate 6). However, also in this case, the switching valve 10 needs to have the third position (the state where both the first runner 3 and the second runner 4 are shut off from the gate 6). The reason is that it is necessary to prevent the resin from leaking from the gate 6 when the mold is opened after the end of the injection step.
[0035]
When a plurality of gates are provided on the inner wall of the cavity, the sandwich molding can be performed in the same manner as described above by simultaneously switching the switching valves provided for the respective gates.
[0036]
However, when the molded product is large and the shape is complicated, the time at which the resin fed from each of the gates reaches the flow end may not be the same for a plurality of gates. In particular, in the case of sandwich molding, it is desirable that the filling of the flow end portions be completed at the same time. Therefore, by providing a timing difference without simultaneously opening and closing a plurality of switching valves, the flow of the resin fed from a plurality of gates can be improved. The filling of the distal end can be adjusted to be completed almost simultaneously.
[0037]
(Example 2)
FIG. 6 shows another example of a hot runner mold for sandwich molding based on the present invention. In the drawing, reference numeral 40 denotes a switching valve, 11 denotes a valve chamber, 42 denotes a first valve body, 43 denotes a through hole, and 44 denotes a second valve body.
[0038]
The rear end of the first valve body 42 is connected to an actuator (not shown), similarly to the valve body 12 in the example (FIGS. 1 to 4) shown earlier. A through hole 43 is provided at the center of the first valve body 42, and a second valve body 44 is incorporated therein. The rear end of the second valve body 44 is connected to another actuator (not shown).
[0039]
The valve chamber 11 is provided behind the gate 6, and houses the distal end portion of the first valve body 42 therein. The downstream ends of the first runner 3 and the second runner 4 open to the side surfaces of the valve chamber 11, respectively. A first flow path 47 and a second flow path 48 are formed at the distal end of the first valve body 42. The first flow path 47 passes through a gap between the outer peripheral surface of the small diameter portion provided at the distal end of the first valve body 42 and the side surface of the valve chamber 11 and reaches the distal end of the first valve body 42. I do. The second flow path 48 is formed inside the distal end portion of the first valve body 42, connects from the outer peripheral surface of the first valve body 42 to the center through hole 43, and connects the center of the first valve body 42. Through to the tip.
[0040]
As in the example shown in FIGS. 1 to 4, the flow path can be switched by driving the first valve body 42 in the valve chamber 11 in the front-rear direction with respect to the gate 6.
In this example, the switching of the flow path is performed between three positions. Here, the state shown in FIG. 6 corresponds to the first position. In the first position, the first valve body 42 and the second valve body 44 are at the retreat limit, and the first runner 3 is connected to the gate 6 via the first flow path 47, and at the same time, the second FIG. 7A in which the runner 4 is connected to the gate 6 through the second flow path 48 shows a state in which the runner 4 is in the second position. In the second position, the first valve body 42 is advanced to the intermediate position while the second valve body 44 is kept at the retreat limit. Thereby, only the first runner 3 is connected to the gate 6 via the first flow path 47, and the second runner 4 is shut off from the gate 6.
[0041]
FIG. 7b shows the state in the third position. In the third position, the first valve body 42 is at the forward limit, and both the first runner 3 and the second runner 4 are simultaneously disconnected from the gate 6. Further, at this time, the gate 6 can be closed from behind by projecting the second valve body 44 forward from the first valve body 42.
[0042]
As described above, by closing the gate 6 from behind using the second valve body 44, it is possible to reliably prevent the resin from leaking from the gate 6 when the mold is opened after the end of the injection process. Can be.
[0043]
As a modification of the above method, in the second position, the second valve body 44 may be advanced to the intermediate position to block the second flow path 48 while the first valve body 42 is kept at the retreat limit. good. Also in this case, only the first runner 3 is connected to the gate 6 via the first flow path 47, and the second runner 4 is shut off from the gate 6.
[0044]
【The invention's effect】
According to the hot runner mold for sandwich molding of the present invention, the path through which the first molten resin is introduced and the path through which the second molten resin is introduced are individually referred to as a first runner and a second runner, respectively. The first molten resin and the second molten resin do not mix before reaching the gate because they are provided and are merged immediately before the gate. In addition, since a switching valve is provided at the junction of the first runner and the second runner, the resin fed into the cavity can be accurately switched, and the molten resin leaks from the gate when the mold is opened after injection. Can be prevented.
[0045]
Therefore, according to the hot runner mold for sandwich molding of the present invention, sandwich molding using a hot runner type mold, which has conventionally been difficult, can be made possible.
[Brief description of the drawings]
FIG. 1 is a view showing an example of a hot runner mold for sandwich molding of the present invention.
FIG. 2 is a sectional view taken along the line AA of the mold shown in FIG.
FIG. 3 is an enlarged sectional view of a gate and a switching valve of the mold shown in FIG. 1;
4A and 4B are diagrams for explaining the operation of the switching valve in the mold shown in FIG. 1, wherein FIG. 4A shows a second position and FIG. 4B shows a third position.
FIG. 5 is a diagram showing an outline of an injection device connected to a hot runner mold for sandwich molding of the present invention.
FIG. 6 is a view showing another example of the hot runner mold for sandwich molding of the present invention.
7A and 7B are diagrams for explaining the operation of the switching valve in the mold shown in FIG. 6, wherein FIG. 7A illustrates a second position and FIG. 7B illustrates a third position.
FIG. 8 is a diagram showing a state in which a conventional sandwich molding injection device is connected to a conventional hot runner mold.
1 ... first sprue, 2 ... second sprue, 3 ... first runner, 4 ... second runner, 6 ... gate, 7 ... cavity, 10 ... ..Switching valve, 11 ... valve chamber, 12 ... valve element, 15 ... actuator, 17 ... first flow path, 18 ... second flow path, 21-24 ... Plate, 40 switching valve, 42 first valve body, 43 through hole, 44 second valve body, 47 first flow path, 48 Second flow path, 51 first nozzle tip, 52 second nozzle tip, 54 connection block, 55 first injection unit, 56 second Injection unit, 57, 58 ... flow path, 71-74 ... plate, 75 ... sprue, 76 ... runner, 77 ... gate, 78 ... cavity 80 ... injection apparatus for sandwich molding, 81 ... first injection unit, 82 ... second injection unit, 83 ... nozzle,
84 ... first flow path, 85 ... second flow path.

Claims (13)

A hot runner mold for performing sandwich molding using two types of resins,
A gate opening on the inner wall of the cavity,
A switching valve provided adjacent to and upstream of the gate;
A first sprue and a second sprue provided on the back of the mold,
A first runner for introducing a first molten resin into the cavity from the first sprue through the switching valve and the gate,
A second runner for introducing a second molten resin from the second sprue into the cavity through the switching valve and the gate,
A hot runner mold for sandwich molding, comprising: 2. The hot runner mold for sandwich molding according to claim 1, wherein the gate is provided at a plurality of locations on the inner wall of the cavity, and a switching valve is provided adjacent to each gate and upstream thereof. 3. The switching valve includes first and second opening / closing mechanisms that are driven independently of each other,
A first opening / closing mechanism is provided between the first runner and the gate,
A second opening / closing mechanism is provided between the second runner and the gate,
The hot runner device for sandwich molding according to claim 1 or 2, wherein: The switching valve,
A first position that connects both the first runner and the second runner to the gate simultaneously and a second position that connects only the first runner to the gate and disconnects the second runner from the gate. location and,
A third position that simultaneously disconnects both the first runner and the second runner from the gate;
The hot runner mold for sandwich molding according to claim 3, comprising: The switching valve includes a valve chamber provided adjacent to and upstream of the gate, and a rod-shaped valve body housed in the valve chamber.
The downstream end of the first runner opens on the side surface of the valve chamber,
The downstream end of the second runner opens to a side surface of the valve chamber,
The valve body has a first flow path that passes between the outer peripheral surface of the valve body and the side surface of the valve chamber and reaches the distal end of the valve body. A second flow path leading to the tip of the body is formed,
The switching valve connects the first runner to the first flow path, connects the second runner to the second flow path at a first position, and connects the first runner to the first flow path. Connected to a flow path, a second position to cut off between the second runner and the second flow path, and cut off between the first runner and the first flow path, the second position A third position to shut off between the runner and the second flow path,
By driving the valve element in the valve chamber in the front-rear direction with respect to the gate, the flow path is switched between the first position, the second position, and the third position. The hot runner mold for sandwich molding according to claim 4, wherein the mold is formed. The switching valve, a valve chamber provided adjacent to and upstream of the gate, a rod-shaped first valve body having a through hole on the axis that is housed in the valve chamber and passes through the center of the gate, A rod-shaped second valve body incorporated in the through hole,
The downstream end of the first runner opens on the side surface of the valve chamber,
The downstream end of the second runner opens to a side surface of the valve chamber,
The first valve body has a first flow path that passes between the outer peripheral surface of the first valve body and the side surface of the valve chamber and that reaches the tip of the first valve body. A second flow path is formed from the outer peripheral surface to the tip of the first valve body through the through hole,
The switching valve connects the first runner to the first flow path, connects the second runner to the second flow path at a first position, and connects the first runner to the first flow path. Connected to a flow path, a second position to cut off between the second runner and the second flow path, and cut off between the first runner and the first flow path, the second position A third position to shut off between the runner and the second flow path,
The flow path is switched between the first position, the second position, and the third position by driving the first valve body in the valve chamber in the front-rear direction with respect to the gate. The hot runner for sandwich molding according to claim 4, wherein the second valve body is configured to protrude forward from the through hole to close the gate. Mold. The switching valve, a valve chamber provided adjacent to and upstream of the gate, a rod-shaped first valve body having a through hole on the axis that is housed in the valve chamber and passes through the center of the gate, A rod-shaped second valve body incorporated in the through hole,
The downstream end of the first runner opens on the side surface of the valve chamber,
The downstream end of the second runner opens to a side surface of the valve chamber,
The first valve body has a first flow path that passes between the outer peripheral surface of the first valve body and the side surface of the valve chamber and that reaches the tip of the first valve body. A second flow path is formed from the outer peripheral surface to the tip of the first valve body through the through hole,
The switching valve connects the first runner to the first flow path, connects the second runner to the second flow path at a first position, and connects the first runner to the first flow path. Connected to a flow path, a second position to cut off between the second runner and the second flow path, and cut off between the first runner and the first flow path, the second position A third position to shut off between the runner and the second flow path,
By driving the first valve body and the second valve body in the valve chamber in the front-rear direction with respect to the gate, between the first position, the second position, and the third position The method according to claim 4, wherein the second valve body is configured to switch forward and to protrude forward from the through hole to close the gate. The hot runner mold for sandwich molding as described. The switching valve,
A first position connecting both the first runner and the second runner to the gate at the same time, and a second position disconnecting both the first runner and the second runner from the gate at the same time,
3. The hot runner mold for sandwich molding according to claim 1, wherein: The switching valve includes a valve chamber provided adjacent to and upstream of the gate, and a valve element housed in the valve chamber.
The downstream end of the first runner opens on the side surface of the valve chamber,
The downstream end of the second runner opens to a side surface of the valve chamber,
The valve body has a first flow path that passes between the outer peripheral surface of the valve body and the side surface of the valve chamber and reaches the distal end of the valve body. A second flow path leading to the tip of the body is formed,
The switching valve connects the first runner to the first flow path, connects the second runner to the second flow path, a first position, the first runner and the first position. Having a second position to shut off between the flow paths and to cut off between the second runner and the second flow path,
The valve body is configured to switch between the first position and the second position by driving the valve body in the valve chamber in the front-rear direction with respect to the gate. The hot runner mold for sandwich molding according to claim 8, wherein The switching valve, a valve chamber provided adjacent to and upstream of the gate, a rod-shaped first valve body having a through hole on the axis that is housed in the valve chamber and passes through the center of the gate, A rod-shaped second valve body incorporated in the through hole,
The downstream end of the first runner opens on the side surface of the valve chamber,
The downstream end of the second runner opens to a side surface of the valve chamber,
The first valve body has a first flow path that passes between the outer peripheral surface of the first valve body and the side surface of the valve chamber and that reaches the tip of the first valve body. A second flow path is formed from the outer peripheral surface to the tip of the first valve body through the through hole,
The switching valve connects the first runner to the first flow path, a first position connecting the second runner to the second flow path, and the first runner and the first position. Having a second position to shut off between the flow paths and to cut off between the second runner and the second flow path,
By driving the first valve body in the valve chamber in the front-rear direction with respect to the gate, it is configured to switch a flow path between the first position and the second position. The hot runner mold for sandwich molding according to claim 8, wherein the second valve body is configured to protrude forward from the through hole to close the gate. A method of performing sandwich molding using two types of resins,
A gate opening on the inner wall of the cavity,
A switching valve provided adjacent to and upstream of the gate;
A first sprue and a second sprue provided on the back of the mold,
A first runner for introducing skin resin from the first sprue into the cavity via the switching valve and the gate,
A second runner for introducing a core resin into the cavity from the second sprue through the switching valve and the gate,
Using a hot runner mold for sandwich molding with
First, the first runner is connected to the gate while the second runner is shut off from the gate by the switching valve, and in that state, the skin resin is injected into the cavity from the first runner,
Then, the second runner is connected to the gate by the switching valve, and in this state, the skin resin is injected into the cavity from the first runner, and at the same time, the second runner passes through the center of the gate from the second runner. Inject core resin into the cavity,
Next, the switching valve shuts off the second runner from the gate, and in that state, injects a skin resin from the first runner into the cavity,
After the cavity is filled with the resin, the switching valve shuts off both the first runner and the second runner from the gate. A method of performing sandwich molding using two types of resins,
A gate opening on the inner wall of the cavity,
A switching valve provided adjacent to and upstream of the gate;
A first sprue and a second sprue provided on the back of the mold,
A first runner for introducing skin resin from the first sprue into the cavity via the switching valve and the gate,
A second runner for introducing a core resin into the cavity from the second sprue through the switching valve and the gate,
Using a hot runner mold for sandwich molding with
In a state where both the first runner and the second runner are simultaneously connected to the gate by the switching valve, first, a skin resin is injected into the cavity from the first runner,
Next, in a state where the injection of the skin resin from the first runner is continued, the core resin is injected into the cavity from the second runner through the center of the gate,
Next, in a state where the injection of the skin resin from the first runner is continued, the injection of the core resin from the second runner is stopped,
After the cavity is filled with the resin, the switching valve simultaneously shuts off both the first runner and the second runner from the gate. A method of performing sandwich molding using two types of resins,
Gates provided at multiple locations on the inner wall of the cavity;
A switching valve provided adjacent to each gate and on the upstream side thereof,
A first sprue and a second sprue provided on the back of the mold,
A first runner for introducing skin resin into the cavity from the first sprue through the respective switching valves and the respective gates,
A second runner for introducing the core resin into the cavity from the second sprue through the respective switching valves and the respective gates,
Using a hot runner mold for sandwich molding with
A sandwich molding method, wherein a time difference is provided in the switching timing of each of the switching valves, and the resin for skin and the resin for core are injected into the cavity.

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