JP2002192569A - Material replacing device in mold, and material replacing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly and certainly substitute the previous molding material in the material passage in a mold with a next molding material at the time of replacement of a material such as the replacement of a color or the like. SOLUTION: The molding material in a sprue 43 and a runner 45 is always held to a molten state and the gate 52 to a product cavity from the sprue 43, and the runner 45 is opened and closed by valve pin 66. A valve drive means 91 for reciprocating the valve pin 66 plural times in such a state that a mold 4 is opened or closed at the time of changeover of the molding material is provided. The valve pin 66 and the gate slide or the molding material in a material passage 59 generates vibration or pulsating movement accompanied by the reciprocating motion of the valve pin 66 to accelerate the discharge of the previous molding material remaining in the material passage 59.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material changing apparatus for a mold such as a valve gate type hot runner mold used for injection molding of a thermoplastic resin and the like, and a material changing method using the apparatus.

[0002]

A hot runner mold used for injection molding using a thermoplastic resin as a molding material is:
In order to increase the molding efficiency, the molding material in the material passage up to the gate to the product cavity is heated and kept in a molten state at all times. On the other hand, since the molding material in the product cavity to be a product must be cooled and solidified, the hot runner mold needs to open and close the gate by some means. As a gate opening / closing method, there is a valve gate method in which a gate is mechanically opened / closed by a valve pin serving as a valve.

In some cases, products of the same shape and different colors are formed by using the same mold and replacing only the molding material (resin) with a different pigment or dye. This is a so-called color change. When performing material change, which is a change of molding material, without being limited to such color change,
In the hot runner mold, before starting molding with the next molding material, injection (shot) from the injection molding machine is performed several times, and the molding material before (old) remaining in the material passage of the fixed mold Must be discharged.

[0004] However, it is not easy to completely discharge the previous molding material remaining in the material passage, and conventionally, it is necessary to perform a large number of shots to discharge the previous molding material remaining in the material passage. For example, 200 shots are not enough, and 500 shots may be needed. The reason why the molding material before remaining in the material passage is not easily discharged is that a heat insulating layer made of the molding material itself is formed so as to extend from the material passage, and the outer surface of the valve pin and the material are removed. One cause is that the molding material adheres to the inner wall surface of the passage or the like. If a number of shots for color change, not for molding the product, must be performed many times, there is a problem that the molding material is wasted and productivity is deteriorated. On the other hand, if the number of shots for color change is small, the remaining molding material mixes with the next molding material product, resulting in defective molded products.

The present invention is intended to solve such a problem, and when changing materials such as changing colors, the previous molding material in the material passage in the mold is quickly and reliably replaced with the next molding material. It is an object of the present invention to provide a material changing device in a mold that can be replaced with a material and a material changing method using the device.

[0006]

According to a first aspect of the present invention, there is provided a material changing apparatus in a mold, wherein a molding material in a material passage is always kept in a molten state, and a gate from the material passage to a product cavity is opened and closed by a valve. A material changing device used for switching a molding material in a mold, comprising valve driving means for reciprocating the valve a plurality of times while the mold is opened or closed.

According to a second aspect of the present invention, there is provided a material changing method using the material changing apparatus in the mold, wherein the valve is reciprocated a plurality of times by the valve driving means. While changing the material from the old molding material to the new molding material.

According to a third aspect of the present invention, there is provided a material changing apparatus for a mold, wherein a molding material in a material passage is always kept in a molten state, and a gate from the material passage to a product cavity is provided by a valve. A material changing device used for switching a molding material in a mold that opens and closes, wherein the molding is closed, a molding material is injected into the product cavity, and then the mold is opened to remove a molding material in the product cavity. A valve driving means for opening and closing the valve twice or more is provided therein.

In molding a product, after closing the mold, the gate is opened, and the molding material is filled into the product cavity from the material passage through the gate. Thereafter, the gate is closed by the valve, and after the molding material in the product cavity is solidified, the mold is opened to take out the molding material in the product cavity, that is, the product. Thereafter, the mold is closed again and the above molding cycle is repeated, while the molding material in the material passage is always kept in a molten state. When changing materials such as changing colors, a similar molding cycle is repeated in order to discharge the previous molding material remaining in the material passage and replace it with the next molding material. The driving means opens and closes the valve at least twice during one molding cycle. When molding a product, the valve only needs to be opened and closed once during one molding cycle. By opening and closing the valve twice or more, discharge of the molding material remaining in the material passage is promoted.

According to a fourth aspect of the present invention, there is provided a material changing method using a material changing apparatus in a metal mold according to the third aspect of the present invention. The steps of injecting the molding material into the product cavity and the step of closing the gate by the valve and opening the mold after the molding material in the product cavity is solidified and taking out the molding material in the product cavity are repeated to the product cavity. The valve is opened and closed separately from the opening of the gate for injection of the molding material and the closing of the gate for blocking the molding material in the material passage from the molding material in the product cavity.

In order to inject the molding material from the material passage into the product cavity, it is necessary to open a gate,
In order to shut off the molding material in the material cavity which is always kept in a molten state and the molding material in the product cavity which is solidified and taken out, it is necessary to close the gate with a valve. Therefore, the valve opens and closes once during one molding cycle, but by opening and closing the valve separately, discharge of the molding material remaining in the material passage can be promoted.

A fifth aspect of the present invention is a method for material replacement in a mold according to the second or fourth aspect of the present invention, wherein the molding machine for supplying a molding material to the mold includes a step of plasticizing the molding material. This is for opening and closing the valve.

[0013] In a molding machine, after a molding material to be supplied to a mold is plasticized and stored in a predetermined amount, the plasticized molding material is injected into the mold. Since the injection step is for injecting the molding material into the product cavity, it is desirable that the gate is always open. Therefore, the opening and closing operation of the added valve is desirably performed during the step of plasticizing the molding material in the molding machine.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a material changing apparatus for a hot runner mold according to the present invention and a material changing method using the apparatus will be described below with reference to the drawings. First, the configuration of an injection molding machine, which is a molding machine, will be described.
As shown in FIG. 3, the injection molding machine includes a mold clamping device 1 and an injection device 2 which is a plasticizing device. The mold clamping device 1 and the injection device 2 are arranged on a base 3. . The mold clamping device 1 opens and closes a fixed mold 5 and a movable mold 6 that are hot runner molds 4 mutually. A fixed platen 7 to which the fixed mold 5 is detachably attached and a movable mold 6 are detachably attached. And a movable side platen 8 to be attached. The movable platen 8 is moved in a direction (mold opening / closing direction) in which the movable platen 8 approaches and separates from the fixed platen 7 by, for example, a hydraulically driven mold clamping cylinder 9. It opens and closes.

The injection device 2 has an injection device base 11
Are slidably supported on a rail 12 fixed on the base 3 in a direction approaching and separating from the mold 4. The injection device base 11 is moved by, for example, driving a hydraulically driven shift cylinder 13. The injection device 2 is of an in-line screw type, and includes a heating cylinder 17 having a nozzle 16 connected to a tip end thereof, which is attached to and detached from the fixed mold 5 as the injection device base 11 moves. The heating cylinder 17 is provided with a heater 18 serving as a heating means on an outer periphery and has a screw 19 incorporated therein. Further, a hopper 20 is provided at an end of the heating cylinder 17 opposite to the nozzle 16. The hopper 20 is charged with a molding material (pellet) such as a thermoplastic resin before plasticization. The screw 19 is a screw 19
Is driven in the axial direction, that is, in the direction approaching and moving away from the mold 4, for example, a hydraulically driven injection cylinder 21.
Through a rod 22. Also this rod
A spline cylinder 23 fixed to 22 has a gear 24 with a screw 19
The rod 22 is spline-fitted so as to be slidable in the axial direction and not to rotate. And the gear
The gear 24 meshes with a gear 26 fixed to a rotation output shaft of a motor 25. That is, the screw 19 is
It is rotated by the drive of.

Next, the configuration of the hot runner mold 4 will be described with reference to FIGS. The fixed mold 5 and the movable mold 6 which are molds form a product cavity 31 having a product shape therebetween when the mold is closed. Fixed type 5
A fixed-side mold plate 32, a fixed-side receiving plate 33 fixed to the back surface of the fixed-side mold plate 32, that is, the surface opposite to the movable mold 6;
On the back side of the fixed-side receiving plate 33, there is provided a fixed-side mounting plate 35 fixed via a spacer block 34, and a support plate 36 is provided between the fixed-side mounting plate 35 and the fixed-side receiving plate 33. The manifold 37 is provided with the interposition.
A cavity block 38 forming the product cavity 31 is embedded and fixed in the fixed side mold plate 32.

The manifold 37 has a sprue bush.
41 is fixed. The sprue bush 41 protrudes toward the fixed-side mounting plate 35, and is located in a through hole 42 formed in the fixed-side mounting plate 35. The inside of the sprue bush 41 is a sprue 43 as a material passage, and a band heater 44 as heating means is provided on the outer periphery of the sprue bush 41.
By the heating of the heater 44, the thermoplastic resin as the molding material in the sprue 43 is always kept in a molten state. A runner 45 as a material passage is formed inside the manifold 37.
The sprue 43 communicates with an inlet portion of the sprue 45. further,
The manifold 37 is provided with a heater 46 as a heating means.
The molding material inside is always kept in a molten state. A locate ring 47 is fixed on the surface of the fixed-side mounting plate 35 opposite to the manifold 37 so as to surround the through hole 42.

A through-hole 51 is formed from the fixed side receiving plate 33 to the cavity block 38, and the tip of the through-hole 51 serves as a gate 52 that opens into the product cavity 31. The gate 52 has a cylindrical shape, and its axial direction coincides with the mold opening / closing direction.

The fixed mold 5 has the gate 52
A valve device 56 for opening and closing the valve is incorporated. Next,
The configuration of the valve device 56 will be described. A substantially cylindrical valve casing 57 is incorporated in the through hole 51. One end of the valve casing 57 is a flange portion 58, which is fixed to the manifold 37 and the fixed-side receiving plate 33. The inside of the valve casing 57 has a material passage 59 having one end communicating with the outlet of the runner 45 in the manifold 37 and the other end communicating with the gate 52. Although the material passage 59 has a substantially cylindrical shape, three or more support blades 60 extending in the mold opening / closing direction are integrally formed on the inner peripheral surface of the front end portion on the gate 52 side. These support blades 60 are located radially with respect to the central axis of the material passage 59. Further, the valve casing 57
The inner material passage 59 has a columnar portion 61 at a portion closer to the gate 52 than the support blade 60. The inner peripheral surface of the columnar portion 61 is located on substantially the same cylindrical surface as the inner edge of the support blade 60.

The valve casing 57 contains a valve pin 66 as a valve. The valve pin 66 has the mold opening / closing direction as the axial direction, and a column-shaped gate closing portion 67 formed at the tip of the product cavity 31 is fitted in the gate 52 so as to be freely inserted into and removed from the gate 52.
Is to close. The valve pin 66 has a through hole formed in the manifold 37 and the fixed-side mounting plate 35.
Hydraulic cylinder device 70 which penetrates 68, 69 and is provided on the fixed side mounting plate 35 as a hydraulic cylinder device
It is connected to. And this hydraulic cylinder device 70
The valve pin 66 is moved in the mold opening and closing direction by the driving of the valve. The hydraulic cylinder device 70 is connected to a hydraulic circuit 71 provided outside the mold 4.

The outer peripheral surface of the valve pin 66 is always slidably in contact with the inner edge of the support blade 60 of the valve casing 57. This allows the gate of the valve pin 66
The tip on the side of 52 is supported, but when the valve pin 66 closes the gate 52, the valve pin 66 fits into the columnar portion 61. On the other hand, when the gate 52 is opened, the tip of the valve pin 66 is located at the middle of the support blade 60. In addition, valve pins
Reference numeral 66 denotes an end of the valve casing 57 on the manifold 37 side, which is supported by a guide bush 72 fixed in the valve casing 57. That is, the valve pin 66 slidably passes through the guide bush 72.

A band heater 73 for heating the material passage 59 and a substantially cylindrical heater cover for covering the heater 73 from outside are provided on the outer peripheral surface of the valve casing 57.
74 are fitted. Further, a temperature sensor 75 is provided along the heater 73. The heating of the heater 73 keeps the molding material in the material passage 59 in a molten state at all times.

Further, the gate of the valve casing 57
A fixing ring 76 is fitted and fixed to the outer peripheral side of the 52 end. The outer peripheral surface of the fixing ring 76 is fitted to a cylindrical fitting surface 77 of the same diameter formed in the through hole 51. As a result, the valve casing 57 is supported by the cavity block 38 at the end on the gate 52 side. The fixing ring 76 and the cavity block 38
Other than the fitting surface 77 with the through hole 51 for heat insulation.
Of the valve casing 57 or heater cover 74
A gap is formed between the outer surface and the outer surface. This gap is
It comprises a portion on the heater 73 side and a portion on the gate 52 side interrupted by the fixing ring 76. The part on the heater 73 side forms an air heat insulating layer 78, and the part on the gate 52 side forms a resin heat insulating layer 79 which is in communication with the material passage 59 and the gate 52 and is filled with a molding material. Note that this resin heat insulating layer 79
May be pre-filled with a sealing ring made of a thermosetting resin or the like that does not melt with the heat of the molten molding material and has excellent heat insulating properties.

The movable mold 6 includes a movable mold plate 81, a movable receiving plate 82 fixed to the back surface of the movable mold plate 81, that is, a surface opposite to the fixed mold 5, and a movable receiving plate 82. And a movable-side mounting plate (not shown) fixed via a spacer block (not shown) on the back side. A core block 83 forming the product cavity 31 is embedded and fixed in the movable mold plate 81. Further, although not shown, the movable die 6 is also provided with a projecting mechanism for projecting and releasing the molded product.

Next, the structure of the valve driving means 91 for driving the valve pin 66 will be described with reference to FIG. The valve driving means 91 includes the hydraulic cylinder device 70 and the hydraulic circuit 71, a control device 92 for controlling the hydraulic cylinder device 70 via the hydraulic circuit 71, and a switch for operating the control device 92. And an operating means 93 such as a normal continuous molding operation section 93A and a molding material switching operation section 93B operated when switching the material. The valve driving means 91 is a material changing device used for switching the molding material in the hot runner mold 4, in which the mold is closed, the molding material is injected into the product cavity 31, and then the mold is opened to open the product cavity 31. It has a function of automatically opening and closing the valve pin twice or more during one molding cycle for removing the molding material.

Next, a molding method using the injection molding machine and the hot runner mold 4 will be described with reference to FIG. In the injection molding machine, the continuous molding operation section 93A
Is operated, the mold closing device 1 repeats the mold closing and the mold opening, and the injection device 2 repeats the measuring process, the injection process, and the pressure holding process. In the weighing process, the hopper
Pellets of thermoplastic resin as a molding material are supplied from 20 into the heating cylinder 17 and the molding material in the heating cylinder 17 is melted and plasticized by heating of the heater 18 and shearing force due to rotation of the screw 19. Then, the molten molding material is sent to the nozzle 16 side (front side) in the heating cylinder 17 and stored therein. At that time, screw 19
Retreats away from the mold 4.

Then, the fixed mold 5 and the movable mold 6 are closed, and a product cavity is provided between the fixed mold 5 and the movable mold 6.
After a predetermined amount of molding material has been accumulated in the front portion of the heating cylinder 17 while the 31 is formed, the valve pin 66 moves in a direction away from the movable mold 5 by driving the hydraulic cylinder device 70 as shown in FIG. Then, the gate 52 is opened. Thereafter, the screw 19 advances to the mold 4 side by driving the injection cylinder 21, and the molding material in the heating cylinder 17 is injected from the nozzle 16 into the mold 4 and supplied (injection step). The injected molding material passes through the sprue 43, the runner 45 of the manifold 37, the material passage 59 in the valve casing 57, and the support blade 60 in which the valve pin 66 is fitted.
It flows into the product cavity 31 from the gate 52 through the gap and through the cylindrical portion 61. Thus, the product cavity 31
After the molding material is filled therein, the pressure is held by the back pressure applied from the injection cylinder 21 to the screw 19 (pressure holding step). Thereafter, as shown in FIG. 2, the valve pin 66 moves toward the movable die 6,
Close 52. Thereby, the molding material in the material passage 59 and the molding material in the product cavity 31 are shut off. After the pressure holding process, the injection device 2 starts the measuring process again.

Further, the molding material in the mold 4, that is, the molded product is sufficiently cooled and solidified (cooling step). Thereafter, the fixed mold 5 and the movable mold 6 are opened to form the molded product. It is removed by a removal device not shown.
Thereafter, the mold is closed again, and the molding cycle including the above steps is repeated. During that time, the molding material in the material passage 59 of the sprue 43, the runner 45 and the valve casing 57 is always kept in a molten state by the heating of the heaters 44, 46 and 73.

Next, a method of changing materials such as changing colors will be described. The color change is to mold products of the same shape and different colors by using the same mold 4 and changing only the molding material to one having a different pigment or dye. When the material is changed, that is, when the old molding material is switched to the new molding material, a pellet of a thermoplastic resin, which is a new molding material, is supplied to the hopper 20 in advance for color change, and the molding material switching operation unit 93B is operated. In the injection device 2, a material change weighing step, a material change injection step, and a material change holding pressure step are performed. In the material replacement weighing step, thermoplastic resin pellets as a molding material are supplied from the hopper 20 into the heating cylinder 17, and the heating force of the heater 18 and the shearing force caused by the rotation of the screw 19 cause the heating cylinder 17 to rotate. The molding material is melted and plasticized, and the molten molding material is sent to the nozzle 16 side (front side) in the heating cylinder 17 and stored. At this time, the screw 19 retreats away from the mold 4.

Then, the fixed mold 5 and the movable mold 6 are kept open, and after a predetermined amount of molding material is accumulated in the front part in the heating cylinder 17, as shown in FIG. The valve pin 66 moves in a direction away from the movable mold 5 by the driving of the gate 52, and the gate 52 is opened. Thereafter, the screw 19 advances to the mold 4 side by the driving of the injection cylinder 21, and the molding material in the heating cylinder 17 is injected from the nozzle 16 into the fixed mold 5 in an open state, and the control device is controlled.
The valve pin 66 is reciprocated continuously or intermittently a plurality of times by the hydraulic circuit 71 and the hydraulic cylinder device 70 via the 92, thereby opening and closing the valve pin 66 a plurality of times (injection process for material change). This injected molding material
Through the sprue 43, the runner 45 of the manifold 37, and further through the material passage 59 in the valve casing 57, between the supporting blades 60 in which the valve pins 66 are fitted, and through the column-shaped portion 61, the gate 52 melts and plasticizes. Inject and discharge to, for example, a discharge tray (not shown). The molding material contained in the discharge tray is cooled and solidified. At this time, the pressure is maintained by the back pressure applied to the screw 19 from the injection cylinder 21 (the material-change pressure-holding step). The back pressure by the back pressure may be the same pressure as the pressure in the above-described pressure holding step during injection molding, but a pressure lower than the pressure is preferable. Meanwhile, the molding material in the material passage 59 of the sprue 43, the runner 45 and the valve casing 57 is supplied to the heaters 44, 46,
By the heating of 73, it is kept in a molten state at all times, is injected sequentially, and can be switched to a new molding material. And
In the material changing injection process, the reciprocating motion of the valve pin 66 is automatically performed by driving the valve driving means 91.

With the reciprocating movement of the valve pin 66, the valve pin 66 and the gate 52 slide, or the material passage
The vibrating or pulsating movement of the molding material in 59 facilitates the discharge of the previous molding material remaining in material passage 59. Particularly, the molding material adhering to the outer surface of the valve pin 66 and the material passage 59 or the inner wall surface of the gate 52 is removed so as to be scraped off. Further, discharge of the molding material before entering the resin heat insulating layer 79 is also promoted. Furthermore, the gate of the molding material in the material passage 59 is pushed by the valve pin 66.
Discharge from 52 to product cavity 31 is also facilitated. As a result, the previous molding material in the material passage 59 can be promptly and reliably replaced with the next molding material, and waste of molding material can be reduced, and productivity can be improved. In addition, the reciprocating motion of the valve pin 66 is automatically controlled after the material change is started by operating the molding material switching operation section 93B of the operation means 93, so that no labor is required.

Next, another method of changing materials, such as changing colors, will be described. Note that the same parts as those in the above embodiment are denoted by the same reference numerals and described. The valve driving means 91 is a material changing device used for switching the molding material in the hot runner mold 4. The valve closing means closes the mold, injects the molding material into the product cavity 31, opens the mold and opens the molding material in the product cavity 31. Has the function of automatically opening and closing the valve pin two or more times during one molding cycle for taking out the mold. At the time of material change, that is, switching of the molding material, the molding material before remaining in the heating cylinder 17 of the injection molding machine can be discharged by purging. In this purging, the entire injection device 2 is retracted in a direction away from the mold 4 by driving the shift cylinder 13, and the nozzle 16 is separated from the mold 4. Next, drive the injection cylinder 21 and the motor 25,
The molding material remaining in the heating cylinder 17 of the injection device 2 is discharged from the nozzle 16 to a discharge tray (not shown). As a result, the molding material hardly stays in the heating cylinder 17 of the injection device 2.

Further, the molding material before remaining in the sprue 43, the runner 45 of the mold 4 and the material passage 59 of the valve casing 57 is gradually discharged by repeating a molding cycle similar to that for molding the above-mentioned product. And replace with the next molding material. That is, the mold clamping device 1 of the injection molding machine repeats the mold closing and the mold opening, and the injection device 2 of the injection molding machine repeats the measuring process and the injection process. However, the material change does not involve molding the product, and the molding pressure does not cause any problem. Therefore, the injection pressure of the molding material in the injection step is set lower than at the time of molding the product. Further, the pressure-holding step is unnecessary and the cooling step may be short, but the setting at the time of molding the product can be used as it is.

In the molding cycle at the time of material change,
After closing the fixed mold 5 and the movable mold 6 as described above, the gate 52 is opened and the molding material is injected into the product cavity 31 from the material passage.
By closing the gate 52, the molding material in the product cavity 31 is solidified and then the mold is opened to take out the molding material in the product cavity 31. In other words, in order to inject the molding material from the material passage 59 into the product cavity 31, the gate 52 needs to be opened, and the molding material in the material passage 59 which is always kept in a molten state is solidified and taken out. To shut off the molding material in the cavity 31, the valve pin 66
Therefore, the valve pin 66 opens and closes once during one molding cycle, but the valve pin 66 opens and closes one or more times separately.

The opening / closing operation of the additional valve pin 66 is performed during the weighing step in the injection device 2, and when there is no molding material in the product cavity 31, or when the molding material in the product cavity 31 is still in the measuring process. It is when it has not solidified. It is also possible to carry out with the mold open. In any case,
The valve pin 66 reciprocates a predetermined number of times during a predetermined time. In addition, the reciprocating motion is automatically performed by driving the valve driving means 91.

With the reciprocating movement of the valve pin 66, the valve pin 66 slides on the gate 52 or the material passage.
The vibrating or pulsating movement of the molding material in 59 facilitates the discharge of the previous molding material remaining in material passage 59. Particularly, the molding material adhering to the outer surface of the valve pin 66 and the material passage 59 or the inner wall surface of the gate 52 is removed so as to be scraped off. Further, discharge of the molding material before entering the resin heat insulating layer 79 is also promoted. Furthermore, the gate of the molding material in the material passage 59 is pushed by the valve pin 66.
Discharge from 52 to product cavity 31 is also facilitated. Thus, the previous molding material in the material passage 59 can be promptly and reliably replaced with the next molding material, and the number of shots required for material replacement can be reduced. Therefore, the waste of the molding material can be reduced, and the productivity can be improved. In addition, the reciprocating motion of the valve pin 66 is automatically controlled after the material change is started by operating the operating means 93, so that no labor is required.

Since the injection step is for injecting the molding material into the product cavity 31, the gate 52 is preferably kept open at all times. However, the opening and closing operation of the added valve pin 66 is performed during the measuring step. Therefore, it is possible to prevent adverse effects from occurring due to the opening and closing operation of the added valve pin 66. That is, at the time of the injection process, the molding material can be quickly injected into the product cavity 31 without any trouble. Further, when the opening and closing operation of the additional valve pin 66 is performed when there is no molding material in the product cavity 31 or when the molding material in the product cavity 31 is not yet solidified, the material passage 59 is pressed by the valve pin 66. Product cavity 31
The effect of discharging the molding material to the mold is also obtained.

Further, if the resin heat insulating layer 79 is buried in advance with a sealing ring, almost no molding material enters the resin heat insulating layer 79, so that the material can be changed more quickly.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above embodiment, the operation of the valve pin as the valve is performed by driving the hydraulic cylinder device 70 as the fluid pressure cylinder device for opening and closing, but the valve for opening and closing the gate uses a spring or the pressure of a molding material. Alternatively, it may be driven.

[0040]

According to the material changing device for the mold according to the first aspect of the present invention, since the valve driving means for reciprocating the valve a plurality of times is provided, the material remains in the material passage at the time of material changing such as color changing. The discharge of the previous molding material can be promoted, and the previous molding material in the material passage in the mold can be quickly and reliably replaced with the next molding material. Therefore, the waste of the molding material can be reduced, and the productivity can be improved.

According to the method of changing the material in the mold according to the second aspect of the present invention, the material is changed from the old molding material to the new molding material while the valve is reciprocated a plurality of times by the valve driving means. Of the molding material can be promoted, and the previous molding material in the material passage in the mold can be promptly and reliably replaced with the next molding material.

According to the material changing device for a mold of the third aspect of the present invention, since the valve driving means for opening and closing the valve twice or more during one molding cycle is provided, the material changing device such as color changing can be used. The discharge of the previous molding material remaining in the passage can be promoted, and the previous molding material in the material passage in the mold can be quickly and reliably replaced with the next molding material.
Therefore, not only can molding material be wasted,
Productivity can be improved.

According to the material changing method in the mold according to the fourth aspect of the present invention, after the mold is closed, the gate is opened and the molding material is injected into the product cavity from the material passage. After the molding material in the product is solidified, the mold is opened and the process of taking out the molding material in the product cavity is repeated, the gate is opened for injection of the molding material into the product cavity, and the molding material in the material passage and the inside of the product cavity are removed. Since the valve is opened and closed separately from the closing of the gate for shutting off the molding material, the discharge of the molding material left in the material passage can be promoted, and the previous molding material in the material passage in the mold can be removed. It can be quickly and reliably replaced with the next molding material.

According to the method for changing the material in the mold according to the fifth aspect of the present invention, in addition to the effects of the second or fourth aspect of the present invention,
Since the valve is opened and closed during the process of plasticizing the molding material in the molding machine that supplies the molding material to the hot runner mold, it is possible to prevent adverse effects due to the opening and closing operation of the added valve.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a hot runner mold according to an embodiment of the present invention, showing a material changing device in a hot runner mold.

FIG. 2 is an enlarged cross-sectional view of the vicinity of the same gate.

FIG. 3 is a side view showing a part of the injection molding machine in cross section.

FIG. 4 is a block diagram of the same.

FIG. 5 is a timing chart of each step during molding of the same product.

[Explanation of symbols]

 4 Hot runner mold 31 Product cavity 43 Sprue (material passage) 45 Runner (material passage) 52 Gate 59 Material passage 66 Valve pin (valve) 91 Valve driving means

Claims (5)

[Claims] 1. A material changing device used for switching a molding material in a mold for keeping a molding material in a material passage in a molten state at all times and opening and closing a gate from the material passage to a product cavity by a valve. A material changing device for a mold, comprising valve driving means for reciprocating the valve a plurality of times while the mold is opened or closed. 2. A material changing method using a material changing device in a mold according to claim 1, wherein the material is changed from an old molding material to a new molding material while the valve is reciprocated a plurality of times by valve driving means. A material changing method in a mold, characterized in that: 3. A material changing device used for switching a molding material in a mold for keeping a molding material in a material passage in a molten state at all times and opening and closing a gate from the material passage to a product cavity by a valve. Valve driving means for closing and injecting the molding material into the product cavity and then opening the mold to take out the molding material in the product cavity to open and close the valve at least twice during one molding cycle. Material changing device in the mold. 4. A material changing method using a material changing apparatus in a mold according to claim 3, wherein a mold is closed, a gate is opened, and a molding material is injected from a material passage into a product cavity. The process of closing the gate by the valve and opening the mold after the molding material in the product cavity is solidified and taking out the molding material in the product cavity is repeated, and opening and closing the gate for injection of the molding material into the product cavity and A material changing method in a mold, characterized in that the valve is opened and closed separately from closing a gate for shutting off a molding material in the material passage and a molding material in a product cavity. 5. The method according to claim 2, wherein the valve is opened and closed during a step of plasticizing the molding material in a molding machine that supplies the molding material to the mold. .