JPH0235471Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a mold cavity internal pressure control device.

(B) Prior Art A conventional mold cavity pressure control device for performing low-foaming molding of synthetic resin is disclosed, for example, in US Pat. No. 3,268,635. This shows an apparatus in which a molten foamable resin material is injected into a pressurized mold cavity by gas pressure, and then the gas pressure is removed to foam the foamable resin material.

(c) Problems to be solved by the invention However, in the conventional mold cavity pressure control device as described above, the gas pressure applied to the mold cavity is controlled sequentially according to the process of the injection molding machine.
It is necessary to adjust the pressure by increasing the pressure, maintaining a constant pressure, and removing the pressure.
Since this was done using a compressor, an accumulator, and a valve, it was troublesome to operate the valves reliably at the appropriate timing, and a complicated control device was required for this purpose. In addition, in Japanese Patent Application Laid-open No. 123173/1973,
A device is shown in which fluid pressure increased by a piston-type accumulator is supplied into a mold cavity from a fluid inlet of a nozzle. However, in this case, there is a problem that fluid pressure cannot be applied to the inside of the mold cavity before injection, and foaming starts at the same time as injection, making it impossible to obtain a molded product with a clean surface. Furthermore, it is not possible to completely discharge residual fluid by creating a negative pressure in the mold cavity after foaming. For this reason, the quality of the molded product, such as the foaming state and shape accuracy, is not stable. Furthermore, it is necessary to provide a fluid inlet inside the nozzle, making the structure complicated. The present invention aims to solve such problems.

(d) Means for solving the problem The present invention achieves the above object by providing a pneumatic cylinder that works in conjunction with a hydraulic cylinder, combining these with a plurality of solenoid valves, and operating them in a predetermined order. do. That is,
The mold cavity pressure control device according to the present invention is for controlling the pressure inside the cavity of a mold for foam molding, which can control the pressure inside the cavity independently of the nozzle of the injection device. The device is designed to operate in conjunction with a hydraulic source 32, a hydraulic cylinder 10, a hydraulic direction switching solenoid valve 36 that switches and controls the supply of hydraulic pressure from the hydraulic source 32 to the hydraulic cylinder 10, and the hydraulic cylinder 10. a pneumatic cylinder 12 connected to the cylinder chamber 12 of the pneumatic cylinder 12;
The first and second limit switches 22 and 2 operate in predetermined states of small volume and large volume, respectively.
4, a pneumatic source 40, and a first pneumatic directional solenoid valve 4 that communicates or blocks communication between the cylinder chamber 12b of the pneumatic cylinder 12 and the pneumatic source 40.
2, a second pneumatic directional solenoid valve 54 that communicates or blocks communication between the cylinder chamber 12b of the pneumatic cylinder 12 and the mold cavity 50, and a pneumatic passage 38 that communicates with the cylinder chamber 12b of the pneumatic cylinder 12 to atmospheric pressure. The first to open or close
The pneumatic pressure of the pneumatic discharge switching solenoid valve 46, the second pneumatic discharge switching solenoid valve 62 that opens or closes the pneumatic passage 52 communicating with the mold cavity 50 to atmospheric pressure, and the pneumatic pressure passage 52 communicating with the mold cavity 50 is set. Pneumatic relief valve 56 that controls the pressure so that it does not exceed the value.
and each of the above solenoid valves 36, 42, 46,
54 and 62 are activated in the cylinder chamber 1 of the pneumatic cylinder 12 before injection based on signals from the first and second limit switches 22 and 24, a signal corresponding to the stroke of the injection molding machine, and a timer signal.
2b is supplied to the mold cavity 50, the pressure inside the mold cavity 50 is maintained at the set pressure of the pneumatic relief valve 56 during injection, and the pressure inside the mold cavity 50 is maintained at the set pressure of the air pressure relief valve 56 after injection. 50 is released to atmospheric pressure, and then the cylinder chamber 12 of the pneumatic cylinder 12 is opened.
By enlarging b, mold cavity 5
It is characterized by having a controller that controls the pressure within 0 to a negative pressure state.

(E) Effect With the above configuration, relatively low air pressure is supplied from the air pressure source into the mold cavity during mold clamping according to the stroke of the injection molding machine, and then the air pressure is supplied to the mold cavity by the stroke of the pneumatic cylinder. The resulting air pressure is set at a relatively high pressure using a relief valve, and during injection, the inside of the mold cavity is maintained at the set pressure by the action of the pneumatic relief valve, and after injection, the pneumatic cylinder is moved in the opposite direction to the above. The pressure inside the mold cavity can be reliably relieved by this stroke. The operation of each solenoid valve is sequence-controlled by a limit switch and a timer so that the above-mentioned effects can be obtained.

(f) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 6 of the accompanying drawings.

The piston rod 10a of the hydraulic cylinder 10 is
Piston rod 12 of two pneumatic cylinders 12
a and a connecting plate 14. A switch rail 16 is attached to the connecting plate 14, and cams 18 and 20 of the switch rail 16 operate a first limit switch 22 and a second limit switch 24, respectively. The first limit switch 22 is configured to operate when the piston rod 12a strokes so that the volume of the cylinder chamber 12b of the pneumatic cylinder 12 is reduced. Further, the second limit switch 24 is configured to operate when the piston rod 12a strokes so that the volume of the cylinder chamber 12b increases. The oil chambers 10b and 10c of the hydraulic cylinder 10 are oil passages 2, respectively.
6 and 28. A speed regulating valve 30 is provided in the oil passage 28 . The oil passage 26 and the oil passage 28 can be switched and connected to a hydraulic pressure source 32 and a hydraulic tank 34 by a hydraulic direction switching solenoid valve 36. Note that as the hydraulic power source 32, a hydraulic power source of an injection molding machine is used. The cylinder chamber 12b of the pneumatic cylinder 12 communicates with the pneumatic passage 38. The pneumatic passage 38 and the pneumatic source 40 can be communicated with or disconnected from each other by a first pneumatic directional solenoid valve 42 . In addition, air pressure source 4
A check valve 44 is provided between the pneumatic directional solenoid valve 42 and the first pneumatic directional solenoid valve 42.
The pneumatic passage 38 can be opened or closed relative to atmospheric pressure by a first pneumatic discharge switching solenoid valve 46 . Note that a muffler 48 is provided on the atmospheric pressure release side of the first air pressure discharge switching solenoid valve 46. A pneumatic passage 52 and a pneumatic passage 38 communicating with the mold cavity 50
A second pneumatic directional solenoid valve 54 between the
is provided. That is, the second pneumatic directional solenoid valve 54 can communicate or block the pneumatic passage 38 and the pneumatic passage 52.
A pneumatic relief valve 56 is connected to the pneumatic passage 52 . A muffler 58 is provided on the atmospheric pressure discharge side of the pneumatic relief valve 56. An air pressure gauge 60 is provided in the air pressure passage 52. Further, a second pneumatic discharge switching solenoid valve 62 is connected to the pneumatic passage 52 . The second pneumatic discharge switching solenoid valve 62 can open or close the pneumatic passage 52 to atmospheric pressure.
A muffler 64 is provided on the atmospheric pressure discharge side of the second pneumatic discharge switching solenoid valve 62 . The operation of the solenoid valves 36, 42, 46, 54, and 62 is controlled by a control (not shown) based on signals from the limit switches 22 and 24, signals from the timers 66 and 68, and signals corresponding to the strokes of the injection molding machine. It is controlled by the device as described below.
Note that molten resin containing a foaming agent can be injected into the above-mentioned mold cavity 50 from a nozzle 70 of an injection molding machine.

Next, the operation of this embodiment will be explained. Second
The figure shows limit switches 22, 24, and timer 6.
6, 68, solenoid valve 36, 42, 46,
The operating states of 54 and 62 are shown in relation to the strokes of the injection molding machine. That is, first, the second pneumatic directional solenoid valve 54 opens in response to a mold closing completion signal from the injection molding machine, and relatively low air pressure from the pneumatic pressure source 40 is applied to the check valve 44, the first pneumatic directional solenoid valve 42, and the pneumatic pressure. Passage 38, 2nd
Air flows into mold cavity 50 through pneumatic directional solenoid valve 54 and pneumatic passageway 52 . At this time, the hydraulic cylinder 10 and the pneumatic cylinder 12 are in the state shown in FIG. 1 (that is, the cylinder chamber 12b is in a large volume state). Simultaneously with the operation of the first pneumatic directional solenoid valve 42, the hydraulic directional solenoid valve 36 is also activated on the a side, and the oil passage 28 is connected to the hydraulic source 32.
communicate with. Therefore, the oil pressure from the oil pressure source 32 acts on the oil chamber 10c, and the piston rod 10a moves to the right in FIG. 1 (direction e in the figure). The piston rod 12a and the switch rail 16, which are connected to the piston rod 10a by the connecting plate 14, also move in the direction e at the same time. As the piston rod 12a moves in the direction e, the volume of the cylinder chamber 12b of the pneumatic cylinder 12 decreases, and the pressure within the cylinder chamber 12b, which had been at a relatively low pressure up to then, begins to rise. The cylinder chamber 12b includes a pneumatic passage 38 and a second pneumatic directional solenoid valve 54.
and the mold cavity 5 via the pneumatic passage 52.
0, the air pressure in the mold cavity 50 also increases. When the air pressure in the mold cavity 50 reaches a predetermined set pressure, the air pressure relief valve 56 opens, excess air is released through the muffler 58, and the air pressure in the mold cavity 50 is maintained at the set pressure. Thus, when the piston rod 10a continues its stroke and the first limit switch 22 is actuated by the cam 18, the second pneumatic directional solenoid valve 54 is closed, and at the same time the hydraulic directional solenoid valve 36 returns to the neutral position, and the piston rod 10a movement in the e direction stops. At the same time, the first air pressure discharge switching solenoid valve 46 opens, and the high air pressure inside the cylinder chamber 12b is released to the atmosphere via the muffler 48. That is, the cylinder chamber 12b
becomes atmospheric pressure. The state of the mold during the steps up to this point is shown in FIG.

The operation of the first limit switch 22 opens the needle valve of the nozzle 70 of the injection molding machine, and as shown in FIG.
Injection into the mold cavity 50 of No. 2 is started. At the same time, the first timer 66 starts counting. During this injection process, the inside of the mold cavity 50 is gradually filled with molten resin 72, so
The volume of air within the mold cavity 50 decreases but is maintained at the set pressure during the injection stroke by the action of the pneumatic relief valve 56. 1st timer 6
When the set time of 6 has elapsed, the second timer 68 starts operating and the second pneumatic discharge switching solenoid valve 62 is opened for the set time. For this reason, the air pressure inside the mold cavity 50 is reduced to the silencer 6.
4 to the atmosphere. Therefore, the air pressure in the mold cavity 50 decreases, and the molten resin 72 is foamed. This state is shown in FIG. When the set time of the second timer 68 has elapsed, the second pneumatic discharge switching solenoid valve 62 is closed.
On the other hand, the second pneumatic directional solenoid valve 54
will be held. At the same time, the hydraulic direction switching solenoid valve 36 operates to the b side, the hydraulic source 32 communicates with the oil passage 26, and the hydraulic pressure of the hydraulic source 32 acts on the oil chamber 10b, so the piston rod 10a moves toward the left in the figure (f in the figure). direction). In addition, piston rod 1
The moving speed of Oa is controlled by a speed regulating valve 30. Therefore, the piston rod 12a also f
direction, the cylinder chamber 12b and the mold cavity 50 connected thereto are brought into a negative pressure state, and the pressure inside the mold cavity 50 is more reliably removed. At this time, the second pneumatic directional solenoid valve 54 is kept open, and the first pneumatic directional solenoid valve 42 and the first pneumatic discharge switching solenoid valve 46 are kept closed. The movement of the piston rod 10a in the direction f continues until the cam 20 actuates the second limit switch 24. That is, when the second limit switch 24 is actuated, the hydraulic directional solenoid valve 36 returns to the neutral position, the second pneumatic directional solenoid valve 54 is closed, and the first pneumatic directional solenoid valve 42 opens, thereby connecting the pneumatic source 40 and It communicates with the cylinder chamber 12b of the pneumatic cylinder 12, returns to its initial state, and prepares for the next molding cycle. Next, the injection molding machine shown in FIG. 2 is cooled,
The following processes such as weighing proceed. During this time, the mold cavity pressure control device does not operate and the above state is maintained. FIG. 6 shows the state in which the molded product is projected.

(g) Effects of the invention As explained above, according to the invention, a pneumatic cylinder is provided that works in conjunction with a hydraulic cylinder, and the connection status of the pneumatic cylinder and the air pressure source to the mold cavity is switched by a plurality of solenoid valves. These solenoid valves and solenoid valves for hydraulic cylinder control are controlled as specified by limit switches, timers, etc., so that the air pressure inside the mold cavity is reliably maintained as specified according to the stroke of the injection molding machine. It becomes possible to obtain a molded product with a controlled and desired low foaming rate. Further, the air pressure source may be one that generates relatively low air pressure, and high pressure air compressors, accumulators, etc. are not required. Also,
Since the mold cavity is kept under constant pressure before injection starts, foaming does not start during injection, and foaming starts as soon as the pressure is released after injection is completed, resulting in smooth foaming on the surface layer. Molded products can be obtained. Furthermore, after foaming, the inside of the mold cavity is reliably evacuated, making it possible to stabilize the quality of the molded product, such as the foaming state and shape accuracy. Further, no nozzle with a complicated structure is required.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the mold cavity internal pressure control device according to the present invention, Fig. 2 is a diagram showing the operating state of each element according to the stroke of the injection molding machine, and Fig. 3 is a diagram showing the mold before injection starts. FIG. 4 is a diagram showing the mold during injection, FIG. 5 is a diagram showing the mold during depressurization cooling, and FIG. 6 is a diagram showing the mold during ejection of the molded product. 10...Hydraulic cylinder, 12...Pneumatic cylinder, 14...Connection plate, 16...Switch rail,
18...cam, 20...cam, 22...first limit switch, 24...second limit switch,
26...Oil passage, 28...Oil passage, 30...Speed adjustment valve, 32...Hydraulic pressure source, 34...Hydraulic tank,
36...Hydraulic directional solenoid valve, 38...
...Pneumatic passageway, 40...Pneumatic pressure source, 42...First
Pneumatic directional solenoid valve, 44... Check valve, 46... First pneumatic discharge switching solenoid valve, 48... Silencer, 50... Mold cavity, 52... Pneumatic passage, 54... Second pneumatic directional switching Directional solenoid valve, 56... Pneumatic relief valve, 58... Silencer, 60... Air pressure gauge, 62... Second pneumatic discharge switching solenoid valve, 64... Silencer, 66... First timer, 68... ...Second timer, 70...Nozzle, 7
2... Molten resin.

Claims (1)

[Scope of Claim for Utility Model Registration] In a mold cavity pressure control device for controlling the pressure in the cavity of a mold for foam molding, the pressure in the cavity can be controlled independently of the nozzle of the injection device, source 32, hydraulic cylinder 10, and hydraulic source 3
2 to the hydraulic cylinder 10, a pneumatic cylinder 12 connected to the hydraulic cylinder 10, and a small volume cylinder chamber 12b of the pneumatic cylinder 12. First and second limit switches 2 each operating in a predetermined state with a large volume.
2 and 24, a pneumatic pressure source 40, a first pneumatic pressure directional solenoid valve 42 that communicates or blocks communication between the cylinder chamber 12b of the pneumatic cylinder 12 and the pneumatic source 40, and a cylinder chamber 1 of the pneumatic cylinder 12.
a second pneumatic directional solenoid valve 54 that communicates or blocks communication between 2b and the mold cavity 50;
and a first pneumatic discharge switching solenoid valve 46 that opens or closes the pneumatic passage 38 communicating with the cylinder chamber 12b of the pneumatic cylinder 12 to atmospheric pressure;
Pneumatic passage 52 communicating with mold cavity 50
a second air pressure discharge switching solenoid valve 62 that opens or closes the air pressure to atmospheric pressure, and a mold cavity 50.
a pneumatic relief valve 56 that controls the pneumatic pressure in the pneumatic passage 52 communicating with the pneumatic passage 52 so as not to exceed a set value, and each of the solenoid valves 36, 42, 4.
6, 54, and 62) are activated in the cylinder chamber 12b of the pneumatic cylinder 12 before injection based on signals from the first and second limit switches 22 and 24, a signal corresponding to the stroke of the injection molding machine, and a timer signal. The air pressure obtained by reducing the air pressure is supplied to the mold cavity 50, and the pressure inside the mold cavity 50 is maintained at the set pressure of the air pressure relief valve 56 during injection, and after injection, the pressure inside the mold cavity 50 is maintained at the set pressure of the air pressure relief valve 56. and a controller for controlling the pressure inside the mold cavity 50 to be in a negative pressure state by opening the pressure inside the mold cavity to atmospheric pressure and then expanding the cylinder chamber 12b of the pneumatic cylinder 12. Features a mold cavity pressure control device.