JPH0338099B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an injection molding machine that enables injection compression molding by slightly opening a mold when injecting molten resin into an annular cavity. In particular, the present invention relates to an injection molding apparatus used for molding discs such as record discs, magnetic discs, optical discs, and information recording discs, which have a gateway in the center.

(Prior art) Regarding the invention of molding discs such as record discs and video discs by injection, US Patent No.
There are No. 4085178, No. 3989436, No. 4260360, and JP-A-58-69028 and JP-A-59-230731, which were previously filed by the applicant of the present application. These disclose means for opening the center of the disk after injection.

By the way, for disks with an open center, especially optical disks, in order to reproduce clear images or high-quality sound, the conditions are that the birefringence is low and that there is a complex between the outer and inner peripheries of the disk. It is required that there be no difference in refractive index, that is, that the birefringence be uniform.

One condition for satisfying this requirement is that when the mold cavity (annular cavity) is filled with molten resin, the air inside the mold cavity is discharged outside the mold cavity by the molten resin. It is necessary, but for this purpose, when clamping the mold,
The mold cavity must be in communication with the outside world.

Another condition is that the forming disk is not bent when the center portion of the forming disk is opened with a punch. This problem is caused by the fact that the center of the molding disk is opened while the mold is closed.

(Problems to be Solved by the Invention) However, in the devices described in the above-mentioned US patents and published publications, the stamper holders that fix the stamper to the mold are in close contact with each other during mold clamping. Therefore, during injection, the structure for removing air from the mold cavity had to be complicated.

Furthermore, in the past, in order to open the center part of the molding disk with the mold closed, the sprue button was moved backward as the punch moved forward, but this retraction of the sprue button has no effect on the forward movement of the punch. Because this is done without creating any resistance, the cut of the opening of the forming disk is rough, and the center of the forming disk bends when it is opened, resulting in residual stress, which results in a distortion of the signal shaping range near the opening. There was a problem that the space became narrower. Also, when the sprue bushing retreats, it would be better to apply a resistance force in the direction of resisting the pressing force of the punch.
For example, if the center punching diameter of the molding disk is 15 mm (in the case of CD), the resin pressure applied to this part during molding is approximately
Assuming 300Kg/cm ² , the resin pressure applied to this part during molding will be approximately 300Kg/cm ² , and the force F resisting this is calculated using the following formula: F = π x 1.5 ² /4 x 300 = 530Kg Therefore, a force of approximately 530 kg or more is required.
In the case of an LD with a center punching diameter of 35 mm, the force is even greater. Therefore, if a compression coil spring is used for the sprue bushing, a space for its insertion must be secured, which may increase the size of the device.Also, the repulsive force of the spring changes at the start and end, so it is constant. A problem occurred in that punching by force was difficult, and the formed disk had a non-uniform birefringence and was likely to generate internal stress.

The present invention has been made to solve these problems, and an object of the present invention is to provide a disk injection molding apparatus that can suppress the generation of residual stress as much as possible.

(Means for Solving the Problems) The present invention provides each of the fixed side mold and the movable side mold with an end surface portion that allows the fixed side mold and the movable side mold to come into close contact with each other during mold clamping. An air vent gap is formed on the outer periphery of the annular cavity, and when the sprue bushing retreats when punching the center of the disc in the formed annular cavity with a punch, a resistance force is applied to the sprue bushing in a direction that resists the pressing force of the punch. That is what it is.

(Function) When the movable platen approaches the fixed platen during mold clamping, the fixed side mold and the movable side mold approach each other, and when a certain stroke is reached, the end faces of the fixed side and movable side molds close together. The close contact and mold clamping force is supported by the end surfaces of the fixed and movable molds.

In this way, when the mold clamping is completed, injection is started and the fixed and movable molds are slightly opened. When the molten resin enters the mold cavity, the air within the mold cavity moves toward the outer periphery of the mold cavity and leaks out of the mold cavity. When injection is complete, the fixed and movable molds are closed again.

Furthermore, when the punch is moved forward to open the center of the forming disk, the sprue button moves backward in response. During the retreat, the sprue button and nozzle are connected to the hydraulic circuit, so the sprue button is moved to a predetermined position by the control valve. By having a resisting force, it moves at a predetermined speed while resisting the pressing force of the punch.

(Example) Examples of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional view of an injection molding apparatus in a mold-clamping state, in which 1 is a fixed plate, 2 is a movable plate, and the fixed plate 1 has a fixed side assembly composed of a plurality of elements. A three-dimensional structure is attached to the movable platen 2, and a movable assembly composed of a plurality of elements is attached to the movable platen 2. Please note that the applicant first filed a patent application
In contrast to the disk injection molding device proposed in No. 61-40538, in which an outer peripheral ring is attached to the fixed mold in correspondence with the outer peripheral stamper holder, an annular protrusion is formed on the fixed mold as described later. , which forms a cavity with compression allowance.

Hereinafter, the fixed side assembly and the movable side assembly will be explained in this order. An inner hole 3 in which a stepped portion 3b is formed is formed on one end surface of the fixed platen 1 on the movable platen 2 side.
A fixed-side mounting member 3 having a shape of 1.a is fixed, and an end face of an annular fixed-side holding member 4 is attached to the end face of the fixed-side mounting member 3 via a bolt 5. The inner hole 3a of the fixed side mounting member 3 has a stepped portion 6a.
A fixed-side fitting member 6 having a formed therein is inserted, one end surface of which contacts the fixed platen 1, and the other end protrudes from the inner hole 3a to fit into the hole 4a of the fixed-side holding member 4.
The fixed-side mounting member 3 and the fixed-side insertion member 6 extend in a fitted state, and the fixed-side fitting member 3 and the fixed-side insertion member 6 have stepped portions 3b and 6a.
They engage with each other to prevent the stationary side insertion member 6 from coming off. In the hole 4a of the fixed side holding member 4,
The fixed side mirror plate 7 is fitted, one end surface of which is in contact with the end surface of the fixed side fitting member 6, and the center portion of the other end surface has an annular protrusion projecting in the direction of the movable platen 2 and having a circular cross section. The end face of the annular projection forms a mirror surface of the annular cavity 8.

Therefore, the fixed side holding member 4 and the fixed side mirror plate 7 constitute the fixed side mold X.

A through hole 11 consisting of a large diameter part and a small diameter part is formed in the center of the fixed side insertion member 6 and the fixed side mirror plate 7, and the large diameter part passes through the fixed side holding member 4. It is located in The through hole 11 has
A sprue bushing 12 consisting of a large diameter part and a small diameter part is movably inserted, and the large diameter part is located in the large diameter part of the through hole 11, and the small diameter part is located in the small diameter part of the through hole 11, respectively. The length of the large diameter portion of the through hole 11 in the axial direction is longer than the large diameter portion of the sprue bush 12.
It is possible to move within the range of these length differences. And the advancement of this spring bush 12 is,
Shoulder portion 13 at the boundary between the large diameter portion and the small diameter portion of the through hole 11
Further, the retraction of the sprue bush 12 is restricted by a ring 14 attached to the rear end of the through hole 11.

A locate ring 16 having a through hole 15 is fixed to the rear end of the fixed side insertion member 6, and a through hole 17 having a larger diameter than the locate ring 16 is formed in the fixed platen 1. A nozzle 19 attached to the heating cylinder 18 can freely come into contact with a recess 12a formed in the rear end surface of the sprue bush 12 through the through hole 17 and the through hole 15.

In the figure, 20 is a spiral cooling groove formed in the fixed side mirror plate 7, and 21 is a cooling water intake hole communicating with the cooling groove 20. Note that the cooling water drainage hole is omitted. Reference numeral 22 denotes a bush fitted into the outer periphery of the through hole 11 located in the fixed side mirror plate 7, and the tip of the sprue bush 12 is movably fitted into the bush.

Next, I will explain about the movable side assembly.
The end face of the movable platen 2 on the fixed platen 1 side has a movable mounting member 23, a movable first member 24, an annular movable second member 25, a movable third member 26, and a recess 27a in the center. The movable-side fourth member 27 and the annular movable-side holding member 28 are attached in this order.

29 is a projecting pin that movably penetrates the movable platen 2, the movable-side mounting member 23, and the movable-side first member 24; 30 is reciprocatably attached to a notch of a mold clamping ram 31 that moves the movable platen 2; The first protrusion plate 30a is a second protrusion plate located in the hole 25a of the movable second member 25, and the protrusion pin 2
One end of 9 is fixed to the first protrusion plate 30, and the other end is fixed to the second protrusion plate 30a.

The movable first member 24 is provided with a cylinder 32, into which a piston 33 whose distal end surface abuts the proximal end of a punch 50 (described later) is slidably inserted, and the piston 33 moves forward. The limit is determined by a regulation plate 34 attached to the opening at one end of the cylinder 32, and the retraction limit is determined by a regulation plate 34 attached to the opening on the other end of the cylinder 32, which is fixed to the movable attachment member 23. This is determined by the stopper 36 that is set.

A recess 39 is formed in the center of the movable third member 26, and a through hole 40a is formed at the bottom of the recess 39. Furthermore, on the outer peripheral side of the recess 39,
A pair of pin holes 41 are formed, and a cylindrical collar 42 is slidably inserted into the pin holes 41.
A second protruding pin 43 is slidably inserted into the collar 42 . The lengths of the collar 42 and the second protruding pin 43 are longer than the length of the pin hole 41, one end of which is fixed to the second protruding plate 30a, and the other end of the second protruding pin 43 is fixed to the pin hole 41. 41 and recess 2 of the movable fourth member 27
It is slidably inserted into the through hole 45 of the drive member 44 which is slidably inserted into the drive member 7a. The tip of the other end of the second ejecting pin 43 has a large diameter, and the large diameter portion can freely come into contact with the stepped portion 45a of the through hole 45.

A movable side fitting member 46 and a movable side mirror plate 47 are fitted into the annular movable side holding member 28, and a recess 46a is formed on the movable side fourth member 27 side of the movable side fitting member 46. A through hole 46b is formed at the bottom of the recess 46a, and a through hole 47a having approximately the same diameter as the through hole 46b is also formed in the movable side mirror plate 47. A bush 48 is inserted into the through holes 46b and 47a, and the end of the bush 48 is located within the recess 46a, and the end surface thereof is fixed to the movable fourth member 27. In the figure, reference numeral 38 denotes a spiral cooling groove formed in the movable side mirror plate 47.

Therefore, the movable side holding member 28 and the movable side mirror plate 4
7 constitutes a movable mold Y.

Through holes 44a and 27b are formed in the center of the driving member 44 and the bottom of the recess 27a, respectively, and the through hole 44a of the driving member 44 has a large diameter part and a small diameter part. One end of a product protruding collar 49 having an inner hole is fixed, and the other end of the product protruding collar 49 is slidably inserted into the through hole 27b and the bush 48 at the bottom of the recess 27a.

The through hole 40a of the movable third member 26, the through hole 44a of the drive member 44, and the product protrusion collar 49
The inner holes are arranged concentrically to form a punch hole, into which a punch 50 is movably inserted. The punch 50 has a large diameter portion;
It consists of a small diameter part and an intermediate diameter part with a diameter between these, and is formed in the order of a large diameter part, an intermediate diameter part, and a small diameter part from the base end, and the large diameter part is located in the recess 39, and , the tapered stepped part between the small diameter part and the intermediate diameter part is
It can freely come into contact with a tapered stepped portion formed in the inner hole of the product protrusion collar 49.

The punch 50 is also formed with a through hole 50a extending in the longitudinal direction thereof, and a protruding pin 51 having one end fixed to the second protruding plate 30a is slidably inserted into the through hole 50a. There is.

On the outer periphery of the tip end of the bush 48, an annular inner hole stamper holder 52 for holding the center portion of the movable stamper 57 is provided so as to be reciprocally movable.
The tip of the inner hole stamper 52 is bent outward and can be freely engaged with the inner circumferential side of the stamper 57. Further, a threaded portion 52a is formed at the base end of the inner hole stamper holder 52, and an umbrella worm gear 53 is screwed into the threaded portion 52a. The gear 53 has a cylindrical shape, and its inner peripheral surface is similar to the bush 4.
8, the threaded portion 5
A threaded portion on the inner circumferential surface of a through hole formed at the bottom of the gear 53 is screwed into 2a. moreover,
A threaded portion is also formed on the end face of the gear 53 on the opening side, and a threaded rod 54 rotatably held by the movable side holding member 28 is screwed into the threaded portion. , the gear 53 rotates, and the rotation of the gear 53 moves the inner hole stamper holder 52 forward and backward.

Reference numeral 55 denotes a spring disposed between the large diameter portion of the punch 50 and the bottom of the movable third member 26, which elastically biases the punch 50 in the right direction in the drawing. 56 is a spring disposed between the second protruding plate 30a and the movable fourth member 27,
This is for elastically biasing the second protruding plate 30a in the right direction.

An annular stamper 57 having an opening in the center is attached to the bottom surface of the movable mirror plate 47.
An annular stamper 5 is provided on the outer peripheral side of the movable mirror plate 47.
An outer circumferential stamper holder 58 for fixing the outer circumferential portion of the stamper 7 to the movable mirror plate 47 is attached with bolts 59.

As shown in FIGS. 2 and 3, the outer peripheral stamper holder 58 is made of an annular member disposed on the outer peripheral edge of the movable side mirror plate 47, and the end surface facing the fixed side mirror plate 7 is located on the movable side. An outer circumferential flat part 58a formed parallel to the radial direction of the mirror plate 47, an inclined part 58b connected to the outer circumferential flat part 58a and inclined in a direction away from the fixed side mirror plate 7, and the inclined part. 58b, it is formed of an outer peripheral flat part 58a and a parallel inner peripheral flat part 58c.

The outer periphery of the fixed mirror plate 7 facing the outer stamper holder 58 has an outer periphery flat part 9a parallel to the outer periphery flat part 58a of the outer periphery stamper holder 58.
and a sloped portion 9 that is continuous with the peripheral flat portion 9a and parallel to the sloped portion 58b of the peripheral stamper holder 58.
b, and an inner circumferential flat part 9c that is connected to the inclined part 9b and parallel to the inner circumferential flat part 58c of the outer circumferential stamper holder 58, and is formed by a pair of opposing outer circumferential flat parts 9a, 58a, and an inclined inner circumferential flat part 9c. Between the portions 9b, 58b and the inner peripheral flat portions 9c, 58c, an air venting gap G is formed during mold clamping, and the inner peripheral side surface 58d of the outer peripheral stamper holder 58 is connected to the annular protrusion of the fixed side mirror plate 7. It comes into sliding contact with the stepped annular side surface 7a.

By the way, during mold clamping, the movable side and fixed side holding members 28, 4 are fixed and movable side mirror plates 7, 4.
It is necessary to make accurate contact so that the parts 7 remain concentric.
For this reason, an inclined portion is formed on each opposing end surface of the fixed side mirror plate 7 and the movable side mirror plate 47.

That is, both upper and lower end portions of the end surface of the fixed side holding member 4 are formed into flat portions 4a and 4b perpendicular to the moving direction of the movable side holding member 28,
A movable side holding member 28 is provided between the flat parts 4a and 4b.
A sloped portion 4c is formed that slopes in a direction away from the surface.

Flat portions 28a and 28b are also formed at both upper and lower end portions of the end surface of the movable side holding member 28, and an inclined portion 28c is formed between the flat portions 28a and 28b. The flat parts 28a, 28b and the inclined part 28c are parallel to the corresponding flat parts 4a, 4b and the inclined part 4c of the fixed side holding member 4. Incidentally, the inclination angle of the inclined portion 4c is set within a range of 4° to 10°, preferably 7° with respect to the moving direction of the movable side holding member 28. Since the end faces of the fixed side and movable side holding members 4, 28 are formed as described above, when the mold is clamped, these members 4, 28 are guided to each other by mutual sliding of the inclined parts 4a, 28c. Therefore, these members 4 and 28 do not shift from each other when they come into contact. Note that if the above-mentioned inclination angle of the inclination part 4c is too large, the guiding function will be reduced, and if it is too small, the inclination part 4c, 2
8c will interfere with each other, and the inclined portions 4c,
28c cannot be smoothly slid against each other. The range of the above-mentioned inclination angle is a range in which these inconveniences do not occur.

Next, the operation of the sprue bush 12 mentioned when explaining the stationary side assembly will be described. In the present invention, the center part of the molded product is opened using the punch 50 while the parting surface of the annular cavity is kept in close contact with the sprue bush 12. The sprue bush 12 is movable, and as the punch 50 moves forward, the sprue bush 12 moves backward. However, in the present invention, the sprue bush 12 is not simply retracted without creating any resistance, but is retracted while advancing the punch 50 while applying a force that resists the pressing force of the punch 50. That is, normally, the nozzle 19 is retreated immediately after the injection of molten resin is completed, but in the present invention, after the injection is completed,
The nozzle 19 is kept in contact with the recess 12a of the sprue bush 12 without retreating, and the contact force is reduced. The contact force of the nozzle 19 applies a pressing force to the sprue bush 12. This pressing force may be constant or may be changed stepwise or slopewise.

Here, a specific mechanism for operating the nozzle 19 as described above will be explained. As shown in FIG. 1, the nozzle 19 is attached to the tip of the heating cylinder 18, and the heating cylinder 18 is fixed to the connecting part 60.
0 is connected to a piston rod 61a of a hydraulic cylinder 61 and is capable of reciprocating movement. Oil holes 62 and 63 are formed at both ends of the hydraulic cylinder 61, and a pipe line 6 is formed in the oil hole 62 on the forward limit side of the hydraulic cylinder 61.
5a is connected, and a pipe line 65b is connected to the oil hole 63 on the reverse limit side, and a four-port three-position switching valve 67 is connected to the pipe lines 65a and 65b, and the switching valve 67
A hydraulic pump 64 and an oil tank 66 are connected to each other. Further, a branch passage 68 connected to an oil tank 66 is connected to a pipe line 65b between the oil hole 63 and the four-port three-position switching valve 67, and an electromagnetic proportional pressure control valve 69 is connected to the branch passage 68. It has been intervened.
The position of the 4-port 3-position switching valve 67 is determined by energizing the solenoids 67a and 67b. For example, when the solenoid 67a is energized,
The 4-port 3-position switching valve 67 takes the A position, and pressure oil is supplied to the forward limit side of the piston rod 61a, and oil on the backward limit side is discharged, so that the nozzle 1
9 retreats. Furthermore, when the solenoid 67b is energized, the 4-port 3-position switching valve 67 assumes the B position.
Pressure oil is supplied to the backward limit side of the piston rod 61a, and oil on the forward limit side is discharged, so that the nozzle 19 moves forward.

By the way, since an electromagnetic proportional pressure control valve 69 is provided in the branch path 68 of the hydraulic circuit, if the set pressure of the valve 69 is appropriately determined, the force applied to the sprue bush 12 can be adjusted as described above. Can be done.

In the above description, the force applied to the sprue bush 12 is adjusted using the electromagnetic proportional pressure control valve 69, but the present invention is not limited to this, and a pressure reducing valve may also be used.

In the above description, the nozzle 19 is used as a means for imparting resistance to the sprue bush 12, but the nozzle 19 is not limited to this, and for example, the sprue bush 1
A resistance force may be applied to the sprue bush 12 by directly applying hydraulic pressure to the rear part of the sprue bush 12.

Note that 70 is a screw rod attached to a mold clamping cylinder (not shown), and the first protruding plate 30 can freely come into contact with it when the mold is opened.

In addition, in FIG. 6, 71 is a molded product take-out arm, and a disk suction cup 7 that sucks a molded disk 72.
3, and a punched plate 74 punched out of the molded disk 72.
It is equipped with an opening suction cup 75 for suctioning. When the mold is opened, the molded product take-out arm 71 descends from above the mold, stops when it reaches a predetermined position, adsorbs the molding disk 72 and the punching 74 to which the sprue is attached, and then moves again. Rise. In addition, 76
is a stay fixed to the fixed platen 1 and slidably passing through the movable platen 2.

FIG. 7 is a sequence diagram of the injection molding process according to the present invention, mainly showing the operation of the punch 50, in which the nozzle 19 advances, the nozzle 19 retreats, punching the molding disk and setting the ejecting circuit, the punch advances, and the punch Retraction and set pressure switching of the electromagnetic proportional pressure control valve are each shown.

Advancement of the nozzle...Switch the selector switch CS-O to automatic or anti-automatic, and press the selector switch
Switch CS-N to repeat and press the selector switch.
When CS-O and CS-N are closed and a mold clamping start signal is input in this state, relay RLSI is energized and RLSI is closed, so solenoid SOL-
H (indicated by reference numeral 67a in the drawing) is energized and excited, the 4-port 3-position switching valve 67 takes the B position, and pressure oil is supplied to the backward limit side of the piston rod 61a, while oil on the forward limit side is discharged. As a result, the nozzle 19 moves forward under high pressure.

Punching the molding disk and setting the ejecting circuit...When mold clamping is completed, a mold clamping completion signal is input to relay RLC, and the relay is energized and contacts
Injection begins as soon as the RLC closes, filling the mold cavity with molten resin. With injection completed in this way, selector switch CS-
Close EJ and selector switch CS-OE
If the switch is switched to automatic and the normal contact LS-O is closed, relay RK ₁ is energized, contact RK ₁ is energized and closed, relay RK ₁ is self-held, and the punching and ejection circuit of the forming disk is set. be done.

Switching the set pressure of the electromagnetic proportional pressure control valve...When injection is completed, relay RTE closes and relay SC ₁
Since the is normally closed, the electromagnetic proportional pressure control valve 6
The set pressure of 9 is switched from high pressure to low pressure. The set pressure can be set to any mode, constant, slopewise, or stepwise.

Advancement of the punch 50...When injection is completed, contact RK ₁ closes as described above, and at the same time, the timer starts counting, and when timing is completed, the timer contact closes.
TRGS closes, solenoid SOL-GF is energized, and punch 50 moves forward. In this way, punch 50
The molded disc is punched out by the following method.

Mold opening: When the punching by the punch 50 is completed, the mold opening starts, and then the punching plate 74 is ejected by the ejecting pin 29 and the product ejecting collar 4 is ejected.
9, the molding disk 72 is released from the mold.

Retraction of the punch 50...When the molding disk 72 is released from the mold as described above, the solenoid SOL
-A signal is input to EB, solenoid SOL-
GB is energized. This solenoid SOL−GB
The punch 50 is retracted by the excitation.

Retraction of the nozzle 19...After injection, the charging process begins, and the screw inside the heating cylinder 18 rotates and retreats, but when the screw stops retreating, the normally open contact relay _SC2 closes, and the selector switch CS closes. -O, CS-N are closed, solenoid K (symbol 67b in the drawing)
Indicated by ) is energized and when the nozzle reaches its retraction limit, the limit switch LSN is activated and the nozzle retraction is stopped. Simultaneously with the stop of nozzle 19, relay SC ₁ is closed and relay SC ₂ is normally open, so that the pressure setting value of electromagnetic proportional pressure control valve 69 is switched to high pressure.

As is clear from the figure, mold opening steps d, e, f
Since this is performed with the punch 50 advanced, the punch 50 does not pass through the opening of the molded product again after punching, so the cut end is not damaged and no chips are generated.

Next, the operation of the device having the above configuration will be described. When a mold clamping cylinder (not shown) is driven to advance the mold clamping ram 31 to the left in the drawing, the movable side holding member 28 approaches the fixed side holding member 4, and the inclined portion 28c of the movable side holding member 28 moves toward the fixed side. In other words, the movable holding member 28 slides along the inclined portions 4c of the holding member 4.
Approach the fixed side holding member 4 while being guided by 8c,
Finally, the flat parts 28a, 28 of the movable side holding member 28
b comes into contact with the flat portions 4a, 4b of the fixed side holding member 4, the forward movement of the movable side holding member 28 is stopped, and mold clamping is completed.

In this way, the fixed side and movable side mirror plates 7,
47 is closed, the pressure inside the mold clamping cylinder (not shown) is increased to a predetermined pressure, and then the heating cylinder 18 is advanced to bring the tip of the nozzle 19 into close contact with the recess 12a of the sprue bush 12. When the molten resin in the heating cylinder 18 is injected into the annular cavity 8, the air in the annular cavity 8 is transferred to the inner circumferential side surface 58d of the outer peripheral stamper holder 58, the stepped annular side surface 7a of the annular protrusion on the fixed side mirror plate 7, The air is discharged from the gap to the outside through the air venting gap G. FIG. 1 shows this state.

By the way, when the mold is closed and the mold clamping force is kept constant and the molten resin is injected into the annular cavity 8, the mold clamping force is the product of the molten resin pressure and the projected area of the shape in which the molten resin spreads circularly inside the annular cavity 8. If the force is set to be slightly smaller than the force, the mold will open slightly during injection and the force acting on the molten resin will be reduced.
At this time, the annular cavity 8 of the mold expands in the thickness direction, and the inner circumferential side surface 58d of the outer peripheral stamper holder 58 and the step annular side surface 7a of the fixed side mirror plate 7 slide, and the molten resin overflows from the annular cavity 8. There isn't. Next, when the injection is completed, the molten resin pressure becomes zero, and the mold clamping force closes the mold again, and the molten resin inside the annular cavity 8 is compressed by the mold clamping force with uniform pressure distribution inside the annular cavity 8. molded products with low birefringence can be obtained.

When the injection of the molten resin is completed as described above, an appropriate holding pressure is applied to the molten resin in the annular cavity 8 to hold it for a predetermined time. In the present invention, after injection is completed, the center of the disk is opened before the resin in the cavity solidifies, but in preparation for this, the 4-port 3-position switching valve 67
is switched to position A, and the contact pressure of the nozzle 19 against the sprue bush 12 is controlled by the electromagnetic proportional pressure control valve 69. At the same time, the cylinder 32 provided on the movable first member 24 operates, and the piston 3
3 moves to the left and thrusts the punch 50 to the left (see Fig. 4). The center of the molded disk is punched out by the operation of the punch 50, but at this time,
Since the sprue bush 12 is provided so as to be retractable, it starts retracting as the punch 50 moves forward. However, the nozzle 19 remains in contact with the recess 12a of the sprue bush 12, and a force is applied to the nozzle 19 by the electromagnetic proportional pressure control valve 69 in a direction that resists the pressing force of the punch 50. Therefore, the sprue bush 12 moves backward as the punch 50 advances, but a force is applied to the sprue bush 12 to resist the pressing force of the punch 50.
Moreover, since this force can be adjusted arbitrarily, the pressing force of the punch 50 can be adjusted. If no force is applied to the sprue bush 12 to resist the pressing force of the punch 50, the sprue bush 12 will retreat without any resistance when the punch 50 moves forward. Since the cut at the opening becomes rough, residual stress is generated, and as a result, the signal shaping range near the opening is narrowed.

When the punching of the molded disc is completed as described above, the movable plate 2 begins to retreat, and the first protruding plate 30 also retreats, but after retreating to a certain extent, the first protruding plate 30 engages the pair of screw rods 70. It stops when it comes into contact with it. The other movable platen 2 has a first protruding plate 3
In order to continue retracting even after stopping at 0, the ejecting pin 29
The protruding pin 51 attached to the second protruding plate 30a through the protruding pin 51 protrudes relatively, and as shown in FIG. 4, protrudes the punched plate 74 punched by the punch 50.

When the movable platen 2 further retreats, the collar 42 relatively protrudes and moves the drive member 44 to the left, so the product ejecting collar 49 protrudes, and as shown in FIG. Release from the mold from 47.

Next, the molded product removal arm 71 descends as shown in the figure, and the molded disk and punching plate 74 are sucked by the disk suction cup 73 and the opening suction cup 75. Thereafter, the molded product removal arm 71 moves to the left and then rises, thereby moving the molding disk and the punching plate 74 to a predetermined position.

FIG. 8 is a diagram illustrating the operation of the present invention described above. As shown by the polygonal line A, the injection process a, the cooling process b for cooling the molded product, the pressure relief process c, the low-speed mold opening process d, and the high-speed mold The opening step e, the low speed mold opening step f, the ejector pin 29 advancing step g, and the ejecting pin 29 retracting step h are performed in this order.

The contact force P of the nozzle 19 with respect to the sprue bush 12 is set to a high pressure until the injection is completed, and is set to a low pressure after the injection is completed, as shown by the polygonal line B.

A polygonal line C indicates the operation of the punch 50.
After the elapse of time t after completion of injection, the robot moves forward. This time t is 0.5 seconds. In this way, in the present invention, punching is performed with the punch 50 immediately after injection is completed, while the molded product is not yet hardened by cooling, so the cut at the opening of the molded product becomes smooth and chips are generated. Therefore, the chips may not be on the surface of the stamper 57 or the stationary mold 4.
Therefore, in the next new injection, molding defects due to contamination of chips will not occur.

The punch 50 retreats at the same time as the ejector pin 29 begins to retreat.

A polygonal line D indicates a charging process, which is performed in the order of a resin supplying process i, a plasticizing process j, and a suction process k. A polygonal line E indicates the operation of the nozzle 19, and during the time t from the completion of injection to the completion of punching by the punch 50, a force is applied due to low pressure, in other words, a force is applied in a direction that resists the pressing force of the punch. In this state, it is in contact with the sprue bush 12, and after punching is completed, it moves backward and stops moving back by coming into contact with the limit switch LSN.

(Effects of the Invention) As is clear from the above, the present invention supports the mold clamping force by bringing the ends of the stationary side mold and the movable side mold into close contact with each other, so that the convex part of the stationary side mold An annular cavity is formed by fitting to the outer circumferential stamper holder, and an air vent gap can be formed on the outer periphery of the annular cavity, so that the structure can be simplified.

In addition, when the sprue bush is retreating when the punch is moving forward, a resistance force is applied to the sprue bush that resists the pressing force of the punch, so the cut at the opening of the forming disk becomes smooth and bending near the opening is also suppressed. As a result, the generation of residual stress is suppressed as much as possible, and the drag force of the sprue bushing can be arbitrarily changed by adjusting the control valve, allowing the center hole of the disk to be punched out by selecting the optimum conditions. Therefore, it is possible to obtain a material with a uniform and low birefringence index.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the device according to the present invention, Fig. 2 is a sectional view showing the main parts of the invention, Fig. 3 is an enlarged sectional view showing the main parts of the invention, and Fig. 4 is a protruding state of the punch. FIG. 5 is a view equivalent to FIG. 1 showing the mold opening state, FIG. 6 is a view equivalent to FIG. 1 showing the molded product removal state, and FIG. 7 is an operation of the apparatus according to the present invention. FIG. 8 is a time chart showing the operation of the apparatus according to the present invention. 1... Fixed plate, 2... Movable plate, 4... Movable side holding member, 7... Movable side mirror plate, 12... Sprue bush,
19... Nozzle, 28... Fixed side holding member, 47... Fixed side mirror plate, 50... Punch, 51... Ejection pin,
57...Annular stamper, 58...Outer stamper holder,
X...Fixed side mold, Y...Movable side mold.

Claims (1)

[Claims] 1. A fixed side mold is provided on a fixed plate fixed to the machine base of an injection molding machine, a movable side mold is fixed on a movable plate that reciprocates with respect to the fixed plate, and the fixed side and movable side molds are opposed to each other. The surface is provided with an inclined part and an end face part, which align the stationary mold and the movable mold and make them come into close contact with each other when mold clamping is completed, and hold the stamper on the mirror surface of the movable mold and An outer stamper holder is provided whose inner periphery defines the outer periphery of the annular cavity, and the outer edge of the mirror surface of the stationary mold can be fitted to the inner periphery of the outer stamper holder with a slight gap for air venting. A sprue bush formed as a convex portion and having a molten resin passage communicating with the center of the annular cavity is movably inserted into the stationary mold, and a position corresponding to the sprue bush is placed in the movable mold. a reciprocating punch that penetrates the center of the environmental cavity, a nozzle that can be freely pressed against the rear end surface of a sprue bush attached to the tip of the heating cylinder, and a cylinder device that moves the heating cylinder back and forth. ,
A hydraulic circuit equipped with a control valve that adjusts the pressing force of the nozzle against the sprue bushing when the punch connected to the cylinder device moves forward is provided, and the center of the disk in the formed annular cavity is punched with the punch. A disk injection molding device characterized in that a resistance force is applied to the sprue bush in a direction that resists the pressing force of the punch.