JPH0338098B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an injection molding machine, and is particularly suitable for molding disks such as record discs, magnetic disks, optical disks, and information recording disks having an opening in the center. Regarding the injection molding equipment used.

(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, the conditions for reproducing clear images or high-quality sound are that the birefringence is low and that there is a complex structure 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.

As one condition for satisfying such requirements, when filling the mold cavity with molten resin,
It is necessary for the air inside the mold cavity to be exhausted outside the mold cavity by the molten resin.
For this purpose, the mold cavity must be in communication with the outside during mold clamping.

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 is possible to apply a resistance force in the direction of resisting the pressing force of the punch.
15mm (in the case of CD), and the resin pressure applied to this part during molding is approximately 300Kg/cm ² , 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 arises in that punching by force is difficult.

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 a fixed mold on a fixed plate fixed to the base of an injection molding machine, and a movable mold on a movable plate that reciprocates with respect to the fixed plate. The fixed side mold and the movable side mold are fixed, and the opposing surfaces of the fixed side mold and the movable side mold are formed with an inclined part and an end face part, which center the fixed side mold and the movable side mold and make them come into close contact with each other when mold clamping is completed, An outer stamper holder for holding the stamper is provided on the mirror surface of the movable mold, and an outer ring whose inner periphery defines the outer periphery of the mold cavity is provided on the stationary mold, and when the mold clamping is completed, the outer periphery is fixed. A sprue bushing having a gap formed between the stamper holder and the outer ring and a molten resin passage communicating with the center of the mold cavity is movably inserted into the stationary mold, and the sprue bush is movably inserted into the fixed mold. A reciprocating punch is provided in the mold at a position corresponding to the sprue bush so as to pass through the center of the mold cavity, and the punch is attached to the tip of the heating cylinder that can be freely pressed against the rear end surface of the sprue bush. a cylinder device that moves the heating cylinder back and forth, and 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. When punching out the center of the disk in the mold cavity, a resistance force is applied in a direction that resists the pressing force of the punch when the sprue bushing retreats.

(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. 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.

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 resistive force, it is possible to retreat 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.

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 insertion member 6 having a shape formed therein is inserted into the fixed side, 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, and one end surface thereof is in contact with the end surface of the fixed side insertion member 6. The central portion of the fixed side mirror plate 7 is formed into a truncated conical shape projecting in the direction of the movable platen 2. Although not shown,
It is also possible to attach a stationary side stamper to the end face of this truncated conical part, and in this case, the stationary side stamper is attached to the outer peripheral ring 10 attached via bolts 9 along the inclined surface of the truncated conical part. It is fixed to the fixed side mirror plate 7 by. The inner circumferential edge of the outer circumferential ring 10 extends to the outer circumferential edge of the gap between the annular stamper 57 and the end face of the truncated conical portion, which will be described later, and defines the outer circumferential surface of the molded product that is filled into the gap and molded. It's becoming like that. 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 47
constitutes the 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 of the bush 48, an annular inner hole stamper holder 52 for holding the center portion of the annular stamper 57 is provided so as to be reciprocally movable. The tip of the inner hole stamper 52 is bent outward,
It can be freely engaged with the inner peripheral side of the stamper 57.
Further, a threaded portion 52a is formed at the base end of the inner hole stamper holder 52, and the threaded portion 52a includes:
An umbrella worm gear 53 is screwed together. The gear 5
3 has a cylindrical shape, and its inner circumferential surface is screwed into the enlarged diameter base end of the bush 48, and the threaded portion 52a
A threaded portion on the inner circumferential surface of a through hole formed at the bottom of the gear 53 is screwed into the gear 53 . Further, a threaded portion is also formed on the end surface of the gear 53 on the opening side,
A screw rod 54 rotatably held by the movable side holding member 28 is screwed into the screw portion.
When the gear 53 rotates, the gear 53 rotates.
3, the inner hole stamper holder 52 moves 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. Reference numeral 56 denotes a spring disposed between the second protrusion plate 30a and the fourth annular member 27, and serves to elastically bias the second protrusion plate 30a in the right direction.

An annular stamper 57 having an opening in the center is attached to the bottom surface of the annular mirror plate 47. An annular stamper 57 is provided on the outer peripheral side of the movable mirror plate 47.
An outer peripheral stamper holder 58 is attached with bolts 59 to fix the outer peripheral part of the stamper to the movable mirror plate 47.

As shown in FIG. 2, the outer peripheral stamper holder 58 is made of an annular member disposed on the outer peripheral edge of the movable mirror plate 47, and the end face facing the fixed mirror plate 7 is attached to the movable mirror plate 47. An outer peripheral flat part 58a formed parallel to the radial direction, an inclined part 58b connected to the outer peripheral flat part 58a and inclined in the direction of the annular stamper 57, and an outer peripheral flat part connected to the inclined part 58b. 58a and a parallel inner peripheral flat portion 58c.

The outer periphery of the fixed mirror plate 7 that faces the outer stamper holder 58 has an outer periphery flat part 10a that is parallel to the flat part 58a of the outer periphery stamper holder 58, and is connected to the flat part 10a to form the outer periphery stamper holder 58. an inclined portion 10b parallel to the inclined portion 58b;
The inner peripheral flat part 10c is formed from a pair of opposing flat parts 10a, 58a and the inclined parts 10b, 58b, and is formed from an inner peripheral flat part 10c that is connected to the inclined part 10b and parallel to the stamper 57. An air venting gap G is formed between the stamper 57 and the stamper 57 when the mold is clamped. More specifically, in terms of numerical values, the gap G between the inner circumferential flat part 10c and the stamper 57 is set to about 10 μm, and the length of the inner circumferential flat part 10c in the radial direction is set to about 3 mm. These numerical values were determined based on the viewpoints of preventing the molten resin from flowing out from the gap G during filling and improving the outflow of air during filling.

The fixed side holding member 4 and the movable side holding member 28 abut each other so that an air venting gap is formed between the outer ring 10 and the outer stamper holder 58 during mold clamping. In other words, the mold clamping force during mold clamping is supported by the annular and stationary side holding members 28 and 4.

By the way, when the mold clamping force is supported by the annular and fixed-side holding members 28 and 4 in this way, when the mold is clamped, the opposing end surfaces of these members 28 and 4 are
It is necessary that the fixed side and movable side mirror plates 7 and 47 abut each other accurately so as to maintain concentricity. In other words, it is necessary that these members 28 and 4 do not shift from each other when they come into contact. For this reason, on each opposing end surface of the fixed side mirror plate 7 and the movable side mirror plate 47,
A sloped portion is formed.

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 7c is too large, the guiding function will be reduced, and if it is too small, the inclination angle of the inclination parts 4a, 2
8a will interfere with each other, and the inclined parts 4a,
This means that smooth sliding between the parts 28a cannot be achieved. 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. This contact 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 connected to a piston rod 61a of a hydraulic cylinder 61 via a connecting part 60. Oil holes 6 are provided at both ends of the hydraulic cylinder 61.
2, 63 are formed, a pipe line 65a is connected to the oil hole 62 on the forward limit side of the hydraulic cylinder 61, a pipe line 65b is connected to the oil hole 63 on the backward limit side,
The pipe lines 65a and 65b are connected to a 4-port 3-position switching valve 6.
7 is connected to the switching valve 67, and a hydraulic pump 64 is connected to the switching valve 67.
and an oil tank 66 are connected. Furthermore, the pipe line 6 between the oil hole 63 and the 4-port 3-position switching valve 67
5b has a branch path 68 connected to the oil tank 66.
are connected to each other, and an electromagnetic proportional pressure control valve 69 is interposed in the branch passage 68 .

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,
Pressure oil is supplied to the forward limit side of the piston 61c,
Since the oil on the retreat limit side is discharged, the nozzle 19 retreats. Furthermore, when the solenoid 67b is energized, 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 the oil on the forward limit side is discharged, and as a result, 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 by the electromagnetic proportional pressure control valve 69, but the invention is not limited to this, and a pressure reducing valve can also be used.Furthermore, when the sprue bush 12 is in the retracted state, A resistance force may be applied to the sprue bush 12 by generating back pressure by removing the hydraulic pressure of the hydraulic system supporting the sprue bush 12 through a throttle.

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.

Further, in FIG. 5, reference numeral 71 denotes 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.

Next, the operation of the device having the above configuration will be described. When the end 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 comes close to the fixed side holding member 4, and the inclined part 28c of the movable side holding member 28 is on 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
When 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 state of mold clamping completion, the outer ring 1
0, the outer stamper holder 58 and the outer ring 10
As described above, an air vent gap is formed between the movable stamper 57 and the movable stamper 57, as shown in FIG.

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 4-port 3-position switching valve 67 is set to the B position as described above, and the heating cylinder 18 is moved forward. Then, the tip of the nozzle 19 is brought into close contact with the recess 12a of the sprue bush 12, and the molten resin in the heating cylinder 18 is injected into the mold cavity. FIG. 1 shows this state.

In the present invention, injection is performed at high speed initially, and when a predetermined position or time is reached, the injection speed is switched to low speed. In this case, a predetermined injection speed may not be obtained at a predetermined position due to the inertia of the screw. For this reason, we have adopted measures to suppress the inertia of the screw by providing back pressure in the injection hydraulic circuit of the injection molding machine, and also adopted measures to change the holding pressure in stages or to reduce the pressure continuously after injection is complete. Good too.

Once the injection of the molten resin is completed as described above, an appropriate holding pressure is applied to the molten resin in the mold cavity to hold it for a predetermined time.
The 4-port 3-position switching valve 67 is switched to the neutral position. At the same time, the cylinder 32 provided on the movable first member 24 is actuated, and the piston 33 moves to the left to project the punch 50 to the left (see FIG. 3).
The center of the forming disk is punched out by the operation of the punch 50, and at this time, since the sprue bush 12 is provided so as to be retractable, the punch 5
0 starts moving forward and moving backward. However, since the nozzle 19 remains in contact with the recess 12a of the sprue bush 12 and the 4-port 3-position switching valve 67 is in the neutral position, the sprue bush 1
2, the nozzle 19 also retreats, and the piston 61c also retreats, and as a result, the oil in the hydraulic cylinder 61 flows out from the oil hole 63, but this flowing oil does not directly flow into the oil tank 66.
Since the oil flows into the oil tank 66 through the electromagnetic proportional pressure control valve 69, resistance occurs when the nozzle 19 retreats, and a resistance force is applied to the sprue bush 12 in the direction of resisting the pressing force of the punch 50. , therefore, the spur button 12 is the punch 5.
When 0 moves forward, it does not move backward without giving a reaction force to the punch. This resistance force can be arbitrarily adjusted by changing the set value of the electromagnetic proportional pressure control valve 69. 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 protrudes relatively to move 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.

Figure 6 is a diagram showing the above process, and as shown by the polygonal line A, the injection process a, the cooling process b for cooling the molded product, the pressure release process c, the low-speed mold opening process d, and the high-speed mold opening process e. , low speed mold opening process f, ejector pin 29
The advancing step g and the ejecting pin 29 retreating 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 resin supplying process i, plasticizing process j, and suction 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.

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. Further, since the nozzle 19 is provided so as to be able to be pressed against the sprue bush 12 by using the hydraulic circuit that operates the heating cylinder, there is an advantage that the structure is simple and that a resistance can be obtained.

(Effects of the Invention) As is clear from the above, the present invention forms an air vent gap in the mold cavity by supporting the mold clamping force by bringing the ends of the fixed and movable molds into close contact with each other. Therefore, the configuration 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. Therefore, the generation of residual stress is suppressed as much as possible. In addition, by adjusting the control valve, the drag force of the sprue bushing can be changed arbitrarily, and the center hole of the disk can be punched under the optimal conditions, suppressing the generation of internal stress and improving the birefringence. Become so.

[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 a view equivalent to Fig. 1 showing the protruding state of the punch, and Fig. 4 is the mold opening state. FIG. 5 is a view corresponding to FIG. 1 showing a state in which the molded product is taken out, and FIG. 6 is a time chart showing the operation of the apparatus according to the present invention. 1...Fixed plate, 2...Movable plate, 10...Outer ring,
12... Sprue bush, 50... Punch, 51... Ejection pin, 57... Annular stamper, X... Fixed side mold, Y... Movable side mold.

Claims (1)

[Scope of Claims] 1. A fixed side mold is provided on a fixed plate fixed to the machine base of an injection molding machine, and a movable side mold is fixed on a movable plate that reciprocates with respect to the fixed plate, and the fixed side and The opposing surface of the movable mold is formed with an inclined part and an end surface part, which align the fixed mold and the movable mold and make them come into close contact with each other when mold clamping is completed, and a mirror surface of the movable mold is formed. an outer circumferential stamper holder for holding the stamper, and an outer periphery ring whose inner periphery defines the outer periphery of the mold cavity on the stationary side mold, and when the mold clamping is completed, the outer periphery stamper holder and the outer periphery ring are connected to each other. A sprue bush having a molten resin passage communicating with the center of the mold cavity is movably inserted into the stationary mold, and the sprue bush is inserted into the movable mold. A reciprocating punch is provided at a corresponding position so as to penetrate the center of the mold cavity, and a nozzle attached to the tip of the heating cylinder that can be freely pressed against the rear end surface of the sprue bush; 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 and backward is provided. A disk injection molding apparatus characterized in that when punching out the center of a disk with a punch, a resistance force is applied in a direction that resists the pressing force of the punch when the sprue bushing retreats.