JPH0382514A - Mold for molding disc - Google Patents

Abstract

PURPOSE:To achieve a central hole-punching finishing work for a disc molded object simply and satisfactorily without moving a sprue bush by a method in which the tip of the sprue bush corresponding to the central hole of the disc molded object is recessed lower than the surface of the parting line of the sprue bush, and the gate to the cavity for molding the disc is formed of the inner diametrical edge of the sleeve bush and the outer diametrical edge of a punch. CONSTITUTION:The tip 15a of the sprue bush corresponding to the central hole 101 of the disc molded object 100 facing the cavity 3 for molding a disc, is recessed lower than the surface P-P of the parting line of a sleeve bush 14, and the gate 33 to the cavity 3 for molding the disc, is formed with the inner diametrical edge 14a of the sleeve bush and the outer diametrical edge 31a of a punch 30. In the molding of the disc molded object 100 by the mold for molding the disc, the injection nozzle of a molding machine body is advanced in the state of mold closing, and then by pushing said injection nozzle to the nozzle touching surface of the sprue bush 15, molten resin is injected into the cavity 3 for molding the disc through the sprue bush 15 and the gate 33, and said cavity is filled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a mold for molding a disc used for injection molding of, for example, an optical disc for recording information.

(Prior Art) In recent years, optical discs that perform optical recording have been put into practical use as information recording media for information recording and occasional reading means.

Conventionally, injection molding apparatuses used to mold this type of optical disc include, for example, Japanese Patent Application Laid-Open No. 139940/1983 (hereinafter referred to as prior art A) and Japanese Patent Application Laid-Open No. 59-1982
Publication No. 230731 (hereinafter referred to as prior art)
Alternatively, there is a device having a configuration as disclosed in Japanese Patent Application Laid-Open No. 63-270112 (hereinafter referred to as prior art iii).

In injection molding equipment with such a conventional structure, especially when finishing a center hole in a disc molded product, the disc molded product is held down by a fixed mold cavity and a movable mold cavity, and then a punch is pressed. By protruding, the sprue bush is pushed back while holding the gate part, and a shear cut is made between the outer diameter edge of the punch and the inner diameter edge of a die (sleeve bush) provided on the outer periphery of the sprue bush. This is the current situation.

(Problem to be Solved by the Invention) However, in the above-mentioned prior art A, in order to relatively retreat the sprue bushing, the timing of finishing the center hole punching of the disc molded product is different between the fixed mold and the movable mold. This can be carried out without opening, and as a result, the resin hardens at the cut portion of the disc molded product, which not only deteriorates the finished state of the center hole, but also requires extra mold opening/closing control.

In addition, because the stationary fixed board is supported by guide bins, etc., and slides, the sliding part with the sprue bushing is strongly rubbed, which only shortens the life of the mold components due to wear and galling. Instead, metal powder and the like generated from the parts are likely to be mixed into the molded disk product, resulting in a serious defect such as a defective product.

Furthermore, in the prior art, the sprue bush itself is directly slid and retracted while the mold is closed, which allows for a wider range of time to finish punching the center hole in the disc molded product. Although the degree of freedom in timing is increased and the finished state of the center hole can be improved, misalignment is likely to occur due to errors in processing accuracy between the injection nozzle on the molding machine main body side and the sprue bush on the mold side.

If such misalignment occurs, the injection nozzle on the molding machine main body side is forcibly pressed against the sprue bush to align the center, which places an uneven load on the sprue bush.
As the injection nozzle advances and retreats during each molding cycle, the parts in contact with each other are strongly rubbed, causing damage to the sprue bush and the tip of the injection nozzle due to wear and galling, which not only shortens the life of the sprue bush but also causes damage to the injection nozzle to the sprue bush. It is necessary to control the touch force and adjust the retraction speed on the molding machine main body side.

Also, according to the prior art, hot sprue.

The entire hot runner system, which consists of a manifold block, hot nozzle, sprue bushing, etc., must slide uniformly, so if it is possible to change the molding conditions or the temperature of a part of the hot runner, the equipment itself must The process becomes complicated, and it is also necessary to consider the lifespan of mold components such as sliding guides.

Furthermore, when such a hot sprue is applied to the prior art opening, due to changes in molding conditions or the temperature of the hot runner, the dimensions change due to thermal expansion caused by temperature changes in the mold components, causing the sprue bush and injection nozzle to change in size. There was a problem in that it was necessary to adjust the fitting of the sliding parts each time.

This invention was made under the above circumstances, and its purpose is to easily and efficiently finish punching a center hole in a disc molded product without moving the sprue bushing. The object of the present invention is to provide a mold for molding a disk.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention forms a disc molding cavity in a fixed mold and a movable mold, and a disc molding cavity is formed on the fixed mold side. In the mold, a sleeve bushing and a sprue bushing are fixed concentrically with the center of the disc molding cavity, and a punch is movably provided on the movable mold side in correspondence with the sprue bushing so as to be movable back and forth with the center of the disc molding cavity, The tip of the sprue bushing corresponding to the center hole of the disc molded product facing the disc molding cavity is recessed from the parting line surface of the sleeve bushing so that the inner diameter edge of the sleeve bushing and the outer diameter edge of the punch The structure is such that a gate to the disc molding cavity is formed by the part and the part.

(Function) That is, in the present invention, the tip of the sprue bushing corresponding to the center hole of the disc molded product facing the disc molding cavity is recessed from the parting line surface of the sleeve bushing, so that the inner diameter edge part of the sleeve bushing is recessed. and the outer diameter edge of the punch form a gate to the disc molding cavity, and the resin on the sprue bushing side is in a semi-molten state after a predetermined holding pressure time has elapsed since the completion of filling the resin into the disc molding cavity through this gate. , the punch is advanced and inserted into the recess on the tip side of the sprue bushing, and the outer edge of the punch and the inner edge of the sleeve bush cut a gate corresponding to the center hole of the disc molded product. Because of this, it is possible to finish punching the center hole in the disc molded product while keeping the sprue bush fixed.

(Example) Hereinafter, the present invention will be described in detail with reference to an illustrated example.

1 to 5 show a first embodiment of a mold for molding, for example, an optical disk according to the present invention.

That is, as shown in FIGS. 1 and 2, 1 is a fixed mold and 2 is a movable mold, and these molds 1 and 2 form a disc molding cavity 3.

The fixed mold 1 is composed of a mold plate 10 and an insert 13 that is assembled and fixed to the mold plate 10 via a spacer 11 and a cotter ring 12, and also includes a mold plate 10 and an insert 13 that is assembled and fixed to the mold plate 10 via a spacer 11 and a cotter ring 12. An outer sleeve bushing 14 and an inner sprue bushing 15 are inserted concentrically with the center of the sprue bushing 3 with a sprue guard 16 interposed therebetween.

These sleeve bushings 14 and sprue bushings 15 are connected to the locate ring 1 through the sprue cover 17 at their rear end surfaces.
The tip 15 of the sprue bush 15 corresponds to the center hole 101 of the disc molded product 100, which will be described later, and faces the disc molding cavity 3.
a is recessed by a distance a from the parting line plane P-P of the sleeve bushing 14, and a punch 30 (described later)
A recess 19 is formed in such a manner that the distal end thereof is fitted with a gap. In addition, 15b in the figure is a nozzle touch surface into which the injection nozzle 40 of the molding machine main body (not shown) is fitted, which is recessed in a semicircular arc shape on the rear end surface of the sprue bush 15.

On the other hand, the movable mold 2 includes a mounting plate 20 mounted so as to be movable back and forth by a drive device (not shown), first and second receiving plates 21 and 22 fixed to this mounting plate 20, and these first and second receiving plates 21 and 22.
and an insert 25 that is assembled and fixed to the second receiving plate 21, 22 via a spacer 23 and a cotter ring 24, and the disc molding cavity 3.
A stand bar center presser 27 and a center sleeve 2B fixed with a wedge 26 in order from the outside are inserted and fixed through an adjustment bushing 29 concentrically with the center of the center sleeve 28. Center pin 31
．． A punch 30 having a double tube structure with a punch 32 is inserted through the sprue bushing 15 so as to correspond to the tip 15a thereof.

This punch 30 can move forward and backward toward the sprue bush 15 side by driving a hydraulic cylinder (not shown), and its tip 30a is placed on the parting line surface of the center sleeve 28 facing the disc molding cavity 3. at least flat or first
As shown in the figure, the disk molding cavity 3 protrudes by a distance C and is formed by the inner diameter edge portion 14a of the sleeve bushing 14 and the outer diameter edge portion 31a of the punch 30.
It forms the gate 33 to the

In addition, 34 in the figure is a protruding pin inserted into the inner center pin 32 forming the punch 30, and the extruding plate 35
It is connected to a hydraulic cylinder 50 via the hydraulic cylinder 50, and is moved forward and backward by the drive of the hydraulic cylinder 50, and when the mold of the molding machine for the disk molded product 100 is opened, the excess resin remaining in the runner and the recess 19 in the sprue bush 15 is cleaned. The molded part is separated from the disc molded product 100.

Further, in the figure, numeral 36 denotes an annular stamper disposed on the side of the disc molding cavity 3 of the movable die 2 through a tightening ring 37, the center of which is positioned and supported by the center presser 27.

Next, as shown in FIG. 3, the molding of the disc molded product 100 using the disc molding die described above is carried out by moving the injection nozzle 40 of the molding machine main body (not shown) forward and touching the nozzle of the sprue bush 15 in the mold closed state. By pressing against the surface 15b, the sprue bushing 15 and the gate 3
3 into the disc molding cavity 3 through the melted resin 60
Inject and fill.

After a predetermined pressure holding time has elapsed since the resin filling was completed, the punch 30 is advanced to form the recess on the tip 15a side of the sprue bushing 15, as shown in FIG. 19, insert the gate 33 corresponding to the center hole of the disc molded product by the minimum distance d that can be cut.

At this time, the punch 30 moves forward while compressing or pushing back the excess resin in the gate portion etc. to the runner side of the sprue bush 15, and furthermore, since the resin in that portion solidifies with the passage of time, it moves into the recess 19. The value of the insertion amount e has a limit on the smaller side.

That is, if the value of the insertion amount e of the punch 30 into the recess 19 is too small, the resin will harden quickly, and it will not be possible to cut cleanly, resulting in an irregular cut surface.

Therefore, the insertion amount e of the punch 30 into the recess 19 is
From the value of , the tip portion 15 of the sprue bush 15 is
Determine the recess amount a of the punch 30 and the recess 19 based on the finished state of the center hole 101 of the disc molded product 100 and the state of occurrence of burrs in the center hole 101 after punching and finishing. The disc molded product 100 shown in FIG. 5 is molded by determining the value of the gap between the mold and the mold at a point where the mold temperature reaches the molding state.

Further, in this case, the optimal value of the gap between the tip 30a of the punch 30 and the recess 19 is about 2 to 10 μm.

Furthermore, FIGS. 6 to 8 show a second embodiment of the present invention, in which a center hole 10 of a disc molded product 100 is shown.
When chamfering the corner edge 101a of No. 1, the amount of recess a of the tip 15a of the sprue bush 15, the gap b, and the punch 3
Projection amount C1 o represents the correlation between the amount d of thrust of the punch 30 into the recess 19 and the amount e of insertion.

[Effects of the Invention] As is clear from the above description, according to the present invention, the tip of the sprue bushing corresponding to the center hole of the disc molded product facing the disc molding cavity is moved from the parting line surface of the sleeve bushing. The inner diameter edge of the sleeve bushing and the outer diameter edge of the punch form a gate to the disc molding cavity, and the resin is filled into the disc molding cavity through this gate for a predetermined holding pressure time. When the resin on the sprue bushing side is in a semi-molten state after passing through, the punch is advanced and inserted into the recess on the tip side of the sprue bushing, and the outer diameter edge of this punch and the inner diameter edge of the sleeve bushing form a disk. Since the gate corresponding to the center hole of the molded product is cut, the center hole of the disc molded product can be finished by simply moving the punch back and forth while the sprue bushing remains fixed without sliding. As a result, there is no need to perform extra mold opening/closing control as in the conventional method, which simplifies the mold control mechanism and reduces costs, as well as reducing wear on the mold components of the sprue part. - It is possible to reliably prevent defects such as shortened lifespan due to galling, etc., and defects such as metal powder being mixed into the disc molded product.

In addition, with conventional sliding type sprue bushes, the resin pressure applied to the tip of the sprue bush facing the cavity side must be received by touch pressure from the injection nozzle of the molding machine main body, which requires a large nozzle touch force. However, since the sprue bushing is fixed, the touch pressure from the injection nozzle on the molding machine body is sufficient to prevent resin leakage on the touch surface, and this prevents large force from being applied to the molding machine body itself. First, stable molding can be performed and a high-quality disc molded product can be obtained.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of essential parts showing a first embodiment of a disk molding die according to the present invention, FIG. 2 is a cross-sectional view showing the overall structure, and FIGS. 3 and 4 similarly illustrate the molding process. FIG. 5 is an enlarged cross-sectional view of the main part of the disc molded product, FIG. 6 is an enlarged cross-sectional view of the main part showing the second embodiment of the present invention, and FIG. 7 is an enlarged cross-sectional view of the main part after resin filling. FIG. 8 is an enlarged sectional view of the main part showing the operating state of the punch, and FIG. 8 is an enlarged sectional view of the main part of the disc molded product. l...Fixed type. 14... Sleeve bushing, 14a... Inner diameter edge part, 15... Sprue bushing, 15a... Work 9... Recessed part, 2... Movable type, 30... Punch, 3 King... No. 1 center pin, 31a...outer diameter edge portion. 32... Second center pin, 33... Gate, 3... Cavity for disc shaping, 60... Molten resin, 100... Disc molded product, 101... Center hole, P- P...Parting line surface.・Tip,

Claims (1)

[Claims] A fixed mold and a movable mold form a disc molding cavity, and a sleeve bush and a sprue bush are fixed to the fixed mold side concentrically with the center of the disc molding cavity. In the mold, a punch is correspondingly provided on the movable mold side and movable back and forth concentrically with the center of the disc molding cavity. The tip of the sprue bush corresponding to the center hole of the disc molded product facing the disc molding cavity is recessed from the parting line surface of the sleeve bush, and the inner edge of the sleeve bush and the outer edge of the punch A disc molding mold characterized in that a gate to a disc molding cavity is formed with.