JPH0353797B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention is applicable to display cabinets for image display devices such as television receivers, computers, and word processors, and particularly to thick front cabinets having a front frame plate. This invention relates to a method for injection molding a net with synthetic resin and a mold thereof.

(Prior Art) In order to obtain a front cabinet for an image display device with high rigidity, it is necessary to make the plate thick, such as 5 to 8 mm, and to make it from a synthetic resin mixed with a foaming agent. However, cathode ray tubes are made of glass, and their curved surfaces tend to deviate from the specified dimensions.
If the edge of the front cabinet that contacts the cathode ray tube is made thicker to increase its rigidity, the cathode ray tube cannot be completely attached when it is installed, resulting in a gap. By making the cabinet part thicker and making the edge that contacts the cathode ray tube thinner to give it more flexibility, it becomes more rigid and can be made into a cathode ray tube.
The attached front cabinet can be obtained without any gaps.

For this reason, front cabinets for image display devices have heretofore been manufactured by the sandwich injection molding method, in which the cabinet portion is made thicker and the cathode ray tube contacting edge made thinner. However, in all conventional examples, the number of gates of the mold is 4 to 10 points. For example, the 9th, 1st
This is shown in FIG. 0. Next, the configuration of the conventional example and the reason why it is necessary to have multiple gates will be explained. In the conventional example, an end 72 of the tunnel gate 7 which is electrically connected to the sprue 70 and the runner 71 opens into the cavity 2 forming the front frame plate 4.
Usually, the round gate hole diameter a is 4 to 5 mm, and when ejecting the product after opening the mold,
Adjust the gate diameter c so that part b can be cut automatically.
It is made as small as 1.8 to 2.3 mm. Note that when the gate diameter c is small, the amount of molten resin flowing out is small;
The molten resin does not reach the end of the cavity 2. For this reason, in the conventional example, as shown in FIG.
1, 42, 43 forming the cavity portion 20,
A large number of tunnel gates 7, 7', 7'', .

(Problems to be Solved by the Invention) In the conventional example, since the molten resin flows as shown by the arrow in FIG. 9, each tunnel gate 7, 7',
Weld lines 10, 10', 10'', etc. as shown in Fig. 11 are formed at each intermediate fused portion of 7'', and a large number of weld lines are formed in proportion to the number of gates. It is also possible to reduce the amount of molten resin containing a blowing agent from the second cylinder of the Sandersch injection molding machine and reduce the molding pressure in order to avoid producing a large number of weld lines, but in that case,
Holes are formed in the core layer and many sink marks occur.

(Means for solving the problems) This invention solves these inconveniences.
That is, a thick front cabinet for an image display device is formed by forming a deep cavity in an injection mold and injecting molten synthetic resin into the cavity to integrate the front frame plate and the cabinet part. In this method, at least the cavity portion of the front frame plate that forms the contact edge of the cathode ray tube is formed shallowly, and a film-like tunnel gate is passed above the cavity and only at one location, so that A molten synthetic resin is injected from the first cylinder through the film-like tunnel gate into the cavity including the shallowly formed cavity portion, and then a blowing agent is injected from the second cylinder of the Sandersch injection molding machine. A method for molding a thick-walled front cabinet for an image display device, characterized in that a molten synthetic resin is injected into the deeply formed cavity through the film-like tunnel gate and molded. In a mold for forming a thick-walled front cabinet for an image display device, which is formed by integrating a cabinet part and a cabinet part, the cavity part of the front frame plate that forms at least the cathode ray tube contact edge is formed shallowly. and a molding metal, characterized in that there is one runner and one tunnel gate electrically connected from the sprue, the tunnel gate is electrically connected above the cavity, and the tunnel gate is formed in a film shape. It is a type.

(Example) First and second molds used for carrying out the method of the present invention
The embodiment will be described with reference to FIGS. 3 and 7. Reference numeral 70 is a sprue formed on a fixed mold 12, and a runner 71 electrically connected to the sprue 70 is formed by the fixed mold 12 and the movable mold 13. A tunnel gate 7 conductive to the movable mold 13 is formed on the movable mold 13, and the tunnel gate 7 is a film gate.
A cavity 2 electrically connected to the tunnel gate 7 is formed of a fixed mold 12 and a movable mold 13. The cavity 2 is a thick front cabinet 6 of a television receiver, in which a front frame plate 4 and a cabinet part 5 are integrated. This is for the front frame forming part 2a.
The width W of the cavity 2 is formed deep to obtain a thick-walled cabinet 6 with a plate thickness of 6 mm.
The width W in the second embodiment is slightly larger than 6 mm. In the present invention, a thick-walled cabinet has a plate thickness of 5 to 8 mm. The present invention also provides a cathode ray tube contact edge 4a of the front frame plate 4.
This is to obtain a front cabinet with a thin wall of 2.5 to 3 mm, and the width w of the cavity portion 2a' forming the cathode ray tube contact edge 4a is
is formed shallowly, and the width w in the first and second embodiments is slightly larger than 3 mm. In addition, in the first embodiment, the front frame forming portion 2a
Among them, the range indicated by the reference numeral l in FIG. Another front frame forming part 2a including the cavity part 2a' is formed shallowly (width w) (Figs. 2 and 3), and in the second embodiment, the entire front frame forming part 2a including the cavity part 2a' is It is formed shallowly (width w) (Fig. 7). That is, at least the cavity portion 2a' forming the cathode ray tube contact edge 4a should be formed shallowly.
The depth of other portions of the front frame forming portion 2a is not limited. Furthermore, in both the first and second embodiments, there is one tunnel gate 7 and one runner 71 for each pair of molds 1, and the tunnel gate 7 is electrically connected to the upper part of the cavity 2. Especially in the first embodiment, there is one tunnel gate 7 and one runner 71. is electrically connected to the upper front frame forming portion 2a, and in the case of the second embodiment, is electrically connected to the upper cabinet forming portion 2b.
Further, the undercut portion d in FIGS. 2 and 7 is constituted by the end of an inclined ejecting pin 13a as shown in the figure, and the ejecting pin 13a is formed by a notched groove 13b.
and is slidably penetrated within the movable mold 13. In addition, in the ejector pin 13a in the second embodiment, a notch 7' for forming a tunnel gate is connected to the notch groove 13b, and as shown in FIG. As a result, a tunnel gate 7, which is a film gate, is formed. Furthermore, the e dimension of the tunnel gate 7 shown in Figures 4 and 8 is 50 to 60 mm, and the f dimension in Figure 4 is 12 to 14 mm, and the g dimension is 10 to 12 mm.
The h dimension in FIGS. 2 and 8 is 2.5 to 3.0 mm.

Next, the Sandersch injection molding machine 8 used to carry out the method of the present invention will be explained with reference to FIG. Note that the same Sandersch injection molding machine 8 is also used for the mold 1 shown in FIG. The Sandermansch injection molding machine 8 is a known one, and a common injection valve 82 is attached to the first cylinder 80 and the second cylinder 81, and the injection valve 82 is opened and closed by sliding of the first plunger 83. The tip opening 85 of the first plunger 83 opens and closes due to the sliding of the second plunger 84 within the plunger 83, and the flow path 86 from the first cylinder 80 enters the body 87.
A flow path 88 from the second cylinder 81 communicates into the first plunger 83 .

The embodiment of the method of the present invention uses the mold 1 and the Sandersch injection molding machine 8, and as shown by the solid line in FIG. 2, the first plunger 83 is slid to the left to open the injection valve 82. Polystyrene is injected in a molten state (220 to 230°C) as the synthetic resin 3 from the first cylinder 80, and the molten resin is passed through the channel 86, the body 87, the sprue 70, the runner 71, and the tunnel gate 7 into the mold. 1 (30
-40 DEG C.) into the cavity 2, and the molten resin is injected into a part of the front frame forming part 2a and the cabinet forming part 2b as shown in the second figure. The molten resin in the shallowly formed cavity 2a' is cooled and solidified, but the molten resin in the deeply formed cavity 2 is still in a fluid state.
After 1.2 to 2.0 seconds, the second plunger 84 is slid to the left as shown by the chain line in FIG.
Open the tip port 85 and from the second cylinder 81,
A synthetic resin 3 containing azodicarbonamide as a blowing agent 9, specifically polystyrene (200-220
°C) is injected in a molten state. At this time, since the injection valve 82 is kept open, the polystyrene from the first cylinder 80 is also injected at the same time, and the polystyrene containing the foaming agent 9 is deeply formed while pushing out the previously injected polystyrene from the first cylinder 80. It is injected into the cavity 2 (shown by the chain line in FIG. 2). After that, the second plunger 84 is slid to the right to close the tip opening 85 of the first plunger 83, and only the polystyrene is injected from the first cylinder 80, and then the first plunger 83 is slid to the left and right. When the injection valve 82 is closed and the injection is completed, only polystyrene is filled into the shallowly formed cavity portion 2a' as shown in the third figure, and polystyrene containing the foaming agent 9 is filled into the deeply formed cavity 2 as a core. polystyrene only forms the skin layer. The molten resin during injection flows as shown by the arrows in FIG. 1, forming the thick front cabinet 6. At this time, since the tunnel gate 7 is a film gate, its width (dimension e) is wide as described above, and the molten resin is spread and injected into the cavity 2, resulting in good flow. In this embodiment, since the width W of the cavity 2 is large (6 mm), there is no chance that the molten resin will solidify before it flows into the entire cavity 2. Furthermore, since the molten resin is injected from only one point of the tunnel gate 7 as mentioned above,
The weld line 10 is the bottom plate 5 of the cabinet section 5.
0 center, and tunnel gate 7
is a film gate, and since the molten resin flows well, the cavity parts 2a and 2b are separated as shown in the second figure.
Even if they intersect at right angles, there is no problem and the molten resin flows smoothly. Regarding the undercut portion d, if the ejector pin 13a is ejected as shown in the imaginary line in FIGS. 4 and 8 after the mold is opened, the ejector pin 13a slides diagonally to the side, and the notch groove 13b
(In the case of the second embodiment, the notch groove 13b and the tunnel gate forming notch 7') are removed from the solidified resin portion. Further, in the figure, 70a, 71a, and 7a are resin parts solidified by the sprue, runner, and tunnel gate, respectively, and the i part or j part (shown in the third and seventh figures) is cut with a nipper or the like in post-processing.

(Effects of the Invention) In the present invention, since the molten resin is injected from only one point of the tunnel gate, there is only one weld line, and since the molten resin is injected from above the cavity through the tunnel gate, the front frame plate and the cabinet are Of course, it is possible to form a cabinet for an image display device by integrating the parts, and the weld line only appears on the bottom plate of the cabinet part.
Even if too much synthetic resin containing a foaming agent is injected into the core layer and the injection pressure is too high, a so-called resin puncture will only occur on the bottom plate of the cabinet, and the bottom plate is an invisible part of the cabinet. In some cases, surface treatment may not be necessary, which can significantly save time and effort. In addition, in the case of a front cabinet having a front frame plate and a cabinet part, as shown in the second figure, the cabinet part 2a
and 2b intersect at right angles, and the flow resistance of the molten resin is large. For this reason, if the tunnel gate is one point,
Moreover, if the tunnel gate is a round hole-shaped gate with a gate hole diameter a of 4 to 5 mm as in the conventional example, there is a risk that the molten resin will not reach the end of the cavity, but in the present invention, the film-shaped tunnel gate Since the molten resin is used, the flow of the molten resin is good, and a cabinet with a front frame plate can be reliably obtained. Furthermore, although the present invention is a method for molding a thick-walled front cabinet with a deep cavity, at least the cavity portion that forms the cathode ray tube contact edge is made shallow, and moreover, only the molten resin is firstly injected through a sandwich injection molding machine, and then Since molten resin containing a foaming agent is injected into the core layer, the thicker part has a sandwich structure with a foaming agent in the core layer, which is highly rigid and the thinner part has flexibility, making it ideal for good contact with the cathode ray tube. It is possible to obtain a front cabinet.

According to the mold of the present invention, not only can the above-mentioned effects be achieved, but also only one runner and one gate are required for each pair of molds, and the cabinet and the mold itself can be manufactured easily and at low cost.

[Brief explanation of drawings]

FIG. 1 is a front view of a movable mold of the mold according to the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the method of the present invention, and FIG. 3 is an enlarged central vertical sectional view of the mold of the present invention. FIG. 4 is a sectional view taken along line A-A, FIG. 5 is a perspective view of a resin part molded according to the present invention, and FIG. 6 is a front view of a movable mold of the mold according to the second embodiment of the present invention. Figure 7 is a central vertical sectional view of the same mold as above, Figure 8 is a cross-sectional plan view of the movable mold of the same mold, Figure 9 is a front view of the movable mold of the conventional mold, and Figure 10 is a front view of the movable mold of the conventional mold. The figures are central cross-sectional plane views of the conventional fixed type and movable type, and FIG. 11 is a perspective view of a resin part molded according to the conventional example. 1... Mold, 2... Cavity, 2a'... Cavity part, 3... Synthetic resin, 4... Front frame plate, 4a... Braun tube contact edge, 5... Cabinet part, 6... Thick wall front Cabinet, 7...
...Tunnel gate, 8... Sandersch injection molding machine, 9... Foaming agent, 70... Sprue, 71...
Runner, 80...first cylinder, 81...second cylinder.

Claims (1)

[Scope of Claims] 1. An image display device in which a front frame plate and a cabinet part are integrated by forming a deep cavity in an injection mold and injecting molten synthetic resin into the cavity. In a method for forming a thick-walled front cabinet, at least a cavity portion of the front frame plate that forms a cathode ray tube contact edge is formed shallowly, and above the cavity,
Moreover, a film-like tunnel gate is connected to only one location, and molten synthetic resin is injected from the first cylinder of the Sandersch injection molding machine into the cavity including the shallowly formed cavity portion through the film-like tunnel gate. Then, a molten synthetic resin containing a foaming agent is injected from the second cylinder of the Sandersch injection molding machine into the deeply formed cavity through the film-like tunnel gate and molded. Method for forming thick-walled front cabinets. 2. In a mold for forming a deep cavity for a thick-walled front cabinet for an image display device in which a front frame plate and a cabinet part are integrated, the cavity portion of the front frame plate forms at least the cathode ray tube contact edge. is formed shallowly, and there is one liner and one tunnel gate electrically connected through the sprue, and the tunnel gate is electrically conductive above the cavity, and the tunnel gate is formed in a film shape. mold for molding.