JPS645807B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The method of the present invention relates to an injection molding method for a synthetic resin molded product having printed sheets stretched on both sides, and in particular, sets a set of preformed front and back printed sheets in a mold, By injecting molten plastic into the inner side, two or more printing sheets are placed side by side on both sides of a synthetic resin molded product in one process, and each molten plastic is sequentially supplied from one molten plastic supply source without going through a switching valve. This invention relates to a method for simultaneously painting both sides of a synthetic resin molded product, which is characterized by injecting into a molding means and sequentially molding one by one.

Prior Art Conventionally, as a means of painting injection molded products,
A method is used in which a preprinted sheet is set in a mold, the sheet is preformed, and then molten plastic is press-fitted onto the back surface. (For example, see Patent Application Publication No. 19132 of 1975, Method for Manufacturing Painted Synthetic Resin Molded Products) Molded products molded based on the above method have a printing sheet embedded in the front surface and are extremely beautiful, but the back side Since it is left as a base material, for example, if both sides are used, such as a front door panel or a plaque, after molding on one side, each back side is glued to obtain a beautiful molded product on both the front and back. That's what I was doing.

This necessitates duplication of molding and bonding and bonding processes, which inevitably results in an expensive product.

Purpose The method of the present invention improves the drawbacks associated with the above-mentioned conventional molding methods, and provides a method for simultaneously painting both sides,
The decrease in molding efficiency due to the lengthening of the molding cycle due to the thickening of the molded product accompanying this is compensated for by the alternate molding method. The purpose of this project is to create a new mass production method for plastic molded products with printed sheets attached to both sides by streamlining the mechanism, and thereby provide quality products at low prices.

Configuration The configuration of the present invention for achieving the above object will be explained using FIGS. 1 to 3 corresponding to the embodiments.
The present invention provides a pair of front and back printing sheets 1 which are preformed.
8 and 18' are closely attached to both sides of the inner wall of the mold 17, the molds are clamped, and molten plastic is press-fitted into the gaps formed inside the corresponding printing sheets 18 and 18', cooled, and molded onto both sides. printing sheet 1
In a method for simultaneously painting both sides of a synthetic resin molded product, in which a synthetic resin molded product is obtained with tensioned resin molded parts, a plurality of sets of molds are connected to one injection device 1, and each mold is connected to an inner fixed mold. 8, an intermediate mold 9, and an outer mold 10, and a mold runner 13, spools 14, 14' are formed across the inner fixed mold 8 and the intermediate mold 9.
A mold 17 corresponding to the molded product is formed between the intermediate mold 9 and the outer mold 10, and the mold runner 13 and spool 1 in all the molds are
After injecting and solidifying a small amount of molten plastic to fill the molds 4 and 14', one of the molds is released and the solidified mold runner 13 and spools 14 and 14' are removed from the mold. A pair of front and back printing sheets 18, 18', which have been molded in advance, are tightly fitted and inserted into the inner wall of the mold 17, and then the molds are clamped, and the injection device 1 is operated to inject and press fit the molten plastic into the mold, thereby forming the same mold. While the plastic inside is cooling and solidifying, the other set of molds is released and the solidified mold runner 13 and spool 1 are removed.
4, 14' and printing sheets 18, 1.
8' is installed in the mold 17, a mold clamping process is performed, and molten plastic is injected and press-fitted. On the other hand, for the mold set in which the molded product has cooled and solidified, the molded product, the solidified mold runner 13, and the spool are removed. 14, 14' are removed, and the above operation is repeated for each set of molds to supply molten plastic to each mold one after another from one injection device 1 without a switching valve, and to continuously produce molded products. An apparatus for carrying out the above-mentioned method will be described below with reference to the drawings. Details of the method of the invention will become clear as the apparatus is described below.

Embodiment FIG. 1 is a partially cutaway side view of an embodiment of a molding apparatus for carrying out the method of the present invention, in which 1 is a molding apparatus equipped with a screw and a base nozzle 2 for molding molten plastic. This is an injection device installed vertically for injection, and 3 is a nozzle member equipped with a runner 4 that communicates with a base nozzle 2 bored at the end of the injection device 1, and the circumferential surface of the nozzle member is a band. The inside of the nozzle member is heated to an appropriate temperature by being surrounded by a heater so as not to impair the fluidity of the plastic in the runner 4, and the ends of the runner 4 are connected to nozzles 5 and 5, respectively.
It is connected to 6. The nozzle member 3 includes a nozzle 5,
6 allows the molten plastic to be supplied and press-fitted into the molds provided at a plurality of locations. That is, the tip nip portion of the member 3 and the fixed mold 8 of the mold
The locations where they come into contact are communicated by nozzles 5, 6 and a spool drilled in a fixed mold 8.

7 is a fixed frame provided perpendicularly to the machine stand 33 and symmetrically with respect to the center;
and a horizontally provided nozzle member 3, and in addition to connecting the two at the base nozzle 2, four horizontally extending struts 22 and the nozzles 5, 6 of the nozzle member and their spools communicate with each other. Inside fixed type 8
support each. The fixed mold 8 is connected to the open surface of the intermediate mold 9 via the open surface (matching surface) 11,
Further, the intermediate mold 9 corresponds to the open surface of the outer mold 10 via an open surface (matching surface) 12, and the outer mold is pivotally supported by a horizontal support 22 and is suspended slidably in the longitudinal direction of the support 22. left and right pressure plates 20,
It is fixed at 21. A cylinder 24 concentric with the axis of the support 22 is formed around the support 22 at the four corner ends of the pressure plates 20 and 21, and at a portion that pivotally supports the support 22.
A piston 23 fixed to the cylinder 2 is fitted, and one space of the cylinder 24 partitioned thereby is the forward chamber 2.
5 has a hydraulic hole 27 at its end, and the other space is a reversing chamber 26, which also has a hydraulic hole 28 at its end. Now, apply pressure oil from each hydraulic hole 27 to the advancement chamber 2.
5, the volume of the forward chamber increases, the volume of the other reverse chamber 26 decreases, and the oil in the same chamber is discharged from the hydraulic hole 28. Move forward towards the center of the device,
The fixed mold 8, the intermediate mold 9, and the outer mold 10 (collectively referred to as molds) are moved so as to reduce the distance between them, so that the open surfaces 11 and 12 face each other, and the molds are evenly compressed. (Please refer to the structure on the left side of the center in the device shown in the first figure.) Note that the pressure plates 20 and 21 are each provided with a valve device in their hydraulic circuit so that their movements can be controlled separately.

In a state where the molds 8, 9 and 10 are pressed uniformly and integrally by the pressure plate 20,
Molten plastic is injected from an injection device 1, and is press-fitted into a mold through a base nozzle 2, a runner 4, and an injection nozzle 5.

In addition, pressure oil is supplied to the hydraulic hole 28 and the cylinder 24
When the volume of the backward movement chamber 26 inside is expanded, the oil inside the forward movement chamber 25 is removed from the hole 27, and as a result, the pressure plate 21
The molds 8, 9 and 10 are moved away from each other so that the open surfaces 11 and 12 are exposed. At this final stage, the double-sided printed synthetic resin molded product molded in the mold, the mold runner, and the spool are removed from the mold using a knock mechanism. Next, a set of front and back printed sheets, which have been preformed by vacuum forming or the like, is placed in the mold, and then the pressure plate 21 is moved forward by operating a hydraulic device, and the molds 8, 9, and 10 are evenly spaced. Tightening,
Next, the injection molding process begins.

Figure 2a is a longitudinal cross-sectional view of a mold used in carrying out the method of the present invention, and Figure 2b is a plan view thereof. It is fixed to a fixed frame 7, and has a nip receiving part in the center of the back side, which receives the nozzles 5, 6, etc. of the nozzle member 3 provided on the fixed frame 7, and opens the opposite side via the spool. The injection device 1 communicates with a mold runner 13 drilled into the surface 11. Further, the mold runner 13 is formed by excavating the mold runner 13 along the longitudinal direction between the open surface 11 of the fixed mold 8 and the intermediate mold 9. The intermediate mold 9 has a mold 17 formed between a mating surface (open surface) 12 and an outer mold 10, and a plurality of gate runners 15, 15' are provided in parallel to the mold 17, and the gate runners The spools 15 and 15' are connected to the ends of the mold runner 13 drilled on opposite sides by spools 14 and 14' rising from the center thereof, and are connected to the ends of the mold runner 13 drilled on opposite sides, respectively, and are also connected to the ends of the mold runner 13 drilled on opposite sides thereof, and are also connected to the ends of the mold runner 13 by means of a flat gate 16 through thin and wide nozzles. It is connected to type 17. (See Figure 2b) The outer mold 10 has an intermediate mold 9.
Knock-cum-passage opening/closing pins 19 are provided corresponding to the positions of the spools 14 and 14' drilled in the spools 14 and 14', and the end surface of the pin 19 is connected to and driven by a hydraulic device provided on the side opposite to the mating surface 12. gate runner 1
5, 15' open in the center of the spool 14,
14' passage is opened and closed. 18 and 18' are a set of front and back molded sheets, which are formed by forming printing sheets (film or paper) in advance by means such as vacuum forming, and are mounted without gaps on the inner surface of the mold 17 provided in the intermediate mold and the outer mold. It is something that

Referring to FIG. 2b, 31 is inserted between the mating surfaces 12 of the intermediate mold and the outer mold, injects the molten plastic into the mold 17, and after press-fitting, cools and solidifies the plastic in the mold 17. This is a syringe needle that injects compressed air into the core, thereby artificially forming a nest (cavity) 32 in the center of a relatively thick molded product and preventing cracks or cracks on the surface of the molded product. This prevents holes or distortion from occurring.

Figure 3 is a partially cross-sectional side view of a molded product in which molten plastic is injected and press-fitted into a mold, cooled and solidified, and then removed from the mold. , 14, 14' are spools connected to both ends, and 15, 15' in the same figure b.
is the cross section of the gate runner, 16 is the flat gate, 1
Reference numerals 8 and 18' indicate a set of front and back printed sheets molded by means such as vacuum forming, which are attached to the surface of the synthetic resin molded product. Reference numeral 19 indicates a dowel pin and a passage opening/closing pin that connects the gate runner 15 in the direction of the arrow. ,15'
serves as a prerequisite for carrying out the method of the invention by pushing up to release the molded article from the mold and by closing the passage of the spools 14, 14'. 32 is a cavity provided in the core of the molded product, which is artificially hollowed to prevent cracks, holes, or distortions from occurring on the surface of the molded product based on the volume change that occurs when thick molten plastic solidifies. This is the nest that was formed.

The apparatus described above is operated in the following manner to obtain a molded article.

(1) First step In FIG. 1, pressurized oil is sent to the hydraulic hole 27 to expand the volume of the advance chamber 25 in the cylinder 24 provided in the pressure plates 20, 21. Move toward the center of the device and press the left and right molds equally. At this time, the dowel pin 19 is press-fitted into the mold and closes the passage of the spools 14, 14'.

(2) Second step: Inject and supply a small amount of molten plastic, enough to fill the runner and spool, from the injection device 1 through the nozzles 5 and 6. At this time, the plastic is prevented from being press-fitted into the mold 17 by the end face of the dowel pin.

(3) Third step: Supply pressure oil to the hydraulic hole 28, move only the pressure plate 20 in the return direction, and open the left mold. (1st
(See the state on the right side from the center of the device in the figure) (a) Solidified mold runner 13, spool 14, 1
4' (see Figure 3a) is removed from the mold.

(b) A set of preformed front and back printing sheets 18,1
8' is placed in the mold 17.

(C) Next, pressurized oil is sent to the hydraulic hole 27, the pressure plate 20 is moved toward the center of the device, and the mold is clamped between the fixed frame 7 and the pressure plate 20, and closed by pressure. (1st
(See the state on the left side of the center in the figure) At this time, the dowel pin 19 returns to its normal position and opens the passage for the spools 14, 14'.

(4) Fourth step, injecting the molten plastic through the nozzle 5;
Press into the left mold and fill.

Molten plastic is not injected or press-fitted into other molds because it is blocked by solidified mold runners and spools.

(b) Waiting for the injection/molded plastic to cool and solidify.

(b) Injection of compressed air into the core of the molded product using the injection needle 32.

(5) Fifth step, during which pressure oil is supplied to the hydraulic hole 28, and the pressure plate 2
1 and open only the right mold. The subsequent steps are exactly the same as the third step performed for the left mold.

(6) Sixth step: The right mold is subjected to exactly the same procedure as the fourth step performed on the left mold. At this time,
Because the left mold is filled with injection molded plastic, no molten plastic is forced into the left mold.

(7) Seventh step: Supply pressure oil to the hydraulic hole 28, move the pressure plate 20 in the return direction, and open the left mold.

(a) Activate the dowel pin 19 to remove the molded product, gate runners 15, 15', etc. from the mold 17.

(b) Mold runner 13 and spools 14, 14'
remove.

(c) A set of preformed front and back printing sheets is attached to both sides of the inner wall surface of the mold 17, respectively.

(d) Pressure oil is sent to the hydraulic hole 27 to operate the pressure plate 20 in the mold clamping direction.

(8) Eighth step; Same as the fourth step above.

(9) Ninth step: Perform the same procedure as the seventh step for the left mold on the right mold.

(10) Tenth step: Perform exactly the same procedure as the eighth step above on the right mold.

As can be readily understood from the above description of the process, according to the method of the present invention, a synthetic resin molded product with a double-sided printed sheet can be obtained by a single injection molding process, and a highly efficient mass production method can be adopted. . Further, although two or more molds are connected to the base nozzle 2, no distribution valve is required for supplying molten plastic. That is, referring to FIG. 4, this figure shows a cross-sectional view of a nozzle member implemented in a conventional device of this type.
Reference numeral 9 designates a switching valve having an L-shaped flow path, and reference numeral 30 also serves as the valve body, with runners 4 provided on the left and right sides, each of whose ends communicate with a nozzle. The flow path of the valve consists of the left and right runners 4 bored in the valve body and the base nozzle 2 of the device 1.
The flow path was switched to the left or right to supply molten plastic.

In the case of such a conventional device, (a) a power source or a mechanism for rotating the switching valve at appropriate timing is required, which complicates the structure;

(b) There is a risk of plastic leaking from the valve sliding surface when molten plastic is injected.

(c) There is a risk of deterioration of the plastic due to friction on the rotating surface of the switching valve.

However, according to the method of the present invention, substantially the same functions and effects can be expected without installing a distribution valve, and moreover, the drawbacks of the conventional device can be improved.

Furthermore, as mentioned above, synthetic resin molded products with double-sided printed sheets are required to be large in size and have thick walls, so it takes time for the plastic to solidify and form, and the volume changes when cooled, causing the molded product to deteriorate. To avoid distortion or scratches, connect multiple molds to one injection device and use the cooling and solidification time of the plastic in one mold to prepare for injection molding in another mold. In addition, it is possible to use the time required to cut out molded products, to avoid changing the flow path of the molten plastic or to use a switching valve, and to inject compressed air into the core of the plastic before cooling it. By artificially creating cavities and reducing the incidence of defective products, there is no wasted processing time, and the efficiency of forming good products is extremely high.

Effects As described above, according to the method of the present invention, a synthetic resin molded product with simultaneous painting on both sides can be obtained by a single molding operation. By connecting two or more molds to one injection molding device and operating them separately, we can reduce the length of molding time that tends to result in large and thick molded products.
To use the time to prepare for molding other molds and to cut out the molded products, spools, etc., and also to use the time as a flow path switching means for molten plastic, thereby eliminating the conventional switching valve structure. This made it possible to significantly improve molding efficiency.

In addition, before the molten plastic solidifies in the mold, compressed air is injected into the core of the molded product to create artificial nests, which reduces the internal stress generated within the molded product as it cools. It has remarkable effects such as extremely reducing the occurrence rate of molding and shortening the time for cooling and solidifying the molded product.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view of an embodiment of an injection molding apparatus for carrying out the method of the present invention, and FIG. 2 shows a mold installed in the apparatus. The figure is a sectional view, and the figure b is a plan view. Figure 3a is a side view of the mold runner and spool, and Figure 3b is a longitudinal sectional view of the molded product (including the dowel pin). FIG. 4 is a longitudinal sectional view of a nozzle member with a switching valve installed in a conventional device, and FIG. 4 shows a state in which the valve is switched. 1... Injection device, 3... Nozzle member, 4... Runner, 5, 6... Nozzle, 8... Inner fixed type,
9... Intermediate mold, 10... Outer mold, 13... Mold runner, 14, 14'... Spool, 15, 15'...
...gate runner, 16,16'...flat gate,
17...Model, 18,18'...Printing sheet, 19
... Knot and passage opening/closing pin, 20, 21 ... Pressure plate, 22 ... Support column, 24 ... Cylinder, 27, 2
8... Hydraulic hole, 31... Syringe needle, 32... Cavity (nest).

Claims (1)

[Claims] 1. After a pair of pre-formed printing sheets are closely attached to both sides of the inner wall of the mold, the molds are clamped and molten plastic is poured into the gaps formed inside the corresponding printing sheets. In the simultaneous painting method for both sides of synthetic resin molded products, in which a synthetic resin molded product is press-fitted, cooled, and printed sheets are stretched on both sides, multiple sets of molds are connected to one injection device, and each mold is Each mold is formed from an inner fixed mold, an intermediate mold, and an outer mold, a mold runner and a spool are provided between the inner fixed mold and the intermediate mold, and a mold corresponding to the molded product is formed between the intermediate mold and the outer mold. , a small amount of molten plastic is injected from the injection device to the extent that it fills the mold runners and spools in all the molds, and after solidifying, one set of the molds is released to release the solidified mold runners and spools. is removed from the mold, and a set of front and back printed sheets, which have been formed in advance, is tightly attached to the inner wall of the mold, inserted, and then the mold is clamped, and the injection device is operated to inject and press fit the molten plastic into the mold, While the plastic in the same mold is cooling and solidifying, the other set of molds is released, the solidified mold runner and spool are removed, the printing sheet is installed in the mold, and a mold clamping process is performed to release the molten plastic. During injection and press-fitting, the molded product is cooled and
For the set of solidified molds, remove the molded product, solidified mold runner, and spool, and repeat the above operation for each set of molds to make one injection of molten plastic without a switching valve. A method for simultaneously painting both sides of a synthetic resin molded product, characterized in that the molded products are continuously obtained by sequentially supplying the molds from an apparatus to each mold. 2. Claim No. 2, characterized in that before the molten plastic injected and press-fitted into the mold is cooled and solidified, compressed air is injected into the core of the molten plastic to artificially generate cavities inside the molded product. A method for simultaneously painting both sides of a synthetic resin molded product according to item 1.