JPH09306275A - Key top molding method and key top molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a clean key top along an outer circumference thereof by injecting a thermal plasticity resin through a resin introducing inlet provided on a side face of a cavity into a cavity and cutting a molding product along the outer circumference of a cavity by means of shearing and cutting. SOLUTION: This molding die is constituted with a movable side cast plate 2 forming a cavity 5 by a fixing side cast plate 3. In addition, a tip end 6 of a pin gate 1 is extended from a fixing side cast plate 3 to a resin introducing cast plate 2, a resin introducing inlet 7 is provided at a part of the side face of the cavity 5 penetrating the resin introducing inlet 7. At the same time, a cross section parallel to a parting line 4 near the resin introducing inlet 7 is shaped along the outer circumference of the cavity, and the thermal plasticity resin is injected into the cavity 5 through pin gates 1 and 6 and the resin introducing inlet 7. Then, a die is opened, a pin gate tip end 6 in the movable side cast plate 2 is pulled out with it attached to the pin gate unit 1, and the molding product is cut along the outer circumference of the cavity by means of shearing and cutting. Thus, a clean key top along the circumference is obtained.

Description

Detailed Description of the Invention

[0001]

[Industrial field of application] The field of industry such as electric equipment, electronic equipment, and communication equipment. In particular, the present invention relates to a plurality of switch assemblies mounted on devices in these fields, that is, a key top molded product of a keyboard switch. Keyboard switches are used in telephone switches, AV remote control switches, pocket computer switches, personal computer keyboards, and countless other places. The present invention relates to a keytop molded product used for these keyboard switches and the like.

That is, in a telephone, particularly a mobile phone, a PHS, a portable radio for business use, etc., since the device is carried in a pants pocket, a Y-shirt pocket, or a bag, the surface of the keyboard switch is worn and the numbers on the upper surface of the key switch When characters are printed, they may be rubbed and disappear.
Therefore, a method has been widely used in which a transparent resin key top is attached to the top surface of the keyboard switch and display printing is performed on the back surface of the key top. The present invention relates to a keytop molded product for such an application.

[0003]

2. Description of the Related Art FIGS. 1 and 2 show an example of a key top assembly of a conventional telephone switch. The key top usually has twelve or more keys 20, and these are thin connecting portions 22.
It is a molded product with a structure connected by. Although it has a complicated shape and it is difficult to mold the whole with one gate, it can be molded by using a pin gate mold. That is, it suffices to provide one pin gate 21 for each key, and the purpose can be achieved by installing the gates at individual locations that do not require precision or clean molding.

[0004]

FIGS. 3 and 4 show an example of a molded product of a key top assembly used for a new type of mobile phone switch. In the conventional molded product shown in FIG. 1, a flange-shaped bead was formed on the lower part of the key, but not on the key top of FIG. This key-top molded product is cut into pieces after providing a printing layer on the front and back surfaces, and each key is bonded onto a rubber-based switch structural component to form the final keyboard switch product, or made of thermoplastic elastomer. The flange is unnecessary because it is combined with the switch structure to form the final product. Mobile phones and PHSs require light, thin, short, and small keyboard switches, and tend to be thinner without flanges. Keyboard switches that meet this purpose are required.

In order to injection-mold a key top or a key top aggregate without a flange-like portion with a transparent resin, it is effective to provide a pin gate for each key and insert the resin because it is necessary to form each key neatly. is there. However, in the prior art, the pin gate was installed on the front surface or the back surface,
With this, the gate marks are visible in the case of transparent resin. For this reason, there was no choice but to install the gate on the side of the key, and it was not possible to directly insert the resin into the cavity corresponding to each key from the pin gate. Then, as shown in FIG. 5 (FIG. 5 is a cross-sectional view of a die for producing the product of FIG. 3), pin gates 40 and 41 are provided.
It is conceivable that resin is put into the frame portion 51 from the side wall, and resin is put into the key-corresponding cavity portion 50 from the side gate 42 provided near the frame portion 51. However, in this method, since the resin is introduced into the cavity of the key top through a long narrow portion, it is not easy to mold a clean key top. That is, molding is possible, but it is necessary to use a high fluidity resin, and the defective rate of molded products is high,
Strict control of molding conditions, selective shipment of molded products, etc. are required, which includes factors that increase the process cost.

[0006]

The present invention is keenly researched on a method for solving the above-mentioned problems of the prior art while making the best use of the feature of the pin gate mold capable of cutting the gate in the mold without having a complicated mechanism. It was achieved as a result of repeating.
That is, the present invention is: (1) In a method of molding a keytop molded product in which a plurality of keytops are connected, a heat-molded product including a movable-side template having a cavity and a fixed-side template provided with a cavity if necessary. A plastic resin injection molding die, in which a tip portion 6 of a pin gate 1 extends to a movable side mold plate 2 beyond a parting line 4 between the fixed side mold plate and the movable side mold plate. , The resin inlet 7 which is a part of the side surface of the cavity 5
A cross section parallel to the parting line of the pin gate near the resin introducing port 7 is formed by using an injection molding die in which the resin introducing port 7 has a shape along the outer periphery of the cavity, A method of molding a keytop, characterized in that after the thermoplastic resin is injection-molded, the resin in the pin gate is pulled out to cut the resin of the pin gate along the outer periphery of the cavity at the resin introduction port 7. (2) In a molding method of a keytop molded product in which a plurality of keytops are connected, a mold for injection molding of a thermoplastic resin comprising a movable side template having a cavity and a fixed side template provided with the cavity Therefore, the tip of the pin gate 11 extends to the parting line 14 between the fixed-side mold plate and the movable-side mold plate or the vicinity thereof, and penetrates into the resin introduction port 17 which is a part of the side surface of the cavity 15. The cross section parallel to the parting line of the pin gate in the vicinity of the resin introduction port 17 uses a mold for injection molding in which the portion of the resin introduction port 17 has a shape along the outer periphery of the cavity. After the resin is injection-molded, the resin in the pin gate is pulled out, and the resin of the pin gate is cut along the outer periphery of the cavity by the resin introduction port 17 of the key top. Form method. . (3) A keytop molded product manufactured by the molding method according to (1) or (2) above. Is provided.

Next, the present invention will be described in more detail. FIG.
[Fig. 2] schematically shows an example of a mold used in the method of claim 1 of the present invention. The present invention will be described based on FIG. 6 as an example. That is, it is a mold used in a molding method of a keytop molded product in which a plurality of keytops are connected to each other, and includes a movable mold plate 2 having a cavity and a fixed mold plate 3 having a cavity provided if necessary. In a mold for injection molding of a thermoplastic resin, the tip portion 6 of the pin gate 1
Extends from the fixed-side mold plate to the movable-side mold plate 2 beyond the parting line 4 between the fixed-side mold plate and the movable-side mold plate, and penetrates the resin introduction port 7 which is a part of the side surface of the cavity 5. A cross section parallel to the parting line of the pin gate near the resin introducing port 7 is an injection molding die characterized in that the portion of the resin introducing port 7 has a shape along the outer periphery of the cavity. . The thermoplastic resin is passed through the pin gates 1 and 6 and the resin inlet 7 into the cavity 5 in the mold.
It is injected inside. After that, as shown in FIG. 8, the mold shown in FIG. 6 is opened, and the pin gate portion is pulled down by the runner stripper plate. The pin gate has already been cut, and the pin gate tip portion 6'which has entered the movable side template beyond the parting line is pulled out while being attached to the pin gate body 1 '. That is,
In the present invention, the pin gate resin is cut along the outer periphery of the cavity 5 '(that is, the key top) by the breakage between the molded product 5'and the pin gate tip portion 6'.
In order to cause such cutting, the pulling force between the pin gate tip 6'and the pin gate body 1'may exceed the shearing force between the pin gate tip 6'and the molding object 5 '. . The resin in the mold has just solidified,
Since the influence of the flow direction and the influence of elasticity are great, the resin tensile force and shear force data described in the resin manufacturer's catalog cannot be used as they are, but the a / b ratio should be 2 or more. Is preferred, and more preferably 3 to 2
0, particularly preferably 4 to 15.

In order to disconnect the above-mentioned pin gate,
The pin gate withdrawal force must be higher than the resin shear force at the resin inlet. For this reason, it is preferable that the pin gate tip partial cross section 8 of the fixed-side template is not circular but has a shape along the outer periphery of the cavity. Conventionally, the pin gate cross section has been determined to be circular because of the ease of die working, but nowadays, wire electric discharge machines are widely used, and the cross sectional shape can be freely set. FIG. 7 is a view of FIG. 6 viewed from above. The cross section parallel to the parting line of the pin gate near the resin inlet 7 and the shape of the pin gate tip section 8 of the fixed-side template may be mostly circular, but the resin inlet to the cavity (that is, the shear force The portion 7 corresponding to the surface expected to be cut is formed into a straight line or a gentle curve according to the shape of the cavity 7. By doing so, the pin gate is fractured along the outer periphery of the cavity, and the pin gate 1'obtained by cutting is smoothly extracted.

Similarly, the example shown in FIG.
This is an example of using a mold having a structure in which the tip end part of the structure stays in the fixed-side mold plate 13. The cavity 15 has a structure in which a fixed-side template is also engraved. This mold is a thermoplastic resin injection mold composed of a movable mold plate 12 having a cavity and a fixed mold plate 13 having a cavity, and the tip of the pin gate 11 has a fixed mold. A resin introduction port 17 that extends to the vicinity of the parting line 14 between the plate and the movable side mold plate and is a part of the side surface of the cavity 15.
For injection molding, characterized in that the cross section parallel to the parting line of the pin gate near the resin introduction port 17 has a shape of the resin introduction port 17 along the outer periphery of the cavity. It is a mold.

When a mold as shown in FIG. 9 is used, it is preferable that the fixed-side mold plate is finished with accurate alignment of the side surfaces of the cavity 15 over the entire circumference. The resin introducing port 17 is formed on a part of the side surface of the cavity 15 in accordance with the pin gate. The cross section parallel to the parting line of the pin gate near the resin introduction port 17 of the fixed-side template 13 has a resin introduction port 17
Similar to the case of FIG. 6, the portion of is shaped along the outer periphery of the cavity and the shape is not circular. When a die as shown in FIG. 9 is used, the key top molded product of the present invention is shown in FIG.
It can be molded in the same manner as in the case of the mold.

[0011]

EXAMPLE A key top for a telephone as shown in FIG.
Molding was performed using the mold having the structure shown in FIGS. 6 and 7. Here, the key top portion 5 has an elliptical shape with a width of 12 mm and a length of 8 mm, and a thickness (height in FIG. 6) of 1.5 mm. The size of the outlet 8 on the fixed side template of the pin gate is a circle with a diameter of 2 mm, but the circumference 0.
The 6 mm portion is shaped to match the outer circumference of the ellipse on the key 5 side.
The pin gate tip 6 has a diameter of 1.6 mm on the movable side mold plate.
A 1.5 mm deep engraving was made with a draft of 10 degrees. In the movable side mold plate, a gap of about 0.3 mm × 0.5 mm was formed between the cavity 5 of the key top and the pin gate tip end portion 6, but an electrode having a width of 0.5 mm was pushed in by electric discharge machining and the gap was reduced to 0. It was enlarged to 5 mm × 0.55 mm.
As a result, the cross-sectional area a of the pin gate near the parting line and the cross-sectional area b of the resin introduction port 7 into the cavity are
a = 0.8 mm × 0.8 mm × π = 2.0 mm ² , b
= 0.5 mm × 0.55 mm = 0.28 mm ² and a / b = 7.1. Further, as shown in FIG. 7, the keys are actually connected to 21 key tops of 3 columns × 7 rows via a lattice frame, and the lattice frame and each key are 0.5 mm.
It has a structure in which a gate having a width of 0.1 mm and, more accurately, a resin outlet gate are connected. The width and thickness of the grid frame is 1
A draft was set at 5 degrees as mm. The ejector pin was installed in the lattice frame.

Using the above mold, injection molding was carried out using a polycarbonate resin as an injection molding material. After injection molding, the mold opened and the pin gate was pulled out first,
As for cutting, all the key tops 21 could be cut along the outer periphery of the cavity as planned. Next, the mold was fully opened, the molded product was extruded by the ejector pin, and the sprue / runner / gate portion was also lifted from the mold. The completed keytop aggregate was beautiful for each keytop 21.

[0013]

The present invention overturns the conventional wisdom about how to use a pin gate. By making the gate on the side instead of the back side or front side, the in-mold cut of the pin gate does not cause tensile force fracture but shear force. It can be broken and cut beautifully along the outer periphery of the cavity, resulting in a beautiful key top molded product. The present invention has the effects as described above. (1) In the molding of a transparent resin key top, if the gate mark is a side face, it cannot be confirmed even when viewed obliquely. You can create a nice looking key top. (2) In the molding of transparent resin key tops, a pin gate is directly set on each key, so that a beautiful key top connected product in which wrinkles, flow marks, jetting, and weld hardly occur.

[Brief description of drawings]

[Figure 1] Telephone key top product diagram

FIG. 2 is a sectional view taken along the line A / A ′ in FIG.

[Figure 3] Telephone key top molded product diagram

4 is a sectional view taken along line B / B ′ of FIG.

FIG. 5: Cross-sectional view of a die for a telephone keytop molded product

FIG. 6 is a pin gate portion (cross-sectional view) of the mold of the present invention.

FIG. 7: Pin gate part (plan view) of the mold of the present invention

FIG. 8 is a pin gate portion (cross-sectional view) of the mold of the present invention.

FIG. 9 is a pin gate portion (cross-sectional view) of the mold of the present invention.

[Description of sign]

 1 Pin gate main body 1'Pin gate main body (resin part) 2 Movable side mold plate 3 Fixed side mold plate 4 Parting line 5 Cavity 5'Objective molding (resin part) 6 Pin gate tip part 6'Pin gate tip part (resin part) 7 Resin introduction port 8 pin gate cross section (fixed side mold plate) 9 pin gate cross section (movable side mold plate) 11 pin gate body 12 movable side mold plate 13 fixed side mold plate 14 parting line 15 cavitity 17 resin introduction port 18 pin gate cross section (fixed side) 19) Pin gate cross section (movable side template) 20 Key top 21 Pin gate mark 40 Pin gate tip, Pin gate mark 41 Pin gate 42 Side gate 43 Exit side gate 50 Key top 51 Lattice frame

Claims (3)

[Claims] 1. A method for molding a keytop molded product in which a plurality of keytops are connected to each other, comprising a thermoplastic resin comprising a movable side template having a cavity and a fixed side template having a cavity if necessary. In the injection molding die, the tip portion 6 of the pin gate 1 extends to the movable side mold plate 2 beyond the parting line 4 between the fixed side mold plate and the movable side mold plate, and the cavity 5 The resin introduction port 7 which is a part of the side surface of the resin is introduced into the resin injection port 7. After injection molding the thermoplastic resin using the injection molding mold, the resin inside the pin gate is pulled out to remove the resin 7
In the key top molding method, the resin of the pin gate is cut along the outer periphery of the cavity. 2. A method for molding a keytop molded product in which a plurality of keytops are connected to each other, a thermoplastic resin injection molding metal comprising a movable side template having a cavity and a fixed side template provided with the cavity. In the mold, the tip portion of the pin gate 11 extends to or near the parting line 14 between the fixed-side mold plate and the movable-side mold plate, and is a part of the side surface of the cavity 15 which is a resin introduction port 17. A cross section parallel to the parting line of the pin gate near the resin introducing port 17 is formed by using an injection molding die in which the resin introducing port 17 has a shape along the outer periphery of the cavity, After molding the thermoplastic resin, the resin in the pin gate is cut along the outer periphery of the cavity at the resin introduction port 17 by pulling out the resin in the pin gate. Up molding method. . 3. A keytop molded product manufactured by the molding method according to claim 1.