JPS62220313A - Mold for multi-layer construction resin molding - Google Patents

Abstract

PURPOSE:To obtain a molding which is of high-precision and stable, by a method wherein the titled resin is cast evenly by providing a runner for skin layer resin between an injection cylinder unit for the skin layer resin and the starting point of the runner and providing further a gate, whose resin circulation cross section has been narrowed, on the runner. CONSTITUTION:A runner plate 8 is provided with a first runner 8a joining a first and second sprues 6a, 6b with each other. A resin sink 8d provided on the runner plate is provided on a straight line connecting between a first gate 8b, whose cross-sectional area is narrower than that of a runner for skin layer resin, and the sprue 6b for core layer resin. A second runner 8a2 communicating with the resin sink 8d and extending evenly and radially on the surface which is flush with Y1-Y'1 surface is provided. As the first gate is provided on a joint between the first runner and second sprue like this, when second resin is cast through the second sprue after injection of first resin, a back flow of the second resin to a first runner side stops at the inside of the first gate. Then it follows that the second resin is distributed and cast to each of the second runners by even quantity and that even resin pressure influencing excessively upon accuracy of a molding is applied evenly to the runner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a mold for forming cylindrical parts such as lens barrels of optical instruments such as photographic devices and lens barrels of business machines.

[Prior art]

Conventional lens barrels have a structure that includes a lens, a lens holding frame, a fixed cylinder, an intermediate cylinder, an operating ring, etc., and by rotating the operating ring around the optical axis, the lens holding frame is controlled to move in a direction parallel to the optical axis via the intermediate cylinder. Many configurations are known. Further, as a construction of the intermediate cylinder, a helicoid part is known in which helicoid parts are provided on the inner and outer peripheries in order to convert the rotational force of the operating ring about the optical axis into parallel movement of the optical axis of the lens holding frame. In the case of a lens barrel, the material is a metal material such as aluminum (
/MZ), brass (Bs), etc., have physical advantages such as excellent strength and high dimensional accuracy, but on the other hand, there are many problems such as heavy weight, high cost due to cutting, and limits on productivity improvement. Injection molding is being performed using resin materials instead of metal materials.

One of the suitable resin materials for the helicoid tube is polycarbonate, ABS, polybutylene terephthalate (
PBT), modified polyphenylene, oxide, etc. are known, and resin materials mixed with glass fiber or carbon fiber are used to further strengthen mechanical strength.

The glass fiber-containing polycarbonate material mentioned above can be used to obtain helicoid tubes by reducing cost, ensuring high precision, and ensuring mechanical strength compared to conventional materials, but the glass fibers are exposed on the inner and outer peripheral surfaces of the helicoid tube, and this Therefore, there remain problems such as the need to improve sliding properties when sliding and screwing with the inner and outer fitting tubes of the helicoid tube.

One way to solve the above problem is to make the cylindrical member have a laminated structure. For example, Tokuko Sho 50-2
Using sandwich molding (hereinafter referred to as SW molding) as described in the specification of Publication No. 8464, glass fibers that form the surface layer of the helicoid cylinder are first mixed into the cavity of the mold for forming the helicoid cylinder. By injecting a resin material with excellent sliding properties, and then injecting a glass fiber-containing resin material to form the core, the surface layer is made smooth, and the core is made of a resin with high mechanical strength, which solves the aforementioned problem. The solved helicoid cylinder can be obtained.

[Problems to be solved by the present invention] Necessary conditions when applying sandwich injection molding to lens barrel members (fixed barrel, cam barrel, helicoid barrel, cosmetic barrel, etc.) of optical equipment such as interchangeable lenses for cameras. i) The injection process is short and injection molding can be performed in a short time.

11) Multiple resin materials should not be mixed.

ii) The core layer injected into the skin layer is uniformly injected in each cross section of the molded article.

Conventional two-color molding machines have a fixed plate connected to first and second injection cylinders, a mold plate provided with a molding gap, and a runner plate located between the fixed plate and the mold plate. A sprue for injecting resin is provided on the fixed plate, and after injecting the first resin, the mold device consisting of the fixed plate, runner plate, and mold plate is rotated or slid relative to each injection cylinder. It was moved to enlarge the gap provided in the template, inject the second resin, and switch the type of resin flowed onto the sprue of the fixed plate.

However, with this type of means, it takes time to rotate or slide, so when ejecting the second tree finger,
The first resin has already cooled and solidified, so the second resin is attached around or in part of the first resin, and the adhesive strength between the first and second resins is weak. , usually used in conjunction with mechanical joints such as flanges to improve adhesive strength. Furthermore, since the second resin is injected after the first resin has cooled, the first cooled resin is subjected to external force due to the injection pressure of the second resin, which makes it difficult to obtain a high-precision molded product. It is considered difficult.

For example, when a lens barrel member is formed by sandwich molding using the injection molding machine shown in FIG. 7a, the skin layer resin material from the first injection cylinder 11A is
Runner +4a of the runner plate 14 through the sprue 12a of No.2.

14b and is injected into the cavity 16A of the mold 16. After injecting a predetermined amount of the skin layer resin material A, the core layer resin material B is transferred from the second injection cylinder 11B to the sprue 12.
a The cavity 16A passes through the runners 14a and 14b.
Sandwich molding is performed by injecting the core layer material forward while pushing the skin layer material injected earlier, but as shown in Figure 7, the core layer material injected later pushes the skin layer material forward. It also enters the sprue 12a through which the layer material passes.

As a result, when the -th injection process is completed and molding is to be continued, if injection is continued from the state shown in Figure 7, the core layer resin B will be inserted into the sprue 12a through which the skin layer resin A passes.
If the mold is heated and the skin layer material and core layer material are sequentially injected, the skin layer resin and core layer resin will mix and it will not be possible to mold the mold.

[Purpose of the invention]

In particular, to solve the above problems, (1) the injection process is short and injection molding can be performed in a short time; (2)
(3) The ratio of the skin layer to the core layer is uniform in each cross section of the molded product. (4) The resin injected in the previous process does not remain in the next process. (5) No resin stagnation outside the injection cylinder (6)
Low pressure loss in the resin flow path during injection (7) No switching means in the resin flow path (8) High stability and stable molded products can be obtained continuously (9) Multiple types 2nd runners or 2nd gates, the resin should be injected equally into each second runner or gate.

(10) The core layer material does not flow back into the first runner of the skin layer material when the core layer material is injected.

As a result of repeated research focusing on the above, the present invention has been arrived at.

(Means for Solving the Problems) The present invention includes attaching a runner plate provided with a plurality of runners for passing the resin through the gaps to a mold member provided with a gap for molding the cylindrical part;
Attach a fixed plate provided with a spray to connect to the core layer resin injection cylinder unit and the skin layer resin injection cylinder unit to the plate, and align the starting points of the plurality of runners with the injection ports of the core layer resin injection cylinder unit in a straight line. A runner for the skin layer resin is arranged between the injection cylinder unit for the skin layer resin and the starting point of the runner, and a gate with a narrow resin flow cross section is provided in the runner for the skin layer resin in the mold. The above-mentioned problem is solved by providing the following feature.

[Detailed description of the invention]

1 to 4 show a first embodiment of the present invention.

'S1 figure shows a cross-sectional view of the main parts of the wooden embodiment device, and the symbols 1,
Reference numerals 2 indicate first and second injection cylinder units, respectively. The resin material A forming the skin layer is injected from the injection port +a of the first injection cylinder unit, and the resin material A forming the skin layer is injected from the injection port 2a of the second injection cylinder unit. A resin phase B forming the core layer is injected.

Reference numeral 4 denotes a mold member provided with a cavity 4a for molding a hollow cylindrical body such as a cylinder member of a lens barrel.

Reference numeral 6 indicates a fixed plate, and the fixed plate 6 has injection ports 1a and 1 of the 15th second injection cylinder unit.
A first sprue JL/-6a for the skin layer resin and a second sprue 6b for the core layer resin, which are connected to the sprue JL/-6b, are provided.

8 is a runner plate located between the mold member 4 and the fixing plate 6. The + line indicates the joint surface between the mold member and the runner plate 8, and the joint surface X+ X'
+ is provided in a direction perpendicular to the cylindrical axis direction of the hollow cylindrical molded body of the mold member 4.

The line Y+Y'l indicates the joint surface between the runner plate 8 and the fixed plate 6. The runner plate 8 includes a first runner 8a connecting the first sprue 6a and the second sprue 6b, a first gate 8b having an area smaller than the cross-sectional area of the runner for the skin layer resin, and a sprue 6b for the core layer resin. A resin reservoir 8d provided on the runner plate on a straight line, and a second runner 8a2--1 communicating with the resin reservoir 8d and extending evenly in a radial shape on the same plane as Y+-Y'+, The second runner and the cavity 4 provided in the template 4
A third runner 8c, which communicates with a is provided.

FIG. 2a shows the fixing plate of the molding apparatus shown in FIG. 1, the first sprue 6a, second sprue 6b, first runner 8a, and second runner 8a in the runner plate.
2----1 third runner 8c,---1 is a perspective view of the first gate 8b and the resin reservoir 8d.

In Figure 2, a indicates the thickness of the second runner 8a2-, and b indicates the thickness of the resin reservoir 8d.

FIG. 3 is a plan view of the sprue and runner in the Y+Y'+ plane of FIG. 1.

Figures 4a--c show the flow states of the first and second resins with and without the present invention.

FIG. 4B shows the flow state of the resin when the first cage 8b according to the present invention is provided, and the first runner 8 of the second resin C is shown in FIG.
The backflow to al is stopped at b1 inside the first gate 8b.

By providing the first gate 8b in FIG.
The back flow of the resin C toward the first runner 8a1 is stopped by the first gate, and the resin reservoir 6b is provided so that the resin is uniformly distributed to each second runner 8a2--8a4. It is distributed (a 1---83).

Referring to the cross-sectional area of the gate 8b, when the skin layer resin is first injected, the skin layer runner 8al is filled with the skin layer resin, and then the core layer resin is injected, the skin layer resin in the gate 8b is When the center temperature of the skin material falls below the transition point temperature of the skin layer resin, the skin layer resin inside the gate 8b receives heat radiation or cooling from the surrounding wall of the gate 8b, which impairs the fluidity of the skin layer resin and causes the core layer resin to dissipate at the gate. A cross-sectional view that prevents entry into the skin layer runner 8a through the skin layer runner 8b is preferable.

Therefore, while the diameter of the gate 8b is 1 mm to 4 mm, the diameter of the runner 8a is set to 3n+m to 8 mm.
The cross-sectional area ratio S8b/58a=O, OIF is preferably set within the range of F5 to 0.5.

Figure 5 shows the case where there are six second runners (5a
1---5 aQ).

In Figure 6, there is no second runner and the third runner 8C is 1
The case is shown below.

5 and 6, the cross-sectional area of the runner 8a is reduced to the tip of the runner 8a near the junction of the skin layer resin material distribution runner 8al and the core layer resin runner 6a, and the core layer A gate 8b is provided to prevent the resin B from flowing in.

[Explanation of effects] As explained above, by providing the first gate at the joint between the first runner and the second sprue, the second resin can be injected from the second sprue after the first resin is injected. The first
The backflow of the second resin toward the runner side is stopped within the first gate, which reduces the mixing of the first resin and the second resin due to the backflow and the resin pressure loss when the second resin is injected. As a result, the second resin is injected in equal amounts to each second runner, and the resin pressure, which has an excessive effect on the precision of the molded product, is now applied equally. In addition, by providing the resin reservoirs at the specified positions, uneven filling of the second runners due to the inertial flow of the first resin and uneven filling of the second runners during steady flow are possible.
The non-uniform filling of the runners has been resolved, and an equal amount can now be injected into each second runner.

In other words, due to the above effects, a highly accurate multilayer structure molded product uniformly filled with the first and second resins was obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main parts of the molding device, Fig. 2b is a perspective view of a part of the sprue and runner, and Fig. 2 is a sectional view of a part of the sprue and runner.
A plan view of a part of the sprue and runners; Figures 4a and b are diagrams of poor resin flow in a part of the sprue and runner; Figure 5 is a perspective view of a part of the sprue and runner resin when there are six second runners; FIG. 6 is a perspective view of a part of the sprue and runner resin without the second runner, and FIGS. 7a and 7b are explanatory views of the prior art.

Claims (2)

[Claims] (1) In injection molding with a cylindrical part, in an injection mold for sandwich molding with a core layer resin at the center of the cylindrical part and a skin layer resin around the center of the cylindrical part, for molding the cylindrical part. A runner plate provided with a plurality of runners for passing the resin through the void is attached to a mold member provided with a space, and an injection cylinder unit for core layer resin and an injection cylinder unit for skin layer resin are connected to the runner plate. A fixing plate provided with a spray is attached, and the starting points of the plurality of runners and the injection ports of the core layer resin injection cylinder unit are arranged in a straight line, and between the injection cylinder unit for the skin layer resin and the starting point of the runner. A mold for a multilayer resin molded product, characterized by having a runner for the skin layer resin. (2) A mold for a multilayer resin molded product according to claim (1), characterized in that in the mold, the runner for the skin layer resin is provided with a gate that narrows the resin flow cross section. .