JPH01123716A - Method and apparatus for injection-molding molded item containing annular part with undercut - Google Patents

Abstract

PURPOSE:To fully automate the drawing-out process of inserts and consequently improve workability and productivity by a method wherein ejector shafts are rotated by shaft rotating mechanism since the midway of an ejecting process and, after that, an ejected molded item is grasped with the unloading arm of a robot so as to be taken out of a mold. CONSTITUTION:Injection molding is done under the condition that inserts 10 are arranged between a fixed mold 12 and a movable mold 13 so as to form the cavity 3 of a molded item. Next, after the completion of mold opening, an ejector plate 15 is pushed forward by being struck by an ejector rod 18 so as to slidingly eject ejector shafts 14 in a space between the fixed mold 12 and the movable mold 13. At the same time, ejector pins 20 and 19 are ejected respectively in the space between both the molds. At this time, through the ejection of the ejector plate 15, the ejector shafts 14 are rotated by means of shaft rotating mechanisms in order to turn the insert 10 in the directions indicated with the arrows A. After hat, the unloading arm of a robot enters between the fixed mold 12 and the movable mold 13 so as to grasp and pull a molded item 1 out of the molds in order to remove the cores 10 from the molded item 1.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an injection molding method for a molded article including an annular portion having an undercut, and an injection molding apparatus for the molded article.
In particular, the present invention relates to an injection molding method and apparatus for plastic eyeglass frames (including whole frames and halves thereof) in which undercuts correspond to lens fitting grooves.

The molding method and molding apparatus of the present invention are particularly suitable for molded products that include an annular portion that is divided at one point on the periphery and has an undercut on the inner peripheral surface, such as a lens that has an edge around the entire periphery and a corner portion. This is useful for manufacturing plastic eyeglass frames that are originally divided into upper and lower parts and are combined together.

(Prior Art) Conventionally, plastic eyeglass frames, mainly sunglasses, etc., have been produced by placing an insert between a fixed mold for injection molding and a movable mold so that a cavity in the shape of the eyeglass frame is formed, and then It is molded by injecting molten synthetic resin into the cavity. Recently, attempts have been made to use so-called super engineering plastics such as polymethylpentene resin and polyethersulfone resin as materials for injection-molded eyeglass frames instead of conventionally used nylon resins and cellulose acetate propionate resins. ing.

(Problems to be Solved by the Invention) In injection molding of plastic eyeglass frames, it is necessary to undercut the inner peripheral surface of the annular part of the molded product in order to form the lens fitting groove. The problem is how to remove the insert from the annular part of the molded product after the resin has been injected without damaging the molded product.

However, in the past, after injection molding, the molded product is removed from the mold together with the insert, and then the insert is removed from the molded product by force removal using the elastic deformation of the molded product. A method was taken. For this reason,
During the extraction process, the undercut portion, that is, the lens fitting groove, is often damaged, which is a major cause of product defects, and is a serious problem in terms of product quality control. In addition, the work of extracting the nests is very troublesome and requires a full-time worker, which poses a problem in terms of productivity.

As a means to solve this problem, a technique has been developed in which, for example, the insert is made into a split mold that can be enlarged and reduced, and the insert is reduced and taken out after resin injection. However, with this technique, the insert is extremely expensive due to its complicated structure and is easily damaged, resulting in a significant increase in product cost.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 82-5826, a technique has been proposed in which the molded product is held in a clamp and the movable insert is pushed out with an ejector pin, thereby removing the insert from the molded product. ing. However, in the case of a molded product including an annular portion divided at one point on the circumference, there is a problem in that if the above-mentioned technique is applied as is, the number of breakage defects tends to increase.

The present invention has been made in consideration of the above-mentioned circumstances, and one purpose thereof is to use injection molding to produce a molded product including an annular portion that is divided at one point on the periphery and has an undercut on the inner peripheral surface. The insert can be automatically extracted from the molded product without causing breakage or damage to the molded product, and without removing the insert from the mold. Therefore, the molded product can be efficiently mass-produced without producing defective products. The object of the present invention is to provide an injection molding method that can perform the following steps.

Another object of the present invention is to provide an injection molding apparatus for the molded product, which is useful for using the above injection molding method, and is capable of sufficiently improving the productivity and quality of the molded product. Our goal is to provide the following.

(Means for Solving the Problems) The injection molding method of the present invention is an injection molding method for a molded product including an annular portion that is divided at one point on the periphery and has an undercut on the inner peripheral surface. is placed between the fixed mold for injection molding and the movable mold so that the cavity of the molded product is formed, and then injection molded, and then after the mold is opened, it is integrally combined with the insert and moved. A flexible ejection shaft is ejected into the space between the fixed mold and the movable mold by an ejection mechanism, and at this time, the ejection shaft is rotated halfway through the ejection process by a shaft rotation mechanism, and then the ejected molded product is taken out by a robot. It is characterized by being gripped by an arm and taken out of the mold.

Further, the injection molding apparatus of the present invention is an injection molding apparatus for a molded product including an annular part that is divided at one point on the circumference and has an undercut on the inner circumferential surface. A fixed mold and a movable mold for injection molding to form a mold, an ejecting shaft integrally connected to the insert and movably provided in either the fixed mold or the movable mold, and the ejecting shaft an ejecting mechanism that protrudes into a space between the fixed mold and the movable mold; and a shaft rotation mechanism that rotates the ejecting shaft midway through the ejecting process;
A robot having a take-out arm that grasps the ejected molded product and takes it out of the mold.

In the case of molding plastic eyeglass frames, the insert is usually a curved plate with a protrusion formed on its outer circumferential surface to correspond to the lens fitting groove, and a part on the periphery that corresponds to the dividing part of the molded product. A type with a protruding portion that contacts is used.

The ejection shaft is integrally coupled with the insert, and is preferably provided inside the movable mold so as to be slidable in the opening/closing direction of the mold. In the case of molding eyeglass frames, a pair of protruding shafts are provided.

The ejecting mechanism can be used, for example, by ejecting the ejecting plate and attaching it to the back side of the shaft. It is preferably provided inside Il so as to be movable in the mold opening/closing direction, and is further provided with a protruding rod on the back side for tapping the ejecting plate, and after opening the mold, the ejecting plate is pushed and moved by striking with the ejecting rod. A type with a shaft protruding into the space between the movable type and the fixed type is used.

The shaft rotation mechanism includes, for example, a combination of a dogleg-shaped groove and a protruding bottle fitted into the groove, or a combination of a cam and a corresponding cam groove, on the outer surface of the ejecting shaft and the inner surface of the mold that slides thereon. , the ejecting shaft is rotated by an angle of 5° to 30″, preferably about 10°, from the middle of the ejecting process.

The robot may be equipped with a take-out arm that enters the space between the stationary mold and the movable mold, grabs the protruding part of the molded product, for example, the spool resin part, and subsequently pulls it out of the insert. As long as it is acceptable, its form and type do not matter.

Further, in the molding apparatus of the present invention, the ejection bottle is preferably provided so as to face the cavity of the molded product during injection injection of the resin, and to move in the same direction in conjunction with the ejection of the ejection shaft after the mold is opened. It will be done.

(Function) In the molding process of the present invention, after resin is injected using a normal method and the mold is opened, the ejecting shaft is ejected by the operation of the ejecting mechanism, whereby the injection molded product faces the cavity. After separating from the mold surface, the ejector shaft is rotated by the rotating mechanism, and this rotation causes the insert to rotate in the same direction, and its protruding part presses against one end face of the divided part of the molded annular part to increase the distance between it and the other end face. The molded part is completely removed from the molded part by expanding the molded part so that the protrusion on the outer circumferential surface of the molded part is almost removed from the undercut of the molded part, and then the robot's take-out arm grabs the protruded molded part and pulls it off. . Therefore, the molded product can be automatically extracted from the insert.

(Examples) Hereinafter, the present invention will be explained in more detail by showing Examples, but the following Examples are not intended to limit the present invention in any way.

The molding apparatus of the embodiment shown in FIGS. 1 to 4 connects left and right annular parts 2a, 2b with a bridge 4, such as a plastic eyeglass frame as shown in FIG.
b has a dividing point 6 at one point on the circumference, that is, at the edge, and an undercut 5 for a lens fitting groove on the inner circumferential surface.
It is suitable for injection molding of square-shaped products formed by forming 0
The dividing point 6 is such that the lower flange 8 can fit into the upper recess 9.

To further describe the configuration of the apparatus of the embodiment, this injection molding apparatus includes a fixed mold 12 and a movable mold 1 that together form the cavity 3 of the molded product 1 with two inserts 1O11O.
Consists of 3. Nested lO is.

It is a curved plate that forms a protrusion (corresponding to the undercut 5) on its outer peripheral surface, and is provided with a protrusion 11 as shown in FIGS. 5 to 8. Further, 7 indicates a spool communicating with the cavity 3.

The movable mold 13 is provided with two ejector shafts 14, 14 which are each integrally connected to the insert lO and fixed to the ejector plate 15 so as to be slidable in the mold opening/closing direction, and the ejector plate 15 is connected to a support shaft 16.14. 16 to be movable in the mold opening/closing direction, and further provided with an ejector rod 18 on the back side of the chain plate 15. When the loft 18 hits, the ejector plate 15 is pushed, and this pushing causes the two ejector shafts 14 to be moved. .14 is projected into the space between the fixed mold 12 and the movable mold 13. A spring 17 is interposed between the ejecting plate 15 and the inner surface of the mold 13 along the support shaft 16, so that the ejecting plate 15 is pushed against the repulsive force of the spring 17.

In addition, the flexible A type 13 has the ejecting pins 20 and 20 facing the cavity 3 corresponding to the annular portions 2a and 2b, and the ejecting pin 19 facing the cavity 3 corresponding to the spool 7.
The pins 19j5 and 20 are fixed to the protruding plate 15 so as to be movable in the mold opening/closing direction.

Therefore, the ejector pin 19.20 is the ejector rod 1
By tapping 8, the ejection shaft 14 is slid and ejected, and at the same time, it is ejected into the space between the fixed fi 12 and the movable mold 13. Reference numeral 21 denotes a spring charcoal pin, and the insert 10, which was pushed out during mold closing, is pushed back to its original position by this pin.

Furthermore, although the apparatus of this embodiment is not shown in FIGS. 1 to 4, FIG. 1O, FIG. 11, or FIG.
The movable shaft 13 is equipped with a shaft rotation mechanism as shown in FIG.
It is designed to rotate by an angle of °. The shaft rotation mechanism shown in FIG. 1θ and FIG.
As shown in Figures (a), (b), and (C) over time, the ejecting shaft 14 and the insert lO rotate so that the position of the pin 24 in the groove changes sequentially. The protruding portion 11 of the child 10 is connected to the flanges 8, 8 of the annular portions 2a, 2b.
By pressing , the distance between the concave portion 9.9 and the concave portion 9.9 is widened.

In addition, in the shaft rotation mechanism shown in FIGS. 12 and 13, as shown over time in FIGS. 12 and 13, the cam 26 on the protruding shaft 14 By fitting into the cam groove 27 provided on the inner surface of the mold halfway, the ejector shaft 14 and the insert lO rotate, and the insert lO
The protruding portion l/1 of O is the flange 8.8 of the annular portions 2a and 2b.
The space between the concave portion 9.9 and the concave portion 9.9 is widened by pressing .

Note that 30 indicates an undercut that becomes a lens fitting groove.

Next, a molding process using the apparatus of the example will be explained. First, the insert 10.10 is placed between the fixed mold 12 and the movable mold 13 so that the cavity 3 of the molded product shown in FIG. to make molded product 1 (Figure 1), molded product 1 at this time
The protrusion 11 of the insert 10, shown in FIG. 5, is located between the flanges 8 and the recess 9 of the annular portions 2a, 2b, as shown in FIG.

Next, the mold opening operation begins, and when it is completed, the ejector plate 15 is pushed against the spring 19 by the striking of the ejector loft 18, as shown in FIG. 2, and the ejector shaft 1
4.14 slides and protrudes into the space between the fixed mold 12 and the movable M111, and at the same time the ejecting pins 20 facing the annular portions 2a and 2b and the ejecting pin 19 facing the resin 23 of the spool move both molds. thrust into the space between.

At this time, when the ejector plate 15 is ejected to the position shown in FIG. 3, the ejector shaft 14.14 is rotated by the above-mentioned shaft rotation mechanism, that is, the insert member 10.10 is moved into the position indicated by the arrow as shown in FIG. The protrusions 11 push the flange 8 of the annular part and widen the distance from the recess 9 (FIG. 8), so that the insert 1O110 is almost removed from the undercuts 5, 5 of the molded product.

After that, the 4th I! As shown in 1, the robot's take-out arm 22 is fixed yJ! 12 and 1J13, grab the spool resin 23 of the molded product 1, pull it out, and remove the insert 1O11O from the molded product 1.

In this way, by using the apparatus of the embodiment, the insert can be automatically removed from the injection molded product.

(Effects of the Invention) As explained above, the injection molding method for a molded article of the present invention can be used to produce a molded article that includes an annular portion that is divided at one point around the circumference and has an undercut on the inner peripheral surface. After molding, the insert can be automatically extracted from the injection molded product without causing breakage or damage to the molded product, especially undercuts, and the insert removal process is fully automated, thus making the extraction process easier. The workability and productivity of the above-mentioned molded products are significantly improved, and high-quality molded products can be mass-produced.

Further, the injection molding apparatus for molded articles of the present invention is an especially effective apparatus for using the above-mentioned injection molding method, and the effects of the method can be sufficiently obtained.

Therefore, the method and apparatus of the present invention are particularly useful for injection molding of plastic eyeglass frames, especially eyeglass frames that are constructed by joining two parts that are originally divided into upper and lower parts at the edge.

[Brief explanation of the drawing]

1 to 4 are diagrams showing a molding process using an injection molding apparatus according to an embodiment of the present invention. Fig. 5 is a plan view showing the molded product immediately after injection of resin, Fig. 6 is a plan view showing the molded product after the ejection shaft has been ejected and rotated, and Fig. 7 is a plan view of the annular portion of the molded product in Fig. 5. 8 is an enlarged view showing the part where the annular part of the molded product shown in FIG. 6 is divided. FIG. 9 is a plan view showing a molded product molded and taken out by the method of the example, and FIG. 10<a> to c) and FIG. Diagram showing the operating process of the mechanism. FIGS. 12(a) to 12(C) and 13(a) to 13(C) are diagrams showing the operating process of another example of the shaft rotation mechanism. In the figure, l... Molded products 2a, 2b... Hege-shaped portion 3... Cavity 5... Undercut 6... Divided point 8... Flange 9... Recessed part 10... Insert 11...Protruding part 12...Fixed mold 13...Movable mold 14...Ejecting shaft 15...Ejecting plate 18...Ejecting rod 22...Robot take-out arm 24...Protruding bin 25...Dog-shaped groove 26...φ cam 27...Cam groove 30 openings/undercut Figure 5 Figure 6 Figure 9 ＼ 81! I No. 1. Figure 10 Figure 11

Claims (2)

[Claims] (1) In an injection molding method for a molded product including an annular portion that is divided at one point on the circumference and has an undercut on the inner peripheral surface, the insert is placed between a fixed mold for injection molding and a movable mold of the molded product. Injection molding is performed by arranging the mold so that a cavity is formed, and then, after opening the mold, a movable ejecting shaft that is integrally connected to the insert is ejected into the space between the fixed mold and the movable mold by an ejecting mechanism. An annular part having an undercut characterized in that the ejecting shaft is rotated in the middle of the ejecting process by a shaft rotation mechanism, and then the ejected molded product is grabbed by a take-out arm of a robot and taken out of the mold. Injection molding method for molded products including. (2) In an injection molding device for a molded product including an annular portion that is divided at one point on the circumference and has an undercut on the inner circumferential surface, the injection molding unit forms a cavity of the molded product together with the insert. a fixed mold and a movable mold; an ejecting shaft that is integrally coupled with the insert and is movably provided in either the fixed mold or the movable mold; and the ejecting shaft is connected to the fixed mold and the movable mold. A robot having an ejecting mechanism that protrudes into the space between, a shaft rotation mechanism that rotates the ejecting shaft from midway through the ejecting process, and a take-out arm that grasps the ejected molded product and takes it out of the mold. An injection molding apparatus for molded products including an annular portion having a characteristic undercut.