JPH01123715A - 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 mechanisms since the midway of a first step ejecting process and then an ejector pin is ejected by a second step ejecting mechanism so far in a space between a fixed mold and a movable 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, in mold opening, both a first step and a second step ejector plates 15 and 16 are moved by pulling. As a result, ejector shafts 14 are slidingly ejected so far in a space between the fixed mold 12 and the movable mold 13. At the same time, ejector pins 22 and 23 are ejected so far in said space between the molds. Further, the ejector plates 15 and 16 are ejected by the first step so as to rotate the ejector shafts 14 by means of shaft rotating mechanisms in order to turn the inserts 10 in the directions indicated with the arrows A. After that, the ejector plate 16 is struck by an ejector rod 20 so as to further eject the pins 22 and 23 in the space between the fixed mold 12 and the movable mold 13 in order to take the inserts 10 out of a 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 useful for molded products that include an annular portion that is divided at one point on the periphery and has an undercut on the inner circumferential 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.

(Conventional technology) 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 Molten synthetic resin is injected 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 was removed from the mold together with the insert, and then the insert was forcibly removed from the molded product using the "elastic deformation" of the molded product manually by an operator. For this reason, the undercut part, that is, the lens fitting groove, was often damaged during the extraction process, and this was a major cause of product defects, making product quality control difficult. In addition, the work of extracting the inserts was very troublesome and required a full-time worker, which was also 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 nest has a complex structure, is extremely expensive, and is easily damaged, resulting in a significant increase in product cost.

In addition, as shown in Japanese Patent Application Laid-open No. 62-5826, a technique has been proposed in which the molded product is held in a clamp and the movable insert is ejected with an ejector to remove the insert from the molded product. ing. However, for molded products that include an annular part that is divided at one point on the circumference, applying the above technology as is will tend to increase the number of breakage defects. However, since it is necessary to include an ejection drive mechanism including an electric circuit, there is a problem that the entire device becomes complicated and large-scale.

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 apparatus useful for using the above-mentioned injection molding method, in which it is sufficient to utilize the original function of the injection molding mechanism, and a separate special drive mechanism is required. An object of the present invention is to provide an injection molding apparatus for the above-mentioned molded product that does not require the provision of.

(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 a cinder cut on the inner peripheral surface. is arranged so that a cavity for the molded product is formed between a fixed mold for injection molding and a movable mold, and injection molding is performed, and then the insert is integrally combined with the insert and is slidable in the mold opening/closing direction. An ejecting shaft is ejected into the space between the fixed mold and the movable mold simultaneously with the opening of the mold by a first stage ejecting mechanism, and at this time, the ejecting shaft is rotated halfway through the first stage ejecting process by a shaft rotation mechanism, and then An ejector pin facing the cavity and movable in the mold opening/closing direction in conjunction with the sliding of the ejector shaft is ejected into the space between the fixed mold and the movable mold by a second stage ejector mechanism, and the first stage ejector is ejected. The molded product is removed from the insert.

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 in one circumference and has an undercut on the inner circumferential surface. A fixed mold and a movable mold for injection molding that form a cavity, and an ejecting shaft that is integrally connected to the insert and is provided on either the fixed mold or the movable mold so as to be slidable in the mold opening/closing direction. and a first stage ejecting mechanism that is provided in the one mold and connects with the other mold via a linking means, and that ejects the ejecting shaft into the space between the fixed mold and the movable mold at the same time as the mold is opened; a shaft rotation mechanism that rotates the ejection shaft midway through the first stage ejection process; and a shaft rotation mechanism that moves the one mold in a mold opening/closing direction in conjunction with sliding of the ejection shaft so as to face the cavity of the molded product. and a second stage ejecting mechanism for ejecting the ejecting pin into a space between the fixed mold and the movable mold to remove the first stage ejected molded product from the insert. It is characterized by this.

In the case of molding plastic eyeglass frames, the insert is usually a curved plate, with a protrusion formed on its outer circumferential surface that corresponds to the lens fitting groove, and further abuts the split part of the molded product at one point around the periphery. A type with a protrusion is used.

The ejecting shaft is integrally connected to the insert, and is often 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 first stage ejecting mechanism includes, for example, an ejecting plate provided in the back of the movable mold on the back side of the ejecting shaft so as to be movable in the opening/closing direction, and a chain plate and a fixed mold connected by a linking means such as a chain. A mechanism is used in which the ejector shaft is simultaneously ejected into the space between the movable mold and the fixed mold by pulling the ejector plate using a chain.

The shaft rotation mechanism includes, for example, a combination of a dogleg-shaped groove and a projection pin fitted therein, or a combination of a cam and a corresponding cam groove, on the outer surface of the ejection shaft and the inner surface of the mold that slides thereon. The ejecting shaft may be rotated by an angle of 5'' to 30°, preferably about 10°, from the middle of the ejecting process.

The ejection pin is provided so as to face the cavity of the molded product during injection injection of resin, and to move in the same direction in conjunction with the ejection of the ejection shaft when the mold is opened. Therefore,
At the end of the first stage ejection, the ejector pin is in contact with the ejected injection molded product.

The second stage ejecting mechanism includes, for example, an ejecting plate separate from the first ejecting plate described above, inside the movable mold on the back side of the ejecting pin, and by hitting the chain plate with an ejecting rod or the like, the ejecting pin is moved into the movable mold. A mechanism that can protrude into the space between the mold and the fixed mold is used.

(Function) In the molding process of the present invention, after resin injection molding, the molded product is separated from the mold surface facing the cavity by the first stage of ejection of the ejection shaft that acts simultaneously with the mold opening, and then the ejection shaft is rotated. The insert also rotates in the same direction, and its protruding portion pushes against one end face of the divided part of the annular part of the molded product, widening the distance between it and the other end face, and the protrusion on the outer circumferential surface of the molded part moves further than the undercut of the molded product. It almost came off,
Thereafter, the molded product is completely removed from the insert by the second stage of ejection of the ejector pin. Therefore, the insert can be automatically extracted, and the automatic extraction proceeds in unison with the mold opening operation.

(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.
2b is suitable for injection molding of a molded product having a dividing point 6 at one point on the circumference, that is, at the edge, and forming an undercut 5 for a lens fitting groove on the inner circumferential surface. , 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 consists of a fixed mold 12 and a T-movable mold 13, which together with two inserts 10 and 10 form the cavity 3 of the molded product I. Become. The insert 1O is a curved plate that forms a protrusion (corresponding to the undercut 5) on the outer peripheral surface, and the fifth
As shown in the figures through FIG. 8, a protrusion 11 is provided.

Further, 7 indicates a spool communicating with the cavity 3.

The movable mold 13 has a first stage ejecting plate 15 disposed on a side farther from the contact surface 31 between the fixed mold 12 and the movable mold 13, and a second stage ejecting plate 16 on a side closer to the contact surface 31.
These protruding plates 15, 16 are provided movably in the mold opening/closing direction by means of support shafts 18, 18. The first ejector plate 15 is connected to the fixed mold 12 by a chain 17, so that when the mold is opened, the ejector plates 15 and 16 of the first and second stages are pulled in the mold opening/closing direction by the linking means 17. A spring 19 is interposed between the second stage ejecting plate 16 and the inner surface of the mold 13 along the support shaft 18, so that the ejecting plate 15, 16 can be pulled against the repulsive force of the spring 19. It is done.

The movable mold 13 also has two ejecting shafts 1 which are each integrally connected to the insert 10 and fitted into holes in the ejecting plate 16.
4.14 is provided slidably in the mold opening/closing direction, and the ejecting shaft 14.14 is ejected into the space between the fixed mold l-2 and the movable mold 13 by pushing the first stage ejecting plate 15. There is. In addition, the movable mold 13 has ejecting bins 22 and 22.
the annular parts 2a and 2b so as to face the cavity 3 corresponding to the annular parts 2a and 2b, and the protruding bottle 23 so as to face the cavity 3 corresponding to the spool 7, and these bottles 22 and 23.
is fixed to the second stage ejecting plate 16 so as to be movable in the mold opening/closing direction.

A hole 21 is provided in the first ejector plate 15 so that the ejector rod 20 can pass through the hole 21 and directly strike the second ejector plate 16. Therefore, the second stage ejector plate 16 is pushed by the ejector rod 20, and the ejector bins 22 and 23 are moved to the fixed mold 12.
and the movable mold 13. At this time, the first stage ejector plate 15 and the ejector shaft 14 do not move. In addition, the push-out bottles 22 and 23
is simultaneously ejected into the space between the fixed mold 12 and the movable mold 13 in conjunction with the sliding and ejection of the ejecting shaft 14 by the pushing of the first stage ejecting plate 15. Reference numeral 25 denotes a spring bamboo charcoal bottle, by which the insert lO pushed out during mold closing is pushed back to its original position.

Furthermore, although the apparatus of this embodiment is not shown in FIGS. 1 to 4, FIG.
A shaft rotation mechanism as shown in FIG. 13 is provided on the movable die 13 side, and when the ejector shaft 14 is ejected by the first ejector plate 15, the ejector shaft 14 is rotated by an angle of about 15'' from the middle of the process. The shaft rotation mechanism shown in FIGS. 1O and 11 is such that the protruding pin 26 of the ejecting shaft 14.h fits into a dogleg-shaped groove 27 provided on the inner surface of the mold. As shown over time in (b) and (C), the ejecting shaft 14g and the insert lO rotate so that the position of the bottle 26 in the groove changes sequentially, and the insert lO rotates.
The protrusion 11 of the O pushes the flanges 8.8 of the annular parts 2a, 2b and widens the distance from the recess 9.9.The shaft rotation mechanism shown in FIGS. 12 and 13 is As shown in FIGS. (a), (b), and (c) over time, the cam 28 on the ejecting shaft 14 fits into the cam groove 29 provided on the inner surface of the mold in the middle of ejecting the shaft 14, so that the ejecting shaft 14 and the nested lO rotate, and the nested lO
The protruding portion 11 presses the flanges 8, 8 of the annular portions 2a, 2b to widen the distance from the recessed portions 9, 9. 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, inserts 10 and 10 are placed between the fixed mold 12 and the movable mold 13 so that the cavity 3 of the molded product shown in FIG. The molded product 1 at this time is shown in FIG. 5. The protrusion 11 of the insert 10 is attached to the flanges of the annular parts 2a and 2b as shown in FIG. 8 and the recess 9.

Next, the mold opens. When the mold is opened to some extent, the first and second ejecting plates 15 and 16 are both connected to the spring 19 by the chain 17, as shown in FIG.
The ejector shaft 14.14 is moved against the fixed type 12! An ejector bottle 22 that slides and protrudes into the space between the II molds 13, and at the same time faces the annular portions 2a and 2b, and an ejector bottle 23 that faces the resin 24 of the spool, respectively, protrudes into the space between both molds. be done. Further, when the ejecting plate 15.16 has been ejected to the position shown in FIG. 3, the ejecting shaft 14.14 is rotated by the above-mentioned shaft rotation mechanism, that is, the insert 1O11O is rotated as shown in FIG. It rotates in the direction of arrow A, and each protrusion 11 pushes the flange 8 of the annular part and widens the distance from the recess 9 (eighth
Figure), insert 10.10 is undercut 5,5 of molded product
It will be in a state where it is almost off.

Thereafter, as shown in FIG. 4, the ejector rod 20 is struck against the ejector plate 16, and the ejector bins 22, 22.
23 is further protruded into the space between the fixed mold 12 and the movable mold 13, and the insert 1O110 is removed from the molded product l.

In this way, by using the apparatus of the embodiment, the insert can be removed from the injection molded product at the same time as the mold is opened.

(Effects of the Invention) As explained above, the injection molding method for a molded product of the present invention is effective in producing 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. After molding, the insert can be extracted from the molded product in conjunction with the mold opening operation without causing damage or damage to the molded product, especially undercuts, and the insert removal process is completely automated. Therefore, the workability of the sampling operation and the productivity of the molded product are significantly improved, and high quality molded products can be mass-produced.

Moreover, the injection molding apparatus for molded products of the present invention is a particularly effective apparatus for using the above-mentioned injection molding method, and not only can the effects of the method be fully obtained, but also the original functions of the injection molding mechanism can be utilized. It is sufficient to do so, and there is no need to separately provide a special drive mechanism, resulting in a very simple structure.

Therefore, the method and apparatus of the present invention are particularly useful for injection molding of plastic eyeglass frames, especially eye and mirror 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. Figure 5 is a plan view showing the molded product immediately after resin injection injection, @4'>0 Figure is a plan view showing the molded product after the first stage ejection, and Figure 7 is the annular portion of the molded product in Figure 5. FIG. 8 is an enlarged view showing the parts 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 FIGS. 10 (a) to C) and FIG. Figures 12(a) to 8(c) and 13(a) to 13(c) are diagrams illustrating the operating process of other examples of shaft rotation mechanisms. In the figure. l... Molded product 2a, 2b... Annular part 3... Cavity 5... Undercut 6... Divided point 8/Flange 9... Recessed part ゛10... Insert 11...・Protruding portion 12...Fixed mold 13'...Movable mold 14...Ejecting shaft 15...First stage ejecting plate 16...Second stage ejecting plate 17...Linking means 20... Extrusion lot 22.23...Ejection pin 26...Ejection pin 27...Dovetail groove 28...Cam 29, φ, cam groove 30...Undercut (2 other people) 1... Molding Product 10... Inko 13, Machitoge 14, Tsukushoshi axis 22.23.1! Outer Pi) 30...Ivy No. 5
Figure 6 Figure 9 Figure 8 Figure 7

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 cavity so that a cavity is formed, and then fixing the ejector shaft, which is integrally connected to the insert and is slidable in the mold opening/closing direction, by the first stage ejector mechanism at the same time as the mold is opened. The ejection shaft is ejected into the space between the mold and the movable mold, and at this time, the ejection shaft is rotated halfway through the first stage ejection process by a shaft rotation mechanism, and then the ejection shaft faces the cavity and opens and closes the mold in conjunction with the sliding movement of the ejection shaft. An undercut characterized in that an ejection pin movable in the direction is ejected into a space between the fixed mold and the movable mold by a second stage ejection mechanism, and the molded product ejected in the first stage is removed from the insert. A method for injection molding a molded article including an annular portion having a cut. (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; a protruding shaft integrally connected to the insert and provided on either the fixed mold or the movable mold so as to be slidable in the mold opening/closing direction; and within the one mold. a first-stage ejecting mechanism that is connected to the other mold via a linking means and projects the ejecting shaft into the space between the fixed mold and the movable mold at the same time as the mold is opened; an ejector pin provided in the one mold so as to face the cavity of the molded product and move in the mold opening/closing direction in conjunction with the sliding of the ejector shaft; , a second stage ejecting mechanism for ejecting the ejecting pin into a space between the fixed mold and the movable mold to remove the first stage ejected molded product from the insert. An injection molding device for a molded product including an annular portion having a ring shape.