GB2276583A

GB2276583A - Plastic moulding apparatus

Info

Publication number: GB2276583A
Application number: GB9406102A
Authority: GB
Inventors: Kohichi Takagi; Hiroyuki Yamada; Takashi Shigematsu
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 1993-03-26
Filing date: 1994-03-28
Publication date: 1994-10-05
Anticipated expiration: 2014-03-28
Also published as: JPH06278141A; GB2276583B; GB9406102D0

Abstract

Plastics moulding apparatus 10 comprises movable and fixed moulds 20, 30 respectively carrying moulding dies 23, 34 facing each other. Movable member 40, having a moulding core 41 projected therefrom to be located between the two moulding dies is moved, in a direction different from that in which the movable mould is moved, by device 50. Spring-loaded plungers 60 guide member 40 so that core 41 lies between the two dies, when concavities 40b allow member 40 to drop so that projecting core pins fit in grooves in the lower die. The dies are then closed for injection. In moulding an epoxy ferrule for connecting optic fibres, the core pins form holes for the fibres and for ferrule guide pins. <IMAGE>

Description

PLASTIC MOULDING APPARATUS The present invention relates to a plastic moulding apparatus which has a moulding core disposed between a pair of moulding dies to manufacture plastic moulded parts.

In general, when manufacturing a plastic moulded part, which has a cavity, by using a pair of moulding dies, a moulding core is provided between both moulding dies to produce the plastic moulded part with one shot of a plastic material to be injected.

As such a plastic moulded part, for example, a ferrule for a multi fiber connector is known.

The ferrule has, at the center thereof, a plurality of fiber holes into which optical fibers are inserted and guide holes into which guide pins are fitted, which are formed lengthwise in parallel on both sides of the fiber holes, and a front part thereof constituting a butting surface to be butted against another ferrule of a multi fiber connector.

Into the plurality of fiber holes of the ferrule are inserted the ends of a plurality of optical fibers which are arranged straight and aligned in parallel, all the optical fibers are fixed to the ferrule with adhesive, then the ends are ground to be flush with the butting surface.

In this case, when the ferrule is buttconnected to another ferrule having the same configuration, the guide pins are fitted into the guide holes in a manner that they extend to corresponding guide holes, thereby precisely aligning the optical axes of mating optical fibers of ferrules.

The ferrule is formed, for example, by transfer moulding using plastic as set forth below.

First, a core and core pins are set in predetermined positions in a pair of moulding dies, both moulding dies are clamped, then a plastic material such as epoxy resin is injected in a cavity, which is formed by the two moulding dies, the core and the core pins.

The plastic material is heated and cured to mould the ferrule.

The core is provided with a plurality of fine moulding pins which have an approximately 125 Am diameter to form the plurality of fiber holes in the ferrule, and the core pins are used to form guide holes in the ferrule into which the guide pins are fitted.

The ferrule thus formed is taken out of the cavity, and the moulding core and the core pins are removed.

The ferrule requires a micron-level moulding accuracy since the optical axes of the optical fibers must be precisely aligned as discussed above. An even higher accuracy is required for a ferrule for a multi fiber connector since the optical axes of multiple optical fibers are to be aligned.

Accordingly, when plastic-moulding a ferrule for a multi fiber connector, it is necessary to accurately position the moulding core in the cavity in addition to ensuring the machining accuracy for the moulding dies and the moulding cores.

In the plastic moulding, the methods for setting the moulding core between a pair of moulding dies are roughly divided into two types.

In one type, the moulding core is set in one mould die of the pair beforehand and the moulding core is removed together with the ferrule after moulding. In the other type, the moulding core is mounted on a movable member which is free to move between the moulding dies, the movement thereof being interlocked with that of the pair of moulding dies. When the moulding dies are closed or opened, the moulding core is automatically placed between or moved away from the moulding dies through the movable member.

The first method, wherein the moulding core is set between the moulding dies, requires complicated and time-consuming operation since a worker must manually place and take the moulding core in and out of the moulding die each time a ferrule is moulded. This caused a problem in that a longer tact time was required for a moulding cycle with consequent higher manufacturing cost of ferrules.

The second method does not suffer from the inconvenience found with the first method since the moulding core can be automatically positioned between and moved away from she moulding dies by the movable member which is interlocked with the closing and opening of the moulding dies.

The movable member, however, is a separate component from the moulding dies and it has a gap between itself and a guiding section which guides the movement. This makes it difficult to position the movable member with submicron level accuracy in relation to the moulding dies, and making the gap extremely small for the purpose of positioning caused the moulding core to interfere with the moulding dies occasionally.

If such interference takes place between the moulding core and the moulding dies, fine moulding pins of an approximately 125 Zm diameter, which are provided on the moulding core, bend or break. As a solution to this problem, there is a conceivable measure wherein the moving speed of the movable member is reduced. This corrective measure, however, merely led to an extended time for moulding a ferrule and was not entirely satisfactory for protecting the moulding pins from breakage or other similar problem.

According to the present invention, there is provided a plastic moulding apparatus for producing plastic moulded parts comprising movable and fixed moulding dies facing each other, a movable member having a moulding core projected therefrom to be located between the moulding dies, said movable member being movable in a direction different from that in which the moulding dies close, actuating means for moving the movable member, and guiding means for guiding the movable member to a position between the moulding dies before the moulding dies are closed, and positioning the movable member at one of the moulding dies before the moulding core is interposed between the moulding dies.

When the movable member is moved to position the moulding die in one of the moulding dies, the guiding means guides the moulding core so that it does not interfere with the moulding dies. Thus, the moulding core is positioned with high accuracy between the two moulding dies without interfering with the moulding dies, thereby avoiding damage or the like to the moulding core.

Preferably, the plastic moulded part is a ferrule for an optical connector.

Further preferably, each of the movable mould and the fixed mould has three components for the moulding dies to form a concavity for the plastic moulded part.

Further preferably, the movable member is disposed so that it is free to move in a specified direction along a guide groove formed in the movable mould.

Preferably, the actuating means is a cylinder which employs liquid pressure or air pressure.

Further preferably, the guiding means is spring plungers which force the movable member in a direction intersecting right angles with the moving direction in cooperation with the movable member.

A preferred embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings, in which: FIG. 1 is a front view which shows a cross section of a preferred plastic moulding apparatus according to the present invention; FIG. 2 is a perspective view which shows an enlarged view of a major section of a layout relationship between a movable mould and a slide core; FIG. 3 is a front view which shows a cross section of a state wherein the slide core has been moved by an actuator to position the moulding core in a moulding die; FIG. 4 is a cross-sectional front view which shows a state wherein the movable mould has been raised and closed from the state shown in FIG. 3; FIG. 5 is a perspective view which shows components of a moulding die composing the movable mould; FIG. 6 is a perspective view which shows components of a moulding die composing a fixed mould; FIG. 7 is a cross-sectional view of the two moulding dies with the movable half closed in relation to the fixed half; FIG. 8 is a perspective view which illustrates an example of a plastic moulded part produced by using a pair of moulding dies and which shows a ferrule as the plastic moulded part, an optical fiber to be mounted on the ferrule, and guide pins; and FIG. 9 is a perspective view which shows two types of cores used for moulding the ferrule shown in FIG. 8.

A known ferrule 1 for a multi fiber connector shown in FIG. 8 is known.

The ferrule 1 has, at the center thereof, a plurality of fiber holes 2 into which optical fibers are inserted and guide holes 4 into which guide pins 3 are fitted and which are formed lengthwise in parallel on both sides of the fiber holes 2, and a front part thereof constituting a butting surface 5 to be butted against another ferrule 1 of a multi fiber connector.

Into the plurality of fiber holes 2 of the ferrule 1 are inserted the ends of a plurality of optical fibers 6 which are arranged straight and aligned in parallel, all the optical fibers 6 are fixed to the ferrule 1 with adhesive, then the ends are ground to be flush with the butting surface 5.

In this case, when the ferrule 1 is buttconnected to another ferrule 1 having the same configuration, the guide pins 3 are fitted into the guide holes 4 in a manner that they extend to corresponding guide holes 4, thereby precisely aligning the optical axes of mating optical fibers 6 of ferrules 1.

The ferrule 1 is formed, for example, by transfer moulding using plastic as set forth below.

First, a core 7 and core pins 8 shown in FIG. 9, are set in predetermined positions in a pair of moulding dies, both moulding dies are clamped, then a plastic material such as epoxy resin is injected in a cavity, which is formed by the two moulding dies, the core 7, and the core pins 8. The plastic material is heated and cured to mould the ferrule 1.

The core 7 is provided with a plurality of fine moulding pins 7a which have an approximately 125 pm diameter to form the plurality of fiber holes 2 in the ferrule 1, and the core pins 8 are used to form guide holes 4 in the ferrule 1 into which the guide pins 3 are fitted.

The ferrule 1 thus formed is taken out of the cavity, and the moulding core 7 and the core pins 8,8 are removed. Hence, the ferrule 1 is configured as shown in FIG. 8.

The following presents a detailed description of a preferred embodiment of the plastic moulding apparatus (hereinafter referred to as "moulding apparatus"), which is designed to mould ferrules for multi fiber connectors, with reference to FIG. 1 through FIG. 7.

As shown in FIG. 1, a moulding apparatus 10 is provided with a movable mould 20, a fixed mould 30, slide cores 40, actuators 50, for moving the individual slide cores 40, and a plurality of spring plungers 60.

The state shown illustrates the initial position of each constituent member before moulding is started.

The mould 20 has a die plate 21, backing 22, and a moulding die 23 which is mounted on the backing 22.

The die plate 21 has a guide groove 21a formed lengthwise at the center of the width to guide the movement of the slide cores 40, and concave grooves 21b, are provided on both sides of the guide groove 21a (see FIG. 2). The movable mould 20 is moved up and down together with the actuators 50, by a driving means not shown.

As shown in FIG. 1, the backing 22 is disposed at the center of the guide groove 21a and mounted as one piece with the moulding die 23 on the die plate 21.

The moulding die 23 has components 25 through 27 on square columns as shown in FIG. 5. By disposing these components 25 through 27 on both sides of the slide cores 40 concavities 23a are formed. A runner 23b (see FIG. 2) for injecting synthetic resin is provided pointing toward the concavities 23a. A core 41 and core pins 42 to be discussed later are disposed in the concavities 23a to form a cavity for moulding a ferrule.

At the center of a top surface of the component 25 is formed a concave groove 25a for holding the core 41.

On both sides of the concave groove 25a, are formed Vshaped grooves 25b, which position the proximal ends of the core pins 42 located on the side of fixing members 43.

The component 26 has a stepped part 26a on the side of the component 25 and it forms, in cooperation with a component 36 of a moulding die 34 to be discussed later, the contour of the ferrule.

The component 27 has a plurality of fine V-shaped grooves 27b for positioning a plurality of moulding pins 41a at the center of a top surface thereof, i.e., a clamping surface 27a. There is also provided V-shaped grooves 27c for positioning the distal ends of the core pins 42 on both sides of the plurality of V-shaped grooves 27b.

Suitable materials that can be employed for moulding the ferrule include synthetic resins, for example epoxy resin.

The mould 30 has a mounting plate 31, a die plate 32, a backing 33, and a moulding die 34 which is attached to the backing 33, facing against the moulding die 23. As in the case of the die plate 21, the die plate 32 has the backing 33 and the moulding die 34 at the center of a groove 32a, which is formed lengthwise at the center of the width.

The moulding die 34 has components 35 through 37 on square columns as shown in FIG. 6. These components 35 through 37 are disposed in positions so that concavities 23a correspond with concavities 34a. A runner (not shown) for injecting synthetic resin is provided in a position which corresponds to the runner 23b.

At the center of a top surface of the component 35 is formed a concave groove 35a for holding the core 41.

On both sides of the concave groove 35a are formed trapezoidal grooves 35b, which position the proximal ends of the core pins 42 on the side of the fixing members 43.

The component 36 has a stepped part 36a formed on the side of the component 35.

In the component 37, trapezoidal grooves 37b, for positioning the distal ends of the core pins 42, are formed in positions that correspond to those of the Vshaped grooves 27c of the component 27 on both sides of a clamping surface 37a.

In the component 27, the V-shaped grooves 27b are formed so that when the moulding dies 23, 34 are closed, the centers of the moulding pins 41a, which are positioned by the fine V-shaped grooves 27b, are aligned horizontally in a position which is slightly lower than the clamping surface 27a and the tops of the moulding pins 41a protrude above the clamping surface 27a by a maximum of d/2 (d/2 2 L > O) as shown in FIG. 7, where "L" denotes a distance between the clamping surfaces 27a, 37a, and "d" denotes a diameter of the moulding pin 41a.

When the V-shaped grooves 27b are formed in this manner, a gap having the distance L ( < d/2) is produced between the clamping surfaces 27a, 37a which extend between the V-shaped grooves 27c and between the trapezoidal grooves 37b when the two moulding dies 23, 34 are closed.

Preferably, in the components 27, 37, a distance L0 between the clamping surfaces 27a, 37a on the outside of the width of the corresponding V-shaped grooves 27c and the trapezoidal grooves 37b is set to O < L0 < L.

The slide cores 40 are movable members which are disposed so that they are free to move toward or away from the moulding dies 23, 34. As shown in FIG. 2, the slide cores 40 have flange-shaped engaging sections formed on both sides 40a, which engage with the concave grooves 21b formed on both sides of the guide groove 21a. Further, semispherical concavities 40b are provided at the bottom of the slide cores 40. In a state wherein the dies are opened as shown in FIG. 1 and FIG. 2, the slide cores 40 are pushed up by the spring plungers 60, the engaging sections 40a being engaged with the tops of the concave grooves 21b formed in the guide groove 21a, thereby being restricted in height.

Further, as shown in FIG. 2, the core 41 and the core pins 42 are mounted on the front surface of the slide core 40 on the side of the moulding die 23 by the fixing members 43 so that they extend toward the moulding die 23. The end surface of the core 41 is provided with a plurality of moulding pins 41a for forming a plurality of fiber holes. In this case, the moulding pins 41a of the core 41 and the core pins 42 are positioned higher than the concavity 23a of the moulding die 23 in the state shown in FIG. 1 wherein the slide cores 40 have been pushed up by the spring plungers 60.

The actuators 50 are cylinders such as hydraulic cylinders and pneumatic cylinders which move the slide cores 40 toward and away from the moulding dies 23, 34.

The distal end of a shaft 50b, which extends from a main body 50a, is linked to the back surface of the slide core 40 in such a manner that the slide core 40 is allowed to move up and down slightly for a distance restricted by the semispherical concavity 40b.

The spring plungers 60 are guiding means for guiding the slide cores 40 in a direction which intersects at right angles with the moving direction.

they are installed to the die plate 21 in a manner that the distal ends thereof jut into the guide groove 2la.

When the slide cores 40 are moved toward the moulding die 23, the plungers 60 guide the slide cores 40 into a direction which intersect at right angles with the moving direction, thereby to position the core 41 and the core pins 42 between the corresponding concavities 23a, 34a without causing them to interfere with the moulding dies 23, 34.

In this case, the profile of the spring plungers 60 is preferably set so that the extension of the tips thereof into the guide groove 21a does not exceed the depth of the semispherical concavities 40b of the slide cores 40.

The preferred moulding apparatus 10 according to the present invention is configured as described above and it is preferably used as set forth below when plastic-moulding the ferrule for a multi fiber connector.

First, the actuators 50 are operated to draw out the shafts 50b from the main bodies 50a.

The slide cores 40 then move toward the moulding die 23 while being guided along the guide groove 21a of the die plate 21. At this time, the slide cores 40 are forced upward by the spring plungers 60 and the engaging sections 40a formed on both sides of the cores 40 move while being engaged with the concave grooves 21b. Thus, the moulding pins 41a and the core pins 42 move toward the moulding die 23 while being positioned higher than the concavities 23a of the moulding die 23, thereby preventing the moulding pins 41a and the core pins 42 from interfering with the moulding die 23.

When the shafts 50b complete their extending, the front surfaces of the slide cores 40 are in contact with respective side surfaces of the backing 22 and the moulding die 23, and the semispherical concavities 40b engage with the distal ends of the spring plungers 60 guiding them as they move down slightly as shown in FIG.

3. Ideally these surfaces are hemispherical although other surface profiles may be used.

This causes the moulding pins 41a and the core pins 42 to be disposed in the concavities 23a of the moulding die 23, with the moulding pins 41a fitting in the fine V-shaped grooves 27b in the component 27, and the core pins 42 fitting in the V-shaped grooves 25b,27c of the components 25,27 as illustrated to be properly and precisely positioned.

After that, the mould 20 is actuated, the die plate 21 is moved up by a driving means, which is not shown, and the moulding die 23 is overlapped with the mating moulding die 34 as shown in FIG. 4, with the slide cores 40 disposed between the die plate 21 and the die plate 32.

This causes the core 41 and the core pins 42 to be properly disposed between the corresponding concavities 23a,34a of the moulding dies 23,34 and clamped in the moulding apparatus 10, thus forming the cavities for the multi fiber connector between the moulding dies 23,34, the core 41 and the core pins 42.

Then, the synthetic resin is injected from the runner 23b or the like of the moulding dies 23, 34 into the cavities to mould a ferrule of a specified shape.

After moulding the ferrule, the mould 20 is moved down by reversing the operation described above and the mould is opened. Then the slide cores 40 are reset by the actuators 50 to the state before the moulding was started. The moulded ferrule is taken out.

As described above, the preferred moulding apparatus 10 according to the present invention is provided with the spring plungers 60, which guide the slide cores 40 in a direction intersecting at right angles with the moving direction; therefore, the moulding pins 41a and the core pins 42 move toward the moulding die 23 while being positioned higher than the concavities 23a of the moulding die 23 and they are properly disposed between the corresponding concavities 23a,34a of the moulding dies 23,34.

Hence, the moulding pins 41a and the core pins 42 are precisely positioned, making it possible to mould the ferrule with high accuracy.

Thus, it can be seen that at least in the illustrated embodiment there is provided a plastic moulding apparatus which is capable of guiding a movable member so that a moulding core does not interfere with moulding dies and of positioning the moulding core with high accuracy, thereby controlling damage or other similar problem; furthermore there is provided a plastic moulding apparatus which is capable of producing highaccuracy plastic moulded parts at low cost with a high yield.

Claims

CLAIMS:

1. A plastic moulding apparatus for producing plastic moulded parts, comprising: movable and fixed moulding dies facing each other; a movable member having a moulding core projected therefrom to be located between the moulding dies, said movable member being movable in a direction different from that in which the moulding dies close; and guiding means for guiding the movable member to a position between the moulding dies before the moulding dies are closed and positioning the movable member at one of the moulding dies before the moulding core is interposed between the moulding dies.

2. The plastic moulding apparatus as claimed in claim 1, wherein said plastic moulded part is a ferrule for an optical connector.

3. The plastic moulding apparatus as claimed in either claim 1 or 2, wherein said movable moulding die has three components to form one concavity for said plastic moulded part.

4. The plastic moulding apparatus as claimed in any one of claims 1 to 3, wherein said fixed moulding die has three components to form the other concavity for said plastic moulded part.

5. The plastic moulding apparatus as claimed in any one of claims 1 to 4, wherein said movable member is disposed so that it is free to move only in a predetermined direction along a guide groove.

6. The plastic moulding apparatus as claimed in any one of claims 1 to 5, wherein said actuating means is a cylinder which employs liquid pressure or air pressure.

7. The plastic moulding apparatus as claimed in any one of claims 1 to 6, wherein said guiding means includes spring plungers which force said movable member in a direction which intersects at right angles with the moving direction in cooperation with said movable member.

8. A plastic moulding apparatus having a movable member supporting a core to be inserted between opposing moulding dies, the movable member being steered into a retaining position for moulding by guide means engaging a receiving surface.

9. A plastic moulding apparatus as claimed in claim 8 wherein the guide means and receiving surface have complementary surfaces.

10. A plastic moulding apparatus as claimed in claim 9 wherein the complementary surfaces are hemispherical.

11. A plastic moulding apparatus for producing plastic moulded parts substantially as hereinbefore described with reference to the accompanying Figures 1 to 7.