JPS5914333B2 - Open core installed in mold for injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a divided tube that is movable in the axial direction of the core rod around a stationary core rod, and arranges the divided portions of the divided tube parallel to the axis in 25 positions by injection molding. The present invention relates to an improvement in an opening core for attachment to a mold for injection molding, which is movable radially inward from a mold to an open position.

The open core has internal threads, protrusions, inward depressions, recesses, hollow parts, through holes, etc., and is used when injection molding synthetic resin products, etc., which may have undercuts in some cases. Used by attaching it to a mold.

The outer surface of this split tube forms the mold for the inner wall of the injection molded article in the injection molding condition. If this inner wall is provided with an undercut, the dividing tube must be made to have a small outer diameter in the mold opening 35 condition, thereby making mold opening possible. Open cores of the type described above require that the segments be able to be biased inwardly during axial-radial movement of the segment along the core rod.

This is only partially achieved with known open cores. The purpose of this invention is to widen the scope of use of open cores. The basic problem of this invention is that although it is easy to construct, it is possible to fully automatically finish not only injection molded products with a circular planar shape, but also injection molded products with a rectangular planar shape and injection molded products with complicated undercuts. The purpose is to provide an open core like this. To achieve this object, the invention provides an equal number of first lateral slides extending axially and arranged every other circumferentially around a stationary core bar with a conical outer surface. a member and a second side sliding member, the first side sliding member and the second side sliding member having different conical inclinations, and the first side sliding member and the second side sliding member guideable along the core rod so that these side slides can be moved radially inwardly from an injection molded configuration to an open mold configuration;
In the open core installed in the mold for injection molding,
a first lateral sliding member has a substantially arcuate cross-section; a second lateral sliding member has a substantially trapezoidal cross-section with an outer base that matches the curvature of the arcuate shape; the trapezoidal side of the side sliding member contacts the arcuate chord of the adjacent first side sliding member, the first side sliding member and the second side sliding member are in dovetail engagement with the core rod, and An open core is provided, characterized in that the conical slope of the first side sliding member is smaller than the conical slope of the second side sliding member.

The invention further provides an equal number of first and second side sliding members extending axially and disposed every other circumferentially around the stationary core bar with a conical outer surface. a partial sliding member is provided, the first side sliding member and the second side sliding member have different degrees of conical inclination, and the first side sliding member and the second side sliding member are arranged along the core rod. In an open core mounted on a mold for injection molding, the core rods can be guided to move these side slides radially inwardly from an injection molding configuration to an open mold configuration. comprising every other continuously converging outer surface portion and a stepwise converging outer surface portion, the first side sliding member having an inner surface parallel to the axis and interrupted by a shoulder and having a sector-shaped shape; a first side slide member having a cross-section, the first side slide member being held in contact with the graduated convergent outer surface portion by a resilient retaining member disposed about the same; a member having a continuously conical inner surface and a substantially rectangular cross-section and dovetailed engagement with the core rod at said continuously converging outer surface portion; and further comprising: a first lateral sliding member; An open core is provided, characterized in that said sector-shaped periphery of runs parallel to said rectangular sides of the second side sliding member.

A small number of side sliding members are required and utilized in this invention.

This reduces the area required for the guiding device and thus allows injection molded parts with small diameters to be produced. Other than the core rod and the side slides, no attachments to the opening core are necessary, especially no protruding head for forming the tip of the opening core. According to the invention, the side slides gather radially during their axial movement, so that they can be opened even if the injection molded part has a long undercut. Furthermore, the mold can be opened even when there is an undercut of an injection molded product having a square or circular planar shape, or a sharp undercut or a side undercut. Due to its construction, the open core is formed in one solid piece, which prevents curling of the injection molded part and allows the highest degree of accuracy to be achieved. Since the lateral sliding members immediately gather together when the mold is opened, no wear occurs even when the opening core is used for a long time. With a suitable selection of materials, this open core can be used for thermoplastic plastic processing, for duroplastic processing, for metal pressure casting, in clamping tools, and in cutting and punching tools. It can also be. The open core according to the invention consists of simple components, so that no large tools are required for its formation. This open core has no upper diameter limit. This open core is less expensive than known open cores. It can be installed on all types of injection molding machines as it does not require any additional couplings. Embodiments of the invention will be described in detail below with reference to the drawings.

The open core according to the invention has a core rod 1.

Two groups of side sliding members 2, 3 are arranged around the core rod. The side sliding members belonging to each group are equally constructed. Each of the first side slides 2 is alternately arranged with a second side slide 3 around the core rod 1. core rod 1
can include an attached central core 4 (FIGS. 3 and 4).
One or more open cores are a component of a mold 7 (shown particularly in FIG. 5c).

Briefly, the molding mold 7 consists of a fixed mold 6 and a movable mold 5 that are movable relative to each other, as shown in FIG. 5c, and an injection molded product 8 is formed between them.

The fixed mold 6 includes, for example, a mounting plate 61 and a hollow plate 62 attached thereto, and the mounting plate 61 is provided with a nozzle 9. The movable mold 5 has a base plate 5 to which the core rod 1 is screwed.
1 and 2 sliding member guide plates 52, 53 and removal plate 54
have. The two configurations of the mold 7 described above are well known. The end of the core rod 1 is formed as a connecting part 11 for connection with a base plate 51 of the movable mold 5. Connecting part 11
A screw 12 is provided at the free end of. At the outer end of the connecting part 11 a central cooling aperture 13 opens, which extends over the entire core rod 1 to the region of the opposite end of the core rod 1 . In the embodiment shown in FIGS. 1a to 5e, the core rod 1
comprises a conical outer surface portion 14, 15 which connects to the connecting portion 11.

The conical inclination of the conical outer surface portion 15 defined by the angle β is greater than the conical inclination of the conical outer surface portion 14 defined by the angle α, which in this example is approximately 2
It's double. a first lateral sliding member 2 sliding along a conical outer surface portion 14 and a second lateral sliding member 3 sliding along a conical outer surface portion 15; first and second lateral sliding members 2; 3, the conical outer surface portions 14, 15 are provided with dovetail grooves 16,
17. The conical outer surface parts 14, 15 and the dovetail grooves 16, 17 start at the connecting part 11 and end at the connecting part 1.
1 ends at the end of the core rod 1 opposite to 1. The first lateral sliding member 2, which slides along the conical outer surface portion 14 of the core rod 1 and is guided in a dovetail groove 16, has a substantially arcuate cross-section.

Each arcuate string 21 is interrupted by a dovetail projection 22 that engages in a dovetail groove 16. The dovetail groove 16 and the dovetail projection 22 constitute a dovetail engagement, which can also be achieved by forming a dovetail groove on the first side sliding member 2 and providing a dovetail projection on the outer surface portion 14. It can be achieved. Each first side slide 2 has at its free end a shoulder 24, the outer surface 25 of which fits into the inner surface of the injection molded part 8 (FIG. 5c). In this embodiment the outer surface 25 is provided with parallel grooves. Remotely from the shoulder 24, each first lateral slide 2 has an annular band 26, by means of which the axial orientation of the first lateral slide 2 in the movable mold 5 of the mold 7 is Movement is achieved. The second lateral sliding member 3, which slides along the conical outer surface portion 15 of the core rod 1 and is guided in the dovetail groove 17, has a substantially trapezoidal cross section;
This trapezoid has an outer base 31 curved to match the arcuate curvature of each first side slide member 2.

The further base 32 is interrupted by a dovetail projection 33 which forms a dovetail engagement with the dovetail groove 17, by means of which the second lateral slide member 13 is guided in the dovetail groove 17. Each trapezoid touches the chord 21 of the adjacent first side sliding member 2 at its side 37. The second lateral slide 3 furthermore has a shoulder 34 at its free end, the outer surface 35 of which adapts to the inner surface of the injection molded part 8 (FIG. 5c) to be produced. Remotely from the outer surface 35 each second lateral slide member 3 has an annular strip 36 . Band-shaped part 2
6 and 36 form a complete annular band. An axial movement of the second lateral slide 3 within the stationary mold 5 (FIG. 5c) of the mold 7 is achieved by means of the annular band. In the embodiment shown in FIGS. 3 and 4, the core rod 1 is formed as a hollow body with an open outer end. The hollow body is filled with a central core 4 which is inserted from the open outer end side. Head 41 of central core 4
serves as a molding core and is formed to correspond to the shape of the injection molded article 8 to be manufactured. If the core rod 1 has a central core 4, it is preferred that the cooling apertures 42 run axially through the central core 4. With this configuration, an injection molded part can be produced which has an extension, for example a cylindrical extension, with an axial hole behind the undercut. In the embodiment shown in FIGS. 6a to 8c, the core rod 1 has three outer surface sections 14 which are continuous with the connecting part 11 and which are stepped and taper towards the free end of the core rod.

The outer surface portion 14 is angularly displaced from the core rod 1 by equal angles.
is installed on top of the Each outer surface section 14 has a bevel 18 in the area of the free end of the core rod 1. Each outer surface portion 14 extends over substantially the entire length 1 of the core rod 1 (excluding the length of the connecting portion 11). The distance between the two outer surface portions 14 is the outer diameter which converges continuously to the free end of the core rod 1. A tray 15 is provided.

Each outer surface portion 15 has a dovetail groove 17 running toward the central center. Each of the outer surface portions 15 starts from the free end of the core rod and extends axially over substantially half of the core rod 1. Between the inner end of the outer surface part 15 and the place where the connection location 11 begins, the core rod is formed in a round shape without any special features.
The first lateral slide 2, which slides along the outer surface part 14 of the core rod 1 with the ramp 18, has an inner surface 28 parallel to the axis, which is interrupted by a shoulder 29. Member 2 is
At least two elastic retaining elements, for example helical springs 23, which are stretched around this first lateral slide 2 in the end region, contact the outer surface part 14 of the core rod 1 with an inner surface 28 parallel to the axis. be held as such.

One of the helical springs 23 is arranged in the annular strip 26. As the helical spring 23, a two-turn helical spring is suitable. Each first side sliding member 2 has a substantially fan-shaped cross section. The second lateral sliding member 3, which slides along the conical outer surface portion 15 of the core rod 1 and is guided in a dovetail groove 17, has a conical inner surface 38.

Each second lateral sliding member 3 with a conical inner surface 38 has a substantially rectangular cross section. Side wall 39 of second side sliding member 3
runs parallel to the side wall 27 of the first lateral sliding member 2 with a sector-shaped cross section (so that the sides of said sector are parallel to the sides of said rectangle) and away from it. Each second side sliding member 3 is guided in the dovetail groove 17 of the outer surface part 15 by means of a dovetail projection 33 which together with the dovetail groove 17 constitutes a dovetail engagement. Each of the outer surface portions 14 parallel to the axis of the core rod 1 is
A ramp 18 is provided at a distance from the free end of the core rod a distance equal to the length of the molding core.

Each of the side slides 2 has a shoulder 29 in the form of a ramp at a distance of one and three times the length of the molding core.
A total of three first lateral sliding members 2 and three second lateral sliding members 3 are provided in this embodiment. Therefore core rod 1
has a substantially regular hexagonal shape in plan view at its free end, in which the three sides separated by successive sides are provided with a groove 17 in the middle. In the injection molding state, the shoulder 24
, 34 (in some cases the head 4 of the central core 4)
1) forms a molding core for the production of the inner wall of the injection molded part 8.

The method of operation of the open core shown in Figures 1a to 5e will now be described.

During the injection molding operation, the mold 7 is closed, that is, the movable mold 5 (and the open core attached to it) and the fixed mold 6 are closed together, as shown in FIG. 5c, and the space between them is closed. A molding material is injected into the cavity through a nozzle 9 to form an injection molded product 8. After the mold 7 is opened after the injection molding operation is completed, that is, after the movable mold 5 and the fixed mold 6 are separated, the sliding member guide plates 52, 53 are first moved as shown in FIG. 5d. Together with the removing plate 54, it is moved axially by a distance S relative to the substrate 51. The sliding member guide plates 52, 53 are screwed together and can pass through a stroke S. Since the core rod 1 is rigidly connected to the base plate 51, the first and second lateral slides 2, 3, which are entrained via the strips 26, 36, move by a distance S. The angle α (FIGS. 1b and 2b) defining the conical inclination of the outer surface portion 14 of the core rod 1 and the first lateral slide member 2 is
is approximately half the size of the angle β defining the conical inclination of the second lateral sliding member 3, so that the second lateral sliding member 3 not only slides in the axial direction by a distance S, but also It slides inwardly along the chord 21 of the adjacent first side sliding member 2. This is the first line along the conical outer surface portion 14 of the core rod 1.
Allowing movement of the side sliding members 2. Since the relation β-2α exists, at the end of the axial movement the inner edge of the free end of the second lateral sliding member 3 is twice as wide as the inner edge of the free end of the first lateral sliding member 2 relative to its starting position. It is moved radially inward by a distance of magnitude. In the state of FIG. 5c, the distance S1 (FIG. 2b) of the inner edge of the second side sliding member 3 from the same center line is also smaller than the distance S2 of the inner edge of the first side sliding member 2 from the center line. . After the course of the stroke S, the injection molded part 8 frees itself inwardly from the first and second side sliding members 2, 3 as a result of successive superimposed parallel axial and radial movements; At this time, the maximum outer diameter of these side sliding members 2, 3 is smaller than the minimum inner diameter of the injection molded product 8. The viewing plate 54 can therefore be moved away from the sliding member guide plates 52, 53, as shown in FIG. 5e. During the return movement of the components of the movable mold 5 of the mold 7 to their starting position, the first and second lateral slides 2, 3 slide back along the core rod 1 back to their starting position. . A new injection molding operation can then be started. In this case, it is preferable that the mold be a multiple molding mold and equipped with many open cores. In the open core shown in FIGS. 6a to 8c, the side sliding members 2, 3 have sliding member guide plates (
5c), the first lateral sliding member 2 is moved parallel to the axis of the core rod 1 on the outer surface part 14;
On the contrary, the second lateral sliding member 3 has a conical outer surface portion 15.
move axially over the top and radially inward.

This movement is caused by forming core (shoulder) 24 as shown in Figure 7b.
, 34 until the inner limits of the core rod 1 are substantially flat against the outer end surface of the core rod 1. In this position, the movement of the second lateral slide 3 inwardly has been achieved to such an extent that the injection molded part that was in contact with this second lateral slide 3 has already been released. No further axial movement of the second lateral sliding member 3 is carried out. However, the first lateral sliding member 2 moves further in the axial direction. This axial movement proceeds until the shoulder 29 of the first lateral sliding member 2 adjacent to the strip 26 is located at the level of the bevel 18 of the outer surface part 14 of the core rod 1. Once this position is reached, the helical spring 23 pushes the first side sliding member 2 radially inward. The injection molded article is then completely released from the molding core in the position of FIG. 8b. This can be pushed out of the opening core by means of a removal plate 54 (see Figure 5e). A group of first lateral sliding elements 2, unless the second lateral sliding element 3 occupies its inner position (which second lateral sliding element reaches this position by means of a conical outer surface part 15). and the second lateral sliding members 3 abut each other at their limit surfaces in the area of the shoulders 24 and 34, so that the first lateral sliding members 2 are not pressed inwardly. Only after the second lateral sliding member 3 has reached the above-mentioned inward position can a further axial and radial inward movement of the first lateral member 2 be achieved. In this way, mold opening can be achieved when the undercut is up to 25% of the inner diameter of the injection molded part. In the mold opening condition, both groups of first and second side sliding members should not assume the same axial position relative to the core rod. Rather, a first lateral slide 2 with an interrupted inner surface can be moved axially over a second lateral slide 3 with a conical inner surface. On this basis and in order to achieve a large degree of conical inclination of the second lateral sliding member with a conical inner surface, the first lateral sliding member with an interrupted inner surface is replaced by the first lateral sliding member with a conical inner surface. It is desirable that the two side slide members be longer than each other (in effect, the first side slide member should span the entire length of the core bar and the second side slide member should span half the length of the core bar).

[Brief explanation of the drawing]

FIG. 1a is an end view of the open core in the injection state as seen in the y direction of FIG. 1b, FIG. 1b is a cross-sectional view through the axis along line w-w in FIG. 1a, FIGS. 2a and 2b The figures correspond to Figures 1a and 1b showing the open core in the mold open state, Figure 3 is a sectional view taken through the axis of the open core with the central core attached in the injection state, and Figure 4 is the mold open state. Figure 5a is a plan view of the open core in the injection molded state attached to the mold, viewed in the y direction of Figure 5b;
The figure is a cross-sectional view passing through the axis line along line w-w in figure 5a,
Figures 5c, 5d and 5e are views sequentially showing the positions of the components of the mold with the opening core attached in the mold opening stage, and Figure 6a is the opening in the injection state as seen in the y direction of Figure 6b. End view of the core, Figure 6b is similar to Figures 6a and 6.
Fig. 6c is a cross-sectional view taken along the axis line w-w in Fig. 6b; Fig. 6c is a transverse sectional view taken along the
Figures b and 7c show the opening cores of figures 6a, 6b and 6c in an intermediate position during mold opening;
Figures corresponding to Figure a, Figure 6b and Figure 6c, respectively;
Figures 8a, 8b, and 8c correspond to Figures 6a, 6b, and 6c, respectively, showing the open state of Figures 6a, 6b, and 6c in the mold open state. be. In the drawing, 1 is a core rod, 2 and 3 are first and second side sliding members, 4 is a central core, 13 is a cooling hole, 14 and 1
5 is an outer surface portion of the core rod, 16 and 17 are dovetail grooves, 18 is a slope, 21 is an arcuate string, 23 is an elastic holding member, and 27 is a first
side wall of the sliding member, 28 is an inner surface of the first side sliding member, 29
is the shoulder, 31 is the outer base of the trapezoid, 37 is the side of the trapezoid, 38
39 is the inner surface of the second side sliding member, 39 is the side wall of the second sliding member, and 42 is the cooling aperture.

Claims (1)

Claims: 1. An equal number of first side sliding members and second side sliding members extending axially and arranged every other circumferentially around a stationary core bar with a conical outer surface. A sliding member is provided, and the first
The conical inclinations of the side sliding member and the second side sliding member are different, so that the first side sliding member and the second side sliding member can be guided along the core rod. In an opening core for attachment to an injection mold, the first side slide member is substantially arcuate in shape, the first side slide member being substantially arcuate in shape, the first side slide member being movable radially inwardly from an injection molding configuration to an open mold configuration. , the second lateral sliding member has a substantially trapezoidal cross-section with an outer base that conforms to the curvature of the arcuate shape, and the trapezoidal sides of the second lateral sliding member are abutting the arcuate chord of an adjacent first side sliding member, the first side sliding member and the second side sliding member are in dovetail engagement with the core bar, and the conical slope of the first side sliding member; An open core characterized in that the conical slope is less than the conical slope of the second side sliding member. 2. An equal number of first and second side sliding members extending axially and arranged every other circumferentially around a stationary core bar with a conical outer surface; 1st
The conical inclinations of the side sliding member and the second side sliding member are different, so that the first side sliding member and the second side sliding member can be guided along the core rod. In an open core installed in a mold for injection molding, in which the slide member can be moved radially inward from an arrangement in an injection molding state to an arrangement in an open state, the outer surface of the core rod is continuous with every other core rod. a first lateral sliding member having an inner surface parallel to the axis and interrupted by a shoulder and having a sector-shaped cross section; A side sliding member is further held in contact with said progressively converging outer surface portion by a resilient retaining member disposed about the same, and the second side sliding member is continuously held in contact with said conical outer surface portion. having an inner surface and having a substantially rectangular cross-section and dovetailed engagement with the core bar at said continuously converging outer surface portion, and said sector-shaped side of said first side sliding member having a substantially rectangular cross-section; An open core, characterized in that it runs parallel to the rectangular sides of the two-sided sliding member.