JP4318394B2 - Injection mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection mold, and more specifically, a mold body provided with a molded product formation recess or projection for forming a molded product formation space on a joint surface at one end, and the mold body. The present invention relates to an injection mold having a larger area than a joining surface and comprising a mold mounting plate which is connected to the other end face of the mold body with a bolt.
[0002]
[Prior art]
Conventionally, a molded product is formed to form a molded product forming space on a joint surface at one end, which is attached to a fixed or movable mold plate that obtains a clamping force by a plurality of tie bars arranged on an outer peripheral portion. For injection molding comprising a mold body provided with a concave or convex portion and a mold mounting plate having an area larger than the joint surface of the mold body and coupled to the other end surface of the mold body with a bolt Various molds have been proposed.
[0003]
5 to 9 show a conventional injection molding machine using such an injection mold.
The injection molding machine shown in FIGS. 5 to 8 is fixed to a mold clamping device 10, a base 11 that supports the mold clamping device, and one end of the base 11, and has a substantially square shape when viewed from the front. The fixed plate 12, two rails 13 fixed on the base 11, and the fixed plate 12 are arranged to face the fixed plate 12, and slide on the rail 13 to move forward and backward with respect to the fixed plate 12. Further, the movable platen 14 having a substantially square shape when viewed from the front, four tie bars 15 having one end fixed to the four corners of the movable platen 14 by the nut 16 and having the threaded portion 15a at the other end, and the fixed platen 12 Two small-diameter large-stroke mold opening / closing cylinders 17 mounted between the movable platen 14, a large-diameter small-stroke mold clamping cylinder 18 incorporated in the four corners of the stationary platen 12, and a clamping cylinder 18. Ram (piston) 19. The ram 19 of the mold clamping cylinder 18 has a sleeve 19a that protrudes outside the fixed platen 12, and a hole through which the tie bar 15 can be inserted at the center.
[0004]
Further, in these drawings, reference numeral 20 denotes a half nut which can be opened in the radial direction and meshes with the screw portion 15a of the tie bar 15 when closed, and 21 denotes a support bar which slidably supports the half nut 20; 22 is a spring that constantly urges the half nut 20 in the direction of the mold clamping cylinder 18, 23 is an injection device installed in an injection port 12 a formed in the center of the stationary platen 12, and 30 is a fixed mold body 31. And a fixed mold 31a including a fixed mold mounting plate 32, a molded product forming recess 31a provided in the fixed mold main body 31, and a movable mold 33 including a movable mold main body 34 and a movable mold mounting plate 35. Reference numeral 34 a denotes a convex part for forming a molded product provided in the movable mold body 34.
[0005]
The fixed die main body 31 is attached to the attachment surface of the fixed platen 12 with a bolt or a clamper via a fixed die attachment plate 32. Similarly, the movable mold body 34 is attached to the attachment surface of the movable platen 14 with a bolt or a clamper via a movable mold attachment plate 35. The mounting surfaces of the fixed platen 12 and the movable platen 14 are formed on surfaces with high flatness. Although not shown, the fixing surfaces of the fixed platen 12 and the movable platen 14 are provided with T-grooves for attaching a female screw for a bolt for attaching a mold attaching plate and a clamper.
Further, the molded product forming recess 31a and the molded product forming convex portion 34a form a molded product forming space (cavity) 36 (see FIG. 7) when the fixed mold main body 31 and the movable mold main body 34 are joined. It is like that.
[0006]
Next, the operation of the mold clamping device 10 of the injection molding machine shown in FIGS.
First, using the mold opening / closing cylinder 17, the movable platen 14 is moved in the direction of the fixed platen 12 at a high speed to close the mold so that the movable mold body 34 and the fixed mold body 31 are brought into contact with each other. At this time, the tip of the tie bar 15 penetrates through the center hole of the ram 19 of the clamping cylinder 18 and the threaded portion 15a enters the opened half nut 20. Here, the half nut 20 is closed and meshed with the threaded portion 15a of the tie bar 15 to couple them together. Next, when the ram 19 of the mold clamping cylinder 18 is moved to the right in FIG. 5, the sleeve 19a pushes the half nut 20, and the half nut 20 pulls the tie bar 15 to the right in FIG. In response to this, the movable platen 14 is pushed in the direction of the fixed platen 12. Thereby, the fixed mold 30 and the movable mold 33 are strongly clamped.
[0007]
In this state, the molten resin is injected into the molded product forming space 36 from the injection port 12 a using the injection device 23. After the resin in the space 36 is cooled and solidified, the mold clamping device 10 is operated in the reverse manner to take out the molded product in the mold.
[0008]
FIG. 7 shows a state in which the mold clamping device 10 is clamped and an injection pressure is applied to the molded product forming space 36. As shown in the figure, the high-pressure resin pressure in the molded product forming space 36 acts in a direction to separate the fixed mold body 31 and the movable mold body 34.
Here, since the state of the force applied to the fixed platen 12 and the fixed mold 30 and the movable platen 14 and the movable mold 33 is substantially symmetrical, the description will be made by paying attention to the one fixed platen 12 and the fixed mold 30 side.
A pressing force (distributed load) p1 due to the movable mold body 34 and a pressing force (distributed load) p2 due to the injection resin are applied to the fixed mold 30 from the left side. A concentration force P1 (4P1 as a whole) is applied via the split nut 20, and both are in equilibrium. Here, the pressing force p1 is a distributed load that is large immediately after mold clamping, but is reduced by the injection of the resin, and the pressing force p2 is a distributed load applied to the projection surface in the mold clamping direction of the molded product forming space 36. .
[0009]
The fixed platen 12 and the fixed mold 30 are three-dimensionally bent as shown in an exaggerated manner in FIG. 8 by the bending moment generated by these pressing forces p1 and p2. As a result, the fixed platen 12 is deformed so that the four corners are fixed and the central part is concave in cross section, and the fixed mold mounting plate 32 in contact with the deformed fixed platen 12 receives a large force at the four corners and similarly the central part is cross-sectional Similarly, the fixed mold main body 31 is deformed into a concave shape in the center. For this reason, the pressing force p1 between the fixed mold 31 and the movable mold main body 34 is reduced at the points m and n at the center of the four sides of the fixed mold main body 31, and a gap is generated near the points m and n. As a result, there was a problem that a problem that burrs occurred in the molded product occurred.
[0010]
FIG. 9 shows another example of a conventional injection molding machine using the above-mentioned injection mold.
The injection molding machine includes a mold clamping device 40, a base 41 that supports the mold clamping device, a fixed plate 42 fixed to one end of the base 41, and the other end of the base 41 facing the fixed plate 42. The fixed end plate 43, the four tie bars 44 connecting the four corners of the fixed plate 42 and the end plate 43 by the mounting bracket 45, and the four corners are arranged between the fixed plate 42 and the end plate 43. A movable platen 46 which is pulled by 44 and slidably moves back and forth on the base 41, a mold clamping cylinder 47 fixed to the end plate 43, and a mold clamping cylinder 47 connected to the movable plate 46. It has a rod 47a, a fixed mold 48, a fixed mold main body 49 and a fixed mold mounting plate 50, a movable mold 51, a fixed mold main body 52 and a fixed mold mounting plate 53.
[0011]
Next, the operation of the mold clamping device 40 shown in FIG. Note that this apparatus differs from the one shown in FIG. 5 only in that the mold opening and closing operation and the mold clamping operation are performed by one mold clamping cylinder 47, and other operations are almost the same. Only the operation of will be described.
[0012]
First, the load state of the fixed platen 42 and the fixed die 48 and the movable platen 46 and the movable die 51 when the mold clamping device 40 is in the mold closed state will be described. Therefore, this load state will be described with reference to a part of FIG. 9 showing the mold open state. The pressing force from the movable mold body 52 is applied to the fixed platen 42 and the fixed mold 48 from the left side in FIG. p3 (distributed load) and pressing force p4 (uniformly distributed load) from the injection resin are applied, and in the same figure, a concentration force P2 (4P2 as a whole) from the tie bar 44 is applied from the right side, while the movable plate 46 and the movable plate 46 are movable. A pressing force p3 from the fixed mold main body 49 and a pressing force p4 from the injection resin are applied to the mold 51 from the right side in the figure, and the attachment portion of the rod 47a of the clamping cylinder 47 from the left side in the figure. Is applied, and the left and right pressing forces are balanced with each other.
[0013]
In the mold clamping device 40, the central portion of the movable plate 46 and the movable mold 51 is pressed by the rod 47a of the mold clamping cylinder 47, so that the pressing forces from the left and right sides are balanced as described above. In such a state, no gap is generated at the center of the mold. However, a problem of bending deformation similar to the case of the mold clamping device 10 shown in FIG. 5 occurs on the stationary platen 42 and the stationary mold 48 side. Therefore, also in the mold clamping device 40, a bending deformation having a concave cross section occurs in the central portion of the stationary platen 42 as in the case of the fixed platen 12 and the movable platen 14 of the mold clamping device 10 shown in FIG. Due to the bending deformation, the clamping force in the vicinity of the central point of the four sides of the mold is reduced, so that there is a problem that burrs are generated in the molded product and the problem of poor dimensional accuracy is caused.
[0014]
Under such circumstances, various methods for solving the problem of bending deformation caused by using a tie bar have been proposed. For example, in Japanese Patent Publication No. 6-41160 and Japanese Utility Model Laid-Open No. 7-352020, a fixing plate of a device having a configuration such as the above-described mold clamping device 40, a member to which a mold is attached but not connected to a tie bar, It has been proposed that the mold clamping device is constituted by three members: a member to be connected and a force transmission member having a small area for connecting the two. In Japanese Patent Laid-Open No. 7-88913, there is no limitation on the method of clamping the fixed plate and the movable plate. However, in order to increase the clamping force at the center of the mold, the mold mounting plate is formed as a molded product formation space (cavity). A mold that can be reduced to a size close to the projection plane is proposed.
[0015]
[Problems to be solved by the invention]
However, in practice, in order to solve the problems of the generation of burrs and the decrease in dimensional accuracy caused by the method of obtaining the mold clamping force using the tie bar as described above, JP-B-6-41160 and JP-A-7-352020 In the proposal, it is necessary to change the configuration of the mold clamping device, and in the proposal of Japanese Patent Laid-Open No. 7-88913, there is a problem that it is difficult to mount the mold with a small mold mounting plate to the fixed plate and the movable plate. Yes, it was not easy to implement.
[0016]
The present invention has been made in order to solve the above-described problems. A large bending deformation of the mold can be achieved only by changing the shape or the configuration of the mold without changing the configuration on the mold clamping device side. It is an object of the present invention to provide an injection mold that can prevent the occurrence of burrs and thereby easily prevent burrs from being generated in the molded product and the dimensional accuracy thereof from being lowered.
[0017]
[Means for Solving the Problems]
In the present invention, in order to achieve the above object, a mold body provided with a molded product formation recess or projection for forming a molded product formation space on the joint surface at one end, and the joint surface of the mold body A mold mounting plate having a larger area and connected to the other end face of the mold body by a bolt, and projecting the mold body in the mold clamping direction of the space for forming the molded product among the other end faces. In an injection mold that is brought into contact with the mold mounting plate only through a force transmission section as a portion corresponding to the surface, the force transmission section is replaced with a steel plate of an appropriate thickness. The mounting surface is attached only to a portion corresponding to the projection surface in the mold clamping direction of the molded product forming space .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an injection mold according to the present invention will be described in detail with reference to the drawings. The injection mold of the present invention can be used in the mold clamping devices 10 and 40 of the conventional injection molding machine shown in FIGS. Regarding the configuration of the fastening device, reference is made to the one shown in FIGS. In addition, the fixed mold or movable mold and the fixed platen or movable platen have almost the same structure, and therefore, these are hereinafter referred to as the mold and It will be described as a stencil.
[0019]
(First embodiment)
1 and 2 show a first embodiment of an injection mold according to the present invention, and particularly show a main part of a mold clamping device of an injection molding machine to which the mold is applied. . An injection mold (fixed mold or movable mold) 70 of this embodiment is a mold platen (fixed platen or movable platen) 60 in which tie bars (not shown) are arranged at four corners, as in the conventional example. And a tightening force is applied by the tie bar via the mold platen 60. The mold 70 includes an injection port provided in the case of a fixed mold, an ejection pin device for taking out a molded product provided in the case of a movable mold, etc., which are not shown in the figure. Yes.
[0020]
The mold 70 includes a mold body 71 having a substantially square shape when viewed from the front, and a mold mounting plate 72 to which the mold body is integrally attached. The mold main body 71 is disposed to face a counterpart mold main body (not shown) (see part of FIG. 5), and has a good flatness joining surface 71a that joins the counterpart mold main body during mold clamping. have. The joint surface 71a is provided with a concave part for forming a molded product (when the mold body is a fixed mold) or a convex part for forming the molded product (when the mold body is a movable mold). When the mold main body 71 is joined to the mating mold main body, the mold main body 71 has a molding product forming space (or a convex portion) and a molding product forming convexity (or a concave portion). Cavity) 75 is formed. In FIG. 1, the molded product forming concave portion is shown by a solid line, and the counterpart molded product forming convex portion is shown by a two-dot chain line.
[0021]
On the other end surface of the mold main body 71 opposite to the joint surface 71a, the peripheral edge portion is removed by an appropriate thickness c to form a step-like removal processed portion 71b. A force transmission portion 71 c that protrudes with respect to the removal processing portion 71 b is formed at the center of the other end surface of the main body 71. An end surface of the force transmission portion 71c is a mounting surface 71d of the mold mounting plate 72, and a plurality of female screws 71e are provided. As shown in FIG. 2, the mounting surface 71 d is formed in a shape (in the case of this embodiment, a quadrangle) that is substantially equal to or slightly smaller than the projection surface in the mold clamping direction of the molded product forming space 75.
[0022]
The mold mounting plate 72 includes a plurality of counterbored bolt holes 72a. The mold mounting plate 72 is fastened to the mold main body 71 through a plurality of bolt holes 72a by a plurality of hexagon socket head bolts 73 screwed into the female threads 71e of the mold main body 71. A plurality of mounting bolt holes 72b for mounting the mold are provided on the outer periphery of the mold mounting plate 72. The mold mounting plate 72 is attached to the mold platen 60 by a plurality of mounting bolts 74 passed through the mounting bolt holes 72b, or the mold platen 60 is attached to the mold platen 60 using a plurality of clampers 76 as shown by two-dot chain lines in the figure. Mounted. Thereby, the mold clamping force applied to the mold 70 is transmitted from the mold plate 60 to the mold main body 71 only through the mold mounting plate 72 and the mounting surface 71d of the force transmitting portion 71c.
[0023]
Next, the operation of the mold 70 having the above configuration will be described.
In the mold main body 71, a pressing force p6 from a counterpart mold main body (not shown) is applied to the joining surface 71a from the left side in FIG. 1, and the projection surface of the molded product forming space 75 is pressed by the injection resin. Pressure p7 is applied. Further, a pressing force p8 from the model number 60 is applied to the mold main body 71 from the right side in FIG. In this state, the left and right pressing forces are balanced. Here, the pressing force p8 applied from the right side in FIG. 1 is a distributed load having a magnitude different depending on the position, but its operating range is the mounting surface 71d of the mold body 71, that is, the molded product forming space 75. It is limited within the force transmitting portion 71c that forms a portion corresponding to the projection surface in the mold clamping direction. Therefore, even if the force on the outer peripheral side increases due to the bending deformation of the mold mounting plate 72, a large bending moment does not occur in the mold body 71 due to these pressing forces. The mold body 71 hardly undergoes bending deformation.
[0024]
In this embodiment, since the system including the mold platen 60 that receives the clamping force from the tie bar, the mold mounting plate 72, and the mold body 71 has an indefinite structure, the external force and deformation received by each part are Although it is complicated, it has been found that the bending deformation of the mold main body 71 can be sufficiently suppressed by finite element analysis. Since the gap formed between the removal processing surface 71b of the mold main body 71 and the mold mounting plate 72 is extremely small even at the outer peripheral portion where the change is large, the removal processing thickness c (the height of the force transmission portion 71c is high). Is equal to or more than 0.2 mm, and c = 0.2 to 0.5 mm is preferable in order to reduce the removal process.
[0025]
(Second Embodiment)
FIG. 3 shows a second embodiment of an injection mold according to the present invention. In FIG. 3, elements having the same functions and operations as the elements shown in FIG. 2 are denoted by the same reference numerals as those shown in FIG. 2 with “′”.
The mold 70 ′ of the present embodiment has substantially the same structure as that of the first embodiment. Therefore, only the difference from the first embodiment will be described. The shape seen from the front is a horizontally long rectangle (rectangle). The difference is that it is formed.
In the mold 70 ′, the lateral bending deformation easily occurs, but the vertical bending deformation hardly occurs. For this reason, in this embodiment, the removal processed surface 71b 'is provided only at both lateral ends of the mold 70'.
[0026]
(Third embodiment)
FIG. 4 shows a third embodiment of an injection mold according to the present invention.
Since the mold 80 of the present embodiment has substantially the same structure as that of the first embodiment, only differences from the first embodiment will be described.
The mold 80 includes a mold body 81, a joining surface 81a of the mold body, a back surface 81b thereof, a plurality of female screws 81c provided on the back surface 81b, and a force transmission portion 82. This is almost the same as the mold 70 shown in FIG. Other elements are denoted by the same reference numerals as those shown in FIG. 1, and the description thereof is omitted.
[0027]
The mold 80 of the present embodiment is different from the mold 70 of the first embodiment in that the force transmission portion 82 is formed using a polished steel plate having an appropriate thickness with an accurate thickness dimension. The force transmitting portion 82 includes a bolt hole 82a, and is clamped and clamped together with a mold mounting plate 72 by a hexagon socket head bolt 73 that is screwed into the female screw 81c of the mold body 81 through the bolt hole 82a. Is fixed.
The shape of the force transmitting portion 82 viewed from the front is the same as the mounting surface 71d of the mold main body 71 of FIG. 1, and the die main body 81 itself is processed by attaching the force transmitting portion 82 to the mold main body 81. Without this, a gap can be formed between the back surface 81b of the mold body 81 and the mold mounting plate 72 as in the case of the mold 70.
The operation of the mold 80 is the same as that of the mold 70 shown in FIG.
[0028]
The molds 70, 70 ', 80 in the above-described embodiment are formed in a quadrangle or rectangle such as a square or a rectangle when viewed from the front. However, the present invention is not limited to this, and a polygon, an ellipse, other It can be applied to any shape of mold.
In the third embodiment described above, the steel plate is attached to the mold main body 81 side and the force transmitting portion 82 is provided on the mold main body side. Of course, the force transmission portion 82 may be provided on the mold mounting plate 72 side.
[0029]
【The invention's effect】
As described above, according to the injection mold according to the present invention, a mold body provided with a molded product forming recess or projection for forming a molded product forming space on the joint surface at one end; The mold body has a larger area than the joining surface of the mold body, and is composed of a mold mounting plate coupled to the other end face of the mold body with a bolt, and the mold body is used for forming the molded product among the other end faces. It is abutted against the mold mounting plate only through a force transmission portion as a portion corresponding to the projection surface in the mold clamping direction of the space, and the force transmission portion is made of a steel plate of an appropriate thickness. Since it is formed by being attached only to the portion of the mounting surface of the mold mounting plate corresponding to the projection surface in the mold clamping direction of the molded product forming space , the following effects can be obtained.
(1) Since the mold clamping force is transmitted to the mold body only through the portion of the other end surface of the mold body corresponding to the projection surface in the mold clamping direction of the molded product forming space, Bending deformation is prevented as much as possible in the mold body. As a result, the tightening force is reduced at the center of the four sides of the joint surface of the mold so that a gap is not generated, and burrs and dimensional accuracy are not reduced.
(2) Since the conventional mold can be manufactured with slight changes and can be mounted on or removed from the mold plate in the same manner as the conventional mold, it is easy to implement. Therefore, the mold can be processed and improved after the occurrence of defects such as burrs.
(3) Since there is no need to change the mold clamping device side, no extra cost is required for implementation.
[Brief description of the drawings]
FIG. 1 is a side view showing a partial cross section of a first embodiment of an injection mold according to the present invention.
FIG. 2 is a cross-sectional view taken along line BB in FIG.
FIG. 3 is a view showing a second embodiment of an injection mold according to the present invention corresponding to FIG.
FIG. 4 is a side view showing a third embodiment of an injection mold according to the present invention, with a partial cross section.
FIG. 5 is a side view showing an example of a mold clamping device in a conventional horizontal injection molding machine, and particularly showing its mold open state.
6 is a cross-sectional view taken along line AA in FIG.
7 is a side view showing a mold clamping state of the mold clamping apparatus shown in FIG. 5. FIG.
FIG. 8 is a perspective view exaggeratingly showing that bending deformation has occurred in the fixed platen and the fixed mold.
FIG. 9 is a side view showing another example of a conventional injection molding machine, in particular, a state in which the mold clamping device is in a mold open state.
[Explanation of symbols]
15 Tie bar 60 Mold bases 70, 70 ', 80 Injection molds 71, 71', 81 Mold bodies 71a, 81a Joint surfaces 71c, 71c ', 82 Force transmission parts 71d, 71d' Mounting surface 72 Mold mounting plate 73 Bolt (Hexagon socket head cap screw)
75, 85 Molded product forming space 76 Clamper c Removal thickness

Claims (3)

A mold body provided with a concave portion or a convex portion for forming a molded product for forming a space for forming a molded product on the joint surface at one end, and an area larger than the joint surface of the mold body, It consists of a mold mounting plate that is connected to the other end surface by a bolt, and the mold main body is only a force transmission part as a part corresponding to the projection surface in the mold clamping direction of the molded product forming space among the other end surfaces. In the injection mold brought into contact with the mold mounting plate ,
The force transmission portion is formed by attaching a steel plate having an appropriate thickness only to a portion corresponding to the projection surface in the mold clamping direction of the molding product forming space in the mounting surface of the mold mounting plate. Mold for injection molding. Is the force transmitting portion as a portion corresponding to the projection surface in the mold clamping direction of the molding product forming space on the other end surface of the mold body substantially equal to the projection surface in the mold clamping direction of the molding product forming space? Alternatively, the injection mold according to claim 1, wherein the mold is slightly smaller. The injection mold according to claim 1 or 2, wherein a protruding height of the force transmitting portion is 0.2 to 0.5 mm .

Images