JPH02263616A - Injection mold - Google Patents

Abstract

PURPOSE:To obtain a mold which has simple structure and also long life and is simple in structure, easy in operation and maintenance and capable of performing efficient production of a molded product, by providing a mechanism where an abutting part against a nozzle and a cavity are communicated by a gate with each other and while mechanism energizes an opening and closing pin, which can interrupt/open the gate in an interrupting direction, the mechanism performs opening operation by interlocking with a mold clamping action. CONSTITUTION:A movable retainer plate 2 is clamped with a retainer plate 1 by pushing a mold clamping block 51 of a mold clamping device 50 against the movable retainer plate 2. A nozzle 61 of an injection device 60 abuts against an abutting part 12 of a mold on the side of the injection device 60 and a molten material is injected toward a cavity 10. During mold clamping, an ejection end of a pressing-down pin 43 is pressed down by a block 51 through force exceeding energizing force of a spring 44, an opening and closing pin 41 is lowered along with a pin plate 42 and a gate 11 is opened. After injection/casting of the molten material into the cavity 10, dwelling of the same is performed for a while and then the mold clamping is released by puling up the block 51. Even if the mold clamping is suspended while the cast material is uncured, the retainer plates 1, 2 are joined to each other by a mold clamping device 30 and the gate 11 is interrupted by the opening and closing pin 41 energized by the spring 44.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to molds for injection molding of plastics and the like, and particularly to molds in which the runner portion is minimized (a so-called runnerless mold).

[Conventional technology] An injection mold has multiple templates (insert, base plate,
The molten material from the injection device is received into the cavity (molding space), which is then hardened or solidified to form a molded product. It is something that creates. In a normal mold, runners such as a sprue, a launch, and a gate are provided in communication in this order between the part that contacts the nozzle of the injection device (that is, the material injection port) and the cavity.

However, for the following reasons, it is desirable that the internal volume of these runners be small, and ideally they should not exist if possible. In other words, although the hardened (or solidified) part in the runner is a useless part that has nothing to do with the molded product, (a) it is necessary to remove it separately from the molded product before using the mold next time. Yes, it takes time, a)
The material is thermosetting plastic or special (not general purpose)
This is because if a product cannot be reused, it becomes a waste of material, and (c) even if it is reused, the loss of working time and energy is unavoidable.

The part of the runner called the gate is generally small in cross-sectional area and length, so the loss described in L is hardly a problem, but since it is directly connected to the cavity, this part must be finished after the molded product is removed. Ideally, it should not exist.

Conventionally, the following molds have been put into practical use or proposed as molds (generally referred to as runnerless molds) that attempt to fulfill this ideal. Namely: a) A mold in which the sprue or launch is heated or insulated so that the material therein is not cured (or solidified) and only the molded product is removed from the mold.

Since ancient times, there have been various methods such as the hot sprue bushing method and the insulation launch method.

b) A mold disclosed in Japanese Patent Application Laid-Open No. 58-45037, in which the part that contacts the nozzle of the injection device is made into a concave conical surface, and the bottom part is made into a sharp edge gate that opens directly into the cavity, and the sprue is and those without runners.

C) The mold shown in Japanese Patent Publication No. 5338, which has a sprue and runner as well as a gate, can be used to mold a molded product by inserting a slide pin into the gate (blocking the gate) after the material has been injected. This eliminates the gate part and separates the sprue and runner parts. This slide pin is driven by a hydraulic cylinder dedicated to the pin provided in the mold or a molded product ejection cylinder of an injection molding machine.

[Problems to be Solved by the Invention] The conventional injection molds of types a), b), and C) above each have the following problems.

First, in a), heating or insulation molds have a complicated structure for heating and insulation or to prevent material from dripping, and they also require temperature control (warm-up) at the start of operation.
is not suitable for discontinuous production.

The mold of JP-A No. 58-45037 listed in b) is
Since the molded product and the gate part are not always separated smoothly, finishing work on the molded product is essential to remove any flakes that may occur there. In addition, the sharp edges of the gate are easily damaged, making maintenance work cumbersome and shortening the service life.

Regarding the mold C) related to Japanese Patent Publication No. 53-5338, firstly, the above-mentioned disadvantages A), O), and 8) cannot be solved because of the presence of a sprue launch. Secondly, since a dedicated hydraulic cylinder or an injection molding machine's ejection cylinder is used to shut off the gate with a slide pin, the former inevitably complicates the structure and increases costs, while the latter In this case, the material is injected into the mold.
After injection and until it hardens (or hardens),
Since the gate is closed, the mold cannot be removed from the injection molding machine, and the injection molding machine cannot be operated efficiently.

This invention aims to solve the above-mentioned problems, and is a mold that can minimize or eliminate the sprue launch and completely separate the gate part from the molded product,
It has a simpler structure, easier operation and maintenance, and has a longer lifespan than before, and the injected material is uncured (or unsolidified).
The purpose of the present invention is to provide an injection mold that allows efficient production of molded products by taking out only the mold from the injection device.

[Means for Solving the Problems] The injection mold of the present invention includes: (1) communicating the contact portion with the nozzle of the injection device with the cavity through a gate; (2) an opening/closing pin capable of blocking and opening the gate; A mechanism is provided that biases the pin in the blocking direction and opens the pin in conjunction with the clamping operation of the mold clamping device, and a removable clamping means is provided between the pair of mold plates. It is something.

[Function] In the injection mold of the invention, first, as described in (2) above, the part of the injection device that contacts the nozzle and the cavity are communicated through a gate with a small internal volume. Generally, gates are
In addition to having a small cross-sectional area for the injection port into the cavity, the length of the mold can be short if it is a so-called small-batch mold that produces a small number of molded products at a time (one to several molded products). The area is small and very little material is wasted in this area. Further, as described in the embodiment, the internal volume of the gate can be made zero by the operation of the opening/closing pin, which will be described later, so that there is no material loss in this part.

When the mold is clamped by the mold clamping device, the above gate is opened by the operation of the opening/closing pin shown in (■) above, so in that state, the nozzle of the injection device is brought into contact with the mold to inject the material. Can be injected. After injection is complete, if you stop clamping the mold while the material is still uncured and unsolidified (semi-molten), the opening/closing pin will block the gate due to the biasing force of the mechanism (■), so there will be no gate inside the cavity. The separated molded product is cured (or solidified) and formed. Even after the mold clamping device stops clamping the mold, the stationary mold plate and the movable mold plate are still connected by the tightening means described in (■) above, and the gate is also closed, so that the material inside the cavity remains uncured (
The mold can be removed from the injection device and transported to another location without leaking the mold (or unsolidified).

This mold also has the following features: In other words, since it is not a runnerless mold that uses heating or insulation means, it has a simple structure and is easy to start operation, and since there is no need to provide a sharp edge on the gate, it is easy to handle (maintain) and has a long life. Since the gate opening/closing pin is operated by the force of the mold clamping device, there is no need for a dedicated drive means.

[Example] Regarding an example of the injection mold of the present invention, longitudinal sectional views of the mold are shown in FIGS. 1 and 2.

Figure 1 is a diagram of the normal state after combination (combination), Figure 2
The figure shows the molten material (thermosetting resin) being injected.

As shown in FIG. 1, this mold includes a stationary mold plate 1 and a movable mold plate 2, each of which forms a cavity 10. The fixed side template l is the base plate 4 on the fixed base 5.
is fixed to the moving side template 2 via the spacer block 3.
is movable along the guide pin 6 from the position shown in the figure in close contact with the stationary template 1 to the end plate 7. In order to move the movable template 2 upward in the figure, insert the mold opening pin 21 fixed to the template 2 from below the hole 5a made in the base plate 4 and the fixed base 5 with another pin (not shown). Push up with z). Furthermore, an ejector plate 23 is provided so that the molded product inside the cavity 10 can be taken out in this state.
The ejector pin 22 and the spring 24 are attached to the stationary template l, and the base plate 4 and the fixing table 5 are provided with an insertion opening 5b for an ejector rod (not shown).

In this mold, a short gate 11 was used to connect a contact portion 12 with a nozzle 61 (see FIG. 2) of an injection device 60 (see FIG. 2) to the cavity IO. This mold is a so-called one-piece mold (one molded product is obtained by one injection molding), and the gate 11 is formed into a single straight line. The reason why the contact portion 12 is formed into a concave spherical surface as shown in the figure is because the nozzle 61, which also has a spherical surface (with a radius slightly smaller than the above-mentioned portion 12), may be slightly misaligned and contact the contact portion. , to prevent any gaps from leaking material.

Then, the opening/closing pin 41 was slidably inserted into the stationary template l so that the gate 11 could be opened and closed at least at the boundary with the cavity 10. This pin 41 slides in a direction intersecting (the flow path direction of) the gate 11, and in the position shown in FIG. Pin 41 in this example
The dimensions of the tip correspond to the length of the gate 11,
In the state shown in the figure, the gate 11 is not only shut off, but also the internal volume of that part is made zero.

The gate 11 is opened by sliding the pin 41 downward in the figure.

The opening/closing pin 41 was passed through the ejector plate 23 in addition to the stationary mold plate 1, and an opening/closing pin plate 42 was connected to the end thereof. The pin plate 42 includes the ejector plate 23 and fixed side template! - A slidable push-down pin 43 is attached to pass through the movable template 2, and a spring 44 is press-fitted between the plate 42 and the base plate 4. Due to this mechanism, the opening/closing pin 41 is normally held by the spring 4.
While the gate 11 is shut off by the biasing force 4, the gate 11 is opened by pushing down the pin 43 protruding from the template 2 against the spring 44. Note that the reference numeral 4a in the figure is a stopper fixed on the base plate 4, which determines the end of the stroke of the pin plate 42.

In addition, a tightening means 30 is interposed between the stationary mold plate 2 and the movable mold plate 2 so that they can be kept in close contact with each other without applying any force from the outside. The tightening means 30 may have the function of keeping the mold plates 1 and 2 in close contact until a separation force of a predetermined strength or more is applied or a special operation is performed. Here, around templates 1 and 2 (
The fitting members 31 and 32 attached to the areas (excluding the periphery of the abutting portion 12) are connected to the ball 33 and the spring 34.
I used a type that combines by the action of . That is, when the members 31 and 32 are fitted together when the templates 1 and 2 are brought into close contact, the ball 33 pressed inward by the spring 34 from the outer member 32 fits into the recess on the circumferential surface of the member 31, and the members 31 and 32 will not come off naturally. Template l
The tightening force of this means 30 is quite strong in order to maintain the close contact between the parts 2 and 2, but it is connected during injection molding (mold clamping) and can be easily removed when the mold is opened to take out the molded product.

By using this mold as a tool, injection molding of thermosetting resin and the like can be performed efficiently.

l) When the previous molded product was taken out, the moving side template 2 was
Although the mold has moved upward in the figure and is away from the stationary mold plate 1, the mold is moved to the mold clamping device 50 and the injection device 6.
0 to an injection molding machine.

2) As shown in FIG. 2, the mold clamping block 51 of the mold clamping device 50
The movable mold plate 2 is brought into close contact with the stationary mold plate 1 by pressing (mold clamping), and the nozzle 61 of the injection device 60 is applied from the side to the contact part 12 of the mold to direct the molten material toward the cavity 10. and eject it.

During mold clamping, the block 51 presses down the protruding end of the push-down pin 43 with a force exceeding the biasing force of the spring 44, so that the opening/closing pin 41 is lowered together with the pin plate 42, and the gate 11 is opened. At this time, the pin plate 42 is lowered until it hits the stopper 4a on the base plate 4, but the push-down pin 43
In order to prevent excessive force from being applied to the block 51, a pad 51 made of an elastic material is placed on the part of the block 51 that contacts the head of the pin 43.
A is attached.

3) When the injection and injection of the molten material into the cavity 10 is completed, the pressure is held for a while, and then the block 51 is pulled up to release the mold clamping, and the injection device 60 is further retreated to the side.

As a result, the mold becomes the state shown in Fig. 1, but even if the mold clamping is stopped for a short time while the injected material is uncured (semi-molten), the clamping means 30 will hold the mold plate!・2 are connected and spring 4
Since the gate 11 is also closed by the opening/closing pin 41 energized by the opening/closing pin 41, the material inside the cavity 10 will not leak. In addition, the opening/closing pin 41 makes the internal volume of the gate 11 zero, and the material in that area is transferred into the cavity 10 or into the injection device 6.
Since the gate 11 is pushed inside the molded product, no part of the gate 11 remains in the molded product, and the material corresponding to the gate 11 is not wasted.

4) After releasing the mold clamp and retracting the injection device 60,
The above-mentioned mold is carried out to another location for the hardening process of the injection material, the mold opening process, or the process of taking out the molded product, and the mold clamping device 5
0. Another mold is carried into the injection molding machine equipped with the injection device 60.

This molding machine completes mold clamping and injection in a short time, and continuously performs mold clamping and injection for molds that are brought in one after another, resulting in extremely high production efficiency per molding machine. This is because even if the mold is separated from the molding machine, the mold plates 1 and 2 are connected as described above and the gate 11 is closed.

5) For the mold that has completed the material hardening process, in the mold opening process, the movable side template 2 is moved to the end plate 7 by pushing the mold opening pin 21 upward from the hole 5a, and then the molded product removal process is performed. As shown in FIG.
3 and eject the molded product using the ejector pin 22.

After this, return to step 1) above to perform the next injection molding.

Although one embodiment has been introduced above, the present invention can also be implemented as follows.

a) It is possible to make not only one mold but several molds. This can be done, for example, by forming a launch-like part of a minimum size and then branching the gate from this part to communicate with each cavity. As an example of such a case, if each opening/closing pin for blocking each gate is connected to the opening/closing pin plate (reference numeral 42), the opening and closing can be performed simultaneously.

b) The mechanism for operating the opening/closing pin is not limited to that shown in the embodiment. For example, an opening/closing pin is formed at one end of a lever, and the lever is attached to the movable template so that it can swing in the vertical direction as shown in Figures 1 and 2, using the lever as a fulcrum. Furthermore, a mechanism in which the gate is biased in the direction of blocking the gate using a spring or the like may be used. In this case, the end opposite to the opening/closing pin is connected to the mold clamping block (symbol 51) of the mold clamping device.
), the end of the opening/closing pin that intersects with the gate is pushed up and the gate is opened.

C) Direction of mold clamping and mold opening, that is, Fig. 1 and Fig. 2
The vertical direction in the figure may be vertical or horizontal. In other words, this mold can be applied to both vertical (vertical) type injection molding machines and horizontal (horizontal) type injection molding machines.

d) It is applicable to injection molding not only of thermosetting resins shown in the examples but also of other materials such as thermoplastic resins.

[Effect of the invention] The injection mold of the present invention provides the following effects.

l) Eliminate the sprue lunch (if only one is used)
Alternatively, it can be minimized (in the case of several gates), and the gate part can be completely separated from the molded product (or the actual internal volume can be made zero as in the example), so the No post-processing is required, and there is almost no material loss.

2) The structure is improved because it is not a runnerless mold that uses heating or insulation means, the gate opening/closing pin does not require a dedicated drive means (hydraulic cylinder, etc.), and there is no need to provide a sharp edge on the gate. It has the advantages of being simple and inexpensive, easy to start operation, easy to maintain and handle, and has a long life.

3) Since only the mold can be taken out from the injection device while the injected material is not cured (or unsolidified), the device can be operated efficiently and productivity can be improved. There is no need for the mold clamping device to be taken out along with the mold.
The structure of the injection molding machine (including the mold clamping device and injection device) is also simple. The above productivity improvement sufficiently compensates for the fact that the number of molds is small. It also has the advantage of being easy to fill and transfer into cavities because of its low resistance.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing an embodiment of the injection mold of the present invention, FIG. 1 being a normal state after combination (bonding), and FIG. 2 being a state in which molten material is being injected. It is a diagram. l... Fixed side template, 2... Moving side template, 10...
Cavity, 11... Gate, 12... Contact portion (with nozzle), 30... Tightening means, 41... Opening/closing pin, 50... Mold clamping device, 60... Injection device, 61・
··nozzle.

Claims (1)

[Claims] An injection mold in which a stationary mold plate and a movable mold plate are combined, clamped by a mold clamping device, and molten material is injected into a cavity from a nozzle of an injection device. , A gate communicates the contact area with the nozzle with the cavity, and an opening/closing pin that can shut off and open the gate, and an opening/closing pin that biases the pin in the blocking direction and opens in conjunction with the clamping operation of the mold clamping device. An injection molding die, characterized in that the injection molding die is provided with a mechanism for locking the template, and a removable tightening means is provided between the pair of templates.