JPS5843259B2 - Hot runner mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for injection molding a thermoplastic resin, and particularly to a hot runner mold that is easy to manufacture and operates reliably, with little leakage of molten resin.

As a runnerless injection molding method, a hot runner one-type mold has been developed.

One known method is the one described in, for example, Japanese Patent Laid-Open No. 50-92354.

That is, a block (hereinafter referred to as a block) that integrally accommodates a sprue for introducing molten resin and a runner, etc., which communicates with the sprue and has one or more resin distribution passages and has a gate, which is an opening, at its tip. (called hot block)
and a cavity block having a molding space (hereinafter referred to as cavity) that communicates with the gate and receives the molten resin during molding. This is intended to keep the mold temperature at a so-called mold temperature, cool and solidify only the resin in the cavity, and minimize the amount of resin left in the passageway to the cavity.

Such molds generally have a contact surface that allows the hot block and cavity block to slide against each other,
A gate surface is provided on the hot block side of the contact surface, and an opening for injecting molten resin into the cavity is provided on the cavity block side, and when the mold is closed, the gate and the opening communicate with each other, and the molten resin is injected into the cavity (injection). be done.

After the resin in the cavity is cooled and solidified, the mold opening operation causes the contact surfaces of the movable block and the intermediate block that constitute the cavity block to move parallel to the gate surface and along the contact surface of the hot block, When the mold is opened, the gate surface is sealed with the contact surface of the intermediate block.

The problem with such a structure is how to maintain an appropriate clearance between the contact surfaces on which the hot block and the cavity block slide.

Since the contact surface repeatedly slides without lubrication, if this clearance is too small, mechanical sliding becomes difficult, and if it is too large, molten resin will leak.

Moreover, since the hot block is usually at a high temperature, it expands thermally during use compared to when making the mold, and thermal distortion also occurs.

For this reason, it is extremely difficult to manufacture a sliding contact surface, requiring a highly precise and smooth surface, as well as measures against thermal expansion.

The present invention solves these problems by providing a hot runner mold that does not leak molten resin, is easy to manufacture, and operates reliably.

The hot runner mold of the present invention includes a hot block having a sprue for introducing molten resin and a gate connected to the sprue by a runner and having a gate surface parallel to the mold opening/closing direction and opening into the gate; Consisting of an intermediate block and a movable block, which have contact surfaces that are parallel to the gate surface of the hot block and are slidable in the mold opening/closing direction with respect to the gate surface, and are arranged in series in the order of proximity to the fixed member of the mold. A chamber, that is, a cavity, for forming a molded product in the closed state of the mold is formed in the movable block and/or the intermediate block of the cavity block, and the cavity is opened from the gate of the hot block. It is for injecting molten resin into the cavity and has an opening that opens to the contact surface, and when the mold is closed, the gate and the opening communicate with each other, and when the mold is opened, the movable block and the intermediate block are connected to the gate surface. Means for shearing the resin between the opening and the gate by moving along the sliding contact surface against the gate surface, and pressing the contact surface in contact with the gate surface of the intermediate block against the gate surface at least in the mold open state. It is characterized by being provided with.

The hot runner mold of the present invention is particularly suitable as a mold for molding a large number of small molded products.

In the case of such a multi-cavity mold, the cavities in the cavity block are arranged linearly or radially, and the openings for introducing the molten resin into the cavities are concentrated on the contact surface of the cavity block.

On the other hand, a hot block is provided adjacent to the cavity block, and this is usually provided with one or more sprues for introducing molten resin and runners communicating with the sprues to distribute the molten resin in the sprues to a number of gates. .

The gates are arranged so as to face the opening of the molten resin in the cavity block, so if the cavities are linear, the gates are also arranged in a straight line, and there is one gate on both sides between two cavity blocks. A hot block with gates arranged side by side is provided, or a cavity block and a hot block with gates arranged on only one side are arranged one-to-one.

If the cavities are arranged in an open-sealed manner and the openings for introducing the molten resin are concentrated in the center, a hot block is provided in the central space and the gates are arranged radially outward. provided.

The hot block is controlled to a desired temperature by an embedded heater or heating pipe.

Injection of molten resin from the gate of the hot block into the cavity is usually performed by pressurizing the molten resin in the hot block by applying pressure from the direction of the inlet into the sprue.

The gate surface of the hot block and the contact surface of the cavity block are preferably made as small as possible in order to minimize the heat transfer that occurs between the hot block and the cavity block, and to facilitate the slitting process of the contact surfaces. .

According to a preferred embodiment of the present invention, the gate portion of the hot block is narrower in the gate extension direction than the hot block body, and the contact surface with the hot block formed around the gate surface is small. It is said that

The contact surfaces of the corresponding cavity blocks, that is, the contact surfaces of the moving blocks and intermediate blocks that intercept the cavity blocks are also made small.

The present invention includes a means for pressing the contact surfaces of the intermediate block toward the gate surface so that the contact surfaces of the intermediate block are tightly pressed against the gate surface in the mold opening state. It may be attached to the intermediate block, or a separate pressing means may be provided on the side opposite to the contact surface of the intermediate block, that is, on the back surface.

When it is attached to the intermediate block, the mold itself has the advantage of being compact, and when it is installed separately, the degree of freedom in mold design increases.

Which method to apply may be selected depending on the purpose.

As the pressing means, various biasing means (or pressing means) can be selected as necessary to generate a force that presses the contact surface of the intermediate block toward the gate surface.

Such biasing means include, for example, springs, hydraulic cylinders, electric cylinders, and the like.

A combination of these may also be used. The timing at which the pressing force is generated in the pressing means can be set arbitrarily depending on the purpose.

One typical method is to always generate a constant pressing force, and this method is used when a large pressing force is not required, for example when the pressure of molten resin is relatively low, or when using a small metal. Suitable for types.

The other method is to generate pressing force only when the mold is open, but this method is used when a relatively high pressing force is required, contrary to the above method, or when you want to ensure more reliable operation when the mold is moving. This is an advantageous method in such cases.

Furthermore, a more preferable method is to reduce or eliminate the pressing force only during movement.

Further, instead of controlling the pressing force between zero and a predetermined value, it can also be controlled between a predetermined low value and a predetermined value.

The value of the pressing force may be selected and designed from various values depending on the dimensions of the target mold, the pressure of the molten resin, etc.

The explanation so far has mainly been about the case where only the contact surface of the intermediate block is pressed against the gate surface, but depending on the embodiment, it may be more preferable to press the movable block as well.

In this case, it is preferable to press both the moving block and the intermediate block toward the gate surface of the hot block when the mold is closed, and to press only the intermediate block when the mold is open.

However, as described above, the intermediate block may always be pressed at a constant value in this case.

In a most preferred embodiment, when the moving block is moved to the mold closing position, the moving block also engages the means for pressing the intermediate block, at which point both the intermediate block and the moving block are pressed by the common pressing means, In the mold opening state, the engagement between the moving block and the pressing means is ensured, while the engagement relationship between the intermediate block and the pressing flat portion is maintained as it is.

That is, since the amount of movement of the intermediate block is generally much smaller than that of the moving block, this method can simplify the mechanism.

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing a hot block 1 and a cavity block 2 from the mold opening surface in a case where a large number of gates and corresponding cavities are arranged in a straight line.
Figure BB shows the arrowhead.

) FIG. 2 is a sectional view taken along the line A--A in FIG. 1, showing the mold in a closed state, and also showing a portion perpendicularly above the plane of FIG. 1.

FIG. 3 shows the mold opening state in which the cavity block 2 has been moved from the state shown in FIG.

1 to 3, molten resin is introduced from a sprue 3 into a hot block 1, passes through a main runner 4, and is distributed to a number of runners 5.

A gate 6 is provided at the tip of the runner 5 and opens to a gate surface parallel to the mold opening/closing direction, and when the mold is closed, the pressure causes the molten resin to flow into the cavity I in the opposing cavity block 2 via the contact surface. is injected from the opening 8.

The hot block 1 and the movable block 2a and intermediate block 2b in the cavity block 2 are in contact with each other via their respective gate surfaces and contact surfaces 9 in the mold closed state.

The fixing member 10 fixes the hot block 1 and serves as a reaction force for the tightening pressure applied from the direction of arrow a in FIG. 2 when the mold is closed.

The other holding member 11 serves as a common support for the moving block 2a.

A plurality of springs 12 are held in a housing portion 13 between the fixing member 10 and the intermediate block 2b, and both ends of the springs 12 are fixed to the bottoms of the housing portion 13 on each side of the fixing member 10 and the intermediate block 2b. Due to the action of the spring 12, a force is applied to the intermediate block 2b in a direction away from the fixing member 10.

Therefore, in the mold-closing state, the intermediate block 2b is tightly pressed against the fixing member 10 against the mold-clamping pressure.

A plurality of stopper members 14 are fixed in the fixing member 10, and the extension portions have enlarged tips and communicate with the space 15 in the intermediate block 2b. It is slidable.

In this example, the contact surface of the intermediate block 2b is
7 and an external surface 18 of
is in contact with the surface of gate 6.

A force is applied to the presser element 17 in the direction of its surface 18 by a spring 19 serving as a biasing means, so that the presser element 17 can slide within the space 20 of the intermediate block 2b.

FIG. 4 shows a partially enlarged cross-sectional view of the pressurizer 17 section taken along the line C--C in FIG. 3.

The pressurizer 17 is slid back and forth in parallel in the space 20 by two guide rods 17a, one end of the guide rod 17a is fixed to the intermediate block 2b, and the other end has an enlarged part to allow the inside of the pressurizer 17 to slide back and forth in parallel. It contacts the bottom of the space 21, and the biasing force of the spring 19 prevents the pressurizer 17 from moving outside.

However, in some cases, a long leaf spring may be provided in the space 20 instead of the combination of the spring 19 and the guide rod 17a.

Further, a hydraulic pressure or a hydraulic cylinder may be used in this portion as the biasing means.

Next, to explain the operation in FIGS. 1 to 4, when molten resin is injected into the cavity 7 from the gate 6 of the hot block 1 in the mold closed state, the resin flows into the cavity 7.
It is cooled and solidified inside.

After that, the holding member 1 is opened by a mold opening mechanism (not shown).
1 in the direction of arrow A in FIG.
The resin between the opening 8 of the cavity 7 and the gate 6 is sheared by the sliding action of a.

At this time, the intermediate block 2b moves in the same direction as the movable block 2a due to the action of the spring 12, and the surface 18 of the presser 17 slides along the surface of the gate 6, sealing the gate 6 under pressure. do.

(FIG. 3) The amount of movement of the intermediate block 2b is regulated by a stopper member 14.

The moving block 2a moves away from the intermediate block 2b, moves further, and is stopped at a sufficient position to take out the molded product from the cavity 7, and then the molded product is moved directly from the cavity 7 or to the bottom of the cavity 7 (not shown). It is ejected by a provided ejector pin.

Next, the holding member 11 is again moved in the direction opposite to the arrow C, the mold is closed, and the molding process begins.

In the above example, the movement of the intermediate block 2b is controlled by the spring 12.
Although it depends on the combination of the stopper member 14 and the stopper member 14, an appropriate moving means is provided externally, or the moving block 2
It can also be moved in synchronization with the movement of a by a cam, link mechanism, etc. connected thereto.

FIG. 5 shows a case where the cavity block 2 is cylindrical, the hot block 1 is placed inside it, a plurality of gates 6 are provided radially outward, and the opening of the cavity is also provided opposite to the gates. Give an example.

In this case, since the gate surface (has a circular arc shape), the surfaces of the moving block, the intermediate block, and its pressurizer are shaped to correspond to the shape, but this is substantially the same as in the previous example.

FIG. 6 is a partial sectional view showing another embodiment of the present invention.

The intermediate block 2b and the movable block 2a are pressed from above the back surface 25 of the contact surface 18 by the pressing member 17 of the common pressing mechanism 23 in the mold-closed state.

This allows the molten resin to be injected into the cavity 7 on the adjacent surface 18.
Since the contact surfaces 18 are brought into close contact with each other under pressure, the smoothness of the entire contact surface 18 and other machining margins are increased.

When the holding member 11 moves during mold opening in the same manner as shown in FIG. 3, the moving block 2a moves away from the pressing element 17 while sliding between the back surface 25 of the moving block 2a and the surface of the pressing element 17.

On the other hand, the intermediate block 2b moves to a position where it seals the surface of the gate 6 and is stopped there, but at this time, the back surface 25 of the intermediate block 2b is engaged with the presser 17, so its contact surface 18 seals the gate surface. Can be pressed.

Figure T a shows the movement cycle of the cavity block in Figure 6, where O on the vertical axis represents the mold open position and S represents the mold closed position, a-)l)-)C→d→a... The movement of the cavity block according to the molding process is shown with respect to the time axis t on the horizontal axis.

FIG. 7 shows changes in the pressing force generated by the pressing mechanism 23 corresponding to the movement cycle of the cavity block described above.

Pl represents the pressing force during the movement of the cavity block, P2 represents the pressing force in the mold opening state, and P3 represents the pressing force in the mold closing state, and the value of each pressing force is Pl<P2<P3
There is a relationship between

By changing the pressing force in this manner, it is possible to sufficiently satisfy the gate sealing effect in the mold closing and mold opening states, and to further ensure the operation when the cavity block is moved.

FIG. 8 shows an example of a control method for applying the change in the pressing force shown in FIG. 7 to the suppression mechanism 23. Pressurized air) is supplied from pressure sources P and S via the current pressure valve 27 and through the pipe 31, and generates a pressing force proportional to the pressure of the working fluid on its output shirt 26a.

28 is a control circuit, which includes a mold opening position signal O and a mold closing position signal S (these are limit switches,
A control command is issued using a proximity switch (or a cavity block movement control signal, etc.) to open and close the three-way solenoid valves 29 and 30.

The pressure in the output pipe 31 of the pressure reducing valve 27 is set to P3, and when both the three-way solenoid valves 29 and 30 are closed, the pressure in the cylinder 2
6 is applied with pressure P3.

When neither of the control signals O and S is input to the control circuit 28, the three-way solenoid valve 29 opens, and one of the fluids from the pressure reducing valve 27 flows from the pipe 32 branched from the pipe 31 to the cylinder 26 via the throttle 29a. part is vented to the atmosphere and the pressure on cylinder 26 is reduced to Pl.

Also, when only the control signal O is input, the three-way solenoid valve 3
0 opens, part of the fluid from the pressure reducing valve 27 is released from the branch pipe 33 to the atmosphere via the throttle 30a, and the cylinder 2
The pressure on 6 is dropped to P2.

When only the control signal S is input, the three-way solenoid valve 2
Both are closed at 9.30.

The pressure P1 in FIG. 7, that is, the pressure while the cavity block is moving, does not necessarily need to be higher than atmospheric pressure, and may be kept at atmospheric pressure.

In that case, the control method shown in FIG. 8 may be modified accordingly.

As explained in detail above, the present invention provides, in a hot runner one-type mold having a hot block and a cavity block, means for pressing the contact surface of the intermediate block in the direction of the gate when the intermediate block contacts the gate surface when the mold is opened; Alternatively, by providing means for pressing the contact surfaces of both the intermediate block and the moving block in the direction of the gate when the mold is closed, it is possible to not only completely prevent leakage of molten resin from the gate. Since there is no need to increase the dimensional accuracy of the sliding contact surface, mold costs can be significantly reduced.

In particular, it was necessary to change the clearance of this sliding contact surface in accordance with the expansion of the material each time the temperature of the hot block or capacity block was changed, but according to the present invention, the clearance of the sliding contact surface can be changed under any molding conditions. Leakage from the gate can be completely prevented without any adjustment.

[Brief explanation of the drawing]

1 to 3 are diagrams showing embodiments of the present invention, in which FIG. 1 is a plan view taken along the arrow B-B in FIG. 2, and FIG. 2 is a plan view taken along the arrow A-A in FIG. The sectional view and FIG. 3 are similar sectional views when the mold is opened from the state shown in FIG. 2. FIG. 4 is a partial sectional view taken along the line CC in FIG. 3, and FIG. 5 is a diagram showing a portion corresponding to FIG. 4 in another embodiment of the present invention. FIG. 6 is a partial cross-sectional view of still another embodiment of the present invention, and FIG.
The figure is a diagram showing an example of the control method. 1: Hot block, 2: Cavity block, 2a:
Moving block, 2b = intermediate block, 3 varnish blue, 4
: Main runner, 5: Runner, 6: Gate, 7: Cavity, 8: Opening, 9: Contact surface, 17: Pressure element, 23: Pressing mechanism, 26: Cylinder, 28: Control circuit.

Claims (1)

[Scope of Claims] 1. A hot block having a molten resin introduction spray and a runner connected to the sprue and having a gate surface parallel to the mold opening/closing direction and opening into the gate; It has a contact surface that is parallel to the gate surface and is slidable in the mold opening/closing direction with respect to the gate surface, and is composed of an intermediate block and a movable block arranged in series in the order of proximity to the fixed member of the mold, and the contact surface is parallel to the gate surface and is slidable in the mold opening and closing direction. It consists of a cavity block that has an opening opening in the surface and a cavity connected to the opening and is movable in the mold opening/closing direction, and when the mold is closed, the opening faces and communicates with the gate, and when the mold is open, the opening is connected to the gate. a hot runner mold comprising means for pressing the contact surface of the intermediate block against the gate surface; 2. The means for pressing the contact surface of the intermediate block against the gate surface includes a presser and a biasing means built into the intermediate block, and the surface of the presser constitutes a part of the contact surface of the intermediate block and presses the gate surface. The hot runner mold according to claim 1, wherein the biasing means applies a biasing force to the presser so as to press the surface of the presser toward the gate surface. . 3. The hot runner mold according to claim 1, wherein the means for pressing the contact surface of the intermediate block against the gate surface is a pressing mechanism provided on the back surface of the contact surface of the intermediate block. 4. The hot runner according to claim 1, wherein the pressing force of the means for pressing the contact surface of the intermediate block against the gate surface is reduced when the intermediate block is moved than when the mold is in an open state. Mold. 5. A hot block having a sprue for introducing molten resin and a gate connected to the sprue by a runner and having a gate surface parallel to the mold opening/closing direction and opening into this, and a gate that is parallel to the gate surface of the hot block and opened to the gate surface. an opening that opens to the contact surface and is composed of an intermediate block and a movable block that are arranged in series in the order of proximity to the fixed member of the mold, and that have a contact surface that is slidable in the mold opening/closing direction. and a cavity block that has a cavity connected thereto and is movable in the mold opening/closing direction, and in the mold clamping state, the opening faces and communicates with the gate, and the movable block and the intermediate A hot runner mold comprising means for pressing a contacting surface of the block against the gate and also pressing a contacting surface of the intermediate block against the gate surface in the mold open state. 6. The hot runner mold according to claim 5, wherein the pressing means is a pressing mechanism provided on the rear surfaces of the contact surfaces of the moving block and the intermediate block. 7. The hot runner mold according to claim 5, wherein the pressing force of the pressing means is equal in the mold closed state and in the mold open state, and is reduced during movement. 8 The pressing force of the suppressing means is in the mold closed state>mold open state>
The hot runner mold according to claim 5, which is adapted to be moved.