JP2008062637A - Valve gate of hot runner mold for injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve gate enabling to be disposed immediately beneath the nozzle of an injection molding machine so that flow resistance of a material flow channel can be reduced. <P>SOLUTION: The valve body 41 is actuated vertically by a driving means 30 and open/close a gate hole 15 by a small diameter shaft 44. When the valve is open, a material injected from a nozzle of an injection molding machine flows into the gate hole 15 from a channel hole 42 formed along the center axis of the valve body 41 through a communicating hole 43. As the material channel 50 is constituted nearly straight except for a part of the communicating hole 43, flow resistance is small so that the flow volume can be increased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a valve gate of a hot runner mold for injection molding.

  In the hot runner mold for injection molding, it is assumed that the valve gate can be mechanically operated to open and close the gate. (1) The mold is forcibly cut without waiting for the molten material (resin, metal) to cool and solidify. Opening can shorten the molding cycle. (2) With a multi-cavity mold, either gate is not used (closed) and molding can be done with only the required cavities. (3) One cavity multi-point In the case of a gate, it is used for the purpose of controlling the flow state of the material by changing the opening / closing timing of each gate.

  A general valve gate opens and closes a gate hole by reciprocating a valve pin by an air or hydraulic cylinder. Among these, as described in, for example, Japanese Patent No. 3743998 (Patent Document 1), the most general structure is such that a cylinder is arranged right above the gate hole above the manifold (on the fixed mounting plate side), and a valve pin Passes through the manifold and longitudinally cuts the material flow path coaxially. In this structure, (1) it is necessary to join the material flow path from the side with respect to the axis of the gate, and the gate cannot be arranged on the same axis as the nozzle touch part of the molding machine. Necessary, (3) Requires space in the height direction (usually fixed mounting plate thickness), (4) Poor mold assembly and maintainability, (5) Flow resistance due to the valve pin running vertically through the material flow path There is a problem that the flow rate is limited.

  A structure for solving these problems is described in, for example, Japanese Patent Application Laid-Open No. 2003-103581 (Patent Document 2). That is, the nozzle touch part and the gate are arranged on the same axis, and the material flow path connecting the nozzle touch part and the gate is curved in an arcuate shape. On the other hand, an annular air cylinder device is arranged outside the material passage, and the arm connected to the reciprocating operation portion of the air cylinder extends to the central axis in a direction not interfering with the material passage, and the material passage is curved. It is connected to the flange portion of the valve pin in the space on the central axis avoided by The valve pin longitudinally cuts the material flow path on the gate side from the curved portion on the same axis as a general valve gate, and opens and closes the gate hole by the reciprocating operation of the air cylinder.

In both Patent Document 1 and Patent Document 2, the valve pin is directly driven by an air cylinder, and the operation direction and stroke of the air cylinder and the valve pin are the same. In this structure, the thrust of the valve pin is also equal to the thrust of the air cylinder. The thrust of the valve pin requires a force that closes the valve without being pushed back to the reaction force from the gate hole (= injection pressure x gate hole area) at the time of injection. The area can be increased. In order to increase the thrust, it is sufficient to increase the air supply pressure using a booster valve or increase the cylinder bore diameter. However, increasing the cylinder bore diameter requires more space for installation in the mold and increases the mold strength. There is also a problem of lowering. In particular, the annular air cylinder of Patent Document 2 has a large valve gate body, which reduces applicability.
Therefore, for example, Non-Patent Document 1 describes a structure in which a rotary operation perpendicular to the central axis is converted into a reciprocating operation by a gear, and the valve pin is moved up and down instead of being driven by an annular air cylinder. As described above, in the method of converting the operation of the original drive means by the motion transmission means, the applicable stroke can be increased without a special increase in the cylinder bore diameter by attenuating the operation stroke and conversely amplifying the thrust. There is an effect that it can be enlarged.

Japanese Patent No. 3743998 JP 2003-103581 A Isao Okamura, “Book to understand hot runners”, Industrial Research Committee, 2001, p. 131 Figure 9.5

The techniques of Patent Document 2 and Non-Patent Document 1 described above are as follows: (1) The nozzle touch part and the gate can be arranged on the same axis, (2) Manifold penetration is not required, and (3) Space in the height direction is reduced (4) There are effects such as (4) improvement of mold assembly and maintenance. However, with respect to the flow resistance, the flow rate cannot be increased because the valve pin vertically cuts the material flow path on the gate side of the curved portion and the curved portion itself becomes a resistance as well as a general valve gate.
Further, in the structure of Patent Document 2, since a cylinder must be disposed near a heater for heating the material flow path, the airtight members such as the O-ring and packing of the cylinder are affected by heat and have durability. There is a problem that it tends to decrease. In Patent Document 2, although the arrangement of the band heater is devised to reduce the thermal influence, the Sylinder is basically exposed to the vicinity of the high temperature portion.

  Further, the technology of Non-Patent Document 1 can amplify the thrust of the driving means and increase the thrust of the valve pin, but minimizes energy loss due to friction at the conversion portion, and efficiently transmits force. Realization is a challenge.

The valve gate according to claim 1 is a valve gate used for a hot runner mold for injection molding, and a main body portion having a material channel inlet communicating with an injection molding machine nozzle and a gate hole facing the cavity, A valve body that operates coaxially with respect to the gate hole and opens and closes the gate hole, and driving means for driving the valve body are provided.
And a flow path hole formed from the upper end surface to immediately before the lower end along the central axis of the valve body, and one or more communication holes communicating with the flow path hole from a side surface near the lower end of the valve body. The upper end of the flow path hole is connected to the material flow path inlet, the communication hole is formed to be connected to the gate hole, and the valve body is moved up and down along the central axis by the drive means, When operated, the gate hole is opened, and when operated downward, a small-diameter shaft formed at the center of the lower end of the valve body blocks the gate hole.

  In the valve gate of claim 2, a rack connected to the drive means reciprocates in the horizontal direction, a pinion gear meshing with the rack rotates in the horizontal direction, and a drive female screw formed on the inner periphery of the pinion gear is provided. The valve body is configured to operate in the vertical direction by being screwed into a drive male screw formed on the outer periphery of the valve body which does not rotate.

  In the valve gate according to the present invention, since the material flow path is formed substantially linear except for a part of the tip of the valve body, the flow resistance is small and the flow rate can be increased. Moreover, since the drive means is disposed at a position away from the high-temperature main body, deterioration of the airtight member due to heat can be prevented. Further, the structure is such that the thrust of the drive means is amplified by screwing the drive screw and the force is transmitted to drive the valve body, so that the thrust of the valve body can be increased and the entire circumference of the valve body can be increased. Because it is driven by, there is an effect that an efficient transmission of force can be realized.

Next, an embodiment of the present invention will be described with reference to FIGS.
In a general hot runner injection mold, a cavity 3 is formed by a fixed mold 1 and a movable mold 2. The fixed mold 1 includes a fixed mold 4, a fixed receiving plate 5, and a fixed mounting plate 6. The fixed mounting plate 6 is positioned by a locating ring 7, and is a base plate for an injection molding machine (illustrated). Not mounted). A bush hole 8 is formed in the fixed side mold plate 4, and a valve gate mounting hole 9 is formed in the fixed side receiving plate 5 and the fixed side mounting plate 6.
In the valve gate 10 of the present invention, the main body portion 11, the nozzle touch portion 20, and the air cylinder (driving means) 30 are integrated and inserted into the valve gate mounting hole 9. At this time, the mold mating shaft 16 is mated with the bush hole 8. Further, the flange plate 23 hits the surface of the fixed side receiving plate 5 and is fixed by the mounting bolt 24.

As for the outer shape of the main body part 11, the upper part is a rectangular part 12 a, the middle part to the lower part is a cylindrical part 12 b, and the lower end of the cylindrical part 12 b is a mold engaging shaft 16. Further, the inner shape is such that on the central axis of the cylindrical portion 12b, a large-diameter pinion gear accommodating hole 13 is formed at the upper portion, a valve guide hole 17 having a smaller diameter than the pinion gear accommodating hole 13 is disposed in the middle portion, and a minimum-diameter gate hole 15 is formed at the lower end portion. The valve guide hole 17 and the gate hole 15 are connected in a tapered shape. Further, a rack guide hole 14 is formed in a horizontal shaft that is orthogonal to the pinion gear accommodation hole 13 and is substantially radially separated therefrom.
A cartridge heater 71 is inserted into the rectangular portion 12a, and sheath heaters 72a and 72b are wound around the cylindrical portion 12b so that the main body portion 11 can be heated to the molding temperature of the material.

Further, an air cylinder 30 as a driving means is attached to the main body 11 via a stay 38 on the extension line of the rack guide hole 14. A rack 31 is attached to the cylinder rod 35 of the air cylinder 30, and reciprocates in the rack guide 14 as the air cylinder 30 operates. The length of the stay 38 and the rack 31 may be sufficiently longer than the minimum length necessary for the cylinder stroke and within a range that can be attached to the mold. By increasing the length, when the main body 11 is heated by the heater, heat transfer to the air cylinder 30 can be reduced, and the airtight members such as the O-ring and packing of the air cylinder 30 can be prevented from being deteriorated by heat. The stay 38 is preferably made of a material having low thermal conductivity such as stainless steel.
The gear of the rack 31 is adapted to mesh with a spur gear having an outer diameter of the pinion gear 32. Further, a stopper holder 36 is mounted on an extension line of the main body 11 opposite to the stay 38, and the advance limit of the cylinder rod 35 and the rack 31 is regulated by adjusting the tightening amount of the stopper bolt 37. Be able to. Here, the cylinder stroke when the forward limit is restricted is represented as Sc.
In place of the air cylinder 30 of the present embodiment, a hydraulic cylinder may be used as the driving unit. Since the hydraulic pressure is usually 10 times higher than the air pressure, the hydraulic cylinder can obtain a very high thrust.

  Further, the cylindrical portion 12b is provided with a dividing portion 12c, and a hollow taper ring 61 and a spring 62 that presses the taper ring 61 are sandwiched so that the inner periphery thereof is along the valve guide hole 17. . The inner diameter of the taper ring 61 mates with the large diameter shaft 45 of the valve body 41 with high accuracy. Moreover, the lower end part narrowed down to the taper shape is formed thin, receives the injection pressure of the material, contacts the large diameter shaft 45, and seals the gap.

Next, the valve body 41 will be described.
The valve body 41 is formed with a flow passage hole 42 that does not penetrate from the upper end surface to immediately before the lower end along a substantially cylindrical central axis. The side surface near the lower end (external shape) is composed of a large-diameter shaft 45, a tapered portion 46, and a small-diameter shaft 44, and a communication hole 43 that communicates from the tapered portion 46 to the flow passage hole 42 is inclined with respect to the central axis. Yes. For the purpose of constituting the flow path, the communication hole 43 may be one place or several places in each direction. However, if the material is divided into several parts, the material flow is divided, and if the material is resin, it may cause welds in the molded product.
A drive male screw 47 is formed above the center of the external shape, and is screwed into the drive female screw 33 of the pinion gear 32. The effective length of the drive female screw 33 is longer than the effective length of the drive male screw 47 by a valve stroke Sv described later.
In the embodiment, the drive male screw 47 and the drive female screw 33 are triple-threaded, and compared to the single-threaded screw, the inclination at the screwing is less likely to occur, and the rotation of the pinion gear 32 is stably transmitted to the valve body 41. .
The upper end portion 48 of the valve body 41 has a cylindrical shape.

Next, the assembly structure will be described together with the assembly procedure.
First, the thrust ring 34 is placed on the bottom of the pinion gear accommodation hole 13.
The rack 31 is placed at the retreat limit position, while the valve body 41 and the pinion gear 32 are inserted into the main body 11 with the drive female thread 33 of the pinion gear 32 screwed to the upper end position of the valve stroke. Then, in the intermediate portion, after the large-diameter shaft 45 is inserted into the taper ring 61, it is inserted into the valve guide hole 17 with high accuracy and slidable.
Further, the rotation of the valve body 41 is restricted by a rotation stopper (not shown).
The pinion gear 32 is accommodated on the thrust ring 34 of the pinion gear accommodation hole 13. The thrust ring 34 is for reducing friction when the pinion gear 34 rotates.

At this time, the small-diameter shaft 44 is located above the gate hole 15 and is in a valve open state.
Next, when the rack 31 is advanced, the pinion gear 32 rotates counterclockwise as viewed from above, and the valve body 41 is lowered by the screwing of the drive female screw 33 and the drive male screw 47. Then, the small diameter shaft 44 is engaged with the gate hole 15 and the valve is closed. Here, the stopper bolt 37 is adjusted so that the valve closing position becomes the forward limit of the rack 31. When the rack 31 is retracted again, the pinion gear 32 rotates clockwise as viewed from above, and the valve body 41 rises. Then, the small diameter shaft 44 is separated from the gate hole 15 and the valve is opened.
Thus, when the cylinder rod 35 and the rack 31 are horizontally operated by the cylinder stroke Sc, the valve body 41 is vertically moved by the valve stroke Sv, and the valve is opened and closed.
In the embodiment, the pitch circle diameter and the number of teeth of the pinion gear 32 and the pitch of the drive female screw 33 and the drive male screw 47 so that the cylinder stroke Sc is 40 millimeters, the valve stroke Sv is 6 millimeters, and the stroke ratio R is 0.15. Is set. By reducing the stroke ratio R, the operating speed of the valve body 41 becomes slower than the operating speed of the air cylinder 30, but on the contrary, the thrust is amplified. If the conversion efficiency of the gears and screws is 100%, the reciprocal of the stroke ratio R, that is, 6.7 times in this example. Therefore, as compared with the case where the air cylinder directly drives the valve pin with the valve gate of the prior art, the thrust of the valve body increases if the air supply pressure and the cylinder bore diameter are constant. Therefore, if the internal pressure of the cavity 3 is constant, the diameter of the gate hole 15 can be increased.
Further, since the drive female screw 33 and the drive male screw 47 transmit force around the entire circumference of the valve body 41, for example, energy loss due to friction such as twisting is small and efficient compared to a structure driven by a one-way cam. Power can be transmitted to.

Next, the upper structure of the main body 11 will be described. The cover 21 is coaxially attached to the upper part of the pinion gear housing hole 13 of the main body 11, covers the upper part of the pinion gear 32, and engages with the inner diameter of the pinion gear 32 to maintain the coaxiality during rotation. The sleeve 22 is further coaxially attached to the cover 21. The inner diameter of the cover 21 guides the outer diameter of the upper end portion 48 of the valve body, and the outer diameter of the sleeve 22 guides the inner diameter of the upper end portion 48. 41 operates on the central axis with high accuracy.
The inner diameter of the sleeve 22 constitutes a part of the material flow path 50 and is connected to the flow path hole of the valve body 41.

A flange plate 23 is further attached to the top of the cover 21. A nozzle touch portion 20 is formed at the center of the flange plate 23, and becomes a portion corresponding to the material flow path inlet 51 of the valve gate 10 in the material flow path 50 from the injection molding machine nozzle 90 to the cavity 3. .
Further, the peripheral portion of the flange plate 23 is used for attachment to the fixed side receiving plate 5.

Next, an example of the operation of this embodiment will be described.
At the time of injection molding, the injection molding machine nozzle 90 is pressed against the nozzle touch part 20.
The main body 11 is heated by the cartridge heater 71 and the sheath heaters 72a and 72b, and the material in the material flow path 50 is in a molten state. Since the air cylinder 30 is mounted away from the main body 11, it is possible to prevent airtight members such as an O-ring and packing from being deteriorated by heat without being directly exposed to high temperatures.

When a predetermined amount of molten material is injected from the injection molding machine nozzle 90 in the valve open state, the molten material passes from the material flow path inlet 51 through the sleeve 22, the flow path hole 42 of the valve body 41, the communication hole 43, and the gate hole. 15 to the cavity 3 is filled. Unlike conventional valve gates, there is no valve pin in the flow path or the flow path is curved, and the material flows almost linearly except for the communication hole 43 portion, so the flow resistance is small. The flow rate can be increased.
At this time, since injection pressure is applied to the material flow path, there is a possibility that the material enters (leaks) into the gaps between the component parts, but the inner diameter of the cover 21, the outer diameter of the sleeve 22, the inner and outer diameters of the upper end 48, and the valve The inner diameter of the guide hole 17 and the outer diameter of the large-diameter shaft 45 are manufactured so as to be mated with high accuracy, thereby preventing leakage. Even if material enters the gap between the valve guide hole 17 and the large-diameter shaft 45, the taper ring 61 comes into contact with the large-diameter shaft 45 and seals under the injection pressure of the material.
Subsequently, when the valve is closed after completion of filling, the small-diameter shaft 44 is engaged with the gate hole 15, the material flow is cut off, and the gate is sealed. When the mold is opened and the product is taken out, a product with a cleanly cut gate can be obtained without causing material scraping or stringing.

In the present embodiment, the case where the gate is coaxial with the nozzle touch portion, that is, a single valve gate is arranged at the mold center has been described. It can also be used for multi-point gates. In that case, the nozzle touch part 20 of the flange plate 23 changes to a connection shape with the flow path hole of the manifold.
At the time of injection molding, the valve opening / closing timing of each multi-point gate can be adjusted in the same manner as a general valve gate. Moreover, the effect which reduces flow resistance and increases flow volume with respect to a general valve gate is acquired.
Furthermore, the valve gate of the present invention is not limited to a valve gate for a mold, and can be used as a shut-off valve for a nozzle of an injection molding machine, for example.

  It is a longitudinal cross-sectional view which shows the open state of the valve gate of embodiment of this invention.   It is AA sectional drawing of FIG.   It is a longitudinal cross-sectional view which shows the closed state of the valve gate of embodiment of this invention.   It is AA sectional drawing of FIG.   It is a principal part enlarged view of FIG.   It is an external view of the valve body of the embodiment of the present invention.   It is a longitudinal cross-sectional view of the pinion gear of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed type 2 Movable type 3 Cavity 4 Fixed side mold plate 5 Fixed side receiving plate 6 Fixed side mounting plate 7 Locating ring 8 Bushing hole 9 Valve gate installation hole 10 Valve gate 11 Main body part 12a Rectangular part 12b Cylindrical part 12c Dividing part 13 Pinion gear accommodation hole 14 Rack guide hole 15 Gate hole 16 Mold mating part 17 Valve guide hole 20 Nozzle touch part 21 Cover 22 Sleeve 23 Flange plate 24 Mounting bolt 30 Air cylinder (drive means)
31 Rack 32 Pinion gear 33 Drive internal thread 34 Thrust ring 35 Cylinder rod 36 Stopper holder 37 Stopper bolt 38 Stay 41 Valve body 42 Channel hole 43 Communication hole 44 Small diameter shaft 45 Large diameter shaft 46 Taper portion 47 Drive male screw 48 Upper end portion 50 Material flow Channel 51 Material channel inlet 61 Taper ring 62 Spring 71 Cartridge heaters 72a, 72b Sheath heater 90 Injection molding machine nozzle

Claims (2)

  A valve gate for use in a hot runner mold for injection molding, a material flow passage inlet communicating with an injection molding machine nozzle, and a main body having a gate hole facing the mold cavity, and coaxial with the gate hole A valve body that operates to open and close the gate hole, and a drive means for driving the valve body, and a flow path hole formed from the upper end surface to just before the lower end along the central axis of the valve body, It has one or more communication holes communicating with the flow path hole from the side surface near the lower end of the valve body, the upper end of the flow path hole is connected to the material flow path inlet, and the communication hole is connected to the gate hole. The valve body is moved up and down along the central axis by the driving means. When operated upward, the gate hole is opened, and when operated downward, the valve body is centered at the lower end of the valve body. Formed into Small diameter shaft Configured for injection molding hot runner mold valve gate to block the gate hole.   The valve body in which the rack connected to the driving means reciprocates in the horizontal direction, the pinion gear meshing with the rack rotates in the horizontal direction, and the drive female screw formed on the inner periphery of the pinion gear does not rotate by itself. 2. The valve gate of a hot runner mold for injection molding according to claim 1, wherein the valve body is configured to operate in the vertical direction by being screwed into a drive male screw formed on the outer periphery of the mold.

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