JP2009190386A - Valve gate of hot runner mold for injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust gate cut height at valve closing time, a flow rate, etc. at the valve opening time in a valve gate for opening and closing the valve by going and returning operations of a driving means, alternatively, to prevent internal pressure from being raised by suddenly compressing material in a valve gate tip interior at the closing operation time, and, further, to prevent the damage of a driving part in case that the valve cannot be normally operated. <P>SOLUTION: An electric driving means is used as driving means of a valve body 41. In a structure that the valve body 41 is vertically operated by the drive of a motor driven cylinder 121 to open and close a gate hole 15, the closing position, the opening position of the valve can be adjusted by positioning the advanced and returned positions of a motor driven cylinder rod 125. Alternatively, the operating speed and a thrust at each operating position can be controlled. Further, the overload of the valve is detected, and the drive can be stopped. <P>COPYRIGHT: (C)2009,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 and 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 them, the most common structure is that a cylinder is disposed directly above the gate hole above the manifold (on the fixed mounting plate side), and the valve pin penetrates the manifold, and the material flow path is coaxially cut. . 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. There are problems such as necessary, (3) space in the height direction (usually fixed mounting plate thickness), (4) mold assembly and poor maintainability. Further, as a means for solving the problems (1) to (4), a valve gate having a structure in which a special annular cylinder device is provided around a central axis is also known.
However, as a problem common to these structures, (5) since the valve pin vertically cuts through the material flow path or because a part of the flow path is curved, flow resistance is generated, and the flow rate is limited. 6) Since the cylinder is located near the heater, air-tight members such as O-rings and packings are susceptible to deterioration due to heat. (7) General air supply, especially when the valve pin is operated directly by an air cylinder. At a pressure (0.5 to 0.8 MPa), there is a problem that it is necessary to use a large air cylinder to obtain the thrust of the valve pin.

  Therefore, in order to solve the problems (5) to (7), in the valve gate previously filed in Japanese Patent Application No. 2006-275789 by the applicant of the present invention, (5) the valve material flow path is the valve body. Since it is configured in a substantially straight line except for a part of the tip, the flow resistance is small and the flow rate can be increased. (6) Since the drive means is disposed at a position away from the high temperature main body, Deterioration due to heat can be prevented. (7) Since the structure of driving the valve body by amplifying the thrust of the drive means by screwing the drive screw and transmitting the force, the thrust of the valve body is increased. The effect of being able to be obtained.

An embodiment of the prior invention will be described with reference to FIGS. 1 to 3 and 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 prior invention, the main body portion 11 and the nozzle touch portion 20 are integrated, and are 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 to form an inner tapered portion 18. In addition, a rack guide hole 14 is formed on a horizontal axis that is orthogonal to the pinion gear accommodation hole 13 and is substantially separated from the radius.
A cartridge heater 71 is inserted into the rectangular portion 12a, and heaters 72a and 72b are attached to the cylindrical portion 12b so that the main body portion 11 can be heated to the molding temperature of the material.

A rack 31 is slidably inserted inside the rack guide hole 14. Further, an air cylinder (driving means) 30 is fixed to the side surface of the stationary side receiving plate 5 via a stay 38, and a rod joint 31a attached to the end of the rack 31 and a drive attached to the end of the cylinder rod 35. The bar 35a is connected. Therefore, the rack 31 reciprocates in the rack guide 14 with the operation of the air cylinder 30.
When the mold is large and the distance from the main body portion 11 to the side surface of the fixed side receiving plate 5 is long, the drive bar 35a is lengthened. The longer this distance is, the less heat is transferred to the air cylinder 30 when the main body 11 is heated by the heater, and it is possible to prevent the air-tight members such as the O-ring and packing of the air cylinder 30 from being deteriorated by heat.
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 air cylinder 30, and the advance limit of the cylinder rod 35 and the rack 31 is adjusted by adjusting the tightening amount of the stopper bolt 37. It can be regulated. Here, the cylinder stroke when the forward limit is restricted is represented as Sc.
When a hydraulic cylinder is used as the driving means instead of the air cylinder 30, the hydraulic pressure is usually 10 times higher than the air pressure, so that a very high thrust can be obtained.

  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, an outer taper portion 46, and a small-diameter shaft 44, and the communication hole 43 communicating from the outer taper portion 46 to the flow passage hole 42 is oblique to the central axis. Communicates.
For the purpose of constituting the flow path, the communication hole 43 may be one place or several places in the equally divided direction. In the case of one location, the flow direction of the material is concentrated. Therefore, when the material is a resin, it is difficult for welds to appear in the molded product, but the pressure distribution may be biased. On the other hand, if the material is divided into several places, the material flow becomes a split flow, which may cause welds in the molded product. However, in terms of flow balance, it is considered that the flow can be made uniform in all directions.
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.
The drive male screw 47 and the drive female screw 33 are triple-threaded screws, and are less likely to be tilted by screwing than the single-threaded screws, 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 bearing 34 a is placed at the bottom of the pinion gear accommodation hole 13. Next, the rack 31 is placed at the retreat limit position, while the valve body 41 and the pinion gear 32 are connected to the main body portion in a state where the drive female screw 33 of the pinion gear 32 is screwed into the valve stroke upper end position. 11 and put on the thrust bearing 34a. 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).
Further, another thrust bearing 34b is placed on the pinion gear. The thrust bearings 34a and 34b can reduce rotational friction of the pinion gear 32.

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 of the prior invention, the pitch circle diameter and the number of teeth of the pinion gear 32 and the drive female screw 33 and the drive male screw 47 are adjusted so that the cylinder stroke Sc is 40 mm, the valve stroke Sv is 6 mm, and the stroke ratio R is 0.15. The pitch is set. If the conversion efficiency of the driving force by the gear and screw is 100%, the thrust of the valve body 41 is amplified to the reciprocal times of the stroke ratio R with respect to the thrust of the air cylinder 30, that is, 6.7 times in this example. Actually, however, it is assumed that the conversion efficiency η is 45%, and the amplification factor is about 3 times.

Next, the upper structure of the main body 11 will be described. The cover 21 is coaxially attached to the upper portion of the pinion gear accommodation hole 13 of the main body 11 and is engaged with the inner diameter of the binion 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.

The above is description of embodiment of prior invention. In this embodiment, the gate is coaxial with the nozzle touch portion, that is, a case where one valve gate is arranged at the mold center, but a plurality of gates are arranged under the manifold and used for a multipoint gate. In this case, the nozzle touch portion 20 of the flange plate 23 changes to a connection shape with the flow passage hole of the manifold.
Moreover, it is not limited to the valve gate for metal mold | dies, For example, it can also be used as a shut-off valve for the nozzle of an injection molding machine.

In the valve gate embodiment of the invention of the prior application, an air cylinder or a hydraulic cylinder is used as the driving means. However, the operating characteristics of the air cylinder and the hydraulic cylinder only reciprocate between two positions, the backward limit and the forward limit. is there. That is, it only operates to a position where the piston is forcibly stopped depending on whether air or hydraulic pressure is supplied to the rear port or the front port of the piston. The operating force is determined by the size of air pressure or hydraulic pressure, the operating speed is determined by the supply amount of the air or hydraulic source and the throttle of the pipe, and the force and speed cannot be changed freely during one operation. .
Due to its operating characteristics, the following problems arise.

(1) The relationship between the forward / backward direction of the cylinder rod 35 and the vertical operation direction of the valve body 41 is such that the valve body 41 descends and the valve is closed when the cylinder rod 35 moves forward.
Incidentally, it may be necessary to finely adjust the valve closing position. For example, when the pinion gear 32 is assembled to the main body 11 and meshed with the teeth of the rack 31, the valve body height moves by about 0.5 mm if one tooth is displaced. Moreover, a level | step difference can arise according to the thermal expansion difference of the valve body 41 and the circumference | surroundings at use temperature (about 200-300 degreeC in resin molding). The height of the gate cut may be the same as the surface of the molded product, or may be slightly concave or convex. Alternatively, it may be considered that the gate tip wears and changes dimensions after long-term use.
For this purpose, in order to finely adjust the valve closing position to a desired position, a stopper holder 36 is provided in the main body 11 and the stopper bolt 37 is adjusted, whereby the forward limit of the cylinder rod 35 can be regulated. . However, the adjustment with the stopper bolt 37 must be performed before the valve gate 10 is assembled to the mold, and cannot be adjusted from outside the mold during the molding.

  (2) Contrary to the problem (1), when the cylinder rod 35 is retracted, the valve body 41 is raised and the valve is opened, but there is no structure for adjusting the retracting limit of the cylinder rod 35, that is, the valve opening position. . Adjusting the valve opening position is considered to be effective when the maximum flow path area is changed and particularly when it is desired to adjust the flow rate of each gate with a multi-point gate, but this cannot be done in the embodiment of the invention of the prior application.

(3) Detailed views of the vicinity of the gate hole 15 in the process of moving the valve from the open position to the closed position are shown in FIGS. (A) is a fully open state, (b) is a half-open state, (c) is a transition point for shifting to a closed state, and (d) is a closed state.
In the inner shape of the lower end portion of the main body portion 11, an interval between the valve guide hole 17 and the gate hole 15 is an inner tapered portion 18. On the other hand, the lower end shape of the valve body 41 includes an outer tapered portion 46 and a small diameter shaft 44. The molten material flowing out from the communication hole 43 of the valve body 41 is accumulated in a space Rm sandwiched between the inner tapered portion 18 and the outer tapered portion 46. (A) shows a state where the valve stroke Sv is opened. As the volume shifts from (a) to (b), the volume of the space Rm decreases, but the accumulated material flows into the cavity 3 from the gate hole 15.
(C) is a state in which the gate hole 15 is opened by the seal length K. Since the gate hole 15 is blocked below this position, the molten material corresponding to the volume reduction of the space Rm between (c) and (d). Is considered to flow backward from the communication hole 43 to the flow path hole 42 or to be compressed in the space Rm. Therefore, there is a possibility that a resistance force is generated against the lowering operation of the valve body 41. Further, in the case of a resin material having a particularly high viscosity, even when the valve body is lowered between (a) and (b), the flow into the gate hole 15 does not catch up and a part of the material passes through the communication hole 43. There is a possibility that the flow reversely flows into the flow path hole 42 or is compressed in the space Rm and a resistance force is generated against the lowering operation of the valve body 41.
Rapid compression of the molten material may denature the physical properties, and the operating resistance of the valve body 41 is undesirable because it reduces the gate seal force. Therefore, if the valve operating speed is changed according to the closing stage, for example, if the control can be performed such that the speed is reduced at the portion where compression occurs, sudden compression can be avoided and the operating resistance can be minimized. Yes, this is not possible with air cylinders or hydraulic cylinders.

Further, explanation will be made by applying mathematical formulas and numerical examples. In FIG.
φD1 (the outer diameter of the large diameter portion 45 of the valve body 41 = the inner diameter of the valve guide hole 17) = φ16 mm
φD2 (inner diameter of flow path hole 42) = φ8 mm
φG (inner diameter of gate hole 15) = φ5 mm
In this case, the pressure receiving area of the force that resists the valve body 41 from being lowered (the valve is closed) is
Av (pressure receiving area of the valve body) = (π / 4) × (φD1 ² −φD2 ² ) ≈150 mm ²
Ag (gate pressure receiving area) = (π / 4) × φG2 ² ≈20 mm ²
Am (pressure receiving area of space Rm) = Av−Ag = 130 mm ²
Can be calculated. For Av and Am, the area of φD2 is deducted on the assumption that it helps to lower the valve body 41.
When the internal pressure of the space Rm is Pm and the internal pressure applied from the cavity 3 to the gate hole 15 is Pg, the drag Fm that resists lowering the valve body 41 is
When (a) to (c) (assuming Pm = Pg),
Fm = Pg × Av
In the case of (c) to (d), if the material corresponding to the volume reduction of the space Rm can flow back to the flow path hole 42,
Fm = Pg × Ag
However, when backflow is not possible and the internal pressure rises due to compression in the space Rm,
Fm = Pm × Am + Pg × Ag
It becomes. On the other hand, the thrust Fv of the valve body 41 is determined by the thrust Fh of the air cylinder 30 and the conversion efficiency η, and the conditions for lowering the valve body 41 (closing the valve) are:
Fv = Fh × 6.7 × η> Fm
It becomes.
When the bore diameter of the air cylinder is 63 mm, the air pressure is 0.5 MPa, and the conversion efficiency η is 45%, Fv is about 4650 N, Pg is about 30 MPa or less with respect to the pressure receiving area Av (150 mm ² ), and the pressure receiving area Ag (20 mm) ^{For 2} ), it is considered that the valve can be closed when Pg is about 230 MPa or less (reverse flow to the channel hole is possible).
For example, if the Pg at the time of filling is about 50 to 60 MPa and the Pg after holding pressure is 20 MPa in the molding of the resin material PP (polypropylene), if the valve is closed after holding pressure, this numerical example has a sufficient margin. It can be said.

(4) Consideration of the problem (3) assumes that the material is in a sufficiently molten state, but in reality, the filling of the material depends on the balance between the temperature at the lower end of the valve gate and the mold temperature. At the same time, the possibility of cooling and solidification must also be considered. When the heater set temperature of the valve gate or the mold temperature is lower than the appropriate temperature, if the cooling is fast, the stage of FIG. 4 (c) to (d), or if the cooling is faster, (b) to (c) Even at the stage, the material in the flow path may solidify or semi-solidify. As the material viscosity increases, the thrust to close the valve may be more than the value calculated by the formula below.
Further, if the valve body 41 is forcibly actuated in a state where the tip is in contact with the solidified material, a load is applied to the drive unit, and there is a possibility that parts such as the drive female screw 33 of the pinion gear 32 are damaged. In order to prevent this, it is considered that an effective method is to provide means for detecting an overload to the drive unit and stop the power source. However, this is not possible with air cylinders or hydraulic cylinders.

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 electric drive 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.
Then, the rack connected to the electric drive 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. 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.

  A valve gate according to a second aspect of the present invention is configured by using a driving device combining a servo motor and a ball screw, or an integrated electric cylinder as the electric driving means.

The valve gate according to the present invention solves the problems of the valve gate of the prior invention and produces the following effects.
(1) By positioning the forward limit of the electric drive means, the gate cut height can be adjusted without disassembling the mold even after the mold is assembled. Further, the stopper bolt 37 of the prior invention is not required, and the valve gate assembly hole 9 can be made small.
(2) The valve opening position can be adjusted by positioning the retracting limit of the electric drive means, which is particularly effective when the flow rate for each gate is to be adjusted with a multipoint gate.
(3) The operating speed of the electric drive means can be changed stepwise, for example, a low speed at the initial operation from the valve open state to the closed state, a high speed in the middle, and a low speed at the end. Thereby, it is possible to prevent the material inside the valve gate tip from being rapidly compressed and the internal pressure from rising.
(4) When the material in the gate hole cools and solidifies quickly, and the valve body 41 cannot operate normally, the overload is detected and the drive is stopped to prevent the drive part from being damaged. Can do.

In the first embodiment, a drive device in which a servo motor and a ball screw are combined is used as the electric drive means, and an example of the device is shown in FIGS.
The fixed side (right side in the figure) of the shaft of the ball screw 111 is rotatably inserted into the support block 113 and is prevented from being removed by a nut 114, and the support block 113 is fixed to the base 118. On the other hand, the support side is rotatably inserted into the bearing 115 and supported. A table 116 is attached to the movable portion 111 a of the ball screw 111, and the table 116 moves linearly by being guided by a slide guide 117 on the base 118.
The fixed side of the shaft of the ball screw 111 is also connected to the rod of the servo motor 101 via the coupling 112. An amplifier 102 and a controller 103 are connected to the servo motor 101. According to the control program, the servo motor 101 rotates at a predetermined speed to a predetermined displacement amount, whereby the ball screw 111 rotates and the table 116 moves at a predetermined distance at a predetermined speed.
A drive bar 35a is fixed to the table 116. When the apparatus is attached to the mold, the drive bar 35a and the rod joint 31a attached to the end of the rack 31 are connected to operate the table 116. In operation, the rack 31 is operated.
About the action | operation of the valve gate which attached the electric drive device of Example 1, it applies to description of the example of operation of the following Example 2. FIG.

Next, the second embodiment uses an integrated electric cylinder as the electric drive means, and the overall size can be reduced as compared with the first embodiment. Some integrated electric cylinders on the market are called mechanical cylinders or robo cylinders depending on the manufacturer, but basically they are composed of an electric cylinder 121, an amplifier 122, and a controller 123 as shown in FIG. The positioning and speed can be changed by the control program.
For example, an electric cylinder having the following specifications is selected as an application example.
Stroke: 50mm
Maximum thrust: 400N
Maximum speed: 200mm / s
In general, the thrust of an electric cylinder is weaker than that of an air or hydraulic cylinder. Since the relationship between the speed and the thrust is as shown in FIG. 10, it is desirable that the speed is switched to a low speed when the thrust is required and the speed is switched to a high speed when the thrust is not so required.

In FIGS. 11 and 12, the driving means is changed to the electric cylinder according to the second embodiment of the present invention as compared with FIGS. 1 and 2 showing the embodiment of the invention of the prior application.
The electric cylinder 121 is fixed to the side surface of the stationary receiving plate 5 via the stay 38, and drives the rack 31 by connecting the rod joint 31a and the drive bar 35a attached to the end of the electric cylinder rod 125. To do. By electrically positioning the forward limit of the electric cylinder rod 125, the stopper bolt 37 of the prior invention is unnecessary.
Other structural aspects are the same as those of the embodiment of the prior invention.

Next, an operation example of the valve gate according to the second embodiment will be described. In addition, Example 1 can be described similarly except that the numerical value in the description is exemplified by the numerical value of Example 2.
First, as shown in FIG. 11, in the example in which the valve gate is disposed at the mold center, the injection molding machine nozzle 90 is pressed against the nozzle touch unit 20. In another example (not shown), one or a plurality of valve gates may be disposed under the manifold block. In this case, the nozzle touch portion 20 of the flange plate 23 is connected to the flow passage hole of the manifold block. The connection shape changes.
Further, the valve of the valve gate 10 is closed except during molding. Before starting the injection molding, with the valve closed, the cartridge heater 71 and the heaters 72a and 72b are energized to heat the main body 11 and melt the material in the material flow path 50. When the molten material is a resin, the heating temperature is about 200 to 300 ° C.

  When injection molding is started, when an injection start signal is sent from the molding machine to the controller 123 of the electric cylinder 121, the electric cylinder rod 125 returns to the backward limit, and the valve is opened. 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. At this time, the flow rate of the material can be controlled by positioning the retracting limit of the electric cylinder rod 125 and adjusting the valve opening position. Particularly in the case of a multipoint gate, it is effective for adjusting the flow rate of each gate.

  Subsequently, after a predetermined time has elapsed from the injection start signal, when the valve body 41 of the valve gate 10 is operated to a closed position by operating the electric cylinder rod 125 at a predetermined speed and a predetermined displacement amount, the small-diameter shaft 44 is moved. The material is engaged with the gate hole 15, the material flow is cut off, and the gate is cut. At this time, the height of the gate cut may be the same as the surface of the molded product, or may be slightly concave or convex. By positioning the forward limit and adjusting the valve closing position, the gate cut height can be easily adjusted without disassembling the mold. The same adjustment can be made when the valve tip is worn.

Further, the details of the operation from the valve open state to the closed state will be described with reference to FIGS. 4 and 10 by applying the numerical formula cited in the consideration of the problem (3) of the prior invention and the numerical example of the electric cylinder. To do. It is assumed that the gear conversion efficiency η is 45% and the amplification factor is about 3 times.
1. When the internal pressure Pg of the cavity 3 drops to 5 MPa or less in the state shown in FIG. 4A after the material has been filled in the cavity 3, the drag Fm that resists closing the valve is equal to the pressure receiving area Av (150 mm ² ). On the other hand, it is 750 N or less. When the speed of the electric cylinder 121 is 50 mm / s and the thrust force Fh = 250N is obtained, the thrust force Fv of the valve body 41 is about three times 750N, and thus the valve body 41 can be lowered.
However, it can be said that it is disadvantageous that an air cylinder having a cylinder diameter φ63 moves even when the internal pressure Pg is about 30 MPa, whereas the valve does not move unless the internal pressure Pg is about 5 MPa or less.
2. Assuming that the internal pressure Pm of the space Rm drops to 1 MPa during operation, the drag Fm drops to 150 N with respect to the pressure receiving area Av (150 mm ² ). Then, the speed of the electric cylinder 121 is set to a high speed of 150 to 200 mm / s, and the valve body 41 can be moved even when the cylinder thrust Fh = 50 N and the valve body thrust Fv = 150 N.
3. Since the pressure receiving area changes to Ag (20 mm ² ) from the moment when the valve is closed (FIG. 4C), when the internal pressure Pm of the space Rm is 1 MPa, the drag Fm decreases to 20 N, and the cylinder thrust Fh = 50 N against the valve body The thrust Fv = 150N is sufficiently strong. However, when the material corresponding to the volume reduction of the space Rm cannot sufficiently flow backward from the communication hole 43 to the flow path hole 42, the material is compressed in the space Rm, the internal pressure is increased, and the resistance is increased. Moreover, it is considered that it is preferable to move slowly in order to avoid the material property from being changed due to rapid compression. Therefore, during the period from FIG. 4C to FIG. 4D (fully closed state), the electric cylinder 121 is preferably operated at a low speed and with a high thrust.
4). When returning from the closed state to the open state before the next shot is ejected, no load is applied, and therefore, it may be operated at a high speed.

  When there are multiple valve gates (multi-point gates), the timing of closing operation does not need to be the same, but it is used for the purpose of moving the weld position in resin molding by shifting the timing for each gate. it can.

  In addition, even if the valve body 41 cannot be normally operated due to the material in the gate hole being cooled and solidified quickly, for example, because the heater set temperature or the mold temperature of the valve gate 10 is lower than the appropriate temperature, Since the cylinder 121 has a protection function against an overload, the drive portion can be prevented from being damaged by stopping the drive.

It is a longitudinal cross-sectional view which shows the closed state of the valve gate of prior invention. It is AA sectional drawing of FIG. It is a principal part enlarged view of the longitudinal cross-sectional view which shows the open state of the valve gate of prior application invention. (A), (b), (c), (d) It is detail drawing which shows each state from a valve open to a closed in FIG. It is an external view of the valve body of embodiment of a prior application invention. It is a longitudinal cross-sectional view of the pinion gear of embodiment of prior invention. It is a top view which shows the drive device of Example 1 of this invention. It is a longitudinal cross-sectional view of FIG. It is explanatory drawing which shows the electric cylinder of Example 2 of this invention. It is a speed-thrust characteristic diagram of the electric cylinder of Example 2 of the present invention. It is a longitudinal cross-sectional view which shows the closed state of the valve gate of Example 2 of this invention. It is AA sectional drawing of FIG.

Explanation of symbols

3 Cavity 9 Valve Gate Assembly Hole 10 Valve Gate 11 Body 15 Gate Hole 17 Valve Guide Hole 18 Inner Taper 30 Air Cylinder (Drive Unit)
31 Rack 31a Rod joint 32 Pinion gear 33 Drive female screw 35 Cylinder rod 35a Drive bar 37 Stopper bolt 41 Valve body 42 Flow path hole 43 Communication hole 44 Small diameter shaft 45 Large diameter shaft 46 Outer taper portion 47 Drive male screw 50 Material flow path 101 Servo motor 111 Ball screw 121 Electric cylinder 125 Electric cylinder rod

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 body portion 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 electric drive means for driving the valve body,
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 channel hole is connected to the material channel inlet, and the communication hole is formed to be connected to the gate hole,
The valve body is moved up and down along the central axis by the driving means, and when operated upward, the gate hole is opened. When operated downward, the valve body is formed at the center of the lower end of the valve body. The small diameter shaft is configured to block the gate hole,
The valve connected to the electric drive means reciprocates in the horizontal direction, a 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. A valve gate of a hot runner mold for injection molding, 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 body.   The valve gate of the hot runner mold for injection molding according to claim 1, wherein the electric drive means is configured by using a drive device combining a servo motor and a ball screw, or an integrated electric cylinder.

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