JP3620724B2 - Molding device for electric injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mold clamping device of an electric injection molding machine provided with a double toggle mold clamping mechanism that opens and closes a mold and applies a mold clamping force to the mold.
[0002]
[Prior art]
Conventional double toggle mold clamping devices include those shown in FIGS. 4, 5, and 6. In FIG. 4, the fixed platen 1 and the mold clamping housing 2 are connected by a plurality of tie bars 3, and the movable platen 4 arranged to face the fixed platen 1 is disposed along the tie bar 3 so as to freely advance and retract. .
[0003]
Toggle link mechanisms 5 a and 5 b are arranged symmetrically between the mold clamping housing 2 and the movable platen 4. The toggle link mechanisms 5 a and 5 b are connected via a single crosshead 7. Yes. The toggle link mechanisms 5 a and 5 b are swingable on the movable platen 4, a drive link 9 that is swingably supported by the crosshead 7, a first driven link 10 that is swingably supported by the mold clamping housing 2, and the movable platen 4. The second driven link 11 is supported by the link link between the drive link 9 and the first driven link 10, and between the first driven link 10 and the second driven link 11, respectively. Linked by a bush.
[0004]
The screw mechanism 6 includes a screw shaft 12 that is rotatably supported with respect to the mold clamping housing 2, and a nut 13 that is disposed on the crosshead 7 and screwed onto the screw shaft 12. Can be driven to rotate by a driving device including a servo motor and a timing belt (not shown).
[0005]
When one screw mechanism 6 is mounted, it is disposed at the center of the opposing toggle link mechanisms 5a and 5b as shown in FIG. 5, and when a plurality of screw mechanisms 6 are mounted, the toggle link mechanism 5a is mounted as shown in FIG. 5b is arranged orthogonal to the opposing direction (horizontal direction in the figure).
[0006]
Next, the operation of the conventional mold clamping device will be described.
[0007]
When the drive device is driven to rotate the screw shaft 12 of the screw mechanism 6, the rotational motion of the screw shaft 12 is converted into the linear motion of the nut 13, and the crosshead 7 advances and retreats. As a result, the toggle link mechanisms 5a and 5b are bent, the movable platen 4 is advanced and retracted along the tie bar 3, and the movable die 8a attached to the movable platen 4 is brought into contact with the fixed die 8b attached to the fixed platen 1. Release the mold, close the mold, clamp and open the mold.
[0008]
The mold clamping operation will be described in detail.
When the drive device is driven to rotate the screw shaft 12 of the screw mechanism 6 in the mold clamping direction, the nut 13 moves forward (moves toward the fixed platen 1) from the mold opening position, and the cross head 7 moves forward together with the nut 13. As the head advances, the crosshead 7 pushes the drive link 9, then the drive link 9 pushes the first driven link 10, then the first driven link 10 pushes the second driven link 11, and the toggle link mechanisms 5 a and 5 b extend. To do. As a result, the movable platen 4 moves forward along the tie bar 3, and the movable mold 8a comes into contact with the fixed mold 8b to enter the mold touch state. When the screw shaft 12 is further rotated to advance the nut 13, the movable mold 8 a is pressed against the fixed mold 8 b, a mold clamping force is applied to the mold, and mold clamping is performed. In this way, the resin injected by an injection device (not shown) is filled in the clamped mold, cooled and solidified, and a molded product is formed.
[0009]
Next, the mold opening operation will be described in detail.
When the drive device is driven to rotate the screw shaft 12 of the screw mechanism 6 in the direction opposite to the mold clamping direction, the nut 13 moves backward (moves in the direction of the mold clamping housing 2), and the cross head 7 moves backward together with the nut 13. To do. As the head moves backward, the crosshead 7 pulls the drive link 9, then the drive link 9 pulls the first driven link 10, and then the first driven link 10 pulls the second driven link 11, and the toggle link mechanisms 5 a and 5 b Bend. As a result, the movable platen 4 moves back along the tie bar 3 and mold opening is performed. Subsequently, an ejector pin (not shown) protrudes from the movable mold 8a, and the molded product is taken out.
[0010]
[Problems to be solved by the invention]
However, the conventional double toggle mold clamping device has the following problems.
In other words, the toggle link mechanisms 5a and 5b arranged vertically opposite to each other are designed on the assumption that they are geometrically symmetrical with respect to the upper and lower sides. The direction, the lubrication state of the link coupling portion, and the clearance due to sliding wear of the link coupling portion are different between the upper and lower toggle link mechanisms 5a and 5b. As a result, the toggle link mechanisms 5a and 5b are geometrically asymmetric in the vertical direction in the load state when the toggle link mechanisms 5a and 5b are operated. For this reason, in the load state of the mold opening and closing process and the mold clamping process, a vertical difference is generated in the reaction force received by the link coupling portion (cross link support point) of the single cross head 7 with the drive link 9, resulting in the cross head 7. A tipping moment acts and the geometric symmetry cannot be maintained. The overturning moment acting on the single crosshead 7 increases as the degree of geometrical asymmetry of the toggle link mechanisms 5a, 5b increases and the load increases. In order to solve this, conventionally, in order to make it easy to linearly move the crosshead forward and backward, a crosshead guide device is provided, and the rigidity of the crosshead 7 is increased. There is a problem that the degree of this weakness increases with operation.
[0011]
Further, since the screw mechanism 6 is disposed perpendicular to the direction (vertical direction) of the opposing arrangement of the toggle link mechanisms 5a and 5b, the distance between the nut 13 disposition position of the cross head 7 and the cross link support position is as follows. Inevitably longer. For this reason, the crosshead overturning moment due to the vertical difference in the reaction force received by the crosslink support point of the crosshead 7 increases, and the degree of geometrical asymmetry of the toggle link mechanisms 5a and 5b increases. As a result, the parallelism of the movable platen 4 with respect to the fixed platen 1 at the time of mold opening / closing deteriorates, the mold guide pin is bent, or the mold clamping force generated in the mold is not uniform in the vertical direction, resulting in molding failure. It may become.
[0012]
Also, when molding with molds such as molded products with asymmetrical upper and lower shapes or molded products with different upper and lower thicknesses, the resin pressure in the mold cavity in the injection process after mold clamping becomes uneven and the mold opens The power will be different up and down. As described above, the mold clamping force before injection is not uniform in the vertical direction, and the mold opening force is not uniform in the vertical direction, the mold opening amount is also nonuniform, and burrs are likely to occur partially. The other part has a problem that it becomes a short shot.
[0013]
In addition to this, an example in which a plurality of screw mechanisms 6 are mounted is disclosed in JP-A-2001-212855. This is achieved by using a synchronization device in which a synchronization timing belt is wound around a synchronization timing pulley attached to each screw mechanism 6 or a synchronization device in which each screw mechanism 6 is connected by a plurality of synchronization gears engaged with each other. Each screw mechanism 6 is caused to perform a synchronous operation.
[0014]
However, when a plurality of screw mechanisms 6 are mounted, the screw mechanisms 6 are synchronized with each other by using a synchronization device such as a gear or a timing belt. Occurs. Since the arrangement direction of the screw mechanism 6 is orthogonal to the opposing arrangement direction of the toggle link mechanisms 5a and 5b, the link pins and bushes provided at the fulcrum portions of the links 9, 10, and 11 when the synchronization shift occurs. Unbalanced load acts in the axial direction. For this reason, uneven wear of the bush is promoted, the mold clamping system is deteriorated, and the life of the bush may be shortened.
[0015]
The present invention is to solve such problems.
[0016]
[Means for Solving the Problems]
The present invention is to solve the conventional problems as described above. In other words, each screw mechanism is equipped with a drive device, each screw mechanism is arranged in the same direction as the opposing arrangement direction of the toggle link mechanism, and each screw mechanism is driven in synchronization to reduce the crosshead overturning moment. The toggle link mechanism can maintain the geometric symmetry, and even if a synchronization shift occurs between each screw mechanism, the influence of the offset load due to the synchronization shift is prevented, and the mold parting surface immediately before the mold touch is prevented. An object of the present invention is to provide a mold clamping device for an electric injection molding machine that can control the position by changing the opening amount.
[0017]
According to the first aspect of the present invention, the movable die (8a) is attached by driving the screw mechanism (6) by a driving device such as an electric motor to move the single crosshead (7) forward and backward. The toggle link mechanism (5a, 5b) disposed oppositely between the movable platen (4) and the mold clamping housing (2) is expanded and contracted, and the movable platen (4) is attached to the fixed mold (8b). In a mold clamping device of an injection molding machine that moves forward and backward with respect to a stationary platen (1), toggle link mechanisms (5a, 5b) are connected to each other via a single crosshead (7), and a plurality of screw mechanisms ( 6), and each screw mechanism (6) is provided with a dedicated drive device, and each screw mechanism (6) is in the same direction as the opposing arrangement direction of the toggle link mechanisms (5a, 5b). It is characterized by being arranged.
[0018]
The invention according to claim 2 is characterized in that, in the invention according to claim 1, the plurality of screw mechanisms (6) are configured to be driven in synchronization with each other. It is.
[0019]
According to a third aspect of the present invention, in the first or second aspect of the present invention, each of the screw mechanisms (6) includes a screw shaft (12) that rotates by driving of each of the driving devices, and the cross. Each has a nut (13) disposed on the head (7) and screwed into each screw shaft (12) to convert the rotational motion of the screw shaft (12) into linear motion. Each screw mechanism (6) is driven so as to change the relative position of each nut (13) immediately before the mold clamping is completed.
[0020]
In addition, the code | symbol in the said parenthesis shows the corresponding member of embodiment mentioned later.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a front view showing a mold clamping state of the double toggle mold clamping apparatus according to the embodiment of the present invention, and FIG. 2 is a front view showing a mold open state of the double toggle mold clamping apparatus according to the embodiment of the present invention. FIG. 3 is a side sectional view of the mold clamping device according to the embodiment of the present invention.
[0022]
In the mold clamping apparatus according to the present embodiment, the fixed platen 1 and the mold clamping housing 2 are connected by a plurality of tie bars 3, and the movable platen 4 arranged to face the fixed platen 1 extends along the tie bar 3. It is arranged to be able to advance and retreat. A fixed mold 8b is attached to the fixed platen 1 and a movable mold 8a is attached to the movable platen 4 so as to face each other.
[0023]
Between the mold clamping housing 2 and the movable platen 4, toggle link mechanisms 5 a and 5 b are arranged vertically symmetrically in the figure, and the toggle link mechanisms 5 a and 5 b are arranged via a single crosshead 7. It is connected. The toggle link mechanisms 5 a and 5 b are swingable on the movable platen 4, a drive link 9 that is swingably supported by the crosshead 7, a first driven link 10 that is swingably supported by the mold clamping housing 2, and the movable platen 4. The second driven link 11 is supported by the second driven link 11. The drive link 9 and the first driven link 10 and the first driven link 10 and the second driven link 11 are linked by link pins, bushes or the like.
[0024]
The screw mechanism 6 includes a screw shaft 12 that is rotatably supported with respect to the mold clamping housing 2 and a nut 13 that is disposed on the crosshead 7 and screwed into the screw shaft 12. It can be rotationally driven by a driving device composed of an electric motor (not shown). A plurality of screw mechanisms 6 are arranged in the same direction as the opposing arrangement direction of the toggle link mechanisms 5a and 5b, whereby a link coupling portion (cross link support point) between the nut 13 arrangement position of the cross head 7 and the drive link 9 is arranged. ) And the distance will be shorter than before. Each screw mechanism 6 is provided with the dedicated drive device, and can be driven in synchronization.
[0025]
Next, the operation of the mold clamping device of the present embodiment will be described.
[0026]
When a driving device (not shown) is driven to rotate the screw shaft 12 of the screw mechanism 6, the rotational motion of the screw shaft 12 is converted into the linear motion of the nut 13, and the crosshead 7 advances and retreats depending on the rotational direction of the screw shaft 12. As a result, the toggle link mechanisms 5a and 5b are bent, the movable platen 4 is advanced and retracted along the tie bar 3, the movable mold 8a is brought into contact with and separated from the fixed mold 8b, the mold is closed, and the mold is clamped and opened.
[0027]
The mold clamping operation will be described in detail.
When the drive device is driven to rotate the screw shaft 12 of the screw mechanism 6 in the mold clamping direction, the nut 13 moves forward (moves toward the fixed platen 1) from the mold opening position, and the cross head 7 moves forward together with the nut 13. As the head advances, the crosshead 7 pushes the drive link 9, then the drive link 9 pushes the first driven link 10, then the first driven link 10 pushes the second driven link 11, and the toggle link mechanisms 5 a and 5 b extend. To do. Therefore, the movable platen 4 moves forward along the tie bar 3, and the movable mold 8a comes into contact with the fixed mold 8b to enter the mold touch state. When the screw shaft 12 is further rotated to advance the nut 13, the movable mold 8 a is pressed against the fixed mold 8 b, a mold clamping force is applied to the mold, and mold clamping is performed. Thereafter, resin is injected and filled into the clamped mold by an injection device (not shown), and cooled and solidified to form a molded product.
[0028]
By changing the driving state of each driving device so that the relative position of the nut 13 of each screw mechanism 6 is changed from immediately before the mold touch to completion of mold clamping, mutual generation of the opposing toggle link mechanisms 5a and 5b occurs. The position control is performed by changing the mold clamping force (or compressive force) or changing the opening amount of the mold parting surface immediately before touching the mold between the opposing toggle link mechanisms 5a and 5b. Thereby, it is possible to perform molding in accordance with mold characteristics such as a molded product having an asymmetric shape and molded products having different upper and lower thicknesses.
[0029]
Next, the mold opening operation will be described in detail.
When the drive device is driven to rotate the screw shaft 12 of the screw mechanism 6 in the direction opposite to the mold clamping direction, the nut 13 moves backward (moves in the direction of the mold clamping housing 2), and the cross head 7 moves backward together with the nut 13. To do. As the head moves backward, the cross head 7 pulls the drive link 9, then the drive link 9 pulls the first driven link 10, and then the first driven link 10 pulls the second driven link 11, and the toggle link mechanisms 5 a and 5 b Bend. Therefore, the movable platen 4 moves backward along the tie bar 3 and mold opening is performed. Subsequently, an ejector pin (not shown) protrudes from the movable mold 8a, and the molded product is taken out.
[0030]
During the operation, the distance between the nut 13 placement position of the cross head 7 and the cross link support point is shorter than the conventional distance, so that the cross link support point is caused by a difference in reaction force received from each toggle link mechanism 5a, 5b. Crosshead tipping moment is reduced. As a result, since the geometrical symmetry of the toggle link mechanisms 5a and 5b can be maintained, the parallelism of the movable platen 4 with respect to the fixed platen 1 at the time of mold opening and closing can be maintained with high accuracy and uniform over the entire mold. Clamping force is generated. Even if a synchronization shift occurs between the screw mechanisms 6, the load distribution acting on the link pins and bushes provided at the fulcrum portions of the links 9, 10, 11 of the toggle link mechanisms 5 a, 5 b is in the axial direction. And uniform.
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, the toggle link mechanisms are connected to each other via a single cross head, and a plurality of screw mechanisms are arranged in the same direction as the opposing arrangement direction of the toggle link mechanism. By disposing in the direction, the distance between the nut disposition position of the single cross head and the cross link support point is shorter than in the conventional case. As a result, the crosshead overturning moment due to the vertical difference in reaction force that the crosslink support point receives from each toggle link mechanism is reduced, and the geometric symmetry of the toggle link mechanism can be maintained. For this reason, the parallelism of the movable platen with respect to the fixed platen when the mold is opened and closed can be maintained with high accuracy, and a uniform mold clamping force can be generated in the entire mold.
[0032]
Further, conventionally, when a synchronization shift occurs between the screw mechanisms, there is a difference in the acting force on the opposite toggle link mechanism due to the influence of the offset load due to the synchronization shift. By shortening the distance between the nut disposition position and the cross link support point as compared with the prior art, it is possible to prevent an unbalanced load from acting in the axial direction of the link pin or bush provided at the fulcrum portion of each link.
[0033]
Further, in the invention according to claim 2 among the present inventions, in the invention according to claim 1, each driving device can drive each screw mechanism such that a plurality of screw mechanisms are driven in synchronization with each other. .
[0034]
Further, among the present inventions, the invention according to claim 3 is the invention according to claim 1 or 2, wherein a change in generated clamping force (or compressive force) between the opposing toggle link mechanisms or an opposing toggle link mechanism is provided. Position control can be performed by changing the opening amount of the mold parting surface immediately before the mutual mold touch. This allows molding to match the mold characteristics of molded products with asymmetric shapes, molded products with different upper and lower thicknesses, etc., injection while controlling at the position immediately before touching the mold, and multistage control during or after injection Advanced injection compression molding methods such as this are possible.
[Brief description of the drawings]
FIG. 1 is a front view showing a mold clamping state of a mold clamping apparatus according to an embodiment of the present invention.
FIG. 2 is a front view showing a mold opening state of the mold clamping device according to the embodiment of the present invention.
FIG. 3 is a side sectional view of a mold clamping device according to an embodiment of the present invention.
FIG. 4 is a front view showing a mold clamping state of a conventional mold clamping apparatus.
FIG. 5 is a side sectional view showing a conventional mold clamping device.
FIG. 6 is a side sectional view showing another conventional mold clamping device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Clamping housing 4 Movable platen 5a, 5b Toggle link mechanism 6 Screw mechanism 7 Cross head 8a Movable die 8b Fixed die 12 Screw shaft 13 Nut

Claims (3)

By driving the screw mechanism (6) by advancing and retracting a single crosshead (7) by the drive unit such as an electric motor, a mold clamping housing movable platen movable mold (8a) is attached (4) (2 ) And the toggle link mechanism (5a, 5b) disposed opposite to each other, and the movable platen (4) is moved forward and backward with respect to the fixed platen (1) to which the fixed mold (8b) is attached. In the mold clamping device of the molding machine,
The toggle link mechanisms (5a, 5b) are connected via a single crosshead (7),
A plurality of screw mechanisms (6) are provided, and each screw mechanism (6) is provided with a dedicated drive device, and each screw mechanism (6) is arranged opposite to the toggle link mechanism (5a, 5b). A mold clamping device for an electric injection molding machine, wherein the mold clamping device is arranged in the same direction as the direction. The mold clamping apparatus for an electric injection molding machine according to claim 1, wherein the plurality of screw mechanisms (6) are configured to be driven in synchronization with each other. Each screw mechanism (6) includes a screw shaft (12) that is rotated by driving of each driving device, and a screw shaft that is disposed on the cross head (7) and screwed to each screw shaft (12). Nuts (13) for converting the rotational movement of (12) into linear movements, and each screw mechanism (6) is relative to each nut (13) immediately before the mold touch and between the completion of mold clamping. 3. The mold clamping apparatus for an electric injection molding machine according to claim 1, wherein the mold is driven so as to change its position.

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