JPH07100885A - Mold clamping device for motorized injection molding machine - Google Patents

Abstract

PURPOSE:To utilize to a high degree a mold thickness adjusting mechanism provided in a mold clamping device, improve the mold clamping cycle and make a mold clamping motor compact. CONSTITUTION:A device comprises a mold carrying mechanism 6 provided with a toggle link 7 driven by a first motor M1 and moving a movable platen 3 and a mold clamping mechanism 8 provided with screws and nuts driven by a second motor M2. The mold clamping mechanism 8 comprises screw sections 15 of fine pitch for mold clamping set on the rear ends of respective tie bars 5, nuts 16 for mold clamping screwed into the screw sections 15 for mold clamping and supported rotatably in the given positions on a rear platen 2 and a transmission means 17 for transmitting the rotating force of the second motor M2 to respective nuts 16 for mold clamping.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping device for an electric injection molding machine, and more particularly to a mold clamping mechanism therefor.

[0002]

2. Description of the Related Art As a mold clamping mechanism in an injection molding machine,
A toggle type mold clamping mechanism using a motor as a drive source is known. With the toggle type mold clamping mechanism, the link structure makes it possible to move the working point at the beginning and end of the expansion and contraction stroke at a low speed and at a high speed at the intermediate position, thus shortening the mold opening / closing cycle and slowing the mold touch. It can be done and the mold can be protected.

On the other hand, the toggle type is provided with a die thickness adjusting mechanism for moving the movable platen with respect to the fixed platen depending on the size and shape of the die because the extension stroke is limited.

The mold thickness adjusting mechanism synchronizes the nuts screwed into the screw parts of the end portions penetrating to the rear platen side of the tie bars connecting the fixed platen and the rear platen with the mold thickness adjusting motor. The mold thickness is adjusted by rotating the movable platen back and forth and moving the movable platen back and forth.

By the way, since such a mold thickness adjusting mechanism is used only when the mold is replaced, the frequency of use of the mold thickness adjusting motor is low. Therefore, advanced use of the mold thickness adjusting mechanism is considered, and Japanese Patent Laid-Open No. 62-179914 discloses a technical idea of using the mold thickness adjusting mechanism as a mold clamping mechanism.

However, this is a so-called linear type, and a ball screw / nut mechanism is used to move the movable platen. Therefore, the moving speed of the movable platen is performed by changing the rotation speed of the motor, and the speed of the motor is controlled to adjust the feed speed of the mold and protect the mold when the mold is touched. You need a program to do it.

Further, generally, the moving speed of the movable platen in the so-called direct-acting type mold clamping unit is slower than that of the toggle type, and the molding cycle tends to be long.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to make an advanced use of a mold thickness adjusting mechanism provided in a mold clamping unit, to shorten a mold clamping cycle, and to reduce the size of a mold clamping motor. The object is to provide a mold clamping device of a type injection molding machine.

[0009]

A mold clamping device for an electric injection molding machine according to the present invention includes a mold conveying mechanism driven by a first motor to move a movable platen by a toggle link.
A mold clamping mechanism including a screw and a nut driven by a second motor is provided. The mold clamping mechanism includes a fine-pitch mold clamping screw portion provided at an end of each tie bar on the rear platen side, and a mold that is screwed into the mold clamping screw portion and is rotatably supported at a fixed position by the rear platen. It is provided with a tightening nut and a transmission means for transmitting the rotational force of the second motor to each of the mold clamping nuts.

[0010]

In the die transport mechanism, the movable platen is moved by the first motor via the toggle link to open and close the die between the die opening completion position and the die touch position.

In the mold clamping mechanism, when the mold is stopped at the mold touch position, each mold clamping nut is rotated by driving the second motor to further move the rear platen to the front body,
Make each tie bar slightly stretched. This locks up the mold and maintains the mold clamping force.

[0012]

1 is a front view showing a mold clamping device of an electric injection molding machine according to an embodiment of the present invention.

The mold clamping device 1 comprises a front fixed platen 4 and a rear rear platen 2 fixed to a base (not shown). The fixed platen 4 and the rear platen 2 are
It is connected by book tie bars 5. Further, between the fixed platen 4 and the rear platen 2, a movable platen 3 that slides in the front-rear direction along the four tie bars 5 is arranged, and between the movable platen 3 and the rear platen 2, a metal platen 3 is provided. A die transfer mechanism 6 is provided. In the die transfer mechanism 6, the toggle link 7 is driven by the first servomotor M1 to move the movable platen 3 back and forth.

Further, the rear end portions of the four tie bars 5, that is, the end portions on the rear platen 2 side are penetrated to the rear side of the rear platen 2, and the second servo motor M is provided in this portion.
A mold clamping mechanism 8 including a screw and a nut driven by 2 is provided.

A mold 22 is provided inside the stationary platen 4.
One side is fixed, and the other side of the mold 22 is fixed inside the movable platen 3 facing the fixed platen 4.
The first and second servomotors M1 and M2 are equipped with brakes.

The die transfer mechanism 6 is generally provided with a toggle link 7 for connecting the rear platen 2 and the movable platen 3.
And a first servo motor M1. The first servomotor M1 is fixed to the rear platen 2 and causes the toggle link 7 to expand and contract. The movable platen 3 is moved back and forth by the expansion and contraction of the toggle link 7.

A ball nut is fixed to the cross head 9 of the toggle link 7, and the ball screw 10 is attached to the ball nut.
Of the ball screw 10 is rotatably supported at a fixed position by the rear platen 2 at a position near the rear end thereof. The rear end of the ball screw 10 is penetrated to the rear of the rear platen 2 and a driven pulley 11 is fixed to this portion.
A drive pulley 13 is fixed to the motor shaft 12 of the first servomotor M1, and a timing belt 14 is mounted on the drive pulley 13 and the driven pulley 11.

The mold clamping mechanism 8 includes a fine-pitch mold clamping screw portion 15 (feed trapezoidal screw) formed at the rear end of each tie bar 5 penetrating the rear platen 2, and each mold clamping screwed to this. A second servomotor M for rotating the nut 16 and each mold clamping nut 16 fixed to the side portion of the rear platen 2.
2 and the second servomotor M2 and the transmission means 17 arranged between the mold clamping nuts 16.

The mold clamping nuts 16 are rotatably supported by the rear platen 2 at fixed positions. The pitch of the mold clamping screw portions 15 is 1 mm in this embodiment.

The transmission means 17 is a second servomotor M2.
Toothed pulley 19 fixed to the motor shaft 18, the toothed pulley 20 fixed to each mold clamping nut 16, and the motor shaft 1.
The timing belt 21 is mounted on the toothed pulley 20 of No. 8 and the toothed pulley 19 of each mold clamping nut 16.

The mold clamping device 1 operates as follows.
Incidentally, it is assumed that the movable platen 3 is now at the mold opening completion position on the rear platen 2 side.

First, the mold conveying mechanism 6 performs a mold closing operation. The first servomotor M1 is driven, the ball screw 10 is rotated via the drive pulley 13, the timing belt 14, and the pulley 11, and the crosshead 9 moves forward along the axial direction of the ball screw 10. Then, the toggle link 7 is extended, and the movable platen 3 moves to the front fixed platen 4 side along the four tie bars 5.

When the extension stroke of the toggle link 7 is fully extended, the state is detected by the increase of torque in the limit switch or the motor, and the driving of the first servomotor M1 is stopped. Next, the brake is activated, the extended state of the toggle link 7 is maintained, and the movable platen 3 is prevented from moving. In this state, as shown in FIG. 1, the movable side mold 22a is stopped about several millimeters before the state where the fixed side mold 22b is touched.

Since the mold closing operation by the mold conveying mechanism 6 is due to the extension operation of the toggle link 7, the moving speed of the movable side mold 22a is slow at the rising from the mold opening completion position, but the mold 22a is at the intermediate position. Since the moving speed of the mold becomes faster, the mold opening / closing cycle can be made faster. On the other hand, before the die touch position, the moving speed of the movable die 22a slows down again and the die 22a is stopped about several millimeters before the die touch position. Therefore, the movable die 22a is fixed. 22
There is no possibility of collision with b, and the mold 22 is protected.

The load of the first servomotor M1 is
Substantially, the movable platen 2 and the movable die 22a are moved only by overcoming the friction with the tie bar 5, and the first servo motor M1 does not require a large output torque. Can be miniaturized. The ball screw 10 may be relatively thin. Cross head 9
Even if the thrust of 1 ton is generated when the mold clamping force of 50 ton is generated, it is only about 200 kg when the mold is conveyed.

Next, the mold clamping mechanism 8 performs the mold clamping operation. The second servomotor M2 is driven, and the mold clamping nuts 16 are synchronously driven via the toothed pulley 19, the timing belt 21, and the pulleys 20. Fine pitch mold clamping screw portion 1 provided at the side end portions of the four tie bars 5.
As a result of the rotation of the mold clamping nuts 16 screwed with the rear platen 5, the rear platen 2 is moved to the front fixed platen 4 side.

By the movement of the rear platen 2, the movable side mold 22a and the fixed side mold 22b connected to the extended toggle link 7 come into contact with each other. Further, the second servo motor M2 is driven, and the die 22 in the abutting state is locked up. In the lockup state, each tie bar 5 is slightly stretched, and the elastic force due to this stretching maintains the mold clamping force. During this period, the toggle link 7 is in the extended state and is in a state of being stretched by the link with respect to the force in the mold clamping direction, and the load applied to the first servomotor M1 for die transfer or its brake is small.

The moving distance of the rear platen 2 required for the mold clamping operation is about several millimeters, and even if the pitch of the mold clamping screw portions 15 is fine, the rotation speed of the second servomotor M2 is increased to perform the mold clamping. The time required can be shortened, and the torque of the second servomotor M2 can be reduced. That is, the second servo motor M2 can be downsized. Further, since the mold clamping screws 15 and the respective mold clamping nuts 16 that are screwed to the mold clamping screws 16 perform mold clamping, a sufficient mold clamping force can be obtained.

The completion of the mold clamping operation is determined by detecting the mold clamping force by the amount of expansion of each tie bar 5, that is, the rotation amount of the second servo motor M2, and when the rotation amount reaches the set value,
The drive of the second servomotor M2 is stopped and the brake is operated to hold the molds 22a and 22b in a state of being clamped with the set mold clamping force.

The mold opening operation is basically the reverse of the above-mentioned step, and the brake of the second servomotor M2 is released, and the mold 22a is stopped in the state where the extension stroke of the toggle link 7 is fully extended. Second servo motor M to the specified position
Reverse 2 and move rear platen 2 backward. Then
The first servomotor M2 is reversely rotated to return the movable platen 3 to the mold opening completion position.

Even in the return movement operation of the movable platen 3, at the start of the return movement operation, the movable die 22a is moved.
Although the moving speed of the mold 22a is slow, the moving speed of the mold 22a becomes fast at the intermediate position, so that the mold can be moved quickly, and the moving speed of the movable side mold 22a becomes slow again before the mold opening completion position and the mold 22a Is stopped, the die 22a is protected.

The positioning of the movable platen 3 with respect to the fixed platen 4 in a state where the toggle link 7 is fully extended is set by the mold clamping mechanism 8 by performing a mold thickness adjusting operation similar to the conventional one. That is, the second platen motor 2 is driven to rotate the mold clamping nuts 16 in synchronism with each other to move the rear platen 2 with respect to the fixed platen 4.

FIG. 2 shows a second embodiment of the transmission means 17 of the mold clamping mechanism 8. The transmission means 17 meshes with the driven gears 24 fixed to the mold clamping nuts 16, respectively. And a driving gear 25 that meshes with the ring gear 23. The drive gear 25 is fixed to the motor shaft 18 of the second servomotor M2.

The ring gear 23 has a large-diameter hole 26 in the center, and abuts on the inside of the holes 26 arranged at positions facing the four driven gears 24 and the drive gear 25, respectively.
It is rotatably supported at a fixed position by two rollers 27.

When the second servomotor M2 is driven, the ring gear 23 rotates via the drive gear 25, and the driven gears 24 meshing with the ring gear 23 rotate in synchronization with each other. As a result, the mold clamping nuts 16 fixed to the driven gears 24 are rotated and lockup is performed.

In the case of the second embodiment, since the transmission means 17 is constituted by the meshing of gears, the second servomotor M2 is used.
The power transmission from the mold to each mold clamping nut 16 becomes more reliable.

The above is an embodiment, and the present invention is not limited to the illustrated specific configuration. For example, a fine-pitch mold clamping screw portion 15 and a mold-clamping nut 16 screwed into the screw portion 15.
May be composed of a ball screw and a ball nut.

[0038]

According to the mold clamping device of the electric injection molding machine of the present invention, the mold can be opened and closed in a short cycle time by the mold conveying mechanism, while the mold can be sufficiently protected. It is possible to reduce the size of the mold clamping motor by making the pitch of the mold clamping screw portion and the screw of the nut fine, and to obtain a sufficient mold clamping force. The conventional mold thickness adjusting mechanism can be effectively used as a mold clamping mechanism. The relatively expensive ball screw can be made thin and low in cost.

[Brief description of drawings]

FIG. 1 is a front view schematically showing a mold clamping device of an electric injection molding machine according to an embodiment of the present invention.

FIG. 2 is a front view showing another embodiment of the transmission means in the mold clamping mechanism.

[Explanation of symbols]

 1 Mold Clamping Device 2 Rear Platen 3 Movable Platen 4 Fixed Platen 5 Tie Bar 6 Mold Transfer Mechanism 7 Toggle Link 8 Mold Clamping Mechanism 9 Crosshead 10 Ball Screw 11 Driven Pulley 12 Motor Shaft 13 Drive Pulley 14 Timing Belt 15 Mold Clamping Screw Part 16 Mold clamping nut 17 Transmission mechanism 18 Motor shaft 19 Toothed pulley 20 Toothed pulley 21 Timing belt 22 Mold 22a Movable side mold 22b Fixed side mold 23 Ring gear 24 Driven gear 25 Drive gear 26 Hole 27 Roller M1 1st Servo Motor M2 Second Servo Motor

Claims (1)

[Claims] 1. A mold conveying mechanism that is driven by a first motor and moves a movable platen by a toggle link, and a mold clamping mechanism that is driven by a second motor by screws and nuts. A fine-pitch mold clamping screw portion provided at an end of each tie bar on the rear platen side, and a mold clamping nut screwed to the mold clamping screw portion and rotatably supported at a fixed position on the rear platen. And a transmission means for transmitting the rotational force of a second motor to each of the mold clamping nuts, the mold clamping device for an electric injection molding machine.