JPH04241910A - Clamping part for molding machine - Google Patents

Abstract

PURPOSE:To provide a clamping part in which characteristics of link means are utilized, which is balanced structurally in view of a load share, and whose usable life is improved. CONSTITUTION:In relation to a link type mold clamping part 1 of molding machines such as an injection molding machine, a rear platen 3 and a movable platen 4 are connected to each other by link means which are operated by a mold opening/clamping motor 21 to open and close a mold. Feed screw parts 7 are formed at the rear ends of tie bars 5 and, on the other hand, tie bar nuts are joined pivotably in predetermined positions to the places where the tie bars penetrate through the rear platen and screwed on the tie bars 5. The tie bar nuts are operated by a mold-clamping servomotor 25 to drive the mold in a lockup state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping section of a molding machine using a mold.

0002

[Prior Art] In a molding machine such as an injection molding machine that performs molding by clamping a mold, those with a link type clamping part have a fixed platen and a rear platen connected by a tie bar, and a movable platen is connected between these platens. is attached to the tie bar so as to be movable in the front-rear direction, and the movable platen is connected to the rear platen by a link mechanism such as a toggle or crank that extends and contracts in the front-rear direction. Then, a link mechanism is driven by a mold clamping servo motor to open and close the mold, and to lock up the mold after closing.Meanwhile, a feed screw is formed at the rear end of the tie bar that passes through the rear platen. This is equipped with a tie bar nut that is rotatably supported in a fixed position on the rear platen and a mold thickness adjustment motor that drives this, so that mold thickness can be adjusted when replacing the mold. .

[0003] Such a link-type mold clamping unit uses a link mechanism to move the movable platen at high speed in the middle of the stroke, and at a low speed in the latter half of the stroke, which requires caution.
In addition, since the movable platen can be moved with a strong force, it is convenient for mold opening, mold closing, and lock-up, but on the other hand, it has the following disadvantages.

[0004] Since a link mechanism such as a toggle is constructed by connecting many parts in the front-rear direction with link pins and crank pins, errors due to wear and distortion at each link joint tend to accumulate in the movement of the movable platen.

Since link pins and the like are subjected to dynamic torsional loads and dynamic shearing or bending loads, these pins have a short service life.

[0006] Furthermore, conventionally, compared to the servo motor for mold clamping, the operating rate of the mold thickness adjustment motor is extremely low, and the load of the motor in the mold clamping part is unevenly distributed, making it difficult to balance the structure of the mold clamping part. Not yet.

[0007] For this reason, in a device that employs a toggle mechanism, the ball screw used to move the crosshead must be an expensive ball screw with a large diameter that can withstand a large mold clamping force.

[0008]

[Problems to be Solved by the Invention] This invention makes use of the characteristics of the link mechanism exhibited in the mold clamping part, and
The challenge is to provide a mold clamping part that is structurally balanced in terms of load sharing.

[0009]

Means for Solving the Problems This invention relates to a link type mold clamping part of a molding machine.

[0010] The fixed platen and the rear platen are connected with a tie bar.

[0011] The fixed platen is fixed in position to the main machine frame,
The movable platen is movable in the front and back direction relative to the main machine frame.

[0012] A movable platen is attached to the tie bar so as to be slidable in the front and rear directions, and is connected to the rear platen by a link mechanism.

[0013] The link mechanism is interlocked and connected to a mold opening/closing motor attached to the rear platen, and is expanded and contracted in the front and rear directions by this motor.

[0014] The tie bar extends rearward through the rear platen, and has a feed screw portion formed at its rear end.

[0015] A tie bar nut is rotatably supported at a fixed position at a tie bar penetrating portion of the rear platen.

The tie bar nut is screwed onto the feed screw to connect the rear platen and the tie bar.

[0017] The tie bar nut is interlocked and connected to a mold clamping servo motor attached to the rear platen.

[0018]

[Operation] The link mechanism is expanded and contracted by the mold opening/closing motor, moves the movable platen back and forth with respect to the fixed platen, and opens and closes the mold.

The tie bar nut is driven by a mold clamping servo motor to move the feed screw portion in the front and back direction, and drives the closed mold by a predetermined amount via the movable platen, thereby locking up the mold.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a mold clamping section 1 in an injection molding machine, which includes a fixed platen 2, a rear platen 3, and a movable platen 4. The fixed platen 2 and the rear platen 3 are connected by four tie bars 5, and the movable platen 4 is located between the platens 2 and 3 and attached to the tie bars 5, so that it can move freely in the front and rear directions. The movable platen 4 and the rear platen 3 are connected by a toggle mechanism 6 (link mechanism).

Each of the tie bars 5 has a front portion fixed to the fixed platen 2 and a rear portion passing through the rear platen 3.
A feed screw portion 7 is formed at the rear end. Further, a tie bar nut 8 is rotatably supported at a portion of the rear platen 3 through which the tie bar 5 passes. That is,
As shown in FIG. 2, a shaft support collar 9 is fixed to the rear surface of each of the above-mentioned penetration points of the rear platen 3, and a tie bar nut 8 screwed onto the feed screw portion 7 of the tie bar 5 is fixed to this via an angular bearing 10. It is rotatably supported on the shaft. Reference numeral 11 is a bearing lock nut, reference numeral 12
is a bearing presser. Note that a sprocket 13 is integrally fixed to the tie bar nut 8 at the rear thereof.

The toggle mechanism 6 includes a first link 14 that is rotatably supported at one end by a link pin P1 on the rear platen 3, and a second link rotatably supported at one end by a link pin P3 on the movable platen 4. 15, and their other ends are rotatably connected to each other by a link pin P2 to form a link node 16. In this embodiment, such a link node 16
, 17 on the left and right. And both link nodes 16,
17 is connected to a crosshead 18 placed in the center thereof at a link pin P2.

A ball screw 19 is pivotally supported through the center of the rear platen 3 in the front-rear direction, and a ball nut 20 integrally formed with the above-mentioned crosshead 18 is screwed into the ball screw 19. The ball screw 19 is interlocked to be driven by a mold opening/closing motor 21 attached to the center of the rear surface of the rear platen 3. Reference numeral 22 is a front limit switch which causes the crosshead 18 to move forward and activate the toggle mechanism 6.
is fully extended, link pins P1 to P of link nodes 16 and 17
3 is activated by the crosshead 18 when they are aligned. Reference numeral 23 denotes a rear limit switch which is activated when the crosshead 18 moves rearward and the toggle mechanism 6 contracts to complete opening of the mold. These limit switches 22 and 23 are arranged at fixed positions with respect to the rear platen by stays from the rear platen 3.

A series of chains 24 are looped around each sprocket 13 of the four tie bar nuts 8, and are driven by a mold clamping servo motor 25 (FIG. 3).

In FIG. 1, reference numeral 26 indicates a mold, and a fixed mold 26a is attached to the fixed platen 2, and a movable mold 26b is attached to the movable platen 4. The figure shows the state in which the mold is in touch.

Although not shown, the injection molding machine equipped with this mold clamping section 1 is equipped with a well-known NC device.

When the injection molding machine is operated, the entire molding process is controlled by the NC device, and operations such as metering, injection, mold closing, mold clamping, mold opening, and mold thickness adjustment are stored in the ROM of this device. Stored sequence programs and RAM
This is done based on the molding program and molding data entered into. Since the control method itself is not particularly different from the conventional method, such as input/output of signals related to the NC device during this time and signal processing inside the NC device, the operation of the mold clamping section 1 will be mainly described below.

When installing or replacing the mold 26, the mold clamping servo motor 25 is driven in the opposite direction to move the rear platen a predetermined amount backward, and then the mold opening/closing motor 21 is driven in the forward direction (with the crosshead 18 facing forward). direction) to fully extend the toggle mechanism 6. Next, the mold 26 is installed between the movable platen 4 and the fixed platen 2, and the mold clamping servo motor 25 is driven in the forward direction to close the rear platen 3.
, the entire movable platen 4 coupled thereto via the toggle mechanism 6 is moved forward to bring the mold into contact as shown in FIG. In this state, the fixed side and movable side molds 26 (a
, b) respectively fixed platen 2 and movable platen 4.
Fixed to. That is, as a result, the mold thickness is adjusted and at the same time, the mold touch position of the rear platen 3 is determined.

The above predetermined amount is the amount necessary to ensure a sufficient gap for mounting the mold between the movable platen 4 and the fixed platen 2 when the toggle mechanism 6 is fully extended.
This is the amount added to the thickness of the mold. In addition, the toggle mechanism 6
The crosshead 18 is extended by the front limit switch 22.
The machine stops when you step on the button, and the mold touch position on the rear platen 3 is stored in the RAM of the NC device.

The mold is opened and closed from the state shown in FIG. 1 as follows.

To open the mold, the mold opening/closing motor 21 is driven in the opposite direction, and the ball nut 20, that is, the crosshead 18 is connected to the rear limit switch 23 via the ball screw 19.
Move back until you step on the button. As a result, the toggle mechanism 6 contracts and the movable platen 4 retreats, resulting in the mold opening state. To close the mold, conversely, the mold opening/closing motor 21 is driven in the forward direction to advance the crosshead 18 until the front limit switch 23 is stepped on, and the link pins P1 to P1 of both link nodes 16 and 17 are pressed.
Let P3 be in a straight line. As a result, the toggle mechanism 6 is fully extended and the mold is in a closed state. Note that once the mold thickness adjustment described above is performed, the mold 26 is brought into the mold touching state every time the mold is closed unless the position of the rear platen 3 is moved.

The lock-up of the mold 26 is performed as follows from the state of the mold touching (FIG. 1). When the activation signal of the front limit switch 22 is confirmed, the mold clamping servo motor 25 is driven in the forward direction by a predetermined amount. The predetermined amount is a rotation amount corresponding to the drive-in amount (the amount of movement of the movable platen from the mold touch position to the lock-up position) determined according to the mold 26, and is input in advance into the RAM of the NC device. It is controlled by the amount of pulses calculated from the data regarding the push-in and distributed to the servo circuit. A chain 24 is driven by a mold clamping servo motor 25, thereby driving tie bar nuts 8 threaded onto the feed screw portions 7 of the four tie bars 5 via sprockets 13. In this case, the rotation of the tie bar nut 8 is in the positive direction, and since the tie bar nut 8 is configured to rotate at a fixed position relative to the rear platen 3, the tie bar nut 8 moves on the feed screw portion 7 due to the rotation. Then, the rear platen 3 as well as the movable platen 4 move forward via the toggle mechanism 6, and the drive to lockup is performed. At this time, each link 14, 15 of the toggle mechanism 6 remains fully extended without rotating, and both link nodes 16, 17
The link pins P1 to P3 are aligned in a straight line. Note that the output of the mold clamping servo motor 25, the diameter of the feed screw portion 7, and the feed pitch are designed so that the necessary mold clamping force is exerted. However, tie bar 5 was originally
The feed screw portion formed at the rear end of the tie bar 5 has a sufficient diameter to withstand the mold clamping force during lock-up, and the mold clamping force is normally shared equally between multiple tie bars. 7 has a sufficient diameter in relation to the above.

[0033] Next, the injection process is carried out by the injection section, and when the set time for pressure holding and cooling has elapsed, first, the mold clamping servo motor 25 is driven in the reverse direction and the rear platen 3 is memorized. The mold is retracted to the above mold touch position and stopped. Further, the mold opening/closing motor 21 is moved backward until the rear limit switch 23 is stepped on, thereby the toggle mechanism 6 is contracted, the movable platen 4 is moved backward, and the mold is opened.

In this state, the molded product is taken out within the set time, and when the set time has elapsed, the mold opening/closing motor 2
1 is driven in the forward direction, the toggle mechanism 6 is extended, and as shown in FIG.
The mold is in touch state.

In the above operation, the mold opening/closing motor 21
The toggle mechanism 6, which is driven by This is done by the mechanism of the feed screw section 7. Therefore, the load sharing between the mold opening/closing motor 21 and the mold clamping servo motor 25 is balanced.

When touching the mold, the movable mold 26b is moved at a relatively high speed until it approaches the fixed mold 26a, and then carefully moved at a low speed due to the characteristics of the toggle mechanism 6. .

Further, since the mold thickness adjustment and the driving-in leading to lock-up are performed with the toggle mechanism 6 fully extended, errors in the front-back direction unlike the conventional ones are reduced. Furthermore, since the links 14 and 15 of the toggle mechanism 6 are in a straight line during driving, where a large force is applied, the compressive force is the main force, and no large force is applied to bend them. In particular, only the bending force acts on each link pin P1 to P3, but the bending force and torsional force act simultaneously as in the conventional case where the link joints 16 and 17 are rotated and pushed in. do not.

By the above-described operations and by repeating the operations, the mold thickness adjustment and injection molding process for a new mold are performed.

The above are examples. The link mechanism may also be a crank mechanism. The interlocking connection between the mold clamping servo motor 25 and the tie bar nut 8 may be through a gear train.

[0040]

[Effect of the invention] The load sharing of the motors (mold clamping servo motor and mold opening/closing motor) in the mold clamping section is balanced, and one mold thickness adjustment motor is prepared only for mold thickness adjustment as in the past. etc., structural imbalances are improved.

[0041] When touching the mold, the movable platen moves at a low speed, and the touch is performed carefully.

[0042] The life of link mechanisms such as toggles is improved.

When the link mechanism is a toggle as in the embodiment, the ball screw for moving the crosshead can be made thinner and the construction can be made at a lower cost.

[Brief explanation of the drawing]

[Figure 1] Plan view with a portion cut away

[Figure 2] Cross-sectional view of main parts

[Figure 3] Side view seen from the rear

[Explanation of symbols]

1 Mold clamping part 2 Fixed platen 3 Rear platen 4 Movable platen 5 Tie bar
6 Toggle mechanism 7 Feed screw 8 Tie bar nut 13 Sprocket

Claims (1)

[Claims] [Claim 1] A fixed platen fixed in position on the main machine frame and a rear platen movable in the front and back directions with respect to the main machine frame are connected by a tie bar, and a movable platen is attached to the tie bar so as to be slidable in the front and back direction. This and the rear platen are connected by a link mechanism that expands and contracts in the front and back direction by a mold opening/closing motor attached to the rear platen, and the tie bar penetrates the rear platen and projects rearward, and its rear end is a feed screw part, A tie bar nut rotatably supported at a predetermined position through the tie bar penetrating portion of the rear platen is screwed together to connect the two, and the tie bar nut is driven and rotated by a mold clamping servo motor attached to the rear platen. The mold clamping part of a molding machine featuring