JP2584325B2 - Mold clamping device of injection molding machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping device for an injection molding machine, and particularly to a structure for maintaining a parallelism of a platen.

2. Description of the Related Art In recent injection molding, moldings such as lenses and discs, which require strictness, are increasing. Along with this,
For the mold clamping device using these molds, it is natural that high precision is required for the platen parallelism during mold clamping,
Since the clearance and parallelism of the guide pins of the mold are strict, high platen parallelism is required even when the mold is opened.

However, the conventional toggle-type mold clamping device uses a sliding bearing structure such as an oil-less metal ring for each rotation node of the link that constitutes the toggle, so the clearance of this part is limited to a certain limit (about 0.02 mm). Cannot be reduced below. Also, in the conventional toggle-type mold clamping device, a trapezoidal screw with a sliding structure is used to screw the mold thickness adjustment nut and the tie bar.
The degree of axial clearance cannot be reduced below.

Therefore, the distance between the rear platen and the fixed platen so that there is no gap between the fixed mold and the movable mold at the time of mold clamping with force in the mold clamping direction, that is, the parallel between the movable platen and the mold mounting surface of the rear platen Even if the degree is adjusted with the mold thickness adjusting nut of each tie bar, when the mold is opened, the movable platen may tilt due to the clearance, the weight of the movable platen, the weight of the mold, etc., which may damage the mold and its guide pins. Was.

Conversely, if the parallelism is adjusted when the mold is opened, the balance between the platen parallelism and the mold clamping force during mold clamping will be lost.

Therefore, a mold plate support for supporting the weight of the movable platen and the mold on the machine base is provided below the movable platen.

As long as the sliding structure is used for each of the rotary joints of the toggle link and the mold thickness adjusting nut as described above, the above-mentioned gap cannot be eliminated and cannot be solved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mold clamping device that can achieve high precision platen parallelism even when a mold is opened without using a mold plate supporter or the like.

Means for Solving the Problems A mold clamping device includes a fixed platen, a rear platen, and a movable platen.

The fixed platen and the rear platen are connected by a plurality of tie bars, and a mold thickness adjusting nut is screwed to each tie bar.

The movable platen is supported by a tie bar between the fixed platen and the rear platen so as to be slidable, and is connected to the rear platen by a toggle mechanism for clamping.

Each rotating node of the toggle link has a rolling bearing structure with no radial clearance.

The mold thickness adjusting nut and the tie bar are screwed by a ball screw structure that eliminates radial clearance and backlash. Rolling bearing structure at each rotation node of the toggle link, ball screw structure by screwing the mold thickness adjusting nut and the tie bar Eliminates clearance in the moving structure of the movable platen.

Embodiment FIG. 1 schematically shows a mold clamping device 1 in an injection molding machine, which includes a fixed platen 2, a movable platen 3, and a rear platen 4. The fixed platen 2 is fixed to a machine base 5, and the rear platen 4 is in a front-rear direction. It is possible to move a little.

The fixed platen 2 and the rear platen 4 have a plurality of tie bars 5
The movable platen 3 is inserted into the tie bar 5 so as to be slidable in the front-rear direction, and is connected to the rear platen 4 by a toggle link mechanism 6.

Each tie bar 5 is fixed to the front surface of the fixed platen 2 with a fixing nut 7 screwed to the front end, and a mold thickness adjusting nut 8 is screwed to the rear end. By adjusting the position of the mold thickness adjusting nut 8, the distance between the fixed platen 2 and the rear platen 4 is adjusted for each tie bar 5, and as a result, the parallelism between the movable platen 3 and the fixed platen 2 on the mold mounting surface is reduced. Can be adjusted.

 Reference numerals 9 and 10 indicate a fixed mold and a movable mold.

The toggle link mechanism 6 is such that each link 11 has a fixed platen 2
Side, the movable platen 3 side, and each other, are connected by a rotary joint 12. Each of the rotary joints 12 is formed of a rolling bearing structure in which a roller or a ball is used as a rolling material and clearance is eliminated in a radial direction in which these rolling materials are assembled under a strong pressure.

Reference numeral 13 denotes a crosshead, which is driven back and forth by a mold clamping motor.

The mold thickness adjusting nut 8 forms a ball screw structure as shown in FIG. 2 with each tie bar 5, is rotatably mounted on the rear surface of the rear platen 4, and is screwed to the tie bar 5. That is, the mold thickness adjusting nut 8 has a structure in which two parts 14, 15 before and after forming a ball screw structure between the tie bar 5 and the tie bar 5, respectively, are connected by bolts 16, and the balls 16 in both directions are opposed to each other by bolts 16. To eliminate the radial clearance and axial backlash.
Elimination of the radial clearance and the axial backlash is also possible by using a ball having a slightly larger diameter than usual as a rolling material.

The rolling bearing structure employed for all of the rotary joints 12 in the toggle link mechanism 6 and the ball screw mechanism employed for the mold thickness adjusting screw 8 have almost all clearance in the direction of the mold clamping axis a when assembled to the injection molding machine. 0. Therefore, the movable platen 3 is moved in the direction of mold clamping or mold opening without tilting without a mold plate support or the like.

When there is a concern about the parallelism between the fixed platen 2 and the movable platen 3 due to a mold exchange or the like, the mold clamping operation is carefully tried. When the fixed mold and the movable mold have close contact with each other, the mold thickness adjusting nut 8 is rotated to separate the distance between the fixed platen 2 and the rear platen 4 for each tie bar 5, that is, the fixed platen 2 The parallelism of the movable platen 3 with respect to is adjusted.

After the parallelism is once corrected in this way, even if the mold is opened or the mold clamping operation is repeated, the parallelism hardly changes.

Effect of the Invention There is almost no deviation in parallelism between the fixed platen and the movable platen.

Therefore, precision molding can be repeated for a long time.

A mold plate or the like is not required for the movable platen, so that the size of the mold clamping device can be reduced and the cost can be easily reduced.

[Brief description of the drawings]

FIG. 1 is a schematic front view, and FIG. 2 is a sectional view of a main part. DESCRIPTION OF SYMBOLS 1 ... Mold clamping device, 2 ... Fixed platen, 3 ... Movable platen, 4 ... Rear platen, 5 ... Tie bar, 6 ... Toggle link mechanism, 8 ... Mold thickness adjustment nut, 12 ... Rotating joint.

Claims (1)

(57) [Claims] A fixed platen and a rear platen are connected by a plurality of tie bars, a movable platen is supported by the tie bars between the two platens and is slidably mounted, and is connected to the rear platen by a mold clamping toggle mechanism. A mold-clamping device comprising a mold-thickness adjusting nut screwed onto each tie-bar, wherein each toggle of the toggle link has a rolling bearing structure with no clearance in the radial direction, and the screwing of the mold-tightening nut and the tie-bar is radial. A mold clamping device for an injection molding machine characterized by having a ball screw structure that eliminates directional clearance and backlash.