JPH0788918A - Mold opening device of injection molding machine - Google Patents

Abstract

PURPOSE:To enable mold opening with high accuracy by preventing the scooping phenomenon of a movable plate at the time of mold opening. CONSTITUTION:Fluid pressure cylinders 4 having piston rods 5 advancing and retreating with respect to a movable plate 2 are fixed to a fixed plate 1 in the vicinity of four corners of the surface opposed to the movable plates 2 of the fixed plate 1 and a pressure fluid is introduced in the protruding direction of the piston rod 5 from the point of time of the completion of mold clamping or the point of time just before the start of mold opening after the completion of cooling to apply pressing force low as compared with mold clamping force to the regions of four places becoming symmetric with respect to the center of the movable plate 2 in the direction opposite to the fixed plate. Therefore, the movable plate 2 is put aside to the fixed plate 2 at the time of the start of mold opening and mold opening can be performed with high accuracy without generating a scooping phenomenon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold opening device for an injection molding machine, which can perform mold opening with high accuracy in a mold clamping device for an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, as a mold clamping device for an injection molding machine,
A toggle type mold clamping device that moves the movable platen forward and backward with respect to the fixed platen, and a direct pressure type mold that moves the movable platen forward and backward with respect to the fixed platen by a ball nut-ball screw mechanism that uses a fluid pressure cylinder or a motor as a drive source. Fastening devices are known.

[0003]

However, among the above-mentioned conventional techniques, the toggle-type mold clamping device has a backlash due to a gap in a pivoting member such as a link pin pivotally mounting the toggle link, and therefore the mold opening is performed. The movable platen moves up and down at the start,
Shaking to the left or right causes a so-called hiccup phenomenon in which a non-uniform force is applied to the molded product. Especially, in the case of the double link toggle type mold clamping device, this hiccup phenomenon becomes more serious under the influence of the dimensional error of the lengths of the upper and lower toggle links.
On the other hand, also in the direct pressure type mold clamping device, there is a problem that the same sipping phenomenon as described above occurs due to a gap between the fluid pressure cylinder and the piston, a gap between the ball nut and the ball screw, and the like.

The present invention has been made in view of the above problems of the prior art, and it is an injection molding machine capable of preventing the occurrence of a rattling phenomenon of the movable plate at the time of mold opening and highly accurate mold opening. The object of the present invention is to realize a mold opening device.

[0005]

To achieve the above object, a mold opening device of an injection molding machine according to the present invention comprises a fixed plate and a movable plate which is arranged so as to be movable back and forth toward the fixed plate. In a mold clamping device having a mold clamping mechanism for clamping and opening the mold by moving the movable plate toward and away from the fixed plate, at the time of completion of mold clamping of the mold clamping device or after completion of cooling and immediately before starting mold opening. From this, a pressing means for applying a pressing force in the direction opposite to the stationary platen, which is smaller than the mold clamping force, is provided at at least two sites symmetrical with respect to the center of the surface of the movable plate facing the stationary platen. It is characterized by that.

Further, the pressing means for applying a pressing force in the direction opposite to the fixed platen may be a fluid pressure cylinder having a piston rod which advances and retreats toward the movable platen, or may be compressed between the fixed platen and the movable platen when the mold clamping is completed. Elastic member.

[0007]

Operation: At the time of completion of mold clamping or immediately after completion of cooling and immediately before the start of mold opening, at least two parts which are symmetrical with respect to the center of the surface of the movable plate facing the fixed plate are smaller than the mold clamping force in the anti-fixing plate. Since the pressing force in the direction is applied by the pressing means, when the mold clamping force disappears due to the mold opening, the movable platen is biased toward the side opposite to the fixed platen, and the hiccup phenomenon does not occur.

[0008]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a main part of an embodiment of a mold opening device of an injection molding machine according to the present invention. (A) is a partial cross-sectional view of the upper half at the time of mold clamping, and (b) is at the time of mold opening. It is a partial cross-sectional view of the lower half.

A fixed platen 1 on which a fixed die 21 is installed upright on a base (not shown) with a predetermined interval, and a mold clamping housing 6 are connected by four tie bars 3 and between them. A movable platen 2 is provided on which a movable die 22 is slidably guided in the axial direction by the tie bar 3.

Near the four corners of the surface of the fixed platen 1 facing the movable platen 2, there are fixed fluid pressure cylinders 4 each having a piston rod 5 which advances and retreats toward the movable platen 2,
By introducing the pressurized fluid in the direction in which the piston rod 5 projects from the time when the mold clamping is completed or immediately after the cooling is completed and immediately before the mold opening is started, the movable platen 2 becomes symmetrical with respect to the center of the surface facing the fixed platen 4 It is configured to apply a pressing force in the direction opposite to the fixed platen, which is smaller than the mold clamping force, to the part.

The mold clamping mechanism for clamping and opening the mold by advancing and retracting the movable platen 2 toward and from the stationary platen 1 of this embodiment is constructed as described below.

The tip of the long link 11 pivotally attached to the movable plate 2 and the tip of the short link 10 pivotally attached to the mold clamping housing 6 are attached to the crosshead 7 and the tip of the cross link 9 is attached. The ball nut, which is pivotally attached to the
When the crosshead 7 advances toward the movable platen 2 by the ball screw mechanism, the long link 11 and the short link 10 are extended and clamped as shown in FIG. (Moving to the tightening housing side), the long link 11 and the short link 10 are contracted and the mold is opened as shown in FIG. 1 (b). Here, the long link 11, the short link 10, and the cross link 9 are pivotally attached by pins 12, respectively.

In the ball nut-ball screw mechanism of this embodiment, the ball nut 14 is rotatably supported by the mold clamping housing 6, but is supported so as not to move in the axial direction, and is screwed to the ball nut 14. A ball screw 13 and a connecting screw portion 1 formed at the tip of the ball screw 13.
3a is inserted into a through hole (not shown) of the crosshead 7 so as to protrude toward the movable plate side and the nut 8 is screwed to fix it to the crosshead 7 so as not to rotate, and the ball nut 14 is fixed to the small pulley by an electric motor 18. The cross head 7 is configured to reciprocate in the axial direction together with the ball screw 13 by rotating in the forward and reverse directions via the timing belt 16 and the pulley 15.

A rotation detector 19 such as a rotary encoder is attached to the electric motor 18, so that the rotational position of the electric motor 18 can be detected and the speed of the electric motor 18 can be controlled. .

When using a fluid pressure cylinder in which the stroke of the piston rod is equal to or greater than the stroke of the movable plate, the tip of the piston rod may be fixed to the movable plate.

Next, the operation of this embodiment will be described.

At the time of completion of mold clamping shown in FIG. 1A or immediately after completion of cooling and immediately before starting mold opening, the piston rod 5 of each fluid pressure cylinder 4 is drawn into the fluid pressure cylinder 4 and its tip end surface is movable. 2 is in contact with the fluid pressure cylinders 4, and the pressurized fluids are introduced into the respective fluid pressure cylinders 4 in the directions in which the piston rods 5 project toward the movable platen 2. Apply a pressing force in the direction opposite to the fixed platen that is smaller than the mold clamping force.

When the mold opening is started, the mold clamping force of the mold clamping mechanism applied to the movable platen 2 disappears, but by the above, the piston rod 5 of each fluid pressure cylinder 4 exerts a pressing force in the direction opposite to the fixed platen. Since the movable platen 2 is added in the vicinity of the four corners, the movable platen 2 is biased toward the non-fixed platen side without swinging up and down, left and right, and high-precision mold opening in which a hiccup phenomenon is prevented is performed.

The present invention can be applied not only to the double toggle type mold clamping device of the above embodiment but also to other mold clamping devices such as a single toggle type mold clamping device and a direct pressure type mold clamping device.

Further, the pressing means for applying a pressing force in the direction opposite to the fixed platen is replaced with a fluid pressure cylinder having a piston rod which advances and retreats toward the movable plate shown in the above embodiment.
It is possible to dispose an elastic member composed of a spring, a rubber block, or the like, which is compressed at the time of mold clamping, between the fixed platen and the movable platen, and apply the pressing force to the movable platen by its elastic force.

Further, the pressing means is not limited to the vicinity of the above-mentioned four corners of the movable plate, as long as it is a symmetrical portion with respect to the center of the surface of the movable plate which faces the fixed plate.
It may be arranged in the vicinity of a corner, or may be arranged in several places around the center of the surface of the movable plate facing the fixed plate.

[0023]

Since the present invention is configured as described above, it has the following effects.

At least two sites symmetrical with respect to the center of the surface of the movable plate facing the fixed plate are compared with the mold clamping force from the time when the mold clamping is completed by the pressing means or immediately after the completion of cooling and immediately before the start of the mold opening. Since a small pressing force is applied in the direction opposite to the fixed platen, the movable platen is biased to the side opposite the fixed platen at the start of mold opening, and highly accurate mold opening can be performed without causing a rattling phenomenon.

[Brief description of drawings]

1A and 1B show a main part of an embodiment of a mold opening device of an injection molding machine of the present invention, FIG. 1A is a partial sectional view of an upper half during mold clamping, and FIG. FIG.

[Explanation of symbols]

 1 Fixed plate 2 Movable plate 3 Tie bar 4 Fluid pressure cylinder 5 Piston rod 6 Mold clamping housing 7 Cross head 8 Nut 9 Cross link 10 Short link 11 Long link 12 Pin 13 Ball screw 13a Coupling screw part 14 Ball nut 15 Pulley 16 Timing Belt 17 Small pulley 18 Electric motor 19 Rotation detector

Claims (3)

[Claims] 1. A fixed platen (1), a movable platen (2) disposed so as to be movable back and forth toward the fixed platen (1), and the movable platen (2) facing the fixed platen (1). A mold clamping device having a mold clamping mechanism for clamping and opening the mold by moving the movable plate (2) of the movable plate (2) from the time when the mold clamping is completed or immediately after cooling is completed. Pressing means for applying a pressing force in the direction opposite to the stationary platen, which is smaller than the mold clamping force, is provided at at least two sites symmetrical with respect to the center of the surface facing the stationary platen (1). A mold opening device for an injection molding machine. 2. A fluid pressure cylinder (4) having a piston rod (5) for advancing and retreating toward a movable plate, wherein the pressing means for applying a pressing force in the direction opposite to the fixed platen. A mold opening device of the described injection molding machine. 3. A stationary plate (1) and a movable plate (2) are provided with a pressing means for applying a pressing force in the direction opposite to the stationary platen when the mold clamping is completed.
The mold opening device of the injection molding machine according to claim 1, wherein the mold opening device is an elastic member that is compressed between the two.