JPH0339223A - Mold clamping device in injection molding machine - Google Patents

Abstract

PURPOSE:To apply uniform and stable mold clamping force to a mold without being influenced by a temperature change of a tie bar, by constituting the title device so that after approching of a movable platen to a stationary platen by a toggle mechanism, mold clamping is performed by pulling the four tie bars by a hydraulic cylinder provided to the stationary platen. CONSTITUTION:When a motor of a reduction gear is started, a movable platen 2 is moved toward a stationary platen 1 with a toggle mechanism. Then when the first link 2 of the toggle mechanism abuts against a stopper 15, the toggle mechanism becomes almost linear at that position and takes a dead point position. Then hydraulic oil is sent to a hydraulic cylinder 6 by starting a small- sized hydraulic pressure generating unit 9, a tie bar 5 is pulled through a piston 7 and clamping of molds 3a, 3b is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold clamping device in an injection molding machine.

(Prior Art) As a mold clamping mechanism for an injection molding machine, especially an electric injection molding machine, (1) a toggle type and (2) a direct pressure type are known (for example, JP-A-60-112417, 1986
(Refer to Publication No.-7924).

The toggle type (1) generates mold clamping force by elongating the tie bars, and is easily affected by changes in tie bar temperature.

There are two types of toggle type: double toggle type and single toggle type, but double toggle type uses a feed screw to move the crosshead directly, and in addition to the drawbacks of the toggle type mentioned above,
The power transmission mechanism uses belts and pulleys, and the problem is that the inertia of the drive system is large, making it impossible to obtain large accelerations.

Furthermore, in the case of the single toggle type, in addition to the disadvantages of the toggle type, the direction in which the mold clamping force is generated is not parallel to the mold clamping straw, so that an uneven load is generated and the mold is easily damaged.

In addition, the direct pressure type (2) uses a feed screw to move the movable platen and directly generate mold clamping force, but if the motors are separated for generating mold clamping force and moving the platen, a clutch mechanism is required and the cycle The problem is that the clutch speed is slow and the life of the clutch is short.

Furthermore, if the same motor is used to generate the mold clamping force and move the platen, a high-output servo motor will be required, resulting in an increase in cost.

(Problems to be Solved by the Invention) It is an object of the present invention to propose a mold clamping device that can realize uniform and stable mold clamping force in a fast cycle in an injection molding machine.

(Means for Solving the Problem) A fixed platen, a movable platen, and a toggle support movable on a base are provided, one ends of four tie bars are fixed to the toggle support or the fixed platen, and the tie bar is provided with a toggle support movable on a base. The other end is connected to a hydraulic cylinder, and the toggle support further includes a first link rotatable by a motor with a reduction gear and positioned at a dead center position by a stopper;
A toggle mechanism is provided that is connected to the movable platen via a second link that is pivotally connected to the first link.

At the dead center position of the toggle mechanism, both molds are brought into contact with each other, and the tie bars are pulled by a hydraulic cylinder to generate mold clamping force.

(Operation) When the reducer motor is started, the movable platen 2 moves toward the fixed platen 1 by the toggle mechanism. When the first link hits the stopper 15, the toggle mechanism becomes substantially straight at that position and reaches the dead center position.

Next, the small hydraulic pressure generating unit 9 is activated to send pressure oil to the hydraulic cylinder, and the tie bar 5 is pulled through the piston 7 to clamp the molds 3a and 3b.

(Example) This will be explained based on the drawings. In Figure 1, 1 is a fixed platen, 2
are movable platens, each of which has molds 3a and 3b attached thereto. A toggle support 4 is movable on the base 16, and a single toggle mechanism attached to the toggle support moves the movable platen 2 to clamp the mold.

Four tie bars 5 parallel to each other are attached to the four corners of the toggle support 4, and these tie bars 5 slidably pass through holes 2a and la provided in the movable platen 2 and fixed platen 1. There is. The end of each tie bar 5 serves as a piston 7 of a hydraulic cylinder 6. The rod-side oil chamber of the hydraulic cylinder 6 is connected to a small hydraulic pressure generating unit 9 via piping 8.
is familiar with

The toggle mechanism includes a bracket 10 fixed to the toggle support 4 and a wt! A first link 2 attached to the shaft 11 of a mechanical motor (for example, a servo motor and a planetary gear reducer), and a second link 1 pivotally attached to this
3, and a bracket 10 fixed to the movable platen 2 to which the second link 13 is pivotally attached.

The lengths of the first link 12 and the second link 13 are such that when the respective links 12 and 13 are in a straight state, the mold 3
a and 3b are set so that they are closed (
Actually, this setting is the mold thickness rA! l! 5 is a stopper fixed to the toggle support 4, which stops the rotation of the first link 12 in the direction of arrow a in FIG. 1 and maintains the dead center position of the toggle. do. In this state, the molds 3a and 3b are completely in contact with each other and are clamped by the hydraulic cylinder 6.

Further, in the embodiment, the hydraulic cylinder 6 is constructed by forming the piston 7 at the end of the tie bar 5, but the present invention is not limited to this, and the hydraulic cylinder may be attached to the end of the tie bar 5, for example. Further, although an example is shown in which the hydraulic cylinder is provided on the fixed platen, it may also be provided on the toggle support 4.

Next, the opening/closing operation of the mold will be explained.

(1) Rotate the motor shaft 11 on the toggle support 4 side of the first link 12 to rotate the first link 12 in the direction of arrow a.

(2) When the first link 12 and the second link 13 are in a substantially straight line as shown in Figure 2 (the dead center of the toggle), the first link L
Position and fix 2. At this time, the molds 3a and 3b are brought into contact, and the servo motor presses the first link 12 against the stopper 15 with a minute torque, stably positioning it (the stopper 15 is held at the dead center position of the toggle mechanism). shall be assembled and adjusted in advance).

(3) After the first link 12 is positioned at the dead center position,
Hydraulic pressure is applied to the hydraulic cylinders 6 provided at the ends of the four tie bars 5 and pulled through the pistons 7 to generate a uniform and stable mold clamping force to bring the molds 3a and 3b into close contact.

(4) To open the mold, after reducing the hydraulic pressure in the cylinder 6 at one end of the tie bar 5 to zero, move the first link 12 of the toggle mechanism upward (
Rotate in the opposite direction of arrow a).

(Effects of the invention) 1) After the movable platen is brought close to the fixed platen by a toggle mechanism, the mold is tightened by pulling the four tie bars with a hydraulic cylinder installed on the fixed platen, which eliminates problems such as temperature changes in the tie bars. Uniform and stable mold clamping force can be applied to the mold without being affected.

2) In the mold clamping state, the toggle mechanism is fixed at its dead center position, so no unbalanced load occurs.

3) Since a pulley with large inertia is not used in the drive system and only a reduction gear with low inertia is required, a large acceleration can be obtained and a high-cycle mold clamping mechanism can be realized.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the mold clamping device according to the present invention in a mold open state. FIG. 2 is a cross-sectional view of the mold in the closed state. In the figure; 1 fixed platen 2 movable platen 3a, 3b
Mold 4 Toggle support 5 Tie bar
6 Hydraulic cylinder 7 Piston 8
Piping 9 Small hydraulic pressure generating unit 10 Bracket 11 (reducer motor) shaft 12 First link 13 Second link I4
Bracket 15 Stopper 6 Base and above Applicant Sumitomo Heavy Industries, Ltd. Sub-Agent

Claims (2)

[Claims] (1) It has a fixed platen, a movable platen, and a toggle support movable on a base, and one ends of four tie bars are fixed to the toggle support or fixed platen,
The other end of the tie bar is connected to a hydraulic cylinder, and the toggle support includes a first link that can be rotated by a motor with a reduction gear and is positioned at a dead center position by a stopper, and a pivot point attached to the first link. A mold clamping device for an injection molding machine, comprising a toggle mechanism connected to a movable platen through a second link attached to the movable platen. (2) At the dead center position of the toggle mechanism, both molds are brought into contact with each other, and the tie bar is pulled by a hydraulic cylinder to generate mold clamping force. Mold clamping device for injection molding machines.