JPH0136589Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement of a mold clamping device for a fixed die plate and a movable die plate in an injection molding machine.

(Conventional structure and its problems) Conventionally, injection molding machines have used toggle type mold clamping devices and direct pressure type mold clamping devices as mold clamping devices, but both of these systems are hydraulically driven. Because this is done by switching the flow direction of the pressure oil between forward and reverse, there are limits to the timing when switching the valve and the time it takes for the pressure oil to reach the specified pressure at the time of switching, making high cycle operation impossible. It was difficult.

In addition, clamp presses generate a large force at the dead center, so they are used in punching presses, etc., but when it is necessary to stop at the dead center, such as in an injection molding machine, this stopping accuracy is difficult. Therefore, it was not used. Therefore, a method was proposed (Japanese Unexamined Patent Publication No. 115419/1983) that uses a servo motor to operate a crank to clamp the mold, but in this case, a stopper is used and the Since the method was to repeat the movement at 180 degrees, the crankshaft would be temporarily stopped at the stop position by the stopper as shown in Figure 3b, and it would be necessary to start from the stop position, which would cause the crankshaft to move by that amount. There was a problem that the speed was slow and prevented high cycle speed.

(Purpose of the invention) The present invention was made in view of the above problems.The movable die plate is reciprocated by driving only one direction of the crankshaft by a servo motor, and high-cycle operation is possible with a simple structure. The present invention provides a mold clamping device for an injection molding machine that enables this.

(Structure of the invention) In order to achieve the above object, the mold clamping device of the injection molding machine of the invention connects a movable die plate to a crankshaft via a crank arm, and rotates the movable die plate in one direction. The plate is configured to reciprocate and press against and separate from a fixed die plate.

(Explanation of Embodiments) The embodiments of the present invention will be explained with reference to the drawings.
is a housing into which the base ends of the tie bars 2, 2, 2, 2 are inserted and supported on all sides, and a fixed die plate 3 is fixed to the tip of the tie bar 2, and a movable die plate is attached using these tie bars 2 as a guide. 4 is arranged so as to be able to move toward and away from the fixed die plate 3.

Reference numeral 5 denotes a crank arm whose tip end is rotatably pivoted and connected to a bracket body 6 protruding from the base end surface of the movable die plate 4 through a pin 7;
Both ends are connected to an eccentric shaft portion 8a of a crankshaft 8 rotatably supported by the housing 1 via a bearing 9.

Reference numeral 10 denotes a servo motor mounted on one side of the housing 1, and its rotating shaft 11 is fitted to one end of the crankshaft 8 with the same center as the crankshaft 8.

Reference numerals 12 and 13 designate male and female molds attached to opposing surfaces of the stationary die plate 3 and the movable die plate 4, and 14 designates a tie bar fixing nut.

With the above configuration, the servo motor 10
When the crankshaft 8 is rotated, the movable die plate 4 moves forward while being slidably guided by the tie rod 2 via the crank arm 5, and the axis of the crank arm 5 is aligned with the center of rotation of the crankshaft 8. When the crank arm 5 extends until they are substantially aligned, the molds 12 and 13 are brought into pressure contact and clamped.
Injection of resin into the mold and holding pressure within the mold are performed.

From this state, when the crankshaft 8 further rotates in the same direction, the movable die plate 4 gradually separates from the fixed die plate 3 to open the mold, and after taking out the product, the crankshaft 8 is rotated again in the same direction by the above-mentioned operation. The mold is clamped by rotating in this direction.

FIG. 3 shows the relationship between the moving speed of the movable die plate 4 and the stroke of the crank arm 5. To explain in more detail based on this figure, the position where the movable die plate 4 is the most distant from the fixed die plate 3, That is, when the servo motor 10 is driven to rotate the crankshaft 8 from a state in which the eccentric shaft portion 8a of the crankshaft 8 is in a horizontal position rearward from the center line of the crankshaft 8 (point O), the eccentric shaft portion 8a is rotated. The above-mentioned mold clamping is performed when the crankshaft 8 is rotated 180 degrees about the center.

At this time, when the crank arm 5 becomes horizontal and reaches near the dead center, the speed of the movable die plate 4 slows down, and the center of the eccentric shaft 8a is approximately Angle sensor 1 such as an encoder when the angle is ±0.1 degree
When the rotation angle is detected by 5 and reaches the dead center of 180 degrees, the rotation of the servo motor 10 is stopped, the movable die plate 4 is stopped, and mold clamping is completed. In this state, the injection and pressure holding described above are performed.

This injection and pressure holding process (mold clamping force retention range) is the third
This is carried out for a period corresponding to the angle θ shown in the figure, and during this period the tie bar 2 is extended and mold clamping force is generated.

After injection and holding pressure in this way, the crankshaft 8 is further
Rotate 180 degrees to open the mold, return to the original position,
Injection molding is completed in one cycle.

(Effects of the invention) As described above, according to the mold clamping device of the injection molding machine of the present invention, the movable die plate is reciprocated by rotational drive in one direction using a crank system, and the mold is clamped and opened with respect to the fixed die plate. Not only is the structure simple, but the speed of the moving die plate decreases rapidly when the dies reach near the dead center where they press against each other, and the dies silently come into contact and press against each other. Moreover, the moving die plate moves at high speed at the stage leading to the dead center, and furthermore, since the crankshaft rotates in one direction, the crankshaft rotates continuously outside the dead center, and as a result, The reciprocating movement of the moving die plate is performed smoothly, making it possible to increase the cycle time of the injection molding machine, and by using a servo motor as the drive source, the accuracy of stopping at the dead center of the crank is improved. It is something that can be done.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a partially sectional side view, FIG. 2 is a partially sectional plan view, and FIG. 3a is a cycle diagram of the present invention.
Figure 3b is a cycle diagram of the conventional example, Figure 4a is a schematic diagram showing the operation of the crankshaft rotating in one direction of the present invention, and Figure 4b is a repetitive motion of the conventional example. FIG. 3 is a schematic diagram of a crankshaft. 1... Housing, 2... Tie bar, 3... Fixed die plate, 4... Moving die plate, 5...
...Frank arm, 8...Crankshaft, 10...
Servomotor.

Claims (1)

[Scope of utility model registration request] In a mold clamping device that crimps male and female molds attached to a fixed die plate and a movable die plate, the movable die plate is connected to a crankshaft via a crank arm, and the movable die plate is connected by rotating the crankshaft in one direction. It is configured to reciprocate and press against and separate from the fixed die plate,
A mold clamping device for an injection molding machine, characterized in that the rotation and stopping are performed by a servo motor in order to accurately stop the mold in the crimped state.