JPH022580Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a screw brake device for accurately holding the position where the screw changes from speed control to pressure control during the injection process of an injection molding machine.

In the injection process of molding a molded product using an injection molding machine, the screw during injection changes from speed control to pressure control. This switching is usually done by the position of the screw, but it is also done by hydraulic pressure or resin pressure in the cavity. In the case of high-speed injection, which has been widely adopted in recent years, the screw does not stop at the set position, and a flow due to inertia (hereinafter referred to as inertia) occurs, making the screw advance/retreat position unstable and having a negative impact on the molded product.

[Prior Art] For this reason, a hydraulic brake system that blocks the drain side of the injection cylinder for moving the screw, or a system that mechanically stops the piston in the injection cylinder described above has been used. However, in the former hydraulic brake system, the faster the speed, the greater the inertia, and it was impossible to completely absorb the inertia simply by blocking the drain circuit. The latter mechanical brake system is better than the former in terms of absorbing inertia, but the mechanism is complicated and costs increase.
This is possible only at a fixed position, and when the screw advance limit position changes, the mechanism must be changed in accordance with that position, which also has the disadvantage of high cost and time required for change.

[Purpose of invention]

The present invention eliminates these drawbacks, and the purpose is to provide a screw brake device for an injection molding machine that can reliably stop the screw at any position and has a simple mechanism and low cost. be.

[Key points of the idea]

The screw brake device for an injection molding machine according to the present invention connects the injection load side oil chamber and drain side oil chamber of the injection cylinder that moves the screw by a pressure reducing valve and a solenoid valve in series, and controls the speed of the screw during injection. The system is characterized in that a solenoid valve is opened by a signal immediately before switching from to pressure control to apply pressure oil to both sides of the piston of the injection cylinder, thereby applying a brake to the screw via the piston.

[Example of idea]

A diagram showing an embodiment of the invention will be described below. Screw 1 inserted into heating cylinder 11
2 is moved laterally from a piston 14 in an injection cylinder 13 by a piston rod 15 and a mounting piece 16, and is also rotated by a hydraulic motor (not shown). The right injection load side oil chamber 13A and the left drain side oil chamber 13B of the injection cylinder 13 are as follows:
A solenoid valve 1 is connected to the hydraulic power source 17 and the tank 18, respectively.
The maximum pressure of the hydraulic power source 17 is controlled by a relief valve 23. Further, when necessary, the pressure oil in the injection load side oil chamber 13A is controlled to flow into the drain side oil chamber 13B of the injection cylinder 13 by a B solenoid valve 22 connected in series with the pressure reducing valve 21. ing.

Next, the operation of the embodiment described above will be explained. When the A solenoid valve 19 is switched from the neutral position shown in the figure to the right side by the injection signal, the pressure oil in the hydraulic source 17 is transferred to the injection cylinder 13.
The injection load side oil chamber 13A flows into the piston 14.
moves to the left, and as a result, the screw 12 moves to the left via the piston rod 15 and the mounting piece 16, injecting the molten resin stored on the left side of the heating cylinder 11.

During injection, a signal immediately before switching any screw from speed control to pressure control, for example, a position signal of the screw 12, causes the B solenoid valve 22 to switch from the illustrated state to the right side, and the drain side oil chamber 13 of the injection cylinder 13
In B, the pressure oil in the injection load side oil chamber 13A is connected to the pressure reducing valve 21.
and B through the solenoid valve 22. As a result, the piston 14 receives pressurized oil on both sides, receives sudden braking, and moves forward at a very low speed. The braking force at this time is determined by adjusting the pressure reducing valve 21. Then, the pressure holding signal causes the B solenoid valve 22 to return to the illustrated position, and the piston 14 and therefore the screw 1
2 will be subject to pressure control.

[Effect of idea]

As explained above, the screw brake device for an injection molding machine according to the present invention is low in cost because it only includes a pressure reducing valve and a solenoid valve in addition to the screw moving mechanism. During braking, pressure oil is applied to both sides of the screw moving piston to generate a large braking force. As a result, the screw reliably stops at the set position, which has the advantage of producing a high-quality molded product. Furthermore, since the brake is generated when the electromagnetic valve is opened, the stopping position of the screw can be arbitrarily selected, and the braking force can also be arbitrarily selected by adjusting the pressure reducing valve.

[Brief explanation of the drawing]

The figure is a sectional view showing an embodiment of the present invention. 12... Screw, 13... Injection cylinder, 1
3A... Injection load side oil chamber, 13B... Drain side oil chamber, 14... Piston, 21... Pressure reducing valve, 22...
...Solenoid valve, 23...Pressure adjustment valve.

Claims (1)

[Scope of utility model registration request] The injection load side oil chamber and the drain side oil chamber of the injection cylinder for moving the screw are connected by a pressure reducing valve and a solenoid valve in series, and the solenoid valve is activated by a signal immediately before switching the screw from speed control to pressure control during injection. A screw brake device for an injection molding machine, wherein a brake is applied to the screw via the piston by opening the piston and applying pressure oil to both surfaces of the piston of the injection cylinder.