JPS6153211B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of inserting an arbitrary object into a cavity and injecting molten resin around the object to cover the object.

A pair of holding members are provided facing each other and protrude into the cavity. An object is inserted into the center of the cavity using the holding members, and the gap around the object is injected and filled with molten resin. The method of retracting the holding member to the cavity surface and applying a resin coating around the object is described in Japanese Patent Publication No. 49-
It has become publicly known from Publication No. 9095.

However, as in the prior art, sequentially detecting the flow position of the molten resin in the cavity and immediately operating the holding member in response to it is easy to coat objects with simple shapes, but it is complicated. For objects, this is extremely difficult because the flow of the resin becomes complicated, and there are also drawbacks such as the need for a detection member for each holding member.

The present invention aims to eliminate the drawbacks of the prior art described above by operating the holding member that supports the object in the cavity regardless of the flow of molten resin. The purpose is to perform the backward movement of all supporting holding members by detecting the forward distance of the injection piston.

Detection of the above-mentioned forward distance can be carried out using conventionally commonly used limit switches, phototubes, timers, etc., and the backward movement of the holding member can be carried out using hydraulic or electromagnetic means operated by signals from the above-mentioned detector. This can be done by means.

The holding member may be placed at any position within the cavity as long as the object can be fixed evenly, but it is preferably placed near the flow end of the molten resin, and if there are multiple gates, the holding member may be placed at any position within the cavity. It is preferable to set it at the line part and the flow end part.

The present invention will be explained in detail below with reference to illustrated embodiments.

In the figure, reference numeral 1 is an injection mold, in which holding members 3, 3, which are made up of eight hydraulically operated pins, are protruded in pairs at the flow end and intermediate positions of the cavity 2, facing each other so as to be freely retractable. There is. An object 4 made of a metal plate inserted into the cavity 2 is fixed in the center of the cavity with the holding members 3, 3, and the molten resin communicating with the gate 5 is placed around the object, that is, between the cavity surface and the object 4. A gap is formed to be filled.

6 is an injection device, and an injection screw 7 is installed in the heating cylinder.
At the rear end of the injection screw 7 is an injection piston 9 that rotates and moves back and forth within the injection cylinder 8.
are connected. The injection piston 8 is also provided with a limit switch 10 for detecting completion of injection, and a limit switch 11 for detecting that the entire circumference of the object 4 is filled with molten resin before completion of injection. Further, the limit switch 11 is electrically connected to a hydraulic device that operates the hydraulic cylinders 3a, 3a of the holding members 3, 3, and the hydraulic cylinders 3a, 3a are actuated by a signal from the limit switch 11.
a is activated.

To coat the object 4 with resin by injection molding, the injection mold 1 is first opened and the object 4 is inserted into the cavity 2.
This insertion is performed by fixing the object 4 using the holding members 3, 3.

Next, the injection mold 1 is closed and the mold is clamped, and then the nozzle of the injection device 6 is touched to the gate 5 to inject the molten resin 12 as shown in FIG. 2. This injection occurs by advancing the injection screw 7 together with the injection piston 9 using hydraulic pressure, and the molten resin 12, which has been placed in advance in the tip of the heating cylinder, flows from the nozzle through the gate 5 into the cavity 2. do. In this case, since the filling amount of the molten resin 12 is proportional to the amount of forward movement of the injection piston 9, the molten resin 12 is placed at a position that is the forward distance required to fill the entire gap around the object 4. When the limit switch 11 is set, when the injection piston 9 reaches that position, the limit switch 11
operates to issue a signal to the hydraulic system, actuating the hydraulic cylinders 3a, 3a, and retracting the tips of the holding members 3, 3 to the cavity surface. Due to the retreat of the holding members 3, the object 4 is supported from the surroundings by the molten resin 12, and the resin in the cavity during the filling stage is losing its fluidity in the surface layer in contact with the cavity surface, but the inside has fluidity and continues to be filled until the forward position of the injection piston 9 is detected by the injection limit switch 10, so even if the holding members 3, 3 move back, the trace remains as a space. There is no residue left behind, and the molten resin 12 immediately flows and fills up the remains of the holding members 3, 3. The injection is completed when the forward distance is detected by the limit switch 10, and the object 4 in the cavity 2 is completely covered with resin.

Although the above embodiment has one gate 5, it is possible to provide a plurality of gates depending on the shape and dimensions of the object 4, and fill the cavity with molten resin from these gates at the same time. In such a case, it is preferable to set the gate at a location where the resin flow and pressure are well balanced.

Further, the backward movement of the holding members 3, 3 is not limited to being performed all at the same time, but may be performed in stages for each position filled with molten resin. In such a case, a plurality of forward distance detectors may be set on the injection piston at slightly different distances.

As described above, the present invention performs the backward movement of the holding member that fixes the object in the cavity by detecting the forward distance of the injection piston, and therefore has the following effects.

1. Setting adjustment is easy because there is a relationship between the forward distance of the injection piston and the flow distance of the resin in the cavity.

2. Holding members can be provided at the flow ends and weld lines, so the flow will not be hindered.
Air also easily escapes from the advancing/retracting gap of the holding member, resulting in a good product.

3 After the object is securely fixed with the filled resin, the holding member is moved backwards, so the object does not shift and is not affected by the flow of the resin, so the coating can be applied evenly over the entire object. be able to.

4 Regardless of the shape or size of the object, resin coating can be applied by injection molding, and the thickness of the coating can be freely designed.

5. The entire surface can be completely covered by simply injecting molten resin, so even if the object is metal, it will not rust, and even if the product is exposed to the wind and rain, it will remain clean and last for a long time.

[Brief explanation of the drawing]

The drawings show the coating method by injection molding according to the present invention; FIG. 1 is a schematic vertical cross-sectional view when an object is inserted and FIG. 2 is a schematic vertical cross-sectional view when injection is performed. DESCRIPTION OF SYMBOLS 1... Injection mold, 2... Cavity, 3... Holding member, 4... Object, 5... Gate, 6... Injection device, 7... Injection screw, 8... Injection cylinder, 9... Injection Piston, 11...Limit switch for detecting forward distance.

Claims (1)

[Claims] 1. Protrude the required number of holding members in pairs into the cavity, insert an arbitrary object into the cavity with the holding members, inject molten resin into the gap around the object, and insert the holding members into the cavity. A method for coating by injection molding, characterized in that, when the object is coated by retracting the holding member to a surface, the retracting operation of the holding member is performed by detecting the forward distance of the injection piston.