JPS6235899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling method in secondary processing of thermoplastic resin pipes, and in particular, to promote cooling while preventing deformation of secondary processed pipes due to cooling. The present invention relates to a cooling method that can improve the molding cycle and shorten the molding cycle all at once.

Thermoplastic resin pipes are used for various secondary processing by taking advantage of their thermoplastic properties. FIG. 1 is a schematic cross-sectional view showing an example thereof, and a secondary processing mold 1 consists of an outer mold 2 and a core mold 3. The core type 3 is the guide part 3
a, a plurality of segments 4, 4' in addition to the large diameter portion 3b
The pipe 5 is formed with a large diameter portion 5b, a raised portion 5c, and a large diameter tip portion 5d, respectively. Reference numeral 6 denotes a cone that moves forward and backward in the left-right direction in the figure. When the cone moves forward as shown in the figure, the segments 4, 4'... expand in diameter, and when it retreats to the left in the figure, the segments 4, 4'... contract in diameter. Eliminates undercuts during demolding. A large number of mechanisms for expanding and contracting the diameter of these segments have been proposed so far, and the figure only schematically shows one example. Therefore, the diameter expanding/contracting mechanism can be changed or omitted (merely using a tampin type), and these changes do not change the technical scope of the present invention, which will be described later.

The forming method according to the above description is a secondary processing method that focuses on expanding force in the direction perpendicular to the pipe axis, and the outer mold 2 is clamped mainly for the purpose of shaping after covering the pipe 5. However, the tube wall of the secondary processed portion has to be thinned due to the expansion of the tube diameter accompanying the expansion force. Since this thinning leads to deterioration of mechanical strength, in addition to the above-mentioned expansion force, compressive force is applied in a direction parallel to the tube axis to reduce the tube length and provide the corresponding amount of tube material to the thin walled portion. Research is being conducted to prevent thin walls. This method is hereinafter referred to as thickening molding to distinguish it from the general molding described above, but it is called 7 in Fig.
The pushing ring shown in numeral 2 is used to push and compress the large-diameter tip 5d of the pipe in the right direction in the drawing to help increase the thickness of the pipe. In addition, the outer mold 2 for thickening molding is placed on the outer periphery of the core mold 3 with a predetermined gap (a gap corresponding to the amount of thickening) left before molding.

Now, when a certain amount of secondary processing is performed using the above-mentioned mold, whether it is one-time molding or thickening molding, the secondary processed product must be cooled and demolded to prepare for the next cycle of molding. Must be. In this case, if the mold is demolded before cooling has progressed sufficiently, and if the inner and outer surfaces of the tube are cooled with water spray from water spray tubes 8 and 9 as shown in FIG. Shrinkage as shown in can occur, resulting in defective products, and this tendency is particularly strong in thickening molding. In order to eliminate this inconvenience, there is a method of cooling the mold 1 for a sufficient amount of time and removing the mold after there is no possibility of shrinkage, or removing the mold 1 from the outer mold 2 and/or the core. Two methods can be considered: providing a cooling medium passage in the mold 3 and sufficiently cooling the pipe together with the mold before demolding. However, these methods do not utilize heat dissipation by radiant heat, and in particular, these methods do not use a cooling medium, so they require an extremely long time for cooling. The other method uses a cooling medium, so the cooling time is not so long, but the temperature of the mold, especially the core mold 3, has dropped significantly, so the core mold 3 must be thoroughly cooled before the next cycle. It is necessary to heat the mold, which not only increases the amount of energy loss but also requires a long time to recover the mold temperature. Incidentally, when a high-temperature thermoplastic resin tube is press-fitted into a cooled mold, defects such as cracks and local deterioration may occur in the resin tube.

In this way, no matter which method is adopted, the molding cycle becomes longer and it is necessary to heat and cool the mold, which is inconvenient from an energy standpoint. The present invention has been made in view of these circumstances, and provides a method for cooling a secondary processed product without the above-mentioned drawbacks, especially without deforming the secondary processed product. The purpose of the present invention is to provide a method that allows cooling to be performed relatively quickly, thereby improving yield and shortening the molding cycle.

However, the configuration of the present invention is to press fit a core mold into a heat-softened thermoplastic resin pipe and expand the diameter of the core mold.
In the method of cooling the pipe after demolding, the secondary processed pipe, which is still in a high temperature state, is removed from the core mold and then fitted into a shape-retaining cooling mold to cool it. has an outer surface shape that follows the inner surface shape of the high-temperature part of the secondary processed pipe, and is configured such that a cooling medium flows therein. Therefore, tube shrinkage during cooling can be prevented and the tube can be cooled relatively quickly, but there is also the advantage that the molding die can be left empty at a high temperature in preparation for the next cycle, which significantly shortens the molding cycle. .

The configuration and effects of the present invention will be explained below based on examples, but the following are merely representative examples, and any changes and implementations in accordance with the spirit of the preceding and later descriptions are within the scope of the technology of the present invention. covered within the scope.

FIG. 3 is a schematic cross-sectional view showing an example of the shape-retaining cooling mold 10, in which a heat-resistant rubber ring 12 is attached to maintain the shape of the raised portion 5c. Since this rubber ring 12 is an elastic body, when it is inserted into the pipe 5, even if it hits the large diameter portion 5d at the tip, it will not expand greatly, and even if it does expand slightly, the pipe will shrink as it cools. Since the diameter is reduced by force, the shape of the pipe is not damaged.
Furthermore, when the cooling mold 10 is removed after cooling, only the rubber ring 12 remains in the raised portion 5c, so it is only necessary to deform it and remove it last. Of course, the core mold 3 shown in FIG. 1 may be replaced with a core mold having a structure having a diameter expansion/contraction mechanism similar to that of the core mold 3 shown in FIG. Also, there is a raised part 5c on the secondary processed pipe (socket in the figure).
If a cooling mold is not available, a simple tampin type cooling mold can be used, thereby simplifying both molding and cooling workability. 13 and 14 are a cooling medium inlet pipe on one side, a cooling medium discharge pipe on the other side, and 11 is a cooling medium passage formed in a spiral shape. In this embodiment, the water sprinkler pipe 8
is used in combination, but this is not an essential requirement for the present invention. Further, the water jacket mechanism as shown in FIG. 3 is merely a typical example, and modifications such as making the inside hollow to enhance the cooling effect of the cooling medium are also possible. When such a shape-retaining cooling mold is used, shrinkage of the pipe due to cooling is completely prevented. Although it is possible to perform almost complete cooling through this process, in order to shorten the molding cycle even more significantly, it is necessary to maintain a critical temperature that does not cause shrinkage due to cooling (70 -60 DEG C.), the mold 10 is removed, and water spray cooling, water immersion cooling, or air cooling as shown in FIG. 2 may be performed.
In addition, when performing the shape-retaining cooling shown in FIG. 3 after the molding shown in FIG. However, it is also possible to transfer the molded material to that shown in FIG. 3 immediately after molding without performing such cooling. Therefore,
Although the temperature of the molded product when transferred to the state shown in FIG. 3 is not restricted in the slightest, the temperature at which the shape retaining function of the mold 10 is effectively exerted is, for example, 80° C. or higher in the case of a hard vinyl chloride pipe.

The present invention is constructed as described above, and its effects are summarized as follows.

The secondary processed product will not be deformed during cooling.

Cooling speed is fast and cycle times can be shortened.

There is no need to heat or cool the mold, so energy loss is low.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view showing an example of secondary processing of thermoplastic resin pipes, Figure 2 is a sectional view of main parts showing water spray cooling, and Figure 3 is a schematic sectional view showing an example of the use of a shape-retaining cooling type. It is a diagram. 3...core type, 8, 9...watering pipe, 10...shape-retaining cooling type.

Claims (1)

[Claims] 1. In the method of press-fitting a core mold into a thermoplastic resin tube that has been softened by heating, expanding the diameter of the core mold, and cooling it after demolding, the core mold is still in a high heat state where it can be deformed. 2.
The secondary processed pipe is removed from the core mold, and then a shape-retaining cooling mold is inserted into the secondary processed pipe, following the inner shape of the high-temperature part of the secondary processed pipe, and in which a cooling medium is circulated. A cooling method in secondary processing, characterized by maintaining the shape of a subsequently processed pipe and promoting cooling.