JPH034369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a urethane foam panel body in which urethane is foamed and shaped within an outer frame that becomes a part of the product.

Conventionally, when manufacturing an insulated door for a refrigerator, for example, by in-situ foaming of urethane, an outer frame, such as a flat box-shaped door frame, is set in a shaping mold consisting of an upper and lower mold, and then urethane is injected into the door frame. The method used was to inject and foam. However, this method has the disadvantage that a large number of expensive molds made of iron, aluminum, or the like must be provided, which increases manufacturing costs.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and its purpose is to allow urethane to be foam-formed within an outer frame that is a part of the product without using a mold consisting of an upper and lower mold. To provide a method for manufacturing a urethane foam panel body, which can be carried out in an atmosphere at approximately room temperature, almost eliminates the need for a heating furnace for after-cure operations, and can reduce manufacturing costs as a whole.

An embodiment in which the present invention is applied to the manufacture of a heat insulating door for a refrigerator will be described below. Fig. 1 shows the finally obtained heat insulating door 1 for a refrigerator, in which a urethane foam 3 is placed inside a flat box-shaped iron plate door frame 2 whose top surface is open. The urethane foam panel body 5 having a structure in which a sheet 4 of kraft paper or the like is bonded to the surface of the urethane foam 3 is manufactured by the method of the present invention, and the door inner panel 6 is later fixed with screws, etc. The heat insulating door 1 is completed by attaching it together with a gasket (not shown). Next, a method for manufacturing the urethane foam panel body 5 will be explained with reference to FIGS. 2 and 3. One feature of the present invention is that various steps from the urethane injection process to the completion of molding are carried out on a conveyor, and in this embodiment, as shown in FIG. A conveyor belt 9 is used. On the underside of this conveyor 9, as shown in FIG. 2D and FIG. 3,
A rigid receiving plate 10 is fixedly arranged so that the conveyor 9 can slide on its upper surface, and a simple positioning projection 11 for determining the position of the door frame 2 is provided on the upper surface of the conveyor 9. In addition, this conveyor 9 carries the door frame 2 described thereon at an injection station P1, a sheet insertion station P2, a spreading station P3, and a compression shaping station P4.
The structure is such that the files are sequentially transferred to When the door frame 2 is located at each of the stations, the conveyor 9 is temporarily stopped and the door frame 2 is transported intermittently. A urethane injection machine 12 is arranged at the injection station P1, a sheet feeding machine 13 is arranged at the sheet insertion station P2, and a pushing and spreading station.
As shown in FIG. 2C, a pushing and spreading device 16 is disposed at P3, which moves a flat presser member 15 up and down using a pneumatic cylinder 14, and a compression shaping station P4 is disposed in the direction of movement of the conveyor 9. A plurality of large compression shaping devices 17 are arranged side by side. This compression shaping device 17 is equipped with a movable member 19 that is moved up and down by an air cylinder 18, as shown in an enlarged view in FIG. It is formed by forming a projecting part 19a with a flat bottom surface having a somewhat small outer size and a flange holding part 19b which presses against the flange part 2a between the door frame 2.

Next, a urethane foam shaping procedure performed using the above-mentioned equipment will be explained. First, for the front stage of injection station P1, move the door frame 2 onto the conveyor 9.
and transferred to injection station P1.
Then, urethane is injected into the door frame 2 as shown with reference numeral 20 in FIG. 2A. The execution time required for this injection step a is about 15 seconds. The door frame 2 injected with the urethane 20 is transferred to the sheet loading station P2, where the sheet 4 is coated above the urethane 20 through the open opening of the door frame 2 by the sheet feeder 13 as shown in FIG. 2B. It is supplied into the door frame 2 so that the The sheet insertion process (b) at sheet insertion station P2 takes about 10 seconds. Next, the door frame 2 is transferred to the spreading station P3,
Here, the pressing member 15 descends and presses the urethane 20 inside through the sheet 4 to spread it flat as shown in FIG. 2C. The execution time of this pushing and spreading step C is about 10 seconds, and after that, the pressing member 15 is raised and left for about 5 seconds without any pressing force being applied, as shown in FIG. 2 C1. The position on the conveyor 9 in this left state is shown as P3a in FIG.
Next, the door frame 2 is transferred to the compression shaping station P4, where the movable mold part 19 is lowered and foaming begins after injection. The urethane 20 in the door frame 2 is pressed and compressed by the protrusion 19a as shown in FIG. 2D. At this time, the flange holding part 19b of the movable member 19 presses the opening flange part 2a of the door frame 2,
This prevents bowing deformation in which both ends of the door frame 2 rise above the upper surface of the conveyor 9 due to repeated pressing and compression as described below on the urethane 20 that resists foaming pressure.

After the above-mentioned pressure compression is performed for about 10 seconds, the movable mold member 19 is raised and maintained in a state where no pressing force is applied to the foaming urethane in the door frame 2, that is, the urethane foam 3 for about 5 seconds. This process is repeated several times, and Figure 3 shows the position of the compressed state.
The left position is shown as P4a, and the left position is shown as P4b. In this way, in this compression shaping step (d), compressive force is intermittently applied to the urethane foam 3 during foaming until the polymer strength reaches the internal pressure of the urethane foam, thereby shaping the urethane foam 3 into the door frame 3. While filling the entire area of the foam, the foam is shaped into a predetermined thickness and surface shape, and is then transferred to the next stage as a completed urethane foam panel 5 as shown at position P5 in FIG. Ru. This kind of compression shaping process
In the repeated pressure compression in (d), the movable mold member 1
It is preferable that the depth of pushing into the door frame 2 in step 9 is deep the first time and then gradually shallower to reach the foam thickness design value in the final step.

In the manufacturing process described above, the rigid receiving plate 10 provided on the lower side of the conveyor 9 is moved by the pressing member 15 and the urethane inside the door frame 2 during the spreading process (a) and the compression shaping process (d). This prevents the conveyor 9 from settling due to the foaming pressure when pressed by the member 19, and is designed to have a strength greater than the foaming pressure load. In addition, each of the above stations
P1 to P4 are installed in an atmosphere at approximately room temperature,
Therefore, the compression shaping process (d) is an after-cure process.
Since this is carried out at approximately room temperature, unlike the conventional method in which the after-cure operation is performed in a heating furnace, large equipment such as a heating furnace is not required, and even if it is required, it can be a simple one.

The reason why there is no problem even if the heating furnace is not required will be explained below. That is, FIG. 4 shows the temporal change characteristics of the foaming pressure, polymer strength, and temperature inside the urethane foam during foaming of urethane. In FIG. 4, the curve L shows the foaming pressure characteristics, the curve M shows the polymer strength characteristics, and the curve N shows the temperature characteristics inside the urethane foam. In addition, dotted line curves L1, M branched from the above curves L, M, N.
1 and N1 indicate the case where the ambient temperature is low.
As can be understood from FIG. 4, in urethane foaming, the foaming pressure decreases faster as the ambient temperature decreases after the maximum foaming pressure is exceeded.
Furthermore, the lower the ambient temperature, the faster the polymer strength increases. Further, the temperature inside the urethane foam, that is, the reaction temperature, becomes lower as the ambient temperature is lower after the maximum value has been passed. The points T ₁ and T ₂ when the polymer height exceeds the foaming pressure are indicated by curves L and L in Figure 4.
1 and M, M1, but as is clear from the indications at this point T ₁ and T ₂ , the time until the polymer strength exceeds the foaming pressure after the maximum foaming pressure. It can be seen that the lower the ambient temperature, the shorter the period. This means that the method of the present invention in which the after-cure operation is performed at room temperature can shorten the after-cure time compared to the conventional method in which the after-cure operation is performed using a heating furnace. Therefore, even if the compression shaping step (d) requires a state of being left for about 5 seconds several times, there is almost no decrease in time efficiency.

According to the present invention, as in the above-mentioned inventions, the movable mold member only needs to be a structure that presses and compresses the urethane in the outer frame into a predetermined shape in the compression shaping process,
Moreover, since it is commonly used for the outer frames that are sequentially transferred by a conveyor, the overall structure is extremely simple compared to the conventional method, which requires a large number of expensive molds that cover the entire outer frame and have a lower mold. In addition, the process related to foam formation can be carried out continuously on a conveyor, and a large heating furnace is not required, making it possible to reduce manufacturing costs in general.

[Brief explanation of the drawing]

The drawings are for explaining one embodiment of the manufacturing method of the present invention, and FIG. 1 is a vertical cross-sectional view of a heat-insulating door, FIGS. 2A to C1 are diagrams showing the execution status of each process, and FIG. FIG. 3 is an explanatory view of the production line, and FIG. 4 is a characteristic curve diagram showing various characteristics during urethane foaming. In the diagram, 2 is the door frame (outer frame), 9 is the conveyor, 1
2 is an injection machine, 13 is a sheet feeder, 15 is a pressing member, 16 is a pushing and spreading device, 17 is a compression shaping device,
19 is a movable member.

Claims (1)

[Claims] 1. The following steps (a), (b), (c) are carried out while a flat box-shaped outer frame with an open upper surface, which is a part of the product, is placed on a conveyor for transportation. A method for producing a urethane foam panel body, characterized in that (d) is carried out in this order in an atmosphere at approximately room temperature. (a): Step of injecting urethane into the outer frame, (b): Step of covering the urethane inside the outer frame with a sheet, (c): Using a presser member that moves up and down, pouring the urethane inside the outer frame through the sheet. (d): Following step (c), the urethane foaming is intermittently compressed and shaped by a movable member that moves up and down.