JPH0221376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a hollow molded product having small additional parts such as protrusions.

Conventionally, when manufacturing a hollow product 2 having a protrusion 1 as shown in FIG. A method of secondarily attaching the molded protrusion 1 has been adopted. However, in this method, the process is divided into several steps, resulting in a significant decrease in productivity, and the basic merit of the blow molding method, which is high productivity, is not utilized. On the other hand, in order to improve productivity, when the protrusion 1 is manufactured integrally with the main body 2' using the blow molding method, in order to spread the parison all the way to the protrusion 1, it is necessary to mold the inside of the parison before mold clamping. The method used was to inflate the parison to a certain extent by blowing pressure fluid into it, then clamp the mold and perform hollow molding. However, the above method has the disadvantage that the expanded parison during mold clamping is eaten away at the entire circumference of the joint surface of the mold, resulting in significant material loss and requiring much effort to remove burrs afterwards. Another method is to partially expand and expand the parison to limit the part that is eaten away, but it is extremely difficult to partially change the hardness and wall thickness of the parison due to the balance with the melt index of the parison. be.

The present invention has been developed in view of the above points, and has a method of improving productivity by generating burrs only around the protruding portions to form the protruding portions, but preventing burrs from occurring in other portions, and It is an object of the present invention to provide a method for manufacturing a hollow molded product having a protrusion with little material loss. The present invention is characterized in that in a blow molding method in which a parison is housed in a mold and then a pressurized fluid is blown into the inside of the parison to form the parison, the mold is used as a pair of first molds for a portion including a protrusion. Divide into a pair of second molds for the part not including the protrusion, first clamp the second mold, then inject pressure fluid, and then clamp the first mold. After that, the pressure fluid is blown again and the protrusions are also integrally molded.

Next, specific embodiments of the manufacturing apparatus used in the method according to the present invention will be described based on the accompanying drawings. A mold for molding a bellows product 2 having a projection 1 shown in FIG. 1 is divided as follows according to the present invention. First, the mold is also divided into two along a symmetry plane A that divides the product 2 into two symmetrical parts.
Next, the cylindrical part and the bellows part are divided at the interface B, and a pair of first molds is used to mold the part 2a that includes the protrusion 1, and a second mold is used to mold the part 2b that does not include the protrusion 1. Divide into 4 molds in total. FIGS. 2, 3, and 4 show schematic cross-sectional views of the manufacturing apparatus in which the mold is divided into four pieces as described above. FIG. 2 shows a state before the manufacturing apparatus used in the manufacturing method according to the present invention starts mold clamping. In FIG. 2, a portion 2a that does not include a pair of opposing protrusions 1
Second molding molds 4 and 4' for molding are arranged symmetrically with respect to the joining surface A' of the molds as a plane of symmetry. A pair of first molds 3 and 3' for molding the portion 2a including the protrusion 1 are similarly disposed symmetrically opposite to each other with respect to the joint surface A'. The first molds 3, 3' and the second molds 4, 4' are slidably connected to each other at the dividing surface B' of the mold corresponding to the boundary B between the cylindrical part and the bellows part mentioned above. There is. Here, the molding-side end surface C' of the first molding mold 3, 3' is separated from the molding-side end surface D' of the second molding mold 4, 4' with respect to the joint surface A'. , 3' and the second molds 4, 4' are set relative to each other. As described above, the hollow mold according to the present invention is divided into four parts: the left mold 5 consisting of the first mold 3 and the second mold 4, the first mold 3' and the second mold 4'. The right mold 5' is divided into right-hand molds 5', which are arranged symmetrically with respect to the joining surface A'. On the back side of each of the left and right molds 5, 5' opposite to the opposing molding surfaces, there are pressing portions 6, 6 of pressing means for pressing and clamping the left and right molds 5, 5', respectively. ' is arranged. The second mold 4 of this pressing part 6, 6',
Two protrusions 7, 7' each having a two-step protruding shape are provided at appropriate positions on the portion facing the back surface of 4'.
Coil springs 9, 9' are fitted onto the tip convex portions 7a, 7a' of the protrusions 7, 7'. On the other hand, the protrusion 7,
At positions corresponding to 7', recesses 8, 8' having a two-stage recessed shape into which the protrusions 7, 7' can fit are formed. and coil spring 9,
The protrusions 7, 7' with the extrapolated portions 9' are inserted into the second mold 4,
It extends inside the recesses 8, 8' carved on the back surface of the recess 4', and abuts the bottom surfaces of the recesses 8, 8' via the coil springs 9, 9'. As described above, the second molds 4, 4' are moved by being pressed by the protrusions 7, 7' via the coil springs 9, 9'. Here, the side surfaces of the protrusions 7, 7' and the inner side surfaces of the recesses 8, 8' are in slidable contact with each other. On the other hand, the first molds 3, 3' are fixed to the contact pressing parts 6, 6', and are slidably connected to the second molds 4, 4'.
It moves integrally with the pressing parts 6, 6'. FIG. 5 is a side view of the left mold 5 viewed from the joint surface A', and it can be seen from this figure that the protrusion 1 is present on the joint A'.

Next, a process of manufacturing a hollow molded product having a protrusion using the manufacturing apparatus configured as described above will be described.

FIG. 2 shows the manufacturing apparatus according to the invention before mold clamping begins. First, the opposing left and right forming molds 5,
5', the soft parison 10 extruded from an extruder (not shown) is poured out and is in a drooping state (drawdown). Next, the pressing means is operated and the pressing parts 6, 6' are pressed against the left and right molds 5,
5' is pressed toward the joint surface A', and the left and right molds 5, 5' are moved in the direction of the arrow at the same speed. The first molding mold 3, 3' and the second molding mold 4,
When the second molding molds 4, 4' of the left and right molding molds 5, 5' consisting of 4' are joined at the joint surface A', the operation of the pressing motion is temporarily stopped. In this state, the first stage of blowing pressure fluid into the inside of the parison 10 is performed. In this example, air is used as the pressure fluid, and the blowing pressure is set to 1.5 Kg/cm ² . parison 1
FIG. 3 shows a state in which air is blown in the direction of the arrow from the pouring source part of the parison to enlarge the parison. Second mold 4, 4' of parison 10
The portion accommodated in the cavity 4a formed by the above is expanded roughly along the peripheral wall of the cavity 4a. However, of the parison 10, the first mold 3,
3', that is, the part corresponding to the part 2a including the protrusion 1, is not clamped, so it swells freely and the inner diameter of this part is locally enlarged to be larger than the root diameter of the bellows part. Ru. This state is the joint surface
When viewed from A', it looks like the parison 10 as shown in Figure 5.
is enlarged as shown by the two-dot chain line, and the cavity 1' of the protrusion 1 is also included in the locally enlarged portion. When the first stage of air blowing is completed, the pressing means starts pressing again, and the pressing parts 6, 6' resume pressing the left and right molds 5, 5'. However, since the second molds 4, 4' have already been joined and do not move, the protrusions 7, 7'
The coil springs 9, 9' interposed between the molds 4, 4' and the recesses 8, 8' are pressed and bent to enter the recesses 8, 8'. On the other hand, the first mold 3,
3' is directly fixed to the pressing parts 6, 6', so it moves together with the pressing parts 6, 6' and is joined at the joint surface A', completing the second stage mold clamping process. FIG. 4 shows this state. At this time, the first
Parison 1 enlarged by staged air blowing
0 was expanded beyond the outline of the portion 2a having the protrusion 1, so the first mold 3 to be joined,
It is sandwiched between the mold surfaces of 3'. Therefore, when the mold clamping is completed and the mold surfaces to be joined of the opposing first molds 3, 3' are brought into close contact by the pressing parts 6, 6', the line forming the outer shell becomes an edge and is enlarged. The parison 10 is then cut. Therefore, a sufficient parison is secured in the cavity of the protrusion 1 as well.
Next, the second stage of air blowing is carried out at a pressure of about 8 kg/cm ² which is several times higher than that in the first stage. Since the second stage of blowing is carried out at high pressure,
Even the inside of a recessed cavity, such as the part having the protrusion 1, is pressurized evenly. By blowing high-pressure air in this second stage, the parison 10 is completely crimped onto the inner wall surface of the entire cavity, and a desired shape is formed.

In the subsequent mold release process, the pressing force of the pressing means is released, the pressing parts 6, 6' are retreated in the opposite direction to the molding process described above, and each mold is placed in the position shown in FIG. 2 before starting molding. return. At this time, the first molds 3, 3' are fixed to the pressing parts 6, 6', so they retreat together with the pressing parts 6, 6', but the second molds 4, 4' are The vehicle is moved backward by an engaging means (not shown) that operates only when the vehicle is being moved backward. After this, a hollow molded product having desired protrusions is obtained through usual finishing steps such as demolding, curing, and deburring.

In this embodiment, as described above, a mechanism is used in which two sets of two types of split molds for molding mutually different parts of a certain molded product are clamped and pressed by one system of pressing means. This is to minimize the increase in equipment costs for the step-by-step blow molding method using the split molds of the present invention. If it is a pressing mechanism, 2
Although this allows for fine adjustment when interlocking different types of molds, the related equipment becomes complicated and expensive.

As described in detail above, according to the present invention, by dividing the mold as appropriate and configuring the molding process in stages according to the division of the mold, a hollow molded product having a protrusion is formed between the protrusion and the main body. can be molded all at once, and the generation of burrs is kept to a minimum, eliminating the need for deburring in the finishing process.
Productivity is significantly improved and material loss can be minimized. It should be noted that the present invention should not be limited to the specific embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, out of four divided molds, each half (for example, 3 and 4, or 3' and 4') can be integrated into three molds. It is also possible to clamp the mold vertically instead of horizontally, but in this case, the parison is injected by moving the pouring nozzle horizontally, and the parison is placed on the lower mold once. Become. Furthermore, the mold can be divided into four or more parts depending on the shape of the molded product.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a hollow molded product having a protrusion;
FIG. 2 is a schematic cross-sectional view of the apparatus for producing hollow molded products having protrusions according to the present invention, showing the state before mold clamping starts, and FIG. 3 shows the apparatus for producing hollow molded products having protrusions according to the present invention. The schematic cross-sectional view shows the state of the mold after the mold clamping is completed for the part that does not include the protrusion, and FIG. Figure 5 shows the state in which all the mold clamping has been completed, and the mold has been completely clamped for the part that includes the mold. Figure 5 is a side view of the left mold seen from the joint surface, and shows the state in which the first stage of air blowing has been completed. The two-dot chain line indicates the enlarged parison. Explanation of the symbols: 1: protrusion, 3, 3': first mold, 4, 4': second mold, 6, 6': pressing part,
7, 7': Protrusion, 9, 9': Coil spring, 1
0: Parison.

Claims (1)

[Scope of Claims] 1. A blow molding method in which a parison is housed in a mold and then a pressurized fluid is blown into the inside of the parison to form the parison, wherein the mold is connected to a pair of first molds for a portion including a projection and a projection. is divided into a pair of second molds for parts that do not include the second mold, and first the second mold is
A protrusion characterized in that after the mold is clamped, pressurized fluid is blown into the mold, and after the first mold is clamped, the pressure fluid is again blown into the protrusion so that the protrusion is also integrally molded. A method for manufacturing a hollow molded product having a part. 2. Claim 1, characterized in that the pair of first molds and the pair of second molds are divided and each mold is composed of an even number of 4 or more. A method for producing a hollow molded product having the protrusion described above.