JPH044930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a blow molding method that can partially provide thick-walled parts, and more specifically, a parison is partially cut open, and the cut-out part is used as a thick wall near the blowing nozzle. This is a blow molding method characterized by increasing the wall thickness.

Elastic air bladders, such as seat lumbar supports or blood pressure measurement bags, have conventionally been made of rubber. However, since rubber molding requires a vulcanization process, productivity is very low and production time is long, resulting in expensive products. Therefore, bags are now being made of thermoplastic elastomers, which are highly productive and do not require a vulcanization process. There are two ways to mold the thermoplastic elastomer that is the material of this bag: a method of forming a sheet and high-frequency welding, and a method of blow molding. Since the elasticity of the thermoplastic elastomer used is significantly lower than that of rubber, rubber cannot be used as a substitute. On the other hand, with blow molding, it is now possible to mass-produce products equivalent to those made of rubber. , connecting parts, protruding parts, etc. cannot be integrally molded, for example,
When it is necessary to connect an air supply pipe made of another material such as a rubber tube to a bag formed by blow molding, this connection can be made by pushing the rubber tube into the air inlet of the bag and gluing it, or by using high-frequency It was done by welding. Such secondary processing is extremely complicated, and the adhesive may ooze out or the welded portion may be thermally deformed or deteriorated, making it unsuitable for commercial use.

The present invention was invented in view of this point, and its purpose is to thicken the wall thickness of the part that forms the air inlet so that it can be integrally formed during molding, and also to have a beautiful appearance. The strength is also to obtain a large air inlet.

The case where the present invention is used in a blood pressure measuring bag will be explained below with reference to the drawings. FIG. 1 is a perspective view of a blood pressure measuring bag 1 obtained according to the present invention. 2 is a main body, and 3 is an air inlet for introducing pressure into the main body. The air inlet 3 is thicker than the main body 2.

Next, the blow molding method of the present invention will be explained based on the drawings. First, the molds 4a and 4b having the external shape of the desired bag 1 on their mold surfaces are separated from each other. Between the molds 4a and 4b which are spaced apart from each other, a parison 5, which is partially cut out and whose cut-out end 8 is thicker than other parts, hangs down. The blowing nozzle is placed in the parison 5 so as to be located between the cut ends 8. In order to extrude this parison 5, the shape near the exit of the resin path formed by the die 6 and the core (not shown) is made similar to the cross-sectional shape of the parison 5 shown in FIG. It is formed. The reason why I said "similar" here is that when a synthetic resin exits from the inside of the die 6 to the outside, it tends to change its shape inward or outward due to the difference in pressure or sheer rate. This is because the resin path within the die must be designed taking these values into consideration. In general, thermoplastic elastomers are extruded at a low sheer rate to ensure no molding defects, so the shape of the parison is relatively similar to that of the resin outlet. Mold clamping is started when the hanging of parison 5 reaches the lower part of the mold. As the mold clamping progresses, the molds 4a and 4b come into contact with the parison 5, and as the mold clamping progresses further, the cut-out end 8 of the parison 5 comes into contact with the air inlet equivalent part 10 on the mold surface, as shown in FIG. the blowing nozzle 7
The end portion 8 corresponds to the vicinity of the air inlet corresponding portion 1.
The wall thickness of the parison 0 is thicker than other parts, and the air inlet formed by the blow nozzle 7 and the mold is filled with the parison. Next, pressurized fluid is ejected into the parison from the blow nozzle 7,
A parison is brought into contact with the cavity surface 9 to shape the shape of the mold surface. After the cooling time has elapsed, the jetting of the pressure fluid is stopped, the blowing nozzle 7 is pulled out, and the mold 4 is removed.
Open a and 4b, take out the bag 1, and complete this blow molding method.

In this example, the shape of the parison is basically a circular parison with a part cut out (so-called circular die extrusion), but the shape is not limited to this, and for example, two sheet-like shapes are used. The present invention can be utilized even if the parison is used. Even in such a case, the present invention is carried out by extruding the parison by making one end (or both ends) thick and hanging the parison so that the air inlet is located at that part.

The idea of making the air inlet thicker in the bag of the present invention can be applied not only to the air inlet of a blood pressure measuring bag, but also to the opening of a water pillow, or the opening for fitting the stopper of an infusion bottle, for example. be. In blow molding, the parison is inflated and molded, so it is not possible to make only one part thick. In particular, as in the blood pressure measurement bag of the embodiment of the present invention, the air pressure is low and the parison is inflated uniformly. In a product for which this is desired, the material of the main body itself must be elastic and thin, whereas the air inlet must be thick.

In the present invention, any synthetic resin material that can be blow molded can be used. In addition, in order to manufacture an elastically moldable bag as in the embodiment, materials such as soft polyvinyl chloride, polyester elastomer, polyurethane elastomer, polyamide elastomer, olefin elastomer, styrene elastomer, etc. can be used. As soft polyvinyl chloride, the average degree of polymerization is 800~
12,000, preferably 1,500 to 10,000 polyvinyl chloride, and 30 to 220 parts by weight per 100 parts by weight of the polyvinyl chloride.
Parts by weight, preferably 50 to 200 parts by weight, are desirable. If the average degree of polymerization of the polyvinyl chloride is less than 800, mechanical strength such as tensile strength will decrease, while if it exceeds 12,000, the surface appearance of the parison during molding will be poor and the moldability will be significantly poor. In addition, the amount of plasticizer added to polyvinyl chloride is 30%.
Below 220 parts by weight, the molded product becomes inelastic;
If the amount exceeds 1 part by weight, mechanical strength such as tensile strength will be significantly reduced. Various other fillers, stabilizers, stabilizing aids, pigments, etc. can also be appropriately blended into the above-mentioned soft polyvinyl chloride.

FIG. 5 shows an automobile lumbar support manufactured according to another embodiment in which the thick end of the parison is provided on the other parting line. The lumbar support 21 is composed of a main body 22, an air inlet 23, and a bracket 24. Bracket 2
No. 4 is obtained by compressing the thick end portion of the parison with a mold. The bracket has mounting holes 25.
In this way, a plurality of air inlets may be provided, and the thick end portions may also be provided at both ends on the parting line.

As described above, the present invention extrudes a parison which is partially cut out and has thick walls at both cut ends, closes the mold by arranging the blow nozzle between the two ends, and closes the mold by disposing the blow nozzle. Since this is a hollow molding method characterized by compressing a thick parison with a mold and a mold to form a thick part on the parting line of the hollow body, the hollow molded body obtained by the blow molding method The main body itself is kept thin so that it can be elastically deformed, and the parts attached to this main body, such as the blood pressure measurement bag, the air inlet of a lumbar support for a car, the mouth of a water pillow, etc.
The wall thickness of the opening for fitting the stopper of the infusion bottle is set to the desired thickness, and the air injection pipe, reinforcement body for water container, etc.
This allows for easy insertion of plugs, etc. In addition, since the present invention is integrally formed during molding, there is no adhesive extrusion as in adhesive bonding, deterioration or deformation of parts as in high frequency welding, and a beautiful appearance can be obtained. There is no risk of liquid or air leaks.

[Brief explanation of drawings]

FIG. 1 is an overall perspective view of a blood pressure measurement bag obtained according to an embodiment of the present invention, FIG. 2 is an overall perspective view showing the method of the present invention, and FIG. 3 is a cross-sectional view of FIG. 2. , Figure 4 is a cross-sectional view showing the state during mold clamping progress,
FIG. 5 is an overall perspective view of the lumbar support obtained by the present invention. 1...Bag body, 3...Air inlet, 4a, 4b...
...Mold, 8...Thick wall part.

Claims (1)

[Claims] 1. Extrude a parison that has been partially cut open and has thick walls at both cut ends, place a blowing nozzle between the two ends, and close the mold;
A blow molding method characterized in that a thick parison is compressed by a blow nozzle and a mold to form a thick part on a parting line of a hollow body.