HK1079488B - Resin-coated steel pipe excellent in mechanical strength such as sliding property - Google Patents

Description

Resin-coated steel pipe having excellent sliding properties and mechanical strength

Technical Field

The present invention relates to a resin-coated steel pipe having excellent slidability and mechanical strength, which uses a crystalline engineering plastic having excellent slidability and mechanical strength or heat resistance as an outer coating resin, and more particularly, to a resin-coated steel pipe having excellent slidability and mechanical strength, which can be applied to a spline shaft of a driving roller conveyor or the like for light and medium loads by greatly improving the adhesion of the crystalline engineering plastic to the steel pipe.

Background

Since crystalline engineering plastics such as PBT (polybutylene terephthalate) resin and nylon resin are excellent in sliding property, mechanical strength and heat resistance, if they can be used as an outer layer coating resin of a resin-coated steel pipe, the resin-coated steel pipe can be obtained which is excellent in sliding property and durability, and therefore, the effects thereof can be greatly expected, and there is a great social demand. It can be said that the spline shaft 1 is most suitable for a member which is required to have good slidability, such as the spline shaft 1 used for a drive roller conveyor for light and medium loads as shown in fig. 6.

However, when the crystalline engineering plastic is used for the outer coating resin of the resin-coated steel pipe, there is no adhesive agent capable of satisfactorily adhering the crystalline engineering plastic to the thin-walled steel pipe, and only the modified polyolefin adhesive polymer is thinly coated on the thin-walled steel pipe and the crystalline engineering plastic is adhered and coated on the surface thereof.

However, the resin-coated steel pipe obtained by bonding and coating the crystalline engineering plastic on the thin steel pipe with the adhesive polymer has a problem that water easily penetrates between the interface between the thin steel pipe and the adhesive polymer, and the coating resin (crystalline engineering plastic) peels off. In particular, when used outdoors or in the agricultural and aquaculture fields, the coating resin is more likely to be peeled off because of the high chance of water penetration, and therefore, the practical applicability is poor.

Further, the crystalline engineering plastics have problems of low dimensional accuracy, poor stability of molded shape, and poor production efficiency, because they have low melt viscosity and large shrinkage, although they have good sliding properties, mechanical strength, and heat resistance.

Further, since the crystalline engineering plastics themselves are expensive in raw materials, they are uneconomical, and there is a current situation where it is desired to cover them as thin as possible to reduce the amount of expensive resin used.

As described above, it is extremely difficult to use crystalline engineering plastics for the outer coating resin of the resin-coated steel pipe, and the degree of practical use has not yet been achieved.

Therefore, at present, the outer coating resin of the resin-coated steel pipe is formed of a synthetic resin such as AAS, ABS, AES, and PETG which can use a rubber-based adhesive which has a better water resistance at the bonding interface with the thin-walled steel pipe and does not cause peeling, although the sliding property, mechanical strength, and heat resistance are inferior to those of crystalline engineering plastics.

Disclosure of Invention

The first object of the present invention is to provide a resin-coated steel pipe which is free from peeling and has excellent sliding properties and mechanical strength by greatly improving the adhesion of a crystalline engineering plastic to a thin steel pipe.

A second object of the present invention is to provide a resin-coated steel pipe which is economically advantageous and has excellent sliding properties and mechanical strength, while improving the manufacturing efficiency.

In order to achieve the above object, a first aspect of the present invention provides a resin-coated steel pipe having excellent slidability and mechanical strength, characterized in that an alloyed resin, which is a mixture of one resin selected from AAS resin, ABS resin and AES resin and one resin selected from PBT resin, nylon resin and polyacetal resin and in which concave and convex portions are formed alternately in a circumferential direction of the outer peripheral surface of the thin-walled steel pipe and concave and convex stripes in which the concave and convex portions are continuous are formed uniformly in a cross section in a pipe axis direction, is bonded to and coated on the outer peripheral surface of the thin-walled steel pipe, and the one resin selected from PBT resin, nylon resin and polyacetal resin is coated on the outer peripheral surface of the alloyed resin to have a thickness necessary for exhibiting slidability and mechanical strength, thereby forming a double-coated structure, the double-covered structure is formed in a spline shape having a uniform cross section in the pipe axial direction.

A second aspect is the resin-coated steel pipe excellent in slidability and mechanical strength according to the first aspect, wherein the one resin selected from the PBT resin, the nylon resin, and the polyacetal resin, which is coated by bonding the outer peripheral surface of the alloyed resin coated on the outer peripheral surface of the thin steel pipe, is coated so as to be thick at groove portions provided in the respective ridge portions of the uneven bars formed of the alloyed resin and having a uniform cross section in the pipe axial direction on the outer peripheral surface of the steel pipe, and so as to be thin at the other portions, and is formed in a spline shape as a whole.

Drawings

FIG. 1A is a perspective view showing a resin-coated steel pipe excellent in slidability and mechanical strength according to the present invention

Sectional view of the upper view of FIG. 1B

FIG. 1C an enlarged view of the X portion of FIG. 1B

FIG. 2 is a front view showing a main part of a cross die type extrusion molding machine

FIG. 3 is a sectional view taken along line III-III of FIG. 2

FIG. 4A shows a front view of an inner resin covered mold ring

FIG. 4B is a cross-sectional view taken along line IV-IV of FIG. 4A

FIG. 5A shows a front view of an outer resin covered mold ring

FIG. 5B is a cross-sectional view taken along line V-V of FIG. 5A

FIG. 6 is a reference drawing showing an example of the state of use of a resin-coated steel pipe excellent in slidability and mechanical strength according to the present invention

Detailed Description

Fig. 1A to C show an embodiment of the resin-coated steel pipe 1 of the first embodiment which is excellent in slidability and mechanical strength. The resin-coated steel pipe 1 having excellent slidability and mechanical strength is suitable for use in, for example, spline shafts used in driving roller conveyors for light and medium loads, which require excellent slidability.

However, alloying of resins has been carried out not only for realizing excellent functions and performances which cannot be obtained by monomers, but also for resins having poor compatibility, recently, resins having been alloyed with a compatibilizing agent have been marketed, and even styrenic resins have been alloyed with various resins and have been marketed. Therefore, attention is paid to the alloyed resin 3 which is a mixture of a styrene resin and a crystalline engineering plastic, and the adhesion to the surface of the steel pipe 2 is secured by the adhesion of a rubber-based adhesive which can adhere to the styrene resin contained in the alloyed resin 3, and the alloyed resin is integrated by the compatibility with the crystalline engineering plastic 4 which becomes the outer layer, whereby the crystalline engineering plastic 4 can be coated on the outer layer. From such consideration, the resin-coated steel pipe 1 is based on the technical idea of not only greatly improving the adhesion of the crystalline engineering plastic 4 to the thin-walled steel pipe 2 but also effectively exhibiting the slidability and mechanical strength by reducing the amount of the expensive crystalline engineering plastic 4 as much as possible.

The resin-coated steel pipe 1 is formed by coating a rubber-based adhesive on the outer peripheral surface of a thin steel pipe 2 having an outer diameter of about 26mm and a circular cross section, and bonding and coating an alloying resin 3 on the surface thereof. The alloyed resin 3 is composed of an AAS resin which is a styrene resin and a PBT resin which is a crystalline engineering plastic.

A double-coated structure in which a cross section is uniform in the pipe axial direction is formed on the outer peripheral surface of the alloyed resin 3, and the double-coated structure is formed by coating a PBT resin 4, which is the same resin as the crystalline engineering plastic constituting the alloyed resin 3, with a thickness necessary for the sliding property and the mechanical strength thereof (the invention of the first aspect).

The alloyed resin 3 is an alloyed polymer of AAS resin containing 20% PBT resin, concave portions and convex portions are formed alternately in the circumferential direction of the outer peripheral surface of the thin steel pipe 2, concave-convex strips 3a and 3b in which the concave-convex portions are continuous are bonded and covered in the pipe axis direction so that the cross sections thereof are uniform, and groove portions 3c capable of accommodating the wall thickness (about 0.5 mm) and the width (about 4 mm) necessary for the PBT resin 4 covering the surface thereof to exert the sliding property and the mechanical strength are formed in the pipe axis direction in the convex strip portions 3b provided in 6 places in total.

The PBT resin 4 is integrally formed with the alloyed resin 3 by covering the outer peripheral surface of the alloyed resin 3, and has a thick wall (about 0.8 mm) covering the groove portions 3c provided in the convex ridge portions 3b of the alloyed resin 3, a thin wall (about 0.3 mm) covering the other convex ridge portions 3b, and a thinner wall (about 0.1 mm) covering the concave ridge portions 3a (the third invention).

The styrene resin constituting the alloyed resin 3 is not limited to AAS resin, and can be substantially the same as ABS resin or AES resin. The crystalline engineering plastic 4 is not limited to the PBT resin 4, and can be substantially the same as the nylon resin or the polyacetal resin (the invention of the second embodiment). That is, if a styrene-based alloying resin containing a crystalline engineering plastic to be coated is present, a resin-coated steel pipe coated with the crystalline engineering plastic to be coated can be implemented.

In the present embodiment, the 6 convex portions 3b are provided at approximately equal intervals in the circumferential direction of the tubular body, but the number of the convex portions 3b is not limited to this. In the present embodiment, the resin-coated steel pipe 1 is formed in a spline shape (shaft), but the resin-coated steel pipe is not limited to this, and may be formed in a cylindrical shape.

The PBT resin 4 is thick at the approximate center of the cross-sectional shape of the raised ridge 3 b. The reason for this is to consider that, when the resin-coated steel pipe 1 of the present embodiment is used for a spline shaft, the substantially central portion of the raised strip portion 3b fitted into the bearing is most likely to slide and be easily worn, while effectively exhibiting slidability and mechanical strength while reducing the amount of the expensive crystalline engineering plastic 4 as much as possible. Further, since the groove 3c of the alloyed resin 3, which makes it possible to make the thickness of the PBT resin 4, restrains the PBT resin 4 being extruded with the groove walls on both sides of the groove 3c, even a PBT resin 4 having a low melt viscosity and being difficult to hold its shape can be manufactured while stably holding the uneven shape.

Specifically, in the example of fig. 1, the thin-walled steel pipe 2 has a wall thickness of less than about 1mm and an outer diameter of about 26 mm. The thickness of the concave portions 3a of the alloyed resin 3 is set to about 0.5mm, the thickness of the convex portions 3b is set to about 1.2mm, the width of the groove portions 3c is set to about 4mm, and the groove wall is set to about 0.5 mm. The thickness of the PBT resin 4 is about 0.8mm in the groove 3c, about 0.3mm in the other convex portion 3b, and about 0.1mm in the concave portion 3 a. Therefore, the resin-coated steel pipe 1 having a spline shape with an overall outer diameter of about 29mm in the convex strip portions 3b and about 27.2mm in the concave strip portions 3a is extruded.

Therefore, if the steel pipe 1 is covered with the resin having excellent sliding properties and mechanical strength, the steel pipe 1 (1) is integrally formed by covering the thin-walled steel pipe 2 with the PBT resin (crystalline engineering plastic) 4 through the alloying resin 3 having compatibility, and therefore has sufficient adhesion to the thin-walled steel pipe 2, and there is no fear of peeling of the PBT resin 4. (2) The PBT resin 4, which has a low melt viscosity and is difficult to hold in shape, is pressed in a form restrained by the groove walls on both sides of the groove portion 3c of the alloyed resin 3, so that the shape is stabilized, and the manufacturing efficiency can be greatly improved. (3) Since the amount of the expensive crystalline engineering plastic 4 is limited to the amount necessary for exhibiting the slidability, the production cost can be reduced, and the cost can be reduced.

Next, an embodiment of an extrusion molding method for producing the resin-coated steel pipe 1 having the above-described structure and excellent slidability and mechanical strength will be described with reference to fig. 2 and the following drawings.

Fig. 2 and 3 show a cross die type extrusion molding machine used in the above-described extrusion molding method. The reference numeral 10 in fig. 3 denotes a structure of a cover die ring of the cross die, which is a main part of the extrusion molding machine. The basic structure is substantially the same as that of the extrusion molding machine described in japanese patent No. 2867244 already obtained by the present applicant.

That is, in this extrusion molding machine, the distribution spacer 14 and the inner resin coating die ring 15 are provided at the tip of the connector 11 attached to the tip of the cross die, which is not shown, via the distribution plate 12, the radial distribution spacer 16 and the outer resin coating die ring 17 are provided at the further tip thereof via the distribution plate 13, and the distribution plates 12 and 13 are fixed in contact with each other. A coupling 20 connected to a heating cylinder is connected to the upper portions of the tangent lines of the distribution plates 12 and 13, the alloyed resin 3 from the crosshead die is adhered and coated on the outer peripheral surface of the thin steel pipe 2 by an inner layer resin coating die ring 15, and the PBT resin 4 from the heating cylinder is coated on the outer peripheral surface of the alloyed resin 3 by an outer layer resin coating die ring 17.

The flow path of the PBT resin (crystalline engineering plastic) 4 from the joint 20 to the outer resin coating ring 17 is formed by connecting the divided both ends of a large semicircular 1 st flow path 18 centered on the thin steel pipe 2 to the inner 2 nd flow paths 19, 19 having a small diameter. The 2 nd flow paths 19 and 19 are shaped such that the connection between the flow paths 19 and 19 is narrowed so as to be uniformly pressed toward the center.

The 2 nd flow paths 19 and 19 connect through holes 17a and 17b (see fig. 5) extending from the radial flow path of the radial distribution spacer 16 to the outer resin-coated mold 17.

As shown in fig. 4A, B, the inner resin coating mold 15 is formed of through holes 15a, 15b, and 15c, the through hole 15a corresponds to the concave ridge portion 3a of the alloy resin 3 to be coated, the through hole 15c corresponds to the groove portion 3c of the alloy resin 3, and the through hole 15c and the through holes 15b and 15b on both sides thereof correspond to the convex ridge portion 3b of the alloy resin 3.

As shown in fig. 5A, B, in order to coat the PBT resin 4 on the alloyed resin 3, the outer layer resin coating die 17 is formed with a through hole 17a capable of covering the PBT resin 4 having a large wall thickness with a width that covers the through holes 15b and 15b adjacent to each other with the through hole 15c of the inner layer resin coating die 15 as the center, and a through hole 17b capable of covering the PBT resin 4 having a small wall thickness corresponding to the through hole 15 a.

When the resin-coated steel pipe 1 having excellent slidability and mechanical strength is extruded by the above-described molding machine, first, the thin-walled steel pipe 2 is moved rightward from the cross die, which is not shown, to bond and cover the alloying resin 3 supplied to the connector 11, the distribution spacer 14, and the inner resin-coated die ring 15.

Then, when the thin steel pipe 2 reaches the outer resin coating ring 17, the PBT resin 4 supplied to the through holes 17a and 17b from the gap between the inner resin coating ring 15 and the outer resin coating ring 17 covers the outer peripheral surface of the alloying resin 3 to strengthen the shape after flowing through the radial distribution spacers 16 from the coupling 20 through the 1 st flow path 18 and the 2 nd flow path 19. Thus, as shown in fig. 1, the resin-coated steel pipe 1 is extruded into a spline shape having an inner layer of the alloy resin 3 and an outer layer of the PBT resin 4, and has a double-coated structure having a uniform cross section in the pipe axial direction.

The embodiments have been described above with reference to the drawings, but the present invention is not limited to the embodiments illustrated in the drawings, and a practitioner usually makes design changes and application modifications within a range not departing from the technical idea thereof.

In the resin-coated steel pipe having excellent slidability and mechanical strength according to the present invention, the crystalline engineering plastic is bonded and coated with the alloying resin compatible with the crystalline engineering plastic, so that the steel pipe has a sufficient bonding force with the steel pipe and there is no fear that the coated crystalline engineering plastic peels off. Further, since the PBT resin, which has a low melt viscosity and is difficult to hold its shape, is extruded in a form of being constrained by the groove walls on both sides of the groove portion of the alloy resin, the shape is stabilized, and the manufacturing efficiency can be dramatically improved. Further, since the amount of the expensive crystalline engineering plastic used is limited to the amount necessary for exhibiting the slidability, the production cost can be reduced, and the cost can be reduced.

Claims (2)

1. A resin-coated steel pipe excellent in sliding property and mechanical strength, characterized in that an alloyed resin is adhered and coated on the outer peripheral surface of a thin-walled steel pipe, the alloyed resin forms concave portions and convex portions alternately in the circumferential direction of the outer peripheral surface of the thin-walled steel pipe, and uneven strips in which the uneven portions are continuous are formed evenly in cross section in the direction of the tube axis, the alloyed resin is a mixture of one resin selected from the group consisting of AAS resin, ABS resin, and AES resin and one resin selected from the group consisting of PBT resin, nylon resin, and polyacetal resin, and further, covering the one resin selected from the PBT resin, the nylon resin and the polyacetal resin on the outer peripheral surface of the alloyed resin in order to exert the sliding property and the mechanical strength thereof, thereby forming a double covering structure formed in a spline shape having a uniform cross section in the pipe axis direction.

2. The resin-coated steel pipe excellent in slidability and mechanical strength according to claim 1 wherein the resin selected from the group consisting of PBT resin, nylon resin and polyacetal resin, which is coated on the outer peripheral surface of the alloyed resin bonded to the outer peripheral surface of the thin steel pipe, is thick at the groove portion provided in each ridge portion in the uneven stripe of the outer peripheral surface of the steel pipe formed of the alloyed resin and having a uniform cross section in the pipe axial direction, and is thin at the other portion, and has a spline shape as a whole.