JP3971191B2 - Manufacturing method of footrest device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a footrest device used as a step for footrests such as manholes, and in particular, by using a hollow metal pipe as a core material and covering the entire surface of the core material with a synthetic resin, it is lightweight and transported. The present invention relates to a method for manufacturing a footrest device that can reduce safety, safety, durability, and cost.
[0002]
[Prior art]
As a known technique of a footrest device in which the outer periphery of a metal footrest core material is coated with a synthetic resin as in the present invention, for example, JP-A-9-95961 (first known technique), Japanese Laid-Open Patent Publication No. 10-88951 (second known technique), Japanese Laid-Open Patent Publication No. 10-292212 (third known technique), Japanese Laid-Open Patent Publication No. 11-280364 (fourth known technique), and the like are well known.
[0003]
The first known technique is constructed by welding a stainless steel round bar leg to both ends of a hollow steel material leg and covering the part other than the leg and the tip of the round bar leg with a synthetic resin. This is the technology of the footrest device.
[0004]
The second known technique uses a metal foothold composed of a foot portion and both side portions as a core material, and covers the entire surface of the foot portion and a portion excluding the tip of the side portion with a synthetic resin, Furthermore, this is a technology of a footrest device in which a phosphorescent member is attached to a part of a leg portion.
[0005]
The third known technique is a technique of a footrest device in which a portion other than the main part of the metal U-shaped step and the tip part of the leg part is covered with a synthetic resin, and a spherical convex part is attached to the leg part. .
[0006]
The fourth known technique is a footrest device in which a fixing plate having a mounting hole is integrally provided at each end of both side legs of a U-shaped metal step, and the entire surface of the step is covered with a synthetic resin. Technology.
[0007]
However, in any of the footrest devices shown in the first to fourth prior arts described above, since the tip portions of both leg portions of the footrest device are not covered with the synthetic resin, the core material of the leg portions is easily corroded. There was a problem with poor durability. Or, as a countermeasure, it is necessary to use an expensive material such as stainless steel.
[0008]
Further, since a metal core material exposed at the tips of both leg portions of the footrest device shown in these known techniques must be drilled with a screw for screwing a nut or the like, a special two for that purpose. There was a problem that the next processing was necessary and workability was poor.
[0009]
In addition, since the footrest devices shown in these known technologies are all made of steel, the weight of each part is not negligible, and the footrest device is assembled at the factory like an assembly type manhole. In the case of installation, the cost of transporting the footrest device to the factory, and the on-site manhole, when the number of installation increases, it becomes a considerable weight, it is not easy to carry the parts during the installation work, and further along the manhole wall In order to perform work on the unstable scaffolding provided, there has been a problem that significantly burdens the operator.
[0010]
Among the above-described conventional techniques, as in the first known technique, for example, the footrest at the center of the footrest device is formed by a hollow rectangular tube formed by pressing a steel plate. There is also a footrest device constituted by providing notches at both ends of a cylinder, inserting leg portions made of round bars into the notches, and welding and fixing them together.
[0011]
However, since the footrest device according to the first known technique uses a hollow square tube for the footrest portion, it is lighter than the conventional one, but the main portion is a hollow square tube made of steel and a round bar. However, there is a problem that it becomes heavy because it is formed more and is not so useful for sufficiently reducing the weight of the footrest device. Furthermore, the footrest device according to the first known technique must be provided with notches at both ends of the hollow rectangular tube, and after inserting a leg portion made of a round bar into the notch, the two must be welded together. Therefore, there was a problem that workability was extremely bad.
[0012]
As a completely new technology developed in view of the above-mentioned many problems, a hollow metal pipe bent into a U-shape as shown in JP-A-2001-254374 is used as a core material, and synthetic resin is applied to the entire surface of the core material. There are a footrest device and a manufacturing method therefor, in which a screw is provided on a part of the outer peripheral surface of the coated resin layer and the hollow metal pipe material is filled with a synthetic resin.
[0013]
[Problems to be solved by the invention]
However, the conventional footrest device and the manufacturing method thereof have a problem that volume shrinkage (hereinafter referred to as shrinkage) occurs when a resin is injected into a hollow core material.
[0014]
Generally, as a prevention of shrinkage, foaming material is mixed to reduce the shrinkage, but the phenomenon of shrinkage occurs. Further, by increasing the cooling time to room temperature after resin injection, it is possible to prevent the occurrence of shrinkage, but there is a problem that productivity is lowered.
[0015]
Therefore, an object of the present invention is to provide a manufacturing method of a footrest device that can prevent the occurrence of shrinkage without reducing productivity.
[0016]
[Means for Solving the Problems]
In order to solve the above problems, a manufacturing method of a footrest device according to the present invention is a manufacturing method of a footrest device attached to a wall surface of a manhole or the like, in which a hollow metal pipe material is placed on both sides of a central footrest portion. A step of bending the U-shaped hollow metal pipe material into a U-shaped shape in which the legs are connected; a step of filling the inside of the U-shaped hollow metal pipe material; and a synthetic resin filled in the inside of the U-shaped hollow metal pipe material. A step of cooling to room temperature, and a step of coating the synthetic resin on the entire outer surface of the U-shaped hollow metal pipe material cooled to room temperature to form a resin layer. Features.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
A method for manufacturing a footrest device according to the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway plan view of a footrest device according to the present embodiment, FIG. 2 is a perspective view of a core material used in the footrest device, and FIG. 3 is a diagram for explaining a method of manufacturing the footrest device. .
[0019]
In FIG. 1 and FIG. 2 (a), 1 is a footrest device , and a synthetic resin is coated on the entire outer surface of a pipe material 2 made of a hollow metal round pipe to form a resin layer 3. Configured.
[0020]
The pipe member 2 made of the hollow metal round pipe is constructed by bending the left and right ends of the hollow metal round pipe in the same direction and providing leg portions 2b on both sides of the footrest portion 2a.
[0021]
A screw 4 that can be screwed into a nut or the like is provided on the outer peripheral surface of the tip resin layer 3 of both leg portions 2 b of the footrest device 1. In addition, a large number of anti-slip protrusions 5 are provided in parallel on the upper surface of the resin layer 3 of the footrest 2 a of the footrest device 1. And the wavelike protrusion part 6 protrudes continuously in the inner edge of the resin layer 3 of the footrest part 2a.
[0022]
In the case of the embodiment shown in FIG. 1 and FIG. 2 (a), a hollow metal round pipe is used as the pipe material 2, but this pipe material 2 is hollow as shown in FIG. 2 (b). It is also possible to use a metal square pipe. Further, the square pipe can be used as a square tube as shown in the figure, a flat square tube, a hexagonal tube, or an octagonal tube.
[0023]
Thus, since a hollow metal pipe is used for the pipe material 2 of the footrest device 1, it can be bent into a U shape very easily. Further, since the entire outer surface of the pipe material 2 is covered with the synthetic resin, the end portions at both ends of the pipe material 2 are not exposed as in the prior art, and therefore are not corroded and are damaged over a long period of time. And can be used safely.
[0024]
Further, since the screws 4 are provided on the outer peripheral surface of the resin layer at the tips of the leg portions 2b on both sides, the processing is extremely simple. Furthermore, since the entire core material is formed of a single hollow metal pipe, the entire footrest device can be significantly strengthened.
[0025]
In the hollow portion of the pipe material 2, a filling resin layer 8 is formed by filling a synthetic resin. As described above, since the hollow metal pipe is filled with the synthetic resin, the strength of the entire footrest device can be further improved.
[0026]
Moreover, it is good also as a thing different from resin of an outer peripheral part, and resin of a main-body part. That is, recycled plastic may be used for the resin inside the hollow. Thereby, production cost can be held down.
[0027]
Hereinafter, a method for manufacturing the footrest device will be described.
[0028]
As shown in FIG. 3, the straight hollow metal pipe member 2 is bent in a U shape so that the leg portions 2b are connected to each other at right angles on both sides of the central foot portion 2a.
[0029]
Next, the pipe material 2 bent into a U-shape is fixed with a fixing jig, and the open ends at both ends are closed with a closing jig. One closing jig is processed for injection of synthetic resin, and the synthetic resin is press-fitted from the closing jig to fill the hollow portion of the pipe material 2 with the synthetic resin. The pipe material 2 filled with the synthetic resin is cooled to room temperature.
[0030]
The synthetic resin is coated on the entire surface of the pipe material 2 to a predetermined thickness by synthetic resin injection molding (insert molding using an injection molding machine), and the outer peripheral surface of the resin layer coated on the legs 2b. Screws 4 are formed on the foot to complete the footrest device 1.
[0031]
As described above, a hollow core material is bent in advance, a resin is injected therein, and after the resin is cured, an outer peripheral resin layer is formed. Thus, the cooling time of the filling resin layer 8 can be ensured by forming the filling resin layer 8 and the outer peripheral resin layer as separate processes. Thereby, shrinkage of the resin can be prevented and occurrence of shrinkage can be prevented.
[0032]
【The invention's effect】
In the manufacturing method of the footrest device according to the present invention, a hollow core material is bent in advance, a resin is injected therein, and an outer peripheral resin layer is formed after the resin is injected and cured. Thereby, shrinkage of the resin can be prevented and occurrence of shrinkage can be prevented.
[Brief description of the drawings]
FIG. 1 is a partially cut-away plan view of a footrest device according to the present embodiment.
FIG. 2 is a perspective explanatory view of a core material used in a footrest device.
FIG. 3 is a diagram for explaining a method of manufacturing a footrest device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Footrest apparatus 2 ... Pipe material 2a ... Footrest part 2b ... Leg part 3 ... Tip resin layer 4 ... Screw 5 ... Slipping stop projection 6 ... Wave-shaped protrusion part 8 ... Filling resin layer

Claims (1)

In the manufacturing method of a footrest device attached to a wall surface such as a manhole for footrest,
Bending the hollow metal pipe material into a U-shape with legs connected to both sides of the central footrest part,
Filling the inside of the U-shaped hollow metal pipe material with a synthetic resin;
Cooling the synthetic resin filled inside the U-shaped hollow metal pipe material to room temperature;
A step of forming a resin layer by covering the entire outer surface of the U-shaped hollow metal pipe material in which the synthetic resin filled therein is cooled to room temperature, and forming a resin layer. Production method.

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