JPS6224257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for connecting a pipe end cap to an agricultural or horticultural support or the like. Agricultural and horticultural supports are used to support the vines of flowers and agricultural crops when they are grown, but generally, in order to improve weather resistance, the outer surface of the thin-walled steel pipe that forms the main body of the support is The pipe is coated with a synthetic resin, and the cut end of the synthetic resin-coated steel pipe is also coated with a synthetic resin cap (hereinafter referred to as "tube end cap") to provide anti-rust treatment. It is customary. For this reason, various methods have been used to attach a cap to the cut end of a steel pipe. The simplest method is to bond the tube end cap directly to the cut end of the steel pipe using an adhesive, but this method does not provide sufficient strength to the bonded part. Moreover, it has the disadvantage that gaps are likely to form in the bonded portion, and furthermore, if rainwater or the like enters the formed gaps, the rust-preventing effect may be diminished. Therefore, in order to eliminate such problems, the following methods have also been proposed. That is, in this method, as shown in FIG. 1, steel pipes a and a are arranged facing each other as shown in FIG. After fitting the protrusions d and d of the resin plug c and connecting the steel pipes a and a in the axial direction through the plug c, the steel pipes a and a are connected using a crosshead die (not shown) or the like. A synthetic resin anticorrosion layer e is applied to cover the entire outer surface of the stopper c, and then the stopper c is cut at its center. However, such a method also generally has problems such as complicated steps, low productivity, and relatively high manufacturing costs. This invention was made in order to solve the problems of the prior art, and it has a high bonding strength at the adhered part, high productivity, low manufacturing cost, and a simple pipe work process. The purpose is to provide a method for connecting end caps. That is, this invention is characterized in that it utilizes thermal welding using ultrasonic waves, and in particular, the cut end of a steel pipe that has been previously coated with an outer surface layer of thermoplastic synthetic resin is
The gist is to heat-weld the cap body integrally to the cut end of a steel pipe coated with an outer skin layer by pressing the cap body against a vibrating thermoplastic synthetic resin cap body by receiving ultrasonic vibrations. It is. One embodiment will be described below with reference to the attached drawings. In Fig. 2, reference numeral 1 denotes an ultrasonic vibration source equipped with a horn 2, whose oscillation frequency is approximately 20 KHz and whose output is approximately 500 W. The horn 2 has a concave cavity 2a having a circular opening at its upper end, and within this concave cavity 2a is a tube end having approximately the same outer diameter as the steel tube 4 coated with a synthetic resin outer skin layer 4b. As shown in FIG. 2, the cap 3 is accommodated with almost no gap around its outer periphery. The tube end cap 3 is made of a thermoplastic synthetic resin appropriately selected from PVC, PP, acrylic, etc., that is, a thermoplastic synthetic resin that is the same as or has good compatibility with the outer skin layer 4b of the steel tube 4. It is formed into a disc-shaped chip with a tapered bottom. However, in such a configuration, the vibration source 1
When the horn 2 is activated, the horn 2 receives ultrasonic vibration from the vibration source 1 and is excited, so that the tube end cap 3 inside the concave cavity 2a also vibrates violently. Therefore, when the steel pipe 4 is pressed against the pipe end cap 3 from directly above, the cut end 4c of the steel pipe 4 rubs violently against the peripheral part of the upper surface of the pipe end cap 3, and the frictional heat generated during the rubbing causes the steel pipe 4 to The cut edge of the tube body itself is firmly welded by biting into the periphery of the upper surface of the softened tube end cap 3. Table 1 shows the relationship between the operating frequency and pressing force of ultrasonic waves and the working time required to connect the tube end caps, as obtained from the inventor's experimental results.

[Table] Here, as for the synthetic resin coated steel pipe 4 used in such cases, it is preferable that the cut end 4c of the cut end 4c be straight with no inclination in order to improve the joint. In order to efficiently convert the vibrational energy applied to the end cap 3 into thermal energy, it is desirable that the cut end has no part such as a tear where stress is concentrated and resonates. Note that the cut end 4 of the steel pipe 4 covered with the outer skin layer
The cut end 4c of the steel pipe 4 may be curved slightly inward, especially in such a case, as shown in FIG. Since it is welded in such a way that it bites deeply, the strength of the welded part can be further increased. As described in detail above, according to the present invention, the cut end of the steel pipe coated with the synthetic resin outer skin layer is simply pressed against the pipe end cap that vibrates due to ultrasonic vibration. Since the end caps can be firmly attached in one piece, it is possible to obtain agricultural and horticultural supports with extremely high joint strength at the attached parts.
Furthermore, since the work involved in connecting the tube end caps is extremely simple, productivity can be significantly improved and agricultural and horticultural supports can be provided at low manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a work process diagram explaining a conventionally known connection method, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG.
The figure is a partial longitudinal sectional view showing another example of an agricultural and horticultural support. (Explanation of symbols) 3 is a tube end cap, and 4 is a steel tube coated with a synthetic resin outer skin layer.

Claims (1)

[Claims] 1. Press the cut end of a steel pipe coated with a thermoplastic synthetic resin outer skin layer against a thermoplastic synthetic resin cap body that vibrates under ultrasonic vibration, and integrally attach the cap body to the cut end of the steel pipe. A method for connecting pipe end caps of agricultural and horticultural supports, etc., characterized in that the caps are attached to each other.