JP3264911B2 - Gas pressure welding method for rebar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of gas-welding a reinforcing steel bar in a reinforced concrete building.

[0002]

2. Description of the Related Art As shown in FIG. 1, a gas pressure welding apparatus for a reinforcing bar holds both ends of a pair of reinforcing bars 1 and 1 'by holding one of a pair of reinforcing bars 1 and 1' with a moving clamp 3 '. A pressure burner 2 for heating the rebar butt portion, and a hydraulic pump 6 for applying a hydraulic pressure for obtaining a butt pressing force of the rebars 1 and 1 ′ by the press welder 2. The hydraulic pump 6 operates the hydraulic ram 4 of the pressure welding device 2 to move the moving clamp 3 ′ in the direction of the reinforcing bar to abut and press the two reinforcing bars 1, 1 ′. The butt portion of the rebar is heated, and the butt portion is compressed by the heating and pressurization to generate a pressure bulge to join the butt portion.

On the other hand, as an upset method using the above-mentioned gas pressure welding apparatus, while heating the butting portion of the reinforcing bars 1 and 1 ', the pressure of the butting portion is increased and reduced to a set upper limit pressure by a pump in multiple stages. Repeatedly, a two-stage upset method or a three-stage upset method for compressing the butted portion to press-contact is widely used. An outline of a typical three-stage upset method will be described with reference to FIG.

The hydraulic pressure of the hydraulic pump is increased from the set lower limit pressure P1 to a set upper limit pressure P2, and the set upper limit pressure is set to P3.
Control the oil pressure so that it changes at a constant level up to the point.
At this point, the hydraulic pump 6 is stopped, and after the stop, pressure reduction accompanying the growth of the compression amount of the reinforcing bar butt is promoted. When the pressure reduction reaches the set lower limit pressure P4, the hydraulic pump 6 is operated again to set the set upper limit pressure. The voltage is increased to the point P5, and the same applies to the points P6 and P
After the points P7 and P9, for example, a three-stage upset is performed.

[0005] In any of the above-mentioned multi-stage upsets, a step for raising the pressure from a set lower limit pressure to a set upper limit pressure is included. However, in order to maintain the set upper limit pressure, a relief valve provided in a hydraulic pump is conventionally used. I'm using

That is, the hydraulic pump 6 is fully operated until the set upper limit pressure is reached, and when the set upper limit pressure is reached, the relief valve is opened, and the subsequent oil supply is released via the relief valve to return to the hydraulic pump 6. To obtain the set upper limit pressure.

[0007]

However, conventionally, in order to reach and maintain the set upper limit pressure by operating the hydraulic pump and the motor fully, conventionally, the service life of the hydraulic pump due to aging is remarkably reduced, and the oil is deteriorated. That is, the performance of the hydraulic pump is reduced. In addition, it wastes power.

[0008]

SUMMARY OF THE INVENTION The present invention eliminates the relief valve system of the hydraulic pump, which causes the above-mentioned problem, makes it possible to properly secure the set upper limit pressure, and solves the above-mentioned problem drastically. It provides a pressure welding method.

The present invention provides a method of gas-welding a reinforcing bar, comprising the steps of butting the reinforcing bars to be joined, and increasing the pressure applied to the butting portion by a hydraulic pump to a set upper limit pressure while heating the butting portion with a gas burner. In the above, without using the relief valve method, the hydraulic pump oil pumping amount is reduced just before the set upper limit pressure reaching point by the hydraulic pump, and the hydraulic pressure according to the oil pumping amount of the hydraulic pump is constantly detected, The above-described pressure is compared with the set upper limit pressure to replenish the oil feed amount in accordance with the compression amount of the abutting portion to achieve the set upper limit pressure to solve the above problem.

This makes it possible to eliminate the conventional overshoot phenomenon due to the inertia of the hydraulic pump after reaching the set upper limit pressure.

[0011]

[0012]

[0013]

[0014]

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a gas pressure welding method for a reinforcing bar, in which the relief valve system of the hydraulic pump 6 which causes the above-mentioned problem is eliminated and a set upper limit pressure can be appropriately secured. 3, 4, and 5 show an embodiment of the present invention.

As described with reference to FIG. 1, one of the pair of reinforcing bars 1 and 1 'is gripped by the fixed clamp 3, the other is gripped by the moving clamp 3', and the ends of both reinforcing bars are pressed against each other. A gas burner 5 for heating the rebar butt portion, and a hydraulic pump 2 for applying a hydraulic pressure for obtaining the butt pressing force of the rebars 1 and 1 ′ by the pressure welding device 2.

Then, the hydraulic pump 6 is stepped up from the set lower limit pressure to the set upper limit pressure, the hydraulic ram 4 of the crimping device 2 is operated, the moving clamp 3 'is moved in the direction of the rebar, and the rebars 1, 1' are moved. While the butt is pressurized to the set upper limit pressure, the butt portion of the reinforcing bar is heated by the gas burner 5 during this pressurization, and the butt portion of the rebar is compressed by the heating and pressurization to generate a press-contact bulge, thereby joining the butt portion. Is achieved.

The present invention relates to a reinforcing bar 1 to be joined as described above.
1 'is butted, and while the butted portion is heated by the gas burner 5, the pressurization of the butted portion by the hydraulic pump 6 is increased to a set upper limit pressure. Instead, the amount of oil pumped by the hydraulic pump 6 is reduced just before reaching the set upper limit pressure by the hydraulic pump 6, and the oil pressure according to the amount of oil pumped by the hydraulic pump 6 is constantly detected. A pressure contact method is employed in which the oil pressure is replenished in accordance with the compression amount of the abutting portion by comparing the oil pressure with the set upper limit pressure to reach the set upper limit pressure.

Preferably, the oil pumping amount of the hydraulic pump 6 is reduced immediately before the point at which the hydraulic pump 6 reaches the set upper limit pressure, and the oil pressure corresponding to the oil pumping amount of the hydraulic pump 6 is constantly detected. And the set upper limit pressure are compared to replenish the oil feed amount in accordance with the compression amount of the abutting portion, thereby adopting a pressure contact method for reaching the set upper limit pressure and maintaining the set upper limit pressure.

As shown by the broken line in FIG. 2, in the conventional method in which the hydraulic pump 6 is fully operated from the lower limit pressure to the set upper limit pressure and the relief valve is used after the set upper limit pressure is reached, the hydraulic pump 6 is operated after reaching the set upper limit pressure. It is difficult to avoid occurrence of an overshoot phenomenon (overshoot waveform P0) due to inertia.

The overshoot phenomenon can be more effectively eliminated by reducing the amount of oil pumped by the hydraulic pump 6 and adopting the pressure contact method just before reaching the set upper limit pressure.

In the multi-stage upset method described with reference to FIG. 2, as shown in FIG. 3, the hydraulic pressure by the hydraulic pump 6 is increased from a set lower limit pressure P1 to a set upper limit pressure P2, and the set upper limit pressure is increased to a point P3. The hydraulic pressure is controlled so as to change at a constant level until the hydraulic pump is stopped at the point P3, that is, the hydraulic pressure is locked without performing new hydraulic pressure feeding. When the pressure reduction reaches the set lower limit pressure P4 point, the hydraulic pump 6 is operated again to increase the pressure to the set upper limit pressure P5 point.
The three-stage upset is performed after points P7 and P9.

According to the present invention, in this multi-stage upset method, P2 ', P2 before the set upper limit pressures P2, P5, P8.
At points 5 'and P8', the oil pumping amount of the hydraulic pump 6 is reduced, and the oil pressure corresponding to the oil pumping amount of the hydraulic pump 6 is constantly detected, and the detected pressure is compared with the set upper limit pressure. The replenishment of the oil pumping amount is performed in accordance with the compression amount of the abutting portion, so that the oil reaches the set upper limit pressure and the set upper limit pressure is maintained at points P3, P6, and P9.
At the point P9, the hydraulic pump 6 is stopped, and the pressure is reduced to the set lower limit pressures P4 and P7 accompanying the growth of the compression amount. At the set lower limit pressure P7, all the oil of the hydraulic pump 6 is discharged to the oil tank.

As a result, the overshoot phenomenon in the multi-stage upset method is effectively eliminated, and the motor M and the hydraulic pump 6 are worn out, oil deteriorated, and the performance is reduced.

As shown in FIG. 5, a branch line 8 branched from a hydraulic line 7 between the hydraulic pump 6 and the pressure welder 2 is used as a detecting means after the point at which the oil pumping amount of the hydraulic pump 6 drops. And a hydraulic pressure detector 9 for detecting a hydraulic pressure applied from the hydraulic pump 6 to the pressure welding device 2 via the pressure pump 6 in parallel with the pressure welding device 2.

As shown in FIG. 4, a comparator 10 is provided for comparing the pressure detected by the oil pressure detector 9 with a set upper limit pressure.
The pump speed controller 10 'is controlled by the signal from the comparator 10 to control the pump speed (control the motor drive voltage). Therefore, the amount of hydraulic pressure supplied from the hydraulic pump 6 to the pressure welding device 2 is controlled, and the set upper limit pressure is maintained.

As shown in FIG. 5, the hydraulic pressure detector 9 includes a diaphragm 11 that is displaced by the hydraulic pressure supplied from the branch line 8, and a strain gauge 12 that outputs a voltage signal as a detection pressure by the displacement of the diaphragm 11. A detector is applied so that the oil pressure applied to the pressure welder 2 can be detected with good reproducibility. The strain gauge 12 is composed of a piezoelectric element that generates a voltage signal by a mechanical external force.

The output of the oil pressure detector 9 is given to a display 13 and constantly displays the detected pressure of the oil pressure detector 9 which changes every moment. This indicator 13 can be provided on the hydraulic pump 6.

As means for reducing the oil pumping amount of the hydraulic pump 6 near the set upper limit pressure, that is, at points P2, P5, P8 or P2 ',
In P5 'and P8', the above-described hydraulic pressure detection control circuit shown in FIGS. 4 and 5 is used as means for reducing the amount of oil pumped by the hydraulic pump 6.

That is, the oil pressure from the set lower limit pressures P1, P4, P7 to the set upper limit pressures P2, P5, P8 is detected by the oil pressure detector 9, and when the oil pressure detects P2 ', P5', P8 '. The detected pressure and the set upper limit pressure are compared by a comparator 10, and a signal from the comparator 10 controls a pump speed controller 10 ′ to control a pump speed (controls a motor drive voltage). Reduce the hydraulic feed rate.

Alternatively, the point at which the hydraulic pump 6 lowers the hydraulic pressure is set by a timer, or the operator visually reduces the pump speed by reducing the pump speed.

For example, the hydraulic pump 6 is provided with an upper limit pressure setting device 14 and a lower limit pressure setting device 15. The set upper limit pressure in the present invention is given from the upper limit pressure setting device 14, for example. According to the present invention, the pressure welding method according to the present invention is properly performed by not being opened at the above set upper limit pressure.

[0033]

According to the present invention, it is possible to appropriately solve the problems of a reduction in the service life of a conventional hydraulic pump due to aging, and a problem of deterioration of oil and hydraulic pump performance caused by the deterioration. To improve power waste. Further, the overshoot phenomenon at the time of reaching the set upper limit pressure can be effectively solved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an outline of a pressure welding device, a gas burner, and a pump forming a pressure welding device.

FIG. 2 is a waveform diagram showing a conventional double-stage upset method using the above-mentioned press-contact device.

FIG. 3 is a waveform diagram showing a multi-stage upset method according to the present invention using the press-contact device.

FIG. 4 is a circuit diagram showing a gas pressure welding method for a reinforcing bar according to the present invention.

FIG. 5 is a sectional view schematically showing the structure of a detector in the circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1 'Reinforcing bar 2 Pressure welder 3 Fixed clamp 4 Hydraulic ram 5 Gas burner 6 Hydraulic pump M motor 7 Hydraulic sending line 8 Dividing line 9 Hydraulic detector 10 Comparator 10' Pump speed controller 11 Diaphragm 12 Strain gauge 13 Display Unit 14 Upper limit pressure setting unit 15 Lower limit pressure setting unit

Claims (1)

(57) [Claims] A method for gas-welding rebars, comprising the steps of: butting rebars to be joined, and heating the butted portion with a gas burner and increasing the pressure applied to the butted portion by a hydraulic pump to a set upper limit pressure. Just before reaching the set upper limit pressure reaching point by the hydraulic pump, the oil pumping amount of the hydraulic pump is reduced, and the oil pressure according to the oil pumping amount of the hydraulic pump is constantly detected, and the detected pressure is compared with the set upper limit pressure. A gas pressure welding method for a reinforcing bar, wherein a replenishing amount of the oil is replenished in accordance with a compression amount of the abutting portion so as to reach a set upper limit pressure.