EP0077952B1 - Method for the frictional connection of reinforcement steels concrete construction - Google Patents

Description

The invention relates to a method for the positive connection of ;; reinforcing bars in reinforced concrete construction by means of a screw sleeve, the bar ends to be connected being peeled and provided with a rolled-up thread, which in the outlet area has a conical thread core which increases in diameter towards the thread end, onto which the sleeve is forcibly screwed onto the rod in such a way that a plastic deformation occurs in the tapering thread area.

In the case of such screwed socket connections of reinforcing bars in reinforced concrete construction, it is known (DE-A-1 784 382) to provide the rollers used in the thread production with a run-up and to force the socket with a constant thread to turn onto the thread of the rods to run out to achieve an increase in the load-bearing capacity of the socket connection. With the otherwise usual screw connections of bars with a thread that does not run out (DE-A-1 659 264), the load-bearing capacity may only be calculated using the core cross-section of the bar thread. Since the core cross-section is naturally much smaller than the cross-section of the full rod, this means that in normal cases, the sleeve cross-section cannot be used economically. In contrast, in the method described at the outset, the rod connection has approximately the same load-bearing capacity as the unimpeded rod. While the steel flows outside the socketed area under load until it breaks, it elongates and contracts to the same extent so that the rod cross-section becomes smaller and smaller, in the threaded area there is a bond between the rod and the socket, which prevents the rod from flowing under the socket . In the thread area there is therefore no reduction in the cross-section of the rod as long as the connection between the sleeve and the rod remains intact. If the bond fails in the first thread of the sleeve, the flow process continues into the thread area, further threads become disengaged due to the transverse contraction of the rod and the connection breaks like a zipper.

The different types of steel used for reinforcing bars have different flow properties. If you want to use steel grades with unfavorable flow behavior for a socket, you must ensure that the first thread of the socket remains in contact for as long as possible and that the flow process on the thread of the rod starts as late as possible.

In the known method, the rods are peeled at their ends with a constant diameter before the thread is rolled up. In the area of the thread running out, the thread tips are therefore not fully formed during the rolling process. However, this means that the first threads, which are of paramount importance, are only partially engaged.

The invention makes it its task to design the thread runout of the rod end thread in such a way that even the critical first threads come fully into engagement with the sleeve immediately at the beginning of the rolled thread, so that steel with unfavorable flow behavior can also be connected without reducing the load-bearing capacity.

The object is achieved by the method described in claim 1. Due to the conical peeling in the thread runout, more material remains in this area, so that the thread tips are fully formed during the subsequent rolling process. The conically widened diameter of the rolled thread in the rod end area brings an additional improvement in the load-bearing capacity if, in the subsequent work step, the sleeve is unscrewed and deformed in the threads of the outlet area.

In a further embodiment of the invention, a roller tool for producing the rod end thread according to the invention is proposed. The degree of taper of the outside diameter of the rod end thread is limited by the elasticity of the sleeve. As a rule, the sleeve will have a constant thread.

The load-bearing capacity of the socket connection can be further improved if the taper of the thread ends is further enlarged and the socket thread is also conical at the ends. The gain in load-bearing capacity must, however, be bought with a more complex production of the socket thread in this solution.

For all sleeve designs, the sleeve thread may only have a conicity that is all the less less than the sleeve's elasticity allows without tearing.

The invention opens up many possible variations in adapting the screwed socket connection to the properties of the available steel grades from an economic point of view.

The invention is illustrated by 5 figures and one way of carrying it out.

• Fig. 1 ein Gewinderollwerkzeug 1 für ein Gewinde mit konstantem Durchmesser 2 und auslaufendem Gewindebereich 3,
• Fig. 2 ein mit konstantem Durchmesser 4 geschältes Stabende 5, auf das mit einem Werkzeug 1 nach Fig. 1 ein Gewinde 6, 7 aufgerollt ist. Die Spitzen 8 der aufgerollten Gewindegänge im Auslaufbereich 7 sind nicht voll ausgebildet.
• Fig. 3 ein mit konischer Aufweitung im Bereich 9 des auslaufenden Gewindes geschältes Stabende 10, auf das mit einem Werkzeug 1 nach Fig. 1 ein Gewinde 11, 12 aufgerollt ist. Die konische Aufweitung 9 ist so bestimmt, daß die Gewindespitzen im Bereich 12 voll ausgebildet sind.
• Fig. 4 ein Gewinderollwerkzeug 13 mit nach Anspruch 2 auch konisch verjüngtem Rillenaußendurchmesser 14 im Auslaufbereich 15.
• Fig. 5 ein mit konischer Aufweitung im Bereich 16 des auslaufenden Gewindes geschältes Stabende 17, auf das mit einem Werkzeug 13 nach Fig. 4 ein Gewinde 18, 19 aufgerollt ist. Dem verjüngten Rillenaußendurchmesser 14 des Werkzeugs 13 entspricht ein Stabgewinde mit konisch wachsendem Außendurchmesser im Auslaufbereich 16.

Show it:

• 1 is a thread rolling tool 1 for a thread with a constant diameter 2 and tapering thread area 3,
• Fig. 2 is a peeled rod end 5 with a constant diameter 4, on which a thread 6, 7 is rolled up with a tool 1 according to FIG. 1. The tips 8 of the rolled threads in the outlet area 7 are not fully formed.
• FIG. 3 shows a rod end 10 with a conical widening in the area 9 of the thread that is being tapped, onto which a thread 11, 12 is rolled up with a tool 1 according to FIG. 1. The Conical widening 9 is determined so that the thread tips are fully formed in the area 12.
• 4 shows a thread rolling tool 13 with a conical tapered groove outer diameter 14 in the outlet area 15.
• 5 shows a rod end 17 peeled with a conical widening in the region 16 of the thread which is running out, onto which a thread 18, 19 is rolled up with a tool 13 according to FIG. 4. The tapered groove outer diameter 14 of the tool 13 corresponds to a rod thread with a conically growing outer diameter in the outlet area 16.

Claims (2)

1. Method for the frictional connection of reinforcing bars in reinforced concrete construction by means of a screwed sleeve in which the ends of the bars which are to be joined are shaved and provided with a rolled thread which, in the washout region, has a minor cylinder whose diameter increases in a taper towards the end of the thread, onto which thread the sleeve is forcibly screwed so that plastic deformation takes place in the washout region of the thread, wherein, in the shaving operation which is required before the thread is rolled on, the shaved diameter increases in a taper in the region of the thread washout and a thread is rolled on whose outside diameter increases in a taper towards the end of the thread, the taper of the thread at the end of the bar being limited to a size such that the sleeve, whose thread is of constant inside diameter or has a shallower taper in the washout region than that on the bar, does not split open when screwed on.

2. Thread rolling tool to carry out the method claimed in claim 1, wherein the major cylinder (14) of the tool tapers down in the region of the thread washout (15), so that the tool can be used to roll a thread (18, 19) whose major cylinder increases in diameter onto the bar (17).

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