Note: Descriptions are shown in the official language in which they were submitted.
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CONCRETE-REINFORCING ROD, PARTICULARLY ANCHOR P~OD, AND METHOD
OF MANUFACTURING IT
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The invention relates to a concrete-reinforcing rod, part-
icularly an anchor rod, with helically-shaped ribs which form partial
pieces of a screw-thread, upon which an anchoring body, provided with
a corresponding counter-screw-thread, can be screwed, as well as to
a method of manufacturing i-t.
A reinforcing rod is known from United States patent
No. 1,151,947; on i-ts surface are provided ribs traveling at a
steep angle to the longitudinal axis of the rod. These ribs are
disposed in groups; the ribs of successive groups being directed
toward one ano-ther and partially overlapping. Aside from the too-
great pitch of the ribs, the effect of a screw-thread canno-t be
attained, even approximately, by means of the opposing orientation of
the same. In the reinforcing rod according to German patent No. ~
1,077,854, the profilings in the form of ribs, customary for improving
adhesion in -the concrete, are so disposed that they lie on a helix
and orm part of a screw-thread. In this way, no chip-removing work,
such as incising, or non-cutting forming work, like rolling up~a
screw-thread cold on the ends of the rods, was necessary any longer
for installing screwable connecting and/or anchoring bodies.
Reinforcing rods of this sort have been manufactured in
such a manner that the ribs, which forrn a partial screw-thread, lay
only on one side of the rod, while the opposite side of the rod
remained smooth. The unilateral introduction of force thus brought
about had an unfavorable influence on the fatigue strength of the ; ~ `~
rod. A further drawback of this rein~orcin~ rod lies in the fact
that, because of the opposite smooth side of the rod, it cannot;
be inserted as rib s-teel in normal steel-concrete construction.
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The reinforcing rod according to German patent No. 1,199,470
voids some of these drawbacks. On the side of the rod opposite
the ribs, it possesses cavities (or recesses, or indentations) like-
wise formed in the path of a warm rolling process, between which ribs
remain standing, which are so disposed that their external boundary
lies on the continuation of the circular cylinder surface of the
other side of the rod, which forms the core of the rod. In their
position with relation to the ribs on the opposite side of the rod,
which form a partial screw-thread, these ribs between the recesses
are so disposed that a screwed-on connecting or anchoring body lies
with its internal surface on the external boundary of these ribs.
However, this does not result in a flawless connection. This steel
rod, which indeed is suited for use as a simple concreie-reinforcing
rod, because it has profilings on both sides, is disadvantageous in
the use of anchoring or connecting bodies as a result of the uni-
lateral introduction of force. Because of its asymmetrical form of
cross-section, it is also difficult to align (or straighten) it in
so-called aligning (or straightening) machines. Besides, its
manufacture turns out to be difficult because the surfaces on the
opposite sides of the rod, which surfaces are to be rolled, are at
different distances from the axis of the rod and necessi`tate
different surface velocities of the roLlers required from manufacture.
A Eurther problem in the manufacture of concrete-reinforcing rods
with hot-rolled ribs which form a part:ial screw-thread reside5 in
variations in texture in the steel which occur in rolling the ribs
and which result in differences in tensile strength. These differences
in tensile strength appear primaril~ in the area of points at which
the individual rib grows upwardly out of the surface of the rod.
Notch tensions occur at this point, which lead to diminution of the
breadth of oscillation of the rod.
These notching tensions act most strongly when the ribs
run perpendicularly to the longitudinal direction of the rod, when
their adhesion-improving effect is naturally at its greatest. In
this case, the material of the ribs must be considered as a dead
weight, because a cross-section perpendicular to the ~xis of the
rod does not necessarily intersect--------------------------------------
a rib. No notching tenslons occur when the ribs run in the longi-
udinal direction of the rod, and the material of the ribs can be
added fully to the cross-section of the rod; ho~ever, an adhesion-
improving efEect does not take place then, because there is no
direct support on the concrete. For this reason, the ribs are
disposed inclined to the longitudinal axis of the rod in the case of
concrete-reinforcing steels. In general, this inclination amounts
to between 40 and 60 degrees. Then the cross-section projection of the
ribs can be relied upon for the adhesion-improving effect, while the
notching tensions are kept within bounds.
If the ribs lie on a helix and are designed to form a
screw-thread, then the inclination of the ribs to the longitudinal
axis of the rod may not be greater than that an anchoring body reliably
obstructs with its internal screw-thread adapted to the partial
screw-thread. However, the pitch of the screw-thread ribs which is
possible under this condition is then so small that notching tensions
cannot be avoided, and the material of the ribs cannot be added to
the carrying cross-section surface. The result is smaller width
oE oscillation oE the rod and poorer utilization of the material.
Experiments to diminish the unfavorable effects of the notching
tensions on the width of oscillation by rounding off the profile of
the ribs have not led to the desired result. Moreover, specially-
shaped tools are necessary, and the service life of the rollers
must he kept very short in order to ma:intain the required profile
with certainty, which means increased ~leed for tools.
~ccording to German patent No. 1,659,067, the helically-
disposed ribs are arranged in the form of a double-thread screw-
thread on two opposite sides of the circumference of the rod. The
double-thread screw-thread makes possible the manufacture of a
steeper pitch of screw-thread and, therewith, a rod which can be
manufactured better, roller-technically. A disadvantage is the small
and insufficient extent of height of the full screw-thread with
relation to the circumference of the rod~ As may be seen from a com-
parison of FIGS. 2 and 3 of the said patent, the height of the rib
depends decisiveIy on the angle to the longitudinal axis. The flatter
the an~le of the rolled rib, the flatter, lower, and less---
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~istinctly can the latter be rolled~ Added to this is the furtherdrawback that the -transmission of force to the counter-screw-thread
in the nut (or Eemale screw), conditioned by the short screw-thread
segments, lying one behind another in longitudinal direction, and
only slightly raised (or in relief~, takes place only to an in-
sufficient extent. As a result of the unavoidable roller tolerances,
which also must be taken into consideration in the counter-screw-
thread, the small, utilizable surface of the screw-thread segments
is diminished still further.
The reinforcing rod of United States patent No. 4,137,686
also exhibits the same disadvantage of relatively short height of
screw-thread with reference to the circumference of the rod and the
segments of screw-thread lying spaced one behind another in the longi-
tudinal axis of the rod.
An aspect of the invention is to avoid these drawbacks. In
the case of a reinforcing rod or anchoring rod of the initially-
described type, this is attained by arranging the screw-thread
partial pieces of successive screw-threads, which pxeferably extend
over more than half of the circumference of the rod, in a continually-
staggered manner with relation to one another, and by at least
partially covering over the gap between the screw-thread partial
pieces by means of a screw-thread partial piece of the following
screw-thread, so that the screw-thread partial pieces which form a
selE-arresting screw-thread, or the gaps, run helically around the
rod. The manufacture of such a rod takes place in such a manner that
a rod blank (or unworked piece) with rolled ribs running diagonally
to the longitudinal axis of the rod, the ribs being oriented in one
direction and preferably including an angle of 40 to 60 degrees to
the longitudinal axis of the rod, is subjected to a torsion in order
to form the self-arresting (or self-blocking, or self-obstructing)
screw-thread consisting of screw-thread partial pieces.
In the first stage of the process, a rod blank is warm-
rolled with ribs. However, the ribs situated on the two opposite
sides are not arran~ed at an opposing angle, in known manner; rather,
they wind in a coil around the rod. secause of the oblique angle to
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longitudinal axis, -the ribs, while avoiding any notching tensions
in the rod, can be rolled to be not only very long, but also
relatively high and distinct. In the second and essential stage
of the process, the rib steel is twisted or torsioned in the
direction in which the ribs are inclined. In that way, the angle
of the ribs becomes ever flatter with increasing twisting, so that
a functional, self-arresting screw-thread now originates from
the original coil-shaped arrangement of the ribs; it is advantageous
that the ribs, already originally long, become still longer
because of expansion of the steel resulting from the torsion
and reach over more than half of the circumference of the rod.
This now-formed screw-thread partial piece is displaced (or
staggered) in a clockwise direction with relation to the next one,
so that every individual screw-thread-rib gap is covered over
by the next screw-thread partial piece. The pitch of the serew-
thread is continuously (or stagelessly) manufacturable in
accordance with the degree of torsion. Right-hand or left-
hand screw-threads are possible, according to the position of
the ribs and corresponding direction of torsion.
Accordingly, this invention provides a concrete
reinforcement comprising a steel rod formed along its
circumference with a succession of ribs forming screw thread
sections lying along a helix and engageable by a female thread,
said sections being separated by uniformly spaced gaps disposed
along a continuous helical track coaxial with said rod,
successive sections overlapping the gaps of the next section
in axial projection, said sections forming collectively a
self-locking screw thread.
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Embodiments of the subject matter of the invention
are represented in the drawings, which also illustrate thè process
in accordance with the invention. Fig. 1 shows a portion
of an anchoring rod before the torsion treatment, Fig. 2 shows
the same after the torsion, and Fig. 3 shows a series of
possible forms of ribs.
The rod 1 according to Fig. 1 has ribs 2, which
are arranged on opposite sides of the surface of the rod.
The ribs 2 enclose an angle of about 45 degrees with the longi-
tudinal axis of the rod. They are manufactured in the warm-
rolling process. As a result of their oblique position, the
ribs 2 are relatively long but, because of gaps 3 existing
between the ribs 2, embrace less than half of the circumference
of the rod. The gaps 3 between -the ribs lie diametrally on the
circumference oE the rod along a generatrix of the cylinder
which forms the rod 1. The manufacture of the rod 1 shown
in Fig. 1 is possible wi-th any preferred forms of ribs, and also
with distinct heights, without any problems.
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The rod 1 is then twisted or torsioned - that is, the
od is twisted within itself - so that displacement of the surface
elements occurs, and , in connection therewith, the steel is strength-
ened, and thè rod is simultaneously straightened (or aligned). Then
a rod 4 in accordance with FIG. 2 exists as a product of the process,
its ribs now forming flat screw-thread partial pieces _ lying closely
adjacent one another. The gaps 6 no longer lie along a generatrix,
as shown in FIG. l; rather, they are displacedly arranged along a
helix on the rod. Because of expansion by reason of torsion, the
screw thread partial pieces _ resulting from the ribs 2 (Fig. 1)
embrace more than half of the circumference of the rod. Adjacent
screw thread partial pieces _ of the next screw-thread course are
displaced (or staggered) in such a manner that the screw thread
partial pieces overlap in axial projection, and therefore a screwed-
on screw nut, with its counter threading over a large extent, is in
engagement with the rod 4. Only because of the torsion does a
screw-thread which is self-arresting, and which is of sufficient
stability, originate from the originally diagonal ribs, which have
no sort of screw-thread function.
FIG. 3 represents examples of cross section forms of
screw-thread courses which are suited especially for the manufacture
of reinforcing rods.
