CZ278078B6 - Split clamping cone for anchoring of prestressing reinforcement - Google Patents

Abstract

The split camping cone (1) for anchoring the pre-stressing reinforcement (7) of pre-stressed constructions, in particular seven-wire cords, is divided by radial cuts into segments (1a, 1b, 1c) mutually connected on the bottom of the partial cuts (9) by joining bridges (4) with a triangular cross-section. The joining bridges (4) hold the individual segments (1a, 1b, 1c) of the clamping cone (1) next to one another until breaking during assembly. The triangular area of the joining bridge (4) has an axial side (a) equalling a maximum of one fifth of the length (L) of the clamping cone (1) and its sloped side (c), which is the bottom of the dividing cross-section (9), has an angle with the axis (o) of the clamping cone (I) (β) of at least 2 degrees.<IMAGE>

Description

Technical field

The invention relates to a clamping cone for anchoring the prestressing reinforcement by a structure. It refers to dividing the clamping cone for anchoring the reinforcement made by radial cuts lying in at least one plane of its axis into at least two parts.

BACKGROUND OF THE INVENTION

The clamping cones used for anchoring the prestressing reinforcement, in particular of multi-wire strands, generally seven-strand, have the shape of a truncated cone with a cylindrical bore with roughening. They consist of at least two parts, ie two segments formed by cutting the clamping cone with one radial cut. As a rule, three-part clamping cones are used, i.e. three segments formed by cutting the clamping cone with three radial cuts made at 120 °. Exceptionally, four-part clamping cones are used.

The clamping cone is cut prior to heat treatment, usually by cementation, after which it is necessary to check the hardness of each segment, followed by reassembling the appropriate number of segments so that the clamping cone is formed. The individual segments are then secured to each other by a steel or rubber ring mounted in the circumferential outer groove of the clamping cone. This assembly is laborious and the clamping cones can be assembled from segments originating from different starting blanks. For example, when assembling a three-part clamping cone, one segment may be less than 120 °, the second with a misaligned hole and the third with a hole whose axis is parallel to the truncated cone axis. When the three segments, which are anchored in the tapered bore of the anchor sleeve, are retained in the anchoring of the prestressing reinforcement, the outer shape of the clamping cone is maintained, but the roughened bore no longer forms a cylindrical surface. The roughening, which is generally in the form of a thread with a very sharp profile, then causes radial pressure on the anchored prestressing reinforcement to cause it to be unevenly clamped and thus to significantly increase the notches in the more squeezed strands of the strand. This reduces the load capacity of such excessively broken wires, which results in a lower load capacity of the whole strand.

One way to overcome these disadvantages is to mark the individual segments before cutting the clamping cone so that they cannot be confused. Assembly of clamping cones from segments marked in this way is practically impracticable in series production.

DE 2 429 353 proposes to treat the outer surface of the clamping cone in a region close to the small truncated cone base and along the joints of the segments with a recess. This avoids that in the critical anchoring area, i.e. the first notches in the anchored prestressing reinforcement, where its clamping is most delicate, the risk of the reinforcement clamping over the edges of the segments is eliminated.

British Patent Specification No. 1 387 818 proposes to slice cross sections of the clamping cone at an angle. This solves the problem of large clearance when assembling the clamping cone from segments with a smaller angle of radial cuts.

According to German Patent DE 3 236 614, the separation gap between the segments is provided with a toothing which ensures the precise connection and interaction of the segments.

None of these patents, however, address the elimination of the effects of manufacturing tolerances and inaccuracies that occur when assembling a clamping cone from randomly selected segments. On the contrary, it is necessary to keep the clamping cone from the corresponding segments.

Because of the problems associated with assembling the taper cones from segments that should correspond to each other, some manufacturers make incomplete radial cuts in the taper cones parallel to the taper cone axis, i.e., the actual thread or the roughing of the cylindrical bore and its vicinity are not cut. Too deep a cut can cause undesirable splitting during manufacture, while shallow difficulty in splitting the clamping cone into segments prior to use. The production of clamping cones with unfinished cuts parallel to its axis places great demands on cutting precision and the alignment of the cylindrical bore with the surface.

SUMMARY OF THE INVENTION

These disadvantages are overcome by the invention of a split clamping cone for anchoring prestressing reinforcement of prestressed constructions, in particular multi-strand strands, divided by sections lying in at least one plane of its axis into at least two parts, the essence is that the individual clamping cone segments are connected triangle-shaped connecting bridges whose axial side lying on the inner surface of the cylindrical bore of the tensioning cone for prestressing reinforcement is at most one fifth of the length of the clamping cone and whose oblique side forming the bottom of the dividing section forms at least 2 ° with the clamping cone .

Said solution makes it possible to guide the cutting tool when splitting the clamping cone so that the movement of the tool into the cut is deflected from the clamping cone axis at a selected angle from 2 'up, so that the extent of the connecting bridge surface can be sensitively controlled. The size of the cross-sectional area of the connecting bridge can be easily selected so as to avoid premature separation of the individual segments. It is preferred that the cutting angle of the cutting tool and thus the inclined angle of the triangular surface of the connecting web is in the range of 2 ° to 10 ° and the length of the axial side then close to one fifth of the length of the clamping cone.

The heat treatment, usually cementation and quenching, which is important especially in the roughened cylindrical bore, is more advantageous in the clamping cone of the invention than in the separate segments, which are generally stacked on top of each other, preventing even cementation media from reaching the roughening surface. The linking bridges acquire hardness throughout the cross-section, which makes it easy to break them when sliding the clamping cone onto the prestressing reinforcement.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below with reference to the accompanying drawing, in which: FIG. 1 is an axial sectional view of a clamping cone according to the invention, partly in view of the outer cone surface; 1.

The drawing shows a three-part clamping cone 1 consisting of three segments 1a; 1b and 1c are separated from each other by cuts 9. The cuts 9 are guided in planes parallel to the axis o of the clamping cone 1 and are oriented radially in the present case so as to form 120 ° to each other. In this case, the cuts in these planes are made by a tool guided at an angle θ at an angle 3 and are not finished. Thus, a connecting bridge 4 of triangular cross-section connecting the adjacent segments 1a and 1b to each other remains at the bottom of the dividing sections 9; 1b and 1c and segments 1c and 1a. The length of the axial side and the triangular surface of the connecting web 4 in this case is equal to 18% of the length

L of the clamping cone 1. The inclined side c of the triangle at the bottom of the cross-section 9 forms an axial side and an angle β. 3 °. Since the face 11 of the frusto-conical clamping cone 1 is perpendicular to the o-axis in this case, the triangle of the surface of the connecting web 4 is rectangular and its third side b has the size a.tgj3.

It can further be seen from FIG. 1 that the clamping cone 1 has a cylindrical bore 8 for the prestressing reinforcement 7, provided with a roughening 3 or thread on its inner surface 10. At the inlet side of the prestressing reinforcement 2 into the opening 8 of the anchor cone 1, the inner surface 10 is provided with a conical taper 6. At the location 5 the hardness of the clamping cone 1 is checked. segments 1a; lb or lc.

After heat treatment, a clamping steel or rubber ring 2 is fitted onto the clamping cone 1, which engages in the outer circumferential groove 12. In use, i.e. during its assembly, the clamping cone 1 is inserted by the start of the cylindrical bore 8 at the end of the prestressing reinforcement 7 With increased force or impact on the face 11, the tapered cone 1 with its conical taper 6 starts to slide onto the prestressing reinforcement 7. Since the cylindrical bore 8 has a smaller diameter than the prestressing reinforcement 7, the separate ends of the segments 1a will be spaced apart; lb; 1c, thereby breaking the connecting bridges 4 at the face 11 of the clamping cone 1. The retaining ring 2 ensures that, after breaking the connecting bridges 4, the individual segments 1a; 1b and 1c do not separate < 1 that the clamping cone 1 can be displaced along the prestressing reinforcement 7 as a whole. The connecting bridges 4 between the segments 1a; lb; 1c can be broken even by striking the clamping cone 1 against a hard object.

Industrial applicability

The invention is generally suitable for the manufacture of anchor cones for anchoring prestressing reinforcement, in particular seven-wire strands.

CZ 278078 Β6

Claims (1)

PATENT CLAIMS Split clamping cone for anchoring prestressing reinforcement of prestressed structures, in particular seven-strand strands, divided by at least one plane of its axis into at least two parts, characterized in that the individual segments (1a, 1b, 1c) of clamping cone (1) are in cuts (9) on the face side (11) connected by a connecting bridge (4) of the cross-section of the triangle, whose axial side (a) lying on the inner surface (10) of the cylindrical bore (8) of the clamping cone (1) is equal to not more than one fifth of the length (L) of the clamping cone (1) and whose inclined side (c) forming the bottom of the dividing cut (9) forms an angle (β) of at least 2 'with the clamping cone axis (o).