DE8626761U1 - Insertion cap for inserting a prestressing steel into a duct - Google Patents

Description

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The invention relates to an insertion cap for inserting a prestressing steel into a casing tube/with a sleeve in which the prestressing steel can be attached, as well as on one end of the sleeve with a rounded closed tip.

Such known insertion caps are placed on the beginning of a prestressing steel in order to insert the prestressing steel into the sheathing tube without damaging it. In addition, the insertion cap, which is also referred to as a threading cap, is intended to prevent the prestressing steel from catching in the sheathing tube or on prestressing steels that have already been inserted. The manufacturing method in which the prestressing steels are pushed into the sheathing tube individually and one after the other is preferred over pulling all the prestressing steels in a bundle into the sheathing tube at the same time or pulling a sheathing tube over the cut-to-length prestressing steel bundle, as it requires less working time. The sheathing tubes of bundled tendons, which consist of several prestressing wire strands or prestressing wires, have recently been filled primarily with the help of an automatic cutting machine that pushes the prestressing steels individually and one after the other into the sheathing tube. The prestressing steels wound onto coils in the prestressing steel mill are pulled off the coil by the machine, pressed into the cladding tube and cut to the required length.

In order for the insertion cap to fulfil its initially mentioned function when inserting a prestressing steel, it consists of a short tube which is closed on one side in a hemispherical shape. The inner surface of the tube, which forms a sleeve, is provided with elevations so that the sleeve sits firmly on the prestressing steel when inserted.

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Because it is expected that a prestressing steel will have to be pulled back a short distance and then pushed forward again because it is stuck in prestressing steel that has already been pushed in - which is particularly the case with long

5 or strongly curved sheathing tubes - the prestressing steel is fixed in the sleeve with threaded pins, which are screwed into a sleeve consisting of a thick-walled tube * - When inserting the prestressing steels of tendons that consist of a large number of prestressing steels

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Prestressing steels are often inserted between the prestressing steels that have already been inserted. * This can lead to a so-called tangling of the prestressing steel bundle, which increases the friction when prestressing the tendon in an undesirable way. Another disadvantage is that the prestressing steels in this case have an unequal length and therefore cannot receive the same tension when prestressing the prestressing steel bundle. When producing the prestressing steel bundle, a higher insertion force is required for the prestressing steels, which dig in between the prestressing steels that have already been inserted, whereby

the required insertion force can exceed the capacity of the insertion machine. This leads to the prestressing steel becoming stuck. Since the insertion force generated by the insertion machine is limited, the prestressing steel often cannot be inserted easily. In this case, additional, labor-intensive measures are required to pull in the prestressing steel.

Attempts have therefore already been made to prevent the chip steels from digging into previously inserted prestressing steels in the cladding tube by providing a ball with a larger diameter than the sleeve or the tube forming the sleeve at the tip of the insertion cap.

However, the "diameter" of the ball can only be slightly larger than the adjacent pipe diameter, since the free space in the casing pipe is limited. Therefore, such a ball cannot completely eliminate all the disadvantages of the known insert cap with the rounded front side.

The present invention is therefore based on the object of designing an insertion cap of the type mentioned at the beginning in such a way that it reliably prevents the prestressing steel from digging into prestressing steels previously drawn into the cladding tube and from tangling the prestressing steel bundle.

This object is achieved according to the invention by a design of the insert cap such that the tip is flat and spoon-shaped when viewed from above*

With such an insertion cap, it is ensured that the prestressing steel always slides over the prestressing steels that have already been inserted, and is therefore not pushed between them. The tip of the insertion cap only takes up a comparatively small volume in the casing tube. It is therefore suitable for inserting the prestressing steel into the casing tube, which already has several prestressing steels

,25, only a small insertion force is necessary.

For this purpose, the spoon-shaped tip is wider and longer than the outer diameter of the sleeve, but less thick than its outer diameter. This results in a large sliding surface with a small volume of the tip of the insert cap.

The embodiments according to claims 3 and 4, which are characterized by a low outlay for producing the insert cap with the spoon-shaped tip,

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Since the sleeve and the spoon-shaped tip form a solid part, it is particularly suitable for inserting tension wires. The tension wires are unwound from rotating unwinding devices, whereby the tip of the tension steel does not twist when inserted. The horizontal position of the spoon-shaped tip, which is fixed when the insertion cap is pushed onto the tension steel tip, is thus retained when the tension wire is inserted into the sheath.

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j, however, the embodiments according to claim 5 and

the following requirements, particularly suitable for inserting prestressing wire strands. The prestressing wire strands are namely pulled from strand coils out of a fixed pull-off cage, whereby the tip of the strand

rotates 360° with each turn that is removed. However, due to the rotatable bearing of the spoon-shaped tip of the insertion cap, the spoon-shaped tip still maintains its position relative to the horizontal, thus avoiding the risk of the strand digging in. For this purpose, the insertion cap is designed in such a way that the sleeve on its side opposite the side that receives the tension wire strand serves as a pivot bearing for a rotating part that has the spoon-shaped tip.

25
s The sleeve preferably consists of

a thick-walled tube into which threaded pins are screwed, which fix the prestressing steel _and act as locking screws. These locking screws must be tightened separately with pin wrenches, but this means that the prestressing wire strand is so firmly seated in the sleeve that it can also be pulled back if this should be necessary in exceptional circumstances. -At one end of the sleeve, several threaded pins are screwed into a cut at right angles to the pipe axis, but these are inserted into a circumferential groove.

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of the rotating part, so that this part can be rotated^ but
to be mounted axially immovably relative to the sleeve.

Especially with this continuous design of the sleeve
with a relatively thick-walled pipe recommends
the additional measure according to claim 9, which achieves

that the tip of the tension wire strand does not touch the I

Wire part presses and thus the relative rotation of the sleeve %

obstructed by the spoon-shaped tip of the rotating part. |

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On the other hand, especially in cases where '(

Safety no tensile forces are exerted on the insertion cap?,

must be made from a thin, material-saving material,

walled tube in which the tension wire strand ■

is clamped with pressed-in circumferential beads.
However, for the storage of the rotating part, a
thick-walled pipe section is provided, which is welded to the thin-walled pipe. If the beads are

are crushed by frequent use, the thin-walled ''

Simply cut off the pipe and replace it with a j

new pipe to be replaced during manufacturing |

more complex part - the thick-walled pipe and the

mounted rotating part&mdash;with the spoon-shaped tip further- j

can be used. :

I The invention is described below with reference to a drawing with
five figures explain in more detail. They show:

Fig. 1 a section through a first embodiment
the insert cap with fixed spoon-shaped

formed tip made of plastic,

Fig. 2 is a plan view of the sliding cap according to Fig. 1,
Fig. 3 a second embodiment of the insert cap,

here with rotating spoon-shaped tip,
35

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Fig. 4 a top view of the insert cap according to Fig. 3

and
Fig. 5 shows a section through a third embodiment of the insertion cap, here also with a rotatable spoon-shaped tip and with an exchangeable prestressing steel holder.

Figures 1 and 2 show the first embodiment of the insert cap, which consists of a piece of pipe 2 with a molded-on spoon-shaped tip 4. The shape of the flat spoon-shaped tip can be seen in detail in the figures. The tubular holder for the prestressing steel 1 has ring-shaped beads 3, which ensure that the prestressing steel is held firmly.

This insert cap is preferably made of plastic, but it can also be made of steel. In the latter case, the spoon is conveniently welded to a pipe that is closed on one side.

In the second embodiment according to Figs. 3 and 4, the insertion cap is shown with a rotating spoon tip. A thick-walled tube 2a is used to hold the prestressing steel - in the illustration a strand la. To fasten the strand, the tube has threaded holes into which threaded pins 7 are screwed as locking screws. The threaded pins have a hardened tip with which the strand is clamped. The tip of the threading cap consists of a rotating part 9 which is welded to a spoon-shaped tip 4a made of flat steel. A pin 10 of the rotating tip has a circumferential groove 5 into which threaded pins 6 engage. So that the strand la does not press against the pin 10 and hinder the rotation of the tip, a grooved pin 8 is inserted across the tube 2a. To facilitate rotation, the groove 5

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greased. By loosening the threaded pins 6, the bucket tip can be easily separated from the prestressing steel holder and replaced.

The embodiment according to Fig. 5 shows an insert cap with a rotating spoon tip, in which the prestressing steel holder consists of a thin-walled tube 11. Circumferential beads 13 are pressed into the tube, which clamp the strand 1a. The thin-walled tube is welded to a thick-walled tube piece 12a, which holds the threaded wire 6. If the beads are crushed by frequent use, the thin-walled tube 11 can simply be cut off and replaced with a new tube. Putting the insert cap on the prestressing steel is easier than with the design with locking screws, since no pin wrenches have to be used to fasten the prestressing steel.

Depending on the intended use, one of the above-described embodiments can be selected, which is optimized for this purpose according to the invention.

Claims (3)

Protection claims: 1. Insertion cap for inserting a prestressing steel into a casing tube, with a sleeve in which the prestressing steel can be attached, and on one end of the sleeve with a rounded closed tip, characterized in that the tip (4, 4a) is flat and spoon-shaped in a plan view. 10 2. Insert cap according to claim 1, characterized in that the spoon-shaped tip (4, 4a) is wider and longer than the outer diameter of the sleeve (pipe section 2, pipe 11), but less thick than its outer diameter. 3. Insert cap according to claim 1 or 2, characterized in that the spoon-shaped tip (4) is formed integrally with the sleeve (pipe section 2). 4. Insert cap according to claim 1 or 2, characterized in that the spoon-shaped tip is a separately manufactured part which is welded to a tube closed on one side. 5. Insert cap, in particular for tension wire strands according to claim 1 or 2, characterized in that the sleeve (pipe section 12a) serves on its side opposite the side receiving the tension wire strand (la) as a pivot bearing of a rotating part (9) which has the spoon-shaped tip (4a). ' 16. Insert cap according to claim 5,
&igr; characterized by that the rotary part (9) has a pin (10) with a circumferential groove (5) into which threaded pins (6) screwed into the sleeve engage, and that the spoon-shaped tip (4a) forms a solid part together with the rotating part. 7. Insert cap according to claims 5 and 6, characterized in that the sleeve consists of a thin-walled tube (ll; _y) in which the tension wire strand (la) can be clamped with beads (13), and a thick-walled tube piece (12a) welded to an end face of the thin-walled tube, which forms the pivot bearing of the rotating part (9). 8. Insert cap according to one of claims 1-6, characterized in that the sleeve consists of a thick-walled tube (2a) into which threaded pins (7) fixing the prestressing steel (la) are screwed. 9. Insert cap according to claims 5 and 8, characterized by a grooved pin (8) extending across the tube, which limits the side of the sleeve (tube 2a) that receives the tension wire strand (la) from the side of the sleeve that forms the pivot bearing. 30 3.5