DE3316134C2 - Method and device for the production of protective tubes with a flat cross-section for concrete reinforcing bars - Google Patents

Abstract

Method and device for the production of protective tubes with a flat cross-section for concrete reinforcing bars. In a pipe with a circular cross-section, in particular a corrugated pipe, a mandrel with a substantially rectangular cross-section is inserted, whereupon the entire length of the pipe is expanded, preferably in a single pressing process, until opposing wall parts rest against the mandrel. Two press bars (2, 3) which can be moved towards and from one another are used for this purpose, the effective length of which is at least equal to the length of the pipe to be deformed, and in a mandrel (4) which can be pushed into the pipe before it is pressed.

Description

The invention relates to a method according to the preamble of claim i.

Another object of the present patent application is a device for implementation this procedure.

It is common to place concrete reinforcements, which are tensioned after the concrete has hardened, in protective pipes to be laid in order to avoid contact between the concrete and the reinforcement bar and thereby the free and to ensure unhindered elongation of the rod during tensioning.

In addition to the reinforcing bars with a circular cross-section or bundles of such bars are also available Flat bars are in use as reinforcement, and also, in many cases, for reasons of availability Space within the girder to be reinforced, common, several reinforcing bars with circular Cross-section to be laid next to each other in the same pipe. The tubes used for this have flat, The cross-section corresponding to the rod and were produced by flattening sheet metal tubes. These sheet metal tubes were made by helically winding a sheet metal strip over a mandrel, the edges of which overlapped each other and were connected to each other by spot welding. the Sheet metal strips could have a slightly corrugated cross-section.

When flattening these products, which are generally known under the designation "spiral tube", resulted but there is the disadvantage that the tube, which was originally circular in cross section, is not flat Received a cross-section, which consisted of two parallel straight lines and two arcs connecting them, but showed a cross-sectional shape corresponding to a biscuit, i.e. H. the two sides were to each other or bent or dented into the interior of the cross-section. This undesirable deformation had to be taken into account be carried, and the flattening could only be done so far that the free space the dented sides still allowed the introduction of the reinforcing bar (s). Expressed differently, one was forced to push back a pipe with a diameter that was too large in itself only partially in order to ίο to be able to accommodate the intended reinforcing bars in the deformed pipe; a corresponding cost inflation was inevitably connected with it.

The invention has set itself the goal of avoiding the specified disadvantages and achieves this goal in the method of the type outlined above by the measure according to the characterizing part of the patent claim 1.

The inventive device for performing this method consists of the features of Claim 2.

Further advantages of the device according to the invention result from the features of the patent claims 3 and 4.

The invention is explained below with reference to the drawing. It show the

F i g. 1 and 2 the previously common procedure for flattening a protective tube made of sheet metal and the

F i g. 3 and 4 show the deformation process according to the invention.

The F i g. 1 and 2 clearly show that a sheet metal tube 1 with an originally circular cross-section when pressing flat between a flat press table 2 and a likewise flat ram

3 receives a biscottel-like cross-section, the lowest height H of which must be so large that a reinforcing bar can still be pushed in with sufficient ease.

According to the method according to the invention, a mandrel 4 of an essentially rectangular shape is inserted into the tube 1 Cross-section inserted. The thickness of the dome 4 preferably corresponds to the thickness (height) of the one to be used Reinforcement, increased by a small amount, to allow the reinforcement to be easily inserted into the To enable flattened tube 1 ', and the width of the dome 4 is so large that the mandrel in the still undeformed pipe can just be pushed in without significant resistance. The one with the thorn

4 provided tube 1 is placed on the press table 2 and the ram 3 is then lowered, preferably by means of a hydraulic device, until the opposing wall parts \ " and V \" are in full contact with the mandrel 4. The deformed tube Γ has been given a flat or oval cross-section which can be seen in FIG. After lifting the ram 3, the mandrel 4 z. B. detected by an extractor, not shown, and pulled out of the flattened tube 1 '.

The press table 2 and the press ram 3 exist in the present embodiment of the press device each from an I-beam, the length of which is at least equal to the length of the tube 1 to be deformed, so that this is deformed in a single pressing process along its entire length. The ram 3 is carried by at least two pistons 5 of a hydraulic press cylinder 6 which is mounted on a stand 7.

Of course, various design changes can be made within the scope of the invention will. So there is the possibility of the pressing device

to be formed from an upper fixed press beam and a lower hydraulic press beam that can be raised and lowered.

The mandrel 4 can be laterally conical at its end to be pushed into the tube in order to To facilitate pushing the dome into the pipe.

Furthermore, the mandrel can be divided in its longitudinal direction and its two parts can be adjusted relative to one another be, whereby the mandrel is adaptable to different pipe diameters. 10

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Claims (4)

Patent claims: 1. Method of making protective tubes with a flat cross-section for concrete reinforcing bars by flattening pipes with a circular cross-section, in particular corrugated pipes that on the pipe wall in diametrically opposite directions and only from the outside pressure is exerted, characterized in that that a mandrel with a rectangular cross-section is inserted into the tube before being flattened and that the flattening of the tube over its entire length in a single pressing process until the wall parts are in contact with the mandrel 2. Apparatus for performing the method according to claim 1, characterized in that it of two press bars which can be moved towards and from one another, the effective length of which is at least equal to the Length of the pipe to be deformed, as well as a mandrel (4), which is before pressing the pipe can be inserted into this. 3. Apparatus according to claim 2, characterized in that the mandrel (4) consists of two parts, which are mutually displaceable transversely to their longitudinal direction. 4. Apparatus according to claim 3, characterized in that the mandrel (4) at at least one end has at least one inclined surface for insertion into the tube (l).