METHOD FOR PRODUCING A SCREW FOUNDATION FOR SECURING ELEMENTS IN THE GROUND

Abstract

A method for producing a screw foundation for securing elements in the ground, provides a cylindrical tube as an initial form and a conical front portion tapering to an insertion tip is then molded on to the cylindrical tube using a non-cutting process, the front portion being provided at least in some regions with a thread-like contour for screwing into the ground. An inner contour for a screwing tool is formed integrally in a rear end of the tube by flow forming, and the front portion and the thread-like contour are formed exclusively by flow forming.

Description

The invention relates to a method for producing a ground screw foundation for securing elements in the ground, in which method a cylindrical tube is provided as an initial form, and subsequently a conical front section is formed on the cylindrical tube, by means of a non-cutting process, which section tapers to an insertion tip, wherein the front section is provided, at least in certain sections, with a thread-like contour so that it can be screwed into the ground.

At the rear end, a ground screw foundation can be configured so that poles or rods can be inserted into it, or it can have a flange-like securing attachment at the rear end, onto which other elements, for example frames or the like, can be screwed.

Such a method is known from DE 198 36 370 C2. This method for the production of a securing apparatus for rods, posts, masts or the like in the ground, in particular the production of a ground anchor, having a base body, wherein at least a partial section of the base body is provided with a screw-like or worm-like outside thread that can be screwed into and back out of the ground, and wherein the base body has essentially a cone-shaped base form with at least one conical partial section, is characterized in that the base body is produced by hammering the base body into the base form, starting with an essentially cylindrical tube.

It is true that this method does offer advantages in production as compared with metal-casting methods, but it is still relatively complicated, because only the base form is produced by means of shaping, namely by hammering a tube to form it. Subsequently, however, it is necessary to weld the outside thread onto the base body as a shaped part, and to affix further fin-like surface elements onto the base body, if necessary, preferably also by means of welding. This method is therefore also complicated.

It is the object of the invention to significantly simplify the production of a ground screw foundation for securing elements in the ground.

This object is accomplished, in the case of a method of the type stated initially, according to the invention, in that an inner contour for a screw-in tool is formed in a rear end of the tube by means of flow forming, and that the front section and the thread-like contour are formed exclusively by means of flow forming.

The ground screw foundation is therefore produced solely by means of flow forming, and thereby the production effort is clearly reduced, and precise and reproducible components can be produced. In this regard, first the inner contour and then the front section and the thread-like contour can be produced or vice versa. As an initial form, a drawn or welded tube can be used.

In a particularly preferred embodiment it is provided that the tube is first elongated, at least in certain sections. In this way, the material properties, on the one hand, and the geometrical dimensions, on the other hand, can be changed.

According to a first embodiment, it is provided that the front section is formed first, and the thread-like contour is formed afterward.

In this regard, it can be provided that the thread-like contour is also formed in the region of the tube that borders on the front section, at least in certain sections.

Alternatively it can be provided that the front section and the thread-like contour are formed at the same time.

In this regard, the thread-like contour can be formed with different flank geometries and/or different pitches in different regions.

In a further embodiment it is provided that the tube is arranged on an inner mandrel during flow forming, at least part of the time. An inner mandrel is used, for example, for the production of the inner contour.

In this regard, it can also be provided that a multi-part inner mandrel is used.

Furthermore it is practical if a tailstock is introduced into the front section during flow forming, at least part of the time.

This tailstock can be controlled under the effect of a spring or by machine.

If a completely closed insertion tip is supposed to be achieved, it is provided that the front end of the insertion tip is closed by means of mechanical forming after flow forming.

The invention will be explained in greater detail below, using an example shown in the drawing. The figures show:

FIG. 1 a longitudinal section through a cylindrical tube as an initial form,

FIG. 2 a longitudinal section through the tube while an inner contour is pressed into it,

FIG. 3 a longitudinal section through the tube during elongation,

FIG. 4 a longitudinal section through the tube while a thread-like contour is pressed into it,

FIG. 5 a longitudinal section through the tube after flow forming, and

FIG. 6 a perspective representation of the finished ground screw foundation.

First of all, it should be pointed out that the scale is not the same in the individual figures.

For a method for the production of a ground screw foundation for securing elements in the ground, first of all a cylindrical tube 1 is provided as an initial form. This tube 1 can be a drawn or welded tube made of metal.

In the method sequence shown, the tube 1 is clamped into a flow forming machine, not shown in any detail, and first an inner contour 2 in the form of a spline shaft is formed in the rear end 1a by means of flow forming. For this purpose, an inner mandrel 3 is inserted into the rear end 1a of the tube 1, which mandrel, on its outer side, has an outer contour 4 that is complementary to the inner contour 2. This outer contour 4 is configured in a center region 3a of the inner mandrel 3; axially toward the left or outside, the inner mandrel 3 has an outer region without an outer contour, not shown, for being jointly clamped into a chuck 13 together with the rear end 1a of the tube 1. Axially toward the right or inside, the inner mandrel 3 has an inner region 3b that has a diameter that is smaller in comparison with the center region 3a, so as to be able to reduce the outside diameter of the tube 1 adjacent to the inner contour 2 of the tube 1 that is to be formed.

After the inner mandrel 3 has been set into the rear end 1a of the tube 1, two spinning rollers 5, for example, arranged symmetrically on the circumference, are set radially against the rear end 1a of the tube 1 and moved axially along the inner mandrel 3. As a result, the inner contour 2 is formed in the tube 1, and axially adjacent to it, a step 6 having a diameter reduction is produced on the tube 1. In this process, of course, the spinning rollers 5 are put into a rotational movement relative to the tube 1, i.e. either the tube 1 is put into a rotational movement, or driven spinning rollers 5 are used.

If this is desirable for geometrical reasons (tube lengthening) and/or reasons of strength, the tube 1 is then elongated axially, in that the spinning rollers 5 are moved to the right, in the axial direction, while being radially set against the tube 1. For this purpose, the inner mandrel 3 can be replaced by an inner mandrel 3′, which differs from the inner mandrel 3 only in that the inner region 3b′ is longer. Alternatively, elongation can also take place without an inner mandrel.

In FIG. 2, the elongated region of the tube 1 that borders on the step 6 has already been shown and identified as 1b, although FIG. 2 still shows the inner mandrel 3 in engagement. In fact, however, elongation only takes place after removal of the inner mandrel 3 and insertion of the inner mandrel 3′ (FIG. 3). In this regard, a tailstock 7 can already have been introduced into the open front end 1c of the tube 1. This tailstock 7 can be controlled under the effect of a spring or by machine. The tailstock 7 serves as a support surface for the front end 1c of the tube 1, so as to produce a conically tapering region 8 by means of radially setting the spinning rollers 5 (FIG. 3).

This conically tapering region 8 is further shaped by the spinning rollers 5 to produce a conical front section 10 that is still open toward the front and tapers to an insertion tip 9, for which purpose spinning rollers 5 are pressed radially more and more against the tube 1 in the direction toward the insertion tip 9.

Afterward or at least at the same time with the conical deformation of the front section, a thread-like contour 11 is formed on the front section 10 by spinning rollers 5′, specifically preferably not only on the front section 10, but rather also adjacent to the cylindrical, elongated region 1b of the tube 1, at least in certain regions (FIGS. 4 and 5).

In FIG. 5, the flow forming processes have been concluded, and the tailstock 7 has been pulled out of the tube 1. For final production of the ground screw foundation 12 for securing elements into the ground, it is now only necessary to close off the front end of the insertion tip 9. This is done by means of suitable shaping, for example by means of compression, punching or folding, and, if necessary, subsequent trimming.

The final ground screw foundation 12 is shown in FIG. 6.

Of course the invention is not restricted to the exemplary embodiments shown. Further embodiments are possible without departing from the basic idea. For example it is not necessary for the inner contour 2 to be produced first; this method step can also be carried out at a later point in time. The formation of the thread-like contour 11 can also take place at the same time with shaping of the front section 10, at least part of the time. The inner contour 2 can also be formed (or pre-formed) by means of tightening the chuck 13 while the inner mandrel 3 is inserted, at least part of the time.

REFERENCE SYMBOL LIST

1 cylindrical tube

1 a rear end

1 b elongated region

1 c front end

2 inner contour

3, 3′ inner mandrel

3 a, 3 a′ center region

3 b, 3 b′ inner region

4 outer contour

5 spinning rollers

6 step

7 tailstock

8 conically tapering region

9 insertion tip

9 a front end

10 front section

11 thread-like contour

12 ground screw foundation

13 chuck

Claims

1. A method for producing a ground screw foundation (12) for securing elements in the ground, in which method a cylindrical tube (1) is provided as an initial form, and subsequently a conical front section (10) is formed on the cylindrical tube (1), by means of a non-cutting process, which section tapers to an insertion tip (9), wherein the front section (10) is provided, at least in certain sections, with a thread-like contour (11) so that it can be screwed into the ground, wherein an inner contour (2) for a screw-in tool is formed on a rear end (1a) of the tube (1) by means of flow forming, and wherein the front section (10) and the thread-like contour (11) are exclusively formed by means of flow forming.

2. The method according to claim 1, wherein the tube (1) is first elongated, at least in certain sections.

3. Method The method according to claim 1, wherein the front section (10) is formed first, and afterward the thread-like contour (11) is formed.

4. The method according to claim 3, wherein the thread-like contour (11) is also formed in the region (1b) of the tube (1) that borders on the front section (10), at least in certain regions.

5. The method according to claim 1, wherein the front section (10) and the thread-like contour (11) are formed at the same time.

6. The method according to claim 1, whereinthe tube (1) is arranged on an inner mandrel (3, 3′) during flow forming, at least part of the time.

7. The method according to claim 6, wherein a multi-part internal mandrel is used.

8. The method according to claim 1, wherein a tailstock (7) is introduced into the front section (10) during flow forming, at least part of the time.

9. The method according to claim 8, wherein a tailstock (7) that is controlled under the impact of a spring or by machine is used.

10. The method according to claim 1, whereinthe front end (9a) of the insertion tip (9) is closed after flow for forming, by means of mechanical forming.