METHOD AND DEVICE FOR SETTING CONNECTING ELEMENTS THAT ARE SELF-DRILLING WITHOUT CHIP FORMATION

Abstract

The invention relates to a method for setting connecting elements (16), such as screws or blind rivets, which are self-drilling without chip formation, in one or more plates, wherein the plate(s) are heated by electrical energy shortly before the start of the setting process, wherein the heating is accomplished by means of an induction coil (26), which is arranged near a point on the plate(s) at which the connecting element (16) is set. The invention further relates to a device (10) for setting a connecting element (16), which is self-drilling without chip formation, in one or more plates, comprising an induction coil (26), which at least before and/or during the setting process is arranged near a point on the plate(s), at which the connecting element (16) is set.

Description

TECHNICAL FIELD

The present invention relates to a method for inserting connecting elements which are self-boring without chip formation, such as screws or blind rivets, into one or more metal sheets, the metal sheet(s) being heated by means of electrical energy shortly before commencement of the insertion operation. In addition, the present invention relates to a corresponding device for inserting a connecting element which is self-boring without chip formation into one or more metal sheets.

Connecting elements which are self-boring without chip formation, which are also referred to as flow-hole drilling screws or flow-hole connecting elements, are increasingly used as the preferred choice in industry, since rough-drilling and thread-cutting can be avoided when they are used and no chips occur when they are handled.

PRIOR ART

However, until now, these connecting elements could only be used in conjunction with normal steel sheets and aluminium sheets. Use in high-tensile steel sheets without rough-drilling ceased, since the thermal energy which can be transmitted by the connecting element is not sufficient to appropriately soften a high-tensile steel sheet.

As a solution to this problem, the closest prior art in this regard, DE 196 34 417 A1, has already proposed heating the material of the metal sheet into which the connecting element is to be inserted by means of electrical energy in the form of an electric arc between a tool used for boring and the metal sheet.

This proposal, however, has considerable drawbacks, since the current density is always substantially higher in the auger bit of the boring tool than in the large-area metal sheet. As a result, the auger bit heats up more than the metal sheet and is softened more than the metal sheet, which is clearly counter-productive from the perspective of the object addressed herein. In addition, the bit of the boring tool, the form of which bit is of exceptionally great significance to correct boring, is damaged or deformed by the electric arc and the associated burning of the contacts, and this in turn can render boring considerably more difficult.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to make it possible to insert connecting elements which are self-boring without chip formation into high-tensile steel sheets directly during heating of the metal sheet and without using a separate boring tool.

According to the invention, this object is achieved by a method in which heating takes place by means of an induction coil which is arranged in the vicinity of a point on the metal sheet(s) at which the connecting element is inserted.

Similarly, the present object can be achieved according to the invention by a device for inserting a connecting element which is self-boring without chip formation into one or more metal sheets, which device is provided with an induction coil which is arranged, at least before and/or during the insertion operation, in the vicinity of the point on the metal sheet(s) at which the connecting element is intended to be inserted.

It is preferable in this case for the induction coil to be concentrically arranged with respect to the point on the metal sheet(s) at which the connecting element is intended to be inserted.

It is particularly preferable for the induction coil to have a central opening and to remain above the metal sheet(s) during the insertion operation, and for the connecting element to be inserted through this central opening in the induction coil.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention is described in greater detail on the basis of the embodiment depicted in the appended drawings, in which:

FIG. 1 is a front view of a device according to the invention for inserting connecting elements which are self-boring without chip formation;

FIG. 2 is a side view of the device in FIG. 1;

FIG. 3 shows detail A in FIG. 1; and

FIG. 4 shows detail B in FIG. 1.

PREFERRED MEANS OF CARRYING OUT THE INVENTION

FIG. 1 shows a device according to the invention for inserting a connecting element which is self-boring without chip formation into one or more metal sheets. The device 10 in this case comprises a retainer 12 which bears, in the manner of an upright drill, a screwdriver 14. At its screwing tool, the screwdriver bears a connecting element 16, which in this case is a screw which is self-boring without chip formation, that is, a connecting element 16 having a self-boring auger bit and outer thread.

In the present embodiment, the connecting element 16 is intended to be inserted into two metal sheets 18, 20 which are arranged on a support 22 having a recess 24 beneath the point at which the connecting element 16 is intended to be inserted.

According to the invention, a circular ring-shaped induction coil 26 is arranged above the recess 24 and above the two metal sheets 18, 20. The induction coil 26 in this case has a central opening which is concentrically arranged with respect to the point at which the connection element 16 is intended to be inserted.

According to the invention, the insertion operation then proceeds as follows.

The induction coil 26 is supplied with an alternating current of suitable frequency and voltage for a sufficiently long period of time for the region of the metal sheets 18, 20 which is beneath the induction coil 26 and thus above the recess 24 to be sufficiently heated.

Thereafter, the connecting element 16 which is self-boring without chip formation is inserted, in the manner in which connecting elements which are self-boring without chip formation known in the prior art are inserted, at the point in the two metal sheets 18, 20 which has now been heated according to the invention.

The recess 24 on one hand provides the space which accommodates the portion of the connecting element 16 which projects downwardly out of and beyond the metal sheets 18, 20 after insertion, and on the other hand prevents the metal sheets 18, 20 from cooling or prevents thermal dissipation therefrom via the support 22.

According to the invention, even metal sheets 18, 20 made of substantially harder steel categories are able to be connected to or fitted with connecting elements which are self-boring without chip formation.

As an alternative to the embodiment explained here for inserting the connecting element 16 into two metal sheets 18, 20, the connection element is also able to be inserted according to the invention into just a single metal sheet, or into three or more metal sheets.

Claims

1. Method for inserting connecting elements (16) which are self-boring without chip formation, such as screws or blind rivets, into one or more metal sheets (18, 20), said method including the steps of: heating the metal sheet(s) (18, 20) by means of electrical energy shortly before commencement of the insertion operation, heating takes place by means of an induction coil (26) arranged in the vicinity of a point on the metal sheet(s) (18, 20) at which the connecting element is inserted (16).

2. The method according to claim 1, wherein the induction coil (26) is concentrically arranged with respect to the point on the metal sheet(s) (18, 20) at which the connecting element (16) is inserted.

3. The method according to claim 2, wherein the induction coil (26) has a central opening and remains above the metal sheet(s) (18, 20) during the insertion operation, and the connecting element (16) is inserted through the central opening in the induction coil (26).

4. Device (10) for inserting a connecting element (16) which is self-boring without chip formation into one or more metal sheets (18, 20), said device comprising: an induction coil (26) arranged, at least before and/or during the insertion operation, in a vicinity of a point on the metal sheet(s) (18, 20) at which the connecting element (16) is inserted.

5. The device (10) according to claim 4, wherein the induction coil (26) is, at least before and/or during the insertion operation, concentrically arranged with respect to the point on the metal sheet(s) (18, 20) at which the connecting element (16) is inserted.

6. The device (10) according to claim 5, wherein the induction coil (26) has a central opening and is arranged such that the connection element (16) penetrates this opening during the insertion operation.