WO2000076710A1

WO2000076710A1 - Weld stud with elliptical weld flange

Info

Publication number: WO2000076710A1
Application number: PCT/GB2000/002258
Authority: WO
Inventors: Robert Volnhals
Original assignee: Emhart Inc.; Black & Decker Europe
Priority date: 1999-06-11
Filing date: 2000-06-09
Publication date: 2000-12-21
Also published as: DE29910229U1

Abstract

The weld stud (1) according to the invention with a free end (2) and a head (3), forming in each case an end face (4, 5) of the weld stud (1), comprises, at the head (3), a weld flange (6), having a substantially elliptical geometry with a main axis (7) and a secondary axis (8). As a result of this design of the weld flange geometry there is a particularly favourable formation of the welding current during welding by the lift and strike process leading to a high quality repeatable welded connection with a small quantity of pores. As the torques transmitted by the welded connection are substantially dependent on the length of the main axis (7) no disadvantages arise in this respect either with an elliptical weld flange compared to a circular weld flange. The weld stud (1) according to the invention is advantageously suited to the welding on a thin sheet metal.

Description

WELD STUD WITH ELLIPTICAL WELD FLANGE

The invention relates to a weld stud with a free end and head which, in each case, form an end face of the weld stud, the head comprising a weld flange.

Weld studs of this type are used as fixing elements in many areas, in particular the car industry. They are welded at their head end to a structure so other components can be fixed to the free end. The free end normally has an external structure, giving the stud a similarity, in particular to a fir tree, this being the reason why these studs were given the name fir tree studs. Weld studs of this type are preferably fixed by the lift and strike process in which, by means of brief contact of the stud with the structure, an arc is ignited which then continues to burn when the stud is lifted from the structure and which fuses structure and welding flange of the stud. The stud is then lowered again into this melt so a very durable welded connection is produced on solidification of the melt.

Depending on the size of the forces and torques which this welded connection has to withstand, the weld flange at the head of the stud is designed with a correspondingly large diameter according to the state of the art.

However, this creates problems such as the need for large currents for welding in the case of large diameters which, in particular in the case of weldings on thin sheet metal, i.e. sheet metal with a thickness smaller than 1 mm, in particular with a thickness smaller than/equal to 0.75 mm, can lead to an undesirable number and/or size of pores in the join region.

A further problem consists in the fact that the current does not flow evenly through the edge regions of the flange so they are not reliably welded.

It is therefore the object of the present invention to provide a weld stud which can be welded, preferably on thin sheet metal, more reliably and with fewer pores. This object is achieved by a weld stud with the features of claim 1. Advantageous embodiments and developments are given in the dependent claims.

The weld stud according to the invention with a free end and a head which, in each case, form an end face of the weld stud, has a weld flange designed on the head which has a substantially elliptical geometry with a main axis and a secondary axis.

The change in the geometry of the weld flange compared to the state of the art to a substantially elliptical geometry results in a more desirable rotationally non- symmetrical distribution of current and a rotationally non-symmetrical melt during the welding process, as a result of which the weld stud can be welded in an advantageous manner with significantly fewer pores, in particular on thin sheet metal. Due to the higher quality of the welded connection there are no disadvantages as a result of the elliptical form with respect to the torques transmitted as these are substantially dependent on the length of the main axis.

According to the invention the ratio of main axis to secondary axis is preferably 10 to 6 up to 9.

It was possible to achieve particularly good welding results with a preferred ratio of the main axis to the secondary axis of about 10 to 8.

A further improved welding result was achievable with a weld stud which is laterally trimmed approximately parallel to its secondary axis.

Further advantageous embodiments are described hereinafter with reference to the schematic drawings, in which:

Fig. 1 is a front view of a weld stud according to the invention;

Fig. 2 is a plan view of the geometry of an untrimmed weld flange; and Fig. 3 is a plan view of the geometry of a trimmed weld flange.

Fig. 1 shows a front view of a weld stud 1 according to the invention. The weld stud 1 with its free end 2, which can comprise, in particular a thread, preferably a fir tree-like external structure 11 and with a head 3, which in each case form an end face 4 or 5 of the weld stud 1 has a cylindrical body 6. Formed on the head 3 is a weld flange 6 having a substantially elliptical geometry. Adjacent to the weld flange 6 in the direction of the free end 2 there is additionally formed a shoulder 9 which is generally formed rotationally symmetrically like the rest of the weld stud and is used as support for a component to be fixed to the weld stud, for example a lug, not shown, or a fixing clip.

Fig. 2 is a plan view of the approximately elliptical geometry of an untrimmed weld flange 6. The substantially elliptical geometry of the weld flange 6 is substantially defined by two axes 7 and 8 which are substantially at right angles to one another. The main axis 7 is preferably about 10 mm and the subsidiary axis 8 about 8 mm.

Fig. 3 also shows a plan view of a substantially elliptical geometry of a laterally trimmed weld flange 6 while keeping the preferred ratios of main axis 7 to subsidiary axis 8. The trimming of the lateral region 10 of the weld flange 6 is preferably approximately parallel to the subsidiary axis 8.

The weld stud 1 according to the invention is advantageously suited to the high quality, repeatable welding, with a low number of pores, of weld studs, in particular on thin sheet metal.

Claims

1. Weld stud (1) with a free end (2) and a head (3), which in each case form an end face (4, 5) of the weld stud (1), wherein the head (3) comprises a weld flange (6), having a substantially elliptical geometry with a main axis (7) and a secondary axis (8).

2. Weld stud (1) according to claim 1, wherein the ratio of the main axis (7) to the secondary axis (8) is approximately 10 to 6 up to 9.

3. Weld stud (1) according to claim 2, characterised in that the ratio of main axis (7) to the subsidiary axis (8) is approximately 10 to 8.

4. Weld stud (1) according to claims 1, 2 or 3, wherein the weld flange (6) is laterally trimmed (10) approximately parallel to its secondary axis (8).

5. Weld stud (1) according to one of the preceding claims, characterised in that the free end (2) comprises an external structure (11), in particular a thread, preferably in the manner of a fir tree.

6. Weld stud (1) according to one of the preceding claims, characterised in that the weld stud (1) consists of aluminium or an aluminium alloy.