EP2186580A2

EP2186580A2 - Method and device for pressing a collar in a metal plate and collar and plate element.

Info

Publication number: EP2186580A2
Application number: EP09176086A
Authority: EP
Inventors: Jan Rosberg
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2008-11-18
Filing date: 2009-11-16
Publication date: 2010-05-19
Also published as: SE0802421A1; SE533132C2; EP2186580A3

Abstract

The invention relates to pressing a collar in a metal plate (10), which involves pressing a collaring portion of the plate into a forming duct for the collar and making a hole in the plate. According to the invention, the plate (10) is stretched in a region (R) which comprises the collaring portion (C) before the pressing of the collaring portion (C) into the forming duct.

Description

TECHNICAL FIELD

The invention relates to a method for pressing a collar in a metal plate, which involves pressing a collaring portion of the plate into a forming duct for the collar and making a hole in the plate.
The invention also relates to a device for implementing the method, a collar formed in a metal plate by such a method or such a device, and a plate element provided with such a collar.

BACKGROUND

Fitting components in fastening holes on metal plates often involves using so-called weld nuts as dollies for threaded fastening elements for the components. The fastening elements may be provided with a conical thread and a non-circular cross-section in order by plastic deformation to form the thread in the weld nut during the tightening stage of the fitting operation.
However, such weld nuts are expensive to use, since they have to be firmly pre-welded on the plate. It is therefore desirable to be able to dispense with the weld nut and instead form the plate with collars for fastening elements.
According to a known method of the kind indicated in the introduction, the collaring portion is pressed down into the forming duct by a traction operation using a traction mandrel. However, such a collaring method results in the plate becoming thinner at the collar, so the strength of the resulting threaded connection will not be sufficient.
A so-called reducing process which gradually forms a collar by redistributing material in a region round the intended collar is certainly a known practice, but involves a large number of pressing steps.

SUMMARY OF THE INVENTION

An object of the invention is to propose a method of the kind indicated in the introduction which can achieve a sufficiently strong collar by a minimum number of pressing steps.
According a version of the invention, the plate is stretched in a region which comprises the collaring portion before the latter is pressed into the forming duct. This stretching provides that region with a surplus of plate material which in the subsequent pressing operation can be compressed towards the resulting collar so that the collar's plate thickness is caused to increase in at least the region of the mouth of the forming duct. Thus the whole collaring operation can also be carried out in only two pressing steps, viz. a stretching step and a compression step.
According to an embodiment of the invention, the stretching involves the forming of a concentric protrusion of the plate in said region.
The forming of the protrusion may involve forming a central hollow in said region. The conical wall portion of the plate which converges towards the hollow may then be regarded as constituting a downward-pointing and therefore partly ready-made collaring portion of the plate.
The pressing in of the collaring portion may be affected by pressure force on the protrusion. The material in the collaring portion will then be subject substantially to compression, thereby thickening the material.
The hole may be formed by punching. The punching may be performed by a hole punch mounted on an upper element of a press tool during the downward pressing of the collaring portion. Although the hole punch may serve as a centre or drift for exerting pressure force against the inner surface of the collar, it will with advantage have a slightly diameter than that inner surface.
A device for implementing the method is distinguished by a first press tool comprising a first upper element provided with a stretching profile and a first lower element provided with a stretching profile which cooperates therewith, and by a second press tool comprising a second upper element and a second lower element provided with a forming duct for the collar.
The second upper element may be provided with said hole punch for making the hole.
The invention also covers a plate element made by a method and a device as above. Although the pre-formed collar in the metal plate may be the first choice, such a plate element is inexpensive to make and may, where so required, be used as an alternative to a weld nut.
Other features and advantages of the invention may be indicated by the claims and the description of embodiment examples set out below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-C depict a cross-sectional view with portions cut away of a first press tool according to the invention in three different press positions during a stretching operation on a metal plate;
FIGS. 2A-D depict a cross-sectional view with portions cut away of a second press tool according to the invention in four different press positions during a collaring operation on a stretched metal plate;
FIG. 3 depicts the circled region in FIG. 2D on a larger scale; and
FIG. 4 is a view as seen from above with a portion cut away of a plate element formed with a collar according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS. 1A-C depict a first press tool with an upper element 30 and a lower element 40, between which a metal plate 10 is to be subjected to a stretching operation. To this end, in the embodiment depicted, the upper element 30 and the lower element 40 are provided with mutually complementary stretching profiles comprising curved surfaces in a circular region R. During the stretching operation, the plate 10 is formed according to the curved surfaces so that it is subjected to area-increasing stretching in both tangential and radial directions in its initially planar region R. In the example depicted, the curved surface of the lower element 40 has approximately the shape of an annular protrusion 42 with a central hollow 44. Accordingly, the complementary surface of the upper element 30 has an annular hollow 32 with a central protrusion 34. As illustrated in FIG. 1C, the upper side of the stretched plate 10 in the region R, like the curved surface of the lower element 40, may be regarded as having an annular protrusion 12 and a central hollow 14.
FIGS. 2A-C depict a second press tool with an upper element 50 and a lower element 60. The upper element 50 has on its planar pressing surface a punch 52 protruding downwards for punching out the hole 16. The lower element 60 has in its planar pressing surface a forming duct 62 situated opposite to the punch 52 to accommodate the pressed-down plate material and forming of the collar 18. The upper element 50 need not necessarily be provided with a punch 52 or some other perforating tool, as the hole 16 may also, within the scope of the invention, be pre-formed in the plate 10 (not depicted).
Before the collaring operation, the stretched plate 10 is placed in the position according to FIG. 2A between the upper element 50 and the lower element 60.
When the upper element 50 approaches the lower element 60 in the position according to FIG. 2B, the punch 52 comes into contact with the hollow 14 and begins to punch out the hole 16 in the plate 10. Somewhat thereafter, the planar pressing surface of the upper element 50 comes into contact with the annular protrusion 12 and begins to press the latter down towards the lower element 60.
A concentric collaring portion C of the stretched area R, comprisng the hole 16 and at least part of the surrounding hollow 14, is situated above the mouth of the forming duct 62. Continued pressing will cause the collaring portion C to be pressed down into the forming duct 62 until the outside of the resulting collar 18 comes into contact with the rounded mouth 64 of the forming duct 62 (FIG. 3) at a forming position approximately between the position in FIG. 2C and the position in FIG. 2D. The rounding radius at the mouth 64 may be relatively large for a good collaring result.
As the whole collar 18 will now be subject to compression, the portion of the collar 18 which is in the duct 62 will endeavour to expand into clear space, which it can do by making its way towards the walls of the duct 62 and down into the duct. The collar 18 will of course thus at least partly shape itself according to the duct 62. The compressive force of the upper element 50 pressing down on the protrusion will at the same time also plastically relocate the plate material so that at least part of the latter is relocated towards the collar 18. This relocation of material results in a material thickening in at least a region at the leading portion of the collar 18, as illustrated in FIGS. 3 and 4. This material thickening is advantageous in cases where the collar 18 is to be used in a threaded connection in conjunction with a self-tapping screw, e.g. a thread-pressing screw. The deformation hardening which occurs during the relocation of the plate material also increases the strength of the collar 18 and the portion adjacent to it of the plate 10.
FIG. 4 illustrates the possibility of forming the collar 18 on a plate element 80 with a supporting flange 82. Although the plate element 80 may be provided beforehand with an internal thread on the collar 18, the example depicts it in the form of an unthreaded so-called weld nut usable in conjunction with a self-tapping screw. The plate element 80 may either be made separately by collar pressing of a circular or undepicted rectangular (material-saving) blank or be punched out from a larger plate provided with a plurality of pressed collars according to the invention.
The invention is not necessarily limited to making circular or annular collars, as it is at least conceivable to provide the collar with some other cross-sectional profile, e.g. oval or polygonal.
The description set out above is primarily intended to facilitate comprehension and no unnecessary limitations of the invention are to be inferred therefrom. The modifications which will be obvious to one skilled in the art from perusing the description may be implemented without departing from the concept of the invention or the scope of the claims set out below.

Claims

A method for pressing a collar (18) in a metal plate (10), which involves
pressing a collaring portion (C) of the plate (10) into a forming duct (62) for forming the collar (18);
and making a hole (16) in the plate;
characterised by
stretching of the plate (10) in a region (R) which comprises the collaring portion (C) before the pressing in of the latter.
A method according to claim 1, whereby the stretching involves forming a protrusion (12) of the plate (10) in said region (R).
A method according to claim 2, whereby the stretching also comprises the forming of a central hollow (14) in said region (R).
A method according to claim 2 or 3, whereby the pressing in of the collaring portion (C) is effected by pressure force on the protrusion (12).
A method according to any one of the foregoing claims, whereby the hole (16) is made by punching.
A method according to claim 5, whereby the punching of the hole (16) is effected during the pressing down of the collaring portion (C).
A device for implementing the method according to any one of the fore-going claims, characterised by
a first press tool comprising a first upper element (30) provided with a stretching profile (32, 34) and a first lower element (40) provided with a complementary stretching profile (42, 44) which cooperates with the latter;
a second press tool comprising a second upper element (50) and a second lower element (60) provided with a forming duct (62) for the collar.
A device according to claim 7, in which the second upper element (50) is provided with a hole punch (52) for making the hole (16).
A collar (18) in a metal plate (10), made by a method or a device according to any one of the foregoing claims.
A plate element (80) with a flange (82) and a collar (18) made by a method or a device according to any one of claims 1-8.