Claims
- 1. A tool set adapted to be mounted in a reciprocative press for connecting sheet metal pieces, the tool set comprising:
- a punch,
- a die comprising an anvil in which a cavity is defined by a contour having a lower end press surface and at least two pairs of opposing sides, means to limit flow of deformed material including one of said pairs of opposing sides being defined by fixed upstanding anvil portions, said upstanding anvil portions extending upwardly from said lower end press surface, said press surface comprising a lower end of said cavity contour, and means to allow flow of deformed material including another pair of opposing sides defined by blades, said blades being positioned opposing one another adjacent said upstanding anvil portions when said blades are in a first position, means to bias said blades toward said first position, each of said blades having a free end and an opposite end, said opposite end being pivotally mounted adjacent said anvil,
- said blades being elastically deflectable away from said first position toward a second position when said punch penetrates into said sheet metal pieces and into said die cavity,
- said punch having an exterior contour smaller than said die cavity contour, said punch contour being spaced at least a first and a second distance from said die cavity contour, said first distance in a first plane of symmetry extending in a first direction towards said blades and a second distance in a second plane of symmetry extending orthogonally to said first plane in a second direction, said first distance being smaller than said second distance when said blades are in said first position,
- said punch contour being sufficiently spaced from said die contour to prevent cutting of said sheet metal pieces when said punch penetrates into said sheet metal pieces and into said die cavity.
- such that said sheet metal pieces flow non-isotropically toward said elastically yielding blades when said punch penetrates into said sheet metal pieces and into said die cavity so as to produce a sheet metal connection which exhibits substantially isotropic strength when subjected to stress in a direction substantially parallel to said sheet metal pieces.
- 2. The tool set of claim 1 wherein said anvil and said blades have mating surfaces extending substantially parallel to a direction of reciprocation.
- 3. The tool set of claim 1 wherein said punch contour is substantially oval in cross-section and said contour of said punch is determined by the thickness and strength of the sheet metal pieces such that when said punch penetrates into said sheet metal pieces the connection formed between the sheet metal pieces comprises a substantially circular boss on a sheet metal piece adjacent the die cavity.
- 4. The tool set of claim 1 wherein each of said blades are pivotally supported by a bearing of a socket against said anvil by spring means.
- 5. The tool set of claim 4 wherein said spring means comprise leaf springs.
- 6. The tool set of claim 4 wherein said bearing is a knife-blade bearing.
- 7. The tool set of claim 1 further comprising debris collection spaces defined by said blades and said anvil.
- 8. The tool set of claim 1 wherein a die cavity side top edge of said free end of each of said blades is rounded.
- 9. The tool set of claim 1 wherein said blades have a wear-reducing coating.
- 10. The tool set of claim 1 wherein the depth of said punch contour is less than the depth of said die cavity.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 3805688 |
Feb 1988 |
DEX |
|
BACKGROUND AND SUMMARY OF THE INVENTION
This is a continuation of application Ser. No. 314,007, filed on Feb. 23, 1989, which was abandoned upon the filing hereof.
The present invention relates to the connection of pieces of sheet metal.
Sheet metal pieces, for example two pieces, are disposed one on top of the other. A punch and a die (hereinafter designated a tool set) are mounted in a press so as to cut, upon actuation of the press, through the superposed sheet metal pieces along two parallel limited cutting lines. Material between these cutting lines is displaced beyond the sheet adjacent the die and compressed between punch and die so that it flows outwards thereby forming an element similar to a rivet head. The cutting elements of the die yield elastically to accommodate the flowing material. The strength of the connection is higher under stress in a direction orthogonal to the cutting lines than parallel thereto. Tool sets to perform such connections are disclosed in European Patent Application 77 932.*
Another tool set is disclosed in German Published Patent Application 31 06 313.** The die has a closed contour and the punch has a similar contour but of a smaller section so that neither of the sheets is cut and the connection produced is fluid-tight. The die contour is defined by deflecting or yielding elements thereof which are pivotally mounted on a socket. This set of tools, and in particular the die, is somewhat cumbersome and the space required often is not available.
It is an object of the present invention to provide a tool set for producing fluid-tight sheet metal connections, the die requiring only a minimum space. It is a further object of the present invention to provide a tool set for producing fluid-tight sheet metal connections which exhibit substantially the same strength in all directions.
It is a further object of the present invention to provide a tool set for the purposes set forth above which is of simple design and may be manufactured at reasonably low expense.
According to the invention, the tool set includes a punch and a die to be mounted in a reciprocative press. The die, in turn, comprises an anvil which is stationary, and deflectable blades which may be elastically deflected in a predetermined direction away from the anvil. The die end facing the punch defines a closed contour of a penetration area while the punch contour is smaller than that of the die such that upon press actuation and penetration of the punch through the sheet metals, neither the one adjacent the punch nor the one adjacent the die is cut. According to a first aspect of the invention, the punch contour, when the punch has penetrated the sheet metals, is closer to the die contour seen in the direction in which the die blades may flex than in the direction orthogonal thereto. As a result, the strength of the connection is substantially isotropic in a direction parallel to the sheet faces.
According to another aspect of the invention, the die anvil and the die blades have plane sides facing one another, and the die contour is defined by two end edges of the blades and by a recess provided in the anvil. This permits manufacture of the blades as simple flat members having parallel main faces. Furthermore, the recess in the anvil does not require a complex method of manufacture. The recess in the anvil causes the material to flow in the direction of the elastically yielding blades. As the penetration causes a non-isotropic deformation, the particular design of the die, in turn, causes a non-isotropic flow of the deformed material. As a result, the strength of the connection or joint is uniform in all directions parallel to the sheet faces.
In many applications, as in household appliances, vehicles and the like, the sheet metal piece connections are visible for the user, and for this reason it is desired that the connection exhibits an attractive form, e.g. a shape and contour similar to that of a rivet head. In accordance with the invention, the contours of the punch and the die may be chosen such that the connection, on the punch side, is of a clearly defined oval shape while exhibiting on the die side the form of an approximately circular boss.
The die blades may be provided with suitable coatings so as to increase their edge life and to avoid depositions due to cold welding.
According to the invention, it is particularly advantageous to separate the functions "deformation" and "elastically yielding" of the die blades of the die such that the die blades themselves are not deformed but biased against the anvil by means of leaf springs. This permits the use, for the blades, of a material of extreme strength so as to permit the connection of particularly hard sheet material, as stainless steel. On the other hand, the leaf springs may be made so soft that the die blades yield even under low load, and this makes the tool set suitable for joining thin sheet metals of mild material, as aluminum. It has been found that the tool set of the invention permits joining of a pair of aluminum sheets each having a thickness of not more than 0.2 mm, joining which was not possible hitherto with the tools of prior art.
Further, it is advantageous to support the blades on open half-shell bearings of a socket and to provide therebeneath receptacle spaces for oil, attrition and dust caused by the joining operation.
It is also advantageous to round the joint-defining edges of the blades so as to minimize potential chipping.
Embodiments of the tool set according to the invention are illustrated in the accompanying drawings and will be described in detail hereunder.
US Referenced Citations (7)
Foreign Referenced Citations (3)
| Number |
Date |
Country |
| 8408792 |
Aug 1985 |
DEX |
| 3532899 |
Mar 1987 |
DEX |
| 2189175 |
Oct 1987 |
GBX |
Continuations (1)
|
Number |
Date |
Country |
| Parent |
314007 |
Feb 1989 |
|
Patent Grant
5046228
