Electrical resistance welding of coated sheet metals

Claim 2

The method of claim 1, wherein in step (b) knifelike metallic edges are elongated edges.

Claim 3

The method of claim 1, wherein in step (b) the knifelike edges are edges produced by embossing.

Claim 4

The method of claim 1, wherein in step (b) the knifelike edges are edges produced by milling.

Claim 5

The method of claim 1, wherein in step (b) the knifelike metallic edges are edges produced by first cylindrically embossing one of said sheets and then milling the embossed projected part of said sheet so as to form an annular knife-shaped edge and a cavity within said annular edge.

Claim 6

The method of claim 1, wherein in step (b) a central cavity and at the periphery thereof an annular milled recess are produced in one of the metal sheets to form a knifelike metallic edge between the cavity and the peripheral annular recess and wherein in step (c) the knifelike metallic edge of said one metal sheet between the central cavity and the peripheral annular recess is exposed to the downward pressure of a punch to cause said knifelike metal edge to contact the opposed blank welding area of the other metal sheet.

Claim 7

The method of claim 1, wherein in step (b) a central cavity and at the periphery thereof an annular milled recess are produced in one of the metal sheets to form a knifelike metallic edge between the cavity and the peripheral annular recess and wherein in step (c) the knifelike metallic edge of said one metal sheet between the central cavity and the peripheral annular recess is exposed to the downward pressure of an electrode to cause said knifelike metal edge to contact the opposed blank welding area of the other metal sheet.

Claim 8

The method of claim 1, wherein for seam welding in step (a) the coating is removed in a continuous seam from at least the inner opposed faces of the coated metal sheets to provide said sheets with continuous blank opposed welding seams, while in step (b) the knifelike metallic edges are produced by first continuously embossing one of said sheets to form a continuous projection of said sheet, continuously milling out of said projection a central groove and on both sides of said central groove groove-shaped recesses, thereby preserving knifelike metallic edges between said central groove and said groove-shaped recesses, whereafter in step (c) contact is established between the continuous knifelike metallic edges and the opposed blank welding seam of the other metal sheet to be welded.

Claim 9

The method of claim 1, wherein in step (a) the outer surface of one of the coated metal sheets is additionally provided with a shallow milled recess opposite to the welding area provided in step (b) with the knifelike metallic edges.

Claim 10

The method of claim 1, wherein in step (b) a central cylindrical cavity and at the periphery thereof an annular recess are produced to form an annular knifelike metallic edge between the central cylindrical cavity and the peripheral annular recess by milling with a milling cutter having an outer-milling cutter for cutting said annular recess, a central-milling cutter having a flat-cutting end face, and a recess between said outer-milling cutter and said central-milling cutter.

Claim 11

The method of claim 1, wherein in step (b) a central cavity and at the periphery thereof an annular recess are produced with a milling cutter having an outer-milling cutter with a plane-cutting end face and a central-milling cutter bevelled at its circumference to form an inwardly bevelled annular knifelike metallic edge between the central cavity and the peripheral annular recess.

Claim 12

The method of claim 1, wherein in step (b) a central cylindrical cavity and at the periphery thereof an annular recess of trapezoidal profile are produced by milling with a milling cutter having an outer-milling cutter bevelled at its outer and inner periphery and a central-milling cutter having a flat-cutting end face to form an outwardly bevelled annular knifelike metallic edge between the central cavity and the peripheral annular recess.

Claim 13

The method of claim 1, wherein in step (b) the knifelike metallic edges are edges produced by embossing one of said metal sheets to form a circular depression with an annular knifelike edge encircling a cavity.

Claim 14

The method of claim 1, wherein in step (a) the one coated metal sheet is provided with a differential diameter bore and wherein in step (b) a welding rivet is inserted into said bore, the end face of the shank of said rivet having an annular knifelike edge surrounding a central recess.

Claim 15

The method of claim 1, wherein in step (a) the one coated metal sheet is provided with a bore and wherein in step (b) a welding rivet is inserted into said bore, the end of the shank of said rivet being provided with an annular knifelike edge and with a central-welding pin.

Claim 16

The method of claim 1, wherein in step (b) grooves of triangular profile are milled out on the blank opposed welding areas of the metal sheets to be welded and wherein welding balls are inserted into said juxtapositioned grooves to provide the knifelike metallic edges.

Claim 17

The method of claim 1, wherein in step (a) the one coated metal sheet is provided with bores and wherein in step (b) welding balls are inserted into said bores, said welding balls protruding on top and bottom from said bores and providing the knifelike metallic edges.

Claim 18

The method of claim 1, wherein in step (b) a welding point is provided by milling at the blank welding area of one of the metal sheets and an intermediate welding piece having an annular knifelike edge is inserted between the point of said one metal sheet and the blank opposed circular welding area of the other metal sheet, whereafter in step (c) contact of said welding point with one surface of the intermediate welding piece and of the blank circular welding area of the other metal sheet with the annular knifelike edge of the intermediate welding piece is established.

Claim 19

The method according to claim 1, wherein in step (b) a hollow intermediate welding piece is inserted between the blank opposed welding areas of the metal sheets, said intermediate welding piece being provided with a contact point on its top face and with an annular knifelike edge on its bottom face.

Claim 20

The method of claim 1, wherein in step (b) an intermediate welding piece provided with annular knifelike edges on its top and bottom faces is inserted between the blank opposed welding areas of the metal sheets.

Claim 21

The method of claim 1, wherein in step (b) an insulating layer is placed between the metal sheets having a coating on their outer faces, said insulating layer having holes at the welding areas and wherein the knifelike metallic edges are provided by inserting into the holes inserts with such knifelike metallic edges.

Claim 22

The method of claim 22, wherein the insert is a sharp-edged ring of sheet metal.

Claim 23

The method of claim 22, wherein the insert is a wire having a rhomboidal cross section and being inserted into the holes of the insulating layer so as to stand on a corner.

Claim 24

The method of claim 22, wherein the insert is a disc having alternately upwardly and downwardly bent prongs.