Electric heating – Metal heating – Of cylinders
Patent
1999-03-29
2000-12-12
Shaw, Clifford C.
Electric heating
Metal heating
Of cylinders
219109, 219110, B23K 1125
Patent
active
061602353
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of measuring the quality of a resistance weld, typically the welded joint which forms the side seam of a metallic can.
Applicant' earlier patents EP 0381312B and EP 0438204B are directed to techniques for monitoring resistance welds in metallic cans, for example by measuring the relative movement of the electrode wheels of the resistance welding apparatus. The present invention provides a further method of measuring the quality of resistance welds, which is capable of generating additional information concerning the welding process.
SUMMARY OF THE INVENTION
Accordingly there is provided a method of measuring the quality of a resistance weld between two overlapping sheets of metal, the formation of the weld having caused material to be flowed out adjacent the edge of each overlapped sheet to form an extrusion, the method including the steps of: weld; and
The weld extrusion is the material which is formed out of the weld interface during the weld process and is normally present adjacent the edge of each overlapped plate being welded. Applicants have discovered that, surprisingly, the width of the weld extrusion gives a direct indication of the temperature at which the weld was carried out. Accordingly, for a continuous process such as a can welding line, the method conveniently includes the additional step of adjusting the temperature of the weld in response to the signal generated representing the width of the weld extrusion.
Preferably the measurement of the width of the weld extrusion is an optical measurement. Conveniently the optical measurement includes the steps of illuminating the area of the weld and measuring the light reflected from the weld extrusion. Alternatively or additionally, the optical measurement includes the steps of illuminating the area of the weld with one or more lines of light at an angle to the longitudinal axis of the weld and in a first plane at an angle to the plane in which the weld lies, viewing the one or more lines in a second plane at an angle to the first plane, and calculating the apparent deviation of the one or more lines as they pass over the weld extrusion. Typically the method includes the step of illuminating the area of the weld with a grid or pattern of lines of light.
The method preferably includes the step of measuring the width of the weld extrusion on both faces of the resistance weld. Where the resistance weld is the side seam in a metallic can, this will involve measuring the width of the weld extrusion on both the internal and external faces of the can. The weld overlap may also be measured as an additional step of the present method.
The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional diagram showing a typical weld;
FIG. 2 is a schematic diagram showing a first embodiment of optical measurement in accordance with the invention, and
FIG. 3 is a schematic diagram showing a second embodiment of optical measurement in accordance with the invention.
DESCRIPTION OF THE PREFERRED ENNOBLEMENTS
Referring to FIG. 1 there is shown, in highly idealised form, a weld between a first plate 1 and a second plate 2, typically the two sides of a welded side seam in a cylindrical can. Extending from the edge 3 of the first plate and adjacent the surface 4 of the second plate is a first extrusion 5. Extrusion 5 will extend along the line of the weld in a continuous, but not necessarily regular fashion. On the opposite face of the weld a second extrusion 6 will be present extending from the edge 7 of the plate 2 and adjacent the opposite surface 8 of the plate 1.
In order to analyse the quality of the weld it is desirable to determine certain dimensions, namely the width A of the extrusion 5; the mashed thickness B of the weld (i.e. the distance after welding between the surfaces 4 and 8); the width C of the extrusion 6; and the weld overlap D (i.e. the distance between
REFERENCES:
patent: 4535215 (1985-08-01), Kliesch et al.
patent: 4652715 (1987-03-01), Kitamura et al.
patent: 5064982 (1991-11-01), Kabasawa et al.
CarnaudMetalbox (Holdings) USA Inc.
Shaw Clifford C.
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