Electric heating – Metal heating – For bonding with pressure
Patent
1997-03-04
1998-09-01
Mills, Gregory L.
Electric heating
Metal heating
For bonding with pressure
2191171, 21912511, 219161, B23K 3704, B23K 9028
Patent
active
058013539
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and an apparatus for joining thin sheets at the circumferences of circular holes in the sheets. In the method of the invention no filler metal is used, instead the joint is welded by fusing the thin sheets together. The welding apparatus of the method comprises a welding machine, a welding jig, a rotating welding head and associated means for gas supply, and a power source.
BACKGROUND AND PRIOR ART
Electric welding methods for joining thin sheets are previously known. Such methods include e.g. spot and projection welding. In these methods the sheets are pressed against each other and a current is allowed to pass through the pressure point, whereby the melting of metal is sufficient for the joining. A disadvantage of spot welding is that the joints are spot-like. This means that water-proof or gas-proof seams, a prerequisite for a pressure vessel or like e.g. heat-exchanger structures, cannot be made. The use of projection welding for joining the edges of circular holes requires expensive equipment. Further, as pressure vessels are concerned, the above methods do not usually provide a sufficiently even and strong joint.
Welding and brazing methods using various filler metals, e.g. in the form of rods or strip, have been applied to joining the edges of holes in thin sheets. Even in these cases the cost of equipment and tools easily rises so that these methods cannot be used when small numbers of products are manufactured. The quality of the seam may also be inferior when filler metal is used. The seam becomes unequal in thickness and uneven. Additional problems may arise regarding penetration. Distortion of thin sheets in connection with welding is also a problem which is very difficult to control.
Even with modern methods, joining thin sheets by welding has proved rather problematic in several cases. The lack of suitable equipment and methods has resulted e.g. in frequent use of mechanical joining means, such as screws, rivets or the like in joining thin sheets. The main problems in welding together thin sheets are changes caused by thermal stress, which change the shapes of the structures. Another major problem has been that in thin sheet work it is difficult to control the melt, which has resulted in low-quality and unsatisfactory seams. Exact allocation of heat has also been problematic in several welding methods. Improper distribution of heat results in possible melting and sagging of metal, and therefore in an inferior seam. In methods being used, elimination of generated heat has not been sufficient, and therefore it has been necessary to limit, for example, the strength of the current very strictly.
SUMMARY OF THE INVENTION
The method and apparatus of the invention seek to provide decisive improvements to the above problems and shortcomings.
The main advantage of the method and apparatus of the invention may be considered to be its applicability to joining thin sheets at a hole irrespective of the sheet material. When thin sheets are joined by the method of the invention, they remain completely straight, and there are no changes caused by thermal stress. The seam produced by the method and apparatus is first-class and is suitable for use in e.g. pressure vessels. It is a further advantage that no filler metal is needed in the welding; an adequate quantity of the parent material is melted to ensure that the resulting seam is sufficiently strong. The seams of the invention do not sag, as excess heat is efficiently conducted away from the welding area. On the basis of the above the resulting melting zone is so narrow that sagging problems do not occur. The apparatus and method of the invention may easily be automatized, and the method is particularly well adaptable to mass production.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail with reference to the accompanying drawings.
FIG. 1 is a side view of a welding machine according to the invention.
FIG. 2 is a side view and a partial cros
REFERENCES:
patent: 3100256 (1963-08-01), Borg
patent: 3640116 (1972-02-01), Hellman
patent: 3666161 (1972-05-01), Keller
patent: 4235359 (1980-11-01), Ikuno et al.
patent: 4236060 (1980-11-01), Butz
patent: 4487356 (1984-12-01), Krieger et al.
patent: 4500026 (1985-02-01), Larsen
patent: 4758706 (1988-07-01), Delquie
Mills Gregory L.
Vahterus Oy
LandOfFree
Superimposed sheet welding system including rotatable welding el does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Superimposed sheet welding system including rotatable welding el, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Superimposed sheet welding system including rotatable welding el will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-271822