Metal fusion bonding – Process – With shaping
Reexamination Certificate
2000-12-22
2002-12-17
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S005700, C228S017500
Reexamination Certificate
active
06494360
ABSTRACT:
BACKGROUND OF THE INVENTION
Various processes and apparatuses are known for the production of straight bead welded tubes from strips and sheet metal blanks, but none of them make possible the economic manufacture in medium size runs of tubes having a relatively short length (for example, 1=3000 mm), a small diameter (for-example, d=50 mm) and a relatively large wall thickness (for example, t=2.5 mm). It is therefore an object of the invention to provide a process and an apparatus for the production of such tubes.
In the prior art process of roller shaping (U.S. Pat. No. 2,110,378) a strip is shaped in a number of successively arranged stages by driven profiled rollers to give a slotted tube which is then welded. The investment cost of an installation suitable for this purpose is very high, so that it is unsuitable for the production of tubes in medium size runs.
In the prior art 3-roller bending, a flat sheet metal blank with two supporting rollers is bent around a working roller. Such a process enables tubes to be produced with a wall thickness of, for example, 1.0 mm and a diameter of 50 mm only with a length of less than 2000 mm, since the supporting rollers sag due to the heavy supporting forces to be applied. There is also the aspect that the resulting slotted tube must be removed from the apparatus and straight bead welded at another place.
A clamping and retaining apparatus for relatively short slotted tubes is also known (DE 44 32 674 C1) in which the slotted tube is retained by bands, which are partially looped around the tube, in a suitable welding position for a welding device which can be driven along the joint gap. To obtain a straight bead welded tube, therefore, a sheet metal blank must be shaped into a slotted tube in a separate apparatus.
In another prior art apparatus (DE-PS 966 111) for the production of straight bead welded tubes from flat sheet metal blanks with parallel longitudinal edges, the sheet metal blank is shaped into a slotted tube in the same apparatus, being retained by the means shaping the tube with the longitudinal edges to be welded in the welding position. Two form tools disposed laterally inverted in relation to one another, which are borne by a tool support, can be driven towards one another, and have outer cylindrical half shells received in their opened receiving position the sheet metal blank at its two longitudinal edges. When the form tool halves are moved together, the sheet metal blank is retained at its two ends fixed in the center, so that the sheet metal blank slides along the cylindrical half shells on both sides until its longitudinal edges impinge on one another at the top point. The sheet metal blank shaped into a slotted tube is retained in this position. Then, to weld the longitudinal edges to one another, the top ends of the form tool halves can be hinged upwards, so that the joint gap is opened up. An important disadvantage of such an apparatus is that there is the risk that the sheet metal blank may bend outwards for lack of internal and external guiding. This risk is particularly great in the case of thin-walled sheet metal blanks.
In a very similar prior art apparatus for the shaping of sheet metal blanks into tubes, which are then welded (DE-PS 593 622) the two form tool halves are formed not by cylindrical half shells, but by axially offset discs with cutaway portions in the shape of arcs of a circle. The apparatus is to be used to form a conical tube from a sheet metal blank. To this end the disc cutaway portions in the shape of arcs of a circle increase in radius in the axial direction. However, in distinction from the other aforedescribed prior art apparatus, in this prior art apparatus an internal conical mandrel is associated with the outer parts of the form tool halves. However, the mandrel is not operative during the entire shaping operation, but only at the end thereof, since it is applied to the sheet metal in the center between the form tool halves. Due to the absence of internal and external guiding during the shaping operation, even the use of such a mandrel does not obviate the risk that the sheet metal blank will bend outwards during the shaping operation.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a process and an apparatus which enable straight bead welded tubes to be produced from sheet metal blanks, more particularly blanks with a thin wall thickness. More particularly, the process and the apparatus are suitable for the processing of sheet metal blanks of different thicknesses, for example, so-called tailored blanks.
The invention therefore starts from a process for the production of a straight bead welded tube from a flat sheet metal blank having parallel longitudinal edges, wherein the sheet metal blank is shaped into a slotted tube by means of two form tool halves having outer cylindrical half shells and disposed laterally inverted in relation to one another which can be moved towards one another, whereafter the longitudinal edges are welded to one another at the top of the form tool, being retained in position by the form tool halves. In such a process according to the invention during shaping the sheet metal blank is borne on the inside by internal cylindrical mandrel halves co-operating with the outer half shells to produce form gaps, the longitudinal edges emerging at the top retaining exposed for welding (sic).
The invention also relates to an apparatus for the production of straight bead welded tubes from flat sheet metal blanks with parallel longitudinal edges having: form tool halves having outer cylindrical half shells and disposed laterally inverted in relation to one another which are borne by a tool support and can be moved towards one another and can be moved out of an opened receiving position for the sheet metal blank into a closed position, in which the longitudinal edges to be welded to one another are held together by the closed tool halves at their top point, the device also having a welding device which can be moved over the form tool halves along the longitudinal edges retained in the welding position. In such an apparatus the invention is characterized in that the form tool halves have cylindrical internal mandrel halves which are associatedly fixed with the outer half shells and which cooperate with the outer half shells to produce form gaps for the sheet metal blank to be inserted, while in the closed position of the form tool halves the form gaps retain the longitudinal edges emerging therefrom at the top exposed for welding.
The process according to the invention and the apparatus according to the invention enable sheet metal blanks of different thicknesses to be formed into a cylindrical tube without any risk that the blank will bend outwards during the shaping operation. More particularly, the invention enables short tubes to be economically produced in medium size runs from sheet metal blanks. Both tubes having a constant wall thickness can be produced, and also tubes which have differential wall thickness over their length or periphery. The special advantage of the invention is that the form tool halves themselves retain the shaped slotted tube with the joint gap in an optimum welding position, to produce the weld by the welding device movable along the joint gap. This means that two separate devices are no longer required for shaping and for retaining the slotted tube in the welding position. This also eliminates the laborious transfer of the slotted tube, with the necessary alignment and clamping.
In a first embodiment of the invention the sheet metal blank is first pushed by one half completely into one of the form gaps and then by its other half into the other form gap. One of the two form tool halves, more particularly the movable one, can have adjacent the entry to the form gap an abutment against which one longitudinal edge of the sheet metal blank can bear when the form tool halves are moved together. This gives the sheet metal blanks satisfactory guiding, making it impossible for the blank to be introdu
Blümel Klaus
Flehmig Thomas
Neuhausmann Thomas
Elve M. Alexandra
Kerns Kevin P.
Proskauer Rose LLP
Thyssen Krupp Stahl AG
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