Electric heating – Metal heating – By arc
Reexamination Certificate
2002-04-12
2004-12-07
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121630, C228S017500, C072S368000
Reexamination Certificate
active
06828523
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
Applicant hereby claims foreign priority benefits under 35 U.S.C. § 119 of Swiss Patent Application No. 1934/199 filed 22 Oct. 1999 and PCT Application No. PCT/CH00/00454, filed 25 Aug. 2000, the disclosure of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to methods for manufacturing welded tubes in general, and to methods for manufacturing welded tubes that include the transfer of tube bodies between a forming apparatus and a welding machine.
2. Background Information
There exists an increasing demand for a production plant for internal high pressure forming (“hydroforming”) of elongated, longitudinally closed, essentially tubular bodies for the production of shaped parts. These bodies may be configured as tubes or hollow bodies with rotationally asymmetrical, or only partly rotationally symmetrical, cross-sections, and may be used for the widest variety of purposes. If the shaped parts fabricated by hydroforming are used, e.g., in a body structure of a car or lorry or other vehicle, the quality of the outer skin of the shaped parts is becoming increasingly important, as these are increasingly used as body components and are therefore visible on the finished body. Today, tubes with a length of approximately one (1) meter to four (4) meters and with diameter-to-thickness ratios of sixty (60) or more are being used for this purpose. However, it is likely that the lengths will continue to increase, and may exceed, e.g., five (5) meters, while the diameter-to-thickness ratios drop to forty (40) or less and also increase to one hundred (100), one hundred and fifty (150) or more. It is moreover likely that rotationally asymmetrical bodies will also be used, e.g., bodies with elliptical or oval cross-sections with partially flattened or parallel side wall parts, and/or bodies with rectangular or triangular cross-sections. The cross-section is governed by the specific application, which may demand every possible cross-sectional shape.
The initial material for such bodies to be processed by hydroforming into shaped parts is a flat sheet-metal blank which constitutes the shell of the future body. The blank is formed in a press or rounding apparatus into an elongated tubular body, which is not longitudinally closed, as the corresponding sheet-metal edges are adjacent but are not yet joined together. Joining is done by welding with an energy beam such as a laser or by some other suitable welding process while the longitudinal edges are held in the butt position. The quality of the weld seam is subject to special requirements, e.g., as to its fluid tightness and elasticity during the ensuing hydroforming.
Generally speaking, elongated welded tubular bodies need to be fabricated with a high quality welded joint and, depending on the application, with a high-quality outer skin, as scratches or indentations on the shaped parts are undesirable or unacceptable. Therefore the basic problem of the invention is to provide methods and apparatuses with which elongated tubular bodies, in particular with a high-quality outer skin, can be produced efficiently.
DISCLOSURE OF THE INVENTION
Hereinafter where mention is made of “tubes”, “tube bodies”, etc., these are to be understood as signifying elongated tubular bodies with variously configured cross-sections according to the remarks made above.
A method for the manufacture of welded tubes is provided. The tube bodies are produced in a press or rounding apparatus and are fed to a welding machine, such as a laser or electron beam type welding machine. The tube is formed when the edges of the tube bodies are welded together. The method includes the transfer of the tube bodies from the press or rounding apparatus to the draw-in of the welding machine. One or more transfer modules, each having a separate drive, are used to convey the tube bodies. The one or more transfer modules, which are operated by a common control arrangement, are controlled so that the intermittently formed tube bodies are presented at the draw-in to the welding machine in as nearly continuous a sequence as possible.
Through the provision between the equipment for forming the tube bodies—(which may be a press that forms the tube bodies in a number of bending steps, or a rounding apparatus)—on the one hand, and the welding machine on the other hand, of a number of transfer modules which are actuated by a common control so that the transfer modules can constitute a buffer between the equipment for forming the tube bodies and the actual welding machine, it becomes possible to harness an intermittent tube body production to a continuous welding operation. For example, three short tube bodies or one long tube body can be formed simultaneously in a press, and by slowing and/or accelerating individual tube bodies in the transfer line, can be arranged into a series of tube bodies that is as continuous and as closely spaced as possible on running through the welding zone.
With a continuous feed of tubes, it is also possible to configure the transfer line so that the tubes are presented in the welding zone for an optimal length of production run.
In accordance with a further aspect, an effort is made to transfer the tube bodies in such a way that their outer skin remains free from damage, and also in particular, that correct orientation of the edges is preserved during transfer, if need be with an initial squeezing of the tube body with a view to a subsequent closure of the gap in the welding area. Squeezing of the tubes may be advisable because after the plastic forming of the blank into a tube there is an elastic spring-back which opens up the gap between the edges somewhat. Also, the gap may be narrow enough or not quite narrow enough, depending on the method used for forming the blank. Furthermore, the use of different sheet-metal alloys and/or thicknesses on one and the same plant can result in different gaps, and this may need correcting in the subsequent processing of the tubular body.
The present method provides substantially damage-free transfer between the press or rounding apparatus and the welding machine by carrying the tube bodies on the inside of the tube during the transfer.
Supporting the bodies from inside protects the outer skin from damage. Means for locating the edges during transfer can also operate internally, or on the edges themselves. Such locating means, e.g., in the form of internally acting rollers and/or leaf spring devices acting on the edges, are advantageous in bringing the tube body to the draw-in to the welding machine ready orientated, so that at that point only slight adjustments of alignment are necessary in addition to the closure of the tubular body. It is also preferred that there be a facility for partially closing the gap in the body while transfer is still taking place, preferably by externally acting drive rollers whose mutual position is adjustable.
It is also desirable to ensure smooth, e.g., jolt-free, run-in of the tube bodies at the draw-in to the welding machine, or as they are passed from the transfer apparatus to the welding machine; even if the transfer apparatus does not assist further closure of a tube to be supplied which is inherently too wide open. It should be possible for the welding machine to handle the widest possible variety of tube dimensions and gap widths. Furthermore, it is advantageous that the quality of the outer skin of the tube should not be impaired by this operation.
The present method utilizes a draw-in means, in particular draw-in rollers, which receive the tube body in an open position of the draw-in means and then close to a predetermined setting to reduce the gap opening of the body and preferably to contact the body so as to advance it. The draw-in means move back to the open position after the body has passed through.
As the draw-in means are in an open position when they receive the tube body, abrupt impact of the body on these means, possibly damaging the outer skin, does not occur. The closing of the draw
Elpatronic AG
Heinrich Samuel M.
McCormick Paulding & Huber LLP
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