Patent Application
20100163530
This application is not based upon any pending domestic or international patent applications.
This application is not referenced in any microfiche appendix.
The present invention relates generally to an automated welding apparatus and method used to simultaneously create two or more parallel joints. More specifically, the present invention involves an apparatus and method wherein each of these parallel joints, two or more welding tips work simultaneously on each joint.
In the metal fabrication business it is common to manufacture items which have two or more long parallel joints. One such example is a header used in a heat exchanger. A header is generally a hollow elongated box constructed out of flat steel plates. In the final assembly a header is usually constructed out of four work pieces without including the end plates (not addressed by this patent as not applicable). The center body portion typically has a form of a rectangular frame with an opposing top and bottom, called wrappers, welded to two opposing side pieces, called a tube and plug sheet. The tube sheet and the plug sheet are welded onto opposing sides of the center body, separated by the wrappers. Because of the thickness of the steel used the welds between the tube and plug sheets and the body require an extremely large weld. This means a significant amount of weld material must be deposited into the joints.
In the past the creation of these joints has taken significant amount of labor due to the large cross-sectional area and the length of the weld.
In an attempt to reduce the amount of labor involved in fabricating these large parallel welds, the prior art shows numerous devices capable of creating parallel welds by simultaneously using one welding tip on each weld.
Other devices found in the prior art address the issue of creating one individual large joint by simultaneously welding on the same joint with two welding tips.
While both of these types of prior art provide an improvement over creating the joints by having to individually manually weld them further improvements in the art is needed.
The present invention involves an apparatus and method to create a plurality of parallel joints by providing a carriage which traverses along the welds. The carriage has two or more welding tips for each joint. Alignment of the welding tips with the joints is maintained by rollers secured to the carriage. These rollers traverse along the surfaces of the work piece.
Productivity can further be improved by securing the work pieces on a pair of turntables having a common axis of rotation. This access of rotation is also parallel with the joints.
With the work pieces mounted in the turntables the welds in both the top and bottom of the header can be created by simply rotating the work pieces to the bottom side once the welds on the top side have been completed.
Further objects and features of the present invention will be apparent to those skilled in the art upon reference to the accompanying drawings and upon reading the following description of the preferred embodiments.
For explaining the present invention in detail it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of the parts illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein are for the purpose of description and not of limitation.
Turning to
The preferred embodiment of the invention as shown in
In the preferred embodiment the spacing between the first welding tip 28 and the second welding tip 30 is approximately 1.25 inches. It is also beneficial to have the second welding tip 30 angled 12 degrees off of vertical such that the second welding tip 30 points toward the first welding tip 28. Likewise it is beneficial to run the second welding tip 30 approximately 100 amps hotter than the first welding tip 28. The higher amperage of the second welding tip 30 ensures a high quality weld by burning the liquid slag out of the weld pool. Weld penetration can be enhanced by using a smaller diameter wire or electrode on the first welding tip. This ensures the weld reaches the bottom of the joint. Further, deposit rates can be improved by having a larger diameter wire or electrode on the second welding tip 30
In the process of the preferred embodiment the three pieces of the header H1, H2 and H3 are mounted in the first and second turntable 24 and 26. The carriage 22 of the welding machine 20 is located at a first end of the header H such that one of each of the first pair of welding tips 28 is aligned with each of the joints J1 and J2. Likewise one of each of the second pair of welding tips 30 is also aligned with each of the joints J1 and J2. The carriage 22 is then traversed from the first end of the header H towards the second end of the header H. As the carriage 22 traverses the header H, the first and second pair of welding tips 28 and 30 are maintained in alignment with the joint J1 and J2 by one or more rollers 36. The rollers 36 contact various surfaces of the header H as the carriage 22 traverses the header H. One or more lasers could be used to guide the carriage 22 in lieu of the rollers.
The first pair of welders 28 join together the parts of the header H1, H2 and H3 using a direct current welding process. Adjacent to the first pair of welder 28 a layer of granular flux is laid into the joints J1 and J2. The second pair of welding tips 30 carry out an alternating current welding process. The direct current welding process and the alternating current welding process create welds W1 and W2 in the joints J1 and J2 respectfully.
When the carriage 22 reaches the second end of the header H the first and second welding tips 28 and 30 are disengaged. The carriage 22 is then traversed back to the first end of the header H. The header H is then rotated in the first and second turntables 24 and 26 along the longitudinal axis such that what had previously been the bottom of header H is now the top. The carriage 22 and first and second pair of welding tips 28 and 30 are then aligned so that the welding machine 20 can be used to weld together the bottom side of the three parts of the header H1, H4 and H3 in the same manner as on the top side of the header H.
It should be noted that the present invention could be adapted with additional welding guns such that it could operate on more than two parallel joints to create more than two welds with the carriage having a first and second welding tip for each additional weld. This would be useful in fabricating equipment with more than two parallel linear welds.
While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.
