Patent Publication Number: US-2018051771-A1

Title: Laser welding of balance weights to driveshafts

Description:
FIELD OF THE INVENTION 
     The present invention relates to driveshafts with balance weights welded thereon and methods of manufacturing the same. The invention also relates to driveshaft balancing equipment incorporating one of or both of paint removal device or welding device. 
     BACKGROUND OF THE INVENTION 
     After manufacture of a driveshaft, it is standard procedure to balance the driveshafts by adding weights in specific places determined by sophisticated balancing equipment, as is well known in the art. The balancing process ensures even rotation of the driveshaft and prevents wear and poor performance. Generally, the driveshaft is manufactured, the driveshaft is measured for balance, then the weights are added, and then the assembly is painted. Alternatively, prior methods have used a painted driveshaft and removed a large area of paint to allow for the balance weights to be welded onto the driveshaft in the appropriate position. However, this method then requires the area around the newly welded balance weight to be re-painted. In addition, methods currently employed do not incorporate the paint removal or attachment of the balance weight, which then would need to be performed at another time and location. 
     Disclosed herein is a driveshaft and method of manufacturing a driveshaft with balance weights that are welded onto an already painted driveshaft. One or both of the paint removal step or welding step can be combined with the balancing process allowing for less handling time and less scrap in the manufacturing process. These improvements can lead to significant cost savings. Also disclosed is balancing equipment used to balance the driveshafts of the invention. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a method of attaching a balance weight to a driveshaft with a coat of paint by first detecting a location on the driveshaft where balance weight is to be applied; then removing paint in that location; abutting the balance weight against the location; and then welding the balance weight to the driveshaft at that location. 
     The present invention also relates to a driveshaft assembly, including a driveshaft with a coat of paint; a balance weight; and a point of attachment between the driveshaft and the balance weight. The point of attachment can be a weld, and the weld is formed between the balance weight and the driveshaft at a location where the coat of paint has been removed. 
     The present invention relates to driveshaft balancing equipment incorporating a device for removing paint from a driveshaft. Driveshaft balancing equipment incorporating a device for welding a balance weight onto a driveshaft are also included in the invention. In one embodiment, the device for one or both of removing paint from the driveshaft or welding the balance weight to the driveshaft is the same device. One or both of the paint removal device or welding device may be a laser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which: 
         FIG. 1  shows a portion of the driveshaft with of one embodiment of the invention. 
         FIG. 2  shows a welded balance weight on a driveshaft in accordance with one embodiment of the invention. 
         FIG. 3  shows various views of a balance weight in accordance with one embodiment of the invention. 
         FIG. 4  shows a balance weight ( FIG. 4A ) and driveshaft ( FIG. 4B ) of one embedment of the invention with areas to be welded indicated. 
         FIG. 5  shows the steps of one embodiment of the invention for the method of applying the balance weights to a driveshaft. 
         FIG. 6  shows driveshaft balancing equipment in accordance with one embodiment of the current invention. 
         FIG. 7  shows driveshaft balancing equipment in accordance with one embodiment of the current invention. 
         FIG. 8  shows driveshaft balancing equipment with a driveshaft that has had paint removed in accordance with another embodiment of the current invention. 
         FIG. 9  shows driveshaft balancing equipment with a driveshaft with balance weights welded thereon in accordance with another embodiment of the current invention. 
     
    
    
     DETAILED DESCRIPTION 
     One end of a finished driveshaft  102  with a balance weight  104  and a coat of paint  112  in accordance with the embodiments of the current invention is shown in assembly  100 . A generic end fitting  200  is shown by the dotted lines on the right hand side of the figure. 
     The driveshaft  102  is a tube with a wall  106 .  FIG. 2  shows a cross-section of a balance weight  104  welded via weld  116  to the wall  106  of the driveshaft  102 . As made clear in  FIG. 2 , the weight  104  is attached to the driveshaft  102  that has a coat of paint  112 . 
       FIG. 3  shows three views ( FIG. 3A  is a perspective view;  FIG. 3B  is a frontal view;  FIG. 3C  is a side view) of the type of balance weight  104  used in typical embodiments of the invention. Reference number  110  is a hole created in the manufacture of the balance weight  104 . In alternative embodiments the balance weight  104  does not have a hole  110 . 
       FIG. 4A  shows the balance weight  104  with two balance welding areas  118  that will be welded to the driveshaft  102 . Any number or size of balance welding areas  118  can be used. The two balance welding areas  118  shown here are simply for explanation purposes and are not limiting in any way. 
       FIG. 4B  shows the driveshaft  102  with a coat of paint  112  where the driveshaft welding areas  114  have been created by removing the coat of paint  112 . As with the balance welding areas  118  shown in  FIG. 4A , the driveshaft welding areas  114  can be of any number or size and are simply for explanation purposes and are not limiting in any way. In typical embodiments, the balance welding areas  118  and the driveshaft welding areas  114  will be complementary in shape and number because in practice they represent the shape of the weld  116  that is formed. 
       FIG. 5  delineates the general steps of the method of applying the balance weight  104  to the driveshaft  102  having a coat of paint  112 . First, the driveshaft  102  is assembled. Here, the driveshaft  102  is shown in cross-section so the wall  106  is represented. After assembly, a coat of paint  112  is applied to the wall of the driveshaft  106 . Once the balancing process has been performed and the location for placement of the balance weight  104  has been determined, a driveshaft welding area  114  may be created by laser ablation of the coat of paint  112  in the driveshaft welding area  114 . For even greater efficiency, the laser ablation can be incorporated in to the balancing process and equipment. After the driveshaft welding area  114  is created, the balance weight  104  is placed in the desired location. The weight  104  may be clamped into place. At this point, the balance weight  104  is welded into the wall of the driveshaft  106  creating a weld  116  between the driveshaft welding area  114  and the balance welding area  118 , creating the final, balanced driveshaft assembly  100 . Again, the process of laser welding can be incorporated into the balancing process and equipment in order to further improved efficiency. 
     In one embodiment, the steps of the method may comprise the following:
     1. Load driveshaft into balancing equipment  210 .   2. Balancing equipment  210  cycles and determines the imbalance, if any.   3. Balancing equipment  210  positons a first end region  205  of the driveshaft  102  toward the balancing actuator  230 , which comprises one or both of paint removal device  250  or welding device  260 , specific to where the balance weight  104  needs added.   4. Paint removal device  250  removes paint  114  on the first end region  205  of the driveshaft  102 .   5. Balancing equipment  210  positions a second end region  206  of the driveshaft  102  toward the balancing actuator  230 , which comprises one or both of paint removal device  250  or welding device  260 , specific to where the balance weight  104  needs added.   6. Paint removal device  250  removes paint  114  on the second end region  206  of the driveshaft  102 .   7. Automation as is known in the art selects and positions balance weight  104  on the second end region  206  of the driveshaft  102 .   8. Welding device  260  welds balance weight  104  to the second end region  206  of the driveshaft  102 .   9. Balancing equipment  210  positions the first end region  205  of the driveshaft  102  toward the balancing actuator  230 , which comprises one or both of paint removal device  250  or welding device  260 , specific to where the balance weight  104  needs added.   10. Automation selects and positions balance weight  104  on first end region  205  of the driveshaft  102 .   11. Balancing actuator  230 , which comprises one or both of paint removal device  250  or welding device  260 , welds the balance weight  104  to the first end region  205  of the driveshaft  102 .   12. Balancing equipment  210  cycles and determines the imbalance.   13. Decision—Repeat steps 2 thru 12 until balance of driveshaft assembly  100  is acceptable.   

     Generally, the driveshaft  102  is usually made from steel. Likewise, the balance weight  104  is usually also made from steel. In alternative embodiments, the balance weight  104  and the driveshaft  102  made be made from different materials, for instance, when one of the driveshaft  102  or balance weight  104  is made from aluminum. Any suitable material can be used for either component. When the coat of paint  112  is removed from the driveshaft welding areas  114 , the steel to steel contact between the driveshaft wall  106  and the balance weight  104  allows for successful welding to occur. By only removing the coat of paint  112  in the driveshaft welding areas, once the balance weight  104  is welded to the driveshaft  102 , no repainting is required, thereby eliminating an additional step in the manufacture of the driveshaft assembly  100  and improving efficiency and lowering cost. In some embodiments, the driveshaft balanced according to this method is not repainted after balancing. In some embodiments, the driveshaft balanced according to this method is repainted after balancing. The type of welding used will most likely by via use of a laser  300 , but any other type of welding known that can attach the balance weight  104  to the driveshaft  102  can be used. In embodiments that use laser welding, the laser  300  can be incorporated into the balancing equipment  210  so that the paint removal and welding can all be performed during the balancing process. 
     The balancing equipment  210  into which one or both of the paint removal device  250  or welding device  260  are to be incorporated is very well known in the art. One, non-limiting example, is a driveshaft balancing equipment  210  manufactured by Schenck Corporation. In one embodiment of the driveshaft balancing equipment  210  modified to incorporate one or both of paint removal device  250  or welding device  260 , uses a laser  300  incorporated in to the balancing equipment  210  to remove the coat of paint  112  at location  114  and weld the weight  104  onto the driveshaft  102 . The paint removal device  250  or welding device  260 , which may be (but does not have to be) the same device is generically referred to as the balancing actuator  230 . 
       FIG. 6  shows a driveshaft  102  with a coat of paint  112  in balancing equipment  210 . The driveshaft  102  is held on either end in the balancer via its endfittings  200  by workholders  220 . The prior art would normally balance an unpainted driveshaft  102 . Here, the balancing occurs on a driveshaft  102  with a coat of paint  112  already applied. 
       FIG. 7  shows driveshaft balancing equipment  210  with a balancing actuator  230  attached to an overhead frame  240 . This is only one type of balancing equipment  210  that can be used in accordance with the current invention. Usually, the balancing actuator  230  will be connected to a server  280  where the server will process information sensed by the balancing actuator  230  and further direct the balancing actuator  230  to slide along the overhead frame  240  as necessary to complete the balancing operation. These processes are all known in the art and are described herein in very basic terms for contextual purposes. 
     The balancing actuator  230  is meant to cover any device known in the art to carry out the balancing operations of the balancing equipment  210 . Therefore, the balancing actuator  230  may include sensing the weight centerline, velocity, resonance, or other characteristics of a rotating driveshaft  102  being balanced. The balancing actuator  230  may also comprise means for determining the desired placement of the balance weights  104  and attaching the balance weights  104  thereon. The embodiments of the current invention are meant to build on the balancing actuators  230  already known and described and used in the prior art. Any balancing equipment  210  that uses any type of balancing actuator  230 , for example, equipment where the balancing actuator  230  is not on an overheard frame  240  should be understood to be within the scope of the invention. 
     One inventive aspect of the embodiment shown in  FIG. 7  is the balancing of a driveshaft  102  with a coat of paint  112 . Another inventive aspect of the embodiment shown in  FIG. 7  is the inclusion of a paint removal device  250  in the balancing actuator  230 . In addition, the balancing actuator  230  can include a welding device  260 . In some embodiments, the paint removal device  250  and the welding device  260  are the same device. In another embodiment, the paint removal device  250  and the welding device  260  are the same device and are a laser  300 . 
       FIGS. 8 and 9  show a close-up of a driveshaft  102  with a coat of paint  112  held by its end-fittings  200  in the balancing equipment by the workholders  220 . The balancing actuator  230  is shown in both figures and can comprise one or both of the paint removal device  250  or welding device  260 . In one embodiment, one or both of the paint removal device  250  or welding device  260  is the same and is a laser  300 .  FIG. 8  shows the driveshaft  102  with paint removed  114 . This corresponds to step  3  in  FIG. 5 .  FIG. 9  shows how the balance weight  104  is welded via welds  116  in the precise location where the paint was earlier removed  114 .  FIG. 9  corresponds to step  5  in  FIG. 5 . 
     Per the provisions of the patent laws, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced other than as specifically illustrated and described without departing from its spirit or scope.