Patent Publication Number: US-2007114215-A1

Title: Method of pacing travel speed

Description:
The present invention relates to the field of electric arc welding and more particularly to a method of pacing the travel speed of a welding operation used to form an assembly to test for physical properties.  
     INCORPORATION BY REFERENCE  
      The invention relates to the construction of a standard weld test assembly using a haptic device of the tactile alarm type. Such devices are well known and are shown in several patents, such as Shahoian 6,697,044 incorporated by reference herein. The haptic device actually employed in practicing the invention is a wrist mounted tactile alarm watch having settable alarm times for vibrating the base of the device worn on the wrist. Such device is sold for use in announcing the time to take a medication. An undated two page stacking sheet shows this medication device referred to as MeDose. This publication is incorporated by reference herein to show the type of haptic device using a tactile alarm for implementation of the present invention.  
     BACKGROUND  
      Many customers of welding wire, especially stick electrodes, require the testing of an assembly with fixed specification to determine physical characteristics of a weld produced by an electrode, such as a stick electrode or a welding wire used for semi-automatic welding. In testing each of these welding electrodes or wires, a standard procedure is performed by an operator. The welder prepares a test assembly with a weld joint formed by the electrode or wire to be analyzed. The weld must use a specific amount of input heat along the test joint. Creation of a weld test assembly requires uniform distribution of heat over a given length of the test weld. Precise specifications are often used by the military and have specific requirements. One of the critical requirements is a given amount of heat energy must be used in the weld per inch of length.  
      A representative example of the use of a welding procedure specification (WPS) is the American Welding Society specification AWS A5 5-96. This is for use of a cellulose stick electrode or several other stick electrodes. The WPS is number MA001. Incorporated by reference herein is a single sheet identifying the specifications for WPS MA001. This procedure is used for welding a test assembly to be subsequently tested for physical characteristics. To create the test assembly, the stick electrode being tested is used to fill the groove between spaced plates. The test groove has a given length, such as 12 inches. Filling by molten metal from the electrode must provide an even distribution of heat between the starting point and ending point of the groove. The weld metal joins the two spaced plates into a standard test assembly.  
      To assure that an even amount of heat is distributed along the groove during the welding process, the power source used for the welding operation is set to a selected power. The operator or welder moves the electrode being analyzed along the test groove at an even speed and then records the time necessary for traversing the set length of the test groove. The amount of heat per inch is then determined by multiplying the power by the lapsed time for the welding operation and then dividing this total consumed energy by the length of the groove. In this manner, the heat per inch of the assembly is determined. The critical specification for the standard test assembly produced by using the present invention is the heat used in the welding process. The welder starts the welding process by initiating the arc. As the arc is moved along the groove the electrode is melted and deposited in the groove. The expired time T must be a given value to assure distribution of the desired heat energy along the groove. This requirement presents practical difficulty. The welder has limited visibility through a welding helmet. Thus, the total weld time is the only variable when a fixed power is used for the welding process. To determine this variable, a timer is actuated by the power source as current flows at the start of the welding operation. The timer is stopped when the welding operation terminates at the end of the test groove. Time is recorded, but there is no way for the welder to pace the travel speed along the test groove. Consequently, the test assembly may be scrapped if the total welding time T is not close to the time necessary for inputting the specified amount of energy along the test groove. The present invention solves this problem by providing a method of pacing the travel speed of a manual arc welding process performed to produce the standard test assembly of the type required to meet a specification, such as WPS MA001. This specification demands that the test groove for joining the plates into a standard test assembly be filled with molten metal with a specified amount of heat per length along the test groove. This requires skill, practice and trial and error.  
     THE INVENTION  
      The present invention paces the travel speed of the manual arc welding process performed by a welder as a weld metal is deposited on a workpiece along a test groove having a given test length. This test length is defined by the spacing between a visible start location marker and a visible end location marker. Such markers are now used to produce a test assembly. The procedure must consume a specific amount of energy distributed generally uniformly in the grooves and between the spaced locations. The travel speed used by the welder along the test groove determines the distribution of heat in the test groove. The novel method assists the welder in pacing the travel speed so the total welding time T is an amount to create the desired heat input along the groove. It is performed by providing a power source with output leads and an arc current and an arc voltage. The output power of the power source is fixed and the output leads are connected across the welding wire and the workpiece. In accordance with standard procedure, total time T for the wire to traverse the test length to consume the specific amount of energy for the groove is a known amount. The novelty of the invention is marking the groove with an indicia visible through the welding helmet and spaced from the start marker a given distance. This distance is usually halfway between the start location marker and the end location marker of the groove. A programmable haptic device is associated with an exposed body part of the welder. This device has a tactile alarm activated after a programmed time from the start of the haptic device. This programmed time is coordinated with the given distance of the added visible marker to indicate a desired speed to be paced by the welder. The haptic device is started when the operator commences welding at the start location marker. In accordance with the invention, the manual rate of travel by the welder is changed according to he relationship of the electrode to the added marker when the tactile alarm is activated.  
      In accordance with another aspect of the present invention, the given distance to the added marker is one-half the test length L between the start location marker and the end location marker. The tactile alarm is actuated at one-half the time T necessary for filling the test groove at the specified level of heat input.  
      In accordance with another aspect of the present invention, the haptic device is a device strapped onto the wrist of the welder. Preferably the wire being used to fill the test groove is a stick electrode.  
      Another aspect of the present invention is combining the novel aspects of the method as so far described with the standard process to measure total time T. Total time T is obtained by using a cycle timer that is started when the welding is at the start location. The timer is stopped when the welder stops welding at the end location. Both of these locations have visual markers and the timer is initiated automatically by current flow in the power source.  
      In accordance with another aspect of the present invention, the specific amount of energy along the test groove is in the range of 30-70 k Joules per inch. Furthermore, the metal forming the groove is preheated to a temperature in the general range of 100-250° F.  
      The primary object of the present invention is the provision of a method for producing a standard test assembly for subsequent physical testing of a welding procedure, which method utilizes a haptic device to assist in pacing the travel speed of the welding operation in the test groove used to join two plates into a standard test assembly meeting precise specifications.  
      Another object of the present invention is the provision of a method, as defined above, which method assures better pacing of the travel speed of the welding operation to produce a desired amount of heat input to the test groove of the test assembly and requiring less skill, less practice and less scrap.  
      These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a pictorial view of a standardized test assembly awaiting preparation for final welding by the method of the present invention;  
       FIG. 2  is a pictorial view of the hand of a welder depositing the weld metal on the test assembly shown in  FIG. 1  by using a stick electrode for which the physical characteristics are to be analyzed;  
       FIG. 3  is a top view of the test assembly shown in  FIG. 1  illustrating the welding process of the present invention;  
       FIG. 4  is a schematic timing diagram illustrating the location of the visual markers used in performing the pacing method of the present invention;  
       FIG. 5  is a simplified block diagram of the automatic timing system used in the prior art for making the standardized test assembly of  FIG. 1  and also used in an aspect of the present invention;  
       FIG. 6  is a view similar to  FIG. 4  illustrating a different spacing of the visual timing markers used in another embodiment of the present invention; and,  
       FIG. 7  is a view similar to  FIGS. 4 and 6  illustrating the location of the visual timing markers in still another embodiment of the present invention. 
    
    
     PREFERRED EMBODIMENT  
      To determine the physical characteristics of a weld performed by a given welding wire, especially a stick electrode, many specifications require production of a standard test assembly, such as set forth in a specific welding procedure specification (WPS). The standardized test assembly for subsequent physical analysis of a weld by a specific electrode is illustrated in  FIG. 1  where test assembly A involves a joint of metal deposited in groove  10  between spaced metal plates  12 ,  14 . The spaced plates define test groove  10  and have a thickness a generally between ½ and ¾ inch with a width b greater than 5 inches. Length c of test groove  10  is greater than ten inches and is preferably twelve inches. Actually the total length of the test groove used in the production of assembly A is greater than test length C, shown later as length L. In the preferred embodiment, tapered walls  20 ,  22  have an included angle e of about 20 degrees and are spaced from each other a distance d defining the bottom root gap of assembly A which gap is generally ½ inch to ⅝ inch and is filled by root bead  30  supported by backing  32  formed from steel, which will be adhered to the under side of assembly A.  
      The present invention involves filling groove  10  with weld metal by a manual welding process performed by welder W, as schematically illustrated in  FIG. 2 . Welder W moves stick electrode E along groove  10  to fill the groove and finalize standardized test assembly A for subsequent physical testing. The resulting weld by electrode E determines the quality of the electrode. This quality is determined by analysis of assembly A after the assembly has been joined by a specified deposition process that is generally consistent along length L of test groove  10 . This welding process is performed by manually moving electrode E, such as a cellulose stick electrode, along test groove  10  by welder W. Only the hand and wrist  40  of welder W is shown in  FIG. 2 . The hand of the welder is protected by glove  42  while electrode E is supported in holder  50  by alligator gripper  52  in accordance with standard stick welding practice. The electric arc welding is performed with a desired power determined by the current and voltage directed to electrode E by power lead  54 . The welding process is performed by a specified setting of current and voltage to determine the power used in welding along groove  10  as electrode E is melted and deposited in the groove. In the past, this welding process was performed between two visual markers defining the test length L shown in  FIG. 3 . This test length is filled by melting electrode E using a set current and voltage. The time to weld length L determines the total energy during the welding process filling groove)  10 . This total energy is divided by the inches constituting length L to determine the amount of Joules per inch used in the welding process along test length L. In the prior procedure, welder W starts the welding operation and proceeds until the test length L is reached. The time is recorded by a system shown in  FIG. 5 . To be acceptable the energy per inch of the welding groove  10  must be within the relevant specification. Only in this instance can the test assembly be employed for subsequent analysis of the weld to determine the quality of electrode E. The difficulty with prior procedures relates to the fact that welder W must be highly skilled to traverse length L in the desired time to conform with the specified input energy along groove  10 . The present invention provides a method of pacing the welding process to assist the welder in traveling over length L in the desired time to have the specified heat input along groove  10 . This novel method involves the use of haptic device D in the form of a tactile alarm  60  with a wrist band  62  supporting the tactile alarm onto wrist  40  of welder W. Set buttons  64   a ,  64   b ,  64   c  and  64   d  are used to set the alarm time of device D to perform the pacing method of the present invention. In practice, tactile alarm  60  is a MeDose vibrating alarm watch. The alarm watch has at least six different settings even though only one setting is used in practicing the preferred embodiment of the present invention. Device D is not used in accordance with the intended purpose of the product, but it is set to minutes for use in welding groove  10 .  
      As described before, assembly A is formed by filling joint or groove  10  with a welding process using electrode E. To determine the start location of the welding process, a visual marker  100  is placed at a first location adjacent test groove  10  on assembly A. At the far end of length L, a second visual marker  102  is located. This second visual marker determines the end of the test welding process and is generally spaced twelve inches from marker  100 . Welder W can visually determine marker  100  through the welding shield and commence the welding process at the start marker. This starting of the welding process activates the timing system shown in  FIG. 5  where power source  110  is driven by supply  112  to produce a specified power across electrode E and test assembly A by power lead  54  and return power lead  120 . To determine welding cycle time T, reed switch  130  is actuated by current flow through coil  132  to produce a start signal in line  134  to energize reset timer  140 . At marker  102  welder W stops the welding process. This deactivates reed switch  130  so actual time T for the welding cycle appears in line  142  and is recorded or displayed by output device  150 . As so far described, the showings in  FIGS. 3-5  represent the prior method for forming standardized assembly A. Welder W starts the welding process at marker  100  and proceeds with the specified power being used by electrode E. At visual marker  102 , the welding cycle is terminated and the total time T is recorded in output device  150 . This time must be within certain narrower tolerances to provide a total heat input, usually specified as heat per inch along length L. To obtain this specification heat input value, the total heat used along length L is used to calculate the heat per inch. This value must be within the specified limits to accept assembly A for subsequent testing of quality of the weld performed by specific electrode E. To produce an acceptable test assembly requires skill. Rejects are not unusual since the welder can not see the time being consumed during the welding process. The welder can not watch a clock through the welding helmet or shield so the travel speed must be estimated and obtained by trial and error.  
      The present invention assists the welder in pacing the weld process. An added marker  200  is positioned along groove  10  as shown in  FIG. 3 . This added marker is at a known spacing from marker  100 . In practice, this spacing is length L divided by 2. In  FIG. 4  the spacing of added marker  200  is shown as it is equated to cycle the specified time T, as being T/N wherein N is 2. Thus, the desired cycle time T for obtaining the specified heat input is divided by 2 to provide time t 1 . Time t 1  is set in haptic device D worn on wrist  40  of welder W as shown in  FIG. 2 . Thus, in accordance with the present invention, filling of groove  10  is commenced at marker  100  where reed switch  130  starts timer  140 . At the same time, welder W actuates device D set to alarm at time t 1 . When the welding process approaches marker  200 , the alarm of device D is actuated. If the tactile alarm occurs before welder W is at added visual marker  200 , the travel speed is thereafter increased. The amount of increase is based upon the amount of spacing between the alarm and reaching added marker  200 . If the alarm occurs after marker  200 , the travel speed of the welding process is decreased. This is again based upon the time between the alarm and reaching marker  200 . In this manner, an adjustment of the travel speed is made at marker  200  to more easily pace the travel of electrode E along groove  10 . In this manner, cycle time T is more easily within the desired tolerances of the specification for test assembly A.  
      In  FIG. 6  the second embodiment of the present invention is illustrated wherein N is 3 so a first added visual marker  210  is ⅓ of the distance L. Time t 1  is ⅓ of the desired cycle time T. Device D is set to alarm at time t 1 . A second visual marker  212  is ⅔ of the distance L and device D is set to expire at a second alarm time t 2  which second alarm time is ⅔ of the desired cycle time T. Thus, the welding process is paced at a first added visual marker  210  and a second added visual marker  212 . Of course, the invention could involve further numbers of visual markers and further spaced tactile alarm times; however, a single marker as shown in  FIGS. 3 and 4  is preferred. Two added markers as shown in  FIG. 6  are probably the maximum number during the short welding cycle.  
      Regarding the invention, a single added marker is the first maker  200  or  210 . Other markers are embodiments of the invention. Another aspect of the invention is schematically illustrated in  FIG. 7  wherein length L includes two added visual markers at times t 1  and t 2 . These markers are not equally spaced along length L; however, the distance x and y are coordinated with the time T so device D is set to cause a tactile alarm at time t 1  and t 2  each of which time are coordinated with an added marker adjacent groove  10 . Other numbers and spacing of added visual markers are within the intended scope of the present invention. By using markers and the haptic device, preferably a tactile alarm, welder W can more precisely pace the travel speed of the welding operation along groove  10 . Each embodiment includes a first added marker and an alarm at time t 1 . The spacing and number of added markers with correlated alarm times are features of other embodiments within the intended scope of the invention.