Abstract:
A pulse synchronize load stabilization routine for adjusting a fastener to a desired torque level with a tool operatively connected to a fastener is provided. The method includes applying a first level of current to the tool, pulsing the tool to cause the fastener to rotate and measuring a dynamic torque load on the fastener while it is rotating. A computer readable medium containing an executable code for adjusting a fastener with a tool operatively connected to the fastener is also provided. Executable code includes a routine which causes the tool to run in a first velocity speed control mode determined if a torque load is at a predetermined level and if the torque load is at a predetermined level, then apply a pulse synchronize load stabilization sequence.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to tools used for turning fasteners such as nuts and bolts. More particularly, the present invention relates to computer controlled tools used for turning multiple fasteners at one time.  
       BACKGROUND OF THE INVENTION  
       [0002]     Often, two assemblies may be attached to each other by using fasteners such as nuts or bolts. In many cases, two objects are attached to each other by using a plurality, sometimes an array, of nuts and bolts. For example, a car wheel attaches to a car often by four to eight lug nuts arranged in an annular array. For a variety of reasons, it is important that the lug nuts be turned to a specific torque when attaching the wheel to the car.  
         [0003]     One problem often encountered when trying to torque a fastener to a specific torque level is that once the fastener is torqued to the desired torque level, that torque level may change in response to other nearby fasteners being torqued. This problem is often exemplified by again using the car wheel example. A first lug nut may be tightened as much as possible by hand. Then once a lug nut, often beside of the first lug nut, is tightened and torqued down, it is then often noticed that the first torque lug nut is now loose and must be again tightened. However, once the first lug nut is again tightened, then the second lug nut, located opposite the first, may be loosened slightly. This problem is related to the fact that the torque at one fastener can affect the torque level of a nearby fastener.  
         [0004]     In many environments, such as manufacturing environments, multiple fasteners may be tightened at the same time by a single tool operating all of the fasteners, and as mentioned, the tightening of one fastener slightly before or after a second fastener can result in the fasteners having different actual torque levels than what was indicated when those fasteners were tightened and measured.  
         [0005]     Accordingly, it is desirable to provide a method and apparatus that can control a tool for attaching a fastener or multiple fasteners to a desired torque level and controlling that tool so that the actual torque level of all the fasteners, once all of the fasteners have been torqued, is at a desired level.  
       SUMMARY OF THE INVENTION  
       [0006]     The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments attaches multiple fasteners to a desired torque level. A pulse synchronous load stabilization method for adjusting a fastener to a desired torque level with a tool operatively connected to the fastener is provided. The method includes: applying a first level of current to the tool, pulsing the tool to cause the fastener to rotate, and measuring a dynamic torque load on the fastener while it is rotating.  
         [0007]     In accordance with one embodiment of the present invention, a method of pulse synchronous load stabilization method for adjusting a fastener to a desired torque level with a tool operatively connected to the fastener is provided. The method includes: (a) setting up high and low current thresholds, (b) applying current to the tool at the low thresholds for a predetermined length of time, (c) determining whether all fasteners are synchronized, (d) if the fasteners are synchronized then skipping to step (g), if the fasteners are not synchronized, then executing steps (e)-(f), (e) applying current to the tool at the high threshold, (f) measuring a level torque associated with fasteners, if the torque level exceeds a desired level, return to step (b), if the torque level does not exceed a desired level, go to step (d), (g) pulsing current to tool while the tool is in a velocity control mode and measure dynamic torque associated with fasteners, and (h) repeating steps (b)-(g) at least one of a predetermined number of times or until a desired torque level is achieved.  
         [0008]     In accordance with another embodiment of the present invention, a method for adjusting a fastener with a tool operatively connected to the fastener is provided. The method includes running the tool in a first velocity speed control mode, determining if a torque load is at a predetermined level, and if the torque load is at the predetermined level, then applying a pulse synchronous load stabilization sequence.  
         [0009]     In accordance with yet another embodiment of the present invention, a method for adjusting a fastener with a tool operatively connected to the fastener is provided. The method includes: running the tool in a high velocity speed control mode, determining if the torque level is at a synchronization level, and if the torque level is at a synchronization level, then applying a pulse synchronous load stabilization sequence, running the tool in a low velocity speed control mode, determining if the torque level is at a predetermined level, if the torque level is at a predetermined level, then: applying a pulse synchronous load stabilization sequence a second time.  
         [0010]     In accordance with yet another embodiment of the present invention, a computer readable medium containing executable code for adjusting a fastener with a tool operatively connected to the fastener is provided. The code contains commands for running the tool in a first velocity speed control mode, determining if a torque load is at a predetermined level, and if the torque load is at the predetermined level, then: applying a pulse synchronous load stabilization sequence.  
         [0011]     In accordance with yet another embodiment of the present invention, a computer readable medium containing executable code for using pulse synchronous load stabilization for adjusting a fastener to a desired torque level with a tool operatively connected to the fastener is provided. The code contains commands for applying a first level of current to the tool, pulsing the tool to cause the fastener to rotate, and measuring a dynamic torque load on the fastener while it is rotating.  
         [0012]     In accordance with yet another embodiment of the present invention, a computer readable medium containing executable code using pulse synchronous load stabilization for adjusting a fastener with a tool operatively connected to the fastener is provided. The code contains commands for running the tool in a high velocity speed control mode, determining if the torque level is at a synchronization level, and if the torque level is at a synchronization level, then applying a pulse synchronous load stabilization sequence, running the tool in a low velocity speed control mode, determining if the torque level is at a predetermined level, if the torque level is at a predetermined level, then applying a pulse synchronous load stabilization sequence a second time.  
         [0013]     In accordance with yet another embodiment of the present invention, a computer readable medium containing executable code using pulse synchronous load stabilization for adjusting a fastener with a tool operatively connected to the fastener is provided. The code contains commands for: (a) setting up high and low current thresholds, (b) applying current to the tool at the low thresholds for a predetermined length of time, (c) determining whether all fasteners are synchronized, (d) if the fasteners are synchronized then skip to step (g), if the fasteners are not synchronized, then execute steps (e)-(f), (e) applying current to the tool at the high threshold, (f) measuring level torque associated with fasteners, if the torque level exceeds a desired level, return to step (b), if the torque level does not exceed a desired level, go to step (d), (g) pulsing current to tool while the tool is in a velocity control mode and measure dynamic torque associated with fasteners, and (h) repeating steps (b)-(g) at least one of a predetermined number of times or until a desired torque level is achieved.  
         [0014]     There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.  
         [0015]     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.  
         [0016]     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a cut away side view illustrating a tool for turning multiple fasteners to a specific torque level attached to a computer controlling the tool according to one embodiment of the invention.  
         [0018]      FIG. 2  is a flowchart illustrating steps that may be followed in accordance with one embodiment of the invention in a fastening process.  
         [0019]      FIG. 3  is a flowchart of a pulse synchronized load stabilization subroutine indicated twice in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0020]     The invention will now be described with reference to the drawing figures, in which like reference will refer to like parts throughout. An embodiment in accordance with the present invention provides a computer program that operates a computer configured to control a fastening tool for fastening table fasteners. The computer program controls the tool to tighten the fasteners to a predetermined level of torque.  
         [0021]      FIG. 1  illustrates an example of a tool  10  controlled by a controller  12  in accordance with the invention. The tool  10  shown in  FIG. 1  is a wheel nut multiple. The tool  10  is referred to as a multiple because the tool  10  tightens multiple fasteners at one time.  FIG. 1  illustrates one use of the tool  10  in accordance with the invention. The tool  10  is used on a car wheel  14  to tighten lug nuts  16  on lug nut bolts  18 . Multiple lug nuts  16  are tightened by the tool  10  at one time.  
         [0022]     As shown in  FIG. 1 , sockets  20  are placed over the lug nuts  16  to tighten the lug nuts  16 . The sockets  20  are attached to sliding spindles  22 . The sliding spindles  22  are spring loaded in order to permit the socket  20  to continue to stay in communication with the lug nut  16  as the lug nut  16  is tightened down on the lug bolt  18 . The sliding spindle  22  is supported by sliding spindle supports  24  which are attached to a plate  26 .  
         [0023]     A transducer  28  is located around shafts which are connected to the sliding spindle  22 . The transducer  28  measures torque that is being applied to the lug nuts  16 . The transducer  28  uses strain gages to mechanically measure the torque applied to the lug nut  16 .  
         [0024]     A gearing assembly  30  transfers power from the motor assembly  32  to the sliding spindle  22 . The gearing assembly  30 , in some embodiments, maybe modular and may be removed and replaced by another gearing assembly  30  to provide different gear ratios to provide more torque and less speed or less torque and more speed according to an operator&#39;s desire or requirements of a particular system.  
         [0025]     In one embodiment, the motor  32  provides high shaft speed but relatively low torque is delivered to the sliding spindles  60 . The gearing assembly  30  provides lower speed and a higher amount of torque. In one embodiment of the invention, the gearing assembly provides a 25:1 reduction in speed. The motor  32  is a direct current (DC) brushless motor, and there is a motor  32  and gearing assembly  30  for each sliding spindle  22 .  
         [0026]     An intelligent tool interface  34  and a PC board  36  are attached to the motor assembly  32  in order to provide power and control to the motor  32 . The intelligent tool interface  34  and the PC board  36  are connected to a controller  12  through a power connection  38  and control connection  40 . The control connections  40  provide torque feedback, motor commutation and other data to the controller  12  so that the controller  12  can run the motor  32  at the desired speed and power levels. The power connections  38  provide operating power to the motor  32 . In some embodiments of the invention, the power connections  38  to the motor  32  may be directly connected to a power source and not connected to a power source via controller  12 .  
         [0027]     Operation of the wheel nut multiple tool  10  includes programming a control sequence into the controller  12 . In some embodiments of the invention, the controller  12  is a field programmable microcontroller which may include a PC computer or any other programmable type of controller. In other embodiments of the invention, the controller  12  is not programmable but includes hardware and/or software to control the wheel nut multiple tool  10  according to a preprogrammed program.  
         [0028]     To attach the tool  10  to the fasteners to be tightened, an operator brings the fasteners to be tightened in close proximity to the sockets  20 . The sockets  20  may be turned so that they align with the lug bolts  18  by having an operator turn the handle  42 .  
         [0029]     The tool  10  permits limited movement of the handle  42  which, in turn, turns or rotates the sliding spindle  22  and sockets  20  in order to permit them to align with the lug bolts  18  and lug nuts  16 . Once the sliding spindle  22  and sockets  20  are aligned with the lug nuts  16  and lug bolts  18 , the wheel  14  is brought closer to the tool  10 . In some embodiments of the invention, the sockets  20  may extend toward the lug nuts  16  and capture them within a cavity  44  inside the socket  20 . Once the sockets  20  are engaged with the lug nuts  16 , the tool  10  is engaged and tightens the lug nuts  16  in accordance with control signals received from the controller  12 .  
         [0030]     While the illustrated embodiment shown in  FIG. 1  is a wheel nut multiple tool  10 , other types of tools may be used in accordance with the invention. In general, any type of tool for rotating fasteners were a torque level applied to the fastener is desired to be at a predetermined level, may be used in accordance with the invention. Although lug nuts  16  are shown and described herein, any type of relating fastener may be torqued in accordance with the invention.  
         [0031]     The controller  12  will control the tool  10  in accordance with instructions programmed in the controller  12 . In some embodiments of the invention, the control sequence programmed on the controller  12  includes a fastening cycle  46 .  
         [0032]      FIG. 2  is a flow diagram of the fastening cycle  46 . The first step in the fastening cycle  46 , step  48 , is to input certain parameters into the controller  12 . The parameters in some embodiments of the invention are the synchronization torque, the target torque, the pulse synchronous load stabilization (PSLS) current (N %), PSLS dwell (T milliseconds), and PSLS repeat (X). These parameters can be changed from job to job and are set according to individual needs of a specific set of fasteners to be tightened and torqued by the tool  10 . For example, the synchronization torque (the torque level the fasteners are to be when the synchronous load stabilization routine is run a first time) must be chosen and entered into the controller  12 . The target torque (the torque level the fasteners are to be when starting the pulse synchronous load stabilization routine is run a final time) also must be determined and entered.  
         [0033]     Another parameter is the PSLS current (N %) with high and low load thresholds is determined and entered into the controller  12 . The high and low load thresholds are related to the fact that applying current to a motor  32  is a rough approximation of how much torque is applied on the fastener. However, because the fasteners often have torque applied, even when the fastener is not moving due to friction and other reasons, a high and low amount of current applied to the motor  32  which will still not turn the fastener, is determined. The high and low are generally considered a plus and minus of some percentage of an average torque load.  
         [0034]     Another programmable parameter is the PSLS dwell (T milliseconds). The PSLS Dwell is how many milliseconds to apply or dwell at the low threshold on the fastener. Also, a number of pulses of current that are applied to the motor  32  which results in pulses of torque applied to the fasteners is a programmed parameter.  
         [0035]     The PSLS repeat (X) is the amount of times the dwell synchronizing pulse process is repeated. The synchronizing pulse process may not be repeated as many times as indicated by the PSLS repeat parameter if the target torque is achieved before the process is repeated PSLS (X) times.  
         [0036]     Once these parameters have been determined according to the individual circumstances of the fasteners and entered into the controller  12 , the next step  49  is to determine if the fastening cycle will be run. If so, the next step  50  is to run the tool  10  at a high speed velocity control mode. In this mode, the velocity at which the fasteners are turned is controlled and the fastener is turned at a high rate of speed down to where the fastener contacts what the fastener will ultimately be urging against (which is a wheel rim  14  in the illustrated embodiment). Turning the fastener until it initially contacts what the fastener will ultimately urge against is called the rundown process. Step  52  is to measure the current applied or delivered to the motor  32  during the running of the tool  10  in the high speed velocity control mode. Current applied or delivered to the motor  32  is a rough approximation of the torque applied to the fastener. Thus, steps  50  and  52  are occurring simultaneously in some embodiments of the invention. In other embodiments of the invention, they may be done sequentially.  
         [0037]     Once the current delivered to the motor  32  has been measured as in step  52 , the next step, step  54  is to compare torque transducer  28  reading input into the computer/controller  12  versus the synchronization torque set point. If the torque transducer reading is less than the synchronization torque set point, then the tool  10  will continue to run in a high velocity control mode, and the current delivered to the motor  32  is monitored (steps  50  through  54  are repeated). If the measured torque transducer reading is indicative that the torque is at the torque set point, then the pulse synchronize load stabilization subroutine (step  56 ), as illustrated in  FIG. 3 , is applied.  
         [0038]     The pulse synchronize load stabilization subroutine  56  is done after the high and low thresholds have been set up and determined and programmed into the controller  12  as in step  66 . In some embodiments of the invention, the high and low thresholds are determined and set up in step  48  (see  FIG. 2 ). The thresholds are used to approximate a peak load on the fastener based on measured peak current plus or minus a programmed percentage. Next, the low current threshold is applied to the tool&#39;s motor  32  which applies a low threshold of torque as illustrated by step  68  in  FIG. 3 . Applying the current at the low threshold will maintain torque on the fastener, without overshooting the programmed torque load. The motor  32  will dwell at the low threshold amount of current for some amount of time (T) in milliseconds (step  70  in  FIG. 3 ). The time (T) program parameter is set by a tool operator.  
         [0039]     The next step  72 , is where all the spindles  22  are synchronized. The torque on each spindle  22  is determined by the transducer  28 , and reported to the controller  12  via the intelligent tool interface  34 . The controller  12  determines if all the spindles  22  have reached the synchronization torque, and have dwelt in the torque threshold for a minimum amount of time. If the spindles  22  are synchronized, then the next step, as illustrated in step  78 , is accomplished where the tool  10  is pulsed in velocity-control mode, and each pulse of current sent to the motor  32  will cause the fastener to turn slightly, thus a dynamic measure of torque may be determined by the transducer  28 . Once all the spindles  22  have synchronized at their dwell point, the tool  10  is operated at very low speed velocity mode, and the spindle  22  is turned less than one degree to determine the dynamic torque on the joint. This stabilizes the clamp force or the load on the fastener.  
         [0040]     The next step, as illustrated as  80  in  FIG. 3 , is to repeat the apply current at low threshold (i±N %) step  68  and continue through the subroutine  56  back to step  80  a predetermined amount of times as programmed previous to the commencement of the pulse synchronize load stabilization  56  subroutine.  
         [0041]     Returning now to step  72  shown in  FIG. 3 , if all the spindles  72  are not synchronized, then extra steps, step  74  and  76  are taken. In step  74 , current is applied at a high threshold. As illustrated as step  76  in  FIG. 3 , the transducer  28  reads the torque load with the high current threshold to determine if it exceeds the programmed torque level. The transducer  28  is monitored by the controller  12  during the high threshold dwell to provide a more accurate torque threshold, and guarantee the joint does not overshoot its programmed torque. If the transducer  28  reading does not exceed the program torque, then the subroutine returns to step  72  to determine if all the spindles  22  are synchronized. If the transducer  28  reading indicates that the programmed torque has been exceeded, then current is applied at the low threshold as indicated in step  68 , and then the subroutine continues from step  68  until the end of the synchronous load stabilization step  82  is achieved.  
         [0042]     Once the pulse synchronize load stabilization  56  subroutine has been run then, and the low speed velocity control mode as indicated by step  58  in  FIG. 2  is run. The tool  10  is run in the low speed run to approach the final target torque. Then as indicated by step  60 , the current is measured during the tightening process of running the tool  10  in the low speed velocity control mode of step  60 .  
         [0043]     At this point, the torque transducer reads the torque on the spindle  22 . If the torque or the spindles  22  achieves the final torque target, then the pulse synchronize load stabilization  56  is again run, and once run a second time, the cycle of fastening is then completed. However, if the torque transducer reading, as measured in step  62 , does not reach the final target torque, then the tool  10  continues to run in a low speed velocity control mode is indicated by step  58 , and the current delivered to the motor  32  is continues to be measured as indicated by step  60 . And again as indicated by step  62 , the torque transducer reading is compared against the final target torque.  
         [0044]     If the torque transducer reading is at or greater than the final target torque, then the pulse synchronous load stabilization routine  56  is run a predetermined number of times, or until a final torque value for all of the fasteners is met. The fastening cycle is then ended (step  64 ).  
         [0045]     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.