Patent Publication Number: US-11046525-B2

Title: Vehicle body tracking system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of non-provisional U.S. patent application Ser. No. 15/815,915, filed on Nov. 17, 2017, which claims priority to and the benefit of Korean Patent Application No. 10-2017-0088168, filed on Jul. 12, 2017, the entirety of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a vehicle assembly system. More particularly, the present disclosure relates to a vehicle body tracking system and method of a vehicle assembly line. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Generally, in a chassis process, a trim process, and a final process of a design assembly line of a vehicular mass production plant, design parts including various internal and external design parts of a vehicle are assembled to a vehicle body. 
     That is, in a chassis process line, a trim process line, and a final process line of the design assembly process, various parts are assembled to the vehicle body. In each of these design process lines, for example, a hanger assembly (also referred to as “P&amp;F conveyor” in the art) is used to transfer the vehicle body along a predetermined transferring section to mount the parts on the vehicle body. 
     In this case, in each of the design process lines, a vehicle body entering a process pitch section divided by an interval set along the transferring direction of the vehicle body is detected. As a device for detecting the vehicle body, there may be a barcode scanner that detects a barcode attached to the vehicle body and identifies a vehicle identification number of the vehicle body. 
     Therefore, in the prior art, the barcode of the vehicle body entering each design process line is scanned through the barcode scanner, thus it is possible to detect in which process pitch interval the vehicle body is positioned in each design process line. 
     However, we have discovered that the conventional bar code scanner simply detects whether the vehicle has entered the process pitch section of the design process line, but cannot accurately determine a position of the vehicle in the design process line. In the related art, the effectiveness of assembling history management is undermined. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure provides a vehicle body tracking system and method of a vehicle assembly line that may precisely determine positions of vehicle bodies transferred to preset process sections of the assembly line in real time. 
     An exemplary form of the present disclosure provides a vehicle body tracking system of a vehicle assembly line for determining, in real time, a position of a vehicle body transferred to process sections divided by a predetermined pitch along an assembly line of a vehicle. The vehicle body tracking system includes: a vehicle body detecting unit configured to be installed at a starting point of the vehicle assembly line and configured to detect the vehicle body; an encoder unit provided at a conveyor unit that travels along the assembly line and transfers the vehicle body and configured to detect a rotation amount of a rotating body rotated by a traveling body of the conveyor unit; and a controller configured to receive a detection signal from the vehicle body detecting unit to acquire identification information of the vehicle body and configured to calculate a moving distance of the vehicle body for each process section by receiving the detection signal from the encoder unit. 
     The vehicle body detecting unit may include a barcode scanner that recognizes a barcode attached to the vehicle body. 
     The barcode scanner may scan the barcode, generate a vehicle identification number of the vehicle body, and transmit the vehicle identification number to the controller. 
     The controller may display the vehicle identification number and the moving distance of the vehicle body, and a process section, according to the moving distance through a display unit. 
     The controller may reset a detection value of the encoder unit to zero (0) when the detection value detected by the encoder unit corresponds to the predetermined pitch of the process section. 
     Another form of the present disclosure provides a vehicle body tracking system of a vehicle assembly line provided at a conveyor unit for transferring a vehicle body along a vehicle assembly process line. The vehicle body tracking system includes: a mounting frame configured to be installed at a power rail of the conveyor unit; a pair of rotating bodies configured to be rotatably installed at the mounting frame; a driven chain configured to be combined to the pair of rotating bodies and a drive chain configured to travel along the power rail, the driven chain configured to travel on an endless track; and an encoder sensor installed at the mounting frame and configured to be connected to at least one rotating body of the rotating bodies, the encoder sensor configured to detect a rotation amount of the at least one rotating body to output the detected rotation amount to a controller. 
     The controller may receive the detected rotation amount from the encoder sensor and calculate a moving distance of the vehicle body for each process section. 
     The rotating body may include a sprocket engaged with the driven chain. 
     The driven chain may include a caterpillar chain. 
     Combination grooves combined with teeth of the sprocket may be continuously formed at an inner circumference of the caterpillar chain, and guide protrusions combined with the drive chain may be continuously formed at an outer circumference of the caterpillar chain. 
     The encoder sensor may be provided to be connected to a center of each rotating body. 
     The controller may receive the detected rotation amount from one of the encoder sensors connected to the rotating body. 
     A pair of chain guides guiding the traveling of the driven chain may be installed at the mounting frame. 
     The pair of chain guides may be disposed to face each other inside the driven chain. 
     The chain guide may be movably installed at the mounting frame through a guide rod. 
     The guide rod may be provided with a pressing spring pressing the chain guide in an outward direction of the driven chain. 
     The vehicle body tracking system of the vehicle assembly line may further include a take-up unit configured to be provided at the mounting frame to be connected to one of the rotating bodies and configured to apply tension to the driven chain through the rotating body. 
     The take-up unit may include a floating frame fixedly installed at the mounting frame, a pair of guide bars provided at the floating frame, a floating block slidably combined to the guide bar and rotatably supporting the rotating body, a floating spring installed at the guide bar between one side of the floating frame and one side of the floating block, and a tension adjusting bolt fastened to another side of the floating frame and supporting another side of the floating block. 
     Yet another form of the present disclosure provides a vehicle body tracking method for a vehicle assembly line for determining, in real time, a position of a vehicle body transferred by a conveyor unit to process sections divided by a predetermined pitch along an assembly line of a vehicle. The tracking method may include steps of: (a) setting a starting point of the assembling process line as a reference position and generating a vehicle identification number of a vehicle body through a vehicle body detecting unit at the reference position; (b) detecting a rotation amount of a rotating body rotated by a traveling body of the conveyor unit through an encoder unit; (c) calculating a moving distance of the vehicle body for each process section by receiving the detected rotation amount from the encoder unit; and (d) displaying, on a display unit, the vehicle identification number, the moving distance of the vehicle body, and a process section based on the moving distance. 
     The step (a) may include scanning a barcode attached to the vehicle body through a barcode scanner and generating the vehicle identification number of the vehicle body. 
     The step (b) may include resetting a detection value of the encoder unit to zero (0) when the detection value detected by the encoder unit corresponds to the predetermined pitch of the process section. 
     The step (c) may include calculating a moving distance of the vehicle body through a formula of A+(N×B)+C, where a position value of the reference position is referred to as “A”, a reset number of an encoder sensor is referred to as “N”, a pitch value of the process section is referred to as “B”, and a distance value according to the detected rotation amount of the encoder sensor is referred to as “C”. 
     The step (d), when a start process section at the reference position is displayed as a first process section through the display unit, may include displaying subsequent process sections as N+1 process sections through the display unit. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  illustrates a schematic view of a vehicle body tracking system of a vehicle assembly line; 
         FIG. 2  illustrates a bottom view of an encoder unit applied to a vehicle body tracking system of a vehicle assembly line; 
         FIG. 3  illustrates a perspective view of an encoder unit applied to a vehicle body tracking system of a vehicle assembly line; 
         FIG. 4  illustrates a perspective view of a take-up unit applied to a vehicle body tracking system of a vehicle assembly line; 
         FIG. 5  illustrates a flowchart of a vehicle body tracking method for a vehicle assembly line; and 
         FIG. 6  and  FIG. 7  illustrate schematic views for explaining a vehicle body tracking method for a vehicle assembly line. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
       FIG. 1  illustrates a schematic view of a vehicle body tracking system of a vehicle assembly line in an exemplary form of the present disclosure. 
     Referring to  FIG. 1 , a vehicle body tracking system  100  of a vehicle assembly line may be applied to a vehicle production process in which various parts are fastened and assembled to a vehicle body  1  that is transferred by predetermined intervals by a conveyor. 
     For example, the vehicle body tracking system  100  of the vehicle assembly line may be applied to a design assembling process in which parts such as an engine, a transmission, and a suspension device are assembled to corresponding assembly positions of the vehicle body  1  in a chassis process line and a trim process line, and in which other parts are assembled to the vehicle body  1  in a finishing process line. 
     However, the scope of the present disclosure is not limited to the vehicle production process in which parts are assembled to the vehicle body  1 , but a technical scope of the present disclosure may be applied thereto if various parts are assembled to various kinds and types of structures in the process. 
     Generally, in the related art, a vehicle body transferring direction is referred to as a T direction, a vehicle width direction is referred to as an L direction, and a height direction of the vehicle body is referred to as an H direction. However, in the exemplary form of the present disclosure, a reference direction is not based on the above-mentioned LTH directions, but on a vehicle body transferring direction, a vehicle body height direction, and a vehicle width direction. 
     Assembly process lines such as the chassis process line, the trim process line, and the design process line as described above include a conveyor unit  2  for transferring the vehicle body  1  to a process section divided by a predetermined constant pitch. 
     Here, the process section corresponds to a section in which the assembly process line is divided by a predetermined constant pitch along the transferring direction of the vehicle body  1 , and different parts may be assembled to the vehicle body  1  in each process section. 
     The conveyor unit  2  is also referred to as a P&amp;F chain conveyor in the art, and it includes a power rail  3  disposed along the assembly process line and a drive chain  4  traveling on an endless track along the power rail  3  by a drive motor. The conveyor unit  2  includes a hanger  7  connected to the drive chain  4  through a hanger carrier  5  and transferring the vehicle body  1  along a free rail  6 . 
     The conveyor unit  2  corresponds to a P&amp;F chain conveyor that is well-known and disclosed, for example, in Korean Patent Publication No. 2006-0118691, which is incorporated herein by reference. Thus, in the present specification, a detailed description thereof will be omitted. 
     The vehicle body tracking system  100  of the vehicle assembly line in one form of the present disclosure has a structure capable of precisely determining positions of vehicle bodies  1  transferred to the process sections of the assembly process line in real time. 
     For this, the vehicle body tracking system  100  of the vehicle assembly line includes a vehicle body detecting unit  10 , an encoder unit  20 , and a controller  90 . 
     The vehicle body detecting unit  10 , which detects the vehicle bodies  1  entering the assembly process line, is installed at a starting position of the assembly process line. 
     The vehicle body detecting unit  10  may include a barcode scanner  11  capable of recognizing a barcode  8  attached to the vehicle body  1  and identifying unique information (a vehicle identification number) of the vehicle body  1 . The barcode scanner  11  may scan the bar code  8  of the vehicle body  1  and generate the vehicle identification number of the vehicle body  1 . 
     In addition, the barcode scanner  11  may generate order information of the vehicle body  1  by using the vehicle identification number. The barcode scanner  11  transmits the generated vehicle identification number and order information to the controller  90 . 
     The barcode scanner  11  corresponds to a barcode reader that is well-known in the art, so in the present specification, a detailed description thereof will be omitted. 
     The encoder unit  20  detects a rotation amount of a rotating body rotated by a traveling body of the conveyor unit  2 , that is, the drive chain  4 . The encoder unit  20  is substantially included in the conveyor unit  2 . 
       FIG. 2  illustrates a bottom view of an encoder unit applied to a vehicle body tracking system of a vehicle assembly line as an exemplary form of the present disclosure, and  FIG. 3  illustrates a perspective view of an encoder unit applied to a vehicle body tracking system of a vehicle assembly line in one form of the present disclosure. 
     Referring to  FIG. 2  and  FIG. 3  together with  FIG. 1 , the encoder unit  20  includes a mounting frame  21 , a rotating body  23 , a driven chain  25 , and an encoder sensor  27 . 
     The mounting frame  21  mounts constituent elements described later, and it is installed at the power rail  3  of the conveyor unit  2 . The mounting frame  21  is disposed at the power rail  3  along the vehicle body transferring direction. In addition, the mounting frame  21  may be formed as one frame or two or more divided frames. 
     The mounting frame  21  may include various parts such as a bracket, a bar, a rod, a plate, a block, a rail, a collar, and the like for supporting constituent elements described later. 
     Since the various parts are those for installing each constituent element at the mounting frame  21  described in detail later, they are generally referred to as the mounting frame  21  except in special cases. 
     A pair of rotating bodies  23  are rotatably installed at the mounting frame  21  with a predetermined interval therebetween. The rotating body  23  includes a sprocket  29  having sprocket teeth  24  engaged with the driven chain  25 . 
     The driven chain  25  is connected to the pair of rotating bodies  23  so as to be able to travel on an endless track. The driven chain  25  is combined with the drive chain  4  traveling along the power rail  3  of the conveyor unit  2  The driven chain  25  includes a caterpillar chain  31 . 
     Combination grooves  33  combined with the sprocket teeth  24  of the sprocket  29  are continuously formed at an inner circumference of the caterpillar chain  31 . Guide protrusions  35  combined with the drive chain  4  are continuously formed at an outer circumference of the caterpillar chain  31 . 
     Accordingly, when the drive chain  4  transfers the vehicle bodies  1  to the process section of the assembly process line through the hanger  7  while traveling, the caterpillar chain  31  is combined with the drive chain ( 4 ) through the guide protrusion  35  and travels on an endless track through the sprocket  29 . In addition, the caterpillar chain  31  is combined with the sprocket teeth  24  of the sprocket  29  through the combination grooves  33  and rotates the sprocket  29 . 
     Reference numeral  39  which is not explained in the drawings denotes a guide roller assembly installed at the mounting frame  21 . The guide roller assembly  39  guides traveling of the drive chain  4 , and has a plurality of guide rollers for inhibiting drooping and separation of the drive chain  4 . 
     The encoder sensor  27  detects a rotation amount of the sprocket  29  as a pulse value and outputs the detected value to the controller  90 , and it is installed at the mounting frame  21  so as to be connected to at least one of the pair of sprockets  29 . 
     For example, the encoder sensor  27  is provided to be connected to a center of each sprocket  29  and includes a sensor end which is connected to the sprocket  29 . The sensor end may be rotated together with the sprocket  29  in a state of being fixed to the sprocket  29 , or may be positioned at a center of the sprocket  29  in a state of being fixed to a separate stationary body. 
     The encoder sensor  27  corresponds to a photoelectric linear encoder sensor or a rotary encoder sensor that is well-known in the art, so in the present specification, a detailed description thereof will be omitted. 
     In one form, the mounting frame  21  is provided with a pair of chain guides  41  for guiding the traveling of the caterpillar chain  31 . The pair of chain guides  41  are disposed to face each other inside the caterpillar chain  31 . 
     The chain guide  41  supports an inside portion of the caterpillar chain  31  traveling on an endless track, and functions to inhibit drooping and separation of the caterpillar chain  31 . 
     Further, for inhibiting the drooping or the separation of the caterpillar chain  31 , the chain guide  41  is movably installed in a direction in which it is moved away from or closer to the mounting frame  21  through a pair of guide rods  43 . 
     In this case, the guide rod  43  is provided with a pressing spring  45  for pressing the chain guide  41  in an outward direction of the caterpillar chain  31 . The chain guide  41  may press the caterpillar chain  31  outwardly with resilient force of the pressure spring  45  and may inhibit or prevent the caterpillar chain  31  from drooping or being separated from the drive chain  4 . 
     In another form, the vehicle body tracking system  100  of the vehicle assembly line further includes a take-up unit  50  for applying tension to the caterpillar chain  31  through the sprocket  29 . 
       FIG. 4  illustrates a perspective view of a take-up unit applied to a vehicle body tracking system of a vehicle assembly line in an exemplary form of the present disclosure. 
     Referring to  FIG. 2  to  FIG. 4 , the take-up unit  50  is provided at the mounting frame  21  so as to be connected to one of the sprockets  29 . The take-up unit  50  has a structure that may inhibit floating of the sprocket  29 , inhibit drooping of the caterpillar chain  31 , and absorb a sudden overload of the caterpillar chain  31 . 
     For this, the take-up unit  50  includes a floating frame  51 , a pair of guide bars  53 , a floating block  55 , a floating spring  57 , and a tension adjusting bolt  59 . 
     The floating frame  51  is fixedly installed to the mounting frame  21  and is disposed in the vehicle body transferring direction. The pair of guide bars  53  are fixedly installed to the floating frame  51  in the vehicle body transferring direction. 
     The floating block  55  rotatably supports the sprocket  29 , and is slidably combined to the guide bar  53  in the vehicle body transferring direction. The floating spring  57  is installed at the guide bar  53  between one side of the floating frame  51  and one side of the floating block  55 . The tension adjusting bolt  59  is bolted to another side of the floating frame  51 , and supports another side of the floating block  55 . 
     In one form, the controller  90  (refer to  FIG. 1 ) includes a program, such as control logic, that controls an overall operation of the vehicle body tracking system  100 . 
     The controller  90  receives a signal from the barcode scanner  11  of the vehicle body detecting unit  10  to acquire a vehicle identification number of the vehicle body  1 , and receives a rotation amount detection value of the sprocket  29  from the encoder sensor  27  of the encoder unit  20  to calculate a moving distance of the vehicle body  1  for each process section. 
     In another form, the controller  90  may calculate the moving distance of the vehicle body  1  for each process section by receiving the rotation amount detection value of the sprocket  29  from one of the encoder sensors  27  provided in the sprockets  29 . 
     When the controller  90  determines that one of the encoder sensors  27  provided in sprockets  29  is malfunctioning, the controller  90  may receive the rotation amount detection value of the sprocket  29  from the encoder sensor  27  provided in another sprocket  29  to calculate the moving distance of the vehicle body  1  for each process section. 
     In addition, the controller  90  may reset the detection value of the encoder sensor  27  to 0 when a detection value corresponding to the pitch of the process section is detected by the encoder sensor  27  of the encoder unit  20 . This is to increase a lifespan and detection accuracy of the encoder sensor  27 . 
     Further, the controller  90  may display the vehicle identification number and the moving distance of the vehicle body  1 , and the process section according to the moving distance, through a display unit  91 . 
     Hereinafter, operations of the vehicle body tracking system  100  of the vehicle assembly line according to the exemplary form of the present disclosure and the vehicle body tracking method for the vehicle assembly line will be described in detail with reference to previously described drawings and other accompanying drawings. 
       FIG. 5  illustrates a flowchart of a vehicle body tracking method for a vehicle assembly line in an exemplary form of the present disclosure. 
     Referring to  FIG. 5  in addition to the above-described drawings, the vehicle body  1  transferred through a buffer section of the design assemble line enters into the assembly process line, for example, the chassis process line, the trim process line, the final process line, and the like. In this case, the assembly process line is continuously divided so that the process sections of the pitch set along the vehicle body transferring direction are provided therein. 
     In one form, the vehicle bodies  1  are transferred to the process sections of the assembly process line through the conveyor unit  2 , and in this case, the drive chain  4  first travels on the endless track along the power rail  3  by a drive motor. The guide roller assembly  39  guides the traveling of the drive chain  4  and inhibits the drive chain  4  from drooping and being separated. 
     Therefore, the hangers  7  connected to the drive chain  4  through the hanger carrier  5  may be transferred along the free rail  6  in a process advancing direction, and the vehicle body  1  mounted on the hanger  7  may be transferred in the process advancing direction. 
     In this case, a starting point of the assembly line is set as a reference position, and the bar code  8  of the vehicle body  1  is scanned through the barcode scanner  11  of the vehicle body detecting unit  10  at the reference position to generate the vehicle identification number of the vehicle body  1  and to transmit the vehicle identification number to the controller  90  (S 11 ). 
     During transferring of the vehicle body  1  through the conveyor unit  2  to the process section of the assembling process line, the caterpillar chain  31  is combined with the drive chain  4  through the guide protrusion  35  and travels on the endless track through the sprockets  29 . In addition, the caterpillar chain  31  is combined with the sprocket teeth  24  of the sprockets  29  through the combination groove  33  and rotates the sprockets  29 . 
     The caterpillar chain  31  is guided along the pair of chain guides and travels on an endless track. In this case, the chain guide  41  may press the caterpillar chain  31  outwardly with elastic force of the pressing spring  45  and may inhibit the caterpillar chain  31  from drooping or being separated from the drive chain  4 . 
     In addition, it is possible to inhibit the floating of the sprocket  29  through the take-up unit  50 , to inhibit the caterpillar chain  31  from drooping, and to absorb a sudden overload of the caterpillar chain  31 . 
     That is, since the floating block  55  rotatably supporting the sprocket  29  is supplied with the elastic force of the floating spring  57  in a state in which the floating block  55  is slidably combined with the guide bar  53 , it is possible to inhibit the floating and drooping of the sprocket  29  while applying tension to the caterpillar chain  31 , and it is possible to absorb an overload applied to the caterpillar chain  31 . 
     In this case, the rotation amount of the sprocket  29  is detected as a pulse value through the encoder sensor  27 , and the detected pulse value is output to the controller  90  (S 12 ). 
     When a detection value corresponding to the pitch of the process section is detected through the encoder sensor  27  (S 13 ), the controller  90  resets the detected pulse value through the encoder sensor  27  to 0 (S 14 ). Then, the controller  90  calculates the moving distance of the vehicle body for each process section of the assembly process line based on the detected value received from the encoder sensor  27  (S 15 ). 
     In this process, assuming that a position value of the above-mentioned reference position is referred to as “A”, a reset number of the encoder sensor  27  is referred to as “N”, a pitch value of the process section is referred to as “B”, and a distance value according to the rotation amount detection value of the encoder sensor  27  is referred to as “C”, a moving distance of the vehicle body  1  is calculated by a formula of A+(N×B)+C. 
     For example, as shown in  FIG. 6 , when a start process section at the reference position is referred to as a first process section (S 1 ) and subsequent process sections are referred to as second, third, . . . , etc. process sections (S 2 , S 3 , . . . ), the vehicle body  1  may be positioned in the third process section S 3  by the conveyor unit  2 . In this case, when a detection value corresponding to each pitch of the first and second process sections S 1  and S 2  is detected through the encoder sensor  27 , the controller  90  resets the encoder sensor  27  two times. 
     Therefore, the controller  90  may calculate the moving distance (mm) of the vehicle body  1  by the formula of A+(2×B)+C, wherein “C” represents a distance value according to the rotation amount detection value in the third process section S 3 . 
     In a case that the vehicle body  1  is positioned in the second process section S 2  by the conveyor unit  2 , when a detection value corresponding to the pitch of the first processing section S 1  is detected through the encoder sensor  27 , the controller  90  resets the encoder sensor  27  once. 
     Therefore, the controller  90  may calculate the moving distance (mm) of the vehicle body  1  by the formula of A+(1×B)+C, wherein “C” represents a distance value according to the rotation amount detection value in the third process section S 2 . 
     In addition, when the vehicle body  1  is positioned in the first process section S by the conveyor unit  2 , since the detection value corresponding to the pitch of the first processing section S 1  is not detected through the encoder sensor  27 , the controller  90  does not reset the encoder sensor  27 . 
     Therefore, the controller  90  may calculate the moving distance (mm) of the vehicle body  1  by the formula of A+(0×B)+C, wherein “C” represents a distance value according to the rotation amount detection value in the third process section S 1 . 
     Accordingly, in the exemplary form of the present disclosure, the moving distance of the vehicle body  1  positioned in the respective process sections may be calculated in the manner described above. 
     As shown in  FIG. 7 , the controller  90  displays respective vehicle identification numbers and moving distances of the vehicle bodies  1  and respective process sections according to the moving distance of the vehicle bodies  1  received from the bar code scanner  11 , through the display unit  91  (S 16 ). 
     In step S 16 , when a start process section at the reference position is displayed as the first process section S 1  through the display section  91 , subsequent process sections are displayed as the second, third, . . . (which are a reset number (N)+1 of the encoder sensor) sections (S 2 , S 3 , . . . ) through the display section  91 . 
     According to the vehicle body tracking system and method of the vehicle assembly line according to the exemplary form of the present disclosure described above, the position of the vehicle body  1  transferred to the set process sections of the assembly process line may be accurately determined in real time through the encoder unit  20 , thus it is possible to improve the assembly history management with high effectiveness and accuracy in the processes of fastening and assembling various parts to the vehicle body  1 . 
     While the present disclosure has been described in connection with what is presently considered to be practical exemplary forms, it is to be understood that the present disclosure is not limited to the disclosed forms, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the present disclosure.