Method for monitoring proper fastening of an article of assembly at more than one location

Abstract

A more reliable and fool-proof method and apparatus for assembling an article of assembly (e.g. with predetermined screw torque requirements) in which the article of assembly has multiple fastening locations. The method comprises holding the article of assembly fixed while providing at least two different types of targets fixed relative to the article of assembly that correspond to the individual fastening locations. Fasteners are fastened into the article of assembly at the fastening locations. When fastening is occurring at one of the fastening locations, one of the targets is being sensed. Based on the target sensed, a target output is generated that differentiates between different types of targets thereby indicating fastening location of the fastening tool. The electronic target output is used for electronic control such as for stopping a conveyor to keep the article of assembly at an assembly station until the fastening operations have been completed.

What is claimed is: 
     
       1. A method for assembling an article of assembly, the article of assembly having a plurality of fastening locations including first and second fastening locations in spaced apart relation, comprising:
 holding the article of assembly in a predetermined position;   providing a plurality of targets including at least a first target fixed relative to the article of assembly corresponding to the first fastening location of the article of assembly and a second target fixed relative to the article of assembly corresponding to the second fastening location, the second target having a different characteristic than the first target;   manually fastening fasteners into the article of assembly at the first and second fastening locations; and   sensing the first and second targets when said fastening is occurring at the first and second locations, respectively, and generating an electronic target output based upon said sensing that differentiates between the first and second targets thereby indicating when a fastening tool is in either of the first and second fastening locations.   
     
     
       2. The method of  claim 1  further comprising conveying the article of assembly through an assembly station. 
     
     
       3. The method of  claim 2  further comprising:
 intermittently stopping the article of assembly at the assembly station for said fastening; and 
 monitoring the location of said fastening to ensure proper fastening of fasteners at the fastening locations. 
 
     
     
       4. The method of  claim 3  further comprising:
 maintaining the fixture at the assembly station and not releasing the fixture for further conveying out of the assembly station until the fastening tool has properly fastened fasteners into the article of assembly at the first and second fastening locations. 
 
     
     
       5. The method of  claim 4 , wherein the fasteners are threaded fasteners, further comprising:
 measuring torque applied to the fasteners;   electronically indicating measured torque applied to the fasteners at at least one of the fastening locations;   determining the location of said fastening that corresponds to the indicating of measured torque;   electronically comparing measured torque with predetermined torque values for the at least one of the fastening locations; and   providing an output indicating whether the predetermined torque values for at least one of the fastening locations have been reached.   
     
     
       6. The method of  claim 5 , further comprising:
 releasing the article of assembly and conveying the article of assembly out of the assembly station when the predetermined torque values have been reached.   
     
     
       7. The method of  claim 1 , further comprising:
 monitoring a sequence of said fastening;   electronically comparing the monitored sequence with a predetermined sequence of fastening among the fastening locations; and   providing a sequence output indicating whether the predetermined sequence has been achieved.   
     
     
       8. The method of  claim 2  further comprising transporting the articles of assembly through the assembly station substantially without stopping on a continuous basis. 
     
     
       9. The method of  claim 8 , further comprising:
 providing at least two types of first and second targets, each different type corresponding to one of the articles of assembly;   generating said target output that differentiates between the at least two types of first and second targets; and   electronically determining the article of assembly subject to said fastening by differentiating between the different types of the first and second targets.   
     
     
       10. The method of  claim 8  wherein the assembly station has an input location receiving fixtures from an upstream station and an output location delivering fixtures to a downstream station, wherein said fastening is conducted in a range between the input location and the output location, further comprising:
 electronically sensing when articles of assembly are exiting the assembly station and providing a fixture position output indicating when fixtures have exited the assembly station through the output location; 
 electronically determining whether said fastening has been properly conducted on each article of assembly exiting the assembly station; and 
 outputting an electronic alarm signal when one of the articles of assembly has exited the assembly station without proper fastening at the first and second fastening locations. 
 
     
     
       11. The method of  claim 10 , further comprising temporarily stopping the conveying of the articles of assembly in response to the electronic alarm signal so corrective action may be performed on the article of assembly. 
     
     
       12. The method of  claim 10 , wherein the fasteners are threaded fasteners, wherein said proper fastening comprises:
 measuring torque applied to the fasteners;   electronically indicating measured torque applied to the fasteners at at least one of the fastening locations;   determining the location of said fastening that corresponds to the indicating of measured torque;   electronically comparing measured torque with predetermined torque values for the at least one of the fastening locations; and   providing an output indicating whether the predetermined torque values for at least one of the fastening locations have been reached.   
     
     
       13. The method of  claim 10  wherein said proper fastening comprises:
 monitoring a sequence of said fastening; 
 electronically comparing the monitored sequence with a predetermined sequence of fastening among the first and second fastening locations; and 
 providing a sequence output indicating whether the predetermined sequence has been achieved. 
 
     
     
       14. The method of  claim 10  further comprising:
 assigning adjacent articles of assembly different types of the first and second targets for purposes of differentiation according to a predetermined fixture sequence; 
 determining the article of assembly subject to fastening operations based upon the predetermined sequence. 
 
     
     
       15. The method of  claim 1  wherein said sensing is accomplished with a machine vision camera and wherein the targets have different visual characteristics, further comprising electronically differentiating between the different visual characteristics contained in the electronic target output to determine the location of the fastening tool. 
     
     
       16. The method of  claim 15  wherein the targets are selected from the group consisting of geometric shapes, colors and alphanumeric characters. 
     
     
       17. The method of  claim 2  wherein said sensing is accomplished with a laser and laser sensing device, said fastening being accomplished with the fastening tool movable in a plane spaced from the article of assembly to selectively position the fastening tool at the fastening locations, the laser and laser sensing device being movable with the fastening tool in said plane, the targets comprising reflective material spaced at different distances perpendicular to said plane. 
     
     
       18. The method of  claim 17  wherein the fastening tool plunges along a fastening axis perpendicular to said plane, the laser and laser sensing device remaining stationary during plunging of the fastening tool. 
     
     
       19. The method of  claim 18  wherein the article of assembly is carried by a conveyor, the fastening tool being movable horizontally relative to the conveyor, the laser and laser sensing device being restricted to horizontal movement along a horizontal axis along with the fastening tool, further comprising a reflective panel extending in the horizontal axis in reflective communication with the laser and laser sensing device with a reflective surface aligned at an oblique angle relative to said plane providing the targets. 
     
     
       20. The method of  claim 1  wherein the article of assembly comprises an automotive seat comprised of at least two parts, the fasteners comprising threaded fasteners for fastening the at least two parts together. 
     
     
       21. The method of  claim 1  further comprising:
 enabling the fastening tool when one of the targets is sensed; and 
 disabling the fastening tool when none of the targets are sensed. 
 
     
     
       22. A method for assembling an article of assembly, the article of assembly having a plurality of fastening locations including first and second fastening locations in spaced apart relation, comprising:
 holding the article of assembly in a predetermined position;   manually fastening fasteners into the article of assembly using a fastening tool at the first and second fastening locations according to a predetermined fastening sequence;   sensing the position of the fastening tool;   electronically comparing the sensed position of the fastening tool with a predetermined sequence of fastening among the first and second fastening locations; and   providing a sequence output indicating whether the predetermined sequence has been achieved.   
     
     
       23. The method of  claim 22 , wherein the article of assembly comprises a vehicle seat. 
     
     
       24. The method of  claim 22 , further comprising enabling the fastening tool when the fastening tool is at one of the first and second locations and a predetermined fastening sequence is followed, and disabling the fastening tool when the predetermined fastening sequence is not followed. 
     
     
       25. The method of  claim 24 , further comprising disabling the fastening tool when not at a fastening location. 
     
     
       26. The method of  claim 24 , further comprising monitoring torque applied during said manual fastening, providing an electronic torque output indicating whether at least one predetermined torque value has been reached. 
     
     
       27. The method of  claim 26 , enabling the fastening tool when the fastening tool is at one of the first and second locations and a predetermined fastening sequence is followed, and disabling the fastening tool when the predetermined fastening sequence is not followed. 
     
     
       28. The method of  claim 27 , further comprising disabling the fastening tool when a predetermined torque value is not reached for one of the fastening locations in the predetermined sequence and the fastening tool is at a fastening location other than said one of the fastening locations. 
     
     
       29. The method of  claim 22 , wherein said sensing comprises sensing targets including first and second targets arranged in relation to the first and second fastening locations, the first and second targets being sensed when said fastening is occurring at the first and second fastening locations, respectively; and generating an electronic target output based upon said sensing that differentiates between the first and second targets thereby indicating when the fastening tool is in either of the first and second fastening locations. 
     
     
       30. The method of  claim 29 , wherein said sensing is conducted with one of a machine vision camera and a laser sensing device. 
     
     
       31. A method for assembling components of an article of assembly, the method comprising the steps of:
 providing at least first and second physically separate components that, when assembled together, form at least a portion of the article of assembly, wherein
 (a) a single set of discrete portions of the first and second components, when placed together, form a single process site consisting of a plurality of fastening locations within the single process site including first and second fastening locations, 
 (b) each of the first and second fastening locations consists of a single opening for receiving a single fastener that, when fastened in the single opening, partially assembles the first and second components together, and 
 (c) wherein the article of assembly is structurally designed so that the first and second fastening locations are positioned within the single process site in spaced apart relation to each other such that a fastener must be inserted in the first fastening location before a fastener is inserted in the second fastening location to reduce the risk of structural failure of the assembled combination of the first and second components that would arise if a fastener were inserted in the second fastening location before a fastener were inserted in the first fastening location, 
   holding the first and second components of the article of assembly in a predetermined position in which the first and second components are placed together to form the single process site;   manually fastening fasteners into the first and second fastening locations of the article of assembly using a fastening tool;   providing an electronic controller having stored in a memory thereof before an operator has commenced any aspect of manually fastening fasteners using the fastening tool
 (a) data representative of the location of the first fastening location within the single process site together with first order data indicating that a fastener must be inserted in the first fastening location at a point in time before a fastener is inserted in the second fastening location, and 
 (b) data representative of the location of the second fastening location within the single process site together with second order data indicating that a fastener must be inserted in the second fastening location at a point in time after a fastener has been inserted in the first fastening location, 
 wherein the location data and the first and second order data for the first and second fastening locations from a predetermined fastening sequence that must be followed in order for the first and second components to be assembled together in a manner that reduces the risk of structural failure of the assembled combination that would arise if a fastener were inserted in the second fastening location before a fastener were inserted in the first fastening location; 
   sensing the position of the fastening tool;   electronically comparing the sensed position of the fastening tool with the data representative of the location of the first and second fastening locations to determine if the fastening tool is located in operative relation to one of the first and second fastening locations and then using the order data associated with the one of the first and second fastening locations to ensure the operator's use of the fastening tool conforms to the predetermined sequence of fastening among the first and second fastening locations by
 (a) enabling the fastening tool, when it is positioned in operative relation to the first fastening location, to insert a fastener in the first fastening location only if the operator has not inserted a fastener in the second fastening location, and 
 (b) enabling the fastening tool, when it is positioned in operative relation to the second fastening location, only if the operator already has inserted a fastener in the first fastening location, 
 which reduces the risk of structural failure of the assembled combination that would arise if a fastener were inserted in the second fastening location before a fastener were inserted in the first fastening location; 
   providing a sequence output each time that the operator attempts to fasten a fastener in one of the first and second fastening locations indicating whether the predetermined fastening sequence has been achieved;   wherein the electronic controller also has stored in its memory first and second predetermined torque values that represent torque values that the operator is supposed to apply to fasteners inserted in the first and second fastening locations when the operator's use of the fastening tool conforms to the predetermined sequence of fastening; and   when the operator's use of the fastening tool conforms to the predetermined sequence of fastening,
 (a) measuring torque applied to fastener by the fastening tool as it is being fastened in the first fastening location and then comparing the measured torque to the first predetermined torque value, 
 (b) requiring that the torque applied to the fastener located in the first fastening location equal the first predetermined torque value before the operator is allowed to insert a fastener in the second fastening location, which reduces the risk of structural failure of the assembled combination that would result if the operator were allowed to insert a fastener in the second fastening location when the torque applied to the first fastener does not equal the first predetermined torque value, 
 (c) measuring torque applied to a fastener by the fastening tool as it is being inserted in the second fastening location and then comparing the measured torque to the second predetermined torque value, and 
 (d) requiring that the torque applied to the fastener located in the second fastening location equal the second predetermined torque value after the first fastener has been inserted in the first fastening location at the first predetermined torque value, which reduces the risk of structural failure of the assembled combination that would result if the operator were allowed to complete assembly of the first and second components when the torque applied to the fastener inserted in the second fastening location did not equal the second predetermined torque value. 
   
     
     
       32. The method of claim 31, wherein the electronic comparison step also includes disabling the fastening tool from performing a fastening operation when it is located at the first fastening location if the operator already has applied a first fastener in the first fastening location with a torque that equals the first predetermined torque. 
     
     
       33. The method of claim 32, wherein the article of assembly comprises a vehicle seat. 
     
     
       34. The method of claim 31, further comprising the step of disabling the fastening tool when it is not disposed in operative relation to a fastening location. 
     
     
       35. The method of claim 31, wherein the first component comprises a seat track. 
     
     
       36. The method of claim 31, wherein the first component comprises a base frame. 
     
     
       37. The method of claim 31, wherein each fastener consists of a threaded fastener. 
     
     
       38. The method of claim 37, wherein each threaded fastener consists of a threaded bolt. 
     
     
       39. The method of claim 31, wherein the first and second components of the article of assembly are provided by means of a continuous moving line conveyor. 
     
     
       40. The method of claim 31, wherein the first and second components of the article of assembly are provided by means of an intermittent conveyor line. 
     
     
       41. The method of claim 31, wherein the first and second components are mounted on an unassembled base frame. 
     
     
       42. The method of claim 41, wherein the holding step comprises clamping the unassembled base frame into a fixture. 
     
     
       43. The method of claim 42, wherein the fixture and unassembled base frame are provided by means of a continuous moving line conveyor. 
     
     
       44. The method of claim 42, wherein the fixture and unassembled base frame are provided by means of an intermittent conveyor line. 
     
     
       45. The method of claim 31, wherein a third fastening location is positioned in spaced apart relation to the first and second fastening locations, the third fastening location consisting of a single opening for receiving a single fastener. 
     
     
       46. The method of claim 45, wherein the predetermined sequence of fastening is for all of the first, second, and third fastening locations. 
     
     
       47. The method of claim 31, wherein the fastening tool forms a part of an assembly station, the method further comprising the step of requiring the first and second components to remain in the assembly station until after it is verified that (a) the operator's use of the fastening tool conformed to the predetermined sequence of fastening for the single process site, and (b) torque values equal to the first and second predetermined torque values were applied to fasteners located in the first and second fastening locations when the operator's use of the fastening tool conformed to the predetermined sequence of fastening for the single process site. 
     
     
       48. The method of claim 47 further comprising the step of producing an alarm simultaneously with when an attempt is made to remove the first and second components from the assembly station before it is verified that (a) the operator's use of the fastening tool conforms to the predetermined sequence of fastening for the single process site, and (b) torque values equal to the first and second predetermined torque values were applied to fasteners located in the first and second fastening locations when the operator's use of the fastening tool conformed to the predetermined sequence of fastening for the single process site. 
     
     
       49. The method of claim 48 wherein the assembly system further comprises a stop mechanism that requires the first and second components to remain in the assembly station. 
     
     
       50. The method of claim 49, wherein the stop mechanism prevents removal of the first and second components from the assembly station. 
     
     
       51. The method of claim 50, wherein the first and second components are carried by a conveyor into and out of the assembly station the movement of which is stopped by the stop mechanism. 
     
     
       52. The method of claim 51, wherein the conveyor comprises an intermittent conveyor. 
     
     
       53. The method of claim 51, wherein the conveyor comprises a continuous conveyor. 
     
     
       54. The method of claim 31, wherein the first and second components comprise components of a vehicle seat. 
     
     
       55. The method of claim 48, wherein the alarm is given as a result of the attempt to remove the first and second components of the assembly station.