System and method for controlling bobbin rotation in a sewing machine

Abstract

A sensing system for detecting motion of a bobbin used in a chain stitch type sewing machine using a needle on one side of a textile workpiece and a rotary bobbin positioned on an opposing side of the textile workpiece includes the bobbin being held in a bobbin case having a side panel forming an aperture. The rotary bobbin has a side surface with arcuate regions around a perimeter of the side surface. In addition, the sensing system includes the first and second optical sensors aligned to detect the presence of the first or second bobbin surface. The sensing system further includes a controller adapted to receive signals from the first and second optical sensors related to the presence of the first or second bobbin surface in the first or second regions and interpret the signals to provide the detecting motion of the bobbin.

What is claimed is: 
     
         1 . A sensing system for detecting motion of a bobbin used in a chain stitch type sewing machine apparatus of a type using a needle on one side of a textile workpiece and a rotary bobbin positioned on an opposing side of the textile workpiece, wherein the bobbin is held in a bobbin case having a side panel forming an aperture, comprising:
 the bobbin having a side surface with arcuate regions around a perimeter of the side surface, the side surface forming a plurality of first surfaces having a first color or reflectivity and a plurality of second surfaces having a second color or reflectivity, the first and second surfaces interleaved along arcuate radial regions with respect to an axis of rotation of the bobbin such that upon rotational movement of the bobbin, the first and second surfaces are alternatively exposed through the aperture;   a first optical sensor aligned to detect the presence of the first or second surface at a first region of the aperture;   a second optical sensor aligned to detect the presence of the first or second surface at a second region of the aperture, the first and second regions separated at differing radial positions with respect to the axis of rotation; and   a controller adapted to receive signals from the first and second optical sensors related to the presence of the first or the second surface in the first or the second regions and interpret the signals to provide the detecting motion of the bobbin.   
     
     
         2 . The sensing system in accordance with  claim 1 , further comprising the signals represent first and second discrete states wherein one of the first and the second discrete states is related to the presence of the first surface at one of the first and second regions and the other of the first and the second discrete states is related to the presence of the second surface at one of the first and second regions. 
     
     
         3 . The sensing system in accordance with  claim 2 , further comprising the side surface having three of the first surfaces and three of the second surfaces with each of the first and second surfaces extends over an arcuate range of 60° with respect to the axis of rotation. 
     
     
         4 . The sensing system in accordance with  claim 3 , further comprising the signals from the first and second optical sensors represent four potential combination codes of the first and the second discrete states. 
     
     
         5 . The sensing system in accordance with  claim 4 , further comprising the combination codes for the first and the second discrete states change twelve times in a complete single rotation of the bobbin. 
     
     
         6 . The sensing system in accordance with  claim 1 , further comprising the textile workpiece is a motor vehicle seat belt or airbag component and the sensing system is implemented to validate the integrity of a sewing process wherein proper rotation of the bobbin established by the sensing system signifies proper feeding of a sewing thread by the bobbin. 
     
     
         7 . A method of validating the integrity of a sewing process by detecting motion of bobbin used in a chain stitch type sewing machine apparatus of a type using a needle on one side of a textile workpiece and a rotary bobbin positioned on an opposing side of the textile workpiece, and having a bobbin case for enclosing the bobbin having a side panel forming an aperture, the method comprising the steps of:
 providing the bobbin having a side surface with arcuate regions around a perimeter of the side surface, the side surface forming a plurality of first surfaces having a first color or reflectivity and a plurality of second surfaces having a second color or reflectivity;   providing the first and second surfaces interleaved along arcuate radial regions with respect to an axis of rotation of the bobbin such that upon rotational movement of the bobbin, the first and second surfaces are alternatively exposed through the aperture;   providing a first optical sensor and aligning the first optical sensor to detect the presence of the first or second surface at a first region of the aperture;   providing a second optical sensor and aligning the second optical sensor to detect the presence of the first or second surface at a second region of the aperture, the first and second regions separated at differing radial positions with respect to the axis of rotation;   receiving signals from the first and second optical sensors related to the presence of the first or the second surface in the first or the second regions; and   processing and interpreting the signals to provide the detecting motion of the bobbin.   
     
     
         8 . The method in accordance with  claim 7 , further comprising the step of representing first and second discrete states as the signals wherein one of the first and the second discrete states is related to the presence of the first surface at one of the first and the second regions and the other of the first and second discrete states is related to the presence of the second surface at one of the first and second regions. 
     
     
         9 . The method in accordance with  claim 8 , further comprising the step of providing the side surface having three of the first surfaces and three of the second surfaces with each of the first and second surfaces extending over an arcuate range of 60° with respect to the axis of rotation. 
     
     
         10 . The method in accordance with  claim 9 , further comprising the signals from the first and second optical sensors represent four potential combination codes of the first and the second discrete states. 
     
     
         11 . The method in accordance with  claim 10 , further comprising the combination codes for the first and the second discrete states change twelve times in a complete single rotation of the bobbin. 
     
     
         12 . The method in accordance with  claim 7 , further comprising the steps of providing the textile workpiece in the form of a motor vehicle seat belt or airbag component, and a sensing system is implemented to validate the integrity of sewing processes wherein proper rotation of the bobbin established by the sensing system signifies proper feeding of a sewing thread by the bobbin.