Abstract:
A stitcher is provided that includes a needle to stitch a workpiece, a motor to operate the needle, and a stitch regulator in communication with and capable of controlling a speed of the motor. A controller is in communication with the stitch regulator. The stitcher also includes at least one accelerometer in communication with the controller to determine an acceleration of the stitcher with respect to the workpiece. A signal representing the acceleration of the stitcher with respect to the workpiece is utilized to adjust the operation of the needle as necessary.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to long-arm stitchers and, more particularly, to a control system for long-arm stitchers and the like. 
       RELATED ART 
       [0002]    Conventional long-arm sewing machines are generally used for quilting and/or sewing fabrics that are not easily moved through a sewing machine. As such, a long-arm sewing machine is designed to move with respect to a workpiece that is held stationary on a frame. However, the workpieces generally include two outer layers and a filler material that is sewn between the outer layers. Often, the filler being stitched into the workpiece is uneven, thereby adding to difficulties for a stitch regulator to properly control a velocity of the stitcher with respect to the workpiece. Moreover, the stitch design of the workpiece may include several different stitch types and/or a stitch pattern that is not straight, thereby complicating the ability to control the stitch pattern. Accordingly, the velocity of stitcher movement with respect to the workpiece must be varied during stitching to maintain a proper stitch length or number of stitches per inch of the workpiece. 
         [0003]    Typically, a stitch regulator is controlled by optical encoders that monitor the stitch pattern as it is being stitch into the workpiece. However, such encoders must be positioned adjacent the workpiece and may resultantly interfere with the stitching operation. In addition, optical encoders are costly and require a significant amount of assembly time. The assembly also generally includes harnesses and cabling to properly install the optical encoder. 
         [0004]    As such, it is desirable to control a stitch regulator utilizing a less costly and more easily assembled system that does not interfere with the stitching process. 
       SUMMARY OF THE INVENTION 
       [0005]    In one embodiment, a control system for a stitcher is provided that includes a motor driving the stitcher, and a stitch regulator in communication with and capable of altering a velocity of the motor. A controller is in communication with the stitch regulator; and at least one accelerometer is in communication with the controller to determine an acceleration of the stitcher with respect to a workpiece. A signal representing the acceleration of the stitcher with respect to the workpiece is communicated to the controller; and the operation of the stitch regulator is modified as necessary based on the signal. 
         [0006]    In another embodiment, a stitcher is provided that includes a needle to stitch a workpiece, a motor to operate the needle, and a stitch regulator in communication with and capable of controlling a speed of the motor. A controller is in communication with the stitch regulator. The stitcher also includes at least one accelerometer in communication with the controller to determine an acceleration of the stitcher with respect to the workpiece. A signal representing the acceleration of the stitcher with respect to the workpiece is utilized to adjust the operation of the needle as necessary. 
         [0007]    In a further embodiment a method of operating a stitcher is provided. The method includes providing a stitch regulator for controlling the operation of the stitcher, and providing an accelerometer in communication with the stitch regulator. An acceleration of the stitcher with respect to a workpiece is measured with the accelerometer, and a signal representing the acceleration of the stitcher is sent to the stitch regulator. The method further includes integrating the signal representing the acceleration of the stitcher to determine a velocity of the stitcher with respect to the workpiece, and controlling the stitch regulator utilizing the velocity of the stitcher with respect to the workpiece. 
         [0008]    Although the present invention is described with respect to a long-arm stitcher, one of ordinary skill in the art would recognize that the present invention also has applicability with standard sewing machines and could be used in both a commercial and/or household setting. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a perspective view of a prior art long-arm stitcher. 
           [0011]      FIG. 2  is a perspective view of the stitcher shown in  FIG. 1  having an accelerometer. 
           [0012]      FIG. 3  is an algorithm of a method of operating the stitcher shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0014]      FIG. 1  illustrates a standard long-arm stitcher  10  including a base  12 , an arm  14 , and a take up lever box  16 . Although the present invention is described with respect to a long-arm stitcher, one of ordinary skill in the art would recognize that the present invention is also applicable to standard sewing machines. Moreover, the present invention is capable of operating with both commercial and household long-arm stitchers and sewing machines. The arm  14  is coupled to the base  12  at a back end  18  of the stitcher  10 . A first portion  20  of the arm  14  extends upward from the base  12 , and a second portion  22  of the arm  14  extends from the first portion  20  substantially parallel to the base  12 . The take up lever box  16  is disposed on the arm  14  at a stitching end  24  of the stitcher  10  that is opposite the back end  18 . The stitching end  24  of the stitcher  10  forms a workspace  26  where a fabric is stitched by an operator of the stitcher  10 . The stitching end includes a needle bar  28  having a needle  30  inserted therein and a hopping foot  32  each extending downward toward a needle plate  34  disposed on the base  12 . The needle plate  34  is attached to a square throat plate  36 . The throat plate  36  is configured to be removed to provide access to a rotary hook assembly (not shown) positioned within the base  12  below the throat plate  36 . 
         [0015]    During operation, the needle bar  28  moves up and down thereby moving the needle  30  to form a stitch in the fabric. The needle bar  28  can be adjusted up or down to provide a proper machine timing height. A small hole in the needle plate  34  restricts movement of the thread as the stitch is formed. The hopping foot  32  raises and lowers with the movement of the needle  30  to press and release the fabric as the stitch is formed. The hopping foot  32  is designed to be used with rulers and templates and has a height that can be adjusted for proper stitch formation. A control box  48  is provided to control the operation of the stitcher  10 . 
         [0016]    The control box  48  includes a stitch regulator  50  that controls a speed of the needle  30 . Specifically, the needle speed is controlled to accommodate varying thicknesses of the workpiece and varying stitch types. The speed is further controlled to accommodate a stitch pattern that may not be linear. 
         [0017]      FIG. 2  illustrates the stitcher  10  having at least one accelerometer  52  positioned on the second portion  22  of the arm  14  to measure an acceleration of the stitcher  10 . As will be appreciated by one of ordinary skill in the art, the at least one accelerometer  52  may be positioned at any location on stitcher  10 . In one embodiment, the accelerometer  52  measures a piezoelectric effect utilizing microscopic crystal structures that become stressed by accelerative forces, thereby causing a voltage to be generated. The voltage is used then used to determine acceleration. Alternatively, the accelerometer  52  may sense changes in capacitance between two microstructures in the accelerometer  52 . Specifically, if an accelerative force moves one of the structures, the capacitance changes. The change in capacitance is then converted to a voltage that is used to determine acceleration. In other embodiments, the accelerometer  52  may utilize hot air bubbles or light. In the exemplary embodiment, the at least one accelerometer  52  is one of a single two-axis accelerometer or includes two separate accelerometers, namely an x-axis accelerometer and a y-axis accelerometer. Accordingly, the accelerometer  52  is capable of measuring the acceleration of stitcher  10  in any of the x-axis and the y-axis. In the exemplary embodiment, the accelerometer  52  is a high accuracy, dual-axis digital inclinometer and accelerometer, model number ADIS16209, from Analog Devices; however, it will be appreciated that any off-the-shelf accelerometer would be acceptable for use with the stitcher  10 . 
         [0018]    The accelerometer  52  is electronically coupled to the stitch regulator  50  and is configured to control the stitch regulator  50  based on the algorithm  100  shown in  FIG. 3 . Specifically, at step  102 , the stitcher  10  is moved to a zero motion position and the accelerometer  52  is calibrated while the stitcher  10  is stationary. The stitcher  10  is then operated, at step  104 , to stitch a pattern in the workpiece. During the operation, the stitch regulator  50  controls a number of stitches per inch that are stitched into the workpiece. 
         [0019]    At step  106 , a signal indicative of the stitcher&#39;s acceleration with respect to the workpiece is received from the accelerometer  52 . The signal is filtered with a low pass filter and sampling losses are removed therefrom, at step  108 , to determine an acceleration of the stitcher  10  in both the x-axis and the y-axis. While the present invention is described with respect to both the x-axis and the y-axis, as will be appreciated by one of ordinary skill in the art, the signal may only be indicative of the stitcher&#39;s acceleration in one of the x-axis or the y-axis. At step  110 , the acceleration signal is integrated to provide a vector velocity of the stitcher  10  in the x-axis and the y-axis, wherein the vector velocities include both a magnitude and a direction. The vector velocity in the x-axis and the vector velocity in the y-axis are summed, at step  112 , to provide a vector sum having both a magnitude and direction indicative of a velocity of the stitcher  10  with respect to the workpiece. 
         [0020]    At step  114 , it is determined whether a position of the stitcher  10  is also desired. If the position is not desired  116 , the velocity of the stitcher  10  is used to determine a correction of the stitch regulator  50 , at step  118 . The stitcher  10  is then operated, at step  104 , to stitch a pattern in the workpiece, wherein the stitch regulator  50  controls the number of stitches per inch based on the velocity correction. 
         [0021]    If the position of the stitcher  10  is desired  120 , the stitcher velocity is integrated, at step  122 , to provide a vector position of the stitcher  10  in the x-axis and the y-axis, wherein the vector positions include both a magnitude and a direction. The vector position in the x-axis and the vector position in the y-axis are summed, at step  124 , to provide a vector sum having both a magnitude and direction indicative of a position of the stitcher  10  with respect to the workpiece. The velocity and position of the stitcher  10  is then used to determine a correction of the stitch regulator  50 , at step  126 . The stitcher  10  is then operated, at step  104 , to stitch a pattern in the workpiece, wherein the stitch regulator  50  controls the number of stitches per inch based on the velocity and position corrections. 
         [0022]    Accordingly, the present invention provides a means to regulate a speed of stitcher needle  30  utilizing the acceleration and position of the stitcher in the x-axis and/or y-axis. Specifically, by determining the acceleration of the stitcher  10 , a velocity and displacement of the stitcher  10  is determined and input into the stitch regulator  50 . As such, the needle  30  can be regulated based on a velocity and/or displacement of the stitcher  10  with respect to a workpiece, thereby enabling automatic correction of a stitch pattern. 
         [0023]    As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.