Patent Publication Number: US-6216353-B1

Title: Centerline detector for a tubular knit fabric lay cutter

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates generally to cutting systems for cutting a garment pattern from a tubular knit fabric lay and, more particularly, to a centerline detector for a tubular knit fabric lay cutter. 
     (2) Description of the Prior Art 
     Fabric cutting is typically performed on a multiplicity of fabric layers referred to as fabric plies. The multiplicity of fabric plies are vertically arranged to form a fabric lay which is moved into a cutting assembly for cutting the plies simultaneously according to a predetermined arrangement of fabric sections which may have varying size and shape. 
     Generally, the vertical arrangement of fabric plies produces a fabric lay with nonuniform edge alignment which results in fabric waste or nonuniform cut fabric sections. More particularly, for tubular knit fabric lays, the amount of edge waste and/or the number and probability of non-uniform cut fabric sections involving the folded edges is substantially increased. 
     Various prior art fabric cutting systems have attempted to measure and control the fabric longitudinal centerline with respect to the cutter in order to decrease the amount of edge waste due to nonuniform edge alignment within the fabric lays. Although the prior art has sought to decrease fabric waste due to section cut layout inefficiency via automated cutting systems which optimize section layout within a given fabric length, such prior art systems have relied upon manual measurement of the fabric edges and calculation of the fabric lay centerline therefrom, generally by interpolation between two points measured at predetermined fabric intervals. Fabric cutting patterns were then readjusted based upon those centerline values. 
     Fabric lay centerline points determined from prior art manual measurements of the nonuniform edges have typically produced centerline error in the range of +/−6 mm within a given fabric length. Particularly for tubular knit fabric lays where fabric sections are cut around the folded edges, fabric lay centerline measurement error is substantially increased because the amount of waste is magnified by at least a power of two for the edge cut sections. When, rarely, cuts are made with respect to both folds, the effect of the error increases to four times! Thus, 5 mm error on both folds of a matching front and back garment piece could result in a 20 mm error in the seam location. This error would be sufficient to produce a second quality, low profit garment. 
     One prior art alternative to centerline calculation involved fabric lay alignment along one edge of the fabric lay. While this method reduces the need for highly accurate centerline measurements, a substantial amount of waste is still produced along the nonaligned edge. For tubular knitted fabrics, further waste results because fabric section cutting may not be optimized without use of both folded edges. 
     Thus, there remains a need for a fabric lay centerline detector for automatically measuring and determining the centerline of a fabric lay, particularly for tubular knit fabric lays, whereby the centerline determination error is substantially reduced thereby decreasing fabric waste and folded edge cut section non-uniformity while, at the same time, can make an accurate measurement even when the fabric lay is covered by a plastic vacuum film. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a centerline detector for a tubular knit fabric lay cutter table. The apparatus includes a nearside side edge compressor for determining the position of the nearside edge of the fabric lay and providing a signal representative of the nearside edge. In the preferred embodiment the nearside compressor includes a first generally vertical movable paddle and an actuator for moving the first paddle against the nearside edge of the fabric lay at a predetermined pressure. 
     The apparatus also includes a farside side edge compressor for determining the position of the farside edge of the fabric lay and providing a signal representative of the farside edge. In the preferred embodiment, the farside compressor includes a second generally vertical movable paddle and an actuator for moving the second paddle against the farside edge of the fabric lay at substantially the same predetermined pressure as the first paddle. 
     A controller is connected to the nearside side edge compressor and the farside side edge compressor for receiving the signal representative of the nearside edge and the signal representative of the farside edge and calculating a first centerpoint of the fabric lay. In the preferred embodiment the centerline detector makes at least two measurements along a length of the fabric lay. The multiple measurements of the centerpoint of the fabric lay can then be used to calculate the centerline of the fabric lay between the two points as well as the centerline angle with respect to the edge of the cutter table. This information can be used by the cutter table to adjust the layout of the fabric garment pieces that the cutter will be used to cut. 
     Finally, in the preferred embodiment, a plastic film tucker upstream from the centerline detector tucks the edges of the plastic film against the nearside edge and the farside edge of the fabric lay to prevent interference with the operation of the centerline detector. The plastic film is generally placed over the fabric lay and a vacuum is applied prior to cutting since the combination of the plastic film and vacuum stabilizes the package and permits faster and more accurate cutting. However, the edges of the plastic film may “tent” adjacent to the edges of the fabric lay and, on occasion, interfere with the operation of the centerline detector. The tucker prevents the “tent” from forming. 
     Accordingly, one aspect of the present invention is to provide a centerline detector for a tubular knit fabric lay cutter table. The apparatus includes: (a) a nearside side edge compressor for determining the position of the nearside edge of the fabric lay and providing a signal representative of the nearside edge; (b) a farside side edge compressor for determining the position of the farside edge of the fabric lay and providing a signal representative of the farside edge; and (c) a controller connected to the nearside side edge compressor and the farside side edge compressor for receiving the signal representative of the nearside edge and the signal representative of the farside edge and calculating a first centerpoint of the fabric lay. 
     Another aspect of the present invention is to provide a centerline detector for a tubular knit fabric lay cutter table. The apparatus includes: (a) a nearside side edge compressor for determining the position of the nearside edge of the fabric lay and providing a signal representative of the nearside edge, the nearside compressor including a first generally vertical movable paddle and an actuator for moving the first paddle against the nearside edge of the fabric lay at a predetermined pressure; (b) a farside side edge compressor for determining the position of the farside edge of the fabric lay and providing a signal representative of the farside edge, the farside compressor including a second generally vertical movable paddle and an actuator for moving the second paddle against the farside edge of the fabric lay at substantially the same predetermined pressure as the first paddle; and (c) a controller connected to the nearside side edge compressor and the farside side edge compressor for receiving the signal representative of the nearside edge and the signal representative of the farside edge and calculating a first centerpoint of the fabric lay. 
     Still another aspect of the present invention is to provide a centerline detector for a tubular knit fabric lay cutter table. The apparatus includes: (a) a nearside side edge compressor for determining the position of the nearside edge of the fabric lay and providing a signal representative of the nearside edge, the nearside compressor including a first generally vertical movable paddle and an actuator for moving the first paddle against the nearside edge of the fabric lay at a predetermined pressure; (b) a farside side edge compressor for determining the position of the farside edge of the fabric lay and providing a signal representative of the farside edge, the farside compressor including a second generally vertical movable paddle and an actuator for moving the second paddle against the farside edge of the fabric lay at substantially the same predetermined pressure as the first paddle; (c) a controller connected to the nearside side edge compressor and the farside side edge compressor for receiving the signal representative of the nearside edge and the signal representative of the farside edge and calculating a first centerpoint of the fabric lay; and (d) a plastic film tucker upstream from the centerline detector for tucking the edges of the plastic film against the nearside edge and the farside edge of the fabric lay to prevent interference with the operation of the centerline detector. 
     These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a tubular knit fabric centerline detector constructed according to the present invention; and 
     FIG. 2 is a cross-sectional view of the tubular knit fabric centerline detector shown in FIG. 1, taken along lines  2 — 2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upwardly”, “downwardly”, and the like are words of convenience and are not to be construed as limiting terms. 
     Referring now to the drawings in general and FIG. 1 in particular, it will be understood that the illustrations are for the purpose of describing a preferred embodiment of the invention and are not intended to limit the invention thereto. As best seen in FIG. 1, a tubular knit fabric centerline detector for a tubular knit fabric lay cutter, generally designated  10 , is shown constructed according to the present invention. 
     The tubular knit fabric centerline detector  10  comprises a centerline detector  12  for detecting the centerline  54  of a tubular knit fabric lay  76  having a multiplicity of tubular knit fabric plies  74  longitudinally controllable and movable via forced air (not shown) directed upward through holes (not shown) in a float table  80 . The tubular knit fabric lay  76  is movable along the float table  80  with respect to a table edge  92  for cutting downstream by a cutter  82  on a cutter table  94 . As the tubular knit fabric lay  76  is pulled longitudinally along the float table  80 , a plastic film  90  is positioned on top of the fabric lay  76  to stabilize the fabric lay during cutting. 
     In a preferred embodiment, the tubular knit fabric lay  76  is covered with a plastic film  90  upstream from the cutter  82 . The fabric lay  76  and plastic film  90  are moved downstream toward the centerline detector  12  on the float table  80  having a horizontal float table surface (as seen in FIG. 1) with holes therein (not shown) and a multiplicity of fans (not shown) for forcing air upwardly through the float table holes thereby decreasing friction between the fabric lay  76  and the float table horizontal surface  80 . When the fabric lay  76  and plastic film  90  combination move downstream to the cutter table  94 , a vacuum source (not shown) applies vacuum through openings (not shown) in a cutter table horizontal surface  95  for releasably securing the tubular knit fabric lay  76  and the plastic film  90  to the cutter table surface  95  while the cutter  82  cuts through the tubular knit fabric lay  76  and the plastic film  90  to form tubular knit fabric garment piece sections  100 . 
     In a preferred embodiment, the centerline detector  12  further comprises a nearside side edge compressor  16  for compressibly determining a first nearside position X 1 , and a second nearside position X 2  of a fabric lay nearside edge  96 ; a farside side edge compressor  20  for compressibly determining a first farside position Y 1 , and a second farside position Y 2  of a fabric lay farside edge  98 ; and a controller  22  in electrical connection to each of the edge compressors  16 ,  20  for automatically calculating the longitudinal centerline  54  of the tubular knit fabric lay  76  along the entire length thereof. 
     More preferably, the centerline detector  12  includes a controller  22  for automatically determining the centerline  54  of a tubular knit fabric lay  76  as the line formed between a first centerpoint position CP 1  and a second centerpoint position CP 2 . The first centerpoint position  40  is preferably calculated as CP 1 =[X 1 +(X 1 +Y 1 )/2] and the second centerpoint position  52  is preferably calculated as CP 2 =[X 2 +(X 2 +Y 2 )/2]. Further, the controller  22  automatically determines either the centerline  54  and/or the centerline angle  56  formed between the centerline  54  and the cutter frame upstream edge  84 . 
     Referring now to FIG. 2, in a preferred embodiment, the nearside side edge compressor  16  further includes a nearside paddle  30  attached to and positionable by a nearside actuator  24  for determining a first nearside position value X 1  (FIG.  1 ). Similarly, in a preferred embodiment, the farside side edge compressor  20  further includes a farside paddle  34  attached to and positionable by a farside actuator  32  having an equal pressure to the nearside actuator for determining a first farside position value Y 1  (FIG.  1 ). Also preferably the actuators  24 ,  32  are pneumatic. Preferably the first nearside and farside position values X 1 , Y 1 , respectively, are determined by respective LVDTs connected to actuators  24 ,  32 . 
     Further, the centerline detector  12  may include drive means for moving the nearside and farside side edge compressors  16 ,  20 , respectively, upstream for measuring a second nearside position value X 2  and a second farside position value Y 2 . In the preferred embodiment, the detector  12  is attached to the cutter frame which may be moved to make multiple measurements along the length of the fabric lay. 
     As best seen in FIG. 2, in a preferred embodiment, the centerline detector  12  further includes a gauge  86  for displaying the centerline pressure value  54 . For example, when pneumatic actuators are used, about 5 psi is sufficient pressure to determine the edges of the fabric lay. The gauge  86  helps the operator to prevent excessive pressure being applied which could cause distortion of the edges of the fabric lay. 
     Also, in a preferred embodiment, the tubular knit fabric lay  76  and the plastic film  90  move longitudinally along the float table  80  toward the cutter downstream and pass between a plastic film tucker  14  which forces the plastic film  90  into contact with the fabric lay nearside edge  96  and the fabric lay farside edge  98  thereby eliminating substantial gaping or “tenting” between the plastic film  90  and the fabric lay edges  96 ,  98  and minimizing measurement error downstream at the centerline detector  12 . 
     Additionally, in a preferred embodiment, the plastic film tucker  14  is removably attached to the float table frame  60  and includes a pair of opposed guide plates  62  having respective flared inlets  64  for gradually guiding the fabric lay  76  and plastic film  90 . Further, in a preferred embodiment, the plastic film tucker  14  includes a pair of rollers  66  attached to each of the opposed guide plates  62  at the respective inlets  64  for forcing the plastic film  90  into contact with the fabric lay nearside and farside edges  96 ,  98 , respectively. In another preferred embodiment, the pair of rollers  66  are removably positioned upstream from the pair of opposing guide plates  62 . 
     In operation, the nearside side edge compressor  16  is moved against the edge of the fabric lay  76  to determine the position of the nearside edge  96  of the fabric lay and provide a signal representative of the nearside edge. At about the same time, the farside side edge compressor  20  is moved against the edge of the fabric lay to determine the position of the farside edge  98  of the fabric lay and provide a signal representative of the farside edge. The controller connected to the nearside side edge compressor and the farside side edge compressor receives the signal representative of the nearside edge and the signal representative of the farside edge and calculates a first centerpoint CP 1  of the fabric lay. In the preferred embodiment the centerline detector makes at least two measurements CP 1 , CP 2  along a length of the fabric lay. The multiple measurements of the centerpoint of the fabric lay can then be used to calculate the centerline of the fabric lay between the two points as well as the centerline angle with respect to the edge of the cutter table  94 . This information can be used by the cutter table to adjust the layout of the fabric garment pieces that the cutter will be used to cut. 
     Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. By way of example, other types of controlled pressure actuators could be used instead of pneumatic cylinders. Also, while plastic film is usually used to stabilize the fabric lay for cutting, other materials, such as paper, could be used. Finally, the opposed guide plates may not be needed when the fabric rollers are positioned upstream before the vacuum section of the cutter bed. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.