Patent Publication Number: US-6042095-A

Title: Method and apparatus for retaining one or more layers of sheet type work material on a support surface

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to devices for performing work operations on one or more layers of sheet-type work material, and deals more particularly with an apparatus and method for retaining the work material on a support surface via vacuum selectively drawn through two or more manifolds. 
     BACKGROUND OF THE INVENTION 
     Work operations are often performed on multiple layers of sheet-type work material, for example, in the mass production of garments, pattern pieces are usually cut from multiple layers of fabric spread one-on-top-of-the-other on a support surface. To facilitate clean accurate cuts, the layers of work material, often referred to as a lay, must be adequately held in place on the support surface during the performance of a cutting operation. Failure to do so can result in movement of the fabric layers relative to one another, detrimentally affecting the performance of the cutting operation. 
     Generally, pattern pieces are cut from the lay using what is referred to as a cutter table that usually includes a permeable, often conveyorized, cutting surface and a moveable cutter head that traverses the support surface, cutting pattern pieces from the layers of material in response to commands issued from a controller. To eliminate any undesired movement of the layers of work material during the performance of a work operation, vacuum is sometimes used in an effort to draw the work material against the support surface. In prior art cutter tables this was usually accomplished via a single centrally located vacuum manifold positioned under the permeable support surface and defining one or more inlets through which vacuum is drawn. 
     A difficulty sometimes encountered when a single centrally located vacuum manifold is employed, is that the portions of the work material located remotely from the manifold tend to be inadequately retained by the vacuum. This inadequate retention can result in movement of the work material during the performance of a work operation, and the generation of inaccurately cut pattern pieces. This problem is further exacerbated as the cutter tables increase in width. 
     In the past, efforts to address the above-described problems have failed. In one proposed solution, the inlets in the centrally located manifold were enlarged to increase the vacuum drawn there through. However, the enlarged inlets weakened the vacuum manifold to such an extent that it deformed during operation. 
     Another proposed solution was to increase the intensity of the vacuum drawn through the inlets. However, in cutting tables where the support surface was conveyorized and movable relative to the frame, the increased vacuum concentration caused the support surface to be drawn against the vacuum manifold, thereby hindering the movement of the support surface relative to the manifold. 
     Based on the foregoing, it is the general object of the present invention to provide an apparatus and method for retaining multiple layers of sheet material against a support surface that overcomes the drawbacks of prior art methods and apparatus for retaining sheet material. 
     It is a more specific object of the present invention to provide a method and apparatus which applies vacuum to the layers of sheet material adjacent to the location of the performance of a work operation. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus for retaining one or more layers of sheet type work material on a support surface that is permeable and coupled to a frame. At least two vacuum manifolds are coupled to the frame and spaced apart from one another, each defining at least one vacuum inlet through which a vacuum means draws vacuum through the permeable support surface to retain the work material thereon. This prevents any undesired movement of the work material relative to the support surface during the performance of a work operation. 
     The present invention also includes means for selectively regulating the vacuum drawn through the inlets in each of the manifolds in an effort to concentrate vacuum at particular locations along the support surface. Preferably these means include a plurality of butterfly valves positioned within, and pivotally coupled to vacuum conduits that extend between the vacuum means and the vacuum manifold, adjacent to each of the inlets. Each of the butterfly valves is moveable between an open position, wherein vacuum can be freely drawn through the vacuum inlets; and a closed position, wherein vacuum is prevented from being drawn through the vacuum inlets. 
     In a preferred embodiment of the present invention, pneumatic cylinders are coupled to each of the butterfly valves as well as to the frame to move the butterfly valves between the open and the closed positions in response to commands issued from the controller. While butterfly valves have been described, the present invention is not limited in this regard as other valves, such as ball and gate valves, can be substituted without departing from the broader aspects of the present invention. In addition, while a pneumatic cylinder has been described, the present invention is not limited in this regard as other actuators, such as, hydraulic cylinders, stepper motors, or servos can be substituted without departing from the broader aspects of the invention. 
     The present invention also resides in a method for retaining one or more layers of sheet type work material on a support surface that employs the above-described apparatus. Prior to the performance of a work operation, vacuum is selectively drawn through the inlets defined by the manifolds in response to commands issued from the controller, thereby retaining the work material against the support surface and preventing any undesired movement of the work material relative to the support surface. During the performance of the work operation, the intensity of the vacuum drawn through the manifolds is adjusted proportionally, relative to the inlets defined by the manifolds, as well as to the manifolds themselves, to concentrate vacuum in the area adjacent to where the work operation is being performed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1, is a partial perspective view of a cutter table embodying the apparatus of the present invention showing a support surface comprised in-part by a plurality of consecutive slats; the support surface being cut away to show a pair of vacuum manifolds each defining a plurality of vacuum inlets; 
     FIG. 2 is a partial simplified schematic of the vacuum manifolds and the proportional control valves of the apparatus shown in FIG. 1; and 
     FIG. 3 is a partial perspective view of the cutter table of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, an apparatus for retaining one or more layers of sheet type work material on a support surface is indicated generally by the reference numeral 10. The apparatus 10 is shown in the illustrated embodiment as a cutter table 12, and includes a frame 14 having a permeable support surface 16 mounted thereon, for carrying one or more layers of sheet-type work material 18. Two vacuum manifolds 20, each defining a plurality of vacuum inlets 22 are mounted to the frame 14, below and adjacent to the support surface 16. The vacuum manifolds 20 are spaced apart relative to one another and extend longitudinally of the frame 14. Vacuum is drawn through the vacuum manifolds by suitable means, such as, but not limited to a vacuum pump 24. 
     Still referring to FIG. 1, the permeable support surface 16 is comprised of a plurality of slats 26 each overlying and being supported by the vacuum manifolds 20 and extending transversely across the frame 14. The slats 26 are linked together to collectively define the support surface 16. The slats 26 are movable in a direction longitudinal of the frame 14 by a suitable drive, such as a motor (not shown) in response to commands issued from the controller. Each slat 26 defines at least two apertures 27 extending therethrough, making the slat permeable, thereby allowing vacuum to be drawn through the support surface 16. A plurality of bristle blocks 28 are attached to each of the slats, each defining a plurality of upstanding bristles for supporting the work material 18 positioned thereon. 
     As shown in FIG. 1, and illustrated schematically in FIG. 2, a plurality of conduits 30 are coupled at one end to the vacuum pump 24 and at an opposite to each of the vacuum manifolds 20 adjacent to the vacuum inlets 22. A proportional control valve assembly 32 is coupled to each conduit 26, between the vacuum pump 24 and the manifolds 20, for controlling the amount of vacuum drawn through a particular conduit. 
     Referring specifically to FIG. 2 the proportional control valve assemblies 32 illustrated therein, each include a butterfly valve 34 (shown in dotted lines) positioned in, and pivotally coupled to each conduit 30. The butterfly valves 34 are moveable between an open position where vacuum can be freely drawn through the associated conduit 30, and a dosed position where vacuum is prevented from being drawn through the conduit. 
     A portion 36 of each butterfly valve 34 extends from each conduit 30 and is attached to a link 38. The link 38 is in turn coupled to a suitable actuator 40, such as a pneumatic cylinder, having a rod 42 pivotally coupled to the link 38 and movable between an extended and retracted position to move the associated butterfly valve 34 between the open and closed positions, in response to commands issued from the controller. 
     While butterfly valves have been shown and described, the present invention is not limited in this regard as other types of valves known to those skilled in the pertinent art to which the invention pertains, such as, but not limited to ball, and gate valves may be substituted without departing from the broader aspects of the present invention. In addition, while the actuators 40 have been shown and described as pneumatic cylinders, the present invention is not limited in this regard as other types of actuators, such as, but not limited to stepper motors, servos, or hydraulic cylinders may be substituted without departing from the broader aspects of the present invention. 
     As shown in FIG. 3, the cutter table 12 includes a support 44 mounted on the frame 14 for movement back-and-forth longitudinally of the cutter table in response to commands issued from the controller. A cutter head 46 is mounted to the support 44 for movement back-and-forth longitudinally of the support and transversely of the frame 14, also in response to commands issued from the controller. A cutting implement, such as, but not limited to a blade (not shown) is mounted to the cutter head and engages the work material 18 during the performance of a cutting operation, to cut pattern pieces 48 from the work material. 
     Referring to FIGS. 1-3, during operation, one or more layers of work material 18 are positioned on the permeable support surface 16. Vacuum is drawn through the inlets 22 defined by the manifolds 20, by energizing the vacuum pump 24 and selectively actuating the pneumatic cylinders 40 to move the butterfly valves 34 between the open and the closed positions in response to commands issued from the controller. The vacuum draws the work material 18 against the support surface 16, preventing any undesired movement of the work material 18. The support 44, and the cutter head 46 then move over the work material, cutting pattern pieces 48 therefrom. As the pattern pieces 48 are being cut, the controller issues commands to the pneumatic cylinders 40, causing them to move the valves 34 between the open and closed positions to vary the intensity of the vacuum relative to the inlets 22 and the manifolds 20. This concentrates the vacuum in the area adjacent to where the work operation is being performed to ensure that no undesired work material motion occurs which could detrimentally affect the integrity of the cut pattern pieces 48. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the present invention has been described by way of example, and not by limitation.