Abstract:
Disclosed is a flexible sheet handling apparatus including a frame having a vacuum passage located around the periphery of the frame. There is also a porous, polymeric plug which covers the vacuum passage. When a vacuum is applied to the vacuum passage and the porous, polymeric plug, a flexible sheet in contact with the porous, polymeric plug is uniformly held only around the periphery of the flexible sheet by the applied vacuum.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the handling of articles and, more particularly, relates to the handling of thin, flexible sheets of material by a vacuum apparatus. 
     In various production scenarios, it is necessary to handle thin, flexible sheets of material. Some of these thin, flexible sheets of material may be somewhat delicate so that special handling is required to avoid damaging these thin, flexible sheets of materials. 
     One particular type of a thin, flexible sheet of material is a so-called greensheet. The greensheet comprises ceramic material in a binder material. There may also be metallization on the greensheet in the form of wiring lines and vias. The binder material of the greensheet allows it to be handled and gives the greensheet a rubbery feel. However, while the greensheet is in the unsintered, i.e., green state, it must be delicately handled to avoid damaging the greensheet. And, when there is metallization on the greensheet, the greensheet can only be handled along the periphery of the greensheet. 
     Present day methods of handling greensheets include various devices which have vacuum cups or vacuum grooves around the device that enable the device to handle the greensheet. However, these devices cause edge damage and embossing of the greensheet, both of which are undesirable. Additionally, because of the spacing between vacuum cups, uneven handling of the greensheet often results. 
     While the present invention is directed to the handling of greensheets, it should be understood that the principles of the present invention have applicability to the handling of thin, flexible sheets of material in general. 
     Various proposals have been made for handling articles, including flexible sheets of material. 
     Baan et al. U.S. Pat. No. 5,971,454, the disclosure of which is incorporated by reference herein, discloses an article handler for picking up ceramic substrates by means of a vacuum. There is a plurality of compartments each of which is covered by a porous filter. The article handler is capable of picking up a variety of sizes of ceramic substrates. 
     Tsukushi U.S. Pat. No. 5,685,513, the disclosure of which is incorporated by reference herein, discloses a vacuum suction attachment pad wherein a pad body on a suction tool is designed to attach firmly to a smooth surface and wherein a plurality of suction ports are attached to a plenum that is attached to a vacuum source. 
     Croyle et al. U.S. Pat. No. 5,535,997, the disclosure of which is incorporated by reference herein, discloses a fabric piece automatic feeder with suction cup picker where a suction tool pad has a plurality of vacuum sources and vacuum ports attach to fabric flat pieces to transport them. 
     Lewecke et al. U.S. Pat. No. 4,703,966, the disclosure of which is incorporated by reference herein, discloses a vacuum lifting arrangement wherein a lift pad has a plenum with an attached piping to a vacuum and a plurality of vacuum ports, and an elastic sealing element in the form of a foam mat provided with a plurality of suction apertures. 
     In view of the efforts of others in this field, it is a purpose of the present invention to handle thin flexible sheets of material without causing damage to them. 
     It is another purpose of the present invention to handle thin flexible sheets of material by an apparatus which is lightweight and relatively inexpensive. 
     These and other purposes of the invention will become more apparent after referring to the following description of the invention considered in conjunction with the accompanying drawings. 
     BRIEF SUMMARY OF THE INVENTION 
     The purposes of the invention have been achieved by providing a flexible sheet handling apparatus comprising: 
     a frame having a periphery; 
     at least one vacuum passage located around the periphery, the at least one vacuum passage having at least one outlet at the periphery; 
     at least one porous, polymeric plug covering the at least one outlet; 
     wherein when a vacuum is applied to the at least one vacuum passage, the at least one outlet and the at least one porous, polymeric plug, a flexible sheet in contact with the at least one porous, polymeric plug is uniformly held only around a periphery of the flexible sheet by the applied vacuum. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The Figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of the flexible sheet handling apparatus according to the present invention. 
     FIG. 2 is a bottom view of the flexible sheet handling apparatus according to the present invention. 
     FIG. 3 is an exploded of the flexible sheet handling apparatus according to the present invention. 
     FIG. 4 is a partial cross sectional view of the frame of the flexible sheet handling apparatus in the direction of arrows IV—IV in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the Figures in more detail, and particularly referring to FIG. 1, there is disclosed in more detail the flexible sheet handling apparatus  10  according to the present invention. The flexible sheet handling apparatus  10  includes a handle  12  for holding the flexible sheet handling apparatus  10 . The handle  12  is attached to cover  26  by fasteners (not shown) while the cover  26  is attached to frame  28  by fasteners  22 . Handle  12  is inclined with respect to the cover  26  for ease of gripping the flexible sheet handling apparatus  10 . Also shown in cover  26  are airholes  24 , the purpose of which will be discussed hereafter. 
     A vacuum source (not shown) would typically be connected to nipple  17  on coupling  16 . Vacuum conduit  18  extends between coupling  16  and switch  14  in handle  12 . Vacuum conduit  20  extends from switch  14  to nipple  21 . Nipple  21  extends into the flexible sheet handling apparatus  10  to provide a vacuum source for the flexible sheet handling apparatus  10 . 
     Referring now to FIG. 2, the bottom of the flexible sheet handling apparatus  10  is shown. Frame  28  contains a vacuum passage  38  that extends around the periphery of the frame  28 . Vacuum passage  38  communicates with nipple  21  through opening  42 . Contained within vacuum passage  38  is a porous, polymeric plug  30 . As shown in the Figures, there are a plurality of such porous, polymeric plugs  30 , one of which has been removed in FIG. 2 so as to expose vacuum passage  38 . 
     The porous, polymeric plug  30  may be any material that has fine, connected porosity. The present inventors have found that a sintered, pelletized polyethylene material (e.g., POREX®, available from Porex Technologies, Fairburn, Ga.) having a pore size of 45 to 75 microns works well for the purposes of the present invention. The porous, polymeric plug  30  is preferably force fitted into the vacuum passage  38 . The vacuum passage  38  has stops  40  to prevent the porous, polymeric plug  30  from extending too far into the vacuum passage  38 . 
     Also shown in FIG. 2 is cross piece  32  which has perforation  36  for receiving a fastener (not shown) for connecting the coupling  16  to the cover  26  and cross piece  32  and perforations  34  for receiving fasteners (not shown) for connecting the handle  12  to the cover  26  and cross piece  32 . Cross piece  32  connects two opposite sides of the frame  28 . The configuration of cross piece  32  as shown in FIG. 2 is for illustration purposes only. It should be understood that cross piece  32  can assume any configuration so long as it provides rigidity to the frame  28  and serves as a platform for the connection of handle  12  and coupling  16 . 
     Referring now to FIG. 3, there is shown an exploded view of the flexible sheet handling apparatus  10 , showing the handle  12 , cover  26 , frame  28  and porous, polymeric plugs  30 . Switch  14  has been removed from the handle  12  to reveal vacuum conduits  18 ,  20 . Opening  42  in frame  28  through which vacuum is applied to the flexible sheet handling apparatus  10  is shown more clearly in FIG.  3 . 
     FIG. 4 is a partial cross section through frame  28  in the direction of arrows IV—IV. As can be seen in FIG. 4, opening  42  connects with vacuum passage  38  in frame  28 . As also can be seen in FIG. 4, cross piece  32  is recessed slightly by a dimension D with respect to the remainder of the frame  28 . The purpose for this recess will be discussed shortly. 
     The operation of the flexible sheet handling apparatus  10  is as follows. The flexible sheet handling apparatus  10  is placed on a flexible sheet (e.g., a greensheet) that needs to be handled such as being picked up and moved to another location. Vacuum is applied through vacuum conduits  18 ,  20 , opening  42 , vacuum passage  38  and finally through porous, polymeric plugs  30  to hold the flexible sheet to the flexible sheet handling apparatus  10 . Assuming vacuum is always on, the handle  12  is grasped and the flexible sheet handling apparatus  10  with the flexible sheet is moved to the new location. Switch  14  is pressed to break the vacuum, thereby releasing the flexible sheet from the flexible sheet handling apparatus  10 . Airholes  24  allow air to bleed in between the cover  26  and the flexible sheet to more expeditiously release the flexible sheet from the flexible sheet handling apparatus  10 . 
     Alternatively, if the vacuum is always off, switch  14  would be pressed to activate the vaccum. The flexible sheet handling apparatus  10  and the flexible sheet would be transported to the new location, at which point switch  14  would be released so as to break the vacuum. 
     The combination of the features of the invention including the location of porous, polymeric plugs  30  only at the periphery of the flexible sheet handling apparatus  10  allow flexible sheets to be handled without damaging them. Also, because the porous, polymeric plugs  30  extend almost around the entire periphery of the frame  28 , and in fact can extend around the entire periphery of the frame  28  if desired, the vacuum that is applied to the flexible sheet is very uniform. That is, there are no substantial gaps where vacuum is absent or low. 
     The recess of the cross piece  32  with respect to the remainder of the frame  28  by a distance D as shown in FIG. 4 allows flexible sheets to be handled without disturbing the central portion of the flexible sheet. For example, in the case of metallized greensheets, there is metallization in the central part of the greensheet. This metallization cannot be touched as any touching will distort the pattern. Accordingly, cross piece  32  is recessed so as to avoid harming the metallization on the greensheet in any way. 
     It will be apparent to those skilled in the art having regard to this disclosure that other modifications of this invention beyond those embodiments specifically described here may be made without departing from the spirit of the invention. Accordingly, such modifications are considered within the scope of the invention as limited solely by the appended claims.