Patent Publication Number: US-11046544-B2

Title: System for preventing paper jams between subsystem transitions

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Cross-referenced is commonly assigned U.S. application Ser. No. 16/391,418, filed Apr. 23, 2019, and entitled APPARATUS FOR CONTROLLING SHEET FLATNESS UNDER AN IMAGING SYSTEM ROBUST TO MEDIA CURL by Rachel L. Tanchak et al.; U.S. application Ser. No. 16/391,428, filed Apr. 23, 2019, and entitled MEDIA HANDLING BETWEEN MODULES ROBUST TO PAPER CURL by Carlos M. Terrero et al., both of which are included in their entirety herein by reference. 
     BACKGROUND 
     The present disclosure relates to an apparatus for removing process curl during paper path transport between adjacent paper path transports, and more particularly, to an apparatus and method for conveying media or sheet material between adjacent sheet transports that prevents sheet material jamming and dog ears forming on the media or sheet material during transit. 
     Currently, there is an urgent need in imaging systems for a media handling system that controls curl between transitions where a sheet is unsupported in different areas of the imaging systems. Subsystem baffle entrance gaps are typically between 3-5 mm, but curl on the sheets could be two to three times as high as the baffle entrance to the subsystem. 
     Sheets are typically transported by drive rollers and idlers and are only constrained in nip contact regions, leaving their inboard and outboard edges unsupported. The unsupported area allows curl on the sheets to catch on the entrance of a following subsystem or not allow for acquisition by a belt of the following subsystem. For example, dog ears or excessive lead edge corner folds can be formed by the lead edge of the sheets catching on baffles or narrow entrances of subsystems creating a fold. Jams are also created at sheet stackers due to the leading edges of sheets catching on narrow baffles and inverter and gravity gates. 
     With respect specifically to inkjet production printing, there is an issue with sheets lifting between the marker transport and dryer module. This is currently managed with baffles that lead to image defects from the baffles contacting a wet image, and jams due to curl obstruction or contamination of the baffles with ink that has not dried. 
     Sheet curl dysfunction is created by several noises such as humidity, ink placement, toner amount, grain direction, etc. Curl is one of the primary causes of jams in inkjet systems and ultra-light weight media transports. 
     In ultra-light weight applications and low media stiffness also causes issues with maintaining optimized sheet trajectory between baffles, underneath scanners and paper-path gates. 
     Attempts at mitigating some of these issues are not sufficient. For example, current decurler technology only addresses process direction curl. Furthermore, the decurler in most paper paths is located on the output module, therefore, it does not address curl further upstream. Increasing baffle entrance gaps have been tried also, however, if the baffle entrance gaps are designed to be over 10-15 mm sheets run the risk of rolling onto themselves causing jams. A pneumatic baffle is shown in U.S. Pat. No. 8,794,624 that selectively directs cut sheet media in a media feed system. 
     Therefore, there is a need for an improvement in managing sheet curl in xerographic and inkjet imaging systems. 
     SUMMARY 
     Accordingly, in answer to this need, a solution is disclosed that includes placing a curved baffle between adjacent paper path transports and applying a thin layer of high velocity uniform or localized air flow over the curved baffle&#39;s surface to control the leading edge of a sheet thereby preventing jams and dog ears. The thin layer of high velocity uniform or localized air flow over the curved surface of the baffle will have a tendency to follow the curved baffle (Coanda effect) and divert the sheet (Bernoulli effect) towards the baffle. By positioning a curved baffle along the media path and by applying a high velocity uniform air stream to it, a lower press area will be created. This will flatten the sheet&#39;s trajectory so that the sheet will be reliably received by a downstream acquisition zone of either a vacuum or electrostatic transport. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various of the above-mentioned and further features and advantages will be apparent to those skilled in the art from the specific article or methods described in the example(s) below, and the claims. Thus, they will be better understood from this description of these specific embodiment(s), including the drawing figures (which are approximately to scale) wherein: 
         FIG. 1  is a partial side view of a first transport conveying a sheet with up-curl into a baffle gap leading into a downstream second transport with entry of the sheet negated by up-curl in the sheet; 
         FIG. 2  is a partial side view of the two transport system of  FIG. 1  including an air knife and curved baffle in accordance with an aspect to the present disclosure; 
         FIG. 3  is a partial end view of the two transport system of  FIG. 2  showing a sheet with excessive up-curl contacting a downstream baffle; and 
         FIG. 4  is a partial end view of the two transport system of  FIG. 3  showing the effects of Coanda and Bernoulli principles on the sheet in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For a general understanding of the features of the disclosure, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to identify identical elements. 
       FIG. 1  shows a partial side view of a media handling system  20  that includes a media transport which employs a first transport using drive rolls  22  forming nips with idler rolls  21  biased against the drive rolls with spring  23  to convey sheet  11  with cross curl between upper baffle  25  and lower baffle  26  into a baffle gap  29  leading into a nip formed between idler roll  21  and drive roll  22  of a downstream second transport with entry between upper baffle  27  and lower baffle  28  of the second sheet transport being negated by the cross curl in sheet  11 . A jam is created at gap  29  due to the cross curl of sheet  11  hitting upper baffle  27  of the second transport. 
     In  FIG. 2 , sheet  11  is shown constrained in its unsupported length by flattening up-curl across its unsupported length during critical transition between first and second transports in accordance with an aspect of the present disclosure by positioning a curved or semi-circular baffle  50  in the media path before baffle gap  29  at the entrance to the second transport. A uniform or localized stream of air is applied by nozzle or air jet  19  in the direction of arrows  42  to curved baffle  50  with the air stream following the surface of the curved baffle (Coanda effect). With air jet regions shown in  FIG. 3 , air streams are localized on inboard and outboard edges of sheet  11  to flatten the excessive curl areas of the sheet as it travels over curved baffle  50 . This critical location and surface will create a lower pressure band (Bernoulli effect), which will flatten the cross curl on the sheet before entering narrow gap  29  of the second transport. A media presence sensor  30  is positioned between drive rolls  22  of the first transport and, if desired, can be used to initiate an air stream from nozzle  19  and cut off the air stream once a sheet gets through the narrow gap  29  and is acquired by the downstream nips formed between idler rolls  21  and drive rolls  22  of the second transport. During the inter-copy gap or at any other time the air stream will not be actuated. 
     Localized air jet regions  29  are shown in  FIGS. 3 and 4  positioned strategically at inboard and outboard edges of sheet  11  with  FIG. 3  showing excessive cross curl in sheet  11  extending above baffle  27  of the second transport. In  FIG. 4  Coanda and Bernoulli effects on sheet  11  are shown and they combine to flatten the sheet so that it can effectively navigate through gap  29 . Uniformed localized air flow over curved baffle  50  in  FIG. 2 , produces the Coanda effect which causes a thin layer of air to follow the curved baffle with the Bernoulli effect pulling the sheet inboard and outboard edges down to the curved surface and thereby preventing jams and dog ears at the entrance of baffle  27  of the second transport. 
     In recapitulation, an improved apparatus is disclosed for flattening outboard and inboard edges of media conveyed between two transports. In some instances, depending on the media type, job construction or image, cross curl is observed on the unconstrained edges of the media that will more likely hit the downstream baffle of a transport causing jams and dog eared media. A solution to this concern is disclosed that employs a curved baffle positioned between adjacent paper path transports. Uniformed/localized high velocity air flow is applied over the surface of the curved baffle only in unconstrained areas of the sheet. The high velocity layer of air will follow the curvature of the curved baffle due to the Coanda effect and the media will be diverted (Bernoulli effect) towards the baffle. Introducing the curved baffle between the adjacent transports and applying a uniform high velocity air stream to it will cause a lower pressure area to be created that will flatten unconstrained edges of the media and ensure entry of the media into a downstream transport. 
     The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material.