Abstract:
In order to provide web handling which mitigates marking of the web, externally-pressurized porous media gas bearings are used for vacuum rollers, which provide differential tension, and also for air turns, which provide non-contact turning of webs. The porous media gas bearings mitigate three of the biggest issues with the current technology, including cost, high flow rates and low pressure, and web marking. By introducing positive pressure or both, various configurations are presented which allow for improved differential tension, or non-contact conveyance. By also employing externally-pressurized radial bearings, more alternatives are provided, including conveyance and lateral motion of webs without the use of motors. Lastly, employing novel lightweight materials allows for yet other configurations which also employ some of the same aforementioned benefits.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Nos. 62/113,169, filed Feb. 6, 2015; and 62/046,870, filed Sep. 5, 2014, whose disclosures are hereby incorporated by reference in their entireties into the present disclosure. 
     
    
     FIELD OF INVENTION 
       [0002]    This application is generally related to vacuum rollers and non-contact air turns used in web handling applications for thin film flexible membranes, such as plastics, vinyl, glass, foil, or other materials, that are employed in production machinery and systems for making the same. 
       BACKGROUND 
       [0003]    Vacuum rollers and air turn bars (hereinafter “air turns”) are used in web handling applications to create differential tension on either side of the roller (tension isolation), to only allow contact on one side of the web (as opposed to pinch rollers which contact both sides), and to reverse the direction of the web flow, respectively. State-of-the-art vacuum rollers and air turns may possess certain features and characteristics which drive up cost and negatively affect quality. 
         [0004]    In the case of common vacuum rollers, tension isolation is accomplished using an inner stationary member which comprises the desired wrap angle. Vacuum is generated within an inner stationary member via a vacuum pump, and when a rotating outer roller passes over the wrap angle portion, vacuum is conducted through a series of holes in the surface of the outer roller, and thus generates the desired friction over the wrap angle. For current art designs, the inner member and the outer roller must have very precise mating surfaces so that vacuum pressure does not escape. Three of the biggest issues with the current technology is that: (1) it is very expensive due to the elaborate design and precision components required, (2) the vacuum flow rate is high, and the vacuum pressure is low, and (3) the web may be marked by the holes in the outer rotating roller. 
         [0005]    Common turn rollers are used in web handling to change the direction of the web as it progresses through its course. State-of-the-art air turns employ the use of pressurized air to lift a web off of the surface of the roll. These are typically manufactured from metal components by creating an arc through which air is passed through a series of channels, utilizing a variety of configurations, such as provided by Advance Systems, Inc. (ASI). These systems, due to the amount of escaping air, typically have high flow rates. Also, as in the case of vacuum rollers, the web may be marked by the air passageways over which the web passes, in the event of contact. 
       SUMMARY 
       [0006]    Embodiments disclosure may utilize a porous material which is externally pressurized, with positive or negative gas pressure, to effect a key function of a gas bearing, porous media vacuum roller or air turn. 
         [0007]    In the case of a vacuum roller, the porous media which covers the outside surface of the roller, or partial arc roller, may allow for a web to be vacuumed uniformly to the porous media surface to create differential tension over a desired wrap angle, or the porous media on the exterior of the roller may be used in conjunction with a porous radial bearing to produce a desired net force that acts upon the web. 
         [0008]    In the case of an air turn, the porous media covers the outside surface of the roller, or partial arc roller, and may allow for a web to traverse over the roller in a non-contact fashion, without the need for the roller to rotate. 
         [0009]    The subject invention solves several key issues contained in the current art: (1) it is a relatively simple (and cost effective) design, because it mitigates the need for highly precise machined surfaces, (2) the vacuum flow rate is relatively low (for example 1 to 10 scfm), and the vacuum pressure can be at least as high as the state-of-the-art technology, and (3) porous media has microscopic sized holes, thus mitigating concerns stemming from the web being marked by the edges of the holes in the roller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing summary, as well as the following detailed description of the preferred embodiments, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating embodiments of the invention, there is shown in the drawings example embodiments. It should be understood, however, that the invention is not limited to the precise arrangements shown. 
           [0011]      FIG. 1A  shows an example of a porous media vacuum roller. 
           [0012]      FIG. 1B  shows an example of a porous media vacuum roller shaft. 
           [0013]      FIG. 1C  shows an example of a porous media vacuum roller partial wrap end plate. 
           [0014]      FIG. 1D  shows an end view of an example porous media vacuum roller shaft and with partial wrap end plate. 
           [0015]      FIG. 1E  shows an example of an alternative porous media vacuum roller end plate. 
           [0016]      FIG. 1F  shows an example of a porous media vacuum roller end plate having flexible wrap angle capability. 
           [0017]      FIG. 2A  shows an example of a porous media roller with a solid shaft and that can serve as a vacuum roller or air turn. 
           [0018]      FIG. 2B  shows an example of a one-piece outer porous media sleeve. 
           [0019]      FIG. 2C  shows an example of a porous media roller including gas conductance passageways. 
           [0020]      FIG. 2D  shows an example of a porous media roller acting as a vacuum roller 
           [0021]      FIG. 2E  shows an example of a porous media roller with a hollow shaft that can serve as a vacuum roller or air turn. 
           [0022]      FIG. 2F  shows an example of a multiple-piece outer porous media sleeve. 
           [0023]      FIG. 2G  shows an example of an arrangement of air turns in a production line. 
           [0024]      FIG. 3A  shows an example of a porous media roller using porous media radial bearings to provide differential tension or act as an air turn. 
           [0025]      FIG. 3B  shows an example of a porous media roller using a porous media radial bearing to act on a web and initiate a traversing motion. 
           [0026]      FIG. 3C  shows an example of a porous media roller using a porous media radial bearing to provide lateral web motion. 
           [0027]      FIG. 4  shows an example of a partial arc porous media air turn. 
           [0028]      FIG. 5  shows a cross section view of a prior art vacuum roller. 
           [0029]      FIG. 6  shows a depiction of prior art pinch rollers. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “back,” “left,” “right,” “inner,” “outer,” “upper,” “lower,” “top,” and “bottom” designate directions in the drawings to which reference is made. Additionally, the terms “a” and “one” are defined as including one or more of the referenced item unless specifically noted otherwise. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof, and words of similar import. 
         [0031]    As illustrated in  FIGS. 1A and 1B , a solid or hollow rotatable shaft  101  manufactured out of metal or some other suitable material may contain axial holes  103  which are connected to grooves  104  contained in the shaft  101  or machined into an outer porous media sleeve  102 . The sleeve  102  may be installed and glued on the outside of the shaft  101 . The holes  103  may be on one or both sides of the shaft, or on one or both sides of the outer porous media sleeve  102 . The outer porous media sleeve may be one continuous member or may be attached to the shaft in segments, so long as the segments are sealed together to prevent escapement of gas. 
         [0032]      FIGS. 1C and 1D  show an example end plate  108  which is attached to one or both ends of the shaft  101  by any mechanical means common in the art. A metal holder  108  houses porous material  105 A and  105 B. The porous material  105  contains a slotted region  106  through which a vacuum is pulled via holes  107 . Vacuum is introduced into the end plate via port  109 , which conducts vacuum pressure to a hole  107  via passageways contained in the holder  108  or porous media  105 A or  105 B. In this depiction, the faces of the porous media  105 A or  105 B and the holder  108  are all in the same plane. Operation of the subject vacuum roller is accomplished by introducing vacuum pressure into port  109 . The vacuum is distributed through a hole  107 , and then into groove  106 . Concurrently, positive gas pressure is introduced into port  110 , and creates a pressurized gap that acts as a bearing between the face of the porous media  105  and the end face of the shaft  101 . The shaft will also need to be borne by a bushing (not shown) to carry the radial load imparted by the shaft&#39;s weight and the loading resulting from web tension acting on the shaft. It is noted that such a bushing may also be a gas bushing as commonly provided by New Way Air Bearings, or the bushing may be integrated with the end plate shown in  FIG. 1D  in the form of a thrust bushing as commonly provided by New Way Air Bearings. 
         [0033]    Further, the end plate of  FIG. 1D  remains stationary as the shaft  101  rotates. As the shaft  101  rotates  111 , holes  103  corresponding to the arc angle defined by the wrap angle of the end plate will receive vacuum that is conducted by such mating holes  103 . The vacuum acts upon the same given arc angle as the shaft  101  rotates, thus providing vacuum in a desired sector of the shaft  101 . As vacuum is applied only to the desired arc length of the shaft  101 , the traversing web is held to the shaft  101  only in that region, and differential tension is able to be generated on either side of the wrap angle. As the shaft  101  continues to rotate out of the wrap angle sector, vacuum pressure is no longer present, and the web does not adhere to the roll in the region outside of the desired wrap angle. 
         [0034]    In an embodiment, differential tension is provided on either side of the wrap angle. This feature mitigates the need for highly machined surfaces, enables a vacuum flow rate that is relatively low (for example 1 to 10 scfm), and a vacuum pressure that may be at least as high as state-of-the-art technology, but with a lower flow rate. This is accomplished by the fact that the proven nature of gas bearings is such that the gaps between the end face and rotor face are extremely small, and such gaps require a very low gas flow rate and produce high pressures (or vacuums) which are very efficient. It should also be noted that since porous media has microscopic sized holes, the outer porous media sleeve member  102  mitigate issues related to the web being marked by the edges of holes present in the prior art. 
         [0035]    An alternative end face is shown in  FIG. 1E . This depiction is very similar to a vacuum preloaded (VPL) gas bearing provided by New Way Air Bearings, except for the fact that the faces of the porous media  112  and the holder  114  are all in the same plane. Another difference with common VPL type bearings is the fact that the vacuum groove  113  is only a partial arc, corresponding to the desired wrap angle of the web. A vacuum port  115 A leads to a vacuum hole  115 B which creates vacuum in the groove  113 . A pressure port  116  leads to the porous media  112  to create a gas bearing functionality at the face of the porous media. 
         [0036]    Another example end face is shown in  FIG. 1F . In this case, the holder  117  contains porous media  118 ; however, this depiction is different than  FIG. 1E  in that groove  119  is a full 360 degrees, and there is a vacuum hole  120  leading into the vacuum groove  119 . Furthermore, close fitting groove fillers  121  are installed in the groove  119  at a desired wrap angle. The groove fillers  121  allow for setting a flexible wrap angle without the need for a new or modified end plate. Depending on the desired wrap angle, one of the multiple vacuum ports is used to conduct vacuum pressure to the groove sector which has been set. The groove fillers  121  are contained in the groove  119  by any mechanical means common in the art, such as threading, as shown. It is not necessary that the groove fillers  121  create a 100 percent air tight vacuum groove to allow for proper functionality. The groove fillers may be other shapes than cylindrical. 
         [0037]    Another embodiment for creating a vacuum roller using porous media technology is shown in  FIGS. 2A through 2D .  FIGS. 2A through 2D  show a rotatable solid shaft  201  with a porous media sleeve  202  installed and glued over the outside. Vacuum pressure from a vacuum pump or equivalent is pulled through port  203  and is conducted through one or a plurality of plenums  204 , which in turn creates vacuum pressure on the entire porous media sleeve  202 . This vacuum pressure draws gas from the atmosphere outside of the roller, and it is conducted through the porous media  202  into the plurality of plenums  204 , and is conducted out of the port  203 . As the shaft  201  rotates, the traversing web  205  is acted upon with vacuum over the desired wrap angle  206 . One portion of the web can be kept taut and the other portion can be slack; hence, differential tension is created by the porous media vacuum roller. The remaining portion  207  of the porous media over which the web does not traverse  202  will also have vacuum pulled on this surface, and this vacuum is effectively not used for the function of creating differential tension. Nevertheless, despite this “unused” vacuum the roll is still quite efficient at creating the desired differential tension due to its low flow and high vacuum capability. 
         [0038]      FIG. 2E  shows an alternative to using a solid shaft as in  FIG. 2A , while employing the same functionality as described for a solid shaft. In  FIG. 2E , a hollow shaft  209  is coupled to a round end plate  208 , which is attached to a journal  210 . A porous media sleeve (not shown, but similar to that in  FIG. 2A ) can be installed and glued to the outside of the hollow shaft  209 . A port  211  is installed into the journal. 
         [0039]      FIG. 2F  shows an alternative to a solid porous media sleeve. Multiple porous media sleeve members  212  can be combined together and installed and glued onto a shaft. 
         [0040]    It is important to note the universality of using the porous media to conduct vacuum or positive pressure in the context of the present described embodiments. For example, in the embodiments of  FIGS. 2A through 2F , it is possible to substitute positive pressure in lieu of vacuum pressure. The only key difference is that if positive pressure is used, the shaft does not need to rotate, and a traversing web will float above the surface of the porous media, resulting in the device acting as an air turn. In such an embodiment, there may be no contact with the web at all, resulting in mitigating issues related to the web being marked by the edges of the holes in a prior art roller. Also, as previously mentioned, this becomes a very cost-effective non-contact roll solution as the vacuum flow rate is relatively low, and the vacuum pressure can be higher than state-of-the-art technology.  FIG. 2G  shows a depiction of a series of non-contact air turns in a production line. 
         [0041]      FIG. 3A  shows a shaft  301 , which may be solid or hollow, covered with an outer porous media sleeve  305 , and with pressure port  304 . Also shown is a porous media radial gas bearing  303  with pressure port  306 , similar to that sold by New Way Air Bearings. The radial gas bearing  303  is pressurized and used to provide force onto the web  302 . Also, pressure is supplied into the porous media sleeve  305  via port  304 . Hence, the pressure introduced into the porous sleeve  305  and the pressure introduced into the radial bearing  303  can both be adjusted to create the desired net force which acts downward on the web  302 . Furthermore, this net force may cause the web to be in contact with the porous media roll, and may result in differential tension on the web. Multiple radial gas bearings may be used, as needed. The advantages of this method are immense—the web does not contact the radial bearing, yet a differential tension is generated. The flow rate is very low as compared to state-of-the-art vacuum roll methods. The simplicity of this method is vastly different than the complex state-of-the-art vacuum roll methods. Other embodiments of this method may include: a porous media roller that rotates, a porous media roller that is stationary, a porous media roller in which pressure is introduced into the porous media, and a porous media roller in which vacuum is drawn from the porous media. 
         [0042]      FIG. 3B  shows that when a pressurized radial bearing  303  is used in conjunction with a pressurized porous media roller, a bias in the orientation of the radial bearing  303  as shown may cause the web  302  to be driven to the right as a result of the input pressures and the orientation of the radial bearing  303 . Even though the shaft is not rotating, the web is driven so that it traverses the shaft in a non-contact fashion. The small arrows on  FIG. 3B  indicate gas flow. 
         [0043]      FIG. 3C  shows a similar phenomenon of a pressurized radial gas bearing  303  used in conjunction with a pressurized porous media roller to control the lateral movement or positioning of a web. By applying force and biasing the radial bearings as shown by the angular representation, the air film between the radial bearing and the web will have a wedge-type, graduated thickness, and this can be used to move the web laterally, in this case, to the right. A variety of biasing force and air wedge profile can be used to create a variety of lateral motions. By providing feedback between the position of the web (which can be sensed by instrumentation) and the biasing of the radial air bearings, this could result in automated adjustment of the lateral position of a web. 
         [0044]      FIG. 4  shows an example of an air turn utilizing carbon fiber materials, including a carbon fiber shaft  401 , carbon fiber/foam supports  402 , and a carbon fiber inner ring  403 , which is glued onto an outer porous media sleeve  404 . A series of grooves are installed into the inside diameter of the porous media outer ring to allow conductance of gas flow. Gas flow is introduced from the inside surface of the carbon fiber inner ring via ports  405 , and flows through channels machined in the outer sleeve  404 . The assembly is a partial wrap angle, but this construction could be used for a variety of wrap angles. The key benefits of this embodiment include the fact that a web does not contact the roller and the fact that it has significant weight advantages over state-of-the-art air turns. Weight savings are important in various web handling applications (such as when low mass components are needed for rapid acceleration). 
         [0045]    In each of the above described embodiments, the vacuum (or positive pressure) may be employed by using any gas, such as air, nitrogen, or other. Also, the porous media may be comprised of any porous or sintered material such as graphite, carbon, silicon carbide, Tungsten carbide, porous diamond, alumina, carbon-carbon, a porous carbon base material with a diamond or diamond-like coating, and the like. The manufacture of porous media may employ ceramic casting techniques commonly known in the art, but may also employ other methods such as 3-D printing. 
         [0046]      FIGS. 5 and 6  show prior art configurations for a vacuum roller and pinch rollers, which are mentioned in the preceding paragraphs. In  FIG. 5 , a roll  502  contains an inner member  505 , inside of which is an area of vacuum, introduced via a vacuum pump. The outside diameter of the inner member  505  and the inside diameter of the roll  502  are very tightly toleranced in order to prevent vacuum leakage. This adds to the cost of the prior art vacuum rolls. Also, the flow rate is very high in this arrangement, and the vacuum pressure which acts on the web  504  by means of being conducted through holes  503  in the roll  502 , is low. The holes  503 , which in reality are closer than shown, still present an issue with causing the web  504  to be marked by the holes  503 . In  FIG. 6 , a traditional pinch roller is shown as being an alternative to producing differential tension. Each of the two rolls  602  and  602  rotate in a different direction and cause the web  601  to traverse, allowing for differential tension on either side of the rolls. However, the obvious detractor from this simple arrangement is the fact that the web  601  is contacted on both sides, with significant pressure (pinching) being applied to the roll. 
         [0047]    While preferred embodiments have been set forth in detail with reference to the drawings, those skilled in the art who have reviewed the present disclosure will readily appreciate that other embodiments can be realized within the scope of the invention, which should therefore be construed as limited only by the appended claims.