Patent Publication Number: US-7707937-B2

Title: Digital impression printing system

Description:
BACKGROUND 
   The following relates to printing systems and methods. It finds particular application to structures that improve print quality. More particularly, it is directed toward structures that use viscous materials for variable data printing. However, other printing techniques are also contemplated. 
   Offset printing is a printing technique in which an inked image is transferred (or offset) to a rubber blanket and then to a printing surface. When used in combination with a lithographic process based on the repulsion of oil and water, the offset technique typically employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing areas attract a film of water, keeping the nonprinting areas ink-free. In other instances, the ink can be applied with a blade or squeegee, as is practiced in the gravure printing process. The ink used for offset printing typically is a highly viscous tar-like material with excellent opacity and little tendency to wick or bleed into the fibers of the paper. The resulting image typically is associated with relatively high image quality (including a sharper and cleaner image than letterpress because the rubber blanket conforms to the texture of the printing surface) and can be formed on various printing substrates (e.g., paper, wood, cloth, metal, leather, rough paper, etc.). However, offset printers generally are inflexible in that every page typically requires a new master. 
   Variable data printing is a form of on-demand printing in which elements such as text, graphics and images may be changed from one printed piece to the next without stopping or slowing down the press. Thus, variable data printing enables the mass-customization of documents. For example, a set of personalized letters can be printed with a different name and address on each letter, as opposed to merely printing the same letter a plurality of times. This technique is an outgrowth of digital printing, which harnesses computer databases and digital presses to create full color documents. However, the image quality of conventional variable data printing typically is inferior to that of offset printing. This is due at least in part to the differences in the ink used. Because offset printing ink is highly viscous, it typically cannot be ejected from ink jet printers or the like. 
   Thus, there is an unresolved need for systems and methods that facilitate producing higher quality images with variable data printing. 
   BRIEF DESCRIPTION 
   In one aspect, a print structure is illustrated. The print structure includes a pattern layer that selectively actuates one or more of a plurality of actuators to selectively form one or more wells in a print surface to create a defined pattern on the print surface. A material is applied to the one or more wells and subsequently transferred to another surface in order to transfer the pattern. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates an exemplary print structure for printing materials; 
       FIG. 2  illustrates a cross section of the exemplary printing structure; 
       FIG. 3  illustrates the exemplary print structure in an “on” state; 
       FIG. 4  illustrates a method for printing with the exemplary print structure; 
       FIG. 5  illustrates a portion of an exemplary print structure with a large ink volume on-off ratio; and 
       FIG. 6  illustrates an exemplary technique for creating the print layer having a plurality of pistons embedded within a sheet. 
   

   DETAILED DESCRIPTION 
   With reference to  FIG. 1 , a print structure  10  for printing various materials such as relatively viscous materials is illustrated. The print structure  10  includes a print layer  12  with a print surface  14  for transferring a material. One or more portions of the print layer  12  can be selectively deformed in order to create one or more wells  16  within the print surface  14 . The one or more wells  16  pattern a structure (e.g., an image) on the print surface  14  and are subsequently filled with the material as illustrated at  18 . Subsequently, the deformations can be released, which transfers the material within the wells  16  from the wells  16  to the print surface  14  as illustrated at  20 . The material can then be transferred from the print surface  14  to another entity  22  as illustrated at  24 . 
   A pattern layer  26  of the print structure  10  resides proximate to the print layer  12 . The pattern layer  26  facilitates forming the pattern on the surface  14  of the print layer  12  by selectively forming the wells  16  within the print layer  12 . In one instance, the pattern layer  26  includes a semiconductor (not shown) that behaves as an insulator unless exposed to energy with predefined characteristics (e.g., energy, wavelength, periodicity, phase, amplitude, etc.). Portions of the semiconductor exposed to such energy are activated and facilitate forming the wells  16  in adjacent portions of the print layer  12 . 
   In one instance, the pattern layer  26  can include a photoconductor (not shown) that is excited by light. In this instance, optical addressing is used to form the wells on the surface  14  of the print layer  12 . For example, upon receiving suitable light the pattern layer  26  can electrostatically form the pattern against the print layer  12 . In this instance, an electric field causes one or more portions of the print layer  12  to deform, thus creating the one or more of the wells  16  within the surface  14 . The material can then be applied to the surface  14  to fill the wells  16 . Upon removing the light source the photoconductor returns to its insulating state. The electrostatic charge is retained and the deformation is maintained. The depressions may then be selectively filled by a viscous ink, for example, with a doctor blade process. The electrostatic charge can be released with a blanket light exposure of the photoconductor, whereupon the wells  16  collapse, which pushes the material to the surface  14 . The material is subsequently transferred from the print surface  14  to the entity  22 , which re-produces the pattern formed within the surface  14  on the entity  22 . 
   The print structure  10  enables variable data printing using viscous inks, which, relative to comparably lower viscosity inks (e.g., those used in ejection printing), run (or bleed) less into a print substrate such as paper. Since viscous inks typically dry in relatively less time than lower viscosity inks and provide highly saturated colors (by virtue of their higher pigment content), the print structure  10  can be used to increase printing speed and/or print highly saturated colors. It is to be appreciated that the print structure  10  can be used for printing highly viscous inks, lower viscous inks, pastes containing metals, semiconductors, ceramics, etc., as well as other materials on various surface such as paper, ceramic, plastic, velum, etc. 
     FIG. 2  illustrates a cross section of one configuration of the print structure  10 . The print structure  10  includes the layer  12  with the surface  14  that selectively holds and transfers materials such as viscous inks. The layer  12  includes a sheet  26  with one or more pistons  28  (e.g., or similar actuators) residing within one or more apertures  30  of the sheet  26 . In one instance, the sheet  26  is a thin foil and the pistons  28  are an array of co-fabricated micro-machined pistons  16 . As depicted, the pistons  28  can have tapered walls that pass through tapered walls of the apertures  30 . Such tapering can be used to limit the travel of each of the pistons  28  to within the sheet  26 , which can prevent the pistons  28  from falling out of the sheet  26  when the layer  12  is not connected to and/or removed from the print structure  10 . 
   Each of the pistons  28  may have a circular shape or non-circular shape, which facilitates mitigating rotation. It is to be appreciated that the pistons  28  and/or the apertures  30  can be associated with various other shapes in order to provide substantially similar and/or different characteristics. A gap  32  resides between the sheet  26  and each of the pistons  28 . In some instances, the sheet  26  is held at electrical ground. In such instances, electrical charge can flow across the apertures  30  to the pistons  28  through at least one of direct surface-to-surface contact, conductivity present in the ink, a conductive grease, as well as through other techniques. Using a conductive grease or ink in the gap  32  can also provide lubrication that mitigates stiction. 
   An inside surface  34  of each of the pistons  28  resides proximate an elastomer layer  36 . The elastomer layer  36  can be a flexible membrane, including a material used for macroscopic artificial muscle devices. In addition, the elastomer  36  can retain a lubricant that forms a bound monolayer. Use of such materials may form protective monolayer on exposed surfaces. In one instance, the inside surface  34  contacts the elastomer layer  36 . 
   A photoconductor  38  is disposed between the elastomer layer  36  and a substrate  40 , which can be formed as a sheet, a cylinder, etc. The photoconductor  38  may be transparent or semi transparent. In some instance, a surface  42  of the substrate  40  facing the photoconductor  38  is coated with a conductive material  44 , which may also be transparent or semi transparent. The conductive material  44  typically is electrically biased with respect to the sheet  12 . For example, the conductive material  44  may be biased with a positive or negative voltage potential with respect to sheet  12 . 
   In an “off” state, the photoconductor  38  behaves as an insulator and thereby limits the electric field across the elastomer  36 . Any deformation of any of the pistons  28  within the elastomer  36  due to electrostatic forces is minimal due to the limited field strength. In an “on” state, the photoconductor  38  is exposed to light through the substrate  40  and the conductive material  44 . In one instance, a raster output scanner (ROS) or image bar is used to source the light. As a result, charge migrates from the conductive material  44  across the photoconductor  38  and creates an electrostatic image against the elastomer  36 . The relatively higher electric field across the elastomer causes one or more of the pistons  28  to be pulled into the elastomer  36 . 
   In the “off” state, the electric field across the elastomer  36  is a function of the following: 
               E   e     =       V   ⁢           ⁢     k   p             t   e     ⁢     k   p       +       t   p     ⁢     k   e             ,         
wherein V is the applied voltage and k p  and k e  are the dielectric constants of the photoconductor  38  and the elastomer  36 , respectively, and t p  and t e  are the thicknesses of the photoconductor  38  and the elastomer  36 , respectively. When the photoconductor  38  is substantially discharged, the field across the elastomer is a function of the following:
 
   
     
       
         
           
             E 
             e 
           
           = 
           
             
               V 
               
                 t 
                 e 
               
             
             . 
           
         
       
     
   
   In order to have a large switching ratio for the electric field applied to the elastomer  36 , the photoconductor  38  is formed to be relatively thick with a small dielectric constant. The deflection of each of the pistons  28  has a super-linear dependence on the electric field across the elastomer  36 . In the “off” state, the deflection can be a fraction of a micron, and in the “on” state, it can be many microns. The photoconductor  38  provides a very compact form of high voltage switch with a suitable on-off ratio. 
     FIG. 3  illustrates the print structure  10  in the “on” state. As depicted, a light source  46  is transmitted through the substrate  40  and the conductive material  44 . Charge  48  migrates from the conductive material  44  through the photoconductor layer  38  to the elastomer layer  38 . In this example, the charge  48  pulls a piston  28 N (where N is an integer equal to or greater then one) through an aperture  30 M (where M is an integer equal to or greater then one) within the sheet  12 , creating a well  50 . 
   In one instance, when the elastomer  36  flexes, its volume does not change appreciably. A consequence of this is that in order for the piston  28  to move down when it is pulled by an electrostatic force, the elastomer  36  must gain volume to the sides of the piston by contracting or bulging. In some artificial muscle actuators, this is accomplished by pre-tensioning the elastomer. A similar approach can be employed in this invention by stretching the elastomer  36  over the print surface. 
   Once the piston  28 N is pulled into the elastomer  36 , a material such as a viscous ink can be applied (e.g., via a squeegee, a roller, etc.) over the surface  14 , including the well  50 . The mechanism used to apply the material exerts a pressure that pushes the ink into the well  50 . In some, but not all, instances, the pressure additionally moves one or more of the other pistons  28 , creating more wells  50  that fill with the material. This could occur, for example, if the pressure is high enough and the applicator is deformable enough to push the pistons  28  down and load them with the material as it passes. 
   The ink volume delivered is a monotonic function of the applied voltage across the elastomer  36 . The above discussion relates to a substantially insulating photoconductor. However, a partially conducting photoconductor enables writing of varied amounts of charge onto the elastomer  36 . This can be achieved by varying light intensity in order to achieve a desired voltage level on the elastomer  36 . 
   The pressure applied to a surface of each of the pistons  38  is a function of the following:
 
 P=−∈   0   k   0   E   e   2 ,
 
where ∈ 0  is the permittivity of free space. This expression is valid for strains of up to approximately 20%. By expressing the strain as a change in the initial thickness of the elastomer  36 , the expression for the thickness of the elastomer  36  is a function of the following:
 
 t   e   3   −t   e0   t   e   2   +c =0,
 
wherein
 
             c   =         ɛ   0     ⁢     k   e     ⁢     t     e   ⁢           ⁢   0       ⁢     V   2       Y       ,     t     e   ⁢           ⁢   0             
is the initial thickness of the elastomer  36  in zero applied field, and Y is the elastic modulus of the elastomer  36 . The constant c is the strain predicted if one does not allow for the field enhancement stemming from the change in elastomer thickness.
 
   After the material is applied to the surface  14  and the charge is removed, the pistons  28  will substantially return to their initial position, pushing any material associated therewith up as they recoil. This results in a surface with material above those areas where the pistons  28  were actuated. The material can then be transferred to another surface, substrate, or the like. In one instance, the surface  14  may be covered with a flexible elastomer to prevent dirt, dust, ink, etc. from clogging the mechanism and/or facilitate cleaning of the print surface  14 . This material may be, for instance, induction welded or laser welded to the metal surface. In these methods, the gap between the pistons and the support grid can stay clean. 
   It is to be appreciated that the print structure  10  can accommodate a constant volume. Several features of the print structure  10  that facilitate accommodation of the constant volume include, but are not limited to, electrodes that slip, the gaps  32  around the pistons  28 , and/or a shape of the heads of the pistons  28 . For example, using a dome shaped piston head (as illustrated in  FIGS. 2 and 3 ) can increase the area of electrode contact as the piston  28  is pulled into the elastomer  36 . This can enhance a non-linear actuation, which can be leveraged to improve the on-off ratio of the structure. In another example, the elastomer  36  can be formed from one or more adhesive based acrylics in which the slipping capability is enabled with a surface treatment or lubricious coating. A carbon grease substantially similar to that used for making artificial muscle can also be used with the structure. Using such carbon grease and/or a comparable conducting lubricant facilitates maintaining electrical conductance between the sheet  12  and the pistons  28 . Additionally or alternately, a thin layer of dielectric lubricant can be used. The thin layer can be associated with a relatively high dielectric constant that would have negligible affect on the overall electric field applied across the elastomer  36 . 
   A photoconductor-elastomer interface  52 , volume conservation can be enhanced by providing a dielectric lubricant at the interface  52  in order to allow it to slip. Although the elastomer  36  can be designed to slip with respect to the photoconductor  38 , which typically is solidly attached to the substrate  40 , it can be held in place by various mechanism in order to hold the structure together. For example, in one instance the elastomer  36  is stretched and clamped or bonded outside of an active area. Incorporation of a lubricant can facilitate the stretching. The sheet  12  and/or the pistons  28  can be attached by adhered dielectric standoffs and/or other mechanisms. The structure can also be held together through the compressive Maxwell stress that actuates the pistons  28 . A typical force on the sheet  12  and/or the elastomer  36  is less than the localized force on the pistons  28 , but is on the order of a couple of PSI when the structure is in an unswitched state. For a printing device with an area of 12 inches by 12 inches, a total force on the order of about 300 lbs typically holds the sheet  12  and/or the pistons  28  against the elastomer  36  and/or the photoconductor  38 . Another technique is to apply a voltage to hold the sheet  12  and subsequently spot-weld the edges of the sheet  12  together to hold it in place. 
   Gaps around the pistons  28  provide the elastomer  36  somewhere to go as the thickness under the pistons  28  is reduced. In one instance, pretension on the elastomer  36  is used to facilitate accommodating the volume around the electrodes. For example, the elastomer  36  can be stretched and clamped at the edges before it is incorporated into the structure. This can also facilitate establishing a suitable thickness for the structure. In one instance, the elastomer  36  is about 0.5 to 1.0 mm think and is stretched about 4× in an x and/or y direction, which can results in a thickness of about 30 to 60 μm. The elastomer  36  may also be fabricated using a molding technique, e.g., from a silicone or an acrylic material. When using molding, the surface of the elastomer  36  facing the pistons may be patterned with gaps to allow for lateral expansion of the elastomer  36  when the pillars are pulled into the elastomer  36 . 
   Optical addressing is described herein. However, other address schemes such as an active matrix backplane of high voltage thin film transistors may also be used for addressing the elastomer-actuated pistons described herein. 
     FIG. 4  illustrates a method for printing with the print structure  10 . At reference numeral  54 , a portion of the surface  14  is deformed to create the one or more wells  50  that form a pattern on the surface  14 . This can be achieved through electrostatic charge or other mechanism. For instance, light can be directed through the substrate  40  and the conductive material  44  to the photoconductor  38 . The light can be sourced from a raster output scanner (ROS) or image bar. The light can induce charge associated with the conductive material  44  to migrate across the photoconductor layer  38  and form an electrostatic image against the elastomer layer  36 , which creates an electric field that pulls one or more of the pistons  28  into the elastomer layer  36 . 
   At  56 , a material such as a viscous ink can be applied (e.g., via a squeegee, a roller, etc.) over the surface  12  and the wells  50 . The mechanism used to apply the material exerts a pressure the pushes the material into the wells  50 . The pistons  28  return to about their initial position, pushing any material associated therewith up as they recoil. Any extraneous or excess material can be eliminated by running a cleaning blade or the like over the surface  14 . At reference numeral  58 , the applied voltage is discharged, allowing all of the pistons  28  to return to about their initial positions. This results in a surface that is inked in those areas where the pistons  28  were actuated. At  60 , the material can be transferred to another surface. 
     FIG. 5  illustrates a portion of the print structure  10  with a large ink volume on-off ratio. For this example, the print structure  10  has a plurality of pistons  28  arrayed at approximately 1000 dots per inch (DPI). The pistons  28  are designed to have a taper of about 5 degrees over a 25 micron length as illustrated at  62 . On the surface  14 , the pistons  28  have a diameter of about 10 microns and, on an opposing surface located proximate the elastomer  36 , the pistons  28  have a diameter of about 5 microns, as illustrated at  64 . The gaps  32  between each of the pistons  28  and the sheet  12  is about 0.25 microns. This provides a vertical flexibility of about 3 microns. 
   The volume displaced by each of the pistons  28  over its range of travel is about 200 cubic microns (0.2 pico-liters). The flexibility of each of the pistons  28  can optionally be designed to be greater than the range of motion that each of the pistons  28  will ever encounter during printing operations. The drag on each of the pistons  28  is inversely proportional to the gaps  32 . An optional patterned dielectric spacer layer  66  is disposed between the sheet  12  and the elastomer  36 . The patterned dielectric spacer layer  66  minimizes interactions between neighboring pistons  28 . This facilitates mitigating pulling portions of the sheet  12  into the elastomer  36  by actuated pistons  28  when an extended area is written with charge. This pixel-wise support structure allows the structure to faithfully reproduce low spatial frequency content of an electrostatic image. 
   In instances where the pistons  28  are made out of electroformed nickel or permalloy, the expansion rate of the pistons  28  typically will range from about 7 to about 13.4 ppm/° C. Over a 12 inch wide drum, a 10° C. temperature change may elicit about a 30 μm change in a size of an array of the pistons  16  across the substrate  40 . In instances where the body of the substrate  40  is formed from glass with an expansivity of about 10 ppm/° C., the run-out between a body of the substrate  40  and the pistons  28  will be only a few microns over 12 inches. The relative run out between the pistons  28  and the substrate  40  typically is an amount that the elastomer  36  can accommodate. With suitable materials selection, a nearly exact thermal expansion match can be achieved. In instances where there is only one patterned element (e.g., the sheet  12  with the embedded pistons  28 ), there is no misalignment of fine features due to temperature changes. 
   The printing structure described herein may include millions (e.g., more than 100 million) functioning pistons  28  in order to produce high resolution images. In one instance, an electroforming technique can be used to create the sheet  12  and the pistons  28  of the printing structure.  FIG. 6  illustrates an exemplary electroforming technique for creating the sheet  12  with the embedded pistons  28 . 
   At reference numeral  68 , an array of posts is fabricated onto a smooth substrate that is metallized with an electroplating seed layer. The posts can be constructed from a photoresist layer or the like in which portions of the photoresist layer are exposed with a dose that fully develops the portions, leaving behind the posts, which may be relatively narrower at an end farthest away from the substrate. The seed layer can be formed from a thin Ti layer with a thin cladding of gold or otherwise. 
   At  70 , a sheet of metal (e.g., nickel, copper, permalloy, etc.) with one or more apertures is plated up from the substrate. This can be achieved by providing an electroplating seed layer on the substrate prior to fabricating the posts and using this seed layer as a cathode during electroplating. Typically, the metal is formed in a space filling layer everywhere except where it is blocked by the posts. Once the sheet of metal is formed, it can optionally be flattened by a chemical mechanical polishing (CMP) technique. A dielectric spacer layer may be introduced by a technique such as spinning and patterning a dielectric such as polyimide or the like. The purpose of this dielectric spacer layer is to prevent the entire foil from getting pulled into the elastomer and thereby limit actuation to the piston. The posts are then removed, for example, by dissolving the posts in a resist stripper. 
   At reference numeral  72 , a mask can be applied to introduce a pattern to define heads for the pistons. In one instance, a negative acting resist is used to introduce a re-entrant sidewall to the resist so that the heads that are formed will be wider at the end closest to the substrate and narrower at the end farthest from the substrate. Such structure may better accommodate a deforming elastomer as described previously. The resulting structure, with its re-entrant holes is coated with a conformal sacrificial layer. A suitable technique for applying the sacrificial layer is electroplating. For example, gold can be electroplated onto the exposed conducting surfaces. At reference numeral  74 , electroforming can be used to plate up metal to define the pistons. The second resist mask and the release layers are removed, separating the pistons from the sheet and separating the sheet and the pistons from the substrate. 
   Table 1 illustrates various input parameters and results (e.g., strains, thicknesses, deflections, etc.) predicted in design calculations based on the known values for the materials employed and reasonable dimensions for the elastomer  36  and/or the photoconductor  38 . In this case, the photoconductor  38  can be a multi-layer active matrix (AMAT) type. A typical example is a combination of a generator layer, such as benzimidazole perylene (BZP), and a thick hole transport layer such as triphenyl diamine derivative (TPD). 
   
     
       
         
             
           
             
               TABLE 1 
             
             
                 
             
             
               Exemplary Modeling Parameters and Results 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
          
             
                 
               Input Parameters 
             
             
                 
                 
             
          
         
         
             
             
             
             
          
             
                 
               Voltage 
               2000 
               Volts 
             
             
                 
               Permitivity 
               8.85E−12 
               F/m 
             
             
                 
               Elastomer Modulus 
               2 
               Mpa 
             
          
         
         
             
             
             
          
             
                 
               Elastomer Dielectric Constant 
               4.8 
             
          
         
         
             
             
             
             
          
             
                 
               Elastomer Relaxed Thickness 
               25 
               μm 
             
             
                 
               Photoconductor Thickness 
               35 
               μm 
             
          
         
         
             
             
             
          
             
                 
               Photoconductor Dielectric 
               2.9 
             
          
         
         
             
             
             
             
          
             
                 
               Piston Diameter 
               5 
               μm 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
          
             
                 
               Results 
                 
               Switched 
               Unswitched 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
             
          
             
                 
               Initial Elastsomer Field 
               80.0 
               MV · m 
               24.1 
               MV/m 
             
          
         
         
             
             
             
             
          
             
                 
               C 
               0.136 
               0.012 
             
             
                 
               Normalized Length 
               0.772 
               0.987 
             
             
                 
               Strain 
               22.82% 
               1.27% 
             
          
         
         
             
             
             
             
             
             
          
             
                 
               Thickness 
               19.29 
               μm 
               24.68 
               μm 
             
             
                 
               Deflection 
               5.71 
               μm 
               0.32 
               μm 
             
             
                 
               Elastomer Field 
               103.7 
               MV · m 
               24.2 
               MV/m 
             
             
                 
               Photoreceptor Field 
               0.0 
               MV/m 
               40.1 
               MV · m 
             
             
                 
               Ink Volume/Pixel 
               112.0 
               μm {circumflex over ( )}3 
               6.2 
               μm {circumflex over ( )}3 
             
             
                 
                 
             
          
         
       
     
   
   From Table 1, the dielectric constant of the photoconductor  38  can be on the order of 2.9. A vertical displacement of the piston  28  on the order of 5 microns can be achieved with an applied voltage of about 2000 Volts. For a piston  28  about 5 microns in diameter, this represents a volume of ink of about 100 μm3, which is equal to about 0.1 pico-liters. Ink jet delivery systems have drop sizes that are typically much larger. Thus, the print structure  10  can provide for variable data printing at higher resolution and with higher quality inks than current ink printers and laser printers. The piston length can be designed such that it is slightly longer than a thickness of the sheet  12  in order to produce a well of zero volume in the off state. 
   It is to be appreciated that the printing structure  10  described herein can be adapted for offset printing, wherein an inked impression from a plate is first made on a rubber-blanketed cylinder and then transferred to the paper being printed. The offset printing technique can be leveraged in instances where paper fibers have an undesirable affect on the pistons  28 . In such instances, an intermediate rubber cylinder may extend the service life of the pistons  28 . 
   The methods described above in  FIGS. 4 and 6  illustrate as a series of acts; however, it is to be understood that in various instances, the illustrated acts can occur in a different order. In addition, in some instance, the one or more of the acts can concurrently occur with one or more other acts. Moreover, in some instance more or less acts can be employed. 
   It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.