Abstract:
A deformable pad ( 100 ) for pad printing has an initially flat side ( 105 ) and an opposite bulged side ( 110 ). An ink image ( 610 ) is applied to the flat side of the pad using an inkjet head ( 605 ) or other ink image source. The pad is then distorted using a ram ( 600 ) or hydrostatic or pneumatic source applied to a chamber ( 1300 ) so that the initially bulged side is flattened and the initially flat side bulges. After distortion, the now bulged side with the ink image is pressed against a receiving surface for transfer of the ink image to the surface. An alternative embodiment starts by deforming a pad to produce a flat surface, inking the surface with an image, then allowing the pad to relax, rendering the previously flat, image-bearing surface newly bulged. The newly-bulged surface is then temporarily urged against a receiving surface for transfer of the ink image.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority of our provisional patent application, Serial Number US60/709,216, filed Aug. 18, 2005. 

   BACKGROUND 
   1. Field of Invention 
   This invention relates to printing, and in particular to printing with a deformable pad. 
   2. Prior Art 
   Pad printing has long been used to apply images to surfaces. This printing technology is especially useful for applying images to uneven, non-flat surfaces of virtually any size. These include products ranging from bottles to cellular telephones to home and industrial appliance panels. 
   The concept of a deformable pad for printing is taught in our U.S. Pat. No. 6,840,167 (2005). The pad comprises a flat sheet of flexible pad material, such as silicone rubber. It is preferably square, 10 cm on a side, and 1.5 cm thick. The pad can be smaller or larger. The size of the pad is determined by the area and shape of the final receiving surface. 
   The pad is initially flat and its edges are restrained by a holding bracket. An inkjet head deposits an image on the flat front pad surface. The pad is then forcibly deformed by a ram applied to the opposite side of the pad. The ram preferably has a curved frontal shape. Since the edges of the pad are restrained, the ram forces the pad into a bulged shape. The bulged pad is then brought into contact with the final receiving surface. The previously-applied inkjet image transfers from the pad to the receiving surface. A printed or decorated receiving surface results. The principal advantage of this system is the ability to transfer multi-color images in a single step. This system has been shown to work well, however operation of its pad can be improved for use in certain machine configurations. 
   SUMMARY 
   An alternative pad design comprises, in one embodiment, a bulged pad. A flat ram is used to deform the pad, but a shaped ram can still be used. 

   
     DRAWING FIGURES 
       FIGS. 1-3  show top, side, and bottom views of an ellipsoidal or circular aspect of a first embodiment. 
       FIGS. 4 and 5  show top and sectional views of a pad with mechanical restraining apparatus, according to the first embodiment. 
       FIG. 6  shows the pad in its undeformed condition receiving an inkjet image. 
       FIG. 7  shows the pad being deformed by a ram. 
       FIG. 8  shows the pad fully-deformed, ready to transfer the inkjet image to a receiving surface. 
       FIG. 9  shows the pad being urged into contact with the final receiving surface, thereby transferring the inkjet image from the pad to the surface. 
       FIG. 10  shows the pad and the receiving surface after the two are separated. 
       FIG. 11  shows a parallelepiped-shaped pad. 
       FIG. 12  shows a pad with a spring-metal insert. 
       FIGS. 13 and 14  show a bulged pad with a vacuum or pressure chamber for changing the shape of the pad. 
   

   DRAWING FIGURE REFERENCE NUMERALS 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               DRAWING FIGURE REFERENCE NUMERALS 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               100 
               Pad 
             
             
               105 
               Surface 
             
             
               110 
               Bulge 
             
             
               111 
               Shape 
             
             
               112 
               Shape 
             
             
               115 
               Region 
             
             
               400 
               Ring 
             
             
               405 
               Ring 
             
             
               410 
               Fastener 
             
             
               600 
               Ram 
             
             
               605 
               Head 
             
             
               610 
               Droplet 
             
             
               800 
               Surface 
             
             
               1200 
               Spring 
             
             
               1300 
               Chamber 
             
             
               1305 
               Connection 
             
             
                 
             
           
        
       
     
   
   DESCRIPTION 
   First Embodiment—FIGS.  1 - 3   
   A pad  100  ( FIG. 1 ) according to one aspect of a first embodiment is preferably cast or molded in silicone rubber of Shore (also known as durometer) hardness between 5 and 85, although other hardness values can be used. The required hardness of the rubber is determined by a number of factors, including the size of the object to be decorated (printed), the thickness of the pad, the ink used, and so forth. Alternatively, pads can be made from gelatin and other elastomers. When at rest, pad  100  has a normally flat surface  105  on its active or front side, and a bulge  110  ( FIG. 2 ) on the back side, surrounded by a flat surface region  115 . Flat surface  105  is typically treated in such a way that it will fully release ink onto a receiving surface (not shown) when the two are brought into contact. In this embodiment, pad  100  is 10 cm in diameter, although smaller and larger sizes can be used, depending on the size of the area to be printed. Pad  100  is 1 cm thick at its edges, and 2.5 cm thick at its center. The diameter of bulge  110  ( FIG. 3 ) at its outer edge is preferably between 5 and 8 cm, In this embodiment, bulge  110  has an axially symmetric domed shape ( FIG. 2 ), although other shapes such as a cylinder, shown in dashed lines  111 , can be used. The cross-sectional shape of bulge  110  can be circular as shown, or another shape such as elliptical as shown by dashed lines  112  ( FIG. 3 ). It can also be a parallelepiped ( FIG. 11 ) or another shape. Different thicknesses can also be used. A flat region  115  surrounds bulge  10 . The intersection between surface  115  and bulge  110  can be sharp or gradual, depending on user preference and the printing job at hand. 
   Operation— FIGS. 4 through 10   
   In preparation for use, pad  100  is restrained by two concentrically disposed annular rings,  400  and  405  ( FIGS. 4 and 5 ). Ring  400  is placed in contact with flat surface  105  on the front side and ring  405  is placed in contact with flat region  115  on the rear side. Mechanical fasteners such as bolts  410  are used to secure pad  100  between rings  400  and  405  together. More or fewer bolts  410  can be used, depending on the stresses encountered during the deformation of pad  100 , as described below. 
   In  FIGS. 6 through 10 , the assembly of  FIG. 5  is inverted so that front surface  105  faces downwardly. A mechanical ram  600  is positioned above bulge  110  of pad  100 . No external force is applied to pad  100  and it is said to be in a resting condition. An inkjet head  605  or other ink source including, but not limited to electrographic, spray, and other marking technologies emits fine droplets  610  onto flat surface  110 . These droplets form an image to be printed in well-known fashion. 
   In  FIG. 7 , inkjet head  605  has been removed. Ink droplets rest on pad  100  in the shape of the image to be printed. Pad  100  is deformed as ram  600  moves downward against it. Pad  100  and rings  400  and  405  are restrained from moving relative to ram  600  by an external restraining mechanism (not shown) which is attached to the same datum as the driving force for ram  600 . Formerly flat surface  105  begins to bulge outward opposite ram  600 . 
   In  FIG. 8 , ram  600  has pushed the back or top surface  110  of pad  100  down to the level of the bottom of ring  405  so that formerly flat side  105  of pad  100  is fully-bulged. Bulge  110  is flattened by ram  600  and formerly flat side  105  of pad  100  now bulges outward. A receiving surface  800 , such as a cellular telephone case, is shown in place below pad  100  prior to transfer of ink droplets  610 . 
   In  FIG. 9 , ram  600 , pad  100 , and rings  400  and  405  move downward as a unit toward the top surface of an object  800 . Side  105  of pad  100  is deformably pressed against the top surface of object  800 , applying ink droplets  610  to the top surface of object  800 . 
   In  FIG. 10 , all of droplets  610  have been transferred to object  800  and ram  600 , pad  100 , and rings  400  and  405  have moved upward as a unit away from the top surface of object  800 . The printing operation is complete. 
   Ram  600  now moves upward (not shown), away from pad  100 , returning pad  100  to its resting condition. Bulge  110  resumes its original shape, shown in  FIG. 6 , and the printing operation can be repeated. The same or a different image can be applied to surface  105  of pad  100  for a subsequent transfer. 
   The flat side of pad  100  is made to bulge during transfer in order to prevent the entrapment of air between pad  100  and the receiving surface of object  800 . As pad  100  is urged against object  800 , the bulged surface of pad  100  executes a rolling motion. This motion prevents formation of air pockets which can otherwise abruptly release air, causing ink droplets  600  to be ejected in a direction parallel to the surface of object  800 , thereby ruining the image. 
   If the receiving surface of object  800  is flat, bulging pad  100  prior to transfer does not distort the image since pad  100  is again flattened by the surface of object  800  during transfer; an image is applied to a first flat surface and then transferred to a second flat surface. However, if the surface of object  800  is irregular, steps must be taken to properly pre-distort the image to be transferred. This pre-distortion step is well-known to those skilled in the art of pad printing. It is normally done in imaging software (not shown) prior to applying droplets  610  to pad  100 . 
   Alternative Embodiments—FIGS.  11  through  14   
   The embodiment of  FIGS. 1-3  has, when seen from below, a circular or ellipsoidal bulge  110  ( FIG. 3 ). The embodiment of  FIGS. 11 to 14  has, when seen from below, a square or rectangular parallelepiped bulge  110 ′ as best seen in  FIG. 11 . Pad  100  includes a border region  115 ′ between bulge  110  and the outer edges to provide for an appropriately (in this case square) shaped restraining ring  400  and mounting ring  405 . Similarly, ram  600  has the same shape as dome or bulge  110 . 
   In another aspect, shown in  FIG. 12 , an internal metal spring  1200  can be inserted or cast into pad  100 . Spring  1200  aids in maintaining the flatness of surface  105  after pad  100  has been deformed and then released to return to its original shape. 
   Instead of steel, an elastomeric material such as a thermoplastic rubber can be used for spring  1200 . In this case, elastomeric spring  1200  extends to near the edges of pad  100  and be anchored by bolts  410 . 
   In yet another aspect,  FIGS. 13 and 14  show a pad which is normally “bulged” in its resting condition. Pad  100  normally has the shape shown in  FIG. 14 . A chamber  1300  with a tubular connection  1305  to a source of pressure or vacuum (not shown) is sealed against the top side of pad  100 . When it is desired to apply an ink image to pad  100 , as shown in  FIG. 13 , a vacuum is drawn through connection  1305  until the bottom side of pad  100  is flat. The ink image, represented by droplets  610 , is then applied to surface  105  by inkjet head  605  while pad  100  is in its deformed condition. When it is desired to transfer ink droplets  610  to a receiving surface (not shown), the vacuum in chamber  1300  is released and replaced by atmospheric or even positive pressure in order to restore the resting shape (bulged) of pad  100 . Pad  100  is then brought into contact with the receiving surface and transfer of the ink image, represented by droplets  610 , is complete. The cycle can then be repeated. 
   In still another aspect,  FIGS. 13 and 14  show a pad which is normally “flat” in its resting condition. It is forced to bulge by either hydrostatic or pneumatic pressure. Pad  100  normally has the shape shown in  FIG. 13 . When it is desired to apply an ink image to pad  100 , as shown in  FIG. 13 , no gauge pressure is applied through connection  1305 . The ink image, represented by droplets  610 , is then applied to surface  105  by inkjet head  605  while pad  100  is in its resting condition. When it is desired to transfer ink droplets  610  to a receiving surface (not shown), chamber  1300  is pressurized and forced into a bulged condition ( FIG. 14 ). Pad  100  is then brought into contact with the receiving surface and transfer of the ink image, represented by droplets  610 , is complete. As in the previous aspect, the cycle can then be repeated. 
   The various alternative embodiments provide additional ways to use the basic concept of the first embodiment. One embodiment may be selected over another when it is desired to print either a small or a large number of parts, for example. Alternatively, one embodiment may be selected over another when printing machine cost, size, or complexity is a consideration. 
   SUMMARY, RAMIFICATIONS, AND SCOPE 
   Thus it is seen that we have provided an improved deformable pad for pad printing. Instead of deforming a flat shape with a domed ram, a flat ram is used to deform a domed pad. Alternatively, a domed ram can still be used. Instead of a mechanical ram, the shape of the pad can be controlled by application of pressure or a vacuum to the back side of the pad. In some applications, this pad provides an advantage in that a simpler ram, i.e. one with a flat face, can be used. In the case of a flat-face ram, the same ram can be used with pads of different sizes and there is no critical requirement to center the ram on the bulge of the pad. 
   While the above description contains many specificities, it will be apparent that the inventive system is not limited to these and can be practiced with the use of additional hardware and combinations of the various components described. For example, a variety of shapes of ram, pad, and restraining members can be used, including rectangular, oval, star-shaped, pentagonal, hexagonal, octagonal, and the like. The size of the pad can vary from very small to very large, depending on the size of the surface to be printed. A wide variety of materials can be used for the components. 
   Accordingly the full scope of the invention should be determined by the appended claims and their legal equivalents, rather than the examples given. Also, while the present system employs elements that are well-known to those skilled in the art of pad printing, it combines these elements in a novel way which produces a new result not heretofore discovered.