Patent Publication Number: US-2012031289-A1

Title: Print Pad Blanket

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application 61/370,370, filed Aug. 3, 2010. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to improvements in three dimensional printing involving extending the life of print pads. 
     BACKGROUND OF THE INVENTION 
     Silicone rubber printing pads are the cost effective standard for pad-transfer printing. For every printing application there is an optimum pad size, shape, and hardness (durometer). Silicone rubber pads are compressed at print time to match the exterior dimensions of the surface to be printed, permitting the entire three-dimensional surface to be reached by the printing surface. 
     Because the surfaces to be printed are hard, and the pad is relatively soft, welts eventually appear in the surface of the print pads resulting in tears and fractures to the silicone pad surface. These welts eventually render the pads useless and the relatively expensive pads must be replaced. 
     A method of covering the soft print heads with a replaceable printing surface is needed to reduce replacement cost of the printing pad. The prior art reveals a collection of alternative print pad designs, but no print pad covers. US Pat. Appl. 2008/0105145 and US Pat. Appl. 2009/0211476 are examples of the prior art. Previous patents including U.S. Pat. No. 7,651,652 to Cameron show a concentration on printing pad manufacture and shape design, not protecting the printing surface from permanent indentation or tearing. 
     SUMMARY OF THE INVENTION 
     The present invention consists of a sheet of smooth, soft material, or a blanket, that is held over the printing surface of a silicone rubber printing pad during the printing process. The entire invention is comprised of the blanket plus several mechanisms to attach it removably to an industry-standard soft silicone printing mechanism and to keep said blanket under tension across the printing head. 
     The blanket is a smooth sheet that is not constrained to the shape of the printing head but is laid across heads of any shape. The blanket is significantly cheaper to produce and easy to attach and remove from the printing mechanism. 
     The sheet material is made of silicone or polyurethane (not limited to). The thickness and hardness (durometer) of the sheet material can be varied to adjust to any print application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . Assembled print head with print head blanket 
         FIG. 2 . Alternate view of the invention 
     
    
    
     DETAILED SPECIFICATION 
       FIG. 1  illustrates an embodiment of a three-dimensional printing mechanism with a print head blanket covering the silicone print head. The key parts of the invention are the pad blanket  102 , the pad adapter  103 , the four tension blocks  104 , the pad clamps  107 , and the standard printing pad  101 . The printing pad  101  in  FIG. 1  is in a characteristic shape, but printing pads  101  of any shape can be covered with this invention. 
     A variety of attachment devices hold the parts together; in  FIG. 1  and  FIG. 2 , these devices are screws, but other attachment means are possible. 
     The pad blanket  102  is held by the pad clamp  107  on each side of the invention across the outer surface of the printing pad  101  under tension supplied by the tensions blocks  104 . The tension on the pad blanket  102  can be adjusted by means of the set screws  108  inserted in the tension blocks  104 . The invention is designed to keep an even tension on the pad blanket  102  at all points of the printing pad  101  surface by means of the pad clamps  107 . 
     The pad blanket  102  is easily removable and can be replaced quickly when the pad blanket  102  becomes permanently indented with welts from printing on hard, three-dimensional surfaces. As a consequence, the more expensive printing pads  101  can be used for thousands of additional print impressions before becoming permanently indented, saving substantial amounts of money in the printing process. 
     The print blanket  102  is comprised of any soft but firm material, such as silicone or urethane. The preferred embodiment uses a print blanket  102  comprised of silicone. 
     This invention has other applications, potentially, and one skilled in the art could discover these. The explication of the features of this invention does not limit the claims of this application; other applications developed by those skilled in the art will be included in this invention.