Patents by Inventor Donald Hoffmann

Donald Hoffmann has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Hidden entry system and image-developing device therefor
    Patent number: 5484169
    Abstract: A hidden entry system comprises a document having a first substrate bearing a localized latent image spaced apart from a removable image-developing device comprising a second substrate having a first surface and a second surface, the first surface of the second substrate bearing a chromogenic composition comprising an image-forming co-reactant, the image-forming co-reactant being a chromogen or a color developer, the second surface of the second substrate bearing a pressure-sensitive adhesive. The image developing device is in superposed relation with the first substrate with the pressure sensitive coating being releasably attached to the first substrate.
    Type: Grant
    Filed: February 17, 1995
    Date of Patent: January 16, 1996
    Assignee: Wallace Computer Services, Inc.
    Inventors: John C. H. Chang, Donald Hoffmann
  • Hidden entry system and image-developing device therefor
    Patent number: 5431452
    Abstract: A hidden entry system comprises a document having a first substrate bearing a localized latent image spaced apart from a removable image-developing device comprising a second substrate having a first surface and a second surface, the first surface of the second substrate bearing a chromogenic composition comprising an image-forming co-reactant, the image-forming co-reactant being a chromogen or a color developer, the second surface of the second substrate bearing a pressure-sensitive adhesive. The image developing device is in superposed relation with the first substrate with the pressure sensitive coating being releasably attached to the first substrate.
    Type: Grant
    Filed: August 23, 1993
    Date of Patent: July 11, 1995
    Assignee: Wallace Computer Services, Inc.
    Inventors: John C. H. Chang, Donald Hoffmann