Apparatus for detecting electrically conductive coatings on documents

• US 4,313,087 A
• Filed: 02/07/1980
• Issued: 01/26/1982
• Est. Priority Date: 02/07/1980
• Status: Expired due to Term

• Current Assignee: Mellon Bank National Association A National Banking Association
• Original Assignee: Edward H. Weitzen, Salvatore F D'Amato
• Inventors: D'Amato, Salvatore F., Weitzen, Edward H.
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US06/119,511
• Time in Patent Office: 719 Days
• Field of Search: 324/65 R, 324/65 P, 104/88, 198/352, 200/46, 209/534, 235/925 B, 235/441
• US Class Current: 324/718
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: G07D 7/023 Measuring conductivity by direct contact
• CPC Class Codes: G07D 7/128 Viewing devices

Abstract

This apparatus tests the genuineness of a document carrying anticounterfeit protection in the form of a usually invisible, electrically conductive coating on at least part of a surface. The apparatus may be arranged to respond to the presence of a coating anywhere on the surface, or it may be arranged to respond only to a coating of specific contour, in a specific location. The apparatus shown comprises an array of contacts and means for supporting a document to be tested in conductive engagement with said contacts. Certain ones of the contacts engage the conductive layer, and are connected in an electric circuit which is completed through the conductive layer. Completion of the circuit is required to produce an indication that the document is genuine. The conductance of the conductive layer must be within a predetermined range in order to produce a signal indicating that the document is genuine. The contacts which engage areas of the document where there should be no conductive layer, may be connected in a second circuit which, if completed through a conductive layer, prevents the production of a signal indicating that the document is genuine.

Claims

1. Apparatus for determining the genuineness of a document of electrically non-conductive material coded by means of an invisible, electrically conductive surface layer of predetermined conductance in a limited locality thereof, comprising:

a. an array of conductance sensing elements separated by insulating means, said array extending over an area greater than the area of said locality;

b. means for receiving the document in a stationary test position wherein said locality of the document is adjacent a portion only of said array of sensing elements; and

c. indicating means, including only said portion of said array of conductance sensing means, said indicating means being operable when the conductance of said layer is within a predetermined range of said predetermined conductance to produce a positive indication that the document is genuine.

2. Apparatus as in claim 1, including:

a. a second portion of said array of conductance sensing elements adjacent at least one other locality of the document in said test position; and

b. means responsive to the conductance sensing elements of said second portion and effective if the conductance in said other locality exceeds a predetermined value to prevent operation of said indicating means to produce said positive indication.

3. Apparatus as in claim 2, in which said limited locality includes at least one band extending across the document surface and said other locality includes all areas of the document surface other than said limited locality.

4. Apparatus for determining the genuineness of a document of electrically nonconductive material coded by means of an invisible electrically conductive surface layer of predetermined conductance in a limited locality thereof, comprising:

a. a support member for receiving the document in a stationary test position with said surface layer facing the support member;

b. an array of spaced electrical contact elements fixed on the support member and adapted to engage said surface layer when the document is in said position;

c. means for engaging the opposite surface of the document and forcing said layer into engagement with the contact elements;

d. means connecting one terminal of an electrical circuit to at least one of the contact elements engaging said limited locality;

e. means connecting a second terminal of said circuit to at least one other of the contact elements engaging said limited locality; and

f. indicating means in said circuit responsive to the conductance between said terminals and operable when said conductance is greater than a predetermined value to produce a positive indication that the document is genuine.

5. Apparatus as in claim 4, including means effective if the conductance is greater than a second predetermined value to prevent operation of said indicating means to produce a positive indication.

6. Apparatus as in claim 4, including means for testing the conductance of said document in a locality other than said limited locality and effective if the conductance in said other locality is greater than a predetermined value to prevent operation of said indicating means to produce a positive indication.

7. Apparatus for determining the genuineness of a document of electrically non-conductive material coded by means of an invisible electrically conductive surface layer of predetermined conductance in a limited area having a location relative to the edges of the document which is defined by the code, comprising:

a. conductance sensing means including an array of electrically conductive elements, each substantially smaller than said area, said elements being separated by insulating means, said array extending over an area substantially greater than the limited area;

b. means for engaging the edges of the document to hold said area in cooperative relationship with only a portion of the elements, said portion being defined by the code;

c. electrical circuit means including only said portion of said elements and responsive to the conductance of said layer; and

d. indicating means operated by said circuit means and effective only when the conductance of said layer is within a predetermined range of said predetermined conductance to produce a positive indication that the document is genuine.