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*** About this annotated text version: This display of U.S. Patent No. 5,559,664 is formatted for easy reading. Primarily, that means that we dispensed with the column format. We have maintained the page and column breaks of the published patent for compatibility, and to keep the page sizes small. We inserted page and column numbers for reference, and added navigation links and links to explanatory notes. These things are in color and are not part of the actual patent text. Also, we replaced non-text characters -- for example, Greek letters -- with their names. These are also in color and enclosed in square brackets.
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United States Patent [19] 1
[11] Patent Number: 5,559,664 2
Dogul et al. [45] 3
Date of Patent: Sep. 24, 1996 4
[54] ELECTROMECHANICAL RELAY SYSTEM
[75] Inventors: James Dogul, Hudson, N.H.; Sandip Sarkar, North Providence, R.I.; Frederick Thomson, Cumberland, R.I.; Robert Thomson, Warwick, R.I. 6
[73] Assignee: Frost Controls, Inc., Smithfield, R.I. 7
[21] Appl. No.: 73,096 8
[22] Filed: Jun. 7, 1993 9
Related U.S. Application Data
[62] Division of Ser. No. 755,566, Sep. 5, 1991, Pat. No. 5,218,196. 10
[51] Int. Cl.(6) G01V 9/04 11
[52] U.S. Cl. 361/191; 361/160; 361/154
[58] Field of Search 361/191, 160, 361/139, 154, 192, 183, 72; 250/221, 221.1, 222.2, 223 R; 340/556, 555, 557; 307/99, 328, 326, 132 E, 132 EA, 141.8, 113 114, 88; 324/415, 418, 419, 420 422
[56] References Cited 12
U.S. PATENT DOCUMENTS
4,217,534 8/1980 Cole 320/25
4,249,074 2/1981 Zettler et al. 250/221
4,266,124 5/1981 Weber et al. 250/221
4,309,696 1/1982 Nagai et al. 340/515
4,317,604 3/1982 Krakauer 312/97.1
4,507,702 3/1985 Grene 361/161
4,724,505 2/1988 Gelbort 361/167
5,000,692 3/1991 Taniguichi et al. 439/160
5,015,840 5/1991 Blau 250/221
5,149,921 9/1992 Picado 187/130
OTHER PUBLICATIONS
High Speed Multi-Contact Lockout Relays Apr. 15, 1987
Primary Examiner 13 -- Peter S. Wong
Assistant Examiner -- Aditya Krishnan
Attorney, Agent, or Firm -- Thomas L. Bohan; Chris A. Caseiro
[57] ABSTRACT 14
A photodetection system and related circuitry designed to sense the intrusion of an opaque object in a light plane. Upon sensing the intrusion. the system quickly initiates a machine-stopping sequence prior to the opaque object coming into contact with the machine while that machine is operating. The system comprises a SYSTEM microcontroller and a WATCHDOG microcontroller, both of which operate an output-control device of the light curtain switch of the invention, wherein the output control device comprises a plurality of electromechanical relays. Both microcontrollers also perform system hardware and software integrity checks. Furthermore, the WATCHDOG microcontroller evaluates the performance of the SYSTEM microcontroller by transmitting a false intrusion signal to a photosource, determining whether the false signal has been detected, and then verifying that the SYSTEM microcontroller has initiated the machine-stopping sequence. The machine-stopping sequence may be overridden by the WATCHDOG microcontroller, or it may be initiated if the false signal is not detected. The combination of electronic, mechanical, and optical modules of the present invention provides improved reliability and accuracy. In addition, the SYSTEM microcontroller and the WATCHDOG microcontroller are designed so as to reduce the system's sensitivity to spurious signals.
23 Claims, 5 Drawing Sheets
15
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