Robert S Thomson

US Patent:

52181960, Jun 8, 1993

Filed:

Sep 5, 1991

Appl. No.:

7/755566

Inventors:

James Dogul - Hudson NH
Sandip Sarkar - North Providence RI
Frederick Thomson - Cumberland RI
Robert Thomson - Warwick RI

Assignee:

Frost Controls, Inc. - Smithfield RI

International Classification:

G01V 904
G08B 1318

US Classification:

250221

Abstract:

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.

US Patent:

55596649, Sep 24, 1996

Filed:

Jun 7, 1993

Appl. No.:

8/073096

Inventors:

James Dogul - Hudson NH
Sandip Sarkar - North Providence RI
Frederick Thomson - Cumberland RI
Robert Thomson - Warwick RI

Assignee:

Frost Controls, Inc. - Smithfield RI

International Classification:

G01V 904

US Classification:

361191

Abstract:

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.

US Patent:

52768740, Jan 4, 1994

Filed:

Aug 27, 1992

Appl. No.:

7/936875

Inventors:

Robert G. Thomson - Westford MA

Assignee:

Digital Equipment Corporation - Maynard MA

International Classification:

G11C 800

US Classification:

395600

Abstract:

A digital data processing system having an index file containing a plurality of file headers includes an arrangement having a file header processing portion for iteratively retrieving file headers from an index file and for establishing in response thereto a descriptor defining a directory in a directory tree, each descriptor defining the relationship of the corresponding directory to a parent directory in the directory tree, and a group vector processing portion, responsive to processing of a file header by the file header processing portion, for generating a group vector comprising a plurality of pointers to said descriptors, each pointer defining the relationship of a directory to one or more child directories in said directory tree.