US 4,075,961 A · Injury protection device for machinery

Abstract

A system for producing a control signal upon intrusion of a human part into a protected area, for example the area about the needle of a sewing machine, whereby radio frequency signals at a predetermined frequency are coupled to the human machine operator from a plate on which he sits or stands. As the operator's fingers or other body part approaches the protected area, an antenna receives the rf signal and applies it to an rf phase lock loop receiver which produces an output pulse when the received signal is at the predetermined frequency and is above a predetermined amplitude to operate solenoids which prevent or terminate machine operation. Preferably, withdrawal of the body part triggers a timer which produces a signal permitting the machine to operate for a given time which is greater than the normal time between intrusions, thus continuously checking that the system is working properly.

Claims16

Dependent claims

A system for producing a control signal to stop operation in response to intrusion of a human body part into a given machine area comprising:

means for detecting presence of a human part in said area and producing a first signal in response to intrusion of said part and a second signal in response to removal of said part,
means for producing a disable signal in response to said first signal which prevents operation of said machine until said second signal is produced,
means for producing an enable signal in response to said second signal for a predetermined time following production of said second signal to permit operation of said machine during said predetermined time and preventing operation thereafter, and
means connected to said disable signal producing means for causing said machine to stop in response to said disable signal and connected to said enable signal producing means for causing said machine to stop in response to the absence of said enable signal.

1 more element

A system for controlling operation of a sewing machine having a foot which holds cloth to be sewed and a sewing needle assembly comprising:

an antenna extending around said foot and assembly,
means for producing a radio frequency signal at a predetermined frequency,
a metal plate connected to said producing means and arranged to be adjacent the human sewing machine operator so as to capacitively couple said radio frequency signal to said human operator so that approach of a part of said operator to said antenna produces a radio frequency signal in said antenna and withdrawal of a part causes cessation of said radio frequency signal in said antenna,
circuit means connected to said antenna for receiving said radio frequency signal and producing a machine disable signal when the amplitude of the received signal exceeds a predetermined level and is roughly at said predetermined frequency,
means for producing a disable signal in response to said signal which prevents operation of said machine until said withdrawal of said signal,
means for producing an enable signal in response to said signal for a predetermined time following production of said signal to permit operation of said machine during said predetermined time and preventing operation thereafter, and
means connected to said disable signal producing means for causing said machine to stop in response to said disable signal and connected to said enable signal producing means for causing said machine to stop in response to the absence of said enable signal.

4 more elements

Dependencies are inferred from the claim text.

Injury protection device for machinery

Life of this patent

Injury protection device for machinery

Life of this patent

Abstract

Claims16