Abstract: Decompression and toxic fume protection apparatus comprising an inner chamber adapted to surround the head of the wearer, an inflatable and concentric outer chamber, a gas reservoir, means for removal of carbon dioxide and passageways for the circulation of gas through the apparatus.

Abstract: A solid state relay is disclosed which is failsafe in the sense that it is prevented from failing in a closed circuit condition. The relay comprises a main switch adapted to be connected in series with a load and voltage source and responsive to relay opening and closing signals. A secondary switch is connected in parallel with the load and is switched a sense opposite that of the main switch by the relay opening and closing signals. If the main switch fails to open, the secondary switch is closed and the load is short circuited by it. Additionally, a fuse in series with the main switch is blown by the current through the secondary switch to latch the relay in the open circuit condition. Self-checking circuits are provided to latch the relay an open circuit condition if there is any circuit failure.

Abstract: An intrusion detection system is disclosed for safeguarding an operator of an industrial machine such as a press brake. A light screen barrier (420) comprises sequentially pulsed beams (422) which are spaced far enough apart to permit penetration by a work piece (144) without obstructing more than one beam whereas penetration by the operator's hand will obstruct at least two adjacent, successively pulsed beams. A pulse train of regularly spaced signal pulses (BRS) with each pulse corresponding to a light beam is produced when none of the light beams are obstructed. A missing pulse detector (600, 40') with a logic circuit (502) produces a control signal for stopping the machine only when two or more adjacent light beams are obstructed causing two or more successive missing pulses in the pulse train.

Abstract: A switching circuit is disclosed for eliminating the effects of contact bounce in a movable contact switch connected between a voltage source and the input of a switching transistor. When the movable contact switch is closed, bouncing of the contacts undesirably produces a momentary voltage pulse which may produce false switching of the switching transistor. To avoid false switching, a coupling circuit is connected between the movable contact switch and the input of the transistor switch and includes a time constant circuit which has a different time constant for a positive going control voltage than for a negative going control voltage. The time constant circuit has longer time constant for a pulse of the polarity of the aforementioned momentary pulse than for the opposite polarity pulse whereby the transistor switch is prevented from responding to the momentary pulse.

Abstract: A monitoring system is disclosed for measuring and classifying the decelerating capabilities of a machine, such as a punch press. The monitoring system includes a timing circuit for measuring the elapsed time from the initiation of brake application to the stopping of the press. Means are provided to distinguish between a regular top-stop in a single stroke press cycle from an emergency stop and to shut down the press if the stopping time is excessive for the type of stop being executed. The monitoring means is provided with a self-checking system which performs dynamic self-checking at the initiation of braking, at the stopping of the press, and at the initiation of clutching. In each self-checking cycle a fault simulating signal is propagated through two independent paths or through a path which has been previously checked.

Abstract: This invention relates to presence sensing systems and more particularly to such systems which utilize beams of radiant energy, such as light beams, to detect the presence of a person or an object within a predetermined space. Additionally the invention relates to presence detecting systems combined with self-checking means to ensure that the detection system is operating properly.