Powered respirators

• US 5,035,239 A
• Filed: 06/22/1989
• Issued: 07/30/1991
• Est. Priority Date: 06/25/1988
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Racal Safety Limited
• Inventors: Edwards, David B.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US07/370,217
• Time in Patent Office: 768 Days
• Field of Search: 128/201.24, 128/201.25, 128/202.22, 128/205.23, 128/204.21, 128/204.23, 128/724, 128/200.28
• US Class Current: 128/205.23
• CPC Class Codes: A62B 18/045 with fans for delivering air for breathing mounted in or on the helmet
• CPC Class Codes: A62B 9/006 Indicators or warning devices, e.g. of low pressure, contamination
• CPC Class Codes: G01L 9/0076 using photoelectric means
• CPC Class Codes: G01L 9/0077 for measuring reflected light

Abstract

A powered respirator is provided with a device sensitive to the pressure within the respirator in the region of the user'"'"'s face and adapted to sound a warning in the event that the sensed pressure goes below a selected threshold value. The device includes a flexible diaphragm exposed on its opposite sides to the sensed and atmospheric pressures respectively, and an infra red emitter and receiver arranged so that the level of energy received by the receiver from the emitter depends upon the flexural position of the diaphragm. In different embodiments the diaphragm may be arranged to reflect the radiation from the emitter onto the receiver or not, or to interrupt a beam of radiation from the emitter to the receiver or not, depending on the pressure differential across it. In either case, when a sufficient energy level is detected at the receiver, indicating a pressure level below the selected threshold, power is switched to a sounder to warn the user of the low pressure condition.

Claims

1. A powered respirator incorporating a differential pressure sensor comprising a flexible pressure-responsive member arranged to be exposed on its opposite sides to the pressure within the respirator in the region of a user'"'"'s face and to a references pressure respectively, and adapted to flex in response to change in the differential between said pressures;

an emitter and a receiver of selected electromagnetic radiation located side by side and facing towards one side of said pressure-responsive member whereby said member flexes towards or away from the emitter and receiver in dependence upon the pressure differential across it;

in a first spacing of said member from the emitter and receiver said radiation being transmitted from the emitter to the receiver via the surface of said one side of said member and in a second spacing of said member from the emitter and receiver such transmission of radiation from the emitter to the receiver being prevented;

said member changing from one of said first or second spacings to the other of said first or second spacings when the pressure in said region falls below a predetermined value in relation to said reference pressure; and

means connected to said receiver to provide an electrical warning signal in response to the change of said member from said one to said other of its spacings.

2. The respirator of claim 1 wherein said reference pressure is atmospheric pressure and said predetermined value is a chosen superatmospheric pressure.

3. The respirator of claim 1 comprising an audible warning device mounted thereon and adapted to be driven from said warning signal.

4. The respirator of claim 1 wherein said pressure-responsive member is in the form of a diaphragm having a disc-like central portion which is jointed to a fixed peripheral portion of the diaphragm through an annular corrugated portion which provides the operative flexibility of the diaphragm whereby in response to change in the differential pressure across the diaphragm said central portion moves relative to said peripheral portion along the axis of the diaphragm while remaining substantially perpendicular to said axis.

5. The respirator of claim 1 wherein said pressure-responsive member is in the form of a diaphragm having a disc-like central portion which is jointed to a fixed peripheral portion of the diaphragm through an annular corrugated portion which provides the operative flexibility of the diaphragm, whereby in response to change in the differential pressure across the diaphragm said central portion moves relative to said peripheral portion along the axis of the diaphragm while remaining substantially perpendicular to said axis.

6. The respirator of claim 5 wherein said diaphragm is mounted in a housing which presents opposed flat surfaces against which said central portion of the diaphragm can lie to limit its extent of travel in either sense.

7. A powered respirator comprising a structure adapted to be worn on the user'"'"'s head and to define, when worn, a confined space in the region of the user'"'"'s face;

means for providing a forced flow of air to said space for respiration by the user; and

means for filtering said flow of air;

the respirator incorporating a differential pressure sensor comprising a flexible pressure-responsive member arranged to be exposed on its opposite sides to the pressure within said space and to a reference pressure respectively, and adapted to flex in response to change in the differential between said pressures;

an emitter and a receiver of selected electromagnetic radiation located side by side and facing towards one side of said pressure-responsive member whereby said member flexes towards or away from the emitter and receiver in dependence upon the pressure differential across it; and

means connected to the receiver to provide an electrical warning signal in the event that the pressure-responsive member is spaced from the emitter and receiver such as to permit the transmission of said radiation from the emitter to the receiver via the surface of said one side of that member, which spacing obtains when the pressure in said space is below a predetermined value in relation to said reference pressure.