Protective breathing apparatus inhalation duct

Abstract

An improved protective breathing apparatus having a vent hole or one way valve incorporated into the inhalation duct so that the breathing apparatus can safely vent and release a pressure differential during the opening of the storage bag from vacuum storage. The use of an air pressure relief mechanism prevents the rupture of the duct and preserves the integrity of the device.

Claims

1. A self-contained breathing apparatus for providing emergency oxygen and adapted for storage in a vacuum-sealed condition until use, comprising: (a) a transparent flexible hood adapted to cover the head of the wearer, including an annular seal carried by one end of the hood for sealing the hood around the neck of the wearer during use; (b) an oxygen-generating canister positioned in the hood, including a starter for initiating a oxygen-producing chemical reaction upon manual activation; (c) an oronasal mask connected in a pneumatic circuit by an inhalation duct and an exhalation duct to the canister for delivering oxygen to the wearer and returning exhaled gases to the canister; and (d) a port positioned in the inhalation duct between the canister and the mask inside the hood for allowing entry into the inhalation duct of air exterior to the hood when air pressure exterior to the hood is greater than the air pressure inside the hood prior to use.

2. A self-contained breathing apparatus according to claim 1, wherein the port in the inhalation duct includes a flap positioned over the port and movable between a closed position over the port wherein air is prevented from passing from a location exterior to the inhalation duct into the inhalation duct during use, and an open position with the flap positioned away from the port to allow ambient air to pass into the inhalation duct through the port.

3. A self-contained breathing apparatus according to claim 1, wherein the inhalation duct is formed of two flat strips joined along spaced-apart, longitudinally-extending edges that are adapted to separate and form an oxygen flow path during oxygen flow from the canister.

4. A self-contained breathing apparatus according to claim 1, wherein the oronasal mask includes a one-way inhalation valve positioned in the mask interior to the hood and communicating for oxygen flow with an opening in the inhalation duct interior to the hood.

5. A self-contained breathing apparatus according to claim 1, wherein the canister is positioned in the hood in a position posterior to the wearer when in use, and further wherein the inhalation duct delivers oxygen to the wearer from a position posterior to the wearer when in use.

6. A self-contained breathing apparatus according to claim 1, wherein the exhalation duct comprises first and second exhalation duct segments communicating with opposing sides of the mask.

7. A self-contained breathing apparatus according to claim 1, and including first and second exhalation duct segments communicating with opposing sides of the mask to a position above the head of the wearer and a unitary exhalation duct extending from the position above the head of the wearer to the canister.

8. A self-contained breathing apparatus for providing emergency oxygen and adapted for storage in a vacuum-sealed condition until use, comprising: (a) a transparent flexible hood adapted to cover the head of the wearer, including an annular seal carried by one end of the hood for sealing the hood around the neck of the wearer during oxygen-generating use; (b) an oxygen-generating canister positioned in the hood, including a starter for initiating a chemical oxygen-producing reaction upon manual activation; (c) an oronasal mask including a one-way inhalation valve positioned in the mask interior to the hood and communicating for oxygen flow with an opening in the inhalation duct interior to the hood; and (d) a one-way valve positioned in the inhalation duct between the canister and the mask inside the hood and movable by differential air pressure between a closed position wherein air is prevented from passing from a location exterior to the inhalation duct into the inhalation duct during use, and an open position that allows ambient air to pass into the inhalation duct through the valve when air pressure exterior to the hood is greater than the air pressure inside the hood prior to use.

9. A self-contained breathing apparatus according to claim 8, and including first and second exhalation duct segments communicating with opposing sides of the mask to a position above the head of the wearer and a unitary exhalation duct extending from the position above the head of the wearer to the canister.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an elevated rear perspective view of a first preferred embodiment of the present invention;

(2) FIG. 2 is a side view, cut away, of the embodiment of FIG. 1;

(3) FIG. 3A is an enlarged cross sectional view of the inhalation duct at the canister interface;

(4) FIG. 3B is an enlarged cross sectional view of the valve opening under a pressure differential at the canister interface;

(5) FIG. 3C is an enlarged cross sectional view of the valve closed as oxygen is delivered through the inhalation duct from the canister; and

(6) FIG. 4 is a side view, cut away, of the embodiment of FIG. 1 with air/oxygen flowing through the inhalation duct.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The protective breathing equipment, or PBE, of the present invention is generally shown in FIGS. 1, 2, and 4. A hood 20 is sized to fit over a human head 15, and includes a substantially airtight neck seal membrane 25 that the head 15 is slipped into and forms a seal to prevent gases or smoke from entering the breathing chamber 30. Behind the user's head 15 is an oxygen generating system 40 described in more detail below. An oronasal mouthpiece 45 allows oxygen supplied from an inhalation duct 60 to enter through a one-way inhalation valve 55, while carbon dioxide expelled from the user is routed back to the oxygen generating system 40 via an exhalation duct 50. Oxygen is produced in a chemical reaction and is communicated from the oxygen generating system 40 contained in a canister 62 through an inhalation duct 60 to the mouthpiece 45 or the breathing chamber 30 generally.

(8) During operation, the user exhales carbon dioxide into the oronasal mouthpiece 45. The exhaled breath travels through the exhalation duct 50 and enters the canister 62 containing KO.sub.2 (potassium superoxide). The exhaled carbon dioxide and water vapor are absorbed and replacement oxygen is released according to the reaction below:
2KO.sub.2+H.sub.2O.fwdarw.2KOH+1.5O.sub.2
2KO.sub.2+CO.sub.2.fwdarw.K.sub.2CO.sub.3+1.5O.sub.2Oxygen Generation:
2KOH+CO.sub.2.fwdarw.K.sub.2CO.sub.3+H.sub.2O
KOH+CO.sub.2.fwdarw.KHCO.sub.3Carbon Dioxide Removal:

(9) The regenerated oxygen gas passes through the inhalation duct 60 and enters the main compartment, or breathing chamber 30, of the hood 20. The interior hood volume above the neck seal membrane 25 serves as the breathing chamber 30. When the user inhales, the one-way inhalation valve 55 allows the regenerated gas to enter the oronasal mouthpiece 45 and thus travel to the respiratory tract of the user. The breathing cycle will continue until the KO.sub.2 canister 62 is exhausted.

(10) The PBE can quickly be donned in the event of a cabin fire by air crew in order to combat the fire. The present invention is particularly well suited to protect the user from the hazards associated with toxic smoke, fire and hypoxia. The hood 20 has a visor 180 to protect the user's eyes and provides a means for continued breathing with a self-contained oxygen generating system 40. In a preferred embodiment, the system has a minimum of 15 minutes of operational life and is disposed of after use.

(11) The PBE hood operation is described in more detail below. During the donning sequence, the user actuates a chlorate starter candle 70 by pulling the adjustment straps 90 in the direction indicated by arrows 95, thereby securing the oronasal mouthpiece 45 against the user's face. The chemical reaction of the starter candle 70 is shown below:
2NaClO.sub.3+Heat.fwdarw.2NaCl+30.sub.2Exothermic

(12) The small chlorate candle 70 (starter candle) produces about 8 liters of oxygen in 20 seconds by the chemical decomposition of sodium chlorate. This candle 70 is mounted to the bottom of the KO.sub.2 canister 62. The starter candle 65 is preferably actuated by pulling a release pin 75 that is deployed automatically by a lanyard 80 when the user adjusts the straps 90 that tension the oronasal mouthpiece against the user's face. The gas of the starter candle 70 discharges into the KO.sub.2 canister 62 on the side where exhaled breath enters the canister from the exhalation duct 50. Some of the oxygen from the starter candle 70 provides an initial fill of the exhalation duct, while the bulk of this oxygen travels through the KO.sub.2 canister 62 and fills the main compartment 30 of the hood 20.

(13) For use on an aircraft, the PBE of the present invention is preferably vacuum sealed and stored at designated locations within the aircraft. Since the active air regeneration chemical (KO.sub.2) is moisture sensitive, the primary function of the vacuum-sealed bag is to maintain an effective moisture barrier. Loss of vacuum resulting in slight inflation of the bag is an indication of the loss of the moisture barrier, requiring replacement of the unit. However, as set forth below the transition from the vacuum sealed protective storage bag to the environment has led to damage to the unit, necessitating the present invention.

(14) When the PBE is used by the aircraft crew, it is opened and returned from a vacuum atmosphere quickly. With that quick return to pressure, a rupture to the inhalation duct may result from its proximity to, and being sucked into, the canister (see FIG. 2), leading to tears and deformation in the air conduit. If the inhalation duct has been torn, it could reduce the runtime of the PBE assembly. This pressure differential when the canister 40 is at vacuum can pull the thin walled exhalation duct 50 into the canister 62 until it stretches and with enough stretching a hole could be created. Here, the exhalation duct is drawn into the opening in the canister by the vacuum existing in the canister 62.

(15) To overcome this problem, FIG. 3 illustrates a hole 115 in the inhalation duct 60 adjacent the canister 62, which can be used to vent the canister 62 through the inhalation duct 60 once the PBE 20 is removed from the airtight packaging. In an alternative embodiment, the hole 115 can include a one-way valve comprising a hole 115 and a flap 117 adjacent the hole 115, heat sealed or otherwise attached so that the flap 117 can releasably seal the inhalation duct 60. The one-way valve allows air into the inhalation duct during venting, but resists air entering the inhalation duct during breathing mode. With the modification of adding a vent hole 115 or one way valve plastic flap 117 to the inhalation duct 60, the canister 62 can safely release the pressure differential during the opening of the vacuum stowage bag. Thus, the opportunity for the thin-walled exhalation duct to be deformed, stretched, or ruptured is significantly reduced as the system reaches equilibrium with the ambient pressure.

(16) FIGS. 3a-3C illustrate the inhalation duct 60 at the interface with the canister 62. The inhalation 60 duct is a flat, lightweight tubing made of two sheets of thin plastic. The duct 60 is placed over a flange 81 having a longitudinal opening 83 leading to the oxygen generating system 40. Oxygen flows in the direction of arrows 87 (FIG. 3C) through the inhalation duct and into the interior of the mask, where it is breathed by the user. The flange 81 includes outer threads 91 that engage with inner threads on the canister 62, forming an airtight seal. The flange 81 when tightened against the canister 62 captures the neck membrane 25 along with a silicon washer 97. FIG. 3A illustrates the condition of the inhalation duct 60 during storage in the vacuum state. The portion of the duct 60 adjacent the interface with the canister is flush against the opening of the flange 81. Because the entire mask is in vacuum pack, there is no pressure differential across the duct 60 and the interface is in equilibrium.

(17) Immediately after the mask has been released from its packing and the vacuum broken, the pressure outside the canister 62 is larger than the pressure inside the canister 62, which has not had an opportunity to vent. Without hole 115, the pressure would cause a portion of the inhalation duct to be sucked into the canister, leading to potential tearing and deformation of the duct 60. However, as shown in FIG. 3B, air (designated by arrows 111) pass through the hole 115 in the duct 60 into the canister 62, equalizing the pressure across the inhalation duct/canister interface and venting the canister. The hole 115 prevents the inhalation duct 60 from being drawn into the canister, preserving the integrity of the duct. The flap 117 is attached on the inside of the duct 60, such that it permits air to enter the duct by separating from the surface of the duct as shown in FIG. 3B. Thus, the flap 117 acts as a one way valve to allow air to pressurize the canister.

(18) Once the canister and mask are fully pressurized, and the oxygen generating system 40 activated, oxygen flows from the canister 62 through the flange 81 and into the inhalation duct 60 where it fills the mask. In position of the flap 117 prevents oxygen from exiting the inhalation duct at the flange by closing the hole 115 upon pressurization from the flowing oxygen or the bias of the flap 117 against the surface of the inhalation duct. Thus, oxygen is not diverted by the presence of the hole 115, and the mask operates normally as intended.

(19) The venting mechanism of the present invention reduces the stress on the inhalation duct 60 by preventing distortion or tearing due to the pressure differential across the duct when the apparatus is brought out of vacuum. Air quickly enters through the hole 115 and pressurizes the canister 62, minimizing the unbalance in pressure.

(20) It will be apparent from the foregoing that while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.