Mine Rescue Breathing Apparatus

Abstract

A closed loop breathing system having a circulation pump for supplying a recipient with an oxygen enriched breathable fluid in response to an inhalation demand sensed by a regulator. The inhalation demand as sensed by the regulator opens a servo valve allowing oxygen to flow through an injection nozzle into a mixing chamber. The flow of oxygen creates a pressure differential across a wall. The pressure differential moves the wall to collapse a bellows thereby forcing breathed air into the mixing chamber to form a breathable fluid under a predetermined pressure. This breathable fluid passes through a filter to remove odors and a heat exchanger to maintain the temperature within a predetermined range before being delivered to the recipient.

Description

BACKGROUND OF THE INVENTION

Closed loop breathing systems have been used in aircraft where at high elevations oxygen is added to augment exhaled gases from a person for rebreathing. Exhaled gases from a person have a high percentage of oxygen along with waste products created by respiration. The waste products which are mainly carbon dioxide and water vapor represent a small percentage of the total volume of exhaled gas. However, if this small percentage of waste product were continued to be rebreathed over a period of time it would constitute a physiological hazard. Therefore, the carbon dioxide is usually removed by absorption with other elements. The storage for the elements and upkeep maintenance entail a significant cost such that it is normally more feasible to vent the breathed air to atmosphere and supply pure oxygen to the person. However, it is now recognized that continuous breathing of pure oxygen over a extended period produces an undesired toxic effect on a person. Therefore, the enrichment of the surrounding air as disclosed in our copending U. S. application Ser. No. 86,240 now U.S. Pat. No. 3,720,501, incorporated herein by reference, can provide a suitable way of supplying breathing air without ill effects to a person over an extended period. The space required for the equipment needed to enrich the air is permanently placed in an area and carried by conduit to the user.

Bottled air under pressure suitable for portability has been connected to a mask which permits the user to move over a wide area. However, the volume of the bottle and corresponding weight to permit extended use inhibits the practicability of such units.

SUMMARY OF THE INVENTION

In rescue operations, such as in mines containing noxious gases, a person must be equipped with enough oxygen to sustain normal breathing for several hours, oftentimes over 4 hours. The carrying of bottles capable of holding this quantity of oxygen would be prohibitive from a weight factor along.

We have devised a lightweight rescue breathing apparatus which can be strapped on the back of a user and which includes a closed loop breathing system operated by a pressure differential pumping means which circulates breathable fluid to the user in response to an inhalation demand. The pumping means has a variable volume reservoir for storing breathed air exhaled from the wearer. Regulator means upon sensing an inhalation demand opens a servo valve permitting oxygen to flow through an injection nozzle into a mixing chamber. This flow of oxygen creates a pressure differential across a wall means. The pressure differential acting on the wall means exerts a force on the variable volume chamber forcing the breathed fluid intp the mixing chamber to form an oxygen enriched breathable fluid. As the oxygen and breathed air enters the mixing chamber, a corresponding volume of breathable fluid is simultaneously moved through a filter to remove odors and a heat exchanger to maintain its temperature within a predetermined range to provide a relatively cool fresh breathable fluid. This corresponding volume of breathable fluid will normally meet the inhalation demand and thereby signal the regulator means to terminate oxygen flow through the injector nozzle. With this oxygen flow terminated the pressure differential is eliminated and the force on the variable volume chamber ceases. The volume of breathable fluid, now breathed fluid, is returned through a conduit to the variable volume reservoir to again be enriched with oxygen in response to the operational inhalation demand.

It is therefore the object of this invention to provide a closed loop breathing system with pumping means for circulating an oxygen-enriched breathing fluid to a recipient in response to an inhalation demand sensed by regulator means.

It is still a further object of this invention to provide a closed loop breathing system with an operational control means for initially activating pumping means.

It is a still further object of this invention to provide a closed loop breathing system with a low fluid pressure signal responsive to the operational fluid transmitted to operate a circulating pumping means.

These and other objects will become apparent to those who read this specification and view the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

The drawing shows a sectional view of a schematic closed loop breathing system having a pressure differential operated pumping means for circulating an oxygen-enriched breathing fluid to a recipient.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The closed loop breathing system 10 shown in the drawing is adapted to provide a recipient with an oxygen-enriched breathable fluid for an extended period of time, normally exceeding 4 hours. The closed loop breathing system 10 is combined into a package and adjustable straps are utilized so that the unit may be strapped on the back of the recipient thereby permitting complete freedom of the hands. It is anticipated that the total component weight of this closed loop breathing system will be under 20 lbs. with the oxygen storage vessel 12 accounting for about one-third of this total weight. As can be seen with this system 10, an man could travel into a mine during a rescue mission and be assured to having an adequate breathing fluid supply during a normal rescue working shift.

In the closed loop breathing system, a face mask 14 is connected to a supply conduit 16 through a check valve means 18 and a return conduit 20 through a check valve means 22. The supply conduit 16 has a pressure relief valve 24 with a resiliently positioned poppet 26 covering a relief port 28 to maintain the breathable fluid pressure in the supply conduit 16 below a predetermined value.

A regulator means 30 is connected to the supply conduit 16 through sensing line 32. The regulator means 30 has a housing 44 with a sensing chamber 34 separated from an atmospheric chamber 36 by a diaphragm 38. The diaphragm 38 acts on one end 46 of a lever arm 40 which is pivotally secured by pin 42 to the housing 44. The other end 48 of the lever arm 40 is secured to a servo valve 50 having a face 52 which is adapted to be seated on shoulder 54 surrounding the inlet port 56 of the oxygen chamber 58. The oxygen chamber 58 has an outlet port 60 connected to a mixing chamber 62 through a conduit 64 having an injection nozzle 66 on the end thereof. An emergency oxygen supply chamber 68 in the housing 44 is separated from the sensing chamber 34 by an emergency flow valve means 70. The emergency flow valve means 70 includes a spring 72 which acts on the back of the shaft 76 to urge poppet 74 against seat 82 surrounding opening 80. The shaft 76 is located in opening 80 and extends into the sensing chamber 34 to a point which is a predetermined distance from end 46 of the lever 40. The emergency oxygen supply chamber 68 has an inlet port 84 which is connected to an operational conduit 86 through conduit 90.

The oxygen chamber 58 of the regulator means 30 is connected to an outlet port 93 communicating with a control chamber 92 in the housing 96 of the pumping means 94. A wall means 98 separates the control chamber 92 from a power chamber 100. The wall means 98 includes a diaphragm 102 whose periphery is secured to the housing 96 and a backing plate 104. The diaphragm 102 is sandwiched between the backing plate 104 and the driving head 106 on the force transmitting shaft 108 which extends from the control chamber 92 through a bearing 110 to a piston 112. A resilient member 114 located in the control chamber 92 acts on the driving head 106 to urge the shaft 108 toward the power chamber 100. The piston 112 acts against a first face 120 of the bellows 116. The other face 122 of the bellows 116 is secured to an end plate 126 by a clamp 124 which surrounds the periphery thereof. The end plate 126 has a return port 128 which is connected to the return conduit 20 coming from the mask 14. The end plate 126 has a supply port 130 which is connected to the mixing chamber 62 by conduit 132. The bellows 116 provides a variable volume reservoir for retaining the breathed fluid exhausted from the recipient through check valve 22 of mask 14. The control chamber 92 has an inlet port 134 with a restricted orifice 136 which is smaller than the inlet port 138 going to the power chamber 100. The inlet ports 134 and 138 are connected to the operational conduit 86 by conduit 140 and 142 to communicate the oxygen at the same fluid pressure to the control chamber 92 and the power chamber 100.

A fluid pressure reducer means 144 is located in the operational conduit 86 upstream from the power chamber 100 and the control chamber 92 for maintaining the oxygen in the operational conduit 86 at a substantially uniform pressure. The pressure reducer means 144 includes a housing 146 with a flow chamber 148 and a supply chamber 150 separated by a wall 152. The wall 152 has an opening 154 to communicate the supply chamber 150 with the flow chamber 148. The flow chamber has an atmospheric port 158 separated from an outlet port 160 by a piston means 156 slidably sealed in the control chamber 148. The piston means 156 has a stem 162 which extends through opening 154 into the flow chamber 150. A head 164 with a slanting face 166 is attached to the stem 162 and located in the supply chamber 150. A first resilient means 168 which acts against heat 164 and the pressure of the oxygen located in the tank 12 which acts over the area of head 164 together urge the slanting face 166 of the stem 162 toward the opening 154 in opposition to the force of a second resilient means 170 and atmospheric pressure acting on face 172 of the piston means 156 to provide a constantly varying orifice through which the oxygen is communicated from the supply chamber 150 to the flow chamber 148.

A low pressure warning means 174 is located upstream from the pressure reducer means 144 to provide a continuous audio signal when the pressure of the oxygen in the tank 12 reaches a predetermined level. The low pressure warning means 174 has a housing 176 with a blind stepped bore 178 located therein. The stepped bore terminates at a point adjacent a storage chamber 180. The storage chamber is connected to the operational conduit 182 going from the operational supply chamber 184 of the control means 186 to the inlet port 188 of the supply chamber 150 of the pressure reducer means 144 by conduit 190. The supply chamber 180 is connected to a first portion 192 of the stepped bore 178 through opening 193. Poppet valve means 200 located in the storage chamber 180 includes a resilient means 194 which urges the face 196 of a valve stem 198 against the housing 176 to close opening 193. The valve stem 198 has an end 195 which extends into the stepped bore 178. A driver means 202 loosely fitted into the first portion of the stepped bore has a series of slots 204 on the periphery of a first face 208 connected to a groove 206 adjacent the first face. A second portion 210 of the stepped bore has a smaller diameter than the first portion to provide a shoulder 212 for limiting the movement of the driver means 202 within the first portion 192. A slot 214 adjacent the shoulder 212 places the groove 206 in communication with the atmosphere when face 213 of the driver abuts the shoulder 212. A third portion 218 of the stepped bore 178 having a larger diameter than the second portion 210 is in communication with the oxygen under pressure through conduit 190. A plunger means 220 has a first end section 222 which is sealed in the second portion 210 of the stepped bore 178 and a second end 224 with a smaller diameter which extends through the housing 176. The first end section 222 is separated from the second end section 224 by a large diameter section 226 which is sealed in the third portion 218 of the stepped bore 178. The area between the large diameter section 226 and the second portion 210 of the stepped bore forms a pressure indicator chamber 228. A resilient means 229 surrounds the second end section 224 and acts on the large diameter portion 226 to urge the driver means 202 toward the valve stem 200. That portion of end 224 which extends through the housing 176 is adapted to contact a bell means 230.

The initial operational control 186 has a first or supply chamber 184 connected to the source of oxygen under pressure in the supply tank 12 through an opening 232. A wall 238 separates the firs chamber 184 from a second chamber 236. The second chamber 236 is connected to the return port 128 by a purge conduit 240. An adjustable seat means 242 has a central opening 244 terminating in a cross bore 246. Valve stem means 248 has a first face 250 located adjacent opening 232 from the supply tank, a second face 252 adjacent the opening 254 in the wall 238 and a third face 256 adjacent the adjustable seat means 242. A resilient means 258 located in the second chamber 234 urges the stem means toward the second chamber. A positioning knob 260 has a stem 262 on the base of thread body 264 which contacts the adjustable seat means 242.

A remote pressure indicator 245 is connected to the storage tank 12 by conduit 247 and is adapted to be positioned in such a manner that a person can read the amount of oxygen supply at any time after strapping the closed loop breathing system 10 on his back.

The storage tank 12 is equipped with a fill means 288 which has a stem 290 with a flexible face 292 covering a plurality of openings 296. The flexible face 292 is held against the opening 296 by a resilient means 298. A cap 274 covers the passage 280 leading to the opening 296 to prevent accidental movement of the stem which would allow the oxygen in the storage tank 12 to escape.

MODE OF OPERATION OF THE PREFERRED EMBODIMENT

Upon strapping the closed loop breathing system 10 on a recipient's back, the operational position knob 260 is rotated counterclockwise to a first mode causing the threaded body 264 to move out of the housing 236. As the threaded body 264 moves, the spring 258 moves the adjustable seat means 242 allowing oxygen under pressure from the source to flow into the first chamber 184. The same oxygen under pressure is simultaneously transmitted through the operational conduit 182 to the low pressure warning means 174, pressure reducing means 144 and the second chamber 234. Oxygen under pressure in chamber 288 acts against the unbalanced areas of the ends of piston 222, the amount of unbalanced force being in direct proportion to pressure and acting in a direction opposite spring 229. At a predetermined low pressure, spring 229 exerts the greater force and causes the opening of poppet means 200. Oxygen under pressure passes into chamber 208, immediately causing a large force on piston 212 which rings bell 230. Gas from chamber 208 is vented to atmosphere through passage 214, and spring 229 becomes dominant and repeats the cycle, giving a repetitive intermittent bell warning as long as low pressure oxygen remains.

Simultaneously oxygen passes through the variable orifice created by the slanted face 166 and opening 154 in the pressure reducing means 144 to flow past outlet 160 into the operational conduit 86 at a predetermined pressure dictated by the strength of the selected resilient means 168 and 170.

From the operational conduit, this oxygen under pressure freely flows into the power chamber 100 but at a restricted rate into the control chamber 92 due to the orifice 136.

Further rotation of the operational positioning knob 260 to a second mode allows the resilient means 258 to move the second face 252 against the wall 238 to seal the second chamber 234.

Moving the operational positioning knob 260 to the fully opened position or third mode, allows the adjustable seat means 242 to move away from face 256 permitting the oxygen in chamber 234 to flow through the purge chamber 240 and into the variable volume reservoir. The quantity of oxygen in the second chamber will be sufficient to purge the supply conduit of all existing fluid. During this purging the expandable bellows 116 will move the wall means to the position shown in the drawing. The wall means will remain in this position for by now the pressure in the power chamber 100 and the control chamber 92 will be balanced

The recipient can now place the mask 14 on his face. As the recipient inhales the fluid pressure in the supply conduit 16 will be lowered. This lowered pressure will be sensed in the sensing chamber 34. When a sufficient pressure differential exists across diaphragm 38, atmospheric pressure which enters chamber 36 through port 27 will move lever arm 40 to move face 52 away from seat 54. With the servo valve 50 unseated, oxygen freely flows from the control chamber 92 through conduit 64 and out the restricted nozzle 66. With oxygen freely leaving the control chamber 92 and restricted flow through orifice 136 limiting the rate of replacement after a period of time a pressure differential will be created across the wall means 102. When a sufficient pressure differential develops, shaft 108 will move piston 112. As piston 112 is moved, the bellows 116 will be collapsed forcing the fluid in the bellows through the supply port 130 into the mixing chamber 62 to be combined with the oxygen flowing from the nozzle. 66. As this combined fluid mixture is formed, a corresponding volume of this fluid mixture is forced through a filter means 300. CO.sub.2, gastric odors and water vapor present in the fluid mixture from the expired breathed fluid return to the bellows from conduit 20 will be removed by the filter means 300. The filter means 300 will normally contain lithium hydroxide in a first section 302 and activated charcoal in a second section 304. The lithium hydroxide in the first section 302 will absorb the CO.sub.2 and water vapor from the expired gas in the fluid mixture; however, heat will be generated during the absorption process. The activated charcoal will remove the gastric odors and chemical dust particles created during the CO.sub.2 and lithium hydroxide reaction from entering the supply conduit 16.

As this fresh fluid passes from the charcoal portion 304 of the filter means, it enters a heat exchanger means 306. The heat exchanger means 306 will provide an air - air relationship along a serpentine portion 308 of the supply conduit 16 to remove the heat absorbed in the first section 302 of the filter means 300. With the moving of the expandable bellows 116 by the piston 112, the pressure in the supply conduit will be correspondingly increased. When the fluid pressure in the supply conduit 16 reaches a predetermined level, this will be sensed by sensing chamber 34 causing the diaphragm 38 to move toward the atmospheric chamber 36. This will permit spring 45 to act on lever arm 40 and cause face 52 of the servo valve 50 to move against seat 54. With the servo valve 50 seated, the pressure differential across wall means 102 will be sequentially reduced as the flow through orifice 136 continues. When the fluid pressure in the control chamber 92 again is balanced with that in the power chamber 100, the resilient means 114 will move piston 112 away from the expandable bellows 116. This occurrence is normally timed to be simultaneous with the expulsion of breathed fluid through check valve 22 from the recipient into the return conduit 20.

This above sequence is repeated with each inhalation-exhalation cycle of the recipient. In the event that the pumping means 94 cannot cycle as fast as the recipient is breathing, the pressure differential across diaphragm 38 will move the end 46 against valve stem 76 allowing oxygen under pressure to directly enter the supply conduit and relieve this inhalation demand.

In the event that a low pressure develops, resilient means 229 will act on the first section 222 to move the plunger means 220 and driver means 202 against the tip 195 of the valve stem 198 to open the communication with the supply chamber 180 with the first section 192 of the stepped bore 178. With the valve means 220 unseated, oxygen under pressure enters the first section 192 of the stepped bore 178 to act on the surface 208 of the drive means. The combination of the fluid pressure acting on face 208 to create a first force and on the large diameter portion 226 quickly overcomes resilient means driving the end 224 of the plunger 226 against the bell 230. When the driver means 202 abuts shoulder 212, the oxygen under pressure in this first portion escapes to the atmosphere by flow from the groove through slot 214 to the atmosphere. When the oxygen under pressure is deleted from this first portion 192, resilient means 229 again acts on the first section 222 to move the plunger means 220 and driver means 202 to open valve means 200 and repeat this sequence. Thus, the operator is provided with a continuous warning when the fluid pressure in tank 12 reaches a predetermined level.

Claims

We claim:

1. In a closed loop breathing system, pumping means for delivering a breathable fluid enriched with oxygen to a recipient in response to an operational signal actuating a regulator means, said pumping means comprising:

a housing having a cavity therein:

wall means for dividing said cavity into a power chamber and a control chamber, said control chamber having a first inlet port connected through an operational conduit to a source of oxygen under pressure and a first outlet port connected to a nozzle means in said regulator means, said power chamber having a second inlet port connected through said operational conduit to the source of oxygen under pressure, said first inlet port having a smaller opening than said second inlet port to proportionally restrict the flow of oxygen into said control chamber;

resilient means located in said control chamber for urging said wall means toward said power chamber;

variable volume reservoir means connected to said wall means having a return port connected to a return conduit coming from said recipient for retaining breathed fluid and a supply port connected to a mixing chamber, nozzle means connected to said regulator means for injecting oxygen into said mixing chamber;

a supply conduit connected to said mixing chamber for communicating said breathable fluid to the recipient;

means for sensing an inhalation demand by the recipient to develop said operational signal, and actuating said regulating means; and

operational control

means connected to said operational conduit for permitting oxygen under pressure to be continually present at the first inlet port of said control chamber and the second inlet port of said power chamber to provide a balanced pressure across said wall means, said regulator means upon receiving said operational control signal allowing oxygen to flow from said control chamber through said nozzle means into said mixing chamber, said oxygen flowing from said control chamber creating a pressure differential acrosss said wall means which overcomes said resilient means and moves the wall means toward said control chamber, said wall means upon moving causing a portion of the breathed fluid in the variable volume reservoir means to flow through the supply port into the mixing chamber, said breathed fluid and oxygen injected into said mixing chamber forming said breathable fluid at a pressure sufficient to alleviate said inhalation demand to thereby permit said regulator means to terminate said oxygen flow through said nozzle means, said oxygen flow termination allowing the oxygen under pressure to flow through the first inlet port to eliminate said pressure differential, said resilient means with the elimination of said pressure differential moving said wall means toward said power chamber causing said variable volume reservoir means to draw therein through said return port from the return conduit a quantity of breathed fluid sufficient to that expelled through said supply port to the mixing chamber.

2. The closed loop breathing system, as recited in claim 1, wherein said variable volume reservoir means includes:

piston means having a shaft which extends through said housing into the control chamber, said shaft being attached to said wall means;

a stationary end plate wherein said return port and supply port are located; and

expandable bellows means connected to said piston means and attached to said end plate, said wall means upon moving transmitting a driving force on said piston means through the shaft causing said bellows means to be compressed and force breathed fluid into the mixing chamber.

3. The closed loop breathing system, as recited in claim 2, which further includes:

filter means located in said supply conduit downstream from said mixing chamber for removing CO.sub.2 and odors from the breathable fluid to insure freshness.

4. The closed loop breathing system, as recited in claim 3, which further includes;

heat exchanger means located in said supply conduit downstream from said filter means to maintain the temperature of said breathable fluid within a predetermined range.

5. The closed loop breathing system, as recited in claim 4, which further includes:

relief means located in said supply conduit downstream from said heat exchanger means for limiting the operating pressure of said breathable fluid.

6. The closed loop breathing system, as recited in claim 5, wherein said regulator means includes:

emergency flow means connected to said source of oxygen and the supply conduit downstream from said heat exchanger for adding additional oxygen to the breathable fluid when said inhalation demand exceeds a predetermined limit.

7. The closed loop breathing system, as recited in claim 6, which further includes:

pressure reducer means located in said operational conduit for maintaining the oxygen in the power chamber and control chamber at a relatively constant pressure.

8. The closed loop breathing system, as recited in claim 7, which further includes:

fluid pressure warning means connected to said operational conduit for giving a continuous audible signal when the pressure of the source of oxygen reaches a predetermined level.

9. The closed loop breathing system, as recited in claim 8, wherein said fluid pressure warning means includes:

a stepped bore within said housing terminating adjacent a storage chamber, said storage chamber being connected to said operational conduit, said storage chamber having an opening into said stepped bore;

poppet valve means resiliently positioned against said opening for retaining oxygen under pressure in said storage chamber;

driver means loosely positioned in a first portion of the stepped bore adjacent said storage chamber, said first portion being in communication with the atmosphere through a slot adjacent a first shoulder which separates the first portion from a second portion of the stepped bore;

plunger means having a first end section connected to said driver means, said first end section and a second end section with a small diameter separated from a large diameter section, said first end section being sealed in said second portion of said stepped bore and said large diameter portion being sealed in a third portion of said stepped bore to form a pressure indicator chamber therein;

said pressure indicator chamber being connected to the oxygen under pressure in the operational conduit;

resilient means surrounding said second end of the plunger means and located in a fourth portion of the stepped bore for urging said driver means toward said storage chamber; and

bell means adjacent said second end, said oxygen under pressure acting on said large diameter section to overcome said resilient means and drive the second end of the plunger against said bell means causing a sound to be created, said resilient means upon the pressure of the oxygen in the indicator chamber reaching a predetermined level urging the plunger means away from the bell means causing the driver means to unseat the poppet valve means allowing oxygen under pressure into the first portion of the stepped bore moving the driver means away from the valve means, said driver means acting on the first end of the plunger to aid the oxygen pressure force acting on the large diameter portion to strike the second end against the bell means, said oxygen under pressure in the first portion of the stepped bore escaping through said slot upon the second end contacting the bell means permitting the resilient means to repeatedly move the driver means into contact with the valve means and provide a continuous signal.

10. The closed loop breathing system, as recited in claim 8, wherein said operational control means includes:

a first chamber adjacent opening from the source of oxygen under pressure, said first chamber being connected to said operational conduit;

a second chamber adjacent the first chamber, said second chamber being connected on a purge conduit to the return port of the variable volume reservoir means, said first and second chambers being connected by a passageway;

adjustable seat means located in said second chamber and in communication with said purge conduit;

stem means having a first face on one end adjacent the one end opening to the source of oxygen, a second face adjacent the passageway and a third face adjacent the adjustable seat means;

resilient means for urging the stem means toward the second chamber; and

positioning means connected to said adjustable seat for moving the first face of the stem means against the housing surrounding the opening in the first chamber from the source of oxygen to prevent the flow of oxygen under pressure into the first chamber in a first mode, said resilient means urging the third face against the adjacent seat in a second mode of the positioning means allowing oxygen under pressure to pass through the opening in the first chamber into the operational conduit and second chamber, said resilient means urging the second face against the passageway in a third mode of the positioning means allowing the oxygen under pressure to flow through the purge conduit to initially charge the breathed fluid in the variable volume chamber with oxygen.