US2988085A - Breathing apparatus - Google Patents

Description

June 13, 1961 L. JONES 2,988,085

BREATHING APPARATUS Filed June 17, 1957 2 Sheets-Sheet 1 INVENTOR LEON JONES BY M ATTORNEY June 13, 1961 L. JONES 2,988,085

BREATHING APPARATUS Filed June 17, 1957 2 Sheets-Sheet :2

22 I06 E I00 104 97 9O '4 2 98 I02 88 34 24 36 as 40 g A c w n4 l H2 no 26 108 H2 '22 ns ns INVENTOR LEON JONES ATTORNEY United States Patent 2,988,085 BREATHING APPARATUS Leon Jones, Garden Grove, Calif., assignor to Robertshaw-Fulton Controls Company, Richmond, Va., a corporation of Delaware Filed June 17, 1957, Ser. No. 665,955 11 Claims. (Cl. 128- 142) This invention relates to breathing apparatus and more particularly to breathing apparatus for use in high altitude flight.

For high altitude flying where the atmospheric air is rarefied, it is desired to normally maintain a predetermined partial pressure of oxygen within the face mask or helmet to meet physiological requirements of the human body. It is, therefore, a principal object of this invention to incorporate in a breathing regulator a means which automatically varies the pressure within the mask or helmet with variations in altitude.

Another object of the invention is to subject the control diaphragm of a demand breathing regulator to the pressure of the oxygen source and to control the oxygen pressure on the control diaphragm in accordance with altitude.

Another object of the invention is produce an improved breathing regulator.

In the preferred embodiment of the invention, a demand regulator valve is connected between a suitable mask or helmet associated with the user of the apparatus and a source of oxygen under pressure. The regulator valve is operative to supply oxygen to the mask or helmet in response to inhalation by the user, and is provided with a means responsive to atmospheric pressure for maintaining a predetermined pressure of oxygen within the mask or helmet at low atmospheric pressure conditions such as when flying at high altitudes.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a breathing apparatus;

FIG. 2 is a plan view of a regulator valve embodying this invention;

FIG. 3 is a section taken along the line 1IIIH of FIG. 2;

FIG. 4 is a section taken along the line IV-IV of FIG. 2; and

FIG. 5 is a sectional view showing a modification of a portion of the structure illustrated in FIG. 3.

Referring more particularly to FIG. 1, the breathing apparatus includes a pressure reducing valve connected to a suitable source of oxygen under pressure (not shown) by a conduit 12. The reducing valve 10 may be of any suitable form and serves to deliver oxygen at a workable pressure to a breathing regulator 14 by means of a conduit 16. The regulator 14 is here shown as mounted on a face mask 18.

Referring more particularly to FIGS. 2, 3, and 4, the regulator valve 14 comprises a casing having a hollow tubular inlet fitting 22 extending upwardly from one side thereof. The casing 20 is also provided with an externally threaded lower portion 24, on which hollow tubular outlet fitting 26 is threaded. The inlet fitting 22 is adapted for connection to the conduit 16 (FIG. 1), and the outlet fitting 26 is adapted for connection to the mask or helmet 18.

The inlet fitting 22 has a suitable filter 28 mounted therein, and is connected by means of a passage 30 to a valve chamber 32 formed within the casing 20. The valve chamber 32 communicates with the outlet fitting 26 by means of a plurality of ports 34 which communicate Patented June 13, 1961 with an opening 36 in the bottom wall of the casing portion 24.

An annular valve seat 38 is formed on the casing 20 within the valve chamber 32 for cooperation with a flexible diaphragm valve member 40 for controlling fluid flow from the inlet passage 30 to the ports 34. The valve member 40 is secured at its periphery to the wall of the casing 20 by means of an annular retaining member 42.

A passage 44 extends through the casing 20 from the inlet passage 30 and opens into the valve chamber 32 on the lower side of the diaphragm valve member 40 to subject the lower side of the diaphragm valve member 40 to the inlet fluid pressure. The passage 44 is provided with a chamber 46 in which a fitting 48 having a metering orifice therein is positioned. With this arrangement, the upper side of the valve member 40 is subjected to the inlet fluid pressure within passage 30, and the lower side of the valve member 40 is subjected to the inlet fluid pressure by means of passage 44.

It will be apparent that the effective area of the valve member 40 exposed to inlet pressure at the lower side thereof is greater than the exposed area of the upper side. This difference in area subjected to inlet fluid pressure accordingly establishes a pressure diiierential on the valve member 40 which normally tends to hold the same in engagement with the seat 38.

The valve member 40 is moved out of engagement with the seat 38 to permit flow of fluid to the ports 34 and outlet fitting 26 by venting the fluid pressure acting on the lower side thereof to reverse the pressure differential acting on the valve member 40. To this end, a passage 50 formd in the casing 20, extends from the valve chamber 32 at the under side of the diaphragm valve member 40 and opens into a chamber 52 formed in the casing 20 which communicates with the interior of the mask or helmet 18 by means of a port 54 opening into the outlet opening 36.

A flexible diaphragm sensing element 56 is secured at its periphery to the upper end of the casing 20 to enclose the chamber 52 and to define the upper wall thereof. The position of the diaphragm sensing element 56 is influenced by the fluid pressure within the chamber 52. Accordingly, since the chamber 52 is in communication with the mask or helmet 18, a reduction in pressure will occur within the chamber 52 when the user of the apparatus inhales causing the diaphragm 56 to flex downward. This movement of the diaphragm 56 in response to inhalation by the user is used to control the venting of the fluid pressure acting on the under side of the valve member 40 to thus control opening of the valve member 40.

A hollow fitting 58 has one end pressed within the end of the passage 50 and the other end thereof projecting Within the chamber 52 to define a pilot valve seat. A pilot valve, indicated generally by the reference numeral 60, is cooperative with the end of the fitting 58 to control fluid flow from the valve chamber 3.2 through the passage 50 to the chamber 52. The pilot valve 60 comprises a rigid lever arm 62 having one end engaging the diaphragm 56 and the other end thereof fixed to a block 64 overlying the fitting 58. One end of a strip 66 of sealing material is secured to the underside of the block 64 and the other end of the strip 66 is clamped to an extending and movable partition 68 of the casing 20 by means of a nut 70 tightened against the partition 68 by a screw 72 seated within the casing 20. A spring 74 has one end attached to the block 64 and the other end thereof attached to the nut 70 for biasing the block 64 downwardly and the end of the lever arm 62 into engagement with the diaphragm 56. During assembly, the screw 72 is tightened to cause downward deflection of the partition 68 until the strip 66 engages the end of the fitting 58.

'with the passage 44.

The spring 74 normally biases the block 64 and strip 66 into engagement with the end of the fitting 58. However, should the diaphragm 56 be flexed downwardly by reduction in pressure within the chamber 52 as a :result of inhalation, displacement of the lever arm 62 will'occur, and the spring 74 will yield adjacent to :the nut 70 againstits bias and move the block 64 outofengagement with the fitting 58 to permit flow of fluid from the passage 50. When the user exhales, the pressure in'chamber 52 will increase-to move the diaphragm '56 upwardly and close the pilot valve 60 tothus re-establish the pressure differential on the valve member 40ucausing the same to engage its seat 38.

It has been found that chattering or vibration o-f the diaphragm valve member40 sometimes occurs due to the rapid pressure change in chamber 32 upon opening and closing of the pilot valve 60. To provide for a more gradual pressure build-up or relief on the underside'of the diaphragm valve member 40 during operation of the pilot valve 60, a surge chamber 76 having a metering orifice 77 is provided in the casing 20 in communication It will be apparent that upon flow of fluid from the valve chamber 32 as a result of opening of the pilot valve 60, the flow of fluid from the chamber 76 as determined by the metering orifice 77 will reduce the rate of pressure drop within the chamber 32. Likewise, the rate of pressure build-up within the chamber 32 will be decreased by pressure build-up in the chamber 76 when the pilot valve 60 is closed.

When the regulator thus far described is used'at high altitudes or under low atmospheric pressure-conditions, it is desired to establish a predetermined pressure within .the mask or helmet 18 independently of-inhalation on the part of the user to provide pressure breathing. Accordingly, the regulator valve is provided with means for .maintaining a predetermined pressure Within'themask or helmet 18 in accordance with the surrounding atmospheric pressure. To this end, a cup-shaped member 78 having an upper inwardly extending flange 80 is-clamped to the upper end of the casing 20 and to the periphery of the diaphragm 56 by means of a cover 82 threaded on the upper end of the casing 20 in engagement with a lower outwardly extending flange '81 of the member 78. The flange 80 is provided with a central bore 84 in which a cup-shaped valve member 86 is positioned. The valve member 86 is provided with an outwardly extending flange 88 terminating in an annular downwardlybent lip 90 above the flange 80.

The valve-member 86, member 78 and diaphragm 56 define a chamber 92 above the diaphragm 56 which communicates with the inlet passage 30 by means of a passage 94 formed in one side of the member 78. The passage thus establishes a fluid pressure within chamber 92 which acts on the upper side of the diaphgarm 56 through a plurality of ports 95 in'the bottom wall of the member 78.

The valve member 86 is cooperative wtih the flange '80 to control the fluid pressure within the chamber 92. When the valve member 86 is in the position shown in FIG. 3, the lip 90 is out of engagement with the flange 80 and fluid pressure is vented from the chamber 92 to the atmosphere through a plurality of ports 96 in the cover 82. However, if the valve member 86 is moved toward the diaphragm 56, the lip 90 will be moved closer to the flange 80 to throttle the flow of fluid from the chamber 92 and increase the fluid pressure within chamber 92.

A11 expansible bellows member 97 is provided for actuating the valve member 86 relative to the flange 80. The bellows member 97 has one end sealed to the bottom wall of the valve member 86 and the other end thereof sealed to a flange 98 of a cup-shaped member 100. The member 100 is provided with a central conical recess or indentation 102 which engages a flange 104 formed on one end of a screw 106 threaded through'the cover 82 in axial alignment with the bellows member 97. A pr 107 is mounted in compression between the valve member 86 and flange 98 within the bellows member 97 and serves to bias the bellows member 97 and valve member 86 downward.

The bellows member 97 is evacuated and will expand in response to .a decreaase in atmospheric pressure to actuate the valve member 86 downward to move the lip toward the flange 80. Thus, the bellowsmember 97 will expand in response to an increase in altitude to move the "lip 90 toward engagement with the flange 80 to increase the fluid pressure within chamber 92.

A relief valve, indicatedgenerally by reference numeral 108, is positioned adjacent the tubular outlet fitting .26 to vent fluid pressure from the interior of theoutlet :fitting 26 when the fluid pressure exceeds a predetermined value. To this end, a hollow tubular casing 110 is secured to the side of the tubular outlet fitting .26 and is provided with atplurality of ports 112 extending through the wall thereof. A valve seating ring 113 is fixed within the tubular casing 110 and is adapted to be engaged by a valve member 114 which is slidably mounted on a guide stem 116 fixed to the end wall of the casing 110. A spring 118 encircles the stern and is mounted in com- .pression between the end Wall of the casing 110 and the valve-member 114 for biasing the valve member 114 into engagement with the seating ring 113.

Fluid is conducted from the hollow interior of the fitting 26 to the underside of the valvemember 114 by means of a drilled passageway 120. The passage :120 also communicates with a hollow tube 122 which may be utilized to supply oxygen to a compensated exhaust valve :(not-shown) within the mask 18.

It will be apparent that a pressure differential exists across the valve member 114 when the same engages the seat therefor since one side of the valve member -1 14 is subjected tothe oxygenpressure within the outlet fitting 26 and'the other-side-thereof is subjected to atmospheric pressure. As long as the pressure diflerential force on the valve member 114 is less than the bias of the spring 118, the valve member 114 will engage the seat. If, however, due to an increase in the fluid pressure in the outlet fitting 26, the pressure differential force becomes greater than the biasing force of thespring 118, the valve member 114 will be moved out of engagement with the seat to vent the excessive fluid pressure in tube '122 to the atmosphere. This will allow the exhalation valve to relieve excess mask pressure.

In operation of the structure illustrated in FIGS. ,2, 3, and 4, when the apparatus is used at low altitudes or at relatively normal atmospheric conditions, the bellows member '97 will be in a contracted condition and the valve member86 will be in its uppermost position-wherein the lip!!!) is out of engagement with the flange 80.

In this'position of the valve member 86, fluidpressure is vented from the chamber "92 to the atmosphere, and the lflnid pressure within chamber'92 will be minimum and approximately atmospheric.

When theuserof the apparatus inhales, a reduction in fluid pressure within chamber 52 will occur and .the diaphragm 56 will be deflected downward .under'tthe influenceof thelfluid pressure within chamber 92. Such movement of the diaphragm 56 will causeopening .of the pilot'valvet60 as previously described to effect opening of the 'valve member 40. When the valve member 40 ,is thus opened, oxygen will be supplied to the mask 18.

.Since the chamber 52 communicates with the interior of the mask 18 by means of the port 54, exhalation on .thegpart of the user will increase the fluid pressure within the chamber 52 to return the diaphragm 56 toits original position to close the pilot valve 60 and valve member 40.

If a decrease in atmospheric pressure should occur, such as during an increase in altitude, the bellows memberi97 will expand to move the valve member'86 downward. This movement of valve member 86 will accordingly position the lip 90 closer to the flange 80 to throttle the flow of fluid from the chamber 92 causing an increase in fluid pressure within the chamber 92.

The increased fluid pressure in chamber 92 will move the diaphragm 56 downward and open the pilot valve 60 to efiect opening of the valve member 40 to cause oxygen flow to the mask 18. However, since the chamber 52 is in communication with the mask, the supply of oxygen to the mask when the user is not inhaling will increase the pressure in chamber 52 causing a pressure force to be exerted on the diaphragm 56 in opposition to the fluid pressure acting on the upper side of the diaphragm 56. This build-up in pressure within chamber 52 will continue until the pressure in chamber 52 equals the pressure in chamber 92 at which point the diaphragm 56 will have returned to its original position closing the pilot valve 60 and valve member 40.

It will be apparent that in operation in the above manner, the diaphragm 56 serves as a pressure regulator to maintain a fluid pressure within the mask 18 as determined by the position of the bellows member 97. Also, since inhalation on the part of the user is elfective to open the pilot valve 60 by establishing a pressure diflerential on the diaphragm 56, it will be apparent that the sensitivity of the device to inhalation is constant irrespective of the atmospheric pressure condition sensed by the bellows member 97. This is due to the fact that the fluid pressure in chambers 52, 92 is always substantially the same. Accordingly, when the user inhales, the same pressure difierence is established across the diaphragm 56 at high atmospheric pressure conditions as is established at low atmospheric pressure conditions. Thus, the device is operative to efiect pressure breathing at low atmospheric pressure conditions without effecting the sensitivity of the device to inhalation and exhalation on the part of the user.

If it is desired to calibrate the response of the bellows member 97 to a particular atmospheric pressure condition, the screw 106 may be rotated to vary the axial position of the bellows member 97 and valve member 86 relative to the flange 80. Such positioning of the bellows member 97 will accordingly vary the pressure condition at which the lip 90 engages the flange 80.

If due to any condition, the pressure within the mask 18 becomes excessive, it will be apparent that relief valve 108 will open to vent the excessive fluid pressure in tube 122 to the atmosphere and allow the exhalation valve (not shown) to vent excess mask pressure.

Referring now to FIG. 5, the tubular outlet fitting 26 is shownas provided with another embodiment of the relief valve 108. More particularly, the bellows-type expansible element 124 is mounted Within the fitting 26 and has one end 126 clamped to the bottom wall of the casing 20 by means of an annular clamp 128 which is engaged by a shoulder of the fitting 26. The other end 160 of the element 124 is secured to a peripheral flange 132 of a movable spider 134 by means of a locking ring 136.

.An annular valve member 138 is formed on the end of the element 124 and is adapted to engage an annular shoulder 140 formed on the wall of the outlet fitting 26 to control communication between the interior of the fitting 26 and a plurality of ports 142 extending through the wall of the fitting 26.

A spring 144 is mounted in tension between the center of the spider 134 and the center of a second spider 146 threaded within the end of the fitting 26. With this arrangement, the spring 144 serves to bias the element 124 to cause expansion of the same and engagement of the valve member 138 with the shoulder 140 to prevent communication between the interior of the fitting 26 and the ports 142. If, however, the fluid pressure within the interior of the fitting 26 should exceed a predetermined value, the element 124 will contract under the influence of the fluid pressure to move the valve member 138 out 6 of engagement with the shoulder to vent the excessive fluid pressure to the atmosphere through the ports 142.

It will be apparent that the pressure at which the valve member 138 moves out of engagement with the shoulder 140 is readily adjusted by rotating the spider 146 to vary the axial position thereof and the tension of the spring 144.

While several embodiments of the invention have been herein shown and described, it will be apparent to those skilled in the art that many changes may be made in the construction and arrangement of parts without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In a regulator valve for controlling the flow of fluid from a source of fluid under pressure, the combination comprising a casing having an inlet passage and an outlet passage for fluid intersected by a valve seat, a diiferential pressure actuated valve member movable relative to said seat for controlling the flow through said passages, passageway means establishing communication between said inlet passage and each side of said valve member whereby each side of said valve member is subjected to inlet pressure, pilot valve means in said casing for controlling the operation of said valve member and including a pilot valve element movable from one position to another to relieve the pressure acting on one side of said valve member for causing actuation of said valve member relative to said seat, a flexible diaphragm sensitive to a pressure condition on one side thereof for actuating said element between said positions upon a change in said condition, means communicating with said inlet passage for subjecting the other side of said diaphragm to the fluid pressure in said inlet passage to actuate said element independently of a change in said pressure condition, and means carried by said casing and being operative in response to atmospheric pressure vari-- ations for varying the pressure acting on the other side of said diaphragm.

2. In a breathing apparatus for supplying fluid under pressure to a breathing mask or the like, the combination comprising a casing having an inlet passage and an outlet passage intersected by a valve seat, a differential pressure actuated valve member having oppositely disposed pressure responsive sides and being cooperable with said seat for controlling the flow of fluid through said passages, communicating means between each of said oppositely disposed sides and said inlet passage, said op positely disposed sides having diflerent effective areas whereby said valve member normally engages said valve seat, pilot valve means in said casing to control the operation of said valve member and including a pilot valve element movable from one position to another to relieve the pressure acting on one side of said valve member to cause movement of said valve member, a flexible diaphragm in said casing defining a chamber on each side thereof with said casing, one of said chambers communicating with said inlet passage and the other of said chambers communicating with the mask, said diaphragm being movable in response to a decrease in pressure in said other chamber caused by inhalation and movable in response to a change in fluid pressure in said one chamber, an operative connection between said diaphragm and said pilot valve element for actuating said pilot valve to open said differential pressure operated valve member upon movement of said diaphragm, means for venting fluid pressure from said one chamber to vary the pressure therein, and an expansible element operatively connected to said venting means for actuating the same to increase the pressure in said one chamber in response to a decrease in atmospheric pressure to eifect opening of said differential pressure actuated valve member to establish a predetermined pressure within the mask.

3. In a breathing apparatus as claimed in claim 2 wherein said venting means comprises an annular membertclamping vsaid diaphragm to said housing having an annular flange on'the end thereof, and a cup-shapedvalve member having a flange overlying said flange .of .said annular member and cooperative therewith, said .expansible element engaging the bottom wall of said cupshaped member.

4. In a breathing apparatus as claimed in claim 3 wherein said expansible element comprises an expansible bellows member.

5. In a breathing apparatus as claimed in claim 4 wherein said bellows member has one end engaging said bottom wall and the other end thereof engaging an adjustable support fixed to said housing.

6. In a breathing apparatus for supplying fluid under pressure to a breathing mask or the like, the combination comprising a housing having an inlet passage and an outlet passage intersected by a valve 'seat, a diflerential pressure actuated valve member cooperable with said seat for controlling flow through said passages, said valve member having different pressure responsive areas, means establishing communication between said inlet passage and each of said areas whereby said valve member normally engages said valve seat, a flexible diaphragm in said housing defining a chamber on one side thereof in communication with said inlet passage and a chamber on the other side thereof in communication with one area of said valve member and the mask, said diaphragm being movable in response to a decrease in pressure in said other chamber caused by inhalation and movable in response to a change in fluid pressure in said one chamber, pilot valve means in said other chamber for controlling communication between said other chamber and said one area of said pressure actuated member including an actuating member engaging said diaphragm, said diaphragm being operative upon movement thereof to open said pilot valve means to vent fluid pressure from said one area of saidpressure actuated valve member to open said pressure actuated valve member to supply fluid to the mask, valve means for venting the fluid from said one chamber to the atmosphere to vary the fluid pressure in said one chamber, and means responsive to variations in atmospheric pressure for closing the last said valve means in response to a decrease in atmospheric pressure 'to cause opening of said pilot valve means for establishing 'a predetermined fluid pressure within the mask.

7. In a breathing apparatus as claimed .in claim 6 wherein means are provided for venting the fluid in said outlet passage to the atmosphere in response to a predetermined fluid pressurein said outlet passage.

.8. Ina relief valve, the combination comprising a casinghaving apassage therethrough for fluid, an expansible element positioned in said passage and having a central opening permitting flow through said passage, a valve'element formed on one end of said expansible element, "a vent passage in said casing, a shoulder on said casing adjacent said vent passageand positioned to be engagedby said valve element, and means for biasing said expansible element to cause said shoulder to be engaged bysaid valve element in opposition to the pressure force of 'the fluid within said passage.

9. In a relief valve, the combination comprising a casing having a passage therethrough for fluid, an expansible element positionedinsaid casing and having an opening for permitting fluid flow through said passage, venting means in said casing, an abutment member in said casing adjacent said venting means, a valve element formed on said expansible element and being movable into engagement with said abutment member to prevent fluid flow to said venting rneans,.rneans operatively connected to said 'ex-pansible element and having a predetermined biasing force urging said valve element into engagement with said abutment member in opposition to the pressure force of the fluid within said casing whereby the valve element will be moved out of engagement with said abutment member to permit fluid flow tosaid venting means when the .pressure force of the fluidexceedsrsaid predetermined biasing force, and means in ,said casing connected to said urging means and being operable .to adjust said predetermined biasing force.

10. In a breathing apparatus for supplying fluid .under pressure to a breathing mask or the like, the combination comprising a casing having an inlet passage and an outlet passage intersected by a valve seat, va differential pressure actuated valve member having oppositely disposed sides and cooperating with said seat for controlling the flow of fluid through said passages, means establis'hing communication between each of said sides and said inlet passage, one of said sides beingsubject to .a greater force than the other whereby said valve ,member normally engages said valve seat, pilot valve means in said casing to control the operation of said valve member and including a pilot valve element movable from one position to another to relieve the pressure acting on said one side of said valve member to cause movement of said valve member, a flexible diaphragm'in said casing and cooperating therewith to define a chamber, said chamber communicating with said inlet passage and said diaphragm being movable in response to a.change in fluid pressure in said chamber, means forming an operative connection between said diaphragm and said pilot valve element for actuating said pilot valve to open said differential pressure operated valve memberupon movement of said diaphragm, means for venting fluid pressure from said chamber to vary thepressure therein, and an expansible element operatively connected to said venting means for operating the same to increase'the pressure in said chamber in response to a decrease'in atmospheric pressure to eifect opening of said .difierential pressure actuated valve member to establish a predetermined pressure within the mask.

11. In a regulator valve, the combination comprising a casing having an inlet passage and an outlet passage intersected by a valve seat, a differential pressure .actuated valve member cooperable with said seat for controlling the flow of fluid through said passages, said valve member having oppositely disposed sides, means 'communicating with said inlet passage to subject each of said sides to inlet fluid pressure, one of said sides having a larger effective area than the other whereby said valve member normally engages said seat, pilot valve means in said casing to control the operation of said valve'member and including a pilot valve element movable fromone position to another to relieve the pressure acting on'said one side of said valve member to cause movement of said valve member, a flexible diaphragm in said casing and cooperating with said casing to define a chamber-oneach side of said diaphragm, one of the chambers communicating with said inlet passage and the other of the chambers communicating with said outlet passage, said diaphragm being movablein response to a change in pressurein the one chamber and being movable in response to a change in pressure in the other chamber, an operative connection between said diaphragm and said pilot valve elementfor actuating said pilot valve to open said differential pressure operated valve member upon movement of said diaphragm, means for venting fluid pressure from theone chamber to vary the pressure therein, and anexpansible element operable in response to variances of a predetermined condition and being operatively connected-toisaid venting means for controlling the operationofthe samezto effect opening and closing of said differential .pressureoperated valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,685,288 Fields et al. Aug. '33, 1954

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