CA2139723A1 - Pressurized protective mask with demand-type ventilator having optimized electrical power consumption - Google Patents

Abstract

A protective system has a mask (1) communicating with a motor-driven ventilator (4) via a tube (3). A pressure sensor (5) is operatively arranged to sense the pressure differential across the mask. Such sensed pressure differential is provided to a controller (8) which adjusts the amount of electrical energy supplied from a battery (7) to the ventilator. The response of the sensor and ventilator to changes in the wearer's breathing demand is less than one second.

Description

~ 2139723 l r~;S:iUKl:~;lJ PR~ lv~; MASK
~1VITH DEMAND-TYPE VENTII~TOR iHAVlNG
OPnMlZED ELECrRlCAL POWER CONSUMPTION
Technical Field The present invention relates generally to the field of pressurized breathing masks, and, more , L~ LIy~ to an ~ driven ventiiator which is operatively arranged to ~ y maintain a pressure in the mask during various demanded fiow conditions.
B~uh~uul~i Art Various systems and equipment have been developed to provide breathing protection against toxic agents in the I , ' ~;. Some of these systems are configured as closed circuits. These are generally self-contained, and are arranged to supply either oxygen or air, as necessary. These systems typically depend upon a volume of stored gas, and are therefore often heavy.
Other systems, configured as open circuits, use various filters for fiitering and/or processing the air chemically to provide breathable air.
Some systems use an electric ventiiator that .~ for some, if not all, of the various pressure drops across the Elters, the valves, the mask, and the hoses.
These systems generally have a self-contained electrical power source (e.g., a battery), an ZO ~l.octrir l~y powered blower or ventilator, one or more filters, and various hoses connect-ing the ventilator to the person's mask or protective headgear. To avoid the entry of toxic products into the mask, it is often desired to maintain the pressure vithin the mask at a pressure greater than that of the atmosphere so that any leakage wiii tend to be from the mask to the ~ILl~u~ rather than vice versa. By the same token, the wear-er's respiration will vary with his activity. To ' hard and heavy breathirlg, aswhen the wearer is under u ull~ ai~l~ load, a powerful ventilator must be used. The operation of such a ventilator places increased demands upon the electrical power source. In addition to this, the filtering capacity of various filters typically diminishes in a manner p~upu~iùl~d to the square of the flow of fiuid Lll~ ~ Lll~u_~,h. It is therefore desirable to optimize the power . of such a ventilator-fiow system as much as possible.
It has been proposed to provide a buffer volume, either in the form of a bag placed near the mask or as a separate buffer volume, between the ventilator and the 213~723 mask to absorb respiration peaics and to decrease the weight of portable electrical power sources. However, these systems are believed to be heavy, ~ ' costly and frag-iie.
European Patent No. 0 413 555 discloses a protective device having a pres-S sure sensor arranged to provide r '- in the form of puises so as to maintain a pressure within the mask. However, due to the range in the wearer's respiration, the fact that different wearers have different physical . l, ~ and breathe differently under various ~ , the system shown in this patent is believed to .
require powerful batteries.
European Patent No. 0 352 938 discloses a protective device that accommo-dates partial clogging of filters by increasing the pressure supplied by the ventilator as the ~ilter begins to clog.
European Patent No. 0 334 555 discloses a protective device having a venti-lator. The input is closed at the beginning of an exhalation cycle, and is reopened at the lS beginning of an inhalation cycle.
French Patent No. 81-09861 discloses a protective system having a two-speed ventilator.
French Patent No. 91-10495 discloses a similar system capable of providing an abnormal voltage for a ~,UI~ ,Li~ short period of time.
Disclosure of the Invention The present invention broadly provides an improved mask that offers pro-tection for various respiratory I ~ , against the i.~lU iU~,LiOII of toxic products.
The improved apparatus includes a supply or source of purified air or oxygen, an axial or centrifugal ventilator which ~ for the pressure drop across the various filters and other line lûsses, and a source of electrical power. The ventiiator motor is minimally supplied with additional eiectrical energy to provide a large fiow to cover peak inhalations of a man at rest, and to impose a minimum rotational speed on the ventila-tor. This rotational speed may be greater than about 500 revolutions per minute, and is ~ ,., l; .... ~ly variable from this level up to the maximum speed of the motor. The appa-30 ratus is aiso arranged to supply electrical energy to the ventilator motor so as to provide a flow suOElcient to cover peak inhalations of a man undergoing strong, but not extreme, physical activity. In this mode, the maximum rotor speed of the ventilator is typically not greater than about 14,000 revolutions per minute. The apparatus may further include a pressure sensor that permits continuous control of the amount of electrical energy pro-35 vided tû the ventilator be~ween upper and lower limitr~, as a functiûn of the demand load pressure. The response time for the ventilator to change speeds is generally less than one second.
Accordingly, the general object of this invention is to provide an improved pressurized ventilator system with increased safety and reduced power, Another object is to provide such a mask with a demand-type regulator.
Still another object is to provide such an improved mask and regulator, in which the electrical power . of the ventilator is coupled to the demand load, and is optimized.
These and other objects and advantages will become apparent from the 10 foregoing and ongoing written `1~ :ri 1;the drawings, and the appended claims.
Brief Description of the Drawines Fig. 1 is a schematic view of the improved apparatus.
Fig. 2 is a ~ ~ y schematic vertical sectional view of the pressure sensor shown in Fig. 1.
l~i Fig. 3 is a r C~ ' y schematic vertical sectional view of another form of pressure sensor that might be used in Fig. 1.
Fig. 4 is a L. ~ y schematic vertical sectional view of a demand-type regulator.
Fig. 5 is a L~b.~ L~I~y transverse vertical sectional view thereof, taken gen-20 erally on line 5-5 of Fig. 4.
Description of the Preferred ~I..b~
At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portiorls or surfaces Wl~i~L~.llLIy throughout the several drawings figures, as such elements, portions or surfaces may be 2~i further described or explained by the entire written ~ ,." of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, ~..,- .~,. . .1 of parts, proportion, degree, etc.) together with the ~ and are to be considered a portion of the entire written descrip-tion of this invention. As used in the following tl~crrirtion~ the terms "horizontal, "verti-30 car' left", "right, "up and "down, as well as adjectival and adverbial derivatives thereof(e.g., "horizontally, "r;bhL~u.dl~", "upwardly", etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms "inwardly" and outwardly" generally refer to the orientation of a surface relative to its axis oE elongation, or axis of rotation, as .l~J~JIU~

2139~2~

As used herein, the term "relative pressurer or "pressure differential" in the mask is intended to broadly refer to the difference between the pressure within the user's mask and the ambient ~ h ;~, pressure. A ~feeble activiLy" WllCi~JU~ to the physical activity of a man at rest who is providing ' ' work of .~
S 15 watts. A "strong activity~ Wll~ /Ulld:~ to the physical activity of a man providing mechanical work at ~ , 160 watts. An "extreme physical activiLy" Wll~yull~b generally to physical activity of a man providing mechanical work of ~ 300 watts.
Turrling now to the drawings, the general purpose of this invention is to 10 provide a protective mask-Lype device Eor protecting the wearer against toxic products in the aLI~Iu~ ; and which optimizes the use of various electrical I I More particularly, this means that the size of various electrical power sources may be reduced, and safety may be increased by reducing the maximum speed and flow oE gases passing through various filters, all while optimizing respiratory comfort. The device also reduces 15 the response time of the sensor and ventilator to changes in the wearer's breathing level.
The device "~ -. for most, if not all, of the pressure drop across various filters and tubing.
These goals are attained by the invention that is essentially .1-- ,.. I,.; . .1 by providing a ventilator motor that is, I~, supplied with a minimum level of elec-20 trical energy (El) in such a manner as to provide an adequate flow to cover the wearer'speak inhalation rate at rest, and to cause the ventilator to rotate at a minimum rotation-al speed (Rl), typically greater than a~ V 500 revolutions per minute, so that the time necessary to have the ventilator rotational speed track or follow changes in the wearer's breathing, will take less than one second. To this end, the ventilator motor may 25 be supplied with electrical energy (Ez) in such a manner as to provide a flow sufficient to cover the peak inhalation rate of a man undergoing strong, but not extreme, physical activity, and to cause the ventilator to rotate at a maximum speed on the ventilator (R2) less than about 14,000 revolutions per minute. The equipment may further include a pressure sensor that controls the level of electrical energy between upper and lower 30 limits (E2) and (El) and rotational speeds between upper and lower limits (R2) and (Rl), as a continuous function of the differential pressure across the mask. As previously indicated, the response time of the sensor and ventilator to changes in the demand pres-sure is typically less than one second.
According to one preferred manner o~ operating the apparatus, the pressure 35 sensor controls the electrical command signal supplied to the ventilator motor in the following manner: (I) when the value of the pressure differential across the mask is less ~139723 s than the threshold pressure diEerential, ~P2 (typically between 0 and 1.5 hecto-pascal), the electrical energy furnished to the ventilator is ' "~ constant and equal to E2 (typically between 4 and 25 watts), (2) when the value oE the pressure differential across the mask is between ~P2 and l~PI (~P2 being less than ~PI) the electrical energy Eur-5 nished to the ventilator is a continuous and decreasing Eunction of the relative pressurein the mask at an average slope of -0.01 to -1.0 hecto-pascal per watt, and (3) when the value oE the relative pressure in the mask is greater than ~PI, the electrical energy Eur-nished to the ventilator motor is ' "y constant and equal to (El), typically be-tween 0.05 and 4 watts.
According to another preferred method oE operation, the sensor will com-mand the electrical energy level (E) provided to the ventilator in the Eollowing manner:
(1) when the pressure in the mask is less than the threshold diEerential ~P2 (typically between 0 and 1.5 hecto-pascal), electrical energy supplied to the ventilator is substan-tially constant and is equal to a maximum value (E2) (typically between 4 and 25 watts), (2) when the pressure diEerential across the mask is between ~P2 and ~PI (~P2 being less than ~PI), the electrical energy supplied to the ventilator motor is equal to some value between El and E2) and (3) when the pressure diEerential across the mask is greater than ~PI, the electrical energy supplied to the ventilator motor is ' "~constant and is equal to El (typically a value between 0.05 and 4 watts).
The electrical energy can be summed over time to End and determine the electrical energy used over such period of time.
It is highly desirable Eor reasons of comfort and safety to the user, that the ventilator follows the breathing demands of the user. This demand can become very rapid, lla~ .ulally with exertion or; If the speed of the ventilator motor were to start at zero, it would be impossible to overcome the inertial forces in order to rapidly increase the ventilator Elow fast enough to follow the user's demand. Similarly, if the ventilator motor were to be operated at too high a speed, the inertia of the rotating parts would not allow the ventilator to reduce aOw rapidly enough to following the de-mand variation in the exhalation aOw. This is very important, especially for fP~trjfllg~l type ventilators that have speciE c nu . ,'~ u~ Indeed, when one closes the outlet of a centrifugal ventilator, the speed of rotation tends to increase and the electrical ~ . tends to decrease. This ~ can be used to maintain a minimum rotation speed using little electrical energy, in order to reduce the response time to changes in the wearer's respiratory cycle. Moreover, it is highly desirable that the wearer knows the amount of electrical energy remaining in his batteries. Thus, ac-cording to the preferred mode of operation, the consumed energy is summed over a 213~723 period of time. The summed energy may be subtracted from an initial value such that the amount of energy remaining in the batteries is displayed. If desired, an electrical reset switch is arranged to "~ reset the display means at each battery change, such that the initial level of charge within the batteries will be ."~ displayedS whenever they are changed.
According to another but still preferred mode of operation, the pressure controller has two like ' mounted on the same structure. Aithough these are very light, they do have a tanglble mass. When ' i, these mem-branes have a tendency to move together and send a signal as if the chamber pressure 10 has changed. This l' introduces errors into the apparatus. To remedy this situation, one typically places two identical ' so as to separate three volumes V1, V2 and V3. Two of these three volumes l with one another. For exam-ple, volume Vl and V2 may, with one another (as shown in Fig. 2). Aiter-natively, volumes Vl and V3 may with one another, (as shown in Fig. 3).
15 The net signal supplied by the pressure sensor is the algebraic difference between the two respective signals of each membrane. Thus, the eEects of the ~ ; on the . ,1",. ,. ~ is eEectively cancelled. The invention also allows for ~ due to .l.nul~ variations. The ' all~ may be i , ~ sensitive. Thus, by sub-tracting the two output signals (ie., I = 11- l2? the i , ~ effects on each can be 20 cancelled. Thus, the improved device can be ~.. l.. ,.l ;....-~ , ' and/or tempera-ture~ ----r Referring now to the drawings, Fig. 1 depicts a mask I as . , ~ the mouth and nose of a wearer 2. A connecting tube 3 l the mask with a ventilator 4. A pressure sensor S positioned between the ventilator and the mask is 25 arranged to sense the pressure diEerential across the mask. Filter assemblies 6 are ar-ranged to chemically filter incoming air. An electrical source 7 (typically one or more batteries) is arranged to provide electrical power via an electronic controller 8 to the ventilator motor. An indicator 9 is operatively arranged to display the remaining amount of electrical energy in the battery. A reset switch 10 is arranged to cause the display to 30 indicate the fresh charge of new batteries, when they are replaced.
Referring now to Fig. 2, two ' 11, 12 are shown as subdividing a chamber within a body into three volumes, Vl, V2 and V3. In this form, volumes V1 and V2 with one another through an opening in membrane 11. Thus, the pressures within volumes Vl and V2 are ' ",~ equal. In this particular case, the35 diEerential pressure between volumes Vl and V3, or V2 and V3, is equal to the algebraic difference of îhe change of pressure indications given by the two 111~ 11~ or, E = I2 -Il.
In Fig. 3, volumes Vl and V3 are shown as v with one anoth-er. Thus, the pressures in volumes Vl and V3 are ' "!~ equal. In this case, the differential pressure existing between volumes V2 amd VD or between V1 and V2, is ' "~ equal to the algebraic difference of the individual indications given by the two ' Or, I = I1 - I2 In Fig. 4, two ' 11, 12 are shown as separating volumes Vl, V2 and V3. In this form, volumes Vl and V3 . with one another. A spring 13 arranged within volume V2 keeps the two membranes 11, 12 apart. The two membranes are connected via parts 14, 15, ~ iv~ly~ to a cap 16 and lever 17. Lever 17 is adapted to rotate about an axis 18. A flexible pipe or conduit 19 provides the flow-to-be-regulated. When the pressure in volume Vl is reduced, spring 13 spreads the two 11, 12 and opens valve 20 to allow the i~ u~ -., of pressurized fluid from tube 19 into the chamber.
In the preEerred . ' ' t, the useful range of the pressure sensor may be typically in the order of h~vm zero to about 4 millibar. The controller 8 provides a minimum threshold of electrical energy El to the ventilator regardless of the value de-termined by the sensor and above a certain maximum value, for example 1.5 millibar.
Similarly, controller 8 is arranged to provide a maximum energy level E2 to the ventilator regardless of the value provided by the pressure sensor less than, for example, Q1 milli-bar. Between these two pressure limits, the controller matches each value of pressure v~ith a ~JIU~)UI Liui~al electrical energy, which is supplied to the ventilator at each distance.
In other words, between the two limits, the electrical energy supplied to the ventilator motor is ~IUIJUlLiUll.ll to the demand flow. The controller 8 then sums and integrates the energy supplied to the ventilator as a function of time. Display 9 allows one to see the energy available by indicating the difference between the energy initially present and the energy consumed. Thus, the displayed amount represents the amount of energy remaining in the battery source. Switch 10 allows for ' of the counter by presenting the initial value on the display when the batteries are installed or changed at the beginning of the mission. This value may represent the energy in Joules, for exam-ple, or the minimum number of hours remaining for self-contained operation at an ex-pected average demand.
The invention has numerous .,~
Therefore, while several preferred L ' of the improved apparatus have been shown and describcd, and several ' ~ thereof discussed, persons skilled in this art vill readily appreciate that variûus additional changes and, ~ r, ~l i",~

2~397~
may be made without departing from the spirit of the inventiorl, as defined and differen-tiated by the following claims.

Claims (7)

1. In a pressurized respiratory protection system having a mask (1), a source of purified air (6), a motor-driven ventilator (4) having a variable fluid flow output, and having a power source (7) arranged to provide power to said ventilator, the improvement which comprises:
a pressure sensor (5) arranged to sense the pressure differential across said mask and to provide an output signal; and a controller (8) and arranged to supply power from said source to said venti-lator, as a function of said sensor output signal, to cause the fluid flow output of said ventilator to vary as a continuous and smooth function of the sensed demand such that at a low-demand condition the ventilator will supply sufficient flow to accommodate peak inhalations of a man at rest, and at a high-demand condition the ventilator will supply sufficient flow to accommodate peak inhalations of a man undergoing strong, but not ex-treme, physical activity.

2. The improvement as set forth in claim 1 wherein said flow is substantially proportional to a wearer's demand between said low-demand and high-demand condi-tions.

3. The improvement as set forth in claim 1 and further comprising an indicator for displaying an energy value as a function of the amount of energy consumed by said ventilator over a period of time.

4. The improvement as set forth in claim 3 wherein said indicator is arranged to display the amount of energy remaining in said power source.

5. The improvement as set forth in claim 4 and further comprising a reset switch for resetting said indicator to an initial value when said power source is changed.

6. The improvement as set forth in claim 1 wherein said pressure sensor has two membranes operatively arranged within an enclosure to subdivide the enclosure into three volumes, and wherein two of said volumes with one another.

7. The improvement as set forth in claim 6 wherein at least one of said mem-branes is piezoresistive.