Abstract:
A system for regulating the airflow to a closed environment using feedback control for the position of a control valve and blower speed. The system provides a control apparatus that regulates airflow to a closed environment, such as the mask of a breathing apparatus, to ensure sufficient breathing air for a wearer of such mask. In order to provide fast response to a change in condition in the breathable environment, the airflow regulator includes a valve control and a blower control.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims benefit of co-pending U.S. Provisional Patent Application Ser. No. 60/838,123, filed with the U.S. Patent and Trademark Office on Aug. 14, 2006 by the inventor herein, the specification of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention is directed to an airflow regulating system and more particularly to an apparatus that is useful in purifying contaminated air for assisting persons to breathe in hostile environments. 
         [0004]    2. Background of the Invention 
         [0005]    There are, at present breathing systems for assisting the breathing of persons who are subject to contaminated air. There are filter/decontamination systems for use in the form of a canister, in connection with a respirator apparatus that rely on cleaning ambient atmosphere to make it suitable for breathing. Such filter systems may or may not make use of auxiliary power. In powered systems, ambient atmosphere is sucked through a suitable filter/decontamination means, or other purifying means, by a powered fan or the like, such that the contaminated ambient air is rendered breathable. The purified resultant air is fed to a headpiece of some kind, such as a tight fitting facemask. The complete system is known as a Powered Air Purifying Respirator (PAPR). Such breathing assists are used by personnel who are subject to breathing ambient atmosphere that would otherwise be considered to be harmfully contaminated, un-breathable, or dangerous air. Firefighters and others in the emergency response arena may use PAPRs equipped with filter canisters, such as HEPA filters, to provide filtered ambient air to any user who is operating in a hazardous environment. 
         [0006]    A dangerous or un-breathable atmosphere is considered to be air containing less than 19.5 volume percent oxygen, or air with the requisite oxygen, but also containing significant proportions of harmful contaminants, e.g. particulate or gaseous. A PAPR system will protect against contaminants so long as the oxygen level in the purified air is above 19.5 volume percent and provided the contaminants are such as can be removed by filtration, e.g. soot and smoke, and/or can be ameliorated by reaction with a suitable purifying material. In practical effect, these systems have been designed to use replaceable filter(s) and air purifying canister(s). However, they are of no value where the ambient atmosphere has an oxygen content that is less than 19.5% by volume. It will be appreciated that, in some situations, (where the oxygen content is at least 19.5%), a wearer may be able to enter an area that has a contaminated atmosphere using only a filter system, provided the filter(s) is capable of meeting the challenge of the contamination, as a result cleaning the atmosphere and enabling the user to breathe and still preserve his health. The filter can be provided with means to eliminate harmful constituents in the wearer&#39;s ambient atmosphere. In particular, filter based decontamination systems, that is, those systems that purify an ambient atmosphere that has become contaminated so as to convert it to breathable air, work best when they pass an air supply under positive pressure through a cleaning element (such as a suitable filter). That is, a pump/fan is used to suck the contaminated atmosphere through a filter, and perhaps into contact with a material that ameliorates the contaminant(s), and to then force the purified, e.g. filtered, air under positive pressure into a facemask or other means associated with the breathing of the wearer, such as a mouth grip, hood, or helmet. While a powered air supplying means, such as a battery-operated pump/fan, is probably preferred, it is also known that air-cleaning systems that are not powered by external means can be used. In these unpowered systems, the user&#39;s lung power provides the necessary impetus to force contaminated air through the cleaning element and feed it to the user. For simplicity, this means of cleaning ambient atmosphere will be referred to as an Air Purifying Respirator (APR). When the air is forced through the system due to the use of a battery, line current or other powered pump or fan arrangement, the operating system is known as a Powered Air Purifying Respirator (PAPR). 
         [0007]    Given the growing demand for PAPR systems, requirements have been identified for providing breath responsive systems that would allow longer filter life, conservation of battery power, and provide air generally on a demand basis so as to better simulate the user&#39;s natural breathing pattern. However, while prior efforts have been made to provide breath-responsive systems, shortcomings of prior constructions have prevented their commercial acceptance. 
         [0008]    Thus, there remains a need for a breathing assist system that is capable of supplying breathable air to a user, but that does so while maximizing efficiency of the apparatus and that preferably supplies only the amount of air that the user&#39;s actual demand for air dictates. 
         [0009]    The above and following comments use a fire fighter as illustrative of the type of person who will benefit from using the instant invention. However, this invention is by no means limited in use to fire fighters. Workers in chemical plants and refineries will have substantial need for the benefits available from the instant invented system. Soldiers in the field that are being subjected to chemical or biological attack will benefit greatly from the instant system. It will be apparent to those of ordinary skill in this art that others will similarly be assisted by the instant invention. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides a solution to the above and other problems by enabling a powered air-purifying respirator system for supplying clean, breathable air from ambient surroundings to a respirator hood or facemask. 
         [0011]    In a first aspect of the present invention, an airflow regulating system is provided that supplies air to the user by controlling the amount of air supplied in response to a sensed condition within the user&#39;s breathable environment. In a particularly preferred embodiment, a pressure transducer that senses the pressure of air within, or the pressure of air delivered to, the user&#39;s breathable environment is provided, and in response to the sensed pressure condition, an airflow regulator controls the amount of air supplied to the user&#39;s breathable air environment. 
         [0012]    In accordance with a particularly preferred embodiment, the system includes a powered blower unit that draws air through one or more filter canisters and directs such filtered air to the user&#39;s breathable environment, for example, a tight-fitting mask over at least a portion of the user&#39;s face. Within the flow path from the blower to the breathable environment, an airflow regulator is provided to control the amount of air that is delivered to the user&#39;s breathable environment at any given time. The airflow regulator is configured to provide fast response (i.e., fast opening and closing of the valve member) in response to changes in a condition within the breathable environment, and preferably changes in the pressure within the breathable environment. In order to provide fast response to a change in condition in the breathable environment, the airflow regulator in accordance with a preferred embodiment includes a valve control that allows forced air from the blower to be directed to the user&#39;s breathable environment. In a further preferred embodiment, the airflow regulator includes a motor control that allows automatic changes in the speed of the blower. 
         [0013]    In accordance with another aspect of a preferred embodiment of the invention, a blower unit is provided that is configured to direct pressurized air to the airflow regulator, and on to the user&#39;s breathable environment. The blower unit preferably comprises a motor driving a centrifugal fan and at least one filter canister to filter air drawn into the blower. Optionally, the blower unit may be provided a purge valve used to divert the flow of air exiting the blower unit from a first port that directs air to the user to a second port that directs the air to the outside environment. Such purge valve may be useful to allow air to constantly be drawn through the filter, and thus keep the filter cool. Moreover, such purge valve assembly may be useful to allow the filters to be cleaned by running clean air through the filters to pull out contaminants, and directing such cleansing air to the outside environment instead of to the user&#39;s breathable environment. 
         [0014]    In accord with and fulfilling these objects, one aspect of this invention is a breathing assisting apparatus comprising a tight fitting facemask, or other conventional means of bringing respirating air to a person in need thereof, that is adapted to be tightly fitted to a person&#39;s face or mouth or nose (or any combination thereof). For ease of understanding, further reference will be made to the use of a facemask. However, this use is illustrative and not limiting. A mouthpiece can also serve the function of bringing the breathable air to the user. 
         [0015]    Other and additional objects of this invention will become apparent from a consideration of this entire specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]    The above and other features, aspects, and advantages of the present invention are considered in more detail, in relation to the following description of embodiments thereof shown in the accompanying drawings, in which: 
           [0017]      FIG. 1  is a schematic diagram of an air supply system according to a first embodiment of this invention. 
           [0018]      FIG. 2  is a diagram of a cutaway portion of the air supply system of  FIG. 1 . 
           [0019]      FIG. 3  is a flow chart of a control algorithm according to a first embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0020]    The invention summarized above and defined by the enumerated claims may be better understood by referring to the following description, which should be read in conjunction with the accompanying drawings. This description of an embodiment, set out below to enable one to build and use an implementation of the invention, is not intended to limit the invention, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
         [0021]    In an effort to avoid the above-described disadvantages, a control system for a powered air-purifying respirator unit is provided. As shown in  FIG. 1 , the system according to a first preferred embodiment is shown generally at  10 , and comprises a blower assembly  13 , a filter manifold  16 , a control valve  19 , a pressure sensor  22 , and a main circuit controller  25 . The system is operatively connected to a facemask  26 . 
         [0022]    Referring to  FIGS. 1 and 2 , in a preferred embodiment, blower assembly  13  comprises a motor and impeller type fan  27 . The blower assembly  13  is operatively connected to the filter manifold  16  that includes a plurality of filter/decontamination elements  30 . The impeller fan  27  provides means for moving ambient air  33  through the filter manifold  16  and through the filter/decontamination elements  30 . In a preferred embodiment, the impeller fan  27  is rotated by a variable speed, electric motor that is powered by one or more batteries. In a preferred embodiment, the battery is a Lithium polymer rechargeable battery or a Nickel-Cadmium rechargeable battery. Other types of batteries can be used. A charging port for the battery may also be provided. The impeller  27  in the blower assembly  13  is adapted to cause ambient air to be drawn through the filters or canisters (containing suitable decontamination) in the filter manifold  16  where the air is to be cleaned of solid particulate matter, harmful gases, and/or odors to produce cleaned air. The cleaned air  36  is forced into the facemask  26  worn by a user to thereby provide breathable air to the wearer. The faceinask  26  is connected to the blower assembly  13  via a hose  39 . 
         [0023]    Further, in a preferred embodiment, the filter manifold  16  comprises a shell  42  for holding at least one filter/decontamination element  30  of standard construction, selected for the threat/contagion environment in which the unit is intended to be used. Such filter/decontamination element  30  may be configured to filter dust, chemicals, gases, biological agents, etc., as is known in the art. Subject to the class of filter/decontamination elements fitted and the time spent in the contaminated area, the filter/decontamination elements  30  may provide breathable air  36  in a chemically, biologically, or nuclear contaminated environment. The filter manifold  16  is sized and configured to hold a plurality of filter/decontamination elements  30  and may be integrally formed with, embedded in, or otherwise sealingly attached to a plenum  45  at the inlet of the blower assembly  13 , such that the only available flow path to the fan impeller  27  is through the filter/decontamination elements  30  in the filter manifold  16 . The filter manifold  16  supports at least one, and preferably a plurality of filter/decontamination elements  30 . The exit from each filter/decontamination elements  30  is preferably operatively associated with the facemask  26  so that contaminated air  33  drawn into each filter/decontamination element  30  by means of the blower assembly  13  is cleaned and then powered by the impeller  27  into the facemask  26  via the hose  39  and control valve  19 . All air passing through any and all specific filter/decontamination element(s)  30  exit into the inlet plenum  45  that is operatively associated with the blower assembly  13 , as stated above. In  FIG. 2 , there are shown three (3) filter/decontamination elements  30  each of which contain filter medium. One or more of the canisters can also contain suitable materials that serve to decontaminate the ambient environmental air by eliminating harmful components that are not filterable. The individual filter/decontamination elements  30  can be used individually or in plural configuration and may be fitted all on one side of the shell  42  or fitted some on one side and some on the other to the desired quantity. As the filter/decontamination element  30  is intended as a disposable unit, the outer shell  42  of filter manifold  16  should be formed of an inexpensive material, such as plastic. The entire filter manifold  16  may simply be disposed of and replaced when it comes time to replace the filter/decontamination elements  30 . In another embodiment, individual filter/decontamination elements  30  may be replaced. 
         [0024]    Control valve  19  is preferably a motor-operated butterfly valve having a stepper motor to enable positioning of the control valve  19  as directed by the main circuit controller  25 . For ease of construction and wearing of the system  10 , the control valve  19  should be located close to the blower assembly and may be integrally formed with, embedded in, or otherwise sealingly attached to the outlet  48  of the blower assembly  13 . 
         [0025]    A purge valve  50  may be provided between the blower assembly outlet  48  and the control valve  19 . The purge valve should be a normally closed, manually operated valve that can be used to divert the flow of air exiting the blower assembly  13  directly to the outside environment. Such purge valve  50  may be useful to allow air to constantly be drawn through the filter/decontamination elements  30 , and thus keep them cool. Moreover, such purge valve  50  may be useful to allow the filter/decontamination elements  30  to be cleaned by running clean air through them to pull out contaminants, and directing such cleansing air to the outside environment instead of to the user&#39;s breathable environment. 
         [0026]    The pressure tap  22  is attached to the hose  39  in a position as close to the facemask  26  as possible. A tube  53  connects the pressure tap  22  to a solid-state pressure transducer in the main circuit controller  25 . The opposite side of the solid-state pressure transducer is vented to atmosphere. The pressure tap  22  senses pressure in the facemask  26  as an indication of breathing need of the user. 
         [0027]    The main circuit controller  25  comprises sensors and drivers to operate the blower assembly  13  and control valve  19 . As indicated above, a solid-state pressure transducer for reading facemask pressure is provided. A stepper motor driver is provided for operation of the control valve motor and a brushless motor driver is provided for operation of the blower motor. The main circuit controller  25  also includes two microcontrollers: one for reading facemask pressure and adjusting the position of the control valve  19  and the other for adjusting the speed of the blower assembly  13 . In a preferred embodiment, the main circuit controller  25  may also include one or more USB ports, a real-time clock, and memory for data logging. 
         [0028]    In a preferred embodiment, the main circuit controller  25  uses a PID controller to operate the control valve  19  and blower motor. The PID controller uses feedback from the valve position and/or blower speed in conjunction with facemask pressure to provide sufficient breathing air to the user. Referring to  FIG. 3 , a flowchart of the basic operation of the system is shown. Initially, at step  100 , the blower assembly  13  is turned on at half speed and the control valve  19  is set to full open. At step  102 , the controller reads the facemask pressure. Then, at step  104 , the PID controller determines an appropriate position for the control valve  19 , based on pressure and the current position of the control valve  19 . If necessary, at step  106 , the main circuit controller  25  sends a signal to the control valve motor to adjust the position of the control valve. At step  108 , the main circuit controller  25  determines if the control valve  19  is operating in a preselected desired range. If so, control of the breathing air pressure to the facemask  26  is maintained by feedback in the PID control loop. If the control valve  19  is not operating in the desired range then, at step  110 , an appropriate speed for the blower is determined from a look-up table based on the current position of the control valve  19 . If necessary, at step  112 , the main circuit controller  25  sends a signal to the blower motor to adjust the speed of the blower. The use of the PID controller and separate control of the valve position and blower speed minimizes movement of the control valve  19  and variation in the speed of the blower. 
         [0029]    The invention has been described with references to a preferred embodiment. While specific values, relationships, materials and steps have been set forth for purposes of describing concepts of the invention, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the basic concepts and operating principles of the invention as broadly described. It should be recognized that, in the light of the above teachings, those skilled in the art can modify those specifics without departing from the invention taught herein. Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with such underlying concept. It is intended to include all such modifications, alternatives and other embodiments insofar as they come within the scope of the appended claims or equivalents thereof. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein. Consequently, the present embodiments are to be considered in all respects as illustrative and not restrictive.