Abstract:
The present invention relates to a fan-forced positive pressure breathing apparatus commonly known as a Powered Air Purifying Respirators (PAPR) system, and specifically concerns the connecting of the breathing components of such equipment. The invention is a method and apparatus for rapid engagement of PAPR breathing components (such as air supply lines and filter elements to a blower housing). The invention also provides for indicating and/or monitoring whether the relative components have been aligned and coupled in sealed engagement.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to fan-forced positive pressure breathing apparatus, commonly known as Powered Air Purifying Respirators (PAPRs). In particular, the invention concerns rapid engagement mounting systems for affixing breathing components to the blower housing of the PAPR. Breathing components might include filter elements, hose attachments for supplied air, or other components required to complete a breathing circuit. Rapid engagement mounting systems are generally defined as reversible attachments that allow the deployment of a breathing component by pressure fit, sliding engagement, or rotational locking with less than one full revolution of the component. 
     Non-powered air purifying respirator equipment involves a breathing mask having a filtered air inlet. Air is drawn through the filter by means of the wearer&#39;s breathing action. When the wearer draws a breath, negative pressure is created in the mask and air is drawn though the filtering element. When the wearer expels a breath, spent air leaves the mask through a valve. PAPRs are employed to continually supply positive pressure to the wearer&#39;s mask. The filtered supplied air replenishes the internal confines of the mask and is continually ejected. To provide ease of replacement of the filter elements on non-powered respirators, bayonet type of attachments are often employed. These attachments require less than one full turn of the filter to engage the cartridge to the respirator body. 
     PAPRs are generally used in industrial applications where the environmental hazards are well defined and quantified. Respiratory hazards might include harmful gases, vapors, and particulate matter. To address generally known and quantified industrial hazards, a PAPR can be configured well in advance of entry into the workplace, and the amount of time a worker spends in a hazardous environment can also be well managed. In industrial settings, PAPR systems that employ multiple-turn screw type attachments for connecting the breathing components require more effort and time to properly affix. 
     First responders (HazMat, police, fire, and civil defense), military or other emergency response units are not afforded the opportunity to preemptively manage hazardous respiratory exposure. Depending on the nature of the exposure, the responder must quickly configure the respiratory system to adapt to the need. Exposure duration and levels are also unknown transients in the protection equation. In certain situations, the responder may not be able to extract themselves from the exposure arena and could be required to make a ‘hot’ change-out of the PAPR breathing components. An example of this situation might be found in a military theater where the user could be required to replenish filters while remaining in the exposed area. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention relates to Powered Air Purifying Respirators (PAPRs) that incorporate breathing components adapted for rapid engagement with the blower housing of the system. In a preferred embodiment, the invention further provides for engagement detection elements that indicate the proper engagement of the breathing component to the PAPR housing. Rapid engagement breathing components combined with engagement detection elements, afford superior wearer protection in situations where a PAPR is required to be quickly configured to a respiratory hazard or when ‘hot’ change-outs of the breathing components are desired. The inclusion of engagement detection elements on a PAPR system provides any user with a higher level of system integrity regardless of the application. 
     PAPR systems of the present invention differ from known PAPRs in two basic aspects that involve both the attachment and detection system. Known PAPR systems employ screw-type attachments to affix filters to the blower housing. These screw-type attachments are multiple-turn in nature and do not lend themselves to rapid engagement of a filter. Multi-turn screw systems are also susceptible to cross threading if care is not taken with their attachment. Rapid engagement attachment systems are particularly suited to rapid configuration and deployment of PAPR systems, especially in first-responder or military situations. 
     Rapid engagement attachments require a minimum, if any, rotation of the breathing component by using highly pitched threads to connect the filter cartridge to the blower housing. In addition, the rapid engagement connection releasably locks the filter cartridge to the blower by using opposing detents to form a seated engagement between the blower housing and filter cartridge. This prevents the filter cartridge from accidentally disconnecting from the blower housing. 
     Attachment systems of known PAPRs also do not employ engagement detection elements. The only indication of proper engagement of the filter to the housing is the resistance to turning that could be misinterpreted if the filter was cross-threaded. The engagement detection system of the present invention provides a definitive indicator of attachment, both at the point of fixing and during use of the system. Engagement detection systems of the invention are especially useful in fail-safe and ‘hot’ change out applications, where actions of the blower motor or flow damper components can be actuated as a function of component engagement. 
     The engagement detection system of the invention may employ electrical, mechanical or optical contacts. As part of a circuit, an electrical or optical contact between the breathing component and the PAPR body is operably coupled to an auditory or visual signal to indicate proper seated and sealed engagement of the components. This type of arrangement could also be used, for instance, to actuate dampers to reverse air flow through the blower housing causing air to exhaust in order to enable ‘hot’ change-outs of the breathing component. In addition or optionally, a mechanical contact could provide an auditory or tactile indication of proper contact and could also incorporate a disengagement fail-safe to prevent the breathing component from reversing off its attachment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be further explained with reference to the attached figures, wherein like structure is referred to by like numerals throughout the several views. 
     FIG. 1 is a perspective and diagramic view of a Powered Air Purifying Respirator (PAPR) system. 
     FIG. 2 is a perspective view of a preferred embodiment of the fan and filter assembly of the PAPR. 
     FIG. 3 is a top view of the preferred embodiment of the fan and filter assembly of the PAPR. 
     FIG. 4 is a front view of the preferred embodiment of the fan and motor housing of the PAPR. 
     FIG. 5 is a sectional view as taken along line  5 — 5  of FIG.  4 . 
     FIG. 6 is a side view of one of the filter cartridges of the preferred embodiment of the PAPR. 
     FIG. 7 is a bottom view of the filter cartridge of FIG.  6 . 
     FIG. 8 is a sectional view as taken along line  8 — 8  of FIG.  7 . 
    
    
     While the above-identified drawing figures set forth one preferred embodiment of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the present invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. 
     DETAILED DESCRIPTION 
     The main components of a Powered Air Purifying Respirator (PAPR) system  10  are shown in FIG.  1 . PAPR  10  includes breathing head-gear  12  and a connected remote fan and filter unit  13 , resulting in a fan-forced positive pressure breathing apparatus. PAPR  10  is designed to be worn by a person working in an atmosphere with unwanted contaminants. PAPR  10  filters unwanted contaminants from the surrounding atmosphere, thus allowing a person wearing PAPR  10  to work in the contaminated area. The filter used with PAPR  10  becomes full of contaminants over time and must be replaced. 
     The present invention focuses on the replacement of filters by providing a rapid engagement connection between a main housing and a replaceable filter cartridge of PAPR  10 . The rapid engagement connection may also be used with other breathing components attached to the housing of PAPR  10 , such as air hoses and pressurized-air-supply adapters. In a preferred embodiment, the present invention also incorporates an engagement detection system that signals the user when the filter cartridge and housing (or other coupled breathing components) are properly engaged. 
     PAPR  10 , shown in FIG. 1, includes a blower housing  14 , a blower  16 , a power source  18 , a breathing tube  20 , one or more replaceable filter cartridges, canisters or other filter units  22 , a housing-fluid (air) inlet  24 , and a filter-fluid (air) outlet  26 . Blower housing  14  contains blower  16 , which is driven by power source  18 . Blower  16  is used to create a negative pressure in a chamber within housing  14 , which draws air through filter cartridge  22 . The air is filtered and then delivered to a user wearing head-gear  12  via breathing tube  20 . Filter-fluid outlet  26  (on the filter cartridge  22 ) attaches to housing-fluid inlet  24  (on the blower housing  14 ), which allows filter cartridge  22  to be periodically replaced. 
     FIGS. 2-8 show a preferred embodiment of components of PAPR  10 . FIG. 2 provides a perspective view of the fan and filter unit  13  of PAPR  10 , while FIGS. 3 and 4 provide top and front views, respectively (in FIG. 4, the filter cartridges  22  are removed for clarity of illustration). FIG. 5 provides a sectional view of the housing  14  of PAPR  10  taken from line  5 — 5  of FIG.  4 . The preferred embodiment of PAPR  10  shown in FIGS. 2-5 includes a blower housing  14  and a pair of filter cartridges  22  attached thereto. The housing  14  and each filter cartridge  22  are conduits which are coupled together to facilitate the flow of fluid (in this case, filtered air). FIGS. 2-4 specifically show two filter cartridges  22  attached to blower housing  14 , however, the present invention is not limited by the number of filter cartridge  22  used with blower housing  14 . One filter cartridge may suffice (see, e.g., FIG.  1 ), or more than two filter cartridges  22  may be used, as desired for a particular filtering application. 
     In addition to the plurality of filter cartridge  22 , shown in FIGS. 2-3 and explained in further detail below, the housing  14  of PAPR  10  includes breathing tube connection  32 , engagement detection indicator  34 , and power switch  36  (such as, for example, a recessed push-button switch). Breathing tube connection  32  is the connection between the housing  14  of PAPR  10  and breathing head-gear  12 . Breathing tube connection  32  may also incorporate a rapid engagement system of the present invention, however, the preferred embodiment shown in FIGS. 2-4 has the rapid engagement system only between the filter cartridges  22  and the blower housing  14 . 
     The engagement detection system of the present invention is explained in further detail below, but its purpose is to provide a person wearing PAPR  10  with an affirmative indication that the breathing system components are properly connected. Power switch  36  allows the user to turn PAPR  10  on and off. When PAPR  10  is turned on, the switch of power source  18 , shown in FIG. 1, is closed; thus, blower  16  is powered. 
     FIG. 4 shows the housing  14  of PAPR  10  with filter cartridges  22  removed, thus revealing (for each filter cartridge  22 ) filter mounting surface  23 , housing-fluid inlet  24  (having housing-fluid-inlet threads  38 ) and housing detents  40  ( 40   a ,  40   b ) thereon. While the preferred embodiment of housing  14  incorporates a pair of housing detents  40  on filter mounting surface  23 , the present invention may include one or more than two detents, and is not limited by the number of housing detents  40  formed on blower housing  14 . In a preferred embodiment, as shown, detents  40   a  and  40   b  are radially aligned on opposite sides of each housing-fluid inlet  24  on housing  14 . 
     The preferred embodiment of PAPR  10  contains two housing-fluid inlets  24 . Each housing-fluid inlet  24  is located on opposite sides of the front of housing  14  and is designed to sealably couple to one of the filter cartridges  22 . Housing-fluid inlet  24  protrudes axially into housing  14  from its respective filter mounting surface  23 , such that it can accommodate filter-fluid outlet  26  of its respective filter cartridge  22 . Housing-fluid inlet  24  has housing-fluid-inlet threads  38  formed therein (see FIG.  5 ). A deformable gasket  39  is mounted on the housing-fluid inlet  24  at an inner end  39   a  thereof. 
     Preferably, housing-fluid-inlet threads  38  are female threads, defined on the inside surface of housing-fluid inlet  24  and are designed to mate with male threads of filter-fluid-outlet threads  52  on filter cartridges  22 , as shown in FIGS. 6-8 and described below. Each of the housing-fluid-inlet threads  38  is highly pitched and extends only about once around the inner circumference of housing-fluid inlet  24 . The threads, for example, may have a pitch of 0.220 inch, and may be formed as stub acme threads. 
     Housing detents  40  ( 40   a ,  40   b ) are spaced radially from the axis of housing-fluid inlet  24 . Preferably, each housing detent  40  is formed in the shape of an arc  41  that protrudes from the filter mounting surface  23  of housing  14  (compare FIGS.  4  and  5 ). Housing detents  40  align with filter detents  50  on the filter cartridge  22  along an engagement axis parallel with the rotational axis of the relative components, as shown in FIGS. 6-8 and described below, such that housing detents  40  engage and releasably lock filter detents  50  when the filter cartridge  22  is sealably mounted on housing  14 . 
     In addition to the components of PAPR  10  shown in FIGS. 2-4 and described above, belt harnesses  42  are shown in FIG.  5 . Belt harnesses  42  allow a user to attach the housing  14  of PAPR  10  to a belt, by sliding a belt through a belt track  42   a , defined on the back of housing  14 . The housing  14  may also have a compartment  42   b  (see FIG. 5) for receiving and retaining a battery pack  42   c  therein (see FIG.  4 ). 
     FIGS. 6-8 show the details of filter cartridge  22 . FIGS. 6 and 7 show side and bottom views of filter cartridge  22 , respectively, while FIG. 8 is a sectional view of filter cartridge  22  taken along line  8 — 8  of FIG.  7 . Each filter cartridge  22  has a filter housing  43  having a bottom surface  44 , an opposed top surface  45 , and a generally cylindrical side wall  46  connecting the bottom and top surfaces  44  and  45 . Filter media  47  (shown in dashed line in FIG. 8) is retained within an internal chamber  48  defined by filter housing  43 , with the chamber  48  in fluid communication with the filter-fluid outlet  26  and with the exterior of the filter housing  43  via a plurality of perforations  49  in the top surface  45 . As noted above, filter cartridge  22  of the embodiment shown in FIGS. 6-8 includes a plurality of filter detents  50  ( 50   a ,  50   b ), thereon. However, the present invention may include only one or more than two filter detent  50  and is not limited by the number of filter detents  50  formed on filter cartridges  22 . 
     As shown in FIG. 7, the bottom surface  44  of filter housing  43  is preferably circular and includes filter-fluid outlet  26  and filter detents  50  thereon. Filter-fluid outlet  26  is located in the center of bottom surface  44  of filter housing  43 . Filter-fluid outlet  26  protrudes axially from bottom surface  44 , as shown in FIG.  6 . 
     Filter-fluid-outlet threads  52 , as shown in FIGS. 6 and 8, are located on the outside surface of filter-fluid outlet  26 . Filter-fluid-outlet threads  52  are male threads and are formed to mate with the female housing-fluid-inlet threads  38 . Filter-fluid-outlet threads  52  are highly pitched and extend over only half the of the outer circumference of filter-fluid outlet  26 ; thus, less than a single rotation (i.e., less than one full revolution) of the filter cartridge  22  is required to sealably attach filter cartridge  22  to blower housing  14 . When so attached, an outer end  54  of the filter-fluid outlet  26  affirmatively engages and deforms the gasket  39  to effect an air-tight seal between the interiors of the filter cartridge  22  and the housing  14 . 
     Filter detents  50 , shown in FIGS. 6-8, are located on the bottom surface  44  of filter housing  43 , and are spaced radially from filter-fluid outlet  26  and project from the bottom surface  44 . Filter detent  50   a  aligns with housing detent  40   a , shown in FIG. 4, such that when filter-fluid outlet  26  is threadably attached to housing-fluid inlet  24 , filter detent  50   a  engages with and seats into housing detent  40   a . The opposed detents of filter detent  50   a  and housing detent  40   a  thus create a male/female seated engagement that sealably secures filter cartridge  22  to blower housing  14 . Filter detent  50   b  and housing detent  40   b  are likewise shaped to form a seated engagement between filter cartridge  22  and blower housing  14  when the cartridge  22  and housing  14  are sealably and threadably coupled together. 
     During normal use of PAPR  10 , blower housing  14  and filter cartridge  22  are bumped, dropped and can otherwise be subjected to accidental disengagement. In addition, filter cartridge  22  must be quickly attached to blower housing  14  and simultaneously provide compression to the gasket  39  to create seal integrity. Therefore, filter-fluid outlet  26  attaches to housing-fluid inlet  24  using a rapid engagement connection. 
     Filter-fluid outlet  26 , shown in FIG. 6, axially aligns with housing-fluid inlet  24 , shown in FIG.  4 . As explained above, housing-fluid inlet  24  and filter-fluid outlet  26  contain highly pitched threads that are designed for a quick connection between blower housing  14  and filter cartridge  22 . Filter-fluid outlet  26  is fully coupled to housing-fluid inlet  24  with less than a single rotation of filter cartridge  22  relative to blower housing  14  (e.g., by relative rotation of less than 360°). This rapid connection sealably connects filter cartridge  22  to blower housing  14  for filtered air passage therebetween. The rapid engagement connection between blower housing  14  and filter cartridge  22 , disclosed and shown herein, can likewise be used to attach other breathing components of the PAPR  10 , or of other breathing systems. In addition, while the disclosed preferred embodiment shows “male” threads on the filter-fluid outlet  26  and “female” threads on the housing-fluid inlet  24 , that relationship may be reversed. 
     The rapid engagement threads of housing-fluid inlet  26  and filter-fluid outlet  24  are complimented with a click-lock feature that serves multiple purposes. One purpose of the click-lock feature is to provide resistance to accidental disengagement of filter cartridge  22  from blower housing  14 . Another purpose is to identify to the user that the seal has been properly made, thus ensuring proper installation. 
     The click-lock feature incorporates housing detents  40 , shown in FIG. 4, and filter detents  50 , shown in FIGS. 6-8. Filter detents  50  and housing detents  40  comprise a pair of opposed detents that are aligned axially, radially, and circumferentially for seated engagement. Filter detents  50  comprise detent elements that are spaced radially from filter-fluid outlet  26 , and function as male projecting detent elements. Housing detents  40  comprise detent elements that are spaced radially from housing-fluid inlet  24  and function as female receptive detent elements, such that they align with filter detents  50  to make seated engagement connections when filter-fluid outlet  26  and housing-fluid inlet  24  are threadably coupled. The seated engagement connection forms an interference fit that releasably locks blower housing  14  and filter cartridge  22  together, to lessen the possibility of filter cartridge  22  becoming inadvertently disconnected from blower housing  14 . This type of seated engagement connection can also be used to attach together other accessory components of PAPR  10  or other breathing systems. In addition, while the disclosed preferred embodiment shows a “male” detent element on the filter cartridge  22  and a “female” detent element on the blower housing, that relationship may be reversed. The terms “detent” and “detent element” as used herein mean any form of structural feature that cooperates with an opposed mating structural feature to achieve the position detection and component interlocking functions describe herein. 
     The click-lock feature of the rapid engagement connection also provides the user with an indication of whether the seal between filter cartridge  22  and housing  14  has been properly made, thus ensuring proper installation. The engagement detection system uses a mechanical, electrical, or optical method of detecting when a proper connection is made between filter cartridge  22  and housing  14 . An audio, visual, or other signal control mechanism is used show the user when a proper connection had been made. 
     An example of a mechanical detection system is the audible clicks heard when filter detents  50  slide over housing detents  40  and snaps into place. Both housing  14  and filter cartridge  22  are made of a resilient material such as plastic. The resilient material slightly deforms under force; thus, the housing detent  40  and the filter detent  50  engage by slight deformation of the detents and their respective support surfaces to allow the filter detent  50  to slide over the housing detent  40 . After deformation, the detents  40  and  50  snap back to their original shapes. When the filter detent  50  passes over the housing detent  40 , there is an audible clicking sound (the filter detent  50  moves in the direction of arrow  56  (FIG. 4) when the filter cartridge  22  is being mounted onto the housing  14 ). One or more clicks may be heard, depending on the number of housing detent arcs  41  formed on surface  23  of housing  14 . For example, if housing  14  contains two detent arcs  41   a  and  41   b,  as shown in FIG. 4, then a user would need to hear two clicks to know that filter cartridge  22  and housing  14  are properly engaged. 
     Another example of a mechanical detection system is the tactile click felt when a filter detent  50  passes over a housing detent  40 . As explained above, the resilient material slightly deforms to allow filter detent  50  to slide over housing detent  40 . When housing detent  40  and filter detent  50  come into initial engagement as the filter cartridge  22  is being mounted on the housing  14 , a slight pressure and resistance to rotation is felt by the user. As this resistance is overcome, a tactile “snapping” sensation is felt, indicating that the detent components are interlocked. Likewise, when the opposed detents  40  and  50  are in seated engagement (and, therefore, the filter cartridge  22  is then releasably locked to the housing  14 ), there is resistance to rotation for separating the filter cartridge  22  from the housing  14 . A tactile “snap” is felt if that resistance is overcome by placing sufficient rotational force on the filter cartridge  22  to unseat the opposed detents  40  and  50  and initiate threaded uncoupling of the filter cartridge  22  and blower housing  14 . 
     The engagement detection system can also use an electrical signal to indicate a proper connection between filter cartridge  22  and housing  14 . The electrical system either provides an audible or visual indication to a user and/or can control the operation of blower  16 . The audible or visual indication comes from engagement detection indicator  34 , shown in FIGS. 2-4. The engagement detection indicator  34  may provide an audible signal (such as a buzz or a tone) or a visual signal (such as turning a light on or off). The inventive engagement detection system may also incorporate a control signal that operates blower  16  or activates dampers in the PAPR  10  air flow stream. 
     There are a number of ways to determine if filter cartridge  22  is properly coupled with housing  14 . For example, housing surface  23  of housing  14  may contain a pair of electrical contacts. When filter cartridge  22  and housing  14  are uncoupled, the contacts would not be connected and would create an open circuit or open state. The open state would indicate that a proper connection has not been made. Once filter cartridges  22  and housing  14  are properly engaged, the contacts of the circuit would be closed (by, for example, a conductive bridge or connector located on surface  44  of filter cartridge  22 ). Thus, a closed circuit would exist to indicate a proper connection. Alternatively, the contacts may define a closed circuit, which is then opened upon the seated mounting of the filter cartridge  22  on the housing  14 , or the conductivity of the circuit may be altered when the components are engaged in order to define a control signal. 
     Such a control signal may activate blower  16  or active dampers within the PAPR  10  air flow stream to direct fluid out of housing-fluid inlet  24 , redirect fluid into housing-fluid inlet  24 , or reverse the flow of fluid (air) in housing-fluid inlet  24 . Controlling the flow of air associated with housing-fluid inlet  24  prevents contaminants from getting into the PAPR system while filter cartridge  22  is improperly seated on the housing  14  or while the filter cartridge  22  is being replaced. Other control functions can also occur based on the status of the connection between filter cartridge  22  and housing  14 . The engagement detection system enhances user awareness and preparedness for operation in contaminated areas of the PAPR system. 
     As seen in dashed lines in FIG. 6, a filter cover  55  may be used in some applications (e.g., wet ones) to at least partially shield the perforations  49  and thus prevent premature contamination of the filter media which would shorten filter life and decrease filter effectiveness. In that case, air would enter the filter cartridge  22  from under the cover  55  via openings allowed by the cover  55  along the side wall  46  of the filer cartridge  22 . 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the inventive coupling may be used to connect a tethered air line to operator-worn breathing components in a non-PAPR system. This would be beneficial in reducing torque placed on such a line during its coupling and uncoupling because relative rotation of the coupled components is minimized.