referring to fig1 , general features of a portable therapeutic gas concentrator are shown . typically gas is drawn into the inlet through an inlet filter 1 into a compressor 2 . compressed air is then delivered at a rate of about 3 lpm to 30 lpm ( through various filters and other devices ) to a gas separation section for selectively adsorbing a component of the gas . the preferred embodiments of the invention , although applicable to a variety of gas concentrator implementations , will be described in detail for the case where the inlet gas is air , and the gas separation section is based on psa , va , vpsa or some combination thereof , utilizing adsorbent beds 3 which selectively adsorb nitrogen , producing oxygen rich product . a variety of gas separation section cycle types and bed arrangements are known in the art , most of which can benefit from the embodiments of the invention . whatever the details of the gas separation section 3 , typically product gas is accumulated in a storage device 4 . storage devices may include a tank in the traditional sense , or may be some other device effective for holding a volume of gas , such as a tube , or some other volume filled with an adsorbent to increase its holding capacity . many modern concentrators used for therapeutic applications also include a programmable controller 5 to operate the concentrator and provide for user interface 8 and communications . also typical are gas exhaust 6 , and delivery to patient , which often is through a conserver device 7 . earlier portable oxygen concentrator designs were heavier and typically had an oxygen output of only around 0 . 1 l / lb of system weight . this low output to weight ratio was largely a result of thicker housing walls and redundant components to aid in sound reduction and vibration isolation . for a system that can be carried by the user by a shoulder strap or backpack system , a higher oxygen output to weight ratio is desired . embodiments of the current invention increase the oxygen to weight ratio by as much as 30 % over prior art concentrators while also achieving lower sound levels and increased durability . by comparison , popular existing systems have much lower oxygen to weight ratios . the inogen one delivered 0 . 75 l of oxygen and weighed 9 . 7 pounds for an output to weight ratio of 0 . 08 l / lb . the respironics everflo in measurements made by the inventors produced 1 . 05 l of oxygen at 10 . 2 pounds for an output to weight ratio of 0 . 10 l / lb . the inventors also tested the airsep freestyle and measured 0 . 45 l of oxygen and weighs 4 . 3 pounds for an output to weight ratio of 0 . 10 l / lb . while efforts have been made to achieve greater oxygen output to weight ratios in transportable units such as continuous flow portable concentrators like the sequal eclipse , these units have integrated cart handles and wheels so they are not designed for the same purpose as a carried or worn concentrator and are not as likely to experience the same level of abuse as the type of concentrator designed by the inventors . as a portable concentrator shrinks to a size where it can be carried , the likelihood of significant drop and impact is greatly increased . system housing wall thickness may be reduced from 0 . 050 ″ down to 0 . 030 ″ or less depending on the flame rating requirements of the selected material . further , as the volume of the concentrator shrinks from around 1200 cubic inches , the noise , vibration , and heat generating components become ever closer to the housing walls , and inlet vents , and exhaust vents . this volume reduction necessitates improved functionality from noise mitigation and vibration mitigation designs while not allowing for additional size or weight to achieve the noise and vibration reductions . for instance the inventors tested the invacare xpo2 and measured a high oxygen to weight ratio of 0 . 12 l / lb producing 0 . 84 l of oxygen at 7 . 3 pounds , but observed noise level increases to above 45 dba as a result . as miniaturization of a portable oxygen concentrator progresses the designers are faced with ever more difficult challenges , and this disclosure details several novel design approaches that offer solutions to weight , noise , and durability requirements . the figures depict exemplary implementations that resemble portions of an as - built novel concentrator . however it is to be understood that the details in the figures are by way of example only and in many cases serve to illustrate a particular version of a novel concept that need not follow the exact configuration of the figures to fall within the teachings and claims of the invention . referring to fig2 a general illustration of the novel concentrator is shown . concentrator housing 21 , battery 22 and user interface 8 are shown . the battery 22 , as depicted in the exemplary figure , forms a nearly seamless integration with the concentrator so that the battery actually forms the bottom of the concentrator and has integral overmolding that functions as an impact absorber and anti - slip footing for the concentrator . since many drops and impacts would be taken by the bottom of the concentrator , the location of the battery provides a level of protection where damage to the battery would not stop the concentrator from functioning on external power such as ac or dc power . in addition , the sliding rails of the battery and the interlocking components that form the mating rail on the concentrator form a particularly strong and rigid area of the concentrator that allow the battery and shell of the concentrator to dissipate energy without harmfully transmitting it to the working internals of the device . the housing 21 of the concentrator is also devoid of corners and flat surfaces to further stiffen the outer shell , which allows for reduced wall thickness without reduced durability . fig3 a and 3 b depict a particular embodiment of the concentrator 21 . base panel 33 connects to side panels 31 and 32 as well as front panel 34 and rear panel 35 as can be seen when front and rear panels 34 and 35 are attached they form an air plenum with an offset flow path , which for the exemplary panel design shown is completely non - overlapping . this offset ducting design is a significant improvement for noise isolation . a mesh screen 37 may be employed as a debris filter on the input air plenum . at least some and preferably all the side , front and rear panels are configured to overlap bottom panel 33 . when battery 22 is installed , it is configured to contact and retain the panels for added rigidity . similarly , top panel 35 also contacts all of the body panels as well . in the exemplary implementation , the air plenum space formed by the mating of panels 31 , 32 and 34 and the similar air plenum space formed by the mating of panels 31 , 32 and 35 create a double walled structure where there are a plurality of connecting points , preferably eight or more . these double walled structures are similar in function to the battery attachment on the bottom of the concentrator where multiple components are mated to increase rigidity and strength while also providing for noise reduction and easy serviceability . in one particular embodiment , the side panels wrap around the front and back of the device to mate together forming the inner wall of the double walled structure and are the two side panels and the top panel are joined with a single screw creating a three point anchor system . the side panels further have mirror imaged cut - outs to form the inner air vent opening at the front of the device and the inner exhaust vent opening at the rear of the device . to form the outer wall of the intake or the exhaust plenum , a convex and stylized panel is installed by engaging retention clips that protrude from the convex outer panel through slots on the side panels . these clips and slots are locked into place when the panel is slid upward and further reinforced because the battery blocks the panel from disengagement in the downward direction . the opening in the end panel is offset from the opening formed in the wall section of the side panels and the air flows through the space formed between the end panels and the wall section of the side panels . the path through both plenums is offset , preferably substantially non - overlapping or completely non - overlapping , to provide noise isolation by eliminating a direct path for noise to exit the device . as shown in fig4 a , b and c panels can be attached to each other via an interference fit such as snapped together with retention clips 42 and 43 . when assembled , retention clips may be further reinforced with fastener mounts 41 to ensure that housing holds its shape during impact to prevent undue deformation to internal components . the multitude of snapping features or other forms of interference fit type of fastening devices also allows for a reduction in the number of screws or fasteners required to assemble the concentrator since panels can be locked in place by two fasteners while maintaining strength around the entire perimeter of the panel through the snap features . this assembly method greatly reduces the assembly time and weight that would be required to have a high number of fasteners . for example , the sequal eclipse is a simple clamshell design that 10 screws to fasten the two halves together . the inventors design uses 13 screws to fasten six panels together for roughly 50 % less fasteners per housing panel . a particular implementation is shown in fig4 b and 4 c . as shown in fig4 b , when side panel 31 is mated with bottom panel 33 , a rail is formed along the length of the panels . when battery 22 is installed , the side panel can no longer be removed because the retention clips must be disengaged in the direction of movement that is blocked by the battery 22 . as shown in fig4 c , back panel 35 attached to side panels 31 and 32 by sliding upwards to engage the retention clips 43 . when battery 22 is installed , back panel 35 is prevented from sliding downward and thus cannot be disengaged by drop or impact . similar arrangements as shown in the figures also apply to the front and other side panels . thus when battery 22 is installed , all four panels are contacted and restrained such that the panels cannot be disassembled with battery in place and structural integrity is greatly increased . referring to fig5 , the plenums formed by the assembled panels are shown . input 52 is offset from opening 53 as output 55 is offset from opening 54 . preferably an air barrier 50 is present within the housing between the input and output plenums , and it carries an air mover 51 , which provides the only airflow path through the barrier . in a particular embodiment barrier 50 has a plurality of functions such as an electronic circuit board and air mover 51 is a cooling fan mounted to the board 50 . the circuit board 50 is preferably sealed to the housing with foam to prevent air leakage back across the air barrier . the air flow through the body is shown . in a particular as built embodiment , the absorber columns are in the input side of the barrier and the compressor is in the output side of the barrier . when assembled the panels and barrier constitute a very rigid shell with controlled noise airflow that is particularly suited to an oxygen concentrator where room air must be drawn into the system as a source of oxygen and the nitrogen rich exhaust gas must be expelled from the concentrator . it is advantageous to separate these gas streams so that there is no excess nitrogen drawn into the air inlet of the compressor . referring to fig6 a , b and c , details of the compressor side of the novel concentrator are shown . in the exemplary version depicted , a compressor bracket 64 is mounted to panel 33 . bracket 64 is preferably mounted to panel 33 with shock / vibration isolating elements which in the exemplary version shown are rubber feet 65 . feet 65 preferably have a durometer between 20 a and 60 a . compressor 62 is in turn mounted to bracket 64 with another set shock / vibration isolation elements , providing two levels of isolation . in the exemplary version , the second set of isolators is fabricated on the bracket as overmolded rubber 64 . panel 33 in an as - built configuration is the only housing panel with structural mounting for a vibrating component . panel 33 is an internal panel where the battery is mounted on the underside of the panel . this panel is particularly suited for compressor mounting since the highly mass dense battery absorbs much of the transmitted vibration and prevents the transmission of vibration to the side panels that may contact the user while the device is being carried . in the inventors &# 39 ; prior art concentrator the compressor was mounted to a separate internal chassis that was then surrounded by housing components which led to added weight and size . the separate internal chassis of the prior art concentrator was also more susceptible to damage during drop or impact because the structure was not supported across much of its surface area . panel 33 is fully supported by battery 22 leading to a much stronger and more resilient design . bracket 64 may be made of aluminum for example and in the exemplary version the compressor 62 is a two piston unit . the two piston inputs are connected by low profile compliant member 63 . element 63 in the embodiment shown is a rubber duct 630 and 631 with one snap fit and one threaded attachment to allow for vertical compliance since the compressor assemblies are pressed onto the motor shaft without a hard stop to prevent bearing loading . it may be made from two joined molded rubber pieces and the air channel preferably is between 0 . 02 and 0 . 08 sq in . the compliant member preferably has a durometer between 20 a and 70 a to prevent the flat surfaces from resonating noise . the inventors tried multiple materials and fabrication methods and achieved unacceptable results until the proper material durometer were selected . the flat geometry of the compliant member allows for adequate cross section to prevent flow loss from the compressor while also minimizing the protrusion height from the concentrator . with the small external dimensions of a carried portable oxygen concentrator all components must be optimized to reduce space in critical directions . prior art intake joining tubes were two hard plastic cylinders that slid internal to one another for compliance and protruded as much as twice as far from the compressor as the inventors compliant member 63 . air filter 61 is preferably arranged with its input and output at right angles and had tortuous air path 610 again for noise isolation . air filter 61 is plumbed to the air blower with compliant tubing in the durometer range of 20 a to 60 a . the compressor mounting arrangement preferably also includes bump stops 66 to limit compressor deflection in the event of the concentrator being dropped or impacted . stops 66 are placed adjacent to mounting feet 65 and compressor 62 . the stops 66 built into bracket 64 substantially prevent the compressor from colliding with delicate components like the printed circuit board or the external housing components . the bump stops 66 adjacent the mounting feet 65 also allow for softer mounting feet to be used without risk of tearing due to over deflection during drop impact . bracket 64 may also include mounting for beds with compliant airflow elements . when assembled , the compressor filter assembly us mounted to the housing through two layers of isolation and only connected to the rest of the system through compliant elements . thus the assembly is highly resistant to shock and displacement while providing vibration and noise isolation . fig7 a and 7 b illustrate another embodiment of the novel concentrator . pressure sensor 72 is designed to mount to a circuit card 50 with two fasteners . the in effect is a stiff fixed mounting that can create a torque or twist on the sensor between the mounting screws and the barbed tubing connections . due to the shock , vibration and general motion experienced in the portable concentrator environment , this fixed mounting point induced strain can couple vibration into the sensor and can affect the quality of the measured reading . the inventors developed clip 73 which snap mounts to the sensor 72 and is a cantilever designed to mount into fastener points intended for the sensor , while suspending the sensor itself so that it is mounted near the barbed tubing connections to relieve any strain or stress on the body of the sensor where the delicate pressure measuring components are housed . this strain relief in effect greatly diminishes the vibration coupled into the sensor and allows for more reliable and more sensitive breath detection capabilities . referring to fig8 , the absorber bed side of the concentrator of one embodiment is detailed . absorber columns 81 are supported , preferably at the top and bottom by isolation elements which fit into the housing panels such as panel 33 . these elements are in the exemplary version shown , foam blocks 82 and 83 with cutouts supporting the columns . the columns are located and held relative to each other by clips 84 . clips 84 and blocks 82 and 83 may also carry one or more other items in addition to absorber beds , including air dryers , an oxygen sensor , and product gas accumulator . thus the columns and other items are floating in the housing with no hard contact to the housing at all . this arrangement greatly improves the durability and survivability of the concentrator while providing yet more noise and vibration isolation . further in some embodiments , the columns are held in the concentrator without any screws whatsoever allowing for a very comply column replacement of the zeolite is ever contaminated . in addition , noise barrier 50 and blower 51 may also be mounted in the foam blocks . the resulting assembly shown in fig9 illustrates the overall concentrator assembly of one embodiment . rigid and strong shell 21 composed of interlocking panels and locked by battery 22 has no direct contact with any interior components . the columns 81 , dryer , accumulator , and all electronics 50 and fan 51 float in a float in a foam chassis 82 and 83 on one side of the air barrier . compressor 62 vibrates too much to use a foam chassis , so it and all directly attached components are supported by two levels of rubberized isolation , again with no direct hard attachment to the exterior housing panels . in one implementation , the only communication between the two sections is by way of compliant airflow elements such as soft plastic tubing and the like . airflow is carefully designed to reduce noise . the result is a very hard shell , with all interior components possessing a large amount of freedom of motion relative to the shell and each other , producing an extremely damage resistant and very quiet design . the foregoing description of the preferred embodiments of the present invention has shown , described and pointed out the fundamental novel features of the invention . it will be understood that various omissions , substitutions , and changes in the form of the detail of the apparatus as illustrated as well as the uses thereof , may be made by those skilled in the art , without departing from the spirit of the invention . consequently , the scope of the invention should not be limited to the foregoing discussions , but should be defined by appended claims .
a portable oxygen concentrator designed for medical use with a novel housing and internal component design that reduces noise and vibration while increasing durability . the improved design of the portable oxygen concentrator further facilitates easy maintenance and repair over the life of the equipment .