Abstract:
A humidifier has a base unit with an engagement face that is configured to interface with a flow generator. The humidifier also has a tank configured to be removably received by the base unit and hold a volume of liquid. The tank has a side wall with an air inlet. The humidifier further has an air flow passage configured to receive an air connector of the flow generator at the engagement face of the base unit. The air flow passage is axially offset from a tank inlet. In addition, a cross-section of the airflow passage inlet and a cross-section of the tank air inlet are substantially perpendicular to a horizontal plane.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/659,963 filed Mar. 26, 2010, which is a continuation of U.S. patent application Ser. No. 10/533,940 (issued as U.S. Pat. No. 8,006,691) filed May 4, 2005, which is a national stage application of PCT/AU04/00810, filed Jun. 21, 2004 in English, which claims the benefit of Australian Application No. 2003903139, filed Jun. 20, 2003, Australian Application No. 2003905136, filed Sep. 22, 2003, and Australian Application No. 2004901008, filed Feb. 27, 2004, each incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to breathable gas supply apparatus, and particularly but not exclusively to such apparatus for use in Continuous Positive Airway Pressure (CPAP) treatment of conditions such as Obstructive Sleep Apnea. It will be described herein in its application to CPAP treatment apparatus, but it is to be understood that the features of the invention will have application to other fields of application, such as mechanical ventilation and assisted respiration. 
     BRIEF SUMMARY OF THE INVENTION 
     The advantages of incorporating humidification of the air supply to a patient are known, and CPAP machines are known which incorporate humidifying devices. One of the objects of the invention is to provide a simple and compact breathable gas supply apparatus incorporating a humidifier which is simple and economic in its construction, compact, and easy to use. Other objects and advantages of the invention will be described throughout the specification. 
     It is to be understood that apparatus described herein contains a number of advances on the prior art, many of which independent inventions, although they contribute together to the realisation of the general object expressed above. 
     The apparatus described herein incorporates novel aspects of architecture which contribute to a reduction in size compared with known units having similar performance. Techniques for noise reduction and damping are described which enable such a smaller machine to have noise performance which is at least as good as known lager machines. 
     The apparatus described achieves full integration of the humidifier with the flow generator, in the sense that air flow, electrical and, if required, data connection between the flow generator and the humidifier are provided automatically upon the physical engagement of the two devices, without the need for any other process of interconnection. 
     In such an integrated device, provisions to guard against flowback of water from the humidifier tank to the flow generator are important, and novel sealing arrangements, and novel arrangements for minimising the occurrence of flowback while at the same time improving the uptake of water vapour in the humidifier are also described. The humidifier is readily detached and replaced on the machine, and has very few parts to be disassembled during cleaning. 
     Also described herein are improved, modular, devices for enabling data connection with the apparatus, including the connection of data storage devices such as memory cards, smart cards, communication ports and the like to be selectively attached by the user or by medical personnel. 
     The various aspects of the invention will now be described with reference to the accompanying illustrations, which show a presently proposed embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a general view of breathable gas apparatus embodying the various features of the invention; 
         FIG. 2  shows the flow generator of the apparatus; 
         FIG. 3  shows the humidifier unit; 
         FIG. 4  is a cutaway view of the flow generator; 
         FIG. 5  is a rear view of the humidifier; 
         FIG. 6  is an exploded view of components of the flow generator; 
         FIG. 7  is an underneath view of a chassis forming part of the flow generator; 
         FIG. 8  is a rear view of the chassis; 
         FIG. 9  is a general view of a fan forming part of the flow generator; 
         FIG. 10  is an underneath view of the fan; 
         FIG. 11  is a cross-sectional view of the fan; 
         FIG. 12  shows the humidifier in partly disassembled state; 
         FIG. 13  is an underneath view of the tank of the humidifier; 
         FIG. 14  is an underneath view of the tank showing an alternative valve; 
         FIG. 15  is a view of the tank cover; 
         FIG. 16  is an underneath view of the tank cover; 
         FIG. 17  is an underneath view of a modified tank cover; and 
         FIG. 18  shows an exemplary modular connector arrangement; 
         FIG. 19  shows an exemplary cover for an exemplary modular connector arrangement; 
         FIG. 19A  shows an exemplary modular connector arrangement with the exemplary cover of  FIG. 19 ; 
         FIG. 20  shows an exemplary modular connector arrangement; and 
         FIG. 21  shows an exemplary modular connector arrangement. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The illustrated apparatus comprises a flow generator  50  and a humidifier  150 , shown in their assembled condition in  FIG. 1 . As shown in  FIG. 2 , the flow generator engages with the separable humidifier at an engagement face  52 , from which protrudes an air connector  53  for the delivery of air from the fan to the humidifier container, and electrical connectors  54  for the delivery of power to the humidifier heater described below. 
     The face  52  also carries a pair of slots  55  which are engaged by corresponding tongues  156  provided on the humidifier engagement face  157  ( FIG. 5 ) by which the flow generator  50  and humidifier  150  are connected together, as will be described in more detail below. 
     Externally, the flow generator  50  is also provided with an LCD screen  58  and associated keys  59  by which the user can set the operating parameters of the unit. 
     The flow generator  50  has an external case of rigid plastics material moulded in two parts, a top case  60  and a bottom case  61 . The lower edge of the top case  60  is stepped and flanged at  62  to mate with the periphery of the bottom case  61 . Overmoulded with the rigid plastics body of the bottom case  61  is a rubber sealing flange  63 , which locates between and seals against the cases  60  and  61  on the one hand, and the outer surface of a chassis  64  described further below. 
     Formed in the bottom case  61  by walls which join the outer wall of the case are the lower portions  65  and  67  of, respectively, a power supply cavity and a resonator cavity. The upper portions  66  and  68  of these cavities are formed in the chassis  64 , described below. 
     The chassis  64  is formed with a peripheral wall  69  flanged around its lower edge to engage with the inner periphery of the overmoulded sealing flange  63 . The chassis  64  includes a downwardly extending fan cavity  70  in which is mounted the fan  90  described below. This cavity  70  is formed by moulded side walls  71  and base  72 , which are formed by moulding thermoplastic around an inserted stainless steel liner  73 . The fan cavity  70  opens to the upper surface of the chassis  64  to enable insertion of the fan  90 , this opening being closed by a lid  74 . Like the cavity  70 , the lid  74  has an imbedded stainless steel plate insert moulded within a thermoplastics material, and at its edges the lid is provided with co-molded elastomer sealing edges. The formation of the cavity  70  by insert moulding from differing materials provides very effective acoustic damping, as does the combination by co-moulding of the hard and soft plastics described already and further described below. In this aspect of the present invention, the use of co-moulding or overmoulding in the combination of materials of different, preferably widely different, stiffness and different, preferably widely different, density has been found to be particularly advantageous in providing acoustic damping. 
     The upper portion  66  of the power supply cavity is formed by a side wall  75  extending downwardly from the roof of the chassis  64 , which sealingly engages the opposed wall of the lower portion  65  of this cavity. Preferably, the lower wall is provided for this purpose with a co-moulded or overmoulded rubber sealing flange similar to the sealing flange  63 . The power supply compartment is thus sealed against the ingress of moisture from the interior of the unit in the case of backflow from the humidifier. Similarly, the air path is sealed from the power supply compartment. The interior is at the same time acoustically sealed from the power supply cavity, which may not be completely sealed from the exterior, due to the necessity of providing mains power input and low voltage power output to the humidifier, via connectors  54  mounted in apertures  78  and  80  respectively in the rear and front walls of the cavity, and if necessary the venting of the compartment to outside air for cooling. 
     Supported on the top of the chassis  64 , in the space formed between the chassis and the top of the top case  60  is a printed circuit board  81  carrying the electronic control components of the unit. At the rear of the board  81  an edge connector  82  and a sliding connector are accessible from a connector aperture  83  in the rear of the case  60 , providing for modular connector arrangements to be described in more detail below. 
     Also provided in the rear wall of the top case is an air inlet  84 , and this communicates with an air inlet passage  85  formed in the roof of the upper portion  66  of the power supply cavity, this passage in turn opening through the inner side wall of that cavity at  87  to the air space surrounding the fan cavity  70  in the interior of the unit. Air drawn into the unit by the fan will thus pass over the roof of the power supply and thereby assist in the dissipation of heat generated by the power supply. 
     A removable air filter body  85 A containing a replaceable filter element attaches to the inlet  84 , as shown in  FIGS. 2 and 6 . 
     From the air space surrounding the fan cavity  70 , inlet air passes to the fan cavity via an inlet tube  88  depending from a horizontal extension of the side wall  71  of the fan cavity. 
     The fan cavity and the space surrounding it and enclosed by the upper and lower cases form a pair of serially connected volume mufflers, and the dimensions of the inlet tube  88  and the air passage  85  are chosen to optimise the noise attenuation produced by these mufflers, within the constraint of avoiding unacceptable air flow restriction. 
     It will now be convenient to describe the features of the fan, which are shown in  FIGS. 9 to 11 . 
     The fan  90  comprises a motor  91 , preferably brushless DC motor, provided with a coaxial impeller  92 , mounted vertically within a fan housing consisting of a cover  93  and a base  94 . An air inlet  95  is provided in the floor of the base  94  on the impeller axis, and cavities in the cover and base form a volute  96  which leads from the impeller to an air outlet  97 . The cover and base  93  and  94  are joined by means of slotted tabs  98  which extend upwardly from the base to snap over stepped ribs  99 , the tabs  98  being further located by fitting between parallel ribs on the cover  93 . The joint between the cover  93  and the base  94  is sealed by an elastomeric sealing ring  101 . 
     The bottom surface of the fan housing base  94  is provided with radial stiffening ribs  102 , and overmoulded to the base  94  is an elastomer damping member  103  which covers that bottom surface between the ribs  102 , and extends around the edge of the base by a flange portion  104  and peripherally spaced tabs  105 . By overmoulding to the rigid plastic base  94  an elastomer of much lower stiffness and much lower density substantial acoustical damping is provided to the fan housing. 
     Moulded integrally with the rigid plastics portion of the fan housing base are feet  106  which extend through the overmoulded elastomer damping member  103  to receive helical mounting springs (not shown) by which the fan is mounted on the base  72  of the fan cavity. 
     The degree of size reduction which is an objective of the present invention requires great care to be taken to minimise the transmission of noise and vibration, particularly from the motor and the impeller of the fan  90 . The mounting springs are therefore chosen to ensure minimal transmission of the vibration frequencies encountered during operation. This is achieved by choosing the springs with reference to the mass of the fan  90 , such that the natural frequency of the system comprising the springs and the fan is at least approximately one tenth of the vibration frequency encountered when the motor is running at its lowest operating speed. 
     The air outlet  97 , upon the introduction of the fan into the fan cavity, is connected by means of a thermoplastic elastomer coupling member with an air outlet passage  109  which extends from the side wall of the fan cavity to a connecting nozzle  110  extending through an aperture  111  provided for this purpose in the front face of the flow generator. 
     The fan  90  therefore floats within its cavity  70  in the chassis  64  with minimum acoustic coupling to the remainder of the flow generator. The characteristics of the mounting springs and the coupling member are chosen to minimize the transmission of characteristic vibration frequencies of the fan. 
     The air outlet passage  109  is formed in the roof of the upper portion  68  of the resonator cavity. Holes  112  communicating with the resonator cavity are provided in the floor of the passage  109  where it crosses this cavity, which acts in the manner of a Helmholtz resonator. By adjusting the dimensions and number of the holes  112 , the frequency response of the resonator can be adjusted for optimum noise cancellation. If desired, a second Helmholtz resonator cavity can be provided opposite the upper portion  68  of the resonator cavity, if the dimensions of the top case  60  allow this. 
     The novel use of Helmholtz resonators for noise attenuation contributes to the success in achieving significant size reduction in the flow generator of the present invention. 
     As shown in  FIG. 12 , the humidifier  150  comprises a base unit  151  designed for simple attachment to and detachment from the flow generator  50 , and a tank  152  which is similarly attachable to and detachable from the base unit. 
     The rear face of the base unit  151  has a peripheral flange  153  which seats in a corresponding peripheral recess  113  surrounding the front face of the flow generator  50  when the two units are brought together by linear movement towards each other. The tongues  156  are moveable vertically and resiliently urged downwardly, so that these tongues engage in the slots  55  and snap home to engage the two units by means of the downwardly extending fingers  158  at the ends of the tongues. 
     An air flow passage  160  passes through the humidifier engagement face  157  and opens to the front wall of the base unit. This passage is surrounded at the rear wall with a cylindrical connecting portion  161  which receives the nozzle  110  of the flow generator upon engagement of the two units. The inner surface of the portion  161  is provided with a sealing device such as a layer of elastomer or other soft resilient material. 
     The rear face of the base unit also carries a connector  162 , in this embodiment a pair of flat male blade connectors, for engagement with a mating connector on the front face of the flow generator, to provide power to the humidifier heater from the power supply in the power supply cavity. Although not shown in the illustrated embodiment, the respective faces may also carry further interconnecting devices, where other electrical or data connections are required to be established between the flow generator and the humidifier or downstream devices including the air conduit or the mask. Such devices may take the form of optically coupled devices, or connectors of other suitable kinds. 
     The use of such an opto-coupling connector enables the implementation of a simple protocol for communications between the flow generator and the humidifier. For example, the current flow levels of the flow generator can be sent to the humidifier controller which then adjusts the operation of the humidifier according to a predetermined algorithm. 
     Within the humidifier base unit  151  but not shown here is provided a variable power supply for a heating element which heats a circular metal pad  163 . A control knob  164  is provided on the upper surface of the unit for adjustment of the heat supplied to the pad  163 . A semicircular wall  165  surrounds the rear part of the pad  163 , and carries at its upper edge an inwardly directed flange  166 . The pad  163  stands proud of the surrounding base surface  168 . 
     It will be observed that the air flow passage  160  opens to the front face of the base unit at the foot of a circular recess  167  of larger diameter, corresponding to the diameter of the tank air inlet  175  described below. The effect of this is to provide a vertical offset between the air flow passage  160  and the inlet  175 , with the former lower than the latter in the normal orientation of the unit. This configuration assists in the prevention of backflow as will be described below. It is to be observed that the axial offset in question could be achieved in other ways. 
     The recess  167  is provided with a sealing layer of elastomer or other sealing material. 
     The tank  152  comprises a cover  170  which is preferably of a transparent plastics material, a metal base  171  preferably of stainless steel, a base flange  172  which functions to couple the cover and the base, and a sealing gasket  173  which locates between the base of the cover and the metal base  171 . 
     The periphery of the base flange  172  is dimensioned to slide into engagement with the wall  165  of the base unit and beneath the flange  166  to engage the tank with the base unit, and the tank cover  170  is provided with a cylindrical air inlet  175  extending from its side wall. The inlet  175  is dimensioned to fit sealingly within the recess  167  when the tank is engaged with the base unit as described above and as shown in  FIG. 3 . An air outlet  176  extends upwardly from the roof of the cover  170  for connection with an air hose for the delivery of humidified air to the patient. 
     The metal base  171  seats within the base flange  172  which is provided with a central aperture, so that the bottom of the metal base  171  is exposed to contact the pad  163  when the tank is engaged with the base unit. The metal base  171  is thus heated by the heating element of the base unit. To assist in achieving good heat transfer between the pad  163  and the base  171 , the former is resiliently biased upwardly, for example by means of a spring or springs (not shown). This has the further advantage of providing for positive retention of the tank in the base unit, by providing around the central aperture in the base flange, a downwardly directed rim (not shown) which will initially depress the heating plate as the tank is moved into position on the base unit, and which forms a central space into which the heating plate moves under its spring pressure, upon full engagement of the tank with the base unit. 
     In alternative embodiments not illustrated here, the tank may be provided with locking detents for retention on the base unit. 
     The lower edge of the cover  170  and the inner edge of the base flange  172  are provided with bayonet type engagement formations  177  and  178  respectively, so the tank components can be assembled and disassembled simply by relative rotation of the cover and the base flange. To assist in this operation, a peripheral groove  179  is provided in the base of the base flange  172 , and this groove is interrupted at intervals by finger-engaging bridges  180 . The inner wall of the groove  179  protects the user&#39;s fingers against accidental contact with the metal base  171 , in case removal of the cover is carried out while the base is still hot. 
     The tank is intended to be filled via the air outlet  176 , and the apparatus may be provided with a filling bottle with a spout dimensioned for a convenient fit with that outlet. Such a bottle may be provided with a spout of the kind incorporating an air bleed passage which will allow the tank to fill to the correct predetermined height. 
     In alternative embodiments, other filling arrangements may be employed. The correct filling height is also indicated by filling level graduations  184  scribed or otherwise marked on the wall of the cover  170 . 
     As will be seen in  FIG. 16 , the air inlet  175  of the cover  170  extends within the cover in the form of an arcuate passage  181 , to open to the interior of the cover at a point beyond, in the direction of air flow, the outlet  176 . The open end  183  of the passage  181  is directed obliquely towards the inner wall of the cover. The outlet  176  is, furthermore, between the convexly curved side of the passage  181 . This configuration has several important consequences. 
     Firstly the curvature of the passage  181  and the oblique orientation of its outlet  183  will induce a swirling action on the air mass within the tank, as the air moves around the tank to escape from the outlet  176 . This swirling action will enhance the uptake of water vapour from the water contained in the tank. 
     Secondly the configuration minimises the risk of water from the tank flowing back into the air inlet passage should the tank be tilted while containing water. Whenever the orientation of the tank is such that the air outlet  176  is below the outlet  183 , water will flow into the air outlet before it will flow into the inlet passage, and whenever the air outlet  176  is above the outlet  183 , then except in the case of inversion of the tank, water will not escape via the arcuate passage  181  unless the tank has been filled with a volume of water which is greater than that which is contained within the sector of the tank below a tangent to the convex surface of the passage  181 . This can be avoided by appropriate setting of the heights of the filling level graduations  184 . 
     Should water escape into the passage  181  due to inversion of the humidifier while it is engaged with the flow generator, its path to the air flow passage  160  will be blocked by the dam formed by the face of the recess  167 , which will then be below the air flow passage  160 . 
       FIG. 17  shows a modified form of tank cover in which a downwardly extending wall  187  is provided across the end of the arcuate passage  181 , this wall extending in a curved wall  188  beyond the outlet  183 . The curved wall  188  assists in the formation of a swirling air flow within the tank, while both walls  187  and  188  tend to protect the outlet  183  against wave action within the tank during transport. 
     If desired, further security against backflow can be provided by locating a non-return valve at an appropriate point. An example of this is shown in  FIG. 14 , where a valve comprising a flexible membrane  185  supported on a spider  186  is placed in the mouth of the tank air inlet  175 . 
     In the illustrated embodiment the arcuate passage  181  is shown as a low profile passage of substantially rectangular cross-section. An alternative approach is to continue this passage as a cylindrical passage having a diameter similar to that of the air passage leading from the flow generator to the humidifier. The advantage of this will be to avoid the introduction of impedance to the flow of air through the humidifier. Generally speaking it is desirable to minimise pressure drop through the humidifier, to avoid interfering with diagnostic or monitoring functions in the flow generator, for example the detection of snoring, which require the detection of sound transmitted back through the system from the patient. 
     The enhanced uptake of water vapour achieved by inducing the swirling of air as it passes through the tank enables, in an alternative embodiment of the invention, the elimination of the heating of the water in the tank  152 . In such an embodiment the heating element and its controls, and the heat transfer components including the pad  163  and the metal tank base  171  are eliminated, and the humidifier becomes a simpler, passive, device. 
       FIGS. 18 to 21  show various forms of modular data connections foreshadowed earlier, utilizing the connector aperture  83  in the rear of the flow generator housing. 
     The connector aperture  83  is provided in the wall of a rectangular recess  115 . An arcuate depression  123  is provided in the upper surface of the unit above the recess  115  to facilitate removal of closure elements from the depression, as described below. 
     Where the flow generator in question is not intended to be employed with any data connection, the connector aperture  83  is closed off by a blank closure element  117 , shaped to fit into the recess  115 . This element snaps into the recess by means of lower tabs  118  and an upper tab  119  which fit corresponding depressions such as  122  in the walls of the recess  115 , to close the connector aperture  83  and conform to the contours of the surrounding surface of the unit. 
     Complementarily shaped closure elements can be provided for the reception of different kinds of data devices. Shown in  FIG. 20  is an element  116   a  provided with a slot for the reception of a smart card  120 . The element  116   a  or the printed circuit board itself may carry the necessary smart card socket. Shown in  FIG. 21  is an element  116   b  provided with a DB type data socket. In this case the element  116   b  is contoured to provide a lower front recess  121  to facilitate gripping of the associated plug. 
     Other forms of element  116  can be provided to enable the connection of devices such as memory cards and pre-programmed devices as required. This facility furthermore enables a wide range of devices to be integrated with the apparatus in modular fashion, for example a clock display which may utilise the system clock contained in the flow generator controller, a voice activation unit, oximetry, ECG and other diagnostic aids, a sound recorder, a light. 
     It is emphasised that the forgoing disclosure has sought to describe many innovations in flow generator and humidifier design, and it is foreshadowed that these will be the subject of separate claims to protection in applications claiming the priority of this document. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.