Abstract:
The mounting arrangement ( 10 ) for a fluid displacement device ( 12 ) comprises an inflatable cushion device ( 16 ) adapted to support the fluid displacement device ( 12 ) and in fluid communication with the fluid displacement device ( 12 ). A portion of the fluid displaced by the fluid displacement device ( 12 ) inflates and/or maintains inflated the cushion device ( 16 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a mounting arrangement and in particular a mounting arrangement for a fluid displacement device.  
           [0002]    The invention has been developed primarily for mounting an electric motor and blower assembly within the housing of a Continuous Positive Airway Pressure (CPAP) treatment apparatus used in the CPAP treatment of, for example, Obstructive Sleep Apnea (OSA) and other ventilatory assistance treatments such as Non Invasive Positive Pressure Ventilation (NIPPV) and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use and is equally suited in mounting various types of fluid displacement devices including fans, pumps and the like.  
         BACKGROUND OF THE INVENTION  
         [0003]    CPAP treatment is a common ameliorative treatment for breathing disorders including OSA. CPAP treatment, as described in U.S. Pat. No. 4,944,310, provides pressurised air or other breathable gas to the entrance of a patient&#39;s airways at a pressure elevated above atmospheric pressure, typically in the range 4-20 cm H 2 O.  
           [0004]    It is also known for the level of treatment pressure to vary during a period of treatment in accordance with patient need, that form of CPAP being known as automatically adjusting nasal CPAP treatment, as described in U.S. Pat. No. 5,245,995.  
           [0005]    NIPPV is another form of treatment for breathing disorders which can involve a relatively higher pressure of gas being provided in the patient mask during the inspiratory phase of respiration and a relatively lower pressure or atmospheric pressure being provided in the patient mask during the expiratory phase of respiration.  
           [0006]    In other NIPPV modes the pressure can be made to vary in a complex manner throughout the respiratory cycle. For example, the pressure at the mask during inspiration or expiration can be varied through the period of treatment.  
           [0007]    Typically, the ventilatory assistance for CPAP or NIPPV treatment is delivered to the patient by way of a nasal mask. Alternatively, a mouth mask or full face mask or nasal prongs can be used. In this specification any reference to a mask is to be understood as incorporating a reference to a nasal mask, mouth mask, full face mask or nasal prongs.  
           [0008]    In this specification any reference to CPAP treatment is to be understood as embracing all of the above described forms of ventilatory treatment or assistance.  
           [0009]    A CPAP apparatus broadly comprises a flow generator constituted by a continuous source of air or other breathable gas such as a hospital piped supply or a blower. The gas supply is connected to a conduit or tube, which in turn is connected to a patient mask which incorporates, or has in close proximity, an exhaust to atmosphere for venting exhaled gases. The blower is typically driven by an electric motor controlled by a servo-controller which is in turn under the control of a microcontroller unit.  
           [0010]    The blower/motor assembly has hitherto been either directly mounted to the chassis or body of the CPAP apparatus, or isolated therefrom, by foam or other elastomeric sheets or molded components to dampen vibration and minimise radiated noise. The use of foam sheets is time consuming and expensive as several sections of sheet may have to be installed. The installation of molded foam components is less time consuming but they are more expensive to produce.  
           [0011]    Other rotating or reciprocating machines use inflatable cushions to dampen the machine&#39;s vibration by interposing one or more of the inflatable cushions between the machine and its chassis, housing, ground or other supporting structure. There are two main types of inflatable cushions.  
           [0012]    A first type is inflated or filled and thereafter sealed. A disadvantage of this type is they leak and collapse if punctured or otherwise damaged. As a consequence, they are not suitable for use in CPAP apparatus which are sealed during manufacture and not serviceable by customers.  
           [0013]    A second type rely on a dedicated constant or intermittent fluid supply to maintain inflation. A disadvantage of this type is the additional complexity and costs associated with the dedicated fluid supply. This second type is also particularly unsuitable for CPAP treatment apparatus which are desirably made as small and lightweight as possible.  
           [0014]    It is an object of the present invention to substantially overcome or at least ameliorate one or more of the deficiencies of the prior art.  
         SUMMARY OF THE INVENTION  
         [0015]    Accordingly, in a first aspect, the present invention provides a mounting arrangement for a fluid displacement device, the mounting arrangement comprising an inflatable cushion device adapted to support the fluid displacement device and in fluid communication with the fluid displacement device, whereby a portion of the fluid displaced by the fluid displacement device inflates and/or maintains inflated the cushion device.  
           [0016]    Preferably, the cushion device is in fluid communication with an outlet or interior of the fluid displacement device. The fluid displacement device is preferably a blower, turbine or fan driven by an electric motor.  
           [0017]    In an embodiment, the mounting arrangement includes a one way valve interposed between the cushion device and the fluid displacement device, the valve being arranged to only allow fluid transmittal from the fluid displacement device to the cushion device.  
           [0018]    In another embodiment, the mounting arrangement includes a pressure regulation valve interposed between the cushion device and the fluid displacement device, or between the cushion device and a zone of lower pressure tan the cushion device (such as atmosphere), the valve being arranged to limit pressurisation of the cushion device to a predetermined maximum.  
           [0019]    In a further embodiment, the mounting arrangement includes the one-way valve and the pressure regulating valve.  
           [0020]    The arrangement preferably also includes other mounting devices produced from foam or other elastomers. These mounting devices can, for example, act as displacement limiting devices when the cushion is not inflated or provide a resilient base for the cushion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a perspective view of a first embodiment of a mounting arrangement according to the invention;  
         [0022]    [0022]FIG. 2 is a sectional cut away view of the arrangement shown in FIG. 1;  
         [0023]    [0023]FIG. 3 is a perspective view of a second embodiment of a mounting arrangement according to the invention; and  
         [0024]    [0024]FIGS. 4 through 15 are schematic side views of third through fourteenth embodiments of mounting arrangements according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    [0025]FIGS. 1 and 2 show a first embodiment of a mounting arrangement  10  according to the present invention. The mounting arrangement  10  includes a fluid displacement device in the form of blower  12 . The blower  12  has a rotor  13  rotationally driven by electric motor  14  and an outlet  15 .  
         [0026]    The underside of the blower  12  is mounted to an inflatable cushion device in the form of open-ended annular membrane  16 . The membrane  16  has an internal generally cylindrical orifice  18 , a generally planar annular base surface  20  and a curved side wall  22  having a pair of spaced apart internal locating rims  26  adjacent its distal edge.  
         [0027]    The blower  12  is formed from two joined casing portions  28  and  30 . The casing portion  30  contains the rotor  13  and has a central cylindrical inlet flange  34  for receiving air drawn through the orifice  18 . The inlet flange  34  is a light snug fit with adjacent upper wall  35  of the orifice  18 .  
         [0028]    The casing portion  30  also includes an annular flange  36  and an opening  38 . The internal diameter of the membrane sidewall  22  is slightly smaller than the external diameter of the flange  36 . The membrane  16  is assembled with the flange  36  by stretching it over the flange  36  and locating the flange  36  between the two locating rims  26 . The resilience of the membrane  16  contracts it into sealing engagement with the periphery of the flange  36 .  
         [0029]    Energising the electric motor  14  causes the rotor  13  to spin. This pressurises the interior of the two housing portions  28  and  30  causing pressurised air (or other breathable gas) to be displaced from the outlet  15  (see FIG. 1). The pressurised air is also displaced through the orifice  38  into interior space  40  defined between the underside of the flange  36  and the interior of the membrane  16 .  
         [0030]    The mounting arrangement  10  is installed within a CPAP apparatus housing (not shown) with the underside of the base surface  20  supported on the chassis or some other rigid component of the housing. When the motor  14  is energised the membrane  16  is inflated which raises and supports the blower  12  and the motor  14  away from the housing chassis or the like to isolate vibration produced by the blower  12  and motor  14  from the housing.  
         [0031]    A calculation of the lifting or supporting force generated by the membrane  16  is set out below.  
         [0032]    1 cm H 2 O=98.1 N/m^ 2  
         [0033]    1N=101.9 g  
         [0034]    Surface area of membrane  16  with 0.15 m outside diameter and 0.03 m inside diameter=0.0169 m^ 2.  
         [0035]    Combined weight of motor  14  and blower  12 =330 g  
         [0036]    Force generated by membrane  16 ; 1 cm H 2 O will lift 98.1×0.0169=1.664N or 169.584 g  
         [0037]    Therefore 330/168.938=1.945 cm H 2 O will be required to lift the motor/turbine assembly.  
         [0038]    This pressure is easily achievable by the blower/motor assembly which typically operates in the range of 2-20 cm H 2 O when used for treating OSA.  
         [0039]    The main advantage of the arrangement  10  is that the membrane  16  is inflated by the blower  12 . This overcomes the leakage problems of prior art devices and also obviates the need for a separate dedicated pressurised fluid source.  
         [0040]    Another advantage is improved vibration isolation compared with other means as the only direct path for vibration is through the thin, flexible cushion (membrane) walls. The air within the cushion can also absorb vibration as the air particles are excited and dissipate the energy. As a result of the above, the inflatable cushion can be made smaller than, yet still have the same vibration isolating properties as, foam or other elastomers. This is beneficial is minimising the overall size of the CPAP apparatus.  
         [0041]    [0041]FIG. 3 shows a second embodiment of a mounting arrangement  50  according to the invention. Like reference to those used in describing the first embodiment will be used to indicate like features. The arrangement  50  is similar to the arrangement  10  except for the addition of six inflatable membranes  52  arranged around the side periphery of the blower  12  and motor  14  which further assist in mounting and locating the blower/motor assembly within the housing of the CPAP apparatus.  
         [0042]    FIGS.  4  to  15  show schematic representations of the third to fourteenth embodiments of the invention. In all of FIGS.  4  to  11  the inflatable cushion device is denoted  60 , the blower/motor assembly  62 , the blower inlet  64  and the blower outlet  66 .  
         [0043]    The embodiment of FIG. 4 is similar to that shown in FIG. 1 except that it has a conduit  68  connecting the outlet  66  of the blower/motor assembly  62  to the cushion  60  rather than the opening  38 . In this embodiment the inlet  64  passes through an interior opening  69  in the cushion  60  similar to the embodiment of FIG. 1.  
         [0044]    [0044]FIG. 5 is similar to the embodiment of FIG. 4 except the inlet  64  is positioned remote from the cushion  60  which thus requires no internal opening.  
         [0045]    [0045]FIG. 6 shows a similar embodiment to FIG. 5 except the blower/motor assembly  62  is arranged on its side relative to the cushion  60 .  
         [0046]    The embodiment of FIG. 7 is similar to shown in FIG. 4 but with the addition of a one-way or non-return valve  70  disposed between the outlet  66  and the cushion  60 .  
         [0047]    [0047]FIG. 8 is similar to the embodiment shown in FIG. 7 except the non return valve  70  is replaced by a pressure regulating valve  72 .  
         [0048]    [0048]FIG. 9 is similar to the embodiment shown in FIG. 8 with the addition of a bleed conduit  74  which can vent excessive pressure to atmosphere through a pressure regulating valve  76 .  
         [0049]    The embodiment of FIG. 10 is similar to that shown in FIG. 9 except the conduit  68  between the inlet  66  and cushion  60  does not contain a pressure regulation valve.  
         [0050]    The embodiment of FIG. 11 is similar to that shown in FIG. 10 except the bleed conduit  74  and pressure regulation valve  76  vent excessive gas back to the inlet  64  of the blower/motor assembly  62 .  
         [0051]    The embodiments of FIGS.  7  to  11  have been described and are shown with the cushion device  60 , inlet  64  and blower/motor assembly  62  arranged in a similar manner to that shown in FIG. 4. However, these embodiments are equally applicable to the component arrangements shown in FIGS. 5 and 6 also.  
         [0052]    The embodiments of FIG. 12 is similar to that shown in FIG. 4 except it includes multiple (two) cushions  60  fed by multiple (two) conduits  68  arranged in parallel.  
         [0053]    The embodiment of FIG. 13 is similar to that shown in FIG. 12 except that the multiple (two) cushions  60  are fed by multiple (two) conduits  68  arranged in series.  
         [0054]    The embodiment of FIG. 14 is similar to that shown in FIG. 4 except additional components  78  are interposed between the cushion  60  and the blower/motor assembly  62 .  
         [0055]    The embodiment of FIG. 15 is similar to that shown in FIGS.  14  except that an external cushion  60   a  supports a casing  80  around the blower/motor assembly  62 . Further, inside the casing  80 , there is provided a series of cushions  60   b  which support the additional components  78  and a cushion  60   c  interposed between the additional components  78  and the blower/motor assembly  62 .  
         [0056]    The embodiment shown in FIGS.  12  to  15  can also include the non-return valves or pressure regulation valves shown in FIGS.  7  to  11 .  
         [0057]    Although the invention has been described with reference to a preferred embodiment, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.