Abstract:
A device is provided for detecting a gas volume flow, especially for a respirator. The device includes a flow sensor, which surrounds a lumen for guiding the gas volume flow, and the flow sensor has an ultrasound transmitter with a sound generator ( 20 ) and an ultrasound receiver. The device has a connection sensor ( 17, 19 ), which is designed to detect a connection, especially an installation position or correctness of the connection or both, of the ultrasound transmitter to the transmitter mount and/or a connection of the ultrasound receiver to the receiver mount and to change at least one of its electrical properties as a function of the connection, or to generate a connection signal, which represents the connection, and to output this signal on the output side.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2007 001 262.6 filed Jan. 8, 2007, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a device for detecting a gas volume flow, especially a respirator. The device comprises a flow sensor, which surrounds a lumen for guiding the gas volume flow, and the flow sensor has an ultrasound transmitter and an ultrasound receiver. The ultrasound transmitter and the ultrasound receiver are arranged at spaced locations from one another such that the ultrasound receiver can receive ultrasound waves transmitted by the ultrasound transmitter and the ultrasound waves pass through the lumen at least in some sections. 
       BACKGROUND OF THE INVENTION 
       [0003]    To avoid cross infections, the flow sensor is designed as a sensor that can be disinfected and/or replaced in devices known from the state of the art for detecting a gas volume flow by means of a flow sensor, especially in medical devices with a flow sensor. In an inexpensive device for detecting a gas volume flow, the ultrasound transmitter and the ultrasound receiver must therefore be separated from the flow sensor for the replacement of the flow sensor. 
         [0004]    An ultrasound spirometer, which has a replaceable flow sensor, is known from DE 42 22 286 C1; the flow sensor has a measuring tube, into which a sterile, easy-to-replace tube can be inserted in an accurately fitting manner. The sterile tube is inserted in an accurately fitting manner and has at a transition to an ultrasound measuring window, which is permeable to sound waves but extensively impermeable to microorganisms and other contaminants. The measuring windows may be formed by a foam, by an elastomer, or by a very thin plate, especially a Mylar film. 
         [0005]    A device for measuring the flow velocity of a gas in a medical application by means of ultrasound run time measurement with a measuring tube and two ultrasound converters that can be inserted into the measuring tube is known from DE 101 56 854 A1. The ultrasound converters are separated from an interior space of the measuring tube by means of membranes. The membranes are of a gas-tight design according to the present invention and inserted into the measuring tube such that the latter forms a gas-tight tube connection. The ultrasound converters separably connected to the measuring tube have a flush contact with the membranes. 
         [0006]    Devices known from the state of the art with a flow sensor for detecting a gas volume flow have ultrasound converters, which can detect a flow velocity of the gas flow, especially by means of doppler interferometry. The device may comprise for this an analysis unit, which is connected to the ultrasound transmitter and the ultrasound receiver and is designed to detect a sound wavelength and/or sound run time of an ultrasound transmitted by the ultrasound transmitter and received by the ultrasound receiver. 
       SUMMARY OF THE INVENTION 
       [0007]    It was recognized according to the present invention that the accuracy of a measurement result depends on the connection and the arrangement of the ultrasound converters in relation to one another. Furthermore, it was recognized that wear of a mount for an ultrasound converter separably connected to a measuring section of the gas line causes errors in measurement in case of wear of the mount. 
         [0008]    The basic object of the present invention is to provide an improved device for detecting a gas volume flow. 
         [0009]    This object is accomplished by a device of the type according to the present invention, in which the flow sensor has a transmitter mount for the ultrasound transmitter and a receiver mount for the ultrasound receiver, and the transmitter mount is designed to be separably connected to the ultrasound transmitter, and the receiver mount is designed to be separably connected to the ultrasound receiver. The device has a connection sensor, which is designed to detect a connection, especially an installation position or correctness of the connection or both, of the ultrasound transmitter to the transmitter mount, especially in a contactless manner, and/or to detect a connection of the ultrasound receiver to the receiver mount, and to change at least one of its electric properties as a function of the connection, or to generate a connection signal, which represents the connection, and to output this on the output side. Correct assembly of an ultrasound transmitter and/or of an ultrasound receiver with the transmitter mount or with the receiver mount of the flow sensor can advantageously be performed by means of the connection sensor in a device of the above-described type. The connection sensor may thus advantageously be a positioning sensor for the ultrasound transmitter. For example, the device may have a connecting device, which is connected to the ultrasound transmitter and to the connection sensor and can activate the ultrasound sensor and/or a gas pump for generating the gas volume flow as a function of the connection signal. 
         [0010]    An ultrasound transmitter, which has a radiation characteristic with non-uniform distribution in space, may also be advantageously used due to the connection sensor. For example, an ultrasound transmitter can have a radiation distribution, especially a sound intensity distribution of a radiated sound as a function of a dihedral angle, which distribution represents a gap function and therefore has a lobe-shaped radiation characteristic in at least one transverse direction to the direction of sound propagation. 
         [0011]    Exemplary embodiments for an electric property of a connection sensor are an ohmic resistance, a capacity or an inductivity or a combination of these. 
         [0012]    In a preferred embodiment, the connection sensor is a magnetic sensor, which is connected to the ultrasound transmitter and can detect a magnetic field in the area of the transmitter mount. The connection sensor may be formed in this embodiment by a Hall sensor or a reed contact. The flow sensor may have for this, in the area of the transmitter mount, a permanent magnet, which is designed to generate a permanent magnetic field. The permanent field is, for example, a ferromagnet. The position of assembly of an ultrasound transmitter with a mount for the ultrasound transmitter can advantageously be selected correctly due to a connection sensor. It is thus advantageously possible to use an ultrasound transmitter with a radially symmetrical housing. 
         [0013]    In a preferred embodiment, the ultrasound receiver is an ultrasound converter, which can be additionally operated as an ultrasound transmitter, and/or the ultrasound transmitter is an ultrasound converter, which can additionally be operated as an ultrasound receiver. Reciprocal detection of a sound wavelength or a sound run time can be advantageously carried out as a result. Furthermore, erroneous assembly of a detection or measuring device can be advantageously detected by the reciprocal detection. 
         [0014]    In an advantageous embodiment, the transmitter mount and/or the receiver mount has a conically shaped contact surface. Sufficient sealing of a contact surface of the ultrasound transmitter with a contact surface of the transmitter mount or of the ultrasound receiver with the receiver mount can advantageously be ensured by the conically shaped contact surface. Correct alignment of the ultrasound transmitter and/or the ultrasound receiver can also be advantageously ensured by means of a conically shaped contact surface. 
         [0015]    An ultrasound sensor can preferably generate and transmit ultrasound waves at a frequency in the range of 350 kHz to 500 kHz and preferably between 400 kHz and 450 kHz. 
         [0016]    In a preferred embodiment, the connection sensor is designed as an ultrasound transmitter and receiver pair detect a sound wavelength. As a result, a cross section of a gas line used can be advantageously detected. For example, the gas line, especially the flow sensor, may be formed by a measuring cell. The measuring cell may advantageously be designed as a sterilizable cell and more advantageously as a sterile disposable article. Due to the detection of the sound wavelength, a measuring cell intended for adults can be advantageously distinguished from a measuring cell intended for respirating newborns. The device may advantageously have for this purpose a measuring cell discriminator, which is designed to generate an output signal, which corresponds to a type of measuring cell used, as a function of a detected sound wavelength. 
         [0017]    The present invention also pertains to a respirator with a device of the above-described type. The respirator may advantageously have a respirator for generating an inspiratory gas flow and an expiratory gas flow. The respirator may advantageously have a compressor, especially a radial compressor, for generating the expiratory and/or inspiratory gas flow. The respirator may advantageously have two or three flow sensors. For example, the respirator may have a flow sensor for detecting an expiratory gas flow, a flow sensor for detecting an inspiratory gas flow and preferably another flow sensor for detecting a gas flow in a lumen used jointly for the expiration and inspiration. 
         [0018]    The present invention also pertains to a flow sensor, especially for a respirator. The flow sensor has a transmitter mount for an ultrasound transmitter and a receiver mount for an ultrasound receiver, the transmitter mount being designed to be separably connected to the ultrasound transmitter, and the receiver mount being designed to be separably connected to the ultrasound receiver. The transmitter mount and/or the receiver mount preferably has a conically shaped contact surface. Exact assembly of an ultrasound converter with a mount for the ultrasound converter can be performed due to the conically shaped contact surface. The probability of tilted assembly is advantageously also reduced by the conically shaped contact surface. A sensor element for a connection sensor, which element can be detected magnetically, is preferably arranged in the area of the transmitter mount and/or the receiver mount. 
         [0019]    The present invention will be described below on the basis of figures and additional exemplary embodiments. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    In the drawings: 
           [0021]      FIG. 1  is a schematic view showing an end section of an ultrasound transmitter; 
           [0022]      FIG. 2  is a schematic directional diagram view of a sound intensity distribution of an ultrasound transmitter shown in  FIG. 1 ; 
           [0023]      FIG. 3  is a schematic directional diagram view of a sound intensity distribution of the ultrasound transmitter shown in  FIG. 1 ; 
           [0024]      FIG. 4  is a schematic view showing an exemplary embodiment of a lumen of a gas line for guiding a gas volume flow in the area of a flow sensor; 
           [0025]      FIG. 5  is a schematic view showing a surface capable of oscillating, which is shown in  FIG. 4 , in a rotated arrangement; 
           [0026]      FIG. 6  is a schematic view showing the lumen shown in  FIG. 4  and in  FIG. 5  together with an ultrasound transmitter; 
           [0027]      FIG. 7  is a schematic view showing the ultrasound transmitter shown in  FIG. 6  with an acoustic sound generator and a reed contact; 
           [0028]      FIG. 8  is a schematic longitudinal sectional view showing an exemplary embodiment of an ultrasound transmitter; 
           [0029]      FIG. 9  is a schematic view showing a top view of a broader end of the ultrasound transmitter shown in  FIG. 8 ; and 
           [0030]      FIG. 10  is a schematic view showing an exemplary embodiment of a flow sensor. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Referring to the drawings in particular  FIG. 1  schematically shows an exemplary embodiment of an end section of an ultrasound transmitter  5 . The ultrasound transmitter  5  has a cylindrically shaped housing. The ultrasound transmitter  5  has a surface  3 , which is capable of oscillating and which forms in this exemplary embodiment one end of the cylindrical end section of the ultrasound transmitter  5 . The oscillating surface  3  (capable of vibrating) has a round surface limitation, a circular surface limitation in this exemplary embodiment. A broken section line to a section A, A′ is shown, which extends in a plane formed by the surface  3  capable of oscillating. Also shown is a broken section line to a section B, B′, which extends at right angles to the broken section line of section A, A′ and in the plane formed by the surface  3  capable of oscillating. A directional diagram of an intensity distribution of the airborne sound generated by the ultrasound transmitter  5  is shown in  FIGS. 2 and 3 . 
         [0032]      FIG. 2  shows a directional diagram of a sound intensity distribution of an airborne sound radiated by the ultrasound transmitter  5  shown in  FIG. 1  in a section plane that extends at right angles to the surface  3  capable of oscillating and in which the section line of the section B, B′ in  FIG. 1  extends. The intensity distribution  7  shown in  FIG. 2  represents a sound intensity generated by the surface  3  capable of oscillating as a function of a dihedral angle. Clearly recognizable is a narrow lobe shape of the intensity distribution  7 , which represents a gap function with one main lobe and two secondary lobes. 
         [0033]      FIG. 3  schematically shows a directional diagram of a sound intensity distribution  9  of the airborne sound generated by the surface  3  capable of oscillating in  FIG. 1  in a section plane that extends at right angles to the surface  3  capable of oscillating and in which the section line of section A, A′ is located. Clearly recognizable is an omnidirectional characteristic of the sound intensity distribution  9 , which represents a sound intensity generated by the surface capable of oscillating as a function of a dihedral angle. 
         [0034]      FIG. 4  schematically shows an exemplary embodiment of a lumen  15 , especially of a gas line or of a flow sensor, for guiding a gas volume flow in the area of a flow sensor. Shown is the surface  3  capable of oscillating of the ultrasound transmitter  5  shown in  FIG. 1 . Also shown is a receiving surface  13 , in which the airborne sound transmitted by the surface  3  capable of oscillating can be received. For example, an ultrasound receiver may be arranged in the receiving surface  13 . Also shown is a section  11  through the intensity distribution of the airborne sound radiated by the surface  3  capable of oscillating, which distribution has an elliptically shaped circumference. The surface  3  capable of oscillating is directed in circumferential rotation about the longitudinal axis of the ultrasound transmitter  5 , which axis extends at right angles to the surface  3  capable of oscillating, such that the elliptically shaped section surface of section  11  is imaged, beginning from the surface  3  capable of oscillating, onto the receiving surface  13 . The airborne sound transmitted by the surface  3  capable of oscillating can thus be received within the receiving surface  13 . A direction arrow  4  of the surface  3  capable of oscillating is shown as well. 
         [0035]      FIG. 5  schematically shows the lumen  15  shown in  FIG. 4  and the surface  3  capable of oscillating, which is shown in  FIG. 4 , and which is rotated by 90° about the longitudinal axis of the ultrasound transmitter  5  shown in  FIG. 1  compared to the surface  3  capable of oscillating, which is shown in  FIG. 4 . The intensity distribution shown in  FIGS. 3 and 4  is likewise rotated now by 90°, which is shown by the rotated sectional arrangement  11 ′ of the section  11  shown in  FIG. 4 . The airborne sound transmitted by the surface  3  capable of oscillating is no longer radiated completely onto the receiving surface  13 , and undesired reflections may therefore develop in this exemplary embodiment on the bordering surfaces of a gas guiding housing surrounding the lumen  15 . These undesired reflections may distort the result of the detection and/or measurement of a gas volume flow flowing through the lumen  15  by means of ultrasound or make detection impossible. The lumen  15  shown in  FIG. 4  and  FIG. 5  is designed with a rectangular, especially square cross section in this exemplary embodiment to illustrate the geometric conditions. Unlike as shown in  FIGS. 4 and 5 , a round cross section of a lumen for guiding a gas volume flow is conceivable and advantageous as well. 
         [0036]      FIG. 6  schematically shows the lumen  15  shown in  FIG. 4  and in  FIG. 5  and the receiving surface  13 . A cylindrically shaped ultrasound transmitter  16  is shown. The ultrasound transmitter  16  has an acoustic sound generator  20 . The ultrasound transmitter  16  also has a reed contact  19 . Also shown is a magnet  17 , especially a ferromagnet, which is connected, for example, to a housing guiding the lumen  15 , and which is designed to generate a magnetic field such that a reed contact  19  arranged in the range of action of the magnet  17  can be closed in an electrically effective manner. 
         [0037]    The reed contact  19  is arranged in the area of an outer circumference of the cylindrically shaped ultrasound transmitter  16 . The reed contact  19  is thus located at a spaced location radially outwardly from a longitudinal axis extending centrally through the ultrasound transmitter  16 . When the ultrasound transmitter  16  is moved by rotation about the longitudinal axis and by positioning along the longitudinal axis, the reed contact  19  can close in an electrically effective manner when the reed contact  19  is brought—by corresponding motion of the ultrasound transmitter  16 —into the range of action of the magnet  17 . Exact positioning of the ultrasound transmitter  16  can thus be ensured, especially when activation of the acoustic sound generator  20  takes place as a function of the electrically effective closing of the reed contact  19 . 
         [0038]      FIG. 7  schematically shows the ultrasound transmitter  16  shown in  FIG. 6  with the acoustic sound generator  20  and with the reed contact  19 , which is arranged in the range of action of the magnet  17 . The acoustic sound generator  20  is connected electrically in series with the reed contact  19 . The acoustic sound generator can thus be activated as a function of the closing of the reed contact  19 . 
         [0039]      FIG. 8  schematically shows a longitudinal sectional view of an exemplary embodiment of an ultrasound transmitter  34 . The ultrasound transmitter  34  has a conical design, such that an external diameter of a housing of the ultrasound transmitter  34  decreases linearly along a longitudinal axis  40 . The ultrasound transmitter  34  has a round cross section and thus forms a section of a circular cone. An acoustic sound generator  30  is arranged in the area of a narrower end of the ultrasound transmitter  34 . The acoustic sound generator  30  is connected in series with a reed contact  32 , the reed contact  32  being located at a spaced location radially outwardly from the centrally extending longitudinal axis  40  and being arranged in the area of the circumference of the ultrasound transmitter  34 . Also shown is a magnet  28 , which is arranged outside the ultrasound transmitter  34  and is designed to electrically close the reed contact  32  when the reed contact  32  is located in the range of action of the magnet  28 . The ultrasound transmitter  34  can thus be activated as a function of the electrically effective closing of the reed contact  32 , especially as a function of the magnetic field acting on the reed contact. The activated ultrasound transmitter  34  can generate and transmit an airborne sound in the ultrasound frequency range. 
         [0040]    The ultrasound transmitter  34  has a groove  36  in the area of a broader end. The groove  36  is intended for introduction into a corresponding recess of a housing for guiding a gas volume flow. The recess may be designed for this such that a rotary motion  42  of the ultrasound transmitter  34  about the longitudinal axis  40  can take place in a predetermined angle range, for example,  30 , so that the ultrasound transmitter  34  can already be pre-positioned by a mechanical coding formed by means of the groove  36 . The pre-positioning may be performed, for example, when introducing the ultrasound transmitter  34  into a corresponding mount of a flow sensor for detecting a gas volume flow along the longitudinal axis  40 . Exact alignment of the ultrasound transmitter  34  in the circumferential direction can take place by a further rotary motion  42  of the ultrasound transmitter  34  about the longitudinal axis  40 . 
         [0041]      FIG. 9  schematically shows a top view of the broader end of the ultrasound transmitter  34 . The groove  36 , the longitudinal axis  40  and the rotary motion  42  are shown. A closed groove  38  extending about the longitudinal axis  40  is also shown by broken line. Such a circumferential groove  38  may be used as a coding for making a distinction between the ultrasound transmitter and the ultrasound receiver. The circumferential groove  38  is also shown in  FIG. 8 . For example, an ultrasound receiver may have the closed groove  38 , and the ultrasound transmitter may have the groove  36 . 
         [0042]      FIG. 10  schematically shows an exemplary embodiment of a flow sensor  60  in a longitudinal sectional view. The flow sensor  60  has a housing  64 , which surrounds a lumen  65  of a respirator and is designed to guide a gas volume flow (breathing gas) in the lumen  65 . The housing  64  may form, for example, a measuring cell designed as a disposable article. The housing  64  of the flow sensor  60  has at least one transmitter mount  76  for an ultrasound transmitter and a receiver mount  74  for an ultrasound receiver. The housing  64  also has magnets  68  and  68 ′, which are arranged in the area of the mount  76  for an ultrasound transmitter. The housing  64  also has a transmitter mount  78  for another ultrasound transmitter and a receiver mount  80  for receiving another ultrasound receiver. A conical contact surface  73  of the transmitter mount  78  and a conical mounting surface  70  of the receiver mount  78  are also shown as examples. For example, the conical mounting surface  70  may be designed such that the ultrasound transmitter  34  shown in  FIG. 8  can be introduced into the transmitter mount  78  along the longitudinal axis  40  and along a longitudinal axis  72  extending through the transmitter mount  78 . 
         [0043]    The lumen  65  extends along a longitudinal axis  62 . A gas volume flow guided in the lumen  65  can thus be moved along the longitudinal axis  62 . The transmitter mount  78  and the receiver mount  80  are arranged opposite each other along the longitudinal axis  72  such that the transmitter mount  78  and the receiver mount  80  enclose between them the lumen  65  at least in some sections. An ultrasound transmitter arranged in the transmitter mount  78  can thus transmit ultrasound waves through the lumen  65 , and these ultrasound waves can be received by a receiver arranged in the receiver mount  80 . A magnet  66  or  66 ′ is arranged in the area of the receiver mount  80 . As a result, an ultrasound converter, which can act both as an ultrasound transmitter and as an ultrasound receiver, can be arranged in the receiver mount  80 . A longitudinal axis  71  extends through the receiver mount  74  along the longitudinal axis thereof and through the transmitter mount  76  along the longitudinal axis thereof. The longitudinal axis  71  and the longitudinal axis  72  are arranged at a predetermined angle in relation to one another. The longitudinal axis  71  and the longitudinal axis  72  are preferably arranged at right angles to one another. The longitudinal axis  71  forms a predetermined angle with the longitudinal axis of  62  of the lumen  65 . The longitudinal axis  72  forms a predetermined angle with the longitudinal axis  62  of the lumen  65 . The predetermined angle is, for example, smaller than or equals 90°. As a result, ultrasound waves which are transmitted in the area of the transmitter mount  76  pass through the lumen  65  with a component in the transverse direction and reach the receiver mount  74  and an ultrasound receiver arranged there after passing through some sections of the lumen  65 . Due to the crossover arrangement of the longitudinal axes  71  and  72 , ultrasound waves transmitted along these can pass through the lumen  65  in mutually different directions. 
         [0044]    The magnets  66 ,  66 ′,  68 ,  68 ′ are used, in conjunction with the reed contacts  19 , not shown in  FIG. 10 , for positioning ultrasound transmitters and ultrasound receivers, likewise not shown. It is possible to equip only the transmitting elements with reed contacts in a four-converter arrangement, so that it can be unambiguously recognized when starting up the system whether, for example, two transmitting elements are located opposite each other due to incorrect assembly. Regardless of the contactless detection, galvanic detection of the connection by means of touching is possible as well, for which a connection sensor can have at least one galvanic contact intended for touching. 
         [0045]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.