Abstract:
A respiratory belt sensing device to aid in monitoring breathing patterns of a user, particularly in diagnosis and treatment of persons with breathing disorders. The device includes a PVDF film member having first and second metalized major surfaces and a perimeter containing a plurality of spaced apart alignment features. It also includes a first tabbed lead and a second tabbed lead respectively attached to the first and second major surfaces of the PVDF film member by an electrically conductive adhesive. The resulting assembly is affixed to the surface of a body encircling belt member. Signals are generated when the PVDF film on the belt member is stressed due to stretching as a user breathes in and out. The generated signals can thereafter be used in diagnosis and analysis.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    I. Field of the Invention 
         [0002]    This invention relates generally to a respiratory sensing belt which incorporates a piezoelectric film as its sensing element, and more particularly to a uniquely respiratory sensing belt design in which a piezoelectric film is subjected primarily to a stretching stress to generate data. 
         [0003]    II. Discussion of the Prior Art 
         [0004]    For many years, devices have been sought and developed to help monitor breathing patterns of human beings in an effective way. This is especially true with respect to respiratory sensors in sleep labs which monitor persons with breathing disorders such as sleep apnea. When using this type of sleep monitoring equipment it is well known that it is very important to have an accurate and reliable way to detect breathing variations. 
         [0005]    In the past, a variety of materials and methods have been used to detect respiratory patterns. Some of these devices used film transducers such as polyvinylidene fluoride (PVDF) as a sensing element. PVDF is a highly non-reactive and pure fluoropolymer also known under the commercial name KYNAR®. PVDF material may exhibit efficient piezoelectric and pyroelectric properties. PVDF is electrically poled before it exhibits piezo and pyroelectric properties. It has been used in many types of sensor and battery applications. There are several examples of past respiratory sensing devices which use PVDF film. One example utilized a piece of PVDF film affixed proximate a person&#39;s airway so that air will impinge upon the film when respiratory gas is inspired or expired. An output signal was thereby produced related to the impingement of respiratory air on the sensor due to temperature changes or vibrations due to snoring. 
         [0006]    Other ways of detecting respiration included using devices with belt and transducer arrangements. Such devices used a transducer arrangement where piezoelectric materials were mounted on belts located around a person&#39;s chest or abdomen. The sensors coupled to the belt could detect expansion and contraction to produce output signals. These signals would then be used to relay information about a subject&#39;s breathing for analysis. A limitation found in many of these devices was that flexing or bending of the PVDF material was required for signal detection. Therefore, if the individual wearing such a respiratory sensing belt was lying on the portion of the belt where the PVDF material was located, the necessary bending and signal generation would not occur and any previously generated signal would effectively disappear. 
         [0007]    Further, the attachment arrangements used in many of the past devices were not particularly well suited for measuring a stretching stress on a belt or like device. Likewise, the configuration used was not well suited for manufacture and the PVDF material proved difficult to work with for these designs. Also, the shape of the PVDF or other sensing element was not ideally shaped to detect longitudinal stress and stretching. Because the PVDF is strictly used to measure changes in stress, the amplitude of the signal changes very little when a person lies on the sensor or when the belt is looser or tighter and there is no signal inversion, as exists with the belts using bending of the sensor as a signal generation. 
         [0008]    Therefore, it is desirable to have a sensing device that can be used with greater versatility, ease of manufacture, and effectiveness. An improved respiratory belt sensing device is needed which overcomes the problems experienced in past methods and devices. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention relates generally to a respiratory sensing belt. The device includes a film member having piezoelectric properties and first and second metalized major surfaces. The surfaces have a symmetric shape and a plurality of alignment features around their perimeter. The invention also includes a first tabbed lead and a second tabbed lead, respectively attached to the first and second major surfaces of the film member by an electrically conductive adhesive. This assembly may then be sandwiched between thin layers of an elastomeric material such as polyurethane, which is capable of being stretched. A label is used to conceal the film member and assembly which is affixed to the surface of an elastic belt member. 
         [0010]    The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an exploded view of the respiratory sensing belt of the present invention; 
           [0012]      FIG. 2  is a top perspective view of the piezoelectric film member; 
           [0013]      FIG. 3  is a top view of the respiratory sensing belt in its assembled configuration; and 
           [0014]      FIG. 4  is an exploded view of an alternate embodiment of the respiratory sensing belt. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    The present invention can be readily understood from  FIGS. 1-4 . As shown in the exploded view in  FIG. 1 , the belt sensing device generally includes a sensor member assembly  10  and a belt member  12 . The sensor member includes a PVDF film member  14 , two pieces of electrically conductive double sided tape  16 , first and second tabbed wire leads  18  and  20 , and a label  22 . These components are assembled as a single uniform sensor member  10 . When assembled, this sensor member  10  will be attached to the outside surface of a belt member  12  such that when the belt is stretched an output signal is generated from the PVDF film. These signals are received by tabbed wire leads  18  and  20 , and passed to circuitry allowing for analysis of the signals transmitted. This configuration and operation will be set forth in the following description more fully. 
         [0016]    The configuration of the film member  14  is important to the capabilities and manufacturability of the sensor assembly. While this film member is generally PVDF film, a similar piezoelectric film material of related properties may be utilized as well. The PVDF film  14  is a single-piece, flat member having an outline of a central rectangular member with two rectangular ends of slightly larger width. This outline can be described as a “dogbone” or “dumbbell” shape. The corners of the film are rounded, containing a slight radius. A more detailed view of PVDF film member  14  can be seen in  FIG. 2 . This film is metalized on both major surfaces. The elongated rectangular shape of the member provides a configuration which can easily detect forces exerted due to stress experienced by the PVDF film  14  in the longitudinal direction along its length. The enlarged head provides a location where signals produced along the film&#39;s length can be concentrated and sensed by tabbed wire leads  18  and  20 . The symmetrical shape of the PVDF member allows for easy manufacture and assembly as the film may be readily reversed or inverted during such operations. Typically, the entire length of the PVDF member  14  is only a few inches long and the width is only a fraction of an inch across. 
         [0017]    As mentioned above, the perimeter of PVDF member  14  is somewhat dumbbell shaped, having a central rectangular section and two enlarged heads at the ends. Four important alignment points  28  are located where the perimeter of the central rectangular section and the perimeter of the enlarged heads come together. In this embodiment, these alignment points  28  not only serve to properly orient the surrounding sensor structure, but also function as locations at which adhesive is applied to hold the PVDF film  14  against the belt member  12 . 
         [0018]    Looking again at the exploded view of  FIG. 1 , the relative locations of the conductive members  16  and tabbed wires  18  and  20  in the sensor assembly can be understood. The two tabbed wires  18  and  20  are found above and below the centrally located PVDF film member  14  at one of the enlarged heads of the film. The assembly surrounding tabbed wire lead  18 , located above the top major surface of the PVDF member, is aligned such that the tab  24  extends longitudinally across the enlarged head of the PVDF member. Accordingly, the leads  18  of the tabbed wire protrude from the sensor body  10  in a direction perpendicular to the 24 of the tabbed wire. Similarly, the lower tabbed wire leads  20  and base  26  are situated in a mirrored configuration on the opposing face of the PVDF film member. It is important to note that the tabbed wires are positioned such that no portion of the tabbed wire  18  contacting the upper major surface of the PVDF film  14  is in contact with the tabbed wire  20  of the lower major surface of the PVDF film  14 . 
         [0019]    Located directly between the tabs  24  and  26  of the tabbed wires and the PVDF film member  14  are pieces of a double-sided, electrically-conductive adhesive tape members  16 . One such material is also known under the commercial name ARCLAD®. These ARCLAD pieces  16 , like the tabbed wire members  18  and  20 , do not make contact with the opposing surfaces of the PVDF film  14  or extend beyond the perimeter of the PVDF film. 
         [0020]    Finally, the label  22  is placed over the entire sensor member assembly and joined to the belt  12 . This is done by applying an adhesive to the bottom face of the label  22  and placing it in alignment with the outer dimensions of the belt  12 . Label  22  may also be made from stretchable material. The final assembled configuration appears as shown in  FIG. 3 . In  FIG. 3 , the entire sensor assembly is covered by the label  22  in this top view. The belt  12  is generally made of an elasticized nylon material that allows for stretching its length in the longitudinal direction. 
         [0021]    Once assembled, the device of the present invention generally operates as follows. First, a user places the belt comprising the present invention around his or her chest or abdomen. Next, when the user inhales air and thereby expands his or her chest cavity or abdomen, tension is applied at opposed ends of the PVDF transducer assembly mounted to the belt. Similarly, when a user exhales air, tension is reduced producing a signal reflecting decreased tension. An electrical signal proportional to the tension stress is produced across the tabbed wires  18  and  20 . These wires extend to amplifying and wave shaping circuitry which can be used by medical personal to diagnose and analyze the respiratory patterns of the user. 
         [0022]    An alternate embodiment of the present invention is set forth in the exploded view of  FIG. 4 . In this embodiment, the PVDF film member  14  is centrally located and joined to tabbed wire members  18  and  20  by conductive, two-sided, tape members  16 . Above and below the PVDF member  14 , conductive tape  16 , and wire lead assembly are double sided adhesive foam members  30 . The adhesive foam members  30  have a dogbone or dumbbell shape very similar to that of PVDF film member  14 . The foam members  30 , however, have enlarged heads at their ends which are slightly longer than those of the PVDF member  14 . Such additional length allows the PVDF film member  14  to be fully contained within its confines. The foam members  30  have plural alignment points  32  where the perimeter of its center section and outer enlarged heads come together. The alignment points  32  for the foam member  30  correspond and match the dimensions of the alignment points  28  of the PVDF member  14 . This common characteristic helps to ensure proper alignment of the various layers of the invention during assembly and manufacturing. The purpose of the foam member  30  is primarily to hold the PVDF film  14  and other components in place during assembly. Without such foam the PVDF film  14  is especially difficult to position and align due to its thin and hard to handle surface. 
         [0023]      FIG. 4  also shows a pair of elastic urethane members  34  and  34 ′ which encompass the sensor member assembly to serve as a single unitary polyether polyurethane envelope to seal the PVDF film member  14  and its assembly from moisture. The urethane members  34  and  34 ′ are largely rectangular in shape and slightly larger than the PVDF film member  14 . Because the urethane members  34  and  34 ′ are slightly larger in their dimension than the PVDF film member  14  and foam members  30 , the PVDF film assembly can be contained entirely within the confines of the urethane members&#39; dimensions. Further, the urethane members  34  and  34 ′ can be easily aligned during manufacturing by matching the notches  36  with the corresponding alignment points  28  and  32  of the PVDF and foam members. 
         [0024]    Once aligned, the urethane members  34  and  34 ′ are sealed around the perimeter of film  14 , foam  30 , and wire leads  18  and  20  by an impulse sealing procedure. In such an impulse sealing operation, temperature and pressure are applied to encase the interior assembly. The resulting assembly is an airtight configuration that is resistant to moisture and corrosive substances that might harm the PVDF film member  14   
         [0025]    Assembly of this embodiment is completed when the urethane envelope is aligned between a label and the surface of the belt member  12  and these three elements are joined with one another. In this embodiment, such attachment is preferably performed by stitching the ends of the members to the belt  12 , but other attachment means can be employed. The stitching  38  generally extends laterally across the width of the belt and sensor assembly at a location corresponding to a second pair of notches  40  at both ends of the urethane layers  34  and  34 ′. Placing the stitching  38  in this location ensures that the stitches will pass through the ends of the foam members  30 , but are just beyond the ends of the PVDF material  14  to avoid any damage to the film. All these members are sized such that when aligned, precise stitching and assembly can take place. The resulting assembled belt has an outside appearance similar to that of  FIG. 3 . 
         [0026]    Those skilled in the art will appreciate that the belt sensor of the present invention may be manufactured in a variety of shapes and sizes to accommodate various sizes and types of persons and belt configurations. The components can be composed of any number of suitable materials. Also, the design of the present invention should not be construed to limit its application to only respiratory sensing applications. 
         [0027]    The invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.