Abstract:
A patient interface assembly having an improved support for use in securing a patient interface device to the head of a patient overcomes the shortcomings of conventional headgear. The improved support provides a self-adjusting anchor point situated anterior to the ear of the patient that provides enhanced stability in mounting the patient interface device to the patient.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a Divisional of U.S. patent application Ser. No. 14/239,267, filed Feb. 18, 2014, which claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/526,458 filed on Aug. 23, 2011, the contents of which are herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention pertains to patient interface assemblies and, in particular, to an improved support for use in securing a patient interface device, such as a mask, to a patient. 
         [0004]    2. Description of the Related Art 
         [0005]    There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient&#39;s respiratory cycle, to treat a medical disorder such as sleep apnea syndrome in particular, obstructive sleep apnea (OSA), or congestive heart failure. 
         [0006]    Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including, such as a mask, on the face of a patient. The patient interface device may be, without limitation, a nasal mask that covers the patient&#39;s nose, a nasal cushion having nasal prongs that are received within the patient&#39;s nares, a nasal/oral mask that covers the nose and mouth, or full face mask that covers the patient&#39;s face. The patient interface assembly interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient&#39;s head. Because such patient interface devices are typically worn for an extended period of time, it is important for the headgear to maintain the mask component of the device in a tight enough seal against the patient&#39;s face without discomfort. 
         [0007]    For patient interface devices, a key engineering challenge is to balance patient comfort against stability of the device. As a patient changes sleeping positions through the course of the night, the mask portions of respiratory patient interface devices may become dislodged, and the seal against the patient may be broken. A dislodged mask portion can be stabilized by the increasing strapping force provided by the headgear, but increased strapping force tends to reduce patient comfort. This design conflict is further complicated by the widely varying facial geometries that a given respiratory patient interface device design needs to accommodate. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, it is an object of the present invention to provide a patient interface assembly having an improved support for use in securing a patient interface device to the head of a patient that overcomes the shortcomings of conventional headgear. The improved support provides a self-adjusting anchor point situated anterior to the ear of the patient that provides enhanced stability in mounting the patient interface to the patient. 
         [0009]    Another object of the present invention is to provide an improved support that can be used in supporting a patient interface device on a patient. Such an improved support likewise provides a self-adjusting anchor point anterior to the ear of the patient. 
         [0010]    An optional feature provided in the improved support is that in addition to a strap that supports the patient interface device being movable with respect to a plurality of connectors that connect the strap with the headgear, the connectors may optionally be themselves movably disposed on the headgear. 
         [0011]    In certain embodiments, the general nature of the invention can be stated as including a patient interface assembly structured to provide a flow of breathing gases to a patient. The patient interface assembly can be generally stated as including a headgear, a patient interface device, and a support. The headgear is structured to extend across at least one of an occipital region and a parietal region of the patient&#39;s head. The patient interface assembly is structured to supply a flow of breathing gases to the mouth or the nose or both of a patient. The support extends between the headgear and the patient interface and can be said to include a strap apparatus and a pair of connectors. The strap apparatus can be said to include a pair of flexible strap segments that extend from opposite sides of the patient interface, with each strap segment extending from two location on the patient interface. The pair of connectors are disposed on opposite sides of the headgear. Each strap segment is movably connected with a connector of the pair of connectors. 
         [0012]    In certain embodiments, the general nature of the invention can be stated as including a support that is structured to extend between a headgear and a patient interface of a patient interface assembly. The headgear is structured to extend across at least one of an occipital region and a parietal region of a patient&#39;s head. The patient interface assembly is structured to supply a flow of breathing gases to the mouth or the nose or both of the patient. The support can be generally stated as including a strap apparatus and a pair of connectors. The strap apparatus can be generally stated as including a pair of flexible strap segments that extend from opposite sides of the patient interface, with each strap segment extending from two location on the patient interface. The pair of connectors are disposed on opposite sides of the headgear. Each strap segment is movably connected with a connector of the pair of connectors. 
         [0013]    These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side elevational view of a patient interface assembly in accordance with a first embodiment of the invention, it being understood that the other side of the patient interface assembly is a mirror image of what is depicted in  FIG. 1 ; 
           [0015]      FIG. 2  is a side elevational view of a patient interface assembly in accordance with a second embodiment of the present invention; 
           [0016]      FIG. 3  is side elevational view of a headgear of the patient interface assembly of  FIG. 2  and depicting a connector of a support of the patient interface assembly of  FIG. 2  being movably situated on the headgear; 
           [0017]      FIG. 4  is side elevational view of a patient interface assembly in accordance with a third embodiment of the present invention; and 
           [0018]      FIG. 5  is a side elevational view of a patient interface assembly in accordance with a fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0019]    As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. 
         [0020]    As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. 
         [0021]    Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
         [0022]    A patient interface assembly  4  in accordance with a first embodiment of the present invention is depicted in  FIG. 1  as being situated on a patient. As suggested above, the other side of patient interface assembly  4  is a mirror image of what is depicted in  FIG. 1  and, thus, is not expressly shown herein for purposes of simplicity of disclosure. The alternative embodiments of patient interface assembly  4  are likewise shown in side elevational views, it being understood that the non-depicted sides are mirror images thereof. 
         [0023]    As can be seen in  FIG. 1 , patient interface assembly  4  can be said to include a headgear  8 , a patient interface device 12 , and a support  16  that extends between headgear  8  and patient interface device  12 . As is understood in the relevant art, patient interface assembly  4  is configured to provide a flow of breathing gases to a patient. 
         [0024]    More particularly, patient interface device  12  is in fluid communication with the patient&#39;s mouth or nose or both in order to provide the flow of breathing gases to the patient. Patient interface device  12  is connectable with a supply line  20  that provides the flow of breathing gases. It is noted that patient interface device  12  shown in  FIG. 1  and the other patient interfaces devices shown in  FIGS. 2, 4, and 5  that are described below are depicted in a schematic and exemplary fashion since virtually any type of patient interface device can be employed in conjunction with the improved breathing apparatus  4  and the improved support  16 . The present invention contemplates that patient interface device can be any devices that communicates a flow of gas with an airway of a user, such as a nasal mask, nasal oral mask, nasal pillows, nasal cannular, or a full or total mask that covers the face. 
         [0025]    Exemplary headgear  8  includes an occipital element  24  that extends across the occipital region of the patient, a parietal element  28  that extends across the parietal region of the patient, and a pair of temporal elements  32  that each extend generally between occipital element  24  and parietal element  28 . Headgear  8  further includes a pair of anterior struts  36  that extend in an anterior direction from temporal elements  32  and which, when situated on a patient, extend across a region anterior to the ears. It is noted, however, that many features of headgear  8  of  FIG. 1  and the headgear depicted in  FIGS. 2-5  are largely of an exemplary nature except as expressly pointed out herein. In this regard, it is noted that headgear  8  can be of other configurations without departing from the present concept. 
         [0026]    Patient interface device  12  can be said to include a mask  40  having a fluid connection  44  for connection with supply line  20 . Patient interface device  12  includes a pair of upper braces  48  situated on mask  40  and a pair of lower braces  52  likewise situated on mask  40 . Upper and lower braces  48  and  52  are in the exemplary form of tunnels and are situated generally in the upper and lower regions of mask  40 , respectively, when mask  40  is situated on the patient. Upper braces  48  are spaced from lower braces  52  in order to cooperate in a self-adjusting manner with support  16 , as will be set forth in greater detail below. Patient interface device  12  further includes an adjustment element  56  that is situated generally between upper braces  48  and which will be described in greater detail below. 
         [0027]    The improved support  16  can be said to include a strap apparatus  60  and a pair of connectors  64 . Each connector  64  is affixed to one of the pair of anterior struts  36  and enables connection of strap apparatus  60  with headgear  8 . Strap apparatus  60  includes an individual, i.e., unitary and single, strap member  68  and a pair of tabs  72  that are connected with strap member  68 . While strap member  68  is, in the depicted exemplary embodiment, an individual, i.e., continuous strap, it is noted that for purposes of the disclosure herein strap member  68  can be said to include a pair of strap segments  76  that extend from the opposite sides of mask  40  and are connect with connectors  64 . 
         [0028]    More particularly, it can be seen from  FIG. 1  that each of the pair of strap segments  76  can be said to extend from the lower midpoint of mask  40 , through one of the pair of lower braces  52 , and extend in an posterior direction therefrom, extending about connector  64 , and then extend in an anterior direction, extend through one of the pair of upper braces  48 , and connects with a portion of a tension loop  80  of the strap member  68  that is formed via cooperation with adjustment element  56 . That is, the user can apply a force to tension loop  80 , which serves as an adjustment element, to increase the tension within strap member  68 , and adjustment element  56  retains tension loop  80  in the desired position to retain the resultant tension within strap member  68 . Adjustment element  56  can be in any of a wide variety of forms that may include engagement structures which pinch strap member  68  to retain it in position, or can employ other structures that are well known in the relevant art. 
         [0029]    Tabs  72  are each situated on strap segments  76  and can be grasped by the patient and pulled rearward, i.e., in a posterior direction, during initial installation of mask  40  on the face of the patient in order to cause strap members  68  to be pulled, perhaps at least partially elastically, and to extend behind and movably engage connectors  64 . While tabs  72  are depicted in  FIG. 1  as physically contacting connectors  64 , such depiction is intended merely for purposes of illustration, it being understood that tabs  72  might not necessarily be disposed so closely to connectors  64  once the tension in strap member  68  reaches a state of equilibrium. 
         [0030]    In this regard, it is expressly noted that strap segments  76  extend about a posterior surface of connectors  64  and are movable with respect thereto in order to enable the tension within the upper and lower portions of strap segments  76  to reach an equilibrium. That is, when the tension in strap member  68  is adjusted by the patient by either pulling or releasing tension loop  80 , or by adjusting patient interface device  12 , the tension in the upper and lower portions of strap segments  76  may at least initially be unequal. However, since each strap segment  76  is movably disposed on its corresponding connector  64 , i.e., is movable with respect thereto, the various tensions within the upper and lower portions of each strap segment  76  will eventually equalize by movement of strap segments  76  along connectors  64 . This is desirable since it equalizes the compression forces of mask  40  at its upper and lower ends where it connects with the patient&#39;s face, which desirably enhances comfort and fit. 
         [0031]    Also notably, the connection of each strap segment  76  with the corresponding connector  64  provides an anchor point  78  that is situated anterior to the ear of the patient and that advantageously is self-adjusting. Such self-adjustment exists not only in terms of tension within strap segments  76 , but it also exists in respect of the positioning of mask  40  on any of a variety of patient having different facial structures. That is, if the patient&#39;s nose and mouth were positioned relatively higher on the face than is depicted in  FIG. 1 , strap segments  76  would still movably extend about connectors  64  to provide self-adjusting anchor points  78  that are situated anterior to the ears. Thus, regardless of the specific position and orientation of mask  40 , the tension within the upper and lower portions of each strap segment  76  will eventually become equalized due to the movable connection between strap segments  76  and connectors  64 . 
         [0032]    Advantageously, therefore, it can be seen that the self-adjusting anchor points  78  that are provided by support  16  to breathing apparatus  4  enable improved comfort for the patient due to the ability of mask  40  to be mounted to the patient irrespective of the specific facial configuration of the patient since the self-adjusting anchor points  78  facilitate the achievement of equilibrium of tension in the upper and lower portions of each strap segment  76 . This advantageously promotes the secure connection between mask  40  and the patient and further promotes comfort for the patient. 
         [0033]    Moreover, it can be seen that since strap member  68  is an individual strap element or cord element that is flexible and that may be at least partially elastic, tension between strap segments  76  situated at opposite sides of mask  40  likewise reaches an equilibrium, which avoids pulling of mask  40  to one side or the other of the patient&#39;s face. In this regard, it can be seen that strap member  68  is not only movably disposed on connectors  64  but also is movably situated within upper braces  48  and lower braces  52 . Despite headgear  8  being relatively rigid, patient interface device  12  can be comfortably and reliably retained on the patient through the use of support  16  with its self-adjusting anchor points  78  situated anterior to the ears of the patient. 
         [0034]    An improved patient interface assembly  104  in accordance with a second embodiment of the present invention is depicted generally in  FIG. 2 . While patient interface assembly  104  is similar to patient interface assembly  4  in many respects, the two nevertheless have some meaningful differences. For example, headgear  108  includes an occipital element  124  and a parietal element  128 , but additionally includes an intermediate element  130  situated between occipital and parietal elements  124  and  128 . This is a further demonstration that virtually any type of headgear can be advantageously employed in breathing apparatus  4 ,  104 , etc. 
         [0035]    It is also noted that a pair of anterior struts  136  that extend in an anterior direction from a pair of temporal elements  132  have a pair of connectors  164  that are movably mounted thereon. That is, while the pair of connectors  64  of breathing apparatus  4  were affixed to the pair of anterior struts  36 , it is noted that connectors  164  are advantageously movably disposed on anterior struts  136 , as is illustrated in  FIG. 3 . The movability of connectors  164  on anterior struts  136  provides a pair of anchor points  178  that are situated anterior of the ears of the patient and that are self-adjusting to an even greater extent than in patient interface assembly  4  since the positions of anchor points  178  are themselves movable. That is, anchor points  78  of patient interface assembly  4  were generally dictated by the position at which connectors  64  were affixed to anterior struts  36  of headgear  8 . However, because connectors  164  of patient interface assembly  104  are actually movably situated on anterior struts  136 , anchor points  178  can themselves move along anterior struts  136 , which provides even greater variability of the fit of patient interface assembly  104  to the patient, which improves comfort. 
         [0036]    Optionally, connectors  164  can additionally be lockable or affixable in particular positions on anterior struts  136 . That is, in scenario discussed above, connectors  164  can be freely floating on anterior struts  136  in order to help achieve equilibrium. This could be referred to as “passive” positioning of connectors  164 . Optionally, however, connectors  164  can be configured to stay or to be retained in particular positions on anterior struts  136  as may be desired by the patient. This could be referred to as “active” positioning of connectors  164 . 
         [0037]    For example, connectors  164  may be configured to have friction between them and anterior struts  136 , and such friction can be configured to be relatively high, or at least higher than the friction between connectors  164  and anterior struts  136  that could typically be overcome in the normal course during use of patient interface assembly  104  and the achievement of equilibrium of tension in strap member  168 . However, connectors  164  could be manually moved by the patient along anterior struts  136  until desired positions are reached, after which connectors  164  would remain in the desired positions. That is, the friction between connectors  164  and anterior struts  136  may be sufficiently great that connectors could not be considered “freely floating” on anterior struts  136 , but the patient could easily overcome such friction to manually move connectors  164  to the desired positions. Thus, while connectors  164  would be movably disposed on anterior struts  136 , they would optionally not be freely floating thereon, and rather would be lockable in desired positions, whether being automatically lockable due to friction, or being manually lockable through the use of a locking mechanism that is released to allow movement but that is refastened to retain connectors  164  in the desired positions. 
         [0038]    It is also noted that a support  116  of patient interface assembly  104  includes both an upper tension loop  180  and a lower tension loop  182 . While a strap member  168  of support  116  is an individual, i.e., single cord member that is flexible and may be at least partially elastic, as is strap member  68  of breathing apparatus  4 , upper and lower tension loops  180  and  182  provide enhanced adjustment of the tension in strap member  168  since it provides for separate fine tuning of the tension in the upper and lower portions of strap member  168 . That is, while a strap apparatus  160  that includes connectors  164  and strap member  168  will ultimately reach a point of equilibrium of the tension within strap member  168  because each strap segment  176  is movably situated on its corresponding connector  164 , and also because connectors  164  are movably situated are situated on anterior struts  136 , it is noted that such equilibrium can be more quickly achieved since upper and lower tension loops  180  and  182  permit separate adjustment of tension in the upper and lower portions of strap segments  176 . By permitting such fine tuning of the tensions in the upper and lower portions of the pair of strap segments  176 , equilibrium of the tensions in the upper and lower portions of each strap segment  176  can be accomplished with relatively less movement of strap segments  176  with respect to connectors  164 , which speeds the reaching of equilibrium and promotes comfort to the patient. 
         [0039]    It is also noted that a pair of upper braces  148  and a pair of lower braces  152  of patient interface device  112  are in the form of channels rather than being in the form of tunnels as were upper and lower braces  48  and  52  of patient interface assembly  4 . Again, the different configuration of upper and lower braces  148  and  152  tends to demonstrate that virtually any type of patient interface device  112  can be employed in conjunction with support  116  to achieve the advantageous breathing apparatus described herein. 
         [0040]    As can be understood from  FIG. 3 , connectors  164  are movably situated on anterior struts  136 . More particularly, each connector  164  can be seen as including a base  184  that is slidably disposed on an edge  186  of anterior struts  136 . Each connector  164  further includes a pair of plates  188  that are slidably disposed on the opposite faces of anterior struts  136  adjacent edge  186 . While strap apparatus  160  includes a pair of tabs  172  that are depicted in  FIG. 2  as being situated adjacent connectors  164 , tabs  172  are not depicted in  FIG. 3  for purposes of simplicity of disclosure. 
         [0041]    The movability of connectors  164  on anterior struts  136  is illustrated through the depiction of a connector  164 A in dashed lines at an alternate position on anterior strut  136  of  FIG. 3 . While the position of connector  164 A is likely exaggerated in view of the position of the nose and mouth of the patient, it is intended merely to demonstrate the movability of connectors  164  on anterior struts  136  and the corresponding movability of anchor points  178  of patient interface assembly  104 . By enabling such variable positioning of anchor points  178 , comfort is increased as is the reliability of the positioning of patient interface device  112  on the patient. 
         [0042]    An improved patient interface assembly  204  in accordance with a third embodiment of the present invention is depicted generally in  FIG. 4 . Patient interface assembly  204  includes certain elements of patient interface assembly  4  and patient interface assembly  104 , but provides a different exemplary combination of desirable elements. Patient interface assembly  204  includes a headgear  208 , a patient interface device  212 , and a support  216  that extends between headgear  208  and patient interface device  212 . Support  216  includes a strap apparatus that is similar to the strap apparatus  160 . It is particularly noted that headgear  208  includes a pair of flexible anterior strap elements  236  in place of the anterior struts  36  and  136 . Anterior strap elements  236  extend generally in an anterior direction from a pair of temporal elements  232  of headgear  208 . 
         [0043]    While a pair of connectors  264  of support  216  are movably disposed on anterior strap elements  236 , it can be seen that anterior strap elements  236  being of a flexible nature result in an even greater degree of variability of the resultant movability of anchor points  278 . A strap member  268  having a pair of strap segments  276  is movably disposed on the pair of connectors  264 , and connectors  264  are themselves movably disposed on anterior strap elements  236 , which are themselves flexible. Such enhanced variability of positioning of anchor points  278  promotes patient comfort and enhances the ability of patient interface device  212  to be reliably maintained on the patient. 
         [0044]    An improved patient interface assembly  304  in accordance with a fourth embodiment of the present invention is depicted generally in  FIG. 5 . Patient interface assembly  304  includes a headgear  308 , a patient interface device  312 , and a support  316  that extends between headgear  308  and patient interface device  312 . Support  316  includes a strap apparatus that is similar to the strap apparatus  160 . The exemplary patient interface device  312  is depicted in  FIG. 5  as being one that provides a flow of breathing gases to the nose only and that further includes a point of connection with the patient&#39;s forehead, which further illustrates that virtually any type of patient interface can be employed with the support variously described herein to provide the resultant advantageous breathing apparatus variously described herein. 
         [0045]    Headgear  308  includes an upper element  326  and a lower element  330 , both of which extend across the occipital region of the patient&#39;s head. A pair of junction elements  334  of headgear  308  each extend between upper and lower elements  326  and  330  on opposite sides of headgear  308 . Headgear  308  further includes a pair of anterior strap elements  336  that extend in an anterior direction on opposite sides of headgear  308  from upper and lower elements  326  and  330 . Again, the different configuration of headgear  308  tends to illustrate how virtually any type of headgear can be employed in conjunction with the improved support variously described herein to form the resultant improved breathing apparatus variously described herein. 
         [0046]    Support  316  includes a unitary strap member  368  that can be said to include a pair of strap segments  376  that extend from opposite sides of patient interface device  312 . Support  316  can also be said to include a pair of flexible connectors  364  that each flexibly and length-adjustably extend between one of the pair of anterior strap elements  336  and one of the pair of strap segments  376 . Connectors  364  can be advantageously situated virtually anywhere along the length of anterior strap elements  336  and strap segments  376 , which provides a high degree of variability of the resultant anchor points  378  that are situated anterior to the ears of the patient. 
         [0047]    Moreover, because the pair of connectors  364  in the exemplary embodiment are formed of a flexible fabric and thus are also length adjustable, the distance between anterior strap elements  336  and strap segments  376  can further be varied to provide even greater variability of the positioning of anchor points  378 . Connectors  364  can be of any of a variety of configurations but, in the present exemplary embodiment, are formed to include hook and loop fasteners or other such fasteners that permit connectors  364  to be length-adjustable. Such enhanced variability of anchor points  378  permits even greater levels of comfort for the patient and reliability of connection of patient interface device  312  with the patient. 
         [0048]    Advantageously, therefore, the various patient interface assemblies  4 ,  104 ,  204 , and  304  each provide anchor points  78 ,  178 ,  278 , and  378  that are situated anterior to the ears of the patient, and each anchor point  78 ,  178 ,  278 , and  378  has two connections with the corresponding patient interface device  12 ,  112 ,  212 , and  312  as is indicated in  FIGS. 1-2 and 4-5 . Such a configuration enables comfortable yet reliable retention of patient interface device  12 ,  112 ,  212 , and  312  on the patient regardless of the particular facial structures of the patient, which is advantageous. An equilibrium in the tension of strap members  68 ,  168 ,  268 , and  368  is reachable by providing a movable connection between such strap members and the corresponding connectors  64 ,  164 ,  264 , and  364 . Additionally, connectors  164 ,  264 , and  364  are movably disposed on headgear  108 ,  208 , and  308 , which provides even greater degrees of comfort to the patient and reliability of the connection between patient interface device  112 ,  212 , and  312  and the patient. Further advantages will be apparent to those skilled in the art. 
         [0049]    In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination. 
         [0050]    Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.