Abstract:
An exhaust system, for a vehicle driven by an internal combustion engine, has a system for removing condensate ( 141 ) that includes a first line section ( 110 ) for fluid connection with exhaust gas ( 160 ), at least one second line section ( 120 ) for fluid connection with exhaust gas ( 160 ), and at least one suction line ( 130; 131; 132; 136; 137; 138 ). The suction line ( 130; 131; 132; 136; 137; 138 ) is disposed between the bottom ( 124 ) of the at least one second line section ( 120 ) and the first line section ( 110 ), and includes an opening ( 135 ) configured to be passed over by exhaust gas ( 160 ) passing through the first line section ( 110 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This present application claims priority of Patent Application No. 10 2013 109 462.7, filed Aug. 30, 2013 in Germany, the entire contents of which are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to an exhaust system for a motor vehicle driven by an internal combustion engine having a system for removing condensate. 
     BACKGROUND OF THE INVENTION 
     Exhaust system are conventionally constructed with passive components, with the exhaust gas flowing through all of them in all operating situations, and with the components together forming the exhaust system. Aside from exhaust gas lines, these components may be a turbocharger, a catalytic converter or a muffler, for example. 
     In recent times, systems to actively manipulate exhaust noise caused by operating an internal combustion engine and propagating through an exhaust system have been added to such exhaust systems. Such systems impart a characteristic noise to the exhaust noise generated by the internal combustion engine and propagating through the exhaust system. The imparted characteristic noise shall fit the image of a respective manufacturer and be popular with customers. Sound waves produced artificially inside the exhaust system are for this purpose superposed onto sound waves originating in the operation of the internal combustion engine and propagating through the exhaust system (exhaust noises). 
     This is achieved by providing a sound generator that is in fluid communication with the exhaust system and introduces sound into the interior of the exhaust system. The artificially produced sound is mixed with the sound produced by the internal combustion engine before they exit together through the tailpipe of the exhaust system. Systems of this kind may also be used for sound attenuation. To achieve a complete destructive interference between the exhaust noise sound waves propagating through the exhaust system and the sound produced by the sound generator, the sound waves originating from the loud speaker have to match the sound waves propagating through the exhaust system in magnitude and frequency and show a relative phase shift of 180 degrees. If the anti-noise sound waves generated at the loudspeaker match the sound waves propagating through the exhaust system in frequency and have a phase shift of 180 degrees relative thereto, but do not match the sound waves in amplitude, only an attenuation of the sound waves of the exhaust noise propagating through the exhaust system results. 
     A respective exhaust system according to the state of the art is described below referencing  FIGS. 1A and 1B : 
     An exhaust system featuring a sound system  1  comprises a sound generator  2  in the form of a soundproofed housing containing a loudspeaker  3  and being connected to an exhaust system  6  in the region of a tailpipe  4  via a sound line  13 . Referencing  FIG. 1A , a bottom of the sound generator  2  and a bottom of the sound line  13  are disposed above a bottom of the tailpipe  4 . The tailpipe  4  has a discharge opening  5  for discharging exhaust gas passing through the exhaust system  6 . An error microphone  7  in the form of a pressure sensor is provided at the tailpipe  4 . The error microphone  7  measures the pressure variations and thus the noise inside the tailpipe  4  in a section downstream of a region where the sound line  13  enters the exhaust system  6 . The region where the sound line  13  enters the exhaust system  6  provides a fluid connection between the exhaust system  6  and the sound generator  2 . The term “downstream” hereby relates to the direction of the exhaust gas flow. The direction of the exhaust gas flow is indicated by arrows in  FIG. 1B . Between the internal combustion engine  10  and the region providing the fluid connection between the exhaust system  6  and the sound generator  2 , a catalytic converter  11  and a muffler  12  are also provided. The loudspeaker  3  and the error microphones  7  are electrically connected to a controller  8 . Further, the controller  8  is connected to an engine control unit  9  of an internal combustion engine  10  via a CAN data bus. The controller  8  calculates a control signal for the loudspeaker  3  based on the sound measured with the error microphone  7  and based on the operating parameters of the internal combustion engine  10  received via the CAN data bus in a way that the control signal is adapted to cause a desired overall sound when superposing with the sound propagating inside the exhaust system  6 , and outputs the control signal to the loudspeaker  3 . The controller may hereto use for instance a Filtered-x Least Means Squares (FxLMS) algorithm, and may try to turn an error signal measured with the error microphone down to zero (in the case of sound cancellation), or to a preset threshold (in the case of sound manipulation) by outputting sound using the loudspeaker. 
     There is a disadvantage with conventional exhaust systems that corrosive condensate may form and accumulate in the sound generator, sound line or other components of the exhaust system like the catalytic converter or the muffler. The sound generator as well as the sound line are particularly prone to a formation of condensate, since they are usually colder than those components of the exhaust system passed through by hot exhaust gas. Furthermore, the flow rate of the exhaust gas in the sound line and the sound generator is almost zero. 
     With an accumulation of corrosive condensate in the sound generator or another component of the exhaust system there is a risk of destroying at least one of the sound generator and the sound line and the other component from inside to outside. 
     To solve this problem, it is known to arrange critical components like sound generator and sound line at a raised level with respect to the exhaust system so that the condensate is enabled to drain. This is also illustrated in the example of  FIG. 1A . The possibilities of arranging the sound generator with respect to the exhaust system are hereby considerably limited. 
     In addition it is known to provide openings on the bottom face of components of the exhaust system, allowing the condensate to drain. Respective openings are, however, only permitted to a very limited degree, since in addition to the condensate also non-treated exhaust gas may escape. Furthermore, the edges of such openings are themselves particularly susceptible to corrosion. 
     SUMMARY OF THE INVENTION 
     Embodiments provide an exhaust system for vehicles driven by an internal combustion engine having a system for draining condensate, the system being of low complexity and very robust, thus enabling a production of the system at low cost. 
     Embodiments of an exhaust system for a vehicle driven by an internal combustion engine having a system for draining condensate comprise a first line section for fluid connection with exhaust gas, at least a second line section for fluid connection with exhaust gas, and at least one suction line. “For fluid connection with exhaust gas” hereby means that in operation the exhaust gas is in contact with the interior wall of the line section, but it is not required that the exhaust gas flows through all or even a portion of the line section. An alternative wording may be “suppliable with exhaust gas” or “for fluid communication with exhaust gas”. The suction line is disposed between the bottom of the at least one second line section and the first line section. The suction line includes a suction opening configured to have exhaust gas flowing through the first line section flow over the suction opening. The exhaust gas flowing over the suction opening entails that the opening of the suction line is located within the first line section and that exhaust gas flowing through the first line section flows past the opening. The opening of the suction line is hereby adequately located in a wall of the first line section. 
     The exhaust gas flowing past the opening formed in the suction line generates a negative pressure in the suction line enabling a transportation of condensate accumulated at the bottom of the at least one second line section through the suction line into the first line section and to drain it together with the hot exhaust gas. In this way it is possible to transport condensate from line sections located at lower levels to line sections located at higher levels by using only passive components and without the use of a drain opening in the at least one second line section. Similarly it is possible to drain condensate from line sections at higher levels to line sections at lower levels or from line sections located at the same level, when a line section at still higher levels prevents the condensate from being drained naturally. 
     According to an embodiment, the condensate transported from the at least one second line to the first line is evaporated in the first line due to the high temperature of the exhaust gas and discharged in gaseous state together with the exhaust gas. 
     According to an embodiment, the suction line is a tube provided in addition to the first line section and the at least one second line section. Alternatively, the suction line may for instance also be formed integrally with the at least one second line section, e.g. by inserting a metal sheet. Further alternatively, the suction line may be a flexible line provided it is sufficiently resistant to pressure. 
     According to an embodiment, the suction line is formed in one piece from metal or synthetic material. 
     According to an embodiment, the suction line comprises exactly two openings located opposite to each other with respect to the longitudinal extension of the suction line. According to an embodiment, a first opening of the suction line is located within the first line to have exhaust gas flowing though it, and a second opening of the suction line is located at the bottom of the second line. 
     According to an embodiment, the suction line has a longitudinal extension being at least 5 times, and in particular at least 10 times, and further in particular at least 20 times a largest diameter of the suction line at the opening located in the first line section. 
     According to embodiments, the suction line has a longitudinal extension being at least 3 times, and in particular 6.5 times, and further in particular at least 13 times of the square root of a cross-sectional area of the suction line at the opening located in the first line section. 
     According to an embodiment, the cross-section of the first line section at the position where the suction line enters the first line section is smaller than a cross-section of the first line section upstream of the position where the suction line enters the first line section. Due to this cross-sectional variation, a negative pressure occurs in the first line section at the position where the suction line enters the first line section. The relevant mechanism of action is hereby that of a Venturi nozzle. The decrease of the first line section&#39;s cross-section may hereby be effected by separate measures or by placing the suction line or part of the suction line inside of the first line section. 
     According to an embodiment, the terms “upstream” and “downstream” are defined in accordance with a flow direction of exhaust gas in the first line section, respectively. Thus, downstream means a direction in flow direction and upstream a direction against flow direction of the exhaust gas. 
     According to an embodiment, the cross-section of the first line section at the position, where the suction line enters the first line section, is decreased by at least 5%, and in particular by at least 10%, and further in particular by at least 20% with respect to the cross-section of the first line section upstream of the position, where the suction line enters the first line section. 
     According to an embodiment, the position, where the suction line enters the first line section, is spaced apart in a direction against the flow direction of the exhaust gas from the position of the first line section, where the first line section has a larger cross-section than at the position where the suction line enters the first line section, by not more than two times the square root of the cross-sectional area, and in particular by the square root of the cross-sectional area, and further in particular by not more than half of the square root of the cross-sectional area of the first line section at the position, where the suction line enters the first line section. 
     According to an embodiment, the first line section has a largest diameter at the position, where the suction line enters the first line section, the largest diameter being smaller than a largest diameter upstream of the position, where the suction line enters the first line section. Due to this variation of the largest diameter, a negative pressure is present at the position where the suction line enters the first line section. The relevant mode of action corresponds to that of a Venturi nozzle. The decrease of the first line section&#39;s largest diameter may hereby be effected by separate measures or only by placing the suction line or part of the suction line inside the interior of the first line section. 
     According to an embodiment, the largest diameter of the first line section at the position, where the suction line enters the first line section, is reduced by at least 3%, and in particular at least 7%, and further in particular at least 14% in comparison to the largest diameter upstream of the position, where the suction line enters the first line section. 
     According to an embodiment, the position where the suction line enters the first line section is spaced apart against the flow direction of the exhaust gas from the position of the first line section, where the first line section has a larger cross-section than at the position, where the suction line enters the first line section, by not more than three times the largest diameter, and in particular by not more than one and a half of the largest diameter, and further in particular by not more than three quarter of the largest diameter of the first line section at the position, where the suction line enters the first line section. 
     According to an embodiment, the suction line has a cross-section being not more than 50% of the cross-section, and in particular not more than 30% of the cross-section, and further in particular not more than 10% of the cross-section of the first and/or the second line section. 
     According to an embodiment, the suction line has a largest diameter being not more than 33% of the largest diameter, and in particular not more than 20% of the largest diameter, and further in particular not more than 7% of the largest diameter of the first and/or second line section. 
     According to an embodiment, the at least one second line section comprises at least one sound generator configured to being connected to a controller for receiving control signals and to generate sound in the at least one second line section. Since the line section coupling the at least one sound generator to the exhaust system is usually only in contact with stagnant exhaust gas, this line section is usually colder than other line sections and thus particularly susceptible to corrosion. 
     According to an embodiment, the at least one second line section defines a constant volume. 
     According to an embodiment, the constant volume defined by the section line section ignores periodic volume changes. Such periodic volume changes may be caused by displacements of a membrane of at least one loudspeaker located in the at least one sound generator the second line section, for example. 
     According to an embodiment, at least in sections of the second line section the bottom of the second line section is located below a bottom of the first line section. 
     According to an embodiment, the first line section has a first end, enabling a fluid connection with an internal combustion engine, and a second end, enabling a fluid connection with an exhaust gas discharge opening (e.g. a tailpipe). 
     According to an embodiment, a pressure of an exhaust gas supplied to the first line section is equal or higher than a pressure of an exhaust gas supplied to the at least one second line section. 
     According to an embodiment, the second line section converges into the first line section. 
     According to an embodiment, the condensate is a liquid. 
     According to an embodiment, the suction line is provided in addition to the first line section and the second line section. Thus, the first line section, the second line section and the suction line are distinct elements. 
     Embodiments of a motor vehicle comprise an internal combustion engine having an engine controller and an exhaust system as described above. Hereby, one end of the first line section is in fluid communication with the internal combustion engine, and the other end of the first line section is in fluid communication with an exhaust gas discharge opening. When the internal combustion engine is in operation, an internal pressure caused by the exhaust gas from the internal combustion engine inside the first line section at a position where the suction line enters the first line section is reduced with respect to an internal pressure upstream of the position, where the suction line enters the first line section. 
     It is noted in this context that the terms “including”, “comprising”, “containing”, “having” and “with”, as well as grammatical modifications thereof used in this specification or the claims for listing features, are generally to be considered to specify a non-exhaustive listing of features like for instance method steps, components, ranges, dimensions or the like, and do by no means preclude the presence or addition of one or more other features or groups of other or additional features. 
     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 
       Further features of the invention will be apparent from the following description of exemplary embodiments together with the claims and the Figures. In the Figures, like or similar elements are indicated by like or similar reference signs. It is noted that the invention is not limited to the embodiments of the exemplary embodiments described, but is defined by the scope of the enclosed claims. In particular, embodiments according to the invention may implement individual features in a different number and combination than in the examples provided below. It is noted that not all possible embodiments necessarily exhibit each and every, or any, of the advantages identified herein. 
       In the following explanation of an exemplary embodiment of the invention, reference is made to the enclosed Figures, of which: 
         FIG. 1A  is a schematic representation of a perspective view of a section of an exhaust system having a sound generator of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle; 
         FIG. 1B  is a schematic representation of a block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle in cooperation with an exhaust system of an internal combustion engine according to the prior art, using the sound generator of  FIG. 1A ; 
         FIG. 2A  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a first of eight embodiments of the invention; 
         FIG. 2B  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a second of eight embodiments of the invention; 
         FIG. 2C  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a third of eight embodiments of the invention; 
         FIG. 2D  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a fourth of eight embodiments of the invention; 
         FIG. 2E  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a fifth of eight embodiments of the invention; 
         FIG. 2F  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a sixth of eight embodiments of the invention; 
         FIG. 2G  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to a seventh of eight embodiments of the invention; 
         FIG. 2H  is a schematic representation and block diagram of a system for modifying exhaust noise from an internal combustion engine propagating through an exhaust system of a vehicle according to an eighth of eight embodiments of the invention; and 
         FIG. 3  is a schematic representation of a motor vehicle comprising an exhaust system having a system according to the invention for manipulating exhaust noise propagating through an exhaust system. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in particular, several embodiments according to the invention are explained with respect to the Figures. In the exemplary embodiments described below, components that are alike in function and structure are designated as far as possible by alike reference numerals. Therefore, to understand the features of the individual components of a specific embodiment, the descriptions of other embodiments and of the summary of the disclosure should be referred to. 
     Referencing  FIGS. 2A to 2H , exhaust gas  160  generated in an internal combustion engine  150  passes through an exhaust gas line  110  of an exhaust system and is discharged through a discharge opening  112  of a tailpipe  113  into atmosphere (surroundings). The direction of flow of the exhaust gas  160  is indicated by an arrow. 
     Between the internal combustion engine  150  and the tailpipe  113 , the exhaust gas line  110  may optionally pass through one or more additional components like a turbocharger, a catalytic converter and/or a muffler. Only the schematic representation of  FIG. 1B  shows these components. It is further noted that more than one exhaust tract may be present. 
     According to the embodiments of all  FIGS. 2A to 2H , the exhaust system further comprises a sound generator  121  with a soundproofed enclosure sealed against external influences and made from sheet metal for accommodating a loudspeaker  122 . The sound generator  121  comprises a sound line  120  which couples the sound generated in the sound generator  121  into the interior of the exhaust gas line  110 . The sound line  120  and the exhaust gas line  110  are in fluid communication for this purpose. Thus, fluid can flow from the sound line  120  to the exhaust gas line  110  and vice versa. The loudspeaker  122  is electrically connected to a controller  123 . The controller  123  outputs an electrical signal transformed into sound by loudspeaker  122 . The controller  123  is electrically coupled to an engine control unit  151  of the internal combustion engine  150  via a CAN data bus, and receives from the engine control unit  151  engine parameters, namely the currently valid engine speed and torque. The controller  123  uses the engine parameters for generating the electrical signal in order to match the sound generated by the loudspeaker  122  with a current operating condition of the internal combustion engine  150 . It is noted that also a different vehicle bus may be used instead of a CAN data bus, in particular a LIN data bus, a MOST data bus or a FlexRay data bus, for example. Further, other, additional, or no engine parameters may be used. In the embodiment shown in  FIGS. 2A to 2H , the bottom  124  of the sound line  120  is located at a lower level than a bottom  111  of the exhaust gas line allowing condensate  141  to accumulate on the bottom  124  of the sound line  120 . Although a bottom of the sound generator  121  is located at a higher level than a bottom  124  of the sound line  120 , a higher level bottom section is located between the lowest level bottom section of the sound generator  121  and the sound line  120 , resulting in the condensate  140  formed in the sound generator  121  not being able to completely drain into the sound line  120  but accumulating at the lowest level bottom section of the sound generator  121  instead. 
     According to the embodiment of  FIG. 2A , a suction line  130  is disposed inside the sound line  120 . In the embodiment illustrated, the suction line  130  is made from synthetic material and retained by a spacer  125  such that the suction line  130  is disposed axially centered in the sound line  120 . The suction line  130  comprises an opening at each of its two ends. An opening of the suction line  130  is arranged at the bottom of the sound generator  121  to immerse in a condensate  140  accumulating at the lowest level bottom of the sound generator  121 . The other end of the suction line  130  comprises a discharge opening  135  arranged axially centered in the exhaust gas line  110  and being aligned along the exhaust gas&#39;  160  direction of flow. 
     The axially centered disposal of the suction line  130  inside the exhaust gas line results in a narrowing of the clear cross-section of the exhaust gas line  110 . A Venturi effect develops causing the exhaust gas  160  passing through the exhaust gas line  110  to generate a dynamic pressure upstream of the suction line  130  and thus a negative pressure downstream of the suction line  130  in the region of the discharge opening  135  of the suction line. The negative pressure sucks the condensate  140  accumulated in the sound generator  121  and outputs the condensate  140  into the exhaust gas line  110 . 
     The embodiment of  FIG. 2B  differs from the embodiment from  FIG. 2A  by the suction line  130  not being disposed axially centered inside the sound line  120 , but positioned in contact with the bottom of the sound line  120 . In the embodiment shown, the suction line  130  is not an element formed separate from the sound line  120 , but is formed by separating a segment from the sound line using a sheet metal. The spacer  125  can therefore be spared. Accordingly, also the discharge opening  135  of the suction line  130  is not disposed in the exhaust gas line  110  in an axially centered manner, but positioned at the bottom  111  of the exhaust gas line  110 . In the embodiment of  FIG. 2B , the opening of the suction line  130  is not disposed at the bottom of the sound generator  121 , but in the region of the lowest level bottom  124  of the sound line  120  for enabling an immersion into condensate  141  accumulated at the lowest level bottom  124  of the sound line  120 . 
     Due to the arrangement of the suction line  130  inside the exhaust gas line  110 , also in this case a Venturi effect develops, that sucks the condensate  141  via the suction line into the exhaust gas line  140 . 
     The embodiment of  FIG. 2C  differs from the embodiments of  FIGS. 2A and 2B  in that two suction lines  130 ,  131  are provided, of which one suction line  131  sucks condensate  140  from the lowest level bottom of the sound generator  121  and one suction line  130  sucks condensate  141  from the lowest level bottom  124  of the sound line  120  and into the exhaust gas line  110 . The suction lines  130 ,  131  may hereby support each other allowing to spare the spacer  125  of  FIG. 2A . 
     The embodiment of  FIG. 2D  differs from the embodiment of  FIG. 2C  in that a single suction line  132  comprising two suction openings  133 ,  134  is provided instead of two separate suction lines  130 ,  131 , with one of the suction openings  133  sucking condensate  141  from the lowest level bottom  124  of the sound line  120  and one of the suction openings  134  sucking condensate  140  from the lowest level bottom of the sound generator  121  and into the exhaust gas line  110 . Like in  FIG. 2A , the suction line  132  is retained coaxially centered in the sound line by a spacer  125 , and the discharge opening  135  of the suction line  132  is disposed inside the exhaust gas line  110  in an coaxially centered manner. The suction opening  133  located closer to the discharge opening  135  is hereby configured with a cross-section being only half of that of the suction opening  134  located, with respect to the suction line  132 , further away from the discharge opening  135 . Depending on each suction opening&#39;s  133 ,  134  distance to the discharge opening  135  along the suction line  132 , it is achieved by this measure that the suction openings  133 ,  134  provide more or less the same resistance to the negative pressure generated by the Venturi effect and have thus the same negative pressure applied to it. 
     The embodiment of  FIG. 2E  differs from the embodiment of  FIG. 2B  in that the discharge opening  135  of the suction line  136  is flush with a bottom  111  of the exhaust gas line  110 , with the suction line  136  thus not extending into the exhaust gas line  110 . In the region of the suction line&#39;s  136  discharge opening  135 , the exhaust gas line  110  is instead provided with a variation  114  of its cross-section forming a Venturi nozzle. 
     The embodiment of  FIG. 2F  differs from the embodiments of  FIGS. 2A to 2D  firstly in that the discharge opening  135  of the suction line  137  is flush with a bottom  111  of the exhaust gas line  110 , with only the exhaust gas  160  passing through the exhaust gas line  110  flowing over it. Thus, the suction line  137  does not extend into the exhaust gas line  110 . Furthermore, the suction line  137  is not disposed inside the sound line  120  but penetrates both a wall of the sound line  120 , and a wall of the exhaust line  110 . In this embodiment, the suction line  137  is made of stainless steel. 
     The embodiments of  FIGS. 2G through 2H  differ from the embodiment of  FIG. 2F  in that measures have been taken in the exhaust gas line in the region of the discharge opening  135  of the respective suction line  137 ,  138  to reduce the cross-section of the exhaust gas line  110  for forming a Venturi structure  114 . 
     According to the embodiment of  FIG. 2G , a reduction in the cross-section is achieved by shrinking the diameter of the exhaust gas line  110  itself. 
     According to the embodiment of  FIG. 2H , the reduction in the cross-section is achieved by the exhaust gas line  110  having basically a constant inner diameter but components installed in there reducing the clear cross-section for the exhaust gas  160  flowing there through. 
     The schematic representation of  FIG. 3  illustrates a motor vehicle comprising the above exhaust system having a system for removing condensate in addition to an internal combustion engine  150 . In  FIG. 3 , however, only a part of the exhaust gas line  110  and the tailpipe  113  with the discharge opening  112  of the exhaust gas line  110  and a part of the sound line  120  are shown. 
     While the disclosure has been described with respect to certain exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the disclosure set forth herein are intended to be illustrative and not limiting in any way. Various changes may be made without departing from the spirit and scope of the present disclosure as defined in the following claims. 
     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.