Abstract:
Board-to-board connectors that may provide a durable and reliable connection, save board space, may be easy to manufacture, and may be simple to use during device assembly. One example may include a receptacle including a number of contacts forming electrical connections with traces or planes in or on a printed circuit board. A boss may be included as part of the receptacle and the boss may be connected to the printed circuit board. An insert may be mated to the receptacle. Contacts in the insert may form electrical connections with traces or planes in a second or flexible circuit board. A cowling may be placed over the flexible circuit board to act as a stiffener. A fastener, such as a screw, may be placed through openings in the cowling, second or flexible circuit board, and insert, and into the boss.

Description:
BACKGROUND 
       [0001]    The number of types of electronic devices that are commercially available has increased tremendously the past few years, and the rate of introduction of new devices shows no signs of abating. Devices, such as tablet, laptop, netbook, desktop, and all-in-one computers, cell, smart, and media phones, storage devices, portable media players, navigation systems, monitors, and others, have become ubiquitous. 
         [0002]    The functionality of these devices has likewise greatly increased. This in turn has led to increased complexity inside of these electronic devices. For example, various types of boards, such as flexible circuit boards, printed circuit boards, and others, are often included in a single device. These boards may be connected together using board-to-board connectors. 
         [0003]    These connectors should typically be reliable, otherwise disconnections between circuits and components could occur leading to a loss of functionality or failure of the device. They should also be durable. This way, if the device is dropped or otherwise jarred, a disconnection may be avoided. 
         [0004]    Often these connectors may be large. This, in turn, may consume board area and space inside an electronic device. This may result in either the device having less functionality, a larger size, or a combination of the two. Smaller connectors may save space, allowing more functionality in a device, they may allow a device to be smaller, or a combination of each. 
         [0005]    Board-to-board connectors may also be somewhat complicated to manufacture. This may lead to increased device costs. Connectors that may be easier to manufacture may reduce costs. 
         [0006]    Further, these connectors may be difficult to use in a manufacturing environment. That is, it may be difficult for assembly operators or machines to connect one board to another using conventional connectors. Connectors that are easier to assemble may reduce operator fatigue and error. 
         [0007]    Thus, what is needed are board-to-board connectors that may provide a durable and reliable connection, save board space, may be easy to manufacture, and may be simple to use during device assembly. 
       SUMMARY 
       [0008]    Accordingly, embodiments of the present invention may provide board-to-board connectors that may provide a durable and reliable connection, save board space, may be easy to manufacture, and may be simple to assemble. 
         [0009]    An illustrative embodiment of the present invention may provide board-to-board connectors that provide a durable and reliable connection by securing a fastener through an insert and into a boss that is integrated in a receptacle. In this example, the boss may be press-fit into the receptacle, the receptacle may be injection-molded or otherwise formed around the boss, or the boss may be otherwise attached or integrated with the receptacle. The insert may be mated to the receptacle. The fastener may be inserted through an opening in the insert and into the boss in order to secure the insert to the receptacle. The fastener may be a screw, bolt, or other type of fastener. An adhesive may be used to further secure the fastener. 
         [0010]    Embodiments of the present invention are particularly well-suited to connecting flexible circuit boards to printed circuit boards. In such a situation, a cowling may be used to act as a stiffener for the flexible circuit board. The cowling may have an opening to accept the fastener. Embodiments of the present invention may be used to connect two or more boards together, where the two or more boards include flexible circuit boards, printed circuit boards, or other appropriate boards. For example, embodiments of the present invention may be used to connect two flexible circuit boards, two printed circuit boards, two flexible circuit boards and one printed circuit board, or other combination. 
         [0011]    An illustrative embodiment of the present invention may provide board-to-board connectors where contacts in a receptacle form electrical connections with traces or planes in or on a first or printed circuit board. Similarly, contacts in an insert may form electrical connections with traces or planes in or on a second or flexible circuit board. Contacts in the insert may mate with contacts in the receptacle. In this way, traces and planes on a first or printed circuit board may be electrically connected to trances and planes on a second or flexible circuit board. 
         [0012]    An illustrative embodiment of the present invention may provide board-to-board connectors that save space by integrating a boss with a receptacle. By not requiring separate fastener components, less board area is consumed. 
         [0013]    An illustrative embodiment of the present invention may provide board-to-board connectors that are easy to manufacture. A receptacle may be mounted on a first or printed circuit board. The receptacle may include a number of contacts having contacting portions that may form electrical connections with traces or planes in or on the printed circuit board. The contacting portions of the contacts may be surface-mount, through-hole, or other type of contacting portions. One or more bosses may be included as part of the receptacle. Specifically, the bosses may be press-fit into the receptacle, the receptacle may be injection-molded or otherwise formed around the boss, or the bosses may be otherwise attached or integrated with the receptacle. The bosses may have a contacting portion that may be electrically connected to a ground or other connection on or in the printed circuit board. The contacting portions of the bosses may be surface-mount, through-hole, or other type of contacting portions. The bottom side of the boss (or bosses) may be closed or have an opening, they may have a flat surface, they may have outwardly flared or flange portions, or they may have other shapes or configurations. An insert may be mated to the receptacle such that contacts in the insert form electrical connections with contacts in the receptacle. Contacts in the insert may have surface-mount, through-hole, or other type of contacting portions that are in electrical connections with traces or planes in a second or flexible circuit board. A cowling may be placed over the flexible circuit board to act as a stiffener. A fastener, such as a screw, may be placed through openings in the cowling, second or flexible circuit board, and insert, and into the boss. 
         [0014]    An illustrative embodiment of the present invention may provide board-to-board connectors that are durable. This may be of particular value in mobile devices, where the need for reduced size and durability is acute. For example, it may be useful to increase the retention force in a board-to-board connector in a mobile device, since such devices may be likely to experience shocks and vibration that may otherwise disconnect a connector. Conventionally, this retention force may be increased by shaping an insert to have a more positive or distinct snap when inserted into a receptacle. But this may decrease lengths of contacts in the insert and receptacle, thereby reducing the contact&#39;s length of engagement or wipe. By providing a fastener to secure an insert to a receptacle, the wipe on embodiments of the present invention may be increased and improved. 
         [0015]    An illustrative embodiment of the present invention may provide board-to-board connectors that are simple to use in a manufacturing environment. In one embodiment, an insert on a flexible circuit board may be aligned with a receptacle on a printed circuit board. A cowling may be placed over or attached to the flexible circuit board. A fastener, such as a screw, may be inserted through a hole in the cowling and into a boss in the receptacle. The screw or other fastener may be tightened or otherwise secured. 
         [0016]    In various embodiments of the present invention, a boss may be formed by stamping, metal-injection molding, machining, micro-machining, 3-D printing, or other manufacturing process. The insert and receptacle contacts and boss may be formed of stainless steel, steel, copper, copper titanium, phosphor bronze, or other material or combination of materials. They may be plated or coated with nickel, gold, or other material. The insert and receptacle housings may be formed of silicon or silicone, rubber, hard rubber, plastic, nylon, liquid-crystal polymers (LCPs), or other nonconductive material or combination of materials. 
         [0017]    Various embodiments of the present invention may employ one, two, three, or more than three bosses and corresponding fasteners. The use of these fasteners may result in board-to-board connectors that are simple to use in a manufacturing environment. They may reduce operator fatigue and error. They may simplify any necessary rework procedures as well. 
         [0018]    Various embodiments of the present invention may incorporate one or more of these and the other features described herein. A better understanding of the nature and advantages of the present invention may be gained by reference to the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  illustrates a perspective view of a portion of an electronic system according to an embodiment of the present invention; 
           [0020]      FIG. 2  illustrates another perspective view of a portion of an electronic system according to an embodiment of the present invention; 
           [0021]      FIG. 3  illustrates a top view of a receptacle mounted on printed circuit board; 
           [0022]      FIG. 4  illustrates a top view of an insert mounted on a flexible circuit board; 
           [0023]      FIG. 5  illustrates a side view of a portion of an electronic system according to an embodiment of the present invention; 
           [0024]      FIG. 6  illustrates a perspective view of a portion of another electronic system according to an embodiment of the present invention; 
           [0025]      FIG. 7  illustrates another perspective view of a portion of an electronic system according to an embodiment of the present invention; 
           [0026]      FIG. 8  illustrates a top view of a receptacle mounted on printed circuit board; 
           [0027]      FIG. 9  illustrates a top view of an insert mounted on a flexible circuit board; 
           [0028]      FIG. 10  illustrates a side view of a portion of an electronic system according to an embodiment of the present invention; 
           [0029]      FIG. 11  illustrates a cut away side view of a portion of an electronic system according to an embodiment of the present invention; 
           [0030]      FIG. 12  illustrates a perspective view of a portion of another electronic system according to an embodiment of the present invention; 
           [0031]      FIG. 13  illustrates a top view of a receptacle mounted on printed circuit board; 
           [0032]      FIG. 14  illustrates a cutaway perspective view of a portion of an electronic system according to an embodiment of the present invention; and 
           [0033]      FIG. 15  illustrates a cutaway side view of a portion of an electronic system according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0034]      FIG. 1  illustrates a perspective view of a portion of an electronic system according to an embodiment of the present invention. In this figure, printed circuit board  100  may be connected to flexible circuit board  400  by a board-to-board connector according to an embodiment of the present invention. This figure, as with the other included figures, is shown for illustrative purposes and does not limit either the possible embodiments of the present invention or the claims. 
         [0035]    Receptacle or socket  200  may be mounted on printed circuit board  100 . Receptacle  200  may include a number of contacts  210 , each including contacts portion  212 . Contact portions  212  may be through-hole, surface-mount, or other contact portions. For example, contact portions  212  may be surface mount contact portions that are at least approximately at the same level as a bottom surface of receptacle  200 . Contact portions  212  may form electrical connections with traces or planes on or in printed circuit board  100 . Boss or nut  220  may be integrated with receptacle  200 . Specifically, boss  220  may be press-fit into receptacle  200 , receptacle  200  may be injection molded around boss  220 , boss  220  and receptacle  200  may be 3-D printed as a unit or separately, or boss  220  may be otherwise attached to receptacle  200 . Boss  220  may include opening  222 . Boss  220  may include a surface-mount, through-hole, or other type of connection portion. For example, a bottom of boss  220  may include a flat surface with or without an opening at approximately a bottom surface of receptacle  200 , where the flat surface of boss  220  is surface mounted to a ground pad or plane portion on printed circuit board  100 . In this way boss  220 , as with the other included bosses, may be connected to ground. 
         [0036]    Insert  300  may be mounted on flexible circuit board  400 . Insert  300  may include contacts  310  to form electrical connections with contacts  210  in receptacle  200 . Cowling  500  may be placed over flexible circuit board  400  to act as a stiffener. Cowling  500 , flexible circuit board  400 , and insert  300  may include opening  510 . Fastener  600  may include a portion  620  inserted through hole  510  into opening  222  of boss  220 . Portion  620  of fastener  600  may be threaded to mate with a threaded opening  222  of boss  220 , portion  620  may be arranged to snap into opening  222  of boss  220 , or portion  620  may mate with opening  220  in boss  220  in other ways. Cowling  500  may include recessed area  520  around opening  510 . Fastener head  610  may reside in recessed portion  520  of cowling  500 . Fastener  600  may be a screw, bolt, or other type of fastener. An adhesive may be applied to fastener  600  or boss  220  (or both) to secure or to further secure fastener  600  to boss  220 . Fastener  610  may be easily inserted and removed thereby providing a connector that is easy to use in a manufacturing environment. This may reduce operator fatigue and error and simplify any rework that may need to be done. 
         [0037]    In this and the other examples, traces on or in a printed circuit board may electrically connect to traces in a flexible circuit board. For example, traces on or in printed circuit board  100  may electrically connect to contact portions  212 , which may be connected to contacts  210  in receptacle  200 . Contacts  210  may mate with contacts  310  in insert  300 . Contacts  310  may electrically connect to traces in flexible circuit board  400 . 
         [0038]      FIG. 2  illustrates another perspective view of a portion of an electronic system according to an embodiment of the present invention. Insert  300  may include contacts  310  having contact portions  312 . Contact portions  312  may be surface-mount, through-hole, or other type of contact portions. Contact portions  312  may form electrical connections with traces or planes in flexible circuit board  400 . 
         [0039]    In this example, traces and planes in or on printed circuit board  100  may be electrically connected to traces and planes in flexible circuit board  400 . In other embodiments of the present invention, traces in three or more boards may be connected. Also, while in these examples, flexible circuit boards are connected to printed circuit boards, in other embodiments the present invention, two or more flexible circuit boards, or two or more printed circuit boards may be connected together. 
         [0040]    In various embodiments of the present invention, printed circuit board  100  may be a main logic board, a motherboard, or other type of printed circuit board. Printed circuit board  100  and flexible circuit board  400  may be located in various electronic devices, such as portable computing devices, tablets, desktop computers, laptops, all-in-one computers, cell phones, smart phones, media phones, storage devices, portable media players, navigation systems, monitors and other devices. 
         [0041]      FIG. 3  illustrates a top view of receptacle  200  mounted on printed circuit board  100 . Receptacle  200  may include contacts  210  and boss  220 . Boss  220  may include opening  222  for accepting an end of a fastener. 
         [0042]      FIG. 4  illustrates a top view of insert  300  mounted on flexible circuit board  400 . Insert  300  may include contacts  310  having contact portions  312 . Flexible circuit board  400  and insert  300  may include opening  510  for accepting an end of a fastener. 
         [0043]      FIG. 5  illustrates a side view of a portion of an electronic system according to an embodiment of the present invention. Receptacle  200  may be mounted on printed circuit board  100 . Receptacle  200  may include contacts having contact portions  212 . Contact portions  212  may connect to traces or planes on or in printed circuit board  100 . Insert  300  may be mated with receptacle  200 . Insert  300  may include contacts  310  having contact portions  312 . Contact portions  312  may form electrical connections with traces or planes on our and flexible circuit board  400 . Cowling  500  may be placed over flexible circuit board  400  to act as a stiffener. 
         [0044]    In the above example, one fastener may be inserted into one corresponding boss to secure a flexible circuit board to a printed circuit board. In other embodiments the present invention, two or more such fasteners and corresponding bosses may be used. These bosses may be located at various portions of a receptacle. For example, these bosses may be placed at ends of a receptacle. Examples are shown in the following figures. 
         [0045]      FIG. 6  illustrates a perspective view of a portion of another electronic system according to an embodiment of the present invention. In this figure, printed circuit board  1100  may be connected to flexible circuit board  1400  by a board-to-board connector according to an embodiment of the present invention. 
         [0046]    Receptacle or socket  1200  may be mounted on printed circuit board  1100 . Receptacle  1200  may include a number of contacts  1210 , each including contacts portion  1212 . Contact portions  1212  may be through-hole, surface-mount, or other contacts portions. Contact portions  1212  may form electrical connections with traces or planes on or in printed circuit board  1100 . Bosses or nuts  1220  may be integrated with receptacle  1200 . Specifically, bosses  1220  may be press-fit into receptacle  1200 , receptacle  1200  may be injection molded around bosses  1220 , bosses  1220  and receptacle  1200  may be 3-D printed as a unit or separately, or bosses  1220  may be otherwise attached to receptacle  1200 . Bosses  1220  may include openings  1222 . Bosses  1220  may include a surface-mount, through-hole, or other type of connection portion. For example, a bottom of bosses  1220  may each include a flat surface that may be closed or have an opening, and may be surface mounted to ground pads or plane portions on printed circuit board  1100 . In this way, bosses  1220  may be grounded. 
         [0047]    Insert  1300  may be mounted on flexible circuit board  1400 . Insert  1300  may include contacts  1310  to form electrical connections with contacts  1210  in receptacle  1200 . Cowling  1500  may be placed over flexible circuit board  1400  to act as a stiffener. Cowling  1500 , flexible circuit board  1400 , and insert  1300  may include openings  1510 . Fasteners  1600  may each include a portion  1620  inserted through holes  1510  into openings  1222  of bosses  1220 . Portions  1620  of fasteners  1600  may be threaded to mate with threaded openings  1222  of bosses  1220 , portions  1620  may be arranged to snap into openings  1222  of bosses  1220 , or portions  1620  may mate with openings  1220  in bosses  1220  in other ways. Cowling  1500  may include recessed areas  1520  around openings  1510 . Fastener heads  1610  may reside in recessed portions  1520  of cowling  1500 . Fasteners  1600  may be screws, bolts, or other type of fasteners. Fastener heads  1600  may reside in recessed portion  1520  of cowling  1500 . An adhesive may be applied to fasteners  1600  or bosses  1220  (or both) to secure or to further secure fasteners  1610  to bosses  1220 . Fasteners  1600  may be easily inserted and removed thereby providing a connector that is easy to use in a manufacturing environment. Again, this may reduce operator fatigue and error and simplify any rework that may need to be done. 
         [0048]    In this and the other examples, traces on or in a printed circuit board may electrically connect to traces in a flexible circuit board. For example, traces on or in printed circuit board  1100  may electrically connect to contact portions  1212 , which may be connected to contacts  1210  in receptacle  1200 . Contacts  1210  may mate with contacts  1310  in insert  1300 . Contacts  1310  may electrically connect to traces in flexible circuit board  1400 . 
         [0049]      FIG. 7  illustrates another perspective view of a portion of an electronic system according to an embodiment of the present invention. Insert  1300  may include contacts  1310  having contact portions  1312 . Contact portions  1312  may be surface-mount, through-hole, or other type of contact portions. Contact portions  1312  may form electrical connections with traces or planes in flexible circuit board  1400 . 
         [0050]    In various embodiments of the present invention, printed circuit board  1100  may be a main logic board, a motherboard, or other type of printed circuit board. Printed circuit board  1100  and flexible circuit board  1400  may be located in various electronic devices, such as portable computing devices, tablets, desktop computers, laptops, all-in-one computers, cell phones, smart phones, media phones, storage devices, portable media players, navigation systems, monitors and other devices. 
         [0051]      FIG. 8  illustrates a top view of receptacle  1200  mounted on printed circuit board  1100 . Receptacle  1200  may include contacts  1210  and bosses  1220 . Bosses  1220  may each include opening  1222  for accepting an end of a fastener. 
         [0052]      FIG. 9  illustrates a top view of insert  1300  mounted on flexible circuit board  1400 . Insert  1300  may include contacts  1310  having contact portions  1312 . Flexible circuit board  1400  and insert  1300  may include openings  1510  for accepting ends of fasteners. 
         [0053]      FIG. 10  illustrates a side view of a portion of an electronic system according to an embodiment of the present invention. Receptacle  1200  may be mounted on printed circuit board  1100 . Receptacle  1200  may include contacts having contact portions  1212 . Contact portions  1212  may connect to traces or planes on or in printed circuit board  1100 . Insert  1300  may be mated with receptacle  1200 . Insert  1300  may include contacts  1310  having contact portions  1312 . Contact portions  1312  may form electrical connections with traces or planes on our and flexible circuit board  1400 . Cowling  1500  may be placed over flexible circuit board  1400  to act as a stiffener. 
         [0054]      FIG. 11  illustrates a cut away side view of a portion of an electronic system according to an embodiment of the present invention. Receptacle  1200  may be mounted on printed circuit board  1100 . Insert  1300  may be mated with receptacle  1200 . Insert  1300  may be attached to flexible circuit board  1400 . Cowling  1500  may be placed over flexible circuit board  1400  to act as a stiffener. Portion  1620  of fastener  1600  may be inserted into boss  1220 . Portion  1620  and an inside of boss  1220  may each be threaded. A bottom of boss  1220  may have an opening as shown, or it may be closed. 
         [0055]      FIG. 12  illustrates a perspective view of a portion of another electronic system according to an embodiment of the present invention. In this figure, printed circuit board  2100  may be connected to flexible circuit board  2400  by a board-to-board connector according to an embodiment of the present invention. 
         [0056]    Receptacle or socket  2200  may be mounted on printed circuit board  2100 . Receptacle  2200  may include a number of contacts (not shown), each including contacts portion  2212 . Contact portions  2212  may be through-hole, surface-mount, or other contacts portions. Contact portions  2212  may form electrical connections with traces or planes on or in printed circuit board  2100 . Bosses or nuts (not shown) may be integrated with receptacle  2200 . Specifically, bosses may be press-fit into receptacle  2200 , receptacle  2200  may be injection molded around the bosses, the bosses and receptacle  2200  may be 3-D printed as a unit or separately, or the bosses may be otherwise attached to receptacle  2200 . The bosses may include openings (not shown). The bosses may include a surface-mount, through-hole, or other type of connection portion. For example, the bosses may each include a flat bottom surface that may be surface mounted to ground pads or plane portions on printed circuit board  2100 . The bosses may instead include outwardly flared or flange portions arranged to mate with a solderable area on printed circuit board  2100 . In this way, the bosses may be grounded. 
         [0057]    Insert  2300  may be mounted on flexible circuit board  2400 . (In this example, insert  2300  is mounted on an underside of flexible circuit board  2400  and is not actually visible.) Insert  2300  may include contacts (not shown) to form electrical connections with contacts in receptacle  2200 . Cowling  2500  may be placed over flexible circuit board  2400  to act as a stiffener. Cowling  2500 , flexible circuit board  2400 , and insert  2300  may include openings. Fasteners  2600  may each include a portion inserted through holes in cowling  2500  into openings of the bosses. Portions of fasteners  2600  may be threaded to mate with threaded openings of bosses the  2220 , portions may be arranged to snap into openings of the bosses, or portions may mate with openings in the bosses in other ways. Cowling  2500  may include recessed areas  2520  around the openings. The heads of fasteners  2600  may reside in recessed portions  2520  of cowling  2500 . Fasteners  2600  may be screws, bolts, or other type of fasteners. Fastener heads  2610  may reside in recessed portion  520  of cowling  500 . An adhesive may be applied to fasteners  2610  or bosses  2220  (or both) to secure or to further secure fasteners  2610  to bosses  2220 . Fasteners  2600  may be easily inserted and removed thereby providing a connector that is easy to use in a manufacturing environment. Again, this may reduce operator fatigue and error and simplify any rework that may need to be done. 
         [0058]    In this and the other examples, traces on or in a printed circuit board may electrically connect to traces in a flexible circuit board. For example, traces on or in printed circuit board  2100  may electrically connect to contact portions  2212 , which may be connected to contacts in receptacle  2200 . Contacts in receptacle  2200  may mate with contacts in insert  2300 . Contacts in insert  2300  may electrically connect to traces in flexible circuit board  2400 . 
         [0059]      FIG. 13  illustrates a top view of receptacle  2200  mounted on printed circuit board. Receptacle  2200  may include contacts  2210  and bosses  2220 . Bosses  2220  may each include opening  2222  for accepting an end of a fastener. 
         [0060]      FIG. 14  illustrates a cutaway perspective view of a portion of an electronic system according to an embodiment of the present invention. Receptacle  2200  may be mounted on printed circuit board  2100 . Receptacle  2200  may include contacts having contact portions. The contact portions may connect to traces or planes on or in printed circuit board  2100 . Insert  2300  may be mated with receptacle  2200 . Specifically, tabs  2320  on insert  2300  may fit in corresponding recesses in receptacle  2200 . Insert  1300  may include contacts having contact portions. The contact portions may form electrical connections with traces or planes on our and flexible circuit board  2400 . Cowling  2500  may be placed over flexible circuit board  2400  to act as a stiffener. Portions  2620  of fasteners  2600  may be inserted into bosses  2220 . Bosses  2220  may have outwardly flared or flange portions  2224 . Portions  2224  may be soldered to contact or solderable areas on printed circuit board  2100 . 
         [0061]      FIG. 15  illustrates a cutaway side view of a portion of an electronic system according to an embodiment of the present invention. Again, receptacle  2200  may be mounted on printed circuit board  2100 . Receptacle  2200  may include contacts having contact portions. The contact portions may connect to traces or planes on or in printed circuit board  2100 . Insert  2300  may be mated with receptacle  2200 . Specifically, tabs  2320  on insert  2300  may fit in corresponding recesses in receptacle  2200 . Insert  2300  may include contacts having contact portions. The contact portions may form electrical connections with traces or planes on our and flexible circuit board  2400 . Cowling  2500  may be placed over flexible circuit board  2400  to act as a stiffener. Portions  2620  of fasteners  2600  may be inserted into bosses  2220 . Bosses  2220  may have outwardly flared or flange portions  2224 . Portions  2224  may be soldered to contact or solderable areas on printed circuit board  2100 . 
         [0062]    The above description of embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Thus, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.