Abstract:
An automatic door bottom having a release mechanism is used on the bottom of a hinged door that is pivotable to be positioned over a sill when closed and includes a movable sealing member having a length corresponding to the width of the door and is housed in a channel mounted on the door. The sealing member is movable vertically downwardly into a sealing position in which the sealing member will contact the door sill when the door is closed. The release mechanism permits the sealing member to be moved upwardly even when the door is in the closed position.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 60/995,659, filed Sep. 26, 2007. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to an automatic door bottom with a release mechanism. An automatic door bottom is a device attached to bottom part of a door by mounting means, for example by screws. The terms Automatic Door Bottom and Door Bottom will be used interchangeably in the description of this invention. 
     The current invention allows a person to selectively seal or unseal a door bottom when said door is in the closed state. Said release mechanism to the automatic door bottom may be actuated remotely or in close proximity. The mechanism utilized to release the automatic door bottom may be through mechanical force or electrical forces. 
     A door is described as an enclosure of an opening. The perimeter of the opening around the door on the left and right vertical sides are referred as jambs. The part of the floor bellow the bottom part of the door is referred as a door sill. The term swing door as used herein describes a door which is pivotally mounted to one of the jambs by mounting means generally referred as hinges. The side of the door nearest to the hinges is referred as the hinged side, the side farthest from the hinges is referred as the unhinged side. The opening and closing of said door occurs by moving the door in a swinging action around the hinges. A gap generally exists between the bottom part of the door and the adjacent sill when the door is in its closed position. 
     The Automatic Door Bottom of the present invention has a housing in the form of an inverted U shaped channel with an open bottom facing toward the door sill and has a length corresponding to the door width. The Automatic Door Bottom has at least one sealing member installed at the open bottom of said channel. 
     A displacement mechanism is coupled to the sealing member at one or multiple points to actuate the sealing member and move it from an extended to a retracted position relative to the bottom of the door. The displacement mechanism has at least one operating member and at least one resilient member. The at least one operating member cooperates with at least one stationary abutment around the perimeter of the door to operate the displacement mechanism, and displace the sealing member to move it to its extended position. A release mechanism is also provided that is activated by other means of actuation to selectively disengage the displacement mechanism from actuating the sealing member even when the door is closed. 
     The sealing member in this invention consists of a compressible and elastic sealing element and a generally H-shaped rigid member to support the sealing element. The sealing member can be reciprocally lowered, i.e. extended, in to a first sealing position and retracted into the channel in a second unsealing position. The first and second position correspond respectively to a closed and an opened door position. The purpose for providing the sealing position is in general to block drafts, light, noise, and foreign objects from passing through the gap between the bottom edge of the door and the sill. 
     Furthermore the described reciprocal action creates a first correlation of a closed door correlated to a sealed gap, and a second correlation of an opened door correlated to an unsealed gap. An Automatic Door Bottom with release mechanism in this invention creates a third correlation where a closed door may also correlate to an unsealed gap. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING 
         FIG. 1  is an elevation view of an Automatic Door Bottom with release mechanism according to the first embodiment of the invention mounted on a closed swing door. 
         FIG. 2  is a partial perspective view of the door of  FIG. 1  showing the door slightly open, and showing the bottom part of the door at the hinged side. 
         FIG. 3  is side cross section view taken along line III-III of  FIG. 1 . 
         FIG. 4  is an elevation view of the other side of the door from that shown in  FIG. 2 , showing one side of a foot operated lever as an actuator for release mechanism. 
         FIG. 5  is a plan, cross section view taken along line V-V in  FIG. 4 . 
         FIG. 6  is an exploded perspective view of the Automatic Door Bottom of  FIG. 1  showing the components of the Automatic Door Bottom with release mechanism according to a first embodiment of the invention. 
         FIG. 7  is a general cross section view similar to  FIG. 3  showing the channel of the Automatic Door Bottom. 
         FIG. 8  is a view similar to  FIG. 3 , illustrating a modified version of an embodiment of the invention with the Automatic Door Bottom flush mounted to the door leaf. 
         FIG. 9  is a view similar to  FIG. 3 , illustrating a modified version of another embodiment of the invention with the Automatic Door Bottom mortise mounted to the door. 
         FIGS. 10   a ,  10   b , and  10   c  together form a partial front view of the displacement mechanism of the first embodiment of the invention. 
         FIGS. 11 ,  12 ,  13 , and  14  are front views of the first embodiment of the invention showing four successive operating stages, in which the seal is lowered from its retracted to its extended position and returned to its retracted position. 
         FIG. 15  is an elevation view of a modified version of the embodiment of  FIG. 1  showing a solenoid as the actuator for the release mechanism. 
         FIG. 16  is a perspective view of the solenoid of  FIG. 15 . 
         FIGS. 17   a ,  17   b , and  17   c  together form a partial front view of a displacement mechanism according to the second embodiment of the invention. 
         FIG. 18  is a front view of the bottom part of the unhinged side of a swing door, showing a door knob as an actuator for the release mechanism. 
         FIG. 19  is a detailed perspective view of the door knob adapter used in the embodiment of  FIG. 18 . 
         FIGS. 20 ,  21 ,  22 , and  23  are front views of the second embodiment of the invention, showing the four successive operating stages. 
         FIGS. 24   a  and  24   b  together form a front view of a displacement mechanism according to a third embodiment of the invention. 
         FIGS. 25 ,  26 , and  27  are front views of the third embodiment of the invention, showing its three successive operating stages. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The contents of U.S. Pat. No. 4,947,584, U.S. Pat. No. 6,125,584, and U.S. Pat Application No. 20040010973 are incorporated hereby in their entirety by reference. 
       FIG. 1  shows the preferred first embodiment of the invention which is a front view of a swing door  21  in its closed position, mounted to a door jamb  26  by means of hinges  23 . The door  21  is provided with door knob  31  which operates a spring loaded latch (not shown in the figure). An alternative for door knob  31 , for example a hand lever, can also be used, but is not shown. An Automatic Door Bottom with release mechanism  22  can be surface mounted on the door or inserted in a hollow in the bottom portion of said door, with two foot operated levers  38 , to operate the release mechanism. Preferably, at least one lever  38  is mounted to the door by mounting plate  156 . Alternatively any form of switching mechanism commonly known to persons skilled in the art may be used, including but not limited to a push button mechanism, upwardly moving latch, laterally moving latch, or a pulling mechanism.  FIG. 4  shows the preferred embodiment with the lever on the other side of the door shown in  FIG. 1 . The operation of levers  38  are a clockwise turn in  FIG. 1  and a counterclockwise turn in  FIG. 4 .  FIG. 3  is a side cross sectional view along line III-III of  FIG. 1 , showing the connection between the bottom of door  21  and lever  38  by a spindle  117 .  FIG. 2  is a perspective view of the door of  FIG. 1 , showing the partially opened door with a more detailed view of the Automatic Door Bottom at the hinge side of the door. 
       FIG. 5  is a plan cross section view along line V-V of  FIG. 4 , showing the detail relationship between the Automatic Door Bottom and levers  38 . In the preferred embodiment levers  38  include a mirror image pair of lever handles  152 , mounted to shafts  148  by means of screws  154 . Each shaft  148  is held in place with a pair of washers  150  to the base plate  153 .  FIG. 4  shows the base plate  153  of lever  38  directly engaging the side of the door shown therein and  FIG. 1  shows the base plates  153  on that side of the door indirectly mounted through mounting plate  156  by screws  157 . Preferably torsional springs  155  are mounted at one end to each of the shafts  148  and at the other end to base plate  153 . This enables levers  38  to spring back to their normal position shown in  FIG. 1 . In an alternative embodiment, the lever can move into various positions manually without the aid of any mechanical forces. The pair of levers  38  are connected to each other by a square shape spindle  117 , and are connected to the release mechanism through a rocker element  116 . The rocker  116  is preferably made from injection molding resilient plastic. All parts of the invention may be constructed from different types of materials commonly known to persons skilled in the art for their desired purpose. 
       FIG. 7  shows a general cross section view of one embodiment of channel  15 , i.e., an extruded inverted U-shape with a length corresponding to the width of door  21 . Channel  15  has top wall  17 , a pair of legs  19  and, optionally, a pair of feet  20  as shown in  FIG. 9 . A pair of rails  18  are provided on the inside surfaces of legs  19  engaged in complementary grooves in one or more blocks referred to in  FIG. 7  by numeral  33  to allow the blocks to move freely along the channel  15 . Various blocks used in this invention have a cut out shape to accommodate rails  18 , but can have different internal shapes and different numerical references are used herein for each shape depending on the block&#39;s functions. Alternatively, additional mechanisms may be inserted into a cavity formed by channel  15  if desired. Mechanisms such as a temperature sensor may be inserted into said cavity above the blocks to notify users of dangerous fire conditions. 
       FIG. 6  is an exploded view of a first embodiment of the invention. The channel  15  is surface mounted to the door by means of mounting screws  107  through in line mounting holes  108 , extending along the length of the Automatic Door Bottom. A pair of levers  38  are connected to channel  15  by spindle  117  through in line holes  109  on both side of legs  19  of the channel. Inside the channel  15 , the spindle  117  pass thorough holes  116   b  of rocker  116 . The rocker  116  is snapped in to in line holes  109  from inside the channel  15 . A hook  116   a  is provided on the rocker to slide into a slot  103   b  through a hole  103   a , formed in a leaf spring  103  to securely couple rocker  116  to the leaf spring as described hereinafter. 
     The displacement mechanism of the present invention consists of a release mechanism referred with numeral  9  and resilient members such as leaf springs  42  and  43 . The leaf springs  42  and  43  are connected to each other by a connecting block  41 . The other end of leaf spring  43  is secured in end block  2 . The end block  2  is fixedly mounted to the channel  15 , by a pin  87  that pass though in line holes  88  of channel  15  channel and hole  1  of end block  2 . 
     The release mechanism  9  also includes a hollow block  128 , adjustment block  125 , and a housing block  7 . The blocks mentioned above generally take shape of block  33 , and are able to move freely along the channel  15  lengthwise. 
     A H-shape rigid housing  13  holds compressible sealing element  14  in place in the assembly. The sealing element has a shaped head which slides into and secures the sealing element to the housing  13  and it is fixed in place, for example, by adhesive or any form of mechanical mounting mechanisms commonly known to persons skilled in the art to form a two part sealing member  36 . The displacement mechanism is connected to the sealing member  36 , by mounting the middle sections of springs  42  and  43  beneath pins  89  which are mounted in through in line holes on the housing  13 . The mounting is in such a way, that a limited movement of sealing member  36  lengthwise is permitted, but downward vertical movement across the width of channel downward is restricted by both leaf springs  42  and/or  43 . 
       FIGS. 10   a ,  10   b , and  10   c  are partial front views of the displacement mechanism of the Automatic Door Bottom with release mechanism according to the first embodiment of the invention. To form a complete figure, join the right side of  FIG. 10A  to the left side of  FIG. 10   b , and likewise join the right side of  FIG. 10   b  to the left side of  FIG. 10C . Tensional mechanisms such as, but not limited to, leaf springs may be used. Alternatively other forms of tensional mechanism may be utilized as commonly known to persons skilled in the art. Leaf springs  42  and  43  are provided as such that the spring constant of spring  42  is smaller than the spring constant of leaf spring  43 . In  FIG. 10A , the housing block  7  is joined directly with spring  42  as shown, or indirectly by another connecting block  41 . The housing block  7  takes the general shape of block  33  as in  FIG. 7 , has a bore hole  7   a  at one end to accommodate a shaft  10 , and an opening  7   b  in its top wall to provide a hollow middle section. The previously described leaf spring  103  is mounted to housing  7  by rivets  124  at one end, and has latch pin  102  in its other end to the left of slot  103   b  as seen in  FIGS. 6 and 10   a . The latch pin  102  extends from the end of leaf spring  103  into the hollow middle of housing  7  to latch shaft  10  by engagement in its annular grove or open cavity  53  formed therein. 
     Hollow block  128  has an interior threaded base which, in cooperation with a hollow adjustment cylinder  131 , is used to adjust the length of operation of the displacement mechanism. An adjustment is executed by turning the head of cylinder  131 , which preferably has a hexagonal shape. A spring  126  is provided to prevent accidental turning of cylinder  131 . 
     Cushion  132  located at the left end of cylinder  131  is removably mounted in the bore formed in cylinder  131  to enable a screw driver to access a screw head  50  formed in the left end of shaft  10  as seen in  FIG. 10   a . The shaft  10  also has one annular grove  51  formed in its left end and is retained in block  128  by a retaining ring  127 . A threaded area  52  is also provided on shaft  10  which is threaded into hollow block  125  which also has an interior threaded bore. A helical spring  8 , assisted with a pair of washers  106 , is situated between block  125  and housing  7 . An operation of turning the screw head  50 , in cooperation with the annular groove  153  being latched by latch pin  102 , will cause hollow block  125  to move along threaded region  52 , effectively adjusting the tension of helical spring  8 . 
       FIGS. 11 ,  12 ,  13 , and  14  show respectively operating stages one, two, three and four of the first embodiment of the invention. Stage one represents the condition of the Automatic Door Bottom when the door is in an open position, stage two represents its condition when the door is in an almost closed position. Stage three represents the condition of the Automatic Door Bottom with the door in its closed position, and stage four represents the door in its closed position with release mechanism activated to allow retraction of the sealing member  36 . 
     At operating stage one with the door open, sealing member  36  is retracted inside channel  15 , cushion  132  is not engaged with jamb  26 , and shaft  10  is latched to housing  7  by means of latch pin  102 . Rocker  116 , is engaged in slot  103   b  of leaf spring  103 . The condition of stage one is shown in  FIG. 11 . 
     As the door is closed, at one point cushion  132  will engage door jamb  26  at the hinged side of the door and cause block  7  to move to the right as the cylinder  131  is pushed into channel  15 . At first, due to its lower spring constant leaf spring  42  will flex down (as seen in  FIG. 12 ), and bring sealing member  36  at coupling point  91  downwardly until sealing member  36  contacts with door sill  25 . Housing  7  moves along the channel to the right in the figure, causing rocker  116  to slide along the slot of spring  103  closer to latch pin  102 .  FIG. 12  shows the condition of Automatic Door Bottom in stage two. 
     A further closing of the door  21  causes rocker  116  to move more closely to latch pin  102 . Such further closing also causes spring  43  to flex and bring the remaining part of sealing member downwardly by applying a downward force at coupling point  92 , until the door is completely closed and sealing element is fully in contact with door sill  25 . Springs  42  and  43  as combined have a spring tension force F 1  as shown in  FIG. 13 . 
     In accordance with the present invention the action of operating either one of the levers  38  cause rocker  116 , in cooperation with leaf spring  103 , to release the latch pin  102  from latching onto shaft  10 . The combined spring force F 1  then causes springs  42  and  43  to unflex, causing housing  7  to move to the left side as seen in  FIG. 14 , and in turn depress helical spring  8 . Since the spring constant of helical spring  8  is designed to be significantly smaller than spring constant of leaf spring  43 , the net result will cause sealing member  36  to retract significantly into the channel  15 . Spring  8  will eventually compress and has spring tension or force F 2  which is significantly smaller than F 1 . 
     When the door  21  is eventually reopened, tension F 2  of helical spring  8  would push shaft  10  out of housing  7  until it is latched again by latch pin  102 . This effectively resets the release mechanism  9  and sets the condition of the Automatic Door Bottom to the stage one of operation as shown in  FIG. 11 . 
     According to this embodiment of the invention, stages one, two, and three are normal operation stages for the Automatic Door Bottom with release mechanism. Operation stage four is optional and active only if release mechanism  9  is actuated by a user. 
     The release mechanism  9  can furthermore be actuated by another means.  FIGS. 15 and 16  show one alternative of actuating the release mechanism by means of a solenoid. This actuating mechanism is preferable for an Automatic Door Bottom  22  mortised mounted to the bottom of door  21  similar to the mounting shown in  FIG. 9 . 
     The solenoid consists of: a frame  136 , a mounting plate  133 , a plunger  137  with a washer  138 , E-ring  140 , end stop  134 , and coil  139 . The mounting plate  133  is mounted into the mortised part of door upward with mounting screws  141 . The plunger  137  projects into the channel  15  at an opening  35  on the top wall  17 . A hook  142  at the end of plunger  137  is slidably engaged into slot  103   b  of leaf spring  103 , by a method similar to insertion of rocker  116  to spring  103  in  FIG. 6 . 
     An action of energizing coil  139  will cause a pulling action by plunger  137 , and actuate the release mechanism  9 . This action can be done by means of a switch that temporarily connects the coil  137  to any suitable source of electricity energy for example a battery. Furthermore the switch can be related to an action of turning the door knob  31  (as in  FIG. 1 ), for example by installing a switch that can be activated by rotation of the door knob. The suitable source of electricity and means to activate the switch are well known to persons skilled in the art. 
       FIGS. 17A ,  17 B, and  17 C show partial front views of a displacement mechanism according to the second embodiment of the invention. To form a complete figure, join the right side of  FIG. 17A  to the left side of  FIG. 17B , and likewise join the right side of  FIG. 17B  to the left side of  FIG. 17C . 
     The release mechanism of this embodiment is referred to by numeral  60  and resembles the release mechanism  9  with several exceptions. Housing  24  resembles housing  7 , with the exception that housing  24  has a termination hole  1 . Shaft  112  is similar to shaft  10 , with the exception that shaft  112  does not have screw head  50  and grove  51 . Housing  24  is fixably mounted at hole  1  to channel  15  by means of mounting means similar to mounting means for end block  2  as described above with respect to  FIG. 4 . 
     Adjustment nut  11  with cushion  12 , is used to adjust the effective length of operation of the displacement mechanism by rotating it on the threaded end of shaft  114 . 
       FIG. 18  shows an alternative actuating mechanism for this embodiment using the operation of door knob  31 . The actuating mechanism consist of an adapter  28  (not shown in this figure) and an actuator  165 . The actuator has a housing  162  mounted in the bottom surface of door  21  by mounting screws  163 . The actuator consists of a shaft  164  having a threaded top end and a hexagonal shaped bottom  170 . The end of bottom  170  is provided with a hook form  171 . The hook  171  is slotted into slot of leaf spring  103 . The shaft is suspended at the lower part with washer  169  and a helical spring  176 . Its upper part passes through a sleeve  167  mounted in housing  162 . At the top most part of shaft  164 , it is connected to shaft  29  by shaft connector  30 . The actuator  165  is operable by knob  31  through adapter  28 . 
     Adapter  28  can be constructed similar to U.S. Pat. No. 6,030,008. An adaptation of the patent to fit this invention is shown in  FIG. 19 . 
     A pair of fastening plates  65  are provided with confining holes  66  and holes  72 . Confining holes  66  are confined into alignment rods  74 . Into holes  72  a rotary wheel  67  is provided with a through hole  68  and two moving teeth  64  engagable with projections  63  of two action arms  69 . The moving teeth  64  of rotary wheel  67  are actuated by door knob  31 , which is engaged with the through hole  68  by mean of spindle  73 , thereby causing the moving teeth to pull up either of the projections  63 , depending on the action of operation of the door knob. As it is seen from the side of door knob  31  in the figure, an action of turning the knob clockwise causes moving teeth  64  to move counterclockwise and engage with right hand side of action arm  69 . And vise versa, an action of turning the knob  31  counterclockwise, cause moving teeth  64  turn clockwise and engage with left hand side of action arms  69 . 
     A body  77  is provided at its lower end with an attachment hole  76  and a collar  75  at its upper end. The attachment hole  76  is provided for connection to shaft  29 . The shaft  29  is fastened to hole  76  by nuts  71  and slip ring  70 . The collar  75  rests on one side of rotary wheel  67 . 
     A spring loaded door latch  27  as shown in  FIG. 18  is operable by the door knob  31  in a way that it is mutually exclusive from adapter  28 . 
     The operation of this actuating mechanism from turning of door knob  31 , creates a pull-up action by shaft  29 , connector  30 , shaft  164 , and hook  171 . A cooperation of sleeve  167 , helical spring  176 , and washer  169  will push the hook  171  down, to reset the pull-up action by operation of actuation. 
       FIGS. 20 ,  21 ,  22 , and  23  show respectively operating stages one, two, three and four according to the second embodiment of the invention. Stage one represents the condition or position of the Automatic Door Bottom with a door in an open position, stage two represents its position with the door in an almost closed position. Stage three represents the position or condition of the Automatic Door Bottom with the door in its closed position, and stage four represents its condition with the door in its closed position and with the release mechanism activated. 
     As door  21  is closing, cushion  12  engages with jamb  26  causing spring  42  to flex and its associated sealing member  36  at the hinged side of the door to move downwardly until contact is made with sill  25 , as is shown in  FIG. 21 . 
     A further closing of door  21  will flex spring  43  and cause the sealing member  36  at the unhinged side of the door to come to contact sill  25  until the sealing member is completely in contact with sill  25  and door  21  is completely closed, as shown in  FIG. 22 . Springs  42  and  43  will retain a combined spring force F 3 . 
     With an actuation mechanism similar to that described with respect to  FIGS. 18 and 19 , the action of turning the door knob  31 , would activate release mechanism  165 . As result latch pin  102  releases the shaft  112  causing helical spring  8  to be depressed by force F 3 , and eventually retain force F 4 . The sealing members as significantly retracted into the channel  15 , as shown in  FIG. 23 . 
     According to this actuation mechanism stage one, two, three and four are normal routine stages of operation of the Automatic Door Bottom. The action of turning door knob  31  will actuate the release mechanism and a precursor to open the door  21 , or it can be an action just to actuate the release mechanism  60  without actually opening the door. 
     Furthermore, alternatives to actuate the release mechanism can be by means of mechanical lever as shown in  FIG. 5 , or by means of solenoids as shown in  FIGS. 15 and 16 . 
     The Automatic Door Bottom  22  according to the second embodiment can be surface mounted similar to  FIG. 3 , or it can be flush mounted similar to  FIG. 8 . 
       FIGS. 24   a ,  24   b  show partial views of the displacement mechanism with release mechanism according to the third embodiment of the invention. To form a complete figure, join the right side of  FIG. 24A  to the left side of  FIG. 24   b .  FIG. 24A  is the same as  FIG. 10A , with one exception, that it is connected to a connecting block  41 . The description of  FIG. 24   a  otherwise follows the same description for  FIG. 10   a.    
     The end block  2  is fixed to channel  15  by similar means as shown in  FIG. 6 . Housing  7  is connected with shaft  34  to connecting block  41  which in turn is connected to leaf spring  4 . As shown in  FIG. 25  a dimple  5  is coupled to sealing members  36  at in line holes at the rigid member  13  by means of pin  89 . This coupling restricts any lengthwise movement of sealing element  36 . The spring constant of leaf spring  4  is provided to be significantly larger that spring constant of helical spring  8 . 
       FIGS. 25 ,  26 , and  27  show respectively operating stages one, two, and three according to the third embodiment of the invention. Stage one represents the condition of the Automatic Door Bottom with a door in its open position, stage two represents the condition with the door in its closed position. Stage three represents the condition with the door in closed position but with the release mechanism activated. 
     During closing of the door  21 , at one point, cushion  132  will engage with jamb  26  causing the release mechanism to be driven into channel  15  along rails  18 . That movement causes spring  4  to flex, forcing sealing members  36  partially out of the lower section of the channel  15  until it contacts with door sill  15 . The location of the spring dimple  5  is arranged such that the portion of sealing member  36  from the coupling point toward the hinged side of the door is relatively longer than the portion of member  36  from the coupling toward the unhinged side. This arrangement is to assure that the portion of the sealing element  14  near the hinged side will contact the sill first, to minimize drag of sealing element  14  against the sill  25  during closing of door  21 .  FIG. 26  shows the second operating stage. Spring  4  will retain a spring force F 7 . An activation of release mechanism by means of actuation as described in  FIG. 5 ,  15 , or  18  will cause shaft  10  to unlatch to housing  7 , and spring  8  to be depressed and eventually retain force F 8 . F 8  is significantly smaller than F 7 .  FIG. 27  shows the third operating stage of the Automatic Door Bottom according to the third embodiment of the invention where door  21  is closed and sealing member  36  is retracted into channel  15 . When the door  21  is opened, cushion  132  disengages from jamb  26  and relieves pressure to shaft  10 . Retained force F 8  would cause the spring to spring and to pull shaft  10  out of housing  7  until its annular grove is latch again by latch pin  102 . The release mechanism  9  is thus reset. 
     All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. Although the invention has been described with reference to a specific and preferred embodiment and technique, it should be appreciated by one of skill in the art that many variations and modifications may be made within the scope of this invention. 
     While the above invention has been described with reference to certain preferred embodiments, the scope of the present invention is not limited to these embodiments. One skilled in the art may find variations of these preferred embodiments which, nevertheless, fall within the spirit of the present invention, whose scope is defined by the claims set forth below.