Patent Publication Number: US-7722092-B2

Title: Pipe joint device by flange

Description:
FIELD OF THE INVENTION 
   The present invention relates, in general, to pipe joint devices using flanges and, more particularly, to a pipe joint device using flanges which effectively maintains a jointed state of pipes regardless of an application of impact to the pipes owing to, for example, an earthquake, or regardless of displacement of the pipes due to temperature variation related to climate change. 
   BACKGROUND 
   Generally, pipe joint devices must firmly joint pipes and need to be easily and simply manipulated by workers on a site. To joint pipes together to provide a pipeline in the related art, pipes having appropriate lengths suitable for being manipulated by workers are arranged along a designed pipeline on a site and are jointed together through a welding process using pipe joints, such as reducers, tees and/or elbows. Furthermore, a valve may be installed in a jointed junction of the pipes when it is necessary to control the flow of fluid passing through the pipeline. Hereinbelow, a conventional technique of jointing a valve to a pipe using flanges will be described with reference to  FIG. 11 . As shown in the drawing, a flange  130  is welded to each of the pipe  110  and the valve  120 , and thereafter, the flange of the pipe is jointed to the flange of the valve using nuts and bolts  150  with a gasket  140  interposed between the two flanges. 
   The above-mentioned pipe jointing technique is advantageous in that it provides a firmly jointed state of the pipe and valve, but the technique is problematic in that cracks may be formed at the jointed junction to cause leakage of fluid from the junction. Furthermore, when the pipe jointing technique is adapted to a city water supply pipeline, the jointed junctions of the pipeline cannot accommodate displacement of pipes which may occur due to the extension and contraction of the pipes caused by temperature variation owing to climate change, or due to the application of impact to the pipes owing to, for example, an earthquake. Such displacement of the pipes may cause breakage of the pipeline, resulting in leakage and contamination of city water. Furthermore, the conventional pipe jointing technique may cause a gas explosion due to gas leakage when the technique is adapted to a gas pipeline, or may cause a safety accident and the loss of lives when the technique is adapted to a pipeline in a nuclear power plant. 
   In addition to the above-mentioned pipe jointing technique, another jointing technique using clamps and rubber packings has been widely used. However, this jointing technique is problematic in that jointed pipes may be removed from rubber packings when horizontal or vertical force is applied to the jointed pipes. In an effort to overcome the above-mentioned problem, a packing having an improved structure was proposed, which is provided with a ring-shaped channel along an inner surface thereof as shown in  FIG. 12 .  FIG. 13  shows pipes  110  jointed together using both the above-mentioned packing  160  and a clamp  170 . When horizontal force is applied to the jointed pipes to make the interval between the pipes wider, the packing  160  is elastically deformed to widen its channel A, thus maintaining its close contact state relative to the pipes  110 . When the horizontal force is removed from the pipes, the packing  160  elastically restores its original shape and returns the pipes to their original positions. The above-mentioned packing having the improved structure is advantageous in that the packing effectively maintains the sealed state of the jointed pipes regardless of an application of external force to the pipes and elastically returns the pipes to their original positions. However, the packing is problematic in that impurities may be deposited in the channel of the packing which could reduce the fluid transmission capacity of a pipeline and cause propagation of bacteria in the channel. Furthermore, the above-mentioned packing is specifically shaped to provide the channel as described above, so that the packing may fail to resist fluid pressure. 
   SUMMARY 
   Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a pipe joint device using flanges, which effectively maintains a jointed state of pipes regardless of an application of impact to the pipes owing to, for example, an earthquake, or regardless of displacement of the pipes caused by temperature variation due to climate change. 
   Another object of the present invention is to provide a pipe joint device using flanges, which is constructed to restore its operational function by being simply processed without being replaced with a new one, even when the pipe joint device becomes worn-out due to lengthy use. 
   In order to accomplish the above objects, the present invention provides a pipe joint device, comprising: flanges mounted to ends of pipes to be coupled together or ends of both a pipe and a pipe joint to be coupled together, the flange having at least one ring groove around an outer circumferential surface thereof; a packing mounted to the flanges and having inner rings around an inner circumferential surface thereof to closely engage with the ring grooves of the flanges; and a clamp having a packing seat to seat the packing therein, with a support sidewall formed by a radial inward extension of each side of the clamp, the clamp being divided into a plurality of clamp parts so that the clamp parts are placed around the packing and are fastened together by a locking member. 
   In the pipe joint device of the present invention, the packing may comprise a main channel formed along a central line of an outer circumferential surface of the packing, and the clamp may comprise a central rib formed on the packing seat to correspond to the main channel. 
   In the pipe joint device of the present invention, the packing may further comprise one or more side channels symmetrically formed around the outer circumferential surface of the packing on opposite sides of the main channel, and the clamp may further comprise one or more side ribs formed on the packing seat to correspond to the side channels. 
   In the pipe joint device of the present invention, the pipe joint may be selected from the group consisting of a valve, a reducer, a tee and an elbow. 
   In the pipe joint device of the present invention, the flanges may be mounted to the ends of the pipes or to the ends of the pipe and the pipe joint through a welding process. 
   In the pipe joint device of the present invention, the flanges may be stopped by the support sidewalls of the clamp so that the pipes or the pipe and the pipe joint are prevented from being removed from the clamp. 
   In the pipe joint device of the present invention, each of the flanges may be provided with a support groove around the outer circumferential surface thereof so that the support sidewalls of the clamp are seated in the ring-shaped support grooves of the flanges to prevent the pipes or the pipe and the pipe joint from being removed from the clamp. 
   In the pipe joint device of the present invention, the packing may have at least one circumferential hollow therein. 
   In the pipe joint device of the present invention, the circumferential hollow may comprise two or more circumferential hollows which are symmetrically formed in opposite sides of the packing. 
   The pipe joint device of the present invention may further comprise an anti-friction member made of metal and covering a whole area or a part of the outer circumferential surface of the packing to reduce friction between the clamp parts and a deformed part of the packing while the clamp parts are fastened together around the packing. 
   The pipe joint device of the present invention may further comprise an adjusting member inserted into each of the support sidewalls of the clamp to compress the packing, placed between the support sidewalls of the clamp, in a direction of thickness of the packing. 
   The pipe joint device of the present invention may further comprise a metal ring placed between each side surface of the packing and an associated support sidewall of the clamp to evenly transmit compression force to each side surface of the packing when the adjusting member is tightened to compress the packing. 
   According to the present invention, a flange having a ring groove is mounted on an end of each pipe, and thereafter, the pipes having the flanges are jointed together using a packing and clamps. Thus, the pipe joint device effectively maintains the jointed state of the pipes regardless of an application of impact to the pipes owing to, for example, an earthquake, or regardless of displacement of the pipes caused by temperature variation due to climate change. The pipe joint device also elastically returns the pipes to their original positions when the external force is removed from the pipes. Thus, the pipe joint device prevents breakage of a jointed junction of pipes and thereby prevents leakage of fluid from the jointed junction. 
   Furthermore, the packing and clamps have channels and ribs, respectively, so that the clamps more effectively hold the packing. Thus, the operational function caused by engagement of the inner ring of the packing with the ring groove of the flange is enhanced. 
   The packing has a circumferential hollow therein, thus increasing the flexibility thereof to be more easily deformed and more easily restore its original shape. Due to the circumferential hollow in the packing, the operational function of an adjusting member is enhanced. 
   Furthermore, it is preferred to shape the packing and the clamps such that the size of the clamps is smaller than the packing so as to allow the inner ring to be in closer contact with the ring groove. In this case, an anti-friction member made of metal and having a smooth surface is preferably used to allow the clamps to be easily fastened together. 
   In addition, when the operational function of the pipe joint device is reduced due to lengthy use, it is possible to restore the operational function of the pipe joint device to some extent by tightening the adjusting member. When a plurality of adjusting members is provided on the pipe joint device, the above-mentioned effect is enhanced. Furthermore, as a metal ring is provided in the pipe joint device, the compression force can be evenly applied from the adjusting members to the sidewalls of the packing when the adjusting members are tightened to compress the packing. 
   Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the figures. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a partially broken, exploded perspective view of a packing according to an embodiment of the present invention, and  FIG. 2  is a partially broken, exploded perspective view of a packing according to another embodiment of the present invention; 
       FIG. 3  is a side view of a pipe joint device according to the present invention, which is in a state of jointing pipes together; 
       FIG. 4  is an exploded perspective view of a pipe joint device having the packing of  FIG. 1 ; 
       FIG. 5  is an exploded perspective view of a pipe joint device having the packing of  FIG. 2 ; 
       FIG. 6  is a sectional view of the pipe joint device of  FIG. 5 , which is assembled to joint pipes together; 
       FIG. 7  is a sectional view of a pipe joint device according to a further embodiment of the present invention, which is assembled to joint pipes together; 
       FIG. 8  is a sectional view showing operation of the pipe joint device of  FIG. 7  when horizontal force is applied to the jointed pipes; 
       FIG. 9  is a front view of the assembled pipe joint device of  FIG. 5 , and  FIG. 10  is an enlarged sectional view of a specified part of the pipe joint device; and 
       FIG. 11  is a view of a conventional pipe joint device. 
       FIGS. 12 and 13  are views of a conventional packing and a pipe joint device using the conventional packing, respectively. 
   

   DETAILED DESCRIPTION 
   As shown in  FIGS. 1 and 2 , a packing according to the present invention is constructed as follows. The packing  20  according to the present invention comprises a main channel  23  or a combination of a main channel  23  and a side channel  23   a , which is formed around an outer circumferential surface of the packing  20 . The side channel  23   a  may comprise one or more side channels symmetrically formed around the outer circumferential surface of the packing  20  on opposite sides of the main channel  23 . The packing  20  further comprises a circumferential hollow  22  and an inner ring  21 . The inner ring  21  is formed around an inner circumferential surface of the packing  20  to closely engage with a ring groove  12  of a flange. The circumferential hollow  22  may comprise a single hollow, which has an elliptical cross-section and is formed along a center circumferential axis of the packing  20 , or two or more hollows which are symmetrically formed in the packing  20  while extending along opposite sides of the center circumferential axis. Of course, the size of the circumferential hollow  22  may be variously changed according to the size of the packing  20  and other design factors. In addition, the inner ring  21  may comprise two or more rings symmetrically placed on opposite sides of the inner surface of the packing  20 . Alternatively, the packing  20  may be configured without an inner ring as will be described later herein because the operational effect expected from engagement of the ring groove  12  of the flange with the inner ring  21  of the packing  20  can be accomplished only by the ring groove  12  of the flange during the engagement of the packing  20  with the flange. 
   In the present invention, an anti-friction member  60  made of metal covers the circumferential outer surface of the packing  20 . The anti-friction member  60  may cover the whole area or a part of the outer circumferential surface of the packing  20 . In that case, the phrase “the covering of the anti-friction member  60  on a part of the packing  20 ” means that the anti-friction member  60  covers only a deformed part  24  which is formed on the packing  20  when clamps  30  are fastened together around the packing  20 . The anti-friction member  60  may be fastened to the packing  20  through a variety of fastening methods, for example, a fastening method using an adhesive. Particularly, when the anti-friction member  60  is designed to cover only the deformed part  24  of the packing  20 , the anti-friction member  60  may be conveniently fastened to the packing  20  by force-fitting the anti-friction member  60  over the packing  20 . In the meantime, when the anti-friction member  60  is designed to cover the whole area or most of the outer circumferential surface of the packing  20 , the anti-friction member  60  may be cut to form a discontinuous ring shape which allows the anti-friction member  60  to be easily fitted over the packing  20 . Furthermore, when the anti-friction member  60  is used with a packing  20  which has the main channel  23  or the combination of the main channel  23  and the side channel  23   a  as shown in the drawings, the anti-friction member  60  must have a shape corresponding to the shape of the packing  20 . In that case, the anti-friction member  60  can be easily fastened to the whole area or a part of the outer circumferential surface of the packing  20  by fitting the anti-friction member  60  over the packing  20  while aligning the uneven surface of the anti-friction member  60  with the uneven surface of the packing  20 . 
   The operation of the anti-friction member  60  will be described hereinbelow with reference to  FIG. 3 . When the clamps  30  are placed around the packing  20  and are fastened together by locking members  34 , the packing  20  is deformed to make the deformed part  24 . High friction is generated at the junctions between the deformed part  24  and the clamps  30  so that it is very difficult to fasten the clamps  30  together around the deformed part  24  using the locking members  34 . Particularly, the packing  20  is made of rubber that generates high friction due to its intrinsic properties, so that execution of the pipe jointing work is very difficult due to the deformed part  24 . However, when the anti-friction member  60  covers the deformed part  24 , the clamps  30  may be easily fastened together by the locking members  34  regardless of the deformed part  24 . Thus, in the present invention, the anti-friction member  60  covers the whole area or a part of the outer circumferential surface of the packing  20 . Particularly when the anti-friction member  60  is designed to cover a part of the outer circumferential surface of the packing  20 , the anti-friction member  60  may comprise a plurality of members that are placed at the junction of the clamps  30  where the clamps  30  are fastened together. Alternatively, the anti-friction member  60  may comprise a single member that is placed at the junction of the clamps  30 . 
     FIG. 4  shows the construction of a pipe joint device having the packing and the anti-friction member of  FIG. 1 . As shown in the drawing, the pipe joint device of the present invention comprises two flanges  11 , the packing  20 , the clamps  30  and adjusting members  40 . 
   The two flanges  11  are fixed to the outer surfaces of the ends of pipes  10  through, for example, a welding process. A ring groove  12  is provided around the outer circumferential surface of each of the two flanges  11 . When the flanges  11  are used with a packing that does not have any inner ring  21 , the ring grooves  12  of the flanges  11  are brought into close contact with the inner circumferential surface of the packing  20 . However, if the flanges  11  are used with a packing having inner rings  21 , the ring groove  12  of each flange  11  closely engages with the associated inner ring  21 . Thus, when the flanges  11  are used with the packing  20  having inner rings  21 , the number and intervals of the ring grooves  12  of the flanges  11  must be designed to correspond to those of the inner rings  21  of the packing  20 . 
   In the present invention, ring grooves may be formed around the outer circumferential surface of the ends of the pipes  10 . In that case, the pipes  10  may be jointed together without using the flanges, so that the ends of the pipes  10  having the ring grooves are directly inserted into opposite ends of the packing  20  to achieve the operational effect expected from the use of the flanges. 
   The packing  20  and the anti-friction member  60  of the present invention are configured as described above. In the above-mentioned embodiment, two inner rings  21  are formed around the inner circumferential surface of the packing  20  because the flanges  11  which are placed in the packing  20  each have one ring groove  12 . 
   Each of the clamps  30  has a packing seat  31  along an inner surface thereof. Both sides of each clamp  30 , which define the packing seat  31  between them, extend inwards in radial directions to form support sidewalls  33 , the inner diameter of which is smaller than the diameter of the packing seat  31 . The support sidewalls  33  of the clamps  30  stop the outside ends of the flanges  11  so that the pipes  10  are not undesirably removed from the packing  20  or the clamps  30 . The packing seat  31  is provided with a central rib  32  which is formed along the packing seat  31  to engage with the main channel  23  of the packing  20 . In the present invention, the pipe joint device has two or three clamps  30  having the same shape formed by dividing a circular clamp body into two or three parts at the same angular intervals. The clamps  30  are placed around the packing  20  and are fastened together by the locking members  34 , such as nuts and bolts, thus jointing the pipes  10  together. 
   The adjusting members  40  comprise setscrews that are threaded into the support sidewalls  33  of the clamps  30  to be tightened or loosened by workers. 
     FIG. 5  shows the construction of a pipe joint device having the packing and the anti-friction member of  FIG. 2 . As shown in the drawing, the pipe joint device of this embodiment comprises side channels  23   a  as well as the main channel  23  on the outer circumferential surface of the packing  20 , unlike the embodiment of  FIG. 4 . The side channels  23   a  are formed on opposite sides of the main channel  23 . To correspond to the structure of the packing  20 , each of the clamps  30  is provided with side ribs  32   a  which are formed along the packing seat  31  on opposite sides of the central rib  32  to engage with the side channels  23   a  of the packing  20 . Furthermore, each of the two flanges  11  has two ring grooves  12  so that four inner rings  21  are formed along the inner circumferential surface of the packing  20  so as to correspond to the four ring grooves  12  of the two flanges  11 . The anti-friction member  60  according to this embodiment has a smaller surface area than that of  FIG. 4  so that the anti-friction member  60  covers only the deformed part  24  of the packing  20 . The remaining elements of the pipe joint device of this embodiment are the same as those of  FIG. 4 . 
     FIG. 6  shows the pipe joint device of  FIG. 5 , which is assembled to joint pipes together. To joint pipes  10  together using the pipe joint device, the two flanges  11  are mounted to the ends of the pipes  10 , and are fixed to the ends through, for example, a welding process. Thereafter, the ends of the pipes  10  having the flanges  11  are inserted into opposite ends of the packing  20  which is covered with the anti-friction member  60  on the whole area or a part of the outer circumferential surface thereof. In that case, if the packing  20  has the inner rings  21 , the position of the packing  20  must be adjusted so that the inner rings  21  are brought into close contact with the ring grooves  12  of the flanges  11 . However, if the packing  20  does not have any inner ring  21 , positional adjustment of the packing  20  is not necessary. Thereafter, the clamps  30  are placed around the packing  20  with a metal ring  50  interposed between each sidewall of the packing  20  and the inner surfaces of the clamps  30 , and are fastened together by the locking members  34 , thus jointing the pipes  10  together. The metal ring  50  may be previously mounted to each sidewall of the packing  20  or may be separately produced and placed on each sidewall of the packing  20  before the clamping process. While the clamps  30  are fastened together as described above, the position of the junction of the clamps  30  is preferably adjusted to form a deformed part  24  on a part of the packing  20  on which the anti-friction member  60  is placed. Thus, the pipe jointing work is easily executed. Furthermore, the support sidewalls  33  of the clamps  30  stop the outside ends of the flanges  11  so that the pipes  10  are not undesirably removed from the clamps  30 . 
   When a packing  20  without an inner ring  21  is used, the inner surface of the packing  20  made of a soft material, such as rubber, is elastically deformed to fill the ring grooves  12  of the flanges  11  in response to compression force applied thereto by the fastened clamps  30 . In other words, parts of the inner surface of the packing  20  protrude to form protrusions similar to the inner rings  21 . Therefore, the operational effect expected from engagement of the ring grooves  12  with the inner rings  21  can be accomplished by a packing  20  without an inner ring  20 . Furthermore, when the packing  20  is compressed by the adjusting members  40 , the inner rings  21  or protrusions, which are formed on the deformed packing  20  and have a shape similar to the inner rings  21 , can more closely engage with the ring grooves  12 . The above-mentioned effect is more prominently revealed when the size of the clamps  30  is slightly smaller than the packing  20 . However, when the clamps  30  in the above case are fastened together, the deformed part  24  of the packing  20  becomes larger to increase friction. Thus, the anti-friction member  60  must be used in that case. 
     FIG. 7  shows a pipe joint device according to a further embodiment of the present invention. As shown in the drawing, the general construction and engagement of elements of this embodiment remains the same as the embodiment of  FIG. 6 , but a ring-shaped support groove  13  is formed around the outer circumferential surface of each flange  11  so that the support sidewalls  33  of the clamps  30  are seated in the ring-shaped support grooves  13  of the flanges  11 . 
     FIG. 8  shows operation of the pipe joint device of the present invention when horizontal force is applied to the jointed pipes owing to, for example, an earthquake or the pipes are elongated due to temperature variation related to climate change. 
   When no external force is applied to the pipe joint device of the present invention which joints two pipes  10   a  and  10   b  together, the inner rings  21   a  and  21   b  and the ring grooves  12   a  and  12   b  of the parts A and B of the drawing maintain their engagement while being in close contact with each other throughout the whole surfaces thereof. However, when a leftward force is applied to the right-hand side pipe  10   b , the right-hand side pipe  10   b  and the associated flange move to the right, while the left-hand side pipe  10   a  and the packing and clamp are maintained in their places. Thus, the inner rings  21   b  and the ring grooves  12   b  of the part B are spaced apart from each other, while the inner rings  21   a  and the ring grooves  12   a  of the part A maintain their engagement in which the rings  21   a  and grooves  12   a  are in close contact with each other throughout the whole surfaces thereof. In a detailed description, in response to the rightward force, the inner rings  21   b  of the part B are deformed such that each of the inner rings  21   b  is spaced apart from the right-hand side surface of the associated ring groove  12   b  while being compressed into the left-hand side surface of the ring groove  12   b . Furthermore, the packing has circumferential hollows therein so that the flexibility of the packing is increased to allow the packing to be more easily deformed. In addition, the support sidewalls of the clamps are seated in the ring-shaped support grooves of the flanges, thus preventing the pipes from being removed from the pipe joint device. 
   When the leftward force is no longer applied to the right-hand side pipe  10   b , the pipe  10   b  elastically moves leftwards to restore its original position owing to the elastic restoring force of the deformed inner rings  21   b . The inner rings  21   b  are brought into close contact with the ring grooves  12   b  throughout the whole surfaces thereof. As described above, due to the engagement of the inner rings  21   a  and  21   b  with the ring grooves  12   a  and  12   b , the pipe joint device of the present invention maintains the jointed state of pipes regardless of an application of horizontal extension or compression force to the pipes. Furthermore, when the external force is no longer applied to the pipes, the pipes are elastically returned to their original positions. 
   The pipe joint device according to the present invention also operates in a similar manner to maintain the jointed state of pipes regardless of an application of vertical force to the pipes. 
   When a predetermined lengthy period has passed after jointing pipes together using the pipe joint device of the present invention, elasticity of the inner rings  21  is reduced. Thus, the above-mentioned operational function of the pipe joint device is reduced. In that case, the operational function of the pipe joint device can be restored to some extent by tightening the adjusting members  40 . 
   As shown in  FIG. 9 , the number of adjusting members  40  may change according to the size of the pipes  10  and other design factors. In the present invention, the adjusting members  40  are preferably mounted on each support sidewall  33  of the clamps  30  at symmetrically opposite positions. Most preferably, eight adjusting members  40  are mounted on the support sidewalls  33  of the clamps  30  such that four adjusting members  40  are mounted on opposite sidewalls of each clamp  30 . 
     FIG. 10  shows a state in which the adjusting members  40  are tightened to compress the packing  20 , thus causing the inner rings  21  to come into closer contact with the ring grooves  12 . As shown in the drawing, a metal ring  50  is placed between the packing  20  and the adjusting members  40  on each side of the pipe joint device. Due to the metal rings  50 , the compression force from the adjusting members  40  is evenly applied to the sidewalls of the packing  20  when the adjusting members  20  are tightened to compress the packing  20 . In an effort to accomplish the above-mentioned operation, the metal rings  50  preferably have a shape capable of filling the hollow defined between each sidewall of the packing and the associated support sidewall  33  of the clamps. 
   As described above, the present invention provides a pipe joint device. To joint pipes together using the pipe joint device of the present invention, a flange having a ring groove is mounted on an end of each pipe, and thereafter, the pipes having the flanges are jointed together using a packing and clamps. Thus, the pipe joint device effectively maintains the jointed state of the pipes regardless of an application of impact to the pipes owing to, for example, an earthquake, or regardless of displacement of the pipes caused by temperature variation due to climate change. The pipe joint device also elastically returns the pipes to their original positions when the external force is removed from the pipes. Thus, the pipe joint device prevents breakage of a jointed junction of pipes and thereby prevents leakage of fluid from the jointed junction. 
   Furthermore, the packing and clamps have channels and ribs, respectively, so that the clamps more effectively hold the packing. Thus, the operational function caused by engagement of the inner ring of the packing with the ring groove of the flange is enhanced. 
   The packing has a circumferential hollow therein, thus increasing the flexibility thereof to be more easily deformed and more easily restore its original shape. Due to the circumferential hollow in the packing, the operational function of an adjusting member is enhanced. 
   Furthermore, it is preferred to shape the packing and the clamps such that the size of the clamps is smaller than the packing so as to allow the inner ring to be in closer contact with the ring groove. In this case, an anti-friction member made of metal and having a smooth surface is preferably used to allow the clamps to be easily fastened together. 
   In addition, when the operational function of the pipe joint device is reduced due to lengthy use, it is possible to restore the operational function of the pipe joint device to some extent by tightening the adjusting member. When a plurality of adjusting members is provided on the pipe joint device, the above-mentioned effect is enhanced. Furthermore, as a metal ring is provided in the pipe joint device, the compression force can be evenly applied from the adjusting members to the sidewalls of the packing when the adjusting members are tightened to compress the packing. 
   It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.