Patent Publication Number: US-2019178592-A1

Title: Coolant distribution unit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 62/597,963 filed Dec. 13, 2017, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a field of a coolant distribution unit (CDU), and more particularly to a coolant distribution unit for a machine room/rack cabinet liquid cooling system. 
     BACKGROUND OF THE INVENTION 
     With the increasing development and popularization of science and technology, various electronic computing devices such as network storage devices or servers have been essential parts of people&#39;s daily lives. Generally, these electronic computing devices are stored in a rack cabinet that is made of cold-rolled steel or alloy. Consequently, these electronic computing devices are protected from electromagnetic interference and arranged in an orderly and neat manner. Moreover, the electronic computing devices in the rack cabinet can be easily maintained or repaired in the future. 
     With the advent of big data and the Internet era, the processing power of the electronic computing device is increasing and the amount of the generated heat is large. It is important to effectively dissipate the heat from the electronic computing devices in the rack cabinet so as to increase the performance and the use lives of these electronic computing devices. In views of the power-saving benefit, it is important to achieve the proper heat dissipation efficacy with less power consumption. 
       FIG. 1  schematically illustrates the architecture of a conventional rack-type heat dissipation system. As shown in  FIG. 1 , the conventional rack-type heat dissipation system  7  comprises plural cold plates  71 , a manifold device  72 , a coolant distribution unit (CDU)  75  and a chiller  76 . The manifold device  72  comprises a first fluid manifold  77  and a second fluid manifold  78 . The plural cold plates  71  correspond to plural electronic computing devices  9  in a rack cabinet (not shown). For example, each cold plate  71  is in thermal contact with the heat source of the corresponding electronic computing device  9 . Each cold plate  71  comprises a cold plate inlet  711  and a cold plate outlet  712 . The first fluid manifold  77  comprises a first manifold inlet  771  and plural first manifold outlets  772  corresponding to the plural cold plates  71 . The second fluid manifold  78  comprises plural second manifold inlets  781  corresponding to the plural cold plates  71  and a second manifold outlet  782 . The coolant distribution unit  75  comprises a first fluid inlet  751 , a first fluid outlet  752 , a second fluid inlet  753  and a second fluid outlet  754 . The chiller  76  comprises a chiller inlet  761  and a chiller outlet  762 . 
     The cold plate inlet  711  of each cold plate  71  is in fluid communication with the corresponding first manifold outlet  772  of the first fluid manifold  77 . The cold plate outlet  712  of each cold plate  71  is in fluid communication with the corresponding second manifold inlet  781  of the second fluid manifold  78 . The first fluid inlet  751  of the coolant distribution unit  75  is in communication with the second manifold outlet  782  of the second fluid manifold  78 . The first fluid outlet  752  of the coolant distribution unit  75  is in communication with the first manifold inlet  771  of the first fluid manifold  77 . In other words, a first fluid circulation loop (also referred as an internal circulation loop) is defined by the plural cold plates  71 , the manifold device  72  and the coolant distribution unit  75  collaboratively. 
     A first working fluid (not shown) is filled in the first fluid circulation loop. In the rack-type heat dissipation system  7 , the manifold device  72  is used for connecting associated conduits, homogenizing the first working fluid and transferring the first working fluid. The coolant distribution unit  75  is capable of uniformly or intelligently transferring the first working fluid to the cold plates  71  through the first fluid manifold  77  of the manifold device  72  according to the practical requirements. 
     The chiller inlet  761  of the chiller  76  is in fluid communication with the second fluid outlet  754  of the coolant distribution unit  75 . The chiller outlet  762  of the chiller  76  is in fluid communication with the second fluid inlet  753  of the coolant distribution unit  75 . That is, a second fluid circulation loop (also referred as an external circulation loop) is defined by the chiller  76  and the coolant distribution unit  75  collaboratively. Moreover, a second working fluid (not shown) is filled in the second fluid circulation loop. The chiller  76  may be considered as a back-end heat dissipation mechanism for removing the heat from the first working fluid that is transferred through the first fluid circulation loop. That is, the first working fluid in the first fluid circulation loop and the second working fluid in the second fluid circulation loop exchange heat in the coolant distribution unit  75 , wherein the first working fluid and the second working fluid are not mixed together. 
     The operations of the conventional rack-type heat dissipation system  7  will be described as follows. When the first working fluid flows through the cold plate  71  along the first fluid circulation loop, the first working fluid is heated by the heat source of the electronic computing device  9  corresponding to the cold plate  71 . Then, the heated first working fluid is transferred to the coolant distribution unit  75  through the second fluid manifold  78  of the manifold device  72 . When the second working fluid flows through the coolant distribution unit  75  along the second fluid circulation loop, the second working fluid is heated by the first working fluid that is introduced into the coolant distribution unit  75 . After the heated second working fluid is outputted from the coolant distribution unit  75 , the second working fluid is transferred to the chiller  76  through the chiller inlet  761 . Consequently, the second working fluid is cooled down. After the second working fluid is cooled down, the second working fluid is transferred to the coolant distribution unit  75  again. Since the first working fluid flowing into the coolant distribution unit  75  along the first fluid circulation loop exchanges heat with the second working fluid, the first working fluid is cooled down. After the first working fluid is cooled down, the first working fluid is transferred to the cold plate  71  again through the first fluid manifold  77  of the manifold device  72 . The above steps are repeatedly done to circulate the first working fluid along the first fluid circulation loop and circulate the second working fluid along the second fluid circulation loop. Since the heat of the electronic computing device  9  is dissipated to the low-temperature site, the efficacy of reducing the temperature of the first working fluid is enhanced. 
     However, as the science and technology change very quickly, the rack cabinets for storing the electronic computing devices  9  have diversified specifications and designs according to different requirements. Even if the rack cabinets comply with the same specifications, the heat dissipation demands are not always identical. In other words, the conventional rack-type heat dissipation system  7  still has some drawbacks. For example, in case that the rack cabinet or the electronic computing devices  9  is abnormal and a great deal of heat is abruptly increased, the coolant distribution unit  75  is unable to adjust the flowrate of the working fluid according to the specification of the rack cabinet. Under this circumstance, the heat dissipating capacities of some rack cabinets in some abnormal situations are insufficient. Therefore, it is important to overcome the above drawbacks. 
     SUMMARY OF THE INVENTION 
     For increasing the application value of the coolant distribution unit, the present invention provides a novel coolant distribution unit. The coolant distribution unit has the function of adaptively adjusting the flowrate of a working fluid. Consequently, the energy utilization of the coolant distribution unit is optimized. 
     For increasing the application value of the coolant distribution unit, the present invention provides a novel coolant distribution unit. The coolant distribution unit comprises an adaptive control module. The data about the operating situation of the coolant distribution unit are transmitted to an external device through the adaptive control module. Consequently, the supervisor at the remote side can realize the operating situation of the coolant distribution unit in real time and further control the operating situation of the coolant distribution unit. 
     In accordance with an aspect of the present invention, there is provided a coolant distribution unit. The coolant distribution unit includes plural fluid inlets, plural fluid outlets and a piping channel. The piping channel is connected with the fluid inlets and the fluid outlets. The coolant distribution unit includes a sensing module, a flowrate control module and an adaptive control module. The sensing module senses at least one of the fluid inlets, the fluid outlets and the piping channel to obtain a sensed data. The flowrate control module controls a flowrate of a working fluid in the piping channel. The adaptive control module is electrically connected with the sensing module and the flowrate control module. The adaptive control module receives the sensed data and transmits the sensed data to an external device. The external device issues a control command to the adaptive control module according to the sensed data. The adaptive control module controls an operation of the flowrate control module according to the control command. 
     In accordance with another aspect of the present invention, there is provided a coolant distribution unit. The coolant distribution unit includes plural fluid inlets, plural fluid outlets and a piping channel. The piping channel is connected with the fluid inlets and the fluid outlets. The coolant distribution unit includes a sensing module, a flowrate control module and an adaptive control module. The sensing module senses at least one of the fluid inlets, the fluid outlets and the piping channel to obtain a sensed data. The flowrate control module controls a flowrate of a working fluid in the piping channel. The adaptive control module is electrically connected with the sensing module and the flowrate control module. The adaptive control module receives the sensed data. The adaptive control module controls an operation of the flowrate control module according to the sensed data. 
     The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates the architecture of a conventional rack-type heat dissipation system; 
         FIG. 2  is a schematic functional block diagram illustrating the concepts of a coolant distribution unit according to an embodiment of the present invention; 
         FIG. 3  is a schematic functional block diagram illustrating the detailed architecture of the coolant distribution unit as shown in  FIG. 2 ; 
         FIG. 4  is a schematic functional block diagram illustrating the detailed architecture of a coolant distribution unit according to another embodiment of the present invention; 
         FIG. 5  is a schematic functional block diagram illustrating the detailed architecture of a coolant distribution unit according to another embodiment of the present invention; and 
         FIG. 6  is a schematic functional block diagram illustrating the concepts of a coolant distribution unit according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For illustration, the structures, organizations or components of the coolant distribution unit shown in the drawings of the present invention are in scale with the elements of the practical product. According to the requirements of descriptions, the components may be scaled up or scaled down in an unequal proportion. The implementations of the coolant distribution unit not limited by the drawings. 
     In this context, the working fluid is the fluid that is used in a heat exchanger and is in the liquid sate in the normal temperature. Generally, water is the widely-used fluid. It is noted that the example of the working fluid is not restricted. In other embodiments, the working fluid is aqueous solution or other organic solution. At different temperatures, the working fluid has the corresponding vapor-liquid equilibrium pressures. The working fluid retained in, transferred through or moved across the piping channel or the overall system is a liquid-state fluid. In practice, the working fluid may be a gaseous working fluid. 
     Please refer to  FIG. 2  and  FIG. 3 .  FIG. 2  is a schematic functional block diagram illustrating the concepts of a coolant distribution unit according to an embodiment of the present invention.  FIG. 3  is a schematic functional block diagram illustrating the detailed architecture of the coolant distribution unit as shown in  FIG. 2 . 
     As shown in  FIG. 2 , the coolant distribution unit  2  comprises a sensing module  16 , a flowrate control module  18 , an adaptive control module  20  and a heat exchange module  21 . Generally, the coolant distribution unit  2  has two fluid inlets and two fluid outlets. For example, the coolant distribution unit  2  comprises a first fluid inlet  11 , a second fluid inlet  13 , a second fluid outlet  15  and a second fluid outlet  17 . The first fluid inlet  11 , the second fluid inlet  13 , the second fluid outlet  15  and the second fluid outlet  17  are in fluid communication with each other through a piping channel  19 . A working fluid can be transferred through the piping channel  19 . The sensing module  16  is used for sensing at least one of the fluid inlets  11 ,  13 , the fluid outlets  15 ,  17  and the piping channel  19  to acquire associated sensed data (e.g., the temperature value, the flowrate value or the pressure value). The flowrate control module  18  is used for controlling the flowrate of the working fluid that is transferred through the piping channel  19 . The adaptive control module  20  is electrically connected with the sensing module  16  and the flowrate control module  18 . The adaptive control module  20  receives the sensed data from the sensing module  16  and transmits the sensed data to an external monitoring center  24  outside the coolant distribution unit  2 . According to the sensed data, the monitoring center  24  issues a control command to the adaptive control module  20 . According to the control command, the adaptive control module  20  controls the operating situation of the flowrate control module  18 . The heat exchange module  21  is connected with the piping channel  19 . Moreover, the heat exchange module  21  is in fluid connected with the fluid inlets  11 ,  13  and the fluid outlets  15 ,  17  through the piping channel  19 . 
     As shown in  FIG. 3 , the heat exchange module  21  comprises a heat exchanger  10 , a fluid storage module  12  and a power module  14 . The high temperature working fluid  31  from plural chassis (not shown) is received by the first fluid inlet  11 . The low temperature working fluid  33  from the external device (e.g., the chiller as shown in  FIG. 1 ) and without carrying waste heat is introduced into the coolant distribution unit  2  through the second fluid inlet  13 . After the high temperature working fluid  31  is transferred through the heat exchanger  10 , the fluid storage module  12  and the power module  14  sequentially and cooled down, the low temperature working fluid  35  is outputted from the coolant distribution unit  2  through the first fluid outlet  15 . After the low temperature working fluid  33  is transferred through the heat exchanger  10 , the high temperature working fluid  37  with the waste heat is outputted from the second fluid outlet  17 . Consequently, the path from the first fluid inlet  11  to the first fluid outlet  15  may be considered as an internal circulation loop of the coolant distribution unit  2 , and the path from the second fluid inlet  13  to the second fluid outlet  17  may be considered as an external circulation loop of the coolant distribution unit  2 . In this context, the high temperature and the low temperature are exemplified for comparison only. For example, the temperature of the high temperature working fluid  31  is higher than the temperature of the low temperature working fluid  33 , and the temperature of the high temperature working fluid  37  is higher than the temperature of the low temperature working fluid  33 . 
     Please refer to  FIG. 3  again. The heat exchanger  10  is a plate-type heat exchanger for transferring the heat between the high temperature working fluid  31  and the low temperature working fluid  33 . That is, the heat from the chassis and carried by the high temperature working fluid  31  is transferred to the low temperature working fluid  33 . After the waste heat from the chassis is carried by the low temperature working fluid  33 , the low temperature working fluid  33  becomes the high temperature working fluid  37 . After the high temperature working fluid  31  is transferred through the heat exchanger  10 , the high temperature working fluid  31  becomes the working fluid  39 . The working fluid  39  is introduced into the fluid storage module  12  for storage. The temperature of the working fluid  39  is lower than the temperature of the high temperature working fluid  31 . It is preferred that the occupied space of the heat exchanger  10  of the coolant distribution unit  2  is small. Consequently, the heat exchanger  10  is not restricted to the plate-type heat exchanger. After the working fluid  39  is left from the heat exchanger  10 , the working fluid  39  is temporarily stored in the fluid storage module  12 . That is, the fluid storage module  12  is a buffer tank. For example, the fluid storage module  12  is a water storage tank or a liquid storage tank with an arbitrary geometric shape. The fluid storage module  12  is made of a material that is unable to react with the working fluid (e.g., stainless steel). The power module  14  comprises one or plural pumps. The power module  14  provides motive power to move the low temperature working fluid  35  from the fluid storage module  12  to the first fluid outlet  15  and then discharge the low temperature working fluid  35 . 
     In this embodiment, the fluid storage module  12  is arranged between the heat exchanger  10  and the power module  14 , but is not limited thereto. In some other embodiments, the positions of the fluid storage module  12  and the power module  14  are exchanged. That is, the power module  14  is arranged between the heat exchanger  10  and the fluid storage module  12 . 
     Please refer to  FIG. 3  again. The sensing module  16  and the flowrate control module  18  are located at proper positions of the coolant distribution unit  2 . The sensing module  16  and the flowrate control module  18  are in communication with the adaptive control module  20 . In an embodiment, the sensing module  16  comprises one or plural thermal sensors  62 . The thermal sensors  62  are located at the positions that the working fluid is transferred through. The flowrate control module  18  comprises at least one proportional valve  86 . The at least one proportional valve  86  is arranged in the piping channel  19  and located near the second fluid inlet  13 . In this embodiment, the plural thermal sensors  62  are arranged in the piping channel  19  and located near the first fluid inlet  11 , arranged in the piping channel  19  and located near the second fluid inlet  13 , arranged in the piping channel  19  and located near the first fluid outlet  15 , and arranged in the piping channel  19  and located near the second fluid outlet  17 . That is, the thermal sensors  62  are used for sensing the high temperature working fluid  31 , the low temperature working fluid  33 , the low temperature working fluid  35  and the high temperature working fluid  37 . The positions of the thermal sensors  62  and the proportional valve  86  are not restricted. In some other embodiments, the thermal sensor  62  is arranged in the piping channel  19  and located near the first fluid inlet  11  only, or arranged in the piping channel  19  and located near the second fluid inlet  13  only, or arranged in the piping channel  19  and located near the first fluid outlet  15  only, or arranged in the piping channel  19  and located near the second fluid outlet  17  only. In some other embodiments, the proportional valve  86  is arranged in the piping channel  19  and located near the first fluid inlet  11  only. Alternatively, other thermal sensors  62  may be arranged in the piping system of the coolant distribution unit  2 . The temperature value of the working fluid sensed by the sensing module  16  is transmitted to the adaptive control module  20  in a wired communication manner. Alternatively, the sensed temperature value is transmitted in a wireless communication manner. The temperature values from the thermal sensors  62  are transmitted from the adaptive control module  20  to a monitoring center  24  outside the coolant distribution unit  2  through a communication means  22 . Consequently, the monitoring center realizes the operating situation of the coolant distribution unit  2 . Moreover, the supervisor of the monitoring center  24  may issue a control command to the adaptive control module  20  according to the temperature values sensed by the thermal sensors  62 . According to the control command, the adaptive control module  20  controls the proportional valve  86  to adjusts the flowrate of the working fluid that is fed into the second fluid inlet  13 . The communication means  22  is a wired communication means or a wireless communication means. 
     In an embodiment, the proportional valve  86  is enabled to adjust the flowrate of the low temperature working fluid  33  from the second fluid inlet  13 . The operation of the proportional valve  86  is controlled by the adaptive control module  20 . For example, if the temperature sensed by the thermal sensor  62  is too high, the sensed data is transmitted to the monitoring center  24  outside the coolant distribution unit  2  through the adaptive control module  20 . After the sensed value is judged, the supervisor of the monitoring center  24  issues a control command to the adaptive control module  20 . According to the control command, the adaptive control module  20  controls or adjusts the operation of the proportional valve  86 . During the operation of the proportional valve  86 , the flowrate of the low temperature working fluid  33  from the second fluid inlet  13  is increased. Consequently, the operation of the coolant distribution unit  2  is optimized. 
       FIG. 4  is a schematic functional block diagram illustrating the detailed architecture of a coolant distribution unit according to another embodiment of the present invention. In comparison with the coolant distribution unit  2  as shown in  FIGS. 2 and 3 , the sensing module  16 ′ of the coolant distribution unit  4  of this embodiment comprises one or plural flow meters. The flow meters are located at the positions that the working fluid is transferred through. The flow meters are used for measuring the flowrate of the working fluid in the piping system of the coolant distribution unit  4 . For example, the flow meter  84  is arranged in the pipe channel  19  of the power module  14  for transferring the low temperature working fluid  35  to the first fluid outlet  15 . The flow meter  84  is arranged in the pipe channel  19  for introducing the low temperature working fluid  33  from the second fluid inlet  13 . The locations of the flow meters are not restricted. For example, the flow meter is arranged in the piping channel  19  and located near the first fluid inlet  11 , arranged in the piping channel  19  and located near the first fluid outlet  15 , or arranged in the piping channel  19  and located near the second fluid outlet  17 . The values of the flowrate measured by the flow meters  82  and  84  may be transmitted to the adaptive control module  20  in a wired communication manner or a wireless communication manner. Similarly, the flowrate value may be transmitted from the adaptive control module  20  to the monitoring center  24  outside the coolant distribution unit  4 . Moreover, the adaptive control module  20  may receive a control command from the supervisor of the monitoring center  24 . According to the command, the operating situation of the coolant distribution unit  4  is adjusted or controlled by the adaptive control module  20 . For example, if the flowrate values measured by the flow meter or pressure meters  82  and  84  are too low, a control command for increasing the flowrate is issued from the monitoring center  24  to the adaptive control module  20 . According to the control command, the adaptive control module  20  controls the operation of the proportional valve  86 . During the operation of the proportional valve  86 , the flowrate of the low temperature working fluid  33  from the second fluid inlet  13  is increased. Consequently, the heat dissipating efficiency of the coolant distribution unit  4  is enhanced. 
       FIG. 5  is a schematic functional block diagram illustrating the detailed architecture of a coolant distribution unit according to another embodiment of the present invention. In comparison with the coolant distribution unit  2  as shown in  FIGS. 2 and 3 , the sensing module  16 ″ of the coolant distribution unit  6  of this embodiment comprises one or plural pressure meters. The pressure meters are located at the positions that the working fluid is transferred through. The flow meters are used for measuring the flowrate of the working fluid in the piping system of the coolant distribution unit  6 . For example, the pressure meter  81  is located near the second fluid inlet  13  and arranged in the piping channel  19  between the heat changer  10  and the second fluid inlet  13 , and the pressure meter  83  is located near the second fluid outlet  17  and arranged in the piping channel  19  between the heat changer  10  and the second fluid outlet  17 . Consequently, the pressure meters  81  and  83  are used for the pressure value of the low temperature working fluid  33  from the second fluid inlet  13  and measuring the pressure value of the high temperature working fluid  37  to be outputted from the second fluid outlet  17 . Consequently, the pressure difference between the piping channel  19  of the second fluid inlet  13  and the piping channel  19  of the second fluid outlet  17  is obtained. The locations of the pressure meters are not restricted. For example, the pressure meter  81  is located near the first fluid inlet  11  and arranged in the piping channel  19  between the heat changer  10  and the first fluid inlet  11 , and the pressure meter  83  is located near the first fluid outlet  15  and arranged in the piping channel  19  between the power module  14  and the first fluid outlet  15 . The values of the pressure measured by the sensing module  16 ″ may be transmitted to the adaptive control module  20  in a wired communication manner or a wireless communication manner. Similarly, the pressure values may be transmitted from the adaptive control module  20  to the monitoring center  24  outside the coolant distribution unit  6 . Moreover, the adaptive control module  20  may receive a control command from the supervisor of the monitoring center  24 . According to the command, the operating situation of the coolant distribution unit  6  is adjusted or controlled by the adaptive control module  20 . 
     As mentioned above, the coolant distribution unit is in communication with the external monitoring center through the adaptive control module  20 . The information about the heat exchange efficiency of the coolant distribution unit is transmitted to the external device to be referred by the supervisor of the monitoring center. The coolant distribution unit can receive the control command from the external device through the adaptive control module  20 . According to the control command, the heat exchange efficiency of the coolant distribution unit is further optimized. The arrangement of the adaptive control module  20  has the following benefit. For example, even if the resources in the environment are limited, the communication control of the adaptive control module  20  of the coolant distribution unit can make full use of the energy source. When the electronic device (e.g., a server or a workstation) in the chassis is operated in the peak period and a great deal of waste heat needs to be dissipated away, the supervisor at the remote side can realize the operational peak through the adaptive control module  20 . Moreover, the supervisor may issue the control command to the adaptive control module  20 . According to the control command, the adaptive control module  20  controls the operation of the flowrate control module  18  to increase the flowrate of the low temperature working fluid  33  from the second fluid inlet  13 . Whereas, when the server or the workstation is operated in an off-peak period and a small amount of waste heat needs to be removed, the adaptive control module  20  controls the operation of the flowrate control module  18  according to the control command. Consequently, the flowrate of the low temperature working fluid  33  from the second fluid inlet  13  is decreased. The arrangement of the adaptive control module  20  has another benefit of avoiding the closed adaptive control of the coolant distribution unit. Since the adaptive control module  20  is in communication with the external device in the wired communication manner or the wireless communication manner, the operating situation of the coolant distribution unit can be transmitted to the external device. Moreover, when the flowrate control module  18  is enabled, the sensed data about the values of the temperature and the flowrate can be transmitted to the external device through the adaptive control module  20 . 
       FIG. 6  is a schematic functional block diagram illustrating the concepts of a coolant distribution unit according to another embodiment of the present invention. As shown in  FIG. 6 , the adaptive control module  40  of the coolant distribution unit  8  further comprises a look-up table  400  and associated data. According to the look-up table  400 , the adaptive control module  40  judges whether the sensed data of the sensing module  16 ,  16 ′ or  16 ″ is in one or plural reasonable ranges. According to the judging result, the adaptive control module  40  directly controls the operation of the flowrate control module  18 . Moreover, the adaptive control module  40  is in communication with the external device in the wired communication manner. Consequently, the process and result of directly controlling or adjusting the operation of the proportional valve may be transmitted to the external monitoring center. In such way, the supervisor of the monitoring center can fully realize the operating situation of the coolant distribution unit  8 . The actions of the sensing module  16 , the flowrate control module  18  and the heat exchange module  21  are similar to those of the coolant distribution units as shown in  FIGS. 2 to 5 , and are not redundantly described herein. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all modifications and similar structures.