Patent Abstract:
A compressor and oil separator assembly for compressing a fluid includes a suction end, a discharge end, and first and second rotors rotatably mounted between the suction and discharge ends. A discharge line communicates with the discharge end, and an oil separator communicates with the discharge line. An oil sump communicates with the oil separator and an oil supply line communicates between the oil sump and the rotors. A bleed line selectively communicates between the discharge line and the oil supply line for equalizing a pressure differential between the suction end and the discharge end without causing substantial backward rotation of the rotors or displacement of oil to the rotors through the oil supply line. Preferably, the assembly further includes a valve that defines a portion of the discharge line and is also coupled to the bleed line.

Full Description:
RELATED APPLICATIONS 
     This application claims priority to provisional application Ser. No. 60/225,409, filed on Aug. 15, 2000. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to compressors, and more particularly to valve arrangements for controlling the flow of fluid through compressors. 
     BACKGROUND OF THE INVENTION 
     It is known to use positive displacement compressors, and more specifically screw compressors, to compress fluids. The rotors or screws of a screw compressor are susceptible to backward rotation when the compressor is stopped because the pressure differential between the discharge side of the compressor and the suction side of the compressor naturally tends to equalize over the rotors. While the compressors can be designed to handle such backward rotation of the rotors, the noise generated by the backward-turning rotors is undesirable. 
     SUMMARY OF THE INVENTION 
     To prevent pressure equalization over the compressor, and the resultant backward rotation of the rotors, it is known to use check valves. For the purposes of this description, the compressor is described as being part of a temperature control system, however, it is to be understood that the compressor need not be used in conjunction with a temperature control system. FIG. 1 schematically illustrates a prior art refrigeration system  10 . The system  10  includes a compressor (represented by the dashed box  14 ) having two screws or rotors  16  and a discharge line  18  through which high-pressure refrigerant and lubricating oil exit the rotors  16  at the discharge end of the compressor  14 . The discharge line  18  communicates with an oil separator  22  that separates the oil from the high-pressure refrigerant. The oil returns to an oil sump  26  where it can be reintroduced into the rotors  16  via an oil supply line  30 . The high-pressure refrigerant exits the compressor  14  through the oil separator  22  and travels to a condenser  34 . After exiting the condenser  34 , the condensed refrigerant passes through an expansion valve  38  before reaching an evaporator  42 . From the evaporator  42 , the low-pressure refrigerant returns to the compressor  14  and the refrigeration cycle repeats. 
     As seen in FIG. 1, a check valve  46  is located at the suction end of the compressor  14 . The check valve  46  prevents high-pressure refrigerant from flowing back through the rotors  16  toward the lower pressure at the suction end of the compressor  14 , and thereby prevents backward rotation of the rotors  16 . An advantage of locating the check valve  46  at the suction end of the compressor  14  is that when the compressor  14  is shut down there is no pressure equalization over the oil system so oil will not be displaced from the oil sump  26  into the rotors  16 . Rather, the pressure is equalized downstream of the discharge end of the compressor  14 . 
     The disadvantage of locating the check valve  46  as shown in FIG. 1 is that the check valve  46  must be relatively large to prevent the high-pressure gas from taking its natural equalization path over the compressor to the lower-pressure suction end. Additionally, any pressure drop caused by the check valve  46  while the system is operating will substantially reduce the system&#39;s capacity. 
     FIG. 2 shows another prior art refrigeration system  10 ′, with like parts having like reference numerals. In the system  10 ′, a check valve  50  is located downstream of the oil separator  22 . The check valve  50  prevents high-pressure refrigerant from flowing back into the oil separator  22  and the rotors  16 . Locating the check valve  50  downstream of the oil separator  22  also provides advantages. First, the check valve  50  can be relatively small because the high-pressure refrigerant will naturally flow toward the lower-pressure environment of the condenser  34 . In other words, because the high-pressure refrigerant downstream of the oil separator  22  does not tend to flow back into the oil separator  22 , the check valve  50  can be relatively small. Additionally, any pressure drop caused by the check valve  50  while the system is operating will only affect power consumption and not system capacity. 
     The disadvantage with the location shown in FIG. 2 is that, in most situations, the volume of high-pressure refrigerant in the oil separator  22  is still large enough to cause noticeable backward rotation of the compressor rotors  16  as the pressure equalizes over the compressor  14 . To alleviate this problem, it is known to add a second check valve  54  at the suction end of the compressor  14 . This second check valve  54  operates in the manner described above with respect to the check valve  46 , so that the volume of high-pressure refrigerant in the oil separator  22  does not flow back through the rotors  16 . While this configuration creates maximum isolation of the compressor  14  from the remaining components of the refrigeration system  10 ′, it necessitates the use of two check valves  50  and  54 , and adds to the cost of the refrigeration system  10 ′. 
     FIG. 3 shows yet another prior art refrigeration system  10 ″, with like parts having like reference numerals. A check valve  58  is located at the discharge end of the compressor  14 , between the rotors  16  and the oil separator  22 . When the compressor  14  stops running, the pressure between the discharge end and the suction end of the compressor  14  equalizes over the oil system via the oil supply line  30 . The disadvantage with this check valve location is that when the pressure is equalized over the oil system, oil from the oil sump  26  is displaced into the rotors  16 , the bearings (not shown), the gears (not shown), and the seal cavities (not shown). Too much oil in the rotors  16  makes the compressor  14  difficult to start and reduces the overall life of the compressor  14 . For example, since oil is not a compressible medium, too much oil in the rotors  16  could create a hydraulic lock situation. To overcome these problems, it has been known to place a solenoid valve  62  in the oil supply line  30 . The solenoid valve  62  is opened when the compressor  14  is running and closed when the compressor  14  is stopped. 
     One disadvantage with using the solenoid valve  62  is the additional cost. Furthermore, failure of the solenoid valve  62  could cause problems. For example, if the solenoid valve  62  is stuck closed when the compressor  14  is running, the compressor  14  will not get lubrication and will eventually seize. If the solenoid valve  62  is stuck open when the compressor  14  is stopped, oil will be displaced to the rotors  16 , creating the difficult starting conditions that the solenoid valve  62  was intended to prevent. 
     The present invention provides a valve arrangement that offers many of the advantages discussed above, without most of the disadvantages. More particularly, the invention provides a valve arrangement having a single, relatively small valve located in the discharge line of the compressor. When the compressor is running, the valve provides the necessary fluid communication between the compressor and the oil separator. When the compressor is shut down, the valve blocks fluid communication between the rotors and the oil separator to prevent the high-pressure fluid from flowing back over the rotors. 
     In addition, the valve arrangement also prevents displacement of oil to the rotors when the compressor shuts down, and does so without the use of a solenoid valve in the oil supply line. To accomplish this, the valve arrangement includes a bleed line communicating between the oil supply line and the discharge line. When the compressor is not operating, the valve and the bleed line provide a pathway for the high and low pressure fluid to equalize over the oil cavities in the compressor while short-circuiting the oil separator and the oil sump. Because the pressure equalization does not occur over the oil sump, substantially no oil is displaced to the rotors. 
     The valve provides selective communication between the discharge end of the compressor, the oil separator, and the bleed line. A movable member in the valve responds to system pressure so that when the compressor is running, the movable member is in a first position that allows communication between the discharge end of the compressor and the oil separator, while blocking communication between the discharge end of the compressor and the bleed line. When the compressor is stopped, the movable member in the valve moves to a second position that blocks communication between the discharge end of the compressor and the oil separator, and allows communication between the discharge end of the compressor and the bleed line. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-3 schematically illustrate prior art temperature control systems having various check valve arrangements. 
     FIG. 4 schematically illustrates a temperature control system embodying the invention, shown in a state where the compressor is running. 
     FIG. 5 schematically illustrates the temperature control system embodying the invention, shown in a state where the compressor is shut down. 
     FIG. 6 is a section view of a compressor embodying the invention. 
     FIG. 7 is a section view of the compressor of FIG. 6, showing the valve arrangement embodying the invention. 
     FIG. 8 is another section view of the compressor of FIG. 6, showing the oil return line and the bleed line. 
     FIG. 9 is an enlarged section view, showing the valve in its closed position when the compressor is not running. 
     FIG. 10 is an enlarged section view, showing the valve in its open position when the compressor is running. 
     FIG. 11 is an exploded view showing the valve of FIG.  10 . 
     FIG. 12 is an exploded view of a valve similar to the valve shown in FIG. 11, but without a biasing spring. 
     FIG. 13 is an exploded view of another valve embodying the invention. 
     FIG. 14 is an exploded view of yet another valve embodying the invention. 
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 4 and 5 schematically illustrate a temperature control system  100  embodying the invention. The system  100  includes a screw compressor (represented by the dashed box  104 ) having two screws or rotors  108  housed in a compression chamber  112  (shown schematically in FIGS.  4  and  5 ). As mentioned above, the compressor  104  is described as being part of the temperature control system  100 , however, it is to be understood that the compressor need not be used in conjunction with a temperature control system. For example, the compressor  104  could be an air compressor or a compressor used to compress other compressible fluids. 
     The compressor  104  includes a suction end  116 , where low pressure refrigerant enters the compression chamber  112 , and a discharge end  120  having a discharge line  124 , through which high-pressure refrigerant and lubricating oil (not shown) exit the compression chamber  112 . The discharge line  124  communicates with an oil separator  128  that separates the oil from the high-pressure refrigerant. The oil returns to an oil sump  132  where it can be reintroduced into the compression chamber  112  and to the rotors  108  via an oil supply line  136 . 
     FIG. 4 illustrates the temperature control system  100  when the compressor  104  is running. The high-pressure refrigerant exits the compressor  104  downstream of the oil separator  128  and travels to a condenser  140 . After exiting the condenser  140 , the condensed refrigerant passes through an expansion valve  144  before reaching an evaporator  148 . From the evaporator  148 , the low-pressure refrigerant returns to the suction end  116  of the compressor  104  and the refrigeration cycle repeats. While the compressor  104  is illustrated as having an integral oil separator  128  and oil sump  132 , it is understood that the oil separator  128 , the oil sump  132 , and the compressor  104  could also be separate units. 
     In the illustrated embodiment, the compressor  104  also includes a bleed line  152  that communicates with the discharge line  124  and the oil supply line  136 . A valve  156  is coupled to the discharge line  124  to define a portion of the discharge line  124 . The valve  156  is also coupled to the bleed line  152 . The valve  156  is movable from a first position (see FIG.  4 ), wherein the discharge line  124  is open to allow high-pressure refrigerant and lubricating oil to travel into the oil separator  128  when the compressor  104  is running, to a second position (see FIG.  5 ), wherein the discharge line  124  is closed so that high-pressure refrigerant and lubricating oil cannot travel back into the rotors  108  when the compressor  104  is shut down. 
     In the illustrated embodiment, the valve  156  moves automatically between the first and second positions due to the pressure differential of the refrigerant in the temperature control system  100 . For example, when the compressor  104  is running (FIG.  4 ), the high-pressure refrigerant and lubricating oil exiting the rotors  108  enters the discharge line  124  and travels toward the oil separator  128 . The valve  156  includes a movable member  160  that is moved to the first position by the high-pressure refrigerant and lubricating oil passing through the valve  156 . In the illustrated embodiment, the valve  156  is a reed valve and the movable member  160  is a reed, however, other types of valves can also be used. When the reed  160  is in the first position, the bleed line  152  is closed so that the high-pressure refrigerant and lubricating oil travel through the valve  156  and to the oil separator  128 . Lubricating oil flows through the oil supply line  136  to lubricate the rotors  108  and the other components (not shown) in the compression chamber  112  (i.e., the bearings, the gears, and the shaft seals). 
     When the compressor  104  is shut down (FIG.  5 ), the reed  160  is moved to the second position by the high-pressure refrigerant and lubricating oil that is trying to pass back through the valve  156  toward the lower pressure at the suction end  116 . As will be described in more detail below, a biasing spring can also be used to move the reed  160  to the second position when the compressor  104  is shut down. When the reed  160  is in the second position, the discharge line  124  is blocked and the bleed line  152  is opened to provide a pathway for the high and low pressure refrigerant to equalize over the oil cavities (not shown in FIGS. 4 and 5) in the compression chamber  112 , while short-circuiting the oil separator  128  and the oil sump  132 . By allowing the pressure to equalize over the bleed line  152 , there is little or no undesirable backward rotation of the rotors  108 . In addition, because the pressure equalization does not occur over the oil sump  132 , substantially no oil is displaced to the rotors  108 . 
     To ensure that the pressure equalizes over the bleed line  152  and not over the oil supply line  136 , the compressor  104  also includes a restrictor or orifice  164  in the oil supply line  136 . The restrictor  164  functions to increase the pressure drop over the oil supply line  136 . Compared to the oil supply line  136 , the bleed line  152  has a relatively large and unobstructed cross-section, and therefore the bleed line  152  provides the path of least resistance for pressure equalization of the refrigerant. 
     To further ensure that equalization occurs over the bleed line  152 , the oil sump  132  in the illustrated embodiment is located at a point that is lower than the point where the bleed line  152  connects with the oil supply line  136 , so that the pressure drop over the oil supply line  136  is larger than the pressure drop over the bleed line  152 . As shown in FIGS. 4 and 5, the oil sump  132  is located at a distance h from the point where the bleed line  152  connects with the oil supply line  136 . It should be understood that restrictor  164  and the elevational difference between the oil sump  132  and the bleed line  152  may not be necessary to ensure that the pressure equalizes over the bleed line  152 . 
     FIGS. 6-10 illustrate the invention as described above embodied in a screw compressor  104  having an integral oil separator  128  and oil sump  132 . Like parts have been given like reference numerals. Referring to FIG. 6, the compressor  104  includes a housing  168  that surrounds the rotors  108  and defines the compression chamber  112 . In FIG. 6, the suction end  116  is on the right side of the compressor  104  and the discharge end  120  is on the left side of the compressor  104 . 
     The oil separator  128  includes a separator element  172  that circumscribes at least a portion of the discharge end  120 . A discharge outlet  176  defined in the housing  168  provides an exit for the high-pressure refrigerant to leave the compressor  104  after the oil has been separated. The oil sump  132  is shown below the lowest portion of the separator element  172 , and includes an oil filter  180  for filtering the oil returning to the oil sump  132 . Oil separated by the separator element  172  drains into the oil sump  132  through passageway  184 . Oil collected in the oil sump  132  travels back to the rotors  108  via the oil return line  136 . A first portion  136   a  of the oil return line  136  is shown in FIG.  6 . Also shown in FIG. 6 is the restrictor or orifice  164 . 
     FIG. 7 is another section view through the compressor  104 . FIG. 7 illustrates more of the oil return line  136 , again showing the restrictor or orifice  164 , as well as second, third, fourth, and fifth portions  136   b-e , respectively, of the oil return line  136 . Oil cavities or ports  188  are shown in the housing  168  and communicate with the oil return line  136  and the compression chamber  112  to provide lubricating oil to the rotors  108  and to various other components. 
     FIG. 7 also shows the reed valve  156  positioned in the discharge line  124  of the compressor  104 . The construction of the reed valve  156  will be described in detail below. 
     FIG. 8 is yet another section view through the compressor  104 . FIG. 8 illustrates how the fifth portion  136 e of the oil return line  136  communicates with the oil ports  188 . Additionally, FIG. 8 shows the bleed line  152  that communicates with the discharge line  124  and the fifth portion  136   e  of the oil return line  136 . The bleed line  152  communicates with the discharge line  124  via the reed valve  156  in a manner that will be described in detail below. FIG. 8 also shows the distance h between the point where the bleed line  152  intersects the fifth portion  136   e  of the discharge line  136  and the oil level in the oil sump  132 . 
     FIGS. 9 and 10 are enlarged section views showing the reed valve  156  coupled to the housing  168  inside the compressor  104 . FIG. 11 is an exploded view of the reed valve  156  shown in FIGS. 9 and 10. As seen in FIG. 11, the reed valve  156  includes a first valve portion  192 , a second valve portion  196 , an intermediate valve portion  200 , and the reed  160 , which are all coupled together to form the valve  156 . The first valve portion  192  includes first and second end portions  204  and  208 , respectively, at opposing ends of a body portion  212 . The end portions  204  and  208  are thicker than the body portion  212  so that when the valve  156  is assembled, the reed  160  is retained between the end portions  204 ,  208  and is movable toward and away from the body portion  212 . Furthermore, when the valve  156  is assembled, the difference in thickness between the body portion  212  and the end portions  204 ,  208  creates opposing slots  214  that communicate with the portion of the discharge line  124  downstream of the valve  156  and the rotors  108 . 
     The body portion  212  includes an aperture  216  that is sized to communicate with the portion of the discharge line  124  adjacent the discharge end of the rotors  108 . The reed  160  is sized so that when positioned against the body portion  212 , the reed  160  covers the entire aperture  216 . The first and second end portions  204 ,  208  each include an aperture  220  for receiving a mounting fastener  224  (see FIGS.  9  and  10 ). In addition to the mounting aperture  220 , the first end portion  204  also includes a bleed line aperture  226  that communicates with the bleed line  152  when the valve  156  is mounted in the compressor  104 . The first end portion  204  also includes a pin spring aperture  228  for receiving a pin spring  232  that helps to hold the valve  156  together before the valve  156  is assembled in the compressor  104 . 
     The second valve portion  196  has a substantially uniform thickness and includes an elongated aperture  234  that extends between respective first and second surfaces  235  and  236  of the second valve portion  196 . The second valve portion  196  also includes mounting apertures  220  for receiving the mounting fasteners  224  and a pin spring aperture  228  for receiving the pin spring  232 . A recess  240  (shown in phantom in FIG. 11) is formed in the second surface  236  and houses a spring  244  that biases the reed  160  toward the body portion  212  of the first valve portion  192  when the valve  156  is assembled. The spring  244  facilitates movement of the reed  160  to the second position for fast closure under low-pressure-differential stopping conditions. A second, elongated recess  248  (shown in phantom in FIG. 11) is also formed in the second surface  236 . The purpose of the elongated recess  248  will be described below. 
     The intermediate valve portion  200  is a relatively thin strip of material that is sandwiched between the first and second valve portions  192  and  196  when the valve  156  is assembled. The intermediate valve portion  200  includes mounting apertures  220  for receiving the mounting fasteners  224  and a pin spring aperture  228  for receiving the pin spring  232 . Additionally, the intermediate valve portion  200  includes an elongated aperture  252  and a first bleed line aperture  256  that communicates with a portion of the elongated recess  248  in the second valve portion  196 . The elongated aperture  252  and the first bleed line aperture  256  are positioned such that the reed can completely cover the elongated aperture  252  and the first bleed line aperture  256  when the reed abuts the intermediate valve portion  200 . The intermediate valve portion  200  also includes a second bleed line aperture  260  that communicates with another portion of the elongated recess  248 . In the illustrated embodiment, the second bleed line aperture  260  is positioned below the first bleed line aperture  256 . The second bleed line aperture  260  is substantially aligned with the bleed line aperture  226  in the first valve portion  192  when the valve  156  is assembled. 
     Referring now to FIG. 9, when the valve  156  is assembled in the compressor  104  and the compressor  104  is shut down, the reed  160  is in the second position (corresponding to the second position shown in FIG. 5) and abuts the body portion  212 , thereby closing the discharge line  124  by covering the aperture  216  that otherwise provides communication to the discharge end of the rotors  108 . As described above, the reed  160  automatically moves to this second position when the compressor  104  is shut down due to the system pressure and/or the biasing spring  244 . As indicated by the arrows in FIG. 9, the high-pressure refrigerant downstream of the rotors  108  and the valve  156  is free to equalize with the lower-pressure refrigerant at the suction end  116  over the pathway defined by the elongated aperture  234  in the second valve portion  196 , the elongated aperture  252  in the intermediate valve member  200 , the first bleed line aperture  256 , the elongated recess  248 , the second bleed line aperture  260 , the bleed line aperture  226  in the first valve portion  192 , and finally, through the bleed line  152 . 
     Referring now to FIG. 10, when the valve  156  is assembled in the compressor  104  and the compressor  104  is running, the reed  160  is in the first position (corresponding to the first position shown in FIG. 4) and abuts the intermediate valve portion  200 , thereby closing the bleed line  152  by covering the first bleed line aperture  256  in the intermediate valve portion  200 . The discharge line  124  is opened and high-pressure refrigerant and lubricating oil exits the discharge end of the rotors  108 , passes through the elongated aperture  216  in the first valve portion  192 , exits the valve  156  laterally through the opposing slots  214  (only one is shown in FIG.  10 ), and continues through the discharge line  124  in the manner previously described. As described above, the reed  160  automatically moves to this first position when the compressor  104  is running due to the system pressure. 
     FIG. 12 illustrates an alternative reed valve  156 ′. The reed valve  156 ′ is substantially the same as the reed valve  156 , with like parts having like reference numerals, except that the reed valve  156 ′ does not include the biasing spring  244  and, therefore, does not include the spring recess  240  in the second valve portion  196 . As discussed above, the spring  244  may not be necessary where system pressure is sufficient to automatically operate the valve  156 ′. The components of the spring valve  156 ′ shown in FIG. 12 each also include a second pin spring aperture  228  for receiving a second pin spring  232 . 
     FIG. 13 illustrates another alternative reed valve  156 ″, with like parts indicated by like reference numerals. The reed valve  156 ″ is different from the reed valves  156  and  156 ′ in that the reed valve  156 ″ does not include an intermediate valve portion  200 . Rather, the reed valve  156 ″ includes a plug  264  that is inserted into the elongated recess  248  in the second valve portion  196 . The plug  264  is inserted into the middle of the elongated recess  248  until substantially flush with the second surface  236 . With the plug  264  in place, the elongated recess  248  forms a U-shaped passageway without the need for the two separate bleed line apertures  156  and  160  in the intermediate valve portion  200 , thereby eliminating the need for the intermediate valve portion  200 . 
     FIG. 14 shows yet another alternative reed valve  156 ′″, with like parts indicated by like reference numerals and with similar parts indicated by triple-prime (′″) reference numerals . As seen in FIG. 14, the first valve portion  192 ′″ has a substantially uniform thickness while the intermediate valve portion  200 ′″ is thicker and includes first and second end portions  204 ′″ and  208 ′″, respectively, at opposing ends of a body portion  212 ′″. The end portions  204 ′″ and  208 ′″ are thicker than the body portion  212 ′″ so that when the valve  156 ′″ is assembled, the reed  160  is retained between the end portions  204 ′″,  208 ′″ and is movable toward and away from the body portion  212 ′″. Furthermore, when the valve  156 ′″ is assembled, the difference in thickness between the body portion  212 ′″ and the end portions  204 ′″,  208 ′″ creates opposing slots  214 ′″ (only one is shown) that communicate with the portion of the discharge line  124  downstream of the valve  156 ′″ and the rotors  108 . 
     Instead of the elongated aperture  252 , the intermediate valve portion  200 ′″ includes three separate apertures  252 ′″. Likewise, instead of the elongated aperture  234 , the second valve portion  196 ′″ includes three separate apertures  234 ′″ that are aligned with the apertures  252 ′″ when the valve  156 ′″ is assembled. Changing the elongated apertures  252  and  234  to three separate apertures  252 ′″ and  234 ′″ reduces the available flow area, and may be desirable for certain applications. 
     While several reed valves  156 - 156 ′″ have been illustrated, other reed valve configurations are also contemplated by the invention. The reed valves can be made from metal or any other suitable materials. It is also understood that various other types of valves could be substituted for the reed valve configurations contemplated. 
     While the valve arrangement of the invention substantially reduces or eliminates the backward rotation of the rotors, it is possible that a small amount of slow backward rotation may still occur as the pressure equalizes through the oil cavities  188 , which are positioned adjacent the center of the rotors  108 . If desired, this small remaining backward rotation can be eliminated by opening the capacity unloader valves (not shown) that are commonly used in conjunction with screw compressors. Opening the capacity unloader valves reduces the pressure in the compression chamber  112  to the same pressure existing at the suction end  116 , thereby eliminating even the smallest amount of pressure equalization occurring over the rotors  108 . 
     Various features of the invention are set forth in the following claims.

Technology Classification (CPC): 5