Abstract:
An adjustable economizer valve is disclosed that does not overlap the pressure build function, which allows a single valve to be used for both high and low gas use applications. The valve will economize well and reduces system pressure when needed in low use applications. The valve also provides maximum pressure build capacity when needed in high gas use applications. The valve seals off the pressure build outlet from the economizer connection with a seal around a pusher post disposed in the valve body. The pusher post has an internal flow path that is sealed by a floating device that can create a seal from diaphragm pressure and can open when diaphragm pressure is removed. In exemplary, non-limiting, embodiments, the floating device can be a ball or a disc plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a non-provisional of U.S. provisional patent application Ser. No. 61/320,817, filed Apr. 5, 2010, and is also a non-provisional of U.S. provisional patent application Ser. No. 61/259,726, filed Nov. 10, 2009, the entirety of which provisional applications are expressly incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention generally relate to the field of economizer valves, and more particularly to a pressure build economizer valve that opens based on increasing system pressure and does not have overlapping pressure build and economizer functions. 
     2. Discussion of Related Art 
     Economizer valves are used in industrial applications for pressure regulation in cryogenic liquid and gas supply systems. Pressure build economizer (PBE) valves combine pressure building and economizer functions into one unit. Existing PBE valves for cryogenic liquid cylinders and bulk tanks are based on three types of designs. The three types include: (1) an active economizer that overlaps the pressure build function, (2) an inactive orifice economizer function, and (3) an active economizer that flows through the pressure build shutoff piston. Existing PBE valves with active economizers that overlap the pressure build function undesirably reduce the pressure build capacity of the system until the cylinder pressure has dropped below normal operating pressures. Existing inactive economizer functions have a fixed orifice economizer such that the economizer function is always open, undesirably limiting the capacity of the pressure build function or the economizer orifice is too small to give adequate pressure reduction within a reasonable period of time. Existing PBE valves with active economizer functions that flow through the piston are costly to manufacture and also have a potential problem of leakage between the pressure build and economizer functions that can create runaway cylinder pressure. 
     It would, therefore, be an advantage to provide a cost effective economizer valve for cryogenic liquid cylinders that has an active economizer that opens based on increasing system pressure and does not have overlapping pressure build and economizer functions. 
     SUMMARY OF THE INVENTION 
     An adjustable economizer valve is disclosed that does not overlap the pressure build function and is not restricted to a small orifice, thus allowing the same valve to be used for both high and low gas use applications. The valve will economize well and reduce system pressure when needed in low gas use applications. It will also provide maximum pressure build capacity when needed in high gas use applications. 
     The disclosed valve seals off the pressure build outlet from the economizer connection with a seal around a pusher post disposed in the valve body. The pusher post has an internal flow path that is sealed by a floating device that can create a seal from diaphragm pressure and open when diaphragm pressure is removed. In exemplary, non-limiting, embodiments, the floating device can be a ball or a disc plate. 
     A valve is disclosed comprising a body having first, second and third ports. A piston pusher and a piston may be included, and the piston pusher may be slidably disposed within a first bore in the body. A first end of the piston pusher may be received by the piston, and the piston may be slidably disposed within a second bore in the body. A second end of the piston pusher may have a pusher recess comprising a side bore permitting media communication between the pusher recess and the vertically oriented bore. The piston further may include a disc member positioned opposite a seat region in the body. The valve may further include a seal member that is selectively engageable with the pusher recess. The valve may have a bonnet connected to the body. The bonnet may have a diaphragm with a bottom face presented to an upper surface of the seal member. 
     A valve is disclosed, comprising a body having first, second and third ports, a piston pusher and a piston. The piston pusher may be slidably disposed within a first bore in the body. A first end of the piston pusher may be received by the piston, and a second end of the piston pusher may have a pusher recess comprising a side bore permitting media communication between the pusher recess and the vertically oriented bore. The piston may be slidably disposed within a second bore in the body. The piston may further include a disc member positioned opposite a seat region in the body. The valve may also include a bonnet assembly including a spring-biased diaphragm, and a seal member having first and second surfaces, where the first surface is selectively engageable with the pusher recess, and the second surface is selectively engageable with the diaphragm. 
     A valve is disclosed, comprising a body having first, second and third ports, a piston pusher and a piston. The piston pusher may be slidably disposed within a first bore in the body. A first end of the piston pusher may be received by the piston. The piston may be slidably disposed within a second bore in the body. A second end of the piston pusher may have a pusher recess engaging a seal member. The piston pusher recess may further comprise a side bore permitting media communication between the pusher recess and the vertically oriented bore. The piston may further include a disc member positioned opposite a seat region in the body. The valve may further include a bonnet connected to the body, the bonnet having a diaphragm such that a bottom face of the diaphragm is presented to an upper surface of the seal member. The diaphragm may be biased toward the seal member by a first spring, and the piston pusher and plate may be biased toward the diaphragm by a second spring. The valve may have first and second configurations for enabling selective flow between the first, second and third ports 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawing illustrates exemplary embodiments of the disclosed device so far devised for the practical application of the principles thereof, and in which: 
         FIG. 1  is a schematic of the disclosed valve in an exemplary cryogenic supply system; 
         FIG. 2  is a cross-section view of the disclosed valve; 
         FIG. 3  is a cross-section view of the valve of  FIG. 2  illustrating a pressure build operating configuration; and 
         FIG. 4  is a cross section view of the valve of  FIG. 2  rotated 90-degrees, illustrating an economizer operating configuration; 
         FIG. 5  is a cross section view of the interaction between the seal member and piston pusher of  FIGS. 2-4 ; 
         FIG. 6  is a cross-section view of an alternative embodiment of the disclosed valve; 
         FIG. 7  is a cross-section view of the valve of  FIG. 6  illustrating a pressure build operating configuration; and 
         FIG. 8  is a cross section view of the valve of  FIG. 6  rotated 90-degrees, illustrating an economizer operating configuration. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     This description is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. Such relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. 
     Referring to  FIG. 1 , the disclosed valve  1 ,  200  may be part of a cryogenic liquid cylinder system used to store and dispense process gases such as oxygen, nitrogen, argon, or carbon dioxide. Such systems can include a cylinder  100  containing a quantity of liquefied gas  110 , as well as a variety of tubing system components configured to maintain and dispense gas when required by a user. The tubing system components may include a liquid fill/withdrawal valve  120  for filling and draining the cylinder, a pressure gage  130  for monitoring the pressure of the gas layer  140  above the liquid  110 , a pressure relief valve  150  and/or burst disc  160 , and a vent valve  170  for venting gas  140  from the top of the cylinder  100 , and a vacuum burst disc  180 . A gas withdrawal valve  190  is operable by a user to dispense gas. As shown, the disclosed valve  1  may be connected via appropriate tubing to the liquefied gas  110 , the gas layer  140 , and the gas withdrawal tube connected to the valve  190 . In this way, the valve  1 ,  200  can perform both the pressure building and economizer functions previously described. 
     Referring now to  FIGS. 2-4 , an embodiment the disclosed valve  1  comprises a body  2 , a bonnet  4 , a piston pusher assembly  6  disposed in the body  2 , and a diaphragm  40  disposed in the bonnet  4 . The body  2  also includes a first port  10  (see  FIGS. 3 and 4 ) connected to the liquid  110  portion of the cylinder  100 , a second port  12  (see  FIG. 2 ) connected to the gas layer  140  above the liquid, and a third port  13  (see  FIGS. 3 and 4 ) connected to the gas withdrawal valve  190 . The body  2  and bonnet  4  are connected to each other via a bolted connection. 
     The piston pusher assembly  6  comprises a piston pusher  14  slidably disposed within a vertically oriented bore  16  in the body  2 . A first end  18  of the piston pusher  14  is received within a recess  20  in a piston  22 , while a second end  24  comprises a pusher recess  26  that engages a seal member  28 , which in the illustrated embodiment is a plate member having a projection portion  27  which is at least partially received within the pusher recess  26  to enable a seal to be selectably formed between the two pieces. It will be appreciated that the seal member  28  may take any of a variety of forms, including a flat or curved plate, a ball member, a cylindrical member, and the like. 
     The pusher recess  26  may further include a side bore  30  to provide media communication between the pusher recess  26  and the vertically oriented bore  16 . The piston pusher  14  may be sealed to the bore  16  via an o-ring  17 . 
     The piston  22  and the piston pusher  14  are biased upward toward a seat region  31  of the body  2  via a spring  32  disposed in a spring bore  34  formed in a body plug  36  which itself is threaded into the bottom of the body  2 . An annular disc  33  is set into the piston  22  and biased into engagement with the seat region  31  of the body  2  via the force of the spring  32 . In one embodiment, the disc  33  is burnished into the piston  22 . Thus, in the illustrated configuration, the disc  33  contacts the seat region  31  to seal off the first port  10  from the vertically oriented bore  16  and the second port  12 . The body plug  36  is sealed to the body  2  via a seal ring  38 . 
     The diaphragm  40  is sandwiched between opposing surfaces of the body  2  and bonnet  4 . In this arrangement, a flat bottom face  52  of the diaphragm  40  is presented to an opposing surface  44  of the seal member  28  which is held by the piston pusher  14  in the manner previously described. In one embodiment, the seal member  28  is a flat plate and the flat bottom face  52  engages the flat top surface of the plate. For embodiments in which the seal member  28  is a ball member, the flat bottom face  52  of the diaphragm  40  may engage the top round surface of the ball member. 
     The diaphragm plate  42  and diaphragm  40  are biased downward by a spring  54 , the compression of which is adjustable via a tension screw (not shown) which is threadably mounted to the top of the bonnet  4 . The tension screw engages the spring to control the set point of the valve (i.e., the pressure at which the valve will switch from the pressure build function to the economizer function). An opposite end of the spring  54  bears against an upper surface of a diaphragm plate  42 , biasing the diaphragm plate  42  toward the piston pusher  14  and seal member  28 . 
     As noted, the disclosed valve  1  is configured to perform both pressure build and economizer functions.  FIGS. 3 and 4  show the internal configuration of the valve when performing each of these functions. 
     Thus,  FIG. 3  shows the valve  1  in the “pressure build” configuration. As can be seen, the force of the spring  54  on the diaphragm plate  42  and diaphragm  40  causes the plate and diaphragm to press down on the seal member  28  and piston pusher  14 . This, in turn, presses down on the piston  22  and unseats the disc  33  from the seat region  31 . In this configuration, the first and second ports  10 ,  12  are in media communication via the vertically oriented bore  16  in the body  2 . Thus, a path is provided between the liquid  110  and the gas layer  140  of the tank (see  FIG. 1 ). As liquid flows through the system tubing to the tank top, it vaporizes, expanding and building pressure in the top of the tank. This enables the system to maintain a desired gas pressure (sometimes referred to as the “pressure build shutoff pressure”) above the liquid in the tank. 
     This pressure build shutoff pressure may be slightly greater than that of the outlet gas pressure. For example, if it is desired to provide process gas at about 100 psi through the gas withdrawal valve  190 , the valve  1  may be set by adjusting the tension screw (not shown) to compress spring  54  so that the pressure build feature allows the gas layer  140  to rise to a pressure build shutoff pressure of about 105 psi. It will be appreciated that these pressure values are merely exemplary and non-limiting, and that the disclosed valve may be used with a variety of other operating and pressure build shutoff pressure values. 
     When the pressure in the first port  10  and the vertically oriented bore  16  approaches the pressure build shutoff pressure of 105 psi, the force of spring  54  is counteracted by the fluid force acting on the underside of the diaphragm  40  via bore  13 A ( FIG. 3 ). As the pressure on the underside of the diaphragm  40  nears 105 psi (again, this value is merely exemplary), the piston pusher  14  rises along with the piston  22  until the disc  33  engages the seat region  31  of the body, shutting off flow between the first port  10  and the second port  12 . 
     If the pressure in the gas layer  140  drops below the pressure build shutoff pressure (e.g., due to substantial gas withdrawal), the force of spring  54  presses the piston  22  and disc  33  downward, unseating the disc  33  from the seat region  31 , and enabling flow between the first and second ports  10 ,  12  to thereby raise the pressure of the gas layer  140  above the liquid  110 . This process repeats to maintain the desired pressure above the liquid. 
     During idle periods where little or no gas is withdrawn via the gas withdrawal valve  190 , there may be a tendency for the system pressure to rise above the pressure build shutoff pressure. This rise in system pressure can be caused by, for example, heat transfer from the ambient surroundings that vaporizes small quantities of liquefied gas. When gas is withdrawn from the system under such an “over-pressure” condition, the valve  1  is configured so that gas is initially taken from the gas layer  140  at the top of the cylinder  100  to quickly return the system pressure to at or near the pressure build shutoff pressure. Once the system pressure has been suitably reduced, the economizer function of the valve  1  shuts off and gas is thereafter produced by pulling from the liquid  110  in the cylinder  100 . 
       FIG. 4  shows the valve  1  configured for drawing gas from the gas layer  140  when the system pressure is above the pressure build shutoff pressure. Initially the diaphragm  40  is in the downwardly deflected condition (see  FIG. 3 ), in which the gas pressure beneath the diaphragm  40  is sufficient to compress the spring  54  and enable the seal member  28  to “float” above the piston pusher recess  26 . As gas is drawn from the third port  13 , gas flows from the second port  12  (again, taking from the gas layer  140  in the cylinder), through the side bore  30  of the piston pusher  14 , and through third intermediate port  13 A. This occurs until the pressure of gas layer  140  begins to drop due to the withdrawal of gas directly from the gas layer  140 . As the pressure of the gas layer drops, the spring  54  begins to move downward which presses the diaphragm  40  against the seal member  28 . This, in turn, forces the piston pusher  14  and piston  22  down. Forcing the seal member  28  downward causes the seal member  28  to seal against the piston pusher recess  26  preventing further flow between the second and third ports  12 ,  13 . As such, gas ceases to be drawn directly from the gas layer. It will be appreciated that where the seal member  28  includes a projection portion  27 , the projection portion itself may seal against the piston pusher recess. 
     The described downward movement of the piston pusher  14  and piston  22  also causes the disc  33  to unseat from the seat region  31 , reestablishing flow from the first port  10  (which is connected to the liquid  110 ) to the second port  12  (which is connected to the gas layer  140 ). In this way, the flow path of the economizer is closed during the pressure build operation when the seal member  28  engages the diaphragm. Economizer flow only occurs when the disc  33  has seated and the diaphragm  40  continues to rise with increased pressure above the pressure build shut off pressure. This eliminates pressure build and economizer function overlap and provides a controlled opening pressure (adjustable active economizer) for the economizer. 
     The economizer flow initiation set point (which is the same as the pressure build shutoff pressure) is adjustable, and it does not overlap the pressure build function which can reduce the pressure build capacity of the system. The disclosed valve is well suited for both high and low gas usage applications. 
       FIG. 5  is a cross-section view of an exemplary seal plate embodiment of the previously described seal member  28 . As can be seen, the seal plate includes a projection portion  27  which is centrally disposed on one side of the plate. The projection portion  27  may thus be received within the pusher recess  26  of the piston pusher  14  when the plate engages the piston pusher. 
     In the illustrated embodiment, the projection portion  27  takes the form of a cone and is configured so that the angled surface  29  of the projection portion  27  engages a corner of the upper rim  15  of the piston pusher  14 . Although a conical shaped surface is shown, the projection portion  27  can instead include a spherical shaped surface. This configuration (conical or spherical shaped projection portion  27 ) results in line contact engagement between the seal plate  28  and the piston pusher  14  which enhances the sealing capability of the arrangement. 
     Referring now to  FIGS. 6-8 , an embodiment of the disclosed economizer valve  100  including an alternative seal member  128  will be described. As can be seen, valve  100  is substantially similar to valve  1  described in relation to  FIGS. 1-5 , with certain differences which will be described. Thus, valve  200  comprises a body  202 , a bonnet  204 , a piston pusher assembly  206  disposed in the body  202 , and a diaphragm assembly  208  disposed in the bonnet  204 . The body  202  also includes a first port  210  connected to the liquid  110  portion of the cylinder  100 , a second port  212  connected to the gas layer  140  above the liquid, and a third port  213  (see  FIG. 8 ) connected to the gas withdrawal valve  190  ( FIG. 1 ). The body  202  and bonnet  204  are connected to each other via a threaded connection. 
     The piston pusher assembly  206  comprises a piston pusher  214  slidably disposed within a vertically oriented bore  216  in the body  202 . A first end  218  of the piston pusher  214  is received within a recess  220  in a piston  222 , while a second end  224  comprises a pusher recess  226  that cradles a seal member  228 , which in the illustrated embodiment is a ball member. The pusher recess  226  further includes a side bore  230  that provides media communication between the pusher recess  226  and the vertically oriented bore  216 . The piston pusher  214  is sealed to the bore  216  via an o-ring  217 . 
     The piston  222  and the piston pusher  214  are biased upward toward a seat region  231  of the body  22  via a spring  232  disposed in a spring bore  234  formed in a body plug  236  which itself is threaded into the bottom of the body  202 . An annular disc  233  is set into the piston  222  and biased into engagement with the seat region  231  of the body  202  via the force of the spring  232 . In one embodiment, the disc  233  is burnished into the piston  222 . Thus, in the illustrated configuration, the disc  233  contacts the seat region  231  to seal off the first port  210  from the vertically oriented bore  216  and the second port  212 . The body plug  236  is sealed to the body  202  via a seal ring  238 . 
     The diaphragm assembly  208  includes a diaphragm  240 , diaphragm plate  242 , diaphragm post  244 , and diaphragm stop  246 . The diaphragm post  244  is connected to the diaphragm plate  242  via a threaded nut  248 . The diaphragm post and diaphragm  240  are sandwiched between a retaining washer  250  and the diaphragm stop  246 , which, in turn, are sandwiched between opposing surfaces of the body  202  and bonnet  204 . In this arrangement, a flat bottom face  252  of the diaphragm post  244  is presented to a surface of the seal member  228  which is held by the piston pusher  214  in the manner previously described. 
     The diaphragm assembly  208  is biased downward by a spring  254 , the compression of which is adjustable via a tension screw  256  which is threadably mounted to the top of the bonnet  204 . The tension screw  256  engages one end of the spring  254  via a plate  258 , to control the set point of the valve  200  (i.e., the pressure at which the valve will switch from the pressure build function to the economizer function). The opposite end of the spring  254  engages an upper surface of the diaphragm plate  242  to bias the diaphragm plate  242  toward the piston pusher  214  and seal member  228 . 
     As noted, the valve  200  is configured to perform both pressure build and economizer functions.  FIGS. 7 and 8  show the internal configuration of the valve when performing each of these functions. Thus,  FIG. 7  shows the valve  200  in the “pressure build” configuration, while  FIG. 8  shows the valve  200  in the “economizer” configuration. 
     As can be seen in  FIG. 7 , the force of the spring  254  on the diaphragm assembly  208  presses down on the seal member  228  and piston pusher  214 . This, in turn, presses down on the piston  222  and unseats the disc  233  from the seat region  231 . In this configuration, the first and second ports  210 ,  212  are in media communication via the vertically oriented bore  216  in the body  2 . Thus, a path is provided between the liquid  110  and the gas layer  140  of the tank ( FIG. 1 ). As liquid flows through the tubing to the tank top it vaporizes, expanding and building pressure. This enables the system to maintain a desired gas pressure (sometimes referred to as the “pressure build shutoff pressure”) above the liquid. This pressure build shutoff pressure may be slightly greater than that of the outlet gas pressure for reasons previously described in relation to the valve  1  of  FIGS. 2-4 . 
     Thus, when the pressure in the first port  210  and the vertically oriented bore  216  approach the pressure build shutoff pressure, the force of spring  254  is counteracted by the fluid force acting on the underside of the diaphragm  240  via bore  213 A. As the pressure on the underside of the diaphragm  240  nears the shutoff pressure, the piston pusher  214  rises along with the piston  222  until the disc  233  engages the seat region  231  of the body, shutting off flow between the first port  210  and the second port  212 . 
     If the pressure in the gas layer  140  drops below the pressure build shutoff pressure (e.g., due to substantial gas withdrawal), the force of spring  254  presses the piston  222  and disc  233  downward, unseating the disc  233  from the seat region  231 , and enabling flow between the first and second ports  210 ,  212  to thereby raise the pressure of the gas layer  140  above the liquid  110 . This process repeats to maintain the desired pressure above the liquid. 
     As previously noted, during idle periods where little or no gas is withdrawn via the gas withdrawal valve  190 , there is a tendency for the system pressure to rise above the pressure build shutoff pressure. This rise in system pressure can be caused by, for example, heat transfer from the ambient surroundings that vaporizes small quantities of liquefied gas. When gas is withdrawn from the system under such an “over-pressure” condition, the valve  200  is configured so that gas is initially taken from the gas layer  140  at the top of the cylinder  100  to quickly return the system pressure to at or near the pressure build shutoff pressure. Once the system pressure has been suitably reduced, the economizer function of the valve  200  shuts off and gas is thereafter produced by pulling from the liquid  110  in the cylinder  100 . 
       FIG. 8  shows the valve  200  configured for drawing gas from the gas layer  140  when the system pressure is above the pressure build shutoff pressure. Initially the diaphragm assembly  208  is in the deflected condition, in which the gas pressure beneath the diaphragm  40  is sufficient to compress the spring  254  and enable the seal member  228  to “float” above the piston pusher recess  226 . Thus, as gas is drawn from the third port  213 , gas flows from the second port  212  (again, taking from the gas layer  140  in the cylinder), through second intermediate port  212 A, through the side bore  230  of the piston pusher  214 , and through third intermediate port  213 A. This occurs until the pressure of gas layer  140  begins to drop (due to the withdrawal of gas directly from the gas layer). As the pressure of the gas layer drops, the spring  254  begins again to move downward, impinging on the seal member  228 , and pressing piston pusher  214  and piston  222  down. This motion causes the seal member  228  to seal the piston pusher recess  226 , which prevents further flow between the second and third ports  212 ,  213  (i.e., gas ceases to be drawn directly from the gas layer  140 ). It also causes the disc  233  to unseat from the seat region  231 , reestablishing flow from the first port  210  (which is connected to the liquid  110 ) to the second port  212  (which is connected to the gas layer  140 ). 
     Thus, the flow path of the economizer is closed during the pressure build operation when seal member  228  of the piston pusher post  214  engages the diaphragm post  244  of the diaphragm assembly  28 . Economizer flow only occurs when the disc  233  has seated and the diaphragm  240  continues to rise with increased pressure above the pressure build shut off pressure. This eliminates pressure build and economizer function overlap and provides a controlled opening pressure (adjustable active economizer) for the economizer. 
     The economizer flow initiation set point (which is the same as the pressure build shutoff pressure) is adjustable, and it does not overlap the pressure build function which can reduce the pressure build capacity of the system. The disclosed valve  200  is well suited for both high and low gas usage applications. 
     One additional advantage of the disclosed valve  1 ,  200  is that it can prevent the reverse flow of liquid through the Economizer port during cylinder fill operations. Reverse flowing liquid through the economizer during the filling process will flash to gas in the top of the tank and create a pressure increase in the tank that can negatively impact the smooth flow of liquid into the tank. The valve will not allow reverse flow of liquid through the economizer because the seal member  28 ,  228  will check the reverse flow from the third port  13 ,  213  to the second port  12 ,  212 . 
     The individual components of the disclosed may be constructed of any of a variety of materials appropriate for the intended application, taking into consideration the temperature and pressure ratings of the application, as well as the operating fluid. In an exemplary embodiment, the body and bonnet may be constructed of bronze. The springs may be constructed of steel or stainless steel. Internal components may be constructed of stainless steel, bronze and/or brass. Sealing components such as o-rings, seal members (disc, ball, etc), seal rings, and discs, as well as diaphragms, may be made from any of a variety of metal, plastic or elastomeric materials suitable for the temperature and media used in a particular application. In one embodiment, the disc is made from polytetrafluoroethylene (Teflon). 
     While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the spirit and scope of the invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.