Patent Abstract:
The invention relates to a double string slurry pump for pumping liquids to the surface of a hydrocarbon well and especially a hydrocarbon well that is producing both natural gas and liquid fluids. The double string slurry pump includes a hollow tube that raises and lowers the plunger and carries the liquids to the surface and an outer tube receives liquids down into the well to periodically flush area around the pump to stir up particles and fines for conveyance out of the wellbore with the liquids. The additional conduit for flushing may be used to provide biocides, solvents or other treatments including with liquids at elevated temperature to create desired results or changes downhole. Moreover, the additional conduit may be provided with ports to provide access to the interior of the gas production path to provide such treatments above the well. The natural gas is produced through the annulus between wellbore casing and the outer production tubing string.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part patent application which claims benefit under 35 USC §120 to U.S. patent application Ser. No. 12/895,019 filed Sep. 30, 2010, entitled “Double String Pump for Hydrocarbon Wells,” which is incorporated herein in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     FIELD OF THE INVENTION 
     This invention relates to down hole rod pumps that are typically used to pump liquids from the bottom of a hydrocarbon wells. 
     BACKGROUND OF THE INVENTION 
     As one travels through Texas and Oklahoma and other oil producing regions, it is common to see oil wells with rocking beam pumps in action. The beam is rocked like a seesaw by a motor while one end the beam lifts and lowers a sucker rod string to drive a pump positioned at or neat the bottom of the well. The sucker rod string is typically made up of a number of twenty-five foot to thirty foot steel rod sections connected end to end to form a long string of rods that extend down into the production tubing of a well. The production tubing itself was inserted into the wellbore after the wellbore was drilled and cased. The production tubing is fixed in the wellbore with a down hole rod pump positioned near the bottom. As the sucker rod moves up and down in the production tubing, the pump draws liquids from the wellbore into a chamber of the pump through a first check valve during a first stroke and then pushes the liquids in the chamber through a second check valve during the return stroke. The liquids pass through the second check valve and into the production tubing above the pump so that the liquids are eventually pumped to the surface and are either piped or trucked to market. 
     Natural gas wells and many low rate oil wells are sometimes provided with pumps to periodically withdraw liquids that enter the wellbore from the formation and tend to accumulate and slowly and eventually stop the production of hydrocarbons the natural gas. The liquid may be water, but may also include hydrocarbon liquids which are sufficiently valuable to collect and transport to market. 
     One of the problems associated with pump systems for small volumes of liquids in wells is that any solids, particularly fines and small particles, that are produced tend to collect and cause trouble for the pump. If the liquid volume were substantially higher, the particles would likely be carried to the surface and not collect at the bottom of the production tubing. With low liquid production rates and intermittent pumping, the particles tend to collect in the production tubing on top of the pump and have been known to damage the pumps and pumping systems well short of their expected service life. This can be especially challenging in coal seam gas production wells where the particles tend to be very fine and abrasive and are susceptible of stacking out rod strings by caking up and packing between plungers and barrels and blocking the travel of check valves and other vital pumping equipment. Coal seam gas wells typically produce water along with highly abrasive coal fines. 
     Many other wells produce sand which is a problem on a much larger scale in terms of total numbers of pumps exposed to particles. Some wells have sand delivered into the formation to hold open the fissures, fractures and perforations to enhance production of gas and liquids. This kind of sand is called proppant. Unfortunately such proppant sand causes many rod pump failures every year as some amounts exit the formation and creates hazard for moving equipment such as the pump in the wellbore. Another type of sand that is even more difficult for pumps to handle is formation sand, often referred to as flour sand. Formation sand is quite fine in nature and very difficult to control due to its fine size and mobility. It is highly abrasive and will wear out the polished surfaces of a pump or bury and stack out the pump. 
     SUMMARY OF THE INVENTION 
     The invention relates to a system for producing gas and liquids from a well where a pump is positioned at or near the bottom of the well and three conduits are arranged to extend into the well from the surface down near the bottom of the well. The first of the three conduits produces gas to the surface and the second of the three conduits is connected to the pump to produce liquids to the surface. The third of the three conduits provides a path for liquid to be delivered to the area of the pump. 
     In another aspect, the invention more particularly includes a system for producing liquids and solids from the bottom of a hydrocarbon well where the system includes a string of production conduit installed in a wellbore where a lower end thereof is near the bottom of the well and where the production conduit defines a gas production path to the surface on one side and an access conduit on the other. A pump including a barrel and a plunger wherein is positioned at the lower end of the production conduit and a string of hollow rod is disposed within the production conduit such that a tubing annulus is formed around the hollow rod string and where the hollow rod string is connected to the plunger that is positioned within the barrel of the pump for movement up and down within the barrel. The production tubing further includes at least one port for delivering liquid from the tubing annulus to the gas production annulus. 
     The invention also relates to a process for producing liquids and solids from the bottom of a natural gas well where an open ended string of production conduit is installed into a wellbore with a seating nipple near the open lower end of the production conduit to define a gas annulus outside of the production conduit and within the well. A pump is installed at the end of a string of hollow rod where the pump includes a barrel and a hollow plunger and where the hollow plunger is connected to and in fluid communication with the hollow rod string and further includes a traveling valve to admit liquids into the hollow interior of the plunger and wherein the barrel includes a standing valve to admit liquids from below the seating nipple into the barrel. The barrel is connected to the seating nipple and seals the interior of the production tubing from the open lower end of the production tubing wherein a tubing annulus is defined within the production tubing above the seating nipple and outside the hollow rod string. Substantially particle free liquid is provided into the tubing annulus to be in contact with the barrel and the outside of the plunger and to pass into the gas annulus to slurry solids and the plunger is raised and lowered to draw liquids through the standing valve and through the traveling valve and directing the liquids into the hollow rod string. 
     In particular aspects of the invention includes the capability to pump or inject clean liquid, chemically treated liquid, or hot liquid within the tubing annulus on top of the barrel and plunger and allow to exit said annulus anywhere up or down the wellbore. 
     The ball checks break the volume above the pump into segments to minimize the suspended solids in any one segment that can settle on top of any one ball check. The volume between these ball checks is sized so that expected pump cycle volume before pump off occurs is greater than the volume between the ball checks so that liquid and solids is advanced above the next ball check or more before the pump shuts down. 
     In a preferred arrangement, a portion of the liquids are produced through the hollow rod string are directed through a filter or settling tank system and then back into the tubing annulus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross section of a prior art version of a pumping system for pumping liquids to the surface of a natural gas well; 
         FIG. 2  is a cross section of a first embodiment of an inventive pumping system shown in a well for pumping liquids to the surface of a natural gas well; 
         FIG. 3  is a fragmentary perspective view of the surface of the well showing the arrangement for providing filtered liquid back to the bottom of the production tubing; and 
         FIG. 4  is a cross section showing a longer length segment of the invention particularly showing check valves and ports at higher elevations in the wellbore. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the preferred arrangement for the present invention, reference is made to the drawings to enable a more clear understanding of the invention. However, it is to be understood that the inventive features and concept may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow. 
     While the explanation of this invention will include the description of conventional components of a pump in a well, a key feature of the invention is the inclusion of an additional conduit that extends from the surface down the well to the vicinity of a pump at the bottom of the well. This additional conduit provides operators and well owners with access to the pump and to other locations down the wellbore to flush the well or provide important chemical treatments to the pump or to the well. Such access to the wellbore and to the pump should enable gas wells to be better maintained and problems to be resolved that are currently quite challenging. The additional conduit is shown in  FIG. 2  and identified as tubing annulus  160 . Tubing annulus  160  can be described as an additional conduit as a produced liquid flow path  155  is inside the hollow rod string  125  and the gas annulus  119  provides the conduit for the gas to flow to the surface. Tubing annulus  160  provides immediate access to the pump  120  without interfering with either of the conduits for produced gases and liquids. 
     Now turning to a more complete explanation of the full wellbore installation, in  FIG. 2 , a wellbore, generally indicated by the arrow  110 , is shown formed or drilled into the ground G. According to conventional procedures, casing  112  is positioned in the wellbore  110  and sealed against the wall of the wellbore with cement  115 . Perforations  118  are extended through the casing  112  and into a hydrocarbon-bearing formation in the ground G by explosive charges to permit hydrocarbons in the hydrocarbon-bearing formation to flow back into the wellbore  110 . The natural gas and other gases are permitted to ascend up the wellbore  110  through gas annulus  119  while liquids accumulate at the bottom of the wellbore  110 . 
     The completion of a conventional gas well would include the insertion of a production string  150  that includes a seating nipple  152  for a pump  120  to be inserted. However, in the present invention, the pump  120  is inserted to the seating nipple using hollow rod string  125  with a plunger  130  arranged to deliver liquid contents into the interior of the hollow rod string  125 . For comparison, please refer to  FIG. 1  where a pump  20  is connected to the surface and installed using conventional sucker rod  25 . The liquid production path  55  is inside the production tubing  50 . In  FIG. 1 , there are only two conduits to the surface. In  FIG. 2 , a third conduit is formed in the tubing annulus  160  between the production tubing  150  and the hollow rod string  125 . 
     The pump is in the natural gas well to pump off, liquids that are produced from the formation with the natural gas. Liquids that accumulate in the well and tend to slow or block the production of the natural gas into the wellbore  10  or  110  so it is generally more productive to maintain the level of liquids below the lowest of the perforations  18  or  118 . The liquid level is drawn down by the pump  20  or  120  from the bottom end of the production tubing  50  or  150 , called a quiet zone  53  or  153  below the pump  20  or  120  and the seating nipple  52  or  152 . 
     The pump  20  or  120  includes a plunger  30  or  130  arranged to move up and down within the barrel  40  or  140 . The plunger  30  or  130  is attached to the bottom end of a hollow rod string  22  and is able to move up and down within the barrel  40  or  140  that is firmly connected or locked into the seating nipple  52  or  152 , but it should be understood that the periphery of the plunger  30  or  130  and the interior of the barrel  40  or  140  are each machined and sized so that any liquid flow around the plunger  30  or  130  is substantially restricted. The preferred path for liquids to travel through the barrel  40  or  140  is also through the interior of the plunger  30  or  130 . Below the barrel  40  or  140  is a strainer nipple  42  or  142  having a number of holes to allow liquids or gas that is in the quiet zone  53  or  153  to pass into the barrel through stranding valve  44  or  144 . Standing valve  44  or  144  is shown to be a ball and seat, but may be any suitable one-way valve technology. As the plunger  30  or  130  is lifted relative to the barrel  40  or  140 , liquids are drawn up through the strainer nipple  42  or  142  and through standing valve  44  or  144  to fill the space in the barrel  40  or  140  below the plunger  30  or  130 . The plunger  30   130  includes a travelling valve  34  or  134 , that like the standing valve  44  or  144 , is shown as a ball and seat, but may be any suitable one-way valve technology. As the plunger  30  or  130  is lowered in the barrel  40  or  140 , standing valve  44  or  144  closes to keep liquid in the barrel but unseat the travelling valve  34  or  134  so that the liquids in the barrel below the plunger  30  or  130  would enter and flow into the plunger  30  or  130 . Liquids that were already in the plunger  30  or  130  before the plunger began its downward movement in the barrel exit the top of the plunger  30  or  130 . In  FIG. 1 , the liquids exit the top of the plunger  30  through one or more vent holes  36 . Liquids that pass out of the vent holes  36  fill the production path  55  and are eventually delivered to the surface. 
     In  FIG. 2 , the liquids exit the top of the plunger  130  into the hollow rod string  125  through check valve  145 . 
     In operation, gas wells often produce sand and other particles that can accumulate at the bottom of the wellbore and cause considerable problems with the pump and interfering with the flow of the liquids into the quiet zone  53  or  153 . The liquid flow rates into gas wells is a relative trickle, and as such, the pump  20  or  120  is expected to operate intermittently to lift liquids out of the bottom of the wellbore  10  or  110 . At the same time, the liquid flow rates are so slow as to allow the solids to settle at the bottom of the well. The excessive collection of solids, especially particles and fines, are a likely cause of pump failure in a well and can plug off the gas annulus  19  or  119  from the quiescent zone  53  or  153 . Using the additional access to the pump area via the tubing annulus  160 , a rush of particle free liquid may be flushed from the surface and progress rapidly to the bottom of the well to jet through ports  154  and into the gas annulus  119 . The jet of such liquids are intended to stir the solids in the bottom of the wellbore to effectively create a slurry of liquids and suspended particles and fines for removing from the well via the pump  120  and liquid production path  155 . The liquids may also scrub the surrounding area to dislodge particles and debris from inside the gas annulus. In some cases, fungus and bacteria may grow inside the well and biocides may be includes with the liquids. The jetting action and other liquid scrubbing effects of the rush of liquid may aid the effectiveness of the biocides. Also, some wells produce waxes and paraffins that may also plug up the production of either or both liquids and gas. Heated liquids and solvents may be added to the liquids to help remove and carry away the waxes and paraffins with the slurry being pumped through the liquid production path  155 . 
     In prior art arrangements such as shown in  FIG. 1 , a number of process or operational schemes may be employed. Typically, the pump  20  is started based on elapsed time from the most recent pump operation cycle and continues until a reduced weight of the plunger  30  is detected, meaning that the liquids at the bottom of the well are reduced and that the pump  20  has had a gas break through. One of the problems with this arrangement that has been identified by the inventor is that particles such as sand and grit are going to pass into the and through the pump  20 , but tend to settle back down in the production path  55  during times of inactivity. In some wells, it is common for just a barrel or two or three barrels to be pumped off the bottom to maintain natural gas production, but these few barrels may not make it to the surface for days or weeks. By the time a specific volume of liquid makes it to the surface, whatever small solids that were entrained with the liquid are substantially settled out. Perhaps these solids may be stirred up during a pumping cycle, only small amounts of the solids ever make it to the surface. These solids collect around the top of the pump  20  and are prone to cause premature failure of the pump by getting into the top of the gap between the outside of the plunger  30  and the inside of barrel  40 . Wear on these highly machined surfaces will likely eventually cause a pump failure. 
     To alleviate these and other problems identified in the embodiment of  FIG. 1 , a pumping system is shown in  FIG. 2  where similar elements are identified with similar numbers except being three digit numbers with the first digit being “1”. For example, casing  112  in  FIG. 2  is essentially the same element as casing  12  in  FIG. 1 . 
     Focusing on the differences between the invention and the embodiment in  FIG. 1  is a plunger  130  is moved up and down inside the barrel  140  by a hollow rod string  125 . The hollow rod string  125  is similar to sucker rod  22 , but is hollow in the center to define the liquid production path  155  inside the hollow rod string  125 . The diameter or effective cross section of the hollow rod string  22  is much smaller than the production path  55  in  FIG. 1 , thus, while each stroke of the pump  120  may move the same volume of liquid as a stroke of pump  20 , the produced liquid moves at a higher velocity up the hollow rod string  125  and gets far closer to the surface for each stroke. With higher velocity, the entrained solids are more likely to be carried farther up the production path  155  with the liquid during each pump operation cycle. Secondly, check valves, such as shown at  145 , are provided at several locations up the production path  155  so that when a pumping cycle is ended and the pump  120  is idled, the particles will only settle down to the top of the last check valve  145  each particle may have passed while travelling to the surface. At a minimum, the check valves or ball checks  145  are spaced within the string so that the volume between them does not exceed the volume expected to be pumped during each a pumping cycle so that particles pass through at least one check valve during each pump cycle and are preferably spaced closer together so that the liquids in the liquid production cycle would pass at least two check valves  145  for each cycle of pump operation. Also, with the smaller diameter in the production path  155 , the pump rate or liquid velocity within the liquid production path should equal or exceed the lift velocity required for the well and for the re-entrainment of the solids into the liquid flow. With a sufficiently small diameter of the rod string  125 , re-entrainment of the solids should be quicker and more certain. 
     Turning now to  FIG. 3 , the downhole pump  120  and well completion arrangement including the production tubing  150  and hollow rod string  125  are operated and supported at the surface by a rocking beam  170  and pipes and vessels. The rocking beam  170  includes a horse-head shaped bracket  171  that is positioned at the end of the rocking beam  170  with a linkage  172  connected to the upper end of the hollow rod string  125 . As the rocking beam  170  lifts and lowers the bracket  171 , the hollow rod string  125  raises and lowers through packing  173 . Packing  173  seals the top of the annulus within the production tubing  150  and outside the hollow rod string  125  as the hollow rod string telescopes in and out of the wellbore  110 . A swivel  174  at the top of the hollow rod string connects to a flexible hose  181  to the interior of the hollow rod string  125  to carry liquids produced from the hollow rod string  125  to a separation vessel  185   a  where solids are allowed to sink, gases may separate to the top and clean liquid is transferred on to storage tank  185   b . The liquids may be delivered to market as indicated by the arrow  186  or recycled back into the well bore  110  through conduit  182 . The liquids may be filtered by any acceptable filtering technology such as a cartridge filter  183 . The clean liquids are then directed through conduit  184  into piping that leads to the inside of production tubing  150 . Natural gas that has passed up the annulus  119  to the top of the well is directed into gas gathering line  188  to be conveyed to market as indicated by arrow  189 . 
     In wells that produce problematic volumes of solids, the solids will tend to settle to the bottom of the hole and even begin to fill the gas annulus  119  while the pump  120  is not in operation. To flush these solids, just prior to initiation of the pump cycle, some of the liquid in tank  185   b  is delivered into the tubing annulus  160  to pass to the bottom thereof and pass through ports  154 . Preferably, a significant volume of liquids are directed into the tubing annulus  160  to blow through the ports  154  with force to stir the solids and create a large volume of a slurry comprised of a lot of fluid and fine and small sized particles. What the inventor has noticed is that once enough liquid has entered the tubing annulus  160  that the weight of the liquid has exceeded the gas pressure, the liquid then siphons more and more liquid into the tubing annulus  160 . Preferably, only an amount of liquid that can be pumped by the pump  120  in a reasonable period of time, such as one hour, is allowed into the tubing annulus. Gas from the gas annulus is allowed to fill the tubing annulus  160  behind or above the added liquids. With the liquid flushing and treating the wellbore, the slurry is then drawn into the pump  120  through the strainer nipple  142  and through the standing valve  144  as described above. The pump  120  continues to pump as liquid is continually delivered to tubing annulus  160  until the solids content of the liquid has satisfactorily diminished or until the volume of clean liquid in tank  185   b  is depleted. The advantage of delivering clean fluid down the tubing annulus  160  is that it remains clean all the way to the ports  154  and thereby prevents the high solids slurry from vulnerable locations inside the barrel  140  near the top of the plunger  130 . 
     Thus, the plunger  130  has clean liquid around the outside thereof and to the extent that any filtered liquid might pass along the small gap around the outside of the plunger  130  and within the barrel  140 , it would tend to sweep any particles in that gap back into a location where such particles are directed up into production path  155 . 
     At the end of the pump operation cycle, it is preferred that the plunger  130  is in the “up” position so that if gas had entered the space below the bottom of plunger  130  and above standing valve  144  that some amount of filtered liquid in the barrel  140  would pass through the small gap during the idle time and occupy enough space to unseat the traveling valve  134  before the plunger reaches it full bottom stroke. As long as the travelling valve  134  can be unseated, the gas will quickly pass into the plunger and the gas lock condition will be alleviated without having to undertake substantial intervention. In an alternative embodiment, double standing and double travelling valves may be preferred where fluid travels through a first of the double valves and then through the second. A double valve arrangement provides redundancy in the event that solid particles block open one of the valves. It is preferred that once the liquid at the bottom of the wellbore  110  is depleted that the pump be stopped. With minimal liquid volumes to be pumped, the velocity of the liquids in liquid production path  155  tends to diminish below the speed which fully entrains the solids. As emphasized above, it is highly desirable to produce the fines and particles to the surface. It is generally seen that vertical velocities of about one half of one foot per second or greater (≧0.5 fps) is sufficient to entrain most solids. 
     In the preferred operation of the well, the pump is stopped in the “up” position until a pump cycle is ready to be undertaken (whether due to elapsed time, reduced gas production or by initiation of an operator at the surface, etc.) a volume of clean liquid is delivered to the tubing annulus  160  from the tank  185   b . The pump area of the well is flushed with the liquids stirring up fines and particles while accomplishing any other intended treatments at the bottom or at other locations at predetermined locations higher in the well. With the fines and particles having been stirred into the liquid, the pump  120  is started and begins its operation of up and down movements to pump the slurry or liquid with suspended fines and particles to the surface. The slurry progresses up the interior of the hollow rod string  125  along the liquid production path  155  at a velocity that will re-entrain fines and particles that have settled out of the liquid from the previous pump cycle back into the liquid to be carried to the surface. The fines that had settled out should have only settled on the top of the last check valve that the slurry passed before the pump shut down at the end of the previous pump cycle. Once the liquid level has been pump down, conventional pump-off control technology detects that the liquid level has diminished and preferably shuts down the pump and ends the pump cycle. With a substantial volume of liquid delivered to the tubing annulus, all of the liquid and solids in the liquid production path is preferably completely produced to the surface along with a substantial portion of newly added liquid. However, some operational schemes may not include a great amount of new liquid so the spacing of the check valves  145  may be more important ins some wells so that any fines that enter the interior of the hollow rod string  125  progress beyond at least one additional check valve at each pump cycle including the recognition that such fines will need to be re-entrained at the start of each pump cycle and therefore on top of a check valve and must flow all the way beyond the next check valve to eventually make it fully to the surface. Such calculations to making sure that solids progress is to space the check valves at a distance that is less than the minimum volume of liquid expected to be pumped for each pump cycle. A reasonable margin of error may be to space the check valves at one barrel distances (depending on the diameter of the hollow rod, about 1000 feet) or at one half barrel distances if the minimum expected volume will be 1 or 2 barrels. 
     While abrasion and wear are the primary concern of the inventor, another aspect of the present invention that may help avoid gas locks is to provide a vent  158  to allow any gas that has entered the quiet zone  153  such as gases dissolved from the hydrocarbon liquid to pass back into the annulus  119  and exit the well  10 . The vent  158  is above the highest opening in the strainer nipple  142  so that the liquid level inside the quiet zone  153  is not lower than the liquid level outside the quiet zone in the annulus  119 . Another strategy to alleviate gas lock is to increase the fluid slippage past the plunger/barrel interface from annulus  160  into barrel  140  to displace traveling valve  134  and push gas into flow path  155 . 
     Chemical treatments such as a scale, corrosion or paraffin inhibitor may be added into production tubing  150  or into the tubing annulus  160 . It should be noted that even hot liquid such as hot water or oil may be added to tubing  150  to enhance production by softening paraffins. The tubing annulus  160  provides many new options for addressing a near endless list of challenges in the oil field. 
     In one further preferred aspect related to  FIG. 3 , a rod rotator may be installed at the top of the well near the location where the bracket  171  attaches to the hollow rod string  125  to rotate the hollow rod string  125  and spread any wear from the up and down motion evenly around the outside of the sucker  125  for longer rod string life. Also, with the rod string  125  being hollow, it will likely and preferably have a larger diameter than equivalent non-hollow rod string of the same strength and will therefore have a larger radius distributing any load on the inside of the production tubing  150  in a manner that will reduce wear on the production tubing  150 . 
     While it should be understood that the invention introduces two tubing strings which enables operators of wells to control the operating environment of the pump  120 . The invention provides a way to flush water or other liquid to the pump from above through the tubing annulus  155 . 
     Turning to  FIG. 4 , the production tubing  150  may include additional ports  154   a  at an elevation above the barrel  140  and further ports  154   b  at various levels above that. With these additional ports, liquids and treatments including hot fluids and chemical treatments may be directed into the gas annulus  119  for treatments as desired. Tools may be inserted into the tubing annulus below ports  154   a  or  154   b  so that the flow of such liquids and treatments may be directed with more focus into the gas annulus at the location desired. 
     One interesting aspect of this arrangement is that with the liquids coming to the surface within a hollow rod string, the liquids exit the well pumping system on the “downstroke” of the rod pump. In conventional rod pumps, the liquid production occurs on the “upstroke.” This point may not seem significant, but it does reveal that the present invention is quite different than prior systems. 
     Finally, the scope of protection for this invention is not limited by the description set out above, but is only limited by the claims which follow. That scope of the invention is intended to include all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are part of the description and are a further description and are in addition to the preferred embodiments of the present invention. The discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application.

Technology Classification (CPC): 5