Abstract:
A device for pumping a stock fluid by supplying and discharging a motivating fluid to a unit is described. The device develops the suction and discharge of the stock fluid through the motion of a movable biasing boundary within a cavity. The movable biasing boundary divides the cavity into a stock fluid cell and a motivating-fluid cell. In the case that the movable biasing boundary comprises a piston, a link joined to the piston may extend outside of the unit as a means for driving the piston toward the motivating fluid cell. Each cell communicates with a fluid circuit that includes a source line, a valve or valves and a discharge line. The controlled supply and discharge of the motivating fluid to move the movable biasing boundary creates the discharge and suction of the stock fluid respectively. A valve directs the supply and discharge of the motivating fluid. Valves in the stock fluid circuit assist with the discharge and suction of the stock fluid from and into the stock-fluid cell to create the pumping action. The use of the devise in commercial food preparation and waste-water management applications to pump grease/water mixtures, grease and gray water is presented.

Description:
BACKGROUND OF THE INVENTION 
     This invention pertains to a fluid motivated pump that may be used in locations where either it would be preferable not to use a pump having an electric motor or electricity is unavailable. A fluid motivated pump of the present invention may be used with food preparation equipment, wastewater equipment and a unit that separates a mixture of insoluble or immiscible fluids into its parts. For example, when used with food preparation equipment, a pump may deliver a grease/water mixture to a separator unit, a gray water part from the separator to a sewer line, and a grease part from the separator to a storage vessel. 
     Certain locations are hazardous because the atmosphere does or may contain gas, vapor or dust in explosive quantities. The National Electrical Code (NEC) divides these locations into Classes and Groups according to the type of explosive agent that may be present. Methane produced during sewage digestion in a wastewater treatment operation is a Class I, Group D atmosphere. Sparks or flames from a non-hazardous location electrical motor may ignite the methane and cause an explosion. A hazardous location electrical motor designed to withstand an internal explosion of methane, and not allow the internal flame or explosion to escape should be used. Two types of hazardous location electrical motors include a totally enclosed, fan-cooled electrical motor that has an external cooling fan and a totally enclosed, nonventilated, electrical motor that depends on convection for air cooling. A non-electrical alternative would be desirable. 
     Also, electrical current. leaking into water presents a hazard. For example, a unit used to separate a grease/water mixture into a gray water part and a grease part may include one or more pumps. A first pump may be used to transmit the grease part to a storage vessel. A second pump may be used to deliver the gray water part to a sewer line. To satisfy electrical codes, a ground-fault interrupter must protect the electrical lines to the motor of each pump. Watertight electrical boxes may also be required. The electrical lines should be either Type TW wires encased in metal or plastic conduit or Type UF (underground feeder) cable. These precautions are required to prevent electrical shock. Again, a non-electrical alternative would be desirable. 
     Submerged pumps can be even more challenging. For certain equipment, it is desirable to include a pump within the equipment. A reason may be esthetics. Another reason may be function. No matter the reason, a pump may be submerged in a reservoir of a water-based fluid. To prevent electrical current leakage, the pump, the electrical motor and wiring must be watertight. In a new pump installation, new and clean parts help water tightness; however, the upkeep of the electrical motor and wiring becomes a challenge over time because of the nature of the water-based fluid. If a grease/water mixture is involved, the grease bonds to the electrical motor casing and wire insulation over time. Also, the grease can hold bits of food and other debris and bond these to the motor and wiring insulation. The constant contact of grease and debris with wire insulation, wire conduit and materials for making watertight seals can rot them, leading to electrical current leakage. Also, replacing rotted parts is nasty. The built-up grease must be removed to create clean surfaces. During cleaning, the built-up grease clings to tools and clothing. A large amount of clothing and cleaning rags is thrown out after becoming fouled with grease. Again, a non-electrical alternative would be desirable. 
     It is apparent that there is a need for a pump that uses a motive method other than an electrical motor. It is also apparent that there is a need for a pump that reduces or eliminates explosion hazards and electrical current leakage hazards. 
     SUMMARY OF THE INVENTION 
     A pump according to the present invention conveys or pumps a fluid (later called a stock fluid) through a motivating fluid provided at a preselected pressure acting against a movable biasing boundary. A pump according to the present invention includes at least one unit having a cavity in fluid communication with at least one valve and at least one additional valve. The at least one valve regulates the providing and discharging of the motivating fluid while the at least one additional valve regulates the drawing or suctioning and discharging of a stock fluid. The movably biasing boundary splits the cavity into a stock-fluid cell and a motivating-fluid cell. Walls of the cavity and at least a portion of the movable biasing boundary define each cell. A motivating-fluid port is in fluid communication with the at least one valve and the motivating-fluid cell. A stock-fluid port is in fluid communication with the at one additional valve and the stock-fluid cell. 
     In a first embodiment, the movable biasing boundary comprises a piston movably disposed within the cavity and a biasing element, such as, a spring, acting on the piston and against the pressure of the motivating fluid. The biasing element may be internal to and/or external to the unit. When external to the unit, the biasing unit may act on the piston through a link. A piston may include a seal at its perimeter contacting the cavity walls to prevent the contamination of the motivating fluid by the stock fluid and vice versa. 
     A pump according to the present invention conveys or pumps at least one stock fluid by directing a motivating fluid through the at least one valve, into the motivating-fluid cell to act on the movably biasing boundary. This action expands the motivating-fluid cell, contracts the stock fluid cell and balances the preselected pressure of the motivating fluid. The at least one valve is then actuated so that the motivating fluid is discharged from the motivating-fluid cell as it contracts through the relaxation of the movably biasing boundary. Concurrently, the stock-fluid cell expands to draw the stock fluid through the at least one additional valve and into the stock fluid cell. The at least one valve and at least one additional valve are actuated to again direct motivating-fluid into the motivating-fluid cell, contract the stock-fluid cell and convey or pump the stock fluid through the at least one additional valve. The repeated alternating between expanding and contracting of the stock-fluid cell conveys the stock fluid. The repeated alternating to convey the stock fluid occurs by the coordinated actuation of the at least one valve and the at least one additional valve. A controller may be used to coordinate the actuation. 
     In another embodiment, the at least one valve comprises a solenoid actuated valve having two alternative paths. The at least one additional valve comprises two check valves, more preferably, duckbill check valves. One check valve is directed to permit stock fluid to be drawn into the stock-fluid cell during its expansion; the other check valve is directed to permit stock fluid to be conveyed or pumped from the stock-fluid cell during its contraction. 
     A pump according to the present invention may include a plurality of units or convey a plurality of stock fluids or both. When at least two units are paired, their movable biasing boundaries may be coupled so that they act in opposition, eliminating the need for other biasing components like springs. This provides additional operating and space saving advantages. 
     A pump according to the present invention uses a fluid as the motive force, eliminating the need for an electrical motor. In this manner, a pump according to the present invention reduces or eliminates explosion hazards and electrical current leakage hazards. In this vein, a pump according to the present invention may be used, for example, in commercial food preparation operations, in wastewater operations, and any other suitable operation that would be apparent to one skilled in the art. 
     Most preferably the motive fluid is a municipal or other convenient water supply, delivered at its conventional pressure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention will be better understood by those skilled in the art after a review of the following description, appended claims, and accompanying drawings where: 
     FIG. 1A depicts a schematic of a fluid motivated pump including two double acting units during a first step in a cycle according to an embodiment of the present invention; 
     FIG. 1B depicts a schematic of a fluid motivated pump including two double acting units during a second step in a cycle according to an embodiment of the present invention; 
     FIG. 1C depicts a schematic of an alternative fluid motivated pump including two double acting units according to an embodiment of the present invention; 
     FIG. 2A depicts a schematic of a fluid motivated pump including one double acting units during a first step in a cycle according to an embodiment of the present invention; 
     FIG. 2B depicts a schematic of a fluid motivated pump including one double acting unit during a second step in a cycle according to an embodiment of the present; 
     FIG. 2C depicts a schematic of an alternative fluid motivated pump including one double acting unit according to an embodiment of the present invention; 
     FIG. 2D depicts a schematic of an alternative fluid motivated pump including one double acting unit according to an embodiment of the present invention; 
     FIG. 3A depicts a schematic of a fluid motivated pump including a plurality of double acting units arranged in a circle according to an embodiment of the present invention; 
     FIG. 3B depicts a schematic of a fluid motivated pump including a plurality of double acting units arrange in two lines according to an embodiment of the present; and 
     FIG. 4 depicts a schematic of a system incorporating fluid motivated pumps according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Applicants discuss below several embodiments of a fluid motivated pump and an embodiment including fluid motivated pump. After reading this detailed description of the preferred embodiment, those skilled in the art will appreciate that other embodiments for the present invention exist and may be contemplated. 
     An embodiment of the present invention includes two double acting units working together. Each unit communicates with a motivating-fluid source and a stock of fluid to be pumped through a group of valves that are opened and closed during a cycle to pump the stock fluid. FIG. 1A depicts a pump  10  during a first step of the cycle. FIG. 1B depicts the pump  10  during a second step of the cycle. Like items in FIGS. 1A and 1B have like numbers. 
     Before discussing the steps of the cycle depicted in FIGS. 1A and 1B, the parts of pump  10  are presented. Pump  10  includes a first unit  36  and a second unit  34 . Each unit  36 ,  34  includes a stock-fluid port  42 ,  40 ; a piston  56 ,  54  splitting a cavity within each unit  36 ,  34  into a stock-fluid cell  52 ,  44  and a motivating-fluid cell  46 ,  50 ; and a motivating-fluid port  66 ,  64 . A link  108  interconnects the pistons and coordinates the motion of the pistons  56 ,  54  within the cavity of each unit  36 ,  34 . Each piston  56 ,  54  may include a ring seal  62 ,  60  at a perimeter of each piston contacting the cavity wall of its respective unit  36 ,  34  to prevent the contamination of the motivating fluid by the stock fluid and vice versa. 
     A line  12  supplies the stock fluid to the stock-fluid cell  52 ,  44  of each unit  36 ,  34  through branches  16 ,  14 ; check valves  22 ,  20 ; bridges  26 ,  24 ; stock-fluid lines  32 ,  30 ; and stock-fluid port  42 ,  40 . A line  116  disposes of the stock fluid from the stock-fluid cell  52 ,  44  of each unit  36 ,  34  through stock-fluid port  42 ,  40 ; stock-fluid lines  32 ,  30 ; check valves  110 ,  106 ; and branches  114 ,  112 . If desired the check valves could be replaced with suitably controlled actuated valves. 
     In a like manner, a line  102  supplies the motivating fluid to the motivating-fluid cells  46 ,  50  of each unit  36 ,  34  through motivating-fluid ports  66 ,  64 ; branches  94 ,  92 ; paths  86 ,  84  of valves  76 ,  74 ; and motivating-fluid lines  72 , 70 . A line  104  disposes of the motivating fluid from the motivating-fluid cells  46 ,  50  of each unit  36 ,  34  through motivating-fluid ports  66 ,  64 ; motivating-fluid lines  72 ,  70 ; paths  82 ,  80  of valves  76 ,  74  and branches  100 ,  96 . A tie  90  coordinates the motion of the valves  76 ,  74  to direct the motivating fluid from branches  94 ,  92  through paths  86 ,  84  to motivating-fluid lines  72 ,  70  and from motivating-fluid lines  72 ,  70 ; through paths  82 ,  80  to and from branches  100 ,  96  respectively. 
     Movement of piston  56  from right to left draws stock fluid into stock-fluid cell  52  of the first unit  36  from line  12  along branch  16  through valve  22 , bridge  26 , stock-fluid line  32  and stock-fluid port  42 , while valve  110  remains closed. Movement of piston  56  from left to right pumps stock fluid from stock-fluid cell  52  of the first unit  36  through stock-fluid port  42 , stock-fluid line  32 , valve  110  and along branch  114  to line  116  for disposal while valve  22  remains closed. Motivating fluid travels to motivating-fluid cell  46  of the first unit  36  from line  102  along branch  94  through path  86  of valve  76 , motivating-fluid line  72  and motivating-fluid port  66  while path  82  of valve  76  remains unavailable. Motivating fluid travels from motivating-fluid cell  46  of the first unit  36  through motivating-fluid port  66 , motivating -fluid line  72 , path  82  of valve  76  and along branch  100  to line  104  for disposal while path  86  of valve  76  remains unavailable. 
     In a like manner, movement of piston  54  from left to right draws stock fluid into stock-fluid cell  44  of the second unit  34  from line  12  along branch  14  through valve  20 , bridge  24 , stock-fluid line  30  and stock-fluid port  40  while valve  106  remains closed. Movement of piston  54  from right to left pumps stock fluid from stock-fluid cell  44  of the first unit  34  through stock-fluid port  40 , stock-fluid line  30 , valve  106  and along branch  112  to line  116  for disposal while valve  20  remains closed. Motivating fluid travels to motivating-fluid cell  50  of second unit  34  from line  102  along branch  92  through path  80  of valve  74 , motivating-fluid line  70  and motivating-fluid port  64  while path  84  of valve  74  remains unavailable. Motivating fluid travels from motivating-fluid cell  50  of the second unit  34  through motivating-fluid port  64 , motivating-fluid line  70 , path  84  of valve  74  and along branch  96  to line  104  for disposal while path  80  of valve  76  remains unavailable. 
     The coordinated opening and closing of valves  22 ,  110 ,  106 , and  20  in the stock-fluid circuit and the availability of paths  86  and  82  of valve  76  and paths  84  and  80  of valve  74  produces the action of piston  56  in the first unit  36  and piston  54  in the second unit  34  to pump the stock fluid. The state of the valves and paths of the first unit  36  and second unit  34  in the steps of the cycle depicted in FIGS. 1A and 1B are summarized in Table 1 below. 
     
       
         
               
             
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                 TABLE  
               
             
             
               
                   
               
               
                 State Summary for Cycle Steps of FIGS. 1A and 1B 
               
             
          
           
               
                   
                 FIGS. 1A 
                 FIGS. 1B 
               
               
                   
                 Step 1 
                 Step 2 
               
               
                   
                   
               
             
          
           
               
                 First Unit 36 
               
             
          
           
               
                   
                 Action of First Unit 36 
                 Suction 
                 Pump 
               
               
                   
                 Valve 22 
                 Opened 
                 Closed 
               
               
                   
                 Valve 110 
                 Closed 
                 Opened 
               
               
                   
                 Path 86 of Valve 76 
                 Unavailable 
                 Available 
               
               
                   
                 Path 82 of Valve 76 
                 Available 
                 Unavailable 
               
               
                   
                 Motivating-fluid Cell 46 
                 Contracting 
                 Expanding 
               
               
                   
                 Stock-fluid Cell 52 
                 Expanding 
                 Contracting 
               
               
                   
                 Piston 56 
                 Right to Left 
                 Left to Right 
               
             
          
           
               
                 Second Unit 34 
               
             
          
           
               
                   
                 Action of Second Unit 34 
                 Pump 
                 Suction 
               
               
                   
                 Valve 20 
                 Closed 
                 Opened 
               
               
                   
                 Valve 106 
                 Opened 
                 Closed 
               
               
                   
                 Path 84 of Valve 74 
                 Unavailable 
                 Available 
               
               
                   
                 Path 80 of Valve 74 
                 Available 
                 Unavailable 
               
               
                   
                 Motivating-fluid Cell 50 
                 Expanding 
                 Contracting 
               
               
                   
                 Stock-fluid Cell 44 
                 Contracting 
                 Expanding 
               
               
                   
                 Piston 56 
                 Right to Left 
                 Left to Right 
               
               
                   
                   
               
             
          
         
       
     
     Step 1 of the cycle includes the pumping of stock fluid from the second unit  34  for discharge and the suctioning of stock fluid into the first unit  36  from a stock-fluid source through line  12 . Referring to the first unit  36  in FIG. 1A, the circuit from motivating-fluid cell  46  to discharge motivating fluid line  104  is open. Also, the circuit from line  12  to draw stock fluid into stock-fluid cell  52  is open. Also referring to the second unit  34  in FIG. 1A, the circuit from line  102  to expand motivating-fluid cell  50  with motivating fluid is open, and the circuit from stock-fluid cell  44  to pump stock fluid through line  116  for discharge is open. Motivating fluid expands motivating-fluid cell  50  by acting on piston  54 . Piston  54  moves from right to left to pump stock fluid from stock-fluid cell  44  while contracting cells  44 . At the same time, piston  54  drives link  108  to move piston  56  of the first unit  36 . As piston  56  moves, the expansion of stock-fluid cell  52  creates suction in the open circuit to line  12  to draw stock fluid into stock-fluid cell  52 . Motivating-fluid cell  46  contracts as piston  56  moves from right to left. Step 1 ends when motivating-fluid cell  50  of the second unit  34  and stock-fluid cell  52  of first unit  36  expand to their greatest volumes and stock-fluid cell  44  of second unit  34  and motivating-fluid cell  46  of first unit  36  contract to their smallest volumes. Then, valves  74  and  76  are actuated, causing path  82  to make way for path  86  in valve  76  and path  80  to make way for path  84  in valve  74 . The resulting pressure change on the sides of pistons  54  and  56  is transmitted to the stock fluid. This causes valves  22  and  106  to close and valves  20  and  110  to open. Valve  72  and  74  may be conjointly actuated by way of a tie  90 , as shown in FIG.  1 A. Once the path and valve states are changed, step 2 of the cycle begins. The apparatus has taken the configuration shown in FIG.  1 B. 
     Step 2 of the cycle includes the pumping of stock fluid from the first unit  36  for discharge and the suctioning of stock fluid into the second unit  34  from a stock-fluid source through line  12 . Referring to the first unit  36  in FIG. 1B, the circuit from line  102  to expand motivating-fluid cell  46  with motivating fluid is open, and the circuit to contract stock-fluid cell  52  to pump stock fluid via line  116  for discharge into is open. Also referring to the second unit  34  in FIG. 1B, the circuit from motivating-fluid cell  50  to discharge motivating fluid via line  104  is open, and the circuit from line  12  to stock-fluid cell  44  to draw stock fluid into stock-fluid cell is open. Motivating fluid expands motivating-fluid cell  46  by acting on piston  56 . Piston  56  moves from left to right to pump stock fluid from stock-fluid cell  52  while contracting cell  52 . At the same time, piston  56  acts through link  108  to move piston  54  of the second unit  34 . As piston  54  moves, the expansion of stock-fluid cell  44  creates suction in the open circuit to line  12  to draw stock fluid into stock-fluid cell  44 . Motivating-fluid cell  50  contracts as piston  54  move from left to right. Step 2 ends as motivating-fluid cell  46  of first unit  36  and stock-fluid cell  44  of second unit  34  expand to their greatest volumes and stock-fluid cell  52  of first unit  34  and motivating-fluid cell  50  of second unit  34  contract to their smallest volumes. Then, valves  74  and  76  are moved back to the positions shown in FIG.  1 A. This causes path  86  to make way for path  82  in valve  76 ; and path  84  to make way for path  80  in valve  74 . The resulting pressure change causes valves  20  and  110  close and valves  22  and  106  open. Once the path and valve states are changed, step 1 of the cycle begins again. 
     Another embodiment of the present invention shown in FIG. 1C includes two double acting units working together similar to those of FIGS. 1A and 1B except that the piston and cell sizes of the motivating fluid differs from those of the stock fluid. Like items in FIGS. 1A,  1 B and  1 C have like numbers. A prime symbol “′” 0  is used to designate a variation of an item. FIG. 1C depicts a pump  10 ′that includes a first unit  36 ′and a second unit  34 ′. Each unit  36 ,  34  includes a stock-fluid port  42 ,  40 ; a piston  56 ′,  54 ′, stock-fluid cell  52 ′,  44 ′ and a motivating-fluid cell  46 ′,  50 ′; and a motivating-fluid port  66 ,  64 . The motivating-fluid cell  46 ′,  50 ′ is larger than the stock-fluid cell  52 ′,  44 ′. Piston  56 ′,  54 ′ have been modified to adapt to the cell differences. Link  51 ′ connects piston  54 ′ within the motivating-fluid cell to a piston  54 “within the stock-fluid cell. An extension  53 ′ of piston  56 ′ within stock-fluid cell connects piston  56 ′ to a piston  56 ″. A link  108  coordinates the motion of the pistons  56 ′,  56 ″,  54 ′ and  54 ” within the respective cells of each unit  36 ′,  34 ′. Each piston  56 ′,  56 ″,  54 ′ and  54 ″ may include a seal  62 ″,  62 ′,  60 ′, and  60 ″ at a perimeter of each piston contacting the cell wall of its respective cell within unit  36 ′,  34 ′ to prevent the contamination of the motivating fluid by the stock fluid and vice versa. An advantage of pump  10 ′ includes the ability to pump the stock-fluid to a higher pressure proportional to the ratio of the areas of the pistons in the motivating-fluid cell and the stock-fluid cell. Another advantage of pump  10 ′ that is shared with pump  10  and pump having a similar design includes the pump&#39;s ability to suction and pump stock fluid at a reasonable operating pressure while not being negatively effected by the operating pressure of the motivating fluid. 
     Another embodiment of the present invention includes one double acting unit working with a biasing element. FIG. 2A depicts a pump  210  during a first step of the cycle. FIG. 2B depicts the pump  210  during a second step of the cycle. Like items in FIGS. 2A and 2B have like numbers. 
     Before discussing the steps of the cycle depicted in FIGS. 2A and 2B, the parts of pump  210  are presented. Pump  210  includes a unit  236 . The unit  236  includes a stock-fluid port  242 ; a piston  256  splitting a cavity within the unit  236  into a stock-fluid cell  252  and a motivating-fluid cell  246 ; and a motivating-fluid inlet/out  266 . A link  308  coordinates the motion of the piston  256  and the biasing element  244 . The piston  256  may include a seal  262  at its perimeter contacting the cavity wall of unit  236  to prevent the contamination of the motivating fluid by the stock fluid and vice versa. 
     A line  212  supplies the stock fluid to the stock-fluid cell  252  of the unit  236  through valve  222 ; bridge  226 ; stock-fluid line  232 ; and stock-fluid port  242 . Line  316  disposes of the stock fluid from the stock-fluid cell  252  of the unit  236  through stock-fluid port  242 ; and stock-fluid line  232 ; valve  310 . 
     In a like manner, a line  302  supplies the motivating fluid to the motivating-fluid cell  246  of the unit  236  through motivating-fluid inlet/out  266 ; branch  294 ; path  286  of valve  276 ; and motivating-fluid line  272 . A line  304  disposes of the motivating fluid from the motivating-fluid cell  246  of the unit  236  through motivating-fluid inlet/out  266 ; motivating-fluid line  272 ; path  282  of valve  276  and branch  300 . A tie  290 , which may be an electrical connection or a mechanical connection, coordinates the availability of path  286  versus path  282  and vice versa. 
     Movement of piston  256  from right to left draws stock fluid into stock-fluid cell  252  of unit  236  from line  212  through valve  222 , bridge  226 , stock-fluid line  232  and stock-fluid port  242 , while valve  310  remains closed. Movement of piston  256  from left to right pumps stock fluid from stock-fluid cell  252  of unit  236  through stock-fluid port  242 , stock-fluid line  232  and valve  310  to line  316  for disposal while valve  222  remains closed. Motivating fluid travels to motivating-fluid cell  246  of the unit  236  from line  302  along branch  294  through path  286  of valve  276 , motivating-fluid line  272  and motivating-fluid port  266  while path  282  of valve  276  remains unavailable. Motivating fluid travels from motivating-fluid cell  246  of the unit  236  through motivating-fluid port  266 , motivating -fluid line  272 , path  282  of valve  276  and along branch  300  to line  304  for disposal while path  286  of valve  276  remains unavailable. 
     The coordinated opening and closing of valves  222  and  310  in the stock-fluid circuit and the availability of paths  286  and  282  of valve  276  produces the action of piston  256  in unit  236  and biasing element  244  to pump the stock fluid. The state of the valves and paths of unit  236  in the steps of the cycle depicted in FIGS. 2A and 2B are summarized in Table 2 below. 
     Step 1 of the cycle includes the suctioning of stock fluid into unit  236  from a stock-fluid source through line  212 . Referring to the unit  236  in FIG. 2A, the circuits from motivating-fluid cell  246  to discharge motivating fluid line  304  is open. Also, the circuit from line  212  to draw stock fluid into stock-fluid cell  252  are open. As biasing element  244  contracts, it acts through link  308  to move piston  256  of unit  236 . As piston  56  moves, the expansion of stock-fluid cell  252  creates suction in the open circuit to line  212  to draw stock fluid into stock-fluid cell  252 . Motivating-fluid cell  246  contracts as piston  256  moves from right to left. Step 1 ends when stock-fluid cell  252  expands to its greatest volumes; motivating-fluid cell  246  contracts to its smallest volume and biasing element  244  contracts to its shortest length. Then, path  282  makes way for path  286  in valve  276 ; valve  222  closes; and valve  310  opens. Valve  272  may have its paths make way by a tie  290  as shown in FIG.  2 A. Alternatively, valves  276  may be arranged in a manner similar to valves  222  and  310  and visa versa. Once the path and valve states are changed, step 2 of the cycle begins. 
     
       
         
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 State Summary for Cycle Steps of FIGS. 2A and 2B 
               
             
          
           
               
                   
                 FIGS. 2A 
                 FIGS. 1B 
               
               
                   
                 Step 1 
                 Step 2 
               
               
                   
                   
               
             
          
           
               
                   
                 Action of Unit 236 
                 Suction 
                 Pump 
               
               
                   
                 Valve 222 
                 Opened 
                 Closed 
               
               
                   
                 Valve 310 
                 Closed 
                 Opened 
               
               
                   
                 Path 286 of Valve 276 
                 Unavailable 
                 Available 
               
               
                   
                 Path 282 of Valve 276 
                 Available 
                 Unavailable 
               
               
                   
                 Motivating-fluid Cell 246 
                 Contracting 
                 Expanding 
               
               
                   
                 Stock-fluid Cell 252 
                 Expanding 
                 Contracting 
               
               
                   
                 Springs 244 
                 Contracting 
                 Expanding 
               
               
                   
                 Piston 256 
                 Right to Left 
                 Left to Right 
               
               
                   
                   
               
             
          
         
       
     
     Step 2 of the cycle includes the pumping of stock fluid from unit  236  for discharge. Referring to unit  236  in FIG. 2B, the circuits from line  302  to expand motivating-fluid cell  246  with motivating fluid is open and the circuit to contract stock-fluid cell  252  to pump stock fluid via line  316  for discharge into are open. Motivating fluid expands motivating-fluid cell  246  by acting on piston  256 . Piston  256  moves from left to right to pump stock fluid from stock-fluid cell  252  while contracting cell  252 . At the same time, piston  256  acts through link  308  to expand biasing element  244 . Step 2 ends as motivating-fluid cell  246  expands to its greatest volume; stock-fluid cell  252  contracts to its smallest volume; and biasing element  244  expands to its greatest length. Then, valve  276  is moved back to the positions shown in FIG.  2 A. This causes path  286  to make way for path  282  in valve  276  and valve  310  closes and valve  222  opens. Once the path and valve states are changed, step 1 of the cycle begins again. 
     Alternative embodiments to those of FIGS. 2A and 2B include, for example, placing the biasing element within the cavity of the unit as shown in FIG.  2 C and replacing the piston and biasing element with a polymeric membrane or bladder as shown in FIG.  2 D. Like items in FIGS. 2A,  2 B,  2 C and  2 D have like numbers. A prime symbol “′” is used to designate a variation of an item in FIG. 2C while a double a prime symbol “″” is used to designate a variation of an item in FIG.  2 D. 
     FIG. 2C depicts a pump  210 ′ that includes a unit  236 ′. The unit  236 ′ includes a stock-fluid port  242 ; a piston  256  splitting a cavity within the unit  236 ′ into a stock-fluid cell  252  and a motivating-fluid cell  246 ; and a motivating-fluid inlet/out  266 . A biasing element  244 ′ within the stock-fluid cell  252  of the cavity of the unit  236 ′ acts directly on piston  256 . The biasing element  244 ′ is depicted in FIG. 2C as compressed to balance the pressure of the motivating fluid. The piston  256  may include a seal  262  at its perimeter contacting the cavity wall of unit  236 ′ to prevent the contamination of the motivating fluid by the stock fluid and vice versa. An advantage of pump  210 ′ includes the decrease in space needed to accommodate the pump when the biasing element is within the stock-fluid cell. It will be appreciated by those skilled in the art that the biasing element may be included within motivating-fluid cell or within both the stock-fluid cell and the motivating-fluid cell rather than solely within the stock as shown in FIG.  2 C. If in the motivating fluid cell, the biasing element should act to compress the motivating fluid cell, such as by an extension spring. 
     FIG. 2D depicts a pump  210 ″ that includes a unit  236 ″. The unit  236 ″ includes a stock-fluid port  242 ; a movably biasing boundary  256 ″ splitting a cavity within the unit  236 ″ into a stock-fluid cell  252  and a motivating-fluid cell  246 ; and a motivating-fluid port  266 . Examples of the movably biasing boundary  256 ″ include a membrane or bladder that may be polymeric or other suitable material. The biasing boundary stretches as motivating-fluid cell expands and relaxes as motivating-fluid contracts to draw stock fluid into expanding stock-fluid cell. The movably biasing boundary  256 ″ is depicted in FIG. 2C as stretched to balance the pressure of the motivating fluid. 
     Yet another embodiment of the present invention includes a plurality of double acting units working together. FIG. 3A depicts a pump  410  including eight units  401 ,  402 ,  403 ,  404 ,  405 ,  405 ,  407  and  408  arranged in a circle. FIG. 3B depicts a pump  610  including eight units  601 ,  602 ,  603 ,  604 ,  605 ,  605 ,  607  and  608  arranged in two lines. To minimize clutter, only selected items have been numbered in each of FIG. 3A and 3B. Is will apparent to those skilled in the art that items having similar appearance perform similar functions. 
     The parts of pump  410  depicted include eight units  401 ,  402 ,  403 ,  404 ,  405 ,  405 ,  407  and  408  arranged in a circle. Each unit  401 ,  402 ,  403 ,  404 ,  405 ,  405 ,  407  and  408  includes a stock-fluid port  442 ; a piston  456  splitting a cavity within each unit into a stock-fluid cell  452  and a motivating-fluid cell  446 ; and a motivating-fluid inlet/out  466 . A link  508  coordinates the motion of each piston  456  and a corresponding biasing element  444 . Applicants contemplate that linkages combined with an eccentric wheel may be used in place of the biasing elements. Each piston  456  may include a seal  462  at its perimeter contacting the cavity walls of its respective unit to prevent the contamination of the motivating fluid by the stock fluid and vice versa. 
     A line  412  supplies the stock fluid to the stock-fluid cell  452  of each unit through a valve  422 ; bridge  426 ; stock-fluid line  432 ; and stock-fluid port  442 . Line  516  disposes of the stock fluid from the stock-fluid cell  452  of each unit  436  through stock-fluid port  442 ; and stock-fluid line  432 ; and valve  510 . 
     In a like manner, a line  502  supplies the motivating fluid to the motivating-fluid cell  446  of each unit through motivating-fluid port  466 ; branch  494 ; and valve  476 . A line  504  disposes of the motivating fluid from the motivating-fluid cell  446  of each unit through motivating-fluid port  466 ; valve  476  and branch  500 . A tie  490  coordinates the availability of paths in valve  476 . 
     The coordinated opening and closing of valves  422  and  510  in the stock-fluid circuit and the availability of paths in valve  476  produces the action of piston  456  in each unit and it corresponding biasing element  444  to pump the stock fluid. The coordination may be accomplished with a controller as shown in FIG.  3 A. The controller synchronizes the paths within the valve  476  to create the proper in-flow and out-flow of motivating fluid. 
     Alternatively, the units may be arranged in a line as in pump  610  of FIG.  3 B. The parts of pump  610  include eight units  601 ,  602 ,  603 ,  604 ,  605 ,  605 ,  606 ,  607  and  608  arranged in two lines. Each unit  601 ,  602 ,  603 ,  604 ,  605 ,  605 ,  606 ,  607  and  608  includes a stock-fluid port  642 ,  642 ′; a piston  656  splitting a cavity within each unit into a stock-fluid cell  652  and a motivating-fluid cell  646 ; and a motivating-fluid port  666 . A camshaft  644  through link  708  coordinate the motion of each piston  656 . Each piston  656  may include a seal  662  at its perimeter contacting its respective unit to prevent the contamination of the motivating fluid by the stock fluid and vice versa. 
     This embodiment also demonstrates that a single motivating fluid may be used to pump a plurality of stock fluids. That is, a line  702  supplies the motivating fluid to the motivating-fluid cell  646  of each unit  601 ,  602 ,  603 ,  604 ,  605 ,  606 ,  605 ,  607  and  608  through motivating-fluid port  666 ; branch  694 ; valve  676 ; and motivating-fluid line  672 . A line  704  disposes of the motivating fluid from the motivating-fluid cell  646  of each unit  601 ,  602 ,  603 ,  604 ,  605 ,  605 ,  606 ,  607  and  608  through motivating-fluid port  666 ; valve  676  and branch  700 . A tie  690  coordinates the availability of paths in valve  676 . 
     A first line  612  supplies a first stock fluid to the stock-fluid cell  652  of units  605 ,  606 ,  607  and  608  through a valve  622 ; bridge  626 ; stock-fluid line  632 ; and stock-fluid port  642 . A first line  716  disposes of the first stock fluid from the stock-fluid cell  652  of units  605 ,  607  and  608  through stock-fluid port  642 ; and stock-fluid line  632 ; and valve  710 . A second line  612 ′ supplies a second stock fluid to the stock-fluid cell  652  of units  601 ,  602 ,  603  and  604  through a valve  622 ′; bridge  626 ′; stock-fluid line  632 ; and stock-fluid port  642 . A second line  716 ′ disposes of the second stock fluid from the stock-fluid cell  652  of units  601 ,  602 ,  603  and  604  through stock-fluid port  642 ; and stock-fluid line  632 ′; and valve  710 ′. 
     The coordinated opening and closing of valves  622 ,  622 ′ and  710 ,  710 ′ in the stock-fluid circuit and the availability of paths in valve  676  produces the action of piston  656  in each unit and camshaft  644  to pump the stock fluid. The coordination may be accomplished with a controller as shown in FIG.  3 B. The controller synchronizes the paths within the valve  676  to create the proper in-flow and out-flow of motivating fluid. 
     A state summary table as was made for pump  10  of FIGS. 1A and 1B and pump  210  of FIGS. 2A and 2B may be made for pump  410  of FIG.  3 A and pump  610  of FIG.  3 B. The compiling of such tables is within the scope of those skilled in the art. Thus, such tables are not presented. 
     In regard to the parts that makeup pumps  10 ,  10 ′,  210 ,  410  and  610  described above as well as aspects of the working of the a pump of the present invention, more discussion follows. In particular, details relating to the valves of the stock-fluid circuit; the unit or units of each pump; the valves of the motivating-fluid circuit; the motivating fluid and controllers for coordinating the opening and closing of the valve follow. 
     The valves of the stock-fluid circuit may be any types that achieve the goal of a pump according to the present invention. A particularly useful valve type is a check valve. Check valves may be placed in the stock-fluid circuit to direct the flow of stock fluid from the stock-fluid source to the stock-fluid cell during its filling and from the stock-fluid cell to the discharge line during pumping. A particularly useful check valve type is that known commercially as a duckbill check valve available from, for example, Linatex Inc., having its US headquarters in Gallatin, Tenn. Check valves are commercially available from industrial suppliers such as W. W. Grainger, Inc. 
     A unit used to suction and pump the stock fluid may be any types that achieve the goal of the pump according to the present invention. Although each unit is depicted in FIGS. 1A,  1 B,  1 C,  2 A,  2 B,  3 A, and  3 B as occupying a substantially rectangular prismatoid, it will be appreciated by those skilled in the art that any shape that accomplishes the pumping of the stock fluid may be used. For example, each unit might be a cylinder having an irregular cross-section or a regular cross-section, such as for example, circular, elliptical, polygonal, etc. A particularly useful unit is a cylinder type unit having a circular cross-section. These units may range from less than an inch in diameter to a foot or more in diameter. The unit may be custom manufactured or purchased as an off the shelf-item. Cylinder type units are commercially available from industrial suppliers such as W. W. Grainger, Inc. 
     The biasing element as used in certain embodiments may be any type that achieves the goal of a pump according to the present invention. A particularly useful biasing element is a spring. Various springs may be used including a helical spring that is stretched as shown in FIGS. 2A,  2 B and  3 A. Alternatively, the helical spring may be compressed while acting against the link of the piston. It will be appreciated by those skilled in the art that other types of springs and their corresponding arrangement may include simple leaf springs, laminated leaf springs, coiled springs, spiral springs, torsion springs and driving springs. Other parts that may function as the biasing element include any elastically compressible or expandable arrangement or material that may act with the link to return a piston to a position so that a motivating-fluid cell volume is minimized when the pressure of the motivating fluid is removed. Examples of biasing elements thus include reversibly compressible or expandable materials such as metals, polymers and composites, bladders including compressible and/or incompressible fluid, and magnet arrangements. One unit of the pump  10  may be regarded as a biasing element for the other. Also, a camshaft and/or the eccentric connection to a wheel may be regarded as a biasing element in embodiments that follow. 
     A piston with a biasing element falls within the broader concept of a movably biasing boundary disposed within the cavity of a unit. Such a movably biasing boundary divides the cavity into the motivating-fluid cell and the stock-fluid cell. Other examples of movably biasing boundary include a polymeric membrane or bladder that stretches as motivating-fluid cell expands and relaxes as motivating-fluid cell contracts to draw stock fluid into expanding stock-fluid cell. 
     The valves of the motivating-fluid circuit may be any types that achieve the goal of a pump according to the present invention. A particularly useful valve type is a solenoid valve. A solenoid valve may be placed in the motivating-fluid circuit to direct the flow of motivating fluid into the motivating -fluid cell to drive a piston while pumping the stock fluid. Also, a solenoid valve may be actuated in the motivating-fluid circuit to bleed the motivating fluid from the motivating fluid cell while suctioning the stock-fluid into the stock-fluid cell. Solenoid valves appropriate for use in a pump of the preset invention include those commercially available from industrial suppliers such as W. W. Grainger, Inc. 
     Motivating fluid may be any type that achieves the goal of a pump according to the present invention. A particularly useful motivating fluid is potable water supplied at pressure such as municipal water supply pressures. Other useful motivating fluids include liquids and compressed gasses such as compressed air. 
     Controllers may be any types that achieve the goal of a pump according to the present invention. A controller may run the spectrum from simple manual control though mechanical, electromechanical to complex computer programmed logic control (PLC). Particularly useful controllers include time circuits and microprocessor circuits. The pump may be selectively actuated by various other methods. For example, a pressure sensor may sense the piston position, the motivating-fluid level or volume, the stock-fluid level or volume and output a signal to actuate the valves in the motivating fluid circuit. Alternately, a timer may toggle the motivating-fluid valve actuation. In addition, the motivating fluid valve actuation may be triggered by sensing that the piston has completed its travel in one direction or another. A mechanical and/or electrical linkage to accomplish this result is within the scope of this invention. 
     A further aspect of the present invention provides an application of the pump of any of the previous embodiments. FIG. 4 shows a system  810  including a first pump  822  and a second pump  842  according to the present invention. The first pump  822  is used to transmit a grease/water mixture  820  from an appliance to a collection line  826  of a separator unit  830 . The second pump  842  is used to transmit a grease part  836  separated in the separator unit  830  to a holding tank  844 . Both pumps  822 ,  842  are useful in commercial food preparation operations. As will become apparent, the water used as the motivating fluid is preferably hot water for pump  842 . 
     Referring to appliance  814  that includes pump  822 , it may be any of the type used in commercial food preparation operations. Such appliances may include any equipment or process that produces or results in a grease/water mixture. Examples of equipment that perform processes that might result in grease/water mixtures include a sink, a dishwasher, a cooker, pasteurizer, a blancher, an oven, a dryer, a grille etc. The appliance may include a tank  816  containing a grease/water mixture  820  that is a stock fluid to be pumped. A line  812  of the pump  822  communicates with the grease/water mixture  820 . A line  902  provides the pump  822  potable water as the motivating fluid at about nominal water pressure (e.g., ranging from about 30 to about 60 pounds per square inch (psi) and more typically from about 40 to about 50 psi). Also, the pump  822  includes a grease/water discharge line  916  and a potable water discharge line  904 , both shown to communicate with collection  826  through line  824 . To remove grease/water mixture from tank  816  to separator  830 , pump  822  is run, and both the grease/water mixture  820  and the potable water are transmitted to separator  830 . 
     Referring to separator  830  that includes pump  842 , it may be any of the type used in commercial food preparation operations. Such separators may include any equipment or process that separates a grease/water mixture into a grease part and a gray water part. A particularly popular and effective separator has been the Big Dipper® separator sold by Thermaco, Inc. of Asheboro, N.C., USA. One model of the Big Dipper® separator uses a rotating oleophilic wheel to pull grease from the top of a body of a grease/water mixture to be scraped off by a blade. Another separator is that described in U.S. patent application Ser. No. 09/439,900, filed Nov. 12, 1999, entitled “Readily Serviceable Separator Unit with a Focusing Plate.” This separator  830  includes a focusing plate  832  that separates a grease/water mixture  834  into a grease part  836  and a gray water part that than passes through the separator  830  in to a sewer line  840 . The grease part  836  is transmitted from the surface of the grease/water mixture  834  to a holding tank  844  for later appropriate disposal. A line  912  of the pump  842  communicates with the grease part  836 . A line  902  communicates with the pump  842  to provide potable water as the motivating fluid at about nominal city water pressure (e.g., ranging from about 40 to about 50 psi). Preferably, the potable water is hot water that can be directed into the separator  830  to add heat to the mixture  834  so the grease stays liquid. Also, the pump  842  includes a grease part discharge line  917  and a potable water discharge line  905 . When pump  842  is run, the grease part  836  is transmitted to the holding tank  844  and the potable water is transmitted to separator  830  just below the grease part  836 . 
     A pump according to the present invention may be constructed from any materials that are compatible with the motivating fluid, as well as the stock fluid. In certain applications, the construction materials may also be dictated by industry and/or government standards. For example, in commercial food preparation operations, county and/or city health codes may need to be consulted and, in the case that the products are being exported, foreign government health codes may need to be consulted. Notwithstanding the above, a pump of the present invention, and its part may be constructed from metals; ceramics including concrete and moldable cements; polymers; composites base on metals, ceramics, and polymers; either partially, completely, or with combinations thereof. 
     The previously described versions of the present invention have many advantages, including allowing the transmission of a stock fluid without the use of an electrical motor. More particularly, the present invention is advantageous for use in commercial food preparation operations to relieve surcharges that might otherwise be charged by municipal authorities. 
     Although the present invention has been described in considerable detail with respect to a certain preferred versions thereof, other versions are possible. Examples include use of a pump of any of the previous embodiments with a flammable fluid to remove an explosive hazard that may otherwise be present when a pump driven by an electrical motor is used. Examples of flammable fluids include heating fuel, gasoline, kerosene, aviation fuel, hydrogen, methane, ethane, propane and the like. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions herein. 
     All patents and other documents identified in the present application are hereby. incorporated by reference.