Abstract:
This invention provides a fluid system for exchanging used hydraulic fluid with fresh hydraulic fluid in an accessed hydraulic circuit. One particular application provides an exchange apparatus for exchanging fluids of the type found in motor vehicle hydraulic circuits. The exchange apparatus may utilize pressurized spent fluid flow as a fluid power medium to activate the auto-replenishing fluid exchanger system to replace the spent fluid with fresh fluid at equalized flow rates. Alternatively, the exchange apparatus may utilize pressurize fresh fluid as a fluid power medium to activate the exchange system. Additional power may be supplied by an external boost pump to supplement the flow of fluid.

Description:
RELATED APPLICATIONS 
   This is a continuation-in-part application of Ser. No. 08/846,982 filed May 1, 2001, now U.S. Pat. No. 6,446,682, issued Sep. 10, 2002, which was a continuation of Ser. No. 09/301,851 filed Apr. 29, 1999, now U.S. Pat. No. 6,223,790, each patent being incorporated by reference herein. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to fluid exchange devices for replacing used fluid with a fresh fluid in a fluid circuit, and more particularly to an apparatus and method of use for achieving a fluid exchange of a fluid circulation circuit such as a vehicular automatic transmission, a vehicular power steering system, a vehicular engine oil system, or a vehicular cooling system. 
   2. Related Background Art 
   Various devices have been utilized to achieve fluid exchanges for vehicular automatic transmissions. Applicant&#39;s U.S. Pat. Nos. 6,378,657; 6,330,934; 6,267,160; 6,223,79; 6,164,346; 6,105,635; 6,082,416; RE36,65; 5,964,278; and 5,318,080 disclose devices, systems, or methods for performing a fluid exchange. Each of these patents are incorporated by reference herein in their entireties. The prior art also includes various externally powered exchange devices wherein the power to effect an exchange procedure is at least in part provided by an electric pump. Some of these externally powered devices utilize a vehicle&#39;s electric system for activation. One unresolved problem has been the need for a fluid exchange system which requires no external power source such as an electric motor or compressed air. 
   A need also exists for a device for servicing vehicular automatic transmissions having the following characteristics: one which requires no external powering source other than the fluid pressure from the accessed fluid circulation circuit; a reciprocating pump having a pump volume which is a fraction of the fluid volume necessary for the fluid exchange; an onboard fresh fluid supply tank reservoir of a capacity sufficient to perform a fluid exchange for most vehicle automatic transmissions; and a pump matching rates of flow and volumes exchanged during the and exchange procedure. 
   U.S. Pat. No. 6,223,790 discloses a system able to operate without electrical or compressed air power in its 1st and 5th embodiments, both embodiments being reciprocating fluid exchangers, and both of which employ a mechanically actuated spring and detent operated fluid control valve. 
   The need remains for such a self powered, fluid flow rate and volume equalized, fluid exchange system where any necessary fluid control valving is provided by an alternative mechanism which does not employ spring and detent, such as disclosed in the first and fifth embodiments of U.S. Pat. No. 6,223,790. 
   A fluid exchange unit for automatic transmissions, power steering and cooling systems which does not require connection to a vehicle&#39;s electric system would be desired. In addition, such a unit can be very portable and useful away from a service station given that no external power supply is required to operate the exchange device This portability is viewed as advantageous and desired by service technicians. 
   SUMMARY OF THE INVENTION 
   The present invention solves problems existent in prior hydraulic fluid exchange systems. The present invention provides a compact fluid exchange system having a pump volume which is substantially smaller than the total volume of fluid replaced during the exchange process. The apparatus can be used to service hydraulic fluid systems having a variety of circuit sizes, configurations, etc. 
   Briefly, the invention includes a cyclical pump having a pair of used fluid chambers and a pair of fresh fluid chambers. The pump receives used fluid from an accessed hydraulic fluid circuit into a used fluid chamber, introduces fresh fluid from fresh fluid chamber into the hydraulic fluid circuit, simultaneously refills the other fresh fluid chamber with fresh fluid, and simultaneously discharges spent fluid from the other used fluid chamber into a spent fluid receptacle. Fluid flow relative to the pump assembly is directed by control valves. The pump cycles until the predetermined exchange volume is satisfied (determined by such means as visual or optical comparison of fluid input and output, sensor devices, etc.). The invention permits connection to both a bulk fresh fluid supply and a floor drain, such as those typically found in vehicle repair facilities. 
   One object of the invention includes a reciprocating pump assembly having a power medium of a pressurized hydraulic fluid, such as used transmission fluid of an operating motor vehicle during a maintenance procedure, or pressurized fresh fluid from an external source. 
   One object of the invention provides a fluid exchange apparatus released from the requirement of having dedicated on-board fluid reservoirs. A remote bulk fresh fluid supply and remote waste fluid receptacle, such as those found in vehicle repair facilities, may be utilized to practice the present invention. In this manner, a smaller, more compact fluid exchange apparatus is provided. 
   One object of the present invention is a device which permits an efficient change between different fresh fluids (grades, additive packages, etc.) between or during exchange procedures. The limited volumetric capacity of the pump assembly and associated conduit results in a limited amount of the previous different fresh fluid charge held within the exchange apparatus. 
   One object of the invention is to provide a fluid exchanger which is self-powered by pressure in the accessed fluid circulation circuit thereby removing the need to connect the exchanger to the electrical system of a vehicle being serviced or to an external electrical outlet or compressed air supply. This allows a high degree of portability and minimizes the potential of electronic component damage. 
   Another object of the invention is to provide a fluid exchanger which is especially suitable to replace the contents of fluid systems in addition to automatic transmissions in vehicles. There is the need for a fluid exchanger which can be adapted and manufactured to replace the contents of fluid circuits such as those of vehicular cooling systems, engine oil systems, and power steering system, and as well the high flow, high pressure hydraulic circuits of heavy construction and other commercial and industrial equipment such as cranes, fork-lifts, front-loaders, plows, road graders, garbage trucks, hydraulically operated industrial and farm implement machinery, and aircraft hydraulic circuits, as well as many other fluid circulation circuits in everyday use or which will be later developed which can or will benefit from complete or near complete fluid exchanging. 
   One object of the invention is to provide a fluid control mechanism for a reciprocating fluid exchanger which may be powered by the accessed fluid circulation circuit, including low flow foreign vehicle automatic transmissions. 
   Another object of the invention is to also provide a fluid control mechanism which is reliably activated and more durable for exchanging the fluid of high fluid flow, high fluid pressure fluid circulation circuits such as large, commercial trucks or other industrial or commercial equipment or machines used in manufacturing. 
   The present invention provides a fluid exchange system in a preferred embodiment which employs a mechanically actuated pilot valve which in turn fluidly operates a used fluid control valve. A fluid exchange machine of the present invention can be utilize in exchange procedures for low to high fluid pressure systems. High pressure systems may include farm tractors, heavy construction machinery, and industrial machines used in manufacturing. 
   Another object of the invention is to provide a self-loading fluid exchanger which exchanges approximately equivalent volumes of fresh fluid for used fluid at approximately the same rates of flow, and a fluid exchanger with a pump capacity much smaller than the fluid capacity of its fresh fluid reservoir. 
   One object of this invention is to provide a simple mechanical automatic bypass valving system which requires no source of electrical power. 
   Another related object of the invention is a means to manually shift the exchanger into bypass mode. 
   Another object of the invention is to provide a fluid exchanger which can be utilized to exchange the fluid in other fluid circulation circuits, such as circuits containing motor or engine oil, hydraulic fluid, antifreeze or other coolant, water, chemicals, or products circulated in fluid circuits used in passenger vehicles, and commercial or industrial vehicles or equipment, or machines used in industry including food processing and chemical processing. 

   
     DESCRIPTION OF THE DRAWINGS 
     The present invention will be described hereafter in the Detailed Description of Preferred Embodiments, taken in conjunction with the following drawings, in which the reference numerals refer to like elements throughout. 
       FIG. 1  is a perspective, partially diagrammatic, illustration of one embodiment of the present invention. 
       FIG. 2  is a cross sectional view of a portion of the embodiment of FIG.  1 . 
       FIG. 3  is a cross sectional view of a portion of the embodiment of FIG.  1 . 
       FIG. 4  is a cross sectional view of a portion of the embodiment of FIG.  1 . 
       FIGS. 5 through 8  are diagrammatic illustrations of operation of the embodiment of  FIGS. 1-4 . 
       FIG. 9  is a diagrammatic cross sectional view of a control valve for use in an alternative embodiment of the present invention. 
       FIG. 10  is a diagrammatic cross sectional view of a bypass valve assembly for use in another embodiment of the present invention. 
       FIG. 11  is a perspective view of a portion of the bypass valve of FIG.  10 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   As shown in  FIG. 1 , one embodiment of the invention includes a pump  425  including two reciprocating pistons  453 ,  455  linked by a connecting rod  452  within a cylinder block  339  as further depicted in FIG.  2 . Pump  425  includes a first and second used fluid pumping chambers  20 ,  30  and a first and second fresh fluid pumping chambers  10 ,  40 . The pumping chambers  10 ,  20 ,  30 ,  40  are variable volume chambers with the volume of each being defined by the relative position of the pistons  453 ,  455  within cylinders  399 ,  401 . As described in more detail hereinafter, in the embodiment of  FIGS. 1 through 8 , the driving force for pump  425  is supplied by pressurized used fluid received from an accessed hydraulic circuit wherein the pressurized used fluid is directed, in alternating manner, to either pumping chamber  20  or pumping chamber  30 . Pump  425  has a used fluid control valve assembly  423  in communication with cylinder block  339  and used fluid received from the vehicle or other device being serviced. In an alternative embodiment, such as a device incorporating the valve of  FIG. 9 , the driving force for pump  425  may be supplied by pressurized used fluid (as provided by the accessed hydraulic circuit) and pressurized fresh fluid (as provided by an external fluid pump). 
   Pump  425  has a left cylinder  399  which is secured in position between a left cylinder head  427  and cylinder block  339  by four headbolts, two of which are shown, a headbolt  431  and a headbolt  433 . Pump  425  has a right cylinder  401  which is secured in position between a right cylinder head  429  and cylinder block  339  by four headbolts, two of which are shown, a headbolt  435  and a headbolt  437 . A conduit tee  405  is suitably connected to a port  445  of cylinder head  427 . Conduit tee  405  includes a pair of checkvalves  407 ,  409 . A conduit tee  406  is suitable connected to a port  447  of cylinder head  429 . Conduit tee  406  includes a pair of checkvalves  411 ,  413 . 
   A fresh fluid supply conduit  415  is attached to a fresh fluid tank assembly  417  at one end and to checkvalve  407  and checkvalve  411  at its other two ends. Tank  417  has a fill cap  421  which is vented and contains a fresh fluid supply  419 . A fresh fluid conduit  403  is attached at one end to a quick connector  335  and attached to checkvalve  409  and  413  at its other two ends. A waste fluid conduit  317  is arranged at one end to discharge a used fluid  430  into a used fluid receiver  381  and connected to a waste port  307  of cylinder block  339  and to a waste port  309  of cylinder block  339  at its other two ends. A waste conduit assembly  311  is arranged at one end to discharge used fluid  430  into used fluid receiver  381  and is connected to a waste port  353  of valve  423  and to a waste port  355  of valve  423  at its other two ends. A sightglass  318  is provided to conduit assembly  311 . Sightglass  318  permits the operator to view the clarity of fluid within conduit  311 , for example so as to determine completion of an exchange procedure. 
   A used fluid supply conduit  369  is connected at one end to a quick connector  333  and connected to a port  347  of valve  423  and a port  301  of cylinder block  339  at its other two ends. Connector  333  is adapted to be coupled into the accessed fluid circuit, such as a vehicles automatic transmission cooling circuit so as to receive used fluid therefrom. 
   A conduit  313  connects a port  357  of valve  423  to a port  303  of cylinder block  339 . A conduit  315  connects a port  359  of valve  423  to a port  305  of cylinder block  339 . 
     FIG. 2  more fully illustrates pump assembly  425 . Pistons  453 ,  455  each include threaded structures  448 ,  454 , respectively, for coupling pistons  453 ,  455  to connecting rod  452 . Pump  425  has a cylinder block  399  which is secured between cylinder head  427  and cylinder block  339  by four headbolts, two of which are shown in FIG.  1 . Pump  425  has a cylinder  401  which is secured between cylinder head  429  and cylinder block  339  by four headbolts, two of which are shown in FIG.  1 . In this particular embodiment, piston  453  and piston  455  are cylindrical in form, as is connecting rod  452 , and cylinder  399  and cylinder  401 . Other shapes and configurations of pistons, connecting rods, and cylinders can be utilized without departing from the art depicted herein in this embodiment. 
   Cylinder head  427  is provided with port  445 . Cylinder head  429  is provided with port  447 . Cylinder block  339  is provided with two ports, a port  377  which connects to first used fluid powering chamber  20 , and a port  379  which connects to second used fluid powering chamber  30 . 
   Cylinder block  339  has a bore  321  into which connecting rod  452  is slidingly received and suitably fitted to provide smooth sliding operation and limited leakage. Cylinder block  339  has two circumferencial glands  329 ,  331  which serve to hold two gaskets of suitable material, one per side (not shown), which gaskets are disposed between cylinder  399  and cylinder block  339 , and between cylinder  401  and cylinder block  339 . Cylinder head  427  has a circumferencial gland  332  which serves to hold a gasket of suitable material (not shown) between cylinder  399  and cylinder head  427 . Cylinder head  429  has a circumferencial gland  329  which serves to hold a gasket of suitable material (not shown) between cylinder  401  and cylinder head  429 . If desired, and/or in high pressure embodiment of the present invention, seals can be provided to rod  452 , and pistons  453  and  455 . 
     FIG. 3  depicts a cross sectional view of cylinder head  339  with a pilot valve spool  323  slidingly received into a pilot valve bore  337 . As described with reference to  FIGS. 5-8 , spool  323  is repeatedly engaged and moved by pistons  453 ,  455  during an exchange procedure as pistons  453 ,  455  travel toward block  339 . Bore  337  includes recessed areas  327 ,  328  at respective ends. Valve spool  323  has a right endstop  330  suitably secured to its right end and a left endstop  325  suitably secured to its left end. Endstops  325  and  330  are slidingly insertable into corresponding recessed areas  327 ,  328 . Various means can be utilized to secure endstops  325  and  330  on end each of valve spool  323 , such as matingly providing male threads to each end of valve spool  323  and female threads to each endstop  325  and  330 . As with securing pistons  453  and  455  to connecting rod  452 , a suitable thread locking compound can be applied to the threads in order to securely fix endstops  325  and  330  to valve spool  323 . Recessed area  328  is sized to slidingly receive endstop  330 , as is recessed area  327  sized to receive endstop  325 . Valve spool  323  is configured to provide fluid communication between two pair of its ports  301 ,  303 ,  305 ,  307 ,  309  at a time. 
   As with cylinders  399 ,  401  and pistons  453 ,  455 , alternate shapes for the pilot valve bore  337  and pilot valve spool  323  other than cylindrical can be used without departing from the art depicted herein, as long as the fit between each is suitably snug to prevent unacceptable levels of leakage. Pilot valve bore  337  has five ports  301 ,  303 ,  305 ,  307 ,  309 . Port  301  is coupled to conduit  369 . Port  303  is coupled to conduit  315 . Port  305  is coupled to conduit  313 . Waste port  307  and waste port  309  are coupled to waste conduit  317 . No detent or position locking mechanism is required to hold spool  323  in place after it has been moved into each one of its two alternate, shifted positions which occur as a result of the movement of pistons  453 ,  455 . 
     FIG. 4  depicts more clearly the used fluid control valve  423 . Valve  423  has a valve body  361 . Valve body  361  has a valve bore  360  into which a valve spool  367  is slidingly received. Valve bore  360  is provided with seven ports  347 ,  349 ,  351 ,  353 ,  355 ,  357 ,  359 . Valve  423  includes a threaded end plug  363  and a threaded endplug  365 . Port  357  is connected to conduit  313  and port  359  is connected to conduit  315 . Valve body  361  is provided with an O-ring gland  362  at one end and an O-ring gland  364  at the other end. Port  349  is in fluid communication with port  377  of cylinder block  339 . Port  351  is in fluid communication with port  379  of cylinder block  339 . In another embodiment, valve assembly  423  may be is secured directly to cylinder block  339  (not shown). This direct mounting of valve  423  to cylinder block  339  directly connects ports  349  and  351  of valve  423  to ports  377  and  379  of cylinder block  339 , respectively. Port  347  is connected to conduit  369 , and ports  353  and  355  are connected to waste conduit  311 . Valve spool  367  is configured to provide fluid communication between two ports at a time depending on its particular position within valve body  361 . The particular position of valve spool  367  in the valve bore  360  determines which adjacent ports communicate with each other. 
   Operation of the Embodiment of FIGS.  1 - 4   
     FIGS. 5 through 8  illustrate operation of the embodiment of the present invention of  FIGS. 1 through 4 .  FIGS. 5 through 8  are partially diagrammatic in that arrows represent fluid flow within the exchange device during an exchange procedure. 
   The closed fluid circulation circuit of an automatic transmission, or other hydraulic fluid circulation circuit is accessed and opened to provide a higher pressure side and lower pressure or return side. Adapters with matingly compatible connections (not shown but understood by those with ordinary skill in the art) are connected at one end of each to one side each of the opened fluid circulation circuit, which in this case is the cooling circuit of an automatic transmission. The remaining end of each adapter is matingly connected to a selection of one of the pair of quick connectors  333  and  335  of  FIG. 1 , with the adapter connected to the pressure side of the circuit connected to quick connector  333  and the adapter connected to the low pressure or return side of the circuit connected to quick connector  335 . The use of specific adapters or connectors is not an necessary element of the present invention. A variety of connection approaches may be made to inteconnect the exchange device of the present invention with a hydraulic circuit, such as an automatic transmission of a vehicle. 
     FIGS. 5 through 8  illustrate that valve spool  367  is movable within valve bore  360  in response to fluid pressures communicated through conduits  313 ,  315 . The position of valve spool  367  in valve bore  360  of used fluid control valve  423  is determined by the position of valve spool  323  in pilot valve bore  337  which itself is determined by whether piston  453  or piston  455  last made contact valve spool  323 . The direction of movement and the actual point of reversal of direction of movement of piston/rod/piston assembly  453 / 452 / 455  as illustrated in  FIGS. 5 through 8  is determined by which of the two positions valve spool  367  of valve  423  is in. There is a causal interdependency between valve spool  323 , valve spool  367 , and the direction of movement of piston/rod/piston assembly  453 / 452 / 455  which results in a circular chain of events. This chain of events starts with the fluid pressure of the accessed fluid circulation circuit maintaining both valve spools  323  and  367  in position while simultaneously moving piston/rod/piston assembly  453 / 452 / 455  in the direction as determined by valve spools  323  and  367 . 
   When the fluid circulation circuit being serviced is pressurized, in this case when the engine is started and operated to render the automatic transmission operative to pump fluid through its cooling circuit, used fluid flows from the cooling circuit through quick connector  333 , into conduit assembly  369  to thereby supply pressurized used fluid to port  347  of control valve assembly  423  and port  301  of cylinder block  339 . Used pressurized fluid from the accessed hydraulic circuit provides the power necessary to effect a fluid exchange using embodiments of the present invention. 
   The particular path of the pressurized used fluid after flowing through port  347  is dependent on the position that valve spool  367  is in within valve bore  360 . In any event, pressurized used fluid is directed in alternating manner to one of the used fluid pumping chambers  20 ,  30 . In operation, the pistons  453 ,  455  move in a repeated cyclical manner. Check valves  407 ,  409 ,  411 ,  413  control the flow of fluid within conduits  403 ,  415 . 
     FIG. 5  illustrates used pressurized fluid being received into valve  423  through ports  347 ,  349  and into port  377  of block  339  where it enters used pumping chamber  20 . Pressurized used fluid within chamber  20  forces piston  453  away from block  339  to have the following effects: (1) fresh fluid within chamber  10  is forced into conduit  403  for introduction into the accessed circuit, (2) used fluid within chamber  30  is directed through ports  351 ,  355  of valve  423  and into conduit  311  for disposal in receiver  381 , and (3) fresh fluid is drawn into chamber  40  through conduit  415  from fresh fluid supply  417 . Piston  453  continues to move away from block  339  until the condition of  FIG. 6  is reached. 
     FIGS. 6 and 7  illustrate movement of valve spools  367 ,  323  relative to that of FIG.  5 .  FIGS. 6 and 7  illustrate used pressurized fluid being received into valve  423  through ports  347 ,  351  and into port  379  of block  339  where it enters used pumping chamber  30 . Pressurized used fluid within chamber  30  forces piston  455  away from block  339  to have the following effects: (1) fresh fluid within chamber  40  is forced into conduit  403  for introduction into the accessed circuit, (2) used fluid within chamber  20  is directed through ports  349 ,  353  of valve  423  and into conduit  311  for disposal in receiver  381 , and (3) fresh fluid is drawn into chamber  10  through conduit  415  from fresh fluid supply  417 . Piston  453  continues to move away from block  339  until the condition of  FIG. 7  is reached, i.e. piston  453  is in contact with valve spool  323 . As piston  453  move closer to block  339 , valve spool  323  is biased into its other position as indicated in FIG.  5 . 
     FIG. 8  illustrates movement of valve spool  323  into its other position thereby effecting a change in the position of valve spool  367 . Upon valve spool  367  assuming the position as indicated in  FIG. 8 , used pressurized fluid being received into valve  423  through ports  347 ,  349  and into port  377  of block  339  where it enters used pumping chamber  20 . Pressurized used fluid within chamber  20  forces piston  455  away from block  339  to have the following effects: (1) fresh fluid within chamber  10  is forced into conduit  403  for introduction into the accessed circuit, (2) used fluid within chamber  30  is directed through ports  351 ,  355  of valve  423  and into conduit  311  for disposal in receiver  381 , and (3) fresh fluid is drawn into chamber  40  through conduit  415  from fresh fluid supply  417 . Piston  453  continues to move away from block  339  until the piston  455  contacts valve  323 . As piston  455  move closer to block  339 , valve spool  323  is biased into its other position as indicated in  FIGS. 6 and 7 . The cyclical interaction between pistons  453 ,  455  and valves  323  and  367 , as illustrated in  FIGS. 5 through 8 , continues during the exchange procedure whereby quantities of used fluid and fresh fluid are exchanged. As pumping chambers  10 ,  20 ,  30 ,  40  have equivalent size, the flow rates between used and fresh fluid are substantially equivalent. The exchange procedure may be terminated by an operator, such as after viewing the used fluid in sightglass  318  to determine completion of the exchange. 
     FIG. 9  illustrates a combination fresh and used fluid control valve assembly  494 . This valve can be substituted for the used fluid control valve  423 , conduit tees  405 ,  406  and checkvalves  407 ,  409 ,  411 , and  413  of the embodiment of  FIGS. 1 through 8 . This substitution is desirable when a pressurized fresh fluid supply is substituted for open, vented tank  417 . Such a pressurized fresh fluid supply (not shown but understood by someone of ordinary skill in the art) can be comprised of the addition of an onboard air powered or electrically powered pump connected in series or parallel (with a bypass around such a pump and a downstream flowing checkvalve) to deliver and/or to augment the flow of fresh fluid  419  from fresh fluid tank  417 . This is indicated when fresh fluid  419  cannot be adequately drawn into pump  425 . An air powered pump (not shown) can be powered by a stored and regulated onboard supply of compressed air held in a suitable pressure vessel. An electric powered pump can be powered by an onboard rechargeable battery or a removable and replaceable battery pack. 
   Valve  494  has a valve body  471  and is provided with a valve bore  472  receiving a valve spool  473 . Valve body  471  has thirteen ports  451 ,  456 ,  449 ,  455 ,  457 ,  459 ,  461 ,  463 ,  465 ,  467 ,  469 ,  477 ,  481 , of which ports  477  and  481  are integral one each with a threaded end plug  475 ,  483 . Both threaded end plugs  475  and  483  are provided with O-ring glands  485  and  479  respectively, to which O-rings which are suitably resistant to fluid  419  of tank  417  and fluid of used fluid receiver  381 . Port  456  is coupled to conduit  352  in fluid communication with port  379 . Port  451  is coupled to a conduit  350  in fluid communication with port  377 . Port  463  is coupled to a conduit  491  which is connected to port  445 . Port  467  is coupled to a conduit  493  which is connected to port  447 . Port  481  is coupled to a conduit  313  which is connected to port  305 . Port  477  is coupled to a conduit  315  which is connected to port  303 . Ports  459  and  469  are coupled to conduit  403  which is coupled to quick connector  335  of FIG.  1 . Ports  461  and  465  are coupled to conduit  415  which is connected to tank  417  of FIG.  1 . Ports  455  and  457  are coupled to conduit  311  which directs fluid into fluid receiver  381  of FIG.  1 . Port  449  is coupled to conduit  369  which is connected to quick connector  333  of FIG.  1 . 
   The combination fresh &amp; used fluid control valve assembly  494  of  FIG. 9  when installed on the first preferred embodiment depicted in  FIGS. 1-8 , provides an additional preferred feature of allowing the use of a pressurized fresh fluid source feeding conduit assembly  415 . 
   In operation, when conduit  313  is provided pressurized fluid from pilot valve spool  323  through conduit  313  while conduit  315  is vented by pilot valve spool  323  through conduit  315 , valve slide  473  of valve assembly  494  is moved to the right side of valve bore  472  and is held in place against threaded end plug  475 . This results in the fluid connection of ports  461  and  463 ,  451  and  449 ,  456  and  457 , and  467  and  469 , which in turn results in the fluid connection of conduits  491  and  415 ,  350  and  369 ,  352  and  311 , and  493  and  403 . 
   This right position (as indicated in  FIG. 9 ) of valve spool  473  in valve bore  472  results in the following events: used fluid from conduit  369  is provided to the left used fluid powering chamber  20  which moves piston/connecting rod/piston assembly  453 / 452 / 455  to the left, thereby providing fresh fluid from the left fresh fluid chamber  10  to conduit  403 , and fresh fluid is simultaneously provided to right fresh fluid chamber  40  from tank assembly  417  through conduit  415 , while also simultaneously forcing used fluid from right used fluid powering chamber  30  to be discharged into conduit assembly  311  for delivery into used fluid receiver  381 . 
   As piston/connecting rod/piston assembly  453 / 452 / 455  reaches its end of stroke against cylinder head  339 , the pilot valve spool  323  is moved into its right position, bring left endstop  330  fully into cavity  328 . This results in pressurized used fluid being provided to conduit  315  and port  477  and pilot valve spool  323  venting the captive fluid through port  481  to conduit  313 . This results in valve spool  473  being moved to its left position against threaded end plug  483 . This shifting of pilot valve spool  473  from its right position to its left position, reverses the movement of piston/connecting rod/piston assembly  453 / 452 / 455 , which then results in the following fluid connections being made by valve assembly  494 , fluid connection is established between ports  463  and  459 ,  451  and  455 ,  456  and  449 , and  467  and  465 , which in turn results in the fluid connection of conduits  491  and  403 ,  350  and  311 ,  352  and  369 , and  493  and  415 . 
   This second position of valve spool  473  in valve bore  472  results in the following events: 
   used fluid from conduit  369  is provided to the right used fluid powering chamber  30  which moves piston/connecting rod/piston assembly  453 / 452 / 455  to the right, thereby providing fresh fluid from the right fresh fluid chamber  40  to conduit  403 , and fresh fluid  419  is simultaneously provided to left fresh fluid chamber  10  from tank assembly  417  through conduit  415 , while used fluid is also discharged from left used fluid powering chamber  20  into conduit assembly  311  for delivery into used fluid receiver  381 . 
   Use of valve  494  allows the provision of a delivery pump to conduit assembly  415 . It also allows the application of a flow-augmenting boost pump to conduit assembly  415 . Each of these options establishes the use of the pumping chambers  10 ,  40  as combination pumping and powering chambers in addition to chambers  20 ,  30 . These options allow the removal of any portion of or all of the total resistance applied to the fluid circulation circuit being serviced with a fluid exchange, thereby allowing the removal of a portion or all of the work being done by the fluid pressure provided by the fluid circulation circuit for the fluid exchange. This is especially useful to increase the speed in which the fluid of low pressure, low flow fluid circulation circuits may be replaced. If the total fluid resistance of a fluid exchange system is significant, flow in the accessed circuit may be reduced to such an extent that damage to the system can occur. Utilization of the present invention may reduce the fluid resistance of a fluid exchange machine so that embodiment of the present invention may be used in a variety of different fluid circuits. 
     FIGS. 10 and 11  illustrate a float operated automatic bypass valve for use in alternative embodiments of the present invention.  FIGS. 10 and 11  do not show the reciprocating parts of the fluid exchanger since a number of embodiments are interchangeably usable. The necessary fluid lines for connecting to the reciprocating part of the fluid exchanger are however shown. 
   A floater operated bypass valve assembly  200  is comprised of a valve body  203  with a valve slide  201 . Valve body  203  is provided with an incoming port  211  for spent fluid from transmission and an outgoing port  213  for fresh fluid delivery. Valve  203  also has an inlet port  219  for fresh fluid provided by the pump and an outlet port  221  for spent fluid from the accessed circuit. Valve slide  201  has an internal fluid passage  209  which, when in proper position with valve slide  201  in its downward position, connects incoming port  211  to outgoing port  213 . Valve slide  201  has a plug  215  which is secured and sealed into the machining access port end of passage  209 , allowing the easy machining of passage  209  without custom casting if so desired. Valve body  203  and valve slide  201  may be constructed of steel, aluminum or other suitable or desired alloys, or can be constructed of a number of suitable plastics including the highly durable acrylics and carbon fiber compounds as well as suitable nylon type compounds or other special plastic compounds fluorinated for durability and prevention of fluid absorption. Valve slide  201  is provided with a vertical vent passage  217  and an anti-rotation vertical alignment slot  222 . Valve body  203  has a threaded port  224  to receive a male threaded pin  220  for anti-rotation slot  222 . 
   Valve slide  201  has a circumferential fluid passage for fresh fluid provided by exchanger  223  and a circumferential fluid passage for spent fluid provided to exchanger  225 . A fresh fluid reservoir tank  227  is provided and is connected to valve body  203  and a reinforcing plate  255  by a set of screws  257  and  259  (the additional two screws are not shown). Tank  227  is provided with a float which is connected to valve slide  201  by a male threaded at both ends shaft  231 , which is screwed into a female threaded receiver  232  of valve slide  201  at one end and which is screwed into float  229  at a female threaded receiver  233 . A fluid vent port  234  and a fluid vent port  236  are provided to tank  227  and support plate  255 . Tank  227  has a fresh fluid outlet port  235  which is connected to a fresh fluid inlet supply tube  244  which is in turn also connected to a two position lever operated on/off ball valve  241  which is in turn connected to a drain outlet tube  239 . Float  229  has a female threaded receiver  238  into which a threaded bearing  237  is screwed. Port  219  is connected to a fresh fluid outlet supply tube  245 . Port  221  is connected to spent fluid inlet tube  243 . A fresh fluid outlet hose  247  connects port  213  to a female quick connect  251 . A spent fluid inlet hose  249  connects port  211  to a female quick connect  253 . Quick connect  251  is connected to an adapter which is in turn connected to the outlet side of an opened cooling circuit of an automatic transmission (not shown). Quick connect  253  is connected to an adapter which is in turn connected to the return side of an opened cooling circuit of an automatic transmission (not shown). Valve body  203  is provided with 4 female threaded receivers, of which two are shown, female threaded receivers  256  and  258  which receive screw  257  and screw  259 . 
   Tank  227  is provided with a cross bar support bracket  263  which has a plunger guide  267  and set of weight saving bracket holes  265 . Plunger guide  267  holds a plunger  273  which has a retainer end  276  on its bottom end and a plunger return spring  271  and a washer  278  on its top end. Plunger  273  is provided with a pivot pin  275 . Bracket  263  has a horizontal lever  277  which has two holes, one placed to hold to pivot pin  275  and the other a slide slot  284  which is rotatable on a slide pin  283  which is affixed to the top of plunger  273 . Horizontal lever  277  is fitted at approximate mid point with a pivot pin  281  which receives a vertical lever  279 . Vertical lever  279  is connected to a manually operated detent assembly (not shown). Note, that pivot pins  275  and  281  and slide pin  283  are provided with suitable fasteners such as end-mounted retainer clip caps (not shown). 
   Tank  227  and all of its integral parts, including float  229  may be made of steel, aluminum, suitable alloys, or suitable plastics or fiberglass compounds. Float  229  should be highly buoyant and filled with air or other suitable gas or lighter than oil foam plastic, each of which should be either shielded from oil by sealing technology (for example fluorination) or comprised of oil insensitive materials. 
   When fresh fluid reservoir tank  227  is empty, float  229  is in its lowermost position and causes valve body  201  via shaft  231  to also be in its lowermost position under power provided by the weight of float  229 , bearing  237  and shaft  231 . Float  229  is constructed of material light enough and large enough to be sufficiently buoyant in automatic transmission fluid to overcome its own weight of shaft  231 , the weight of valve slide  201 , and any resistance to movement of shaft  231  and valve slide  201 , all cumulative, such that valve slide  201  will rise to its uppermost position when tank  227  has a sufficient volume of fluid to allow the reciprocating exchanger to operate. On the other hand, the sum total weights of float  229 , bearing  237 , shaft  231  and valve body  201  must be great enough to overcome any resistance to movement that exists when the fluid level in tank  227  has dropped below a level providing any buoyancy to float  229 . 
   Fresh automatic transmission fluid is added into the fresh fluid reservoir tank  227  to a level well above the float and it is contained herein until consumed and discharged by the reciprocating fluid exchanger disclosed in this specification which can be connected to tubes  243 ,  244  and  245 . This fresh fluid then displaces float  229  thereby raising float  229  to its uppermost position which simultaneously raises shaft  231  which pulls valve slide  201  to its uppermost position. Note: if the operator has inadvertently filled tank  227  with the wrong type of fluid desired, he or she can drain that fluid out at drain outlet tube  239  by opening ball valve  241  until that fluid is all out. 
   Vertical lever  279  is held by a detent mechanism in its upward position (detent mechanism not shown) and is not holding float  229  in its downward position. Of course, the operator can choose to move this lever  279  to a lower detented position at anytime which will move lever  277  downward to overcome plunger return spring  271  and any buoyancy provided by any fluid in tank  227 , thereby causing plunger  273  to move its downward position to make contact with bearing  237  to thereby simultaneously force float  229  and valve slide  201  to their downward positions. Vertical lever  273  can be so moved if the operator desires to use lever  279  as a manual override for the automatic bypass valve function provided by fluid buoyancy to float  229  and can also be manually raised at any time from its lower detented position to its upper detented position. 
   When vertical lever  279  causes valve slide  201  to move its downward position this causes the valve slide to assume its downward position which establishes a bypass fluid connection between hoses  249  and  247  through ports  211  and  213  through the internal fluid passage  209  of valve slide  201 . Correspondingly when the fluid level in tank  227  is depleted to the point of denying sufficient buoyancy to float  229 , valve slide  201  also is caused to move its downward position under the sum total weight of float  229 , bearing  237 , shaft  232  and the valve slide  201  itself, thereby also establishing a bypass connection between hoses  247  and  249 . 
   When a bypass connection is established between hoses  247  and  249 , the transmission can freely circulate its fluid through the exchange device and its cooling circuit without any fluid exchanging occurring or without any significant loss of volume of fluid. This can allow the operator time to evaluate the flow rate and clarity of the fluid, as well as determine the current level of fluid in the transmissions pan as verified by checking the dipstick indication. 
   When vertical lever  279  is in its upward detent position and there is a sufficient level of fluid in tank  227 , the buoyancy provided to float  229  by the fluid raises valve slide  201  to its upward position when thereby causes port  211  to communicate with port  221  through the circumferential fluid passage  225  while simultaneously causing port  213  to communicate with port  219  through circumferential fluid passage  223 , while also simultaneously causing fluid passage  209  to be blocked by valve body  203 . When valve slide  201  is caused to be in its upward position by buoyancy provided to float  229  by a sufficient volume of fluid contained in tank  227 , the communication of port  211  and  221  and the simultaneous communication of port  213  to  219  occurs and this causes the reciprocating fluid exchanger to operate if the transmission is operative to pump fluid into its cooling circuit to circulate therein. 
   This operation of the reciprocating fluid exchanger then is accompanied by the flow of fresh fluid from tank  227  to the fresh fluid inlet of the reciprocating exchanger (not shown) through tube  244 , the flow of spent fluid from the transmission cooling circuit into and through connector  253  through hose  249 , through port  211 , through circumferential fluid passage  225 , through port  221  and into and through tube  243  to the reciprocating exchanger, and this is also simultaneously accompanied by the outflow of fresh ATF from the reciprocating exchanger to the transmission cooling circuit into and through tube  245 , via passage through port  219 , through circumferential fluid passage  223 , through port  213 , through hose  247  and through connector  251 . 
   As long as the fluid level of tank  227  is high enough to provide sufficient buoyancy to float  229 , valve slide  201  stays in its upward position and allows the reciprocating fluid exchanger to operate as long as the transmission is operative to pump spent fluid into its cooling circuit to circulate it therein. As soon as the reciprocating exchanger has consumed enough fresh fluid from tank  227  as provided through port  235  and tube  244  to cause the fluid level to drop in tank  227  to the point of denying sufficient buoyancy to float  229 , float  229  drops to its lower position along with valve slide  201  thereby causing the bypass valve assembly  200  to function in its bypass mode. As long as there is a sufficient volume of fresh fluid in tank  227  to provide enough or sufficient buoyancy to float  229  to cause valve slide  201  to assume and remain in its upper position, bypass valve assembly  200  will function in and remain in its fluid exchange mode. 
   Known to those of ordinary skill in the art are various methods of connecting conduits together and to valves and to quick connectors or other fittings, and these methods include the use of many types of hose barbs, push-lock and ferrule secured, or other types such as tubing inserted into plastic push-lock receivers. For sake of brevity these are not shown. Also known to those of ordinary skill in the art are various methods of establishing fluid communication between desired fluid system components, such a flexible hose type conduits of appropriate composition for the fluid being exchanged, and use of other types of tubing and conduit material including flexible plastic, bent metals of a variety of compositions, and braided high pressure, reinforced hydraulic hose with machine or hand installed end fittings. For sake of brevity these are not shown. As is known to those of ordinary skill in the art, the actual composition and type of any conduit selected as well as the inside diameter chosen must be based on length of fluid delivery, pressure of the fluid and acceptable resistance levels, and the desired operating characteristic of the conduit arrangements. For example, if a fluid exchange system is designed to exchange the fluid of very low flow fluid circulation circuits, a relatively large inside diameter, and relatively short selection and arrangement of conduits is desirable and indicated. For sake of brevity the extensive type, compositions and pressure and chemical resistance ratings of the various type of conduits, flexible and rigid will not be discussed herein since these considerations are understood by those with ordinary skill in the art. 
   Many other types and configurations of movable fluid separation members (in these embodiments pistons  453 ,  455 ) can be used such as diaphragms linked by a connecting rod, or linked rotors. In addition the number of fluid chambers provided, the number of fluid separation members, the number of connecting rods, and the number of pilot valves and fluid control valves can be quite varied without departing from the art. For example, one could construct a fluid exchange system comprised of two pilot valves, each with isolated functions providing half the needed actuation of a pilot valve or valves if more than one used. Such a system could include two pilot valves with isolated functions providing half the needed control and could incorporate four pistons and three connecting rods between them linking them. Alternatively, one could use three diaphragms with two connecting rods and size theses diaphragms such that the volumes of fluid moved by two during operation of the system to exchange fluid equal the volume moved by the third, thus provided proper approximate equalization between fresh fluid introduction to the fluid circulation circuit and used fluid delivery out of the fluid circulation circuit having its fluid exchanged. Any number of sizes and configurations of fluid separation members with the numeric double number of chambers can be selected with the appropriate corresponding number of connecting rods, and as well. Any number of sizes and configurations of pilot valves and fluid control valve can be selected according to this novel art, as long as the necessary functions required for proper reciprocating operation will be provided for, as will be further explicated. A wide selection of suitable materials can be used to construct the preferred embodiments including special fiberglass resins and exotic plastic compounds, depending on the heat and pressures which must be handled, and materials which include specialized aluminum alloys and aluminum/magnesium alloys, as well as various grades of steel. In this case the preferred embodiments pump assembly, pilot valve and fluid control valve are constructed of aircraft grade aluminum alloy. If diaphragms are used as the fluid separation members, the use of seals, if needed at all, is only an issue where the connecting rod slidingly impacts its bore. One could of course alternatively position the used fluid powering chambers at either ends of the pump, one each, and the fresh fluid pumping chambers at the inside bordering the cylinder block, one to each side of it, and this would result in the piston/rod/piston assembly being pushed rather than being pulled. The same pilot valve configuration could be used without affecting the overall fluid changing function, and this would be true for the use of other types of linked fluid separation members, such as diaphragms or rotors. In the case of using pistons as the fluid separation members, such as in the preferred embodiments herein, piston rings and seals of various types can be fitted. Or alternatively, relatively tight piston to cylinder wall clearances can be used providing sufficient sealing without the cost of such seals. In the preferred embodiments herein piston to cylinder wall clearances are approximately 0.001 inch providing an acceptable seal without significant piston to cylinder wall resistance. 
   Not shown but understood by those with ordinary skill in the art is the manner in which the embodiment of  FIG. 1  is connected to an opened fluid circulation circuit which will have its fluid exchanged. After the fluid circulation circuit is opened at a suitable location, adapters which are matingly compatible are then connected to either side of the opened circuit, one each. These adapters terminate in quick connectors which are matingly compatible with the quick connects  333 ,  335  of FIG.  1 . The adapter connected to the pressure side of the circuit must then be connected to quick connect  333  and the adapter connected to the low pressure side must then be connected to quick connect  403 . If a fluid flow alignment mechanism (such as depicted in U.S. Pat. Nos.: Re.36,650; 6,082,418; 6,27,160; or 6,330,934) is incorporated into conduits  369 ,  403 , it is not necessary for the operator to identify the higher pressure side of the opened circuit before connecting conduits  369 ,  403  to the adapters which have been connected to either side of the opened circuit, one to each. Adapters can be constructed of a wide variety of suitable materials and lengths and this will not be discussed further because it is understood by those with ordinary skill in the art and for the sake of brevity. 
   Another preferred embodiment (not shown) is one which has no pilot valve, but instead has an equivalent structure comprised of a combination of position sensors mounted in either the cylinder block or cylinder heads of the pump assembly and an electrical solenoid operated hydraulic valve receiving fluid pressure from the fluid pressure of the fluid circulation circuit being serviced, directly or indirectly. There are a number of types of position sensors available which function suitable such as use of magnetically triggered micro-switches, hall-effect sensors as well as other more sophisticated types such as inductive sensors. These sensors can be configured and arranged to alternatingly activate a latching relay configuration which in turn alternatingly energizes and holds energized an electric solenoid until de-energized by a second sensor signal at opposite end of stroke which then de-energizes the solenoid of a two-position four way valve or equivalent. Latching relays can mechanical or solid state. Because latching relays can hold their connection even after the triggering electric current is stopped, they are applicable to this embodiment. In this way pressurized fluid pressure and venting are alternatingly provided to each end of the fluid control valve under control of the latching relay and the triggering signals which activate the relays switching of connections. Thus, this positions sensor based valve actuating mechanism can be arranged and configured for a piston to trigger a positions sensor when it reaches its end of stroke, which in turn triggers a latching relay which holds the solenoid on and the valve in that first position until the alternate position sensor is activated by the opposite end of stroke position of that piston (or any other piston used) which thereby unlatches the relay removing power from the solenoid and allows its spring return to the opposite position to hold the valve in its alternate and second position. This embodiment requires an electric supply, but a rechargeable battery or plug in batter pack can be used to allow the desired portability of the unit away from any power supplies and without connection to the electrical systems of the vehicles being serviced. Many other valve types can be used to provide same or the equivalent function, such as the use of two two-position three way valves, one for each end of the control valve which alternatingly provides pressure and vent to waste for each sensed piston end of stroke. One could also use a equivalent selection and arrangement of two position two-way valves such as simple solenoid operated on/off valves, or even a selection of check valves and/or priority valves which attain the same functional results without the same exact, specific structure. What is important is the overall function of the valve configuration, best referred to as a valve control system or configuration, rather than the particular and specific types of valves used and their arrangement and configuration. 
   In addition, one could use a compressed air powered pilot valve and fluid control valve, with the pilot valve in the cylinder block or at each cylinder head with spring return or equivalent operated by compressed air and which alternatingly routes compressed air and venting to each end of the fluid control valve. Any needed compressed air could be provided to and stored in an onboard pressure tank of the fluid exchange unit and this would still allow the highly desired portability within or around the service center. 
   It is understood that even though numerous characteristics and advantages of the present invention have been disclosed in the foregoing description, the disclosure is illustrative only and changes may be made in detail. Other modifications and alterations are within the knowledge of those skilled in the art and are to be included within the scope of the appended claims.