Transmission fluid exchanger

A hand held transmission fluid exchanger including a housing block having parallel new and used fluid passages therein, such passages being joined by a return passage having a pressure relief valve therein. The method involves connecting such exchanger with a conventional on-demand transmission fluid supply system having a meter therein and holding the dispensing gun open so that flow is controlled by valves incorporated in the exchanger.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to fluid exchangers for exchanging
 transmission fluid in an automatic transmission.
 2. Description of the Prior Art
 It has long been recognized that the transmission fluid in automatic
 transmissions should be exchanged periodically to remove impurities and
 provide new clean effective transmission fluid. Many efforts have been
 made to provide a satisfactory device to achieve this function in an
 efficient and convenient manner.
 It has been recognized that benefit may be taken of the transmission pump
 itself to pump used fluid from the transmission to a used fluid tank while
 simultaneously pumping new fluid into the transmission upstream of the
 transmission pump. Typically, some automobile transmissions incorporate a
 bypass which protects the transmission from overpressurization. This
 bypass may be effective to relieve pressure in the event the pump pumping
 used fluid in should overpressurize the transmission. However, not all
 transmissions incorporate this internal bypass arrangement and there
 exists a risk of overpressurizing the transmission.
 One effort to solve the fluid exchange problem led to the development of a
 fluid exchanger mounted on a small cart and having inlet and outlet
 control valves for controlling the rate at which fluid is pumped into the
 transmission. Such exchangers typically employ rather elaborate plumbing
 which may allow for pressure relief in the event a certain pressure is
 exceeded. A device of this type is shown in U.S. Pat. No. 5,370,160 to
 Parker and assigned to the assignee of the instant application. Such
 devices, while having enjoyed substantial commercial success, are
 relatively expensive to manufacture and are somewhat bulky to store and
 use.
 Other efforts have led to the proposal of a small hand held exchanger
 including fluid pumps and valves for controlling flow to and from the
 automatic transmission. A device of this type is shown in my U.S. Pat. No.
 5,743,357 and assigned to the owner of the assignee of the instant
 application. While providing significant benefits, such devices suffer the
 shortcoming that there is no provision to prevent overpressurization of
 the transmission.
 Other efforts have been made to sense transmission pressures and equalize
 such pressures to avoid overpressurization. One such device incorporates a
 rather elaborate pre-exchange adapter purportedly used for sensing the
 pressure in the transmission. Efforts have then been made to balance the
 inlet and outlet pressures from such transmission across a diaphragm or
 piston. A device of this type is shown in U.S. Pat. No. 5,472,064 to
 Viken. While offering some benefits, such devices still suffer the
 shortcoming that use thereof is relatively time consuming and the systems
 involve the risk that diaphragm or piston, under high pressure, may result
 in damage and substantial spillage.
 Thus, there exists a need for a transmission fluid exchanger which
 eliminates the expense of incorporating a fluid pump and which protects
 the transmission against overpressurization. Other benefits could be
 derived from providing for a single hook up which would allow for sensing
 of the transmission pressure by a single gauge which could also be used
 for sensing the pressure differential during the exchange procedure.
 SUMMARY OF THE INVENTION
 In one form, the automatic transmission fluid exchanger of the present
 invention is characterized by a housing having a new fluid passage to be
 connected to the outlet of an on-demand meter gun suspended from a fluid
 dispenser reel. The exchanger includes a used fluid passage therein and
 connected by a return passage for return of used transmission fluid in the
 event a certain pressure is exceeded. A pressure sensing gauge may be
 provided for first sensing the operating pressure of the transmission and
 then sensing pressure differentials during operation of the system.
 In another form, the automatic transmission fluid exchanger of the present
 invention includes a sensor passage connected between the new and used
 fluid passages and including a pair of spaced apart valve seats therein, a
 poppet being floatably received between such seats so that it can be
 pressurized from one seat to the other as the pressure differential builds
 up thereacross from one side to the other. A pressure gauge may be mounted
 on such housing in fluid communication with the valve chamber to sense
 pressure therein.
 In the method of the present invention, the exchanger can be coupled with
 an on-demand automatic transmission fluid supply system including a
 conventional dispenser gun having a dispenser meter built in. The gun may
 be coupled with the exchanger and the gun valve handle strapped in
 position to hold the gun open so that the flow control valves in the
 exchanger can be utilized to control the inlet and outlet flow rates.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 The automatic fluid exchanger of the present invention includes, generally,
 a lightweight, small housing 11 having respective new fluid and used fluid
 passages 13 and 15 formed therein and includes on the respective inlet
 ends respectively a new fluid inlet valve 19a and used fluid outlet valve
 21. The respective outlet and inlet ends of the respective flow passages
 13 and 15 include quick disconnect couplings, generally designed 25 and
 27, for connection with the automatic transmission in a vehicle, generally
 designated 31 (FIG. 2). The new fluid inlet valve 19 may be connected
 through a coupling hose, generally designated 33, to an on-demand
 transmission fluid dispenser gun, generally designated 35, suspended from
 an overhead reel 37. Referring to FIG. 3, the new fluid and used fluid
 passages 13 and 15 are connected in communication with one another by
 means of a return passage, generally designated 39, having a pressure
 relief valve device, generally designated 41, therein. The passage 39 is
 in fluid communication with a pressure gauge 45.
 Consequently, the new fluid inlet valve 19 may be connected with the nozzle
 of the gun 35 to suspend the exchanger from the overhead reel 37. When the
 exchanger is to be used, the valve included in the gun 35 may be held open
 so that new fluid flow may be controlled by the exchanger valve 19. With
 the flow control valves 19 and 21 closed, the transmission of the vehicle
 31 may be operated to communicate the pressure generated by the
 transmission pump through the passage 15 and valve 14 to the gauge 45 to
 determine the magnitude of operating pressure generated by the
 transmission pump. Then, the valves 19 and 21 may be opened and
 manipulated to balance the flow rate to and from the transmission and to
 maintain the desired pressure to avoid overpressurization. Should the
 pressure from the transmission exceed some predetermined level, as for
 instance 30 psi, the pressure relief valve 41 will be opened so that the
 fluid from the transmission can flow through the return passage 39 and
 back through the new fluid passage 13 to the upstream location in the
 transmission thereby positively preventing overpressurization.
 Conveniently, the housing 11 is constructed of a block 51 of transparent
 plastic such as LEXAN. The housing is about 71/2 inches long, 5/12 inches
 wide and 11/2 inches thick, weighing about six pounds. The block 51 is of
 rectangular shape and planar on its opposite ends 53 and 54. Referring to
 FIG. 3, equal diameter parallel bores are machined in the block to form
 the respective passages 13 and 15. The block is formed centrally with a
 transverse aperture 55 through the depth thereof for receipt of the
 pressure gauge 45. Machined inwardly from one side of the housing block is
 a first bore defining a used fluid relief passage section 59 which extends
 laterally from the passage 15. The outer end of the access bore to such
 section 59 is plugged by a plug 61. Machined in from the opposite side of
 the housing block is a new fluid return passage section 65 which likewise
 has the outer access bore plugged by a plug 67. The used fluid relief
 passage section 59 and new fluid return passage section 65 cooperate to
 form the return passage 39. Machined in from the end 54 of the block is a
 large diameter bore defining a spring compartment 71. The inner end of the
 spring compartment is formed with a conical valve seat which steps down to
 a longitudinal used fluid return passage section 75. The conical seat 74
 is so sized that the ball 73 seats thereagainst with substantially a full
 diametrical half exposed to the new fluid side as will be discussed
 hereinafter. The spring compartment bore 71 is threaded at its external
 extremity for receipt of a threaded adjustment plug 72. Mounted in the
 spring compartment 71 interposed between such poppet and plug is a
 conically shaped coil spring 81 which resiliently presses a ball poppet 73
 against the seat 74. The plug 72 may be adjusted to apply the necessary
 pressure to such spring to cause it to hold the ball poppet 73 on the seat
 74 until a selected pressure differential is reached across such ball. The
 spring is thus set to a bias which will allow the valve 41 to open at a
 pressure less than that which would damage the transmission. Machined
 inwardly from the aperture 55 is a pressure gauge passage section 85 into
 which is screwed a threaded nipple 87 mounting the pressure gauge 45.
 It will be appreciated by those skilled in the art that the new fluid
 section 65 of the return is laterally offset to the downstream side of the
 poppet 73 such that new fluid pressure will pressurize such poppet toward
 the seat 74 to positively maintain such poppet seated until the pressure
 in the used fluid passage builds up to the point where the transmission
 pressure exceeds the new fluid pressure to thus drive such ball off the
 seat.
 The bypass valve 41 may take many different configurations, such as a ball
 valve, flapper valve, piston valve or the like. It is only important that
 the valve provide for isolation between the inlet and outlet passages but,
 at some predetermined pressure, allow for recirculation from the used
 fluid passage to the new fluid passage.
 As known by those skilled in the art, some transmissions include internal
 bypass valves which might open at about 60 psi to thus provide a safety
 measure to prevent overpressurization and consequent damage to the
 transmission and seals incorporated therein. Not all transmissions
 incorporate such a bypass and, even for those that do, it is beneficial to
 have an additional safety measure to positively prevent overpressurization
 and consequent damage to the transmission. This is particularly true when
 the exchanger takes advantage of the relatively high pressures typically
 employed in an on-demand transmission fluid delivery system.
 The housing 11 includes respective end plates, generally designated 87 and
 89, on the opposite ends thereof. The end plate 87 is formed with through
 bores aligned with the respective new and used fluid passages 13 and 15,
 the new fluid bore being threaded at its outer extremities for receipt of
 a check valve nipple 95 included in a check valve, generally designated
 97, which mounts the flow control valve 19. The used fluid outlet bore is
 also internally threaded for receipt of a threaded nipple 101 mounting the
 used fluid outlet valve 21. It will be appreciated that the end walls 53
 and 54 are both formed around the passageways 13 and 15 with O-ring glands
 that mount O-rings 107 to provide sealing engagement with the end plates
 to prevent leakage.
 The end plate 89 is formed with respective outlet and inlet bores aligned
 with the respective passages 13 and 15 and such bores are internally
 threaded for receipt of respective nipples 109 and 111 which mount the
 respective quick disconnect couplings 25 and 27.
 The end plates 87 and 89 are further formed at their opposite sides with
 through bores 112 and 114 for receipt of the opposite ends of respective
 tie rods 116 and 118 which can be tightened down to compress such end
 plates against the opposite end faces 53 and 54 of the housing block. As
 will be appreciated by those skilled in the art, the housing 11 may
 conveniently be constructed with a length of about ten inches, width of
 about seven inches and depth of about two inches. The overall device might
 weigh about five or six pounds so it can be conveniently suspended from
 the overhead reel 37.
 Referring to FIG. 2, a used fluid dump tank, generally designated 115, is
 connected with the used fluid outlet valve 21 by means of a dump fluid
 hose, generally designated 117. With continued reference to FIG. 2, the
 respective couplings 25 and 27 are connected with the transmission system
 of a vehicle 31 by means of respective upstream and downstream connector
 hoses, generally designated 119 and 121, respectively.
 In operation, it will be appreciated that the exchanger of the present
 invention may be conveniently connected to the transmission fluid
 dispenser gun 35 by the coupling 33 (FIGS. 2 and 3). It will be
 appreciated that conventional suspension guns 35 are typically provided
 with a wand or spout connected to a fitting 34. Such wand may be removed
 and a quick disconnect fitting mounted thereon for connection with the
 quick disconnect 36 of the coupling 33. The conventional dispenser guns 35
 typically incorporate a trigger handle 38 which is depressible to open the
 gun valve and allow pressurization from the source to force transmission
 fluid through the gun. My new method contemplates use of a releasable
 fastener such as a hook and pile strap 42 which is wrapped around the body
 of the gun and the trigger 38 to hold the trigger actuated valve open. It
 will be appreciated that any desirable belt, clamp or clip may be utilized
 to hold the trigger down and the gun valve open. The gun 35 typically
 incorporates a meter having a display 40 which displays the quantity of
 fluid counted during a single dispensing procedure. This meter will be
 re-set to zero before the operation is commenced.
 The used fluid dump coupling hose 117 may then be coupled between the used
 fluid passage outlet and the dump tank 115. Entry is then gained to the
 automatic transmission vehicle 31 upstream of the transmission pump. This
 may be through cooling line connections as by insertion of spigots or any
 other convenient manner. The new fluid coupling 119 is thus connected with
 the downstream end of the new fluid passage 13 by means of the quick
 disconnect coupling 25 and the opposite end of such coupling 119 then
 coupled to the upstream location in the transmission. A downstream
 location in the transmission system is then accessed, as by accessing a
 cooling line returning from the transmission, and inserting a pet cock or
 the like. The distal end of the used fluid coupling 121 is then connected
 with the downstream pet cock and the coupling coupled with the used fluid
 inlet quick disconnect coupling 27.
 With the flow control valves 19 and 21 closed, the automobile engine can
 then be started and the transmission actuated to pump transmission fluid
 from the transmission out of the coupling hose 121. It will be appreciated
 by those skilled in the art that should the technician hook the inlet and
 outlet hoses 119 and 121 up wrong, the transmission pressure will be
 introduced to the new fluid passage 13. Fluid flow from such passage to
 the new fluid supply will be blocked by the check valve 97 to thus
 communicate pressure directly to the gauge 45. Flow from such new fluid
 passage 65 back to the used fluid passage 15 is blocked by the ball poppet
 73. The transmission pressure could be on the order of 60 psi thus giving
 the technician a ready indication that the hoses have been hooked up
 backward. The technician may then switch the hoses and continue with the
 procedure.
 Operation of the transmission with the hoses hooked up correctly will
 introduce used fluid into the upstream end of the used fluid passage 15 to
 flow laterally through the used fluid return section 59 (FIG. 3). Assuming
 the used fluid control valve 121 has remained closed, the transmission
 will build pressure up in the passage 13 and return section 15 to the
 point where the poppet ball 83 will be lifted off the seat 73 to permit
 such transmission fluid to flow on out the new fluid return section 65
 against the bias of the spring 81 to the used fluid passage 13 and back
 into the upstream location of the transmission thus completing a bypass
 loop. The pressure gauge 45 will sense this pressure so the technician
 will know the transmission pressure. This pressure may then be recorded
 for future reference to assist the operator in his endeavor to avoid
 overpressurizing the transmission with the incoming new fluid passing
 through the new fluid passage 13.
 The operator may then concurrently open the used fluid valve 21 and new
 fluid valve 19 to commence flow of used fluid through the passage 15 to
 the dump tank 115 of used fluid into the passage 13. The pressure in the
 used fluid passage 15 will thus drop thus lowering the pressure in the
 used fluid return section 59 allowing the poppet 83 to be urged back onto
 the seat 74 by the spring 81.
 The pressurized new fluid introduced through the valve 79 will flow through
 the check valve 95 to build up pressure in the new fluid passage 13 and
 flow new fluid through the coupling hose 119 to the upstream location in
 the transmission system to replace transmission fluid being displaced
 through the used fluid coupling hose 121. The valves 19 and 21 may be
 adjusted to balance the flow in and out of the transmission. The quantity
 of fluid flowing into the transmission will be counted on the meter 40 to
 give the operator an indication of the quantity of fluid being introduced
 to the transmission. As the pressure builds up in the new fluid passage
 13, it will be appreciated that such pressure will be communicated through
 the new fluid return passage section 65 to ball poppet 73 thus tending to
 pressurize such ball poppet more firmly on its seat 74 to seal against
 bypassing of the used fluid being pumped by the transmission pump to the
 passage 15. As long as the pressure differential across that poppet ball
 73, as assisted by the spring 81, remains positive toward the closed valve
 position, the return valve 41 will remain closed.
 The new fluid valve 19 may be manipulated to control flow of new fluid to
 the point where the pressure sensed by the pressure gauge 45 does not
 exceed the operating pressure previously established for the transmission
 itself to thus avoid overpressurizing of the transmission and consequent
 possible damage to the transmission seals and the like. As new fluid
 continues to flow into the transmission, it will be appreciated that the
 fluid pressure through the gun 35 will drop thus reducing the pressure at
 the supply tank (not shown) which is sensed at that location to actuate an
 air compressor or the like to maintain the supply fluid pressurized so
 that flow will continue. If during the operation, there is any irregular
 activity which might affect the balance of flow and cause the pressure in
 the used fluid passage 15 to build up, the pressure differential across
 the ball may become sufficient to lift such ball 83 off its seat and allow
 the used fluid to escape past such ball and flow back into the new fluid
 passage 13 and back to the transmission in a loop.
 It is a characteristic of the hot transmission fluid flowing from the
 transmission and the cold new fluid flowing through the passage 13 that
 such fluids will typically not mix but, rather, maintain a laminar flow.
 The transparency of the housing 11 thus acts as somewhat of a window so
 the operator can view flow in the passage 13. The used fluid will
 typically have somewhat of a dirty appearance readily distinguishable from
 the color of the incoming new fluid. Consequently, the operator will have
 a ready view for comparison of the color of the two fluids for a ready
 comparison to obtain an indication of the extent to which fluid flowing
 from the transmission is clean or contaminated.
 The operator can also view the color of both fluids in the respective new
 fluid and used fluid passages 13 and 15 and when the fluid in the used
 fluid passage 15 approaches that of the new fluid passage 13, he or she
 will know that the transmission fluid in the transmission has been
 sufficiently exchanged. The new fluid valve 19 may then be closed, the
 transmission stopped and the used fluid control valve 21 also closed. The
 operator may then observe the counter meter 40 on the gun 35 to determine
 the quantity of transmission fluid consumed in the operation. This amount
 will then be recorded so the vehicle owner will have an accurate
 indication of the quantity of transmission fluid used in the process. The
 new and used fluid coupling hoses 119 and 121 are then disconnected from
 the transmission and the pet cocks in the transmissions cooling hoses
 closed and the vehicle is then ready for delivery to their owners. The
 meter 40 on the dispenser gun 35 may then be reset to zero and the
 exchanger is ready for the service of the next vehicle.
 The hand held exchanger shown in FIG. 5 is similar to that shown in FIGS.
 1-3 except that the housing, generally designated 134, includes an
 integral sensor valve device, generally designated 135, for selectively
 sensing pressure between the new and used fluid passages 13 and 15,
 respectively. The sensor valve 135 is formed by a sensor passage,
 generally designated 136, machined in the housing to extend transversely
 between the used fluid bypass passage 59 and the new fluid passage 13. The
 passage 136 is in the form of a series of stepped bores, including a
 reduced-in-diameter orifice 137 leading from the used fluid return passage
 59 and having a conical valve seat 138 formed adjacent thereto to form a
 transition upwardly to a larger diameter valve chamber 139 and having
 seated thereon a sensor ball poppet 140. Formed on the new fluid side of
 such chamber 139 is an internally threaded bore 141 which receives an
 externally threaded insert 143 to form a valve seat 142 facing the seat
 138. The insert 143 includes an axially outwardly opening diametrical slot
 151 on the external end thereof for receipt of the blade of a screwdriver
 or the like. Formed on the new fluid side of such insert 143 is an
 enlarged-in-diameter access passage section 155 leading from the new
 passage 13.
 In this embodiment, a transversely extending sensing port 157 is formed to
 lead laterally from the valve chamber 139 and is configured at its
 enlarged extremity with internal threads for receipt of the external
 threads of a nipple included in the pressure gauge 45.
 In operation, the fluid exchanger shown in FIG. 6 may be hooked up like the
 fluid exchanger described in FIGS. 1-5 to place the new and used fluid
 passages 13 and 15 in communication with the respective upstream and
 downstream locations in the transmission. Similarly, the pressure
 adjustment plug 72 will be adjusted for the desired relief pressure to
 protect the transmission. It will be appreciated that this relief pressure
 may be set for the model of vehicle for which the transmission fluid is to
 be changed. The bypass pressure may be set at any desired level to protect
 the transmission being serviced. In any event, once the coupling hoses 119
 or 121 are hooked up, the car engine might be started to pressurize the
 transmission to its operating pressure. The technician can observe the
 sensor poppet 140 through the window-like transparency of the housing 134.
 If the poppet is driven away from the new fluid passage 13 toward the seat
 138, the technician will know that the transmission pump is pressurizing
 the new fluid passage so such hoses must be hooked up incorrectly. It will
 be appreciated that such pressurization of the new fluid passage also
 serves to maintain the check valve 97 and relief valve 41 closed while
 pressurizing the gauge 45 with the transmission pressure. In any event,
 the connection of the hoses may be reversed and the exchange procedure
 started.
 As the pressure differential across the poppet 140 varies, such poppet will
 be urged to the one end or the other of the valve chamber 139 to seat
 against either the seat 138 or the seat 142. The gauge 45 will sense the
 pressure on the open side of the poppet ball 140. The flow control valves
 19 and 21 may be adjusted to vary the flow therethrough in effort to
 maintain approximately equal flow in both directions. The pressure in the
 new and used fluid passages will thus tend to equalize. It is a
 characteristic of most pressurization systems in on-demand sources feeding
 supply reels 37 that they will tend to oscillate on and off resulting in
 the poppet ball 140 oscillating back and forth between the seats 138 and
 142 thus giving the technician an indication that the flow rates are
 fairly well balanced. This adjustment may then be maintained so the
 technician will be assured that new fluid is being flowed into the
 transmission at substantially the same rate as used fluid is being
 removed.
 The pressure gauge 45 is operative to sense the pressure from either the
 transmission or new fluid source as communicated from either the used
 fluid passage 15 or new fluid passage section 13.
 It will be appreciated that, should the transmission pressure build up
 excessively, the orifice 137 will restrict flow through the sensor valve
 chamber 139 thus causing the differential to build up across the bypass
 poppet 73 to thereby allow the used fluid to bypass back to the new fluid
 passage 13 and back to the transmission.
 When the color of the used fluid in the used fluid transmission approaches
 the color of the new fluid in the new fluid passage, the technician will
 know that the exchange of fluid has been completed. He or she may then
 close the flow control valves 19 and 21, stop the automobile engine and
 disconnect the coupling hoses 119 and 121. As before, the technician will
 then record the quantity of fluid used as indicated by the meter 40 (FIG.
 2).
 From the foregoing, it will be appreciated that the transmission fluid
 exchanger of the present invention is relatively inexpensive to
 manufacture and conveniently utilizes the on-demand pump incorporated in
 an on-demand dispenser system already installed in many service station
 installations and utilizes the meter typically incorporated in
 conventional dispenser guns already part of the installation facility.
 Additional features of the present invention are that a single pressure
 gauge can be utilized to determine the operating pressure of the
 transmission and to then monitor the pressure of the exchanger system
 during operation so as to allow the operator to make adjustments to avoid
 overpressurization.
 While particular forms of the invention have been illustrated and
 described, it will be apparent that various modifications can be made
 without departing from the spirt and scope of the invention.