Abstract:
An apparatus and method for determining direction of flow in a fluid or pneumatic system. The apparatus comprises first and second conduits having clear portions, the first and second conduits being capable of determining fluid flow direction in the system by observing fluid through their clear portions. The apparatus further comprises a valve assembly connecting the first conduit to the second conduit, the valve assembly including a shut-off valve. The valve assembly can comprise a release valve for releasing fluid from the valve assembly, and a release mechanism for opening the release valve. The system may include a transmission system and a fluid circuit with a first port and a second port, a transmission service system being connected to the first port and the second port of the fluid circuit according to the direction of fluid flow determined by the apparatus.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of U.S. provisional application serial No. 60/292,476, filed May 21, 2001, which is hereby fully incorporated by reference in the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to fluid or pneumatic systems. More particularly, the present invention relates to method and apparatus for determining the direction of flow in such systems. 
     2. Related Art 
     The servicing of pressurized fluid systems often requires knowledge of the direction of the fluid in those systems. For example, in the automotive servicing industry, flushing an automatic transmission requires knowledge of the direction of flow of the transmission fluid so that equipment used to flush the transmission can be properly connected to the transmission fluid system. The direction of fluid flow in a vehicle&#39;s transmission fluid system could be determined by opening the transmission fluid system with the vehicle turned off, and then starting the vehicle and observing the flow of transmission fluid out of the opened transmission fluid line. However, the above method of determining the direction of fluid flow in a vehicle&#39;s transmission fluid system could result in injury to service personnel from hot transmission fluid, or minimally, a mess from spilled transmission fluid. Thus, there is a need for a device to determine the direction of fluid flow in a vehicle transmission fluid system that is safe to operate and does not result in a mess of spilled transmission fluid. 
     A similar need exists for a device to indicate the direction of fluid flow in automotive, heavy equipment, truck, and bus engine applications including the servicing of power steering, cooling, hydraulic, and air conditioning systems. The power steering, cooling, hydraulic, and air conditioning systems that are used in the automotive, heavy equipment, truck, and bus manufacturing industries typically use a variety of types and sizes of connectors and conduits. Thus, there is a need for a device to determine the direction of fluid flow in the above mentioned power steering, cooling, hydraulic, and air conditioning systems that can connect to the variety of types and sizes of connectors and conduits that these systems contain. 
     There is a similar need to determine the air flow direction in the servicing of pneumatic systems, such as pressurized air systems and vacuum systems. However, the air flow direction in pneumatic systems can be difficult to determine, especially when air flow is low, since air flow is not readily visible. Sophisticated flow analyzers exist that can determine the direction of low air flow in pneumatic systems. However, these analyzers are typically not cost effective for individual service technicians and small service centers to own and operate. 
     Therefore, there exists a need for a device to determine the direction of fluid or air flow in a fluid or pneumatic system. More specifically, there exists a need for a device to determine the direction of fluid or air flow in a fluid or pneumatic system that is inexpensive and easy to operate, and is able to connect to a variety of types and sizes of connectors and conduits included in fluid or pneumatic systems. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to apparatus and method for determining direction of flow in a fluid or pneumatic system. More specifically, the invention provides an easy to operate, inexpensive apparatus for visually determining direction of fluid or air flow in a system. 
     In one aspect, such apparatus comprises a first conduit having a clear portion, the first conduit being capable of determining fluid flow direction in the system by observing fluid through its clear portion. The apparatus further comprises a second conduit having a clear portion, the second conduit also being capable of determining fluid flow direction in the system by observing fluid through its clear portion. For example, the clear portions of the first and second conduits can include clear tubes. By way of further example, the first and second conduits can be clear in their entirety. 
     The apparatus may further comprise a valve assembly connecting the first conduit to the second conduit, the valve assembly including a shut-off valve. The valve assembly can comprise a release valve for releasing fluid from the valve assembly, and a release mechanism for opening the release valve. The system may include a transmission system and a fluid circuit with a first port and a second port, a transmission service system being connected to the first port and the second port of the fluid circuit according to the direction of fluid flow determined by the apparatus. The apparatus may further comprise a number of adapters for connecting the first and second conduits of the apparatus to the first and second ports of the fluid circuit. 
    
    
     These and other aspects of the present invention will become apparent with further reference to the drawings and specification, which follow. It is intended that all such additional systems, features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein: 
     FIG. 1A illustrates a fluid flow indicator loop according to one embodiment of the present invention; 
     FIG. 1B illustrates an application of the fluid flow indicator loop of FIG. 1A; 
     FIG. 2 illustrates a flow diagram describing a method of using the fluid indicator loop of FIG. 1A; 
     FIG. 3A illustrates a fluid flow indicator loop according to one embodiment of the present invention; 
     FIG. 3B illustrates an application of the fluid flow indicator loop of FIG. 3A; 
     FIG. 4 illustrates a flow diagram describing a method of using the fluid indicator loop of FIG. 3A; 
     FIG. 5 illustrates a flow indicator loop according to one embodiment of the present invention; and 
     FIG. 6 illustrates a flow indicator loop according to one embodiment of the present invention. 
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The present invention may be described herein in terms of functional block components and various processing steps. It should be appreciated that such functional blocks may be realized by any number of hardware components configured to perform the specified functions. It should be further appreciated that the particular implementations shown and described herein are merely exemplary and are not intended to limit the scope of the present invention in any way. 
     FIG. 1A illustrates an exemplary fluid flow indicator loop in accordance with one embodiment of the present invention. Fluid flow indicator loop  100  in FIG. 1A comprises adapters  102  and  104 , clear tubings or conduits  106  and  108 , and shutoff valve assembly  110 . Shutoff valve assembly  110  includes shutoff valve  112 , release valve  114 , and release valve button  116 . 
     Now discussing FIG. 1A in more detail, a first end of clear tubing  106  is attached to adapter  102 , and a second end of clear tubing  106  is attached to shutoff valve assembly  110 . A first end of clear tubing  108  is attached to adapter  104 , and a second end of clear tubing  108  is attached to shutoff valve assembly  110 . In one embodiment, clear tubings or conduits  106  and  108  may be made of clear plastic reinforced tubing, glass or any other conduit in which flow of fluid may be visually detected, with a typical inside diameter of ⅜ inch. However, the diameter and the length of clear tubings  106  and  108  can vary. Adapters  102  and  104  may be female quick disconnect adapters. 
     Continuing with FIG. 1A, shutoff valve  112  can be a ball or gate valve, and can be made of brass, PVC plastic, stainless steel, or galvanized steel. The internal diameter of shutoff valve  112  can vary to accommodate different system requirements and flow rates. Release valve  114  is situated on the bottom of shutoff valve assembly  110  and is activated by release valve button  116 . However, in other embodiments, release valve  112  may be situated in other locations on shutoff valve assembly  110 . Also, in one embodiment, release valve  112  may be activated by a different mechanism, such as a knob or lever. 
     Also shown in FIG. 1A, a first end of hose  120  is attached to adapter  118 , and a second end of hose  120  is attached to a fluid system (not shown in FIG.  1 A). A first end of hose  124  is attached to adapter  122 , and a second end of hose  124  is also attached to a fluid system (not shown in FIG.  1 A). For example, the second ends of hoses  120  and  124  can be attached to first and second ports of pressurized fluid passageways, fluid circuits, or pressurized fluid systems in an automobile, truck, bus, or heavy equipment vehicle. By way of further example, the second ends of hoses  120  and  124  can be attached to an automotive transmission fluid circuit. In one embodiment of the present invention, adapters  118  and  122  can be male quick disconnect adapters. Adapters  118  and  122 , respectively, connect to adapters  102  and  104  on fluid flow indicator loop  100  in FIG.  1 A. The operation of fluid flow indicator loop  100  will be discussed in detail in relation to FIG.  2 . 
     FIG. 1B illustrates an exemplary transmission service system. In one embodiment, transmission service system  150  may be used to replace waste fluid with fresh fluid in a vehicle&#39;s transmission after fluid flow indicator loop  100  in FIG. 1A is used to determine the fluid flow direction in hoses  120  and  124  of transmission service systems  150 , as described in FIG. 2, and thereafter removed from the vehicle&#39;s transmission fluid circuit. Transmission service system  150  includes adapters  156  and  172 , tubings  158 ,  162 , and  170 , pump  160 , clean tank  164 , control system  166 , and waste tank  168 . 
     In FIG. 1B, a first end of hose  120  is attached to adapter  118 , and a second end of hose  120  is attached to a vehicle&#39;s transmission fluid circuit (not shown in FIG.  1 B). A first end of hose  124  is attached to adapter  122 , and a second end of hose  124  is also attached to a vehicle&#39;s transmission fluid circuit not shown in FIG.  1 B. Hoses  120  and  124  are appropriately determined as “fluid in” and “fluid out” after fluid flow direction has been determined by fluid flow indicator loop  100  in FIG.  1 A. Hoses  120  and  124  are then connected to adapters  156  and  172  of transmission service system  150  via adapters  118  and  122 . For example, if hose  120  was determined as “fluid in” and hose  124  was determined as “fluid out,” adapters  118  and  122 , respectively, would be connected to adapters  156  and  172  in FIG.  1 B. In the above example, fresh fluid would be pumped through hose  120  from clean tank  164  by pump  160 , and waste fluid would be drained into waste tank  168  through hose  124 . In one embodiment, control system  166  would automatically determine the required amount of clean fluid that would be pumped through hose  120  to fill the vehicle&#39;s transmission (not shown in FIG.  1 B). By way of further example, if hose  124  was determined as “fluid in” and hose  120  was determined as “fluid out,” adapters  122  and  118 , respectively, would be connected to adapters  156  and  172  in FIG.  1 B. 
     In flowchart  200  of FIG. 2, the operation of an embodiment of the present invention is illustrated by connecting fluid flow indicator loop  100  (see FIG. 1A) to a vehicle&#39;s transmission fluid circuit. Although a vehicle&#39;s transmission fluid circuit is used to illustrate the operation of an embodiment of present invention in FIG. 2, the present invention can be used to determine the direction of fluid flow in various fluid systems. For example, the present invention can detect fluid flow direction in automotive, truck, bus, and heavy equipment applications including power steering, cooling, hydraulic, and air conditioning systems. Additionally, an embodiment of the present invention can be used for testing air flow direction in air or pneumatic systems. 
     Continuing with FIG. 2, at step  202 , a vehicle comprising a transmission fluid circuit to be serviced is started up and the vehicle&#39;s engine is allowed to reach operating temperature. At step  204 , the vehicle&#39;s engine is shut off after the engine reaches operating temperature. In other words, preferably, flow of fluid through the transmission fluid circuit of the vehicle is substantially stopped. At step  206 , after ensuring that shutoff valve  112  is closed, fluid flow indicator loop  100  is connected into the transmission fluid circuit of the vehicle. For example, in FIG. 1A, adapters  118  and  122 , respectively, would connect the first ends of hoses  120  and  124  to adapters  102  and  104  of fluid flow indicator loop  100 . The second ends of hoses  120  and  124  (not shown in FIG. 1A) would be connected into the transmission fluid circuit of the vehicle. In one embodiment, adapters  118  and  122 , and hoses  120  and  124  are a part of an adapter kit, including a plurality of various sizes and length of hoses, hose clamps, fuel lines, washers, bolts, unions, nuts, fuel pressure lines, cooler lines, etc. The adapters in the adapter kit allow fluid flow indicator loop  100  to accommodate the different fluid system connectors that are used in the automotive, trucking, bus, and industrial equipment industries. It should be noted that in other embodiments, flowchart  200  may begin at step  206  and fluid flow indicator loop  100  may be connected to any fluid circuit in order to determine the direction of fluid flow in that fluid circuit; therefore, use of fluid flow indicator loop  100  to determine the direction of fluid flow in a vehicle&#39;s transmission fluid circuit is merely exemplary. 
     Referring back to FIG. 2, at step  208 , the vehicle&#39;s engine is started to allow flow of fluid into the fluid circuit and the fluid flow direction is observed, e.g. by visual detection, through the clear tubing of fluid flow indicator loop  100 . For example, in FIG. 1A, fluid flow will be observed in clear tubing  106  if fluid is flowing out of hose  120 , which is connected to clear tubing  106  via adapters  118  and  102 . By way of further example, fluid flow will be observed in clear tubing  108  if fluid is flowing out of hose  124 , which is connected to clear tubing  108  via adapters  122  and  104 . At step  210 , shutoff valve  112  of fluid flow indicator loop  100  is opened after the direction of fluid flow is detected to allow normal circulation of transmission fluid and thereby prevent damage to the vehicle&#39;s transmission. 
     At step  212 , the vehicle&#39;s engine is shut off, and the hoses from the vehicle&#39;s transmission fluid circuit that are connected to the fluid flow indicator loop  100  are appropriately determined as “fluid in” and “fluid out.” For example, if fluid flow was detected in clear tubing  106  in FIG. 1A, hose  120  would be determined as “fluid out” and hose  124  would be determined as “fluid in.” By way of further example, if fluid flow was detected in clear tubing  108  in FIG. 1A, hose  124  would be determined as “fluid out” and hose  120  would be determined as “fluid in.” At step  214 , release valve  114  is opened to release residual pressure and to allow fluid in fluid flow indicator loop  100  to drain into a waste container. At step  216 , fluid flow indicator loop  100  is disconnected from the vehicle&#39;s transmission fluid circuit. It should be noted that in some embodiments, step  216  may be the last step of flowchart  200 , wherein after fluid flow indicator loop  100  is disconnected, the fluid circuit is also re-established. 
     However, in some other embodiments, at step  218 , a transmission service system, such as transmission service system  150  in FIG. 1B, is connected to the vehicle&#39;s transmission fluid circuit. For example, if hose  120  in FIG. 1B was determined as “fluid in” and hose  124  was determined as “fluid out” at step  212 , hose  120  would be connected to transmission service system  150  via adapters  118  and  156 , and hose  124  would be connected to transmission service system  150  via adapters  122  and  172 . Thus, fresh fluid would be pumped into the vehicle&#39;s transmission fluid circuit from clean tank  164  via hose  120  in FIG. 1B, and waste fluid would be drained out of the vehicle&#39;s transmission fluid circuit into waste tank  168  via hose  124 . 
     FIG. 3A illustrates an exemplary fluid flow indicator loop in accordance with another embodiment of the present invention. Fluid flow indicator loop  300  in FIG. 3A comprises adapters  302 ,  304 ,  324 , and  326 , tee fittings  306  and  308 , clear tubings  310  and  312 , shutoff valve assembly  314 , shutoff valves  316  and  318 , and tubings  320  and  322 . Shutoff valve assembly  314  comprises shutoff valve  328 , release valve  330 , and release button  332 . 
     Now discussing FIG. 3A in more detail, a first end of tee fitting  306  is attached to adapter  302 , and a second end of tee fitting  306  is attached to shutoff valve  316 . A first end of tee fitting  308  is attached to adapter  304 , and a second end of tee fitting  308  is attached to shutoff valve  318 . In one embodiment of the present invention, adapters  302  and  304  can be female quick disconnect adapters. Shutoff valves  316 ,  318 , and  328  can be ball or gate valves, and can be made of brass, PVC plastic, stainless steel, or galvanized steel. The internal diameter of shutoff valves  316 ,  318 , and  328  can vary to accommodate different system requirements and flow rates. 
     Continuing with FIG. 3A, a first end of clear tubing  310  is attached to tee fitting  306 , and a second end of clear tubing  310  is attached to shutoff valve assembly  314 . A first end of clear tubing  312  is attached to tee fitting  308 , and a second end of clear tubing  312  is attached to shutoff valve assembly  314 . Clear tubings or conduits  310  and  312  may be made of clear plastic reinforced tubing, glass or any other conduit in which flow of fluid may be visually detected, with a typical inside diameter of ⅜ inch. However, the diameter and the length of clear tubings  310  and  312  may vary in other embodiments. Release valve  330  is situated on the bottom of shutoff valve assembly  314  and is activated by release valve button  332 . However, in other embodiments, release valve  330  may be situated in other locations on shutoff valve assembly  314 . Also, in another embodiment release valve  330  may be activated by a different mechanism, such as a knob or lever. 
     Also in FIG. 3A, a first end of tubing  320  is attached to shutoff valve  316 , and a second end of tubing  320  is attached to adapter  324 . A first end of tubing  322  is attached to shutoff valve  318 , and a second end of tubing  322  is attached to adapter  326 . In one embodiment of the present invention, adapters  324  and  326  can be female quick disconnect adapters. 
     Also shown in FIG. 3A, a first end of hose  334  is attached to adapter  336 , and a second end of hose  334  is attached to a fluid system (not shown in FIG.  1 A). A first end of hose  338  is attached to adapter  340 , and a second end of hose  338  is also attached to a fluid system (not shown in FIG.  1 A). For example, the second ends of hoses  334  and  338  can be attached to first and second ports of pressurized fluid passageways, fluid circuits, or pressurized fluid systems in an automobile, truck, bus, or heavy equipment vehicle. By way of further example, the second ends of hoses  334  and  338  can be attached to an automotive transmission fluid circuit. In one embodiment of the present invention, adapters  336  and  340  can be male quick disconnect adapters. Adapters  336  and  340 , respectively, connect to adapters  302  and  304  on fluid flow indicator loop  300  in FIG.  3 A. The operation of fluid flow indicator loop  300  will be discussed in detail in relation to FIG.  4 . 
     FIG. 3B illustrates an exemplary transmission service system prior to connection to fluid flow indicator loop  300 . In one application of the present invention, transmission service system  350  in FIG. 3B may be connected to fluid flow indicator loop  300  to replace waste fluid with clean fluid in a vehicle&#39;s transmission (not shown in FIG.  3 B). Transmission service system  350  includes adapters  362  and  378 , tubings  364 ,  368 , and  376 , pump  366 , clean tank  370 , control system  372 , and waste tank  374 . Fluid flow indicator loop  300  in FIG. 3B comprises adapters  302 ,  304 ,  324 , and  326 , tee fittings  306  and  308 , clear tubings  310  and  312 , shutoff valve assembly  314 , shutoff valves  316  and  318 , and tubings  320  and  322 . Shutoff valve assembly  314  comprises shutoff valve  328 , release valve  330 , and release button  332 . 
     Now discussing FIG. 3B in more detail, a first end of tee fitting  306  is attached to adapter  302 , and a second end of tee fitting  306  is attached to shutoff valve  316 . A first end of tee fitting  308  is attached to adapter  304 , and a second end of tee fitting  308  is attached to shutoff valve  318 . In one embodiment of the present invention, adapters  302  and  304  can be female quick disconnect adapters; Shutoff valves  316 ,  318 , and  328  can be ball or gate valves, and can be made of brass, PVC plastic, stainless steel, or galvanized steel. The internal diameter of shutoff valves  316 ,  318 , and  328  may vary to accommodate different system requirements and flow rates. 
     Continuing with FIG. 3B, a first end of clear tubing  310  is attached to tee fitting  306 , and a second end of clear tubing  310  is attached to shutoff valve assembly  314 . A first end of clear tubing  312  is attached to tee fitting  308 , and a second end of clear tubing  312  is attached to shutoff valve assembly  314 . Clear tubings  310  and  312  can be made of clear plastic reinforced tubing, with a typical inside diameter of ⅜ inch, which may vary. Release valve  330  is situated on the bottom of shutoff valve assembly  314  and is activated by release valve button  332 . However, in other embodiments, release valve  330  may be situated in other locations on shutoff valve assembly  314 . Also, in another embodiment release valve  330  may be activated by a different mechanism, such as a knob or lever. A first end of tubing  320  is attached to shutoff valve  316 , and a second end of tubing  320  is attached to adapter  324 . A first end of tubing  322  is attached to shutoff valve  318 , and a second end of tubing  322  is attached to adapter  326 . In one embodiment of the present invention, adapters  324  and  326  can be female quick disconnect adapters. 
     In FIG. 3B, a first end of hose  334  is attached to adapter  336 , and a second end of hose  334  is attached to a vehicle&#39;s transmission fluid circuit (not shown in FIG.  3 B). A first end of hose  338  is attached to adapter  340 , and a second end of hose  338  is also attached to a vehicle&#39;s transmission fluid circuit (not shown in FIG.  3 B). Hose  334  is connected to adapter  302  on fluid flow indicator loop  300  via adapter  336 . Hose  338  is connected to adapter  304  on fluid flow indicator loop  300  via adapter  340 . Hoses  334  and  338  are appropriately determined as either “fluid in” or “fluid out” after fluid flow direction has been determined by fluid flow indicator loop  300  in FIG.  3 A. Based on such determination, fluid flow indicator loop  300  is connected to transmission service system  350  in FIG.  3 B. For example, if hose  334  is determined as “fluid in” and hose  338  is determined as “fluid out,” adapters  324  and  326 , respectively, on fluid flow indicator loop  300  are connected to adapters  362  and  378  on transmission service system  350 . In the above example, fresh fluid would be pumped through hose  334  from clean tank  370  by pump  366 , and waste fluid would be drained into waste tank  374  through hose  338 . In one embodiment, control system  372  would determine the required amount of fresh fluid that would be pumped through hose  334  to fill the vehicle&#39;s transmission (not shown in FIG.  3 B). 
     By way of further example, if hose  338  is determined as “fluid in” and hose  334  is determined as “fluid out,” adapters  326  and  324 , respectively, on fluid flow indicator loop  300  are connected to adapters  362  and  378  on transmission service system  350  in FIG.  3 B. In the above example, fresh fluid would be pumped through hose  338  from clean tank  370  by pump  366 , and waste fluid would be drained into waste tank  374  through hose  334 . 
     In flowchart  400  of FIG. 4, the operation of an embodiment of the present invention is illustrated by connecting fluid flow indicator loop  300  in FIGS. 3A and 3B to a vehicle&#39;s transmission fluid circuit. Although a vehicle&#39;s transmission fluid circuit is used to illustrate the operation of an embodiment of present invention in FIG. 4, the present invention can be used to determine the direction of fluid flow in various fluid systems. For example, the present invention can detect fluid flow direction in automotive, truck, bus, and heavy equipment applications including power steering, cooling, hydraulic, and air conditioning systems. Additionally, an embodiment of the present invention can be used for testing flow direction in air or pneumatic systems. 
     Referring to FIG. 4, at step  402 , a vehicle comprising a transmission fluid circuit to be serviced is started up and the vehicle&#39;s engine is allowed to reach operating temperature. At step  404 , the vehicle&#39;s engine is shut off after the engine reaches operating temperature. In other words, preferably, flow of fluid through the transmission fluid circuit of the vehicle is substantially stopped. At step  406 , after ensuring that shutoff valves  316 ,  318 , and  328  in FIG. 3A, are closed, fluid flow indicator loop  300  is connected into the transmission fluid circuit of the vehicle. For example, in FIG. 3A, adapters  336  and  340 , respectively, would connect the first ends of hoses  334  and  338  to adapters  302  and  304  of fluid flow indicator loop  300 . The second ends of hoses  334  and  338  (not shown in FIG. 3A) would be connected into the transmission fluid circuit of the vehicle. Adapters  336  and  340 , and hoses  334  and  338  are included in the adapter kit. It should be noted that in other embodiments, flowchart  400  may begin at step  406  and fluid flow indicator loop  300  may be connected to any fluid circuit in order to determine the direction of fluid flow in that fluid circuit; therefore, use of fluid flow indicator loop  300  to determine the direction of fluid flow in a vehicle&#39;s transmission fluid circuit is merely exemplary. 
     At step  408 , the vehicle&#39;s engine is started to allow flow of fluid into the fluid circuit and the fluid flow direction is observed through the clear tubing of fluid flow indicator loop  300 . For example, in FIG. 3A, fluid flow will be observed in clear tubing  310  if fluid is flowing out of hose  334 , which is connected to clear tubing  310  via adapters  336  and  302 , and tee fitting  306 . By way of further example, fluid flow will be observed in clear tubing  312  if fluid is flowing out of hose  338 , which is connected to clear tubing  312  via adapters  340  and  304 , and tee fitting  308 . At step  410 , after the direction of fluid flow is detected, shutoff valve  328  in fluid flow indicator loop  300  in FIG. 3A is opened to allow normal circulation of transmission fluid and thereby prevent damage to the vehicle&#39;s transmission. 
     At step  412 , the hoses from the vehicle&#39;s transmission fluid circuit that are connected to fluid flow indicator loop  300  are appropriately determined as “fluid in” and “fluid out.” For example, if fluid flow was detected in clear tubing  310  in FIG. 3A, hose  334  would be determined as “fluid out” and hose  338  would be determined as “fluid in.” By way of further example, if fluid flow was detected in clear tubing  312  in FIG. 3A, hose  338  would be determined as “fluid out” and hose  334  would be determined as “fluid in.” At step  414 , the vehicle&#39;s engine is either shut off or, in a preferred embodiment, is left running, since fluid flow indicator loop  300  allows the vehicle&#39;s transmission fluid circuit to be serviced without shutting off the vehicle&#39;s engine. 
     At step  416 , a transmission service system, such as transmission service system  350  in FIG. 3B, is connected to the vehicle&#39;s transmission fluid circuit. For example, if hose  334  was determined as “fluid in” and hose  338  was determined as “fluid out,” adapters  324  and  326 , respectively, on fluid flow indicator loop  300  are connected to adapters  362  and  378  on transmission service system  350 . By way of further example, if hose  338  was determined as “fluid in” and hose  334  was determined as “fluid out,” adapters  326  and  324 , respectively, on fluid flow indicator loop  300  are connected to adapters  362  and  378  on transmission service system  350  in FIG.  3 B. 
     At step  418 , shutoff valve  328  of fluid flow indicator loop  300  in FIGS. 3A and 3B is closed, and shutoff valves  316  and  318  are opened. The vehicle&#39;s engine is restarted if it was shut off at step  414 ; however, in a preferred embodiment, the vehicle&#39;s engine is not shut off at step  414  and restarting of the vehicle&#39;s engine is not necessary. The vehicle&#39;s transmission fluid circuit is now able to receive fresh fluid from clean tank  370  on transmission service system  350  in FIG. 3B, and deposit waste fluid in waste tank  374 . 
     FIG. 5 illustrates an exemplary flow indicator loop in accordance with one embodiment of the present invention. Flow indicator loop  500  in FIG. 5 comprises adapters  502  and  504 , one way check valves  506  and  508 , check valve nozzles  510  and  512 , clear tubings  514  and  516 , and shutoff valve assembly  518 . Shutoff valve assembly  518  comprises shutoff valve  520 , release valve  522 , and release button  524 . 
     Now discussing FIG. 5 in more detail, adapters  502  and  504 , respectively, are attached to one way check valves  506  and  508 . In one embodiment of the present invention, adapters  502  and  504  can be female quick disconnect adapters. Check valve nozzles  510  and  512 , respectively, are attached to one way check valves  506  and  508 . A first end of clear tubing  514  is attached to one way check valve  506 , and a second end of clear tubing  514  is attached to shutoff valve assembly  518 . A first end of clear tubing  516  is attached to one way check valve  508 , and a second end of clear tubing  516  is attached to shutoff valve assembly  518 . Clear tubings or conduits  514  and  516  can be made of clear plastic reinforced tubing, glass or any other conduit in which vapor, smoke or any gaseous flow may be visually detected, with a typical inside diameter of ⅜ inch, which may vary. 
     Continuing with FIG. 5, shutoff valve  520  can be a ball or gate valve, and can be made of brass, PVC plastic, stainless steel, or galvanized steel. The internal diameter of shutoff valve  520  can vary to accommodate different system requirements and flow rates. Release valve  522  is situated on the bottom of shutoff valve assembly  518  and is activated by release valve button  524 . However, in other embodiments, release valve  522  may be situated in other locations on shutoff valve assembly  518 . Also, in another embodiment release valve  522  may be activated by a different mechanism, such as a knob or lever. 
     An air or pneumatic system (not shown in FIG. 5) can be connected to flow indicator loop  500  via adapters  502  and  504 . A smoke and luminescent mixture can then be injected through either check valve nozzle  510  or  512  of flow indicator loop  500 . Air flow can thus be detected by observing the direction of smoke travel through clear tubings  514  and  516  of flow indicator loop  500 . For an air or pneumatic system with very low air flow, visual detection of smoke travel through clear tubings  514  and  516  can be assisted through the use of a black light. 
     FIG. 6 illustrates an exemplary flow indicator loop in accordance with one embodiment of the present invention. Flow indicator loop  600  in FIG. 6 comprises adapters  602 ,  604 , and  626 , one way check valves  606  and  608 , check valve nozzles  610  and  612 , clear tubings  614 ,  616 ,  628 ,  630 ,  632 , and  634 , shutoff valves  636  and  638 , tee connector block  640 , connectors  642  and  644 , and shutoff valve assembly  618 . Shutoff valve assembly  618  comprises shutoff valve  620 , release valve  622 , and release button  624 . 
     Now discussing FIG. 6 in more detail, adapters  602  and  604 , respectively, are attached to one way check valves  606  and  608 . In one embodiment of the present invention, adapters  602  and  604  can be female quick disconnect adapters. Check valve nozzles  610  and  612 , respectively, are attached to one way check valves  606  and  608 . A first end of clear tubing  614  is attached to one.way check valve  606 , and a second end of clear tubing  614  is attached to shutoff valve assembly  618 . A first end of clear tubing  616  is attached to one way check valve  608 , and a second end of clear tubing  616  is attached to shutoff valve assembly  618 . Clear tubings or conduits  614  and  616  can be made of clear plastic reinforced tubing, glass or any other conduit in which vapor, smoke or any gaseous flow may be visually detected, with a typical inside diameter of ⅜ inch, which may vary. 
     Continuing with FIG. 6, shutoff valve  620  can be a ball or gate valve, and can be made of brass, PVC plastic, stainless steel, or galvanized steel. The internal diameter of shutoff valve  620  can vary to accommodate different system requirements and flow rates. Release valve  622  is situated on the bottom of shutoff valve assembly  618  and is activated by release valve button  624 . However, in other embodiments, release valve  622  may be situated in other locations on shutoff valve assembly  618 . Also, in another embodiment release valve  622  may be activated by a different mechanism, such as a knob or lever. 
     Also shown in FIG. 6, connector  642  is attached to check valve nozzle  610 . A first end of clear tubing  628  is attached to connector  642 , and a second end of clear tubing  628  is attached to shutoff valve  636 . A first end of clear tubing  630  is attached to shutoff valve  636 , and a second end of clear tubing  630  is attached to tee connector block  640 . Adapter  626  is attached to tee connector block  640 . In one embodiment of the present invention, adapter  626  can be a female quick disconnect adapter. A first end of clear tubing  632  is attached to tee connector block  640 , and a second end of clear tubing  632  is attached to shutoff valve  638 . A first end of clear tubing  634  is attached to shutoff valve  638 , and a second end of clear tubing  634  is attached to connector  644 . Connector  644  is attached to check valve nozzle  612 . Shutoff valves  636  and  638  can be ball or gate valves, and can be made of brass, PVC plastic, stainless steel, or galvanized steel. The internal diameter of shutoff valves  636  and  638  can vary to accommodate different system requirements and flow rates. Clear tubings  628 ,  630 ,  632 , and  634  can comprise clear plastic reinforced tubing, with a typical inside diameter of ⅜ inch, which may vary. 
     An air or pneumatic system (not shown in FIG. 6) can be connected to flow indicator loop  600  via adapters  602  and  604 . A vapor mixture can then be injected through adapter  626  of flow indicator loop  600 . In one embodiment, the vapor mixture can be a smoke and luminescent mixture. Air flow can thus be detected by observing the direction of vapor travel through clear tubings  614 ,  616 ,  628 ,  630 ,  632 , and  634  of flow indicator loop  600 . A vapor mixture can be injected through either check valve nozzle  610  or check valve nozzle  612  of flow indicator loop  600  in FIG.  6 . For example, a vapor mixture may be injected through check valve nozzle  610  by opening shutoff valve  636 , closing shutoff valve  638 , and injecting a vapor mixture through adapter  626 . By way of further example, a vapor mixture may be injected through check valve nozzle  612  by closing shutoff valve  636 , opening shutoff valve  638 , and injecting a vapor mixture through adapter  626 . Thus flow indicator loop  600  allows a vapor mixture to be injected into an air or pneumatic system through a single adapter, i.e. adapter  626 . Flow indicator loop  600  further allows the injected vapor mixture to be diverted through either of two check valve nozzles, i.e. check valve nozzles  610  and  612 , by opening and closing the appropriate shutoff valves, i.e. shutoff valves  636  and  638  in FIG.  6 . 
     A novel method and system for determining the direction of fluid or air flow in a fluid, air or pneumatic system has been hereby presented. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. Those skilled in the art will recognize that changes and modifications may be made to the embodiments without departing from the scope of the present invention. These and other changes or modifications are intended to be included within the scope of present invention, as broadly described herein.