Conventional flushing systems used to flush a cooling system typically direct a flushing fluid through the cooling system in the same forward direction in which coolant normally flows through the cooling system. Because most cooling systems are constantly in use with fluid flowing therethrough, this forward flushing is typically sufficient for clearing out any clogs in the cooling system. In this regard, one manufacturer of a conventional flushing system suggests that half way through the flush, the user should disconnect the system from the cooler and reverse the connection so as to flush from the reverse direction.

Recently, a cooling system for transmission fluid has been developed that employs a thermostatically-controlled valve for selectively passing the transmission fluid through the cooler when the temperature of the fluid exceeds a threshold level and for bypassing the cooler when the temperature of the transmission fluid has not yet reached a predetermined temperature. With such thermostatically-controlled coolers, debris is more likely to collect in the cooler due to the intermittent flow of fluid through the cooler ducts. Moreover, the nature of such debris makes it difficult to remove the debris solely by forward flushing using conventional methods.

SUMMARY OF THE INVENTION Accordingly, it is, therefore, an aspect of the present invention to provide a flushing system that is capable of removing debris in thermostatically-controlled coolers. It is a further aspect of the present invention to provide a flushing system that more effectively flushes any form of hydraulic system. Another aspect of the present invention is to provide a flushing system that is configured to enable programmable control of the operations of the flushing system to thereby allow the operations of the flushing system to be customized for the various coolers for which it may be used to flush.

To achieve these and other aspects and advantages, the flushing system of the present invention comprises a reservoir containing a flushing fluid, a valve for alternately reversing the direction of flow of the flushing fluid through the cooling

system, and a pump to cause the flushing fluid to flow through the valve and back to the reservoir. Further, the flushing system may include a heating element for heating the flushing fluid to a temperature exceeding that at which a thermostat, provided at the cooling system inlet and outlet, responds by opening a valve to allow fluid to flow through the cooling system.

The above aspects of the present invention may further be obtained by practicing a method of flushing a cooling system comprising the steps of providing a reservoir containing flushing fluid, pumping the flushing fluid from the reservoir through a direction shifting valve and through the cooling system, directing the flushing fluid back to the reservoir, changing the direction of flow of the flushing fluid, and repeating the cycle.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Fig. 1 is a block diagram illustrating a thermostatically-controlled cooler with which the present invention may be used showing the flow of fluid when the fluid passing therethrough is not above a predetermined temperature; Fig. 2 is a functional block diagram of a thermostatically-controlled cooler with which the flushing system of the present invention may be used showing the flow of fluid when the temperature of the fluid exceeds the predetermined threshold level of the thermostatically-controlled valve; Fig. 3 is a functional block diagram of the flushing system according to the present invention illustrating the flow of fluid therethrough when operating in an alternating direction flow control mode and the fluid is flowing in a forward direction; Fig. 4 is a functional block diagram of the flushing system according to the present invention illustrating the flow of fluid therethrough when operating in an alternating direction flow control mode and the fluid is flowing in a reverse direction; Fig. 5 is a functional block diagram of the flushing system according to a second embodiment of the present invention illustrating the flow of fluid therethrough when operating in an alternating direction flow control mode and the fluid is flowing in a forward direction;

Fig. 6 is a functional block diagram of the flushing system according to the second embodiment of the present invention illustrating the flow of fluid therethrough when operating in an alternating direction flow control mode and the fluid is flowing in a reverse direction; and Fig. 7 is a functional block diagram of the flushing system according to the second embodiment of the present invention illustrating the flow of fluid through the flushing system during an optional final rinse cycle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figs. 1 and 2 show a thermostatically-controlled cooling system which includes a cooler 10, an in-flow line 12, an out-flow line 14 and a thermostatically-controlled valve 20. Fig. 1 illustrates the flow of fluid through valve 20 when the temperature of the fluid supplied through an inlet 13 is below a predetermined threshold level. As shown, the fluid is not permitted to flow through cooler 10 when it has not yet reached the predetermined threshold level.

Fig. 2 illustrates the flow of fluid through valve 20 when the temperature of the fluid has reached the predetermined threshold level. As apparent from this figure, the fluid flowing in inlet 13 passes through valve 20 to in-flow line 12 and exits cooler 10 from out-flow line 14 and passes through valve 20 to outlet 15. The fluid flowing into and out of this cooling system may come from a variety of different sources, such as a transmission or engine block of a vehicle. When the temperature of the fluid subsequently drops back below the threshold level, valve 20 switches to the state shown in Fig. 1 and bypasses cooler 10 until the temperature again exceeds the threshold level.

A first and most preferred embodiment of the flushing system of the present invention is shown in Figs. 3 and 4 in various states of operation, and is referenced generally with the reference numeral 30. Flushing system 30 includes a reservoir 40 which preferably includes a plurality of heating elements 41 and 42 for heating the flushing fluid contained in reservoir 40 to a temperature at which the thermostatically- controlled valve 20 will respond by allowing fluid to flow through cooler 10.

Reservoir 40 further includes a level switch 44, which includes a high level fluid sensor 45, a low level fluid sensor 46, and a temperature sensor 47. If either high level fluid sensor 45 or low level fluid sensor 46 is triggered, level switch 44 shuts

down the flushing unit. Reservoir 40 is preferably provided in a thermally-insulated tank.

Flushing system 30 further includes a pump 50 that draws flushing fluid in reservoir 40 through a filter 52 and pumps this fluid through a flow direction-shifting solenoid valve 54, through a one-way valve 56 and to the inlet 13 of thermostatically- controlled valve 20. As fluid flows through solenoid valve 54 and toward cooler 10, a small amount of fluid enters a pilot control line 58 to activate one-way check valve 60 to allow fluid to flow through valve 60 on its return from cooler 10. In this manner, the fluid in reservoir 40 is pumped up through the flushing system 30 into and through cooler 10. The flushing fluid exits cooler 10 through out-flow line 14 and valve 20 and passes through the actuated one-way check valve 60, a filter 62, and back into reservoir 40. This flow of fluid out of and into reservoir 40 is illustrated in Fig. 3 and is hereinafter referred to as a forward flush. Pump 50 is preferably driven by an electric or pneumatic motor 64 that receives air originating from a source (not shown).

Flushing system 30 also includes two pressure transducers 70 and 72 which monitor the fluid pressure in the lines of the system. If fluid pressure falls outside of the acceptable range, transducers 70 and 72 cause flushing system 30 to shut down by shutting off motor 64.

Fig. 4 shows flushing system 30 when used to flush cooler 10 in an opposite direction (hereinafter a "reverse flush"). To effect the reverse flush, flow direction- shifting solenoid valve 54 is electrically actuated to change status thereby passing the flushing fluid provided from pump 50 to the outlet of thermostatically-controlled valve 20 via a one-way valve 66. In a similar manner to the forward flush, on its way toward cooler 10 in the reverse flush, a small amount of fluid enters a pilot control line 59 to activate one-way check valve 68. Flow direction-shifting solenoid valve 54 further causes the fluid passing through cooler 10 and exiting the inlet 13 of valve 20 to be directed through one-way valve 68, through filter 62 and back into reservoir 40.

To most effectively clear any blockages in cooler 10, flow direction-shifting solenoid valve 54 is preferably alternatingly switched between the states shown in Figs.

3 and 4 to alternatingly shift between forward and reverse flushes. Although the time period for switching between the reverse and forward flushes may vary considerably,

for a transmission cooler 10 it is preferred that the direction of flow be switched at approximately five second intervals over a total period of five to ten minutes. It is contemplated that these time periods may be selected through an electric control panel that varies the duty cycle of the electric signal provided to valve 54 that causes it to switch states. Temperatures in reservoir 40 are typically in the range of approximately 200OF. The fluid pressure output from pump 50 is preferably on the order of 100 to 300 psi. As the fluid leaves pump 50, some fluid may be forced through a relief valve 80 if the flow rate or pressure of the fluid is higher than normal as it exits pump 50.

Although the present invention is specifically described with respect to a thermostatically-controlled cooler, it should be clear to those skilled in the art that flushing system 30 may be used to flush other types of hydraulic systems. It will be appreciated that if there is no thermostatically-controlled valve, the flushing fluid need not be heated and heating elements 41 and 42 could be eliminated from the system.

However, it is noted that using a heated fluid in itself has advantages such as having a high energy level to clear debris in the cooling system and to clean the system.

By utilizing electrically controllable heaters, motor, and valves, the flushing system of the present invention may be controlled by a programmed device or any other electronic circuitry to customize the operations of the flushing system for use in flushing various cooling systems. For example, the switching of valve 54 and the heat generated by heating elements 41 and 42 may be controlled by a programmable device or electronic circuit that allows these parameters to be selected by the user.

A second embodiment of the flushing system of the present invention is shown in Figs. 5 and 6 in various states of operation, and is referenced generally with the reference numeral 130. Flushing system 130 includes a reservoir 140 which may include a single chamber or two chambers 141 and 142 separated by a divider 143 which may be a screen to permit fluid flow between the two chambers or may provide a water-tight seal to prevent the fluids from mixing. Reservoir 140 preferably includes a plurality of heating elements 145, 146 and 147 for heating the flushing fluid contained in reservoir 140 to a temperature at which the thermostatically-controlled valve 20 will respond by allowing fluid to flow through cooler 10.

Flushing system 130 further includes a first pump 150 that draws flushing fluid in reservoir 140 through a filter 152 and pumps this fluid through a one-way valve 156 and a flow direction-shifting valve 158 to the inlet 13 of thermostatically-controlled

valve 20. In this manner, the fluid in chamber 141 of reservoir 140 is pumped up through the flushing system 130 into and through cooler 10. The flushing fluid exits cooler 10 through out-flow line 14 and valve 20 and passes through a filter 160, a one- way valve 162, and flow direction-shifting valve 158 back into chamber 141 of reservoir 140. This flow of fluid out of and into reservoir 140 is illustrated in Fig. 5 and is hereinafter referred to as a forward flush.

First pump 150 is preferably driven by an electric or pneumatic motor 154 that receives air originating from a source 170. The air supplied from source 170 passes through a filter 172, a pressure-relief device 174 having a meter 176 and through a separator 178 before reaching motor 154. A restricter valve 179 is operably connected to pneumatic pump 154.

Fig. 6 shows flushing system 130 when used to flush cooler 10 in an opposite direction (hereinafter a "reverse flush"). To effect the reverse flush, flow direction- shifting valve 158 is electrically actuated to change status thereby passing the flushing fluid provided from pump 150 to the outlet of thermostatically-controlled valve 20 via a one-way valve 164. Flow direction-shifting valve 158 further causes the fluid passing through cooler 10 and exiting the inlet 13 of valve 20 to be directed into a return back into reservoir 140. To most effectively clear any blockages in cooler 10, flow direction-shifting valve 158 is preferably alternatingly switched between the states shown in Figs. 5 and 6 to alternatingly shift between forward and reverse flushes.

Although the time period for switching between the reverse and forward flushes may vary considerably, for a transmission cooler 10 it is preferred that the direction of flow be switched at approximately five second intervals over a total period of five to ten minutes. It is contemplated that these time periods may be selected through an electric control panel that varies the duty cycle of the electric signal provided to valve 158 that causes it to switch states.

Although not shown in the drawings, thermostats are preferably provided in chambers 141 and 142 so as to maintain the temperature of the flushing fluid at a level sufficient to cause thermostatically-controlled valve 20 to allow the flow of the fluid to cooler 10. Such temperatures are typically in the range of approximately 200OF. The fluid pressure output from first pump 150 is preferably on the order of 100 to 300 psi.

Fig. 7 shows the flow of fluid during an optional final flush. As shown in Figs. 5-7, flushing system 130 may further include a second pump 180 controlled by

an electric motor 182 to pump fluid from second chamber 142 through a one-way valve 184 to inlet 13 of thermostatically-controlled valve 20. The flushing fluid supplied from pump 180 then passes through cooler 10 and exits outlet 15 of valve 20.

Cooling system 130 may also include an electrically-actuated valve 186 that is coupled in a second return path to reservoir 140. As shown in Figs. 5 and 6, this valve is closed during the alternating forward/reverse flush cycles but is opened when the final flush is taking place. In the event that separate fluids are used for the alternating flushing cycle and the final flush whereby wall 143 provides a water-tight seal between chambers 141 and 142, the return path through valve 186 preferably empties into chamber 142 rather than chamber 141, as shown in Fig. 7. Further, a valve similar to valve 186 may be provided in the first return path through filter 160 and one-way valve 162 to prevent the final flushing fluid from otherwise becoming mixed with the other fluid in chamber 141.

The above description is considered that of the preferred embodiments only.

Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents.