Abstract:
The present invention relates to a system of creating and applying a heated cleaning fluid to a surface. The system includes a housing with a first, a second and a third exhaust gas opening. A first, second, and third heat exchanger are enclosed within the housing. The first and second exchangers are serially arranged, while the third is at an angle relative to the first and second and directly adjacent to the first opening. Super heated exhaust gas flows through first opening and third exchanger. Heated gas flows through the second opening and passes below the third exchanger. Super heated exhaust gas exiting the third exchanger mixes with the heated gas in a mixing chamber of the housing, which is then supplied to the first and second exchangers. Fluid passes through the three exchangers and exits the third exchanger heated. That heated fluid passes to a cleaning wand for application.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/180,355 filed May 21, 2009 entitled “Heat Exchange Configuration for Use in a Mobile System Cleaning Apparatus,” which is incorporated by reference in its entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a new and beneficial configuration of three heat exchange cores housed within a compact housing and used to produce heated fluid, steam and or a heated cleaning solution in portable cleaning systems. The present invention makes highly efficient use of heat sources available in a mobile cleaning system to quickly elevate fluid to be used in the system to a desired working temperature and to maintain that fluid at a stable working temperature throughout a variety of working conditions. 
     BACKGROUND OF THE INVENTION 
     Steam cleaning devices are often used to clean items, such as rugs, carpet, or upholstered furniture. Such devices are usually mobile and are used at the site of the cleaning job. As is understood by those working in the art, cleaning fluids used in such devices typically consist of a mixture of heated water, steam and a chemical solution that is delivered to an article to be cleaned by a cleaning wand assembly. While these are typical fluids, other fluids or combination of fluids, could certainly be used in a given environment. In any case, fluid supplied to the cleaning wand assembly often and preferably is heated substantially and that fluid temperature is to be maintained over a variety of operating conditions. 
     DESCRIPTION OF THE PRIOR ART 
     To heat fluid, prior art steam cleaning devices typically pass preheated fluid through typical heat exchangers, causing heat applied to the exchangers (typically in the form of a heated gas) to pass to the fluid, resulting in heated fluid. The thermodynamic properties and functionality of heat exchangers, as well as the design and implementation of heat exchangers, is well within the working knowledge of those working in this art. These artisans also understand that typically it is a heated gas which is placed in contact with the external surfaces of the heat exchanger, causing heat to transfer from the gas to the exchanger. Such gases can be super heated, such as exhaust gas exiting an internal combustion engine or merely heated, such as exhaust gas generated by vacuum pumps, etc. 
     As one working in the field would expect, heated fluid exits heat exchangers and is typically directed to a cleaning wand assembly for application to an article to be cleaned. The cleaning wand assembly typically contains a trigger mechanism for controlling when the heated fluid exits the wand, typically through a jet or other orifice located at the end of the wand itself. The wand also often may contain a vacuum suction inlet port. That port is typically in communication with a spent fluid recovery tank. That port is typically used to recover solid fluid and to direct that fluid to the waste water tank. As those working in the field understand, the tank is typically kept under vacuum by an engine driven blower, vacuum pumps, etc. and this vacuum is supplied to the suction inlet port by appropriate conduit pipe, etc. 
     Steam cleaning devices additionally often contain a thermostat (usually set at a predetermined temperature), placed downstream of the heat exchanger(s) in order to gauge the temperature of the heated fluid before it exits through the hand held wand. If the heated fluid destined to exit the heat exchanger exceeds the predetermined temperature of the thermostat, often the entire device will be directed to shut down. The device then needs to be sufficiently cooled, typically by waiting an appropriate amount of time, before restarting the device, or evacuating the device and refilling it with fresh, cool fluid. Accordingly, there is a great need to constantly monitor and control the temperature of fluid used in the system. 
     It has been observed that the trigger mechanism in the wand of prior art devices can create two additional problems in a typical cleaning environment. First, overheating of the fluid regularly occurs due to constant activation and deactivation of the trigger mechanism in the wand. Specifically, when the trigger mechanism is deactivated, heated fluid does not exit the wand, stagnating in the wand, heat exchanger(s) etc. When this occurs, the fluid often becomes overheated, exceeds the predetermined set temperature of the thermostat, causing the thermostat to shut down the device. 
     Second, periodic or sporadic use of the trigger mechanism can create wide temperature fluctuations in fluid exiting the device. When the trigger mechanism is deactivated and the heated fluid supply is not allowed to exit the wand, the fluid temperature again rises in the heat exchanger(s). Even if not overheated to beyond the predetermined temperature of the thermostat, the heated fluid leaving the wand will often momentarily be super heated when the trigger mechanism is activated. Subsequently, the fluid temperature drops and stabilizes. These fluid temperature fluctuations negatively affect cleaning characteristics of cleaning systems, as is well known to those working in the art. Thus, there is a need for a system which will minimize, if not eliminate, these undesirable temperature fluctuations. 
     As those working in the field understand, there are a number of prior art devices which use organic heat sources, in combination with heat exchangers, to create heated fluid. For instance, U.S. Pat. No. 4,949,424 to Shero is such a system, whose disclosure is incorporated here by this reference. Specifically, Shero directs incoming fluid through a first heat exchanger, which heats the fluid to a temperature in the range of about 100 to 120° Fahrenheit. That partially heated fluid is then directed through a second heat exchanger, which is placed parallel to the first exchanger and which heats the fluid to a range of about 200° to 230° Fahrenheit. After the fluid is directed through both heat exchangers sequentially, a portion of the volume of the heated fluid is diverted back into the incoming fluid supply, causing a continuously circulating flow of somewhat heated fluid, raising the incoming cold fluid temperature by approximately 5° to 20° Fahrenheit, and helping to control heat fluctuations and the momentary burst of superheated water exiting the end of the wand when the trigger mechanism is initially activated. However, while the disclosed device certainly controls fluid temperature fluctuations better than some previous devices, it still does not provide for optimum fluid temperature fluctuation control, nor does the disclosed device efficiently and effectively utilize organic sources of heated and super heated gases to constantly heat fluid. 
     U.S. Pat. No. 5,469,598 to Sales discloses a marginally more efficient system for heating and maintaining the heat of incoming fluids and is incorporated into this disclosure by this reference. However, the device of Sales is not significantly better than that disclosed in Shero and, as those working in the field understand, there is still a great need for a system which will provide for optimal fluid temperature fluctuation control, efficient utilization of organic sources of heated and super heated gases and timely and consistent production of heated fluids. 
     In Sales, super heated exhaust gas from an internal combustion engine is a main source of heat supplied to primary heat exchangers used to heat incoming fluid. These primary exchangers are configured in parallel and sequentially heat the fluid. After being initially directed through the two heat exchangers, exhaust gas is directed through a conduit and towards a third heat exchanger. Residual heat from recovered waste water, steam and exhaust gas from a vacuum pump are also collected and directed to the third heat exchanger. All these secondary sources of heat merge (i.e. the somewhat cooled but still warm exhaust gas, a vacuum pump exhaust gas, heated gas relating to recovered waste water and steam) together and are directed through the third heat exchanger and used to preheat the cold fluid supply. 
     Though better then prior art devices, the device of Sales still wastes a substantial amount of available heat which could be used to heat fluid. For instance, the secondary heat sources are at different temperatures at the time they are exposed to each other and are allowed to cool each other due to the distance the heat must travel in the system before being applied to the third heat exchanger. Obviously this results in substantial dilution of the temperature of the secondary heat sources. Two problems arise from this dilution. First, the overall temperature of the heated fluid decreases substantially in proportion to the period of time the device is in use. In fact, the overall temperature of the heated fluid can decrease more than 100° Fahrenheit over a half hour period of use, negatively effecting temperature stability. Second, the temperature of the heated fluid also fluctuates substantially in proportion to the period of time that the triggering mechanism of the wand is activated. 
     Specifically, these inventors have discovered that during delivery of heated fluid for a cycle period of 20 seconds, the temperature of the fluid in the prior art device fluctuated by approximately 30° Fahrenheit. Such fluctuations are undesirable and there is a long felt but unsolved need for a device that avoids these deficiencies. There is also a need for a device which efficiently utilizes super heated engine exhaust gas, in combination with secondary heat sources, to heat fluid to a desired temperature and to maintain that fluid at a more constant temperature through a variety of cleaning environments than is presently available. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an apparatus that utilizes organic heat sources typically found on a steam cleaning device more efficiently and effectively than prior art devices to produce heated fluid which exhibits a higher heat sustainable and constant temperature throughout a variety of operational environments. It is a further object of the present invention to avoid the fluctuations and instability of the temperature of the heated fluid both when the device is in constant use over time, and when a wand triggering mechanism is periodically cycled that are present in prior art devices. These and other advantages are achieved by the device of the present invention. 
     The present invention preferably includes a primary super heated gas generating means, such as exhaust from an internal combustion engine, and a heated gas generating means, such as a vacuum pump exchange. The preferred device also includes a fluid supply system, a vacuum generator for recovering dirty fluid, and a cleaning tool assembly for the delivery of heated fluid to a surface to be cleaned. It should be understood by those skilled in the art that a cleaning wand assembly could be replaced by any cleaning tool such a triggered jet, etc. 
     The present invention also preferably includes a common housing to enclose a first and a second heat exchanger, which are in sequential arrangement, as well as a third heat exchanger. The third heat exchanger is preferably placed at an angle relative to the first and second heat exchangers. Contrary to the prior art, the third heat exchanger is exposed to super heated exhaust gas received directly from the internal combustion engine before being mixed with the cooler heated gases generated by a vacuum, etc. Indeed, it is only after traveling through the angled third heat exchanger that the exhaust gas and vacuum blower exhaust gases mix and caused to pass over the two remaining heat exchangers located within the housing. 
     The novel arrangement of these exchangers, in combination with the novel approach of applying heated and super heated gases thereto as described herein, limits the amount of temperature dilution of the heated gases used to heat fluid and thus the initial fluid supply will be heated to much higher temperature than previously achievable, while maintaining a streamlined, cost efficient design. Also, because the overall temperature used to preheat an incoming fluid supply is much higher than with prior art systems, the overall temperature of the heated fluid that is delivered from the wand assembly will constantly be higher than known of in prior art devices. In fact, the inventors have determined that the temperature of the overall heated fluid can be approximately 375° Fahrenheit, compared to approximately 250° Fahrenheit typically achieved by prior art devices. Additionally, the fluctuations in heated fluid temperature when the wand&#39;s triggering mechanism is activated is decreased substantially, by approximately 15° Fahrenheit in a 20 second cycle period and approximately 10° Fahrenheit in a 10 second cycle cleaning period. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a cleaning apparatus in accordance with the present invention. 
         FIG. 2  is a schematic view of the housing, heat exchangers and flow of various heated gases to and through the housing and exchangers. 
         FIG. 3  is a chart showing initial high temperatures of fluids achieved and temperature fluctuations achieved by a tested prior art system. 
         FIG. 4  is a chart showing initial high temperatures of fluids achieved and temperature fluctuations achieved by the system of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details herein are not to be interpreted as limiting, but merely as a basis for the claim and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     The mobile cleaning apparatus  10  (typically installed within a van or truck) of the present invention is shown in  FIG. 1 . An incoming fluid supply for use in the apparatus flows through inlet  20  to the fluid box  22 , which is a storage apparatus for initially holding incoming cold fluid and later preheated fluid which is used in the cleaning process. As one of skill in the art will understand from review of the drawing, the fluid coming in from the inlet  20 , typically water, can be held in the fluid box and mixed with preheated fluid to create a preheated supply of fluid for use by the overall system. A pump  24  moves fluid from the fluid box  22  for heating and use throughout the system. 
     A heat generating unit  30 , such as an internal combustion engine, serves as the main source of super heated gas for heating fluid. Exhaust gases generated by the heat generating unit  30  are supplied to a housing  40 . That housing contains at least three heat exchangers  42 ( a ),( b ) and ( c ). These exchangers are of common construction and typical in the industry. When in operation, the heat generating unit  30  produces super heated exhaust gas and the vacuum pump produces heated exhaust gas, and both these gases flow into the housing  40  (explained in detail below). 
     A cleaning wand or tool (not shown) related to wand assembly  60  serves as the outlet for the heated fluid. It is understood by those skilled in the art that the cleaning wand of wand assembly  60  could be replaced by any appropriate cleaning tool, such as a triggered jet, etc. A check valve  64  regulates flow of heated fluid which is directed through a solution outlet  62  and ultimately a wand. When the trigger mechanism of the cleaning wand (not shown) is activated, the check valve  64  will allow heated fluid to flow through the solution outlet  62  of the wand assembly  60 . A chemical injection system  68  can inject a chemical solution into the hot fluid, providing for great flexibility in creating cleaning solutions which ultimately exit the cleaning wand of wand assembly  60 . A cleaning solution screen part  66  is also provided so that a user can constantly monitor the composition and/or temperature of cleaning solution which will exit the wand. 
     A vacuum unit (not shown), such as a vacuum pump, is used as part of an overall system to recover spent cleaning solution which deposits spent solution into the waste fluid recovery tank  70  for storage. It is believed that those skilled in the art understand how these type of vacuum systems operate in portable cleaning system environments and they will not be further explained here. Hot air from the vacuum unit  90  is also recovered and directed towards the housing  40  to further heat an incoming fluid supply. 
     The cleaning apparatus of  FIG. 1  additionally may preferably include a temperature control valve  80  which is set to a predetermined temperature. Typically, if the trigger mechanism of the cleaning wand of the wand assembly  60  is not activated for a period of time, hot fluid will stagnate and exceed the predetermined temperature set on the temperature control valve  80 . When that occurs, the temperature relief valve  82  opens, allowing hot fluid to flow into the waste fluid recovery tank  70 . Additionally, a temperature balance orifice  84 , placed in line with and before the cleaning wand of the wand assembly  60 , will also direct fluid to the fluid box  22 . 
     A pressure gauge  50  measures the pressure of fluid as it is being pumped by the water pump  24 . A pressure regulator  52  can constantly maintain and/or adjust the pressure of the fluid being supplied to the cleaning wand of the wand assembly  60  to facilitate desired cleaning operations as set by the technician or operator. The pressure regulator  52  is of conventional design and is generally understood by those working in this art field. A pulse hose  54  attached to the pressure regulator  52  provides protection from fluctuations in pressure while the cleaning apparatus  10  is in operation. 
     As shown in  FIG. 2 , the housing  40  is described in detail and contains at least three heat exchangers  42 ( a ), ( b ) and ( c ). Two of these heat exchangers,  42 ( a ) and  42 ( b ), are placed in a sequential relationship relative to each other. The third heat exchanger  42 ( c ) is positioned at an angle relative to the first and second heat exchangers  42 ( a ) and ( b ). Hot air from the vacuum unit  90  flows into the housing  40  below heat exchanger  42 ( c ) and into a mixing chamber  43  of the housing  40  before contacting heat exchanger  42 ( b ). Super heated exhaust gas from the heat generating unit  30  is directed through the angled heat exchanger  42 ( c ) and mixes with the heated gases in mixing chamber  43 . The mixed heated gases next pass through heat exchangers  42 ( b ) and finally  42 ( a ) and further heat the fluid as it passes through those heat exchanger before exiting housing  40  through exhaust port  44 . 
     As will be understood by those of skill in the art, the hot exhaust gas from the heat generating unit  30  need only travel a short distance before reaching the angled third heat exchanger  42 ( c ), resulting in super heated gas being allowed to pass through heat exchanger  42 ( c ) before that gas is cooled and exposed to the lower temperature hot exchange gas generated by the vacuum unit  90 . Thus, when the hot exhaust gas (having lost some heat in preheating fluid in exchanger  42 ( c )) and hot air from the vacuum unit  90  are mixed, the overall heat transferred to the heat exchangers  42 ( b ) and ( a ) is of a higher temperature than the gases presented to the heat exchangers of the prior art, resulting in a final fluid with a higher initial temperature and reducing fluctuations in temperature when the cleaning apparatus  10  is in operation. 
     The arrangement of the three heat exchangers  42 ( a ), ( b ) and ( c ) in housing  40 , with the third heat exchanger  42 ( c ) positioned at an angle relative to the first and second heat exchangers  42 ( a ) and ( b ), more efficiently uses available heat from various organic exhaust gases of the overall system in comparison to how those gases are used in prior art devices. First, as all three heat exchangers  42 ( a ), ( b ) and ( c ) are typically and preferably placed within the housing in close proximity, the super heated exhaust gas from the heat generating unit  30  need only travel a short distance before being exposed to and mixed with the hot air from the vacuum unit  90 . Thus, the exhaust gas will not lose substantial heat energy before being exposed to the hot but generally cooler air of the vacuum unit  90 . Second, because the super heated exhaust gas is diverted first to the angled third heat exchanger  42 ( c ), it is not immediately exposed to the cooler air from the vacuum unit  90 , allowing the exhaust gas to remain at substantially the same temperature it had been upon leaving the heat generating unit  30 , causing the combination of the hot exhaust gas and hot air from the vacuum unit  90  to also remain at an overall higher temperature. This was not achieved in prior art devices. Since there is less temperature dilution due to the length of travel and immediate exposure of the main heat source to other heat sources, the heated fluid, and resulting heated fluid that is delivered from the cleaning wand of the wand assembly  60 , is at a higher overall temperature, preferably initially at about 375° Fahrenheit, compared to approximately 250° Fahrenheit as found in prior art devices. This initial temperature differentiation is shown on the charts of  FIGS. 3 and 4 . Indeed, the inventor learned that the configuration of heat exchangers, packaged in a single unitized housing, in combination with the application of super heated and heated gases in the described manner, resulted in approximately a 30% increase in overall initial temperature of the heated fluid. 
     Additionally, since the portion of the heated fluid from the housing  40  is diverted back to the fluid box  22  is at an overall higher temperature than previously available, the incoming water supply is preheated to a higher overall temperature than was previously possible. The novel arrangement of the exchangers, coupled with the novel supply of organic heated gases, also allows for a readily available supply of hot fluid at a higher temperature than previously available, while the cleaning apparatus  10  is in use. In addition, this also results in less fluctuation in temperature of the heated fluid when the trigger mechanism on the cleaning wand of the wand assembly  60  is activated. As is shown in  FIGS. 3 and 4 , the temperature of the heated fluid delivered is substantially more stable over time, by approximately 15° to 20° Fahrenheit in a 20 second cycle period and 5° to 10° Fahrenheit in a 10 second cycle period, not achievable by prior art devices, all while maintaining a streamlined, cost efficient design. 
     It will be appreciated by those skilled in the art that other various modifications could be made to the device without the parting from the spirit in scope of this invention. All such modifications and changes fall within the scope of the claims and are intended to be covered thereby.