Abstract:
A portable power washer with an on-demand gas-heated water supply, is provided with a water heater for receiving water from an external water supply and rapidly heating the water by passing it though a heat exchanger proximate one or more gas burners. After the water flows through the heater it flows into a pump adapted for use with hot water and is pressurized by the pump for delivery to a high pressure hose. A nozzle or valve at the end of the hose opposite the pump allows a user to cause a stream of hot, pressurized water to eject from the nozzle and against a surface to be cleaned. The pump may be powered by an electric motor or gasoline engine and the device is typically assembled upon a wheeled cart for ready mobility.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of the prior filed, co-pending provisional patent application Ser. No. 60/824,459, filed Sep. 4, 2006, which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to devices for providing heated, pressurized fluid and particularly to high pressure washing devices, and more particularly to a portable pressure washer including a means for heating a stream of water prior to pressurization via a pump, and still more particularly to such a device in which the water is heated by an on-demand water heater comprising a heat exchanger heated by one or more gas-fired burners. 
         [0003]    Pressurized washing systems are known in prior art. Pressure washers are often portable and may comprise a pump powered by an electric motor and mounted on a wheeled cart. Water is supplied to the pump from an external source, such as a garden hose, under low pressure but relatively high volume. When activated, the pump draws from the low pressure water supply and increases the fluid pressure creating a high pressure, relatively low volume, water stream that is delivered to a high pressure hose. The end of the high pressure hose typically is fitted with a nozzle that includes a valve that may be selectively opened and closed thereby initiating or halting the flow of a stream of highly pressurized water from the nozzle. The user may thereby utilize the high pressure water device by opening the valve to direct a stream of pressurized water against a surface for cleaning, such as the exterior wall of a building. Additional elements may include a tank for holding detergent cleaning fluid, and tubing and a valve providing a route for the detergent to be drawn from the detergent tank into the pressurized water stream. Pressure washers are also sometimes provided with a tank and heating element for heating the pressurized water before it is expelled from the nozzle. In these systems, water is pumped into the pressurized tank where it is heated for several minutes prior to use. These systems suffer from several disadvantages, namely, the inherent danger to the user of working near pressurized hot water, and the limited supply of water at the desired temperature. Often, either the tank is depleted during use prior to completion of the cleaning operation, or water that is pumped into the tank to re-supply the expelled volume causes the contents of the tank to cool to a sub-optimum temperature. In addition, many such devices in the prior art are heated by burning diesel fuel or oil causing harmful and noxious emissions and necessitating periodic disassembly and cleaning of the heater to remove soot deposits. 
         [0004]    Stationary devices for continuously heating water on-demand, as opposed to storing heated water in a hot water tank or reservoir, are known in the prior art. Such devices typically include a metal conduit following a spiral or convoluted path through, or otherwise in contact with, a heat exchanger. The heat exchanger is typically heated by an electric heating element or by flame through use of propane, natural gas, or butane fueled burners. A typical gas used in such devices is commonly known by the acronym LPG (liquid propane gas). Electrically heated devices are often installed under sink counters in restaurant or residential kitchens for selectively and rapidly heating water to temperatures well in excess of those typically found in hot water tanks. These on-demand water heating devices may be constructed so that heating is initiated upon detection of water flow through the system. 
         [0005]    It would be advantageous, therefore, for a mobile, high pressure washer to be provided with a means for heating water on-demand continuously during use. It would also be advantageous if such a heating means was provided on the low pressure side of the pump so that tubing, fittings, and valves associated with the heating means would not be subjected to constant high fluid pressure during operation of the device, thereby avoiding the associated dangers and inefficiencies of a pressurized hot water tank. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    A device for producing a pressurized stream of hot liquid in accordance with the present invention includes a frame and a pump for pumping a liquid, the pump supported by said frame and coupled to a means for providing mechanical action to the pump. The pump includes a heat and pressure resistant piston and a heat and pressure resistant gasket for sealing the piston. An on-demand heater in fluid communication with the pump for delivering heated liquid to the pump is also mounted on the frame. The heater includes means for heating liquid continuously flowing through the heater during operation of the pump. A heat-resistant and pressure-resistant hose may be attached to the pump for receiving heated liquid under high pressure. 
         [0007]    One embodiment of the invention includes a hot water, high pressure washer comprising a tubular steel, aluminum or plastic frame; wheels attached to the frame to provide for washer mobility; an electrical motor or combustion engine for providing power to the pump; a water inlet fitting for receiving a relatively low pressure external water supply from a source such as a garden hose; an on-demand water heater for heating the water to a desired temperature; a pump, including temperature-resistant gaskets, pistons or piston caps, and piston rings, for receiving heated, relatively low pressure water from the heater and delivering it under relatively high pressure to a pressure and heat resistant hose; and a nozzle provided at the end of the hose distal from the pump, the nozzle typically being provided with a valve for initiating and controlling the flow of water from the hose. A wand or gun comprising a rigid tube with a nozzle at the terminal end and a trigger for initiating the flow of pressurized liquid from the nozzle at the grip may be attached to the end of the hose distal from the pump. The invention may further comprise a pressure-limiting means for controlling operation of the pump to a desired, preselected system pressure. In a preferred embodiment, the water heater includes a heat exchanger heated by a gaseous fuel-fired burner system (an ignition source and one or more gas-fired burners). The preferred fuels for the burners include combustible gaseous fuels such as propane, butane, natural gas or equivalent fuels or mixtures thereof. The pressure washer system may further include a removable fuel tank installed upon the cart and in gaseous communication with the burner system. 
         [0008]    Advantages of a high pressure hot water washer according to the present invention include: reduction in water usage for cleaning operations, since hot or warm water typically cleans more efficiently than cold water or water at ambient temperature; reduction in unit weight since no tank or reservoir is required to hold a large volume of heated water; elimination of time spent waiting for prior art hot water washers to heat water, since the present invention heats water on-demand and continuously as water flows through the heater to the pump and nozzle; reduction in the emission of pollutants, since on-demand heaters of the type used in the present invention burn propane and other relatively clean-burning fuels as opposed to diesel burners often used to heat the hot water tanks of prior art hot water washers; versatile use as a cold-water high pressure washer by reducing or halting the gas flow to the heater burners; versatile use as a low pressure hot water supply by turning off or disconnecting the pump so that the flow of water is maintained by pressure provided by the water source; and, safe indoor use through utilizing an alternative embodiment of the invention including an electric motor for providing power to the pump and a heater including electric heat elements versus gas burners. 
         [0009]    A method according to the present invention includes the steps of passing water through a heater, the heater comprising a coil mounted proximate a heat exchanger that is mounted proximate one or more gas burners, engaging an igniter proximate the burners to ignite and burn any residual gas proximate the burners, flowing a combustible gas to the burners, engaging the igniters to ignite the gas flowing from the burners, flowing water heated within the coil by the burners from the coil to the inlet of a pump in fluid communication with the coil, and moving one or more ceramic pistons within the pump past a heat-resistant gasket to pressurize the heated water and eject the heated water from an outlet of the pump to a high pressure and high temperature resistant hose in fluid communication with the outlet. 
         [0010]    Other advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example an embodiment of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0011]      FIG. 1  is a front elevational view of a water heating and pressurization apparatus. 
           [0012]      FIG. 2  is a top plan view of the apparatus of  FIG. 1 . 
           [0013]      FIG. 3  is a side elevational view of the apparatus of  FIGS. 1 and 2 . 
           [0014]      FIG. 4  is a rear elevational view of the apparatus of  FIGS. 1 through 3 . 
           [0015]      FIG. 5  is a cutaway view of the heater showing various internal details. 
           [0016]      FIG. 6  is a side elevational view of an alternative embodiment of a water heating and pressurization apparatus. 
           [0017]      FIG. 7  is a side elevational view of the apparatus of  FIG. 6  showing the hood tilted forward to provide access to the removable gas fuel tank. 
           [0018]      FIG. 8  is a top and front perspective view of an embodiment of a water heating and pressurization apparatus. 
           [0019]      FIG. 9  is a top and rear perspective view of an embodiment of a water heating and pressurization apparatus including a rearwardly projecting frame extension for holding a gaseous fuel tank. 
           [0020]      FIG. 10  is a top and front, perspective and exploded view of the apparatus of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    As required, a detailed embodiment of the present invention is disclosed herein; however, it is to be understood that the disclosed embodiment is merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
         [0022]    Referring now to  FIGS. 1 through 7  of the drawings, there is shown a portable water heating and pressurization apparatus, in this particular embodiment a high pressure washer, indicated by the reference numeral  1 . Only selected elements of the washer  1  are shown and described herein as it should be appreciated that high pressure washers and their function, structure and assembly, absent the improvements of the present invention, are well known in the prior art. As illustrated, the washer  1  comprises a combustion engine  5  (such as a gasoline or diesel engine) that powers a fluid pump  10  that draws heated water through and from an on-demand fluid heater  15  and delivers it to a pressure and heat resistant hose  20 . The heater  15  may typically be selected from the prior art to heat the required volume per time unit of water anticipated for use in washing operations to an elevated temperature relative to the temperature of water entering the heater  15 . 
         [0023]    The hose  20  is coiled upon a reel  25  attached to a frame  30 . The reel  25  is typically sized to accommodate a hose  20  approximately 30 meters in length. The frame  30  may comprise any appropriate rigid material such as plastic or tubular steel, but preferably comprises tubular aluminum covered in selected areas, such as the handle  31 , with rubber. The frame  30  provides a structure for attaching washer components such as the pump  10 , engine  5 , and reel  25 . A hood  35 , comprising a curved metal, fiberglass, or plastic panel, is hingedly attached to the frame  30  so that it may be titled forward as shown in  FIG. 7 . The hood  35  provides a covering for protecting the pump  10 , engine  5  and other components from dust, spray from the hose  20  when in operation, and the elements; for dampening engine noise; and for providing an aesthetically pleasing outer appearance. Wheels  40  attached to the lower portion of the frame  30  provide mobility, allowing the washer  1  to be rolled from one location to another. 
         [0024]    Other components and features of the washer include a detergent reservoir or tank  46  in fluid communication with the fluid stream, wherein detergent may be drawn from the detergent tank  46  and expelled through the nozzle  92  of the hose  20  along with water pressurized by the pump  10 . A temperature and/or pressure safety valve (not shown) is in fluid communication with the heater  15  and is calibrated or constructed to allow hot water to vent from the heater  15  prior to rupture of heater  15  due to over-pressurization related to over-heating. 
         [0025]    The frame  30  may comprise a U-shaped piece  32  of rigid material, such tubular aluminum, having a horizontal handle  31  and downwardly extending arms  33  and  34 . Side brackets  45  and  47  attach to the lower portions of the arms  33  and  34 , respectively, and extend forward. A horizontally disposed bottom plate  36  or equivalent structure is attached to the lower portions of the side brackets  45  and  47  to extend therebetween and provide a support platform for washer  1  components such as the pump  10 , engine  5 , detergent tank  46  and associated subcomponents such as valves, connecting tubing and other fittings. As shown in  FIGS. 3 ,  4 ,  7  and  9 , the washer  1  assembly may further include a gaseous fuel tank  50 , such as disposable or refillable propane tanks  50  commonly found in the prior art, for providing gaseous fuel to the heater burners  55 . 
         [0026]    The burners  55  are ignited via an electrical, battery powered ignition system. In one embodiment, the heater burners  55  are ignited using one or more ignition pins  73  and  74 . The ignition pins  73  and  74  produce a spark when provided the proper current by the three volt automatic pulse ignition. The primary component of the automatic pulse ignition is the pulse generator  70  that is typically powered by a power supply  81  containing two standard “A” size batteries. Unlike prior art on-demand heaters, the heater  15  used in some embodiments of the present invention starts ignition prior to initiating the flow of gas. This assures that all gas is combusted before initiating heating and limits the quantity of gas resident in the heater  15  during ignition. 
         [0027]    The ignition system may include a gas flow detector that causes the ignition system to activate, producing a spark in proximity to one or more of the burners  55 , upon detecting flow of gaseous fuel to the burners  55 . The heater burners  55  and associated thermostat and fuel-control valves are typically calibrated to heat water passing through the heater  15  to a temperature between 60 and 70° C. 
         [0028]    The heater  15 , external views shown in  FIGS. 1-4 ,  6  and  7  and internal view shown in  FIG. 5 , may comprise a winter/summer switch for adjusting the calibration of the thermostat to account for higher or lower ambient temperatures, a water inlet  60  for receiving water from an external source such as spigot or tap connected to a municipal water supply (typically via garden hose  57 ), a water discharge valve  61 , a micro-active switch  62 , a water adjusting valve  63  for adjusting the flow rate of water through the heater  15 , a sensor pin  64  for controlling heater fuel combustion, a primary ignition pin  73  for igniting one or more burners, one or more burners  55  for heating a heat exchanger  65 , a back plate  66  that provides a support surface for heater  15  components, a combustion fume collection hood  67  for collecting combustion fumes produced by the burner  55 , a gas inlet  68  for receiving gaseous fuel from the fuel tank  50 , a hot water outlet  69  from which heated water flows from the interior of the heater  15  to the hose  20  via the pump  10 , a pulse generator  70 , a solenoid valve  71 , a gas adjusting valve  72  for increasing or decreasing the flow of gaseous fuel from the tank  50  to the burner  55 , a secondary ignition pin  74  for igniting one or more burners  55 , a protection pressure switch  75 , and, optionally, an exhaust motor for driving an exhaust fan that draws combustion fumes upward and through the fume collection hood to exit the top of the heater  15  through the exhaust pipe  76 . The heater  15  is attached to the frame  30  using threaded fasteners each surrounded by an elastomeric collar comprising rubber or rubber-like material, such as ethylene propylene diene monomer, to isolate the heater from vibration caused by the engine  5 . The dampening effect of the rubber collars between the heater  15  and the frame  30  ensure that only minimal vibration is transferred from the engine  5  to the heater  15 . 
         [0029]    The water inlet  60  and water outlet  69  are in fluid communication with one another via an elongate, generally tubular, fluid-confining conduit  85  coiled within the heater  15  about and/or within the heat exchanger  65 . The heat exchanger  65  and the conduit  85  (also referred to herein as a coil) each comprise a material adapted for heat-transference such as copper or aluminum. The heat exchanger  65  is positioned within the heater proximate and above a means for generating heat, such as an electric heating element or one or more gas burners  55 . Heat from the heat generation means (gas burner  55 ) is transferred via the heat exchanger  65  to the coil  85  and then to water flowing through the coil  85 . Typically, the water is heated to between 60 and 70° C., a temperature range typically optimal for cleaning operations. 
         [0030]    In an alternative embodiment of the washer  1 , shown in  FIGS. 6 and 7 , the pump  10  is powered by an electric motor  90  instead of a gasoline engine  5 . Typically, the flow rate of water through the heater  15  is calibrated to provide a 25° C. change in water temperature after passage through the heater  15 . 
         [0031]    The pump  10  receives heated water from the heater  15  and includes internal seals, gaskets and piston caps comprising heat resistant materials such as VITON® (fluorocarbon rubber), styrene butadiene rubber, butyl rubber, chloro butyl rubber, bromo butyl rubber, nitrile rubber (acrylonitrile butadiene rubber), neoprene (chloroprene rubber), ethylene propylene diene rubber, TEFLON® (polytetrafluoroethylene or PTFE), HYPALON® (chlorosulphonated polyethylene), fluorosilicon rubber, and/or urethane. The pump  10  typically has one to four pistons. During operation of the pump  10 , reciprocating movement of a piston relative to a piston seal or gasket fixed within the pump  10 , draws fluid from the heater  15  and thereafter expels the fluid at high pressure from the pump  10 . 
         [0032]    Preferably, the pistons comprise a ceramic material, at least on the portion of the outer piston surfaces that contact the hot water being pumped and slide past the piston seal. Although the piston seal may comprise any of various heat-resistant polymer materials, it preferably comprises fiber-armed PTFE. An appropriate fiber-armed PTFE seal may be obtained from Trelleborg, AB, Germany. The piston may comprise a solid rod of ceramic or may comprise an outer, cylindrical sleeve of ceramic fitted upon an inner rod of steel or other suitable material. Ceramic typically comprises aluminum oxide and a binder and may contain other constituents such as manganese oxide, silicon oxide, zirconium oxide, and hafnium oxide. A suitable ceramic for use in high pressure pumps for pumping heated fluids, or pumps equipped with ceramic pistons, may be selected from the prior art. An appropriate pump  10  may have a working pressure range of approximately 60 to 200 bar and a working flow rate of approximately 11 to 15 liters per minute, although pressures and flow rates outside of these ranges may also be operable. 
         [0033]    After connecting a water supply source to the water inlet  60 , the typical heating sequence includes user activation of a trigger  94  on a handle  88  of the hose  20 . Trigger activation causes water to flow through the washer  1  fluid path including through the heater  15  and pump  10 . The flow of water activates the micro-active switch  62  which initiates the flow of electricity from the power supply  81  to the pulse generator  70 . The pulse generator  70  supplies pulses of electricity to the ignition pins  73  and  74  causing them to generate sparks in proximity to the burners  55 . Subsequently, the solenoid valve  71  opens allowing gas to flow from the fuel tank  50  to the gas inlet  68  and then to the burners  55 , where flame is ignited by the ignition pins  73  and  74 . Heat from the burner  55  flames rises to heat the heat exchanger  65 . As water at ambient temperature flows into the heater  15  from the water source it is thereby heated as it passes through the heat exchanger  65 . Heated water exits the heater  15  through the hot water outlet  69  and then flows through a heat and pressure resistant hose  87  to the pump  10  where it is pressurized. Preferably, the hose  87  used to connect the heater  15  to the pump  10  is selected as capable of withstanding over 300 psi, since activation and release of the trigger  94  on the spray gun  88  may create a surge of back pressure through the fluid flow path of the washer  1 . Pressurized hot water flows from the pump  10  to the high pressure hose  20  and exits the hose  20  at the nozzle  92 . 
         [0034]      FIGS. 8 and 9  illustrate two variations  100  and  101  on a further embodiment of the invention.  FIG. 8  illustrates an embodiment of a washer  100  wherein the heater  15 , pump  10  and engine  5  are mounted in an open frame  30 .  FIG. 9  illustrates an embodiment of a washer  101  wherein the frame  30  includes a generally horizontal extension  97  extending from the lower rear portion of the frame  30  and adapted to receive and hold the tank  50 . In addition, extension  97  serves as a foot lever for raising the front portion of the washer  101  so that the washer  101  may be wheeled about on the rear wheels  40 . When depressing extension  97  the front of the frame  30  is rocked upward as the frame  30  pivots about the wheels  40 . 
         [0035]      FIG. 10  is a is an exploded view of the washer  101  of  FIG. 8  additionally showing a spray gun  88 , with trigger  94 , wand  96 , and nozzle  92 , mounted on the high pressure hose  20  leading from the pump  10 . 
         [0036]    It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and allowable equivalents thereof. It should be appreciated, that the washer  1  may both with and without heating water as it passes through the heater  15 .