Abstract:
The invention is an on-demand electric water heater which includes one heater housing having an electric cartridge heating element surrounded by at least one water heating chamber containing a partition member mounted on the top cover or base cover of the heater housing to define opposing flow passages along the longitudinal direction of the electric cartridge heating element such that as cold water enters the housing and proceeds along the opposing flow passages, heat generated by the electric cartridge heating element is absorbed by the incoming cold water flowing along the opposing flow passages to minimize heat losses from the on-demand electrical water heater.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not applicable. 
       REFERENCE TO SEQUENCE LISTING 
       [0003]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention is directed to providing hot water through the use of a tankless water heater unit which is specifically adapted to heat water on a continuous on-demand basis as the water passes from a conventional water source along a path of water flow through the unit and along an outlet path for commercial or residential use. 
         [0006]    2. Description of the Related Art 
         [0007]    The most common approach today to obtaining heated water in both domestic and commercial settings involves the utilization of large storage tanks for the storage of hot water. Although such heated storage tank systems can provide hot water at a relatively good flow rate, inefficiency is prevalent in such types of water heater assemblies due to the fact that the water maintained within such storage tanks is effectively reheated continuously even when the storage tank is not being utilized on a regular or continuous basis. 
         [0008]    Another approach to providing hot water involves the use of continuous flow or “tankless” water heaters wherein the water is almost instantaneously heated as it passes along a continuous flow system. Such continuous flow or tankless water heating systems are far more efficient from the standpoint of expending energy for the purpose of heating water which is currently being used. However, one serious common drawback of traditional tankless continuous water heating systems is their inability to provide hot water at high flow rates. Typically, traditionally tankless water heater systems have difficulty providing domestic hot water (e.g., for shower water with a temperature of approximately 90°-100° F. (32°-38° C.)) at flow rates greater than approximately six gallons per minute (22.7 liters per minute). Such existing factors in the currently available continuous flow water heaters result in restricting usage to limited domestic applications and no usage in commercial applications wherein industrial applications processed hot water is typically water with a temperature of at least 140° F. (60° C.) or higher. 
         [0009]    Other than limited flow rates, there are additional drawbacks which have been defined in the use of continuous flow “tankless” water heaters. It is difficult to regulate the output temperature as flow rates fluctuate without the use of expensive and complex controls. Another existing and known problem with instantaneous water heaters is the lack of reliability with frequent breakdowns, therefore, requiring the need for frequent maintenance and repair. 
         [0010]    The prior art has proposed some continuous flow water heaters of the type referred herein. The patent to Insley, U.S. Pat. No. 4,762,980, discloses an apparatus for electrically heating water utilizing at least two electrically powered heating resistance elements disposed sequentially along a path of flow but wherein separate chambers in which the separate heating elements are arranged are connected by a single common port or opening located at a common end of both the chambers and heating elements. Insley discloses his heating elements as a continuous electric resistance heating coil extending successfully through separate interior channels rather than two totally segregated elements. The heating coils controlled by temperature controller means having a temperature sensor to reduce or eliminate the effects of radiant energy generated by the heating coil on the temperature sensor. 
         [0011]    Todd, U.S. Pat. No. 4,567,350, discloses an instantaneous electric water heater for both household and commercial use including a plurality of sequentially arranged individual heating chambers connected in series flow relationship between a cold water inlet and a hot water outlet wherein heating elements are energized by a flow switch at the time the hot water is demanded and are controlled by an adjustable thermostat which sets the outlet hot water temperature. An adjustable regulator is provided to assure that the water flow rate will not exceed the capacity of the heater to heat the water to a minimal acceptable level. 
         [0012]    U.S. Pat. No. 4,604,515 issued to Davidson and U.S. Pat. No. 4,638,147 issued to Dytch et al. includes a solid state switch to control electrical current to the heating elements. Dytch mounts the solid state switch on a wall of the heating chamber, thereby cooling the switch while recovering generated heat. Dytch also teaches locating a temperature sensor at the outlet of the heater. 
         [0013]    Hurko, U.S. Pat. No. 4,808,793 discloses a tankless electric water heater having an instantaneous hot water output which includes an open ended folded tubular conduit having a separate metal sheath emerging heating element inserted into each end of the conduit. This patent also discloses the use of a self regulating (PTC) heating cable either disposed in or wrapped around the tubular conduits which is continuously energized independently of the metal sheathed heating elements so as to maintain the water in the tubular conduits at a constant predetermined temperature. 
         [0014]    U.S. Pat. No. 5,479,558 to White, Jr. et al. describes a flow-through tankless water heater with a flow switch. The flow switch has an arm and a ball joint, but requires significant water flow to energize the flow switch. 
         [0015]    U.S. Pat. No. 6,552,283 to Cabrera describes a flow switch. The flow switch has a floating magnetic set of balls that have a specific gravity higher than water yet will float upwardly in a pipe when water flows, thereby coming into proximity with a magnetic switch and energizing the heating elements. The floating set of magnetic balls must be retained within the pipe to prevent them from flowing out of the water heater. This requires screens within the flow of water which, in many circumstances, corrode or clog during use. 
         [0016]    A need therefore continues to exist for hot water delivery systems that can provide hot water in a more energy efficient manner than storage tanks systems yet still deliver hot water at the higher flow rate associated with storage tank systems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0017]    The present invention relates to an instantaneous on-demand hot water system which passes the incoming water through at least one surrounding continuous flow chamber. Each chamber includes an electric heating element which is activated as the continuous flow of water enters the chamber. 
         [0018]    In accordance with the present invention, the instantaneous on-demand water heater provides hot water at a high flow rate and even temperature by passing the water to be heated through a tortuous labyrinth path in a chamber enclosure surrounding the electrical heating element providing the source of heat. In order to insure that the instantaneous on-demand hot water system consumes power only when the user demands hot water, the instantaneous water heater has a flow control responsive to the flow of water to turn on the electric heating element. Further, the electric heating element, as a safety device, is also controlled by a high temperature sensing switch which will shut off the electrical heating element upon sensing that the high temperature limit has been exceeded. Also, an adjustable thermostat is used to set the final temperature of the hot water output of the heating device. 
         [0019]    The on-demand heating system in accordance with the present invention utilizes a vertically oriented enclosure containing an inner upright baffle which directs the flow of the incoming water from its water inlet located at the lowest point of the enclosure, upwards along the length of the vertically oriented enclosure to the top of the enclosure where the incoming water is made to overflow the baffle and reverse its flow from upward to downwards into direct contact with the outer wall of the internal electric heating element such that heat carried outwards from the electric heating element is absorbed by the flowing water as it flows along the path within the surrounding chamber. 
         [0020]    Accordingly, it is a principal object of the present invention to provide an improved on-demand instantaneous electric hot water system. 
         [0021]    It is another object of the present invention to provide an improved energy efficient electrical hot water system. 
         [0022]    It is yet another object of the present invention to provide an on-demand hot water system which has precise temperature regulation to insure that the water is delivered at an even temperature. 
         [0023]    Yet a further object of the invention is to provide an on-demand water heater having means for regulating against excessive hot water demand, means for limiting the water temperatures in the event of thermostat malfunctions, and means for activating the water heater only when hot water is desired by the user. 
         [0024]    Other objects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a schematic diagram of the on-demand electric hot water heater system; 
           [0026]      FIG. 2  is a cross-sectional view of the cartridge heater element of the present invention; and 
           [0027]      FIG. 3  illustrates the use of the present invention in the making of a cup of coffee. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    With reference to the figures, an on-demand instantaneous hot water heating system  5  having a cold water inlet  10  and hot water outlet  12  is shown. The improved water heater will provide instant hot water to a location or locations where hot water is to be delivered. Such locations may include a bathroom or kitchen sink, a shower stall, a washer in the laundry room and/or a bathing facility, including any one of many industrial or commercial applications. 
         [0029]    As the cold water enters, it passes through a flow control valve  14  in communication with the cold water inlet  10  and a control unit  56  which helps maintain a constant flow rate for the incoming water. A one-way check valve  16  also communicates with the cold water inlet  10  to prevent backflow from the on-demand instantaneous hot water heating system  5 . 
         [0030]    In the illustrated embodiment, the cold water enters the first of a series of tubular heating chambers  18  surrounding a cartridge heating element or heating source  20 . The radially outermost heating chamber consists of an outermost tube  22  of copper or stainless steel tubing surrounding one or more inner tubes or partitions  24   a  of copper or stainless steel tubing. Both inner and outermost tubes  24   a,    22  have a first end  26  and second end  28 . The outermost tube  22  is permanently interconnected at the first end  26  to a top cover  30  and to a base cover  32  at the second end  28  to create a sealed tubular housing  33  that is completely sealed with the exception of a cold water inlet  10  in the outermost tube  22  and a hot water outlet  12  in the base cover  32 . The electrical cartridge heating element  20  is approximately centrally mounted within a passage  36  in the top cover  30  and sealed in the top cover  30  by a elastomeric seal  35  mounted within the passage  36 . The electrical cartridge heating element  20  is suspended within the sealed tubular housing  33  and has a stainless steel outer surface. The electrical cartridge heating element  20  is an off-the-shelf item and is readily available in a variety of output capacity sizes from a variety of heater control suppliers. 
         [0031]    The one or more inner tubes  24  have only one of their first or second ends  26 ,  28  fixed or interconnected with either the top cover  30  or the base cover  32 . In the preferred embodiment shown, the second end  28  of the first inner tube  24   a  is permanently fixed to the base cover  32  while the first end  26  extends to within approximately one-half (½) inch of the top cover  30  to leave an opening  38  between the first end  26  and the bottom  39  of the top cover  30 . A second inner tube  24   b  is mounted radially inwards of the first inner tube  24   a.  This second inner tube  24   b  has its first end  26  permanently fixed to the top cover  30  while its second end  28  is suspended downwards to within approximately one-half (½) inch of the top  37  of the base cover  32  to leave an opening  40  between the second end  28  of the second inner tube  24   b  and the base cover  32 . A third inner tube  24   c  is radially inward of the second inner tube  24   b  and like the first inner tube  24   a,  its second end  28  is fixed to the base cover  32  while its first end  26  extends toward the top cover  30  but terminates approximately one-half (½) inch away from the bottom surface  39  of the top cover  30  to define an opening  42  between the first end  26  of the third inner tube  24   c  and the top cover  30 . This arrangement defines two chambers A, B, each chamber having an inner tube acting like a baffle or partition to define longitudinal passages, one being an inlet passage and the other a return passage through which the water flows that surrounds the cartridge heating element  20 . 
         [0032]    The cold water, after flowing through the one-way check valve  16  and flow control valve  14  enters the first chamber A via a three-quarter inch to one inch cold water inlet connection  10  near the second end  28  of the outermost tube  22  and enters into the inlet passage  44  between the outermost tube  22  and the first inner tube  24   a  after passing through the adjustable flow control valve  14  and begins to rise in the inlet passage  44  towards the top cover  30 . When the water level reaches the top of the first inner tube  24   a  where the opening  38  exists, the water will spill over the first inner tube  24   a  and by way of an opening  38 , the water will begin to flow downwards along the return passage  46  between the first inner tube  24   a  and the second inner tube  24   b  within the first chamber A. A great deal of turbulence is created in the flow of the water by the fact that the water is forced to completely change direction as it flows through the opening  38  and downwards along the return passage  46  between the first and second inner tubes  24   a,    24   b.  Because of this turbulence, the water flow becomes a good heat absorber of any heat that radially dissipates from the cartridge heating element  20 . As the water continues to flow downwards in the return passage  46  between the first and second inner tubes  24   a,    24   b,  it will be diverted by the base cover  32  and be forced through the opening  40  to change directions and begin to flow upwards in the incoming passage  48  of the second chamber B between the second inner tube  24   b  and the third inner tube  24   c.  Again, the flow will be very turbulent because of the reversal of directions from the return passage  46  in the first chamber A to the incoming passage  48  of the second chamber B. Any heat that is radially dissipated from the cartridge heating element  20  will be absorbed by the turbulent water flow in the various passages surrounding the cartridge heating element  20  which results in preheating of the incoming cold water and significantly reduces heat losses from the cartridge. 
         [0033]    The flow pattern of the first chamber A now repeats itself. That is, the water will rise in the incoming passage  48  between the second inner tube  24   b  and the third inner tube  24   c  until it reaches the opening  42  near the top cover  30  and spill over into the second chamber&#39;s return passage  50  between the outer surface of the cartridge heating element  20  and the third inner tube  24   c  where it will absorb the majority of the heat output of the cartridge heating element  20  as it travels downward towards the hot water outlet  12  in the base cover  32 . An outlet passage  52  is created in the base cover  32  so that the heated water can flow out of the sealed tubular housing  33  and into a three-quarter inch to one inch outlet connection where a hot water temperature probe  54  monitors the temperature of the heated water. This hot water is then delivered to its final use destination. 
         [0034]    In the preferred embodiment, the radial distance between the cartridge heating element  20  and the third inner tube  24   c,  as well as the radial distance between the third  24   c  and second inner tube  24   b,  second  24   b  and first  24   a  inner tubes and first  24   a  inner tube and the outermost tube  22 , was selected to be approximately 20 to 30 thousands of an inch (0.020-0.030) in order to obtain an output flow of approximately 18 ounces per minute for a 140° F. rise in water temperature using a 3000 watt, ¾ inch diameter cartridge heating element  20 . The cold water incoming temperature was measured to be between 55° F. and 60° F. With this arrangement, a ¾ inch diameter 4000 w cartridge heating element  20  produced a hot water flow rate of approximately 24 ounces per minute, again, with 140° F. rise in water temperature. From these results, it appears that the preferred embodiment produces an approximate flow of six ounces of hot water per minute with a 1000 watt cartridge and 140° F. temperature rise and the flow increases in direct relationship to the wattage of the cartridge heating element  20  used. That is, a 2000 watt cartridge will produce 12 ounces per minute at hundred and 140° F. rise in temperature while a 3000 watt heating cartridge will produce hot water flow of 18 ounces per minute 140° F. rise in water temperature. As the radial distance between incoming passages and return passages within each chamber increases, in an attempt to attain higher capacity heaters, the wattage output of the cartridge heating element  20  will need to be calculated in order to obtain a predetermined temperature rise in the hot water as it passes through the tubular housing. Because of its design and the passages of water surrounding the cartridge heating element  20 , the on-demand cartridge heater is very efficient since any heat loss radially is absorbed by the water in the surrounding passages and this captured heat will preheat the incoming cold water, thereby, significantly increasing the efficiency of the cartridge heater housing. A person skilled in the art will quickly recognize that the number of chambers used to surround the hot water cartridge may vary as a function of the application. For example, a larger cartridge heater, i.e. 12,000-15,000 watt having higher heat losses may benefit from four chambers surrounding the heater cartridge to capture heat loss and to use such heat loss to preheat the colder incoming water. 
         [0035]    At the hot water outlet  12  is located a hot water temperature probe  54 , which may incorporate a high temperature cut-off switch for added safety protection. Such safety item is generally required by local building codes. 
         [0036]    As shown in  FIG. 1 , an electronic control unit  56  is mounted between an electrical power source  58  and the cartridge heating element  20 . The electronic control unit  56  supplies power to the heating element  20 . The electronic control unit  56  also communicates with the flow control valve  14  and hot water temperature probe  54  so as to enable programming of the flow of water through the cartridge heating element  20  as well as to probe the hot water temperature outlet of the cartridge heating element  20  to enable continuous operation within the prescribed parameters of the on-demand instantaneous hot water heating system  5 . The electronic control unit  56  is powered through a switch  60  which may be conveniently placed depending upon the application. 
         [0037]    As set forth above, larger capacity cartridge heaters will result in the ability to significantly increase larger hot water delivery rates. It is also within the knowledge of a person skilled in the art, that if greater flow rates are needed a plurality of cartridge heaters with a known capacity may be used in conjunction with a set-up using a manifold to collect the output of the plurality of cartridge heaters to provide a large supply of on-demand instant hot water. 
         [0038]      FIG. 3  illustrates an application of the current invention. The on-demand instantaneous hot water system illustrated in  FIG. 1  is mounted with a housing  62  of a modern coffee maker, having a brewing chamber  64  overhanging a coffee pot  66  sitting on an electric warming device  68 . When a pot of coffee is desired, the appropriate measure of coffee grounds is placed within a filter (not shown) in the brewing chamber  64  and the switch is activated. Hot water is instantaneously delivered to the brewing chamber  64  by the cartridge heater system for the desired number of cups selected by the user. 
         [0039]    From the foregoing, it will be seen that the invention is one well adapted to obtain all of the objects herein set forth, together with other advantages which are obvious and which are inherent to the structure. 
         [0040]    It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and well within the scope of the claims. Although one embodiment has been shown in the drawings, many other embodiments may be made of the invention without departing from the scope thereof. It is to be understood that all matter herein set forth shown in the accompanying drawings is to be interpreted as illustrated and not in a limiting sense.