Abstract:
A relatively small water pump-DC motor combination, powered by batteries, provides sufficient pump power to create the flow between the hot and cold water lines necessary to maintain a substantially immediate hot water response when the hot water tap is opened. The pump is controlled by a thermal sensor signaling the pump to commence operation when the temperature in the hot water line upstream of the hot water tap is less than a predetermined value. Preferably, each of the batteries is rechargeable, most preferably utilizing a wireless system, where the power source is a distance away from the pump battery, to provide additional protection against electrical short circuits in the presence of water. Commonly available batteries of between 10 and 24 Volts can be used.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a battery-powered water pump for providing for the recirculation of hot water so as to provide immediate hot water when a tap is turned on utilizing a minimal sized pump to provide the additional small amount of pressure differential required for this recirculation in a normal single family home with a water heater tank, for example as is typical in the U.S. 
         [0003]    2. Description of the Related Art 
         [0004]    In many of the dry, or drought-plagued parts of North America, and possibly elsewhere, hot water is often continually circulated within the closed water system of a house or business, in order to have hot water substantially immediately available when a faucet is turned on; this avoids, or at least reduces, the wasting of flowing water while waiting for the hot water to reach a tap in a bathroom or kitchen of a home or office center. By circulating the hot water continuously to the most distant hot water tap, it becomes substantially immediately available at various other tap points in a system as needed. 
         [0005]    Some systems, instead of continuously circulating the water in the system, a pump can be made to operate in a continual pulse mode, i.e., on for a period and off for a period, on a continuing basis. For example, a pulse mode can comprise 150 seconds on and 10 minutes off, all day, every day, or only during certain pre-programmed periods. The prior devices all utilized house current to power relatively inefficient pumps, located either at or near the hot water tank, especially for new house construction, or located at the farthest tap site and pumping between the hot and cold water lines at those locations, for aftermarket installation in older buildings. The pump motors were powered by AC current. Examples of prior art systems are shown in  FIGS. 1A and 1B ; in  FIG. 1A , a system in a newly constructed residence is shown where the water pump is located adjacent the water heater and is operated by electronic controls. Such a system has been offered and sold by Taco, Inc., as an ON COMMAND™ SYSTEM for Re-Circulation Piping, which includes specially prepared and installed piping for recirculating the hot water directly back to the water heater, whether the heater includes a hot water tank or is a so-called “tankless water heater”. In all cases, these prior art systems all required a socket for the house AC current to power the pump motor, which in the case of the under sink, post-construction system, required calling in an electrician to install a socket at the undersink location meeting local safety codes. 
         [0006]    In  FIG. 1B  is shown a system that could be installed, under a sink, for example, in an older house without changing the overall house piping, but requiring the installation of a special under sink electric socket, also as exemplified by an ON COMMAND™ system, from Taco, Inc. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention reflects the novel recognition that a relatively small pump-motor combination powered by batteries can provide sufficient pump power to create the flow necessary to maintain a substantially immediate hot water response when the hot water tap is opened, even at the tap farthest from the building hot water heater. Preferably, each of the batteries is rechargeable, most preferably utilizing a wireless system where the power source is a distance away from the battery, e.g., on a wall or in the ceiling of the bathroom or kitchen, to provide additional safety against electrical short circuits in the presence of water. The water pump comprises a water pump mechanism coupled to a DC motor powered by batteries. In the preferred systems, the batteries are in turn coupled to a charger unit, that most preferably receives power wirelessly from a distant, across the room, source. There are also wireless power transmitters being developed for allowing a single power source to wirelessly charge batteries throughout an entire house. Commonly available batteries of between 10 and 24 Volts can be used, and many are rechargeable using common household current. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1A  is a diagram of a prior art 110V AC-powered pump installed in a hot water system of a newly constructed house, with a dedicated hot water return line; 
           [0009]      FIG. 1B  is a diagram showing a possible location of a prior art pump installed in a retrofitted hot water system of a house that does not have a dedicated hot water return line; 
           [0010]      FIG. 1C  is a close-up picture showing the pump of  FIG. 1B  retrofitted between the hot and cold water lines under a sink in a house; 
           [0011]      FIG. 2  is a diagrammatic sketch representing the retrofitted connection of the DC, battery-powered, motor pump of this invention, into the previously constructed plumbing system of a house; 
           [0012]      FIGS. 3A , B are isometric drawings of different views of a preferred battery-powered DC motor pump of the present invention; 
           [0013]      FIG. 4  is an exploded isometric view showing the internal construction of one example of a battery-powered pump of the present invention; 
           [0014]      FIG. 5  is a diagrammatic picture showing a preferred example of a wirelessly rechargable, battery-powered motor pump of the present invention, and a broadcast power transmitter at one preferred location in a bathroom; 
           [0015]      FIG. 6A  is an isometric drawing of an example of a wirelessly rechargable battery-powered DC motor pump of the present invention; 
           [0016]      FIG. 6B  is an exploded isometric view showing the internal construction of an example of a wirelessly rechargable, battery-powered DC motor pump of the present invention, shown in  FIG. 6A ; 
           [0017]      FIG. 7  is a highly diagrammatic sketch showing the AC powered broadcast transmitter, located at a distance from the transmitter, the power receiver and circulator, with charger powered from the broadcast power receiver; and 
           [0018]      FIG. 8  is a highly diagrammatic sketch showing the broadcast power receiver and circulator with charger powered from the broadcast power receiver, together with the battery powering the pump motor and the controller and Drive for operating the pump in accordance with this invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring to  FIGS. 2-4 , there is shown an example of a battery-powered circulator system of the present invention which comprises an electronically controlled water circulator mechanism, generally indicated by the numeral  25  (powered by a battery  30 ),coupled between the hot and cold water tap lines  17  and  19 , respectively, under, e.g., the sink farthest from the water heater  15 . By circulating the hot water to this tap, all intervening taps, including showers, are also made available to substantially instant hot water. 
         [0020]    The circulator system includes an electronic controller unit  7 , provided with a digital readout  8 , which controls the operation of the battery-powered DC motor pump with respect to turning the pump on or off at specified times, i,e., determining when and how often the hot water is to be circulated. In addition, in another embodiment there can also be provided a thermistor, or temperature sensor, that locks out the controller from starting circulation if the temperature in the hot water line is above a preset value, e.g., 100° F., OR stops the pump when the hot water temperature has increased a preset ΔT, e.g., 10° F. after the circulator began operation. This electronic controller/thermistor control system, and the pump motor, shown as stator  3  and rotor  2 , are all powered by the battery unit  1 , which in one of the preferred embodiments ( FIGS. 3A ,B and  4 ) includes a recharging unit powered through a wire directly to a socket in the wall of the house adjacent the tap; and in a second, even more preferred embodiment ( FIGS. 5 and 6A ,B), includes a wireless power receiver for receiving transmitted power from a distant power source, e.g., on a wall across the room from the tap to recharge the battery. 
         [0021]    Most generally, the invention is based upon the novel recognition that a small, low power pump can provide the necessary pressure differential needed to cause circulation of the water from the water heater, into the hot water line, to the cold water line and back to the water heater from the cold water line. Both of the hot and cold water lines, when the taps are all closed, have substantially the same line pressure, so that only a small pressure differential is required from the pump to circulate the water in the hot water line into the cold water line, and thus draw in fresh hot water into the hot water line from the hot water heater. This allows for an efficient low pressure circulator, such as the wet rotor, centrifugal, DC motor-driven pump shown in the drawings, which can draw as little as 1-5 watts of electrical power when it is operating. It was also realized that the pump need only operate during a few minutes of each hour in order to maintain instant hot water, in most modem insulated homes, even in the coldest weather met in the contiguous 48 states of the United States, i.e., temperate North America. 
         [0022]    The energy use of the pump will be over a short period of time. Therefore, although a battery is generally more rapidly discharged than re-charged, the rapid discharge period during pump operation, will continue for only a relatively short period of time, e.g., for about 12 minutes of each hour. The wireless charger power capacity can then be significantly smaller, as it will be able to charge over a longer period of time, than the battery is discharging. This has the benefit of permitting the use of lower cost components, and results in a reduced risk of overcharging the battery. 
         [0023]    As shown, the circulator is located between the most distant location from the hot water heater, in the building, containing both a hot and a cold water tap, e.g., in a single sink. The circulator connects to the hot and cold water lines under the sink, through standard NPT connections, 9 or 10 and 109 or 110 fittings, respectively, depending upon the layout of the original plumbing under the sink. The thermistor measures the temperature of the water on the hot water side of the pump, and sends its signal to the controller. The thermistor sensor can preferably be molded into the wall of the pump casing inlet  105 . 
         [0024]    In one preferred embodiment, as shown in  FIGS. 3A , B and  4 , as well as in  FIGS. 5-6B , the circulator system includes an outer housing or shell, including a pump rotor casing  22 , which includes the pump inlet and outlet  105  and  106 , a wet rotor cartridge assembly  65  formed from permanent magnets  2 , and a stator  3 , formed of wire-wound soft magnetic core material, surrounding the rotor and connected to the DC power supply, e.g., a battery. The stator is held within a motor housing  57 , which is connected to the electronics enclosure  5 , holding the programmable electronic timer and digital readout  7 ,  8 . The motor fits within its housing  4 , part of the overall system housing  1 ; the rotor  2  is mechanically directly connected to a centrifugal impeller  42 , located within the pump casing  22 , which operates to circulate the water between the hot water inlet line  9 ,  10  and the cold water outlet line  109 , 110 . 
         [0025]    The pump motor is capable of drawing electric power in a range up to 12 Watts, but usually as little as 1-5 watts is sufficient, as a pressure head of not more than 5 ft, is sufficient to circulate the water for this purpose, as the differential between pressure heads in the hot and cold water lines are usually on the order of 1-2 ft, or less. Similarly, a maximum flow rate of between 1 and 5 gpm will generally be sufficient for this purpose, so that larger, more powerful pumps are not preferred. For such pumps ⅜ in. or ½ in. npt connections would be sufficient. All connections and materials of construction will have to meet regulatory requirements, such as the NSF/ANSI  372  requirements, or other local jurisdiction requirements. 
         [0026]    As shown, the wired charger of  FIGS. 3A , B and  4  must be connected to a wall socket to reach the house current, in order to recharge the battery. The recharger unit is housed within the upper plastic casing  1 , adjacent the battery unit  6 . For longevity and compact size, a 12 V or 24 V Lithium Ion battery is preferred, although a slightly larger NiCd battery would also be useful. 
         [0027]    In the event a battery requires recharging, it can be removed and charged in an external location from the pump system, and a substitute battery inserted during the charging period. Alternatively, the battery within the circulator system can be electrically connected to a charger which in tutu is electrically connected to a source of electric power such, as a house current socket in the wall of a room. In order for that to be a permanent connection, it is necessary for the socket to be reasonably close to the pump location, which in many jurisdictions requires a special socket construction to avoid a short circuit due to the potential of wet conditions near a water tap, e.g., in a bathroom or kitchen. 
         [0028]    Referring to the wirelessly rechargeable, battery-powered DC motor pump of  FIGS. 5-6B , numeral  51  generally indicates the Wireless Power Transfer Pumping System of the present invention, which includes a broadcast power receiver connected to the battery charger, and  52  designates a wireless power transmitter on the wall or the ceiling of a bathroom or kitchen. 
         [0029]    In the wireless pumping system  51 , the motor housing  57  covers and protects the motor and the battery and charger housing  52  covers the battery  61  which is electrically connected to the motor stator windings  56 , and to the electronic controller  58 , within the electronics housing  59 , which controls the operation of the motor, and thus the circulator pump. The casing  55  covers and protects the centrifugal pump impeller  65 , which is operationally connected to the wet rotor cartridge assembly  54  of the low voltage DC pump motor. The wet rotor  54  in this case is preferably formed of permanent magnets, such as is disclosed in copending, commonly owned U.S. Patent application No. 61/716,060, filed Oct. 19, 2012. A low voltage DC motor stator  56  surrounds the rotor  54  and is electrically connected to the battery  61 . The battery  61  is adjacent to and electrically connected to a recharger, also located within the housing  52 , which in turn is connected to the wireless power receiver  63 . A cover  71  closes off the end of the electronics housing  59 , surrounding the readout  8 , as a protective seal. 
         [0030]    The preferred wirelessly rechargeable version of this invention avoids the problem of constructing special sockets for a wired recharger by placing the power broadcaster away from the water location and broadcasting the power to the broadcast receiver adjacent the charger. Although no commercial such units are presently available, there are many designs that could be used. One such example, which is effective over distances of more than two meters, is described in U.S. Patent Publication 2011/0025131. The theory behind the wireless power transfer was described in a  SCIENCE  article from 2007, Vol. 317, pp 83-86, entitled  Wireless Power Transfer Via Strongly Coupled Magnetic Resonances,  by Andre Kurs et al. Kurs utilizes nonradiative (so-called “near-field”) magnetic resonant induction at megahertz frequencies, to achieve nonradiative wireless power transference. 
         [0031]    In a further advance, the Toyota automobile company has developed a system for recharging electric powered vehicles using power broadcast over a distance of about two meters, or more, as described in U.S. Patent Publication No. 2010/0295506, utilizing nonradiative near-field magnetic resonant induction. One such broadcast system useful for the present invention, in accordance with the Kurs concept, is diagrammatically shown in  FIGS. 7-8 , where the source of power for the nonradiative near-field magnetic resonant induction primary coil  200  is a house AC circuit. The primary coil  200  can be located either at a wall across the room, or above the pump in the ceiling, as long as the sink will not present significant interference to the magnetic resonant field, preventing its contacting the secondary wireless receiver coil  205 , usually located under the sink, adjacent the battery and charger, as in  FIG. 5 . 
         [0032]      FIG. 8 , diagrammatically details the power storage and recharger system, shown within a dashed line and generally designated by the reference numeral  250 , comprising the secondary receiver coil  205  and the intervening recharging system  210 , which comprises a bulk capacitor  210  and a charger  230 . The wireless receiver  205  feeds current to the bulk capacitor which holds the charge until reaching its design discharge voltage level, as controlled by the circuit in the charger  230 , when it begins to discharge at a level suitable to be received by the battery  215 . The controller  212  and the motor pump  51  are all powered from the power storage unit, in this case a rechargeable storage battery  215 . The low power requirement of the pump/motor/drive system  51 , unlike the automobile motors in the Toyota system, can operate directly from the battery voltage without requiring a voltage step-up. The capacitor serves to cache, or pool, the power received from the wireless receiver  205  until it reaches a suitable voltage. 
         [0033]    Alternative power storage units include a super capacitor of large capacitance, but a chemical storage battery, such as a lithium-ion battery, lithium-ion polymer battery, nickel-metal hydride (NiMH) battery, nickel cadmium (NiCd) battery, or even a lead acid battery, is preferred for this type of low power application, among the rechargeable power sources presently commercially available. 
         [0034]    The above examples and descriptions are intended to be exemplary only. It is understood that one of ordinary skill in the art will comprehend the full scope of this invention to be set only by the scope of the claims set forth below.