Abstract:
A transfer switch is provided for transferring the supply of electrical power to a load between a utility source and a generator that generates electrical power when started. The transfer switch includes a transfer relay that selectively connects the load to one of the utility source and the generator in response to the application of electrical power on the coil of the transfer relay by the generator. A generator relay having a coil operatively connected to the utility source is also provided. The generator relay provides a signal to the generator to start in response to the absence of electrical power on the coil of the generator relay by the utility source.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to stand-by electrical generators, and in particular, to a transfer mechanism for transferring the supply of electrical power to essential devices in a residential home between a utility source and a stand-by electrical generator.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     As is known, virtually all residential homes utilize electrical power received from a utility company. Typically, utility companies have an excellent record of providing uninterrupted or infrequently interrupted power to their customers at proper voltage levels and line frequency. However, due to the increasing demand for power, power outages have become more frequent. While power outages usually last only for a short duration, an extended power outage may cause more than simple aggravation for customers of the utility. A power outage may render a homeowner&#39;s appliances, such as the sump pump, refrigerator or freezer inoperable. If a power outage occurs during a rainstorm, the failure of the sump pump to operate may result in the flooding of the homeowner&#39;s basement.  
         [0003]     In order to combat these occasional disruptions in service, many residential customers of the utility companies have equipped their homes with stand-by electrical generator systems. These stand-by electrical generator systems include internal combustion engines that drive electrical generators. If the commercial power from the utility company fails, the internal combustion engine of the stand-by electrical generator system is automatically started causing the electrical generator to generate electrical power. When the electrical power generated by the electrical generator reaches the proper voltage and frequency desired by the customer, a transfer mechanism transfers the load imposed by the homeowner from the commercial power lines to the electrical generator.  
         [0004]     Typically, the transfer mechanism incorporates switches that isolate the electrical power supplied by the utility company from the generator. In a residential application, the switches are flipped either manually or automatically between the utility source and the generator in order to provide power to the electrical system of the home. These prior art transfer mechanisms often require a homeowner to transfer the entire electrical system of the home onto the generator. Such an arrangement does not provide the homeowner with the ability to decide which circuits of the home&#39;s electrical system are to be powered. It can be appreciated that the demands of the entire electrical system of the home can be quite significant. As a result, the generator must be of sufficient size to power the entire electrical system of the home. This, in turn, increases the overall cost of the stand-by electrical generator system for the homeowner. Further, prior stand-by electrical generator systems require that the transfer mechanism to be interconnected to the utility source, the generator and the electrical system of the home. This usually requires the homeowner to employ an electrical contractor to make the necessary connections. Once again, the hiring of an electrical contractor increases the overall cost to the homeowner for a stand-by electrical generator system.  
         [0005]     Therefore, it is a primary object and feature of the present invention to provide a transfer mechanism that transfers the electrical power supplied to essential devices within a residential home between a utility source and stand-by electrical generator.  
         [0006]     It is a further object and feature of the present invention to provide a transfer mechanism that automatically transfers the electrical power supplied to essential devices within a residential home from a utility source to a stand-by electrical generator in response to a power outage.  
         [0007]     It is a still further object and feature of the present invention to provide a transfer mechanism for transferring the electrical power supplied to essential devices within a residential home between a utility source and a stand-by electrical generator that may be simply and easily installed by a homeowner.  
         [0008]     In accordance with the present invention, a transfer switch is provided for transferring the supply of electrical power to a load between a utility source and a generator that generates electrical power when started. The transfer switch includes a transfer relay having a utility input, generator input, an output and a coil operatively connected to the generator. The output of the transfer relay is selectively connected to one of the utility input and the generator input in response to the application of electrical power to the coil by the generator. A power cord interconnects the utility input of the transfer relay to the utility source. The power cord has a first end terminating in an electrical plug receivable within an electrical outlet electrically connected to the utility source and a second end electrically connected to the utility input of the transfer relay. A generator cord electrically connects the generator to the generator input of the relay. A first duplex outlet is electrically connected to the output of the relay. The outlet is adapted for receiving an electrical plug for the load therein.  
         [0009]     The transfer switch may also include a second duplex outlet electrically connected to the generator. The second duplex outlet is adapted for receiving the electrical plug for the load therein. A manual exercise switch connectable to the generator may also be provided. The manual exercise switch is movable between a first non-actuated position and a second actuated position for starting the generator. A generator control structure is operatively connected to the utility source and to the generator. The generator control structure includes a generator relay having a first contact connected to the generator, a second contact connected to the generator and a coil connected to the utility source. The generator relay is movable between an open arrangement wherein the first and second contacts are isolated from each other and a closed arrangement wherein the first and second contacts are electrically coupled in response to the absence of electrical power on the coil by the utility source. The generator control structure may also include a starting relay having a first contact connected to the generator, a second contact connected to the coil of the transfer relay and a coil connected to the utility source. The starting relay is movable between an open arrangement wherein the first and second contacts are isolated from each other and a closed arrangement wherein the first and second contacts are electrically coupled in response to the absence of electrical power on the coil by the utility source.  
         [0010]     The transfer switch may also include a utility display device connectable to the utility source. The utility display device generates a visual display in response to the application of electrical power by the utility source. Similarly, a generator display device is connected to the generator source. The generator display device generates a visual display in response to the application of electrical power by the generator.  
         [0011]     In accordance with the present invention, a transfer switch is provided for transferring electrical power to a load between a utility source and a generator that generates electrical power when started. The transfer switch includes the transfer relay having a utility input, generator input, an output, and a coil operatively connected to the generator. The output is selectively connected to one of the utility input and the generator input in response to the application of electrical power on the coil by the generator. The transfer switch also includes a generator relay having a first contact connected to the generator, a second contact connected to the generator and a coil connected to the utility source. The generator relay is movable between an open arrangement wherein the first and second contacts are isolated from each other and a closed arrangement wherein the first and second contacts are electrically coupled in response to the absence of electrical power on the coil by the utility source. A first duplex outlet is electrically connected to the output of the transfer relay. The first duplex outlet is adapted for receiving an electrical plug for the load therein.  
         [0012]     A power cord interconnects the utility input of the transfer relay to the utility source. The power cord has a first end terminating at an electrical plug that is receivable within an electrical outlet electrically connected to the utility source and a second end electrically connected to the utility input of the transfer relay. A second duplex outlet is electrically connected to the generator. The second duplex outlet is adapted for receiving the electrical plug for the load therein. A manual exercise switch is also connectable to the generator. The manual exercise switch is movable between a first non-actuated position and a second actuated position for starting the generator.  
         [0013]     The transfer switch may also include a starting relay having a first contact connected to the generator, a second contact connected to the coil of the transfer relay and a coil connected to the utility source. The starting relay is movable between an open arrangement wherein the first and second contacts are isolated from each other and a closed arrangement wherein the first and second contacts are electrically coupled in response to the absence of electrical power on the coil of the starting realy by the utility source. A utility display device is also connected to the utility source. The utility display device generates a visual signal in response to the application of electrical power by the utility source. In addition, a generator display device is connected to the generator source. The generator display device generates a visual display in response to the application of electrical power by the generator.  
         [0014]     In accordance with a still further aspect of the present invention, a transfer switch is provided for transferring the supply of electrical power to a load between a utility source and a generator that generates electrical power when started. The transfer switch includes a transfer relay having a utility input, a generator input, an output, and a coil operatively connected to the generator. The output of the transfer relay is selectively connected to one of the utility input and the generator input in response to the application of electrical power upon the generator. A power cord has a first end terminating at an electrical plug that is receivable within the electrical outlet electrically connected to the utility source and a second end electrically connected to the utility input of the transfer relay. A first duplex outlet is electrically connected to the output of the transfer relay. The first duplex outlet is adapted for receiving an electrical plug for the load therein. The second duplex outlet is electrically connected to the generator. The second duplex outlet is also adapted for receiving the electrical plug for the load therein.  
         [0015]     The transfer switch may also include a generator relay having a first contact connected to the generator, a second contact connected to the generator and a coil connected to the utility source. The generator relay is movable between an open arrangement wherein the first and second contacts are isolated from each other and a closed arrangement wherein the first and second contacts are electrically coupled in response to the absence of electrical power on the coil by the utility source. A manual exercise switch is connected to the generator. The manual exercise switch is movable between the first non-actuated position and a second actuated position for starting the generator. The transfer switch also includes a starting relay having a first contact connected to the generator, a second contact connected to the coil of the transfer relay and a coil connected to the utility source. The starting relay is movable between an open arrangement wherein the first and second contacts are isolated from each other and a closed arrangement wherein the first and second contacts are electrically coupled in response to the absence of electrical power on the coil by the utility source. A utility display device is connectable to the utility source. The utility display device generates a visual display in response to the application of electrical power by the utility source. A generator display device is connectable to the generator. The generator display device generates visual display in response to application of electrical power by the generator.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The drawings furnished herewith illustrate a preferred construction of the present invention in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description of the illustrated embodiment.  
         [0017]     In the drawings:  
         [0018]      FIG. 1  is a top plan view of a transfer mechanism in accordance with the present invention;  
         [0019]      FIG. 2  is an exploded view of a transfer mechanism in accordance with the present invention; and  
         [0020]      FIG. 3  is a schematic diagram of the transfer mechanism of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring to  FIGS. 1 and 2 , a transfer mechanism in accordance with the present invention is generally designated by the reference numeral  10 . It is contemplated that transfer mechanism  10  include housing  12  defined by base  14  and cover  16 . It is intended that housing  12  house the component parts of transfer mechanism  10 , as hereinafter described.  
         [0022]     Referring to  FIGS. 2 and 3 , transfer mechanism  10  includes generator cord  17  and power cord  18  comprising ground line  20 , neutral line  22  and hot line  24 . Plug  26  is electrically coupled to a first end of power cord  18  such that ground terminal  28  of plug  26  is connected to ground wire  20  of power cord  18 ; neutral terminal  30  of plug  26  is connected to neutral line  22  of power cord  18 ; and hot terminal  32  of plug  26  is connected to hot line  24  of power cord  20 . Ground terminal  28 , neutral terminal  30  and hot terminal  32  of plug  26  are configured for receipt in a standard three-prong wall outlet (not shown) in the United States. As is conventional, the wall outlet is connected to a source of electrical power as provided by a utility.  
         [0023]     Neutral line  22  of power cord  18  is connected to neutral terminal  34  of single pole, double throw, transfer relay  36 . Transfer relay  36  includes a normally closed terminal that defines utility input terminal  38 , a normally open terminal that defines generator input terminal  40 ; and a common terminal that defines output terminal  48 . Utility input terminal  38  is electrically connected to hot line  24  of power cord  18 ; generator input terminal  40  is electrically connected to electrical generator  41  through circuit breaker CB 2  and line  46 ; and output terminal  48  is interconnected to hot terminal  50  of first duplex outlet  52  by line  54 . By way of example, first duplex outlet  52  may take the form of a ground fault circuit interrupter outlet, but other outlets may be used without deviating from the scope of the present invention.  
         [0024]     Transfer relay  36  also includes magnetic coil  56  having input  58  connected to double pole, double throw relay  60  by line  64 , as hereinafter described, and an output electrically connected to neutral terminal  34 . As is conventional, output terminal  48  is normally connected to utility input terminal  38  by a movable contact. As the current flows through magnetic coil  56  of transfer relay  36 , magnetic coil  56  becomes energized so as to attract and move the movable contact. As a result, the movable contact within transfer relay  36  disengages from utility input terminal  38  and becomes electrically coupled to generator input terminal  40  so as to operatively connect generator input terminal  40  to output terminal  48 . If flow of current through magnetic coil  56  is stopped, the movable contact within transfer relay  36  returns to its original position such that utility input terminal  38  is electrically coupled to output terminal  48  of transfer relay  36 .  
         [0025]     Double pole, double throw relay  60  includes first and second relays  60   a  and  60   b,  respectively, and a magnetic coil  78 . First relay  60   a  includes first normally closed terminal  62  connected to input  58  of magnetic coil  56  of transfer relay  36  by line  64 ; first normally open terminal  63 ; and first common terminal  66  connected to generator input terminal  40  of transfer relay  36  by line  68 . Second relay  60   b  of double pole, double throw relay  60  includes second normally closed terminal  70  that communicates with the electrical generator on line  72 ; second common terminal  74  that communicates with the electrical generator on line  76 ; and second normally open terminal  77 . Line  72  and line  76  are interconnected by manual exercise switch SW, for reasons hereinafter described.  
         [0026]     Magnetic coil  78  of a double pole, double throw relay  60  has an input  80  connected to utility input terminal  38  of transfer relay  36  by line  82  and an output  84  connectable with the negative terminal of utility running light L 1  and with the negative terminal of generator running light L 2  through line  86 . The positive terminal of utility running light L 1  is connected to input  80  of magnetic coil  78  of double pole, double throw relay  60  by line  92 . The positive terminal of generator running light L 2  is connected to line  46  at node  89  by line  90 .  
         [0027]     As is conventional, operation of first and second relays  60   a  and  60   b,  respectively, of double pole, double throw relay  60  is controlled by magnetic coil  78 . When current does not flow through magnetic coil  78  of double pole, double throw relay  60 , first and second relays  60   a  and  60   b,  respectively, are normally closed such that first and second common terminals  66  and  74 , respectively, are electrically connected to corresponding first and second normally closed terminals  62  and  70 , respectively, by corresponding movable contacts. When current flows through magnetic coil  78 , first and second relays  60   a  and  60   b,  respectively, become open such that the movable contacts of relays  60   a  and  60   b,  respectively, of double pole, double throw relay  60  disengage first and second normally closed terminals  62  and  70 , respectively, from corresponding first and second common terminals  66  and  74 , respectively, and electrically couple first and second common terminals  66  and  74 , respectively, to corresponding first and second normally open terminals  63  and  77 , respectively. When the flow of current through magnetic coil  78  of double pole, double throw relay  60  is stopped, the movable contacts return to their original position thereby electrically coupling first and second normally closed terminals  62  and  70 , respectively, with corresponding first and second common terminals  66  and  74 , respectively.  
         [0028]     First and second duplex outlets  52  and  98 , respectively, of transfer mechanism  10  include corresponding hot terminals  50  and  97 , respectively, neutral terminals  102  and  104 , respectively, and ground terminals  94  and  96 , respectively, for supplying electrical power thereto. As heretofore described, hot terminal  50  of first duplex outlet  52  is interconnected to output terminal  48  of transfer relay  36 . Hot terminal  97  of second duplex outlet  98  is connected to electrical generator  41  through circuit breaker CB 3  and line  105 .  
         [0029]     Ground terminals  94  and  96  of first and second duplex outlets  52  and  98 , respectively, are interconnected to ground line  20  of power cord  18 . Ground line  20  of power cord  18  is also connected to line  76  at node  100 . Neutral terminals  102  and  104  of first and second duplex outlets  52  and  98 , respectively, are interconnected to neutral line  110  which, in turn, has a first end connected to neutral terminal  34  of transfer relay  36  and a second end connected to negative terminal of generator running light L 2  at node  112 .  
         [0030]     Referring to  FIG. 2 , in order to assembly transfer mechanism  10 , first and second duplex outlets  52  and  98 , respectively, are positioned on base  14  of housing  12  and interconnected thereto by screw and washer combination  114  and  116 , respectively, that extend through a corresponding ear in first and second duplex outlets  52  and  58 , respectively, and into a threaded passageway in base  14 . Screw  118  extends through base  14  and transfer relay  36 . Nut and washer  120  and  122 , respectively, are threaded onto screw  118  to mount to transfer relay  36  on base  14 . Similarly, screw  124  extends through base  14  and through double pole, double throw relay  60 . Nut and washer  126  and  128 , respectively, are threaded onto screw  124  to interconnect double pole, double throw relay  60  to base  14 . Finally, screw  129  extends through base  14  and mounting block  130 . Mounting block  130  is provided to facilitate the connection of generator cord  17  and the electrical components of transfer mechanism  10 , as heretofore described. It can be appreciated that generator cord  17  includes lines,  46 ,  72 ,  76 ,  105  and  110 , as described. Nut and washer  132  and  134 , respectively, may be threaded on screw  129  in order to mount mounting bracket  130  on base  14 . It is contemplated to utilize multiple screws, nuts and washers to connect each of the components to base  14  without deviating from the scope of the present invention.  
         [0031]     Cover  16  of housing  12  includes openings  136  and  138  for receiving circuit breakers CB 2  and CB 3 , respectively, therein to provide a homeowner access thereto. In addition, cover  16  of housing  12  includes openings  139  and  140  for receiving utility running light L 1  and generator running L 2  in order to provide a user visual access thereto. Opening  142  in cover  16  receives manual exercise switch SW therein, and first and second duplex outlet openings  144  and  146 , respectively, in cover  16  provide user access to first and second duplex outlets  52  and  98 , respectively. Cover  16  may be positioned on base  14  and screw  148  may be threaded therebetween to interconnect cover  16  and base  14 , and to maintain the configuration of housing  12 . Generator cord  17  extends through recess  150  in cover  16  and is maintained therein by end panel  152 . It is understood that housing  12  provides an electrically isolated enclosure for all of the components of transfer mechanism  10  heretofore described.  
         [0032]     In operation, electrical generator  41  is initially maintained in a stand-by mode and is not running. Terminals  28 ,  30  and  32  of electrical plug  26  are inserted into a standard three-prong outlet such that electrical power from the utility source travels on power cord  18  to transfer mechanism  10 . It can be appreciated with the electrical generator in its stand-by mode, no electrical power is generated thereby. When electrical power is provided by the utility source, transfer relay  36  will be in its normally closed position such that electrical power supplied by utility source will flow through transfer relay  36  from utility input terminal  38  to output terminal  48  which, in turn, provides electrical power to hot terminal  50  of first duplex outlet  52 . In addition, magnetic coil  78  of double pole, double throw relay  60  becomes energized thereby opening the movable contacts of first and second relays  60   a  and  60   b,  respectively, of double pole, double through relay  60  such that first common terminal  66  of relay  60   a  is electrically coupled to first normally open terminal  63  and such that second common terminal  74  is electrically coupled to second normally open terminal  77 . With relay  60   b  open, the generator remains in its stand-by mode. In addition, the electrical power supplied by the utility source illuminates the utility running light L 1 .  
         [0033]     In the event of a power outage from the utility source, utility running light L 1  goes dark and magnetic coil  78  of double pole, double throw relay  60  is de-energized. With magnetic coil  78  of double pole, double throw relay  60  de-energized, relays  60   a  and  60   b  close such that lines  72  and  76  communicate with each other through relay  60   b  of double pole, double throw relay  60  thereby sending a signal to electrical generator  41  instructing electrical generator  41  to start. As electrical generator  41 , begins generating electrical power, such electrical power flows through relay  60   a  of double pole, double throw relay  60  and energizes magnetic coil  56  of transfer relay  36 . With magnetic coil  56  of transfer relay  36  energized, output terminal  48  of transfer relay  36  becomes disengaged from utility input terminal  38  and electrically coupled to generator input terminal  40  so as to operatively connect hot terminal  50  of first duplex outlet  52  to electrical generator  41 . In addition, electrical generator  41  provides electrical power to hot terminal  97  of second duplex outlet  98 . It can be appreciated that first duplex outlet  52  may be used to provide electrical power to essential devices within a residential home, such as a sump pump or a freezer, since transfer mechanism  10  of the present invention seamlessly transfers the supply of electrical power from the utility source to electrical generator  41  in the event of a power outage. During a power outage, second duplex outlet  98  may be used to power other appliances as a homeowner seems fit in order to improve the standard of living during a power outage. Generator running light L 2  is illuminated whenever electrical generator  41  is running to provide a homeowner with a visual indication that a power outage has occurred and that electrical generator  41  is operational.  
         [0034]     When the power outage ends and the supply of electrical power from the utility returns, magnetic coil  78  of double pole, double throw relay  60  is energized so as to open first and second normally closed relays  60   a  and  60   b,  respectively. With relays  60   a  and  60   b  of double pole, double throw relay  60  open, lines  72  and  76  are no longer in communication thereby advising electrical generator  41  to shut down. In addition, with relay  60   a  of double pole, double throw relay  60  open, magnetic coil  56  of transfer relay  36  is de-energized such that output terminal  48  of transfer relay  36  disengages from generator input terminal  40  and is, once again, electrically coupled to utility input terminal  38  thereby connecting hot terminal  50  of first duplex outlet  52  to the utility source. In addition, utility running light L 1  is illuminated. With electrical generator  41  stopped, electrical power is no longer supplied to second outlet  98  or to generator running light L 2 . As a result, second duplex outlet  98  can no longer be used to power appliances in the home and generator running light L 2  is no longer illuminated.  
         [0035]     In order to insure proper operation of electrical generator  41 , it is contemplated to start the engine of the electrical generator  41  at predetermined time intervals between power outages. By closing the manual exercise switch SW, a homeowner may simulate the appearance a power outage by the utility to electrical generator  41 . As a result, the engine, and hence electrical generator  41 , will start upon closure of manual exercise switch SW and run for a predetermined period of time. Thereafter, electrical generator  41  will shut down. When electrical generator  41  is exercising, as heretofore described, both the utility running light L 1  and the generator running light L 2  will be illuminated. In addition, while the first duplex outlets will be supplied with electrical power from the utility source, the second duplex outlets  98  will be supplied with electrical power from electrical generator  41 .  
         [0036]     Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing and distinctly claiming the subject matter that is regarded as the invention.