Abstract:
A motor is disclosed that operates on either AC outlet power or DC battery power with decreased power drop when switching between AC and DC power. The AC power to the motor may be stepped down by using a clipper circuit, while the DC power supplied to the motor may be increased by switching motor field windings from a series wound circuit to a parallel wound circuit. The motor may be used in a vacuum motor embodiment, or in other consumer devices that utilize electric motors.

Description:
FIELD OF THE DISCLOSURE  
       [0001]     The present invention relates generally to electrical motors that may be used in consumer rechargeable products, and more particularly to a motor that accommodates both alternating current and direct current power sources.  
       BACKGROUND OF THE DISCLOSURE  
       [0002]     Existing rechargeable devices, such as vacuum cleaners, may use a direct current (DC) motor that is powered by a rechargeable battery, where the battery is charged by an auxiliary circuit connected to an alternating current (AC) power supply, such as a standard wall outlet. When the device is plugged into the AC power supply, the AC supply is effectively converted to DC and used to charge the battery while providing power to the DC motor. When the AC power supply is removed, the battery may continue to provide DC power to the motor. When AC power is used, the AC is converted into DC and stepped down to match the battery power level. DC motors using battery supplied power may be relatively weak compared to AC power motors using the same outlet source.  
         [0003]     In other consumer devices, a universal motor may be used to power the device. Universal motors accept both AC and DC power without the need for an AC-DC conversion circuit. These universal motors are usually series wound circuits in which the motor field coils are connected in series. The problem with universal motors is that often, the voltage from an AC source is higher than the voltage from a DC battery, and thus a huge power discrepancy exists in switching between an AC outlet source and DC battery power supply. This difference in power is very noticeable and further highlights the poor performance of a universal motor using battery-only power.  
         [0004]     Therefore, there is a need to provide a circuit for a rechargeable motor that will enable the motor to run on both an AC outlet source and DC battery, preferably with less discrepancy in power when switching between AC and DC power.  
       SUMMARY OF THE INVENTION  
       [0005]     The claimed method and system provide an electric motor that runs on AC and DC power with a reduced motor power difference when switching between an AC power source and a DC power source. The AC voltage to the motor may be stepped down by using a clipper circuit, while the DC power supplied to the motor may be increased by switching motor field windings from a series wound circuit to a parallel wound circuit.  
         [0006]     While the specific method and system will be described to apply to a vacuum motor embodiment, it is emphasized that this system may be applied to other consumer devices that utilize electric motors.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  illustrates a perspective view of the front of an electric motor embodiment of the claimed invention;  
         [0008]      FIG. 2  is a top sectional view of the electric motor of  FIG. 1 ;  
         [0009]      FIG. 3  illustrates a side perspective view of the rotor, winding board, and lower housing of electric motor of  FIG. 1 ;  
         [0010]      FIG. 4  illustrates a top view of the electric motor of  FIG. 1 ;  
         [0011]      FIG. 5  is an electro-mechanical diagram of a series wound AC motor circuit used in an embodiment of the claims;  
         [0012]      FIG. 6  is an electro-mechanical diagram of a parallel wound DC motor circuit used in an embodiment of the claims;  
         [0013]      FIG. 7  illustrates a switching apparatus that may be used in an embodiment of the claims;  
         [0014]      FIG. 8  illustrates an electrical diagram of a clipper circuit that may be used in an embodiment of the claims;  
         [0015]      FIG. 9  illustrates a general electrical connection diagram of a clipper circuit, a battery, a switch and a motor in an embodiment of the claims; and  
         [0016]      FIG. 10  illustrates a vacuum cleaner which may include a motor in accordance with the claimed invention.  
     
    
     DETAILED DESCRIPTION  
       [0017]     Although the following text sets forth a detailed description of the claimed invention it is to be construed as exemplary only and does not describe every possible embodiment. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims.  
         [0018]     It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only, so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. § 112, sixth paragraph.  
         [0019]     Referring now to the drawings, and particularly to  FIG. 1 , an example of an electric motor  10  is disclosed. The motor  10  includes a stator  12 , a lower housing  16  (shown on the top in  FIG. 1 ), and an upper housing  24 . Supported by the stator  12  is a set of coils, including a first coil  20  forming a first pole and a second coil  22  forming a second pole. Fastened to the stator  12  is the upper housing  24 . An armature, indicated generally at  26 , mounted on a motor shaft  17  with a commutator  28  is rotatably mounted by a lower bearing  27  within the lower housing  16  and an upper bearing  29  within the upper housing  24 , and is rotatable about shaft  17 , as is known in the art. While the described embodiment illustrates only two coils, it should be noted that any number of coils could be included in the stator and similar parallel connections can be made between each field coil.  
         [0020]     The stator  12  can comprise a series of laminations  30 , each of which is an annular plate with a large interior opening. The laminations  30  can be made from cold rolled steel, for example SAE  1010  or  1008 , and can be welded together via plasma welding, as is known in the art. By stacking several laminations  30 , a tubular shape with an exterior annular surface  32  and an interior annular surface  34  (See  FIG. 2 ) is created.  
         [0021]     As illustrated in  FIG. 2 , the interior annular surface  34  also includes a first hook-like protrusion  35  and a second hook-like protrusion  37 , each of which project inwardly towards the center of shaft  17  supporting armature windings  19 . The first protrusion  35  is used to support the first coil  20 , while the second protrusion  37  is used to support the second coil  22 , as is commonly known. Each of the first protrusion  35  and the second protrusion  37  include pole tips  39  that define kidneys  41 .  
       Lower Housing  
       [0022]     The lower housing  16 , best seen in  FIGS. 1 and 3 , may be coupled to the upper housing  24  using a bracket  19  (partially shown in  FIG. 3 ), and includes structure to receive current from the coils  20 ,  22  and carry it to and from the armature  26 .  
         [0023]     The lower housing  16  may be made of a non-conductive material, for example a thermoplastic such as a glass-filled polyester. The lower housing includes a first brush housing  64  and a second brush housing  66 . Disposed within each brush housing  64 ,  66  is an electrically conductive brush  65 ,  67 , which is urged, usually by a spring-loaded member  69 , radially inward toward shaft  17  and the armature  26 . As is known in the art, the brushes  65 ,  67  transmit current to the rotating armature  26  through the commutator  28 .  
       Physical Wiring  
       [0024]     Referring now to  FIGS. 1-4 , the wiring of the motor  10  will be described. In general, the wiring of motor  10  may consist of a first magnet wire and a second magnet wire. The first magnet wire may be illustrated ( FIG. 4 ) as having a first start end  70  connected to a terminal connector  71 , a first field coil portion  72 , and a first finish end  73  connected to a connector  74 . The second magnet wire may be illustrated as having a second start end  75  connected to a terminal connector  76 , a second field coil portion  78 , and a second finish end  79  connected to a connector  80 .  
         [0025]     The first magnet wire is wrapped many times around the first hook-like protrusion  35  of the stator  12 , as shown in  FIG. 2 , to form the first coil  20 . The length of the first magnet wire disposed within the first coil  20  is known as the first coil portion  72 . The connector  71  may connect the first start portion with a terminal wire T 3  and a terminal wire T 5  and the connector  74  may connect the first finish portion to a terminal wire T 8 .  
         [0026]     A first brush wire  81  has a first end disposed on a connector  82  and a second end disposed on the first brush housing  64 . The first brush wire  81  is electrically connected to the first brush  65  slidingly disposed within the first brush housing  64  (See  FIG. 3 ), as is known in the art. The connector  82  may connect the first brush wire  81  to a terminal wire T 7 .  
         [0027]     As shown in  FIG. 3 , the first brush  65  is urged forward to the motor shaft  17  and into physical and electrical contact with the commutator  28  and the armature  26 . The armature  26  spins around the axis of shaft  17  while in contact with the first brush  65 .  
         [0028]     A second brush  67  is disposed within the second brush housing  66  opposite the first brush housing  64 . The second brush  67  is also urged forward into contact with the armature  26 . A second brush wire  77  connects the second brush housing  66  to the connector  76 , such that the second brush wire and second start wire are electrically contacted. The connector  76  may connect the second brush wire  77  and second start wire to a terminal wire T 12 .  
         [0029]     The second magnet wire may also be a single wire having a second finish end  79 , a second coil portion  78 , and a second start end  75 . The second magnet wire is wrapped many times around the second hook like projection  37  of the stator  12 , as shown in  FIG. 2 , to form the second coil  22 . The length of the first magnet wire disposed within the second coil  22  is known as the second coil portion  78 . The second magnet wire then exits the second coil  22  and is connected to the connector  80 . The connector  80  may be connected to a terminal wire T 6 .  
       Series and Parallel Field Coil Circuits  
       [0030]      FIG. 5  illustrates an electrical diagram of an AC series wound field coil circuit, while  FIG. 6  illustrates an electrical diagram of a DC parallel wound field coil circuit. Generally, an AC power source may be connected through a switch consisting of a first terminal T 8  and a second terminal T 6 . In the series field coil circuit, the first terminal T 8  may be connected to the finish end  73  of the first field coil  72 . The start end  70  of the first field coil  72  may be connected to a first brush  65 . The first brush  65  may electrically contact a rotor, or armature  26 , which may also electrically contact the second brush  67 . The second brush  67  may be connected to the start end  75  of the second field coil  78 . The finish end of the second field coil  79  may be connected to the second terminal T 6 , thereby forming a series field coil circuit.  
         [0031]     Generally, a DC power source may be connected through a switch consisting of a terminal T 5 , a terminal T 6 , and a terminal T 7 . In the parallel field coil circuit, the first terminal T 7  may be connected to the first brush  65 . The first brush  65  may electrically contact the rotor  26 , which may also electrically contact the second brush  67 . The second brush  67  may be connected to the finish end  73  of the first field coil  72 . The start end  70  of the first field coil  72  may be connected to the second terminal T 5 ,T 6  of the switch. The second brush  67  may also be connected to a start end  75  of a second field coil  78 . A finish end  79  of the second field coil  78  may be connected to the second terminal T 5 ,T 6  of the switch, thereby forming a parallel field coil circuit.  
       Current Flow and Use of Motor  
       [0032]     With reference to  FIGS. 1-4 , the current flow will now be described for an AC series field coil circuit. Current may be supplied to the motor  10  by a two terminal power source (not shown). Current flows from a first power source terminal through the first finish wire  73  and into the first coil portion  72  and through the first coil  20 . Current then travels out of the first coil  20  and through the connector to the first brush wire  81  and into the first brush  65 .  
         [0033]     The first brush  65  is electrically conductive and is urged into contact with the commutator  28  on the armature  26 , thereby supplying current to the armature  26 . The energized armature  26  is also in contact with the second brush  67  inside the second brush housing  66 . Current flows through the second brush  67  and into the second brush wire  77  that is connected to the second start wire  75 . Current then flows from the second start wire  75  into the second coil wire, thereby energizing the second coil  22 . Finally, current flows through the second finish wire  79  out to a second power source terminal. As is known in the art, a current flowing through the first coil  20  and the second coil  22  generates a magnetic field. The armature  26 , with current flowing through it, is induced to rotate about the shaft  17 .  
         [0034]     The current flow for a parallel DC field coil circuit will now be described. Current may be supplied to the motor  10  by a two terminal DC power source (not shown). Current flows from a first power terminal through the first brush wire  81  to the first brush  65 . The first brush  65  is electrically conductive and is urged into contact with the commutator  28  on the armature  26 , thereby supplying current to the armature  26 . The energized armature  26  is also in contact with the second brush  67  inside the second brush housing  66 . Current flows through the second brush  67  and into the second brush wire  77 . Current then flows from the second brush wire through the first finish wire  73 , through first coil portion  72 , and through the first coil  20 . Current then flows out of the first coil  20  through the first start wire  70  and to a second terminal of the power source.  
         [0035]     In this parallel circuit, the first finish wire  73  is also connected to the second start wire  75  and the second finish wire  79  is connected to the first start wire  70 , thereby forming a parallel coil combination. Thus, current also flows from the second brush  67  to second start wire  75  into the second coil portion  78 , thereby energizing the second coil  22 . Current then flows through the second finish wire  79  to the power source. As in the series circuit, the first brush  65  supplies current to the armature  26  and the energized armature  26  is also in contact with the second brush  67  inside the second brush housing  66 . Current flows through the second brush  67  and into the second brush wire  94  and into the parallel coils. As is known in the art, a current flowing through the first coil  20  and the second coil  22  generates a magnetic field. The armature  26 , with current flowing through it, is induced to rotate about the shaft  17 . Further, the physical arrangement of the coils and the polarity of the DC power supply may determine the direction of rotation, as known in the art, and thus in an embodiment of the claims, the arrangement of the coils or the polarity of the DC supply may be adapted so that the direction of rotation of the armature is the same for both AC and DC power.  
         [0036]      FIG. 7  illustrates a switch that may be used to connect between the AC and DC power sources, on the one hand, and the series field coil circuit and the parallel field coil circuit, described above, on the other. The switch may be a four pole, double throw switch that is commercially available. However, other types of switches having different configurations may also be used, as known to those skilled in the art. The 4-pole, double throw switch may consist of 12 terminals T 1 -T 12 , that may be divided into three rows. In a first position, the switch may connect T 1  with T 5 , T 2  with T 6 , T 3  with T 7 , and T 4  with T 8 . In a second position, the switch may connect T 5  with T 9 , T 6  with T 0 , T 7  with T 11 , and T 8  with T 12 .  
         [0037]     In one embodiment of the claims, a DC powered parallel circuit may be switched to an AC powered series circuit using the switch of  FIG. 7 . In this embodiment, the terminal wires of  FIG. 5 , T 3 , T 5 , T 6 , T 7 , T 8 , and T 12  are connected to respectively marked terminals of  FIG. 8 . Further, a first and second terminal of an AC power source may be connected to T 2  and T 4  of  FIG. 7 , and a first and second terminal of a DC power source may be connected to T 9  and T 11 . In this embodiment, T 9  is also connected to T 10 . When the switch is in the first position, the AC series circuit described above is connected. When the switch is in the second position, the DC parallel circuit described above is connected.  
       Clipper Circuit  
       [0038]      FIG. 8  illustrates a clipper circuit that may be used to reduce the voltage of an AC power source. The clipper circuit may consist of a DIAC Q 1  and a TRIAC Q 2 , (sometimes called an alternistor or a thyristor). This circuit may be designed to cutoff the peak voltage of an alternating signal, thus being called a clipper circuit. Generally, a TRIAC Q 2  does not effectively conduct current between its main terminals P 1 , P 2  unless a gate voltage is applied at its gate G terminal. Thus, an AC signal across the TRIAC Q 2  will maintain its voltage unless a gate signal is applied, thereby shorting any signal across its main terminals P 1 ,P 2  and clipping the signal voltage. The DIAC Q 1  blocks applied voltages in either direction until a breakover voltage is applied. Thus, the level of clipping is directly related to the breakover voltage of the DIAC Q 1 . Resistor R 3  and C 2  form a snubber circuit which is used to reduce the rate of change of voltage across the TRIAC. Variable resistor R 2  and capacitor C 1  are used to control the rate of change of voltage across the DIAC, thus providing control over the timing of the clipping mechanism.  
         [0039]     The circuit of  FIG. 8  may be connected across an AC power source that may be applied to the field coil circuits described above. In another embodiment, the clipper circuit may be further used to charge a battery used to supply DC power to the parallel circuit. In this embodiment, a further rectifying circuit, as is known in the art, may be implemented with the clipper circuit of  FIG. 8  before supplying a voltage to the batteries, as illustrated in  FIG. 9 .  
         [0040]      FIG. 9  illustrates an overall embodiment of the claimed system. A wall outlet AC power source  100  is fed into a clipper circuit  102 . The clipper circuit reduces the effective voltage of the AC power and is channeled to a switch  104 . A rectifying circuit  106  may also be connected to the AC power source to provide a DC charging current to a set of batteries  108 . In one embodiment, the rectifying circuit charges the batteries while the switch  104  is arranged to channel AC power to the motor. As further illustrated in  FIG. 9 , switch  104  provides connections to the motor  110 . Specifically, the switch  104  provides connections for a series wound circuit connected to AC power when the switch is in a left position and provides connections for a parallel wound circuit connected to the batteries when the switch is in a right position. The circuits and connections are the same as those described above.  
         [0041]      FIG. 110  illustrates a vacuum cleaner embodiment of the claims. Similar components of  FIG. 9  are labeled in  FIG. 10 . In the vacuum cleaner embodiment of  FIG. 10 , AC outlet power is channeled into the vacuum cleaner device through a power cord  100 , which connects to a combination clipper circuit  102  and rectifying circuit  106 . A DC battery  108  is connected to the rectifying circuit  106 . A wire cord provides the AC and DC power to a switch  104 . The switch is coupled to the electric motor  110  as illustrated in  FIG. 10  where the wiring may be connected in a similar fashion as illustrated in  FIG. 9 .  
         [0042]     Existing motor systems may rely solely on a DC series wound motor having low power output or a universal motor that may only match the power of a DC battery, i.e., the AC is brought down completely to a DC power level (which may be typically much weaker than original AC power level).  
         [0043]     The claimed motor switches from a series wound circuit to a parallel wound circuit when DC operating power is used. Switching from a series wound to parallel wound circuit decreases the effective impedance of the field winding, thereby increasing DC operating power. When the motor is operating on AC power, a series field coil circuit is used to increase impedance and decrease operating power. A clipper circuit may be used across the AC power supply to further reduce the effective AC power supplied to the motor when the motor is operating on AC. The claimed motor increases the average power performance of the motor while decreasing the power discrepancy in motor operation when switching between AC and DC power.  
         [0044]     Many modifications and variations may be made in the techniques and structures described and illustrated herein without departing from the spirit and scope of the present claims. Accordingly, it should be understood that the methods and apparatus described herein are illustrative only and are not limiting upon the scope of the claims.