Abstract:
Bi-stable permanent magnet actuation is a technique employed to move and magnetically hold an armature in electromechanical devices including some valves, wherein, permanent magnets are employed in a manner that places their magnetic field in a bi-stable state to allow a control coil to divert the permanent magnet&#39;s magnetic field in one of two directions within the surrounding magnetic material. Control is established using an actuation system comprising, a power source to deliver the desired level of energy, a voltage conditioner such as a DC/DC converter matched to the power source and electromechanical device, an energy storage device such as a capacitor, an output circuit such as an H-Bridge switching circuit, and a control circuit for controlling delivery of short duration current pulses from the energy storage device through the output circuit to the electromechanical device&#39;s control coil. Thus, an energy efficient bi-stable permanent magnet actuation system is produced.

Description:
RELATED APPLICATIONS 
       [0001]    The present application may find use in systems such as is disclosed in the U.S. Patent application entitled “COMPACT ELECTROMECHANICAL MECHANISM AND DEVICES INCORPORATING THE SAME,” having pub. No. 20120175974A1, pub. date Jul. 12, 2012, pending; U.S. Patent application entitled “DIVERGENT FLUX PATH MAGNETIC ACTUATOR AND DEVICES INCORPORATING THE SAME,” having Ser. No. 13/489,638, filed Jun. 6, 2012, pending; U.S. Patent application entitled “DIVERGENT FLUX PATH MAGNETIC ACTUATOR AND DEVICES INCORPORATING THE SAME,” having Ser. No. 13/489,682, filed Jun. 6, 2012, pending; U.S. Patent entitled “PERMANENT MAGNET LATCHING SOLENOID,” having U.S. Pat. No. 6,265,956 B1, date Jul. 24, 2001; J.P. patent, “SOLENOID ACTUATOR,” having U.S. Pat. No. 7,037,461, date 1995, U.S. Patent entitled “LATCHING SOLENOID WITH MANUAL OVERRIDE,” having U.S. Pat. No. 5,365,210, date Nov. 15, 1994; U.S. Patent entitled “ELECTROMAGNETIC DEVICE,” having U.S. Pat. No. 3,381,181, date Apr. 30, 1968; U.S. Patent entitled “DUAL POSITION LATCHING SOLENOID” having U.S. Pat. No. 3,022,450, date Feb. 20, 1962, the disclosures are hereby incorporated by reference. 
         [0002]    Applications related to the foregoing applications include U.S. Patent application entitled “VARIABLE LIFT OPERATION OF BISTABLE ELECTROMECHANICAL POPPET VALVE ACTUATOR,” having U.S. Pat. No. 4,829,947, date May 16, 1989, U.S. Patent application entitled “SOLENOID OPERATED VALVE WITH MAGNETIC LATCH,” having U.S. Pat. No. 3,814,376, date Jun. 4, 1974, the disclosures of which applications are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates generally to an energy savings bi-stable permanent magnet actuation systems, and more particularly, to an energy efficient Bi-stable Permanent Magnet Activation System (BSPMAS) that can deliver short duration current pulses to control coil that produce a short duration secondary magnetic field to divert the primary magnetic field from a permanent magnet to alternately attract moving magnetic pole pieces or the armature in a bi-stable permanent magnet actuator. 
       BACKGROUND OF THE INVENTION 
       [0004]    Bi-stable permanent magnet actuation is a technique employed to move and magnetically hold an armature in electromechanical devices including some valves. The permanent magnets are employed in a manner that places their magnetic field in a bi-stable state to allow control coil to divert the magnetic field in one of two directions within the surrounding magnetic material. Examples of bi-stable permanent magnet actuators include U.S. Pat. Nos. 3,022,450; 3,381,181; 5,365,210; 6,265,956 B1; 7,037,461, U.S. Ser. Nos. 13/489,638; 13/489,682, and Pub. No. 20120175974 A1, each having a magnetic body incasing the permanent magnet, two controls coil, and central pole piece with the control coil placed with one on either side of the permanent magnet and about the central pole piece. The control coil are connected to control electronics, connected to a power source, and form a single current directional path to produce a single directional path magnetic field to divert the permanent magnet&#39;s magnetic field in one of two directions from the permanent magnet to bi-directionally attract movable:
   Central pole piece to the fixed pole ends of the magnetic body as done in U.S. Pat. Nos. 3,022,450; 3,381,181; 5,365,210; 7,037,461; 6,265,956 B1, and U.S. Ser. No. 13/489,638;   Pole ends of the magnetic body to a fixed central pole piece as done in U.S. patent pub. No. 20120175974A1; or   Single pole end of the magnetic body to a fixed central pole piece as done in U.S. Ser. No. 13/489,682.
 
The moveable parts being referred to as an armature.
   
 
         [0008]    Typical the control electronic simple use switches connected between the power source and the control coil to direct an electrical current from the power source in one of two directions to the control coil that produce a secondary magnetic field which diverts the primary magnetic field of the permanent magnet. The secondary magnetic field reduces the primary magnetic field in one direction and increases the magnetic field in the other to cause movement of the armature. Once the armature has fully moved the power to the control coil can be turned off. The control electronics can produce a bi-directional current from a power source using an H-bridge switching circuit wherein a pair of switches is simultaneously turned on to discharge a current to the control coil with the current duration time controlled in respect to the type of switches (mechanical or integrated circuits) used. The power supply is typically fixed at or above the voltage required to achieve the proper current to the control coil. Since the control electronics typically just turns on the H-bridge switching circuit to allow the current flow from the power supply to the control coil, the amount of energy (power×on time) dissipated by the control controls will be higher than is actually necessary to cause full movement of the armature. Thus requiring the switching means in the H-bridge to be quite power intensive. 
         [0009]    Using fixed voltage power sources makes versatility to energy saving application, like solar power, much harder, especially when high voltages or high currents are needed. Still further, as a bi-stable permanent magnet actuator increases in size the control coil increase proportionally, which increases their resistance, which increases the voltage required to get the proper current through the control coil, which increases the size of the power source. 
         [0010]    What is needed, therefore, is a control electronics system and control coil design that is more adaptable to energy saving applications. 
       SUMMARY OF THE INVENTION 
       [0011]    A bi-stable permanent magnet actuator system (BSPMAS) that is more adaptable to energy saving applications includes control electronics comprising: a power source that can be of any power level to include low voltage batteries and solar cells with low average watts (energy per time), a voltage conditioner such as a DC/DC converter, an energy storage device such as a capacitor, an output circuit such as an H-Bridge switching circuit, and a control circuit for controlling delivery of current pulses from the energy storage device through the output circuit to the control coil, and can include segmented, parallel connected control coil to reduce the input voltage from the power source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a better understanding of the invention, reference is now made to the drawings, wherein like numerals represent similar objects throughout the figures where: 
           [0013]      FIG. 1  shows several forms of a bi-stable permanent magnet actuator. 
           [0014]      FIGS. 2 and 3  are alternate schematic diagram of a typical BSPMAS including representation of the center pole piece and permanent magnet of a bi-stable permanent magnet actuator; 
           [0015]      FIG. 4 , an alternate schematic diagram of the control coil designed to reduce the voltage requirement from the voltage conditioner to the storage capacitor; and 
           [0016]      FIG. 5  is a current trace from a 1 k-lb. holding force bi-stable permanent magnet actuator. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring to  FIG. 1 , a bi-stable permanent magnet actuator  40  can be produce in several forms, as shown, an outer magnetic body  49  incases control coil  42 ,  44  about a center pole piece  45 , one on either side of a permanent magnet  47 . The outer housing  49  is broken into three parts: a fixed outer part  49   a  and pole ends  49   b,    49   c  that may be moveable or fixed. A shaft  41  is shown that is used to convey the movement and force from the bi-stable permanent magnet actuator  40 . It is understood that bi-stable permanent magnet actuators  40  can be produced with only one coil  42  or  44 . 
         [0018]    The control coil  42 ,  44  form a single current directional path in one of two directions to produce a single directional path magnetic field in one of two directions to divert the permanent magnet&#39;s  47  magnetic field in one of two directions from the poles of the permanent magnet  47 , wherein: 
         [0019]      FIG. 1   a,  to bi-directionally attract the moveable central pole piece  45  to fixed pole end  49   b  or  49   c  as done in U.S. Pat. No. 3,022,450 and U.S. Ser. No. 13/489,638 with the shaft  41  firming attached to the central pole piece  45  but free to move through the fixed pole ends  49   b,    49   c;    
         [0020]      FIG. 1   b,  to bi-directionally attract the moveable pole ends  49   b,    49   c  to a fixed central pole piece  45  as done in U.S. patent pub. No. 20120175974A1 with the shaft  41  firming attached to the fixed pole ends  49   b,    49   c  but free to move through the central pole piece  45 ; 
         [0021]      FIG. 1   c,  to single directionally attract a moveable pole end  49   c  to a fixed central pole piece  45  as done in U.S. Ser. No. 13/489,682 with the shaft  41  firming attached to the fixed pole end  49   c,  but free to move through the central pole piece  45  and the fixed pole end  49   b.    
         [0000]    The moveable parts being referred to as an armature. 
         [0022]    The unique characteristic of a bi-stable permanent magnet actuator  40  is that the current to the control coil  42 ,  44  is only required until the armature has completed moving, which is on the order of 10 s of millisecond. Power sources are typically designed to deliver a continuous current at a fixed voltage. Whereas, a fast control switch is needed to allow the gage of wire in the control coil of bi-stable permanent magnet actuators  40  to be smaller than normally would be required for continuous application of the current, otherwise the actuator would be much larger and less efficient. Further the input power (voltage×current) drives the size of the power source. For example, a bi-stable permanent magnet actuator  40  requiring 50 amps at 120 volts requires a 6 k watt power source, even though the power is only required for 10 s of milliseconds. These maybe reasons why such actuators have not become common place in the years since the invention of the bi-stable permanent magnet actuator  40  of U.S. Patent entitled “DUAL POSITION LATCHING SOLENOID” having U.S. Pat. No. 3,022,450, date Feb. 20, 1962, represented by  FIG. 1   a.  Another reason may also be due to the more recent invention of rare earth magnets which allow bi-stable permanent magnet actuators  40  to have much higher activation and holding magnetic forces, which can be much higher than conventional solenoid actuators and allow for much wider operating gaps. 
         [0023]    Referring to  FIG. 2  and  FIG. 3 , alternate schematic diagrams of a BSPMAS  10  are shown including representation of the center pole piece  45  and permanent magnet  47  of the bi-stable permanent magnet actuators  40  of  FIG. 1 . BSPMAS  10  includes a power source  12 ; voltage conditioner  14 ; electrical energy storage capacitor  20 ; control circuit  50  including power switch  52  and voltage sensor (zener diode)  54 ; an output circuit  30   a  of  FIG. 2  or  30   b  of  FIG. 3 ; and the control coil  42 ,  44  of a bi-stable permanent magnet actuator  40 . The voltage conditioner  14  needs to be matched to the power source  12  and the voltage needed by the bi-stable permanent magnet actuator  40 . The voltage conditioner  14  can be a pass-through if no conditioning is needed, a DC/DC or AC/DC converter, a simple voltage multiplier, or a variety of other voltage conditioning circuits. A unique feature is that if the time between current pulses is long, the power source&#39;s  12  input voltage and current can be very small as from low voltage batteries and solar cells with low average watts (energy per time), whereby a voltage conditioner  14  incorporating a voltage multiplier can step-up the voltage to the storage capacitor  20  over time with a small current to the storage capacitor  20  as indicated by the small arrow  62  on the upper output of the voltage conditioner  14 . Whereas, only the energy (power×time=voltage×charge) needed for the activation pulse is required to be delivered by the power source  12 . 
         [0024]    Although  FIGS. 2 and 3  shows a single energy storage capacitor  20 , it is well-understood in the art that a bank of capacitors may be used, or any other energy storage device that can rapidly release stored electrical energy. It is also well-understood in the art that a variety of voltage sensors  54  can be used. 
         [0025]    In  FIG. 2 , four legs are arranged in the form of an “H” (an “H-bridge  30   a ”), each leg of the H -bridge  30   a  having switches  32   a,    34 ,  36   a,  and  38 , respectively. The H-bridge  30   a  is connected to the capacitor  20  and control coil  42 ,  44 , and is used to generate a high current pulse from the capacitor  20  as indicated by the large arrow  64  bidirectional through the control coil  42 ,  44 . The control circuit  50  controls the H-bridge  30   a  to switch direction of the current to the control coil  42 ,  44  using switches  32   a,    34 ,  36   a,  and  38 . A first direction current pulse is discharged from the storage capacitor  20  by activating switches  32   a  and  38 . A second direction current pulse opposite to the first current pulse can be discharged from the storage capacitor  20  by activating switches  36   a  and  34 . The two control coils  42  and  44  are parallel connected to reduce the voltage requirement from the voltage conditioner  14  to the storage capacitor  20 . It is understood that the BSPMAS  10  of  FIG. 2  would still function with bi-stable permanent magnet actuators  40  having only having one coil  42  or  44 . It should be appreciated that a variety of H-bridge output circuits such as the one described with respect to  FIG. 2  may be used within the scope of the present invention. Furthermore, it should be noted that additional switches may be incorporated in each leg of the H-bridge  30   a  to reduce the current through each switch. 
         [0026]    In  FIG. 3 , four legs are arranged in the form of a dual switch  30   b,  each leg having switches  36   b,    38  and diodes  32   b,    36   b,  respectively. The dual switch  30   b  is connected to the capacitor  20  and control coil  42 ,  44 , and is used to generate a high current pulse from the capacitor  20  as indicated by the large arrow  64  bidirectional through the control coils  42  or  44 . The control circuit  50  controls the dual switch  30   b  to switch direction of the current to the control coils  42  or  44  using switches  34  and  38 , respectfully. A first direction current pulse to control coil  42  is discharged from the storage capacitor  20  by activating switch  34 . A second direction current pulse to control coil  44  opposite to the first current pulse can be discharged from the storage capacitor  20  by activating switch  38 . It is understood that the BSPMAS  10  of  FIG. 3  would function only with bi-stable permanent magnet actuators  40  having both control coils  42  and  44 . It is also understood that the diodes  32   b,    36   b  and switches  34 ,  38  could change places and still function as desired. Furthermore, it should be noted that additional switches and diodes may be incorporated in each leg of the dual switch  30   b  to reduce the current through each switch and diode. 
         [0027]    It is well-understood in the art that power switch  52 ; H-bridge  30   a  switches  32   a,    34 ,  36   a  and  38 ; and dual switch  30   b  switches  34 , and  38 , and others incorporated could be a variety of switches from manual or electrically controlled mechanical switches to integrated circuits. 
         [0028]    Referring now to  FIG. 4 , an alternate schematic diagram of the control coils  42  and  44  designed to reduce the voltage requirement from the voltage conditioner  14  to the storage capacitor  20 . Control coils  42  and  44  are each divided into parallel connected control coil  42 ( 1 ),  42 ( 2 ),  42 ( 3 ) to  42 (n) and  44 ( 1 ),  44 ( 2 ),  44 ( 3 ) to  44 (m), n and m are the maximum number of the coil segments. The maximum number of segments n and m need not be equal if so desired. Unequal maximum number of segments n and m maybe desirable when the magnetic force on one side is needed to be larger than on the other at current activation. All segments  42 ( 1 ),  42 ( 2 ),  42 ( 3 ) to  42 (n) and  44 ( 1 ),  44 ( 2 ),  44 ( 3 ) to  44 (m) are placed about the center pole piece  45  of a bi-stable permanent magnet actuator  40  as shown for the control coil in in  FIG. 1 . 
         [0029]    Operation of the BSPMAS  10  of  FIG. 2 ,  FIG. 3  or with coil option of  FIG. 4  is similar and begins by closing switch  52  by control circuit  50  or by an operator if a simple mechanical switch is used to allow current from the power source  12  to inner the voltage conditioner  14 . The voltage on the storage capacitor  20  will then rise until the control circuit  50  senses, through sensor  54  or other means, the proper voltage needed before activating the output circuit  30   a  or  30   b.    
         [0030]    Typical time durations that the high current  64  through output circuit  30   a  or  30   b  is turn on can be very small, on order of 10 s of milliseconds. As a long time duration example from activation to armature final movement (˜45 ms),  FIG. 5  shows the current trace through a bi-stable permanent magnet actuator  40  in like to  FIG. 1   b  from a bank of four parallel connected 2200 uF capacitors rated at 200V to provide a 8800 uF storage capacitor  20 . The capacitor  20  was charged to 120 V at a rate of 0.1 amps. The bi-stable permanent magnet actuator  40  was designed with a magnetic holding force of approximately 1 k lbs. using rare earth permanent magnets and a bidirectional armature movement of approximately 0.150 inches. The control coils  42  and  44  were wound using 32 awg wire (fusing current 52 A@32 ms, 0.091 amps continuous). Each control coil  42  and  44  was composed of four parallel connected control coils. The output circuit was a mechanical switch (rated at 3 amps, continuous) forming an H-Bridge  30   a  switch allowing the time to close to be long (˜370 ms). The armature movement part (˜30 ms) of the trace is shown in  FIG. 5  with the current tail-off indicating the drain off of the storage capacitor  20  while the mechanical switch was still closed. The dotted line in  FIG. 5  represents the current trace had the power source  12  been from a typical power supply rated at ˜6 k watts. The area between the dotted line and the solid line represents the energy saved. Opposite activation produces a similar current trace with movement of the armature in the opposite direction. 
         [0031]    Numerous characteristics and advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many aspects, only illustrative. Changes may be made in details, particularly in matters of shape, size and arrangement of parts without exceeding the scope of the invention. The invention&#39;s scope is defined in the language in which the appended claims are expressed.