Abstract:
A solenoid actuator includes an electrical circuit with a first power input terminal, a second power input terminal, a first coil wound around a first axis and configured to generate a first magnetic field while electrical current flows through the first coil, and a second coil wound around a second axis configured to generate a second magnetic field while electrical current flows through the second coil. An electric switch connects or disconnects the first coil and second coil in series or parallel. Thus, the electric switch can energize or de-energize the second coil. A movable member, such as a rod, bar, spool, or hollow tube, influenced by the magnetic fields generated by the first and second coils is configured to move with respect to the first and second coils from a first position to a second position in response to the magnetic field generated by the first coil.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of and claims the benefit of priority under 35 U.S.C. §120 from U.S. Ser. No. 11/949,436 filed Dec. 3, 2007, and the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to an energy efficient solenoid device. One application of the invention is to move a movable member from a first position to a second position. In one example, the invention relates to an energy efficient solenoid coupled to a valve such as a ball valve, spool valve, plug valve, or needle valve. 
         [0004]    2. Description of the Related Art 
         [0005]    Solenoids are typically used to convert electrical energy into mechanical energy to shift position of a movable mechanical member, for example, a plunger or needle in a needle valve. 
         [0006]    An alternative technology used to turn electrical energy into mechanical energy is a piezoelectric device. These devices are often used for sonic transducers and small motors such as those used for focusing cameras. However, piezoelectric devices can fail in a frozen or “stuck” position, which is undesirable for mechanisms requiring a fail-safe design. Piezoelectric devices are typically more expensive than solenoids used for comparable applications. Solenoids typically are more easily made to fail in a safe position than are piezoelectric devices. 
         [0007]    Solenoids typically include an electrically conductive wire that is circularly wound through a number of turns in the form of a coil. A magnetically conductive rod is disposed inside the wound coil. As current passes through the coil, a magnetic field is generated and causes the conductive rod to move relative to the coil from a first position to a second position. In some applications, a biasing member such as a spring forces the rod to return to the first position when the current ceases to flow through the coil. 
         [0008]    One common application of a solenoid is in an electronic door lock such as those commonly used in remotely controlled security doors. When a user pushes a button connected to a solenoid coupled to the door lock, the button connects the coiled wire to a power source, thereby creating a magnetic field within the coiled wire. This field causes a magnetically conductive plunger to move into or out of a locking position. After the button has been released, a biasing member, such as a spring, returns the plunger to its original position. Accordingly, the force generated by the coil must be greater than the amount of biasing force generated by the spring. Generally, two levels of force are required of the coil. First, the coil must generate enough force to shift the plunger from the first position to the second position. The force required to move the plunger from the first position to the second position is called the “shifting” force. Second, the coil must be able to generate enough force to hold the plunger in the second position. This is called the “holding” force. Generally, the electrical power required to produce the shifting force is greater than the electrical power required to produce the holding force. The difference in power required to produce the shifting force is due to the air gap, friction and possible resistance from fluid or components in contact with the plunger. 
         [0009]    Often, an important factor in determining the components to be used in the solenoid is the cost of the component themselves. In other situations, power consumption is a more important factor. Power consumption generally correlates to the amount of heat generated by the solenoid. 
         [0010]    In situations where either low heat or low power consumption are a concern, it is preferable to reduce the amount of current used to generate the holding force. This is because solenoids typically spend much more time with the plunger in the second position, in which the coil generates a holding force, than the solenoids spend actually shifting, during which the coil generates the shifting force. 
       SUMMARY OF THE INVENTION 
       [0011]    One aspect of the present invention is to provide an energy efficient solenoid that provides an appropriate amount of electrical energy with the force required to shift a solenoid and an appropriate amount of energy to hold a solenoid in position once the solenoid has shifted. 
         [0012]    Accordingly, one aspect of the present invention provides a solenoid actuator including an electric circuit with a first power input terminal and a second power input terminal. The circuit further includes a first coil wound around a first axis and configured to generate a first magnetic field while electric current flows through the first coil. A second coil wound around a second axis is configured to generate a second magnetic field while electric current flows through the second coil. The first and second coils can have the same axis or have different axes, i.e., the first and second axes can be collinear, offset and parallel, or at an angle to each other. An electric switch is configured to switch from a first state in which the first coil is connected in series with the first and second power input terminals without being connected in series with the second coil, to a second state in which the first coil is connected in series with the second coil. Thus, the electric switch can energize or de-energize the second coil. A movable member, such as a rod, bar, spool, or hollow tube, influenced by the first and second magnetic fields generated by the first coil and the second coil is configured to move with respect to the first and second coils from a first position to a second position in response to the magnetic field generated by the first coil. In one example, the movable member moves in a direction parallel to one of the first and second axes. 
         [0013]    Another aspect of the present invention provides an automatic valve, which can include a standard valve such as a 3-way air valve and electric circuitry for operation of the 3-way air valve. The circuitry includes a solenoid disposed within or connected to the valve. The solenoid includes an electric circuit with a first power input terminal and a second power input terminal. The solenoid further includes a first coil wound around a first axis and configured to generate a first magnetic field while electric current flows through the first coil and a second coil wound around a second axis and configured to generate a second magnetic field while electric current flows through the second coil. The solenoid further includes an electric switch configured to switch from a first state in which the first coil is connected in series with the first and second power input terminals without being connected in series with the second coil, to a second state in which the first coil is connected in series with the second coil. Additionally, the solenoid includes means for controlling time at which the electric switch changes state. The solenoid includes a movable member influenced by the first and second magnetic fields generated by the first coil and the second coil and configured to move with respect to the first and second coils from a first position to a second position in response to the magnetic field generated by the first coil. 
         [0014]    Another aspect of the invention includes a method of actuating a solenoid. The method includes providing a first coil and second coil. The method further includes electrifying the first coil with a first electric current such that a first magnetic field generated by the first coil during electrification moves the movable member from a first position to a second position. The method includes changing a state of a switch connected between the first coil and second coil such that a second electric current, different from the first electric current, flows in series connection through the first and second coils and generates a second magnetic field in the second coil that holds the movable member in the second position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other advantages of the invention will become more apparent and more readily appreciated from the following detailed description of the exemplary embodiments of the invention taken in conjunction with the accompanying drawings where: 
           [0016]      FIG. 1  is a schematic representation of a solenoid valve with a spring return mechanism; 
           [0017]      FIG. 2A  depicts one example, in cross-section, of a solenoid including a rod internal to two coils; 
           [0018]      FIG. 2B  depicts another example, in cross-section, of a solenoid including two coils overlapping each other; 
           [0019]      FIG. 2C  depicts another embodiment of the invention in which the solenoid moves a movable bar; 
           [0020]      FIG. 3  is an electrical schematic representing one example of the inventive solenoid with an electronic switch in a first position, typically used for shifting a mechanical member from a first position to a second position; 
           [0021]      FIG. 4  is an electrical schematic representing one example of the inventive solenoid with an electronic switch in a second position, typically used for holding the mechanical member in the second position against the biasing force of the biasing member; 
           [0022]      FIG. 5  is an electrical schematic representing another example of the inventive solenoid with an electronic switch in a first position, typically used for shifting a mechanical member from a first position to a second position; 
           [0023]      FIG. 6  is an electrical schematic representing one example of the inventive solenoid depicted in  FIG. 5  with an electronic switch in a second position, typically used for holding the mechanical member in the second position against the biasing force of the biasing member; 
           [0024]      FIG. 7  is an electrical schematic representing yet another example of the inventive solenoid with an electronic switch in a first position, typically used for shifting a mechanical member from a first position to a second position; and 
           [0025]      FIG. 8  is an electrical schematic representing one example of the inventive solenoid depicted in  FIG. 7  with an electronic switch in a second position, typically used for holding the mechanical member in the second position against the biasing force of the biasing member. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    With reference to  FIG. 1 , one example of an application of a solenoid is in a valve such as the spring-return 3-way valve  1 , which includes a solenoid  20  for shifting the valve from a first position to a second position. When the solenoid  20  is not energized, the 3-way valve  1  is in the first position. When the solenoid  20  is energized, the 3-way valve  1  moves to the second position in response to a shifting force generated by the solenoid  20 . Once the 3-way valve  1  is in the second position, the solenoid  20  must maintain sufficient force, i.e., a “holding force,” to hold the 3-way valve  1  in place against the force produced by the valve spring  3 , which functions as a biasing member. When current ceases to flow through the solenoid  20 , the solenoid  20  ceases to generate force, and the valve spring  3  causes the 3-way valve  1  to move back to the first position. 
         [0027]      FIG. 2A  is a cross-section view of one example of a solenoid  20  as may be used in combination with the 3-way valve  1 . The solenoid  20  includes a shift coil  30  and hold coil  40  disposed around a rod  25 . In the example shown in  FIG. 2 , the rod  25  is connected to a spring  10 , which biases the rod toward a first position. The spring  10  may be included in the solenoid  20 , or the spring  10  may be omitted, depending on whether the rod  25  is to be internally biased (as shown in  FIG. 2A ), externally biased (as shown by the valve spring  3  in  FIG. 1 ), or unbiased. The rod  25  typically moves axially along its longitudinal axis in and out of the solenoid  20  in response to electrification of the shift coil  30 . Movement of the rod  25  causes a spool  26  (shown in  FIG. 2B ) to move within a fluid passageway  29   b  in a valve  28   b  to connect various fluid passageways. Alternatively, the spool  26  can be replaced with a plunger  27  (shown in  FIG. 2A ) that opens or blocks a fluid passageway  29   a  in a valve  28   a . In other embodiments, the rod  25  moves other devices unrelated to valves. For example, rod  25  or other component moved by the shift coil  30  can be used to cause an electrical switch to change state, i.e., an electrical relay. 
         [0028]    In  FIG. 2A , the solenoid  20  is shown with the shift coil  30  disposed completely separated in an axial direction from the hold coil  40 . In other words, the shift coil  30  and hold coil  40  do not overlap along their axes. This arrangement allows for a simple manufacturing process for each coil separate from the manufacture process of the other coil. 
         [0029]    In an alternative embodiment, the shift coil  30  is disposed partially or completely around the hold coil  40  as shown in  FIG. 2B . In other words, the shift coil  30  and the hold coil  40  overlap along their axes. This nested arrangement provides a beneficial reduction in overall size required for the solenoid  20 . Additionally, the rod  25  can be made shorter, and therefore will typically weigh less than rods used with coils that do not overlap. This reduction in size and weight of the rod  25  allows the solenoid  20  to operate with a shorter response time. 
         [0030]    J As discussed above, if a biasing member is provided within or is mechanically coupled to the solenoid  20 , the amount of force generated by the coils must be greater than the amount of biasing force generated by the spring. Generally, two levels of force are required of the coil. First, the solenoid  20  must generate enough force to shift a plunger from the first position to the second position. The force required to move the plunger from the first position to the second position is called the “shifting” force. Second, the coil must be able to generate enough force to hold the plunger in the second position, for example, against the force generated by a biasing member such as the valve spring  3  or the spring  10 . This is called the “holding” force. Generally, the electrical power required to produce the shifting force is greater than the electrical power required to produce the holding force. 
         [0031]    The solenoid  20  depicted in  FIG. 2  also includes an optional universal voltage input  60  electrically connected to the shift coil  30  and to first and second voltage inputs  65  and  66 . The universal voltage input  60  is part of an electric circuit  15  that includes the shift coil  30 , hold coil  40 , and an electric switch  50  (shown in  FIG. 3 ). The electric switch  50  may be controlled by the timer  55 . In other embodiments, the universal voltage input  60  is omitted for simplicity sake, and the appropriate voltage for operation of the shift coil  30  and hold coil  40  is supplied directly to the first and second input leads  65  and  66 . 
         [0032]      FIG. 2C  depicts another embodiment of the invention. In this embodiment, the shift coil  30  is disposed around a first leg  71  of a U-shaped member  70 , and the hold coil  40  is disposed around a second leg  72  of the U-shaped member  70 . Typically, the U-shaped member is made of a material such as iron or steel that responds to magnetic force. The legs of the U-shaped member help focus the magnetic field created by the shift coil  30  and hold coil  40 . The movable member in this embodiment is a movable bar  25 ′ that pivots relative to the U-shaped member  70 . The movable bar  25 ′ can pivot around a hinge or bend position, for example. In one application, the solenoid  20  in this embodiment is connected to a valve and blocks an air passage upon actuation. In another application, the solenoid  20  opens or closes an electrical switch upon actuation. 
         [0033]      FIG. 3  schematically represents the electric circuit  15  used in the solenoid  20 . As shown in  FIG. 3 , the solenoid  20  includes a first electrical input  65  and second electrical input  66 . These electrical inputs can be free wires extending from the solenoid and internally connected to the solenoid. In an alternative embodiment, the first and second electric inputs can be terminals on the solenoid  20 , for example. 
         [0034]    In the example shown in  FIG. 3 , the first and second electrical inputs are connected to a universal voltage input  60 , which converts an input voltage to a voltage appropriate to operate a shift coil  30  and a hold coil  40 . For example, the universal voltage input  60  may be configured to convert 120 and/or 240 VAC, into 6 VDC. Additionally, the universal voltage input  60  may be configured to convert  12  and/or 24 VDC into 6 VDC. 
         [0035]    As further shown in  FIGS. 3 and 4 , an electric switch  50  is disposed in the electric circuit  15  between the shift coil  30  and the hold coil  40 . In  FIG. 3 , the electric switch  50  is in a first state. In  FIG. 4 , the electric switch  50  is in a second state. The electric switch  50  is used to connect or disconnect the two coils at the appropriate time. An optional timer  55  may be included in or on the solenoid  20  in order to delay the change of state of the electric switch  50 . For example, when the solenoid  20  receives an activation signal or is first energized from an external source such as a relay, current will flow through the shift coil  30  to develop a magnetic field creating a shifting force sufficient to move a rod disposed within or around the shift coil  30 . At this time, the electric switch  50  is in a first state, and a relatively high electric current flows through the shift coil  30 , preferably from 50 to 200 mA, more preferably around 80-100 mA. After a predetermined delay controlled by the timer  55 , the electric switch  50  will change from a first state, in which the hold coil  40  is not connected in series with the shift coil  30 , to a second state, in which the hold coil  40  is connected in series with the shift coil  30  as shown in  FIG. 4 . The time delay for switching the electric switch from the first state to the second state is preferably in the range of 5 milliseconds to 500 milliseconds, but other times are possible. When the timer  55  activates the hold coil  40  within this time range, the shift coil  30  has sufficient time to shift the rod  25 , but does not unnecessarily waste energy and generate heat. In one example, the timer  55  is a circuit including a resistor and capacitor. The capacitor requires a certain period of time in order to charge up. Once the capacitor is charged, then the electric switch  50  changes state. 
         [0036]    In another variation, the timer  55  may be omitted, and the electric switch  50  will change state in direct response to the movement of the rod  25 . For example, once the rod has moved in response to movement of the shift coil  30 , the rod  25  may complete an electrical circuit. One benefit of this arrangement is that the hold coil  40  will not reduce the amount of current flowing through the shift coil  30  prematurely. In other words, it is preferable for the solenoid  20  to produce the shifting force until the rod  25  has reached its desired position. It is preferable for the solenoid  20  to change to the holding force after the rod  25  has reached its desired position. 
         [0037]    One benefit of the series arrangement for the shift coil  30  and hold coil  40  shown in  FIG. 4  is that the hold coil  40  can act in concert with the shift coil  30  while also functioning as an added resistor or impedance device. In other words, during actuation of the solenoid  20 , the amount of current flowing through the shift coil  30  and hold coil  40  while the shift and hold coils are connected in series will be less than the amount of current flowing through the shift coil  30  when the hold coil  40  is in a disconnected state. Therefore, assuming the voltage applied to the electric circuit  15  is constant, the amount of power consumed by the solenoid  20  will be less when the hold coil  40  is connected in series with the shift coil  30  than when the shift coil  30  is connected in the electric circuit  15  without the hold coil  40 . In other words, less power is consumed when the holding force is generated than when the shifting force is generated. Therefore, the solenoid  20  is more energy efficient than conventional solenoids because, as discussed above, the electrical power required to produce the holding force is typically lower than the electrical power required to produce the shifting force. Thus, it is appropriate for the solenoid  20  to use less energy when only the holding force is required. 
         [0038]    In one example of the invention, the wire used to create the shift coil  30  is wrapped with fewer “turns” than the number of turns used to create the hold coil  40 . For example, the shift coil  30  may have only one tenth as many turns as the hold coil  40  has. One benefit of this arrangement is that the shift coil  30  can produce a large magnetic field due to high current, but takes up relatively little space. Additionally, the wire used to form the shift coil  30  may be larger in diameter than the wire used in the hold coil  40 . In one example, the shift coil  30  includes 36 gauge wire, and the hold coil  40  includes 44 gauge wire. However, other gauges of wire are sometimes used for either of the coils. 
         [0039]    The shift coil  30  typically has a lower impedance than the hold coil  40  due to the larger gauge wire and fewer turns used in the shift coil  30 . For example, the shift coil  30  may have a total impedance (or resistance in the case of pure DC voltage) of 75Ω. In contrast, the hold coil  40  may have a total impedance of 2000Ω. Therefore, the overall current used by the electric circuit  15  is lower when the hold coil  40  is placed in series with the shift coil  30  than when the hold coil  40  is omitted from the electric circuit  15 . Thus, the overall energy used by the electric circuit  15  is less when the solenoid  20  is in the holding state. For example, if the voltage applied to the electric circuit  15  is 6 VDC and only the shift coil  30 , measured at a resistance of 75Ω, provides any significant impedance (resistance), then the current flowing through the electric circuit  15  will be 6 VDC/75Ω=80 mA, and total power consumption will be 480 mw. After the electric switch  50  changes state to include the hold coil  40  in the electric circuit  15 , total current will be 6 VDC/(75+2000)Ω=2.89 mA, and total power consumption will be 17.3 mW. 
         [0040]    Accordingly, power consumption during the shift operation, i.e., when the shift coil  30  receives current, but the hold coil  40  does not, is approximately 500 mW. When the holding coil  40  is energized and the solenoid  20  generates the holding force, the power consumption is approximately 20 mW. Thus, by adding the hold coil  40  to the electric circuit  15  in series with the shift coil  30 , the power consumption of the solenoid  20  during the holding state is significantly lower than during the shifting state. An additional benefit of the reduction in power consumption is the corresponding reduction in heat produced by the solenoid  20  during the holding state. 
         [0041]    Even though less current flows through the shift coil  30  and the hold coil  40  while the electric switch  50  is in the second state, the holding force generated by the shift coil  30  and hold coil  40  is sufficient to maintain the rod  25  in the second position. 
         [0042]    In another embodiment, shown in  FIGS. 5 and 6 , the shift coil  30  and hold coil  40  are used independently. Once the shift coil  30  causes the rod  25  to shift, the hold coil  40  receives all the electric current, and the shift coil  30  receives none.  FIG. 5  shows the shifting state.  FIG. 6  shows the holding state. 
         [0043]    In another embodiment, shown in  FIGS. 7 and 8 , the shift coil  30  and hold coil  40  are in parallel, but both receive electric current during the shifting state and only one receives current in the holding state. During the holding state, only the hold coil  40  receives current.  FIG. 7  shows the shift state.  FIG. 8  shows the hold state. 
         [0044]    Although the description above contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. From the foregoing, it can be seen that the present invention provides at least some contribution to the field.