Abstract:
An electro-pneumatic transducer for controlling gas pressure is disclosed. The transducer includes a nozzle body and a valve housing interconnected therebetween by a nozzle and a solenoid assembly including a magnetized valve assembly and a solenoid having a top portion and a bottom portion, which when energized generate a magnetic field having a predetermined polarity in response to which the magnetized valve assembly is actuated to control gas flow through the nozzle. The transducer also includes a control circuit adapted to receive an input signal. The control circuit is configured to energize the solenoid in response to the input signal to generate the magnetic field thereabout to actuate the valve assembly. The transducer further includes a capacitor coupled to the control circuit, wherein upon loss of the input signal, the control circuit signals the capacitor to provide an electrical signal to the solenoid to actuate the valve assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims a benefit of priority to U.S. Provisional Application Ser. No. 60/921,195 filed on Mar. 30, 2007 entitled “High Performance Transducer,” the entire contents of which is being incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates generally to pressure transducers, more specifically to electro-pneumatic transducers adapted to maintain operating pressure in the event of signal loss. 
         [0004]    2. Description of the Related Art 
         [0005]    Current-to-pressure (“I/P”) electro-pneumatic transducers that utilize voice coils are well known in the art. These transducers control the pressure output in response to a predetermined electronic or electric control signal. Transducers are often exposed to extreme weather, such as excessive moisture, temperatures and winds, which may interfere with the operation of the transducer. In particular, dust and moisture may enter into the transducer and disrupt the signals, thereby interrupting controlled pressure output of the transducers. 
         [0006]    In the event of signal loss, the output pressure is affected accordingly, such as the pressure simply drops to the equilibrium pressure created by the minimum biasing force of the suspension spring associated with the voice coil of the transducer. In some instances, it is desirable to maintain the pressure output (e.g., higher pressure or zero output pressure) even upon loss of signal. The ability to maintain pressure allows the process, in which the transducer is disconnected, to recover quicker and safer from the signal loss. Similarly, the ability to maintain zero output pressure in the event of signal loss is also beneficial for safety reasons. Therefore there is a need for a transducer which is adapted to maintain output pressure despite signal loss. 
       SUMMARY 
       [0007]    The present disclosure provides for a transducer coupled to a booster chamber, the transducer having a vent nozzle and a voice coil mounted on a suspension spring with a permanent magnet that controls the pressure within the booster chamber. The suspension spring acts with respect to the nozzle to vent gas. The booster chamber also includes a diaphragm pressure transformer, which controls the primary output pressure. As the current supplied to the coil is increased, the pressure within the booster chamber increases accordingly. 
         [0008]    The transducer also includes a control circuit coupled to a solenoid valve assembly. The circuit senses the control signal and responds accordingly to effectively maintain the booster chamber pressure in the event of a signal loss. The circuit provides for a so-called “lock in last position” functionality to the transducer allowing the transducer to lock the last pressure output in which the transducer was operating immediately prior to loss of a control signal. Further, the transducer includes a specialized sealing and vent assembly which allow for deployment of the to transducer in harsh environments. 
         [0009]    According to one aspect of the present disclosure, an electro-pneumatic transducer for controlling gas pressure is disclosed. The transducer includes a nozzle body and a valve housing interconnected therebetween by a nozzle and a solenoid assembly including a magnetized valve assembly and a solenoid having a top portion and a bottom portion, which when energized generate a magnetic field having a predetermined polarity in response to which the magnetized valve assembly is actuated to control gas flow through the nozzle. The transducer also includes a control circuit adapted to receive an input signal. The control circuit is configured to energize the solenoid in response to the input signal to generate the magnetic field thereabout to actuate the valve assembly. The transducer further includes a capacitor coupled to the control circuit, wherein upon loss of the input signal, the control circuit signals the capacitor to provide an electrical signal to the solenoid to actuate the valve assembly. 
         [0010]    A method for controlling for an electro-pneumatic transducer having a nozzle body and a valve housing interconnected therebetween by a nozzle is also contemplated by the present disclosure. The method includes the steps of providing an electro-pneumatic transducer. The transducer includes a solenoid assembly having a magnetized valve assembly and a solenoid having a top portion and a bottom portion, which is energized in response to an input signal to generate a magnetic field having a predetermined polarity. The magnetized valve assembly is actuated in response to the magnetic field to control gas flow through the nozzle. The method also includes the steps of determining whether the input signal deviates from a predetermined operational level to detect a drop in the input signal and signaling a capacitor coupled to the solenoid to provide an electrical signal therefrom to the solenoid to actuate the valve assembly in response to the drop in the input signal. 
         [0011]    According to another aspect of the present disclosure, an electro-pneumatic transducer for controlling gas flow is disclosed. The transducer includes a nozzle body and a valve housing interconnected therebetween by a nozzle and a solenoid assembly including a magnetized valve assembly and a solenoid. The solenoid includes a housing and a central bore defined therethrough, the solenoid further includes a top portion and a bottom portion, which when energized generate a magnetic field having a predetermined polarity. The magnetized valve assembly includes a plunger assembly having a shaft adapted to slide through the central bore, a magnetized portion disposed on a top portion of the shaft, a flexible member disposed on the magnetized portion and a coil spring disposed about the shaft adapted to bias the plunger assembly, the magnetized valve assembly is adapted to actuate to control gas flow through the nozzle in response to the magnetic field. The transducer also includes a control circuit adapted to receive an input signal. The transducer further includes a capacitor coupled to the control circuit; the control circuit is configured to charge the capacitor in response to the input signal. Upon reaching a predetermined charge, the control circuit signals the capacitor to energize the solenoid to actuate the valve assembly. The transducer further includes a capacitor coupled to the control circuit, wherein upon loss of the input signal, the control circuit signals the capacitor to provide an electrical signal to the solenoid to actuate the valve assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
           [0013]      FIG. 1  is an isometric view of an electro-pneumatic transducer according to the present disclosure; 
           [0014]      FIG. 2  is a cross-sectional view of the electro-pneumatic transducer of  FIG. 1  according to the present disclosure; 
           [0015]      FIG. 3  is an isometric view of valve and nozzle assemblies of the electro-pneumatic transducer of  FIG. 1  according to the present disclosure; 
           [0016]      FIG. 4  is an isometric view of the electro-pneumatic transducer of  FIG. 1  with parts disassembled according to the present disclosure; 
           [0017]      FIG. 5  is an isometric view of the electro-pneumatic transducer of  FIG. 1  with parts disassembled according to the present disclosure; 
           [0018]      FIG. 6  is an isometric view of a valve housing of the electro-pneumatic transducer of  FIG. 1  with parts disassembled according to the present disclosure; 
           [0019]      FIG. 7  is an isometric view of a solenoid assembly of the electro-pneumatic transducer of  FIG. 1  with parts disassembled according to the present disclosure; 
           [0020]      FIGS. 8A-B  are cross-sectional views of the solenoid assembly of the electro-pneumatic transducer of  FIG. 1  according to the present disclosure; 
           [0021]      FIG. 9  is an isometric view of the solenoid assembly of the electro-pneumatic transducer of  FIG. 1  with parts disassembled according to the present disclosure; 
           [0022]      FIG. 10  is cross-sectional view of a plunger assembly of the solenoid assembly of  FIG. 9  according to the present disclosure; 
           [0023]      FIGS. 11A-B  are cross-sectional views of the plunger assembly of  FIG. 10  according to the present disclosure; and 
           [0024]      FIG. 12  is a flow chart illustrating a method for controlling the electro-mechanical transducer of  FIG. 1  according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Particular embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
         [0026]      FIGS. 1-4  show an electro-pneumatic transducer  2  having a nozzle body  4 , which is disposed on top of a valve housing  6 . The transducer  2  also includes an electro-pneumatic converter section  3  coupled to the nozzle body  4  and a booster chamber  5  coupled to the valve housing  6 . The converter section  3  includes a voice coil  150  having a magnet assembly  152 . The voice coil  150  may be any type of magnetically controlled diaphragm which acts as a primary control of the flow of gas into the transducer  2 . 
         [0027]    The nozzle body  4  includes at least one inlet port  8  for supplying a gas (e.g., at reduced pressure) from the voice coil  150  and a vent port  10  for venting the gas (e.g., at higher pressure). Since the vent port  10  allows the gas to escape the body of the transducer  2 , the vent port  10  includes an effective seal which permits selective venting of the gas. 
         [0028]    The transducer  2  is coupled to the booster chamber  5  through the valve housing  6 . The booster chamber  5  includes an amplifying diaphragm  200  coupled to a booster vent  202 , an exhaust valve  204  and a supply valve  206 . The amplifying diaphragm  200  leverages the pressure in the booster chamber  5  to modify the pressure of the supplied gas via the supply valve to the desired pressure based on the control signal and provides enhanced flow capacity. 
         [0029]    The transducer  2  also includes a solenoid cap plate  12  disposed between gaskets  14  and  16 , all of which are disposed in between the nozzle body  4  and the valve housing  6  as shown in  FIG. 4 . The supplied gas flows through the nozzle body  4 , the solenoid cap plate  12  and the valve housing  6  to the booster chamber  5 . Accordingly, the solenoid cap plate  12  and the valve housing  6  serve as a conduit for the supplied gas from the nozzle body  4  to the booster chamber  5 . 
         [0030]      FIG. 5  shows one embodiment of the valve housing  6  including a solenoid assembly  18 , a control circuit  20  and a capacitor  22 . The valve housing  6  may have a substantially rectangular shape with a cavity  24  adapted to fully enclose the solenoid assembly  18 , the control circuit  20  and the capacitor  22  therein. In another embodiment shown in  FIG. 6 , the valve housing  6  may include an upper valve housing  26  and a lower valve housing  28 . The lower valve housing  28  includes a lower cavity (not explicitly shown) for at least partially enclosing the solenoid assembly  18 , the control circuit  20  and the capacitor  22 . The upper valve housing  28  also includes an upper cavity (not explicitly shown) for enclosing any portions of the solenoid assembly  18 , the control circuit  20  and the capacitor  22  which extend from the lower valve housing  28 . 
         [0031]      FIG. 7  illustrates the solenoid assembly  18  including a solenoid  30  and a magnetized valve assembly  31  which includes a magnetized elastic member  32  a flapper seal  36  disposed thereon. The solenoid  30  is a two-way pulse activated solenoid, which includes a housing  38  enclosing a coil (not explicitly shown). When the coil is energized either by a positive or negative pulses (e.g., two-way activation), the coil generates a magnetic field in one of the two directions—with the top portion of the solenoid  30  being either north or south and the bottom portion being of opposite polarity. The housing  38  is also constructed from a magnetized metal (e.g., steel). The valve assembly  31  also includes a spring holder  34  disposed on top of the solenoid  30 . The spring holder  34  includes a depression  35  adapted to fit around the outer edge of the elastic member  32 . 
         [0032]    In  FIG. 7 , the elastic member  32  is shown as a spring disc. In embodiments, the elastic member  32  may be a cantilever or a coil spring constructed from magnetizable elastic materials, such as metals. The elastic member  32  is permanently magnetized or remanenced and may include one or more arcuately shaped slits  33  cut therethrough, which impart elasticity to the elastic member  32 . The slits  33  are disposed around the periphery of the elastic member  32  allowing the center of the elastic member  32  to move along longitudinal axis A-A relative to the outer portion thereof. The spring holder  34  also separates the elastic member  32  from the top portion of the solenoid  30 , allowing the elastic member  32  to move axially in the space therebetween. The elastic member  32  may be formed from any type of magnetizable metal, such as tempered steel, such that the top portion of the elastic member  32  is one polarity (e.g., north) and the bottom portion is of the opposite polarity (e.g., south). 
         [0033]      FIGS. 8A-B  illustrate the operation of the solenoid assembly  18 . In particular,  FIG. 8A  shows a cross-sectional view of the solenoid assembly  18  with the valve assembly  31  in an open configuration and  FIG. 8B  shows the valve assembly  31  in a closed configuration. The valve assembly  31  operates by opening and closing a nozzle  40 , which is disposed in the solenoid cap plate  12  (e.g., machined therein). In another embodiment shown in  FIG. 6 , the nozzle  40  may be disposed in the upper valve housing  26 . The nozzle  40  allows for the supplied gas to flow from the nozzle body  4  through the solenoid cap plate  12  and into the valve housing  6  to the booster chamber  5 . 
         [0034]    The valve assembly  31  also includes a flapper seal  36  ( FIG. 7 ), which is affixed to the elastic member  32 , such that the flapper seal  36  moves with the elastic member  32 . The flapper seal  36  is opened or closed against the nozzle  40  to either allow or block the flow of the supplied gas. The opening and closing of the valve assembly  31  is controlled by changing the polarity of magnetic pulse created by the solenoid  30 . The control circuit  20  controls the polarity of the solenoid  30  by directing the polarity of the current flow therethrough. When the solenoid  30  is powered by a first electric signal (e.g., a positive pulse), the top portion of the solenoid  30  temporarily assumes one polarity (e.g., north) and the bottom portion assumes the opposite polarity (e.g., south). When the control circuit  21  reverses the current flow by supplying a second electric signal (e.g., a negative pulse), the polarity of the solenoid  30  is temporarily reversed accordingly. 
         [0035]      FIG. 8A  depicts the valve assembly  31  in the open configuration, which occurs when the solenoid  30  is powered by the first electrical signal (e.g., positive pulse). In this configuration, the solenoid  30  temporarily assumes a magnetic field in which the top portion of the solenoid  30  is of the opposite polarity than the bottom portion of the elastic member  32 . As a result, the elastic member  32  is attracted toward the top portion of the solenoid  30  thereby moving the flapper seal  36  from the nozzle  40  allowing for flow of the supplied gas. The valve assembly  31  remains open until the polarity of the solenoid  30  is reversed. More specifically, the elastic member  32  remains attached to the metallic housing  38  due to permanent magnetization or remanence thereof. The open configuration may be maintained as long as the transducer  2  is powered and receives an input signal. 
         [0036]      FIG. 8B  depicts the valve assembly  31  in the closed configuration, which occurs when the solenoid  30  is powered by the second electrical signal (e.g., negative pulse). In this configuration, the polarity of the solenoid  30  is temporarily reversed and the top portion of the solenoid  30  is of the same polarity as the bottom portion of the elastic member  32 . As a result, the elastic member  32  is pushed upwards and contacts the nozzle  40  with the flapper seal  36  thereby blocking the flow of supplied gas. After the pulse has ceased and the magnetic field has dissipated, the spring force of elastic member  32  maintains the closed position of the flapper seal  36  against the nozzle  40  until the polarity of the solenoid  30  is reversed again. 
         [0037]    With reference to  FIG. 5 , the control circuit  20  is coupled in series with a primary conversion circuit (not explicitly shown). The control circuit  20  is also coupled to the capacitor  22 , which is recharged continually whenever the input signal is active. The control circuit  20  receives an electrical input signal and transmits the input signal to the conversion circuit, which may be a constant current driver circuit. The conversion circuit converts the input signals into an electrical signal for controlling the voice coil  150 . More specifically, the conversion circuit supplies the voice coil  150  with a current that is proportional to the value of the current of the input signal, which is adjusted by an external potentiometer. 
         [0038]    The control circuit  20  also senses when the input signal is outside a predetermined operational level. In particular, the control circuit  20  senses when the input signal drops below the minimum predetermined operational level. The operational level may be a predetermined range (e.g., from about 4 mA to about 20 mA) and the signal deviation may be about 20% (e.g., 3.6 mA or 24 mA) or less from the minimum value of the predetermined range. 
         [0039]    When a drop in the input signal below a predetermined threshold is detected, the circuit  20  signals the capacitor  22  to discharge and provide the second electrical signal (e.g., negative pulse) to the solenoid  30 . The second electrical signal causes the solenoid  30  to temporarily assume a magnetic field in which the top portion of the solenoid  30  is of the same polarity as the bottom portion of the elastic member  32  thereby closing the valve assembly  31  as discussed above with respect to  FIG. 8B . The spring force of elastic member  32  maintains the closed position of the flapper seal  36  against the nozzle  40  until the polarity of the solenoid  30  is reversed again. 
         [0040]    When the input signal is recovered, the circuit  20  begins to recharge the capacitor  22 . Once the capacitor  22  is sufficiently charged, the circuit  20  then transmits the first electrical signal (e.g., positive pulse) to the solenoid  30 . The circuit  20  signals the capacitor  22  to discharge and provide the first electrical signal (e.g., positive pulse) to the solenoid  30 . The first electrical signal causes the solenoid  30  to temporarily assume a magnetic field in which the top portion of the solenoid  30  is of the opposite polarity as the bottom portion of the elastic member  32  thereby opening the valve assembly  31 , as discussed above with respect to  FIG. 8A . In another embodiment, the capacitor  22  may be used to provide the second electrical signal (e.g., negative pulse) to the solenoid  30  to close the valve assembly  31 , if the signal loss occurs while the valve assembly  31  is in the open configuration. 
         [0041]    In conventional electro-mechanical transducers, upon a signal loss, the valve assembly would not be operated since the signal loss prevents any control of the components of the transducer. The transducer  2  according to the present disclosure prevents a total loss of control over the components (e.g., valve assembly  31 ) by providing the capacitor  22  for opening the valve assembly  31  and allowing the elastic member  32  to remain in either open or closed position upon occurrence of signal loss. 
         [0042]      FIGS. 9 ,  10  and  11 A and B illustrate another embodiment of a solenoid assembly  50  including a solenoid  52  and a magnetized valve assembly  51  which includes a plunger assembly  54 . The solenoid  52  includes a housing  53  enclosing a coil (not explicitly shown) which when energized by electrical current generates a magnetic field. The housing  53  is constructed from a magnetized metal (e.g., steel). 
         [0043]    As shown in more detail in  FIG. 10 , the plunger assembly  54  includes a shaft  56  having a coil spring  58  disposed thereabout. The plunger assembly  54  also includes a magnetized portion  60  disposed at the top end of the shaft  56 . The magnetized portion  60  may be formed from any type of magnetizable metal, such as tempered steel or may be a ferrous magnet, such that the top portion of the magnetized portion  60  is one polarity (e.g., north) and the bottom portion is of the opposite polarity (e.g., south). The plunger assembly  54  also includes a flexible member  62  (e.g., an elastomer cover) having a seal pad  64 . 
         [0044]    The plunger assembly  54  is disposed within a central bore  68  of the solenoid  50 . The plunger assembly  54  includes a coil spring  70 , which is also disposed within the central bore  68  and biases the plunger assembly  54  in the upward direction, toward the nozzle  40 , thereby pushing the flexible member  62  and the seal pad  65  to impinge upon the nozzle  40 . The shaft  56  is adapted slideably fit within the bore  68 . 
         [0045]    With reference to  FIGS. 9 and 11A  and B, the solenoid assembly  50  also includes a solenoid spacer  66 . The solenoid spacer  66  stages the top end of the plunger assembly  54  a predetermined distance from the nozzle  40 . The flexible member  62  is attached to and moves with the top end of the plunger assembly  54 . More specifically, the flexible member  62  may include a flanged circumference which folds around under the flange of the top end of the plunger assembly  54  thereby fixing the flexible member  62  thereto. This allows the seal pad  64  to move along longitudinal axis B-B to effect a two-state, open-closed valve as it impinges upon and moves away from the nozzle  40 . 
         [0046]      FIG. 11A  depicts the valve assembly  51  in the open configuration, which occurs when the solenoid  52  is powered by the first electrical signal (e.g., positive pulse). In this configuration, the solenoid  52  temporarily assumes a magnetic field in which the top portion of the solenoid  52  is of the opposite polarity than the bottom portion of the magnetized portion  60 . As a result, the magnetized portion  60  is attracted toward the top portion of the solenoid  52  thereby drawing the magnetized portion along with the seal pad away from the nozzle. This action opens the nozzle  40  allowing for continuous flow of gas. The valve assembly  51  remains open until the polarity of the solenoid  52  is reversed. More specifically, the magnetized portion  60  remains attached to the metallic housing  53  due to permanent magnetization or remanence thereof. The open configuration may be maintained as long as the transducer  2  is powered and receives an input signal. 
         [0047]      FIG. 11B  depicts the valve assembly  51  in the closed configuration, which occurs when the solenoid  52  is powered by the second electrical signal (e.g., negative pulse). In this configuration, the polarity of the solenoid  52  temporarily assumes a magnetic field in which the top portion of the solenoid  52  is of the same polarity as the bottom of magnetized portion  60 . As a result, the plunger assembly  54 , namely the shaft  56 , the magnetized portion  60  and the elastomer, are pushed upwards against the nozzle  40 . This force overcomes the magnetic attraction between the housing  53  and the magnetized portion  60 , and impinging the seal pad  64  upon the nozzle  40  thereby blocking the flow of supplied gas. The spring force of coil spring  70  maintains the closed position of the seal pad  64  against the nozzle  40  until the polarity of the solenoid  52  is reversed again. 
         [0048]    During the loss of input signal, the solenoid  52  receives the second electrical signal (e.g., negative pulse), thereby closing the valve assembly  51  as discussed above in  FIG. 11B . Simultaneously, the circuit  20  continues to supply the last stable current signal to the voice coil  150  for a short duration, drawing power from the capacitor  22  instead of the input signal. This allows the circuit  20  to maintain the booster control pressure, while the valve assembly  51  closes. This eliminates a drop in pressure which would otherwise occur during the plunger assembly  54  transitioning from an open to closed configuration. 
         [0049]      FIG. 12  shows a flow chart of a method for operating the transducer  2  in the event of a signal loss according to the present disclosure. The method is described with respect to the solenoid assembly  18  and it is understood that the method may be applied to the solenoid assembly  50 . 
         [0050]    In step  100 , during initial operation, when the input signal is within the operational range, the capacitor  22  is charged to a predetermined level. In step  102 , the control circuit  20  senses when the capacitor has been charged to a predetermined level. In step  104 , the circuit  20  signals the capacitor  22  to discharge and provide an electrical signal (e.g., a positive pulse) to the solenoid  30 . The first electrical signal (e.g., a positive pulse) causes the solenoid  30  to temporarily assume a magnetic field in which the top portion of the solenoid  30  is opposite polarity of the bottom portion of the elastic member  32  thereby opening the valve assembly  31  as discussed above with respect to  FIG. 8A . 
         [0051]    In step  106 , the circuit  20  monitors the input signal to determine whether the input signal is above the threshold value. If yes, method proceeds to step  108  and the circuit  20  updates the signal current to the voice coil  150  to be proportional to the input signal. In step  110 , the control circuit maintains the charge on the capacitor. Method loops back to step  106  and continues to monitor the input signal. If the input signal is below the threshold value, method branches to step  112  to maintain the last signal stored for the voice coil  150 . Method simultaneously executes step  114  and the control circuit  20  signals the capacitor to discharge and provide an electrical signal (e.g., a negative pulse) to the solenoid  30 . A second electrical signal (e.g., a negative pulse) causes the top portion of the solenoid  30  to be of the same polarity as the bottom portion of the elastic member  32 , thereby closing the valve assembly  31  as discussed above with respect to  FIG. 8B . In step  116 , the control circuit is ready to respond to the restoration of the input signal. If no signal is present, the previous closed configuration of the valve assembly  31  is maintained, due to the biasing force of the elastic member  32  or coil spring  70  under the plunger assembly  54 . Upon restoration of the control signal, the method branches back to step  100  to start the process over. 
         [0052]    The described embodiments of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present disclosure. Various modifications and variations can be made without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.