Abstract:
A high pressure transducer is disclosed. The transducer includes a supply inlet configured to provide a gas supply to the high pressure transducer at a supply pressure and a pressure divider section coupled to the supply inlet. The pressure divider section is configured to reduce the supply pressure to a reduced pressure as a function of a first predetermined ratio. The transducer also includes a low pressure control section coupled to the pressure divider section and configured to receiving the gas supply at the reduced pressure and an amplifying section coupled to the low pressure control section. The low pressure control section varies the reduced pressure to produce a variable control pressure to actuate the amplifying section in response thereto. The amplifying section is also configured to multiply the variable control pressure as a function of a second ratio to obtain an output pressure. Further, the transducer includes a main supply valve coupled to the amplifying section, wherein the amplifying section controls the main supply valve.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application claims a benefit of priority to U.S. Provisional Application Ser. No. 60/832,052 filed on Jul. 20, 2006 entitled “High Pressure Transducer,” the entire contents of which is being incorporated by reference herein. 

   BACKGROUND 
   1. Field 
   The present disclosure relates generally to pressure transducers, more specifically to highly responsive gas transducers capable of operating under high pressures. 
   2. Description of the Related Art 
   Pressure transducers have advanced significantly in the past few decades driven in part by their demand in machine and process industries. As high performance electronic control interfaces replaced manual pneumatic control interfaces, which required manual inputs to change transducer settings, the demand for high pressure transducers continued to grow accordingly. Although the process industry is satisfied with signal pressures of no more than 30 PSIG, continued drive in automation of the machine industry fueled the demand for pressure transducers capable of operating under much higher pressures. In the machine industry, typical source pressures can reach up to 150 PSIG, with some transducer designs operating above that threshold. Currently, the machine industry is utilizing pressures over 500 PSIG to perform specific operations, further driving the need for transducers capable of controlling such high pressures. Unlike in the lower pressure transducer segment, selection of transducers to fill the demand for such high pressure needs is very limited. Transducers well-suited for this task are required to be highly accurate, responsive as well as stable. 
   The current state of the art is an electro-pneumatic transducer. A challenging aspect of designing such transducers for high pressure operation is the primary electro-mechanical converting system. This section is responsible for converting the electrical input control signal into a pressure signal through the use of an electro-mechanical converting element. The electro-mechanical system actuates a pressure control system which allows for the flow of control gas. Conventional transducers utilize electro-magnetism and/or piezoelectric elements in the electro-mechanical converting system. 
   Conventional pressure control systems utilize high gain pneumatic flapper nozzle valve in either variable orifice or fixed orifice configurations. Traditional flapper nozzle valve technology is not viable due to high gas consumption. Attempts to limit gas consumption resulted in the need for smaller orifices and nozzle sizes, which require sophisticated filtering to prevent clogging. Thus, there is a need for efficient transducers having high response rates under high pressure conditions. 
   SUMMARY 
   The present disclosure provides a high pressure transducer which overcomes the shortcomings of conventional high pressure transducers, namely slow response time and high gas consumption. The pressure transducer according to the present disclosure includes a low pressure control section adapted for receiving a low pressure source from a pressure divider section. The low pressure control section includes a plurality of proportional solenoid valves for generating a variable control pressure in response to a control signal. An output amplifying section is also provided, which includes a plurality of area ratio pistons to amplify the variable control pressure signal to achieve desired high output pressure. The pressure transducer also includes a pressure sensor and a feedback circuit for controlling the low pressure control section and the pressure amplifier to prevent detrimental effects of high friction therein. 
   According to one aspect of the present disclosure, a high pressure transducer is disclosed. The transducer includes a supply inlet configured to provide a gas supply to the high pressure transducer at a supply pressure and a pressure divider section coupled to the supply inlet. The pressure divider section is configured to reduce the supply pressure to a reduced pressure as a function of a first predetermined ratio. The transducer also includes a low pressure control section coupled to the pressure divider section and configured for receiving the gas supply at the reduced pressure and an amplifying section coupled to the low pressure control section. The low pressure control section is configured to vary the reduced pressure to obtain a variable control pressure which actuates the amplifying section. The amplifying section is also configured to multiply the variable control pressure as a function of a second ratio to obtain an output pressure. Further, the transducer includes a main supply valve coupled to the amplifying section, wherein the amplifying section controls the main supply valve. 
   A method for controlling a high pressure transducer is also contemplated by the present disclosure. The method includes the steps of providing a gas supply at a supply pressure through a supply inlet to the high pressure transducer, receiving the gas supply at a pressure divider section coupled to the supply inlet and reducing the supply pressure to a reduced pressure as a function of a first predetermined ratio. The method also includes the steps of supplying a low pressure control section which is coupled to the pressure divider section with the gas supply at the reduced pressure, wherein the low pressure control section varies the reduced pressure to obtain a variable control pressure output and transporting the variable control pressure output of the low pressure control section to an amplifying section which is coupled to the low pressure control section to actuate the amplifying section. The method further includes the steps of multiplying the variable control pressure as a function of a second ratio to obtain an output pressure and outputting the gas supply at the output pressure through a main supply valve coupled to the amplifying section, wherein the amplifying section controls the main supply valve. 
   According to another aspect of the present disclosure, a high pressure transducer is disclosed. The transducer has a supply inlet configured to provide a gas supply to the high pressure transducer at a supply pressure and a pressure divider section coupled to the supply inlet and including a ratio piston assembly having a small ratio piston and a large ratio piston. The pressure divider section is configured to reduce the supply pressure to a reduced pressure as a function of the ratio of the small and large ratio pistons The transducer also includes a low pressure control section coupled to the pressure divider section and configured for receiving the gas supply at the reduced pressure and an amplifying section coupled to the low pressure control section. The low pressure control section is configured to vary the reduced pressure to obtain a variable control pressure which actuates the amplifying section. The amplifying section includes a multiplying ratio piston assembly configured to multiply the variable control pressure as a function of the ratio of the multiplying ratio piston assembly to obtain an output pressure. The transducer also includes a main supply valve coupled to the amplifying section, wherein the amplifying section controls the main supply valve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
       FIG. 1  is a side cross-sectional view of a high pressure transducer according to the present disclosure; 
       FIG. 2  is a front cross-sectional view of a high pressure transducer according to the present disclosure; 
       FIG. 3  is a schematic diagram of a low pressure control section of the high pressure transducer of  FIG. 1 ; 
       FIG. 4  is a graph illustrating pressure changes within the low pressure control section according to the present disclosure; 
       FIG. 5  is a schematic diagram of a control circuit for the high pressure transducer of  FIG. 1 ; 
       FIG. 6  is a schematic diagram of a pressure path through the high pressure transducer of  FIG. 1 ; and 
       FIG. 7  is a flow chart illustrating a method for controlling the high pressure transducer of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   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. 
     FIGS. 1 and 2  show a high pressure transducer  1  for controlling flow of a gas. The pressure transducer  1  includes a pressure divider section  2 , a low pressure control section  4 , an amplifying section  22 , and a main supply valve  36 . The pressure divider section  2  reduces supply pressure of the gas by a predetermined ratio to a reduced pressure. The reduced pressure gas then operates the low pressure control section  4  which varies the reduced pressure to obtain variable control pressure to actuate the amplifying section  22 . More specifically, the low pressure control section  4  includes feed-and-bleed solenoid valves  18   a  and  18   b  ( FIGS. 2 and 3 ) as the primary electro-pneumatic conversion mechanism which produces the variable control pressure. 
   The amplifying section  22  amplifies the variable control pressure by an inverse of the predetermined ratio to restore the gas pressure substantially to the original supply pressure to control the main supply valve  36 . The amplifying section  22  includes a multiplying ratio piston assembly  38  having one or more area ratio pistons  26  which amplify the variable control pressure of the low pressure control section  4  to achieve the high output pressure range. A high accuracy pressure sensor and electronic feedback control circuit  100 , which is shown in more detail in  FIG. 5 , prevents detrimental effects of high friction on components of the multiplying ratio piston assembly  38  by controlling the transducer  1  using a closed control loop. Thus, the main supply valve  36  is actuated using gas having a pressure lower than the supply pressure thereby reducing the demands on the low pressure control section  4  and increasing the response time thereof. 
   The transducer  1  includes a high pressure supply inlet  6  and an outlet  49 . The supplied gas may be any type of gas suitable for operation of the transducer  1  such as air, nitrogen, oxygen, carbon dioxide, etc. The supply inlet  6  includes a gas supply conduit  7  which provides the gas into the pressure divider section  2 , which then supplies the low pressure control section  4  with the gas at a reduced pressure. The pressure divider section  2  reduces the high supply pressure by a predetermined ratio (e.g., ⅛), which is an inverse of the ratio (e.g., 8) used by the amplifying section  22  to convert the variable control pressure gas into high output pressure substantially equal to the supply pressure. 
   The pressure divider section  2  includes a ratio piston assembly  8  having one or more pneumatic pistons (e.g., a lower small area piston  9  and an upper large area piston  14 ) and a flapper nozzle valve  10 . The pressure divider section  2  employs force balance principals and opposing area ratios of the lower small area piston  9  and an upper large area piston  14  to control the outlet pressure of the flapper nozzle valve  10 . The gas supplied to the pressure divider section  2  is provided to the lower small area piston  9  which then actuates the flapper nozzle valve  10 . 
   The output of the flapper nozzle valve  10  provides a feedback signal, the reduced pressure gas, which is applied to the upper large area piston  14  thereby balancing the force produced by the supply pressure acting on the lower small area piston  9  and modulating the flapper nozzle about a reduced pressure gas. The flapper nozzle valve  10  modulates the supply pressure as a function of the supply pressure divided by the area ratio of the pistons  9  and  14  of the ratio piston assembly  8 . In other words, the supply pressure of the gas is reduced by a predetermined ratio which is defined by the relationship between the lower small area piston  9  and an upper large area piston  14 . 
   The flapper nozzle valve  10  also includes a flapper column  12  which functions as a force limiter and a seal for flapper nozzle valve  10 . The flapper column  12  may be formed from an elastic polymer or an elastomer. In the event of a sudden supply pressure loss, the balancing force on the ratio piston assembly  8  is lost and the full force of the large area piston  14  is applied against the flapper nozzle valve  10 . The spring action of the polymer flapper column  12  compresses thereby allowing the lower small area piston  9  to rest against a non-critical portion of the flapper nozzle valve  10  and protecting the seal face of the flapper column  12  from damage. 
   The output of the pressure divider section  2  also includes an integral surge volume chamber  51  for the solenoid valves  18   a  and  18   b  and a safety relief valve  16  which protect the low pressure control section  4  from high pressure in the event of a failure of the pressure divider section  2 . If the pressure divider  2  fails, or if excessively high supply pressure is applied to the transducer  1 , the safety relief valve  16  limits the pressure applied to the sensitive low pressure control section  4 . 
   With reference to  FIG. 3 , the low pressure control section  4  includes two, quick response, low capacity, solenoid valves  18   a  and  18   b  (e.g., the feed solenoid valve  18   a  and the bleed solenoid valve  18   b ) controlled by a digital electronic pulse width modulated (“PWM”) controller  20 , which receives control signals from a proportional-integral-derivative (“PID”) controller  112 . The PWM controller  20  and the PID controller  112  are components of the control circuit  100  which is shown in more detail in  FIG. 5 . 
   The PWM controller  20  varies the current supplied to the solenoid valves  18   a  and  18   b  thereby controlling the pressure in the low pressure side  28  of the amplifying section  22 . The feed solenoid valve  18   a  receives the reduced pressure gas, and admits gas to the low pressure side  28  of the amplifying section  22 , whereas the bleed solenoid valve  18   b  withdraws the gas from the low pressure side  28 . When in the closed configuration, the solenoid valves  18  facilitate a so-called “lock in last place” failure mode in the event of power loss. 
   The feed solenoid valve  18   a  and the bleed solenoid valve  18   b  are connected in series forming a network with two variable restrictions. Supply pressure enters at supply end of the network, which is the feed solenoid valve  18   a , and outlet end of the network, which is the bleed solenoid valve  18   b , is open to atmosphere. The variable restriction is effected by manipulating the solenoid valves with pulse width modulated control thereby creating a variable restriction as the PWM duty cycle changes from 0 to 100%. 
   The PWM signals controlling the two solenoid valves are complementary to each other, such that when one solenoid valve is at 80% duty cycle, the other is at 20%; when one solenoid valve is at 40% the other valve is at 60%, etc. The PWM control of the feed solenoid valve  18   a  is directly related to the output of the PID controller  112  where the bleed solenoid valve is inversely related or complementary to the output of the PID controller  112 . As the PID controller  112  traverses from 0 to 100% output, the feed solenoid valve  18   a  control traverses from 0 to 100% and the bleed solenoid valve  18   b  traverses from 100 to 0%. As this occurs, the pressure present between the two solenoid valves  18   a  and  18   b  traverses from zero pressure to full supply pressure and effectively changes the electrical signal output of the PID controller  112  into a pneumatic signal output as shown in  FIG. 4 . This configuration provides the primary electric-to-mechanical conversion function within the transducer  1  by generating the variable control pressure. While the pressure output does not track exactly from 0 to 100% with the output of the PID controller  112 , gains and offsets within the PID controller  112  compensate for the mismatch. 
   Referring back to  FIGS. 1 and 2 , the amplifying section  22  includes a low pressure side  28  which receives the variable control pressure from the low pressure control section  4  and a high pressure side  34 , which outputs amplified gas. The amplifying section  22  also includes a diaphragm actuator  24  on the low pressure side  28 . The diaphragm actuator  24  is coupled with a sliding o-ring seal  30  and an exhaust sleeve  42  on a high pressure side  34  to generate the area ratio needed to multiply the pressure of the low pressure control section  4 . The area ratio is substantially the inverse of the area ratio between the pistons  9  and  14  of the piston assembly  8 , such that the gas pressure is restored to the original input gas pressure. In embodiments, the diaphragm actuator  24  is configured to operate at pressures of up to about 300 PSI and the sliding o-ring seal  30  is configured to operate at pressures of up to about 1,500 PSI. 
   The amplifying section also includes a multiplying ratio piston assembly  38  which actuates the main supply valve  36  allowing the supplied gas from the inlet  6  to flow through the transducer  1  to the output  49 . The ratio piston assembly  38  includes an area ratio piston  26 , an exhaust valve sleeve  42  and an exhaust valve seat  46 . The exhaust valve sleeve  42  incorporates a ball joint feature  44  which allows for the exhaust valve sleeve  42  to self-align with the valve seat  46  within the piston assembly  38 . 
   The main supply valve  36  includes a sliding piston  48  disposed within a supply area  50  which pressure balances the main supply valve  36  with the supply pressure interposed therein and outlet pressure ported to chambers on either side the supply area  50 . The exhaust valve  40  is also pressure balanced by employing an effective valve diameter which is substantially the same diameter as the exhaust sleeve&#39;s sliding seal  30 . 
     FIG. 5  shows the control circuit  100  which includes a control input  102  such as an electrical control signal or manual input mechanism allowing for setting of desired output pressure for the transducer  1 . The control input  102  transmits the control signals to an amplifier  104  to increase the power of the control signal. The amplified signal is thereafter scaled by a scaling circuit  106  and branches to both the error amplifier  110  and feed forward circuit  108  to the PID controller  112 . The PID controller  112  generates an output to the PWM controller  20  based on the error between a measured process variable and the desired control signal. The PID controller  112  calculates and then outputs a corrective action that adjusts the control output response based upon three parameters: proportional, integral, and derivative. 
   The PID controller  112  processes the error signal and transmits the processed signal to the PWM controller  20  which then controls the solenoid valves  18   a  and  18   b  as discussed above with respect to  FIG. 3 . The solenoid valve  18   a  is a feed valve, wherein the solenoid valve  18   b  is a bleed valve. The feed valve  18   a  is supplied by the low pressure gas from the pressure divider  2 . The feed valve  18   a  thereafter controls the amplifying section  22  to generate a desired output. 
   A pressure sensor  116  monitors the pressure in the pressure divider section  2  and a pressure sensor  114  monitors the output pressure at the outlet  49  in the main supply valve  33 . The pressure signals are transmitted to respective amplifiers  118  and  120  and scaling circuits  122  and  124  prior to being passed to the PID controller  112  for processing. The PID controller  112  compares the measured pressures within the pressure divider section  2  and the outlet pressure with corresponding control signal and based on the deviation from the control signal controls the PWM controller  20  to adjust the solenoid valves  18   a  and  18   b . This allows the solenoid valves  18   a  and  18   b  to match the output pressure to the desired output pressure derived from the control signal. 
     FIG. 6  illustrates the pressure changes within the transducer  1 . In the embodiment, the supply pressure of the gas supplied to the transducer  1  is 1000 PSI. The gas supply is divided by the pressure divider  2 , resulting in the reduced pressure of 125 PSI, which is approximately ⅛ th  of the original supply pressure. The pressure is reduced as a function of the ratio of the pistons  9  and  14  of the piston assembly  8  within the pressure divider. The reduced pressure is supplied to the low pressure control section  4 , which operates within a pressure range from about 0 PSI to about 100 PSI for the given supply of reduced pressure. The low pressure control section  4  then uses the reduced pressure to produce a variable control pressure. The variable control pressure controls the amplifying section  22  which outputs gas at an output pressure from about 0 PSI to about 750 PSI as the amplifying section  22  actuates the main supply valve  33 . As seen in the diagram of  FIG. 6 , the resulting output pressure is substantially equal to the supply pressure, although the supply pressure is initially reduced to the reduced pressure, varied, and thereafter amplified to achieve the desired output pressure. 
     FIG. 7  illustrates a method for controlling the pressure transducer  1 . In step  200 , the gas is supplied to the transducer  1  through the supply inlet  6 . A portion of the gas supply is directed to the pressure divider section  2 , wherein in step  202 , the original supply pressure is reduced by a predetermined ratio as dictated by the area ratio between the pistons  9  and  14  of the ratio piston assembly  8 . In step  204 , the gas at the reduced pressure is supplied to the low pressure control section  4 . In step  206 , the feed and bleed solenoid valves  18  and  18   b  control the amplifying section  22  by varying the reduced pressure gas producing a variable control pressure. The variable control pressure gas is amplified in step  208  by the amplifying section  22  by the inverse of the predetermined ratio to restore the variable control pressure gas to substantially the original supply pressure. In step  210 , the main supply valve  36  is opened to output the amplified gas through the outlet  49 . 
   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.