Abstract:
A pneumatically actuated fluid control valve includes a piston and a piston actuator including a permanent magnet. First and second piston actuator positions for magnetically disposing the piston in valve open and valve closed positions are provided. A pneumatic actuator driving circuit pneumatically moves the piston actuator from one to the other of first and second piston actuator positions to dispose the piston in the open and closed positions. The valve includes an annular valve assembly. One valve assembly position is a normally closed position and a positive air flow control signal moves the piston to open the valve. Another valve assembly position is a normally open position and a positive air flow control signal moves the piston to close the valve.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   This invention relates to valves and, in particular, the field of pneumatic valves. 
   2. Description of Related Art 
   It is well known in the field of valves to provide valve control signals for remotely causing valves to open and close, in order to permit fluid flow therethrough. A common method for performing this was to provide a solenoid capable of moving a piston between valve open and valve closed positions. In solenoid controlled valves of this type, a control current was applied to the coil of the solenoid to energize the solenoid and produce electromagnetic flux capable of moving the piston. Many examples of such solenoid actuated valves are known. 
   One example of a solenoid actuated valve is taught in U.S. Pat. No. 3,379,214, entitled “Permanent Magnet Valve Assembly,” issued to Weinberg on Apr. 23, 1965. Weinberg teaches a permanent magnetic valve assembly, having an electromagnetically actuated valve member, wherein a coil was energized to provide electromagnetic flux. A permanent magnet was also provided to provide permanent magnetic flux. When the flux of the coil that was energized opposed and exceeded the flux of the permanent magnet, a plunger was shifted. A flux in the opposite direction by an opposing current could move the piston in the opposite direction. 
   U.S. Patent Application Publication No. 2001/0050705, entitled “Magnetically-Actuated Fluid Control Valve”, published on Dec. 13, 2001 and based upon U.S. patent application Ser. No. 09/930,098, also included a magnetic actuator containing both a permanent magnet and an electromagnet. An armature, configured as a see-saw and coupled to the magnetic actuator, caused the valve to open by displacing selected regions of a diaphragm and forcing the diaphragm into contact with a valve seat. 
   However, solenoid actuated valves can be dangerous in explosive surroundings. For example, they can be dangerous on oil drilling platforms or in use with chemicals in a chemical plant. The danger caused by solenoid valves arises from the fact that the electric current applied to the solenoid coils, for energizing the coils to provide electromagnetic flux to move the pistons under fault conditions can ignite flammable or explosive materials in the vicinity of the valves. 
   One solution to the problem was to limit the magnitude of the solenoid-actuating current to a level below the level which could possibly ignite a fire or cause an explosion, in a worst case scenario, within the particular hazardous environment where the valve was used. However, limitations on the amount of current that can be used to energize a solenoid places limitations on the size of the piston that can be moved as well as the speed and acceleration of the piston movement. Therefore, it was very difficult and expensive to obtain adequate solenoid activated valves suitable for many applications within hazardous areas. 
   Another solution was to provide valves that were actuated using permanent magnets rather than solenoids. For example, U.S. Pat. No. 4,942,852, entitled “Electro-Pneumatic Actuator,” issued to Richeson on Jul. 24, 1990, teaches a valve suitable for internal combustion engines. The actuator taught by Richenson was a pneumatically powered transducer for use as a valve mechanism actuator. The transducer had a piston which was powered by a pneumatic source and held in each of its extreme positions. Air control valves were held in their closed positions by pressured air and/or permanent magnet latching arrangements and the control valves are released to supply air to the piston. When the piston was thus released it was driven to the opposing extreme position by the permanent magnetic field. However, even though the Richeson valve used permanent magnet actuation, it was not completely free of electrical circuits. 
   U.S. Pat. No. 3,517,699, entitled “Magnetic-Pneumatic Proximity Switch,” issued to Marcum on Oct. 20, 1967, teaches a magnetic-pneumatic proximity switch. In the Marcum system, air flow was controlled by a valve without electrical circuit. Instead, a magnetic proximity switch was provided. The magnetic proximity valve taught by Marcum operated as a restriction device in a pneumatic circuit that opened and closed, thereby controlling a spool valve. The spool valve in turn controlled the flow of an operating fluid to or from a working piston and cylinder device. 
   U.S. Pat. No. 4,630,645, entitled “Pneumatic Switching Device, E.G., For Safeguarding Against Overpressure,” issued to Spa on Dec. 23, 1986, also taught a valve that could be actuated without any electrical current. In the Spa device, a piston was received in a bore of a housing. The piston had a narrowed portion between two end surfaces. Two seals were provided in the narrowed portion that acted cooperatively with seats projecting from the wall of the housing bore towards the piston axis. A compression spring acted on one end face of the piston. The other piston end face delimited a pressure chamber with the housing wherein the air valve was in communication with the pressure chamber. A pilot air aperture had a restriction opening into the chamber and an out flow aperture opened between both housing seats. A signal pressure aperture opened into the bore beyond each seat. The pivotal lever engaged an actuation pin of the air valve. 
   U.S. Pat. No. 4,964,424, entitled “Pneumatic Valve Assembly For Controlling A Stream of Compressed Air,” issued to Helbig on Oct. 23, 1990. The valve assembly taught by Helbig was adapted for controlling compressed air stream in response to a non-contacting actuation. It included a pivoted one-arm or double-arm lever, a permanent magnet on one side or on each of both sides of its pivotal axis and via a ferromagnetic or magnetic actuating member. The actuating member was moved into proximity of the permanent magnet or magnets by means of a plunger, causing a pilot orifice to be opened or closed. A pilot air stream flowed through the orifice for actuating a pilot piston to move a valve piston to positions in which the valve was opened or closed. Permanent magnets were provided on the lever on both sides of its pivotal axis. The permanent magnets were interconnected by a magnetic yoke. The magnetic yoke was oppositely poled so that a magnet which was moveable into the proximity of both permanent magnets outside the valve body constituted an actuating member that attracted one permanent magnet on the double-armed lever and repelled the other of the permanent magnets. European Publication EP0715109A1 also teaches a valve having a permanent magnet actuation mechanism. 
   All references cited herein are incorporated herein by reference in their entireties. 
   BRIEF SUMMARY OF THE INVENTION 
   A pneumatically actuated fluid control valve for permitting flow of a fluid from a valve inlet to a valve outlet includes a piston having a valve open piston position and a valve closed piston position for controlling the fluid flow and a piston actuator including a permanent magnet having magnetic flux for applying the magnetic flux to the piston. At least first and second piston actuator positions are provided for magnetically disposing the piston in a selected one of the valve open and valve closed positions. The pneumatically actuated fluid control valve is provided with a pneumatic actuator driving circuit for pneumatically disposing the piston actuator in the first and second piston actuator positions thereby pneumatically moving the piston from one to the other of the valve open and valve closed piston positions. The pneumatically actuated fluid control valve includes an annular valve assembly and the piston is disposed in the center of the annular valve assembly. A first valve assembly position is a normally closed valve assembly position and a positive air flow control signal into the magnet driving assembly adjusts the chamber volume to apply increasing magnet flux to the piston and to move the piston from the valve closed position to the valve open position. A second valve assembly position is a normally open valve assembly position and a positive air flow control signal into the magnet driving chamber adjusts the chamber volume to apply decreasing magnetic flux to the piston and to move the piston from the valve open position to the valve closed position. A further magnet driving chamber and a further air flow control signal can be provided for applying opposing pressures to the piston in accordance with two separate air flow control signals to apply a differential pressure to the piston actuator to control the actuator according to the difference in pressures. 

   
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: 
       FIG. 1  shows a cross-sectional representation of the pneumatically actuated pilot valve of the present invention. 
       FIG. 2  shows an alternate embodiment of the pneumatically actuated pilot valve set forth in  FIG. 1 . 
       FIG. 3  shows an alternate embodiment of the pneumatically actuated pilot valve set forth in  FIG. 1 . 
       FIG. 4  shows a differential pressure diaphragm valve operated in accordance with a pilot signal provided by the pneumatically actuated pilot valve of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1 , there is shown the pneumatically actuated pilot valve  20  of the present invention. In response to an air flow control signal  28  applied to the pneumatically actuated pilot valve  20 , the pilot valve  20  provides a pilot signal outlet flow for use in controlling the opening and closing of a further fluid valve. 
   The pilot valve  20  includes a piston  60  disposed within a piston cylinder  36 . When the piston  60  is in its extreme downward position it presses against a valve seat  66  formed by an annular portion of the bottom of a valve seat chamber  64 . The pressure of the piston  60  against the valve seat  66  causes a fluid flow circuit between the pilot valve ports  22 ,  26  to be interrupted. The piston  60  is sealingly biased in the closed position against the valve seat  66  by a piston spring  38 . The pneumatically actuated pilot valve  20  is thus a normally closed valve. 
   In order to open the pilot valve  20  and permit a fluid flow between the pilot valve ports  22 ,  26 , the piston  60  must be moved upwardly against the closing force of the piston spring  38 . In order to move the piston  60  in this manner, an upward force is applied to the piston  60  by applying the magnetic flux of a permanent magnet  44  to the piston  60 . The permanent magnet  44  is disposed within a magnet assembly  40 . The magnet assembly  40  is an annular assembly disposed within the magnet assembly cavity  50  surrounding the piston cylinder  36 . An actuator spring  52  is disposed within the magnet assembly cavity  50  pressing against the magnet assembly  40  at its upper end and against an actuator spring seat  56  at its lower end in order to bias the magnet assembly  40  upward. 
   The permanent magnet  44  is moved toward the piston  60  by applying the positive air flow control signal  28  to the control inlet port  24 . When a positive air flow control signal  28  is driven into the control inlet port  24 , the magnet driving chamber  34  is expanded by the fluid pressure of the air flow control signal  28 . The expansion of the magnet driving chamber  34  forces the magnet assembly  40  downward and brings the permanent magnet  44  closer to the piston  60  against the force of an actuator spring  52 . The magnetic flux of the permanent magnetic  44  is thus applied to the piston  60  in response to the fluid signal applied to the control inlet port  24 . Continued travel of the permanent magnet  44  through the magnet cavity  50  causes the magnetic flux applied to the piston  60  to increase. 
   In response to the pressure of the positive air flow control signal  28  applied to the control inlet port  24 , the permanent magnet  44  travels a distance  48  through the magnet assembly cavity  50 . The increasing upward force applied to the piston  60  by the permanent magnet  44  as it travels the distance  48  eventually causes the piston  60  to be actuated. When the piston  60  is actuated, it separates from the valve seat  66  thereby permitting fluid to flow between the ports  22 ,  26  by way of the valve seat chamber  64 . Thus valve  20  can be used as a stand above valve as well as a pilot valve. 
   When the positive fluid flow applied to the annular magnet driving chamber  34  is withdrawn, the downward force upon the magnet assembly  40  is decreased. This permits the actuator spring  52  to expand within the magnet assembly cavity  50 , thereby forcing the permanent magnet  44  in the upward direction. As the permanent magnet  44  travels upward the magnetic flux applied to the piston  60  is decreased. When the force applied to the piston  60  by the magnetic flux of the permanent magnet  44  decreases enough the downward force applied to the piston  60  by the piston spring  38  overcomes the upward force due to the magnetic flux, and the piston spring  38  sealingly forces the piston  60  against the valve seat  66 . When the piston  60  is sealingly pressed against the valve seat  66  the fluid circuit between the ports  22 ,  26  of the pneumatically actuated fluid control valve  20  is interrupted and the pilot valve  20  is closed. 
   It will be understood that elements of the pneumatically actuated pilot valve  20  can cooperate to form a pneumatically actuated valve assembly  32 . The pneumatically actuated valve assembly  32  includes an annular valve assembly housing  30  which houses the magnet assembly  40 , the magnet driving chamber  34  and the actuator spring  52 . The control inlet port  24  is coupled to the valve assembly housing  30 . The entire valve assembly  32  fits over the piston cylinder  36  and is detachably secured to the pilot valve  20  in order for the pilot valve  20  to operate as described above. 
   Furthermore, when the valve assembly  32  is detached from the pilot valve  20  it can be removed from the piston cylinder  36 , inverted, and fit back over the piston cylinder  36  in its inverted position. The valve assembly  32  can then be detachably secured in its inverted position to provide a pneumatically actuated pilot valve that operates as described in detail below. Significantly, the detachable valve assembly  32  of the pilot valve  20  can be interchanged between its inverted and non-inverted positions without breaking the fluid circuit between the valve ports  22 ,  26 . 
   Thus, the pilot valve  20  can be interchanged in this manner between a normally closed valve and a normally open valve as required by the user. Additionally, a solenoid valve can be converted into a pneumatically actuated valve using the valve assembly  32 . In order to make such a conversion the valve assembly  32  can be substituted for a solenoid actuator as found in many existing solenoid valves by merely removing a solenoid assembly originally provided with the solenoid valve and fitting the valve assembly  32  over the existing piston cylinder  36  of the solenoid valve. The method for attaching and detaching the valve assembly  32  is the conventional method used for solenoid valve assemblies, requiring the removal and replacement of a single nut (not shown). 
   Referring now to  FIG. 2 , there is shown the pneumatically actuated pilot valve  80 . The pneumatically actuated pilot valve  80  is an alternate embodiment of the pneumatically actuated pilot valve  20  wherein the pneumatically actuated valve assembly  32  of the pilot valve  20  is inverted to provide the inverted pneumatically actuated valve assembly  92  of the pilot valve  80 . 
   The pilot valve  80  includes a piston  120  disposed within a piston cylinder  96 . When the piston  120  is in its extreme downward position it presses against a valve seat  126  formed by an annular portion of the valve seat chamber  124 . The pressure of the piston  120  against the valve seat  126  causes the fluid flow circuit between the pilot valve ports  82 ,  86  to be interrupted. The piston  120  is maintained in a spaced apart relationship with the valve seat  126  by an upward force due to the magnetic flux of the permanent magnet  104  acting against the downward force of the piston spring  98  when the actuation spring  112  forces the magnet assembly  100  toward the bottom of the magnet assembly cavity  110 . The pneumatically actuated pilot valve  80  is thus a normally open valve. 
   The permanent magnet  104  is an annular magnet within the magnet assembly  100 . The magnet assembly  100  is disposed within the magnet assembly cavity  110  surrounding the piston cylinder  96 . The actuator spring  112  is disposed within the magnet assembly cavity  110  pressing against the magnet assembly  100  at its upper end and against an actuator spring seat  116  at its lower end in order to bias the magnet assembly  100  downwardly. 
   In order to close the pilot valve  80  and interrupt fluid flow between the pilot valve ports  82 ,  86 , the piston  120  must be forced downward by the force of the piston spring  98 . In order to move the piston  120  in this manner, the upward force applied to the piston  120  by the magnetic flux of a permanent magnet  104  must be decreased by moving the permanent magnet  104  in the upward direction. 
   The permanent magnet  104  is moved upward away from the piston  120  by applying a positive air flow control signal  88  to the control inlet port  84 . When the positive air flow control signal  88  is driven into the control inlet port  84 , the magnet driving chamber  94  is expanded by the fluid pressure of the air flow control signal  88 . The expansion of the magnet driving chamber  94  caused by the air flow control signal  88  forces the magnet assembly  100  upward against the actuator spring  112  and moves the permanent magnet  104  away from the piston  120 . Upward travel of the permanent magnet  104  through the magnet cavity  110  causes the magnetic flux applied to the piston  120  by the permanent magnet  104  to decrease. 
   In response to the pressure of the positive air flow control signal  88  applied to the control inlet port  84 , the permanent magnet  104  travels a distance  108  through the magnet assembly cavity  110 . The decreasing force applied to the piston  120  by the permanent magnet  104  as it travels the distance  108  eventually allows the downward force applied by the piston spring  98  to overcome the upward force due to the magnetic flux of the permanent magnet  104 . This causes the piston  120  to be actuated. When the piston  120  is actuated, it is sealingly pressed against the valve seat  126  by the piston spring  98  thereby preventing fluid from flowing between the valve ports  82 ,  86 . 
   When the positive fluid flow applied to the annular magnet driving chamber  94  is withdrawn, the upward force applied to the magnet assembly  100  is decreased. This permits the actuator spring  112  to expand within the magnet assembly cavity  110 , thereby forcing the permanent magnet  104  in the downward direction. As the permanent magnet  104  travels downward the magnetic flux applied to the piston  120  increases. When the force applied to the piston  120  by the magnetic flux increases enough the force of the piston spring  98  is overcome and the piston  120  separates from the valve seat  126 . When the piston  120  is separated from the valve seat  126  the fluid flow between the ports  82 ,  86  of the pneumatically actuated fluid control valve  80  can resume. 
   Referring now to  FIG. 3 , there is shown the pneumatically actuated pilot valve  140 . The pneumatically actuated pilot valve  140  is an alternate embodiment of the pneumatically actuated pilot valve  20 . The pilot valve  140  is provided with two control input ports  144   a,b  which receive respective air flow control signals  148   a,b . The control input ports  144   a,b  communicate with respective magnet driving chambers  154   a,b  disposed on opposing sides of the magnet assembly  160  within the housing of the valve assembly  150 . The relative pressures of the air flow control signals  148   a,b  thus determine the vertical position of the magnet assembly  160  within the valve assembly housing. As the relative pressures of the air flow control signals  148   a,b  vary the magnet assembly  160  can travel a distance  168 . 
   When the pressure of the air flow control signal  148   b  exceeds the pressure of the air flow control signal  148   a  the magnet assembly  160  is moved to its upward position. Under these conditions magnetic flux from the permanent magnet  164  is not operatively applied to the piston  180 . Therefore, the piston spring  158  forces the piston  180  sealingly against the valve seat  186 , thereby preventing fluid flow between the valve ports  142 ,  146  by way of the valve chamber  184 . 
   When the pressure of the air flow control signal  148   a  is increased to exceed the pressure of  148   b  the magnet assembly  160  travels downward and the magnetic flux applied to the piston  180  by the permanent magnet  164  increases, thereby applying an increasing upward force to the piston  180 . Eventually, the upward force applied to the piston  180  overcomes the downward force of the piston spring  158  and opens the pilot valve  140 . If the pressures of the air flow control signals  148   a,b  are maintained equal to each other at this point the pilot valve  140  can remain open. When the magnet assembly  160  travels farther in the downward direction, the permanent magnet  164  closes the pilot valve  140  as previously described with respect to the pilot valve  20 . 
   Referring now to  FIG. 4 , there is shown the differential pressure diaphragm valve  190  operating under the control of the pneumatically actuated pilot valve  20 . The differential pressure diaphragm valve  190  includes a valve housing  192 . The interior of the valve housing  192  is divided into an upper valve chamber  188  and a lower valve chamber  216 . The upper valve chamber  188  is separated from the lower valve chamber  216  by a diaphragm  200 . 
   The lower valve chamber  216  is provided with a valve inlet port  212  and a valve outlet port  224  for permitting fluid flow therebetween. A valve outlet pipe  228  within the lower valve chamber  216  can communicate with the interior of the lower valve chamber  216  at one end and with the valve outlet port  224  at its other end. The interior end  218  of the valve outlet pipe  228  sealingly presses against an annular area of the lower diaphragm side  208  at the diaphragm region  220 . The lower diaphragm side  208  presses against the inner end  218  of the valve outlet pipe  228  to thereby prevent the entry of fluid from the lower valve chamber  216  into the valve outlet pipe  228  and the outlet port  224 , thereby sealing the differential pressure diaphragm valve  190 . 
   The diaphragm  200  is provided with at least a leak hole  204  therethrough. The leak hole  204  through the diaphragm  200  causes the pressure in the upper valve chamber  188  to equalize with the pressure in the lower valve chamber  216  when the diaphragm valve  190  is closed. The pressure within the upper valve chamber  188  causes downward force to be applied to the upper diaphragm side  216 . The magnitude of the downward force thus applied is related to the pressure within the upper valve chamber  128  and the surface area of the upper diaphragm side  222  upon which the pressure is applied. The downward pressure upon the diaphragm  200  generated in this manner forces the diaphragm  200  toward the inner end  218  of the valve outlet pipe  228 . 
   The pressure of the fluid within the lower valve chamber  216  applies an upward force to the lower diaphragm side  208 . The upward force applied to the lower diaphragm side  208  in this manner is related to the pressure of the fluid within the lower valve chamber  216  and the surface area over which the pressure is applied. However, the pressure applied to the lower diaphragm side  208  does not operate upon as much surface area as the pressure applied to the upper diaphragm side  222 , because the inner end  218  of the valve outlet pipe  228  prevents pressure from being applied to the diaphragm  200  within the diaphragm region  220 . Thus, the pressure equalized between the valve chambers  188 ,  216  by the leak hole  204  results in more downward force being applied to the diaphragm  200  than upward force. This differential downward force on the diaphragm  200  is the force which sealingly presses the diaphragm  200  against the inner end  218  of the valve outlet pipe  228  and closes the differential pressure diaphragm valve  190 . 
   When the diaphragm  200  is no longer pressing against the inner end  218  fluid within the lower valve chamber  216  can enter the valve outlet pipe  228 . The fluid in the outlet pipe  228  flows through the valve outlet pipe  228  and exits the diaphragm valve  190  by way of the outlet port  224 , provided that the upstream pressure of the diaphragm valve  190  is greater than the downstream pressure. Thus, the pneumatically actuated pilot valve  20  can control the differential pressure diaphragm valve  190  without the use of electricity and the pilot valve  20  is therefore intrinsically safe for controlling valves when disposed in hazardous environments. 
   When the air flow control signal  28  is applied to the control inlet port  24  of the pneumatically actuated pilot valve  20 , fluid is removed from the upper valve chamber  188  by way of the fluid line  196  and received into the valve inlet port  22  of the pneumatically actuated pilot valve  20 . As fluid is removed from the upper valve chamber  188 , fluid leaks into the upper valve chamber  188  from the lower valve chamber  216  by way of the leak hole  204  in the diaphragm  200 . 
   If the number and size of the leak holes  204  are selected such that fluid leaks through the leak holes  204  into the upper valve chamber  188  at a rate that is slower than the rate at which the fluid is removed from the upper valve chamber  188  through the feed line  196 , the pressure within the upper valve chamber  188  drops. As the pressure within the upper valve chamber  188  drops the amount of downward force applied to the upper diaphragm side  222  drops. Eventually, the downward force applied to the upper diaphragm side  222  becomes less than the upward force applied to the lower diaphragm side  208 . When this happens the diaphragm  200  is deflected upward and the diaphragm region  220  moves away from its sealing contact with the inner end  218  of the valve outlet pipe  228 . 
   When the diaphragm  200  is no longer pressing against the inner end  218  fluid within the lower valve chamber  216  can enter the valve outlet pipe  228 . The fluid in the outlet pipe  228  flows through the valve outlet pipe  228  and exits the diaphragm valve  180  by way of the outlet port  224 , provided that the upstream pressure of the diaphragm valve  180  is greater than the downstream pressure. Thus, the pneumatically actuated pilot valve  20  can control the differential pressure diaphragm valve  180  without the use of electricity and the pilot valve  20  is therefore intrinsically safe for controlling valves when disposed in hazardous environments. 
   While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.