MXPA98004181A - Aeread valve assembly - Google Patents

Abstract

The present invention relates to a valve assembly adapted to provide selective fluid communication between a gas supply and a pressure conduit and adapted to provide selective fluid communication between the pressure conduit and a bulk material handling structure, said assembly valve characterized in that it comprises: a valve housing including a valve body and a piston seat, the valve body includes a first end, a second end, a gate adapted to provide fluid communication with the pressure conduit, and a inner wall forming a chamber, the chamber is in fluid communication with the gate, the second end of the valve body includes a fluid conduit adapted to provide fluid communication between a gas supply and the chamber of the valve body, the piston seat has a first end removably coupled with the body of valve and a second end having an outlet gate adapted to provide fluid communication between the valve body chamber and the bulk material handling structure, a piston located within the chamber of the valve body between the second end of the body of valve and piston seat, the piston selectively slidable within the chamber between an extended position, where the piston makes sealing contact with the piston seat and insulates and closes the outlet gate, and a retracted position in the piston seat. where the piston is detached from the piston seat by opening the outlet gate, and a polarizing member extends between the second end of the valve body and the piston, the polarizing member biases the piston elastically from the retracted position to the extended position; where the piston seat is selectively removable from the valve body for inspection, repair on and replace

Description

AEREATOR VALVE ASSEMBLY Background of the Invention The present invention is directed to an air valve assembly for use with aerators such as air guns, and in particular to an air valve assembly having a sliding piston that includes a cylindrical edge to maintain correct alignment of the piston and a plurality of fluid conduits extending through a diaphragm of the piston. The storage of granular material and similar balumba in tanks, silos and the like creates many problems, particularly in the unloading of such materials in bulk since the bulk material has a tendency to stop flowing because of bedding and other problems. Aerators such as air guns are used in connection with the handling and aeration of bulk material. An aerator stores a large volume of air or some other gas under pressure in a pressure tank and then quickly releases the air instantaneously into the storage receptacle so that the blow of air causes any obstruction of the bulk material to be released. , thus allowing bulk material to flow freely from the storage container.

SUMMARY OF THE INVENTION A valve assembly is adapted to provide selective fluid communication between a pressurized gas supply and a pressure conduit, and is also adapted to provide selective fluid communication between the pressure conduit and the storage reservoir. The valve assembly includes a valve assembly having a valve body, a cap and a piston seat. The valve body includes a first tubular member having a first end, a second end and a gate adapted to provide fluid communication with the pressure conduit. The first tubular member includes an inner wall forming a chamber that is in fluid communication with the gate. The cap is attached to the second end of the first tubular member of the valve body and includes a fluid conduit extending through the cap that is adapted to provide fluid communication between the chamber of the first tubular member and the supply of pressurized gas. The piston seat includes a second tubular member having a first end that makes sealing contact with the first tubular member of the valve body and a second end that includes an outlet port adapted to provide fluid communication with the storage reservoir. There is a piston located within the chamber of the first tubular member of the valve body between the cap and the piston seat. The piston can be selectively slid within the chamber of the first tubular member between an extended position and a retracted position. The piston includes a central diaphragm and a cylindrical edge extending outwardly from the outer peripheral edge of the diaphragm. The diaphragm includes a first side and a second opposite side. One or more perforations extend through the diaphragm from the first side to the second side and form respective fluid passages through the diaphragm. The first tubular member includes a cylindrical bearing that forms part of the inner wall of the first tubular member. The cylindrical edge extends along and adjacent to the inner wall of the cylindrical bearing. A polarizing member, such as a helical spring, extends between the cap and piston and elastically biases the piston from its retracted position to its extended position. When the piston is in the extended position, the fluid passages of the piston diaphragm provide fluid communication between the fluid conduit of the cap and the gate of the first tubular member of the valve body, so as to provide fluid communication between the gas supply Pressurized and the pressure conduit, and the piston makes sealing contact with the piston seat and does not allow fluid communication between the outlet port of the piston seat and the gate of the first tubular member. When the piston is in retracted position, the piston allows fluid communication between the gate of the first tubular member of the valve body and the outlet port of the piston seat so that fluid communication is provided between the pressure conduit and the storage tank.

Brief Description of the Figures Figure 1 is a cross-sectional view of the aerator valve assembly of the present invention with the piston extended in the loading position. Figure 2 is a cross-sectional view of the aerator valve assembly shown with the piston retracted in the discharge position. Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2. Figure 4 is a cross-sectional view taken along line 4-4 of Figure 2. Figure 5 is a partial view in cross section of the beveled sealing surface of the piston seat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The aerator valve assembly 10 of the present invention includes a valve housing 11 having a valve body 12 in a general T-shape. The valve body 12 includes an elongated hollow cylindrical conduit or tube 14 that it has a longitudinal central axis 16. The tube 14 includes a first end 15 and a first flange 18 and a second end 17 having a second flange 20. The tube 14 includes a gate 21. The first flange 18 includes a seat with circular recess 22 extending along the internal circumference of the flange 18. The valve body 12 also includes a cylindrical extension conduit or centrally located tube 24 generally having a first end 26 fixed to the tube 14 and a second end 28 having a flange 30. The tube 14 includes an inner wall 31 forming a chamber 32 that is in fluid communication with the gate 21. The extension tube 24 includes a fluid conduit 34 which is in fluid communication with the gate 21 and the chamber 32. The flange 30 of the extension tube 24 is adapted to be connected to a pressure conduit or tank 36. A packing 38 is preferably provided between the flange 30 and pressure tank 36 to provide a tight seal between them. The fluid conduit 34 of the extension tube 24 is adapted to be placed in fluid communication with the chamber 40 of the pressure tank 36. Preferably the tubes 14 and 24 are made entirely of metal. The tube 14 of the valve body 12 includes a cylindrical seat 44 in general extending around the circumference of the inner surface of the tube 14 and extending longitudinally of the second end 17 of the tube 14 inwards to a position adjacent to the gate 21 A cylindrical bearing 46 is located within the cylindrical seat 44. The bearing 46 includes an inner cylindrical surface 48 that forms part of the inner wall 31 of the tube 14. The bearing 46 includes a first end 50 located adjacent to the gate 21 and a second end 52 located at the second end 17 of the tube 14. The inner surface 48 of the bearing 46 has approximately the same diameter as the diameter of the inner wall 31 of the tube 14, preferably the bearing 46 is a bearing that is self-lubricating with a steel back with a porous bronze internal structure, and an overlay of PTFE. A preferred bearing is that with Model No. 104DU48 manufactured by Garlock Bearing Inc. The valve housing 11 also includes a cap 58. The cap 58 includes a circular plate 59 in general which is adapted to be removably fixed by making contact with the cap. sealing with the flange 20 of the tube 14. The cap 58 includes a central hub 60 having a cylindrical side wall 62 in general and a generally circular and flat end wall 64 projecting from the plate 59 into the chamber 32 A generally circular rod 66 extends outwardly from an outer wall of the plate 59 towards an outer end 68. A fluid conduit 70 extends through the shell 58 of the outer end 68 of the rod 66 towards the inner end wall 64. of the hub 60. The conduit 70 includes a bore 72 with internal thread located at the outer end 68 of the stem 66 which is in fluid communication with a generally cylindrical bore 74 extending concentrically within the stem 66 towards the hub 60. The cylindrical bore 74 is in fluid communication with a generally conical-shaped bore 76 extending inward from the inner end wall 64 of the hub 60. The conical bore 76 converges inwardly of the inner end wall 64 of the hub 60 towards the cylindrical bore 74. An elastomeric O-ring 82 is located between the flange 20 and the plate 59 to create a hermetic seal between both .. The central hub 60, the rod 66 and the fluid conduit 70 are located concentrically around the central axis 16. As shown in Figure 1, the cylindrical side wall 62 of the hub 60 is separated from the cylindrical bearing 46 and the tube 14 creating an annular cavity 84. Between both. Preferably, the cap 58 is made entirely of metal. The rod 66 of the cap 58 is adapted to be connected to a valve 90, so that the valve 90 is in fluid communication with the fluid conduit 70. The valve 90 is also in fluid communication with a supply of pressurized gas 92, such as air or nitrogen, and with a gas outlet 94. The valve 90 can be a solenoid valve and is adapted to selectively place the fluid conduit 70 in fluid communication with the supply of pressurized gas 92 or with the gas outlet 94. The valve housing 11 also includes a piston seat 100. The piston seat 100 includes a generally cylindrical tube 102 having a hollow bore that forms a fluid conduit 104. The tube 102 extends from a first end 10 to a second end 108. The first end 106 of the tube 102 includes a generally cylindrical base 110 that extends outwardly from and around the tube 102. The base 110 has an ex-wall. 112 generally cylindrical. The outer wall 112 has a diameter greater than the diameter of the outer wall of the tube 102. The base includes a circular rim 114 extending outwardly. The piston seat 100 is located within the tube 14 of the valve body 12 so that the tube 102 is located concentrically about the axis 16. The outer wall 112 of the base 110 is located adjacent to the inner wall 31 of the tube 14 and the flange 114 of the piston seat 100 is located within the circular seat 22 of the first flange 18 of the valve body 12. An elastomeric O-ring 116 is located between the flange 114 and the flange 18 to create a seal between them. The portion of the tube 102 of the piston seat 100 extending beyond the base 110 is separated from the inner wall 31 of the tube 14 of the valve body 12 so that an annular chamber 118 is formed therebetween. The second end 108 of the tube 102 includes an outlet gate 119 and a generally cylindrical recess 120 formed along the inner circumference of the tube 102. As best shown in Figure 5, the second end 108 of the tube 102 includes a bevelled inner sealing surface 122. The sealing surface 122 is disposed at an angle "A" with respect to the inner wall of the tube 102 and the central axis 16. Preferably the angle WA "is approximately twenty-seven degrees. Piston 100 is made entirely of metal as well as cast aluminum The valve housing 11 also includes an extension tube assembly 128 preferably made entirely of metal The extension tube assembly 128 includes a generally cylindrical extension tube 130. having a first end 312 and a second end 134. The second end 134 of the extension tube 130 includes a flange 136. The first end 132 of The extension tube 130 is threaded and adapted to engage by screwing with a flange 138 with a bore with internal screwing. The flange 136 of the extension tube 130 is adapted to be removably connected to the first flange 18 of the tube 14 thus compressing the rim 114 of the piston seat 100 between the flanges 18 and 136. The tube 130 includes a fluid conduit 140 which is in fluid communication with the fluid conduit 104 of the piston seat 100. The tube 130 is located concentrically about the axis 16. The flange 138 is adapted to be fixed by bolting, welding or the like to a material handling structure to bulk such as a storage or storage container 144 having a chamber 146 adapted to receive and pass through there granular material. The fluid conduit 140 is adapted to be placed in fluid communication with the chamber 146 of the storage tank 144. The storage receptacle 144 may be a storage tank., silo, transfer duct, duct network or other handling structure of bulk material. The aerator valve assembly 10 also includes a piston 150. The piston 150 includes a diaphragm resembling a generally circular plate 152 and an annular rim 154. The rim 154 forms a hollow cavity 156 having an open end. The diaphragm 152 includes an outer peripheral rim 157. The rim 154 extends along the peripheral rim 157 around the perimeter of the diaphragm 152 and extends outwardly and generally perpendicular to the diaphragm 152. A plurality of perforations 158 are extending through the diaphragm 152 from an internal side 160 of the diaphragm 152 towards an external side 162 the diaphragm 152. The perforations 158 form respective fluid conduits. The perforations 158 are located symmetrically with respect to themselves around the center of the diaphragm 158 and about the axis 16.

The diaphragm 152 includes an outwardly projecting raised portion 164 which is located in the center of the outer side 162 of the diaphragm 152. The projection 164 is generally circular and includes a generally circular flat surface 166, and an angled circular sealing surface 168 that it extends around the circular perimeter of the flat surface 166 and is disposed at an angle with respect to the flat surface 166. The perforations 158 are located between the sealing surface 168 and the outer peripheral edge 157 of the diaphragm 152. The annulled sealing surface 168 is disposed at the same angle as the beveled sealing surface 122 of the piston seat 100, so that the sealing surface 168 and the sealing surface 122 join and form a seal in a cooperative and complementary manner when the sealing surfaces 122 and 168 they are coupled with one another. Preferably the piston 150 is made entirely of metal, such as forged aluminum. The piston 150 is slidably located within the chamber 32 of the tube 14 of the valve body 12 between the cap 58 and the piston seat 100. The edge 154 of the piston 150 is located towards the cap 58 and the projection 164 of the diaphragm 152 of the piston 150 is located towards the piston seat 100. The diaphragm 152 and the edge 154 of the piston 150 are located concentrically about the axis 16. The piston 150 is slidable longitudinally along the axis 16 between the piston seat 100 and the cap 58. As shown in Figure 1, the rim 154 of the piston 150 slidably engages the inner surface 48 of the cylindrical bearing 46 of the valve body 12 around the outer perimeter of the rim 154. The rim 154 also extends around the central hub 160 of the cap 58 and towards the annular cavity 84 formed between the hub 60 and the valve body 12. The edge 154 is transversely spaced from the cylindrical side wall 62 of the hub 60 to provide an annular space therebetween. An elastic helical spring 170 extends from the inner side 160 of the diaphragm 152 of the piston 150 to the inner surface of the plate 59 of the cap 58. The spring 170 extends around the circumference of the cylindrical side wall 62 of the central hub 60 of the capacete 58 and extends within the cavity 156 of the edge 154 adjacent to and along the internal perimeter of the edge 154 of the piston 150. The spring 170 elastically biases the piston 150 toward the piston seat 100 and toward the extended loading position. Preferably the spring 170 is made entirely of metal. The spring 170 provides a rapid movement of the piston 150 from the retracted discharge position, as shown in Figure 2, to the extended loading position, as shown in Figure 1, after evacuation of the compressed gas from the discharge duct. pressure 36. The spring 170 is designed to have a transverse external diameter such that the polarizing force provided by the spring 170 is directed in the outer diameter of the diaphragm 152 of the piston 150. This spring arrangement provides consistent piston concentricity and linear movement within of the chamber 32 of the tube 14 and inside the bearing 46 and thus a suitable seal of the piston 150 with the piston seat 100. The spring 170 recreates a seal between the piston 150 and the piston seat 100 after the discharge of the piston. pressurized gas from the pressure conduit 36 thus preventing the bulk material from passing through the outlet gate 119 and entering the annular chamber 118, dis decreasing the cycle time, and reducing the shock or impact forces. The piston 150 can slide longitudinally along the axis 16 between an extended load position as shown in Figure 1, where the piston 150 makes sealing contact with the second end 108 and the sealing surface 122 of the piston seat 100, and a retracted discharge position as shown in Figure 2 wherein the piston 150 is separated from the second end 108 of the piston seat 100. When the piston 150 is moved from the extended position to the retracted position, as shown in FIG. Figure 2, the piston 150 compresses the spring 170. The inner side 160 of the diaphragm 152 can make contact with the end wall 64 of the cap 58 and cover the fluid conduit 70 in the retracted position as shown in Figure 2. The cylindrical bearing 46 facilitates the longitudinal sliding movement of the internally disposed piston 150 and increases the life of the component, eliminates scratching of the metal, and ensures consistency in the sealing of the piston and displacement of the piston. The edge 154 of the piston 150 provides improved alignment and control of the piston as the piston 150 slides longitudinally within the valve body 12. During operation, when the piston 150 is in the extended load position, as shown in Figure 1 , the sealing surface 168 of the piston 150 makes sealing contact with the beveled sealing surface 122 of the piston seat 100 to create a metal-to-metal seal between them. Thus, a fluid conduit is sealed and sealed from the fluid conduit 70 in the shell 58, through the perforations 158, to the fluid conduit 140 of the piston seat 100 by the piston 150. However, when the Piston 150 is in the extended loading position as shown in Figure 1, a fluid conduit extends from the fluid conduit 70 of the cap 58 to the gate 21 and the fluid conduit 34 of the extension tube 24 of the body of the valve 12 through the perforations 158. As shown in Figure 1, a gas entering the conduit 70 will flow through it into the recess 156 formed by the rim 154 of the piston 150, through the fluid conduits 158 in the diaphragm 152 of the piston 150 towards the annular cavity 118 formed between the piston seat 100 and the tube 14. The gas flows from the annular chamber 118 through the gate 21 towards the fluid conduit 34 of the extension tube 24 and towards the camera 40 of the pressure tank 36. The gas flowing through the fluid conduit 70 is not allowed to enter the fluid conduit 104 by means of the piston 150. The metal-to-metal seal between the piston 150 and the piston seat 100 eliminates the need to use rubber or other elastomeric materials to provide the seal between the piston and the piston seat. As a consequence high temperatures, and potential contamination or degradation of the elastomeric seal or rubber that could otherwise occur, do not impair the operation of the aerator valve assembly 10. The aerator valve assembly 10 can be used at operating temperatures of up to about of 1093.3 ° C The valve assembly 10 can then be used in handling structures of bulk material such as preheating towers for cement kilns. When the pressure of the gas within the chamber 40 of the pressure tank 36 is equal to the pressure of the supply of as 92, the pressure on both sides 160 and 162 of the piston is equal and the system is static. When the desired gas pressure has been reached within the pressure tank 36, the valve 90 closes the flow from the supply of pressurized gas 92 to the aerator valve assembly 10. When the gas is to be discharged into the pressure tank 36 towards the storage tank 144, the valve 90 places the gas outlet 94 in communication with the duct 70 of the cap 58. As shown in Figure 2, the gas located on the inner side 160 of the piston 150 is evacuated from the assembly of aerating valve 10 through conduit 70 and gas outlet 94 to a place of lower pressure. This reduces the pressure of the remaining gas located between the piston 150 and the cap 58 on the inner side 160 of the piston 150 and creates a pressure differential with the gas pressure exerting a force on the outer side 162 of the piston 150. The pressure of the gas on the outer side 162 of the piston 150 is now greater than the pressure of the gas that it exerts a force on the inner side 160 of the piston 150. The gas pressure differential creates a differential in the force applied by the gas on the outer side 162 and the inner side 160 of the piston 150. The force of the gas acting on the side external 162 of the piston 150 of the higher pressure gas in contact with the outer side 162, which attempts to slide the piston 150 towards the retracted position, is greater than the accumulation of the forces exerted on the piston 150 by the pressure of the gas on the inner side 160 of the piston 150 plus the polarizing force exerted by the spring 170 on the piston 150, which try to slide the piston to the extended position. The differential between the gas pressures, and the resulting difference between the pressure forces of the gases applied on the piston 150, cause the piston 150 to slide from the extended load position, as shown in Figure 1, towards the cap 58 to the retracted discharge position, as shown in Figure 2, while compressing the spring 170. The movement of the piston 150 from the extended position to the retracted position breaks the seal created between the piston 150 and the piston seat 100. and opens a fluid conduit from the fluid conduit 34 of the extension tube 24, through the gate 21 to the conduit 104 of the piston seat 100. Thus the pressurized gas stored in the chamber 40 of the pressure tank 36 flows to through the conduit 34 and the gate 21 towards the annular cavity 118 where the gas flows between the piston 150 and the second end 108 of the piston seat 100, through the outlet gate 119 towards the duct 140. Gas flows from duct 140 to chamber 146 of storage tank 144 to release granular material therein. The gas stored within the chamber 40 of the pressure tank 36 is discharged through the fluid conduit 140 into the chamber 146 of the storage tank 144 at a discharge rate of approximately Mach one. Immediately after the gas in the pressure tank 36 is discharged, the pressure of the gas located on the outer side 162 of the piston is reduced such that the spring 170 can slide the piston 150 from the retracted position, as shown in Figure 2. , towards the extended position, as shown in Figure 1, to reseal the piston 150 with the piston seat 100. Then the loading and unloading cycles of the aerator valve assembly 10 are continued. The connection threaded between the extension tube 130 and flange 138 allows for easy removal and replacement of aerator valve assembly 10 from storage tank 144. In addition, since flange 18 of tube 14 is removably connected to flange 136 of tube 130, the tube 14 can be selectively removed from the tube 130 so that the piston seat 100, the piston 150 and the spring 170 can be easily removed and replaced from within the tube 14. The characteristics of the invention have been particularly shown and described in conjunction with the illustrated embodiment of the invention, however, it should be understood that these particular arrangements merely illustrate, and that the invention must be fully interpreted within the terms of the claims. Attached

Claims (20)

1. A valve assembly adapted to provide selective fluid communication between a gas supply and a pressure conduit and adapted to provide selective fluid communication between the pressure conduit and a bulk material handling structure, said valve assembly characterized in that it comprises: a valve housing including a valve body, a cap and a piston seat, the valve body includes a first end, a second end, a gate adapted to provide fluid communication with the pressure conduit, and an interior wall that As a chamber forms, the chamber is in fluid communication with the gate, the cap is attached to said second end of said valve body and includes a fluid conduit extending therethrough adapted to provide fluid communication between the supply of gas and the chamber of said valve body, the piston seat has a outlet gate adapted to provide fluid communication with the bulk material handling structure; a piston located within said chamber of the valve body between the cap and the piston seat, the piston selectively slides within the chamber between an extended position and a retracted position, the piston includes a diaphragm and an edge, the Diaphragm has a first side, a second opposite side and an outer peripheral edge, the edge extends along the outer peripheral edge of the diaphragm and out of the diaphragm, the edge located near and adjacent said inner wall of the valve body, the diaphragm includes one or more fluid passages extending through the diaphragm from the first side to the second side; and a polarizing member extending between the cap and the piston, the polarizing member biases the piston elastically from the retracted position to the extended position; wherein the piston is in the extended position said one or more fluid conduits of the diaphragm provide fluid communication between the fluid conduit of the cap and the gate of the valve body and the piston makes sealing contact with the piston seat and seals the gate of the piston seat outlet and does not allow fluid communication with the gate of the valve body, and when the piston is in the retracted position the piston allows fluid communication between the valve body gate and the piston seat outlet hatch .

2. The valve assembly according to claim 1 characterized in that the valve body includes a bearing that forms a portion of the inner wall of the valve body, said piston being slidable between the extended position and the retracted position adjacent to the bearing.

3. The valve assembly according to claim 2 characterized in that the bearing is generally cylindrical.

4. The valve assembly according to claim 1 characterized in that the edge is generally cylindrical and forms a cavity within the edge. .-

5. The valve assembly according to claim 4 characterized in that the polarizing member comprises a spring, the spring has a first end located within the edge cavity and a second end located adjacent to the shell.

6. The valve assembly according to claim 5 characterized in that the first end of the spring extends along and adjacent to the edge.

7. The valve assembly according to claim 5 characterized in that the cap includes a hub extending inward towards the chamber of the valve body, and the spring extends around the hub.

8. The valve assembly according to claim 7 characterized in that the hub of the shell forms an annular cavity with the valve body adapted to receive the edge of the piston and the second end of the spring.

9. The valve assembly according to claim 7 characterized in that the hub of the cap includes an end wall and the fluid conduit of the cap extends through the end wall, wherein the second side of the diaphragm of the piston is adapted to be coupled with the end wall of the cap bucket and to cover the fluid conduit in the cap when the piston is in the retracted position.

10. The valve assembly according to claim 1 characterized in that the piston seat is made of metal and said piston is made of metal so that when the piston is in the extended position and engages with the piston seat a metal seal is formed with metal between the piston and the piston seat.

11. The valve assembly according to claim 1 characterized in that the piston seat includes a sealing surface that forms the outlet gate, and the first side of the diaphragm of the piston includes a sealing surface, said sealing surface of said piston is adapted to be coupled in a manner complementary to the sealing surface of the piston seat when the piston is located in the extended position.

12. The valve assembly according to claim 1 characterized in that the first side of the diaphragm of the piston includes a sealing surface adapted to be coupled in a complementary manner with the piston seat, said one or more fluid conduits of the diaphragm located between the sealing surface of the diaphragm and the outer peripheral edge of the diaphragm.

13. The valve assembly according to claim 1 characterized in that the valve body includes a first generally tubular member extending between the first end and the second end of the valve body, the first tubular member includes the gate of the valve body, said seat The piston includes a second generally tubular member having a first end and a second end, the first end of the second tubular member makes sealing contact with the first tubular member, the second end of the second tubular member located within said first tubular member and includes the exit gate.

14. The valve assembly according to claim 13 characterized in that it includes an annular chamber formed between the first tubular member and the second tubular member, the annular chamber is in fluid communication with the gate of said first tubular member.

15. The valve assembly according to claim 14 characterized in that the valve body includes a third tubular member fixed to the first tubular member, the third tubular member includes a fluid conduit in fluid communication with the gate of the first tubular member, the fluid conduit of the third tubular member adapted to provide fluid communication with the pressure conduit.

16. The valve assembly according to claim 13 characterized in that it includes an extension tube fixed removably to the first end of the first tubular member of the valve body, said first end of the second tubular member is removably secured to the first end of the first tubular member through the extension tube.

17. A valve assembly adapted to provide selective fluid communication between a gas supply and a pressure conduit and adapted to provide selective fluid communication between the pressure conduit and a structure 2 for handling bulk material, said valve assembly characterized in that it comprises: a valve housing including a valve body and a piston seat, the valve body includes a first end, a second end, a gate adapted to provide fluid communication with the pressure conduit, and an inner wall forming a chamber, the chamber is in fluid communication with the gate, the second end of the valve body includes a fluid conduit adapted to provide fluid communication between a gas supply and the valve body chamber, the piston seat has a first end removably coupled with the valve body and a second end having an outlet gate adapted to provide fluid communication between the valve body chamber and the structure of the valve body. handling of bulk material; a piston located within the chamber of the valve body between the second end of the valve body and the piston seat, the piston selectively slidable within the chamber between an extended position, wherein the piston makes sealing contact with the piston. piston seat and thus seals and closes the outlet gate, and a retracted position where the piston is separated from the piston seat thus opening the outlet gate; Y 2S a polarizing member extending between the second end of the valve body and the piston, the polarizing member biases the piston elastically from the retracted position towards the extended position; wherein the piston seat is selectively removable from the valve body for inspection, repair and replacement.

18. The valve assembly according to claim 17 characterized in that the valve body includes a first generally tubular member extending between the first end and the second end of the valve body, the first tubular member includes the gate of the tubular body, the seat of the valve body, The piston includes a second generally tubular member having a first end and a second end, said first end of the second tubular member adapted to make sealing contact with the first tubular member, the second end of the second tubular member located within the first tubular member and includes the exit gate.

19. The valve assembly according to claim 18 characterized in that it includes an annular chamber formed between the first tubular member and the second tubular member, the annular chamber is in fluid communication with the gate of said first tubular member. 2b

20. The valve assembly according to claim 17 characterized in that it includes an extension tube removably connected to the first end of the valve body, the first end of the piston seat being removably secured to the first end of the valve body by the tube of extension. Summary of the Invention An aerator valve assembly adapted to provide selective fluid communication between a pressurized gas supply and a pressure conduit and adapted to provide selective fluid communication between the pressure conduit and a bulk material handling structure. The valve assembly includes a valve housing including a valve body, a shell adapted to be connected to the supply of pressurized gas, and a piston seat having an outlet gate adapted to provide fluid communication with the material handling structure. in bulk. The valve body includes a gate adapted to provide fluid communication with the pressure conduit. There is a piston located within a chamber of the valve body between the cap and the piston seat. The piston can be selectively slid from an extended position where the piston creates a metal-to-metal seal with the piston seat to create a seal that closes the outlet gate and a retracted position where the seal breaks. The piston includes a diaphragm which is adapted to engage the piston seat and which includes a plurality of fluid conduits adapted to provide fluid communication between the gas supply and the gate of the valve body. The piston includes a cylindrical edge extending from the diaphragm which slidably engages a bearing on the inner wall of the valve body to provide for correct alignment of the piston. A polarizing member extends between the piston and the cap and elastically biases the piston from the retracted position to the extended position.