Abstract:
An accumulator having an internal valve opened by applying air pressure to a diaphragm with a small solenoid to apply air to the diaphragm where the air is supplied from a pilot air supply. When the internal valve operated by the diaphragm opens, it snaps to a fully open position thereby opening the valve and uncovering a passageway leading to a filter for cleaning. The passageway is sufficiently wide that the resulting flow of air through the passageway is so explosive that air pressure on the filter is distributed over the surface area of the filter for a brief moment, blowing the dust on the filter free.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
     This patent application is based on and claims the priority of U.S. provisional patent application Ser. No. 60/967,065 filed 31 Aug. 2007 in the name of Stephen B. Maguire for an invention entitled “Diaphragm Actuated Blow-Back Valve and Reservoir”; the priority is claimed under the applicable provisions of 35 USC 119 and 35 USC 120. The disclosure of U.S. provisional patent application 60/967,065 is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     This invention relates to processing and conveyance of granular resin pellets and other powdery materials that must be filtered prior to use. More specifically, this invention relates to apparatus and methods of providing compressed air to a filter of a resin conveying device powered by vacuum, wherein the compressed air is applied in a direction opposite to that of the vacuum draw to clear the filter of dust and other unwanted particulate matter. 
     BACKGROUND OF THE INVENTION 
     In plastic fabrication manufacturing operations, it is not uncommon for the resin and similar particulate/powdery materials, consumed in the operation to be shipped to the manufacturing facility in heavy containers. These containers are delivered to a manufacturing facility and are stored until required for use in the manufacturing process. When the resin or other particulate matter is required for manufacture, the container is either emptied all at once, or portions of the particulate matter are removed from time to time on an as-needed basis.  The containers are usually too heavy to be lifted manually. Typically a vacuum loader is used to remove the contents. 
     These plants typically have a supply of “pilot” air, which is at pressure just above ambient, in conduits running throughout the plants. The pilot air is controlled by solenoid or other types of valves and is used for a variety of purposes in the manufacturing plant. 
     These plants also typically have vacuum lines running through the plant in which relatively low level, i.e. close to but below ambient pressure, is maintained. This moderate vacuum is used for various functions in the manufacturing process. 
     These plants also typically high pressure air in containers or tanks located at strategic positions within the plant. This high pressure air is typically used for air blown cleaning and sometimes for blow molding, if manufacturing of finished parts is a part of the plant operation. An air compressor may be present if the plant uses significant amounts of high pressure air. 
     A vacuum loader includes one or more tubes coupled to a vacuum source. The tube(s) is placed within the material storage container and the loader is activated. The resin or particulate material is drawn and conveyed by suction (resulting from vacuum generated by the vacuum loader) from the container to an intermediate location, such as a dryer, prior to being fed to an injection molding machine or an extruder. 
     Known vacuum loaders filter the air drawn from the material storage container to reduce the presence of contaminants within the particulate resin. It is common for the vacuum source to pull air from the top of a chamber portion of the vacuum loader, to assist in manufacturing the desired product.  
     Vacuum is used to convey resin pellets and resin recycle material into position for processing by molding or extrusion. It is also common to place a filter in the vacuum loader, beneath the top chamber, so that all of the air drawn (typically upwardly) through the vacuum loader must pass through the filter. As a result, the air drawn through the top chamber of the vacuum loader is largely free of dust particles and other contaminants. When the vacuum drawing stops, however, the dust and contaminants remain, clogging the filter. This reduces the quantity of air that may be drawn by vacuum through the filter when the system resumes operation. It also compromises the level of suction furnished by the vacuum source. 
     To overcome this, it is known to blow compressed air downwardly through the filter, in a direction opposite to the direction in which the vacuum is drawn when the system operates. This “blast” of compressed air is typically provided by an air accumulator in conjunction with a solenoid operated valve. A typical accumulator includes an associated reservoir for accumulating a large volume of compressed air within a reservoir space adjacent to the filter. A solenoid actuated valve is positioned between the reservoir and the filter. When the valve is in a closed position, pressurized air accumulates within the reservoir of the air accumulator. Upon opening the solenoid valve, compressed air within the air accumulator, being exposed to the vacuum environment in the vacuum loader, evacuates the accumulator as an air blast, which is directed downwardly through the filter. The air blast applies more air to the filter at a greater pressure, for a longer time period and in a direction opposite that of the air drawn through the filter during normal operation. This reverse flow of air against the normal direction of flow of air drawn by the vacuum source cleans the filter by blasting the dust and contaminants off the filter. Without such an accumulator, the volume and pressure  of air available to blow dust off the filter in the vacuum loader is limited by the amount of air that can flow through the pilot air supply line. 
     A solenoid operated valve and an air accumulator provide an improvement over other known vacuum loaders and filters that do not have such components. The resulting improvement however, has several limitations. For example, the resulting air blast from the accumulator acts only on a single area of the filter. This is because flow of air into the vacuum loader chamber, where the filter to be cleaned is located, is limited by the size, namely the cross-sectional area, of the internal orifice of the actuating solenoid, through which the “cleaning blast air” must pass. Even when using an accumulator having an associated reservoir, the resulting air blast is limited by the cross-sectional area of the passageway through the solenoid valve, thereby only clearing a correspondingly sized area on the filter; the remainder of the filter is not cleaned. 
     While simply providing a larger solenoid valve is a possible solution, there are significant cost increases associated with larger solenoid valves. Costs associated with providing a solenoid valve large enough to cover the entire filter is prohibitive. Even with this approach, there is still reduced effectiveness of the vacuum source due to the remaining clogged portions of the filter, when a solenoid valve having a passageway with a cross-sectional area less than the area of the filter is used. 
     A second approach to this problem is to provide multiple outlets for the air blast against the filter using multiple reservoir chambers and/or multiple solenoid valves. However, this does little to improve the situation. The available “plant” air flow in modern  plastic resin processing facilities is simply too limited to provide sufficient volume and pressure for a multi-outlet configuration to function effectively. 
     As is apparent, there is a continued need for a highly efficient device to provide periodic air blasts in sufficient volume, at sufficient force over a sufficient area to effectively clean filter units of vacuum loaders, especially those in plants concerned with conveying granular resin pellets and regrind material to injection molding machines and extruders for fabrication. 
     SUMMARY OF THE INVENTION 
     In one of its aspects, this invention provides a high pressure accumulator chamber having a valve that is opened by applying air pressure to a diaphragm through action of a small solenoid. When the valve actuates, it snaps to a fully open position. Opening action of the valve opens a passageway that is preferably about one (1″) inch in diameter, leading from an accumulator chamber to a vacuum loader filter that is to be cleaned. 
     The one inch diameter passageway is sufficiently wide that the resulting flow of air through the passageway is “explosive” and so is effective as a cleaner, as the “explosive” flow of air uniformly distributes itself over the essentially the entire surface area of the filter for a brief moment. As a result this invention provides a blowback device able to substantially remove all unwanted particles from the filter of a vacuum loader or other vacuum powered device. 
     The invention preferably includes a blowback assembly for attachment to a vacuum loader. The blowback attachment includes a housing, preferably cylindrical in shape, having a high pressure accumulator chamber, a pilot air chamber, a chamber housing the stem of the  diaphragm valve and an exhaust conduit leading from the high pressure accumulator chamber to the vacuum loader selective fluid communication of the high pressure accumulator chamber with an air filter of the vacuum loader. The diaphragm of the diaphragm valve assembly isolates a pilot air chamber. The diaphragm is an elastomeric diaphragm positioned between the pilot air chamber and the exhaust conduit, and is operatively connected to a valve stem. In a preferred embodiment, the valve stem is positioned to close an intermediate passageway, that is approximately 1 inch in diameter, which connects the exhaust conduit and the high pressure accumulator chamber. Sealing engagement of the valve stem in the intermediate passageway is controlled by allowing the elastomeric diaphragm to flex in response to a pilot air introduced into the pilot air chamber 
     In a preferred embodiment, the blowback dust removal attachment of the invention is fabricated using three co-axial cylindrical casing components with a lower cylindrical casing component housing the high pressure chamber, a middle cylindrical casing component housing the valve stem, and an upper cylindrical casing component housing the pilot air chamber. The three cylindrical casing components are retained together by a plurality of rod-like elements such that the interior wall surfaces of the cylindrical casing components form the cylindrical chamber walls. The resulting housing is preferably a rigid, inelastic material able to withstand fluid pressures in excess of 200 lbs/in 2 . 
     In operation, the valve stem is actuated by movement of the diaphragm. Pilot air is supplied to the pilot air chamber by from a source of plant air at low pressure, with pilot air flow into the pilot air chamber controlled by a solenoid actuated valve. The influx of pilot air into the pilot air chamber causes flexing of the diaphragm away from the pilot air chamber, leading to movement and a rapid opening of the valve stem. This actuation of the valve stem  opens the passageway connecting the exhaust conduit and the high pressure accumulator chamber so the pressurized gas (which is typically air), within the high pressure accumulator effectively immediately passes through the exhaust conduit and into a line, connected to the vacuum source, in which the filter is located. The pressurized gas is thereby directed by the conduit towards the air filter in the line leading to the vacuum source, in a direction opposite that of the normal flow of air therein, thereby largely if not entirely blowing dust and undesired particles off the filter. 
     As the pressurized air evacuates the accumulator chamber, the pilot air leaves the pilot air chamber since the solenoid valve, when the solenoid is not actuated, provides open communication with ambient air. This allows the diaphragm to return to its neutral state and the valve stem immediately moves in response to an associated spring to reseal the passageway between the accumulator chamber and the exhaust conduit. High pressure air then resupplies the accumulator chamber with pressurized air and the blowback dust removal attachment is ready for another next cycle. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric exterior view of a blowback assembly manifesting aspects of the invention. 
         FIG. 2  is an exploded isometric view of the blowback assembly illustrated in  FIG. 1 . 
         FIG. 3  is a front exterior elevation of the blowback assembly illustrated in  FIGS. 1 and 2 .  
         FIG. 4  is a vertical section taken at arrows A-A in  FIG. 3 . 
         FIG. 5  is an isometric view of a conventional vacuum loader equipped with a blowback assembly as illustrated in  FIGS. 1 through 4 . 
         FIG. 6  is a front elevation of the vacuum loader—blowback assembly illustrated in  FIG. 5 . 
         FIG. 7  is a view identical to  FIG. 6 , showing some dimensions of the vacuum loader—blowback assembly in the preferred embodiment of the invention. 
         FIG. 8  is an exploded view of a motor and motor cover located at the top of the vacuum loader equipped with the blowback assembly, as illustrated in  FIGS. 5 ,  6  and  7 . 
         FIG. 9  is a top view of the motor cover on the vacuum loader shown in  FIGS. 5 through 8  taken normally to the top exterior surface of the motor cover. 
         FIG. 10  is a sectional view taken at lines and arrows B-B in  FIG. 9 . 
         FIG. 11  is an isometric view similar to  FIG. 5  with part call-out numbers included. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention relates to processing and conveyance of granular resin pellets and other powdery materials, which materials during or after conveyance must be filtered prior to use. More specifically, this invention relates to apparatus and methods of providing compressed air to an air filter of a vacuum powered and vacuum conveying resin transport device wherein compressed air is applied to the filter, in a direction opposite that through which air is drawn by the vacuum, to clear the filter of unwanted particles. The invention provides a filter  “blowback” device providing a blast of compressed air, in a reverse direction through a filter to clear the filter of dust. 
     Referring to  FIGS. 1 through 7 , a vacuum loader manufacturing aspects of the invention is illustrated with a blowback assembly designated generally  5  and a vacuum source designated generally  10 . In  FIGS. 1 through 4 , the blowback assembly  5  of the invention is illustrated in greater detail. As illustrated in these figures, blowback assembly  5  includes a housing that may be cylindrically shaped and comprised of at least three separate cylindrical casing components designated generally  15 ,  25 , and  30  which are coaxial, contiguous, and coupled together by internal rod elements  31 . 
     Referring to  FIG. 2 , the first cylindrical casing component  15  includes a preferably cylindrical wall with an open upper end  16  and an open lower end  17  and an open passageway therebetween. This passageway forms the accumulator chamber  60  of the blowback assembly  5 . To form accumulator chamber  60 , a bottom disk  20  is provided sized to concentrically fit within open lower end  17  of cylindrical casing component  15 . Bottom disk  20  further contains a lip  23  with a diameter approximately the same as the exterior side of the first cylindrical casing component. Lip  23  retains bottom disk  20  within lower end  17  of first cylindrical casing component  15 . Spaced between lip  23  and lower end  17  of first cylindrical casing component  15  is a sealing mechanism, which may be an O-ring or a rubber gasket, or equivalent structure. The sealing mechanism provides a fluid-tight seal between lower end  17  and bottom disk  20 , thereby sealing lower end  17  of first cylindrical casing component  15 . 
     The bottom disk  20  may further include a pressurized air fitting  21 . Fitting  21  is preferably received within a hole  22  that is generally centered in bottom disk  20 . Fitting  21   desirably threadedly engages hole  22 . Fitting  21  may be L-shaped such that one end may be received by bottom disk  20  and the remaining end may receive a pressurized air hose, which has not been illustrated in the drawings. Fitting  21  receives pressurized air flowing into the accumulator chamber  60  of first cylindrical casing component  15 . Fitting  21  is removably secured to a pressurized air hose, as needed. 
     Referring to  FIGS. 1 through 7 , coupled to open upper end  16  of first cylindrical casing component  15  and closing the upper end of the accumulator chamber  60 , is a second cylindrical casing component  25 . Second cylindrical casing component  25  is also preferably comprised of a cylindrical wall with an open upper end  26 , an open lower end  27 , and a passageway extending therethrough. While second cylindrical casing component  25  is preferably of external diameter that is the same as the external diameter of the cylindrical casing component  15 , open lower end  27  of second cylindrical casing component  25  is of a slightly reduced diameter to interconnect with and be received by first cylindrical casing component  15 . As shown in  FIGS. 2 and 4 , the open lower end  27  of the second cylindrical casing component  25  is desirably slightly stepped-down diameter such that the stepped down portion is approximately the same diameter as the interior of first cylindrical casing component  15  while the remainder of the second cylindrical casing component  25  is the same external diameter as first cylindrical casing component  15 . The stepped-down diameter portion  27  of second cylindrical casing component  25  concentrically fits within and frictionally engages the interior surface of first cylindrical casing component at open upper end  16  of the first cylindrical casing component  15  such that the two cylindrical casing components connect. A sealing mechanism, such as an O-ring or a gasket, may be slidingly engaged over the stepped down portion of the second cylindrical casing component  25  such  that, when the first and second cylindrical casing components  15 ,  25  are connected, the sealing mechanism provides a fluid seal therebetween. 
     While upper end  26  of the second cylindrical casing component  25  is also open, as illustrated in  FIG. 2 , like open lower end  27  this opening is also of reduced diameter. Upper end  26  of second cylindrical casing component  25  further includes an annular flange  28  extending perpendicularly inwardly from the cylindrical side wall of second cylindrical casing component  25 , having a reduced diameter opening passing therethrough. Annular flange  28  may be integrally molded as a part of second cylindrical casing component  25  or may be a separate element or insert that is adhesively bonded or otherwise fixed to the open upper end  26  of the second cylindrical casing component  25 . Preferably, annular flange  28  is beveled approaching the center opening therein so as to form a conical shape. This conical shape facilitates opening and closing of the valve stem  51  of the diaphragm valve assembly  35 . 
     Open upper end  26  of second cylindrical casing component  25  is also adapted to receive a third cylindrical casing component  30 . Like first and second cylindrical casing components  15  and  25 , third cylindrical casing component  30  is similarly sized. As shown in  FIGS. 1 through 4 , third cylindrical casing component  30  has a closed upper end  32  and an open lower end  33 , defining a cavity therein. The cavity serves as a pilot valve chamber and receives bursts of pressurized air to open and close the accumulator. Open lower end  33  of third cylindrical casing component  30  has a relatively uniform external diameter that is approximately the same as the external diameter of the second cylindrical casing component. Third cylindrical casing component  30  is secured to second cylindrical casing component by tie rods  31 . A diaphragm  50  of the solenoid-actuated valve system is secured between third  cylindrical casing component  30  and second cylindrical casing component  25  to form a fluid seal therebetween. 
     As illustrated in  FIGS. 1 and 3 , the third cylindrical casing component  30  may further include an air hose fitting  34  extending therefrom. Fitting  34  is preferably received in the side wall of the third cylindrical casing component  30  by a hole or it may alternatively be received by top wall  32  of third cylindrical casing component  30 . Fitting  34  preferably threadedly engages the wall of third cylindrical casing component  30 . The externally facing end of fitting  34  is adapted to receive a pressurized air hose, which has not been shown in the drawings. Accordingly, fitting  34  acts as a conduit for conveying pressurized pilot air into a pilot valve chamber, which is defined by the interior cavity of the third cylindrical casing component  30 . Fitting  34  may be secured to the pressurized air hose by any suitable method. 
     Each of the three cylindrical casing components may be any material that can withstand high pressure conditions without compromising the integrity of the cylindrical casing components  15 ,  25 ,  30 . Each cylindrical casing component is constructed to withstand pressure greater than 200 pounds per square inch. 
     The exterior surfaces of the cylindrical casing components are preferably of uniform diameter of approximately 3 inches. Each cylindrical casing component may be of any length. The preferred final length of the assembly, e.g. the axial length of all three cylindrical casing components combined is approximately nine and three-sixteenths (9 and 3/16) inches. Most preferably, the first cylindrical casing component provides the longest part of the housing such that the accumulator chamber  60  is the largest of the chambers within the  cylindrical casing components. The second cylindrical casing component provides a slightly smaller internal chamber with the third providing the smallest internal chamber. 
     As noted above, and illustrated in  FIG. 4 , the three cylindrical casing components  15 ,  25 ,  30 , when assembled, form a plurality of chambers therein. As seen in  FIGS. 2 and 4 , such chambers are formed by the exterior walls of the first, second and third cylindrical casing components, the interior surface of the second cylindrical casing component  25  and by the diaphragm  50 . 
     Referring to  FIG. 4 , interior walls extending from the annular flange  28  of the second cylindrical casing component  25  in part define a first interior chamber  40  and a second interior chamber  45 . The first interior chamber  40  extends from and is in fluid communication with the reduced diameter opening of the upper open end  26  of the second cylindrical casing component  25 . This chamber is preferably cylindrical with a longitudinal axis co-axial with that of second cylindrical casing component  25 . First interior chamber  40  is preferably sized to receive a spring mechanism  55  such as the coil spring disclosed herein. 
     At the opposing end of first chamber  40  is opening  41  As shown in  FIG. 4 , opening  41  provides a passageway from first chamber  40  into second chamber  45 ; first chamber  40  and second chamber  45  are in fluid communication with each other by way of opening  41 . Opening  41  is preferably of reduced diameter relative to that of first chamber  40 . Most preferably, the diameter is provided by annular shoulder  42  extending perpendicularly from chamber  40  walls to form opening  41 . As discussed further herein and illustrated in  FIG. 4 , shoulder  42  provides support for spring  55 , facilitating functioning of diaphragm valve assembly  35 .  
     Second chamber  45  is also cylindrical. However, the longitudinal axis of second chamber  45  is perpendicular to that of both first chamber  40  and second cylindrical casing component  25 . As further shown in  FIG. 4 , at one end of second chamber  45  opening  41  leads to first chamber  40 . In addition to opening  41 , second chamber  45  further includes a second opening  46  and a third opening  47 . Second opening  46  is preferably in direct opposition to opening  41 . Second opening  46  is formed at approximately lower end  27  of second cylindrical casing component  25  such that second opening  46  provides a fluid communication pathway between second chamber  45  and lower end  27 . Furthermore, as illustrated in  FIG. 4 , when first cylindrical casing component  15  and second cylindrical casing component  25  are interconnected, the walls forming second opening  46  serve to demarcate the second cylindrical chamber component  45  from first cylindrical casing component housing accumulator chamber  60  and form a passageway therebetween. This passageway is preferably approximately one inch (1″) in diameter so as to maximize the volume of pressurized fluid reaching the targeted filter. 
     The interior walls at second opening  46  may be beveled to approximately a 45 degree angle. This bevel facilitates sealing engagement with a sealing element  52  of the diaphragm valve assembly  35  so as to form a valve between the chambers of second cylindrical casing component  25  and accumulator chamber  60  and the first cylindrical casing component  15 . The beveled portion of second opening  46  engages an opposing beveled portion of sealing element  52  to provide a removable seal between accumulator chamber  60  of the first cylindrical casing component  15  and the chambers of the second cylindrical casing component  25 . 
     The third opening  47  of the second interior chamber  45  is provided through a side wall of the second cylindrical casing component  25 . Based on the illustrated orientation of second cylindrical chamber component  45 , third opening  47  is perpendicular to opening  41 , second opening  46 , and the longitudinal axis of the second chamber  45 . As further illustrated in  FIGS. 5 and 6 , third opening  47  is adapted to align with a chosen inlet or outlet of the vacuum leader or vacuum source  10 . Most preferably, the third opening  47  is adapted to communicate with the chosen inlet or outlet of the vacuum loader or vacuum source  10  such that pressurized air flow exiting the second interior chamber  45  by way of the third opening  47  is directed toward and through the filter of the vacuum source  10  or vacuum loader or other vacuum device so as to eliminate unwanted particles therein. 
     As indicated above, extending through the second cylindrical casing component is a diaphragm valve assembly  35 . More specifically, the diaphragm valve assembly  35  is comprised of a diaphragm  50 , a valve stem  51 , a sealing element  52 , a coupling mechanism  53 , an O-ring  54 , and a spring  55  wherein the assembly  35  is sized to extend between the upper end  26  of the second cylindrical casing component  25  to and through the third opening  46  of the second chamber  45 . Diaphragm  50  is a disk-shaped element with diameter that is equal to that of the exterior diameter of the second and third cylindrical casing components  25 ,  30 . Diaphragm  50  is preferably sized to extend between upper end  26  of the second cylindrical casing component  25  and lower end  33  of third cylindrical casing component  30  such that when third cylindrical casing component  30  is coupled to second cylindrical casing component  25 , diaphragm  50  forms a fluid seal therebetween so that diaphragm  50  acts as a sealing member between the second and third cylindrical casing components  25 ,  30 . Diaphragm  50  further provides isolation of pilot valve chamber  36 , within third cylindrical casing component  30 . Diaphragm  50  is preferably an elastomeric polymer which is adapted to retain its elasticity when flexed, without rupturing under high pressure conditions. The  material used to manufacture diaphragm  50  should be adapted to both flex along annular flange  28  of second cylindrical casing component and along the beveled portion contained therein and return to a normal flat condition in response to rapid pressure fluctuations and without rupturing 
     Extending perpendicularly from diaphragm  50  is valve stem  51 . Valve stem  51  is cylindrically shaped with a uniform diameter that is slightly smaller than that of opening  41 . Valve stem  51  is sized to extend from diaphragm  50  through first and second chambers  40 ,  45  of second cylindrical casing component  25  to and through second opening  46  of second chamber  45 . In one embodiment, valve stem  51  is comprised of a relatively rigid and inflexible material, desirably a metallic composition, and coupled to diaphragm  50 . Valve stem  51  may be bonded or glued to diaphragm  50  or secured to diaphragm  50  using mechanical coupling means, so as to maintain the seal between second and third cylindrical casing components  25 ,  30  during operation. 
     Coupled to the end of valve stem  51  opposing diaphragm  50  by coupling mechanism  53  is sealing element  52 , which is preferably a disk-shaped polymeric composition selected and sized to provide sealing engagement for second opening  46  from accumulator chamber  60 . One end of sealing element  52  is preferably beveled so as to sealingly engage the opposing beveled region of second opening  46 . The beveled portions of sealing element  52  and second opening  46  provide complementary regions forming an openable seal between accumulator chamber  60  and second chamber  45 . Sealing element  52  may be any composition useful in sealing a valve or passageway between and/or across a pressure gradient.  
     Sealing element  52  is coupled to valve stem  51  by way of coupling mechanism  53 . Preferably coupling mechanism  53  is a screw, bolt or the like that threadedly engages an interior passageway within valve stem  51 . As shown in  FIG. 4 , sealing element  52  may be further secured to valve stem  51  by way of an O-ring  54 , which is securable within an annular groove extending about an exterior side of the sealing element  52 . The O-ring is sized to provide constrictive force on sealing element  52  such that it is secured to shaft and/or coupling mechanism  53 , but without hindering the engagement of sealing element  52  with second opening  46 . 
     Spring  55  of the valve assembly is adapted to slide over valve stem  51  so as to be secured between diaphragm  50  and sealing element  52 . More specifically, the spring is preferably a coil spring with an internal diameter slightly larger than the diameter of valve stem  51 . 
     Referring to  FIG. 4 , diameter of spring  55  is slightly larger than opening  41  of the first chamber and has a length closely approximating the distance between annular shoulder  42  and diaphragm  50 , when installed as illustrated. Spring  55  provides actuation for the diaphragm valve assembly to move along the longitudinal axis of the blowback assembly  5 . More specifically, spring  55  provides actuation to oscillate sealing element  52  into and away from a sealing engagement with second opening  46 . Such oscillations are provided by the flexibility of diaphragm  50  and in response to a pilot air supply introduced into the pilot valve chamber. 
     As shown in  FIGS. 1 and 3 , the bottom disk  20 , first, second and third cylindrical casing components  15 ,  25 ,  30  and diaphragm valve assembly  35  are all coupled together by one or more rods  31 . Specifically, as shown in  FIG. 2 , each of bottom disk  20 , second and third cylindrical casing components  25 ,  30  and diaphragm  50  contain a plurality of holes  65  spaced about the periphery of each of these parts. These holes are positioned to align along the length of the blowback assembly  5  and are sized to receive a rod  31  with a plurality of threads at each end. 
     As illustrated in  FIG. 4 , rod  31  is sized to pass from the holes  65  in bottom disk  20 , through the holes in diaphragm  50 , through the hole in the second cylindrical casing component  25 , and, ultimately, through the holes in the third cylindrical casing component  30 . 
     A securing mechanism  66 , such as a nut, may be coupled to both ends of rod  31  as shown such that the opposing forces generated by each nut tighten the pieces of the blowback assembly  5  and, effectively, seal the interior side of the blowback assembly  5  and each of the chambers contained therewithin. 
       FIGS. 1 through 4  illustrate three such rods  31  as being secured therein, however, the invention is not limited to this configuration. A greater number or fewer rods may be used, so long as the seals discussed herein are effective. Finally, the invention is not limited to rod construction and assembly. 
     The blowback assembly  5  may be coupled to a plate so as to be easily secured to a vacuum source  10 . More specifically, plate  70  is preferably metallic and uses at least one U-bolt  75  securing the blowback assembly  5  thereto. As illustrated in  FIG. 2 , plate  70  preferably contains a hole  71  passing therethrough which is adapted to align with third opening  47  of second cylindrical casing component  25  and a corresponding hole in the vacuum source (not illustrated) that is juxtaposed to the filter. Such alignment is further facilitated by an extension member  72 . More specifically, extension member  72  aligns third opening  47 , hole  71 , and the hole in the vacuum source. In a further embodiment, the extension member  72  is sealingly coupled to both the third opening  47  and the vacuum source such that fluid passes therebetween without escaping from either location. Accordingly, when the blowback assembly  5  is secured to the plate  70  by way of U-bolt  75 , the third opening  47  is in fluid communication with the hole passing through the plate such that air exiting the second cylindrical casing component  25  passes therethrough and into the vacuum source. 
     As illustrated in  FIGS. 5 and 6 , blowback assembly  5  and plate assembly are preferably secured to vacuum source  10  such that the third opening  47  of the second cylindrical casing component  25  is in fluid communication with the interior of the vacuum source  10 . Preferably the blowback assembly  5  is positioned relative to the air filter of the vacuum source such that any air flow exiting the third opening passes through the filter in a direction opposite, or at least perpendicular, to the ordinary flow of air drawn by the vacuum source. 
     The blowback assembly  5  may be secured to the vacuum source by any suitable method. For example, the plate assembly may be secured to the vacuum source by a plurality of screws or bolts such that the blowback assembly  5  and the vacuum source are in fluid communication. 
     In operation, the blowback assembly  5  accumulates pressurized air, release of which is controlled by the solenoid actuated valve (which is conventional and is not illustrated) of the diaphragm valve assembly  35 . Blowback assembly  5  is ordinarily in the configuration illustrated in  FIG. 4  and is connected to the vacuum source as discussed above and as illustrated in  FIGS. 5 through 7 . In this configuration, pressurized air is pumped into the accumulator chamber  60  by hoses coupled to fitting  21  until a desired pressure is reached in accumulator chamber  60 . Preferably, the pressurized air within accumulator chamber  60  is at  least 200 lbs/in 2  (two hundred pounds per square inch) and the blowback assembly remains in this configuration while the vacuum source is used for transporting particulate resin material via suction. 
     When the vacuum source is no longer in use, blowback assembly  5  utilizes air pressure within accumulator chamber  60  to clean the air filter of the vacuum source. Specifically, after the vacuum source turns off, a pilot supply of air is briefly and quickly introduced via fitting  34  into the pilot valve chamber within third cylindrical casing component  30 . The air is introduced in sufficient volume and at sufficient pressure to cause elastomeric diaphragm  50  to rapidly flex downwardly (considering the orientation showing in  FIG. 4 , for example) against the beveled surface of the annular upper wall  28  with the second cylindrical casing component  25 . This, in turn, causes sealing element  52  to move downwardly, considering  FIG. 4 , snapping away from the second opening  46 . High pressure air within accumulator chamber  60  then flows from accumulator chamber  60  into second chamber  45  of second cylindrical casing component  25  where the air is directed through third opening  47  and onto the vacuum source. Because axis of third opening  47  is perpendicular to the direction vacuum pulls air through the filter, the pressurized air forced out of third opening  47  blows through the air filter essentially uniformly over the air filter surface in a direction opposition of normal air flow of air as drawn by the vacuum. Opening  47  is approximately 1 inch in diameter, facilitating the elimination of dust and particles trapped on the filter. 
     As the burst of air is released from the accumulator chamber into the vacuum source, thereby cleaning the filter, pressure within the pilot valve chamber is almost immediately relieved. This reduces pressure on the diaphragm and on spring element  55  Accordingly,  force exerted on diaphragm  50  by spring element  55  causes diaphragm  50  to return to its neutral configuration. Such movement by diaphragm  50  away from the upper annular wall  28  of second cylindrical casing component also causes sealing element  52  to reengage with the beveled walls of second opening. Accordingly, the blowback assembly quickly returns to its neutral configuration. Accumulator chamber  60  is then resupplied with pressurized air through fitting  21 , so the blowback assembly is ready for the next cycle. 
     The invention is advantageous through use of the accumulator and the solenoid valve. Having an accumulator allows the loader to accumulate a larger volume of air immediately adjacent to the filter. The solenoid valve is relatively small and requires only a pilot air supply to actuate the valve to an open position. When the solenoid valve opens, it snaps open, immediately leaving an approximately 1 inch length and diameter passage uncovered. The resulting flow of air is so intense and explosive, air pressure on the filter is effectively uniformly distributed over the entire surface area of the filter for a very brief moment, and essentially all of the dust is blown free from the filter.