Abstract:
An elbow fitting for a pneumatic product conveying system expands from the inlet pipe along the outer side of the elbow fitting to enable a layer of accumulated product particles to be formed so as to move at a lower velocity than the velocity of the incoming product stream while establishing a moving contact surface for deflecting incoming product particles toward the outlet pipe with a minimum of pressure resistance and product attrition. The outer portion of the elbow fitting is removable from the body portion to allow the outer portion to be replaced when wear becomes an issue in the performance of the elbow fitting. The wear member is affixed to the body portion by a flange that creates a seam extending from the step feature diagonally to the rear wall. A gasket or O-ring is trapped within the flange to seal the wear member against the body portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims domestic priority on U.S. Provisional Patent Application Ser. No. 61/175,039, filed on May 3, 2009, and entitled “Elbow Fitting with Removable Wear Member for Pneumatic Conveying System”, the content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to pneumatic transport systems and, more particularly, to a fitting for pneumatic pipes to permit a change in direction of the material being conveyed therein. 
       BACKGROUND OF THE INVENTION 
       [0003]    Conveying free flowing bulk material, such as granules, pellets, resins and free-flowing powders, injected into a high velocity stream of air contained within a pipe or tube is well known in industry as pneumatic conveying. Velocities of pneumatic conveying systems are in the range of 400 ft/min to 10000 ft/min and operate in different manners. In a dilute phase, the product is completely immersed in a rapid moving air flow with a low product to air flow ratio. In a dense phase, the product being conveyed moves in plugs through the conduits and operates at a relatively low velocity with a high product to air ratio. An intermediate phase operates at an optimized velocity with a medium product to air ratio as the product is partially dispersed in the gas flow while product will concentrate along the bottoms of horizontal runs of the conveying conduit. The higher the velocity of the air moving through the conduits of the conveying system, the higher the degradation of the product and the damage of pipes and elbows, particularly when abrasive product material is being conveyed through the system. Degradation of the product being conveyed and erosion of the conduits and elbows are caused by friction between interacting conveyed material and between the conveyed material and the walls of the pipes. 
         [0004]    Elbow fittings used in pneumatic conveying systems typically suffer wear at the elbow curve in line with the product flow into the elbow fitting, whether the elbow fitting is a short radius elbow or a long radius sweep elbow fitting. Free flowing bulk material flowing into the elbow fitting impact the curved surface of the elbow and are redirected. Centrifugal forces exerted on the particles moving around the outer surface of the elbow fitting generate friction, making the surface of the fitting warm to the touch, which also results in wear within the elbow fittings, particularly when abrasive particles are being conveyed. This heat can have a detrimental effect on the product being conveyed, particularly when the product is heat sensitive, such as plastic pellets on which the edges of the pellets will melt and adhere to the pipe. 
         [0005]    One known attempt to overcome the problem of changing direction in a pneumatic conveying system is found in U.S. Pat. No. 4,387,914, issued to Hammertek Corporation on Jun. 14, 1983. In this Hammertek patent, the elbow fitting is formed with a vortex opening in substantial alignment with the incoming product stream from the straight section of pipe. The vortex section emulates a blocked “T” fitting by providing a chamber in which a loose ball of product particles slowly rotates to deflect incoming product without causing excessive wear on the fitting. 
         [0006]    Another known attempt to overcome the aforementioned problems of changing directions in a pneumatic conveying system is taught in U.S. Pat. No. 5,288,111, issued to Waeschle Maschinenfabrik GmbvH on Feb. 22, 1994. In the Waeschle patent, an angularly disposed baffle plate is positioned within an expanded elbow section that has a greater cross-sectional area than the cross-section of the pipe carrying the incoming product. The expanded elbow cross-section increases in size from the inlet pipe by expanding inwardly toward the inner elbow side. The outer elbow side of the expanding section defines a linear relationship with the inlet pipe to direct the stream of product particles into engagement with the baffle plate that is oriented at between 55 and 65 degrees with respect to the axis of the inlet pipe. Accordingly, the expanded elbow cross-section is not intended to provide a flow of material along the outer side of the elbow fitting. Excessive wear on the baffle plate is, therefore, incurred due to the direct impact with the incoming product stream. 
         [0007]    Other deflector plate elbow fittings for pneumatic conveying systems are taught in U.S. Pat. No. 4,595,319, issued to Richard H. Cook for Cubeco, Inc. on Jun. 17, 1986; and in U.S. Pat. No. 4,733,889, issued to Edwin L. Haines for The Goodyear Tire and Rubber Company on Mar. 29, 1988. Both patents provide for an expanded elbow cross-section in conjunction with the obliquely arranged deflector plate or corresponding linear deflecting portion of the elbow outer side. In U.S. Pat. No. 4,606,556, issued to Robert E. Metzger for Fuller Company on Aug. 19, 1986, a stepped deflector plate is positioned at the outer elbow side to provide for a reduced wear elbow fitting. As the steps or ribs wear, the extra thickness of the material will permit a longer life for the fitting. In U.S. Pat. No. 4,995,645, issued to Josef Pausch for General Resource Corporation on Feb. 26, 1991, an open expanded area at the impact zone for the incoming particles is provided to create an accumulation of product in alignment with the incoming stream of product particles. The elbow section is expanded with a flare at 15 degrees to provide improved product flow after impacting the accumulated material. 
         [0008]    In U.S. Pat. No. 5,024,466, issued to Gregory R. Brotz on Jun. 18, 1991, the elbow fitting is formed with an expanded box section at the outer elbow side in which a screen is positioned to engage product particles. The expanded box section is coupled to a vacuum system to hold particles against the screen member to form an accumulation area of product into which the incoming product particles impact. The captured product particles are retained against the screen until worn sufficiently to be replaced by other product particles. While the structure of the Brotz patent provides a layer of product to absorb the impact of incoming product particles and thus reduce wear on the outer side of the elbow, the Brotz apparatus does not contemplate a moving flow of material along the outer elbow side. 
         [0009]    A solution to providing an elbow fitting with minimal wear characteristics can be found in U.S. Pat. No. 6,951,354, granted on Oct. 4, 2005, to Jerome I. Paulson, and in U.S. Pat. No. 7,300,074, granted on Nov. 27, 2007, to Jerome I. Paulson, both of which have been assigned to Pelletron Corporation. In these two patents, an elbow fitting expands from the inlet pipe along the outer side of the elbow fitting to define a generally triangularly shaped configuration that retains a layer of slowly moving particles being conveyed within the pneumatic conveying system along the outside surface of the fitting to deflect incoming product flow. In U.S. Pat. No. 7,300,074, a step feature was added to the outer surface structure of the elbow fitting to create a Bernoulli Effect causing the accumulated product particles to enter the air flow after the incoming flow of product particles has ceased. Even though wear characteristics were substantially reduced by the expanded elbow fitting, ultimately some wear along the outside surface of the elbow fitting occurs, which will require the replacement of the elbow fitting. 
         [0010]    Accordingly, it would be desirable to provide an expanded elbow fitting that will have enhanced service features that allows for replacement of the worn portion of the elbow fitting. 
       SUMMARY OF THE INVENTION 
       [0011]    It is an object of this invention to overcome the aforementioned disadvantages of the known prior art by providing an elbow fitting having a removable outer wear member for use in pneumatic conveying systems. 
         [0012]    It is another object of this invention to provide an elbow fitting that incorporates a flanged connection through which a removable wear member is connected to the body portion of the elbow fitting. 
         [0013]    It is a feature of this invention that the elbow fitting expands along the outer side of the fitting to provide an accumulation layer of product particles. 
         [0014]    It is an advantage of this invention that the incoming product particles impact into a slower moving accumulation layer along the outer side of the elbow fitting. 
         [0015]    It is yet another object of this invention to provide an elbow fitting that will allow for the outer wear member to be replaced when wear characteristics of the elbow fitting becomes a substantial factor in the operation of the elbow fitting in a pneumatic conveying system. 
         [0016]    It is another feature of this invention that the accumulation layer of product particles moves along the outer side of the elbow fitting at a slower velocity than the velocity of the incoming particle stream. 
         [0017]    It is still another feature of this invention that the moving accumulation layer of product on the outer side of the elbow fitting continually provides a fresh impact zone for incoming product particles. 
         [0018]    It is another feature of this invention that the expansion in depth of the outer side of the elbow fitting is accomplished through the formation of a step forming a sharp drop in the outer surface of the elbow fitting. 
         [0019]    It is another advantage of this invention that the step in the outer side of the elbow fitting creates a Bernoulli Effect to cause accumulated product particles to re-enter the air flow stream through the elbow fitting after the incoming flow of product particles has ceased. 
         [0020]    It is still another feature of this invention that the flange connecting the replaceable wear member to the body portion of the elbow fitting extends diagonally from the step feature in the elbow fitting to the rear wall thereof. 
         [0021]    It is another feature of this invention that the body portion of the elbow fitting incorporates both the inlet and outlet legs of the elbow fitting. 
         [0022]    It is yet a further feature of this invention that the expanded portion of the elbow fitting forms a triangular shape. 
         [0023]    It is still another advantage of this invention that the removable wear member can be removed to access the interior of the elbow fitting to clean out both the inlet and outlet legs of the elbow fitting and attached piping. 
         [0024]    It is yet another advantage of this invention that the seam formed between the replaceable wear member and the body portion does not detract from the performance of the elbow fitting. 
         [0025]    It is still another feature of this invention that the replaceable wear member and the body portion of the elbow fitting can be formed from different materials. 
         [0026]    It is a further advantage of this invention that the formation of the replaceable wear member from a harder material than the body portion of the elbow fitting will enhance the life of the elbow fitting without substantially increasing the cost of the elbow fitting. 
         [0027]    It is yet another feature of this invention that the shape of the elbow fitting provides an ideal aerodynamic shape for the flow of air and product through the fitting. 
         [0028]    It is yet another advantage of this invention that heat generated from friction along the outer side of the elbow fitting is minimal and eliminates the melting of plastic particles from engagement with the elbow fitting. 
         [0029]    It is a further advantage of this invention that the moving accumulation layer of product is uniformly distributed over an expanded triangular fitting configuration to provide a resultant reflective force upwardly toward the outlet pipe at approximately 90 degrees. 
         [0030]    It is still a further advantage of this invention that the elbow fitting provides a directional change for a pneumatic product conveying system with minimum pressure resistance and product attrition. 
         [0031]    It is still another advantage of this invention that the reduction in resistance results in lower energy requirement for imposing a change in direction for the flow of product through a pneumatic transport system. 
         [0032]    It is still another feature of this invention that the expanded shape for the outer side of the elbow fitting utilizes gravity and Bernoulli&#39;s Law to reduce the velocity of the accumulated product layer. 
         [0033]    It is yet another object of this invention to provide an elbow fitting with a replaceable outer wear member for pneumatic product conveying systems that is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
         [0034]    These and other objects, features and advantages are accomplished according to the instant invention by providing an elbow fitting for use in a pneumatic product conveying system in which the fitting expands from the inlet pipe along the outer side of the elbow fitting to enable a layer of accumulated product particles to be formed so as to move at a lower velocity than the velocity of the incoming product stream while establishing a moving contact surface for deflecting incoming product particles toward the outlet pipe with a minimum of pressure resistance and product attrition. The outer portion of the elbow fitting is removable from the body portion to allow the outer portion to be replaced when wear becomes an issue in the performance of the elbow fitting. The wear member is affixed to the body portion by a flange that creates a seam extending from the step feature diagonally to the rear wall. A gasket or O-ring is trapped within the flange to seal the wear member against the body portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The advantages of this invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
           [0036]      FIG. 1  is a side elevational view of a 90 degree elbow fitting having a replaceable wear member forming the outer portion of the elbow fitting incorporating the principles of the instant invention; 
           [0037]      FIG. 2  is a front elevational view of the elbow fitting depicted in  FIG. 1 , looking into the inlet portion of the fitting; 
           [0038]      FIG. 3  is a top plan view of the elbow fitting depicted in  FIG. 1 , looking into the outlet portion of the fitting; and 
           [0039]      FIG. 4  is an exploded side elevational view of the elbow fitting depicted in  FIG. 1 , the replaceable wear member being separated from the body portion. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0040]    Referring now to  FIGS. 1-4 , a 90 degree elbow fitting incorporating the principles of the instant invention can best be seen. The elbow fitting is intended for use in a pneumatic product conveying system utilizing only the dilute and intermediate phases of conveying by connecting to a conventional inlet pipe (not shown) and an outlet pipe (not shown) to provide a directional change for the path of travel of the product within the pneumatic system. The operation and general structural details of the expanded elbow fitting are disclosed in U.S. Pat. No. 6,951,354, issued to Jerome I. Paulson on Oct. 4, 2005, and in U.S. Pat. No. 7,300,074, issued to Jerome I. Paulson on Nov. 27, 2007, the contents of both issued patents being incorporated herein by reference in their entirety. 
         [0041]    The elbow fitting  10  is preferably formed from a durable metallic material, such as aluminum, cast iron or stainless steel, and includes an inlet portion  16  and an outlet portion  17 , each of which are sized to mate with the inlet pipe (not shown) and the outlet pipe (not shown) in a known manner, such as through a known compression coupling (not shown). Between the inlet portion  16  and the outlet portion  17 , the elbow fitting  10  includes an inlet transition section  18  and similar outlet transition section  19  connected, respectively, to the inlet portion  16  and the outlet portion  17 . Lastly, a curved expanded section  12  interconnects the inlet and outlet transition sections  18 ,  19 . 
         [0042]    The inlet and outlet transition sections  18 ,  19  transcend between a circular cross-section of the inlet and outlet portions  16 ,  17  and a generally triangular cross-sectional configuration of the curved expanded portion  12 . The triangular shape of the curved expanded portion  12  generally carries through the curved expanded portion  12 , except as required to curve from one direction to another at the apex  15  of the curved expanded portion  12 . Preferably, the triangular shape of the triangular cross-section of the curved expanded portion  12 , as is best seen in  FIG. 1 , has three curved apexes connected with the adjacent apex by a linear portion, one of which defines a bottom portion  14  having a width greater than the diameter of the inlet and outlet portions  16 ,  17 . 
         [0043]    The law of gravity and centrifugal force will urge bulk material particles flowing through the elbow fitting  10  outwardly into the expanded area  12  to provide a slurry layer of accumulated particles along the outer side  25  of the curved expanded portion  12  of the elbow fitting  10 . Due to the expanded cross-sectional area of the curved expanded portion  12 , compared to the inlet portion  16 , Bernoulli&#39;s Law requires that the velocity of the product particles will be slowed, as compared to the velocity of the bulk material product particles traveling through the circular inlet portion  16 . This layer of accumulated particles provides a moving impact zone for the incoming bulk material particles exiting the inlet portion  16 , which can then be deflected upwardly toward the outlet pipe  13  to effect a change of direction for the product being conveyed. 
         [0044]    The slowly moving layer  29  of accumulated product particles along the outer side  25  of the curved expanded section  12  also prevents an elevation of the temperature of the fitting  10  that would be normally attributable to friction from the impact of the incoming bulk material particles against the outer side of the fitting  10 . As a result, the bulk material will not be damaged by the elevation in temperature. 
         [0045]    The curved expanded section  12  is preferably formed with a curved outer side  25 , or for the sake of manufacturing convenience may be formed from a pair of linear portions  26 ,  27  interconnected by a curved portion  29 . The linear portions  26 ,  27  are not perpendicular but are disposed through an angular deflection of approximately 100 degrees, which is at approximately 80 degrees to the line of the incoming product stream through the inlet portion  16 . Since the layer of accumulated product particles along the outer side  25  serves to deflect incoming bulk material product particles toward the outlet portion  17 , the outer side  25  does not need to function as a deflector plate that needs to be disposed at 55 to 65 degrees with respect to the axis of the inlet portion  16 . 
         [0046]    The outlet transition section  19  provides a smooth transition from the triangular shape of the curved expanded portion  12  to the circular shape of the outlet portion  17 . Thus, the layer of accumulated product particles is directed back into the outlet pipe (not shown) to provide a continuous flow of particles through the elbow fitting, including the moving accumulated layer along the outer side  25  of the fitting. 
         [0047]    While the elbow fitting  10  described above is particularly suitable for use in either dense phase or dilute phase pneumatic product transport systems, one skilled in the art will recognize that the same principles for effecting a directional change for slurry product transport systems also apply. The elbow fitting  10  described above provides a lower resistance to effecting directional changes in the flow of bulk material product particles through the system. As a result, the energy required to effect directional changes is lower than known long radius elbows. Damage to the product being conveyed, or to the elbow fitting, due to frictional losses and impact, as is known for long radius elbow fittings, will be significantly reduced. Accordingly, superior results with lower energy costs are associated with the instant invention. The exchange of the removable member  40  of the elbow fitting  10  can be accomplished without removing the entire elbow fitting  10  from the conveying system and, thus, will save costs. 
         [0048]    The downward expansion of the outer surface  25  of the elbow fitting  10  is preferably accomplished through a sharp step  30  at the inlet transition portion  18 . The step  30  has a slope angle, as is best seen in  FIG. 1 , which is substantially greater than the slope angle of the inlet portion  16 , which is at a nominal zero angle, and the slope angle of the bottom linear portion  27  of the curved expanded portion  12 , which is at approximately 10 degrees. The formation of the step  30  creates a Bernoulli effect that allows the layer of accumulated product particles to be formed along the outer surface of the curved expanded portion  12 , but creates pressure differentials when the incoming flow of bulk material product particles into the elbow fitting  10  ceases, which will draw the particles from the accumulated layer along the outer surface  25  into the air flow through the elbow fitting  10 . Thus, when the pneumatic conveying system stops conveying product particles, the final flow of air through the system to clean product particles out of the system will effectively clean the particles from the elbow fitting  10  as well. 
         [0049]    Without the formation of the step  30 , it is believed that the stream of air entering the inlet portion  16  to purge the fitting  10  of remaining product particles would pass over the accumulated solids along the bottom floor  26  of the outer expanded surface  25  and strike the back wall  27  of the fitting  10 , causing a high pressure condition on the surface of the accumulated solids and preventing the particles from purging from the elbow fitting  10 . 
         [0050]    By modifying the bottom surface  26  of the elbow fitting  10  to extend the bottom inlet portion  16  along the line of the expected accumulated layer while opening the sides of the fitting  10  outwardly to form the curved expanded portion  12  to a point at which the sharp drop or step  30  could be incorporated, the purge air flow was directed upwardly into the main air flow entering the fitting  10  through the inlet portion  16 . The result is a reduction in pressure and the creation of pressure differentials relative to the accumulated particles permitting them to be purged back into the main air flow and discharged from the fitting  10 . The incorporation of the sharp drop or step  30  into the bottom surface  26  of the elbow fitting  10  improves purge performance substantially. 
         [0051]    With all the movement of the particles along the interior surface  21  of the elbow fitting  10 , even though substantially slowed through the expanded triangular portion  12 , the movement of the particles along the outer surface  25  of the elbow fitting  10  will still cause some wear to the elbow fitting  10 , particularly when abrasive bulk material is being conveyed through the system. When the wear in the expanded triangular portion  12  becomes a factor in the performance of the elbow fitting  10 , the fitting  10  needs to be replaced. Tests have shown that substantially all of the wear in the outer surface  25  of the fitting  10  occurs along the expanded triangular portion  12 , and particularly at the curved portion  29  and the back wall  27  where the particles make a directional transition from moving from the direction of the inlet portion  16  to the direction of the outlet portion  17 . 
         [0052]    To facilitate the replacement of the worn portions of the elbow fitting  10 , the elbow fitting  10  is preferably formed in two parts, a body portion  35  that extends from and incorporates the inlet portion  16  and the outlet portion  17 , and a removable wear portion  40  that encompasses the bottom floor portion  26 , the back wall portion  27  and the curved portion  29  interconnecting the linear floor and back wall portions  26 ,  27 . Accordingly, the removable wear portion  40  will suffer the majority of the wear characteristics for the elbow fitting  10 . The line of separation  45  between the body portion  35  and the removable wear portion  40  lies on a diagonal that extends from the step  30  to the outlet transition portion  19 . A gasket  39 , shown in dashed lines in  FIG. 2 , or an appropriate O-ring (not shown) is positioned along the line of separation  45  between the body portion  35  and the removable wear portion  40  to seal the line of separation  45 . 
         [0053]    The fitting  10  is provided with a mounting flange  42  having a first part  43  formed into the body portion  35  and a second part  44  formed into the removable wear portion  40  to mate against the first part  43 . The two parts  43 ,  44  of the mounting flange  42  can be coupled together by removable fasteners (not shown). When clamped together, the parts  43 ,  44  of the mounting flange  42  orients a finely machined line of separation  45  that is of minimal effect to the movement and positioning of the layer of accumulated product particles, as the accumulated layer of particles will only engage the line of separation  45  adjacent the step  30  and adjacent the back wall  27 . 
         [0054]    To replace the wear portion  40 , the fasteners clamping the parts  43 ,  44  of the mounting flange  42  together are removed and the removable wear portion  40  can be detached from the body portion  35  while the body portion  35  remains connected to the pneumatic conveying system (not shown) so that the entire elbow fitting  10  does not have to be removed from the pneumatic conveying system. A new removable wear portion  40  can then be installed by mating the parts  43 ,  44  of the mounting flange  42  and re-connecting the fasteners to clamp a gasket  39  along the line of separation  45 . Since the connection of the elbow fitting  10  to the pneumatic conveying system does not have to be disturbed, the replacement of the wear member  40  can be accomplished with minimal disruption to the operation of the pneumatic conveying system. 
         [0055]    Providing a removable wear member  40  on the elbow fitting  10  also provides the ability to clean the interior of the elbow fitting  10  and attached piping by accessing both of the inlet and outlet portions  16 ,  17  retained within the body portion  35  once the wear member  40  has been removed from the fitting  10 . Furthermore, the removable wear member  40  can be constructed from different material than the body portion  35  so as to enhance the wearability of the wear member  40 , or provide other operational advantages, without requiring that the entire elbow fitting  10  be formed of the same material as the replaceable wear member  40 . 
         [0056]    For example, for applications where the elbow fitting  10  is being used in the conveying of minerals, particularly minerals that provide an extreme wear condition within the elbow fitting  10 , the replaceable wear member  40  can be formed from carbon steel to provide enhanced wear characteristics, while the body portion is constructed from hardened steel. Since carbon steel is significantly more expensive than hardened steel, an elbow fitting  10  with only the replaceable wear member  40  being formed from carbon steel would be less expensive to manufacture than requiring the entire elbow fitting to be formed from carbon steel. As noted above, the wear member  40  can be replaced without scrapping the body portion  35  which provides a significant cost savings in high wear applications. 
         [0057]    As a further example, the use of the elbow fitting  10  in sanitary applications, such as food and pharmaceutical industrial uses, the entire elbow fitting  10  would be manufactured from stainless steel; however, the ability to remove the removable wear member  40  allows the entire pneumatic conveying lines to be cleaned between uses to maintain the sanitary conditions thereof without requiring the entire conveying line to be disassembled. By removing the wear member  40 , the operator has access to both directions of the conveying lines for cleaning purposes. Providing the elbow fitting with an internal electro-polished finish forms a near mirror finish on the interior of the elbow fitting  10  which virtually eliminates any porous areas within the elbow fitting  10  for material to gather. 
         [0058]    It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention.