Patent Publication Number: US-8985400-B2

Title: Micro particle flow facilitator

Description:
FIELD OF THE INVENTION 
     This invention relates generally to facilitating the flow of dry granular material, and, more specifically to, although not limited to, facilitating the flow of fine powders through a storage chamber exit orifice. 
     BACKGROUND OF THE INVENTION 
     Granular material is typically held in storage chambers until use. The ability of the material to flow through the exit orifice of the chamber depends in large part upon the particle size, shape and moisture content. The typical funnel shape of the storage chamber, along with gravity helps facilitate the flow of the material, and for most granular material that is enough. An excellent example of free-flowing material is sand. Fine powders, on the other hand, are much more resistant to flow due to their cohesive nature and/or bulk density and consequently need more than just the help of gravity to keep them flowing. An excellent example is baking flour, which is very resistant to flow and consequently needs the scraping action of a “flour sifter” to exit its chamber. In an effort to achieve a steady, even flow of material, the most common method of solving this flow problem is vibrating and/or pressurizing the entire storage chamber. However, there are still some powders that will not flow evenly, even with the use of vibration and air pressure. As a result, the phenomena of caking, bridging and rat holing are often seen in fine powders. 
     Referring now to  FIG. 1 , there is shown three prior art diagrams illustrating the phenomena of caking, bridging and rat holing that fine powders often exhibit. Caking occurs when a large amount of powder sticks to the sides of the chamber, and refuses to flow downward. Bridging occurs when the powder forms a bridge over the exit orifice, and effectively prevents the flow of material entirely. Rat holing occurs when a channel forms down the middle of the chamber, and a large amount of powder is left clinging to the sides of the chamber. In general, each of these three problems is seen at the entrance to the exit orifice. 
     Accordingly, there is a need for a flow facilitator that addresses the above-described problem phenomena often encountered at the entrance to the exit orifice. 
     SUMMARY OF THE INVENTION 
     The invention satisfies this need. In one aspect of the invention, the invention is a unique micro particle flow facilitator comprising: (a) a bourdon tube having a flexible duct capable of expanding and contracting in response to pulsations of a pressurized fluid, the duct being hollow, closed-ended and having an inlet port; and (b) a fluid pulsator for providing the pulsations of a pressurized fluid to the inlet port of the bourdon tube, the pulsator being in fluid-tight communication with the inlet port of the bourdon tube and having a fluid inlet port for connection to a source of pressurized fluid. 
     In another aspect of the invention, the invention is a flow distribution system for dispensing powders and other granular material. The system comprises the flow facilitator of the invention operatively disposed within a granular material dispensing chamber. 
     In a third aspect of the invention, the invention is a method for dispensing powders and other granular material using the flow distribution system of the invention. 
    
    
     
       DRAWINGS 
       These and other features, aspects and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings where: 
         FIG. 1  is a diagram of the common phenomena of caking, bridging and rat holing that fine powders often exhibit; 
         FIG. 2A  is a diagram of a bourdon tube usable in the invention; 
         FIG. 2B  is a cross-sectional view of the bourdon tube illustrated in  FIG. 2A , taken along line AA; 
         FIG. 3A  is a diagram illustrating the furling of a bourdon tube; 
         FIG. 3B  is a diagram illustrating the unfurling of a bourdon tube; 
         FIG. 4  is a diagram of a first micro particle flow facilitator having features of the invention; 
         FIG. 5A  is a first diagram of the furling/unfurling motion of a bourdon tube within a dispensing chamber; 
         FIG. 5B  is a second, more detailed diagram of the furling/unfurling motion of a bourdon tube within a dispensing chamber; and 
         FIG. 6  is a diagram of a second micro particle flow facilitator having features of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well. 
     In one aspect of the invention, the invention is a unique micro particle flow facilitator  10 , illustrated for example in  FIG. 4 , comprising a bourdon tube  12  and a fluid pulsator  14 . 
     A bourdon tube  12  useable in the invention is illustrated in  FIG. 2A . The bourdon tube  12  comprises a flexible duct  16  capable of expanding and contracting in response to pulsations of a pressurized fluid, typically a pressurized gas such as pressurized air. The flexible duct  16  is hollow, closed-ended and has an inlet port  18 . 
     The bourdon tube  12  is typically C-shaped and the flexible duct  16  is a flattened, curved tube (see  FIG. 2B ). When pressure is applied to the interior of the flexible duct  16 , the expansion of the duct  16  tends to straighten out the duct  16 . Accordingly, pulsating pressure applied to the duct  16  causes the duct  16  to alternatively unfurl (straighten) and furl (curl back to its normal C-shape). Rapid pressure pulsations can cause the closed end  20  of the duct  16  to vibrate.  FIG. 3  illustrates the vibration, expansion and contraction motion of the bourdon tube  12 . When the bourdon tube  12  is disposed within a granular material dispensing chamber  22 , the alternating straightening and curling of the duct  16  continuously agitates granular material within the dispensing chamber  22 , to thereby minimize material flow problems, such as caking, bridging and rat holing. 
     In one embodiment, the duct  16  of the bourdon tube  12  has an approximate diameter of 1.29 inches, and is made of beryllium copper. Other appropriate materials can also be used. In this bourdon tube  12  embodiment, the duct  16  has an approximate height of 0.38 inches. 
     The fluid pulsator  14  is used for providing the pulsations of a pressurized fluid to the inlet port  18  of the bourdon tube  12 . The pulsator  14  is in fluid-tight communication with the inlet port  16  of the bourdon tube  12  and has a fluid inlet port  24  for connection to a source of pressurized fluid. 
     In a typical embodiment, the fluid pulsator  14  is a pulsating pneumatic valve which can be any of a wide variety of pulsating valves known to those of skill in the art. One such pulsating valve is an electronically controlled four port direct operated poppet solenoid valve Series VQD1000 sold by SMC Corporation of Tokyo, Japan. 
     Other forms of fluid pulsators  14  are also possible, including various mechanical pulsators. Possible mechanical pulsators  14  include (1) A rotary motion pulsator driving a cam against a bellows or piston connected to a hydraulic fluid filled tube or hose connected to the bourdon tube  12 ; (2) an electric motor driving a cam against bellows or piston connected to a hydraulic fluid filled tube or hose connected to the bourdon tube  12 ; and (3) an electric solenoid or linier motor driving against a bellows or piston connected to a hydraulic fluid filled tube or hose connected to the bourdon tube  12 . 
     In another aspect of the invention, the invention is a flow distribution system  26  for dispensing powders and other granular material. The distribution system  26  comprises the flow facilitator  10  described above operatively disposed within a granular material dispensing chamber  22 . As noted above,  FIG. 4  illustrates a typical flow distribution system of the invention. 
     The dispensing chamber  22  has an upper portion  28 , a lower portion  30 , side walls  32  and a bottom  34 . The bottom  34  defines an exit orifice  36 . The dispensing chamber  22  has a vertical longitudinal central axis  38  disposed through the exit orifice  36 . 
     The side walls  32  in the lower portion  30  of the dispensing chamber  22  typically converge toward the exit orifice  36 . Most typically, the side walls  32  in the lower portion  30  of the dispensing chamber  22  terminate at the periphery of the exit orifice  36 . 
     In some embodiments, the dispensing chamber  22  is enclosed such that the dispensing chamber  22  can be pressurized. In such embodiments, the dispensing chamber  22  further comprises a pressurizing connection  40  for attachment to a source of pressurized gas. Pressurizing the dispensing chamber  22  can frequently facilitate the downward flow of granular material through the dispensing chamber  22 . 
     The bourdon tube  12  is typically disposed within the dispensing chamber  22  in a plane perpendicular to the central axis  38 . Also, it is typical to dispose the bourdon tube  12  proximate to the side walls  32  in the lower portion  30  of the dispensing chamber  22 . Where the bourdon tube  12  is C-shaped, the bourdon tube  12  is most typically disposed concentrically around the central axis  38  of the dispensing chamber  22 , as illustrated in  FIGS. 4 ,  5 A and  5 B. 
     Typically, but not necessarily, the fluid pulsator  14  is placed external to the dispensing chamber  22 . 
     A third aspect of the invention is a method for dispensing powders and other granular material using the flow distribution system  26  of the invention. The method comprises the steps of: 
     (a) providing the flow distribution system  26  for dispensing powders and other granular material described above; 
     (b) connecting a source of pressurized fluid to the fluid inlet port  24  of the pulsating valve  14 ; 
     (c) placing the granular material into the dispensing chamber  22 ; 
     (d) controlling the flow of pressurized fluid with the fluid pulsator  14  to direct pulsations of pressurized fluid to the bourdon tube  12 ; and 
     (e) dispensing the granular material from the dispensing chamber  22  via the exit orifice  36 . 
       FIG. 6  illustrates the method of the invention applied to the field of micro-sandblasting with abrasive powders and other surface conditioning media. The media is placed inside the pressurized dispensing chamber  22 . The pulsating valve  14  with an inlet port  24  coupled to a pressured gas source, such as a pressurized air source, controls the movement of the bourdon tube  12  inside the pressurized dispensing chamber  22 . The pressurized dispensing chamber  22  along with the bourdon tube  12  along with the movement of the bourdon tube  12  keeps the fine powder flowing steady as a second pressurized gas source carries the powder out and through a media blast nozzle  42 . 
     Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth herein above and described herein below by the claims.