US3712681A

US3712681A - Pneumatic conveying apparatus for light material

Info

Publication number: US3712681A
Application number: US00199851A
Authority: US
Inventors: J Marino; R Demaison
Original assignee: Pfizer Inc
Current assignee: Pfizer Inc
Priority date: 1971-11-18
Filing date: 1971-11-18
Publication date: 1973-01-23
Anticipated expiration: 1990-01-23

Abstract

Light dry material, such as asbestos, fed through a tubular screw pneumatic conveyor forms a sealing plug against blow-back in the free space between separated sections of the feed screw. The seal is consolidated by a restrictive orifice plate, which may be flexible, in the sealing plug zone having a passageway smaller than the tubular housing and larger than the shaft. The length of the sealing plug is varied by adjusting a spacing device connected to one of the screw sections to provide the most effective seal for a particular material. Variable spacing is provided, for example, by removable spacer plates or a movable flange which can be locked into one of many axial positions. The air-borne light material is mixed with water to form a slurry for application to a surface.

Description

United States Patent Marino et al.

[4 1 Jan.23,1973

[54] PNEUMATIC CONVEYING Primary Examiner-Richard E. Aegerter APPARATUS FUR LIGHT MATERIAL Assistant ExaminerH. S. Lane [75] Inventors: Joseph J. Marino, Ridgefield; Atmmeyf'Anhur Connolly et Raymond J. Demaison, Old Greenwich, both of Conn. [57] ABSTRACT [73] Assign: Pfizer Inc. New York, Light dry material, such as asbestos, fed through a tubular screw pneumatic conveyor forms a sealing plug I:lledi 1971 against blow-back in the free space between separated [211 App] NOJ 199,851 sections of the feed screw. The seal is consolidated by a restrictive orifice plate, which may be flexible, 1n the I sealing plug zone having a passageway smaller than [52] US. Cl. ..302/20, 198/64, 198/216, the tubular housing and larger than the shaft. The

222/413 239/428 length of the sealing plug is varied by adjusting a spac- [Sl] Int. Cl. ..B65g 53/04, B05b 7/06 ing device connected to one of the screw sections to [58] Flew Search 0 198/64 provide the most effective seal fora particular materi- 222/413 239/428 al. Variable spacing is provided, for example, by removable spacer plates or a movable flange which [.56] References Cited can be locked into one of many axial positions. The UNITED STATES PATENTS air-borne light material is mixed with water to form a slurry for application to a surface. l,553,539 9/1925 Kinyon ..l98/2l4 X 18 Claims, 8 Drawing Figures g e r Vibrator y 70 w Ail ,p Q al Elite! I 40 3g 32 i 56 QJL'I .41 It 1.1; 1. I

:1 h 0 a 7": I h -44 s4 50 40 1122- e:--',.-.0 e m '6 PNEUMATIC CONVEYING APPARATUS FOR LIGHT MATERIAL BACKGROUND OF THE INVENTION nozzle 14 from which a slurry 15 is discharged through Apparatus l includestubular screw conveyor housing l,954,005 and 3,370,890 for use with dry Portland ceing a variety of light dry materials without'blow-back.

SUMMARY In accordance with this invention the effectiveness of the sealing plug is improved by a restrictive orifice plate in the sealing plug zone, which helps to compact the material in the plug. The orifice plate may be flexible or rigid depending upon the particular material being conveyed. The length of the sealing plug may be varied to improve its efficiency for a particular material by connecting at least one of the screw sections to a spacing device, comprised for example by removable spacer plates or an axially adjustable flange. The distance between the sections may thus be varied, for example, from about 2 to 10 inches and more particularly between 3 and 6 inches to form an adequate sealing plug for a light material such as fibrous asbestos.

BRIEF DESCRIPTION OF THE DRAWINGS I Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following, description in conjunction with the accompanying drawings wherein similar referencecharacters refer to similar parts and in which:

FIG. I is a partially diagrammatic side view in elevation of one embodiment of this invention in a slurry forming system; 1

FIG. 1A is a fragmentary top plan view of the discharge portion of the embodiment shown in FIG. 1;

v FIG. 2 is an enlarged cross-sectional side view in elevation ofthe embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view taken through FIG. 2 along the line 3-3;

FIG. 4 is a cross-sectional view taken through FIG. 2 along the line 44;

FIG. 5 is a cross-sectional view taken through FIG. 6 along the line 5-5;

FIG. 6 is a partial side view in elevation ofa modified form of the left-hand side of the apparatus shown in FIG. 2; and

FIG. 7 is a fragmented view partially broken away in I cross-section of a modified central portion of the apparatus shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 1A is shown pneumatic conveying apparatus 10 which discharges an airborne mixture of light dry material supplied to hopper 12 to a mixing 18 mounted on carriage 20. Hopper I2 is connected to feed one end of housing 18 through inlet connection 22. Vibrator 24. for example compressed air-operated, insures a consistent feed of a light dry material from hopper I2into inlet 22. Hopper 12 has a diagonally open top 30 to facilitate loading material into it.

Light material It is, for example, dry fibrous asbestos which is difficult to convey and feed because of its softness compressibility and hygroscopic tendency. More free-flowing light, as well as heavy materials can also be fed into apparatus 10 and such materials may be hard or soft, porous or non-porous or vary in size or particle distribution. Material 11 typically is a porous refractory or insulating composition which is mixed with water to form a slurry which is applied to cover a surface with an insulating coating. Insulation is thus applied to steam turbines, steel building structures, steam pipes or boiler casings. Such insulating material usually has a particle size varying from about 300 mesh to as inch diameter and a density of about 10 to 200 lb. per cubic foot. The ultimate slurry usually contains about 25 percent by wt. of water, but the amount of water may be varied to provide the desired slurry consistency.

Inlet 22 connects hopper 12 with the interior of tubular housing 18 within which is mounted shaft 32 inserted in

suitable bearings

34 and 36. Shaft 32 is rotated by a suitable motor and speed reducer 38 unit (shown in FIG. 2) connected to sprocket 40 on the end of shaft 32, which is connected to motor and speed reducer 38 unit by sprocket chain 42 (also shown in FIG. 2). 1

a A pair of screw conveyor sections

orhelical screw flights

44 and 46 are separately mounted on shaft 32 with a free section P (later described in detail) between their adjacent ends. Conveyor flights or

sections

44 and 46 may also be discontinuous, such as in the form of suitably inclined plates or paddles (not shown). Conveyor screw section 44 is connected to the end of shaft 32 adjacent bearing 36 by a variable spacing device 48, which is later described in detail in conjunction with FIGS. 2, 3 and 6. Variable spacing device 48 permits the distance between adjacent ends of

screws

44 and 46 to be varied and thus lengthen or shorten section P.

FIGS. 2 and 4 show sealing zone P between the ends of

screw conveyor flights

44 and 46 in which a restricted orifice plate I00is inserted perpendicularly within housing I8 between connecting flanges 102 of housing I8. The effective opening or orifice diameter 104 of orifice plate is larger than shaft 32 and smaller than the inside diameter of housing 18 to form a restriction in sealing plug 84. Effective opening or orifice diameter 104 varies to provide optimum sealing and feeding for particular materials. For fibrous asbestos it has, for example, a diameter of about 4 inches and is normally circular. Effective opening 104 may, however be non-circular such as square, oblong or star-shaped for particular materials.

Orifice plate 100 may be made of a flexible material such as chemically resistant rubber, or a rigid material such as stainless steel-depending on the material being fed. Orifice plate 100 ranges for example from one-sixteenth to one-quarter inch thick and is for example three-sixteenths inch thick. It is advantageously and economically made of relatively stiff pure gum rubber, which is dimensionally stable under operating conditions. For a 6-inch free diameter within housing 18, it has for example an orifice diameter of 3% inches. This in conjunction with 2 inch diameter shaft provides a radial clearance between shaft 32 and orifice diameter 104 of five-eighths inch. This clearance for different operating conditions advantageously varies for example from one-half to l inch. Orifice plate 100 may also be made of stiffer material such as, mild or stainless steel (No. 3 l6 for example) or a strong plastic. It may likewise be made of spring steel, in which case the orificc in said plate may be substantially equal to the diameter of shaft 32, in which case said plate will be provided with radial slits extending from the orifice. Said slits in combination with the spring nature of the steel plate will provide, under pressure from conveyed material 11, an effective opening greater than the diameter of shaft 32 through which material 11 may pass.

FIG. 7 shows a modified sealing zone PB in which there is no orifice plate 100 between flanges 102 of housing sections 18B contiguous to sealing plug 84B. Careful adjustment of variable spacing device provides an adequate seal for a specific material without an orifice plate 100.

The right-hand end of conveyor housing 18 is designated its discharge end because an air-borne mixture of light dry material 11 is discharged through outlet connection 50 and elbow 52 into connecting hose 54 which conveys material 11 to mixing nozzle 14. Hose 54 is for example, about 50 to 300 feet long or longer, and about 1% to 2 inches in diameter. The required air is furnished to housing 18 through inlet coupling 56. Compressed air is provided from compressed air source 58, which is for example an air compressor, through valve 60 and cross connection 62 to air pressure regulator 64. Compressed air is ultimately supplied to housing 18 through air .filter 66, which removes oil and water and other undesirable foreign contaminants. The air for operating vibrator 24 is obtained from cross connection 62. Gauge 70 is connected to tee connection 68 to read the pressure supplied to housing 18, and the input air pressure is read on gauge 72 connected to cross connection 62. Air is, for example, supplied from the compressor at a line pressure of about 50 to I25 p.s.i.g., whereas the pressure from regulator 64 is supplied to housing 18 at approximately to 50 p.s.i.g., and usually between'approximately to 25 p.s.i.g. Water is supplied to mixing nozzle 14 from line 74 and through valve 76 at a pressure sufficient to mix and apply the slurry 15, such as normal water line pressure.

Details of apparatus 10 are more clearly shown in FIG. 2. Spacing device 48 at the left-hand side of FIG. 2 and in FIG. 3 includes a number of diametrically split spacing discs 78 secured together between the end of screw flight 44 and shaft 32 by four long nut and bolt connectors 80. Six l-inch thick discs are, for example,

held between end flanges 82 of spacing device 48, thus permitting a 6-inch variation in the distance between adjacent ends of

screw sections

44 and 46. Several additional l-inch thick plates may also be installed to provide an overall variation in the length of the plug section of, for example, from 2 to 10 inches. In other words, the length of zone or section P may be varied, for example, from about 2 to 10 inches (and more particularly from 3 to 6 inches for fibrous asbestos) to provide the most efficient seal for the particular type of material being fed through housing 18. Discs or plates 78 may have thicknesses other than 1 inch, for example one-sixteenth, one-fourth or one-half inches. The lack of conveyor elements in zone P provides a sealing plug 84 of substantially dense material, which prevents the compressed air designated by arrows 86 and fed into housing 18 through connection 56 from blowing backwardly through material 11 and out through hopper l2. Heavier denser material might, for example, feed better with a shorter sealing section P, whereas lighter materials might require a longer sealing section P to provide an adequate sealing action.

At the right-hand end of FIG. 2 the compressed air flow designated by arrows 86 entrains material 11 and carries it through outlet connections 50, elbow 52 and connecting pipe 54 to mixing nozzle 14 (shown in FIG. 1). Sealing plate 88 confines the air and refractory material mixturewithin housing 18 and prevents it from blowing into contact with bearing34.

FIGS. 5 and 6 show a modified spacing device 48A including an axially adjustable flange 90A mounted to slide axially back and forth on a cage or four bars 92A spaced from and parallel to main shaft 32A. The axial position of adjusting flange 90A is maintained by inserting locking lugs 94A through perforated locking plates 96A. The number of axially spaced holes 98A in locking plates 96A governs the spacing and number of positions of spacing between the ends of screw conveyor sections 44 and 46 (shown in FIG. 2) in the same amount previously described. Mixing nozzle 14 dependably feeds slurry 15 to pipe 16, which is for example 1% inches in internal diameter and about I to 10 feet long. Mixing nozzle 14 is, for example, about l /inches in size and mixes about 50 to I00 CFM of air with about 30 to 50 pounds/minute oflight dry material and about I to 5 gallons/minute of water to form a slurry which is supplied to pipe 16 and discharged e.g. in a fan-shaped slurry effluent 15. The discharge will be varied to suit the particular application, and of course need not be fan-shaped unless desired. Thus, for some applications it may be preferred to discharge the material directly from pipe 16 or, for example, through a bent elbow mounted at the end ofpipe l6.

Orifice plate 100 may be used in sealing plug P to improve its sealing action with or without a variable spacing device 48. An orifice plate, as previously described, significantly improves sealing characteristics for the described light materials at a given setting of spacing device 48 or with a fixed spacing. The complete apparatus 10 provides optimum sealing action for a wide variety of materials by use of orifice 100 and the availability of variable spacing device 48.

We claim:

I. A pneumatic conveying apparatus for substantially dry material comprising a tubular conveyor housing, a

conveyor shaft longitudinally disposed in said housing, bearing means supporting said shaft to rotate within said housing, inlet means on one end of said tubular conveyor housing for supplying said material to it, outlet means on the other end of said conveyor housing, air pressure supply means connected to said other end of said tubular housing adjacent said outlet means whereby said dry material is air-borne into said outlet means, a pair of conveyor sections mounted separately from each other upon said shaft and having an open space between them within which said shaft is free of conveyor elements and whereby a sealing plug of said material is formed, variable spacing means connecting at least one of said conveyor sections to said apparatus whereby the space between said conveyor sections can 'be varied to adjust the length of said sealing plug for improving its efficiency, an orifice plate being disposed in said open space between said conveyor sections, and said orifice plate having an effective opening greater than said shaft and smaller than said tubular housing whereby said material is compressed to a substantially small diameter in said sealing plug to consolidate said sealing plug.

2. A pneumatic conveying apparatus for substantially dry material comprising a tubular conveyor housing, a conveyor shaft longitudinally disposed in said housing, bearing means supporting said shaft to rotate within said housing, inlet means on one end of said tubular conveyor housing for supplying said material to it, outlet means on the other end of said conveyor housing, air pressure supply means connected to said other end of said tubular housing adjacent said outlet means whereby said dry material is air-borne into said outlet means, a pair of conveyor sections mounted separately from each other upon said shaft and having an open space between them within which said shaft is free of conveyor elements and whereby a sealing plug of said material is formed, an orifice plate being disposed in said open space between said conveyor sections, and said orifice plate having an effective opening greater. than said shaft and smaller than said tubular housing whereby said material is compressed to a substantially small diameter in said sealing plug to consolidate said sealing plug.

3. An apparatus as set forth in claim 2 wherein said orifice plate is flexible.

4. An apparatus as set forth in claim 3 wherein said orifice plate is relatively stiff rubber.

5. An apparatus as set forth in claim 3 wherein said orifice plate ranges in thickness from about one-sixteenth to one-fourth inch.

6. An apparatus as set forth in claim 2 wherein said orifice plate is rigid.

7. An apparatus as set forth in claim 2 wherein the radial distance between said shaft and the inner edge of said effective opening in said orifice plate ranges approximately from one-half to 1 inch.

8. An apparatus as set forth in claim 2 wherein said conveyor sections comprise helical screw flights.

9. An apparatus as set forth in claim 2 wherein a mixing nozzle is provided, a hose connecting said outlet means to said mixing nozzle, water pressure means is connected to said mixing nozzle for converting said airborne material into a slurry, and conduit means connected to the outlet from said mixing nozzle for applyingsaid slurry. g

0. A pneumatic conveying apparatus for substantially dry material comprising a tubular conveyor housing, a conveyor-shaft longitudinally disposed in said housing, bearing means supporting said shaft to rotate within said housing, inlet means on one end of said tubular conveyor housing for supplying said material to it, outlet means on the other end of said conveyor housing, air pressure supply means connected to said other end of said tubular housing adjacent said outlet means whereby said dry material is air-borne into said outlet means, a pair of conveyor sections mounted separately from eachiother upon said shaft and having an open space between them within which said shaft is free of conveyor elements and whereby a sealing plug of said material is formed, and variable spacing means connecting at least one of said conveyor sections to said apparatus whereby the space between said conveyor sections can be varied to adjust the length of said sealing plug for improving its efficiency.

11. An apparatus as set forth in claim l0wherein said variable spacing means comprises a plurality of removable spacers.

12. An apparatus as set forth in claim 11 wherein said removable spacers comprise diametrically split circular plates.

13. An apparatus as set forth in claim 10 wherein said variable spacing means joins one of said conveyor sections to said shaft.

14. An apparatus as set forth in claim 10 wherein said variable spacing means comprises an axially adjustable flange an an axially engageable locking means between said flange and said apparatus.

15. An apparatus as set forth in claim 14 wherein said adjustable flange is axially supported upon a cage of bars spaced from and disposed parallel to said shaft whereby said flange is maintained substantially perpendicular to said shaft.

16. Anapparatus as set forth in claim 15 wherein perforated locking plates are disposed about the periphery of said flange and disengageable locking means are engageable between said locking plates and said flange for holding it in axially adjusted positions.

17. An apparatus as set forth in claim 10 wherein said conveyor sections comprise helical screw flights.

18. An apparatus as set forth in claim 10 wherein a mixing nozzle is provided, a hose connecting said outlet means to said mixing nozzle, water pressure means is connected to said mixing nozzle for converting said airborne material into a slurry, and conduit means connected to the outlet from said mixing nozzle for applying said slurry.

Claims

1. A pneumatic conveying apparatus for substantially dry material comprising a tubular conveyor housing, a conveyor shaft longitudinally disposed in said housing, bearing means supporting said shaft to rotate within said housing, inlet means on one end of said tubular conveyor housing for supplying said material to it, outlet means on the other end of said conveyor housing, air pressure supply means connected to said other end of said tubular housing adjacent said outlet means whereby said dry material is air-borne into said outlet means, a pair of conveyor sections mounted separately from each other upon said shaft and having an open space between them within which said shaft is free of conveyor elements and whereby a sealing plug of said material is formed, variable spacing means connecting at least one of said conveyor sections to said apparatus whereby the space between said conveyor sections can be varied to adjust the length of said sealing plug for improving its efficiency, an orifice plate being disposed in said open space between said conveyor sections, and said orifice plate having an effective opening greater than said shaft and smaller than said tubular housing whereby said material is compressed to a substantially small diameter in said sealing plug to consolidate said sealing plug.

2. A pneumatic conveying apparatus for substantially dry material comprising a tubular conveyor hOusing, a conveyor shaft longitudinally disposed in said housing, bearing means supporting said shaft to rotate within said housing, inlet means on one end of said tubular conveyor housing for supplying said material to it, outlet means on the other end of said conveyor housing, air pressure supply means connected to said other end of said tubular housing adjacent said outlet means whereby said dry material is air-borne into said outlet means, a pair of conveyor sections mounted separately from each other upon said shaft and having an open space between them within which said shaft is free of conveyor elements and whereby a sealing plug of said material is formed, an orifice plate being disposed in said open space between said conveyor sections, and said orifice plate having an effective opening greater than said shaft and smaller than said tubular housing whereby said material is compressed to a substantially small diameter in said sealing plug to consolidate said sealing plug.

3. An apparatus as set forth in claim 2 wherein said orifice plate is flexible.

6. An apparatus as set forth in claim 2 wherein said orifice plate is rigid.

9. An apparatus as set forth in claim 2 wherein a mixing nozzle is provided, a hose connecting said outlet means to said mixing nozzle, water pressure means is connected to said mixing nozzle for converting said air-borne material into a slurry, and conduit means connected to the outlet from said mixing nozzle for applying said slurry.

10. A pneumatic conveying apparatus for substantially dry material comprising a tubular conveyor housing, a conveyor shaft longitudinally disposed in said housing, bearing means supporting said shaft to rotate within said housing, inlet means on one end of said tubular conveyor housing for supplying said material to it, outlet means on the other end of said conveyor housing, air pressure supply means connected to said other end of said tubular housing adjacent said outlet means whereby said dry material is air-borne into said outlet means, a pair of conveyor sections mounted separately from each other upon said shaft and having an open space between them within which said shaft is free of conveyor elements and whereby a sealing plug of said material is formed, and variable spacing means connecting at least one of said conveyor sections to said apparatus whereby the space between said conveyor sections can be varied to adjust the length of said sealing plug for improving its efficiency.

11. An apparatus as set forth in claim 10 wherein said variable spacing means comprises a plurality of removable spacers.

16. An apparatus as set forth in claim 15 wherein perforated locking plates are disposed about the periphery of said flange and disengageable locking means are engageable betweEn said locking plates and said flange for holding it in axially adjusted positions.

18. An apparatus as set forth in claim 10 wherein a mixing nozzle is provided, a hose connecting said outlet means to said mixing nozzle, water pressure means is connected to said mixing nozzle for converting said air-borne material into a slurry, and conduit means connected to the outlet from said mixing nozzle for applying said slurry.