Method and apparatus for fiberizing and cellulosic product thereof

Abstract

A method and apparatus for fiberizing feed stock in the form of shreds or the like to form a low density cellulosic product. The shredded feed stock is fed to a material handling rotor that functions as a centrifugal blower. The apparatus includes a housing that defines a cylindrical rotor chamber formed about a horizontal axis and a volute-shaped internal passage having at least one convolution formed around the rotor chamber. Located within the housing is a cylindrical screen with perforations that open into the rotor chamber. The centrifugal blower rotor is mounted in the rotor chamber and has a plurality of radial vanes with rakes attached to the outer ends closely spaced from the inner surface of the screen so that they continuously wipe pass the perforations to prevent clogging or blinding.

What is claimed is: 
     
       1. Apparatus for fiberizing organic material to form a low density fibrous product comprising: a housing defining; a cylindrical rotor chamber having a central axis,   a volume-shaped passage formed around said rotor chamber,   a tangential outlet from said volute-shaped passage, and   axial inlet means for feeding said organic material into the central portion of said rotor chamber;     a discharge duct communicating with a radially outward portion of said tangential outlet for removing the fibrous product from the apparatus;   air return means communicating between a radially inward portion of said tangential outlet and said axial inlet means for recirculating a substantial portion of the air from said tangential outlet directly to said rotor chamber;   means for delivering said organic material to said axial inlet means;   a perforate cylindrical screen mounted in said housing about said axis between said rotor chamber and said volute-shaped passage;   a centrifugal blower rotor mounted in said rotor chamber for rotation about said axis and having a plurality of radial vanes with rakers mounted at the outer ends thereof, said rakers being closely spaced from the inner surface of said screen to prevent clogging of the openings in said screen; and   drive means for turning said rotor at a speed sufficient to generate a flow velocity for said air and fibrous product that is received in said volute chamber, that causes centrifugal concentration of said fibrous product in the radially outward portion of said volute chamber,   whereby said fibrous product is concentrated in the radially outward portion of the flow at the tangential outlet for delivery to said discharge duct and the radially inward portion of the flow that is received by said air return means at the radially inward portion of said tangential outlet is relatively free of said fibrous product.   
     
     
       2. Apparatus as defined in claim 1, wherein said axial inlet means comprises two axial openings located on opposite sides of said rotor chamber for feeding said organic material from opposite axial directions. 
     
     
       3. Apparatus as defined in claim 2, wherein said air return means comprises a pair of air return ducts extending between said radially inward portions of said 
     
     
       4. Apparatus as defined in claim 3, wherein said air return ducts are of sufficient size to return about 60 percent of the air flow volume from said tangential outlet to said axial inlets. 
     
     
       5. Apparatus as defined in claim 1, wherein said screen has openings therein that comprise about 50 percent of the surface area thereof. 
     
     
       6. Apparatus as defined in claim 1, wherein said openings in said screen are between 5/32 inch and 7/32 inch in diameter. 
     
     
       7. Apparatus as defined in claim 1, wherein said rakers are radially spaced from the inner surface of said screen about 0.065 inch. 
     
     
       8. Apparatus as defined in claim 1, wherein said drive means operate said rotor at peripheral speeds from 15,000 to 30,000 fpm. 
     
     
       9. Apparatus as defined in claim 1, wherein said rakers are provided with a plurality of laterally spaced radial teeth. 
     
     
       10. Apparatus as defined in claim 9, wherein said raker teeth on each vane are laterally staggered relative to the raker teeth on adjacent vanes. 
     
     
       11. Apparatus as defined in claim 1, wherein said rakers are radially adjustable on their respective vanes. 
     
     
       12. A method for fiberizing organic material to form a low density, fibrous product comprising: feeding said organic material to the central portion of a cylindrical rotor chamber;   driving a centrifugal rotor with radial vanes at relatively high speed in said chamber to generate a high velocity air flow with said organic material entrained therein to force said organic material radially outward in said rotor chamber at relatively high velocity;   forcing said material in said air flow radially outward through perforations in a cylindrical screen surrounding said rotor to fiberize said material;   conveying said air and fiberized product exiting said screen at a relatively high flow velocity through a volute passage surrounded said screen and having a tangential outlet and thereby centrifugally separating said fiberized product from a portion of the air volume flowing through said volute chamber so that said fiberized product is concentrated in the radially outward portion of the flow at said tangential outlet;   conveying the flow from the radially outward portion of said tangential outlet through a discharge duct to a collecting means; and   returning the air flow from the radially inward portion of said tangential outlet comprising a substantial portion of the air volume therein directly to said rotor chamber.   
     
     
       13. A method as defined in claim 12, wherein said organic material is fed into said rotor chamber through two axial openings located on opposite sides of said rotor chamber. 
     
     
       14. A method as defined in claim 12, wherein said separated portion of said air volume that is returned to said rotor rotor chamber comprises about 60 percent of the air flow through said screen. 
     
     
       15. A method as defined in claim 12, wherein said air volume flowing through said screen flows into and through a volute chamber surrounding said screen. 
     
     
       16. A method as defined in claim 12, wherein said rotor is operated at peripheral speeds of about 15,000 to about 30,000 fpm. 
     
     
       17. A method as defined in claim 12, wherein the velocity of said flow of air and feed stock generated by said rotor is from about 2000 to about 15,000 fpm. 
     
     
       18. A low density, fibrous product made in accordance with the method of clain 12. 
     
     
       19. A fibrous product as defined in claim 18 having a settled density of between about 0.7 and about 1.9 pounds per cubic foot. 
     
     
       20. A fibrous product as defined in claim 18, having a settled density of between about 1.3 and about 1.6 pounds per cubic foot. 
     
     
       21. A fibrous product as defined in claim 18, having an R value of about 3.8. 
     
     
       22. A fibrous product as defined in claim 18, wherein coarse pieces constitute less than 4 percent of the total volume. .Iadd. 
     
     
       23.  Apparatus for comminuting feed stock to form a low density, fibrous product comprising: a housing defining:   a cylindrical rotor chamber having a central axis extending within a central portion of said rotor chamber,   a passage formed around said rotor chamber.   an outlet from said passage, and   inlet means for feeding said feed stock into the central portion of said rotor chamber;   means for delivering said feed stock to said inlet means entrained in a flowing fluid stream;   a perforate screen mounted in said housing about said axis between said rotor chamber and said passage;   a rotor mounted in said rotor chamber for rotation about said axis and having a plurality of radial members;   means associated with an outermost end portion of at least one of said radial members so as to be spaced closely adjacent said perforate screen for preventing blinding of said screen as said feed stock passes through said perforate screen;   drive means for turning said rotor; and   means for generating a fluid stream velocity of air and said feed stock of at least 1000 f.p.m. through the perforations in said screen. .Iaddend. .Iadd.   
     
     
       24.  Apparatus as defined in claim 23, wherein said means for generating a fluid stream velocity further includes an auxiliary flow generator. .Iaddend. .Iadd.25. Apparatus as defined in claim 24, wherein said auxiliary flow generator is located downstream of said outlet. .Iaddend. .Iadd.26. Apparatus as defined in claim 23, wherein said fluid stream velocity produced through said perforations is between 1000 and 15,000 f.p.m. .Iaddend. .Iadd.27. Apparatus as defined in claim 23, wherein said passage formed around said rotor is volute-shaped and wherein said outlet is tangential and located at the downstream end of said volute-shaped 
     
     
        passage. .Iaddend. .Iadd.28.  Apparatus as defined in claim 27, further comprising air return means communicating between a radially inward portion of said tangential outlet and said inlet means. .Iaddend. .Iadd.29. Apparatus as defined in claim 28, wherein said air return duct is of sufficient size to return about 60 percent of the air flow volume from said tangential outlet to said outlet. .Iaddend. .Iadd.30. Apparatus as defined in claim 23, wherein said screen has openings therein that comprise about 50 percent of the surface area thereof. .Iaddend. .Iadd.31. Apparatus as defined in claim 30, wherein said openings in said screen are between approximately 5/32 and 7/32 inch in diameter. .Iaddend. .Iadd.32. Apparatus as defined in claim 23, wherein said rakers are radially spaced from the inner surface of said screen about 0.065 inch. .Iaddend. .Iadd.33. Apparatus as defined in claim 23, wherein said drive means operates said rotor at peripheral speeds from 15,000 to 30,000 f.p.m. .Iaddend. .Iadd.34. Apparatus as defined in claim 23, wherein said rakers are provided with a plurality of laterally spaced radial teeth. .Iaddend. 
     
     
        .Iadd.35.  Apparatus as defined in claim 34, wherein said raker teeth on each vane are laterally staggered relative to the raker teeth on adjacent vanes. .Iaddend. .Iadd.36. Apparatus as defined in claim 23, wherein said rakers are radially adjustable on their respective radial members. .Iaddend. .Iadd.37. Apparatus for fiberizing organic material to form a low density fibrous product comprising; a housing defining;   a cylindrical rotor chamber having a central axis extending within a central portion of said rotor chamber;   a passage formed around said rotor chamber;   an outlet from said passage;   axial inlet means for feeding said organic material into the central portion of said rotor chamber;   a discharge duct communicating with said outlet for removing the fibrous product from the apparatus;   means for delivering said organic material to said axial inlet means;   a perforate cylindrical screen mounted in said housing about said axis between said rotor chamber and said passage;   a centrifugal blower rotor mounted in said rotor chamber for rotation about said axis and having a plurality of radially extending vanes;   raker means disposed at an outermost end portion of at least one of said vanes for agitating said feed stock as said feed stock passes through said screen to prevent blinding of said screen, said raker means being positioned closely adjacent an inner surface of said screen; and   drive means for turning said rotor at a speed sufficient to generate a flow velocity for said air and fibrous product that is received in said passage, that causes centrifugal concentration of said fibrous product in the radially outward portion of said passage. .Iaddend. .Iadd.38. Apparatus for comminuting feed stock to form a low density fibrous product having a settled density of between about 0.7 and 1.9 pounds per cubic foot comprising:   a housing defining:   a cylindrical rotor chamber having a central axis,   a passage formed around said rotor chamber,   an outlet from said passage, and   inlet means for feeding said feed stock into the central portion of said rotor chamber;   means for delivering said feed stock to said inlet means entrained in a flowing fluid stream;   a perforate screen mounted in said housing about said axis between said rotor chamber and said passage;   a rotor mounted in said rotor chamber for rotation about said axis and having a plurality of radially extending members;   raker means disposed at outermost end portions of said radially extending members and positioned so as to be spaced approximately 0.065 inch from an inner surface of said screen, said rakers operating to agitate said feed stock as said feed stock approaches and passes through said screen to thereby prevent blinding of said screen;   drive means for turning said rotor; and   means including said rotor for generating a fluid stream velocity of air and said feed stock of at least 1000 f.p.m. through the perforations in said screen. .Iaddend. .Iadd.39. A method for fiberizing organic material to form a low density, fibrous product having a settled density of between about 0.7 and about 1.9 pounds per cubic foot comprising:   feeding said organic material to the central portion of a cylindrical rotor chamber;   driving a centrifugal rotor with radial vanes at relatively high speed in said chamber to generate a high velocity air flow with said organic material entrained therein to force said organic material radially outward in said rotor chamber at relatively high velocity;   forcing said organic material entrained in said air flow radially outward through perforations in a cylindrical screen surrounding said rotor to fiberize said organic material into said fibrous product;   conveying said air and fibrous product exiting said cylindrical screen at a relatively high flow velocity through a passage surrounding said cylindrical screen and having an outlet and thereby centrifugally separating said fibrous product from a portion of the air volume flowing through said passage so that said fibrous product is concentrated in the radially outward portion of the flow at said outlet;   using a raker bar disposed at an outermost end portion of at least one of said radial vanes and positioned closely adjacent an inner surface of said screen to agitate said material as said material passes closely adjacent said perforations in said cylindrical screen just prior to said material passing through said perforations, to thereby prevent blinding of said screen by said material; and   conveying the flow of said fiberized product from said outlet through a   
     
     
        discharge duct to a collecting means. .Iaddend. .Iadd.40.  A method for comminuting feed stock to form a low density product comprising: feeding said feed stock to a central portion of a cylindrical rotor chamber;   generating a high velocity fluid flow of air with said feed stock entrained therein to force said feed stock radially outward in said rotor chamber at relatively high velocity;   driving a rotor having radial rakers about a central axis of said rotor chamber, said rakers being closely spaced from the inner surface of a perforate cylindrical screen mounted around said rotor;   forcing said resulting fluid flow radially outward through the perforations of said screen at a fluid stream velocity of at least about 1000 f.p.m. through the perforations in said screen in comminute said feed stock;   using said rakers to prevent blinding of said screen by said feed stock and to agitate said feed stock closely adjacent said screen to further facilitate comminuting said feed stock; and   
     
     
       discharging the comminuted product. .Iaddend. .Iadd.41.  A method as defined in claim 40, wherein said rotor further has radial vanes to which said rakers are attached and said high velocity fluid flow is produced by the rotation of said rotor. .Iaddend. .Iadd.42. A method as defined in claim 40, wherein said high velocity fluid flow is produced in part by auxiliary glow generating means separate from said rotor. .Iaddend. .Iadd.43. A method as defined in claim 41, wherein said auxiliary flow generating means is located downstream of the location where the comminuted product is discharged. .Iaddend. .Iadd.44. A method as defined in claim 40, including the additional step of centrifugally separating the comminuted product from a portion of the air volume flowing through said screen. .Iaddend. .Iadd.45. A method as defined in claim 44, wherein said separated portion of said air volume is returned to said rotor chamber. 
     
     
        .Iaddend. .Iadd.46.  A method as defined in claim 45, wherein said separated portion of said air volume comprises about 60% of the air flow through said screen. .Iaddend. .Iadd.47. A method as defined in claim 44, wherein said air volume flowing through said screen flows into and through a volute chamber surrounding said screen. .Iaddend. .Iadd.48. A method as defined in claim 40, wherein said rotor is operated at peripheral speeds of about 15,000 to about 30,000 f.p.m. .Iaddend. .Iadd.49. A method as defined in claim 40, wherein the velocity of said fluid stream velocity is from about 1000 to about 15,000 f.p.m. .Iaddend. .Iadd.50. A comminuted product made in accordance with the method of claim 40. .Iaddend. .Iadd.51. A comminuted product as defined in claim 50 having a settled density of between about 0.7 and about 1.9 pounds per cubic foot. 
     
     
        .Iaddend. .Iadd.52.  A method for comminuting feed stock to form a low density product having a settled density of between about 0.7 and about 1.9 pounds per cubic foot comprising: feeding said feed stock to the central portion of a cylindrical rotor chamber:   generating a high velocity fluid flow of air with said feed stock entrained therein to force said feed stock radially outward in said rotor chamber at relatively high velocity;   driving a rotor having radial rakers about the central axis of said rotor chamber, said rakers being radially spaced approximately 0.065 inch from the inner surface of a perforate cylindrical screen mounted around said rotor;   forcing said resulting fluid flow radially outward through the perforations of said screen at a fluid stream velocity of at least about 1000 f.p.m. through the perforations in said screen to comminute said feed stock;   using said rakers to prevent blinding of the openings in said screen by said product as said product passes through said openings; and   discharging the comminuted product to a collection means. .Iaddend.   
     
     
        .Iadd.  .  Apparatus as defined in claim 23, wherein said means for preventing blinding of said screen comprises a raker adjustably secured to said outermost end portion of said at least one radial member. .Iaddend. .Iadd.54. Apparatus as defined in claim 23, wherein said means for preventing blinding of said screen further operates to continuously agitate said feed stock when said feed stock is closely adjacent said perforate screen to thereby further help comminute said feed stock. .Iaddend. .Iadd.55. A low density, fibrous comminuted product having a settled density of about 0.7 to about 1.9 pounds per cubic foot formed by: feeding feed stock into a cylindrical rotor chamber having a plurality of radially extending vanes rotating sufficiently rapidly to generate a fluid stream having a radially outward velocity through the screen of at least about 1000 feet per minute;   causing said fluid stream having said feed stock entrained therein to be passed through a screen positioned closely adjacent outermost end portions of said vanes to thereby comminute said feed stock;   using a plurality of raker bars disposed at said outermost end portions of said vanes to prevent blinding of said screen and to further agitate said feed stock to aid in comminuting said feed stock; and discharging said comminuted feed stock representing said product from same rotor chamber.   
     
     
        .Iaddend. .Iadd.56.  A comminuted product as defined in claim 55 having a settled density of between about 1.3 and about 1.6 pounds per cubic foot. 
     
     
        .Iaddend. .Iadd.57.  A comminuted product as defined in claim 55 having an R value of about 3.8. .Iaddend. .Iadd.58. A comminuted product as defined in claim 55, wherein said product comprises coarse pieces and fine pieces, and wherein said coarse pieces constitute less than about 4 percent of the total volume of said product. .Iaddend.