Drying and gas or vapor contact with solids – Apparatus – With fluid current conveying of treated material
Reexamination Certificate
1999-11-30
2001-02-13
Wilson, Pamela (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
With fluid current conveying of treated material
C034S588000, C034S068000, C131S290000, C131S296000
Reexamination Certificate
active
06185843
ABSTRACT:
The subject invention relates to pneumatic conveyance tobacco dryers.
In the process of drying particulate tobacco in a pneumatic conveyance tobacco dryer a flow of hot gaseous medium-air, steam or an air/stem mixture for example—is established through an elongate pneumatic conveyance duct, and the tobacco is fed into the duct, whereby the tobacco particles become entrained in the flow of the hot gaseous medium. The tobacco is subsequently separated from the gaseous medium by means of a separator, such, for example, as a cyclone or a tangential separator. The contact time of the tobacco particles with the gaseous medium is short, being typically in a range of from less than one second up to about 6 seconds.
Heretofore, difficulties have been experienced in the feeding of tobacco to a pneumatic conveyance dryer in such manner as to avoid the creation of static accumulations of tobacco particles at localities within the conveyance duct, with the accompanying risk of the occurrence of fires in the duct.
The subject invention has as an object the provision of means for obtaining an improved mode of feeding particulate tobacco into the conveyance duct of a pneumatic conveyance dryer.
The subject invention provides a pneumatic conveyance tobacco dryer comprising a pneumatic conveyance duct and a downwardly extending tobacco feed chute, said duct comprising a first portion, a second, upwardly extending portion and a third, curved portion extending from the first portion to the lower end of the second portion and whereby the first portion is in gas flow communication with the second portion, the lower end of the feed chute opening into the second portion of the duct and being located to the same side of said second portion of the duct as is the first portion of the duct, characterised in that in vertical, axial section of the third portion of the duct, the interior curved surface at the outside of the curve of the third portion conforms to a line at constant distance (radius) from a point which is located below the junction of the second and third portions of the duct, and which line continues, at the constant distance from said point, above the level of said point.
By preference, the said constant radius line terminates at such level above the level of said point that a radial line, extending from the point to the constant radius line at said level above that of the point, extends at or about 10 degrees to the horizontal.
It is preferable that, as viewed in vertical axial section of the third portion of the pneumatic conveyance duct, the interior curved surface at the inside of the curve of the third portion conforms to a second line at constant distance (radius) from a second point, which second point is located above the level of the first mentioned point, and said second line does not continue, or does not substantially continue, at the said constant distance from said second point, above the level of said second point. suitably, the second point is at the same level, or at about the same level, as is the upper termination of the first mentioned line of constant radius.
Advantageously, as viewing a vertical, axial section of the second portion of the pneumatic conveying duct, the location of the upper junction of the interior of the tobacco feed chute with the interior of the second portion of the duct is offset from a vertical line extending from the lower junction of the interior of the chute with the interior of the duct, the upper junction being located to the same side of said vertical line as is located the first portion of the duct. Again as viewing a vertical section of the second portion of the duct, a straight line extending from the said lower junction to the said upper junction suitably extends at an angle to the vertical of or about 7 degrees. Plate means may extend downwardly from the said upper junction in alignment with the just mentioned notional line interconnecting the said upper and lower junctions. The plate means may extend, for example, for about one sixth of the distance between the upper and lower junctions.
The second portion of the pneumatic conveyance duct preferably extends vertically. The second portion of the duct suitably comprises two abutting sections, the first of which sections extends upwardly from the lower end of the tobacco feed chute and is of constant internal transverse cross-section, and the second of which sections extends upwardly from the upper end of the first section and is upwardly divergent internally. In such case it is advantageous that, as viewing a vertical section of the second portion of the duct, the interior of the second section thereof is upwardly divergent at that side of the duct opposite that at which the interior of the tobacco feed chute opens into the duct. Suitably, the divergence is linearly proportional. The divergence may, for example, be in the proportion of 1 in 10, in which case the divergent interior wall of the said second section would extend at 5.7 degrees to the vertical.
Suitably, the included angle between the respective axes of the said second portion and the tobacco feed chute is at or about 30 degrees.
Suitably, the internal transverse cross-section of the third portion of the pneumatic conveyance duct is of rectangular conformation and the arrangement is such that the wider of the central transverse and longitudinally extending planes of the interior of the said third portion, i.e. planes parallel to the wider internal walls of the third portion, are curved in accordance with the curving of the third portion. Suitably, the internal transverse cross-section of the second portion of the duct too is of rectangular conformation, in which case the respective internal transverse cross-sections of the second and third portions of the duct at the juncture therebetween are the same and in the same orientation.
Suitably, an airlock for the feed of tobacco is provided at the upper end of the tobacco feed chute.
REFERENCES:
patent: 4251356 (1981-02-01), Harte
patent: 4523598 (1985-06-01), Weiss et al.
patent: 5307822 (1994-05-01), Egri
patent: 5908032 (1999-06-01), Poindexter et al.
Hirsch Werner
Stone William John
Tatham Ian Ernest
Weiss Arno Eugen
British American Tobacco (Investments) Limited
Pitney Hardin Kipp & Szuch LLP
Wilson Pamela
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