Tobacco – Method or apparatus for making reconstituted tobacco – Slurry
Reexamination Certificate
1999-05-27
2001-04-17
Silverman, Stanley S. (Department: 1731)
Tobacco
Method or apparatus for making reconstituted tobacco
Slurry
C131S370000, C034S487000, C034S452000
Reexamination Certificate
active
06216706
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for producing reconstituted tobacco sheets. More particularly, the present invention relates to a method and apparatus for producing reconstituted tobacco sheets in a relatively rapid and uniform manner.
BACKGROUND AND SUMMARY
In the manufacture of tobacco products, tobacco by-products such as tobacco stems, leaf scraps, and tobacco dust produced during the manufacturing process can be recycled to reclaim their useful tobacco content. In the past, such tobacco by-products have been formed into what is known in the industry as reconstituted tobacco sheets.
Commonly owned U.S. Pat. No. 5,203,354 discloses a process for manufacturing reconstituted tobacco sheet by casting a tobacco containing slurry containing 20% solids and 80% liquid onto a rotating cylindrical dryer which is heated by gas, electricity or steam and the dryer reduces the moisture content of the slurry to 12-40%. In order to avoid deterioration of flavor and other properties of the tobacco the dryer surface temperature is from 180 to 200° F. A process for making reconstituted tobacco sheet by casting or extruding a tobacco slurry at 80-200° F. onto a continuous stainless steel belt and drying the slurry at 200-700° F. is described in commonly owned U.S. Pat. No. 5,724,998. Commonly owned U.S. Pat. No. 5,584,306 discloses a process for making reconstituted tobacco sheet by reverse-roll coating a slurry at 120-160° F. onto a stainless steel belt traveling at a line speed of 20-400 feet/minute and drying the slurry in a primary dryer and secondary dryer after which the sheet is doctored from the belt. In the examples of the '306 patent the belt speed was 30 fpm, the dryer was a gas-fired, air impingement dryer, and the sheet emerging from the secondary dryer had a moisture content of approximately 15% and sheet weight of 11.6-14.6 g/ft
2
.
U.S. Pat. No. 5,099,864 describes a process for making reconstituted tobacco sheet wherein a tobacco slurry at 140-180° F. and solids content of 14-20% is cast as a 15-40 mil thick sheet on a stainless steel belt moving at 1.5 m/min and dried to a moisture content of about 14% and weight of 75-150 g/m
2
. U.S. Pat. Nos. 4,306,358 and 5,743,022 describe apparatus for the drying of a reconstituted tobacco slurry.
During the drying process, prior art processes have utilized air impingement dryers and other drying equipment to remove the excess moisture. In order to effect rapid removal of water from the slurry, gas-fired air impingement dryers have been placed both above and below the conveyor belt downstream of the casting device. In such gas-fired, air impingement dryers, the thin layer of slurry arrives in a relatively cool state due to heat transferred to the steel belt and during heating by the dryers, a skin or “film” can form on the surface of the slurry which lowers the rate at which moisture can be evaporated from the slurry.
In view of the state of the art of making reconstituted tobacco sheet, there is a need for a processing apparatus and method which overcomes the slow evaporation problem caused by prior art techniques for drying reconstituted tobacco slurries. It would be desirable if such apparatus could be incorporated in existing processing equipment.
SUMMARY OF THE INVENTION
The invention provides an apparatus for producing a reconstituted tobacco sheet from an aqueous slurry wherein the apparatus includes an endless conveyor belt, a source supplying slurry to the conveyor at a deposition point, a steam heating arrangement which preheats the slurry as it enters a drying apparatus which reduces the moisture content of the thus-produced sheet to a desired level. The sheet can be further dried in a secondary drying apparatus which reduces the moisture content to a lower level. The steam heating arrangement can comprise a steam box arranged such that a portion of the conveyor above an upstream portion of the steam box is exposed to the open air and a portion of the conveyor above a downstream portion of the steam box is located in an air lock of the heating arrangement.
The invention also provides a method for producing a reconstituted tobacco sheet from an aqueous slurry, the method including steps of depositing the slurry on a conveyor, heating a portion of the conveyor with a steam heating arrangement so that the slurry is preheated to a preheat temperature, and drying the sheet in a drying apparatus which reduces the moisture content of the sheet to a desired level. The conveyor can be a stainless steel belt and the steam heating arrangement preferably heats the belt such that moisture evaporates from the slurry from the inside to the outside thereof. Due to the steam heating arrangement the speed of the belt can be increased considerably compared to heating arrangements which omit the steam heating arrangement.
REFERENCES:
patent: 1567023 (1925-12-01), Larsson
patent: 3145716 (1964-08-01), Geitz et al.
patent: 3224108 (1965-12-01), Flaming
patent: 3228113 (1966-01-01), Fannon, Jr.
patent: 3295222 (1967-01-01), Geitz
patent: 3827639 (1974-08-01), Relue et al.
patent: 4306358 (1981-12-01), King, Jr.
patent: 4341228 (1982-07-01), Keritsis et al.
patent: 4421126 (1983-12-01), Gellatly
patent: 5099864 (1992-03-01), Young et al.
patent: 5203354 (1993-04-01), Hickle
patent: 5584306 (1996-12-01), Beauman et al.
patent: 5724998 (1998-03-01), Gellatly et al.
patent: 5743022 (1998-04-01), Taylor
patent: 5845415 (1998-12-01), Sundqvist
Gomes Joao
Kumar Ashok
Burns Doane , Swecker, Mathis LLP
Philip Morris Incorporated
Silverman Stanley S.
Walls Dionne A.
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