Cigarette manufacturing method

A cigarette manufacturing method and machine, whereby a shredded tobacco stream is fed along a channel extending through at least one carding unit and having at least one output portion closed by a suction conveyor belt and for feeding a mat of tobacco onto the suction conveyor belt; and the shredded tobacco stream is cleaned, upstream from the carding unit, to remove relatively heavy parts, such as lumps of tobacco and/or woody tobacco parts and/or any foreign bodies, from the shredded tobacco stream.

TECHNICAL FIELD

The present invention relates to a cigarette manufacturing method and machine.

BACKGROUND ART

In cigarette manufacturing machines, shredded tobacco is normally fed via an input hopper to a gravity channel connected via a carding unit to a basin, from which extends upwards an upflow channel closed at the top end by a conveyor belt permeable to air. In the upflow channel, an upward air current, at least partly produced by suction through the conveyor belt, draws up the light part of the tobacco comprising powder and relatively minute shreds, while any heavier parts, such as lumps, woody parts, or foreign bodies (stones and similar) fall by gravity into the basin and are rejected.

Though widely used and relatively effective, the above method may result in problems caused by the heavier parts, particularly the foreign bodies, damaging the carding unit.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a cigarette manufacturing method and machine designed to eliminate the aforementioned drawback, and which are cheap and easy to implement.

According to the present invention, there is provided a cigarette manufacturing method as claimed in claim1and, preferably, in any one of the following Claims depending directly or indirectly on claim1.

According to the present invention, there is also provided a cigarette manufacturing machine.

BEST MODE FOR CARRYING OUT THE INVENTION

Number1inFIGS. 1 and 2indicates as a whole a cigarette manufacturing machine comprising a channel2extending through an input unit3(FIG. 2) for supplying a shredded tobacco stream4; and a manipulating unit5(FIG. 1) for receiving shredded tobacco stream4from input unit3, and for forming a mat6of shredded tobacco on the bottom surface of a conveyor belt7, which is made of material permeable to air, and runs directly beneath a suction box8for retaining mat6on conveyor belt7by suction.

As shown inFIGS. 2 and 3, in input unit3, channel2comprises a substantially constant-section input conduit9for receiving shredded tobacco stream4from a container (not shown), and for feeding it to a flared conduit10increasing in section in the flow direction11of shredded tobacco stream4. As shown inFIG. 2, flared conduit10is located in series with input conduit9, and terminates at a node12connecting the top end of a cleaning tower13to the input end of an output conduit14of input unit3.

Output conduit14comprises an input portion, which forms a top extension of cleaning tower13and winds about a suction cage15rotating about a substantially horizontal axis16and shielded partly by a bottom plate17. Suction cage15defines, with its free outer portion, part of the lateral surface of output conduit14, and is powered so that the part of its surface contacting shredded tobacco stream4flowing along output conduit14rotates about axis16in the same direction as direction11. At its output end, output conduit14is closed by a slide valve18rotating about an axis19parallel to axis16.

As shown inFIG. 3, suction cage15forms one of the many inputs of a primary-air suction system20, which comprises a distribution header21and, as opposed to forming part of manufacturing machine1, preferably forms part of a suction system (not shown) of the tobacco plant (not shown) in which manufacturing machine1is installed.

As shown inFIG. 2, cleaning tower13comprises a substantially sinusoidal upflow channel22tapering downwards in section, and a bottom portion of which forms a basin23closed at the bottom by a rotary slide dump valve23a. Above basin23, upflow channel22is defined laterally by two lateral walls24and25, of which wall25is fixed, while wall24is adjustable to and from wall25to adjust the section of upflow channel22. For which purpose, in the example embodiment shown, wall24is hinged at26, is rotated by an actuator27about an axis parallel to axis16, and is fitted at the top with a transverse plate28fitted in transversely sliding and fluidtight manner to a seal29fitted to one wall of flared conduit10at node12.

Just above basin23, upflow channel22communicates with an intake header30for a secondary-air stream30a, which “bubbles” along upflow channel22and is preferably pumped along header30from the outside. Alternatively, the secondary air may simply be drawn in from outside by the low pressure generated inside cleaning tower13by the primary air drawn by suction system20.

As shown inFIG. 3, along input conduit9, channel2communicates, via an annular header31, with two different auxiliary pneumatic circuits32and33. Auxiliary pneumatic circuit32comprises a conduit34branching from distribution header21and communicating with annular header31to supply flared conduit10with an auxiliary-air stream35, which is mixed with a primary-air stream36drawn along input conduit9by suction by suction system20through suction cage15; and pneumatic circuit33comprises two boxes37located on opposite sides of flared conduit10and communicating, on one side, with flared conduit10, and, on the other side, via respective conduits38, with the inlet of a pump39, the outlet of which communicates, via a conduit40, with annular header31to supply annular header31with a recirculated-air stream41.

As shown inFIG. 1, in manipulating unit5, channel2comprises a hopper42communicating with output conduit14via rotary slide valve18. Shredded tobacco stream4is fed by hopper42into a box43and onto a belt conveyor44for feeding shredded tobacco stream4to a carding unit45housed inside box43. Carding unit45feeds shredded tobacco stream4to a vibrating tray46—also supplied in known manner by an external conveyor47with recirculated tobacco obtained, in known manner not shown, by shaving mat6—and to a gravity conduit48, the bottom end of which is controlled by a further carding unit49, which receives the tobacco from gravity conduit48and distributes it evenly on a conveyor50sloping slightly upwards to the bottom end of an upflow conduit51closed at the top end by conveyor belt7.

The shredded tobacco stream4reaching the input of input conduit9is therefore substantially all drawn, by the primary-air stream drawn through suction cage15, onto the underside of conveyor belt7, to form mat6, along channel2, which, as stated, comprises, in succession, input conduit9, flared conduit10, output conduit14, hopper42, box43, conveyor44, tray46, gravity conduit48, conveyor50, and upflow conduit51. As it flows along channel2, shredded tobacco stream4expands sharply inside flared conduit10, which has the effect of breaking up any lumps in the tobacco, and of freeing the rest of the tobacco of so-called “heavy” parts defined by any remaining lumps and/or woody tobacco parts and/or foreign bodies.

Expansion is enhanced by supplying further air by means of auxiliary pneumatic circuits32and33, of which at least auxiliary pneumatic circuit32may be dispensed with when working with particularly light shredded tobacco.

The heavy parts are eliminated at node12, by the secondary-air stream flowing from header30up along upflow channel22allowing the “light” parts in shredded tobacco stream4to “float” through node12to output conduit14and hopper42, while the heavier parts drop in the opposite direction down upflow channel22into basin23.

Obviously, the specific weight and nature of the parts deposited in basin23depend on the speed of the secondary air flowing along upflow channel22; which speed can be regulated, for a given flow rate along header30, by actuator27. In this connection, it should be pointed out that the sinusoidal shape of lateral walls24an25, by producing significant turbulence inside upflow channel22, not only assists in separating the heavy from the light parts and in feeding the light parts up along cleaning tower13, but also exponentially enhances the effect of actuator27varying the section of upflow channel22.

FIG. 4shows an alternative embodiment of input unit3, any parts of which in common with input unit3inFIG. 2are indicated using the same reference numbers. In theFIG. 4input unit3, channel2comprises a substantially constant-section input conduit9for receiving shredded tobacco stream4from a container (not shown) and feeding it to a vertical flared conduit10increasing in section in the flow direction11of shredded tobacco stream4.

As shown inFIG. 4, flared conduit10is located in series with input conduit9, and comes out inside a vertical cleaning tower13, which is defined at the top by flared conduit10on one side, and, on the other side, by a suction cage52rotating about a horizontal axis53and connected to primary-air suction system20. Suction cage52rotates clockwise to feed shredded tobacco stream4from cleaning tower13to hopper42, which is located beneath suction cage52and alongside cleaning tower13. To assist detachment of shredded tobacco4from suction cage52into the inlet of hopper42, suction through suction cage52is cut off in known manner at the inlet of hopper42, which may also be provided with a fixed plate fitted to suction cage52, and with an air jet directed to detach shredded tobacco4from suction cage52into the inlet of hopper42. In an embodiment not shown, a rotary slide valve is provided at the inlet of hopper42.

Cleaning tower13tapers downwards, and is defined at the bottom by a basin54closed at the bottom by a rotary slide dump valve55. Above base54, cleaning tower13is defined laterally by a lateral wall56beneath suction cage52, and by a lateral wall57beneath flared conduit10. Lateral wall57has a number of holes58, through which an air stream59is directed to blow shredded tobacco stream4from flared conduit10to suction cage52. In an alternative embodiment not shown, lateral wall56also has holes for the passage of air stream59.

As it flows along channel2, shredded tobacco stream4expands sharply inside flared conduit10, which has the effect of breaking up any lumps in the tobacco, and of freeing the rest of the tobacco of so-called “heavy” parts defined by any remaining lumps, woody tobacco parts, and/or foreign bodies. The heavy parts are eliminated in cleaning tower13by force of gravity, so that the “light” parts of shredded tobacco stream4are captured by suction cage52, while the heavier parts drop down along cleaning tower13into basin54. Obviously, the specific weight and the nature of the parts deposited in basin54depend on the flow rate and speed of air stream59through holes58in lateral wall57.

In other words, in manufacturing machine1described, the shredded tobacco stream4reaching carding units45and49—of which, carding unit45may be dispensed with—is substantially clean and poses no threat to carding units45and49.

Moreover, given the expansion inside flared conduit10and the amount of air available through input unit3and cleaning tower13, cleaning of shredded tobacco stream4on manufacturing machine1is far superior to that achievable, on known manufacturing machines, immediately upstream from upflow conduit51; and the shredded tobacco stream4reaching carding units45and49is more uniform. Finally, it should be stressed that, in manufacturing machine1, the shredded tobacco stream4flowing along channel2is substantially cleaned at the expense of primary air produced in the tobacco plant anyway, and normally for other purposes, outside manufacturing machine1. Consequently, cleaning shredded tobacco stream4on manufacturing machine1involves no additional power equipment which is not already provided for, for other purposes, in the tobacco plant.

The above obviously also applies to any machine producing multiple cigarette rods, in which the end portion of channel2is defined in known manner by a number of parallel upflow conduits51closed at the top by respective conveyor belts7.