Improvement in cigarette making

Abstract: A method for making cigarettes includes heating the cut filler, which has a moisture content of greater than 12.4% by weight to a temperature greater than 35°C prior to making the cigarettes therefrom. Apparatus for use in the method is a modified conventional maker, in which winnowing of the filler is achieved by entraining the particles of filler in hot air. The hot air is provided by a fan 44 which blows air through a heat exchanger 52 and along ducting 54 to the jet block 34 of the maker. Hot air is also supplied to the flotation chamber of the maker from heating coil 66 through ducting 68.

Description: This invention relates to the processing of cigarette tobacco and in particular to the making of cigarettes with reduced packing density without significant loss of firmness. In the manufacture of cigarettes, as a rule, pneumatic conveying systems are used to transport the cut tobacco filler to the cigarette maker. An air lock at the entrance to the cigarette maker is used to separate the tobacco from the driving air stream, with the tobacco dropping out of the air lock into a hopper. The hopper is equipped with means to form a uniform tobacco flow, open out the bulk tobacco and generate single fibres, and to eliminate foreign parts and stems. Generally the tobacco is fed in small portions into a reservoir from which a steep-angle conveyer belt armed with needles or spikes continuously feeds the tobacco into a bulking chute. A level sensor in combination with a speed control of the steep-angle conveyer belt keeps the level in the hopper constant. At the downstream end of the chute is a discharge roller armed with needles. This roller, or carded drum, picks up the tobacco at a uniform rate generating a continuous flow of tobacco. A relatively fast rotating picker-roller then combs the tobacco out of the carded drum and projects it into a fast-moving air stream belt. This leads substantially to a desirable distribution of single tobacco particles, necessary for the subsequent separation of winnowers (generally veins and stems of the tobacco leaf) and for the formation of a relatively uniform tobacco rod. In some machines a rotating collector tube supports the upward acceleration of the fibres. During this transport and heavy particle separation process some degradation of tobacco particles occurs leading to a loss in quality of resulting cigarettes. The tobacco rod is formed by a narrow perforated conveyor belt of about eight to ten millimetres in width moving quickly at right angles to the direction of pneumatic conveyance. Degradation in cigarette making machines occurs mostly in the elevator conveyor, carding drums and picker winnower assemblies. Characteristics of cigarettes which are affected by the tobacco are generally considered to include (a) smoking flavour, (b) occurrences of spotting, (c) firmness of the tobacco rod, (d) collapse during smoking, (e) cull strength, and (f) degree of end fallout. Characteristics, or attributes, (c) to (f) are purely physical and normally can be predicted with a high degree of confidence by four properties of the tobacco rod. Those properties are (i) tobacco packing density, (ii) blend filling power, (iii) level and type of add-backs, and (iv) particle size distribution. The fragility of cigarettes is closely related to the packing density of the tobacco and to particle size. Reduction of the packing density using current manufacturing methods has not been satisfactorily achieved as the resulting cigarettes tend to be too fragile leading to significant handling losses. Further, the tobacco particle size normally found in cigarettes produced by current manufacturing methods is generally well below that which would produce optimum quality cigarettes. There are several reasons for this, including (α) the size of the threshed lamina, (β) the primary processing, (γ) the handling of the cut filler, and (δ) degradation of tobacco particles in the cigarette making machine. DE-C-903 436 discloses a drier for cut tobacco in which relatively warm air is blown through a layer of tobacco on a conveyor belt. DE-A-2 211 520 discloses apparatus for preparing tobacco comprising a tobacco supply including a carded drum, a conveyor for conveying the separated tobacco fibres to a tobacco rod former and a heat source for heating the separated tobacco fibres prior to the said conveying means. It has been desired to provide an improvement in the cigarette making process to reduce tobacco degradation. It has also been desired to provide a cigarette making process which results in cigarettes with reduced packing density without significant loss of firmness. According to this invention there is provided apparatus for preparing tobacco comprising means for supplying tobacco, means for separating supplied tobacco into fibres, means for conveying the separated tobacco fibres to a tobacco rod former and a heat source for heating the separated tobacco fibres prior to said conveying means conveying the separated tobacco fibres to the rod former, characterised in that the apparatus further comprises a flotation chamber in fluid communication with the supplying means and the conveying means, means for winnowing undesired components from the separated tobacco fibres in the flotation chamber before the undesired components are conveyed to the rod former and first ducting for directing air from the heat source to the flotation chamber to heat tobacco fibres therein. Also according to this invention there is provided a method of preparing tobacco comprising the steps of providing to a pneumatic chimney a supply of tobacco fibres having a moisture content greater than approximately 12.4%, pneumatically conveying the supply of tobacco fibres to a tobacco rod former via driven air, and heating the tobacco fibres in the pneumatic chimney prior to arrival at the tobacco rod former characterised in that the tobacco fibres are heated in the pneumatic chimney to a temperature greater than approximately 35°C. According to one aspect of the invention particles of tobacco filler having a moisture content of between 13.5% and 17% by weight are heated by being exposed to a heating means having a temperature of between 35° and 60° Celsius before being formed into tobacco rods. Preferably a temperature range of between 43° and 52° Celsius is employed. The heating means may be selected from infrared radiation sources, hot water jackets, heating coils, microwave radiation sources or air heated by any one or more of the foregoing. The heating process may take place during the acceleration of the tobacco filler particles from the distributor up to the permeable rod conveyor belt or from the tobacco feeding system supplying the distributor. According to another aspect of the invention there is provided an improved cigarette making machine wherein the improvement comprises the provision of means to heat tobacco filler particles prior to the making of cigarettes. As previously indicated, the heating means may comprise or may be selected from infrared radiation sources, hot water jackets, heating coils, microwave radiation sources or air heated by any one or more of the foregoing. Preferably the heating means is heated air fed into the pneumatic conveying system either prior to entry of the tobacco filler into the cigarette maker or prior to the making of tobacco rod. The making of cigarettes from tobacco fibres heated in this way has been found to result in reduced degradation of the tobacco during transport and reduced degradation within the cigarette maker. The first effect arises because the employment of an elevated temperature during cigarette making increases the moisture loss during the transport of tobacco material between the hopper and the cigarette maker. To produce cigarettes at a fixed final moisture content, the initial moisture content in the cut filler must be higher than would be the case were the tobacco to be at a lower temperature. This increase in moisture content is believed to result in better resistance to degradation during mechanical and pneumatic handling. Previously, attempts to produce cigarettes using cut filler at ambient temperature and having a high moisture content resulted in inferior products. A second effect arises from the imparting of a false order to the tobacco particles due to the heating itself, contributing to increased pliability of the tobacco particles which has the effect of potentially reducing degradation during the cigarette making process. Further, the filling power of the tobacco particles is increased. This leads to the achievement of lower packing densities. Experimental investigations have shown that warm tobacco packs less densely than cool tobacco. It may be expected from this that tobacco, when processed at an elevated temperature (and held at a controlled cigarette density) would yield firmer cigarettes than would be possible at the standard working temperature. It has been observed that finished cigarettes are hotter than normal and a cooling period or process prior to packing is required. So that the invention may be more clearly understood reference is made to the accompanying non-limitative drawings in which Figure 1 is a section through the hopper of a Molins MK-9 cigarette maker prior to modification; Figure 2 is a section through portion of the hopper of a Molins MK-9 cigarette maker modified according to the invention; Figure 3 is a schematic diagram of the pipeline of the small fan circuit of a Molins MK-9 cigarette maker modified according to the invention; and Figure 4 shows a partially phantom rear perspective view of the hopper and small fan circuit of a Molins MK-9 cigarette maker modified according to the invention. In Figure 1 the numeral 10 denotes a predistributor hopper containing cut tobacco 12. Level sensor 14 in combination with a speed control of steep-angle conveyor 16 keeps the level of tobacco below a predetermined maximum so that the pressure against the steep-angle conveyor 16, and consequently the amount of tobacco picked up by needles 18, is very uniform. The steep-angle conveyor continuously feeds cut tobacco past refuse roller 20 and elevator cleaner 22 into a bulking chute 24. A carded drum 26 armed with needles 28 at the downstream end of bulk chute 24 picks up the cut tobacco at a uniform rate thereby generating a continuous flow of tobacco. Counter-rotating smaller carded drum 30 thins out the layer of cut tobacco on the surface of carded drum. A relatively fast rotating picker-roller 32 combs the tobacco off the surface of the carded drum 26 and projects it into an upwardly directed fast-moving air stream generated by air passing through jet block 34. Rotating collector tube 36 supports the upward acceleration of the cut tobacco. Winnowers are separated out of the air stream because of differences in ratio of particle mass to aerodynamic resistance. Further separation occurs in flotation chamber 38 with the winnowers falling into spill pipe 40. The tobacco particles are accelerated up chimney 42 to the cigarette forming part of the maker. Modification of the cigarette maker to put the invention into effect includes removing the standard and small fan 44 and small fan motor 46 from within the confines of the making machine and relocating them to the rear of the machine. The fan speed is increased by using different pulleys. Ducting 48, incorporating sliding joints to allow for variation between machines, is installed between fan 44 and dust separator 50. A heat exchanger 52 is interposed in existing ducting 54 between the small fan 44 and the flotation chamber 38, at a 90° bend 56. The plastic air diffuser in the ducting is replaced by a stainless steel diffuser 58 to prevent warping. Air, after heating in heat exchanger 52, passes along ducting 54 to the stainless steel diffuser from whence it is diverted evenly up the chimney door after passing through jet block 34. The tobacco particles are heated whilst being transported over the jet block 34 and within the flotation chamber 38. Return air goes through ducting 48, via dust separator 50, to small fan 44 thus completing the loop. The dust separator 50 performs the same functions as in an unmodified cigarette maker. The temperature of the air stream after heating of the tobacco has occurred is measured by a thermocouple at the top of chimney 42. The temperature is monitored by a Eurotherm control device (not shown here) which also activates a motorised, three-way mixing valve in the pipes (not shown here) which supply water to the heat exchanger 52. The water temperature in the heat exchanger 52 is maintained at a substantially constant 82° Celsius by means of a boiler system (not shown here). With water flow controlled and air speed substantially constant, the heat exchanger 52 maintains air temperature in the ducting 54 at between 35° Celsius and 60° Celsius. In the flotation chamber 38, a perspex cover plate 60 is fitted to the front of the chamber, allowing a two to eight millimetre adjustable gap 62 for air entry. An aluminium strengthening bar 64 is used at the base of the cover to prevent warping. Heated air to the flotation chamber 38 is drawn through a heating coil 66 (Figures 3 and 4), located at the rear of the machine, and a 50 millimetre by 600 millimetre duct 68 located under the machine. The hot water supplied to the heating coil 66 is connected in series to the heat exchanger 52. Tobacco stem is extracted to the central dust system after separation in the flotation chamber. As in the standard MK-9 making machine, the object of the flotation chamber is to remove overlarge stem pieces from the tobacco mix. For the process of the invention, the temperature of the air drawn into the chamber is increased by a six row heating coil. This heating coil provides even heat transfer from aluminium fins within the casing. Hot water flow rate through the coil is the same as for the heat exchanger. Variations in inlet temperature are slight, as the air is drawn into the chamber at a low velocity. Stem extraction to the central system is via a spill pipe 40, which is installed as a kit and passes under the machine. Air temperature in chimney 42 is dependent on the flotation chamber setting. An enlarged rear vent 70 is provided to direct air flow and stop tobacco entering the spill pipe and dust extraction system. A motor driven mixing valve is used to proportion water to the heat exchanger. With velocity held constant by the fan, air passing through can be controlled to ±1° Celsius. Temperature is sensed at the chimney exit by a PT100 thermocouple and a Eurotherm type 818 controller may be used to adjust the three way mixing valve in the water supply. Flow to the system may be stopped either by turning off the control or manually controlling the valve. The Eurotherm device may incorporate preset alarms which can be used to shut down the making machine should water temperature be outside pre-defined upper and lower limits.

Claims: Apparatus (10) for preparing tobacco comprising means for supplying tobacco, means (26,30) for separating supplied tobacco into fibres, means for conveying the separated tobacco fibres to a tobacco rod former and a heat source (52,66) for heating the separated tobacco fibres prior to said conveying means conveying the separated tobacco fibres to the rod former, characterised in that the apparatus further comprises a flotation chamber (38) in fluid communication with the supplying means and the conveying means, means for winnowing undesired components from the separated tobacco fibres in the flotation chamber before the undesired components are conveyed to the rod former and first ducting (68) for directing air from the heat source to the flotation chamber to heat tobacco fibres therein. Apparatus according to claim 1 wherein the tobacco supplying means supplies tobacco having a moisture content greater than approximately 12.4%. Apparatus according to claim 1 or 2 wherein the tobacco supplying means supplies tobacco having a moisture content up to approximately 17%. Apparatus according to claim 1, 2 or 3 wherein the heat source heats the separated tobacco fibres to a temperature greater than approximately 35°C. Apparatus according to any preceding claim wherein the heat source has a temperature between approximately 35°C and approximately 60°C. Apparatus according to claim 1, 2, 3 or 4 wherein said heat source has a temperature between approximately 43°C and approximately 52°C. Apparatus according to any preceding claim wherein the conveying means comprises a fan (44) providing driven air to convey the tobacco fibres. Apparatus according to any preceding claim wherein the conveying means comprises a pneumatic chimney (42) providing driven air conveying the separated tobacco fibre and further comprises second ducting (54) for directing the heated air from the heat source (52,66) to the driven air of the pneumatic chimney conveying the separated tobacco fibres to heat the tobacco fibres. Apparatus according to claim 8, wherein the second ducting (54) for directing the heated air comprises ducting leading from the heat source (52,66) to the pneumatic chimney (42) at a location where the separated fibres are initially conveyed by driven air of the pneumatic chamber. Apparatus according to claim 8 or 9 wherein the conveying means further comprises a fan (44) providing the driven air to the pneumatic chimney, the fan driving air past the said heat source (52,66) to be heated to the pneumatic chimney (42) via the second ducting (54). Apparatus according to claim 8, 9 or 10 wherein the heat source (52,66) heats the diverted air between approximately 35°C and approximately 50°C. Apparatus according to claim 8, 9, 10 or 11 further comprising third ducting (48) for directing air to the heat source to be heated, the third ducting being in fluid communication with the pneumatic chimney (42), whereby a closed air loop is formed. Apparatus according to claim 12 wherein the pneumatic chimney (42) conveys the heated tobacco fibres to a conveyor belt moving at a right angle thereto, wherein the third ducting (48) for directing air to the heat source is in fluid communication with the pneumatic chimney (42) at an upper portion of the chimney prior to the conveyor belt. Apparatus according to any of claims 8 to 13 wherein the heat source comprises a first heater (52) for heating air driven to the pneumatic chimney (42) and a second heater (66) for heating air driven to the flotation chamber (38). Apparatus according to any of claims 8 to 14 wherein the pneumatic chimney (42) has an upper aperture communicating directly with the tobacco rod former. Apparatus according to any preceding claim wherein the heat source is a heat exchanger (52). Apparatus according to any preceding claim wherein the heat source is a heat exchanger (52) containing heated water. Apparatus according to claim 17 wherein the heated water is approximately 82°C. Apparatus according to any preceding claim further comprising a controller for controlling the temperature of the heat source. Apparatus according to any preceding claim wherein the heat source comprises a heating coil (66). Apparatus according to any preceding claim further comprising means for varying a volume of the flotation chamber, the volume varying means varying a temperature of heated air to heat tobacco fibres therein. Apparatus according to any preceding claim wherein the tobacco supplying means supplies tobacco having a moisture content greater than approximately 13.5%. Apparatus according to any preceding claim wherein the tobacco supplying means supplies tobacco having a moisture content between approximately 13.5% and approximately 17%. A method of preparing tobacco comprising the steps of providing to a pneumatic chimney (42)a supply of tobacco fibres having a moisture content greater than approximately 12.4%, pneumatically conveying the supply of tobacco fibres to a tobacco rod former via driven air, and heating the tobacco fibres in the pneumatic chimney prior to arrival at the tobacco rod former characterised in that the tobacco fibres are heated in the pneumatic chimney to a temperature greater than approximately 35°C. A method according to claim 24 wherein the providing step comprises providing tobacco having a moisture content up to approximately 17%. A method according to claim 24 or 25 wherein the heating step comprises heating the tobacco fibres to a temperature between approximately 35°C and approximately 65°C. A method according to any of claims 24, 25 or 26 wherein the heating step comprises heating the tobacco fibres to a temperature between approximately 43°C and approximately 52°C. A method according to any of claims 24 to 27 wherein the heating step comprises heating the driven air between approximately 35°C and approximately 50°C. A method according to any of claims 24 to 28 wherein the providing step comprises providing tobacco having a moisture content greater than approximately 13.5%. A method according to any of claims 24 to 29 wherein the providing step comprises providing tobacco having a moisture content between approximately 13.5% and approximately 17%.

Inventors: GOLDBERG HENRY, GROSSER HARALD, MITCHELL JAMES, WALLACE RONALD, GOLDBERG, HENRY, GROSSER, HARALD, MITCHELL, JAMES, WALLACE, RONALD
Applicants: PHILIP MORRIS PROD, PHILIP MORRIS PRODUCTS INC.
Application year: 1993
Main classification: A24C5
IPC codes: A24C5