NL2012318C2 - A method of and a device for generating batches of fibrous material in a pneumatic conveying system. - Google Patents

Description

Title A method of and a device for generating batches of fibrous material in a pneumatic conveying system.

Technical Field

The present invention relates generally to pneumatic conveying and, more specifically, to controlled generation of batches of fibrous material for conveying the material in dune or plug flow mode through a transport line of a pressure and/or vacuum pneumatic conveying system.

Background of the Invention

Pneumatic conveying of various materials or products by a pneumatic fluid through transport lines or transport pipes of a pneumatic conveying or transport system is widely used. Generally, the pneumatic fluid is a gas and in most cases the fluid is air.

Pneumatic conveying systems for the transport of fibrous material may be categorized into various modes of operation. A first mode of operation, for example, comprises continuous feeding, wherein it is an object to maintain a continuous flow of material through the transport line, at least for the amount of the material to be transported. In a second mode of operation, for example, the fibrous material is conveyed through the transport line in suspension flow, by which the fibres are conveyed substantially apart from each other. In a third mode of operation the fibrous material is conveyed through the transport line by separate, spaced apart batches of fibrous material, also called plugs or dunes. Generally, a plug occupies a larger cross-section of the transport line than a dune. In a mixed mode, the fibrous material is conveyed by a substantially continuous layer of material comprising separately spaced dunes, also called dune and layer flow mode.

In a pneumatic conveying system for producing manufactured tobacco products, like cigarettes, cut tobacco is conveyed in batches by a fluid flow through a transport line from a storage or feeding or tobacco delivery device to a tobacco processing device, such a cigarette maker. A pneumatic tobacco conveying system is typically operated in a vacuum or low pressure or suction fluid flow operation.

By operating the pneumatic tobacco conveying, or in general the pneumatic conveying of material that is vulnerable or prone to damaging during transport, in batch type mode, damaging is substantially limited to the cut tobacco that is in direct contact with the wall of the transport line or feed line, such as a transport pipe. Cut tobacco inside the batch will encounter substantially less damaging or degradation during transport. This, contrary to operation of a pneumatic conveying system in suspension flow mode in a device for feeding cut tobacco to a tobacco processing device, because in this transport mode each tobacco fibre is separately exposed to mechanical stresses during transport. A cigarette maker is generally filled by a few batches of cut tobacco. Typically, the tobacco is delivered at a so-called air lock of the cigarette maker that separates the pneumatic fluid, such as air, from the cut tobacco. If a required amount of cut tobacco is received at the air lock, the tobacco is dropped into the cigarette maker, and the air lock is filled again after a delay time depending on the processing capacity of the maker, i.e. the number of cigarettes or other tobacco products that may be manufactured by the maker per unit of time, and of course the amount of tobacco delivered.

In practice, during the delay time, the pneumatic conveying is stopped or halted and tobacco stalls in the conveying pipe, until the cigarette maker initiates a new feeding request. It will be appreciated that during the delay time, tobacco in vertical pipe sections or stretches drops down. To prevent the presence of multiple batches or dunes in vertical pipe stretches, which bears the risk of clogging of cut tobacco in the transport line, the interval between batches or dunes in the conveying system needs to be controlled. At restart of the conveying, all the stalled material inside the conveying pipe needs to exceed the static break-loose wall friction against the transport pipe and be accelerated by the air flow. The fluid pressure difference, such as an air pressure difference, required for accelerating the stalled batches, in practice, ranges between about 1500 and 3500 Pa. The overall system pressure change depends on the feeding distance and may range between 4000 - 8000 Pa.

By way of example, in a practical single transport line cigarette processing system, about 6 - 7 kg of cut tobacco may be delivered to a cigarette maker in about 15-35 seconds, with a fluid flow velocity or speed ranging from about 9-23 m/s and a tobacco velocity or speed ranging from about 7-21 m/s. Typically, transport pipes vary in length between 50 - 500 m and have an internal diameter of about 80 - 150 mm. Pipe lengths of 200 m are fairly standard. Batches, i.e. dunes or plugs, of cut tobacco measured in longitudinal or lengthwise direction of the transport pipe typically have a length between about 0.5 - 2 m and may have a mutual distance or spacing interval of about 5 - 15 m.

Presently widely used cigarette makers provide production capacities that range from 6,000 up to 14,000 cigarettes per minute for a high-speed cigarette maker. This requires that an amount of tobacco of about 4 - 15 kg per minute is to be delivered at the cigarette maker. Ultra high-speed cigarette makers, such as commercially known under the product name PROTOS-M8™ by Hauni, may produce 20,000 cigarettes per minute or even more. Such ultra high-speed cigarette makers require a delivery of about 13 - 18 kg cut tobacco per minute or even more.

For serving high-speed and ultra high-speed cigarette makers, in practice, two transport lines operate in parallel to feed the required amount of tobacco per minute to the cigarette maker. From a control point of view, parallel operating feed transport lines present several problems, in particular if one the transport lines is malfunctioning and when tobacco stalls or clogs in a transport line.

In practice, there is a need for a controlled generation of batches, such as dunes or plugs of fibrous material, like cut tobacco, tea leaves or other materials vulnerable to transport damaging, having an improved fiber distribution to minimize material degradation resulting in less short fibers and less dust. In particular, the volume or amount and size of dunes or plugs and/or the interval or distance between dunes or plugs in the transport line should be adjustable. The purpose of such adjustable or controllable batch conveyance is to optimize the material loading, i.e. the mass of material over the mass of consumed fluid, in a controlled manner, resulting in an overall yield improvement and an improved amount of material to be delivered per unit of time.

Summary

It is an object of the present invention to provide a reliable and controllable method for generating batches of fibrous material for pneumatic conveying by a pneumatic fluid flow in a transport line of a pneumatic conveying system.

It is a further object of the present invention to provide a batch generating device for generating batches of fibrous material for pneumatic conveying by a pneumatic fluid flow in a transport line of a pneumatic conveying system.

In a first aspect, there is provided a method of generating a batch of fibrous material for pneumatic conveying by a pneumatic fluid flow in a transport line of a pneumatic conveying system from a material inlet, connecting to a material storage or feeding device, to a material outlet, connecting to a material processing device, and past an applied material conveying resistance arranged in the transport line at the material inlet thereof, the method comprising the steps of: - collecting material in the transport line at the material inlet from the storage or feeding device by a fluid flow operating upstream of the material conveying resistance at a first conveying capacity value insufficient for conveying the collected material past the material conveying resistance, - sensing static pressure in the transport line downstream of the material inlet, and - controlling the fluid flow upstream of the material conveying resistance at a second conveying capacity value higher than the first conveying capacity value, for conveying the collected material as a batch of material past the material conveying resistance, dependent on the sensed static pressure.

The method according to the invention is both applicable in a pressure or over-pressure and/or vacuum pressure or suction type pneumatic conveying system. The term ‘applied material conveying resistance’ refers to a conveying resistance or conveying impedance functionally, i.e. intentionally, applied in the transport line, i.e. the transport path of the material to be conveyed.

In the material collecting step, fibrous material from the storage or feeding device is fed into the transport line of the conveying system from the material inlet thereof, however the conveying capacity of the fluid flow operating at the material inlet is controlled to be at a first conveying capacity value insufficient, i.e. too low, for transporting the fibrous material past the material conveying resistance. As a result, fibrous material is collected in the transport line near the material inlet thereof.

As the amount of material collected gradually increases, the static pressure in the transport line downstream of the material inlet sensed at the front of the material collected, seen in the conveying direction, changes. That is, in the case of a vacuum pressure or suction type pneumatic conveying system, the absolute value of the negative static pressure, i.e. the vacuum pressure, increases. For a pressure or over-pressure pneumatic conveying system, the static over-pressure decreases. However, the value of the material velocity and material pick-up pressure in the case of a vacuum pressure conveying system remain too low to transport the fibrous material past the material conveying resistance. Thus, at the material inlet of the transport line a batch of fibrous material is formed.

Knowing the pressure development characteristics of the applied material resistance, the amount and rate at which the static pressure downstream of the material inlet develops over time, is a measure for the amount or volume of the fibrous material collected. Accordingly, sensing or measuring the static vacuum pressure at the front of the material collected provides a measure for the amount of material collected at the material inlet.

Once a desired or intended amount of material is collected, by controlling the fluid flow upstream of the material conveying resistance to be at a second conveying capacity value higher than the first conveying capacity value and sufficient to exceed the material resistance and static or break-loose wall friction of the collected fibrous material against the transport line, i.e. the launching resistance, the collected material starts conveying as batch of material past the material conveying resistance.

Accordingly, with the method of the invention, by suitably controlling the fluid flow upstream of the material conveying resistance at the first and the second conveying capacity, respectively, dependent on the static pressure build up in the transport line downstream of the material inlet and upstream of the material conveying resistance, the amount, i.e. the weight, or volume of a batch of tobacco may be accurately controlled.

In an embodiment of the method according to the invention, the fluid flow upstream of the material conveying resistance is controlled from the first to the second conveying capacity value dependent on at least one of a set pressure value and a set material collecting or material feeding time period or time interval. The set pressure value or material collecting or feeding time period or time interval may depend on the material properties, such as for example the blend of the cut tobacco to be conveyed, the shape and cross-sectional dimensions of the transport line, environmental conditions, and the like.

More particularly, when the pneumatic conveying system is a suction or vacuum conveying system, the sensed static pressure is a vacuum pressure, and the fluid flow upstream of the material conveying resistance is controlled at the second conveying capacity value dependent on at least one of: - the sensed static vacuum pressure is at or above a set static vacuum pressure threshold, and - the sensed static vacuum pressure increases at a set rate of change during a set time interval.

When the pneumatic conveying system is a pressure conveying system, the sensed static pressure is an over-pressure, the fluid flow upstream of the material conveying resistance is controlled at the second conveying capacity value dependent on at least one of: - the sensed static pressure is at or below a set static pressure threshold, and - the sensed static pressure decreases at a set rate of change during a set time interval.

The static pressure is real time or nearly real time sensed or measured and compared against the set threshold. The rate at which the static vacuum pressure develops or changes may be calculated by differentiation of the real time or quasi real time sensed static pressure.

For control and feedback purposes, the shape and/or material density of batches formed may be monitored and measured. Based on these measurements, a set static pressure threshold and a set time interval may be adapted such that a batch comprises a desired or required volume or amount of material.

In a further embodiment of the method according to the invention, the fluid flow upstream of the material conveying resistance is controlled by opening or closing a fluid flow gate of the transport line downstream of the material conveying resistance.

In the case of a vacuum or suction type conveying system, this fluid flow gate or aperture or orifice operates as a shunt of the pneumatic fluid flow upstream of the material conveying resistance. Such that when this shunt or fluid flow gate is opened, the pneumatic fluid flow upstream of the material conveying resistance is decreased compared to the case in which the shunt or fluid flow gate is closed or less opened. In case of air as the transport medium, the amount of negative pressure or vacuum pressure in the transport line for launching the batch of collected material depends on the amount of so-called false air injection via the fluid flow gate downstream of the material conveying resistance. It will be appreciated that by this embodiment of the invention the fluid flow in the pneumatic conveying system downstream of the fluid flow gate may be kept at conveying capacity value required for conveying already generated batches. That is, conveying of already generated batches may be continued, independent of the generation of a new batch.

For a pressure or over-pressure type conveying system, this fluid flow gate operates as a shunt of the pneumatic fluid flow downstream of the material conveying resistance. Such that when this shunt or fluid flow gate is opened, the static pressure in the transport line is too less to convey the material past the material conveying resistance.

Those skilled in the art will appreciate that the fluid flow gate may be positioned outside the conveying path of the batch of fibrous material, thereby avoiding damaging of the fibrous material by a control valve or other device for opening and closing the fluid flow gate.

In accordance with the invention, in a practical embodiment thereof, for building a batch of material, the fluid flow upstream of the material conveying resistance is controlled at a first conveying capacity value ranging between 20 - 30 % of the fluid flow conveying capacity downstream of the material conveying resistance, and the fluid flow upstream of the material conveying resistance is controlled at a second conveying capacity value ranging between 80 - 100 % of the fluid flow conveying capacity downstream of the material conveying resistance.

It will be appreciated that the first conveying capacity value, among others, controls the speed or rate at which the batch is formed during the material collecting step, and in that the second conveying capacity value, among others, determines the acceleration by which the batch is conveyed or launched into the conveying system.

In another embodiment of the invention, the material conveying resistance may be controlled for compacting the collected material into a compact batch if the fluid flow upstream of the material conveying resistance is at the second conveying capacity value. That is, the material conveying resistance may be actively controlled to form a temporarily higher resistance when launching the collected material in the conveying system, thereby compacting the collected material into a stable and compact batch, and to form a reduced resistance once the batch is conveying. In the meaning of this embodiment, the term controlled includes shaped or designed. Material conveying resistances for the purpose of the invention may be formed by throttle type valves, controllable shutters, part or parts of a transport line having a reduced or restricted cross-section, whether or not controllable.

In an embodiment of the invention for compacting the collected material, the material conveying resistance is comprised of a first applied material conveying resistance, arranged in the transport line at the material inlet, and a second applied material conveying resistance, arranged in the transport line at a distance downstream of the first material conveying resistance, the static pressure in the transport line is sensed between the first and second material conveying resistance, and the fluid flow for conveying the batch is controlled at a second conveying capacity value for conveying the collected material as a batch of material past the first and second material conveying resistances. A typical example of such a first and subsequent second conveying resistance, seen in the conveying direction of the material, in accordance with the invention, is a vertically positioned substantially S-shaped part of a transport line, for example.

In a start-stop pneumatic conveying system, such as a typical cut tobacco conveying system as described above, in accordance with the method of the invention, during the delay time in which the pneumatic fluid flow in the transport line is stopped or halted, the fluid flow upstream of the material conveying resistance may be controlled or set at the first conveying capacity value for collecting new material in the transport line, after which the fluid flow upstream of the material conveying resistance is controlled at the second conveying capacity value, thereby repetitively alternately generating a plurality of batches of collected material. A series of batches may also be generated by controlling the fluid flow capacity upstream of the material conveying resistance from a third conveying capacity value insufficient for taking-up any or hardly any material at the material inlet, to the first conveying capacity value for collecting material, etc. The interval between batches is determined by the amount of time during which no material is picked-up. In this embodiment, the material storage or feeding device may be continuously filled with material. Conveying will continue, of course, as long as material is requested by the material processing device.

In another embodiment of the method according to the invention, in particular for repetitively alternately generating a plurality of batches of fibrous material, the interval between the batches is controlled by jointly controlling the value of the fluid flow upstream of the material conveying resistance and the feeding ratio of material at the material inlet. That is, material is fed from the material storage or feeding device for collecting at the material inlet in dependence of the repetitively, alternately controlled fluid flow upstream of the material conveying resistance. Such that material is allowed to be fed into the inlet when the fluid flow upstream of the material conveying resistance is at its first conveying capacity value, and the material feed is stopped or blocked when the fluid flow upstream of the material conveying resistance is at its second conveying capacity value. Controllable material storage or feeding devices for use for the purpose of the invention are, inter alia, known in practice as gravity-, bowl-, or rotary drum feeder.

If a dune and layer mode of operation is required, for example, at the material inlet a continuous feed of material may be provided, while the conveying capacity value of the fluid flow upstream of the material conveying resistance may be controlled at an intermediate conveying capacity value, between the first and second conveying capacity value, and sufficient for feeding material at the material inlet and conveying same past the material conveying resistance, thereby forming a continuous layer of material in the transport line.

In a yet further embodiment of the invention, for supporting the launching of a batch of material, when the fluid flow upstream of the material conveying resistance is at the second conveying capacity value, an additional fluid flow is injected from the material inlet, in particular wherein the additional fluid flow is pulsewise injected from the material inlet. This additional fluid flow is of a value to support the launching of the batch by overcoming the static break-loose wall friction against the transport pipe and thereby decreases the time needed for accelerating the batches to the desired transport speed.

In practice, with the method according to the invention, wherein the material to be conveyed is cut tobacco and the material processing device is a cigarette maker, a plurality of batches may be generated providing an amount of cut tobacco to the cigarette maker ranging between 10 and 20 kg/min through a single transport line. This implies that with the method according to the invention highspeed and ultra high-speed cigarette makers may be served from a single transport line, to feed and load the required amount of tobacco per minute into the cigarette maker.

The method according to the invention is in particular well-suited for the pneumatic conveyance of any type of fibrous material beyond cut tobacco, such as tea leaves and many fibrous materials vulnerable to transport damages in a transport line of a pneumatic conveying system.

In a second aspect there is provided a batch generating device for generating a batch of fibrous material for pneumatic conveying in a transport line of a pneumatic conveying system, the batch generating device comprising: - a device material inlet, arranged for connecting to a material storage or feeding device, - a device material outlet, arranged for connecting to the pneumatic conveying system, such that in use a pneumatic fluid flow is operative from the device material inlet to the device material outlet, - an applied material conveying resistance arranged between the device material inlet and the device material outlet, - a static pressure sensor, arranged downstream of the device material inlet, for sensing static pressure in the device, and - control equipment, comprising an electronic control unit arranged for controlling the fluid flow upstream of the material conveying resistance at a first conveying capacity value, for collecting material at the device material inlet and insufficient for conveying the collected material past the material conveying resistance, and at a second conveying capacity value higher than the first conveying capacity value for conveying the collected material as a batch of material past the material conveying resistance, dependent on the sensed static pressure.

The static pressure sensor may be any of a commercially available pressure sensor operatively connecting to the control equipment, and the control equipment may comprise a processor for sensing or calculating and monitoring static pressure development and controlling the conveying capacity of the fluid flow upstream of the material conveying resistance.

In an embodiment of the batch generating device according to the invention, the control equipment comprises a valve having a controllable opening arranged for opening and closing a fluid flow gate or aperture or orifice of the device, by the control unit, which fluid flow gate being arranged downstream of the material conveying resistance. In practice, fast responsive servo type valves are preferred.

In another embodiment of the batch generating device according to the invention, the control unit is arranged for repetitively alternately controlling the fluid flow upstream of the material conveying resistance at the first and second conveying capacity value, for generating a plurality of batches of collected material. In an exemplary embodiment thereof, the device material inlet connects to a controllable material storage or feeding device, wherein the control equipment is arranged for controlling a feeding ratio of material at the inlet in dependence of controlling of the fluid flow upstream of the material conveying resistance.

In a further embodiment of the invention, in particular for compacting a dune of material, the batch generating device comprises a material conveying resistance having a first applied material conveying resistance, arranged at the device material inlet, and a second applied material conveying resistance, arranged at a distance of the first material conveying resistance towards the device material outlet, wherein the static pressure sensor is arranged between the first and second material conveying resistance.

In a preferred embodiment of the invention, the batch generating device comprises a substantially elongated S-shaped transport line, a first end of which comprising the device material inlet and a second end of which comprising the device material outlet, wherein the static pressure sensor is arranged for sensing static pressure in the S-shaped transport line at an elongated part thereof between a first bend connecting to the first end and a second bend connecting to the second end, and a fluid flow gate arranged at the second bend and comprising a valve operatively connected to the control unit and having a controllable opening for opening and closing the fluid flow gate by the control unit, wherein in use the elongated part of the S-shaped transport line is in an upright position and the first bend comprises a first applied material conveying resistance and the second bend comprises a second material conveying resistance.

Such an S-shaped transport line batch generating device is very beneficial for use in a vacuum or suction type pneumatic conveying system for the generation of batches, i.e. dunes or plugs, of fibrous material prone to transport damaging, such as cut tobacco, in that the complete conveying path from the inlet to the outlet thereof is free from possible material damaging movable parts, such as movable sleeves or the like, and transport line cross-sectional constrictions or constricting valves, such as throttle type valves. This, because the batch generating device is completely constructed as part of the transport line, such as a transport pipe.

It has been found that constructing the first and second bend or curve having a bend radius or radius of curvature of about 5-7 times the cross-section diameter of the transport pipe of a transport line contributes to optimal pressure development conditions, gentle compaction of a batch and continuous batch conveyance and batch interval control.

In a yet another embodiment of the batch generating device according to the invention, for supporting the launching of the batch of material, an additional fluid flow injecting device is provided, arranged at the device material inlet and operatively connected to the control unit for supporting conveying of the collected material past the material conveying resistance by providing an additional fluid flow. Preferably, the fluid flow injecting device, or batch launcher, is arranged for pulsewise injecting the additional fluid flow at the device material inlet.

In a third aspect there is provided a pressure, i.e. an over-pressure, or vacuum pressure, i.e. a suction, type pneumatic conveying system arranged for pneumatic conveying of fibrous material by a pneumatic fluid flow in a transport line of the pneumatic conveying system, from a material storage or feeding device to a material processing device, the pneumatic conveying system comprising fluid flow generating equipment and a batch generating device operatively arranged according to any of the embodiments of the invention disclosed above, for conveying fibrous material comprising any of cut tobacco, tea leaves and other fibrous materials, in particular materials vulnerable to transport in the transport line of the pneumatic conveying system.

With the batch generation method and batch generating device according to the invention, the ratio of the amount of material transported, for example expressed by its weight in kg, and the amount of fluid, such as air, likewise expressed in kg, also called loading or loading ratio, by a pneumatic conveying system, may be effectively optimized in that the volume or amount and size of dunes or plugs is accurately adjustable by sensing and monitoring the vacuum pressure development and/or the rate of change of the vacuum pressure downstream at the material inlet, while the material is picked-up and collected by the batch generator, and/or in that the interval or distance between dunes or plugs in the transport line is adjustable by jointly controlling the value of the fluid flow upstream of the material conveying resistance and the feeding ratio of material at the material inlet, for example.

For control and feedback purposes, the shape and/or material density of batches formed may be monitored and measured and used for setting or adapting static pressure thresholds, a material feeding ratio by controlling the delivery of a material feeding device, for example, and/or the feeding or collecting time or time interval, such that a batch comprises a desired or required volume or amount of material.

By being able to accurately control the batches generated in accordance with the invention, a set material transport velocity and/or mass flow rate is accurately achievable, taking into account an amount of material to be delivered in a certain time period.

The above-mentioned and other features and advantages of the invention are illustrated in the following description with reference to the enclosed drawings which are provided by way of illustration only and which are not limitative to the present invention.

Brief Description of the Drawings

Fig. 1 shows, in a schematic, perspective and illustrative manner, a typical transport of fibrous material travelling in dune flow mode through a transport line of a pneumatic conveying system.

Fig. 2 shows, in a schematic, perspective and illustrative manner, a typical transport of fibrous material travelling in dune and layer flow mode through a transport line of a pneumatic conveying system.

Fig. 3 shows, in a schematic and illustrative manner, a cross-sectional view the transport of fibrous material according to Fig. 2 in longitudinal direction of the transport line.

Fig. 4 shows, in a schematic and illustrative manner, an exemplary embodiment of a vacuum type pneumatic conveying system for feeding cut tobacco from a storage or feeding or tobacco delivery device to a tobacco processing device, such as a cigarette maker, comprising a plurality of batch generating devices operated in accordance with the invention.

Fig. 5 shows, in a schematic, and illustrative manner, in a longitudinal cross sectional view, an embodiment of a batch generating device in accordance with the invention.

Fig. 6 shows a basic flow chart of an embodiment of the method according to the invention.

Fig. 7 shows, in a schematic, and illustrative manner, in a cross sectional view, a preferred embodiment of a batch generating device in accordance with the invention.

Fig. 8 shows a graph of the static pressure build up versus time sensed in a practical embodiment of a batch generating device constructed as shown in Fig. 7.

Fig. 9 shows, in a schematic, perspective and illustrative manner, in a cross sectional view, detail of a further embodiment of the batch generating device in accordance with the invention.

Detailed Description

Figure 1 shows, in a schematic, partly cut-away perspective view, part of a transport line 1, such as a circular cylindrical transport pipe, of a pneumatic conveying system in which fibrous material 2, such as cut tobacco, is transported in a typical batch flow mode, comprising dunes 3, 4. The dunes 3, 4 are conveyed by a pneumatic fluid flow in the transport line 1, such as a gaseous medium like air, schematically indicated by arrow 6.

Figure 2 shows, in a same manner as Figure 1, a typical dune and layer flow mode, having between the dunes 3, 4 a layer 5 of fibrous material, such as cut tobacco.

Figure 3 shows the dunes 3, 4 and layer 5 of fibrous material in a cross-sectional view of Figure 2 in longitudinal direction of the transport line 1. Parameter H indicates the height of a dune 3, 4 measured in radial direction of the transport line 1. Parameter h indicates the height of the layer 5 measured in radial direction of the transport line 1. The length of a dune 3, 4 measured in longitudinal direction of the transport line 1 is indicated by a parameter L. The distance length between two subsequent dunes 3, 4 in longitudinal direction of the transport line 1 is indicated by a parameter D, also called the dune interval. It will be appreciated that the height H and distance D may vary from dune to dune and between dunes, respectively. Likewise, the height h of the layer 5 may vary between subsequent dunes. In the most optimum transport mode, however, for achieving an even and continuous as possible transport of the fibrous material 2, the various heights H, h and distances D differ slightly from dune to dune, this to obtain a constant and homogeneous delivery of an amount of fibrous material at a material processing device.

Batches of fibrous material that more or less completely occupy the cross-section of the transport line 1 are called plugs, this instead of dunes which just occupy part of the cross-section of the transport line 1, as illustratively shown in Figures 1 and 2. In both dune and plug flow mode, gaseous medium 6 may still flow across or through and along the material in the transport line 1.

Figure 4 shows, in a schematic and illustrative embodiment, an example of a system 10 for feeding cut tobacco from a storage or feeding or tobacco delivery unit 12-1 to a tobacco processing device 13, such as a cigarette maker, by a vacuum pressure or suction type pneumatic conveying system 11. The cut tobacco, or in general fibrous material, is transported in batches, i.e. in dune or plug flow mode or dune and layer flow mode, from the storage or feeding or cut tobacco delivery unit 12-1 to the tobacco processing device 13 via an intermediate transport line 14, also called a feed line of the pneumatic conveying system 11.

The system 10 typically comprises a plurality of cut tobacco storage or feeding or delivery units 12-1, 12-2, ..., 12-n (n > 1) each containing, for example, a different blend of cut tobacco. For selecting a particular delivery unit 12-1, 12-2, ..., 12-n a so-called blend selector 15 is provided. The blend selector 15 comprises a plurality of inputs 16-1, 16-2, ..., 16-m (m > 1) that each connect to a respective output 17-1, 17-2, ..., 17-m of the blend selector. In the embodiment shown, delivery unit 12-1 connects via a feed line 18-1 to input 16-1 of the blend selector 15. At the corresponding output 17-1 of the blend selector 15 the transport or feed line 14 to the cut tobacco processing device 13 connects, such that cut tobacco from the delivery unit 12-1 is introduced and transported or conveyed to the cut tobacco processing device 13.

For producing tobacco products by the tobacco processing device 13 having a different blend, a respective one of the other storage or feeding or delivery units 12-2, ..., 12-n has to be connected, with its feed line 18-x (x=2, ..., n), to input 16-1 of the blend selector 15, of course by first disconnecting the feed line 18-1. A particular storage or feeding or delivery unit 12-1, 12-2, ..., 12-n may comprise several feed lines 19-x, 20-x, etc. (x=1, 2, ..., n) for connecting the respective delivery unit to a respective (other) input 16-1, 16-2, ..., 16-n of the blend selector 15, at each output 17-2, ..., 17-n of which, by a respective pneumatic conveying system, a further cut tobacco processing device may connect.

In the embodiment shown, the pneumatic conveying system 11, downstream of the cut tobacco processing device 13, comprises a unit 21, such as a fan or equivalent device for creating a low pressure or vacuum in the transport line 14. To prevent entrance of dust or other substances of cut tobacco from the transport line 14 into the unit 21, a dust filter 22 is provided in front of the unit 21, when viewed in the material transport direction, schematically indicated by arrows 24.

In the embodiment shown, the unit 21 is operative for a plurality of cut tobacco processing devices 13, via a plurality of pneumatic conveying systems 11, the transport lines 14 of which are collected by a line collector unit 23 which collects, for example, six transport lines 14.

Tobacco transport in the transport line 14 is operated according to a demand driven start-stop process. For providing an amount of tobacco for processing by the cut tobacco processing device 13, a so-called air lock 25 is incorporated in the transport line 14 at the cut tobacco processing device 13. Behind the air-lock 25, when viewed in the transport direction 24, a valve 26 is included in the transport line 14. This valve 26, also called maker valve, is operated by the cut tobacco processing device 13, such as a cigarette maker. The maker valve 26 operates for closing and opening of the transport line 14, i.e. for stopping and starting the material transport there through.

For controlling the pneumatic fluid flow in the transport line 14, a fluid flow control unit 27, for example in the form of at least one flow control valve such as a servo motor driven pressure regulator-reducer, is incorporated in the transport line 14 between the maker valve 26 and the line collector unit 23. The fluid flow control unit 27 operatively connects 38 to and is operated by a control system 28.

Reference numerals 29, 30 and 31 indicate devices of the control system 28 for determining physical parameters, such as pressure and velocity or speed of the material and pneumatic fluid transport in the transport line 14 at a position in front of the cut tobacco processing device 13, when viewed in the transport direction 24, and the shape and/or density of the batches. The values measured by any of the devices 29, 30 and 31 are provided to a digital processing device or electronic processor or computer 32.

The feed lines 18-x, 19-x, 20-x, (x=1, 2, ..., n) are provided with a batch generating device 35 according to the invention, for generating batches of cut tobacco in accordance with a desired operational mode and a desired loading or loading ratio of the cut tobacco transport, dependent on the particularities of the cut tobacco processing device 13, such as a cigarette maker. Each of the feed lines 18-x, 19-x, 20-x, (x=1, 2, ..., n) may be provided with a batch generating device 35 at their respective material inlet or intake 34, operative according to the invention.

Each of the batch generating devices 35 may be operatively, communicatively connected 37 to the control system 28, i.e. the digital processing device or electronic processor or computer 32, for forwarding sensed or measured values, such as static vacuum pressure measurements, and for receiving control commands and feedback information from the control system 28, for controlling the generation of batches of cut-tobacco in accordance with the invention. For clarification purposes, only the connections 37 to the control system 28 of the batch generating devices 35 in the feed lines 18-1, 18-2 and 19-n are shown. It will be appreciated that the batch generating devices 35 may operate automatically, in a stand-alone mode, for example.

For generating repetitive batches of cut tobacco, the batch generating devices 35 and corresponding storage or feeding or delivery units 12-1, 12-2, ..., 12-n may need to be jointly controlled, i.e. for controlling the feeding ratio of material at a material inlet 34. To this end, the batch generating devices 35 and corresponding storage or feeding or delivery units 12-1, 12-2, ..., 12-n are communicatively connected, as indicated by connections 36. Those skilled in the art will appreciate that the storage or feeding or delivery units 12-1, 12-2, ..., 12-n may each connect separately to the digital processing device or electronic processor or computer 32. Controllable material storage or feeding devices for use for the purpose of the invention are known in practice as gravity-, bowl-, or rotary drum feeder. Again, for clarification purposes, only the connections 36 of the batch generating devices 35 in the feed lines 18-1, 18-2 and 19-n are shown.

The processing device 32 is suitably programmed for processing the input received from each of the devices 29, 30, 31 and, if applicable, the batch generating devices 35 and storage or feeding or delivery units 12-1, 12-2, ..., 12-n, for controlling the material transport in the feeding line 14 by suitably operating the batch generating devices 35, the storage or feeding or delivery units 12-1, 12-2, ..., 12-n, and the fluid flow control unit 27. Such to provide a desired batch wise material transport in dune flow mode, plug flow mode or dune and layer flow mode in the transport line 14 from the storage or feeding or delivery unit 12-1 to the cut tobacco processing device 13, for example.

Servo motor driven pressure regulator-reducer valves and velocity sensing or determining or measurement devices, as such, are known to the skilled person and commercially available. The latter may include indirect velocity or speed measurement devices such as pressure and pressure difference measurement devices measuring pressure of the pneumatic fluid at several positions in and along the transport line, from which the particular velocities may be determined. Examples of known material speed measurement devices are capacitively operating dielectric devices, electrical capacitance tomography (ECT) measurement devices, coriolis force meters, electrostatically operating devices, particle tagging, acoustic measurements, etc. Measurement data in both analogue and/or digital form may be processed.

As will be appreciated by those skilled in the art, a number of other control mechanisms may be provided at the pneumatic conveying system 11, such as valves for releasing pneumatic fluid from the material delivery unit 12, the transport line 14, safety valves, and the like (not shown). Direct controlled, fast responding servo drive valves provide for a fast response to control dune instabilities and to prevent clogging of the material in the transport line as adequate as possible.

In operation, in the state of the system 10 as shown in Figure 4, the unit 21 is operative to create a low-pressure or vacuum in the transport line 14 and the respective batch generating device 35 and, if applicable, the storage or feeding or delivery unit 12-1, such that batches of cut tobacco are introduced into the transport line 14, from the material delivery unit 12-1, and transported to the cut tobacco processing device 13. By the air-lock 25 cut tobacco from the transport line 14 is received and collected. Once the cut tobacco processing device 13 requires an amount of cut tobacco, it closes the maker valve 26 and the cut tobacco 33 is released from the air-lock 25 and delivered to the cut tobacco processing device 13, after which the maker valve 26 is opened again. The amount of cut tobacco delivered and the flow mode of the fibrous material in the transport line 14 are typically achieved by controlling the pneumatic fluid in the transport line 14 from the control system 28 operating the flow control unit 27 and the batch generating device 35 and, if applicable, the storage or feeding or delivery unit 12-1. By advance balancing calculations, in the batch generating device 35 a required pick-up pressure is controlled, for introducing cut tobacco in the transport line 14 from the material delivery unit 12-1 to support a desired loading or loading ratio of the cut tobacco transport.

In the case of a pressure or over-pressure pneumatic conveying system, a fluid flow for conveying the fibrous material in the transport direction 24 through the transport line 14 is operated at the material inlet 34, for example by a source of pneumatic fluid operating through a hopper type delivery units 12-1, 12-2, ..., 12-n or the like.

Figure 5 shows, in an illustrative manner, a preferred embodiment of a batch generating device 35 in accordance with the invention. The device 35 comprising a substantially elongated transport pipe 40, such as circle cylindrical transport pipe, having the same inner dimensions as a transport pipe of a transport line 14 of a pneumatic conveying system in which the batch generating device 35 is used, such as the system 10 shown in Figure 4. A first end of the transport pipe 40 of the batch generating device 35 forms a device material inlet 41 and a second end of the transport pipe 40 opposite the first end forms a device material outlet 42 for directly connecting to a transport line of a pneumatic conveying system. The device material inlet 41 connects a storage or feeding or delivery unit 43, comprising fibrous material 44 to be transported.

Between the device material inlet 41 and the device material outlet 42, a material conveying resistance 45 is applied. In the embodiment shown, the applied material conveying resistance 45 is constructed as a local constriction or reduction of the cross-section of the transport pipe 40. Material conveying resistances for the purpose of the invention may also be formed by throttle type valves or shutters or the like, arranged in the transport pipe 40, either fixed or controllable such that the amount of resistance or impedance applied may be varied. To this end, the material conveying resistance 45 may be of an inflatable, elastic and smooth membrane 46, such that when deflated the inner surface of the membrane 46 is flush with the inner surface of the transport pipe 40. The membrane 46 may be formed inside the transport pipe 40 or as a separate part connecting between two sections of the transport pipe 40, for example.

In operation, a pneumatic fluid flow operates in the transport pipe 40 in the direction from the device material inlet 41 to the device material outlet 42, such as indicated by arrow 47 at the device material outlet 42. In the case of vacuum pressure or suction type pneumatic conveying system, the fluid flow 47 may be generated by the unit 21 shown in Figure 4. In the case of a pressure or overpressure type pneumatic conveying system, the fluid flow 47 may be generated from the material device inlet 41, through a hopper type storage or feeding or delivery unit 43, by a blower or other source of fluid flow, schematically indicated by arrow 48.

In the example embodiment of the batch generating device 35 shown, downstream of the material conveying resistance 45, that is viewed with respect to the operational direction of the fluid flow 47, a controllable valve 49, such as a throttle type valve, is arranged for controlled opening and closing of a fluid flow aperture or orifice or gate 50 of the transport pipe 40. The gate 50 may connect to the transport pipe 40 by a dust filter 51, blocking dust or fibers from leaving the transport pipe 40 through the valve 49. The dust filter 51 is permeable for the fluid flow 47. In practice, a fast responsive servo type valve is preferred.

Downstream of the device material inlet 41 a sensor 52 connects to the transport pipe 40, for sensing static pressure in the device 35. In the particular embodiment shown, the static pressure sensor 52 is arranged between the device material outlet 42 and the material conveying resistance 45 for sensing the static pressure between the material conveying resistance 46 and the fluid flow gate 50. For the purpose of the invention, the static pressure sensor 52 may be any of a commercially available pressure sensor.

The controllable valve 49 and the pressure sensor 52 operatively connect to control equipment 53, comprising a control unit or control module such as processor or micro-computer for measuring or monitoring and calculating static pressure development in the device 35 and controlling the conveying capacity of the fluid flow upstream of the material conveying resistance 45, i.e. seen with respect to the operational direction of the fluid flow 47. As indicated, in the case of a controllable material conveying resistance 45, the control equipment 53 may operatively control the resistance or impedance value of the material conveying resistance 45. The control equipment 53 likewise may control the amount of fluid flow provided by the source 48, in the case of an over-pressure conveying system, for example. In operation, the control equipment 53 may connect to a common or general control system of a pneumatic conveying system, such as the control system 28 of the conveying system 10 shown in Figure 4.

The operation of the batch generating device 35 is now disclosed with reference to the basic flow chart 60, shown in Figure 6. In the flow chart of Figure 6, the course of the subsequent operational steps, or forward direction, is from the top of the drawing to the bottom thereof. Backward steps are indicated by an arrow. It is assumed that the batch generating device 35 is operated with vacuum pressure or negative pressure.

In use, the fluid flow in the transport line 40 of the batch generating device 35 at the device material inlet 41, i.e. upstream of the material conveying resistance 45, is indicated by arrow 55, while the fluid flow through the valve 49, i.e. the fluid flow gate 50 is indicated by arrow 54.

With block 61 “Start collecting material”, the start of the pneumatic fluid flow 47 as such is indicated. That is, a vacuum pressure or suction fluid flow is brought into operation in the batch generating device 35, from the device material outlet 42 thereof. In the system shown in Figure 4, for example, this may be achieved by suitably operating the fluid flow control unit 27. In the remainder of this description, it is assumed that the fluid flow is air.

In block 62, “Control fluid flow at first value”, the valve 49 at the fluid flow gate 50 is opened to the extent that fluid flow 55 operating upstream of the material conveying resistance 45 is at a first conveying capacity value sufficient for collecting fibrous material 44 from the feeder 43 into the device material inlet 41. The fluid flow 55 flows across or through and along the fibrous material collected in the transport pipe 40.

However, this first conveying capacity value is insufficient for transporting collected fibrous material past the material conveying resistance 45, such that the collected material gathers between the device material inlet 41 and the material conveying resistance 45 in the transport pipe 40, indicated by reference numeral 56. Opening of the valve 49 results in a so-called false air fluid flow 54, such that the pick-up pressure upstream of the material conveying resistance 45 is too less for conveying material past the material conveying resistance 45.

In practice, the first conveying capacity value may range between 20 - 30 % of the fluid flow conveying capacity downstream of the material conveying resistance, i.e. the conveying capacity of the fluid flow 47 in the transport pipe 40 at the device material outlet 42.

As a result of the gradual intake and collection of material 56, the static pressure sensed by the pressure sensor 52 increases. That is, the absolute value of the negative pressure increases. Sensing static vacuum pressure build up in the transport pipe 40 is shown by block 63, “Sense static pressure”.

Knowing the pressure change characteristics of the applied material conveying resistance, the amount and rate at which the vacuum pressure upstream of the material conveying resistance during the material collecting step builds up, is a measure for the amount or volume of the fibrous material 56 collected. Accordingly, during the collecting step, from the sensed vacuum pressure it is calculated or determined whether a batch of a required amount of material or volume is collected, i.e. decision block 64 “Batch formed?”.

As long as an insufficient amount of material is collected, i.e. decision block 64 result “No”, the static pressure build up remains to be sensed. If sufficient material is collected, a batch may be formed, i.e. decision block 64 result “Yes”. In a next step, the fluid flow 50 upstream of the material conveying resistance 45 is now controlled to be at a second conveying capacity value higher than the first conveying capacity value, for transporting the collected material 56 as a batch of material past the material conveying resistance 45. That is, block 65, “Control fluid flow at second value”.

In the embodiment of the batch generating device 35 shown in Figure 5, the fluid flow 55 is controlled at the second conveying capacity value by closing the valve 49 to the extent that the second conveying capacity value ranges between 80 - 100 % of the fluid flow conveying capacity downstream of the material conveying resistance, i.e. the fluid flow conveying capacity at the device material outlet 42.

For compacting the collected material 55 into a compact batch if the fluid flow upstream of the material conveying resistance 45 is at the second conveying capacity value, the material conveying resistance 45 may be actively controlled to form a temporarily higher resistance when launching the collected material 56. As a result hereof, the collected material 56 is compacted into a stable and compact batch. Once the batch is conveying, the material conveying resistance may be reduced to effectively prevent no resistance or impedance for conveying the batch.

Also for the purpose of compacting the material 56 collected, in the embodiment of the batch generating device 35 shown in Figure 5, at a distance downstream of the first material conveying resistance 45, an additional or second material conveying resistance 57 may be applied in the transport pipe 40. This second material conveying resistance 57 may be of the same type as the first material conveying resistance 45. The static pressure in the transport pipe 40 is sensed between the first 45 and second 57 material conveying resistance.

The additional material conveying resistance 57 is designed or controlled such that when the fluid flow 55 for conveying the batch is at the second conveying capacity value, the collected material 56 moving past the first material conveying resistance 45 experiences a further conveying resistance from the second material conveying resistance 57, as a result of which the batch is compacted. The fluid flow is controlled at a second conveying capacity value such that the batch of material moves past the first and second material conveying resistances 45, 57.

Different from what is illustrated in Figure 5, wherein the fluid flow gate 50 and the valve 49 connect between the first and second material conveying resistances 45, 57, it will be appreciated that the fluid flow gate 50 and valve 49 may connect to the transport pipe 40 at the device material outlet 42, that is downstream of the second material conveying resistance 57. In addition to the embodiment shown in Figure 5, in a further embodiment, an additional fluid flow gate 50 and respective valve 49 may connect to the transport pipe 40 downstream of the second material conveying resistance 57 at or near the device material outlet 42, and controlled by the control module or equipment 53. In practice, the pressure sensor 52 may be comprised of a plurality of pressure sensors positioned spaced apart and along the transport pipe 40 of the batch generating device 35.

Instead of controlling the conveying capacity value of the fluid flow 55 upstream of the material conveying resistance 45 by controlling the amount of opening of the valve 49, it will be appreciated that the conveying capacity value of the fluid flow 55 upstream of the material conveying resistance 45 may also be controlled by controlling the fluid flow 47 at the device material outlet 42 of the batch generating device 35. In the event that the batch generating device 35 is used in a conveying system 10 as illustrated in Figure 4, for example, the fluid flow 47 may be directly controlled by controlling the vacuum pressure generated by the unit 21, for example. However, controlling the fluid flow 55 upstream of the material conveying resistance 45 by a valve 49 as shown and described, has the advantage that the fluid flow 24 in the system 10 as such may be kept at a level for transporting already generated batches, for example. That is, the pneumatic transport of already generated batches may be kept independent of the generation of a new batch.

In the case of a pressure or over-pressure pneumatic conveying system, the fluid flow 55 upstream of the first material conveying resistance 45 is operated from the device material inlet 41 through a hopper type storage or feeding or delivery unit 43, by a compressor or blower or other source of pneumatic fluid flow 48. For collecting fibrous material at the device material inlet 41, the valve 49 is opened or partially opened, and the fluid flow from the source 48 is controlled such that the fluid flow 55 upstream of the material conveying resistance 45 is at the first conveying capacity value, such that fibrous material is collected 56 into the transport pipe 40 at device material inlet 41. While collecting material 56, the static pressure sensed by the pressure sensor 52 drops and is at a level insufficient for conveying the collected material past the material conveying resistance 45. By closing the valve 49 and increasing the fluid flow from the source 48 such that the conveying capacity of the fluid flow 55 upstream of the material conveying resistance 45 increase to the second conveying capacity value, the material collected 56 is conveyed as a batch past the material conveying resistance 45. It will be appreciated that the fluid flow 55 upstream of the first material conveying resistance 45 may be controlled by solely controlling the compressor or blower or other source of pneumatic fluid flow 48.

In a like manner as disclosed above, the batch formed may be compacted by controlling the resistance applied by the first conveying resistance 45 or by applying a second material conveying resistance 57, for example.

Figure 7 shows, in an illustrative manner, a preferred embodiment of a batch generating device in accordance with the invention. The device is generally designated by reference numeral 70. Parts of the batch generating device 70 that are equal or equivalent to parts of the batch generating device 35 shown in Figure 5 are indicated by same reference numerals.

The batch generating device 70 comprises a substantially elongated, essentially S-shaped transport line 40, such as circle cylindrical transport pipe, having the same inner dimensions as a transport pipe of a transport line 14 of a pneumatic conveying system in which the batch generating device 70 is used, such as the system 10 shown in Figure 4.

The batch generating device 70 is shown in use, in which the elongated part 73 of the essentially S-shaped transport pipe 40 is in an upright or vertical or substantially or essentially vertical position. In this position, the lower end of the essentially S-shaped transport pipe 40 forms the device material inlet 41 and the upper end of the essentially S-shaped transport pipe 40 forms the device material outlet 42 for directly connecting to a transport line of a pneumatic conveying system. The device material inlet 41 connects by a first bend or curvature 71 to the elongated part 73 at one end thereof, and the device material outlet 42 connects by a second bend or curvature 72 to the elongated part 73 at another end, opposite the one end, thereof.

In the upper half of the elongated part 73 a static pressure sensor 52 is arranged, for sensing static pressure in the S-shaped transport pipe 40 between the first and second bend 71, 72. At the second bend 72 a fluid flow aperture or orifice or gate 50 connects to the S-shaped transport pipe 40. In the embodiment shown, the fluid flow gate 50 is likewise formed by a piece 58 of transport pipe. A valve 49, such as a servo controlled valve, connects to the fluid flow gate 50, for controlled opening or closing thereof. Although not explicitly shown, a dust filter 51 may be arranged between the gate 50 and the valve 49.

The device material inlet 41 connects to a storage or feeding or delivery unit 43, from which fibrous material 44 to be transported is picked-up and collected 56 in the lower part of the S-shaped transport pipe 40 that connects to the device material inlet 41, for generating a batch of material.

In the embodiment shown in Figure 7, the storage or feeding or delivery unit 43 comprises a belt from which fibrous material, such as cut tobacco for example, is provided. The feeding or delivery unit 43 is of a type known as gravity-, bowl-, or rotary drum feeder, for example, schematically indicated by arrow 74. With such a feeder 74 the amount or volume, for example expressed in kg, of fibrous material 44 delivered for forming a batch by the batch generating device 70 may be exactly controlled and dosed.

The static pressure sensor 52 may be of a commercially available type, arranged for electric reading, and connects electrically to the control module or equipment 53. The servo controlled valve 49 may likewise be of a commercially available type, preferably a so-called high-speed or fast responsive electrically actuated servo-type valve, and connects electrically to the control module or equipment 53. For control purposes, the feeder 74 is also electrically coupled to the control module or equipment 53.

In operation, the control module or equipment 53 may connect to a common or general control system of a pneumatic conveying system, such as the control system 28 of the conveying system 10 shown in Figure 4.

In use the first bend 71 forms an applied first material conveying resistance and operates in conjunction with the lower portion of the vertically, or substantially or essentially vertically positioned elongated part 73 of the S-shaped transport pipe 40 to impede the conveying of material picked-up at the device material inlet 41 into the transport pipe 40, comparable to the first material conveying resistance 45 shown in Figure 5.

The second bend 72 forms an applied second material conveying resistance and operates in conjunction with the upper portion of the vertically, or substantially or essentially vertically positioned elongated part 73 of the S-shaped transport pipe 40 to impede the conveying of a batch 59 of material through the transport pipe 40, comparable to the second material conveying resistance 57 shown in Figure 5.

The vertically, or substantially or essentially vertically positioned elongated part 73 of the S-shaped transport pipe 40 is generally or roughly divided in an upper and lower portion by the position of the static pressure sensor 52.

As will be appreciated by those skilled in the art, in the embodiment of the batch generating device 70 shown in Figure 7, no moving parts or confinements or other restrictions are introduced in the transport path from the device material inlet 41 to the device material outlet 42. Positioning of the fluid flow gate 44 at the upper portion of the second bend 72 of the S-shaped transport pipe 40 is advantageous in that hardly no portion of a batch 59 will strike against the connecting joint of the piece 58 of transport pipe and the second bend 72, thereby preventing as much as possible transport damage of the material to be transported.

The operation of the batch generating device 70 is now disclosed with reference to the basic flow chart 60, shown in Figure 6, and a graph showing static pressure build up versus time sensed in a practical embodiment of a batch generating device 70 in a vacuum pressure or suction type pneumatic conveying system, as illustrated by Figure 8.

In the graph shown in Figure 8, at the horizontal axis the time t expressed in seconds, [s], is indicated. The static pressure P expressed in Pascal, [Pa], sensed by the static pressure sensor 52 located at the upper portion of the elongated part 73 of the S-shaped transport pipe 40, is indicated at the vertical axis of the graph. As the batch generating device 70 is operated with vacuum pressure or negative pressure, the static pressure is indicated by negative values. The pressure and time values indicated are for illustrative purposes only.

In use, the fluid flow in the S-shaped transport pipe 40 of the batch generating device 70 downstream of the system material 41 and upstream of the applied first material conveying resistance comprising the first bend 71 is indicated by arrow 55. The fluid flow in the pipe section 58 connecting to the fluid flow gate 50 is indicated by arrow 54 and the fluid flow at the device material 42 is indicated by arrow 47.

In use, a vacuum pressure or suction fluid flow 47 is brought into operation in the batch generating device 70, from the device material outlet 42 thereof, such as generally indicated by block 61 of the flow chart 60. In the system shown in Figure 4, for example, this may be achieved by suitably operating the fluid flow control unit 27 and/or the unit 21. In the remainder of this description, it is assumed that the fluid flow is air.

In block 62, the valve 49 at the fluid flow gate 50 is opened to the extent that the fluid flow 55 operating at the material device inlet 41 upstream of the first material conveying resistance is at a first conveying capacity value sufficient for collecting 56 fibrous material 44 from the feeder 43 into the device material inlet 41. However, this first conveying capacity value is insufficient for transporting the collected material 56 past the first material conveying resistance comprised by the first bend 71 and the lower portion of the elongated part 73 of the essentially S-shaped transport pipe 40. Reference is made to time to in the graph of Figure 8.

In practice, the first conveying capacity value of the fluid flow conveying capacity of the fluid flow 55 may range between 20 - 30 % of the fluid flow conveying capacity of the fluid flow 47 at the material device outlet 42, i.e. the fluid flow conveying capacity in the transport line 14 of the system 10 shown in Figure 4, for example.

As a result of the gradual intake and collection of material at the first bend 71, the static vacuum pressure sensed by the pressure sensor 52 at the front 75 of the collected material 56 increases, that is the absolute value of the negative pressure increases. Sensing static vacuum pressure build up in the S-shaped transport pipe 40 is shown by block 63 in the flow chart 60.

When knowing the pressure change characteristics of the applied first material conveying resistance, the amount and rate at which the vacuum pressure downstream of this first material conveying resistance during the material collecting step develops, i.e. builds up, is a measure for the amount or volume of the fibrous material collected 56. Accordingly, during the collecting step, from the sensed vacuum pressure in the transport pipe 40 one may calculate or determine whether a sufficient or a required amount or volume of material is collected 56, i.e. decision block 64 in the flow chart 60.

As long as an insufficient amount of material is collected 56, i.e. decision block 64 result “No”, the static pressure build up remains to be sensed and the intake of fibrous material at the material device inlet 41 by the fluid flow 55 operating across and along the material already collected 56 continues. If sufficient material is collected, a batch 59 may be formed, i.e. decision block 64 result “Yes” and in a next step, the fluid flow 55 upstream of the first material conveying resistance, i.e. operating at the front 75 of the collected material 56 is now controlled to be at a second conveying capacity value higher than the first conveying capacity value, for transporting the collected material as a batch 59 of material past the material conveying resistance, i.e. the lower bend 71 and the lower portion of the elongated part 73. Such as represented by block 65 of the flow chart 60.

In the embodiment of the batch generating device 70 shown in Figure 7, the fluid flow at the front 75 is controlled at the second conveying capacity value by closing the valve 49 to the extent that the second conveying capacity value ranges between 80 - 100 % of the fluid flow conveying capacity of the fluid flow 47 at the device material outlet 42.

With reference to the graph of the static pressure build shown in Figure 8, the angle a indicates the rate of change at which the static vacuum pressure sensed by the static pressure sensor 52 increases. The steepness of the curve in the interval from tO to t1, expressed by the parameter a, indicates the amount of tobacco collected per unit time. The steeper a is, the faster material is collected for forming the batch 59. The value of the parameter a is representative of or is determined by the pressure change characteristics of the material conveying resistance. Accordingly, the negative or vacuum static pressure build-up in the interval from to to t1 is a reference for the batch volume measured at 20 - 30% of the conveying air capacity at the device material outlet 42.

Once a sufficient or desired amount of material is collected, the valve 49 is closed. The valve 49 may be closed when a set static pressure threshold is reached, which static pressure threshold is representative of an amount of material collected, and/or after lapse of a set time interval to - t1, i.e. a set feeding time period which, for a given parameter a is also representative for the amount or volume of the material collected 56.

Closure of the valve 49 at time t1 results in a static pressure increase till time t2, which marks the point in time at which the fluid flow operating at the front 75 of the collected material 56 has reached the second conveying capacity value for conveying the material as a batch 59 in the direction of the device material outlet 42.

Once launched, i.e. block 66 of the flow chart 60, the static vacuum pressure reduces, which means, according to Bernoulli’s law, that the velocity of the batch 59 increases. Next, the moving batch 59 will encounter the second material conveying resistance of the batch generating device 70, formed by the upper portion of the elongated part 73 and the second bend 72. This is represented by time t3 in the graph of Figure 8. As a result, the static vacuum pressure sensed by the pressure sensor 52 increases again till the fluid flow operating at the batch 59 reaches a conveying capacity value for conveying the batch past the second conveying resistance.

In the graph of Figure 8 at time t4 the static pressure has reached a conveying capacity value for conveying the batch 59 past the second material conveying resistance and eventually leaves the batch generating device 70 at the material outlet thereof, as represented by time t5. From time t4 full batch acceleration is handled by the vacuum pressure, transforming the static pressure in full dynamic pressure, providing adequate batch conveyance. The value of the static pressure at time t5 likewise serves as a reference for the batch volume generated.

The pressure difference experienced by the batch 59 at time t2 and time t4, indicated by H in the graph of Figure 8, operates to compact the batch 59 into a stable batch or dune, before same leaves the device material outlet 42.

By controlling the fast acting (servo) valve 49, the interval D (Figure 3) between the batches, i.e. the dunes or plugs, is created. When the valve 49 is completely opened, i.e. maximum false air intake from the fluid flow gate 50, no or hardly any material will be picked-up at the device material inlet 41. By further closing the valve 49 such that the fluid flow 55 is at its first conveying capacity value, the batch generating cycle is started anew.

It is noted that for large feeding capacities of high speed cigarette makers, for example, it is important to decrease the feeding and batch building time. For this reason, special feed hoppers are applied, preventing rat holes, i.e. air bypasses, from the feeder.

Additionally the time for accelerating the batches may be decreased by a batch accelerator or batch launcher 80, as shown in Figure 9. Parts of the batch launcher 80 that are equal or equivalent to parts of the batch generating device 70 shown in Figure 7 are indicated by same reference numerals. The single purpose of the pulse batch launcher 80 is to overcome the launching resistance, for transporting the batch 59. For convenience sake, Figure 9 only shows the lower part of the S-shaped transport pipe 40 of the batch generating device 70. The batch launcher 80 is operative at the back 85 of the batch 59, i.e. opposite the device material inlet 41.

In the embodiment shown, the feeding device 82 is of controllable type, such as a so-called rotary drum feeder, having a rotary drum 83 filled with material 44 for collecting at the device material inlet 41. The rotary drum 83 is controlled from the control module or equipment 53, jointly controlling the value of the fluid flow 55 upstream of the first material conveying resistance, i.e. the first bend 71, and the feeding ratio of material at the device material inlet 41. A feeder belt 86 operative for feeding fibrous material 44 to be collected may likewise be controlled from the control equipment or module 53. For example by controlling a variable frequency drive motor of the feeder belt 86.

Launching of the batch 59 is supported in that the batch launcher 80 provides an additional fluid flow from an opening 81 thereof opposite the back 85 of the batch 59, in a direction as shown by arrows 84, when the fluid flow 55 upstream of the material conveying resistance, i.e. at the front 75 of the batch 59, is at the second conveying capacity value. Preferably, the additional fluid flow 84 is pulsewise injected from the launcher 80, and same is controlled from the control module 53. This additional fluid flow 84 is of a value to support the launching of the batch 59 by overcoming the static break-loose wall friction against the transport pipe 40 and thereby decreasing the time needed for accelerating the batches 59 to the desired transport speed.

The invention may be practiced otherwise than as specifically described herein, and the above mentioned embodiments and examples are merely intended as an illustration to the skilled reader.

Claims (20)

A method for producing a load of fibrous material for pneumatic transport through a pneumatic fluid stream in a conveying line of a pneumatic conveying system from a material inlet connected to a material storage or feeding device to a material outlet connected to a material processing device and past a material processing device material transport resistance disposed in the transport line at the material inlet thereof, which method comprises the steps of: - collecting material in the transport line at the material inlet from the storage or supply device by means of a fluid flow operating upstream of the material transport resistance with a first transport capacity value insufficient for transporting the collected material past the material transport resistance, - sensing static pressure in the transport line downstream of the material inlet, and - controlling the fluid flow upstream of the material transport resistance at a second transport capacity value higher than the first transport capacity value for transporting the collected material past the material transport resistance as a load of material, depending on the observed static pressure. The method of claim 1, wherein the fluid flow upstream of the material transport resistance is controlled by opening or closing a fluid flow port of the transport line downstream of the material transport resistance. Method according to any of the preceding claims, wherein the fluid flow upstream of the material transport resistance is controlled at a first transport capacity value between 20-30% of the fluid flow transport capacity downstream of the material transport resistance, and wherein the fluid flow upstream of the material transport resistance is controlled on a second transport capacity value between 80 - 100% of the fluid flow transport capacity is controlled downstream of the material transport resistance. A method according to any one of the preceding claims, wherein the pneumatic conveying system is a suction or vacuum conveying system, wherein the observed static pressure is a vacuum pressure, which fluid flow is controlled upstream of the material conveying resistor at the second conveying capacity value depending on at least one of - the observed static vacuum pressure is at or above a set static vacuum pressure threshold, - the observed static vacuum pressure increases according to a set amount of change during a set time interval. A method according to any one of claims 1 to 3, wherein the pneumatic conveying system is a pressure conveying system, wherein the observed static pressure is an overpressure, wherein the fluid flow is controlled upstream of the material conveying resistor at the second conveying capacity value depending on at least one of: the observed static pressure is at or below a set static pressure threshold, and - the observed static pressure decreases according to a set amount of change during a set time interval. A method according to any one of the preceding claims, wherein the fluid flow upstream of the material transport resistance is repeatedly alternately controlled to the first and the second transport capacity value to produce a plurality of charges of collected material and, if applicable, to a third transport capacity value insufficient for collecting material at the material inlet. Method according to any of the preceding claims, wherein a degree of supply of material is controlled at the material inlet in dependence on controlling the fluid flow upstream of the material transport resistance. A method according to any one of the preceding claims, wherein if the fluid flow is controlled upstream of the material transport resistance to the second transport capacity value, an additional fluid flow is injected from the material inlet to support the transport of the collected material beyond the material transport resistance, in particular wherein the additional fluid flow is injected pulse-wise from the material inlet. A method according to any one of the preceding claims, wherein the material transport resistance for compacting the collected material is controlled. A method according to any one of the preceding claims, wherein the material transport resistance is composed of a first applied material transport resistance located in the transport line at the material inlet, and a second applied material transport resistance located in the transport line at a distance downstream of the first material transport resistance, static pressure in the transport line between the first and second material transport resistance is observed and the fluid flow for transporting the charge is controlled to a second transport capacity value for transporting the collected material past the first and second material transport resistors as a load of material. A method according to any one of the preceding claims, wherein the fibrous material is one of cut tobacco, tea leaves and other fibrous materials vulnerable to transport in a transport line of a pneumatic transport system. A method according to any one of the preceding claims, wherein the material is cut tobacco and the material processing device is a cigarette maker and wherein a plurality of charges are generated for providing the cigarette maker via a single transport line with an amount of cut tobacco between 10 and 20 kg / min. A charge generating device for producing a load of fibrous material for pneumatic transport in a conveyor line of a pneumatic conveying system, which charge generating device comprises: - a device material inlet adapted for connection to a material storage or supply device, - a device material outlet adapted for connection to the pneumatic conveying system, such that during use a pneumatic fluid flow is active from the device material inlet to the device material outlet, - an applied material transport resistance located between the device material inlet and the device material outlet, - a static pressure sensor, located downstream of the device material inlet, for detecting static pressure in the device material inlet device, and - control equipment, comprising an electronic control unit adapted to control the fluid flow upstream of the material transport standing on a first transport capacity value for collecting material at the device material inlet and insufficient for transporting the collected material beyond the material transport resistance, and on a second transport capacity value higher than the first transport capacity value for transporting the collected material past the material transport resistance as a load of material , depending on the observed static pressure. A charge generating device according to claim 13, wherein the control unit is adapted to repeatedly alternately control the fluid flow upstream of the material transport resistor at the first and second transport capacity values to generate a plurality of charges of collected material. A charge generating device as claimed in claim 13 or 14, wherein the device material inlet is connected to a controllable material storage or supply device, wherein the control unit is adapted to control a rate of supply of material at the device material inlet depending on controlling the fluid flow upstream of the material transport resistance. A charge generating device as claimed in claim 13, 14 or 15, wherein the control equipment comprises a valve connected to the control unit which has an opening controllable by the control unit for controlling the fluid flow by opening and closing a fluid flow port of the device, which fluid flow port downstream of the material transport resistance. A charge generating device according to claim 13, 14, 15 or 16, wherein the material transport resistor comprises a first applied material transport resistor located at the device material inlet, and a second applied material transport resistor located at a distance from the first material transport resistor in the direction towards the device material outlet, wherein the static pressure sensor is located between the first and second material transport resistance. A charge generating device according to claim 13, 14, 15, 16 or 17, with a substantially elongated S-shaped conveyor line, a first end of which forms the device material inlet and a second end of which forms the device material outlet, wherein the static pressure sensor for detecting static pressure in the S-shaped transport line at an elongated part thereof is located between a first bend connected to the first end and a second bend connected to the second end, and a fluid flow port located at the second bend and comprising a fluid flow port operatively connected to the control unit valve with a controllable opening for opening and closing the fluid flow port by the control unit, in which the elongated part of the S-shaped transport line is in an upright position during use and the first bend comprises a first applied material transport resistance and the second bend a second applied material transport resistance . The charge generating device according to claim 13, 14, 15, 16, 17 or 18, further comprising an additional fluid flow injection device located at the device material inlet and operatively connected to the control unit for supporting the transport of the collected material beyond the material transport resistance, in particular in which the fluid flow injection device is arranged for pulse-injecting the additional fluid flow from the device material inlet. A pressure or vacuum type pneumatic transport system adapted for pneumatically transporting fibrous material through a pneumatic fluid flow in a transport line of the pneumatic transport system, from a material storage or supply device to a material processing device, which pneumatic transport system comprises fluid flow generating means and a charge generating device operatively arranged according to a of the preceding claims.