HK1018584A - Method and apparatus for automatic and continuous pneumatic feeding of tobacco - Google Patents

Description

Method and device for the automatic continuous pneumatic feeding of tobacco

The present invention relates to apparatus for continuously feeding material to a manufacturing machine, and more particularly to continuously pneumatically feeding shredded tobacco to a cigarette making machine.

In the prior art, it is known to pneumatically transport tobacco from one location to another, and in particular to transport tobacco from a hold or other storage area to a cigarette making machine. However, the prior art devices have inherent problems in keeping the tobacco travel entrained with air at a constant speed or preventing the pneumatic conveying system from stopping and starting when the cigarette making machines have filled their bins as well. Typically, in these prior art systems, the reservoir of the making machine is filled by a signal that the level of tobacco in the reservoir of the making machine is low. When such a bin low signal is received, a vacuum is established in the pneumatic conduit in order to transfer the tobacco from the cargo compartment to the bin of the making machine. The vacuum generated in the conduit is from a single vacuum source and at a given pressure. If multiple production machines require tobacco due to empty bins, the velocity of the tobacco in the pneumatic tube may vary greatly, as well as the pressure within the tube itself. In addition, once the reservoir of the making machine is full, the vacuum source is turned off and the tobacco being conveyed in the pneumatic tube is stopped in the tube until the vacuum source is restarted after another cigarette making machine needs to add tobacco. The effect of the change in the speed of the tobacco in the transfer duct or the build-up and interruption of the pressure in the duct is detrimental to the tobacco itself and causes the tobacco to become dusty, thereby reducing the charge value of the tobacco being transferred. Therefore, there is a need for a device that automatically controls the rate at which tobacco is fed to a pneumatic conveying system and that automatically controls the rate at which tobacco is pneumatically conveyed.

It is therefore an object of the present invention to overcome the above problems and to provide a system which can control the tobacco entering a pneumatic conveying system, and which can also control the speed at which the tobacco is conveyed in said system.

It is another object of the present invention to minimize deterioration of tobacco in a pneumatic conveying system.

In addition to the above objects, the present invention comprises a method and apparatus for automatically controlling the rate at which tobacco is fed from a cargo space into a pneumatic conveying duct system and for automatically controlling the rate at which tobacco is fed into the pneumatic conveying duct system.

More specifically, the invention comprises a method and apparatus for continuously pneumatically conveying tobacco from a cargo space to a cigarette making machine which includes a first flow measuring transmitter in a pneumatic conduit of the cargo space and another flow measuring transmitter on a cyclone of the making machine. These flow measurement transmitters may actuate a flow control valve to regulate the velocity of the air flowing in the pneumatic conduit, thereby controlling the velocity of the tobacco being conveyed. The tobacco is fed from the hold through the sliding door into an airtight portal which distributes the tobacco into the air stream. A Programmable Logic Controller (PLC) is used to process the data from the flow measurement transmitter and to adjust the flow control valve to maintain a constant rate of tobacco flow. In addition, the PLC is used to process data from a height measurement transmitter on the cigarette making machine and adjust a sliding door on the cargo compartment to control the amount of tobacco in the feed air stream.

Finally, the invention comprises an apparatus for continuously feeding tobacco from a hold to at least one cigarette making machine, comprising: a vibratory feed tray secured to said cargo tank and positioned below a discharge opening in said cargo tank, said vibratory feed tray having an outlet, said outlet having at least one opening, and a sliding door slidably mounted in said opening; an airtight access opening provided directly below the sliding door; a cyclone connected to said at least one cigarette making machine, said cigarette making machine having an outlet aperture at one end; pneumatic tubing connecting said airtight inlet and outlet to said cyclone separator and further connecting the cyclone separator to a vacuum source; an ultrasonic height measuring transmitter in said cigarette making machine; and a controller connectable to the height measurement transmitter and the sliding door.

The invention will be better understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 is a perspective view of the entire system of the tobacco continuous pneumatic conveying system of the present invention;

FIG. 2 is a perspective view of a feed section of the system shown in FIG. 1;

FIG. 3 is a top view of the feed block shown in FIG. 2;

FIG. 4 is a front view of the feed section shown in FIG. 3;

FIG. 5 is a bottom cross-sectional view of an alternative portion of the feed section shown in FIG. 3;

FIG. 6 is an enlarged plan view of the separation section and cigarette making section shown in FIG. 1;

FIG. 7 is a schematic of a programmable logic controller that can automatically control the velocity of air in a pneumatic system;

FIG. 8 is a schematic of a programmable logic controller that automatically controls the rate of pumping of tobacco from the cargo compartment to the vibratory feed tray;

FIG. 9 is a schematic of a programmable logic controller that automatically controls the feed rate of tobacco into a pneumatic conveying tube;

FIG. 10 is a plan view of another embodiment of a continuous pneumatic conveying system for tobacco without an absorber.

The automatic and continuous conveying system for tobacco of the present invention, indicated by the reference numeral 10, is schematically illustrated in fig. 1. The system 10 is comprised of a plurality of segments. The first stage is a feed section 30 which includes a cargo compartment 29 and an oscillating feed tray 34 which receives tobacco from the compartment 29 and dispenses the tobacco into an aerodynamic duct 12 while metering the tobacco into the duct 12. A vacuum source delivers metered amounts of tobacco from the hold 29 through the duct 12 to the separation section 50 which includes a cyclone separator 52 and a multistage absorber 54. A multistage absorber 54 is provided for removing heavier tobacco particles, such as stems, veins and bulbs, from the lamina portion of tobacco. The lightweight tobacco particles are transported from the absorber 54 to a cigarette making section 70 which consists of a cyclone 71 and a cigarette making machine 80 which has a tobacco storage bin 72 above it for storing tobacco. The reservoir 72 receives tobacco from the cyclone 71. The total distance of the tobacco from the hold 29 to the reservoir 72 of the production machine may be a few metres when the segments are close to each other to a few hundred metres when the segments are dispersed in a tobacco production plant. The entire conveyor system 10 shown in FIG. 1 is controlled by a plurality of programmable logic controllers 100,101 and 102 that continuously measure demand on the system and increase or decrease the air flow in the pneumatic tube 12 and the amount of tobacco entering the system according to the rate of demand of the making machine 80.

Shown in fig. 2 is a perspective view of the feeder segment 30 of the present invention, which segment is formed by a hold 29 containing cut tobacco which is slowly fed into a vibratory feed tray 34. The cargo space 29 may include different amounts or percentages of multiple types of tobacco in a mixing device, such as converted tobacco, cut tobacco, reconstituted tobacco, and other multiple forms of tobacco. As shown in fig. 2, at the end of the hold 29 are small rollers 39 that agitate the compressed tobacco, thereby separating the tobacco and allowing the tobacco to fall in loose form into the vibratory feed tray 34. A belt conveyor 38 is provided along the bottom of the hold to move the tobacco forwardly from the rear of the hold to contact the tobacco with the small rollers 39. The forward end of the cargo compartment 29 has a discharge opening to provide a means for continuously feeding tobacco into the feed tray 34.

Shown in fig. 1: above the vibratory feed tray 34, at the forward end of the cargo space 29, is an ultrasonic height measuring transmitter 33 which measures the depth of tobacco on the vibratory feed tray 34. The height measuring transmitter 33 is an ultrasonic emitter/detector that measures the depth of the tobacco to control the speed of the conveyor belt 38, and the stopping and starting of the belt 38 to increase or decrease the amount of tobacco in the feed tray 34. The ultrasonic height measuring transmitter 33 ensures that tobacco falls from the cargo space 29 into the feed tray 34 at a controlled and steady rate. Additional means known in the art for detecting the depth of tobacco in the feed tray, such as optical means, sensors, and the like, may also be used for measuring the depth of tobacco in the feed tray 34. The height measurement transmitter 33 determines the rate at which the cargo space 29 delivers cut tobacco to the conveyor system and ensures that the feed tray 34 is not crushed by tobacco falling from the cargo space 29. The measurement data read by the measurement transmitter 33 is fed to a programmable logic controller 101 which controls the speed of the conveyor belt 38 in the cargo compartment 29, and the speed of the roller bar 39, based on the depth measurement data. An additional conveyor belt (not shown) is provided along the bottom of the hold 29 and is used to convey tobacco from the rear of the hold 29 to the front section adjacent the opening of the drum 39.

The first and second sliding doors 31 and 32 are integral with the vibratory feed tray 34 of the present invention. Vibratory feed tray 34 is of a V-shaped configuration with first and second inclined surfaces 35 and 36, as shown in fig. 2,3 and 4. The feed tray 34 may be connected to a vibration motor 37 which vibrates the opposed downwardly inclined surfaces 35 and 36 so that tobacco may be fed into the holes 31a and 32a formed in the underside of the sliding doors 31 and 32, the sliding door 31 may be connected to the surface 35, and the sliding door 32 may be connected to the surface 36. The holes 31a and 32a feed the material into separate rotary airtight ports 41 and 42, such as those made by the KICE company. The sliding doors 31 and 32 open and close depending on the amount of tobacco required by the cigarette making machine 80 or other making machine that is loaded onto the airtight ports 41 and 42. The sliding doors 31 and 32 open and close the openings 31a and 32a to the airtight ports 41 and 42, increasing or decreasing the flow of tobacco into the system 10. For example, when more tobacco is required by the making machine 80, the sliding door 31 is opened, allowing a larger volume of tobacco to enter the airtight access opening, and subsequently pneumatically delivering more tobacco to the making machine 80.

The vibratory feed tray 34 is connected to the bins 72 of the two cigarette making machines so that each cargo compartment 29 feeds two separate cigarette making machines. In a preferred embodiment, the vibratory feed tray 34 has the capacity to dispense about 40 pounds of tobacco per minute, thereby feeding each of the production machines connected to the feed tray 34 at a rate of about 20 pounds per minute. The corresponding flow rate of tobacco at the rotating airtight ports 41 and 42 is approximately 275 standard cubic feet per minute (SCFM), and a comparable flow rate at the production machine 80 is approximately 4000 to 4500 SCFM. The pneumatic tubing 12 at these locations has a diameter of about 3 inches.

As shown in fig. 3, the vibratory feed tray 34 is inclined in half, and half of the inclined surface 35 feeds the hole 31a and half of the inclined surface 36 feeds the hole 31 a. The tobacco is transported downwardly from the hold 29 in a uniform manner by the action of the rollers 39 and conveyor belt 38, distributing the tobacco across the entire width of the feed tray 34. As shown in FIG. 5, the sliding door 31 may be attached to the air cylinder 43 and have a linear sensor 44 that measures the position of the air cylinder 43 and sends its corresponding position to a Programmable Logic Controller (PLC)102 that controls a closed loop system including a height measuring transmitter 75 at the manufacturing machine 80 and the sliding door 31 at the cargo space 29. The sliding door 31 opens and closes the aperture 31a feeding the airtight access 41, thereby controlling the amount of tobacco that can enter the pneumatic conveying duct 12, keeping it flowing at a constant rate and speed. The action of the sliding door 31 or 32 is controlled directly by a height measuring transmitter 75 in the tank 72 of the manufacturing machine. The hopper 72 of the making machine of the present invention allows tobacco to enter the cigarette making machine 80 continuously. An ultrasonic level measuring transmitter 75 located in the hopper 72 of the making machine determines the actual level of tobacco in the cigarette making machine 80 itself. A predetermined optimal height in the cigarette making machine 80 is programmed into the PLC 102. The height measuring transmitter 75 continuously measures the height of the tobacco in the production machine 80 and controls the sliding door 31 according to said measurement data. If tobacco addition is required, the sliding door 31 is opened larger. If the making machine 80 is already filled with tobacco, the sliding door 31 is closed. The measurement data for tobacco in the cigarette making machine 80 is determined as: due to the complete closing of the sliding door 31, the amount of tobacco left in the pneumatic tube 12 will fill the remainder of the reservoir 72 of the making machine.

The programmable logic controller 102 accepts as inputs the positions of the sliding doors 31 and 32, as well as other data relating to the continuous flow of tobacco in the pneumatic conveying duct 12. As shown in fig. 1, a flow measurement transmitter 45 is provided in the pneumatic conduit 12 upstream of the vibratory feed tray 34 in order to measure the air flow in the conduit 12. A further flow measurement transmitter 53 is provided downstream of the absorber cyclone 52 to measure the velocity of the air again after it has reached the separation section 50. A modulating flow control valve 51 is connected by pneumatic conduit 12 to a vacuum source for controlling the pressure and velocity through the conveyor system 10. The flow control valve 51 operates in accordance with a programmable logic controller 100 which calculates the appropriate settings for the valve 51 based on the measurements from the flow measurement transmitters 53 and 45, optimally to maintain a continuous flow of tobacco and at a constant rate. The flow control valve 51 is a standard actuatable valve, such as a FisherV flow control ball valve. As indicated previously, the other PLC102 also controls the air cylinder 43 which forces tobacco through the sliding door 31 into the rotating airtight portal. For simplicity, only one air cylinder is shown, but the two sliding doors 31 and 32 are similarly driven. Thus, the PLC102 automatically controls the rate at which tobacco is fed into the pneumatic conveying system, and the PLC 100 automatically controls the speed at which the tobacco is pneumatically conveyed. PLC102 receives as input from a height measurement transmitter located in tank 72 of the fabrication machine. The height measurement transmitter ultrasonically detects the height of the tobacco in the reservoir 72 and determines the rate at which the tobacco is being used by the production machine 80. In this way, the continuous tobacco conveying system automatically compensates for the velocity of the tobacco in the conveying duct 12, and also automatically compensates for the air flow or vacuum required to move the tobacco different distances from the cargo space 29 to the making machine 80. The system will adjust based on simultaneous readings of the current state of the system and adjust the air flow and the amount of tobacco in the system regardless of how much tobacco is being demanded by the making machine from the hopper in order to maintain a continuous flow and flow at a constant rate, preventing damage to the tobacco that may occur during transport.

There are three separate closed control loops which are monitored by the PLCs 100,101 and 102, which are also reacted to, and which are shown schematically in FIGS. 7,8 and 9. The first 101 is used to control the rate at which tobacco is pumped into the tray 34 using the conveyor belt 38 and rollers 39, in accordance with the measurement data from the ultrasonic height measuring transmitter on the vibratory feed tray 34. This PLC 101 takes as input data the measurement of the height of the tobacco in the vibratory feed tray 34 and drives the belt 38 and the rollers 39 in accordance with this data. The second PLC 100 controls the velocity of the air in the pneumatic conveying duct 12 and therefore the velocity of the tobacco itself. The PLC 100 receives the measurement data from the flow rate measurement transmitters 45 and 53 as input quantities for driving the flow control valve 51. This control ensures a constant velocity of the air in the delivery system. The flow control valve 51 is directly connected to a vacuum source and may provide low pressure in order to move large volumes of tobacco. Finally, PLC102 controls the rate of feed of tobacco into the hopper of the production machine, accepting as input measurement data from height measuring transmitters 75 in production machine 80, PLC102 may be connected to sliding doors 31 to control the input of tobacco into airtight portal 41. This in turn limits the volume of tobacco in the pneumatic tube 12. The three independent controllers 100,101 and 102 control the amount of tobacco delivered and the speed of the tobacco contained in the duct 12. The system 10 is also calibrated so that when the tobacco level is high, as measured at the production machine 80, the sliding door 31 is closed, preventing the detrimental shut-off of the vacuum in the duct 12 in order to allow the tobacco to fall in place. Reestablishing vacuum after such a shut-off occurs can damage the tobacco and increase its dust. Thus, the system of the present invention determines the amount of tobacco remaining in the duct 12 after the door 31 is closed, ensuring that all of the tobacco can fill the remainder of the production machine 80 and the hopper 72.

As shown in fig. 6, the separation section 50 is comprised of a cyclone 52 and an absorber 54. The cyclone separator 52 reduces the velocity of the tobacco and separates the tobacco from the air stream so that the tobacco falls from the air stream into the rotating airtight ports 55, thereby preventing loss of pressure in the closed loop pneumatic conveying duct 12. A rotary airtight inlet and outlet 55 delivers the tobacco from the cyclone separator 52 to a four-pass multistage absorber 54 for separating stalks, bulbs, sediment and other heavier components of the tobacco from the tobacco used in the cigarette making machine 80. The stems, bulbs and precipitates are stored in a storage container for later use in reconstituted tobacco or other products.

After separating the heavier material from the tobacco leaves in the four-pass multistage absorber 54, the tobacco material is fed through a duct 60 to the cyclone 71 of the production machine, the duct 60 having enclosed therein a sufficient vacuum generated by the blower 16 to move the material to the cyclone 71 of the production machine. The tobacco material is presented to the cyclone 71 of the making machine where it is separated from the air stream and passed through an additional rotary airtight access 73. The rotating airtight portal 73 stores the tobacco material being conveyed in the making machine's bin 72, which is continuously monitored by an ultrasonic level measuring transmitter 75, which feeds the tobacco directly into the cigarette making machine 80. The bin 72 as used herein is the inlet portion of the bin of the cigarette making machine 80 and is therefore integral with the machine. Tobacco is fed from the rotary airtight portal 73 through the hopper 72 of the above making machine into the cigarette making machine 80 itself. The height measurement transmitter 75 is an ultrasonic transmitter/detector that determines the current height of tobacco in the hopper 72 of the production machine and sends this information to the PLC 102. The height measurement transmitter in the hopper 72 of the making machine sends a request for more tobacco to the PLC102, and additional tobacco is transferred from the cargo space 29 to the making machine 80 through the opening of the sliding door 31 as required.

During operation, a height measuring transmitter at the production machine 80 determines when a higher level of tobacco is obtained therein. At this point, a high signal is sent to the PLC102, which prevents tobacco from entering the pneumatic tube 12 by closing the sliding door 31 feeding the airtight access. The remaining amount of tobacco in the duct system 12 is calculated so that the production machine 80 is not overfilled. The vacuum source to the pneumatic tube 12 continues to be on, continuing to prevent the tobacco from remaining in the tube 12 when the source is turned off, as occurs in the prior art. The flow or volume of tobacco is controlled entirely by the action of the sliding door 31, without the vacuum source, thereby increasing the efficiency of the system and reducing the damage to the tobacco itself. Thus, the PLC102 calculates the amount of tobacco in the pneumatic tube 12 and the amount of tobacco required to fill the making machine's reservoir 72 to its desired fill value as detected by the height measurement transmitter 75, ensuring that the tobacco is continuously transferred to the making machine's reservoir 72. This prevents damage to the tobacco from being initiated by turning off the vacuum source and when the tobacco needs to be added by the making machine 80. Of particular concern during operation of pneumatic conveying systems is the generation of dust which is a good indication of the continuous processing of tobacco in the conveying system. Typically, the dust generated by pneumatic conveying processing systems for tobacco is about 2%. The present invention can reduce the amount of dust generation to less than 0.5%.

In fig. 10, another embodiment is shown in which the absorber 54 and absorber cyclone 52 are eliminated from the system. In this embodiment, the pneumatic conduit is in direct flow communication with the cyclone 71 of the production machine. The cyclone separator 71 is connected to a rotating airtight access 73 which allows the tobacco to be separated by a high velocity air stream to be fed into the making machine 80 through the making machine's hopper 72. Likewise, an ultrasonic height measuring transmitter 75 is used to control the sliding door 31. This embodiment does not require an absorber and associated cyclone. The air classification system of the maker 80 removes stalks, bulbs and other heavier materials from the tobacco stream.

The foregoing detailed description has been given primarily for clearness of understanding, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention or exceeding the scope of the appended claims.

Claims (22)

1. An apparatus for continuously feeding tobacco from a cargo compartment to at least one cigarette making machine, comprising:

a vibratory feed tray secured to said cargo tank and positioned below a discharge opening in said cargo tank, said vibratory feed tray having an outlet, said outlet having at least one opening, and a sliding door slidably mounted in said opening;

a first rotary airtight inlet/outlet provided below the sliding door;

a first cyclone connected to the at least one cigarette making machine;

pneumatic tubing connecting said airtight access port to said cyclone separator and further connecting the cyclone separator to a vacuum source;

a first ultrasonic height measuring transmitter in the cigarette making machine; and

a first controller connectable to the height measurement transmitter and the sliding door.

2. The apparatus of claim 1, further comprising:

a first flow measurement transmitter in the pneumatic conduit between the cyclone separator and the vacuum source to measure the velocity of air in the conduit;

a flow control valve in said pneumatic conduit between said cyclone and said vacuum source;

a second controller connectable to the flow control valve and the first flow measurement transmitter.

3. The apparatus of claim 2, further comprising a second flow measurement transmitter located in said conduit in front of said airtight access port, said second flow measurement transmitter being connectable to said controller.

4. The apparatus of claim 1, wherein said cargo tank further comprises:

a plurality of roller bars and a belt conveyor at one end of the cargo compartment;

a second ultrasonic height measurement transmitter secured above the vibratory feed tray; and

a second controller connectable to the plurality of roller bars, the belt conveyor, and the second height measurement transmitter.

5. The apparatus of claim 1, wherein said vibratory feed tray is V-shaped in cross-section having first and second downwardly inclined surfaces.

6. An apparatus according to claim 1, further comprising a second rotary airtight access port between the cyclone separator and the at least one cigarette making machine.

7. The apparatus of claim 1, further comprising:

a four-pass multistage absorber between said first airtight portal and said first cyclone separator, said absorber having a second cyclone separator in front thereof, said second cyclone separator storing tobacco into said airtight portal; and

wherein the second cyclone is in flow communication with the vacuum source.

8. The apparatus of claim 7, further comprising a second rotating hermetic access port between the second cyclone and the absorber.

9. The apparatus of claim 1, wherein said tobacco is fed into said first airtight port at a rate of about 20 pounds per minute.

10. The apparatus of claim 1 wherein the air flow rate at said first airtight portal is about 275 standard cubic feet per minute.

11. The apparatus of claim 10, wherein the pneumatic tubing has a diameter of about 5 inches.

12. The apparatus of claim 1, wherein the sliding door is attachable to the air cylinder block.

13. The apparatus of claim 12, further comprising a linear sensor attachable to the sliding door.

14. An apparatus for continuously feeding tobacco from a cargo space to two cigarette making machines, comprising:

continuously feeding said tobacco from said hold into a vibratory feed tray having first and second tobacco discharge openings therein, a first sliding door slidably closing said first opening and a second sliding door slidably closing said second opening;

the first airtight inlet and outlet are arranged below the first opening, and the second airtight inlet and outlet are arranged below the second opening;

first and second cigarette making machines;

pneumatic tubing connecting said first airtight access port to said first cigarette making machine and said second airtight access port to said second cigarette making machine, said pneumatic tubing being further connected to a vacuum source;

a cigarette level detection device in each of said cigarette making machines; and

first controller means connectable to said detection means and to said first and second sliding doors.

15. An apparatus according to claim 14, further comprising a first cyclone connected to the first cigarette making machine and in flow communication with the first airtight access and a second cyclone connected to the second cigarette making machine and in flow communication with the second airtight access.

16. The apparatus of claim 14, wherein said means for delivering tobacco from said cargo compartment comprises:

a plurality of roller bars and a belt conveyor at one end of the cargo compartment;

an ultrasonic height measurement transmitter secured above the vibratory feed tray;

a second controller connectable to the plurality of roller bars, the belt conveyor, and the height measurement transmitter.

17. The apparatus of claim 14, further comprising:

means for detecting the velocity of air in said duct;

a flow control valve in said pneumatic conduit; and

a third controller connectable to the sensing device and the flow control valve.

18. The apparatus of claim 17, wherein said sensing means comprises a flow measurement transmitter inserted into said pneumatic conduit.

19. A method for continuously transferring tobacco from a cargo compartment to a cigarette making machine, comprising:

feeding tobacco from said hold into a feed tray;

discharging tobacco from said feed tray into an airtight access opening, said discharging being at a preselected tobacco level in said cigarette making machine;

pneumatically transferring tobacco in a duct continuously from said airtight access opening to said cigarette making machine;

the flow rate of tobacco in said duct is controlled by opening and closing a flow control valve in accordance with said measurement by measuring the velocity of the air flow in said duct.

20. The method of claim 19, wherein an ultrasonic height measuring transmitter measures the height of tobacco in said production machine.

21. The method of claim 19, wherein said dispensing tobacco into said feed tray further comprises:

measuring the depth of tobacco in said feed tray with an ultrasonic height measuring transmitter; and

actuating a conveyor belt in said cargo space to dispense said tobacco onto said feed tray in accordance with said measurements by said height measuring transmitter.

22. The method of claim 19, wherein said discharging tobacco from said feed tray further comprises:

opening and closing a sliding door according to said measurement of said height measuring transmitter;

(iii) upon said opening and closing of said sliding door, allowing tobacco to fall from said feed tray into said duct;

wherein the sliding door covers an exit opening to the airtight access opening.