Cigarette making machine
Our British patent specification No. 1,340,201 describes an invention whereby, amongst other things, the flap seal commonly used in the Molins Mark 8 and Mark 9 cigarette making machines can be obviated. The arrangement described in that specification involves the use of a suction pipe for removing discard tobacco from below the trimming device. Partly as a result of that suction pipe, suction pressure is maintained in the space below the cigarette filler stream and downstream of the chimney at a level greater than the suction pressure at the upper end of the chimney; this ensures that air flows from the chimney into that suction space, rather than in the reverse direction. 
     It is not always convenient or desirable to use a suction pipe for conveying away the discard tobacco. The Mark 8 and Mark 9 cigarette making machines conventionally use a conveying screw, and it is some cases convenient to go on doing so. This invention is particularly concerned with an arrangement which avoids the need for a flap seal but allows the continued use of the conveying screw or of some other mechanical conveying device for removing discard tobacco. 
     According to this invention a cigarette making machine comprises an air-pervious band, a channel through which tobacco is showered towards the band with the aid of an air stream to form a cigarette filler stream on the band, the air stream being induced at least partly by suction acting through the band to hold the tobacco against the band, whereby there is also suction pressure in the channel at the end adjacent to the band, characterised by a partly-tubular casing which covers the cigarette filler stream as it leaves the shower channel, and inclined air inlets which are arranged to introduce air streams into the part-tubular casing in directions having components in the direction of movement of the cigarette filler stream. 
     This arrangement allows the flap seal to be removed since the inclined air streams prevent or substantially prevent any reverse flow of air along the filler stream. 
     A preferred arrangement according to this invention is one in which the inside of the casing is arranged to have a pressure below atmospheric, and in which the air inlets draw in air from the atmosphere. However, as an alternative the inside of the casing may be at approximately atmospheric pressure, and air may be blown in through the air inlets from a manifold containing air at a pressure slightly above atmospheric. For example, the pressure in the manifold may be approximately 5 mm water guage; for that purpose the manifold may be connected to the outlet of the fan generating suction pressure for the purpose already mentioned. 
    
    
     An example of a machine according to this invention is shown in the accompanying drawings. In the drawings: 
     FIG. 1 is a diagrammatic front view of part of the machine; 
     FIG. 2 is an enlarged sectional view of the part of the machine identified by the arrow II in FIG. 1; 
     FIG. 3 is a section on the line III--III in FIG. 1; and 
     FIG. 4 shows how the discard tobacco is conveyed from the suction enclosure around the trimming device. 
    
    
     As shown in FIG. 1, the machine is basically like a Molins Mark 9 cigarette making machine; details of the machine not shown in the drawings may be similar to those of the Mark 9. It includes a chimney 10 up which tobacco is showered by an upwardly moving air flow towards a suction band 11 on which the tobacco forms a cigarette filler stream 11A. The filler stream is trimmed by a trimming device 12 and is then deposited on a wrapper web 13 in which the stream is enclosed to form a continuous cigarette rod in a well known manner. 
     The trimming device 12 is contained in a suction enclosure 14. Discard tobacco removed from the filler stream by the trimming device is conveyed transversely by a conveying screw 15 rotating at about 1000 R.P.M. At the downstream end of the screw (see FIG. 4) there is a rotary member 16 which rotates at about 1/4 the speed of the screw and lies between part-cylindrical walls 17 defining an outlet from the suction enclosure. The member 16 has paddles or vanes 16A which cooperate with the walls 17 to form an air seal preventing any significant flow of air into the suction enclosure in that area. Angular adjustment of the screw 15 is possible to enable the screw to be set so as to project the tobacco through the rotary member 16 without needing to be conveyed forward by the vanes 16A. After leaving the suction enclosure in this manner, the tobacco may be conveyed by a vibratory tray (not shown) to return it into the hopper of the machine. 
     As a result of suction which is applied through the suction band 11 from a suction chamber 18, suction pressure is maintained in the enclosure 14. This suction pressure is, however, less than suction pressure at the upper end of the chimney 10 which results partly from the application of suction through a supercharger louvre 19. 
     Between the chimney 10 and the suction enclosure 14, the lower surface of the cigarette filler stream 11A is enclosed in a semi-tubular casing 20 defining a narrow channel 21 (see particularly FIG. 3). Air is admitted into the channel 21 through several inlets which lie obliquely in relation to the direction of movement of the tobacco, stream, so as to produce air jets having components in the direction of movement of the tobacco stream. In particular, the inlets form five groups each comprising four inwardly inclined air inlet bores 20A. In addition there are air inlet bores 20B at the upstream end of the channel 20, and two pairs of forwardly inclined air inlet bores 22 which admit air respectively from the front and back of the chimney 10; when viewed from above, the two pairs of the inlet bores 22 converge approximately towards the centre of the upstream end of the channel 21. 
     In addition there are a number of air inlets 23 in the suction enclosure 14 to ensure that tobacco landing on the part 24 of the wall of the suction enclosure is swept downwards into a channel 25 containing the screw 15. 
     Between the edges of the wrapper web 13 and adjacent lower edges of guides 26 confining the sides of the trimmed filler stream 11A there are gaps (e.g. of 0.8 mm) which allow atmospheric air to flow sideways into the suction space below the filler stream at a rate sufficient to ensure that there is substantially no longitudinal air flow along and relative to the filler stream. In other words, the inflow of air through the gaps at each point along the filler stream (in the region of the web 13) approximately equals the air flow upwards through the filler stream 11A and band 11, thus avoiding the production of a longitudinal air flow which could disturb the trimmed filler stream.