GB1588507A

GB1588507A - Method and machine for making cigarette filters

Info

Publication number: GB1588507A
Application number: GB846680A
Authority: GB
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1976-07-02
Filing date: 1977-06-28
Publication date: 1981-04-23

Description

(54) METHOD AND MACHINE FOR MAKING CIGARETTE FILTERS (71) We, MOLINS LIMITED, a British Company, of 2 Evelyn Street, Deptford London SE8 5DH, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is concerned with a method and machine for making cigarette filters from filter tow. Filter tow commonly comprises crimped fibres of cellulose acetate, but it could in principle be of other materials having similar physical characteristics.

According to one aspect of the invention a machine for making cigarette filters from filter tow comprises means for feeding tow towards a rod-forming unit, means for blowing air into the tow during its movement towards the rod-forming unit, a. suction conveyor which is downstream of the blowing means and is arranged to compress the tow laterally while drawing air out of the tow, and means surrounding the tow in the region between the blowing means and the suction conveyor for restricting the air flow outwards from the tow in said region.

According to another aspect of the invention a method of making cigarette filters from filter tow comprises the steps of feeding filter tow while blowing air into the tow to fluff up the tow, laterally compressing the tow while drawing air out of the tow, confining the tow beneath the positions at which air is blown into and subsequently drawn out of the tow, and restricting the flow of air outwards from the tow whilst confining the tow beneath'said positions.

Other aspects of the invention- will be clear from the following description and claims.

The invention is further described, by way of example only, with reference to the accompanying drawings, -in which' Figure 1 is a fragmentary partly sectioned view of a filter making machine ' Figures 2A to 2G are section, on a larger scale, on the lines A to G in Figure 1;.

Figure 3 is a fragmentary pardy- sectioned view of a machine similar to that of Figure 1 but modified according to the invention and Figures 4 and 5 are sectionS, - on a larger scale, on The lines IV-IV - and V-V in Figure 3.

The machine shown in Figure 1 includes a condensing cone 25 into which cellulose acetate or other tow is fed through the right hand end of the cone. Thee cone begins the compression of the tow, and this compression is continued by a suction wheel 26 comprising an air-pervious rim 26a mounted between side walls 26d and 26e Figure 2F). It should be noted' that the rim 26a is recessed from the outer edge of the walls 26d and 26e so as to form a shallow circumferential groove ground the wheel.

Between the side walls 26d and 26e of the wheel' there is a fixed member 26c formed with a recess 26b which is'connected with a source of suction via a pdrt 26h' so that air is drawn inwards through the rim 26a of the wheel, as shown by the approx mately radial arrows in Figure 1.

The cone 25 is cut away to allow the suction wheel 26 to enter the cone to grip the tow and to compress it between the wheel and a wrapper web 27. The decreasing cross-section of the passage formed between the wheel and the web 27 is shown by Figures 2C - to 2E. Further compression of the tow occurs up to the section line F, at which point the cross-sectional area of the tow is preferably approximately equal to and certainly not much greater'that'the cross-sectionalarea of the final rod, e.g. 60 square mm. Where the final rod cross-section is about 50 square mm.

At the section line G, the tow parts from the wheel, and its compression' aiid final shaping is continued by å tongue 29. The slight increase in cross-section of thé-'channel between the wheel and web-27 betweeii the section lines F and G facilitates the action of the tongue (which serves in effect also as a stripping shoe)' in stripping the tow froni the wheel.Furthermore, the fixed member 26c is formed with a second recess- 26f'which is supplied with air at atmospheric or above-atmospheric pressure so that air flows outwards from the recess 26f and helps to remove the tow from the periphery 26a of the wheel. Substantially all the air flowing out of the recess 26f is drawn into the recess 26b, as shown generally by the arrow 26g.

The cone 25 may be formed with a number of apertures 25a on both sides, as shown in the drawings.

It will be understood that the main compression of the tow is carried out by the wheel 26. Some further compression and shaping of the tow is achieved by the tongue 29, which converges slightly towards the wrapper 27 and is appropriately shaped in cross-section so as to form the tow into a cylindrical cross-section. The paper is supported throughout by a base member 28 formed with a longitudinal groove of curved cross-section in its upper surface in which the web 27 moves.

The tongue 29 is formed with two apertures providing pressure tappings at longitudinally spaced points 30 and 31 from which pipes 33 deliver pressure signals to a comparator device 34. An electrical output from the comparator device 34 depends upon the pressure difference at the two pressure tappings and is indicative of the pressure drop through the tow. The output of the comparator may be used to control the rate at which tow is fed into the cone 25 so as to maintain a substantially constant pressure drop. For a nuller description of a suitable comparator and the way in which it may be used to control the tow feed reference is directed to our copending Application Nos. 27583/76, 53688/76 (Serial No.

1,588,506).

In order to avoid or minimise air leakage from or into the tow between the tongue and the wrapper web 27, the edges of the wrapper web 27 may be pressed against the sides of the tongue by air pressure supplied through slots - or apertures in the adjacent parts of the base member 28. This pressure on the web 27 would in practice be transmitted via a woven tape (not shown) by which the web 27 would be supported in the usual way.

The air-pervious rim portion 26a of the wheel 26 may, for example, be a very fine metal gauze (e.g. with 0.010 inch diameter holes) or a woven tape, e.g. of nylon.

Figure 3 shows an alternative machine which is basically the same as that shown in Figure 1 in regard to the suction wheel 26, wrapper web feed 27, tongue 29, and the pressure drop measuring device including the comparator 34. However, the tow feed upstream of ithè wheel 26 is-different.

In Figure 3 the tow is fed initially through a fluffing unit 40 comprising a conical inner part 41 and a surrounding outer part 4 which defines with the inner part 41 an annular space 43 having an annular outlet 44. Compressed air is applied to the space 43 through inlets 45 and 46 to produce an annular flow of air inwards into the tow through the outlet 44, e.g. at a flow rate of about 6 cubic feet/minute. This flow of air counters the tendency for the crimping of the cellulose acetate fibres to be removed by stretching. In other words, the fluffing units tends to maintain or restore the crimping of the fibres which is ncessary to provide the desired pressure drop through the finished filter rod.

The fluffing unit 40 has an outlet portion 47 which is joined via a duct 48 and a con- necting ring 49 to a duct 50 which feeds the tow towards the suction wheel 26. The inner part 41 of the fluffing unit is of circular cross-section, as is the outlet 47; and the duct 48, the connecting ring 49 and the duct 50 change progressively 'from a circular cross-section - to an oval cross-section as shown in Figure 4, which is a cross-section on the line IV-IV.

The combination of the fluffing unit 40 with the suction wheel 26 is useful in that it enables more air to be blown into the tow by the fluffing unit than would be possible without the suction wheel 26. This is because the suction wheel draws the air forward (preventing a reverse flow of air which could otherwise occur) and removes most of the air from the tow before the tow enters the region below the tongue 29.

The connecting ring 49 may have apertures 49a to let in more air from the atmosphere if necessary; the ring may be closely surrounded by a flexible sleeve formed with a similar set of holes which can be brought partly or fully into alignment with the holes 49a by rotation of the sleeve to control the air flow. In addition the duct 50 may have a number of air inlet apertures 50a near the wheel 26 along both sides of the duct as shown in the drawings.

The examples described above are concerned with the manufacture of filter rods including a wrapper of paper or other material around the tow. As an alternative this invention may be applied to a machine which makes filter rods having no wrapper, e.g. as described in British Patent Specification No.

1,169,932.

Reference is directed to our copending Application Nos. 27583/76, 53688/76 (Serial No. 1,588,506), from which the present application is divided, which claims matter disclosed in the present specification, WHAT WE CLAIM IS: 1. A machine for making cigarette filters from filter tow, including means for feeding tow towards a rod-forming unit, means for blowing air into the tow during its move

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. is supplied with air at atmospheric or above-atmospheric pressure so that air flows outwards from the recess 26f and helps to remove the tow from the periphery 26a of the wheel. Substantially all the air flowing out of the recess 26f is drawn into the recess 26b, as shown generally by the arrow 26g. The cone 25 may be formed with a number of apertures 25a on both sides, as shown in the drawings. It will be understood that the main compression of the tow is carried out by the wheel 26. Some further compression and shaping of the tow is achieved by the tongue 29, which converges slightly towards the wrapper 27 and is appropriately shaped in cross-section so as to form the tow into a cylindrical cross-section. The paper is supported throughout by a base member 28 formed with a longitudinal groove of curved cross-section in its upper surface in which the web 27 moves. The tongue 29 is formed with two apertures providing pressure tappings at longitudinally spaced points 30 and 31 from which pipes 33 deliver pressure signals to a comparator device 34. An electrical output from the comparator device 34 depends upon the pressure difference at the two pressure tappings and is indicative of the pressure drop through the tow. The output of the comparator may be used to control the rate at which tow is fed into the cone 25 so as to maintain a substantially constant pressure drop. For a nuller description of a suitable comparator and the way in which it may be used to control the tow feed reference is directed to our copending Application Nos. 27583/76, 53688/76 (Serial No. 1,588,506). In order to avoid or minimise air leakage from or into the tow between the tongue and the wrapper web 27, the edges of the wrapper web 27 may be pressed against the sides of the tongue by air pressure supplied through slots - or apertures in the adjacent parts of the base member 28. This pressure on the web 27 would in practice be transmitted via a woven tape (not shown) by which the web 27 would be supported in the usual way. The air-pervious rim portion 26a of the wheel 26 may, for example, be a very fine metal gauze (e.g. with 0.010 inch diameter holes) or a woven tape, e.g. of nylon. Figure 3 shows an alternative machine which is basically the same as that shown in Figure 1 in regard to the suction wheel 26, wrapper web feed 27, tongue 29, and the pressure drop measuring device including the comparator 34. However, the tow feed upstream of ithè wheel 26 is-different. In Figure 3 the tow is fed initially through a fluffing unit 40 comprising a conical inner part 41 and a surrounding outer part 4 which defines with the inner part 41 an annular space 43 having an annular outlet 44. Compressed air is applied to the space 43 through inlets 45 and 46 to produce an annular flow of air inwards into the tow through the outlet 44, e.g. at a flow rate of about 6 cubic feet/minute. This flow of air counters the tendency for the crimping of the cellulose acetate fibres to be removed by stretching. In other words, the fluffing units tends to maintain or restore the crimping of the fibres which is ncessary to provide the desired pressure drop through the finished filter rod. The fluffing unit 40 has an outlet portion 47 which is joined via a duct 48 and a con- necting ring 49 to a duct 50 which feeds the tow towards the suction wheel 26. The inner part 41 of the fluffing unit is of circular cross-section, as is the outlet 47; and the duct 48, the connecting ring 49 and the duct 50 change progressively 'from a circular cross-section - to an oval cross-section as shown in Figure 4, which is a cross-section on the line IV-IV. The combination of the fluffing unit 40 with the suction wheel 26 is useful in that it enables more air to be blown into the tow by the fluffing unit than would be possible without the suction wheel 26. This is because the suction wheel draws the air forward (preventing a reverse flow of air which could otherwise occur) and removes most of the air from the tow before the tow enters the region below the tongue 29. The connecting ring 49 may have apertures 49a to let in more air from the atmosphere if necessary; the ring may be closely surrounded by a flexible sleeve formed with a similar set of holes which can be brought partly or fully into alignment with the holes 49a by rotation of the sleeve to control the air flow. In addition the duct 50 may have a number of air inlet apertures 50a near the wheel 26 along both sides of the duct as shown in the drawings. The examples described above are concerned with the manufacture of filter rods including a wrapper of paper or other material around the tow. As an alternative this invention may be applied to a machine which makes filter rods having no wrapper, e.g. as described in British Patent Specification No. 1,169,932. Reference is directed to our copending Application Nos. 27583/76, 53688/76 (Serial No. 1,588,506), from which the present application is divided, which claims matter disclosed in the present specification, WHAT WE CLAIM IS:

1. A machine for making cigarette filters from filter tow, including means for feeding tow towards a rod-forming unit, means for blowing air into the tow during its move

ment towards the rod-forming unit, a suction conveyor which is downstream of the blowing means and is arranged to compress the tow laterally while drawing air out of the tow, and means surrounding the tow in the region between the blowing means and the suction conveyor for restricting the air flow outwards from the tow in said region.

2. A machine according to claim 1, wherein said means surrounding the tow includes a duct provided with air outlets.

3. A machine according to claim 2, wherein at least some of the outlets are at least partly closable.

4. A machine according to claim 2 or claim 3, wherein the blowing means includes an annular air outlet through which air is blown into the tow from all sides.

5. A machine according to claim 4, wherein said duct has a cross-sectional shape which changes progressively from substantiallly circular to substantially oval.

6. A machine according to any preceding claim, further including means downstream of the suction conveyor for sensing the pressure drop through the tow, and means for adjusting the tow feed in response to the pressure drop sensor to maintain the pressure drop substantially constant.

7. A machine according to claim 6, wherein the suction conveyor is arranged to compress the tow to substantially its final cross-sectional area and is followed by a tongue which shapes the tow to its final cross-section, and in which the pressure drop sensing means comprises means for comparing the pressure at two longitudinally spaced tappings in the tongue.

8. A method of making cigarette filters from filter tow, including the steps of feeding filter tow while blowing air into the tow to fluff up the tow, laterally compressing the tow while drawing air out of the tow, confining the tow between the positions at which air is blown into and subsequently drawn out of the tow, and restricting the flow of air outwards from the tow whilst confining the tow between said positions.

9. A method according to claim 8, further including the steps of monitoring the air pressure drop through the tow and using the pressure drop signal to control the tow feed so as to maintain the pressure drop substantially constant.

10. A method according to claim 8 and substantially as herein described with particular reference to the accompanying drawings.