GB2135912A

GB2135912A - Filter cigarette manufacture

Info

Publication number: GB2135912A
Application number: GB08403208A
Authority: GB
Inventors: John Kenneth Horsley; John Rogers
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1983-02-08
Filing date: 1984-02-07
Publication date: 1984-09-12
Also published as: GB2135912B; GB8403208D0

Abstract

A method of manufacturing ventilated cigarettes in which PVA or equivalent adhesive is applied to a web (12) of tipping paper by a nozzle (10) having an outlet (32) which extends transversely with respect to the direction of movement of the web and of which at least one portion is closed at regular intervals by a blocking member (50A) so as to leave perforated areas (48) [Fig. 3] of the web or parts (42,44) thereof free of adhesive. <IMAGE>

Description

SPECIFICATION Filter cigarette manufacture This invention is concerned with the manufacture of ventilated cigarettes, i.e. filter cigarettes having apertures near the mouth end to admit atmospheric air during smoking. For that purpose, the band of tipping paper which joins the tobacco rod to the filter may be formed with a band of fine perforations or with one or more rows of larger perforations extending around the finished cigarette. When applying adhesive to the tipping paper (normally before individual portions are cut from a continuous web of tipping paper), it is desirable to leave the tipping paper substantially free of adhesive in the region of the perforations to avoid the risk of adhesive closing or partially blocking the perforations. The application of adhesive in that manner will in this context be referred to as "skip gap gumming".

Skip gap gumming is readily achievable by printing the adhesive on the tipping paper by means of a combination of rollers of which one is formed with appropriate recessed and raised portions. However, the use of rollers involves problems, particularly since the usual polyvinyl acetate (PVA) adhesive gradually tends to build up deposits on the rollers through exposure of excess PVA to the atmosphere.

The present invention is concerned with avoiding such problems by applying PVA or equivalent waterbased adhesive by means of a nozzle.

The use of a nozzle for PVA gumming was proposed in British patent specification No. 1497661.

However, the gummer described in that specification makes no provision for skip gap gumming.

According to the present invention, in a method of manufacturing ventilated cigarettes, PVA or equivalent adhesive is applied to a web of tipping paper by a nozzle having an outlet which extends transversely with respect to the direction of movement of the web and of which at least one portion is closed at regular intervals by a movable blocking member so as to leave perforated areas of the web or parts thereof substantially free of adhesive.

The adhesive is preferably delivered to the nozzle by a positive-displacement pump providing a constant flow for a given web velocity.

An example of a method according to this invention and of apparatus for carrying out the method is shown in the accompanying drawings. In these drawings: Figure 1 is a diagrammatic side view of the apparatus, showing the nozzle partly in section; Figure 2 is a fragmentary undeneath view of the nozzle; Figure 3 shows the adhesive-coated web as it leaves the nozzle; Figure 4 is an enlarged sectional view of the metering pump shown in Figure 1; and Figure 5 is an enlarged sectional view of the outlet of the nozzle.

Figure 1 shows a nozzle 10 in the act of applying adhesive to a web 12, adhesive being delivered to the nozzle by a positive displacement pump 14from a source 16.

The nozzle 10 comprises a body 18 formed with an adhesive inlet 20 leading to a chamber 22 containing the head 24 of a vertically movable needle valve.

While the nozzle is in operation, the needle valve is held in a raised position (as shown) by a pneumatic or soienoid-operated actuator 26, thus permitting adhesive to flow into a transverse manifold 28.

When the actuator 26 is de-energised, the needle valve 24 drops onto a seat 30 so as to interrupt the flow of adhesive to the manifold 28.

One or more inclined passages 30 extend from the manifold 28 to the upper end of a narrow extrusion slot 32. The slot 32 is defined by a vertical face of a part 1 8A which may be integral with the block 18, and a detachable part 34 secured to the block 18 by a number of screw or other fasteners 36. Removal of the fasteners 36 enables the part 34 to be separated from the block, thus allowing the extrusion slot 32 to be cleaned. Alternatively, the part 18A may be integral with the part 34.

As shown in Figure 2, the extrusion slot 32 comprises two parts 32A and 32B separated by a thin dividing wall 38, thus providing a "dry line" 40 along the centre of the web 12; this avoids excessive contamination by adhesive of the disc knife which eventually cuts the double cigarette assembly in half to form two individual filter cigarettes in the conventional manner.

As shown in Figure 3, the web 12 has two longitudinally extending areas 12Aand 12Bformed with a number of rows of perforations. Figure 3 also shows outlines 42 and 44 of successive "window areas" along the two perforated areas; these window areas are required to be kept substantially free of adhesive. Each window area 42 or 44 extends along a substantial part of the length of each portion which will be cut from the web 12, that is along cut lines 46. Areas 48 between successive window areas are required to be coated with adhesive to ensure that the lap formed by each portion of the web when it is wrapped around filter and cigarette assemblies is properly secured.

In order to form the adhesive-free window areas 42 and 44, corresponding parts of the portions 32A and 32B of the extrusion slot are closed by fingers 50A and 50B on an arm 50 which is pivoted to the body 18 by a pivot pin 52. Figure 5 is an enlarged view of the outlet end of the extrusion slot and shows one of the fingers 50A in a position in which it prevents flow of adhesive from the slot across part of the width of the nozzle so as to form one of the window areas. Figure 1 shows the arm 50 in a position in which it has been displaced slightly in a clockwise direction about the pivot 52 by a cam 54 acting on a foilower roller 56 on the arm 50.A spring 56 secured to the upper end of the arm 50 and to a fixed pin 58 normally urges the arm in a counterclockwise direction so as to close the relevant portions of the extrusion slot unless the follower roller 56 is being engaged by one of a number of projecting portions 54A on the cam.

The cam 54 is carried by a shaft 54B which is driven by gearing at the appropriate speed. The nozzle is preferably mounted on the machine frame (by means not shown) separately from the cam so that it can be removed for cleaning while leaving the cam in position on the mahine.

The path of the web 12 extends around a number of rollers 60 in such a way that the tension in the web holds the web lightly but firmly against the nozzle.

Instead of the flow of adhesive being controlled by an internal valve, as shown in Figure 1,there may be an external closure device such as a roller as described in British patent specification No.

1497661; other features described in that specification may also be included.

The pump 14 comprises two lobed rotors 62 and 64 rotating in a casing having part-cylindrical inner surfaces 66 and 68. Lobes 62A and 64A on the two rotors move with small running clearances with respect to the respective surfaces 66 and 68.

Moreover, the hub portions of the rotors are so shaped that the tips of the lobes lie just clear of the corresponding surfaces of the hub portions so as to form a running seal. Thus adhesive admitted through an inlet 70 in one end wall of the pump (see Figure 1) is delivered through an outlet 72 in the same end wall at a metered rate depending upon the speed of rotation of the rotors; recesses 70A and 72A in the pump casing are aligned respectively with the inlet 70 and outlet 72A to convey adhesive to and from the rotors as shown.

The rotors are mounted on shafts 62B and 62C which carry, in a separate compartment of the pump, meshing drive gears 74 and 76 which are shown in Figure 1. The gears ensure that the rotors rotate at equal speeds, the lobes of the rotors being so shaped that they never come into actual contact with one another. This is in contrast with a conventional gear pump and is important in the present context as it avoids excessive "working" of the adhesive.

One of the shafts extends beyond the corresponding gear and out of the casing and receives a drive from the machine at an appropriate speed. Preferably the speed of rotation of the pump rotors is automatically varied in accordance with the speed of the web 12. Thus changes in the speed of the web 12, for example while the machine is being accelerated to its full operational speed, do not significantly affect the thickness of the layer of adhesive which will be applied to the web.

The various parts of the pump casing are axially aligned by pins 78 and are secured together by bolts (not shown) passing through bores 80.

Claims

1. A method of manufacturing ventilated cigarettes in which PVA or equivalent adhesive is applied to a web of tipping paper by a nozzle having an outlet which extends transversely with respect to the direction of movement of the web and of which at least one portion is closed at regular intervals by a blocking member so as to leave perforated areas of the web or parts thereof substantially free of adhesive.

2. A method according to claim 1, in which the adhesive is delivered to the nozzle by a positivedisplacement pump providing a constant flow for a given web velocity.

3. A method according to claim 2 in which the positive-displacement pump comprises two lobed rotors which are both driven, the arrangement being such that the lobes of the two rotors never come into contact with one another.

4. A method according to claim 1 and substantially as described with reference to the accompanying drawings.