This invention relates to apparatus for cutting web or sheet material, particularly but not exclusively for use in machinery for assembling rod-like articles of the tobacco industry.

Filter cigarette assembling machines are capable of producing filter cigarettes by wrapping uniting bands around adjacent end portions of aligned filter rod and tobacco section assemblies. In typical machines successive wrapper sections carrying adhesive are rolled around successive assemblies each comprising a double length filter portion interpose between two single length tobacco sections. The double length filter cigarettes thus formed are subsequently severed at their mid-points to produce individual filter cigarettes.

Wrapper sections for uniting the assemblies are conventionally obtained by delivering a wrapper web to cutter apparatus in which successive leading ends of the web are severed by means of a rotary knife co-operating with a counter- surface. Typically the web is conveyed on a suction drum which provides the counter-surface and on which the severed wrapper section is subsequently conveyed towards an assembly position. An arrangement of this kind is disclosed in GB941832, to which reference is directed for details.

Cutting apparatus, particularly that of the kind described, may be heated, in order to activate and/or assist in setting of adhesive carried by the wrapper

sections and used to unite the wrapper sections to the rod assemblies. In this case, but also more generally, the apparatus may take a considerable period to reach a stable operating temperature following start-up. Moreover, different parts of the apparatus may warm up at different rates and assume different equilibrium temperatures. For example, where a rotary knife cooperates with a suction drum the latter may be heated, the rotary knife gradually increasing in temperature during operation after start up, by conduction and/or convection and/or radiation from the drum, until equilibrium is reached. A consequence of this is that, due to differential expansion effects as the apparatus warms up during running, in conventional apparatus there may be difficulty in setting the knife clearances so that a desired interference with the web is achieved and/or maintained. Commonly a compromise setting is made between the requirements for running"cold"and that for running"hot".

The invention provides apparatus for cutting a web or sheet of material, particularly but not exclusively wrapper material for uniting rod-like articles of the tobacco industry, comprising a rotary knife and a counter-knife arranged to co- operate with the rotary knife to sever said material, including means for locating the rotary knife and counter-knife to achieve a desired interference with the material, wherein the locating means is arranged to compensate at least partly for variations from said desired interference caused by thermal expansion. The locating means may include means arranged to achieve a temperature bearing a

predetermined relationship to that of one or more other parts of the apparatus and/or means arranged to expand thermally by an amount bearing a predetermined relationship to the amount of thermal expansion of one or more other parts of the apparatus. In a preferred arrangement the apparatus includes heating means, which may be associated with said one or more other parts of the apparatus (eg including the counter-knife).

In a preferred arrangement at least one of the rotary knife, counter-knife, and means supporting the rotary knife and/or counter-knife, are constructed from or substantially consist of material having a first thermal expansivity, and the locating means is constructed from or substantially consists of material having a second thermal expansivity. In this arrangement the dimensions or other parameters of the locating means may be selected such that thermal expansion of at least one of the rotary knife, counter-knife, and supporting means causes or tends to cause change of the interference (including a gap) between the rotary knife and counter knife-in a first direction, and such that thermal expansion of the locating means causes or tends to cause change in the opposite direction. Thus, where the counter-knife comprises a drum, which may be heated, and where the drum and rotary knife are mounted on a common frame, the locating means may comprise a member rotatably supporting the drum or counter-knife and having a connection to the common frame which allows relative movement of the axes of the drum and rotary knife on thermal expansion of the member. The member may

comprise a plate carrying the rotary knife for example, and having first and second spaced connections to the common frame, one of the connections being adapted to allow movement of the member relative to the frame. The connection allowing relative movement could, for example, comprise a rigid connection to the frame in a portion of the member adapted to flex to allow such movement. Where the frame is constructed mainly of steel (or cast iron), the member may consist mainly of aluminium, which has a coefficient of expansion of approximately double that of steel (or cast iron): thus, an aluminium member having a relatively short dimension can provide thermal compensation for a steel member having a relatively long dimension. Where the locating means includes means having surfaces in contact, relative movement of which occur on thermal expansion, one or both surfaces may be adapted to facilitate said relative movement, eg by surface treatment or profiling or relieving intended to reduce frictional resistance to said movement.

The invention also includes apparatus for cutting a web or sheet of material, particularly but not exclusively wrapper material for uniting rod-like articles of the tobacco industry, comprising a rotary knife and a counter-knife, first mounting means supporting one of said rotary knife and counter-knife, second mounting means supporting the other of said rotary knife and counter-knife, and means connecting said first and second mounting means such that relative movement due to thermal expansion is allowed. The connecting means may

comprise a flexible link. The first and second mounting means may be arranged to be in thermal contact with each other. The first and second mounting means may comprise or consist of materials having different coefficients of expansion.

The invention also includes apparatus for cutting a web or sheet of material, said apparatus comprising a rotary knife, at least one counter-surface cooperable with said knife to sever said material and a mounting for said rotary knife and the or each said counter-surface, said mounting being adapted to compensate for thermal expansion, which occurs in use of the apparatus, whereby a desired relationship between said rotary knife and the or each said counter- surface can be substantially maintained.

In any of its aspects the invention is applicable to conventional cutting apparatus, particularly such apparatus for cutting wrapper web in a filter cigarette assembly machine and where the web is conveyed on a heated suction drum. In such apparatus, although the knife clearance may be set after the suction drum itself has reached normal operating temperature, the associated support frame and counter-knife, or counter-surface, continue to warm up during normal operation, reaching an equilibrium temperature only after a considerable running period. Such continuing increase in temperature, particularly of the frame supporting the suction drum and rotary knife, causes an increase in distance between the axes of rotation of the drum and knife. The cutting interference between wrapper web carried on the suction drum and the rotary knife therefore becomes less. Any expansion of

the rotary knife itself is insufficient to compensate for this, as the rotary knife generally has a lower equilibrium temperature than the suction drum and frame.

By provision of locating means, which may include mounting means for the rotary knife, and which may allow relative movement of the axes of the suction drum and rotary knife, the effects on knife clearance of thermal expansion may be substantially reduced or eliminated The locating or mounting means may be arranged to be in good thermal contact with the frame or other part of the apparatus, e. g. so that it reaches the same temperature as the frame or other part of the apparatus or otherwise reaches a predictable temperature relative to that of the frame or other part.

The invention will be further described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of apparatus for cutting wrapper material in a filter cigarette assembly machine : Figure 2 is a sectional view on the line 11-11 in Figure 1.

Figure 3 is a side elevation showing a modification of the apparatus shown in Figure 1 ; Figure 4 is a section on line IV-IV in Figure 3 ; and Figure 5 is a sectional view looking in the direction of the arrow V in Figure 3 and showing an alternative modification of the apparatus..

Apparatus for cutting a web of wrapper material to produce wrapper

sections for umting tobacco sections and filter rods in a filter cigarette assembling machine includes a suction drum 10 rotatable about an axis 12 and a knife drum 14 rotatable about a parallel axis 16. The knife drum 14 carries twelve radially extending knives, one of which is indicated at 18, and the suction drum 10 carries a corresponding number of anvil inserts, one of which is indicated at 19. On rotation of the drums 10 and 14 in opposite directions each knife 18 co-operates with a corresponding anvil 19 to sever successive leading sections from a web of wrapper material delivered to the drum 10. The mounting for each knife 18 includes a mechanism 20 for adjustment of the radial position of each knife so as to achieve a desired interference with a web supported by the corresponding anvil on drum 10. Normally the knife is set with the objective of cutting the web without excessive wear and/or damage to the knife and/or anvil. A mechanism for adjustment of the radial position of a knife in a cutter drum is disclosed in GB878556, the content of which is incorporated herein by reference.

After being severed from the web, wrapper sections are conveyed on the suction drum 10, typically to a position at which the drum co-operates with a rolling plate to wrap each wrapper section around a double length filter portion and adjacent end portions of axially aligned single length tobacco sections, thereby to form a double length filter cigarette. For more details of the wrapping operation reference is directed to said GB941832, the content of which is incorporated herein by reference.

The suction drum 10 is mounted on a frame member 22 rigidly connected to the structure of the filter cigarette assembling machine. The knife drum 14 is mounted on a base plate 24 attached to the frame member 22 by way of two main fixing screws 26 and two secondary fixing screws 28. The plate 24 is provided with profile slots 30 defining a bridge portion 32 including a relatively wide part 32A, through which the secondary screws 28 pass, and a pair of relatively narrow links 32B connecting the part 32A to the main body of the plate 24. It will be understood that the drums 10 and 12 are respectively mounted on the frame member 22 and plate 24 by way of bearings allowing rotation about the respective axes 12,16.

The mounting arrangement of the illustrated apparatus at least partly alleviates problems concerned with running the apparatus at different temperatures, and compensates for temperature variation, as will be described with reference to expansion during warming up. It will be appreciated however that such compensation applies equally during contraction due to cooling and generally for any operating temperature variations. During warming up of the apparatus the heated suction drum 10 expands as its temperature increases, and heat is gradually transferred also to the frame member 22 and by way of this to the plate 24 and knife drum 14. In conventional apparatus, where the suction drum 10 and knife drum 14 are mounted on a common frame member, the distance between the axes 12 and 16 increases during warming up but, because the knife drum 14 does not

reach similar temperatures to those reached by the drum 10 and frame member 22, the consequence is that where the drums and frame member are constructed of a similar materials, e. g. steel, the clearance between the knives 18 and the anvils on the suction drum increases In the present apparatus, however, the base plate 24, which has good thermal contact with the frame member 22, is constructed of a material, e. g. aluminium, having a coefficient of expansion which is greater than that of the suction drum 10 and frame member 22. On expansion of the base plate 24 the main fixing screws 26 hold the outer end of the base plate fixed relative to the frame member 22 but the secondary fixing screws 28 effectively allow movement of the main body of the plate relative to the frame member by flexing of the links 32B. Thus, where the base plate 24 is constructed of aluminium and the frame member 22 (and suction drum 10) are constructed of steel, the dimensions of the plate 24 may be selected so that expansion of the plate (which occurs at approximately twice the rate of the frame member) can be arranged to compensate for increased clearance between the knives 18 and the anvils of the suction drum which would otherwise occur, so that the clearance between the knives and the anvils remains substantially constant over a range of temperatures which may extend from normal ambient temperature ("cold") to normal operating temperature ("hot"), or at least from an initial temperature, reached after the suction drum has warmed up, to normal operating temperature.

The surface of the plate 24 in contact with the frame member 22, or the

adjacent surface of the frame member, could be adapted to facilitate relative movement, thereby alleviating problems associated with any tendency of the plate to stick and hence move jerkily in response to thermal expansion or contraction.

Thus the surface or surfaces could have low friction coatings and/or one or both surfaces could be profile or relieved, eg by having grooves parallel to the longitudinal axis of the plate. Although a reduction in contact area may be beneficial in overcoming frictional resistance to relative movement, sufficient contact should preferably remain for adequate thermal transfer, so that the plate 24 is in good thermal contact with the frame member 22.

It will be appreciated that the plate 24 can be screwed to the frame member by means other than fixing screws. For example, the plate could be secured to the frame member by means of nuts and bolts, welding or rivets.

Figures 3 and 4 show a modified form of the apparatus shown in Figures 1 and 2 and to avoid unnecessary further description, only the modification will be described herein and like reference numerals will be used to describe parts common to both versions of the apparatus.

In place of the connection at the bridge portion 32 of Figure 1, the base plate 24 of the modified version of the apparatus is provided with two slots 50.

The slots 50 are arranged in parallel spaced apart relationship and extend parallel to a line passing through and perpendicular to each of the axes 12,16. Respective fixing screws 52 pass through the slots 50 and cooperate with the screws 26

(Figure 1) to secure the base plate 24 to the frame member 22. A disc spring 54 is fitted between the head of the screws 26 and the base plate 24. The screws 52 are tightened to a suitable torque to hold the adjacent end of the base plate against the frame member 22.

It will be appreciated that during use of the apparatus, as the various parts warm up and expand at different rates, the screws 26 hold the adjacent end of the plate fixed relative to the frame member, whilst the screws 52 effectively allow the main body of the base plate to move relative to the frame member in the lengthways direction of the slots 50 Thus, where the base plate is constructed of aluminium and the frame member and suction drum 10 are constructed of steel, the arrangement of the screws and slots can be selected to permit a predetermined amount of movement of the base plate to compensate for the increased clearance between the knives 18 and the anvils of the suction drum which would otherwise occur, so that the clearance remains substantially constant over a range of temperatures which may extend from normal ambient temperature ("cold") to normal temperature ("hot"), or at least from an initial temperature, reached after the suction drum has warmed up, to the normal operating temperature of the apparatus.

It will be appreciated that the lengthways extent of the slots 50 does not need to be significantly greater than the diameter of the screws 52 since only a small movement of the plate will be required.

The screws may be fitted with bushes (not shown) which fit accurately around the screw shank and in the slots so as to prevent movement of the plate in directions transverse to the lengthways direction of the slots.

It will be understood that the disc springs 54 may be replaced by a plurality of suitably arranged disc springs arranged in nose-to-nose and/or tail-to- tail relationship. Alternatively, a coil spring or spring washer could be fitted in place of the disc spring.

An alternative modification to the apparatus shown in Figure I would be to replace the screw connection at the end of the base plate adjacent the suction drum 10 with a slide arrangement as shown in Figure 5. In this arrangement, the frame member is provided at least one upstanding V-section rib 60 which may be an integral part of the frame member or part of a member secured to the frame member The rib 60 extends parallel to a line extending between and perpendicular to the axes 12,16 and mates with a V-groove 62 provided in the underside of the base plate 24. It will be appreciated that with this arrangement, the end of the base plate adjacent the screws 26 will be held fixed relative to the frame member, whilst the main body of the plate is effectively allowed to move relative to the frame member as described above.

It will be understood that the arrangement of Figure 5 could be modified by providing parallel V-grooves in the frame member and base plate and fitting ball bearings into the diamond shaped grooves formed when the frame member. and base plate are secured together with the respective grooves disposed opposite one another.