GB2094211A

GB2094211A - Apparatus for perforating webs of wrapping material for tobacco or the like

Info

Publication number: GB2094211A
Application number: GB8209722A
Authority: GB
Original assignee: Hauni Werke Koerber and Co KG
Current assignee: Koerber AG
Priority date: 1980-04-25
Filing date: 1981-04-13
Publication date: 1982-09-15
Also published as: IT8121336A0; GB2094211B; GB2074493A; IT1137157B; JPS56169578A; GB2074493B

Abstract

Apparatus for making holes in a running web of tipping paper for filter cigarettes has a carrier 38 for a battery of suitably distributed perforating units 39a, b, c and 41 a, b, c each of which has an optical system 46 for focusing upon the running web a discrete beam 69 of coherent radiation which is furnished by a laser L. The making of holes entails the development of contaminants, and such contaminants are removed by air streams which are circulated through the perforating units not only to remove the contaminants but also to cool the optical systems of the respective perforating units. <IMAGE>

Description

1 GB 2 094 211 A 1

SPECIFICATION

Apparatus for perforating webs of wrapping material for tobacco or the like The present invention relates to apparatus for per forating webs, sheets, strips or bands of flexible material, such as paper, imitation cork, cardboard, a synthetic plastic substance orthe like. More particu larly, the invention relates to improvements in apparatus which can be utilized with advantage to form perforations in a running (continuous or inter rupted) web of cigarette paper or the like while the web is transported lengthwise in a cigarette making, filter tipping or other tobacco and/or filter material processing machine. Still more particularly, the invention relates to improvements in perforating apparatus wherein the means for forming perfora tions includes one or more devices for focusing one or more beams of coherent radiation onto the 85 running web of paper or the like.

It is already known to form perforations in a web of cigarette paper, imitation cork or similar flexible strip, band or sheet material which is used in the manufacture of rod-shaped smokers' products. The perforations are desirable, especially if the permea bility of the material of the web is not sufficiently high, in orderto ensure that, when a smoker draws a column of tobacco smoke into his or her lungs, the smoke is mixed with a certain quantity of cool atmospheric airwhich penetrates into the interior of the smokers' product by way of the perforations and contributes to interception and/or neutralization of certain amounts of nicotine, condensate and/or 36 other deleterious or presumably deleterious ingre dients of tobacco smoke. For example, many types of filter cigarettes are formed with annuli of perfora tions which are provided in a shorttube serving to connect the filter plug to the tobacco-containing portion of the cigarette. The tube is a converted uniting band which is obtained by severing a running web of cigarette paper, imitation cork or like strip-shaped material (called tipping paper) at regu lar intervals to form a succession of discrete uniting bands. Successive uniting bands are attached to and rolled around groups of coaxial filter plugs and cigarettes in a suitable filtertipping machine, such as the machines known as MAX or MAX S manufac tured and sold by the assignee of the present application.

If the perof rations are to be formed in the wrapper of a plain cigarette, they are normally provided close to that end of the cigarette which is inserted into the mouth during smoking.

It is also known to make perforations by resorting to an apparatus which is equipped with one or more lasers. Reference may be had to German Offenle gungsschrift No. 2,754,104. It has been found that coherent radiation which is emitted by a laser is especially suited to ensure the formation of perfora tions having a predicatable size and/or shape, as well as that a laser is capable of perforating a rapidly running web of cigarette paper or the like. Perforat ing apparatus which employ one or more lasers are further disclosed in commonly owned U.S. Pats.

Nos. 4,193,409 and 4,249,545, and in commonly owned U.S. -patent application Serial No. 834,648 filed September 19, 1977 by Heitmann et al.

A drawback of presently known perforating appar- atus is that they are likely to become contaminated, for example, by the material which is separated from the running web during making of the perforations therein. The contamination is likely to occur regardless of whether the apparatus employs one or more mechanical perforating devices, one or more electrical perforating devices (e.g., pairs of electrodes which define spark gaps through which the material of the running web is advanced) or one or more lasers or other sources of coherent radiation. Such contamination necessitates frequent interruptions in operation of the machine in which the perforating apparatus is installed. This is especially undesirable if the machine is a modern high-speed maker of cigarettes orfilter rods because such machines turn out inordinately large quantities of rod-shaped articles per unit of time (e.g., a modern cigarette maker can produce up to and in excess of 100 plain cigarettes per second) so that each and every interruption of operation of such a machine entails tremendous losses in output.

The invention resides in the provision of an apparatus for making holes (e.g., minute perforations) in a sheet-like materal, particularly in a running web of wrapping material for rod-shaped articles which constitute or form part of smokers' products. The apparatus comprises at least one perforating unit or head having means (e. g., including a collector lens) for making holes in the sheet-like material (the lens can be arranged to focus a beam of coherent radiation upon the sheet-like material) with attendant development of contaminants and the tendency of such contaminants to accumulate in the region of the unit (e.g., in the region of a nozzle having a radiation discharging outlet or orifice for a beam of coherent radiation which is focused upon the sheet-like material), and means for conveying at least one stream of gaseous fluid (e.g., air or nitrogen) past the aforementioned region so that the conveyed fluid entrains and removes contaminants from such region.

If the perforating apparatus is designed to form holes or perforations by resorting to one or more beams of coherent radiation, it further comprises at least one source of coherent radiation (preferably at least one laser).

The unit further comprises a substantially closed housing which may form a removable or integral part of a carrier capable of accommodating two or more perforating units which can be disposed in one or more rows extending in parall elism with a running web of wrapping material if the sheet-like material is a web, and such housing is then provided with a radiation admitting inlet (such inlet can be defined by a window which includes or accommo- dates the aforementioned focusing means for coherent radiation) and a radiation discharging outlet (e.g., the aforementioned orifice). The apparatus preferably further comprises a shroud which is interposed between the sheet-like material and the unit and has an aperture in register with the orifice 2 GB 2 094 211 A 2 so thatthe optical system can focus the beam upon the sheet-like material. The shroud can be formed with a slide surface along which the sheet-like material can be transported by suitable guide rolls of a machine in which the apparatus is put to use.

The housing is preferably formed with a chamber between the inlet and outlet means, and the housing and the shroud preferably define at least one compartment which communicates with the outlet means. The conveying means then comprises means for establishing a pressure differential be tween the compartment and the chamber so that a gaseous fluid which is admitted into the chamber can flow through the outlet means and into the compartment. The fluid not only removes contami nants from the region of the nozzle and aperture in the shroud but can also cool the optical system at the inlet means for admission of radiation into the housing. Still further, some of the admitted gaseous fluid can issue from the aperture of the shroud to form a layer or cushion of gaseous lubricant be tween the sheet-like material and the adjacent surface of the shroud.

The novel features which are considered as char acteristic of the invention are set forth in particular in the appended claims. The improved perforating apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best under stood upon perusal of the following detailed deSGrip tion of certain specific embodiments with reference to the accompanying drawing.

Figure 1 is a schematic front elevational view of a filter tipping machine including a perforating appar atus which embodies the present invention; Figure 2 is a greatly enlarged plan view of the perforating apparatus, substantially as seen in the direction of arrow 11 in Figure 1; Figure 3 is a transverse vertical sectional view as seen in the direction of arrows from the line 111-111 of 105 Figure 2; and Figure 4is a longitudinal vertical sectional view as seen in the direction of arrows from the line IV-IV of Figure 2.

Referring firstto Figure 1, there is shown a filter tipping machine of the type known as MAX S which is manufactured and sold bythe assignee of the present application. The construction of the filter tipping machine, which is directly coupled to a cigarette making machine (for example, a machine known as SE 80 manufactured and sold by the assignee of the present application) is as follows:

The frame F of the filter tipping machine supports a rotary drum-shaped conveyor 1 which can be said to form part of the aforementioned cigarette making machine and delivers two rows of plain cigarettes of unit length to a pair of staggered rotary drum shaped aligning conveyors 2. The plain cigarettes of one row of cigarettes in the axially parallel peripher al flutes of the row forming conveyor 1 are adjacent to one axial end, and the plain cigarettes of the other row are adjacent to the other axial end of this conveyor. Furthermore, the cigarettes of one row are transported by oddly numbered flutes whereas the cigarettes of the other row are transported by evenly numbered flutes of the conveyor 1. The two rows of cigarettes are transferred into the peripheral flutes of the corresponding aligning conveyors 2 which rotate in a counterclockwise direction, as viewed in Figure 1, and are driven at different speeds and/or transport the respective cigarettes through different distances so that, when a flute of the front aligning conveyor 2, as viewed in Figure 1, reaches a transfer station T1, it is an accurate axial alignment with a flute of the rear aligning conveyor 2. Such flutes deliver a pair of coaxial plain cigarettes of unit length into the adjacent flute of a rotary drum-shaped assembly conveyor 3 which is driven to rotate in a clockwise direction, as viewed in Figure 1 The top portion of the frame F supports a magazine 4 for a supply of parallel rod-shaped filter rod sections (not specifically shown) of six times unit length. The outlet opening 4a at the lower end of the magazine 4 receives a portion of a rotary drum- shaped severing conveyor 6 which is driven to rotate in a clockwise direction, as viewed in Figure 1, and has peripheral flutes extending an parallelism with its axis. Such flutes remove from the magazine 4 discrete filter rod sections of six times unit length and transport successive filter rod sections past two rotary disc-shaped knives 7 which rotate about parallel axes and are staggered with respect to each other, as considered in the axial direction of the severing conveyor 6. The conveyor 6 cooperates with the knives 7 to convert successive filter rod sections of six times unit length into sets of three coaxial filter plugs of double unit length, and the filter plugs of successive sets are transferred onto a rotary staggering conveyor 8. The conveyor 8 is assembled of three discs which may but need not rotate about a common axis and are driven at different speeds and/or transport the respective filter plugs through different distances so that the filter plugs of each set are staggered with respect to each other, as considered in the circumferential direction of the conveyor 8, prior to transfer of successive filter plugs of double unit length into successive peripheral flutes of a rotary drum-shaped shuffling conveyor 9. The conveyor 9 is driven to rotate in a clockwise direction, as viewed in Figure 1, and cooperates with two stationary cams 9a (only one shown) to convert the single row of axially staggered filter plugs into a row wherein each preceding filter plug is in accurate alignment with the next-following plug prior to transfer of successive plugs of the thus obtained row into successive flutes of a combined accelerating and inserting conveyor 11. The conveyor 11 is a rotary drum whose flutes deliverfilter plugs of double unit length into successive flutes of the assembly conveyor 3 at a second transfer station T2 which is located upstream of the transfer station T1. The pairs of plain cigarettes of unit length which are delivered into the flutes of the assembly conveyor 3 at the transfer station T, are spaced apart from each other by a distance which at least equals the axial length of a filter plug of double unit length, and the inserting conveyor 11 delivers filter plugs into successive flutes atthe station T2 in such positions that, upon arrival at the transfer station TI, the filter plugs are located in the gaps between the 3 GB 2 094 211 A 3 corresponding plain cigarettes of unit length. The assembly conveyor 3 advances the thus obtained groups of three coaxial rod-shaped articles each through the space between two suitably configu- rated condensing cams 3a (only one shown) which cause the plain cigarettes to move axially toward each other and into abutment with the respective end faces of the corresponding filter plug of double unit length.

The assembly conveyor 3 delivers the successive condensed groups (each such group contains two coaxial plain cigarettes of unit length and a filter plug of double unit length therebetween) into successive flutes of a rotary drum-shaped transfer conveyor 12.

This conveyor further receives adhesive-coated unit ing bands from a rotary drum-shaped suction con veyor 19 which cooperates with the blades 21a of a rotary cutter 21.

The uniting bands are obtained in response to severing of the leader of a continuous web 13 of cigarette paper, imitation cork or another suitable flexible strip-shaped wrapping material (also called tipping paper). Such material is drawn off a reel 14 which is mounted on a spindle 114 and is caused to travel around a plurality of guide rolls 15 prior to reaching a so-called curling device 17 of the type disclosed in commonly owned U.S. Pat. No.

3,962,957 granted June 15,1976 to Alfred Hinzmann.

After advancing beyond the curling device 17, successive increments of the web 13 enter the nip of two advancing rolls 16 at least one of which is driven to advance the web in a direction toward a guide roll 73. The leader of the web 13 adheres to the foraminous peripheral surface of the suction con veyor 19 and is caused to advance past successive 100 blades 21 a of the rotating cutter 21. The latter cooperates with the conveyor 19 to convert the web 13 into a series of discrete web portions or uniting bands of predetermined length, The conveyor 19 draws the web 13 from the guide roll 73 and transports the web past a perforating apparatus 37 which is constructed and assembled in accordance with the present invention. A second guide roll 73a is located immediately or closely upstream of the roller-shaped applicator 18a of a paster 18 which costs one side of the web 13 with a suitable adhesive. The applicator 18a receives adhesive from a source of supply here shown as a tank 18b by way of a withdrawing roll 18c and coats a portion of or the entire underside of the travelling web 13. 115 The conveyor 19 applies successive discrete unit ing bands to successive groups of coaxial rod shaped articles in the oncoming flutes of the transfer conveyor 12. The uniting bands are preferably applied in such a way that they are disposed 120 substantially tangentially of the respective groups and adhere to the corresponding filter plugs as well as to the innermost portions of the respective plain cigarettes of unit length. Such groups, each of which carries an adhesive-coated uniting band, are there upon transferred onto the peripheral surface of a rotary drum-shaped wrapping conveyor 22 which cooperates with an adjustable (stationary or mobile) rolling device 23 to convolute the oncoming uniting bands around the respective groups so that each group constitutes a filter cigarette of double unit length.

The wrapping conveyor 22 delivers successive filter cigarettes of double unit length into successive flutes of a rotary drum-shaped drying conveyor 24 which can embody or is associated with suitable testing means for detection of filter cigarettes having defective wrappers. At least those filter cigarettes of double unit length whose wrappers are satisfactory are thereupon delivered into successive flutes of a rotary drum-shaped severing conveyor 26 which cooperates with a rotary disk-shaped knife 26a to sever each filter cigarette of double unit length midway across its filter plug so that each such cigarette yields two coaxial filter cigarettes of unit length. Each filter cigarette of unit length contains a plain cigarette of unit length, a filter plug of unit length, and one-half of a convoluted tubular uniting band which binds the filter plug to the respective plain cigarette.

The severing conveyor 26 delivers successive pairs of filter cigarettes of unit length into successive flutes of a rotary drum-shaped conveyor 27 of a turn-around device 29 of the type disclosed in commonly owned U.S. Pat. No. 3,583,546 granted to Gerhard Koop. The turn- around device 29 further comprises a second rotary drum-shaped fluted conveyor 27a which receives one filter cigarette of each pair from the conveyor 27, a third rotary drum- shaped fluted conveyor 28 which receives the other filter cigarette of each pair from the conveyor 27, a fourth rotary drum-shaped fluted conveyor 28a, and a set of orbiting arms 29a which receive motion from a driving unit 29b.

The operation of the turn-around device 29 is as follows: The conveyor 27 receives pairs of coaxial filter cigarettes of unit length from successive flutes of the severing conveyor 26. One filter cigarette of each pair is delivered into the oncoming flute of the conveyor 28, whereas the other filter cigarette of each pair enters the oncoming flute of the conveyor 27a. Successive flutes of the conveyor 27a deliver the respective filter cigarettes of unit length to oncoming arms 29a which turn each filter cigarette end-for-end and deliver the inverted cigarettes into successive flutes of the conveyor 28a. The conveyor 28a delivers the inverted filter cigarettes of unit length into alternate flutes of the conveyor 28. It is to be noted that the conveyor 27 delivers successive non-inverted filter cigarettes of unit length into alternate flutes of the conveyor 28 so that the latter provides room for acceptance of inverted cigarettes from the conveyor 28a. The arrangement is preferably such that the conveyor 28a delivers inverted filter cigarettes of unit length into the spaces between successive pairs of non-inverted cigarettes on the conveyor 28. Thus, the conveyor 28 transports a single file of aligned filter cigarettes of unit length in a clockwise direction, as viewed in Figure 1, and the filter plugs of all filter cigarettes on the conveyor 28 face in the same direction. Successive flutes of the conveyor 28 deliver successive filter cigarettes of unit length to a testing conveyor 31, for example, a conveyor of the type disclosed in commonly owned U.S. Pat. No. 3,962,906 granted June 15,1976to Uwe 4 GB 2 094 211 A 4 Heitmann et aL The cigarettes which are defective are segregated from satisfactory cigarettes on a rotary drum-shaped conveyor 32 which follows the testing conveyor 31 and may cooperate with an additional testing device which monitors the tobacco-containing ends of successive cigarettes. The cigarettes which are found to be defective by the testing unit including the conveyor 31 and/or by the testing unit including the conveyor 32 are segre- gated during travel past an ejecting device (not shown) of any known design, and the remaining (satisfactory) cigarettes of unit length are delivered onto the upper reach of an endless belt conveyor 36. The upper reach of the conveyor 36 cooperates with a braking roll 33 and this conveyor is trained over pulleys 34 of which only one is shown in Figure 1. The upper reach of the conveyor 36 delivers satisfactory filter cigarettes of unit length into storage, directly to a packing machine, or into a reservoir system (e.g., a system of the type which is known as Resy and is manufactured and sold by the assignee of the present application).

The operation of the wrapping conveyor 22 and rolling device 23 will be understood upon perusal of the disclosure in commonly owned U.S. Pat. No. 3,483,873 or No. 3,527,234, both granted to Alfred Hinzmann.

The frame F further supports a spindle 114a for a fresh reel 14a of wrapping material 13a the leader of which is held at a splicing station SPL. When the supply of running web 13 on the reel 14 is nearly exhausted, a splicing device (not specifically shown) at the station SPL is actuated to attach the leader of the web 13a to the trailing portion of the web 13. A splicing device which can be used in the filter tipping 100 machine of Figure 1 is disclosed, for example, in commonly owned U.S. Pat. No. 3,730, 811 granted May 1, 1973 to Hans-Joachim Wendt. The disclosures of all of the aforementioned commonly owned patents are incorporated herein by reference.

The driven parts of the filter tipping machine receive motion from a main prime mover M, e.g., a variable speed electric motor which can rotate the advancing rolls 16 and the suction conveyor 19 (i.e., the means for transporting the web 13 along an elongated path extending from the reel 14 to the transfer conveyor 12, namely, to the path for the groups of rod-shaped articles) at a plurality of different speeds.

The perforating apparatus 37 which is illustrated in detail in Figures 2, 3 and 4 comprises a main support or carrier 38 which is secured to the frame F of the filter tipping machine at a level below the paster 18. The support 38 carries six discrete perforating units or heads 39a, 39b, 39c and 41 a, 41 b, 41 c which are disposed in two rows extending in parallelism with the direction of travel of the web 13 toward the applicator 18a of the paster 18. The perforating units 39a, 39b, 39c which form one of the rows are staggered with reference to the perforating units 41 a, 41 b, 41 Gwhich form the other row, as considered in the longitudinal direction of the web 13.

The construction of each of the six perforating units 39a-39c and 41 a-41 c is the same. Figure 3 shows the details of the perforating unit 41 a which comprises a housing or casing 42. In the illustrated embodiment, the housing 42 constitutes an integral part of the carrier 38; however, it is equally within the purview of the invention to provide a discrete housing (e.g., a sleeve or cylinder) which is inserted into a bore or socket of the carrier 38. In other words, each of the six perforating units can be fully assembled independently of the carrier 38 prior to insertion into the carrier in an optimum orientation with reference to the path of movement of the web 13 along the perforating apparatus 37. The carrier 38 (and more particularly that portion of the carrier 38 which defines or constitutes the housing 42 of the perforating unit 41 a) has a bore or socket 42a for component parts of the perforating unit 41 a. Such parts include an annular frame or mount 45 for an optical element 46 which is a collector lens serving to make holes by focusing a laser beam 69b upon a selected portion of the running web 13. The mount 45 and the lens 46 can be said to constitute a window or inlet 43 which admits the laser beam 69b into a chamber 51 located downstream of the lens 46, as considered in the direction of propagation of the beam 69b toward the path of the web 13. The perforating unit 41 a further includes a ring-shaped nozzle 47 which is inserted into the discharge end of the bore or socket 42a and defines a centrally located outlet opening or orifice 44 forthe laser beam 69b. The aforementioned chamber 51 is located between the mount 45 and the nozzle 47 and communicates with a channel or port 52 for admission of compressed gas, e.g., air, from a suitable source 52A. Such source is preferably common to all six perforating units and may constitute a blower or fan which is normally provided in the filter tipping machine to supply compressed air to various component parts for example, to the ports of rotary drum-shaped conveyors wherein compressed gas expels fragments of tobacco andlor other contaminants.

The perforating apparatus 37 further comprises a plate-like arcuate cover or shroud 48 which is disposed between the orifices 44 of nozzles 47 of the six perforating units 39a-39c, 41 a-41 c and the path of the web 13. The concave side of the shroud 48 faces the nozzles 47 and is spaced apart from the respective orifices 44, and the convex side of the shroud 48 serves as a guide for and can be contacted by one side of the web 13 which advances from the curling device 17 toward the paster 18 of the filter tipping machine. The convex external surface of the shroud 48 is smooth so that it offers little or negligible resistance to travel of the web 13 therealong. Figure 3 shows one of the six apertures 49 which are provided in the shroud 48 to allow the respective laser beam 69b to penetrate through the shroud and to impinge upon the material of the running web 13 at intervals determined by means which controls pulsing of the laser L.

That portion of the web 13 which advances along the convex side of the shroud 48 is trained over the aforementioned guide rolls 73 and 73a which are sufficiently close to the respective ends of the shroud 48 (as considered in the longitudinal direction of the web 13) to ensure that the web portion between the guide rolls 73 and 73a hugs the convex GB 2 094 211 A 5 surface of the shroud. This ensures thatthe web portion between the guide rolls 73,73a is invariably maintained at a predetermined distance from the optical elements 46 of the six perforating units 39a-39c and 41a-41c, namely, atthe foci of such optical elements. The guide rolls 73,73a can be said to constitute or to form part of means (forming part of the filtertipping machine of Figure 1) for trans porting the web 13 pastthe perforating units 39a-39c and41a-41c.

Figure 4 shows that the dimensions of the three perforating units 41 a, 41 b, 41 c shown therein are identical. The same preferably holds true for the other three perforating units (39a-39c). In view of such identity of all six perforating units, the centrally located perforating units 39b and 41 b are located at a level somewhat above the levels of the respective perforating units 39a, 39c and 41 a, 41 c in the same rows. This ensures that each of the six laser beams 69b is properly focused upon the web portion between the guide rolls 73 and 73a. It goes without saying that all of the six optical elements 46 can be located in a common plane if the optical elements of the median perforating units 39b and 41 b are dimensioned and configured so as to focus the 90 corresponding laser beams 69b upon the respective portions of the web 13 running from the guide roll 73 toward the guide roll 73a. In the illustrated embodi ment, the six optical elements 46 can be said to be located in an arcuate plane whose radius of curva ture is the same as that of the plane including the convex outer side of the shroud 48.

In the illustrated embodiment of the perforating apparatus 37, the carrier 38 is formed with two elongated parallel channels or tunnels 68 and 68a which extend in parallelism with the longitudinal direction of the web 13 between the guide roils 73, 73a and are located at a level below the sockets or bores 42a for the component parts of the perforating units 39a-39c and 41a-41c. The tunnel 68 communi cates with the lower end portions of sockets 42a for the perforating units 39a-39c, and the tunnel 68a communicates with the lower end portions of sock ets 42a for the perforating units 41 a-41 c. The left hand end portions of the tunnels 68, 68a communi cate with a third tunnel 67 which is also machined into or otherwise formed in the carrier 38 and serves to admit a first or main laser beam 69 issuing from the laser L. The direction in which the undivided beam 69 enters the channel 67 is indicated by the a rrow 74 (see Fi g u re 2).

The tunnels or channels 67 and 68, 68a contain means for splitting thebeam 69 into six beams 69b, one for each of the six perforating units 39a-39c and 41 a-41 c. The beam splitting means includes two mirrors or reflectors 71 and 71a in the tunnel 67 and three mirrors or reflectors 72, 72a, 72b in each of the channels or tunnels 68, 68a. The mirror 71 reflects one-half of the beam 69 into the channel or tunnel 68 and transmits the other half of the beam 69 so that such other half impinges upon the totally reflecting mirror 71a and is reflected into the tunnel 68a. The first mirror 72 in the channel ortunnel 68 reflects one-third of the corresponding beam 69a into the socket 42a for the perforating unit 39a and allows two-thirds of the corresponding beam 69a to reach the second mirror 72a which reflects one-half of the impinging beam and permits the other half to impinge upon the mirror 72b. The mirrors 72a and 72b in the channel or tunnel 68 thereby reflect two beams 68b into the sockets 42a of the respective perforating units 39b and 39c. Analogously, the beam 69a which is totally reflected by the mirror 71 a is reflected in part by the mirror 72 in the tunnel 68a, in part by the next-following mirror 72a in the tunnel 68a, and the remainder of such beam 69a is totally reflected by the mirror 72b in the tunnel 68a so that each of the perforating units 41 a to 41 c receives a beam 69b whose intensity is preferably the same as that of the beams 69b issuing from the orifices 44 of nozzles 47 forming part of the perforating units 39a-39c.

It will be recalled that the focal points of all six optical elements 46 are located in the plane of the web portion between the guide rolls 73 and 73a. This ensures that the perforating action of all six beams 69b is the same or at least closely approximates a preselected perforating action.

As already mentioned above, the shroud 48 is spaced apartfrom the orifices 44 of the six nozzles 47. This ensures that compressed air or another gas which is admitted into the chambers 51 can issue from the corresponding perforating units 39a-39c and 41 a-41 c to enter one of two elongated rectangu- lar compartments 54 and 56 between the upper side of the carrier 38 and the concave inner side of the shroud 48. The compartment 54 communicates with the orifices 44 of nozzles 47 in the perforating units 39a-39c (see Figure 2), and the compartment 56 communicates with the orifices 44 of the nozzles 47 forming part of the other row of perforating units 41 a-41 c. Figure 2 further shows that the front, rear and lateral portions of the shroud 48 are secured to or at least sealingly contact the convex upper side of the carrier 38 so that the compartments 54 and 56 are at least substantially sealed from the surrounding atmosphere. The compartments 54 and 56 respectively communicate with pairs of suction ports 57 and 61 which are machined into or otherwise formed in the carrier 38. The discharge ends of the ports 57 and 61 respectively communicate with pairs of suction channels 58 and 62 of the carrier 38, and the discharge ends of the channels 58 and 62 respectively communicate with nipples 59 and 63 which are provided at the opposite lateral sides of the carrier 38 and are connected to a preferably common suction generating device (e.g., to the suction side of the blower or fan 52A which supplies compressed air to the channels or ports 52 discharg- ing into the chambers 51 of the six perforating units). The connection between the ports 52 and the pressure side of the fan 52A comprises channels 64 and 66. The channel 64 communicates with the ports 52 for the chambers 51 of the perforating units 39a-39c, and the channel 66 communicates with the ports 52 for the chambers 51 of the perforating units 41 a-41 c. The reference characters 53 and 53' denote in Figure 2 two nipples which are respectively connected with the inlet ends of the channels 66 and 64 in the carrier38. Thefan 52Acan be said toform 6 GB 2094211 A 6 part of or to constitute a means for conveying gaseous fluid past those regions (of nozzles 47 and apertures 49) where the contaminants tend to accumulate when the apparatus 37 is in use.

The two compartments 54 and 56 can be replaced with a single compartment and one of the nipples 59, 63 can be omitted. It is further possible to provide a discrete compartment for each of the six perforating units, to provide a common compartment for each pair of perforating units, or to provide a larger compartment forfour or five perforating units and a smaller compartment for the remaining perforating units orunit.The same holdstrueforthe ports 52 which supply compressed gaseous fluid to the chambers 51 of the six perforating units, i.e., it is possible to connect all of these ports to a single nipple 53 or 53', to provide a discrete nipple for each of the six ports 52, and so forth.

It is further within the purview of the invention to employ a partially or greatly simiplified carrier for the perforating units. For example, instead of utilizing a carrier which is formed with a large number of channels, ports, tunnels, chambers, compartments, etc., it is possible to employ a much simpler carrier which is connected with a large number of flexible and/or rigid conduits in the form of pipes or tubes serving to convey the beams 69, 69a, 69b, to supply streams of compressed air to the chambers 51, and/or to withdraw air from the compartments 54,56 or directly from the regions at the outer ends of the six orifices 44. The illustrated carrier 38 is preferred at this time because, even though its design is somewhat complex, it contributes significantly to compactness of the improved perforating apparatus 37 so that the latter can be readily installed in existing filter tipping machine (or at least in many types of presently utilized filter tipping machines) wherein (as a rule) the space is at a premium. It is further clear that the perforating apparatus 37 need not be installed between the curling device 17 and the paster 18 but can be installed at any one of a number of other locations in or on the frame F of the filter tipping machine shown in Figure 1 or an analogous filter tipping machine.

The operation of the perforating apparatus 37 is as 110 follows:

When the filter tipping machine of Figure 1 is in use, the web 13 advances along an elongated path from the reel 14 toward the suction conveyor 19 and overlies the convex surface of the shroud 48 between the guide rolls 73 and 73a. As explained above, the lowermost portions of the guide rolls 73 and 73a are sufficiently close to the levels of the adjacent portions of the convex surface of the shroud 48 to ensure that the web 13 hugs those portions of the shroud which are formed with the apertures 49 for the respective beams 69b of coherent radiation. The laser L is preferably a C02 laser which can be installed at the rear side of the frame F (namely, at that side which faces away from the observer of Figure 1). This laser emits the undivided beam 69 which propagates itself in the direction of the arrow 74 and enters the channel ortunnel 67 of the carrier 38 to be thereupon split into two beams 69a by the mirrors 71, 71 a and thereupon into the beams 69b by the corresponding mirrors 72, 72a and 72b. The mirrors 72, 72a and 72b in the tunnels 68, 68a direct the corresponding beams 69b into the respective sockets or bores 42a so that the beams 69b are focused by the optical elements 46, penetrate across the chambers 51, through the orifices 44 of the nozzles 47 and through the corresponding apertures 49 of the shroud 48 to impinge upon the running web 13 at a frequency which is selected by the frequency of the pulse generator for the laser L. Such frequency, plus the speed of the web 13 in a direction from the guide roll 73 toward the guide roll 73a, determines the number of holes or perforations P in the web 13, i.e., the distances between the neighboring perforations P. Figure 2 shows that the perforating units 39a- 39c and 41 a-41 c of the two rows are slightly staggered with reference to each other, as considered at right angles to the direction (arrow D) of advancement of the web 13, so that the six beams 69b form two groups 75 and 75a of three parallel files of perforations P each. When a filter plug of double unit length is severed by the rotary disc-shaped knife 26a of the filter tipping machine shown in Figure 1, the severing plane is located between the groups 75 and 75a so that the tubular wrapper (convoluted half of the uniting band) of each of the resulting filter plugs of unit length is formed with three annuli of peroforations P.

The pressure side of the fan 52A supplies com- pressed air to the nipples 53 and 53'which, in turn, admit streams of compressed air into the respective channels 66 and 64 for admission into the associated ports 52 which lead to the respective chambers 51. Instead of air, the fan 52A can circulate another neutral gas, e.g., a protective gas of the type normally employed in connection with laser beams or nitrogen which reduces the likelihood of combustion of web 13 under the action of beams 69b when the web consists of or contains readily combustible material. The compressed gas which enters a chamber 51 issues from such chamber by way of the orifice 44 of the associated nozzle 47 to enter the corresponding compartment 54 or 56 between the carrier 38 and the shroud 48. The streams of compressed gas which flow continuously from the chambers 51 into the corresponding compartments 54 and 56 uninterruptedly clean the nozzles 47 by entraining impurities which are likely to accumulate in the orifices 44 and tend to clog the corresponding nozzles 47 and/or apertures 49 of the shroud 48. The gaseous fluid which accumulates in the compartments 54,56 is evacuated by way of the corresponding suction ports 57, 61, suction channels 58, 62 and nipples 59,63 and can be caused to pass through one or more filters or other intercepting means prior to reaching the suction side of the fan 52A. The filter or filters between the outlets of the nipples 59, 63 and the suction side of the fan 52A ensure that the impurities which are withdrawn from the compart- ments 54,56 cannot be admitted into the chambers 51. It is clear that the filters are not absolutely necessary if the fan 52A merely serves to evacuate contaminated (impurities-containing) gases from the compartments 54,56 and the apparatus 37 or the filtertipping machine comprises a separate source A- i 7 GB 2 094 211 A 7 of compressed gas which delivers compressed gaseous fluid to the nipples 53 and 53'.

It has been found that the improved perforating apparatus 37 (and more specifically the means for circulating a stream of compressed gaseous fluid along a portion of the path for each of the six beams 69b) reliably prevents malfunctioning by removing any and all impurities which would normally tend to accumulate in the nozzles 47 and/or in the apertures 49 to thereby interfere with the formation of perfora tions P having an optimum size and/or shape. In addition, the streams of relatively cool gaseous fluid which are admitted into the chambers 51 and flow from these chambers, through the respective orifices 44 and into the associated compartments 54, 56 exchange heat with the optical elements 46 and other components of the performing units 39a-39c and 41 a-41 c. Still further, a portion of each of the just discussed streams of relatively cool gaseous fluid penetrates through the corresponding aperture 49 of the shroud 48 to flow along the convex side of the shroud and form a thin cushion of gaseous fluid which reduces the extent of frictional contact be tween the underside of the web 13 and the shroud. It goes without saying that the pressure of compress ed air in the chambers 51, the diameters of the orifices 44 and the diameters of the apertures 49 are selected with a viewto ensure that the gaseous fluid which is free to penetrate between the web 13 and the convex side of the shroud 48 does not lift the web 13 well off and above the shroud so that the web portion between the guide rolls 73 and 73a remains in the focal planes of the optical elements 46. In fact, the quantity of compressed gaseous fluid which issues via apertures 49 can be readily selected 100 with a view to actually ensure that the web portion between the rolls 73 and 73a is located at an optimum distance from all six optical elements 46.

Proper guidance of the web portion between the guide rolls 73 and 73a is advisable and advan tageous for the aforediscussed reasons, i.e., primari ly to ensure the formation of perforations P having an optimum size and shape so thatthe permeability of the perforated web can be calculated in advance with a high degree of reliability and reproducibility.

As pointed out hereinabove, the improved perfor ating apparatus can be used with advantage in or on a filter tipping machine. However, it is clear that such apparatus can be used with equal or nearly equal advantage in other types of machines which process 115 or manufacture smokers' products. For example, it is possible to utilize the apparatus 17 in a cigarette rod making machine wherein the apparatus forms one or more rows or files of perforations in a continuous web of cigarette paper, i.e., in the material which is used to confine a continuous tobacco filler before the resulting cigarette rod is severed to yield a succession of discrete plain cigarettes of unit length or multiple unit length. Furthermore, the improved perforating apparatus or an analogous apparatus can be used with equal advantage to form perfora tions in webs of material which is not utilized in connection with the making and/or processing of smokers' products. Such material may be paper, cardboard, cellophane, a web or foil of synthetic plastic material or a combination of such or bodies (e.g., a laminate consisting of two or more layers). Also, the number of perforating units can be reduced to one, two, three, four or five, or increased to seven or more without departing from the spirit of the invention.

Furthermore, the apparatus can be equipped with different means for causing currents of air or another gas to flow from the chambers 51 into the compart- ments 54, 56 and from such compartments to the atmosphere or for recirculation into the chambers 51. Thus, whereas the illustrated apparatus utilizes means for supplying air at superatmospheric pressure into the chambers 51 and for maintaining in the compartments 54,56 a pressure which is below atmospheric pressure, it is also possible to simply connect the compartments 54, 56 to a suction generating device and to connect the bores or ports 52 with the atmosphere. Also, it is possible to connect the bores 52 with a source of compressed air and to provide outlets for escape of air from the compartments 54,56 into the surrounding atmosphere. All that counts is to ensure that the pressure differential between the interior of each chamber 51 and the interior of the corresponding or associated compartment 54 to 55 suff ices to ensure that currents of air will flow in directions to entrain contaminants from the region of apertures 49 and to thus ensure long-lasting uninterrupted satisfactory oper- ation of the performing apparatus. The solution which is shown in the drawing has been found to be especially satisfactory because it increases the likelihood of removal of any and all contaminants which, in the absence of pronounced currents of air.. would deposit on the shroud 48 and/or in the nozzles 47 and/or in the ports leading to the chambers 51 and/or from the compartments 54 and 56. Moreover, the currents of air keep the contaminants away from the optical elements 46 and ensure adequate cooling of the perforating units. Guidance of currents of air through the carrier 38 as well as the provision of channels 67 and 68 for the radiation beams in the carrier 38 contributes to compactness of the improved apparatus but, and as already mentioned above, the apparatus can be readily designed to reduce the number of ports, channels and other cavities in the carrier 38 by resorting to conduits which supply air to the chambers, which withdraw air from the compartments, and which convey the beams of coherent radiation close to or directly into the optical elements of the-perforating units.

The illustrated carrier 38 is preferred atthis time on the additional ground that it enhances the safety of the perforating apparatus 37 because the laser beams 69,69a and 69b are not exposed and cannot cause injury to attendants. The path for the beam 69 is closed all the way from the laser Lto the channel ortunnel 67 so that the beams 69, 69a and 69b are fully confined at all times.

Claims

1. Apparatus for making holes in a sheet-like material, particularly in a running web of wrapping material for rod-shaped articles which constitute or 8 GB 2 094 211 A 8 form part of smokers' products, comprising at least one perforating unit having means for making holes in the sheet-like material with attendant develop ment of contaminants and the tendency of such contaminants to accumulate in the region of said unit; and means for conveying at least one stream of gaseous fluid past said region so that the conveyed fluid entrains and removes contaminants from such region.

2. The apparatus of claim 1, further comprising at least one source of coherent radiation arranged to furnish at least one beam of coherent radiation, said means for making holes comprising means for focusing the beam upon the sheet-like material.

3. The apparatus of claim 2, wherein said unit further comprises a housing for said means for making holes, said housing having radiation admit ting inlet means and radiation discharging outlet means, and further comprising a shroud interposed between said unit and the sheet-like material and having an aperture in register with said outlet means.

4. The apparatus of claim 3, wherein said hous ing has a chamber communicating with said outlet means, said housing and said shroud defining at least one compartment communicating with said outlet means said conveying means including means for circulating at least one stream of gaseous fluid from said chamber into said compartment by way of said outlet means.

5. The apparatus of claim 4, wherein said hous ing is a closed housing and is further provided with means for admitting gaseous fluid to said chamber, and further comprising means for permitting eva cuation of gaseous fluid from said compartment.

6. The apparatus of claim 5, wherein said shroud is spaced apart from said outlet means.

7. The apparatus of claim 6, further comprising carrier means for said housing and said shroud.

8. The apparatus of claim 5, wherein said circu lating means includes means for establishing a pressure differential between said fluid admitting means and said evacuation permitting means.

9. The apparatus of claim 1, further comprising a carrier and at least one additional perforating unit, said units having housings in said carrier.

10. The apparatus of claim 9, further comprising at least one source of coherent radiation, said means for making holes including means for focusing - coherent radiation furnished by said source upon the sheet-like material and each of said housings having radiation admitting inlet means, radiation discharg ing outlet means and a chamber communicating with the respective outlet means, and further com prising a shroud disposed between said units and the sheet-like material and having apertures in register with said outlet means, said shroud and said housings defining at least one compartment com municating with said outlet means and said con veying means including means for circulating gaseous fluid from the chambers of said housings into said compartment by way of the respective outlet means.

11. The apparatus of claim 10, wherein said radiation source includes a laser arranged to emit a 130 beam of coherent radiation and further comprising means for splitting said beam into discrete beams, one for each of said units and for directing the discrete beams into the radiation admitting inlet means of the respective housings.

12. The apparatus of claim 11, wherein said housings have means for admitting gaseous fluid into the respective chambers and said carrier has at least one port for evacuation of fluid from said compartment, said circulating means including means for establishing a pressure differential between the fluid admitting means of said housings and said port so that streams of gaseous fluid flow from said fluid admitting means, through the respec- tive chambers and outlet means, and into and from said compartment.

13. The apparatus of claim 1, wherein said sheet-like material is a continuous web and further comprising means fortransporting the web lengthwise along a predetermined path, carrier means adjacent to one side of said path and a plurality of additional perforating units, said units being installed in said carrier means and forming at least one row extending in substantial parallelism with the longitudinal direction of the web in said path.

14. The apparatus of claim 13, wherein said units form a plurality of rows and wherein the units of each of said rows are staggered with reference to each other, as considered transversely of said path.

15. The apparatus of claim 14, further comprising a source of coherent radiation arranged to emit at least one beam of coherent radiation, means for splitting said beam into a plurality of discrete beams, one for each of said units, and for directing the discrete beams to the respective units, each of said units having a housing provided with radiation admitting inlet means, radiation discharging outlet means and a chamber communicating with the respective outlet means, and further comprising a shroud interposed between said units and said path and having apertures in register with said radiation emitting outlet means so that the discrete beams can be focused upon the web in said path, said shroud and said carrier means defining a plurality of compartments, one for each of said rows and each communicating with the outlet means of the housings in the respective row, said conveying means including means for establishing a pressure differential between each of said compartments and the chambers of the units in the respective row so that streams of gaseous f luid f low from said chambers, through the respective outlet means and into the corresponding compartments.

16. The apparatus of claim 15, wherein the number of said rows equals two and each of said rows comprises three units.

17. The apparatus of claim 15, wherein said carrier means has first port means for admission of gaseous fluid to said chambers and gas evacuating second port means communicating with said compartments.

18. The apparatus of claim 17, further comprising a plurality of gas admitting channels provided in said carrier means, one for each of said rows and each arranged to admit gaseous f luid to the respec- z 9 GB 2 094 211 A 9 tive first port means.

19. The apparatus of claim 1, further comprising a housing for said unit and a shroud interposed between the sheet-like material and said housing, said housing having a chamber and an outlet communicating with said chamber, said housing and said shroud defining at least one compartment communicating with said outlet and said conveying means comprising means for admitting a gaseous fluid at a first pressure into said chamber and means for maintaining the interior of said compartment at a second pressure below said first pressure so that the fluid which is admitted into said chamber flows into said compartment by way of said outlet.

20. The apparatus of claim 19, wherein said first pressure exceeds and said second pressure is less than atmospheric pressure.

21. Apparatus according to claim 19 or20,further comprising a source of coherent radiation arranged to emit at least one beam of coherent radiation, means for splitting said beam into a plurality of discrete beams, one for each of said units, and for directing the discrete beams to the respective units, each of said units having a housing provided with radiation admitting inlet means, radiation discharging outlet means and a chamber com- municating with the respective outlet means, and further comprising a shroud interposed between said units and said path and having apertures in register with said radiation emitting outlet means so that the discrete beams can be focused upon the web in said path, said shroud and said carrier means defining a plurality of compartments, one for each of said rows and each communicating with the outlet means of the housings in the respective row, said conveying means including means for establishing a pressure differential between each of said compartments and the chambers of the units in the respective row so that streams of gaseous fluid flow from said chambers, through the respective outlet means and into the corresponding compartments.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1982. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

21. The apparatus of claim 1, further comprising at least one source of coherent radiation, a carrier and a plurality of additional perforating units, said units being installed in said carrier and said means for making holes including means for focusing discrete beams of coherent radiation upon the sheet-like material, said source being arranged to emit at least one beam of coherent radiation and said carrier having channel means with inlet means for said one beam and means provided in said channel means for splitting said one beam into discrete beams, one for each of said units, and for directing the respective discrete beams against the corresponding focusing means.

22. The apparatus of claim 21, wherein said units form a plurality of rows and said channel means includes a first channel arranged to receive said one beam from said source and a plurality of additional channels, one for each of said rows and each communicating with said first channel, said beam splitting means including first reflector means provided in said first channel to split said one beam into a plurality of second beams and to direct each second beam into a discrete second channel, and second reflector means provided in said second channels, one for each unit of the respective row and each arranged to split the respective second beam into discrete beams and to direct the thus obtained discrete beams against the respective focusing means.

23. The apparatus of claim 21, wherein said beam splitting means comprises at least one partial- ly reflecting and at least one totally reflecting 115 reflector.

24. The apparatus of claim 1, wherein said sheet-like material is an elongated web and further comprising means for transporting the web along a predetermined path and a shroud interposed be tween said path and said unit, said shroud having a slide surface defining a portion of said path.

25. The apparatus of claim 24, wherein said slide surface is of arcuate shape.

26. The apparatus of claim 25, wherein said 125 arcuate surface is a convex surface and said trans porting means includes means for maintaining the web in contact with said convex surface.

27. The apparatus of claim 1, further comprising a source of coherent radiation, said unit comprising a housing having a radiation admitting inlet and a radiation discharging outlet, said means for making holes comprising an optical system disposed in said housing between said inlet and said outlet and arranged to focus coherent radiation entering via said inlet upon the sheet-like material by way of said outlet.

28. The apparatus of claim 27, wherein said optical system comprises a collector lens having a focus located in the plane of the sheet-like material.

29. The apparatus of claim 28, wherein the sheet-like material is a continuous web and further comprising means for transporting the web past said unit so that successive increments of the running web are located in said plane.

30. The apparatus of claim 1, further comprising a source of coherent radiation, a carrier for said unit and means for directing coherent radiation from said source to said carrier, said carrier having a socket for said unit and said unit having a radiation admitting inlet defined by a window including optical means for focusing radiation upon the sheet-like material and said unit further having a nozzle defining a radiation discharging outlet interposed between said optical means and the sheet-like material, said optical means constituting said hole making means.

31. The apparatus of claim 30, wherein said unit has a chamber intermediate said optical means and said nozzle, said conveying means including means for admitting gaseousfluid into said chamber and said chamber communicating with said outlet, said nozzle being disposed in said region.

32. The apparatus of claim 31, wherein said fluid admitting means includes channel means provided in said carrier.

33. The apparatus of claim 1, wherein said means for making holes includes means for focusing a beam of coherent radiation upon the sheet- like material and further comprising a source of coherent radiation, said source including a laser.

34. The apparatus of claim 1, wherein the sheetlike material is a web of wrapping material for use in a machine for the processing of commodities which constitute or form part of smokers' products, and further comprising means for transporting the web past said unit, said transporting means forming part of the processing machine.

35. Apparatus for making holes in a sheet-like material, substantially as herein described with reference to and as illustrated in the accompanying drawings.

AMENDED CLAIMS CLAIMS 1. Apparatus for making holes in a sheet-like material, particularly in a running web of wrapping material for rod-shaped articles which constitute or form part of smokers' products comprising - at least one source of coherent radiation arranged to furnish at least one beam of coherent radiation, - a carrier means and - a plurality of perforating units, each having means for focusing the beam upon the sheet-like material, GB 2 094 211 A said perforating units being installed in said carrier means.

2. Apparatus according to claim 1, wherein each perforating unit comprises a housing having radia tion admitting inlet means and radiation discharging outlet means and being arranged in said carrier means.

3. Apparatus according to claim 1 or 2, further comprising a shroud interposed between said carrier means and the sheet-like material and having aper- 75 tures in register with the outlet means of said perforating units.

4. Apparatus according to claim 3, wherein said shroud is spaced apart from said outlet means.

5. The apparatus of anyone of the preceding claims, wherein said radiation source includes a laser arranged to emit a beam of coherent radition and further comprising means for splitting said beam into discrete beams, one for each of said perforating units and for directing the discrete beams into the radiation admitting inlet means of the respecitve housings.

6. The apparatus of anyone of the preceding claims, wherein said sheet-like material is a con tinuous web and further comprising means for transporting the web lengthwise along a predeter mined path, carrier means adjacent to one side of said path and a plurality of perforating units, said units being installed in said carrier means and forming at least one row extending in substantial parallelism with the longitudinal direction of the web in said path.

7. The apparatus of claim 6, wherein the units of each rows are staggered with reference to each other, as considered transversely of said path.

8. The apparatus of anyone of the claims 6 or7, wherein the number of said rows equals two and each of said rows comprises three perforating units.

9. The apparatus of any one of the claims 1 to 8, further comprising at least one source of coherent radiation, a carrier and a plurality of perforating units, said units being installed in said carrier and including means for focusing discrete beams of coherent radiation upon the sheet-like material, said source being arranged to emit at least one beam of coherent radiation and said carrier having channel means with inlet means for said one beam and means provided in said channel means for splitting said one beam into discrete beams, one for each of said units, and for directing the respective discrete 115 beams against the corresponding focusing means.

10. The apparatus of claim 9, wherein said units form a plurality of rows and said channel means includes a first channel arranged to receive said one beam from said source and a plurality of additional 120 channels, one for each of said rows and each communicating with said first channel, said beam splitting means including first reflector means pro vided in said first channel to split said one beam into a plurality of second beams and to direct each second beam into a discrete second channel, and second reflector means provided in said second channels, one for each unit of the respective row and each arranged to split the respective second beam into discrete beams and to direct the thus obtained discrete beams against the respective focusing means.

11. The apparatus of claim 9, wherein said beam splitting means comprises at least one partially reflecting and at least one totally reflecting reflector.

12. The apparatus of anyone of the preceding claims, wherein said sheetlike material is an elongated web and further comprising means for transporting the web along a predetermined path and a shroud interposed between said path and said unit, said shroud having a slide surface defining a portion of said path.

13. The apparatus of claim 12, wherein said slide surface is of arcute shape.

14. The apparatus of claim 13, wherein said arcuate surface is a convex surface and said trans porting means includes means for maintaining the web in contact with said convex surface.

15. The apparatus of any one of the preceding claims, further comprising a source of coherent radiation, each of said units comprising a housing having a radiation admitting inlet and a radiation discharging outlet, said unit further comprising an optical system disposed in said housing between said inlet and said outlet and arranged to focus coherent radiation entering via said inlet upon the sheet-like material byway of said outlet.

16. The apparatus of claim 15, wherein said optical system comprises a collector lens having a focus located in the plane of the sheet-like material.

17. The apparatus of anyone of the preceding claims, further comprising a source of coherent radiation, a carrier for said unit and means for directing coherent radiation from said source to said carrier, said carrier having a socket for said unit and said unit having a radiation admitting inlet defined by a window including optical means forfocusing radiation upon the sheet-like material and said unit further having a nozzle defining a radiation discharg- ing outlet interposed between said optical means and the sheet-like material.

18. The apparatus of anyone of the preceding claims, wherein the sheetlike material is a web of wrapping material for use in a machine for the processing of commodities which constitute or form part of smoker's products, and further comprising means fortransporting the web past said unit, said transporting means forming part of the processing machine.

19. Apparatus for making holes in a sheet-like material, particularly in a running web of wrapping material for rod-shaped articles which constitute or form part of smoker's products comprising - at least one source of coherent radiation arranged to furnish at least one beam of coherent radiation, - a carrier means and - a plurality of perforating units, each having means for focusing the beam upon the sheet-like material, said perforating units being installed in said carrier means, further comprising - means for conveying at least one stream of gaseous fluid between the perforation units and the sheet-like material.

20. Apparatus according to claim 19, comprising at least one source of coherent radiation, said 11 GB 2 094 211 A 11 perforating units including means for focusing coherent radiation furnished by said source upon the sheet-like material and each of said housings having radiation admitting inlet means, radiation discharg- ing outlet means and a chamber communicating with the respective outlet means, and further comprising a shroud disposed between said units and the sheet-like material and having apertures in register with said outlet means, said shroud and said housings defining at least one compartment communicating with said outlet means and said conveying means including means for circulating gaseous fluid from the chambers of said housings into said compartment by way of the respective outlet means.